Journal of Periodontology
Volume 91, Issue 3 p. 311-338
BEST-EVIDENCE CONSENSUS
Free Access

Effect of gingival phenotype on the maintenance of periodontal health: An American Academy of Periodontology best evidence review

David M. Kim, 

Corresponding Author

David M. Kim

Advanced Graduate Program in Periodontology, Department of Oral Medicine, Infection and Immunity, Harvard School of Dental Medicine, Boston, MA

Correspondence

David M. Kim, Harvard School of Dental Medicine, 188 Longwood Avenue, Boston, MA 02115, USA.

Email: [email protected]

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Seyed Hossein Bassir, 

Seyed Hossein Bassir

Advanced Specialty Education Program in Periodontics, Department of Periodontology, Stony Brook School of Dental Medicine, New York, NY

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Thomas T. Nguyen, 

Thomas T. Nguyen

Division of Periodontology, Department of Oral Medicine, Infection and Immunity, Harvard School of Dental Medicine, Boston, MA

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First published: 06 November 2019
https://doi.org/10.1002/JPER.19-0337
Citations: 58

Abstract

Background

Gingival thickness, keratinized tissue width, and bone morphotype are three important parameters used to categorize periodontal phenotypes. These elements all play an important role in the maintenance of periodontal health. The aim of this review is to explore the importance of converting thin phenotype into a thick phenotype for periodontal health maintenance.

Methods

Three clinically relevant focused questions were defined to understand the role of gingival phenotype around teeth. 1) What are the factors affecting gingival phenotype (e.g., age, sex, dental arch, race, crown forms, etc.)? 2) Is there a difference between thin versus thick gingival phenotype in terms of gingival health? 3) Does the conversion of gingivae from a thin to thick gingival phenotype in sites without mucogingival defects help with periodontal health maintenance?

Results

Extensive electronic and manual literature search identified a total of 1,129 citations. After title, abstract, and full-text screenings, 30 articles were included in the present review. Twenty-five studies met the inclusion criteria and provided data for focused question 1. It was found that periodontal phenotype varies among different individuals and different areas of the mouth within the same individual. Asian individuals tend to have thinner gingival phenotype compared with white subjects. Eleven studies met the inclusion criteria for the focused question 2. Prevalence and severity of gingival recession was higher at the sites with thin gingiva compared with the sites with thicker gingiva. No studies provided data for focused question 3.

Conclusions

Available evidence indicates that subjects with thin and narrow gingiva tend to have more gingival recession compared with those with thick and wide gingiva. Currently, there is no published evidence to support conversion of thin to thick gingival phenotype in sites without gingival recession or mucogingival deformity.

1 INTRODUCTION

The 2017 World Workshop on the Classification of Periodontal and Peri-Implant Disease and Conditions has recommended adoption of the term “periodontal phenotype” by the periodontal community.1 This term is based on both gingival phenotype (three-dimensional gingival volume such as gingival thickness (GT) and keratinized tissue width [KTW]) and thickness of the facial and/or buccal bone plate (bone morphotype).1 The periodontal phenotype can be modified by environmental factors and clinical interventions such as overhanging restorations, orthodontics, or autogenous gingival grafting procedures.1 Terms such as “scalloped and thin” or “flat and thick” gingiva coined by Ochsenbein and Ross2 as well as “thick-flat” and “thin-scalloped” biotypes coined by Seibert and Lindhe3 are commonly used in dentistry. The latest systematic review on gingival morphology assigned gingival biotypes to three types: “thin scalloped,” “thick flat,” and “thick scalloped.”4 Gingival thickness, KTW and bone morphotype were three important parameters used to categorize biotypes and they were important in development or progression of mucogingival defects.4 However, by definition, biotype is genetically predetermined, cannot be modified and does not incorporate environmental factors and clinical intervention that can alter the periodontal tissue profile.1

The gingival phenotype (GT portion) has been previously measured via different techniques, such as by direct visual inspection, dental probe transparency, transgingival probing, ultrasonic transducer, parallel profile periapical radiography, and cone-beam computed tomography.2, 5-13 Among these various techniques, dental probe transparency is a non-invasive way of measuring gingival phenotype and is highly reproducible, with 85% agreement between duplicate recordings.5

Another aspect of gingival phenotype, KTW, can be determined by a vertical measurement using a periodontal probe positioned between the gingival margin and the mucogingival junction. A 1963 study by Bowers14 serves as a good reference on understanding the significance of the width of attached gingiva (AG) in human.

Several predisposing factors such as a thin periodontal phenotype, as well as a lack of AG, can contribute to gingival recession.12, 15 Areas of a thin labial bone plate and thin gingiva were commonly correlated with the canine eminences, the mesial roots of maxillary first molars, and mandibular incisors.16 Patient-contributed trauma and iatrogenic interventions, such as improper toothbrushing technique, deep cervical restorative margins and orthodontic tooth movement have all been associated with gingival recession.1, 12, 15

A systematic review and meta-analysis of long-term outcomes of untreated buccal gingival recessions has reported a high probability of progression even in individuals with good oral hygiene.17 Agudio et al.18 have compared periodontal conditions of 47 patients with gingival augmentation sites versus untreated homologous contralateral sites, with a mean follow-up period of 23.6 ± 3.9 years. At the end of the follow-up period, 83% of the 64 treated sites showed recession reduction while 48% of the 64 untreated sites experienced an increase in recession.

Two systematic reviews from the 2014 American Academy of Periodontology (AAP) Regeneration Workshop outlined the indications and assessed the efficacy of soft tissue non-root coverage procedures as well as soft tissue root coverage procedures.15, 19 Both reviews noted that autogenous gingival grafts and subepithelial connective tissue graft (SCTG)-based procedures provided the best clinical outcomes.15, 19 However, there was a lack of selected studies that evaluated both components of gingival phenotype (GT and gingival width).20, 21

The purpose of this Best Evidence Consensus (BEC) was to explore the importance of converting thin phenotype into a thick phenotype for maintaining periodontal health and particularly before extensive restorative and orthodontic treatments.

Three broad questions were considered:
  • 1)

    Does the conversion of gingivae from a thin to thick phenotype offer clinical value for maintaining periodontal health?

  • 2)

    In patients having a thin tissue phenotype that requires restorative treatment, will a surgical procedure to thicken tissue phenotype improve tissue stability?

  • 3)

    Does periodontal phenotypic conversion therapy, via soft or hard tissue grafting, offer clinical value to patients requiring orthodontic treatment?

The current BEC review group was commissioned to review the literature specific to the first question.

2 MATERIALS AND METHODS

The authors (DMK, SHB, and TTN) critically reviewed and analyzed the literature associated with the topic of interest. The present systematic review was conducted according to the PRISMA (Preferred Reporting Items for Systematic Review and Meta-Analyses) guidelines.22

2.1 Focused questions

To answer the first broad question, three clinically relevant focused questions were asked and answered following the systematic review:
  • 1)

    What are the factors affecting gingival phenotype (e.g., age, sex, dental arch, tooth position, race, crown forms, etc.)?

  • 2)

    Is there a difference between thin versus thick gingival phenotype in terms of gingival health?

  • 3)

    Does the conversion of gingivae from a thin to thick gingival phenotype in sites without mucogingival defects helps with periodontal health maintenance?

2.2 Inclusion and exclusion criteria

The Population, Intervention, Comparison, and Outcome (PICO) framework was used to guide the inclusion or exclusion of studies for each question using the following criteria:
  • A.

    Focused Question 1:

    1. Population: studies in adult human subjects;

    2. Intervention: studies with or without an intervention were included;

    3. Comparison: included studies had to assess the gingival phenotype by reporting the gingival width as well as GT or type gingival biotype/phenotype;

    4. Outcome: studies had to report the effect of different variables such as age, sex, dental arch, tooth position, race, crown forms, and etc. on the gingival phenotype.

  • B.

    Focused Question 2:

    1. Population: studies in adult human subjects;

    2. Intervention: studies with or without an intervention were included;

    3. Comparison: included studies had to have a group consisting of sites with thin gingival biotype/phenotype and they had to have a group consisting of sites with thick gingival biotype/phenotype;

    4. Outcome: studies had to provide data on gingival or periodontal outcome variables such as bleeding on probing, gingival index, plaque index, probing depth, clinical attachment level, radiographic bone loss or gingival recession.

  • C.

    Focused Question 3:

    1. Population: studies in adult human subjects;

    2. Intervention: site with thin gingival biotype/phenotype that received periodontal conversion therapy;

    3. Comparison: site with thin gingival biotype/phenotype that did not receive periodontal conversion therapy;

    4. Outcome: data on gingival or periodontal outcome variables including bleeding on probing, gingival index, plaque index, probing depth, clinical attachment level, radiographic bone loss, or gingival recession.

Studies focusing on treating sites with gingival recession or mucogingival defects were excluded because the goal of this focused question was to assess whether conversion of thin to thick gingival phenotype in sites without gingival recession or mucogingival involvement offers additional clinical value for maintaining periodontal health. The importance and indications of treating sites with gingival recession or mucogingival defects are well established and have been reported in the previously published systematic reviews.15, 17, 19

All study designs were considered for inclusion in this systematic review, including randomized controlled trials (RCTs), non-randomized controlled trials, prospective or retrospective cohort trials, and cross-sectional studies.

Exclusion criteria included 1) studies that did not fulfill the above-mentioned inclusion criteria for each focused question; 2) non-English studies; 3) in vitro studies, ex vivo and animal studies; 4) editorials, letters, and reviews.

2.3 Search strategy and study selection

Details of search strategy and study selection are presented in the supplementary Appendix 1 in online Journal of Periodontology.

2.4 Quality assessment

The level of evidence for each focused question was determined according to the Strength of Recommendation Taxonomy (SORT) criteria based on the following ranking system23:
  • SORT level A recommendation is for consistent, good-quality patient-oriented evidence.
  • SORT level B recommendation is based on inconsistent or limited-quality patient-oriented evidence.
  • SORT level C recommendation is based on consensus, disease-oriented evidence, usual practice, expert opinion, or case series for studies of diagnosis, treatment, prevention, or screening.

2.5 Statistical analyses

A meta-analysis was not possible to perform since the outcome variables and methods used to assess gingival phenotype were varied among the studies. Hence, the results are presented in narrative form.

3 RESULTS

A flow diagram of the search strategy is presented in Figure 1. The electronic and manual search identified a total of 1,129 citations. Screening of the titles and abstracts of the articles resulted in exclusion of 996 articles that were irrelevant to the topic of the present review. The full-text of the remaining 133 articles were obtained and reviewed. In total, 30 articles were included in the present review. Twenty-five studies5, 8, 10, 24, 45 met the inclusion criteria and provided data for focused question 1, and 11 studies8, 25, 27, 28, 31, 36, 46-50 met the inclusion criteria for the focused question 2. No studies provided data for the focused question 3.

Details are in the caption following the image
Figure 1
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Flowchart diagram of the search strategy

3.1 Focused question 1

What are the factors affecting gingival phenotype (e.g., age, sex, dental arch, race, crown forms, etc.)? The characteristics and results of the included studies for this clinically focused question are presented in Table 1. All 25 included studies5, 8, 10, 24-45 reported data for both KTW and GT.

Table 1. Summary of the included studies evaluating factors affecting gingival phenotype
Studies Objectives Study design Study population; (sample size); groups Country; ethnicity/race Mean age (range) and sex Evaluated sites Evaluation method Results Conclusions
Alkan et al., 201844 1. To evaluate the relationship of GT and KTW with different malocclusion groups and amount of crowding. Cross-sectional Periodontally healthy subjects; (n = 181). Three malocclusion groups (Angle Class I, II, and III) and divided into subgroups according to crowding (mild 0 to 3 mm, moderate 4 to 6 mm, and severe >6 mm) Turkey; NR 17.27 (11-28); 63M/118F Maxillary anterior teeth GT: transgingival probing (endodontic file with a rubber stopper); KTW: periodontal probe

  1. Prevalence of thin gingival biotype was 29.8% while it was 70.2% for thick biotype.

  2. Maxillary Cs were observed to have thin gingival biotype in all groups.

  3. The KTW for maxillary Cs was narrower in the severe crowding group than in the mild/moderate crowding groups.

 1. No relationship between Angle classification and GT and KTW.
Alpiste-Illueca, 200410 1. To develop and evaluate a radiographic technique for measuring the dentogingival unit (epithelial and CT attachment). Cross-sectional Periodontally healthy subjects; (n = 88) Spain; NR NR (20 to 40); M/F: NR Maxillary left CI GT: parallel profile radiograph technique; KTW: periodontal probe

  1. 1.75 ± 0.24 mm for CT attachment thickness, 0.45 ± 0.20 mm for bone plate thickness at crestal level.

  2. The dimensions of the CT attachment are the least variable component.

  3. The thickness of the facial bone plate was the parameter with the great variation (usually thinner at the bone crest level than at the middle and apical thirds).

  1. A statistically significant relationship between gingival width and thickness of CT attachment (P = 0.026) and gingival sulcus depth (P = 0.018).

  2. The gingiva was thicker and sulcus depth less pronounced with increasing gingival band length.
Chou et al., 200839 1. To examine the forms of the crowns in the maxillary anterior teeth and corresponding gingival characteristics among healthy Taiwanese subjects. Cross-sectional Periodontally healthy subjects; (n = 112) Taiwan; Asian (Taiwanese) 22.7 (19 to 29); 58M/54F Maxillary anterior teeth GT: ultrasonic device; KTW: periodontal probe

  1. Mean GT of males versus females were 1.3 mm versus 1.15 mm for CI, 0.96 mm versus 0.9 mm for LI and 1.07 mm versus 0.94 mm for C.

  2. Mean KTW of males versus females were 5.94 mm versus 5.98 mm for CI, 5.76 mm versus 5.71 mm for LI and 5.51 mm versus 5.22 mm for C.

  3. Three crown-gingival classification: narrow (N), square (S) and compound ©.

  4. N = 43%, thinnest GT, minimal KTW, the slimmest crown shape. 0.90 ± 0.16 mm for GT and 4.88 ± 0.82 mm for KTW. S = 23%, similar GT, medium KTW, the stoutest form of maxillary anterior teeth. 1.02 ± 0.12 mm for GT and 5.58 ± 0.66 mm for KTW. C = 34%, bulkiest GT, ample KTW, mid crown width/crown length ratio 1.27 ± 0.19 mm for GT and 6.79 ± 0.77 mm for KTW.

 1. Crown forms and corresponding gingival characteristics are different in Taiwanese versus Caucasians.
Cook et al., 201128 1. To evaluate the difference in labial plate thickness in patients identified as having thin versus thick/average periodontal biotypes. Cross-sectional Subjects without periodontitis or severe gingivitis; (n = 60). Thin biotype: (n = 26) and thick/average biotype (n = 34) United States; NR NR; NR Maxillary anterior teeth GB: probe visibility; KTW: periodontal probe; Buccal bone thickness: CBCT

  1. Thin biotype was associated with thinner labial plate thickness (P <0.001), narrower KTW (P <0.001), greater distance from the CEJ to the initial alveolar crest (P =0.02).

  2. No relationship between biotype and tooth height-to-width ratio or facial recession.

 1. Periodontal biotype is associated with labial plate thickness, alveolar crest position, KTW, gingival architecture and probe visibility, but unrelated to buccal GR.
De Rouck et al., 20095 1. To identify the existence of gingival biotypes in periodontally healthy volunteers. Cross-sectional Periodontally healthy subjects; (n = 100) Belgium; white 28 (19-56); 50M/50F Maxillary CI GB: probe visibility; KTW: periodontal probe

  1. Thin gingiva, slender teeth, a narrow KTW and a highly scalloped gingival margin in one-third of subjects (mainly female).

  2. Thick gingiva, quadratic teeth, a broad KTW and a flat gingival margin in two-third of subjects (mainly male).

 1. Thin gingiva in mainly female subjects and thick gingiva in mainly male subjects.
Eger et al., 19968 1. To determine the validity and reliability of measuring GT with an ultrasonic device and measure GT in relationship to tooth type and age. Cross-sectional Periodontally healthy males; (n = 200); Three age groups: 20 to 25 yrs (n = 80), 40 to 45 yrs (n = 60), 55 to 60 yrs (n = 60) Germany; NR NR; 200M Maxillary and mandibular non-molar teeth GT: ultrasonic device; KTW: periodontal probe; PD, GR: clinical examination; CW/CL: Measurements on casts

  1. 1 In the maxilla, mean GT varied between 0.9 and 1.3 mm.

  2. In the mandible, mean GT varied between 0.8 and 1.5 mm.

  3. Reproducibility of GT measurements with the ultrasonic device was high.

  4. GT was a significantly influenced by PD, GR, KTW, and tooth type on and not by CW/CL.

  1. There are individual differences in GT, and a significant influence of PD, GR, KTW and tooth type on GT.

  2. No association between GT and shape and form of the tooth
Egreja et al., 201229 1. To evaluate the correlation between KTW and GT. Cross-sectional Periodontally healthy subjects; (n = 60) Brazil; NR NR (20-35); 30M/30F Maxillary right CI, LI, and C GT: transgingival probing (endodontic file with a rubber stopper); KTW: same endodontic file and caliper

  1. LI has the largest mean KTW (5.54 ± 1.09 mm) followed by the CI (4.62 ± 1.02 mm) and C (4.32 ± 1.33 mm)

  2. CI has the largest mean GT (1.17 ± 0.20 mm) followed by the LI (1.04 ± 0.24 mm) and C (0.87 ± 0.27 mm).

  3. No statistically significant difference for the mean KTW and GT between men and women.

  4. Positive correlation (P <0.05) was found between GT and KTW in CI, LI, and C.

 1. A positive correlation exists between GT and KTW for the maxillary anterior teeth in patients 20 to 35 years of age.
Fischer et al., 201833

  1. To determine the difference in mid-buccal GT between three different GBs.

  2. To analyze the association between GB and KTW.

 Cross-sectional Subjects without PD >3 mm and gingival recession; (n = 60); Thin GB (n = 30); moderate GB (n = 15); and thick GB (n = 15) 23 (19-37); 21M/39F Maxillary CI GT: customized digital caliper; GB: probe visibility; KTW: periodontal probe

  1. Median GT was 0.43 mm (thin GB), 0.74 mm (moderate GB) and 0.83 mm (thick GB).

  2. Significant differences in GT were found between thin GB versus moderate GB (P = 0.002) and between thin GB versus thick GB (P < 0.01).

  3. KTW was directly correlated with GT (P <0.001).

  1. The presence of a thick gingiva is associated with a wide band of KT.

  2. KTW directly correlated with GT.
Fischer et al., 201532 1. To evaluate a possible relationship between GB, GT, PH, and KTW. Cross-sectional Subjects without PD >3 mm and GR; (n = 36). Thin GB (n = 12); very thin GB (n = 6); thick GB (n = 12); very thick GB (n = 6) Germany; white 24.9 (18-35) 17M/19F Maxillary anterior teeth GT: customized digital caliper; GB: probe visibility; KTW: periodontal probe; PH: digital caliper; PD: periodontal probe

  1. GT: 0.40 ± 0.07 for thin GB 0.72 ± 0.11 mm for thick GB (P <0.0001).

  2. PH: 3.76 ± 0.50 mm for thin GB and 3.95 ± 0.41 mm for thick GB (P =0.02).

  3. KTW: 3.01 ± 1.26 mm for thin GB and 4.63 ± 0.86 mm for thick GB (P =0.04).

  4. When Stratification into moderate and very “thin”/“thick” GB was done, no significant differences were found between the moderate groups.

 1. Between thin and thick GB, a statistically significance could be detected in buccal GT, KTW, and PH.
Ghassemian et al., 201643 1. To evaluate correlations between clinical and tomographic parameters in individuals with thin and thick biotypes. Cross-sectional Subjects with PD <5 mm needing oral surgery in the posterior mandible; (n = 100). Thin GB (n = 50) and thick GB (n = 50) Italy; NR 40 (20-67); 40M/60F Mandibular anterior teeth GB: probe visibility; KTW: periodontal probe; GR: periodontal probe; Buccal bone thickness: CBCT

  1. Mean thickness of alveolar bone ranged from 4.51 to 6.66 mm, and mean thickness basal bone ranged from 8.2 to 8.9 mm.

  2. No statistically significant differences were detected among biotypes, whereas other variables (tooth torque, age and smoking) were often predictors of reduction in bone thickness (BT).

  3. Male sex was often a predictor of positive changes in BT.

  4. Previous orthodontic therapy was a protective factor against developing bone loss >5 mm.

 1. Biotype does not play a role in influencing alveolar BT, while other variables (tooth torque, sex, age and smoking habit) do influence alveolar BT.
Goaslind et al., 197724 1. To explore GT in specific areas of healthy FG and AG and to relate these measurements to other anatomic parameters. Cross-sectional Male subjects with clinically healthy gingiva; (n = 10) United States; NR NR (25-36); 10M Selected maxillary and mandibular anterior and posterior teeth GT: a transformer probe assembly excited by an oscillator and coupled to a digital voltmeter; KTW: periodontal probe

  1. FG thickness averaged 1.56 mm, AG thickness averaged 1.25 mm and the total mean thickness for all areas measured was 1.41 mm.

  2. Thickness in mandibular free and AG and maxillary free gingiva increased from anterior to posterior. Thickness in maxillary AG remained fairly constant.

  3. The mean width of AG was 3.54 mm (0.5 to 8.0 mm) and decreased from anterior to posterior.

  4. A significant inverse relationship (P <0.05) was noted between the width of AG and GT.

  1. GT varied considerable within and between subjects.

  2. GT was greater at sites with the narrower gingiva.
Joshi et al., 201735 1. To assess and compare the GB among sexes by clinical, photographic, and radiographic parameters. Cross-sectional Subjects without PD >3 mm and gingival recession; (n = 800) India; Indian 21.33 for males and 22.08 for females (18-25); 400M/400F Maxillary anterior teeth GT: parallel profile radiograph technique; GB: probe visibility; KTW: periodontal probe; Buccal BT: parallel profile radiograph technique; PH and CW/CL ratio: digital photographs

  1. A decreased PH with thick GB in males.

  2. Increased PH with a thin biotype in females.

  3. Positive correlation between GB and alveolar BT among both genders.

  1. Sex significantly affects GB.

  2. Thinner gingival biotype with reduced alveolar BT in females compared with males.
Kolte et al., 201434 1. To determine the variation in GT and KTW in the anterior segment with respect to age, sex and dental arch location. Cross-sectional Periodontally healthy subjects; (n = 120). Three age groups: 16 to 24 yrs (n = 40) 25 to 39 yrs (n = 40) >40 yrs (n = 40) India; NR NR; 60M/60F Maxillary and mandibular anterior teeth GT: transgingival probing (endodontic file with a rubber stopper); KTW: periodontal probe fitted with an endodontic rubber stopper

  1. Significantly greater GT and narrower KTW were found in younger age group compared with the older age group.

  2. The mean GT and KTW were significantly less in females than males.

  3. Greater GT and with smaller KTW were found in mandible compared with maxilla.

 1. GT and KTW are influenced by age, sex and dental arch location.
La Rocca et al., 201242 1. To determine the relationship between GT and KTW with regard to bone thickness in the anterior segment. Cross-sectional Periodontally healthy subjects; (n = 15); Maxillary sites (n = 90 teeth); mandibular sites (n = 90 teeth) Spain; NR 29.53 (22-49); 8M/7F Maxillary and mandibular anterior teeth GT: transgingival probing (endodontic file with a rubber stop); KTW: periodontal probe; PD: periodontal probe; Buccal bone thickness: CBCT

  1. The mean KTW was 4.48 mm, and generally larger for maxillary teeth versus mandibular teeth.

  2. Mean GT: Crestal 1.01 mm, mid 1.06 mm, and apical 0.83 mm

  3. Mean BT: Crestal 1.24 mm, mid 0.81 mm, and apical 2.78 mm.

  4. 4. The GT was not significantly correlated to the BT, while KTW was directly corelated with the crestal BT (P <0.05).

  1. No significant association was found between GT and BT.

  2. Significant association exists between KTW and crestal BT
Lee et al., 201340 1. To assess tooth morphology and gingival biotypes of Asian subjects. Cross-sectional (n = 49) United States; Asian (Chinese, Japanese, Korean and Vietnamese descent) 39 (NR) 20M/29F Seven teeth (maxillary CI, C, 2nd PM, and 1st M, Mandibular CI, C and 1st M) GB: probe visibility; KTW: periodontal probe; GR: periodontal probe; root/tooth length: panoramic radiographs

  1. The mean KTW was greatest for the maxillary CI (4.83 mm) and the lowest for the mandibular C.

  2. High positive frequencies of thin biotype and moderate recession (highest for the mandibular CI, followed by mandibular C, and maxillary CI and C).

 1. Asian patient exhibited high frequencies of thin GB, especially in the anterior teeth (>60% incidence) as well as more recession in the posterior region than in the anterior.
Lee et al., 201836 1. To determine the facial gingival profiles (GT and KTW) of periodontally healthy sites in an Asian population. Cross-sectional Subjects with healthy normal or reduced periodontium; (n = 51, 1,109 teeth). Sites with healthy periodontium: 78.4%. Sites with reduced periodontium that previously treated for periodontitis: 21.6% Singapore; Asian (Chinese, Malay, Indian, Eurasians) 30.3 (NR) 24M/ 27F Maxillary and mandibular incisors to the first molars GT: transgingival probing (endodontic file with a rubber stop); GB: probe visibility; KTW: periodontal probe

  1. Mean GT was 1.39 ± 0.52 mm, mean KTW was 4.59 ± 1.34 mm.

  2. Considerable variation within and between subjects were found.

  3. GT increased from anterior to posterior areas. Lowest means of GT were found around mandibular CIs to first premolars and maxillary C.

  4. The lowest KTW was noted for the mandibular CS and all premolars, while the widest GW was found at the incisors.

  5. GT and KTW were significantly correlated with tooth type, plaque, recession, but not age, sex and ethnicity.

  6. Poor correlation was found between GT and GB

  1. A high frequency of thin GB and low GT at the anterior teeth was noted in this Asian cohort.

  2. There is poor correlation between measuring GB using probe visibility and thickness of gingiva.
Müller and Eger, 199726 1. To identify subjects with different gingiva phenotype. Cross-sectional Periodontally healthy male subjects; (n = 42) Germany; whites NR (20-25) 42M Maxillary and mandibular non-molar teeth GT: ultrasonic device; KTW: periodontal probe; PD, GR: clinical examination; CW/CL: Measurements on casts

  1. Mean GT ranged between 0.76 ± 0.14 mm to 1.28 ± 0.37 mm.

  2. Mean GW ranged from 3.21± 1.02 mm to 4.80 ± 1.49 mm.

  3. Existence of different gingival phenotypes:

    • - Cluster A: two-third of individuals with normal GT, GW, and CW/CL.
    • - Cluster B: 21% of individuals with thicker and wider gingiva, and quadratic maxillary anterior teeth.
    • - Cluster C: 12% of individuals with normal GT, high CW/CL and a narrow KTW.

 The data indicated the existence of different gingival phenotypes.
Müller et al., 200027 1. To study thickness of masticatory mucosa and KTW in individuals with different periodontal phenotypes. Cross-sectional Periodontally healthy young subjects; (n = 40) Germany; whites (n = 37) and Asians (n = 3) (19-30) 19M/21F Maxillary and mandibular teeth. GT: ultrasonic device; KTW: periodontal probe; PD, CAL, GR: clinical examination; CW/CL: Measurements on casts

  1. Clusters A1 and A2 (thin gingival/slender tooth form) comprised of 75% of all subjects.

  2. Clusters A1 and A2 were differentiated by gingival width (A2 wider).

  3. Cluster B (relatively thick/wide gingiva and a quadratic tooth shape).

  4. Mean thickness of masticatory mucosa as well as KTW and crown form differed significantly among clusters.

  1. Sex and periodontal phenotype significantly affect the thickness of masticatory mucosa

  2. Palatal gingiva was at least 2× as thick as facial/buccal gingiva.

  3. Masticatory mucosa is thinner in women compared with men.
Olsson et al., 199325 1. To assess the relationship between the form of the crowns and GT as well a group of morphological characteristics in the maxillary anterior teeth. Cross-sectional 16 to 19 years old volunteers; (n = 108) Sweden; white 17.1 (16-19) Maxillary anterior teeth GT: transgingival probing (syringe needed with an endodontic depth marker); KTW: periodontal probe; GI, PD, CAL: clinical examination; CW/CL: Photographs

  1. Individuals with a long-narrow form of the CIs displayed a narrow zone of KTW, shallow PD and a pronounced scalloped contour of the gingival margin compared with individuals with a short-wide crown.

  2. The GT in CI was significantly associated with the KTW, buccolingual width of the crown and the presence of an interproximal gingival groove.

  3. The GT in LI was significantly correlated with the PD at the buccal surface.

  4. No significant association was found between GT and other variables in canines.

  1. Subjects with a long-narrow CIs have a less GT, a narrow KTW, shallow PD and a pronounced scalloped gingival contour.
Pascual et al., 201738 1. To determine whether there is a relationship in between maxillary and mandibular anterior teeth with regards GT and BT. Cross-sectional Subjects without history of periodontal disease; (n = 15); Maxillary sites (n = 90 teeth); Mandibular sites (n = 90 teeth) Spain; NR 29.53 8M/7F Maxillary and mandibular anterior teeth GT: transgingival probing (endodontic file with a rubber stop); KTW: periodontal probe; PD: periodontal probe; Buccal bone thickness: CBCT

  1. There were no significant differences between maxillary and mandibular teeth in terms of GT and BT at the crestal third and midpoint of (P >0.05).

  2. Apical BT measurements were significantly greater around anterior teeth in the mandible compared with the maxillary.

 1. GT and BT dimensions of maxillary and mandibular teeth are comparable, especially in the coronal third.
Peixoto et al., 201545 1. To assess how GB and tooth crown form are affected by PH, KTW, CW/CL, and gingival angle. Cross-sectional Subjects anterior teeth without any dental and periodontal defects; (n = 50) Portugal; NR NR (18-30); 20M/30F Maxillary anterior teeth GB: probe visibility assessed on digital photographs; KTW: assessed on digital photographs; PH, gingival angle and CW/CL: digital photographs

  1. No significant correlation was found between sex and GB or KTW.

  2. A statistically significant relationship between sex and PH (P = 0.005), crown width/crown length ratio (P = 0.017) and gingival angle (P = 0.041).

  1. No significant association was found between sex and GB

  2. It was found that there is association between sex and crown width/ crown length ratio, PH, and gingival angle.
Shah et al., 201531 1. To evaluate the GT and its relation to sex, presence of GR and the KTW in a subset of the Indian population. Cross-sectional NR; (n = 400) India; Indian 28.82 (20-35); 200M/200F Maxillary anterior teeth GT: transgingival probing (endodontic file with a rubber stop); GB: Thin for <1 mm GT and thick for >1 mm GT; KTW: periodontal probe; PD: periodontal probe

  1. The prevalence of thin GB was 43.25% and thick GB was 56.75%.

  2. The mean GT: CI (1.11 ± 0.17 mm), LI (1.01 ± 0.16 mm) and C (0.82 ± 0.17 mm).

  3. The mean GW: CI (4.38 ± 1.18 mm), LI (5.18 ± 1.25 mm) and C (4.11 ± 1.16 mm).

  4. There were no significant associations between GB and age, sex, or the presence of recession.

  5. GT and KTW were significantly correlated (P <0.05)

 It was found that patients with thin GT presented with a limited KTW.
Shao et al., 201837

  1. To assess the distribution of periodontal biotype in a young Chinese population.

  2. to assess the accuracy of different techniques for the measurement of GT.

 Cross-sectional Periodontally healthy students; (n = 31, 372 teeth) China; Asian (Chinese) 22.2 (18-27); 15M/16F Maxillary and mandibular anterior teeth GT: transgingival probing (endodontic file with a rubber stop); GB1: Thin for < 0.8 mm GT and thick for > 0.8 mm GT; GB2: probe visibility; KTW: periodontal probe; GI, PD, CAL: periodontal probe; Buccal BT: CBCT

  1. Thin tissue based on transgingival probing: 28.49% and based on probe visibility: 40.32%

  2. Mean GT via transgingival probing was 1.03 ± 0.31 mm and via CBCT was 1.03 ±

  3. Thick-flap biotype: 137 teeth (36.83%); Average-scalloped biotype: 96 teeth (25.81%); Average-flap biotype: 39 teeth (10.48%); Thin-scalloped biotype: 100 teeth (26.88%)

  4. No significant differences was found in buccal BT between four GBs.

  5. Significant differences between males and females in transgingival probing and labial bone thickness (P <0.05)

 1. The most common GB in this Chinese population was thick-flap type.
Stein et al., 201330 1. To assess the relation of different morphometric parameters with GT and buccal BT at different apico-coronal levels. Cross-sectional Volunteers without known periodontal or dental diseases; (n = 60) Germany; white 31.53 (18-61) 24M/36F Maxillary left central incisor GT: parallel profile radiograph technique; GB: probe visibility; KTW: periodontal probe; Buccal BT: parallel profile radiograph technique; CW/CL and Height of the gingival scallop: digital photographs

  1. Mean GT ranged from 0.59 ± 0.17 mm to 1.46 ± 0.37 mm

  2. Mean KTW was 4.92 ± 1.01 mm.

  3. Mean buccal BT ranged from 0.57 ± 0.23 mm to 0.85 ± 0.45 mm.

  4. Positive correlation between CW/CL and GT at CEJ.

  5. Negative correlation between GB and GT.

  6. Positive correlation between the GT and the buccal BT

  7. CW/CL and KTW were significant predictors of GT at CEJ.

  1. Crown form and KTW are predictors for the GT over the CEJ.

  2. Crown form is predictor for buccal BT.
Stellini et al., 201341 1. To assess the correlation between tooth shapes and gingival and periodontal characteristics. Cross-sectional Volunteers without destructive periodontal dis- ease; (n = 50); Groups based on crown shapes: Triangular (n = 9); Square (n = 15); Square-tapered (n = 26) Italy; white (Italian) 23 (18-29) 31M/19F Maxillary central incisors GT: a needle fitted with a rubber stopper measured by electronic gauge; KTW: electronic gauge; Bone sounding depth: periodontal probe; CW/CL and PH: digital photographs

  1. Median KTW and GT were 4.8 mm and 1.51 mm.

  2. Triangular teeth in 19% of male, 16% of female. Square teeth in 23% of male, 42% of female; square-tapered teeth in 58% of male, 42% of female.

  3. Statistically significant differences were observed for GT (P =0.012) and KTW (P < 0.001) and PH (P <0.001) between groups.

  4. No significant differences in sex among three tooth-shape groups (P = 0.34).

 1. The shape of the maxillary CI crowns correlate with the extent of the KTW, GT, and PH.
  • AG = attached gingiva; BT = bone thickness; C = canine; CAL = clinical attachment level; Cs = canines; CBCT = cone-beam computed tomography; CEJ = cemento-enamel junction; CI = central incisor; CL = crown length; CT = connective tissue; CW = crown width; FE = free gingiva; GB = gingival biotype; GI = gingival index; GR = gingival recession; GT = gingival thickness; KTW = keratinized tissue width; LI = lateral incisor; LIs = lateral incisors; M = molar; MGJ = mucogingival junction; NR = not reported; PD = probing depth; PH = papilla height; PM = premolar; M = molar; Yrs = years.

3.1.1 Association between keratinized tissue width and gingival thickness

The association between KTW and GT were addressed in eleven studies.8, 24-33 In general, the majority of the studies found a positive correlation between the KTW and GT in maxillary anterior teeth.8, 25, 28-33

Egreja et al.29 evaluated whether there was a correlation between the KTW and GT and noted a positive correlation (P <0.05) between them for the maxillary anterior teeth. Several other studies have reported a similar positive correlation between KTW and GT.26, 27, 31, 33

However, no statistically significant difference for the mean KTW and GT between men and women was found in the Egreja et al. study.29 This latter finding conflicts with other studies that have observed that GT was greater in men.5, 27, 34

Further, Egreja et al.29 study reports that maxillary central incisors (CIs) exhibit a greater mean GT (1.17 mm) than maxillary lateral incisors (LIs) (1.04 mm) and canines (Cs) (0.87 mm). Goaslind et al.,24 Müller and Eger,26 and Shah et al.31 have also reported similar results for the maxillary anterior teeth, that is, CIs exhibiting the greater mean GT and maxillary Cs exhibiting the smallest mean GT. With regard to the gingival width, it is reported that LIs have the widest zone of gingival keratinized tissue (KT; mean 5.54 mm) followed by the CIs (mean 4.62 mm) and Cs (4.32 mm).29 Similarly, Müller and Eger26 and Shah et al.31 reported that maxillary LIs and Cs had the highest and lowest mean width of gingival KT. Müller and Eger,26 in a white population, reported a KT width of 4.8 mm for LIs, 4.44 mm for CIs and 4.21 mm for Cs, while Shah et al.31 reported a KT width of 5.18 mm for LIs, 4.38 mm for CIs and 4.16 mm for Cs in an ethnic Indian population.

With regard to comparison GT and KTW of teeth, the data indicates that maxillary CIs presented with the greatest mean GT, followed by LIs and Cs.24, 26, 29, 31 On the other hand, maxillary LIs have the greatest KTW, followed by the CIs and Cs.26, 29, 31

Therefore, the available evidence indicates that GT and WKT are positively correlated in maxillary anterior teeth with CIs having the greatest mean GT and LIs having the widest WKT. It should be noted that the majority of the studies only focused on maxillary anterior teeth. There is only limited evidence available regarding the correlation of GT and WKT for the other teeth.

3.1.2 Association between gingival phenotype and gingival thickness

The association between GB and GT were evaluated in six studies.30-33, 35, 36 The majority of studies that assessed maxillary anterior teeth found a positive relationship between GB, GT, and KTW in maxillary anterior teeth.32, 33, 35 However, non-significant or weak correlations were found between measuring GB using probe visibility and thickness of gingiva in two studies were posterior teeth36 or mandibular anterior teeth37 were included in the analysis.

Fischer et al.32 evaluated a possible relationship between GB and GT, papilla height (PH) and KTW in maxillary anterior teeth of 36 periodontally healthy patients. A statistically significant difference was found in buccal GT, KTW and PH of patients with thin GB versus thick GB. After establishing these clinically significant relationships, Fischer et al.33 then evaluated the relationship between GB (determined by probe visibility) and GT (measured using a customized digital caliper). In this study, 60 White dental school students’ maxillary CIs were initially categorized into three groups (thin GB, moderate GB, and thick GB). The authors reported a median GT ranging from 0.43 mm to 0.83 mm. In addition, the authors reported a significant difference in GT between thin GB versus moderate GB (P = 0.002) and between thin GB versus thick GB (P <0.01). Moreover, they found that KTW was directly correlated with GT, and the presence of a thick gingiva was associated with a wide band of KT.

In general, literature suggests that GT is correlated with GB in the anterior maxilla. The data for regions other than anterior maxilla are limited and conflicting.

3.1.3 Association between gingival phenotype and age, sex, dental arch, and race

Age and sex

The association between age and GT was assessed in six studies.8, 28, 31, 34, 36, 43 Five out of the six studies demonstrated that there is no relationship between age and the GT.8, 28, 31, 36, 43

Eger et al.8 observed no difference in mean GT among individuals ranging from 20 to 60 years of age. Cook et al.,28 in US subjects, reported no significant association between periodontal biotype classification and age or sex for maxillary anterior teeth. Shah et al.,31 in 400 young Indian subjects, also reported no significant relationship between GB and age, sex.

Thus, the current evidence does not support a relationship between age and GT and sex and GT.

Dental arch

Five studies compared the thickness of maxillary and mandibular teeth.24, 34, 36-38 The majority of studies found that GT varies within and between individuals. However, there is no major difference between overall GT in the maxilla and the mandible.36, 38

In terms of dental arch, Pascual et al.38 reported no significant differences at the crestal and middle portions of maxillary and mandibular anterior teeth in terms of their gingival and facial bone thickness. However, the facial bone thickness was greater in mandibular anterior teeth compared with maxillary teeth at the most apical aspect of the root.38

Gingival tissue thickness in Asian population

Differences in gingival tissue thickness between groups from different ethnic or racial backgrounds are known to exist. Four studies evaluated the gingival phenotype in Asian populations.36, 37, 39, 40 A common clinical impression is that Asians tend to have susceptibility for gingival recession due to their thin gingival tissues.36, 39, 40 Most gingival and periodontal studies have focused on White subjects which has resulted in a lack of similar information for other ethnic groups. Thus, Chou et al.39 conducted a clinical study to evaluate gingival characteristics in an Asian (Taiwanese) population. The authors examined gingival characteristics of 112 healthy Taiwanese subjects and reported Asian (Taiwanese) subjects might be more prone to gingival recession and more challenging when performing esthetic reconstruction of the maxillary anterior teeth.

Lee et al.40 conducted a cross-sectional comprehensive survey of tooth morphology and GB in Asian subjects (people of Chinese, Japanese, Korean, and Vietnamese origin) living in the United States. The authors noted that Asian patients exhibited a high percentage of thin GB as well as moderate recession. Müller and Eger26 reported 12% of white males exhibited thin gingiva. In a similar study, De Rouck et al.5 reported a 33% prevalence rate of thin gingiva in mostly whites females. In contrast, Lee et al.40 reported a high incidence (>60%) of thin GB in the anterior teeth of Asian patients.

Lee et al.36 evaluated the gingival profile (GT and KTW) of teeth with a healthy periodontium in Asian populations (Chinese, Malay, Indian, and Eurasians). GT increased from anterior to posterior teeth in both maxillary and mandibular arches. The maxillary molars exhibited the greatest GT while mandibular incisors showed the thinnest. Of the 370 maxillary anterior teeth, 63.8% were classified as having a thin GT (<1.5 mm) compared with 92.4% of mandibular anterior teeth. Both GT and KTW were not influenced by age, sex, ethnicity (Chinese and non-Chinese) and type of periodontium (healthy normal and reduced). In conclusion, there was a high prevalence of thin GT and thin marginal gingiva associated with the anterior teeth in this cohort.

The current evidence suggests that Asian subjects have a thin gingival phenotype compared with white subjects.

3.1.4 Association between gingival and periodontal phenotypes and crown forms

In 1977, Weisgold reported an association between tooth shape and gingival architecture.51 A square tooth shape was associated with a flat gingival architecture and a thick GT while a triangular shape tooth was associated with a scalloped gingival architecture and a thin GT.51

The relationship between gingival and periodontal phenotypes and crown forms have been assessed in twelve studies.5, 8, 25-27, 30, 35, 37-39, 41, 45 However, these studies reported inconsistent findings regarding the crown form as a predictor factor for gingival and periodontal phenotypes.8, 25, 30, 35, 41 The data on the association between gingival and periodontal phenotypes and crown forms is presented in supplementary Appendix 2 in online Journal of Periodontology.

3.1.5 Association between periodontal phenotype and thickness of labial plate

The role of labial or buccal plate thickness on periodontal phenotype has been investigated in eight included studies.10, 28, 30, 35, 37, 38, 42, 43 The available evidence indicates there are variations in the buccal plate thickness within subjects based on tooth positioning and location of the measured point.10, 28, 30, 35, 37, 38, 42, 43 Although the majority of the studies suggest that periodontal phenotype is associated with thickness of buccal plate,28, 30, 35, 42 other studies found there is no association between periodontal phenotype and labial or buccal plate thickness.37, 43 The data on the association between periodontal phenotype and thickness of labial plate are presented in supplementary Appendix 3 in online Journal of Periodontology. There is a disagreement regarding the role of the labial plate thickness on periodontal phenotype.

3.1.6 Gingival phenotype and malocclusion

The data on the effect of on malocclusion of the gingival phenotype are presented in supplementary Appendix 4 in online Journal of Periodontology.

3.1.7 Summary

A summary of the observations specific to the clinically relevant focused question #1 are:
  • GT varies among different individuals as well as different areas of the mouth within the same individual.24
  • There was a positive correlation between the KTW and GT in maxillary anterior teeth.26, 29, 31, 33
  • Maxillary CIs presented with the greatest mean GT, followed by LIs and Cs.24, 26, 29, 31
  • Maxillary LIs have the greatest KTW, followed by the CIs and Cs.26, 29, 31
  • Gingival phenotype does not appear to be influenced by either age or sex.8, 28, 31, 36, 45 However, other studies have reported higher prevalence of thin gingival phenotype in females versus males.5, 27, 35
  • Asian subjects seemed to have thin gingival phenotype compared with white subjects.36, 39, 40
  • There is a disagreement in terms of tooth shape predicting gingival phenotype8, 25, 30, 35, 41 and the role of thickness of the labial plate on periodontal phenotype.28, 30, 35, 37, 42, 43

Conclusion: SORT Level B

3.2 Focused question 2

The second of the three clinically relevant focused questions is: Is there difference between thin versus thick gingival phenotype in terms of gingival health?

For this focused question, a total of 11 references8, 25, 27, 28, 31, 36, 46-50 met our inclusion criteria. Table 2 presents the characteristics and results of the included studies assessing the difference between thin versus thick gingival phenotype in terms of gingival health.

Table 2. Summary of the included studies evaluating the difference between thin versus thick gingival phenotype in terms of gingival health
Studies Objectives Study design Study population; mean age (range); sex; evaluated sites; intervention and groups Outcome variables and evaluation methods Results Conclusions
Relationship between GT and plaque, BOP, and PD
Claffey and Shanley, 198646 1. To investigate the relationship of GT and BOP in shallow buccal sites (≤3.5 PD) to loss of probing attachment after non-surgical therapy. Prospective cohort
  • - 15 patients with moderately or severely advance periodontal disease
  • - 34.7; (NR)
  • - Sex: NR
  • - Maxillary and mandibular non-molar teeth
  • - A single appointment of supra- and subgingival instrumentation. Sites were grouped as follows:
    1. GT <1.5 mm with BOP (n = 44)
    2. GT <1.5 mm without BOP (n = 93)
    3. GT >2.0 mm with BOP (n = 39)
    4. GT >2.0 mm without BOP (n = 39)
 Clinical examinations were done at baseline and 3 months after the treatment; GT: transgingival probing (stainless steel wire with 1 mm increments); Relative CAL: using a stent and periodontal probe; BOP, GR, PD, PI: clinical examination
  1. Thin and non-bleeding sites had a mean attachment loss of 0.3 ± 0.8 mm after non-surgical therapy.
  2. No change in PD was observed for the thin and non-bleeding sites, whereas all other groups showed a reduction in PD compared with the baseline.
  3. The mean attachment loss after non-surgical therapy was significantly greater in non-bleeding thin sites (baseline GT ≤ 1.5 mm) compared with bleeding thin sites and bleeding thick sites (baseline GT ≥ 2.0 mm).
  4. Thin and non-bleeding group had more sites with attachment loss compared with the other groups.
 The attachment loss that observed after non-surgical periodontal therapy may be primarily due to the changes in shallow, thin healthy sites.
Müller and Heinecke, 200247 1. To study the effect of GT and KTW on BOP in young subjects with mild plaque-induced gingivitis. Cross-sectional
  • - 40 systemically healthy young volunteers
  • - NR; (19 to 30)
  • - 19M/21F
  • - Maxillary and mandibular teeth
  • - None
 GT: ultrasonic device; KTW: periodontal probe; BOP, CAL, PD, PI: clinical examination
  1. BOP was significantly correlated with smoking status, plaque and tooth type.
  2. When adjusted for smoking, tooth type and clinical variables, gingival phenotype did not affect bleeding tendency.
 No association between GT and KTW on BOP in patients with mild plaque-induced gingivitis.
Müller and Könönen, 200548 1. To evaluate subject variation of buccal GT in young subjects with mild gingivitis. cross-sectional
  • - 33 subjects mild or moderate plaque-induced gingivitis
  • - 22 (19 to 23)
  • - 33F
  • - Maxillary and mandibular teeth
  • - None
 GT: ultrasonic device; Bleeding index, BOP, CAL, PI, PD, % of calculus: clinical examination
  1. A positive significant association was found between GT and PD and between GT and PI.
  2. A negative significant associated with GT and average bleeding index.
  1. Higher bleeding tendency was found in subjects with thin gingiva.
  2. PD was associated with GT.
  3. Lower PI scores were found for subjects with thinner gingiva.
Olsson et al., 199325 1. To assess the relationship between the form of the crowns and GT as well a group of morphological characteristics in the maxillary anterior teeth. Cross-sectional
  • - 108 volunteers
  • - 17.1 (16 to 19)
  • - Sex: NR
  • - Maxillary anterior teeth
  • - None
 GT: transgingival probing (syringe needed with an endodontic depth marker); KTW: periodontal probe; GI, PD, CAL: clinical examination
  1. The GT in CIs is significantly affected by the bucco-lingual width of the crown, KTW and the presence of interproximal gingival groove.
  2. GT was positively associated with PD at the buccal surface in CIs, LIs, and Cs. This association reached a level of significance (P <0.01) for LIs.
  3. The mean CAL was significantly greater in LIs with long-narrow crowns compared with those with short-wide crowns. No significant differences were found for CIs and Cs for this variable.
  1. There is a strong relationship between KTW and GT.
  2. There is a positive relationship between GT and PD.
Relationship between GT and gingival recession
Cook et al., 201128 1. To evaluate the difference in labial plate thickness in patients identified as having thin versus thick/average periodontal biotypes. Cross-sectional
  • - 60 subjects without periodontitis or severe gingivitis
  • - Age: NR
  • - Sex: NR
  • - Maxillary anterior teeth
  • - None; Groups:
    1. Thin GB (n = 26)
    2. Thick/Average GB (n = 34)
 GB: probe visibility; KTW: periodontal probe; BOP, GR, PD, CAL: clinical examination; Buccal bone thickness: CBCT
  1. Subjects with a thin GB were more likely to have scalloped gingival architecture.
  2. No significant relationship was observed between GB and GR. However, only 6.1% of all examined teeth had GR.
  1. Subjects with thick/average GB have thicker labial plate and a smaller distance from the CEJ to the alveolar crest than those with thin biotype.
  2. GR is not associated with GB. However, this finding should be interpreted with caution due to the limited sample size of sites with GR
Eger et al., 19968 1. To determine the validity and reliability of measuring GT with an ultrasonic device and measure GT in relation to tooth type and age. Cross-sectional
  • - 42 subjects with healthy gingivae or mild gingivitis
  • - NR (20 to 25)
  • - 42M
  • - Maxillary and mandibular non-molar teeth
  • - None
 GT: ultrasonic device; KTW: periodontal probe; PD, GR: clinical examination
  1. At a site-level analysis, GT was significantly associated with PD (P <0.0001), GR (P = 0.034), KTW (P <0.0001) and tooth type (P <0.0001)
  2. At a subject-level analysis, GT was significantly associated with PD (P = 0.018), KTW (P <0.0001) and tooth type (P <0.0001).
 GT is significantly associated with PD, GR, KTW, and tooth type.
Lee et al., 201836 1. To determine the facial gingival profiles (GT and KTW) of periodontally healthy sites in an Asian population. Cross-sectional
  • - 51 Chinese subjects with healthy normal or reduced periodontium
  • - 30.3 (NR)
  • - 24M/27F
  • - Maxillary and mandibular incisors to the first molars
  • - None
 GT: transgingival probing (endodontic file with a rubber stop); GB: probe visibility; KTW: periodontal probe
  1. Sites with recession had significantly thinner GT (1.28 ± 0.54 mm) compared with sites with no recessions (1.40 ± 0.52 mm) (P = 0.01).
  2. Sites with recessions had significantly narrower KTW (3.83 ± 1.13 mm) compared with sites with no recession (4.72 ± 1.33 mm) (P <0.0001).
 Sites with no recession displayed significantly greater KTW and GT compared with sites with recession.
Liu et al., 201750 1. To assess the gingival biotype in subjects with and without a history of periodontal disease in a Chinese population. Cross-sectional
  • - 50 Chinese subjects
  • - 23.5 (NR) for subjects with healthy periodontium and 46.4 (NR) for subjects with treated chronic periodontitis
  • - 24M/26F
  • - Maxillary CIs and LIs
  • - None; groups:
    1. Subjects with healthy periodontium (n = 30)
    2. Subjects with treated chronic periodontitis (n = 20)
 GT: transgingival probing (customized digital caliper); GR: standardized digital photographs; CW/CL: clinically using periodontal probe
  1. Mean GT in periodontally healthy subjects was 1.05 ± 0.31 mm, and it was 0.89 ± 0.29 mm in periodontitis patients.
  2. Patients with treated periodontitis had significantly thinner GT compared with healthy patients (P <0.05).
  3. Sites with thin gingiva (GT < 1 mm) had significantly greater GR compared with sites with thick gingiva (GT > 1 mm) in subjects with treated periodontitis (P <0.05).
  4. There was a significant correlation between the GT and GR (P = 0.032) in subjects with treated periodontitis.
 GT in subjects with treated periodontitis is significantly correlated with GR.
Maroso et al., 201549 1. To assess the relationship between GT and GR in subjects without history of periodontitis. Cross-sectional
  • - 55 subjects without history of periodontitis
  • - 24.82 (18 to 35)
  • - 24M/31F
  • - Maxillary and mandibular anterior teeth
  • - None
 GT: transgingival probing (a needle with a rubber stent and a digital caliper); BOP, CAL, GBI, GR, PD, PI: clinical examination
  1. Mean GT was 1.40 mm with a range of 1 to 1.97 mm.
  2. A statistically significant negative correlation was found between GT and GR (P = 0.02). The smaller the GT, the greater the GR.
 GT is negatively associated with GR in young adults with low degrees of gingival inflammation.
Müller et al., 200027 1. To study thickness of masticatory mucosa and KTW in individuals with different periodontal phenotypes. Cross-sectional
  • - 40 Periodontally healthy subjects
  • - NR; (19 to 30 years)
  • - -19M/21F
  • - Maxillary anterior teeth
  • - None
 GT: ultrasonic device; KTW: periodontal probe; PD, CAL, GR: clinical examination
  1. The mean PD was significantly greater in subjects with thick and wide gingiva and quadratic shape of teeth (2.00 ± 0.15 mm) compared with the subjects with thin and narrow gingiva with slender shape teeth (1.69 ± 0.26 mm) (P <0.01).
  2. Subjects with thin and narrow gingiva tended to have more GR and higher bleeding/plaque ratio, but these differences were not statistically significant.
 Subjects with thick and wide gingiva as well as quadratic shape of teeth had significantly greater PDs compared with those with thin and narrow gingiva with slender shape teeth.
Shah et al., 201531 1. To evaluate the GT and its relationship to sex, presence of GR and the KTW in a subset of the Indian population. Cross-sectional
  • - 400 Indian subjects
  • - 28.82 (20 to 35 years)
  • - 200M/200F
  • - Maxillary anterior teeth
  • - None
 GT: transgingival probing (endodontic file with a rubber stop); GB: Thin for <1 mm GT and thick for >1 mm GT; KTW: periodontal probe; PD: periodontal probe
  1. 66 Patients presented with GR. Among those, 32 subjects had thick GB and 34 had thin GB.
  2. For subjects presenting with GR, the mean GT was 1.12 mm for CIs, 1.00 mm for LIs, and 0.79 mm for Cs.
  3. No significant difference was observed between the overall GT and GT of subjects with gingival recession.
 This observational study did not find any correlation between GT and the presence of GR
  • BOP = bleeding on probing; C = canine; CAL = clinical attachment level; CBCT = cone-beam computed tomography; CEJ = cemento-enamel junction; CI = central incisor; CL = crown length; CW = crown width; F = female; GB = gingival biotype; GBI = gingival bleeding index; GI = gingival index; GR = gingival recession; GT = gingival thickness; KTW = keratinized tissue width; LI = lateral incisor; Lis = lateral incisors; M = male; NR = not reported; PI = plaque index; PD = probing depth.

3.2.1 Association between GT and PD, BOP, and biofilm

Four studies investigated the role of gingival phenotype on periodontal health by assessing periodontal parameters such as PD, BOP, and plaque index at sites with thin versus thick gingival phenotype.25, 46-48 Three studies had a cross-sectional design,25, 47, 48 and only one study had a prospective cohort design.46

Two studies assessed the relationship of GT and BOP in subjects with healthy or mild gingivitis47 and in subjects with mild to moderate gingivitis.48 According to Müller and Heinecke,47 reporting the results of a cross-sectional study of 40 systemically healthy young adults (19 to 30 years) with healthy or mild gingivitis, sites with thin gingiva and insufficient KTW are not more likely to bleed after probing than sites with thicker tissue. No association was found between GT and KTW on BOP. Nevertheless, a follow-up study by Müller and Könönen48 looked at the facial GT in 33 young female adults (19 to 23 years) with mild to moderate plaque-induced gingivitis and found that sites with thin gingival phenotype had higher tendency to bleed compared with sites with thick gingival phenotype. This data may suggest that the association of GT and BOP depends on the severity of gingivitis.

The relationship between GT and PD were assessed in two studies.25, 48 Olsson et al.,25 in a cross-sectional study, assessed the relationship between the maxillary CI crown forms and the thickness of the gingiva in 108 whites aged 16 to 19 years. The PD was consistently greater in subjects with short-wide form of the CI crowns versus those subjects with a long-narrow form of the CI crowns. In addition, the authors found a positive association between GT and PD at the facial surface in CIs, LIs, and Cs. This association reached a level of significance (P <0.01) for LIs. Similar findings were reported in the study by Müller and Könönen.48 They reported greater periodontal probing depths were associated with thick gingiva and lower plaque index scores were noted at sites with thin gingiva.

Only one study investigated the effect of GT on the outcome of periodontal therapy. Claffey and Shanley46 assessed the relationship of GT and BOP in shallow sites to attachment loss after non-surgical periodontal therapy. Based on the GT, they categorized sites into thin (≤1.5 mm) or thick (≥2.0 mm) GT. Following non-surgical debridement in shallow probing depth sites (≤3.5 mm) initially non-bleeding thin GT sites displayed a mean attachment loss of 0.3 mm, while non-bleeding thick GT sites displayed a less noticeable mean attachment loss. In addition, no reduction in PD was observed for the thin and non-bleeding sites, while all other sites had a reduction in PD compared with the baseline. They authors concluded that the observed attachment loss following non-surgical periodontal therapy was likely the result of changes in healthy sites with shallow PD and thin gingival tissue.

Therefore, the available limited evidence indicates that PD is greater in subjects with thick gingival phenotype.25, 48 It should be noted that this statement is based only two cross-sectional studies. In addition, there is conflicting evidence regarding the association of BOP and thin gingival tissue.

3.2.2 Association between GT and gingival recession

The association between GT and recession were evaluated in seven articles.8, 27, 28, 31, 36, 49, 50 Several studies reported that subjects with thin and narrow gingival width tend to have more recession.8, 27, 36, 49, 50 Maroso et al.49 conducted a cross-sectional study investigating the correlation between GT and GR in healthy adults (aged 18 to 35 years) without a history of periodontitis. The study reported that GT was inversely correlated to gingival recession in this cohort (P = 0.02); the thinner the GT, the greater the recession. Eger et al.8 in a cross-sectional study of 42 healthy males between age 20 to 25 years with healthy gingivae or mild gingivitis used an ultrasonic device to investigate the influence of GT on clinical periodontal parameters. The study reported that GT is significantly correlated with PD, gingival recession, and KTW. Müller et al.27 studied the thickness of masticatory mucosa and gingival width in subjects with different periodontal phenotypes. The study assessed the maxillary anterior teeth of 40 subjects (19 to 30 years) using cluster analysis to define periodontal phenotypes. It was found that subjects with thin and narrow gingiva tended to have more gingival recession and a higher bleeding/plaque ratio, although these differences were not statistically significant.

Similar findings are reported in the Asian population. Lee et al.36 in a study consisting of 51 Chinese subjects, evaluated the facial gingival profile of teeth with a healthy or reduced periodontium. It was reported that sites with recession have thinner GT (1.28 ± 0.54 mm versus 1.40 ± 0 .52 mm) and narrower KTW (3.83 ± 1.13 mm versus 4.72 ± 1.33 mm) compared with sites with no recession. Significantly greater GT and KTW were observed in sites with no recession compared with those with recession. Another study by Liu et al.50 studied GB in Chinese subjects with and without a history of periodontal disease. Thirty periodontally healthy subjects and 20 subjects with treated chronic periodontitis were included in the study. The mean GT in periodontally healthy subjects was 1.05 ± 0.31 mm while the mean GT in periodontitis patients was 0.89 ± 0.29 mm. Patients with treated periodontitis had significantly thinner GT compared with healthy patients (P <0.05). In addition, in subjects treated for chronic periodontitis, sites with thin gingiva had significantly greater recession than sites with thick gingiva (P <0.05). The study concluded that GT, in subjects with treated periodontitis, is significantly correlated with gingival recession.

Two studies reported no association between GT and recession.28, 31 A study by Cook et al.28 was designed to evaluate labial bone plate thickness of maxillary anterior sites with thin versus thick/average periodontal biotypes in 60 healthy subjects. Interestingly, a secondary finding of the study was the lack of a significant association between periodontal biotype classification and GR. However, it should be noted that only 6.1% of all evaluated teeth demonstrated gingival recession, suggesting that the results should be considered with caution. Shah et al.31 examined the anterior maxillary teeth of 400 ethnic Indian subjects between the ages of 20 and 35 years and reported that 66 (16.5%) patients presented with GR, 32 (8%) of which had thick GB and 34 (8.5%) had thin GB. The authors reported no significant difference between the overall GT (n = 400) of those presenting with gingival recession (n = 66) and those not presenting with gingival recession (n = 334).31 It should be noted that power analysis was not performed to calculate the sample size in this study. So it is not clear whether this study had enough power to detect a true difference.

Based on the available evidence, it can be concluded that subjects with thin tissue and narrow gingival width tend to have more gingival recession.8, 27, 36, 49, 50

3.2.3 Summary

A summary of the observations specific to the clinically relevant focused question #2 are:
  • PD was greater in subjects with thick gingival phenotype.25, 48
  • There is disagreement regarding the association of BOP and thin gingival tissue.27, 47, 48
  • Subjects with thin tissue and narrow gingival width tend to have more gingival recession.8, 27, 36, 49, 50

Conclusion: SORT Level B

3.3 Focused question 3

The last of the three clinically relevant focused questions is: Does the conversion of gingivae from a thin to thick gingival phenotype in sites without gingival recession or mucogingival involvement offer clinical value for maintaining periodontal health?

Reviewers were not able to find any relevant articles that met the inclusion criteria for this focused question. Studies focusing on treatment of already existing gingival recession or mucogingival defects were excluded because the goal of this focused question was to assess whether conversion of thin to thick gingival phenotype in sites without gingival recession or mucogingival involvement offered a clinical value for maintaining periodontal health.

Conclusion: SORT Level C

4 DISCUSSION

Resistance to trauma and recession, superior soft tissue handling property compared with thin tissue, promotion of creeping attachment, reduction in clinical inflammation and enhancing predictable surgical outcomes were all positive characteristics of thick gingival tissue quality that have been reported in the literature.52 It is believed that a high volume of extracellular matrix and collagen, as well as increased vascularity, allow for the survival of thick soft tissue.52

For clinically relevant focused question #1, a positive correlation was noted between KTW and GT/GB in maxillary anterior teeth. Asian subjects seemed to have thin gingival phenotype compared with white subjects. For clinically relevant focused question #2, PD was greater in subjects with thick gingival phenotype and subjects with thin and narrow gingiva tend to have more gingival recession. The reviewers were unable to identify any articles related to the outcome question (clinically relevant focused question #3). However, the 2017 World Workshop on mucogingival conditions in the natural dentition provides guidelines for clinicians to answer this question.12 For cases with no gingival recession, two different case scenarios can be considered:

Case a. Thick gingival biotype without gingival recession: Prevention through good oral hygiene technique and close monitoring is recommended.

Case b. Thin gingival biotype without gingival recession: This is a case that may lead to a greater risk for future recession. Clinicians should pay close attention to prevention and careful monitoring. Cases of severe thin gingival biotype can be considered for prophylactic mucogingival surgery, especially before orthodontic treatment, restorative dentistry with intrasulcular margins, or dental implant therapy.

Thus, it is important for the clinician to identity the types of gingival and periodontal phenotype as well as the surgical technique to best enhance the quality of soft tissue and treatment outcomes.

A patients’ gingival and periodontal phenotypes have an important role in the outcomes of non-surgical and surgical periodontal therapies, restorative treatment, implant treatment and orthodontic treatment.11

In those mucogingival surgical procedures using a coronally advanced flap for root coverage, it has been suggested that an initial flap thickness of 0.8 to 1.2 mm is best for achieving complete coverage.53, 54 For example, Baldi et al.53 reported a flap thickness of >0.8 mm was associated with 100% root coverage.53 Huang et al.54 reported that when a coronally advanced flap was used to treat gingival recession, an initial GT of ≥1.2 ± 0.3 mm was associated with complete root coverage. Hwang and Wang52 reported that GT influences the mean gain in root coverage and the incidence of complete root coverage, especially for connective tissue graft-based and guided tissue regeneration-based root coverage procedures. In surgical crown lengthening procedures, Pontoriero and Carnevale55 noticed the coronal regrowth of the soft tissue margin at interproximal and buccal/lingual sites was significantly more pronounced (P <0.001) in patients with a thick tissue biotype as compared with the thin tissue biotype.

The effect of gingival phenotype on periodontal health parameters of restored teeth has also been investigated. Koke et al.56 reported that intracrevicular crown margin placement lead to early gingival recession and attachment loss despite careful supportive therapy. Recession was also more likely to occur at sites with a narrow band of KT. Tao et al.57 conducted a prospective clinical study to assess 5-year outcomes of metal-ceramic crown restorations for maxillary CIs for patients with thin and thick gingival biotypes in a Chinese Population. The failure-free rate of the metal-ceramic crowns for patients with a thin biotype was 78.0%, and for patients with a thick biotype it was 94.0% following these patients up to 65 months of function (P = 0.02). Thus, a patient's gingival biotype had a significant effect on the outcomes of metal-ceramic crown restorations in maxillary CIs.

With respect to dental implants, Kois58 found a greater thickness of peri-implant mucosa in the presence of a thick gingival biotype compared with a thin biotype. Thin gingival tissues tended to be delicate and almost translucent in appearance, contributing to an undesirable visibility of metal copings through the tissue, resulting in a grayish appearance at the gingival margin.59 A thick biotype was significantly associated (P <0.05) with maintaining the presence of the gingival papilla in immediate dental implants restored with a fixed single-crown prosthesis,60 while there was a trend toward more recession in patients with a thin tissue biotype.59 Sites with thin tissue biotype, particularly those in a facial or buccal position, should be regarded as at risk of marginal tissue recession.59, 61 The presence of a thick peri-implant soft tissue also contributes to a more stable crestal bone levels.62-65

The gingival phenotype likely has an important role in voiding periodontal problems during orthodontic treatment.15 Several authors reported that gingival recession may develop during orthodontic therapy when teeth have an inadequate zone of gingiva.66-68 It has been recommended that areas with <2 mm of AG should undergo gingival augmentation before the initiation of orthodontic therapy.69 Anterior teeth are commonly proclined during orthodontic treatment and maxillary anterior teeth tend to have thin tissue, they are at high risk for recession and might require preventive soft tissue grafting before proclination.36

Limitation of currently reviewed studies (see supplementary Appendix 5 in online Journal of Periodontology).

5 CONCLUSIONS

Understanding the role of gingival and periodontal phenotype becomes essential as periodontists work closely with restorative dentists and orthodontists to provide a strong foundation for restorative, dental implant, and orthodontic treatments. The gingival phenotype varies within and between individuals, and the role of ethnicity that has been genetically determined should be investigated in more detail. Available evidence indicates that subjects with thin and narrow gingiva tend to have more recession compared with those with thick and wide gingiva. Currently, there is no evidence to support converting thin to thick gingival phenotype in sites without gingival recession or a mucogingival deformity.

ACKNOWLEDGMENT

The authors report no conflicts of interest related to this study.