Analysis of the gingival biotype based on the measurement of the dentopapillary complex.

BACKGROUND: The gingival morphology of the maxillary anterior region plays an important role in determining the final esthetic outcome. Knowledge of the periodontal biotype is of fundamental importance because the anatomical characteristics of the periodontium, such as gingival thickness, gingival width and alveolar bone morphology, will determine periodontium behavior when submitted to physical, chemical, or bacterial injury or during periodontal or implant surgical procedures and orthodontic treatment.
MATERIALS AND METHODS: 50 subjects with healthy periodontal tissues with no loss of attachment and (b) presence of all anterior teeth in both upper and lower jaw were selected. On clinical examination gingival thickness was recorded based on the transparency of periodontal probe. Following parameters are recorded from dental cast, i.e., crown length, crown width, papillary length (PL) and papillary width.
RESULTS: There was highly significant correlation between gingival biotype and crown length and area of papilla with P value -0.002 and 0.013 respectively. Significant correlation was found between area of crown and PL with P value -0.013 and 0.016. The results of discriminant function analysis showed that average crown length was the best single determinant of biotype and area of papilla was the next best choice.
CONCLUSION: Within the limits of the current investigation, the existence and correlation of different gingival biotypes and dentopapillary complex dimension has been confirmed. These findings can be utilized as objective guidelines for determining the biotype and response of gingiva to many dental operative procedures.

INTRODUCTION

Knowledge of the periodontal biotype or phenotype is of fundamental importance to an oral clinician because the anatomical characteristics of the periodontium, such as gingival thickness, gingival width and alveolar bone morphology, will determine the behavior of periodontium when submitted to physical, chemical, or bacterial insult or during therapeutic procedures viz periodontal surgeries,[1] implant,[23] orthodontic treatment.[4] A direct correlation exists between gingival biotype and susceptibility to gingival recession following surgical and restorative procedures. Specifically, it was pointed out how thick and thin gingival biotypes respond differently to inflammation, restorative trauma and parafunctional habits. These traumatic events result in various types of periodontal defects, which respond variably to different treatments. Therefore, an accurate diagnosis of gingival tissue biotype is of the utmost importance in devising an appropriate treatment plan and achieving a predictable esthetic outcome.

There is a considerable intra and inter-individual variation in both width and thickness of the facial gingiva, giving rise to the assumption that different gingival phenotypes might exist in any adult population. The bulky slightly scalloped marginal gingiva with short and wide teeth[5] on one hand and thin highly scalloped marginal gingiva with slender teeth on the other may serve to illustrate the existence of markedly different periodontal entities or so-called “gingival biotype.” The term “gingival or periodontal phenotype” was coined by Muller.[6] Gingival biotype is known to be dependent upon many factors such as age, gender, growth, tooth shape, tooth position, tooth size and genetically determined factors.

The characteristics of gingival thickness, gingival width and subjacent alveolar bone thickness have been used as a base for the classification of periodontal biotypes. However, for some authors, use of the term periodontal phenotype more correct to describe features of the periodontium, which are influenced by both genetic[7] and environmental factors. In these studies, gingival thickness, gingival width and the shape of the dental crown are taken to relate to define the classification of periodontal phenotype.

Gingival biotype refers to a composite or aggregate of four features of the soft tissues and the teeth they surround that build up to a specific picture by Sammut.[8] These are:

The gingival width (keratinised tissue width): Which refers to the width of the keratinised tissue when measured from the gingival margin to the mucogingival junction

Gingival thickness (thick or thin): The thickness of the tissue in a bucco-palatal dimension. If you insert a probe into the midbuccal sulcus of the maxillary central incisor and you can see it through the tissue then it is thin by this definition. If you can’t see it, it is thick

Papilla height (PH)/proportion: The part of the gum that fits in between teeth

Crown width/height ratio: Long, slender teeth tend to be associated with contact points distant from the alveolar crest and long papillae that fill the embrasures.

Over past few years, several studies have tried to sought a better understanding of anatomical characteristics of periodontium with the purpose of defining the periodontal biotype of each individual. As such there have been no defined objective criteria for identifying gingival biotype.[9] So the cross sectional analysis of variants had been planned to get insight into the association/relation between gingival biotype and the dentopapillary complex if any significant determinants can be objectively defined to classify the biotype.

MATERIALS AND METHODS

50 subjects with healthy periodontal tissues with no loss of attachment and (b) presence of all anterior teeth in both upper and lower jaw were selected from those visiting the outpatient Department of Periodontology and Oral Implantology, National Dental College and Hospital, Derabassi.

Subjects with crown restorations or fillings involving the incisal edge on anterior maxillary teeth, pregnant and lactating females, subjects taking medications with any known effect on the periodontal soft tissues, volunteers with clinical signs of periodontal disease defined as having pockets >3 mm were excluded from the study.

The study protocol was duly reviewed and approved from the institutional ethical committee.

All the eligible subjects were explained about the study and a written informed consent was obtained.

Selected subjects were greeted and seated for the appointment on the dental chair in a comfortable position. Alginate impressions of selected study participants were made and poured with dental stone.

Gingival thickness on maxillary anterior teeth was clinically recorded and was categorized into thick or thin on a site based level. This evaluation was based on the transparency of the periodontal probe through the gingival margin while probing the sulcus at the mid-facial aspect of both central maxillary incisors. If the outline of the underlying periodontal probe could be seen through the gingiva, it was categorized as thin and if not, it was categorized as thick [Figures 1 and 2]

Figure 1

Thin gingival biotype

Figure 2

Thick gingival biotype

Dental casts were obtained which is the positive replica of the whole mouth. Following parameters were recorded from the dental cast

Crown length (CL)[9] was measured between the incisal edge of the crown and the free gingival margin, or if discernible, the cemento-enamel junction

Crown width (CW)[9] i.e., the distance between the approximal tooth surfaces, was recorded at the border between the middle and the cervical portion

Papillary height (PH)[9] was assessed to the nearest 0.5 mm using the same periodontal probe at the mesial and distal aspect of both central incisors. This parameter was defined as the distance from the top of the papilla to a line connecting the mid-facial soft tissue margin of the two adjacent teeth. The mean value will calculated for the three papilla

Papillary width (PW) was calculated at the base of papilla between two approximated tooth surfaces

From canine to canine, the area of the facial papilla (AP), the facial surface area of the anterior tooth (AT), the proportion of the dento-papillary complex (AP/AT).

Data so collected was put to statistical analysis via SPSS software. Statistical analysis: Intra-examiner repeatability of the clinician who performed all clinical examinations was analysed. For total continuous variables, intra-examiner repeatability was evaluated using Pearson's correlation coefficient. Mean values and standard deviations were calculated per subject for all continuous variables. Significant disparities were assessed using the independent-samples t-test.

RESULTS

The study population consisted of 50 periodontally healthy subjects with a mean age of 35 years. Results showed that the crown length ranged from 7.9 mm to 12 mm for thin biotype and for 6 mm to 10.5 mm for thick biotype [Figure 3]. The crown width ranged from 6 mm to 11.5 for thin biotype and 6 mm to 9.5 for thick biotype [Figure 4]. The papillary length (PL) ranged from 3.3 mm to 6 mm for thin biotype and is 3 mm to 6 mm for thick biotype [Figure 5]. The Papillary width (PW) ranged from 4.3 mm to 7 mm for thin biotype and 3.5-6.3 mm for thick biotype [Figure 6]. Area of papilla ranged from 13.2 mm to 36 mm sq and for thick biotype is 12-30 mm sq [Figure 7]. Area of crown ranged from 55.2 mm to 95.6 mm sq for thin biotype and 42-96 mm sq for thick biotype [Figure 8]. Area of papilla/area of crown ranged from 0.02 to 0.48 for thin biotype and for thick biotype is 0.022-6.44 [Figure 9].

Figure 3

Mean crown length for thick and thin gingival biotype

Figure 4

Mean crown width for thick and thin gingival biotype

Figure 5

Mean papillary length for thick and thin gingival biotype

Figure 6

Mean papillary width for thick and thin gingival biotype

Figure 7

Mean area of papilla for thick and thin gingival biotype

Figure 8

Mean area of the crown for thick and thin gingival biotype

Figure 9

The ratio between area of papilla/area of the crown for thick and thin gingival biotype

DISCUSSION

In recent years, the dimensions of different parts of the masticatory mucosa, especially gingival thickness, has become the subject of considerable interest in periodontics from both an epidemiologic and a therapeutic point of view.[10] Since studies have concluded that the thickness of the gingiva plays a vital role in development of mucogingival problems and in the success of treatment for recession and wound healing, assessment of gingival thickness is relevant to clinical periodontics.

Clinical appearance of normal gingival tissue reflects the underlying structure of the epithelium and lamina propria. It has been long known that clinical appearance of healthy marginal periodontium differs from subject to subject and even among different tooth types. Many features are directly genetically determined, others seem to be influenced by tooth size, shape and position and biological phenomena such as growth or ageing. The particular shape, topographical distribution and width of the gingiva are clearly functions of the presence and position of erupted teeth. Moreover, tooth shape itself seems to have an important impact on the clinical features of the surrounding gingiva and probably also the underlying tooth supporting periodontal tissues.

The thickness of masticatory mucosa is evaluated by the invasive methods[611] and non-invasive methods.[12] Invasive methods include using injection needle, probe, or cephalometric radiograph and non-invasive methods such as ultrasonic devices. Although the ultrasonographic method of assess in gingival thickness is non-invasive, drawbacks included the relative unavailability of the instrument, difficulty in maintaining the directionality of the transducer and non-reliable results when the thickness of gingiva exceeds 2-2.5 mm. Hence, to overcome these problems, De Rouck et al. (2009)[3] introduced a method to check for the gingival thickness based on the transparancy of the periodontal probe through the gingival margin while probing the sulcus at the midfacial aspect of incisors. If the outline of the underlying periodontal probe could be seen through the gingival margin, it was categorized as thin if not, it was categorized as thick. This method was employed in the study as it was relatively easy and non-invasive. Maxillary incisors were selected as reference teeth because differences between biotypes are most explicit for these teeth and because their specific features are easily found in other parts of the dentition.[1314]

The results of the present study showed that the mean value of crown length for thin biotype is 9.706 mm and for thick biotype is 8.478 mm. The mean value of crown width for thin biotype is 7.844 mm and for thick biotype is 7.87 mm. The mean PL for thin biotype is 5.13 mm and for thick is 4.44 mm. The mean papillary width for thin biotype is 4.921 mm and for thick biotype is 4.622 mm. The mean area of papilla for thin biotype is 25.1004 mm sq and for thick biotype is 24.500 mm sq. The mean area of the crown for thin biotype is 76.327 mm sq and for thick biotype is 66.541 mm sq. The mean value of the area of papilla/area of the crown for thin biotype is 0.3280 and for thick biotype is 0.5382 [Table 1]. There was highly significant correlation between gingival biotype and crown length and area of papilla with P value −0.002 and 0.013 respectively. Significant correlation was found between area of crown and PL with P value −0.013 and 0.016. The results of discriminant function analysis showed that average crown length was the best single determinant of biotype and area of papilla was the next best choice. The cut-off value of average crown length was calculated to be 8.62 [Table 2].

Table 1

Comparative analysis of mean values of all the parameters in both study groups

Table 2

Correlations between variables using Pearson's correlation analysis

Similar findings have been reported earlier by Anand et al.[6] who correlated the prevelance of thick and thin biotype with gender and tooth morphology. Results showed that Cluster A displayed slender tooth form crown width/crown length (CW/CL 0.77), gingival width and (GW) 4.80 mm, papillary height (PH) 4.52 mm and a thin gingiva. Cluster B presented similar features CW/CL 0.79, GW 4.50 mm and PH 4.29 mm with no statistical significant differences from Cluster A. Cluster B showed clear thick gingiva. Cluster C differed from the other Clusters in many parameters. Subjects showed a more quadratic tooth form (CW/CL 0.88), a broad zone of keratinized tissue (GW 5.42 mm) low papillae (PH 2.84 mm) and thick gingival.

Another study by Lee,[9] suggested clinical guidelines for discriminating the thin biotype, which might be susceptible to gingival recession and found that the results of discriminant function analysis showed that AP Sum 5 (area of facial papilla) was the best single determinant of biotype and PL Sum 5 (PL) was the second best choice in the study population next best choice. The cut-off value of PL Sum 5 was calculated to be 23.73 mm.

Considering the growing attention paid to anterior esthetics by both patients and clinicians, such findings can help enhance the knowledge of the morphologic and anatomic form of the gingiva, which can be utilized as a guide to achieve optimal soft-tissue esthetics. A thorough understanding of the biotype form of the gingival tissue is mandatory, for a clinician so as to predict the tissue response to various pathologies as well as before treatment planning, to optimize the final outcome of the periodontal therapy.

Within the limits of the current investigation, the existence and correlation of different gingival biotypes and dentopapillary complex dimension has been confirmed. The results of discriminant function analysis showed that average crown length was the best single determinant of biotype and area of papilla was the next best choice. The result of the present study showed that there was highly significant correlation between gingival biotype and crown length and area of papilla. These findings can be utilized as objective guidelines for determining the biotype and response of gingiva to many dental operative procedures. But further long-term studies should be carried on with large sample size to ascertain these findings.