A Clinical Study

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The Shape of the Maxillary Central Incisors and Its Correlation with Maxillary Anterior Papillary Display: A Clinical Study

Ashish S. Nichani, BDS, MDS1 The shape and form of the teeth Arshia Zainab A. Jameel Ahmed, BDS2 have been reported to affect the V. Ranganath, BDS, MDS3 morphology of the periodontium.1 Early pragmatic reports implied that the position of the gingival margin influenced the convexity of the The aim of this study was to define shapes of maxillary central incisors and tooth in the cervical area.2,3 determine their relationship with the visual display of interdental papillae during Ochsenbein and Ross in 1969 smiling. A sample of 100 patients aged 20 to 25 years were recruited. Photographs were the first to describe the types were taken and gingival angle, crown width (CW), crown length (CL), contact of gingival anatomy as flat and high- surface (CS), CW/CL ratio, CS/CL ratio, gingival smile line (GSL), and interdental smile line (ISL) were measured. The data showed an increase in GA leading ly scalloped. They reported that a to an increase in CW and CS/CL ratio. Women showed a higher percentage square tooth was associated with of papillary display compared with men. This study reinforces the proposed a flat gingiva, whereas a tapered hypothesis that the shape of the teeth and papilla affect the periodontium. tooth had a scalloped gingiva, and Int J Periodontics Restorative Dent 2016;36:541–547. doi: 10.11607/prd.2559 that the gingival contour followed the contour of the underlying al- veolar bone.4 The term periodontal biotype was later defined by Seibert and Lindhe, who classified gingiva as either thin-scalloped or thick-flat.5 Tooth shape has been classified time and again into triangular, ovoid, or square forms. Patients with triangular teeth due to their soft tis- sue biotype and high scalloped gingival margin have been known to be more vulnerable to open embrasure spaces leading to formation of black 1 Professor, Department of Periodontology, AECS Maaruti College of Dental Sciences and triangles.1 The width and height of Research Centre, Bangalore, India. 2Postgraduate Student, Department of Periodontology, AECS Maaruti College of Dental anterior teeth help the dentist de- Sciences and Research Centre, Bangalore, India. tect features that are not esthetically 3Professor and Head, Department of Periodontology, AECS Maaruti College of Dental pleasing so that appropriate treat- Sciences and Research Centre, Bangalore, India. ment measures can be provided.6,7

Correspondence to: Dr Ashish S. Nichani, AECS Maaruti College of Dental Sciences and Several components contribute Research Centre, # 108 Hulimavu Tank Band Road, BTM 6th Stage 1st Phase Kammanahalli, to an esthetically pleasing smile, Off Bannerghatta Road, Bangalore 560076, India. such as its ratio with facial outlines, Email: [email protected] tooth shape and color, and the gin- ©2016 by Quintessence Publishing Co Inc. gival contour and exposure.8,9

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© 2016 BY QUINTESSENCE PUBLISHING CO, INC. PRINTING OF THIS DOCUMENT IS RESTRICTED TO PERSONAL USE ONLY. NO PART MAY BE REPRODUCED OR TRANSMITTED IN ANY FORM WITHOUT WRITTEN PERMISSION FROM THE PUBLISHER. 542

The supracoronal tissues in pa- the study. The participants had an to the long axis of the tooth; crown tients with a low smile line might not intact maxillary dentition and were width (CW), measured between the always be visible. The appearance in good physical health. Written in- mesiodistal tooth surfaces at the of the interdental papillae in an api- formed consent was obtained from junction between the cervical and cocoronal location during smiling all participants after they were ad- middle sections of the crown length; is critical as it restores the esthetics vised about the nature of the study and contact surface (CS), measured of the gingival architecture.10,11 The according to a protocol approved by from the most apical portion of the high interdental smile line (HISL) the Ethics Committee of the AECS contact area to the most incisal por- and low interdental smile line (LISL) Maaruti College of Dental Scienc- tion on the mesial surfaces of the form an essential element of smile es and Research Centre (157). The central incisors (Fig 1). The narrow- line analysis. Interdental smile line study was conducted in accordance ness of one-third of the apical por- (ISL) describes the postural position with the Helsinki Declaration of 1975, tion of the crown was calculated as of the clinical crown length of the as revised in 2000. Patients with de- CW/CL ratio. The CS/CL ratio was maxillary anterior teeth to the ver- structive periodontal disease, exces- generated by dividing CS by CL. milion border of the upper lip. The sive restorations, traumatized lips, Three additional photographs presence or absence of interdental pregnancy or lactation, current med- were taken that provided a right papillae during smiling is a critical ication use, history of tooth trauma, frontal, frontal, and left frontal view component in the esthetic rehabili- or orthodontic treatment that affect- of each patient during smiling, which tation of a patient.12 ed the thickness of periodontal tis- aided in performing the smile line Tooth shape is crucial when re- sues were excluded from the study. analysis. A high gingival smile line storative procedures are performed A prestudy power analysis indicated (HGSL) displayed the midfacial tis- in the esthetic zone. Esthetics encir- a minimum sample size of 10 to yield sues of all maxillary anterior teeth cles all facets of dentistry, and smile a power of 85% with an α of 5%. upon smiling, whereas a low gingival is considered an effective tool for an- A Williams periodontal probe smile line (LGSL) did not. A variant alyzing optimal esthetic outcomes. (Hu-Friedy) was placed parallel to the of GSL called Cupid’s bow gingival An attempt was made in this study occlusal plane, and photographs were smile line (CB-GSL) did not display to define the shape of the maxillary taken with and without the probe with the midfacial gingiva of the maxil- central incisors into three groups a digital camera (HX300, Sony). lary central incisors but revealed the (triangular, square, and square/ta- midfacial gingival tissues distal to it pered) and to determine the visual (Fig 2). A HISL revealed the interden- display of interdental papillae during Clinical measurements tal papillae of the maxillary anterior smiling in an Indian population. teeth upon smiling, whereas a LISL Computer software (ImageJ, Nation- did not (Fig 3). A Cupid’s bow in- al Institutes of Health) that processes terdental smile line (CB-ISL) did not Materials and methods digital images was used to measure display the interdental papillae of the the assessments. The measurements maxillary central incisors but revealed Subjects assessed included gingival angle interdental papillae distal to it. (GA), which was measured as the A sample of 100 patients (50 men angle that formed between the lines and 50 women) aged 20 to 25 years meeting at the facial gingival margin Data analysis visiting the Outpatient Department from the mesial and distal aspects of of Periodontology at the AECS contact area; crown length (CL), mea- Descriptive statistics was performed Maaruti College of Dental Sciences sured between the most apical por- to statistically demonstrate the cor- and Research Centre, Bangalore, tion of the facial gingival margin and relation between different measure- India, were randomly recruited for the incisal edge of the crown parallel ments regarding the shapes of the

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a b

c d Fig 1 Measurement of (a) gingival angle, (b) crown length, (c) crown width, and (d) contact surface.

Fig 2 (a) High gingival smile line. (b) Low gingival smile line. (c) Cupid’s bow gingival smile line. a

b c

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a b Fig 3 (a) High interdental smile line. (b) Low interdental smile line.

a b c Fig 4 (a) Triangular central incisors. (b) Square-tapered central incisors. (c) Square central incisors.

maxillary central incisors. Pearson additional analysis was done where Pearson correlation revealed a sta- correlation analysis was performed the subjects were grouped in clus- tistically significant correlation be- to assess the correlation between ters using k-means algorithm. The tween the three different groups of different groups of measurements. Euclidean distances of three uniform measurements (Table 1, P < .001). A PowerPoint (Microsoft) presenta- parameters (GA, CW/CL ratio, and ANOVA revealed a statistically sig- tion was made in which the pho- CS/CL ratio) were used, and ANOVA nificant correlation between the tographs of the participants were was applied to search for differenc- three different groups of measure- randomly placed and evaluated es among clusters. ments (Table 2). An increase in by the faculty of periodontal and CS association among the three prosthodontic courses. For each clusters was also seen (Table 3). photograph, the evaluators prompt- Results The subjects were divided into ly categorized the shape of the cen- three groups (triangular, square- tral incisors into one of three groups The data analysis revealed that tapered, square). Results showed (triangular, square-tapered, or increase in GA was directly pro- statistically significant P( < .001) cor- square) (Fig 4). Analysis of variance portional to CS/CL ratio and CW. relations between different mea- (ANOVA) was applied to search for It also implied that if the CW in- surements regarding the shapes of differences among the groups. An creased it yielded a greater CS. the maxillary central incisors.

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Analysis of the papillary display during smiling Table 1 Means and standard deviations for descriptive statistics Variable Subjects (n) Mean SD Confidence interval P Sex variability revealed that females CW/CL ratio 100 0.73 0.08 ± 0.02 < .001* showed a higher percentage of GA (degrees) 100 84.52 9.17 ± 1.8 < .001* HGSL compared to males (69% vs CS/CL ratio 100 0.53 0.06 ± 0.01 < .001* 30%). In the study group as a whole, *Statistically significant. 24% had a HGSL whereas 62% were found to have a LGSL and 14% of the subjects displayed CB-GSL Table 2 CS/CL ratio for different tooth shapes (Fig 5). A HISL was seen in 81% of Subjects Minimum Maximum Mean SD the participants, compared with 19% Group (n) (%) (%) (%) (%) P showing a LISL. The results showed Triangular 14 36 46 42.47 3.8 < .001* that 62% of all patients classified as Square- 51 47 55.2 51.61 2.62 < .001* LGSL were found to have HISL, in tapered which all maxillary interdental papillae Square 35 55.6 70.6 60.22 4.4 < .001* are revealed when smiling (Table 4). *Statistically significant.

Discussion Table 3 Cluster analysis CW/CL ratio GA CS/CL ratio The importance of tooth form/shape Clusters (%) (degrees) (%) has been published in several esthet- Cluster A, triangular (n = 14) 59.5 65.58 47 ic guidelines. Olsson and Lindhe13 Cluster B, square/tapered (n = 51) 67.3 74.15 50.4 and Olson et al14 studied the rela- Cluster C, square (n = 35) 78.7 87.57 55.3 tionship between tooth dimensions CW = crown width; CL = crown length; GA = gingival angle; CS = contact surface. and biotype and showed that more recession of the facial margins was seen in long tapered maxillary cen- sexes, whereas triangular maxillary Patients with a high smile line or vis- tral incisors than in short wide teeth. central incisors were least common. ible cervical margins are esthetically The fundamentals of proportionality The maxillary central incisors dominated by the contact points of in humans are mostly expressed in in the present study were classified the maxillary teeth, which represent the teeth, and there has been a trend as triangular, square-tapered, or the pink esthetics.18–20 to reestablish the geometric rela- square according to the relationship Stappert et al determined the tionships in the teeth while restoring between the CL and lengths of the percentage of proximal contact them.15,16 Olsson et al14 indicated that CS. The results showed that to cat- area proportion (PCAP) of maxillary a tapered maxillary central incisor egorize a maxillary central incisor as anterior teeth and concluded that when compared to a wide central triangular, the CS/CL ratio had to be the mean PCAP between central incisor displayed a scalloped gingival < 47%. A ratio of 47% to 55.3% de- incisors, central and lateral incisors, margin, thin free gingiva, a narrow fined the tooth as square-tapered, lateral incisors and canines, and ca- zone of keratinized gingiva, and a and a ratio > 55.3% categorized the nines and premolars were 41%, 32%, shallow probing depth. The results of tooth as square (Table 3). To achieve 20%, and 18%, respectively. He a study done by Wolfart et al17 dem- optimal esthetics, an understanding stressed the importance of PCAP, as onstrated that oval maxillary central of tooth shapes is of prime impor- it determines the papillary and inci- incisors were commonly seen in both tance prior to periodontal surgery. sal embrasures.21

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a HISL, revealing the interdental 90 papilla for patients with high, aver- Variable age, or low smile lines as defined 80 Low by Tjan et al. An average smile ac-

70 High cording to Tjan et al revealed 75% to 100% of the maxillary anterior teeth 60 and the interproximal gingiva only.23 This was seen in 81% of subjects 50 in the present study. Therefore, an 40 important factor affecting a smile Patients (%) includes the display of interdental 30 papilla, which in turn affects esthet- 20 ics. Results of the present study also showed a decrease in the papillary 10 display as the CS increased.

0 GSL ISL Conclusions Fig 5 Analysis of papillary display. GSL = gingival smile line; ISL = interdental smile line. The shape of the maxillary central incisor cannot be isolated when planning esthetic treatments. Char- Table 4 Correlation between the shape of the teeth and acteristics such as tooth shape and GSL and ISL gingival biotype must be taken into Triangular Square-tapered Square Total consideration for a better esthetic GSL result. Hence, understanding the Variant 3 (18.7%) 8 (14.5%) 3 (10.3%) 14 (14%) shape of the maxillary incisors and Low 9 (56.2%) 35 (63.6%) 18 (62%) 62 (62%) how it affects the visual display of High 4 (25.1%) 12 (21.8%) 8 (27.5%) 24 (24%) the interdental papilla and is a piv- otal esthetic element of a patient’s ISL smile allows the dentist to set opti- Low 0 (0%) 12 (21.8%) 7 (24.1%) 19 (19%) mum treatment goals in the esthet- High 16 (100%) 43 (78.1%) 22 (75.8%) 81 (81%) ic-restorative management of the GSL = gingival smile line; ISL = interdental smile line. patient.

The presence or absence of in- 5 mm, there was 100% papilla fill; a terdental papilla has always been distance of 6 mm resulted in a pa- Acknowledgments a concern of periodontists, restor- pilla fill of 56%; and a distance > 7 ative dentists, and patients. In their mm resulted in 27% papilla fill. This The authors would like to acknowledge Dr classic study, Tarnow et al showed suggested that the apical contact Rajani, Dr Rajesh, Dr Manoranjan, Dr Ra- the importance of underlying of the proximal contact area corre- chana, Dr Vinod, and Dr Bindushree of the Department of Periodontology at AECS crestal bone for an adequate pa- sponded with the peak of the inter- Maaruti College of Dental Sciences and Re- 22 pilla fill. Their results showed that dental papilla. search Centre for their support and words of when the distance between con- In the present study, the major- encouragement. The authors reported no tact point and crestal bone was ≤ ity of subjects evaluated displayed conflicts of interest related to this study.

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