ORIGINAL ARTICLE Year : 2018  Volume : 8  Issue : 2  Page : 6267 Evaluation of maxillary anterior teeth and their relation to the various geometric proportions in Indian population sample Ajay Mootha, Snehal Jaiswal Department of Prosthodontics, M.A. Rangoonwala College Dental Sciences and Research Centre, Pune, Maharashtra, India Correspondence Address: Purpose: The position and size of the anterior teeth have direct influence on clinical appearance of the smile. The anterior teeth rarely follow all the mathematic rules of a proportionate smile. To determine maxillary anterior teeth proportions in Indian Population, their correlation with existing mathematical parameters and their reliability should be evaluated. Materials and Methods: A total of 350 participants were evaluated for healthy maxillary anterior teeth. Based on the inclusion/exclusion criteria, 230 were included in the study. Five photographs of the anterior maxillary area with three different angles were performed under standardized conditions. Images were analyzed and the data were collected. Results: The observed values of width and height were closely related to Proportion Gauge. Width proportions between two adjacent teeth and the observed tooth proportions are in concordance with the values given by Digital Smile Design (DSD^{®}). Variables defined were analyzed in Minitab software using descriptive statistics and inferential tests (ttest with 95% confidence interval). Conclusions: The Proportion Gauge and DSD^{®} Protocol can be used for rehabilitation of maxillary anterior teeth in the studied population.
Clinical Relevance to Interdisciplinary Dentistry The anterior teeth proportions evaluation will help to benchmark which proportion ratio can be utilized to give best esthetics in esthetic rehabilitation casesThe teeth proportion to be followed will guide the crown lengthening procedures and gingival tissue management as and when requiredThe results help in understanding the concept of the importance of analyzing smile in motion rather than just static mathematical ratios. Introduction The ideal dimensions of teeth vary from person to person. For many years, the primary objective of the dental professionals has been restoration of health, function, and form of the teeth. With the advent of newer materials and technology, it has become imperative to provide esthetic results in harmony with the natural oral structures. The selfperception of smile, the smile line along with the other aspect such as the size of teeth, visibility of teeth, and upper lip position are the critical factors related to smile attractiveness and they also have an influence on personality traits. Color of teeth and gingival display are also important. In addition, the position and size of the anterior teeth also have a direct influence on the clinical appearance of the smile. Diversity that exists in nature and the final result rarely follows all the mathematic rules of a proportionate smile. Several authors have presented guidelines regarding the anterior tooth proportions to achieve excellent esthetics. The study has been conducted to understand the tooth proportions seen in the six healthy anterior maxillary teeth of the general population and their relation with the existing mathematical proportions given by several authors. Lombardi, in 1973 was the first to propose that dental and facial esthetics can be optimized if central incisor to lateral incisor width and lateral incisor to canine width are repeated in a constant proportion when the patient is viewed from the front.[1] This proportion was called Golden Proportion and is approximately 1.618–1. In 1978, Levin advocated that the visible width of maxillary lateral incisor is 62% of central incisor and the visible width of canine is 62% of lateral incisor [Figure 1] when viewed in frontal plane.[2],[3]{Figure 1} Preston, in 1993 concluded that only 17% of the lateral incisors were in Golden Proportion with the central incisors and also observed that canines did not follow the Golden Proportion rule. He suggested that the optimal proportion between lateral and central incisors should be 66% instead of 62% and proportion between the width of the lateral incisor and canine should be 84% [Figure 2] when viewed frontal plane.[4]{Figure 2} Further, in 1999, Snow gave another mathematical theory suggesting that the when viewed from the frontal perspective, each canine should occupy 10% of the total intercanine distance followed by lateral incisor occupying 15% and central incisor occupying 25% of the total intercanine distance [Figure 3]. This theory was known as Golden Percentage.[5]{Figure 3} The Recurring Esthetic Dental (RED) proportion suggests that the ratio between two adjacent teeth should remain distally constant. It was given by Ward in 2001. But unlike the Golden Proportion, the values of RED proportion should lie in the range of 60% to 80% [Figure 4].[6] The relationship between the relative height of the teeth and the preferred RED proportion has been reported by Rosenstiel, Ward, and Rashid.[7] Studies have shown preference for 75% to 78% widthtoheight ratio of central incisors.{Figure 4} Recently, “Proportion Gauge,” an instrument designed by Stephen J Chu has been a valuable tool to make a visual and objective evaluation of size of the teeth. It is useful in reconstruction of esthetic smile based on the measurement. The instrument has color codes; red for central incisor, blue for lateral incisor, and yellow for canine [Figure 5].[8],[9] The values have been derived from a study conducted by Stephen J Chu, wherein the most of the patients evaluated for tooth proportions showed standard deviation of 0.5 mm from the average values obtained.[10] The width values were 8–9 mm for central incisors, 6–7 mm for lateral incisors, and 7–8 mm for canines. Chu also suggested that the ratio of width and height should not exceed 78%.[8]{Figure 5} The development of the Digital Smile Design (DSD ®) concept started in 2007 and has evolved markedly over the past few years. DSD ® is a multiuse conceptual dental treatment planning tool that is used in interdisciplinary esthetic dentistry to strengthen diagnostic vision, improve communication/education, and enhance predictability throughout the course of the treatment. It involves the creation of facially guided smile frame.[11] DSD ® recommends RED proportion to determine the ideal width of the centrals, laterals, and canines from the frontal perspective and not the Golden Proportion.[12] It says that from a frontal view if the width of central incisor is “A,” then the lateral should be “0.7A” and canine “0.5A” [Figure 6]. They also recommend the ideal central incisor proportion (width/height ratio) to be around 80% and usually work with the limits of 70%–90%.[7],[8]{Figure 6} Materials and Methods The study was performed at the Department of Prosthodontics, M.A. Rangoonwala College of Dental Sciences and Research Centre, Pune. The institutional ethical committee approved the study and informed consent was obtained from the participants. A total of 350 participants were evaluated with an aim to examine anterior maxillary region. Out of the total 350 participants evaluated, 190 were male and 160 female. The participants ranged in the age group of 18–30 years. The inclusion criteria were to include only healthy anterior maxillary teeth and the participants with anterior cavities or restorations, history of or ongoing orthodontic treatment, malalignments, gingival recessions, and periodontal problems were excluded from the study. The institutional ethical committee approved the study and participants were informed of the nature of the study. Due to the inclusion–exclusion criteria, 230 participants who comprised 115 males and 115 females were included for the study. Written informed consent was obtained from each participant. A standardized photographic collection was established with the help of a lip retractor to have a complete view of the anterior maxillary area; a measurement scale was used as reference to calibrate the image processing software; and the lateral cephalogram head support was used to stabilize the head in vertical and horizontal plane [Figure 7] such that the Frankfort's plane was parallel to the ground and participant was always at the same distance (60 cms).[13],[14] The lighting conditions of the room and of the digital camera (Canon 70D, Canon 100 mm IS L macro lens and flash) were always constant.{Figure 7} Five photographs with 3 different angles were performed: 1 frontal [Figure 8], 2 perpendicular to the lateral incisor [Figure 9] and [Figure 10], and 2 perpendicular to the canines under standardized conditions [Figure 11] and [Figure 12]. The images were analyzed by Adobe ® Photoshop ® CC2015. The teeth width and height were measured from the photograph and the relation between them was recorded. To analyze the images, we set the measurement scale by selecting the known length of 10mm marked on the scale, and then with the help of ruler tool, we measure the width and height of each tooth.{Figure 8}{Figure 9}{Figure 10}{Figure 11}{Figure 12} The different geometrical relations and proportions between the six maxillary teeth were measured on the photographs and recorded as per the theories described in the introduction. The variables defined were analyzed in Minitab ® Statistical Software by descriptive statistics and inferential tests (ttest with a 95% confidence interval). Results In this study, the mean values for width ttest (P< 0.05) analysis did not reveal significant differences as compared to mean values for height ttest analysis regarding gender. In [Graph 1], the mean values of observed width proportions (bar A) from the frontal perspective of caninetolateral incisor and central incisor to lateral incisor have been compared to the values suggested by Golden Proportion (bar B), Preston's Proportion (bar C), and DSD ® (bar D). In the [Graph 2], the mean values of widthtoheight proportions (84%–86%) have been compared with the values suggested by DSD ®. The [Graph 3] shows comparison of the observed mean values of width and height and the values given by Proportion Gauge. All the observed values are closely related except for the width of lateral incisor and height of central incisor although the widthtoheight ratio exceeds maximum ratio of 78% followed by Proportion Gauge. The [Chart 1] compares the mean values of observed width proportions and the intercanine distance in the frontal perspective with the values suggested by the Golden Percentage. The observed values are closely related to the values of lateral incisors but poor relation with the central incisor and the canine.[INLINE:1][INLINE:2][INLINE:3][INLINE:4] The observed values of width proportions of caninetolateral incisor and lateral incisor to central incisor as well as the observed widthtoheight proportion values are in concordance with the values given by DSD ®. Discussion A total of 230 participants with healthy maxillary anterior teeth were chosen from 350 participants evaluated for the study. The mean values of the width and height of central incisors, lateral incisors, and canine in males and females show variations, especially with the height being more in males. The differences need to be taken into consideration while esthetic rehabilitation of the patient based on gender. The average widths of 8.49 mm in central incisor, 7.09 mm in lateral incisor, and 7.58 mm in canine are in concordance with Santoro's (8.80 mm, 6.83 mm, and 7.76 mm),[15] Magne's (9.10 mm, 7.07 mm, and 7.90 mm),[16] and Woelfel's (8.6 mm, 6.6 mm, and 7.6 mm) studies.[17] [Graph 3] shows that the mean values of the width and height of the maxillary anterior teeth are found to be consistent with the values suggested by the Proportion Gauge except for height of maxillary central incisor although the observed width to height ratio (84%–86%) exceeds the maximum proportion limit of 78%. The Proportion Gauge values have a standard deviation of 0.5 mm,[10] which gives rise to variations in the final percentage, even when the average values for the height and width are similar to the literature. From [Graph 1], the observed width proportion in frontal perspective of lateraltocentral incisor (70.5%–71.1%) and the caninetolateral incisor (77.2%–77.3%) was found to be closely related to the range given by RED Proportion (60%–80%). DSD ® recommends RED Proportion of 70%, thereby the observed values being in concordance with the values suggested by DSD ®. The observed values are not found to be consistent with the values given by either Golden Proportion or Preston's Proportion. As per [Graph 2], the widthtoheight proportion of the maxillary anterior teeth was found to be 86% for centrals, 85% for laterals, and 84% for canines. DSD ® follows the proportion of 80% for the central incisors and allows a variation within the range of 70%–90%. As shown in [Chart 1], from frontal perspective, the centrals occupy 21.9%–22.4%, the laterals occupy 15.5%–15.9% while the canines occupy 11.9%–12.3% of the total intercanine width. The values observed show poor correlation to the Golden Percentage given by Snow which was 25% for centrals, 15% for laterals, and 10% for canines with slight difference in the centrals and canines. The observed values are closely associated to values seen in studies by Murthy, Ramani (22% for centrals, 15.5% for laterals, and 12.5% for canines), and Agrawal (21.11%–21.50% for central incisors, 15.44%–15.90% for lateral incisors, and 12.91%–13.10% for canines).[18],[19] Conclusions From the studied population: Males have teeth size significantly larger than femalesGolden Proportion, Golden Percentage, and Preston's Proportion cannot be considered as a guide for the rehabilitation of the maxillary anterior teethThe average dimensions obtained for height and width of the maxillary anterior teeth are similar to the values proposed by the Proportion Gauge and can be used as a benchmark for rehabilitation of the maxillary anterior sectorThe width proportion between two adjacent teeth when observed in a frontal perspective is found consistent with RED Proportion and DSD ®The widthtoheight ratio lies in the range suggested by the DSD ®DSD ® concept can be utilized for rehabilitation of the maxillary anterior teeth in the studied population. The results in this study are based on static records, whereas DSD ® utilizes dynamic dentofacial analysis which involves analyzing smile in motion for better smile design and treatment planning. Not only the geometric measurements but also the dynesthetic principles need to be taken into consideration for a rehabilitation procedure. Further studies with larger sample size will give more depth to the knowledge needed for the esthetic rehabilitation procedures. Financial support and sponsorship Nil. Conflicts of interest There are no conflicts of interest. References


