JICDRO is a UGC approved journal (Journal no. 63927)

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Year : 2022  |  Volume : 14  |  Issue : 1  |  Page : 31-36

Graphical evaluation of the geometric tooth form: A gender-based AutoCAD analysis of maxillary central incisor

1 Department of Prosthodontics and Crown and Bridge, Hitkarini Dental College and Hospital, Jabalpur, India
2 Department of Public Health Dentistry, Pacific Dental College and Hospital, Udaipur, Rajasthan, India
3 Faculty of Dental Sciences, Al-Baha University, Al-Baha, Kingdom of Saudi Arabia
4 Department of Prosthodontics Crown and Bridge, Sharad Pawar Dental College, Wardha, Maharashtra, India
5 Department of Conservative Dentristry, Hitkarini Dental College and Hospital, Jabalpur, Madhya Pradesh, India
6 Private Practitioner, Jabalpur, Madhya Pradesh, India

Date of Submission23-Apr-2021
Date of Decision21-Jun-2021
Date of Acceptance03-Jul-2021
Date of Web Publication4-Jul-2022

Correspondence Address:
Dr. Sneha Mantri
8, Gulmohur Duplex, Ivory Towers, South Civil Lines, Jabalpur, Madhya Pradesh
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/jicdro.jicdro_18_21

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Background: No universally accepted parameter exists for selecting/restoring the form of maxillary central incisors (MCIs). Aim: The purpose of this cross-sectional, observational clinical study was to digitally determine the prevalent form of MCIs among males and females of the Central Indian population with AutoCAD software. Materials and Methods: This is a clinical study comprising 200 dental and engineering students (female: 100; male: 100) aged between 18 and 35 years. The pictures of the right (MCI) of each participant were clicked. The images were calibrated in the vertical position to standardize according to the long axis of the tooth. The AutoCAD computer program was used to evaluate the geometric form of the tooth graphically. The results revealed that the tooth form was classified as oval, triangular, or quadrangular. The intergroup comparison using one-way analysis of variance was made, followed by the intragroup comparison using Tukey's test for quantitative data. For comparison between males and females based on tooth form, the data were assessed using Student's t-test as quantitative analysis, and for qualitative assessment, Chi-square test was used. The significance level was set at 0.05. Remeasuring 40 samples from each group tested intraexaminer consistency by applying Bland–Altman and scatter regression analysis. Results: Males had 57% oval, 29% tapered, and 14% quadrangular, while females had 60% oval, 23% tapered, and 14% quadrangular tooth form. Conclusions: The oval tooth form was the most common, both in males and females, followed by the tapered and the quadrangular form. No gender variation was seen in tooth forms.

Keywords: AutoCAD, esthetics, maxillary central incisor, tooth form

How to cite this article:
Mantri S, Asawa K, Bhat N, Godbole S, Mantri S, Bal AS. Graphical evaluation of the geometric tooth form: A gender-based AutoCAD analysis of maxillary central incisor. J Int Clin Dent Res Organ 2022;14:31-6

How to cite this URL:
Mantri S, Asawa K, Bhat N, Godbole S, Mantri S, Bal AS. Graphical evaluation of the geometric tooth form: A gender-based AutoCAD analysis of maxillary central incisor. J Int Clin Dent Res Organ [serial online] 2022 [cited 2022 Aug 7];14:31-6. Available from: https://www.jicdro.org/text.asp?2022/14/1/31/349749

   Introduction Top

Every person is highly unique and entails different anatomical, functional, and esthetic requirements. When a person is smiling, the anterior maxillary teeth are the center of visual attraction. The prominent position of the maxillary central incisors (MCIs) projects an illusion of being the lightest and dominant teeth in the mouth, making them the most influential teeth of the dental composition.[1],[2] The teeth display variations and nuances and exhibit individuality in a given dentition.[3]

Maxillary anterior teeth have functional and esthetic components. While designing/creating a restoration, the form is of significant consideration.[4] The literature reveals that there are three basic tooth forms: square, ovoid, and triangular.[5] The physical form of the tooth is governed by its outline, encompassing the incisal border, proximal ridges, and cervical line. Pincus states “The shape of a tooth is represented by its silhouette, that means by the portion that reflects the light straight forward.”[6] Various facets should be contemplated when observing an ideal smile, such as the symmetric composition of teeth, color and shapes of teeth,[7] gingival topography (flat or scalloped) texture, and color of gingival tissue.[8],[9] Studies have asserted that tooth forms are determined by sex, gender,[10],[11] age of an individual,[11] periodontal phenotype,[12] facial form,[5],[13] and also, the patient's emotions.[10],[14],[15] Proper proportions are significant for making them appear pleasant and in harmony with the face. The size, form, and position should also conform with the facial shape.

The selection of the tooth shape in smile designs or edentulous patients remains a challenge in the restorative procedure,[16] but the patient's satisfaction is the ultimate goal. There are no parameters for selecting tooth shape, and different theories govern the profession, as giving round form from the incisal edges in women and straight lines for men, experiences of the dentist, and the patient's request. With the exponential use of digital photography and technology, customizing smile design has elevated conceptual and technical treatment standards. They provide the best possible options considering esthetics, symmetry, form, the position of teeth, and their relation to the facial features, thus catering to an individual's esthetic and function.[17],[18] However, the desire to apprehend the basics of anatomy, form, and occlusion remains vital. The dentist's perception and knowledge of these fundamental principles can be an enduring learning process. According to the literature, several available methods and techniques for tooth selection are based exclusively on central incisors because of their visibility and the dominant position in the arch. Most of the studies are of a different population with very scarce information related to the Indian population, based on subjective evaluation. When preextraction records for edentulous patients are not procurable, it becomes arduous to select the proper size and shape of the anterior teeth. Thus, the study intends to digitally determine the basic form of MCI between males and females and postulate a guideline for selecting/restoring the central incisors during clinical practice among the Central Indian population. The present study aims to assess the common form of MCI and evaluate if any gender differences exist. The null hypothesis states that no difference exists between genders in terms of MCI tooth forms.

   Materials and Methods Top

A cross-sectional, observational, photographic study was carried out to determine the form of the right MCI among dental college students of Central India. Their backgrounds were verified to confirm they belonged to the same population. Digital images of the incisor were interpreted graphically by AutoCAD (AutoCAD 2014, Auto Desk Inc., San Rafael, California, USA) to classify the right MCI into the following forms: oval, triangular, or quadrangular. The frequency of a particular tooth form was associated with gender. The institutional research committee was permitted to carry the study.

According to the pilot study's findings, the study's power was 80%, the acceptable error was 5%, and the sample size was calculated to be 192. To avoid attrition, we took the round figure of 200 samples, 100 males and 100 females. A total of 367 individuals were screened. Two hundred dentate subjects, 100 males and 100 females, who fulfilled the following inclusion criteria were selected by convenience sampling. Inclusion criteria comprised individuals aged between 18 and 35 years, male or female, no history of trauma or congenital conditions affecting anterior tooth form, no history of orthodontic treatment, an absence of replaced/restored anterior maxillary teeth, healthy periodontium, and the willingness of the individual to participate in the study. Exclusion criteria of pictures comprised images with rotated head position, apparent asymmetry, crowding or overlapping of the anterior tooth, gingival recession/enlargement, images of a lousy resolution, and unwilling to consent to participate in the study.

For each photograph, a consistent distance of 10 cm was used. A tripod stand (BENRO T660EX, China) was used to adjust the height of the camera (Canon 700 D Digital SLR Camera, Canon India Pvt. Ltd.), according to the position of the individual's eyes. A macro lens of 105 mm was used to capture the subject's photographs with a 1:1 flash mode ratio. Patients were directed to sustain their head upright, holding firm, and maxillary occlusal plane analogous to the floor. Intraoral photographs of MCI were obtained holding the lens corresponding to the labial surface of the teeth. Cheek retractors were used to achieve proper visibility of the MCI.

One of the most well-known CAD software is on the market is AutoCAD CAD systems. The templates in the system can be changed, creating tangible prototypes of patterns scanned in CAD software. Digitizing is the procedure of vectorizing shapes so that they can be edited and manipulated on a computer. For high-resolution images from AutoCAD drawings, the plotter was configured accordingly, and these options are saved locally on the computer and are not dependent on any files. These options are saved locally on the PC and are not dependent on any files.

The AutoCAD software analyzed the shape of the right MCI of each patient (version 2014). The image was cropped and centered, adjusting the vertical position according to the long axis of the tooth. The outline of the tooth was traced, and the tooth image was removed, leaving the outline [Figure 1]a and [Figure 1]b. Two vertical tangents were drawn on the mesial and distal sides of MCI. Two horizontal lines were drawn: one on the lower intersection of the mesial tangent and another on the upper intersection of the distal tangent of the tooth contour. Halfway with the previous two lines (line B), a center line was drawn, which denotes the maximum tooth width. A vertical line was drawn from the center of line B upward to the cervical outline divided into five equal parts. A horizontal line A was drawn at the intersection of the first and second parts from the cervical outline [Figure 2]. This line A represented the width of the cervical region. The dental ratio was obtained by dividing the value of line A by the value of line B. Tooth forms were classified according to the numerical values obtained [Figure 3], according to the study by Wolfart et al.,[19] as triangular (≤0.61), oval (>0.61 and <0.70), or quadrangular (≥0.70). The concordance of the clinical observations was calculated using quantitative and qualitative analysis. The data were tabulated and processed with statistical software.
Figure 1: (a) MCI cropped and outline traced, (b) tooth image removed

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Figure 2: M – mesial tangent, D – distal tangent, X and Y horizontal lines intersection at mesial and distal tangents, Line A – horizontal line at the first and second intersections from the cervical outline. Line B denotes maximum tooth width, Z-vertical line upward from the center of line B divided into five equal parts

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Figure 3: calculating the dental ratio by dividing the value of Line A by the value of Line B

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   Results Top

The recorded data were compiled and entered in a spreadsheet computer program (Microsoft Excel 2007) and then exported to the data editor page of SPSS version 20.0 (SPSS Inc., Chicago, Illinois, USA). The data were found to be normal by the Kolmogorov–Smirnov test; hence, parametric tests were applied. The intergroup comparison using one-way analysis of variance (ANOVA) was made, followed by intragroup comparison using Tukey's test for quantitative data (mean values of numerical ratio). For comparison between males and females based on tooth form, data were assessed using Student's t-test as quantitative analysis, and for qualitative assessment, the Chi-square test was used. The significance level was set at 0.05. In the present study, the age of females was as follows: the mean age ± standard deviation (SD) = 21.55 ± 3.49 and for males mean age ± SD = 21.12 ± 4.61, respectively. The overall age was mean age ± SD = 21.33 ± 4.08.

[Figure 4] presents the qualitative analysis of tooth forms between males and females. Out of the total males, 57% had ovoid, which is close to females who had ovoid tooth form (60%). The Chi-square test results were found to be nonsignificant (P = 0.589). [Figure 5] compares different tooth forms, tapered, oval, and quadrangular, between males and females. There was no significance found between males and females for different tooth forms according to the Student's t-test. [Table 1] compares different tooth forms among males and females. One-way ANOVA was applied for intergroup comparison followed by Tukey's test for intragroup comparison. The results indicated that the mean numerical ratio was highly significant (P = 0.001) among all the three-tooth forms, both in males and females. (P = 0.001). Forty teeth from each gender were randomly selected and coded, and the procedure for measurement was repeated. After getting the values, they were decoded and compared to check the intraexaminer consistency of the previous measurements. The scatter plot suggested that measurement 1 showed a high positive correlation (r = 0.800) with measurement two, which could be observed using simple linear regression [Figure 6] and the Bland–Altman plot [Figure 7]. The green line in the Bland–Altman plot shows a 95% confidence interval with upper and lower limits. Moreover, the orange line shows the mean difference between the two measurements.
Figure 4: bar graph showing qualitative analysis tooth form between genders

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Figure 5: bar graph showing mean numerical ratio of tooth form between genders

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Figure 6: scatter plot for correlation between two measurements

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Figure 7: Bland–Altman plot – mean difference between two measurements

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Table 1: Comparison between different tooth forms among males and females

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   Discussion Top

Each tooth accounts for various characteristics that define its individuality. The tooth shape, size, surface characteristics, and optical properties are essential characteristics that substantially contribute to defining the esthetic appearance.[20] Creating esthetic and functional anterior tooth contours requires remarkable skill and knowledge.

Performing a restorative treatment in partially or completely edentulous patients may encounter difficulty in selecting the form of teeth in rehabilitation. There is a consensus in the dental research community that the selection of artificial anterior teeth in oral rehabilitation does not provide a natural appearance, even though some methods are published.[13],[21] Perception related to size, color, age, shape, and gender is grounded on natural preconceptions native to an individual's cultural background. Perception prejudices can be cultural and artistic. The validity of the methods regarding selecting dimensions and shape of the teeth is questionable, and the patients may display an artificial appearance that is not in harmony. Tooth form is the physiognomies of the lines, curves, contours, and angles of multiple teeth that allow their identification and distinction from another tooth. Every geometrically based visual concept creates a natural impulse in the intuition of an observer; in other words, the graphic of tooth form can integrate ideas into practice through the application of geometry. Evaluation by geometric form is an objective form of analysis.[22]

In the present study, no significant difference was found between males and females related to the form of right MCI. Thus, the null hypothesis was accepted. These results agree with those of Wolfart et al.,[19] which established no significant difference between the genders for the similar groups of MCI form; their results revealed the least prevalence of the triangular form. In our study, the quadrangular form was least prevalent. The results of Brunetto et al.[23] diverged and found a significant difference in the form related to gender; however, they found quadrangular form least common, which was similar to the findings of our study. These variations may be due to difference in the population and the regional and cultural background. The oval category was the most prevalent in our study, with 57% in males and 60% in females. A similar prevalence of oval form was observed in studies conducted by Brodbelt et al.,[24] Wolfart et al., and Brunetto et al.[19],[23] A study conducted with the South Indian population also found the oval shape as the most prevalent, and the triangular shape was the least common for both genders,[25] which was analogous to our study. Mahn et al.[26] conducted a study to evaluate the tooth forms and gender correlation prevalence. They found no correlation between tooth forms and gender. Lajnert et al. correlated the shape of maxillary anterior teeth with patient satisfaction related to esthetics. According to them, patients with triangular form were more satisfied with their appearance.[27] Pillai et al. conducted a morphometric analysis of the MCI to determine its crown form. They found a significant difference in the form between male and female samples but not between right and left sides. The oval form was more common in both types.[28]

The mean numerical ratio for intragroup was highly significant (P = 0.001) among all the three-tooth forms, both in males and females [Table 1]. The present research results propose that using the oval tooth form regardless of gender will be in harmony compared to the quadrangular and oval tooth form in the studied population.

From a clinical viewpoint, it is vital for the restorative dentist to know the best possible choices available to select/restore the maxillary incisor, which is the most dominant tooth in the arch for a particular patient. A study among the local population will help propose a guideline for tooth form selection, customized for the specific population, which could be adapted in esthetic rehabilitation. Having a consistently repeatable protocol for the basic framework will save much time. The present study among the Central Indian population accomplishes the advantages mentioned earlier. When creating a framework, it is essential to follow the basic commonalities of teeth and allow room for detail variability. Similar studies in other geographical areas, including a larger population, can be done to confirm the present study results. The limitations of this research were that the authors studied only the basic forms of teeth: tapered, ovoid, and quadrangular. The hybrid forms, which combine basic forms, e.g., tapered-ovoid, quadrangular-ovoid, tapered quadrangular, and many more, were not considered. Further studies can be performed to classify the tooth forms into various anatomical combinations mathematically and provide new ways for clinicians and technicians to give artificial teeth a more dynamic appearance and study the prevalence of hybrid forms on a larger sample.

   Conclusions Top

Comprehensive knowledge regarding the form of the maxillary incisors related to a specific population can be implemented to create a complemented smile, increase the acceptance of treatment, and ultimately succeed in prosthodontic service. Within the limitations of this research, the outcome of the evaluated group of the Central Indian population concluded that the oval tooth form was most common while the square form was least common. There is no correlation or gender-based variances between the tooth form and sex of an individual. Hence, the results of this study do not favor the dentogenic concept. The previous theory related to genders, which recomended that women present more rounded, soft, and delicate teeth (tapering/ovoid), and men should have square teeth is not reconfirmed by the results of this study. The dentist who works with esthetics should not only consider gender when arranging teeth and selecting tooth molds with stereotyped notions but also consider other components, including gingival architecture, organic expressions of the patient's personality, lifestyle, and other features that differentiate one individual from another. Knowledge and understanding of the prevalence of central incisor tooth form will help clinicians predictably plan the restoration of anterior teeth.

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