Correlation between arch form and facial form: A cross sectional study.

Arch form is a key determinant in teeth position. Teeth selection and placement must be based on the functional and esthetic needs of the patient. Keeping in mind, the biomechanics involved with the prosthesis. The aim of the study was to evaluate the correlation between arch form and facial form. About 40 individuals in the age group of 20-25 years were involved in the study. The arch form and facial form were analyzed statistically to check for any correlation. It was found that, 63.63% of leptoprosophic individuals had squarish arch form while, 54.6% of mesoprosophic faces had ovoid arch form.

Arch form refers to the overall configuration of the dental arch, and this takes into account the symmetry, roundness, elongation and convexity. The size and shape of the dental arches have a considerable effect on diagnosis and treatment planning, space availability, stability of prosthesis and esthetics. Facial form can be classified as leptoprosopic, euryprosopic and mesoprosopic depending on the facial indices.[1] It is common to use facial measurements as a guide for selection of anterior teeth. The selection of maxillary anterior teeth must be in proportion with facial measurements to achieve good esthetics. The aim of this study is to determine the correlation between the facial form and arch form, which could be used as a guide in teeth selection.

Aim

The aim of this study was to determine the correlation between facial form and arch form in dentulous patients.

Materials and Methods

A cross sectional study was conducted in the Department of Prosthodontics, Sree Balaji Dental College and Hospital, Chennai. Forty subjects in the age group of 20–25 years were involved in the study, and their informed consent was obtained. Inclusion criteria were involved presence of the full complement of teeth and subjects in the age group of 20–25 years. Exclusion criteria were the presence of craniofacial syndromes, previous dentoalveolar surgery, orthodontic treatment and dental anomalies.

To determine the facial form, the bizygomatic width was measured using a sliding caliper. The facial length was measured using sliding caliper from Nasion to Gnathion (N-Gn). Facial form was then obtained from the formulae,[2]

Depending on the value, the facial form is divided into three categories (Banister's classification) as euryprosophic, mesoprosophic and leptoprosophic.

To determine the arch form, the distance between the intercanine line to incisal surface of maxillary central incisor was measured. The arch form was divided into three groups as squarish, ovoid and tapering [Figure 1].

Figure 1

Measuring arch dimension

Results

Association of each archform tested with the respective class of occlusion using Pearson Chi-square test. The overall results showed a significant association with P = 0.749 depicting that there is a correlation between various arch forms and the facial form [Table 1 and Figure 2].

Table 1

Percentage of arch form and facial form

Figure 2

Bar graph depicting prevalence of arch form and facial form

Discussion

The pattern of arch form in the overall sample and the individual face types were seen to find any possible associations of the arch forms with the craniofacial pattern. The anterior ratio characterizes the anterior curve of the arch. This part of the arch depends on the length and width of the incisivocanine arch.[3] When the anterior ratio was considered in the whole sample, similar results for both the arches were seen in both the maxillary and mandibular arches.

In the upper arch, the predominant arch form in leptoprosophic faces was squarish arch (63.63%) whereas ovoid arches were predominant in mesoprosophic faces (54.6%).

In prosthetics, arch form plays a major role in teeth selection and arrangement. The recent trend in prosthetic is to replace the teeth by placing implants. Implant position and number are based on the biomechanics, which varies between arches.

In completely edentulous maxilla, the number of implants placed in premailla depends on the arch form and the facial cantilever. Squarish arch form has fewer cantilever forces anteriorly when compared to the tapering arches. Thus, tapering arches require additional implant in the premaxilla to counter act these harmful forces.

This study gives us an idea about the facial form in relation with the arch form and location of the implant with respect to the facial proportion and arch form.