Lower incisor dentoalveolar compensation and symphysis dimensions in class II and class III patients

Abstract

Aim: The aim was to study and compare lower incisor dentoalveolar compensation and mandibular symphysis morphology of patients with Class II and Class III malocclusion. Materials and Methods: Lower incisor inclination (incisor mandibular plane angle [IMPA]), as well as buccal (LA) and lingual (LP) cortex depth, and mandibular symphysis height (LH) were measured in 60 lateral cephalometric X-rays of adult patients without prior orthodontic treatment. The subjects were divided into three groups based on antero-posterior skeletal malocclusions-Class I (control group), Class II and Class III groups. Results: IMPA and symphysis dimensions showed significant differences between the sagittal malocclusion groups. In Class III subjects, the lower incisor apex was closer to the buccal cortex, therefore, value of LA was decreased and LH was increased. In Class II subjects, the lower incisor apex was near to the lingual cortex, there value of LP was reduced and LH increased. Conclusion: Narrow alveolus was observed in Class II and III subjects compared to the Class I subjects. Natural compensation elongates the symphysis and influences the lower incisor position. Thus limiting the pre-surgical decompensation and increasing the risk of damage to periodontal tissues.

Correlation Between Degree of Mandibular Incisors Crowding, Lower Incisor Position and Vertical Craniofacial Configuration in Different Malocclusions

“…9 Implementation of cephalometric radiography in orthodontics has revolutionized the diagnosis, have been extraordinarily useful to in treatment planning procedures by allowing accurate valuations of skeletal and dental mal-relationships. 10 Several cephalometric analyses, 6,8 have been used to facilitate diagnosis by enabling accurate assessment of skeletal and dental relationships occurring in a different type of malocclusions.…”

Geometric morphometric analysis of mandibular symphysis in Class III skeletal base

“…Bangar et al [11] found that MS in Class III skeletal bases has reduced concavity on the labial surface and increased vertical dimension compared to Class I and Class II skeletal bases. Maniyar et al [17] also found that Class III skeletal base with retroclined incisors has taller MS. This is not in agreement with our result where our study indicates that MS variation in Class III skeletal base can be observed at the alveolar part, basal part, or both, where it varies from narrow and elongated or wide and short as mentioned previously.…”

“…Variation in MS morphology has been associated with individual variation [5], vertical facial proportions [5][6][7][8][9][10], sagittal skeletal relationship [11], incisor inclination [1,12,13], muscular and functional activities [4,14,15], and sexual dimorphism [3,16]. Studies on facial type and morphology of MS have mentioned that those with short face or forward growth of mandible has wider MS while those with long face or backward growth of mandible exhibits elongated and thin MS [8][9][10]17]. Moshfeghi et al [18] further emphasized that mandibular morphology is associated with the direction of mandibular growth.…”

Lower Incisor Positions in Different Malocclusions and Facial Pattern

“…The position of the lower incisors has always been considered a major deciding factor in treatment planning and one of the key treatment objectives, to achieve the lower incisor stability. Several factors play a role in attaining lower incisor stability [4]. Numerous studies have proven that proclined lower incisors at the end of treatment, have always been considered an undesirable side effect of orthodontic treatment and is disadvantageous for two main reasons (1) it can lead to negative periodontal ramifications and (2) can result in reduced stability.…”

“…The position of lower incisor is key to achieve good facial aesthetics and have marked functional effects i.e., resisting incisor over eruption, providing harmony and functionality to TMJ, allowing appropriate anterior guidance and protrusive movements, to protect organic occlusion [1,2]. It has been proven that within dentofacial complex a compensatory mechanism exists that attempt to maintain a proportional and harmonious facial pattern, when either maxilla or mandible deviates from normal growth, then remaining orofacial structures responds to mask this discrepancy [3][4][5]. In this regard dental compensation acts as natural camouflage to sagittal and vertical discrepancies to achieve normal incisor relationship.…”