Evaluation of the association between tongue posture and the transverse dental compensation in Class III skeletal patients - a retrospective, record-based study.

Abstract

Background: To assess the association between tongue posture and transverse dental compensation patterns in teeth of Class III skeletal patients and to compare the above associations between Class III skeletal patients and Class I skeletal patients.

Material and methods: This retrospective study was conducted in the Department of Orthodontics and Dentofacial Orthopedics, Manipal College of Dental Sciences, Mangalore. The records of 126 subjects including skeletal class I subjects as the control group (n = 63) and skeletal class III patients as the experimental group (n = 63) were obtained. The tongue-to-palate distance of all the subjects was measured using the method described by Graber (Graber et al., 1997) on lateral cephalograms. CBCT images were standardized and acquired by keeping the patient's head in the natural position. Buccolingual inclinations were measured on CBCT coronal sections as the angle between the reference plane (line perpendicular to the line joining the buccal and lingual crest of the alveolar bone) and the long axis of each tooth. SPSS software, version 25.0 was used to perform the statistical analyses. To analyze the association between tongue posture and buccolingual inclination of teeth, the Pearson correlation coefficient was calculated, with a power of 80%.

Results: Statistically significant differences were found for skeletal Class III malocclusion. The degree of buccal tipping at 17, 15, 14, 27, 25, 24 and the tongue-to-plate distance at D3 and D4 were significantly correlated, with a p value <0.001. The degree of buccal tipping at 16, 26 and the tongue-to-plate distance at D1, D2, D3, D4 and D5 showed a moderate positive correlation and was significant. In general, a positive correlation was observed between the degree of buccal tipping of maxillary posterior teeth and the tongue posture at D1-D5. A moderate positive correlation was observed between the degree of lingual tipping of molars and premolars and the tongue-to-palate distance at D1, D2, D3, D4 and D5.

Conclusions: Based on the observations of skeletal Class III patients, the following conclusions can be drawn:a) The tongue assumes a lower and more anterior position than does the tongue in Class I subjects.b) The tongue-to-palate distance increases at positions D2-D5, revealing a strong association between tongue forces and buccal flaring of maxillary posterior teeth.c) Lingual tipping of mandibular posterior teeth showed a constant moderate association with tongue position at D1-D5 and was significant, but not as significant as that observed for maxillary posterior teeth. Key words:Tongue posture, buccolingual tooth inclination, skeletal class III, dentoalveolar compensation, soft tissues.