Relationship with occlusal force, mandibular flexure, chewing and facial pattern

Objectives: To evaluate the influence of vertical facial pattern on maximum occlusal force (MOF), medial mandibular flexure during the opening and (MMFO) protrusion (MMFP) position and chewing movement pattern in 78 adult subjects (mean age=23.2± 2.3). Methods: The facial patterns were classified in accordance with Ricketts's methods from cephalometric analysis in three groups: G1-mesofacial (MF); G2- brachyfacial (BF) and G3- dolichofacial(DF). MOF was measured bilaterally, during 7 seconds, using a strain gauges placed on the first molars. For MMFO and MMFP calculation, impressions of the mandibular occlusal surface were made with vinyl polysiloxane material in rest (R), maximum opening (MO) and maximum protrusion (MP) positions. The impressions were scanned, and reference points were selected on the occlusal surface of the contralateral first molars using Image Tool software. MMFO and MMFP were calculated by subtraction the intermolar distance. The mandibular kinesiography was used to evaluate chewing movement patterns and the opening and closing path configurations (OCC) in the frontal (Types I, II, and III) and sagital (Types I and II) planes were determined. Data from MOF were analyzed by ANOVA followed by Student Newman Keuls pos hoc (p<0.05). MMFO and MMFP data were submitted to ANOVA one-way and Tukey pos hoc (p< 0.0001). Results: The facial patterns showed significant differences in MOF (p<0.05) and MMFO (p<0.01) and the BF group showed the highest values followed by MF and DF groups. Regarding to MMFP, no significant differences (p=0.2164) were observed between BF and MF, but they were statistically different of DF (p<0.0001) which showed the lowest value. The kinesiography analysis in the frontal plane showed that BF group exhibited predominantly OCC Type I. In contrast, Type II OCC was more frequent in the DF groups in the sagital plane. Conclusion: In this study, the facial pattern influenced the maximum occlusal force and medial mandibular flexure during the opening and protrusion.