Assistant Professor, Islamic Azad University- Khorasgan branch (Isfahan)



Aim: The purpose of this study was toevaluate the relationship between the ultrasonographic thickness of masseter muscle and the width of dental arches.
Materials and Methods: The sample comprised of 44 persons (22males, 22females), who did not undergo orthodontic treatment and they had at least 28 teeth with CL 1 occlusion. The thickness of the masseter muscle was measured ultrasonografically with the muscles both in relaxation and under contraction. Maxillary and madibular inter-molar and inter-canine width were measured with an digital caliper for the distance between the palatal surfaces of the permanent first molar and cingulumes of canines.
Results: There was a significant association between mandibular inter-molar width and sex (PV=0.037). Masseter muscle thickness in both sides and either in relaxation or contraction showed a direct significant association with sex (PV=0.001). Maxillary inter-molar and inter- canine and mandibular inter-canine width showed a direct significant association with masseter thickness during contraction in tight side (PV=0.037), whereas in relaxation no statistically significant relationship was found (PV =0.07).
Conclusions: The fmdings of this study indicated that the thickness and functional capacity of the masseter muscle may be considered as one of the factors influencing the width of the maxillary dental arch and inter canine mandibular dental arch width.