Statement of problem. The determination of a correct vertical dimension of occlusion is a critical procedure in clinical dentistry. Purpose. The objectives of this study were to analyze the relation between mandibular rest position and electrical activity of masticatory muscles and to compare clinical and electromyographic rest position in subjects with different vertical facial morphologic features. Material and methods. Clinical rest position and electromyographic rest position were investigated in 40 subjects. Electromyographic rest position ranged from 0.4 to 12.7 mm (average 7.7 ± 2.7 mm). Clinical rest position ranged from 0.1 to 4.4 mm (average 1.4 ± 1.1 mm). The average difference between electromyographic rest position and clinical rest position was 6.3 ± 2.5 mm (range 0.3 to 10.3 mm). Sixteen subjects were selected according to the Frankfort mandibular plane angle and separated in two groups with the first group (eight subjects) having a mandibular plane angle ≤20 degrees and the second group having a mandibular plane angle ≥28 degrees. Results. Rest position was significantly greater ( p Conclusion. This study suggests that a jaw posture with a few millimeters of interocclusal distance involves a great reduction of masticatory muscle activity. (J Prosthet Dent 1997;78:48-53.)

Mandibular rest position and electrical activity of the masticatory muscles

Craniofacial vertical dimension is a more accurate measure of facial proportion than mere measurement of the mid and lower part of the face. Craniomaxillary dimension is skeletally determined, whereas facial height of the lower part of the face is partly dependent on the vertical dimension of occlusion. Alterations in the vertical dimension of occlusion can dramatically affect the esthetics of the soft facial tissue. The "Golden Proportion" quantitatively defines ideal measured relationships and encourages a scientific appreciation of beauty. Faces with deficiencies in lower facial balance (brachyfacial) often exhibit insufficient height of the occlusal plane. The scientific literature has suggested a pliability of skeletal muscle allowing for physiologic variance in vertical facial height. Temporomandibular joint compliance is demonstrated with elevations in resting muscle length. Facial balance and location of the occlusal planes are the primary determinants for establishing an appropriate vertical dimension of occlusion.

Vertical dimension: a dynamic concept based on facial form and oropharyngeal function.

Functional orthopedic magnetic appliance (FOMA) III—Modus operandi*

Objective: To investigate the electromyographic activities of the anterior temporal (T) and masseter (M) muscles in different facial skeletal types. Materials and Methods: The samples consisted of 105 subjects (38 males and 67 females; mean age 22.0 ± 6.7 years) and were classified into six groups according to the values of ANB and SN-GoMe: group 1 for Class I malocclusion and normodivergent type (n = 27), group 2 for Class I and hyperdivergent type (n = 20), group 3 for Class II and normodivergent type (n = 10), group 4 for Class II and hyperdivergent type (n = 23), group 5 for Class III and normodivergent type (n = 12), and group 6 for Class III and hyperdivergent type (n = 13). Temporal muscle activity (TMA), masseter muscle activity (MMA), and T/M ratio were evaluated at resting and clenching status. Results: Although there was no significant difference in resting MMA among all groups, group 6 showed a higher resting TMA than did other groups and a significant difference in resting T/M ratio ...

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John D Rugh

Papers

Mandibular rest position in subjects with high and low mandibular plane angles.