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Fifty mentalis muscles were examined on 25 adult human cadavers with edentulous mandibles. The following observations were made: 1. 1. The right and left mentalis muscles were symmetrically placed on either side of the midline of the edentulous mandible, and they were found to be apart by a mean distance of 12 mm. 2. 2. The mean width of the mentalis muscle at the origin was approximately 5 mm. 3. 3. The medial fibers of the mentalis muscle crossed the midline to join the mentalis muscle of the opposite side. The most superficial fibers of the mentalis muscle coursed upward to join the obicularis oris. 4. 4. Sixty-seven per cent (20 of 30) of the muscles examined originated on the crest of the bone of the residual ridge. Twenty-seven per cent (8 of 30) of the muscles examined originated between the crest of the bone of the residual ridge and the fornix of the labial vestibule. 5. 5. Twenty-one of 30 (70 per cent) mentalis muscles examined in Group B had origins which correlated with elevations on the mucous membrane surface as recorded in modeling compound.

The described procedure will allow more freedom for the muscles under the basal seat of the lower denture to move in the region of the mentalis muscle. Consequently, the tendency of the denture to move is lessened. The lower lip should be mechanically elevated by the dentist in the border-molding procedure, because the mentalis muscles will not be activated and they will not be recorded in the impression surface in any great detail.