Alveoloplasty with ridge extensions on the lingual side of the lower jaw to solve the problem of a lower dental prosthesis.

W HEN people lose teeth, the problem of constructing a prosthesis without the aid of natural teeth, and which rests only on the alveolar ridge, must be met. In the maxilla where the surface of the hard palate covered with immovable mucous membrane is utilized for the adhesion and retention of the prosthesis, the problem is lessened because of the increased flat surface area. In the mandible conditions are less favorable as the available surface area for a prosthesis covering immovable mucous membrane is much smaller. Parts of the alveolar ridge anteriorly (if teeth were extracted recently) or posteriorly at. the beginning of the ascending ramus may offer a limited resting surface for a total prosthesis. In most cases the floor of the mouth rises between the cuspid and molars. This can be seen by having the patient lift his tongue, first to the left, then to the right, as far as the alveolar ridge. Sometimes the floor of the mouth even overlaps the ridge (Fig. 4). If patients with total lower prostheses chew well, they have learned to stabilize the prosthesis by neither moving the tongue too much nor opening the mouth too wide when eating or speaking. This requires a considerable degree of practice. Behind the posterior edge of the mylohyoid muscle, lingually from the angle of the jaw, there is a muscle-free area just as buccally below the lower edge of the buccinator muscle there is such an area also. Patients do not endure posterior wings of the prosthesis equally well. The main obstacle is the mylohyoid muscle which in case of atrophy of the alveolar process is inserted close to the alveolar ridge, hindering the making of really deep-reaching lingual wings on a lower prosthesis (Fig. 1). This muscle extends lingually at an angle of about 45 degrees, inward and downward, and tightens like an oblique plate. The second obstacle is the mucous membrane of the floor of the mouth which starts from the mandibular ridge and rises with every lifting of the tongue and floor of the mouth (Figs. 3 and 4). In performing the alveoloplasty both these obstacles must be removed. The mucous membrane and the muscle must be separated from the mandibular ridge so that the prosthesis can extend deeply on the lingual side of the lower jaw in order to rest in a completely stable position. This can be achieved by a surgical operat.ion, with absolute security of a successful result in most cases. The separation of t,he mylohyoid muscle from the mandibular attachment is of no consequence as far as function is concerned. In none of the cases have