SALONEN MAM*, RAUSTIA AM, OIKARINEN KS (Institute of Dentistry and Oulu University Hospital Oulu, Finland)
It has been shown that alveolar bone resorption in the edentulous subjects proceed individually and may progress to the basal bone. Insertion of endosseus implants to the edentulous areas has degreased or even stopped alveolar resorption. Improvements in retention of dentures has improved masticatory function, too. This may be seen as remodelling of bony structures due to increased muscular activity and bites force.
The aim of this pilot study was to evaluate changes in the alveolar crest and basal bone of the mandible in edentulous subjects with implant retained overdentures in long-term. Altogether 27 subjects, 15 women 12 men, (mean age 55 years, range 40-75) with implant retained overdenture in the lower jaw was included in the study. Subjects had 3 to 4 titanium plasmasprayed screw implants (TPS) inserted in the region between mental foramina. Overdenture was retained with round retention bar with posterior extensions. Computerized planimetrical measurements of the changes in the mandible were done in the panoramic radiographs (PM 2002 CC, Planmega, Helsinki, Finland) taken immediately after implantation and 4 and 7 years thereafter. The tracings measured from the radiographs based on then study by Wilding et al, (J Oral Rehabil 1987;14:557-567) and were modified. Mandible posteriorly from the mental foramen was divided to upper (A) and lower (B) area on right and left sides. Area A showed changes in the alveolar crest beneath the overdenture and area B showed changes in the basal bone respectively. In 60% of the subjects area A was unchanged or decreased in 4 years and in 50% in 7 years. Area B was increased in 66% of subjects both in 4 and 7 years. There was noted significant effect of age (>52 years) on the amount of resorption in women (p = 0.02, ANOVA). Sex or period of edentulousness did not have significant correlation to the changes in posterior mandibular bone.
It can be concluded that on subjects with implant retained overdentures the resorption of alveolar bone in edentulous areas continues individually. However, the improved masticatory function with implant retained overdentures benefit apposition of basal bone in the mandible.