M.E. Geertman

Bite Forces with Mandibular Implant-retained Overdentures

Sensitivity or pain of the mucoperiosteum covering the mandibular edentulous ridge is often thought to limit bite forces in complete-denture wearers. Therefore, bite forces with mandibular implant-retained overdentures may depend on the degree of implant support. This study analyzed the effects of different degrees of support for the mandibular denture on bite forces measured four years after denture treatment as part of a randomized controlled clinical trial. All subjects had received new maxillary dentures and (1) mainly implant-borne overdentures on a transmandibular implant (TMI), (2) mucosa-borne overdentures on two cylindric permucosal IMZ implants, or (3) new conventional dentures in the mandible. Fifty-three women and 15 men (mean age, 59.1 yrs; range, 41 to 77) participated in this trial. Both unilateral and bilateral bite forces were recorded at different positions with a miniature strain gauge transducer and a mechanical bite fork, respectively. The subjects were asked to bite at three force levels. Results indicated that women had significantly lower maximum bite forces than men. Persons with mandibular implant-retained overdentures had significantly higher unilateral and bilateral maximum bite forces than complete-denture wearers. However, bite forces did not differ between the mainly implant-borne (TMI) and mucosa-implant-borne (IMZ) implant systems. Therefore, it appears that differences in support for the mandibular overdenture by dental implants are not reflected in bite force capabilities.

Comminution of Food with Mandibular Implant-retained Overdentures:

When complete-denture wearers are treated with from four to six implants and mandibular implant-borne prostheses, masticatory performance improves. No significant improvement has been observed with two implants and implant-mucosa-borne overdentures, suggesting that the masticatory performance of edentulous subjects depends on the degree of support for their mandibular prostheses by implants or alveolar mucosa. To verify this hypothesis, we studied, in a randomized clinical trial, the comminution of an artificial test food during mastication. The trial involved the provision of a new maxillary denture and either a new conventional mandibular denture, a mandibular overdenture retained by two permucosal cylindric implants through a single bar-clip attachment, or a mandibular overdenture retained by a transmandibular implant through five clips on a triple-bar construction with cantilever extensions. In comparison with the subjects wearing mandibular implant-retained overdentures, the subjects with conventional complete dentures needed between 1.5 and 3.6 times more chewing strokes to achieve an equivalent reduction in particle size. No differences in masticatory performance and efficiency were found between the subjects who had received two permucosal cylindric implants and those who had received a transmandibular implant. The results suggest that the increased retention and stability of the mandibular denture, rather than the degree of support by implants or alveolar mucosa, determine the wearers ability to comminute food during mastication.

Clinical aspects of a multicenter clinical trial of implant-retained mandibular overdentures in patients with severely resorbed mandibles

In a multicenter clinical trial treatment, the effects of overdentures on different implant systems in patients with severely resorbed mandibles were compared 1 year after the insertion of new dentures. The implant systems used were the transmandibular implant (TMI), the IMZ (IMZ), and the Brånemark system (BRA). Treatment was randomly assigned to 88 patients according to a balanced allocation method. Evaluation included peri-implant and radiographic parameters. According to the Delphi method a Clinical Implant Performance scale (CIP) was constructed based on all conceivable complications of the different implant systems. During the healing period, one IMZ and one BRA implant were lost, and one TMI implant was removed after functional loading. The results of the peri-implant and radiographic parameters and the CIP scale revealed no significant differences between the three implant systems.

Randomized prospective clinical trial of two implant systems for overdenture treatment: a comparison of the 2-year and 5-year results using the clinical implant performance scale.

In a prospective randomized clinical trial, edentulous patients were treated with dental implants and overdentures. The results of treatment with two IMZ implants connected by a Dolderbar, and a transmandibular implant (TMI) were compared. By using the clinical implant performance scale, the clinical and radiographic data were evaluated and compared after a two-year and five-year follow up. After the five-year follow up, significantly less problems and complications were recorded in the IMZ group than in the TMI group (Wilcoxon, P=0.03). When compared to the two-year follow up, there was, however, a gradual increase of scores on the clinical implant performance scale in the IMZ group, while in the TMI group only a slight increase was recorded.

Transmandibular implant versus intramobile cylinder implants: a randomized, prospective clinical trial

A randomized, controlled clinical trial was conducted to compare two different implant treatment modalities for edentulous patients with severely resorbed mandibles. In one modality (the IMZ group), two intramobile cylinder implants were placed, connected by a Dolder bar and provided with an overdenture, and in the other (the TMI group), a transmandibular implant with a triple bar and cantilever extensions was placed, likewise provided with an overdenture. The conditions of the overdentures, the peri-implant tissues, and the implants were evaluated. Orthopantomograms were taken for radiologic evaluation. An overall complication scale which took account of all aspects was devised to compare the results. The follow-up period was 2-4 years, with a mean follow-up of 3 years. The condition of dentures and oral hygiene aspects were comparable for both groups. The complication rate in the TMI group was significantly higher than that in the IMZ group. The scores on the complication scale resulted in a significant difference between the TMI and the IMZ groups (Wilcoxon, P = 0.0044).