Objectives: This research was carried out to determine whether mandibular implant supported overdenture or maxillary implant supported overdenture is more effective in prevention of combination syndrome.
Materials and Methods: Totally, fourteen patients with completely edentulous upper arch and mandibular bilateral distal extensions (Kennedy class I) with the canines or first premolar as the last standing tooth were selected to participate in this study. Inclusion criteria: Patients had well-formed residual ridge covered with dense fibrous connective tissue, Angle class I ridge relationship, and adequate inter arch space. Patients with systemic diseases that might affect the oral tissues or bone, neuromuscular disorders, temporomandibular joint disorders and smokers were excluded. Patients were randomly divided into two equal groups, Group I: patients were rehabilitated with mucosa supported maxillary complete denture and lower tooth-implant partial denture retained by two osseointegrated implants on each side of the lower arch in the first molar area and RPI direct retainer. Group II: patients were rehabilitated with implant retained and supported maxillary complete overdenture by four osseointegrated implants in the anterior maxillary area and tooth-tissue supported partial denture retained by RPI direct retainer. In this study, marginal bone height changes in the premaxillary region and mucosal thickness at the crest of maxillary ridge were evaluated at the time of prostheses insertion, six, twelve and eighteen months.
Results: In this study, an insignificant difference was detected between the two groups at the different follow-up intervals, regarding marginal bone loss and mucosal thickness. After 18 months follow up, bone loss & mucosal thickness were 0.5±0.2, 0.6±0.3 mm for group I and 0.5±0.2, 0.3±0.2 mm for group II respectively. Although group II showed decrease in marginal bone loss and decrease in mucosal thickness compared to group I however difference between groups were statistically insignificant.
Conclusion: Within the limitations of the number of studied patients and follow up period of this study it could be concluded that, preventing the degenerative oral changes that occurs when complete maxillary dentures opposes the Kennedy class I partial dentures may be possible through accurate treatment planning and, the development of stable posterior occlusion that controls of occlusal pressures on the anterior maxilla. Also, maxillary implant retained overdentures should be considered preferable treatment option, whenever the available bone quantity and quality permits.