Influence of the sumastructure on the peri‐implant tissue; in beagle dogs

The purpose of this study was to compare clinical, radiographic and histological differences around titanium oral implants loaded with either acrylic‐veneered metal or ceramo‐metal fixed prostheses. Five beagle dogs were used in this investigation. At the beginning of the study, all mandibular premolars and first molars were extracted. After 3 months of healing, 2 Brånemark implants were installed on each side of the mandibles. Three months later, abutments were inserted on each implant and a daily oral hygiene regime was initiated. One month after abutment connection, the implants on one side of the mandible were restored with an acrylic‐veneered metal fixed prosthesis, whereas, on the other side a ceramo‐metal fixed prosthesis was inserted. The prostheses were constructed in occlusion with the maxillary first molars. The following clinical parameters were measured around each implant at this time (i.e., baseline), and thereafter, at monthly intervals up to 5 months: Plaque Index; Gingival Index; implant mobility (using the Periotest®); probing depth and clinical attachment level (using the Florida Probe®). In addition, standardized radiographs were taken at baseline and 5 months after insertion of the prostheses and evaluated by subtraction radiography. Another Brånemark fixture was installed on each side of the mandibles 3 months before the end of the study. These implants remained unloaded and submerged for the entire study period. Five months after prosthesis insertion, the animals were killed, and implants with their supporting peri‐implant tissues were processed for histological evaluation. Analyses of the clinical, radiographic and histometric parameters revealed no significant differences between the acrylic‐veneered and ceramometal loaded implants. All clinical and radiographic parameters remained stable over time. Histological comparison of the alveolar bone height levels around both loaded groups with those from the unloaded, submerged implants revealed that a similar and slight loss of bone height (approximately 0.6 mm) occurred on the loaded groups following abutment connection. It was concluded that both acrylic‐veneered metal and ceramo‐metal suprastructures appear to be suitable for the restoration of endosseous oral implants. Additional long‐term studies in humans, however, are needed evaluating both types of implant‐supported prostheses, in a variety of clinical conditions. before final restorative recommendations are made.