The Effect of Restorative Emergence Angle on Soft and Hard Tissue Around Splinted Implants: A Preclinical Study

To investigate the impact of the restorative emergence angle and splinting configurations on peri-implant soft and hard tissues.

Thirty implants were placed in the mandibular premolars (P2, P3, P4) of five beagle dogs. In a split-mouth design, each animal received both narrow (NE) (emergence angle = 30°) and wide (WE) (emergence angle = 60°) abutments on each side of the mandible. The implants were subsequently splinted. Radiographic images were captured at 0, 4, 12, and 24 weeks post-restoration. Biopsy samples were then collected for histomorphometric analysis and circularly polarized light examination. All analyses were performed based on the splinted positions: either the mesial or distal end of the terminal implant, the splinted zone of the terminal implant, or the splinted zone of the middle implant.

Radiographic evaluation showed more pronounced bone remodeling in the WE group. In histomorphometric analysis, both the vertical distance from the implant shoulder to the alveolar bone crest and the infiltrated connective tissue areas were significantly larger in the WE group. Conversely, the NE group exhibited a longer connective tissue attachment. Analysis using circularly polarized light indicated a significantly reduced area fraction of collagen fibers in the peri-implant epithelium of the WE group, as well as in the oral epithelium of the splinted zone.

A wide emergence angle of implant prostheses can compromise connective tissue attachment, hinder the formation of an adequate soft tissue seal, and potentially lead to marked bone remodeling.