Comparison between Two Design Concepts of Four Implants Placement Used to Support Telescopic Mandibular Overdenture: A Prospective Study of Implant Marginal Bone Height Changes.

Aim: The aim of this present study was to compare two placement designs of four implants used to support a telescopic mandibular overdenture regarding the marginal bone height changes.
Materials and Methods: Each patient received four implants. Two anterior implants were installed vertically in the canine area. Patients were randomized into two groups according to the direction of posterior implants installed in the premolar area. Group I: where the implants were installed vertically parallel to the anterior implants and group II: where the implants were installed 30 ^º distally. The implants were delayed loaded with a telescopic mandibular overdenture. The implant's marginal bone changes were evaluated after 6 and 12 months of overdenture insertion.
Results: Mean marginal bone loss of anterior implants showed a statistically significant difference between both groups. The vertically parallel posterior implants in group I showed statistically significant higher marginal bone loss than posterior implants in group II after follow-up periods. The 30 ^º distally tilted posterior implants maintained the implant marginal bone after 12 months of overdenture insertion.
Conclusion: Rehabilitation of the edentulous mandible with telescopic overdenture supported by four parallel implants is a promising successful treatment option.
Clinical Significance: Tilting the posterior implants will improve the anteroposterior spread that in turn increases the support and the survival rate of the implants. Also, using this technique gives us an opportunity to use fewer implants.