Evaluation of a hydroxylapatite (HA)/resorbable suture implant for alveolar ridge augmentation

A new type of hydroxylapatite (HA) particle configuration and implant system for alveolar ridge augmentation was investigated. The PermaRidge implant system was designed to provide better HA particle handling and retention characteristics. Torous-shaped particles were bound together with resorbable sutures into rope-like bundles. The implants were placed as a single unit rather than as individual particles delivered via syringe. Six adult beagle dogs underwent bilateral mandibular tooth extraction. After an eight-week healing period, the animals had PermaRidge implants placed on the right side and HA particles alone placed on the left side. Two animals were killed at each of four, eight, and 16 weeks post-operatively. Radiographically, the PermaRidge implants maintained initial augmentation height throughout the course of the study. There was no compaction of the implant or problems with containment and migration of the HA particles. The HA particles alone demonstrated an approximate 25% decrease in augmentation height with time in situ. The majority of augmentation height was lost within the first four weeks post-operatively. There was also significant particle compaction and migration present in the implant sites. Histologically, the PermaRidge implants demonstrated bone growth into the augmentation, often extending 2-3 particle diameters (2-3 mm). The remainder of the implant was filled with dense connective tissue. There was intimate contact of the ingrown bone with the HA surface. The HA particles alone demonstrated minimal bone ingrowth, with extensive fibrous tissue infiltration. The results indicate that the PermaRidge implant system may provide a viable alternative to HA particles alone for the augmentation of the deficient alveolar ridge.