EFFECTS OF GUIDED BONE REGENERATION AROUND COMMERCIALLY PURE TITANIUMAND HYDROXYAPATITE-COATED DENTAL IMPLANTS .2. HISTOLOGIC ANALYSIS

THE PURPOSE OF THIS STUDY was to determine which treatment of a large osseous defect adjacent to an endosseous dental implant would produce the greatest regeneration of bone and degree of osseointegration: barr ier membrane therapy plus demineralized freeze-dried bone allograft (D FDBA), membrane therapy alone, or no treatment, The current study hist ologically assessed changes in bone within the healed peri-implant oss eous defect. In a split-mouth design, 6 implants were placed in edentu lous mandibular ridges of 10 mongrel dogs after preparation of 6 cylin drical mid-crestal defects, 5 mm in depth, and 9.525 mm in diameter. A n implant site was then prepared in the center of each defect to a dep th of 5 mm beyond the apical extent of the defect, One mandibular quad rant received three commercially pure titanium (Ti) screw implants (3. 75 x 10 mm), while the contralateral side received three hydroxyapatit e (HA) coated root-form implants (3.3 x 10 mm), Consequently, the coro nal 5 mn of each implant was surrounded by a circumferential defect ap proximately 3 mm wide and 5 mm deep. The three dental implants in each quadrant received either DFDBA (canine source) and an expanded polyte trafluoroethylene membrane (ePTFE), ePTFE membrane alone, or no treatm ent which served as the control. Clinically, the greatest increase in ridge height and width was seen with DFDBA/ePTFE, Histologically, stat istically significant differences in defect osseointegration were seen between treatment groups (P < 0.0001: DFDBA/ePTFE > ePTFE alone > con trol). HA-coated implants had significantly greater osseointegration w ithin the defect than Ti implants (P < 0.0001). Average trabeculation of newly formed bone in the defect after healing was significantly gre ater for HA-coated implants than for titanium (P < 0.0001), while the effect on trabeculation between treatments was not significantly diffe rent (P = 0.14). Finally, there were significantly less residual allog raft particles in defect areas adjacent to HA-coated implants than Ti implants (P = 0.0355). The use of HA-coated implants in large size def ects with DFDBA and ePTFE membranes produced significantly more osseoi ntegration histologically than other treatment options and more than T i implants with the same treatment combinations. Tile results of this study indicate that, although the implants appeared osseointegrated cl inically after 4 months of healing, histologic data suggest that selec tion of both the implant type and the treatment modality is important in obtaining optimum osseointegration in large size defects.