Osseointegration in the Absence of Primary Stability: An Experimental Preclinical Mandibular Minipig Overpreparation In Vivo Model.

OBJECTIVES

The effect of osteotomy overpreparation, and thus lack of primary stability, on implant osseointegration and crestal bone volume maintenance was investigated by comparing placement of dental implants with either a standard osteotomy preparation (NP) or an overprepared osteotomy (OP) where the final osteotomy drill was larger in diameter than the implant placed.

METHODS

Bone-level implants (Ø3.3 mm diameter) were placed in the mandible of minipigs with two preparation techniques: an NP (Group 1) and an OP to a final osteotomy of 3.5 mm in diameter (Group 2) and submerged for 2 and 8 weeks. An Implant Stability Quotient (ISQ) was measured for each implant at placement. Implant survival, defined histologically as the absence of fibrous encapsulation and the presence of direct bone-to-implant contact, osseointegration and crestal bone formation were analysed histologically and histomorphometrically to compare the preparation techniques.

RESULTS

A 100% survival for both preparation types was observed. The mean ISQ at insertion for Groups 1 and 2 was 69.35 a.u. (95% CI: 68.02-70.68) and 11.95 a.u. (95% CI: 10.53-13.37) respectively (p < 0.001). At 2 and 8 weeks, there was no difference between the two groups for total bone-to-implant contact (tBIC) (p > 0.05). Group 2 demonstrated significantly higher mean first bone-to-implant contact (fBIC), coronal bone-to-implant contact (cBIC) and bone-area-to-total-area (BATA) at 2 and 8 weeks compared to Group 1 (p < 0.05).

CONCLUSION

Implants inserted into an overprepared osteotomy with no primary stability successfully osseointegrated. At 2 and 8 weeks, OP resulted in significantly more coronal bone apposition and maintenance of coronal bone volume as measured by fBIC, cBIC and BATA.