Twist removal of healed vs. nonhealed implants—a mechanical and histological study in mini pigs

Abstract

PurposeThe objective of this study was to evaluate the effect of removal torque (reverse torque) of titanium implants in peri-implant bone.MethodsThe P1-M1 teeth were extracted bilaterally of 6 mini pigs (BR-1). Each animal received 6 titanium implants, three for each side of mandible. On the right side of mandible, 3 implants reminded 9 months (9M) under masticatory activity and on the left side, other 3 implants were placed and immediately removed (IR). All 36 implants were removed by removal torque, and the recorded values were statistically analyzed. Animals were euthanized right after the removal torque and recording. Each third (cervical, medium, and apical) of peri-implant bone was extracted and analyzed histological and immunohistochemically. Student’s t test was used to determine statistical differences in the values between the 9M and IR samples. Data were presented as means with standard deviations. The level of significance was set at 5% (P < 0.05).ResultsRemoval torque was higher in 9M experimental situation than in IR. Histological characteristics of mature bone were presented in the 9M experimental condition, and immature bone characteristics were presented in the IR experimental condition. Removal torque caused small fractures and rounding in the bone grooving. Immunohistochemical analysis reinforced the histological results; Student’s t test provided statistically significant differences to osteocalcin expression in 9M samples and no statistically significant differences expression to collagen I in both experimental conditions (P < 0.05).ConclusionsRemoval torque caused microscopical fractures and smoothing in the peri-implant bone grooves, but it does not compromise the bone healing.

Pre-Clinical Models in Implant Dentistry: Past, Present, Future

“…As for the tibia, the oral model may be useful for histological analyses such as cytotoxicity and viability of new compositions [ 287 , 288 , 289 , 290 ] but also for assessments on 1:1 scale models of mechanical properties [ 47 , 268 , 291 ], stress distribution [ 287 , 288 ], and the effects of different implant and abutment shapes [ 264 , 284 , 292 , 293 , 294 , 295 ]. Thanks to pigs having similar bone properties to those of humans, resistance to insertion [ 273 ] or removal torque can be measured during [ 296 ] or after healing [ 268 ]. It is possible to perform classical analysis such as measurement of bone area [ 273 ], marginal bone level [ 273 ], crestal bone loss [ 275 ], , resonance frequency [ 273 ], or implant stability quotient [ 297 ].…”