Implant biomechanical stability variation at early implantation times in vivo: an experimental study in dogs.

PURPOSE: To demonstrate the degree of stability decrease and subsequent increase of dental implants at early implantation times in a beagle model. MATERIALS AND METHODS: The mandibular premolars and first molars of eight beagle dogs were extracted and the ridges allowed to heal for 8 weeks. Thirty-two (n = 16 each group) implants were placed bilaterally, and remained in vivo for 1 and 3 weeks. The implants with comparable dimensions were divided as follows: group 1, Straumann Bone Level with SLActive surface; group 2, Nobel Speedy Replace RP with TiUnite surface. During insertion and following sacrifice, the implants were torqued to determine insertion and interface failure values. Histologic sections were prepared for microscopy. Statistical analysis was performed using Kruskal-Wallis and multiple paired and non-paired t tests considering unequal variances at a 95% level of significance. RESULTS: High insertion torque values were observed along with a significant decrease at 1 week in vivo (P = .003). At 3 weeks, the biomechanical fixation levels increased and were comparable to the insertion torque value. Histology showed that interfacial bone remodeling and initial woven bone formation was observed around both implant groups at 1 and 3 weeks. CONCLUSIONS: As time elapsed early after implantation, the biomechanical stability of dental implants initially decreased and subsequently increased.

Effect of drilling dimension on implant placement torque and early osseointegration stages: an experimental study in dogs.

PURPOSE: Primary stability has been regarded as a key factor to ensure uneventful osseointegration of dental implants. Such stability is often achieved by placing implants in undersized drilled bone. The present study evaluated the effect of drilling dimensions in insertion torque and early implant osseointegration stages in a beagle dog model. MATERIALS AND METHODS: Six beagle dogs were acquired and subjected to bilateral surgeries in the radii 1 and 3 weeks before death. During surgery, 3 implants, 4 mm in diameter by 10 mm in length, were placed in bone sites drilled to 3.2 mm, 3.5 mm, and 3.8 mm in diameter. The insertion torque was recorded for all samples. After death, the implants in bone were nondecalcified processed and morphologically and morphometrically (bone-to-implant contact and bone area fraction occupancy) evaluated. Statistical analyses were performed using the Kruskal-Wallis test followed by Dunn's post hoc test for multiple comparisons at the 95% level of significance. RESULTS: The insertion torque levels obtained were inversely proportional to the drilling dimension, with a significant difference detected between the 3.2-mm and 3.8-mm groups (P = .003). Despite a significant increase in the bone-to-implant contact over time in vivo for all groups (P = .007), no effect for the drilling dimension was observed. Additionally, no effect of the drilling dimension and time was observed for the bone area fraction occupancy parameter (P = .31). The initial healing pathways differed between implants placed in bone drilled to different dimensions. CONCLUSIONS: Although different degrees of torque were observed with different drilling dimensions and these resulted in different healing patterns, no differences in the histometrically evaluated parameters were observed.