Effects of Implant Diameter on Implant Stability and Osseointegration in the Early Stage in a Dog Model

Purpose: To determine the optimal implant diameter under limited bone width by comparing the effects of implants with different diameters on implant stability, peri-implant bone stability, and osseointegration. In addition, to evaluate the reliability of resonance frequency analysis (RFA) in detecting osseointegration and marginal bone level (MBL). Materials and Methods: Mandibular premolars and first molars of seven beagle dogs were extracted. After 8 weeks, their mandibular models and radiographic information were collected to fabricate implant templates. Implant sites were randomly divided into three groups according to diameter: circle divide 3.3, circle divide 4.1, and circle divide 4.8 mm. Implant stability quotient (ISQ) measurement and radiographic evaluation were performed after surgery (baseline) and at 4, 8, and 12 weeks. Three dogs were euthanized at 4 weeks to observe osteogenesis and implant-tissue interface biology. Four dogs were euthanized at 12 weeks to observe osseointegration. Hard tissue sections were prepared to analyze osteogenesis (fluorescence double labeling) and osseointegration (methylene blue-acid fuchsin staining). Results: At baseline and at 4, 8, and 12 weeks, the ISQ values of circle divide 4.1-and circle divide 4.8-mm implants did not differ (P > .05), but both had higher values than the circle divide 3.3-mm implants (P < .05). The mean marginal bone resorption (MBR) associated with circle divide 3.3-, circle divide 4.1-, and circle divide 4.8-mm implants was 0.65 +/- 0.58 mm, 0.37 +/- 0.28 mm, and 0.73 +/- 0.37 mm, respectively. The buccal MBR of circle divide 4.8-mm implants was significantly higher than that of circle divide 4.1-mm implants (P < .05). The bone-to-implant contact (BIC) percentage at 12 weeks did not differ for any group (P > .05). The correlation coefficients between the ISQ and MBL of the circle divide 3.3-, circle divide 4.1-, and circle divide 4.8-mm implants were -0.84 (P < .01), -0.90 (P < .001), and -0.93 (P < .001), respectively, while that between the ISQ and BIC was 0.15 (P < .05). Conclusions: During the early healing stage, the performance of circle divide 4.1-and circle divide 4.8-mm implants in terms of implant stability was better than that of circle divide 3.3-mm implants. Implant diameter may not influence BIC percentage. RFA can be used to evaluate implant stability and MBL but is not suitable to assess the degree of osseointegration.