Comparison of the physical, thermal, and biological effects on implant bone site when using either zirconia or stainless-steel drill for implant bone site preparation.

BACKGROUND/PURPOSE: Zirconia has been a popular material in dental implantology with good biocompatibility. But few research focused on its application in implant drills. This study aimed to investigate the physical, thermal, and biological effects on using the zirconia and stainless-steel drills for implant bone site preparation. METHODS: We performed a series of experiments to evaluate the physical wearing properties of zirconia and stainless-steel drills of identical diameter and similar shape. During the implant site preparation thermal test, we subjected both drills onto a resin-embedded bone, utilizing a thermal couple device without irrigation. Moreover, we conducted a cell study by collecting bone cells in vivo while preparing the implant site with both tested drills. The cell activity was evaluated through cell proliferation colorimetric analysis (XTT) and alkaline phosphatase (ALP) activity measurements. RESULTS: The zirconia drill outperforms the stainless-steel drill in terms of requiring less force, maintaining stability over repeated cutting tests, and generating lower temperatures during drilling (stainless-steel drill: 45.48 ± 1.31 °C; zirconia-coated drill: 32.98 ± 1.21 °C, P = 0.000247). Meanwhile, both types of drills show similar results in XTT colorimetric analysis and ALP activity test. CONCLUSION: The thermal effect study is more favorable for using the zirconia drill than the stainless-steel drill for bone preparation. Cytological analysis indicate that the zirconia drill produces a similar impact on bone cells activity as the stainless-steel drill. Therefore, we conclude that the zirconia drills offer a good cutting effect similar to currently available stainless-steel drills in various aspects.

Differences in the biomechanical behaviors of natural teeth and dental implants.

OBJECTIVE: The lack of a PDL, which acts as an energy absorber, is a contributor to implants' early failure; however, these discrepancies are not well understood because of limited in vivo research. This study investigated the discrepancy in biomechanical behaviors between natural teeth and dental implants by detecting micro-movements in vivo. METHODS: We designed a device that could measure precisely mechanical behaviors such as creep, stress relaxation, and hysteresis by using load-control displacement on teeth and implants. We also compared energy dissipation between natural teeth and dental implants by subtracting the area of the hysteresis loop of natural teeth from that of dental implants. RESULTS: Biphasic curves with an initial phase of rapid response and a subsequent phase of slow response were confirmed in creep and stress relaxation curves for the load-time relationship in natural teeth. By contrast, the behavior of creep or stress relaxation was less prominent when the dental implants were tested. We observed that the periodontal ligament under an axial intrusive load of 300g in a loading rate 3g/s could dissipate the energy of 7.35±1.18×10-2 mJ, approximately 50 times that of the dental implants (1.47±1.22×10-3) with statistically significant (p<0.05). SIGNIFICANCE: We confirmed natural teeth could achieve greater energy dissipation compared to dental implants, which owe to that natural teeth exhibited fluid and viscoelastic properties.

Neutralized Dicalcium Phosphate and Hydroxyapatite Biphasic Bioceramics Promote Bone Regeneration in Critical Peri-Implant Bone Defects.

The aim of this study was to evaluate the efficacy of bone regeneration in developed bioceramics composed of dicalcium phosphate and hydroxyapatite (DCP/HA). Critical bony defects were prepared in mandibles of beagles. Defects were grafted using DCP/HA or collagen-enhanced particulate biphasic calcium phosphate (TCP/HA/Col), in addition to a control group without grafting. To assess the efficacy of new bone formation, implant stability quotient (ISQ) values, serial bone labeling, and radiographic and histological percentage of marginal bone coverage (PMBC) were carefully evaluated four, eight, and 12 weeks after surgery. Statistically significant differences among the groups were observed in the histological PMBC after four weeks. The DCP/HA group consistently exhibited significantly higher ISQ values and radiographic and histological PMCB eight and 12 weeks after surgery. At 12 weeks, the histological PMBC of DCP/HA (72.25% ± 2.99%) was higher than that in the TCP/HA/Col (62.61% ± 1.52%) and control groups (30.64% ± 2.57%). After rigorously evaluating the healing of biphasic DCP/HA bioceramics with a critical size peri-implant model with serial bone labeling, we confirmed that neutralized bioceramics exhibiting optimal compression strength and biphasic properties show promising efficacy in fast bone formation and high marginal bone coverage in peri-implant bone defects.