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Objective The purpose of this study was to determine the relationships and differences in three-dimensional (3D) bone mineral density (BMD) and microtrabecular structures between autogenous bone grafts and their adjacent native bone after a healing period following maxillary sinus augmentation. Materials and methods Nine rod-shaped human bone biopsy samples were taken from patients receiving two-stage sinus augmentation therapy in implantation areas and analyzed using microcomputed tomography (micro-CT). Before micro-CT scanning, two BMD phantoms were placed near to the bone biopsy samples for executing BMD calculations of the grafted and native bone samples. In addition, 3D structural parameters of the trabeculae were analyzed for both the grafted and native bone, including percentage of bone volume [bone volume (BV)/tissue volume (TV)], bone-specific surface [bone surface (BS)/BV], trabecular thickness (Tb.Th), trabecular number (Tb.N), trabecular separation (Tb.Sp), trabecular pattern factor (Tb.Pf), and structure model index (SMI). Results No significant correlations with regard to BMD and trabecular-structure parameters were found between native bone and grafted bone; however, BS/BV and Tb.Pf were higher and Tb.Th and Tb.Sp were 37.35% and 12.74% lower in grafted bone than in native bone. For grafted bone, there were significant correlations (P

Objectives: The aim of this study was to investigate the effects of two different microrough surface treatments on miniscrews with loading over different time periods in vivo. Material and methods: Twenty-four New Zealand white rabbits were selected. One hundred and forty-four miniscrews with a machined (MA), sandblasted and acid-etched (SLA) or sandblasted and alkaline-etched (SL/NaOH) surface were implanted into the tibia of the rabbits. Then, orthodontic forces with Ni–Ti coils were applied immediately to two of the three miniscrews in each tibia, with the center one serving as the control. After 2, 4, 8 and 12 weeks, the rabbits were sacrificed. The removal torque value (RTV) was tested and bone-to-implant contact (BIC) was examined. Results: In most groups, there were no differences between the RTV in the unloaded and loaded conditions at different time periods. In the loaded condition, the RTV of the SLA groups increased significantly after 4 weeks of healing. The RTV in the SL/NaOH groups increased after 8 weeks, and reached a significant difference with the SLA groups after 12 weeks. After 12 weeks, the BIC in the SLA and SL/NaOH groups was higher than in the MA groups. A regression test revealed a moderate correlation between the BIC and the RTV. Conclusions: There were no differences between the loaded and unloaded conditions in most groups. The RTV and BIC increased with time. In the loaded condition, the RTV of the SLA surface increased earlier, at 4 weeks, while the SL/NAOH group showed the highest RTV after 8 weeks.

Objectives Three-dimensional finite element (FE) models of splinted prosthetic crowns were studied and stress analyses were evaluated with different types of implant support, including standard, wide or two implant(s) for partial, posterior edentulous restorations. Material and methods The FE models were constructed based on a cadaver mandible containing the 2nd premolar and the 1st molar. The crowns of these two teeth were modeled as connected and disconnected to mimic the splinted and non-splinted designs, respectively. One standard implant was placed at the premolar region, while three types of implant support, one at a time (the standard implant, wide implant and two implants), were used to support the molar crown. A 100 N oblique load was applied to the buccal cusp on each crown. The FE simulation was validated experimentally via strain gauge measurement. Results The experimental data were well correlated with the FE predictions (r(2)=0.97). When compared with the standard implant used in the molar area, the wide implant and two implants reduced the peak stress in crestal bone by 29-37% for both splinted and non-splinted cases. Inserting the standard implant into both the premolar and molar area, the bone stresses were identical for splinted and non-splinted designs. However, splinting the adjacent crowns has shown to decrease the bone stresses at the premolar region by 25%, while the wide implant or two implants were placed at the molar region. Conclusion The biomechanical advantages of using the wide implant or two implants are almost identical. The benefit of load sharing by the splinted crowns is notable only when the implants on the premolar and molar regions have different supporting ability.

Three-dimensional finite element (FE) models of splinted prosthetic crowns were studied and stress analyses were evaluated with different types of implant support, including standard, wide or two implant(s) for partial, posterior edentulous restorations.The FE models were constructed based on a cadaver mandible containing the 2nd premolar and the 1st molar. The crowns of these two teeth were modeled as connected and disconnected to mimic the splinted and non-splinted designs, respectively. One standard implant was placed at the premolar region, while three types of implant support, one at a time (the standard implant, wide implant and two implants), were used to support the molar crown. A 100 N oblique load was applied to the buccal cusp on each crown. The FE simulation was validated experimentally via strain gauge measurement.The experimental data were well correlated with the FE predictions (r(2)=0.97). When compared with the standard implant used in the molar area, the wide implant and two implants reduced the peak stress in crestal bone by 29-37% for both splinted and non-splinted cases. Inserting the standard implant into both the premolar and molar area, the bone stresses were identical for splinted and non-splinted designs. However, splinting the adjacent crowns has shown to decrease the bone stresses at the premolar region by 25%, while the wide implant or two implants were placed at the molar region.The biomechanical advantages of using the wide implant or two implants are almost identical. The benefit of load sharing by the splinted crowns is notable only when the implants on the premolar and molar regions have different supporting ability.