Purpose: The purpose of this article is to review the mechanical requirements of the tissue–implant interface and analyze related theories.
Study selection: The osseointegration capacity of titanium implants has been investigated over the past 50 years. We considered the ultimate goal of osseointegration to which form a desirable interfacial layer and a bone matrix with adequate biomechanical properties.
Results: Occasionally, the interface comprises porous titanium and bone ingrowth that enables a functionally graded Young's modulus, thereby allowing reduction of stress shielding. However, the optimal biomechanical connection at the interface has not yet been fully clarified. There have been publications supporting several universal mechanical testing technologies in terms of bone–titanium bonding ability, although the separation of newly formed bone quality is unlikely.
Conclusions: The understanding of complex mechanical bone behavior and size-dependent properties ranging from a nano- to a macroscopic level are essential in the biomechanical optimization of implants. The requirements of regenerated tissue at the interface include high strength, fracture toughness related to ductility, and time-dependent energy dissipation and/or elastic–plastic stress distribution. Moreover, a strong relationship between strain signals and peri-implant tissue turnover could be expected, so that ideal implant biomechanics may enable longevity via adaptive bone remodeling.

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Alveolar ridge plays a pivotal role in supporting dental prosthesis particularly in edentulous and semi-dentulous patients. However the alveolar ridge undergoes atrophic change after tooth loss. The vertical and horizontal volume of the alveolar ridge restricts the design of dental prosthesis; thus, maintaining sufficient alveolar ridge volume is vital for successful oral rehabilitation. Recent progress in regenerative approaches has conferred marked benefits in prosthetic dentistry, enabling regeneration of the atrophic alveolar ridge. In order to achieve successful alveolar ridge augmentation, sufficient numbers of osteogenic cells are necessary; therefore, autologous osteoprogenitor cells are isolated, expanded in vitro, and transplanted to the specific anatomical site where the bone is required. Recent studies have gradually elucidated that transplanted osteoprogenitor cells are not only a source of bone forming osteoblasts, they appear to play multiple roles, such as recruitment of endogenous osteoprogenitor cells and immunomodulatory function, at the forefront of bone regeneration. This review focuses on the current consensus of cell-based bone augmentation therapies with emphasis on cell sources, transplanted cell survival, endogenous stem cell recruitment and immunomodulatory function of transplanted osteoprogenitor cells. Furthermore, if we were able to control the mobilization of endogenous osteoprogenitor cells, large-scale surgery may no longer be necessary. Such treatment strategy may open a new era of safer and more effective alveolar ridge augmentation treatment options.

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Purpose: Proper occlusal contact is important for the long-term success of prosthodontic therapy. We clarified the effects of occlusal loading force on occlusal contact in natural dentition by comparing measured values for occlusal loading and occlusal contact area.
Methods: Masseter muscle activity was measured in 10 subjects (2 male, 8 female; mean age, 27 years) with natural dentition using electromyography, with clenching at full strength with nothing interposed between the upper and lower teeth defined as 100% maximum voluntary contraction (MVC). Pressure-sensitive film (Occluzer) was used to examine occlusal contact points at 20, 40, 60, 80, 100 and 120% MVC. A material for checking accuracy of fit (BiteEye) was used to examine occlusal contact points at 20, 40, 60 and 80% MVC. ANOVA and the Bonferroni method were used to assess the results, with the level of significance set at 5%. Coefficients of variation (CV) were also calculated by dividing the standard deviation by the mean.
Results: Occlusal loading and occlusal contact area increased with clenching strength; however, CV showed differences between the methods at low and high MVC.
Conclusions: With Occluzer, testing should be carried out at clenching strength 竕･60% MVC. With BiteEye, testing should be carried out from light clenching strength at 20% MVC to moderate clenching strengths at 40–60% MVC. Occluzer and BiteEye (10 μm) gave similar occlusal contact areas at 60–80% MVC. These results suggest that combined use of Occluzer and BiteEye gives an accurate picture of occlusion from weak to strong clenching strength.

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Purpose: The aim of the present study was to investigate the reactivity of zirconia to phosphate-bonded investment on the process of hot-pressing technique.
Methods: Disc-shaped specimens, 16 mm diameter and 0.4 mm thick were prepared by cutting and grinding. These specimens were finally sintered. Half of them were sandblasted. The non-sandblasted specimens were used for controls. Both of zirconia discs with and without sandblasting were invested into the three kinds of phosphate-bonded investment. The investments were fired and broken to take out specimens. The biaxial strengths were measured in the way of the biaxial flexural tests according to ISO-6872.
Results: The biaxial strengths were ranged 762–1200 MPa at the average. The biaxial strengths of sandblasted zirconia discs heated with phosphate-bonded investment were decreased significantly (p < 0.01). SEM and EPMA revealed that the various compounds were observed on the sandblasted specimens. XRD revealed that surfaces of specimens heated with the phosphate-bonded investment showed the formation of phosphate compounds.
Conclusions: The phosphate compounds inhibit stress-induction phase transformation of zirconia and decrease the biaxial strength.

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Purpose: The objective of this study was to evaluate the microtensile bond strength (μTBS) of two resin cements bonded to dentin pre-treated with experimental niobophosphate bioactive glass (NBG).
Methods: The experimental bioactive glass was prepared by mixing different amounts of NbO₅; (NH₄)₂HP₄; CaO; Na₂CO₃. The particle size distribution and composition of the bioactive glass powder were determined. Twenty flat dentin surfaces from sound extracted human molars were polished with 600-grit SiC paper and air-abraded using experimental bioactive glass niobium powder. The bonding procedures were accomplished by the application of two resin cements: self-etching Panavia F or self-adhesive RelyX U-100. The resin-bonded specimens were cut and the μTBS test was performed after 24 h. The failure mode was determined with a stereomicroscope at 40× magnification. The results were statistically analyzed by two-way ANOVA and Tukey tests (α = 0.05).
Results: The two-way ANOVA did not detect interactions between factors, but only a difference between the self-etching and self-adhesive cement (p = 0.001). The self-etching resin cement Panavia F obtained a higher μTBS than the self-adhesive cement Relyx U-100. The predominant failure mode of the cements was adhesive/mixed between the resin cement and dentin.
Conclusion: A new bioactive glass containing niobium did not interfere with the immediate bonding performance of self-etching and self-adhesive cements.

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Purpose: A crown restoration engaged by a clasp as an abutment tooth for a removable partial denture (RPD) occasionally might be removed and eliminated due to secondary caries or apical lesions. However, if the RPD is clinically acceptable without any problems and refabricating the RPD is not recommended, the new crown must be made to retrofit to the existing clasp of the RPD.This in vitro study evaluated the conventional and CAD/CAM procedures for retrofitting crown restorations to the existing clasps by measuring the fitness accuracy and the retentive forces.
Methods: The crown restoration on #44 was fabricated with CP titanium and zirconium on the plaster model with #45 and #46 teeth missing to retrofit to the existing clasp using conventional thin coping and CAD/CAM procedures. The gap distance between the clasp (tip, shoulder, and rest regions) and the fabricated crown was measured using silicone impression material. The retentive force of the clasp was also measured, using an autograph at a crosshead speed of 50 mm/min. The obtained data were analyzed by one-way ANOVA/Tukey's multiple comparison test (α = 0.05).
Results: The CAD/CAM procedure caused significantly smaller gap distances in all of the clasp regions, as compared to the conventional procedure (p < 0.05). The retentive force of the CAD/CAM crown was significantly higher than for the conventional one (p < 0.05).
Conclusion: When a crown restoration must be remade to retrofit an existing clasp, CAD/CAM fabrication can be recommended so that both appropriate fitness and retentive force are obtained.

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Purpose: The aim of this research was to evaluate the effectiveness of a clinical instructional video with a structured worksheet for independent self-study in a complete denture program.
Methods: 47 multilingual dental students completed a task by watching an instructional video with subtitles regarding clinical complete denture procedures. After completion, students evaluated their learning experience, and 11 students participated in focus group interviews to gain further insight. A mixed-methods approach to data collection and analysis provided descriptive statistical results and a grounded theory approach to coding identified key concepts and categories from the qualitative data.
Results: Over 70% of students had favorable opinions of the learning experience and indicated that the speed and length of the video were appropriate. Highly positive and conflicting negative comments regarding the use of subtitles showed both preferences for subtitles over audio and vice versa. The use of a video resource was considered valuable as the replay and review functions allowed better visualization of the procedures, which was considered a good recap tool for the clinical demonstration. It was also a better revision aid than textbooks. So, if the students were able to view these videos at will, they believed that videos supplemented their self-study. Despite the positive response, videos were not considered to replace live clinical demonstrations.
Conclusions: While students preferred live demonstrations over the clinical videos they did express a realization of these as a supplemental learning material for self-study based on their ease of access, use for revision, and prior to clinical preparation.

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Purpose: The aim of this article was to investigate the accuracy in the reproducibility of full-arch implant provisional restorations to final restorations between a 3D Scan/CAD/CAM technique and the conventional method.
Methods: We fabricated two final restorations for rehabilitation of maxillary and mandibular complete edentulous area and performed a computer-based comparative analysis of the accuracy in the reproducibility of the provisional restoration to final restoration between a 3D scanning and CAD/CAM (Scan/CAD/CAM) technique and the conventional silicone-mold transfer technique. Final restorations fabricated either by the conventional or Scan/CAD/CAM method were successfully installed in the patient. The total concave/convex volume discrepancy observed with the Scan/CAD/CAM technique was 503.50 mm³ and 338.15 mm³ for maxillary and mandibular implant-supported prostheses (ISPs), respectively. On the other hand, total concave/convex volume discrepancy observed with the conventional method was markedly high (1106.84 mm³ and 771.23 mm³ for maxillary and mandibular ISPs, respectively).
Conclusions: The results of the present report suggest that Scan/CAD/CAM method enables a more precise and accurate transfer of provisional restorations to final restorations compared to the conventional method.

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