Yoshito Minesaki

In vitro evaluation of the effect of thermal and mechanical fatigues on the bonding of an autopolymerizing soft denture liner to denture base materials using different primers.

PURPOSE This in vitro study evaluated the effect of priming procedures on bonding of an autopolymerizing silicone denture liner (Sofreliner) to a denture base material after fatigue processes using cyclic thermal stressing and repetitive mechanical stressing. MATERIALS AND METHODS Denture base specimens were fabricated by use of an autopolymerizing denture base resin and Co-Cr alloy into a cylinder shape 8-mm diameter and 4-mm high. The bonding surfaces of denture base specimens were polished with 600-grit silicon carbide paper. Resin denture base specimens were pretreated with applications of resin primer (Sofreliner Primer or Reline Primer for resin). Metal specimens were pretreated with application of metal primer (Reline Primer for metal) or coated with adhesive resin (C&B Metabond) followed by application of resin primer (Sofreliner Primer). Tensile specimens were fabricated by polymerizing a 2-mm thickness of Sofreliner between a pair of pretreated denture base cylinders. Repetitive mechanical stressing was performed by using a University of Alabama-type wear-testing apparatus as a stress generator. Vertical 75 N load with 15 degrees rotation was applied 66,700, 133,300, 266,700, and 400,000 times, then residual tensile resistance to failure was measured. Seven specimens were fabricated for 16 groups--four cyclic loading groups for four pretreatment groups. Residual tensile resistance to failure of specimens before the fatiguing process and after 5000, 10,000, 20,000, and 30,000 thermocycles were used as reference. The mean values of each group were statistically analyzed by three-way ANOVA and Bonferroni/Dunn test at a 95% confidence level. Failure modes were assessed for all specimens measured. RESULTS In the denture-bonded groups, residual tensile resistance to failure of Sofreliner Primer-treated group was significantly higher than that of the Reline Primer at each thermocycling interval (p < 0.0001) and up to 133,300 times of cyclic loading (p < 0.0001). In the metal-bonded groups, residual tensile resistance to failure of the intermediate adhesive resin group was higher than the metal primer-applied group up to 5000 thermocycles (p < 0.0001); however, there was no significant difference between them after 66,667 cyclic loads (p= 0.1698). Although adhesive resin-coated specimens of metal-bonded groups showed mixed failure, metal primer-applied groups and both denture-bonded groups consistently revealed cohesive failure of the soft denture liner after cyclic loading. CONCLUSIONS Application of Sofreliner Primer for a resin denture base provided better bonding after thermocycle and cyclic load testing than did Reline Primer. Using an intermediate adhesive resin layer on a Co-Cr denture base material improved the bonding for up to 5000 thermocycles; however, it did not affect cyclic loading parameters.

Twelve-year results of a direct-bonded partial prosthesis in a patient with advanced periodontitis: A clinical report

Prosthodontic treatment for patients with advanced periodontitis is a therapeutic challenge. A minimally invasive technique is preferred to preserve the remaining mobile abutment teeth. This report describes the initial clinical treatment and 12-year follow-up of a direct-bonded prosthesis reinforced with a cast metal framework, used as a conservative treatment option to replace periodontally involved maxillary lateral incisors.

Effects of polymerization method on flexural and shear bond strengths of a fiber-reinforced composite resin.

This study investigated the effects of indirect composite polymerization on the postcuring mechanical properties of a fiber-reinforced composite. An indirect composite seated on glass fibers preimpregnated with polymerized monomer was polymerized by 1) photoirradiation using a halogen-fluorescent polymerizing unit for 5 min, 2) method 1 plus secondary heating at 100°C for 15 min, 3) photoirradiation using a metal halide light unit for 60 s, or 4) preliminary polymerization using a halogen light unit for 20 s followed by method 3. After polymerization, the flexural and shear bond strengths of the fiber-reinforced composite were examined, as was the flexural strength of non-fiber-reinforced composite specimens polymerized using the same methods. Among non-fiber-reinforced composite specimens, flexural strength was lower for method 1 than for the other three methods; however, among fiberreinforced composite specimens, the four methods did not significantly differ in flexural strength or shear bond strength. Composite-fiber interface separation without breakage of the fiber after flexural strength testing was not observed in specimens polymerized by methods 2 or 4. In conclusion, use of a conventional unit for high-intensity light irradiation after preliminary irradiation, or light irradiation followed by secondary heating, is recommended for polymerization of composite material seated on polymerized glass fiber.

Bonding durability between acrylic resin adhesives and titanium with surface preparations

The purpose of the present study was to evaluate the efficacy of pretreatment on the bonding durability between titanium casting and two acrylic adhesives. Cast titanium disk specimens treated with four polymer-metal bonding systems as follow: 1) air-abraded with 50-70 μm alumina, 2) 1)+Alloy Primer, 3) 1)+M.L. Primer and 4) tribochemical silica/silane coating system (Rocatec System). The specimens were bonded with M bond or Super-bond C&B adhesive. The shear bond strengths were determined before and after thermocycling (20,000 cycles). The surface characteristics after polishing, and for the 1) and 4) preparations were determined. The bond strengths for all combinations significantly decreased after thermocycling. The combination of Super-bond C&B adhesive and 2) led to significantly higher bond strength than the other preparations after thermocycling. The maximum height of the profile parameters for the polishing group was lower than other preparations.

Effect of metal conditioner on bonding of porcelain to cobalt-chromium alloy

PURPOSE The purpose of this study was to evaluate the efficacy of two different metal conditioners for non-precious metal alloys for the bonding of porcelain to a cobalt-chromium (Co-Cr) alloy. MATERIALS AND METHODS Disk-shaped specimens (2.5×10.0 mm) were cast with Co-Cr alloy and used as adherend materials. The bonding surfaces were polished with a 600-grid silicon carbide paper and airborne-particle abraded using 110 µm alumina particles. Bonding specimens were fabricated by applying and firing either of the metal conditioners on the airborne-particle abraded surface, followed by firing porcelain into 5 mm in diameter and 3 mm in height. Specimens without metal conditioner were also fabricated. Shear bond strength for each group (n=8) were measured and compared (α=.05). Sectional view of bonding interface was observed by SEM. EDS analysis was performed to determine the chemical elements of metal conditioners and to determine the failure modes after shear test. RESULTS There were significant differences among three groups, and two metal conditioner-applied groups showed significantly higher values compared to the non-metal conditioner group. The SEM observation of the sectional view at bonding interface revealed loose contact at porcelain-alloy surface for non-metal conditioner group, however, close contact at both alloy-metal conditioner and metal conditioner-porcelain interfaces for both metal conditioner-applied groups. All the specimens showed mixed failures. EDS analysis showed that one metal conditioner was Si-based material, and another was Ti-based material. Si-based metal conditioner showed higher bond strengths compared to the Ti-based metal conditioner, but exhibited more porous failure surface failure. CONCLUSION Based on the results of this study, it can be stated that the application of metal conditioner is recommended for the bonding of porcelain to cobalt-chromium alloys.

Study on Adhesion Fixed Partial Denture Applied Composite Resin Teeth as Pontic. In vitro Measurement of Bonding Durability.

The adhesion fixed partial denture applied resin teeth as pontic, i.e., adhesionpontic bridge, is effective prosthodontic treatment to conserve the tooth substrate of intact abutment teeth.The purpose of this study was to improve the bond strength and durability between adhered pontic applied composite resin teeth and abutment teeth. At first, the bond strength of resin teeth pontic bonded to extracted human teeth with two self-curing resin adhesives were measured after thermocycling test up to 50, 000 times, and the specimen bonded with Super-Bond C & B showed higher bond strength than with Enamagic. However, the bond strength with Super-Bond C & B after thermocycling 50, 000 times decreased to about30% of the value before thermocycling, and the failure of all specimens occurredat the adhesion interface between composite resin teeth and Super-Bond C & B.Then some methods to reinforce the bonding durability of Super-Bond C &B to composite resin teeth were evaluated. The highest bond strength was obtained in the specimen with the hole in the proximal plane of composite resin teeth.The results suggested that the combination of mechanical retention and bond applied resin adhesives is effective to achieve the durable bond and lengthen thelife of adhesion pontic bridge.

Study on Effects of an Extracoronal Direct Retainer's Arm to the Periodontal Ligament of an Abutment Tooth Utilizing Finite Element Method. Part 1. The Introduction of Three-Dimensional Finite Element Analysis.

Direct retainers arm is placed on an abutment tooth when an edentulous space is restored by prosthetic treatment with a removable partial denture. Various attempts have been made to investigate the effects of the retainer of a partial denture on an abutment tooth during functional loading. However, no analysis seems to have been reported about the effects of retainers on the abutment teeth when the denture base rotates toward and away from an edentulous ridge. Attention was paid to the lower second premolar tooth, and the three-dimensional finite element method was used.The results were as follows:1. When only a retentive force was applied, the von Mises stress in the periodontal ligement increased.2. When both retentive and reciprocal forces were properly applied, the von Mises stress in the periodontal ligament was less than that with the retentive force only.3. When both retentive and reciprocal forces were properly set, and a reciprocal force was one-third of a retentive one, the value of the von Mises stress was within 2.4 MPa. Thus, it was suggested that the reciprocation effectively released the stress in the periodontal ligament of an abutment tooth.4. Effective factors for stress relaxation of the periodontal ligament were suggested to exist in the design of a retainers arm.

A Study on Adhesion of Dental Porcelain to Castable Glass Ceramics. Part II Fabrication of Tensile Test Pieces and Tensile Test.

Castable glass ceramics-porcelain jacket crown, in which castable glass ceramics are used as a coping and dental porcelain is partially or completely fired, is recommended from an aspect of esthetics. The adhesive strength between two ceramic materials is considered to be important for this jacket crown. The purposes of this study were to evaluate the adhesion of two ceramic materials under tensile load and to establish fabrication of tensile test pieces.The following results were obtained.1. Established method for fabricating tensile test pieces and tensile test are adequate to know the behavior of ceramic materials under a tensile load.2. Dental porcelain used in this study showed favorable adhesion to castable glass ceramic, without detracting the inherent physical properties of castable glass ceramic.3. The white layer, which shows the formation at the surface of castable glass ceramic after the ceraming process, does not affect the adhesion of dental porcelain to castable glass ceramic.4. Reinforcement of the white layer is expected to be obtained by firing dental porcelain.

3/4冠・陶材焼付冠支台の補綴物が歯牙の動揺度と支持組織の負担力に与える影響

A mechanical simulation model of tooth and alveolar bone in the application of 3/4 crown and porcelain-fused crown restorations was made and analyzed using three-dimensional finite element technique. The results obtained were as follows. 1. When the physiological tooth mobility was less than 150 microns, the teeth were sufficiently fixed using the splint and the bridge connected with more than two teeth, in the case of 20 percent absorption of the alveolar bone, and more than three teeth in the case of 40 percent absorption. In the case of 60 percent absorption, the teeth were fixed with the splint of six teeth connections, and were fixed with the bridge of five teeth connections. 2. The periodontium supporting force decreased markedly according to the increase of the number of the abutment teeth. 3. The teeth accompanied with the absorption of the alveolar bone were connected, in order to inhibit the tooth mobility and the periodontium supporting force. In this application, it had the inhibitory action when the replacing ratio of metal and ceramics to a crown of the tooth was less than 35 percent. 4. According to the finite element analysis, the design bases of fixed restorations applied in the teeth accompanied with the absorption of the alveolar bone were preferred.

Studies on Mechanical properties of Soft Lining Materials

Viscoelastic properties of silicone material (code-named MDX-4-4210) and 4 commercial soft liners and related materials (Kurepate, Neo-Snugger, Super-Soft and Viscogel) were examined using a stress relaxation testing instrument. All measurements were preformed in water at a temperature of 37±0.5°C.In the case of other 4 materials, except Visco-gel, the decreasing rates of relative stress {f(t)/f(0)} with time were relatively small. Furthermore, the decreases of stress relaxation modulus {Er(t)} of these materials with period soaked in water at 37°C were also very small, with exception of Visco-gel. Code-named MDX-4-4210 showed the most superior elastic properties in materials used. The relative stress in Visco-gel diminished markedly with time.These results indicate that all materials, excluding Visco-gel, have possessed the favourable properties as soft liners and related materials since it is necessary for these materials to remain in oral cavity for long period of month.