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This study aimed to evaluate the effect of three pretreatment conditioners and surface preparations on a composite resin adhesive for a gold alloy. Cast disk specimens were made and bonded with RelyX Unicem luting agent under six surface conditions: 1) polished with No.600 carbide paper, 2) air-abraded with alumina, 3) Alloy Primer metal conditioner was applied after alumina-abrasion, 4) Monobond Plus multipurpose conditioner was applied after alumina-abrasion, 5) M. L. Primer metal conditioner was applied after alumina-abrasion, and 6) Rocatec multipurpose silica-coating system was applied. The bond strengths were determined before and after thermocycling (50,000 cycles). The bond strengths of the alumina-abrasion group were significantly decreased after thermocycling. The Rocatec and M. L. Primer exhibited higher bond strengths than other treatments. The application of metal conditioners and multipurpose surface preparations was recommended for improved bonding between the evaluated adhesive resin and gold alloy.

The aim of this study was to clarify the temperature dependence of color, i.e. the thermochromism of restorative composite resins at typical intraoral temperatures. Five brands of restorative composite resins were used. The CIE L*a*b* color values were measured using a spectrophotometer at specimen temperatures of 4, 23, 37, 60, and 80ºC. The temperature dependence of the refractive index of the materials at 4-80ºC were also determined using a refractometer. The values of L* for all materials decreased, and those of a* and b* for most of the materials increased, with increasing temperature. The color difference (ΔE*) for all materials increased with increasing specimen temperatures. The refractive index of the A4 shade of the materials consistently decreased with increasing temperatures. Most of the materials exhibited perceptible thermochromism related to intraoral thermal conditions. Optical properties that change in response to temperature could help explain the thermochromism of materials.

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.Yoshito Minesaki, Sadaaki Murahara, Yutaro Kajihara, Yoshihisa Takenouchi, Takuo Tanaka, Shiro Suzuki, and Hiroyuki MinamiEffect of metal conditioner on bonding of porcelain to cobalt-chromium alloyThe Journal of Advanced Prosthodontics 2016;8:1-8https://doi.org/10.4047/jap.2016.8.1.1

This study investigated the effect of adherend temperature on shear bond strengths of auto-polymerizing resin to denture base resin and 4-META/MMA-TBBO resin to silver-palladium-copper-gold (Ag-Pd-Cu-Au) alloy. Bonding procedure was carried out when adherend temperature was 10, 23, 37, or 55°C, and shear bond strengths (SBSs) were measured before and after thermocycling. Before thermocycling, there were no significant differences in bond strength among the four adherend temperatures for each adhesive resin: 31.59±6.11-32.89±2.12 MPa for auto-polymerizing resin; 35.43±2.2-38.38±0.61 MPa for 4-META/MMA-TBBO resin. After thermocycling, optimal adherend temperature to achieve the highest bond strength was 37°C for auto-polymerizing resin to denture base resin (30.02±2.29 MPa) and 10ºC for 4-META/MMA-TBBO resin to Ag-Pd-Cu-Au alloy (37.14±2.17 MPa).

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.

This study evaluated the effect of a fiber-premixed indirect resin composite (FMC) substructure on the fracture resistance of mesialocclusal-distal (MOD) indirect composite restorations adhered to extracted human upper premolars. The teeth received a standardized MOD cavity preparation, and indirect composite inlays were fabricated with or without using the FMC. Inlays were cemented into the cavity preparations using either Super-Bond C&B or Panavia F2.0. A total of 28 specimens, namely seven specimens for four groups, were thus fabricated. Failure load and failure energy were determined after thermocycling (4-60 degrees C for 5,000 cycles). In terms of failure load, no significant differences were found among the four groups. In terms of failure energy, FMC substructure exerted a significantly favorable effect on Super-Bond C&B-bonded group but a negative one on Panavia F2.0-bonded group. In conclusion, the failure energy of the group using FMC substructure and which was adhered using Super-Bond C&B was significantly higher than the other groups.

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° 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.

The purpose of this study was to evaluate the effect of thermal cycling on the surface texture of restorative materials. Disk-shaped specimens made of seven resin composites (Beautifil: BF; Esthet-X: EX; Filtek Supreme: FS; Inten-S: IS; Point 4: PT; Solare: SR; and Venus: VS) were finished with 1-microm alumina suspension, and then thermocycled between 4 and 60 degrees C in distilled water for 20,000 or 50,000 cycles with a dwell time of 60 seconds. Staining susceptibility and mean surface roughness, Ra, were examined, and surface texture was observed by scanning electron microscopy. Dye penetration test showed that the surfaces of all resin composites were more stained after thermal cycling. Mean Ra of all resin composites, except PT, significantly increased after 50,000 thermal cycles. Dislodgement of filler particles was observed for all resin composites after thermal cycling, except FS. It was concluded that thermal cycling significantly affected the surface texture of the seven examined resin composites.

PURPOSE Fracture of an acrylic denture base is a common problem in prosthodontic practice. Although various reinforcement methods have been used, when a fractured denture base is repaired with autopolymerizing resin recurrent fractures frequently occur at the repairing interface or adjacent areas. The purpose of this study was to evaluate the maximum flexural load of denture base resin repaired with autopolymerizing resin and several reinforcement systems after thermocycle stressing. MATERIALS AND METHODS Rectangular (10 x 70 x 3 mm) flexural specimens were fabricated by repairing a pair of heat-cured denture base resin specimens using autopolymerizing resin and a series of reinforcement materials. The materials included 4 metal wires and a woven glass fiber. Each reinforcement was embedded in the center of the specimens. Flexural specimens repaired without reinforcement were prepared as controls. Specimens were subjected to 50,000 thermocycles (4 approximately 60 degrees C, 1-minute dwell time). A 3-point flexural test was carried out by loading the center of the repaired site at 5 mm/minute crosshead speed with 50 mm span jig supports. The load necessary to cause fracture was recorded for each specimen. All data were statistically analyzed using ANOVA and the Bonferroni/Dunn test (alpha < 0.05). RESULTS The average load to fracture of specimens repaired with nonreinforced autopolymerizing resin was 68.4 N after 50,000 thermocycles. Specimens reinforced with 1.2 mm diameter stainless steel wire exhibited the highest value (89.8 N). The value for specimens reinforced with 1.2 mm diameter Co-Cr-Ni wire was 86.6 N. These fracture loads were significantly higher than those for specimens without reinforcement (p < 0.05). Low elasticity reinforcement, such as pure titanium wires, woven metal wire, and woven glass fiber were not effective in increasing the load to fracture values of flexural specimens. CONCLUSIONS Specimens reinforced with 1.2 mm diameter stainless steel wires or Co-Cr-Ni wires resulted in significantly higher loads to fracture as compared to specimens without reinforcement. The use of pure titanium wire, woven metal wire, and woven glass fiber did not improve the fracture loads.

目的: 本研究では, 新規に開発された反応性有機質複合フィラー含有硬質レジン人工歯の審美的性質を評価する目的で, 色素浸漬試験による色調変化を従来の硬質レジン人工歯と比較した.方法: 実験には, 新規硬質レジン人工歯デュラクロスフィジオ (以下DPとする) と4種類の市販硬質レジン歯を用いた. 試験片は, 義歯技工ステップを加えた場合と加えない場合の2種類の条件で作製した. 完成した試験片は, 0, 5, 000, 10, 000回のいずれかの回数の水中熱サイクルを負荷してから, カレー溶液あるいは塩基性フクシン溶液中に一定時間浸漬した後, 色調変化を測定した. また, カレー溶液色素浸漬試験では, 浸漬後の試験片を蒸留水中に保管した場合の色調を測定して, 色調の回復程度を観察した. また, 色素浸漬試験前後の人工歯の表面性状を走査電子顕微鏡で観察した.結果: カレー溶液浸漬後, 新規人工歯DPはほかの人工歯と同様に着色が認められたが, その程度は小さかった. また, 蒸留水保管3日後における色調回復の程度は, DPが最も大きかった. 塩基性フクシン溶液浸漬後でも, DPの色調変化は, ほかの2種類の人工歯より小さかった.結論: 新規硬質レジン人工歯DPは, 従来の硬質レジン人工歯よりも着色しにくいことが明らかになった. また, 義歯の洗浄を徹底することによって, 義歯使用中の着色を防止できる可能性が示された.

Bond strengths were evaluated for (1) metal primer systems when the metal was contaminated by a dentin conditioner and (2) a dentin adhesive system when dentin was contaminated by metal primers. Disc specimens were cast in a silver-palladium-copper-gold (Ag-Pd-Cu-Au) alloy and dentin specimens were prepared by grinding the labial surface of bovine teeth. Specimens were treated with (1) metal primer alone, (2) dentin conditioner alone, (3) metal primer followed by dentin conditioner and (4) dentin conditioner followed by metal primer. A resin cement was poured into a mould over a restricted bonding area and allowed to set. Metal specimens were shear stressed to failure after thermocycling (4-60 degrees C; 20,000 cycles). Dentin specimens were stressed in the same manner after 24 h of immersion in 37 degrees C water. The results were compiled and analysed by anova. Data for dentin specimens treated with dentin conditioner only or with the combination of dentin conditioner and metal primer were not significantly different, statistically. Post-thermocycled groups indicated that bond strengths to the alloy significantly decreased (P < 0.05) when the primed metal surface was contaminated with dentin conditioner regardless of the timing of its application.

Statement of Problem. Indirect composite restoratives have been improved in their wear resistance and physical properties. Several new indirect composites claim to be successfully used for full coverage crowns, but there is limited information for wear values of these new indirect composites. Purpose. The purpose of this study was to evaluate the wear characteristics of 7 indirect composite restoratives and to compare them with a type III gold alloy by means of an in vitro wear test. Material and Methods. Seven indirect composites (2 photopolymerized and 5 photo/heat-polymerized types) and a type III gold alloy (control) were used. Cylindrical Class I cavities (4-mm diameter and 3-mm depth) were prepared in occlusally flattened extracted human molars. Inlays with respective materials were fabricated on duplicated stone casts according to the manufacturers' instructions. Three types of in vitro wear tests were completed by use of the University of Alabama wear simulator. The wear tests included generalized wear as simulation of the wear during mastication, localized wear as simulation of attrition by occlusal contact, and antagonistic enamel wear, which simulated the wear of enamel created by direct contact with the restorative materials. Seven specimens were tested for each material and wear mode, and the wear depths were measured on profilometric tracings with a 2-dimensional profilometer with 1-μm accuracy. All data were analyzed by 1-way analysis of variance, and multiple comparisons were performed with Fisher's test, for which the significant level was set at.05. Results. The gold alloy control exhibited a very small amount of wear in both generalized wear (0.2 ± 0.1 μm) and localized wear (13.8 ± 5.0 μm) as compared with all composite specimens. The antagonistic enamel wear of gold alloy was similar with the value of Sculpture. The material group, which was post polymerized or post heat-treated, included BelleGlass, Sculpture, Estenia, and Cristobal+ and showed small values ranging from 1.6 to 2.2 μm in the generalized wear. For the localized wear, Estenia exhibited the minimum value (12.8 ± 4.9 μm) that was statistically the same as the value of the gold alloy control. However, Estenia exhibited the greatest antagonistic enamel wear value (66.0 ± 14.0 μm) of all materials tested in this study. It was statistically significant with other materials ( P ≤.05). Conclusion. Within the limitations of this study, it was concluded that some indirect composite restoratives have similar wear resistance to the type III gold alloy tested. Antagonistic enamel was abraded more by highly filled composite materials. (J Prosthet Dent 2002;88:431-6.)

目的: 硬質レジン前装冠は, 審美的修復物として臨床においてしばしば用いられている. 接着技法の進歩により, 前装部レジンが金属フレームから脱落することを経験する機会は減少している. しかし, それに伴い, 装着後長期間経過すると, 変色や光沢の消失など前装部レジンの劣化が認められ, 審美性の低下が引き起こされる. 熱サイクル負荷は, 前装用硬質レジンの劣化を引き起こす原因の1つと考えられるが, その影響は解明されていない. 本研究では, 熱サイクル負荷が, 前装用硬質レジンの表面性状に与える影響について検討を行った.方法: 4種類の光重合型の前装材料を用いて, 正方形 (8×8×1.5mm) の試験片を作製し, 測定面は臨床での技法に準じて研磨した. 4°Cと60°Cの水中に60秒ずつ浸漬する熱サイクル負荷を最大で50, 000回付与した後に, 肉眼的観察や色素浸透試験, 表面粗さの測定, 走査型電子顕微鏡 (SEM) による微細構造の観察を行った.結果: 熱サイクル負荷後の試験片では, 肉眼的には粗造感と光沢の消失が認められ, 色素浸透試験による色素の浸透は増大した. また, 表面粗さは負荷前に比較して増加した. さらに, SEM観察では, クラックや陥凹の発生が認められた.結論: これらのことから, 熱サイクル負荷は, 硬質レジンの表面性状に多くの変化を引き起こし, 審美性を低下させる要因であることが明らかとなった.

The purpose of this study was to find a means to prevent the adhesion of carboxylate temporary cements to the abutment teeth and an easy way to remove the cements stuck to the dentin surface.At first, the effect of tannin-fluoride component in cements on adherence to abutment teeth was examined, and carboxylate cements showed strong stickiness with and without tannin-fluoride. Then experimental solvents for carboxylate temporary cement were manufactured and the removing ability of stuck cement to dentin was evaluated. Shear bond strengths of adhesive resin cements to the dentin surface treated with the trial solvent of 2.5% ammonia solution were measured. Ammonia solution showed excellent removing ability and had little influence on shear bond strength of adhesive resin cements. The treated dentin surface showed almost no change in micromorphological characteristics.The results suggested that ammonia solution is a practical solvent for carboxylate temporary cements.

A direct retainer's arm is placed on an abutment tooth when an edentulous space is restored by the prosthetic treatment with a removable partial denture. Few analyses, however, have been reported about the effects of retainers on the abutment teeth when the denture base rotates toward and away from an edentulous ridge. A lower second premolar tooth was focused on, and the effects of an extracoronal direct retainer's arm to the periodontal ligament of the abutment tooth were analyzed utilizing the three-dimensional finite element techniques.The results were as follows:1. In case the retentive force is located on one side of a tooth and the reciprocal force on the other side, 1) the smallest von Mises stress (relative stress) on periodontal membrane was observed when the reciprocal force appears on the survey line rather than on the proximal surface, on the proximal-buccal corner and on the proximal-lingual corner, 2) and when the value of the reciprocal force is one-third of the retentive force, reciprocal force works appropriately.2. The proper retentive force is suggested to be lower than 205 g, considering the yield stress of periodontal membrane.3. It is desirable to make the guiding plane which limits the take-off direction of the denture by producing the reciprocal force on the neck of the retainer's arms when they are located on both sides of atooth.

Direct retainer's 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 retainer's arm.

The effects of resin-bonded bridge design parameters (adhesive area, shape and metal frame thickness) on the bonding strength of the resin-bonded bridge were investigated by using the adhesion test when the resin-bonded bridge of the upper anteriors was designed as a prerequisite. The adhesion test was performed using a universal testing machine to test the bond strength and toughness of specimensmade with a metal frame bonded to an abutment metal mold.The results were as follows:1. Maximum bonding force (bf) increased as the metal frame thickness (tm) increased. The values of the maximum bonding force were 10-13 kgf for tm 0.5 mm, 34-46 kgf for tm 1.0 mm, and 68-84 kgf for tm=1.5 mm.2. Maximum bonding strength, in which bf was divided by the adhesive area, increased as the adhesive area increased.3. The durability of the resin-bonded bridge was discussed by comparing the toughness. The toughness increased as the metal frame thickness (tm) increased. The values of toughness were 4-13 kgf · mm for tm= 0.5 mm, 10-31 kgf · mm for tm= 1.0 mm, and 20-44 kgf · mm for tm =1.5mm.4. In order to increase the durability of the resin-bonded bridge, the proposed design conditions were the metal frame thickness (tm) should be as large as possible and the large adhesive area and/or additional groove and wing form among the design parameters should be especially effective.

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.

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.

This study investigated the efficacies of adhesive resin cements (Clearfil SA Luting, Maxcem, G-CEM, RelyX Unicem Clicker, Vitremer Paste) for bonding to Ag-Pd-Cu-Au alloy not surface-pretreated with metal primer. For control, Panavia F 2.0 -developed for use with a proprietary metal primer, Alloy Primer- was tested with and without metal primer application. Pairs of alloy disks (10.0 and 8.0 mm in diameters, 3.0 mm thickness) were air-abraded with alumina and bonded with one of the cements. Shear bond strengths (SBSs) were measured before and after 50,000 times of thermocycling. Among Maxcem, RelyX Unicem Clicker and the control, there were no statistical differences in SBS before and after thermocycling. After thermocycling, Clearfil SA Luting exhibited the highest SBS among all the cements. Results showed that Clearfil SA Luting, Maxcem, and RelyX Unicem Clicker were efficacious for bonding to Ag-Pd-Cu-Au alloy after air abrasion surface treatment for the latter.

Restoration of an edentulous space with a removable partial denture presents various problems of the design of a retainer set on a distal molar, when the molar shifts in angle or position. The two-dimensional finite element technique was used to analyze the design factors of the retainer's arm influencing the periodontium of an abutment tooth, for a direct retainer being set on a tilted molar.The results obtained are as follows:1. When only a retentive arm is used, the von Mises stress of the periodontium increases as the shifted position or angle of a retentive tooth increases.2. When both retentive and reciprocal arms are properly located, von Mises stress is less than what with the retentive arm only. It is suggested that the reciprocation is effective for the stress -relaxation of the periodontium of a abutment tooth.3. When both retentive and reciprocal arms are properly located and a retentive force is equal to a reciprocal one, the value of von Mises stress is within 0.10 kg/mm2.4. Effective design factors of a retainer's arm for the stress relaxation of the periodontium are suggested.

The purpose of this study was to characterize the surface damages of zirconia by Nd:YAG dental laser irradiation through a systematic evaluation of the associated microstructural changes. Disk specimens of yttria-stabilized tetragonal zirconia polycrystals (Y-TZP) and ceria-stabilized zirconia/alumina nanocomposite (Ce-TZP/Al2O3 nanocomposite) were irradiated by Nd:YAG dental laser. The specimens were characterized using scanning electron microscopy, X-ray diffractometry, and wavelength dispersive X-ray spectroscopy. Every single irradiated spot was indicated by a circular black pit surrounded by a circular raised rim with a sunken depression at the center. On surface changes, many cracks were formed inside each irradiated pit. On changes in elemental composition, the concentration of oxygen decreased while that of zirconium increased. After heating in air, the assembly of circular black pits turned white, although the depression and raised rim remained. This study showed that Nd:YAG dental laser irradiation induced cracking and reduced oxygen content on the surface of zirconia. Consequently, these phenomena reduced the mechanical strength of zirconia. Therefore, Nd:YAG dental laser welding should not be performed on tetragonal zirconia.

This study evaluated the effect of 1% hydrofluoric acid (HF) treatment on the bonding of an adhesive cement (Panavia F 2.0) to an indirect resin composite (Estenia C&B). Pairs of composite disks (10 and 8 mm in diameter by 3 mm thickness) were prepared. Adhesive surfaces were pretreated with either airborne particle abrasion or HF etching before being soaked for 30 seconds, five minutes or 10 minutes, with or without application of silane coupling agent. Adhesive specimens were fabricated by cementing a pair of treated disks. Shear bond strength was determined before and after 50,000 times of thermocycling (4 and 60 degrees C). All data were statistically analyzed using two-way ANOVA and Bonferroni's test (a=0.05). Bond strength achieved with five minutes of HF etching (18.3+/-1.1 MPa) was significantly higher (P=0.0025) than that obtained with airborne particle abrasion followed by application of silane coupling agent (14.3+/-1.8 MPa) after thermocycling.

PURPOSE This study investigated the effects of silanation and adhesive monomer, 10-methacryloyloxydecyl dihydrogen phosphate (MDP), on the bond durability of resin cement to zirconia. METHODS Two sizes of zirconia disk were prepared. The bonding surfaces of the disks were air-particle abraded with 50 microm Al2O3, and then bonded with one MDP-containing or three non-MDP-containing cements to fabricate test specimens. For the silanated specimen group, air-particle abraded surfaces were treated with respective silane coupling agents, including two MDP-containing or two non-MDP-containing agents, before the bonding procedure. Five test specimens for each group were subjected to thermo-cycles before shear bond strengths were determined. The data were statistically analyzed. RESULTS For test groups without silanation, the specimens bonded with MDP-containing resin cement showed significantly higher bond strength. In contrast, all specimens bonded with non-MDP-containing resin cements failed during the thermo-cycling process. For the silanated groups, the specimens pre-treated with MDP-containing silane coupling agent and bonded with non-MDP-containing resin cement exhibited the highest shear bond strength. The shear bond strength of specimens pre-treated with MDP-containing silane coupling agent and bonded with MDP-containing resin cement was the next highest. In contrast, all specimens pre-treated with non-MDP-containing silane coupling agent bonded with non-MDP-containing resin cements failed during the thermo-cycling process. CONCLUSION Within the limitations of this study, MDP adhesion monomer was effective in improving the bond durability of resin cement to zirconia.

To determine the effects of silanation for core buildup composites on bond strength of resin cement.Three core buildup composites including FluoroCore LV, Core Restore, and Clearfil Photo Core, of which filler loadings were 65 wt%, 74 wt%, and 83 wt% respectively, were used. All composite specimens were randomly divided into four surface treatment groups of eight each as following; 1) 600-grit ground only, 2) 600-grit ground plus silanation, 3) 600-grit ground plus air-particle abrasion, 4) air-particle abrasion plus silanation. Following these treatments, 4-META/MMA-TBB resin (CB Metabond) was bonded to the specimen surfaces. Completed specimens were stored in 37 degree C water for 24 hours, and then thermocycled 20,000 times (4 degree C - 60 degree C) before shear bond strengths were tested. Data were analyzed by two-way ANOVA and Scheffé's test for statistical significance (P0.05).Clearfil Photo Core, of which filler loading was the highest among the resin composites tested, treated with air-particle abrasion plus silanation obtained the highest bond strength. However, silanation alone was not effective for improving the bond strength.

summary This study evaluated the effects of surface pre-treatments on the bonding of auto-polymerizing silicone soft denture liner to a Co–Cr alloy denture base after cyclic thermal stressing. The bonding surfaces of Co–Cr alloy cylinders (8 mm diameter and 4 mm high) were polished with a 600-grit silicon carbide paper. The bonding surfaces received one of three pre-treatments, which included either the application of a metal primer, a metal primer after air abrasion, or a resin primer after adhesive resin coating. Tensile specimens were fabricated by polymerizing a 2-mm thickness of soft denture liner between a pair of pre-treated denture base cylinders. Failure loads were measured by tensile testing after subjecting the specimen to 0, 5, 10, 20, and 30 thousand thermal cycles. Seven specimens were fabricated for 15 groups, including three pre-treatments and five thermal cycle groups. Failure loads of resin-bonded specimens, which were formerly reported, were used as references. All data were statistically analysed by two-way anova and Bonferroni test at the 95% confidence level. Adhesive resin coating of the metal surface was effective in enhancing the failure loads up to 5000 thermal cycles. However, failure loads of all metal-bonded groups were significantly lower than those of resin-bonded groups at all thermal cycling intervals. The results of this in vitro study implied that polymerizing adhesive resin on the Co–Cr alloy might be a promising method, when the clinicians need to acquire improved bonding of an auto-polymerizing soft denture liner to Co–Cr alloy denture bases.

Bonding failures of repair resin to denture base resin occurs when denture base resin is wet, however, little is known of how water relates to failures.This study evaluated the influence of water absorbed in denture base resin on the bond strength and resistance to cyclic thermal stresses of autopolymerizing resins bonded to denture base resin.Denture base resin disks (n = 180; 12 mm diameter and 3 mm thick) were fabricated from heat-polymerized acrylic resin (Lucitone 199). The disks were divided into groups (n = 60) with 3 conditions of water content: (1) complete water saturation (control), (2) superficial desiccation by blowing air on the specimen, or (3) complete desiccation. Each denture base specimen received 1 of 3 surface treatments (n = 20) including: (1) no treatment, (2) airborne-particle abrasion, or (3) methylene chloride application. An autopolymerizing repair resin (Repair Material, n = 10) or reline resin (Tokuso Rebase Normal set, n = 10) was applied to the bonding area (5 mm diameter) and polymerized at 37 degrees C for 10 minutes. The resistance to cyclic thermal stress was determined after subjecting the specimens to 50,000 thermal cycles between 4 degrees C and 60 degrees C water baths with a 1-minute dwell time (n = 5 per group). Bond strength (MPa) was measured by shear bond testing at a 1.0 mm/min crosshead speed until the applied resin debonded from denture base resin. Data were statistically analyzed by 3-way analysis of variance and multiple comparisons among the groups were performed with Bonferroni test (alpha = .05).The mean bond strengths of repair resin to airborne-particle-abraded denture base specimens were not significantly influenced by either thermal cycling or water content. The mean bond strengths of reline resin significantly decreased after thermal cycling (P.0001) regardless of the conditions of surface treatment and water content. For methylene chloride treated specimens, bond strengths of both repair and reline resins to completely water saturated specimens were significantly higher than those of completely desiccated specimens (P = .0048 for repair resin, P.0001 for reline resin) after thermal cycling.Bond strengths of autopolymerizing resin to denture base resin were not significantly influenced by water content of denture base resin but were significantly influenced by resin type, thermal cycling, and surface treatment.

In addition to the transformation of soft palate substance defect in a functional moment, considering conformity, blockade and speech etc., the authors have thought it preferable that the prosthesis be fabricated with elastic material. For this reason, a silicone rubber material (MDX-4-4210, Dow Corning Corporation) has been clinically applied to soft palate substance defect, and examined concerning physical properties. To obtain the physical properties of this material, a stress relaxation was recorded after the specimens were subjected to strain. Taking into account the stress relaxation curve from the results in this study, an analysis of a mechanical three element model has been put into practice. According to the results of the analysis of the mechanical model, the effects of time, curing condition and water temperature on physical properties have been compared.It was found that this material is extremely stable, and not influenced by time, curing condition or water temperature. Also this material has approximated the action as an elastic material in an occlusal moment with negligible viscosity.Finally the authors report that the prognosis of two clinical applications has been favorable.

On the assumption that the all ceramic crown was cemented on an abutment tooth, the effect of the cementing materials on the strength of the ceramic crown was analyzed using two-dimensional finite element technique. The results obtained were as follows: 1. When the compressive load was applied to the ceramics, the principal stress in the cementing material was compressive in the region of Young's modulus of the cementing materials 200-700 kg/mm2, but was in tension beyond it. 2. When the tensile load was applied to the ceramics, the principal stress in the cementing material was in tension, and decreased as Young's modulus of the cementing materials decreased. 3. When the adhesive effect of the cementing material was investigated with examining the presence of the crack between the ceramics and the cementing material, the principal stress in the ceramics increased as the crack propagated. 4. The creation and propagation of the crack, the increase of the principal stress in the ceramics and the destruction of the ceramics were suggested. 5. When the analyzed results were compared with the mechanical properties of the cementing materials from the point of view of the breaking strength, it was considered that the adhesive resin cement was favorable as the cementing material of the ceramic crown. And the Young's modulus of the adhesive resin cement was about 400 kg/mm2.

A method for measuring the thermal diffusivity of human teeth and some dental materials was described. In addition, the thermal diffusivity of human dentin, together with some dental materials, was presented and discussed.

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.