Intra‐oral adhesive systems for ceramic repairs: a comparison

The aim of this investigation was to compare the bond strength of restorative composite resin to dental ceramic conditioned with primers and adhesives of various commercial repair kits. Three intra‐oral ceramic repair systems—Silistor (Heraeus Kulzer), Cimara (Voco), Ceramic Repair (Vivadent)—were used on all‐ceramic (IPS Empress 2, Ivoclar‐Vivadent) substrate. Shear bond strength of restorative composite resin to substrate was tested after thermocycling and without thermocycling (n=10). Substrate surfaces of the specimen after loading were examined microscopically (SEM). The highest bond strengths in both water‐stored (7.0±5.7 MPa) and thermocycled conditions (2.5±1.8 MPa) were obtained with the Vivadent repair system, while the lowest values were observed with the Cimara system (0.6±1.4 MPa and 0.0±0.0 MPa, respectively). Shear bond strengths appeared to be significantly affected by thermocycling (ANOVA, P<0.05). It is concluded that there are significant differences in the bond strengths of resin composites and ceramic substrate. The roughened surface does not necessarily provide a better bond strength; the bond strength of composite decreases with storage in water and after thermocycling. Bond strength values were generally low for all of the tested materials.     

表面融附玻璃陶瓷对氧化锆与树脂粘接强度的影响

目的 评估氧化锆玻璃陶瓷表面融附处理后粘接力的变化.方法 将60个氧化锆陶瓷试件平均分为3组,分别接受以下表面处理:50 μm氧化铝喷砂(Sb组);融附玻璃陶瓷(Fu组);氧化铝喷砂后融附玻璃陶瓷(Sb-Fu组).另以20个铸瓷试件作为铸瓷对照组.所有试件应用树脂粘接材料Super bond C＆B粘接在核树脂圆柱上,其中1/2试件经过冷热循环老化(10 000次,5～55℃),测量所有试件的粘接强度.结果 未经过冷热循环处理的Sb、Fu、Sb-Fu和铸瓷对照组试件的粘接强度标准差±均值分别是24.76±2.80、29.08±5.80、28.67±7.20和31.30±2.90 MPa,Sb组的粘接强度明显低于其他3组(P＜0.05),而Fu和Sb-Fu组与铸瓷对照组相比差异无统计学意义;冷热循环后,4组的粘接强度分别是24.45±3.90、28.50±3.70、25.41±2.00和32.19±3.90 MPa,Sb和Sb-Fu组明显低于铸瓷对照组(P＜0.01).Fu和Sb-Fu组多为树脂内聚断裂和混合断裂.结论 玻璃陶瓷融附处理比单纯喷砂更能提高氧化锆的粘接强度.     

Shear Bond Strength of Four Resin Cements Used to Lute Ceramic Core Material to Human Dentin

Purpose: This study evaluated the effect of four resin cements on the shear bond strength of a ceramic core material to dentin. Materials and Methods: One hundred twenty molar teeth were embedded in a self‐curing acrylic resin. The occlusal third of the crowns were sectioned under water cooling. All specimens were randomly divided into four groups of 30 teeth each according to the resin cement used. One hundred twenty cylindrical‐shaped, 2.7‐mm wide, 3‐mm high ceramic core materials were heat‐pressed. The core cylinders were then luted with one of the four resin systems to dentin (Super‐Bond C&B, Chemiace II, Variolink II, and Panavia F). Half of the specimens (n = 15) were tested after 24 hours; the other half (n = 15) were stored in distilled water at 37°C for 1 day and then thermocycled 1000 times between 5°C and 55°C prior to testing. Shear bond strength of each specimen was measured using a universal testing machine at a crosshead speed of 1 mm/min. The bond strength values were calculated in MPa, and the results were statistically analyzed using a two‐way analysis of variance (ANOVA) and Tukey HSD tests. Results: The shear bond strength varied significantly depending on the resin cement used (p < 0.05). The differences in the bond strengths after thermocycling were not remarkable as compared with the corresponding prethermal cycling groups (p > 0.05). Significant interactions were present between resin cement and thermocycling (p < 0.05). After 24 hours, the specimens luted with Variolink II (5.3 ± 2.2 MPa) showed the highest shear bond strength, whereas the specimens luted with Chemiace II (1.6 ± 0.4 MPa) showed the lowest. After thermocycling, the bond strength values of specimens luted with Chemiace II (1.1 ± 0.1 MPa) and Super‐Bond C&B (1.7 ± 0.4 MPa) decreased; however, this was not statistically significant (p > 0.05). The increase in the shear bond strength values in the Panavia F (4.5 ± 0.7 MPa) and Variolink II (5.5 ± 2.1 MPa) groups after thermocycling was also not statistically significant (p > 0.05). Conclusion: Variolink II and Panavia F systems showed higher shear bond strength values than Chemiace II and Super‐Bond C&B. They can be recommended for luting ceramic cores to dentin surfaces.     

Shear bond strength of dental porcelains to nickel-chromium alloys

The continuous technological advance and increasing availability of new base metal alloys and ceramic systems in the market, coupled to the demands of daily clinical practice, have made the constant evaluation of the bond strength of metal/porcelain combinations necessary. This study evaluated the metal/porcelain shear bond strength of three ceramic systems (Duceram, Williams and Noritake) in combination with three nickel-chromium (Ni-Cr) alloys (Durabond, Verabond and Viron). Thirty cast cylinder specimens (15 mm high; 6 mm in diameter) were obtained for each alloy, in a way that 10 specimens of each alloy were tested with each porcelain. Bond strength was measured with an Emic screw-driven mechanical testing machine by applying parallel shear forces to the specimens until fracture. Shear strength was calculated using the ratio of the force applied to a demarcated area of the opaque layer. Mann-Whitney U test was used for statistical analysis of the alloy/ceramic combinations (p<0.05). Viron/Noritake had the highest shear bond sregnth means (32.93 MPa), while Verabond/Duceram (16.31 MPa) presented the lowest means. Viron/Noritake differed statistically from other combinations (p<0.05). Viron/Duceram had statistically significant higher bond strengths than Verabond/Duceram, Verabond/Williams and Durabond/Noritake (p<0.05). It was also found significant difference (p<0.05) between Verabond/Noritake, Verabond/Duceram and Durabond/Noritake. No statistically significant difference (p>0.05) were observed among the other combinations. In conclusion, the Noritake ceramic system used together with Viron alloy presented the highest resistance to shear forces, while Duceram bonded to Verabond presented the lowest bond strength. Viron/Duceram and Verabond/Noritake provided intermediate results. The combinations between the Williams ceramic system and Ni-Cr alloys had similar shear strengths among each other.     

Alternative Pretreatment Modalities with a Self‐Adhesive System to Promote Dentin/Alloy Shear Bond Strength

Purpose: The aim of this study was to evaluate alternative pretreatment modalities to enhance the dentin/alloy shear bond strength using a self‐etch adhesive system. Material and Methods: Ninety discs were fabricated and divided into three groups (n = 30). The discs of the first group were cast in gold palladium (Au‐Pd); those of the second group were cast in palladium silver alloy (Pd‐Ag); the discs of third group were cast in nickel chromium alloy (Ni‐Cr). Each group was further divided into three subgroups (n = 10) according to the dentin pretreatment used to lute the discs. Subgroup U (no pre‐treatment): Rely X Unicem resin cement. Subgroup GU: G‐Bond then Rely X Unicem. Subgroup ZU: Zinc‐Zeolite pretreatment then Rely X Unicem. Shear bond strength was determined using a compressive mode of force applied at the dentin/alloy interface using a monobevelled chisel‐shaped metallic rod. Data were collected and statistically analyzed to assess the effect of alloy type, pretreatment modality, and their interactions on the shear bond strength. Scanning electron microscopic examination (1000×) at the dentin/resin interface was performed. Two‐way ANOVA was used in testing significance for the effect of pretreatment, alloy, and their interaction. Duncan's post hoc test was used for pairwise comparison between the means when the ANOVA test was significant. The significance level was set at p≤ 0.05. Statistical analysis was performed with SPSS 15.0^®. Results: Regarding the pretreatment modality, the mean shear bond strength and 95% CI of subgroups ZU (18.00 MPa; 16.8 to 19.2) and GU (16.91 MPa; 15.4 to 18.4) were significantly higher than subgroup U (12.81 MPa; 11.4 to 14.2). Regarding the alloy type, the mean shear bond strength and 95% CI of Ni‐Cr groups (18.39 MPa; 16.9 to 19.9) were significantly higher than Au‐Pd (15.33 MPa; 13.8 to 16.8) and Pd‐Ag (13.99 MPa; 12.3 to 15.7). Conclusions: Pretreatment of dentin with G‐Bond and Zinc Zeolite improved the dentin/alloy shear bond strength. Base metal alloys provided superior bond strength values with any adhesive modality compared to noble alloys. Treatment of the dentin surface prior to the application of a self‐adhesive system is of great importance to enhancement of the dentin/alloy bond strength.     

Evaluation of low-fusing ceramic systems combined with titanium grades II and V by bending test and scanning electron microscopy

The bond strength by three point bending strength of two metal substrates (commercially pure titanium or grade II, and Ti-6Al-4V alloy or grade V) combined to three distinct low-fusing ceramic systems (LFC) and the nature of porcelain-metal fracture by scanning electron microscopy (SEM) were evaluated. The results were compared to a combination of palladium-silver (Pd-Ag) alloy and conventional porcelain (Duceram VMK68). Sixty metal strips measuring 25x3x0.5mm were made - 30 of titanium grade II and 30 of titanium grade V, with application of the following types of porcelain: Vita Titankeramik, Triceram or Duceratin (10 specimens for each porcelain). The porcelains were bonded to the strips with dimensions limited to 8x3x1mm. The control group consisted of ten specimens Pd-Ag alloy/Duceram VMK68 porcelain. Statistical analyses were made by one-way analysis of variance (ANOVA) and Tukey test at 5% significance level. Results showed that the bond strength in control group (48.0MPa ± 4.0) was significantly higher than the Ti grade II (26.7MPa ± 4.1) and Ti grade V (25.2MPa ± 2.2) combinations. When Duceratin porcelain was applied in both substrates, Ti grade II and Ti grade V, the results were significantly lower than in Ti grade II/Vitatitankeramik. SEM analysis indicated a predominance of adhesive fractures for the groups Ti grade II and Ti grade V, and cohesive fracture for control group Pd-Ag/Duceram. Control group showed the best bond strength compared to the groups that employed LFC. Among LFC, the worst results were obtained when Duceratin porcelain was used in both substrates. SEM confirmed the results of three point bending strength.     

Shock absorbability of various restorative materials used on implants.

The purpose of this study was to compare, using an in vitro model, the stress absorbing ability of a microfilled composite resin and of a new low fusion ceramic (Duceram LFC) to that of gold alloy and conventional ceramic, when used as restorative materials in implant-supported prosthesis. Test crowns made of the tested materials were rigidly connected to a Br?nemark implant clone. The maximum amplitude of the force transmitted to the bone-implant interface, and the time to reach this amplitude were measured after applying a 100 N impact load on the occlusal surface. The gold alloy restorations transmitted the highest impact force in the shortest delay at the bone-implant interface. Microfilled composite resin Dentacolor, and low fusion ceramic Duceram LFC did not reduce the amplitude of the impact-force when compared to conventional ceramic. Nevertheless, the time to reach the maximum amplitude of this force was longer when using composite resin than when using ceramic, while Duceram LFC had no influence on this criteria.     

Evaluation of bond strength of metal brackets by a resin to ceramic surfaces

OBJECTIVE: The purpose of this study was to evaluate the bond strength of three different ceramic brands with two different ceramic surfaces (glazed and deglazed), with and without silane application. METHODOLOGY: Using the three different ceramics (Empress 2, Finesse, and Ceramco II), two metallic brackets were bonded to each sample, one with the adhesive system and the other one with a silane application. The samples were thermocycled, and then the debonding tests were performed with the Instron Universal Testing Machine. All the results were statistically analyzed with a three-way analysis of variance (ANOVA) test. RESULTS: The three-way ANOVA (brand, ceramic surface, with/without silane) indicated significant differences among them (p < 0.05). ANOVA showed that the greatest bond strength value (megapascals, MPa) was for Empress 2 deglazed with the silane application (8.873 MPa), followed by Finesse glazed with the silane application (7.072 MPa). CONCLUSION: The ceramic surface has a direct effect on adhesion. Therefore, Empress 2 deglazed achieved the greatest value in bond strength. To achieve the ideal values of 6-10 MPa, applying silane to the ceramic surface before bonding the brackets is recommended, even though silane can damage the ceramic surface.     

Evaluating The Fracture Toughness and Flexural Strength of Pressable Dental Ceramics: An In Vitro Study

The study was undertaken to evaluate the biaxial flexural strength, biaxial flexural strength after etching with 9 % HF acid and fracture toughness of three commonly used pressable all ceramic core materials. Ninety glass ceramic specimens were fabricated from three commercially available leucite based core ceramic material (1) Esthetic Empress, (2) Cergo, and (3) Performance Plus. Thirty discs of each material were divided into three groups of 10 discs each. Biaxial flexural strength (30 discs,) Biaxial flexural strength for samples treated with 9 % HF acid (30 discs) and fracture toughness (30 discs) were evaluated. Core material Performance Plus had the lowest biaxial strength of 124.89 MPa, Cergo had strength of 152.22 MPa and the highest value of 163.95 was reported for Esthetic Empress. For samples treated 9 % HF, Performance Plus had the lowest biaxial strength of 98.37 MPa, Cergo had strength of 117.42 MPa and the highest value of 143.74 was reported for Esthetic Empress. Core material Performance Plus had the lowest fracture toughness of 1.063 MPa, Cergo had strength of 1.112 MPa and the highest value of 1.225 was reported for Esthetic Empress. The results shows that Esthetic Empress had better mechanical properties compared to Cergo had Performance Plus in relation to the parameters tested.     

Tensile bond strength of two ceramic and three resin composite inlay materials placed using a resin luting agent.

The tensile bond strength of inlay materials to dentin was evaluated. Five materials, two direct resin composite inlay products, one hybrid resin composite, a preformed ceramic block, and a conventional porcelain material were bonded to bovine dentin and bonded together using a dual-polymerizing resin luting agent. Specimens were tested with and without thermocycling. Some bar-to-bar bonding groups fractured through the bar. Significantly higher (P < .05) bar-to-bar bonds were recorded than the bar-dentin bonds, irrespective of the inlay materials. VitaDur N showed the lowest bar-to-bar failure values (7.6 MPa) compared to the four other inlay materials (14.4 MPa to 22.2 MPa), but had the highest dentin bond strength (4.5 MPa). Unexpectedly, thermal loading increased the bond strength to bovine dentin, although this was only statistically significant for VitaDur N. The dentin bond strength of Charisma (1.4 MPa) was inferior (P < .02) to all other materials (2.6 MPa to 4.5 MPa) when thermocycled before testing.     

The Effect of a Bleaching System on Properties Related to Different Ceramic Surface Textures

Purpose: This study examined the effect of a manufacturer's proposed bleaching protocol on surface properties of a low‐fusing ceramic. Materials and Methods : Forty ultra low‐fusing ceramic samples (Ducera LFC) were constructed for this study. Half the discs were autoglazed, and the other half were overglazed. The two main groups (autoglaze, overglaze) were further divided into subgroups of four. Group I: autoglazed (control group I), bleached autoglaze, diamond polished, diamond polished and bleached. The same division was applied to Group II: overglazed (control group II), bleached overglazed, diamond polished, diamond polished and bleached. The total number of subgroups was eight. Control groups I and II (n = 10) were both immersed in distilled water, which was changed daily for 1 week. The other six subgroups (n = 30) were subjected to the following protocol: 2‐hour bleaching using carbamide peroxide 35%, followed by six 8‐hour bleaching applications using 15% carbamide peroxide gel. Every two bleaching procedures were interrupted by a 10‐hour fluoride gel application. At the end of each bleaching step, the treated specimens were washed under running water in readiness for the next application. Results: Bleaching did not significantly affect the surface roughness of the autoglazed group; however, it significantly increased the roughness of the overglazed ceramic, especially after polishing. Regarding whiteness, the overglazed group had significantly increased values compared to the autoglazed group. It appeared that bleaching whitened the overglazed specimens significantly, whereas polishing alone showed less whiteness. There appeared to be a strong inverse relation between the roughness and the whiteness of the autoglazed specimens as affected by the bleaching. On the other hand, a weak inverse relation was found between the roughness and whiteness of the overglazed specimens, as affected by the bleaching. Conclusions: In‐office bleaching with 35% carbamide peroxide, followed by home bleaching with 15% carbamide peroxide and a fluoride gel may affect the roughness and whiteness of overglazed and polished/overglazed Duceram LFC restorations. No significant change in roughness or whiteness was detected by this bleaching system on autoglazed Ducera LFC. Ceramic restorations should be protected before any bleaching for fear of altering their roughness and whiteness. Patients should be advised that their existing porcelain restorations may not match their natural teeth after bleaching.     

不同树脂水门汀和瓷表面处理对玻璃陶瓷粘结强度的影响

目的：评价4种不同的树脂水门汀以及2种不同的瓷表面处理方法对玻璃陶瓷粘结强度的影响。方法：选用IPse．Max Press热压铸瓷制作直径分别为5mm和4mm，高2mm的圆柱形瓷片。经打磨抛光后分为喇大组：（1）4％氢氟酸酸蚀40sec，（2）4％氢氟酸酸蚀40sec＋硅烷化处理1min。各组内分别选用VariolinkII，Multflink Sprint，RelyX Unicem，BisCem将大小瓷片成对粘固。再分别经37℃水储24h，以及水储后冷热循环5000次测定剪切强度，并用电镜观察瓷片表面形态。结果：硅烷化处理能明显提高粘结强度。经HF＋硅烷处理后Multflink Sprint（31．7±4．5MPa），BisCem（29．2±4．4MPa）和RelyX Unicem（28．1±5．5MPa）3组显示出较VafiolinkII（21．8±4．2MPa）高的粘结强度。冷热循环后除硅烷处理且用VariolinkII和RelyX Unicem粘固的实验组外，其余各组粘结强度均显著下降。结论：4种树脂水门汀与经HF和硅烷联合处理的玻璃陶瓷问能达到理想的粘结强度。     

Shear bond strength of microwaveable acrylic resin for denture repair

Microwaveable acrylic denture resins are believed to provide an effective means of repairing fractured dentures. This in vitro investigation compared the bond strength of a microwaveable acrylic resin as a denture repair material to two established auto-polymerized resins. Fifty-one specimens were made using Lucitone 199 as a simulated denture base, and were then divided into three groups of 17 samples each. Each test group was bonded with the following acrylic resins: Acron Mc, Rapid Repair and Palapress. A shear bond strength test was carried out 24 h after the samples were bonded. Fracture analysis showed that bond failure was adhesive for all groups. Shear bond values showed a statistically significant difference at P < 0.05 level between Acron Mc and Rapid Repair; Palapress and Rapid Repair, and indicated that Acron Mc and Palapress were superior to Rapid Repair as a repair material. However, there was no statistical difference found between Acron Mc and Palapress. Microwaveable acrylic resins produce repaired junctions of adequate strength.     

Intra-oral adhesive systems for ceramic repairs: a comparison

The aim of this investigation was to compare the bond strength of restorative composite resin to dental ceramic conditioned with primers and adhesives of various commercial repair kits. Three intra-oral ceramic repair systems--Silistor (Heraeus Kulzer), Cimara (Voco), Ceramic Repair (Vivadent)--were used on all-ceramic (IPS Empress 2, Ivoclar-Vivadent) substrate. Shear bond strength of restorative composite resin to substrate was tested after thermocycling and without thermocycling (n = 10). Substrate surfaces of the specimen after loading were examined microscopically (SEM). The highest bond strengths in both water-stored (7.0 +/- 5.7 MPa) and thermocycled conditions (2.5 +/- 1.8 MPa) were obtained with the Vivadent repair system, while the lowest values were observed with the Cimara system (0.6 +/- 1.4 MPa and 0.0 +/- 0.0 MPa, respectively). Shear bond strengths appeared to be significantly affected by thermocycling (ANOVA, P < 0.05). It is concluded that there are significant differences in the bond strengths of resin composites and ceramic substrate. The roughened surface does not necessarily provide a better bond strength; the bond strength of composite decreases with storage in water and after thermocycling. Bond strength values were generally low for all of the tested materials.     

Effect of Artificial Saliva Storage on Microhardness and Fracture Toughness of a Hydrothermal Glass-Ceramic

Purpose: This study evaluated the effect of artificial saliva storage on the hardness, crack length, and fracture toughness of a glazed, polished, and bleached hydrothermal low‐fusing glass‐ceramic (Duceram LFC). Materials and Methods: Forty ceramic discs were constructed. The discs were assigned to four groups (n = 10) according to their surface finish: Gp1—Autoglaze, Gp2—Autoglaze/ground/diamond‐polished, Gp3—Overglaze, Gp4—Overglaze/ground/diamond‐polished. Each group was further divided into two subgroups forming eight total subgroups (n = 5). Subgroup A was unbleached; Subgroup B was bleached. Testing was performed before and after 21 days of artificial saliva storage. Data were presented as means and standard deviation (SD). ANOVA was used, along with Duncan's post hoc test for pairwise comparison between the means when ANOVA test was found significant (p≤ 0.05). Results: Surface treatments such as glazing, polishing, and bleaching, saliva storage, and the interaction between these variables had a statistically significant effect on mean values of microhardness, crack length, and fracture toughness of the specimens. There was a statistically significant increase in microhardness and fracture toughness mean values, while crack length values decreased after saliva storage. Polished specimens recorded the smallest crack lengths and fracture toughness, and highest hardness values before and after saliva storage. No difference in fracture toughness values was evident between glazed and polished specimens. Mean crack lengths decreased after saliva storage in all the tested specimens. Hardness values increased after saliva storage. The autoglazed group showed significantly higher fracture toughness, lower crack length, and microhardness than the overglazed group. Conclusions: Surface finishing procedures and artificial saliva storage had a statistically significant effect on mean values of microhardness, crack length, and fracture toughness. This in vitro study suggests that fracture toughness of ceramics may be affected by different surface treatments such as glazing, polishing, bleaching, or a combination; however, in this study Duceram LFC proved its self‐healing property after 3‐week storage in artificial saliva.     

To Evaluate the Effect of Various Surface Treatments on the Shear Bond Strength of Three Different Intraoral Ceramic Repair Systems: An In Vitro Study

Fractures of metal-ceramic restoration pose an esthetic and functional dilemma both for patient and the dentist. Intraoral repair systems eliminate the remake and removal of restoration. Many intraoral repair materials and surface treatments are available to repair intraorally fractured metal-ceramic restoration. Bond strength data of various materials and specific technique used for repair are necessary for predicting the success of a given repair system. This study evaluated the shear bond strength of three different intraoral repair systems for metal-ceramic restorations applied on exposed metal and porcelain surface. One hundred and twenty metal discs (20 mm in diameter × 0.7 mm thick) were fabricated with nickel–chromium alloy (Mealloy, Dentsply, USA). Feldspathic porcelain (Duceram, Degudent, Germany) were applied over one test surface of the discs in the thickness of 1.8 mm followed by conventional firing. The defect, which simulates clinical failures were created in 1/4th area of the metal-ceramic discs. The metal-ceramic discs samples were divided into ceramic substrate (Group I, n = 60) and metal substrate (Group II, n = 60), according to the defect location. Then, samples of ceramic substrate (Group I) and metal substrate (Group II) were subdivided into A, B according to the surface treatments (A; roughening with diamond bur and B; abraded with 50 μ Al₂O₃) and repaired with one of the intraoral repair systems tested (a. Ceramic repair system, Ivoclar Vivadent; b. Clearfil repair system, Kurary, c; Porcelain repair system, 3 M ESPE). All the repaired samples were stored in distilled water at 37 °C for 24 h. After thermocycling at 6–60° C, all the samples were stored at 37 °C for additional 7 days. Shear bond strength of all the samples were calculated by using Universal testing machine. The mean shear bond strength values for the group I (A/B) were as follows: Ceramic repair system (9.47 ± 1.41/14.03 ± 2.54 MPa), Clearfil repair system (14.03 ± 2.32/14.64 ± 2.28 MPa), and Porcelain repair system (14.41 ± 3.96/14.86 ± 3.10 MPa). The mean shear bond strength values for the group II (A/B) were as follows: Ceramic repair system (9.42 ± 1.44/18.61 ± 2.60 MPa), Clearfil repair system (14.44 ± 3.23/14.98 ± 2.73 MPa), and Porcelain repair system (11.86 ± 2.24/13.24 ± 2.72 MPa). Air abrasion with 50 μm aluminum oxide particles is the preferred surface treatment. Porcelain repair system showed the highest shear bond with air abrasion for ceramic substrate and for metal substrate Ceramic repair system showed the highest bond strength with air abrasion as a surface treatment. This study suggest that the three repair systems tested are adequate for intraoral chairside repair of metal-ceramic restoration when air abrasion is used for surface treatment of the substrate (Ceramic repair system, Ivoclar Vivadent, Germany; Clearfil repair system, Kurary, Japan; Porcelain repair system, 3M ESPE, Germany).     

An Investigation into the Role of Core Porcelain Thickness and Lamination in Determining the Flexural Strength of In‐Ceram Dental Materials

Purpose: A biaxial flexure test was conducted to evaluate the effect of reducing the thickness of In‐Ceram core material and veneering with Vitadur α dentine porcelain on its flexural strength. Materials and Methods: Four groups of 10 discs were tested; group I discs were In‐Ceram discs with mean thickness of 1.58 ± 0.08 mm, group II discs were In‐Ceram discs with mean thickness of 1.0 ± 0.11 mm, group III discs were laminated In‐Ceram core porcelain/Vitadur α discs with a mean total thickness of 2.06 ± 0.15 mm and core porcelain thickness of 1.0 ± 0.11 mm; group IV discs were Vitadur α discs with a mean thickness of 2.08 ± 0.16 mm. Results: Mean flexural strength values decreased between groups: 436 ± 38 MPa for group I, 352 ± 30 MPa for group II, 237 ± 24 MPa for group III, and 77 ± 14 MPa for group IV. The result of ANOVA and Tukey tests indicated that the mean flexural strength of group II was significantly less than group I, indicating that thickness of the In‐Ceram core provides critical flexural strength to the final product. The addition of ≈ 1 mm of Vitadur α veneering porcelain to In‐Ceram core significantly (p= 0.05) reduced the flexural strength as compared to the nonveneered In‐Ceram core specimens (group II). The Vitadur α specimens (group IV) were significantly weaker than all the other groups. Conclusion: This study indicates that lamination should be avoided in areas where maximum strength is required for In‐Ceram all‐ceramic crowns and bridges.     

Ceramic (Feldspathic & IPS Empress II) vs. laboratory composite (Gradia) veneers; a comparison between their shear bond strength to enamel; an in vitro study

Summary Patient demand for aesthetic dentistry is steadily growing. Laminates and free metal restorations have evolved in an attempt to overcome the invasiveness nature of full veneer restorations. Although many different materials have been used for making these restorations, there is no single material that fits best for all purposes. Two groups of ceramic material (Feldspathic and IPS Empress II) and one group of laboratory composite (Gradia) discs (10 discs in each group; 4 mm in diameter and 2 mm in thickness) were prepared according to the manufacturer’s instruction. The surface of ceramic discs were etched and silanized. In Gradia group, liquid primer was applied on composite surfaces. Thirty freshly extracted sound human molars and premolars were randomly divided into three groups. The enamel surface of each tooth was slightly flattened (0·3 mm) on the buccal or lingual side and then primed and cemented to the prepared discs with the aid of a dental surveyor. The finishing specimens were thermocycled between 5 °C and 55 °C for 2500 cycles and then prepared for shear bond strength testing. The resulting data were analyzed by one‐way anova and Tukey HSD test. The fractured surfaces of each specimen were inspected by means of stereomicroscope and SEM. There is significant difference between the bond strength of materials tested. The mean bond strengths obtained with Feldspathic ceramic, IPS Empress II and Gradia were 33·10 ± 4·31 MPa, 26·04 ± 7·61 MPa and 14·42 ± 5·82 MPa, respectively. The fracture pattern was mainly mixed for ceramic groups. More scientific evidence needed for standardization of bonding protocols.     

Effects of Six Surface Treatment Methods on the Surface Roughness of a Low-Fusing and an Ultra Low-Fusing Feldspathic Ceramic Material

Purpose: The purpose of this in vitro study was to determine the effects of six surface treatment methods on the surface roughness of two feldspathic ceramic materials.
Materials and Methods: One hundred twenty metal discs were cast (Remanium CS). A low-fusing feldspathic ceramic (Vita Omega 900) was fired onto 60 metal discs, and an ultra low-fusing feldspathic ceramic (Finesse) was fired onto the other 60 metal discs. Six surface treatment methods were selected: (1) autoglazing (AUG), (2) overglazing (OVG), (3) polishing (POL), (4) fine diamond disc grinding + polishing + autoglazing (FDPA), (5) coarse diamond disc grinding + polishing + autoglazing (CDPA), (6) polishing + autoglazing (PA). Omega specimens were assigned to six experimental groups representing six surface treatment methods (Om-AUG, Om-OVG, Om-POL, Om-FDPA, Om-CDPA, Om-PA) (n = 10). Finesse specimens were also assigned to six experimental groups (Fn-AUG, Fn-OVG, Fn-POL, Fn-FDPA, Fn-CDPA, Fn-PA) (n = 10). Treated ceramic surfaces were examined by means of profilometry and transmission electron microscopy.
Results: In Omega groups mean roughness values ranged as follows: group Om-AUG = Om-POL > Om-OVG > Om-CDPA = Om-FDPA > Om-PA ( p < 0.001). No significant difference was found between groups Om-AUG/Om-POL and Om-CDPA/Om-FDPA ( p > 0.05). In Finesse groups mean roughness values ranged as follows: Fn-CDPA > Fn-FDPA = Fn-AUG = Fn-POL = Fn-OVG > Fn-PA ( p < 0.001). No significant difference was found between Fn-FDPA, Fn-AUG, Fn- POL and Fn-OVG ( p > 0.05).
Conclusions: For both ceramic types, the smoothest surfaces were obtained with polishing prior to autoglazing. Diamond disc grinding prior to polishing and autoglazing (Fn-FDPA, Fn-CDPA) displayed the roughest surfaces in ultra low-fusing ceramic (Finesse). Autoglazing alone and polishing displayed the roughest surfaces in low-fusing ceramic material (Om-AUG, Om-POL).     

Effect of water exposure on the fracture toughness and flexure strength of a dental glass.

OBJECTIVES: The low fusing dental glass (Duceram LFC) has been advertised as presenting a superior chemical resistance and augmented strength after 16h exposure to water or 4% acetic acid. The purpose of this study was to evaluate the effect of prolonged exposure to water on two mechanical properties (fracture toughness and flexure strength) of LFC. METHODS: Disks and bars were mirror polished and annealed prior to aging in: (1) air (control), (2) water for 24h at 80 degrees C and (3) water for 8 weeks at 80 degrees C. Fracture toughness (K(Ic)) was determined by indentation fracture (IF) and indentation strength (IS) using a 19.6N Vickers indentation load. Flexure strength values were obtained from three-point bending at 0.1mm/min. Statistical analysis was performed using the Weibull distribution, Tukey and Bartlett tests (P<0.05). RESULTS: Both techniques (IS and IF) showed a significant improvement in the K of Duceram LFC after 8 weeks in water (0.88 and 1.14MPa m(0.5)) as opposed to the 24-h values both in water and air (0.77-0.78MPa m(0.5)). However, for flexure strength the Weibull characteristic (S(0)) and the m parameter did not change significantly with water storage (S(0)=90-100MPa, Weibull m =7-8). SIGNIFICANCE: The increase in toughness of Duceram LFC after aging in water is an interesting and favorable observation for a restorative material exposed to the oral environment. Nevertheless, in comparison with other contemporary ceramics, the toughness of this LFC remains in the range of soda-lime-glass or classic feldspar porcelains.