Bonding strengths of porcelain repair systems with various surface treatments

Survival assessment of fractured porcelain-fused-to-metal crowns surface roughened by sandblasted and repaired by composite resin after in vitro thermal fatigue

Background/purpose

Intraoral repair usually takes the convenience of the patient's daily life as the starting point, taking into account the bonding strength, operational feasibility, and safety. This study aimed to evaluate the survival of composite resin by simulating cavity fracture repair in porcelain-fused-to-metal (PFM) crowns and referring to the G.V. Black classification of caries as ceramic- and metal-site exposure.

Materials and methods

Mechanical sandblast experimental and a nonsandblast control groups comprised 120 samples, and interfacial locking was enhanced through acid etching, bonding, and light-curing composite resin restoration. Classes of VI buccal (B), III mesial (M), and IV mesiobuccal (MB) types, were investigated. Load tests were performed on two sets, with one set at room temperature for 24 h and the other via thermal cycling at 5 °C/50 °C 720 times. Loading was gradually applied to the samples until a maximum of 450 N was reached.

Results

Results showed that 24 h survival rates of B-, M - , and MB-repaired PFM crowns were 88%, 84%, and 88%, respectively. The repaired PFM survival rates for B, M, and MB were 52%, 44%, and 28%, respectively, after thermal cycling and loading tests. Multiple logistic regression and chi-square test (α = 0.05) showed that the regression results of factors affecting survival assessment were only significant between groups after thermal fatigue (P < 0.05). Survival rate of repairing metal-site in the MB model was significantly higher than that of ceramic-sites repairing in non-blasted samples. For the MB cavity model, sandblasting can significantly improve the survival rate of the repair of ceramic parts in the MB model (P < 0.05).

Conclusion

Our results suggest that sandblasting can be further considered, especially for MB cavity fractures when ceramic-site restorations are required.

Do different protocols affect the success rate or bond strength of glass-ceramics repaired with composite resin? A systematic review and meta-analysis

STATEMENT OF PROBLEM

Intraoral repair techniques prevent unnecessary replacement of ceramic restorations, thereby increasing the survival rate. However, adhesion between ceramics and the composite resin is challenging and how different protocols influence adhesion is unclear.

PURPOSE

The purpose of this systematic review and meta-analysis was to analyze the influence of different protocols on repairing glass-ceramic surfaces with composite resins.

MATERIAL AND METHODS

PubMed, Scopus, ISI Web of Science, and Embase electronic databases were searched to select studies comparing bond strength values or survival rates of glass-ceramic repaired with composite resins using different surface treatment protocols. No publication year or language restriction was applied. Data sets were extracted from all included studies, and the mean differences calculated. A 95% confidence interval was calculated by using the random effect model (Rev Man 5.4).

RESULTS

The search identified 5037 studies, and 165 were assessed for eligibility. Finally, 123 in vitro studies were included in the systematic review and 48 in the meta-analysis. Considering different glass-ceramics, bond strength tests, and aged or not aged specimens, 37 meta-analyses found the effect of repair protocols: only adhesive, silane plus adhesive alone or preceded by hydrofluoric (HF) acid, airborne-particle abrasion (APA) with Al2O3 particles, silica-coated APA (SCAPA), diamond rotary instrument (DRI), and laser irradiation (LI).

CONCLUSIONS

For feldspathic porcelain, HF acid, APA, SCAPA, or DRI improved the repair micromechanical retention; applying silane is essential to HF-conditioned surfaces but the use of adhesive is optional when silane is applied. Results for leucite and lithium disilicate were inconclusive in terms of suggesting a treatment other than HF acid plus silane and adhesive applications.

Assessment of Intra-Oral Repair Systems for Veneered Zirconia and Zirconia Only

The aim of this study was to compare bond strength resin composites to porcelain laminate veneers in the indirect repair method to composite resins used in the direct repair method for cases of porcelain veneer fracture of zirconia-based fixed dental prostheses. In the study, the groups were formed with different percentages of areas to be repaired to mimic porcelain fractures in the mouth. The experimental group of veneered zirconia were as follows: Group A = 100% Zr surface; Group B = 70% Zr, 30% porcelain surface; Group C = 50% Zr, 50% porcelain surface; Group D = 30% Zr, 70% porcelain surface; Group E = 100% porcelain surface. The repairs of the specimens were made using composite resin systems in half of the groups and using porcelain laminate veneers in the other half. Specimens were embedded in acrylic blocks before surface treatments and repairs were applied. After surface conditioning, laminate veneers were applied to the first half of the groups, and composite repair systems were applied to the second half of the groups. After all specimens were aged by thermal cycling, their bond strength values were measured using a Universal Testing Machine, and the obtained data were recorded. The specimens were examined with a stereomicroscope and classified according to failure types (adhesive/cohesive/mixed). Bond strength values were evaluated based on independent-samples t-test statistics. According to the comparisons among the groups, the bond strength of the indirect repairs made with the laminate material was higher than the bond strength of the repairs made with the composite. There was a statistically significant difference in favor of the indirect repair groups among all groups except for Group C. The highest bond strength was found in Group A in the indirect repair method, while the lowest bond was found in the direct repair method in Group E. Adhesive failure was mostly seen in the groups that were repaired with the composite.

Comparison of feldspathic veneer surface treatments on ceramic bracket SBS, ARI and surface roughness after different debonding/polishing methods: An in vitro study

OBJECTIVES

To analyse, in vitro, surface properties and the shear bond strength after debonding and polishing procedures of ceramic brackets directly bonded to 0.3-0.5-mm thick feldspathic veneers.

MATERIALS AND METHODS

Fifty six feldspathic ceramic veneers samples (0.3 to 0.5-mm thick) were allocated into groups according to veneers surface treatment procedures: (S) glaze layer was retained; (SHF) hydrofluoric (HF) acid etch; (SOXA) Al2O3 sandblasting; and (SB) diamond burs roughening. Specimens were treated with silane Monobond N® and ceramic brackets bonded with Transbond XT^®. Shear bonding strength (SBS) was assessed with a universal testing machine and ARI evaluated under a stereomicroscopic coupled to a digital camera. Remaining bonding composite was removed using a porcelain polishing kit and surface roughness assessed with a stylus profilometer.

RESULTS

No statistically significant differences were identified for SBS among the study groups (S, SHF, SOXA and SB) (P>0.05). The majority of the specimens presented ARI scores 3 and 2 (P>0.05). All of the study groups presented increased surface roughness after debonding and polishing procedures (P<0.05), with significant greater values observed in SB group (RaF: 1.27±0.41; RzF: 6.23±1.82), (P<0.05).

CONCLUSIONS

Surface treatment with hydrofluoric acid etch, Al₂O₃ sandblasting and diamond bur did not enhance SBS of orthodontic brackets bonded to ceramic veneers. Ceramic surfaces treated with diamond burs presented significantly increased roughness after adhesive removal.

The Effect of Mechanical and Chemical Surface Preparation Methods on the Bond Strength in Repairing the Surface of Metal-Ceramic Crowns with Composite Resin: a Systematic Review and Meta-Analysis

The aim of this study was to find the most effective surface preparation methods to enhance the bond strength between the composite resin and surface remaining from ceramic fracture. In this systematic review and meta-analysis, 39 studies were examined. The information related to the studies was extracted and categorized based on the type of the substrate material and applying or not applying thermal cycles (p<0.05). In the meta-analysis of substrate metal-ceramic samples without aging, application of air abrasion resulted in a significant increase of the bond strength to composite resin when using chemical compounds of the group without the mentioned functional monomers. Application of mechanical and chemical surface preparation methods can result in enhanced bond strength of the composite to the substrate material, which depends on the type of substrate material.

Repair bond strength of composite resin to zirconia restorations after different thermal cycles

PURPOSE

This in vitro study investigated the repair bond strength of the zirconia ceramic after different aging conditions.

MATERIALS AND METHODS

In order to imitate the failure modes of veneered zirconia restorations, veneer ceramic, zirconia, and veneer ceramic-zirconia specimens were prepared and were divided into 4 subgroups as: control (37℃ distilled water for 24 hours ) and 3000, 6000, 12000 thermal cycling groups (n=15). Then, specimens were bonded to composite resin using a porcelain repair kit according to the manufacturer recommendation. The repair bond strength (RBS) test was performed using a universal testing machine (0.5 mm/min). Failure types were analyzed under a stereomicroscope. Two-way ANOVA and Bonferroni test were used for statistical analysis.

RESULTS

The RBS values of zirconia specimens were statistically significant and higher than veneer ceramic and veneer ceramic-zirconia specimens in control, 3000 and 6000 thermal cycling groups (P<.05). When 12000 thermal cycles were applied, the highest value was found in zirconia specimens but there was no statistically significant difference between veneer ceramic and veneer ceramic-zirconia specimens (P>.05). Veneer ceramic specimens exhibited cohesive failure types, zirconia specimens exhibited adhesive failure types, and veneer ceramic-zirconia specimens exhibited predominately mixed failure types.

CONCLUSION

Thermal cycling can adversely affect RBS of composite resin bınded to level of fractured zirconia ceramics.

Comparing two intraoral porcelain repair systems for shear bond strength in repaired cohesive and adhesive fractures, for porcelain-fused-to-metal restorations: An in vitro study

Aim

The objective of research was to evaluate the shear bond strength of two commercially available intraoral porcelain repair systems, Clearfil repair system (Kuraray) and P and R repair system (Shofu) for repairing cohesive and adhesive fracture in metal-ceramic restorations.

Settings and Design

In vivo - comparative study.

Materials and Methods

Ninety samples of Nickel-Chromium metal discs were fabricated. Each disc was veneered with 2 mm thickness of ceramic material using custom made metal jig. Samples were divided into control (Group I n = 10) and two test groups (Group II n = 40 and Group III n = 40). Adhesive and cohesive fractures were created in test group samples, Group II (Ceramic substrate or cohesive defect) and Group III (metal substrate or adhesive defect). The samples of ceramic substrate (Group II) and metal substrate (Group III) were further subdivided into A and B containing 20 samples each according to the repair material used (A; Clearfil porcelain repair system and B; P and R porcelain repair system). All specimens were subjected to a standard shear load in the UTM until fracture occurred. Data were analyzed using one-way analysis of variance and post hoc Bonferroni test.

Statistical Analysis used

One-way analysis of variance (ANOVA) and post hoc Bonferroni test.

Results

Clearfil repair system showed significantly higher shear bond strength value (29.16 Mpa) as compared to P and R repair system (27.23 Mpa) for cohesive fractures. Whereas if compared for repairing adhesive fractures P and R repair system had significantly higher shear bond strength values (26.59 Mpa) than Clearfil repair system (25.74 Mpa).

Conclusions

From the present study, it was be concluded that for cohesive fracture Clearfil repair system is a better material and for adhesive fractures P and R repair material gives better results.

Disilicate Dental Ceramic Surface Preparation by 1070 nm Fiber Laser: Thermal and Ultrastructural Analysis

Lithium disilicate dental ceramic bonding, realized by using different resins, is strictly dependent on micro-mechanical retention and chemical adhesion. The aim of this in vitro study was to investigate the capability of a 1070 nm fiber laser for their surface treatment. Samples were irradiated by a pulsed fiber laser at 1070 nm with different parameters (peak power of 5, 7.5 and 10 kW, repetition rate (RR) 20 kHz, speed of 10 and 50 mm/s, and total energy density from 1.3 to 27 kW/cm²) and the thermal elevation during the experiment was recorded by a fiber Bragg grating (FBG) temperature sensor. Subsequently, the surface modifications were analyzed by optical microscope, scanning electron microscope (SEM), and energy dispersive X-ray spectroscopy (EDS). With a peak power of 5 kW, RR of 20 kHz, and speed of 50 mm/s, the microscopic observation of the irradiated surface showed increased roughness with small areas of melting and carbonization. EDS analysis revealed that, with these parameters, there are no evident differences between laser-processed samples and controls. Thermal elevation during laser irradiation ranged between 5 °C and 9 °C. A 1070 nm fiber laser can be considered as a good device to increase the adhesion of lithium disilicate ceramics when optimum parameters are considered.

Effect of Silane Heat Treatment by Laser on the Bond Strength of a Repair Composite to Feldspathic Porcelain

PURPOSE

Ceramic restoration fracture may occur in the oral cavity. Intraoral repair of fractured porcelain could be advantageous to both patient and dentist. The aim of this study was to evaluate the effect of heat treatment of the silane coupling agent by Er:YAG and CO₂ lasers on the microshear bond strength of a repair composite to feldspathic porcelain.

MATERIALS AND METHODS

Sixty ceramic blocks were prepared and randomly divided into six groups (n = 10): (i) HF + silane (HS); (ii) silane + CO₂ laser (SC); (iii) CO₂ laser + silane (CS); (iv) silane + Er:YAG laser (SE); (v) Er:YAG laser + silane (ES); (vi) bur + HF + silane (BuHS). An adhesive resin was applied to the prepared ceramic surfaces and light-cured. Two transparent plastic tubes were placed perpendicularly to each ceramic block. The composite resin was then placed on the treated ceramic surface and light-cured for 40 seconds. The bonded blocks were stored in distilled water at 37°C for 24 hours and subjected to 3000 thermocycles. Microshear bond strength (μSBS) tests were performed using a wire and loop method. Data were analyzed using one-way ANOVA and Duncan's multiple range tests (p ≤ 0.05).

RESULTS

The comparison of the mean μSBS values showed no significant differences between the ES and HS groups (p = 0.914). On the other hand, the specimens in these groups exhibited significantly higher bond strengths than those in the other groups (p < 0.01). The mean μSBS of the BuHS group was statistically similar to that of CS and SE groups (p > 0.05). The μSBS for the SC group was significantly lower than that of the other groups (p < 0.01), with the exception of the CS group (p = 0.674).

CONCLUSIONS

Treatment with Er:YAG laser prior to silane application can be as effective as HF etching. Heat treatment of silane by CO₂ or Er:YAG lasers does not improve the bond strength between feldspathic porcelain and composite resin.

Effect of Surface Treatments on the Bond Strength to Turkom-Cera All-ceramic Material

AIM

The aim of this study was to evaluate the effect of surface treatments on shear bond strength (SBS) of Turkom-Cera (Turkom-Ceramic (M) Sdn. Bhd., Puchong, Malaysia) all-ceramic material cemented with resin cement Panavia-F (Kuraray Medical Inc., Okayama, Japan).

MATERIALS AND METHODS

Forty Turkom-Cera ceramic disks (10 mm × 3 mm) were prepared and randomly divided into four groups. The disks were wet ground to 1000-grit and subjected to four surface treatments: (1) No treatment (Control), (2) sandblasting, (3) silane application, and (4) sandblasting + silane. The four groups of 10 specimens each were bonded with Panavia-F resin cement according to manufacturer's recommendations. The SBS was determined using the universal testing machine (Instron) at 0.5 mm/min crosshead speed. Failure modes were recorded and a qualitative micromorphologic examination of different surface treatments was performed. The data were analyzed using the one-way analysis of variance (ANOVA) and Tukey honestly significant difference (HSD) tests.

RESULTS

The SBS of the control, sandblasting, silane, and sandblasting + silane groups were: 10.8 ± 1.5, 16.4 ± 3.4, 16.2 ± 2.5, and 19.1 ± 2.4 MPa respectively. According to the Tukey HSD test, only the mean SBS of the control group was significantly different from the other three groups. There was no significant difference between sandblasting, silane, and sandblasting + silane groups.

CONCLUSION

In this study, the three surface treatments used improved the bond strength of resin cement to Turkom-Cera disks.

CLINICAL SIGNIFICANCE

The surface treatments used in this study appeared to be suitable methods for the cementation of glass infiltrated all-ceramic restorations.

The effect of silane applied to glass ceramics on surface structure and bonding strength at different temperatures

PURPOSE

To evaluate the effect of various surface treatments on the surface structure and shear bond strength (SBS) of different ceramics.

MATERIALS AND METHODS

288 specimens (lithium-disilicate, leucite-reinforced, and glass infiltrated zirconia) were first divided into two groups according to the resin cement used, and were later divided into four groups according to the given surface treatments: G1 (hydrofluoric acid (HF)+silane), G2 (silane alone-no heat-treatment), G3 (silane alone-then dried with 60℃ heat-treatment), and G4 (silane alone-then dried with 100℃ heat-treatment). Two different adhesive luting systems were applied onto the ceramic discs in all groups. SBS (in MPa) was calculated from the failure load per bonded area (in N/mm²). Subsequently, one specimen from each group was prepared for SEM evaluation of the separated-resin–ceramic interface.

RESULTS

SBS values of G1 were significantly higher than those of the other groups in the lithium disilicate ceramic and leucite reinforced ceramic, and the SBS values of G4 and G1 were significantly higher than those of G2 and G3 in glass infiltrated zirconia. The three-way ANOVA revealed that the SBS values were significantly affected by the type of resin cement (P<.001). FIN ceramics had the highest rate of cohesive failure on the ceramic surfaces than other ceramic groups. AFM images showed that the surface treatment groups exhibited similar topographies, except the group treated with HF.

CONCLUSION

The heat treatment was not sufficient to achieve high SBS values as compared with HF acid etching. The surface topography of ceramics was affected by surface treatments.

An assessment of shear bond strength between ceramic repair systems and different ceramic infrastructures

The purpose of this study was to evaluate of shear bond strengths between two ceramic repair systems and different ceramic infrastructure materials. One hundred cylindrical specimens of ceramic infrastructure were fabricated with non precious metal alloy, zirconia, alumina, galvano, and glass ceramic: 20 non precious metal alloy (NP), 20 zirconia (Z), 20 alumina (A), 20 galvano (G), and 20 glass ceramic (GC). Specimens were divided into 2 subgroups. One half of the specimens were applied by Clearfil™ (CR) repair system and, another half of that were applied by Cimara&Cimara(®) Zircon (CZ) repair system. Bonded specimens were stored in 37°C distilled water for 24 h and were thermocycled at 5-55°C for 1,200 cycles with a 30-sec dwell time and 5-sec transfer time. Shear bond strengths were determined with a mechanical testing device. And mode of failure was recorded. Mann Whitney-U and Kruskal Wallis tests were applied to the data at 95% confidence interval level. Infrastructure groups displayed the following values in megapascals: NP = 10.70 ± 1.88; Z = 9.15 ± 0.80; A = 11.65 ± 0.70; GC = 10.95 ± 0.80; and G = 6.88 ± 0.88. The Mann Whitney-U test results showed no significant difference between the repair systems. The Kruskal Wallis test results demonstrated significant difference between the infrastructures. The lowest bond strength values were observed in G group. In conclusion, average bond strength values were in accordance with previously reported values, therefore it can be suggested that intraoral repair of ceramic restorations can be temporary, but a satisfying alternative for patients.

Comparison of shear bond strength of two porcelain repair systems after different surface treatment

Introduction:

Intraoral chair side porcelain repair system is a quick, painless and highly patient acceptable procedure, without removal of restoration or fabrication of new restoration. There are very limited studies conducted to evaluate the shear bond strength of repair systems after different surface treatment.

Objectives of Research:

The objective of research was to evaluate the shear bond strength of two intraoral porcelain repair systems Clearfil repair system (Kuraray) and Ceramic repair system (Ivoclar) to repair metal-ceramic restoration after three different surface treatment.

Materials and Methods:

Totally, 120 discs of base metal alloy were fabricated. The opaque, dentine and enamel of ceramic were applied to achieve the uniform thickness. Defect was created, and repair was done using two repair systems after different surface treatment. Shear bond strength was measured.

Results:

Analysis of variance was utilized. Ceramic repair system after 40% phosphoric acid surface treatment showed the highest mean value and Clearfil repair system after surface treatment with 37% phosphoric acid showed the lowest. The statistical difference was found to be significant between the groups.

Conclusion:

The shear bond strength of Ceramic repair system with 40% phosphoric acid etching showed highest shear bond strength as compared to other system and surface treatment used in the study.

A comparative evaluation of bond strength of feldspathic porcelain to nickel-chromium alloy, when subjected to various surface treatments: An in vitro study

Purpose of the Study:

The purpose was to evaluate the effect of various surface treatments and sandblasting with different particle size on the bond strength of feldspathic porcelain with predominantly base metal alloys, using a universal testing machine.

Materials and Methods:

Totally, 40 specimen of nickel-chromium alloy were prepared in an induction casting machine. The groups divided were as follows: Group I-sandblasted with 50 μ Al₂O₃, Group II-sandblasted with 110 μ Al₂O₃, Group III-sandblasted with 250 μ Al₂O₃ and Group IV-sandblasted with 250 μ Al₂O_3, followed by oxidation and again sandblasted with 250 μ Al₂O₃. The dimensions of each specimen were adjusted so as to maintain the thickness of ceramic at 1 mm. The specimen were loaded on the assembly of the universal testing machine, and a cross head speed of 0.5 mm/min was used to apply a compressive force at the junction of metal and feldspathic porcelain. The force application continued until adhesive fracture occurred, and the readings of the load applied to that particular specimen were recorded.

Results:

The means for shear bond strength for Group I, II, III and IV were found to be (226.92 ± 1.67), (233.16 ± 3.85), (337.81 ± 16.97) and (237.08 ± 4.33), respectively. Means of shear bond strength among the groups were compared using one-way analysis of variance test. Comparison between individual groups were made with Tukey's Honestly Significant Difference post-hoc test.

Conclusion:

Different particle size and surface treatment have an important role on the bond strength of ceramic-metal interface. Greater particle size demonstrated higher bond strength.

In vitro tensile strength of luting cements on metallic substrate

The aim of this study was to determine the tensile strength of crowns cemented on metallic substrate with four different types of luting agents. Twenty human maxillary molars with similar diameters were selected and prepared to receive metallic core castings (Cu-Al). After cementation and preparation the cores were measured and the area of crown's portion was calculated. The teeth were divided into four groups based on the luting agent used to cement the crowns: zinc phosphate cement; glass ionomer cement; resin cement Rely X; and resin cement Panavia F. The teeth with the crowns cemented were subjected to thermocycling and later to the tensile strength test using universal testing machine with a load cell of 200 kgf and a crosshead speed of 0.5 mm/min. The load required to dislodge the crowns was recorded and converted to MPa/mm(2). Data were subjected to Kruskal-Wallis analysis with a significance level of 1%. Panavia F showed significantly higher retention in core casts (3.067 MPa/mm(2)), when compared with the other cements. Rely X showed a mean retention value of 1.877 MPa/mm(2) and the zinc phosphate cement with 1.155 MPa/mm(2). Glass ionomer cement (0.884 MPa/mm(2)) exhibited the lowest tensile strength value. Crowns cemented with Panavia F on cast metallic posts and cores presented higher tensile strength. The glass ionomer cement showed the lowest tensile strength among all the cements studied.

Intraoral treatment of veneering porcelain chipping of fixed dental restorations: a review and clinical application

BACKGROUND

Every dental ceramic system can experience failure of the veneering porcelain. However, the increasing popularity of all-ceramic crowns and fixed dental prostheses (FDPs) seems to have led to an increasing need to repair chipped veneering porcelain.

OBJECTIVES

The authors compared different methods to repair fractured ceramic restorations (porcelain-fused-to-metal and all-ceramic) and explain the basic principles of adhesion in these systems. They also evaluated the frequency and causes of failure in dental ceramic systems.

METHODS

This review is based on the results of PubMed and Google Scholar searches, as well as on a hand search of the scientific literature, resulting in 300 articles from 1977 to 2012. The authors used multiple key words (ceramic, repair, bonding, hydrofluoric acid, air abrasion, silane, phosphates, silicon dioxide) and different strategies (connecting different key words with OR, NOR and AND and truncation of the stem of words) to search the databases.

RESULTS

Because of differences in the material composition of ceramic systems (composed of metal, alumina or zirconia, glass-ceramics and feldspathic ceramics), different treatments are required for the exposed material surfaces after chipping. Use of hydrofluoric acid etching, air abrasion, tribochemical coating, silanization and metal primers or zirconia primers seem to be the most successful conditioning methods for durable bonding and repair.

CONCLUSIONS AND CLINICAL IMPLICATIONS

Intraoral repair of a restoration offers a satisfying option for the patient when the restoration cannot be removed or replaced. Its success depends largely on the conditioning methods used for the fractured surfaces.

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).

Fracture strength of porcelain fused to metal crowns made of cast, milled or laser-sintered cobalt-chromium

AIMS

The aim was to compare the fracture strength of porcelain fused to metal crowns with copings fabricated in Co-Cr using different manufacturing techniques (casting, milling and laser-sintering) with crowns manufactured in a high-gold alloy.

METHODS

A total of 50 identical crowns were fabricated and sub-divided into five groups; cast Co-Cr, milled Co-Cr, two groups of laser-sintered Co-Cr and a control group cast in a high-gold alloy. After thermocycling (5000 cycles, 5-55°C) and pre-load (30-300 N, 10,000 cycles) the crowns were loaded until fracture. Load (N) and fracture mode were recorded.

RESULTS

There was a significant difference (p < 0.05) in fracture strength between the control group and one of the laser-sintered groups. The mean values (N) for the groups were as follows: cast Co-Cr, 1560 ± 274; milled Co-Cr, 1643 ± 153; laser-sintered Co-Cr 1, 1448 ± 168; laser-sintered Co-Cr 2, 1562 ± 72; control group, 1725 ± 220.

CONCLUSION

There is no difference in strength between Co-Cr crowns produced using the different production technologies: casting, milling or laser-sintering. Metal ceramic crowns made with copings fabricated in a high-gold alloy present numerically higher fracture strength than crowns made with copings fabricated in Co-Cr alloys. The difference is confirmed when analyzing the fracture surfaces, but the difference in fracture strength value is limited and is only significant with regard to one of the two laser-sintered groups.

Effect of four different surface treatments on shear bond strength of three porcelain repair systems: An in vitro study

Background:

Ceramic fracture in metal ceramic restorations are serious and pose an aesthetic and functional dilemma both for the patients and the dentist. This has created a demand for the development of practical repair options which do not necessitate the removal and remake of entire restorations.

Aim:

To evaluate and compare the effect of four different surface treatments on shear bond strength of metal ceramic specimens with three commercially available porcelain repair systems.

Materials and Methods:

Specimens were fabricated with a base-metal ceramic alloy and divided into three groups, to evaluate three porcelain repair systems. Each group was divided into four subgroups based on surface treatment (A) sandblasting, (B) sandblasting followed by etching with 9% HF (Hydrofluoric acid) on surrounding ceramic, (C) Use of a diamond bur on exposed metal followed by etching with 37% H₃PO₄ and (D) Control groups (D₁, D₂, D₃ for three groups of porcelain repair system which was not subjected to further treatment after finishing with 240 grit silicon carbide paper grinding. Shear bond strength of each group of specimens based on surface treatment were evaluated with a universal testing machine after storing in distilled water for 7 days. One way ANOVA and Tukey-HSD procedure were used to compare the mean values between and among the groups.

Results:

The mean shear bond strength of group III (10.402 ± 1.055) were significantly higher than group I (8.647 ± 0.990) and group II (8.099 ± 0.600) for all surface treatments. However the mean values of shear bond strength of sub-group A were significantly higher than sub-group C and D but were not significantly higher than sub-group B.

Conclusion:

The results of this study suggest that in fractured metal ceramic restorations the exposed metal surface treated with sandblasting or sandblasting and etching the surrounding ceramic surface with HF can increase the shear bond strength of the repaired metal ceramic area. Porcelain repair systems which contain hybrid composites and 4-META as primer had increased bond strength.

Addition of a pontic to all-ceramic Turkom-Cera fixed partial denture restorations

High-strength all-ceramic materials are commonly used in dentistry. When complications occur in an all-ceramic restoration, the restoration is usually replaced. This article describes the time-saving ability and cost-effectiveness of this novel technique for the addition of a pontic in two complicated clinical cases. Turkom-Cera^™ [Turkom-Ceramic (M) Sdn. Bhd.] with aluminum oxide (99.98%) is an all-ceramic system that offers the option of addition of a new pontic to the sintered framework. The new pontic was cut off from an alumina blank [Turkom-Ceramic (M) Sdn. Bhd.], moistened, and attached to the framework using alumina gel [Turkom-Ceramic (M) Sdn. Bhd.]. The framework was veneered with veneering porcelain (Vita VM 7; VITA Zahnfabrik). The two cases presented here involving the addition of a pontic to sintered framework were followed up for at least 1 year. No complication was detected or reported by the patients. Alumina- and zirconia-based ceramics are particularly suitable for for all-ceramic restorations in high-stress bearing areas. However, replacement of a failed all-ceramic restoration is not the most practical solution, considering both cost and tooth-related factors. This attractive feature of the Turkom-Cera allows the repair of a fractured ceramic coping or the addition of a new pontic to restorations.

Influence of different power outputs of intraoral Nd:YAG laser on shear bond strength of a resin cement to nickel-chromium dental alloy

Up to now, there is no any experience about the application of dental lasers to bond resin composites to metal surfaces in dentistry. The aim of this preliminary study was to evaluate if the laser irradiation of ceramic-covered alloy surface would improve the bond strength of resin to metal, and if different parameters of laser output may influence the strength of this bond. Fifty three cylinders (thickness of 5 mm and diameter of 10 mm) were made up of a commercially available nickel-chromium alloy by lost-wax technique. Forty prepared specimens were divided into four groups. Five specimens in each group were covered by slurry of dental opaque porcelain and irradiated by Nd:YAG laser using different output parameters for each group. Other five specimens in each group were treated using the same laser parameters without porcelain covering. Five sandblasted specimen served as control group. Panavia F2.0 was bonded on the metal surfaces using polyethylene tubes. In ceramic-coated specimens, silane was applied to achieve chemical bond between silica particles and resin cement. All specimens were thermocycled and subjected to shear bond strength (SBS) test (50 kgf at 0.5 mm/min). Two specimens of each ceramic-coated laser-treated groups were studied using scanning electron microscopy and wavelength dispersive X-ray spectroscopy which showed stabilization of silica particles on the metal surface. ANOVA procedure showed that although shear bond strength was significantly higher in porcelain-covered laser treated samples, but the effect of power output of laser irradiation was not significant (P = 0.917). There were no statistically significant difference between SBS in control samples and laser treated specimens without porcelain covering. It can be concluded that Nd:YAG laser surface treatment may improve the silica coating of alloy surface to achieve better resin-metal bond.

Adhesion of Resin Composite to Hydrofluoric Acid-exposed Enamel and Dentin in Repair Protocols

Intraoral repairs of ceramic fixed-dental-prostheses (FDP) often include cervical recessions that require pretreatment of the exposed tooth surfaces either before or after the ceramic is conditioned with hydrofluoric (HF) acid gel. The sequence of repair protocol may cross-contaminate the exposed etched enamel or dentin surfaces during the application or rinsing process and thereby affect the adhesion. This study evaluated the influence of HF acid gel with two concentrations on bond strengths of composite to enamel and dentin. Human third molars (N=100, n=10 per group) with similar sizes were selected and randomly divided into 10 groups. Flat surfaces of enamel and dentin were created by wet ground finishing. Before or after the enamel (E) or dentin (D) was conditioned with phosphoric acid (P), substrate surfaces were conditioned with either 9.5% HF (HF9.5) or 5% HF (HF5). Subsequently, a bonding agent (B) was applied. The experimental groups by conditioning sequence were as follows where the first letter of the group abbreviation represents the substrate (E or D) followed by the acid type and concentration: group 1 (EPHF9.5), group 2 (EPHF5), group 3 (EHF9.5P), group 4 (EHF5P), group 5 (DPHF9.5), group 6 (DPHF5), group 7 (DHF9.5P), and group 8 (DHF5P). Group 9 (EPB) and group 10 (DPB) acted as the control groups. Repair resin was adhered incrementally onto the conditioned enamel and dentin in polyethylene molds. Each layer was photo-polymerized for 40 seconds. All specimens were thermocycled (×1000, 5°-55°C) and subjected to shear test (universal testing machine, 1 mm/min). Specimens that debonded during thermocycling were considered as 0 MPa. The bond strength data were analyzed using Kruskal-Wallis test and failure types using the chi-square test (α=0.05). Overall, the bond results (MPa) were lower on dentin than on enamel (p&lt;0.01). EPB (25.6 ± 6.6) and DPB (20.2 ± 4.9) control groups showed significantly higher results than those of other groups (p&lt;0.05). While higher mean bond strengths were obtained in group 1 (EPHF9.5) (11.5 ± 2.1) and group 2 (EPHF5) (7.3 ± 0.6), lower results were obtained when HF acid gels were applied prior to phosphoric acid (EHF9.5P: 5.0 ± 1.1, EHF5P: 3.6 ± 0.1) (p&lt;0.05). On dentin, the results were the lowest in group 8 (DHF5P: 1.5 ± 1.6), being significantly lower than those of group 5 (DPHF9.5) (p&lt;0.05). Scanning electron microscope (SEM) images revealed predominantly mixed failures with less than half of the composite left on both enamel and dentin surfaces (64 out of 80) (p&lt;0.05), indicating that in general, adhesion was not ideal. Contamination of the enamel or dentin surfaces with HF acid gel impairs the bond strength of composites. Considering both the bond strength results and failure types, when dental tissues are to be repaired next to ceramic, application of phosphoric acid before HF acid gel application can be recommended. HF acid gel concentration did not influence the results except on enamel.

Bond strength comparison of amalgam repair protocols using resin composite in situations with and without dentin exposure

The replacement of defective amalgam restorations leads to loss of tooth material and weakens the tooth, creating an increased risk of cusp fracture. The repair of such defects is a minimal intervention technique. The current study compared the repair bond strengths of a resin composite to amalgam and an amalgam-dentin complex after various surface conditioning methods. The specimens (N = 50) consisted of sound human canines with cylindrical preparations (diameter: 2.3 mm, depth: 3 mm) with amalgam-dentin complex (N = 30, n = 10/per group) and two groups with amalgam only (N = 20, n = 10/per group). The teeth were embedded in auto-polymerized polymethylmethacrylate (PMMA). The preparations were filled with non-Gamma 2 amalgam. The enamel was removed to expose dentin. The specimens with the amalgam-dentin complex were randomly assigned to one of the following conditioning methods: Group 1: Silicacoating amalgam, etching dentin, silane application on amalgam, primer/bonding on dentin, opaquer on amalgam, resin composite on both; Group 2: Etching dentin, silicacoating amalgam, silane application on amalgam, primer/bonding on dentin, opaquer on amalgam, resin composite on both and Group 3: Etching dentin, primer/bonding on dentin, opaquer, resin composite. The specimens with only amalgam were assigned to one of the following conditioning methods: Group 4: Silicacoating, silane application, opaquer, resin composite and Group 5: Opaquer, resin composite. For the two control groups, where no dentin was involved (Groups 4 and 5), bonding was achieved only on amalgam and Group 5 had no conditioning. The specimens were kept in water at 37 degrees C for five weeks before bond strength (MPa +/- SD) testing (Universal Testing Machine). After debonding, the failure types were analyzed. The results were significantly affected by the surface conditioning method (ANOVA). Only dentin conditioning (Group 3) showed the highest bond strength (39.9 +/- 14). The unconditioned control group (Group 5) showed the least favorable results (1.4 +/- 0.5). Multiple comparisons (Tukey-Kramer adjustment) showed that the mean values of Group 1 (34.1 +/- 11.4), 3 (39.9 +/- 14) and 4 (35.5 +/- 4) were not significantly different (p > 0.05), but between Groups 2 (22.8 +/- 6.6) and 3 (39.9 +/- 14), significant differences were observed (p = 0.0027). For reliable repair of amalgam restorations, including dentin fractures, the amalgam surface should first be silica coated, then the dentin/enamel should be etched, washed and rinsed thoroughly. Finally, the amalgam should be silanized and primer/bonding applied onto the dentin.

Microtensile bond strength of resin cement to a feldspathic ceramic

OBJECTIVE

The purpose of this study was to evaluate the microtensile bond strength of resin cement to a feldspathic ceramic after treating the surface with (a) hydrofluoric (HF) acid, (b) air abrasion, (c) Er:YAG laser irradiation, (d) Nd:YAG laser irradiation, and (e) HF acid etching after either air abrasion or laser irradiation.

BACKGROUND DATA

It is unknown whether the laser application or its combination with another treatment method can be used as a tool to roughen the surface of a feldspathic ceramic in order to increase the bond strength between the resin cement and ceramic surface.

MATERIALS AND METHODS

Forty feldspathic ceramic blocks (Ceramco(TM)) were prepared and divided into eight equal groups (n = 5) according to the following surface treatments: no treatment; etching with 9.5% HF acid; air abrasion with 50 μm Al(2)O(3); Er:YAG laser irradiation; Nd:YAG laser irradiation; air abrasion plus acid etching; Er:YAG laser plus acid etching; and Nd:YAG laser plus acid etching. After surface treatment, a silane-coupling agent and resin cement (Panavia F(TM)) were applied to each block. After storing for 24 h at 37°C and thermocycling between 5°C and 55°C for 1000 cycles, the microtensile bond strength of each specimen was measured.

RESULTS

The highest bond strength was obtained from HF acid etching. HF acid etching after each laser irradiation significantly increased the bond strength (p < 0.05). However, HF acid etching after air abrasion decreased bond strength when compared to air abrasion alone.

CONCLUSIONS

HF acid etching is the most effective surface treatment method for a feldspathic ceramic. However, laser irradiation with either the Er:YAG or Nd:YAG laser is not an adequate method for improving the bond strength of Panavia F. The laser application should be combined with HF acid etching.

Effect of filler ratio in adhesive systems on the shear bond strength of resin composite to porcelains

This in vitro study evaluated the effect of six different adhesive systems on the shear bond strength of resin composite to feldspathic and low-fusing porcelains. Sixty porcelain blocks were prepared for each low-fusing (Matchmaker) and feldspathic (MVK95) porcelain specimen. After surface preparation, the porcelain specimens were divided into six groups (n = 10) for different adhesive systems (Adper Prompt L-Pop, QuadrantUnil Bond, Te-Econom, PQ1, One-StepPlus and Prime&Bond NT). After adhesive application, a universal resin composite (FiltekZ250) was condensed on the specimens. The prepared specimens were then stored in distilled water at 37 degrees C for 24 hours, then all the samples were thermal cycled 1000 times between 5 degrees C and 55 degrees C. Shear testing was performed on a universal test machine using a crosshead speed of 0.5 mm/minute. The statistical analysis of the bond strength data included two-way ANOVA. Then, the means were compared by Tukey HSD test (alpha = 0.05). The lowest bond strength was observed in Adper Prompt L-Pop. No statistically significant difference was observed between One-Step Plus and Prime&Bond NT. The highest bond strength was observed in PQ1. When low-fusing or feldspathic porcelain restorations are repaired with resin composite, self-etching adhesive systems may not be indicated. If maximum bond strength is the goal in porcelain resin bonding, adhesive systems that have a high filler ratio should be used.

Ceramic restoration repair: report of two cases

The esthetic and functional rehabilitation of patients with multiple missing teeth can be performed with several techniques and materials. Ceramic restorations provide reliable masticatory function and good esthetics. However, fracture can occur in some cases due to their brittle behavior. In some cases, the replacement of an extensive prosthesis is a problem due to the high treatment cost. In this paper, two cases are presented, in which fractures occurred in extensive metal-ceramic fixed partial dentures, and their replacement was not possible. Ceramic repair was chosen and the sequences of treatment with and without presence of the ceramic fragment are also discussed. The cases illustrate that, in some situations, fractured metal-ceramic partial dentures can be successfully repaired when prosthetic replacement is not a choice. Prosthodontists must use alternatives that allow a reliable repair to extensive metal-ceramic fixed partial dentures. Surface preparation of the ceramic with hydrofluoric acid in conjunction with a silane coupling agent is essential for a predictable bonding of composite resin. The repair performed with composite resin is an esthetic and functional alternative when extensive fixed partial dentures cannot be replaced.

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 degrees C for 1 day and then thermocycled 1000 times between 5 degrees C and 55 degrees 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.

Repairing Ceramic Restorations: Final Solution or Alternative Procedure?

This article provides an overview of dental ceramics. It addresses possible modes of failure and factors that may influence the decision to either repair or replace ceramic restorations. The authors' intention was to present ceramic repair as a reliable, low-cost, low-risk technique.

Orthodontic bonding to several ceramic surfaces: are there acceptable alternatives to conventional methods?

INTRODUCTION

The objectives of this study were to determine the effects of various surface conditioning methods on 3 types of ceramic materials (feldsphatic, leucite-based, and lithia disilicate-based) in orthodontic bonding.

METHODS

A total of 210 ceramic disk samples were fabricated and divided into 3 groups. In each group, 5 subgroups were prepared by sandblasting; sandblasting and hydrofluoric (HF) acid; sandblasting and silane; sandblasting, HF acid, and silane; and tribochemical silica coating and silane. Mandibular incisor brackets were bonded with light-cured adhesive. The samples were stored in water for 24 hours at 37 degrees C and then thermocycled. Shear bond tests were performed, and the failure types were classified with adhesive remnant index scores.

RESULTS

In all 3 ceramic groups, the lowest shear bond strength values were found in the sandblasted-only samples. For the feldspathic and lithia disilicate-based ceramic, the highest bond strength values were obtained with silica coating (15.2 and 13.2 MPa, respectively). For the leucite-based ceramic, HF without silane produced the highest bond strength value (14.7 MPa), but comparable values were obtained with silicatization also (13.4 MPa).

CONCLUSIONS

The silica-coating technique could replace the other conditioning techniques in bonding brackets to ceramic. However, debonding must be done carefully because of the risk of porcelain fracture.

Effect of Feldspathic Ceramic Surface Treatments on Bond Strength to Resin Cement

OBJECTIVE

The objective of this study was to evaluate the shear bond strength of resin cement to feldspathic ceramic with various surface treatments.

BACKGROUND DATA

Application of adhesive techniques is well established in restorative dentistry, yet the influence of surface treatments on the bond strength of resin cement to ceramic materials prior to luting or repair procedures remains unclear.

METHODS

One hundred samples made of a feldspathic ceramic were divided into 10 groups (n = 10): (1) control (no treatment); (2) 10% hydrofluoric acid (HF); (3) 37% phosphoric acid (H(3)PO(4)); (4) 1.23% acidulated phosphate fluoride acid (APF); (5) diamond bur; (6) air abrasion with Al(2)O(3); (7) Al(2)O(3) + HF; (8) CoJet-Sand; (9) Er:YAG laser, and (10) Al(2)O(3) + Er:YAG laser. Afterwards, silane was applied and a resin cement cylinder was built. After 24 hours at 37 degrees C, the prepared specimens were submitted to a shear bond strength test and stereoscopic evaluation to determine the type of failure after rupture.

RESULTS

Bond strength means were statistically different for the different surface treatments. The highest bond strengths were obtained with HF, CoJet-Sand, and Al(2)O(3). The groups treated with Al(2)O(3) + Er:YAG laser, diamond bur, and Al(2)O(3) + HF had moderate bond strengths. The lowest bond strengths were obtained with H(3)PO(4), APF, Er:YAG laser, and the control group.

CONCLUSIONS

The HF, CoJet-Sand, and Al(2)O(3) techniques were the most effective surface treatments. The null surface treatment proposed with the Er:YAG laser showed low bond strength, and seems to be inadequate for clinical use with the parameters tested.

The effect of sandblasting on adhesion of a dual-cured resin composite to methacrylic fiber posts: Microtensile bond strength and SEM evaluation

OBJECTIVES

To evaluate the influence of different surface treatments on the microtensile bond strength of a dual-cured resin composite to fiber posts.

METHODS

Thirty-two glass methacrylate-based fiber posts (GC Corp.) were used in the study. Posts were divided into two groups, according to the surface pretreatment performed. Group 1: sandblasting (Rocatec-Pre, 3M ESPE). Group 2: no pretreatment. In each of the two groups posts received three types of additional "chair-side" treatments. (1) Silane application (Monobond S, Ivoclar Vivadent); (2) adhesive application (Unifil Core self-etching bond, GC); (3) no treatment was performed. A dual-cured resin composite (Unifil Core, GC) was applied on the posts to produce cylindrical specimens. Specimens were cut to obtain microtensile sticks that were loaded in tension at a cross-head speed of 0.5mm/min until failure. The morphology of the post/composite interface and the post surface morphology were evaluated under SEM. Statistical analysis was performed with two-way ANOVA and Tukey test for post hoc comparisons (p<0.05).

RESULTS

Post surface pretreatment did not prove to be a significant factor in post-composite bond strength (p=0.08), whereas "chair-side" treatment modalities and the interaction between pretreatment and treatment showed a significant influence on bond strength (p<0.001). When no "chair-side" treatment was performed, bond strength was significantly higher on sandblasted posts. Additional adhesive application resulted in significantly lower bond strength on sandblasted posts. When no pretreatment was performed, silane application resulted in higher bond strength than adhesive application.

CONCLUSIONS

Sandblasting may give an increase in microtensile strength to methacrylate-based glass fiber posts, eliminating the need for additional "chair-side" treatments. Reducing the number of clinical steps could contribute to simplify the clinical procedures.

Long-term bond between dual-polymerizing cementing agents and human hard dental tissue

OBJECTIVES

To examine the long-term adhesion of seven dual-polymerizing cementing agents to human dentin in vitro.

METHODS

Two hundred and eighty extracted non-carious human molars were ground flat to expose dentin surfaces. The bond strengths of cementing agents with their respective bonding systems were examined: one compomer cement (PermaCem), five resin cements (RelyX ARC, Panavia F, Variolink II, Nexus 2, Calibra) and one self-adhesive universal resin cement (RelyX Unicem). One subgroup (n=10) was tested after 150 days of storage in water at 37 degrees C (time t(1)), the other subgroup (n=10) was tested after 150 days of storage plus 37,500 thermal cycles (time t(2)). All specimens were stressed in shear at a constant crosshead speed of 0.5mm/min until failure. Statistical analysis was performed by ANOVA, taking effect interactions into account. The Tukey method was used for multiple paired comparisons (alpha=0.05).

RESULTS

The three-way ANOVA (cementing agents, polymerization methods, times of measurements) showed Variolink II to have the highest strength at 9.9+/-4.5MPa. Values were slightly higher at t(1) (5.9+/-4.7MPa) than at t(2) (4.9+/-4.2MPa) (p=0.0044). Polymerization with light activation (6.5+/-5.1MPa) yielded higher strengths than polymerization without (4.3+/-3.3MPa) (p<0.0001). Separate two-way ANOVAs for t(1) and t(2) showed that the two main effects (cementing agent, polymerization method) and their interactions differed significantly.

SIGNIFICANCE

Cementing agents/adhesive systems and the polymerization method influence the long-term bond to hard dental tissues.

Shear bond strength of metal-ceramic repair systems

STATEMENT OF PROBLEM

When clinical fractures of the ceramic veneer on metal-ceramic prostheses can be repaired, the need for remake may be eliminated or postponed. Many different ceramic repair materials are available, and bond strength data are necessary for predicting the success of a given repair system.

PURPOSE

This study evaluated the shear bond strength of different repair systems for metal-ceramic restorations applied on metal and porcelain.

MATERIAL AND METHODS

Fifty cylindrical specimens (9 x 3 mm) were fabricated in a nickel-chromium alloy (Vera Bond II) and 50 in feldspathic porcelain (Noritake). Metal (M) and porcelain (P) specimens were embedded in a polyvinyl chloride (PVC) ring and received 1 of the following bonding and resin composite repair systems (n=10): Clearfil SE Bond/Clearfil AP-X (CL), Bistite II DC/Palfique (BT), CoJet Sand/Z100 (CJ), Scotchbond Multipurpose Plus/Z100 (SB) (control group), or CoJet Sand plus Scotchbond Multipurpose Plus/Z100 (CJSB). The specimens were stored in distilled water for 24 hours at 37 degrees C, thermal cycled (1000 cycles at 5 degrees C to 55 degrees C), and stored at 37 degrees C for 8 days. Shear bond tests between the metal or ceramic specimens and repair systems were performed in a mechanical testing machine with a crosshead speed of 0.5 mm/min. Mean shear bond strength values (MPa) were submitted to 1-way ANOVA and Tukey honestly significant difference tests (alpha=.05). Each specimen was examined under a stereoscopic lens with x30 magnification, and mode of failure was classified as adhesive, cohesive, or a combination.

RESULTS

On metal, the mean shear bond strength values for the groups were as follows: MCL, 18.40 +/- 2.88(b); MBT, 8.57 +/- 1.00(d); MCJ, 25.24 +/- 3.46(a); MSB, 16.26 +/- 3.09(bc); and MCJSB, 13.11 +/- 1.24(c). On porcelain, the mean shear bond strength values of each group were as follows: PCL, 16.91 +/- 2.22(b); PBT, 18.04 +/- 3.23(ab); PCJ, 19.54 +/- 3.77(ab); PSB, 21.05 +/- 3.22(a); and PCJSB, 16.18 +/- 1.71(b). Within each substrate, identical superscript letters denote no significant differences among groups.

CONCLUSIONS

The bond strength for the metal substrate was significantly higher using the CJ system. For porcelain, SB, CJ, and BT systems showed the highest shear bond strength values, and only SB was significantly different compared to CL and CJSB (P<.05).

CLINICAL IMPLICATIONS

This study suggests that when fracture involves only feldspathic porcelain, any of the evaluated systems may be used, since the fracture occurred on the porcelain substrate and not on the bond interface of porcelain-restorative material. However, for the nickel-chromium alloy tested, the CoJet Sand system showed the best results for repair.

An indirect repair technique for fractured metal-ceramic restorations: a clinical report

Metal-ceramic crowns and fixed partial dentures have the potential for fracture of the ceramic veneer. Fractured porcelain poses a serious cosmetic and clinical problem. It may be desirable to repair a broken retainer of a fixed prosthesis rather than to remove the prosthesis and risk the possibility of destroying the entire restoration or damaging the abutment teeth. This article presents an indirect method that may be used to repair metal-ceramic restorations that are otherwise clinically and radiographically acceptable. With this technique, a new metal-ceramic crown is fabricated and is cemented on the prepared fractured retainer of the prosthesis.

Effect of flame cleaning of ceramic surface on the bond strength of composite to ceramic

This study tested the hypothesis that flame cleaning of ceramic surface would increase the bond strength of composite to ceramic than pressure-vaporized steam cleaning. Eris and IPS-Empress ceramic blocks were fabricated, polished (control), airborne-particle abraded with 50-microm alumina particle (A), etched with 5% hydrofluoric acid gel for 2 min (E), or treated with a combination of A and E (AE). They were subjected to either steam cleaning for 20 s or flame cleaning over a gas burner for 2 s. Followed by an application of an adhesive resin, a composite was built-up. Twenty micro-tensile test specimens (approximately 0.9 x 0.9 x 16 mm) were obtained from each group and loaded to failure under tensile force using a universal testing machine at a crosshead speed of 0.5 mm min(-1). anova showed statistically significant differences in the mean bond strength by ceramic, surface roughness, and cleaning method (P < 0.0001). The groupings of the mean bond strength were as follows: flame-cleaned > steam-cleaned; IPS-Empress > Eris; and AE > E > A for IPS-Empress and AE > E approximately A for Eris (Duncan's multiple analysis; alpha = 0.05). This in vitro study suggests that mechanical bond of composite to ceramic can be improved with flame cleaning of ceramic surface.

Evaluation of shear bond strength of composite to porcelain according to surface treatment

This study evaluated the shear bond strength of porcelain/composite using 40 metal + porcelain + composite cylindrical specimens divided into 4 groups, according to porcelain surface treatment: 1) no treatment, 2) mechanical retentions performed with diamond burs, 3) etching with phosphoric acid+silane, and 4) etching with hydrofluoric acid+silane. After being stored in distilled water at room temperature for one week, the specimens were submitted to a shear force (load) and the data were analyzed statistically (ANOVA). The means (in Mpa) of the groups were: 4.71 (group 1); 4.81 (group 2); 11.76 (group 3); 11.07 (group 4). There were no statistically significant differences between groups 1 and 2 and between groups 3 and 4.

Effect of surface topography on the bond strength of a composite to three different types of ceramic

STATEMENT OF PROBLEM

Mechanical retention based on the surface topography is critical for the success of chairside repair of chipped or fractured ceramic prostheses with a composite.

PURPOSE

The purpose of this study was to investigate whether the tensile bond strength of a composite to 3 dental ceramics was affected by surface roughening procedures on the ceramics.

MATERIAL AND METHODS

Three ceramics, Eris (ERV), Empress 1 (E1C), and an experimental ceramic (EXC), were used to fabricate 12 rectangular blocks (5 x 5 x 10 mm). After polishing with a series of SiC papers (120 through 1200 grit size), 4 surfaces were created on each ceramic as follows: 1) as-polished (P); 2) airborne-particle abraded with 50 microm Al(2)O(3) (A); 3) etching with 5% hydrofluoric acid gel (E); and 4) a combination of airborne particle abrasion and etching (A/E). An adhesive (Heliobond) was applied on the roughened ceramic surface and a composite (Tetric Ceram) was built-up incrementally. Twelve groups of different ceramic/surface treatment combinations were prepared. Twenty ceramic/composite specimens per group (0.9 x 0.9 x 20 mm) were obtained from each block with a slow speed diamond saw. Each specimen was subjected to a tensile force at a crosshead speed of 0.5 mm/min using a universal testing machine until failure. The mode of failure was determined by scanning electron microscopy. ANOVA and Duncan's multiple range test (alpha=.05) were used to analyze the bond strength values.

RESULTS

Specimens of all as-polished groups and EXC(A) group separated during sectioning. The mean bond strength values (SDs) in MPa for the remaining groups were as follows: ERV(A): 2.6 (0.8); E1C(A): 2.8 (1.1); ERV(E): 3.1 (1.3); ERV(A/E): 9.3 (1.3); E1C(E): 10.5 (1.5); E1C(A/E):13.5 (3.3); EXC(E): 19.2 (4.7); and EXC(A/E): 23.1 (5.4). ANOVA showed statistically significant differences in the bond strength for both ceramics (P<.0001) and surface treatments (P<.0001). Duncan's analysis yielded following statistical subsets of the bond strength values: EXC > E1C > ERV by ceramic; A/E > E > A by surface treatment. The mode of failure was a combination of adhesive and cohesive failures.

CONCLUSION

The tensile bond strength of a composite to ceramic was significantly different depending on the surface topography of ceramic. Among the surfaces investigated, combined surface roughness was the most effective surface topography in terms of the bond strength increase.

Evaluation of alternative intra-oral repair techniques for fractured ceramic-fused-to-metal restorations

Ceramic fractures are serious and costly problems in dentistry. Moreover, they pose an aesthetic and functional dilemma both for the patient and the dentist. This problem has created demand for the development of practical repair options which do not necessitate the removal and remake of the entire restoration. Published literature on repair techniques for fractured fixed partial dentures, concentrating on the data obtained both from in vitro and in vivo studies, reveals that the repair techniques based on sandblasting and silanization are the most durable in terms of adhesive and cohesive failures compared with those using different etching agents.

Tensile bond strengths of composites to a gold-palladium alloy after thermal cycling

STATEMENT OF PROBLEM

Many different materials and methods have been used to fabricate or repair veneer facings with composites, but only a few of these have been studied.

PURPOSE

This study compared the tensile bond strengths of composites to a gold-palladium alloy with the use of several surface treatment methods.

MATERIAL AND METHODS

Forty alloy specimens were cast in Eclipse (52% gold and 37.5% palladium) in the form of truncated cones. These specimens were divided equally into 4 groups. In group I, the bonding surfaces of the metal cones were treated with Silicoater MD. Truncated cones of Dentacolor composite were bonded to the metal surfaces and light-polymerized. In group II, the bonding surfaces of the metal cones were air-particle abraded with 50 microm aluminum oxide and coated with C&B Metabond. Truncated cones of Epic-TMPT composite were bonded to the metal surfaces and light-polymerized. In group III, the bonding surfaces of the metal cones were air-particle abraded with CoJet-Sand. Truncated cones of Pertac-Hybrid composite were bonded to the metal surfaces and light-polymerized. In group IV, the bonding surfaces of the metal cones were air-particle abraded with CoJet-Sand. Truncated cones of Visio-Gem were bonded to the metal surfaces and light-polymerized. After 24 hours of water immersion at 37 degrees C and 1000 thermal cycles in water at 5 degrees C and 55 degrees C, tensile forces were applied to all specimens with a universal testing machine. Analysis of variance was applied to the data (P<.05), and differences among means were determined with a Tukey-Kramer interval of 5.4 MPa.

RESULTS

Tensile bond strengths in MPa were as follows: Dentacolor, 14 +/- 5; Epic-TMPT, 12 +/- 4; Pertac-Hybrid, 13 +/- 5; and Visio-Gem, 18 +/- 4. The tensile bond strength of Visio-Gem was significantly higher than that of Epic-TMPT, but no differences were found among Dentacolor, Pertac-Hybrid, and Epic-TMPT (P<.05).

CONCLUSION

Within the limitations of this study, all 4 bonding systems tested produced high bond strengths between composites and a gold-palladium alloy after thermal cycling.

4-META use in dentistry: a literature review

4-META (4-methacryloyloxyethy trimellitate anhydride) was invented and patented in Japan in January 1979 and patented in the United States in April 1979. For the first 8 years, 4-META dental products (manufactured by Sun Medical Co, Kyoto, Japan) were not readily available in North America. Most of the early research therefore was done in Japan and reported in Japanese. A second wave of products (manufactured by Parkell, Farmingdale, N.Y.) became available in the United States in 1987, which precipitated research in English. This article is a chronological review of the literature published between 1978 and 1998 on 4-META dental adhesive materials. Thirteen commercial products are reviewed in terms of their physical strength; research on the mechanisms of 4-META action and the biocompatibility of 4 META was excluded.

Shear bond strengths of 2 intraoral porcelain repair systems to porcelain or metal substrates

STATEMENT OF PROBLEM

When clinical fractures of the ceramic veneer on ceramometal can be repaired, the need for remake can be eliminated or postponed. A number of ceramic repair materials are available; bond strength data would be useful for predicting the success of a given repair system.

PURPOSE

This in vitro study evaluated shear bond strengths of 2 porcelain repair systems intended for intraoral bonding of resin to porcelain and metal.

MATERIAL AND METHODS

Sixty cylindrical specimens were fabricated with feldspathic porcelain and/or a high noble alloy: 20 porcelain (P), 20 porcelain and metal (PM), and 20 metal (M). Specimens were divided into subgroups of 10, and resin composite cylinders were bonded with 1 of 2 systems: CoJet-System (CJ) or Ceramic Repair (CR). Bonded specimens were stored in 37 degrees C distilled water for 24 hours before being thermocycled at 5 degrees C to 55 degrees C for 300 cycles with a 30-second dwell time. The specimens then were stored for an additional 8 days before being subjected to shear force in a universal testing machine at a crosshead speed of 5 mm/min. Stress at failure was calculated in MPa, and mode of failure was recorded. Analysis of variance (ANOVA) was applied to the data. Comparisons between substrates were made with the Duncan multiple range test (P <.05), and differences between the 2 repair systems within like substrate groups were examined with the Student t test.

RESULTS

Bonding groups exhibited the following values in megapascals: PM-CR = 19.3 +/- 4.1; PM-CJ = 25.0 +/- 3.1; M-CR = 14.3 +/- 4.9; M-CJ = 23.0 +/- 2.3; P-CR = 18.3 +/- 4.2; P-CJ = 22.4 +/- 5.6. The ANOVA results showed significant differences between the CJ and CR groups. The Student t test revealed that the mean data for the CJ groups were significantly higher than for the CR groups (P <.05). The Duncan multiple range test demonstrated significant differences between the PM and M groups (P <.05) for the CR system only.

CONCLUSION

Under the conditions of this study, CJ achieved significantly higher bond strengths to PM and M substrates. Significant differences in strength were found between PM and M, but only within the CR system.