RESUMEN
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).
RESUMEN
AIM OF THE STUDY: There is dearth of literature regarding the effects of oxidation heat treatment (OHT) as surface pretreatments on bond strength of base metal alloys and porcelain. MATERIALS AND METHODS: Forty-five bar specimens of each two commercially available base metal alloys Mealloy and Wirorn-99 (were fabricated. Dimensions of each specimen were 15.0 × 2.0 × 0.5 mm (according to the ISO 6872-1984). According to the surface pretreatments the samples of the two groups were categorized into three subgroups: With OHT only, with sandblasting only (with Al2O3 of 110 µm) and with OHT and sandblasting. Application of commercially available Duceram porcelain in thickness of 2.00 mm was applied over the surface of metal with the pretreatments. Samples were then placed under SEM for EDX examination to evaluate ionic changes that occurred at the metal-ceramic interface. Flexural bond strength of each sample was calculated under Universal Testing Machine. RESULTS: The one-way ANOVA indicated no significant influence of either metal type (P=0.811) or any surface pretreatment (P=0.757) on the metal-ceramic bond strength. CONCLUSION: OHT resulted in the increase in amount of oxides at the metal-ceramic interface. However, neither metal type nor surface pretreatments affected bond strength.
