Implant-retained overdenture following hemiglossectomy: a 10-year clinical case report.

A clinical evaluation of an implant-supported overdenture placed in the edentulous mandible after hemiglossectomy is described. The deltopectoral flap covering the mandibular ridge was replaced with a free mucosal graft. Four Brånemark system implants were inserted into the anterior part of the mandible, but one of the four fixtures did not show osseointegration. The superstructure was designed as a spaced round bar-attachment supported by three implants so as to retain the complete overdenture. In addition to the metal clip, a silicone-based soft denture liner material was applied in the female portion of the attachment so as to prevent the attachment from making a clattering noise upon mastication. Although the overdenture required adjustment at regular intervals, the treatment was successful both aesthetically and functionally for up to at least 10 years.

Abrasion resistance of titanium nitride coatings formed on titanium by ion-beam-assisted deposition.

To improve the physical properties of the pure titanium surface, thin titanium nitride (TiN) films were deposited by means of ion-beam-assisted deposition. Film structure was confirmed as TiN by X-ray diffraction analysis. Surface hardness and abrasion resistance were significantly improved on TiN-coated specimens. Five combinations of oral hygiene instruments and materials were applied to the specimens as simulations of the oral environment. Treatment with the metal scaler and ultrasonic scaler severely changed the surface features and significantly increased the surface roughness parameters on pure titanium controls, whereas only small scratches and dull undulations were seen on the TiN-coated specimens. Profilometric tracings and scanning electron micrographs demonstrated the improved abrasion resistance of the TiN-coated specimens.

Effectiveness of two-liquid silane primers on bonding sintered feldspathic porcelain with a dual-cured composite luting agent.

The purpose of the current study was to evaluate the effect of two-component ceramic primers on the bond strength of a composite material joined to a sintered porcelain material. Two sizes of porcelain discs (VMK 68; 10 and 8 mm in diameter by 2.5 mm thick) were ground (No. 1000 SiC), and surface-conditioned using one of the following systems: (i) unprimed, (ii) Liquid A of the Porcelain Liner M material (PLM-A), (iii) Liquid B of Porcelain Liner M (PLM-B), (iv) Liquids A and B of Porcelain Liner M (PLM-AB), (v) Liquid A of the Tokuso Ceramics Primer material (TCP-A), (vi) Liquid B of Tokuso Ceramics Primer (TCP-B) and (vii) Liquids A and B of Tokuso Ceramics Primer (TCP-AB). All specimens were bonded with the Bistite II dual-cured composite luting agent, and shear bond strengths were determined both after 24 h immersion in water and after subsequent thermocycling (4-60 degrees C, 1 min each, 20,000 cycles). Of the seven groups assessed, two groups (PLM-AB and TCP-AB) showed the greatest bond strength both before (30.7 MPa for PLM-AB and 29.7 MPa for TCP-AB) and after (19.7 MPa for PLM-AB and 22.4 MPa for TCP-AB) thermocycling (P < 0.05). No significant differences were found between the PLM-AB and TCP-AB groups regardless of the application of thermocycling (P > 0.05). It can be concluded that both of the acid-catalysed two-liquid ceramic primers showed superior bonding to the unhydrolysed single-liquid silane agents (PLM-B and TCP-A) when the feldspathic porcelain was bonded with the Bistite II luting composite.

Bonding between resin luting cement and glass infiltrated alumina-reinforced ceramics with silane coupling agent.

The purpose of this study was to evaluate the shear bond strengths of three dual-cured resin luting cements (Linkmax HV, Panavia Fluoro Cement, and RelyX ARC) to glass-infiltrated alumina-reinforced ceramic material and the effect of four silane coupling agents (Clearfil Porcelain Bond, GC Ceramic Primer, Porcelain LinerM, and Tokuso Ceramic Primer) on the bond strength. The two type-shaped of In-Ceram alumina ceramic glass-infiltrated specimens were untreated or treated with one of the four ceramic primers and then cemented together with one of the three dual-cured resin luting cements. Half of the specimens were stored in water at 37 degrees C for 24 h and the other half thermocycled 20,000 times before shear bond strength testing. Surface treatment by all silane coupling agents improved the shear bond strength compared with non-treatment. The specimens treated with Clearfil Porcelain Bond showed significantly greater shear bond strength than any of the other three silane coupling agents regardless of resin luting cements and thermocycling except for the use of Panavia Fluoro Cement at 20,000 thermocycles. When the alumina-reinforced ceramic material was treated with any silane coupling agent except GC Ceramic Primer and cemented with Linkmax HV, no significant differences in bond strength were noted between after water storage and after 20,000 thermocycles. After 20,000 thermocycles, all specimens except for the combined use of Clearfil Porcelain Bond or GC Ceramic Primer and Linkmax HV and GC Ceramic Primer and Panavia Fluoro Cement showed adhesive failures at the ceramic-resin luting cement interface.

Comparative strength of metal-ceramic and metal-composite bonds after extended thermocycling.

The relative strengths of ceramic-to-metal and composite-to-metal bonds were compared after prolonged thermocycling. A total of 104 cast discs were produced from a gold alloy (Pontor LFC). A ceramic material (Duceragold) was fused to 24 discs to assess the strength of the metal-ceramic bond. An indirect composite material (New Metacolor Infis) was bonded to the remaining discs after surface preparation by Rocatec tribochemical coating, tin plating and priming with a phosphate conditioner [10-methacryloyloxydecyl dihydrogen phosphate (MDP), Cesead II], priming with a thione conditioner (V-Primer) or no treatment (unprimed control). Shear bond strengths were determined before and after thermocycling at 20,000 and 100,000 cycles. Pre-thermocycling bond strengths were ranked in the order: metal-ceramic (40.5 MPa); Rocatec treatment (33.1 MPa) and tin plating-MDP (31.0 MPa); V-Primer (20.9 MPa); and control (11.9 MPa). The bond strengths of the first three groups were not significantly different after 20,000 thermocycles, whereas those of the V-Primer and control groups were significantly reduced. After extended thermocycling (100,000 cycles) the metal-ceramic group had the highest mean shear bond strength (28.5 MPa; P < 0.05), followed by the Rocatec (23.9 MPa) and tin plating-MDP (22.1 MPa) groups. The metal-ceramic bond was the most durable, although its strength was reduced by 29.6% after extended thermocycling. On the basis of these results, we recommend the Rocatec and tin plating-MDP systems for composite-to-metal bonding. Metal-ceramic bonding, however, is superior to metal-composite bonding within the limitation of the current experiment.

Mechanical strength of laser-welded cobalt-chromium alloy.

The purpose of this study was to investigate the effect of the output energy of laser welding and welding methods on the joint strength of cobalt-chromium (Co-Cr) alloy. Two types of cast Co-Cr plates were prepared, and transverse sections were made at the center of the plate. The cut surfaces were butted against one another, and the joints welded with a laser-welding machine at several levels of output energy with the use of two methods. The fracture force required to break specimens was determined by means of tensile testing. For the 0.5-mm-thick specimens, the force required to break the 0.5-mm laser-welded specimens at currents of 270 and 300 A was not statistically different (p > 0.05) from the results for the nonwelded control specimens. The force required to break the 1.0-mm specimens double-welded at a current of 270 A was the highest value among the 1.0-mm laser-welded specimens. The results suggested that laser welding under the appropriate conditions improved the joint strength of cobalt- chromium alloy.

Effect of heat treatments on machinability of gold alloy with age-hardenability at intraoral temperature.

OBJECTIVE: This study investigated the effect of heat treatment on the machinability of heat-treated cast gold alloy with age-hardenability at intraoral temperature using a handpiece engine with SiC wheels and an air-turbine handpiece with carbide burs and diamond points. METHODS: Cast gold alloy specimens underwent various heat treatments [As-cast (AC); Solution treatment (ST); High-temperature aging (HA), Intraoral aging (IA)] before machinability testing. The machinability test was conducted at a constant machining force of 0.784N. The three circumferential speeds used for the handpiece engine were 500, 1,000 and 1,500 m/min. The machinability index (M-index) was determined as the amount of metal removed by machining (volume loss, mm(3)). The results were analyzed by ANOVA and Scheffé's test. RESULTS: When an air-turbine handpiece was used, there was no difference in the M-index of the gold alloy among the heat treatments. The air-turbine carbide burs showed significantly (p<0.05) higher M-indexes than the diamond points after any heat treatments. With the SiC wheels, increasing the circumferential speed increased the M-index values for each heat treatment. The specimens heat-treated with AC, HA and IA had similar M-indexes at the lower speeds (500 and 1,000 m/min). The ST specimens exhibited the lowest M-index at the lower speeds. However, at the highest speed (1,500 m/min), there were no significant differences in the M-indexes among the heat treatments except for HA, which showed the highest M-index. CONCLUSION: There was no effect of heat treatment on the machinability of the gold alloy using the air-turbine handpiece. The heat treatments had a small effect on the M-index of the gold alloy machined with a SiC wheel for a handpiece engine.

Properties of dual-curable luting composites polymerized with single and dual curing modes.

The purpose of this study was to evaluate the influence of visible-light exposure on water absorption, solubility and colour stability of dual-curable luting composites. Using eight dual-curable luting composites (2bond2, Bistite II, G-CERA Cosmotech II, Imperva Dual, Linkmax, Lute-It, Panavia Fluoro Cement and Variolink II), disk specimens were prepared by the following two methods: (i) dual-cured specimens; exposed with visible-light from a light-curing unit, and (ii) chemical-cured specimens; chemically polymerized without exposure. Five specimens were produced for each material and curing mode. Water absorption and solubility were determined according to standardized testing methods, and the data were compared using analysis of variance (ANOVA) and contrasts. With regard to colour stability, the colour difference (DeltaE*) values between 24 h and the other immersion periods (1, 2, 3, 4, 8, 12, 16, 20 and 24 weeks) were calculated and then analysed by repeated measure ANOVA. The dual-cured specimens exhibited significantly lower solubility values than the chemical-cured specimens except for the Lute-It material. The dual-cured Linkmax material exhibited the lowest solubility (0.51 +/- 0.01 microg mm(-3)) and the lowest DeltaE* value after 24 weeks (2.64 +/- 0.39). The dual-curable luting composites should be light-exposed after seating of restorations in order to reduce water absorption and solubility, and to improve colour stability.

Properties of a new photo-activated composite polymerized with three different laboratory photo-curing units.

This study determined the hardness, solubility and curing depth of a new photo-activated composite polymerized with three different laboratory photo-curing units for the purpose of evaluating the post-curing properties of the material. A new photo-activated composite material for both direct and indirect applications (DiamondCrown) was polymerized with three photo-curing units equipped with the following light sources: (i) two halogen lamps (DiamondLite-VL. Halogen Light Curing Booth); (ii) two metal halide lamps (Hyper LII) and (iii) two xenon stroboscopic tubes (UniXS II). Knoop hardness, water solubility and curing depth were determined for groups of five specimens according to standardized testing methods. All data were compared using analysis of variance (anova) and Scheffe's S intervals (P < 0.05). The Knoop hardness number (KHN) generated with the metal halide unit (63.3 +/- 2.4 KHN) was statistically (P < 0.05) greater than those produced by the other two curing units. Water solubility values for both the halogen unit (2.5 +/- 0.5 microg mm(-3)) and the metal halide unit (2.5 +/- 0.5 microg mm(-3)) were significantly (P < 0.05) lower than for the xenon unit (3.8 +/- 0.5 microg mm(-3)). Of the three photo-curing units, the metal halide curing-unit consistently exhibited the greatest depth of cure. The composite material appears to be reliable, although its post-curing properties were found to be influenced by the type of curing unit.

Adhesive bonding of super-elastic titanium-nickel alloy castings with a phosphate metal conditioner and an acrylic adhesive.

The purpose of the current study was to evaluate the bonding characteristics of super-elastic titanium-nickel (Ti-Ni) alloy castings. Disk specimens were cast from a Ti-Ni alloy (Ti-50.85Ni mol%) using an arc centrifugal casting machine. High-purity titanium and nickel specimens were also prepared as experimental references. The specimens were air-abraded with alumina, and bonded with an adhesive resin (Super-Bond C & B). A metal conditioner containing a phosphate monomer (Cesead II Opaque Primer) was also used for priming the specimens. Post-thermocycling average bond strengths (MPa) of the primed groups were 41.5 for Ti-Ni, 30.4 for Ti and 19.5 for Ni, whereas those of the unprimed groups were 21.6 for Ti, 19.3 for Ti-Ni and 9.3 for Ni. Application of the phosphate conditioner elevated the bond strengths of all alloy/metals (P < 0.05). X-ray fluorescence analysis revealed that nickel was attached to the debonded resin surface of the resin-to-nickel bonded specimen, indicating that corrosion of high-purity nickel occurred at the resin-nickel interface. Durable bonding to super-elastic Ti-Ni alloy castings can be achieved with a combination of a phosphate metal conditioner and a tri-n-butylborane-initiated adhesive resin.

Surface treatment of dentin with GLUMA and iron compounds for bonding indirect restorations.

The purpose of this study was to evaluate five dentin bonding systems simulating indirect restorations. The surface of bovine and human dentin was primed with a glutaraldehyde agent (GLUMA) and placed in a humidor at 37 degrees C for 168 h. In an experimental bonding system (GLUMA/CY/SB), the surfaces were etched with phosphoric acid, primed with cytochrome c, and then bonded to an acrylic rod with a self-curing resin (4-META/MMA-TBB). Specimens using two commercially available bonding systems [All-Bond 2 (AB2) and Super-Bond C & B (10-3/SB)] and two controls with and without GLUMA (GLUMA/10-3/SB and CY/SB) were also prepared. Tensile testing revealed that the bond strengths were influenced by the bonding system, 168 h dentin exposure and their interaction, but not by the tooth origin. AB2 showed the lowest bond strength. With the 10-3/SB system, exposing the dentin to humidity resulted in a decrease in bond strength. After 168 h of exposure, no significant differences were observed between 10-3/SB and CY/SB. The most effective bonding was obtained with the bonding systems of GLUMA/10-3/SB and GLUMA/CY/SB. Improved outcome is expected with these bonding systems when building up abutment teeth with indirect restorations.

Evaluation of two thione primers and composite luting agents used for bonding a silver-palladium-copper-gold alloy.

The purpose of the current study was to evaluate the bond strength and durability of two metal adhesive systems bonded to a silver-palladium-copper-gold (Ag-Pd) alloy. Disk specimens were cast from an Ag-Pd alloy (Castwell M.C. 12), air-abraded with 50 micro m grain-sized alumina, and they were bonded with two primer-cement bonding systems (Alloy Primer and Panavia Fluoro Cement; Metaltite and Bistite II). For each cement, unprimed specimens were also prepared as experimental controls. Shear bond strengths were determined both before and after thermocycling (4-60 degrees C, 1 min each, 100 000 cycles). The average post-thermocycling bond strengths in MPa (n=8) were: 39.0 for the Metaltite-Bistite II system, 32.2 for the Alloy Primer-Panavia Fluoro Cement system, 23.1 for the Bistite II material and 21.0 for the Panavia Fluoro Cement material. The use of proprietary primers, both of which contain thione functional monomer, enhanced the post-thermocycling bond strengths of both cements (P < 0.05). After thermocycling, however, the difference in bond strength between the two cements was not significant regardless of the use of the primers (P > 0.05). It is concluded that the combined use of the thione primer and the luting agent is necessary for bonding the Ag-Pd alloy examined.

Effect of silane primers and unfilled resin bonding agents on repair bond strength of a prosthodontic microfilled composite.

This study examined the effect of silane primers and bonding agents on bonding between layers of a light-activated composite material when repaired in the laboratory process. Disk specimens were prepared with the dentin portion of a composite material (Dentacolor DA-30) and abraded with a silicon carbide rotary cutting instrument. The specimens were conditioned with either one of the two silane primers (Porcelain Liner M and Silicer) or one of the two unfilled resin bonding agents (Dentacolor Opaker liquid and New Metacolor Photo Opaque liquid), or one of four combinations of two primers and two bonding agents. An intact surface with a thin air-inhibited unpolymerized layer, and an unprimed surface with only silicone carbide abrasion were also used for references. After placement of the enamel portion of the same brand of composite material (Dentacolor SA-30) on each surface of the dentin material, the specimens were light-exposed, and stored for 24 h in either dry or wet condition. Shear bond strengths were then determined with a mechanical testing device. The results showed that combined use of a silane primer and a bonding agent generally showed the greatest magnitude of bond strength regardless of material variation. The use of an unfilled resin bonding agent after application of a silane primer (Porcelain Liner M) is recommended to ensure adequate repair bonding between layers of the composite material.

Effect of disinfectants containing glutaraldehyde on bonding of a tri-n-butylborane initiated resin to dentine.

The purpose of this study was to evaluate the effects of disinfectants on the bond strength of resin to dentine. The surface of bovine dentine was exposed to formaldehyde (FA) aqueous solutions, glutaraldehyde (GA) aqueous solutions, 2-hydroxyethyl methacrylate aqueous solutions (HEMA), a commercially available dentine primer (Gluma CPS desensitizer, GLUMA), isotonic sodium chloride solution (IS), and distilled water (DW), and placed in a humidor (HU) at 37 degrees C, or non-stored (baseline). All dentine surfaces were conditioned with a 10% citric acid and 3% ferric chloride solution (10-3 liquid), and then bonded to an acrylic rod with a self-curing adhesive resin (Super-Bond C&B). The mean tensile bond strengths determined 24 h after bonding were compared by analysis of variance (ANOVA) and Fisher's protected LSD test (n=5, P < or = 0.05). The exposure of dentine to IS, DW and HU for both 48 and 168 h resulted in a decrease in bond strength when compared with the baseline. The highest bond strengths after 168 h of exposure were obtained with 5% GA, 10% HEMA, and GLUMA, the values of which were equivalent to baseline and were significantly higher than that of FA. It is concluded that disinfectant pre-treatment with 5% GA or GLUMA stabilizes the bonding of tri-n-butylborane (TBB) initiated luting agent to bovine dentine conditioned with 10-3 liquid.

Influence of visible-light exposure on colour stability of current dual-curable luting composites.

This study was conducted to evaluate influence of visible-light exposure on colour stability of dual-curable luting composite. Using six dual-curable luting composites [Bistite II (BI), Clapearl DC (CL), Dicor Light Activated Cement (DI), G-Cera Cosmotech II (GC), Lute-It (LU) and Variolink II (VA), disk specimens were prepared with the following two methods: (i) dual-cured specimens, exposure with visible-light from a photo-curing unit for 120 s and (ii) chemical-cured specimens, chemically cured without exposure. Five specimens were produced for each material and curing mode. After 24 h, all specimens were immersed in distilled water at 37 degrees C for 24 weeks, during which colour accuracy was measured with a dental colorimeter. The colours characterized in the Commission Internationale d'Eclairage (CIE) L*a*b* colour space were first determined 24 h after preparation (baseline colour evaluation), and again after 1, 2, 3, 4, 8, 12, 16 and 24 weeks. The colour difference (Delta E*) values between 24 h and the other immersion periods were calculated, and then analysed by repeated measure analysis of variance (ANOVA). In addition, the Delta E* values after 24 weeks for dual-cured specimens were compared with those for chemical-cured specimens by one-way ANOVA and by contrasts for each composite (P < 0.05). The Delta E* values were influenced by the material and curing mode as well as immersion period (P=0.0001). After 24 weeks the dual-cured specimens showed significantly lower Delta E* values than the chemical-cured specimens, except for the VA material. The CL material exhibited the least colour change (1.9 +/- 0.2) among the dual-cured specimens, and the VA material showed the least (4.5 +/- 0.9) among the chemical-cured specimens after 24 weeks. Dual-curable luting composites should be polymerized with the dual modes to ensure colour stability.

Relation between cavity design and marginal adaptation in a machine-milled ceramic restorative system.

The purpose of the current study was to evaluate the influence of inclination of the cusp as well as convergence/divergence of the cavity wall on marginal adaptation in a machine-milled ceramic restorative system. Sixty inlay specimens were prepared from a pre-fabricated feldspathic porcelain (Vitablocs Mark 2) by means of a computer integrated manufacturing system (Cerec 2). Specimens were divided into 12 groups according to original cavity preparations consisting of four inclinations of the cusp (0 degree, 15 degrees, 30 degrees and 45 degrees) and three types of cavity form (tapered box, regular box, and undercut box). The restorations were cemented with a dual-activated luting agent (Clapearl DC) and cut into two halves with a low speed cutting saw, after which adaptation at the occlusal surface of each inlay specimen was measured with a microscope. The results showed that the inclination of the cusp did not affect adaptation of the restorations (P > 0.05), whereas the inlay specimens inserted into undercut cavity preparation exhibited significantly poor adaptation as compared with those inserted into regular and tapered cavities in two inclinations of the cusp (0 degree and 15 degrees; P < 0.05). The experimental results suggest that either regular or tapered box form cavity preparation is preferable to the undercut box form to improve occlusal marginal adaptation of the Cerec 2 ceramic restorative system.

Adhesive bonding of composite material to cast titanium with varying surface preparations.

The purpose of the present study was to evaluate the surface preparation effects of eight metal conditioners and an adhesive system on bonding between a prosthodontic composite material and cast titanium. Eight primers designed for conditioning base metal alloys (Acryl Bond, All-Bond 2 Primer B, Alloy Primer, Cesead II Opaque Primer, Eye Sight Opaque Primer, Metafast Bonding Liner, Metal Primer II, and MR Bond) as well as a surface modification technique (Siloc) were assessed. Disk specimens cast from titanium (T-Alloy H) were either primed with one of the eight primers or treated with the Siloc system, and then bonded with a light-activated composite material (Artglass). Bond durability was evaluated by thermocycling (4 and 60 degrees C, 1 min each, 20, 000 cycles). After thermocycling, two groups either primed with the Cesead II Opaque Primer material or treated with the Siloc system exhibited significantly greater bond strength (20.0 and 19.0 MPa) than the other groups (0.2-12.6 MPa, P < 0.05). These two systems are considered to be useful for improving bonding between the titanium and the composite material tested.

Joint strength of laser-welded titanium.

OBJECTIVE: The objective of this study was to examine the joint strength of titanium laser-welding using several levels of laser output energy [current (A)]. METHODS: Cast titanium plates (0.5 x 3.0 x 40 and 1.0 x 3.0 x 40 mm(3)) were prepared and perpendicularly cut at the center of the plate. After the cut halves were fixed in a jig, they were laser-welded using a Nd: YAG laser at several levels of output energy in increments of 30A from 180 to 300A. The penetration depths of laser to titanium were measured under various conditions for output energy, pulse duration, and spot diameter to determine the appropriate conditions for these parameters. Based on the correlation between the results obtained for penetration depth and the size of the specimens (thickness: 0.5 and 1.0 mm, width: 3.0 mm), the pulse duration and spot diameter employed in this study were 10 ms and 1.0 mm, respectively. Three laser pulses (spot diameter: 1.0 mm) were applied from one side to weld the entire joint width (3.0 mm) of the specimens. Uncut specimens served as the non-welded control specimens. Tensile testing was conducted at a crosshead speed of 2 mm/min and a gage length of 10 mm. The breaking force (N) was recorded, and the data (n=5) were statistically analyzed. RESULTS: For the 0.5 mm thick specimens, the breaking force of the specimens laser-welded at currents of 240, 270, and 300A were not statistically (P>0.05) different from the non-welded control specimens. There were no significant differences in breaking force among the 1.0mm thick specimens laser-welded at currents of 270 and 300A, and the non-welded control specimens. SIGNIFICANCE: Under appropriate conditions, joint strengths similar to the strength of the non-welded parent metal were achieved.

Colour reproducibility of a photo-activated prosthetic composite with different thicknesses.

This study determined the colour accuracy of a photo-activated prosthetic composite with various thicknesses and shades for the purpose of evaluating the relationship between material thickness variation and colour reproducibility. Four light shades (A1, B1, C1 and D2) and four dark shades (A4, B4, C4 and D4) of a representative photo-activated prosthetic composite (Artglass) for body paste were assessed. The specimens were prepared with thicknesses of 0.5, 1.0, 1.5, 2.0, 2.5 and 3.0 mm. The L*a*b* colour parameter of each shade was measured using a dental colorimeter (ShadeEye) connected to a computer. The overall colour accuracy of groups of five specimens was compared by means of analysis of variance (ANOVA) and Scheffe's S multiple range test (P=0;05). In addition, L*a*b* colour difference (Delta E*) values between the 3.0 mm thickness and the other thicknesses were calculated. Three-factor ANOVA revealed that all colour parameters were influenced by the thickness as well as by the shade letter and shade tab (P < 0.05). The L* value consistently decreased for all shades as thickness increased, although there was no obvious correlation between the thickness of the material and either the a* or b* values. Among the Delta E* values, the values between the 2.5 and 3.0 mm thicknesses were the lowest, and values were found to be lower than 2.0 for all shades. The colour accuracy of the photo-activated prosthetic composite was related to the thickness of the material regardless of the shade. For acceptable colour reproducibility, a composite material thickness of at least 2.5 mm was found to be required.

Shear bond strength of resin composite veneering material to gold alloy with varying metal surface preparations.

STATEMENT OF PROBLEM: Although adequate surface preparation is indispensable to achieve a consistent and durable bond between resin composite materials and the metal substructures of veneered restorations, information on the bonding performance of current metal adhesive systems is limited. PURPOSE: The purpose of this study was to evaluate the surface preparation effects of 4 metal conditioners and 1 adhesive system on bonding between a prosthetic resin composite veneering material and a gold casting alloy. MATERIAL AND METHODS: Four primers containing sulfur derivative monomer and designed for conditioning noble metal alloys (Alloy Primer, Infis Opaque Primer, Metal Primer II, and Metaltite) and a surface modification technique (Siloc) were assessed. Cast disk specimens made of gold alloy (Pontor LFC) were either primed with 1 of the 4 primers or treated with the Siloc system and bonded with a light-activated prosthetic resin composite material (New Metacolor Infis). Control specimens were also prepared without the use of a bonding agent. Shear bond strengths were determined before and after thermocycling (20,000 cycles) for evaluation of bond durability. RESULTS: All of the primed and Siloc-treated groups showed improved 24-hour shear bond strengths compared with the control group. After thermocycling, the groups either primed with the Metaltite conditioner or treated with the Siloc system exhibited the highest mean shear bond strengths. CONCLUSION: The Metaltite conditioner and Siloc system each represent a useful method for improving the bond between the gold alloy and resin composite material tested.