SiOx-C coating: a composite-to-metal bonding mechanism

Comparative evaluation of effect of metal primer and sandblasting on the shear bond strength between heat cured acrylic denture base resin and cobalt-chromium alloy: An in vitro study

AIMS

The aim of this study was to evaluate the effect of metal primers and sandblasting on the shear bond strength (SBS) of heat cured acrylic denture base resin to cobalt-chromium (Co-Cr) alloy.

MATERIALS AND METHODS

A total number of 40 disk shaped wax patterns (10 mm in diameter and 2 mm in thickness) were cast in Co-Cr alloy. Samples were divided into 4 groups depending on the surface treatment received. Group 1: No surface treatment was done and acts as control group. Group 2: Only sandblasting was done. Group 3: Only metal primer was applied. Group 4: Both metal primer and sandblasting were done. After surface treatment samples had been tested in Universal Testing Machine at crosshead speed of 0.5 mm/min in shear mode and scanning, electron microscope evaluation was done to observe the mode of failure.

STATISTICAL ANALYSIS

All the observations obtained were analyzed statistically using software SPSS version 17; one-way analysis of variance (ANOVA) and post-hoc Tukey test were applied.

RESULTS

The one-way ANOVA indicated that SBS values varied according to type of surface treatment done. The SBS was highest (18.70 ± 1.2 MPa) when both sandblasting and metal primer was done when compared with no surface treatment (2.59 ± 0.32 MPa).

CONCLUSIONS

It could be concluded that the use of metal primers along with sandblasting significantly improves the bonding of heat cured acrylic denture base resin with the Co-Cr alloy.

Zygomatic implants/fixture: a systematic review

Patients with moderate to severe atrophy challenge the surgeon to discover alternative ways to use existing bone or resort to augmenting the patient with autogenous or alloplastic bone materials. Many procedures have been suggested for these atrophied maxillae before implant placement, which include Le Fort I maxillary downfracture, onlay bone grafts and maxillary sinus graft procedures. A zygomatic implant can be an effective device for rehabilitation of the severely resorbed maxilla. If zygomatic implants are used, onlay bone grafting or sinus augmentation would likely not be necessary. The purpose of this article is to review the developments that have taken place in zygomatic implant treatment over years, including anatomic information for installing the zygomatic implants, implant placement techniques, stabilization, and prosthodontic procedures.

Effects of silica coating and silane surface conditioning on the bond strength of rebonded metal and ceramic brackets

Objective

The aim of this study was to evaluate the effects of tribochemical silica coating and silane surface conditioning on the bond strength of rebonded metal and ceramic brackets.

Material and Methods

Twenty debonded metal and 20 debonded ceramic brackets were randomly assigned to receive one of the following surface treatments (n=10 for each group): (1) sandblasting (control); (2) tribochemical silica coating combined with silane. Brackets were rebonded to the enamel surface on the labial and lingual sides of premolars with a light-polymerized resin composite. All specimens were stored in distilled water for 1 week and then thermocycled (5,000 cycles) between 5-55°C. Shear bond strength values were measured using a universal testing machine. Student's t-test was used to compare the data (α=0.05). Failure mode was assessed using a stereomicroscope, and the treated and non-treated bracket surfaces were observed by scanning electron microscopy.

Results

Rebonded ceramic brackets treated with silica coating followed by silanization had significantly greater bond strength values (17.7±4.4 MPa) than the sandblasting group (2.4±0.8 MPa, P<0.001). No significant difference was observed between the rebonded metal brackets treated with silica coating with silanization (15±3.9 MPa) and the sandblasted brackets (13.6±3.9 MPa). Treated rebonded ceramic specimens primarily exhibited cohesive failure in resin and adhesive failure at the enamel-adhesive interface.

Conclusions

In comparison to sandblasting, silica coating with aluminum trioxide particles followed by silanization resulted in higher bond strengths of rebonded ceramic brackets.

Effect of metal type and surface treatment on in vitro tensile strength of copings cemented to minimally retentive preparations

STATEMENT OF PROBLEM

Due to the potential lack of ideal preparation form, the type of alloy and its surface pretreatment may have clinically relevant correlations with the retentive strength of castings to minimally retentive preparations.

PURPOSE

The purpose of this study was to evaluate the effect of alloy type and surface pretreatments of base and noble metal copings on their tensile strength to minimally retentive preparations.

MATERIAL AND METHODS

Minimally retentive, standardized crown preparations were made on recently extracted human third molars (n=68). Noble (IPS d.SIGN 53) and base metal (Rexillium NBF) copings were fabricated. All copings received heat treatment for oxide formation. Three experimental groups were then developed for each metal type (groups ranging from 10 to 12 specimens each): oxide only, airborne-particle abraded, or metal-primed. Copings were cemented using a self-adhesive universal resin cement (RelyX Unicem) and were thermal cycled (500 cycles between 5 and 55 degrees C) and stored (24 hours, 37 degrees C) before debonding using a universal testing machine. Frequency of debond location was compared among specimen groups. A 2-way ANOVA was used to test for interaction between the metal type and surface treatment, and, if no significant interaction was found, to test the main effects for metal type and surface treatment (alpha=.05). A multinomial logit model using the likelihood ratio test was used to describe the effect of metal type and surface treatment on failure site location (alpha=.05).

RESULTS

The 2-way ANOVA indicated no significant influence of any factor on debond load: metal type (P=.885), surface treatment (P=.555), or their interaction (P=.644). The multinomial logit statistical model showed that noble metals and metal primers significantly (P<.05) shifted debond failures to occur more frequently at the resin/tooth interface or within the tooth itself.

CONCLUSIONS

Neither metal type nor surface pretreatment affected bond strength. However, alloy type and surface treatment affected site of debond location. (J Prosthet Dent 2007;98:199-207).

Shear bond strength of three veneering resins to a Ni-Cr alloy using two bonding procedures

Composite veneering materials are used as alternatives to porcelain in fixed prosthodontics. Mechanical retention of the resin on the metal framework has been associated with the formation of gaps at the resin/alloy interface, and failure of the restoration. Several chemical bonding systems have been introduced to promote resin adhesion. The purpose of the present study was to evaluate the shear bond strength of three photocured composites (Artglass, Solidex & Signum+) to a Ni-Cr alloy.72 wax disks covered with 150-mum diameter beads were cast and divided in two equal groups. In the first group, Metal Photo Primer was applied on the casting surface, while the Siloc system was used in the second. Each group was divided in three subgroups of 12 samples, in which the three composites were photocured. Half of the specimens of each subgroup were subjected to 1000 and 5000 thermal cycles (5 and 55 degrees C) respectively. All specimens were tested in shear in a universal testing machine. The Siloc-Solidex group showed the highest bond strength (17.3 +/- 3.7 MPa). No statistically significant difference was found between specimens treated with Metal Photo Primer or Siloc. Thermocycling did not significantly affect the bond strength values. Solidex showed an adhesive failure mode for both alloy surface treatments, while Artglass and Signum+ exhibited combination failures. Conclusively, the appropriate alloy surface treatment - resin combination can significantly improve the resin-alloy shear bond strength. Specifically, Solidex resin exhibited significantly higher bond values compared with Artglass and Signum+, for both surface treatments and thermocycling procedures.

Effect of alloy type and surface conditioning on roughness and bond strength of metal brackets

The effect of 5 different surface conditioning methods on bonding of metal brackets to cast dental alloys was examined. The surface conditioning methods were fine (30-microm) or rough (125-microm) diamond bur, sandblasting (50-microm or 110-microm aluminum oxide [Al2O3]), and silica coating (30-microm silica). Fifty disc-shaped specimens of 5 different alloys (gold-silver, palladium-silver, nickel-chromium, cobalt-chromium, and titanium) were ground with 1200-grit silicone carbide abrasive and polished before being reused for each conditioning method. Polished surfaces were used as negative controls. After measuring surface roughness (RZ), metal brackets were bonded to the conditioned alloys with a self-curing resin composite. Specimens were thermocycled (5000 times, 5 degrees-55 degrees C, 30 seconds), and shear bond tests were performed. Significantly higher (P<.001) surface roughnesses were observed with use of the rough diamond bur (RZ approximately 33 microm), 110-microm Al2O3 (RZ approximately 14 microm), and fine diamond bur (RZ approximately 10 microm), compared with the controls (RZ approximately 1 microm). Silica coating (RZ approximately 4 microm) and 50-microm Al2O3 (RZ approximately 4 microm) demonstrated no significant difference (P>.001) in roughness when compared with the controls. The control group showed no resistance to shear forces (0 MPa). Bond values were greater (19 MPa) when silica coating was used, compared with 50-microm Al2O3 (7 MPa) and 110-microm Al2O3 (8 MPa) for all alloys tested. However, interaction between alloys and conditioning methods exhibited significant differences (P<.0001).

Comparison of retentive systems for composites used as alternatives to porcelain in fixed partial dentures

STATEMENT OF PROBLEM

The bond strength between framework metals and composites, used as alternatives to porcelain, requires further study because adhesive failures can promote microleakage, discoloration, and stains in composites.

PURPOSE

The aim of this in vitro study was to analyze and compare the tensile strength between the base metal Ni-Cr alloys: (Wirocer and Wiron 99) and 2 composites (Artglass and Solidex) with 2 types of mechanical retention (0.4-mm and 0.6-mm beads); 2 types of chemical treatment (Siloc system and Metal Photo Primer system) and the combination of both treatments on a metal framework; to verify whether these composite systems were strong enough to be used as alternatives to porcelain.

MATERIAL AND METHODS

A total of 144 specimens, cylindrical metal rods (3 mm diameter x 60 mm length), were cast in Ni-Cr alloy (Wiron 99 or Wirocer), divided into 6 equal groups corresponding to 6 types of retention: airborne particle abrasion/control (A), chemical (C), mechanical with 0.4-mm (M4) and 0.6-mm beads (M6), and chemical/mechanical with 0.4-mm (CM4) and 0.6-mm beads (CM6). Composite rings formed around the rods (6.0 mm diameter X 2.0 mm thickness) of Artglass or Solidex were light polymerized in the UniXS unit (wavelength range of 320-520 nm for 540s) according to the manufacturer's specifications. Specimens were invested, and their tensile strength was measured at fracture with an EMIC-MEM 2000 universal testing machine at a crosshead speed of 2.0 mm/min and 500 kgf load cell. Statistical analysis was carried out with analysis of variance and Tukey's test at significance level P=.01.

RESULTS

The highest mean retention values were recorded for groups CM6 (63.57 MPa) and M6 (63.05 MPa). The lowest mean retention values were recorded for groups A (30.63 MPa) and C (25.07 MPa). No significant difference was found regarding the alloys used in this study (P<.01). There was a significant difference in shear strength (P<.01) between Solidex (52.33 MPa) and Artglass (43.18 MPa).

CONCLUSION

Within the limitations of this study, mechanical retention with 0.6-mm beads and chemical/mechanical retention with 0.6-mm beads increased the metal-composite tensile bond strength. No significant difference was found between these 2 retention systems. Chemical and airborne particle abrasion/control retentions were statistically weaker than the other types of retention tested. The retention means corresponding to the commercial-grade Ni-Cr alloys used were statistically different. The composite Solidex showed a tensile strength mean statistically higher than Artglass. All values observed were higher than that recommended for metal-ceramic dental restorative systems (25 MPa-ISO 9693).

Investigation of microleakage at the interface between a Co-Cr based alloy and four polymeric veneering materials

STATEMENT OF PROBLEM

. Marginal adaptation and resistance to microleakage are important factors for clinical success in fixed prosthodontics. Alloy corrosion that sometimes occurs under a veneer in the cervical area may result in cervical staining, a metallic taste, or even failure of the interface.

PURPOSE

This study investigated cervical microleakage between a Co-Cr alloy and 4 indirect polymeric veneering materials used with different conditioning systems.

MATERIAL AND METHODS

Sixteen metallic frameworks (copings) were obtained by fabricating 0.6-mm calibrated wax patterns on a master cast abutment. The wax patterns were provided with 0.4-mm beaded retention on the veneering surfaces and cast in a Co-Cr based alloy (Biosil F) used for fixed partial dentures. The Co-Cr copings were divided equally into 4 groups and veneered with 4 polymeric materials (Signum, Solidex, Superpont C+B, and Targis). Three chemical conditioning systems (Siloc, Targis-Link, and Silicoater MD) were used with the respective veneering system recommended by the manufacturer; Conolar opaque was used for Superpont C+B. No control group was created. After 2 weeks of storage in distilled water at 37 degrees C, 2000 cycles at 5-55 degrees C, and 24 hours of storage in 0.5% basic fuchsine, specimens were embedded in clear liquid casting resin and sectioned along a perpendicular cervical-incisal plane through the middle of the cervical collar. The surfaces of the resulting sections were examined in the cervical area with a metallurgical microscope to detect dye penetration. Leakage was quantitatively evaluated with the use of a scoring system (established by the authors) that indicated the presence/absence of dye in 3 regions of the cervical interface from the collar to the incisal margin. Scores were compared and analyzed with the use of 1-way analysis of variance followed by post-hoc Tukey's honestly significant difference test (P=.05).

RESULTS

Superpont C+B was associated with the highest microleakage scores (3.75 +/- 0.5). The least microleakage at the interface was produced by Targis (1 +/- 0.816), followed by Solidex (2.5 +/- 1.0) and Signum (2.25 +/- 0.975). Only the difference between Targis and Superpont C+B was significant (P<.05).

CONCLUSION

Within the limitations of this in vitro study, the extent of cervical microleakage between the coping and veneer depended on the particular polymeric material used for veneering. The extremes of the study were Targis/Targis-Link (lowest leakage scores) and Superpont C+B (highest leakage scores). Differences among the chemical retention systems tested were not significant.

The use of chairside silica coating for different dental applications: a clinical report

This article describes an alternative approach to conditioning an alloy surface prior to veneering with composite. The procedure is based on silica coating and silanization of the alloy surface, which can be performed chairside.

Immediate stabilization at stage II of zygomatic implants: rationale and technique

The severely resorbed maxilla presents a challenge for the maxillofacial surgeon and the restorative dentist planning implant restorations. The Zygomatic implant, as introduced by Brånemark, allows for the surgical placement of implants to restore resorbed maxillae without major grafting procedures. A minimum of 2 implants in the anterior maxilla are used in conjunction with 1 implant in each zygoma to support a prosthesis. Fabricating a passive bar to connect the implants at phase II surgery may require 1 to 2 days. With the adhesive abutment cylinder luting technique, a rigid framework can be delivered within 1 hour of uncovering the implants. This approach saves considerable time over conventional techniques and allows for the restoration of severely resorbed maxillae in an efficient and routine manner. The technique also eliminates the necessity for a technician to be available on-site for the procedure.

Effect of three adhesive primers on the bond strengths of four light-activated opaque resins to noble alloy

The effect of commercial adhesive primers for noble metals on the bond strength of light-activated opaque resin has not been determined. This study evaluated the effect of three adhesive primers on the shear bond strengths of each of the four light-activated opaque resins to silver--palladium--copper--gold (Ag--Pd--Cu--Au) alloy. The adhesive primers Alloy Primer (AP), Metal Primer II (MPII) and Metaltite(MT) were used. Four commercial light-activated opaque resins (Axis (AX), Cesead II (CEII), Dentacolor(DE) and Solidex (SO) were used to bond a light-activated resin-veneered composite to Ag--Pd--Cu--Au alloy. The specimens were stored in water at 37 degrees C for 24 h and then immersed alternatively in water baths at 4 and 60 degrees C for 1 min each for up to 20,000 thermal cycles before shear mode testing at a cross-head speed of 0.5 mm min(-1). All the primers examined improved the shear bond strength between opaque resin and Ag--Pd--Cu--Au alloy compared with non-primed specimens prior to thermal cycling. After 20,000 thermal cycles, the bond strengths of combined use of AP and DE and that of MT and each of AX, CE or DE were significantly greater than any other groups. Significant difference was observed between the bond strengths at thermal cycles 0 and 20,000, with the combined use of MT and DE. With the combination of appropriate adhesive metal primers and light-activated opaque resins, complicated surface preparations of metal frameworks of resin-veneered prostheses that are composed of casting Ag-Pd-Cu-Au alloy may be negligible.

Effectiveness of metal surface treatments in controlling microleakage of the acrylic resin-metal framework interface

STATEMENT OF PROBLEM

Microleakage at the junction between the metal alloy and acrylic resin in a removable partial denture may result in discoloration, fluid percolation, and acrylic resin deterioration. The junction between a metal alloy and acrylic resin is an area of clinical concern. Failure of a removable partial denture may be linked to this interface. Enhancing resistance to microleakage at this interface may improve the long-term union between the 2 materials.

PURPOSE

This investigation was designed to determine the effects of various metal surface treatment protocols on microleakage and bond strength between the metal alloy and acrylic resin used in the fabrication of a removable partial denture.

MATERIAL AND METHODS

Ninety-six nickel-chromium-beryllium alloy specimens were randomly divided into 8 groups. After adaptation of baseplate wax, each specimen was invested. Subsequent to wax removal, each specimen was divided into a control half and an experimental half. Air abrasion, tinplating/oxidation, and silanation were evaluated individually and in all combinations. Heat-polymerized acrylic resin was processed against all specimens before storage in distilled water at 37 degrees C for 72 hours. Each specimen then was thermocycled in distilled water (3000 cycles) before immersion in sodium fluorescein dye for 24 hours. Counting grids that exhibited dye penetration under ultraviolet light exposure allowed assessment of microleakage.

RESULTS

Air abrasion resulted in a significant decrease in microleakage when used individually and in all combinations (P<0.05). All experimental combinations that did not involve air abrasion demonstrated no significant reduction in measured microleakage between the experimental and control sides. Tukey's pair-wise comparison of the difference in the mean number of squares exhibiting microleakage between the control and treated sites for each experimental group revealed a significant difference, based on the involvement of air abrasion. Groups involving air abrasion did not differ significantly from each other (P<0.05). In addition, no significant difference was detected between groups not involving air abrasion (P<0.05).

CONCLUSION

Air abrasion, alone and in combination with tinplating/oxidation and with silanation, resulted in a significant reduction in microleakage between the metal alloy and acrylic resin.

Shear bond strength of techniques for bonding esthetic veneers to metal

STATEMENT OF PROBLEM

New composites with improved qualities have been introduced to the dental profession as alternatives to porcelain. There is concern about the strength and reliability of new metal-resin bonding systems when these composites are used as esthetic veneers over metal frameworks.

PURPOSE

This in vitro study compared the shear bond strength of 2 metal-resin bonding techniques with the bond strength of conventional porcelain fused-to-metal (PFM). Effects of water storage and thermocycling were also evaluated.

MATERIAL AND METHODS

Ninety disks, cast in a medium gold, high noble PFM alloy, were divided equally into 6 groups, and received 3 treatments for veneering: conventional feldspathic porcelain on 1 group, and a composite (Artglass) bonded to the metal, using 2 metal-resin bonding techniques. Specimens were tested in shear, half of them after a 24-hour dry storage at room temperature and the rest after 10-day storage in normal saline solution at 37 degrees C and thermocycling. Fractured specimens were evaluated under x10 magnification to determine the nature of failure. Statistical analysis was performed with 2-factor analysis of variance (ANOVA).

RESULTS

Mean shear bond strength values before and after wet storage and thermocycling were 29.66 and 22.91 MPa for the PFM group; 21.43 and 17.92 MPa for the Siloc group; and 19.34 and 15.64 for the etched group, respectively. The PFM group exhibited significantly higher bond strength values compared with the other 2 groups (P<.001). All groups showed a significant decrease in bond strength values after wet storage and thermocycling (P<.001).

CONCLUSION

Wet storage and thermocycling caused a significant decrease in shear bond strength of all specimens. Shear bond strength of conventional feldspathic PFM was significantly higher than that of the 2 metal-resin bonding techniques tested. The 2 latter techniques did not reveal any statistically significant differences.

Effect of sandblasting and silicoating on bond strength of polymer-glass composite to cast titanium

STATEMENT OF PROBLEM

There is little information regarding the mechanical and chemical retention of polymer-glass composite to cast titanium.

PURPOSE

This study examined whether sandblasting in conjunction with silicoating improves the bond strength of the polymer-glass composite to cast titanium.

MATERIALS AND METHODS

Disk patterns (10 mm in diameter, 2.5 mm thick) were cast with commercially pure titanium (CP Ti) and Type IV gold alloy. Three pretreatments were applied: 50 microm Al(2)O(3) sandblasting (50 SB), 250 microm Al(2)O(3) sandblasting (250 SB), and 600-grit SiC paper polishing (600 SiC). After surface preparation, the Siloc system (silicoating) was applied on the disks. The 50 SB specimens without Siloc system were also prepared as controls. Then sticky tape with a circular hole (4.76 mm diameter) was placed onto the disk to define the bonding area. Artglass (polymer-glass) opaque, dentin, and enamel composites were applied using Teflon matrices and then light-polymerized. Shear bond strength (n = 8) was determined at a crosshead speed of 5 mm/min. Results were analyzed statistically with 2-way ANOVA and the Tukey-Kramer test (alpha=.05).

RESULTS

The Siloc system significantly (P <.05) improved the mean shear bond strength of Artglass to both metals in the 50 SB specimens. Statistical differences (P <.05) in shear bond strength were found among surface treatments for the silicoated CP Ti specimens, in which 250 SB specimens yielded the greatest bond strength. The Type IV specimens treated with Siloc system showed no significant differences in shear bond strength between the 50 SB and the 250 SB specimens.

CONCLUSION

Sandblasting with coarser alumina particles in conjunction with silicoating significantly enhanced bond strength of polymer-glass composite to cast titanium.

Bond strengths of resin-to-metal bonding systems

STATEMENT OF PROBLEM

Resinous materials for the veneers of fixed prostheses commonly require mechanical retention on metal substructures because there is no chemical adhesion. However, mechanical retention does not restrict creation of a marginal gap at the resin-metal interface, which can cause discoloration or detachment of resinous material. The development of a chemical resin-to-metal bonding could resolve this problem and also reduce the need for mechanical retention (pearls, wires) on metal frameworks.

PURPOSE

This study evaluated six current methods with the use of various storage conditions to predict clinical efficacy.

MATERIAL AND METHODS

Six resin-to-metal bonding systems were tested: Silicoater, Silicoater MD, Rocatec, OVS, Sebond, and Spectra-Link. All specimens were examined in bending tests after 24 hours of dry storage (category A), after 24 hours of water storage and thermocycling (category B), and after 2 months of water storage and thermocycling (category C). Tensional tests were completed for all bonding systems after dry storage, and microscopic examination (optical and SEM) was performed for all specimens.

RESULTS AND CONCLUSIONS

This study indicated that certain systems can provide stable bonding of resin to metal substructures despite prolonged wet storage and intensive thermocycling. These systems can also be used clinically without retentive configurations on metal frameworks, resulting in better esthetics. Some bonding systems revealed progressive weakening of bond strengths, so research is needed to verify their clinical efficacy.

Effects of adhesive primers on bond strength of self-curing resin to cobalt-chromium alloy

PURPOSE

This study evaluated the effects of four adhesive primers on the shear bond strength of a self curing resin to cobalt-chromium alloy.

MATERIAL AND METHODS

The adhesive primers Acryl Bond (AB), Cesead Opaque Primer (COP), Metal Primer II (MPII), and MR Bond (MRB) were used. A brass ring placed over the casting alloy disk surface nonprimed or primed with each primer was filled with the self-curing methyl methacrylate polymethyl methacrylate resin. The specimens were stored in water at 37 degrees C for 24 hours and then alternately immersed in water baths at 4 degrees C and 60 degrees C for 1 minute each for up to 20,000 thermal cycles before shear mode testing at a crosshead speed of 0.5 mm/min.

RESULTS

All the primers examined improved the shear bond strength between the resin and cobalt chromium alloy compared with nonprimed specimens before thermal cycling. However, after 20,000 thermal cycles, the bond strengths of resin to cobalt chromium alloy primed with COP or MPII primers were significantly greater than those of specimens primed with AB or MRB primers and nonprimed controls.

CONCLUSION

This study indicated that COP and MPII are effective primers to obtain higher bond strength between resin and cobalt-chromium alloy.

Resin-bonded fixed partial dentures: a review of three decades of progress

The resin-bonded fixed partial denture has undergone significant changes in design, materials and tooth preparation since its development in 1973. The selection of resin cement and micromechanical retention have closely paralleled alloy-resin-bonding research. Despite impressive in vitro research results, only 74 percent of the prostheses are still functional at the end of four years. Understanding the limitations, indications and design of resin-bonded fixed partial dentures will result in improved longevity and patient satisfaction.

The bond strength of polymers and metal surfaces using the 'silicoater' technique

The silicoater technique, or silicoating, is a chemical bond system (makes mechanical retentions unnecessary) which prevents the rising of a gap in the margin area between resin and metal. This procedure solves the problems of fracture and detachment of the veneer or its discolourization. The purpose of this investigation was to find out the values of the bond strength achieved by using the silicoater technique on Ag-Pd alloy with smooth surface and with mechanical retentions on the surface. Ninety specimens were divided into groups, subjected to water storage and thermocycling. The values of the bond strength were investigated in combination with this technique with Ag-Pd alloy and three veneer materials. The silicoater technique gave the best results in combination with Dentacolor XS veneer material and mechanical retentions on the surface of the dental alloy.

Influence of prolonged thermal cycling and water storage on the tensile bond strength of composite to NiCr alloy

OBJECTIVES

The purpose of this study was to evaluate the bond strength and bond durability of new adhesive systems (both micromechanical and chemo-mechanical) to a beryllium-free nickel-chromium alloy (NiCr).

METHODS

Plexiglass tubes filled with composite were bonded to NiCr alloy discs. Groups of 24 samples were bonded using six different bonding systems. Subgroups of eight bonded samples were stored in an isotonic artificial saliva solution (37 degrees C) either for 1 d, 30 d or 150 d. In addition, the 30 and 150 d samples were thermal cycled for 7,500 or 37,500 cycles, respectively.

RESULTS

The bond strength of a conventional BisGMA composite to sandblasted NiCr was statistically significantly lower than that of chemo-mechanical bonding systems and decreased continuously during the storage time of 150 d. The additional use of a silane on the sandblasted alloy resulted only in a slight, statistically insignificant increase in bond strength. Statistically significantly higher and more durable bonds to NiCr alloy were achieved either with the combination of silica coating and use of a conventional BisGMA composite or with the combination of sandblasting and the use of a composite modified with a phosphate monomer. In these systems, the bond strengths were limited by the cohesive strength of the resin composites. However, a newly developed composite containing the same active phosphate monomer showed a statistically significant decrease in bond strength (cohesive strength) over storage time.

SIGNIFICANCE

Longer-term storage times in a wet environment are needed in laboratory tests to examine the durability of bonding systems.

Effect of heat-curing cycle and gypsum contamination on the bond strengths of composite bonded to a silane-treated alloy

Silane-coated alloy specimens bonded to composite resin were tested for shear bond strengths and compared with an identical specimen group exposed to gypsum invested heat-processing conditions. The results indicate that the bond of composite resin to silane-coated alloy is not impaired by investing, boil-out, cleaning, packing, and curing during the process of securing artificial teeth to a partial denture framework. In a second part of this study, the alloy specimens were silane-coated and exposed to the gypsum invested heat-processing procedure before the composite resin was bonded to them. In addition, the specimens were exposed to one of three different cleaning agents (ethyl acetate, ethyl alcohol, and soap and water). Results in the second part of the study indicate that ethyl acetate is an effective cleaning agent to use when a silane-coated alloy surface previously exposed to gypsum processing is to be bonded to composite resin.

Bond strength of composite to alloy treated with bonding systems

PURPOSE

The in-vitro bond strengths of a composite bonded to a nickel-chromium-beryllium alloy treated by eight bonding systems were measured after three storage conditions.

MATERIALS AND METHODS

Nickel-chromium-beryllium alloy samples were treated by eight commercial bonding systems including adhesive composite cements, all-purpose bonding agents, and silica-coating systems. A composite was bonded to the alloy samples. Sample groups were stored in water for 24 hours at 23 degrees C, or thermocycled, or stored for 6 months at 23 degrees C and then debonded in tension.

RESULTS

Bond strengths after 24 hours storage were: adhesive composite cements, 14.2 to 22.1 MPa; all-purpose bonding agents, 11.4 to 14.6 MPa; and silica-coating systems, 18.6 to 20.2 MPa. Bond strengths after thermocycling were: adhesive composite cements, 12.6 to 20.6 MPa; all-purpose bonding agents, 9.9 to 17.7 MPa; and silica-coating systems, 11.1 to 19.2 MPa. Bond strengths after 6 months were: adhesive composite cements, 12.0 to 13.1 MPa; all-purpose bonding agents, 8.7 to 14.1 MPa; and silica-coating systems, 14.8 to 18.4 MPa.

CONCLUSIONS

Only two bonding systems showed decreased bond strength after thermocycling, as compared with 24 hours' storage; whereas four bond systems showed decreased bond strength after 6 months' storage. Bond strengths measured after thermocycling were not predictive of those measured after 6 months' storage.

Adhesive abutment cylinder luting

The connection between dental implants must be passive so that stress is not introduced between bone, implant, and prosthesis. To achieve this passivity clinically is difficult if not impossible with current procedures. A technique is presented in which premachined titanium abutment cylinders are clinically luted to a cast framework to create a stress-free connection. Possible advantages and disadvantages are discussed.

Early bond strength of luting cements to a precious alloy

Previous studies have reported that glass-ionomer and adhesive resin cements can bond to various alloys, while zinc phosphate cements lack this adhesive property. This study evaluated the bonding properties of three luting cements during the first seven days after cementation. Thirty cylinders were cast with a high-noble porcelain-fused-to-metal (PFM) alloy and luted in pairs with one of the cements. The joints were stored in water at 37 degrees C for one, two, or seven days before being fractured in shear. The cylinders were re-used to provide 40 joints within each test group. The data were subjected to a Weibull analysis, a curve-fitting method shown to be appropriate for comparing the bond strengths of dental materials. The results showed that the zinc phosphate cement was the weakest material, whereas the adhesive resin produced the strongest joints. Microscopic observations of the fractured samples did not reveal any specific differences between the samples in terms of their mechanism of fracture. The glass-ionomer cement reached its maximum bond strength after two days, whereas storage time had no influence on the zinc phosphate cement. The adhesive resin cement was slightly, but not significantly, weaker after one week in water. We suggest that excessive loading of restorations cemented with glass ionomer should be avoided for the first two days after the placement. The use of an adhesive resin cement can be recommended on endodontically treated teeth, but further studies are needed to evaluate its biocompatibility and adhesion to dentin.

Bond strength of composites to etched and silica-coated porcelain fusing alloys

In vitro bond strengths of two composite veneering materials to two porcelain fusing alloys were measured utilizing two storage conditions. The alloys were etched or treated with silica applied by blasted, thermal or pyrogenic techniques and then silanated. Bond strengths were higher for the Ni-Cr-Be than the Au-Pd alloy with most values greater than 18 MPa. Bond strengths to etched and silanated Au-Pd alloy were low (less than 6.5 MPa), whereas samples treated with silica and silanated had significantly higher values. Bond strengths to the Ni-Cr-Be alloy were highest with the thermal and pyrogenic silica treatments. After thermocycling, most bond strengths to the Au-Pd alloy decreased, but were the same or higher to the Ni-Cr-Be alloy. Cohesive failures of the opaquers were observed.

Shear strength of laboratory-processed composite resins bonded to a silane-coated nickel-chromium-beryllium alloy

The shear bond strengths of three commercial laboratory curing composite resin veneers bonded to a nickel-chromium-beryllium alloy treated with the Silicoater system were evaluated. Two light-cured resins and one heat- and pressure-cured resin were evaluated. No statistically significant difference in bond strengths among the three resins was found. Microscopic analysis of the fracture surfaces indicated that all failures were complex and cohesive in nature within the resin and composite. On the basis of the shear bond strengths measured, any of the composite resin veneers tested appear to be clinically acceptable.

Silane effects on luting resin bond to a Ni-Cr alloy

This study investigates the effect of a silane coupling agent on the shear bond strength of four commercially available resin luting systems (two of which rely on mechanical retention and two which have a chemical bond to metal) when bonding a prepared Ni-Cr alloy to etched bovine enamel. Silane application reduced the bond strengths of the two chemically adhesive resins and increased the bond strength of one of the mechanically retained resins. For the other mechanically retained resin, silane application did not significantly increase the bond strength but the plane of fracture changed from resin/metal to resin/enamel: from this an increase in metal resin bond strength can be inferred.

Alternative alloys for resin-bonded retainers

Traditionally, resin-bonded fixed partial dentures have been made with nickel-chrome-beryllium alloys and cemented with conventional resin luting cements. However, alternative alloys for resin-bonded retainers offer improved physical and biocompatible properties, and resin-metal bond strengths twice that of traditional methods can be achieved. The superior bonds obtained with etched base metals bonded with adhesive resins and silica-coated alloys bonded with silane-coupling agents make these the most desirable techniques available.

Application of silica coating technique for removable prosthodontics. A clinical report

A technique for constructing a maxillary removable partial overdenture using the Silicoater system has been described.

Evaluation of the electrolytic etching depth of a nickel-chromium base alloy used in resin-bonded cast restorations

This study examined the relation of the electrolytic etching depth of a nickel-chromium base alloy to the etching time. Cast samples (22 mm long, 4 mm wide, 1.5 mm thick) were etched in the Eltrokor etching unit, using Korolyt A as the etching solution with a constant current density of 400 mA/cm2. On each sample an approximately 3 mm long area was etched for 5, 7, 9, and 11 minutes. Between each etched area, a field of approximately 2 mm long remained unetched. The surface of each sample was scanned with a profilometer. The distance of the compensation plane of the scanned etched profile to the unetched areas was then measured for each etching time. The average etched depth with an etching time of 5 minutes is 30.4 microns (SD 2.39); with a time of 7 minutes the depth is 44 microns (SD 3.49); with a time of 9 minutes the depth is 59.8 microns (SD 4.10); and with an etching time of 11 minutes the depth is 72.9 microns (SD 2.94). Taking the average of all etching depths per etching time, the average loss of substance is 6.409 microns per minute etching time.

Strength of bond with Comspan Opaque to three silicoated alloys and titanium

In Sweden high-gold alloys or cobalt-chromium alloys are used for resin-bonded prostheses. The bond strength between a resin cement and different sandblasted or silicoated metals were measured before and after thermocycling; in connection with this some rapid thermocycling methods were studied. The effect of different storage times and different protection coatings on bond strength were tested. Finally, the influence of rubbing and contamination with saliva on bond strength were investigated. Silicoating increased the bond strength significantly. The highest bond strengths were these of silicoated Wirobond and titanium, unsusceptible to thermal stress; the bond strengths of the sandblasted metals were the weakest, and sensitive to thermocycling as well. The influence on bond strength for silicoated gold alloys, protected with an unpolymerized composite resin coating, stored in sealed plastic bags up to 7 days, was negligible. Rubbing and contamination with saliva did not influence bond strength. Preferably, silicoated Wirobond and titanium should be used for resin-bonded prostheses, but gold alloys may still be adequate for clinical use. The experimental method described for storing, sealing, and cleaning the silicoated metal surfaces in this article can be recommended for laboratory and clinical use.

Factors influencing metal-resin tensile bond strength to filled composites

This study evaluated the effect of metal surface conditioning, application of a silicon layer, water storage, and resin filling on tensile bond strength of a metal-resin system using three experimental composites (un-, micro-, and macrofilled) having the same self-curing resin composed of Bis-GMA and TEGDMA (2:1 wt%). Test specimens were prepared by bonding the resin between pairs of Ni-Cr-Be alloy cast disks (diameter, 8 mm) previously subjected to heat treatments simulating porcelain firing procedures. A specially constructed apparatus facilitated the absolutely parallel alignment and orientation of the disk faces to each other, maintaining a constant resin thickness of 100 microns. Before being bonded, the sand-blasted metal surfaces were either electrolytically etched and/or silicoated. Prior to being tested, assemblies were stored in water at 37 degrees C for one and 30 days. Thereafter, the specimens were processed in a universal testing machine at a cross-head speed of 2 mm/min until failure. Bond strengths ranged from 4.2 to 20.5 MPa. Data were analyzed by ANOVA with a factorial design (conf. level = 99%). The results showed that: (i) bond strength was increased when the metal was silicoated, (ii) the combination of sandblasting/silicoating produced the best values, and (iii) the 30-day water storage combined with silicoating enhanced the strength of the bond. The resin filling had no significant effect, indicating that neither its presence nor type affects bonding strengths to metal.