Effect of an adhesive primer on the integrity of occlusal veneer-metal interface and wear of composite resin veneered restorations

Wear and damage at the bonded interface between tooth enamel and resin composite

OBJECTIVE

To investigate the wear mechanisms and evolution of damage in tooth enamel-resin composite bonded interfaces caused by sliding contact, and to develop an understanding of interface degradation from a tribological viewpoint that supports clinical recommendations for improving interface integrity.

METHODS

Reciprocating wear tests were performed on bonded interface samples involving commercial resin composite (Tetric N Ceram Bulk Fill), resin cement (Rely X U200) and tooth enamel using the ball-on-flat configuration. The bonded samples were subjected up to 5 × 10⁴ cycles of sliding contact, and the wear depth and wear track morphology were characterized after increments using white light interferometry and scanning electron microscopy, respectively. Optical microscopy was also used to evaluate cracks and their propagation in the samples.

RESULTS

In the early stages of sliding contact, wear evolved most rapidly at the interface, followed by the enamel and the resin composite. Gradually, the difference between the wear depth at the interface and other areas decreased. Furthermore, cracks and brittle fracture appeared in the enamel during the early stages of wear, adjacent to the interface. With continuing cyclic loading, enamel wear manifested primarily as ploughs, with discontinuous pits and peeled material. Cracking decreased to only a few cracks extending to the inner enamel and parallel to the interface.

CONCLUSIONS

Cracking and damage occurred in the enamel during the early stages of sliding contact and accelerated by poor margin finishing. Cracks caused by wear under sliding contact could be one of the reasons for secondary caries and tooth discoloration.

Effect of thione primers on adhesive bonding between an indirect composite material and Ag-Pd-Cu-Au alloy

The current study evaluated the effect of primers on the shear bond strength of an indirect composite material joined to a silverpalladium-copper-gold (Ag-Pd-Cu-Au) alloy (Castwell). Disk specimens were cast from the alloy and were air-abraded with alumina. Eight metal primers were applied to the alloy surface. A light-polymerized indirect composite material (Solidex) was bonded to the alloy. Shear bond strength was determined both before and after the application of thermocycling. Two groups primed with Metaltite (thione) and M. L. Primer (sulfide) showed the greatest post-thermocycling bond strength (8.8 and 6.5 MPa). The results of the X-ray photoelectron spectroscopic (XPS) analysis suggested that the thione monomer (MTU-6) in the Metaltite primer was strongly adsorbed onto the Ag-Pd-Cu-Au alloy surface even after repeated cleaning with acetone. The application of either the thione (MTU-6) or sulfide primer is effective for enhancing the bonding between a composite material and Ag-Pd-Cu-Au alloy.

Effect of a metal priming agent on wear resistance of gold alloy-indirect composite joint

The purpose of the current study was to evaluate the effect of a metal priming agent on wear resistance of gold alloy-composite joint. Four types of plate specimen were prepared: composite (Estenia C&B or Epricord) alone, type 4 gold alloy alone, alloy-composite joint without priming agent, and alloy-composite joint bonded with a priming agent (Alloy Primer). Three-body wear test was performed using the plate specimens, gold alloy antagonist, and polymer slurry. Joined specimens with priming exhibited less wear depth (in microm; 21.0 for Estenia and 24.9 for Epricord) than the joined specimens without priming (57.8 for Estenia and 46.7 for Epricord). Wear depth of the single plate specimens when abraded with the gold alloy antagonist was ranked as follows: Estenia (9.6), gold alloy (12.8), and Epricord (19.1). It was concluded that the use of a metal priming agent at the alloy-composite interface effectively enhanced the wear resistance of the joined area when under cycled loading.

Effect of noble metal adhesive systems on bonding between an indirect composite material and a gold alloy

In this study, the bond strength between an indirect composite and a gold alloy was determined for the purpose of evaluating noble metal bonding systems. A single liquid primer designed for conditioning noble metal alloys (Infis Opaque Primer) and tri-n-butylborane-initiated adhesive resins (Super-Bond C & B), with or without the powder component, were assessed. Cast gold alloy disks (Casting Gold type IV) were air-abraded with alumina, followed by six surface preparations, and were then bonded with a light-activated composite material (New Metacolor Infis). Shear testing was performed both before and after thermocycling for evaluation of bond durability. The results showed that three primed groups improved post-thermocycling bond strengths compared to each of the corresponding unprimed groups (P < 0.01). The bond strength was reduced for all six groups by the application of thermocycling (P < 0.01). After thermocycling, the group primed with the Infis Opaque Primer material and bonded with the Super-Bond C & B resin exhibited the greatest bond strength (23.4 MPa). The Infis Opaque Primer and Super-Bond bonding system increased the post-thermocycling bond strength of the control group by a factor of approximately ten. This simple technique is applicable in the fabrication of composite veneered restorations and cone-telescope dentures.

Effect of laboratory procedures and thermocycling on the shear bond strength of resin-metal bonding systems

STATEMENT OF PROBLEM

During fabrication or repair of removable partial dentures, resin-to-metal or resin-to-denture tooth bonds may be stressed by laboratory procedures.

PURPOSE

The purpose of this in vitro study was to evaluate the effect of steam cleaning, boiling, ultrasonic cleaning (laboratory procedures), and thermocycling on shear bond strength of resin bonds to metal and denture teeth.

MATERIAL AND METHODS

Resin-metal bonding systems and their specific veneer resins (Rocatec, Sinfony; Rocatec, Visio-Gem, HLC-BOND, Zeta LC and Ducera experimental veneer resin) were tested on a Co-Cr alloy (Wirobond C). The veneer resins were bonded to resin denture teeth. The experimental groups (n=7) were subjected to the following conditions: 24-hour storage of the specimens in air (group I, control group), storage in air and treated with simulated laboratory procedures (2 minutes steam cleaning, 15 minutes ultrasonic cleaning at room temperature, 1 hour boiling in water, group II), storage in air with thermocycling (5000 cycles, 5 degrees to 55 degrees C, group III), storage in air with laboratory procedures followed by thermocycling (group IV), and storage in air with thermocycling followed by laboratory procedures (group V). Shear strength tests (MPa) were performed with a universal testing machine until fracture. After shear bond testing, the failure mode of the resin-metal and resin-denture tooth bonds was assessed. Statistical analysis of the results was carried out with one-way analysis of variance and Bonferroni-Dunn's multiple comparisons post hoc analysis for test groups (alpha=0.05).

RESULTS

Except for Ducera/denture tooth specimens (groups III to V: 8.7 +/- 3.4-9.1 +/- 1.7; 10.8 +/- 1.9 MPa control group), the Wirobond C and denture tooth specimens (groups III, IV and V: 1.4 +/- 0.9-11.9 +/- 2.3 MPa), showed significantly lower shear bond strengths than the corresponding control groups (7.5 +/- 2.9-21.0 +/- 3.4 MPa, P<.05). The shear bond strengths of group II of Sinfony/Wirobond C (11.6 +/- 3.3 MPa, P<.0001), Visio-Gem/Wirobond C (7.4 +/- 1.9 MPa, P<0.0001), Ducera/Wirobond C (11.8 +/- 2.9 MPa, P<.0001) and of Zeta/denture tooth (3.9 +/- 1.6 MPa, P=.0005) were significantly decreased by steam, boiling, and ultrasonic procedures compared with the corresponding control groups (21.0 +/- 3.4 MPa; 14.7 +/- 4.0 MPa; 19.1 +/- 2.3 MPa; 7.5 +/- 2.9 MPa, respectively). No significant differences were noted among groups III, IV, and V. Co-Cr specimens subjected to the Rocatec system and bonded with Sinfony and HLC BOND/Zeta specimens showed cohesive failure. Adhesive failure was observed for the experimental veneer resin on the Co-Cr specimens and for all veneer resins on the denture teeth.

CONCLUSION

Simulation of laboratory procedures and thermocycling caused a significant drop in shear bond strength of metal-resin and denture tooth-resin bonds for most of the tested veneer resins. Thermocycling before shear testing had the same effect on veneer resin bond strength as the simulated laboratory procedures.

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.

Wear and surface roughness of current prosthetic composites after toothbrush/dentifrice abrasion

STATEMENT OF PROBLEM

Surface changes of prosthetic composites caused by toothbrushing are known, although composite materials have been improved and are now widely used for various kinds of prosthetic restorations.

PURPOSE

This study evaluated the influence of toothbrushing on abrasive wear and surface roughness of current prosthetic composites.

MATERIAL AND METHODS

Seven composite materials (Artglass, Axis, Cesead II, Conquest Sculpture, Estenia, Infis, and Targis) were assessed, and a machinable ceramic material (Cerec 2 Vitablocs) was used as a reference. Composite specimens polymerized with their proprietary curing units and sectioned ceramic specimens were stored in water for 14 days, and subsequently subjected to toothbrush-dentifrice abrasion. The amount of vertical loss and the surface roughness of each specimen after 20,000 strokes were determined with a profilometer. Average values of groups of 5 specimens were compared with ANOVA and Duncan new multiple range test.

RESULT

Significantly (P < .05) less wear was observed with respect to the Targis (10.01 microm; SD = 0.53 microm) and Estenia (13.04 microm; 1.95 microm) materials than for the other composites assessed, whereas Artglass (34.08 microm; 3.66 microm) and Conquest Sculpture (31.78 microm; 4.67 microm) materials demonstrated the most wear. The least surface roughness was exhibited by Conquest Sculpture (Ra, 0.54 microm; 0.07 microm) material, and the greatest by Cesead II (1.10 microm; 0.13 microm). Ceramic material showed a more wear-resistant (4.54 microm; 0.79 microm) and smoother (0.26 microm; 0.02 microm) surface than any of the composite materials.

CONCLUSION

Abrasion and surface roughness of the prosthetic composites caused by toothbrushing varied in accordance with the material. Type of prosthetic composite significantly influenced the surface condition after toothbrushing.

Effect of noble metal conditioners on bonding between prosthetic composite material and silver-palladium-copper-gold alloy

STATEMENT OF PROBLEM

Mechanical retentive devices and the application of complicated surface preparation have been indispensable for bonding composite material to the metal substructure of restorations.

PURPOSE

This study evaluated the priming effects of 4 metal conditioners on bonding between a prosthetic veneering material and a silver-palladium-based casting alloy.

MATERIAL AND METHODS

Four primers designed for conditioning noble metal alloys (Alloy Primer, Metaltite, Metal Primer II, and V-Primer) were assessed (all materials contain organic sulfur compounds). Cast disk specimens made of silver-palladium-copper-gold alloy (Castwell M.C.12) were primed with 1 of the 4 primers, and bonded with a light-activated prosthetic composite material (Axis). Shear testing was performed before and after thermocycling for evaluation of bond durability.

RESULTS

All primed groups showed improved 24-hour bond strengths compared with the unprimed group. After thermocycling, 3 groups primed with the Metal Primer II, Alloy Primer, and Metaltite agents exhibited the highest bond strength.

CONCLUSION

Use of 1-liquid metal conditioners containing sulfur compounds was a simple and useful method for improving bonding between the alloy and the composite material tested.