Jeffrey Chai Chang

Tensile bond strengths of five luting agents to two CAD-CAM restorative materials and enamel

STATEMENT OF PROBLEM CAD-CAM restorative materials are popular because they have high esthetic value and short fabrication time. Unfortunately these materials are brittle and tend to fracture under heavy occlusal load. PURPOSE The purpose of this in vitro study was to investigate the tensile bond strengths of 5 luting agents to 2 CAD-CAM restorative materials and enamel. Material and methods One hundred truncated cones, with a 3-mm diameter bonding surface and 5-mm diameter base, were fabricated with Dicor MGC (n=50) or Cerec Vitablocs Mark II (n=50) with the Cerec system. Enamel surfaces of the crowns of 100 freshly extracted noncarious, anterior teeth, stored in 0.9% saline solution with 0.25% sodium azide (NaN(3)) as disinfectant, were prepared with sandpaper disks (320-grit size) on the Buehler Variable Speed Grinder-Polisher. The bonding surfaces of the Dicor MGC or Cerec Vitablocs Mark II truncated cones from each of the 2 tests systems were airborne particle abraded, chemically etched, and cemented on the prepared enamel surface of the tooth specimens with 5 luting agents: Vita Cerec Duo Cement, EnForce, Panavia 21, C&B Metabond, and Fuji Duet. All specimens were thermocycled 1000 times, in 5 degrees C and 55 degrees C water with a dwell time of 30 seconds in each temperature. Tensile force (MPa) was applied perpendicular to the bonding surfaces of the specimens with a universal testing machine until fracture. Fracture patterns were examined with a microscope at original magnification x10. The differences in the tensile bond strengths were analyzed with the Tukey-Kramer test (alpha=.05). RESULTS The mean tensile bond strengths of Dicor MGC bonding to enamel with luting agents in descending order in MPa were EnForce (10.12 +/- 2.25), Panavia 21 (7.28 +/- 1.77), Cerec Duo (5.32 +/- 1.65), Fuji Duet (3.73 +/- 1.78), and C&B Metabond (3.11 +/- 1.11). EnForce had a significantly higher bond strength than C&B Metabond, Fuji Duet, Cerec Duo, and Panavia 21 (P=.05). The mean tensile bond strengths of Cerec Vitablocs Mark II bonding to enamel with luting agents in descending order in MPa were as follow: Fuji Duet (11.51 +/- 2.79), EnForce (9.44 +/- 2.03), C&B Metabond (8.98 +/- 3.29), Cerec Duo (8.66 +/- 4.71), and Panavia 21 (5.10 +/- 2.49). Within this group, there was no significant difference between Fuji Duet and EnForce, but the bond strength of Fuji Duet was significantly higher than that of C&B Metabond, Panavia 21, and Cerec Duo (P=.05). The mean tensile strength of all the luting agents bonded to Cerec Vitablocs Mark II and enamel (8.74 MPa) was higher than Dicor MGC and enamel (5.91 MPa). CONCLUSION In this in vitro study; within the Dicor MGC group, the mean bond strength of Panavia 21 with enamel was significantly higher than C&B Metabond, Panavia 21, Cerec Duo, and Fuji Duet. Within the Cerec Vitablocs Mark II group, the mean bond strength of Fuji Duet was significantly higher than C&B Metabond, Panavia 21, and Cerec Duo but was not significantly higher than EnForce.

Tensile bond strengths of dual-cured cements between a glass-ceramic and enamel

STATEMENT OF THE PROBLEM Dual-cured cements have been used with castable ceramic restorations, but the tensile bond strengths of these materials have not been thoroughly researched. PURPOSE OF THE STUDY This study compared the tensile bond strengths between Dicor castable ceramics and enamel of four dual-cure cements: Twinlook, Optec Dual-Cure Luting Cement, Clearfil CR Inlay, and Dual Cement. MATERIAL AND METHODS Truncated cones made of Dicor castable ceramics were cemented to enamel of freshly extracted anterior teeth with these four cements. Before testing, all specimens were immersed in water at 37 degrees C for 24 hours, and thermocycled 1000 times in 5 degrees C and 55 degrees C water, with a dwell time of 30 seconds each. Tensile force was used to separate each specimen with the Instron universal testing machine. RESULTS Clearfil CR Inlay cement exhibited the highest mean tensile bond strength (18.4 MPa), followed by Dual (18.3 MPa), Twinlook (15.2 MPa), and Optec Dual-Cure luting (14.9 MPa) cements. One-way analysis of variance did not reveal any significant differences (p = 0.05) among groups. A majority of the fracture was adhesive at the ceramic and cement interface. CONCLUSION All four dual-cured cements formed strong bonds between enamel and Dicor cement, ranging from 14.90 MPa to 18.35 MPa, and there was no statistically significant difference.

Microleakage of a 4-methacryloxyethyl trimellitate anhydride bonding agent with amalgams

Microleakage contributes to deterioration of materials, recurrent decay, growth of microorganisms at the interface, and postoperative tooth sensitivity. This study examined the microleakage between amalgams and tooth surfaces with a cavity liner, a 4-methacryloxyethyl trimellitate anhydride bonding agent (Amalgambond) and six different types of amalgams. Class 1 cavity preparations in extracted human molars were filled with different combinations of liners and amalgams and were stored at 37 degrees C in physiologic saline solution. After 1 week half of each amalgam restoration was removed. Within the same group the same cavity treatment was performed and the same type of amalgam was packed as before. Microleakage was determined after 2000 thermal cycles. Statistical analysis indicated that Amalgambond significantly reduced microleakage of different amalgams compared with the Copalite-lined and unlined controls. No microleakage was detected at the interface between the existing and replacement amalgams.

A soldering index made with 4-META adhesive resin

Soldering indexes are most often made of fast-setting impression plaster or autopolymerizing resin. Lack of adhesive bonding between these materials and the casting requires the use of a bulky index to support the fixed partial denture components. The advent of adhesive resins improves the quality of the index and simplifies the procedure. A procedure for making a soldering index with 4-META adhesive resin is described that involves direct bonding of the resin to the metal castings. This procedure is accurate, simple, and time-saving. It can be used inside or outside the mouth, in prosthodontic or implant dentistry.