Resin-bonded prostheses: microleakage and luting agent thickness of etched and cast-meshwork retainers

Effects of adhesive fixed prosthesis retainer design on resultant resin luting agent thickness

STATEMENT OF PROBLEM

Resin cement thickness may influence the success or otherwise of adhesive fixed prostheses and needs to be quantified for future stress analyses.

PURPOSE

This study evaluated the effect of different complexities of retainer preparation design on resultant resin lute thickness.

MATERIAL AND METHODS

Five retainer designs were evaluated for resin luting thickness (Panavia Ex) after cementation to appropriately selected natural teeth as follows: (1) flat plate retainer; mandibular canine; (2) occlusal rests, mandibular premolar; (3) occlusal rests, proximal grooves, mandibular premolar; (4) modified three-quarter crown, mandibular premolar; and (5) occlusal strut, maxillary premolar. Five samples of each design were prepared in vitro. A mesiodistal and a buccolingual section were obtained from each sample with a diamond saw. Measurements were carried out on the fluorescent cement lute with a confocal microscope. Mean resin thickness and cervical resin thickness were analyzed with analysis of variance and Tukey tests.

RESULTS

Resin thickness (micron) for each of the retainer designs were as follows (mean +/- SD): design 1, 58 +/- 40; design 2, 67 +/- 42; design 3, 80 +/- 28; design 4, 87 +/- 15; and design 5, 85 +/- 29. There were no significant differences among the designs (mean global value 75.4). The three-quarter crown (design 4) had a significantly wider cervical resin thickness (P < or = .01) than designs 1, 2, and 3.

Influence of saliva contamination and abrasion on resin to tin-plated alloy bond strengths

This investigation studied the effects of abrasion and salivary contamination on the shear bond strength of a composite resin bonded to tin-plated gold alloy. Experimental groups (n = 15) consisted of: group 1, no surface treatment; group 2, enamel abraded; and group 3, saliva-contaminated. After surface stressing and bonding, groups were thermocycled before shear testing. Fractured interfaces were analyzed by use of light microscopy and SEM. Specimens in group 3 (12.2 +/- 2.5 MPa) had significantly lower bond strengths than group 1 (17.9 +/- 6.8 MPa). The shear bond strengths of resin bonded to tin-plated metal were significantly affected by salivary contamination but not by abrasion.

Shear bond strength of two resin adhesives for acid-etched metal prostheses

This study compared the shear bond strength of Panavia EX and Comspan Opaque adhesive resins with electrolytically etched or sandblasted Rexillium III or Litecast B metals bonded to extracted teeth. An analysis of variance revealed that there is no difference in bonding strength among etched or sandblasted Rexillium III metal with either Panavia EX or Comspan Opaque resins. With Litecast B metal, sandblasting produced a greater bond strength than etching with Panavia Ex resin (38.19 MPa sandblasted; 30.53 MPa etched). Conversely, Comspan Opaque resin had a value of 30.10 MPa etched and 15.40 MPa sandblasted. The etched Rexillium III and Panavia EX resins recorded a greater bond strength (38.38 MPa) than Comspan Opaque resin (27.83 MPa) or sandblasted Rexillium III metal (Rexillium III 34.74 MPa; Comspan Opaque 20.39 MPa) and Litecast B metal (Panavia EX 38.19 MPa; Comspan Opaque 15.40 MPa). Eighty percent of the failures occurred at the cement-metal interface with both cements.