Filler Shape Film Thickness and Strength Post Retention

Research

Filler Shape, Film Thickness and Strength Relationships for Post Retention

R.A. Stannard and S.R. Stannard
IADR - Brisbane, Australia (2006)

Objectives
To improve cement retention of fiber posts and overall tooth integrity in endodontic treatment. Evaluate filler shapes, spherical vs. whisker, for post retention (PR). Fiber post use in endodontic treatment has many advantages over conventional metal post or cast post and core treatment. Esthetics, translucence for cement curing, ease of removal and post flexure are some of these potential advantages.

Methods
To optimize this system, resin/filler variations were evaluated for filler shape, film thickness (FT), diametral tensile strength (DTS), compressive strength (CS), and fiber post retention (PR) (1.2mm post at 7mm) for four different resin cements. All cements were 30% filled, silanated, and were two part, dual cure. Two spherical fillers, S1-4µ (control) and S2-9.6µ, and two whisker fillers,W1-0.1mm and W2-0.4mm, were evaluated. Each strength (n=5) and PR (n=7) measurements at 0.5in/min. Post retention on human single rooted teeth, EDTA and H20 irrigation only. ANOVA and material comparisons were analyzed p < 0.05. Results: FT in µ was: S1-5µ, S2-20.5µ, W1-125µ and W2 -202µ. D.T.S. in MPa±S.D. was: S2 (27.9±2.2); S1 (31.5±2.5); W2 (32.7±1.5); W1 (34.6±1.0) S2 < S1 = W2 < W1. C.S. in MPa±S.D. was: W2 (121.9±2.4); W1 (147.0±5.9); S2 (181.1±27.1); S1 (274.6±28.7) W2 < S1 = W1 = S2. PR in kg±S.D. was W2 (7.8±2.5); S1 (11.8±3.4); W1 (13.0±5.5); S2 (14.6±7.8); W2 < S1 = W1 = S2.

Conclusions
D.T.S. was greatest for cements containing whisker fillers while C.S. was greatest for cements containing spherical fillers. Post retention was influenced more by film thickness. The cement with the greatest film thickness provided the lowest retention. Cements of quite different physical and handling properties could, however, provide equal retention values.