Effect of dentin desensitizers and cementing agents on retention of full crowns using standardized crown preparations

Statement of problem. Past research has not controlled preparation surface area when examining the influence of dentin desensitizers on the retentive strength of cemented cast crowns, leading to inconsistent results. Purpose. This research controlled crown preparation surface area and evalua ted. the the effect of various dentin desensitizers and conventional cement ing agents on the in vitro retentive strength of cast crowns. Methods and material. Freshly extracted human molars were prepared for a st andardized crown preparation (26 degrees total convergence, 4 mm axial heig ht) with a custom-made pantograph. Dentin desensitizers included none (cont rol), a polymerizable material (All-Bond 2), and a nonpolymerizable desensi tizer (Gluma Desensitizer). Cementing agents included zinc phosphate (Fleck 's), glass ionomer (Ketac-Cem) resin-modified glass ionomer (Fuji II), and resin cement (Panavia 21). Twelve teeth were prepared for each test conditi on (144 teeth total). Individual castings were made from a base metal alloy (Rexillium III). Crowns were removed after storage at 26 degrees C for 48 hours at 100% relative: humidity! using a universal testing machine at a cr osshead speed of 1.27 mm/min. The proportion of cement retained on the toot h and casting after debonding nas quantified according to treatment. Statis tical treatment included 1- and 2-way ANOVAs, followed by the Tukey-Kramer post hoc test at a preset alpha of 0.05. Results. Resin cement exhibited the highest retentive strength and all dent in treatments resulted in significantly different retentive values (All-Bon d 2 (5.68 +/- 0.70 MPa) > control (4.67 +/- 0.48 MPa) > Gluma. (4.12 +/- 0. 37 MPa)). Retention of resin-modified glass ionomer was between thr resin c ement and glass ionomer groups: All-Bond 2 (3.46 +/- 0.26 MPa) > Gluma (2.8 1 +/- 0.15 MPa) = control (2.96 +/- 0.18 MPa). Conventional glass ionomer v alues were between those of Fuji Plus and zinc phosphate groups: All Bond 2 (2.23 +/- 0.20 MPa) = control (2.36 +/- 0.20 MPa) > Gluma (1.98 +/- 0.23 M Pa). Zinc phosphate had the: lowest retention values: control (1.68 +/- 0.0 8 MPa) > Gluma (0.81 +/- 0.11 MPa) > All-Bond 2 (0.67 +/- 0.14 MPa). The ma jority! of cement was retained on the debonded tooth surface versus thr cas ting, with the excetption of zinc phosphate: when: used with dentin pretrea tments. Conclusion. Controlled crown surface areas reduced the variation in strengt h values permitting high discrimination among retention values of desensiti zer/cement combinations. In all but 1 combination, Gluma desensitizer signi ficantly! decreased crown retention. With resin cement and resin-modified g lass ionomer, use of All-Bond 2 desensitizer significantly increased crown retention values.