Retention of resin restorations by means of enamel etching and by pins

Abstract

An investigation was conducted into the effect of acid etching of the enamel and the use of pins on the retention of direct filling resins when used for restoration of fractured incisor teeth. The retention secured by these techniques as related to the cavity design also was studied. Four different cavity preparations were used. The retention of the resin in all four was compared when there was no pretreatment of the enamel, when the enamel was etched by 50 per cent phosphoric acid, and when pins were used for retention. Retention was assessed on the basis of resistance of the restoration to displacement by a lingual force. No significant difference was observed in retention as related to cavity design in the control specimens. In all four cavity preparations, acid etching of the enamel and the use of two retentive pins increased the resistance of the restorations to displacement. (However; when only one "L" shaped retentive pin was employed in Conjunction with a flat incisal preparation the force required to accomplish displacement was no greater than for controls.) The acid etch technique when employed with a cavity preparation that extended 1.7 mm. or more onto the lingual surface of the enamel generally offered a higher resistance to lingual force than double pin retained restorations. There was no significant difference between the resistance offered by a circumferential preparation when the resin was retained by either acid etching or by two pins. In the acid etch technique the enamel surface area and its distribution are important factors in retention.