The effect of storage time of removable partial denture wax pattern on the accuracy of fit of the cast framework.

STATEMENT OF PROBLEM Situations may arise in dental laboratories that could result in a time lapse between preparing the wax pattern of the removable partial denture framework and its casting into the cobalt-chromium alloy. PURPOSE This study investigated the effect of storage time of the wax pattern before casting and the influence of the palatal major connector design on the accuracy of its fit on the master casts. MATERIAL AND METHODS Forty-two frameworks were prepared with two designs of major connectors, which were divided into three subgroups according to the storage time of the wax patterns: 24 hours, 1 week, and 1 month. Discrepancies in the fit of the connectors to their respective casts were measured at specific locations for both connector designs. RESULTS In both framework design groups, there was a significant deterioration in fit (p < 0.0005) of the major connectors with the increase in storage time of their wax patterns on their respective refractory casts. Gap discrepancies were more pronounced towards the center of the palate. CONCLUSIONS The greatest discrepancies appeared at the middle sections of the connectors more than at the lateral section (p < 0.0005). Furthermore, frameworks with modified palatal plate major connectors exhibited greater inaccuracies in their fit than those with the anterior posterior palatal strap design, as evidenced by the increase in mean gap discrepancies under the palatal plate design (p < 0.0005).