Internal adaptation of cast titanium crowns

Abstract

As the adaptation of titanium crowns obtained by Rematitan Plus investment, specific for titanium, is not recognized to be suitable, this study evaluated the effect of the concentration of the specific liquid and the temperature of the mold of investments on the internal misfit of crowns cast on commercially pure titanium. Individual dies of epoxy resin were obtained, representing teeth prepared for full-crown restoration with a 6-degree axial surface convergence angle and shoulder (1.0 mm). For the waxing of each crown, a ring-shaped stainless steel matrix (8.0mm internal diameter; 7.5 mm height) was adapted above the individual dies of epoxy resin. The Rematian Plus investment was mixed according to the manufacturer's instructions using two different concentrations of the specific liquid: 100%, 75%. Casting was performed in a Discovery Plasma Ar-arc vacuum-pressure casting machine with molds at temperatures of 430°C, 515°C and 600°C. The crowns were cleaned individually in a solution (1% HF + 13% HNO3) for 10 min using a ultrasonic cleaner, with no internal adaptations, and luted with zinc phosphate cement under a 5 kg static load. The crown and die assemblies were embedded in resin and sectioned longitudinally. The area occupied by cement was observed using stereoscopic lens (10X) and measured by the Leica Qwin image analysis system (mm2). The data for each experimental condition (n=8) were analyzed by Kruskal-Wallis non-parametric test (á=0.05). The results showed that liquid dilution and the increase in mold temperature did not significantly influence the levels of internal fit of the cast titanium crowns. The lowest means (±SD) of internal misfit were obtained for the 430°C/100%: (7.25 mm2 ±1.59) and 600°C/100% (8.8 mm2 ±2.25) groups, which presented statistically similar levels of internal misfit.

Internal fit of two all-ceramic systems and metal-ceramic crowns

“…In addition, there is a lack of studies that measure the internal fit and further differentiate the measures of occlusal and axial fit, which hinder any comparison with other studies outcomes 22 . Moreover, the replica technique used in the present study to evaluate the IF of crowns has been extensively used as a non-destructive, reliable and valid method 8 .…”

“…Finally, though marginal fit has been associated with marginal gingivitis, occlusal fit may play a significant role on structural durability of all-ceramic crowns and the axial wall cement space can influence the retention of fixed prostheses 25 . In addition, there is a lack of studies that measure the internal fit and further differentiate the measures of occlusal and axial fit, which hinder any comparison with other studies outcomes 22 . Moreover, the replica technique used in the present study to evaluate the IF of crowns has been extensively used as a non-destructive, reliable and valid method 8 .…”

Investigation of Stresses in Teeth Prepared with Different Tapers and Restored with Cast Crowns

“…The margin should have a chamfer configuration, be smooth and distinct and its width should be approximately 0.5 mm, which will allow adequate bulk of metal at the margin (Rosenstiel et al, 2001). The fit of cast denture restoration is essential because it may influence the thickness of the cement margin, periodontal soundness, and the risk of secondary caries, which are decisive factors accounting for the clinical success of restorations (Rocha et al, 2007). Over the past decades, the search for dental materials of good quality and safe to patient's health has increased significantly.…”