Abstract
The objective was to evaluate the effect of luting agents and the preparation design on the internal fit of zirconia restorations. Sixty dies were prepared and divided in occlusal convergence angle of 6° (OC6) and 12° (OC12). CAD/CAM zirconia copings were fabricated (Lava All-Ceramic System). A zinc phosphate cement (ZPC); a glass ionomer cement (GIC); and a resin cement (RC) were studied. Specimens were sectioned and coping/die discrepancies were evaluated through Stereoscopic Microscopy. A closer fit was observed in OC12 when compared to OC6 (p < 0.001). For OC6 no significant differences were observed in between ZPC, GIC, and RC (p > 0.05). For OC12, a significantly closer fit was recorded on the ZPC subgroup when compared to the GIC subgroup (p < 0.001). Preparations of 12 degrees demonstrated a closer internal fit when compared to 6 degrees. Preparations of 12 degrees achieved better internal fit values with ZPC (Fortex) followed by RC (RelyX Unicem), and GIC (Ketac Cem). No differences were found when comparing different luting agents over 6° degrees preparations.
Highlights
Through the years, several definitions have been proposed for the term internal adaptation or internal fit [1,2,3]
This study shows the remarkable relation between preparation design and cements when internal fit of ceramic restorations is evaluated
Preparations with a total occlusal convergence angle of 12-degrees achieved better internal fit values when compared with 6-degree preparations
Summary
Several definitions have been proposed for the term internal adaptation or internal fit [1,2,3]. Internal adaptation can be defined as the accuracy with which a restoration sits onto the corresponding tooth preparation [4]. Several critical factors are dependent upon the clinician’s knowledge and execution capabilities related with tooth preparation design (total preparation occlusal convergence angle, finish line design, occlusal reduction, and surface roughness), impression material selection, and technique, all capable of impacting upon the accuracy of the working cast and, affecting the resulting restorations. From the dental laboratory perspective, apart from a knowledgeable and careful material selection and execution, adjusting the thickness of cement spacing to meet the future requirements of the luting agent and cementation technique will be determinant to improve the clinical fit of the restoration after cementation [4,5,9,10,11]
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