Evaluation of Multiple-Mechanical-Properties of Luting-Cements and Retention of Temporary Crowns

Objectives: To evaluate mechanical properties of temporary luting cements and the influence in retention capacity of temporary crowns.
Methods: Evaluated properties were: diametral-tensile-strength (DTS), Knoop (KHN) microhardness, setting-time (ST), and pulling-strength (PS). Three temporary luting cements were evaluated: [LF] calcium-hydroxide-cement (Life®, Kerr); [TB] zinc-oxide-and-eugenol-cement (TempBond®, Kerr); [NE] zinc-oxide-non-eugenol-cement (TempBond® NE, Kerr). For the DTS, cylindrical samples of 8mm x 7mm (n=10) for each study group were fabricated using PVS molds and following-manufacturer-instructions. Samples were tested using an universal-testing-machine (Instron) speed of 0.5mm/min until failure. For KHN cylindrical samples of 10 mm in diameter and 2mm in depth (n=10) per group were fabricated, using PVS-molds and following-manufacturer-instructions . For ST (n=10) samples per study group were fabricated. For PS, 30 sound-extracted-human-third -molars were used. Metal-ceramic-crown-preparations were made. Taper was determined with electronic goniometer (Olympus Imaging America Inc.) and the height of the preparations were measured with an electronic caliper (Mitutoyo 500 Digimatic). Provisional-crowns were made (PMMA Jet acrylic, Land Dental Manufacturing Co). Cements were manipulated and luting load was 2.5 Kg/5 minutes. Retention was tested using the same universal testing machine with speed of 0.5mm/min. Statistical-analysis ANOVA was performed with a pre-set alpha of 0.05.
Results: For DTS, no statistical differences were found among groups (p>0.05), with mean values of 1.28MPa for LF, 1.22Mpa for TB, and 1.15Mpa for NE. For KHN, statistically-significant-differences (p<0.0001) were found. LF had the highest microhardness value (12.7±1.88) followed by TB (3.67±0.99) and NE (1.29±0.28). For ST, there were statistical-significant-differences (p<0.0001). TB (3.73±0.28) and NE (3.82±0.47) had a significant longer setting time than LF (2.86±0.29). For PS, statistical differences were found. Mean-dislodgment-forces were 47.8N for LF, 27.94N for TB, and 21.1N for NE (P<0.001). Height and convergent angle of the preparation did not show significant differences.
Conclusions: Conclusions: Temporary cements-based-on-calcium-hydroxide showed stronger retentive capacity than cements -based-on-zinc-oxide.