Biomaterials: Ceramic and Adhesive Technologies

Advances in Ceramics for Dental Applications

The purpose of this study is to present current dental ceramic materials and processing methods. The clinical indication was emphasized on basis of the material's microstructure and composition. Studies of ceramic characterization were also discussed, as they impact the clinical indication and serve as a parameter for the development of new materials. The novel strategies were mostly found aiming to mimic the natural dental structures, provide mechanical reliability, and develop predictable restorations in terms of adaptation and design.

Bur choice when removing zirconia restorations

PURPOSE

Removal of zirconia restorations can be challenging and time consuming, requiring dental burs with optimal cutting efficiency to minimize iatrogenic complications. Yet, there are very few burs marketed for this purpose and little evidence of their comparative benefit. This study evaluated one specialized bur and compared its cutting efficiency with three general-purpose burs (one single use and two multiple use) MATERIALS AND METHODS: This study was designed to assess the cutting efficiency of four burs on a high strength zirconia substrate. One of these burs is a multiple use bur marketed for high strength ceramics (Komet 4ZR), another is a single use general-purpose bur (Piranha 837.012 coarse), and two are multiple use general-purpose burs (Brassler 6837.31.012C coarse and Komet 6837.314.012 coarse). The cutting efficiency of each bur was determined by measuring the time taken to perform serial 2 mm cuts into a block of zirconia. Ten burs in each group were tested with repeated cuts until the time taken for a 2 mm cut was twice that of the first 2 mm cut (50% loss of efficiency). This study was performed under reproducible conditions using a custom designed and fabricated rig assembly.

RESULTS

The results demonstrated a statistically significant difference in the cutting efficiency between bur types. The single use general-purpose bur (Piranha 837.012) was the most efficient for all cut numbers p <2.2 × 10^-16 . The performance of all burs decreased with each cut, with cutting efficiency dependent on time point/cut number (p = 0.02). The rate of deterioration varied between burs, but this difference was not sufficient to be statistically significant.

CONCLUSIONS

This study demonstrated that a single use bur is more efficient than 3 multiple use burs. The cutting efficiency of a single use general-purpose bur (Piranha 837.012 coarse) on Cerec Zirconia Mono L was statistically superior to that of multiple patient use burs in this study, including one marketed for use on high strength ceramics. Because single use burs are comparatively inexpensive and require no sterilization, they should be strongly considered for the removal of zirconia restorations. This article is protected by copyright. All rights reserved.

Initial curing characteristics of composite cements under ceramic restorations

PURPOSE

To assess the degree of conversion (DC) of dual-curing composite cements when cured through ceramic-veneered zirconia disks.

METHODS

Portions of mixed cement, either G-CEM LinkForce (GC), Panavia V5 (Kuraray Noritake) or ResiCEM (Shofu), were placed on the ATR crystal of a Fourier Transform Infrared Spectroscope (FTIR; iS50, Thermo Scientific) and squeezed to a 100-µm film thickness using a microscopy cover glass. DC (%) of the composite cements applied in self-curing mode was measured in the dark at 37°C. Following the dual-curing mode, the cements were light-cured directly (positive control) or through a ceramic-veneered zirconia disk (0.5-mm thick zirconia with a 1.0-mm thick veneering ceramic) for 40 sec using two light-curing units (G-Light Prima 2, GC; PenCure, Morita). Per experimental group, 5 tests were conducted to measure DC in self-cure and dual-cure mode (n=5). FTIR spectra of the composite cement films were acquired to determine DC every min up to 30 min. DC of the composite cements was statistically compared using two-way repeated-measures ANOVA (α=0.05).

RESULTS

For all cements investigated, the self-curing mode resulted in significantly lower DC at 10, 20 and 30 min than the light-curing mode. When the composite cements were light-cured through the zirconia disk, DC at 30 min dropped significantly for ResiCem (Shofu), while not for Panavia V5 (Kuraray Noritake) and G-CEM LinkForce (GC).

CONCLUSIONS

Self-curing slows down polymerization but does not reach for all composite cements the highest (light-cured) DC. Ceramic-veneered zirconia-based restorations may affect DC of some composite cements.