Innovation Glass-Ceramic Spray Deposition Technology Improving the Adhesive Performance for Zirconium-Based Dental Restorations.

Glass-ceramic spray deposition (GCSD) is a novel technique for coating lithium disilicate (LD) glass-ceramics onto zirconia through simple tempering steps. GCSD has been proven to improve the bonding of zirconia to resin cement, but the effect of etching time on GCSD and the long-term durability of the bond achieved remain unknown. The effects of air abrasion with aluminum particles (ABB) and air abrasion (GAB) or etching with 5.0% hydrogen fluoride (HF) for 20, 60, 90, and 120 s (G20, G60, G90, and G120) on the resin cement−zirconia bond were studied. LD was included as a control (LDG). The microstructure, sub-micron roughness, wettability, and phase changes of samples were analyzed. After resin cement was bonded to zirconia, half of the samples were subjected to thermocycling (5000 cycles at 5−55 °C). The bond strengths of the samples were determined in shear bond strength (SBS) tests (n = 10 per group). An LD structure can be formed on zirconia after GCSD and proper etching processes, which result in high roughness and a hydrophilic nature. GCSD and HF etching significantly improved SBS, with G90 and G120 samples with pre- or post-thermocycling exhibiting SBS values comparable to those of LDG (p > 0.760). The surface characteristics of the LD layer are influenced by the etching time and affect the SBS of the bond of zirconia to resin cement. HF etching for 90−120 s after GCSD results in zirconia with SBS and bond durability comparable to LD.

Food Security Sensing System Using a Waveguide Antenna Microwave Imaging through an Example of an Egg.

In this paper, we present a form of food security sensing using a waveguide antenna microwave imaging system through an example of an egg. A waveguide antenna system with a frequency range of 7-13 GHz and a maximum gain of 17.37 dBi was proposed. The maximum scanning area of the waveguide antenna microwave imaging sensing system is 30 × 30 cm2. In order to study the resolution and sensitivity of the waveguide antenna microwave imaging sensing system, the circular and triangular high-k materials (with the same thickness but with different dielectric constants of the materials) were used as the testing sample for observing the microwave images. By using the proposed waveguide antenna microwave imaging sensing system, the high-k materials with different dielectric constants and shapes could be easily sensed. Therefore, the waveguide antenna microwave imaging sensing system could be potentially used for applications in rapid, non-destructive food security sensing. Regarding the example of an egg, the proposed waveguide antenna microwave imaging sensing system could effectively identify the health status of many eggs very quickly. The proposed waveguide antenna microwave imaging sensing system provides a simple, non-destructive, effective, and rapid method for food security applications.

Surface changes and bacterial adhesion on implant abutment materials after various clinical cleaning procedures.

BACKGROUND: Supportive treatments are essential to long-term dental implant success; however, professional cleaning procedures may alter the surfaces of implant abutments and lead to adverse biological responses. This study aimed to evaluate four clinically used cleaning procedures by examining surface changes and subsequent bacterial adhesion on abutment materials. METHODS: Discs of titanium and zirconia were polished and divided into five groups: titanium curette treatment, carbon fiber reinforced plastic curette treatment, ultrasonic scaling with carbon fiber tip treatment, air polishing with glycine powder, and control group without any treatment. After instrumentation, the arithmetical mean roughness (Ra), hydrophilicity, and surface free energy were recorded. The bacterial adhesion was evaluated after 1 h of Streptococcus mitis incubation by optical microscope and quantified by turbidity test. RESULTS: Among the titanium samples, titanium curette treatment group showed significant surface morphology changes, increased Ra, hydrophilicity, surface free energy, and higher optical density of adhered bacteria. As for the zirconia samples, the differences in surface morphology, Ra, and bacterial adhesion between groups were nonsignificant. CONCLUSION: Comparing to titanium, zirconia was less susceptible to surface changes after tested cleaning procedures. Titanium curette should be used with care on titanium abutments.

Surgical considerations and management of bilateral labially impacted canines.

Canines are among the most commonly impacted teeth. When a canine is positioned labially, the untoward soft-tissue responses following surgical exposure may cause unfavorable esthetic outcomes. Therefore, decision making as to the choice of a proper surgical technique to uncover labially impacted teeth is critical. This case presentation describes two different surgical approaches for two maxillary impacted canines in a 12-year-old girl. A sequential approach included a first stage of surgical exposure using apically positioned flaps and orthodontic extrusion of both impacted teeth. A successive laterally positioned flap was used for the left maxillary canine to achieve a harmonious soft-tissue contour. In this case, close monitoring and cooperation during the various treatment phases led to proper canine positioning and a successful esthetic result, with good periodontal health and functional occlusion.

Photoconductive method for measuring light transmission to the root of metal-ceramic and all-ceramic restorations.

OBJECTIVES: In this study, the authors attempted to develop a photoconductive method for measuring light transmission through a crown restoration to the root dentin; metal-ceramic crowns with four coping designs (metal collar, and metal framework ending 0, 1, and 2mm coronal to the axiogingival line angle) and two all-ceramic crowns (Empress II and In-Ceram Alumina) were compared. METHODS: According to pre-registered templates, 36 crowns were fabricated for an extracted central incisor. A cadmium sulfide (CdS) photoconductive cell was secured onto the root of a tooth, which was fixed in a light box. The validity and reliability of the experimental design were verified, and the impedance of the cell was recorded when the crowns were placed on the prepared tooth with or without try-in pastes under a constant luminance. RESULTS: A significant correlation (r= -0.99, p<0.001) was found between the light intensity and impedance of the CdS cell, and a 1.15% coefficient of variation between repeated measurements was observed. In this study, Empress II crowns had the smallest impedance, indicating that they provided the best light transmission. Conventional metal-ceramic crowns had the least light transmission, which was significantly improved by reducing the metal collar (p<0.05). The framework of metal-ceramic crowns which ended 2mm coronal to the axiogingival line angle showed as much light transmission as the In-Ceram crowns. The impedance increased when try-in pastes were employed in all test groups. SIGNIFICANCE: The photoconductive method was proven to be a reliable technique for measuring the light transmitted through restorations into the adjacent tissue.

Effects of simulated clinical grinding and subsequent heat treatment on microcrack healing of a lithium disilicate ceramic.

Grinding intaglio surfaces of ceramic restorations with diamond burs is a common procedure to improve fit. This study evaluated the effects of simulated diamond bur grinding and subsequent veneer firing and glazing on a lithium disilicate glass-ceramic. The results revealed a significant reduction in the roughness and strength of the material after diamond bur grinding, whereas the strength was restored through crack healing and formation of a glass layer after heat treatment. The finding indicates that grinding of lithium disilicate ceramics with diamond burs may introduce flaws and cracks, and therefore subsequent heat treatments, veneer firing, or glazing, are suggested.