Effect of ceramic calcium-phosphorus ratio on chondrocyte-mediated biosynthesis and mineralization.

The osteochondral interface functions as a structural barrier between cartilage and bone, maintaining tissue integrity postinjury and during homeostasis. Regeneration of this calcified cartilage region is thus essential for integrative cartilage healing, and hydrogel-ceramic composite scaffolds have been explored for calcified cartilage formation. The objective of this study is to test the hypothesis that Ca/P ratio of the ceramic phase of the composite scaffold regulates chondrocyte biosynthesis and mineralization potential. Specifically, the response of deep zone chondrocytes to two bioactive ceramics with different calcium-phosphorus ratios (1.35 ± 0.01 and 1.41 ± 0.02) was evaluated in agarose hydrogel scaffolds over two weeks in vitro. It was observed that the ceramic with higher calcium-phosphorus ratio enhanced chondrocyte proliferation, glycosaminoglycan production, and induced an early onset of alkaline phosphorus activity, while the ceramic with lower calcium-phosphorus ratio performed similarly to the ceramic-free control. These results underscore the importance of ceramic bioactivity in directing chondrocyte response, and demonstrate that Ca/P ratio is a key parameter to be considered in osteochondral scaffold design. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 2694-2702, 2017.

An evaluation of wear when enamel is opposed by various ceramic materials and gold.

STATEMENT OF PROBLEM: Ceramic restorations have been known to cause wear of opposing enamel. PURPOSE: The purpose of this study was to evaluate enamel wear caused by 3 ceramic substrates in the glazed and polished conditions. MATERIAL AND METHODS: Sixty ceramic discs (10 x 2 mm)-20 each of Finesse, All-Ceram, and IPS-Empress-were prepared and glazed. Each group of 20 was divided into 2 groups of 10. The surfaces of one group were ground and polished using a porcelain polishing kit (Dialite). The remaining 10 were left as glazed. Ten specimens of a type III gold alloy were cast into rectangular shapes of 10 x 12 x 2 mm and polished. Seventy human cusps were prepared from sound, caries-free, extracted teeth and abraded against the substrates in a wear machine for a total of 10,000 cycles. The cusp height loss was traced before and after the wear test using a profile projector. Mean surface roughness (R(a)) values for the substrates were also recorded with a profilometer before testing. Differences in R(a) were evaluated using 1- and 2-way ANOVA and the Scheffe post hoc test (alpha = .05). RESULTS: One-way ANOVA indicated that enamel height loss was significantly different by material (P < .001) and surface condition (glazed and polished or glazed; P < .05). Gold, polished Finesse, and polished All-Ceram were the least abrasive, whereas glazed IPS-Empress was the most abrasive. There was no significant interaction effect between substrate type and surface condition. Significant differences were found when R(a) of the substrate condition was compared with enamel wear (P < .01). CONCLUSIONS: Gold, polished Finesse, and polished All-Ceram caused the least enamel wear, whereas IPS-Empress caused the most wear. Cast gold was significantly different than glazed IPS-Empress (P < .05), whereas other groups overlapped. There was significant correlation between R(a) and enamel wear (P < .01).

Dental calculus composition following use of essential-oil/ZnCl2 mouthrinse.

PURPOSE: To test the hypothesis that anticalculus agents cannot completely inhibit calculus formation but can influence the types of calcium phosphate which form, i.e., they can influence the composition of the inorganic component of human dental calculus (HDC). MATERIALS AND METHODS: The composition of HDC specimens obtained from a 16-week multi-center clinical study using three regimens were analyzed, investigators blinded. The treatment regimens were: (a) standard dentifrice (SD), (b) pyrophosphate antitartar dentifrice, and (c) SD with Tartar Control Listerine Antiseptic mouthrinse (containing essential oils and 0.09% zinc chloride). 25 individual samples and eight pooled samples from each group were analyzed using X-ray diffraction, infrared spectroscopy, and scanning electron microscopy. RESULTS: (1) relative frequency of occurrence for: (a) bacteria: Group A = 100%, Group B = 60%, and Group C = 25%; (b) Carbonate hydroxyapatite (CHA): Groups A, B, and C = 100%; (c) dicalcium phosphate dihydrate (DCPD): Group A = 55%; Group B = 45%; Group C = 80%; (2) The relative amount of DCPD is inversely proportional to that of CHA in HDC: the higher the amount of DCPD, the lower the amount of CHA. Group C regimen with essential oil/ZnCl2 mouthrinse and standard dentifrice showed a significant anti-microbial effect and favored the formation of DCPD, the most soluble Ca-P.