Viability and Alkaline Phosphatase Activity of Human Dental Pulp Cells after Exposure to Yellowfin Tuna Bone-Derived Hydroxyapatite In Vitro.

The bone of yellowfin tuna (Thunnus albacares) contains high calcium and phosphor and can be synthesized into hydroxyapatite (HA). Due to its mineral content and similarity in chemical composition with human hard tissue, HA may have potency as a pulp capping material. The aim of this in vitro study was to evaluate the viability and alkaline phosphatase (ALP) activity of dental pulp cells after exposure to HA synthesized from yellowfin tuna bone (THA). Pulp cells were isolated from human-impacted third molar. To evaluate the viability of the pulp cells, the cells were cultured and exposed to various concentrations (6.25 to 200 µg/ml) of THA for 24, 48, and 72 hours. For ALP activity assay, pulp cells were cultured with odontoblastic differentiation media and exposed to THA for 7, 11, and 15 days. ALP activity was then determined using an ALP colorimetric assay kit. Results showed that the viability of the cells was more than 91% after exposure to various concentrations of THA and the cells demonstrated normal cell morphology in all observation periods. The ALP activity test revealed that groups exposed to THA for 7, 11, and 15 days showed higher ALP activity than the control groups (p < 0.05). It is concluded that THA had no cytotoxic effect on pulp cells; furthermore, it enhanced proliferation as well as ALP activity of the pulp cells.

Biofilm composition and composite degradation during intra-oral wear.

OBJECTIVES: The oral environment limits the longevity of composite-restorations due to degradation caused by chewing, salivary and biofilm-produced enzymes and acids. This study investigates degradation of two resin-composites in relation with biofilm composition in vitro and in vivo. METHODS: Surface-chemical-composition of two Bis-GMA/TEGDMA composites was compared using X-ray-Photoelectron-Spectroscopy from which the number ester-linkages was derived. Composite-degradation was assessed through water contact angles, yielding surface-exposure of filler-particles. Degradation in vitro was achieved by composite immersion in a lipase solution. In order to evaluate in vivo degradation, composite samples were worn in palatal devices by 15 volunteers for 30-days periods in absence and presence of manually-brushing with water. PCR-DGGE analysis was applied to determine biofilm composition on the samples, while in addition to water contact angles, degradation of worn composites was assessed through surface-roughness and micro-hardness measurements. RESULTS: In vitro degradation by lipase exposure was highest for the high ester-linkage composite and virtually absent for the low ester-linkage composite. Filler-particle surface-exposure, surface-roughness and micro-hardness of both resin-composites increased during intra-oral wear, but filler-particle surface-exposure was affected most. However, based on increased filler-particle surface-exposure, the high ester-linkage composite degraded most in volunteers harvesting composite biofilms comprising Streptococcus mutans, a known esterase and lactic acid producer. This occurred especially in absence of brushing. SIGNIFICANCE: Degradation during intra-oral wear of a low ester-linkage composite was smaller than of a high ester-linkage composite, amongst possible other differences between both composites. S. mutans herewith is not only a cariogenic, but also a composite-degradative member of the oral microbiome.

Effects of surface conditioning on repair bond strengths of non-aged and aged microhybrid, nanohybrid, and nanofilled composite resins.

This study evaluates effects of aging on repair bond strengths of microhybrid, nanohybrid, and nanofilled composite resins and characterizes the interacting surfaces after aging. Disk-shaped composite specimens were assigned to one of three aging conditions: (1) thermocycling (5,000 ×, 5-55 °C), (2) storage in water at 37 °C for 6 months, or (3) immersion in citric acid at 37 °C, pH 3 for 1 week; a non-aged group acted as the control. Two surface conditionings were selected: intermediate adhesive resin application (IAR-application) and chairside silica coating followed by silanization and its specific IAR-application (SC-application). Composite resins, of the same kind as their substrate, were adhered onto the substrates, and repair shear bond strengths were determined, followed by failure type evaluation. Filler particle exposure was determined by X-ray photoelectron spectroscopy and surface roughness analyzed using scanning electron and atomic force microscopy. Surface roughness increased in all composite resins after aging, but filler particle exposure at the surface only increased after thermocycling and citric acid immersion. Composite resin type, surface conditioning, and aging method significantly influenced the repair bond strengths (p < 0.05, three-way analysis of variance) with the least severe effects of water storage. Repair bond strengths in aged composite resins after IAR-application were always lower in non-aged ones, while SC-application led to higher bond strengths than IAR-application after thermocycling and water storage. In addition, SC-application led to more cohesive failures than after IAR-application, regardless the aging method.

Immediate repair bond strengths of microhybrid, nanohybrid and nanofilled composites after different surface treatments.

OBJECTIVES: To evaluate immediate repair bond strengths and failure types of resin composites with and without surface conditioning and characterize the interacting composite surfaces by their surface composition and roughness. METHODS: Microhybrid, nanohybrid and nanofilled resin composites were photo-polymerized and assigned to four groups: (1) no conditioning (Control), (2) no conditioning, polymerized against a Mylar strip (Control, with strip), (3) intermediate adhesive resin (IAR) application, and (4) chair-side silica coating, silanization and intermediate resin application (SC). Resin composites, similar as their substrates, were adhered onto the substrates. Shear force was applied to the interface in a universal testing machine and failure types were evaluated under light microscopy. Surface characterization was done by contact angle measurements, X-ray photoelectron spectroscopy, scanning electron and atomic force microscopy. RESULTS: Significant effects of the resin composite type and surface conditioning were observed. Conditioning the composites with their IARs does not result in significant improvements in bond strength compared to the control with strip (bond strengths between 14.5 and 20.0 MPa). SC increased the bond strength in all composites except TE by an average 8.9 MPa, while in all composites the surface roughness increased from 7 to 384 microm. Failure types in this group were exclusively cohesive. Physico-chemical modelling of the composite surfaces showed that the surfaces were dominated by the resin matrix, with a major increase in silica-coverage after SC for all composites. CONCLUSION: Intermediate adhesive resin conditioning did not improve the composite-to-composite immediate repair strength. Silica coating and silanization followed by its corresponding IAR, strongly increased repair bond strengths and provided exclusively cohesive failures in the substrate in all composites.