In Vitro Caries Models for the Assessment of Novel Restorative Materials.

Due to the high failure rates of traditional dental restorations, there is an ongoing effort to develop modified and new restorative biomaterials in dentistry. Being the most commonly used restorative material, most of these efforts primarily aim to improve dental composite. Generally, the main objective of such modifications is to enhance the restorative physical and antimicrobial properties in order to limit micro-leakage and inhibit bacterial biofilm cultivation. Herein, we describe the process of designing a simple in vitro model to assess the physical and antimicrobial properties of novel restorative materials in addition to evaluating their effect on the fragile balance between enamel de- and remineralization.

Bactericidal and Bioactive Dental Composites.

Aim: Antimicrobial and bioactive restorative materials are needed to develop a bacteria free environment and tight bond with the surrounding tissue, preventing the spread of secondary caries and thus extending the lifetime of dental restorations. The characteristic properties of new dental bioactive and antibacterial composites are presented in this work. The new composites have been microstructurally characterized and both long and short term properties have been studied. Methods: The Ag-doped sol-gel derived bioactive glass (Ag-BG) was incorporated into resin composite in concentrations 5, 10, and 15 wt.%, to fabricate new Ag-doped bioactive and antibacterial dental composites (Ag-BGCOMP). The microstructural properties and elemental analysis of the developed Ag-BGCOMP was observed. The total bond strength (TBS) was measured immediately and after long term of immersion in medium using microtensile testing. The capability of Ag-BGCOMPs to form apatite layer on their surface after immersion in Simulated Body Fluid (SBF) as well as the bacteria growth inhibition in a biofilm formed by Streptococcus mutans (S. mutans) were evaluated. Results: Homogeneous distribution of Ag-BG particles into the resin composite was observed microstructurally for all Ag-BGCOMPs. The TBS measurements showed non-statistically significant difference between control samples (Ag-BG 0 wt.%) and Ag-BGCOMP specimens. Moreover, the total bond strength between the surrounding tooth tissue and the material of restoration does not present any statistically significant change for all the cases even after 3 months of immersion in the medium. The bioactivity of the Ag-BGCOMPs was also shown by the formation of a calcium-phosphate layer on the surface of the specimens after immersion in SBF. Antibacterial activity was observed for all Ag-BGCOMPs, statistically significant differences were observed between control samples and Ag-BGCOMPs. Accordingly, the number of dead bacteria in the biofilm found to increase significantly with the increase of Ag-BG concentration in the Ag-BGCOMPs. Conclusions: New resin composites with antibacterial and remineralizing properties have been manufactured. Characterization of these materials provides a rationale for future clinical trials to evaluate clinical benefits and outcomes in comparison with currently used dental materials. Significance: The new developed composites could ultimately prevent restoration failure and could advance patients' wellbeing.

Orai1 expression pattern in tooth and craniofacial ectodermal tissues and potential functions during ameloblast differentiation.

BACKGROUND: Orai1 is a plasma membrane protein that forms the pore of the calcium release activated calcium channel. Humans with mutated Orai1 present with hereditary combined immunodeficiency, congenital myopathy and anhidrotic ectodermal dysplasia. Consistent with the ectodermal dysplasia phenotype, enamel formation and mineralization is also abnormal in Orai1 deficient patients. The expression pattern and potential functions of Orai1 in enamel formation remains unclear. To contribute toward understanding the role of Orai1 in amelogenesis we characterized ORAI1 protein developmental pattern in comparison with other ectodermal organs. We also examined the effects of Orai1 down-regulation in ameloblast cell proliferation and differentiation. RESULTS: Our data show strong expression of ORAI1 protein during the ameloblast secretory stage, which weans at the end of the maturation stage. In salivary glands, ORAI1 is expressed mainly in acini cells. ORAI1 expression is also found in hair follicle and oral epithelium. Knockdown of Orai1 expression decreases cell proliferation and results in RNA expression levels changes of key ameloblast genes regulating enamel thickness and mineralization. CONCLUSIONS: This study provides insights in the anhidrotic ectodermal dysplasia phenotype due to Orai1 mutation and highlights the importance of calcium signaling in controlling ameloblast differentiation and maturation during tooth development.

Designing dental composites with bioactive and bactericidal properties.

OBJECTIVES: The aim of this work was to fabricate and evaluate new antibacterial and bioactive composites capable of strictly controlling oral bacteria, enhancing apatite layer formation and retaining their mechanical properties. METHODS: A new Ag-doped bioactive glass (Ag-BG) was incorporated into flowable dental composite (COMP) in different concentrations (1, 5, and 15 wt.%) in order to fabricate new combined bioactive and antibacterial composite materials (Ag-BGCOMPs). The antibacterial properties, bioactivity, and total bond strength of the Ag-BGCOMPs were evaluated. RESULTS: The bioactivity of the Ag-BG was confirmed after its immersion in simulated body fluid (SBF). The total bond strength between the surrounding tooth tissue and the new composites or the control (dental composite alone) has not shown any statistically significant difference in the performed pilot study. Antibacterial activity was observed against Escherichia coli (E. coli) and Streptococcus mutans (S. mutans) for the Ag-BGCOMP 5 wt.% and 15 wt.% but not for the Ag-BGCOMP 1 wt.% or the control. CONCLUSIONS: This work contributes to our long term aim which is the fabrication of dental materials capable of reducing bacteria invasion and enhancing remineralization of the surrounding dental tissues. SIGNIFICANCE: We anticipate that these new composites could ultimately prevent restoration failure by inhibiting the formation of secondary caries and by remineralizing the hard tissues surrounding tooth lesions.