Objective Self-healing of bone from damage caused by infection, trauma, or surgical removal of cysts is limited. Generally, external intervention is needed to increase bone repair and regeneration. In this study, biocompatible light-cured hyaluronic acid hydrogels loaded with nano-hydroxyapatite and chitosan were prepared using a new photoinitiating system based on riboflavin for bone regeneration applications. Method Four light-cured hydrogel groups were prepared as follows: Group I, a control group with no additions; Group II, loaded with nano-hydroxyapatite; Group III, loaded with chitosan; and Group IV, loaded with both nano-hydroxyapatite and chitosan. The new photoinitiating system consisted of riboflavin as a photoinitiator, dimethylaminoethyl methacrylate (DMAEMA) as a coinitiator (being used with riboflavin for the first time), and diphenyliodonium chloride as an accelerator. For each group, X-ray-diffraction, surface morphology by scanning electron microscope, mechanical properties, water uptake (%), and cell viability (%) were tested. The osteogenic potential was then tested in a rabbit model, and histomorphometric assessment was conducted. Results In the four groups, the light-cured hydrogels were obtained after a short irradiation time of 10 s using a dental light-curing unit. The prepared hydrogels were biocompatible. Simultaneous addition of nano-hydroxyapatite and chitosan increased the mechanical properties threefold and the osteogenic potential, twofold, with a statistically significant difference compared with the control group. Conclusions Light-cured hyaluronic acid composite hydrogels loaded with nano-hydroxyapatite and chitosan—prepared by using the new photoinitiating system—are promising materials that can be used in bone regeneration applications.

INTRODUCTION:Fluoride-releasing restorative materials can be used as a reservoir releasing small amounts of fluoride to the teeth over a long time.Giomer represents a new class of dental materials that uses the pre reacted glass technology (PRG) with excellent mechanical and esthetic properties. OBJECTIVES: The aim of this study is to evaluate the fluoride release ability of Giomer (Beautifil II) compared to Compomer (Dyract XP) and their fluoride recharge ability after exposure to topical fluoride varnish. MATERIALS AND METHODS:The sample consisted of 80 freshly extracted primary anterior teeth. Standardized buccal class V cavities were prepared. Sample was randomly divided into 2 groups: Group I: included 40 teeth restored with Beautiful II. Group II: included 40 teeth restored with Dyract XP following the manufacturer's guidelines. Fluoride release was evaluated in the artificial saliva on 1st, 7th, 14th and 21st days. After 21days of release, 5%NaF varnish was applied on buccal surface of all specimens. The amount of fluoride release after recharge was measured in the artificial saliva after 1st, 7th, 14th and 21st days using fluorine ion-specific electrode. Data were analyzed using Friedman's two-way analysis of variance by ranks, Dunn-Sidak method, Mann-Whitney U test and Wilcoxon Signed Ranks to achieve the aim of the study. RESULTS: Beautiful II released significantly higher amount of fluoride compared to Dyract XP in first 7 days at p<0.0125. Dyract XP released significantly higher amount of fluoride after 14 and 21 days at p<0.0125. After 5%NaF varnish treatment there was no significant difference in fluoride re-release amount of both Beautiful II and Dyract XP at p>0.0125. CONCLUSIONS: Fluoride release (ppm) was found to be significantly higher in Beautiful II than Dyract XP in the first week. Giomer could be considered a suitable class V restoration of primary teeth in high caries risk children.

INTRODUCTION: Removable partial dentures (RPDs) are fabricated to replace the lost teeth of a partially edentulous individual. The serviceability of an RPD is dependent on the bond strength at the resin-framework interface. The esthetically unacceptable display of metal clasps, the increased weight of the prosthesis, the potential for metallic taste, and allergic reactions to metals led to the introduction of a number of thermoplastic materials in clinical practice such as nylon and acetal resins. An alternative restoration material (poly-ether-etherketone [PEEK]) has been successfully used over the last years. OBJECTIVES: to evaluate the shear bond strength and the effect of aging on bond strength of two different resin based materials to polyether-ether-ketone [PEEK]. MATERIALS AND METHODS: Fifty two PEEK cylinders was prepared. Specimens was randomly assigned into two parallel groups, 26 specimens each according to the resin materials used. The bond strength and aging of resin material to poly-ether-ether-ketone [PEEK] was evaluated. RESULTS: the initial shear bond strength of PMMA to PEEK was significantly higher than that of composite resin to PEEK. However, after aging process the shear bond strength of PMMA to PEEK decreased while that of composite resin to PEEK remained unchanged. There was no significant difference between the shear bond strength of both PMMA and composite resin to PEEK after aging. CONCLUSIONS: PMMA can be used as a veneering material with PEEK with comparable results to traditionally used composite resin. Moreover, owing to the adequate bond strength between PEEK and PMMA, PEEK frameworks could be relined in the traditional method similar to metal frameworks

Introduction: In-situ photo-cured hydrogels for bone regeneration offer an advantage compared to solid scaffolds or membranes is that it can be used by minimally invasive techniques and can fill irregularly shaped defects easily. Objective: was to prepare an injectable photo-curable hyaluronic acid hydrogel scaffold loaded with bioactive nano-hydroxyapatite using riboflavin as a natural source photoinitiator for bone regeneration and to investigate the effect of addition of nano-hydroxyapatite on the physiochemical and mechanical properties of the prepared hydrogel. Also, the osteogenic potential of the prepared hydrogels was assessed in a rabbit model. Materials and methods: Two groups were prepared, (Group I) photo-cured hyaluronic acid as a control group and (Group II) photo-cured hyaluronic acid/nano-hydroxyapatite. Laboratory Alexandria Dental Journal Volume XX. Issue X ii characterization tests: FTIR, XRD, SEM, mechanical, swelling and degradation rate tests were performed. Cell viability % using the MTT assay was used to assess the biocompatibility. In vivo bioactivity was assessed in a rabbit model and histomorphometric analysis was done. Results: Statistical analysis of results revealed that the addition of nano-hydroxyapatite increased significantly the mechanical properties of the hydrogels. SEM images demonstrated that the addition of nano-hydroxyapatite caused the formation of interconnected pores. MTT assay showed that hydrogel extract didn't affect cell viability after 48h. Histomorphometric analysis results revealed that the photo-cured (GMA-HA/HAP) hydrogel increased the osteogenic potential by one and a half folds compared to the control group and this proved its bioactivity. Conclusion: Results suggest that the prepared photo-cured hyaluronic hydrogel is a promising biomaterial to deliver bioactive nano-hydroxyapatite and has an osteogenic potential.

INTRODUCTION: Investigators have been searching for ideal maxillofacial prosthetic materials in order to gain patient acceptance and can be fabricated easily in the dental setting. OBJECTIVES: To evaluate the influence of adding different concentrations of titanium oxide nanoparticles (TiO2 NPs) on the mechanical properties of facial silicone elastomer (SE) after different extra-oral aging methods. MATERIALS AND METHODS: TiO2 nanoparticles were mixed with MED-4210 maxillofacial silicone elastomer at 1.5 %, 2% and 2.5 % weight percentage (w/w). Unmodified silicone was served as control group. Each of the above groups were evaluated to mechanical properties before aging conditions. Control & 2.5% nano-TiO2 silicone elastomers groups were subjected to six equal aging conditions groups as follow. Dry storage in dark for 6 months, storage in simulated sebum solution for 6 months, storage in simulated acidic perspiration for 6 months, accelerated artificial daylight weathering for 360 hours, storage in antimicrobial silicone-cleaning solution for 30 hours and mixed aging of sebum under UV light for 360 hours. After aging exposures, they were evaluated to the mechanical properties. Data were analyzed using the Kolmogorov-Smirnov test, F-test (ANOVA) and Post-hoc pair-wise test. RESULTS: TiO2 nanoparticles addition improved the mechanical properties in terms of tensile strength and percentage elongation, tear strength and shore A hardness of MED-4210 maxillofacial silicon elastomer before and after extra-oral aging conditions (P < 0.05). Pair-wise comparison between control group and 2.5% nano-TiO2 silicone elastomers composite exhibited significant differences according to the mechanical properties after aging. CONCLUSIONS: Reinforcement of MED-4210 maxillofacial silicon elastomer with TiO2 nanoparticles introduces a favorable material with physical and anti-ageing properties in our in vitro study.