No abstract

The objective of this study was to evaluate the effect of different concentrations of NaOCl with and without passive ultrasonic irrigation (PUI) on mechanical properties of human dentin for applications in regenerative endodontics (RE). Sixty single‐rooted teeth were sectioned into 2 halves (n = 120). Dentin bars were produced from one half for flexural strength and the other half was used for microhardness. Specimens were randomly assigned into 10 groups: G1 and G2 (control): distilled water for 30 and 60 min, respectively; G3: 1.5%NaOCl for 30 min; G4:1.5%NaOCl for 60 min; G5: 1.5%NaOCl + PUI for 30 min; G6: 1.5%NaOCl + PUI for 60 min; G7: 5.25%NaOCl for 30 min; G8: 5.25%NaOCl for 60 min; G9: 5.25%NaOCl + PUI for 30 min; G10: 5.25%NaOCl + PUI for 60 min. An increase in NaOCl concentration showed highly significant reduction in mechanical properties. There was no significant difference between 1.5% NaOCl and control group except for specimens treated with PUI for 60 min. NaOCl in concentrations recommended for RE did not have a significant effect on mechanical properties of dentin. However, PUI with increased irrigation time might have an effect even with low NaOCl concentration.

INTRODUCTION: CAD/CAM denture base materials are milled from pre-polymerized pucks of resin that are highly condensed. So, they provide no polymerization shrinkage eliminating its subsequent disadvantages. This technology offered improved fit, strength properties and more bio-hygienic denture bases compared with conventional processing of the denture base material. OBJECTIVES: The aim of the study was to evaluate the physico-mechanical properties of CAD/CAM denture base material and the effect of thermo-cycling on it compared with the conventional one. MATERIALS AND METHODS: The study was conducted on two parallel groups, divided according to the denture material used. Group (1) conventional PMMA (control group), group (II) CAD/CAM PMMA (study group) of 40 specimens each (16 for impact strength, 16 for flexural strength, 8 for surface roughness and grinded powder form both materials for residual monomer test). Each group was divided into 2 subgroups: (A) No thermo-cycling and (B) Thermo-cycling, then subjected to 4 different tests, impact strength, flexural strength, surface roughness and residual monomer tests. Data were collected, tabulated and statistically analyzed. Significance level was set at 5%. Bar charts were used for graphical presentations. RESULTS: Our study revealed a highly statistically significant decrease in residual monomer of CAD/CAM PMMA material in both conditions before and after thermo-cycling when compared to conventional PMMA material, which therefore leads to enhanced impact strength and significantly reduced surface roughness after heat treatment. On the other hand, also a highly significant reduction of its flexural strength after thermocycling has been observed. CONCLUSIONS: CAD/CAM dentures with lower amount of methacrylate monomer exhibit more favourable physico-mechanical properties and they have a long-term biocompatibility even with thermal changes making them a more satisfactory as a denture base material for edentulous patients.

INTRODUCTION:Bulk-fill composites are promising restorative materials which may minimize placement time yet provide successful, durable esthetic restoration. OBJECTIVES: The purpose of this in vitro study was to evaluate marginal microleakage of nano-hybrid bulk-fill composite, and compare it to incrementally placed conventional nano-hybrid composite when used to restore proximal cavities in primary molars. MATERIALS AND METHODS:The sample consisted of 44 freshly extracted sound primary molars. Standardized proximal cavity preparations were prepared and the sample was divided randomly into 2 equal groups: Group I (n=22): Teeth were restored with nano-hybrid bulk-fill composite, Group II (n=22): Teeth were restored with incrementally placed conventional nano-hybrid composite. All specimens were thermocycled and immersed in 2% methylene blue dye at 37C˚ for 24 hours. Methylene blue penetration was assessed on a 4 point grading scale (0 to 3) using a stereomicroscope to evaluate the microleakage of the restorations. Data were statistically analyzed using Mann-Whitney test and Wilcoxon Signed Ranks test. RESULTS: No statistically significant difference has been found in the microleakage scores of group I at occlusal and cervical margin (p=1.000). In group II, no statistically significant difference has been found in the microleakage scores between occlusal and cervical margins (P=0.366). Comparing the microleakage scores of group I and group II, no statistically significant difference has been found (p=0.240). Although no significant difference was detected, bulk-fill composite showed lower microleakage scores than incrementally placed conventional composite. CONCLUSIONS: Bulk-fill composite restoration marginal integrity was comparable to incrementally placed conventional composite in proximal cavities of primary molars.

INTRODUCTION:Polyetherether ketone (PEEK) is a semicrystalline thermoplastic polymer that has been proposed as a substitute for metals in dental implants biomaterials because of its mechanical and biological properties. OBJECTIVES: This study was aimed to prepare and characterize PEEK implant materials modified by different methods using nanoparticles of hydroxyapatite to overcome its limited bioactivity. The study also evaluated the ability of the modified PEEK implant to enhance osseointegration in a rabbit model. METHODS: Four groups of PEEK specimens were prepared. Group1: specimens were constructed from untreated PEEK (control group), group2: specimens were coated with nanoparticles of hydroxyapatite (nHA) after etching the PEEK surfaces with sulfuric acid (98%) for one minute, group3: specimens were be coated with nanoparticles of hydroxyapatite (nHA) after PEEK surfaces treatment with Nd: YAG laser and group4: specimens were be constructed from melt-blended PEEK powder with nanoparticles of hydroxyapatite (nHA/PEEK). Each of the four groups were characterized by scanning electron microscope (SEM), Energy-dispersive X-ray (EXD), Fourier-transformed infrared spectroscopy (FTIR), X-ray Diffraction (XRD), contact angle measuring device and flexural strength test. The ability of each of the four groups to enhance bone osseointegration was evaluated in a rabbit model, by using histomorphometrical analysis. RESULTS: Data was collected, summarized and statistically analyzed using the suitable methods. CONCLUSION: PEEK biocompatibility and its chemical inertness can be improved with coating the surface with nano sized HA or mix blended of PEEK with nHA which does not affect its mechanical strength.