Retention Force of Glass Ionomer Based Luting Cements with Posterior Primary Zirconium Crowns - A Comparative in Vitro Study.

OBJECTIVE: To determine the retentive force of three glass-ionomer luting cements used with prefabricated primary zirconium crowns (PPZCs) and to assess whether the retentive force was dependent on cementation material or different PPZCs brands. STUDY DESIGN: Four mandibular right second molar PPZCs were selected, one each from four manufacturers-NuSmile®ZR, Sprig Crowns, Cheng Crowns and Kinder Krowns. Silicone impressions of the outer surface of crowns were taken; stone dies prepared and reduced to fit the corresponding brand. 24 alginate impressions of each die obtained and filled with core buildup flowable composite. 96 composite tooth-replicas thus achieved were divided into four groups and further categorized into three subgroups of eight samples based on luting cements used - BioCem, FujiCEM®2 and KetacCem. Samples were thermocycled, placed in artificial saliva for one week followed by assessment of retentive force for crown dislodgment and failure mode. RESULTS: Data was statistically evaluated using two-way ANOVA, HSD (P <0.05). KetacCem had the lowest retentive force while BioCem showed comparatively higher value to FujiCEM®2. Adhesive failure modes were predominant with cement mainly adhering to crown's internal surface. CONCLUSIONS: Resin-based GI cements offered superior retention than conventional GI cements for PPZCs and retentive force was dependent on cement type.

Effect of metformin on dental pulp stem cells attachment, proliferation and differentiation cultured on biphasic bone substitutes.

OBJECTIVE: To evaluate to the effect of metformin on attachment of human dental pulp stem cells (hDPSCs) and their proliferation and osteogenic differentiation on biphasic hydroxyapatite/beta-tricalcium phosphate granules of macro-porous biphasic calcium phosphate (MBCP). MATERIALS AND METHODS: This in vitro study included four groups: A:hDPSCs + MBCP + Metfromin, B:hDPSCs + MBCP, C:hDPSCs + Metformin and D:hDPSCs (control). Attachment of hDPSCs to bone granules in groups A and B was observed by scanning electron microscopy on days 1 and 7 of cultivation. Cell viability was assessed by MTT assay on days 1, 3, and 7 after cell seeding. Differentiation of the hDPSCs was assessed by measurement of alkaline phosphatase activity on days 3, 7, 14 and 21 after cell culturing in standard and osteogenic media. The data was analyzed by two-way ANOVA at a significance level of p = 0.05. RESULTS: The hDPSCs had firmly attached to the surface of MBCP granules, especially in group A. The MTT values increased in all groups from day 1 to day 7 (p < 0.001). The highest MTT values were observed in group C followed by the control group and groups A and B (p < 0.001). Alkaline phosphatase activity also increased in all groups between days 3 to 21 (p < 0.001) except between days 7 and 14 in standard media (p = 0.094). In standard media, groups with MBCP granules (A and B) showed higher activity (p < 0.05). In osteogenic media, the groups with metformin (A and C) showed higher alkaline phosphatase activity (p < 0.05). CONCLUSION: This in vitro study showed that 100 Mol/L metformin increased attachment and proliferation of hDPSCs on biphasic granules. Osteogenic differentiation of hDPSCs also increased in the presence of metformin.

Effect of combined application of high- and low-intensity lasers on dentin hypersensitivity: A randomized clinical trial.

Background. Diode lasers (DLs) have demonstrated equal or better desensitizing effects than fluoride varnish, 10% potas-sium nitrate (NK) gel and Gluma. The current study evaluated the desensitizing effect of combined application of DLs with two different output powers and compared it with single DL therapy. Methods. Sixty-two hypersensitive teeth were allocated randomly into two groups: the single group was treated with 3-W DL beam once and in the combined group, the teeth were irradiated three times (the first time with 0.2-W and then with 3-W and the second and third times, 48 and 96 hours after the baseline visit, with 0.2-W DL beams). The amount of dentin hyper-sensitivity (DH) was evaluated, immediately before and after each visit, and 1 week and 1 and 3 months after the first visit. Data analysis was performed using chi-squared test, repeated measurement of ANOVA and Mann-Whitney U test. P<0.05 was considered statistically significant. Results. Statistically significant changes were observed in the means of VAS indices between all the measurement intervals and pretreatment measures, in both experimental groups (P<0.001). The difference in VAS reduction among the groups was not significant when the hypersensitive teeth were stimulated by a periodontal probe and a jet of air (P=0.63 and P=0.12). Conclusion. The results of the present study showed that using both high-intensity and combined DL beams gives rise to significant reductions in DH. There was no significant difference between combined and single laser therapies in the treatment of tooth hypersensitivity.