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Enamel Microhardness (enamel + microhardness)

Distribution by Scientific Domains

Medical Sciences	100%

Selected Abstracts

Enamel microhardness and bond strengths of self-etching primer adhesives

EUROPEAN JOURNAL OF ORAL SCIENCES, Issue 2 2010
Olabisi A. Adebayo
Adebayo OA, Burrow MF, Tyas MJ, Adams GG, Collins ML. Enamel microhardness and bond strengths of self-etching primer adhesives. Eur J Oral Sci 2010; 118: 191,196. © 2010 The Authors. Journal compilation © 2010 Eur J Oral Sci The aim of this study was to determine the relationship between enamel surface microhardness and microshear bond strength (,SBS). Buccal and lingual mid-coronal enamel sections were prepared from 22 permanent human molars and divided into two groups, each comprising the buccal and lingual enamel from 11 teeth, to analyze two self-etching primer adhesives (Clearfil SE Bond and Tokuyama Bond Force). One-half of each enamel surface was tested using the Vickers hardness test with 10 indentations at 1 N and a 15-s dwell time. A hybrid resin composite was bonded to the other half of the enamel surface with the adhesive system assigned to the group. After 24 h of water storage of specimens at 37º°C, the ,SBS test was carried out on a universal testing machine at a crosshead speed of 1 mm min,1 until bond failure occurred. The mean ,SBS was regressed on the mean Vickers hardness number (VHN) using a weighted regression analysis in order to explore the relationship between enamel hardness and ,SBS. The weights used were the inverse of the variance of the ,SBS means. Neither separate correlation analyses for each adhesive nor combined regression analyses showed a significant correlation between the VHN and the ,SBS. These results suggest that the ,SBS of the self-etch adhesive systems are not influenced by enamel surface microhardness. [source]

Effect of a combination of fluoride dentifrice and varnish on enamel surface rehardening and fluoride uptake in vitro

EUROPEAN JOURNAL OF ORAL SCIENCES, Issue 1 2003
Lucianne Cople Maia
The purpose of this study was to evaluate the effect of combining fluoride dentifrice (FD) and varnish (FV) on in vitro enamel surface rehardening and on fluoride uptake under a pH-cycling regimen. Seventy-eight bovine enamel blocks with early lesions were used and 52 were divided into four treatment groups: (a) placebo non-fluoridated dentifrice (PD); (b); FD (1100 p.p.m. F as NaF); (c); FV (Duraphat) + PD; and (d) FV + FD. The FV was applied to enamel blocks of groups FV + PD and FV + FD before the pH-cycling regimen, and all of them were submitted to dentifrice during cycling. Surface enamel microhardness was determined on the dental blocks before and after demineralization, and after the pH-cycling regimen. The percentage of surface microhardness recovery (%SMHR) was calculated. Fluoride in the blocks was also determined, after removing three layers of enamel. The highest values of percentage SMHR were observed for the FD group. The greatest fluoride uptake was found in the FD and FV + FD groups, but the difference between them was not statistically significant. It was found that the frequent use of fluoride dentifrice resulted in greater benefit in enamel surface rehardening, with a similar effect on fluoride uptake, when compared with its combination with a single fluoride varnish application. [source]

Bleaching Agents with Varying Concentrations of Carbamide and/or Hydrogen Peroxides: Effect on Dental Microhardness and Roughness

JOURNAL OF ESTHETIC AND RESTORATIVE DENTISTRY, Issue 6 2008
JULIANA JENDIROBA FARAONI-ROMANO DDS
ABSTRACT Purpose:, To evaluate the effect of low and highly concentrated bleaching agents on microhardness and surface roughness of bovine enamel and root dentin. Methods:, According to a randomized complete block design, 100 specimens of each substrate were assigned into five groups to be treated with bleaching agents containing carbamide peroxide (CP) at 10% (CP10); hydrogen peroxide (HP) at 7.5% (HP7.5) or 38% (HP38), or the combination of 18% of HP and 22% of CP (HP18/CP22), for 3 weeks. The control group was left untreated. Specimens were immersed in artificial saliva between bleaching treatments. Knoop surface microhardness (SMH) and average surface roughness (Ra) were measured at baseline and post-bleaching conditions. Results:, For enamel, there were differences between bleaching treatments for both SMH and Ra measurements (p = 0.4009 and p = 0.7650, respectively). SMH significantly increased (p < 0.0001), whereas Ra decreased (p = 0.0207) from baseline to post-bleaching condition. For root dentin, the group treated with CP10 exhibited the significantly highest SMH value differing from those groups bleached with HP18/CP22, HP7.5, which did not differ from each other. Application of HP38 resulted in intermediate SMH values. No significant differences were found for Ra (p = 0.5975). Comparing the baseline and post-bleaching conditions, a decrease was observed in SMH (p < 0.0001) and an increase in Ra (p = 0.0063). Conclusion:, Bleaching agents with varying concentrations of CP and/or HP are capable of causing mineral loss in root dentin. Enamel does not perform in such bleaching agent-dependent fashion when one considers either hardness or surface roughness evaluations. CLINICAL SIGNIFICANCE Bleaching did not alter the enamel microhardness and surface roughness, but in root dentin, microhardness seems to be dependent on the bleaching agent used. [source]