Diabetes negatively affects tooth enamel and dentine microhardness: An in-vivo study.

OBJECTIVE: This study was performed to evaluate the effect of type 1 diabetes mellitus (T1DM) on the microhardness of tooth enamel and dentine in mice. DESIGN: Seventy male C57BL/6 J mice were used in this study. Thirty-five mice were rendered diabetic by administration of streptozotocin (STZ), and the remaining animals received citrate buffer (normal/non-diabetic). In each group, specimens were divided into 7 subgroups of 5 mice based on the time points 0, 1, 4, 8, 12, 20, and 28 weeks. The microhardness value (MHV) of the second molars' enamel and root dentine were tested with a Vickers microhardness tester. Five specimens from each subgroup were evaluated for dentinal tubular density by scanning electron microscope (SEM) and color dot map analysis to determine the color intensity of strontium (Sr) and magnesium (Mg) by using ImageJ software. RESULTS: The MHV of enamel was significantly reduced in STZ specimens in time points of 12 weeks (STZ: 274.39 ± 15.42, normal: 291.22 ± 15.28), 20 weeks (STZ: 247.28 ± 19.65, normal: 290.68 ± 11.52), and 28 weeks (STZ: 232.87 ± 15.07, normal: 282.76 ± 10.36) (P < 0.05). When comparing the MHV of dentine in subgroups of the normal group, after 20 weeks (169.1 ± 7.5) and 28 weeks (168.6 ± 7.81), the MHV increased significantly (P < 0.05). However, in the STZ group, a significant reduction of MHV was noticed between 28 weeks (131.69 ± 6.2) specimens with other subgroups (P < 0.05). CONCLUSIONS: T1DM negatively affected enamel and dentine microhardness, and enamel was influenced much more negatively and rapidly compared with dentine in diabetic groups.

The evaluation of physical properties of a polyurethane expandable endodontic sealer: a preliminary study.

Endodontic sealers play a vital role in providing 3-dimensional (3D) filling of complex root canal system (RCS). This study intended to compare the physical properties of a Polyurethane Expandable Sealer (PES), AH Plus and EndoSequence. Three properties including setting time, radiopacity and flow (rheology) were evaluated based on ISO 6876 standard. For evaluation of each of these physical properties, five samples from experimental groups: AH Plus, EndoSequence, PES (controlled expansion) and PES (high expansion) were used (n = 5). Data were analysed by one-way ANOVA and Post Hoc Tukey tests (a = 0.05). EndoSequence showed the longest setting time (P < 0.000); AH Plus showed that highest radiopacity (P < 0.000); and PES (high expansion) showed the highest flow (diameter and surface area) (P < 0.000). EndoSequence and PES (controlled expansion) showed promising and comparable physical properties to the AH Plus sealer in terms of flow, setting time and radiopacity.

The impact of pH on cytotoxic effects of three root canal irrigants.

AIM: Cytotoxicity of root canal irrigants is important due to their close contact with host tissues. This study was to assess the possible impact of pH on cytotoxic effects of MTAD, 17% EDTA, and 2.6% NaOCl on the human gingival fibroblasts using MTT assay. MATERIALS AND METHODS: Human gingival fibroblasts were exposed to the irrigants and their viability was assessed after 1, 6, and 12 h. The pH of the medium was measured in each interval. Light absorption values were measured for each culture medium using Elisa Reader device. RESULTS: NaOCl had significantly less cytotoxicity than EDTA and MTAD. Also irrigants cytotoxicity decreased in 12, 1, and 6 h, respectively. CONCLUSION: It seems that variation of the pH resulted in variation in the cytotoxicity of solutions; i.e., it follows the pattern of the pH variation.

A study of the relation between erosion and microhardness of root canal dentin.

OBJECTIVE: The aim of this study was to find a relation between erosion and microhardness of root canal dentin after irrigation with different canal irrigants. STUDY DESIGN: Seventy-two single-canal human premolar teeth were selected and enlarged by rotary Protaper files. The middle part of each root was transversely sectioned to a 4-mm slice. The initial microhardness values of intact specimens were measured at depths of 100 microm and 500 microm from the pulp-dentin interface using a Vickers microhardness tester. the specimens were divided into 6 groups of 12 specimens and were treated as follows: 1: 2.6% NaOCl, 2: 17% EDTA (5 minutes) then 2.6% NaOCl (5 minutes), 3: 17% EDTA (1 minute) then 2.6% NaOCl (1 minute), 4: MTAD (5 minutes), 5: 2% Chlorhexidine (5 minutes), and 6: saline (control), respectively. Posttreatment microhardness values were obtained in the same manner as the initial ones. Afterwards, the specimens were prepared for scanning electron microscopy analysis. The amount of dentin erosion was examined. RESULTS: Group 2 showed the most erosive effect on dentin (P < .0001) along with the least decrease of dentin microhardness at depth of 100 microm, whereas MTAD showed the most reduction of dentin microhardness and less erosive effect on dentin. CONCLUSION: It can be concluded that erosion is not the main factor in decreasing the dentin microhardness, whereas the amount of irrigant penetration might be the main cause.