naghmeh golriz

 This study aimed to investigate and compare the penetration and durability of two dentin desensitizers, sodium fluoride varnish and casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) paste, using electron microscopy.

 The study was performed on 60 dentin specimens prepared from extracted human premolars. After applying 17% EDTA to remove the smear layer, the specimens were divided into two groups. MI Paste and Bi-fluoride varnish were applied to the specimens. Microscopic images of 20 samples were obtained immediately. Twenty other samples were accessed after 15 days, and the other 20 were accessed after 30 days of toothbrushing and thermal cycling. Both surface and longitudinal cross-sectional images (after sample fracture) were studied. Data were analyzed with two-way ANOVA and Mann-Whitney U test at a significance level of P<0.05.

 The mean depth of material penetration was significantly time-dependent and fluctuated in both groups. There was a significant difference between the mean level of plugs between 0, 15, and 30 days (P<0.001). Penetration increased with time for the MI Paste group, while in the Bi-fluoride group, the increase was significant at 15 and 30 days than immediately after application. The mean thickness of the plugs was significantly different at the three time periods, and MI Paste showed a sudden decrease in plug thickness after 15 days.

  Immediately after application, Bi-fluoride occluded dentinal tubules more effectively, and its durability after abrasion and thermal fatigue were higher than MI Paste.

The tongue controls the bolus during mastication, keeps the bolus in the oral cavity and generates pressure to direct the bolus through the hypopharynx. A decrease in tongue movement and strength can increase the oral and pharyngeal food residues. Food residues have the potential to increase the risk of dental caries. The aim of this study was to investigate the correlation between tongue strength and the prevalence of dental caries in individuals with Down syndrome. 

  Sixteen children with Down syndrome participated in this cross sectional study; none of them had dysphagia and they had normal diet. The tongue strength was measured using the Iowa Oral Performance Instrument (IOPI) and dental caries were assessed by Decayed – Missing –Filled Teeth Index (DMFT). A speech therapist measured and investigated tongue strength and a dentist did the dental examination and filled out the DMFT form.

The mean age of participants was 11.06 (SD=2.83). Most of the participants were female (n=14, 87.50%). All of the subjects had mixed dentition. The mean of tongue strength was 10.23KPas (SD= 7.08). There was no correlation between tongue strength and the total number of DMF plus dmf, according to Pearson correlation (p=0.96; r= -0.01).

Tongue strength was very low in these children compared with reports in the literature. There was no correlation between the tongue strength and number of DMF and dmf; the main reason is that the development of dental problems such as caries are multi factorial. In other word there are additional factors apart from poor tongue strength that can cause caries.

Mineral trioxide aggregate (MTA) can cause coronal discoloration after the regenerative endodontic therapies. Prevention of the MTA-induced discoloration in the esthetic zone is of great importance for patients and clinicians. The present study aimed to evaluate the effectiveness of different types of dentin bonding agents (DBA) in preventing crown discoloration caused by white MTA (WMTA). A total of 36 extracted maxillary incisors were selected. After performing the endodontic procedures, the teeth were divided into 3 groups. In groups 1 and 2, before applying the WMTA in access cavity, Adper Single Bond (SB) and Clearfil SE Bond (CSE) were used for 5th and 6th, respectively. While the access cavity was impregnated with WMTA in group 3. In these three groups access cavities were sealed. The color of the samples was examined by a spectrophotometer. The ∆E was calculated after 2 months storage in incubator and physiologic serum. The collected data were analyzed with the help of the Kolmogorov-Smirnov, independent t-test, and Tukey's range test. A p-value less than 0.05 was considered statistically significant. There was no significant difference between WMTA+SB and WMTA+CSE (P=0.546). However, the ∆E of the WMTA group between WMTA+SB and WMTA+CSE was significant (P<0.001). The DBAs can prevent MTA-induces discoloration. Although differences between 5th and 6th generations of DBAs were not statistically significant, the samples prepared with 6th generation of adhesives showed lower crown discoloration.