mandana nasseri

This study aimed to compare the effects of requirement-based and test-based formative assessment methods on pre-clinical endodontic competence and performance of dental students.

This interventional field study was conducted on dental students of Shahid Beheshti Dental School in the first and second semesters of 2021 academic year (third-year students), taking practical basic endodontics 1. After receiving theoretical instructions and practical demonstrations, the students in both groups were asked to perform root canal therapy for extracted maxillary anterior and mandibular/maxillary canine teeth as part of their requirement. Their errors were assessed and recorded by two calibratedinstructors. Next, group 1 students performed root canal therapy for mandibular incisors and premolars as their requirement and returned the treated teeth on a specific date every 3 weeks. Group 2 students did not have a specific requirement and only participated in an examination which included endodontic treatment of the same group of teeth treated by group 1 students at the same designated dates. The treated teeth were assessed by instructors for errors. A final examination was held at the end of the semester for both groups. The two groups were compared by independent t-test, ANCOVA, Pearson Chi-square, and Mann-Whitney tests (alpha=0.05).

No significant difference was found between the two groups in access cavity preparation, root canal instrumentation, or obturation (P>0.05).

Requirement-based and test-based formative assessment methods had similar effects on pre-clinical endodontic competence and performance of dental students

 Ensuring strong adhesion of silicate-based cement to dentin during root canal therapy is crucial for achieving optimal results. This review aims to evaluate how different intracanal medicaments impact the tensile bond strength of silicate-based cement in root canal treatments.

 A thorough electronic search was performed using the PubMed and Google Scholar databases for articles published from 2000 to 2023.

 The studies included in this review evaluated the effects of various intracanal medicaments, including calcium hydroxide, chlorhexidine, triple antibiotic paste, double antibiotic paste, simvastatin, and bioactive glass, on the bond strength of silicate-based cements like mineral trioxide aggregate (MTA), Biodentine, and calcium-enriched mixture (CEM) cement. The results demonstrated varied impacts of these medicaments; some improved bond strength, while others had minimal effect. Specifically, calcium hydroxide frequently enhanced bond strength, and some antibiotic pastes showed similar benefits. In contrast, medicaments such as phenolic preparations and formaldehyde were found to have limited efficacy and potential toxicity.

 The type, concentration, and application site of intracanal medicaments significantly impact bond strength. This review highlighted the potential advantages of these medicaments, including improved root canal disinfection and enhanced push-out bond strength of commonly used dental cements. These insights can help dental professionals optimize root canal treatments and improve patient outcomes.

 This study investigated the amount of debris and smear layer remaining followed chemomechanical preparation using three systems: ProTaper Universal, reciprocating SafeSider, and hand K-Flexofiles with scanning electron microscope (SEM). 

 Sixty-five mandibular molars with mesiobuccal canal curvature (25 to 40°) were extracted and divided into one control group (n=5), and three experimental groups (n=20) according to the preparation method; K-Flexofile, ProTaper Universal and SafeSider instruments. All canals were irrigated with 3 ml of 5.25% sodium hypochlorite solution and 3 mL of 17% EDTA. Subsequently, the canals were irrigated with 5 ml of normal saline. Then the teeth were examined under the scanning electron microscope (SEM). Kruskal-Wallis, Dunn-Q Bonferroni, and Friedman tests were used for statistical analysis of results. 

 To assess the accumulation of debris, statistically significant differences were observed only in the coronal area among ProTaper Universal, SafeSider, K-Flexofile, and the control group. (P=0.029). To evaluate the residual smear layer amount, statistically significant differences were observed only in the coronal and middle areas, following the preparation of the canals using ProTaper Universal, SafeSider, and hand K-Flexofiles and control groups (P=0.019). 

 Based on the present in vitro study, we can declare that the canals were utterly cleaned of debris and smear layer in none of the groups. Manual Flexofile and ProTaper Universal groups result in cleaner canal walls than reciprocal SafeSider, in the coronal and middle thirds.

Precise knowledge regarding the topography of the tooth apex and location of the apical assessing the constriction are necessary for good and efficient root canal treatment and its long term prognosis. Since radiography is among the most commonly used methods for termination point, it is essential to be able to determine the exact location of apical constriction by radiography. The aim of this study is to evaluate the distance of apical constriction from anatomic and radiographic apices in extracted maxillary second premolars using clearing technique. It also compared the reliability of radiographic results with that of histologic findings. In this in-vitro experimental study, 50 extracted maxillary second premolars of patients presenting to various dental care centers in Tehran were selected. After cleaning and disinfecting the root surfaces and preparing the access cavity, 2% methylene blue was injected into the canals along with theuse of negative pressure. Then, demineralization and clearing process were done using 5% nitric acid and methyl salicylate. Samples were evaluated under stereomicroscope at X16 magnification. In order to evaluate the distance between apical constriction and radiographic apex, a #10 file was fixed at the apical constriction under the stereomicroscope.Covering the apices with sealer, radiographs were taken from all samples.The reliability of radiographic results was compared with that of histologic findings. The mean distance of apical constriction from the anatomic and radiographic apices was 0.9 and 1.05 mm, respectively. Sensitivity, specificity, positive and negative predictive values of radiographic results were 87.8%, 88.8%, 93% and 62%, respectively. The likelihood ratio for positive and negative radiographic results was 7.9 and 0.1%, respectively. The diagnostic odds ratio was 57.6% which is indicative of the acceptableaccuracy and validity of the radiographic results in assessing the distance of apical constriction from the anatomic apex. This study demonstrated that the distance of apical constriction from the anatomic and radiographic apices in the maxillary second premolars was approximately 1 mm and therefore, the process of cleaning, shaping and obturation should end at this point. This study emphasizes on the accuracy of radiographic findings and importance of having sufficient anatomic knowledge for achieving a good treatment outcome in a clinical setting.