Agnieszka Droździk

Effect of different water flows on root surface temperature during ultrasonic removal of posts

OBJECTIVE This in vitro study evaluated rises in temperature on the outer root surface of human incisors during ultrasonic post removal with different water flows. STUDY DESIGN Thirty-six extracted teeth (12 maxillary central incisors, 12 maxillary lateral incisors, and 12 mandibular incisors) were used. After root canal preparation, the teeth were obturated, and prefabricated posts were cemented into the prepared spaces. Posts were ultrasonically instrumented dry and with irrigation at 20 mL/min and 40 mL/min. Temperature changes on the entire mesial outer surfaces of the roots were measured at 10-second intervals using an infrared thermal imaging camera. RESULTS Increases in root surface temperature were significantly lower when posts were instrumented with 40 mL/min water irrigation compared with dry vibration and 20 mL/min irrigation, which also significantly differed from each other. Statistical analysis among tooth groups showed differences in the mean temperature rise of maxillary central incisors and maxillary lateral incisors compared with mandibular incisors when posts were instrumented dry or with 20 mL/min irrigation. There were no significant differences in mean temperature rises between the studied groups when 40 mL/min irrigation was used. CONCLUSIONS Water cooling during ultrasonic post instrumentation significantly reduced temperature increases on the outer root surface; however, the intensity of the cooling was also important. Our results suggest that copious water irrigation during post removal is an effective method to protect the roots surrounding tissue.

Evaluation of alginate as a substitute for root-surrounding tissues in electronic root canal measurements.

Alginate as a substitute for root-surrounding tissue was investigated. The electronic working lengths of root canals under clinical conditions were compared with an in vitro simulation of the same teeth extracted and embedded in alginate. The working lengths in 26 teeth were determined on two occasions using an electronic apex locator, before extraction and after extraction with the same teeth embedded in an alginate mass. The apical 4 mm of the root canals were exposed following the measurements, and the distances between the apical constrictions and the tips of files repositioned in the canals were measured and recorded. The mean distance between the file tip and the constriction was +0.33 mm (±0.38) in vivo and +0.32 mm (±0.30) in vitro. The Wilcoxon signed-rank test indicated that these means were not significantly different. The apical constriction was assessed to be within the limits of 0.5 mm in 80.7% of in vivo cases and in 76.9% of extracted teeth. Statistical analysis demonstrated that there was no significant difference between the results recorded in vivo and in vitro regarding apical constriction localisation. Based on the results of this study, the alginate mass is a useful tool in evaluating the performance of electronic apex locators.

The Role of Nrf2 in Pathology of Pleomorphic Adenoma in Parotid Gland

Background Pleomorphic adenoma (benign mixed tumor) is one of the most common salivary gland tumors. However, the processes involved in its carcinogenesis are not well defined. This study aimed to define the contribution of Nfr2 (nuclear factor (erythroid-derived 2)-like 2) to pleomorphic adenoma pathology. The Nrf2-controlled gene system is one of the most critical cytoprotective mechanisms, providing antioxidant responses. Material/Methods The study was carried out in pleomorphic adenoma and control parotid gland tissues, investigating gene expression of NFE2L2, as well as KEAP1 (Kelch-like ECH-associated protein 1) and NQO1 (quinone oxidoreductase), at mRNA and protein (immunohistochemistry) levels. Functional evaluation of Nrf2 system in the parotid gland was evaluated in HSY cells (human parotid gland adenocarcinoma cells). Results Pleomorphic adenoma specimens showed cytoplasmic and nuclear Nfr2 expression in epithelial cells, as well as more variable lower Nrf2 level in mesenchymal cells. In the parotid gland, Nrf2 was expressed in cytoplasm of serous, mucous, and duct cells. Nuclear Nrf2 expression was predominantly seen in serous cells, whereas mucous and duct cells were mostly negative. Comparable mRNA levels of NFE2L2 and NQO1 genes and significantly higher expression of KEAP1 in pleomorphic adenoma were seen. HSY cell incubation with oltipraz demonstrated significant elevation of NFE2L2 after 24 and 48 hours of stimulation, whereas NQO1 was elevated, but significantly only after 24 hours, and KEAP1 expression remained unchanged. Conclusions Summarizing both in vitro and in vivo observations, it can be stated that Nrf2 may play a role in the pathology of pleomorphic adenoma.

Influence of Water Cooling on Root Surface Temperature Generated During Post Space Preparation

INTRODUCTION This in vitro study evaluated the temperature increases on the root surface of teeth during preparation of post space with and without water cooling. METHODS Thirty premolar teeth with a single canal were used. After root canal obturation, the teeth were divided into 2 groups, and post spaces were prepared by using a drill without cooling (dry group) and with water irrigation of 25 mL/min(-1) (wet group). Temperatures were measured on the entire root surface by using a thermal imaging camera. RESULTS Root surface temperature increases were significantly lower when post spaces were created with water cooling compared with dry post preparation (P < .0001 for root canal filling removal and P < .0001 for post space preparation). In both groups, significantly higher temperatures were recorded during the post space preparation than during the filling removal (P < .001 for nonirrigated teeth and P < .001 for irrigated teeth). CONCLUSIONS Irrigation during post space preparation significantly influenced the outer root surface temperature. The risk of irreversible injury to the root surrounding tissues is potentially minimized when post space is prepared by using water cooling.

Comparison of Effectiveness of Endoxal and Endosal in Removal of Smear Layer from Root Canal Dentine Surface: A SEM Study

Background. During biomechanical root canal preparation, a smear layer, consisting of organic and inorganic parts, appears on the surface of the canal dentine. Dent. Med. Probl. 2016, 53, 4, 483–489 DOI: 10.17219/dmp/63934