Accuracy of two electronic apex locators in primary teeth with and without apical resorption: a laboratory study.

AIM: To evaluate the accuracy of the Root ZX (J Morita Corp., Kyoto, Japan) and Tri Auto ZX (J Morita Corp.) devices for measuring root canal length in primary teeth with and without apical resorption. METHODOLOGY: Thirty-four extracted human primary molar teeth with resorption and 19 primary teeth without resorption were collected. After endodontic access preparation, the actual lengths of the teeth were determined. The teeth were then embedded in an alginate model to determine the electronic working length measurement. Statistical evaluation was completed using Student's t-tests. RESULTS: For the Root ZX, there was no significant difference between those teeth with root resorption and those without. However, for the Tri Auto ZX, there was a significant difference in the electronic measurements between those teeth with root resorption and those without (P < 0.05). Significant differences were found amongst the measurements of the two apex locators (P < 0.05). For root canals with resorption, the respective accuracy rates (within +/-0.5 mm) of Root ZX and Tri Auto ZX were 83.33% and 89.47%; within +/-1 mm, the Root ZX and Tri Auto ZX demonstrated 98.95% and 100% accuracy, respectively. For root canals with no resorption, the percentage of measurements within +/-0.5 mm of the apical construction was 89.28% for the Root ZX and 80.35% for the Tri Auto ZX. The accuracy within +/-1 mm of the Root ZX and the Tri Auto ZX was 98.22% and 100%, respectively. CONCLUSION: Within the limitations of this laboratory study, the presence of resorption affected the performance of the Tri Auto ZX more than the Root ZX.

The role of dental pulp cells in resorption of deciduous teeth.

OBJECTIVE: To address the question whether dental pulp cells of exfoliating human deciduous teeth have some roles for controlling or regulating the root resorption via secreting key molecules (OPG, RANKL, CSF-1, TGFbeta, MCP-1 and Cbfa-1) in osteoclastogenesis, we used a sensitive reverse transcriptase polymerase chain reaction (RT-PCR) method for detection of mRNA expressions for the cytokines listed. STUDY DESIGN: The dental pulps were retrieved from incisor and molar teeth in the late stage of shedding (n = 30) and from sound premolar teeth extracted for orthodontic reasons (control group; n = 30). The RT-PCR assays were used to identify targeted gene expression. RESULTS: Of the cytokines examined, RANKL and CSF-1 expressions showed significantly higher occurrence in deciduous dental pulps than in permanent teeth pulpal tissues (P < .040). CONCLUSIONS: The findings may suggest an interactive role for pulp tissue cells in the physiologic root resorption process. The cells of dental pulp may have some cytokine-producing cells which mediate monocyte-macrophage lineage to form osteo/odontoclasts, and the RANKL/RANK system might be involved in human deciduous teeth resorption.