Akira Senda

Possibility of root canal preparation by Er:YAG laser

OBJECTIVE The purpose of this study was to evaluate the cutting efficiency and morphological changes of root dentin irradiated by an Er:YAG laser in vitro. STUDY DESIGN Thirty-two root dentin blocks were divided into 4 groups. The irradiation conditions were as follows: Group 1 (G1): 30 mJ, 10 pps, 1 mm/s, 20 times; Group 2 (G2): 30 mJ, 10 pps, 1 mm/s, 10 times; Group 3 (G3): 30 mJ, 10 pps, 2 mm/s, 20 times; and Group 4 (G4): 30 mJ, 25 pps, 1 mm/s, 10 times. After being irradiated, the blocks were observed by mu-CT and their width and depth were measured. Moreover, SEM observations were performed. RESULTS There were significant differences between G1 and G2, between G1 and G3, between G2 and G4, and between G3 and G4 for both width and depth (P < .05). The SEM observations showed that no smear layer was present on the surface of any of the samples. CONCLUSION These results show that the Er:YAG laser operated under the conditions used in this study is an effective tool for root canal preparation.

In Vitro Comparison of Subjective Image Quality of the Pana Digital Intraoral X-Ray Imaging System and Conventional Intraoral Radiography in Caries Detection

The aim of this study was to evaluate observer performance with a charge coupled device-based intraoral X-ray imaging system, Pana Digital system, in comparison with conventional film-based radiography (Ektaspeed Plus). A total of 118 teeth mounted in plaster were radiographed using both the Pana Digital system and conventional film. The occlusal and approximal surfaces of the resultant images were evaluated by six observers in relation to the caries depth. For the verification of the caries depth, the teeth surfaces were rated histologically by two examiners according to the same rating scores used for the X-ray imaging assessment. The sensitivity, specificity, positive predictive value, negative predictive value and diagnostic accuracy of the two image modalities were calculated together with Cohens kappa values. No significant difference was found in any diagnostic parameters at any thresholds between the two modalities. The Kappa values for the Pana Digital system showed relatively lower levels than those of conventional film in occlusal caries assessment, whereas no apparent differences were found between the two modalities in any scores of depth for approximal caries assessment. The results of the present study, in which there was no discrepancy in diagnostic abilities, suggested that the Pana Digital system could play a useful role in clinical caries diagnosis.

Influence of X-ray beam angulation in the detection of proximal caries: Interobserver agreement in the CCD system

The aim of this study was to assess the influence of changes in horizontal and vertical X-ray beam angulation on interobserver agreement in the diagnosis of approximal caries using a charge coupled device-based digital dental imaging system (digital system) in comparison with a conventional film-based radiography (film system).A total of 40 teeth were radiographed. Projection angles were varied within a range of±20° in the horizontal and vertical direction using both systems. The resulting radiographs of approximal surfaces were observed by six radiologists, and the presence and absence of caries and the depth of any caries they found were evaluated. Results were analyzed by comparing Cohens kappa values.The overall kappa values in both systems belonged to the same category of agreement strength for any horizontal or vertical beam angle. The deviation of the horizontal angulation, if anything, reduced the kappa values in the digital system, except for score 2 based on rating score for caries depth. On the other hand, the influence of vertical angulation was smaller than that of horizontal angulation at scores 0, 1 and overall.The results of the presentin vitro study, in which there was no apparent discrepancy in the influence of beam angulation on interobserver agreement of the diagnostic abilities, suggest that the digital system plays a useful role in clinical caries diagnosis.

Characteristic changes of lased dentin

The present study investigated the effect of CO2 laser irradiation on dentin underneath the carious dentin that is to be removed.The investigation consisted of two experiments. In the first experiment, morphological and elemental changes of extracted human dentin irradiated by the CO2 laser were observed by microscope, SEM and XMA. In the second experiment, changes in hardness of bovine dentin irradiated by the CO2 laser were examined. Panalas C10, a CO2 laser with a flexible optical fiber, was used with different total energies for both experiments. The present study showed that CO2 laser irradiation made a significantly harder arched layer underneath the superficial carbonized layer in dentin. It seemed that this harder layer occurred where the dentin tubules were plugged with particular structural elements, and where there was a high concentration of calcium and phosphorus. It is suggested that use of the CO2 laser irradiation to remove carious dentin may have an additional effect that enhances the mechanical and chemical properties of the dentin layer underneath the carious dentin.