[Histological evaluations on periapical tissues after irradiation by erbium-doped yttrium aluminum garnet laser in Labradors dogs].

PURPOSE: To investigate the thermal effects on periapical tissues of Labrador dogs after intra-canal irradiation by erbium-doped yttrium aluminum garnet (Er:YAG) laser at different powers based on the antibacterial experiment of Enterococcus faecalis and Escherichia coli in root canals with an isthmus, to assess the histological changes, and to prove the safety for clinical applications. METHODS: Two hundred root canals of 10 healthy adult Labradors dogs were selected and divided into 5 groups. Excepted one as control group, root canals in other 4 groups were irradiated by Er:YAG laser with 1.5, 2.0, 2.5, 3.0 W for 30 s. Ten Labradors dogs were sacrificed at 0 (immediately after irradiation), 2 days, 2 weeks, 1 and 2 months. After preparation of pathological specimen, histological changes after laser irradiation in periapical tissues were evaluated and scores of inflammation were graded. Statistical analysis was performed using SPSS 13.0 software package. RESULTS: No significant difference was observed at the apical area between 1.5, 2.0, 2.5 W and control groups at most periods (P>0.05), whereas significant difference was observed between 3.0 W and other groups for all periods (P<0.05). CONCLUSIONS: These results suggest that if proper output powers (2.0-2.5 W) of laser irradiation are chosen, disinfection in root canals can be finished successfully and thermal effects on the periapical tissues can be minimized.

Effect of radiation dose on the prevalence of apical periodontitis--a dosimetric analysis.

OBJECTIVES: The objective of this study is to analyse the effect of the radiation dose of oral radiotherapy for cancer on the presence of apical periodontitis in patients without dental pre-screening or specific preventive measures. MATERIALS AND METHODS: All selected patients had been diagnosed with cancer in the head and neck region and presented in the dental clinic post radiotherapy with side effects (mainly radiation caries). The panoramic radiographs of these patients were examined for several parameters, including tooth decay and apical periodontitis. The total radiation dose per tooth was determined. RESULTS: A total of 36 patient files were included, which accounted for 628 teeth to be scored. Tooth decay was present in 88.2% of teeth. Radiographic signs of apical periodontitis were found in 9.1% of the teeth. Teeth with apical periodontitis had significantly more caries present. The radiation dose was significantly higher for teeth with apical periodontitis (37.2 vs. 24.9 Gy). Binary logistic regression found the radiation dose to be the only explanatory variable in the presence of apical periodontitis. CONCLUSIONS: This study found that in zones with higher radiation dose, inflammation of the jawbone due to bacterial infection of the root canal is more likely to develop. This is probably due to bone changes post radiotherapy. CLINICAL RELEVANCE: An increase of this prevalance of apical periodontitis in irradiated bone found in this study needs to be taken into account in the dental evaluation before the start of radiotherapy.

Stimulatory effect of low-level laser therapy on root development of rat molars: a preliminary study.

Several studies suggest a biomodulatory influence of low-level laser irradiation in the inflammatory and reparative processes of dental tissues. The aim of this study was to investigate the stimulatory effect of 808-nm laser irradiation on root development of rat molars and also to evaluate the histological reaction of pulp and periapical tissues. Twenty-four 30-day-old Wistar male rats were randomly assigned to three-time and five-time laser therapy groups. After initial x-ray, using mammography equipment, laser energy was applied at a wavelength of 808 nm (2 J/cm(2), 100 mW, 20 s) to the midroot area of the lower molars of one side of mouth at repeated intervals of the 48 h. The animals were killed 1 day after the final treatment, and root length development of the experimental samples was compared to contra-lateral non-irradiated molars using mammography. The histological reaction of the pulp and periapical tissue was evaluated under light microscopy. Root development was more advanced in irradiated groups than in the non-irradiated controls (p < 0.001). No significant differences, however, could be found between the root development changes in the three-time and five-time laser therapy groups (p > 0.05). Histological findings showed that the occurrence of secondary cement formation was significantly higher in the irradiation groups compared to the controls (p = 0.003). However, there were no statistically significant differences for the frequencies of pulp hyperemia, periodontal ligament fiber organization, or lamina dura remodeling between the groups (p > 0.05). Under the conditions used in this study, 808-nm low-level laser accelerates the rat molar root development in the presence of favorable histological reactions.

A histopathological study of the morphological changes at the apical seat and in the periapical region after irradiation with a pulsed Nd:YAG laser.

In this study, the effects of pulsed Nd:YAG laser irradiation on the apical seat and periapical region of instrumented root canals were investigated. One hundred and ninety-two teeth, including incisors and molars (239 root canals), in 18 healthy adult beagle dogs were used. After extirpation of the pulp under anaesthesia, each root canal was shaped up to at least a size 40 K-file, and then laser irradiated using the following parameters: 1 W, 15 pps for 2, 3, and 4 s; 2 W, 15 pps for 2 s. The effectiveness of debris removal and carbonization on the root canal walls immediately laser irradiation were examined and inflammation of the periapical region at 1, 2, and 4 weeks after laser irradiation was examined using light microscopy. Effective debris removal was observed in most cases in the laser-treated groups and was dependent on irradiated energy. Carbonization was observed in the irradiated root canals except at the parameter of 1 W for 2 s. Periapical inflammation was observed at 1 W for 2 s to the same extent as in the control group (P > 0.01). These results suggest that the pulsed Nd:YAG laser is useful for debris removal with no adverse effects immediately after extirpation of the pulp if appropriate parameters are selected.

Tissue response following CO2 laser application in apical surgery: light microscopic assessment in dogs.

The potential advantages of CO2 laser in apical surgery have not been established histologically. Therefore, the long-term effects of CO2 laser on the apical and periapical tissues were examined histologically in dogs 6 months after apical surgery. Lased specimens and unlased controls showed periapical inflammatory and osteogenic reactions. Lased root surfaces revealed craters with a superficial charred layer closely associated with new cementum-like matrix. The subjacent dentin appeared tubule-free and eosinophilic. Lased bone trabeculae showed a charred layer with a deeper osteocyte-free zone. The charred layer was covered by new bone. Detached charred segments in the marrow space and periapical inflammatory infiltrate were intimately associated with multinucleated giant cells, some containing minute char particles. Such cells were absent from the root and trabecular char linings. In addition, the charred surfaces were free of hard tissue resorption. These results suggest that CO2 laser does not hinder healing when applied in apical surgery.