Effect of low-level laser therapy on irradiated parotid glands--study in mice.

The objective of this study was to evaluate the effect of low-level laser therapy (LLLT) on radiotherapy-induced morphological changes and caspase-3 immunodetection in parotids of mice. Forty-one Swiss mice were divided into control, radiotherapy, 2- and 4-J laser groups. The experimental groups were exposed to ionizing radiation in a single session of 10 Gy. In the laser groups, a GaAlAs laser (830 nm, 100 mW, 0.028 cm2, 3.57 W/cm2) was used on the region corresponding to the parotid glands, with 2-J energy (20 s, 71 J/cm2) or 4 J (40 s, 135 J/cm2) per point. LLLT was performed immediately before and 24 h after radiotherapy. One point was applied in each parotid gland. The animals were euthanized 48 h or 7 days after radiotherapy and parotid glands were dissected for morphological analysis and immunodetection of caspase-3. There was no significant difference between groups in the immunodetection of caspase-3, but the laser groups had a lower percentage compared to the radiotherapy group. LLLT promoted the preservation of acinar structure, reduced the occurrence of vacuolation, and stimulated parotid gland vascularization. Of the two LLLT protocols, the one using 4 J of energy showed better results.

Radiotherapy-induced salivary dysfunction: Structural changes, pathogenetic mechanisms and therapies.

PURPOSE: This review addressed the structural changes observed in salivary glands and pathogenic mechanisms resulting from oxidative stress caused by radiotherapy. The preventive and regenerative therapies for altered acinar morphology and glandular function were also reviewed. Among acute and late microscopic alterations in glandular tissue, there are particularly changes indicative of cell death, hypovascularization, formation of fibrous tissue and edema. A critical role was identified for the Akt-MDM2-p53 pathway in the suppression of DNA damage-induced apoptosis in acinar cells. Prophylactic treatment with pilocarpine, cevilemine, bethanechol and isoproterenol has shown a positive effect on salivary flow, but lasting results have not been observed. Growth factors, histamine and lidocaine, have also demonstrated radioprotective effects on the salivary glands. Stem cell preservation and transplantation may be an alternative to maintain tissue homeostasis and thus allow glandular regeneration. CONCLUSION: Knowledge of the structural changes observed in the salivary glands contributes to proving the short- and long-term efficacy of the therapies investigated. It is important to know the mechanisms involved in radiation-induced damage, since the control of the pathogenic mechanisms can inhibit the initial process of tissue degeneration. The challenge for investigators is to protect normal cells selectively, without promoting tumor growth.

Clinically relevant dimensions of 3-rooted maxillary premolars obtained via high-resolution computed tomography.

INTRODUCTION: This study aimed to characterize the dimensions of a selection of 3-rooted maxillary premolars through high-resolution computed tomographic analysis considering measures of clinical interest for root canal treatment, such as root wall thickness, canal diameters, and distances between 2 canals in fused roots and between the root apex and foramen. METHODS: Fifteen 3-rooted human maxillary premolars extracted for therapeutic reasons were individually scanned using a high-resolution desktop high-resolution computed tomographic system. Starting from the apical foramen, the selected cross-sectional images corresponding to each millimeter of the roots were evaluated. Measures of clinical interest were determined using Image J software (version 1.41; National Institutes of Health, Bethesda, MD). RESULTS: Root wall thickness as thin as 0.4 and 0.6 mm was detected in the apical portion of buccal and palatal roots, respectively. In the cervical portion, buccal roots had narrower root walls (0.817-1.670 mm) compared with palatal roots (1.361-2.720 mm). In all thirds, the palatal canal was wider compared with the mesiobuccal and distobuccal canals. In the buccopalatal direction, all roots had thicker root walls toward the furcation, whereas in the mesiodistal direction the mesiobuccal and distobuccal roots had the thinnest walls along their distal and mesial aspects, respectively. Both buccal canals revealed dentin apposition 2 mm from the canal orifice, resulting in cervical constriction. Generally, the distance between the root apex and the foramen was greater in distobuccal roots in comparison with the others with a tendency for foramina to be eccentric. CONCLUSIONS: Three-rooted premolars are a clinical challenge not just because of their low frequency and difficulties regarding diagnosis and root canals access but also because of their fragile roots. These phenomena are critical in terms of the amount of dentin removed during the preparation of root canals and during post space preparation.