Effect of Er:YAG laser energy densities on thermally affected dentin layer: Morphological study.

BACKGROUND AND AIMS: Physical and chemical composition of dentin is subject to modification when irradiated with Er:YAG laser. Temperature rise causes water evaporation and micro-mechanical ablation of dentin. The misuse of laser parameters could affect negatively dentin collagen fibers leading to failure in bonded composite restorations. The aim of this in vitro study was to evaluate the effect of Er:YAG laser radiation at different levels of energy on the morphology of thermally affected dentin layer. MATERIALS AND METHODS: Forty-eight freshly extracted human third molars were randomly divided into six groups (n = 8). In all groups, except for the control groups, dentin was subject to irradiation with H02 handpiece Er:YAG laser in non-contact mode (SSP mode = 50 µs; 10 Hz; speed of 1 mm/second; air 6 mL/min; and water 4 mL/min) with the following levels of energy (40, 60, 80, 100, and 120 mJ) respectively. Teeth were sliced longitudinally. Photo-ablated cavities were observed. The cavity depth and dentin fiber collagen deterioration were measured. RESULTS: Laser irradiation increased the depth of dentinal crater from 46.57 µm to 178.2 µm, when energy level increased from 40 mJ to 120 mJ. A superficial black layer, representing dentinal affected collagen fibers, was present in all groups except for control group. When comparing the thickness of the black layer, there was no significant difference between groups. It increased at 40 mJ to 28.17 µm then decreased to 15.19 µm at 60 mJ and then increased again for 80 mJ to 19.93 µm, 100 mJ to 22.87 µm and 120 mJ to 28.53 µm. Only one group (60 mJ) showed low values and significant difference as compared to the other irradiated groups, when multiple comparisons tests (ANOVA) were made using Newman-Keuls test. CONCLUSION: Dentin organic matrix presented the minimum alteration when Er:YAG laser is used specifically at an appropriate level of energy (60 mJ).

Safety Irradiation Parameters of Nd:YAP Laser Beam for Endodontic Treatments: An In Vitro Study.

Objective. Nd:YAP laser has several potentialities of clinical applications in endodontics. The aim of our study is to determine the safety range of irradiation parameters during endodontic application of Nd:YAP laser that can be used without damaging and overheating the periodontal tissue. Material and Methods. Twenty-seven caries-free single-rooted extracted human teeth were used. Crowns were sectioned to obtain 11 mm root canal length. Temperature increases at root surfaces were measured by a thermocouple during Nd:YAP laser irradiation of root canals at different energy densities. Canal irradiation was accomplished with a circular and retrograde movement from the apex until the cervical part of the canal during 10 seconds with an axial speed of 1 mm/s. Each irradiation was done in a canal irrigated continuously with 2.25% NaOCl solution. Results. Periodontal temperature increase depends on the value of energy density. Means and standard deviations of temperature increases at root surfaces were below 10°C (safe threshold level) when the average energy densities delivered per second were equal to or below 4981 J/cm(2) and 9554 J/cm(2), respectively, for irradiations using a fiber diameter of 320 µm and 200 µm. Conclusions. Within the limitations of this study and under specific irradiation conditions, Nd:YAP laser beam may be considered harmless for periodontal tissues during endodontic applications.

Bisphosphonate related osteonecrosis of the jaw: a study of 18 cases associated with fungal infection.

Osteonecrosis of the jaw (ONJ) is a serious complication associated with oral and intravenous bisphosphonate therapy. Its pathogenesis is not well understood and its management is difficult. Microbiological investigations have detected a variety of oral pathogens such as Actinomyces, Enterococcus, Candida albicans, Aspergillus, Haemophilus influenzae, alpha-hemolytic streptococci, Lactobacillus, Enterobacter, and Klebsiella pneumoniae. To better treat it, it is important to understand its causes and complications. Materials and Methods. Our present study addresses a microscopic observation of curetted jaw necrotic lesions related to bisphosphonates. Results. A mycotic infestation has been found in all of the 18 cases studied. Discussion. An identification of the fungal agent and its incrimination in the pathogenesis of bisphosphonates related osteonecrosis of the jaw could change radically the management of this condition.

A Four-Year Monocentric Study of the Complications of Third Molars Extractions under General Anesthesia: About 2112 Patients.

Introduction. The aim of this study was to assess the complications resulting from third molar extraction under general anesthesia. Material and Methods. The retrospective study included all patients who underwent impacted third molars extraction from January 2008 until December 2011. 7659 third molars were extracted for 2112 patients. Postoperative complications were retrieved from medical files. Results. No complications were related to general anesthesia. The most frequent postoperative complication was infection (7.15%). Lingual nerve injuries affected 1.8% of the patients. All of them were transient and were not related to tooth section. Inferior alveolar nerve injuries were reported in 0.4% of the cases. 95.8% of these patients were admitted for one-day ambulatory care, and only two patients were readmitted after discharge from hospital. Discussion. This surgical technique offers comfort for both surgeons and patients. Risks are only linked to the surgical procedure as we observed no complication resulting from general anesthesia. One-day hospitalization offers a good balance between comfort, security, and cost. The incidence of complications is in agreement with the literature data, especially regarding pain, edema, and infectious and nervous complications. It is of utmost importance to discuss indications with patients, and to provide them with clear information.

Evaluation of dental pulp temperature rise during photo-activated decontamination (PAD) of caries: an in vitro study.

Photo-activated decontamination (PAD) has been reported in caries treatment as an aid in dentine decontamination. The aim of this study is to verify the harmlessness for pulp vitality of photo-activated decontamination (PAD) in caries treatment. Twenty freshly extracted single-rooted teeth were used. Deep class I cavities with a

Eosinophils and mastocytes in healing laser excision wounds.

Eosinophils can influence fibroblasts and the extracellular matrix in vitro and can participate in tissue remodelling in vivo. Therefore; we analysed the expression of eosinophils and mastocytes in healing laser excisions and control excisions made by scalpel. Carbon dioxide (CO(2)) laser (continuous wave, 5 W) or scalpel excision wounds were created in the dorsal tongue mucosa of 96 rats. Sixteen additional rats were kept as untreated controls. Specimens from the tongues were cut at 16 different healing time points and fixed in 10% formalin. Histological staining with slow Giemsa was done to determine microscopically the eosinophils and mastocytes. Mastocytes were always present, especially in large numbers around blood vessels, in scalpel and in laser wounds. The maximum number of eosinophils was almost two times higher in scalpel excisions than in laser excisions. The peak value was reached after 6 days in laser wounds and after 3 days in scalpel wounds. The increase reverted to normal levels after 10 days in laser wounds and after 6 days in scalpel wounds. The appearance and disappearance of eosinophils was slower in laser wounds. Mastocytes were always present in both groups. This identification as a potential source of transforming growth factor (TGF) alpha and TGF beta clearly permits a role for the eosinophils and influences epithelial cell proliferation, angiogenesis and organization of the wound.

Safety parameters for pulp temperature during selective ablation of caries by KTP laser in vitro.

OBJECTIVE: To define the optimal parameters of KTP laser irradiation during a selective caries removal. MATERIALS AND METHODS: Twelve decayed human teeth, recently extracted were used. Their root canals were prepared for insertion of a thermocouple probe into the pulp chamber. The demineralized tissues were colored by Acid Red 52 before proceeding to different conditions of irradiation. RESULTS: Pulpal temperature increases (below 3 degrees C) were found under the following parameters with 15 sec of continuous lasing: 400 mWatts, 0.10-msec pulse width, PRR <50 Hz for efficient caries removal. A resting time average of 70 sec was necessary to allow pulp temperature to get back to its baseline. CONCLUSION: KTP laser can be used safely and without any pulp over-heating under certain irradiation conditions.

Myofibroblasts in healing laser excision wounds.

BACKGROUND AND OBJECTIVE: The lack of myofibroblasts, cells responsible for wound contraction, has been suggested to be the underlying factor to the clinically observed minimal contraction in CO2 laser wounds. However, the histologic background to this phenomenon in laser excisions has not been thoroughly clarified. Therefore, we analyzed the expression of myofibroblasts in healing laser excisions and control excisions made by scalpel. STUDY DESIGN/MATERIALS AND METHODS: CO2 laser (continuous wave, 5 W) or scalpel excision wounds were created in the dorsal tongue mucosa of 144 rats. Sixteen additional rats were kept as untreated controls. Specimens from the tongues were cut at 16 different healing time points and fixed in 10% formalin. Immunohistochemical stainings with monoclonal antibodies to vimentin and to alpha-smooth muscle actin were done to determine microscopically the contractile type of myofibroblasts. RESULTS: The maximum amount of myofibroblasts was almost three times higher in scalpel than in laser excisions. The peak value was reached at 4 days in laser and at 3 days in scalpel wounds. The increase reverted to normal levels at 14 days in laser and at 6 days in scalpel wounds, respectively. CONCLUSION: Myofibroblasts appeared and disappeared slower in laser wounds. There were clearly fewer myofibroblasts in CO2 laser than in corresponding scalpel excisions known to heal by contraction. The lack of contractile myofibroblasts, therefore, is suggested as the reason for the minimal degree of contraction in CO2 laser excision wounds.

Non Hodgkin's lymphoma of the maxilla as a first clinical manifestation of HIV infection. Report of a case.

Non-Hodgkin's lymphoma (NHL) of the oral cavity is rare. When it occurs, one should be suspicious of infection with the human immunodeficiency virus (HIV). NHL is the second most common malignancy associated with the acquired immunodeficiency syndrome (AIDS). This report describes the occurrence of a maxillary NHL as a primary clinical manifestation of HIV infection.