ABSTRACT
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).
ABSTRACT
BACKGROUND/AIMS: Evaluation of the degree of hepatic fibrosis is especially important in patients with chronic liver disease. Our aim was to study the diagnostic accuracy of abdominal ultrasonography for cirrhosis or fibrosis. METHODS: Twenty-three clinical (n=12) and Doppler ultrasonic (n=11) variables were recorded in 243 patients with chronic (alcoholic and viral) liver disease under conditions close to those of clinical practice. Fibrosis was classified into six grades by two pathologists. Diagnostic accuracy was evaluated by discriminant analysis, first globally using all variables, then by stepwise analysis. RESULTS: A) Diagnosis of cirrhosis: 1) whole group (n=243): diagnostic accuracy was globally 84%, and 84% with two variables: spleen length, portal velocity; 2) compensated chronic liver disease (n=191): diagnostic accuracy was globally 85%, and 82% with two variables: liver surface, liver length (right kidney); 3) alcoholic compensated chronic liver disease (n=109): diagnostic accuracy was globally 86%, and 88% with two variables: spleen length, liver length (middle clavicle); 4) viral compensated chronic liver disease (n= 83): diagnostic accuracy was globally 86% and 86% with one variable: liver surface. By subtracting the proportion of patients who could not be investigated due to anatomical limitations, the highest calculated univariate diagnostic accuracy decreased by 7%. B) Diagnosis of fibrosis: diagnostic accuracy was globally 84% for extensive fibrosis. CONCLUSIONS: Cirrhosis can be correctly diagnosed in 82-88% of patients with chronic liver disease using a few ultrasonographic signs. However, the diagnostic accuracy of ultrasound is decreased by the anatomical limitations of this technique.
