Rosane de Fátima Zanirato Lizarelli

Effect of Nd:YAG Irradiation and Fluoride Application on Dentine Resistance to Erosion in Vitro

OBJECTIVE In this paper we evaluated the effect of two fluoridated agents and Nd:YAG irradiation separately and in combination on dentine resistance to erosion. BACKGROUND DATA The morphological changes in dentin induced by laser treatment may reduce the progression of erosive lesions. Due to the possibility of a synergistic effect of laser with fluoride, this study was conducted. MATERIALS AND METHODS Eighty bovine dentine samples (4 x 4 mm) were randomly divided into eight groups, according to the following treatments: G1: untreated (control); G2: acidic phosphate fluoride gel (APF 1.23%) for 4 min; G3: fluoride varnish (NaF 2.26%) for 6 h; G4: 0.5 W Nd:YAG laser (250 microsec pulse, 10 Hz, 35 J/cm2, 30 sec); G5: 0.75 W Nd:YAG laser (52.5 J/cm2); G6: 1.0 W Nd:YAG laser (70 J/cm2); G7: APF + 0.75 W Nd:YAG laser; and G8: NaF + 0.75 W Nd:YAG laser. After the treatments, half of each dentine surface was protected with nail varnish. The samples were stored in artificial saliva (30 mL/sample) for 24 h and submitted to four erosive 1-min cycles. Between the erosive attacks, the blocks were maintained in artificial saliva for 59 min. The erosive wear was evaluated by profilometry. RESULTS The mean wear (+/-SD, microm) was: G1: 1.20 +/- 0.20; G2: 0.47 +/- 0.06; G3: 0.81 +/- 0.11; G4: 1.47 +/- 0.32; G5: 1.52 +/- 0.24; G6: 1.49 +/- 0.30; G7: 0.49 +/- 0.11; and G8: 1.06 +/- 0.31 (Tukeys test, p< 0.05). CONCLUSIONS Laser irradiation was not able to reduce dentine erosion. However, fluoride application was able to increase the dentines resistance to erosion, and APF showed better results than fluoride varnish.

In Vitro Evaluation of Enamel Erosion After Nd:YAG Laser Irradiation and Fluoride Application

OBJECTIVE Previous investigations have demonstrated improved enamel demineralization resistance after laser irradiation. Due to the possibility of a synergistic effect between laser and fluoride, this study investigated the effect of fluoridated agents and Nd:YAG irradiation separately and in combination on enamel resistance to erosion. METHODS One hundred bovine enamel blocks were randomly divided into 10 groups: G1, untreated (control); G2, acidic phosphate fluoride (APF) (1.23% F) for 4 min; G3, fluoride varnish for 6 h (NaF, 2.26%); G4, 0.5 W Nd:YAG laser (250 microm pulse width, 10 Hz, 35 J/cm(2), with uniform velocity for 30 sec in each application); G5, 0.75 W Nd:YAG laser (52.5 J/cm(2)); G6, 1.0 W Nd:YAG laser (70 J/cm(2)); G7, APF + 0.75 W Nd:YAG laser; G8, 0.75 W Nd:YAG laser + APF; G9, fluoride varnish + 0.75 W Nd:YAG laser; and G10, 0.75 W Nd:YAG laser + fluoride varnish. During 10 d the erosive cycle was conducted by immersion of the blocks in Sprite light((R)) for 1 min, followed by immersion in artificial saliva for 59 min. This procedure was consecutively repeated four times per day. In each day, during the remaining 20 h, the blocks were maintained in artificial saliva. The wear was evaluated by profilometry (days 5 and 10). Data were tested by two-way ANOVA and Bonferronis tests (p < 0.05). RESULTS The mean wear at days 5 and 10 was, respectively: G1, 1.83 and 2.67 microm; G2, 1.04 and 2.60 microm; G3, 1.03 and 2.48 microm; G4, 1.13 and 2.47 microm; G5, 1.07 and 2.44 microm; G6, 1.0 and 2.35 microm; G7, 0.75 and 2.27 microm; G8, 0.80 and 2.12 microm; G9, 0.76 and 2.47 microm; and G10, 1.09 and 2.46 microm. At day 5, all the experimental groups presented significant lesser wear when compared to control group. However, at 10 d, only G7 and G8 were still different from control. CONCLUSIONS The association between APF application and laser irradiation seems to be an alternative preventive measure against dental erosion.

Histometric evaluation of the healing of the dental alveolus in rats after irradiation with a low-powered GaA1As laser

The aim of the present work was to evaluate histometrically the effect of the irradiation with semiconductor diode GaAlAs 790 nm low-powered laser in the chronology of alveolar repair of rats. Lasers of low intensity possesses an eminently analgesic, anti-inflammatory and bioestimulant effect, producing an increase of the local micro-circulation and in the speed of healing. Groups of five animals had their upper right incisors extracted under anesthesia and the mucous sutured; three groups received 1.5 J/cm2 of irradiation immediately after the extraction with laser for sweeping on the operated area. After that, the animals were sacrificed in the periods of 7, 14 and 21 days after the dental extraction. The material was decalcified and processed for inclusion in paraffin. Longitudinal sections of 7 micrometers in the alveolus were made and stained with HE. The histometric analysis was performed with the Merz grid, and 2000 points were counted in each cervical, middle and apical thirds of the alveolus, assessing the percentage of the bone tissue. The result shows that low-powered intensity laser produced acceleration in osseous formation (10%) in some periods.

A Comparative in Vitro Study to Diagnose Decayed Dental Tissue Using Different Methods

OBJECTIVE The purpose of this study was to compare diagnoses of decayed dental tissue (occlusal) using five different methods in vitro. BACKGROUND DATA Previous studies have showed occlusal surface caries are very difficult to diagnose at early stages. Early carious lesions detection through conventional diagnosis methods, including radiographic, visual and tactile exams, is questionable because they can end up with a risk of a false-positive or false-negative diagnosis. MATERIALS AND METHODS We used 22 teeth in vitro, premolars and molars, which suggested carious lesions. Three calibrated examiners using pre-determined scores made the exams. The methods used were GI, visual inspection; GII, tactile inspection (explorer probe); GIII, conventional radiographic exam; GIV, digital radiographic exam (Digora for Windows 1.51 and 1.51N, SoredexOrion Co.); GV, low-intensity laser for diagnosis (DIAGNOdent, KaVo, Germany); and GVI, histological inspection. The examiners did not communicate among themselves during the exams. RESULTS There was significant statistical difference among the evaluated methods. Under the Friedman statistical test, GI, GIII, and GIV were different from GV at the 0.1% level. Comparing GII with GV, we observed statistical difference at the 1% level. CONCLUSION GV was highly statistically different from the others groups, even when compared with GVI, which means that dentists must use every method they can get to avoid a false-negative diagnosis.

Study of microleakage at class V cavities prepared by Er : YAG laser using rewetting surface treatment

OBJECTIVE This study was conducted to analyze microleakage in Class V cavity preparation, using rewetting (or not) just after burr or Er:YAG laser preparation of enamel and dentin walls in permanent teeth. BACKGROUND DATA Several studies reported microleakage around composite restorations when cavity preparation was done or treated by Er:YAG laser. As the hybridized laser is removed when this laser is used to cut dental hard tissue, there is a need for new materials or techniques to minimize gaps and microleakage. RESULTS Primer solution showed significant effect in enamel and dentin, at the level of 5%, when Er:YAG laser was used as a cutting tool. Using primer solution after phosphoric acid in preparations with the laser, microleakage was similar in degree to when cavities were prepared with the burr. CONCLUSION Re-wetting surface just after Er:YAG irradiation and chemical treatment with phosphoric acid using HEMA aqueous solution seems to improve the quality of bioattachment between the adhesive system and enamel/dentin, showing similarities between restoration behaviors independently of the cutting tool, whether burr or laser.

Influence of effective number of pulses on the morphological structure of teeth and bovine femur after femtosecond laser ablation

Femtosecond lasers have been widely used in laser surgery as an instrument for contact-free tissue removal of hard dental, restorative materials, and osseous tissues, complementing conventional drilling or cutting tools. In order to obtain a laser system that provides an ablation efficiency comparable to mechanical instruments, the laser pulse rate must be maximal without causing thermal damage. The aim of this study was to compare the different morphological characteristics of the hard tissue after exposure to lasers operating in the femtosecond pulse regime. Two different kinds of samples were irradiated: dentin from human extracted teeth and bovine femur samples. Different procedures were applied, while paying special care to preserving the structures. The incubation factor S was calculated to be 0.788±0.004 for the bovine femur bone. These results indicate that the incubation effect is still substantial during the femtosecond laser ablation of hard tissues. The plasma-induced ablation has reduced side effects, i.e., we observe less thermal and mechanical damage when using a superficial femtosecond laser irradiation close to the threshold conditions. In the femtosecond regime, the morphology characteristics of the cavity were strongly influenced by the change of the effective number of pulses.

Low-powered laser therapy associated with oral implantology

The objective of this present work to evaluate in the level of pain and tumor the effect of the low-power density laser irradiation of GaAlAs 790 nm in implanted patients during the postoperative period. Forty five clinic situations were selected and divided in three different groups: Group I, control, without laser application, but with analgesic and anti-inflammatory medication; Group II, patients were irradiated on the day of the surgery, after the same concluded, and on the two subsequent days; and Group III, patients were irradiated on the day of the surgery, on the day of the surgery, before and after the end of the same, and in the two subsequent days after. All the applications were accomplished using the same energy parameters and by the same operator. The measures, with relationship to the pain and the tumor, they were accomplished in the immediate postoperative, in the postoperative (24 hours and also 72 hours after) always by the same examiner. The statistical analysis sustained the clinic observations. In our study, the low power density laser of GaAlAs 790 nm suggested the same clinical results when pain and tumor formation were controlled by analgesic and anti- inflammatory medication.

Análise micromorfológica de esmalte e dentina expostos ao laser de Nd: YAG em regime de picossegundos

The efficiency of the ablation obtained with a picosecond-pulsed laser system minimizes material collateral damage because of the etching and plasma formation mechanism. It prevents the excessive generation of shock waves and promotes a considerable decrease of mechanical side effects. In this study, a Nd:YAG picosecond-pulsed Q-switched and mode-locked laser (Antares 76-s, Coherent, Palo Alto, CA) was used. Fifteen microcavities were prepared in the enamel, and nine microcavities were prepared in the dentin of three recently extracted human molars. The parameters for irradiating enamel followed a fixed frequency of 100 Hz and an average power level of 1.3 W; for dentin, the frequency was fixed in 15 Hz, and the average power level varied between 800, 700 and 600 mW. Enamel proved more capable to dissipate shock waves than dentin, since cracks originating from microcavities were more frequent in dentin. In conclusion, it seems that in order to keep defined edges, it is important to choose shorter irradiation periods when average power levels are kept high, which results in lower and best-localized total energy delivery.

Comparative study in vitro of microleakage in class V cavity preparation with and without Er:YAG laser

The evaluation of microleakage is a method conventionally used to evaluate the composite restoration in cavities prepared by laser or conventional drill. The samples were five sound molar human extracted teeth with cavity preparation Class V in each surface (buccal, lingual, mesial and distal) divided in: GI -- cavity preparation with Er:YAG laser, adhesive agent Single Bond (3M), composite Z100 (3M) color A2; GII -- cavity preparation laser, 35% phosphoric acid etching, adhesive, composite; GIII -- cavity preparation with a drill, adhesive, composite; GIV -- cavity preparation with a drill, acid etching, adhesive, composite. The samples were sealed with a coating of nail varnish except on the area of the restoration and immersed in 50% aqueous solution of silver nitrate for 24 hours while kept in darkness. Samples were rinsed, soaked in photorevealing solution and exposed to fluorescent light for 6 hours. After, they were embedded in epoxy resin and sectioned longitudinally using the diamond saw microtone under running water. The specimens were observed under optical microscopy and the results were analyzed under Kruskall Wallis resulting in difference statistically between GI X GIV at the 5% level; and under Mann-Whitney resulting non-difference statistically between groups divided in cervical or occlusal walls.

Aged composite resins ablation under different parameters of Er:YAG laser: ablation rate and morphological aspects

This work presents a study to understand the interaction between Er:YAG laser and composite resin. The main purpose is the development of a new ultra-conservative clinical technique: differential ablation for composite resin restorations using Er:YAG laser. A hybrid composite resin (Z100, 3M, USA) formatted as tablets recently cured was used and after artificial aging method the teeth were irradiated with a Er:YAG laser and two different conditions were considered, energy level per pulse (100, 300 and 500mJ), frequencies (5, 10 and 15Hz) and different water fluxes. Diameter and depth of each resulted microcavity was measured and the material removed volumes were calculated. The resulted values were plotted and feted to allow a comparative observation of the material removed as a function of energy level per pulse. Frequencies of 5 and 10Hz were similar between them and seemed to allow the highest material ablated volume, however considering the energy per pulse parameter, 300mJ was more efficient than the others, mainly when water flux was around 0.1ml/s. The highest water flux showed lower ablation rate with the lowest fluency. Water fluxes presented an important factor considering composite ablation, even because it could modulate depth and surface regularity of the irradiated material.