Reginaldo Santana da Silva

Evaluation of dentin root canal permeability after instrumentation and Er:YAG laser application

Smear layer removal with EDTA from root canal walls allows greater cleaning and disinfection of root canals. However, because Er:YAG laser acts on the removal of the smear layer, the objective of investigation was to analyze in vitro the effect of Er:YAG laser on dentin root canal wall permeability after endodontic instrumentation and irrigation with water or sodium hypochlorite and Er:YAG laser application.

Surface tension of calcium hydroxide associated with different substances

The purpose of this study was to evaluate the surface tension of calcium hydroxide (CH) associated with different substances (deionized distilled water, camphorated paramonochlorophenol, 2% chlorhexidine digluconate, Otosporin, 3% sodium lauryl ether sulphate; Furacin, PMC Furacin) using tensiometer. The action of the substances studied on the dentinal structure enhances the property of surface tension. This method consists in the application of force to separate a platinum ring immersed in the substances. Thus, torsion was applied to the screw until the platinum ring separated during substances testing. Considering the methodology applied, the following can be concluded: distilled water alone or associated with CH presented a high surface tension (70.00 and 68.40 dynes/cm); calcium hydroxide in association with anionic detergent showed low surface tension (31.60 dynes/cm); camphorated paramonochlorophenol plus CH presented low surface tension (37.50 dynes/cm); 2% chlorhexidine associated with calcium hydroxide showed high surface tension values (58.00 dynes/cm); Otosporin plus calcium hydroxide showed low surface tension (35.40 dynes/cm); paramonochlorophenol Furacin mixed with calcium hydroxide presented surface tension equal to 45.50 dynes/cm; sodium hypochlorite presented high surface tension (75.00 dynes/cm). Antimicrobial agents more indicated in endodontics, i.e. CH, chlorhexidine and hypochlorite, presented the highest surface tension.

Effect of energy (J) on temperature changes at apical root surface when using Er:YAG laser to enlarge root canals

The use of lasers for cleaning, shaping and disinfecting root canals must not produce heat which damages periapical tissue and alveolar bone. The aim of the present study was to determine the increase of external temperature at the apical surface of the root canal after Er:YAG laser irradiation with a 250 micrometer diameter fiberoptic guide with and without distilled and deionized water at 3 different total energies. Thirty single-rooted teeth were instrumented to #25 K-file using distilled and deionized water for irrigation. They were divided into three groups according to total energy (15J, 30J and 45J with 15 Hz and 140 mJ per pulse). Each group was irradiated with water and then without water. The increase in temperature at the apical root surface was measured with a multimeter and a thermocouple. Changes in apical temperature were significantly different in all groups (p less than 0.01; 15 J less than 45 J less than 30 J). Less time was necessary for return to initial room temperature at 15 J. We conclude that in vitro use of the Er:YAG laser (total energy of 15, 30, and 45 J) increased external apical root temperature and that the root canal must be filled with distilled and deionized water to reduce the risk of an increase in temperature.

Cutting efficiency of short and very short pulsed Er:YAG lasers at different frequencies on dentine and enamel

This study was to determine the weight loss caused by the use of Er:YAG laser on enamel and dentine using short and very short pulses and two frequencies. Researchers have reported that the Er:YAG laser ablates dental hard tissues more effectively and efficiently, with less thermal damage to the tooth, than other hard lasers. In this study, one hundred and twenty molars were cut into crown hemisections, were dried for 1 h at 37 degrees C and then weighed with a precision balance. Group 1: enamel short pulse 10 Hz; group 2: dentine short pulse 10 Hz; group 3: enamel very short pulse 10 Hz; group 4: dentine very short pulse 10 Hz; group 5: enamel short pulse 15 Hz; group 6: dentine short pulse 15 Hz; group 7: enamel very shot pulse 15 Hz; group 8: dentine very short pulse 15 Hz. The results of short and very short pulse were statistically similar regardless of the type of tissue and the frequency used. Concluding, enamel ablation with the Er:YAG laser shows lower efficiency than dentin ablation, very short pulse mode ablates dental tissue with the same efficacy than short pulse mode.

First detection of lead in black paper from intraoral film An environmental concern

Lead (Pb) contamination in the black paper that recovers intraoral films (BKP) has been investigated. BKP samples were collected from the Radiology Clinics of the Dental School of Ribeirão Preto, University of São Paulo, Brazil. For sake of comparison, four different methods were used. The results revealed the presence of high lead levels, well above the maximum limit allowed by the legislation. Pb contamination levels achieved after the following treatments: paper digestion in nitric acid, microwave treatment, DIN38414-54 method and TCLP method were 997 microg g(-1), 189 microg g(-1), 20.8 microg g(-1), and 54.0 microg g(-1), respectively. Flame atomic absorption spectrometry (FAAS) and inductively coupled plasma mass spectrometry (ICP-MS) were employed for lead determination according to the protocols of the applied methods. Lead contamination in used BKP was confirmed by scanning electron microscopy coupled with energy dispersive X-ray microanalysis (SEM-EDS). All the SEM imaging was carried out in the secondary electron mode (SE) and backscattered-electron mode (QBSD) following punctual X-ray fluorescence spectra. Soil contamination derived from this product revealed the urgent need of addressing this problem. These elevated Pb levels, show that a preliminary treatment of BKP is mandatory before it is disposed into the common trash. The high lead content of this material makes its direct dumping into the environment unwise.

Effects of Er:YAG and Nd:YAG laser irradiation on the permeability of instrumented root canal walls

The aim of this study was to evaluate the effect of Er:YAG and Nd:YAG laser on radicular dentine permeability when using distilled and deionized water and 1% sodium hypochlorite as irrigating solutions. Thirty human maxillary canines obtained from laboratory stock and conserved in 0.1% thymol until use were divided randomly into six groups of five teeth each. The root canals were instrumented with K files and the step-back technique. The surgical diameter was achieved 4 files above the original anatomical diameter. Group I, the teeth were irrigated with distilled and deionized water; Group II, the teeth were irrigated with 1% sodium hypochlorite, Group II the teeth were irrigated with distilled and deionized water and then Er:YAG laser was applied with 140mJ, 15Hz, 300 pulses and 42J; group 4 the teeth were irrigated with 1% sodium hypochlorite and Er:YAG laser was applied in the same parameters as Group III, Group V, the teeth received irrigation with distilled and deionized water and Nd:YAG laser application with 150mJ, 15Hz, 2,25W and Group VI the teeth were irrigated with 1% sodium hypochlorite and Nd:YAG laser was applied with the same parameters as Group V. During laser application the teeth were always filled with irrigating solution. The fiber optic tip was introduced until the apex and the laser was activated. The tip was withdrawn gently with helicoidally movement from the apex until the pulp chamber. After preparation the teeth were immersed in 10% copper sulfate for 30 minutes, in vacuum for the first 5 minutes. The teeth were then placed in a 1% rubianic acid alcohol solution for the same periodsin solution and in vacuum as above. Upon completion of this reaction the teeth were sectioned transversally, in 150micrometers slices, and sanded, washed, dehydrated, cleared and mounted on glass slides for microscopic examination. The quantification of the penetration of copper ions was done by morphmetric analysis with a 400-point grid. The data was submitted to statistical analysis and shoed normality and hemocedacity of the sample, parametric analysis was applied. The Tukey test showed that the cervical and middle thirds were statistically similar (p>0.05) and greater than the apical third (p<0.05). The Scheffe test showed greater dentine permeability in root canals where water and Er:YAG laser were used and significant different from the other treatments (p<0.05). The use of 1% sodium hypochlorite with Nd:YAG laser, distilled and deionized water with Nd:YAG laser and the use of water, were statistically similar (p<0.05) and increased less dentine permeability when compared to other groups. The use of 1% sodium hypochlorite with and without Er:YAG laser application presented statistically similar permeability values (p>0.05) and positioned in an intermediate among the treatments.

In-vitro study of intrapulpar temperature changes when using Er:YAG laser for class V cavity preparation

Various studies have recommended parameters for the use of Er:YAG laser for the treatment of caries of the enamel and dentin without studying the increase in temperature caused by laser in the individual groups of teeth. The Er:YAG laser has been indicated for the removal of caries, cavity preparation and preparation and disinfection of root canals. The authors studied the intrapulpar temperature change in 10 incisors, 10 canines, 10 pre-molars and 10 molars during Class V cavity preparation with focused short pulse and very short pulse Er:YAG laser, using the following parameters: 10 Hz frequency, 500 mJ per pulse, 6 s, 10 mm distance, 25 ml/min water flow, at 23 degrees C and 65 percent humidity. The greatest increase in temperature was found in the incisors and the least increase in the molars at both pulse modes. The very short pulse mode caused less of an increase in temperature in the pulp chamber in all teeth than the short pulse mode.