Jun-Ichiro Kinoshita

A study on acquired acid resistance of enamel and dentin irradiated by Er,Cr:YSGG laser.

OBJECTIVE This investigation was performed to evaluate the acid resistance of lased enamel and dentin by Er,Cr:YSGG laser to artificial caries-like lesions by spectrophotometry, and the ultrastructure of lased areas was investigated by scanning electron microscopy (SEM) in vitro. BACKGROUND DATA In recent years, many studies have been performed to evaluate the effects of Er,Cr:YSGG laser on dental hard tissues. However, there have been only a few studies to determine if this laser is suitable for caries preventive treatments. METHODS An Er,Cr:YSGG laser was used to irradiate the enamel or dentin samples from 30 extracted human molars at 6 W (67.9 J/cm2) or 5 W (56.6 J/cm2) pulse energy, respectively, with or without water mist. Samples were subjected to 2 microl of 0.1 M lactic acid solution (pH 4.8) for 24 h at 36 degrees C. The parts per million (ppm) of calcium ion (Ca2+) dissolved in each solution was determined by atomic absorption spectrophotometery, and the morphological changes were investigated by SEM. RESULTS The lowest mean Ca2+ ppm was recorded in the lased samples. SEM observation showed that the lased areas were melted and seemed to be thermally degenerated. After acid demineralization, the thermally degenerated enamel or dentin surfaces were almost unchanged. CONCLUSIONS The results of this study suggested that Er,Cr:YSGG laser irradiation with and without water mist appears to be effective for increasing acid resistance.

Root surface temperature increase during Er:YAG laser irradiation of root canals.

The authors measured the temperature of the root surface during root canal preparation using Er:YAG laser irradiation and evaluated the thermal effect on the periodontal region. Twenty extracted human teeth with single roots were divided into two groups of 10. These were irradiated using an Er: YAG laser at 2 Hz and 136 to 184 or 170 to 230 mJ/pulse for 1 min with a water spray. The temperature of the root surface was monitored using thermocouples throughout the procedure. The teeth were longitudinally bisected and observed by stereoscopy and scanning electron microscopy. The temperature on the root surface increased by less than 6 degrees C at the apical area and by less than 3 degrees C at the central area. A morphological evaluation revealed no carbonization or melting. These results suggest that the thermal effect on periodontal tissues during root canal preparation using an Er: YAG laser at less than 230 mJ/pulse for 1 min is minimal.

Effects of Erbium, Chromium : YSGG laser irradiation on root surface : Morphological and atomic analytical studies

OBJECTIVE The purpose of this study was to investigate the morphological and atomic changes on the root surface by stereoscopy, field emission-scanning electron microscopy (FE-SEM), and energy dispersive X-ray spectroscopy (SEM-EDX) after erbium, chromium:yttrium, scandium, gallium, garnet (Er,Cr:YSGG) laser irradiation in vitro. SUMMARY BACKGROUND DATA There have been few reports on morphological and atomic analytical study on root surface by Er,Cr:YSGG laser irradiation. METHODS Eighteen extracted human premolar and molar teeth were irradiated on root surfaces at a vertical position with water-air spray by an Er,Cr:YSGG laser at the parameter of 5.0 W and 20 Hz for 5 sec while moving. The samples were then morphologically observed by stereoscopy and FE-SEM and examined atomic-analytically by SEM-EDX. RESULTS Craters having rough but clean surfaces and no melting or carbonization were observed in the samples. An atomic analytical examination showed that the calcium ratio to phosphorus showed no significant changes between the control and irradiated areas (p > 0.01). CONCLUSIONS These results showed that the Er,Cr:YSGG laser has a good cutting effect on root surface and causes no burning or melting after laser irradiation.

Acquired Acid Resistance of Enamel and Dentin by CO2 Laser Irradiation with Sodium Fluoride Solution

OBJECTIVE The purpose of this study was to investigate the caries-preventive effect of CO2 laser irradiation with or without sodium fluoride (NaF) solution at human dental enamel and dentin in vitro. BACKGROUND DATA The capability of caries prevention with CO2 laser irradiation has been reported in many previous studies, but few studies have been performed with regard to the combined effect of fluoride and laser. MATERIALS AND METHODS Forty extracted human incisor teeth were used for the enamel study, and 40 molar teeth were used for the dentin study. Samples were then divided into four categories: control (no treatment); CO2 laser irradiation only; NaF treatment only; and NaF treatment followed by CO2 laser irradiation. Each sample was immersed in 2 mL of lactic acid (0.1 M, pH 4.8) solution for 24 h at 37 degrees C in 100% humidity. The parts per million (ppm) of calcium ion (Ca2+) dissolved in each solution was determined by atomic absorption spectrophotometry. The samples were also observed by stereoscopy and scanning electron microscopy (SEM). RESULTS The lowest mean Ca2+ ppm was recorded at the enamel or dentin samples treated with NaF and laser. Statistical analysis of the data was considered significant (p < 0.01). SEM observation showed that surfaces were changed to melted, smooth, and mirror-like appearances when CO2 laser irradiation was applied with NaF solution. CONCLUSION It can be concluded that CO2 laser irradiation with NaF solution has more caries-preventive effect than CO2 laser irradiation only at the enamel and dentin surfaces.

Comparative study of carious dentin removal by Er,Cr:YSGG laser and Carisolv.

OBJECTIVE The present study aimed to compare carious dentin removal by air turbine, Carisolv and erbium,chromium:yttrium,scandium,gallium,garnet (Er,Cr:YSGG) laser, and examine morphological changes before and after these caries removal techniques under light microscopy and scanning electron microscopy (SEM). BACKGROUND DATA Although there have been numerous studies on removing caries by Er,Cr:YSGG laser, none has compared Er,Cr:YSGG laser and Carisolv, or reported on the usage of DIAGNOdent as a diagnostic tool particularly for advanced caries in in vitro experiments. MATERIALS AND METHODS Sixty extracted human teeth diagnosed as advanced caries were divided into three groups based on the treatment received, namely air turbine, Carisolv, and Er,Cr:YSGG laser groups. Each group was sub-divided into two in order to examine the results with or without finishing using nylon brush, 15% ethylene diamine tetraacetic acid (EDTA) or low-power laser, respectively. After evaluation by DIAGNOdent, specimens were observed under light microscopy or SEM. RESULTS Light microscopic observations varied considerably in the three treatment groups. SEM revealed that the surfaces treated by air turbine were very smooth, but with substantial debris. The Carisolv group exhibited a very rough surface with a thick smear layer, while the Er,Cr:YSGG group demonstrated smooth undulations with little smear layer and debris. Among the finishing techniques, the laser group demonstrated the best efficiency. DIAGNOdent scores supported the results of light microscopy. CONCLUSION These results suggest that caries removal by Er,Cr:YSGG laser is very effective even without finishing and DIAGNOdent is useful for diagnosing advanced caries in in vitro experiments.

Morphological Study on the Capability of Er:YAG Laser Irradiation for Root Canal Preparation

OBJECTIVE The purpose of this study was to evaluate morphologically the capability of Er:YAG laser irradiation for root canal preparation in vitro. BACKGROUND DATA There have been no reports on root canal preparation using Er:YAG laser irradiation. METHODS Forty extracted human teeth were divided randomly into two groups of 20. Laser irradiation was performed using three different sizes of fiber tips at the two different parameters (G 1, 2 Hz and 136-184 mJ/pulse; G 2, 2 Hz and 170-230 mJ/pulse). After laser irradiation, the teeth were bisected longitudinally and observed by stereoscopy and field emission-scanning electron microscopy (FE-SEM). The time required for preparation in each group was recorded and the achievement degree of root canal preparation was scored according to our criteria. Statistical analysis of the times was performed using one-way analysis of variance (ANOVA). A value of p < 0.01 was considered significant. RESULTS Root canals were prepared using laser irradiation at 50% of teeth in G 1 and 40% in G 2. Remnant pulp tissue after laser irradiation was observed at 30% of teeth in G 1, but not recognized in G 2. Irradiated areas were scale-like and clean, but rough and irregular by FE-SEM. The statistical analysis revealed that the time required for preparation at high energies was significantly shorter compared with that at low energies (p < 0.01). CONCLUSION These results suggest that Er:YAG laser irradiation is capable of root canal preparation if appropriate parameters are selected.

The Application of Tooth Temperature Measurement in Endodontic Diagnosis: A Review

Teeth with vital pulp are those with an adequate vascular supply, so the circulatory status, and not sensitivity response of the pulp tissue, has been proposed to assess pulp vitality. Some experimental methods have been used to assess this; one of them is the measurement of tooth temperature, which may indicate the pulp vasculature. Some authors have found no differences between the temperatures of teeth with vital and nonvital pulp; however, others found that teeth with nonvital pulp have lower temperatures than teeth with vital pulp. Temperature measurement as a diagnostic procedure has been described with the use of thermocouple, thermistors, infrared thermography, and cholesteric liquid crystals. Many factors may influence the results of the temperature measurement procedure. For creating controlled conditions, each patient should be examined in a thermologic environment. Patients should be asked to refrain from smoking and eating/drinking for 60 minutes before the procedure. The room should be insulated and draft free, and the temperature should be maintained at 20 degrees C. It is desirable to have them lie down or sit with adequate support for the head. The use of a rubber dam is also advocated. Tooth temperature measurement as a diagnostic procedure is reviewed to include description of devices for the test, associated factors, and value of the test.

Study on Acid Resistance of Human Dental Enamel and Dentin Irradiated by Semiconductor Laser with Ag(NH3)2F Solution

OBJECTIVE The purpose of this study was to investigate the acquired acid resistance of human dental enamel and dentin treated by 38% diamine silver fluoride [Ag(NH3)2F] solution and semiconductor (diode) laser irradiation in vitro. BACKGROUND DATA There have been no reports on the acid-resistant effect by combined use of fluoride and semiconductor laser. METHODS Sixty crowns of extracted human molars were divided into two groups for enamel and dentin samples, and each group was subdivided into three subgroups of 10 each. Each subgroup of enamel and dentin samples served as a control; one was treated with Ag(NH3)2F and the other was treated with Ag(NH3)2F and semiconductor laser irradiation at 2 W for 30 sec. Then all samples were immersed in 5 ml of 0.1 M lactic acid (pH 4.8) at 37 degrees C for 24 h. The concentration of calcium ion (Ca2+) dissolved in the solution was measured by atomic absorption spectrophotometry, and the samples were observed by stereoscopy and scanning electron microscopy (SEM). RESULTS In both enamel and dentin samples, dissolved Ca2+ concentration in Ag(NH3)2F- or Ag(NH3)2F- and laser-treated group was significantly decreased compared with that in the control (p < 0.01). SEM findings showed that numerous cubic particles ranging from 0.1 to 0.5 mcirom were observed only in the combined treated groups of both enamel and dentin samples. CONCLUSIONS A significantly decreased solubility of human enamel and dentin was acquired after treatment by Ag(NH3)2F and semiconductor laser irradiation, which suggested that this combined use has the capability of a more efficient acid-resistant effect on human dental hard tissues.

Removal of Carious Dentin by Er:YAG Laser Irradiation with and without Carisolv™

OBJECTIVE The purpose of this study was to investigate the effectiveness of caries removal by using an Er:YAG laser irradiation with and without Carisolv, in vitro. BACKGROUND DATA Effective ablation of dental hard tissues using Er:YAG laser has been reported and its application to caries removal has been expected. METHODS Five extracted human teeth were selected for Carisolv and burr treatment. One-half of the lesion was treated with the Carisolv and then removed. The other half was removed using burr treatment. Fifty teeth were subjected to Er:YAG laser treatment with and without Carisolv. First, Carisolv was applied on one-half of each carious lesions for 1 min and followed by the Er:YAG laser irradiation at 60-140 mJ, 2 Hz for another 1 min; the other half was treated with Er:YAG laser only. The cavity was carefully assessed by DIAGNOdent. Each lesion was photographed before and after treatment, and the treated cavity was observed by microscopy and with scanning electron microscope (SEM). RESULTS Our results revealed that application of Carisolv followed by Er:YAG laser irradiation at 100-140 mJ pulse energy effectively removed dentin caries. From the SEM study, it was found that the cavity surface treated with the laser revealed various patterns of microirregularity, often accompanied by microfissure propagation. There was also no smear layer. CONCLUSIONS It was revealed that Er:YAG laser and Carisolv could provide an alternative technique for caries removal for conventional mechanical drilling and cutting.

Effects of KTP Laser Bleaching on Traumatized Tooth Enamel

Background: Bleaching of traumatized discolored teeth is considered an important issue in esthetic dentistry. Various methods have been introduced for bleaching, some of which may have adverse effects on soft or hard tissues of the tooth. Objectives: The objective of the study was to evaluate the effects of KTP laser bleaching on enamel of traumatized teeth. Materials and Methods: A square of 36 mm2 was chosen on the labial surface of 32 extracted teeth. The corners were drilled in order to indicate the location precisely. The shade of each sample was recorded and the teeth were divided into four groups, each with eight teeth: group A (Smartbleach with KTP laser for 30 seconds), group B (Smartbleach with G-Light for 5 minutes), group C (only Smartbleach for 10 minutes) and group D (control group with no bleaching). After one session of bleaching, shade assessment was performed again. In another experiment on nine teeth, Smartbleach with KTP laser was used for 150 seconds to 1500 seconds. The samples were critically processed and observed by using scanning electron microscope (SEM) to assess enamel damage. Data was statistically analyzed using Kruskal-Wallis test (confidence interval level were set at 95%). Results: Smartbleach was highly effective when used with KTP laser (P = 0.0419). Enamel damage was observed after frequent KTP bleaching and 750 seconds of KTP bleaching was recognized as the limit by morphological evaluation via SEM, indicating a major difference between under and over 750 seconds of bleaching. Conclusions: Application of KTP laser may increase the bleaching effect of Smartbleach, nevertheless it may cause some enamel damage.