Dentin decalcification during lithium treatment: case report.

Severe dental decay and changes in tooth structure have been reported in association with the use of lithium in Psychiatry, but lithium effects on tooth inorganic composition remain unknown. A 30-year-old woman with bipolar disorder, treated with lithium carbonate presented severe dental decay. Dentin samples from lithium and healthy volunteers were collected and submitted to ionic and ultrastructural analysis. Samples from the lithium patient exhibited irregular peritubular walls and the mineral crystals were irregularly arranged in the intertubular dentin. In addition, a decrease in Mg/P/Ca and an increase of Zn concentrations were detected. These data suggest that the severe dental decay and changes in the tooth structure observed for the lithium-treated patient are related to dentin mineral loss and that this pathological condition is different from caries lesions.

Effects of ultramorphological changes on adhesion to lased dentin-Scanning electron microscopy and transmission electron microscopy analysis.

Dentin irradiation with erbium lasers has been reported to alter the composite resin bond to this treated surface. There is still a lack of studies reporting the effect of erbium lasers on dentin organic content and elucidating how laser treatment could interfere in the quality of the resin-dentin interface. This study aimed to evaluate the effect of erbium laser irradiation on dentin morphology and microtensile bond strength (µTBS) of an adhesive to dentin. Seventy-two dentin disks were divided into nine groups (n = 8): G1-Control (600-grit SiC paper); Er:YAG groups: G2- 250 mJ/4 Hz; G3- 200 mJ/4 Hz; G4- 180 mJ/10 Hz; G5- 160 mJ/10 Hz; Er,Cr:YSGG groups: G6- 2 W/20 Hz; G7- 2.5 W/20 Hz; G8- 3 W/20 Hz; G9- 4 W/20 Hz. Specimens were processed for cross-sectional analysis by scanning electron microscopy (SEM) (n = 3), transmission electron microscopy (TEM) (n = 2), and adhesive interface (n = 3). Forty-five dentin samples (n = 5) were restored and submitted to µTBS testing. ANOVA (α = 5%) revealed that G1 presented the highest µTBS values and irradiated groups did not differ from each other. TEM micrographs showed a superficial layer of denatured collagen fibrils. For SEM micrographs, it was possible to verify the laser effects extending to dentin subsurface presenting a rough aspect. Cross-sectional dentin micrographs of this hybridized surface revealed a pattern of modified tags with ringlike structures around it. This in vitro study showed that erbium laser irradiation interacts with the dental hard tissue resulting in a specific morphological pattern of dentin and collagen fibrils that negatively affected the bond strength to composite resin.

In vitro evaluation of erbium, chromium:yttrium-scandium-gallium-garnet laser-treated enamel demineralization.

This study evaluated the effect of different parameters of erbium, chromium:yttrium-scandium-gallium-garnet (Er,Cr:YSGG) laser irradiation on enamel mineral loss in a simulated caries model. Forty-five enamel samples obtained from third molar teeth (3 mmx 3 mm) were randomly divided into five groups (n = 9): G1-Er,Cr:YSGG laser at 0.25 W, 20 Hz, 2.8 J/cm(2); G2-Er,Cr:YSGG laser at 0.50 W, 20 Hz, 5.7 J/cm(2); G3-Er,Cr:YSGG laser at 0.75 W, 20 Hz, 8.5 J/cm(2); G4-sodium fluoride (NaF) dentifrice (positive control); G5-no treatment (negative control). After irradiation, the samples were submitted to 2 weeks of pH cycling. After the acid challenge, the samples were assessed by cross-sectional microhardness at different depths from the enamel surface. Analysis of variance (ANOVA) and Student-Newman-Keuls tests were performed (alpha = 5%). The percentage of lesion inhibition for each group was: G1 37%; G2 38%; G3 64%, and G4 50.5%. Regarding the relative mineral loss values (micrometers x volume percent), groups G1 (1,392 +/- 522) and G2 (1,292 +/- 657) did not differ significantly from each other, but both had higher values than group G3 (753 +/- 287); the groups irradiated with Er,Cr:YSGG laser did not differ from group G4. Although the findings of the study revealed that Er,Cr:YSGG laser irradiation at 8.5 J/cm(2) can be an alternative for the enhancement of the enamel's resistance to acid, lower energy densities also produced a cariostatic potential comparable to the use of fluoride dentifrice.

Stem cell proliferation under low intensity laser irradiation: a preliminary study.

BACKGROUND AND OBJECTIVES: Phototherapy with low intensity laser irradiation has shown to be effective in promoting the proliferation of different cells. The aim of this in vitro study was to evaluate the potential effect of laser phototherapy (660 nm) on human dental pulp stem cell (hDPSC) proliferation. STUDY DESIGN/MATERIALS AND METHODS: The hDPSC cell strain was used. Cells cultured under nutritional deficit (10% FBS) were either irradiated or not (control) using two different power settings (20 mW/6 seconds to 40 mW/3 seconds), with an InGaAIP diode laser. The cell growth was indirectly assessed by measuring the cell mitochondrial activity through the MTT reduction-based cytotoxicity assay. RESULTS: The group irradiated with the 20 mW setting presented significantly higher MTT activity at 72 hours than the other two groups (negative control--10% FBS--and lased 40 mW with 3 seconds exposure time). After 24 hours of the first irradiation, cultures grown under nutritional deficit (10% FBS) and irradiated presented significantly higher viable cells than the non-irradiated cultures grown under the same nutritional conditions. CONCLUSIONS: Under the conditions of this study it was possible to conclude that the cell strain hDPSC responds positively to laser phototherapy by improving the cell growth when cultured under nutritional deficit conditions. Thus, the association of laser phototherapy and hDPSC cells could be of importance for future tissue engineering and regenerative medicine. Moreover, it opens the possibility of using laser phototherapy for improving the cell growth of other types of stem cells.

Influence of the additional Er:YAG laser conditioning step on the microleakage of class V restorations.

The purpose of this study was to evaluate the influence of an additional Er:YAG laser conditioning step after laser cavity preparations, on the microleakage of class V composite restorations. Forty-eight bovine incisors were randomly divided into four groups: G1(control) cavities prepared with bur, G2- cavities prepared with laser (400 mJ/2 Hz), G3- cavities prepared and subsequently conditioned with Er:YAG laser (60 mJ/2 Hz); G4-idem for G3, but the laser conditioning was carried out without water-spray. All the cavities were restored using Clearfill SE Bond and Z-250 composite resin. The samples were thermal cycled for 700 cycles and then immersed in 50% silver nitrate solution. The sectioned restorations were exposed to a photoflood lamp to reveal silver nitrate penetration. The Kruskal-Walis one-way analyses of variance test and post hoc Wilcoxon pair-wise comparison were used to compare microleakage degrees. At the gingival margin G2 showed a lower microleakage mean than the control bur-prepared cavities (p = 0.0003). At occlusal margins there were no statistically significant differences between the groups (p = 0.28). It may be concluded that Er:YAG laser class V cavity preparations do not need to be followed by an additional laser conditioning step to result in levels of microleakage similar to or lower than those obtained after bur preparations.

Adhesion of composite luting cement to Er:YAG-laser-treated dentin.

Although some studies claim to the increase of composite resin adhesion to Er:YAG-laser-treated dentin, there are still no reports on the adhesion of composite resin cements to the irradiated surface. This in vitro study evaluated the tensile bond strength (TBS) of a composite resin cement to dentin treated with the Er:YAG laser. Sixty human dentin samples were divided into four groups (n = 15): G1 (Control)-no treatment; G2-Er:YAG laser 60 mJ, 2 Hz, with water cooling, non-contact (19 J/cm(2)); G3-Er:YAG laser 60 mJ, 10 Hz, 50/10 fiber, contact, without water cooling (40 J/cm(2)); G4-Er:YAG laser 60 mJ, 10 Hz, 50/10 fiber, contact, with water cooling (40 J/cm(2)). After the surface treatment, each sample was submitted to bonding procedures. The analysis of variance (ANOVA) and Tukey tests revealed no statistical significant difference on TBS values for groups G1 (13.73 +/- 3.05 MPa), G2 (12.60 +/- 2.09 MPa) and G4 (11.17 +/- 4.04 MPa). G4 was not statistically different from G3 (8.64 +/- 2.06 MPa). Er:YAG laser irradiation with different settings can constitute an alternative tool to the use of composite resin-luting cements.

Effect of Er:YAG laser on enamel acid resistance: morphological and atomic spectrometry analysis.

BACKGROUND AND OBJECTIVES: This study evaluated the effect of Er:YAG laser on enamel acid resistance. STUDY DESIGN/MATERIALS AND METHODS: Seventy human enamel slabs were randomly divided into seven groups (n = 10): G1, Er:YAG laser (Key Laser 2, KaVo, Germany) 60 mJ, 2 Hz, 33.3 J/cm2 (handpiece no. 2051, non-contact); G2, Er:YAG laser 80 mJ, 2 Hz, 44.4 J/cm2 (handpiece no. 2051, non-contact); G3, Er:YAG laser 120 mJ, 2 Hz, 66.6 J/cm2 (handpiece no. 2051, non-contact); G4, Er:YAG laser 64 mJ, 2 Hz, 20 J/cm2 (handpiece no. 2055, contact); G5, Er:YAG laser 86.4 mJ, 2 Hz, 26.9 J/cm2 (handpiece no. 2055, contact); G6, Er:YAG laser 135 mJ, 2 Hz, 42.2 J/cm2 (handpiece no. 2055, contact); G7, control. After laser irradiation, samples were submitted to an acid challenge. For both the nos. 2051 and 2055 handpieces, irradiation was performed with a water cooled spray (5.0 ml/minutes). The calcium and phosphorous ions delivered from the tooth surface were quantified by atomic emission spectrometry, and morphological analysis of the enamel surface was performed under scanning electron microscopy. Kruskal-Wallis and multiple comparisons tests were applied to distinguish significant differences among the treatments (alpha = 5%). RESULTS: Groups G1, G2, and G4 presented decreased demineralization. The SEM evaluation revealed different surface alterations as a result of the different energies used. CONCLUSION: Lower energies can decrease enamel solubility without severe alterations of the enamel.

Tensile bond strength of a flowable composite resin to ER:YAG-laser-treated dentin.

BACKGROUND AND OBJECTIVES: This in vitro study evaluated the influence of a flowable composite resin (FCR) on the tensile bond strength of resin to dentin treated with the Er:YAG Laser (L) and diamond bur (DB). STUDY DESIGN/MATERIALS AND METHODS: Ninety dentin surfaces obtained from 45 third molars were ground and randomly divided into six groups (n = 15): G1-DB, G2-DB+FCR, G3-L (100 mJ, 10 Hz, 37.04 J/cm2), G4-L (100 mJ, 10 Hz, 37.04 J/cm2)+FCR, G5-L (250 mJ, 2 Hz, 92.60 J/cm2), and G6-L (250 mJ, 2 Hz, 92.60 J/cm2)+FCR. After surface etching with 37% phosphoric acid and the application of an adhesive system, inverted conical specimens were prepared with a hybrid composite resin. In groups G2, G4, and G6 a FCR was placed before the hybrid composite resin. After 24 hours-storage in distilled water, the tensile test was performed in a universal testing machine (0.5 mm/minute, 500 N). RESULTS: Data were submitted to Kruskal Wallis test (P = 0.01). The mean bond strength values (MPa+/-SD) were: G1-13.54 (+/-2.99), G2-14.67 (+/-2.32), G3-9.49 (+/-3.09), G4-14.60 (+/-2.76), G5-8.97 (+/-3.89), and G6-13.02 (+/-2.18). Groups G1 and G2 presented the highest bond strength values, which were statistically similar to those of G4 and G6. The groups treated with laser and without the FCR (G3 and G5) showed the lowest shear bond strength values. CONCLUSIONS: FCR can increase the adhesion to dentin treated with Er:YAG laser within different parameters.

Effect of ER:YAG and diode laser irradiation on the root surface: morphological and thermal analysis.

BACKGROUND: The aim of the present study was to compare the effects of Er:YAG and diode laser treatments of the root surface on intrapulpal temperature after scaling and root planing with hand instruments. METHODS: Fifteen extracted single-rooted teeth were scaled and root planed with hand instruments. The teeth were divided into 3 groups of 5 each and irradiated on their buccal and lingual surfaces: group A: Er:YAG laser, 2.94 microm/100 mJ/10 Hz/30 seconds; group B: diode laser, 810 nm/1.0 W/0.05 ms/30 seconds; group C: diode laser, 810 nm/1.4 W/0.05 ms/30 seconds. The temperature was monitored by means of a type T thermocouple (copper-constantan) positioned in the pulp chamber to assess pulpal temperature during and before irradiation. Afterwards, the specimens were longitudinally sectioned, and the buccal and lingual surfaces of each root were analyzed by scanning electron microscopy. RESULTS: In the Er:YAG laser group, the thermal analysis revealed an average temperature of -2.2 +/- 1.5 degrees C, while in the diode laser groups, temperatures were 1.6 +/- 0.8 degrees C at 1.0 W and 3.3 +/- 1.0 degrees C at 1.4 W. Electronic micrographs revealed that there were no significant morphological changes, such as charring, melting, or fusion, in any group, although the specimens were found to be more irregular in the Er:YAG laser group. CONCLUSIONS: The application of Er:YAG and diode lasers at the utilized parameters did not induce high pulpal temperatures. Root surface irregularities were more pronounced after irradiation with an Er:YAG laser than with a diode laser.