Acid challenge exacerbates activation of matrix metalloproteinases in permanent teeth undergoing radiotherapy.

The aim of this study was to investigate the effect of acid challenge on the activation of matrix metalloproteinases (MMPs) in the Dentinoenamel junction of primary and permanent teeth submitted to radiotherapy. For this purpose, a total of 178 dental fragments obtained from molars were used, and randomly divided into 2 groups (primary and permanent teeth) / 4 experimental subgroups (irradiated and non-irradiated, demineralized and non-demineralized). The fragments were exposed to radiation, with a dose fraction of 2 Gy, for 5 consecutive days, until a total dose of 60 Gy was reached, with a total of 30 cycles, for 6 weeks. To determine the activity of MMPs on the dentinoenamel junction (DEJ), in situ zymography assays on 0.6mm dental fragments were performed. To assess whether MMP activity would be impacted by an acidic environment, the fragments were placed in a demineralizing solution (pH of 4.8). The finding was that irradiation activated MMPs in DEJ and these effects were more evident in permanent when compared with primary teeth. When the effect of an acid challenge on MMPs activity was investigated, demineralization was observed not to increase MMPs activity in non-irradiated teeth, but it did increase MMPs activity in irradiated teeth. In conclusion, an acid challenge was found to exacerbate activation of MMPs in DEJ of permanent teeth submitted to irradiation, but not in primary teeth.

Effect of the usage of Er,Cr:YSGG laser with and without different remineralization agents on the enamel erosion of primary teeth.

The aim of the present study was to evaluate the effects of different remineralization agents associated with erbium, chromium:yttrium-scandium-gallium-garnet (Er,Cr:YSGG) (0.5 W power, 20 Hz frequency, 60% water, 40% air, 25 mJ pulse energy, 8.84 J/cm2 fluence, 60 µs pulse duration, 600 µm tip diameter, and an approximate 1-1.5 mm distance to the target) laser irradiation on erosion induced by the consumption of carbonated drinks in human primary enamel. There were 8 groups and 10 primary teeth in each g0roup. The distribution was as follows: group 1, casein phosphopeptide-amorphous calcium phosphate with fluoride (CPP-ACPF); group 2, Er,Cr:YSGG laser+CPP-ACPF; group 3, fluor varnish; group 4, Er,Cr:YSGG Laser+fluoride varnish; group 5, ROCS® medical mineral gel; group 6, Er,Cr:YSGG laser + ROCS® medical mineral gel; group 7, Er,Cr:YSGG laser; and group 8, artificial saliva. The samples in the groups were submerged in artificial saliva and acid twice a day for 6 s at 6-h intervals and were then exposed to an erosion cycle 15 times. In the groups in which the Er,Cr:YSGG laser was applied in combination with the remineralization agents, the laser application was made first, and then the remineralization agents were applied for 4 min in each group. The Friedman and Wilcoxon signed-rank tests and the Bonferroni correction were used in statistical analyses, and the significance level was taken as p < 0.05. According to the results, all agents had a statistically significant difference (groups 1, 2, 3, 4, and 6: p = 0.005, p < 0.017; groups 5 and 7: p = 0.007, p < 0.017) between BL-RM periods. However, all agents had a statistically significant remineralization effect on primary teeth enamel (groups 1, 2, 3, 6, and 7: p = 0.005, p < 0.017; group 4: p = 0.011, p < 0.017) except that group 5 (p = 0.074, p < 0.017) between DM-RM periods. The coadministration of an agent with the laser did not make any difference at a statistical level (p = 0.804, p > 0.05). The results were supported by scanning electron microscopy (SEM) and X-ray diffraction (XRD) analysis. As a result of this study, CPP-ACPF had a notable impact in terms of the remineralization effect on eroded enamel, and the Er,Cr:YSGG laser alone may be an alternative method, which may be related to the modified hydroxyapatite structure, 38.5% H0.56Ca4.56O13P3Y0.44, that was determined in XRD analysis.

Angiogenic protein synthesis after photobiomodulation therapy on SHED: a preliminary study.

This study evaluated the viability, proliferation, and protein expression after photobiomodulation (PBM) of stem cell from human exfoliated deciduous teeth (SHED). The groups were the following: G1 (2.5 J/cm2), G2 (3.7 J/cm2), and control (not irradiated). According to the groups, cells were irradiated with InGaAlP diode laser at 660 nm wavelength, continuous mode, and single time application. After 6 h, 12 h, and 24 h from irradiation, the cell viability and proliferation, and the protein expression were analyzed by MTT, crystal violet, and ELISA multiplex assay, respectively. Twenty-four hours after PBM, SHED showed better proliferation. Over time in the supernatant, all groups had an increase at the levels of VEGF-C, VEGF-A, and PLGF. In the lysate, the control and G2 exhibited a decrease of the VEGF-A, PECAM-1, and PLGF expression, while control and G3 decreased VEGF-C, VEGF-A, and PDGF expression. The dosimetries of 2.5 J/cm2 and 3.7 J/cm2 maintained viability, improved proliferation, and synthesis of the angiogenic proteins in the supernatant in the studied periods on SHED.

Effect of single and multiple doses of low-level laser therapy on viability and proliferation of stem cells from human exfoliated deciduous teeth (SHED).

The present study aimed to evaluate in vitro whether the low-level laser (LLL) delivering fractionated total energy (multiple irradiation) or single irradiation stimulates regeneration-associated events (viability and proliferation) in stem cells from human exfoliated deciduous teeth (SHED). Cells received LLL irradiation (InGaAlP-660 nm), according to the following experimental groups: G1 (single irradiation 2.5 J/cm2, 10 mW, 10 s, 0.10 J), G2 (single irradiation 5.0 J/cm2, 10 mW, 20 s, 0.20 J), G3 (single irradiation 7.5 J/cm2, 10 mW, 30 s, 0.30 J), G4 (two irradiations 2.5 J/cm2, 10 mW, 10 s; total energy 0.20 J), G5 (three irradiations 2.5 J/cm2, 10 mW, 10 s; total energy 0.30 J), and G6 (non-irradiated). Cell viability was assessed by MTT and trypan blue exclusion (TBE) methods, while cell proliferation was evaluated by crystal violet (CV) and sulforhodamine B (SRB) assays after 24, 48, and 72 h after the first irradiation. By MTT, there was no difference between groups at 24 and 72 h. At 48 h, the groups subjected to multiple irradiation (G4 and G5) presented higher cell viability rates. The average percentages of viable cells for all groups by TBE method were 91.04%, 96.63%, and 97.48% at 24, 48, and 72 h, respectively. By CV, there was no significant difference between groups at 24 and 48 h; at 72 h, G2, G3, and G4 presented higher cell proliferation. By SRB, G1 and G4 presented lower proliferation rates in all the periods. When the groups presenting the same total energy were compared, G2 (0.20 J) presented lower cell viability rates and higher cell proliferation rates in comparison with G4; G3 (0.30 J) presented similar results to those of G5, with higher cell viability and proliferation. The application of laser delivering fractionated total energy (two or three applications of 2.5 J/cm2) induced higher cell viability at 48 h, while the single irradiation with 2.5 J/cm2 did not stimulate metabolic activity in such period and the proliferation over time. The 5.0 and 7.5 J/cm2 single doses and the three applications of 2.5 J/cm2 maintained cell viability and stimulated proliferation of SHED at 72 h.

Laser treatment contributes to maintain membrane integrity in stem cells from human exfoliated deciduous teeth (shed) under nutritional deficit.

This study aimed to analyze the effects of laser irradiation on the membrane integrity and viability of stem cells from human exfoliated deciduous teeth (SHED) that were kept in serum starvation. Nutritional deficit was used to mimic the cellular stress conditions of SHED isolation for regenerative dental approaches, where laser therapy could be beneficial. SHED were cultured under serum starvation (MEMα + 1%FBS) for 1 or 24 h pre-irradiation (protocols A and B, respectively). Then, cells received low-level laser therapy (LLLT; 660 nm) at 2.5 J/cm2 (0.10 W; groups I and V), 5.0 J/cm2 (0.20 W; groups II and VI), 7.5 J/cm2 (0.30 W; groups III and VII), or remained non-irradiated (groups IV and VIII). During irradiation, cells were maintained in 1% FBS (groups I-IV) or 10% FBS (normal culture conditions; groups V-VIII). Membrane integrity was evaluated by quantifying lactate dehydrogenase (LDH) release (immediately after irradiation), and cell viability was assessed by the MTT assay (24, 48, and 72 h post-irradiation). Serum starvation did not alter LDH release by non-irradiated SHED, while LDH release decreased significantly in groups irradiated in 1% FBS (I and III), but not in groups irradiated in 10% FBS (V-VII), regardless the pre-irradiation conditions (protocols A/B). Cell viability was significantly higher 24 h after irradiation, in most protocol A groups. In contrast, cell viability remained mostly unaltered in protocol B groups. LLLT contributed to maintain membrane integrity in SHED subjected to nutritional deficit before and during irradiation with 0.10 or 0.30 W. Short serum starvation before irradiation improved SHED viability at 24 h post-irradiation.

A preliminary comparison between the effects of red and infrared laser irradiation on viability and proliferation of SHED.

The aim of this preliminary study was to compare the effects of different energy densities from red and infrared low-level laser (LLL) on viability and proliferation of stem cells from human exfoliated deciduous teeth (SHED). SHED were irradiated with red laser (R) or infrared laser (IR) set with the following dosimetry: 1.2 J/cm2 (0.05 J), 2.5 J/cm2 (0.1 J), 5.0 J/cm2 (0.2 J), and 7.5 J/cm2 (0.3 J). Positive (C+) and negative (C-) control groups comprised non-irradiated cells. Data were analyzed by two-way ANOVA followed by Tukey's test (P < 0.05). At 24- and 48-h period, group R5.0 showed significantly higher cell viability rates than R1.2 and R2.5. At 48 h, R2.5 also revealed lower proliferation than R5.0. Comparing to the C+ group, R2.5 exhibited lower viability at 72 h, and proliferation at 24 and 48 h. Groups R1.2, IR1.2, and IR5.0 were less viable at 24 h, while R1.2, IR2.5, and IR5.0 revealed lower proliferative capacity at 48 h. Overall, our results showed that LLL can favor viability and proliferation of SHED, especially when cells receive red laser irradiation at 5.0 J/cm2. Therefore, according to this preliminary investigation, 5 J/cm2 applied by red LLL induced high rates of cell viability and proliferation, while the same irradiation dose using infrared laser led to negative effects. LLL irradiation with 1.2 and 2.5 J/cm2 was deleterious to metabolic activity and proliferation of SHED regardless of the type of laser. Further studies are necessary to gain in-depth knowledge about the effects of different wavelengths of LLL on SHED viability and proliferation.

Radiotherapy Reduces Microhardness and Mineral and Organic Composition, and Changes the Morphology of Primary Teeth: An in vitro Study.

OBJECTIVE: We aimed to evaluate whether radiotherapy causes changes in the mineral composition, hardness, and morphology of enamel and dentin of primary teeth. MATERIALS AND METHODS: Thirty specimens of primary teeth were subjected to radiotherapy. At baseline and after 1,080, 2,160, and 3,060 cGy, the specimens were subjected to microhardness, FT-Raman spectroscopy, and scanning electron microscopy (SEM) analysis. The pH of artificial saliva was determined, as were the calcium and phosphate concentrations. The data were subjected to the Shapiro-Wilk normality test, showed a nonnormal distribution, and were compared by the Kruskal-Wallis test. RESULTS: The results showed that the microhardness of the enamel surface decreased after 2,160 cGy (281.5 ± 58 kgf/mm2) when compared to baseline (323.6 ± 59.5 kgf/mm2) (p = 0.045). For dentin, the surface hardness decreased after 1,080 cGy (34.9 ± 11.4 kgf/mm2) and 2,160 cGy (26 ± 3.5 kgf/mm2) when compared to baseline (56.5 ± 7.7 kgf/mm2) (p < 0.0001). The mineral and organic contents of phosphate (p < 0.0001), carbonate (p < 0.0001), amide (p = 0.0002), and hydrocarbons (p = 0.0031) of enamel decreased after 3,060 cGy (5,178 ± 1,082, 3,868 ± 524, 999 ± 180, and 959 ± 168 kgf/mm2, respectively). For dentin, we noticed a growing increase in phosphate v2, amide, and hydrocarbon content after 1,080 cGy (8,210 ± 2,599, 5,730 ± 1,818, and 6,118 ± 1,807 kgf/mm2, respectively) and 2,160 cGy (1,0071 ± 2,547, 7,746 ± 1,916, and 8,280 ± 2,079 kgf/mm2, respectively) and a reduction after 3,060 cGy (6,782 ± 2,175, 3,558 ± 1,884, and 3,565 ± 1,867 kgf/mm2, respectively) (p < 0.0001). SEM images showed cracks on enamel and degradation of peritubular dentin. CONCLUSION: We concluded that radiotherapy caused a reduction in surface hardness, changed mineral and organic composition, and promoted morphological changes on the enamel and dentin of primary teeth.

The effect of Er,Cr:YSGG laser, fluoride, and CPP-ACP on caries resistance of primary enamel.

The aim of this in vitro study was to determine the effect of different remineralization agents and laser on caries resistance of primary enamel. In the study, 150 sound primary molars were used. The initial microhardness values were measured and the teeth were randomly assigned to ten treatment groups (n = 15): no treatment/negative control (C), NaF, APF, fluoride varnish (FV), CPP-ACP, laser (L), L + NaF, L + APF, L + FV, L + CPP-ACP. The microhardness values were measured after the treatments and the pH cycle. The obtained data were analyzed statistically. One sample from each group was examined before treatment, after treatment, and after the pH cycle with a scanning electron microscope. While microhardness values after treatment compared to baseline increased, microhardness after the pH cycle decreased compared to after treatment values in all experimental groups (p < 0.05). In regard to the difference in microhardness after the pH cycle and baseline, there were no statistically significant differences between groups C and NaF and between C and CPP-ACP (p > 0.05). There was a significant difference between groups L and L + FV (p < 0.05), while no significant difference was noted between groups L and L + NaF, L + APF, L + CPP-ACP (p > 0.05). As a conclusion, FV is more effective when used in combination with laser than laser alone. NaF, CPP-ACP, and laser may be insufficient in protecting the primary teeth against acid attacks compared to FV used with laser.

Evaluation of Antibacterial Efficiency of Different Root Canal Disinfection Techniques in Primary Teeth.

BACKGROUND: A successful primary root canal treatment depends on effective shaping and cleaning the root canal system and finally filling it with a hermetic sealer. Clinically, roots of primary teeth are difficult to shape and the irrigation/disinfection protocol has great importance on prognosis. OBJECTIVE: The present study evaluated the antibacterial efficiency of Endosafe (Orangedental GmbH & Co. KG), photo-activated disinfection (PAD; Orangedental GmbH & Co. KG), diode laser (Epic 10; Biolase, Inc.), ozone (O3, Ozonytron; Biozonix, München, Germany), and sodium hypochloride applications in primary root canals that were infected with Enterococcus faecalis after standard mechanical instrumentation. METHODS: The study was conducted on roots of 100 human primary molar teeth, which were extracted due to excessive caries. The roots were divided in 5 groups with 15 roots in each root disinfection protocol. In addition, 15 samples and 10 samples served as positive and negative controls, respectively. The Shapiro-Wilk test, the Kruskal-Wallis test and then by post hoc group comparisons with the Bonferroni-adjusted Mann-Whitney U test (unpaired observations) was used. RESULTS: Sodium hypochlorite (NaOCl) exhibited the highest antibacterial effect (0 colony-forming units per mL). Diode laser irradiation was statistically more effective than the ozone, PAD, and Endosafe groups (p < 0.001). Endosafe, PAD, and ozone groups showed similar antibacterial effect (p > 0.05). Although not statistically significant, the Endosafe was more effective in reducing the bacterial count when compared with ozone and PAD. CONCLUSIONS: The five tested irrigation systems were shown to be effective in disinfection of the E. faecalis-contaminated primary root canals and best results were obtained with 2.5% NaOCl and diode laser.

Low-level laser irradiation induces in vitro proliferation of stem cells from human exfoliated deciduous teeth.

The aim of this study was to evaluate the effect of low-level laser irradiation (LLLI) on the proliferation and viability of stem cells from human exfoliated deciduous teeth (SHED). Cells were irradiated or not (control) with an InGaAlP laser diode (660 nm, 30 mW, continuous action mode) using two different energy densities (0.5 J/cm2-16 s; 1.0 J/cm2-33 s). Irradiation was performed at 0 and 48 h, with the laser probe fixed at a distance of 0.5 cm from the cells. Cell proliferation was analyzed at 0, 24, 48, and 72 h by the Trypan blue exclusion method and MTT assay. Cell cycle and Ki67 expression were analyzed by flow cytometry. Apoptosis-related events were evaluated by expression of annexin V/PI and nuclear morphological changes by staining with DAPI. Differences between groups at each time were analyzed by the Kruskal-Wallis and Mann-Whitney tests, adopting a level of significance of 5% (p < 0.05). The results showed that an energy density of 1.0 J/cm2 promoted an increase in cell proliferation at 48 and 72 h compared to the control and 0.5 J/cm2 groups. Cell cycle analysis revealed a predominance of cells in the S and G2/M phases in the irradiated groups. This finding was confirmed by the increased expression of Ki67. Low positive staining for annexin V and PI was observed in all groups, and no nuclear changes were detected, indicating that cell viability was not affected by the energy densities tested. It can be concluded that the LLLI parameters used (660 nm, 30 mW, 1.0 J/cm2) promote the proliferation of SHEDs and the maintenance of cell viability.

The Effects of Photobiomodulation Delivered by Light-Emitting Diode on Stem Cells from Human Exfoliated Deciduous Teeth: A Study on the Relevance to Pluripotent Stem Cell Viability and Proliferation.

OBJECTIVE: Photobiomodulation (PBM) can modulate the proliferation of some types of stem cells. However, few reports have addressed the effects of PBM delivered by light-emitting diode (LED) on stem cells obtained from the pulp tissue of deciduous teeth. The aim of the present study was to investigate the effect of PBM delivered by red LED (630 nm, 75 mW, 37 mW/cm2) with different radiant exposures on the cell cycle, mitochondrial membrane potential, and senescence of stem cells from human exfoliated deciduous teeth (SHED). MATERIALS AND METHODS: Cultures were irradiated with LED (2, 4, 8, 16, and 32 J/cm2). After 24 h, the cell cycle and mitochondrial membrane potential of the cultures were evaluated using flow cytometry. Nonirradiated cultures served as control. RESULTS: Cultures irradiated with 16 J/cm2 had higher percentages of cells in the synthesis phase than control cultures (p < 0.05), and no significant differences were found regarding the percentage of cells with viable mitochondria between irradiated and control cultures. No significant difference in cell senescence was found between control cultures and cultures irradiated with 2 or 16 J/cm2. CONCLUSIONS: LED irradiation at 630 nm (37 mW/cm2, 75 mW) with radiant exposure of 16 J/cm2 was capable of inducing a proliferative response in stem cells from the pulp tissue of deciduous teeth without affecting mitochondrial function or inducing senescence.

Transdentinal photobiostimulation of stem cells from human exfoliated primary teeth.

AIM: To evaluate the effects of infrared light-emitting diode (LED) irradiation on stem cells from human exfoliated deciduous teeth (SHEDs). METHODOLOGY: Exfoliated primary teeth were obtained (n = 3), and SHEDs obtained from the teeth were seeded on the pulpal surface of 0.2-mm-thick dentine discs produced from permanent molars. The cells were incubated for 24 h by placing the discs in plain Dulbecco's modified Eagle's medium (DMEM). The DMEM was then replaced with new culture medium formulated for odontoblast differentiation. After 12 h in the second medium, SHEDs were irradiated through the dentine discs using an infrared LED (850 nm) with a power density of 80 mW cm-2 . Energy doses (EDs) delivered to the occlusal surface of the dentine discs were 0 (control), 2 and 4 J cm-2 (n = 6). Subsequent tests were performed 72 h after irradiation. These tests included cell viability (MTT), alkaline phosphatase activity (ALP), total protein production (TP), scanning electron microscopy (SEM), as well as gene expression for ALP, Col I, DSPP and DMP-1. Data were analysed using Kruskal-Wallis and Mann-Whitney t-tests (α = 0.05). RESULTS: Both EDs (2 and 4 J cm-2 ) significantly increased cell viability and ALP activity. For TP, ALP and Col I gene expression, only the 4 J cm-2 group had significantly higher values compared to the control group. Cell morphology was not affected by irradiation. CONCLUSION: Infrared LED irradiation was capable of biostimulating SHEDs through a 0.2 mm thickness of dentine, especially at the 4 J cm-2 level.

Effects of low-level laser therapy on stem cells from human exfoliated deciduous teeth.

OBJECTIVE: This study aimed to evaluate the influence of different laser therapy energy densities on SHED viability and proliferation. MATERIAL AND METHODS: SHED were irradiated according to the groups: I (1.2 J/cm2 - 0.5 mW - 10 s), II (2.5 J/cm2 - 10 mW - 10 s), III (3.7 J/cm2 - 15 mW - 10 s), IV (5.0 J/cm2 - 20 mW - 10 s), V (6.2 J/cm2 - 25 mW - 10 s), and VI (not irradiated - control group). Cell viability was assessed 6 and 24 h after irradiation measuring the mitochondrial activity and using the Crystal Violet assay. Cell proliferation was assessed after 24, 48, and 72 h of irradiation by SRB assay. RESULTS: MTT assay demonstrated differences from 6 to 24 hours after irradiation. After 24 h, groups I and IV showed higher absorbance values than those of control group. Crystal Violet assay showed statistically differences in the absorbance rate from 6 to 24 h after irradiation for groups III and VI. At 24 h after irradiation, Group III absorbance rate was greater than that of groups I, II, and IV. Group VI absorbance rate was greater than that of groups I and IV. SRB assay showed that the group I had higher rates than those of groups II, III, V, and VI, at 24 h after irradiation. After 48 h, group I exhibited the greatest cell proliferation rate followed by groups III, V, and VI. After 72 h, group III exhibited the lowest cell proliferation rate than those of groups II, IV, and V. CONCLUSIONS: The Low-Level Laser Therapy energy densities used in this study did not cause loss of cell viability and stimulated SHED proliferation within the parameters described in this study.

Effects of low-level laser therapy on stem cells from human exfoliated deciduous teeth

ABSTRACT Low-Level Laser Therapy stimulates the proliferation of a variety of types of cells. However, very little is known about its effect on stem cells from human exfoliated deciduous teeth (SHED). Objective This study aimed to evaluate the influence of different laser therapy energy densities on SHED viability and proliferation. Material and Methods SHED were irradiated according to the groups: I (1.2 J/cm2 - 0.5 mW – 10 s), II (2.5 J/cm2 – 10 mW – 10 s), III (3.7 J/cm2 – 15 mW – 10 s), IV (5.0 J/cm2 – 20 mW – 10 s), V (6.2 J/cm2 – 25 mW – 10 s), and VI (not irradiated – control group). Cell viability was assessed 6 and 24 h after irradiation measuring the mitochondrial activity and using the Crystal Violet assay. Cell proliferation was assessed after 24, 48, and 72 h of irradiation by SRB assay. Results MTT assay demonstrated differences from 6 to 24 hours after irradiation. After 24 h, groups I and IV showed higher absorbance values than those of control group. Crystal Violet assay showed statistically differences in the absorbance rate from 6 to 24 h after irradiation for groups III and VI. At 24 h after irradiation, Group III absorbance rate was greater than that of groups I, II, and IV. Group VI absorbance rate was greater than that of groups I and IV. SRB assay showed that the group I had higher rates than those of groups II, III, V, and VI, at 24 h after irradiation. After 48 h, group I exhibited the greatest cell proliferation rate followed by groups III, V, and VI. After 72 h, group III exhibited the lowest cell proliferation rate than those of groups II, IV, and V. Conclusions The Low-Level Laser Therapy energy densities used in this study did not cause loss of cell viability and stimulated SHED proliferation within the parameters described in this study.

Low-intensity laser phototherapy enhances the proliferation of dental pulp stem cells under nutritional deficiency.

Dental trauma in immature permanent teeth can damage pulp vascularization, which leads to necrosis and cessation of apexogenesis. Studies on tissue engineering using stem cells from human exfoliated deciduous teeth (SHEDs) have yielded promising results. Laser phototherapy (LPT) is able to influence the proliferation and differentiation of these cells, which could improve tissue engineering. SHEDs (eighth passage) were seeded into 96-well culture plates (103 cells/well) and were grown in culture medium supplemented with 15% defined fetal bovine serum (FBS) for 12 h. After determining the appropriate nutrition deficiency status (5% FBS), the cells were assigned into four groups: 1) G1 - 15% FBS (positive control); 2) G2 - 5% FBS (negative control); 3) G3 - 5% FBS+LPT 3 J/cm2; and 4) G4 - 5% FBS+LPT 5 J/cm2. For the LPT groups, two laser irradiations at 6 h intervals were performed using a continuous wave InGaAlP diode laser (660 nm, with a spot size of 0.028 cm2, 10 mW) in punctual and contact mode. Cell viability was assessed via an MTT reduction assay immediately after the second laser irradiation (0 h) and 24, 48, and 72 h later. We found that G3 and G4 presented a significantly higher cell growth rate when compared with G2 (p < 0.01). Moreover, G4 exhibited a similar cell growth rate as G1 throughout the entire experiment (p > 0.05). These findings indicate that LPT with 5 J/cm2 can enhance the growth of SHEDs during situations of nutritional deficiency. Therefore, LPT could be a valuable adjunct treatment in tissue engineering when using stem cells derived from the dental pulp of primary teeth.

Impact of CO2 laser and stannous fluoride on primary tooth erosion.

This study evaluated in vitro the effect of input power of CO2 laser, either associated or not to stannous fluoride (SnF2) gel, for the control of intrinsic erosion in primary teeth. One hundred four enamel slabs (3 × 3 × 2 mm) from human primary molars were flattened and polished. Adhesive tapes were placed on their surface leaving a window of 3 × 1 mm. Slabs were then cycled four times in 0.01 M hydrochloric acid (pH 2, 2 min) and in artificial saliva (2 h) for creation of erosive lesions. Specimens were randomly assigned into eight groups (n = 13) according to fluoride application [absent (control) or 0.4% stannous fluoride gel (SnF2)] and input power of CO2 laser [unlased (control), 0.5, 1.0 or 1.5 W]. The CO2 laser irradiation was performed in an ultra-pulse mode (100 µs of pulse duration), 4-mm working distance, for 10 s. Specimens were then submitted to further erosive episodes for 5 days and evaluated for enamel relative permeability. Fluoride did not show any protective effect for any of the laser-treated groups or control (p = 0.185). However, a significant effect was detected for input power of CO2 laser (p = 0.037). Tukey's test showed that there was a significant statistically difference between specimens irradiated with 0.5 and 1.5 W (p = 0.028). The input power of 0.5 W showed lower permeability. Variation of input power CO2 laser can influence enamel permeability, at the power of 1.5 W which promoted greater permeability.

Shear Bond Strength of Intraoral Laser Welding and its Effect on Intrapulpal Temperature Rise in Primary Teeth: An in Vitro Study.

OBJECTIVE: This study compared the shear bond strength (SBS) of conventional welding (CW) and intraoral laser welding (LW) on fixed space maintainers (SMs), and investigated the intrapulpal temperature change (ITC) during LW. BACKGROUND DATA: Lasers have been used for intraoral welding. MATERIALS AND METHODS: The SBS test used 26 molar bands divided into two groups, CW and LW. Stainless steel wires were welded to the middle of the buccal and lingual aspects of all the bands, using an Nd:YAG laser for the LW group and silver solder and flux soldering media for the CW group. The samples, fixed to acrylic resin blocks, were subjected to shear testing. In the ITC test, 25 exfoliated primary second molar teeth were used to adapt molar bands. J-type thermocouple wire was positioned in the pulp chamber. ITCs were determined during Nd:YAG laser welding of stainless steel wires to the bands. Mann-Whitney U test was used to determine differences in SBS between the groups. ITCs were analyzed by paired t test. RESULTS: The SBS between groups showed significant differences (LW: 489.47 ± 135.70; CW: 49.71 ± 17.76; p < 0.001). The mean ITC during LW was 3.64 ± 0.79 (min: 2.4; max: 5.10). None of the samples' ITCs exceeded the critical threshold value (5.5 °C). CONCLUSIONS: LW obtained a higher-strength joint than CW. ITCs during LW do not present a thermal risk to primary teeth. The intraoral use of LW for SMs in primary teeth is recommended in terms of strength and ITCs.

Effect of laser preparation on adhesion of a self-adhesive flowable composite resin to primary teeth.

The aim of the study was to evaluate the adhesion of a self-adhering flowable composite resin to primary tooth enamel and dentin after silicon carbide paper (SiC) and laser pretreatment. Adhesive properties were evaluated as shear bond strength (SBS) and scanning electron microscopic (SEM) characteristics. A total 120 primary canine teeth were randomly divided into two groups to study enamel and dentin. Each group was divided into 6 subgroups (n = 10) according to type of surface preparation (SiC or Er:YAG laser) of enamel or dentin. Three methods were used to build cylinders of restoration on tooth surface: OptiBond All-In-One + Premise Flowable composite, OptiBond All-In-One + Vertise Flow and Vertise flow. After restoration, samples were tested for SBS and failure mode. Twenty eight samples were examined by SEM. The results of the study showed SBS of Vertise Flow was lower than others in enamel and dentin samples pretreated with SiC and in dentin samples pretreated with laser (P < 0.001). Compared to SiC pretreatment, laser pretreatment led to a significantly higher SBS with Vertise Flow on enamel (P < 0.001). Vertise Flow associated with the adhesive led to a higher SBS in enamel and dentin compared to Vertise Flow alone. Adhesive and mixed failure modes were observed more frequently in Vertise Flow groups. SEM images showed that Vertise Flow led to more irregularities on enamel and more open dentinal tubules after laser ablation compared SiC pretreatment.

Low-intensity laser phototherapy enhances the proliferation of dental pulp stem cells under nutritional deficiency

Abstract Dental trauma in immature permanent teeth can damage pulp vascularization, which leads to necrosis and cessation of apexogenesis. Studies on tissue engineering using stem cells from human exfoliated deciduous teeth (SHEDs) have yielded promising results. Laser phototherapy (LPT) is able to influence the proliferation and differentiation of these cells, which could improve tissue engineering. SHEDs (eighth passage) were seeded into 96-well culture plates (103 cells/well) and were grown in culture medium supplemented with 15% defined fetal bovine serum (FBS) for 12 h. After determining the appropriate nutrition deficiency status (5% FBS), the cells were assigned into four groups: 1) G1 - 15% FBS (positive control); 2) G2 - 5% FBS (negative control); 3) G3 - 5% FBS+LPT 3 J/cm2; and 4) G4 - 5% FBS+LPT 5 J/cm2. For the LPT groups, two laser irradiations at 6 h intervals were performed using a continuous wave InGaAlP diode laser (660 nm, with a spot size of 0.028 cm2, 10 mW) in punctual and contact mode. Cell viability was assessed via an MTT reduction assay immediately after the second laser irradiation (0 h) and 24, 48, and 72 h later. We found that G3 and G4 presented a significantly higher cell growth rate when compared with G2 (p < 0.01). Moreover, G4 exhibited a similar cell growth rate as G1 throughout the entire experiment (p > 0.05). These findings indicate that LPT with 5 J/cm2 can enhance the growth of SHEDs during situations of nutritional deficiency. Therefore, LPT could be a valuable adjunct treatment in tissue engineering when using stem cells derived from the dental pulp of primary teeth.

Laser-induced breakdown spectroscopy analysis of human deciduous teeth samples.

Laser-induced breakdown spectroscopy (LIBS) analysis of human deciduous teeth has been performed by employing Nd:YAG laser (1064 nm, 10 ns) for the evaluation of plasma parameters as well as elemental analysis. The plasma parameters, i.e., electron temperature and electron number density of laser-induced teeth plasma at various fluencies, have been evaluated. Both parameters show an increasing trend up to a certain value of laser fluence, i.e., 2.6 J/cm(2). With further increase in laser fluence up to a value of 3.9 J/cm(2), a decreasing trend is observed which is due to shielding effect. With further increase in laser fluence up to a maximum value of 10.5 J/cm(2), the insignificant changes in plasma parameters are observed which are attributed to saturation phenomenon governed by self-regulating regime. Emission spectroscopy results exhibit that laser fluence is the controlling factor for both plasma parameters. The elemental analysis was also performed at constant laser fluence of 2.6 J/cm(2) by evaluating the variation in detected elemental concentration of Ca, Fe, Sr, Zn, and Pb in three different parts of human teeth, i.e., enamel, dentine, and cementum. The lower concentration of Ca as compared to the standard values of CaCO3 (self-fabricated pellet) reveals that enamel is the most deciduous part of the human teeth. However, at the same time, it is also observed that the highest concentration of micro minerals is also found in enamel, then in dentine, and lowest in cementum. Carious or unhealthy tooth is identified by enhanced concentration of micro minerals (Pb, Sr, Zn, and Fe). The highest concentration of micro minerals as compared to other parts of teeth (dentine and root cementum) and lower concentration of Ca as compared to standard CaCO3 pellet in enamel confirm that enamel is the most deciduous part of the teeth.