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

Surface and Mineral Changes of Primary Enamel after Laser Diode Irradiation and Application of Remineralization Agents: A Comparative In Vitro Study

OBJECTIVES

The purpose of this study is to evaluate the remineralization potential of primary teeth enamel after being exposed to different laser diode therapies.

METHODS

Ninety-six vestibular primary teeth enamel samples were divided into eight groups (n = 12) with varying treatments: control (G1), CPP-ACP-fluoride varnish (G2), diode lasers at 980 nm (G3), 808 nm (G4), 450 nm (G5), 980 nm + CPP-ACP-fluoride varnish (G6), 808 nm + CPP-ACP-fluoride varnish (G7), and 450 nm + CPP-ACP-fluoride varnish (G8). Each sample was assessed using a DIAGNOdent® (KaVo Dental, Biberach, Germany), at baseline, post-treatment, and post-pH cycle remineralization. SEM imaging was performed before and after treatment and following the pH cycle.

RESULTS

The results indicated that the 980 nm and 808 nm diode lasers, both alone and in combination with CPP-ACP-fluoride varnish, either maintained or increased the calcium (Ca) weight percentage (Wt%) in the enamel. The 980 nm diode laser combined with CPP-ACP-fluoride varnish (G6) showed a significant increase in Ca Wt%, suggesting a strong remineralization effect. Similarly, the 808 nm diode laser alone (G4) also promoted a substantial increase in Ca Wt%. In contrast, the 450 nm diode laser, whether applied alone or in combination with CPP-ACP-fluoride varnish, resulted in a lower Ca Wt% and an increase in phosphorus (P) Wt%. Most groups, except for the CPP-ACP-fluoride varnish alone (G2), demonstrated an increase in P Wt%, indicating a complex interaction between laser therapy and enamel remineralization.

CONCLUSIONS

The combined use of laser therapy with CPP-ACP-fluoride varnish significantly enhanced the remineralization of temporary teeth enamel. The 980 nm diode laser + CPP-ACP-fluoride varnish showed the most pronounced improvement in remineralization, while the 808 nm diode laser alone also effectively increased calcium solubility. These findings suggest that higher-wavelength diode lasers, particularly when combined with remineralizing agents, can effectively enhance the mineral content of primary teeth and promote enamel remineralization.

Effect of Er:YAG Laser Irradiation on Preventing Enamel Caries: A Systematic Review and Meta-Analysis

Caries is a global health problem, and its prevention has become a main goal of modern dentistry. Laser irradiation is believed to have potential in preventing dental caries. The purpose of this systematic review and meta-analysis was to evaluate whether Er:YAG laser irradiation has the potential to prevent enamel caries. Based on inclusion and exclusion criteria, PubMed, Web of Science, and EMBASE databases were searched; 2 reviewers independently used these search strategies to review titles and abstracts, with no language or date restrictions, up to June 2023. For the quantitative analysis, continuous variables were analysed by standard mean difference (SMD) with a 95% confidence interval (CI). The statistical analyses were conducted using Review Manager and Cochrane Collaboration (2020). A total of 51 potentially eligible studies were identified, of which 16 in vitro studies were eventually included in the quantitative meta-analysis. Three studies showed a low risk of bias, and 13 studies a medium risk of bias. In general, there was no significant difference between the calcium ions released under acidic conditions after laser irradiation. The final results indicated that after Er:YAG laser irradiation, enamel could maintain higher surface microhardness in acidic environments, as well as smaller lesion depth and less mineral loss, revealing its potential in preventing enamel caries. However, the effect of laser irradiation on the release of calcium ions in acidic solutions and the surface microhardness of demineralised enamel was not significant. Therefore, more in vitro and clinical trials are needed in to evaluate whether Er:YAG laser irradiation can effectively prevent enamel caries in clinical settings.

Synthesis and characterization of hydroxyapatite nanoparticles and their effects on remineralization of demineralized enamel in the presence of Er,Cr: YSGG laser irradiation

BACKGROUND

This study aims to synthesize and characterize hydroxyapatite nanoparticles (nano-HA) and evaluate their effects on the remineralization of demineralized enamel in the presence to Er,CR: YSGG laser irradiation.

MATERIALS AND METHODS

Enamel specimens from 44 human molars were divided into four groups: control, demineralized enamel, demineralized enamel treated with nano-HA, and demineralized enamel treated with nano-HA followed by Er,Cr:YSGG laser irradiation (0.5, 20 Hz, 60 µs, 20 s). Vickers microhardness test was used to evaluate the enamel surface hardness. The morphology and chemistry of enamel surfaces were assessed using scanning electron microscopy (SEM) and Raman spectroscopy, respectively.

RESULT

The result of this study showed that the application of Er,CR: YSGG laser irradiation to demineralized enamel treated with nano-HA had the highest impact on its microhardness.

CONCLUSION

ER,CR: YSGG laser irradiation promotes enamel remineralization after treatment with nano HA.

Effect of Er,Cr:YSGG Laser on the Prevention of Primary and Permanent Teeth Enamel Demineralization: SEM and EDS Evaluation

Objective: To evaluate in vitro the effect of the erbium, chromium:yttrium-scandium-gallium-garnet (Er,Cr:YSGG) laser on resistance of primary and permanent human enamel to demineralization using water cooling and fluoride coapplication as variable parameters. Methods: Enamel specimens were prepared from extracted primary and permanent teeth (n = 225 each). The specimens were separated into 15 subgroups (n = 15/group) based on laser application at three different power settings (0.25, 0.50, and 0.75 W), laser application with and without water cooling, and application of acidulated phosphate fluoride (APF) gel before laser treatment. Morphological changes were assessed with scanning electron microscopy (SEM), and the specimens' chemical contents were determined with energy-dispersive X-ray spectroscopy. Results: In both the primary and permanent teeth, the highest Ca and P content was observed in the noncooled 0.75 W laser group (p < 0.05), irrespective of APF pretreatment (p > 0.05). The Ca and P content for the noncooled APF +0.75 W laser group was lower than that for the APF group and the noncooled 0.75 W laser group. For both dentitions, the F mass content for the APF+laser groups was significantly higher than laser-only groups (p < 0.05). Under SEM, both the primary and permanent enamel exhibited cracks, craters, and surface roughness without water cooling, consistent with increased power output. Conclusions: Er,Cr:YSGG laser application at 0.75 W without water cooling increased enamel resistance to demineralization. Compared with topical APF application, Er,Cr:YSGG laser application barely improved enamel resistance against demineralization, and coapplication did not result in a synergistic effect.

Influence of Er,Cr:YSGG laser on root dentin submitted to erosive and/or abrasive challenges

This study evaluated how Er,Cr:YSGG laser, associated or not with 5% fluoride varnish, influences the surface roughness and volume loss of bovine root dentin submitted to erosive and/or abrasive wear. One hundred and twenty dentin specimens were divided into the groups: without preventive treatment (WPT), 5% fluoride varnish (FV); Er,Cr:YSGG laser irradiation (L), and varnish combined with laser (FV + L). The specimens (n = 10) were subdivided into: 1 = erosion (E); 2 = abrasion (A); and 3 = erosion followed by abrasion (E + A). The erosive solution used was a soft-drink (pH = 2.42 at 4ºC) applied in 5-min cycles twice a day for 10d. Abrasive wear involved brushing for 60s with an electric brush (1,600-oscillations/s) at a load of 2.0N. Surface roughness and volume loss were evaluated using a laser scanning confocal microscope. Roughness data were submitted to one-way ANOVA and Tukey post-hoc test. For volume loss, the Kruskal-Wallis and Dunn's post-hoc tests were used (α = 5%). The lowest values of roughness were found in the control areas of all subgroups (p > 0.05). In the experimental area, the [(WPT) + (E+A)] subgroup had a significantly higher roughness (5.712 ± 0.163 μm 2 ) than the other subgroups (p < 0.05). The L and (FV + L) groups had statistically similar roughness, regardless of the type of wear. The (FV + L) group had the lowest volume loss, regardless of the type of wear performed: [(FV + L) + (E)] = 7.5%, [(FV + L) + (A) = 7.3%, and [(FV + L) + (E + A)] = 8.1%. The subgroup [(WPT) + (E + A)] had the highest volume loss (52.3%). The proposed treatments were effective in controlling dentin roughness. Laser irradiation can be an effective method to increase root dentin resistance after challenges and limit problems related to non-carious lesions.

[Comparison of the effect and safety of Er:YAG laser combined with fluoride and methylene blue-photodynamic therapy on caries prevention]

OBJECTIVE

To compare the anti-caries effect and safety of Er:YAG laser combined with fluoride and methylene blue-photodynamic therapy (MB-PDT).

METHODS

A total of 28 rat dental caries models were established and randomly divided into seven groups: photodynamic therapy (PDT) group, laser combined with fluoride group, laser group, sodium fluoride group, and 0.9% saline control group. Spectrophotometric optical density was used to reflect the growth of Streptococcus mutans. Laser-induced fluorescence diagnostic (LF) instrument was utilized to detect the demineralization degree of dental caries. Histopathological sections were employed to observe the damage of dental pulp and buccal mucosa.

RESULTS

The optical density (OD) value of the PDT and combination groups was significantly lower than that of other treatment groups (P<0.05). An increase in LF value and demineralization occurred in varying degrees with different treatment methods. Histopathological observation showed that pulp and buccal mucosa injury was more obvious in the combination group of 70 mw·cm⁻² and Er:YAG laser group compared with other groups.

CONCLUSIONS

Under the same parameters, the combined group and PDT have good germicidal efficacy, but PDT has fewer adverse reactions and less damage. It is an effective and safe method for caries prevention.

Thermal, morphological, and spectral changes after Er, Cr:YSGG laser irradiation at low fluences on primary teeth for caries prevention

The aim of this study was to determine the temperature increase in the pulp chamber and possible thermal effects on molecular structure of primary teeth during the irradiation with Er,Cr:YSGG laser. Primary central incisors were divided into three groups (n = 20). Labial surfaces in each group were irradiated by Er,Cr:YSGG laser within different power and frequencies as following groups: I: 0.25 W, 20 Hz, II: 0.50 W, 20 Hz, III: 0.75 W, 20 Hz. A thermocouple was placed inside the pulp chamber so that the temperature increments were recorded during the enamel irradiation. Morphological changes of enamel surfaces were experimentally evaluated by SEM. Fourier-transform infrared spectroscopy and RAMAN analyses were carried out to determine the differentiations in the molecular structure. The experimental results obtained were analyzed statistically by means of one-way analysis of variance. Statistically significant differences were detected between groups (p < .05). Group III exhibited the highest values for the temperature parameters. Besides, the conical craters, cracks, and formation of ablation areas were observed for all the groups. Also, it was obtained that the hydroxyapatite lost the hydroxyl ions due to the thermal effect of the laser. Temperature rise throughout the Er,Cr:YSGG laser irradiation for prevention of primary enamel demineralization presented a positive correlation with the laser output power level. The formations of adverse morphological and spectral changes were detected on the surface of teeth after the laser application. On this basis, the Er,Cr:YSGG laser applications should be treated with much more caution considering enamel surface and pulpal tissues in primary teeth.

Combined effect of Er,Cr:YSGG laser and casein phosphopeptide amorphous calcium phosphate on the prevention of enamel demineralization

OBJECTIVES

To compare the effect of use of laser, casein phosphopeptide-amorphous calcium phosphate (CPP-ACP), and their combination on prevention of enamel demineralization using polarized light microscopy to assess lesion depth.

MATERIALS AND METHODS

Eighty premolars were randomly allocated to four equal groups (n = 20): Group I: Control group, no preventive measures. Group II: CPP-ACP. Group III: Er,Cr:YSGG laser. Group IV: Er,Cr:YSGG laser followed by CPP-ACP. Specimens were subjected to thermocycling and brushing protocols equivalent to 1 year intraorally. Then, all teeth were subjected to acid challenge. Teeth were then sectioned longitudinally and examined under a polarized light microscope and lesion depth was measured.

RESULTS

Group IV resulted in the least lesion depth with a significant difference between it and all other groups. CPP-ACP alone and laser alone also showed a significant difference in white spot lesion (WSL) depth compared to the control group; however, no significant difference was found between them.

CONCLUSIONS

The combined use of laser and CPP-ACP showed the best prevention against WSL development. The use of CPP-ACP or laser alone also resulted in a significant reduction in lesion depth but was significantly less than their combined use, with no significant difference between them.

Influence of Er, Cr: YSGG (2780 nm) and Nanosecond Nd: YAG Laser (1064 nm) Irradiation on Enamel Acid Resistance: Morphological and Elemental Analysis

BACKGROUND

Enamel demineralisation is an initial step of the serious dental problem including dental caries, white spot lesions and dental erosion.

AIM

Compare the effect of Er, Cr: YSGG (λ = 2780 nm) and nanosecond Nd: YAG (λ = 1064 nm) laser on enamel acid resistance.

MATERIAL AND METHODS

Thirty non-carious human premolars, extracted for orthodontic reasons, were used. The experimental groups (n = 10 each group) were: Group I, untreated (control); Group II, Er, Cr: YSGG laser irradiation (0.75 W, 20 Hz, 140 μs, 10 s); Group III, nanosecond pulsed Nd: YAG laser irradiation (0.8 W, 10 Hz, 7 ns, 10 s). Scanning electron microscope and Energy Dispersive X-ray Spectroscopy (EDX) were used to assess acquired enamel resistance to PH cycling.

RESULTS

After subjecting the three experimental groups to PH cycling, scanning electron microscopic examination revealed irregular porous dissoluted enamel surface in group I. However, groups II and III demonstrated partially dissoluted enamel surface. EDX analysis demonstrated the lowest mean percentage decrease in calcium and phosphorus content in group II followed by group III, then the highest mean percentage decrease was observed in untreated group I. One-way ANOVA revealed significant differences (p < 0.0001) between the tested groups.

CONCLUSIONS

Both Er, Cr: YSSG and nanosecond Nd: YAG laser irradiation were able to improve the acid resistance of enamel. However, enamel surface treated with Er, Cr: YSSG laser showed the lowest mean percentage decrease of calcium and phosphorus (highest acid resistance).

Influence of Er,Cr:YSGG laser, associated or not to desensitizing agents, in the prevention of acid erosion in bovine root dentin

This in vitro study evaluated the influence of the Er,Cr:YSGG laser, associated or not to desensitizing agents, in the prevention of acid erosion in bovine root dentin. Eighty dentin specimens were selected and divided into eight groups (n = 10): G1: negative control; G2: positive control (5% fluoride varnish-FV); G3: Er,Cr:YSGG laser; G4: FV + laser; G5: 3% potassium oxalate; G6: 3% potassium oxalate + laser; G7: biphasic calcium silicate/phosphate gel (gel); G8: gel + laser. Laser parameters: 0.5 W, 6.25 J/cm² at 1-mm distance. The erosive drink used was a cola soft-drink (pH = 2.42 at 4 °C), lasting 5 min, twice a day, with 6-h intervals between the challenges, during 14 days. Kolmogorov-Smirnov and Levene's tests were satisfied. The surface roughness data were submitted to ANOVA and Tukey post hoc tests. For the wear profile, Kruskal-Wallis and Dunn post hoc tests were used. Afterwards, the Spearman correlation test was performed. All statistical tests assumed a significance level of 5% (α = 0.05). G1 presented the highest surface roughness value after the erosive challenge (3.586 μm² ± 0.205 μm²) and the G7 presented the lowest surface roughness value after the erosive challenge (1.071 μm² ± 0.180 μm²). For the lost volume, G4 presented the lowest percentage (9.7% ± 0.9%), while G1 had the highest percentage (41.8% ± 2.5%), both with p < 0.05. There was a weak correlation between the response variables (ρ = 0.33). All groups presented lower values of surface roughness and loss of volume when compared to the negative control group. For the surface roughness, the biphasic calcium silicate/phosphate gel presented the best result. For volume loss, the 5% fluoride varnish + Er,Cr:YSGG laser showed the best results compared to the other groups.

In Vitro Comparison Of Fluoride Gel Alone and in Combination With Er,Cr:YSGG Laser on Reducing White Spot Lesions in Primary Teeth

Introduction: Laser therapy has been suggested as a method for caries-prevention, and ErCr:YSGG laser is increasingly used in dentistry. This study aimed to compare the efficacy of fluoride gel alone and in conjunction with Er,Cr:YSGG laser for remineralization of white spot lesions (WSLs) in primary teeth. Methods: This study was conducted on 20 primary teeth with WSLs extracted for orthodontic reasons. Three sections were made of each tooth at the site of WSLs. The surface area of WSLs was measured under a stereomicroscope at ×25 magnification. Samples were assigned to 3 groups of control (group 1), exposure to 1.23% APF gel for 4 minutes (group 2) and Er,Cr:YSGG laser (0.5 W power, 20 Hz frequency, 60% water, 40% air, pulse duration of 5±1 seconds) plus fluoride (group 3). All samples were stored in artificial saliva for 10 days and then the surface area of the WSLs was measured again under a stereomicroscope. Data were analyzed using the Kruskal-Wallis, MannWhitney and Wilcoxon signed rank tests. Results: The reduction in surface area of the WSLs was significantly different between the control and fluoride (P<0.001) and also the control and laser plus fluoride groups (P<0.001); the difference between fluoride and laser plus fluoride groups was not significant (P=0.265). Comparison of the surface area of WSLs before and after the intervention showed no significant difference in group one (P=0.737) while this difference in groups 2 (P<0.001) and 3 (P<0.001) was statistically significant. Conclusion: The results showed that Er,Cr:YSGG laser irradiation plus 1.23% APF gel was not significantly different from the application of fluoride gel alone in enhancing the remineralization of WSLs.

SEM Evaluation of Enamel Surface Changes and Enamel Microhardness around Orthodontic Brackets after Application of CO2 Laser, Er,Cr:YSGG Laser and Fluoride Varnish: An In vivo Study

Introduction

One of the most undesirable consequences of orthodontic treatment is occurrence of enamel demineralization around orthodontic brackets. Numerous in vitro studies have reported the prevention of enamel demineralization by surface treatment with lasers and fluoride varnish.

Aim

To evaluate the changes on the enamel surface and microhardness around orthodontic brackets after surface treatment by CO₂ laser, Er, Cr:YSGG laser and fluoride varnish in vivo.

Materials and Methods

A double blind interventional study was carried out on 100 premolars which were equally divided into five groups, out of which one was the control group (Group 0). The intervention groups (Group I to IV) comprised of patients requiring fixed orthodontic treatment with all 4 first premolars extraction. Brackets were bonded on all 80 premolars which were to be extracted. Enamel surface treatment of Groups I, II and III was done by CO₂ laser, Er, Cr:YSGG laser and 5% sodium fluoride varnish respectively and Group IV did not receive any surface treatment. A modified T-loop was ligated to the bracket and after two months, the premolars were extracted. Surface changes were evaluated by Scanning Electron Microscopic (SEM) and microhardness testing. Comparison of mean microhardness between all the groups was assessed using post-hoc test with Bonferroni correction.

Results

Group I showed a melted enamel appearance with fine cracks and fissures while Group II showed a glossy, homogenous enamel surface with well coalesced enamel rods. Group III showed slight areas of erosions and Group IV presented areas of stripped enamel. Significant difference was observed between the mean microhardness (VHN) of Group I, Group II, Group III, Group IV and Group 0 with p<0.001. A significant difference of p<0.001 was observed while comparing Group I vs II,III,IV,0 and Group II vs III,IV,0. However, difference while comparing Group III vs IV was p=0.005 and difference between the mean microhardness of Group 0 vs Group III was non significant.

Conclusion

Surface treatment with Er,Cr:YSGG laser causes a positive alteration of the enamel surface increasing its ability to resist demineralization with optimum microhardness as compared to CO₂ laser and sodium fluoride varnish.

Effects of Root Debridement With Hand Curettes and Er:YAG Laser on Chemical Properties and Ultrastructure of Periodontally-Diseased Root Surfaces Using Spectroscopy and Scanning Electron Microscopy

Introduction: The efficacy of erbium-doped yttrium aluminum garnet (Er:YAG) laser for root debridement in comparison with curettes has been the subject of many recent investigations. Considering the possibility of chemical and ultra-structural changes in root surfaces following laser irradiation, this study sought to assess the effects of scaling and root planing (SRP) with curettes and Er:YAG laser on chemical properties and ultrastructure of root surfaces using spectroscopy and scanning electron microscopy (SEM). Methods: In this in vitro experimental study, extracted sound human single-rooted teeth (n = 50) were randomly scaled using manual curettes alone or in conjunction with Er:YAG laser at 100 and 150 mJ/pulse output energies. The weight percentages of carbon, oxygen, phosphorous and calcium remaining on the root surfaces were calculated using spectroscopy and the surface morphology of specimens was assessed under SEM. Data were analyzed using one-way analysis of variance (ANOVA). Results: No significant differences (P > 0.05) were noted in the mean carbon, oxygen, phosphorous and calcium weight percentages on root surfaces following SRP using manual curettes with and without laser irradiation at both output energies. Laser irradiation after SRP with curettes yielded rougher surfaces compared to the use of curettes alone. Conclusion: Although laser irradiation yielded rougher surfaces, root surfaces were not significantly different in terms of chemical composition following SRP using manual curettes with and without Er:YAG laser irradiation. Er:YAG laser can be safely used as an adjunct to curettes for SRP.

Optimal power settings of aluminum gallium arsenide lasers in caries inhibition - An in vitro study

Context:

Incipient carious lesions are characterized by subsurface dissolution due to more fluoride ions in the 50-100 microns of the tooth's outer surface.

Aims:

To determine an optimal power setting for 810 nm aluminum gallium arsenide laser for caries inhibition.

Materials and Methods:

Fifty-four caries-free extracted teeth were sectioned mesiodistally. The samples were divided into 18 groups for each power setting being evaluated. Each group had six samples. The laser used is 810 nm aluminum gallium arsenide laser with power setting from 0.1 watts to 5 watts. Laser fluorescence based device was used to evaluate the effect of irradiation.

Statistical Analysis Used:

Paired “t” test, one-way analysis of variance (ANOVA), Tukey's post hoc test, and the Pearson's correlation test.

Results:

The paired t-test showed that there is minimum divergence from the control for 3.5 watts. Tukey's post hoc test also showed statistically significantly results for 3.5 watts. The Pearson's correlation test showed that there was negative correlation between the watts and irradiation.

Conclusions:

The power setting that gave statistically significant results was 3.5 watts.

Caries inhibition with a CO2 9.3 μm laser: An in vitro study

BACKGROUND AND OBJECTIVES

The caries preventive effects of different laser wavelengths have been studied in the laboratory as well as in pilot clinical trials. The objective of this in vitro study was to evaluate whether irradiation with a new 9.3 μm microsecond short-pulsed CO2 -laser could enhance enamel caries resistance with and without additional fluoride applications.

STUDY DESIGN/MATERIALS AND METHODS

One hundred and one human tooth enamel samples were divided into seven groups. Each group was treated with different laser parameters (CO2 -laser, wavelength 9.3 μm, 43 Hz pulse-repetition rate, pulse duration between 3 µs at 1.5 mJ/pulse to 7 µs at 2.9 mJ/pulse). A laboratory pH-cycling model followed by cross-sectional microhardness testing determined the mean relative mineral loss delta Z (ΔZ) for each group to assess caries inhibition in tooth enamel by the CO2 9.3 µm short-pulsed laser irradiation. The pH-cycling was performed with or without additional fluoride.

RESULTS

The non-laser control groups with additional fluoride had a relative mineral loss (ΔZ, vol% × µm) that ranged between 646 ± 215 and 773 ± 223 (mean ± SD). The laser irradiated and fluoride treated samples had a mean ΔZ ranging between 209 ± 133 and 403 ± 245 for an average 55% ± 9% reduction in mineral loss (ANOVA test, P < 0.0001). Increased mean mineral loss (ΔZ between 1166 ± 571 and 1339 ± 347) was found for the non-laser treated controls without additional fluoride. In contrast, the laser treated groups without additional fluoride showed a ΔZ between 470 ± 240 and 669 ± 209 (ANOVA test, P < 0.0001) representing an average 53% ± 11% reduction in mineral loss. Scanning electron microscopical assessment revealed that 3 µs pulses did not markedly change the enamel surface, while 7 µs pulses caused some enamel ablation.

CONCLUSION

The CO2 9.3 µm short-pulsed laser energy renders enamel caries resistant with and without additional fluoride use. The observed enhanced acid resistance occurred with the laser irradiation parameters used without obvious melting of the enamel surface as well as after irradiation with energies causing cutting of the enamel. Lasers Surg. Med. 48:546-554, 2016. Published 2016. This article is a U.S. Government work and is in the public domain in the USA.

Comparative evaluation of surface topography of tooth prepared using erbium, chromium: Yttrium, scandium, gallium, garnet laser and bur and its clinical implications

Background:

Erbium, chromium: Yttrium, scandium, gallium, garnet (Er, Cr: YSGG) laser has been successfully used in the ablation of dental hard and soft tissues. It has been reported that this system is also useful for preparing tooth surfaces and etching, but no consensus exist in the literature regarding the advantage of lasers over conventional tooth preparation technique.

Materials and Methods:

Labial surfaces of 25 extracted human maxillary central incisors were divided into two halves. Right half was prepared with diamond bur and left half with Er, Cr; YSGG laser and a reduction of 0.3–0.5 mm was carried out. Topography of prepared surfaces of five teeth were examined under scanning electron microscope (SEM). The remaining samples were divided into 4 groups of 10 specimens each based on the surface treatment received: One group was acid etched and other was nonetched. Composite resin cylinders were bonded on prepared surfaces and shear bond strength was assessed using a universal testing machine.

Results:

The SEM observation revealed that the laser prepared surfaces were clean, highly irregular and devoid of a smear layer. Bur prepared surfaces were relatively smooth but covered with smear layer.

Highest bond strength was shown by laser prepared acid etched group, followed by bur prepared the acid etched group. The bur prepared nonacid etched group showed least bond strength.

Conclusions:

Er, Cr: YSGG laser can be used for preparing tooth and bond strength value achieved by laser preparation alone without surface treatment procedure lies in the range of clinical acceptability.

Inhibition of enamel demineralisation using "Nd-YAG and diode laser assisted fluoride therapy"

AIM

This in vitro study was to evaluate the irradiation efficacy of the Diode laser and the Nd-YAG laser either un-assisted or assisted by acidulated phosphate fluoride (APF) treatment on enamel's acid resistance.

METHODS

Seventy-two enamel samples, obtained from 12 extracted human molars, were randomly assigned to 6 groups as follows: (1) Control (C); (2) Exposed to APF gel (F); (3) Diode laser (DL); (4) Irradiated with Diode laser through APF gel (DL/F); (5) Nd-YAG laser (NL) and (6) Irradiated with Nd-YAG laser through APF gel (NL/F). The specimens were individually demineralised in an acidified hydroxyethylcellulose system, and the acid resistance was evaluated by determining the calcium ion dissolution using atomic absorption spectrometry.

RESULTS

The average concentration of the calcium ion determined in groups 1 to 6 was 901, 757, 736, 592, 497 and 416 parts per million micrograms/gram, respectively. The results showed that demineralisation in the NL/F group was significantly less than the other groups and the control group was significantly greater than the other groups (P < 0.001).

CONCLUSION

The effect of Nd-YAG laser irradiation, used alone or in combination with APF, in decreasing the enamel demineralisation was greater than all the other groups.

The combined use of Er,Cr:YSGG laser and fluoride to prevent root dentin demineralization

The use of erbium lasers to prevent caries in enamel has shown positive results. However, it is not known if Er,Cr:YSGG laser can also be used to increase acid resistance of root dentine, which is another dental tissue susceptible to the action of cariogenic bacteria.

OBJECTIVE

To analyze the effects of the Er,Cr:YSGG laser (λ=2.78 μm, 20 Hz) irradiation associated with 2% neutral sodium fluoride (NaF) to prevent root dentin demineralization.

MATERIAL AND METHODS

One hundred human root dentin samples were divided into 10 groups (G) and treated as follows: G1: no treatment; G2: NaF; G3: laser (4.64 J/cm2) with water cooling (WC=5.4 mL/min); G4: laser (4.64 J/cm2) without WC; G5: laser (8.92 J/cm2) with WC; G6: laser (8.92 J/cm2) without WC; G7: laser (4.64 J/cm2) with WC and NaF; G8: laser (4.64 J/cm2) without WC and NaF; G9: laser (8.92 J/cm2) with WC and NaF; G10: laser (8.92 J/cm2) without WC and NaF. The NaF gel was applied alone or after 4 min of irradiation. After 14 days of acid challenge, the samples were sectioned and the Knoop microhardness (KHN) test was done at different depths (30, 60, 90 and 120 μm) from the outer dentin surface. Data were analyzed by one-way ANOVA and Fisher's test (α=5%).

RESULTS

The results showed that G8 and G10 presented higher KHN than the G1 for the depths of 30 and 60 μm, indicating an increase of the acid resistance of the dentin in up to 35% (p<0.05).

CONCLUSIONS

The use of Er,Cr:YSGG laser irradiation at 4.64 J/ cm2 and 8.92 J/cm2 without water cooling and associated with 2% NaF can increase the acid resistance of human root dentin.

Use of new minimum intervention dentistry technologies in caries management

Preservation of natural tooth structure requires early detection of the carious lesion and is associated with comprehensive patient dental care. Processes aiming to detect carious lesions in the initial stage with optimum efficiency employ a variety of technologies such as magnifying loupes, transillumination, light and laser fluorescence (QLF® and DIAGNOdent® ) and autofluorescence (Soprolife® and VistaCam®), electric current/impedance (CarieScan(®) ), tomographic imaging and image processing. Most fluorescent caries detection tools can discriminate between healthy and carious dental tissue, demonstrating different levels of sensitivity and specificity. Based on the fluorescence principle, an LED camera (Soprolife® ) was developed (Sopro-Acteon, La Ciotat, France) which combined magnification, fluorescence, picture acquisition and an innovative therapeutic concept called light-induced fluorescence evaluator for diagnosis and treatment (LIFEDT). This article is rounded off by a Soprolife® illustration about minimally or even non-invasive dental techniques, distinguishing those that preserve or reinforce the enamel and enamel-dentine structures without any preparation (MIT1- minimally invasive therapy 1) from those that require minimum preparation of the dental tissues (MIT2 - minimally invasive therapy 2) using several clinical cases as examples. MIT1 encompasses all the dental techniques aimed at disinfection, remineralizing, reversing and sealing the caries process and MIT2 involves a series of specific tools, including microburs, air abrasion devices, sonic and ultrasonic inserts and photo-activated disinfection to achieve minimal preparation of the tooth. With respect to minimally invasive treatment and prevention, the use of lasers is discussed. Furthermore, while most practices operate under a surgical model, Caries Management by Risk Assessment (CaMBRA) encourages a medical model of disease prevention and management to control the manifestation of the disease, or keep the oral environment in a state of balance between pathological and preventive factors. Early detection and diagnosis and prediction of lesion activity are of great interest and may change traditional operative procedures substantially. Fluorescence tools with high levels of magnification and observational capacity should guide clinicians towards a more preventive and minimally invasive treatment strategy.

In-vivo occlusal caries prevention by pulsed CO2 -laser and fluoride varnish treatment--a clinical pilot study

BACKGROUND AND OBJECTIVES

High caries prevalence in occlusal pits and fissures warrants novel prevention methods. An 86% reduction in dental enamel smooth surface demineralization in-vivo following short-pulsed 9.6 µm-CO(2) -laser irradiation was recently reported. The objective of this study was to conduct a blinded 12-month-pilot clinical trial of occlusal pit and fissure caries inhibition using the same CO(2) -laser irradiation conditions.

STUDY DESIGN/MATERIALS AND METHODS

Twenty subjects, average age 14 years, were recruited. At baseline, second molars were randomized into test and control groups, assessed by International Caries Detection & Assessment System (ICDAS-II), SOPROLIFE light-induced fluorescence evaluator in daylight and blue-fluorescence mode and DIAGNOdent. An independent investigator irradiated test molars with a CO(2) -laser, wavelength 9.6 µm, pulse-duration 20 µs, pulse-repetition-rate 20 Hz, beam diameter 800 µm, average fluence 4.5 ± 0.5 J/cm(2), 20 laser pulses per spot. At 3-, 6- and 12-month recall teeth were assessed by ICDAS, SOPROLIFE and DIAGNOdent. All subjects received fluoride varnish applications at baseline and 6-month recall.

RESULTS

All subjects completed the 3-month, 19 the 6-month and 16 the 12-month recall. At all recalls average ICDAS scores had decreased for the test and increased for the control fissures (laser vs. control, 3-month: -0.10 ± 0.14, 0.30 ± 0.18, P > 0.05; 6-month: -0.26 ± 0.13, 0.47 ± 0.16, P = 0.001; 12-month: -0.31 ± 0.15, 0.75 ± 0.17, P < 0.0001; mean ± SE, unpaired t-test) being statistically significantly different at 6- and 12-month recalls. SOPROLIFE daylight evaluation revealed at 6- and 12-months statistically significant differences in changes between baseline and recall for test and control molars, respectively (laser vs. control, 6-month: 0.22 ± 0.13, 0.17 ± 0.09, P = 0.02; 12-month: 0.28 ± 0.19, 0.25 ± 0.17, P = 0.03). For SOPROLIFE blue-fluorescence evaluation mean changes in comparison to baseline for the control and the laser treated teeth were also statistically significant for the 6- and 12-month recall.

CONCLUSION

Specific microsecond short-pulsed 9.6 µm CO(2) -laser irradiation markedly inhibits caries progression in pits and fissures in comparison to fluoride varnish alone over 12 months.

Use of laser in orthodontics: applications and perspectives

Laser technology got in these years a more and more important role in modern dentistry and, recently, also in orthodontics was proposed the utilization of laser devices. The aim of this work is to describe the utilization of this technology both in soft and hard oral tissues to improve orthodontic treatment. Several cases, with different wavelengths (532, 810, 980, 1064, 2940 and 10600 nm) and in different times of the treatment (before, during and after) are presented. All the cases reported showed, according to the literature, that the use of the laser related to orthodontic treatment offers several advantages when compared with conventional methods. In the soft tissues surgery it allows to reduce or eliminate the use of anesthetic injection, to avoid use of sutures and to bond bracket in dry enamel; associated with orthophosphoric acid, it gives a stronger adhesion of the brackets to the enamel and, in the case of porcelain brackets, it detaches them without damages; at low power (LLLT) it permits to control the pain of the first period after bonding and, by increasing the speed of teeth movement in the bone, reduces the time of the treatment.

Use of laser in orthodontics: applications and perspectives

Laser technology got in these years a more and more important role in modern dentistry and, recently, also in orthodontics was proposed the utilization of laser devices. The aim of this work is to describe the utilization of this technology both in soft and hard oral tissues to improve orthodontic treatment. Several cases, with different wavelengths (532, 810, 980, 1064, 2940 and 10600 nm) and in different times of the treatment (before, during and after) are presented. All the cases reported showed, according to the literature, that the use of the laser related to orthodontic treatment offers several advantages when compared with conventional methods. In the soft tissues surgery it allows to reduce or eliminate the use of anesthetic injection, to avoid use of sutures and to bond bracket in dry enamel; associated with orthophosphoric acid, it gives a stronger adhesion of the brackets to the enamel and, in the case of porcelain brackets, it detaches them without damages; at low power (LLLT) it permits to control the pain of the first period after bonding and, by increasing the speed of teeth movement in the bone, reduces the time of the treatment.

Nanoleakage in primary teeth prepared by laser irradiation or bur

The aim of this in vitro study was to analyze hybrid layer and nanoleakage of composite resin restorations in cavities prepared by either Er,Cr:YSGG laser or bur, followed by acid etching in primary teeth. Ten extracted primary molar teeth were randomly allocated into two groups consisting of ten cavities according to surface treatment regimen: Er,Cr:YSGG laser + acid etching(group 1) and bur + acid etching(group 2). Restorations of all samples were completed. Then, teeth were sectioned and immersed to ammoniacal silver nitrate solution. After polishing, hybrid layer thicknesses were examined under scanning electron microscopy (SEM) and ion analysis was carried out with SEM/energy dispersive X-ray spectroscopy preparation in terms of nanoleakage. Hybrid layer thickness and the amount of silver ions were assessed for the acid-etched groups. The collected data were analyzed with independent sample t test and Spearman's rank correlation. In groups 1 and 2, the mean hybrid layer thicknesses were 4.25 ± 1.41 and 5.24 ± 1.07 μm and the silver ion percentages were 10.97 ± 13.81 and 22.79 ± 21.62 %, respectively. Although no significant correlation was observed between the increase of hybrid layer thickness and the amount of silver ions, more silver ions were observed in group 2 (p < 0.05). According to the results of this study, acid-etched cavities prepared with laser promoted better results when compared to the acid-etched cavities prepared with bur.

Caries inhibition in vital teeth using 9.6-μm CO2-laser irradiation

The aim of this study was to test the hypothesis that in a short-term clinical pilot trial short-pulsed 9.6 μm CO(2)-laser irradiation significantly inhibits demineralization in vivo. Twenty-four subjects scheduled for extraction of bicuspids for orthodontic reasons (age 14.9 ± 2.2 years) were recruited. Orthodontic brackets were placed on bicuspids (Transbond XT, 3M). An area next to the bracket was irradiated with a CO(2)-laser (Pulse System Inc, Los Alamos, New Mexico), wavelength 9.6 μm, pulse duration 20 μs, pulse repetition rate 20 Hz, beam diameter 1100 μm, average fluence 4.1 ± 0.3J∕cm(2), 20 laser pulses per spot. An adjacent nonirradiated area served as control. Bicuspids were extracted after four and twelve weeks, respectively, for a quantitative assessment of demineralization by cross-sectional microhardness testing. For the 4-week arm the mean relative mineral loss ΔZ (vol% × μm) for the laser treated enamel was 402 ± 85 (mean ± SE), while the control showed significantly higher mineral loss (ΔZ 738 ± 131; P = 0.04, t-test). The difference was even larger after twelve weeks (laser arm ΔZ 135 ± 98; control 1067 ± 254; P = 0.002). The laser treatment produced 46% demineralization inhibition for the 4-week and a marked 87% inhibition for the 12-week arm. This study shows, for the first time in vivo, that the short-pulsed 9.6 μm CO(2)-laser irradiation successfully inhibits demineralization of tooth enamel in humans.

Clinical comparison of bur- and laser-prepared minimally invasive occlusal resin composite restorations: two-year follow-up

This study evaluated the two-year clinical performance of two minimally invasive cavity preparation techniques, bur and laser, in Class I occlusal resin composite restorations. Twenty-seven patients, each having at least one pair of occlusal caries, were enrolled in this study. For each patient, one of the cavities was prepared with a diamond bur, and the other was prepared with Er, Cr:YSGG laser. The cavities were restored with a nanofilled flowable resin composite, Grandio Flow, using an etch-and-rinse adhesive, Solobond M. A total of 108 restorations were placed in molars by a single operator. The restorations were evaluated according to modified Cvar/Ryge criteria. The evaluations were performed at baseline, 6, 12, 18 and 24 months after initial placement by two calibrated operators. The Chi-square and Fisher's exact test were used for statistical analysis. All the patients were available during all evaluated periods, resulting in a recall rate of 100%. The retention rates of the restorations at 24 months were 98.1% for bur and 100% for the laser-prepared group. After 24 months, 5.6% of the bur-prepared and 7.4% of the laser-prepared restorations were rated Bravo in marginal discoloration (p > 0.05). Bur-prepared (9.3%) and laser-prepared (13%) restorations were rated Bravo in marginal adaptation (p > 0.05). There were no significant differences between the two cavity preparation techniques regarding the evaluated parameters (p > 0.05). Both cavity preparation techniques performed equally, with excellent outcomes after a 24-month period.

The effect of Er,Cr:YSGG laser and air abrasion on shear bond strength of a fissure sealant to enamel

PURPOSE

The authors conducted an in vitro study to evaluate the shear bond strength of a fissure sealant to enamel pretreated with erbium,chromium:yttrium, scandium,gallium,garnet (Er,Cr:YSGG) laser or air abrasion followed by acid etching.

METHODS

The authors sectioned extracted sound premolars mesiodistally and used the buccal and lingual surfaces for experimental analysis. They divided specimens randomly into three groups of 15 each according to the enamel surface pretreatment methods: group A, 37 percent phosphoric acid; group B, air abrasion followed by acid etching with 37 percent phosphoric acid; group C, irradiation with Er,Cr:YSGG laser followed by acid etching with 37 percent phosphoric acid. After applying a bonding system, the authors bonded cylinders of sealant to the enamel surfaces by using transparent gelatin tubes (0.7 millimeter in diameter and 1 mm in height) and then polymerized them. They stored all specimens in distilled water at 37 degrees C for 24 hours. They tested shear bond strength by using a universal testing machine with a crosshead speed of 0.5 mm per second. The authors analyzed the data by means of one-way analysis of variance and Tukey-Kramer post hoc tests (alpha = .05).

RESULTS

The bond strength of group B specimens was statistically higher than those of group A and group C specimens (P < .05). The authors found no statistically significant differences in shear bond strength between surfaces treated with Er,Cr:YSGG laser and those treated with acid etching alone (P > .05).

CONCLUSION

Pretreatment of enamel surfaces with air abrasion increased the bond strength of fissure sealant, but pretreatment with Er,Cr:YSGG laser did not increase the effectiveness of conventional acid etching of enamel in sealant bonds.

Effect of Er,Cr: YSGG Laser on the Microtensile Bond Strength of Two Different Adhesives to the Sound and Caries-affected Dentin

The microtensile bond strength of a three-step etch-and-rinse and a two-step self-etch adhesive is not negatively affected by Er,Cr:YSGG laser irradiation in sound and caries-affected dentin.

Intrapupal temperature variation during Er,Cr: YSGG enamel irradiation on carries prevention

Studies have shown the cariostatic effect of Er,Cr:YSGG (2.78 mm) laser irradiation on human enamel and have suggested its use on caries prevention. However there are still no reports on the intrapulpal temperature increase during enamel irradiation using parameters for caries prevention. The aim of this in vitro study was to evaluate the temperature variation in the pulp chamber during human enamel irradiation with Er,Cr:YSGG laser at different energy densities. Fifteen enamel blocks obtained from third molars (3 x 3 x 3 mm) were randomly assigned to 3 groups (n=5): G1--Er,Cr:YSGG laser 0.25 W, 20 Hz, 2.84 J/cm(2), G2--Er,Cr:YSGG laser 0.50 W, 20 Hz, 5.68 J/cm(2), G3--Er,Cr:YSGG laser 0.75 W, 20 Hz, 8.52 J/cm(2). During enamel irradiation, two thermocouples were fixed in the inner surface of the specimens and a thermal conducting paste was used. One-way ANOVA did not show statistically significant difference among the experimental groups (alpha=0.05). There was intrapulpal temperature variation < or = 0.1 degrees C for all irradiation parameters. In conclusion, under the tested conditions, the use of Er,Cr:YSGG laser with parameters set for caries prevention lead to an acceptable temperature increase in the pulp chamber.

Shear bond strength of composite bonded to erbium:yttrium-aluminum-garnet laser-prepared dentin

The purpose of this study was to evaluate the dentin bond strength to resin composite following erbium:yttrium-aluminum-garnet (Er:YAG) laser preparation using different adhesive systems. Seventy dentin specimens prepared from human molar teeth were randomly assigned to seven groups of ten. The first five groups were prepared with an Er:YAG laser 2940 nm at the manufacturer's recommended settings and (1) acid etched, and etch-and-rinse adhesive Excite was applied; (2) Excite was applied; (3) two-step self-etching adhesive AdheSE was applied; (4) laser etched (120 mJ/10 Hz), and Excite was applied; (5) laser etched, and AdheSE was applied. The last two groups were added as controls (prepared with a diamond bur): (6) acid etched, and Excite was applied; (7) AdheSE was applied. Nanohybrid composite cylinders 4 mm x 2 mm were bonded to the dentin surfaces. After the specimens had been stored in distilled water and had undergone thermocycling, the shear bond strength was tested and the data were analyzed statistically. The Duncan multiple comparison test showed that specimens prepared with a diamond bur and with acid and Excite applied showed the highest mean bond strength (13.01 +/- 2.09 MPa), followed by those prepared with Er:YAG and with AdheSE applied (11.5 +/- 3.59 MPa) and those prepared with a diamond bur and with AdheSE applied (10.75 +/- 1.95 MPa), but there were no significant differences among them (P > 0.05). Er:YAG-prepared specimens, with acid, Excite (3.28 +/- 0.95 MPa) and specimens that were laser etched and with AdheSE applied (3.37 +/- 0.63 MPa) showed the lowest mean values for bond strength (P < 0.05). The results suggested that dentin surfaces prepared with Er:YAG laser may provide comparable composite resin bond strengths depending on the adhesives used.

Erbium, chromium:yttrium scandium gallium garnet laser for caries removal: influence on bonding of a self-etching adhesive system

This study evaluated the influence of the dental substrates obtained after the use of different caries removal techniques on bonding of a self-etching system. Forty, extracted, carious, human molars were ground to expose flat surfaces containing caries-infected dentine surrounded by sound dentine. The caries lesions of the specimens were removed or not (control--G1) either by round steel burs and water-cooled, low speed, handpiece (G2), or by irradiation with an erbium, chromium:yttrium scandium gallium garnet (Er,Cr:YSGG) laser (2W, 20 Hz, 35.38 J/cm(2), fiber G4 handpiece with 0.2826 mm(2), non-contact mode at a 2 mm distance, 70% air/20% water--G3) or using a chemo-mechanical method (Carisolv--G4). Caries-infected, caries-affected and sound dentines were submitted to a bonding system followed by construction of a resin-based composite crown. Hour-glass shaped samples were obtained and submitted to a micro-tensile bond test. The bond strength data were compared by analysis of variance (ANOVA), complemented by Tukey's test (P <or= 0.05). The samples of sound dentine presented higher bond strengths than did samples of caries-affected dentine, except for the groups treated with the Er,Cr:YSGG laser. The highest bond strengths were observed with the sound dentine treated with burs and Carisolv. The bond strengths to caries-affected dentine were similar in all groups. Additionally, bonding to caries-affected dentine of the Er,Cr:YSGG laser and Carisolv groups was similar to bonding to caries-infected dentine. Thus, caries-affected dentine is not an adequate substrate for adhesion. Moreover, amongst the caries removal methods tested, the Er,Cr:YSGG laser irradiation was the poorest in providing a substrate for bonding with the tested self-etching system.

Analysis of the interfacial micromorphology of adhesive systems in cavities prepared with Er,Cr:YSGG, Er:YAG laser and bur

The purpose of this in vitro study was to evaluate the interaction pattern of adhesive systems on laser and bur cavities. Cavities were prepared according to the following groups (n=9): (G1) conventional diamond bur (No. 1013); (G2) Er:YAG laser (250 mJ, 4 Hz, 80.6 J/cm2); (G3) Er,Cr:YSGG laser (3.5 W, 20 Hz, 61.7 J/cm2). After cavity preparation, specimens were divided into three subgroups differing the adhesive systems used (n=3): (GA) AdheSE; (GB) Clearfil standard error (SE) Bond; (GC) Single Bond. After insertion of a micro-hybrid composite resin, the specimens were sectioned across the bonded surface dividing the teeth into two halves, which were prepared for SEM analysis. Cavities prepared with laser appeared to be more irregular than the bur cavities. Different patterns of gap formation and resin tags could be observed, showing the differences, advantages, and disadvantages of both types of cavities. Under the settings of the present study, resin tags were more pronounced in lased dentin than bur prepared dentin independently of the bonding systems used. On the other hand gap formation between dentin and resin in laser prepared cavities was observed suggesting collagen alteration.

Effect of Er,Cr:YSGG laser irradiation on eruption of rat mandibular incisor after disturbance of the enamel organ in the pulp

To investigate the efficacy of Er,Cr:YSGG (erbium,chromium:yttrium scandium gallium garnet) laser irradiation in root canal preparation and to evaluate its effect on eruption of rat incisors after disturbance of the enamel organ in the pulp, 20 canals of lower left incisor teeth were prepared by K-files followed by Er,Cr:YSGG laser irradiation, and 20 canals of right incisors were subjected to K-files only (control). At 1 week after irradiation, both sides of incisors erupted at the same level from the gingival margin. Histological findings showed that laser irradiation produced a slightly larger damage in the pulp than that of control. Scanning electron microscope observation revealed that laser-treated surface revealed a rough, irregular, and very clean surface; there was almost no evidence of debris or smear layer, and dentinal tubules were opened. Adequate power of Er,Cr:YSGG laser irradiation is effective in root canal preparation without disturbance of the eruption.

Ultramorphological and Histochemical Changes After ER,CR:YSGG Laser Irradiation and Two Different Irrigation Regimes

The purpose of this study was to evaluate the ultramorphological and chemical changes in Er,Cr:YSGG laser-treated radicular dentin in comparison with two different irrigation regimes. Extracted human premolars were assigned into three experimental groups. Group 1: After each file size, root canals were irrigated with 5.25% NaOCL, followed by a final irrigation with 5.25% NaOCL. Group 2: At each file size, biomechanical preparation was performed in conjunction with Rc-Prep, followed by 5.25% NaOCL irrigation; and 5.25% NaOCL for the final flush. Group 3: 5.25% NaOCL was used after each file size, followed by Er,Cr:YSGG laser irradiation; and a final flush with 5.25% NaOCL. Scanning electron microscopic (SEM) evaluations revealed failure of smear removal in NaOCL-irrigated specimens. RC-Prep + NaOCL-treated dentin revealed moderate-to-total presence of the smear layer with distinct areas of exposed collagen. Er,Cr:YSGG laser irradiation of radicular dentin also resulted in partial or total removal of the smear associated with a few small regions of thermal injury, including carbonization and partial melting. Energy dispersive X-ray analysis (SEM-EDX) showed no significant difference between the Ca/P ratios of the test groups, suggesting absence of changes at the molecular level.

Composite resin bond strength to primary dentin prepared with Er, Cr:YSSG laser

This in vitro study evaluated the shear bond strength of a hybrid composite resin bonded to primary dentin prepared with an Er, Cr:YSGG hydrokinetic laser compared to conventional bur prepared primary dentin. The results suggest that primary dentin surfaces treated with the Er, Cr:YSGG laser, with or without etching, may provide comparable or increased composite resin bond strengths depending upon bonding agent used.

Change of Enamel after Er:YAG and CO2Laser Irradiation and Fluoride Treatment

OBJECTIVE

Our aim was to compare acquired acid resistance in dental enamel after Er:YAG and CO(2) laser irradiation in vitro with additional fluoride treatment.

BACKGROUND DATA

The application of lasers in dental hard tissue can impact dental constituents and fluoride with complex interactions.

METHODS

Bovine enamels were divided into four groups according to their surface condition: unlased, Er:YAG laser-ablated, fluoridetreated after Er:YAG laser ablation, and CO(2) laser-irradiated after Er:YAG laser and fluoride treatment. Calcium distribution in enamel after pH-cycling process and crystallographical change after laser treatment were evaluated.

RESULTS

The crystallinity of enamel was much improved after Er:YAG laser ablation. The CO(2) laser irradiation in the fluoride-treated laser enamel formed alpha-TCP and fluorapatite. The change of calcium distribution in enamel was least in the CO(2) laser-irradiated specimens; the fluoride-treated specimen after Er:YAG laser ablation was next. Additional fluoride treatment both after Er:YAG and before CO(2) laser irradiation improved the acid resistance of enamel.

CONCLUSION

Both external treatment of fluoride and irradiation of CO(2) laser after Er:YAG laser ablation greatly reduced calcium loss in enamel during the pH cycling process.

Efficacy of Root Canal Preparation by Er,Cr:YSGG Laser Irradiation with Crown-Down Techniquein Vitro

OBJECTIVE

The purpose of this study was to compare the efficacy of Er,Cr:YSGG laser in root canal preparation and its effectiveness in removing debris and smear layer with the efficacy of the conventional hand instrument, in vitro.

BACKGROUND DATA

Recently, the use of the Er,Cr:YSGG laser device in root canal preparation has been excepted in the dental clinic. However, there have been no published reports on root canal preparation by using the Er,Cr:YSGG laser irradiation.

MATERIALS AND METHODS

A total of 40 straight root canals were prepared by an Er,Cr:YSGG laser at a output power of 2 W, and 40 canals were shaped by using the K file under irrigation with NaOCl and H2O2 by using the crown-down technique (control). The achievement degree of root canal preparation and debris score was morphologically investigated.

RESULTS

The results showed that great improvement in the cleanliness of the walls was found using the laser technique as compared with the control technique; a significant decrease in smear layer or debris was also recognized in laser-prepared canals (p < 0.01). But canal preparations with the laser device sometime result in ledge, zipped, perforation, or over-instrumentation.

CONCLUSION

The results demonstrated that root canal preparations with the laser device were significantly worse than in the control group. Further development in laser device and technique are required to ensure its success in root canal preparation.

Effect of Er:YAG laser on enamel acid resistance: Morphlogical 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.

Lasers in dentistry

BACKGROUND

During the last two decades, much has been written in both the scientific literature and the popular press about lasers and their use in the dental office. Both soft- and hard-tissue applications have been discussed, including frenectomy, gingival contouring, caries removal and bleaching.

OVERVIEW

Almost one-third of patients surveyed by the American Dental Association in the late 1990s thought it was very important that their dentists have lasers, which could put pressure on dentists to invest in this tool to attract patients. The authors describe the different types of dental lasers and examine the science behind their applications in dentistry.

CONCLUSION AND CLINICAL IMPLICATIONS

Although lasers do have legitimate uses in dentistry, they do not take the place of any of the more conventional tools in the dentist's armamentarium. Before investing in a laser, dentists should fully understand the differences between the various types, including what the scientific literature says about their applications.

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.

Clinical assessment of Er,Cr:YSGG laser application for cavity preparation

In this study, an erbium,chromium:YSGG (Er,Cr:YSGG) laser emitting at a wavelength of 2.78 microm was clinically applied to remove caries and prepare cavities, and the clinical outcome was evaluated. Effective clinical application of Er,Cr:YSGG laser had been expected from previous studies. This study included 44 patients (26 females, 18 males; aged 23-58) with a total of 50 cavity preparations by the Er,Cr:YSGG laser irradiation at 3-6 W with water spray. Patient acceptance and prognosis were evaluated. Most cases (94%) were prepared without anesthesia, and no pain was felt in 34 cases (68%). No adverse reaction was observed in any of the cases, and patient acceptance for this system was favorable. All cases had a good prognosis. In 45 cases (90%), overall clinical evaluation was satisfactory. From the present study, it can be concluded that the Er,Cr:YSGG laser system is an efficient, effective, and safe device for caries removal and cavity preparation.

Analysis of surface roughness of enamel and dentin after Er,Cr:YSGG laser irradiation

OBJECTIVE

The purpose of this investigation was to compare the surface roughness of enamel and dentin following the Er,Cr:YSGG laser irradiation and acid etching.

BACKGROUND DATA

Laser-roughened enamel or dentin surfaces have been expected to enhance restorative materials bond strength.

MATERIALS AND METHODS

Er,Cr:YSGG laser irradiation was performed in one half of each polished enamel or dentin sample at 3 W (33.9 J/cm2, with air 70% and water 20%,) pulse energy for 6 sec. Then the other half was treated with 37% phosphoric acid for 30 sec. Surface roughness and morphological studies were performed.

RESULTS

It was found that surface roughness was significantly increased with the laser system. Scanning electron microscopy analysis showed that irradiated surface produces a rough surface that was completely lacking of a smear layer; there was also no cracking of enamel or dentin.

CONCLUSION

Er,Cr:YSGG laser irradiation could provide an effective and alternative method to the acid etch technique.