In vitro assessment of laser efficiency for caries prevention in pits and fissures

Clinical and ex-vivo effect of LASERs on prevention of early-enamel caries: systematic review & meta-analyses

To investigate the in vivo and in situ effect of different types of lasers in prevention of enamel demineralization in high caries risk cases (around orthodontic brackets, around restoration and in caries susceptible pits and fissures). PubMed was searched using the following keyword sequence; (Laser therapy OR laser irradiation OR laser application) AND (enamel caries prevention OR enamel demineralization OR enamel remineralization OR early enamel caries OR early-enamel caries OR enamel resistance OR enamel decalcification OR white spot lesions WSLs OR incipient lesion OR enamel decay OR enamel Dissolution OR enamel microhardness) AND (clinical trial OR Randomized clinical trial OR In situ study). The latest literature search was ended by "30 January 2023". PubMed was used as a primary data base for study selection. Scopus, EBSCO, and Google scholar are checked in our study after results of systematic search on PubMed. Only duplicates were found. Two meta-analyses were carried out. The first, clinical meta-analysis on incidence of white spot lesions (WSLs) following CO2 laser irradiation of enamel. The second meta-analysis on ex-vivo/in situ effect of CO2 laser on microhardness of enamel. In each meta-analysis three studies were included. Risk of bias was assessed. The search identified eight studies (four ex-vivo and four clinical trials). Regarding the clinical meta-analysis, the overall standardized mean difference was 0.21 [ 95% confidence interval (CI): 0.15-0.30, p < 0.00001]. This indicates that the incidence of new WSLs in patients who received low power CO2 laser treatment was highly significantly lower than placebo groups. The heterogeneity was considerable (I2 = 71%). In the second meta-analysis, the overall standardized mean difference was 49.55 [ 95% confidence interval (CI): 37.74, 61.37, p < 0.00001]. This indicates that microhardness of enamel receiving low power (0.4-5 W) CO2 laser irradiation is highly significantly lower than control untreated enamel. The heterogeneity was substantial (I2 = 48%). Within the limitations of this study, Low level laser therapy concept with CO2 laser seems to be effective in preventing enamel caries.Prospero registration number: CRD42023437379.

CO2 laser irradiation for debonding ceramic orthodontic brackets

This study evaluated shear bond strength (SBS), adhesive remnant index (ARI) and fracture mode of chemically and mechanically retained ceramic brackets bonded with different composite resins and irradiated with CO2 laser. The null hypothesis was that ceramic brackets bonded with different composite resins and irradiated with CO2 laser would have similar SBS values. Ninety human premolars were divided into four experimental groups according to the combination of type of composite resin (Transbond XT and Z 250) and type of ceramic bracket (Fascination and Mystique), and two control groups (n=15). In the four experimental groups, the brackets were irradiated with CO2 laser at 10 W for 3 seconds before SBS testing. Enamel surface ARI was calculated after debonding under electron microscopy scanning. ANOVA and the Mann-Whitney test were used for statistical analysis. The laser groups had lower SBS values than the non-irradiated groups (control) (p<0.05). The mechanically retained brackets (Mystique) had the higher (p<0.05) and Z250 had the lower SBS values after CO2 laser irradiation. The groups bonded with Z250 had the highest ARI. Adhesive fractures were the most prevalent. The null hypothesis was rejected. CO2 laser decreased SBS efficiently and facilitated debonding of mechanically and chemically retained ceramic brackets.

Preventing Enamel Caries Using Carbon Dioxide Laser and Silver Diamine Fluoride

Objective: This study was intended to investigate the caries prevention potential of carbon dioxide (CO₂) laser (λ = 10,600 nm) irradiation followed by application of silver diamine fluoride (SDF) to enamel. Materials and methods: Human enamel specimens were randomly allocated to four groups (n = 10 per group). Group 1 specimens were treated with SDF; Group 2 specimens were treated with a CO₂ laser; Group 3 specimens were irradiated with a CO₂ laser then treated with SDF, and Group 4 specimens received no treatment. All specimens were subjected to pH cycling for cariogenic challenge. Lesion depth, microhardness, surface morphology, and elemental analysis were assessed. Results: The lesion depths for Groups 1-4 were 33 ± 16, 80 ± 9, 18 ± 15, and 102 ± 9 μm, respectively (p < 0.001; Group 3 < Group 1 < Group 2 < Group 4). Knoop hardness values for Groups 1-4 were 61 ± 19, 68 ± 20, 78 ± 27, and 36 ± 8, respectively (p = 0.002; Group 4 < Groups 1, 2, and 3). The enamel in Group 4 but not in the other groups showed a roughened surface resembling an acid-etched pattern. Calcium-to-phosphorus molar ratios of Groups 1-4 were 1.68 ± 60.09, 1.61 ± 0.06, 1.69 ± 0.10, and 1.49 ± 0.10, respectively (p < 0.001; Group 4 < Groups 1, 2, and 3). Conclusions: Using the CO₂ laser or SDF separately enhanced the resistance of enamel to cariogenic challenge. Moreover, there was an additional effect of the combined use of the CO₂ laser and SDF for preventing enamel demineralization.

Efficacy of CO lasers in preventing dental caries in partially erupted first permanent molars: a randomized 18-month clinical trial

The aim of this controlled randomized double-blinded clinical trial was to evaluate the use of a CO₂ laser with or without topical application of acidulated fluorides in the prevention of dental caries in partially erupted first permanent molars. We selected 61 healthy children at high risk of caries, all between 6 and 8 (7.1 ± 0.8) years of age and with 4 partially erupted first permanent molars. A CO₂ laser device emitting at 10.6 μm was used (0.5 W, 0.05 mJ per pulse, 10 kHz). Each first molar in an individual was randomly assigned to one treatment: (L) CO₂ laser (0.066 J/cm²); (FL) 1.23% acidulated fluoride gel and CO₂ laser (0.066 J/cm²); (V) 5% fluoride varnish, or (S) sealant (control). Patients were followed-up at 3, 6, 12, and 18 months after treatment, through direct visual examination and by an operator blinded to the treatments (kappa ≥ 0.70). The International Caries Detection and Assessment System (ICDAS-II) index was used to assess the soundness of tooth structure or the presence of white spot lesions, cavitated enamel, and/or dentin lesions. The Yildiz Visual Index was used to evaluate sealant retention. Results were evaluated using Kaplan-Meier survival analysis, and the hazard ratio of the treatments was estimated using shared frailty models with a gamma distribution, which considered the patient as a cluster. There were no significant differences among treatments compared to sealants. After 18 months, the use of a CO₂ laser with or without acidulated fluorides was shown to be effective in preventing caries on the occlusal surface of partially erupted permanent first molars in children at high risk for caries.

The clinical effects of laser preparation of tooth surfaces for fissure sealants placement: a systematic review and meta-analysis

BACKGROUND

This systematic review aimed to assess the clinical effects of laser preparation compared to other types of chemical or mechanical preparation of tooth surfaces used in fissure sealant placement.

METHODS

A systematic literature search was conducted up to January 2019, through Pubmed, Scopus, Medline/EMBASE via OVID and the Cochrane library. Only randomized clinical trials were included.

RESULTS

Five studies were included in the systematic review and three were included in the meta-analysis. All the studies used acid-etching as a comparator to lasers. All the included studies were rated as having an overall high risk of bias introduced by performance bias. Three studies assessed the clinical effects of fissure sealants placed by acid or laser etching, one compared acid etching versus laser combined with acid etching and one investigated the influence of lasers on the objective and subjective parameters of stress during sealant application in children. The meta-analysis showed no significant difference between laser preparation and conventional acid-etching preparation at 3- (P = 0.08), 6- (P = 0.49), and 12-month (P = 0.87) follow-ups. One study reported that laser preparation as an adjunct to acid-etching enhanced the retention rate. No significant difference in the incidence of caries was reported. And no significant differences were found in heart rates, oxygen saturation or degree of the patient dental anxiety between acid-etching and laser preparation.

CONCLUSION

The present limited evidence suggests that lasers could be an effective pretreatment method. The retention rate was similar to that of conventional acid etching. However, the included studies had an overall high risk of bias and more rigorously designed research is needed.

Laser-assisted prevention of enamel caries: a 10-year review of the literature

Since the invention of lasers in dentistry, investigations in caries prevention by the use of laser radiation have been proposed. There are several mechanisms stated for this purpose such as photothermal and/or photochemical interaction processes with the enamel. Alone or in conjugation with topical fluoride application, this treatment modality may improve enamel acid resistance in high-caries-risk populations. Data collection was done by searching the keywords caries, prevention, and laser in PubMed, Embase, Web of Science, Cochrane Library, and Google Scholar. Lasing protocols of the collected literature and their effectiveness as well as examination methods used to verify treatment outcomes have been evaluated. One hundred eighteen publications were found for the last 10 years. The wavelengths investigated for caries prevention are mainly located in the near and the mid-infrared spectral range. In the evaluated period of time, investigations using CO₂; Er:YAG; Er,Cr:YSGG; Er:YLF; fundamental, second, and third harmonic generations of Nd:YAG; diodes; and argon ion lasers were found in the databases. Accounting for 39% of the literature, CO₂ laser was the most examined system for this purpose. Reviewing the literature in this narrative review showed that all laser systems presented a positive effect in varying degrees. Laser irradiation could be an alternative or synergistic to topical fluoridation for enamel caries prevention with longer lasting effect. Further research should be focused on selecting proper laser settings to avoid damage to enamel and developing effective evidence-based clinical protocols.

Chemical and Morphological Changes of Primary Teeth Irradiated with Nd:YAG Laser: An Ex Vivo Long-Term Analysis

OBJECTIVE

The aim of this study was to assess any long-term chemical and morphological Nd:YAG laser modifications on irradiated primary enamel.

BACKGROUND DATA

Previous studies on irradiated primary human enamel employed methodologies that evaluated the short-term effects only.

METHODS

One hundred and eighty-six irradiated (with and/or without fluoride) primary enamel teeth from high-caries-risk children, which were exfoliated over a 1-year period, were collected, and the sample surface area was submitted for scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, and X-ray energy-dispersive spectrometry (EDS). The subsurface was analyzed by Knoop microhardness and light microscopy (LM). Data were analyzed by one way ANOVA and Tukey tests (α=0.05) and Kruskall-Wallis and Tukey tests (α=0.05).

RESULTS

FTIR analysis revealed a higher concentration of phosphate and carbonate in the irradiated (0.987±0.064) and lower concentration in the control groups (1.477±0.310). SEM analysis showed that the control samples exhibited a slightly smoother surface than the irradiated groups. The EDS analysis did not show any differences in the amount of calcium, phosphorus, or fluoride among the groups. The microhardness analysis revealed that sealant (249.86±7.15) and laser irradiation (262.44±22.69) led to higher hardness values than the negative control group (128.35±25.19). LM indicated significantly reduced caries formation in the laser (5.35±5.38%) and the laser plus acidulated phosphate fluoride (APF) groups (10.35±0.88%) compared with the negative control group (72.56±12.86%).

CONCLUSIONS

Even with the limitations of the present study, these results suggest that Nd:YAG irradiation clinically modified the chemical composition of the enamel surface regardless of fluoride concentration, which successfully inhibited demineralization of primary tooth enamel over a 1-year period without significant morphological changes.

Effect of carbon dioxide laser irradiation on enamel surface microhardness around orthodontic brackets

INTRODUCTION

In this study, we aimed to determine the effect of carbon dioxide laser irradiation on enamel surface microhardness.

METHODS

In this single-blind interventional clinical trial, 16 patients needing at least 2 premolars extracted for orthodontic purposes participated. In each subject, 1 premolar was treated with the carbon dioxide laser (beam diameter, 0.2 mm; power, 0.7 W); the other was exposed to a visible guiding light as the control. A t-loop was ligated to the bonded brackets to increase caries risk. After at least 2 months, the teeth were extracted, and the surface microhardness was measured. Scanning electron microscope evaluation was performed on 1 sample from each group. Normal distribution of the data was assessed by the Kolmogorov-Smirnov and Shapiro-Wilks tests. Mean microhardness values of the 2 groups were compared using paired t tests.

RESULTS

The data had normal distributions. Means and standard deviations of the microhardness in the laser-treated and control groups were 301.81 ± 94.29 and 183.9 ± 72.08 Vickers hardness numbers, respectively; this was different significantly (P <0.001). Scanning electron microscopy showed the enamel surface melting in the laser-treated specimens.

CONCLUSIONS

Carbon dioxide laser treatment results in higher enamel surface microhardness around orthodontic brackets. Patients at high risk of caries might benefit from this intervention. Exact control of the laser irradiation parameters is recommended.

In vitro effects of two topical varnish materials and Er:YAG laser irradiation on enamel demineralization around orthodontic brackets

The aim of this in vitro was to evaluate the effects of tricalcium phosphate (TCP) and amorphous calcium phosphate (ACP) containing varnish materials and Er:YAG laser irradiation on enamel demineralization around orthodontic brackets. Forty extracted human premolar teeth were randomly divided into four treatment groups (i.e., 10 in each group): (1) 5% NaF-ACP varnish, (2) 5% NaF-TCP varnish, (3) Er:YAG laser, and (4) control (no treatment). Er:YAG laser was operated at a wavelength of 2.94 μm and the energy output was 80 mJ per pulse; a pulse duration of 200 μsec and and a frequency of 2 Hz were used with water cooling. All samples were then put into pH cycles. Surface microhardness values and representative SEM images were assessed. Surface microhardness values were evaluated using Kruskal-Wallis and Mann-Whitney U tests. The results revealed that demineralization was significantly lower in the TCP and ACP varnish groups, whereas mean surface microhardness values of the TCP varnish were found higher than the ACP (P < 0.05). TCP and ACP varnish materials were found effective for reducing enamel demineralization around orthodontic brackets. Use of Er:YAG laser irradiation as described in this study for inhibition of demineralization was found not satisfactory.

Self-etch bonding agent beneath sealant: Bond strength for laser-irradiated enamel

OBJECTIVES

This study evaluated the in vitro shear bond strength (SBS) of a resin-based pit-and-fissure sealant (Fluroshield [F], Dentsply/Caulk) associated with either an etch-and-rinse (Adper Single Bond 2 [SB], 3M/ESPE) or a two-step self-etch adhesive system (Adper SE Plus [SE], 3M/ESPE) on Er: YAG laser-irradiated enamel.

MATERIALS AND METHODS

Seventeen sound third molar crowns were embedded in acrylic resin, and the mesial-distal enamel surfaces were flattened. The enamel sites were irradiated with a 2.94-μm wavelength Er: YAG laser (120 mJ, 4 Hz, noncontact mode/17 mm, 20 s). The specimens were randomly assigned to three groups according to the bonding technique: I - 37% phosphoric acid etching + SB + F; II - SE + F and III - F applied to acid-etched enamel, without an intermediate layer of bonding agent. In all of the groups, a 3-mm diameter enamel-bonding site was demarcated and the sealant cylinders were bonded. After 24 hours in distilled water, the shear bond strength was tested at a crosshead speed of 0.5 mm/minute. The data were analyzed by one-way ANOVA and Tukey's test. The debonded specimens were examined with a stereomicroscope to assess the failure modes.

RESULTS

The mean SBS values in MPa were I = 6.39 (±1.44); II = 9.50 (±2.79); and III = 5.26 (±1.82). No statistically significant differences were observed between groups I and III; SE/F presented a significantly higher SBS than that of the other groups (P = 0.001). With regard to the failure mode, groups I (65%) and II (75%) presented adhesive failures, while group III showed 50% adhesive failure. Cohesive failure did not occur.

CONCLUSION

The application of the two-step self-etch bonding agent (Adper SE Plus) beneath the resin pit-and-fissure sealant placement resulted in a significantly higher bond strength for the Er:YAG laser-irradiated enamel.

Influence of laser irradiation on pits and fissures: an in situ study

OBJECTIVE

The aim of this in situ study was to analyze the influence of the Er:YAG, Nd:YAG, and CO(2) lasers on the enamel acid resistance of pits and fissures.

BACKGROUND DATA

The laser tissue interaction has been studied as a method of preventing occlusal caries.

METHODS

Thirteen volunteers wore palatal acrylic appliances containing human occlusal enamel blocks that were divided into four groups (G1, control; G2, Er:YAG; G3, Nd:YAG; G4, CO(2)). Each palatal acrylic appliance was used in the four studied groups and was used for 14 consecutive days. A sucrose solution was applied to the specimens six times per day. The specimens were then sectioned in half, and a microhardness test was applied. The other halves were analyzed using polarized light microscopy to measure the caries-like lesion areas, and a morphological analysis was conducted using a scanning electron microscope (SEM).

RESULTS

For the statistical analysis of the data obtained from the microhardness test (Knoop hardness number. [KHN]) (α=5%), Fisher's exact test was performed, and the group means were as follows: G1, 247±71; G2, 258±70; G3, 272±73; and G4, 298±56. The results demonstrated that the control group was significantly different from G3 and G4, which presented higher microhardness values. The Wilcoxon signed-rank test was used to analyze the data obtained from the caries-lesion area measurements (mm(2)) (α=5%) (G1, 0.01±1.08; G2, 0.13±0.18; G3, 0.05±0.17; and G4, 0.09±0.22). The results no showed significant differences among the groups in this analysis.

CONCLUSIONS

Based on the results from the present study, it may be concluded that the CO(2) and Nd:YAG lasers increased the enamel acid resistance in pits and fissures.

Effect of Nd:YAG laser combined with fluoride on the prevention of primary tooth enamel demineralization

Most studies dealing with the caries preventive action of Nd:YAG laser have been done in permanent teeth and studies on primary teeth are still lacking. The aim of this study was to evaluate in vitro the effect of Nd:YAG laser combined or not with fluoride sources on the acid resistance of primary tooth enamel after artificial caries induction by assessing longitudinal microhardness and demineralization depth. Sixty enamel blocks obtained from the buccal/lingual surface of exfoliated human primary molars were coated with nail polish/wax, leaving only a 9 mm² area exposed on the outer enamel surface, and randomly assigned to 6 groups (n=10) according to the type of treatment: C-control (no treatment); APF: 1.23% acidulated phosphate fluoride gel; FV: 5% fluoride varnish; L: Nd:YAG laser 0.5 W/10 Hz in contact mode; APFL: fluoride gel + laser; FVL: fluoride varnish + laser. After treatment, the specimens were subjected to a des-remineralization cycle for induction of artificial caries lesions. Longitudinal microhardness data (%LMC) were analyzed by the Kruskal-Wallis test and demineralization depth data were analyzed by oneway ANOVA and Fisher's LSD test (á=0.05). APFL and APF groups presented the lowest percentage of microhardness change (p<0.05). Demineralization depth was smaller in all treated groups compared with the untreated control. In conclusion, Nd:YAG laser combined or not with fluoride gel/varnish was not more effective than fluoride alone to prevent enamel demineralization within the experimental period.

Argon and Nd:YAG lasers for caries prevention in enamel

OBJECTIVE

The aim of this study was to investigate the effect of Nd:YAG and argon laser irradiations on enamel demineralization after two different models to induce artificial caries.

BACKGROUND DATA

It is believed that the use of the high-intensity laser on the dental structure can lead to a more acid-resistant surface.

MATERIALS AND METHODS

Twenty-one extracted human third molars were sectioned into tooth quarters. The quarters were distributed in three groups: Group I (control), untreated; Group II, Nd:YAG laser (60 mJ, 15 pps, 47.77 J/cm(2), 30 sec); and Group III, argon laser (250 mW, 12 J/cm(2), 48 sec). Tooth quarters from each group were subjected to two different demineralization models: cycle 1, a 14 day demineralization (pH 4.5; 6 h) and remineralization (pH 7.0; 18 h) solutions, 37 °C and cycle 2, 48 h in demineralization solution (pH 4.5). Samples were prepared in slices (60-100 μm thick) to be evaluated under polarized light microscopy. Demineralization areas were measured (mm(2)) (n=11). Data were analyzed by ANOVA and Tukey's test (p<0.05).

RESULTS

Means followed by different letters are significantly different: 0.25 A (control, cycle 48 h); 0.18 AB (control, cycle 14 days); 0.17 AB (Nd:YAG, cycle 14 days); 0.14 BC (argon, cycle 48 h); 0.09 BC (Nd:YAG, cycle 48 h), and 0.06 C (argon, cycle 14 days).

CONCLUSIONS

The argon laser was more effective for caries preventive treatment than Nd:YAG laser, showing a smaller demineralization area in enamel.