Effects of Nd:YAG Laser on Enamel Microhardness and Dental Plaque Composition: Anin SituStudy

Effects of topical fluoride on primary tooth enamel microhardness after diode laser treatment

Objectives

Tooth decay is controlled and prevented using fluorides. Specifically, a combination of laser irradiation and topical fluoride application can improve fluoride absorption. Although laser irradiation is recommended in traditional technology for caries prevention, little is known about the efficacy of caries-inhibiting laser diodes. Further, most studies have focused on permanent teeth. The objective of this study was to explore the effect of laser diode radiation mixed with topical fluoride on the enamel surface microhardness of primary teeth.

Material and method

The 60 primary teeth were divided into 60 plates. Baseline Vickers microhardness was established for each enamel surface. The samples were then divided into three groups. 4 % NaF varnish (group A) and 4 % NaF varnish using diode 2 and 3 W lasers (groups B and C, respectively). The final microhardness was measured and statistically evaluated using SPSS version 16. ANOVA was used to compare the means of the tested groups, which had a P-value of 0.05, indicating significance.

Result

The mean and standard deviation of microhardness for the different groups was tested. Group C (4 % NaF with a diode laser at 3 W) showed a higher average Vickers hardness (VHN) than Group B (4 % NaF with a diode laser at 2 W), whereas group A showed the lowest average VHN. There was a significant difference in microhardness between groups (P 0.05).

Conclusion

This study explored the effect of laser mixed with topical fluoride on enamel surface microhardness of primary teeth. The use of a diode laser (Quanta System, Italy) with a fluoride varnish applied to the enamel surface has a greater effect on the resistance of the enamel to caries.

Effects of Laser and Fluoride on the Prevention of Enamel Demineralization: An In Vitro Study

Introduction: Investigations have demonstrated that fluoride is an essential element in preventive dentistry. However, there are still controversies about the preventive effects of various kinds of laser. The aim of this study was to examine the effect of diode laser irradiation (810 nm) with or without fluoride therapy in the prevention of deciduous enamel demineralization. Methods: Sixty deciduous molar crowns were randomly assigned to 6 groups: C: received no treatment; F: fluoride varnish application; 2L: 2 times diode laser irradiation; 4L: 4 times diode laser irradiation; F2L: 2 times laser irradiation over fluoride varnish; F4L: 4 times laser irradiation over fluoride varnish. Teeth in all groups were subjected to a pH-cycling process to produce artificial caries-like lesions. Results: The analysis of variance (ANOVA) of microhardness values indicated a significant great effect for laser, fluoride, and the interaction of laser- fluoride on reducing the final microhardness value (P<0.001). However, the 2L group was an exception. Despite the 4L group, it did not show a significant prevention of enamel microhardness loss (P=0.125). These 2 groups exhibited different effects in the absence of fluoride (P _2L-4L=0.05) while in the presence of the fluoride varnish, no statistically significant difference was observed between them (P _F2L-F4L=0.257). Moreover, no statistically significant difference was observed between the laser-fluoride combination group and the fluoride group (P _F2L-F=0.133, P _F4L-F=0.926). Conclusion: Our results suggest that fluoride varnish, diode laser, and their combination decrease the loss of the enamel microhardness value and potentially prevent deciduous enamel demineralization. However, the combination of laser and fluoride was not more effective than fluoride.

Evaluation of Mineral Content and Photon Interaction Parameters of Dental Enamel After Phosphoric Acid and Er:YAG Laser Treatment

OBJECTIVE

The purpose of this study was to evaluate the effects of laser and acid etching on the mineral content and photon interaction parameters of dental enamel in human teeth.

BACKGROUND DATA

The composition of dental enamel may vary, especially at the surface, depending on the reactions that occur during dental treatment.

MATERIALS AND METHODS

Forty maxillary premolars were divided randomly into 2 groups of 20 teeth. In the first group, half of teeth crowns were etched by using 37% phosphoric acid; in the second group, half of teeth crowns were etched by using an erbium:yttrium-aluminum-garnet (Er:YAG) laser. The remaining half crowns in each group were used as untreated controls. We characterized the calcium (Ca), phosphorus (P), magnesium (Mg), sodium (Na), and potassium (K) contents in each specimen by using wavelength dispersive X-ray fluorescence spectrometry. The total atomic cross-section ([Formula: see text]), effective atomic number ([Formula: see text]), and electron density (N_e) of the tooth samples were determined at photon energies of 22.1, 25, 59.5, and 88 keV by using a narrow beam transmission method. Data were analyzed statistically by using the Mann-Whitney U test.

RESULTS

The mineral contents after Er:YAG laser and phosphoric acid etching did not differ significantly (p > 0.05), and no significant variation in [Formula: see text], [Formula: see text], or N_e was observed.

CONCLUSIONS

Therefore, we conclude that the Er:YAG laser and phosphoric acid systems used in this study did not affect mineral composition or photon interaction parameters of dental enamel.

Devices for In situ Development of Non-disturbed Oral Biofilm. A Systematic Review

Objective: The aim of this review was to assess the types of devices used for in situ development of oral biofilm analyzed microbiologically.

Materials and Methods: A systematic search of the literature was conducted to identify all in situ studies of oral biofilm which used an oral device; the Ovid MEDLINE and EMBASE databases complemented with manual search were used. Specific devices used to microbiologically analyze oral biofilm in adults were included. After reading of the selected full texts, devices were identified and classified according to the oral cavity zone and manufacturing material. The “ideal” characteristics were analyzed in every group.

Results: The search provided 787 abstracts, of which 111 papers were included. The devices used in these studies were classified as palatal, lingual or buccal. The last group was sub-classified in six groups based on the material of the device. Considering the analyzed characteristics, the thermoplastic devices and the Intraoral Device of Overlaid Disk-holding Splints (IDODS) presented more advantages than limitations.

Conclusions: Buccal devices were the most commonly used for the study of in situ biofilm. The majority of buccal devices seemed to slightly affect the volunteer's comfort, the IDODS being the closest to the “ideal” model.

Clinical Relevance: New devices for in situ oral biofilm microbiological studies should take into account the possible effect of their design on the volunteer's comfort and biofilm formation.

Effect of erbium, chromium: yttrium, scandium, gallium, garnet laser and casein phosphopeptide-amorphous calcium phosphate on surface micro-hardness of primary tooth enamel

Objective:

The aim was to evaluate the effect of Er, Cr: YSGG laser and casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) on surface micro-hardness of primary tooth enamel.

Materials and Methods:

A total of 30 freshly extracted caries free primary anterior teeth were cleaned and stored in 1% thymol. Teeth were embedded in acrylic resin such that only their buccal surfaces were exposed and were divided into four groups. Group I: Five intact teeth (negative control). The remaining 25 teeth were immersed for 30 min in 1% citric acid for demineralization. Group II: Five demineralized teeth (positive control), Group III: CPP-ACP (GC tooth mousse-GC International, Itabashi-Ku, Tokyo, Japan) application and Group IV: Etching using Er, Cr: YSGG laser + CPP-ACP application. Groups III and IV were subjected to pH cycling for 5 days. Surface micro-hardness of all the teeth was measured using Brinell hardness tester (Fuel Instruments and Engineers Pvt. Ltd.). Data were analyzed using ANOVA.

Results:

Mean surface micro-hardness of Groups I and II were 177.43 kgf/mm² and 164.86 kgf/mm², respectively. Group IV showed a higher mean surface micro-hardness (230.68 kgf/mm²) compared with that of Group III (190.28 kgf/mm²). In comparison to all other groups, laser etching prior to CPP-ACP application increased surface micro-hardness significantly (P < 0.001).

Conclusion:

Laser irradiation of primary teeth followed by CPP-ACP application increased surface micro-hardness of 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.

The effects of lasers and fluoride on the acid resistance of decalcified human enamel

OBJECTIVE

In order to preserve the maximum amount of healthy enamel and increase the acid resistance of decalcified enamel, a CO(2) laser, an Nd:YAG laser, and acidulated phosphate fluoride (APF) were used to treat incipient carious lesions, then their effects were compared.

MATERIALS AND METHODS

One hundred and sixty samples of human caries-free premolars were immersed in pH-cycling solution (pH = 5) for 2 d for decalcified lesion formation. Then the tooth samples were randomly divided into eight groups and the lesions were treated using the different modalities: a control group, an APF only group, an APF = Nd:YAG laser group, and APF = CO(2) laser group, an Nd:YAG laser = APF group, a CO(2) laser = APF group, a CO(2) laser only group, and an Nd:YAG laser only group. The energy density setting for the two types of lasers was 83.33 J/cm(2). After treatment the tooth samples were immersed in pH-cycling solution again for 2 d for acid challenge. As for the acid-resistance evaluation, the calcium concentration dissolved from the enamel surface was analyzed by an electrolyte analyzer. Scanning electron microscopy (SEM) was used to assess morphologic changes and polarized light microscopy (PLM) was used to evaluate optical changes in the lesions.

RESULTS

The control group showed a statistically significantly (p < 0.05) higher calcium concentration compared with all the other groups. The APF group also had a statistically significantly higher calcium concentration (p < 0.05) than did the laser groups. However, there was no statistically significant difference in any of the laser groups whether combined with fluoride or not (p > 0.05). Upon SEM analysis, melted surfaces and crater-like holes 1-20 microm in diameter were found in the CO(2) laser and Nd:YAG laser groups. On PLM, positive birefringence and reversal of birefringence after acid challenge of the lased enamel were seen.

CONCLUSIONS

Using lasers and fluoride on decalcified enamel appears to increase the enamel's acid resistance, and the effects of the lasers were better than those of fluoride treatment.

in vitroEvaluation of Enamel Demineralization after Er:YAG and Nd:YAG Laser Irradiation on Primary Teeth

OBJECTIVE

This in vitro study evaluated the influence of both Er:YAG and Nd:YAG laser irradiation on deciduous enamel demineralization.

BACKGROUND DATA

Although there are still few studies on the use of the high-intensity laser for caries prevention in deciduous teeth, it is believed that its use on the dental structure can lead to a more acid-resistant surface.

METHODS

Forty enamel samples obtained from 22 deciduous first molar teeth were ground and randomly divided into four groups (n = 10): group 1 (G1), no treatment (negative control); G2, fluoride (positive control); G3, Er:YAG laser (2 Hz, 60 mJ, 40.3 J/cm(2)); G4, Nd:YAG laser (80 mJ, 10 Hz, 0.8 W). After the surface treatment, the samples were submitted to an acid challenge that consisted of a 5-day immersion in demineralizing (3 h) and remineralizing solution (21 h). Next, a microhardness test was preformed.

RESULTS

Analysis of variance (ANOVA) and Student Newman Keuls tests were performed (alpha = 5%). The percentage of lesion inhibition for each group was as follows: G2, 59.4%; G3, 35.7%; and G4, 40.4%. As regards the percentage loss of mineral volume, there was no statistical difference between groups G2 (444.37 +/- 146.42) and G3 (441.81 +/- 207.08) when compared with group G1 (281.03 +/- 134.57). All experimental groups presented a lower mineral loss compared with the non-irradiated samples (G4).

CONCLUSION

The findings of the present study revealed that both Nd:YAG and Er:YAG lasers can be an alternative tool for enhancing deciduous enamel acid resistance.