In vivo caries-like lesion prevention with argon laser: pilot study

Imaging of Dental Hard Tissue Surfaces Prepared by an Ultrashort Pulsed Laser System (USPL)

The aim of this study was to compare surface structures of laser-irradiated dental hard tissues using confocal (CFM), atomic force (AFM), and scanning electron microscopy (SEM). The general potential of the AFM in analyzing laser-irradiated surfaces was determined in this context. Specimens of human enamel and dentin were irradiated using an 8.6 W Nd:YVO4 laser with a pulse duration of 8 ps, λ Center=1,064 nm, and a pulse repetition rate of 500 kHz. Surface topology of irradiated areas (1 mm2) was investigated using AFM, CFM, and SEM. Surface roughness R z was measured only with the AFM and the CFM. For non-irradiated enamel and dentin surfaces, roughnesses for CFM and AFM are in the nanometer range. However, major differences in roughness were determined for laser-prepared surfaces. For enamel, R z (CFM)=2.33 μm is much higher compared with R z (AFM)=0.09 μm; in the case of dentin, R z (CFM)=5.35 μm is also much higher compared with R z (AFM)=0.093 μm. Information regarding structural properties of surfaces needs real dimensions, particularly for use in dentistry. In this respect, AFM technology provides no additional results that lead to a significant improvement.

Lasers in orthodontics

Many types of dental lasers are currently available that can be efficiently used for soft and hard tissue applications in the field of orthodontics. For achieving the desired effects in the target tissue, knowledge of laser characteristics such as power, wavelength and timing, is necessary. Laser therapy is advantageous because it often avoids bleeding, can be pain free, is non-invasive and is relatively quick. The high cost is its primary disadvantage. It is very important to take the necessary precautions to prevent possible tissue damage when using laser dental systems. Here, we reviewed the main types and characteristics of laser systems used in dental practice and discuss the applications of lasers in orthodontics, harmful effects and laser system safety.

Risk factors and management of white spot lesions in orthodontics

The formation of white spot lesions or enamel demineralization around fixed orthodontic attachments is a common complication during and following fixed orthodontic treatment, which mars the result of a successfully completed case. This article is a contemporary review of the risk factors, preventive methods and fate of these orthodontics scars. The importance of excellent oral hygiene practice during fixed orthodontic treatment must be explained. Preventive programs must be emphasized to all orthodontic patients. Suggestions are offered in the literature for ways to prevent this condition from manifesting itself.

Análise química e morfológica do esmalte dentário humano tratado com laser argônio durante a colagem ortodôntica

INTRODUÇÃO: as principais utilizações do laser argônio na Ortodontia são a redução do tempo de polimerização durante a colagem ortodôntica e o aumento da resistência à cárie do esmalte dentário. OBJETIVO: o objetivo deste trabalho foi avaliar as alterações químicas e morfológicas do esmalte dentário humano tratado com laser argônio nos parâmetros da colagem ortodôntica. MÉTODOS: quinze primeiros pré-molares hígidos, extraídos por indicação ortodôntica, foram selecionados e seccionados no sentido do longo eixo em dois segmentos iguais. Uma metade de cada elemento dentário foi tratada e a outra permaneceu sem tratamento. Um total de 30 amostras foi analisado, criando o grupo laser (n = 15) e o grupo controle (n = 15). O tratamento foi feito com laser argônio com 250mW de potência por 5 segundos, com densidade de energia de 8J/cm². RESULTADOS: a análise de difração de raios X demonstrou duas fases em ambos os grupos, as fases apatita e monetita. A redução da fase monetita foi significativa após o tratamento com laser, sugerindo maior cristalinidade. A análise de Espectroscopia de Energia Dispersiva (EDS) indicou aumento na razão cálcio-fósforo no grupo laser, compatível com a diminuição da fase monetita. A morfologia superficial do esmalte dentário apresentou-se mais lisa após o tratamento com laser argônio. CONCLUSÕES: o aumento de cristalinidade e a lisura superficial do esmalte no grupo laser são fatores sugestivos de aumento de resistência à cárie no esmalte dentário.

Laser-activated fluoride treatment of enamel as prevention against erosion

BACKGROUND

Erosion is the loss of dental hard tissues from an acidic challenge, often resulting in exposure of dentinal tubules and hypersensitivity to environmental stimuli. Laser-activated fluoride (LAF) therapy with 488nm laser energy has been shown previously to increase the resistance of human enamel and dentine to acid dissolution. The aims of this study were to investigate the action spectrum of LAF in protecting tooth enamel from softening in response to an erosive challenge, and to examine for any temperature change with the treatment.

MATERIALS AND METHODS

Buccal and lingual surfaces of extracted sound molar and premolar teeth were used to prepare matched pairs of enamel slabs (N = 10 per group). After application of 1.23% neutral sodium fluoride gel (12 300ppm F ion), slab surfaces were lased with 488, 514.5, 532, 633, 670, 830 or 1064nm wavelength (energy density 15J/cm(-2); spot size 5mm), then exposed to an erosive challenge (1.0M HCI for five minutes). The Vicker's hardness number (VHN) was recorded before fluoride gel application and again following the acid challenge. Negative controls did not receive laser exposure.

RESULTS

All wavelengths of laser light examined provided a protective LAF effect against softening, compared with the negative control surfaces.

CONCLUSION

From these findings, we conclude that the action spectrum of the LAF effect extends across the visible spectrum, providing protection to dental enamel from an erosive challenge.

Cavity generation in dental enamel using a copper-HyBrID laser

Applications of Cu-HyBrID laser (copper laser with Hydrogen Bromide In Discharge) in Dentistry and AFM (atomic force microscopy) evaluations of dental tissues irradiated by laser are seldom reported in the literature. This work presents an AFM investigation of the cross-section of a cavity generated in human dental enamel by laser thermal evaporation using the Cu-HyBrID laser. The results exposed the structural and morphological differences between the fused and non-fused dental enamel, provide qualitative information about the susceptibility of these tissues to abrasive polishing, and revealed the extension of the thermal damage. Quantitative information concerning the wall thickness and the dimensions of the cross-section of non-fused enamel rod were also obtained.

Laser-activated fluoride treatment of enamel against an artificial caries challenge: comparison of five wavelengths

BACKGROUND

Laser-activated fluoride (LAF) therapy with 488 nm laser energy has been shown previously to increase the resistance of human enamel and dentine to acid dissolution in laboratory models of dental caries. The aims of this study were to examine whether LAF therapy, conducted using a range of wavelengths in the visible and near infrared regions, can protect human dental enamel from an artificial cariogenic challenge.

MATERIALS AND METHODS

Buccal and lingual surfaces of extracted sound, molar and premolar teeth were used to prepare matched pairs of enamel slabs (N=10 per group). After application of neutral sodium fluoride gel (12300 ppm F ion), slab surfaces were lased (energy density 15 J/cm2; spot size 5mm, wavelength 532, 633, 670, 830 or 1064nm), then exposed to an artificial cariogenic challenge for a period of seven days. The Vicker's hardness number (VHN) was recorded before and after laser treatment and again following the cariogenic challenge. Negative controls did not receive laser exposure.

RESULTS

All wavelengths of laser light examined provided an effective LAF effect, compared with the unlased negative control surfaces.

CONCLUSION

Using this in vitro model, we conclude that the action spectrum of the LAF effect extends across the visible and near-infrared regions of the spectrum.

In vitro caries formation in primary tooth enamel: role of argon laser irradiation and remineralizing solution treatment

BACKGROUND

The authors evaluated the effects of argon laser (AL) diation and remineralizing solution (RS) treatment alone and in combination on carieslike lesion formation in primary tooth enamel in an in vitro study.

MATERIALS AND METHODS

The authors divided 10 caries free primary tooth enamel surfaces into four segments and assigned them to one of four treatment groups: no treatment control, AL irradiation alone at 13.5 joules per square centimeters (0.270 watts, 5-millimeter beam, 10 seconds), RS treatment alone for two minutes and AL irradiation before RS treatment. The authors created in vitro caries using a modified ten Cate solution. They evaluated longitudinal sections (three per tooth segment, 30 per treatment group) for mean lesion depth.

RESULTS

After lesion formation, mean lesion depths (+/- standard deviation) were 179 +/- 16 micrometers for the no treatment controls, 137 +/- 19 microm for AL irradiation alone, 87 +/- 9 microm for RS treatment alone and 68 +/- 12 microm for AL irradiation before RS treatment. All treatment groups had mean lesion depths that were significantly less than those for the matched no-treatment control group (analysis of variance [ANOVA], Duncan multiple range [DMR] test, P < .05). AL irradiation before RS treatment significantly reduced lesion depth compared with AL irradiation alone or RS treatment alone (ANOVA, DMR test, P < .05).

CONCLUSIONS

The maximum reduction in lesion depth in primary tooth enamel was achieved when the RS--which contained calcium, phosphate and fluoride in a carbopol base--was combined with AL irradiation.

CLINICAL IMPLICATIONS

It would appear that to improve clinical caries resistance to enamel dissolution, AL irradiation before RS treatment could be used.

Bond strength of a dentin bonding system using two techniques of polymerization: visible-light and argon laser

OBJECTIVE

The aim of this work was to study one dentin-bonding system associated with posterior teeth restorative composite resin by means of tensile bond strength tests varying the technique of polymerization: visible light and argon laser.

BACKGROUND DATA

Previous studies have demonstrated the ability of the argon laser to polymerize light-activated materials.

METHODS

Sixty specimens were prepared by grinding the labial surface of bovine teeth embedded in acrylic resin. The dentin bonding system used was Single Bond (3M), which has a poliacenoic acid copolimer, associated with a posterior teeth restorative composite resin (Filtek P60, 3M). The bonding sites were treated according to the instruction of the manufacturers. The 60 teeth, duly embedded and ground, were assigned to four groups with 15 teeth each: group 1, the adhesive was light cured during 10 sec with visible light (Curing Light, 3M) with power density of 410 mW/cm2 and the composite resin was light cured during 20 sec with visible light; group 2, the adhesive and the composite resin were cured during 10 seconds with argon laser with 150 mW of power; group 3, the adhesive and the composite resin were cured during 10 sec with argon laser with 200 mW of power; and group 4, the adhesive and the composite resin were cured during 10 sec with argon laser with 250 mW of power. The composite resin was light cured in layers of 1 mm of thickness until the model of teflon with 3 mm in height was completely filled.

RESULTS

The tensile bond strength test was performed in a Mini-Instron (model 4442) and the results for group 1 were 19.75 MPa (+/-4.65), group 2 were 16.09 MPa (+/-7.27), group 3 were 11.56 MPa (+/-4.50), and group 4 were 11.90 MPa (+/-5.78).

CONCLUSIONS

One can conclude that the tensile bond strength promoted by the polymerization with visible light presented greater tensile bond strength than the polymerization with argon laser with 200 mW and 250 mW, but there was no significant difference between visible light and argon laser with 150 mW. There was no significant difference between argon laser with 150 mW and argon laser with 200 mW or 250 mW.

Pulpal safety of 9.6 microm TEA CO2 laser used for caries prevention

BACKGROUND AND OBJECTIVES

Lasers are used for several procedures involving hard and soft tissues of the oral cavity. A potential future application is the use of the CO2 laser to alter the surface structure of tooth enamel to render it more resistant to caries. A new 9.6 microm wavelength transverse excited atmospheric pressure (TEA) CO2 laser (Argus Photonics, Jupiter, FL) has been investigated as a device that can be used for this purpose without harming the dental pulp.

STUDY DESIGN/MATERIALS AND METHODS

Erupted caries- and restoration-free third molars (n = 24 participants; 74 teeth) were used in the study. Teeth were irradiated at an incident fluence of 1.5 J/cm2, a repetition rate of 10 Hz and a spot size 1 mm in diameter. At the low and high settings, 200-400 pulses at 5-8 microseconds pulse duration were delivered at 12 mJ per pulse for a total energy of 2.4 or 4.8 J delivered for 20 or 40 seconds, respectively. Other teeth were subjected to a sham dental procedure (positive control) or no procedure (negative control). Prior to testing, radiographs were taken of all teeth, and they were assessed pulpally using heat, cold, and electricity to determine vitality. The teeth were removed either immediately or at 1 week or 1 month after testing.

RESULTS

Teeth were bioprepared and examined histologically for signs of inflammation. Only one tooth developed symptoms of sensitivity to cold for 10 days following exposure to the high power level. The sensitivity was of fleeting duration and was judged to be reversible pulpitis. All teeth tested responded normally at pre-testing and pre-extraction time periods. Histological examination of all teeth disclosed no indication of an inflammatory response in the pulp tissue at any time point. All sections appeared normal with no changes seen in the normal pulpal morphology.

CONCLUSIONS

We conclude that the 9.6 microm wavelength laser causes no permanent/serious pulpal damage at the energy levels used and can be used safely for caries prevention treatments in humans.

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.

X-ray opaque waveguide for dentistry

OBJECTIVE

The aim of this study is the design, realization, and examination of a new x-ray contrast hollow waveguide which will be suitable for x-ray diagnostics or treatment required in medicine, as dentistry, maxiollofacial surgery or oncology.

BACKGROUND DATA

With the growing usefulness of laser radiation therapeutic interventions, a strong demand for radiation delivery from the laser source to the interaction place has appeared. For more complicated surgery, especially for internal intervention, an x-ray is necessary. In such cases, as a minimum, the end of the delivery system must be x-ray contrasted to distinguish where the interaction of radiation with tissue would take place. Up to now, neither fiber, hollow waveguide, nor other delivery system have been x-ray opaque.

MATERIALS AND METHODS

A new type of hollow glass waveguide was designed, fabricated, and examined as a delivery system for an endodontic treatment. The system is composed from the cyclic olefin polymer coated silver hollow glass waveguide with special covering for x-ray visibility. The inner diameter of the waveguide was 320 microm, the outer diameter was 630 microm, and its length was 100 mm. After the delivery system was created, the hollow waveguide was checked under an x-ray machine and its opacity was measured. For actual treatment, an Er:YAG laser system generating a mid-infrared radiation was used. The root canals of 10 molars were treated endodontically, and the result of that treatment was compared with the common cleaning methods. During treatment, digital x-ray images were taken with conventional files, using this new designed hollow waveguide.

RESULTS

The position of a metal instrument demonstrates the quality of opacity after conventional step-back technique. The hollow waveguide is visible in the left tooth canal. A bone density analysis shows no differences between a left (waveguide) and right (tooth) canal.

CONCLUSION

It was demonstrated that no differences exist between x-ray opacity of the metal instrument used for endodontic treatment and a special hollow waveguide. The digitalized, three-dimensional image helps to detect a precise position of customary instrument or waveguide in root canal.

Enamel caries initiation and progression after argon laser irradiation: in vitro argon laser systems comparison

OBJECTIVE

The purpose of this in vitro laboratory study was to determine the effect of low-fluence argon laser (AL) irradiation delivered from two different argon laser systems on enamel caries-like lesion initiation and progression.

BACKGROUND DATA

Previous in vitro investigations and a recent in vivo pilot study have shown that AL irradiation of enamel provided a protective effect against in vitro and in vivo cariogenic challenges.

MATERIALS AND METHODS

Twenty extracted human molars were selected, and 10 teeth were assigned to the HGM argon laser group and 10 were assigned to the LaserMed argon laser group. The exposed buccal windows of sound enamel were exposed to low-fluence irradiation, while the lingual windows of enamel were not exposed to laser irradiation and served as the no-treatment (control) group. Enamel caries-like lesions were created using an acidified gel. Two longitudinal sections were taken per sample (n = 20 lesions per group) and evaluated by polarized light microscopy for body of the lesion depths after lesion initiation (8 weeks) and progression (12 weeks) periods.

RESULTS

After lesion initiation and progression, the body of lesion depths were similar for both argon-irradiated groups (p > 0.05). With the no-treatment (control) group, there were significant increases in lesion depth with a 61-78% increase for the lesion initiation period and a 50-69% increase for the lesion progression period when compared with the argon laser-treated groups.

CONCLUSION

Argon laser irradiation provides a certain degree of protection against in vitro enamel caries initiation and progression. Resistance to a continuous caries challenge was similar with either argon laser delivery systems (HGM and LaserMed). Argon laser irradiation may prove to be beneficial in reducing the caries susceptibility of sound enamel and white spot lesions in the clinical environment.

The effects of argon laser irradiation on enamel decalcification: An in vivo study

Enamel decalcification is a significant problem in orthodontic patients. The argon laser has been shown to reduce decalcification during an acidic challenge in vitro. The purpose of this study was to investigate the in vivo effects of argon laser irradiation on enamel decalcification during orthodontic treatment. Nine volunteers whose treatment plans included 4 first premolar extractions were enrolled in the study. The 36 extracted premolars were assigned to 1 of the following 4 groups: group 1, control group with no treatment; group 2 (pumice-laser), teeth were pumiced for 3 seconds and treated with a 325 mW, 5-mm diameter laser beam for 60 seconds; group 3 (pumice-etch-laser), teeth were pumiced for 3 seconds, acid-etched with 30% phosphoric acid for 30 seconds, and treated for 60 seconds with laser; and group 4 (laser only), teeth were treated for 60 seconds with laser. A specially designed (oversized) orthodontic band was fitted on each of the premolars to create a pocket for decalcification. The bands were cemented in place for 5 weeks. After extraction, the teeth were sectioned and examined under polarized light microscopy. Images of lesions were digitally analyzed and measured. Average lesion depths were calculated from 3 depth measurements recorded 10 microm apart. Average lesion area was calculated with the aid of imaging analysis software. Data were analyzed with analysis of variance (P <.05) and Student t tests. Significant differences were found in lesion depth (P <.001) and lesion area (P <.01) among the 4 test groups. The average lesion depths were 15.93 +/- 9.31 microm (control), 6.45 +/- 8.70 microm (pumice-laser), 1.71 +/- 4.82 microm (pumice-etch-laser), and 1.34 +/- 3.80 microm (laser only). The average lesion areas were 1028.67 +/- 725.68 microm (2) (control), 555.49 +/- 948.20 microm (2) (pumice-laser), 79.91 +/- 226.03 microm (2) (pumice-etch-laser), and 55.71 +/- 157.59 microm (2) (laser only). The average lesion depth in the laser-only group was reduced by 94.1% and the average lesion area was reduced by 94.4% when compared with the control group. In the pumice-etch-laser group, the average lesion depth was reduced by 89.1% and the average lesion area was reduced by 92.2% when compared with the control group. There were no significant differences in lesion depth and lesion area between maxillary and mandibular teeth (P <.06 and P <.08, respectively) and between the teeth on the right and left sides (P <.68 and P <.55, respectively). These results show that argon laser irradiation is effective in reducing enamel decalcification during orthodontic treatment. Pumicing and etching do not appear to reduce the effect of laser on enamel solubility.