Pulpal effects of argon: fluoride excimer laser irradiation and acid-etching of rat molar enamel

Physico-chemical changes of human enamel irradiated with ArF excimer laser

BACKGROUND AND OBJECTIVES

Irradiation of tooth enamel by lasers can alter its structure and chemical composition. The purpose of this work was to determine the compositional changes and to elucidate the mechanisms of laser-enamel interaction using ArF excimer laser.

STUDY DESIGN/MATERIALS AND METHODS

Human enamel irradiated with ArF excimer laser (wavelength, 193 nm) at different fluences, was examined using X-ray diffraction, infrared (IR) spectroscopy and microprobe analysis.

RESULTS

Ablation without significant compositional changes in irradiated enamel was evident when low fluences (approximately 200-380 mJ/cm2) were used. However, fluences between 640 and 2,300 mJ/cm2 resulted in an increased Ca/P ratio, decreased amount of carbonate and protein, and the formation of tricalcium phosphate and tetracalcium phosphate, suggesting the involvement of a photothermal mechanism.

CONCLUSIONS

The results show that ArF excimer laser can alter the chemical composition and morphology of the highly mineralized (96%) dental enamel, depending on the fluence used.

ArF-193 Excimer Laser and Emdogain® in the Treatment of Experimental Periodontitis: An Experimental Study in Rabbits

OBJECTIVE

We aimed to investigate how the progress made on laser technology during the last ten years could overcome this obstacle and allow the use of lasers in periodontology, together with the application of a number of products permitting the regeneration of periodontal tissues.

BACKGROUND DATA

The use of lasers in dentistry remains controversial, in spite of their increasing application in medical practice. The main reason for this discrepancy is the frequent report of damage to surrounding tissues and the dental pulp, due to the energy transfer, from the site of laser impact.

METHODS

Experimental periodontitis was initiated in fifteen rabbits. Animals were divided into five equal groups. In the control group, no therapy was applied. The remaining four groups were treated with curettage or ArF 193 excimer laser, under conditions of strict control of frequency, fluency, and application, without or with the application of a periodontal healing product (Emdogain). Laser was applied by the use of a new, articulated arm for beam delivery. Pocket depth and microscopic analysis were performed three weeks after treatment.

RESULTS

Our results show that all treatment groups decreased pocket depth significantly. ArF193 excimer laser does not produce any histological damage to the dental pulp, and facilitates periodontal regeneration. This result is highly facilitated by the application of Emdogain).

CONCLUSIONS

The use of UV lasers, under a tight control of its energy, may be a valuable tool for the treatment of periodontal diseases, especially combined with the use of healing products. Further study is need to confirm these results.

Safety of the ArF193 excimer laser for the removal of dental plaque and calculi: an in vitro histological study

OBJECTIVE

To assay the safety of the ArF excimer laser in the integrity of human pulp elements.

BACKGROUND DATA

The use of lasers in dentistry remains controversial, in spite of their increasing application in medical practice. The main reason for this discrepancy is the frequent report of damage to surrounding tissues and the dental pulp, due to the energy transfer, from the site of laser impact. The progress made on laser technology during the last 10 years, could overcome this obstacle and allow the use of lasers in dentistry.

METHODS AND RESULTS

The present study reports the use of the ArF 193 excimer laser, under conditions of strict control of frequency and fluency, for the ablation of dental carries, plaque, and calculi, by the use of a new, articulated arm. We have tested 10 teeth, extracted for prosthetic reasons, immediately after extraction. Our in vitro results show that the ArF193 excimer laser does not produce any harm to the dental pulp (at least at the photo- or electronic microscopy level), whereas in a matter of seconds, it can be effective in removing all dental deposits. In addition, the use of the flexible articulated arm, makes this treatment comfortable and easier for both the dentist and patient.

CONCLUSION

Under a strict control of laser technology, and the use of the new articulated arm presented, the use of the ArF excimer laser in dentistry is safe and comfortable.

The effect of pulpotomy using CO2 and Nd:YAG lasers on dental pulp tissue

The histological response of the dental pulp after laser irradiation was studied. After pulpotomy was performed in the premolar and molar teeth of dogs, the exposed pulp tissue at the root canal opening was lased using either a CO2 or Nd:YAG laser. The laser parameters were 2 W, 10 ms, 5 times per second for 1, 2 and 3 s for CO2 laser and 2 W, 20 pulses per second for 1, 2 and 3 s for the Nd:YAG laser. Observations were made 30 and 45 days after treatment. The results revealed that laser irradiation caused carbonization, necrosis, infiltration of inflammation cells, oedema and haemorrhage in the pulp tissue. Under the conditions of this experiment, there was little histological evidence of repair to the treated pulp with a newly formed dentine barrier, which was in contrast to the control samples treated with a calcium hydroxide-containing cement (Dycal).

Jet-assisted laser tools for tooth preparation

Previous oral calcified-tissue laser ablations have yielded inadequate results because of the difficulty in producing a desired effect on a surface without concomitant pulp or osseous damage. The purpose of this study was to characterize a new modality of ablating teeth using argon and diode lasers (488.5 nm, 805 nm) in combination with the repetitive placement of specific photoabsorptive dyes. In this design, energy from laser light, that would otherwise be reflected, is coupled to the tooth-dye interface. Thirty-two specimens of recently extracted human enamel were sectioned and prepared into 3 x 2 x 2 rectangular blocks and smoothed with a polishing point. Two-microliter droplets of dye were placed on the external enamel surface and subsequently air-dried. Specimens were then ablated with the laser-dye combinations, producing craters approximately 100-200 mum in depth and devoid of visual carbonization. Similar irradiations were performed on enamel specimens without dye application, and displayed no cavitation or surface carbonization. SEM studies showed evidence of crater formation within the enamel surface. Optimization of laser parameters integrated with specific dispensing of dye is necessary before this technique can be studied further.

Pulpal effects of a high rep rate Nd:YAG laser

Molar teeth in male rats were used in this study to assess the effects of enamel surface treatments of pulp survivability. The occlusal surfaces of the first and third molars in each quadrant were treated with an Nd:YAG laser (Pulsemaster, Incisive Technologies, Inc.) using a 300-mum contact tip fiber, in a figure-8 motion, for a 30 sec ablation time. The second molars were not treated. Energy parameters/animal were as follows: (1) 0.6 W, 30 mJ energy, and 20 Hz, (2) 1.2 W, 30 mJ energy, and 40 Hz, (3) 1.8 W, 30 mJ energy, and 60 Hz, (4) 2.4 W, 30 mJ energy, and 80 Hz, (5) 0.6 W, 60 mJ energy, and 10 Hz, (6) 1.2 W, 60 mJ energy, and 20 Hz, (7) 1.8 W, 60 mJ energy, and 30 Hz, (8) 1.0 W, 100 mJ energy, and 10 Hz, and (9) 2.0 W, 100 mJ energy, and 20 Hz. Animals were sacrificed at two time periods (1 and 6 weeks, postoperatively). SEM analysis of enamel was performed at 2000x magnification to observe the parameter difference in surface quality. Microscopic examination of the histological samples was accomplished at 250x magnification. Surface analyses of tooth structure revealed a wide dispersion of enamel roughness, ranging from slightly etched to moderately cavitated. Power levels above 2.4 W exhibited significantly more roughness than lower energy parameters. Efforts were made to correlate the pulp biology effect with enamel surface condition to determine a safe threshold for survivability of the pulp tissue.(ABSTRACT TRUNCATED AT 250 WORDS)

Laser applications in dentistry: a review of the literature

While there are many applications of lasers in dentistry, few have advantages over existing technology. To date, lasers should be considered to be an adjunct to conventional techniques. There are also considerations of cost and rapid obsolescence of current laser equipment. The possible adverse effects of lasers on the tissues adjacent to those being irradiated, to users and to patients must also be considered.

The effects of low-level energy density Nd:YAG irradiation on calculus removal

This study assessed the effects of using an Nd:YAG laser to remove dental calculus from root surfaces. Human extracted molar teeth, with extensive calculus attachment to root surfaces, were irradiated with an Nd:YAG beam [power densities (PD) = 1.09 W/cm 2 and 2.19 W/cm 2; energy densities (ED) = 49.2 J/cm 2 and 98.4 J/cm 2]. An additional group of teeth was instrumented with a Gracey 11/12 curette. A separate group of untreated specimens served as controls. Specimens were examined under scanning electron microscopy and rated as to the degree of calculus detachment from root surfaces. Nd:YAG irradiation at low ED did not appreciably affect the integrity of the calculus root surface attachment. The higher-ED Nd:YAG irradiation appeared to mimic the type of calculus removal depicted with conventional hand instrumentation. Root surface damage from both laser ablations was negligible.