Background, aims

Since the development of the ruby laser by Maiman in 1960, a variety of papers on potential applications for lasers in dentistry have been published. The purpose of this paper is to summarise laser applications for the treatment of dentine hypersensitivity. The effects of laser on pulp tissue and problems on laser treatment are also reviewed. This article reviews the role of lasers for the treatment of dentine hypersensitivity since 1985, summarises many research reports from the last decade, and surmises what the future may hold for lasers in this treatment.

Method

To date, 4 kinds of lasers have been used for the treatment of dentine hypersensitivity, and the effectiveness ranged from 5.2 to 100%, which was dependent on the laser type and parameters used. The mechanism involved in laser treatment of dentine hypersensitivity are relatively unknown.

Results

These require clarification to result in safely effective treatment optimization. In general, the efficiency for the treatment of dentine hypersensitivity using lasers is higher than other methods, but in severe cases, it is less effective.

Conclusion

It is necessary to consider the severity of dentine hypersensitivity before laser use.

Objective

The purpose of this study was to investigate the effects of dentin ablation using a carbon dioxide (CO2) laser emitted at 9.3 microm by scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM).

Background data

There have been no reports on effects of CO2 laser irradiation emitted at 9.3 microm on dentin by SEM and CLSM.

Methods

Thirty extracted human teeth showing no clinical signs of caries were used. All teeth were horizontally sectioned to approximately 200 microm thickness and sections were irradiated using a 9.3 microm CO2 laser at different parameters as follows: 26 mJ [energy density (ED) 53.0 J/cm2] and 30 mJ (ED 61.1 J/cm2). After laser irradiation, samples were treated with sodium hypochlorite, stained using rhodamine-123, and observed with CLSM followed by SEM procedures.

Results

No craters or cracks were observed, but many small molten and rehardened particles were documented on the sample surface using SEM. Some small cracks were seen in the subsurface layer, and some patent dentinal tubules were detected using CLSM.

Conclusion

These results suggest that laser irradiation at these parameters affected the sample surface only (less than 20 microm) and would be less harmful to thermal damage of dental pulp for dentin ablation.

Dentin was visualized using a new fluorescence technique and confocal laser scanning microscopy. Thirty extracted human teeth showing no clinical signs of caries were investigated. All teeth were horizontally sectioned to approximately 200 μm thickness and sections were subjected to different pretreatment conditions as follows: vacuum only, ultrasonication only, sodium hypochlorite only, sodium hypochlorite and vacuum, sodium hypochlorite and ultrasonication, and a combination of sodium hypochlorite, vacuum, and ultrasonication. Some samples were left untreated to serve as control. Following pretreatment, rhodamine 123 fluorescent dye was used for staining at concentrations ranging from 10-3 to 10-7M for 1 to 24 h at pH 6.0, 6.5, or 7.4. Optical staining occurred at pH 7.4 and concentrations ≥ 10-5 M over 3 h or longer. Surface images obtained using confocal laser scanning microscopy were similar to those observed by scanning electron microscopy without the need for sample-altering conventional scanning electron microscope preparation techniques. Subsurface imaging to a depth of approximately 60 μm was achieved using confocal laser microscope techniques. This fluorescence technique offers a useful new alternative for visualization and quantification of dentin. © 1997 Society of Photo-Optical Instrumentation Engineers.

In this study, a fluorescence technique was developed for visualization of dentin using confocal laser scanning microscopy (CLSM). Eighteen extracted human teeth were used: 13 showing no clinical signs of caries and 5 with visually apparent decay. Preliminary study: All teeth were horizontally sectioned to approx. 200 μm thickness and pre-treated as follows: no pretreatment; vacuum only; ultrasonication only; sodium hypochlorite (NaOCl) only; vacuum and NaOCl; ultrasonication and NaOCl; or vacuum, ultrasonication and NaOCl. Samples were stained with Rhodamine 123 fluorescent dye at a concentration of 10-5 M in phosphate buffer saline for 1 to 24 hours. Caries study: Dentin surfaces, some with pre-existing caries, were visualized using CLSM. Most dentin tubules in sound dentin appeared open using CLSM, but most dentin tubules in carious dentin appeared closed or narrowed. Surface images obtained using CLSM were similar to those seen by SEM, but additional subsurface imaging was possible using CLSM at depth intervals of 1 μm to a depth of 30 - 50 μm. This technique shows good potential for non-invasive surface and subsurface imaging of dentin structures.