The effects of the Nd:YAG laser on amalgam dental restorative material.

The Nd:YAG laser has been marketed as an instrument for use on both hard and soft dental tissues. Its potential for use on hard tissues is limited but it may be the instrument of choice for use in certain soft tissue procedures. The aim of this study was to examine the effects of the Nd:YAG laser on amalgam restorations which are frequently placed on tooth surfaces adjacent to areas of soft tissue which may be subjected to the laser. The amalgam used was Tytin. The laser firing was controlled by a computer and a constant repetition rate of 40 Hz was used. Energy per pulse was altered as follows: 30 mJ, 40 mJ, 60 mJ, 80 mJ, 120 mJ and 140 mJ. Exposure times of 0.05 s (2 pulses), 0.125 s (5 pulses), 0.25 s (10 pulses), 0.5 s (20 pulses), 1 s (40 pulses), 2 s (80 pulses), 3 s (120 pulses), 4 s (160 pulses), and 5 s (200 pulses) were used. The width of defect was measured using a measuring microscope with 10x magnification and it was established that the damage threshold lies between 0.125 s (5 pulses) and 0.25 s (10 pulses) for 30 mJ per pulse. Scanning electron microscope observations revealed that the melting of amalgam at exposure times of 5 s actually decreased the size of the observed defect. The data were analysed using a two-way ANOVA statistical test. There was a significant (p < 0.001) correlation between the width of the defect and exposure time up to an exposure time of 4 s and the width of defect and the energy per pulse setting. The findings indicate that amalgam restorations are damaged by inadvertent laser exposure and clinicians must take measures to protect such restorations during lasing of soft tissues.

A comparison of three methods for the diagnosis of sound, stained, and carious dentine: conventional, mechanico-acoustic, and laser-acoustic methods.

OBJECTIVE: The authors examined two novel and objective methods for diagnosing stained, carious, and sound dentine, a mechanico-acoustic method and a laser-acoustic method, and compared these with the conventional but subjective method of visual and tactile assessment using a dental probe. SUMMARY BACKGROUND DATA: It is accepted clinical practice to leave stained but relatively firm dentine on the pulpal surface of dental cavities prepared for restoration. The problem for the clinician is in deciding which dentine is carious and which is stained but acceptable to be left in situ. There is no objective method for making this decision, it is usually made on the basis of visual examination and tactile assessment using a dental probe. METHODS: The authors used Fourier analysis of acoustic waves arising from mechanical (dental probe) or laser (Er:YAG laser) interaction with the tooth surface and compared the results with the subjective assessment of the same tissue surfaces as judged by a clinician using visual and tactile assessment with the same dental probe. RESULTS: The results showed that both the mechanico-acoustic and laser-acoustic methods were more accurate and more objective than the conventional visual/tactile method and that an analysis of both the integral and spectral signals produced by the Er:Yag Laser (lambda = 2.94 microns) allowed for a more accurate diagnosis than the other two methods examined. CONCLUSIONS: Both mechanico-acoustic and laser-acoustic methods of diagnosing sound, stained, and carious dentine were more accurate than the subjective visual/tactile method using a dental probe. The laser-acoustic method was the most accurate of all of the methods compared. An advantage of the laser-acoustic method is that it could be included into the actual process of cavity preparation when using an Er:YAG laser, providing an objective and more accurate assessment of the nature of the remaining dentin and may therefore be more economic of time, eliminating the necessity for constant cessation of drilling to assess the nature of the target tissue.

A comparison of the effects of Nd:YAG and Ho:YAG laser irradiation on dentine and enamel.

This preliminary study was undertaken to investigate the effects of Nd:YAG and Ho:YAG lasers on enamel and dentine of extracted teeth. The Ho:YAG laser (spot size 250 microns, energy density 4160 J/cm2) produced a cleaner puncture in dentine with less melting of the surrounding tissue than did the Nd:YAG laser (spot size 20 microns), energy density 50,000 J/cm2), which produced considerable melting and recrystallization of dentine and was more difficult to control. It was possible to cut enamel and dentine with both lasers, but considerable melted and recrystallized enamel was produced. From the limited observations of this study it appears that the Ho:YAG laser is more suitable for cutting both enamel and dentine than the Nd:YAG laser. More work needs to be done to ascertain the effect on enamel and dentine of modification of the parameters of both lasers.

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.

Restoration of a dentition affected by dentinogenesis imperfecta using In-Ceram: a case report.

A patient suffering from dentinogenesis imperfecta and consequent noncarious tooth destruction was rehabilitated using In-Ceram crowns. The problems encountered in the diagnosis, treatment planning and treatment are discussed.