The effects of the Nd:Y AG laser on amalgan dental restorative material

Abstract

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 10ϫ 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 d e f e c t 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.

Orthodontic Bonding: Review of the Literature

“…Er:YAG laser has the ability to ablate amalgam surfaces. It increases the surface area by creating crater-like scratches that are 100 μ m in diameter [ 102 , 103 ]. In one in vitro study, laser treatment with Er, Cr:YSGG was found to be a suitable alternative and produced higher SBSs than air-abraded amalgam [ 104 ].…”

Effect of surface treatment with sandblasting and Er,Cr:YSGG laser on bonding of stainless steel orthodontic brackets to silver amalgam

“…They reported that amalgam is ablated by this laser system (6). Er:YAG laser system, with or without water, can ablate amalgam, and the presence of water does not de-crease the efficiency of ablation, though it prevents temperature rise (7). The mechanisms of both Er,Cr:YSGG and Er:YAG lasers are similar (17).…”

“…Despite favorable results for bond strength in the laser group, it should be remembered that the dental amalgam is an alloy of mercury with other metals; a small amount of un-reacted mercury is present in the unset amalgam structure, which increases the possibility of mercury vapor release during the ablation process, threatening the dental staff health (7). Although in the present study temperature rise and its side effects were low as a result of a change in the delivery system and use of water spray (18-20), measurement of the mercury vapor released is suggested when using Er,Cr:YSGG laser.…”

“…Although there is a paucity of data on the effects of these lasers on restorative dental materials, it has been reported that Er:YAG laser system, with or without water, can ablate amalgam surfaces, and produce fine crater-like scratches on amalgam surface, with a diameter of 100 µm (6,7). …”

Amalgam Surface Treatment by Different Output Powers of Er:YAG Laser:SEM Evaluation

“…Despite surface evaluation, mercury vapor release during laser ablation should be considered as a hazardous factor for dental staffs. 13 Further studies are needed to assess the bond strength of orthodontic brackets to amalgam restorations besides mercury vapor release and thermal changes evaluation.…”