Shedding light on lasers

Lasers present contemporary uses in the field of endodontics, especially for refractory cases and mainly for smear layer removal and biofilm disinfection

Dr. David Keinan

The process of light amplification by stimulated emission of radiation (LASER) is a well-known phenomenon being used in various scientific fields. The energy is produced when excited atoms return to their base level and release photons. By using different laser mediums, the wavelength of the laser device is regulated and produces various energy levels. This energy was found to be applicable to various aspects in dentistry such as cavity preparation, bleeding control, soft tissue cutting, and disinfection. Therefore, it is not surprising that many studies have been conducted on laser technology for endodontic treatment (Green J, Weiss A, Stern A, 2011). Common lasers such as Er: YAG, Nd:YAG are used for cleaning, while CO2 lasers have been used for soft tissue surgery.

The main use of endodontic lasers includes smear layer removal and canal disinfection. Laser treatment was found efficient for reducing bacterial infection and can significantly enhance the long-term success of endodontic treatment (Siqueira JF Jr, 2001). Studies have demonstrated variable cleaning into dentinal tubules with Nd: YAG or diode lasers. The disinfection effectiveness of Er: YAG laser was found to be similar to sodium hypochlorite at various concentrations (Arnabat J, Escribano C, Fenosa A, et al., 2010; Folwaczny M, Mehl A, Jordan C, et al., 2002). This lethal effect of lasers can be increased by increasing the number of irradiation cycles (Moritz A, Schoop U, Goharkhay K, et al., 1999). Except for the photon effect on the bacteria, lasers can activate and increase the flow of the irrigants during root canal treatment. Laser active irrigation (LAI) was shown as an advanced technique to effectively remove debris from the canal walls (de Groot SD, Verhaagen B, Versluis M, et al., 2009; De Moor RJ, Blanken J, Meire M, et al., 2009; Sahar-Helft S, Slutzky-Goldberg I, Moshonov J, et al., 2011). This goal is achieved by forming large elliptical vapor bubbles that expand and then implode, therefore having a cavitation effect on the biofilm on the canal wall (de Groot SD, Verhaagen B, Versluis M, et al., 2009). In a similar way, the laser tip coronally positioned produces a forced streaming in a technique called photon-induced photoacoustic streaming (PIPS) (Pedullà E, Genovese C, Campagna E, et al., 2012).

The antimicrobial effect of a specific wavelength of lasers can be enhanced by using a photosensitizer on the treated area. This antimicrobial photodynamic therapy (aPDT) was considered for use against different oral pathogens, especially in the form of biofilm (Mang TS, Tayal DP, Baier R, 2012; Mang TS, Mikulski L, Hall RE, 2010). It was also noted that the weakened or changed biofilm matrix may be more easily removed or destroyed (Mang T, Rogers S, Keinan D, et al., 2016).

Laser treatment also has been also utilized to reduce dentinal hypersensitivity (Kimura Y, Wilder-Smith P, Yonaga K, et al., 2000; Senda A, Gomi A, Tani T, et al., 1985; Stabholz A, Neev J, Liaw LL, et al., 1993; Matsumoto K, Funai H, Wakabayashi H, et al., 1985). The mechanism of action may have two effects. The first involves physical blockage of the opened dentinal tubules by melting the dentin (Stabholz A, Neev J, Liaw LL, et al., 1993), and the second involves nerve analgesia by the energy of the laser (Matsumoto K, Funai H, Wakabayashi H, et al., 1985). The Er:YAG laser was found to have less pulpal damage from thermal changes during the irradiation (Belal MH, Yassin A, 2014).

In conclusion, lasers present contemporary uses in the field of endodontics, especially for refractory cases and mainly for smear layer removal and biofilm disinfection. The use of laser in endodontics is still limited mainly due to costs, but further studies are needed in order to explore their superiority over current methods of treatment.

Dr. David Keinan is a chief dental officer, medical corps for the Israel Defense Forces.

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