Laser Literature Review - June 2021

Compiled by Dr Igor Cernavin, Prosthodontist, Honorary Senior Fellow University of Melbourne School of Medicine, Dentistry and Health Sciences, Director and Cofounder of the Asia Pacific Institute of Dental Education and Research (AIDER), Australian representative of World Federation of Laser Dentistry (WFLD)

Zhuang et al1 analyzed the effects of the Er:YAG laser used with different parameters on dentinal tubule (DT) occlusion, intrapulpal temperature and pulp tissue morphology in order to determine the optimal parameters for treating dentin hypersensitivity.

They concluded that 0.5 W (167 J/cm2) is a suitable parameter for Er:YAG laser to occlude DTs, and it is safe to the pulp tissue.

Simoes and coworkers2 evaluated, through a literature review, the applicability of high- and low-intensity lasers in the treatment of Dentine Hypersensitivity for the past 10 years, as well as its therapeutic potential. They found that high- and low-intensity lasers, associated or not with other therapies, have demonstrated beneficial effects in the treatment of DH, being considered a promising, safe, easy, and effective field of research, reducing pain sensitivity and preserving pulp vitality.

Bozkaya et al3 assessed whether photobiomodulation therapy improved implant stability and affect the microbiota around dental implants in the early stage of osseointegration and concluded that it did not.

Won Sang Yoo and coworkers4 investigated whether photobiomodulation restored normal thyroid follicular cells affected by ionizing radiation and examined the mechanism, .and concluded that it was effective.

Walinski et al5 reported that removing laminate veneers on anterior teeth by using an Er,Cr:YSGG dental laser can be completed faster than previously reported while maintaining thermal safety.

Oliveira and coworkers6 evaluated the effect of different protocols of low-level intensity laser therapy (LLLT) irradiation on the osseointegration of implants placed in grafted areas. They concluded that LLLT performed on implants placed in grafted areas enhances the osseointegration process.

Papadopoulos et al7 evaluated the efficacy of intracoronal bleaching treatments of non-vital teeth either activated or not by Er,Cr:YSGG laser (2780nm) operating at 1.25 or 2.5W. The abstract is reproduced in full.

BACKGROUND: Non-vital tooth discoloration is a common condition in dental practice. The aim of this in vitro study was to evaluate the efficacy of intracoronal bleaching treatments of non-vital teeth either activated or not by Er,Cr:YSGG laser (2780nm) operating at 1.25 or 2.5W.

METHODS: Twenty four human canines were artificially stained after implementation of root canal treatment. Subsequently, the teeth were randomly divided into three groups (n=8): Group 1 (control) received intracoronal bleaching treatment with a bleaching gel containing 35 % hydrogen peroxide for 40min, Group 2 received the same treatment assisted with Er,Cr:YSGG laser (2780nm) operating at 1.25W average power for 30s and Group 3 received the same treatment with Group 2, but the average power was adjusted to 2.5W. The bleaching treatments repeated after one week. Spectrophotometric analysis of tooth color change (DeltaE) was implemented 7 days after both bleaching sessions.

RESULTS: The results of two-way ANOVA revealed that there was a tendency of no significant difference in color change between the three experimental groups (p=0.063). However, the between-group comparisons showed that laser 2.5W group had significantly higher DeltaE than the control group after the first bleaching session. Moreover, a significant interaction between bleaching treatment and number of applications was detected (p=0.026).

CONCLUSIONS: Er,Cr:YSGG laser irradiation significantly increased DeltaE only after the first bleaching session when operating at 2.5W. After the second bleaching session DeltaE was not different compared to the control group, irrespectively of the laser power settings.

Maria Aparecida Traverzim and coworkers8 published an article on the Effect of Photobiomodulation on analgesia during childbirth and concluded that LED can be considered an alternative, since it caused pain reduction without changing other parameters during labor, compared with hot shower, a method included in hospital protocols, proving to be safe.

Xue et al9 published a review of the effects of a 9.3-mum carbon dioxide (CO2) laser and silver diamine fluoride (SDF) on the prevention of enamel demineralisation and inhibition of cariogenic bacteria. The abstract is reproduced in full.

OBJECTIVE: To investigate the effects of a 9.3-mum carbon dioxide (CO2) laser and silver diamine fluoride (SDF) on the prevention of enamel demineralisation and inhibition of cariogenic bacteria.

METHODS: Enamel blocks were applied with Laser (Group-1), SDF (Group-2), Laser + SDF (Group-3) and no treatment (Group-4), and then subjected to an 8-day pH-cycling for cariogenic challenge. Lesion depth and cross-sectional micro-hardness were assessed. Surface morphological and chemical changes were studied using scanning electron microscope (SEM) with energy dispersive spectroscopy (EDS). For the antibacterial activity, treated enamel blocks were incubated with Streptococcus mutans. The biofilm morphology, kinetics and viability were assessed by SEM, colony-forming units (CFUs) and confocal laser scanning microscope (CLSM), respectively.

RESULTS: Lesion depths (mum) for Group-1 to Group-4 were 88 ± 21, 26 ± 11, 13 ± 9 and 115 ± 25, respectively (p < 0.001; Group-2 and Group-3 < Group-1 < Group-4). Group-3 had a significantly higher cross-sectional micro-hardness than the other three groups. EDS determined that Group-4 had the lowest calcium-to-phosphorus molar ratio among the groups (p < 0.001). SEM images showed apparent bacteria accumulation on enamel surfaces in Group-4, but not in other groups. Log CFUs for Group-1 to Group-4 were 6.2 ± 0.6, 2.9 ± 0.8, 2.2 ± 1.1 and 7.3 ± 0.3, respectively (p < 0.001; Group-2 and Group-3 < Group-1 < Group-4). CLSM images revealed that live bacteria dominated in Group-4, but not in other groups.

SIGNIFICANCE: The irradiation with a 9.3-mum CO2 laser alone can prevent the demineralisation of enamel and reduce the adhesion of cariogenic bacteria. Moreover, adding SDF can significantly increase the preventive effect and antibacterial ability.

Alia and coworkers10 evaluated and compared the pain perception, anxiety level, and acceptance of Er,Cr:YSGG laser (2780 nm) with a conventional rotary method during cavity preparation in children. They concluded that it was more effective and acceptable, as it was less anxiety-provoking and may cause less pain when compared with the air rotor.

Ebrahimi et al11 published a systematic review and meta-analysis to determine the effect of photobiomodulation (PBM) as an adjunctive treatment to periodontal therapies to evaluate secondary intention gingival wound healing and post-operative pain. They concluded that PBM can be effectively used as a method to improve secondary intention wound healing.

Yang and coworkers12 explored the efficacy of laser therapy in reducing swelling and pain in female patients after alveolar bone grafting and concluded that it was quite effective and improved the quality of life of these patients.