Effect of HeNe and pulsed Nd:YAG laser irradiation on intradental nerve responses to mechanical stimulation of dentine

Laser Analgesia Associated with Restorative Dental Care: A Systematic Review of the Rationale, Techniques, and Energy Dose Considerations

It is a common experience amongst laser dentists and patients that mid-IR wavelength application in cavity preparation may be achieved without causing any associated pain. The erbium family of lasers (Er,Cr:YSGG 2780 nm and Er:YAG 2940 nm) are frequently used without employing injectable local anesthesia as an adjunct: the phenomenon arising from the application of these devices is known as laser analgesia. This review seeks to apply a systematic approach to the examination of appropriate published studies but also to highlight the need for much more structured clinical investigations that consolidate photonic dose and methodology. A search of published data using PRISMA criteria was carried out to examine clinical trials into laser analgesia in conjunction with restorative dentistry, applying inclusion and exclusion criteria. From this, 10 published articles were selected for analysis. Suitability assessment was carried out, using a modified Cochrane risk of bias methodology. In 8/10 of the included studies, laser-induced analgesia is claimed to be better and effective, while in 2/10 of the studies, no difference was exhibited compared to the control group. Statistical analysis of three split mouth studies concluded that only one of these investigations reviewed demonstrated a significant analgesic effect for laser treatment while the other two did not support this observation. From this data, it is inconclusive to assess the predictability of laser analgesia in cavity preparation. A possible rationale and laser operating parametry has been discussed. Successful implementation of this treatment modality remains technique sensitive and subject to further investigation.

Efficacy of erbium-doped yttrium aluminium garnet for achieving pre-emptive dental laser analgesia in children: A study protocol for a randomized clinical trial

INTRODUCTION

A current non-pharmacological mean for attaining painless conservative treatment is presented by laser analgesia (LA), considered as bio-photomodulation of pulp reactivity aiming reduction of nociceptive impulse formation. Currently no consensus is reached regarding a detailed protocol with laser parameter settings for pre-emptive LA. The purpose of this study is determining the efficacy of erbium-doped yttrium aluminium garnet (Er:YAG) laser in achieving pulpal analgesia and quantifying duration and extent of any effects assessed.

METHODS AND ANALYSIS

The proposed study is a double-blind placebo-controlled randomized split-mouth clinical trial with 2-way repeated measures design. Eligible patients of age 10 to 12 years undergo 2 single-visit treatments, receiving LA or placebo analgesia (PA) prior to caries ablation, randomized via computer-generated, permuted-block sequence. Primary outcome measure is pain felt during treatment, reported by patient on visual-analogue scale.

SECONDARY OUTCOMES

changes in pulpal sensibility to electrical and cold-stimuli; patient experience during LA/PA; pain-related behavior according to Faces, Legs, Activity, Cry, Consolabilty (FLACC) scale; heart-rate dynamics. Data will be analyzed with intention-to-treat concept by Student t test for paired samples, P < .05. Pre-test on 20 subjects resulted in n = 41 patients needing to be recruited.

ETHICS AND DISSEMINATION

This study protocol has been approved by the Committee for Scientific Research Ethics, Medical University - Plovdiv, Bulgaria (Reference number P-8604, Protocol of approval N:6/23.11.2017) and registered on a publically accessible database. This research received institutional funding from the Medical University - Plovdiv, Bulgaria under project SPD-03/2017. Findings will be reported in scientific publications and at research conferences, and in project summary papers for participants.

TRIAL REGISTRATION

ClinicalTrials.gov (Registration number: NCT03412721).

Concept of experimental preparation for treating dentin hypersensitivity

BACKGROUND

Dentinal hypersensitivity (DH) is a diagnostic and therapeutic problem that is now appearing more frequently in modern dentistry. The aim of this work was to elaborate formulation of a new, original desensitizing preparation with prolonged action based on the knowledge of similar commercializations and to compare their performance in vitro.

METHODOLOGY

The analyses were performed with the aid of NMR spectroscopy. The experimental and commercial preparations were examined in vitro after thermocycling on human teeth by optical microscopy. The presence of the material on tooth tissue, its ability to penetrate into the tooth structure and its layer thickness were subjected to statistical analysis.

RESULTS

A detailed knowledge on composition of commercial material was achieved from spectroscopic measurements. A new adhesive monomer was synthesized and incorporated into an experimental desensitizing formulation. The new monomer appeared to have comparable performance to the commercial one when regarding the affinity to tooth tissue and resistance to thermocycling.

CONCLUSIONS

The experimental formulation comprising a new adhesive monomer seems to be promising and could be applied in dental practice providing that biocompatibility is satisfactory.

Layer-specific modulation of neuronal excitability by 660-nm laser irradiation in mouse neocortex

It has been reported that laser light irradiation (LLI) could regulate neuronal activities in the forebrain, but little is known if and how LLI in the red wavelength range affects neuronal excitability. Here, we investigated the effects of a continuous diode laser at 660 nm on intrinsic membrane properties and excitability of presumed pyramidal neurons in the thalamocortical input layer (layer 3/4) and in layer 5 of mouse primary auditory cortex using the whole-cell patch-clamp recording technique. In layer 3/4 neurons, 660-nm laser irradiation (LLI-660) at 20 mW for 5 min gradually increased resting membrane potentials, which reached a plateau after irradiation. Concomitantly, LLI-660 decreased onset latency of first action potentials (spikes) without changing spike threshold or peak amplitude, but increased inter-spike interval of initial bursting spike doublets and their peak amplitude ratio. None of these changes was observed in layer 5 neurons. Instead, LLI-660 at 20 mW rapidly reduced spike width ~5 % within 1 min of irradiation onset. The magnitude of this reduction did not change during 5 or 10 min irradiation, and returned quickly to at least baseline levels after turning the LLI off. Decreasing laser power to 10 mW reduced spike width to a lesser extent, suggesting laser power dependence of this phenomenon. These data suggest that LLI-660 regulates different aspects of neuronal excitability in cortical neurons in a layer-dependent manner possibly by affecting different voltage-gated ion channels.

Pulsed Nd: YAG laser induces pulpal analgesia: a randomized clinical trial

This double-blind, randomized, clinical trial investigated the effectiveness and underlying mechanism of neural inhibition of pulsed Nd:YAG laser induction of pulpal analgesia compared with 5% EMLA anesthetic cream. Forty-four paired premolars from 44 orthodontic patients requiring bilateral premolar extraction from either dental arch were randomly assigned to the 'Laser plus Sham-EMLA' or 'EMLA plus Sham-Laser' treatment group. Analgesia was tested by an Electric Pulp Tester (EPT) and the cutting of a standardized cavity, which was terminated when participants reported sensitivity, and Visual Analogue Scale (VAS) and numbness were recorded. Statistical analyses were done by paired t test, McNemar's test, and a chi-squared test (p < 0.05). Sixty-eight percent of laser- and 59% of EMLA-treated teeth had completed cavities with statistically significant EPT increases above baseline. No significant within-patient differences were found for either group. No laser-treated participants reported numbness. The trial confirmed that the pulsed Nd:YAG laser effectively induced pulpal analgesia, by suppression of intradental nerve responses to electrical and mechanical stimuli. Such a laser provides an alternative for dental pain management (ANZ-Clinical Trial Registry: N12611001099910).

Surgical lasers and hard dental tissue

The cutting of dental hard tissue during restorative procedures presents considerable demands on the ability to selectively remove diseased carious tissue, obtain outline and retention form and maintain the integrity of supporting tooth tissue without structural weakening. In addition, the requirement to preserve healthy tissue and prevent further breakdown of the restoration places the choice of instrumentation and clinical technique as prime factors for the dental surgeon. The quest for an alternative treatment modality to the conventional dental turbine has been, essentially, patient-driven and has led to the development of various mechanical and chemical devices. The review of the literature has endorsed the beneficial effects of current laser machines. However utopian, there is additional evidence to support the development of ultra-short (nano- and femto-second) pulsed lasers that are stable in use and commercially viable, to deliver more efficient hard tissue ablation with less risk of collateral thermal damage. This paper explores the interaction of laser energy with dental hard tissues and bone and the integration of current laser wavelengths into restorative and surgical dentistry.

Effects of Er:YAG and Nd:YAG lasers on dentin permeability in root surfaces: a preliminary in vitro study

OBJECTIVE

This in vitro study evaluated the effects of Nd:YAG and Er:YAG lasers on reducing dentin permeability by sealing opened tubules.

BACKGROUND DATA

According to hydrodynamic theory, dentine hypersensitivity occurs when dentin is exposed with tubules opened. Consequently, a painful sensation occurs due to an intensification of the dentinal permeability. Treatment, therefore, should be based on a decrease of this permeability, achieved by the obliteration of dentinal tubules. The Nd:YAG laser is known for its capacity to seal dentinal tubules; however, few studies concerning treatment with Er:YAG laser are available.

METHODS

The Nd:YAG laser was used, based on two parameters: (A) 1.0 W, 10 Hz, and (B) 1.5 W, 15 Hz. The Er:YAG laser was used at 60 mJ, 2 Hz, four applications of 20 sec each, at 6 mm from the surface. After irradiation, all samples were immersed in 1% Rodamine B dye solution, in order to evaluate the penetration of the dye solution and observe the decrease/increase of dentinal permeability after the laser treatment.

RESULTS

The laser conditions used in the present study decreased the permeability as follows: (a) when using the Er:YAG laser at 60 mJ, 2 Hz in 26.05%, and (b) when using the Nd:YAG laser at 1.5 W, 15 Hz in 19.03%--with no statistical difference between them. Additionally, the Nd:YAG laser at 1.0 W, 10 Hz, decreased permeability in 4.59%, with a smaller effect.

CONCLUSIONS

According to the results of this in vitro study, the Er:YAG laser at 60 mJ, 2 Hz, and the Nd:YAG laser at 1.5 W, 15 Hz are useful for decreasing dentin permeability.

Usefulness of low-level laser for control of painful stomatitis in patients with hand-foot-and-mouth disease

OBJECTIVE

The aim of this study was to evaluate the usefulness of low-level laser therapy (LLLT) for the control of painful stomatitis in patients with hand-foot-and-mouth disease (HFMD).

BACKGROUND DATA

LLLT has been successfully applied to various painful oral mucosal diseases, although there have been few reports on LLLT for HFMD patients.

MATERIALS AND METHODS

Through a randomized double-blind placebo controlled trial, the painful period of HFMD stomatitis was compared between the LLLT group (n=11) and the placebo LLLT one (n=9), which had similar clinical backgrounds. The LLLT parameters supplied were as follows: wavelength of 830 nm, power of 30 mW, frequency of 30 Hz, and energy output of 1.1 J/cm2. Acceptability and safety of the treatment were also evaluated.

RESULTS

The painful period was shorter in the LLLT group (4.0 +/- 1.3 days) than in the placebo LLLT one (6.7 +/- 1.6 days) with a statistically significant difference (p<0.005). The treatment was judged acceptable for 90.0% (18 of 20) of patients. No adverse events were observed in any cases.

CONCLUSION

LLLT is a useful method to control HFMD stomatitis by shortening the painful period, with its high acceptability and lack of adverse events.