Laser Application in Dentistry: Irradiation Effects of Nd:YAG 1064 nm and Diode 810 nm and 980 nm in Infected Root Canals-A Literature Overview

Thermal Effects on Dental Pulp during Laser-Assisted Bleaching Procedures with Diode Lasers in a Clinical Study

Background In the current cosmetics industry, bleaching is often associated with lasers. However, such treatment also harbors risks. Tooth death is observed at pulpal temperature increases ≥5.6 °C. Therefore, it seems important to investigate the effects of using different lasers. The aim of this study was to determine pulpal temperature increases at different laser parameters during bleaching by modeling a realistic environment and to compare the temperature recording using a thermocouple and thermal camera. The authors assumed that there are laser settings for the lasers used at which the pulpal temperature increases are <5.6 °C and that the temperature recordings with thermocouples and thermal cameras differ only minimally. Methods Human teeth were used, which were extracted for dental reasons. During experiment, teeth were bleached conventionally and by laser activation at 940 nm, 445 nm, and 970 nm. The temperature in the pulp was recorded using thermocouples. In a second setup, longitudinally halved teeth were bleached, while the temperature in the pulp was recorded with a thermocouple and thermal camera. Descriptive statistics were used. The significance level is 0.05. Results In addition to conventional bleaching, temperature increases <5.6 °C were observed for bleaching at 940 nm 1.5 W, at 445 nm 0.3 W, and at 970 nm 0.5 W. For bleaching procedures using 940 nm 7 W, 940 nm 2 W, 445 nm 0.5 W, and 970 nm 1 W, the temperature increase was ≥5.6 °C. Significant differences (p < 0.05) were found in the maximum temperature increases (°C) between all groups. Temperature recordings using a thermocouple and thermal camera differed by about 2.3 °C. The working hypotheses were confirmed. Conclusion With laser bleaching, attention must be paid to the type of laser, its power, and the time in order to avoid excessive overheating of the dental pulp.

Effects of Nd: YAG laser on tumour necrosis factor-alpha, interleukin-1beta and interferon-gamma levels in teeth with apical periodontitis: A clinical study

This study aimed to evaluate the levels of tumour necrosis factor-alpha (TNF-α), interleukin-1beta (IL-1β) and interferon-gamma (IFN-γ) with asymptomatic apical periodontitis (AP). A total of 60 participants were randomly divided into two groups: the conventional irrigation (control) and the Nd: YAG laser irradiation. The interstitial fluids were obtained after root canal cleaning (day 0) and 1 week later (day 7). The TNF-α, IL-1β and IFN-γ levels were assayed using the enzyme-linked immunosorbent assay. The Mann-Whitney U, continuity correction chi-square, Pearson chi-square and Fisher exact tests were used. An increased level of cytokines on day 7 in the control group was observed, without statistically significant differences (p > 0.05). All cytokine levels decreased over time in the laser group. Only the IL-1β level showed a significant difference (p < 0.05). Nd: YAG irradiation has a positive effect on decreasing the proinflammatory cytokine level and may help to control infection in teeth with AP.

Evaluation of Er:YAG and Er,Cr:YSGG lasers on intraradicular bonding using modified glass fiber tips

The aim of this study was to determine whether erbium laser irradiation emitted by modified glass-fiber tips would improve the intraradicular bonding of fiber posts. Forty human canines were endodontically treated and prepared for fiber-post placement. Roots were divided into five groups (n=8); according to the laser-tip combinations (2,940 nm Er:YAG and 2,780 nm Er,Cr:YSGG). Non-irradiated root canals served as control. Posts were cemented with self-adhesive resin cement and subjected to push-out test. Failure modes were characterized, and intraradicular bonded interfaces were analyzed by SEM and submitted to nanoleakage evaluation. Data were analyzed by two-way ANOVA and Tukey test (α=0.05). No significant differences were observed in cervical and middle sections (p>0.05), while significantly higher bond strengths were observed in apical sections (p<0.05). Laser irradiation reduced adhesive failures, cement-dentin gap formation, and nanoleakage apically. Laser-irradiation protocols employing end- or radial-firing tips improved bonding to apical intraradicular dentin contributing to more uniform bonded interfaces.

Application of three-dimensional reconstruction technology in dentistry: a narrative review

BACKGROUND

Three-dimensional(3D) reconstruction technology is a method of transforming real goals into mathematical models consistent with computer logic expressions and has been widely used in dentistry, but the lack of review and summary leads to confusion and misinterpretation of information. The purpose of this review is to provide the first comprehensive link and scientific analysis of 3D reconstruction technology and dentistry to bridge the information bias between these two disciplines.

METHODS

The IEEE Xplore and PubMed databases were used for rigorous searches based on specific inclusion and exclusion criteria, supplemented by Google Academic as a complementary tool to retrieve all literature up to February 2023. We conducted a narrative review focusing on the empirical findings of the application of 3D reconstruction technology to dentistry.

RESULTS

We classify the technologies applied to dentistry according to their principles and summarize the different characteristics of each category, as well as the different application scenarios determined by these characteristics of each technique. In addition, we indicate their development prospects and worthy research directions in the field of dentistry, from individual techniques to the overall discipline of 3D reconstruction technology, respectively.

CONCLUSIONS

Researchers and clinicians should make different decisions on the choice of 3D reconstruction technology based on different objectives. The main trend in the future development of 3D reconstruction technology is the joint application of technology.

Analyze the clinical effect of YAG laser combined with sodium hypochlorite in root canal treatment of pulpitis

OBJECTIVE

To compare and analyze the clinical therapeutic effects of sodium hypochlorite combined with Nd: YAG laser and sodium hypochlorite alone for root canal disinfection in patients with pulpitis.

METHODS

Patients with pulpitis were divided into control group and observation group according to random number table method. Both groups received root canal treatment, while the control group received root canal irrigation with 1% sodium hypochlorite. The observation group was irrigated with 1% sodium hypochlorite combined with Nd: YAG laser. Periodontal index, inflammatory index, life quality score and bacterial infection clearance rate of the two groups were compared before and 3 months after treatment.

RESULTS

The total effective rate of the observation group was 95.35%, which was higher than that of the control group 79.07% (p < .05). After 3 months of treatment, the periodontal index and inflammation level of both groups decreased, and the observation group was lower than that in the control group (p < .05). The life quality score and infection clearance rate of observation group were significantly higher than control group (p < .05).

CONCLUSION

Compared with root canal irrigation with 1% sodium hypochlorite alone, sodium hypochlorite combined with Nd: YAG laser for root canal disinfection can significantly improve the therapeutic effect, relieve inflammatory reaction, and decrease bacterial infection.

Efficiency of diode laser in control of post-endodontic pain: a randomized controlled trial

OBJECTIVES

As post-endodontic pain control is one of the main targeted addressed in endodontics, our aim was delignated to compare two different methods for low-level laser application utilizing diode laser: low-level laser therapy (LLLT) and laser-activated irrigation (LAI) in the control of post-endodontic pain.

MATERIALS AND SUBJECTS

A total of 180 patients received single-visit root canal treatment; they were randomly allocated into 3 equal groups. Group I received LAI, group II received LLLT, and group III served as control with normal root canal treatment and mock laser intervention (ML group). Postoperative pain was recorded using visual analogue scale (VAS) after 24, 48, and 72 h. Data were tabulated and statistically analyzed.

RESULTS

At 24 h, there was a statistically significant difference between median pain scores in the three groups (P value < 0.001) with ML group scored highest score followed by LAI and then LLLT group. At 48 h, there was a statistically significant difference between the three groups (P value < 0.001), with ML group scoring highest median pain scores while LLLT and LAI showed statistical insignificant scores. At 72 h, there was no statistically significant difference between the 3 groups (P value = 0.179).

CONCLUSION

LLLT is superior to LAI and ML group in the control of immediate postoperative pain after 24 h while after 48 h both LAI and LLLT were equally effective, but they still showed significant differences when compared to ML group.

CLINICAL RELEVANCE

Diode laser can be used by clinicians as it decreases the post-endodontic pain in patients with symptomatic apical periodontitis undergoing endodontic treatment.

Analysis of Temperatures Generated during Conventional Laser Irradiation of Root Canals-A Finite Element Study

The success of endodontic treatment is dependent on the removal of bacteria. A modern strategy to reduce bacterial load is laser irradiation. During this procedure, there is a local increase in temperature with possible side effects. The aim of this study was to determine the thermal behavior of a maxillary first molar when performing the conventional irradiation technique using a diode laser. For this study, a 3D virtual model of a maxillary first molar was created. The preparation of the access cavity, the rotary instrumentation of the palatal root canal and the laser irradiation protocol were simulated. The model was exported in a finite element analysis program where the temperature and heat flux were studied. Temperature and heat flux maps were obtained, and the temperature increase on the internal wall of the root canal was analyzed. The maximum temperature value exceeded 400 °C and was maintained for less than 0.5 s. The obtained temperature maps support the bactericidal effect of diode laser and the limitation of damage to surrounding tissues. On internal root walls, the temperature reached several hundred degrees Celsius, but for very short durations. Conventional laser irradiation is an adjuvant method of decontamination of the endodontic system.

Efficacy of Potassium Titanyl Phosphate Laser and Sodium Hypochlorite on Postoperative Pain Intensity Following Pulpotomy in Teeth with Symptomatic Irreversible Pulpitis: A Randomized Clinical Trial

Introduction: This study evaluated the postoperative pain intensity in permanent teeth with symptomatic irreversible pulpitis treated by pulpotomy using physiological saline, sodium hypochlorite (NaOCl), or the potassium titanyl phosphate (KTP) laser. Materials and methods: Ninety patients diagnosed with symptomatic irreversible pulpitis in permanent molars were randomly divided into three groups according to the pulpotomy procedures. Preoperative pain levels were recorded. Complete hemostasis was achieved with physiological saline (control group), NaOCl, or the KTP laser after initial bleeding control. Patients were asked to mark their pain level on the visual pain scale at 6, 24, 48, and 72 h and 7 and 30 days depending on the severity of pain. The permanent restoration was completed after 7 days. Data were statistically analyzed using Kruskal-Wallis, Mann-Whitney U, Friedman, and Bonferroni tests at a significance level of p < 0.05. Results: According to the present study, the statistical difference between the groups in terms of preoperative pain and percussion pain levels was insignificant (p > 0.05). There was no significant difference between groups in terms of demographic data (p > 0.05). The postoperative pain level of the KTP laser group was significantly lower at 6 h compared with the saline group (p < 0.05). There was no significant difference between groups in terms of the postoperative pain level at other time intervals (p > 0.05). The highest pain scores were observed in all groups at 6 h (p < 0.05). Conclusions: The KTP laser can be preferred primarily for reducing postoperative pain in pulpotomy treatments. The KTP laser or NaOCl-assisted pulpotomy can be an effective treatment for pain reduction in permanent teeth with symptomatic irreversible pulpitis. This report is registered at clinicaltrials.gov (ID: NCT05424796).

Antimicrobial and cleaning effects of ultrasonic-mediated plasma-loaded microbubbles on Enterococcus faecalis biofilm: an in vitro study

BACKGROUND

Enterococcus faecalis (E. faecalis) is the most frequently isolated bacteria from teeth with root canal treatment failure. This study aims to evaluate the disinfection effect of ultrasonic-mediated cold plasma-loaded microbubbles (PMBs) on 7d E. faecalis biofilm, the mechanical safety and the mechanisms.

METHODS

The PMBs were fabricated by a modified emulsification process and the key reactive species, nitric oxide (NO) and hydrogen peroxide (H₂O₂) were evaluated. The 7d E. faecalis biofilm on human tooth disk was constructed and divided into the following groups: PBS, 2.5%NaOCl, 2%CHX, and different concentrations of PMBs (10⁸ mL^-1, 10⁷ mL^-1). The disinfection effects and elimination effects were verified with confocal laser scanning microscopy (CLSM) and scanning electron microscopy (SEM). Microhardness and roughness change of dentin after PMBs treatment were verified respectively.

RESULTS

The concentration of NO and H₂O₂ in PMBs increased by 39.99% and 50.97% after ultrasound treatment (p < 0.05) respectively. The CLSM and SEM results indicate that PMBs with ultrasound treatment could remove the bacteria and biofilm components effectively, especially those living in dentin tubules. The 2.5% NaOCl presented an excellent effect against biofilm on dishes, but the elimination effect on dentin tubules is limited. The 2% CHX group exhibits significant disinfection effect. The biosafety tests indicated that there is no significant changes on microhardness and roughness after PMBs with ultrasound treatment (p > 0.05).

CONCLUSION

PMBs combined with ultrasound treatment exhibited significant disinfection effect and biofilm removal effect, the mechanical safety is acceptable.

Does luminosity and smear layer influence 810 nm laser energy transmission through human dentine?

PURPOSE

The aim of this study was to evaluate the influence of luminosity values and smear layer on transmission characteristics of 810 nm near infrared laser energy through dentine, using extracted human teeth.

METHODS

A total of 200 teeth treated with endodontic medicaments to cause discolouration (Ledermix, Doxypaste or Odontopaste) were selected, to give a range of values for tooth shade (luminosity values). Sectioned teeth had smear layer created or removed. Near-infrared laser energy transmission was assessed using an 810 nm diode laser (90 mW, CW mode) with the tip placed at 2 mm and 4 mm from the external root surface, and a laser power metre.

RESULTS

Both tooth shade and smear layer had independent attenuating effects. Transmission of laser energy was significantly lower in teeth with darker shades. There was a strong positive correlation between relative luminosity (lighter tooth colour) and transmitted laser power (r = 0.9271 for the Spearman rank correlation, P = 0.0022). When a smear layer was present, this significantly reduced the transmission of laser energy through the sample, compared to when no smear layer was present.

CONCLUSION

The results of this laboratory study highlight the attenuating influence of a darker tooth shade and the presence of smear layer on the transmission of 810 nm light when directed onto the surface of human dentine. Such effects may be relevant to photo biomodulation, Photodynamic Therapy and other dental laser treatments.

Push-out bond strength of two calcium silicate-based cements used for repair of artificial furcal perforation following different power outputs of Nd:YAG laser

Proper bond strength of endodontic materials is an essential factor in the final success of root canal treatments, including perforation repairs. This study was designed to evaluate the effect of two power outputs of Nd:YAG laser (1064 nm) on push-out bond strength (PBS) of ProRoot mineral trioxide aggregate (MTA) and calcium-enriched mixture cement (CEM Cement) in the repair of artificial furcal perforations. This ex vivo study enrolled 66 extracted human molars. After preparing the access cavity, perforations were created on the floor of the pulp chamber with a diameter of 1.4 mm. The teeth were randomly distributed into the following six groups according to the repair material (MTA and CEM) and power output of laser irradiation (1 W and 1.5 W); A: MTA (case), B: CEM (case), C: Nd:YAG (1 W)/MTA, D: Nd:YAG (1 W)/CEM, E: Nd:YAG (1.5 W)/MTA, and F: Nd:YAG (1.5 W)/CEM. Then, a universal testing machine was utilized to assess the PBS. Data analysis was performed using ANOVA and T tests. Significant level was considered at P < 0.05. The highest mean ± SD of PBS was noted in Group Nd:YAG (1 W)/MTA (58.92 ± 36.13), followed by Nd:YAG (1.5 W)/MTA > Nd:YAG (1.5 W)/CEM > Nd:YAG (1 W)/CEM > MTA > and CEM. A significant difference was noted between laser and non-laser applications (P < 0.05). However, the increase of power output from 1 to 1.5 W had no significant influence on PBS (P > 0.05). The PBS of MTA groups was always significantly greater than that of CEM groups (P < 0.05). Although Nd:YAG laser irradiation positively influenced on PBS values in both material studied, increasing power output was not effective.

Reactive Oxygen Species Enlightened Therapeutic Strategy for Oral and Maxillofacial Diseases-Art of Destruction and Reconstruction

Reactive oxygen species (ROS) are byproducts of cell metabolism produced by living cells and signal mediators in biological processes. As unstable and highly reactive oxygen-derived molecules, excessive ROS production and defective oxidant clearance, or both, are associated with the pathogenesis of several conditions. Among them, ROS are widely involved in oral and maxillofacial diseases, such as periodontitis, as well as other infectious diseases or chronic inflammation, temporomandibular joint disorders, oral mucosal lesions, trigeminal neuralgia, muscle fatigue, and oral cancer. The purpose of this paper is to outline how ROS contribute to the pathophysiology of oral and maxillofacial regions, with an emphasis on oral infectious diseases represented by periodontitis and mucosal diseases represented by oral ulcers and how to effectively utilize and eliminate ROS in these pathological processes, as well as to review recent research on the potential targets and interventions of cutting-edge antioxidant materials. The PubMed, Web of Science, and Embase databases were searched using the MesH terms "oral and maxillofacial diseases", "reactive oxygen species", and "antioxidant materials". Irrelevant, obsolete, imprecise, and repetitive articles were excluded through screening of titles, abstracts, and eventually full content. The full-text data of the selected articles are, therefore, summarized using selection criteria. While there are various emerging biomaterials used as drugs themselves or delivery systems, more attention was paid to antioxidant drugs with broad application prospects and rigorous prophase animal experimental results.

5-Aminolevulinic Acid and Red Led in Endodontics: A Narrative Review and Case Report

The present study aims to discuss the main factors involving the use of 5-aminolevulinic acid together with red LED light and its application in endodontic treatment through a narrative review and a case report. Persistence of microorganisms remaining on chemical-mechanical preparation or intracanal dressing is reported as the leading cause of failure in endodontics. Photodynamic therapy has become a promising antimicrobial strategy as an aid to endodontic treatment. Being easy and quick to apply, it can be used both in a single session and in several sessions, as well as not allowing forms of microbial resistance. 5-aminolevulinic acid in combination with red LED light has recently been studied in many branches of medicine, with good results against numerous types of bacteria including Enterococuss faecalis. The case report showed how bacterial count of CFU decreased by half (210 CFU/mL), after 45 min of irrigation with a gel containing 5% of 5-aminolevulinic acid compared to the sample before irrigation (420 CFU/mL). The subsequent irradiation of red LED light for 7 min, the bacterial count was equal to 0. Thus, it is concluded that the use of 5-aminolevulinic acid together with red LED light is effective in endodontic treatment.

Impacted Palatal Canines and Diode Laser Surgery: A Case Report

Introduction

Maxillary canine is the most frequent dental element that could likely remain impacted in the bone structure, with a percentage between 1 and 5%. This study presents a case report using a diode laser for surgical-orthodontics disinclusion of a palatal mucosal impacted permanent left upper canine (2.3) and the simultaneous application of an orthodontic bracket.

Methods

After cementation of the trans-palatal bar to the upper first molars with a hook for orthodontic traction, local anaesthesia with articaine was performed, followed by surgical operculectomy using a diode laser (810 nm wavelength, continuous wave mode with a power output of 3 W, and a 0.4 mm diameter optical fiber), and the orthodontic bracket with a passive metal looped ligature was applied. Subsequently, active elastic traction was applied on 2.3 and the upper arch was bonded for the application of a series of orthodontic wires, lace-back, and metal ligatures. A progressive reactivation of the elastic traction and extraction of 6.3 was necessary to translate the canine into the correct arch position.

Results

Diode laser surgical-orthodontic disinclusion of impacted upper canine was performed successively, resulting in a dry surgical field ideal for orthodontic bracket adhesion. No pain and no swelling have been reported from the patient. The orthodontic treatment allowed the canine to be moved to the correct position in the arch.

Conclusions

This case showed that the diode laser is a valid alternative for the surgical-orthodontic disinclusion of an included tooth element.

Root canal cleaning in roots with complex canals using agitated irrigation fluids

The internal topography of the root canal is complex, especially for the mesial root of the permanent first molar. In response to such challenges, enhanced irrigation protocols have been developed, using laser pulses to agitate fluids and enhance the removal of microbial deposits. The aim of this laboratory study was to assess the effectiveness of laser agitation of sodium hypochlorite in removing multispecies biofilms grown in the mesial root of the permanent first molars. The five agitation groups (N = 12 roots for each) were: 940 nm diode laser (superpulsed mode, 50 μs/pulses at 20 Hz using 20 mJ/pulse); 1064 nm Nd: YAG laser (200 μs/pulse at 20 Hz using 20 mJ/pulse); 2940 nm Er: YAG laser (50 μs/pulse at 15 Hz using a 400/14 conical tip in the SWEEPS protocol, with 20 mJ/pulse); passive ultrasonic agitation at 28 kHz (positive control); and irrigation with a 27-gauge side vented needle for 2 min per canal (negative control). Biofilm removal was assessed by confocal microscopic imaging of root slices at 1, 4 and 7 mm from the root apex. None of the tested methods were effective in completely eradicating biofilm from the most confined regions of the root canal system. The greatest challenge was cleaning the isthmus regions. There was a positive correlation between canal cleaning and isthmus cleaning, suggesting that increased effectiveness in cleaning root canal walls is associated with more effective isthmus cleaning. Wider and narrow isthmuses were cleaned better than long and narrow isthmuses.

Comparison of the Treatment Efficacy of Endo-Perio Lesions Using a Standard Treatment Protocol and Extended by Using a Diode Laser (940 nm)

Marginal and periapical periodontal diseases cause massive destruction of tooth tissues and surrounding tissues, such as alveolar bone and maxillary sinus floor, visible on radiographs. Lesions involving the apical and marginal periodontium are endo-perio (EPL) lesions. This study aimed to compare the treatment efficacy of endo-perio lesions using a standard treatment protocol and a standard diode laser-assisted treatment protocol. The 12 patients were divided into the study (a) and control (b) group. Periodontal indices, tooth vitality and mobility, occlusal status, and radiographic diagnosis were evaluated. Standard EPL treatment was then performed-without (a) and with (b) the use of diode laser (940 nm). Again, after six months, the above-mentioned parameters were evaluated and compared. The treatment of endo-perio lesions is a significant challenge for modern dentistry. Diode lasers are increasingly used in addition to traditional treatment methods. The conventional use of a 940 nm diode laser with an average power of 0.8 W in pulsed mode allows for the depth of periodontal pockets to be reduced. In addition, the use of a diode laser has a significant effect on tooth mobility and reduces bone loss.

Impact of Adjunctive Laser Irradiation on the Bacterial Load of Dental Root Canals: A Randomized Controlled Clinical Trial

Successful root canal treatment depends on the adequate elimination of pathogenic bacteria. This study evaluated the effectiveness of a novel 445-nm semiconductor laser in reducing bacteria after chemomechanical root canal treatment. Microbiological specimens from 57 patients were collected after emergency endodontic treatment, in the following sequence: 1, removal of the temporary filling material; 2, chemomechanical treatment; 3, rinsing with sodium hypochlorite (3%) along with one of three adjuvant protocols (n = 19 in each group). The adjuvant procedures were: (a) sodium hypochlorite rinsing alone (3%); (b) laser irradiation; (c) combined sodium hypochlorite rinsing and laser irradiation. The diode laser was set to 0.59 W in continuous-wave mode (CW) for 4 × 10 s. After the flooding of the root canal with saline, specimens were collected using paper points and analyzed microbiologically. Statistically significant reductions in the bacterial load were observed in all three groups (p < 0.05): 80.5% with sodium hypochlorite rinsing alone and 58.2% with laser therapy. Both results were lower than with the combination of sodium hypochlorite rinsing and 445-nm laser irradiation, at 92.7% (p < 0.05). Additional disinfection of the root canal can thus be achieved with 445-nm laser irradiation after conventional chemical disinfection with sodium hypochlorite solution.

Effect of Nd:YAG and Er:YAG laser tooth conditioning on the microleakage of self-adhesive resin cement

Statement of problem

Recently, the application of lasers in restorative dentistry has been considered for cavity preparation and surface conditioning of enamel and dentin. However, the beneficial effects of cavity surface conditioning by laser irradiation on microleakage are still controversial.

Purpose

This study aimed to compare the microleakage of self-etch adhesive resin cement with Nd:YAG and Er:YAG laser tooth surface conditioning to evaluate the capabilities of these lasers as a reliable replacement for etching cavities.

Materials and methods

Fifty-four class V cavities were prepared on the buccal and lingual surfaces of 27 sound human premolar teeth. The samples were randomly divided into three groups (n = 18): group 1: no conditioning; group 2: conditioned with Er:YAG laser (2940 nm, 10 Hz, 1.2 W); group 3: conditioned with Nd:YAG laser (1064 nm, 1.5 W, 10 Hz). All the cavities were filled with self-adhesive resin cement. After curing and polishing, the samples were immersed in 2% methylene blue solution for 24 h, and after being embedded in acrylic resin, they were sectioned longitudinally and examined under a stereomicroscope. The data were submitted to Kruskal–Wallis and Dunn tests (α = 0.05).

Results

The lowest microleakage mean rank was observed in the Er:YAG group (19.19), and the highest mean rank was noted in the Nd:YAG group (33.08), with significant differences between the three groups (P-value = .01). Pairwise comparisons demonstrated significant differences between the Er:YAG and Nd:YAG groups (P-value = .004) as well as Er:YAG and no conditioned groups (P-value =.022).

Conclusion

The irradiation of the Er:YAG laser (2940 nm, 10 Hz, 1.2 W) on cavity surface resulted in less marginal microleakage of self-etch adhesive resin cement restorations compared to Nd:YAG (1064 nm, 1.5 W, 10 Hz) and no conditioning groups.

Establishment of Pulp Damage Repair Models in Miniature Pigs Using Diode Lasers

Objective: To establish a controlled pulp damage repair model in miniature pigs by using a diode laser. Background: Laser is a novel kind of controllable energy, and it is widely used in dentistry. Methods: The premolars of four 24- to 28-month-old miniature pigs were divided into three laser groups, according to the output powers of a diode laser, and the nonirradiated first molars acted as controls. The teeth in laser groups were irradiated under three parameters (output powers 1.5, 2.5, 4 W, continuous wave, frequency 50 Hz for 60 sec). The dental and gingival morphology was observed at 0, 7, 14, and 21 days after laser irradiation. The animals were sacrificed for qualitative and quantitative pulp histopathological analysis. Results: The three laser groups present no seriously irreversible dental and gingival damage. In the 1.5-W group, dental pulp exhibited angiectasis and hyperemia with no inflammation, and did not significantly differ with the control groups at 21 days (p > 0.05). In the 2.5-W group, pulpal inflammation was highest at 7 days and then decreased significantly at 21 days, and the tissue repair appeared at 14 days (p < 0.05). In the 4-W group, pulpal inflammation was significantly highest at 7 days, with an increase in the degree of tissue repair (p < 0.05). Conclusions: The output power of 1.5 W developed a reversible pulpitis model; the output powers of 2.5 and 4 W within 7 days led to the development of irreversible pulpitis models, which proceeded as chronic pulpitis with obvious tissue repair.

Bactericidal effect of Er,Cr:YSGG laser irradiation on endodontic biofilm: An ex vivo study

AIM

This ex vivo study aimed to evaluate the of Er,Cr:YSGG laser effectiveness in the decontamination of an endodontic biofilm.

MATERIALS AND METHODS

Seventy-three single rooted human teeth, freshly were chosen. Each tooth was exposed to four associated species in an endodontic biofilm (Enterococcus faecalis, Streptococcus salivarius, Porphyromonas gingivalis, and Prevotella intermedia) and randomly allocated to one of the seven experimental groups. The group 1 (7 teeth) was used to finalize the reliable biofilm-forming technique. The groups 2 and 3 (15 teeth each group) were irradiated with two different Er;Cr:YSGG laser settings (0,75 W - 40 Hz and 4 W - 40 Hz, respectively). The groups 4 and 5 (15 teeth each group) were irrigated with two different solutions and laser irradiated with the same settings (1,5 W - 15 Hz). The group 6 (6 teeth) was the control group treated only with 4 ml 2,5% NaOCl irrigation during 60 s.

RESULTS

The observations of group 2 and 3 specimens showed the ripeness of the biofilm with the presence of Enterococcus faecalis and Streptococcus salivarius in chains but in group 3 thermal edge effects produced by the optic fiber in the canal walls were present. The group 4 specimens observation showed an average cleaning of the root canal walls while on the canal walls of group 5 samples the apical third presented several debris and smear layer and in the centre cracks and melting dentin of the radicular wall were observed.

CONCLUSION

In those experimental conditions, this study, demonstrated that Er,Cr:YSGG laser has a canals decontamination ability when associated to NaOCl irrigation.

Temperature Change from Diode Lasers in Oral Mucosa: An Ex Vivo Study

Objective: The aim of this ex vivo study was to assess the mean temperature change deep in tissue during diode laser (980 vs. 810 nm) irradiation using continuous and pulsed laser and initiated versus noninitiated tips. Background data: Previous studies have determined thermal effects of diode lasers on tissue damage but have yet to compare the incision qualities of 980 versus 810 nm diode lasers. Further studies need to be done to determine the efficiency of diode lasers to create a safer protocol for clinicians. Methods: Ninety-six incisions of 20 mm length were made in three bovine tongues using diode lasers (980 and 810 nm). Both continuous and pulsed modes were tested with initiated (using blue articulating paper) and noninitiated glass fibers (n = 12 per group). Thermocouples attached to LabChart^® software were used to measure mean temperature changes. Mean, standard deviations, and p values were conducted for each group to test the statistical significance (p < 0.05). Results: Quality of incisions were better using the initiated tips for both laser wavelengths. Pulsed mode with 810 nm diode laser produced the least mean temperature change in tissue. Overall, both pulsed and continuous mode showed similar thermal effects on tissue. Conclusions: Within the limitations of this study, noninitiated tips are responsible for diffuse irradiation in tissue and are associated with tissue temperature increase during surgery. Low incision quality was observed using noninitiated tips. The temperature changes seem to be dependent on the laser wavelength and are higher for 980 nm compared with 810 nm pulsed diode laser.

Evaluation of postoperative pain/discomfort after intracanal use of Nd:YAG and diode lasers in patients with symptomatic irreversible pulpitis and asymptomatic necrotic pulps: a randomized control trial

OBJECTIVES

This study aimed to investigate the ability of the diode and Nd:YAG lasers to decrease postoperative pain/discomfort after intracanal application in vital and devital endodontic cases.

MATERIAL AND METHODS

One hundred two patients with symptomatic irreversible pulpitis and asymptomatic necrotic pulps were selected and randomly divided into three groups. After chemomechanical preparation, Nd:YAG and diode laser was applied to first and second groups for final treatment of the root canals. In the control group, no further disinfection protocol was performed upon traditional procedures. Then all the teeth were obturated in the same appointment. Pre- and postoperative pain were recorded using the VAS at 0, 12th, 24th, 48th, and 72nd hours following the treatment Kruskal-Wallis and Dunn test.

RESULTS

VAS scores were significantly the most at 12-h period compared with other time periods after treatment for all groups. There was no significant difference among Nd:YAG laser, diode laser, and control groups in non-vital cases (p > 0.05). In vital cases, Nd:YAG laser group represented significantly fewer scores compared with diode laser and control groups at 48-h period (p < 0.05).

CONCLUSIONS

The processes involving the use of Nd:YAG and diode lasers after chemomechanical preparation was found to be equivalent in terms of postoperative pain intensity after completion of treatment in one session both in vital or non-vital cases except in vital cases in Nd:YAG group at 48 h.

CLINICAL RELEVANCE

Adjunct clinical use of Nd:YAG or diode lasers to traditional chemomechanical preparation did not cause any improvement or deterioration on postoperative discomfort and pain in patients with symptomatic irreversible pulpitis and asymptomatic necrotic pulps.

Effect of using diode laser on Enterococcus faecalis and its lipoteichoic acid (LTA) in chronic apical periodontitis

The purpose of this study was to evaluate the effect of diode laser irradiation on Enterococcus faecalis (E. faecalis) and its lipoteichoic acid (LTA). Ninety-six freshly extracted single-rooted teeth were divided into six groups, n = 8 per group. Groups 1, 2, 3, and 4 as laser group (810 nm PILOT™ Diode Laser, 400 μm fiber diameter, continuous mode, 30 s time) with powers at 1.0 W, 1.5 W, 2.0 W, and 2.5 W respectively. Group 5 or positive control group (3 ml of 1% sodium hypochlorite (NaOCl) irrigation) and group 6 or negative control group (3 ml of normal saline (0.9% NaCl) irrigation). Root canal samples were collected before and after receiving laser irradiation and irrigation solution. Cultivable bacteria were determined by counting the colony (CFU/ml). Evaluation of temperature on the external root surface of teeth was done with K type thermocouple using laser at different powers. Enzyme-linked immunosorbant assay (ELISA) was performed to measure the LTA levels and the correlations between E. faecalis count, LTA levels, and rise in temperature were observed using Pearson's correlation test. E. faecalis LTA was subjected to laser irradiation and its structural damage was examined by thin layer chromatography (TLC). Compared with the control groups, all laser groups showed a decreased colony counts and decreased LTA levels with statistically significant difference (p ˂ 0.05). The bactericidal effect and LTA reduction of laser was better at 2.5 W power. Laser at 2.5 W power had temperature rise of more than 7 °C which is beyond the safe thermal threshold level. No statistically significant correlation was found between E. faecalis count, levels of LTA, and rise in external root surface temperature (p ˃ 0.05). TLC results showed a structural damage in the glycolipid moiety of E. faecalis LTA. Diode laser can effectively reduce the E. faecalis count and its LTA levels.

Applications of Lasers in Refractory Periodontitis: A Narrative Review

OBJECTIVE

The purpose of the study is to evaluate the various lasers in dentistry and to investigate if it can be used for treatment of refractory periodontitis.

METHODS

The study followed partially the PRISMA guidelines as it is a narrative review. A number of articles were selected from a period of 1980 to 2020 from databases, PubMed, PubMed central, Cochrane and Scopus. Articles related to the effects of lasers on periodontitis both refractory and aggressive were investigated.

RESULTS

After reviewing the literature, 70 articles were found, related to application of lasers in periodontal diseases. Out of the 70, 11 articles pertained to the effect of laser for the treatment of Refractory and inflammatory periodontitis. 5 articles related to experimental animal models, one pertaining to in-vitro and six studies related to in-vivo in human cohorts.

DISCUSSION

It was found that lasers if used in controlled parameters by incorporating laser assisted treatment such as Photodynamic therapy and low level laser therapy can be of use as an adjunct therapy for treatment of refractory periodontitis. The use of different wavelengths in the initial and maintenance phase of periodontal disease plays a positive role. The presence of in-vitro and animal model studies is one of the limitation to this study. The available studies have shown marked reduction in inflammation and better clinical and microbiological parameters. The drawback of this study is the limited literature involving laser management for refractory periodontitis in human cohorts.

CONCLUSION

Different wavelengths of laser and choice of laser assisted periodontal treatment plays an important role in the overall progress and prognosis of periodontal disease activity.

Lithiasis of Minor Salivary Gland Mimicking a Venous Malformation: Contextual Diode Laser Photocoagulation and Excision

Sialolithiasis is the most common disease of the major salivary gland. Lithiasis of minor salivary gland, instead, is very rare. Diagnosis is often challenging as frequency, clinical appearance and symptoms are relatively unknown. We report on a case of minor salivary gland lithiasis of the cheek resembling a venous malformation and its management by diode laser.

Comparison of diode laser - Oral tissue interaction to different wavelengths. In vitro study of porcine periodontal pockets and oral mucosa

Background

The aim of this in vitro study was to evaluate the effect of diode lasers at different wavelengths and power settings in handmade incisions in periodontal pockets and in oral mucosa of porcine tissue considering thermal damage, necrosis and the affected area of the soft tissue.

Material and Methods

Combining the following laser wavelengths, 445nm, 532nm (KTP), 810nm, 980nm, 1064nm and 1470nm, and a power range from 0.5W to 2.0W in a continuous wave mode (CW), we made handmade incisions in porcine periodontal pockets and oral mucosa. After histological processing, we measured the area of ​​lost tissue, the area of ​​thermal damage and the area of ​​necrosis. Then, we performed ANOVA to evaluate the difference between groups and two-way ANOVA to identify the influence of the laser-type variables and the power on the results.

Results

We applied an ANOVA test to evaluate the results, where statistical analysis showed clear differences between the 1470nm and 810nm laser groups that refer to thermal damage and necrosis in the periodontal pocket surface. Regarding the oral mucosa surface, the 1064nm laser showed differences in the analysis of lost tissue. According to the applied power, all the variables we studied (lost tissue area, area of thermal damage and necrosis) showed higher values when using a power of 2.0W instead of 0.5W.

Conclusions

According to our results, the 810nm diode laser for oral soft-tissue biopsy using power ranges between 0.5W and 2W would be the best choice to avoid thermal damage in peri-incisional margins.

Key words:Laser surgery, soft tissue, diode laser, KTP laser, thermal damage, necrosis.

Therapeutic effect of laser on pediatric oral soft tissue problems: a systematic literature review

In recent years, extensive evidence has been published about usage of laser in oral lesions. The aim of the present study was to review the effectiveness of laser radiation in the treatment of pediatric oral soft tissue problems. The relevant keywords were searched in EBSCO, Medline (via Ovid), PubMed, Scopus, and Web of Science (WOS) databases. Then, eligible case series and controlled clinical trial studies, which published up to the end of 2018, were extracted and scrutinized. In this study, the age range of ≤ 21 years or the average age of ≤ 21 years was considered as the pediatric group. After limiting the search results, removing duplicate titles and eligibility evaluation, 17 papers were enrolled to the study (seven controlled clinical trials and ten case series). Er:YAG (2940 nm), CO₂ (10,600 nm), Er,Cr:YSGG (2780 nm), and diode (650, 660, and 975 nm) lasers indicated successful clinical results on mucocele excision, frenectomy, gingival incision and re-contouring, and treatment of vascular malformations. In addition, 660-nm diode laser radiation was an effective adjuvant treatment for halitosis and gingivitis induced by multi-bracket appliances. Reduction or absence of pain and bleeding, suitable homeostasis, reduction of operation time, less analgesic consumption, and antibacterial effect were among the advantages of the laser radiation in the studies. Laser as a main or adjuvant tool can have an effective role in surgical and non-surgical treatments of pediatric oral soft tissue problems. Conducting further randomized controlled trial studies on different soft tissue lesions can contribute to drawing better conclusions.

Evaluation of chemical and morphological changes in radicular dentin after different final surface treatments

The aim of this study was to evaluate the chemical and morphological effects of different lasers as a final surface treatment for endodontic therapy through energy dispersive X-ray spectroscopy (EDS) and scanning electron microscopy (SEM) respectively. Twenty-five maxillary canines were selected and instrumented with K3 system. Roots were randomly distributed into five groups (n = 5) according to the surface treatment: GI (distilled water), GII (NaOCl + EDTA), GIII (NaOCl + EDTA + 980 nm diode laser), GIV (NaOCl + EDTA+ 1,064 nm Nd:YAG laser), and GV (NaOCl + EDTA+ 2,780 nm Er, Cr:YSGG laser). Lasers were applied for 20 s and samples were bisected, exposing the treated surface and then subjected to elements quantification by EDS and morphological evaluation by scanning electron microscope (SEM). EDS data were submitted to ANOVA-two way, and SEM scores were submitted to two-way Kruskal-Wallis and Dunn's tests. The EDS analysis showed no difference for the chemical elements and Ca/P ratio between groups (p > .05). Statistical analysis showed more intense results for GV and less intense results for GI (p < .05). The GIII showed an amorphous organic matrix surface, while GV provided greater removal of intertubular dentin forming craters, and GIV promoted dentin fusion. The EDS method used in this study was not able to verify any chemical changes in root canal dentin; Nd:YAG, Er, Cr:YSGG, and 980 nm diode laser were capable of modifying the dentin morphology, correlating characteristics features for each one, which are essential clinical knowledge to establish the correct indication for each case. RESEARCH HIGHLIGHTS: EDS was not able to verify any chemical changes in root canal dentin after 980 nm diode, Nd:YAG and Er;Cr:YSGG laser treatments Nd:YAG, Er, Cr:YSGG, and 980 nm diode laser modified dentin morphology, correlating characteristics features for each one.

Effectiveness of photopolymerization in composite resins using a novel 445-nm diode laser in comparison to LED and halogen bulb technology

Challenges especially in the minimal invasive restorative treatment of teeth require further developments of composite polymerization techniques. These include, among others, the securing of a complete polymerization with moderate thermal stress for the pulp. The aim of this study is to compare current light curing sources with a blue diode laser regarding curing depth and heat generation during the polymerization process. A diode laser (445 nm), a LED, and a halogen lamp were used for polymerizing composite resins. The curing depth was determined according to the norm ISO 4049. Laser output powers of 0.1, 0.5, 1, and 2 W were chosen. The laser beam diameter was adapted to the glass rod of the LED and the halogen lamp (8 mm). The irradiation time was fixed at 40 s. To ascertain ΔT values, the surface and ground area temperatures of the cavities were simultaneously determined during the curing via a thermography camera and a thermocouple. The curing depths for the LED (3.3 mm), halogen lamp (3.1 mm) and laser_{(0.5/1 W)} (3/3.3 mm) showed no significant differences (p < 0.05). The values of ΔT_surface as well as ΔT_ground also showed no significant differences among LED, halogen lamp, and laser_{(1 W)}. The ΔT_surface values were 4.1_LED, 4.3_{halogen lamp}, and 4.5 °C for the laser while the ΔT_ground values were 2.7_LED, 2.6_{halogen lamp}, and 2.9 °C for the laser. The results indicate that the blue diode laser (445 nm) is a feasible alternative for photopolymerization of complex composite resin restorations in dentistry by the use of selected laser parameters.

Influence of Nd:YAG laser on the penetration of a bioceramic root canal sealer into dentinal tubules: A confocal analysis

OBJECTIVE

The aim of this in vitro study, is to evaluate the penetration of a bioceramic root canal sealer into dentinal tubules at 3 mm and 5 mm from the apex after Nd:YAG laser irradiation.

METHODS

Forty freshly extracted human mandibular premolars were prepared using Reciproc® and irrigated with 17% ethylenediaminetetraacetic acid (EDTA). Teeth were divided into 4 groups: group 1, obturated with control sealer (AH Plus®); group 2, obturated with bioceramic sealer (Endosequence BC Sealer®); group 3, Nd:YAG laser + control sealer (AH Plus®); and group 4, Nd:YAG laser + bioceramic sealer (Endosequence BC Sealer®). The samples were transversely sectioned 3 mm and 5 mm from the apex and examined using confocal laser scanning microscopy. Two parameters were measured: 1) sealer penetration into dentinal tubules of the root canal and 2) sealer penetration into the perimeter of the root canal walls.

RESULTS

Penetration analysis showed that bioceramic sealer had a higher penetration at depths of 3 and 5 mm than that of the control sealer, regardless of laser use (p <0.05). Perimeter analysis showed that there was no difference between both sealers at a depth of 3 mm (p <0.05), regardless of laser use. At a depth of 5 mm, bioceramic sealer and laser showed a greater perimeter of penetration (p <0.05) than the control sealer.

CONCLUSION

The use of Nd:YAG laser did not compromise the penetration of bioceramic sealer into dentinal tubules of root canals at 3 mm and 5 mm from the apex.

Evaluation of Antibacterial Efficiency of Different Root Canal Disinfection Techniques in Primary Teeth

BACKGROUND

A successful primary root canal treatment depends on effective shaping and cleaning the root canal system and finally filling it with a hermetic sealer. Clinically, roots of primary teeth are difficult to shape and the irrigation/disinfection protocol has great importance on prognosis.

OBJECTIVE

The present study evaluated the antibacterial efficiency of Endosafe (Orangedental GmbH & Co. KG), photo-activated disinfection (PAD; Orangedental GmbH & Co. KG), diode laser (Epic 10; Biolase, Inc.), ozone (O₃, Ozonytron; Biozonix, München, Germany), and sodium hypochloride applications in primary root canals that were infected with Enterococcus faecalis after standard mechanical instrumentation.

METHODS

The study was conducted on roots of 100 human primary molar teeth, which were extracted due to excessive caries. The roots were divided in 5 groups with 15 roots in each root disinfection protocol. In addition, 15 samples and 10 samples served as positive and negative controls, respectively. The Shapiro-Wilk test, the Kruskal-Wallis test and then by post hoc group comparisons with the Bonferroni-adjusted Mann-Whitney U test (unpaired observations) was used.

RESULTS

Sodium hypochlorite (NaOCl) exhibited the highest antibacterial effect (0 colony-forming units per mL). Diode laser irradiation was statistically more effective than the ozone, PAD, and Endosafe groups (p < 0.001). Endosafe, PAD, and ozone groups showed similar antibacterial effect (p > 0.05). Although not statistically significant, the Endosafe was more effective in reducing the bacterial count when compared with ozone and PAD.

CONCLUSIONS

The five tested irrigation systems were shown to be effective in disinfection of the E. faecalis-contaminated primary root canals and best results were obtained with 2.5% NaOCl and diode laser.

Dispersion of near-infrared laser energy through radicular dentine when using plain or conical tips

The aim of this study was to investigate the influence of tip design on patterns of laser energy dispersion through the dentine of tooth roots when using near-infrared diode lasers. Diode laser emissions of 810 or 940 nm were used in combination with optical fiber tips with either conventional plain ends or conical ends, to irradiate tooth roots of oval or round cross-sectional shapes. The lasers were operated in continuous wave mode at 0.5 W for 5 s with the distal end of the fiber tip placed in the apical or coronal third of the root canal at preset positions. Laser light exiting through the roots and apical foramen was imaged, and the extent of lateral spread calculated. There was a significant difference in infrared light exiting the root canal apex between plain and conical fiber tips for both laser wavelengths, with more forward transmission of laser energy through the apex for plain tips. For both laser wavelengths, there were no significant differences in emission patterns when the variable of canal shape was used and all other variables were kept the same (plain vs conical tip, tip position). To ensure optimal treatment effect and to prevent the risks of inadvertent laser effects on the adjacent periapical tissues, it is important to have a good understanding of laser transmission characteristics of the root canal and root dentine. Importantly, it is also essential to understand transmission characteristics of plain and conical fibers tips.

Evaluation of Antibacterial Efficacy of Photodynamic Therapy vs. 2.5% NaOCl against E. faecalis-infected Root Canals Using Real-time PCR Technique

Background

Bacteria like E. faecalis can produce intra- and extra-radicular biofilms. Theoretically, the adjustable penetration ability of lasers enables better access to root canal system. Therefore the aim of the present study was to compare the ability of photoactivated laser and 2.5% NaOCl irrigation solution to eliminate E. faecalis from the root canals by real-time PCR technique.

Material and Methods

Sixty extracted human upper central incisors were selected and sterilized in an autoclave. The root canals were infected with E. faecalis (PTCC 1237, Persian Type Culture Collection, Iran) and then incubated for 24 hours. The samples were randomly divided into 3 groups. No intervention was made in the control group (group 1). In group 2, laser therapy was performed with a power of 100 mW by diode laser for 120 seconds. In group 3, the canals were irrigated with 5 mL of 2.5% NaOCl; then all the samples were sonicated in 15 mL of normal saline in test tubes in order to isolate the bacteria. DNA extraction was performed followed by real-time PCR technique for all the samples.

Results

Inhibition of bacterial growth in all the experimental samples was significantly more than that in the control group. There was a significant difference between photodynamic therapy and 2.5% NaOCl. The effect of NaOCl in all the samples was better than photodynamic therapy. The results of the mean CT (cyclic threshold) were 40, 30.2 and 15.35 for 2.5% NaOCl, photodynamic therapy and control group, respectively.

Conclusions

Based on the results of this experimental study, 2.5% NaOCl eliminated E. faecalis from infected root canals more effectively compared to photodynamic therapy.

Key words:Photoactivated laser, Enterococcus faecalis, antibacterial agents, sodium hypochlorite.