Thermal effects of the Er:YAG laser on a simulated dental pulp: a quantitative evaluation of the effects of a water spray

Do erbium lasers promote changes in the tooth enamel during debonding of ceramic laminate veneers? A systematic review

The longevity of ceramic laminate veneers can be influenced by several factors, which can result in the need for a removal process. Laser removal has emerged as a good alternative to facilitate the procedure, and its repercussions on tooth enamel have been investigated. We aimed to evaluate the efficacy of erbium lasers for debonding ceramic laminate veneers without damaging the tooth enamel. This systematic review based on the PICOS model adhered to the PRISMA statement. The PubMed/MEDLINE, Web of Science, Embase, and Scopus databases were systematically searched until December 1, 2022, and 2902 studies were retrieved. After screening, four in vitro studies that analyzed the dental morphology using scanning electron microscopy, optical analysis, stereomicroscopy, or x-ray dispersion spectroscopy were included. The risk of bias was assessed using the Cochrane Collaboration tool. Our findings suggest that erbium lasers are useful for ceramic laminate veneer removal without damaging the tooth enamel. However, the removal is influenced by the type and thickness of ceramic and type of cement used. It could be concluded that the application of Erbium laser did not promote superficial changes in the dental enamel. This effect was observed in all analysis performed.

Heat generated during dental treatments affecting intrapulpal temperature: a review

INTRODUCTION

Heat is generated and transferred to the dentine-pulp complex during various dental procedures, such as from friction during cavity preparations, exothermic reactions during the polymerisation of restorative materials and when polishing restorations. For in vitro studies, detrimental effects are possible when intra-pulpal temperature increases by more than 5.5°C (that is, the intra-pulpal temperature exceeds 42.4°C). This excessive heat transfer results in inflammation and necrosis of the pulp. Despite numerous studies stating the importance of heat transfer and control during dental procedures, there are limited studies that have quantified the significance. Past studies incorporated an experimental setup where a thermocouple is placed inside the pulp of an extracted human tooth and connected to an electronic digital thermometer.

METHODS

This review identified the opportunity for future research and develop both the understanding of various influencing factors on heat generation and the different sensor systems to measure the intrapulpal temperature.

CONCLUSION

Various steps of dental restorative procedures have the potential to generate considerable amounts of heat which can permanently damage the pulp, leading to pulp necrosis, discoloration of the tooth and eventually tooth loss. Thus, measures should be undertaken to limit pulp irritation and injury during procedures. This review highlighted the gap for future research and a need for an experimental setup which can simulate pulp blood flow, temperature, intraoral temperature and intraoral humidity to accurately simulate the intraoral conditions and record temperature changes during various dental procedures.

Femtosecond laser dentistry for precise and efficient cavity preparation in teeth

High fluence focused femtosecond laser pulses were used to perform fast, high precision and minimally damaging cavity cutting of teeth at room temperature without using any irrigation or cooling system. The optimal ablation rates were established for both enamel and dentin, and the surfaces were assessed with optical and scanning electron microscopy, Raman spectroscopy and optical profilometry. No chemical change in the composition of enamel and dentin was observed. We explored temperature variations inside the dental pulp during the laser procedure and showed the maximum increase was 5.5°C, within the acceptable limit of temperature increase during conventional dental treatments.

Adipokines in dental pulp: physiological, pathological, and potential therapeutic roles

BACKGROUND

Hundreds of adipokines have been identified, and their extensive range of endocrine functions-regulating distant organs such as oral tissues-and local autocrine/paracrine roles have been studied. In dentistry, however, adipokines are poorly known proteins in the dental pulp; few of them have been studied despite their large number. This study reviews recent advances in the investigation of dental-pulp adipokines, with an emphasis on their roles in inflammatory processes and their potential therapeutic applications.

HIGHLIGHTS

The most recently identified adipokines in dental pulp include leptin, adiponectin, resistin, ghrelin, oncostatin, chemerin, and visfatin. They have numerous physiological and pathological functions in the pulp tissue: they are closely related to pulp inflammatory mechanisms and actively participate in cell differentiation, mineralization, angiogenesis, and immune-system modulation.

CONCLUSION

Adipokines have potential clinical applications in regenerative endodontics and as biomarkers or targets for the pharmacological management of inflammatory and degenerative processes in dental pulp. A promising direction for the development of new therapies may be the use of agonists/antagonists to modulate the expression of the most studied adipokines.

Multisensorial Assessment of Laser Effects on Shellac Applied on Wall Paintings

The assessment of five different laser treatments in the conservation of wall paintings was devised on the basis of the surface temperature monitoring by infrared thermography (IRT), ultraviolet-induced fluorescence-visible (UV-VIS) imaging, and optical coherence tomography (OCT). A series of yttrium-aluminum-garnet (YAG) lasers were tested for removal of shellac layers from wall painting mock-ups. The mock-ups were realized as buon fresco with different mineral based pigments (earths and iron oxide) on a lime- and sand-based mortar. After the carbonatation process, all the samples were treated with shellac (5% in ethanol). The effects of neodymium (Nd):YAG, holmium (Ho):YAG, and erbium (Er):YAG laser sources, in different operative modes, on average temperature of the surface, color, and morphology were inspected with complementary sensors. The results show the necessity to adopt a combined approach in establishing safe laser operating conditions to avoid any undesired effects induced on the artefacts by the laser treatments. We demonstrate, for the first time, the performance of the Ho:YAG laser in the removal of a conservation treatment.

Aerosols generation using Er,Cr:YSGG laser compared to rotary instruments in conservative dentistry: A preliminary study

Background

In restorative dentistry, the use of high-speed air turbine, which generates aerosols, can be associated with the transmission of airborne diseases. New laser technologies could be useful in reducing the amount of aerosols, but there is a lack of scientific research on this topic.

Material and Methods

This is a descriptive study to analyze the amount of aerosols produced after class I cavity preparation using high-speed air turbine (group 1) and Er,Cr:YSGG laser with two different parameters (groups 2 and 3). Fluorescein dye was incorporated into the coolant reservoir in order to visualize the production of aerosols during each procedure. Tooth preparation was performed in a typodont with human lower molar tooth under rubber dam isolation. The procedure was carried out in a transparent plastic box to avoid aerosols dispersion. Sixteen grade I cellulose filter discs were distributed along the surfaces of the box. The area contaminated with aerosols in the filters was measured using ultraviolet illumination.

Results

In group 1, the contaminated surface area covered with fluorescein dye reached 77.3% (1349 cm2) of the total; in group 2 (laser with 80% water) we observed 7.3% (128 cm2) and in group 3 (laser with 40% water) it was 3.8% (68 cm2). The reduction in water parameter from 80% to 40% coincided with 48% reduction of the contaminated area on the filter discs. Focusing on the surfaces of the box, we noted that the mean contamination on the left side was more than on the right side in all three experimental groups. In group 1 using air turbine, we measured a mean of 102.6[±7.5 SD]cm2 on the left side, compared to 70.6[±32.3 SD]cm2 on the right side. In laser groups 2 and 3, a mean of 12.8[±14.9 SD]cm2 and 6.8 [±5.7SD]cm2, respectively, was described on the left surface versus 0 cm2 of surface contamination on the right surface.

Conclusions

The contaminated area during the procedure of class I cavity preparation, is reduced by 70% using Er,Cr:YSGG laser compared to high-speed turbine. A slightly higher contamination was observed between laser groups with 80% versus 40% water. The use of Er,Cr:YSGG laser in restorative dentistry can be a valid treatment alternative to reduce aerosols production compared to conventional high-speed rotary instruments. Key words:Er,Cr:YSGG laser, Aerosols, SARS-CoV-2, Rotary instruments, conservative dentistry.

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.

Qualitative evaluation of hybrid layer formation using Er:YAG laser in QSP mode for tooth cavity preparations

The purpose of this study was to evaluate the thickness and qualitative characteristics of the hybrid layer after two cavity preparation methods, using Er:YAG laser in QSP mode and conventional carbide burs. Additionally, two different adhesive techniques were investigated using etch-and-rinse and self-etch adhesive systems. Sixty sound human third molars were used and were randomly divided into four groups (n = 15). In the first two groups, large (4 mm length, 3 mm wide, and 3 mm deep) class I cavities were prepared using Er:YAG laser (2.94 μm) in QSP mode, while in the other two groups, the cavities were prepared using carbide burs. After cavity preparations, two different adhesive techniques with GLUMA® 2 Bond (etch-and-rinse) and Clearfil™ Universal Bond Quick (self-etch) were applied. For the qualitative evaluation of the formed hybrid layer, photomicrographs were taken using SEM, and elemental semi-quantitative analysis was performed using EDS to confirm the extent of the hybrid layer. One-way ANOVA was applied to verify the existence of statistically significant differences, followed by Tukey test for post hoc comparisons (Bonferroni corrected), and the level of significance was set at a = 0.05. The laser-treated groups exhibited higher hybrid layer thickness than bur-treated groups (p < 0.001). Between the laser-treated groups, etch-and-rinse technique presented higher hybrid layer thickness than self-etch technique (p < 0.001), while between the bur-treated groups, no significant differences were detected (p = 0.366). Er:YAG laser cavity preparations in QSP mode may be advantageous for adhesion of composite restorations, but more data are necessary to confirm its clinical effectiveness.

Bulk-Fill Restorative Materials in Primary Tooth: An Intrapulpal Temperature Changes Study

Objectives:

It was aimed to investigate the temperature changes in primary teeth pulp chamber during the curing/setting of bulk-fill restorative materials with different nanoparticle contents.

Methods:

Twenty-five extracted, primary mandibular second molars were prepared as a Class II cavity. Five bulk-fill restorative materials consisting of Equia Fil (HVGIC), glass carbomer (GC) cement, Sonic Fill (SF), X-tra Fil (XF), and Quix Fil (QF) were tested. The measurement of the pulp chamber temperature changes (starting temperature 37°C) during setting/curing was performed with a J type thermocouple. The data, differences between highest and initial temperature values, were recorded and analyzed by one-way ANOVA.

Results:

The temperature changes in the pulp chamber were in EF (2.81°C), GC (7.92°C), SF (3.33°C), XF (3.43°C), and QF (3.02°C). There were statistically significant differences between temperature changes in groups (P < 0.05).

Conclusion:

The tested bulk-fill resin composites and high-viscosity glass ionomer cement do not increase the intrapulpal temperature in primary teeth during the curing/setting.

Effect of 2.94 µm Er: YAG laser on the chemical composition of hard tissues

The aim was to investigate the effect of the Er-YAG laser radiation on morphology and chemical composition of enamel, dentin, and bone. The specimens of the three groups were irradiated with a very long pulse mode (VLP) of 2.94 µm Er-YAG laser with 100 mJ pulse energy and energy density of 8.42 J/ c m 2 for 30 s, at a repetition rate of 15 Hz. The organic and inorganic content of the samples were investigated by Fourier Transforms Infrared spectroscopy (FTIR). The morphological characteristics were investigated with scanning electron microscopy (SEM) and elemental analysis (calcium and phosphorus) with energy-dispersive X-ray spectroscopy (EDX). FTIR data were analyzed with a One-Way ANCOVA test and EDX data with the independent sample t-test. Following the laser radiation, FTIR showed a significant decrease in the organic content of all tissues. The weight percentage (wt %) calcium content of dentin and bone increased significantly following irradiation with a p-value of .002 for both tissues, but the wt % of phosphorus content was not influenced significantly. The morphological alterations expressed signs of fusion in all the samples.

Thermal Scanning of Dental Pulp Chamber by Thermocouple System and Infrared Camera during Photo Curing of Resin Composites

Introduction:

Due to thermal hazard during composite restorations, this study was designed to scan the pulp temperature by thermocouple and infrared camera during photo polymerizing different composites.

Methods and Materials:

A mesio-occlso-distal (MOD) cavity was prepared in an extracted tooth and the K-type thermocouple was fixed in its pulp chamber. Subsequently, 1 mm increment of each composites were inserted (four composite types were incorporated) and photo polymerized employing either LED or QTH systems for 60 sec while the temperature was recorded with 10 sec intervals. Ultimately, the same tooth was hemisected bucco-lingually and the amalgam was removed. The same composite curing procedure was repeated while the thermogram was recorded using an infrared camera. Thereafter, the data was analyzed by repeated measured ANOVA followed by Tukey’s HSD Post Hoc test for multiple comparisons (α=0.05).

Results:

The pulp temperature was significantly increased (repeated measures) during photo polymerization (P=0.000) while there was no significant difference among the results recorded by thermocouple comparing to infrared camera (P>0.05). Moreover, different composite materials and LCUs lead to similar outcomes (P>0.05).

Conclusion:

Although various composites have significant different chemical compositions, they lead to similar pulp thermal changes. Moreover, both the infrared camera and the thermocouple would record parallel results of dental pulp temperature.

Erbium:Yttrium Aluminum Garnet Laser-Activated Sodium Hypochlorite Irrigation: A Promising Procedure for Minimally Invasive Endodontics

OBJECTIVE

This study was to evaluate the potential of Erbium:Yttrium Aluminum Garnet laser-activated sodium hypochlorite irrigation (Er:YAG + NaOCl) for minimally invasive endodontics (MIE).

BACKGROUND DATA

Er:YAG laser irradiation can dramatically enhance the penetration of NaOCl, which may be a promising protocol for MIE.

METHODS

Extracted human teeth were contaminated with Enterococcus faecalis for 4 weeks. The infected canals were then shaped to different apical terminal working widths (ATWW, 15#/0.04, 20#/0.04, 25#/0.04, 30#/0.04, and 40#/0.04) and treated with either Er:YAG + NaOCl (0.3 W, 20 sec) or NaOCl alone. Then, the ATWW were fixed at 15#/0.04, and the canals were treated with Er:YAG + NaOCl at 0.3 W for 40 and 60 sec, or at 0.5 and 1.0 W for 20 sec. Finally, bacterial reductions were evaluated using the cell count method.

RESULTS

Er:YAG + NaOCl showed a higher disinfection efficacy at each ATWW compared with NaOCl alone (p < 0.001). The maximum bacterial reduction was 99.9% for the 40#/Er:YAG + NaOCl group and 93.6% for the 40#/NaOCl group. To achieve similar disinfection efficacy, the Er:YAG + NaOCl group needed a smaller ATWW than the NaOCl group. At a fixed ATWW, increasing the output power of the Er:YAG laser was more effective than increasing the radiation time to improve the disinfection efficacy of Er:YAG + NaOCl. The 15#/Er:YAG + NaOCl group reached the maximum bacterial reduction of 99.2% when the Er:YAG laser was activated at 1.0 W for 20 sec.

CONCLUSIONS

The 15#/Er:YAG + NaOCl with the Er:YAG laser irradiation at 1.0 W for 20 sec may be considered a promising procedure for MIE.

Intrapulpal Thermal Changes during Setting Reaction of Glass Carbomer® Using Thermocure Lamp

Objectives. To measure the temperature increase induced during thermocure lamp setting reaction of glass carbomer and to compare it with those induced by visible light curing of a resin-modified glass ionomer and a polyacid-modified composite resin in primary and permanent teeth. Materials and Methods. Nonretentive class I cavities were prepared in extracted primary and permanent molars. Glass carbomer (GC) was placed in the cavity and set at 60°C for 60 sn using a special thermocure lamp. Resin-modified glass ionomer (RMGIC) and polyacid-modified composite resin (PMCR) were placed in the cavities and polymerized with an LED curing unit. Temperature increases during setting reactions were measured with a J-type thermocouple wire connected to a data logger. Data were examined using two-way analysis of variance and Tukey's honestly significant difference tests. Results. The use of GC resulted in temperature changes of 5.17 ± 0.92°C and 5.32 ± 0.90°C in primary and permanent teeth, respectively (p > 0.05). Temperature increases were greatest in the GC group, differing significantly from those in the PMCR group (p < 0.05). Conclusion. Temperature increases during polymerization and setting reactions of the materials were below the critical value in all groups. No difference was observed between primary and permanent teeth, regardless of the material used.

Effect of new innovative restorative carbomised glass cement on intrapulpal temperature rise: an ex-vivo study

This study aimed to evaluate the temperature changes that occurred in the pulp chamber when using GCP Glass Carbomer Fill (GCP) and two different resin-modified glass-ionomer (RGI) restorative materials at different dentin thicknesses. A standardized Class I occlusal cavity with 1 mm or 2 mm dentin thickness was prepared in the extracted human molar teeth. RGI and GCP fills were placed in the cavities and cured with two different light-curing units. This study included a total of 120 samples, with 20 samples in each group. The pulp microcirculation method was used for measuring the intrapulpal temperature changes. Statistical analysis was performed using the two-way ANOVA and Tukey HSD multiple comparison tests. Statistically significant differences were observed between 1 mm and 2 mm dentin thicknesses (p < 0.001). The GCP groups (both 1 mm and 2 mm dentin thicknesses) exhibited higher temperatures than the other groups (p < 0.001), and Fuji II LC and Photac Fil Quick Aplicap showed similar values (p > 0.05). The highest temperature changes were observed with 1 mm dentin thickness. While RGI materials in both dentin thicknesses did not cause temperature changes that were harmful to the pulp, GCP CarboLED LCU caused the highest intrapulpal temperature rise, and these values were borderline harmful to the dental pulp.

Thermal effects and morphological aspects of varying Er:YAG laser energy on demineralized dentin removal: an in vitro study

The aim of this study was to evaluate thermal changes, dentin ablation removal capacity, and morphological aspects of sound and demineralized human dentin surface irradiated with different output energies of an erbium: yttrium-aluminium-garnet (Er:YAG) laser. Eighty sound human tooth specimens were assigned into two groups: demineralized dentin and sound dentin (control group). The dentin groups were subdivided into four subgroups (n = 10) according to the irradiation energy used (120, 160, 200, or 250 mJ) at a constant frequency level of 6 Hz, in focused mode, and under refrigeration. Quantitative analysis of the sound and carious dentin ablation was performed using light microscopy (LM) by measuring (mm) the remaining demineralized tissue with the Axion Vision™ software. Qualitative analysis was performed using the images obtained with a scanning electron microscope (SEM), and the temperature increase was recorded with an infrared digital thermometer. The Er:YAG laser promoted a gradual increase in temperature for all groups, and no difference was observed between the sound and demineralized dentin. The groups of 200 and 250 mJ showed the highest values, yet a variation in temperature did not exceed 5 °C. The energy output of 120 mJ selectively removed demineralized tissue when compared to 250 mJ, while also providing more regular surfaces in the cavity preparation. It was concluded that the temperature increase during sound and demineralized dentin removal had a strong positive correlation with the Er:YAG laser energy level output. However, the higher energies used did not present selectivity to the demineralized tissue, and the parameters used did not cause an increase in temperature over 5 °C.

Antibacterial effects of two different types of laser and aqueous ozone against Enterococcus faecalis in root canals

OBJECTIVE

The purpose of this study was to investigate the antibacterial effects of two different types of laser and aqueous ozone in human root canals infected by Enterococcus faecalis.

BACKGROUND DATA

Many techniques have been developed to find an alternative to sodium hypochlorite as a disinfection agent for infected root canals. However, no study has evaluated the exactly the same antimicrobial agent with sodium hypochlorite (NaOCl).

METHODS

Eighty mandibular premolar teeth with single roots and canals were selected. Following root canal preparation and irrigation, sterilization was performed in an autoclave. E. faecalis was incubated in the root canals and kept at 37°C for 24 h. The teeth contaminated with E. faecalis were divided into one negative control group (NaOCl) and three experimental groups; (Er:YAG laser, KTP laser, and aqueous ozone groups)(n=20). A disinfection procedure was performed for 3 min in order to standardize all groups. After this procedure, the microbial colonies were counted.

RESULTS

The results indicated that whereas the NaOCl group exhibited the highest antibacterial effect among all groups, the aqueous ozone showed the highest antibacterial effect among the experimental groups. Whereas a statistically significant difference was noted between the aqueous ozone and laser groups (p<0.05), the difference between the Er:YAG and KTP lasers was not statistically significant (p>0.05).

CONCLUSIONS

The results showed that when aqueous ozone was applied with the aim of disinfecting the root canals, it exhibited a higher antibacterial effect than the KTP and Er:YAG lasers. However, the antibacterial effect of the aqueous ozone was insufficient when compared with NaOCl.

Evaluation of dental anxiety in patients undergoing dentoalveolar surgery with laser treatment

OBJECTIVE

The purpose of this study was to evaluate dental anxiety in patients undergoing apicectomy procedures performed with conventional instruments or an erbium-doped yttrium aluminum garnet (Er:YAG) laser.

METHODS

Twenty-eight patients undergoing apicectomy were divided into two groups; roots were removed with an Er:YAG laser in group A (n=14) and with conventional instruments in group B (n=14). All patients completed preoperative State-Trait Anxiety Inventories (STAI) and postoperative questionnaires.

RESULTS

Although state anxiety, trait anxiety, and postoperative questionnaire scores were lower in patients undergoing Er:YAG laser treatment than in those treated with conventional instruments, the differences were not statistically significant.

CONCLUSIONS

Surgical instruments affect the anxiety levels of dental patients. Even with the STAI scores being lower for patients treated with Er:YAG, use of the Er:YAG laser alone cannot contribute to the resolution of dental anxiety. A patient's individual condition is the major factor influencing that patient's anxiety level.

Thermal irritation of teeth during dental treatment procedures

While it is reasonably well known that certain dental procedures increase the temperature of the tooth's surface, of greater interest is their potential damaging effect on the pulp and tooth-supporting tissues. Previous studies have investigated the responses of the pulp, periodontal ligament, and alveolar bone to thermal irritation and the temperature at which thermal damage is initiated. There are also many in vitro studies that have measured the temperature increase of the pulp and tooth-supporting tissues during restorative and endodontic procedures. This review article provides an overview of studies measuring temperature increases in tooth structures during several restorative and endodontic procedures, and proposes clinical guidelines for reducing potential thermal hazards to the pulp and supporting tissues.

Thermal effects and morphological aspects of human dentin surface irradiated with different frequencies of Er:YAG laser

This study reports the effects on micromorphology and temperature rise in human dentin using different frequencies of Er:YAG laser. Sixty human dentin fragments were randomly assigned into two groups (n = 30): carious or sound dentin. Both groups were divided into three subgroups (n = 10), according to the Er:YAG laser frequency used: 4, 6, or 10 Hz (energy: 200 mJ; irradiation distance: 12 mm; and irradiation time: 20 s). A thermocouple adapted to the tooth fragment recorded the initial temperature value (°C); then, the temperature was measured after the end of the irradiation (20 s). Morphological analysis was performed using images obtained with scanning electron microscope. There was no difference between the temperatures obtained with 4 and 6 Hz; the highest temperatures were achieved with 10 Hz. No difference was observed between carious and sound dentin. Morphological analyses revealed that all frequencies promoted irregular surface in sound dentin, being observed more selectively ablation especially in intertubular dentin with tubule protrusion. The caries dentin presented flat surface for all frequencies used. Both substrates revealed absence of any signs of thermal damage. It may be concluded that the parameters used in this study are capable to remove caries lesion, having acceptable limits of temperature rise and no significant morphological alterations on dentin surface.

MATHEMATICAL MODELING FOR THE PREDICTION AND IMPROVEMENT OF TOOTH THERMAL PAIN: A REVIEW

Tooth pain, especially tooth thermal pain, is one of the most important symptoms and signs in dental clinic and daily life. As a special sensation, pain has been studied extensively in both clinic and experimental research aimed at reducing or eliminating the possible negative effects of pain. Unfortunately, the full underlying mechanism of pain is still unclear, because the pain could be influenced by many factors, including physiological, psychological, physical, chemical, and biological factors and so on. Besides, most studies on pain mechanisms in the literature are based on skin pain sensation and only few are based on tooth pain. In this paper, we present a comprehensive review on both neurophysiology of tooth pain mechanism, and corresponding thermal, mechanical, and thermomechanical behaviors of teeth. We also describe a multiscale modeling approach for quantifying tooth thermal pain by integrating the mathematic methods of engineering into the neuroscience. The mathematical model of tooth thermal pain will enable better understanding of thermal pain mechanism and optimization of existing diagnosis and treatment in dental clinic.

Thermal alteration and morphological changes of sound and demineralized primary dentin after Er:YAG laser ablation

The purpose of this study was to assess the influence of Er:YAG laser pulse repetition rate on the thermal alterations occurring during laser ablation of sound and demineralized primary dentin. The morphological changes at the lased areas were examined by scanning electronic microscopy (SEM). To this end, 60 fragments of 30 sound primary molars were selected and randomly assigned to two groups (n = 30); namely A sound dentin (control) and B demineralized dentin. Each group was divided into three subgroups (n = 10) according to the employed laser frequencies: I-4 Hz; II-6 Hz, and III-10 Hz. Specimens in group B were submitted to a pH-cycling regimen for 21 consecutive days. The irradiation was performed with a 250 mJ pulse energy in the noncontact and focused mode, in the presence of a fine water mist at 1.5 mL/min, for 15 s. The measured temperature was recorded by type K thermocouples adapted to the dentin wall relative to the pulp chamber. Three samples of each group were analyzed by SEM. The data were submitted to the nonparametric Kruskal-Wallis test and to qualitative SEM analysis. The results revealed that the temperature increase did not promote any damage to the dental structure. Data analysis demonstrated that in group A, there was a statistically significant difference among all the subgroups and the temperature rise was directly proportional to the increase in frequency. In group B, there was no difference between subgroup I and II in terms of temperature. The superficial dentin observed by SEM displayed irregularities that augmented with rising frequency, both in sound and demineralized tissues. In conclusion, temperature rise and morphological alterations are directly related to frequency increment in both demineralized and sound dentin.

Application of laser technology for removal of caries: a systematic review of controlled clinical trials

OBJECTIVE

To evaluate the scientific evidence regarding laser technology for removal of carious tissue.

MATERIAL AND METHODS

A search for literature on the effect of treatment and on economic aspects of laser technology identified 23 papers. No relevant studies on economic aspects were found. Regarding the effect of treatment, 16 papers were selected for assessment according to established criteria.

RESULTS

Cavity preparation and caries excavation by erbium laser were evaluated in three studies of medium quality. The time required to remove carious tissue was evaluated in five studies assessed as being of medium quality for this outcome. In four studies the effect of laser treatment on the dental pulp was included as an outcome but, due to the short follow-up time, the quality was assessed as low. Two studies that included the longevity of the restoration as an outcome were also assessed as being of low quality because the follow-up time was inadequate. Patient response was evaluated in three studies, which were assessed as being of medium quality with respect to this outcome.

CONCLUSIONS

There is limited scientific evidence that laser treatment is as effective as a rotary bur for removing carious tissue. Treatment time is prolonged. There is limited scientific evidence that adults prefer laser treatment. No conclusions can be drawn regarding biological or technical complications, children's perception of laser treatment or the cost-effectiveness of the method.

SEM analysis of enamel surface treated by Er:YAG laser: influence of irradiation distance

BACKGROUND

Depending on the distance of laser tip to dental surface a specific morphological pattern should be expected. However, there have been limited reports that correlate the Er:YAG irradiation distance with dental morphology.

PURPOSE

To assess the influence of Er:YAG laser irradiation distance on enamel morphology, by means of scanning electron microscopy (SEM).

METHODS

Sixty human third molars were employed to obtain discs (approximately =1 mm thick) that were randomly assigned to six groups (n=10). Five groups received Er:YAG laser irradiation (80 mJ/2 Hz) for 20 s, according to the irradiation distance: 11, 12, 14, 16, or 17 mm and the control group was treated with 37% phosphoric acid for 15 s. The laser-irradiated discs were bisected. One hemi-disc was separated for superficial analysis without subsequent acid etching, and the other one, received the phosphoric acid for 15 s. Samples were prepared for SEM.

RESULTS

Laser irradiation at 11 and 12 mm provided an evident ablation of enamel, with evident fissures and some fused areas. At 14, 16 and 17 mm the superficial topography was flatter than in the other distances. The subsequent acid etching on the lased-surface partially removed the disorganized tissue.

CONCLUSIONS

Er:YAG laser in defocused mode promoted slight morphological alterations and seems more suitable for enamel conditioning than focused irradiation. The application of phosphoric acid on lased-enamel surface, regardless of the irradiation distance, decreased the superficial irregularities.

Effect of erbium:yttrium-aluminum-garnet laser energies on superficial and deep dentin microhardness

This study evaluated the microhardness of superficial and deep dentin irradiated with different erbium:yttrium-aluminum-garnet (Er:YAG) laser energies. Seventy-two molars were bisected and randomly assigned to two groups (superficial dentin or deep dentin) and into six subgroups (160 mJ, 200 mJ, 260 mJ, 300 mJ, 360 mJ, and control). After irradiation, the cavities were longitudinally bisected. Microhardness was measured at six points (20 microm, 40 microm, 60 microm, 80 microm, 100 microm, and 200 microm) under the cavity floor. Data were submitted to analysis of variance (ANOVA) and Fisher's tests (alpha = 0.05). Superficial dentin presented higher microhardness than deep dentin; energy of 160 mJ resulted in the highest microhardness and 360 mJ the lowest one. Values at all points were different, exhibiting increasing microhardness throughout; superficial dentin microhardness was the highest at 20 microm with 160 mJ energy; for deep dentin, microhardness after irradiation at 160 mJ and 200 mJ was similar to that of the control. The lowest energy increased superficial dentin microhardness at the closest extent under the cavity; deep dentin microhardness was not altered by energies of 160 mJ and 200 mJ.

Temperature variation on the external root surface during intracanal Er:YAG laser irradiation

OBJECTIVE

To evaluate the temperature changes on the root's external surface during Er:YAG laser irradiation with different tips and pulse repetition rates.

BACKGROUND DATA

There have been limited reports that correlate temperature variations with Er:YAG laser irradiation using different tips and pulse repetition rates.

MATERIALS AND METHODS

Sixty roots of central incisors were sectioned 10 mm from the apex, biomechanically prepared, embedded in acrylic resin, and randomly distributed into six groups: the teeth in group I, group II, and group III were irradiated with an Opus 20 laser with a sapphire tip at 8, 10, and 15 Hz, respectively; the teeth in group IV, group V, and group VI were irradiated with the fiberoptic tip of a Kavo Key laser at 6, 10, and 15 Hz, respectively. Laser irradiation was applied for 20 sec to all teeth and temperature changes were recorded with thermocouples in the root surfaces.

RESULTS

There were significant differences (p < 0.05) among pulse repetition rates: 6 and 8 Hz (2.36 degrees +/- 0.91 degrees C), 10 Hz (4.92 degrees +/- 1.60 degrees C), and 15 Hz (8.23 degrees +/- 2.78 degrees C); and radicular thirds: apical (8.33 degrees +/- 2.69 degrees C), middle (4.70 degrees +/- 1.60 degrees C), and cervical (2.48 degrees +/- 0.83 degrees C). No significant differences were seen between the two types of laser tips used (p > 0.05).

CONCLUSION

The temperature changes on root external surfaces remained above the critical threshold (13 degrees C) during Er:YAG laser irradiation, except for irradiation with 15 Hz in the apical third. However, the type of Er:YAG laser tip used (sapphire or fiberoptic) did not affect the temperature variation.

Bond durability in erbium:yttrium-aluminum-garnet laser-irradiated enamel

This study sought to evaluate the influence of thermocycling and water storage on the microtensile bond strength of composite resin bonded to erbium:yttrium-aluminum-garnet (Er:YAG)-irradiated and bur-prepared enamel. Eighty bovine incisors were selected and sectioned. Specimens were ground to produce a flat enamel surface. Samples were randomly assigned according to cavity preparation device: (I) Er:YAG laser and (II) high-speed turbine, and were subsequently restored with composite resin. They were subdivided according to the duration of water storage (WS)/number of thermocycles (TCs): 24 h WS/no TCs; 7 days WS/500 TCs; 1 month WS/2,000 TCs; 6 months WS/12,000 TCs. The teeth were sectioned into 1.0 mm(2)-thick slabs and subjected to tensile stress in a universal testing machine. Data were submitted to two-way analysis of variance (ANOVA) and Tukey's test at a 0.05 significance level. The different periods of water storage and thermocycling did not influence the microtensile bond strength (microTBS) values in the Er:YAG laser-prepared groups. In bur-prepared enamel, the group submitted to 12,000 TCs/6 months' WS (IID) showed a significant decrease in bond strength values when compared to the group stored in water for 24 h and not submitted to thermocycling (IIA), but values were statistically similar to those obtained in all Er:YAG laser groups and in the bur- prepared groups degraded with 500 TCs/1 week WS (IIB) or 2,000 TCs/1 month WS (IIC). It may be concluded that adhesion of an etch-and-rinse adhesive to Er:YAG laser-irradiated enamel was not affected by the methods used to simulate degradation of the adhesive interface and was similar to adhesion in the bur-prepared groups in all periods of water storage and thermocycling.

Temperature rise in cavities prepared by high and low torque handpieces and Er:YAG laser

OBJECTIVE

The aim of this study was to compare intrapulpal temperature increases produced by a high-speed high-torque (speed-increasing) handpiece, a high-speed low-torque handpiece (air-turbine) and an Er:YAG (Erbium: Yttrium-Aluminum-Garnet) laser.

SUBJECT AND METHODS

Thirty bovine incisors were reduced to a dentine thickness of 2.0 mm. Class V preparations were prepared to a depth of 1.5 mm, measured with a caliper or by a mark on the burs. A thermocouple was placed inside the pulp chamber to determine temperature increases ( degrees C). Analysis was performed on the following groups (n = 10) treated with: G1, low-torque handpiece; G2, high-torque handpiece; and G3, Er:YAG laser (2.94 microm at 250 mJ/4 Hz), all with water cooling. The temperature increases were recorded with a computer linked to the thermocouples.

RESULTS

The data were submitted to ANOVA and Tukey statistical test. The average temperature rises were: 1.92+/-0.80 degrees C for G1, 1.34+/-0.86 degrees C for G2, and 0.75+/-0.39 degrees C for G3. There were significant statistical differences among the groups (p = 0.095). All the groups tested did not have a change of temperature that exceeds the threshold of 5.5 degrees C.

CONCLUSION

Temperature response to the low and high torque handpieces seemed to be similar, however the Er:YAG laser generated a lower temperature rise.

Assessment of Thermal Alteration during Class V Cavity Preparation Using the Er:YAG Laser

OBJECTIVE

The aim of this study was to evaluate in vitro the pulp thermal alterations during class V cavity preparations using the Er:YAG laser and high-speed water flow.

MATERIALS AND METHODS

Forty human teeth were selected and prepared for the thermocouple adaptation in the pulp chamber. The specimens were assigned to four groups: (1) laser 300 mJ/3 Hz, (2) laser 300 mJ/4 Hz, (3) high-speed 9 mL/min water flow, and (4) high-speed 100 mL/min water flow. The temperature was measured before the beginning and at the end of the preparation, as well as during the procedures. The groups were analyzed by scanning electron microscopy.

RESULT

Data analysis disclosed temperature reduction at high-speed drilling with the high-speed total water flow group, and these values were statistically different from the other groups. The results of the 9-mL/min water flow group were similar to those of the 300-mJ/3-Hz group and different from the 300-mJ/4-Hz laser group.

CONCLUSION

The laser promoted a greater increase in temperature only when compared with high-speed handpiece and water flow rate of 100 mL/min.

Effect of Energy and Pulse Repetition Rate of Er: YAG Laser on Dentin Ablation Ability and Morphological Analysis of the Laser-Irradiated Substrate

OBJECTIVE

The aim of this study was to assess the effect of energy and pulse repetition rate of the Er:YAG laser (2.94 microm) on dentin ablation ability and substrate morphology.

BACKGROUND DATA

Previous studies have demonstrated the ability of the Er:YAG laser for ablating dentin substrate.

METHODS

Fifteen crowns of molars were sectioned in four fragments, providing 60 samples, which were ground to expose dentin. Initial mass was obtained by weighing the fragments. Twelve groups were randomly formed, according to the combination of laser energies (200, 250, 300, and 350 mJ) and pulse repetition rates (2, 3, and 4 Hz), usually advised for cavity preparation. The final mass was obtained, and dentin mass loss was calculated by the difference between the final and initial mass. Afterwards, specimens were prepared for scanning electron microscopy (SEM). Data were submitted to analysis of variance (ANOVA) and Scheffé test (p < 0.05).

RESULTS

Pulse repetition rate of 4 Hz was statistically similar to 3 Hz, and laser energy of 350 mJ was statistically similar to 300 mJ. Increased pulse repetition rates provided higher ablation depth and slight enlargement of dentinal tubules, whereas increased energies yielded greater ablation of intertubular dentin.

CONCLUSION

The ablation ability of the Er:YAG laser on dentin raised with the increase of energy and/or pulse repetition rate, the latter exhibiting a stronger influence on mass loss rate and on morphological alterations.

Effect of a Novel Er:YAG Laser in Caries Removal and Cavity Preparation: A Clinical Observation

OBJECTIVE

We evaluated the applicability of a novel Er:YAG laser under clinical conditions.

BACKGROUND DATA

The Er:YAG laser has been demonstrated to be a safe and effective alternative to the conventional turbine bur, but the relatively low cutting speed prevented the wide application of Er:YAG laser in clinical cavity preparation.

METHODS

A Smart 2940 D laser developed by Deka Corporation was used for cavity preparation in 95 teeth of 45 patients. Parameters were as follows: wavelength 2.94 microm, pulse energy 700 mJ, repetition rate 8 Hz. Pain, discomfort, assessment during cavity preparation, prognosis factor, and overall clinical evaluation were assessed during or after treatment.

RESULTS

No adverse reaction was observed in any tooth. No intraoperative pain or only slight intraoperative pain was described in 85 teeth (89.5%). Cavity preparation was completed with the laser system alone in 90 teeth (94.7%). Overall clinical evaluation showed no safety problems, with a very good or good rating in 86 teeth (90.5%). The overall operation time was 49 sec on average.

CONCLUSION

The Smart 2940 D is an efficient, effective, safe, and suitable instrument for caries removal and for cavity preparation. It greatly shortens operation time.

Acceptance and Efficiency of Er:YAG Laser for Cavity Preparation in Children

OBJECTIVE

To evaluate the clinical efficiency and patient acceptance during cavity preparation in children, a direct comparison was made between Er:YAG laser preparation and conventional mechanical preparation of caries using a split-mouth design.

BACKGROUND DATA

The Er:YAG laser system was developed for cutting dental hard tissue and has been approved as a useful alternative method for cavity preparation.

METHODS

Children with previously unrestored and matched carious cavities in non-pulpally involved anterior teeth were selected, and the sequential order of treatment was randomized. In total, 40 children from 4 to 12 years old took part in the study. Two teeth each in the 40 patients were prepared without anesthesia and restored with a light-cured compomer following application of a bonding agent. The time spent on cavity preparation and the behavior of the patients during cavity preparation were recorded; finally, a modified face scale was used for pain assessment. In addition, the children were asked to indicate whether they found the laser or the mechanical approach more uncomfortable, and their preferred treatment when undergoing future caries therapy.

RESULTS

The analysis of pain indicated that 82.5% of children felt no pain at all with the laser preparation, and they also showed much more body and head movement with the conventional mechanical preparation. Although the Er:YAG laser took about 2.35 times longer to prepare the same type of cavity, 92% of the children said that they would prefer laser preparation for further caries therapy.

CONCLUSION

Cavity preparation with the Er:YAG laser would seem to be an option for fearful children, since it produces less pain and has acceptable efficiency compared to the conventional mechanical preparation.

Periodontal tissue healing following flap surgery using an Er:YAG laser in dogs

BACKGROUND AND OBJECTIVES

The purpose of this study was to compare periodontal tissue healing following flap surgery using an Er:YAG laser with that of conventional surgery.

STUDY DESIGN/MATERIALS AND METHODS

Bilateral premolars with experimentally induced periodontitis in six dogs were treated by periodontal flap surgery. Degranulation and root debridement in the furcation were performed using an Er:YAG laser or curet. At 3 months postsurgery, animals were sacrificed and decalcified specimens were prepared for histological and histometric analysis.

RESULTS

Degranulation and root debridement were effectively performed with an Er:YAG laser without major thermal damage and significantly faster than with a curet. Histologically, the amount of newly formed bone was significantly greater in the laser group than in the curet group, although both groups showed similar amounts of cementum formation and connective tissue attachment.

CONCLUSIONS

The Er:YAG laser irradiation can be safely and effectively utilized in periodontal flap surgery, and has the potential to promote new bone formation.