Intrapulpal temperature changes during root surface irradiation with an 809-nm GaAlAs laser

The Effects of Antimicrobial Photodynamic Therapy Used to Sterilize Carious Dentin on Rat Dental Pulp Tissue

Antimicrobial photodynamic therapy (aPDT) used to sterilize carious dentin may irritate pulp tissues because of tissue-penetrating laser and singlet oxygen generation. This study aimed to assess the effects of aPDT on rat pulp tissues. A cavity formed in a rat maxillary first molar was treated with aPDT. The combined photosensitizer and laser irradiation conditions in the aPDT groups were as follows: methylene blue and 100 mW for 60 s, brilliant blue (BB) and 100 mW for 60 s, BB and 50 mW for 120 s, and BB and 200 mW for 30 s. Each cavity was treated with an all-in-one adhesive and filled with flowable resin. aPDT was not applied for the control. In each group, the rats were sacrificed on postoperative days 1 and 14, and thin sections of the treated teeth were prepared. Pulp tissue disorganization (PTD), inflammatory cell infiltration (ICI), and tertiary dentin formation (TDF) were evaluated. At 1-day evaluation, there were significant differences between the aPDT group and controls with respect to PTD and ICI (p < 0.01); 14 days later, almost all specimens showed tertiary dentin formation. The application of aPDT caused reversible damage to the rat pulp, while in the long term, healing occurred with the formation of tertiary dentin.

Efficacy of near infrared dental lasers on dentinal hypersensitivity: a meta-analysis of randomized controlled clinical trials

Conventional therapies have aimed to try to help individuals suffering with dentine hypersensitivity (DH/DHS). A relatively new approach, laser therapy claims to be beneficial while having immediate and long-lasting effect. Therefore, our analysis aims to explore the immediate and 1-month efficacy of near-infrared laser (NIR) therapy in treating dentinal hypersensitivity. A systematic literature search conducted in databases, and analysis was undertaken utilizing a meta-analysis approach. Randomized controlled clinical trials comparing near-infrared lasers and placebo/no treatment in patients (> 18 years) were included. The risk of bias for included studies was assessed using Cochrane RoB tool (for randomized studies). Random effects meta-analyses model of standardized mean differences and 95% confidence intervals were performed using RevMan 5.4 software. A comprehensive electronic and manual search yielded a total of 1081 potential articles. Following the implementation of the inclusion and exclusion criteria, a total of 6 studies were included in the analysis. Near-infrared laser therapy led to statistical significant reduction in immediate and 1-month follow-up VAS (visual analog scale) scores compared to placebo/no treatment (p < 0.05). Statistical heterogeneity across the studies was high (I²-96%). The findings suggest that near-infrared laser therapy does have a significant immediate effect in reducing dentine hypersensitivity compared to placebo/no treatment. Furthermore, this effect is not diminished and endured at 1-month follow-up.

Could We Set a Convenient Irradiation Time to Reduce the Possibility of Thermal Pulp Damage During Diode Laser as an Adjunct to Periodontal Treatment? An In Vitro Analysis

Background: To identify the most effective time procedure for irradiation to prevent possible harmful pulp temperature rises during diode laser (DL) as an adjunct to scaling and root planning (SRP) treatment. Methods: One hundred fifty freshly extracted human teeth (30 molars, 30 premolars, 30 canines, 30 upper incisors, and 30 lower incisors) were irradiated using a 940-nm DL with a power output at 0.8 W and exposure time of 10, 20, 30, 40, 50, 60 sec per specimen. The thermocouple was used to measure intrapulpal temperature. As an addition, the impact of dark deposits on the root surface was investigated for the intrapulpal temperature rise. The threshold value of 5.6°C is predetermined to damage the pulp. Temperature variations were measured at every 10 sec for five different types of teeth, and statistical analysis was performed. Results: Despite large differences between tooth types, the observed temperature increases for all tooth types were below the threshold of 5.6°C in 20 sec. Dark deposits on the tooth surface reduced the reliable working time of DLs (p < 0.01). Conclusions: DLs as an adjunct to SRP treatment at 0.8 W in molars, premolars, canine, upper incisors, and lower incisors for 42, 37, 38, 27, and 21 sec, respectively, generate acceptable temperature rises for pulp but should be changed as 39, 21, 26, 23, and 13 sec, respectively, in the presence of dark deposits.

A Spectrophotometric Study on Light Attenuation Properties of Dental Bleaching Gels: Potential Relevance to Irradiation Parameters

Background: During in-office bleaching, appropriate light sources are applied in order to enhance the activity of the bleaching gels applied onto teeth. For this method to be effective, a high absorption of light within the gel is necessary. Variation in the light attenuation capability of the gel, the duration of application and light activation can contribute towards safety hazards associated with this procedure. Methods: In this study, seven different gels and hydrogen peroxide have been evaluated for their optical properties by means of spectrophotometry (440–1000 nm). The transmitted light spectrum was used to estimate the intensity loss for each gel. The mean intensity decreases observed were statistically analysed using an analysis of variance (ANOVA). Results: The five more-pigmented gels tested indicated a very similar intensity loss of around 80%, whereas the remaining two gels showed significantly less attenuation (predominantly, p < 10⁻⁶). Conclusions: Throughout the spectrum of wavelengths examined, and according to the underlying studies evaluated, five of the gels assessed demonstrated an attenuation high enough to possibly avoid overheating of the underlying enamel dentine and pulp. An evaluation of appropriate irradiation parameters is proposed.

Effect of Indocyanine Green and Infrared Diode Laser to Streptococcus mutans Biofilms

Objective: The aim of this study was to quantitatively and qualitatively evaluate the effects of the indocyanine green (ICG)-near-infrared (NIR) photoreaction on Streptococcus mutans biofilms. Background: ICG recently emerged as a photosensitive agent for photodynamic therapy. Although the effects of ICG-NIR on S. mutans inhibition are documented, little is known about its influence on biofilms, which are resistant to antimicrobial treatment and a major cause of plaque that leads to dental caries. Methods: ICG was used as a photosensitizer with a diode laser irradiated in a rectangular shape (810 nm, 300 mW) as a light source on S. mutans ATCC 25175 biofilms. Viability was determined by the colony forming unit (CFU) count and confocal laser-scanning microscopy. The biofilm surface temperature was measured with a one-channel thermocouple thermometer. Results: ICG and NIR diode laser significantly decreased the CFU count of S. mutans compared with the control group in a time-dependent manner. When irradiated with light after ICG application, temperature changes of 8.4°C, 12.4°C, and 14.9°C were observed with 10, 30, and 60 sec of irradiation, respectively. Conclusions: The ICG-NIR diode laser photoreaction can inhibit S. mutans biofilms, especially at 60 sec. An optimized protocol is needed for clinical application of ICG-NIR diode laser treatment.

Feasibility of transgingival laser irradiation for antimicrobial photodynamic therapy

AIM

Diode lasers are commonly used for antimicrobial photodynamic therapy (aPDT). This study aimed to assess the feasibility of transgingival laser irradiation during aPDT and evaluate whether the photosensitizer can be activated.

MATERIALS AND METHODS

Four diode laser settings were assessed for transgingival irradiation: 120 mW, 80 mW, 60 mW, and 40 mW. Fifteen soft-tissue pieces from a pig's lower jaw were prepared. The specimens' thickness was measured and transgingival laser irradiation was performed. A digital power meter measured laser power on the other side of the tissue. The power outcome after staining of the nonbuccal aspect of the tissue with photosensitizer dye was assessed similarly.

RESULTS

Transgingival laser irradiation (average soft-tissue thickness: 0.84 ± 0.06 mm) resulted in different power transmission depending on the power settings and photosensitizer. The lowest values were observed with the 40 mW setting and photosensitizer (median 3.3 mW, max. 5.0 mW, min. 2.3 mW, interquartile range 1.2), and the highest at 120 mW without photosensitizer (median 41.3 mW, max. 42.7 mW, min. 38.0 mW; interquartile range 1.5).

CONCLUSIONS

This study indicates that transgingival irradiation may be suitable for aPDT, since power transmission through the gingival tissue was observed in all specimens. However, the decrease in laser power caused by both the soft tissue and the photosensitizer has to be taken into account.

In vitro effect of diode laser against biofilm of Aggregatibacter actinomycetemcomitans

Objective:

The main objective is to investigate the antibacterial effect of diode laser against Aggregatibacter actinomycetemcomitans biofilm.

Materials and Methods:

Biofilms of A. actinomycetemcomitans plus Streptococcus sanguinis grown on bovine root surfaces were treated with an 810-nm diode laser using a noncontact pulsed mode with a pulse interval and pulse length of 20 ms. Four protocols, that is, one episode of 1.5 or 2.5 W for 30 s and three episodes of 1.5 or 2.5 W for 30 s were tested. No treatment and 0.2% chlorhexidine treatment served as negative and positive controls, respectively. Viable bacterial number was determined by colony counting.

Results:

Treatment with chlorhexidine and all laser protocols except that using single episode of 1.5 W reduced the number of A. actinomycetemcomitans in either single-species or dual-species biofilm compared to negative control. A higher percentage of A. actinomycetemcomitans reduction was demonstrated after increasing the power output or repeating the irradiation.

Conclusions:

The laser protocols used in this study could reduce the number of viable bacteria but not eradicate A. actinomycetemcomitans biofilm.

Temperature Development on the External Root Surface During Laser-Assisted Endodontic Treatment Applying a Microchopped Mode of a 980 nm Diode Laser

OBJECTIVE

The aim of this article was to investigate the temperature increase of the external root surface during laser-assisted endodontic treatment using a diode laser (980 nm) in a microchopped mode.

METHODS

Ten freshly extracted, human maxillary incisors with mature apices were collected, prepared to size F4 at working length (ProTaper; Dentsply Maillefer, Ballaigues, Switzerland), mounted to a holder, and irradiated (using spiral movements in coronal direction) with a diode laser (GENTLEray 980 Classic Plus; KaVo, Biberach, Germany) with a 200 μm fiber in four different treatment groups: Group 1 (control group) was irradiated in six cycles of 5-sec irradiation/20-sec pause with 2.5 W in the pulse mode. Groups 2 to 4 were irradiated at six cycles of 5-sec irradiation/20-sec pause in the microchopped mode (Group 2-1.6 W; Group 3-2.0 W; Group 4-2.5 W). The applied mode was 25 ms on/25 ms off. Within the on period, the laser delivered an intermittent sequence of energy complexes and the maximum output was equal to the nominated output of the device (12 W). Canals were kept moist by sterile saline irrigation in between irradiations, and temperature changes were continuously measured using a thermal imaging camera. Recordings were analyzed by a mixed model (analysis of variance [ANOVA] for repeated measurements).

RESULTS

The highest mean of temperature rise, 1.94°C ± 1.07°C, was measured in Group 4, followed by Group 3 (1.74°C ± 1.22°C) and Group 2 (1.58°C ± 1.18°C). The lowest increase occurred in Group 1 (1.06°C ± 1.20°C). There was a significant difference (p = 0.041) between the groups. Significant differences were found between Groups 1 and 4 (p = 0.007) and 1 and 2 (p = 0.035). In addition, a marginally significant difference between Groups 1 and 2 (p = 0.052) was noted. There was no significant difference between Groups 2, 3, and 4. Despite the low mean values reported, the highest temperature increase (+5.7°C) was measured in one of the specimens of treatment Group 2 at the middle third.

CONCLUSIONS

Under the conditions used and within the limitations of the study, the microchopped diode laser irradiation is a safe possible treatment option in laser-assisted endodontic treatment, concerning the temperature elevation on the external root surface.

Intrapulpal temperature changes during root surface irradiation with dual-wavelength laser (2780 and 940 nm): in vitro study

This work reports that the ablation volume and rate of porcine skin changed significantly with the change of skin water content. Under the same laser irradiation conditions (532 nm Nd:YAG laser, pulse width = 11.5 ns, pulse energy = 1.54 J, beam radius = 0.54 mm), the ablation volume dropped by a factor of 4 as the skin water content decreased from 40 wt. % (native) to 19 wt. % with a change in the ablation rate below and above around 25 wt. %. Based on the ablation characteristics observed by in situ shadowgraph images and the calculated tissue temperatures, it is considered that an explosive rupture by rapid volumetric vaporization of water is responsible for the ablation of the high water content of skin, whereas thermal disintegration of directly irradiated surface layer is responsible for the low water content of skin.

Radiofrequency heating of metallic dental devices during 3.0 T MRI

OBJECTIVES

To estimate the risk of injury from radiofrequency (RF) heating of metallic dental devices in use during 3.0 T MRI.

METHODS

The whole-body specific absorption rate (WB-SAR) was calculated on the basis of saline temperature elevation under the maximum RF irradiation for 15 min to determine the operation parameters for the heating test. The temperature changes of three types of three-unit bridges, a full-arch fixed dental prosthesis and an orthodontic appliance in use during MRI with a 3.0 T MR system (Magnetom(®) Verio; Siemens AG, Erlangen, Germany) were then tested in accordance with the American Society for Testing and Materials F2182-09 standardized procedure under the maximum RF heating during 15 min RF irradiation.

RESULTS

The system console-predicted WB-SAR was approximately 1.4 W kg(-1) and that measured with a saline phantom was 2.1 W kg(-1). In the assessment of RF heating, the highest temperature increase was +1.80 °C in the bridges, +1.59 °C in the full-arch fixed dental prosthesis and +2.61 °C in the orthodontic appliance.

CONCLUSIONS

The relatively minor RF heating of dental casting material-based prostheses in Magnetom Verio systems in the normal operating mode should not pose a risk to patients. However, orthodontic appliances may exhibit RF heating above the industrial standard (CENELEC standard prEN45502-2-3); therefore, the wire should be removed from the bracket or a spacer should be used between the appliance and the oral mucosa during MRI.

Radiofrequency heating and magnetically induced displacement of dental magnetic attachments during 3.0 T MRI

OBJECTIVE

The aim of this study was to estimate the risk of injury from dental magnetic attachments due to their radiofrequency (RF) heating and magnetically induced displacement during 3.0 T MRI.

METHODS

To examine the magnetic attachments, we adopted the American Society for Testing and Materials F2182-02a and F2052-06 standards in two MRI systems (Achieva 3.0 T Nova Dual; Philips, Tokyo, Japan, and Signa HDxt 3.0 T; GE Healthcare, Milwaukee, WI). The temperature change was measured in a cylindrical keeper (GIGAUSS D600; GC, Tokyo, Japan) with coping of the casting alloy and a keeper with a dental implant at the maximum specific absorption rate (SAR) for 20 min. To measure the magnetically induced displacement force, three sizes of keepers (GIGAUSS D400, D600 and D1000) were used in deflection angle tests conducted at the point of the maximum magnetic field strength.

RESULTS

Temperature elevations of both coping and implant were higher in the Signa system than in the Achieva system. The highest temperature changes in the keeper with implant and keeper with coping were 0.6 °C and 0.8 °C in the Signa system, respectively. The temperature increase did not exceed 1.0 °C at any location. The deflection angle (α) was not measurable because it exceeded 90°. GIGAUSS D400 required an extra 3.0 g load to constrain the deflection angle to less than 45°; GIGAUSS D600 and D1000 required 5.0 and 9.0 g loads, respectively.

CONCLUSIONS

Dental magnetic attachments pose no risk due to RF heating and magnetically induced displacement at 3.0 T MRI. However, it is necessary to confirm that these keepers are securely attached to the prosthesis before imaging.

Effects of three different irrigating solutions and KTP laser irradiation on apical leakage: an electrochemical study

OBJECTIVE

The purpose of this study was to evaluate the effect of three different irrigating solutions (17% EDTA, 10% citric acid and 2.5% NaOCl) and KTP laser irradiation on apical leakage using an electrochemical method.

MATERIALS AND METHODS

Sixty extracted single-rooted human teeth with mature apices were instrumented up to a size 35 K-file. After using each file and before proceeding to the next, canals were irrigated with 2 ml of 2.5% NaOCl. All teeth were then randomly divided into four groups. In group 1, the root canals were irrigated with a final flush of 17% EDTA. In group 2, the root canals were irrigated with a final flush of 10% citric acid. In group 3, the root canals were irradiated with KTP laser at 1 W, 4.45 J/cm(2). In group 4, the root canals were irrigated with a final flush of 2.5% NaOCl. The root canals were then filled using the cold lateral condensation method. Apical leakage was evaluated using an electrochemical method over a period of 10 days. Data were analysed using Tukey HSD and Friedmann tests with p = 0.05 as the level for statistical significance.

RESULTS

The 17% EDTA and 10% citric acid groups had statistically less apical leakage than the 2.5% NaOCl group at days 7, 8, 9 and 10 (p < 0.05); however, no significant differences were found between the tested groups at the other time intervals (p > 0.05). No significant difference was found between the KTP laser group and other groups tested at all time intervals (p > 0.05).

CONCLUSION

All groups were unable to eliminate apical leakage. However, final irrigation with 17% EDTA and 10% citric acid following root canal preparation reduced postobturation apical leakage compared with 2.5% NaOCl irrigation. When KTP laser and the other three irrigants were compared, no significant difference was found.

Effect of light-activated bleaching on pulp chamber temperature rise: an in vitro study

This study aimed to compare the pulp chamber temperature changes that occur with the use of different light sources during vital bleaching with and without application of bleaching agents. One hundred and forty-four mandibular incisor teeth were divided into four groups (n = 36) according to the use of halogen light, light-emitting diode, 3 W and 1.5 W diode laser. The teeth in the main groups were divided into three subgroups (n = 12). First subgroup had no bleaching gel application. By White and Whiteness HP were applied with a thickness of 2 mm to the other subgroups respectively. The labial surfaces of the teeth were irradiated with a total time of 20 s. Temperature changes in the pulp chamber were measured and analysed by using anova and Tukey test. The 3 W diode laser induced the highest pulp chamber temperature rise (P = 0.000). Bleaching gel application reduced the temperature changes in the diode laser groups (P < 0.05). Diode laser activation during vital bleaching induces pulp chamber temperature rise, which may cause thermal tissue damage.

Temperature variation during apicectomy with Er:YAG laser

OBJECTIVE

The purpose of this in vitro study was to evaluate the generated temperature of the Er:YAG laser, with three different pulse durations for apicectomy, compared with tungsten bur and surgical saw.

BACKGROUND DATA

Apicectomy is an endodontic surgery performed to remove the root apex and curette adjacent periapical tissue because of lesions of the apical area that are not healing properly.

METHODS

Sixty single-rooted extracted human teeth were resected by three cutting methods: tungsten bur, surgical saw, and Er:YAG laser irradiation with three different pulse durations; pulse duration 50 μs, pulse duration 100 μs, and pulse duration 300 μs. Teflon-insulated, type K thermocouples were used to measure temperature changes during the apicectomy process. Data were analyzed using the general linear models procedure of the SPSS statistical software program.

RESULTS

Although there was no statistically significant difference for the mean values of temperature changes at 1 mm away to the cutting site of teeth, there was statistically significant difference among groups for the mean values of temperature changes at 3 mm away to the cutting site of teeth. Additionally, there was statistically significant difference among groups for the total time required for apicectomy.

CONCLUSIONS

The laser irradiation with pulse duration 50 μs appears to have the lowest temperature rise and the shortest time required for apicectomy of the three pulse durations. However, Er:YAG laser for apicectomy in all pulse durations could be used safely for resection in endodontics in the presence of sufficient water.

Efficacy of tooth bleaching with and without light activation and its effect on the pulp temperature: an in vitro study

The aim of this in vitro study was to evaluate the colour stability of bleaching after light activation with halogen unit, laser, LED unit or chemical activation up to 3 months after treatment. Four groups of teeth (n = 20) were bleached with Opalescence Xtra Boost (38% hydrogen peroxide) using four different methods: activation with halogen, LED, laser or chemical activation only. All teeth were bleached in one session for four times (4 × 15 min) and the colour was evaluated using a spectrophotometer at the following time points: before bleaching, immediately after bleaching, 1 day, and 1 and 3 months after the end of bleaching. Between the tested time points, the teeth were stored in 0.9% NaCl solution. Additionally, the temperature increase in the pulp chamber was measured using a measuring sensor connected to a computer. Bleaching with the halogen unit showed the highest colour change. Halogen unit, laser and chemical activation resulted in whiter teeth after 1 and 3 months compared to the colour after the end of the bleaching procedure (p ≤ 0.05). Three months after the end of bleaching, the shade changes observed were-halogen: 7.1 > chemical activation: 6.2 > LED: 5.4 > laser: 5.2. Halogen showed the highest temperature increase (17.39°C ± 1.96) followed by laser (14.06°C ± 2.55) and LED (0.41°C ± 0.66) (p < 0.0001). Chemical activation did not affect the temperature in the pulp chamber. The use of light activation did not show any advantages compared to chemical bleaching. Although halogen unit showed the higher shade's change, its use resulted also in the higher pulp temperature. According to the present findings, light activation of the bleaching agent seems not to be beneficial compared to bleaching without light activation, concerning the colour stability up to 3 months after bleaching and the pulp temperature caused during the bleaching procedure.

Bond strength of a self-adhesive resinous cement to root dentin irradiated with a 980-nm diode laser

OBJECTIVE

To assess the bond strength of Rely-X Unicem (RX), in comparison with Cement-Post (CP), to the cervical, middle and apical thirds of root canal dentin irradiated with a 980-nm diode laser.

MATERIAL AND METHODS

Forty maxillary canines were separated into four equal groups according to the cement used and the laser surface treatment: RX/laser irradiation (LI) group; RX/no irradiation (NI) group; CP/LI group; and CP/NI group. Two slices (2-mm thick) of each root third were submitted to a push-out test to assess the bond strength of the cement to the root canal dentin. The data obtained were submitted to two-way ANOVA and fracture analysis was performed by scanning electron microscopy.

RESULTS

The type of cement as well as 980-nm LI at the different root canal thirds significantly affected the bond strength values (p < 0.05). LI promoted an increase in bond strength of RX in all root thirds (p < 0.05). For all groups, bond strength to the cervical third was highest, followed by the middle and apical thirds (p < 0.05). When the cements were compared, RX always presented the highest bond strength in comparison with CP, irrespective of the laser application (p < 0.05). Fracture analysis showed a predominance of mixed failures for RX and of adhesive failure between dentin and cement for CP, irrespective of the laser application.

CONCLUSION

The 980-nm LI promoted an increase in bond strength of the self-adhesive resinous cement to root dentin.

In vitro analysis of human tooth pulp chamber temperature after low-intensity laser therapy at different power outputs

In vitro studies have provided conflicting evidence of temperature changes in the tooth pulp chamber after low-level laser irradiation of the tooth surface. The present study was an in vitro evaluation of temperature increases in the human tooth pulp chamber after diode laser irradiation (GaAlAs, λ = 808 nm) using different power densities. Twelve human teeth (three incisors, three canines, three premolars and three molars) were sectioned in the cervical third of the root and enlarged for the introduction of a thermocouple into the pulp chamber. The teeth were irradiated with 417 mW, 207 mW and 78 mW power outputs for 30 s on the vestibular surface approximately 2 mm from the cervical line of the crown. The highest average increase in temperature (5.6°C) was observed in incisors irradiated with 417 mW. None of the teeth (incisors, canines, premolars or molars) irradiated with 207 mW showed temperature increases higher than 5.5°C that could potentially be harmful to pulp tissue. Teeth irradiated with 78 mW showed lower temperature increases. The study showed that diode laser irradiation with a wavelength of 808 nm at 417 mW power output increased the pulp chamber temperature of certain groups of teeth, especially incisors and premolars, to critical threshold values for the dental pulp (5.5°C). Thus, this study serves as a warning to clinicians that "more" is not necessarily "better".

Non-surgical periodontal therapy assisted by potassium-titanyl-phosphate laser: a pilot study

As the American Academy of Periodontology indicates, the treatment of chronic periodontitis should be achieved in the least invasive manner through non-surgical periodontal therapy. However, complete removal of subgingival plaque and calculus is hindered with increasing probing depth (PD) and furcation involvement using hand, sonic or ultrasonic instruments. Many authors have suggested that the use of laser as an adjunct to scaling and root planing (SRP) might improve the effectiveness of conventional periodontal treatment. The aim of this study was to evaluate potassium-titanyl-phosphate (KTP) laser in non-surgical periodontal therapy. Seven hundred and thirty sites with probing depths of 4-6 mm were involved in the study. The sites were divided into four groups: control (SRP, chlorhexidine gel 0.5%), group A (SRP, chlorhexidine gel 0.5%, three sessions of KTP laser irradiation); group B (SRP, three sessions of KTP laser irradiation) and group C (SRP, irrigation with povidone-iodine 10%, three sessions of KTP laser irradiation). KTP laser was used with the following parameters: output power 0.6 W, time on 10 ms, time off 50 ms, 30 s per irradiation, fluence 19 J/cm(2). All the sites showed improvement in all clinical parameters. Clinical attachment loss (CAL), pocket probing depths (PPDs) and bleeding on probing (BOP), especially in the lased groups, showed significant results (P < 0.001). Our experience showed KTP laser to be a significant help in SRP; nevertheless, more studies are necessary to confirm our results.

Effect of simulated pulpal microcirculation on intrapulpal temperature changes following application of heat on tooth surfaces

AIM

To evaluate ex vivo whether a simulated pulpal microcirculation inside a pulp chamber influenced intrapulpal temperature rise following application of heat on tooth surfaces.

METHODOLOGY

An ex vivo model that allowed the circulation of 37 degrees C warm water inside the pulp chamber of an extracted human tooth was designed. The experimental model resembled pulpal microcirculation. After application of specific thermal stimuli for 30 s to the external surface of 15 maxillary central incisors, lateral incisors and canines, temperature changes were measured in the pulp chamber. The Greenhouse-Geisser and Bonferroni tests were used for analysis of the data. The level of significance was set at 0.05.

RESULTS

Significant differences were found in all three groups of teeth between temperature measurements with or without intrapulpal water flow. Additionally, temperature changes resulting from the application of different stimuli to the group of lateral incisors were significantly greater compared with the other groups of teeth (P < 0.05).

CONCLUSIONS

The importance of the cooling effect of simulated pulp microcirculation in the thermal behaviour of the dentine was established. Thickness of tooth tissue influenced significantly pulp temperature rise ex vivo.

Effects of KTP Laser Irradiation, Diode Laser, and LED on Tooth Bleaching: A Comparative Study

OBJECTIVE

This in vitro study examines the whitening efficacy of a light-emitting diode (LED), a diode laser, and a KTP laser irradiation in dental bleaching by analyzing the change in color achieved from the treatment, the temperature increase induced in the pulpal cavity, as well as enamel microhardness measurement after treatment.

BACKGROUND DATA

Bleaching techniques achieved significant advances with the use of coherent or incoherent radiation sources to activate the bleaching agents.

METHODS

A hydrogen peroxide bleaching agent, Hi-Lite, was stimulated with an LED, a 980-nm diode laser at 0.8 W, or a 532-nm KTP laser at 1.0 W for 30 sec on 64 extracted human incisors. During irradiation, the temperature in the pulpal cavity was monitored. The color change was evaluated using the CIE L*a*b* color space measurement system, and Vikers enamel microhardness was tested after treatment.

RESULTS

A mean total color difference value (DeltaE*) greater than 5.0 was obtained in each group. KTP-laser-induced bleaching gave a significantly higher DeltaL* (8.35) after treatment (p < 0.01). Neither LED nor the two lasers produced significant differences in the enamel microhardness after treatment (p > 0.01). Mean maximal pulpal temperature rise was 2.95 degrees C for LED, 3.76 degrees C for KTP laser, and 7.72 degrees C for diode laser, respectively.

CONCLUSION

The results of this study suggest that KTP laser is effective at providing brighter teeth. According to the conditions used in this study, the LED and KTP laser induced a safer pulpal temperature increase when assisted with Hi-Lite bleaching gel.

Histological evaluation of the use of diode laser as an adjunct to traditional periodontal treatment

OBJECTIVE

The aim of this study was to describe in vivo effects of scaling and root planing associated with 980-nm diode laser irradiation on periodontally diseased root surfaces.

BACKGROUND DATA

Rapid advances in the development of laser technologies used in dental offices demand careful evaluation of the respective histopathologic effects of each new system. There have been no reports of scaling and root planing associated with 980-nm diode laser effects on root surfaces after in vivo application.

METHODS

Single rooted teeth and multiple rooted teeth considered for extraction due to severe periodontal disease were included in the study. For light microscopic investigation, a resin-embedding technique was used to cut the undecalcified teeth into 30-microm-thick cross-sections and stained. The following parameters were recorded by a blind examiner: remaining debris, root surface morphology, and thermal side effects.

RESULTS

Root surfaces instrumented with hand instruments and diode laser in vivo did not show detectable surface alterations. There were no signs of thermal side effects in any of the teeth treated.

CONCLUSION

The present in vivo study showed that associated therapy was suitable for non-surgical periodontal treatment. The results suggest that the diode laser may be routinely used as an adjunct to scaling and root planing without damage to the cementum tissue.

Bactericidal effects of diode laser onStreptococcus mutans after irradiation through different thickness of dentin

BACKGROUND AND OBJECTIVES

A reliable method to eradicate the bacteria of residual carious dentin has not yet been developed. The aim of this study was to evaluate the antibacterial effect of a diode laser on Streptococcus mutans through different thickness (500, 1,000, and 2,000 microm) of human dentin. The thermal effect of laser irradiation was also investigated.

STUDY DESIGN/MATERIALS AND METHODS

Dentin specimens were inoculated with 2 microl of S. mutans on one side and irradiated by a diode laser on the other side with a power output ranging from 0.5 to 7 W. The laser tip was swept with the whole irradiation area of 7 mm x 3 mm at a speed of about 10 mm/second with a total irradiation time of 30 seconds. Cooling with distilled water (30 ml/minute) was applied simultaneously during laser irradiation. After laser irradiation, the bacteria was removed from the dentin surfaces and cultured for 48 hours at 37 degrees C anaerobically to assess the colony forming units (CFU) per ml. The morphology of the lased bacteria and the temperature rise during laser irradiation were observed by scanning electron microscope (SEM) and measured by thermocouple, respectively.

RESULTS

The results revealed that 7 W of laser power could kill 97.7% of CFU through 500 microm thickness of dentin. However, the bactericidal efficiency was significantly reduced as the dentin thickness was increased. The morphological changes of lased bacteria ranged from less affected such as loss of their wall bands and existence of minicells to more severely degenerated, such as disintegration and fusion of cells with pores on the cell wall. Only the dentin specimens with a thickness of 500 microm exhibited a temperature rise greater than 5.5 degrees C after receiving 5 or 7 W of laser irradiation.

CONCLUSIONS

A diode laser can eliminate the Streptococcus mutans of the residual carious dentin without inducing high pulpal temperature rise when the remaining dentin thickness is greater than 1 mm.

Thermal injury through intraradicular heat transfer using ultrasonic devices

BACKGROUND

The use of ultrasonic energy is a highly efficient method of removing obstructions and cements within the root canal space when re-treatment or rehabilitation of that ultrasonic energy dislodges and removes cemented objects from the bonded interface of the canal wall. When using this method, there is less potential for structural loss or root damage and significantly less operator stress than when using other methods.

CASE DESCRIPTIONS

There is little evidence in published research of the considerable heat transfer that occurs during use of ultrasonic devices to remove posts, pastes and separated instruments in teeth. The authors present three cases of patients who experienced serious burn injuries during application of ultrasonic energy for restorative dentistry. The authors also offer techniques and strategies for safe and effective use of ultrasonic devices.

CLINICAL IMPLICATIONS

On the basis of the best available evidence, the authors recommend strategies to provide safe and effective therapy while using ultrasonic devices in intraradicular obstruction removal. The intent of the suggested protocols is to provide advanced and sophisticated therapies in a safe and regulated manner with patient safety as an overriding priority.

Effects of Laser Irradiation on Tensile Strength of Bovine Dentin

OBJECTIVE

The purpose of the present study was to investigate the tensile strengths of dentin after laser irradiation using three kinds of dental lasers to elucidate the laser-irradiation effect on dentin properties.

BACKGROUND DATA

Different kinds of laser devices have been developed in dentistry. The characteristics of each laser are determined by its original wavelength; however, one common feature is to generate heat in irradiated tissues, and such heat possibly affects dentin collagen, which contributes to tensile strength of the tissues.

MATERIALS AND METHODS

Er:YAG, CO2, and diode (GaAlAs) lasers were used to irradiate bovine dentin. Subsequently, tensile test specimens were made from the irradiated dentin and tensile tests were conducted. The tensile strengths were analyzed using the paired-t test and Weibull analysis. Irradiated dentin was also observed transversally using light microscopy.

RESULTS

The tensile strengths of the lased dentin and the control group for the Er:YAG, CO2, and diode lasers were 73.1 and 78.5, 70.3 and 74.3, and 64.3 and 71.0 MPa, respectively. The tensile strength of the dentin had a tendency to decrease with laser irradiation. Weibull analysis indicated that the laser influence was different among the three kinds of laser apparatuses and seemed to correspond to the depths the laser beam reached, which were suggested by light microscopy observation.

CONCLUSION

Laser irradiation could possibly decrease dentin tensile strength, which suggests the importance of careful use of laser for hard tissue treatment, considering its energy-transforming characteristics.

Pulpal temperature rise during light-activated bleaching

The purpose of this study was to measure intrapulpal temperature rise induced by two kinds of bleaching gels when the tooth was exposed to a variety of light-curing units and a diode laser in vitro. The root portions of 80 extracted intact human maxillary central incisors were sectioned with a carborundum disk approximately 2 mm below the cementoenamel junction perpendicular to the long axis of the teeth. Two bleaching agents containing heat-enhancing colorant was applied to the labial surface. Light-curing units used were a conventional halogen (40 s), a high-intensity halogen (30 s), a light-emitting diode unit (40 s), and a diode laser (15 s). The temperature rise was measured in the pulpal chamber with a J-type thermocouple wire that was connected to a data logger. Ten specimens were used for each system and bleaching-agent combination. Differences between the starting temperature and highest temperature reading were taken and the calculated temperature changes were averaged to determine the mean value in temperature rise. Temperature rise values were compared using two-way analysis of variance (ANOVA) at a preset alpha of 0.05. Temperature rise varied significantly depending on curing unit and diode laser used. The diode laser induced significantly higher temperature increases than any other curing unit (11.7 degrees C). The light-emitting diode unit produced the lowest temperature changes (6.0 degrees C); however, there were no statistically significant differences among the curing units and there were no statistically significant differences between bleaching agents. Light activation of bleaching materials with diode laser caused higher temperature changes as compared to other curing units and the temperature rise detected was viewed as critical for pulpal health.

Diode Laser (980 nm) as Adjunct to Scaling and Root Planing

OBJECTIVE

The aim of this study was to evaluate clinical efficacy of InGaAsP diode laser as adjunct to traditional scaling and root planing.

BACKGROUND DATA

The use of laser is one of the most recent methods in nonsurgical periodontal treatment. Efficacy and side effects of each type of laser treatment have yet to be determined.

METHODS

Thirty patients suffering from moderate periodontal disease have been considered. They were randomly selected to undergo either scaling and root planing with curets, or scaling and root planing combined with InGaAsP laser (980 nm and 2 W). The papilla bleeding index (PBI), bleeding on probing (BOP), and clinical attachment level (CAL) were registered at the beginning and end of treatment.

RESULTS

At the end of treatment, PBI average in the group treated with laser was 0.24 versus 0.43 in the group under conventional treatment (p = 0.014). In the group undergoing scaling and root planing, BOP decrease is 19.55% less (p < 0.0001) than in the group also treated with laser. Nevertheless, CAL differences cannot be considered significant between both groups (p = 0.67).

CONCLUSIONS

Scaling and root planing in combination with laser produce moderate clinical improvement over traditional treatment.