Pulpal Temperature Rise Research Articles

An SEM study on the effect of 9.3-µm CO2 laser on dentinal tubules for hypersensitivity treatment.

In-vitro studies were performed on dentin of extracted human molars to investigate the effectiveness of 9.3μm CO2 laser irradiation to occlude dentinal tubules. The observed occlusion of dentinal tubules with the irradiation was compared with application of three reagents: 2% Sodium Fluoride gel, an aqueous solution of hydroxyapatite nanoparticles and an equal mix of the two. We show that 9.3μm CO2 laser irradiation occludes dentinal tubules, and the use of laser irradiation produces better occlusion of the opened tubules compared to the use of topical reagents. Nine extracted and cleaned human molars were cut to obtain dentin disks of thickness of 3-5mm. Each disc was divided into four quarters, and each quarter served as two samples corresponding to irradiated and non-irradiated group counterparts. Five disks were used to study the effect of various laser irradiation energies on the dentinal tubules to find a good pulse fluence for occlusion of the dentinal tubules, and four disks were used for studying the effects of reagents and irradiation at the pulse fluences found in the first part of the study. The samples were irradiated with a beam diameter of 1mm (1/e2) at 15Hz pulse repetition rate, scanned automatically using a set of scanning mirrors. Samples were imaged using Scanning Electron Microscope (SEM) which were processed to determine tubule diameter. Safety of the irradiation treatment was investigated on 6 samples by measuring pulpal temperature rise. The effect of three topical reagents corresponding to 2% Sodium Fluoride gel (F), Hydroxyapatite nanoparticles (HA) and an equal mix of F and HA (HAF) on dentinal tubule occlusion was evaluated and compared with the laser irradiation. In all examined cases, laser irradiation at a fluence of 0.81J/cm2 resulted in a temperature increase less than 3°C which is safe, and no surface cracking was observed. There is a threshold pulse fluence of 0.27J/cm2 above which, laser produced surface melting. At a pulse fluence of 0.81J/cm2 a layer of recast of melted dentin was formed. Under this layer, peritubular dentin melting and occluding of the dentinal tubules was observed. Application of either F or HA or HAF did not produce visible occlusion effect on open tubules after washing and microbrushing with excess distilled water. 9.3μm CO2 laser irradiation on extracted human molar dentin at pulse fluence of 0.81J./cm2 resulted in tubule area reduction by 97% without rising pulpal temperatures to unsafe levels.

Influence of light exposure techniques on in vitro pulp temperature rise during bulk fill composite Class I restorations.

This in vitro study assessed peak temperature and temperature increase (ΔT) within the pulp chamber during different extended photoactivation techniques (EPT-applying similar radiant exposure values) to resin-based composites (RBCs) placed in a Class I cavity preparation in an extracted human lower third molar. A T-type thermocouple was placed in the pulp chamber and connected to a temperature analysis device (Thermes, Physitemp). The tooth was attached to an assembly simulating the in vivo environment (controlled baseline pulp chamber temperature and fluid flow). The real-time pulp chamber temperature was evaluated throughout the photoactivation (Bluephase N, Ivoclar Vivadent) of two bulk-fill RBCs: Tetric N Ceram Bulk Fill (TBF; shade: IVA; Ivoclar Vivadent); Surefill SDR flow + (SDR, shade: Universal; Dentsply Sirona), which were exposed to different curing techniques: 40s-occlusal surface; 20s-occlusal + 10s-buccal + 10s-lingual surfaces; 10s-buccal + 10s + lingual + 20s-occlusal surfaces. Each EPT delivered 42.4J/cm2. Vickers hardness (VHN) was measured on the removed, sectioned RBC restorations at the top and bottom middle areas after curing. ΔT and VHN data were analyzed using 2-way ANOVA followed by Bonferroni post-hoc test (α = 0.05). Peak temperature data were analyzed using one-way ANOVA and Dunnett's post-hoc test (α = 0.05). SDR showed higher ΔT values than TBF (p = 0.008) in some EPTs. Neither technique resulted in ΔT values greater than 5.5 °C. Both composites had acceptable bottom/top hardness ratios (greater than 80%), regardless of the photoactivation technique. The evaluated EPTs may be considered safe as a low-temperature increase was noticed within the pulp chamber.

Evaluation of the laser wavelength role on tooth bleaching in terms of color change, roughness, and microhardness with pulpal rapid temperature monitoring: an in vitro study.

This in-vitro study evaluates the efficacy of the teeth bleaching approach using different laser wavelengths (405nm blue diode, 940nm infrared diode, and Er,Cr:YSGG 2780nm lasers) in comparison to the conventional method using light-emitting diode (LED) sources (420-480)nm. Eighty caries-free sound human premolars were randomly divided into four groups (N=20). Each group received a different bleaching procedure. Then each group was further subdivided into two subgroups (N=10) stained with different solutions. The pulp chamber temperature rise was recorded using an optical fiber sensor with a novel design and fabrication. The color was analyzed using a digital spectrophotometer. Five samples of each subgroup were tested for surface roughness, while the others were tested for Vickers microhardness. The bleaching process with a short wavelength 405nm blue diode laser showed the best results for the shade, with a minimum pulpal temperature increase indicating no possible necrosis and hence maintaining tooth vitality. Additionally, a remarkable reduction in bleaching time was achieved compared to the conventional approach. This process also yielded the highest color change (Δ E) and increased microhardness, with no noticeable change to the tooth roughness. The 405nm blue diode laser applied for bleaching showed the best bleaching activity against tested stains and negligible pulpal temperature rise with a noticeable reduction in the bleaching time. The proposed novel method to measure temperature change could be used to develop a promising smart sensor for quick, effective, repeatable, and in-situ monitoring of human body temperature.

In-vitro pulpal temperature increases when photo-curing bulk-fill resin-based composites using laser or light-emitting diode light curing units.

To evaluate the in vitro pulpal temperature rise (ΔT) within the pulp chamber when low- and high-viscosity bulk-fill resin composites are photo-cured using laser or contemporary light curing units (LCUs). The light output from five LCUs was measured. Non-retentive Class I and V cavities were prepared in one upper molar. Two T-type thermocouples were inserted into the pulp chamber. After the PT values reached 32°C under simulated pulp flow (0.026 mL/min), both cavities were restored with: Filtek One Bulk Fill (3M), Filtek Bulk Fill Flow (3M), Tetric PowerFill (Ivoclar Vivadent), or Tetric PowerFlow (Ivoclar Vivadent). The tooth was exposed as follows: Monet Laser (1 and 3s), PowerCure (3 and 20 s), PinkWave (3 and 20 s), Valo X (5 and 20 s) and SmartLite Pro (20 s). The ΔT data were subjected to one-way ANOVA followed by Scheffe's post hoc test. Monet 1s (1.9J) and PinkWave 20 s (30.1J) delivered the least and the highest amount of energy, respectively. Valo X and PinkWave used for 20 s produced the highest ΔT values (3.4-4.1°C). Monet 1s, PinkWave 3s, PowerCure 3s (except FB-Flow) and Monet 3s for FB-One and TP-Fill produced the lowest ΔT values (0.9-1.7°C). No significant differences were found among composites. Short 1- to 3-s exposures produced acceptable temperature rises, regardless of the composite. The energy delivered to the tooth by the LCUs affects the temperature rise inside the pulp. The short 1-3s exposure times used in this study delivered the least amount of energy and produced a lower temperature rise. However, the RBC may not have received sufficient energy to be adequately photo-cured.

Erbium laser-assisted ceramic debonding: a scoping review.

Removal of ceramic restorations and appliances can be time consuming, invasive, and inconvenient. Erbium lasers offer an alternative noninvasive method for debonding of ceramic appliances. This paper aims to provide a comprehensive review of current literature on the effectiveness of erbium lasers for removal of ceramic restorations and appliances from natural teeth and dental implants. A comprehensive search of 7 databases, including Medline (Ovid), Embase, Dentistry and Oral Sciences Source (DOSS), Web of Science, Cochrane Library, and ProQuest Dissertations and Theses was performed. The inclusion and exclusion criteria were agreed prior to the literature search. Two reviewers independently screened the title and abstract. A third reviewer then broke the tie, if any. The selected articles then underwent full text review and the data was extracted. The search identified 4117 unique articles published through June 10, 2021. Studies were assessed and categorized based on the type of restoration/appliance, type of abutment, type of laser, laser settings, efficacy of debonding, and pulpal temperature rise. Thirty-eight full-text articles were reviewed for inclusion. Time for ceramic debonding varies depending on the type of restorations and materials. Removal of zirconia crowns from teeth and implant abutments requires a longer period of time compared to lithium disilicate crowns. Temperature increases were reported as 5.5 degrees or less. Laser setting and laser type affect the debonding time and the increase in temperature. Examinations of debonded ceramics demonstrated no known structural damages resulting from laser applications. Erbium lasers are effective noninvasive tools to remove all ceramic restorations/appliances from natural teeth and implant abutments without causing harm to abutments. Laser-assisted debonding should be considered as a viable alternative to rotary instrumentation for ceramic crowns; however, clinical studies of erbium-assisted ceramic retrieval are needed.

In-office dental bleaching with violet light emitting diode: bleaching efficacy and pulpal temperature rise.

ObjectivesThis study evaluated the bleaching efficacy of different in-office protocols associated with violet light emitting diode (V-LED), and measured the pulpal temperature rise caused by V-LED with or without gel application.Materials and MethodsBovine incisors were distributed in 4 groups (n = 10): VL – V-LED; HP – 35% hydrogen peroxide (control); HYB – hybrid protocol, V-LED applied without gel for 10 irradiation cycles followed by V-LED applied with gel for another 10 irradiation cycles; and HPVL – gel and V-LED applied for 20 irradiation cycles. Three bleaching sessions were performed with 7-day intervals. Bleaching efficacy was evaluated with , ΔE00 and ΔWID. Data were recorded at baseline, 7, 14, 21 and 70 days. For pulpal temperature rise, thermocouples were placed inside the pulp chamber of human incisors. To determine intrapulpal temperature, the teeth were irradiated with V-LED with or without application of bleaching gel. Color difference data were analyzed by 2-way repeated measures ANOVA and Tukey’s test. Pulpal temperature was analyzed by t-test (α = 5%).ResultsVL exhibited lower color ( and ΔE00) and whiteness changes (ΔWID) than the other groups. HPVL presented higher color change values than HYB. HYB and HPVL showed not different ΔWID values; and HP showed the highest whiteness changes at all times. There were significant differences comparing ΔT with gel (8.9°C) and without gel application (7.2°C).ConclusionsHPLV was more efficient than HYB. The 2 protocols with VL showed similar results to control. Gel application combined with VL promoted higher pulpal temperature than to the no gel group.

Whitening Efficiency of Laser 940 nm and LED (450-505) nm on Extrinsic Stained Teeth (in vitro study)

Background: Teeth staining is one of the esthetic problems faced by dentists and patients. Many methodshave been suggested as crowns, restorations and bleaching. Dental bleaching effectiveness depends on manyfactors including technique and materials.Objectives: Studying the effect of diode laser 940 nm and light emitting diode (450-505) nm in bleaching ofstained teeth regarding : whitening efficiency; pulp temperature; surface roughness and topography.Materials and Methods: 40 extracted anterior teeth divided into 6 groups immersed at 37 oC in eithertea; coffee; cola ; juice for 14 days, tobacco stained teeth as well as control group were also included (immersed in distilled water ). These groups were subdivided into laser group or light emitting diode groupbleached according to manufacturer specifications. Shades of teeth were recorded before and after bleaching.Furthermore, temperature changes during bleaching were recorded using thermocouple Thermometer. Allspecimens were examined under light microscope, Atomic Force Microscope and Sectioning ElectronicMicroscope to study the surface roughness and topography.Results: the light emitting diode group yielded slight significant whitening efficiency with more pulptemperature rise (3.4 ºC) compared to the laser group (1.4 ºC). Both groups showed non-significant effect onroughness and topography compared to control group.Conclusion: Although light emitting diode group showed slightly significant shade improvement, but theincrease in pulp temperature was greater than that of laser group indicated better prognosis and safety whendiode laser 940 nm used. Conducting between efficiency and preservation, diode laser is superior in safetyand slightly similar whitening efficiency.

The effect of laser-activated bleaching with 445 nm and 970 nm diode lasers on pulp chamber temperature rise: an in vitro study

The aim of this study was to determine the pulp chamber temperature changes during bleaching procedures with irradiation from 445 nm and 970 nm diode lasers at different powers. A total of 120 human maxillary central incisors were used for this study. Diode lasers at two different wavelengths were irradiated in this evaluation: 970 nm at 1.5 W of power, 970 nm at 2 W, 445 nm at 1 W and 445 nm at 1.5 W. A thermometer was inserted into the pulp chamber and the temperature increase after bleaching was recorded. The results indicated that there was not a significant difference between the groups at the same wavelengths (P > 0.05). However, there was a significant difference between groups at different wavelengths (P < 0.05). The highest recorded pulp temperature increase was for the 970 nm diode laser with 2 W of power (2.0 0.5), and the lowest pulp temperature rise was 0.1 0.2 for the 445 nm diode laser with 1 W of power. According to the results of this study it can be concluded that the temperature elevation after bleaching with the diode laser at the wavelengths 970 nm and 445 nm is in the safe range, and both wavelengths with the parameters applied in this study can be used as prudent in-office bleaching techniques.

Can We Determine an Appropriate Timing to Avoid Thermal Pulp Hazard During Gingivectomy Procedure? An In Vitro Study with Diode Laser.

Objective: Diode laser (DL) is a frequently preferred tool for soft tissue incision and ablation in oral surgery. The aim of this study was to find the most effective irradiation time protocol to avoid potential harmful temperature rise in pulp during DL-assisted gingivectomy. Materials and methods: Ninety human freshly extracted teeth (30 anterior, 30 premolar, and 30 molar) were irradiated using a 940 nm DL with power output of 1 and 2 W and exposure time of 10, 20, 30, 40, 50, and 60 sec per specimen. Intrapulpal temperature was evaluated with thermocouple. Additionally, the effect of dark deposits on root surface for intrapulpal temperature rise was investigated. Temperature differences with every 10 sec were evaluated for three different teeth types, and statistical analyses were performed. Results: Anterior and premolar teeth exceeded the threshold values earlier than molar teeth for both 1 and 2 W. Despite the significant differences among the types of teeth, at 10 sec, temperature rise recorded for all types of teeth was below the critical value of 5.6°C, which cause pulp damage. Dark deposits on teeth surface boosted thermal effect of DLs (p < 0.01). Conclusions: Gingivectomy with DLs at 1 W on anterior, premolar, and molar teeth for 20, 40, and 60 sec, respectively, generates acceptable temperature rise; however, it should be <10, 20, and 40 sec at 2 W, respectively. Especially in the anterior teeth, DLs should be performed with caution to avoid pulp damage.

Laser Aided Ceramic Restoration Removal: A Comprehensive Review.

Introduction: All-ceramic restorations are being widely used due to its various advantages. However, they have restricted durability and may have to be removed. The conventional procedure for removal is grinding the restoration with rotary instruments which are considered time-consuming and inconvenient. A newer advantageous method is the application of lasers for debonding ceramics from the tooth surface. The objective of this study is to provide a comprehensive literature review on laser-aided ceramic restorations debonding. Methods: We searched PubMed and Google Scholar databases. Seven articles from 2011 to 2018 were identified. Studies were assessed for the efficacy of laser application and the amount of pulpal temperature rise. Results: Studies selected were categorized according to variables including shear bond strength, debonding time and intrapulpal temperature. Oztoprak and Iseri investigated that erbium-doped yttrium, aluminum, and garnet (Er:YAG) laser application reduced shear bond strength of ceramic laminate veneers. The time of debonding took an average of 190 seconds in Rechmann's study and 106 seconds in Morford's study. One of the main issues while using the laser is thermal irritation of the pulp. A 5.5°C temperature increase may cause pulpal damage according to Zach and Cohen. Philips et al and Rechmann et al reported no intrapulpal harm due to temperature increase. Additionally, Phillips et al demonstrated that the laser setting affects both the debonding time and the temperature alterations and that a laser adjustment of 2.5 W/25 Hz would be the best safest group. Conclusion: Removal of ceramic crowns and veneers from tooth surfaces can be successfully done by Er:YAG laser application in a less time-consuming procedure and without any harm to the underlying dentin. However, a temperature rise in the pulp may occur which could be overcome by adequate air water cooling.

Pulp Temperature Rise Induced by Light-Emitting Diode Light-Curing Units Using an Ex Vivo Model.

The aim of this research was to compare the pulp temperature (PT) rise induced by four light-emitting diode light-curing units (LED LCUs) (Bluephase 20i, Demi Ultra, SPEC 3, and Valo) in different curing modes. Immediately after extraction, the pulp chamber of 11 premolars was accessed from the palatal cervical third of the crown for insertion of fiber Bragg grating (FBG) sensors for temperature measurement and kept in a 37.0° water bath. The teeth were then submitted to a random sequence of curing modes with four irradiations at 30 s intervals. Care was taken to ensure complete pulp temperature reset between curing modes. The curing modes were classified as high-energy (above 80 J/cm2) or low-energy (below 40 J/cm2) according to the total energy density delivered. Statistical analysis was performed with repeated ANOVA measures and Pearson’s correlation for the association between energy density and temperature variation. The significance level was set to 0.05. All curing units promoted a statistically significant PT rise (p < 0.01). After four emissions, the PT rise was higher than 5.0 °C for the high-energy curing modes. The low-energy modes induced approximately a 2.5 °C rise. A strong positive correlation was found between energy density and PT increase (R = 0.715; p = 0.01). Exposure of intact premolars to LED LCUs induced significant and cumulative PT rise. Curing modes emitting high energy densities produced higher PT variations. Radiant exposure was positively correlated to PT variation.

Controlling In Vivo, Human Pulp Temperature Rise Caused by LED Curing Light Exposure.

The objective of this study was to evaluate the in vivo effectiveness of air spray to reduce pulp temperature rise during exposure of intact premolars to light emitted by a high-power LED light-curing unit (LCU). After local Ethics Committee approval (#255945), intact, upper first premolars requiring extraction for orthodontic reasons from five volunteers received infiltrative and intraligamental anesthesia. The teeth (n=9) were isolated using rubber dam, and a minute pulp exposure was attained. The sterile probe from a wireless, NIST-traceable, temperature acquisition system was inserted directly into the coronal pulp chamber. Real-time pulp temperature (PT) (°C) was continuously monitored, while the buccal surface was exposed to a polywave LED LCU (Bluephase 20i, Ivoclar Vivadent) for 30 seconds with simultaneous application of a lingually directed air spray (30s-H/AIR) or without (30s-H), with a seven-minute span between each exposure. Peak PT values were subjected to one-way, repeated-measures analysis of variance, and PT change from baseline (ΔT) during exposure was subjected to paired Student's t-test (α=0.05). Peak PT values of the 30s-H group were significantly higher than those of 30s-H/AIR group and those from baseline temperature (p<0.001), whereas peak PT values in the 30s-H/AIR group were significantly lower than the baseline temperature (p=0.003). The 30s-H/AIR group showed significantly lower ΔT values than did the 30s-H group (p<0.001). Applying air flow simultaneously with LED exposure prevents in vivo pulp temperature rise.

Pulpal Temperature Rise: Evaluation after Light Activation of Newer Pulp-Capping Materials and Resin Composite.

Background:To evaluate temperature changes in pulp chamber during light activation of newer pulp- capping materials and composite resin using light-emitting diode.Materials and Methods:A standardized Class I cavity was prepared in 80 extracted, intact, noncarious mandibular first molars, keeping remaining dentin thickness of 0.5 mm. The teeth were divided into four groups of 20 teeth each. Following this, apical third of the mesial root of each tooth was cut and a K type thermocouple attached to digital thermometer was inserted into pulp chamber from the sectioned mesial root. Whole assembly with teeth was suspended in water bath with constant temperature at 37°C. The previously divided teeth in four groups, were lined with Calcimol LC (Group A), Activa (Group B), TheraCal LC (Group C), and Ionoseal (Group D), followed by 3 increments of Filtek Z350 × T universal restorative. The temperature rise following light activation of pulp-capping material, bonding agent, and composite was noted.Results:The temperature rise in the pulp chamber after light activation of Activa was highest among all pulp-capping materials, followed by teeth lined with Calcimol LC, Ionoseal, and least in teeth with TheraCal LC.Conclusions:Temperature rise in the pulp chamber after light activation of newer pulp-capping materials and composite was below critical threshold for irreversible pulpal damage. Among all the pulp-capping materials, TheraCal LC showed lowest temperature rise in pulp chamber.

The effect of ultra-fast photopolymerisation of experimental composites on shrinkage stress, network formation and pulpal temperature rise

Objectivesto complement our previous work by testing the null hypotheses that with short curing times and high DC, TPO-based resin composites would exhibit (1) higher polymerization stresses and consequently display (2) higher temperature rise and (3) higher flexural modulus, flexural strength and hardness, compared to a conventional CQ-based experimental composite. MethodsTwo experimental resin composites using either Lucirin-TPO or camphorquinone/DMAEMA as photoinitiators were prepared. Light curing was carried out using spectral outputs adapted to the absorption properties of each initiator. Different irradiation protocols were selected (0.5, 1, 3, 9s at 500, 1000 and 2000mW/cm2 for Lucirin-TPO based composites and 20 or 40s at 1000mW/cm2 for Lucirin-TPO and camphorquinone-based composites). Degree of conversion (DC) was measured in real time by means of FT-NIR spectroscopy. Pulpal temperature rise (ΔT) was studied in a tooth model. Polymerization stress was monitored using the Bioman instrument. For cured specimens, flexural modulus and flexural strength were determined using a three point bending platform and Vickers hardness was determined with a microhardness indentor on samples prior to and after 24h incubation in 75/25 ethanol/H2O. Premolars were restored with both materials and microleakage at the teeth/composite interfaces following restoration was assessed. ResultsLucirin-TPO-based composites irradiated at radiant exposures of 3J/cm2 and more exhibited significantly higher DCs, associated with increased flexural moduli and hardness compared to CQ-based composites. For an ultra-short irradiation time of 1s at 1000mW/cm2, TPO-composites displayed similar polymerization stresses compared to CQ-controls with yet a 25% increase for flexural modulus and 40% increase for hardness measured after EtOH/H2O sorption. Higher stress rates were however observed in all curing protocols compared to CQ-composites. Microleakage was similar between TPO and CQ-composites irradiated at 1000mW/cm2 for 3 and 20s respectively, while a significant increase was observed for TPO-composites irradiated for 1s. ΔT measured through a 0.6mm thick dentin layer were all below 5.5°C; TPO-composites exhibited similar or lower values compared to controls. SignificanceThe use of Lucirin-TPO in resin composites along with appropriate curing conditions may allow for a major reduction of irradiation time while improving mechanical properties. The amount of stress observed during polymerization in TPO-based composites can be similar to those using CQ and the cohesion at the restoration-tooth interface was not affected by short curing times. Contrary to other studies, we found that the temperatures increases measured during polymerization were all well below the 5.5°C threshold for the pulp.

Temperature rise in pulp and gel during laser-activated bleaching: in vitro

The aim of this study was to evaluate the increase in temperature induced by various light sources during in-office bleaching treatment, under simulated blood microcirculation in pulp conditions. Ten freshly extracted human maxillary central incisors were used for the study. The roots of the teeth were removed from approximately 2 mm below the cementoenamel junction and fixed on an apparatus for the simulation of blood microcirculation in pulp. A J-type thermocouple wire was inserted into the pulp chamber through an artificial access at the lingual surfaces of the teeth, and another thermocouple wire was fixed on the labial surface of the teeth meanwhile. An in-office bleaching agent, intense red in color and with 30% water content, was applied to the labial surfaces of the teeth, and repeating measurements were made for each tooth using three different light sources: Er:YAG laser (40 mJ, 10 Hz, 20 s), 810-nm diode laser (4 W, 20 s, CW), and high-intensity light-emitting diodes (LED) (1,100 mW/cm(2), 20 s) as the control. Temperature increase in the pulp chamber and within the bleaching gel during light application were recorded and statistically evaluated. The highest pulp temperature increases were recorded for the diode laser group (2.61 °C), followed by the Er:YAG laser (1.86 °C) and LED (1.02 °C) groups (p < 0.05; analysis of variance (ANOVA), Tukey's honestly significant difference (HSD)). Contradictorily, the lowest gel temperature increases were recorded for diode laser (6.21 °C) and followed by LED (12.38 °C) and Er:YAG (20.11 °C) groups (p < 0.05; ANOVA, Tukey's HSD). Despite the significant differences among the groups, the temperature increases recorded for all groups were below the critical value of 5.6 °C that can cause irreversible harmful changes in pulp tissue. It can be concluded that, with regard to temperature increase, all the light sources evaluated in this study can be used safely for in-office bleaching treatment within the described parameters.

Effects of different dentin thicknesses and air cooling on pulpal temperature rise during laser welding

The neodymium/yttrium-aluminum-garnet (Nd/YAG) laser has been suggested to repair broken prostheses in the mouth. This study investigated the effects of different dentin thicknesses and air cooling on pulpal temperature rise during laser welding. Three intact human maxillary molars were prepared for full-veneer crown. For each tooth, dentin thicknesses in mesiobuccal cusp was 2, 3, or 4 mm. Twenty dies were duplicated from each of the prepared teeth. For metal copings with 0.5-mm thickness, wax patterns were prepared with dip wax technique directly onto each of dies. All patterns were sprued and invested. The castings were made using a nickel-chromium alloy (Nicromed Premium, Neodontics). A hole with 0.5-mm diameter was prepared on the mesiobuccal cusp of each crown. The Nd/YAG laser (9.85 W; 1 Hz repetition rate; fluence, 1.230 J/cm(2); Fidelis Plus 3, Fotona) was used for welding with or without air cooling (n = 10). The temperature rise was measured in pulpal chamber with a J-type thermocouple wire that was connected to a data logger. Differences between start and highest temperature reading were taken, and temperature rise values were compared using two-way analysis of variance and Tukey's honestly significant difference tests (α = .05). Pulpal temperature rise varied significantly depending on the dentin thickness and air cooling (p < 0.05). The non-air cooling group induced significantly the highest temperature increases. There were no significant differences between 2- and 3-mm dentin thicknesses groups (p > 0.05); however, pulpal temperature rise was the lowest for 4-mm dentin thickness group (p < 0.05). The highest values of thermal increase were found in the pulp chamber (6.8°C) when no air cooling was used in 2-mm dentin thickness group. Laser welding on base metal castings with Nd/YAG laser can be applied with air cooling to avoid temperature rises known to adversely affect pulpal health when dentin thickness is 2 or 3 mm.

The effect of dentin desensitizer with different layers on thermal changes on the pulp during fabrication of provisional restoration

This study investigated the effects of different desensitizers and an adhesive material application on pulpal temperature rise during direct provisional restoration polymerization. Two dentin desensitizers (Systemp, Ivoclar; BisBlock, Bisco) and a dentin adhesive (Prime Bond, Dentsply) were applied to the dentin surfaces as single layer or double layer. One autopolymerizing methacrylate (Prevision, Heraeus Kulzer) and one light polymerizing composite (Revotek LC, GC) provisional restoration materials were used in this study. A total of 160 dentin disks were prepared from extracted molars. These dentin disks were placed on an apparatus developed to measure temperature rise. After the desensitizer or dentin adhesive application, provisional materials were polymerized according to the manufacturers' instructions. The temperature increase was measured under the dentin disk with a J-type thermocouple wire that was connected to a data logger. Differences between initial and highest temperature reading were taken, and 10 readings were averaged to determine the mean value in temperature rise. Statistical analysis was performed with three-way analysis of variance followed by Tukey HSD test (alpha = 0.05). Temperature rise varied according to the provisional restoration material used (composite resin, methacrylate) (p < 0.001), the agent thickness (single, double) (p < 0.001), and the agent (desensitizer, adhesive) (p < 0.001). The composite resin-based provisional material induced higher thermal changes than methacrylate based provisional material (p < 0.01). The thickness of desensitizing agents affected the thermal changes; however, the desensitizers did not affect on the intrapulpal temperature although the type of provisional material used may be effective.

Evaluation of dental pulp temperature rise during photo-activated decontamination (PAD) of caries: an in vitro study

Photo-activated decontamination (PAD) has been reported in caries treatment as an aid in dentine decontamination. The aim of this study is to verify the harmlessness for pulp vitality of photo-activated decontamination (PAD) in caries treatment. Twenty freshly extracted single-rooted teeth were used. Deep class I cavities with a <or= 0.5 mm dentine thickness between the floor of the cavity and the roof of cameral pulp were prepared. Following the manufacturer's instructions, cavities were filled with a photo-sensitizer (Phenothiazinechloride: 10 mg /ml), irradiated during 30 s with a 660-nm diode laser (output power: 40 mW in continuous wave; total delivered energy density: 4.87 J/cm(2)). Pulp temperature raises were recorded using a thermocouple (ALCr). Measurements were recorded every second during the irradiation and 150 s afterwards. Six records were repeated for each tooth. After 30 s of irradiation, the mean of temperature rise was 0.83 degrees C +/- 0.22 degrees C. All records showed temperature increases lower than the 3 degrees C (safety level for pulp injury). Based on our in vitro study, we can conclude that the dental pulp temperature rise following the use of PAD technique for the decontamination of dentine can be considered as save procedure for pulp vitality.

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

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

In vitro pulp chamber temperature rise from irradiation and exotherm of flowable composites

The aim of this study was to investigate the pulpal temperature rise induced during the polymerization of flowable and non-flowable composites using light-emitting diode (LED) and halogen (quartz-tungsten-halogen) light-curing units (LCUs). Five flowable and three non-flowable composites were examined. Pulpal temperature changes were recorded over 10 min in a sample primary tooth by a thermocouple. A conventional quartz-tungsten-halogen source and two LEDs, one of which was programmable, were used for light curing the resin composites. Three repetitions per material were made for each LCU. There was a wide range of temperature rises among the materials (P < 0.05). Temperature rises ranged between 1.3 degrees C for Filtek Supreme irradiated by low-power LED and 4.5 degrees C for Grandio Flow irradiated by high-power LED. The highest temperature rises were observed with both the LED high-power and soft-start LCUs. The time to reach the exothermic peak varied significantly between the materials (P < 0.05). Pulpal temperature rise is related to both the radiant energy output from LCUs and the polymerization exotherm of resin composites. A greater potential risk for heat-induced pulp damage might be associated with high-power LED sources. Flowable composites exhibited higher temperature rises than non-flowable materials, because of higher resin contents.