A study of temperature rise in the pulp chamber during composite polymerization with different light-curing units

AIM: The study compared pulp temperature rise during polymerization of resin-based composites (RBCs) using halogen and LED light-curing units (LCUs). METHODS AND MATERIALS: A total of 32 teeth extracted from patients aged 11-18 years were used in the study. Thermocouples placed on the roof of the pulp chamber using a novel 'split-tooth' method. In Group 1 a halogen LCU with a light intensity of 450 mW cm(-2) was used and in Group 2, an LED LCU with a light intensity of 1100 mW cm(-2) was used. The teeth were placed in a water bath with the temperature regulated until both the pulp temperature and the ambient temperature were stable at 37 degrees C. Continuous temperature records were made via a data logger and computer. The increase in temperature from baseline to maximum was calculated for each specimen during the curing of both the bonding agent and the RBC. RESULTS: The rise in pulp temperature was significantly higher with the LED LCU than with the halogen LCU for bonding and RBC curing (p<0.05). The major rise in temperature occurred during the curing of the bonding agent. During the curing of the RBC, rises were smaller. CONCLUSIONS: Curing of bonding agents should be done with low intensity light and high intensity used only for curing RBC regardless of whether LED or halogen LCUs are used.     

In vitro pulp chamber temperature rise during composite resin polymerization with different curing lights.

The damaging effect of temperature increase on the pulp tissue during restorative treatment has been a matter of concern in dentistry for many years. Aesthetic restorative dentistry relies on polymerization of light-activated resin composites which can cause damaging effects to the dental pulp as a result of temperature rise caused by both the exothermic reaction process and the energy absorbed during irradiation. This in vitro study was carried out to measure the increase in pulp chamber temperature induced during composite resin-polymerization with various light curing units in three different and common clinical situations (Veneer, Class II, Class III) and the clinical implications of the results. Measurement of pulp temperature changes during polymerization was performed with a Al-Cr Thermocouple positioned at the pulp-dentin junction. Mean values were calculated from six measurements with each light curing unit.     

Temperature rise during adhesive and resin composite polymerization with various light curing sources

This study evaluated the temperature rise in two different adhesive (Clearfil SE Bond [CSEB] and EBS-Multi [EBSM]) and composite systems (Clearfil AP-X [CAPX,] Pertac II [PII]) by the same manufacturer when illuminated by four different light sources: Light-emitting diode (LED), Plasma arc curing (PAC), high intensity quartz tungsten halogen (HQTH) and quartz tungsten halogen (QTH). Forty dentin disks were prepared from extracted premolars. These dentin disks were placed in apparatus developed to measure temperature rise. Temperature rise during photopolymerization of adhesive resin and resin composite was then measured. The mean values of temperature increases for adhesive and resin composites did not differ significantly (p=0.769). The highest temperature rise was observed during photopolymerization of EBSM with PAC (5.16 degrees C) and HQTH (4.28 degrees C), respectively. Temperature rise values produced by QTH (1.27 degrees C - 2.83 degrees C for adhesive resin; 1.86 degrees C - 2.85 degrees C for resin composite) for both adhesive and resin composites were significantly lower than those induced by PAC and HQTH (p<0.05). However, these values were significantly higher than those produced by LED (1.16 degrees C - 2.08 degrees C for adhesive resin; 1.13 degrees C - 2.59 degrees C for resin composite). Light sources with high energy output (PAC and HQTH) caused significantly higher temperature rise than sources with low energy output (QTH and LED). However, in this study, no temperature rises beneath 1-mm dentin disk exceed the critical 5.6 degrees C value for pulpal health.     

Pulp chamber temperature rise during curing of resin-based composites with different light-curing units.

AIMS: The purpose of the present study was to measure the intrapulpal temperature rise occurring during polymerisation of different shades of resin-based composites (RBCs), and two light-emitting diode (LED) units. METHODS: Seventy non-carious permanent molars, that had been extracted for orthodontic purposes and stored in 2% thymol for not more than four months, were selected. Patient age range was 11-18 years. Standard cavity preparation with standardised remaining dentine thickness and placement of thermocouples (TCs) was prepared using a novel split-tooth technique. Cavities were filled with one of two shades of RBC (A2 and C4, Filtek Z250, 3M ESPE, Seefeld, Germany), and cured with two LED high-intensity units (Elipar Freelight2, 3M ESPE, Seefeld, Germany; Bluephase, Ivoclar Vivadent, Schaan, Liechtenstein) and a conventional halogen light-curing unit (LCU) (Prismetics Lite 2, Dentsply, Weybridge, Surrey, UK) as a control. RESULTS: Pulp temperature rises during bonding [A2 results: H;2.67/0.48:E;5.24/1.32;B;5.99/1.61] were always greater than during RBC curing [A2 results: 2.44/0.63;E3.34/0.70;B3.38/0.60], and these were significant for both LED lights but not for the halogen control, irrespective of shade (Mann-Whitney test: 95% confidence limits). Temperature rises were at times in excess of the values normally quoted as causing irreversible pulp damage. Pulp temperature rises during bonding were higher with the LED lights than with the halogen control. There was no significant difference in temperature rise between the two LED lights when bonding but there was a significant difference between the two LED lights and the halogen control LCUs (Kruskal-Wallis Test: 95% confidence limits). CONCLUSIONS: The results support the view that there is a potential risk for heat-induced pulpal injury when light-curing RBCs. The risk is greater during bonding and with high energy, as compared to low-energy output systems. As the extent of tolerable thermal trauma by the pulp tissues is unknown, care and consideration should be given to the choice of LCU and the exposure time when curing RBCs, and especially during bonding.     

Degree of conversion and temperature rise during polymerization of composite resin samples with blue diodes

To ensure an adequate clinical composite filling light source for photopolymerization is of great importance. In everyday clinical conditions commonly used unit for polymerization of composite material is halogen curing unit. The development of new blue superbright light emitting diodes (LED) of 470 nm wavelengths comes as an alternative to standard halogen curing unit of 450-470 nm wavelengths. The purpose of this study was to compare the degree of conversion (DC) and temperature rise of four hybrid composite materials: Tetric Ceram, Pertac II, Valux Plus and Degufill Mineral during 40 s illumination with standard halogen curing unit Heliolux GTE of 600 mW cm(-2) intensity, Elipar Highlight soft-start curing unit of 100 mW cm(-2) (10 s) and 700 mW cm(-2) (30 s) intensity and 16 blue superbright LED of minimal intensity of 12 mW cm(-2) on the surface and 1 mm depth. The results revealed only a little bit higher DC values in case of polymerization with even 66 times stronger halogen curing units which showed twice higher temperature than blue diodes. Temperature and DC obtained are higher on the surface than on 1 mm depth regardless on the light source used.     

Hardness of a bleaching-shade resin composite polymerized with different light-curing sources

The microhardness of a bleaching-shade resin composite polymerized with different light-curing units was evaluated. Composite samples (3M ESPE Filtek Supreme) were applied to brass rings (2 mm in thickness, 5 mm in diameter). Three commercial LED lights were used to polymerize the specimens and the results were compared to those of a conventional halogen light. The light sources used in the present study were: Demetron Optilux 401 (QTH), 3M ESPE Elipar FreeLight (LED 1); Kerr L.E. Demetron I (LED 2), and ColtoluxLED lights (LED 3). The microhardness of the top and bottom surfaces was assessed with a digital Vickers hardness-measuring instrument, under load. At the bottom surface, no significant difference among the light sources was observed (two-way ANOVA). At the top surface, the QTH light source presented significantly higher hardness values compared to the values observed when LED 1 and LED 3 were used. There were no significant differences between the QTH and LED 2 light sources. Significantly higher hardness values were also found at the top surface when compared to the values observed at the bottom surface. The power density of the polymerization light sources seemed to be responsible for the observed resin composite hardness, not their irradiance.     

Temperature rise caused in the pulp chamber under simulated intrapulpal microcirculation with different light-curing modes

Objective:To evaluate and compare intrapulpal temperature rise with three different light-curing units by using a study model simulating pulpal blood microcirculation.Materials and Methods:The roots of 10 extracted intact maxillary central incisors were separated approximately 2 mm below the cement-enamel junction. The crowns of these teeth were fixed on an apparatus for the simulation of blood microcirculation in pulp. A J-type thermocouple wire was inserted into the pulp chamber through a drilled access on the palatal surfaces of the teeth. Four measurements were made using each tooth for four different modes: group 1, 1000 mW/cm² for 15 seconds; group 2, 1200 mW/cm² for 10 seconds; group 3, 1400 mW/cm² for 8 seconds; and group 4, 3200 mW/cm² for 3 seconds. The tip of the light source was positioned at 2 mm to the incisor''s labial surface.Results:The highest temperature rise was recorded in group 1 (2.6°C ± 0.54°C), followed by group 2 (2.57°C ± 0.62°C) and group 3 (2.35°C ± 0.61°C). The lowest temperature rise value was found in group 4 (1.74°C ± 0.52°C); this value represented significantly lower ΔT values when compared to group 1 and group 2 (P  =  .01 and P  =  .013, respectively).Conclusions:The lowest intrapulpal temperature rise was induced by 3200 mW/cm² for 3 seconds of irradiation. Despite the significant differences among the groups, the temperature increases recorded for all groups were below the critical value of 5.6°C.     

Degree of conversion and in vitro temperature rise of pulp chamber during polymerization of flowable and sculptable conventional,bulk-fill and short-fibre reinforced resin composites

ObjectiveDetermine the degree of conversion (DC) and in vitro pulpal temperature (PT) rise of low-viscosity (LV) and high-viscosity (HV) conventional resin-based composites (RBC), bulk-fill and short-fibre reinforced composites (SFRC).MethodsThe occlusal surface of a mandibular molar was removed to obtain dentine thickness of 2 mm above the roof of the pulp chamber. LV and HV conventional (2 mm), bulk-fill RBCs (2–4 mm) and SFRCs (2–4 mm) were applied in a mold (6 mm inner diameter) placed on the occlusal surface. PT changes during the photo-polymerization were recorded with a thermocouple positioned in the pulp chamber. The DC at the top and bottom of the samples was measured with micro-Raman spectroscopy. ANOVA and Tukey’s post-hoc test, multivariate analysis and partial eta-squared statistics were used to analyze the data (p < 0.05).ResultsThe PT changes ranged between 5.5–11.2 °C. All LV and 4 mm RBCs exhibited higher temperature changes. Higher DC were measured at the top (63–76%) of the samples as compared to the bottom (52–72.6%) in the 2 mm HV conventional and bulk-fill RBCs and in each 4 mm LV and HV materials. The SFRCs showed higher temperature changes and DC% as compared to the other investigated RBCs. The temperature and DC were influenced by the composition of the material followed by the thickness.SignificanceExothermic temperature rise and DC are mainly material dependent. Higher DC values are associated with a significant increase in PT. LV RBCs, 4 mm bulk-fills and SFRCs exhibited higher PTs. Bulk-fills and SFRCs applied in 4 mm showed lower DCs at the bottom.     

Increases in intrapulpal temperature during polymerization of composite resin

STATEMENT OF PROBLEM: The polymerization of dental composite resins can generate increases in intrapulpal temperature that may damage the pulp. The development of new polymerization devices such as the argon laser makes the assessment of these temperatures important. PURPOSE: This study compared increases in temperature generated by argon laser and halogen light when polymerizing a bonding system and a composite resin, and also sought to determine whether both types of polymerization lights generate temperature increases below the safe limit of 5.5 degrees C. MATERIAL AND METHODS: Thermocouples linked to a temperature reading system were positioned in the pulp chamber of 10 extracted bovine incisors. Class V cavities were prepared, etched, and filled with a 1-bottle bonding system (Single Bond) and composite resin (Z-100). The test groups were as follows (n = 5 for all groups): halogen light for bonding system (HB); halogen light for composite resin (HC); argon laser for bonding system (LB), and argon laser for composite resin (LC). The polymerization parameters were halogen light operated at 600 mW/cm2 for 40 seconds, which served as control, and argon laser operated at 200 mW for 10 seconds. Data were analyzed by a 2-way (light versus material) analysis of variance (ANOVA) (alpha = .05). RESULTS: The average temperature increases were 2.35 degrees C (HB), 2.69 degrees C (HC), 1.25 degrees C (LB), and 1.5 degrees C (LC). Significant differences between halogen light and argon laser (P = .002), but not between composite and bonding system, were demonstrated. CONCLUSIONS: The argon laser produced significantly lower increases in pulpal temperature than the halogen light, independent of the thickness of the polymerized material.     

Temperature rise during orthodontic bonding with various light-curing units--an in vitro study

The purpose of this in vitro study was to investigate the temperature changes in the pulp chamber during bracket bonding using three different light sources. Bracket bonding was performed on one lower first premolar and one lower central incisor at two different distances (surface and 10 mm). The measurements were taken with a J-type thermocouple wire, placed in the pulp chamber and connected to a data logger. Analysis of variance revealed that pulp chamber temperature changes were influenced by the light source, the tooth type, and the distance from the tip of the light guide to the bracket surface. Halogen induced significantly higher intrapulpal temperature changes than light-emitting diode and Xenon Plasma Arc (PAC) (P = .000). The temperature increase was significantly higher when the light-guide tip was positioned at the surface of the teeth than at the 10-mm distance with all light-curing units (P = .000). All light-curing units produced higher intrapulpal temperature increase in the mandibular incisor than in the premolar. Power PAC produced significantly higher heat changes in the incisor than in the premolar. Orthodontic bonding with different light-curing units did not exceed the critical 5.5 degrees C value for pulpal health.     

不同光固化模式对大体积充填树脂固化效率影响的研究

目的比较不同光固化模式对Tetric N-Ceram Bulk Fill以及3M Filtek Bulk Fill flowable大体积充填树脂固化效率的影响。方法制作树脂样本60个,分为A~D四组,A、B两组采用Tetric N-Ceram Bulk Fill树脂制作,分别使用标准模式与软启动模式进行固化,C、D两组采用3M Filtek Bulk Fill flowable树脂制作,固化模式同上,固化结束后每组采用三种不同方法(ISO4049国际标准法、显微硬度法、交联程度法)检测大体积充填树脂的固化效率,结果采用SPSS 22.0软件进行统计分析。结果在标准光照模式下,大体积充填树脂的固化效率比软启动光照模式高,差异有统计学意义(P<0.05),不同的光照模式对树脂的显微硬度无显著影响,差异无统计学意义(P>0.05)。结论大体积充填树脂在标准模式的下固化效率高,光固化模式的改变对树脂的显微硬度无影响。     

Temperature rise during polymerization of light-activated resin composites

There has been a steady rise in the use of resin-based composites in the restoration of large posterior cavities. Visible light-activated materials have come to dominate the market for direct posterior composites because of the convenience offered to the operator by their command set nature. Manufacturers have produced more powerful light-activation units in response to concerns over inadequate depth of cure. However, some authors have warned of the danger to the dental pulp induced by excessive heat generated during polymerization. Variables governing heat generation include output intensity of the light-activation unit, quality of light filter, irradiation time, material composition and material surface-light guide exit window distance, residual dentine thickness and cavity dimensions. This in vitro study assessed the relative influence of some of these factors under controlled conditions. The findings suggest that minimum irradiation times should be used when curing bonding agents in unlined cavities where residual dentine thickness is limited and high output intensity light-activation units are employed. Material composition is identified as an important variable in determining the magnitude of the temperature rise.     

Temperature rise in the pulp chamber during different stripping procedures

OBJECTIVE: To measure the temperature changes in the pulp chamber when different stripping procedures were used without any type of coolant. MATERIALS AND METHODS: Ninety intact, freshly extracted human teeth were used in this study. The teeth were separated into nine groups of 10 teeth each. Mesial and distal sides of the teeth were used separately. The stripping procedures were performed on three different tooth groups (incisor, canine, premolar) with a metal handheld stripper, perforated stripping disk, or tungsten carbide bur. A J-type thermocouple wire was positioned in the center of the pulp chamber and was connected to a data logger during application of stripping procedures. The results were analyzed by analysis of variance (ANOVA) and the Duncan test. RESULTS: Two-factor ANOVA revealed significant interaction between the stripping procedure and the tooth type (P = .000). The results of this study demonstrate that tungsten carbide burs used on mandibular incisors had the highest temperature variation (DeltaT) values, which exceeded the critical level (5.5 degrees C), and this was significantly higher than those of the other stripping procedures (DeltaT: 5.63 +/- 1.73 degrees C). On the other hand, six of the nine groups also produced temperature increases above the critical level (5.5 degrees C) for some of the specimens. CONCLUSIONS: Frictional heat is a common side effect of stripping procedures, and appropriate measures (ie, cooling application) should be taken particularly for high-speed hand-piece stripping of mandibular incisors.     

Temperature rise in the pulp chamber induced by a conventional halogen light-curing source and a plasma arc lamp

PURPOSE: To assess and compare the pulp chamber temperature increase during resin-based composite polymerization with two different light-curing units. METHODS: A Class I cavity was prepared in an extracted lower molar under standardized conditions using a specially designed industrial robot system. The dentin layer between the pulp chamber and the floor of the cavity was 1 mm thick. Pulp chamber temperature rises (starting temperature: 20.0 +/- 0.1 degrees C) were recorded for four different series of investigations using both the halogen curing lamp Elipar Visio (light-curing: 40 s) and the plasma arc lamp Apollo 95E (light-curing: 3 seconds): Group A: Operation of the light-curing units directly over the untreated, empty cavity; Group B: Resin-based composite polymerization without previously applied cement base or bonding agent; Group C: Resin-based composite polymerization with a previously applied cement base; Group D: Resin-based composite polymerization with a previously applied bonding agent. In each of the four groups 10 measurements were carried out for every light-curing unit. Data were statistically analyzed using ANOVA, post-hoc Scheffé test and t-test. RESULTS: The lowest temperature increase (0.3 degrees C) was recorded during composite polymerization with a previously applied cement base using the Apollo 95E unit (Group C, P < 0.05). The highest temperature increase was induced when using the Elipar Visio unit directly over the untreated cavity (Group A, P < 0.05). In Groups A, C and D higher pulp chamber temperature measurements were obtained when using the Elipar Visio unit as compared to the Apollo 95E plasma arc lamp (P < 0.01). In Group B, no significant differences were recorded during the composite polymerization when using the two different light-curing units (P > 0.05).     

LED固化灯光照强度对光固化复合树脂聚合收缩的影响

目的采用数字图像相关法动态研究LED光固化灯不同光照强度对光固化复合树脂聚合收缩的影响。方法收集12颗大小接近的新鲜离体磨牙,随机分为3组,制备大小为2.0 mm×2.0 mm×2.0mm的邻(?)面洞形,洞面酸蚀冲洗后涂粘接剂光照10 s,充填3M Z350纳米复合树脂,邻面快速制造散斑,LED固化灯垂直(?)面光照40s,3组光照强度分别为300 mW/cm~2、500 mW/cm~2和800 mW/cm~2,数码相机同步实时采集光照过程中试件表面散斑的变化序列图像,用数字图像相关法计算获得各序列图上逐个像素点水平方向(x)和垂直方向(y)位移,统计线性收缩率,描绘各像素点的时域变化曲线,并用SPSS 12.01统计软件包进行方差分析和配对t检验。结果 3种光照强度下树脂x方向线收缩率分别为0.081%～0.486%、0.004%～0.316%和0.063%～0.560%,y方向线收缩率分别为0.088%～0.981%、0.003%～0.77%和0.157%～1.252%,3组之间差异有统计学意义(P<0.05);3组第20 s树脂游离面收缩x方向位移差异无统计学意义,y方向位移差异有统计学意义。结论 LED光固化灯500 mW/cm~2光照时引起的树脂聚合收缩最小。     

Direct post and core pattern made with light-curing composite resin

An unfilled Bis-GMA composite resin can be used advantageously for making an accurate cast post and core pattern. The technique is faster and easier than normal pattern fabrication methods using an unfilled acrylic resin, wax, or a combination of the two.