Evaluation of photopolymerization efficacy and temperature rise of a composite resin using a blue diode laser (445 nm)

The purpose of this study was to evaluate the photopolymerization efficacy of a diode laser (445 nm) for use with a composite containing camphorquinone and to estimate the safety of the method related to the temperature rise. Five cylindrical composite specimens were prepared for each thickness: 1, 2, and 3 mm. Three light-curing modes were investigated: a light emitting diode (LED) unit and a diode laser (445 nm) with output powers at 0.7 W or 3 W. Evaluation of the polymerization efficacy was based on Vickers hardness measurements, and the highest temperatures at the bottom of the specimens were recorded using a K-type thermocouple. The highest microhardness was observed after the diode laser curing operating at 3 W. A comparison of the microhardness of the 0.7 W laser cured specimens with the LED cured specimens showed a statistically significant difference in favor of the laser curing. Laser curing operating at 3 W resulted in extremely high temperatures. Laser curing at 0.7 W resulted in statistically significantly higher maximum temperatures than did LED curing for both 1 mm thick (52.9°C against 45.4°C) and 3 mm thick (43.6°C against 40.9°C) specimens. Diode laser (445 nm) may be an alternative for photopolymerization of composite materials and may result in a higher degree of conversion and depth of cure of composites than what has been seen with LED curing units when they emit at the same energy density.     

二极管激光照射牙本质后的形态变化研究

目的:探讨用980 nm波长二极管激光照射牙本质表面后其形态变化,以了解二极管激光对牙本质表面的作用,辅助临床选择最佳治疗方案。方法:选择离体上下颌第三磨牙,垂直于牙体长轴磨除面釉质均匀暴露牙本质,并制成2 mm厚的牙本质片,将牙本质片划分为4个区域,每个区域12 mm2,用牙科二级管激光治疗仪分别以2、3、4 W照射牙本质片5 s,并重复一次。标本干燥喷金后扫描电镜观察牙本质形态变化。结果:3种能量均可封闭牙本质小管,并随能量密度增加牙本质小管封闭面积增加。但随着能量增加,管间牙本质的熔融程度增加。结论:使用980 nm波长二极管激光,在2 W,166 J/cm2能量密度时即可有效封闭牙本质小管口且可避免牙本质过度熔融,可以作为牙本质敏感症的治疗参数。     

Biostimulation of bone marrow cells with a diode soft laser

In recent years, the use of low-intensity red light in regeneration of soft tissue has been increasingly pursued. As far as hard tissue is concerned, the biostimulating effect of laser has already been demonstrated successfully in more rapid healing of tibial bone fractures in mice at a dosage of 2.4 J. However, the effect of light of a low dose laser directly on osteoblasts has not been investigated yet. The aim of this study was to determine the effect of continuous wave diode laser irradiation on osteoblasts derived mesenchymal cells. Three groups of 10 cultures each were irradiated 3 times (days 3, 5, 7) with a pulsed diode soft laser with a wavelength of 690 nm for 60 s. Another 3 groups of 10 cultures each were used as control groups. A newly developed method employing the fluorescent antibiotic tetracycline was used to compare bone growth on these culture substrates after a period of 8, 12 and 16 days, respectively. It was found that all lased cultures demonstrated significantly more fluorescent bone deposits than the non-lased cultures. The difference was significant, as tested by the Tukey Test (P < 0.0001) in the cultures examined after 16 days. Hence it is concluded that irradiation with a pulsed diode soft laser has a biostimulating effect on osteoblasts in vitro, which might be used in osseointegration of dental implants.     

Temperature changes and hardness of resin-based composites light-cured with laser diode or light-emitting diode curing lights

Odontology - The temperature and Vickers Hardness (VH) at the top and bottom surfaces of three resin-based composites (RBCs) were measured when light-cured using five light-curing units (LCUs). The...     

Effect of light-emitting diode photopolymerization modes on the push-out bond strength of a methacrylate-based sealer

Introduction

The objective of this study was to investigate and compare the effect of different light-emitting diode (LED) polymerization modes on the bond strength of a methacrylate-based sealer used with Resilon or gutta-percha.

Methods

Forty extracted single-rooted teeth were sectioned off below the cementoenamel junction, and the root canals were instrumented by using rotary instruments to ISO #30/0.06 taper. The roots were randomly assigned into 1 of the following groups for root canal obturation: (1) RealSeal + Resilon and (2) RealSeal + gutta-percha. In each group, specimens were further subgrouped according to the LED polymerization mode used to cure RealSeal: (1) standard (20 seconds of maximum intensity) and (2) exponential (5 seconds of exponential power increase, followed by 15 seconds of maximum intensity). Specimens were stored in 100% humidity for 1 week at 37°C. Push-out test was performed at a crosshead speed of 1 mm/min on 2-mm-thick root slices obtained from coronal to apical direction. Multivariate analysis of variance and Tukey tests were used for statistical analysis of the data (P = .05). Failure modes were examined under the scanning electron microscope.

Results

The tested polymerization modes had no significant effect on the bond strength values (P > .05). RealSeal + gutta-percha yielded significantly greater bond strength than RealSeal + Resilon (P < .05). In all groups, the bond strength values decreased significantly from coronal to apical direction (P < .05). Adhesive failure at the sealer-dentin interface was the predominant fracture mode.

Conclusions

The exponential photopolymerization mode had no significant advantage over the standard regimen in terms of dentin bond strength.     

二极管激光和Pro-argin抛光膏治疗牙本质敏感症的研究

目的:研究二极管激光和Pro-argin抛光膏治疗牙本质敏感症(dentine hypersensitivity,DH)的临床效果。方法:选择80例DH患牙,随机分为A组(二极管激光治疗组,n=40)和B组(Pro-argin抛光膏治疗组,n=40),分别给予相应处理,处理前后评估患牙探诊敏感程度、VAS值。另外,选取健康离体牙制作牙本质切片,分别给予上述两种处理,扫描电子显微镜下观察牙本质小管状态。结果:A、B两组治疗后探诊敏感程度、VAS值均较治疗前明显减轻,差异有统计学意义(P<0.05),A、B两组间探诊敏感程度变化百分比、VAS值变化百分比相比无显著性差异(P>0.05);牙本质切片扫描电镜观察发现,经两种方法处理后,横剖面均可观察到绝大部分牙本质小管形成良好的管塞,纵剖面观察到A组形成厚度约10μm、相对均一的牙本质管塞,B组形成3～15μm、厚度不均一的牙本质管塞。结论:二极管激光与Pro-argin抛光膏均可用于即刻缓解DH疼痛。     

Clinical comparison between the bleaching efficacy of light‐emitting diode and diode laser with sodium perborate

The aim of this clinical study was to test the efficacy of a light‐emitting diode (LED) light and a diode laser, when bleaching with sodium perborate. Thirty volunteers were selected to participate in the study. The patients were randomly divided into two groups. The initial colour of each tooth to be bleached was quantified with a spectrophotometer. In group A, sodium perborate and distilled water were mixed and placed into the pulp chamber, and the LED light was source applied. In group B, the same mixture was used, and the 810 nm diode laser was applied. The final colour of each tooth was quantified with the same spectrophotometer. Initial and final spectrophotometer values were recorded. Mann–Whitney U‐test and Wicoxon tests were used to test differences between both groups. Both devices successfully whitened the teeth. No statistical difference was found between the efficacy of the LED light and the diode laser.     

Subgingival calculus detection with fluorescence induced by 655 nm InGaAsP diode laser radiation

BACKGROUND: It has been suggested that the 655 nm InGaAsP diode laser radiation can induce considerably higher amounts of fluorescence in subgingival calculus than in cementum. This in vitro study evaluated the use of fluorescence induced by the diode laser radiation for the detection of subgingival calculus. Methods: The study sample consisted of 30 extracted molars, premolars, canines, and incisors. The root surface of each sample was partially covered with subgingival calculus. The source of laser radiation was an InGaAsP diode laser emitting visible radiation at a wavelength of 655 nm. The fluorescent radiation reflected from the cementum and calculus was detected by a photoelectric cell integrated within the diagnostic system. The samples were randomly assigned to 3 experimental groups of 10 teeth each for detection of calculus in various media. Specifically, the fluorescence was determined in air (group A), in electrolytic salt solution (group B), and in blood (group C). For each sample, the intensity of the fluorescent light was evaluated separately for cementum and calculus in triplicate measurements. The statistical analysis was performed using a t test at a level of significance of 5% (P<0.05). RESULTS: The intensities of fluorescence radiation emitted by cementum were 0.4 (+/-0.51) in air, 0.4 (+/-0.51) in electrolytic solution, and 2.13 (+/-0.59) in blood. For calculus, the relative intensities of fluorescence radiation were 54.1 (+/-29.09) in air, 60.77 (+/-28.35) in electrolytic salt solution, and 39.63 (+/-29.79) in blood. The differences in fluorescence between cementum and calculus within each experimental unit were significant (group A: P= 0.0002, group B: P= 0.0001, group C: P= 0.031). The intensity of fluorescence in calculus was also significantly different between the 3 experimental groups. CONCLUSION: The present study indicates that subgingival calculus can be reliably detected on extracted teeth using laser fluorescence induced by the 655 nm diode-laser radiation. In vivo studies are necessary to evaluate the clinical utility of this procedure.     

Argon laser: a light source alternative for photopolymerization and in-office tooth bleaching

The argon laser is an alternative light source that can be used for the photopolymerization of resin-based dental materials and for tooth bleaching. The argon laser emits specific laser lines with wavelengths that correspond to the absorption peak of camphoroquinone, the initiator of polymerization for the adequate photocuring of resin composite. The collimated beam of the argon laser does not decrease with distance and an optical fiber has access to all cavity areas. In addition, the temperatures produced by an argon laser when curing resin-based materials and performing in-office tooth bleaching are significantly lower than those of conventional photocuring units. Argon is one of the three dental laser wavelengths that have been cleared by the FDA for tooth whitening. This article reviews the literature to examine the role that argon lasers can play in dental treatment.     

Dye-assisted diode laser ablation of carious enamel and dentine

Carious dentine and enamel from extracted human teeth were ablated using a semiconductor diode laser in conjunction with an applied dye, indocyanine green. This technique offers selective ablation with minimal risk of thermal damage to surrounding dental tissues because uptake of the dye and its irradiation by the laser together control the ablation. In this study, various laser powers and dye concentrations were used to ablate previously extracted human teeth with moderate caries. The mass of material ablated and the temperature rise in the pulp and at the surface were recorded, and the ablated surface was examined by microscopy. The ablation was efficient and the rise in the pulp temperature slight. Ablation efficiency and surface temperature were both found to increase with laser irradiance and with dye concentration. No surface cracks or fissures were seen in electron microscope examination and the hardness of the laser-treated surfaces was comparable to that of healthy tissue. The dye-assisted laser ablation technique offers considerable potential for clinical caries removal and dentine, enamel and pulp sterilization, whilst leaving healthy tissue intact. The diode laser can deliver its energy via simple optical fibre and is cheaper and much smaller than the conventional high power lasers used in other studies.     

半导体激光在牙龈瘤临床治疗中的应用体会

目的 ：探讨半导体激光在不同类型牙龈瘤临床治疗中的应用。方法 ：将34例牙龈瘤患者随机分为2组,其中研究组（n=19）采用波长980 nm的半导体激光治疗,并根据临床表现的不同进行瘤体照射或切除治疗,对照组（n=15）采用传统手术刀切除法治疗,比较2组患者术后疼痛程度。结果：所有患者愈合良好,术后患者无明显疼痛,研究组疼痛程度明显低于对照组,并且在观察期间内未发现明显的复发现象。结论：根据牙龈瘤临床表现的不同,运用不同模式的半导体激光进行治疗,术中出血量少、术后反应轻,具有较好的临床应用前景。