Pattern of transmission of laser light in teeth

This study examined the transmission of helium neon laser light in 20 dog and human teeth. The effect of probe position and angulation was observed both macroscopically and at a microscopic level using con-focal microscopy. In all teeth in both species, laser light was transmitted through teeth to the pulpal surface with the light following the path of the enamel prisms and dentinal tubules. Probe angulation did not affect the pattern of light transmission, nor did probe position; however, the position of the probe on the tooth surface determined which section of the pulp was illuminated. Enamel and dentine together are able to collect and distribute light within the tooth, with both enamel prisms and dentinal tubules acting as optical fibres.     

Laser light transmission in teeth: a study of the patterns in different species

AIM: The aim of this study was to investigate the pattern of light transmission through teeth of different species and to examine laser light propagation within enamel from various animal sources. METHODOLOGY: Sectioned teeth from five species--pig, horse, sheep, cat and rat--were evaluated. Samples were illuminated individually by a helium-neon laser light from the buccal surface using a probe 0.5 mm in diameter placed at varying angles between 60 and 120 degrees C. The pattern of light transmission was observed macroscopically. Further evaluation of laser light transmission in enamel was achieved using confocal microscopy. RESULTS: In each species, light was transmitted through the tooth to the pulp, but in the cat and the rat, light was also transmitted to the far side of the tooth. Despite the different patterns of enamel in the species, light was transmitted through enamel to dentine. CONCLUSION: Light from a laser Doppler probe appeared to reach the dental pulp in all the species: however, in the mammals with smaller teeth, light may also have been able to reach the periodontium and thus the reflected signal may not be entirely of pulpal origin.     

Laser light passage through restored and carious posterior teeth

Laser Doppler flowmetry (LDF) has been used to investigate pulpal blood flow as a means of pulp vitality testing. Transmission of laser light from the tooth surface to the pulp space may be influenced by caries and restorations. One hundred and twenty‐two first and second molars that had caries into dentine, restorations or significant loss of coronal tissue were sectioned in half axio‐bucco‐lingually. The two sections were illuminated with a laser from their buccal and lingual aspects 2 mm coronal to the amelocemental junction. Light reaching the pulp space was recorded. Buccal and lingual illumination sites were equally effective for 67 teeth (55%). Buccal sites alone were effective for 35 teeth (29%), despite over one‐third of these surfaces being restored or featuring enamel or dentine caries. A lingual position alone was effective for 20 teeth (16%). Caries affected light transmission, but for over half the teeth, the pulp could be illuminated from all four probe positions. No effect was found when the influence of mesial and distal restorations on transmission into the corresponding tooth section was examined. The pulp spaces of most (84%) restored, and carious posterior teeth could be illuminated by laser light from their buccal aspect and these teeth could potentially be vitality tested using LDF.     

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.     

4种材料修复乳磨牙龋的临床疗效比较

目的:比较不同材料修复乳磨牙龋的临床疗效。方法:选择合适患儿115例,446个乳磨牙。采用随机和自身对照方法,应用4种不同材料对其进行充填修复。结果:经1~2年观察,银汞合金、光固化复合树脂、玻璃离子水门汀、Dyract复合体材料组修复乳磨牙龋成功率分别为61.48%、66.34%、60.47%和90.43%。结论:4种材料修复乳磨牙龋各有其优缺点,Dyract复合体材料修复乳磨牙龋临床效果较好。     

半导体激光辅助直接盖髓术在龋源性露髓患牙中的效果评价

目的：探讨半导体激光联合氢氧化钙行直接盖髓术是否可以提高深龋露髓患牙的保髓成功率。方法：选取深龋露髓患牙100例,随机分为试验组和对照组,每组各50例。试验组以功率1.5 W、波长808 nm、直径320 μm、距离2~3 mm、连续波激光照射露髓点2 s,控制出血;以功率1 W、波长808 nm、直径320 μm、距离2~3 mm、连续波激光每2 mm照射1 s,进行窝洞净化,用氢氧化钙制剂盖髓;对照组直接采用氢氧化钙制剂盖髓。随访观察1年后,评价2组患牙的牙髓活力。采用SPSS 19.0软件包对数据进行统计学分析。结果：试验组 50例患牙,失访3例,1年后成功率为89.4%;对照组50例患牙,失访5例,1年后成功率为73.3%,2 组之间差异显著（P<0.05）。结论：半导体激光联合氢氧化钙用于深龋露髓患牙直接盖髓术,可明显提高保髓成功率,值得推广应用。     

Molecular structural analysis of carious lesions using micro‐Raman spectroscopy

In clinical situations carious dentine tissues can be discriminated by most caries fluorescence detection tools, including a new fluorescence intra‐oral camera. The objectives of this study were: (i) to analyze the Raman spectra of sound, carious, and demineralized dentine, (ii) to compare this spectral analysis with the fluorescence variation observed when using a fluorescence camera, and (iii) to evaluate the involvement of the Maillard reaction in the fluorescence variations. The first positive hypothesis tested was that the fluorescence of carious dentine obtained using a fluorescence camera and the Raman spectra variation were closely related. The second was that the variation of fluorescence could be linked with the Maillard reaction. Sound dentine, sound dentine demineralized in aqueous nitric acid solution, carious soft dentine, sound dentine demineralized in lactic acid solution, sound dentine demineralized in aqueous nitric acid solution and immersed in methylglycoxal solution, and sound dentine demineralized in aqueous nitric acid solution and immersed in methylglycoxal and glucose solutions, were studied using micro‐Raman spectroscopy. Modifications in the band ratio of amide, phosphate, and carbonate were observed in the decayed and demineralized groups compared with the sound dentine group. The results indicate that a close relationship exists between the Maillard reaction and fluorescence variation.     

The permeability of artificial dentine carious lesions

OBJECTIVE: This study aimed to verify whether two demineralisation solutions, with different fluoride concentrations, would produce subsurface lesions in dentine, as assessed by microradiography, with different mineral loss profiles and, subsequently, to determine the dentine permeability of the two altered tissues. METHODS: Forty-five human coronal portions were prepared and randomly divided into two test groups (20 specimens each) with the remaining five as a control group. Each test group was exposed to a demineralisation solution containing either 1 or 5 ppm fluoride for five days. RESULTS: There were highly significant differences between the two test groups for all microradiographic parameters, except for lesion depth. The increase in dentine permeability from baseline to day 5 was statistically significant within each of the two test groups, but not for the control group. CONCLUSION: The differences in the mineral content profile of the two lesions did not influence the magnitude of change in their permeability.     

Candida albicans does not invade carious human dentine

AIM: Candida albicans has been proposed to be a caries pathogen, but the evidence for its specific role is lacking. To be considered significant in caries progression, a marked amount of yeasts should be present in a lesion. The aim of the study was to investigate the presence of C. albicans in dentinal caries lesions. MATERIALS AND METHODS: To demonstrate the extension of caries and to identify the bacteria in a lesion, sections of 10 carious human teeth were stained with Gram and Giemsa stains. C. albicans was detected with periodic acid-Schiff (PAS) staining and by immunohistochemistry using a C. albicans-specific antibody 3H8. Thirty sections were used for each staining (in total 120 sections). RESULTS: Extensive bacterial invasion and intensive staining by PAS occurred in all samples. However, with the C. albicans-specific antibody, only 30 (3.3%) sections stained weakly positive, with a few stained cells on the lesion surface. However, the positive identification of C. albicans, based on the morphology of the cells, was not possible. CONCLUSIONS: The results do not support the previous suggestion that C. albicans is important in the dentine caries pathology. In addition, because of its unspecific nature, PAS turned out to be an unsuitable method for detecting yeasts in carious tooth samples.     

Comparison of laser fluorescence devices for detection of caries in primary teeth

The aim of this in vivo study was to evaluate the performance of fluorescence‐based devices in detecting occlusal caries lesions in primary molars compared with conventional methods. Two examiners assessed 44 occlusal surfaces of first and second primary molars in 20 patients using two fluorescence devices: DIAGNOdent (LF) and DIAGNOdent pen (LFpen). Teeth were also assessed by visual examination and bitewing radiograph. Histological examination served as the gold standard after extraction. By using the McNemar test, the sensitivity, specificity, accuracy, and area under the receiver operating curve were calculated as outer enamel (D1), inner enamel (D2) and dentine caries (D3) lesion thresholds. The intra‐ and inter‐examiner reproducibility were calculated using the Cohen's unweighted kappa statistics. At the D1 threshold, the LFpen sensitivity was statistically higher than LF and radiographic examination (P < 0.001), whereas there was no statistically significant difference among the groups at the D2 and D3 thresholds (P > 0.05). All methods demonstrated the highest sensitivity values at D3. At the D1 and D2 thresholds, there were no significant differences between the LFpen specificity and the other methods. All methods presented similar performance in detecting all lesions considering the area under the receiver operating curve. The LFpen showed better performance than LF. Furthermore, visual examination and the LFpen device seem to be sufficient for detection of occlusal caries in primary molars.     

应用Nd:YAG激光防龋的研究进展

Nd:YAG激光因能改变牙齿硬组织的表面形态、改变釉质和牙本质的晶体结构、促进牙齿硬组织对氟的吸收而被应用于预防龋病。本文着重就Nd:YAG激光对牙体硬组织的作用，对牙齿硬组织吸氟能力的影响以及对牙髓的影响等方面的研究进展作一综述。     

Evaluation of selective caries removal in deciduous teeth by a fluorescence feedback-controlled Er:YAG laser in vivo

This study investigated the ability and efficacy of an Er:YAG laser with a fluorescence feedback system for caries removal in deciduous teeth. Seventy-nine carious lesions were excavated using a fluorescence-controlled Er:YAG laser. Endpoint of treatment was defined by emission of fluorescence from the dentine surface below the pre-selected threshold level of 7 units and the subsequent termination of Er:YAG laser radiation. Dentine samples were obtained from the cavity floor, and viable counts of both Streptococcus mutans and Lactobacilli, expressed as colony forming units (log CFU), were evaluated. Preparation time was recorded to assess efficacy of the treatment procedure. S. mutans and/or Lactobacilli were found in 25 out of 79 lesions. Regarding the counts for S. mutans and Lactobacilli, the median log CFU was 0 (min, 0; max, 5.5) and 0 (min, 0; max, 6), respectively, with 2.4% of all samples yielding more than 100 CFU S. mutans and 4.8% yielding more than 100 CFU Lactobacilli. In 8 out of 79 cases, laser excavated cavities were not judged being caries-free using the conventional tactile criterion for assessing caries tissue. Focussing on these teeth, the median log CFU was 0 (min, 0; max, 0.5) for S. mutans and 0 (min, 0; max, 1.6) for Lactobacilli. The mean time for treatment was 2.3 +/- 1.2 min. Of the children, 93.8% rated the laser treatment to be comfortable. The study indicates that the fluorescence feedback-controlled Er:YAG laser might be an appropriate device for caries removal in children using the suggested threshold level of 7 units.     

乳牙龋坏非创伤性充填的1年临床结果观察

目的：探索适合中小城镇及农村的非创伤性充填治疗（ART）技术,评价ART修复乳牙龋坏的效果。方法：1997年在四川省成都及周边地区小学选取6～8岁儿童198名,由经过中专口腔专业训练的医生采用ART技术对乳牙龋坏进行充填,在1个月内对该儿童作了324个充填。结果：1年议后复查297个充填体。248个根据标判断为“成功”,成功率为88．89％。结论：ART不失为一种有前途的龋病充填治疗方法,是可以在农村及中小城镇广泛采用的有前景的防治措施。     

4例磨牙区多生牙

多生牙是一种牙齿数目多于人体生理牙数的发育异常,其主要发生在上颌的前牙区,发生在磨牙区的多生牙较为少见,本文报道4例发生在磨牙区的多生牙病例。     

同一个体乳牙列龋与恒牙列龋的相关性研究

目的：探讨同一个体乳牙龋与其年轻恒牙龋之间是否具有相关性，是否可以通过乳牙龋预见其恒牙龋的发生。方法：对293名5～6岁替牙期的儿童进行4年的跟踪调查，记录其在1999年和2003年时的乳、恒牙患龋情况，并进行统计学分析。结果：乳牙列龋与恒牙列龋之间相关性存在统计学意义。结论：乳牙列患龋严重的儿童，其恒牙患龋的可能性相对增高，可达乳牙列无龋者的4倍。特别是乳磨牙龋对其恒牙龋更具有预见价值。     

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目的评价应用Beyond冷光美白技术对无髓变色牙进行内漂白的临床疗效。方法将2007年1月至2008年6月在中国医科大学口腔医学院综合急诊科就诊的无髓变色牙患者93例随机分为3组,分别采用常规内漂白、Beyond冷光美白技术内漂白、Beyond冷光美白技术复合常规内漂白进行治疗,观察其有效率。结果第1次复诊时,Beyond冷光美白技术复合常规内漂白患者有效率达66.7%,第6次复诊时,有效率达96.9%,与其他2组比较差异有统计学意义(P<0.05)。根管治疗完成与开始内漂白的时间间隔越短,患者就诊次数越少。结论Beyond冷光美白技术复合常规内漂白对无髓变色牙有明显增白作用。     

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乳牙易患龋,且进展快,对儿童口腔局部和机体都有不良影响。因乳牙终将被替换,乳牙龋病常被忽视,得不到及时治疗。为提高人们对乳牙龋病认识,沈阳市大东区牙病防治所在所辖区幼儿园和小学校进行儿童口腔保健知识宣教,并行乳牙龋病治疗,取得良好疗效。现报道如下。     

Interaction of pulsed carbon dioxide laser beams with teeth in vitro

Beams of pulsed carbon dioxide lasers with energy densities of about 10, 100 or 200 J/mm² have been applied perpendicularly to third molars in vitro for the purpose of preparing cavities or pin holes for retention. A pulsed beam with an energy density of about 10 J/mm² produced a hole approximately 2 mm deep with a diameter of about 0.2 mm. With a beam of 100 J/mm² the hole produced penetrated the tooth to a depth of 4 mm. Minor cracks around the hole in both enamel and dentin could be observed. Around the position where the beam entered the enamel matrix a white mineralized layer was observed, while a brown discoloration was formed around the hole in the dentin at the beam exit. With an energy density of 200 J/mm² the formation of cracks and discoloration was very pronounced. X-ray diffraction of lased tissue revealed an apatite structure. The wall in the lased hole exhibited a Vicker hardness number similar to that of enamel.     

Beyond冷光美白术对无髓变色牙的临床疗效观察

目的:评价应用Beyond冷光美白技术采用内外联合漂白方式对无髓变色牙的临床疗效。方法:选择牙齿变色病人180例,随机分成3组,分别采用内漂白、外漂白、内外联合漂白技术进行治疗,观察其有效率;对进行内外联合漂白的外伤变色牙的外伤时间和漂白次数进行统计分析。结果:1周后,内外联合漂白有效率达到95%,4周后,内外联合漂白有效率达到98.3%,与其他组相比均具有统计学意义;外伤导致牙齿变色并进行内外联合漂白的病人,外伤时间与漂白次数成正比。结论:Beyond冷光美白技术采用内外联合漂白方式对无髓变色牙有明显的增白作用。     

Root canal treatment in Denmark is most often carried out in carious vital molar teeth and retreatments are rare

AIM: To study the reasons given by a representative sample of Danish general dental practitioners (GDPs) for undertaking root canal treatment and, to investigate their confidence in performing root canal treatment on molar teeth. METHODOLOGY: A questionnaire was sent to 600 Danish GDPs randomly selected from the roster of the Danish Dental Association. They were asked to recall various factors about their experience of the last root filling they completed, including the reason for treatment and the pulp diagnosis. Self-assessments on 100-mm visual analogue scales (VAS) were reported concerning the confidence in performing root canal treatment of a molar. End-point definitions were 'very easy' (0) and 'very difficult' (100), respectively. Time reports of molar treatments were given in categorized groups. RESULTS: The most frequent reason for performing root canal treatment was caries within the tooth involved (55%). The majority of treatments involved teeth with vital pulps (54%). Retreatments were carried out in 2% of the cases. The confidence in performing root canal treatment varied but was relatively high, expressed as VAS-values below 50. The creation of an aseptic working field was regarded as the most difficult procedure followed by root canal preparation. Fifty-six percent of the responders stated a time frame of 46-75 min to complete root filling in a molar tooth. CONCLUSIONS: Root canal treatment in Denmark was reported to be undertaken most often because of caries. Treatment was typically performed in molar teeth with vital pulp. Even though apical periodontitis was frequently noted in root filled teeth, retreatments were rare. From a subjective perspective root canal treatment was not considered to be very difficult and was carried out relatively rapidly.