暂时冠桥修复材料聚合过程中髓腔内温度变化的体外研究

目的:体外测量6种暂时冠桥修复材料直接法制作暂时修复体时牙髓腔内温度的变化。方法:选取1个健康的人离体下颌第三磨牙,标准全冠预备后,将一热电偶置入髓腔,另一端与一电子温度计相连,将4种Bis-acryl复合树脂(Protemp3Garant、Luxatemp、ProtempⅡ和Fast-Temp)和2种聚甲基丙烯酸甲酯树脂(Quick Resin和Curefast)分别按照使用说明混合后,填入预先准备的硅橡胶印模中,在基牙上复位,记录实验材料聚合过程中髓腔内的温度变化。结果:ProtempⅡ组髓腔最大升温值(3.8℃)低于Protemp3Garant组(4.6℃)、Luxatemp组(4.8℃)和Fast-Temp组(4.8℃),有显著性差异(P<0.05),后三组之间无显著性差异(P>0.05)。4种Bis-acryl复合树脂最大升温值又显著低于QuickResin组(9.1℃)和Curefast组(8.7℃)(P<0.05),QuickResin和Curefast之间无显著性差异(P>0.05)。结论:4种Bis-acryl复合树脂聚合过程中髓腔升温低于两种聚甲基丙烯酸甲酯树脂,适合直接法制作暂时修复体。     

Calculus removal with diamond-coated ultrasonic inserts in vitro

BACKGROUND: Efficient calculus removal is a primary goal in periodontal therapy. Diamond-coated ultrasonic inserts (DIs) offer promise for improved scaling and were evaluated in vitro. METHODS: Extracted human teeth with moderate to severe calculus had areas of calculus ( approximately 5 x 5 mm) delineated with small burs. Each calculus area was treated under 2.5x magnification to the point of visible root cleanliness with sharp Gracey curets (hand instruments [HIs]), plain ultrasonic inserts (PIs), or ultrasonic inserts with fine-grit diamond coating; the latter two were used in a magnetostrictive ultrasonic instrument at a medium power setting. Each curet or insert was used for four teeth and then replaced by a new instrument. The time needed to clean each tooth/surface was recorded. The total area treated and the area of the residual calculus were calculated using an imaging analysis program. RESULTS: The mean time required for clinical calculus removal was 29.7 seconds for DIs, 91.9 seconds for PIs, and 49.8 seconds for HIs (all P <0.0001 from each other). Overall, the mean percentage of residual calculus was 6.3% for DIs, 5.4% for PIs, and 3.1% for HIs (significant differences between HIs and the other treatments). CONCLUSIONS: In vitro calculus removal was faster with DIs, followed by HIs and PIs. More residual calculus was found with the DIs; however, the 1% to 3% difference (93.7% clean versus 94.6% clean versus 96.9% clean with DIs, PIs, and HIs, respectively) does not seem to be clinically significant.     

Pulp chamber temperature changes with visible-light-cured composites in vitro

Due to the low compliance nature of the dental pulp, it is vulnerable to cavity preparation and restoration procedures. The vulnerability may be due to temperature increases within the pulp tissue generated by those procedures. Placement of composites includes the use of visible-light-cure lamps which emit heat and cause a temperature increase in the pulp. This study measured the temperature increase occurring in the pulp chamber with the placement of a two-surface posterior composite using six visible-light-cure lamps. The data indicate that the lamps vary in the amount of temperature increase generated from one to another; that the greater portion of the temperature increase occurred during the placement of the first layer of composite; and that one lamp caused significantly lower temperature increases.     

ObturaII热牙胶根管充填系统根管充填时牙根表面温度变化

目的利用红外成像仪测定Obtura II热牙胶根管充填系统,进行离体上颌中切牙热牙胶根管充填时根管表面温度变化。方法选择12颗离体上颌中切牙常规根管预备后,用Obtura II系统进行热牙胶根管充填。用红外成像仪测定根管充填前离体牙牙根表面的温度,热牙胶进入根管并到达根管工作长度时再次测定根管表面温度,前后的差值代表根管表面温度的变化。结果Obtura II热牙胶根管充填系统充填时可导致根管表面温度升高,差异有显著性,变化范围为4.5~9.8℃,平均7.3℃。结论Obtura II热牙胶根管充填系统根管充填时根管表面温度升高,有统计学意义。     

ObturaⅡ热牙胶根管充填系统根管充填时牙根表面温度变化

目的利用红外成像仪测定ObturaⅡ热牙胶根管充填系统,进行离体上颌中切牙热牙胶根管充填时根管表面温度变化.方法选择12颗离体上颌中切牙常规根管预备后,用Obtura Ⅱ系统进行热牙胶根管充填.用红外成像仪测定根管充填前离体牙牙根表面的温度,热牙胶进入根管并到达根管工作长度时再次测定根管表面温度,前后的差值代表根管表面温度的变化.结果Obtura Ⅱ热牙胶根管充填系统充填时可导致根管表面温度升高,差异有显著性,变化范围为4.5～9.8℃,平均7.3℃.结论Obtura Ⅱ热牙胶根管充填系统根管充填时根管表面温度升高,有统计学意义.     

In vitro assessment of temperature change in the pulp chamber during cavity preparation

STATEMENT OF PROBLEM: Tooth preparation with a high-speed handpiece may cause thermal harm to the dental pulp. PURPOSE: This in vitro study evaluated the temperature changes in the pulp chamber during 4 different tooth preparation techniques and the effects of 3 different levels of water cooling. MATERIAL AND METHOD: The tip of a thermocouple was positioned in the center of the pulp chamber of 120 extracted Shuman premolar teeth. Four different tooth preparation techniques were compared: (1) Low air pressure plus low load (LA/LL), (2) low air pressure plus high load (LA/HL), (3) high air pressure plus low load (HA/LL), and (4) high air pressure plus high load (HA/HL) in combination with 3 different water cooling rates. Control specimens were not water cooled; low water cooling consisted of 15 mL/min, and high water cooling consisted of 40 mL/min. Twelve different groups were established (n=10). An increase of 5.5 degrees C was regarded as critical value for pulpal health. The results were analyzed with a 3-factor ANOVA and Bonferroni adjusted Mann Whitney U test (alpha=.004). RESULTS: For all techniques without water cooling (LA/LL/0, LA/HL/0, HA/LL/0, and HA/HL/0), the average temperature rise within the pulpal chamber exceeded 5.5 degrees C during cavity preparation (7.1 degrees C; 8.9 degrees C; 11.4 degrees C, and 19.7 degrees C, respectively). When low water cooling was used with high air pressure and high load technique (HA/HL/15), the average temperature rise exceeded 5.5 degrees C limit (5.9 degrees C). However, when high water cooling (LA/LL/40, LA/HL/40, HA/LL/40, and HA/HL/40) was utilized, the critical 5.5 degrees C value was not reached with any air pressure or load (3.1 degrees C, 2.8 degrees C, 2.2 degrees C, and -1.8 degrees C, respectively). CONCLUSION: Within the limitations of this in vitro study, the results indicate that reducing the amount of water cooling or increasing air pressure and load during cavity preparation increased the temperature of the pulp chamber in extracted teeth.     

Measurements of the root surface temperature during thermo-mechanical root canal filling in vitro

Summary. The temperature rise at the root surface during thermo-mechanical root canal obturation was studied in vitro in 15 human teeth. The mean temperature elevation at a point 5 mm coronal to the apex was found to be 35°C. The impact of the results on the periodontal tissues during conditions in vivo are discussed.     

Pressure and temperature changes in heat-cured acrylic resin during processing.

OBJECTIVES: The aims of this study were to measure the pressure and temperature changes of acrylic resin during processing, to record the highest temperature reached when fast cured in boiling water and to determine the elevated boiling point of monomer under high pressure. METHODS: A subminiature pressure transducer (temperature compensated to 94 degrees C) and a thermocouple were placed on the palate of a standardized maxillary complete denture base. A heat-cured resin (Trevalon C) was polymerized by a long heating cycle (72 degrees C for 6.5 h and 92 degrees C for 1.5 h). Recordings of pressure and temperature (n=6) were made at initial clamping of denture flasks and throughout the processing cycles of resin. The temperature of the resin was also monitored during a fast cycle, which was accomplished by placing the flask directly into boiling water for 40 min. RESULTS: The pressure of acrylic dough inside the clamped flask was initially 11.5 atm (SD=3.2) and reached a peak of 22.0 atm (SD=3.5) during the long heating cycle. The elevated boiling point of monomer at increased pressure was calculated to be about 193 degrees C (at 11.5 atm) and 228 degrees C (at 22.0 atm). These elevated boiling points are higher than the maximum temperature 131 degrees C (SD=6.6) reached during the fast curing cycle. No porosity was observed even in the denture bases heat-cured by the fast cycle. SIGNIFICANCE: The highest temperature reached by heating of resin during processing is well below the elevated boiling point of monomer. Monomer therefore does not boil in clamped denture flasks under sufficient pressure. Thus adequate clamp pressure prevents gaseous porosity irrespective of curing cycle used.     

Comparison of temperature changes in the pulp chamber induced by various light curing units, in vitro

This study compared the temperature increase in a pulp chamber as a result of using various light-curing units during resin composite polymerization, and it determined the effect of remaining dentin thickness on temperature rise. A Class II occlusodistal cavity with a remaining dentin thickness of 2 mm was prepared in an extracted human mandibular molar. A 2-mm layer of fine hybrid resin composite was placed on the floor of the proximal box. A K-type thermocouple was inserted into pulp chambers filled with heat sink compound, and pulp chamber temperature rise (starting temperature: 37.0 +/- 0.1 degrees C) during polymerization of the composite was measured. The light-curing units tested included two halogen lights, Spectrum 800 and Elipar Trilight (Standard and Exponential mode); a light-emitting diode (LED, Elipar Freelight) and a plasma arc (Virtuoso, Xenon Power Arc). Irradiation time was 40 seconds for the halogen and LED lights and 3 seconds for the plasma arc light. Five measurements were carried out for every light-curing unit. The same experimental design was conducted after the cavity preparation was modified, leaving a 1-mm thick dentin layer. The Kruskal-Wallis and multiple comparison tests were used to evaluate the differences among the tested curing units. Mann Whitney-U tests were used to compare the mean temperature rise in each curing unit for different remaining dentin thicknesses. The increase in pulp chamber temperature ranged between 1.40-3.8 degrees C. The highest temperature rise was observed when using Elipar Trilight Standard mode, and the lowest temperature rise was observed with light emitting diode for both remaining dentin thicknesses. The only significant differences in temperature rise were observed between Elipar Trilight Standard mode and LED. No significant difference (p > 0.01) existed for the different modes of Elipar Trilight. A statistically significant higher temperature rise was observed within each curing unit at a depth of 1 mm compared to 2 mm. Although the tested light-curing units caused a temperature rise in the pulp chamber, none exceed the critical value of 5.5 degrees C.     

Increase of temperature during osteotomy. In vitro and in vivo investigations

Direct temperature measurements using copper-constantan thermocouples were performed during in vitro and in vivo bone cuttings while the load of the oscillating saw and irrigation were varied. Very high temperatures during continuously applied load were observed. Consequent irrigation may reduce temperature elevation, but only intermittent sawing combined with irrigation diminishes temperature elevation adequately, which allows for an osteotomy without discernible bone damage. In practice, the available oscillating saws should be handled with great care, which implies that the osteotomy should be performed with maximum irrigation and intermittent use.     

Retention force changes in implant-supported titanium telescope crowns over long-term use in vitro

summary Titanium is used to fabricate spherical and bar attachments for overdentures on osseointegrated implants. This in vitro study investigated the long term effects of commercially pure titanium on the retention force of telescope crowns with conical interface. Combinations of various materials for the inner and outer crowns were tested. Telescope crowns of pure titanium showed retention force charac teristics comparable to telescope crowns fabricated conventionally in a precious alloy.     

加热氟化钠对髓腔内温度变化影响的离体牙实验观察

目的:体外实验观察器械加热后放置于不同磨损牙面上所涂的氟化钠糊剂上不同时间髓腔内温度的变化。为临床使用加热氟化钠导入法治疗牙本质过敏症提供实验依据。方法:收集成人完整离体磨牙,根据SmithBGN对牙齿磨损分类,将牙合面制成轻、中、重度磨损,用加热不同时间的金属器械放置在不同磨损程度的牙面上不同时间,观察髓腔内温度变化,以所测温度最高值减测量前基础温度值,所得出髓腔温度上升绝对值进行比较分析。结果:加热器械5和10s,放置牙面不同时间,髓腔温度上升值不同,在最初10~20s内,髓腔温度随器械放置时间延长而上升。在相同时间内,磨损程度越重,髓腔温度上升值越高。结论:器械加热导入氟化钠过程中,器械温度一定时,器械放置时间和牙齿磨损程度是影响髓腔温度的主要因素。