Tooth preparation: a study on the effect of different variables and a comparison between conventional and channeled diamond burs.

PURPOSE: The purpose of this study was to evaluate the different variables involved in tooth cutting to characterize intrapulpal temperature generation, cutting efficiency, and bur durability when using conventional and channeled diamond burs. MATERIALS AND METHODS: Forty premolars and 60 molars were selected for the study. Four diamond burs were paired according to grit size: 125-microm grit: Brasseler Coarse (Control 1) and TDA System (Test 1) burs; and 180-microm grit: Brasseler CRF (Control 2) and NTI Turbo Diamond (Test 2) burs. Each bur was used twice when cutting the premolar teeth, whereas it was used for 60 cuts when cutting the molar teeth. The data were analyzed to compare the correlation of bur design, grit and wear, amount of pressure, advancement rate, revolutions per minute, cutting time and rate, and proximity to the pulp chamber with intrapulpal temperature generation, cutting efficiency, and bur longevity. The mean values of test and control burs in each group were compared using an ANOVA (p < 0.05 for significant differences) for temperature generation and an ANOVA and the Tukey multiple range test (p< or = 0.05) for cutting efficiency and bur longevity. RESULTS: No significant difference was found in intrapulpal temperature generation while cutting premolar and molar teeth with conventional and channeled diamond burs. In both groups, the mean temperature recorded during and after the cutting procedure was lower than the baseline temperature. For premolar teeth, no significant difference was established for control and test burs for the load required to cut into the tooth and the cutting rate. However, both test burs showed significantly fewer revolutions per minute when compared to their control counterparts. For the molar teeth, the Brasseler CRF bur required a significantly lower cutting load when compared to the NTI bur, whereas no difference was noted between the other pair of burs. The cutting rate was significantly higher for both control burs, whereas revolutions per minute (rpm) were greater for control coarser burs only. Overall, channeled burs showed a significantly lower cutting efficiency when compared to conventionally designed burs. CONCLUSION: Within the limitations of this study, channeled burs showed no significant advantage over conventional diamond burs when evaluating temperature generation and bur durability. Moreover, the cutting efficiency of conventional burs was greater than that of channeled burs.     

Cutting efficiency of air-turbine burs on cast titanium and dental casting alloys

OBJECTIVE: The purpose of this study was to investigate the cutting efficiency of air-turbine burs on cast free-machining titanium alloy (DT2F) and to compare the results with those for cast commercially pure (CP) Ti, Ti-6Al-4V alloy, and dental casting alloys. METHODS: The cast metal (DT2F, CP Ti, Ti-6Al-4V, Type IV gold alloy and Co-Cr alloy) specimens were cut with air-turbine burs (carbide burs and diamond points) at air pressures of 138 or 207 kPa and a cutting force of 0.784 N. The cutting efficiency of each bur was evaluated as volume loss calculated from the weight loss cut for 5 s and the density of each metal. The bulk microhardness was measured to correlate the machinability and the hardness of each metal. RESULTS: The amounts of DT2F cut with the carbide burs were significantly (p < 0.05) greater than for the other titanium specimens at either 138 or 207 kPa. The diamond points exhibited similar machining efficiency among all metals except for Type IV gold alloy. The increase in the volume loss of Co-Cr alloy (Vitallium) cut with the diamond points showed a negative value (-29%) with an increase in air pressure from 138 to 207 kPa. There was a negative correlation between the amounts of metal removed (volume loss) and the hardness (r2 = 0.689) when the carbide burs were used. SIGNIFICANCE: The results of this study indicated that a free-machining titanium alloy (DT2F) exhibited better machinability compared to CP Ti and Ti-6Al-4V alloy when using carbide fissure burs. When machining cast CP Ti and its alloys, carbide fissure burs possessed a greater machining efficiency than the diamond points and are recommended for titanium dental prostheses.     

Dental Cutting with Diamond Burs: Heavy-Handed or Light-Touch?

PURPOSE: The cutting efficiency of diamond dental burs using different handpiece loads was evaluated against simulated enamel, a machinable glass ceramic (Macor). MATERIALS AND METHODS: An ultra-high-speed dental handpiece was mounted in a frictionless bearing so that the pressure applied at the contact interface between the dental bur and the cutting substrate was controlled. One type of coarse- and two types of medium-grit diamond burs were studied. Handpiece loads of 44, 91.5, and 183 g were applied at the bur/Macor interface, and cutting efficiency was determined as the amount of Macor removed in ten 30-second-duration cuts that were 4 mm in length. The data were analyzed by one-way ANOVA and a post-hoc Scheffé test at an a priori alpha = 0.05. RESULTS: Cutting efficiency depended on both the diamond grit of the bur and the load applied to the handpiece. CONCLUSIONS: The pressure used by most dentists, about 100 g at the bur tip, appears to be optimal for medium-grit burs. If the pressure applied to the handpiece is markedly increased, there was no increase in cutting efficiency for medium-grit burs. In contrast, an increased handpiece pressure raises the cutting efficiency of coarse-grit burs but the effect of this enhanced rate of cutting on the pulpal tissues is uncertain. Cutting efficiency also appeared to be dependent on debris accumulation between the diamond chips.     

Effect of four anticorrosive dips on the cutting efficiency of dental carbide burs

Because tungsten-carbide dental burs corrode during sterilization in an autoclave, four anticorrosive dips were studied to determine their effect on the burs in maintaining cutting efficiency.     

氮化钛涂层对MANI金刚砂钻针垂直切割性能的影响

目的：研究氮化钛涂层对金刚砂钻针垂直切割性能的影响。方法：选取同一批次直径为1.0mm的MANISF-13金刚砂钻针24只,随机分成A、B两组,每组12只。A组采用直流反应磁控溅射方法在金刚砂钻针表面镀氮化钛涂层,B组作为对照,未镀氮化钛涂层。分别测定A、B两组金刚砂钻针的垂直切割效率。结果：当切割次数为1次和2次时,A组金刚砂钻针的切割效率稍低于B组,但两者之间的切割效率无显著性差异;当第3次切割时,A组金刚砂钻针切割效率却高于B组,两者之间的切割效率也无显著性差异;当切割次数在4、5和6次时,A组金刚砂钻针切割效率明显高于B组,其差异具有显著统计学意义（P〈0.05）;B组金刚砂钻针切割第6次后已经丧失切割能力,而A组金刚砂钻针的切割效率却仍保持在0.475mm/min。结论：氮化钛涂层在保证一定切割效率的前提下可以明显延长金刚砂钻针的使用寿命。     

三种灭菌法对高速裂钻腐蚀和切削率的影响

目的:观察湿热灭菌法、干热灭菌法、化学浸泡灭菌法处理高速裂钻后其表面腐蚀情况,以及对高速裂钻切削率的影响。方法:100根新高速裂钻随机分成10组分别用3种灭菌方法处理5、10、15次,体视显微镜观察处理前后裂钻表面形态的变化,参考Siegel标准自制设备测试裂钻的垂直和侧向切削率,统计分析灭菌处理对切削率的影响。结果:3种灭菌方法中,湿热灭菌法引起的裂钻表面腐蚀最严重;干热法最轻;湿热灭菌法引起的裂钻切削率下降幅度最明显,化学浸泡法、干热法次之。灭菌次数与腐蚀程度、切削率的降低幅度成正比,处理15次后,裂钻的垂直和侧向切削率均有明显下降。结论:湿热灭菌法引起的裂钻腐蚀改变最明显、切削率降低幅度最大,化学浸泡法、干热法较轻,建议牙用高速裂钻类小器械采用玻璃珠灭菌器进行灭菌。     

Comparative efficiency testing 330 carbide dental burs utilizing Macor substrate

Traditionally, it has been difficult to compare the clinical performance of carbide dental burs. The purpose of this laboratory study was to investigate the comparative cutting efficiency of number 330 dental burs from six manufacturers. These burs were tested utilizing custom-built equipment consisting of a frictionless air sled to which the Macor substrate was attached. The substrate was fed to the bur at constant pressure. The efficiency of each bur, defined as the distance of the cut divided by the time taken, then was calculated. Of the six bur types tested, only one was found to be markedly superior, and four types were comparable in performance.     

三种金刚石车针的体外对比评价

目的利用体外模拟实验对比研究了德国WILOFA车针、日本Mani和中国Tengyuan车针的性能。方法用体式显微镜分别观察了从三种车针腐蚀下来的金刚石形貌以及购货态下的车针工作部表面形貌,用专用设备对它们的磨削效率与耐磨性能进行了体外评价,比较了三种车针磨削速率与耐磨性能的稳定性差异。结果德国WILOFA车针和日本Mani车针在金刚石选择和车针表面金刚石排布模式上基本相同,中国Tengyuan车针与前两者存在很大差异。对车针磨削性能在磨削效率和绝对磨削总量两个指标上和耐磨性能稳定性的统计学结论为：WILOFA车针稳定性最优,Mani车针次之,Tengyuan车针最低。结论WILOFA车针和Mani车针磨削性能相似,Tengyuan车针明显低于前两者。     

Comparing cutting efficiencies of diamond burs using a high-speed electric handpiece

This study sought to compare the cutting efficiency of different diamond burs on initial use as well as during repeated use, alternating with sterilization. Long, round-end, tapered diamond burs with similar diameter, profile, and diamond coarseness (125-150 microm grit) were used. A high-torque, high-speed electric handpiece (set at 200,000 rpm) was utilized with a coolant flow rate of 25 mL/min. Burs were tested under a constant load of 170 g while cuts were made on a machinable ceramic substrate block. Each bur was subjected to five consecutive cuts for 30 seconds of continuous operation and the cutting depths were measured. All burs performed similarly on the first cut. Cutting efficiencies for three of the bur groups decreased significantly after the first cycle; however, by the fifth cycle, all bur groups performed similarly without any significant differences (p > 0.05). A scanning electron microscope revealed significant crystal loss after each use.     

四种金刚砂钻针切割效率及耐用性的比较研究

目的 比较4种金刚砂钻针初次及多次使用后的切割效率。方法 ①4种金刚砂钻针各15支，以砝码、滑轮和滑道控制钻针在100g力作用下水平向切割树脂试块10秒。重复20次，记录第1次及第20次的切割长度以比较侧向切割效率和耐用性。②4种金刚砂钻针各15支，以天平和砝码控制钻针在100g力作用下垂直向切割树脂试块5秒。比较垂直向切割效率。结果 KOMET的侧向切割效率最高，SCHEZER与DIATECH无明显差别，均高于MANI。KOMET、MANI和DIATECH的垂直向切割效率无差别并均高于SCHEZER。4种钻针在连续侧向切割20次后效率均明显降低。第20次测试中，SCHEZER的切割效率最高，其次为KOMET，高于DIATECH和MANI。耐用性从高到低依次为：SCHZER、MANI、DIATECH、KOMET。结论 在操作中如果同时需要侧向及垂直向切割，推荐使用KOMET钻针。在主要需要侧向切割时建议选用性能价格比较高的SCHEZER钻针。     

The effects of tooth preparation on pressure measured in the pulp chamber: a laboratory study

PURPOSE: The purpose of this study was to determine pressure changes in the pulp space during tooth preparation with either diamond or tungsten carbide burs in a high-speed dental handpiece in the laboratory. MATERIALS AND METHODS: Twenty premolar teeth were collected and randomly assigned to two groups: group 1 received preparation with diamond burs and group 2 with tungsten carbide burs. The teeth were mounted on a pressure transducer and the pulp chambers were filled with saline. A 0.1-mm thickness of tooth tissue was removed from the proximal surface of each tooth, alternating dry and wet cutting, until the pulp chamber was exposed. Pressure and temperature changes were recorded during tooth preparation. RESULTS: At 0 to 1 mm of remaining dentin depth dry cutting with diamond and tungsten carbide burs generated a mean positive pulpal pressure of 12 kPa and 6 kPa, respectively. Wet cutting under the same conditions produced 0.6 kPa and 0.15 kPa, respectively. The difference between wet and dry cutting was highly significant (P < 0.001). Diamond burs produced significantly higher pressure increases than carbide burs at all levels for both wet and dry techniques (P < 0.05). When cutting farther than 2 mm from the pulp, tooth preparation created a mean 0.09-kPa pressure increase, which was not influenced by either coolant use or bur type. The temperature change was minimal during wet cutting and only minor temperature increases were recorded during dry cutting. CONCLUSION: From this laboratory study it is concluded that significant pressure changes occur in the pulp chamber during tooth preparation of extracted teeth when the remaining dentin thickness is less than 2 mm.     

Comparison of Sectioning Rates Among Carbide and Diamond Burs Using Three Casting Alloys

PURPOSE: This study compared the sectioning rates of commercially available high noble, noble, and base metal casting alloys using two new cross-cut tungsten carbides specifically manufactured for alloy sectioning and two medium grit diamond burs. MATERIALS AND METHODS: Rectangular bars cast from a base metal alloy (Ni-Cr-Mo-Be), a noble alloy (Pd-Cu-Au), and a high noble alloy (Au-Ag-Cu-Pd) were sectioned under controlled conditions. Two types of cross-cut tungsten carbide and two types of medium grit diamond burs were tested using a high-speed handpiece under a coolant flow rate of 20 mL/min and an applied load at the bur tip of 0.9 N (91.5 g). Three 4-mm cuts were made through the alloy specimens using six burs of each type. The time required for Cuts 1, 2, and 3 was recorded, and sectioning rates in millimeters per minute were calculated as a relative measure of cutting efficiency. For each alloy, the total time required for the three cuts was analyzed using one-way analysis of variance (one-way ANOVA) and Scheffé tests (alpha = 0.05) to determine differences in sectioning rate among bur types. RESULTS: In general, mean sectioning rate for Cut 1 through Cut 3 decreased with longer use of the bur. Regarding total sectioning times, the carbide burs sectioned the base metal alloy significantly faster (P < .001) than the diamond burs. However, diamond burs sectioned the high noble alloy significantly faster (P < .001) than the carbide burs. Diamond burs also sectioned the noble alloy more quickly than the carbide burs, but the difference was not statistically significant. CONCLUSIONS: The cross-cut tungsten carbide burs should be used to section the base metal alloy but the medium grit diamond burs should be used to section the high noble alloy.     

Assessing the cutting efficiency of different burs on zirconia substrate

Cutting dental zirconia for endodontic access preparation is difficult. Therefore, this study aimed to determine cutting efficiency of various burs when cutting this material. An air turbine handpiece was used in a customised test rig to cut sintered zirconia specimens, using a conventional blue band diamond, two different zirconia‐cutting diamond and a zirconia‐cutting tungsten carbide bur. Position and speed of the bur were continuously determined using wireless data acquisition over two successive five‐minute runs. Differences in cutting efficiency were statistically analysed. Burs were examined using light and scanning electron microscopy (SEM). All diamond burs cut zirconia more efficiently than the tungsten carbide bur. Overall, all burs showed decreasing cutting efficiency over time. SEM images showed discernible wear and damage to the cutting portion of each bur head. It is concluded that zirconia‐cutting burs are advantageous regarding durability, and carbide burs are rather ineffective against carbide substrate.     

A comparison of decontamination methods used for dental burs

OBJECTIVES: This study investigated the bacterial and fungal contamination of used dental burs. A novel assay system for comparison of efficacy of pre-sterilisation cleaning techniques for dental burs was used to evaluate manual scrubbing, enzymic agents and washer-disinfectors. METHODS: Thirty dental burs contaminated during cavity preparation were analysed for micro-biological total viable counts and species of bacteria and fungi present. To simulate clinically contaminated burs, a culture of Streptococcus sanguis NCTC 7863 was used to inoculate unused dental burs, alone and combined with blood, saliva or a mixture of blood and saliva. Contaminated burs were subjected to six pre-sterilisation cleaning techniques and the log reduction in contamination achieved by each method was assessed. RESULTS: The microbial count from used dental burs ranged from 0 to 6.92 x 10(4) CFU ml(-1). Many potentially pathogenic species were identified. The decontamination assay demonstrated that autoclaving alone was not sufficient to sterilise dental burs. Manual scrubbing in air was less efficacious than manual scrubbing under water (p<0.001). The most effective method of pre-sterilisation cleaning for dental burs was a washer-disinfector. CONCLUSIONS: Enzymic agents are suitable for soaking contaminated dental burs immediately after use. Washer-disinfectors are recommended as the method of choice for pre-sterilisation cleaning of contaminated dental burs.     

The grinding efficiency of diamond burs.

Deterioration of round diamond burs during 8 minutes of operation was found to be more pronounced for burs with low particle densities than for burs with high particle density. No definitive relationship was found between the initial grinding rate and initial particle density.     

Conventional and single-use burs. Cavity preparation comparison

Our work's aim, was to value the wear of conventional and monouse burs, while preparing the cavity. Usually the conventional burs give better technical efficiency, but the monouse ones represent a notable progress both in technology and prevention.     

The magnitude of cutting forces at high speed

STATEMENT OF THE PROBLEM: Previous research has used a range of cutting forces for preparing teeth, but there are no data available on the forces actually imposed while cutting teeth with high-speed handpieces. PURPOSE: The purpose of this study was to measure the forces imposed while cutting teeth with tungsten carbide burs used in high-speed handpieces. MATERIAL AND METHODS: Thirty-one dentists each cut 8 conventional class II MO and DO preparations in intact extracted third molars, by use of 2 different air turbine handpieces with different torque-speed characteristics. Two different flat fissure, plain and cross-cut tungsten carbide burs, cutting wet and dry in each handpiece/bur combination. The teeth were mounted in a custom-made transducer unit that displayed the forces imposed by the bur. Data were analysed with a 1-way ANOVA (alpha =.05) and Spearman correlation test. RESULTS: The results showed that there was no significant difference in the applied force between plain and cross-cut burs, cutting wet or cutting dry, but there was a significant difference between the high and the lower torque handpieces. The higher torque handpiece was used at a mean cutting force of 1.44 N and the lower torque handpiece at 1.20 N (P<.002). The overall general mean force observed was 1.30 N. CONCLUSION: It was concluded that the forces used in cutting teeth with the tungsten carbide burs tested related both to the type of the handpiece and to the forces chosen by clinical operators. There was no difference between the plain and cross-cut burs, there was no difference between the cutting wet or dry, and the higher torque handpiece required a higher mean cutting force.     

Cutting efficiency of diamond burs operated with electric high‐speed dental handpiece on zirconia

Zirconia‐based dental restorations are becoming used more commonly. However, limited attention has been given to the difficulties experienced, concerning cutting, in removing the restorations when needed. The aim of the present study was to compare the cutting efficiency of diamond burs, operated using an electric high‐speed dental handpiece, on zirconia (Zir) with those on lithium disilicate glass–ceramic (LD) and leucite glass–ceramic (L). In addition, evaluation of the cutting efficiency of diamond burs on Zir of different thicknesses was performed. Specimens of Zir were prepared with thicknesses of 0.5, 1.0, 2.0, and 4.0 mm, and specimens of LD and L were prepared with a thickness of 1.0 mm. Cutting tests were performed using diamond burs with super coarse (SC) and coarse (C) grains. The handpiece was operated at 150,000 rpm with a cutting force of 0.9 N. The results demonstrated that cutting of Zir took about 1.5‐ and 7‐fold longer than cutting of LD and L, respectively. The SC grains showed significantly higher cutting efficiency on Zir than the C grains. However, when the thickness of Zir increased, the cutting depth was significantly decreased. As it is suggested that cutting of zirconia is time consuming, this should be taken into consideration in advance when working with zirconia restorations.     

Comparison of cutting rates among single-patient-use and multiple-patient-use diamond burs

PURPOSE: The purpose of this study was to compare the volumetric cutting rates of 6 cylindrical-shaped single-patient-use and 2 cylindrical-shaped multiple-patient-use diamond burs using a machinable ceramic material. The degree of wear among burs from each type was also compared using scanning electron microscopy. MATERIALS AND METHODS: Six types of single-patient-use diamond burs and 2 types of multiple-patient-use diamond burs with similar cylindrical shape and dimensions were selected. Five burs of each type were evaluated using a high-speed handpiece mounted on a custom testing device. Using a 6-mm cutting length of each bur, 20 cuts, each 12.2-mm long, were made at exactly one half the diameter of the bur. Mean volumetric cutting rate through the ceramic substrate for Cuts 1 through 20 was calculated for each bur type in cubic millimeters prepared per second. A repeated measures analysis of variance (alpha = 0.05) and post hoc one-way analysis of variance with Scheffé's test was used to compare cutting rates among bur types for Cuts 2, 10, and 20. The topography of one bur from each group was evaluated with scanning electron microscopy after Cut 2 and again after Cut 20. RESULTS: For Cut 2, the mean cutting rates ranged from 3.3 to 5.3 mm3/s. The mean cutting rates for all bur types decreased approximately 20% by Cut 20. Bur type and length of use significantly influenced cutting rate (p < .002). However, only one type of single-patient-use diamond bur had a significantly lower mean cutting rate after Cut 2, 10, and 20, compared with other single- and multiple-patient-use diamond burs. Scanning electron microscopy showed all burs exhibited wear of diamond particles, as well as loss of diamond particles and binder. CONCLUSIONS: Five of six single-patient-use diamond burs had mean volumetric cutting rates through a ceramic that were similar to 2 multiple-patient-use diamonds for as many as 20 cuts. The gradual reduction in cutting rate during the 20 cuts for all bur types was a result of bur wear.     

不同金刚砂车针对两种氧化锆切削行为的研究

目的 研究临床常见两种不同类型氧化锆材料的耐磨性和被切削表现以及不同金刚砂车针对两种氧化锆的切削效率。方法 使用 Mani 和 RAICH 金刚砂车针在匀速恒力状态下切削多色多层氧化锆（MY 锆）与超透氧化锆（ST锆）,并且用 Micro-CT系统对体积损失部分进行扫描重建,计算两种氧化锆的体积损失,评价其耐磨性。用两种氧化锆材料的体积损失与车针质量损失之比来评价两种车针的切削效率。使用 SEM 观察切削前后的两种氧化锆材料和两种金刚砂车针的表面微观形貌。结果 多色多层氧化锆体积损失较超透氧化锆大,且随切削深度增加而减少。多色多层锆体积损失为 MY 1st=20.07 mm³,MY 2nd=16.73 mm³,MY 3rd=13.5 mm³。超透氧化锆体积损失为 ST=12.64 mm³。耐磨性排序：ST＞MY 3rd＞MY 2nd ＞MY 1st。RAICH车针平均切削效率为109.21;Mani车针的平均切削效率为110.59,经t检验,差异无统计学意义（P>0.05）。结论 多层多色氧化锆越靠近浅层越容易切削,比超透氧化锆更容易切削;两种车针的切削效率基本相等。