Thermographic assessment of root canal obturation using thermomechanical compaction

The potential interaction is described between caffeine and antipyrine, two drugs with a high probability of being concomitantly administered for the evaluation of liver metabolism. In order to determine the influence of antipyrine on the elimination of caffeine, salivary caffeine clearance was measured in six healthy volunteers prior to and 2 and 5 days after the administration of a single oral dose of 1000 mg of antipyrine. Total caffeine clearance increased on average by 24% (from 1.65 to 2.05 ml/min, P = 0.1) 2 days after antipyrine dosing, and 25% (from 1.65 to 2.06 ml/min, P < 0.01) 5 days after the administration of antipyrine, whereas the half-life decreased by around 24% (from 5.3 to 4 h, P = 0.09) after 2 days and 26% (from 5.3 to 3.9 h, P = 0.05) after 5 days. The apparent volume of distribution did not change. These results suggest that antipyrine is able to increase the elimination of caffeine, probably by means of inducing its hepatic metabolism. When both drugs are used sequentially in the same patient to assess the drug metabolizing activity of the liver, the caffeine test should be performed first.     

Comparison of thermoplasticized gutta-percha root canal obturation technique to the lateral condensation

Exercise tolerance in postcardiac transplantation patients versus healthy controls was studied at different intervals after the surgery using bicycle ergometry. Being low after the transplantation, exercise tolerance in the patients increased throughout the rehabilitation period but still did not reach the values characteristic for healthy subjects. Initial heart rate in the above patients was higher, while chronotropic and inotropic reserves of the transplanted heart appeared lower than in the controls. The data obtained help objectively assess the condition of the patients with transplanted heart.     

Long-term sealing efficacy of four root surface sealing materials used in endodontic leakage studies

Fifty extracted human maxillary anterior teeth were biomechanically instrumented and divided into five equal groups, four experimental and a control. The teeth in the experimental groups had their root surface coated with one of four sealants; epoxy, casting resin, sticky wax, or nail polish. The roots of the remaining teeth were not coated and served as controls. All of the teeth were mounted in the caps of scintillation vials. Five microliters of [3H]uridine were deposited in the root canal space and disintegration counts were obtained over time periods of 1, 4, 8, 12, and 36 wk. At the conclusion of the experiment, sticky wax was demonstrated to provide a superior seal (p < 0.0001).     

Initial biological testing of root canal sealing materials--a critical review

A number of systems for the biological testing of dental materials have been suggested. This paper presents a critical review of the protocols suggested in the ISO standards for the initial and secondary biological testing of root canal sealing materials.     

Effectiveness of two rotary instrumentation techniques for cleaning the root canal

An in vitro study was undertaken to compare the efficiency of two rotary endodontic devices for cleaning the root canal wall(s). Only mesial roots of mandibular first molar were used. Forty roots were classified into two equal groups. Group (I) was instrumented using the Canal Finder system, Group (II) was instrumented using Nickel Titanium files. In both groups half of the specimens received a final flush of 17% EDTA and 5.25% NaOCl solutions. Roots were sectioned longitudinally and Scanning Electron Micrographs were taken at three levels (Coronal, Middle and Apical) of each section of the prepared roots. Statistical analysis of the results showed that the Canal Finder system produced a clean canal surface when 17% EDTA and 5.25% NaOCL were used as an irrigating solutions, while Nickel Titanium files had a superior cleaning efficiency than the Canal Finder with either irrigating solution.     

Effect of two obturation techniques on the filling of lateral canals and the main canal

The three-dimensional obturation of the root canal system is widely accepted as a key factor for successful endodontic therapy. The purpose of this study was to evaluate the obturation of lateral canals and the main canal using cold lateral condensation versus the gutta-percha coated rigid carrier. Thirty epoxy blocks with five lateral canals placed at varying angles from the main canal were used. Each experimental group was obturated by a board certified endodontist with clinical experience in the respective obturation technique. The length of gutta-percha and sealer in the lateral canals was measured under a microscope (x30, Unitron) to the nearest 0.5 mm. The blocks were sectioned with an Isomet Plus precision saw (Buehler, Lake Bluff, IL) and copious water irrigation perpendicular to the main canal at the apex, the height of contour, and at 0.8, 1.6 and 2.4 mm from the canal apex. A microscope (x100, Leitz, Switzerland) was used to determine voids. There was significantly (p < .001) more gutta-percha in the lateral canals with the gutta-percha coated rigid carrier technique. In contrast, the cold lateral condensation technique had significantly (p < .001) more sealer in the lateral canals. However, there was no significant (p < .05) difference, in gutta-percha-plus-sealer filling of the lateral canals, between the two techniques. In the apical 1 mm of the main canal there were significantly (p < .011) fewer voids with the gutta-percha coated rigid carrier technique compared to the cold lateral condensation. In the model chosen, the gutta-percha coated rigid carrier technique and the cold lateral condensation technique were equally effective in filling lateral canals. In filling the main canal, however, the coated rigid carrier technique was more effective.     

Scanning electron microscopic evaluation of two compaction techniques using a composite resin as a root canal filling material

The canals of 20 human dental roots were instrumented using a a step- back technique. The smear layer was removed, and the canals were obturated with composite resin. Two different techniques of compaction were used: either vertical or lateral motions were used to condense composite resin inside the root canal that was then photopolymerized layer by layer using the argon laser (488 nm). The beam was delivered into the root canal by means of an optical fiber 320 micrometers in diameter. Longitudinal and cross-sections of the samples and resin replicas of the root canals were examined using a light and scanning electron microscope. Scanning electron microscopic examination revealed that laterally compacted resin fillings showed fewer voids than those obtained by vertical compaction. In both experimental groups, adhesion of the resin to the dentin walls, pulled-out resin tags, microfailure, and resin fracture, leaving a layer of resin associated with the wall surface were observed.     

In vitro evaluation of the cytotoxicity of two glass-ionomer root canal sealers

The cytotoxicity of two glass-ionomer root canal sealers (Ketac-Endo and Endion) was tested by using an established cell line, BHK21/C13. Under aseptic conditions, the sealers were prepared according to the manufacturers' directions, and 0.1 ml of each material was placed in petri dishes. After setting for 6 h, the sealers were covered with 20 x 10(4) cells per dish. The cultures were incubated at 37 degrees C for 24 h, 48 h, and 72 h. Cytotoxicity was assessed by a quantitative technique at three observation periods. Endion was highly cytotoxic, causing a significant decrease in cell density. Ketac-Endo proved to be a very biocompatible material.     

A new muffle model system to study root canal morphology and instrumentation techniques

A new muffle model system is presented using the principle of internal indexing. The system is composed of a metal stand, four pins, and a single Teflon mold that is used for the investment of all teeth. This system is very precise, reproducible, and versatile. The sectioned specimens can easily be stored assembled, as opposed to previous systems that rely on external indexing.     

A comparison of root surface temperatures using different obturation heat sources

OBJECTIVE: To investigate the relationship between radiographic signs of subluxation in the cervical vertebrae and their clinical diagnostic value. DESIGN: Controlled, clinical study. SETTING: Institute of Clinical Anatomy and Biomechanics and NanFang Hospital of the First Military Medical University, Guangzhou, China. SUBJECTS: Eighty-seven subjects with cervicodynia and 21 asymptomatic volunteers. INTERVENTIONS: Radiological signs of subluxation from anteroposterior, lateral, open-mouth and dynamic radiographs of the cervical vertebrae of the subjects were measured and analyzed. MAIN OUTCOME MEASURES: The right and left odontoid lateral mass interspace, divergence of the spinous processes, sign of double contour and position of odontoid process were studied. RESULTS: The bilateral odontoid lateral mass interspaces were asymmetrical in most cases, and the divergence of spinous processes, sign of double contour and position of odontoid process were also common. Cervical vertebrae C5, C4 and C6 showed no special variations. CONCLUSION: There was little evidence to support the contention that signs of subluxation in the cervical vertebrae are of diagnostic significance. Subluxation should be defined in two ways: as a purely roentgenological diagnosis and as a combination of roentgenological signs with clinical signs.     

An evaluation of canal morphology at different levels of root resection in mandibular incisors

One hundred randomly selected mandibular incisors were examined to assess the prevalence and location of two canals and to describe the canal anatomy that may be encountered during apical surgery. Sections of the root were cut at 1, 2, and 3 mm from the apex, simulating a 20-degree beveled surgical resection. The sections were digitally imaged at x 50 magnification, and canal dimensions were measured using imaging software. The prevalence of two canals was 2% at 1 mm, 0% at 2 mm, and 1% at 3 mm. At these levels in the roots, the canal was rarely divided by hard tooth structure. An isthmus of tissue was present 20% of the time at 1 mm, 30% at 2 mm, and 55% at 3 mm. Four distinct canal types were noted: (i) round, (ii) oval, (iii) long oval, and (iv) ribbon. In 75% of the teeth, the canal shapes varied from one level to the next. The more coronally the root-end resection was made, the more elongated the canal tended to become.     

磁性液体密封结构中漏磁的研究

为了研究磁性液体密封结构几何参数的变化对漏磁场的影响规律,选取不同的密封间隙、极齿宽度、齿槽宽度、齿槽深度及密封级数建立物理模型,用有限元方法计算各模型的漏磁场.结果表明在密封结构的轴向和径向距离上存在某一临界值,在临界值的两侧,漏磁场磁感应强度随密封结构几种几何参数的变化趋势不同:在轴向距离大于临界值时,轴向漏磁场磁感应强度随间隙的增大而增大,随级数的增加而减小,随齿宽的增大而减小,随槽宽和槽深的增大而增大;在径向距离小于临界值时,径向漏磁场磁感应强度随间隙的增大而减小,随级数的增加而增大,随齿宽的增大而增大,随槽宽的增大而增大,随槽深的增大而减小;径向距离大于临界值时的情况与小于临界值时的情况刚好相反.     

轧钢机主机列设备的泄漏与密封

分析了轧钢机主机列设备泄漏的原因,根据不同的漏油类型,通过改进设备的密封结构、采用新的密封材料及加强润滑与密封的管理、选用合适的润滑油,可达到根治润滑油泄漏的目的.     

Effect of restoration thickness on the sealing ability of TERM

An in vitro study was done using a fluid filtration device to compare microleakage of Temporary Endodontic Restorative Material (TERM) at various thicknesses. Forty-four extracted mandibular molars had their roots removed at the cementoenamel junction, occlusal table flattened, and a standardized endodontic access made in the crown. The teeth were restored with TERM in thicknesses of 1, 2, 3, and 4 mm, and quantitatively measured for leakage (microliters/min) at intervals of 1 and 24 h and 1, 3, and 5 wk. Thermocycling was accomplished at the 5-wk interval. Positive controls received 4-mm-thick IRM or gutta-percha restorations and were measured at 24 h only. Repeated measures of analysis of variance found no significant difference (p < 0.05) in leakage values in any group over time or between any of the different thicknesses. Positive controls showed significantly more leakage than all other groups. TERM maintained as tight a seal at 1-, 2-, and 3-mm thicknesses as it did at 4 mm and may be suited for clinical situations where less than 4 mm of restorative space exists.     

感染根管内细菌定植状态的观察

目的:了解慢性根尖周炎患牙根管内的细菌感染状态,以指导临床治疗和评估预后.方珐:采用组织学与扫描电镜相结合的方法对临床不能保留的7例慢性根尖周炎患根进行超微结构观察,将新鲜拔除的患根沿牙长轴近、远、中向劈为两半,一半做组织学切片,采用Brown&Brenn染色观察,另一半做扫描电镜观察.结果:组织学切片细菌特染显示,大量细菌附着于根管壁表面并定植于根管壁牙本质小管深部,用测微尺测量细菌侵入深度为140～1000μm,根尖1/3段感染较重.扫描电镜结果显示,根管壁表面可见到致密、半封闭状态的网状细菌膜结构,大量球菌、杆菌和/或丝状菌镶嵌于无定形的基质中,集中于根尖1/3段.结论:慢性根尖周炎的根管内细菌以生物膜形式定植在根尖1/3区,并侵入牙本质小管深部,形成感染难以清除的区域.     

An in vitro comparison of thermoplasticised gutta-percha obturation techniques with cold lateral condensation

This study compared the apical sealing ability, obturation time and extrusion of gutta-percha and sealer when root canals were obturated using either cold lateral condensation or one of the three methods using thermoplasticised gutta-percha (Alpha Seal, Thermafil or JS Quick Fill) in vitro. One hundred and thirty-one root canals from 78 extracted human teeth were used; 116 canals were divided into five groups so that they were balanced with respect to prepared canal anatomy, and the remaining 15 canals were used as positive and negative controls. The canals in the first four groups were prepared with hand files using the step-down technique to a standard apical size and flare. The last group was prepared using engine-driven rotary nickel-titanium files (McSpadden) to a similar apical size and flare. One of the four obturating techniques was used to fill the canals in each of the first four groups. The fifth group was obturated using the Alpha Seal technique. The roots were immersed in india ink, demineralised and rendered transparent to assess the extent of maximum lincar dye penetration. The Alpha Seal groups had the highest number of specimens without any leakage. There was a significant difference in the proportions of specimens that did not leak when the Alpha Seal (P < 0.01) and cold lateral condensation groups (P < 0.05) were compared with JS Quick Fill. Cold lateral condensation had a higher proportion of specimens with leakage in canals with curvature greater than 20 degrees than in canals with curvatures less than 20 degrees (P < 0.05). The curvature of canals had no effect on the sealing ability of the other techniques. The method of canal preparation had no effect on the sealing ability of Alpha Seal. Alpha Seal, Thermafil and JS Quick Fill were significantly quicker to perform than cold lateral condensation.     

The challenge of preparing the curved root canal

Heavily restored teeth which become pulpally involved are now often root canal treated rather than extracted. While this is laudable it has a significant impact on the practice of endodontics today. The curved calcified canal can prove very difficult to prepare to its natural shape by conventional techniques and there is always the likelihood of iatrogenic damage. To compensate for this many clinicians tend to under-prepare these canals, perhaps leaving them inadequately cleaned and certainly remarkably difficult to fill to length. The purpose of this article is to outline the stages of and the rationale behind a hand instrumentation preparation method which uses the balanced force method of movement of files from canal entrance to apical constriction. In the authors' experience this technique has gone a long way towards solving the problem of cleaning and shaping the fine curved canal. With some practice, but no extra expense, the technique described will not only speed up canal preparation but will also make it more predictable.     

An evaluation of linear model analysis techniques for processing images of microcirculation activity

Clinicians in several countries have expressed concerns about possible adverse effects of shortening obstetric length of stay. A population-based survey of 1366 mothers who gave birth in Victoria, Australia, in 1993 was used to investigate social and obstetric characteristics of mothers discharged home 'early', and to assess whether shorter stays were associated with adverse health outcomes, or a lesser degree of satisfaction, or both. Women's views and experiences of length of hospital stay were gathered via a statewide postal survey of women who gave birth in a 2-week period; 62.5% (n = 1336) responded. Assessment of the relationship between length of stay (1-2 days vs. > or = 5 days, and 3-4 days vs. > or = 5 days) and four main outcome measures (infant feeding at 6 weeks, period prevalence of feeding problems, maternal confidence and depression) showed no association between these variables and length of stay after adjusting for other obstetric and social factors in separate regression analyses. For stays of 3-4 days, the adjusted odds ratio (OR) for formula feeding at 6 weeks was 1.35 [95% confidence interval (CI) 0.9-1.9]; for feeding problems OR = 0.87 [0.7-1.2]; for lacking confidence OR = 0.81 [0.6-1.2]; and for depression OR = 0.96 [0.7-1.4]. Large randomised trials of early obstetric discharge are required to resolve continuing uncertainties about the safety, and possible benefits of shorter hospital stays.