The effect of serial preparation versus nonserial preparation on tissue removal in the root canals of extracted mandibular human molars

Traditional methods of root canal preparation were compared with a serial type of preparation that included the use of rotary instruments. The serial type of preparation method proved more effective in debriding the root canals than did the traditional methods.     

The effect of tooth preparation on microleakage behavior

Many factors contribute to the microleakage of a restoration. One of the more important is the method of cavity preparation. This study compared the microleakage behavior of composite restorations placed in cavities prepared by different techniques. It also compared and correlated the microleakage data produced by an electrochemical vs a staining technique. Class V cavities were prepared in 48 premolars by four techniques: (1) tungsten carbide bur in a high-speed handpiece followed by acid etching; (2) air abrasion (27 microns Al2O3) followed by acid etching; (3) air abrasion (50 microns Al2O3) and (4) air abrasion (27 microns Al2O3), with n = 12 in each group. All teeth were restored with Prime and Bond 2.1 and Tetric Flow, then thermocycled between 5 degrees and 55 degrees C for 5000 cycles with a one minute dwell at each temperature. After thermocycling, a PVC-covered Cu wire was inserted apically into the pulp chamber of each tooth and sealed into position. Leakage was continuously followed by a conductimetric method for 75 days. The teeth then were immersed in 50% AgNO3 for two hours, rinsed in distilled water for 60 seconds, then placed in a rapid photographic developer solution for two hours, followed by rinsing and sectioning for microscopic examination. Electrochemical data were examined by ANOVA and Newman-Keuls multiple comparison tests, while Kruskal-Wallis and Rank Sum Difference tests were used on the staining evaluations. Spearman's rho test was used to correlate the two test techniques. Electrochemical data for cavities prepared with a bur or air abrasion followed by acid etching prior to restoration showed significantly less (p < or = 0.05) microleakage (mean leakage currents of 1.89 & 1.57 microA, respectively) than teeth prepared with air abrasion alone (mean leakage currents of 3.60 & 3.40 microA, respectively). Rank sum AgNO3 staining data (196 & 242 vs 371 & 368) supported these findings. The correlation between the electrochemical and staining data was significant (p < or = 0.05) for all four groups of test specimens.     

单尖法根管充填临床对比研究

目的比较单尖法、冷牙胶侧方加压法、Beefill 2 in 1热牙胶充填3种方法的临床效果。方法 180例牙髓病、根尖周病患者随机分为A、B、C 3组,分别采用冷牙胶侧方加压、Beefill2 in 1热牙胶充填、单尖法根管充填。观察患牙根充的时间、术后疼痛情况、恰充率、牙根纵折发生率及根充成功率。结果 C组根充的时间为(62.6±7.2)s,短于其他两组(P<0.01);C组术后疼痛率为1.67%,低于其他两组(P<0.05);C组的恰充率为98.33%,高于其他两组(P<0.05);C组牙根纵折发生率低;C组的根充成功率为96.61%与其它两组比较无统计学差异(P>0.05)。结论单尖法根管充填疗效高、操作时间短、牙折发生率低、值得临床推广应用。     

Effect of different sealers on thermoplasticized Gutta-percha root canal obturations.

The objective of this study was to test the hypothesis that the apical seal provided by thermoplasticized root canal obturations depends on the film thickness of the sealer used. The root canals of 120 maxillary cuspid teeth were instrumented and divided into six equal groups of 20 teeth. A thermoplasticized gutta-percha root canal obturator was used to make an impression of the lubricated canal and coated with a sealer cement before reseating. Five different sealer cements of known film thickness were studied. They were, in the decreasing order of film thickness, Roth's Type I Cement, Seal-apex, Lee Endofil, AH26, and Ketac-Cem. The control group that received no sealer was prepared as recommended by the manufacturer. The degree of microleakage was based on the depth of dye penetration from the apical end measured by two independent examiners. The data collected were analyzed by analysis of variance and Weibull distribution. Analysis of variance shows that the control group exhibited significantly higher dye penetration depth (p < 0.05) while there were no significant differences among the other five groups. Analysis by Weibull distribution function shows that Lee Endofil and AH26 exhibited a higher percentage of lower linear dye penetration values compared with other groups.     

The antimicrobial effect of apical box versus apical cone preparation using iodine potassium iodide as root canal dressing: A pilot study

Abstract

Purpose. The purpose was to study the reduction of intra-canal microflora in premolars with apical periodontitis instrumented with either apical box or apical cone preparation and to provide measurements of intervention effects to allow proper power calculation in future clinical trials. Methods. Twenty-four patients were centrally randomized to apical box preparation (size #60) or cone preparation (apical size #25). The groups were comparable regarding the presence of primary caries and type of coronal restoration. In the course of canal preparation each tooth was irrigated with 2.5% NaOCl (12 ml). Lastly, the canals were filled with 17% EDTA (2 × 30 s) and 5% iodine potassium iodide (IKI) for 10 min. The canals were sampled for micro-organisms on four occasions: before instrumentation, after instrumentation, after application of IKI dressing and at the beginning of the second appointment 1 week later. Between the treatment sessions, the root canals were sealed with IRM cement. In the laboratory, culture techniques were used to measure microbial growth, which was classified as: none, very sparse, sparse, moderate, heavy or very heavy. Results. Initially, microbes were recovered in 88% of the teeth. Growth was classified as none in 35% of the teeth after instrumentation and in 50% after the application of IKI. Irrespective of the time of sampling, no significant difference in microbial growth reduction was observed between the two types of apical preparation. Based on the 1-week post-sampling, a power calculation revealed that over 900 patients are needed to show a difference of 9% between the two protocols tested. Conclusions. Future trials should be conducted using stringent protocols and as multi-centre trials for reaching the required information size.     

The effect of a single scaling with or without oral hygiene instruction on gingival bleeding and calculus formation

Abstract. 136 students of both sexes aged 14–18 years who were deprived of regular dental care participated in a 22-month longitudinal study. All students underwent scaling of the assigned teeth in 2 quadrants according to a randomized split-mouth design on contralateral quadrants. 2 groups of students were formed, one group received oral hygiene instruction (OHI). Follow-up-examinations on gingival bleeding and calculus were carried out 6, 12, and 22 months after the scaling session. The prevalence of calculus on assigned teeth at baseline was high with a mean score of 1.10. At the end of the study, new calculus formation on scaled teeth reached a mean score of 0.58. Formation of calculus still continued on non-scaled teeth, but at a lower rate than on scaled teeth. Scaling resulted in an approximately 20% reduction of the gingival bleeding score which remained during the 22 months follow-up period, OHI had no significant effect on the calculus and bleeding scores. Since the effect of scaling alone on the gingival condition was small and the effect of a single OHI negligible, the practice of occasional scaling without repeated OHI, which is commonly employed in developing countries, should be considered as clinically irrelevant and of little use in improving the standard of periodontal health.     

Effect of apical resections and reverse fillings on Thermafil root canal obturations

This in vitro dye leakage study examined the influence of apical root resection and reverse amalgam fillings on the apical seal of root canals obturated with Thermafil. Fifty human canine teeth were instrumented and obturated with either laterally condensed gutta-percha or Thermafil using Roth's zinc oxide-eugenol Type I regular sealer. After 24 h, one of the following additional procedures was performed on 30 of the teeth: 2-mm apical resection, 4-mm apical resection, and 2-mm apical resection plus reverse amalgam filling 2 mm in depth and diameter. The external root surfaces were coated with enamel paint and the teeth were exposed to 1% methylene blue dye at 37 degrees C for 2 wk. The roots were split longitudinally and the depth of linear dye penetration was measured through a stereozoom microscope. Statistical analysis showed no significant differences in the linear dye penetration among the various groups of teeth.     

C形根管系统充填方法的比较

目的探索C形根管系统的最佳充填方法。方法 收集各种原因拔除的下颌第二磨牙共90颗,对确诊为C形根管系统的32颗离体牙分组并用不同的方法充填,检测充填的密实性和根尖封闭效果。结果热牙胶充填的染色线长度最短,与其他两组相比有统计学意义。结论热牙胶充填的渗漏最少,充填效果最好。     

The effect of single plane curvature on half-round cast clasps

The quality of retention produced by a half-round cast clasp is affected by its curvature in the plane of its flat side. Uncurved clasps and those that curve 90 degrees, 180 degrees, and 270 degrees become progressively stiffer. Conversely, as the radius of the curvature increases, so does the flexibility of the clasp.