EGTA与EDTA溶液去除根管壁玷污层能力的比较

目的：比较EGTA与EDTA去除根管玷污层的能力，为临床应用提供实验依据。方法：新鲜拔除24颗牙齿分为4组，即：15％EDTA、5％EGTA、10％EGTA、15％EGTA。实验组又分为：根管预备后冲洗(简称：甲组)，边扩边冲洗组(简称：乙组)。常规开髓、拔髓后15％EDTA、5％EGTA、10%EGTA、15％EGTA分别冲洗根管，剖开根管后在扫描电镜下观察根管壁玷污层及根管壁牙本质小管开口情况。结果：15％EDTA无论在根管上、中、下1／3均能较理想去除根管壁玷污层，牙本质小管开口清楚、密集。5％EGTA去除根管玷污层效果欠佳，而10％、15％EGTA效果较好。结论：15％EDTA，10%、15％EGTA均有较好去除根管壁玷污层的能力，而且冲洗效果与注射针头进入深度密切相关。     

The effect of root canal preparation on microleakage within endodontically treated teeth: an in vitro study

AIM: The purpose of this study was to evaluate the effects of smear layer and canal instrumentation on leakage in root-filled teeth. METHODOLOGY: Six groups (n = 12) of freshly extracted human canines and premolars with closed apices and single roots were used. Groups A, B, C, and D were instrumented with engine-driven rotary nickel-titanium MCXIM files and Groups E and F were instrumented with conventional stainless steel hand files. Groups A, C, and E were flushed with 3.0 mL of 17.0% REDTA to remove the smear layer prior to obturation. All teeth were flushed with 5.25% NaOCl, then obturated with AH-26 sealer and either the lateral condensation (Groups C-E) or thermomechanical compaction technique (Groups A and B). Copper wire was placed coronally in contact with the gutta-percha in each tooth and, after immersion in 0.9% NaCl solution, a 10 volt dc voltage was connected between each tooth and a stainless steel electrode. The current flow in the circuit was observed for 45 days. One way ANOVA and Duncan's Multiple Range Test were used to compare Groups A-F at time intervals of 10, 20, 30 and 45 days and identify statistically significant differences. RESULTS: Significantly less microleakage occurred when the smear layer was removed and when the canals were obturated with thermoplasticized gutta-percha. Canals instrumented with engine-driven NiTi files exhibited less leakage than hand-instrumented canals irrespective of obturation method. CONCLUSIONS: Smear layer removal is beneficial to root canal sealing. Obturation with thermoplasticized gutta-percha provides a superior seal whilst canal instrumentation with engine-driven NiTi files reduces the extent of microleakage in root canals.     

临床根管预备对电子根尖定位仪精确性影响的研究

目的探讨根管预备对电子根尖定位仪(Electronic Apical Locator,EAL)精确性的影响。方法采用数字随机法把根管分为4组:初尖锉组:使用初尖锉取得手感法的根管工作长度并使用EALs(Root ZXand Raypex-5)测量根管工作长度;②扩一组:比初尖锉大1号的锉预备根管并使用EALs测量根管工作长度;③扩二组:扩至比初尖锉大2号的锉并用EALs测得根管工作长度;④扩三组:扩至比初尖锉大3号的锉并用EALs测得根管工作长度。将各组测量值与拔牙后直视状态下测得的根管长度进行比较。结果初尖锉组测量根管工作长度的准确率为:手感法55%,Root ZX85%,Raypex-590%;扩一组、扩二组和扩三组依次分别为:Root ZX90%、90%、95%,Raypex-595%、100%、100%。结论电测法测定根管工作长度准确率高,临床根管预备不会降低EAL的精确性。     

三种方法预备后牙细弯根管的比较

目的探讨逐步后退法、逐步深入法、被动逐步后退法（超声波与手用器械联合应用、三种不同方法预备后牙细弯根管对根管壁的清理能力及操作时间的差别。方法应用逐步后退法、逐步深入法、被动逐步后退法（超声波与手用器械联合应用）对45个新鲜拔除的人恒磨牙近中颊侧根管进行预备．并记录操作时间，将牙根纵向劈开，分为根冠1／3、根中1／3及根尖1／3，扫描电镜下评价其根管内壁牙本质碎屑和玷污层的形成情况。结果三种方法对根管清理能力差异无统计学意义（P〉0．05）而无论使用何种预备方法，其对根中1／3及根冠1／3处的清理能力优于根尖1／3部．两者差异有统计学意义（P〈0．05）。3种方法根管预备时间分别为：逐步后退法（12．8±1．26）min．逐步深入法（9．02±0．74）min，被动逐步后退法（超声与手用器械联合应用法）（12．21±1．90）min．三组差异无统计学意义（P〉0．05）。结论三种根管预备方法均不能达到完全的根管清理，尤其是对于根尖1／3部，清洁效果很不理想：总体上看，根中及根冠1／3清洁度显著优于根尖1／3。被动逐步后退法（超声与手用器械联合应用）及逐步后退法操作均较费时、费力，而逐步后退法根管预备时间略短于另两种方法且较省力。     

An In Vitro Study to Evaluate the Retention of Complete Crowns Prepared with Five Different Tapers and Luted with Two Different Cements

This study includes comparatively evaluating and drawing general conclusion about the best advisable taper and cement for maximal retention. Eighty extracted human maxillary premolar teeth with sound surfaces were selected using dial vernier caliper. Selected teeth were randomly divided into five different taper groups (0°, 3°, 6°, 9° and 12°). The crown preparations with different tapers respectively were achieved by graduated customized device. Preparations were verified with special set up. Crowns were cast with Co–Cr alloy; metal copings were luted with glass ionomer and zinc phosphate cement. Retention was measured (MPa) by separating the metal crowns from the teeth under tension on a universal testing machine, data was recorded and statistically analyzed. Glass ionomer cemented 0° and 12° taper group showed increase in retentive strength (p = 0.003 hs), when compared to zinc phosphate cement. 9° and 12° group showed decreased retentive strength (p = 0.001 vhs) when compared with 0° taper group. No significant difference found between 0° and 3° and 6° group. The choice of cement for crowns prepared within this ideal range (0°–6° taper) might be of limited clinical significance. 3° and 6° taper with zinc phosphate or glass ionomer cement shown to be ideal for maximum retention.     

Five-year study of Class II restorations in permanent teeth using amalgam, glass polyalkenoate (ionomer) cermet and resin-based composite materials

The aim of this study was to compare the clinical performance of an amalgam, a glass polyalkenoate (ionomer) cermet material and a resin-based composite material used in small Class II cavities in permanent teeth. All restorations were inserted under rubber dam. They were examined yearly for 3 years. One clinician continued the study up to 5 years. The clinical examination focused on two criteria: clinically acceptable and failure. In addition, impressions were taken of the prepared cavities immediately before restoration and at each clinical examination using an elastomeric material. The study comprised 274 Class II restorations (88 amalgams, 95 cermets and 91 resin composites) placed in 142 adolescent patients. One hundred and sixty-seven restorations were in molar and 107 in premolar teeth. Patient dropout after 5 years resulted in the loss of 161 restorations, evenly distributed for restorative material and type of tooth involved. Four amalgam restorations, 22 glass ionomer cermet and nine resin composite restorations failed. The glass ionomer cermet and amalgam restorations failed primarily due to bulk fractures, while the resin composite restorations failed due to secondary caries and bulk fractures.     

Comparison of curved canals preparations using profile, GT and Hero 642 rotary files

This study compared preparations of curved canals, using Profile, GT file and Hero 642 rotary files. A total of 30 mesiobuccal canals of extracted first and second mandibular molars were used in this study. The teeth were embedded in resin and a pre-operative radiograph was taken. The specimens were then randomly divided into three instrument groups. Pre- and post-instrumentation radiographic images were scanned and superimposed using the VISI CAD/CAM program. At nine horizontal sections at 1 mm increments from the apex, it calculated pre- and post-instrumentation cross sectional areas (mm(2)) and enlargements to the inner aspect and outer aspects (mm). A Kruskal-Wallis test found no statistical difference among the groups in terms of total areas removed by each instrument (P > 0.05). It also found no significant difference in any group between the total of the inner and outer enlargements (P > 0.05). However the GT file removed significantly more material from the outer side of the canal than the inside at sections 3-5, and the Hero removed significantly more material from the outer side at sections 7-9 (P < 0.05). All instruments produced preparations that maintained original canal curvatures.     

平衡力法预备弯曲根管的临床评价

目的：评价用平衡力法预备弯曲根管的临床疗效。方法：选取有弯曲根管的牙髓炎和根尖周炎患牙48个，试验组用弹性K锉(Flexofile)，使用平衡力法预备根管；对照组用K挫，逐步后退技术预备根管，两组均用侧向加压充填法充填根管，根据治疗前、中、后的x线片评价根管预备和充填的效果。结果：两组在根管预备中无器械折断。试验组无根尖阻塞、台阶形成等并发症发生，发生根管偏移少，能较好地维持根管的弯曲度和走向。对照组1例有台阶形成，发生根管偏移的明显多于试验组(P＜0．05)。结论：平衡力法预备弯曲根管可以节约成本，缩短操作时间，较好地维持根管的定向和弯曲度，减少根管偏移。安全有效，实用性强，可作为临床上预备弯曲根管的有效方法。     

两种方法预备磨牙弯曲根管的效果比较

目的比较镍钛机动器械Her0642冠向下法和手动K锉平衡力法预备磨牙弯曲根管的效果。方法选择100颗需作根管治疗的磨牙，随机分为两组，试验组使用镍钛机动器械Her0642，以冠向下法预备根管，对照组使用手动K锉，以平衡力法预备根管，两组均以侧向加压法完成充填。记录两组出现的台阶数及根管预备的时间，根据治疗后的X线片评价两组根管预备的效果。结果两组出现台阶数的差异无统计学意义。试验组预备根管的时间明显少于对照组（P〈0．05）。两组适充根管数的差异无统计学意义，但Hero642预备的根管锥度较大，成形效果好。结论镍钛机动器械Hero642使用简单，预备根管耗时短，可获得较好的成形效果。     

即刻桩腔预备对三种根管预备方法预备的直根管根尖封闭性的影响

目的 研究三种不同根管预备方法根管预备、根管充填后即刺桩腔预备对直根管根尖封闭性的影响.方法 离体直单根管上前牙124个,其中120个随机平均分为3组(n=40),A组:不锈钢根管锉常规法;B组:G 型钻根管冠部预处理 不锈钢根管锉常规法;C组:手用Pr01raper镍钛根管锉冠向下法,刺余4个随机平均分为阴性对照组和阳性对照组.所有根管均用侧方加压法充填,即刻手持垂直加压器去除部分充填材料,然后P型钻桩腔预备.用染料渗透法评价各组根尖封闭能力.结果 B组G型钻根管冠部预处理 不锈钢根管锉常规法预备的根管和C组手用ProTaper镍钛根管锉冠向下法预备的根管即刻桩腔预备后,其根尖微渗漏较A组常规法预备的轻(P<0.05).结论 大锥度根管预备,根管充填后即刻桩腔预备的根尖封闭性较好.