口腔内科学——龋病及牙体硬组织非龋性疾病

银汞粘接剂和银汞充填术后敏感症；下颌第一恒磨牙Ⅰ类洞型三维有限元模型的建立；瓷化树脂与银汞合金治疗恒磨牙龋损的临床比较；两种材料修复楔状缺损的黏接性能对比研究；上颌前磨牙桩道预备后剩余根管壁厚度和抗折强度的研究；……[编者按]     

上颌前磨牙根管治疗后MOD洞型不同修复方式对牙体抗力的影响

目的：使用不同方式修复上颌前磨牙牙体缺损后,比较牙体修复方式和材料对牙齿抗力的影响。方法：选择60颗单根上颌前磨牙,随机分为4组：A组,对照组;B组,复合树脂充填组;C组,复合树脂覆盖牙尖充填组;D组,聚合瓷嵌体覆盖牙尖修复组。完成所有的修复后,制备抗折强度检测试件。使用万能试验机进行压力试验,直到样本劈裂。每个样本劈裂时的压力及劈裂的类型,分别进行记录。结果：C组和D组的抗折强度明显高于B组（P〈0．05）,C组和D组抗折强度差别不明显。样本的劈裂形式四组存在差异,劈裂形式为Ⅱ型的比例D组低于C组。结论：覆盖牙尖的修复方式修复根管治疗后牙齿的大面积缺损（MOD洞型）,有利于提高牙齿的抗力;聚合瓷嵌体修复要优于复合树脂充填修复。     

2种桩系统修复前磨牙近中面洞型的抗力研究

目的 比较研究根管治疗后前磨牙近中面洞型经3种方法 修复后的抗力,并评价聚乙烯纤维桩系统(Ribbond桩)修复牙体缺损对修复体抗力的影响。方法 40颗完整离体单根前磨牙分成4组。第一组为对照组,另外三组根管治疗后预备近中面洞型。第二组使用复合树脂直接充填;第三、四组分别用石英纤维桩(DTLightpost)和Ribbond桩制作桩,复合树脂直接充填。热循环10000次后,置于INSTRON测试仪上测试断裂载荷,记录试件折裂时测试机读数及试件折裂模式。结果 对照组、复合树脂组、石英纤维桩组、聚乙烯纤维桩系统组的断裂载荷依次为:(1191.04±362.59)N,(578.81±117.87)N,(909.33±250.20)N,(831.56±220.16)N。实验组断裂载荷均显著低于对照组(P<0.05),石英纤维桩和聚乙烯纤维桩系统两组间无统计学差别(P=0.50),且均高于树脂直接充填组(P<0.05)。结论 使用石英纤维桩和Ribbond桩修复前磨牙近中面洞型均显著提高了抗折能力,且Ribbond桩能够显著改善折裂模式。?     

根管治疗后邻(牙合)面缺损前磨牙修复方式的生物力学研究

目的 从生物力学角度比较不同方法修复根管治疗后邻面缺损前磨牙的效果,并探讨最佳的修复方案。方法 收集完整离体前磨牙10对,每对牙分别接受不同的处理,试验组制备根管治疗及邻面缺损洞型模型,对照组为同名完整离体牙。研究金属烤瓷全冠修复和桩冠修复后的力学问题。采用横梁加载速度1.00 mm/min缓慢匀速加载于与牙体长轴成45 °颊尖舌斜面中点,测试破坏载荷,用SPSS10.0软件包进行配对分析。结果 金属烤瓷全冠修复时,患牙的抗折能力不能达到完整离体牙水平;桩冠修复后,患牙的抗折能力高于完整离体牙水平。结论 从生物力学角度而言,根管治疗后邻面缺损前磨牙的最佳修复方法是桩冠修复。     

离体前磨牙邻面颈部龋一种新洞型抗折裂性能的实验研究

目的对邻面颈部龋一种新洞型及传统洞型进行抗折裂负荷测试,并对新洞型与传统洞型的抗折裂性能进行比较。方法收集200颗完整的离体前磨牙,随机分成A、B、C、D 4组,A组为对照组,B组制备成牙合面洞,C组制备成邻颊(舌)面洞+牙合面洞(即新洞型,简称“双洞型”),D组制备成邻牙合面洞,模拟根管治疗后行银汞充填,用微机控制电子万能测试机对离体牙进行抗折裂负荷测试,测试各组实验牙折裂时的压力强度值。结果牙体折裂时的压力强度均值分别是:A组4 523.17 N,B组2 357.41 N,C组2 343.25 N,D组1 784.22 N。经统计学分析:C组抗折力明显高于D组,C组与B组抗折力接近,B、C、D抗折力明显低于A组。结论新设计的“双洞型”抗折力优于传统的邻牙合面洞型。     

前磨牙楔状缺损修复后的抗折裂强度研究

目的研究楔状缺损深及牙齿颊舌径的1/4或1/2的前磨牙采用不同材料充填后牙体的抗折裂强度及牙齿折裂模式。方法收集正畸拔除的新鲜前磨牙60颗,颊侧颈部设计颊舌径1/2和1/4楔状缺损,对1/2深度根管治疗后分别选择复合树脂、复合体或玻璃离子水门汀三种材料充填,运用万能材料试验机对前磨牙颊尖垂直向载力直至牙体断裂。记录牙断裂时的受力数值,并观察断裂模式。结果不同深度的楔状缺损其抗折裂强度不同,但各组间差异无统计学意义(P>0.05)。充填后前磨牙抗折裂强度显著增加(P<0.01),而不同充填材料对牙齿抗折裂强度无显著差异(P>0.05)。结论楔状缺损深及前磨牙颊舌径的1/4以上时容易导致前磨牙折裂。材料充填后可以提高前磨牙的抗折裂能力且与充填材料的种类无关。     

充填材料对牙齿抗折裂性能影响的实验研究

目的：比较不同材料充填的牙齿抗折裂强度,旨在获得一组新型的根管充填冠部修复技术,并探讨该技术与传统方法对牙齿抗折裂强度的影响,为其临床应用提供实验依据。方法：取224个近3个月内拔除的人后牙,随机分为7组。其中5组为实验组,制备邻Huo面洞型,开髓预备根管后分别以5种材料充填修复。2组为对照组：完整对照组,空白对照组。用电子力学测试机加压于牙齿Huo面,进行抗折裂强度测试。结果：采用亲型根管充填技术的牙抗折裂强度高于完整牙齿抗折裂强度（P＜0.05)。结论：用环氧树脂根管封闭剂加金属尖充填根管,玻璃离子水门汀垫底并粘着金属嵌体做冠部充填。可以有效地强化剩余的牙体结构,提高充填牙的抗折裂强度。     

银汞桩核抗折裂强度的体外研究

目的：比较不同深度的银汞桩核修复后牙体组织的抗折裂强度和折裂模式。方法：选取40个完整拔除的下颌单根管前磨牙，常规根管治疗后，按颊舌径的大小分为4组，每组10个。Ⅰ、Ⅱ、Ⅲ组制作不同深度的银汞桩核，Ⅳ组为对照组。试件的底座固定在电子式万能测试仪上加载，记录试件折裂时测试机上的读数以及试件折裂的模式。结果：Ⅰ、Ⅱ、Ⅲ组之间无显著性差异（P〉0．05），Ⅰ、Ⅱ、Ⅲ组与Ⅳ组之间有显著性差异（P〈0．01）。结论：银汞桩核抗折裂强度与深度无关，其强度能满足人日常咀嚼食物所需的[牙合]力。     

横向轴钉加固上颌第一前磨牙的实验研究

本文为证实横向轴钉结合ＥＢ复合树脂修复无髓上颌第一前磨牙的抗折强度，对四组２４颗离体牙进行抗折力测试。每组６颗牙，一组为正常对照组，三组均制成标准ＭＯＤ洞型的修复组。结果：正常组抗折力是１７３３．３３Ｎ（１７６．８７ｋｇｆ），ＥＢ复合树脂修复组是６０６．６７Ｎ（６１．８４ｋｇｆ），横向轴钉结合ＥＢ复合树脂修复组是（１１３０Ｎ（１１５．３ｌｋｇｆ），银汞修复组是５３５Ｎ（５４．５９ｋｇｆ）。统计学处理表明：横向轴钉结合复合树脂修复的抗折力明显高于其它二组，且有显著性差异（Ｐ＜０．０１）。     

后牙复合树脂充填的抗折裂性能

本实验选择上颌第一双尖牙，按要求制备成ＭＯＤ洞型，单独充填光敏复合树脂、分别衬垫玻璃离子粘固剂（ＧＩＣ）与光敏固化氢氧钙后，充填光敏复合树脂，充填ＧＫ高铜银汞合金和不充填窝洞，测试各组的牙体抗折裂性能并比较。结果发现，衬垫ＧＩＣ组的牙体抗折力最高，其次为单独充填光敏复合树脂组，未充填组牙体抗折力最低，差别均极显著（Ｐ〈０．０１）。提示我们，临床应用复合树脂充填能增强牙体的抗折裂性能，采用ＧＩＣ衬垫     

Effect of bonded restorations on the fracture resistance of root filled teeth

AIM: To evaluate the fracture resistance of root filled maxillary premolars restored with different techniques. METHODOLOGY: One hundred and twenty single-rooted maxillary premolar teeth were divided randomly into six groups of 20 teeth and subjected to the following procedures: group 1: intact teeth. Group 2: endodontic access cavities prepared. Group 3: MOD cavities were prepared, root canals were filled and no restoration was placed. Group 4: teeth were prepared as group 3 and restored conventionally with amalgam. Group 5: teeth were prepared as group 3 and restored with amalgam using a bonding material. Group 6: teeth were prepared as group 3 and restored with composite resin using the same bonding material. Teeth were embedded in acrylic resin and the loads for fracture strength were applied vertically with a constant speed of 1 mm min(-1). Data were evaluated statistically with anova and Tukey's tests. RESULTS: The mean force of fracture values were 1191.41, 599.86, 233.03, 494.72, 962.81 and 856.48 N for groups 1, 2, 3, 4, 5 and 6, respectively. The fracture resistance of group 5 was similar to group 1 (P > 0.05). The mean force at fracture of group 5 and group 6 was not significantly different. The fracture resistance of groups 5 and 6 was significantly higher than group 4 (P < 0.001). CONCLUSIONS: The group, restored with conventional amalgam, had the weakest resistance to fracture when compared with the bonded restorations. No statistically significant differences were found between the bonded amalgam and composite resin groups.     

离体前磨牙3种修复方法的抗力研究

［摘要］目的 探讨离体前磨牙根管充填后不同修复方法对牙体抗折性能的影响因素。 方法60颗离体下颌前磨牙随机分为4组,A组为空白对照组,B、C、D组分别按同一标准根管治疗后,牙冠统一制备成近中洞型（MO）备用,B组采用复合树脂修复,C组采用全瓷嵌体修复,D组采用高强度纤维复合树脂修复。四组样本通过负荷加载（加载头与牙齿长轴呈135°,横梁位移速度1 mm/min）,实验记录各样本折裂时的最大负荷值,并观察其折裂模式。 结果 A组折裂负荷值最高(1 413.91±95.93)N,D组其次 (1324.66±88.56)N,B组折裂负荷值最低(796.57±118.85)N, C组(961.05±101.45)N, A组与D组负荷值差异无统计学意义（P>0.05）,其余组间均有统计学差异（P＜0.05））;折裂模式D组与其它3组有统计学差异（P＜0.05）,其余组间均无统计学差别（P>0.05）。 结论 高强度纤维复合树脂修复,可以明显提高修复体的折裂负荷值,折裂模式也更有优势。     

In vitro fracture resistance of root-filled teeth using new-generation dentine bonding adhesives

AIM: To compare the fracture resistance of root-filled premolar teeth restored with new-generation dentine bonding adhesives. METHODOLOGY: Sixty extracted single-rooted human maxillary premolar teeth were used. Access cavities were prepared, and the roots were instrumented with K-files to an apical size 50 using a step-back technique. Root fillings were accomplished using gutta percha (Sure-Endo, Seoul, Korea) and AH Plus root canal sealer (Dentsply DeTrey, Konstanz, Germany) using the lateral condensation technique. The teeth were then randomly divided into six groups of 10 teeth each. A mesiodistocclusal (MOD) cavity was prepared in the teeth to the level of the canal orifices so that the thickness of the buccal wall of the teeth measured 2 mm at the occlusal surface and 3 mm at the cemento-enamel junction. Preparations were restored using the following adhesive systems: Etch & Prime 3.0 (Degussa AG, Hanau, Germany), Clearfil SE Bond (Kuraray, Osaka, Japan), Prompt L-Pop (ESPE, Seefeld, Germany), Panavia F (Kuraray, Osaka, Japan), Optibond Plus (Kerr, Orange, CA, USA) and Admira Bond (Voco, Cuxhaven, Germany); all preparations except those of the Panavia F and Admira Bond groups were further restored with resin composites. The Panavia F group was restored with amalgam and the Admira Bond group with Ormocer (Voco, Cuxhaven, Germany). The teeth were mounted in a Universal Testing Machine (Hounsfield, Surrey, UK), and the buccal walls were subjected to a slowly increasing compressive force until fracture occurred. The force of fracture of the walls of each tooth was recorded and the results in the various groups were compared. Statistical analysis of the data was accomplished using one-way anova. RESULTS: There was no significant difference in the fracture resistance of any of the test groups. CONCLUSIONS: In this laboratory study, the type of dentine bonding agents had no influence in the fracture resistance of teeth.     

In vivo fractures of endodontically treated posterior teeth restored with enamel-bonded resin

The cumulative survival rate of 190 endodontically treated posterior teeth were assessed in a retrospective study; all teeth had an MO/DO or an MOD cavity restored with a composite resin without cuspal overlays after previous acid-etching of the enamel. In contrast to our previous study on endontically treated posterior teeth restored with amalgam, the survival rate of the MOD resin-restored teeth was equal to that of MO/DO teeth. Teeth restored with a light-activated resin had a much lower survival rate than teeth restored with a chemically-activated material, the cause presumably being that the light-activated resins were insufficiently irradiated. Nearly 25% of the teeth had been restored with a microfilled resin for anterior use and these teeth had a lower survival rate than had teeth restored with a macrofilled or hybrid resin. It was also found that a beveling technique did not decrease the fracture rate while the use of an intermediate layer of low-viscosity resin resulted in a significant improvement.     

In vivo fractures of endodontically treated posterior teeth restored with enamel-bonded resin

Abstract The cumulative survival rate of 190 endodontically treated posterior teeth were assessed in a retrospective study; all teeth had an MO/DO or an MOD cavity restored with a composite resin without cuspal overlays after previous acid-etching of the enamel. In contrast to our previous study on endontically treated posterior teeth restored with amalgam, the survival rate of the MOD resin-restored teeth was equal to that of MO/DO teeth. Teeth restored with a light-activated resin had a much lower survival rate than teeth restored with a chemically-activated material, the cause presumably being that the light-activated resins were insufficiently irradiated. Nearly 25% of the teeth had been restored with a microfilled resin for anterior use and these teeth had a lower survival rate than had teeth restored with a macrofilled or hybrid resin. It was also found that a beveling technique did not decrease the fracture rate while the use of an intermediate layer of low-viscosity resin resulted in a significant improvement.     

Influence of different transitional restorations on the fracture resistance of premolar teeth

Controversy exists over the most favorable material and type of restoration to be used to transitionally restore teeth destined to be crowned. This in vitro study uses fracture resistance testing to compare eight different transitional restorations in maxillary premolars. Ninety sound maxillary premolars were randomly selected and allocated to nine groups, each comprising 10 teeth. One group remained unrestored and was used as the control. Teeth in the remaining groups were prepared to a standard cavity form using: a copy milling process removing the palatal cusp. Restorations were placed using amalgam with dentin pins and cavity varnish; amalgam with an amalgam bonding agent; resin composite with dentin pins and a dentin bonding agent; resin composite with a dentin bonding agent only; resin-modified glass ionomer with dentin pins; resin-modified glass ionomer cement alone and cermet with dentin pins and cermet alone. Each restored tooth was then subjected to axial loading via a bar contacting the buccal and restored palatal cusps until failure of the restored tooth occurred. The mean load-to-fracture values were statistically compared and the modes of failure recorded. It was found that the choice of restorative material and type of restoration had little effect on the fracture resistance of the restored tooth with the exception of those teeth restored with reinforced glass ionomer cement alone, which exhibited a significantly lower resistance to fracture than the other restored teeth. However, the choice of restorative material/technique did influence the mode of failure. Failure in teeth restored with resin-modified glass ionomer cement alone produced the least damage to the remaining tooth tissue when failure occurred. Consequently, this material may offer the most favorable range of properties for the transitional restoration of extensively broken-down maxillary premolar teeth destined to be crowned. Furthermore, the findings of this study fail to support the use of dentin pins in the placement of bonded build-up restorations.     

Long-term durability of root-end sealing with 4-MEtA/MMA-TBB resin

The purpose of this study was to compare root-end sealing using 4-META/MMA-TBB resin with that using conventional retrograde root filling technique, and thereby determine if 4-META/MMA-TBB resin offers long-term prevention against dye leakage from the root canal of human teeth. Thirty-five teeth had the apical 2.5 mm of the root resected. In the Sealing (SB) group, 4-META/MMA-TBB resin was applied to the resected surface. In the Filling (Am and EBA) groups, a root-end cavity was prepared and retrofilled with high copper amalgam alloy or reinforced zinc oxide-eugenol cement. Root canals were filled with methylene blue dye solution. Then, dye leakage outside the root canal was measured for 50 weeks. The integrated amount of leakage in SB group was significantly lower than those in Am group (p < 0.05) and EBA group (p < 0.05). Therefore, it can be concluded that root-end sealing using 4-META/MMA-TBB resin resulted in better, long-term sealing than conventional retrograde root filling.     

Fracture resistance of endodontically treated premolars restored with ormocer and packable composite

In this study, mesiodistocclusal (MOD) cavity preparations of endodontically treated maxillary premolars that were enlarged to size #50 were restored using three restorative materials (one ormocer, one packable composite, and one high-copper amalgam) and two application techniques (with or without coronal radicular technique). Copper rings were filled with self-curing polymethylmethacrylate resin and the teeth were placed into resin up to the level of the CEJ. The teeth were grouped according to the restorative material and technique, mounted in a Universal Testing Machine, and the buccal walls subjected to a slowly increasing compressive force until fracture occurred. The force of fracture of the walls of each tooth was recorded and the results in the various groups compared. The group restored with packable composite without radicular extension showed the highest resistance to fracture (p < 0.05). Both groups restored with amalgam were significantly weaker than all the other groups (p < 0.05).     

Failure characteristics of endodontically treated premolars restored with a post and direct restorative material

Ninety-one extracted maxillary premolar teeth were restored with a prefabricated post and amalgam, composite resin or glass-cermet core. Each group was again divided into three groups of 9-13 teeth to be subjected to an increasing load in one of three standardized directions (10, 45 and 90 degrees to the long axis of the tooth). Failure load and characteristics of failure were recorded. The glass-cermet-restored teeth had a lower strength than the other groups for every load direction (Student's t-test: P less than 0.01). Amalgam and composite resin groups showed a significant difference only for the 10 degrees loading condition (Student's t-test: P less than 0.02). Teeth restored with amalgam cores displayed a higher mean failure load, in combination with a 46% occurrence of root fracture.     

Resistance to fracture of endodontically treated premolars restored with glass ionomer cement or acid etch composite resin

MOD cavity preparations in 64 endodontically treated premolars were restored using four different methods. Copper rings were filled with commercial hard-setting cement and the teeth were placed into the cement up to the level of the cementoenamel junction. The teeth were grouped according to restorative method, mounted in an Instrom T.T. machine, and the buccal walls subjected to a slowly increasing compressive force until fracture occurred. The force of fracture of the walls of each tooth was recorded and the results in the various groups compared. All teeth fractured in a similar manner irrespective of the restorative method used. The resistance to fracture of the teeth was the same when they were restored with glass ionomer cement as a base over which an amalgam or composite resin was placed or with acid-etched resin. When the entire cavities were filled with glass ionomer cement the resistance to fracture of the teeth decreased significantly compared with the acid etch resin technique.