根管治疗牙冠方渗漏的研究现状

根管治疗是目前治疗牙髓病和根尖周病最有效和最根本的方法，评价其成败的关键因素是根管系统的三维严密充填，而根管充填后存在的微渗漏是导致充填失败的重要原因。根管微渗漏包括冠方渗漏和根尖渗漏，它们均可导致细菌及其产物通过冠方渗漏进入牙髓腔，又经根尖渗漏再次进入根尖周组织，引起治疗的失败。一直以来，根尖渗漏是研究的重点，而近年来，冠方渗漏也愈来愈引起广大学者的注意。本文从研究冠方渗漏的重要性、冠方渗漏的影响因素、冠方渗漏的体外实验及冠方渗漏与根尖渗漏的关系等几方面入手，对根管治疗牙冠方渗漏的研究状况作一综述。     

桩道制备后根管冠方渗漏的体外实验

目的 本实验拟用染色实验，比较根管内牙胶余留全长、3、5、7mm两周后的冠方渗漏，为探讨桩道制备后根管充填的封闭性能做一参考：方法取86颗单根离体牙，按照牙胶余留量及暂时充填材料的不同分为8组，常规根管充填并桩道预备后，用次甲基蓝进行由冠方向根方的渗漏，2周后测量渗漏深度，统计结果并加以分析。结果各组均有渗漏，其中以牙胶封闭且根管内牙胶余留3mm组的渗漏距离最大．以氧化锌水门汀封闭且未去除根管内牙胶组的渗漏距离最小。但是8组的渗漏深度差异无统计学意义（P=0．1033）。结论桩道制备会增加根管充填的冠方渗漏，而氧化锌水门汀的封闭性能较牙胶强，但在两周时间内渗漏对根尖部封闭性能影响不大．     

不同桩核修复系统在长期水储存条件下的根管微渗漏表现

目的：长时间水储存后桩核修复体冠外微渗漏情况。方法：选用72颗上颌单根管牙,随机分为6组,其中4组为实验组,2组为对照组。所有组别牙齿置人蒸馏水中储存半年后,用体视显微镜观察修复体冠方染料微渗漏情况。结果：采用纤维桩树脂核系统修复的牙体和传统铸造桩核修复后的牙体冠方微渗漏情况有明显差别,而采用DCBOND的实验组与另外两组树脂粘接剂问有明显差别。结论：DCBOND树脂粘接剂进行纤维桩核修复后在冠方微渗漏方面本实验显示了优越性。     

不同根管预备器械对根管充填后冠方微渗漏影响的实验研究

目的:比较不同根管预备器械对根管充填后冠方微渗漏的影响。方法:选择60个单根管前磨牙(弯曲度为10～20°)随机分为6组,分别以不锈钢K锉、VDW K锉、手动Protaper、机用Protaper、Hero642、Mtwo预备根管。采用冷侧压法进行根管充填,染色法比较不同根管预备器械对根管冠方封闭性能的影响。结果:不同根管预备器械对充填后根管冠方微渗漏影响不同,其中Hero 642预备组、Protaper预备组、VDWK锉组冠渗漏长度少于不锈钢K锉组,且差异有统计学意义(P<0.05),Hero 642预备组产生的冠方微渗漏最小。结论:不同根管预备器械预备根管后对冠渗漏影响不同,镍钛旋转器械预备根管后产生的冠方微渗漏较小,不锈钢K锉根管预备后产生的冠方微渗漏较大。     

桩核粘固后不同间隔时间预备对冠方微渗漏的影响

目的 比较铸造桩核粘结后不同间隔时间备牙对冠方微渗漏的影响。方法 66颗离体单根管下颌前磨牙,其中60颗随机分为6组,制作铸造桩核。2、4、6组分别于铸造桩 核用磷酸锌水门汀粘结2、10、30 min后备牙,1、3、5组桩核粘结后不备牙作为对照,其余6颗牙分别作为阴性及阳性对照。所有牙齿经1周染色后,作透明处理,评价冠方微渗漏的情况。结果 间隔时间相同的各备牙组与不备牙组的微渗漏差异有统计学意义（P<0.05）;不备牙组之间的微渗漏差异无统计学意义（P>0.05）;间隔2 min和10 min备牙组与间隔30 min备牙组的微渗漏差异亦有统计学意义（P<0.05）。结论 备牙时高速手机产生的震动会明显增加桩冠的冠方微渗漏,桩核粘结后备牙的间隔时间至少为10～30 min。     

关于根管系统严密封闭的研究现状

根管治疗术完成后根管系统冠根方的严密封闭可清除根管内绝大部分感染源，彻底切断感染途径，确保根管治疗术的远期疗效；而冠方和（或）根方封闭不良，病原微生物及其代谢产物可通过封闭材料与根管壁之间的微隙渗漏进入根尖周组织导致根管治疗术失败。本文就冠根方封闭效果与根管治疗术远期疗效的相关性，冠方与根方封闭的关系及其影响因素，根管封闭的研究方法等方面的研究现状作一综述。     

玷污层对Thermafil充填法和侧压充填法冠方渗漏的影响

目前认为,冠方渗漏是根管治疗失败的原因之一。渗漏大多发生在封闭剂与根管壁之间,并受玷污层的影响。另一影响渗漏的因素是封闭剂与牙组织结合的方式,化学结合较单纯的机械结合提供更为可靠的封闭作用。玻璃离子体与牙组织有化学结合。本研究的目的是测定以玻璃离子体作为封闭剂的侧压充填法和Themafil充填法在去除或保留玷污层时冠方渗漏情况。     

塑化根管根尖及冠方封闭性的研究

目的 评价塑化根管的根尖及冠方封闭性.方法 57个离体塑化根管置于37℃恒温水浴箱中4个月,分为根尖微渗漏组和冠方微渗漏组,分别封闭冠方和根尖孔.在2%亚甲蓝溶液中浸泡1周后,于距根尖1mm、4mm处横截,在立体显微镜下观察横截面蓝染情况.结果 ①根尖封闭性:距根尖1mm处无蓝染率为82.9%,距根尖4mm处无蓝染率为95.1%;②冠方封闭性:距根尖4mm处无蓝染率为87.5%,距根尖1mm处无蓝染率为93.8%.结论 离体亚甲蓝渗透试验显示塑化良好的根管,来自根尖和冠方的微渗漏均较小.     

根管细菌渗漏体外模型的建立

目的：建立检测微细菌培养模型，以用于评价根管充填封闭情况。方法：牙根的冠根两端各连接一细菌培养储室，冠方储室置1mL无菌培养基并接种0．1mL菌液，根方储室起始为无菌培养基。每隔3d将冠方储室中菌液吸出1mL，并注入1mL新鲜BHI培养基，共90d。当根尖储室中培养基发生浑浊即为细菌渗漏发生，记录细菌渗漏发生时的天数。选择18个直根管前牙，其中牙胶充填组6个，用冷牙胶侧方加压充填技术充填；空管组6个，根管只预备不充填；根管密封组6个，根管充填并严密封闭根管口和根尖孔。用设计的模型检测密封状况。结果：全部空管组6个样本在1d内根方储室中出现浑浊；根管密封组6个样本的根方储室在90d内均未发生浑浊。牙胶充填组有2个样本分别在44d和46d发生浑浊。结论：此模型方法简单易行且实用有效，具有一定的临床相关性和可行性。     

不同厚度材料封闭冠方根管的微渗漏对比研究

目的:对比研究根管口充填3mm或4mm厚度三种不同材料的冠方微渗漏。方法:选取140颗离体下颌前磨牙并在距离釉牙骨质界冠方2mm处截断牙冠。经根管清理、预备成型后随机分为6个实验组和1个对照组,每组20个样本。实验组的样本根管充填后根管冠方分别充填3mm或4mm厚玻璃离子体、Cavit暂封膏或氧化锌丁香油水门汀,对照组不作处理。用印度墨水对所有样本染色,透明处理后在体视显微镜下测量根管冠方染色长度,采用SPSS13.0软件进行统计分析。结果:不同材料及不同厚度的微渗漏间差异有统计学意义,P<0.05。不同材料的微渗漏由高到低排序为对照组>ZOE>Cavit>GI,组间两两比较差异有统计学意义,P<0.05。另外,4mm充填厚度微渗漏低于3mm充填厚度微渗漏,P<0.05。结论:玻璃离子体冠方封闭性能优于Cavit暂封膏,Cavit暂封膏封闭性能优于氧化锌丁香油水门汀。4mm厚度的充填材料比3 mm厚度的充填材料更有利于减少冠方微渗漏。     

Microleakage and enamel finish.

Cavity preparations that are finished with hand instruments allow significantly less marginal leakage than those which are completed only with rotary instruments. This does not mean that hand-instruments walls are perfectly smooth; it only means that these walls allow less marginal leakage. Cavity preparations restored with composite resin showed more marginal leakage than those restored with amalgam. Also, the degree of marginal leakage was greater in cavity preparations restored with composite resin than in those restored with amalgam. Cavity preparations are more prone to marginal leakage at sharply defined cavosurface acute angles than at the smooth or straight surfaces of the cavity. This pattern of marginal leakage was true for both amalgam restorations and composite restorations, but the degree of marginal leakage was greater when composite resin was used as a restorative material. Since less marginal leakage was found in the finished cavity preparations, it is obvious that all cavity preparations must be finished with hand instruments. This may not completely eliminate the problem of marginal leakage, but it will reduce the potential secondary caries both in degree and frequency. Also, since sharply defined acute angles did exhibit more marginal leakage, this part of the cavity preparation needs special attention. With amalgam and composite restorations at least, these angles should not be sharply defined but should be slightly round, so that better condensation of restorative materials can be obtained. This may reduce the degree of marginal leakage.     

Post-academic dental specialties. 15. Prevention of coronal leakage after placement of lining cement

One of the main origins of unsuccesful endodontic treatment is coronal leakage. In the prevention of coronal leakage a good sealing restoration seems mandatory. The effect of 2 types lining cement used as coronal barrier on filled root canals was studied over time. Fifty extracted human canines were prepared and filled by gutta-percha with a quantifiable initial coronal leakage. After placement of the lining cements in 2 groups of 20 canines, leakage was assessed at 96 hours and at 26 weeks and compared with the leakage in a control group of 10 canines. Placement of a coronal barrier of lining cement on the orifice of the root canal after endodontic treatment revealed a significant reduction of coronal leakage. In this study leakage decreased over time.     

A comparison of four in vitro marginal leakage tests applied to root surface restorations.

Marginal leakage associated with a variety of restorative materials, placed in root surface cavities of extracted teeth, was assessed by immersing the teeth in either acidified gelatin, eosin dye, silver nitrate or a solution of radiocalcium. The allocation of a score, dependent on the depth of tracer penetration at the interface, allowed comparisons to be made between the leakage tests employed. The rank order of the four leakage tests was generally consistent. Eosin resulted in the most severe leakage, followed by silver nitrate and radiocalcium, whilst acidified gelatin was the least sensitive method for demonstrating marginal leakage. Differences in leakage scores were not, however, always statistically significant. None of the four tests investigated was ideal, although eosin dye was considered to be the most appropriate method of demonstrating marginal leakage associated with root restorations.     

Studies of microleakage with restorative materials A new air pressure method

Abstract— A new method and apparatus are described for registering in vitro leakage of dental restorative materials. Methodological studies and studies of the error of the method were carried out. The method is based on the principle that the so-called space between the mould and the restorative material acts as a choke in a current of air. The air stream passed is an expression of the leakage due to available leakage area. The construction of the apparatus and its functions are illustrated in Figs. 1 to 4. The methodological studies showed that the method is suitable for comparative quantitation of leakage. The average area of leakage cannot be calculated. When leakage is registered, air flows into passages available for such leakage. The investigation of the error of the method showed that its precision is high.     

An in vitro investigation of the apical seal produced by a new thermoplasticized gutta-percha obturation technique

This investigation quantitatively analyzed apical leakage in teeth in which one of two new thermoplasticized gutta-percha obturating techniques were used. Apical leakage observed after use of the thermoplasticized techniques was compared to leakage found in teeth that had been obturated with conventional lateral condensation. Statistically significant differences (P less than 0.05) were found among the three groups. The lateral condensation group exhibited the least leakage, followed by the thermoplasticized group, and the thermoplasticized twist-off group exhibited the most apical leakage.     

In vivo study of temporary filling materials used in endodontics in anterior teeth.

The sealing efficacy of temporary endodontic filling materials was tested in vivo. The following materials were studied: Cavit, Caviton, gutta-percha, three types of zinc phosphate cement, and zinc oxide and eugenol. All the materials were tested in the access cavity of the same anterior tooth in ten different patients for a minimum of 1 week. Seepage was determined bacteriologically by culturing a cotton pellet which was sealed into the access cavity. On the basis of the quantity of microorganisms grown anaerobically, differentiation was made between no leakage, minor leakage, and gross leakage. Findings with Cavit and Caviton are essentially the same and show no or minor leakage in the vast majority of tests. Gutta-percha showed gross leakage in six out of eight tests. Phosphate cements showed no leakage in more than two thirds of the tests.     

The assessment of apical leakage of root-filled teeth by the electrochemical technique

Since its inception by Jacobson and von Fraunhofer¹ in 1976, several studies have used the electrochemical method to assess the leakage occurring around root canal fillings. This study has examined aspects of the electrochemical technique and the effects that this test method may have on leakage results. The findings have raised concerns about the application of the technique. It is evident that electrochemical leakage testing over 30 days can influence the electrochemical leakage reading at 30 days and may influence the linear dye penetration recorded at 30 days. It is suggested that testing for electrochemical leakage should not precede the assessment of linear dye penetration.     

Evaluation of the influence of smear layer on the apical and coronal sealing ability of two sealers

The aim of this in vitro study was to determine the effect of the smear layer on apical and coronal leakage in root canals obturated with AH26 or RoekoSeal sealers. A total of 160 maxillary anterior teeth extracted for periodontal reasons were used. The root canals were prepared to a size #7 with ProFile.06 taper Series 29 rotary instruments in a crown-down manner. Eight groups were created by all possible combinations of three factors: smear layer (present/absent), leakage assessment (apical/coronal), and sealer used (AH26/RoekoSeal). All teeth were obturated using lateral condensation technique of gutta-percha. A fluid filtration method was used to test apical or coronal leakage. According to the results of this study, the smear (+) groups displayed higher apical and coronal leakage than those smear (-) groups for both root canal sealers (p < 0.05). There was no statistically significant difference in either apical or coronal leakage between RoekoSeal and AH26, regardless of the presence or absence of the smear layer (p > 0.05). However, apical leakage was significantly higher than coronal leakage for both root canal sealers used in this study (p < 0.05). Under the conditions of this study, the results indicate that removal of the smear layer has a positive effect in reducing apical and coronal leakage for both AH26 and RoekoSeal root canal sealers.     

Marginal leakage with different composite restorative materials in vitro

In this preliminary study the degree of marginal leakage was assessed for different cavity designs using both ultra violet-curing and self-curing composite restorative materials and sealants. Butt joint restorations placed in etched and sealant primed cavities failed to prevent leakage. Both saucer-shaped and funnel-shaped cavities and cavities with rounded margins were able to prevent leakage when the restorations were bonded to etched and sealant primed peripheral enamel. Further, less than 1 mm of gingival enamel available for bonding seemed to be sufficient in most instances to prevent leakage.     

A standardized technique for linear dye leakage studies: immediate versus delayed immersion times

A dye leakage study was performed in vitro to compare the extent of leakage into root canals obturated with gutta-percha following immediate versus delayed immersion in Indian ink. Sixty extracted human teeth with single canals were instrumented and obturated with gutta-percha and sealer. Each group of 20 teeth was then immersed in the ink either immediately after obturation or after a delay of 1 or 7 days. After 7 days in Indian ink, the teeth were rendered transparent by clearing, and the linear extent of ink penetration was measured with a stereomicroscope. Complete leakage was observed in the two positive control teeth, and no leakage was evident in the two negative controls. Statistical analysis of the results indicated that there was no significant difference in leakage between the three experimental groups.