Endodontic microsurgery(EMS)can handle challenging endodontic cases effectively.However,the com-plexity and postoperative outcome of EMS are closely related to multiple factors such as the patient's general condition,the affected tooth,and the surrounding anatomical structures.This article draws on international and domestic medical standards,including the American Society of Anesthesiologists,the American Association of Endodontists,the World Health Organization,and the expert consensus on the assessment of root canal treatment difficulty in China.Based on the basic principles,procedures,and anatomical data of EMS,combined with long-term clinical experience,clinical epidemio-logy,and evidence-based medicine,this article analyzes the difficult and complex factors of EMS cases.This work aims to provide references for treatment decisions,doctor-patient communication,application and promotion,clinical tea-ching,and hierarchical referral in EMS.

OBJECTIVES:To investigate the outcome of endodontic microsurgery and analyze the potential prognostic factors, and to evaluate the value of surgical classification by Kim and Kratchman. METHODS:Collecting clinical examination and radiographical examination of endodontic microsurgery cases (which were followed up at least 1 year), which were classified according to Kim and Kratchman, and we analyzed the outcome of endodontic microsurgery and its potential prognostic factors. RESULTS:302 patients (400 teeth) who received endodontic microsurgery were included. The one year success rate of endodontic microsurgery was 94.25%. Different classification had significant influences on the outcome of endodontic microsurgery (P<0.05), and the success rate of class B and C were better than those of class D, E, and F. The position of teeth had significant influences on the outcome of endodontic microsurgery (P<0.05). The success rate of maxillary teeth was higher than that of mandibular teeth. The success rate of anterior teeth was higher than that of posterior teeth (P<0.05). The quality of root end filling and first or second surgery had no effect on the outcome (P>0.05). CONCLUSIONS:Endodontic microsurgery is an effective treatment method for saving affected teeth, and it can get a good result. Tooth position and classification are the potential prognostic factors. The surgical classification of Kim and Kratchman can help to predict the outcome of endodontic microsurgery.

AIM:To observe the curative effects of intentional replantation in the treament of maxillary antenor teeth with radicular grooves.METHODS:9 patients with radicular grooves on maxillary anterior teeth were treated by conventional root canal treatment and then intentional replantation.Follow-up examination was conducted 1 week,1 month and 3 years after treatment respectively.RESULTS:At 1-week recall after intentional replantation,7 of 9 teeth still had sinus tract,gingival tumefaction,purulent discharge and bled on probing from the teeth,the pocket depth were 4 ～ 6 mm,with teeth percussion(+-) and mobility of degree Ⅰ °;sinus tract closed in 2 cases.Radiographic examination revealed an extensive periradicular radiolucency involving the periapical and periodontal membrane.At 1-month recall,the sinus tract almost closed in 9 cases;the gingival were normal,the pocket depth were 2 ～3 mm,teech percussion(-),with no mebility.Radiographic examination revealed a dramatic decline of periradicular radiolucency of the periapical and periodontal membrane.At the evaluation appointment 3 years after treatment the gingival were normal without swelling,.purulent discharge,bleeding and gingival atrophy;the adjacent labial alveolar mucosa was health,the pocket depth was ＜2 mm,teech percussion(-),with no loose degree of the 9 teeth.The patients were asymptomatic with occlusion.Radiographic examination showed complete periapical and periodontal membrane healing.CONCLUSION:Intentional replantation is effective for the treatment of radicular grooves.

目的 探讨不同位置机用镍钛器械分离(IS)对根管治疗预后的影响.方法 回顾性分析滞留根管内的机用镍钛锉Protaper分离123例资料,内容包括拍X线牙片、询问病人主观感觉、进行体格检查,记录根管弯曲度和IS的型号、位置及根尖指数.结果 123例Protaper IS发生于弯曲根管(＞50°)为93.5％,且主要位于磨牙根管中为65.2％;IS型号发生率最高是F1,位于根管弯曲后端最高为67.5％;123例患者IS预后中,成功63例(51.2％),位于弯曲前端、弯曲部及弯曲后端的成功率依次增高,差异有统计学意义(P＜0.05);术前活髓牙较死髓牙预后成功率高(P＜0.05).结论 不同位置机用镍钛分离器械对根管治疗预后有一定影响,但是否取出分离器械需综合评估IS的位置、根管弯曲度及牙髓状态等因素.

目的 探讨应用现代根管治疗技术诊治C形根管系统的疗效.方法 通过X线片、锥形束CT(CBCT)、牙科显微镜,对106例具有C形根管系统的患牙进行形态学分类;采用机用镍钛器械K3进行根管预备,次氯酸钠超声冲洗,热牙胶连续波加压技术充填根管.结果 106例C形根管系统形态类型发生率为C1形32例(30.1％),C2形18例(16.7％),C3形54例(51.3％),其他2例(1.9％);73.6％的C形根管患牙X线片表现为锥形融合牙根,26.4％表现为近、远中独立牙根;预备充填成功率为97.2％,效果好.结论 现代根管诊疗技术是准确诊断C形根管系统类型及高质量根管预备充填的有效方法.

磨牙、咀嚼硬物、外伤均可能导致牙根隐裂［1］，其临床表现多与牙周炎或牙髓治疗失败相似，因此常易误诊为牙周炎或牙髓治疗失败，有些隐裂患牙往往在拔除后或手术翻瓣直视下才能明确诊断［2］。四川大学华西口腔医学院牙体牙髓科接诊了1例陈旧前牙外伤病例，经传统根尖手术仍不能消除窦道，再次行显微根尖手术后发现此病例既有根尖病损，又伴有牙根隐裂造成的病损，遂行显微手术治疗，现报道分析如下。

Root defects primarily include root caries, fractures, cracks, external resorption, and perforation. In periradicular microsurgery, root defects are not rare; whether the defect can be completely repaired or not is crucial for the prognosis of the tooth. Several types of root defects, diagnosis, surgical repair procedures, and follow-up methods are summarized.

磨牙、咀嚼硬物、外伤均可能导致牙根隐裂［1］，其临床表现多与牙周炎或牙髓治疗失败相似，因此常易误诊为牙周炎或牙髓治疗失败，有些隐裂患牙往往在拔除后或手术翻瓣直视下才能明确诊断［2］。四川大学华西口腔医学院牙体牙髓科接诊了1例陈旧前牙外伤病例，经传统根尖手术仍不能消除窦道，再次行显微根尖手术后发现此病例既有根尖病损，又伴有牙根隐裂造成的病损，遂行显微手术治疗，现报道分析如下。

Purpose: To investigate the level and distribution of stresses in composite-restored mandibular first molars with various combinations of base materials. Methods: The finite element package Abaqus was used for the stress analysis. Several different base materials were evaluated [light-cured glass ionomer (LC-GI), chemically-cured calcium hydroxide (CC-CH), and light-cured calcium hydroxide (LC-CH)] in combination with light-cured composite (LC-CP). Four models of restored molars with Class I deep cavity preparations were simulated, including (1) LC-GI/LC-CP, (2) CC-CH/LC-CP, (3) CC-CH/LC-GI/LC-CP, and (4) LC-CH/LC-GI/LC-CP. A 250N static single-point load was applied vertically on the central fossa of the tooth to simulate physical loading conditions. Results: In each case, the peak stresses were found to be concentrated mainly at the interfaces between the various materials and the dental tissues. In the residual tooth structures, the maximum Von Mises stresses were 20.01 MPa in model LC-GI/LC-CP, 23.85 MPa in model CC-CH/LC-CP, 23 MPa in model CC-CH/LC-GULC-CP and 21.83 MPa in model LC-CH/LC-GULC-CP. In the LC-CP restorations, the maximum Von Mises stresses were 43.68 MPa in model LC-GI/LC-CP, 42.24 MPa in model CC-CH/LC-CP, 42.29 MPa in model CC-CH/LC-GI/LC-CP and 42.55 MPa in model LC-CH/LC-GULC-CP. In the bases, the maximum Von Mises stresses were 5.71 MPa in model LC-GI/LC-CP, 0.85 MPa in model CC-CH/LC-CP, 4.69 MPa in model CC-CH/LC-GI/LC-CP, and 4.93 MPa in model LC-CH/LC-GI/LC-CP. (Am J Dent 2011;24:3-7).

Objective To determine the expression level of each gtf under various conditions and its relationship with the ability to produce extracellular polysacchradides(EPS) in different strains of S.mutans. Methods Twenty strains of S.mutans of clinical isolations with different EPS producibility and UA159 were selected,and their ability to produce EPS under 1% sucrose and 2% sucrose were tested.Then in two strains,the relative quantity of gtfA,B,C,D's mRNA were examined by real-time PCR methods. Results In all strains,the quantity of EPS was prominently enhanced by sucrose.The expression levels of gtfA,B,C,D were increased in 1% sucrose in both strains.In 2% sucrose,the expression levels of gtfB,C,D were decreased and gtfA was increased in the strain which produced less EPS.gtfB,D were decreased and gtfA,C were increased in the strain which produced more EPS. Conclusion The expression level of gtfs from S.mutants and its ability to produce extracellular polysaccharides were influenced by sucrose concentration.

It was the aim of the study to analyze stress distribution in tooth and restoration by occlusal load of Class I. Comparative analysis was used to evaluate effects of four kinds of cement bases on the stresses in resin composite restorations. The elastic moduli and Poisson's ratios of the three kinds of restorative materials were tested. Micro‐CT was used to scan the first mandibular molar, and the three‐dimensional finite element model of the tooth with class I cavity was built by ABAQUS. Occlusive load of 250N was applied on the model. Then von Mises stresses distribution in the enamel, dentin, resin composite and bases were analyzed by occlusive loading of different cement bases. As single‐layer base, the maximum von Mises stresses of the enamel and the dentin of the Dycal base were much lower than those of the VIT base. As double‐layer base, the maximum von Mises stresses of the enamel and the dentin of VIT and Dycal were much higher than those of VIT and Ultra‐blend plus. Cement bases should have a high elastic modulus in order to reduce the stress of the enamel and the dentin. The present study would help clinicians to make an informed choice of the cement bases to avoid the fracture of tooth or restoration. Copyright © 2010 John Wiley & Sons, Ltd.

Objective:To detect the influence of concentrations of sucrose on expression of wapA,the adherence as-sociated gene of S.mutans.Method:Total RNA was extracted from S.mutans after being cultured in 0.5%,1.0%,5.0% su-crose and then reversely transcripted to cDNA.By utilizing TaqMan RT-RCR technique,we checked wapA expression.Re-sult:In different concentrations of sucrose,wapA expression didn't changed significantly;In 0.5% and5.0% sucrose,wapA expression of more-adherent S.mutans strains was significantly higher than that of less-adherent strains.Conclusion:The supply of sucrose plays little effect on wapA expression;There might be some correlation between different expression of wa-pA gene and S.mutans sucrose-dependent adherence.

OBJECTIVETo establish a new evaluation system of curved root canal deviation by the technique of micro-CT.METHODSCurved simulated root canals were prepared with ProTaper NiTi-hand files by crown-down technique. After root canals were scanned by micro-CT and analyzed by image processing software, the planar area and centers' transportation of each cross-section were compared to evaluate the prepare effect of ProTaper, and a three-dimensional model about it were established.RESULTSThe same cross-section's area of the root canals which was prepared with ProTaper NiTi-hand files were essentially consistent. With the data analysis of micro-CT, a system of combining planar and three-dimensional index to evaluate the root canal deviation were established. The shapes of root canal before and after prepared with ProTaper showed less deviation, which proved the shaping ability of ProTaper could meet the requirements for clinical use.CONCLUSIONA three-dimensional root canal central axis model is established using micro-CT. It provides a new method to analyze the shaping ability of the instrumentation after root canal preparation. It will give us a more direct view to analyze the situation of the root canal deviation combining the two-dimensional image and the three-dimensional model.

Objective:To detect the differently-expressed genes of S.mutans cultured in 0.5% and 1% sucrose by microarray technique.Methods:Gene chips were constructed and the gene expressions of S.mutans under different conditions were detected.Results:In 0.5% sucrose environment,compared with 1.0% sucrose environment,expressions of about 40 S.mutans genes were changed.23 genes associated with virulence,pathogenesis,bacterial component metabolism,and so on,were down-regulated.While 17 genes related to sugar transport and energy metabolism were up-regulated.Conclusion:Regulation of S.mutans by environment factors is very complex and is a result of cooperations of multifactors and multigenes.Microarray technique is efficient to detect differently expressed genes in S.mutans.

Polymerization shrinkage is the primary negative characteristic of light-cured composite resins which used for cavity filling. The stress caused by shrinkage may have adverse clinical consequence such as postoperative sensitivity, micro-leakage, secondary caries. This review is meant to introduce the research progresses on the factors responsible for polymerization shrinkage stress and the methods of decreasing the stress in clinics.

Objective To examine the influence of concentrations of glucose on expression of spaP,the main initial adherence associated gene of S.mutans.Methods Total RNA was extracted from S.mutans after being cultured in 0.2%,1.0%,5.0% glucose and reversely transcripted to cDNA.By utilizing TaqMan real-time RCR technique,spaP expression was evaluated.Results The expression of spaP was significantly upregulated by glucose in a dose-dependent manner in more-adherent S.mutans strains.Conclusion The upregulation of spaP expression by glucose may be one of the mechanisms underlying the increased initial adherence.

OBJECTIVE To determine the expression level of each gtf under different pH cultural conditions and to find the relationship between gtf expression levels with environmental pH in different strains of Streptococcus mutans (S.mutans). METHODS S. mutans form clinical isolation with different extracellular polysaccharides (EPS) producibility and UA159 were selected. Their ability to produce EPS under pH5.5 and pH7 were tested. Then in two strains, the relative quantity of gtfA, gtfB, gtfC, gtfD's mRNA which were related to S. mutan's ability to produce EPC, were examined by real-time reverse transcription-polymerase chain reaction (real-time RT-PCR) methods under different pH culture condition. RESULTS At pH5.5, expression levels of gtfA, gtfB, gtfD were increased while that of gtfC were decreased in both strains, and that of gtfB, gtfC were higher in strain which produces more ECP. CONCLUSION The expression levels of gtfs related closely to the cariogenicity of S. mutan.

Objective:To detect the influence of acidic environment on expression of spaP,the main initial adherence associated gene of S. mutans. Methods:Total RNA was extracted from S. mutans after being cultured in the medium at initial pH of 5.5 or 7.0 and then reversely transcripted to cDNA. By utilizing TaqMan RT-RCR technique,spaP expression was checked.Results:In acidic environment,spaP expression of S. mutans was decreased significantly. No matter the initial pH of medium was acidic or neutral,spaP expression of more-adherent S. mutans strains was generally higher than that of less-adherent strains. Conclusion:The inhibition of spaP expression may be one of the mechanisms underlying the decreased initial adherence of S. mutans in acidic environment; There might be some correlation between the expression of spaP gene and S. mutans initial adherence.

OBJECTIVE:To analyze the possible damage to the remaining tooth and composite restorations when various mixing ratios of bases were used.METHODS:Testing elastic modulus and poission's ratio of glass-ionomer Vitrebond and self-cured calcium hydroxide Dycal with mixing ratios of 1:1, 3:4, 4:3. Micro-CT was used to scan the first mandibular molar, and the three-dimensional finite element model of the first permanent mandibular molar with class I cavity was established. Analyzing the stress of tooth structure, composite and base cement under physical load when different mixing ratios of base cement were used.RESULTS:The elastic modulus of base cement in various mixing ratios was different, which had the statistic significance. The magnitude and location of stress in restored tooth made no differences when the mixing ratios of Vitrebond and Dycal were changed. The peak stress and spreading area in the model with Dycal was more than that with Vitrebond.CONCLUSION:Changing the best mixing ratio of base cement can partially influence the mechanistic character, but make no differences on the magnitude and location of stress in restored tooth. During the treatment of deep caries, the base cement of the elastic modulus which is proximal to the dentin and restoration should be chosen to avoid the fracture of tooth or restoration.

OBJECTIVETo study the influence of hand-mixed methods on the compressive strength of the zinc phosphate dental cement.METHODSThree skilled nurses used three kinds of common clinical hand-mixed methods (included the unidirectional rotation method, the alternate pro and con bidirectional rotation method and the pulling and pushing with folding method) to mix the zinc phosphate dental cement on the same condition (i.e. same indoor temperature and humidity, the same mixing ratio, mixing time, mixing frequency and the same mixing instruments and so on). The mixed zinc phosphate cement was packed into the plastic cylinders with 10 mm-high and 5 mm-bore. After the mixed zinc phosphate cement coagulated, compressive strength was tested separately.RESULTSThe compressive strength of the zinc phosphate dental cement mixed with the alternate pro and con bidirectional rotation method was the best, and the value was (106.11+/- 4.82) MPa. The compressive strength of the zinc phosphate dental cement mixed with the pulling and pushing with folding method was lower, and the value was (77.57 +/- 6.26) MPa. The compressive strength of the zinc phosphate dental cement mixed with the unidirectional rotation method was the lowest, and the value was (54.41 +/- 5.08) MPa. The compressive strength of the zinc phosphate dental cement mixed with the unidirectional rotation method and the pulling and pushing with folding method could not achieve the clinical required compressive strength (about 100 MPa), while the compressive strength mixed with the alternate pro and con bidirectional rotation method was above 100 MPa.CONCLUSIONThe alternate pro and con bidirectional rotation method to mix the zinc phosphate dental cement is recommended in clinic.