Analysis Of Clinical Outcomes Of Endodontic Microsurgery And Surgical Preservation Treatment Of Vertical Root Fracture

With the progress and development of technology and materials of root canal therapy,many studies have shown that the success rate of root canal is above 90% 5 years after therapy[1-4],but there are still many causes leading to treatment failure.Re-treatment is mainly used for treatment failure caused by infection inside root canal.However,in regard to persistent infection outside root canal,true cysts or foreign body reaction,a root apical surgery is demanded.Comparing to traditional apical surgery with low success rate due to limitations of surgical equipment,technology and materials,endodontic microsurgery,which helps clarify the causes for failure of previous endodontic treatment owing to highly improved surgical vision based on magnification and lighting of surgical microscope,has evidently higher success rate.Moreover,the trauma is reduced thanks to ultrasonic preparation system and micro-surgical instruments.A majority of studies have indicated a very wide range(83.8%-95.2)of success rate of endodontic microsurgery more than one year after treatment[5-8].But there are differences of root-end filling materials,evaluation criteria and observation periods between those studies.Vertical root fracture is one of the main factors leading to extraction of endodontically treated teeth,the treatment in regard to which should be adapted respectively as early diagnosis is difficult due to complicated causes and clinical and imaging features are diversified according to different teeth and severity of fracturing.In order to analyze the prognosis of endodontic microsurgery and explore the preservation treatment of vertical root fracture,this study is divided into three parts: in the first part,we explore and analyze the causes of failure of previous endodontic treatment during endodontic microsurgery.The second part is about evaluation and analysis of the clinical outcomes of apical microsurgery between short-term(1 year)and long-term(4 years)follow-up periods.The third part includes two experiments,in the experiment 3,we discusse the characteristics of vertical root fracture,and in the experiment 4,we explore the root of the surgical preservation of teeth and postoperative efficacy observation.Experiment 1: analysis of causes of endodontic treatment failure in 388 cases of endodontic microsurgeryThis study aims to explore and analyze the causes of endodontic treatment failure in endodontic microsurgery.The cases put into analysis were those having received endodontic microsurgery operated by the same doctor in the Department of Operative Dentistry&Endodontics,School of Stomatology,The Fouth Medical University between July 2010 and July 2013.All the patients have received endodontic microsurgery,which meaned that expecting incision and suturing,all the left surgical procedures were performed using micro instruments and ultrasonic retrotips under the microscope,including osteotomy,apicoectomy,retro-preparation and retro-filling of root cana1.During the surgical procedure,the surface of the apical root was resected following by methylene blue staining and was examined and recorded carefully with 16×~25× magnification by microscope in order to analyze causes of failure of the previous endodontic treatment.310 cases(388 teeth)were included in the study from July 2010 to July 2013.There were 15 causes of failure as follows: periapical cysts(19.8%),leaky canal/ underfilling(19.8%),vertical root fracture(14.4%),overfilling(9.0%),file separation(5.4%),lateral root perforation(4.6%),missing canal(3.4%),root canal calculus(3.1%),anatomical complexity(2.8%),perforation(2.6%),root fracture(2.6%),apical fenestration(2.1%),traditional apical surgical treatment failed(2.1%),microfracture crazing(1.8%)and unknown(1.8%).The frequency of possible failure causes differed according to the tooth position(P <.001).Microscopic exploration of causes of endodontic treatment failure during microsurgical surgery is significant for a successful surgery.Many types of endodontic treatment failure are inappropriate or cannot be re-treated in a non-surgical way due to their complex causes,and endodontic microsurgery is an effective method.Experiment 2:Comparison of clinical outcomes of endodontic microsurgery:1-year versus 4-year follow-upThe purpose of this study was to evaluate and analyze the clinical outcomes of endodontic microsurgery between short-term and long-term follow-up periods.Data were collected who had received endodontic microsurgery in our department,from July 2010 to December 2012.All teeth with the data of completed 4-year follow-up were selected.Clinical and radiographic evaluations were performed respectively 1 year and 4 years after surgery according to Rud's criteria.Cases were divided into 4 groups,including success–success group,failure–failure group,success–failure group and failure–success group.The different success rates of cases with 1-year follow-up and cases with 4-year follow-up were put into comparison in order to analyze the causes of change and factors of long-term prognosis between success–failure and failure–success groups.A total of 124 patients(162 teeth)were examined.The success rates of 1-year and 4-year follow-up were 88.3%(143/162)and 87.0%(141/162)respectively.There was no significant difference between the follow-up periods(P>0.05).6 teeth were classified as success–failure group,causes of the change because of periodontitis,vertical root fractures,secondary caries and traumatic dental injuries.4 teeth were classified as failure–success group and cause was intervention treatment after diagnosis.There was no significant difference in the clinical outcome after endodontic microsurgery between short-term and long-term follow-up periods.1-year outcomes could basically predict the long-term situation.The study suggested that both short-term and long-term clinical outcomes can be improved by strict surgical indications,standardized operations,avoidance of non-surgery factors like secondary caries and dental trauma as well as re-operation of failure cases.Experiment 3:Using Micro CT to study the radiographic characteristics of vertical root fracturesThe objective of the present study was to analyze the radiographic characteristics of VRFs in extracted,endodontically treated teeth,by Micro CT.All cases included in this study were collected by the same doctor.Doctor carry out flap exploration to confirm the existence of vertical root fractures under the surgical microscope.Choosing the teeth and roots whereby the fractured segments are incompletely separated.The teeth and roots were examined by Micro CT(Y.XLON Y.Sheethe,Germany),the 3D resolution was set to 10 ?m,and the Vgstudio Max 2.2 software was used for 3D reconstruction.From the vertical extent of fracture,horizontal extent of fracture,course of fracture in the axial plane and association of fracture and isthmus four aspects of research.A total of 8 VRFs in 7 teeth were selected.7 roots of the VRFs extended from the apex to the cervical region.As far as the horizontal plane,6 roots of VRFs traversed the root completely from buccal to oral,buccal-central and central groups both have only 1 root.Course of fracture in the axial plane is more uniform,straight line accounted for 3 roots,oblique line and Z-shaped accounted for 2 roots,curve accounted for 1 root.An isthmus was present and the VRFs were associated with an isthmus in 5 evaluated roots,but the VRFs bypassed the isthmus in 1 root,2 roots have no isthmus present.Micro CT scan can accurately and without injury to show the morphological characteristics of VRFs in endodontically treated teeth,the morphology of VRF is complex,showing a variety of cracks,the width of the variable.The morphological characteristics of VRF and its regularity require more samples for further study.Experiment 4:Surgical preservation treatment of vertical root fractures and clinical outcomes of surgeriesThe objective of this study was to discusses different preservation treatments and clinical outcomes of surgeries.All cases were collected from our department between September 2009 to September 2014,the teeth were performed endodontic microsurgery or flap elevation,and diagnosed vertical root fracture.The tooth underwent endodontic microsurgery to visualize presence or not and the extent of fracture line.According to the morphological characteristics and the extent of fracture line,using different preservation treatments,treatment methods of complete vertical root fractures include extraction,amputation,hemisection and incomplete vertical root fractures uses endodontic microsurgery.According to outcomes of the clinical and radiographic examination,to analysis 1-year clinical outcomes of each treatment.A total of 99 teeth were included in the study.Among them,49 teeth were extracted,38 were treated by amputation,3 were treated by hemisection,and 22 were treated by endodontic microsurgery.Among 22 teeth were treated by endodontic microsurgery,,11 cases were returned during the 6 to 45 months,10 teeth were healed by endodontic microsurgery,1 was failed.Flap elevation could be used to diagnose vertical root fracture in endodontic microsurgery.In order to maximize the preservation of teeth,different forms of fracture line required different treatments.But the long-term prognosis of endodontic microsurgery need to be further observed.