Clinical Applications And Evaluation Of Subgingival Posts

In the dental clinical practice, the treatment and restoration of defected teethare common cases. More and more doctors and patients pay attention to it.Keeping residual crowns and roots can not only avoid the pain of pulling out thetooth, but also keeping periodontal sensors and reducing the alveolar boneabsorption. Meanwhile, the residual crowns and roots which have done perfectroot canal therapy play an important role in restoring the morphology andfunction of the denture. It is often use post-core crown that restore residual rootsand crowns which are located above gingival; For those roots which are damagedunder the margin of their gingival, crown lengthening surgery or forcedorthodontic eruption may be used to restructure the biological width. Thenpost-core crown would be followed. Permanent restoration would be finishedafter a period of time because the two methods both need multidisciplinarycooperation. Within this period of this time, temporary restoration seems somedifficult. Some patients are reluctant to accept. If take fixed bridge orimplant-borne prosthesis after extraction the defected teeth, it needs patients withcertain economic basis meet the operation indication and3months of waiting forrestoration time. And the two methods will also make simple restore morecomplicated if the residual roots have enough length. The post-core crown restoration of residual roots is commonly used in theclinical. It is often used for residual roots which their margin above the gingival.It has some characteristics such as simple, convenient and shortcut. Our researchapply post-core crown technology to subgingival roots. Because the roots arebelow the gingival, it is difficult to impress and disinfect the root canal. So ourstudying designed preformed subgingival post. After routine root canalpreparation, the subgingival post can be immediately implanted into the rootcanal with resin core forming. It is at this time tooth preparation could be done.This method has both highlighted the advantages of the post-core crown andretained the residual roots delaying the alveolar bone absorption, expanded theindication, saved the patient’s time and the charges.The purpose of designing preformed subgingival post is trying to keepingthose unconventional indications of subgingival roots which can still be used. Thepreformed subgingival post mainly consists of3parts: the post part which isinserted in the prepared canal, the abutment part connecting with bone and softtissue and the core part which provides retention and support for the crown. Itmade for titanium. The design idea comes from implant-borne prosthesis. Thehypothesis is that healthy gingival and bone tissue could produce around thesubgingival posts, which could successfully restored the residual root withoutbeing pulled out.Our research groop have testified the preformed subgingival post canrestored the residual roots by finite element study. In priate practice,there shouldbe different specifications for preformed subgingival post because the residualroot with different position and defect. For simplifying the design and theproduction process of the preformed subgingival post, the test aims to explore theanterior residual roots restored with the preformed subgingival post. Our research designed9specification of subgingival posts on the basis of TheChinese Tooth Measurement and Statistical Data Table (Wang Huiyun).According to the condition of the roots, doctors would choose differentspecifications. When the subgingival posts are bonded in the right place, theywould be meet different situation by the performer appropriate grind.Our research is to observe the following index:1. Gingiva margin index.Detection gingival index, the quantity of gingival crevicular fluid and themarginal adaptation of the crown after1month,6months and12months.2.Measuring X rays index. Measure the distance of the apex of root to the lowest ofthe osalveolare, the length and the width of the adjacent teeth before prosthesisand after prosthesis6months and12months.3. Satisfaction survey. Patients fillin visual analogue scale to evaluate the prosthesis from the point of themselves.The results of this research showed as following:1. In periapical films with paralleling technique, the static consistencycheck both the length of the adjacent teeth T2and width of it T3were over0.75(r＞0.4).It showed that the results of imaging study were credible.2. The gingival index and the quantity of gingival crevicular fluid seemed aslight increase after prosthesis1month,6months and12months,but there was nostatistical difference.(P>0.05)3. The marginal adaptation of the crown was evaluated according toModified U.S. Public Health Service criteria.18cases were up to A standard afterprosthesis1month,16cases were up to A standard and2cases were up to B afterprosthesis6months. When12months,14cases were up to A standard and1casereach B(2cases failed,1caselost)4.The result of visual analogue scale showed, the following aspects such asretention, chew, aesthetic measure, comfortable and language function are all statistically significant（P<0.05）.5. The distance of the apex of residual root to the lowest of the osalveolarehad no notable variation in different time.（P<0.05）6. The2cases were both mandibular first premolars with single crown.Investigate the reason, basically had the following sides: mandibular firstpremolars which standing dental arch would suffer more torsion in the process ofchewing, the2cases would undergo more occlusal force because of single crown,mandibular premolars are not fit for preformed subgingival post because theirsection usually are dumb-bell shape, some mandibular premolars have two rootcanals. So in the future, we should more strictly select indications.Concludion:1. Using the preformed subgingival post can greatly simplified clinicaloperation difficulty. The design of the abutment parts make the preformedsubgingival pos more flexible restoring the anterior teeth.2. After a year of observation,the anterior roots defected3mm belowgingiva could be restored with the preformed subgingival post. Patients weremore satisfied with it. The preformed subgingival post provided a new methodrestoring residual roots below gingiva.3. For premolar or molar residual roots, the abutment part of the preformedsubgingival post can not fit for the root section, and the post part which in thecanal can not fit for two or three root canals. So the preformed subgingival postcan not restored with premolar and molar teeth. We need continuousimprovement.