Research progress on conservative endodontic access cavities and its stress analysis of teeth / 口腔疾病防治

@#Conservative endodontic access cavity (CEC) is the first step of minimally invasive endodontics. After that operation, teeth retain the dental hard tissue, such as crest and peri-cervical dentin, to a large extent. It is of great significance to reduce the tissue excision and achieve a favorable prognosis. There are a variety of approaches and corresponding cavities in CEC. The methods to determine the medullary approach include X-ray localization, micro CT/cone beam CT localization and digital guide plate localization. Among them, X-ray film and micro CT/cone beam CT are simple and commonly used in the clinic. For more complex root canal systems, the use of a digital guide plate can establish a more accurate pulp opening pathway and reduce the unnecessary loss of tooth hard tissue. However, the positioning price of a digital guide plate is high, and it has not been widely used in the clinic. The hole types of CEC include minimally invasive medullary hole type, super conservative minimally invasive medullary hole type, "Truss" hole type and cutting end hole type. The stress analysis of CEC and traditional endodontic access (TEC) cavity are mainly based on the loading of teeth by a universal mechanical testing machine in vitro, finite element analysis and clinical observation. Most scholars’ studies have shown that minimally invasive endodontics can improve the fracture resistance of teeth, but the differential capacities of CEC and TEC remain controversial. How does on balance the purpose of pulp treatment and the maximum retention of tooth tissue? Further exploration is still needed.

Endodontia guiada como alternativa para o tratamento de canais severamente calcificados / Guided endodontics as an alternative for the treatment of severely calcified canals

ntrodução: a calcificação pulpar é um dos fatores que tornam o tratamento endodôntico desafiador e capaz de comprometer o acesso dos instrumentos e soluções irrigadoras por toda extensão do canal radicular, impossibilitando sua adequada desinfecção. A Endodontia Guiada traz mais previsibilidade e segurança ao tratamento endodôntico nessa situação complexa. Métodos: uma vez constatada calcificação severa com necessidade de intervenção endodôntica, o paciente é encaminhado ao centro radiológico para o planejamento da Endodontia Guiada. Um modelo 3D da arcada a ser tratada é obtido por meio de um scanner de bancada e, posteriormente, transferido para um software de planejamento virtual de implante. A TCFC é adicionada a esse software e ambas são sobrepostas, com base em estruturas visíveis radiograficamente. O software Simplant é programado para projetar uma broca física, utilizada para o acesso endodôntico guiado, sobreposta virtualmente à calcificação do canal radicular. De posse da guia impressa, essa é posicionada na arcada do paciente e o procedimento clínico, executado. Conclusão: a técnica de Endodontia Guiada é rápida, previsível e clinicamente viável. Além disso, pode ser executada por profissionais menos experientes, não necessitando da utilização de microscópio operatório (AU).

Introduction: Pulp calcification is one of the factors that make endodontic treatment challenging and capable of compromising access of instruments and irrigant solutions to the entire extension of the root canal, making it impossible to disinfect it adequately. Guided endodontics makes the endodontic treatment more predictable and safer in this complex situation. Materials and Methods: Once severe calcification requiring endodontic intervention has been found, the patient is referred to the radiology center for the planning of guided endodontics. A 3D model of the arch to be treated is obtained by means of a bench scanner, afterwards transferred to a virtual implant planning software program. The CBCT is added to this software and both are superimposed on the basis of radiographically visible structures. The Simplant software is programmed to project a physical bur used for guided endodontic access, virtually superimposed on the root canal calcification. Once the printed guide has been obtained, it is positioned in the patient's arch and the clinical procedure is performed. Conclusion: The guided endodontic technique is easy, predictable and clinically feasible to perform. Moreover, it may be performed by less experienced professionals, and does not require the use of an operating microscope (AU).

Three-dimensional finite element analysis of different endodontic access methods and full crown restoration in the maxillary central incisor / 华西口腔医学杂志

OBJECTIVE@#This study evaluates the effects of different endodontic access methods and full-ceramic crown on the stress distribution in the maxillary central incisor by using three-dimensional finite element analysis.@*METHODS@#Computed tomography scans of the maxillary central incisor were used to construct a three-dimensional finite element model of the maxillary central incisor. According to the different methods of endodontic and the prosthetic treatments, four models were established, namely, group A (traditional access cavity preparation with resin filling), group B (traditional access cavity preparation restored full-ceramic crown), group C (minimally invasive endodontics with resin filling) and group D (minimally invasive endodontics restored full-ceramic crown). A static force of 100 N and a direction of 45° was applied to the long axis of the tooth at the junction of the incisal section one-third and middle section one-third. The maximum principal stress, the von Mises stress and the modified von Mises stress of the tooth tissue were analyzed using the finite-element analysis software.@*RESULTS@#1) Stress peaks: the stress peaks of the maximum principal stress, the von Mises stress and the modified von Mises in group A were the largest, except that the stress peak of von Mises stress in group D was slightly lower than that in group C. The stress peaks of the maximum principal stress and the modified von Mises in group C were the lowest. The stress peaks of the maximum principal stress and the modi-fied von Mises stress in group D were lower than those in groups A and B. 2) Stress distribution: compared with group A, the stress distribution of cervical dentin and the area of stress concentration in group C was lower and smaller. In the root dentin, the stress distribution in group C was more uniform than that in group A, and the stress was dispersed to several areas of the root apex. After crown restoration, no significant difference was observed in stress distribution between groups B and D in the root region. The stress distribution state of group B was not significantly different from that of group A. No significant difference was observed in the stress distribution state between groups D and C.@*CONCLUSIONS@#1) From the perspective of biomechanics, the minimally invasive access was adopted for the maxillary central incisor. 2) Full crown restoration is recommended after traditional access cavity preparation. No obvious advantage is observed in stress analysis for minimally invasive endodontics-restored full-ceramic crown.

Coronal microleakage of four temporary restorative materials in Class II-type endodontic access preparations

OBJECTIVES: The purpose of this study was to evaluate the microleakage of 4 temporary materials in teeth with Class II-type endodontic access preparations by using a glucose penetration model. MATERIALS AND METHODS: Glucose reaction test was performed to rule out the presence of any reaction between glucose and temporary material. Class II-type endodontic access preparations were made in extracted human premolars with a single root (n = 10). Each experimental group was restored with Caviton (GC), Spacer (Vericom), IRM (Dentsply-Caulk), or Fuji II(GC). Microleakage of four materials used as temporary restorative materials was evaluated by using a glucose penetration model. Data were analyzed by the one-way analysis of variance followed by a multiple-comparison Tukey test. The interface between materials and tooth were examined under a scanning electron microscope (SEM). RESULTS: There was no significant reaction between glucose and temporary materials used in this study. Microleakage was significantly lower for Caviton and Spacer than for Fuji II and IRM. SEM observation showed more intimate adaptation of tooth-restoration interfaces in Caviton and Spacer than in IRM and Fuji II. CONCLUSIONS: Compared to IRM and Fuji II, Caviton and Spacer can be considered better temporary sealing materials in Class II-type endodontic access cavities.