Fracture resistance of upper central incisors restored with different posts and cores

OBJECTIVES: To determine and compare the fracture resistance of endodontically treated maxillary central incisors restored with different posts and cores. MATERIALS AND METHODS: Forty-eight upper central incisors were randomly divided into four groups: cast post and core (group 1), fiber-reinforced composite (FRC) post and composite core (group 2), composite post and core (group 3), and controls (group 4). Mesio-distal and bucco-lingual dimensions at 7 and 14 mm from the apex were compared to ensure standardization among the groups. Twelve teeth were prepared for crown restoration (group 4). Teeth in other groups were endodontically treated, decoronated at 14 mm from the apex, and prepared for posts and cores. Resin-based materials were used for cementation in groups 1 and 2. In group 3, composite was used directly to fill the post space and for core build-up. All samples were restored by standard metal crowns using glass ionomer cement, mounted at 135degrees vertical angle, subjected to thermomechanical aging, and then fractured using a universal testing machine. Kruskal-Wallis and Mann-Whitney U tests were used to analyze the data. RESULTS: Fracture resistance of the groups was as follows: Control (group 4) > cast post and core (group 1) > fiber post and composite core (group 2) > composite post and core (group 3). All samples in groups 2 and 3 fractured in restorable patterns, whereas most (58%) in group 1 were non-restorable. CONCLUSIONS: Within the limitations of this study, FRC posts showed acceptable fracture resistance with favorable fracture patterns for reconstruction of upper central incisors.

Root Dentin Strain and Temperature Rise During Endodontic Treatment and Post Rehabilitation

This study investigated the effects of endodontic treatment procedures and different post systems rehabilitation steps on the strain and temperature rise on apical and cervical root dentin regions. Twenty-one extracted human canine teeth had two strain gages attached to the distal root surface and two thermocouples attached to the mesial root surface (cervical and apical). The strain and temperature rise were recorded during the following procedures: root canal preparation, final rinse and drying, root canal filling and canal relief. Then the teeth were divided into three groups (n=7), according to the type of post system: CPC, cast post and core; FGP, fiberglass post; and PSP, prefabricated steel post. Data continued to be recorded during the post space preparation, post modeling (only for CPC), post trying and post cementation. Data were subjected to a two-way ANOVA followed by Tukey's test (α=0.05). The post-space preparation caused the highest temperature rise (4.0-14.9 °C) and the highest strain in the apical region during irrespective of post type. The resin cement light-activation resulted in significant temperature increases in the cervical region for all of the groups. The canal relief and the post-space preparation produced highest temperature rises. The CPC post modeling resulted in higher root strain level similarly the level of post preparation. The PSP resulted in highest strain during post trying and post cementation.

Este estudo investigou os efeitos de diferentes etapas do tratamento endodôntico e da inserção de diferentes tipos de retentores na deformação e aumento de temperatura na dentina radicular apical e cervical. Vinte e um dentes caninos humanos extraídos tiveram dois extensômetros colados à superfície da raiz distal e dois termopares ligados à superfície da raiz mesial (cervical e apical). A deformação e aumento de temperatura foram registrados durante os seguintes procedimentos: preparo do canal radicular, irrigação final e secagem, obturação do canal, alívio do canal; em seguida, os dentes foram divididos em três grupos (CPC, núcleo moldado e fundido; FGP, pino de fibra de vidro, e PSP pino pré-fabricado em aço-inoxidável, n=7). Os dados foram continuamente mensurados durante a modelagem do núcleo (somente para o CPC), inserção e cimentação dos retentores. Os dados foram submetidos a análise de variância fatorial, seguido pelo teste de Tukey (α=0,05). O preparo do canal para o retentor causou o maior aumento de temperatura (4,0-14,9 °C) e maior deformação na região apical independente do tipo de retentor. A ativação com luz resultou em significativo aumento de temperatura na região cervical, para todos os grupos. O alívio do canal e o preparo para o pino produziram maiores aumentos de temperatura. A modelagem do CPC resultou em maior nível de deformação da raiz em nível similar ao preparo para o retentor. O PSP resultou em maior deformação durante a inserção e ao final da cimentação.

Longitudinal clinical evaluation of post systems: a literature review

In this survey, retrospective and prospective clinical studies dealing with cast-post-and core and fiber posts were reviewed regarding the rate of survival of restorations and the most prevalent failures. Electronic searches of the literature were performed in MEDLINE by crossing the key words: "Fiber post and clinical study", "Fiber post and clinical evaluation", "Cast post-and-core and clinical study", and "Root post and retrospective survival study". The cut-off dates were December 1990 through the end of December 2010. Review of literature showed that several interrelated biological, mechanical, and aesthetic factors are involved in the survival rate of restorative procedures in endodontically treated teeth, and post selection should fulfill and optimize these factors. Data based on long-term clinical studies are essential for the general practitioner when making clinical decisions. An adequate selection of teeth and post system must be made, and a minimal amount of existing tooth substance should be removed. A ferrule must be present for safe indication of the fiber posts. Fiber glass posts have demonstrated good survival in clinical studies, with similar performance to cast-post-and cores. Metallic posts have good clinical survival, but the associated failures are mostly irreversible, unlike what happens with the glass fiber posts.

O objetivo foi realizar revisão de estudos clínicos retrospectivos e prospectivos de pinos e núcleos metálicos e pinos de fibra em relação à taxa de sobrevivência e tipo de falhas prevalentes. A revisão de literatura foi realizada utilizando a base de dados MEDLINE com os seguintes termos para pesquisa: “Pino de fibra e estudo clínico”, “Pino de fibra e avaliação clínica”, “Pinos e núcleos metálicos e estudo clínico”, “Pinos intra-radiculares e estudo clínicos retrospectivos”. O período avaliado foi de Dezembro de 1990 até o final de Dezembro de 2010. Vários fatores biológicos, mecânicos e estéticos estão envolvidos na taxa de sobrevivência do procedimento restaurador de dentes tratados endodonticamente. A seleção do pino deve satisfazer e otimizar esses fatores. Dados com base em estudos clínicos de longo prazo são essenciais para o clínico geral na tomada de decisões. Adequada indicação na seleção do sistema de pino devem ser feitas. Adicionalmente, desgaste mínimo da estrutura dentária existente deve ser priorizado. A presença de férula deve estar presente para garantir e melhorar a previsibilidade de pinos de fibra. Pinos de fibra de vidro têm demonstrado boa sobrevivência em estudos clínicos, com desempenho semelhante aos pinos metálicos e núcleos moldados e fundidos. Retentores metálicos apresentam boa sobrevivência clínica, no entanto as falhas envolvidas são em sua maioria irreversíveis, ao contrário do que acontece com os pinos de fibra de vidro.

Adaptación del sistema espiga muñón en relación a la preparación del conducto / Fit of the cast post and core system with different canal preparations

Se realizó un estudio in vitro que tuvo por objetivo medir el grado de adaptación del sistema espiga muñón, debido a que es uno de los factores fundamentales para lograr un buen anclaje de estos artificios, medido a nivel del núcleo de éste con respecto a los planos radiculares y de la espiga a las paredes del conducto, cuando es conformado con fresas Peeso y cuando es conformado usando fresas Peeso terminando con fresas del sistema Mooser. Seleccionamos 40 dientes que se dividieron al azar en dos grupos de 20, denominados P y M, respectivamente. Se confeccionó en cada muestra, previamente tratado su conducto mediante método indirecto, un perno muñón colado que fue probado en la preparación donde se midió el ajuste del muñón propiamente tal, después de logrado el asentamiento adecuado mediante desgastes en las interferencias de la espiga fueron cementados, posteriormente se realizaron dos cortes transversales a todo el espesor de la raíz a diferentes alturas, donde se midió la interfase entre la espiga y las paredes del conducto (adaptación). Los resultados fueron analizados utilizando los test de Mann-Whitney, Tukey y test T pareado, con software Systat versión 11, encontrándose que la mejor adaptación se observa en las muestras del grupo M en los dos sitios observados, comparadas con las del grupo P Estas diferencias son estadísticamente significativas.

We carried out a research aimed to determine the adaptation of the system called cast post and core, because it's one of the main factors to achieve a good adaptation of these devices measured from the core of this device to radicular plan, and from the post to the canal protesic's surface, when this one was prepared with Peeso's burs, and when was also prepared starting with Peeso's burs but finishing with Mooser system's burs. For that objective, we selected 40 teeth that were divided randomly into two groups of 20, called P and M respectively. A cast post and core was made in each sample through indirect method, previously treated the protesic canal. The cast post and core was tested in the preparation where the fit of the core was measured. Once achieved the proper settlement through the wearing out of the post's interferences and once the cast post and core was cemented, we made two cross cuttings to the thickness of the root at two differents levels, where the interface between the post and canal protesic's surface was measured (adaptation). The results were analyzed using the Mann-Whithny test, Tukey and paired T test, with Systast software version 11, having found that the best adaptation was observed in the samples of group M at the two points analyzed, compared to group P. These differences are statistically significant.

Stress distribution of periodontally involved teeth restored with various posts: three-dimensional finite element study / 대한치과보철학회지

STATEMENT OF PROBLEM: The endodontically treated tooth is generally restored with post and core, owing to the brittle and the loss of large amount of tooth structure. As periodontal treatment was developed, there are many cases that periodontally involved teeth used in prosthetic treatment. PURPOSE: The purpose of this study was to analyze the stress distribution in the dentin and post structures by the various post materials and the amount of remaining alveolar bone height. MATERIAL AND METHOD: The 3-dimensional finite element models of mandible 1st premolars were divided into six types according to the various amount of remaining alveolar bone and post type. All types were modeled using equal length, diameter and shape of the post. Three types of post and core materials were used: prefabricated titaniumpost and amalgam core, prefabricated stainless steel post and amalgam core, and cast gold post and core. 300 Newton force was applied to functional cusp of mandible 1st premolar. RESULTS: The results were as follows: First, there was no apparent difference in the pattern of stress distribution according to the alveolar bone condition concentrate on the post middle area. Second, there was difference in pattern of stress distribution according to the core materials, gold post and core generated same than amalgam core. Third, there was no apparent difference in the pattern of stress distribution within the dentin according to the post and core materials. But a cast gold post and core generated the lowest maximum stress value, a stainless steel post generated the highest maximum stress value. Fourth, in the reduced alveolar bone model, maximum stress value is 1.5 times than that of the normal alveolar bone model. CONCLUSION: Within the limitations of this study, to provide minimal stress to the root with alveolar bone reduced, the post length may be as long as apical seal was not destroyed. To prevent fracture of tooth, it is rational to use gold alloy which material was good for stress distribution for post materials.