[Fatigue and fracture resistance of the flared roots restored with computer aided design and computer aided manufacturing glass fiber posts].

OBJECTIVE: To evaluate the fatigue and fracture resistance of the flared roots restored with computer aided design (CAD) and computer aided manufacturing (CAM) glass fiber posts. METHODS: In the study, 32 maxillary central incisors with roots longer than 13 mm were selected and their canals were flared, and the roots were allocated into 4 groups (n=8) by a random number chart: CAD/CAM glass fiber posts, prefabricated quartz fiber posts, cast gold alloy posts, and CAD/CAM zirconia posts. The posts were luted to the roots by resin cement and fabricate zirconia crown for every specimen. An addition-type silicone impression material was used to simulate the periodontal ligament. All the specimens were submitted to 1.2×10(6) cycles loaded with a 49 N force, at 45 degree to the long axis of the teeth simultaneously with 3 000 thermal cycles (5 °C-50 °C-5 °C). After that, the specimens were subjected to a load at a crosshead speed of 1 mm/min in a servo-hydraulic testing machine applied at 45 degree to the long axis of the tooth until fracture. The data were subjected to ANOVA test and the patterns of the failure were examined. RESULTS: After the cycling loading, 4 crowns from prefabricated quartz fiber posts groups were deboned, and no other failure was found after the cycling loading; the fracture strengths of CAD/CAM glass fiber posts group [(441.5± 103.2) N] and cast gold alloy posts group [(462.9±170.0) N] were higher (F=4.613, P<0.05) than those of CAD/CAM zirconia posts group [(284.1±99.0) N] and prefabricated quartz fiber posts group [(315.4±112.3) N]; the entire specimens presented unfavorable failures. CONCLUSION: Although further in vitro and in vivo studies are necessary, the results of this study show that the use of CAD/CAM glass fiber posts and cast gold alloy posts may achieve better outcomes in flared roots than that of CAD/CAM zirconia posts and prefabricated quartz fiber posts.

Posts--when it all goes wrong! Part 1: case assessment and management options.

UNLABELLED: Posts have been used for many years to retain restorations or cores for extra-coronal restorations in endodontically treated teeth.This article discusses the variety of post systems that are available and the incidence and reasons for failure of teeth that have been restored with posts. The treatment options available for the management of such failures are considered, in addition to the indications for both non-surgical and surgical management of endodontic failures. The attitudes of dentists and the perceived complications of attempting post removal are reviewed, along with the evidence to support the prevalence of complications. CLINICAL RELEVANCE: Failure of post-retained restorations is a relatively frequent finding due to failure of the restoration itself or the endodontic treatment. It is therefore important to understand and be aware of the various treatment options available, their indications and associated risks.

Influence of post system and remaining coronal tooth tissue on biomechanical behaviour of root filled molar teeth.

AIM: To investigate ex vivo the influence of post system and amount of remaining coronal tooth tissue on the fracture resistance, fracture mode and strain of root filled molar teeth. METHODOLOGY: Seventy mandibular human molar teeth were divided into seven groups (n = 10), one control (sound teeth) and six experimental groups resulting from the interaction between the two study factors: post system (Pa, post absence; Gfp, glass fibre post; Cmp, cast Ni-Cr alloy post and core) and amount of remaining coronal tooth tissue (Fe, 2 mm of ferrule; NFe, no ferrule). Teeth in the experimental groups were restored with metal crowns. For the strain gauge test, two strain gauges per sample were attached on the buccal and proximal root surfaces, and the samples of each group (n = 5) were submitted to a load of 0-100N. Fracture resistance (N) was assessed in a mechanical testing device (n = 10). Strain gauge and fracture resistance data were analysed by two-way anova (3 × 2) followed by the Tukey's HSD and Duncan's test (α = 0.05). The failure mode was evaluated using an optical stereomicroscope and classified according to the location of the failure. RESULTS: The absence of ferrule was associated with lower fracture resistance regardless of the post system. Groups restored with glass fibre post and cast Ni-Cr alloy post and core had similar fracture resistance and higher values than groups without posts, regardless of the remaining coronal tooth tissue. Teeth with no ferrule and cast Ni-Cr alloy post and core resulted in catastrophic fractures and those with no ferrule and glass fibre post or no ferrule and post absence resulted in restorable failures. Buccal strain was higher in sound teeth and lower in teeth without posts. Glass fibre post insertion decreased the buccal strain compared to the teeth with ferrule and absence of post. CONCLUSIONS: Two millimetre of ferrule had a significant influence on cusp strain, fracture resistance and failure mode. The glass fibre post was as effective as the cast Ni-Cr alloy post and core in the restoration of root filled molars regardless of the remaining tooth tissue. Absence of a post decreased the fracture resistance and increased the cusp strain.

Reinforcement of thin-walled root canal structures for placement of esthetic dowels: a clinical report.

Thin-walled root canals always present a challenge to dentists to select a restorative treatment that does not further weaken the thin tooth structure. The prognosis of dowel and core restorations can be unpredictable. This clinical report describes the treatment of a patient with extensive caries extending into the root canal of an endodontically treated maxillary central incisor. The use of a flowable composite resin in combination with a quartz fiber reinforced post is described, resulting in the rehabilitation of a structurally compromised root canal with satisfactory esthetic and functional outcomes.

Effects of endodontic post surface treatment, dentin conditioning, and artificial aging on the retention of glass fiber-reinforced composite resin posts.

STATEMENT OF PROBLEM: Several post surface treatments with or without the application of a bonding agent have been recommended to improve the bond strength of resin cements to posts. A regimen that produces the maximum bond strength of glass fiber-reinforced composite resin posts has not been verified. PURPOSE: The purpose of this study was to evaluate the influence of post surface conditioning methods and artificial aging on the retention and microleakage of adhesively luted glass fiber-reinforced composite resin posts. MATERIAL AND METHODS: Seventy-two endodontically treated single-rooted teeth were prepared for glass fiber-reinforced composite resin posts. The posts were submitted to 3 different surface treatments (n=24), including no treatment, etching with phosphoric acid, and airborne-particle abrasion. Subgroups of the posts (n=8) were then allocated for 3 different experimental conditions: no artificial aging, no bonding agent; no artificial aging, bonding agent; or artificial aging, bonding agent. The posts were luted with resin cement (Calibra). Post retention was measured in tension at a crosshead speed of 2 mm/min. The posts assigned for microleakage investigation were placed in fuchsin dye for 72 hours. The dislodged posts and the post spaces were examined microscopically to evaluate the mode of failure and explore the microleakage. Data were analyzed by 2-way ANOVA followed by Tukey HSD test (alpha=.05). RESULTS: The mean (SD) retention values for test groups ranged from 269 (63.8) to 349 (52.2) N. The retention values of the airborne-particle-abrasion group were significantly higher than those of the acidic-treatment and no-treatment groups. The application of bonding agent on the post surface produced no significant influence on retention. The mean retention values after artificial aging were significantly higher than without artificial aging. Microscopic evaluation demonstrated that the failure mode was primarily mixed. CONCLUSIONS: Treating the surface of the posts with phosphoric acid for 15 seconds before cementation produced no significant improvement in post retention. Airborne-particle abrasion of the surface of the post significantly improved post retention.

Multidisciplinary treatment of a complicated crown-root fracture.

Complicated crown-root fractures are challenging for pediatric dentists to treat. Many treatment strategies have been proposed, each with their own advantages and disadvantages. The purpose of this report was to suggest a new method to treat a complicated crown-root fracture using fragment reattachment with the aid of a splint and an intracanal fiber post. It is recommended that the fractured fragment be stabilized to its original position instead of being extracted if the biological width is minimally invaded. Furthermore, the use of an intracanal post is recommended to reinforce the root in a horizontal root fracture.

Zirconia ceramic post systems: a literature review and a case report.

Cast metal post-core systems have a long history of successful use because of their superior physical properties. However, their high elastic modulus can cause stress concentrations within the surrounding radicular dentin, resulting in root fractures. Moreover, the increasing demand for more esthetically appealing and biocompatible restorations has led to the development of tooth-colored, translucent, metal-free post-core systems. Notably, prefabricated zirconia ceramic post systems have been introduced to satisfy this trend toward a heightened awareness of esthetics, whereby the translucency of all-ceramic crowns can be successfully maintained with the use of ceramic post-core materials. Owing to the keen interest in and widespread use of zirconia ceramic post systems, many in vitro studies on zirconia posts have been published in the last 15 years. The aim of this article was to present data about the retention, fracture resistance, microleakage, light transmission, esthetic advantages, and radiodensity of zirconia posts. Two clinical survival rate studies were also presented. Based on the results of these studies, zirconia posts have been shown to improve the esthetic quality of all ceramic crowns and thus their usage is recommended. Apart from literature review, a case report in which a fractured fiber post was replaced with a custom-made zirconia post was also presented.

An alternative post-and-core method for patients with limited interarch space.

BACKGROUND: The authors describe a technique for placement of a three-unit posterior fixed partial denture where one abutment lacked sufficient interarch space. CASE DESCRIPTION: This method involves the use of a cast post and core with a precision attachment soldered into the core to provide the necessary retention and resistance. The prosthesis is retained by a combination of cement and screw retention. CLINICAL IMPLICATIONS: This method is desirable when there is insufficient interarch space for a conventional post-and-core restoration. Achieving internal reinforcement by connecting the precision attachment to the residual root should provide the prosthesis with retention and added stability.

Crown vs. composite for post-retained restorations: A randomized clinical trial.

OBJECTIVES: This randomized clinical trial compared the survival of composite resin restorations and metal-ceramic crowns on endodontically treated teeth that received a glass fiber post using 2 different cementation methods. METHODS: Forty-seven patients (age 42.5 ± 11.5) with fifty-seven endodontically treated teeth with extensive coronal damage but always with one intact surface were randomly allocated according to the type of coronal restoration: metal-ceramic crown or composite resin. In case of crown restoration, a core buildup was performed with microhybrid composite resin. The dentin bonding agent and composite resin used were the same for both direct and indirect restorations. Descriptive analysis was performed using FDI clinical criteria and survival of restorations/teeth analyzed using Kaplan-Meier statistics and log-rank tests. RESULTS: 57 restorations (30 composite resin and 27 crowns) were made in 47 patients. The recall rate was 100% and follow up time ranged between 1 and 5 years. One tooth was extracted 11 months post-restoration due to root fracture (composite group). Eight composite restorations and one crown had reparable failures, all due to secondary caries or restoration fracture. The overall annual failure rate (AFR) was 0.92% after 50 months for success of the restorations, with 1.83% for the composite group and 0.26% for the metal-ceramic crown group. The log-rank test showed no difference for survival according to the type of restoration (p=0.344). However, for success rates, metal-ceramic crowns demonstrated better performance (p=0.022). CONCLUSIONS: Indirect restorations provided higher acceptable clinical performance and lower need for re-intervention, but both types of restorations presented good survival rates. (NCT01461239). CLINICAL SIGNIFICANCE: When endodontically treated teeth with at least one intact surface must be restored, composite resin restorations and metal-ceramic crows are acceptable alternatives to achieve good survival and success rates.

A customized acrylic resin shell for fabricating an amalgam core on the coronally debilitated, endodontically treated posterior tooth.

This article describes a technique for fabricating a custom acrylic resin shell that will ensure a properly designed amalgam core for the coronally debilitated, endodontically treated posterior tooth. A few simple procedures result in a core foundation for root protection, an ideal crown preparation, and a more predictable final restoration.

The use and predictable placement of Mineral Trioxide Aggregate in one-visit apexification cases.

Endodontic treatment of the pulpless tooth with an immature root apex poses a special challenge for the clinician. The main difficulty encountered is the lack of an apical stop against which to compact an interim dressing of calcium hydroxide (Ca(OH)2), or the final obturation material. In these situations the unpredictability of the result, the difficulty in creating a leak-proof temporary restoration for the duration of treatment, and the difficulty in protecting the thin root from fracture may lead to complications when using traditional (Ca(OH)2-based) apexification techniques. Furthermore, given the increased mobility of today's society, lengthy treatment protocols are fraught with problems, and may not be followed through to completion. This may lead to ultimate failure of the case. Mineral Trioxide Aggregate (MTA) has recently been introduced for use in endodontics. Current literature supports its efficacy in a multitude of procedures including apexification. The focus of this paper is to propose a one-visit apexification protocol with MTA as an alternative to the traditional treatment practices with Ca(OH)2. One-visit apexification may shorten the treatment time between the patient's first appointment and the final restoration. The importance of this approach lies in the expedient cleaning and shaping of the root canal system, followed by its apical seal with a material that favours regeneration. Furthermore, the potential for fractures of immature teeth with thin roots is reduced, as a bonded core can be placed immediately within the root canal.

Prefabricated post-and-core systems: an overview.

Restorative dentists should have a working knowledge of more than one post-and-core system. This review is designed to encourage them to consider systems they might not have considered otherwise. Many restorative dentists learn to use one prefabricated post-and core system, and they have only one system on hand. When the system on hand is the solution, there is no need for an alternative. However, no single prefabricated post-and-core system can fit all endodontic restorative requirements. The best way to pick an optimum system design is to compare alternatives. The vast assortment of available system components, many supported solely by experimental data without direct clinical corroboration, makes comparison and selection a challenging process.

Restoration and reinforcement of endodontically treated teeth with a polyethylene ribbon and prefabricated fiberglass post.

In the past it was considered appropriate to place a cast post and core in every pulpless tooth without regard to the remaining supportive tooth structure present. Recent research and the advent of adhesive bonding techniques have caused clinicians to reevaluate their restorative protocol. This article reviews the current literature with regard to restoration of the endodontically treated tooth and presents a method for restoration and reinforcement utilizing a combination of polyethylene ribbon and a prefabricated fiberglass post.

Posts and cores: when to use them.

The two overriding factors for successful post restoration are: 1. Retention, i.e., resistance to torsional forces. Published research is clear that threaded posts are the method of choice for the restoration of endodontically treated teeth in order to achieve optimal success. Prethreaded and self-threaded are the two systems from which to choose. The words active and passive should be applied to the method of producing threads, not the posts. The most gentle way to produce a thread is with a thread cutter. 2. Stress distribution of some cylindrical threaded posts has been shown to be far superior to nonthreaded cylindrical and nonthreaded tapered posts. With the acceptance of threaded, cylindrical prefabricated posts, new terminology has evolved, and the use and meaning of these words has been made more precise.

Desadaptação apical e cervical de núcleo metálico fundido em função do material e da técnica de moldagem indireta / Apical and cervical maladaptation of cast metal core due to the used material and the indirect impression technique

Avaliou-se, microscopicamente, a desadaptação cervical e, radiograficamente, a desadaptação apical de núcleos metálicos fundidos (NMFs) moldados com silicone de condensação e adição, comparando a utilização ou não de suporte intrarradicular. Por meio do corpo mestre foram obtidos 40 moldes divididos em quatro grupos: Silicone de condensação com suporte intrarradicular, Silicone de condensação sem suporte, Silicone de adição com suporte e Silicone de adição sem suporte. Sobre os modelos foram modelados pinos em resina Dencrilay e fundidos com liga de cobalto-cromo. A desadaptação cervical foi medida com microscópio comparador de dupla coordenada digital (30x). A desadaptação apical foi medida a partir de 40 radiografias digitais e análise em software, através da distância entre o ponto mais apical do núcleo até o início do material obturador. Pelo coeficiente de correlação intraclasse, o comprimento da porção intrarradicular do NMF ficou aquém do comprimento real do conduto para os quatro grupos estudados. A análise de variância e o teste de Tukey aplicados aos dados de desadaptação cervical revelaram que as técnicas com e sem suporte não diferiram entre si, quando usado silicone de condensação. Com o silicone de adição, a técnica com suporte ocasionou a maior desadaptação cervical. Quanto à região apical, constatou-se que a desadaptação não foi afetada pela utilização de suporte intrarradicular (p = 0,651), pelo material de moldagem (p = 0,322), nem pela interação de ambos (p = 0,180). Concluiu-se que a utilização de suporte intrarradicular durante a moldagem para a confecção de NMF para ambos os silicones torna-se dispensável (AU).

This study evaluated microscopically and radiographically, the cervical and apical maladaptation of cast metal cores obtained from molds with silicone polymerized by condensation and addition, comparing the need to use intra-radicular support. Through the master body, 40 molds were obtained and divided into four groups: Condensing silicon with, Condensing silicon without support, Silicone addition with support, and Silicone addition without support. The models were modeled in Dencrilay resin and cast with cobalt-chromium alloy. Cervical maladaptation was measured with double digital coordinate comparator microscope (30x). The apical maladaptation was measured from 40 digital radiographs and software analysis, through the gap between the most apical point of the core and the beginning of the filling material. According to the intraclass correlation coefficient, the length of the intra-radicular portion of the cast metal cores was below the actual length of the conduit for the four groups studied. The analysis of variance and Tukey's test applied to the data of cervical maladaptation revealed that the techniques with and without support did not differ from each other when using condensation silicone. With addition silicone, the technique with support caused most cervical maladjustment. As for the apical region, it was found that the maladaptation was not affected by the use of intra-radicular support (p = 0.651), by the molding material (p = 0.322) or by the interaction of both (p = 0.180). It was concluded that intra-radicular support during molding for the manufacture of cast metal cores, for both silicones, becomes dispensable (AU).

Fracture resistance of teeth restored with post-retained restorations: an overview.

INTRODUCTION: Posts have been used efficiently to retain restorations for badly destructed teeth. This article critically analyzes the concerned topics related to the fracture resistance of teeth restored with dowel-retained restorations. METHODS: A systematic review of PubMed/MEDLINE, Cochrane, and Scopus databases was completed (from 1960 to 2010). Single or combined key words were used to obtain the most possible comprehensive list of articles. Checking the references of the relevant obtained sources completed the review along with a manual search to locate related articles on the topic. In vivo and ex vivo (laboratory, computer-based finite element, and photoelastic stress analysis studies) investigations related to the topic were included. RESULTS: Many factors have been proposed to influence the fracture resistance of post-restored teeth. Recognizing the significance of these factors on the fracture resistance of teeth would aid in choosing the suitable treatment modality for every individual case. Fracture resistance was improved if tooth structure loss was limited, a ferrule was obtained, a post with similar physical properties to natural dentine was used, and adhesive techniques for post luting and coronal restoration were used. Adhesively luted resin/fiber posts with composite cores appear to be the best currently available option in terms of tooth fracture and biomechanical behaviour. CONCLUSIONS: Most guidelines were based mainly on ex vivo studies and to a lesser extent on limited in vivo studies. The lack of long-term controlled randomized clinical studies was the main hindrance to reaching a conclusive and undisputable opinion regarding endodontic posts in terms of tooth fracture and biomechanical behaviour.

Effect of root canal preparation, type of endodontic post and mechanical cycling on root fracture strength

Objective: To evaluate the impact of the type of root canal preparation, intraradicular post and mechanical cycling on the fracture strength of roots. Material and Methods: eighty human single rooted teeth were divided into 8 groups according to the instruments used for root canal preparation (manual or rotary instruments), the type of intraradicular post (fiber posts- FRC and cast post and core- CPC) and the use of mechanical cycling (MC) as follows: Manual and FRC; Manual, FRC and MC; Manual and CPC; Manual, CPC and MC; Rotary and FRC; Rotary, FRC and MC; Rotary and CPC; Rotary, CPC and MC. The filling was performed by lateral compactation. All root canals were prepared for a post with a 10 mm length, using the custom #2 bur of the glass fiber post system. For mechanical cycling, the protocol was applied as follows: an angle of incidence of 45°, 37°C, 88 N, 4 Hz, 2 million pulses. All groups were submitted to fracture strength test in a 45° device with 1 mm/ min cross-head speed until failure occurred. Results: The 3-way ANOVA showed that the root canal preparation strategy (p<0.03) and post type (p<0.0001) affected the fracture strength results, while mechanical cycling (p=0.29) did not. Conclusion: The root canal preparation strategy only influenced the root fracture strength when restoring with a fiber post and mechanical cycling, so it does not seem to be an important factor in this scenario. .

A novel post-and-core restoration system--results of three years of clinical application of the "Wuerzburg Post".

The Wuerzburg Post is a new post-and-core restoration system designed to eliminate the weak parts of post-and-core restorations and the associated problems, respectively. In contrast to conventional posts, the Wuerzburg Post is a short and thick post, which no longer relies on cementation or luting for retention in the root, but on stress-free positive locking, which it achieves by means of a post which can be spread into a predefined and form-congruent undercut cavity. The second key feature is an annular groove which runs in the dentin, girded by a corresponding structure, ensuring regular force transmission and stress dissipation, as opposed to the classic ferrule design. There are two versions: one with a machined core which can be prepared like a classic build-up to support crowns and bridges, and another one with a 2.25 mm ball end to connect to common dies which can be integrated into removable prostheses. As the system utilizes prefabricated parts made from Titanium, a precise fit is ensured, enabling the user to restore teeth quickly and easily. Over the course of the past three years, 129 posts were inserted, most commonly on upper and lower incisors and canines. The main application was restoration of fractured telescopes. During the observation period, five failures were observed. Two of the failiures did not cause significant damage to the tooth, and were subsequently immediately repairable. The survival rate amounts to over 95% after three years under risk.

Distribuição das tensões relacionadas ao uso de retentores em dentes tratados endodonticamente utilizando o método dos elementos finitos / Stress distribution related to the use of retainers in endodontically treated teeth using the finite element method

A restauração dos dentes tratados endodonticamente, com grande fragilidade de suas estruturas, traz dúvidas ao clínico quanto à melhor forma de atuar nesses elementos. Os retentores intrarradiculares, sejam núcleos metálicos fundidos ou pré-fabricados, são geralmente necessários para a restauração destes elementos. Cada um desses materiais imprime uma força diferente nas estruturas adjacentes, sendo o entendimento destas uma necessidade para a melhor escolha e aplicação clínica do retentor. Objetivo: A proposta do presente trabalho é analisar e avaliar a distribuição de tensões no complexo dente-periodonto pelo método dos elementos finitos bidimensional com a utilização de diferentes tipos de retentores. Método: Este estudo tem por base modelos matemáticos de um canino superior tratado endodonticamente com a utilização de retentores intrarradiculares metálicos fundidos em NiCr, metálicos pré-fabricados em titânio. Os modelos foram submetidos a uma carga de 100 N por palatina em um ângulo de 45º. A análise e avaliação das tensões foram realizadas para cada um dos modelos e seus diferentes tipos de pinos. Resultados: A maior concentração de tensões se deu com o uso do pino metálico pré-fabricado de titânio, com valores de tração que oscilam entre 1.207 MPa a 4.878 MPa e de compressão entre -9.806 MPa a -2.464 MPa. O pino metálico fundido imprimiu tensões de menores valores, mais homogêneas e uniformes, tendo seus valores de tração variando de 1.287 MPa a 4.919 Mpa e seus valores de compressão variando de -9.607 MPa a 2.344 Mpa. Conclusão: Os pinos intrarradiculares metálicos pré-fabricados de titânio geram forte estresse no sistema dente-periodonto, sendo o menos indicado clinicamente. O mais indicado para uso clínico foi o pino metálico fundido, cuja tensão se manifestou de maneira mais uniforme no elemento dentário.

The restoration of endodontically treated teeth with great structure fragility challenges the clinician about the best way to proceed on these elements. The use of intracanal retainers, either post and core systems of prefabricated posts, is usually necessary to restore this kind of teeth. Each one of these materials exerts a different force on the adjacent structures and understanding these forces is mandatory for a better choice and clinical application of intracanal retainers. Objective: The purpose of this study was to analyze and evaluate the stress distribution in the tooth-periodontium complex by the two-dimensional finite element method, using different types of retainers. Methods: This study was based on mathematical models of an endodontically treated maxillary canine, using a NiCr cast intracanal posts and a prefabricated titanium post. The models were subjected to a 100 N load directed palatally at a 45º angle. The strains for each of the models and different types of post were analyzed and evaluated. Results: The highest stress concentration occurred with the use of the prefabricated titanium post, with traction values ranging from 1207 MPa to 4878 MPa and compression values between -9806 and -2464 MPa. The NiCr cast post exhibited lower tension values, with a more homogeneous and uniform distribution, traction values ranging from 1287 MPa to 4919 MPa and compression values ranging from -9607 MPa to 2344 MPa. Conclusion: Prefabricated titanium intraradicular posts induced strong stress to the tooth-periodontium complex and is less indicated clinically. The metal cast post appears more adequate cast for clinical use, as the resulting tension was distributed more uniformly along the tooth.