Efeito da elevação da margem gengival e do material restaurador no comportamento em fadiga e distribuição de tensão de molares restaurados com inlays mod / Effect of deep margin elevation and restorative material on the fatigue behavior and stress distribution of molars restored with MOD inlays

Este estudo avaliou o efeito da elevação da margem gengival (DME) e dos materiais restauradores (cerâmica vítrea reforçada por leucita [C] vs. resina composta indireta [R]) no comportamento de fadiga e distribuição de tensão de molares superiores com margens proximais com 2 mm de profundidade restauradas com inlays mesio-ocluso-distal (MOD). Para isso, 52 terceiros molares humanos extraídos foram distribuídos aleatoriamente em quatro grupos (n = 13): C; DME + C; R; e DME + R. Restaurações do tipo inlay foram confeccionados no CAD-CAM e cimentadas adesivamente em todos os dentes. O comportamento em fadiga foi avaliado com o ensaio de vida acelerada stepwise stress (10.000 ciclos/step; step=50 N; 20 Hz; carga inicial=200 N). As cargas e o número de ciclos de falha em fadiga foram analisados com ANOVA de 2 fatores e teste de Tukey (p <0,05), também foram realizados gráficos de sobrevivência de Kaplan-Meier. A distribuição de tensões foi avaliada utilizando a análise por elementos finitos. Os modelos foram considerados isotrópicos, lineares, homogêneos e apresentaram contatos colados. Uma carga axial (400 N) foi aplicada à superfície oclusal. A distribuição de tensões foi analisada com o critério de tensão principal máxima. Para o comportamento em fadiga, não houve diferença para o fator DME (p> 0,05). Para o fator material restaurador, a carga e o número de ciclos para falha foram estatisticamente maiores nos grupos R (p <0,05). A análise por elementos finitos mostrou que os inlays de resina composta concentraram mais tensões na estrutura do dente, enquanto os inlays de cerâmica concentraram mais tensões na restauração. Falhas não reparáveis foram mais frequentes nos grupos de inlays de resina composta. Foi possível concluir que a DME não foi prejudicial para o comportamento em fadiga e na distribuição de tensão. As inlays de resina composta foram mais resistentes ao teste de fadiga, embora o modo de falha tenha sido mais agressivo(AU)

Objectives: This study evaluated the effect of deep margin elevation (DME) and restorative materials (leucite-reinforced glass-ceramics [C] vs. indirect resin composite [R]) on the fatigue behavior and stress distribution of upper molars with 2-mm deep proximal margins restored with MOD-inlay. Methods: Fiftytwo extracted human third molars were randomly assigned into four groups (n=13): C; DME+C; R; and DME+R. Inlays were fabricated in CAD-CAM and bonded to all teeth. The fatigue behavior was assessed with the stepwise stress test (10,000 cycles/step; step=50N; 20 Hz; initial load=200 N). Fatigue failure loads and number of cycles were analyzed with 2-way ANOVA and Tukey's test (p<0.05) and Kaplan-Meier survival plots. The stress distribution was assessed with finite element analysis. The models were considered isotropic, linear, homogeneous, and presented bonded contacts. A tripod axial load (400 N) was applied to the occlusal surface. The stress distribution was analyzed with the maximum principal stress criterion. Results: For fatigue, there was no difference for DME factor (p>.05). For the material factor, the load and number of cycles for failure were statistically higher in the R groups (p<.05). The finite element analysis showed that resin composite inlays concentrated more stress in the tooth structure, while ceramic inlays concentrated more stress in the restoration. Non-reparable failures were more frequent in the resin composite inlays groups. Conclusions: DME was not negative for fatigue and biomechanical behaviors. Resin composite inlays were more resistant to the fatigue test, although the failure mode was more aggressive(AU)

[Influence of surface treatment with sodium hypochlorite solution on dentin bond strength].

OBJECTIVE: To evaluate the influence of sodium hypochlorite (NaOCl) solution used during root canal therapy on dentin bond strength. METHODS: In the study, 15 freshly extracted human third molars with complete dental crowns, caries and filling-free were selected. The occlusal enamel was removed perpendicular to the long axis of the tooth to expose middle flat surfaces of sound dentin. The occlusal dentin surfaces were then polished using 600-grit silicon papers for 1 min and rinsed with deionized water for 1 min. The teeth were randomly divided into three groups according to the treatment received: group A (negative control group), the samples were immersed in deionized water for 20 min; group B, the dentin surfaces were immersed in 2.50% NaOCl solution for 20 min, with the solution being renewed every 5 min; group C, the dentin surfaces were immersed in 5.25% NaOCl solution for 20 min, with the solution being renewed every 5 min. All the treated dentin surfaces were bonded using a self-etching adhesive system (SE bond) with a 5 mm in height resin composite (AP-X). After storage in deionized water at 37 °C for 24 h, the adhesive samples were sectioned longitudinally to produce 1.0 mm×1.0 mm stick specimens(n=45) for micro-tensile bond strength testing (MPa). Failure modes (adhesive failure, cohesive failure or mixed failure) at the dentin-resin interface were observed using a stereomicroscope. The micro-tensile bond strength data among the three groups were analyzed by a one-way ANOVA, then the Post-hoc test(LSD) was employed for pairwise comparison. The distribution of failure modes among the groups were analyzed by chi-square test. RESULTS: Significant decreased bond strength values were found for the 2.50% NaOCl-treated group (26.04±5.74) MPa and 5.25% NaOCl-treated group (24.46±3.77) MPa when compared with the strength of negative control group (48.71±7.77) MPa,P=0.000. Compared with the negative control group, themicro-tensile bond strength of the 2.50% NaOCl-treated group and 5.25% NaOCl-treated grouphad dropped by 46.5% and 50.2%. However, there was no significant difference of bond strength between the 2 NaOCl-treated groups (P=0.214). The distribution of failure modes showed significant difference in all the three groups (2=56.324, P=0.000). The mixed failure (68.9%) was the most mode of fracture in the negative control group, followed by adhesive failure(24.4%), and the cohesive failure was least(6.7%). The proportion of adhesive failure mode was higher in NaOCl-treated groups than in negative control group (P=0.000). There was no significant difference of the distribution of failure modes between the 2.50% NaOCl-treated group and 5.25% NaOCl-treated group(P=0.197), and there was no cohesive failure mode detected in the two groups. CONCLUSION: The micro-tensile bond strength of dentin to composite resin was lower after exposure to NaOCl solution.

Three- to nine-year survival estimates and fracture mechanisms of zirconia- and alumina-based restorations using standardized criteria to distinguish the severity of ceramic fractures.

OBJECTIVES: The aims of this study were set as follows: 1. To provide verifiable criteria to categorize the ceramic fractures into non-critical (i.e., amenable to polishing) or critical (i.e., in need of replacement) 2. To establish the corresponding survival rates for alumina and zirconia restorations 3. To establish the mechanism of fracture using fractography MATERIALS AND METHODS: Fifty-eight patients restored with 115 alumina-/zirconia-based crowns and 26 zirconia-based fixed dental prostheses (FDPs) were included. Ceramic fractures were classified into four types and further subclassified into "critical" or "non-critical." Kaplan-Meier survival estimates were calculated for "critical fractures only" and "all fractures." Intra-oral replicas were taken for fractographic analyses. RESULTS: Kaplan-Meier survival estimates for "critical fractures only" and "all fractures" were respectively: Alumina single crowns: 90.9 and 68.3 % after 9.5 years (mean 5.71 ± 2.6 years). Zirconia single crowns: 89.4 and 80.9 % after 6.3 years (mean 3.88 ± 1.2 years). Zirconia FDPs: 68.6 % (critical fractures) and 24.6 % (all fractures) after 7.2 and 4.6 years respectively (FDP mean observation time 3.02 ± 1.4 years). No core/framework fractures were detected. CONCLUSIONS: Survival estimates varied significantly depending on whether "all" fractures were considered as failures or only those deemed as "critical". For all restorations, fractographic analyses of failed veneering ceramics systematically demonstrated heavy occlusal wear at the failure origin. Therefore, the relief of local contact pressures on unsupported ceramic is recommended. Occlusal contacts on mesial or distal ridges should systematically be eliminated. CLINICAL RELEVANCE: A classification standard for ceramic fractures into four categories with subtypes "critical" and "non-critical" provides a differentiated view of the survival of ceramic restorations.

Minimally Invasive Long-Term Management of Direct Restorations: the '5 Rs'.

The assessment and operative long-term management of direct restorations is a complex and controversial subject in conservative dentistry. Employing a minimally invasive (MI) approach helps preserve natural tooth structure and maintain endodontic health for as long as possible during the restorative cycle. This paper discusses how minimally invasive techniques may be applied practically to reviewing, resealing, refurbishing, repairing or replacing deteriorating/failed direct coronal restorations (the'5 Rs') and provides an update of contemporary MI clinical procedures. CPD/CLINICAL RELEVANCE: The assessment and long-term clinical management of deteriorating/failing direct restorations is a major component of the general dental practice workload and NHS UK budget expenditure for operative dentistry.

Key systemic and environmental risk factors for implant failure.

Dental implants are an important treatment option for patients interested in replacing lost or missing teeth. Although a robust body of literature has reviewed risk factors for tooth loss, the evidence for risk factors associated with dental implants is less well defined. This article focuses on key systemic risk factors relating to dental implant failure, as well as on perimucositis and peri-implantitis.

Key local and surgical factors related to implant failure.

The concept of osseointegration has revolutionized the treatment options for the replacement of missing teeth in both partially and completely edentulous patients. Dental implants are widely used because clinical practice and studies have documented its successful outcomes. However, implants can occasionally fail, and such failures can be classified as early or late. Measures that can aid in the early recognition of failing osseointegrated implants are needed, as are measures that can facilitate appropriate treatment methods aimed at saving failing implants by determining the probable etiologic factors. This article summarizes our current understanding of the local factors that can be linked to implant failure.

Use of cone-beam computed tomography in early detection of implant failure.

Preimplant planning with complex imaging techniques has long been a recommended practice for assessing the quality and quantity of alveolar bone before dental implant placement. When maxillofacial imaging is necessary, static film or digital images lack the depth and dimension offered by computed tomography. Cone-beam computed tomography (CBCT) offers the dentist not only a radiographic volumetric view of alveolar bone but also a 3-dimensional reconstruction. This article reviews the use of CBCT for assessing implant placement and early detection of failure, and compares the performance of CBCT with that of other imaging modalities in the early detection of implant failure.

Prosthetic failure in implant dentistry.

Although osseointegrated dental implants have become a predictable and effective modality for the treatment of single or multiple missing teeth, their use is associated with clinical complications. Such complications can be biologic, technical, mechanical, or esthetic and may compromise implant outcomes to various degrees. This article presents prosthetic complications accompanied with implant-supported single and partial fixed dental prostheses.

Complications associated with implant-retained removable prostheses.

Implant-supported removable prostheses improve patients' satisfaction with treatment and quality of life. Improvements in the implant's surface and in attachment elements have made this treatment method very successful. However, some biological and mechanical complications remain. Mechanical complications associated with implant-supported overdentures and implant-supported removable partial dentures are loss of retention of attachment systems, the need to replace retention elements and to reline or repair the resin portion of the denture, and implant fracture. Despite their success, implant-supported removable prostheses require periodic maintenance.

Esthetic failure in implant dentistry.

The definition of failure for dental implants has evolved from lack of osseointegration to increased concern for other aspects, such as esthetics. However, esthetic failure in implant dentistry has not been well defined. Although multiple esthetic indices have been validated for objectively evaluating clinical outcomes, including failure of an implant-supported crown, only one author has determined a failure threshold. On the basis of objective indices, esthetic failures in implant dentistry can be categorized as pink-tissue failures and white-tissue failures. This article discusses esthetic failures, the factors involved in these failures, and their prevention and treatment.

'The last post?': assessment of the failing post-retained crown.

Failure of a post-retained restoration can provide a challenge to the general dental practitioner (GDP) in terms of diagnosis, treatment planning and communication with the patient. The cause of failure must be identified, and a thorough assessment of the restoration, remaining tooth and its functional and aesthetic demands carried out in order to plan treatment to provide the most reliable result. Clinical Relevance: This article discusses the assessment of failing post-retained crowns, with discussion of reasons for failure, thereby assisting the GDP in decision-making and treatment planning for such teeth.

Making sense of complication reporting associated with fixed dental prostheses.

The current reporting of complications associated with FDPs is inadequate and misleading. Complications,which incur significant monetary costs, will particularly impact the perceived value (worth or importance)that patients derive from their prostheses.Effective documentation of complications should include type (biologic and technical), incidence, and severity. The fiscal burden of treatment should be quantified. Comparisons of different restorative materials,techniques, and procedures should be meaningful.Data collated prospectively or retrospectively and pooled over time should allow for comparisons within and between different practice settings. The proposed classification, based on the fiscal consequences of complications, achieves these objectives.Effective documentation of complications in conjunction with actual or projected survival data and personal clinical experience will enable clinicians to provide realistic information of the expected clinical service of dental prostheses.

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.

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.

Evaluation of 3- to 8-year treatment outcomes and success rates with 6 implant brands in partially edentulous patients.

The use of osseointegrated implants as a foundation for the prosthetic replacement of missing teeth has become widespread, with new dental implant systems being introduced every year. There is growing interest in identifying the factors associated with implant failure, such as implant type. This study was designed to establish the relationship between implant type and success. Eighty-eight patients (mean age, 52 years) with 268 implants (110 BioHorizons, 60 ITI, 60 Paragon, 18 Xive, six 3i, and 19 Allfit) participated in this 5-year retrospective study. Statistical significance was defined for P < .05. Peri-implant probing depth was associated with bone loss and bleeding on probing. Implant failure was not associated with implant brand. Maximal (or minimal) peri-implant probing depth and bone loss values were seen at anterior regions (or premolars). Maximal (or minimal) bleeding on probing was seen at the posterior (or anterior) region. No significant differences were observed between the different systems in terms of implant failure.

Influence of etiologic factors in peri-implantitis: literature review and case report.

Peri-implantitis is a pathology that has been described in many clinical studies and case reports. However, it is still not clear how the roles of its etiologic agents work. This article is based on a review of the literature and a case report. It aims to offer data related to the factors that cause this pathology, and to analyze how these factors interact, leading to the contamination of the peri-implant tissue.

Standardizing failure, success, and survival decisions in clinical studies of ceramic and metal-ceramic fixed dental prostheses.

UNLABELLED: The recent increase in reports from clinical studies of ceramic chipping has raised the question of which criteria should constitute success or failure of total-ceramic prostheses. Terminologies such as minor chipping [1], partial chipping, technical complications [2,3], and biological complications have crept into the dental terminology and they have complicated our classification of success and failure of these crown and bridge restorations. Some journals have permitted the reporting of fractures as "complications" and they are not necessarily classified as failures in the study. One study has attempted to classify chipping fractures according to their severity and subsequent treatment [4]. This is a promising approach to resolve the challenges to the classification of chipping fracture. The term 'chipping fracture' is more descriptive than 'chipping' since the latter term tends to imply an event of minor consequence. Two types of statistics are reported routinely in these studies, i.e., percent success, which is a measure of restorations that survive without any adverse effects, and percent survival, which is a measure of all restorations that survive even though they may have exhibited chipping fracture or they may have been repaired. Why has this scenario occurred? One possible explanation is that many of these types of fractures are very small and do not affect function or esthetics. Another reason is that corporate sponsors prefer to use the term chipping since it does not connote failure in the sense that the term fracture does. In any event, we need to be more precise in our scientific observations of fracture and classifications of the various types of fracture including details on the location of fracture and the prosthesis design configuration. Because of the lack of standardized methods for describing chipping fractures, materials scientists are unable to properly analyze the effect of material properties and design factors on the time-dependent survival probability of ceramic fixed dental prostheses (FDPs). Based on the review of clinical trials and systematic reviews of these trials, the present study was designed to develop guidelines for classifying the functional performance, success, survival, and susceptibility to chipping fracture, and subsequent treatment of ceramic and metal-ceramic restorations. OBJECTIVE: To develop comprehensive descriptive guidelines and a clinical reporting form to assist dental scientists in their analyses of chipping fracture behavior of metal-ceramic and all-ceramic prostheses with particular emphasis on veneered-zirconia restorations. These guidelines are required to optimize the recording of fracture features that can be used to differentiate ceramic chipping fracture from bulk fracture and to assist dentists in identifying subsequent treatment that may minimize the need to replace affected restorations. A recording form for clinical fracture observations must be sufficiently clear and complete so that dental health professionals can translate the most relevant information in a context that allows their patients to fully understand the potential risks and benefits of treatment with ceramic restorations. It should clearly allow a clinician to determine whether or not a ceramic fracture constitutes a failure, which requires replacement of the prosthesis, or whether the fracture surface is relatively small or located in a nonfunctional area, i.e., one that is not contribute to occlusion, esthetics, proximal contacts, or food impaction. To accomplish this task, a review of the relevant publications of clinical trials was necessary to identify the variability in reporting of fracture events. The reviews were focused on clinical research studies of zirconia-based FDPs and PFM FDPs, which had been monitored through recall exams for three years or more. These reports and systematic reviews of all relevant publications were published in English dental journals between 2004 and 2010.The primary focus in this review was on the susceptibility to chipping fracture or bulk fracture of veneered zirconia-based fixed dental prostheses (FDPs) and metal-ceramic FDPs, which are also referred to in this paper as porcelain-fused-to-metal (PFM) FDPs.

Failures in implants.

The burning problem that all the implantologists are confronted today is the complications and failures occurring with the treatment of osseointegrated implants. To further optimize the treatment outcome, etiologies and factors associated with implant failures should be elucidated. Conceivably such knowledge is needed for developing adequate treatment and prevention strategies. Hence, this paper is intended to provide an insight regarding various aspects of failures that affect dental implants.