Fracture resistance and bonding performance after antioxidants pre-treatment in non-vital and bleached teeth

Abstract This study aimed to evaluate the effect of antioxidant solutions on fracture strength and bonding performance in non-vital and bleached (38% hydrogen peroxide) teeth. One hundred and eighty dentin specimens were obtained, 60 for each test: fracture strength, hybrid layer thickness, and bond strength. The groups (n=10) were randomly composed according to post-bleaching protocol: REST - restoration, without bleaching; BL - bleaching + restoration; SA - bleaching, 10% sodium ascorbate solution, and restoration; AT - bleaching, 10% α-tocopherol solution, and restoration; CRAN - bleaching, 5% cranberry solution, and restoration; CAP - bleaching, 0.0025% capsaicin solution, and restoration. Data were analyzed with ANOVA, Kruskal-Wallis, Dunn, and Qui-Square tests (α=0.05). The highest fracture strength values were observed in REST (1508.96 ±148.15 N), without significant difference for the bleached groups (p>0.05), regardless of the antioxidant use. The hybrid layer thickness in the group that was not subjected to bleaching (REST) was significantly higher than in any other group. The bond strength in the bleached and antioxidants-treated groups (SA, AT, CRAN, CAP) has no differences with the bleached group without antioxidants (BL). Adhesive failures were predominant in the groups that did not receive the antioxidant application. In conclusion, the evaluated antioxidants did not show an effect on the fracture strength, hybrid layer thickness, or bond strength of dentin bleached after endodontic treatment. The application of 10% sodium ascorbate, 10% alpha-tocopherol, 5% cranberry, or 0.0025% capsaicin solutions is not an effective step and should not be considered for the restorative protocols after non-vital bleaching.

Resumo Este estudo teve como objetivo avaliar o efeito de soluções antioxidantes na resistência à fratura e resistência de união em dentes tratados endodonticamente e clareados (38% de peróxido de hidrogênio). Cento e oitenta espécimes de dentina foram obtidos, 60 para cada teste: resistência à fratura, espessura da camada híbrida e resistência de união. Os grupos (n=10) foram compostos aleatoriamente de acordo com o protocolo pós-clareamento: REST - restauração, sem clareamento; BL - clareamento + restauração; SA - clareamento, solução de ascorbato de sódio a 10% e restauração; AT - clareamento, solução de α-tocoferol a 10% e restauração; CRAN - clareamento, solução de cranberry a 5% e restauração; CAP - clareamento, solução de capsaicina 0,0025% e restauração. Os dados foram analisados ​​com os testes ANOVA, Kruskal-Wallis, Dunn e Qui-Quadrado (α=0,05). Os maiores valores de resistência à fratura foram observados em REST (1508,96 ±148,15 N), sem diferença significativa para os grupos clareados (p>0,05), independente do uso de antioxidantes. A espessura da camada híbrida no grupo que não foi submetido ao clareamento (REST) foi significativamente maior do que em qualquer outro grupo. A resistência de união nos grupos clareado e tratado com antioxidantes (SA, AT, CRAN, CAP) não apresentou diferenças com o grupo branqueado sem antioxidantes (BL). As falhas adesivas foram predominantes nos grupos que não receberam a aplicação do antioxidante. Em conclusão, os antioxidantes avaliados não mostraram efeito sobre a resistência à fratura, espessura da camada híbrida ou resistência de união à dentina clareada após tratamento endodôntico. A aplicação de soluções de ascorbato de sódio 10%, alfa-tocoferol 10%, cranberry 5% ou capsaicina 0,0025% não é uma etapa eficaz e não deve ser considerada para os protocolos restauradores após clareamento não vital.

In Vitro Comparative Study Of The Influence Of Instrument Taper On The Fracture Resistance Of Endodontically Treated Teeth

Context: Preparation of the root canal system is recognized as being one of the most important stages in root canal treatment which removes organic debris and microorganisms from the root canal system by means of chemico- mechanical preparation and irrigation of the canals. The use of nickel-titanium instruments has drastically reduced the time and the difficulties that were encountered with traditional hand instruments made up of stainless steel. Utilizing properties of super-elasticity, shape memory and different tapers of these instruments reduces not only the possibility of canal transportation but also affects both the geometry and volume of root canals. This subjects the root dentin to stress and consequently dentinal defects which increases the risk of root fracture during or after root canal treatment. Clinicians now have the opportunity to choose from differently tapered instruments having unique characteristics in their geometry and metallurgy. These are progressively tapered instruments, fixed tapered instruments, and variable tapered instruments, which come with the benefit of conforming to the root canal anatomy as well as removing dentin as little as possible while cleaning and shaping. The aim of this study was to examine the influence of instrument taperAim: on the fracture resistance of endodontically treated roots under in vitro experimental conditions.Conclusion: Under the limitations of this study in in-vitro conditions there were no significant differences between the fracture loads between the different file systems used, however samples prepared with Hyflex EDM recorded the highest fracture resistance, followed by ProTaper NEXT, ProTaper Gold and NeoEndo Flex respectively.

Biomechanical and chemical behavior of various bioactive materials in class II restorations / Desempeño biomecánico y químico de diferentes materiales bioactivos en restauraciones clase II

The aim of this in vitro study was to evaluate the biomechanical and chemical behavior of various bioactive materials in class II MOD restorations. Forty- eight standardized class II MOD cavities were prepared in sound extracted human molar teeth. The specimens were divided into four groups according to the restorative material: Group 1 (Filtek™ Z350 XT), Group 2 (Biodentine™ as a liner, and then restored with Filtek™ Z350 XT), Group 3 (Cention N™), and Group 4 (Activa™ Bioactive-Restorative). The samples were tested for fracture resistance by subjecting them to a compressive load in a Universal testing Machine. The failure modes of each specimen were evaluated. The alkalinizing potential and calcium ion release of the materials were measured. SEM-EDAX analyses were also performed for all materials. Data were analyzed using ANOVA and post hoc Tukey test (p<0.05). Group 1 showed the higher fracture resistance (p<0.05). Group 3 had greater fracture resistance values but no statistical difference from Group 4. Biodentine™ showed greater biomineralization potential. Class II MOD restorations of Group 1 displayed the higher fracture resistance; however, it was highly associated with catastrophic failure. Conversely, Biodentine™ presented a more significant bioactivity potential, and its use, as in Group 2, promoted the most favorable failure mode.

El objetivo de este estudio, in vitro, fue evaluar el desempeño biomecánico y químico de varios materiales bioactivos en restauraciones clase II MOD. Se prepararon cuarenta y ocho cavidades clase II MOD estandarizadas en dientes molares humanos extraídos. Las muestras se dividieron en cuatro grupos según el material de restauración: Grupo 1 (Filtek™ Z350 XT), Grupo 2 (Biodentine™ como base y luego restaurado con Filtek™ Z350 XT), Grupo 3 (Cention N™) y Grupo 4 (Activa™ Bioactivo-Reparador). La prueba de resistencia a la fractura fue realizada en una máquina de ensayo universal Instron. Se evaluaron los modos de falla de cada espécimen. Se midió el pH y la liberación de iones de calcio de los materiales. Se realizaron análisis SEM-EDAX. Los datos se analizaron mediante ANOVA y la prueba post hoc de Tukey (p<0,05). El grupo 1 mostró la mayor resistencia a la fractura (p<0,05). El Grupo 3 tuvo mayores valores de resistencia a la fractura que el Grupo 4, pero sin diferencia estadística. Biodentine™ mostró un mayor potencial de biomineralización. Las restauraciones Clase II MOD del Grupo 1 mostraron la mayor resistencia a la fractura; sin embargo, estuvo altamente asociado con fallas irreparables. Por el contrario, Biodentine™ presentó un potencial de bioactividad más significativo y su uso, como en el Grupo 2, promovió el modo de falla más favorable.

Comparison of Fracture Resistance of Simulated Immature Teeth Using Four Different Commercially Available Apexification Materials ? An invitro Study

Introduction: The aim of this study was to compare the fracture resistance of simulated immature teeth using four different apical plug materials, i.e. Pro? Root MTA, Neo? MTA Plus, Biodentine, and Bioactive Glass. Materials and Methods: 80 extracted human maxillary anterior teeth were divided into 4 groups for this study. They were prepared using Peeso reamers to simulate immature teeth and to mimic Cvek’s stage 3 of root development. A 5 mm apical barrier was placed using different materials. The remaining canal was obturated using gutta?percha and AH plus sealer. The final samples were stored at 37°C and 100% humidity for 4 weeks. Fracture resistance of the teeth was measured in Newtons using a universal testing machine. The comparison of fracture resistance between the four groups was done using Kruskal Walis ANOVA followed by post hoc Mann Whitney U test for pairwise comparison. Results: Biodentine group showed the highest fracture resistance as compared to the other three groups and the difference was highly significant (P < 0.001). Conclusions: Biodentine can be advocated over MTA as an effective material for the management of teeth with wide open apex. Bioactive glass also has shown promising results in increasing the fracture resistance of simulated immature teeth.

Comparison of Fracture Resistance of Endodontically Treated Teeth Restored with Different Aesthetic Post and Core Systems Under All Ceramic Restoration Luted with Two Types of Cements

Context: Fracture of endodontically treated teeth is a grave sequela that a clinician should seriously ponder. Suitable selection of restorative materials is a requisite for long?term clinical success. Aims: To compare the fracture resistance of endodontically treated teeth restored with three different posts luted using two different cements under all ceramic crowns. Settings and Design: This in vitro study was conducted in the Department of Prosthodontics, Government Dental College, Kottayam, Kerala, India. Methods and Material: Thirty endodontically treated single?rooted mandibular premolars in which post spaces were prepared and divided into three different groups. Group 1 (n = 10): zirconia post group. Group 2 (n = 10): quartz fibre post group. Group 3 (n = 10): glass fibre post group. Each group is sub?divided into two based on the luting system: resin?modified glass ionomer cement (RMGIC) or dual?cure resin cement (DCRC). The fracture resistance testing was performed in a universal testing machine with a crosshead speed of 0.5 mm/min. Statistical Analysis Used: The mean fracture resistance were analysed using independent sample Student t?test and one?way ANOVA. Results: Within the zirconia post group, the mean fracture resistance was higher in DCRC sub?group compared to the RMGIC sub?group and the difference was statistically significant (p = 0.017). The difference in fracture resistance between three different post systems was not found to be statistically significant with respect to both the luting systems. Conclusions: It was observed that when zirconia post is used, the mean fracture resistance was higher in dual?cure resin group compared to the resin?modified GIC group.

Fracture resistance of pressed ZLS crowns versus pressed LD crowns under thermo-mechanical cycling

Resumo Este estudo teve como objetivo avaliar a resistência à fractura do silicato de lítio reforçado com zircônio todo o material cerâmico "Celtra Press" em comparação com um "IPS e-max Press" em condições orais simuladas. Quatorze coroas cerâmicas foram fabricadas em moldes epóxi que foram duplicados a partir de moldes principais de aço inoxidável e divididos em dois grupos iguais (n=7) de acordo com o material de construção; Grupo A: Coroas fabricadas com material IPS e-max Press e Grupo B: Coroas fabricadas com material Celtra Press. As coroas foram então cimentadas nos seus moldes correspondentes com um cimento de resina auto-adesivo e submetidas a ciclos térmicos e cargas cíclicas. Em seguida, foram carregadas para fraturar numa máquina universal de ensaios. Os resultados foram tabulados e analisados estatisticamente utilizando os testes Kolmogorov-Smirnov e Shapiro-Wilk. O teste t de Student usado para comparar os valores médios. O nível de significância foi fixado em P ≤ 0,05 e intervalo de confiança de 95%. A análise estatística foi realizada utilizando o software Graph Pad Instat (Graph Pad, Inc.) para Windows. Os valores médios ± SD da resistência à fractura foram registados para o grupo Disilicate de lítio (1706,01 ±154,32 N) enquanto que os valores médios ± SD registados com o grupo celtra foram (1550,67±196,71 N). As coroas cerâmicas de silicato de lítio reforçado com zircónio produziram valores de resistência à fractura comparáveis aos das coroas cerâmicas de dissilicato de lítio e ambos os materiais testados estão dentro dos valores clinicamente aceitáveis na área posterior.

Abstract The aim of this study was conducted to assess the fracture resistance of zirconia reinforced lithium silicate all ceramic material "Celtra Press" compared to lithium disilicate one "IPS e-max Press" under simulated oral conditions. Fourteen ceramic crowns were fabricated on epoxy dies which were duplicated from stainless steel master die and divided into two equal groups (n=7) according to the material of construction; Group A: Crowns fabricated with IPS e-max Press material and Group B: Crowns fabricated with Celtra Press material. The crowns were then cemented onto their corresponding dies with a self-adhesive resin cement and subjected to thermocycling and cyclic loading. Then they were loaded to fractur in a universal testing machine. The results were tabulated and statistically analyzed using Kolmogorov-Smirnov and Shapiro-Wilk tests. Student t-test used to compare mean values. The significance level was set at P ≤ 0.05 and 95% Confidence interval. Statistical analysis was performed using Graph Pad Instat (Graph Pad, Inc.) software for windows. The mean ± SD values of fracture resistance were recorded for lithium Disilicate group (1706.01 ±154.32 N) meanwhile the mean ± SD value recorded with celtra group were (1550.67±196.71 N). Zirconia reinforced lithium silicate ceramic crowns produced comparable fracture resistance values to lithium disilicate ceramic crowns and both tested materials are within the clinically acceptable values in the posterior area.

Resinas acrílicas utilizadas em placas estabilizadoras: resistência a fraturas e ensaio microbiológico / Acrylic resins used in stabilizer plates: resistance to fractures and microbiological testing

O aprimoramento da tecnologia CAD/CAM permitiu a confecção de placas estabilizadoras digitais, no entanto, há lacunas acerca do comportamento desses dispositivos frente a variáveis mecânicas e biológicas ainda desconhecidas. Dessa forma, o objetivo desse trabalho foi verificar se as resinas utilizadas na tecnologia digital das placas fresadas e impressas são capazes de influenciar na resistência à fratura e na adesão de micro-organismos em detrimento das resinas empregadas na confecção das placas termopolimerizáveis convencionais e se as propriedades testadas se relacionam com a variação da espessura desses dispositivos. Para tanto, foi realizado um estudo in vitro que contou com as fases mecânica e microbiológica, sendo cada uma composta pelos grupos Convencional (GC) (n=30), Fresado (GF) (n=30) e Impresso (GI) (n=30), de acordo com o método de confecção, possuindo cada um três subgrupos (n=10) que variaram a espessura dos espécimes de 1 a 3 mm. Na fase mecânica, as amostras, com formato de barras de 65 mm, foram testadas quanto à resistência à fratura na máquina de ensaios universal, com célula de carga de 500 kgf e velocidade de 1 mm/min; na microbiológica, a forma foi de discos com 15 mm de diâmetro, submetidos à adesão de micro-organismos à superfície com a exposição a Streptococcus mutans e mantidos por 24h a 35 °C em estufa para sucessiva contagem de UFC, com controle positivo. Os testes foram feitos em triplicata e os dados foram armazenados no SPSS 22.0 e a análise estatística contou com a ANOVA e o pósteste de Tukey. Nos resultados da fase mecânica, o ANOVA identificou diferenças estatisticamente significativas entre os grupos (p≤0,005), mostrando que GC e GF apresentaram melhores resultados. O pós-teste de Tukey considerou diferença estatisticamente significativa entre GF e GI (p=0,031), elencando GF como superior. Para a fase microbiológica, não foram verificadas diferenças estatísticas entre os grupos (p>0,005) em nenhuma das análises. Observou-se que para a resistência a fraturas, as resinas do modo fresado descreveram resultados superiores e/ou próximos aos da técnica convencional; e que as resinas da técnica digital e convencional, quanto à adesão superficial de micro-organismos, não diferiram entre si (AU).

CAD/CAM technology allowed the stabilizing splints manufacture, however there are gaps about these devices' behavior in face of mechanical and biological variables that are still unknown. Thus, the objective of this project was to verify if the resins used in digital technology of milled and printed stabilizer splints can influence fracture resistance and microorganism adhesion, in detriment of the resin applied in manufacture of conventional thermopolymerizable splints and if the tested properties are related to thickness variation of these devices. The method included mechanical and microbiological steps, each one composed by Conventional (CG) (n=30), Milled (MG) (n=30) and Printed (PG) (n=30) groups, according to the method of preparation, each one having three subgroups (n=10) that varied the specimen thickness from 1 to 3 mm. In the mechanical step, the samples, in the form of 65 mm bars, were tested for fracture resistance in a universal testing machine, with load cell of 500 kgf and speed of 1 mm/min; in the microbiological step, the shape was in form of 15 mm diameter discs, subjected to microorganism adhesion to the surface with exposure to Streptococcus mutans and kept for 24 hours at 35 °C in oven for successive CFU counting, with positive control. The tests were performed in triplicate and data were stored in SPSS 22.0 and statistical analysis used ANOVA and Tukey's post hoc. In the results of mechanical step ANOVA had identified statistically significant differences between the groups (p≤0,005), showing CG and MG had presented better results. Tukey´s post hoc had considered statistically significant difference between MG and PG (p=0,031), listing MG as superior. For the microbiological step, they did not show statistical differences between the groups (p>0.005) in any analysis. It was observed milled resins described superior results and/or close to the conventional technique one, for fracture resistance; and resins of digital and conventional technique, regarding the microorganism adhesion to the surface, did not differ from each other (AU).

Transfixação horizontal de pino de fibra de vidro em um dente tratado endodonticamente: relato de caso clínico / Horizontal transfixion of a fiberglass post into an endodontically treated tooth: a clinical case report

O objetivo deste relato de caso foi descrever em detalhes a técnica de transfixação de pino de fibra de vidro no sentido horizontal e restauração de resina composta em um dente molar tratado endodonticamete. Paciente, sexo feminino, 51 anos de idade, buscou o Centro Universitário da Serra Gaúcha (FSG ­ Caxias do Sul ­ Rio Grande do Sul) com a necessidade de realizar tratamento endodôntico do elemento molar número 26. Após a avaliação inicial, foi realizada a endodontia. O elemento havia pouca sustentação das paredes vestibular e palatina, então foi proposto a colocação de pino intrarradicular seguido de coroa, entretanto, por questões financeiras a paciente não aceitou. Logo, foi proposto a técnica de transfixação horizontal de pino de fibra de vidro associado a uma restauração de resina composta de forma direta. O procedimento foi realizado em sessão única e foi utilizado um pino de fibra de vidro número 1 disposto transversalmente entre as paredes mesiopalatina e distovestibular. A restauração foi realizada com resina composta Filtek Z350, devolvendo estética e função ao elemento dentário. Pode-se concluir que a técnica de transfixação horizontal de pino de fibra de vidro associado à resina composta é uma alternativa restauradora que possibilita maior resistência aos dentes tratados endodonticamente, apresenta resultados funcionais e estéticos satisfatórios, além de possibilitar uma maior sobrevida aos mesmos(AU)

The purpose of this case report was to describe in detail the technique of horizontal transfixion of a fiberglass post into an endodontically treated tooth. Female patient, 51 years old, sought the University Center of Serra Gaúcha (FSG - Caxias do Sul ­ Rio Grande do Sul) with the need to perform the endodontic treatment of molar element number 26. After the initial evaluation, endodontics was performed. The element had little support for the buccal and palatal walls, so an intraradicular postplacement followed by a crown was proposed, for financial reasons the patient did not accept it. Therefore, the technique of horizontal transfixion of a fiberglass pin was proposed, associated with a restoration of direct composite resin. The procedure was performed in a single session and a number 1 fiberglass post was fixed crosswise between the mesiopalatal and distobuccal walls. The restoration was carried out with composite resin Filtek Z350, restoring aesthetics and function. It can be concluded that the horizontal transfixion of a fiberglass post associated with composite resin technique is a restorative alternative that allows greater resistance to endodontically treated teeth, provides satisfactory esthetics and better survival rates(AU)

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.

Effects of the resin base and retention depth on fracture resistance of molars restored with nano-ceramic endocrowns / 北京大学学报(医学版)

OBJECTIVE@#To compare the effects of resin base and different retention depth on the fracture resistance of mandibular molars restored with nano-ceramic endocrowns.@*METHODS@#Forty mandibular molars selected and randomly divided into 5 groups: ① The control group which was consisted of intact teeth, ② the non-resin base group, ③ the 2 mm retention depth group, ④ the 3 mm retention depth group, ⑤ the 4 mm retention depth group, respectively. After tooth preparation, in vitro root canal therapy was conducted, which was followed by endocrown design, production and adhesive of groups ②-⑤. All the samples were under load (N) of the universal mechanical testing machine after embedding. The fracture pattern of each sample was observed under stereomicroscope. Then the microstructure of the fracture surface was observed by scanning electron microscopy.@*RESULTS@#The fracture loads of each group were respectively: the control group fracture load was (3 069.34±939.50) N; experimental groups: fracture load of (2 438.04±774.40) N for the group without resin base; fracture load of (3 537.18±763.65) N for the group with 2 mm retention depth. The fracture load of the retention depth 3 mm group was (2 331.55±766.39) N; the fracture load of the retention depth 4 mm group was (2 786.98±709.24) N. There was statistical significance in the effect of resin base and different retention depth on the fracture loads of molars restored with nano-ceramic endocrown (P < 0.05). Repairable fractures in each group were as follows: control group 2/8, non-resin base group 1/8, retention depth of 2 mm group 1/8, retention depth of 3 mm group 2/8, and retention depth of 4 mm group 0/8. The effects of the retention depth and the presence of resin base on the fracture resistance of the resin nano-ceramic endocrowns were statistically significant (P < 0.05). Scanning electron microscopy showed more arrest lines and small twist hackles on the fracture surface of the restorations with resin base (retention depths of 2 mm, 3 mm, and 4 mm), with cracks extending towards the root. In addition to the characteristics above, more transverse cracks parallel to the occlusal surface, pointing outwards from the center of the pulp cavity retention, were also observed on the fracture surface of the non-resin base restorations.@*CONCLUSION@#When molar teeth with nano-ceramic endocrowns are restored, resin base and the retention depth of 2 mm help the teeth to obtain optimal fracture strength.

Influência da férula na resistência à fratura de restaurações com utilização ou não de retentores intrarradiculares em dentes tratados endodonticamente: uma revisão da literatura / Influence of the ferrule on the fracture resistance of restorations with or without the use of intraradicular posts in endodontically treated teeth: a literature review

Objetivo: realizar uma revisão de literatura narrativa sobre a importância e a influência do efeito férula na resistência à fratura de restaurações em dentes tratados endodonticamente com utilização ou não de retentores intrarradiculares. Metodologia: Foram utilizados os seguintes descritores indexados no DeCS (Descritores em Ciências da Saúde): "Férula", Prótese Dentária", "Falha da Restauração Dentária", "Técnica de Retentor Intrarradicular" e "Pinos de Retenção Dentária" para busca nas bases de dados PubMed, Embase, Lilacs, Web of Science, Scopus e Cochrane Library. Resultados: Os dados da maioria dos estudos in vitro ou in vivo incluídos nesta revisão sugerem o uso da férula para aumento da resistência à fratura e longevidade dos dentes tratados endodonticamente. Tem sido recomendada a confecção de uma férula com altura uniforme de 2 mm e espessura superior a 1,5 mm. Conclusão: O uso de retentores radiculares foi indicado pela maioria dos trabalhos, sendo geralmente recomendados os pinos de fibra de vidro ao invés de núcleos metálicos fundidos para minimizar os riscos de fratura radicular em razão do módulo de elasticidade semelhante à dentina, além de possibilidade de retratamentos em casos de falhas adesivas. Apesar disso, ainda são necessários estudos clínicos com acompanhamento a longo prazo para avaliar a longevidade das restaurações de dentes tratados endodonticamente utilizando pinos de fibra de vidro sem ou com a presença de férula em diferentes espessuras e alturas.

Objective: This study aimed to conduct a narrative literature review on the importance and influence of the ferrule effect on the fracture resistance of restorations in endodon-tically treated teeth with or without the use of intraradicular posts. Methodology: The following descriptors indexed in the DeCS (Health Sciences Descriptors) were used: "Ferrule", Dental Prosthesis", "Dental Restoration Failure", "Post and Core Technique", and "Dental Posts", to search on the databases of PubMed, Embase, Lilacs, Web of Science, Scopus, and Cochrane Library data. Results: Data from most of the in vitro or in vivo studies included in this review suggest the use of the ferrule to increase fracture resistance and longevity of endodontically treated teeth. It has been recommended to make a ferrule with a uniform height of 2 mm and a thickness greater than 1.5 mm. Conclusion: The use of intraradicular posts was indicated by most studies, and fiberglass posts are generally recommended instead of cast metal cores to minimize the risk of root fracture due to the modulus of elasticity similar to dentin, in addition to the possibility of retreatments in ad-hesive failure cases. Despite this, clinical studies with a long-term follow-up are essential to evaluating the longevity of restorations of endodontically treated teeth using fiberglass posts without or with the presence of ferrule in different thicknesses and heights.

Effect of preconditioning the fractured coronal fragments with remineralizing agents on fracture resistance of re-attached teeth

Background: Fragment re-attachment has been considered as one of the treatment modalities for the management of fractured anterior teeth. Hydration of fractured fragments aids in inhibiting the loss of ions and maintains vitality and esthetics. Aim: The study aimed to evaluate the effect of preconditioning the fractured fragments with remineralizing agents on fracture resistance of re-attached teeth. Settings and Design: This was an in vitro study. Materials and Methods: Sixty freshly extracted noncarious human permanent maxillary central and lateral incisors were randomly allocated into three Groups of 20 each: Group 1: 2% sodium fluoride (2%NaF), Group 2: casein phosphopeptide–amorphous calcium phosphate (CPP-ACP), and Group 3: self-assembling peptide P11-4 (SAP). These were further divided into two subgroups of 10 teeth each, based on contact time with remineralizing agents, i.e., 30 min and 2 h. Fractured fragments were treated with remineralizing agents for a specified contact time and then re-attached with flowable composite resin. Force required to fracture the re-attached tooth was recorded in Newtons using universal testing machine. Statistical Analysis: Unpaired t-test, one-way analysis of variance test, and post hoc Tukey test were used for the statistical analysis. Results: A higher fracture resistance was noticed in fragments treated with 2% NaF (30 min- 215.6 N, 2 h- 188.5 N) compared to CPP-ACP (30 min- 141.3 N, 2 h- 111.1 N) and SAP (30 min- 134.8 N, 2 h- 149.5 N). At 30 min interval, it was found to be more in 2% NaF and CPP-ACP groups compared to 2 h. However, it increased with time in the SAP group. A statistically significant difference was found between the groups at both time intervals (P = 0.007 and 0.017). Conclusion: Preconditioning of fractured coronal fragments with 2% NaF showed higher fracture resistance compared to CPP-ACP and self-assembling peptide P11-4. Samples treated with SAP P11-4 exhibited good fracture resistance at 2 h contact time.

Fracture Resistance of Teeth Restored with Bulk-Fill and Fiber-Reinforced Composites in Class II Cavities / Resistencia a la fractura de dientes restaurados con resinas de relleno y resinas reforzadas con fibra en cavidades clase II

ABSTRACT: This study aimed to evaluate the fracture resistance of teeth restored with conventional, bulk-fill, and fiber-reinforced composite materials regarding intact teeth. Standard cavities were prepared on 70 sound third molar teeth. The teeth were randomly divided into six groups: intact teeth, conventional Bis-GMA based composite, fiber-reinforced composite, Bis-GMA based bulk-fill composite, ormocer based bulk-fill composite, glass containing resin-based bulk-fill composite. The data was obtained by a Universal Testing Machine and analyzed statistically. Fracture resistance of the teeth restored with conventional composite was significantly lower than the other groups (p0.05). The obtained data showed that restoring teeth with bulk-fill and fiber-reinforced composites could be recommended in Class II cavities.

RESUMEN: El objetivo del presente estudio fue evaluar la resistencia a la fractura de los dientes restaurados con materiales compuestos convencionales, de relleno y reforzados con fibras, en relación con los dientes intactos. Se prepararon cavidades estándar en 70 dientes de terceros molares sanos. Los dientes se dividieron al azar en seis grupos: dientes intactos, compuesto convencional basado en Bis-GMA, compuesto reforzado con fibra, compuesto de relleno a base de Bis-GMA, compuesto de relleno a base de ormocer, compuesto de relleno a base de vidrio que contiene resina. Los resultados fueron obtenidos utilizando una máquina universal de pruebas y analizados estadísticamente. La resistencia a la fractura de los dientes restaurados con el composite convencional fue significativamente menor que la de los otros grupos (p0,05). Los datos obtenidos mostraron que la restauración de dientes con composites de relleno y reforzados con fibra podría ser recomendada en cavidades de Clase II.

Fracture resistance of simulated immature teeth reinforced with different mineral aggregate-based materials

Abstract This study assessed the fracture resistance of simulated immature teeth reinforced with calcium aluminate cement (CAC) or mineral trioxide aggregate (MTA) containing calcium carbonate nanoparticles (nano-CaCO3). The microstructural arrangement of the cements and their chemical constitution were also evaluated. Forty-eight canines simulating immature teeth were distributed into 6 groups (n=8): Negative control - no apical plug or root canal filling; CAC - apical plug with CAC; CAC/nano-CaCO3 - apical plug with CAC+5% nano-CaCO3; MTA - apical plug with MTA; MTA/nano-CaCO3 - apical plug with MTA+5% nano-CaCO3; and Positive control - root canal filling with MTA. The fracture resistance was evaluated in a universal testing machine. Samples of the cements were analyzed under Scanning Electron Microscope (SEM) to determine their microstructural arrangement. Chemical analysis of the cements was performed by Energy Dispersive X-ray Spectroscopy (EDS). The fracture resistance of CAC/nano-CaCO3 was significantly higher than the negative control (p<0.05). There was no significant difference among the other groups (p>0.05). Both cements had a more regular microstructure with the addition of nano-CaCO3. MTA samples had more calcium available in soluble forms than CAC. The addition of nano-CaCO3 to CAC increased the fracture resistance of teeth in comparison with the non-reinforced teeth. The microstructure of both cements containing nano-CaCO3 was similar, with a more homogeneous distribution of lamellar- and prismatic-shaped crystals. MTA had more calcium available in soluble forms than CAC.

Resumo Este estudo avaliou a resistência à fratura de dentes imaturos simulados reforçados com cimento de aluminato de cálcio (CAC) ou trióxido agregado mineral (MTA) contendo nanopartículas de carbonato de cálcio (nano-CaCO3). O arranjo microestrutural dos cimentos e sua constituição química também foram avaliados. Quarenta e oito caninos simulando dentes imaturos foram distribuídos em 6 grupos (n=8): Controle negativo - sem plug apical ou obturação do canal radicular; CAC - plug apical com CAC; CAC/nano-CaCO3 - plug apical com CAC + 5% nano-CaCO3; MTA - plug apical com MTA; MTA/nano-CaCO3 - plug apical com MTA + 5% nano-CaCO3; e Controle positivo - obturação dos canais radiculares com MTA. A resistência à fratura foi avaliada em máquina universal de ensaios. Amostras dos cimentos foram analisadas em Microscópio Eletrônico de Varredura (MEV) para determinar seu arranjo microestrutural. A análise química dos cimentos foi realizada por Espectroscopia de Energia Dispersiva de Raio-X (EDS). A resistência à fratura de CAC/nano-CaCO3 foi significativamente maior do que o controle negativo (p<0,05). Não houve diferença significativa entre os outros grupos (p>0,05). Ambos os cimentos apresentaram microestrutura mais regular com a adição de nano-CaCO3. As amostras de MTA apresentaram mais cálcio disponível em formas solúveis do que CAC. A adição de nano-CaCO3 ao CAC aumentou a resistência à fratura dos dentes em comparação aos dentes não reforçados. A microestrutura de ambos os cimentos contendo nano-CaCO3 foi semelhante, com uma distribuição mais homogênea de cristais de formato lamelar e prismático. MTA apresentou mais cálcio disponível nas formas solúveis do que CAC.

Fracture Resistance of Anterior CAD/CAM Nanoceramic Resin Endocrowns with Different Preparation Designs / Resistência à Fratura de Endocrowns de Resina Nanocerâmica CAD / CAM Anterior Com Diferentes Projetos de Preparação

Objective: The aim of the study was to evaluate the effect of extension of endocrown in pulp space and the effect of ferrule on the fracture resistance of anterior endocrowns made of nano-ceramic resin blocks. Material and Methods: Twenty-eight freshly extracted human upper central incisor teeth were prepared to receive CAD/CAM nanoceramic resin endocrowns with four different designs. The specimens were divided into two groups (n = 14) according to the extension of the endocrown inside root canal (A:short and B:long), then each group was further subdivided into another two subgroups (n = 7) according to the presence or absence of ferrule effect (1:ferrule and 2: no ferrule). Endocrowns were then fabricated using CEREC in lab and nanoceramic resin blocks (DENTSPLY Sirona, Germany) and LAVA ultimate (3M ESPE, Germany) blocks size 14L. Results: Two-way ANOVA showed that the ferrule (p > 0.0001) had statistically significant effect on the fracture resistance. However, the extension of the endocrown into the canal had no statistical significant effect on the fracture resistance (p = 0.837). The interactions between the independent variables (extension into the canal and ferrule) had statistically significant effect on the fracture resistance (p = 0.029). Load to fracture for group 1A was 439.53 N, 1B was 306.46 N, 2A was 516.29 N and 2B was 242.04 N. Conclusions: Fracture resistance was not improved by the long or short extensions of the endocrowns in the pulp space, however, the ferrule effect shows significant improvement of the fracture resistance of the nanoceramic resin endocrowns. (AU)

Objetivo: O objetivo deste estudo foi avaliar o efeito da extensão da coroa endocrown na câmara pulpar e o efeito férula na resistência à fratura de coroas endocrowns anteriores confeccionadas através de blocos de resina nanocerâmica. Material e Métodos: Vinte e oito dentes incisivos centrais superiores humanos recém-extraídos foram preparados para receber endocrowns de resina nanocerâmica CAD / CAM com quatro diferentes tipos de preparos. Os espécimes foram divididos em dois grupos (n = 14) de acordo com a extensão da endocrown dentro do canal radicular (A: curto e B: longo), então cada grupo foi subdividido em outros dois subgrupos (n = 7) de acordo com presença ou ausência do efeito férula (1: com férula e 2: sem férula). As endocrowns foram usinadas através do CEREC In Lab e blocos de resina nanocerâmica (DENTSPLY Sirona, Alemanha) e blocos de LAVA ultimate (3M ESPE, Alemanha) tamanho 14L. Resultados: ANOVA dois fatores demostrou que a férula (P> 0,0001) teve efeito estatisticamente significativo na resistência à fratura. No entanto, a extensão do endocrown no canal não teve efeito estatisticamente significativo na resistência à fratura (P = 0,837). As interações entre as variáveis independentes (extensão no canal e férula) tiveram efeito estatisticamente significativo na resistência à fratura (P = 0,029). A carga para fratura do grupo 1A foi de 439,53 N, 1B foi de 306,46 N, 2A foi de 516,29 N e 2B foi de 242,04 N. Conclusões: A resistência à fratura não foi melhorada pelas extensões longas ou curtas das endocrowns na câmara pulpar, no entanto, o efeito férula mostrou uma melhora significativa na resistência à fratura das coroas endocrowns de resina nanocerâmica (AU)

Effect of Thermo-Mechanical Aging and Repressing on Fracture Resistance of Lithium Disilicate Crowns / Efeito do envelhecimento termomecânico e reprensagem na resistência à fratura de coroas de dissilicato de lítio

Objective: The recycling of heat pressed lithium disilicate glass-ceramic leftover material has been reported to be done by dental laboratories. The effect of this procedure on the fracture resistance of single crowns is unknown, especially when it is functioning inside the oral cavity with subsequent exposure to temperature changes and cycles of mastication. Material and Methods: A total of 28 lithium disilicate glass-ceramic crowns (IPS emax Press) were constructed and randomly assigned into two groups (n = 14); Group (P): Included crowns fabricated from new e.max ingots. Group (R): Included crowns fabricated from repressed e.max buttons. Specimens of each group were divided into two equal subgroups (n = 7) according to whether the aging of specimens will be performed or not before fracture resistance testing. Subgroup (N), samples were subjected to fracture resistance without thermo-mechanical aging, while subgroup (A), samples were subjected to thermo-cycling and cyclic loading before being subjected to fracture strength testing. Different methods; SEM, XRD, EDAX were used to characterize the properties of lithium disilicate glass-ceramics before and after repressing. Results: The highest statistically significant fracture resistance value was recorded for the subgroup (RN) repressed/non-aged, followed by the subgroup repressed/aged (RA), while the lowest statistically significant mean value was recorded for the subgroup pressed/aged (PA). There was no significant difference between pressed/non-aged (PN) and repressed/aged (RA) subgroups. Conclusion: Repressing of leftover buttons may increase the fracture resistance of IPS emax Press crowns. Thermo-mechanical aging may negatively affect the fracture resistance of IPS emax Press crowns, yet Repressing may decrease this effect. Clinical implications:This is a novel approach that targets a point of research that has not been investigated before. It elaborates how repressing may decrease the effect of aging and increase the fracture resistance of lithium disilicate crowns. Thus, recycling of lithium disilicate glass ceramics might decrease its failure and prolong their serviceability (AU)

Objetivo: A reutilização de material residual de vitrocerâmicas de dissilicato de lítio prensadas a quente tem sido realizada pelos laboratórios de prótese. O efeito deste procedimento na resistência à fratura de coroas unitárias é desconhecido, especialmente quando estão em função na cavidade oral com subsequente exposição às variações de temperatura e ciclos mastigatórios. Material e Métodos: Vinte e oito coroas de dissilicato de lítio (IPS e.max Press) foram confeccionadas e divididas aleatoriamente em dois grupos (n = 14); Grupo (P): Incluiu coroas fabricadas de pastilhas novas de e.max; Grupo (R): Incluiu coroas fabricadas de e.max reprensado. As amostras de cada grupo foram divididas em dois subgrupos iguais (n = 7) de acordo com a realização de envelhecimento dos espécimes antes do teste de resistência à fratura. As amostras do subgrupo (N) foram submetidas ao teste de resistência à fratura sem envelhecimento termomecânico, enquanto as amostras do subgrupo (A) foram submetidas ao envelhecimento termomecânico antes do teste de resistência à fratura. Diferentes métodos (MEV, DRX e EDS) foram usados para caracterizar as propriedades da cerâmica de dissilicato de lítio antes e depois da reprensagem. Resultados: O maior valor de resistência à fratura estatisticamente significativo foi do subgrupo (RN) reprensado/não envelhecido, seguido pelo subgrupo reprensado/envelhecido (RA), enquanto o menor valor médio estatisticamente significativo foi do subgrupo prensado/envelhecido (PA). Não houve diferença estatística entre os subgrupos prensado/não envelhecido (PN) e reprensado/envelhecido (RA). Conclusão: A reprensagem de material residual pode aumentar a resistência à fratura de coroas de IPS e.max Press. O envelhecimento termomecânico pode afetar negativamente na resistência à fratura deste material, enquanto a reprensagem pode diminuir este efeito. Relevância clínica: Esta é uma nova abordagem que busca estudar um tema que não havia sido investigado anteriormente. Este estudo demonstrou como a reprensagem pode diminuir o efeito do envelhecimento e aumentar a resistência à fratura de coroas de dissilicato de lítio. Assim, a reutilização de vitrocerâmicas de dissilicato de lítio pode diminuir o risco à falha e aumentar o tempo de vida útil (AU)

Estratégias minimamente invasivas de acesso e preparo e os diferentes desfechos na terapia endodôntica / Minimally invasive access and root canal preparation strategies and the different outcomes in endodontic therapy

As cavidades de acesso dominaram a recente discussão sobre a Endodontia minimamente invasiva (EMI). No entanto, a rotulagem da EMI é mais ampla, envolvendo o uso de instrumentos com conicidades reduzidas ou geometrias inovadoras que permitam a remoção mínima de dentina. Além disso, aprimoramentos metodológicos têm sido sugeridos para mimetizar condições clínicas. Buscando responder algumas questões acerca da EMI, a presente tese é dividida em dois estudos. O estudo 1 avaliou a influência do acesso ultraconservador (UltraAC) na instrumentação, na qualidade da obturação e na capacidade máxima de carga para fratura em molares inferiores após o preparo do canal com o sistema XP-endo Shaper (XP) ou Reciproc (RC) em condições clínicas simuladas. Para isso, quarenta molares inferiores foram microtomografados e pareados em quatro grupos (n = 10), de acordo com o acesso e a instrumentação: TradAC/RC, TradAC/XP, UltraAC/RC e UltraAC/XP. Os dentes foram reescaneados e os parâmetros da instrumentação e obturação foram analisados. Os dentes foram restaurados e submetidos à ciclagem termomecânica e à capacidade máxima de carga para a fratura. O teste ANOVA foi usado para a análise estatística (P < 0,05). Os grupos TradAC apresentaram menor porcentagem (%) de área não preparada do que os grupos UltraAC (P < 0,05). O grupo UltraAC/XP apresentou a menor % de dentina removida (P < 0,05). A % de debris foi menor nos grupos UltraAC/XP e TradAC/XP do que no UltraAC/RC e TradAC/RC (P < 0,05). Os grupos UltraAC demonstraram maior % de espaços vazios e de material obturador na câmara pulpar (P < 0,05). Não houve diferença na capacidade máxima de carga para a fratura entre os grupos (P > 0,05). O estudo 2 avaliou o uso de instrumentos com conicidade reduzida - Bassi Logic ,03 (BL), com diferentes designs (XP) e como grupo de comparação o sistem Reciproc, na eficácia da instrumentação dos canais em condições clínicas simuladas. Vinte e quatro molares foram microtomografados, acessados de forma tradicional e divididos em três grupos (n = 8), de acordo com o preparo: BL, XP e RC. Nos grupos BL e RC, os canais mesiais foram instrumentados com 25/,03 ou R25 e o canal distal com 25/,03 e 40/,03 ou R25 e R40, respectivamente. No grupo XP, o mesmo instrumento foi utilizado em todos os canais (30/,04). Após o preparo, os dentes foram reescaneados e a % de área não preparada e de dentina removida foram avaliadas separadamente para os canais mesiais e distal. Os dados foram analisados com os testes ANOVA e de Tukey (P < 0,05). Verificou-se que o grupo BL apresentou maior % de área não preparada para ambos os canais em relação aos grupos XP e RC (P < 0,05). No entanto, não houve diferença na % de dentina removida entre os grupos (P > 0,05). Com base nos estudos, conclui-se que as estratégias minimamente invasivas adotadas no acesso e na instrumentação foram desvantajosas frente a tratamentos tradicionais, não justificando o seu uso(AU)

Access cavities have dominated the recent discussion on minimally invasive Endodontics (EMI). However, the issue of MIE is broader than access cavities, such as the use of instruments with reduced taper or innovative geometries that allow minimal dentin removal. Furthermore, methodological improvements have been suggested to mimic clinical conditions. Seeking to answer some questions about EMI, this thesis is divided into two studies. The first study evaluated the influence of ultraconservative access (UltraAC) on canal shaping, filling ability and maximum load capacity for fracture of mandibular molars after root canal preparation with XP-endo Shaper (XP) or Reciproc (RC), under simulated clinical conditions. Thus, forty mandibular molars were scanned and paired into four groups (n = 10), according to access and instrumentation protocol: TradAC/RC, TradAC/XP, UltraAC/RC and UltraAC/XP. Teeth were rescanned and the instrumentation and filling parameters were analyzed. The teeth were restored and submitted to thermomechanical cycling and maximum load capacity for the fracture. ANOVA test was used for statistical analysis (P < 0.05). The TradAC groups had a lower percentage (%) of unprepared area than the UltraAC groups (P < 0.05). The UltraAC/XP group had the lowest % of dentin removed (P < 0.05). The % of debris was lower in the UltraAC/XP and TradAC/XP groups than in the UltraAC/RC and TradAC/RC groups (P < 0.05). The highest % of voids and filling material in the pulp chamber was observed in the UltraAC groups (P < 0.05). There was no difference in the maximum load capacity for the fracture between the groups (P > 0.05). The second study evaluated the use of a reduced taper endodontic instrument system - Bassi Logic .03 taper (BL), expandable heat-treated system (XP) and, as comparison, the Reciproc system, on the ability to shape canals under simulated clinical conditions. For that, twenty-four mandibular molars were scanned and divided into three groups (n = 8), according to root canal instrumentation system: BL, XP and RC. In the BL and RC groups, the mesial canals were instrumented with 25/.03 or R25 and the distal canal with 25/.03 and 40/.03 or R25 and R40, respectively. In the XP group, the same instrument was used in all root canals (30/.04). After preparation, the teeth were rescanned and the % of unprepared area and dentin removed were evaluated separately for the mesial and distal canals. Data were analyzed using ANOVA and Tukey tests (P < 0.05). It was found that the BL group had a higher % of unprepared area for both root canals compared to the XP and RC groups (P < 0.05). However, there was no difference in the % of dentin removed between groups (P > 0.05). Based on the studies, it is concluded that there is no justification for the use of EMI since in general, UltraAC did not promote advantages over TradAC and the use of instruments with reduced taper resulted in a larger unprepared area, which could possibly influence the cleaning of the root canal system (AU)

An evaluation of the effect of different veneer materials on fracture resistance of zirconia core / Avaliação dos diferentes efeitos de materiais de revestimento na resistência à fratura do núcleo de zircônia

Objectives: this in vitro study was done to evaluate the effect of packable P60 composite and Tetric N-Ceram composite veneer material on fracture strength of zirconia cores. Material and Methods:Twenty four zirconium cores (Vita, Germany) with 0.7 mm thickness were fabricated by CAD/CAM technology and then subjected to air abrasion with 50 µm of Al2O3. Cores were randomly divided into three groups according to veneering material (group A: control group sandblasted with 50 µm Al2O3 veneered by IPS E-max Ceram porcelain, group C: sandblasted with 50 µm Al2O3, etching with hydrofluoric acid and veneered with P60 composite, group E: sandblasted with 50 µm Al2O3, etching with hydrofluoric acid and veneered with Tetric N-Ceram composite). All crowns were subjected to fracture strength test in the testing machine, with load application by steel ball indenter and 0.5 mm/min. cross head speed. Results: statistical analysis was carried out utilizing one-way ANOVA, LSD. The results of fracture strength value test showed the highest mean value was registered for group (A), and the lowest mean for group (E). One-way ANOVA test represented that, there was a statistically high significant different among all groups. LSD results showed a high significant difference increase in fracture resistance for Group A at p value (*p < 0.001 High significant). Conclusions: Within the limitation of this study, sandblasting zirconia core with 50 µm Al2O3 and veneering with conventional ceramic produced restoration with acceptable fracture resistance value (AU)

Objetivo: o objetivo desse estudo in vitro foi avaliar o efeito dos compósitos P60 compactáveis e material laminado de compósitos Tetric-N Ceram na resistência à fratura de núcleos de zircônia. Material e métodos:Vinte e quatro núcleos de zircônia (Vita, Germany) com 0.7 mm de espessura fabricados por tecnologia de CAD/CAM e sinterizados em alta temperatura (1450ºC por 60 min) de acordo com as instruções do fabricante. Núcleos totalmente de zircônias foram submetidos a abração com 50 µm de Al2O3. Os núcleos de zircônia foram divididos de forma randomiza em três grupos de acordo com o material de revestimento (grupo A: grupo controle jateado com 50 µm Al2O3 folheado com porcelana IPS E-max Ceram, grupo C: jateado com 50 µm Al2O3 , coberto com concentração 9,5% de ácido fluorídrico e folheado com resina composta compatível, grupo E: jateado com 50 µm Al2O3 coberto com concentração 9,5% de ácido fluorídrico e folheado com porcelana IPS E-max Ceram. Todos os espécimes (coroas) foram submetidos a teste de resistência a fratura com máquina de teste universal, essa máquina utilizou para aplicação de carga bola de aço com 6mm de diâmetro 0,5 mm/min de velocidade da cruzeta. Resultados: análise estatística foi realizada utilizando One-way ANOVA, LSD. O resultado da resistência a fratura mostra que o maior valor médio foi registrado no grupo A e a menor média para o grupo E. O resultado do teste One-Way ANOVA representaram que houve uma diferença estatisticamente alta e significante entre todos os grupos. LSD foi executada para mostrar a fonte de significância. Os resultados do LSD mostraram um aumento da diferença significativa alta na resistência à fratura para o grupo A no valor de p (p < 0.001 signicancia alta). Conclusão: Dentro das limitações desse estudo o uso convencional de jateamento com 50 µm Al2O3 e estratificação com cerâmica convencional produziu restauração com valor aceitável de resistência a fratura (AU)

Influência do acesso minimamente invasivo na fratura de dentes tratados endodonticamente - uma revisão de literatura / Influence of minimally invasive access on fracture of endodonti-cally treated teeth- a literature review

O acesso à cavidade pulpar é a etapa do tratamento endodôntico que tem como objetivo expor a embocadura dos canais radiculares. Por muito tempo, o formato ideal da cavidade era aquele que proporcionasse a criação de uma trajetória reta ao canal, com a remoção completa do teto da câmara pulpar. Porém, nas últimas décadas, foi investigado um desgaste excessivo de dentina que possibilita a redução da resistência do dente. Então, propuseram novo formato de cavidade de acesso, que permite a preservação máxima possível das estruturas de suporte, objetivando aumentar a resistência de dentes tratados endodonticamente. Apesar das vantagens, supostamente atribuídas aos acessos minimamente invasivos, esse formato tem sido questionado por dificultar a visibilidade da entrada dos canais, localização, e possibilidade de deixar áreas intocadas nas paredes dos canais. Diante disso, este trabalho realizou um levantamento bibliográfico a fim de verificar se há consistência científica quanto à interferência do acesso coronário na resistência dentária. Concluiu-se que o acesso minimamente invasivo não apresentou diferença quanto ao aumento da resistência à fratura de dentes tratados endodonticamente quando comparado ao acesso tradicional, entretanto, o tema ainda é relevante e os benefícios dessa técnica devem ser investigados clinicamente a longo prazo.

Access to the pulp cavity is the stage of endodontic treatment that aims to expose the mouth of the root canals. For a long time, creating a straight path to the canal, with the complete removal of the pulp chamber roof, was the ideal cavity format. However, in recent decades, excessive dentin wear, which makes it possible to reduce tooth strength, has been investi-gated. So, a new access cavity format, which allows the maximum possible preservation of the support structures, was proposed to increase the resistance of endodontically treated teeth. Despite the advantages supposedly attributed to minimally invasive accesses, this format has been questioned for hindering the visibility of the entrance to the channels, the location, and the possibility of leaving untouched areas on the walls of the channels. Therefore, this work carried out a bibliographical survey to verify the scientific consistency regarding the interference of coronary access in dental resistance. The minimally inva-sive access showed no difference regarding increased fracture resistance of endodontically treated teeth compared to the traditional access. However, the topic is still relevant, and its benefits, in the long term, should be clinically investigated.

Evaluation of fracture resistance of zirconia monolithic restorations: an in vitro study / Avaliação da resistência à fratura de restaurações monolíticas de zircônia: um estudo in vitro

Objective: was to evaluate fracture resistance of zirconia monolithic restorations after aging procedures. Material and methods: Monolithic translucent zirconia 3-unit FPDs were fabricated using Cerec inLab CAD/CAM system on 2 stainless steel dies with a uniform 120 degrees circumferential deep chamfer finish line of 1 mm width. FPDs were divided into 2 groups, first group (Group A) was subjected to aging procedures in an autoclave at hydrothermal conditions 134 oC /2 bars for 5 hours. Second group (Group B) was not subjected to any aging procedures (control group). All specimens of each group were loaded compressively in a universal testing machine at cross head speed 0.5 mm/min until fracture occurred. The percentage of monoclinic (m) phase was detected by XRD device. Scanning electron microscope (SEM) was used to examine the fractured surfaces for Aged TZI (Group A) and Non-aged TZI (Group B). Student's t-test was used to compare between fracture resistances of both groups. The significance level was set at P ≤ 0.05. Results: The fracture resistance mean (SD) values of non-aged TZI (Group B) was 2406.9 ± 306.8 N which showed statistically significantly higher than that of aged group (Group A) which was 1964.5 ± 234.5 N. The percentage of monoclinic (m) phase detected by XRD device software in non-aged TZI (Group B) was nearly 0 weight % and in aged TZI (Group A) was about 42 weight %. Conclusions:Accelerated artificial aging decreases the fracture resistance of monolithic TZI FPDs. (AU)

Objetivo: Foi avaliar a resistencia à fratura de restaurações de zircônia monolítica após procedimentos de envelhecimento.Material e Métodos: 3 unidades de FPDs de zircônia monolítica translucida foram fabricadas utilizando o sistema Cerec inLab CAD/CAM com 2 matrizes de aço inoxidável com uma linha de acabamento de chanfro profundo circunferencial de 120 graus de largura de 1 mm. As FPDs foram divididos em dois grupos, primeiro grupo (Grupo A) foi submetido a procedimentos de envelhecimento em autoclave em condições hidrotérmicas de 134 °C /2 bars por 5 horas. O segundo grupo (Grupo B) não foi submetido a nenhum processo de envelhecimento (grupo controle). Todos os espécimes de cada grupo foram carregados compressivamente em uma maquina de teste universal na velocidade de 0.5 mm/min até a fratura ocorrer. A porcentagem da fase monoclínica (m) foi detectada pelo dispositivo XRD. O microscópio eletrônico de varredura (MEV) foi utilizado para examinar as superfícies fraturadas para TZI envelhecido (Grupo A) e TZI não envelhecido (Grupo B). O teste t de estudantes foi usado para comparar as resistências à fraturas de ambos os grupos. O nível de significância foi estabelecido em P ≤ 0.05. Resultados: Os valores médios de resistência à fratura (SD) do TZI não envelhecido (Grupo B) foi 2406.9±306.8 N, o qual se mostrou estatisticamente significativamente maior do que o grupo envelhecido (Grupo A), que foi 1964.5±234.5 N. A porcentagem da fase monoclínica (m) detectada pelo software do dispositivo XRD em TZI não envelhecido (Grupo B) foi próximo de 0% em peso e em TZI envelhecido (Grupo A) foi cerca de 42% em peso. Conclusão: O envelhecimento artificial acelerado diminui a resistência à fratura de FPDs TZI monolítico (AU)