CAD/CAM system influence marginal fit of different ceramic types?

OBJECTIVE: This study aimed to evaluate the marginal fit of zirconia and lithium disilicate ceramic restorations processed by computer-aided design (CAD)/computer-aided manufacturing (CAM) system. MATERIALS AND METHODS: Ten models were prepared from a metal die, on which scanning was carried out to obtain the virtual model for the processing of zirconia and lithium disilicate ceramics using the CAD/CAM technique. Gypsum models were fabricated and used for scanning the restorations. The infrastructures were designed using software, and CAD/CAM was used to fabricate the restorations (n = 10). The analysis of the marginal discrepancy was measured at 12 points of the margin using the original metallic die. For each crown, an arithmetic average of the discrepancy values was obtained. RESULTS: The marginal fit of the copings of lithium disilicate was 133.10 ± 26.87 µm and zirconia was 127.34 ± 47.97 µm. There was no statistically significant difference (P = 0.7709) between the materials. CONCLUSION: The marginal fit is similar between lithium disilicate and zirconia ceramics milled in the CAD/CAM system used.

O OSCE na avaliação clínica odontológica: relato de experiência com estudantes de graduação / OSCE in Dental clinical evaluation: the report of an experience with undergraduate students

O Exame Clínico Objetivo e Estruturado (OSCE) é um exame organizado em estações que simulam a realidade clínica e os estudantes são avaliados em tarefas específicas como anamnese, exame físico, comunicação com paciente, procedimentos clínicos não invasivos, entre outras. É realizado o rodízio de alunos e um ou dois examinadores pontuam o desempenho dos mesmos em cada tarefa, com critérios e tempo previamente determinados. O objetivo desse estudo foi relatar a experiência de aplicação do OSCE na graduação e como estruturá-lo. O primeiro OSCE aplicado pelo curso de Odontologia da Universidade do Oeste Paulista (UNOESTE) para alunos de graduação foi no ano de 2016, com o objetivo de avaliação de competências dos alunos que ingressariam nas clínicas no semestre seguinte. A avaliação foi aplicada aos 70 alunos do final do terceiro ano e os conteúdos selecionados foram Dentística, Periodontia, Endodontia, Radiologia, Biossegurança, Anestesiologia e Diagnóstico Bucal. O OSCE pode ser considerado uma técnica de avaliação adequada para o alcance de competências clínicas na formação de cirurgiões-dentistas, por proporcionar ao aluno de graduação a vivência de atividades similares à realidade que enfrentará no atendimento clínico e em sua futura atuação profissional. Esse método de avaliação propicia aos estudantes a oportunidade de serem avaliados de forma mais objetiva e poder aprender com o feedback do seu desempenho no exame (AU).

The Objective and Structured Clinical Examination (OSCE) is an exam organized in stations that simulate clinical reality and students are evaluated in specific tasks such as anamnesis, physical examination, communication with patients, noninvasive clinical procedures, among others. Students rotated through stations, and one or two examiners score their performance in each task, with predetermined criteria and time. The objective of this study was to report on the experience of applying the OSCE in undergraduate and how to structure it. The first OSCE applied for Dental undergraduate students at Universidade do Oeste Paulista (UNOESTE) was in 2016, with the objective of evaluating the competencies of the students who would enter the clinics in the following semester. The evaluation was applied to 70 students at the end of the third year and the contents selected were Restorative Dentistry, Periodontics, Endodontics, Radiology, Biosafety, Anesthesiology and Oral Diagnosis. The OSCE can be considered an adequate evaluation technique for the attainment of clinical competences in the training of dental surgeons, as it provides the undergraduate student with the experience of activities similar to the reality he will face in clinical care and his future professional performance. This assessment method gives students the opportunity to be evaluated more objectively and to learn from feedback on their exam performance (AU).

A plataforma Moodle no treinamento de estudantes de Odontologia na avaliação de restaurações classe II em resina composta / Dental students training on the evaluation of class II composite restorations using the Moodle platform

O objetivo do estudo foi analisar o padrão de conduta de acadêmicos de Odontologia frente a restaurações classe II em resina composta cuja situação clínica seja de caráter duvidoso. Deste modo, pode-se detectar dificuldades comuns dos estudantes na tomada de decisão da conduta clínica, por meio de critérios de avaliação padronizados, bem como aperfeiçoar uma metodologia auxiliar de ensino digital baseada na plataforma Moodle. Participaram da pesquisa 65 estudantes da disciplina de Dentística que já haviam recebido treinamento teórico sobre critérios clínicos para avaliação de restaurações conforme FDI (World Dental Federation). A coleta de dados foi feita por meio de questionários disponíveis no site Aprender Unoeste (plataforma Moodle). Os estudantes analisaram 22 imagens de restaurações classe II em resina composta disponíveis no site observando os seguintes itens: parâmetros estéticos (brilho superficial, manchamento superficial e marginal, correspondência de cor e translucidez), parâmetros funcionais (fratura do material e retenção, adaptação marginal, forma anatômica proximal/contorno) e parâmetros biológicos (recorrência de cáries e integridade dental). A média de acertos dos alunos foi 6,3±0,7 (sobre pontuação máxima = 10), sendo que os parâmetros estéticos apresentaram menor percentual de acertos. Após o preenchimento do questionário os estudantes obtinham o feedback imediato de suas avaliações, tendo então a possibilidade de verificar seus erros e qual seria a resposta adequada. O estudo detectou dificuldades dos estudantes de Odontologia na análise de restaurações em resina composta e possibilitou que estes adquirissem experiência visual clínica, desenvolvendo seu senso crítico, como auxílio de novas metodologias de ensino-aprendizagem (AU).

The study aimed to evaluate the clinical conduct of dental undergraduate students regarding unsatisfactory Class II composite restorations with doubtful prognosis, in order to detect their difficulties and to improve learning methods using a Moodle online platform. A total of 65 sixth semester students were enrolled, they were attending Operative-Restorative Dentistry discipline and received previous theoretical training on restorations evaluation according FDI (World Dental Federation) criteria and randomly selected as volunteers. Data was collected using a questionnaire available on a specific online Moodle platform. Students analyzed 22 digital images of class II composite restorations observing aesthetic parameters (i.e., surface gloss, surface and marginal staining, color matching and translucency), anatomical aesthetic form, functional parameters (i.e., restoration fracture and retention, marginal adaptation, proximal anatomical shape/contour) and biological parameters (i.e., recurrence of caries and tooth integrity). The maximum individual score for correct answers was established as 10 points. Immediate feedback was provided allowing students to check the appropriate responses once the questionnaire was finished. The average of correct answers was 6.3 (0,7 standard deviation). Graduation students present a considerable high difficulty to determine the clinical success of composite restorations. The proposed new teaching/learning methodology enhances the visual experience and the critical contributes to accelerate the learning curve on this topic (AU).

Analysis of Vertical Marginal Adaptation of Zirconia Fixed Dental Prosthesis Frameworks Fabricated by the CAD/CAM System: A Randomized, Double-Blind Study.

PURPOSE: The purpose of this study was to evaluate the marginal adaptation of fixed dental prosthesis frameworks fabricated by computer-aided design/computer-assisted manufacture (CAD/CAM) with three different systems of data acquisition. MATERIALS AND METHODS: A total of 50 specimens were fabricated as follows: using the conventional method (Ni-Cr) (n=10); iTero/industrial milling (Group 1, n=10); Cerec Bluecam/industrial milling (Group 2, n=10); 3S/industrial milling (Group 3, n=10); and Cerec BlueCam/Sirona milling (Group 4, n=10). The specimens were numbered and randomized, and the vertical marginal discrepancy was analyzed. RESULTS: Intraobserver analysis indicated no statistically significant difference (paired t test, P=.822) between periods before and after analysis. The conventional method (321 µm) showed greater discrepancy when compared with the CAD/CAM system (89 µm) (P<.001). The intraoral system showed a lower rate of marginal discrepancy when compared with the extraoral system (3S) (P<.001). The closed system presented a higher marginal discrepancy (114 µm) than the open intraoral system (iTero) at P<.001. In addition, the intraoral system when open showed statistically significant differences in mean marginal discrepancy values compared with the same system in closed condition (P>.05). CONCLUSION: The CAD/CAM systems showed less marginal discrepancy than the conventional method for the fabrication of the frameworks.

Optical impression systems for CAD-CAM restorations.

Computer-aided design/computer-aided manufacturing images can be taken through either direct or indirect imaging. For the indirect systems, the digitalization is obtained from the impression material or cast, and for the direct ones the image is taken directly from the mouth using intraoral scanners.The direct acquisition systems have been constantly improved because these are less invasive, quicker, and more precise than the conventional method. Besides, the digital images can be easily stored for a long time. Therefore, the aim of this paper was to describe and discuss based on the literature the main direct image acquisition systems available on the market: CEREC Bluecam (Sirona), Lava C.O.S. System (3M ESPE), iTero System (Cadent/Straumann), and E4D System (D4D Technologies).

Effect of static and cyclic loading on ceramic laminate veneers adhered to teeth with and without aged composite restorations.

PURPOSE: Existing composite restorations on teeth are often remade prior to the cementation of fixed dental prostheses. The aim of this study was to evaluate the effect of static and cyclic loading on ceramic laminate veneers adhered to aged resin composite restorations. MATERIALS AND METHODS: Eighty sound maxillary incisors were collected and randomly divided into four groups: group 1: control group, no restorations; group 2: two Class III restorations; group 3: two Class IV restorations; group 4: complete composite substrate. Standard composite restorations were made using a microhybrid resin composite (Anterior Shine). Restored teeth were subjected to thermocycling (6000 cycles). Window preparations were made on the labial surface of the teeth for ceramic laminate fabrication (Empress II). Teeth were conditioned using an etch-and-rinse system. Existing composite restorations representing the aged composites were silica coated (CoJet) and silanized (ESPE-Sil). Ceramic laminates were cemented using a bis-GMA-based cement (Variolink Veneer). The specimens were randomly divided into two groups and were subjected to either static (groups 1a, 2a, 3a, 4a) or cyclic loading (groups 1b, 2b, 3b, 4b). Failure type and location after loading were classified. Data were analyzed using one-way ANOVA and Tukey's test. RESULTS: Significantly higher fracture strength was obtained in group 4 (330 ± 81 N) compared to the controls in group 1 (179 ± 120 N) (one-way ANOVA, p < 0.05). Group 1b survived a lower mean number of cyclic loads (672,820 cycles) than teeth of groups 2b to 4b (846x103 to 873x103 cycles). Failure type evaluation after the fracture test showed predominantly adhesive failures between dentin and cement, but after cyclic loading, more cohesive fractures in the ceramic were seen. CONCLUSION: Ceramic laminate veneers bonded to conditioned aged composite restorations provided favorable results. Surface conditioning of existing restorations may eliminate the necessity of removing aged composite restorations.

Caracterização in vitro de um novo sistema de resina composta de laboratório / In vitro characterization of a new laboratory composite resin

Objetivo: este estudo caracterizou algumas propriedades de uma resina composta de processamento laboratorial (Resilab, Wilcos do Brasil), indicada para confecção de coroas com e sem metal, pontes anteriores e posteriores, inlays, onlays e facetas laminadas. Metodologia: as propriedades avaliadas foram rugosidade superficial, dureza, resistência à flexão, resistência adesiva a três ligas metálicas (Au, NiCr e CoCr) e microinfiltração da interface resina/metal. Todos os espécimes foram submetidos a dois ciclos de polimerização, conforme instruções do fabricante. Dez espécimes circulares (4x3 mm) foram preparados para os testes de dureza (VHN) e rugosidade superficial (Ra). A resistência flexural em três pontos (MPa) foi medida a partir de espécimes retangulares (10x5x2 mm), sob velocidade de 1 mm/min. Os ensaios que envolveram ligas metálicas (resistência adesiva e microinfiltração) foram submetidos à análise estatística (p<0,05) (Anova, Tukey, Kruskal-Wallis). Resultados: não houve diferenças entre as médias de resistência de união. Quanto à infiltração marginal, o grupo CoCr diferiu dos grupos Au e NiCr em espécimes sem retenção mecânica e submetidos a ciclagem térmica. Conclusão: considerando os resultados deste estudo in vitro e a literatura pesquisada, o sistema Resilab mostrou comportamento satisfatório quanto às propriedades estudadas. A resistência de união não dependeu da liga metálica utilizada.

Aim: this study aimed to determine some of the properties of a laboratory composite indicated for metallic and non-metallic crowns, anterior and posterior bridges, inlays, onlays and laminate veneers. Methology: the properties evaluated were surface roughness, flexural strength, shear bond strength to three metal alloys and the microleakage at the composite/ metal interface. All specimens were subjected to cycles of polymerization, according the manufacturer instructions. Ten round specimens (4x3 mm) were prepared for hardness (VHN) and surface roughness tests (Ra). The three-point flexural strength was measured on rectangular shaped specimens (10x5x2 mm), at 1 mm/min speed. The experiments involving dental alloys (bond strength and microleakage) were submitted to statistical analysis (p<0, 05) (Anova, Tukey, Kruskal-Wallis). Results: there were no statistically significant diferences between the bond strength means. As for the marginal leakage, the CoCr group differed of the Au and NiCr groups in specimens without mechanical retention and subjected to thermocycling. Conclusion: according to our results and the literature search, the Resilab system showed satisfactory performance regarding the properties evaluated. The bond strength was not dependable on the metal alloy used.

The adhesive system and root canal region do not influence the degree of conversion of dual resin cement.

OBJECTIVES: The aim of this study was to evaluate the influence of two adhesive systems and the post space region on the degree of conversion of dual resin cement and its bond strength to root dentin. MATERIAL AND METHODS: One three-step etch-and-rinse (All-bond 2, Bisco) and another one-step self-etch (Xeno III, Dentsply) adhesive systems were applied on 20 (n=10) crownless bovine incisors, at 12-mm-deep post space preparation, and a fiber post (DT Light Post, Bisco) was cemented using a dual cure resin cement (Duo-Link, Bisco). Three transverse sections (3 mm) were obtained, being one from each study region (cervical, middle and apical). The degree of conversion of the dual cure resin cement was determined by a micro-Raman spectrometer. The data (%) were submitted to repeated-measures analysis of variance and Tukey's test (p<0.05). RESULTS: For both groups, the degree of conversion means (%) (All bond 2cervical = 69.3; All bond 2middle = 55.1; All bond 2apical= 56; Xeno IIIcervical = 68.7; Xeno IIImiddle = 68.8; Xeno IIIapical = 54.3) were not significantly different along the post space regions (p<0.05). CONCLUSION: Neither the adhesive nor the post space region influenced the degree of conversion of the cement layer.

The adhesive system and root canal region do not influence the degree of conversion of dual resin cement

OBJECTIVES: The aim of this study was to evaluate the influence of two adhesive systems and the post space region on the degree of conversion of dual resin cement and its bond strength to root dentin. MATERIAL AND METHODS: One three-step etch-and-rinse (All-bond 2, Bisco) and another one-step self-etch (Xeno III, Dentsply) adhesive systems were applied on 20 (n=10) crownless bovine incisors, at 12-mm-deep post space preparation, and a fiber post (DT Light Post, Bisco) was cemented using a dual cure resin cement (Duo-Link, Bisco). Three transverse sections (3 mm) were obtained, being one from each study region (cervical, middle and apical). The degree of conversion of the dual cure resin cement was determined by a micro-Raman spectrometer. The data ( percent) were submitted to repeated-measures analysis of variance and Tukey's test (p<0.05). RESULTS: For both groups, the degree of conversion means ( percent) (All bond 2cervical = 69.3; All bond 2middle = 55.1; All bond 2apical= 56; Xeno III cervical = 68.7; Xeno IIImiddle = 68.8; Xeno III apical = 54.3) were not significantly different along the post space regions (p<0.05). CONCLUSION: Neither the adhesive nor the post space region influenced the degree of conversion of the cement layer.

Bond strength of two resin cements on dentin using different cementation strategies.

PURPOSE: This study evaluated the microtensile bond strength of two resin cements to dentin either with their corresponding self-etching adhesives or employing the three-step "etch-and-rinse" technique. The null hypothesis was that the "etch-and-rinse" adhesive system would generate higher bond strengths than the self-etching adhesives. MATERIALS AND METHODS: Thirty-two human molars were randomly divided into four groups (N = 32, n = 8/per group): G1) ED Primer self-etching adhesive + Panavia F; G2) All-Bond 2 "etch-and-rinse" adhesive + Panavia F; G3) Multilink primer A/B self-etching adhesive + Multilink resin cement; G4) All-Bond 2 + Multilink. After cementation of composite resin blocks (5 x 5 x 4 mm), the specimens were stored in water (37 degrees C, 24 hours), and sectioned to obtain beams (+/-1 mm(2) of adhesive area) to be submitted to microtensile test. The data were analyzed using 2-way analysis of variance and Tukey's test (alpha = 0.05). RESULTS: Although the cement type did not significantly affect the results (p = 0.35), a significant effect of the adhesive system (p = 0.0001) was found on the bond strength results. Interaction terms were not significant (p = 0.88751). The "etch-and-rinse" adhesive provided significantly higher bond strength values (MPa) with both resin cements (G2: 34.4 +/- 10.6; G4: 33.0 +/- 8.9) compared to the self-etching adhesive systems (G1: 19.8 +/- 6.6; G3: 17.8 +/- 7.2) (p < 0.0001). Pretest failures were more frequent in the groups where self-etching systems were used. CONCLUSION: Although the cement type did not affect the results, there was a significant effect of changing the bonding strategy. The use of the three-step "etch-and-rinse" adhesive resulted in significantly higher bond strength for both resin cements on dentin. CLINICAL SIGNIFICANCE: Dual polymerized resin cements tested could deliver higher bond strength to dentin in combination with "etch-and-rinse" adhesive systems as opposed to their use in combination with self-etching adhesives.

Comparison of resin push-out strength to root dentin of bovine- and human-teeth.

AIM: To compare the push-out strength of bovine- and human-root dentin and, thus, evaluate the suitability of bovine-root dentin to substitute human-root dentin for bond strength testing. MATERIALS AND METHODS: Ten single-rooted human-teeth and ten bovine incisors were prepared using a #3 bur of a fiber post system (12 mm long). The posts were duplicated with resin cement (Duolink). The root canals were treated with All Bond 2 adhesive system and the resin posts were cemented using Duolink. The specimens were cut perpendicular to their long axis, yielding disc-specimens with 1.5 mm thickness, which were submitted to a push-out test (1 mm/min). Ten bond strength values per group (n = 10) were used for statistical analysis (Student t test, alpha =.05). RESULTS: Statistically significant differences were found for the bond strength values between bovine- (4.1 +/- 1.3 MPa) and human-root dentin (8.6 +/- 5.7 MPa) (P =.0001). CONCLUSION: The push-out strengths of bovine- and human-root dentin were statistically different.

Durability of the bond strength of self-adhesive resin cements to human dentin.

This study subjected two self-adhesive resin cements and two conventional resin cements to dry and aging conditions, to compare their microtensile bond strengths (microTBS) to dentin. Using four different luting systems (n = 10), 40 composite resin blocks (each 5 x 5 x 4 mm) were cemented to flat human crown dentin surfaces. The specimens were stored in water for 24 hours (37 degrees C), at which point each specimen was sectioned along two axes to obtain beams that were divided randomly into two groups: dry samples, which were tested immediately, and samples that were subjected to accelerated aging conditions (12,000 thermocycles followed by storage for 150 days). The microTBS results were affected significantly by the luting system used (P < 0.0001). Only the microTBS of Rely-X Unicem was reduced significantly after aging; the microTBS remained stable or increased for the other self-adhesive resin cement and the two conventional cements.

Fatigue resistance of teeth restored with fiber posts and different post cementation strengths.

This study sought to evaluate how different post cementation strategies affected the fatigue resistance of bovine teeth restored with glass fiber posts. The canals of 63 single-rooted bovine teeth (each 16 mm in length) were prepared to 9 mm using a preparation drill from a double-tapered fiber post system. Each specimen was embedded in a PVC cylinder using acrylic resin up to 3 mm of the most coronal portion of the specimen and was allocated into one of seven groups (n = 9) based on the strategies for cementation. After cementation, a standard core build-up was made with composite resin. The specimens were stored for seven days and submitted to mechanical cycling (50 N, 8 Hz, 37 degrees C). After fatigue testing, a score was given to each specimen, based on the number of fatigue cycles required to fracture the specimens; the scores were submitted to statistic analysis (Kruskal-Wallis, alpha = 0.05). The strategy for post cementation did not affect the resistance to fatigue (P = 0.8669). Based on the results, the resistance to fatigue does not appear to depend on the post cementation strategy.

Effect of acid neutralization and mechanical cycling on the microtensile bond strength of glass-ceramic inlays.

OBJECTIVES: To evaluate the hypothesis that a process of hydrofluoric acid precipitate neutralization and fatigue load cycling performed on human premolars restored with ceramic inlays had an influence on microtensile bond strength results (MTBS). METHODS: MOD inlay preparations were performed in 40 premolars (with their roots embedded in acrylic resin). Forty ceramic restorations were prepared using glass-ceramic (IPS Empress). The inner surfaces of all the restorations were etched with 10% hydrofluoric acid for 60 seconds, rinsed with water and dried. The specimens were divided into two groups

Adhesive cementation of zirconia posts to root dentin: evaluation of the mechanical cycling effect.

This study evaluated the effect of mechanical cycling on the bond strength of zirconia posts to root dentin. Thirty single-rooted human teeth were transversally sectioned to a length of 16 mm. The canal preparation was performed with zirconia post system drills (CosmoPost, Ivoclar) to a depth of 12 mm. For post cementation, the canals were treated with total-etch, 3-steps All-Bond 2 (Bisco), and the posts were cemented with Duolink dual resin cement (Bisco). Three groups were formed (n = 10): G1 - control, no mechanical cycling; G2 - 20,000 mechanical cycles; G3 - 2,000,000 mechanical cycles. A 1.6-mm-thick punch induced loads of 50 N, at a 45 degrees angle to the long axis of the specimens and at a frequency of 8 Hz directly on the posts. To evaluate the bond strengths, the specimens were sectioned perpendicular to the long axis of the teeth, generating 2-mm-thick slices, approximately (5 sections per teeth), which were subjected to the push-out test in a universal testing machine at a 1 mm/min crosshead speed. The push-out bond strength was affected by the mechanical cycling (1-way ANOVA, p = .0001). The results of the control group (7.7 +/- 1.3 MPa) were statistically higher than those of G2 (3.9 +/- 2.2 MPa) and G3 (3.3 +/- 2.3 MPa). It was concluded that the mechanical cycling damaged the bond strength of zirconia posts to root dentin.

Effect of adhesive system type and tooth region on the bond strength to dentin.

PURPOSE: This study evaluated the bond strength of two etch-and-rinse adhesive systems (two- and three-step) and a self-etching system to coronal and root canal dentin. MATERIALS AND METHODS: The root canals of 30 human incisors and canines were instrumented and prepared with burs. The posts used for luting were duplicated with dual resin cement (Duo-link) inside Aestheti Plus #2 molds. Thus, three groups were formed (n = 10) according to the adhesive system employed: All-Bond 2 (TE3) + resin cement post (rcp) + Duo-link (Dl); One-Step Plus (TE2) + rcp + Dl; Tyrian/One-Step Plus (SE) + rcp + Dl. Afterwards, 8 transverse sections (1.5 mm) were cut from 4 mm above the CEJ up to 4 mm short of the root canal apex, comprising coronal and root canal dentin. The sections were submitted to push-out testing in a universal testing machine EMIC (1 mm/min). Bond strength data were analyzed with two-way repeated measures ANOVA and Tukey's test (p < 0.05). RESULTS: The relationship between the adhesives was not the same in the different regions (p < 0.05). Comparison of the means achieved with the adhesives in each region (Tukey; p < 0.05) revealed that TE3 (mean +/- standard deviation: 5.22 +/- 1.70) was higher than TE2 (2.60 +/- 1.74) and SE (1.68 +/- 1.85). CONCLUSION: Under the experimental conditions, better bonding to dentin was achieved using the three-step etch-and-rinse system, especially in the coronal region. Therefore, the traditional etch-and-rinse three-step adhesive system seems to be the best choice for teeth needing adhesive endodontic restorations.

Evaluation of light transmission through translucent and opaque posts.

OBJECTIVES: The transmission of light through translucent posts was observed, and the microhardness of light-cured cement used to secure these posts was evaluated at different depths. METHODS: Fifteen single-rooted standard bovine teeth, 16 mm in size, were used. The root canals were prepared using #3 drills Light-Post (five teeth) and Aestheti Post (five teeth) systems (BISCO), with a working-length of 12 mm. In five teeth, translucent posts were cemented (Light-Post #2), while another five teeth received opaque posts (Aestheti Post #2). The roots were painted with black nail varnish to prevent the passage of light through the lateral walls of the roots. The root canals of all the specimens were treated with the All-Bond 2 adhesive system (BISCO) and cemented with light-cured cement (Enforce, Dentsply). All the roots were transversally cut to obtain six specimens 1.5 mm thick. Every two sections corresponded to a specific region of the root (cervical, middle, apical), making it possible to observe the cement microhardness at different levels. The groups (n = 10) were defined as: GI: translucent post (TP)/cervical region; G2: TP/middle region; G3: TP/apical region; G4: Opaque post (OP)/cervical region; G5: OP/middle region; G6: PO/apical region. Five root canals were only filled with cement for use as a control (G7). Then, Vickers microhardness analyses were performed. RESULTS: In G3, G5 and G6, the cement was not sufficiently hard to allow for microhardness analysis. When submitted to the ANOVA test, G1 (35.07), G2 (24.28) and G4 (28.64) presented no statistical differences. When the previous groups were compared to G7 (51.00) using the Kruskal-Wallis test, a statistical difference was found. CONCLUSION: Translucent posts allow cement polymerization up to the middle portion of the root.

Adhesive cementation of zirconia posts to root dentin: evaluation of the mechanical cycling effect

This study evaluated the effect of mechanical cycling on the bond strength of zirconia posts to root dentin. Thirty single-rooted human teeth were transversally sectioned to a length of 16 mm. The canal preparation was performed with zirconia post system drills (CosmoPost, Ivoclar) to a depth of 12 mm. For post cementation, the canals were treated with total-etch, 3-steps All-Bond 2 (Bisco), and the posts were cemented with Duolink dual resin cement (Bisco). Three groups were formed (n = 10): G1 - control, no mechanical cycling; G2 - 20,000 mechanical cycles; G3 - 2,000,000 mechanical cycles. A 1.6-mm-thick punch induced loads of 50 N, at a 45° angle to the long axis of the specimens and at a frequency of 8 Hz directly on the posts. To evaluate the bond strengths, the specimens were sectioned perpendicular to the long axis of the teeth, generating 2-mm-thick slices, approximately (5 sections per teeth), which were subjected to the push-out test in a universal testing machine at a 1 mm/min crosshead speed. The push-out bond strength was affected by the mechanical cycling (1-way ANOVA, p = .0001). The results of the control group (7.7 ± 1.3 MPa) were statistically higher than those of G2 (3.9 ± 2.2 MPa) and G3 (3.3 ± 2.3 MPa). It was concluded that the mechanical cycling damaged the bond strength of zirconia posts to root dentin.

Effect of mechanical cycling on the push-out bond strength of fiber posts adhesively bonded to human root dentin.

This study evaluated the effect of mechanical cycling on the bond strength of fiber posts bonded to root dentin. The hypotheses examined were that bond strength is not changed after fatigue testing and bond strength does not present vast variations according to the type of fiber post. Sixty crownless, single-rooted human teeth were endodontically treated, with the space prepared at 12 mm. Thirty specimens received a quartz fiber post (Q-FRC) (DT Light-Post), and the remaining 30 specimens received a glass fiber post (G-FRC) (FRC Postec Plus). All the posts were resin luted (All Bond+Duolink), and each specimen was embedded in a cylinder with epoxy resin. The specimens were divided into six groups: G1- Q-FRC+no cycling; G2- Q-FRC+20,000 cycles (load: 50N; angle of 450; frequency: 8Hz); G3- Q-FRC+2,000,000 cycles; G4- G-FRC+no cycling; G5- G-FRC+20,000 cycles; G6- G-FRC+2,000,000 cycles. The specimens were cut perpendicular to their long axis, forming 2-mm thick disc-samples, which were submitted to the push-out test. ANOVA (alpha = .05) revealed that: (a) Q-FRC (7.1 +/- 2.2MPa) and G-FRC (6.9 +/- 2.1MPa) were statistically similar (p = 0.665); (b) the "no cycling" groups (7.0 +/- 2.4MPa), "20,000 cycles" groups (7.0 +/- 2.1MPa) and "2,000,000 cycles" groups (7.0 +/- 2.0MPa) were statistically similar (p = 0.996). It concluded that mechanical cycling did not affect the bond strength of two fiber posts bonded to dentin.

Effects of mechanical cycling on the bonding of zirconia and fiber posts to human root dentin.

PURPOSE: To evaluate the effect of cyclical mechanical loading on the bond strength of a fiber and a zirconia post bonded to root dentin. MATERIALS AND METHODS: Forty single-rooted human teeth (maxillary incisors and canines) were sectioned, and the root canals were prepared at 12 mm. Twenty randomly seleced specimens received a quartz fiber post (FRC) (D.T. Light-Post) and 20 others received a zirconia post (ZR) (Cosmopost). The posts were resin luted (All Bond 2 + resin cement Duo-link) and each specimen was embedded in epoxy resin inside a PVC cylinder. Ten specimens with FRC post and 10 specimens with ZR post were submitted to fatigue testing (2,000,000 cycles; load: 50 N; angle of 45 degrees; frequency: 8 Hz), while the other 20 specimens were not fatigued. Thus, 4 groups were formed: G1: FRC+O cycles; G2: FRC+2,000,000 cycles; G3: ZR+O cycles; G4: ZR+2,000,000 cycles. Later, the specimens were cut perpendicular to their long axis to form 2-mm-thick disk-shaped samples (4 sections/specimen), which were submitted to the push-out test (1 mm/min). The mean bond strength values (MPa) were calculated for each tooth (n = 10) and data were submitted to statistical analysis (alpha = 0.05). RESULTS: Two-way ANOVA revealed that the bond strength was significantly affected by mechanical cycling (p = 0.0014) and root post (p = 0.0325). The interaction was also statistically significant (p = 0.0010). Tukey's test showed that the mechanical cycling did not affect the bonding of FRC to root dentin, while fatigue impaired the bonding of zirconium to root dentin. CONCLUSION: (1) The bond strength of the FRC postto root dentin was not reduced after fatigue testing, whereas the bonding of the zirconia post was significantly affected by the fatigue. (2) Cyclical mechanical loading appears to damage the bond strength of the rigid post only.