In Vitro Comparison of Microleakage, Marginal Fit, and Cement Thickness of Conventional and Prepless Lithium Disilicate Veneers

PURPOSE: To assess the influence of two preparation techniques on the microleakage, marginal fit, and cement thickness of lithium disilicate veneers. MATERIALS AND METHODS: A total of 24 human maxillary central incisors were divided randomly into two groups according to preparation technique (n = 12): minimally invasive preparation with butt-joint design (0.3-mm depth) and a chamfer finish line (group MP); and no preparation (NP). All teeth were restored with lithium disilicate veneers cemented with photopolymerizable resin cement. Specimens were aged thermally (6,000 cycles of 5°C to 55°C) and mechanically (100,000 cycles at 100 N, 4 Hz). Specimens were immersed in fuchsin for 24 hours employing a standard dye penetration technique, then sectioned and evaluated under a stereomicroscope (x20). Data were analyzed by ANOVA and Kruskal-Wallis tests (P < .05). RESULTS: There was significant microleakage (P = .0163) at the cervical area compared to the proximal area. The marginal fit was similar, with no statistical difference (P = .212) between groups MP (153 ± 81 µm) and NP (111 ± 74 µm). Group MP showed a significantly (P = .006) reduced cement thickness at the cervical area (87 ± 27 µm) compared to group NP (210 ± 89 µm). CONCLUSION: Although the preparation technique was shown to influence the cement thickness, it did not show any influence on microleakage or marginal fit.

Stress distribution in lower second molar mesialization using mini-implants: a pilot study using 3D finite element analysis / Distribuição de tensões na mesialização do segundo molar inferior usando mini-implantes: um estudo piloto usando análise de elementos finitos 3D

Objective: to analyze the stress distribution in a 3D model that simulates second molar mesialization using two different types of mini-implants. Material and Methods: a mandible bone model was obtained by recomposing a computed tomography performed by a software program. The cortical and trabecular bone, a lower second molar, periodontal ligament, orthodontic tube, resin cement and the mini-implants were designed and modeled using the Rhinoceros 4.0 software program. The characteristics of self-drilling orthodontic mini-implants were: one with 7 mm length, 1 mm transmucosal neck section and 1.6 mm diameter and another with 5 mm length and 1.5 mm diameter. A total of 235.161 and 224.505 elements were used for the mesh. These models were inserted into the bone block and then subjected to loads of 200 cN (centinewton). The results were calculated and analyzed by the Ansys 17.0 software program for qualitative verification through displacement and maximum principal stress maps. Results: it was possible to observe that the periodontal ligament presented low displacement and stress values. However, the physiological values presented are among those capable to provide orthodontic movement, with compression and tensile area visualization staggered between 0.1 and -0.1 MPa (megapascal). Conclusion: within the limitations of the study, the mini-implants tested showed similar results where the load on the tooth allowed dental displacement (molar mesialization), with a tendency to rotate it, theoretically allowing the second molar to take the location of the first molar. (AU)

Objetivo: analisar a distribuição de tensões em um modelo 3D que simula a mesialização do segundo molar usando dois tipos diferentes de mini-implantes. Material e Métodos: um modelo de osso mandibular foi obtido por recomposição de uma tomografia computadorizada realizada por um software. O osso cortical e trabecular, um segundo molar inferior, ligamento periodontal, tubo ortodôntico, cimento resinoso e os mini-implantes foram projetados e modelados no software Rhinoceros 4.0. As características dos mini-implantes ortodônticos auto perfurantes foram: um com 7 mm de comprimento, 1 mm de secção transmucosa e 1,6 mm de diâmetro e outro com 5 mm de comprimento e 1,5 mm de diâmetro. Para a malha, foram utilizados 235.161 e 224.505 elementos. Esses modelos foram inseridos no bloco ósseo e então submetidos a cargas de 200 cN (centinewton). Os resultados foram calculados e analisados pelo software Ansys 17.0 para verificação qualitativa por meio de mapas de deslocamento e tensões máximas principais. Resultados: foi possível observar que o ligamento periodontal apresentou baixos valores de deslocamento e tensões. Porém, os valores fisiológicos apresentados são capazes de proporcionar movimentação ortodôntica, com visualização da área de compressão e tração escalonada entre 0,1 e -0,1 MPa (megapascal). Conclusão: dentro das limitações do estudo, os mini-implantes testados apresentaram resultados semelhantes onde a carga sobre o dente permitiu o deslocamento dentário (mesialização do molar), com tendência a girá-lo, permitindo teoricamente que o segundo molar ocupe do lugar do primeiro molar (AU)

Effect of Biologically Oriented Preparation Technique on the Stress Concentration of Endodontically Treated Upper Central Incisor Restored with Zirconia Crown: 3D-FEA.

The aim of this study was to evaluate the effect of biologically oriented preparation technique on the stress concentration of endodontically treated upper central incisors restored with zirconia crown (yttria-stabilized zirconia polycrystalline ceramic) through finite element analysis (FEA). Four models of maxillary central incisors containing enamel, dentin, periodontal ligament, cortical and medullary bone were created in CAD. Each model received a polymeric core-build up with nanofilled dental resin composite. The evaluated models were SM-preparation in shoulder 90°; CM-chamfer preparation; BOPT-biologically oriented preparation technique and BOPTB-BOPT preparation 1 mm below the cement-enamel junction. All models received zirconia crowns (5Y-TZP), fiberglass post and 1 mm ferrule. The models were imported into the analysis software with parameters for mechanical structural testing using the maximum principal stress and the tensile strength as the analysis criteria. Then, load of 150 N was applied at the cingulum with 45° slope to the long axis of the tooth, with the fixed base for each model. The type of marginal preparation affected the stresses concentration in endodontically treated teeth and in the zirconia crown margin. Considering the stress magnitude only, BOPT is a viable option for anterior monolithic zirconia crowns; however, with the highest stress magnitude at the restoration margin.

Assessment of patient and dentist preference between conventional and digital diagnostic waxing.

Patient expectations for rehabilitations of a high esthetic standard as well as the demand for fast but efficient care have provided new work perspectives in dentistry. Dentists also have to choose between conventional and digital workflows. The aim of the present randomized restorative trial was to compare diagnostic waxing (DW) performed conventionally with its digital counterpart and to assess the two approaches from the point of view of both patient and dentist. Twenty patients with esthetic complaints were selected to undergo molding processes to obtain conventional study models on the one hand, and intraoral scanning to obtain virtual models on the other. Both the 2D planning and 3D virtual models were sent to the laboratory for the performance of DW. The restorative trial was evaluated by one evaluator dentist, while patient opinion was determined through customized questionnaires. The results show that although 80% of patients rated the digital method to be more convenient in terms of execution time and comfort and indicated that scanning was the most reliable way to obtain an impression, 65% chose the conventional DW for their esthetic restoration after the mock-up tests were performed and analyzed. The evaluating dentist preferred the conventional DW technique in 50% of cases assessed. The conclusion is that although digital technology has its advantages, the final esthetic result does not always meet the expectations and demands of patients and dentists.

Influence of Preparation Design, Restorative Material and Load Direction on The Stress Distribution of Ceramic Veneer in Upper Central Incisor / Influência do desenho de preparo, material restaurador e direção de carga na distribuição de tensão de laminado cerâmico em incisivo central superior

Objective: Evaluate the effect of four preparation designs, two ceramic materials, and two occlusion contact types on the stress distribution of ceramic veneer in upper central incisor. Material and methods: 3D-models were performed in the modeling software containing enamel, dentin, pulp, periodontal ligament and a base of polyurethane resin. The designs were modeled and exported to the computer aided engineering software to perform the static structural analysis. For the mesh, a total of 155429 tetrahedron elements and 271683 nodes were used, after a 10% convergence test. Two materials, lithium disilicate and feldspathic ceramics, were simulated. A static load of 100 N on 45º was applied on the incisal and middle thirds of the palatal tooth region, guided by the occlusal plane. The base was constrained in all directions. The Maximum Principal Stress was the failure criteria chosen for the analysis. Results:The Finite Element Analysis showed that the most conservative designs presented less stress concentration on the ceramic veneer. However, the highest tensile stress concentrations were observed on lithium disilicate veneer with extend design, on the middle third. The type of occlusal contact presented different stress patterns among the preparation designs; the incisal contact showed higher stress concentration compared to middle third contact regardless the ceramic material. Conclusion: To perform a ceramic veneer in upper central incisor, the feldspathic ceramic presented promising results and should be recommended when the extended design was done. Regarding contact types, the incisal contact is more prone to failure regardless the ceramic and preparation design. (AU).

Objetivo: Avaliar o efeito de quatro desenhos de preparo, dois materiais cerâmicos e dois tipos de contato oclusais na distribuição de tensão de laminado cerâmico em incisivo central superior. Material e métodos: Modelos 3D foram realizados em software de modelagem contendo esmalte, dentina, polpa, simulador de ligamento periodontal e uma base de resina de poliuretano. Os desenhos foram modelados e exportados para o software de engenharia para realizar análise estatística estrutural. Para a malha, foram usados um total de 155429 elementos tetraedros e 271683 nós, após teste de convergência de 10%. Dois materiais, dissilicato de lítio e cerâmica feldspática, foram simulados. Uma carga estática de 100N em 45º foi aplicada no terço incisal e médio na região palatina do dente, guiada pelo plano oclusal e a base foi restringida em todas as direções. A tensão de tração foi o critério de falha escolhido para a análise. Resultados: A análise de elementos finitos mostrou que os desenhos mais conservadores apresentaram menor concentração de tensão no laminado cerâmico. Contudo, as maiores concentrações de tensões foram observadas no laminado de dissilicato de lítio com preparo estendido no terço médio. O tipo de contato oclusal apresentou diferentes padrões de tensões entre os diferentes desenhos, o contato incisal mostrou maior concentração de tensão em relação ao contato do terço médio independentemente do material cerâmico Conclusão: Para a confecção de laminado cerâmico em incisivo central superior, a cerâmica feldspática apresentou resultados promissores e é recomendada quando for feito preparo estendido. Em relação aos tipos de contato, o contato incisal é mais sujeito a falhas independentemente da cerâmica e desenho do preparo. (AU)

Influência do tipo de preparo na adaptação interna e infiltração marginal em laminados cerâmicos / Influence of the design preparation on the internal adaptation and marginal infiltration in ceramic laminate veneers

Este estudo laboratorial teve como objetivo avaliar a infiltração marginal, adaptação interna e gap cervical de laminados cerâmicos, em função da realização ou não de preparo. Método: Vinte e quatro incisivos centrais superiores hígidos, com volumes e tamanhos padronizados, foram subdivididos em dois grupos, n=12, de acordo com o tipo de preparo. GRUPO CP - minimamente invasivo com linha de término na extensão do preparo; GRUPO SP ­ sem preparo, somente remoção de áreas retentivas. Todos os espécimes foram moldados com silicone de adição (Virtual Ivoclar - Vivadent), e sobre os modelos obtidos foram confeccionados laminados em cerâmica de Dissilicato de Lítio (Emax Press Ivoclar-Vivadent) com espessuras entre 0.3/0.7mm. Após ajustes, as peças foram cimentadas com cimento resinoso fotopolimerizável (Variolink Esthetic LC Ivoclar ­ Vivadent), seguindo as recomendações do fabricante. Em seguidas os espécimes foram envelhecidos em cicladoras térmica, 6.000 ciclos de 5 a 55ºC, e mecânica com 100N por 100.000 ciclos. Após o término das ciclagens todos foram imersos em substância corante por 24 horas e cortados paralelamente ao eixo do dente e horizontalmente para avaliação da infiltração marginal, adaptação interna e gap cervical em esteriomicroscópio. Os resultados apontaram que, na infiltração marginal, o grupo CP teve a maior média na região cervical (1,601 mm) comparado ao grupo SP (1,471 mm), porém não estatisticamente significante. Em ambos os grupos a infiltração marginal na região cervical foi maior que na proximal, diferindo estatisticamente. A adaptação interna foi melhor no grupo CP nos três terços analisados, porém somente no terço cervical houve diferença estatisticamente significante. O gap cervical teve menores valores no grupo SP, porém sem diferença estatisticamente significante. Conclui-se que o tipo de preparo não apresentou influência significativa em termos de infiltração marginal e adaptação, mostrando que ambas as situações podem ser clinicamente aceitáveis(AU)

This laboratory study aimed to evaluate the marginal infiltration, internal adaptation and cervical gap of ceramic laminate venners, by whether or not preparation. Method: Twenty-four upper central incisors with standard volumes and sizes were subdivided into two groups, n = 12, according to the type of preparation. CP GROUP - minimally invasive with finishing line in preparation extension; GRUPO SP - without preparation, only removal of retentive areas. All the specimens were molded with addition silicone (Virtual Ivoclar - Vivadent), on the obtained models laminates in ceramic of Lithium Dissilicate (Emax Press Ivoclar - Vivadent) were made with thicknesses between 0.3 / 0.7mm. After adjustments, the pieces were cemented with photopolymerizable resin cement (Variolink Esthetic LC Ivoclar - Vivadent), following the manufacturer's instructions. Then the specimens were aged in thermal cycling machine, 6,000 cycles of 5 to 55ºC, and mechanical with 100N per 100,000 cycles. After the cycling, all specimens were immersed in dye substance for 24 hours and cut parallel to the axis of the tooth and horizontally for evaluation of marginal infiltration, internal adaptation and cervical gap in stereomicroscope. The results showed that, in marginal infiltration, the CP group had the highest mean in the cervical region (1.601 mm) compared to the SP group (1.471 mm), but not statistically significant. In both groups the marginal infiltration in the cervical region was greater than in the proximal one, differing statistically. Internal adaptation was better in the CP group in the three thirds analyzed, but only in the cervical third there was a statistically significant difference. The cervical gap had lower values in the SP group, but without statistically significant difference. It was concluded that the type of preparation did not have significant influence in terms of marginal infiltration and adaptation, showing that both situations can be clinically acceptable(AU)