Analysis of the marginal adaptation of different crowns fabricated with computer-aided technology using an intraoral digital scanner

Aim: The aim of this study was to evaluate the marginal adaptation of ceramic and composite resin crowns fabricated with computer-aided design and computer-aided manufacturing (CAD/CAM) technology using an intraoral digital scanner. Methods: A human mandibular right second molar was prepared for a ceramic crown. The impressions were made using intraoral scanning device and crowns were milled. Tem crowns were fabricated for each group (n=10): GF ­ Feldspathic Ceramic (Cerec Blocs, Sirona), GL - Lithium Disilicate Ceramic (IPS e.max CAD, Ivoclar), GG - composite resin (Grandio Blocs, VOCO) and GB - composite resin (Brava Block, FGM). The marginal gap was measured for each specimen at 4 points under magnification with a stereomicroscope. All data were statistically analyzed using one-way ANOVA followed by the Tukey's test (α=.05). Results: The lowest marginal discrepancy value was observed in GB (60.95 ± 13.64 µm), which was statistically different from the GL (84.22 ± 20.86 µm). However, there was no statistically significant difference between these groups when compared with the other groups, GF (73.26 ±8.19 µm) and GG (68.42 ± 11.31 µm). Conclusion: It can be concluded that the composite resin presented the lowest variance compared to the lithium disilicate glass ceramic, although the marginal gap of all materials tested was within the acceptable clinical limit (120 µm)

Marginal adaptation of provisional crowns made of acrylic and bisacrylic resins using different impression materials

Aim: To evaluate the marginal adaptation of provisional crowns made of acrylic and bisacrylic resins using different impression materials. Methods: a metal die and a matrix applied through a direct technique were used to fabricate the specimens. The impression materials used as a matrix were divided into four groups: Irreversible hydrocolloid(IH), laboratory silicone (LS), condensation silicone (CS), and addition silicone (AS). After the impression procedures, each matrix was loaded with the provisional prosthetic materials, Alike, Duralay, Protemp 4, and Structur 3 (n = 12). Marginal discrepancy was evaluated using a stereomicroscope at ×45 magnification. The images obtained were transferred to the Corel Draw X7 program, and the distances from the cervical margins of the specimen to the reference lines at the metal die were measured vertically. The data were analyzed by using 2-way ANOVA followed by the Tukey test (α=.05). Results: the acrylic resins had higher values ​​of marginal discrepancy compared to the bisacrylic resins. A statistically significant difference was found between all impression materials, and the irreversible hydrocolloid presented higher values of discrepancy (303.28­613.31 µm), whereas addition silicone had the lowest (48.61­190.06 µm). Conclusions: the bisacrylic resins had a better marginal adaptation compared to the acrylic resins. The addition silicone promoted a better marginal adaptation of the provisional prosthetic materials tested, followed by condensation silicone, laboratory silicone, and irreversible hydrocolloid

Evaluation of the marginal accuracy of provisional restorations made of acrylic resins

Aim: To evaluate the marginal accuracy of provisional crowns made with acrylics resins and to identify the surface(s) with the highest marginal discrepancy. Methods: A direct technique was used to fabricate 96 provisional restorations with 8 materials: Dencrilay, Dencôrlay, Dencôr, Vipicor, Duralay, Resinlay Speed, Refine Bright and Alike (n=12). The provisional crowns were made on a prepared molar-shaped metal die with a vinyl polysiloxane impression as a matrix. Marginal discrepancy of provisional restorations was analyzed at buccal, lingual, mesial and distal surfaces of metal die finish line in a stereomicroscope lupe at 100X. The images obtained were transferred to the Corel Draw X7 program and the distances from the cervical margins of the specimen to the reference lines were measured vertically. Comparisons were made with 1-way analysis of variance and the Tukey test (p <0.05). Results: The Alike resin exhibited the lowest marginal discrepancy (0.018 mm) and was significantly different from the Dencôrlay (0.037 mm), Filter Bright (0.034 mm), Duralay (0.033 mm) and Vipicor (0.032) resins. The buccal surface showed the highest marginal discrepancy (0.040 mm) compared to those of other surfaces (distal 0.029mm, lingual 0.028mm and mesial 0.024mm). Conclusion: The marginal adaptation of all materials and surfaces tested in this study were within a clinical acceptable limit. The Alike resin showed the best performance compared to Dencôrlay, Refine Bright, Duralay, and Vipicor resins. The buccal surface showed the highest marginal discrepancy than those of the other tested surfaces

Effect of colorant solutions on the color stability of provisional prosthetic materials

Aim: To evaluate the color stability of acrylic and bis-acrylic resins after immersion in 3 staining solutions. Methods: Forty-eight samples (10 x 2 mm) of each provisional restorative material (Duralay, Dencrilay, Structur 2 and Protemp 4) were fabricated and distributed into four groups (n = 12): G1 ­ distilled water (control group); G2 ­ a cola flavored soft drink; G3 ­ wine and G4 ­ coffee. The specimens were immersed for seven days at 37°C in the solutions, which were changed every 24 hours. The color of all specimens was measured with a spectrophotometer (VITA Easyshade Advance) before (T0) and after immersion (T1), and the color changes (ΔE) were calculated. Nonparametric Kruskal-Wallis tests were used, followed by Dunn's test with a significance level of 5%. Results: For the acrylic resins (Duralay and Dencrilay), the largest color change values were obtained in group G4 ­ coffee, whereas in the bis-acrylic resins (Protemp 4 and Structur 2), the largest color difference was observed in groups G3 ­ wine and G4 ­ coffee. The acrylic resins showed statistically significantly less color change than the bis-acrylic resins. Conclusions: The coffee and the wine promoted larger color changes in the provisional prosthetic materials tested in this study. The acrylic resins showed more color stability than the bis-acrylic resins

Comportamento do tecido mole peri-implantar na interface com o titânio: uma revisão de literatura / Behavior of peri-implant soft tissue in the interface with titanium: a literature review

A adesão do tecido mole ao titânio, biologicamente capaz de preservar e proteger as estruturas peri-implantares, contribui para a estabilidade da mucosa peri-implantar e manutenção da estética rosa. Assim, o objetivo deste trabalho foi, por meio de uma revisão de literatura, descrever a interação entre o titânio utilizado nos componentes protéticos e implantes e o tecido mole, para a manutenção da estabilidade e saúde dos tecidos peri-implantares. Concluiu-se que a estabilidade dos tecidos moles peri-implantares é um dos critérios de sucesso para reabilitações com implantes, uma vez que o estabelecimento de uma íntima relação entre o tecido mole e o titânio do implante, bem como dos componentes protéticos, promove uma barreira protetora à penetração de bactérias e seus produtos metabólicos, favorecendo o desempenho do implante em longo prazo.

The soft tissue’s adhesion to titanium, biologicaly capable to preserve and protect the peri-implant structures contributes to peri-implant mucosa’s stability and maintenance of pink aesthetics. Thus, the object of this study was, through a literature review, to introduce the interaction between the titanium used in the prosthetic and implant components and the soft tissue to the maintenance of stability and the health of peri-implant tissues. It was concluded that the peri-implant soft tissue’s stability is one of the criteria of success to rehabilitation with implants,once the establishment of an intimate relation between the soft tissue and the titanium of the implant, as well asthe prosthetic components, promote a protective barrier to penetration of bacteria and its metabolic products,favoring the implant’s long-term performance.

Avaliação dos instrumentos utilizados pelos cirurgiões-dentistas para higienização dos abutments de titânio / Evaluation of instruments used by dentists for cleansing titanium abutments

Apesar de o titânio ser um metal resistente, ele é facilmente arranhado, o que pode alterar a rugosidade da superfície dos abutments e implantes, levando ao aumento do acúmulo de biofilme. Assim, o objetivo deste trabalho foi avaliar quais os instrumentos utilizados pelos cirurgiões-dentistas na cidade de Salvador para higienização das superfícies de abutments de titânio e implantes. Para tanto, foram selecionados 40 cirurgiões-dentistas especialistas nas áreas de Implantodontia, Periodontia e Prótese, e aplicado um questionário com 6 perguntas referentes aos instrumentos utilizados como marca, frequência e motivo da escolha. Os resultados demonstraram que 46% dos cirurgiões-dentistas associam a frequência de limpeza no consultório à colaboração do paciente, 57% utilizam cureta plástica para tal limpeza, 72% preferem instrumentos de origem internacional, 86% escolhem o instrumento devido à sua eficácia, 34% indicam para limpeza diária o uso de escova interdental e 82% dos dentistas relataram ter conhecimento dos danos que alguns instrumentos podem causar na superfície dos abutments de titânio. Concluiu-se que as curetas plásticas são as mais utilizadas para limpeza em consultório e a limpeza diária, realizada pelo paciente, é indispensável para o sucesso e longevidade dos implantes

In spite of the fact that titanium is a very strong and resistant metallic element, it is easily scratched. That may alter the surface roughness of abutments and implants and consequently increase biofilm accumulation. The objective of this paper was to evaluate the instruments used by dentists of the city of Salvador to cleanse the implants and the titanium abutment surface. Forty dentists were chosen for the research. They were specialists in Dental Implant, Periodontics and Prothetics and were asked to answer a questionnaire with six questions related to the cleansing instruments like: its brand, frequency of use and reasons for choice. The results showed that 46% of the dentists attribute the frequency of cleansing in the dental office to the patient’s cooperation. 57% of them use plastic curette; 72% have preference for the instruments made abroad; 86% choose the instrument because of their effectiveness; 34% recommend the use of inter-dental toothbrush and 82% informed that they knew of the damage that some instruments may cause to the titanium abutment surface. Some conclusions: a) plastic curettes are the most commonly used instruments for cleansing in the dental office and b) daily cleansing by patients is essential for the success and longevity of implants.

Evaluation of surface characteristics of Ti-6Al-4V and Tilite alloys used for implant abutments

The aim of this study was to evaluate surface free energy (SFE), surface roughness (SR) and surface hardness (SH) of two commercially available materials for fabricating dental implant abutments. In addition, the specimens were investigated by scanning electron microscopy (SEM) to determine the surface morphology. Twenty five discs (5 x 2 mm) of Ti-6Al-4V and Tilite (Ni-Cr-Ti) alloys were used in this study. Surface free energy was determined by the contact angle formed between a drop of distilled, deionized water and the surface of the specimen of each material. The surface roughness was measured with a mechanical profilometer and the surface hardness was evaluated by means of the Vickers hardness micro indentation test. SFE, SR and SH data were analyzed using one-way ANOVA (p < 0.05). Statistical differences (p < 0.05) were found between Ti-6Al-4V (36.2 erg.cm-2; 0.2 æm) and Tilite (30.9 erg.cm-2; 0.16 æm) for SFE and SR. However, the differences between the surface hardness values of Ti-6Al-4V (325.0 kg/mm²) and Tilite (324.3 kg/mm²) were not statistically significant (p > 0.05). Evaluations by SEM revealed different surface morphology. Within the limits of this study, it can be concluded that the Ti-6Al-4V and Tilite alloys showed differences in surface properties, except for surface hardness, suggesting that both alloys may be considered appropriate for producing abutments. Further studies are, however, necessary to elucidate the biological responses to implant abutments made with these alloys.

O objetivo deste estudo foi avaliar a energia livre de superfície (ELS), rugosidade superficial (RS) e dureza de superfície (DS) de dois materiais disponíveis comercialmente para fabricação de "abutments" de implante. Em acréscimo, os espécimes foram investigados por microscopia eletrônica de varredura (MEV) para determinar a morfologia de superfície. Vinte e cinco discos de ligas de Ti-6Al-4V e Tilite (Ni-Cr-Ti) (5 x 2 mm) foram usados neste estudo. A energia livre de superfície foi determinada pela mensuração do ângulo de contato formado entre uma gota de água destilada e deionizada e a superfície do espécime para cada material. A rugosidade superficial foi mensurada com uso de um rugosímetro e a dureza de superfície foi avaliada por meio do teste de microdureza Vickers. Os dados foram analisados usando Análise de variância (P < 0,05). Foram encontradas diferenças significantes (P < 0,05) para os valores de ELS e RS entre Ti-6Al-4V (36,2 erg.cm-2; 0,2 æm) e Tilite (30,9 erg.cm-2; 0,16 æm). Entretanto, os valores de dureza de superfície não foram diferentes para ambos os materiais (Ti-6Al-4V - 325,0 kg/mm² e Tilite - 324,3 kg/mm²) (P > 0,05). A análise topográfica dos materiais pela MEV revelou superfícies diferentes. Dentro das limitações deste estudo, concluiu-se que as ligas de Ti-6Al-4V e Tilite mostraram diferenças nas propriedades de superfícies, exceto dureza, sugerindo que ambas as ligas são adequadas para a confecção de "abutments". Entretanto, estudos são necessários para evidenciar as respostas biológicas aos "abutments" de implantes confeccionados com essas ligas.

Influence of storage solution on enamel demineralization submitted to pH cycling / Influência da solução de armazenagem na desmineralização do esmalte submetido à ciclagem de pH

Dentes humanos extraídos são freqüentemente utilizados para propósitos educacionais ou de pesquisa. Desta forma, é necessário o armazenamento dos mesmos em soluções desinfetantes que não alterem a estrutura dental. Para tanto, sessenta espécimes foram divididos nos seguintes grupos: esmalte armazenado em formol (F1), armazenado em timol (T1), armazenado em formol e submetido à ciclagem de pH (F2) e armazenado em timol e submetido à ciclagem de pH (T2), sendo avaliados por meio de análise de microdureza longitudinal e tiveram a porcentagem de volume mineral pro micrômetro determinada. Diferenças entre os grupos foram encontradas até a profundidade de 30µm da superfície do esmalte (p<0,05), onde o grupo mais desmineralizado era T2. Foi concluído que a solução de armazenagem influenciou na reação do substrato dental a um desafio cariogênico, sugerindo que o formaldeído pode aumentar a resistência do esmalte à desmineralização promovida pelo modelo de ciclagem de pH, quando comparado à desmineralização ocorrida no esmalte armazenado em timol.