Evaluation of the occlusal contact area of molar dental implants comparing two different thicknesses (16 µm and 200 µm) of articulating occlusal papers and forces (200 and 250 N): a pivot in vitro study

Introduction: The goal of this pilot study was to evaluate the differences between checking occlusion on implants crowns using 16 or 200 µm thickness of articulating occlusal paper, and to compare the stained occlusal area between the groups after bite forces of 200 and 250 N. Methods: It was included 10 casts of articulated-type IV gypsum, 10 NiCr crowns, articulating occlusal papers (16 µm and 200 µm thick), and a compression test machine. Compressive forces (200 and 250 N.mm) were applied on models, to check the occlusal contact area of fixed and cemented crowns. The contact areas on the crowns were measured through images obtained by the scanning electron microscope. Statistical tests were performed considering the significant level of 5% (p≤0.05). Results: The stains found using 200 µm of articulating paper were higher than those with 16 µm, independent of the force applied. However, the stains obtained in lower teeth with different strengths (200 and 250N) marked with 16 µm articulating paper were not possible to score. The articulating paper variable had significant statistical results (p=0.002), while the variables force (p=0.443) and articulating paper-force interaction (p=0.607) were not significant. The mean area found in staining using the 200 µm and 16 µm papers was, respectively, 8.3380 mm2 and 3.4759 mm2. Conclusion: It was possible to confirm that 200 µm of articulating occlusal paper showed better and significant results to stain the occlusal area, permitting a more accurate adjustment independent of the force applied.

Avaliação clínica da sobrevida de três sistemas de implantes em diferentes densidades ósseas: um estudo retrospectivo de 707 implantes em 194 pacientes / Clinical evaluation of three different dental implant systems in varied bone densities: a retrospective study of 707 implants and 194 patients

Objetivo: avaliar, através de um estudo retrospectivo, a sobrevida clínica de três sistemas de implantes em diferentes densidades ósseas. Material e métodos: dois sistemas de implantes nacionais titânio c.p. grau 2 e um sistema internacional titânio c.p. grau 3 foram utilizados conforme as recomendações dos fabricantes. Esses implantes serviram como suporte para pró teses unitá ria, parcial fixa, total fixa e removível em variados sí tios da cavidade oral. Os sí tios foram classificados de acordo com a densidade óssea. As análises uni e multivariada com regressão logística foram usadas para verificar a influência do sexo, idade, localização anatômica e tipo de implante na taxa de sobrevivência (nível de significância 5%). Resultados: 707 implantes de titânio puro com diferentes macrogeometrias e tratamento de superfície foram inseridos em 194 pacientes. Dos implantes instalados, o índice geral de sobrevivência foi 94,5%. A taxa de sobrevivência foi maior no sexo masculino do que no feminino (96,5% x 93,3%). O valor OR para o sexo feminino fi cou entre 1,96 (univariada) e 2,35 (multivariada). Conclusão: dentro dos limites deste estudo, a idade maior ou igual a 40 anos, o sexo feminino, o uso de implantes cilíndricos de titânio c.p. grau 2 com superfície tratada por ácido e jateada com óxido de alumínio, e a densidade óssea D4 que não seja na região mandibular apresentam-se como fatores de resultados estatisticamente significativos.

Objective: to perform a retrospective evaluation on the clinical survival of three implant systems placed at different bone densities. Material and methods: two grade 2 c.p. titanium national systems and one grade 3 c.p. titanium international system were used according the manufacture's recommendations. These were restored with single-tooth, partial fixed/removable prostheses in several oral cavity sites classified according to their bone densities. Uni- and multivariate logistic regression analysis were used to calculate the influence of gender, age, anatomic location, and implant type on the survival rates (5% level of significance). Results: 707 dental implants with different macrogeometries and surface treatments were inserted in 194 patients. The overall survival rate was 94.5%. The survival was higher for male and females (96.5% versus 93.3%). The Odds ratio for female gender was 1.96 (univariate) and 2.35 (multivariate). Conclusion: within the limits of this study, age ≥ 40 years, female, cylindrical shaped Grade 2 c.p titanium, acid-etched and aluminum oxide blasted, and the D4 bone density (except for the mandibular arch) can be considered factors with signifi cant influence on the survival results.

Precisão dimensional e resistência à fadiga de conectores tipo link para pilares protéticos de zircônia / Fit accuracy and fatigue strength of link connectors for zirconia abutments

Objetivo: verificar a precisão dimensional e a resistência à fadiga de conectores tipo link sobre pilares de zircônia. Material e métodos: oito implantes dentários de 3,5 mm X 8,5 mm foram montados em uma base de poliacetal (E=3GPa), em 30 graus de inclinação, e receberam links de titânio com plataformas hexagonais de 4,5 mm e 3,5 mm, ambos com comprimento de 11,5 mm. Depois, os pilares de zircônia foram apertados com 32 Ncm com uso de torquímetro digital. Três sequências de testes de fadiga foram usadas: link 4,5 ­ carga inicial 100 N, incrementos de 100 N em intervalos de 12 mil ciclos; link 4,5 ­ carga inicial 100 N, incrementos de 100 N em intervalos de 200 mil ciclos; e link 3,5 ­ carga inicial 100 N, incrementos de 100 N em intervalos de 200 mil ciclos até a fratura. Os testes foram realizados em meio seco, e a força com variação senoidal entre 100 N e 800 N. As imagens das interfaces entre o link e a zircônia foram verificadas por microscopia eletrônica de varredura. Resultados: para o link 4,5, na primeira tentativa, a carga máxima foi de 700 N até os 96 mil ciclos (sem fratura), na segunda tentativa, a carga máxima foi de 800 N, não havendo fratura aos dois milhões de ciclos. Para o link 3,5, a carga máxima foi de 500 N e 814.578 ciclos, ocorrendo fratura na base da zircônia. O espaço entre a base do link e o pilar de zircônia foi de 437,1 nanômetros. Conclusão: a precisão no encaixe do componente protético ao implante aumentou a resistência à fadiga da estrutura. As cargas de fratura após a fadiga estão acima do esperado para componentes de zircônia. O espaço entre a base do link e o pilar de zircônia é menor que o tamanho médio das bactérias Mutans encontradas na cavidade oral, o que possivelmente reduzirá a infiltração bacteriana.

Objective: to analyze the fit accuracy and the fatigue strength of zirconia abutments with titanium link-type connectors. Material and methods: eight dental implants (3.5 x 8.5 mm) were inserted into a polyacetal base (E=3GPa) at 30-degree inclination and received zirconia abutments with Ti links (4.5 mm and 3.5 mm hex platforms; 11.5 mm length). Eight zirconia abutments were tightened to 32 Ncm with a digital torque wrench. Three fatigue test protocols were used: link 4.5: initial load 100 N (100 N increments after each 12,000 cycles); link 4.5: initial load 100 N (100 N increments after each 200,000 cycles), and link 3.5: initial load 100 N (100 N in increments after each 200,000 cycles) until fracture. The tests were performed in a dry environment with sinusoidal variation between 100 N and 800 N. The interfaces between the links and the zirconia abutments were observed by scanning electron microscopy. Results: the maximum load in the first fatigue test of link 4.5 was 700 N at 96,000 cycles (without fracture); on the second fatigue test, the maximum load was 800 N with no fracture until 2 million cycles. For the link 3.5, the maximum load was 500 N and the fracture at the base of the zirconia abutment occurred at 814,578 cycles. The space between the base of the Link and the zirconia abutment was 437.1 nm. Conclusion: the fit accuracy of the prosthetic component to the implant platform increased the fatigue resistance of the structure. The maximum fatigue load fracture is higher than expected for zirconia components. The space between the base of the link and the zirconia abutment is lower than the mutans spp. found in the oral cavity, which might reduce dental leakage.