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      Relation between implant/abutment vertical misfit and torque loss of abutment screws

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          Abstract

          This study investigated whether there is a direct correlation between the level of vertical misfit at the abutment/implant interface and torque losses (detorque) in abutment screws. A work model was obtained from a metal matrix with five 3.75 x 9 mm external hex implants with standard platform (4.1 mm). Four frameworks were waxed using UCLA type abutments and one-piece cast in commercially pure titanium. The misfit was analyzed with a comparator microscope after 20 Ncm torque. The highest value of misfit observed per abutment was used. The torque required to loose the screw was evaluated using a digital torque meter. The torque loss values, measured by the torque meter, were assumed as percentage of initial torque (100%) given to abutment screws. Pearson's correlation (α=0.05) between the misfit values (29.08 ± 8.78 µm) and the percentage of detorque (50.71 ± 11.37%) showed no statistically significant correlation (p=0.295). Within the limitations of this study, it may be concluded that great vertical misfits dot not necessarily implies in higher detorque values.

          Translated abstract

          Este trabalho teve como objetivo correlacionar o nível de desajuste vertical pilar/implante a perda do torque aplicado (destorque). Um modelo de trabalho foi obtido a partir de uma matriz metálica com cinco implantes tipo hexágono externo (Titamax, Neodent, Curitiba, Brasil) com plataforma regular (4,1 mm). Sobre esta matriz, quatro infra-estruturas foram enceradas utilizando pilares tipo UCLA e fundidas em monobloco com titânio comercialmente puro (Tritan grau I, Dentaurum, Alemanha). Os desajustes foram analisados com um microscópio óptico comparador (Mytutoyo, Japão) após torque de 20 Ncm. O maior valor de desajuste observado por pilar foi utilizado. O valor do torque de desaperto, avaliado com um torquímetro digital (TQ-680, Instrutherm, Brasil), foi calculado em porcentagem do valor do torque inicial (100%) dado aos parafusos protéticos. O teste de correlação de Pearson (p<0,05), entre os valores de desajuste (29,08 ± 8,78 µm) e as porcentagens da perda de torque (50,71 ± 11,37%), não mostrou correlação estatisticamente significante (p=0,295) entre tais fatores. Dentro das limitações do estudo, pode ser concluído que não necessariamente grandes valores de desajustes verticais implicarão em grades perdas de torque.

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          Most cited references19

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          Osseointegration and its experimental background.

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            The effect of implant/abutment hexagonal misfit on screw joint stability.

            P P Binon (2015)
            A series of 10 incrementally larger, machined ASTM Grade 23 titanium non-segmented (UCLA type) abutments was loaded off axis with 133 N and cycled at 1150 vertical strokes per minute and 28 counterclockwise rotations per minute to determine screw joint stability. Abutment internal hexagonals ranged from 0.1065 to 0.1110 inches. External hexagonal mean flat-to-flat width was 2.684 mm. Rotational misfit between international and external hexagonals ranged from 1.94 degrees for the smallest abutment to 14.87 degrees for the largest. Screw joint failure ranged from 134,000 to 9.3 million cycles. The tightest matrix/patrix hexagonal screw joint failed at a mean of 6.7 million cycles. This study indicated that there was a direct correlation between hexagonal misfit and screw joint loosening. A rotational misfit of under 2 degrees provided the most stable and predictable screw joint.
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              Fit of implant frameworks fabricated by different techniques.

              This study evaluated the precision of fit between an implant framework and a patient simulation model that consisted of five implant abutments located in the mandibular symphysis area. One-piece cast frameworks were compared with Procera machined and laser-welded frameworks with laser videography.
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                Author and article information

                Contributors
                Role: ND
                Role: ND
                Role: ND
                Role: ND
                Role: ND
                Role: ND
                Journal
                bdj
                Brazilian Dental Journal
                Braz. Dent. J.
                Fundação Odontológica de Ribeirão Preto (Ribeirão Preto )
                1806-4760
                2008
                : 19
                : 4
                : 358-363
                Affiliations
                [1 ] Federal University of Rio Grande do Norte Brazil
                [2 ] Universidade de São Paulo Brazil
                [3 ] Federal University of Uberlândia Brazil
                [4 ] Universidade de São Paulo Brazil
                Article
                S0103-64402008000400013
                10.1590/S0103-64402008000400013
                19180328
                cd701125-397a-40dd-9234-f16baa8cd492

                http://creativecommons.org/licenses/by/4.0/

                History
                Product

                SciELO Brazil

                Self URI (journal page): http://www.scielo.br/scielo.php?script=sci_serial&pid=0103-6440&lng=en
                Categories
                DENTISTRY, ORAL SURGERY & MEDICINE

                Dentistry
                dental prosthesis implant-supported,prosthesis fitting,torque
                Dentistry
                dental prosthesis implant-supported, prosthesis fitting, torque

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