A rationale method for evaluating unscrewing torque values of prosthetic screws in dental implants

Abstract

ObjectivesPrevious studies that evaluated the torque needed for removing dental implant screws have not considered the manner of transfer of the occlusal loads in clinical settings. Instead, the torque used for removal was applied directly to the screw, and most of them omitted the possibility that the hexagon could limit the action of the occlusal load in the loosening of the screws. The present study proposes a method for evaluating the screw removal torque in an anti-rotational device independent way, creating an unscrewing load transfer to the entire assembly, not only to the screw.Material and methodsTwenty hexagonal abutments without the hexagon in their bases were fixed with a screw to 20 dental implants. They were divided into two groups: Group 1 used titanium screws and Group 2 used titanium screws covered with a solid lubricant. A torque of 32 Ncm was applied to the screw and then a custom-made wrench was used for rotating the abutment counterclockwise, to loosen the screw. A digital torque meter recorded the torque required to loosen the abutment.ResultsThere was a significant difference between the means of Group 1 (38.62±6.43 Ncm) and Group 2 (48.47±5.04 Ncm), with p=0.001.ConclusionThis methodology was effective in comparing unscrewing torque values of the implant-abutment junction even with a limited sample size. It confirmed a previously shown significant difference between two types of screws.

A thermosensitive chitosan‐based hydrogel for sealing and lubricating purposes in dental implant system

“…The preload, also called clamping force, is induced by the compression between implant and abutment when abutment is tightened into implant with a certain torque . The preload is crucial for the stability of abutment, and the greater resistance to screw loosening relies on greater preload . However, it has been reported that the percentage of the tightening torque transformed to preload is only 10%, while 90% is utilized to overcome the friction between implant and abutment .…”

“…relies on greater preload. 14 However, it has been reported that the percentage of the tightening torque transformed to preload is only 10%, while 90% is utilized to overcome the friction between implant and abutment. 15 An effective method to increase preload is decreasing the friction.…”

Pérdida de torque de los tornillos de fijación del pilar en implantes sometidos a cargas cíclicas

“…Esta complicación se ha establecido como un 6% de las complicaciones protésicas. La acumulativa incidencia de complicaciones relacionadas con el tipo de conexión es del 5.8% al 12.7% en 5 años 20,23,35,38,40,41,42 y solo el 35% de los tornillos se mantienen estables en los primeros 3 años 38 . El 26% de las prótesis atornilladas y el 43% de los tornillos se aflojan en el primer año de función 43 .…”

“…La precarga es la tensión, en voltios (V) transferibles posteriormente a newton (N), que se genera al apretar un tornillo a un torque determinado 4,33,41,42,45,53,54,55,56,57,58 . El tornillo se estira y posteriormente se produce una recuperación elástica que sitúa a las espiras en tensión creando una fuerza compresiva entre la cabeza del tornillo y el pilar, entre las espiras del tornillo y el implante y en la interfase implante-pilar, lo que deja el pilar y el implante ensamblados en una unión estable comprimida 4,7,33,34,40,41,44,45,57 , lo que permite la resistencia a las cargas externas y mejora la resistencia a la fatiga de la unión implante-pilar 7,34,40,45,54,59 .…”

“…Los estudios citados anteriormente son comparables al presente protocolo, sin embargo en la literatura científica existe una gran variabilidad de protocolos de ensayo, desde aquellos que no someten las muestras a ciclado mecánico 35,36,38,42,53,58,65,70,62 hasta otros trabajos en los que se realiza termociclado de las muestras a una temperatura de 37°C para simular la temperatura del medio ambiente oral 34,72,95 .…”