Machined and plastic copings in three-element prostheses with different types of implantabutment joints: a strain gauge comparative analysis

Abstract

ObjectiveUsing strain gauge (SG) analysis, the aim of this in vitro study was quantify the strain development during the fixation of three-unit screw implant-supported fixed partial dentures, varying the types of implant-abutment joints and the type of prosthetic coping. The hypotheses were that the type of hexagonal connection would generate different microstrains and the type of copings would produce similar microstrains after prosthetic screws had been tightened onto microunit abutments.Materials and methodsThree dental implants with external (EH) and internal (IH) hexagonal configurations were inserted into two polyurethane blocks. Microunit abutments were screwed onto their respective implant groups, applying a torque of 20 Ncm. Machined Co-Cr copings (M) and plastic prosthetic copings (P) were screwed onto the abutments, which received standard wax patterns. The wax patterns were cast in Co-Cr alloy (n=5), forming four groups: G1) EH/M; G2) EH/P; G3) IH/M and G4) IH/P. Four SGs were bonded onto the surface of the block tangentially to the implants, SG 1 mesially to implant 1, SG 2 and SG 3 mesially and distally to implant 2, respectively, and SG 4 distally to implant 3. The superstructure’s occlusal screws were tightened onto microunit abutments with 10 Ncm torque using a manual torque driver. The magnitude of microstrain on each SG was recorded in units of microstrain (µε). The data were analyzed statistically by ANOVA and Tukey’s test (p<0.05).ResultsMicrostrain values of each group were: G1= 338.1±223.0 µε; G2= 363.9±190.9 µε; G3= 415.1±53.5 µε; G4= 363.9±190.9 µε. No statistically significant difference was found between EH and IH, regardless of the type of copings (p>0.05). The hypotheses were partially accepted.ConclusionsIt was concluded that the type of hexagonal connection and coping presented similar mechanical behavior under tightening conditions.

Strain Gauge analysis of non-axial loads in three-element implant-supported prostheses

“…Concerning to the linear positioning of the strain gauges, this study is in agreement of the study conducted by Heckmann et al, 2004, among others, who studied the microstrain around the implants with 3-element superstructures [30,[32][33][34][35][36][37][38]. This position justifies the little variation found in the microstrain means of the non-axial loads executed by this present study, and the highest values were found in the points farthest from the implant e (A' and B').…”

Load-Application Devices: A Comparative Strain Gauge Analysis

“…In this study, the strain gauges were bonded tangentially to the implant platform on the polyurethane block. This positioning of the strain gauges method has been used in previous studies (13,(15)(16)(17)(18)20). In addition, the flat surface of the polyurethane block facilitates the positioning and bonding of the strain gauges when compared with other studies, which are bonded to the implants (11), to the abutment (22) and to the metallic structures of the prosthesis (15,20).…”

“…Several techniques have been employed to evaluate the biomechanical loads on implants, such as photoelastic stress analysis (8)(9)(10), finite elements stress analysis (6,11), mathematical calculations (12) and strain gauge analysis (9,11,(13)(14)(15)(16)(17)(18).…”

“…Materials have different resistivities, which can be measured accurately at the site where the strain gage is attached, using a Wheatstone's bridge circuit (9,19). This technique has been proposed to evaluate strains in implant-supported prostheses in vitro (9,11,13,(16)(17)(18)20), in vivo (15) and under static (13,16) and/or dynamic loads (21).…”

Estudo comparativo das microdeformações resultantes de cargas estáticas axiais e não axiais em próteses de três elementos implantossuportadas

“…O osso que os circunda não constitui um substrato homogêneo, de modo que suas propriedades físicas variam conforme a idade, o estado funcional e os fatores sistêmicos do paciente 7 . Diante disso, estudos in vitro têm empregado materiais considerados homogêneos e isotrópicos 6,9,20 . Associado a esses fatores, foi utilizado neste estudo um modelo homogêneo com propriedades elásticas uniformes, preconizadas em estudos que visam a simular o osso humano.…”