Multiple-unit implant frames: one-piece casting vs. laser welding and brazing

Abstract

The linear distortion of prostheses over implants, one-piece casting and cast in sections followed by laser welding by laser and brazing was evaluated in an edentulous mandibular model with five parallel abutments, with a distance of 10mm from center to center. Seventy five gold cylinders were tightened with screws on the abutments with 10Ncm torque. The cylinder/analogue assemblies were measured by microscopic examination (0.001mm accuracy) and the obtained results were compared with the GC (control group). Fifteen metal frames were waxed and cast in a gold alloy (Stabilor, Degussa Hulls, Brazil) and divided into three groups with five elements each, as followed: GM (one-piece casting), GB (section and brazing) and GL (section and laser welding). In all groups, measurements were taken at the right, left, buccal and lingual sides of the cylinder/analogue interface and the results were submitted to analysis of variance (ANOVA) and to the Tukey test (5%). The smallest amount of distortion was seen in the laser group (GL with a mean value of 13.58), followed by the brazing group (GB with a mean value of 24.33) and one-piece (GM with a mean value of 40.00). The greatest distortion was found in the one-piece group (GM).

Comparative analysis of ceramic flexural strength in co-cr and ni-cr alloys joined by TIG welding and conventional brazing

“…The welding process is widely used during the manufacture of fixed dental prostheses. Currently, several techniques are employed, and each has its own advantages and disadvantages 14,25 .…”

“…When the metal framework of the prosthesis does not fit perfectly on the abutments, the metallic infrastructure is sectioned, and the welding process is carried out after adjusting to the abutments; this procedure aims to improve the adaptation of prostheses to abutments or implants, thereby restoring the force previously lost following the sectioning of the metallic infrastructure 14 . The joining of metals in prosthetic structures can be achieved by brazing or via laser or tungsten inert gas (TIG) welding 9,15 . In the brazing process, the bonding between metals is produced by heating an additional metal that has a melting point lower than that of the base metal to a suitable temperature.…”

Effect of joining the sectioned implant-supported prosthesis on the peri-implant strain generated in simulated mandibular model

“…conducted a study to compare the misfit of framework fabricated by one-piece casting and cast in sections followed by laser welding and brazing. [ 14 ] Based on the results of the study, they concluded that less distortion in framework was observed when they were cast in sections and reunited by laser welding. They stated that the probable reason for the least strain generated by employing laser welding technique to reunite the sectioned prosthesis could be a small heat affected zone in the metal and the lesser amount of material added to the welded region which reduces the volume of metal that is going to contract on cooling, thus leading to less distortion of welded framework.…”

Interaction phenomena between oral implants and bone tissue in single and multiple implant frames under occlusal loads and misfit conditions: A numerical approach

“…Further investigation should be performed to consider different characteristics of the peri-implant bone tissue and different misfit configurations, such as longitudinal, transversal, or angular, which lead to different effects. For example, the numerical analysis of the case of a linear misfit of 0.04 in the intrusive direction, as representation of another possible defect of the casting process, 29 shows that the stress state induced in the case of osseointegration of the implants could again be comparable with that arising from occlusal loading, with a compressive maximum stress of about 50 MPa. An angular misfit in the plane of section I in Figure 2 is also considered.…”

“…It is assumed that the misfit is caused by a bar-implant misalignment of 0.05 mm in the distal-mesial direction, in agreement with the possible defects arising from the manufacturing of a bar [26][27][28] and related in particular to one-piece casting. 29 The numerical procedure for inducing a misfit is carried out by using two sets of rigid elements that form two frames joined with the implant and bar surfaces in contact [ Figure 3(b)]. The misfit is obtained by imposing a null gap between the frames.…”