Abstract: Microplasma welding is a less expensive alternative to
laser welding in dental technology. The aim of the study was to
highlight discontinuities present in the microplasma welded joints of
dental base metal alloys by visual analysis. Five base metal alloys
designated for fixed prostheses manufacture were selected for the
experiments. Using these plates, preliminary tests were conducted by
microplasma welding in butt joint configuration, without filler
material, bilaterally and with filler material, proper for each base
metal. Macroscopic visual inspection was performed to assess
carefully the irregularities in the welds. Electron microscopy allowed
detection of discontinuities that are not visible to the eye and
revealing details regarding location, trajectory, morphology and size
of discontinuities. Supplementing visual control with microscopic
analysis allows to detect small discontinuities, which escapes the
macroscopic control and to make a detailed study of the weld.
Abstract: Knowledge of factors, which influence stress and its
distribution, is of key importance to the successful production of
durable restorations. One of this is the marginal geometry. The
objective of this study was to evaluate, by finite element analysis
(FEA), the influence of different marginal designs on the stress
distribution in teeth prepared for cast metal crowns. Five margin
designs were taken into consideration: shoulderless, chamfer,
shoulder, sloped shoulder and shoulder with bevel. For each kind of
preparation three dimensional finite element analyses were initiated.
Maximal equivalent stresses were calculated and stress patterns were
represented in order to compare the marginal designs. Within the
limitation of this study, the shoulder and beveled shoulder margin
preparations of the teeth are preferred for cast metal crowns from
biomechanical point of view.