14 research outputs found
Mechanical and elemental characterization of solder joints and welds using a gold-palladium alloy
Purpose. This study was conducted to determine whether newer infrared or
laser welding technologies created joints superior to traditional
furnace or torch soldering methods of joining metals. It was designed to
assess the mechanical resistance, the characteristics of the fractured
surfaces, and the elemental diffusion of joints obtained by four
different techniques: (1) preceramic soldering with a propane-oxygen
torch, (2) postceramic soldering with a porcelain furnace, (3)
preceramic and (4) postceramic soldering with an infrared heat source,
and (5) laser welding.
Material and methods. Mechanical resistance was determined by measuring
the ultimate tensile strength of the joint and by determining their
resistance to fatigue loading. Elemental diffusion to and from the joint
was assessed with microprobe tracings. Scanning electron microscopy
micrographs of the fractured surface were also obtained and evaluated.
Results. Under monotonic tensile stress, three groups emerged: The laser
welds were the strongest, the preceramic joints ranged second, and the
postceramic joints were the weakest. Under fatigue stress, the order was
as follows: first, the preceramic joints, and second, a group that
comprised both postceramic joints and the laser welds. Inspection of the
fractographs revealed several fracture modes but no consistent pattern
emerged. Microprobe analyses demonstrated minor diffusion processes in
the preceramic joints, whereas significant diffusion was observed in the
postceramic joints.
Clinical Implications. The mechanical resistance data conflicted as to
the strength that could be expected of laser welded joints. On the basis
of fatigue resistance of the joints, neither infrared solder joints nor
laser welds were stronger than torch or furnace soldered joints
Bioengineered Periodontal Tissue Formed on Titanium Dental Implants
The ability to use autologous dental progenitor cells (DPCs) to form organized periodontal tissues on titanium implants would be a significant improvement over current implant therapies. Based on prior experimental results, we hypothesized that rat periodontal ligament (PDL)-derived DPCs can be used to bioengineer PDL tissues on titanium implants in a novel, in vivo rat maxillary molar implant model. Analyses of recovered implants revealed organized PDL tissues surrounding titanium implant surfaces in PDL-cell-seeded, and not in unseeded control, implants. Rat PDL DPCs also exhibited differentiative potential characteristic of stem cells. These proof-of-principle findings suggest that PDL DPCs can organize periodontal tissues in the jaw, at the site of previously lost teeth, indicating that this method holds potential as an alternative approach to osseointegrated dental implants. Further refinement of this approach will facilitate the development of clinically relevant methods for autologous PDL regeneration on titanium implants in humans
Effectiveness of Contour Augmentation with Guided Bone Regeneration: 10-Year Results
In aesthetic sites, the integrity of the facial bone wall dimension in the anterior maxilla is jeopardized by physiologic and structural changes postextraction. An effective regenerative protocol is key to reestablish and maintain the hard and soft tissue dimensions over time. The present prospective case series study examined the effectiveness of early implant placement with simultaneous contour augmentation through guided bone regeneration with a 2-layer composite graft in postextraction single-tooth sites over an observation period of 10 y among 20 patients. The median peri-implant bone loss was 0.35 mm between the 1- and 10-y examination. A success rate of 95% was obtained, with pleasing aesthetic outcomes and a high median Pink Esthetic Score (8). Implant crowns (ICs) revealed significant median facial recession between IC and IC (0.17 mm). The facial bone wall dimensions were assessed by preoperative cone beam computed tomography and 2 subsequent scans taken at 6 and 10 y. The median facial bone wall thickness increased significantly from 0 mm at surgery to 1.67 mm at the 10-y examination. The facial vertical bone wall peak (DIC) was located at a median distance of 0.16 mm coronal to the implant shoulder. The facial vertical bone loss of DIC amounted to 0.02 mm between 6 and 10 y. Equivalence testing was performed for the null hypothesis of a difference of >0.2 mm per year between 2 respective time points, showing stable bone conditions. Modulating factors influencing the regenerative outcomes at 10 y were the preoperative proximal crest width and soft tissue thickness. In conclusion, the present study confirmed the long-term effectiveness of early implant placement with simultaneous contour augmentation through guided bone regeneration with a 2-layer composite graft in postextraction single-tooth sites offering stable bone conditions with low risks of mucosal recessions over an observation period of 10 y ( ClinicalTrials.gov NCT03252106)