The purpose of this study was to investigate setting and thermal expansion of dental soldering investments. In order to compare expansion rates and to investigate the effect of water/powder ratio on expansion, setting and thermal expansion of four dental soldering investments were measured under three different water/powder ratio conditions: standard, 20% decreased and 20% increased. Setting expansion of investments was measured by use of dialgauge method. Each measurement was started two minutes later from the beginning of spatulation and recorded every one minute for one hour. Thermal expansion of cylindrical test specimens, 10mm diameter, 50mm length, was recorded in a Thermodilatometer at heating rate of 10degrees C per minute from 25degrees C to 700degrees C. The results of this study were obtained as follows: 1. Setting expansion rates under the standard water/power ratio condition were 0.198% in Speed-E, 0.090% in Deguvest, 0.080% in CM and Hi-temp. Setting expansion of Speed-E was significantly different from those of CM, Deguvest and Hi-temp, and setting expansion of Deguvest was significantly different from those of CM and Hi-temp(p<.05). 2. Under the decreased water/powder ratio condition, there was significant increase in setting expansion of 4 dental soldering investments(p<.05). 3. There were no significant differences in setting expansions of investments except Hi-temp between standard and increased water/powder ratio condition(p<.05). 4. Thermal expansion rates under the standard water/powder ratio condition were 1.923% in Deguvest, 1.629% in Speed-E, 1.619% in Hi-temp and 1.580% in CM. No significant difference in thermal expansions under the standard water/powder ratio condition existed only between Speed-E and Hi-temp(p<.05). 5. Under the decreased water/powder ratio condition, there was significant increase in thermal expansion of CM and Deguvest but decrease in thermal expansion of Speed-E(p<.05). 6. Under the increased water/powder ratio condition, there was significant decrease in thermal expansion of CM, Deguvest and Speed-E but decrease in thermal expansion of Hi-temp(p<.05).
Dental Soldering* ; Heating ; Hot Temperature ; Investments*

OBJECTIVETo measure the microstructure of laser-welded cast pure titanium by different gap distance.

METHODSForty specimens were sectioned and welded at four gaps (0.00 mm, 0.25 mm, 0.50 mm and 1.00 mm). Took microhardness test and metallographic examination of welded zone surface.

RESULTSThere were no difference in microhardness value and metallographic observation between welded specimens. The width of heat-effected zone was different. The smaller grains and needle-like alphamartensitic structure were found in the heat-affected zone.

CONCLUSIONThe effects of the joint gap were not significant.

Dental Soldering ; Lasers ; Materials Testing ; Titanium

OBJECTIVEThis study was intended to design a kind of resisting part dint of device in order to preventing the base plate break while being subjected to the dint when partial base plate dint concentrates because of the increase of the magnetic attachment to the original movable artificial teeth.

METHODSTen patients who should increase magnetic attachment was adopted in the study, and we increased a kind of new designed partial cast base plate on the original base plate using laser welding technique, then designed magnetic attachment and artificial teeth.

RESULTSNone of ten sufferers appeared the phenomenon of the break of the base plate.

CONCLUSIONThe application of the laser welding technique can prevent the break of the base plate when partial dint increase because of the increase of the magnetic attachments.

Dental Soldering ; Humans ; Lasers ; Magnetic Phenomena ; Magnetics ; Welding

OBJECTIVETo investigate the influence of the laser welding on bond of porcelain fused to cast pure titanium.

METHODSTwenty cast titanium plates were divided into two groups: laser welded group and control group. The low-fusing porcelain was fused to the laser welded cast pure titanium plates at fusion zone. The bond strength of the porcelain to laser welded cast pure titanium was measured by the three-point bending test. The interface of titanium and porcelain was investigated by scanning electron microscopy (SEM) and energy depressive X-ray detector (EDX). The non-welded titanium plates were used as comparison.

RESULTSNo significant difference of the bond strength was found between laser-welded samples [(46.85 +/- 0.76) MPa] and the controls [(41.71 +/- 0.55) MPa] (P > 0.05). The SEM displayed the interface presented similar irregularities with a predominance. The titanium diffused to low-fusing porcelain, while silicon and aluminum diffused to titanium basement.

CONCLUSIONSLaser welding does not affect low-fusing porcelain fused to pure titanium.

Dental Casting Technique ; Dental Porcelain ; Dental Soldering ; methods ; Lasers ; Materials Testing ; Titanium

OBJECTIVETo study micro morphology and element-mixing distribution of different alloys welded in laser and analyze the feasibility of laser welding different alloys.

METHODSAlloys and titanium were matched into 4 groups: Au-Pt with Ni-Cr; Au-Pt with pure Ti; pure Ti with Ni-Cr; Ni-Cr with Co-Cr. They were welded in laser. Changes in metallography after hybridization of crystalline grain, ranges of heat-affected zone and pores were observed through SEM with ultra-thin windowed X-ray energy atlas. Meanwhile 10 testing points were chosen with area of 300 micro m x 900 micro m along the welding surface from the side A alloy to the side B alloy, than the element mixing distribution and tendency were analyzed with X-ray energy atlas.

RESULTS1. Hybridization of different alloys: (l) in the group of Au-Pt with Ti, there was titanium element mixing into Au-Pt tissue gradually and evenly on the Au-Pt side of the interface without clear boundary and increasing in size of crystalline grain. However, there was titanium crystalline grain increasing in size, irregular morphology and small sacks on the titanium side with clear boundary. (2) in the group of Ni-Cr with Ti, there was mixing regularly, slow transition and interlocks between crystalline grains on the Ni-Cr side of the in terface. Poor transition, clear boundary and small cracks were observed on titanium side. (3) in the group of Co-Cr with Ni-Cr, there was good transition, obscure boundary on both sides resulting from network, cylinder and branch structure growing. 2. Element-mixing distribution of different alloys. In fusion zone, the metal elements in matched groups mixed well and hybridized into new alloys except titanium blocks. The location of wave peak depended on the composition of alloys. Most of elements were from the alloy far from the fusion zone.

CONCLUSIONThe hybridization between pure titanium and any other alloys is not good The effect of laser welding different alloys is ideal except with pure titanium.

Alloys ; Chromium Alloys ; chemistry ; Dental Alloys ; chemistry ; Dental Soldering ; Titanium ; chemistry ; Welding

PURPOSE: Adequate passive-fitting of one-piece cast 3-element implant-supported frameworks is hard to achieve. This short communication aims to present an alternative method for section of one-piece cast frameworks and for casting implant-supported frameworks. MATERIALS AND METHODS: Three-unit implant-supported nickel-chromium (Ni-Cr) frameworks were tested for vertical misfit (n = 6). The frameworks were cast as one-piece (Group A) and later transversally sectioned through a diagonal axis (Group B) and compared to frameworks that were cast diagonally separated (Group C). All separated frameworks were laser welded. Only one side of the frameworks was screwed. RESULTS: The results on the tightened side were significantly lower in Group C (6.43 +/- 3.24 microm) when compared to Groups A (16.50 +/- 7.55 microm) and B (16.27 +/- 1.71 microm) (P<.05). On the opposite side, the diagonal section of the one-piece castings for laser welding showed significant improvement in the levels of misfit of the frameworks (Group A, 58.66+/-14.30 microm; Group B, 39.48+/-12.03 microm; Group C, 23.13+/-8.24 microm) (P<.05). CONCLUSION: Casting diagonally sectioned frameworks lowers the misfit levels. Lower misfit levels for the frameworks can be achieved by diagonally sectioning one-piece frameworks.
Axis, Cervical Vertebra ; Dental Implants ; Dental Prosthesis, Implant-Supported ; Dental Soldering ; Denture, Partial, Fixed ; Prostheses and Implants ; Prosthesis Fitting ; Prosthodontics ; Welding

OBJECTIVEIn order to compare the influence of casting and laser welding on magnetic retentive force, the magnetic retentive forces of laser-melted and cast post-keepers of the magnetic attachments were measured in vitro.

METHODS5 cast and 6 laser-melted post-keeper specimens (Magfit MD800) were formed, respectively. Using untreated keeper as control group, the vertical magnetic retentive forces were measured by a universal testing machine.

RESULTSThe average vertical magnetic retentive force of the laser-melted post-keeper group and the cast post-keeper group in vitro were (4.223 +/- 0.217,0)N, (3.792,9 +/- 0.296,4)N, respectively. Compared with the cast post-keeper group, the average vertical magnetic retentive force of the laser-melted post-keeper groups was much higher in vitro (P < 0.05).

CONCLUSIONLaser welding had less influence on the magnetic retentive force of the magnetic attachments than casting.

Dental Alloys ; Dental Casting Investment ; Dental Casting Technique ; Dental Prosthesis Retention ; instrumentation ; Dental Soldering ; methods ; Denture Precision Attachment ; Electromagnetic Fields ; Lasers ; Magnetics ; instrumentation ; Post and Core Technique ; Stainless Steel ; Welding ; methods

OBJECTIVEIn order to introduce the laser welding technology into root-cap making, this study compared the surface characters and internal structures of laser-melted and cast post-keeper to provide experimental data for clinical application of the technique.

METHODSUsing untreated keeper as the control group, the surface characters and metallographic structures of the keepers were examined by stereomicroscope, metallographic microscope and SEM, and element analysis were conducted with EPMA.

RESULTSThe laser-melted post-keeper basically kept the original smooth and the internal structure of the keeper, the heat reaction zone was extremely small and elements diffused mutually around the fusion zone obviously. While in the cast post-keeper, the surface was rough and had an oxide-layer. The internal structure changed and a fusion band formed between the base alloy and the keeper, but element diffusion was limited to the fusion zone.

CONCLUSIONCompared with casting, laser welding technique demonstrated less influence on the surface and internal structure of the keepers.

Dental Alloys ; Dental Casting Investment ; Dental Casting Technique ; Dental Prosthesis Retention ; instrumentation ; Dental Soldering ; methods ; Denture Precision Attachment ; Electromagnetic Fields ; Hot Temperature ; Lasers ; Magnetics ; instrumentation ; Stainless Steel ; Welding ; methods