This study was conducted to evaluate the fatigue strength of Ti-6Al-4V laser-welded joints with several diameters and joint openings. Sixty dumbbell rods were machined in Ti-6Al-4V alloy with central diameters of 1·5, 2·0 and 3·5 mm. The specimens were sectioned and then welded using two joint openings (0·0 and 0·6 mm). The combination of variables created six groups, which when added to the intact groups made a total of nine groups (n = 10). Laser welding was executed as follows: 360 V per 8 ms (1·5 and 2·0 mm) and 380 V per 9 ms (3·5 mm) with focus and frequency regulated to zero. The joints were finished, polished and submitted to radiographic examination to be analysed visually for the presence of porosity. The specimens were then subjected to a mechanical cyclic test, and the number of cycles until failure was recorded. The fracture surface was examined with a scanning electron microscope (SEM). The Kruskal-Wallis test and Dunn test (α = 0·05) indicated that the number of cycles required for fracture was lower for all specimens with joint openings of 0·6 mm, and for 3·5-mm-diameter specimens with joint openings of 0·0 mm. The Spearman correlation coefficient (α = 0·05) indicated that there was a negative correlation between the number of cycles and the presence of porosity. So, laser welding of Ti-6Al-4V structures with a thin diameter provides the best conditions for the juxtaposition of parts. Radiographic examination allows for the detection of internal voids in titanium joints.

Widely used in dentistry, Ti-6Al-4V alloy is difficult to cast and solder, as it frequently exhibits pores inside the structure. This study was conducted to evaluate the effect of joint openings and diameters of laser-welded joints executed in Ti-6Al-4V structures on the presence of pores as checked by radiographic procedures. Sixty dumbbell rods with central diameters of 1.5, 2.0 and 3.5 mm were created from Ti-6Al-4V-wrought bars. Specimens were sectioned and welded using two joint openings (0.0 and 0.6 mm). The combination of variables created six groups (n = 10). Laser welding was executed using 360V/8ms (1.5 and 2.0 mm) and 380V/9ms (3.5 mm), with the focus and frequency set to zero. The joints were finished, polished and submitted to radiographic examination. The radiographs were visually examined for the presence of pores in the joints, qualitatively. The percentage of radiographic presence of pores was calculated without counting pores per joint. Data were analyzed using a chi-square test (α = 0.05). For the 1.5-mm specimens, the incidence of pore presence was significantly higher (p = 0.0001) when using 0.6-mm joint openings (40%) compared to 0.0-mm openings (0%). For the 2.0-mm specimens, there was no significant difference between groups (p = 0.2008). However, for the 3.5-mm specimens, the incidence of pore presence was lower (p = 0.0061) for 0.6-mm openings (50%) compared to 0.0-mm openings (70%). Therefore, laser welding of Ti6Al-4V structures with thin diameters provides the best condition for the juxtaposition of the parts.

OBJECTIVE. The purpose of this study was to evaluate the influence of veneer application on the misfit level of implant-supported frameworks. MATERIALS AND METHODS. Thirty commercially pure titanium (Tritan, Dentaurum, Pforzheim, Germany) frameworks were fabricated from a metallic index containing five Branemark-type multi-unit abutments. Analogs of the abutments were positioned into the framework to manufacture an index for each framework, which permitted the evaluation of the marginal gap caused only by the veneer coverage. The frameworks were grouped (n = 10) in the following manner: (G1) heat-cured acrylic resin (Clássico, Clássico, São Paulo, Brazil); (G2) light-cured resin (Versyo.com, Heraeus Kulzer, Brazil); and (G3) porcelain (Triceram, Dentaurum, Pforzheim, Germany). Marginal refinement with spark erosion was then conducted. The marginal gap was verified before and after the veneer coverage and the spark erosion procedure, following the single screw test protocol (tightening force of 10 Ncm). Data were submitted to an analysis of variance (ANOVA) in a split-plot design for repeated measurements followed by a Tukey test (p = 0.05). RESULTS. The veneer application was associated with a significant increase in the mean misfit values of all groups. The lowest values were presented by G2. After the spark erosion process, the mean misfit value decreased only on G3. CONCLUSIONS. Heat-cured acrylic resin and porcelain produced the highest values of marginal gaps, whereas light-cured acrylic resin produced the lowest. In addition, the spark erosion process was effective only in the marginal gap of the porcelain application group.

This study evaluated fatigue strength of CP-Ti laser-welded joints. Sixty (20/diameter) CP-Ti casted dumbbell rods with diameters of 1.5, 2.0, and 3.5 mm were sectioned and welded using two joint openings (0.0 (00) and 0.6 mm (06)). Six groups were formed, amounting to a total of 9 (n=10) with inclusion of intact groups. Welding was executed using 360 V/8 ms (1.5 and 2.0 mm) and 380 V/9 ms (3.5 mm). Joints were finished, polished, and submitted to radiographic examination to visually analyze presence of porosity (PP). Specimens were submitted to cyclic tests, and the number of cycles until failure (NC) was recorded. Fractured surfaces were examined by SEM. Kruskal-Wallis and Dunn (=0.05) tests demonstrated that NC was lower for all diameters with 06, and for 3.5 mm/00. NC and PP were found to have a negative correlation (Spearman Coefficient). For CP-Ti frameworks with thin diameters, laser welding is better when structures are juxtaposed.

<p class="MsoBodyText" style="line-height: 150%;"><span style="font-size: 11.0pt; line-height: 150%; mso-ansi-language: PT;" lang="PT">Esse </span><span style="font-size: 11pt; line-height: 150%;">estudo foi conduzido para avaliar a possibilidade de visualiza&ccedil;&atilde;o de porosidade interna em radiografias periapicais de uni&otilde;es soldadas a laser, confeccionadas em estruturas de tit&acirc;nio cp, em diferentes situa&ccedil;&otilde;es de soldagem. Foram confeccionados halteres em resina acr&iacute;lica, com di&acirc;metros centrais de 1,5; 2,0; e 3,5 mm, por meio de uma matriz met&aacute;lica bipartida. Os halteres em resina foram fundidos em Ti cp e ap&oacute;s acabamento e polimento, seccionados em duas partes iguais. As partes foram alinhadas e fixadas de tal forma que as dist&acirc;ncias entre elas fossem 0,0 e 0,6 mm. A combina&ccedil;&atilde;o entre as vari&aacute;veis (dist&acirc;ncia de soldagem e di&acirc;metro dos halteres) gerou seis grupos (n=10). A soldagem a laser foi realizada com as seguintes especifica&ccedil;&otilde;es: </span><span style="font-size: 11.0pt; line-height: 150%;">360V/8ms (1,5 e 2,0 mm) e 380V/9ms (3,5 mm), com foco e freq&uuml;&ecirc;ncia regulados em zero, em um aparelho de soldagem a laser Desktop-F. As uni&otilde;es obtidas receberam acabamento, polimento e foram submetidas &agrave; an&aacute;lise radiogr&aacute;fica com exposi&ccedil;&atilde;o &agrave; radia&ccedil;&atilde;o (90 KV, 15 mA, 0,6 seg e 10 a 13 mm de dist&acirc;ncia) utilizando filme periapical. As radiografias foram analisadas visualmente quanto &agrave; presen&ccedil;a de porosidade nas uni&otilde;es soldadas, e os dados obtidos, submetidos ao teste Qui-Quadrado (5%). Com isso, verificou-se ser poss&iacute;vel visualizar porosidade interna nessas uni&otilde;es. Em corpos de prova de menores di&acirc;metros, 1,5 e 2,0 mm, a incid&ecirc;ncia &eacute; maior quando a dist&acirc;ncia &eacute; 0,6 mm. Entretanto, em corpos de prova de 3,5 mm, a incid&ecirc;ncia &eacute; alta para ambas as uni&otilde;es, n&atilde;o diferindo estatisticamente entre si.<strong></strong></span></p> <p class="MsoBodyText" style="line-height: 150%;"><strong><span style="font-size: 14.0pt; line-height: 150%; text-shadow: auto;">UNITERMOS</span></strong></p> <span style="font-size: 11.0pt; font-family: &quot;Times New Roman&quot;,&quot;serif&quot;; mso-fareast-font-family: &quot;Times New Roman&quot;; mso-ansi-language: PT-BR; mso-fareast-language: PT-BR; mso-bidi-language: AR-SA;">&nbsp;Tit&acirc;nio; fundi&ccedil;&atilde;o odontol&oacute;gica; soldagem a laser; radiografia dental.</span>