The effect of metal primer application and Nd:YAG laser irradiation on the shear-bond strength between polymethyl methacrylate and cobalt-chromium alloy.

OBJECTIVE: The purpose of this study was to compare the shear-bond strengths (SBSs) of an acrylic resin and a cobalt-chromium (Co-Cr) alloy after applying a metal primer, Nd:YAG laser irradiation, or both to the sandblasted surface of the Co-Cr alloy. BACKGROUND DATA: The serviceability of a removable partial denture (RPD) is dependent on the bond strength at the resin-alloy interface. No previously published studies exist on the use of Nd:YAG lasers for preparing the surface of a Co-Cr alloy in an RPD to obtain a high-strength bond between PMMA and the alloy. METHODS: One-hundred twenty Co-Cr alloy specimens were sandblasted and randomly assigned to four equal groups: Group I, sandblasting; Group II, sandblasting + metal primer; Group III, sandblasting + Nd:YAG laser; and Group IV, sandblasting + Nd:YAG laser + metal primer. To establish the most appropriate fluence for modifying the surface of the sandblasted cast specimens, we conducted a preliminary study. Nd:YAG laser irradiation at a fluence of 46.9 J/cm(2) was selected. After the various surface treatments, each alloy specimen was embedded in PMMA to determine the SBS between PMMA and the alloy. RESULTS: Group II and III specimens exhibited higher SBSs than did those of the Group I specimens (p < 0.05), and Group IV specimens showed higher SBSs than did those of the Group II and III specimens (p < 0.05). A significant difference existed in failure types among groups (p < 0.05). Failure type was predominantly adhesive for groups I and III, but predominantly mixed for groups II and IV. CONCLUSIONS: Nd:YAG laser irradiation at a fluence of 46.9 J/cm(2) roughens the sandblasted surface of a Co-Cr alloy and increases the strength of the bond between PMMA and the alloy. This bond strength can be increased further by applying a metal primer to the laser-irradiated surface.

Microtensile bond strength of resin cement to a feldspathic ceramic.

OBJECTIVE: The purpose of this study was to evaluate the microtensile bond strength of resin cement to a feldspathic ceramic after treating the surface with (a) hydrofluoric (HF) acid, (b) air abrasion, (c) Er:YAG laser irradiation, (d) Nd:YAG laser irradiation, and (e) HF acid etching after either air abrasion or laser irradiation. BACKGROUND DATA: It is unknown whether the laser application or its combination with another treatment method can be used as a tool to roughen the surface of a feldspathic ceramic in order to increase the bond strength between the resin cement and ceramic surface. MATERIALS AND METHODS: Forty feldspathic ceramic blocks (Ceramco(TM)) were prepared and divided into eight equal groups (n = 5) according to the following surface treatments: no treatment; etching with 9.5% HF acid; air abrasion with 50 µm Al(2)O(3); Er:YAG laser irradiation; Nd:YAG laser irradiation; air abrasion plus acid etching; Er:YAG laser plus acid etching; and Nd:YAG laser plus acid etching. After surface treatment, a silane-coupling agent and resin cement (Panavia F(TM)) were applied to each block. After storing for 24 h at 37°C and thermocycling between 5°C and 55°C for 1000 cycles, the microtensile bond strength of each specimen was measured. RESULTS: The highest bond strength was obtained from HF acid etching. HF acid etching after each laser irradiation significantly increased the bond strength (p < 0.05). However, HF acid etching after air abrasion decreased bond strength when compared to air abrasion alone. CONCLUSIONS: HF acid etching is the most effective surface treatment method for a feldspathic ceramic. However, laser irradiation with either the Er:YAG or Nd:YAG laser is not an adequate method for improving the bond strength of Panavia F. The laser application should be combined with HF acid etching.

Shear bond strength of repair composite resin to an acid-etched and a laser-irradiated feldspathic ceramic surface.

OBJECTIVE: The purpose of this study was to evaluate the shear bond strength of a repair composite resin to a feldspathic ceramic surface that had been either etched with 9.5% hydrofluoric acid (HFA), irradiated by an Er:YAG or Nd:YAG laser, or etched with 9.5% HFA after being irradiated by each laser type. BACKGROUND DATA: New findings have shown that combined laser irradiation and acid etching of a ceramic surface can be used to roughen ceramic surfaces. METHODS: Seventy-eight feldspathic ceramic discs were assigned to six surface treatment groups (n = 13): C, no treatment; HFA, 9.5% HFA etching; ER, Er:YAG laser irradiation; ND, Nd:YAG laser irradiation; ER + HFA, Er:YAG laser irradiation followed by HFA etching; ND + HFA, Nd:YAG laser irradiation followed by HFA etching. The surface of one disc from each treatment group was examined under a scanning electron microscope. After the surface treatments and silanization, a repair composite resin was applied to each disc using a commercial ceramic repair kit. Shear bond strength testing was then done after storing the specimens in distilled water for 24 h at 37 degrees C and thermocycling. Each ruptured specimen was examined under a stereoscopic light microscope. RESULTS: The highest shear bond strength was found after HFA etching, and the lowest was found after Er:YAG laser irradiation. HFA etching also caused the most pronounced changes of all the surface treatments. When HFA was applied after either laser irradiation, the fissures and cracks were larger than those seen on the only laser-irradiated surfaces. CONCLUSIONS: HFA etching is the most effective surface treatment for increasing the shear bond strength between a repair composite resin and a feldspathic ceramic surface. The shear bond strength after laser irradiation can be increased by HFA etching, but the strength of the bond is still smaller than that after HFA etching alone.

[Handwashing habit of intensive care workers]. / Yogun bakim çalisanlarinin el yikama aliskanliklari.

BACKGROUND: The aim of this study was to determine the habit of handwashing among health care workers in the intensive care unit of hospitals' general surgery department. METHODS: Potential handwashing opportunities were detected and observations were recorded. Handwashing habit of health care workers was monitored for over 1710 min., during 30 min. observation periods. RESULTS: In this study which had 1710 minutes of observation period, the overall habit of handwashing of the medical staff was 23%. Compliance among physicians, nurses and other health care workers were 12%, 34% and 19% respectively (p<0.05). CONCLUSION: The handwashing habit of healthcare workers in our unit is unacceptably low. We believe that introduction of social pressure models will help to improve handwashing awareness of the health care worker.

A comparison of two different methods and materials used to repair polycarbonate crowns.

AIM: The aim of this study was to evaluate the bond strength and crown-repair material interface of polycarbonate crown repaired using flowable resin composite and hybrid resin composite following two different surface preparations. METHODS AND MATERIALS: The facial surfaces of fifty-two polycarbonate crowns were flattened and roughened. Specimens were then divided into four test groups. A bonding agent alone (Groups 1 and 2) or a combination of methylmethacrylate (MMA) + bonding agent (Groups 3 and 4) was applied to the prepared surfaces. Then either a flowable (Groups 1 and 3) or a microfilled hybrid (Groups 2 and 4) resin composite was placed on the surfaces. Forty-eight of the original fifty-two specimens were used for shear bond strength testing. Failure types (adhesive, cohesive, and mixed) were evaluated. The remaining four specimens, one from each group, were used for crown-resin composite interface analysis using a scanning electron microscope (SEM). RESULTS: There were significant differences in both mean shear bond strength values and failure types (P<0.05). The SEM evaluation revealed a close interface relationship in Groups 3 and 4. CONCLUSION: MMA monomer application on a polycarbonate crown prior to application of an adhesive agent improved the shear bond strength of the repair material.

Fracture resistance of various temporary crown materials.

AIM: The aim of this study was to evaluate the fracture resistance of various provisional crown materials using an in vitro model test system. METHODS AND MATERIALS: In the present study polycarbonate crowns, prefabricated by the manufacturer (3M Polycarbonate Crown), and the temporary crowns, fabricated in the dental laboratory environment, were fabricated using bis-acryl composite (Protemp II), autopolymerizing PMMA resin (BISICO Temp S), and heat-polymerized PMMA resin (Major C&B-V Dentine). All temporary crowns were stored in distilled water for 24 hours at room temperature prior to testing. The crowns were seated on metal dies, fabricated from Cr-Co alloy (AZ Dental, Konstanz, Germany), and then tested using the indenter of a Hounsfield testing machine (Hounsfield Tensometer, Hounsfield Test Equipment, Raydon, England). The tip of the indenter was located at a position one-third of the way down the inciso-palatine surface at 135 masculine. The data were statistically analyzed for differences using one-way analysis of variance (ANOVA) and the Tukey HSD test (P < .05). Additionally, the types of failure obtained from the fracture load test were examined using 10x magnification with a stereo microscope. RESULTS: The results of the present study indicated polycarbonate crowns were significantly different from the BISICO Temp S, Protemp II, and Major C&B-V Dentine (P < .05) groups. CONCLUSION: This in vitro study shows polycarbonate crowns may be preferable to the other types of temporary crowns used in this study.

Repairing a preveneered stainless steel crown with two different materials.

PURPOSE: The objective of this study was to determine the in vitro shear bond strength of 2 different repair materials for anterior preveneered stainless steel crowns (SSCs) after bond failure in the prefabricated veneers. METHODS: Sixteen preveneered anterior SSCs were used. Each of the preveneered crowns was cemented with a luting glass ionomer cement onto cast die. Each die was placed into a mechanical testing machine. A force was applied on the veneer at the incisal edge, with a crosshead speed of 0.05 inches/minute until the initial original facial facing material fractured or dislodged. Fracture or dislodgment failure of the initial original facial facings was evaluated and photographed. Specimens were divided into 2 equal repairing procedure groups. Group 1 was repaired using Tetric Flow, a flowable resin composite. Group 2 was repaired using Major Resin, a crown and bridge veneering resin. After the repairing procedure, crowns were stored in water at room temperature for 24 hours and then thermocycled. The crowns repaired were debonded in the test machine in the same manner as the initial facial facing fracture test. The debonding failure of the repaired crowns also was evaluated and photographed. RESULTS: There was a statistically significant difference between the initial original veneer material and groups 1 and 2 (P < .000) and between groups 1 and 2 (P < .001). CONCLUSIONS: In this in vitro study, it was determined that shear forces of the repair materials were lesser than bond forces of the original veneer material to the stainless steel metal base.