Intraoral metal laser welding: a case report

The possibility of laser welding of dental prostheses offers great advantages: first, the operator has the possibility of welding on the master model, which decreases the number of passages and thus the possibility of errors and damage, and secondly, the patient attends only a few sessions, and, due to the possibility of fixing the damaged prostheses, there is no need to resort to the technician’s laboratory. In a previous study we described the experimental phases of intraoral welding, from the in vitro model on animal jaws with evaluations of the temperature variations during welding through thermal chamber and type K thermocouples. In this study we describe the intraoral welding in vivo on human subjects by using, as in the previous study, a fibre-delivered neodymium:yttrium–aluminum–garnet (Nd:YAG) laser. The in vivo phase allowed a restored prosthesis to be positioned and intraorally welded in the upper central sector with optimal results both in patient’s comfort and in aesthetic effects. This first in vivo test confirmed that the use of a laser technique for the intraoral welding of metal prostheses is possible, with no particular problems and risks for the biological structures close to the welding zone.     

Semi-solid albumin solder improved mechanical properties for laser tissue welding

BACKGROUND AND OBJECTIVE: A semi-solid albumin solder formulated with hydroxypropylmethylcellulose (HPMC) was designed to improve the characteristics of liquid and solid solders. STUDY DESIGN/MATERIALS AND METHODS: Acute tensile strengths were determined on canine small bowel in vitro by using liquid 50% bovine serum albumin (BSA), semi-solid 48% BSA with HPMC, and solid 60% BSA solder. Long-term healing of liquid and semi-solid solders, compared with a suture control, was evaluated in a porcine skin model, with tensile strength as well as histologic findings obtained on postoperative day 7. RESULTS: Acutely, semi-solid solder demonstrated a significantly (P < 0.05) higher tensile strength when compared with liquid or solid solder. At 7 days, HSA semi-solid and BSA semi-solid had significantly (P < 0.05) higher tensile strength than suture control; however, no differences were seen for liquid or solid solder groups. No differences in histology were appreciable between any of the solder groups in a porcine skin model. CONCLUSION: Acutely and at 7 days, semi-solid solder was stronger than 50% liquid albumin with better handling characteristics.     

Peri-epineurial tissue to supplement laser welding of nerve

The principal difficulty with laser repair of nerves has been the inability to provide enough initial tensile strength to prevent separation of nerve ends. In previous experimental studies, dehiscence rates of laser-repaired nerves ranged between 12 to 25% whereas that for conventional epineurial suture repair was 0%. In our study, sciatic nerves of rats were transected bilaterally. Results of anastomosis by conventional epineurial suture on one side were compared with those of tissue welding by the CO2 laser using peri-epineurial sheath as a structural adjunct on the other side. At the time of reexploration at 7, 12, and 16 weeks, there was no dehiscence in nerves of either the laser with peri-epineurial sheath group or the suture repair groups. Electrophysiological and morphometric values after use of peri-epineurial tissue as an adjunct to tissue welding by the CO2 laser were comparable to those of conventional suture repair.     

Light-curing of dental resins with GaN violet laser diode: The effect of photoinitiator on mechanical strength

The purpose of this study was to evaluate whether a Gallium Nitride (GaN) -based violet laser diode (VLM500) could be used as a light source for light-cured dental resins. Three experimental unfilled resins containing different photoinitiators (camphorquinone, CQ; phenyl propanedione, PPD; or mono acylphosphineoxide, MAPO) were evaluated. These resins were light-cured with a VLM500 laser diode, and their ultimate micro-tensile strengths (μTS) were compared to those cured with three different LED light sources (Curenos, G-Light Prima-normal mode and G-Light Prima-PL mode). The VLM500 produced high μTS values in all three resins, and we concluded that this violet laser diode can be used as a light source for light-cured dental resin materials.     

Retropubic and transobturator midurethral slings: a decision analysis to compare outcomes including efficacy and complications

Introduction and hypothesis  

The objective of this paper is to compare retropubic (RP) and transobturator (TO) midurethral slings using decision analysis techniques.     

Assessment and validation of CT scanogram to compare per-operative and post-operative mechanical axis after navigated total knee replacement

Our objective was to assess and validate low-dose computed tomography (CT) scanogram as a post-operative imaging modality to measure the mechanical axis after navigated total knee replacement. A prospective study was performed to compare intra-operative and post-operative mechanical axis after navigated total knee replacements. All consecutive patients who underwent navigated total knee replacement between May and December 2006 were included. The intra-operative final axis was recorded, and post-operatively a CT scanogram of lower limbs was performed. The mechanical axis was measured and compared against the intra-operative measurement. There were 15 patients ranging in age from 57 to 80 (average 70) years. The average final intra-operative axis was 0.56° varus (4° varus to 1.5° valgus) and post-operative CT scanogram axis was 0.52° varus (3.1° varus to 1.8° valgus). The average deviation from final axes to CT scanogram axes was 0.12° valgus with a correlation coefficient of 0.9. Our study suggests that CT scanogram is an imaging modality with reasonable accuracy for measuring mechanical axis despite significantly low radiation. It also confirms a high level of correlation between intra-operative and post-operative mechanical axis after navigated total knee replacement.

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Résumé  Cette étude a pour but d’analyser et d’évaluer les images scanner et les modalités des clichés post-opératoires après prothèse totale du genou implantée avec navigation. Matériel et méthode: une étude prospective a été réalisée pour comparer les axes mesurés en per et post-opératoire, après navigation, chez les patients ayant bénéficié d’une prothèse totale du genou avec navigation et inclus de mai à décembre 2006. Les axes per et post-opératoires ont été rapportés et comparés avec l’axe mécanique obtenu et mesuré en per-opératoire. Résultats: 15 patients d’age moyen de 70 ans (57 – 80 ans) ont été analysés. L’axe final per-opératoire a été de 0.52° varus (4° à 1,5°) et, l’axe post-opératoire mesuré par scanner a été de 0.52° varus (3,1° à 1,8°). La déviation axiale médiane est de 0.12° valgus avec un coefficient de corrélation de 0,9. En conclusion, notre étude permet de penser que le scanner est une modalité d’évaluation raisonnable de mesure de l’axe mécanique en dépit d’une irradiation significative mais néanmoins assez basse. Cette étude permet également de confirmer un haut niveau de corrélation entre la mesure de l’axe per-opératoire et la mesure de l’axe post-opératoire dans les prothèses totales du genou avec navigation.

     

Improved microvessel repair: laser welding with an anti-thrombotic solder

BACKGROUND AND OBJECTIVES: Concentrated protein solutions can be used as thermally polymerized solders in laser welding. Solders supplemented with biologically active chemicals may provide in situ drug delivery for localized therapeutics. These studies characterize a serum albumin (SA) solder containing heparin, designed to reduce microvascular thrombosis rates. STUDY DESIGN/MATERIALS AND METHODS: Samples of heparin added to 30% SA to obtain heparin-to-albumin molar ratios (HAMR) of 4:1 and 2:1 were thermally polymerized, and heparin release into saline was measured. Using a rat thrombosis model, patency was determined for suture, and 0 U/ml (control), 2.5 U/ml, 50 U/ml heparin solder repairs. RESULTS: Heparin release was five times higher for 4:1 than 2:1 HAMR solder acutely, but was equivalent after 2 days. Animal patency rates were: 50% suture, 0% control, 50% low heparin, 66% high heparin (P < 0.05 vs. control). CONCLUSIONS: Solders incorporating heparin should provide in situ anti-thrombotic therapy reducing the risk of microvascular thromboses.     

Laser assisted microvascular anastomosis of arteries and veins: laser tissue welding

Using a milliwatt CO2 laser, a series of 160 arteries and 105 veins have been anastomosed in Wistar rats. Three stay sutures and a laser tissue welding technique were used. These were compared with a series of conventionally sutured vessels in terms of patency, speed and ease of procedure, and aneurysm formation. Patency rates of successful first time anastomoses are comparable with conventional suturing methods but the aneurysm rate is higher. Laser assisted anastomosis is faster to learn and perform than conventional suturing, but microsurgical skills are still needed. Despite the large number of variables the laser assisted technique has a high success rate, and work to minimise variables and optimise the laser parameters may improve these results.     

In vivo comparison of THC:YAG laser welding to sutured closure of biliary tissue

Percutaneous endoscopic approaches to cholelithiasis are an alternative to extracorporeal shockwave lithotripsy which offer advantages of fewer restrictions on stone size and type as well as avoidance of fragmented stone passage complications. Endoscopic techniques would be facilitated by methods of welding gallbladder tissues. The technical constraints imposed by the endoscopic approach favor nonsuture methods of fusing gallbladder tissues. To evaluate a laser method for fusing biliary tissue, we have compared the healing response of laser-welded versus polyglycolic acid suture-closed incisions in canine gallbladder tissue in vivo. The laser used was a thulium-holmium-chromium:YAG laser producing 200-microsecond, 300-millijoule pulses at 2.15 microns. Serial sacrifice of dogs that underwent laser or suture closure of incisions made in the fundus of the gallbladder revealed that all repairs healed without evidence of leakage or infection. Laser-welded cholecystotomy sites had complete fibrous healing of the wound by two weeks postoperatively and reepithelialization by three weeks after operation. Suture-closed wounds were still without complete epithelization four weeks after the procedure. Laser welding may be a useful technique in endoscopic biliary surgery.     

Nonablative dermal remodeling with a 585-nm, 350-microsec, flashlamp pulsed dye laser: clinical and ultrastructural analysis.

BACKGROUND: A nonablative 350-microsec, 585-nm, flashlamp pulsed dye laser is currently being used for the treatment of rhytides. OBJECTIVE: To analyze both clinical rhytid improvement and electron microscopic evidence of ultrastructural changes after treatment with a nonablative 350-microsec, 585-nm, flashlamp pulsed dye laser. RESULTS: At 6 months after two treatments, 40% of the treated subjects noted mild improvement in rhytid appearance. Nontreating physician evaluation revealed some degree of improvement in 50% of the treated subjects. Mild improvement in quality and texture of the skin was also reported by 50% of the subjects. Electron microscopic evaluation showed ultrastructural changes that are consistent with new collagen formation. CONCLUSION: Treatment with a nonablative 350-microsec, 585-nm, flashlamp pulsed dye laser can lead to both clinical and electron microscopic evidence of improvement in photo-damaged skin.     

Physiological studies using laser Doppler flowmetry to compare blood flow to the zones of the free TRAM flap

The latissimus dorsi musculocutaneous island flap was once the standard for breast reconstruction. With the increased use of tissue expanders and the development of the transverse rectus abdominis musculocutaneous flap for autologous tissue breast reconstruction, use of the latissimus dorsi has decreased. To reassess the role of the latissimus dorsi musculocutaneous flap in breast reconstruction, a retrospective review was performed to evaluate women who had skin-sparing mastectomy followed by immediate reconstruction with a latissimus dorsi flap and permanent implants. The postoperative aesthetic results and donor site morbidity, including contour deformity and scarring, were examined. Satisfactory results were obtained in 17 of 18 patients. Complications were noted in 5 patients, and all were minor. Using the latissimus dorsi musculocutaneous flap and a permanent breast prosthesis for immediate reconstruction is successful because it provides sufficient muscular coverage of the implant. In addition, it provides a good aesthetic result using a single-stage procedure. Illustrative cases are presented.     

CO2 and argon laser vascular welding: acute histologic and thermodynamic comparison

CO2 and argon lasers have been used successfully for vascular welding in both experimental and clinical settings. This study compared the thermodynamics during CO2 and argon laser welding of 1-cm longitudinal arteriotomies in a canine model. Continuous recordings using an AGA 782 digital thermographic system with spatial and thermal resolution of +/-0.2 mm and +/-0.2 degree C, respectively, were analyzed. A HGM argon laser using a 300-microns optic fiber held at 1 cm from the vessel edges (spot diameter = 2.8 mm) with concomitant room temperature saline irrigation (1 drop/sec) was used for argon welds. Total exposure time was 150 sec/cm. CO2 welds were performed with a Sharplan CO2 laser (spot diameter = 0.22 mm) with no irrigation for total exposure time of 10 sec/cm. Thermodynamic results and laser parameters are summarized as follows: Argon-n = 20; power = 500 mW; energy fluence = 1,400 J/cm2; Tmax = 48.8 degrees C; T mean +/- S.D. = 45.1 +/- 2.7 degrees C; CO2-n = 20; power = 150 mW; energy fluence = 3,000 J/cm2; Tmax 84.0 degrees C; T mean +/- S.D. = 60.7 +/- 9.8 degrees C. There was a significant difference (P less than .05) in thermal measurements between successful CO2 and argon vascular welds. Temperature rise during the argon welds was limited by saline irrigation. In contrast, during CO2 laser welding, the temperature rose quickly to its maximum and was maintained at a relatively high level as the laser progressed (0.1 cm/sec) along the anastomosis.(ABSTRACT TRUNCATED AT 250 WORDS)     

A prospective randomized trial to compare CO2 laser with standard electrocautery for making thoracotomy incisions

It has been claimed that surgical incisions made with the carbon dioxide laser are superior to those made by diathermy in terms of blood loss, wound healing and postoperative pain. We have done a small controlled trial to test this hypothesis in 16 patients, comparing thoracotomy incisions made by these two techniques. Incisions made by the laser were slower and had greater blood loss and we were unable to demonstrate any differences between the techniques in wound healing or postoperative pain.     

Qualitative microanalysis of ions and ultrastructural changes in dentin exposed to laser irradiation and to metal salts solution

BACKGROUND AND OBJECTIVES: This study evaluated the ultrastructural changes in dentin after treatment with the Nd:YAG laser and/or metal salt solutions and verified the presence of Sn++, Sr++, and F- in dentin structure. STUDY DESIGNS/MATERIALS AND METHODS: Sixty dentin disks were randomly divided into groups (n = 10): (I) control (no treatment), (II) Nd:YAG (1.5 W, 100 mJ, 15 Hz, 125 J/cm2), (III) 10% SnF2 aqueous solution for 30 minutes, (IV) Nd:YAG+10% SnF2 aqueous solution for 30 minutes, (V) 10% SrCl2 toothpaste for 30 minutes, (VI) Nd:YAG+10% SrCl2 toothpaste for 30 minutes. Then, all samples were prepared for scanning electron microscopy (SEM) and the samples from Groups I to IV for the energy dispersive X-ray microanalysis (EDX). RESULTS: SEM evaluation revealed occluded dentinal tubules and a dentin surface altered by the laser irradiation. The EDX microanalysis revealed Sn++ at a depth of 250 microm in Group IV and not deeper than 100 microm in Group III. In Group V, Sr++ was not deeper than 50 microm, but it could be detected at a depth of 500 microm in Group VI. F- was found only in Group IV. CONCLUSIONS: Ultrastructural changes caused by laser irradiation can increase dentin uptake of Sn++, Sr++, and F-.