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ePaper created 2018-03-13, 09:28:55 | version 1.38.0
| case series In-office welding by Nd:YAG laser Prof. Carlo Fornaini & Prof. Caroline Bertrand, France Introduction Just after the introduction of the first laser by Maiman in 1960,1 there was a very fast evolution of this new tech- nology, characterised by constant progression in tech- niques and applications, increasing the possibility to have smaller and cheaper devices and introducing ever-new wavelengths. Laser welding was first introduced in the jewellery industry during the 1970s and soon after suc- cessfully used by dental technicians as well.2 The first lasers used were the carbon dioxide and Nd:YAG lasers, but the market was rapidly conquered by the second, owing to the results that could be obtained with it.3, 4 Laser welding offers a great number of advantages compared with traditional welding. Firstly, the laser device saves time in the commercial laboratory because all welding is done directly on the master cast. Inac- curacies in assembly caused by transfers from the master cast along with investment are reduced.5 The heat source is a concentrated light beam of high power, which can minimise distortion problems in metals.6 By using laser technology, it is possible to weld very close to acrylic resin or ceramic parts with no physical (crack- ing) or colour damage.7 This means it is possible to save time and money during the restoration of broken pros- theses or orthodontic appliances, because it is not nec- essary to remake the non-metallic parts. This welding technique may be used on every kind of metal, but its property of being very active on titanium makes it par- ticularly advisable for prostheses supported by endos- seous implants.8 Many laboratory tests have demonstrated that laser- welded joints have a high reproducible strength for all metals, consistent with that of the substrate alloy.9 All these advantages led to this method being extensively used in dental technicians’ laboratories and stimulated companies to put on the market increasingly upgraded appliances. Some aspects, such as large dimensions, high costs and delivery systems, today still characterise those machines that use fixed lenses, strictly limiting their use to dental technicians’ laboratories. The aim of this study is to show, through the descrip- tion of a series of clinical cases, the utilisation of a laser device normally used for surgery in the dental office to weld orthodontic appliances and to demonstrate the advantages of this technique. The appliance used, the Fidelis Plus III (Fotona), is a combination of two dif- ferent laser wavelengths, the Er:YAG ((cid:1037) = 2,940 nm) and Nd:YAG ((cid:1037) = 1,064 nm). The first allows the den- tist to treat hard tissue (enamel, dentine and bone) with a mechanism that, utilising the affinity of this laser for water and hydroxyapatite, induces the explosion of intracellular water molecules and so causes the abla- tion of the tissue.10 Its utilisation may be extended also to dermatology, where it can be employed in the treat- ment of keloid scars and wrinkles with resurfacing, in addition to the elimination, by vaporisation, of lesions such as condyloma, naevi, warts and mollusca conta- giosa.11 The Nd:YAG laser allows the dentist to perform surgery with complete haemostasis, utilising the affinity of this wavelength for haemoglobin and thus avoiding the use of sutures.12 The delivery system for this laser is provided by optic fibres of different sizes, chosen according to the kind of application needed, ranging from 200 μm (endodontics) to 900 μm (whitening). In addition to a pulse duration of microseconds, which is necessary during dental interventions, the peculiarity of the Fidelis Plus III appliance is the possibility of pulse durations of milliseconds (15 or 25), which can be utilised in phlebology, in the treatment of lesions of vascular origin, owing to the affinity of this wavelength for haemo- globin.13 In our previous work,14 we demonstrated, by in vitro tests on different metal samples, the good quality and high resistance of a joint welded by this device, while in this paper we demonstrate the clinical application of this technique. Material and methods The laser device used was, as already stated, the Fidelis Plus III, with a 900 μm fibre and a 2 mm spot handpiece (R32, Fotona), normally utilised in derma- tology, or in some cases a prototype provided by Fotona itself. The parameters that we normally use for weld- ing are: – Wavelength: – Energy: – Frequency: – Spot diameter: – Pulse duration: – Fluence: – Working distance: 8 mm 1,064 nm 9.9 J 1 Hz 1 mm 15 m/s 1,260 J/cm2 06 ortho 1 2018