D2 ORTHO TRIBUNE Dental Tribune Middle East & Africa Edition | 4/2019 In-office welding by Nd:YAG laser By 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 technology, characterised by con- stant progression in techniques and applications, increasing the possi- bility 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 con- quered by the second, owing to the results that could be obtained with it.3, 4 Laser welding offers a great num- ber of advantages compared with traditional welding. Firstly, the laser device saves time in the commer- cial laboratory because all welding is done directly on the master cast. Inaccuracies 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 min- imise distortion problems in met- als.6 By using laser technology, it is possible to weld very close to acrylic resin or ceramic parts with no physi- cal (cracking) or colour damage.7 This means it is possible to save time and money during the restoration of bro- ken prostheses or orthodontic appli- ances, because it is not necessary to remake the non-metallic parts. This welding technique may be used on every kind of metal, but its prop- erty of being very active on titanium makes it particularly advisable for prostheses supported by endosse- ous implants.8 Many laboratory tests have demon- strated that laserwelded points 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’ labora- tories 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’ laborato- ries. The aim of this study is to show, through the description 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 (λ = 2,940 nm) and Nd:YAG (λ = 1,064 nm). The first allows the dentist 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 dermatol- ogy, where it can be employed in the treatment of keloid scars and wrin- kles with resurfacing, in addition to the elimination, by vaporisation, of lesions such as condyloma, naevi, warts and mollusca contagiosa.11 The Nd:YAG laser allows the dentist to perform surgery with complete hae- mostasis, 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 mi- croseconds, which is necessary dur- ing dental interventions, the peculi- arity 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 treat- ment of lesions of vascular origin, owing to the affinity of this wave- length for haemoglobin.13 In our previous work,14 we demon- strated, 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 dermatology, or in some cases a pro- totype provided by Fotona itself. The parameters that we normally use for welding 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 Clinical cases Case 1 A 9-year-old female patient in ortho- dontic treatment in our office came in urgently owing to damage to the rapid palatal expander applied to her maxillary molars. The clinical exami- nation revealed that the brace had been damaged close to the connec- tion with the arm (Fig. 1). The patient had just finished one stage of the ex- pansion, and since it was very risky to leave her without an appliance, we decided to weld it directly in the of- fice with the Fidelis laser. The expander was prepared with the conventional procedure required be- fore laser welding (sandblasted with alumina powders of 50 µm in diam- eter using the Miniblaster, Deldent; cleaned with acetone and both parts dried). The appliance was directly welded in the office using CoCr-Sch- weißdraht welding wire (DENTAU- RUM). After a few minutes only, the appliance was ready to be recement- ed into the patient’s mouth (Fig. 2). Case 2 An 8-year-old male patient in treat- ment in our office with a Schwartz removable orthodontic appliance came to us for periodic checking of the appliance, and we saw that one of the Adam’s hooks had broken (Fig. 3). We welded it without filler metal (Fig. 4), and the plastic shield, although very close to the welding zone, was not damaged or modified (Fig. 5). We were able to reseat the repaired ap- pliance in the patient’s mouth after only some minutes (Fig. 6). Case 3 An 8-year-old male patient in treat- ment in our office with a Frankel removable orthodontic appliance came to us for periodic checking of the appliance, and we saw that one of the wires had broken (Fig. 7). We welded it without metal filler (Fig. 8), Fig. 1: The damaged appliance removed from the mouth. Fig. 2: The repaired appliance. Fig. 3: The Schwartz appliance with a broken Adam’s hook. Fig. 4: Laser welding process without filler metal. Fig. 5: The hook repaired without damaging the nearby acrylic part. Fig. 6: The appliance replaced into the mouth. and the plastic shield, although very close to the welding zone, was not damaged or modified. We were able to reseat the repaired appliance in the patient’s mouth after only some minutes. Case 4 A 14-year-old male patient came to our office with the lingual wire of his appliance broken. The appliance was an orthodontic appliance called De- laire consisting of two wires, one ves- Fig. 7: The Frankel orthodontic appliance with a fractured wire. Fig. 8: The orthodontic appliance repaired. ÿPage D3