Endoral welding

The technique of endoral welding originated in Italy in the early 1970s by Dr. Pier Luigi Mondani. He hypothesized that implant restraint made with Scialom needles or monophasic screws would allow improved results and probability of success in applications subject to immediate loading(1). This was following the introduction of titanium for endoral prostheses and simultaneously with experiments with screws that would provide better support for such applications (e.g., Garbaccio screw).

During the next 40 years, implantology techniques were refined; the use of submerged or biphasic implants was favored, and short- and long-term clinical outcomes, especially n relation to osseointegration, were kept under observation.

Research aimed at reducing patient discomfort and – consequently – the need for immediate or short-term loading of implants, required a reexamination of available techniques and allowed for a reevaluation of intra-oral welding procedures in light of the knowledge and results obtained as prosthetic techniques evolved.

Please note that the procedures and related results are depending on both techniques and experience of operator, who is the only person in charge of deciding the best treatment and solution that can be applied for a specific clinical case. Some of the methods described and discussed below can be applied with underlying bone structure allows immediate loading; also implant manufacturer should confirm that the procedures can be applied. Text below is informative and it does not contain any medical advice. Current medical opinion is expressed by recent publications that in the following document could not have been treated extensively nor we can assure that they are up to date with latest publications. Should you have any suggestion, correction or question, feel free to contact us.

Starting from the comparative observations that have demonstrated the equivalence between osseointegration achievable with submerged implants and emergent implants not subject to masticatory trauma and protected by the action of the tongue(2, 3), numerous studies have focused on the short- and medium-term results obtained with stabilization and restraint techniques associated with immediate loading, especially to limit discomfort in the case of edentulous patients or where bone support is inadequate(4).

We present below some of the relevant studies published between 2000 to the present:

• A review of the available literature on intraoral welding procedures, published in 2015, concludes that although long-term observations (greater than 5 years) are limited, the success of immediately loaded endosseous implants is high, and that monophasic implants have higher reliability and lower risk of complications(5, 6). Conclusion shows that, with available data, short and medium term results are positive and endoral welding seems to be effective when fast mouth rehabilitation is required (7).
• Published in 2013, a study performed on 211 full arch prosthetic implants installed in a single surgical session, and stabilized with endoral welding, analyses marginal bone losses and concluded optimistically about the reliability of this method when applied for fixed and immediately loaded prosthesis (8).
• A study on 1301 non-submerged implants, published on 2001 compared immediate loading loaded implants compared with submerged implants (only the implants with acceptable primary retention were loaded immediately). Immediately loaded implants shown better success rate than those stabilized with temporary crowns or plastic prosthesis (with or without metallic frame) (9).

There are multiple documented cases of implants made with intra-oral welding techinques, whose analisys concludes that secondary stabilization limits micro-movements and improves success rates (10).

The use of titanium wires or plates welded to the emergent part of the implant stabilizes it during the osseointegration period, especially in the three months following the operation. In some cases, it is possible to remove the soldered wire at the same time as the permanent prosthesis is placed.

Intraoral welding uses a high-intensity current for a very short time interval. The following image shows a simplified schematic of the device’s working principle:

The machine is connected to the power grid (A) from which it draws energy to charge an electrolytic capacitor, that is, a device capable of storing energy in the form of electrostatic charge (C1).

The isolation transformer (T1) has the dual purpose of isolating the patient from the power grid and reducing the very low line voltage < 40V. The constructional design of the galvanic isolation inside the transformer must ensure–according to precise rules defined by harmonized standards–that loss of isolation between the two parts is not possible. For these reasons, a direct contact with the output terminals of the transformer presents no risk of electrocution.

A voltage control and regulation circuit (not shown in the picture) monitors the electrical charging parameters, rectifies the voltage from AC to DC, and controls the closing and opening of the charging switch (SW1) according to the energy level set on the device. The higher the welding energy, the higher the charge level of the capacitor.

After the charging phase is finished, a circuit verifies that there is a low-impedance path between the two sides of the clamp (B) before closing the semiconductor switch (SW2), which discharges the energy stored in the capacitor (C1) at the soldering point in a few milliseconds.

The passage of current within titanium, which has higher resistivity than the rest of the electrical charge path, causes the temperature in the contact area between wire and implant to rise rapidly, close to the material’s function temperature. The rapidity of the phenomenon limits heat exchange with other areas to a minimum. A first pulse breaks the structure of the surface crystals, the second causes the joining between the structures in which the atoms within the two parts are organized. The clamp pressure allows the current to join the two parts by a process called syncrystallization, and which is similar to the metal sintering process.

Depending on the results of implant application and the stability of the bone support, a decision is made whether to retain the restraining support or remove it following integration with bone. Welding can be applied to monophasic, biphasic screws, blades, or needles.

Endoral welding techniques, in addition to containing new implants, aid in the recovery of fractured, loosened implants or in the stabilization of local prostheses.

A test made on 2013 on a limited number of patients shown that the welding quality that can be obtained with Nd:YAG laser is equal or better than what can be performed with sincrystallization and that tissue temperature increase is lower (5°C average deviation) (11). By contrast, intra oral welding with electrical apparatus makes use of lower cost devices and it is simpler. In our laboratory we verified that overheating can be reduced to a minimum if pliers are kept in place for some seconds after the pulse.

1. Mondani PL, Mondani PM: The Pierluigi Mondani intraoral electric solder. Principles of development and explanation of the solder using syncrystallization – Riv Odontostomatol Implantoprosthesis 1982 Jul-Aug(4), 28-32 – http://www.ncbi.nlm.nih.gov/pubmed/6130503
   2. Pasqualini U: The Occlusal Pathologies – Masson 1993.
   3. Dal Carlo L: Tongue’s Influence on the Integration of Endosseous Implants – Doctor OS Mag;14(5):479-484, 2003
   4. Dal Carlo L: Welding of submerged implants: over 12 years of clinical experience – RIS Rivista Italiana di Stomatologia 2008;2:34-42
   5. Barrachina-Diez JM, Tashkandi E, Stampf S, Att W (2013) Long-term outcome of one-piece implants
   6. Tramonte SU, Dominici AD, Kurtzman, GM: Immediate loading with intraoral welding for improved implant stability during healing. Int J Oral Implant Clin Res 2: 85-91.
   7. Andreescu CF: Survival Rate of Immediately Loaded Implants Restored using the Intraoral Welding Technique: A Literature Review. Dent Health Curr Res 1:2.
   8. Degidi M, Nardi D, Piattelli A: A six-year follow-up of full-arch immediate restorations fabricated with an intraoral welding technique – Implant Dent. 2013 Jun;22(3):224-31. doi: 10.1097/ID.0b013e31829261ed. – http://www.ncbi.nlm.nih.gov/pubmed/23644910
   9. Hruska A, Borelli P, Bordanaro AC, Marzaduri E, Hruska KL: Immediate loading implants: a clinical report of 1301 implants – J Oral Implantol. 2002;28(4):200-9 – http://www.ncbi.nlm.nih.gov/pubmed/12498468
   10. Fogli V, Camerini M, Lauritano D, Carinci F: Success and High Predictability of Intraorally Welded Titanium Bar in the Immediate Loading Implants – Case Rep Dent. 2014;2014:215378. doi: 10.1155/2014/215378. Epub 2014 May 22 – http://www.ncbi.nlm.nih.gov/pubmed/24963419
   11. Rossi F, Pasqualini ME, Dal Carlo L, Shulman M, Nardone M, Winkler S: Immediate Loading of Maxillary One-Piece Screw Implants Utilizing Intraoral Welding: A Case Report – J Oral Implantol. 2015 Aug;41(4):473-5. doi: 10.1563/aaid-joi-D-14-00332. Epub 2015 Feb 3 – http://www.ncbi.nlm.nih.gov/pubmed/25647017