|Year : 2018 | Volume
| Issue : 2 | Page : 66-68
Cold welding: A possible mechanical complication related to a failing dental implant cover screw
Peter Óvári, Veronika Agnes Jancsik, Jozsef Piffkó
Department of Oral and Maxillofacial Surgery, Albert Szent-Györgyi Medical Center, University of Szeged, Hungary
|Date of Web Publication||17-Dec-2018|
Dr. Veronika Agnes Jancsik
Department of Facial, Oral and Maxillofacial Surgery, Medical School, University of Szeged, 57 Kálvária Street, Szeged
Source of Support: None, Conflict of Interest: None
| Abstract|| |
Cold welding is a very useful mechanical effect in dental implant therapy when abutments are fixed. However, this effect may cause very challenging situation for the clinicians when occurring in the “wrong place, wrong time.” The incidence of cover screw complications was reported to range 0.5%–8%. According to our investigation, this value may be even higher when conical design present. Although some manufacturers offer so-called retrieval kits, in some cases, these are very time-consuming and not always effective, and when the complication occurs, the planned dental implant therapy could be in danger. This article summarizes a case report when the conical connected cover screw affected from cold welding was removed with a carbide bur.
Keywords: Cover screw, screw-removal techniques, two-stage dental implant surgery
|How to cite this article:|
Óvári P, Jancsik VA, Piffkó J. Cold welding: A possible mechanical complication related to a failing dental implant cover screw. J Dent Implant 2018;8:66-8
|How to cite this URL:|
Óvári P, Jancsik VA, Piffkó J. Cold welding: A possible mechanical complication related to a failing dental implant cover screw. J Dent Implant [serial online] 2018 [cited 2019 Jun 26];8:66-8. Available from: http://www.jdionline.org/text.asp?2018/8/2/66/247578
| Introduction|| |
Dental implant supported prostheses has been very effective and reliable treatment option since the past three decades. Implants with a conical prosthetic connection are increasingly popular. A successful treatment depends on various biological and mechanical factors, and conical connection facilitates greater stability, smaller microgap, superior preservation of the crestal bone, and soft tissue., However, there are mechanical complications which are barely described in the literature, for example, complications in the conical connected cover screw management. The management of a failed cover screw may play a key role in the dental implant therapy because to initiate the prosthetic phase, the screw has to be removed without damaging the internal threads of the dental implant.,,
In the background for a failing cover, screw may be several factors, which are summarized in [Table 1] as listed above.
These alterations can lead to either a broken cover screw body or a worn-out screw head., The purpose of this article to present an easy method for the removal of a cold-welded cover screw with conical connection.
| Case Report|| |
A 64-year-old female patient was referred to the department for oral surgery for the second stage surgery with implant placed in the area tooth number #4. The implant placement procedure (Ankylos, C/X, B11, Dentsply) was carried out 6 months prior her visit, due a maxillary lateral sinus membrane elevation was also conducted during the first stage of the surgery. After the intraoral radiographic verification of osseointegration [Figure 1], the second stage of implant surgery was carried out, with the following techniques described by Bernhart et al. The procedure consisted of the vertical incision on the gingival crest covering the cover screw, and this was followed by a round incision about 1–3 mm around the tissue to be removed. On the platform of the implant, new bone formation was detected, which was gently removed by a 5/6 implant Gracey scaler (Tess Corporation). After this, we attempted to remove the cover screw by manual ratchet applying a reverse torque not >30 Ncm. Several retrievals later, the friction slot of the cover screw became worn out [Figure 2]. Since prior the radiographic examination showed no evidence of the bone growth of the edges, we suggested that maybe cold welding is the cause for the failed manual removal of the cover screw.
Cold welding is a very challenging situation due to the high risk of the internal thread damage. After explaining the patient the risk, we decided to remove the cover screw by drilling through the screw with the implant handpiece with a tapered carbide bur (Ankylos retrieval kit, Dentsply). The drilling method included first a clockwise insertion of the bur on low speed on 20 Ncm, for approximately 3-mm deep. This was followed by reverse rotation movement with applying a gentle apical pressure until the cover screw was completely removed [Figure 3]. According to the radiographic examination internal thread if the implant were intact, the abutment fitting was also tested both clinically and by radiograph. After inserting the healing abutment (Ankylos, GH, 4.5 mm), the flap was closed with single knot technique using 5–0 monofilament [Figure 4]. Full contour zirconia prosthesis was delivered to the patient 1 month after the second stage. The result of the 1-year postoperative control is demonstrated in [Figure 5]a, and the radiographic examination result in [Figure 5]b.
|Figure 5: (a) One-year postoperative control of the fabricated bilayered zirconia crown. (b) One-year postoperative radiographic control|
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| Conclusion|| |
The above-described case presented a rare complication of cover screw removal the so-called cold welding. Causes for cold welding may be various: nonvisible defect of the cover screw, overtorquing during inserting the screw, but the false direction of unscrewing may also cause cold welding. Unfortunately, in this case, we also could not exclude 100% the presence of bone growth between the implant platform and the internal threads, due to the visible bone growth over the implant platform edges. However, we also could not exclude conical connection as a predisponating factor since it provides a very secure fit but a very tight connection.
While the manual retrieval of cover screw removal failed, analyzing the risk-benefit ratio, and the wish of the patient to save the implant, we decided to apply the drilling through the center of the cover screw method. This method is very easy, safe, cost-effective, applicable on all implant systems but should be concerned if internal bone growth may present due causing damage in the internal threads. Therefore, we suggest this method only in cases where this risk does not occur.
Even for a practicing clinician facing complications in the management of cover screw removal may be very challenging. The problems during the removal may vary from case to case, and so, there is no universal solution for clinical situations with different background. By highlighting several retrieval methods, we hope the case letter may be helpful for all colleagues.
Declaration of patient consent
The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5]