The success of dental implants is based primarily

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1 Removal of a fractured implant abutment screw: A clinical report Ibrahim Nergiz, Dr, a Petra Schmage, Dr, b and Raed Shahin, BDS, Dr c Centre of Dental and Oral Medicine, University of Hamburg, Germany The failure of dental implants is due not only to biological factors, such as unsuccessful osseointegration or the presence of peri-implantitis, but may also result from technical complications. Fracture of the implant abutment screw can be a serious problem, as the fragment remaining inside the implant may prevent the implant from functioning efficiently as an anchor. The procedure used for the removal of fractured screw fragments and the successful utilization of the existing prosthesis are described in this clinical report. (J Prosthet Dent 2004;91:513-7.) The success of dental implants is based primarily on the extent of osseointegration. 1,2 However, the failure of dental implants may also be related to implant-supported restorations or peri-implantitis. Failures of implant-supported restorations result from technical problems and can be divided into 2 groups: those relating to the implant components, and those relating to the prosthesis Technical problems related to implant components include abutment screw fractures. 7,12 Such complications have been reported at an increasing rate. 8,13-18 The primary reason for screw fracture is undetected screw loosening, which can be due to bruxism, an unfavorable superstructure, overloading, or malfunction. 9,10,14,18 Therefore, the number, position, dimension, and design of implants, as well as the design of the prosthesis, are critical factors to be considered during the treatment planning phase ,15,16 To withstand high bending stress, implants should be as long and as wide as possible, used in adequate numbers, and have a position which allows axial loading. 12,13,16,18 Implant components are known to fracture more frequently in the posterior region and in partially dentate patients compared to completely edentulous patients. 4,5,8,10,11,13,14,16 The average occlusal masticatory force was reported to be between 450 N and 550 N in patients who were completely dentate to the second premolar. 11,19 A decrease of the occlusal force to a level between 200 N and 300 N was recorded for fixed as well as for removable implant-supported restorations. 11,19 Implant abutments fail when lateral forces exceed 370 N for abutments with a joint depth of at least 2.1 mm and 530 N with a joint depth of at least 5.5 mm. 6 Cemented cores resisted forces of approximately 1000 N. 20 In This paper was presented as a poster at the First Meeting of the German Society for Oral Implantology, Austria and Switzerland, November 30 through December 2, 2000, Salzburg, Austria. a Associate Professor, Department of Restorative and Preventive Dentistry. b Assistant Professor, Department of Restorative and Preventive Dentistry. c Assistant Professor, Department of Prosthetic Dentistry. comparison, the stress level of natural teeth restored with cemented dowels and cores was reported to be 4 times lower. Therefore, implants should be strong enough to withstand masticatory forces. 20 Yet fractures of the implant abutment or of the abutment screw were also observed as a consequence of screw loosening and undetected micromovements of the abutment under functional loading. 18 During routine follow-up, loose screws were found in 25% of patients. 8 The initial tensile preload generated within the screw on initial tightening provides mechanical resistance against masticatory forces. 16,21 However, under functional loading, the initial tensile preload is loosened by a factor known as the settling effect. 18 In view of the importance of correct torque application in the initial phase of tightening, a torque control wrench is recommended for the procedure. 7,11,18,21 Additionally, implant systems with antirotational components, such as an internal hexagon, as well as those in which the abutment engages deep into the implant body, will enhance the strength of the system. 3,6,11,12 Implant systems with no protection against rotation often present with higher complication rates. 3,6 Once an abutment fracture has occurred, the fractured screw segment inside the implant must be removed. Otherwise, the implant may remain osseointegrated but will lose its ability to retain the prosthesis, so that the existing prosthodontic restoration can no longer be used. 7 Methods for retrieving screw fragments with the implant in situ have been reported. 7 If the fragment is not jammed, an attempt to unscrew it using an explorer or a straight probe might be successful. The tip of the instrument is moved carefully in a counter-clockwise direction over the surface of the screw segment until it loosens. An implant repair kit (ITI Dental Implant System; Institut Straumann, Waldenburg, Switzerland) is available and consists of drills, 2 drill guides, and 6 manual tapping instruments. 7 One drill is 1.6 mm in diameter and is used counter-clockwise at a speed of at least 600 rpm, together with the respective drill guide. Once the fragment has been perforated, the 6 manual tapping instruments are used successively with the second drill guide in a clockwise direction to remove the retained fragment and to section the threads. The JUNE 2004 THE JOURNAL OF PROSTHETIC DENTISTRY 513

$Radiograph showed no marginal bone loss but revealed fractured screw fragment inside implant.$ $fractured fragment is not unscrewed but is cut into splinters, while the threads are recut at the same time.$ $7 This clinical report presents a situation in which a fractured implant abutment screw was successfully retrieved using an alternative repair kit (IMZ$

2 THE JOURNAL OF PROSTHETIC DENTISTRY NERGIZ, SCHMAGE, AND SHAHIN Fig. 1. Nonfunctioning implant prior to fragment removal. Fig. 3. Implant repair kit used. (A) center bit, (B) 1.3-mmdiameter twist drill, (C) 1.9-mm-diameter twist drill, (D) conical instrument to retrieve fragment, (E) manual tapping instrument. A, B, and C were used with drill guides. Fig. 2. Radiograph showed no marginal bone loss but revealed fractured screw fragment inside implant. fractured fragment is not unscrewed but is cut into splinters, while the threads are recut at the same time. Though the manufacturer purports that the new abutment will fit after the cutting of the threads, the new abutment may be slightly rotated and misfit may result. 7 This clinical report presents a situation in which a fractured implant abutment screw was successfully retrieved using an alternative repair kit (IMZ TwinPlus Fig. 4. Center bit (left) and conical instrument (right) for retrieving fragment. Note centrally drilled fragment remaining on conical instrument. Repair Set K 3.3; Dentsply Friadent, Mannheim, Germany), and a new magnet-containing abutment was placed to allow the patient to wear the existing prosthesis. 514 VOLUME 91 NUMBER 6

NERGIZ, SCHMAGE, AND SHAHIN THE JOURNAL OF PROSTHETIC DENTISTRY Fig. 6. Torque control wrench fixed onto magnet applicator. Fig. 5. New magnet inserted using application instrument.

$Clinical and radiographic examination of the implant region showed that the screw of 1 magnet fractured 9 months after placement of the mandibular denture (Figs 1 and 2).$ $Two treatment options were considered: attempting to retrieve the fractured screw, or removing the implant and replacing it with a new one.$

3 NERGIZ, SCHMAGE, AND SHAHIN THE JOURNAL OF PROSTHETIC DENTISTRY Fig. 6. Torque control wrench fixed onto magnet applicator. Fig. 5. New magnet inserted using application instrument. CLINICAL REPORT A 60-year-old partially edentulous man consulted the Department of Restorative and Preventive Dentistry, University of Hamburg, complaining that his mandibular denture was loose owing to the loss of an abutment. Clinical examination of the patient revealed an implantsupported overdenture prosthesis retained with 2 magnets (Steco Titanmagnetics inserts; Steco-System- Technik, Hamburg, Germany) in 2 implants (ITI Dental Implant System; Institut Straumann) in the mandibular canine region. Both implants were 15 mm in length and 4.5 mm in diameter. The maxilla had been restored with a complete denture. Clinical and radiographic examination of the implant region showed that the screw of 1 magnet fractured 9 months after placement of the mandibular denture (Figs 1 and 2). The apical part of the screw remained threaded into the implant. Both implants were osseointegrated and showed no sign of peri-implantitis. Two treatment options were considered: attempting to retrieve the fractured screw, or removing the implant and replacing it with a new one. After consultation with the patient it was decided that the fractured screw should be removed and the implant restored. The implant repair system (IMZ TwinPlus Repair Set K 3.3; Dentsply Friadent) consisting of 4 burs, 1 tapping Fig. 7. Intaglio surface of prosthesis evaluated for fit. Fig. 8. Patient with restored magnet. instrument to recut the threads, and 3 drill guides (Fig 3), was used according to the manufacturer s instructions. First, the center bit, rotating counter-clockwise with a maximum speed of 1300 rpm, was used to roughen the fragment at its center. Next, 2 twist drills JUNE

4 THE JOURNAL OF PROSTHETIC DENTISTRY NERGIZ, SCHMAGE, AND SHAHIN with diameters of 1.3 mm and 1.9 mm were used to perforate the fragment centrally, rotating clockwise at a maximum speed of 2000 rpm. The center bit and the 1.9-mm-diameter twist drill were used with the first drill guide, the 1.3-mm-diameter twist drill with the second drill guide, and the tapping instrument with the third drill guide. Using combined crown/prosthetic/deciduous tooth extraction pliers (Meyer-Haake, Wehrheim, Germany), the drill guides were fixed in position directly on the top of the implant to allow strong axial preparation while ensuring that the drills did not damage the internal aspect of the implant. Next, the conical instrument for retrieving the fragment was inserted into the hole drilled into the fragment; the fragment was then removed under gradual rotation. The rotation was performed in a counter-clockwise direction at a maximum speed of 10 rpm. If the threads inside the implants are damaged, they may be recut with the manual tapping instrument. To allow the drilling in the middle of the fragment, the top portion of the screw was roughened using the center bit. The thinner twist drill could then be positioned to perforate the center of the fragment under copious irrigation with standard saline solution. The drill guides were individually adapted to the implant using a composite (Superlux Molar; DMG, Hamburg, Germany). The conical instrument for retrieving the fragment was subsequently inserted into the hole and used to unscrew the fragment (Fig 4). The inner aspect of the implant body was rinsed with saline solution and evaluated thoroughly. No damage to the threads was detected. A new magnet abutment was then inserted into the implant using a magnet application instrument (Steco- System-Technik) (Fig 5). The torque of 18 N-cm, recommended by the manufacturer (Steco-System- Technik), was controlled using a torque control wrench (IMZ ; Dentsply Friadent) (Fig 6). The fit between the magnet insert and the implant was carefully evaluated to rule out the presence of marginal gaps. The fit of the prosthesis was then re-evaluated using a soft silicone impression material (Xantopren VL plus; Heraeus Kulzer, Hanau, Germany), and the occlusion was carefully adjusted (Figs 7 and 8). The patient was then placed on a maintenance recall schedule. Afterwards, the fractured surface of the coronal part of the magnet insert, which had been collected by the patient, was analyzed by light microscopy (Axiophot Pol; Zeiss, Oberkochen, Germany). No porosity or surface irregularity was revealed in the titanium. DISCUSSION The presented situation illustrates some of the complications inherent in the utilization of implant components. The reason for the screw fracture was assumed to be the unrecognized loosening of the screw aggravated by nonaxial movements during prosthetic loading, culminating in the fracture. 9,14,18 The repair system described was developed for the IMZ implant system but may be used for other implant systems as well. The method of perforating the fragment first and achieving retention to unscrew it afterwards was successful. 7 However, the method is complex and difficult for routine application because the procedure can be time-consuming and involves the risk of damaging the threads inside the implant. The success achieved with the repair system may be unpredictable and dependent upon the individual situation. In some situations failure might occur owing to a reduced interocclusal distance, a restless patient, or the inadequate skills of the dentist. Roughening the fragment initially and using drill guides for axial drilling helped to reduce the risk of damaging the internal aspect of the implant body. The drill guides should be positioned with great care. Screwing out the perforated fragment was advantageous because the implant threads remained intact. Only if the threads had been damaged would they have been recut with the tapping instrument. Magnet-retained overdentures are commonly used. Failures have related primarily to the stability of the coronal complex with the encapsulated magnet. 17 The results of light microscopic examination suggest that failure was not due to weakness of the material or to a manufacturing defect of the magnet insert. 9,12-14 The retentive ability of the magnet inserts alone would have provided the required stabilization of the prosthesis. Unfortunately, the implants did not protect the magnet insert against rotation and the magnet insert did not extend deep enough into the implant. 6,12 The bending forces were suspected to be high, due to the poor fit of the prosthesis or to a planning error. 9,10 Even if the prosthesis fit well, the abutment may have loosened under functional loading owing to the settling effect. 18 The authors assumed this to be the reason for failure in the presented situation. Additionally, 4 rather than 2 implants may have been preferable for prosthesis retention. 15 The ultimate aim of a routine recall system is to avoid complications such as screw or abutment fractures. However, their occurrence may represent an early warning sign. 7,14 For this reason, it is essential not only to retrieve the fractured component but also to determine the reason for failure and to modify the prosthesis if necessary. Regular recall appointments might prevent further screw fractures, as problems could be diagnosed and treated earlier. 4 However, the question remains as to how often the removal of fractured fragments could be successfully repeated in the same implant. 516 VOLUME 91 NUMBER 6

5 NERGIZ, SCHMAGE, AND SHAHIN THE JOURNAL OF PROSTHETIC DENTISTRY CONCLUSION Using the described technique, fractured implant fragments were successfully removed. Nevertheless, the aim of prosthodontic treatment should be to avoid any fracture of implant abutments and to use the described repair system only in exceptional circumstances. REFERENCES 1. Albrektsson T, Brånemark PI, Hansson HA, Lindstrom J. Osseointegrated titanium implants. Requirements for ensuring a long-lasting, direct boneto-implant anchorage in man. Acta Orthop Scand 1981;52: Schenk RK, Buser D. Osseointegration: a reality. Periodontol ;17: Behr M, Lang R, Leibrock A, Rosentritt M, Handel G. Complication rate with prosthodontic reconstructions on ITI and IMZ dental implants. Clin Oral Implants Res 1998;9: Carlson B, Carlsson GE. Prosthodontic complications in osseointegrated dental implant treatment. Int J Oral Maxillofac Implants 1994;9: Brägger U, Aeschlimann S, Bürgin W, Hammele CH, Lang NP. Biological and technical complications and failures with fixed partial dentures (FDP) on implants and teeth after four to five years of function. Clin Oral Implants Res 2001;12: Möllersten L, Lockowandt P, Lindén LA. Comparison of strength and failure mode of seven implant systems: an in vitro test. J Prosthet Dent 1997;78: Luterbacher S, Fourmousis I, Lang NP, Bragger U. Fractured prosthetic abutments in osseointegrated implants: a technical complication to cope with. Clin Oral Implants Res 2000;11: Wie H. Registration of localization, occlusion and occluding materials for failing screw joints in the Brånemark implant system. Clin Oral Implants Res 1995;6: Green NT, Machtei EE, Horwitz J, Peled M. Fracture of dental implants: literature review and report of a case. Implant Dent 2002;11: Taylor TD, Agar JR, Vogiatzi T. Implant prosthodontics: current perspective and future directions. Int J Oral Maxillofac Implants 2000;15: Brunski JB, Puleo DA, Nanci A. Biomaterials and biomechanics of oral and maxillofacial implants: current status and future developments. Int J Oral Maxillofac Implants 2000;15: Binon PP. Implants and components: entering the new millennium. Int J Oral Maxillofac Implants 2000;15: Piattelli A, Piattelli M, Scarano A, Montesani L. Light and scanning electron microscopic report of four fractured implants. Int J Oral Maxillofac Implants 1998;13: Eckert SE, Meraw SJ, Cal E, Ow RK. Analysis of incidence and associated factors with fractured implants: a retrospective study. Int J Oral Maxillofac Implants 2000;15: Rangert B, Krogh PH, Langer B, Van Roekel N. Bending overload and implant fracture: a retrospective clinical analysis. Int J Oral Maxillofac Implants 1995;10: Sato Y, Shindoi N, Hosokawa R, Tsuga K, Akagawa Y. A biomechanical effect of wide implant placement and offset placement of 3 implants in the posterior partially edentulous region. J Oral Rehabil 2000;27: Riley MA, Williams AJ, Speight JD, Walmsley AD, Harris IR. Investigations into the failure of dental magnets. Int J Prosthodont 1999;12: Bakaeen LG, Winkler S, Neff PA. The effect of implant diameter, restoration design, and occlusal table variations on screw loosening of posterior single-tooth implant restorations. J Oral Implantol 2001;27: Mericske-Stern R, Assal P, Mericske E, Bürgin W. Occlusal force and oral tactile sensibility measured in partially edentulous patients with ITI implants. Int J Oral Maxillofac Implants 1995;10: Wiskott HW, Belser UC. Mechanical resistance of cemented post and core buildups for ITI-Bonefit implants. Clin Oral Implants Res 1992;3: Siamos G, Winkler S, Boberick KG. Relationship between implant preload and screw loosening on implant-supported prostheses. J Oral Implantol 2002;28: Reprint requests to: DR IBRAHIM NERGIZ DEPARTMENT OF RESTORATIVE AND PREVENTIVE DENTISTRY UNIVERSITY OF HAMBURG, DENTAL CLINIC. MARTINISTRAßE 52, HAMBURG GERMANY FAX: nergiz@uke.uni-hamburg.de /$30.00 Copyright ª 2004 by The Editorial Council of The Journal of Prosthetic Dentistry doi: /j.prosdent Bound volumes available to subscribers Bound volumes of The Journal of Prosthetic Dentistry are available to subscribers (only) for the 2004 issues from the publisher at a cost of $92.00 ($ international) for Vol. 91 (January-June) and Vol. 92 (July-December). Shipping charges are included. Each bound volume contains a subject and author index, and all advertising is removed. The binding is durable buckram with the journal name, volume number, and year stamped in gold on the spine. Payment must accompany all orders. Contact Elsevier Inc., Subscription Customer Service, 6277 Sea Harbor Dr, Orlando, FL 32887, or call or Subscriptions must be in force to qualify. Bound volumes are not available in place of a regular Journal subscription. JUNE

Implant osseointegration and successful restoration

Implant osseointegration and successful restoration Prosthodontic Complications in a Prospective Clinical Trial of Single-stage Implants at 36 Months Jacqueline P. Duncan, DMD, MDSc 1 /Elena Nazarova, DMD, PhD 2 /Theodora Vogiatzi, DDS 1 / Thomas D. Taylor,