Crown fractures, framework fractures, and abutment screw loosening or screw fracture are examples of mechanical implant failures. Abutment screw loosening is a serious problem that can result in abutment screw fractures. This clinical report describes the production method of a custom-made abutment screwdriver piece for a patient with abutment screw loosening.
Dental implants are reliable and predictable treatment option for restoration of single tooth deficiencies if they are able to functionally integrate into the bone structure.1 With proper treatment planning, appropriate placement, adequate prosthetic design, and proper maintenance, dental implants can achieve a 97% to 99% success rate.2 However, despite high success and survival rates, biological and mechanical failures and complications may be observed in some clinical situations.3
In dental implantology, mechanical implant failures may be related to implant components or the prosthesis.4 Although there have been many innovations, abutment screw loosening is still a significant complication, especially in single crowns.3–6 Abutment screw loosening can be affected by component interface geometry and passive fit.7 Bruxism, unsuitable interproximal contact between the tooth and the prosthesis, overloading, malfunction, and different thermal expansions of different implant components can also cause abutment screw loosening.8,9 Frequent screw loosening can be a risk factor for abutment screw or dental implant fractures, and modification of the prosthetic restorations is required to treat this problem.4,10
In clinical practice, there are a few precautions that can be taken to prevent screw loosening. Comprehensive diagnostic examinations are very important in determining the factors that may lead to this complication. Also, it is very important for clinicians to be familiar with the torque wrench and to follow the manufacturer's recommendations during placement, especially during placement of the restoration in the mouth. In addition, clinicians should always ensure that the abutment screw head is free of debris to allow the screwdriver to hold the abutment screw, because only in this way can appropriate torqueing be applied.3 Attention should also be paid to other criteria such as the preload of the screw, the antirotational mechanism at the implant abutment interface, and the precise fit of implant components; additionally, clinicians should ensure that the restoration is free of premature occlusal contacts.11
In today's dentistry, a large number of implant systems with different designs have been produced, and the majority of these implants are used in many countries. In addition, due to the increase in demand in the domestic implant market, many countries have begun to compete with international implant systems to develop their own national systems. As a result, a large number of implant systems with different designs have become available worldwide. Due to increased patient mobility today, it is inevitable that the clinician will need to assemble the data to consult during the application of the prosthesis, as another clinician may handle following procedures; this information will be especially crucial if there are complications. For this reason, a new requirement, radiographic recognition of dental implant brands, has emerged. The creation of radiographic dental image data will aid diagnosis in situations where an implant and its manufacturer are not identifiable.12
The options for identifying the details of implant bodies include intraoral examination, intraoral radiography, three-dimensional imaging, and panoramic radiography.13 In the radiographic diagnosis of implants, it is necessary to examine the implant properties correctly. To facilitate diagnosis, the implants can be examined in 3 parts: coronal, midbody, and apical. Coronal features include interface, flange, collar, and microthreading. The characteristics of the midbody of the implant include the implant taper, implant threads, and thread type. The features of the apical part of the implant include apex shape, round holes, oblong holes, apical chamber, and apical grooves.13,14
In recent years, an application (available as computer software or on a website) has been in development to help in the identification of implants using a series of questions on implant imaging.15 A database has been created for the data obtained from implant manufacturers for the application. In the database, information such as shape, surface, presence of threads, and coronial section differences, as well as the diameter and height characteristics of the implant system, are compiled. The designed application interrogates the known features of the implant, allowing the user to enter information about the implants, such as implant definition, gear, surface, collar, diameter, and length. With the launch of the search function in the software or on the website, the system shows a list of potential implant manufacturers and implant names.15,16
Unfortunately, all radiographic diagnostic techniques have been made in accordance with diagnostic procedures. Some implant systems have special characteristics that make recognition easy, but others have very similar characteristics, so the analysis of fine structures is required. It is also difficult to keep up with the ongoing development of implant designs. For this reason, sometimes recognition of an old or new dental implant can become a major problem for a dentist who treats a patient who does not have dental records.17
In this case, for a patient with a loose abutment screw where the original screwdriver could not be provided due to the ambiguity of the implant brand, production of a special custom-made screwdriver piece is described to repeat the prosthetic treatment.
Case Report and Technique
A 35-year-old healthy female patient was referred to our clinic with a complaint concerning about implant-supported crown on the mandibular right first molar. The patient said that the implant-supported crown was made by a dentist in another country 4 years ago. The patient said that the restoration had come loose a few times. Although the dentist had remade the restoration, the problem continued. In addition, the patient had pain in the gingiva around the implant-supported crown and had difficulty chewing. An intraoral examination revealed that the implant-supported crown was moveable. A panoramic radiograph was taken and marginal discrepancy of the crown was shown in the radiograph (Figure 1).
The crown was controlled to remove it without damaging the abutment and implant. Despite the crown being moveable, it was removed easily. It was noticed that the abutment had a loose screw and could easily be removed. Following removal of the abutment, it was noted that the abutment and fixation screw were manufactured as 1 piece, and there were no compatibility problems.
After the abutment and crown were removed from the mouth, swollen and inflamed periodontal tissue was observed. The probable reason for this biological complication was that the crown had inadequate marginal adaptation, and a microgap between the abutment and implant had been caused by screw loosening. In addition, the marginal line of the abutment was 1–1.5 mm below the gingiva in the lingual region, and this may have increased tissue inflammation (Figure 2a, b).
It was decided that the restoration should be renewed because of inconsistencies seen on the intraoral and radiographic examinations, but the implant brand had to be determined because the implants were not inserted in our clinic.
First, the patient was asked to try to contact the dentist who performed the implant surgery, but unfortunately, she was unsuccessful. Therefore, to learn the implant brand, the used implant's radiographic features were searched on a website.16 After the introduction of the radiographic findings into the system, 17 different companies with implant brands that could have been used in the patient were identified. Some of these companies were being used in our country, while others were not. Because the number of filtered implant brands is high, all radiograph, photograph, and size information concerning the abutment data was sent to all companies used in Turkey via email in an attempt to identify the brand. However, the brand of the implant could not be determined. Therefore, to avoid damage to the implant abutment during torquing, the production of a custom-made screwdriver piece was planned.
For the custom-made screw production, the initially removed abutment was cleaned with compressed steam and dried with air. The abutment was scanned using a probe, and the data were transferred to a computer and saved. A coping of about 1 mm thickness, which was compatible with the solid abutment, was designed using a computer-aided design (CAD) program (Figure 3), and a wax coping model was produced via a computer-aided manufacturing (CAM) technique (Figure 4). After that, among the brands used for routine applications in our clinic, the BioHorizons 2-part abutment screwdriver (BioHorizons IPH, Inc, Birmingham, Ala) was selected to provide the appropriate torque value.3 The interior part of the abutment screwdriver was removed, and casting wax was employed for the interior part of this piece. The adapted casting wax model was then attached to the plastic coping (Figure 5a through d). The obtained model was casted from nickel–chromium, graded, and polished. The casted piece was adapted to the implant screwdriver and prepared for intraoral use (Figure 6a through d).
After periodontal examination, to reveal the abutment margin and preserve the width of the keratinized tissue, apically repositioned flap surgery was scheduled. Local infiltration anesthesia was performed. The incision began horizontally on the abutment, and a partial thickness flap was elevated to the mucogingival line. To expose the implant shoulder, the partial-thickness flap was apically repositioned and sutured with 4-0 Vicryl. In addition, a diode laser was used for exposing the lingual shoulder of the implant. Postoperative care included 1 week of analgesics (100 mg of ibuprofen) taken twice daily and an antimicrobial mouth rinse (0.12% chlorhexidine) used twice daily for 1 week. The patient was given a soft diet and an ice compress on the day of surgery and informed that she should avoid any mechanical trauma. A CAD–CAM temporary restoration was made from a poly-methyl methacrylate (PMMA) block. The patient wore the temporary restoration until recovery of the gingiva occurred and the definitive restoration was performed. Postoperative healing was uneventful, and the patient reported a small amount of discomfort for a few days (Figure 7a, b).
As a result of the procedures, postoperative gingival healing was evaluated and it was decided that the abutment could be inserted into the implant with passive fit and then made impression protocol. After inserting the abutment, it was seen that there were not any problems, no stasis, and no bleeding on the gingiva. The custom-made implant screwdriver was placed on the abutment and torqued with 30 N cm twice at a 10-minute interval (Figure 8).
The impression was made with polyether impression material and a prefabricated stock tray. After polymerization of the impression material, the prefabricated stock tray was removed from the mouth, and the abutment was inserted into the impression. A die pin was attached to the abutment with a self-cure acrylic resin material. After polymerization, the impression waited for 45 seconds, following the manufacturer's instructions. A Type IV improved synthetic cast was poured into the impression, and a master model was obtained. A new metal–ceramic restoration was generated by applying a well-known standard protocol (Figures 9 and 10). The patient was satisfied with her new restoration.
In this clinical report, the production of a custom-made abutment screwdriver was described. This appliance was applied successfully in the patient and helped to solve a serious problem. Screw loosening was also observed before a screw fracture occurred.
Failure to determine the implant brand caused 2 problems. The first problem was that the prosthetic piece of the implant system, especially the screwdriver—which was the key point in solving the problem—was not available. However, considering that the CAD–CAM system is currently widespread,18 this solution was reliable and easy to apply. The upper piece of the custom-made screwdriver was produced via the conventional wax-modeling method. The piece of the custom-made screwdriver settled on the abutment was produced by the CAD–CAM technique, and the two pieces were then combined. The custom-made screwdriver could be produced directly from nickel–chromium blocks using the CAD–CAM technique. However, in our clinic this technique was not used, as the CAD–CAM software was not suitable for the desired production technique. Due to the precision of this system, the CAD–CAM technique was also preferred for design of the coping instead of classical wax modeling.
The second problem was that tightening torque of the abutment to the implant was not known. It was necessary to determine the tightening torque to minimize the possibility of screw loosening. For this reason, a literature search was performed. Definitive tightening torque values of implant firms were specified from 15 to 35 N cm, and the recommended minimum torque value for preventing screw loosening was found to be 30 N cm in the literature.19 In the current report, the abutment was torqued with 30 N cm and retorqued 10 minutes later with 30 N cm to avoid the “settling effect” (embedment relaxation).9,20 The settling effect is the main cause for screw loosening,21 and the mechanism of settling effect is based on no surface being completely smooth.22
To solve the problem, 2 options were evaluated. One of them involves tightening the loosened abutment screw with a portage. This option was not desired because of the possibility of damage to the abutment. If this option was selected, the torque value could not have been at desired levels. Another of them was to extract the implant, to place bone graft, and after healing, place the implant again. This option was not also desired because it would require a long time and would be traumatic.
In this case, the combined structure of the abutment and screw facilitated the solution. If the abutment and screw were not combined into one piece, the screwdriver would not be made. Because in 2-piece abutment systems the size of screwdrivers were very little and making such a screwdriver requires much more technologically advanced equipment.
After cementation, the patient was followed for 1 year and through the renovation of the restoration, the problems (soft tissue, abutment looseness) have been totally resolved. The patient had no problems or complications with soft tissue, implants, or prosthetic restoration. In implantology, it was seen that archiving of all information related to the patient and implant systems in a central data bank is crucial.
The authors report no conflict of interest in this work.