October 1, 2012
by Mathieu Beaudoin, DMD, MSc. Perio, FRCD(c)
In the last three decades, dentists have placed and restored implants to meet patient’s functional and esthetic needs. As the field evolved, we have learned through shared collective experience to evaluate clinical surgical and prosthetic parameters and risks factors to successfully manage difficult situation involving compromised soft and hard tissues. The accumulated research clearly supports the notion that the long-term prognosis of treatments utilizing implants with textured surfaces is excellent.1–3 However, we are less confident in predicting how long these implants can sustain function without incurring complications. Studies clearly show that a low percentage of dental implants will develop complications. As more implants are placed to meet a growing demand in a longer living population, and by placing them in younger individuals with decades of life expectancy, we will be faced with number of complications and failures requiring appropriate management.
Biological complications include inflammation and infection limited to the soft tissues around the implant while a failing implant has been defined as immobile but demonstrating a progressive bone loss.4 At this time, there is no clear consensus on how to manage failing implants. This is due to our lack of understanding of the etiology of failure be it due to biomechanical overload and/or bacterial-host response. Once the etiological factors were removed, the clinician often has to rely on weak scientific evidence to treat the pathological bone loss around implants. Conservative approaches include debridement, either mechanical or with light therapy and the use of antiseptics and antibacterial drugs. More invasive rescue procedures involving surgical approaches combined with surface decontamination and guided bone regeneration procedures that are primarily used when conservative approaches fail to restore peri-implant tissues. The predictability of such protocols submitted to specific scrutiny remains unknown.
In facing these complications the clinician will select the best direction to take, weighting the risks versus benefits of all the different possible treatments while taking in consideration the likelihood of favourable outcomes. Given the uncertainty that still characterizes these methods, at times, the most predictable and most appropriate way to treat bone loss around failing implants is to “explant” the fixture and start afresh. Trephines, burs, piezoelectric devices and various forcepses have served the clinicians well in the past to remove integrated implants and these instruments continue to be use today. The common end-result though is of a compromised surrounding bone. At times, irreversible damage to neighboring structures, such as roots and nerves occur, making this approaches less desirable. The utilization of such instruments tends to leave dramatic architectural defects in the bone that pose significant challenges for post-extractional reconstruction.
Given that the integration of an implant is a micro-mechanical lock and that most implants are threaded and self-taping, it would be logical that the most appropriate way to remove an implant would be to simply “unscrew it” or “break” osseo-integration. The explanation is predicated on breaking the mechanical bond (resistance to back-up the implant counter clockwise) at the bone-implant interface. Most studies assessing implant torque removal show that fixtures with rough surfaces can be explanted by applying a sufficient amount of force in a counter clockwise direction.5,6 This allows preservation of the surrounding bone obviating the need for major bone reconstruction, making implant removal and replacement more predictable.
Such instrumentation has been recently brought to the market. The “Neobiotech NEO FR fixture remover Kit” (“The Kit”) is a specially designed dynamometric key in conjunction with reverse components. The use of the “The Kit” begins with the appropriate selection of the “fixture remover screw” (FRS) diameter, available in six diameters to fit most implant types of screw access connection chambers. The FRS features a specific thread design at the apical tip that screws into the receiving implant chamber while the opposite end consists of a fixed constant diameter supported by a 1.6 hex top. The FRS is inserted in a “clockwise” direction into the screw access implant chamber using a hand held driver and then “torqued” with the dynamometric key at 40-60 Ncm. Subsequent to insertion of the FRS the selection of the corresponding gold colored “Fixture Remover” (FR) is determined. The FR is manually screwed on the FRS in a “counter-clockwise” direction. Once the FR is seated the dynamometric key is set in a “counter-clockwise” direction and force is applied until the implant becomes mobile. To retrieve the FR component for re-use from the removed implant a “Vise” is clamped on the removed implant while the dynamometric key is set in a “clockwise” direction using the required force. However, the FRS remaining in the removed implant should be discarded. A word of caution must guide the practitioner in utilizing such a device: if the torque applied to the FRS exceeds the resistance to distortion of the implant material or FRS material–the attempt can result in altering the interface between the implant and the FRS or even fatigue fracture of the FRS complicating the removal of the implant.
The following two cases illustrate how implants have been removed with “The Kit”.
A 20-year-old female consulted for the undesirable appearance of the gingiva on the labial aspect of her implant-supported crown at #21 (Figs. 1a-e). Her dental history revealed that both teeth, #11 and #21, avulsed as a teenager following an accident. At the age of 18, reconstructive and regenerative grafting procedures were performed to reconstruct the prospective implant recipient sites. After six months of healing two standard external hex implants of 13 mm in length were placed (Fig. 1b). Two years after implantation, the patient had noticed moderate gingival recession corresponding to the implant replacing tooth # 21 (Fig. 1c). A consultation with the same surgeon resulted in another grafting procedure utilizing particulate xenograft with the goal to provide better support for the soft tissue. A few weeks following the surgery, the gingival recession has increased. Then, another corrective surgery was performed consisting of the removal of the labial frenum. The recession did not reverse but remained at the same level.
In spite of a favourable smile line the patient expressed a strong desire to address the recession. On clinical examination the recession on the facial aspect of #21 measured 3mm and there was a clear discrepancy between the levels of the marginal gingiva when compared to the adjacent right central incisor. The probing depth was 7mm. After removal of the two cemented and splinted crowns (Fig. 1d), it became evident that the mesio-distal positions of both implants were favourable with adequate inter-dental and inter-implant spaces. However, while the implant at #11 was slightly buccaly positioned the implant at #21 was severely misplaced in the bucco-lingual dimension (Fig. 1e).
After discussing the different esthetic issues and treatment possibilities ranging from maintaining these implants to removing both implants, the patient opted for the removal of both implants in order to proceed with an orthodontic treatment to ideally realign the lateral incisors and canines before an attempt was made to re-treat the sites with two implants. As explained, further bone augmentation may be necessary.
A provisional restoration was fabricated and cover screws were placed on both implants for 2 weeks to maximize soft tissue closure (Fig. 2). To prepare for the eventual bone reconstructi
on, a preliminary approach was planned to remove the two implants utilizing a novel technique rather than using trephines that results in at least 1.5mm bone loss around the original osteotomy site. The fibrotic and scarred tissue in the anterior area in conjunction with a shallow vestibular fold and a prominent nasal spine posed a significant challenge for bone reconstruction and in achieving tension-free soft tissue closure. It was therefore planned to reconstruct soft tissues at the time of implant removal with a periodontal plastic procedure.
Following a full thickness flap reflection the implant at #21 site a horizontal bone loss exposing up to the seventh thread on its facial aspect was noted. The implant at the #11 site also showed bone loss exposing up to the third thread (Fig. 3a). Since both implants were integrated on a large percentage of their surfaces, using conventional devices such as trephines or burs would have resulted in substantial bone loss of the already thin alveolar ridge. Instead, a specially designed implant removal kit including a dynamometric key (“The Kit”; Figs. 3b and c) was utilized to remove the implants. The torque wrench allows for an application over 450 Ncm in a antirotational direction, therefore providing sufficient force to brake integration and mobilize most implants regardless of their surface configurations (Figs. 3 d,e,f). Both implants were successfully “unscrewed” with a reverse torque of 350 Ncm.
Following implant removal, two autogenous connective tissue grafts were harvested from the hard palate and sutured in layers perpendicularly to each other over the defect covering both sites (Fig. 4). After three months of healing, the bone reconstruction phase was completed (Fig. 5 a-g). To achieve tension-free soft tissue primary closure, a split thickness flap was dissected from the palatal aspect toward the buccal. Evidence of severe bone atrophy was noted at the recipient site an autogenous bone block was harvested from the chin, adapted and screwed in place. Particulated autogenous bone was used to fill in the small voids at the periphery of the block and complete de reconstruction.
Currently the case is in the healing phase and the orthodontic treatment is in progress. The site will be reevaluated for implant placement with tridimensional imaging approximately 4 months post-op. Since the purpose of this paper is to illustrate the use of the “The Kit” the author felt that publication was warranted before final retreatment results were available.
A healthy 26-year-old male had teeth #36 and #37 replaced with implants two years prior to presentation (Fig. 6a). He then experienced recurring swelling in the area despite repeated antibiotic treatments and debridement. The restorative components consisted of splinted screw retained crowns with absence of occlusion on the first molar. There was a faulty contact point between #36 and the adjacent natural tooth #35 with evidence of food impaction. The probing depth was 9mm on the mesial aspect of #36 with purulent discharge. The peri-implant tissues were normal around #37. The radiographic examination revealed a vertical bone loss on the mesial aspect of the implant at #36 exposing up to the three threads on the mesial and up to the two thread on the distal aspects (Fig. 6b). After discussing the treatment options with the patient we proceeded with an exploratory surgery. The patient consented to an array of procedures, from decontamination of the implant surface combined with regenerative bone grafting procedure to removal of the implant. First the implant-supported crowns were removed allowing the soft tissues to heal for two weeks. Then bucclo-lingual flaps were raised and the site was explored. A circumferential bony defect with horizontal loss of the buccal alveolar plate was noted (Fig. 6b). Although regenerative methods after decontamination of the implant surface would have been tenable, albeit with a questionable predictability, it was decided to remove the implant. The patient’s young age weighted heavily in making this decision. Again, “The Kit” was utilized at torque setting of 250 Ncm of reverse torque (Figs. 6c,d). The site was grafted and augmented with allogenic mineralized bone and a collagen membrane and re-entry is planned for implant replacement in a few months.
When facing failing implants characterized by significant peri-implant bone loss all possible treatment options have to be reviewed with the patient. If replacing the implant was the treatment of choice it is desirable that the least invasive method was utilized. Utilizing the “The Kit” obviates the need to use more conventional techniques resulting in bone loss. The use of this kit allows a better chance for a successful retreatment.
The author wishes to thank Rudy Huber from HuberMED inc., the exclusive distributor in Canada, for providing the Neobiotech NEO FR fixture remover Kit and dynamometric key.
For more details about the NEO FR fixture remover Kit: www.hubermed.com
Special thank to Dr. Peter Birek for his contribution to this article.OH
Dr. Mathieu Beaudoin maintains a private practice in Montreal and focuses on periodontal therapy and implantology. He has no affiliation with and received no incentives from companies distributing any of the aforementioned devices.
Oral Health welcomes this original article.
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