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Complications Encountered in Temporary Orthodontic Anchorage Device Therapy
Complications Encountered in Temporary Orthodontic Anchorage Device Therapy Christopher E. Roncone Although absolute anchorage with the use of fixed skeletal implants is not a recent concept in orthodontic mechanotherapy, its popularity in recent years has increased exponentially as a result of the advent and widespread manufacture of temporary anchorage devices (TADs). TADs are an invaluable asset to contemporary orthodontics, facilitating tooth movement that might otherwise require (1) surgical repositioning of the jaws, (2) extraction of permanent teeth, and/or (3) extended use of extraoral anchorage. As more orthodontists incorporate TADs into their therapeutic regimens, the clinician should be cognizant of the variety of iatrogenic sequelae that may occur with the employment of such adjuncts. Complications include, but are not limited to, encroachment upon adjacent anatomical structures, mucosal perforations or tears, peri-implantitis, and unintended tooth movement. A review of some common problems with clinical examples, as well as protocols for prevention is presented. (Semin Orthod 2011;17:168-179.) © 2011 Elsevier Inc. All rights reserved.
uring the past several decades the discipline of orthodontics has benefited from a variety of innovations that have enhanced clinical practice. The preadjusted appliance, light-cured adhesives, metallurgical hybridization of arch wires, and self-ligating brackets are just a few examples. Although each of these technologies has readily integrated into routine practice, the placement and use of maxillomandibular bone anchors— orthodontics’ most recent clinical adjunct— has proven more elusive in this regard. This is attributable, perhaps, to the fact that placement of such fixtures has long been the purview of oral surgeons or periodontists; those who have received surgical training in their residency programs. The most contemporary incarnation of skeletal anchorage, however—the temporary anchorage device, or TAD— has evolved such that placement by orthodontists is not only feasible
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but has become increasingly commonplace.1 This can be ascribed to the simplicity of the procedure itself, as well as its minimal invasiveness and comparatively low cost compared with conventional surgical intervention. Despite its simplicity, however, complications will invariably arise, partly because of the relative inexperience of the clinicians performing it. These complications include soft tissue injury, hard tissue damage, biomechanical errors, and failure intrinsic to the implant itself (eg, fracture inhalation, ingestion, infection).
Soft-Tissue Injury Soft-tissue injury can occur either during placement of a TAD or subsequently during the course of its use. Both can require extensive reparation.
Placement Injuries Private Practice, Temecula, CA. Address correspondence to Christopher E. Roncone, DDS, MS, 32140 Temecula Parkway, Ste 201, Temecula, CA 92592. E-mail: [email protected] © 2011 Elsevier Inc. All rights reserved. 1073-8746/11/1702-0$30.00/0 doi:10.1053/j.sodo.2011.01.003
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Aside from absolute anchorage, one of the primary biomechanical advantages that TADs offer is the ability to exploit the dentition’s center of resistance (Fig 1). Relocating the point of force application— either tensile or compressive— from the orthodontic appliance to a region
Seminars in Orthodontics, Vol 17, No 2 (June), 2011: pp 168-179
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Figure 1. (A) Preorthodontic panorex exhibiting multiple missing teeth. The treatment plan entailed closing all maxillary space except for the left lateral incisor. The maxillary right second molar is to be protracted (note position relative to impacted third molar). (B) Although the maxillary right second molar has been protracted, it still exhibits distoangular root inclination because of the inferior placement of the maxillary right TAD. (C) Apical repositioning of maxillary right TAD to upright the maxillary right second molar root.
nearer the anatomical center of resistance enhances the translatory movement of teeth. This is in contrast to the cyclical succession of crowntipping and root-uprighting observed with traditional orthodontic mechanotherapy.2,3 This often necessitates, however, that the TAD be placed relatively apically; sometimes beyond the mucogingival junction. Mucosal tissue, as opposed to keratinized gingival tissue, generally
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demonstrates the least durability and hence is the most susceptible to impairment (Fig 2).4-6 A variety of implant systems are available on the market and most, if not all, include the option of drilling a pilot hole. This step is a necessity when one uses a self-tapping rather than a self-drilling system. An initial method to minimize soft-tissue laceration during the placement of a TAD is the proper preparation of the implant site before drilling the pilot hole, particularly when placing it in the mucosal tissue. Several techniques have been proposed. Park et al7 advocate a small vertical stab incision with flap reflection, whereas other authors8 recommend the use of a biopsy tissue punch of appropriate diameter. Eliminating soft tissue from the proximity of the intended pilot hole will decrease the likelihood of its entanglement with the surgical drill. Figure 3 demonstrates the consequence and rectification of such entanglement. Any clinician who has contoured a denture tooth using an acrylic bur while wearing latex gloves can envision an analogous circumstance. In the event of soft-tissue entanglement, aside from initial insult often more problematic is the extrication of the surgical drill from the mucosa after osseous engagement where the clinician must reverse the handpiece engine direction while maintaining drill stability. Any long-axis deviation of the drill while doing so could potentially increase the diameter of the pilot hole. While there is usually a diameter differential of approximately 20% between the pilot hole drill and TAD (ie, a 1.2-mm pilot hole drill for a 1.5-mm TAD), this disparity is required to ensure implant engagement in sound cortical bone; that which is uncompromised by the inherently traumatic procedure of drilling itself.9 One may proffer that a reasonable alternative to the aforementioned complications is to simply use a self-drilling implant system. Although it may seem intuitive that elimination of a pilot hole may reduce the incidence of mucosal perforations, tears can still occur during advancement of the TAD itself. Figure 4 demonstrates the result of mucosal encroachment into the TAD threads during insertion despite appropriate pilot hole establishment. This is particularly true with TADs exhibiting a significant degree of taper from tip to transmucosal collar. The diameter of soft tissue preparation should be at least
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Figure 3. (A) Drilling of pilot hole without adequate soft-tissue preparation. The mucosa became ensnared in the surgical drill necessitating sutural restoration. (B) Repair of mucosal laceration with 4-0 silk. (Color version of figure is available online.)
Figure 2. (A) Maxillary right TAD repositioned apically to enable second molar root uprighting which resulted in mucosal tear. The original implantation site is visible mesial to the second premolar crown (arrow). (B) Mucosal tear sutured with 4-0 plain gut and healed well despite proximity to frenal attachment (A). (C) Biomechanics used to upright root of maxillary right second molar. Auxiliary wire permitted force delivery nearer center of resistance and a clockwise moment. (Color version of figure is available online.)
as large as the widest part of the TAD. Furthermore, a distinct advantage of pilot hole creation when placing TADs interradicularly is the enhanced ability of the clinician to differentiate cortical bone from root. It has been well demonstrated that cortical bone thickness varies not only between individuals but also within the same individual in different areas of the maxilla and mandible.10-13 As such, one must be able to distinguish the cortex from root penetration or approximation. Self-drilling TADs require a nominal amount of pressure to penetrate and advance the implant through the cortical plate. Without a pilot hole, the clinician may be deprived of the tactile perception required to recognize that the root surface has been compromised.14 In addition, although a pilot hole drill could also potentially contact a root, less pressure needs to be exerted with a drill than with a self-drilling TAD. Failure of the drill to advance after a few millimeters—the juncture at which,
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TAD located in vestibular mucosa 1 week after placement. The degree of tissue mobility in this particular region is evident by the numerous frenal attachments in the area. Although not as common, attached keratinized tissue is not immune from such sequelae. Figure 6 shows an orthodontic implant inserted into the hard palate. In this particular instance a bulk of composite was placed over the implant head to minimize tongue discomfort. It also, however, complicated hygienic maintenance of the TAD. Regardless of the site of implantation, proper oral hygiene of the TAD and surrounding area cannot be overemphasized. Soft-tissue inflammation and the resultant presence of chronic inflammatory cells can affect the underlying bone and lead to implant failure.7 A rubber tip stimulator or water irrigation device should be used in any area that is not accessible with a conventional toothbrush. Even with a meticulous hygienic protocol, however, movable mucosa still remains susceptible to irritation and hence inflammation. Figure 4. (A) Mucosal tear distal to TAD (arrow). Although a tissue punch was used here, the threads of the TAD entangled the mucosa during insertion and resulted in a 5-mm tear. The hematoma mesial to the TAD is the result of local anesthetic infiltration. (B) Sutural repair of mucosal laceration with 4-0 plain gut. (Color version of figure is available online.)
depending upon anatomical location, the clinician would normally expect a marked decrease in resistance as cancellous bone is encountered— could indicate root encroachment. Moreover, a self-drilling TAD is sharper and more likely to penetrate a root than either a self-tapping TAD or a pilot hole drill—neither of which can easily puncture a root.15
Damage from Adjuncts Although soft-tissue damage from attachments, such as coil springs or elastomeric modules, can occur with traditional orthodontic therapy, greater care must be taken when such adjuncts are used in conjunction with TADs. These adjuncts may extend to areas, such as the vestibule, retromolar pad, and maxillary tuberosity which are more susceptible to impingement. Figure 7
Postplacement Injuries Once the TAD is in place, subsequent injury can arise from either the TAD itself or from adjuncts attached to the TAD. Peri-Implantitis In addition to its inherent fragility, another deleterious characteristic of movable soft tissue is its proclivity toward irritation or ulceration. Figure 5 demonstrates inflammation surrounding a
Figure 5. Soft-tissue inflammation surrounding a TAD placed in mucosa. Note also several frenal attachments which must be avoided. This makes movable mucosa a less desirable location for TAD placement. (Color version of figure is available online.)
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exhibits mucosal overgrowth of an auxiliary wire that extended too deeply into the maxillary vestibule. In this case envelopment was so complete that surgical excision was required to liberate the wire. Instances in which there exist a large distance between a TAD and the site of attachment of a spring or elastomeric chain, the use of an auxiliary wire to prevent soft tissue impingement may be useful to counteract arch curvature (Fig 8).
Hard Tissue Trauma Root Damage Perhaps the greatest concern when placing TADs in tooth-borne regions is the possibility of root encroachment, as is evidenced by the volume of literature devoted to the topic.16-20 Sim-
Figure 6. (A) Inflammation of palatal gingiva surrounding TAD. A ball of composite was placed over TAD to minimize irritation to the tongue. A high palatal vault complicated hygienic maintenance of implant. (B) Extent of induration of edematous tissue after TAD removal. Inflammation completely resolved in 3 weeks. (Color version of figure is available online.)
Figure 7. Mucosal overgrowth of protraction auxiliary wire. (Color version of figure is available online.)
ilarly, the orthodontic literature is replete with strategies to avoid root contact either via radiological navigation or clinical positioning guides.21-28 Precise placement and avoidance of roots is paramount not only to the clinical success of the TAD but also in the prevention of iatrogenic complications and their subsequent medicolegal consequences. When a root is violated, the severity of the injury depends upon the extent of the damage and the speed with which the insult is alleviated. Obviously, root penetration is much more severe a consequence than root impingement. Similarly, root impingement which is immediately corrected (eg, a root is contacted upon insertion
Figure 8. Use of an auxiliary wire to prevent coil spring impingement on soft tissue. This is useful in instances in which there is a long span between TAD and site of spring attachment because of the curvature of the alveolus. (Color version of figure is available online.)
Complications of TAD Therapy
but then the TAD is redirected) will repair more rapidly and to a greater extent than a TAD left in place wherein chronic inflammatory cells have been recruited and clastic activity has begun.29 Fortunately for both the patient and practitioner, several studies have indicated that when an insult affects only the periodontal ligament and cementum, complete healing typically ensues after removal of the TAD.5,13,14,18,30,31 Injuries involving pulpal tissue, however, are more serious and may result in the loss of the affected tooth. The initial step in avoiding root transgression is proper treatment planning. When a TAD is planned for an interradicular region, divergence of the adjacent roots should be accomplished by accentuated bracket positioning. This should be performed at the onset of treatment to ensure that mature bone exists at the target location by the time the TAD is ready to be placed. To avoid moving a root into an existing TAD, site selection should take into account not only the initial position of the TAD but also the location of the TAD relative to the dentition both during and at the conclusion of proposed tooth movement. Tactile perception, although useful, should not be the only feedback upon which an operator relies when placing a temporary orthodontic implant. As previously noted, bone density, even in identical anatomical sites, varies widely among individuals. What might be perceived as root impingement in one individual may just be particularly dense cortical bone in another. Therefore, periapical radiographs should be used to verify TAD position during placement (Fig 9). Ideally one should take a progress periapical after a sufficient amount of TAD threads have engaged the cortical plate to provide stability, but before full insertion when redirection is considerably more difficult (Fig 10). This is obviously unnecessary in edentulous regions. If periapical radiographs are not able to be obtained, profound anesthesia should be avoided to elicit patient reaction while inserting a TAD.14 If a root is encountered during insertion, the patient will generally report the sensation of a dull pain. Another potential complication—although possibly occurring in any type of orthodontic tooth movement—is apical root resorption. Unique to orthodontic implant therapy, however, is the fact that TADs enable magnitudes of tooth movement not previously observed by
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Figure 9. (A) Periapical radiograph taken at time of TAD placement reveals impingement on anterior aspect of mesial root of first molar. (B) TAD was immediately removed and periapical obtained to document extent of root damage. (C) One month after initial insult defect in root has been repaired though lamina dura has not yet completely reossified. TAD was repositioned anteriorly the same day of initial placement.
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Figure 10. TAD position and angulation is radiographically assessed prior to complete insertion into interradicular regions simplifying redirection when necessary. (Color version of figure is available online.)
non-surgical means. Figure 11A, B show initial and progress lateral cepholgrams in which an extreme overjet was abridged. As can be seen in Figure 11C, D, the patient experienced moder-
ate apical root resorption of the maxillary anterior teeth. Whether this particular patient was predisposed to root resorption and experienced it irrespective of TAD usage cannot be ascertained. Although not necessarily indicative of a causal relationship, anecdotal evidence suggests this may be the case as the only teeth exhibiting root resorption were those that moved the greatest distance. Figure 12 demonstrates a patient in whom TADs were used to intrude molar teeth to correct an anterior open bite malocclusion. Significant apical root resorption is noted after the molar intrusion. Mimura described a similar circumstance and postulated that teeth moved with the assistance of TADs may contact structures— such as the cortical bone lining the incisive foramen and the lingual cortical plate—which are not normally encountered in conventional orthodontic therapy.32
Figure 11. (A) Initial lateral cephalogram exhibiting significant overjet and lip incompetence. (B) Progress lateral cephalogram demonstrating substantial maxillary incisor retraction. Note remnant of bone labial to the maxillary incisors and improvement in lip competence. (C) Apical root resorption noted on the maxillary central incisors after extensive incisor retraction. (D) Apical root resorption noted on the distal aspect of the maxillary right canine following extensive retraction.
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Figure 12. (A) Pretreatment lateral cephalogram exhibits a high angle Class II malocclusion with anterior openbite. (B) Progress lateral cephalogram showing openbite resolution after 18 months of molar intrusion. (C) Root resorption noted on palatal root of maxillary first molar after significant orthodontic intrusion. (D) Root resorption exhibited on distal aspect of maxillary second premolar likely caused by cortical plate forming the inferior aspect of the maxillary sinus.
Osseous Damage Although not a very common occurrence, damage to bone can occur, particularly during pilot hole creation. Osseous drilling necessitates a nominal degree of trauma to the immediate surrounding bone. Several precautions can be undertaken to minimize this insult, all of which aim to minimize heat generation and reduce the risk of osseous necrosis. Foremost is proper drill speed. A high-torque, slow drill speed in the range of 300-500 rpm is ideal.14 To achieve this, a speed reduction (64:1 or 16:1 gear ratio) contra-angle attachment should be used. Variable speed handpieces can also be used at low rpm, however maintaining the proper rpm with a rheostat can be more difficult. Irrigating handpieces are available, but are not generally part of an orthodontist’s armamentarium, nor need they be. Sterile saline expressed from a sterile Monoject (Vitality Medical, Salt Lake City, UT) syringe onto the bur while drilling will suffice. If
a closed water system is used, sterile water or normal saline can be delivered from the air/ water syringe. It is important that only sharp drills be used as dull drills generate excessive heat. Finally, insertion of the TAD, whether handor engine-driven, should be done slowly. Bone is viscoelastic and will expand in response to pressure from the advancing TAD. This is particularly true with tapered TADs as diameter increases with insertion.
Biomechanical Errors As with traditional orthodontic mechanics, proper vector control using implants is vital to ensure predictable movement of teeth. Poor vector management can, in fact, be magnified using TADs because of their enhanced capacity for absolute tooth movement. Figure 13 demon-
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verse anatomical plane. The use of multilobulated crimpable hooks is useful in this regard as the retraction vector can be altered as needed to counteract any cant effects which may develop (Fig 14).
Intrinsic Failure Complications involving TAD ingestion or inhalation are relatively rare. Such occurrences, however, should be incorporated into any comprehensive informed consent. Ingestion of a TAD is generally a benign event.33 Inhalation, by contrast, could have far more deleterious consequences requiring extensive medical intervention. Precautions such as safety ties,34 when practical, or placement of gauze in the posterior oropharynx should be considered. Although it is easy to secure small hand drivers with dental floss or the equivalent to permit retrieval, TADs due to their minute dimensions generally do not lend themselves to such precautions. Implant drivers (hand drivers, engine drivers, etc.) should actively engage the TAD so that it is securely held and cannot be displaced by gravity alone. As implant systems have evolved, most have incorporated this feature. Far more prevalent is the failure of the TAD itself.4 Potential causes include (1) placement of the TAD into inferior quality bone, (2) lack of primary stability, (3) excessive loading of the TAD after placement, (4) trauma to the TAD from masticatory or other forces, and (5)
Figure 13. (A) Pretreatment occlusion exhibiting normal occlusal plane. (B) Improper vector management producing a canted mandibular occlusal plane. (C) Elastomeric chain used to protract mandibular second molar. The tensile force has both horizontal and vertical components. (Color version of figure is available online.)
strates the result of inadequate directional control. The same is true when using multiple TADs. Bilateral placement of TADs at, or just inferior (in the case of the maxilla) to, the mucogingival junction may not ensure nor necessarily produce an identical result with regard to the trans-
Figure 14. Although bilateral TADs were placed in identical positions relative to the mucogingival junction, a maxillary occlusal cant developed during incisor retraction. Asymmetric application of coil springs was used to correct the cant. (Color version of figure is available online.)
Complications of TAD Therapy
osseous injury during placement. As might be expected, the literature devoted to this topic is quite voluminous. It should be noted that an inherent limitation of orthodontic implants, which is often overlooked, is their design not to osseointegrate (they are by definition temporary). It must, therefore, be expected that a certain percentage of ideally placed orthodontic implants will fail; particularly when failure rates of traditional, osseointegrated, prosthetic implants can range from 2% to 8%.35-37 Loosening of a TAD is fairly innocuous and often a slightly mobile TAD—if otherwise asymptomatic— can continue to be used. A worst-case scenario is that the TAD fails and must be replaced with a larger diameter implant or relocated to a suitable alternate site. More problematic is TAD fracture, which is most likely when a TAD endures excessive torque either upon insertion or removal. Because of the extent and variety of orthodontic implants available, a spectrum of maximum torque values exists. Factors such as design, diameter, amount and acuteness of taper, and titanium composition affect the torsional properties of TADs. It is therefore incumbent upon manufacturers to specify the maximum torque values for each of the orthodontic implants they produce. Unless these TADs are both placed and removed with a torque-calibrating device, however—which is usually not the case—the values are relatively meaningless. As a general rule, fracture tends to be greater in small diameter TADs (⬍1.5 mm), TADs made of pure (nonalloyed) titanium, and those that are inserted via the drill-free method, as greater torsional strain is encountered.8,14 In the event of fracture, remediation is dependent upon the location of the fracture and its position relative to the periosteum. If a sufficient length of the implant body remains above the soft tissue, the implant may be grasped with a hemostat or Mathieu plier and removed. If, however, the fracture is either subgingival or submucosal, a small flap may need to be elevated to expose the body remnant. If flush with the periosteum a small round bur in a slow speed handpiece may be used to trench around the implant to expose enough of the body to enable proper purchase by an instrument. Lastly, a trephine may be used to excise both the fractured TAD and a small diameter of bone surrounding it.
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Such an intervention, however, is generally beyond the scope of both the orthodontist’s training and armamentarium and referral should be made to the appropriate specialist. Finally, each clinician should adhere to an established surgical protocol to reduce the incidence of postoperative infection. Steps include the use of an aseptic surgical technique, pre- and postoperative antimicrobial rinse, and an appropriate postoperative antibiotic regimen.
Discussion This article outlines the more common problems encountered during placement of temporary orthodontic implants. This is, however, not an exhaustive list of possible complications. Kravitz and Kusnoto38 in a review enumerate additional anomalies, such as air subcutaneous emphysema and partial osseointegration (a complication of which is TAD fracture upon removal). Most of the complications mentioned can be appropriately described as “errors of inexperience;” these are not problems that would generally be encountered by a clinician proficient in the surgical procedure. Proper treatment planning, recognition of potential complications, and familiarity with the implant system can significantly limit these sequelae. As with any new technique, however, clinical aptitude is attained with experience. Unlike surgeons, or even recent orthodontic graduates, who have had the benefit of residency programs to refine their surgical skills, the orthodontic practitioner must acquire proficiency without the supervision normally afforded those learning a new technique.
Conclusions Ever since Creekmore and Eklund’s landmark article39 in 1983, the possibility of absolute skeletal anchorage has been an aspiration of orthodontic clinicians. The introduction and use of TADs in the last decade has revolutionized orthodontic mechanotherapy and enabled “orthognathic-like” results. For the orthodontist who is considering or just beginning to place implants, the following recommendations are suggested:
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1. Insert the first several TADs in “safe” regions—areas in which the possibility of encroachment upon adjacent anatomical structures is negligible (eg, an edentulous ridge or well-ossified extraction site). This will permit the clinician to acquire a feel for the implantation procedure with minimal risk. 2. Propensity for inflammation and susceptibility to injury make the oral mucosa rather inhospitable to TADs and should be avoided when possible. Instances in which placement in such tissue cannot be avoided, emphasis must be placed on exquisite oral hygiene of the TAD and surrounding area. Similarly, frenal attachments should be avoided when possible; however, hard tissue limitations occasionally prevent this. In these instances, an incisional frenectomy can be performed.40 3. Because soft-tissue complications of some sort are inevitable if enough TADs are placed, it is advisable to have a basic suture kit available so that minor complications can be managed by the orthodontist. 4. In cases of root trauma, insults should be corrected as soon as possible and compromised teeth should be monitored with periapical radiographs. Fortunately, the recuperative potential of a dental root is immense as is evidenced by its tolerance of an apicoectomy. 5. A review of dental anatomy is beneficial, particularly as it pertains to the greater palatine artery and nerve. 6. Orthodontic implant complications are ubiquitous and not unique to any particular implant system. There are inherent differences among the various systems available and it is beneficial to understand the advantages and disadvantages of each.
Acknowledgments The author thanks Dr Glenn Sameshima and the University of Southern California School of Dentistry, Department of Orthodontics for their assistance in the research for the manuscript.
References 1. Buschang PH, Carrillo R, Ozenbaugh B, et al: 2008 survey of AAO members on miniscrew usage. J Clin Orthod 42:513-518, 2008 2. Smith RJ, Burstone CJ: Mechanics of tooth movement. Am J Orthod 85:294-307, 1984
3. Kusy RP, Tulloch JF: Analysis of moment/force ratios in the mechanics of tooth movement. Am J Orthod Dentofac Orthop 90:127-131, 1986 4. Baumgaertel S, Razavi MR, Hans MG: Mini-implant anchorage for the orthodontic practitioner. Am J Orthod Dentofac Orthop 133:621-627, 2008 5. Kadioglu O, Büyükyilmaz T, Zachrisson BU, et al: Contact damage to root surfaces of premolars touching miniscrews during orthodontic treatment. Am J Orthod Dentofac Orthop 134:353-360, 2008 6. Cheng SJ, Tseng IY, Lee JJ, et al: A prospective study of the risk factors associated with failure of mini-implants used for orthodontic anchorage. Int J Oral Maxillofac Implants 19:100-106, 2004 7. Park HS, Jeong SH, Kwon OW: Factors affecting the clinical success of screw implants used as orthodontic anchorage. Am J Orthod Dentofac Orthop 130:18-25, 2006 8. Herman R, Cope JB: Miniscrew implants: IMTEC mini ortho implants. Semin Orthod 11:32-39, 2005 9. Chen Y, Shin HI, Kyung HM: Biomechanical and histological comparison of self-drilling and self-tapping orthodontic microimplants in dogs. Am J Orthod Dentofac Orthop 133:44-50, 2008 10. Ono A, Motoyoshi M, Shimizu N: Cortical bone thickness in the buccal posterior region for orthodontic miniimplants. Int J Oral Maxillofac Surg 37:334-340, 2008 11. Kim HJ, Yun HS, Park HD, et al: Soft-tissue and corticalbone thickness at orthodontic implant sites. Am J Orthod Dentofac Orthop 130:177-182, 2006 12. Park HS, Lee YJ, Jeong SH, et al: Density of the alveolar and basal bones of the maxilla and the mandible. Am J Orthod Dentofac Orthop 133:30-37, 2008 13. Gracco A, Lombardo L, Cozzani M, et al: Quantitative cone-beam computed tomography evaluation of palatal bone thickness for orthodontic miniscrew placement. Am J Orthod Dentofac Orthop 134:361-369, 2008 14. Hembree M, Buschang PH, Carrillo R, et al: Effects of intentional damage of the roots and surrounding structures with miniscrew implants. Am J Orthod Dentofac Orthop 135:280-281, 2009 15. Sung JH, Kyung HM, Bae SM, et al: Surgical procedures for microimplant placement, in Microimplants in Orthodontics. Daegu, Korea, Dentos, 2006, pp 39-61 16. Kuroda S, Yamada K, Deguchi T, et al: Root proximity is a major factor for screw failure in orthodontic anchorage. Am J Orthod Dentofac Orthop 131(4 suppl):S68S73, 2007 17. Asscherickx K, Vande Vannet B, Wehrbein H, et al: Success rate of miniscrews relative to their position to adjacent roots. Eur J Orthod 30:330-335, 2008 18. Chen YH, Chang HH, Chen YJ, et al: Root contact during insertion of miniscrews for orthodontic anchorage increases the failure rate: An animal study. Clin Oral Implants Res 19:99-106, 2008 19. Maino BG, Weiland F, Attanasi A, et al: Root damage and repair after contact with miniscrews. J Clin Orthod 41:762-766, 2007 20. Asscherickx K, Vannet BV, Wehrbein H, et al: Root repair after injury from mini-screw. Clin Oral Implants Res 16:575-578, 2005
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21. Choi HJ, Kim TW, Kim HW: A precise wire guide for positioning interradicular miniscrews. J Clin Orthod 41: 258-261, 2007 22. Suzuki EY, Suzuki B: Accuracy of miniscrew implant placement with a 3-dimensional surgical guide. J Oral Maxillofac Surg 66:1245-1252, 2008 23. Kim SH, Choi YS, Hwang EH, et al: Surgical positioning of orthodontic mini-implants with guides fabricated on models replicated with cone-beam computed tomography. Am J Orthod Dentofac Orthop 131(4 suppl):S82S89, 2007 24. Kravitz ND, Kusnoto B, Hohlt WF: A simplified stent for anterior miniscrew insertion. J Clin Orthod 41:224-226, 2007 25. Ludwig B, Glasl B, Lietz T, et al: Radiological location monitoring in skeletal anchorage: Introduction of a positioning guide. J Orofac Orthop 69:59-65, 2008 26. Suzuki EY, Buranastidporn B: An adjustable surgical guide for miniscrew placement. J Clin Orthod 39:588590, 2005 27. Reddy KB, Kumar MP, Kumar MN: A grid for guiding miniscrew placement. J Clin Orthod 42:531-532, 2008 28. Cousley RR, Parberry DJ: Surgical stents for accurate miniscrew insertion. J Clin Orthod 40:412-417, 2006 29. Gunraj MN: Dental root resorption. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 88:647-653, 1999 30. Kang YG, Kim JY, Lee YJ, et al: Stability of mini-screws invading the dental roots and their impact on the paradental tissues in beagles. Angle Orthod 79:248-255, 2009 31. Renjen R, Maganzini AL, Rohrer MD, et al: Root and pulp response after intentional injury from miniscrew placement. Am J Orthod Dentofac Orthop 136:708-714, 2009
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32. Mimura H: Treatment of severe bimaxillary protrusion with miniscrew anchorage: Treatment and complications. Aust Orthod J 24:156-163, 2008 33. Choi BH, Li J, Kim HS, et al: Ingestion of orthodontic anchorage screws: An experimental study in dogs. Am J Orthod Dentofac Orthop 131:767-768, 2007 34. Gibbons AJ, Charette MJ: Use of a safety tie in the placement of miniscrews. Br J Oral Maxillofac Surg 46: 66-67, 2008 35. den Hartog L, Slater JJ, Vissink A, et al: Treatment outcome of immediate, early and conventional singletooth implants in the aesthetic zone: A systematic review to survival, bone level, soft-tissue, aesthetics and patient satisfaction. J Clin Periodontol 35:1073-1086, 2008 36. Huynh-Ba G, Friedberg JR, Vogiatzi D, et al: Implant failure predictors in the posterior maxilla: A retrospective study of 273 consecutive implants. J Periodontol 79:2256-2261, 2008 37. Jung UW, Choi JY, Kim CS, et al: Evaluation of mandibular posterior single implants with two different surfaces: A 5-year comparative study. J Periodontol 79:1857-1863, 2008 38. Kravitz ND, Kusnoto B: Risks and complications of orthodontic miniscrews. Am J Orthod Dentofac Orthop 131(4 suppl):S43-S51, 2007 39. Creekmore TD, Eklund MK: The possibility of skeletal anchorage. J Clin Orthod 17:266-269, 1983 40. Park YC, Lee KJ: Biomechanical principles in miniscrewdriven orthodontics, in Nanda R, Uribe FA (eds): Temporary Anchorage Devices in Orthodontics. St. Louis, Mosby, 2009, pp 93-144
uring the past several decades the discipline of orthodontics has benefited from a variety of innovations that have enhanced clinical practice. The preadjusted appliance, light-cured adhesives, metallurgical hybridization of arch wires, and self-ligating brackets are just a few examples. Although each of these technologies has readily integrated into routine practice, the placement and use of maxillomandibular bone anchors— orthodontics’ most recent clinical adjunct— has proven more elusive in this regard. This is attributable, perhaps, to the fact that placement of such fixtures has long been the purview of oral surgeons or periodontists; those who have received surgical training in their residency programs. The most contemporary incarnation of skeletal anchorage, however—the temporary anchorage device, or TAD— has evolved such that placement by orthodontists is not only feasible
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but has become increasingly commonplace.1 This can be ascribed to the simplicity of the procedure itself, as well as its minimal invasiveness and comparatively low cost compared with conventional surgical intervention. Despite its simplicity, however, complications will invariably arise, partly because of the relative inexperience of the clinicians performing it. These complications include soft tissue injury, hard tissue damage, biomechanical errors, and failure intrinsic to the implant itself (eg, fracture inhalation, ingestion, infection).
Soft-Tissue Injury Soft-tissue injury can occur either during placement of a TAD or subsequently during the course of its use. Both can require extensive reparation.
Placement Injuries Private Practice, Temecula, CA. Address correspondence to Christopher E. Roncone, DDS, MS, 32140 Temecula Parkway, Ste 201, Temecula, CA 92592. E-mail: [email protected] © 2011 Elsevier Inc. All rights reserved. 1073-8746/11/1702-0$30.00/0 doi:10.1053/j.sodo.2011.01.003
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Aside from absolute anchorage, one of the primary biomechanical advantages that TADs offer is the ability to exploit the dentition’s center of resistance (Fig 1). Relocating the point of force application— either tensile or compressive— from the orthodontic appliance to a region
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Figure 1. (A) Preorthodontic panorex exhibiting multiple missing teeth. The treatment plan entailed closing all maxillary space except for the left lateral incisor. The maxillary right second molar is to be protracted (note position relative to impacted third molar). (B) Although the maxillary right second molar has been protracted, it still exhibits distoangular root inclination because of the inferior placement of the maxillary right TAD. (C) Apical repositioning of maxillary right TAD to upright the maxillary right second molar root.
nearer the anatomical center of resistance enhances the translatory movement of teeth. This is in contrast to the cyclical succession of crowntipping and root-uprighting observed with traditional orthodontic mechanotherapy.2,3 This often necessitates, however, that the TAD be placed relatively apically; sometimes beyond the mucogingival junction. Mucosal tissue, as opposed to keratinized gingival tissue, generally
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demonstrates the least durability and hence is the most susceptible to impairment (Fig 2).4-6 A variety of implant systems are available on the market and most, if not all, include the option of drilling a pilot hole. This step is a necessity when one uses a self-tapping rather than a self-drilling system. An initial method to minimize soft-tissue laceration during the placement of a TAD is the proper preparation of the implant site before drilling the pilot hole, particularly when placing it in the mucosal tissue. Several techniques have been proposed. Park et al7 advocate a small vertical stab incision with flap reflection, whereas other authors8 recommend the use of a biopsy tissue punch of appropriate diameter. Eliminating soft tissue from the proximity of the intended pilot hole will decrease the likelihood of its entanglement with the surgical drill. Figure 3 demonstrates the consequence and rectification of such entanglement. Any clinician who has contoured a denture tooth using an acrylic bur while wearing latex gloves can envision an analogous circumstance. In the event of soft-tissue entanglement, aside from initial insult often more problematic is the extrication of the surgical drill from the mucosa after osseous engagement where the clinician must reverse the handpiece engine direction while maintaining drill stability. Any long-axis deviation of the drill while doing so could potentially increase the diameter of the pilot hole. While there is usually a diameter differential of approximately 20% between the pilot hole drill and TAD (ie, a 1.2-mm pilot hole drill for a 1.5-mm TAD), this disparity is required to ensure implant engagement in sound cortical bone; that which is uncompromised by the inherently traumatic procedure of drilling itself.9 One may proffer that a reasonable alternative to the aforementioned complications is to simply use a self-drilling implant system. Although it may seem intuitive that elimination of a pilot hole may reduce the incidence of mucosal perforations, tears can still occur during advancement of the TAD itself. Figure 4 demonstrates the result of mucosal encroachment into the TAD threads during insertion despite appropriate pilot hole establishment. This is particularly true with TADs exhibiting a significant degree of taper from tip to transmucosal collar. The diameter of soft tissue preparation should be at least
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Figure 3. (A) Drilling of pilot hole without adequate soft-tissue preparation. The mucosa became ensnared in the surgical drill necessitating sutural restoration. (B) Repair of mucosal laceration with 4-0 silk. (Color version of figure is available online.)
Figure 2. (A) Maxillary right TAD repositioned apically to enable second molar root uprighting which resulted in mucosal tear. The original implantation site is visible mesial to the second premolar crown (arrow). (B) Mucosal tear sutured with 4-0 plain gut and healed well despite proximity to frenal attachment (A). (C) Biomechanics used to upright root of maxillary right second molar. Auxiliary wire permitted force delivery nearer center of resistance and a clockwise moment. (Color version of figure is available online.)
as large as the widest part of the TAD. Furthermore, a distinct advantage of pilot hole creation when placing TADs interradicularly is the enhanced ability of the clinician to differentiate cortical bone from root. It has been well demonstrated that cortical bone thickness varies not only between individuals but also within the same individual in different areas of the maxilla and mandible.10-13 As such, one must be able to distinguish the cortex from root penetration or approximation. Self-drilling TADs require a nominal amount of pressure to penetrate and advance the implant through the cortical plate. Without a pilot hole, the clinician may be deprived of the tactile perception required to recognize that the root surface has been compromised.14 In addition, although a pilot hole drill could also potentially contact a root, less pressure needs to be exerted with a drill than with a self-drilling TAD. Failure of the drill to advance after a few millimeters—the juncture at which,
Complications of TAD Therapy
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TAD located in vestibular mucosa 1 week after placement. The degree of tissue mobility in this particular region is evident by the numerous frenal attachments in the area. Although not as common, attached keratinized tissue is not immune from such sequelae. Figure 6 shows an orthodontic implant inserted into the hard palate. In this particular instance a bulk of composite was placed over the implant head to minimize tongue discomfort. It also, however, complicated hygienic maintenance of the TAD. Regardless of the site of implantation, proper oral hygiene of the TAD and surrounding area cannot be overemphasized. Soft-tissue inflammation and the resultant presence of chronic inflammatory cells can affect the underlying bone and lead to implant failure.7 A rubber tip stimulator or water irrigation device should be used in any area that is not accessible with a conventional toothbrush. Even with a meticulous hygienic protocol, however, movable mucosa still remains susceptible to irritation and hence inflammation. Figure 4. (A) Mucosal tear distal to TAD (arrow). Although a tissue punch was used here, the threads of the TAD entangled the mucosa during insertion and resulted in a 5-mm tear. The hematoma mesial to the TAD is the result of local anesthetic infiltration. (B) Sutural repair of mucosal laceration with 4-0 plain gut. (Color version of figure is available online.)
depending upon anatomical location, the clinician would normally expect a marked decrease in resistance as cancellous bone is encountered— could indicate root encroachment. Moreover, a self-drilling TAD is sharper and more likely to penetrate a root than either a self-tapping TAD or a pilot hole drill—neither of which can easily puncture a root.15
Damage from Adjuncts Although soft-tissue damage from attachments, such as coil springs or elastomeric modules, can occur with traditional orthodontic therapy, greater care must be taken when such adjuncts are used in conjunction with TADs. These adjuncts may extend to areas, such as the vestibule, retromolar pad, and maxillary tuberosity which are more susceptible to impingement. Figure 7
Postplacement Injuries Once the TAD is in place, subsequent injury can arise from either the TAD itself or from adjuncts attached to the TAD. Peri-Implantitis In addition to its inherent fragility, another deleterious characteristic of movable soft tissue is its proclivity toward irritation or ulceration. Figure 5 demonstrates inflammation surrounding a
Figure 5. Soft-tissue inflammation surrounding a TAD placed in mucosa. Note also several frenal attachments which must be avoided. This makes movable mucosa a less desirable location for TAD placement. (Color version of figure is available online.)
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exhibits mucosal overgrowth of an auxiliary wire that extended too deeply into the maxillary vestibule. In this case envelopment was so complete that surgical excision was required to liberate the wire. Instances in which there exist a large distance between a TAD and the site of attachment of a spring or elastomeric chain, the use of an auxiliary wire to prevent soft tissue impingement may be useful to counteract arch curvature (Fig 8).
Hard Tissue Trauma Root Damage Perhaps the greatest concern when placing TADs in tooth-borne regions is the possibility of root encroachment, as is evidenced by the volume of literature devoted to the topic.16-20 Sim-
Figure 6. (A) Inflammation of palatal gingiva surrounding TAD. A ball of composite was placed over TAD to minimize irritation to the tongue. A high palatal vault complicated hygienic maintenance of implant. (B) Extent of induration of edematous tissue after TAD removal. Inflammation completely resolved in 3 weeks. (Color version of figure is available online.)
Figure 7. Mucosal overgrowth of protraction auxiliary wire. (Color version of figure is available online.)
ilarly, the orthodontic literature is replete with strategies to avoid root contact either via radiological navigation or clinical positioning guides.21-28 Precise placement and avoidance of roots is paramount not only to the clinical success of the TAD but also in the prevention of iatrogenic complications and their subsequent medicolegal consequences. When a root is violated, the severity of the injury depends upon the extent of the damage and the speed with which the insult is alleviated. Obviously, root penetration is much more severe a consequence than root impingement. Similarly, root impingement which is immediately corrected (eg, a root is contacted upon insertion
Figure 8. Use of an auxiliary wire to prevent coil spring impingement on soft tissue. This is useful in instances in which there is a long span between TAD and site of spring attachment because of the curvature of the alveolus. (Color version of figure is available online.)
Complications of TAD Therapy
but then the TAD is redirected) will repair more rapidly and to a greater extent than a TAD left in place wherein chronic inflammatory cells have been recruited and clastic activity has begun.29 Fortunately for both the patient and practitioner, several studies have indicated that when an insult affects only the periodontal ligament and cementum, complete healing typically ensues after removal of the TAD.5,13,14,18,30,31 Injuries involving pulpal tissue, however, are more serious and may result in the loss of the affected tooth. The initial step in avoiding root transgression is proper treatment planning. When a TAD is planned for an interradicular region, divergence of the adjacent roots should be accomplished by accentuated bracket positioning. This should be performed at the onset of treatment to ensure that mature bone exists at the target location by the time the TAD is ready to be placed. To avoid moving a root into an existing TAD, site selection should take into account not only the initial position of the TAD but also the location of the TAD relative to the dentition both during and at the conclusion of proposed tooth movement. Tactile perception, although useful, should not be the only feedback upon which an operator relies when placing a temporary orthodontic implant. As previously noted, bone density, even in identical anatomical sites, varies widely among individuals. What might be perceived as root impingement in one individual may just be particularly dense cortical bone in another. Therefore, periapical radiographs should be used to verify TAD position during placement (Fig 9). Ideally one should take a progress periapical after a sufficient amount of TAD threads have engaged the cortical plate to provide stability, but before full insertion when redirection is considerably more difficult (Fig 10). This is obviously unnecessary in edentulous regions. If periapical radiographs are not able to be obtained, profound anesthesia should be avoided to elicit patient reaction while inserting a TAD.14 If a root is encountered during insertion, the patient will generally report the sensation of a dull pain. Another potential complication—although possibly occurring in any type of orthodontic tooth movement—is apical root resorption. Unique to orthodontic implant therapy, however, is the fact that TADs enable magnitudes of tooth movement not previously observed by
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Figure 9. (A) Periapical radiograph taken at time of TAD placement reveals impingement on anterior aspect of mesial root of first molar. (B) TAD was immediately removed and periapical obtained to document extent of root damage. (C) One month after initial insult defect in root has been repaired though lamina dura has not yet completely reossified. TAD was repositioned anteriorly the same day of initial placement.
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Figure 10. TAD position and angulation is radiographically assessed prior to complete insertion into interradicular regions simplifying redirection when necessary. (Color version of figure is available online.)
non-surgical means. Figure 11A, B show initial and progress lateral cepholgrams in which an extreme overjet was abridged. As can be seen in Figure 11C, D, the patient experienced moder-
ate apical root resorption of the maxillary anterior teeth. Whether this particular patient was predisposed to root resorption and experienced it irrespective of TAD usage cannot be ascertained. Although not necessarily indicative of a causal relationship, anecdotal evidence suggests this may be the case as the only teeth exhibiting root resorption were those that moved the greatest distance. Figure 12 demonstrates a patient in whom TADs were used to intrude molar teeth to correct an anterior open bite malocclusion. Significant apical root resorption is noted after the molar intrusion. Mimura described a similar circumstance and postulated that teeth moved with the assistance of TADs may contact structures— such as the cortical bone lining the incisive foramen and the lingual cortical plate—which are not normally encountered in conventional orthodontic therapy.32
Figure 11. (A) Initial lateral cephalogram exhibiting significant overjet and lip incompetence. (B) Progress lateral cephalogram demonstrating substantial maxillary incisor retraction. Note remnant of bone labial to the maxillary incisors and improvement in lip competence. (C) Apical root resorption noted on the maxillary central incisors after extensive incisor retraction. (D) Apical root resorption noted on the distal aspect of the maxillary right canine following extensive retraction.
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Figure 12. (A) Pretreatment lateral cephalogram exhibits a high angle Class II malocclusion with anterior openbite. (B) Progress lateral cephalogram showing openbite resolution after 18 months of molar intrusion. (C) Root resorption noted on palatal root of maxillary first molar after significant orthodontic intrusion. (D) Root resorption exhibited on distal aspect of maxillary second premolar likely caused by cortical plate forming the inferior aspect of the maxillary sinus.
Osseous Damage Although not a very common occurrence, damage to bone can occur, particularly during pilot hole creation. Osseous drilling necessitates a nominal degree of trauma to the immediate surrounding bone. Several precautions can be undertaken to minimize this insult, all of which aim to minimize heat generation and reduce the risk of osseous necrosis. Foremost is proper drill speed. A high-torque, slow drill speed in the range of 300-500 rpm is ideal.14 To achieve this, a speed reduction (64:1 or 16:1 gear ratio) contra-angle attachment should be used. Variable speed handpieces can also be used at low rpm, however maintaining the proper rpm with a rheostat can be more difficult. Irrigating handpieces are available, but are not generally part of an orthodontist’s armamentarium, nor need they be. Sterile saline expressed from a sterile Monoject (Vitality Medical, Salt Lake City, UT) syringe onto the bur while drilling will suffice. If
a closed water system is used, sterile water or normal saline can be delivered from the air/ water syringe. It is important that only sharp drills be used as dull drills generate excessive heat. Finally, insertion of the TAD, whether handor engine-driven, should be done slowly. Bone is viscoelastic and will expand in response to pressure from the advancing TAD. This is particularly true with tapered TADs as diameter increases with insertion.
Biomechanical Errors As with traditional orthodontic mechanics, proper vector control using implants is vital to ensure predictable movement of teeth. Poor vector management can, in fact, be magnified using TADs because of their enhanced capacity for absolute tooth movement. Figure 13 demon-
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verse anatomical plane. The use of multilobulated crimpable hooks is useful in this regard as the retraction vector can be altered as needed to counteract any cant effects which may develop (Fig 14).
Intrinsic Failure Complications involving TAD ingestion or inhalation are relatively rare. Such occurrences, however, should be incorporated into any comprehensive informed consent. Ingestion of a TAD is generally a benign event.33 Inhalation, by contrast, could have far more deleterious consequences requiring extensive medical intervention. Precautions such as safety ties,34 when practical, or placement of gauze in the posterior oropharynx should be considered. Although it is easy to secure small hand drivers with dental floss or the equivalent to permit retrieval, TADs due to their minute dimensions generally do not lend themselves to such precautions. Implant drivers (hand drivers, engine drivers, etc.) should actively engage the TAD so that it is securely held and cannot be displaced by gravity alone. As implant systems have evolved, most have incorporated this feature. Far more prevalent is the failure of the TAD itself.4 Potential causes include (1) placement of the TAD into inferior quality bone, (2) lack of primary stability, (3) excessive loading of the TAD after placement, (4) trauma to the TAD from masticatory or other forces, and (5)
Figure 13. (A) Pretreatment occlusion exhibiting normal occlusal plane. (B) Improper vector management producing a canted mandibular occlusal plane. (C) Elastomeric chain used to protract mandibular second molar. The tensile force has both horizontal and vertical components. (Color version of figure is available online.)
strates the result of inadequate directional control. The same is true when using multiple TADs. Bilateral placement of TADs at, or just inferior (in the case of the maxilla) to, the mucogingival junction may not ensure nor necessarily produce an identical result with regard to the trans-
Figure 14. Although bilateral TADs were placed in identical positions relative to the mucogingival junction, a maxillary occlusal cant developed during incisor retraction. Asymmetric application of coil springs was used to correct the cant. (Color version of figure is available online.)
Complications of TAD Therapy
osseous injury during placement. As might be expected, the literature devoted to this topic is quite voluminous. It should be noted that an inherent limitation of orthodontic implants, which is often overlooked, is their design not to osseointegrate (they are by definition temporary). It must, therefore, be expected that a certain percentage of ideally placed orthodontic implants will fail; particularly when failure rates of traditional, osseointegrated, prosthetic implants can range from 2% to 8%.35-37 Loosening of a TAD is fairly innocuous and often a slightly mobile TAD—if otherwise asymptomatic— can continue to be used. A worst-case scenario is that the TAD fails and must be replaced with a larger diameter implant or relocated to a suitable alternate site. More problematic is TAD fracture, which is most likely when a TAD endures excessive torque either upon insertion or removal. Because of the extent and variety of orthodontic implants available, a spectrum of maximum torque values exists. Factors such as design, diameter, amount and acuteness of taper, and titanium composition affect the torsional properties of TADs. It is therefore incumbent upon manufacturers to specify the maximum torque values for each of the orthodontic implants they produce. Unless these TADs are both placed and removed with a torque-calibrating device, however—which is usually not the case—the values are relatively meaningless. As a general rule, fracture tends to be greater in small diameter TADs (⬍1.5 mm), TADs made of pure (nonalloyed) titanium, and those that are inserted via the drill-free method, as greater torsional strain is encountered.8,14 In the event of fracture, remediation is dependent upon the location of the fracture and its position relative to the periosteum. If a sufficient length of the implant body remains above the soft tissue, the implant may be grasped with a hemostat or Mathieu plier and removed. If, however, the fracture is either subgingival or submucosal, a small flap may need to be elevated to expose the body remnant. If flush with the periosteum a small round bur in a slow speed handpiece may be used to trench around the implant to expose enough of the body to enable proper purchase by an instrument. Lastly, a trephine may be used to excise both the fractured TAD and a small diameter of bone surrounding it.
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Such an intervention, however, is generally beyond the scope of both the orthodontist’s training and armamentarium and referral should be made to the appropriate specialist. Finally, each clinician should adhere to an established surgical protocol to reduce the incidence of postoperative infection. Steps include the use of an aseptic surgical technique, pre- and postoperative antimicrobial rinse, and an appropriate postoperative antibiotic regimen.
Discussion This article outlines the more common problems encountered during placement of temporary orthodontic implants. This is, however, not an exhaustive list of possible complications. Kravitz and Kusnoto38 in a review enumerate additional anomalies, such as air subcutaneous emphysema and partial osseointegration (a complication of which is TAD fracture upon removal). Most of the complications mentioned can be appropriately described as “errors of inexperience;” these are not problems that would generally be encountered by a clinician proficient in the surgical procedure. Proper treatment planning, recognition of potential complications, and familiarity with the implant system can significantly limit these sequelae. As with any new technique, however, clinical aptitude is attained with experience. Unlike surgeons, or even recent orthodontic graduates, who have had the benefit of residency programs to refine their surgical skills, the orthodontic practitioner must acquire proficiency without the supervision normally afforded those learning a new technique.
Conclusions Ever since Creekmore and Eklund’s landmark article39 in 1983, the possibility of absolute skeletal anchorage has been an aspiration of orthodontic clinicians. The introduction and use of TADs in the last decade has revolutionized orthodontic mechanotherapy and enabled “orthognathic-like” results. For the orthodontist who is considering or just beginning to place implants, the following recommendations are suggested:
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1. Insert the first several TADs in “safe” regions—areas in which the possibility of encroachment upon adjacent anatomical structures is negligible (eg, an edentulous ridge or well-ossified extraction site). This will permit the clinician to acquire a feel for the implantation procedure with minimal risk. 2. Propensity for inflammation and susceptibility to injury make the oral mucosa rather inhospitable to TADs and should be avoided when possible. Instances in which placement in such tissue cannot be avoided, emphasis must be placed on exquisite oral hygiene of the TAD and surrounding area. Similarly, frenal attachments should be avoided when possible; however, hard tissue limitations occasionally prevent this. In these instances, an incisional frenectomy can be performed.40 3. Because soft-tissue complications of some sort are inevitable if enough TADs are placed, it is advisable to have a basic suture kit available so that minor complications can be managed by the orthodontist. 4. In cases of root trauma, insults should be corrected as soon as possible and compromised teeth should be monitored with periapical radiographs. Fortunately, the recuperative potential of a dental root is immense as is evidenced by its tolerance of an apicoectomy. 5. A review of dental anatomy is beneficial, particularly as it pertains to the greater palatine artery and nerve. 6. Orthodontic implant complications are ubiquitous and not unique to any particular implant system. There are inherent differences among the various systems available and it is beneficial to understand the advantages and disadvantages of each.
Acknowledgments The author thanks Dr Glenn Sameshima and the University of Southern California School of Dentistry, Department of Orthodontics for their assistance in the research for the manuscript.
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32. Mimura H: Treatment of severe bimaxillary protrusion with miniscrew anchorage: Treatment and complications. Aust Orthod J 24:156-163, 2008 33. Choi BH, Li J, Kim HS, et al: Ingestion of orthodontic anchorage screws: An experimental study in dogs. Am J Orthod Dentofac Orthop 131:767-768, 2007 34. Gibbons AJ, Charette MJ: Use of a safety tie in the placement of miniscrews. Br J Oral Maxillofac Surg 46: 66-67, 2008 35. den Hartog L, Slater JJ, Vissink A, et al: Treatment outcome of immediate, early and conventional singletooth implants in the aesthetic zone: A systematic review to survival, bone level, soft-tissue, aesthetics and patient satisfaction. J Clin Periodontol 35:1073-1086, 2008 36. Huynh-Ba G, Friedberg JR, Vogiatzi D, et al: Implant failure predictors in the posterior maxilla: A retrospective study of 273 consecutive implants. J Periodontol 79:2256-2261, 2008 37. Jung UW, Choi JY, Kim CS, et al: Evaluation of mandibular posterior single implants with two different surfaces: A 5-year comparative study. J Periodontol 79:1857-1863, 2008 38. Kravitz ND, Kusnoto B: Risks and complications of orthodontic miniscrews. Am J Orthod Dentofac Orthop 131(4 suppl):S43-S51, 2007 39. Creekmore TD, Eklund MK: The possibility of skeletal anchorage. J Clin Orthod 17:266-269, 1983 40. Park YC, Lee KJ: Biomechanical principles in miniscrewdriven orthodontics, in Nanda R, Uribe FA (eds): Temporary Anchorage Devices in Orthodontics. St. Louis, Mosby, 2009, pp 93-144