MINI-IMPLANT SUPPLEMENT
Journal of Orthodontics, Vol. 41, 2014, S54–S61
Mini-implant applications in orthognathic surgical treatment Richard R. J. Cousley1 and Mark J. Turner2 1
Orthodontic Department, Peterborough and Stamford Hospitals NHS Foundation Trust, UK; 2Department of Oral and Maxillofacial Surgery, Peterborough and Stamford Hospitals NHS Foundation Trust, UK
Orthognathic surgical treatment conventionally relies on the use of full arch fixed orthodontic appliances. However, the introduction of orthodontic mini-implants has altered surgical options in terms of providing an alternative to fixation (intermaxillary fixation, IMF) screws and even to maxillary osteotomy. This paper describes the integration of mini-implants within orthognathic treatments in terms of ‘surgery first’ treatments and by introducing the concept of the conversion of bimaxillary cases into mandible-only surgery treatments. Key words: Orthodontic mini-implant, TAD, surgery first, orthognathic surgery, vertical anchorage Received 7 May 2014; accepted 25 May 2014
Introduction Given that orthodontic mini-implants were developed in the late 1990s from maxillofacial bone screw technology, it seems appropriate for them to be applied now as an adjunct to maxillofacial surgery. For example, some orthognathic surgical patients benefit from the use of mini-implants for intermaxillary fixation (IMF) and traction purposes, instead of conventional surgical hooks on orthodontic fixed appliances. This is especially the case where the treatment plan involves either the use of lingual fixed appliances or aligners (rather than labial brackets), or a ‘surgery first’ approach. Interestingly, the concept of using modified surgical screws to achieve intra-operative IMF (Arthur and Berardo, 1989) predates the introduction of mini-implants, and IMF screws are now used extensively in Oral and Maxillofacial Surgery. They offer significant advantages over traditional toothborne methods (eyelet wires and arch bars) of applying IMF, including less periodontal trauma, easier maintenance of oral hygiene, and the avoidance of tooth extrusion problems. The insertion of IMF screws is also much quicker than the application of traditional tooth borne IMF methods, does not require a healthy dentition, and is less likely to expose the operator to needle-stick type injury (caused by eyelet wire ends). A recent review of the IMF screws supplied by six manufacturers reported that they have the following typical features: titanium or stainless steel composition, 2 mm body diameter, 9–21 mm lengths and both self-tapping and self-drilling formats (Cornelius and Ehrenfeld, 2010). Address for correspondence: R. Cousley, Orthodontic Department, Peterborough City Hospital, Bretton Gate, Peterborough PE3 9GZ, UK. Email: [email protected] # 2014 British Orthodontic Society
The body and thread designs correspond to the osteosynthesis mini-screws produced by these respective surgical manufacturers. Notably, there appears to be a difference between the recommended and actual uses of these IMF screws, since the commercial literature advises against their use in paediatric cases and recommends their insertion at sites apical to the dental roots. However, clinical reports indicate that many surgeons site IMF screws interproximally (Hashemi and Parhiz, 2011), perhaps because it is clinically easier to insert them through attached mucosa rather than the mobile soft tissues at the sub-apical level. This may partly account for the reportedly high failure rate (6–25%) of IMF screws in trauma cases (Coletti et al., 2007), since the relatively large (2 mm) diameter and length of IMF screws greatly increases the risk of root contact (Figure 1a), especially in sites where interproximal access is limited, e.g. by the convergent tipping of adjacent roots. Interproximal insertion also increases the risk of root damage, irrespective of their short term (intra-operative) use (Hashemi and Parhiz, 2011). Furthermore, the high profile and bulky head size of an IMF screw means that the head projects out towards the lip and cheek, increasing patient discomfort. This also potentially destabilizes the screw if traction is required over a period of weeks or months, because an unfavourable lever effect generates excessive strain at the cortical bone rim (Buchter et al., 2006; Gracco et al., 2009). Orthodontic mini-implants overcome many of these problems, because they are available with a smaller body
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(a) Radiograph showing six IMF screws in a trauma case where several screws are likely to have been drilled into tooth roots (despite reasonable interproximal spaces being present) and this caused the fracture of one of the screws. The upper midline screw is also coronally inclined. (b) Photograph comparing 6 and 9 mm (body) length miniimplants, with 1.5 mm body diameters, and a 2 mm diameter IMF screw. The mini-implant head is also smaller, facilitating wire and elastic placement, and avoiding lip/cheek trauma. (c, d) Post-operative photograph and panoramic radiograph (OPG) showing that four mandibular mini-implants have been inserted or angled too coronally by an inexperienced surgeon (yet IMF was successfully applied). (e) Five analogues have been inserted into a stone model, enabling their positions to be carefully checked before fabrication of a guidance stent. (f) A 3D stent being used to guide five mini-implants insertions, where no maxillary appliance exists pre-operatively
Figure 1
diameter (e.g. 1.5 mm), designed for interproximal sites, easy to remove, entail minimal risks, and many designs have a lower head and neck profile than IMF screws (Figure 1b). The head design may even be customized specifically for ease of application of intermaxillary wire and elastic traction, and contoured for patient comfort. Mini-implants are particularly useful in trauma cases
which can be managed with a period of IMF, such as the closed reduction of mildly displaced condylar fractures where there is a tendency to develop condyle-ramus telescoping, resulting in an anterior open bite, especially in those patients with a high mandibular plane angle. Mini-implants may be inserted under local anaesthesia in anterior sites in these patients and are better tolerated
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than IMF screws (where the protrusive profile would irritate the lip). From a clinical perspective, it is important that maxillofacial surgeons understand the design and technique differences between their typical armamentarium, in terms of IMF and osteosynthesis screws (which they routinely use to stabilize fixation plates), and orthodontic mini-implants. In particular, the latter involves a selfdrilling insertion technique directly into the interproximal bone and using relatively low force/insertion torque. Deviations from the correct technique may result in positional problems (Figure 1c and d) which lead to limited primary stability and potential root damage; screw fracture; and a compromise in longer-term (secondary) stability, if mini-implants are planned to remain in situ post-operatively. This is because their primary stability in bone declines within 3 weeks, before the remodelling process then provides secondary stability (Ure et al., 2011). Furthermore, it may be helpful if a guidance stent is available for surgeons, especially where intra-oral access and/or interproximal space are limited. An ideal stent provides physical, not just visual, guidance for the screwdriver, to replicate the ideal position and three-dimensional directions of the mini-implant insertions intra-operatively,
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following a pre-surgical planning stage (Figure 1e and f) (Cousley and Parberry, 2006; Cousley, 2009). The integral use of mini-implants within orthognathic surgical treatments will be discussed here using three specific clinical scenarios: ‘Surgery First’ treatment, miniimplant fixation in surgical patients with compromised dentitions, and the use of molar intrusion to optimize vertical control in orthognathic patients. ‘Surgery First’ treatment The ‘Surgery First’ concept was introduced by Nagasaka et al. (2009) in a case report where four anterior (two maxillary and two mandibular) mini-implants were used as temporary anchorage in a class III orthognathic case where minimal pre-surgical orthodontics had been performed. This concept has been further developed for bimaxillary surgery and often relies on mini-implant usage for both intra-operative IMF and post-operative elastic traction (Herna´ndez-Alfaro et al., 2011; Kim et al., 2012). Patients with short dental roots may also benefit from this form of IMF since it minimizes the risks of root resorption and extrusion, which are associated with tooth-borne IMF and elastic traction.
Figure 2 Pre- and post-operative photographs (a, c) and a post-operative lateral cephalogram (b) of a 46-year-old man who presented with a post-traumatic Class III malocclusion and both anterior and right lateral openbites. Ten mini-implants were inserted, either parallel to the occlusal plane or apically angulated (b), and used for intraoperative IMF during a maxillary osteotomy. A Class I occlusion, with good bilateral occlusal interdigitation, was achieved without the need for orthodontics, and this was stable one year later (d)
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Pre-treatment photograph (a) and lateral cephalogram (b) of a 16-year-old girl who presented with a Class III malocclusion. Her maxillary arch alignment and arch form were sufficient to enable mandibular surgery to proceed following lower arch orthodontics (c) and the insertion of five maxillary mini-implants, as seen on postoperative radiographs (d, e). The mini-implants were also used post-operatively for elastic traction (f, g) to correct asymmetrical Class III occlusal contacts. The mini-implants were explanted and the maxillary teeth bonded 1 month after surgery (h) and all appliances debonded 6 months later, after a total of 14-month treatment (i)
Figure 3
The ‘Surgery First’ approach involves patients having their orthognathic surgery early during their combined treatment process, with only a brief or even no period of time with pre-surgical fixed appliances in situ. The feasibility of this approach depends on whether a realistic class I malocclusion can be achieved without the need for extensive pre-surgical orthodontics. Therefore, the potential immediate post-operative occlusion must be assessed using the patient’s study models to determine the suitability of individual patients for this approach. Appropriate patients typically present with either post-traumatic (Figure 2) or class III dentofacial deformities (Figure 3). In particular, there should be no occlusal interferences, caused by teeth such as palatally displaced upper lateral incisors or over-erupted canines, which would prevent a reasonable interdigitation of the immediate post-operative occlusion.
The ‘Surgery First’ approach aims to avoid the patient experiencing a worsening of their malocclusion and facial profile with pre-surgical orthodontic decompensation, and to increase treatment efficiency (by reducing the total time in fixed appliances) (Kim et al., 2012). However, it does require fixation points for IMF purposes (in lieu of surgical hooks on fixed appliances). Such fixation can be achieved with the use of orthodontic mini-implants (Cousley, 2013). In such circumstances, the patient’s pretreatment OPG should be examined for potential miniimplant insertion sites and whether root proximities would prevent placement of mini-implants at suitable points around the dental arches for stable IMF. Where the roots appear to be close or they are incompletely visualized on the panoramic radiography, then it is advisable to take supplementary intra-oral periapical radiographs or conebeam computed tomography views to provide accurate
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(a) An OPG taken following a 10 mm mandibular advancement osteotomy. The right plate fixation was unstable, resulting in vertical collapse, premature contact of the right molars and an antero-left lateral openbite. The short upper incisor lengths contra-indicated normal elastic traction so the occlusion was stabilized by new mandibular fixation, and three maxillary mini-implants coupled with an anterior box elastic (b–d)
Figure 4
information on the root proximity and morphology. These mini-implants are used for intra-operative IMF and, unlike IMF screws, they remain in place in case postoperative intermaxillary traction is required (Figure 3f and g). They may be inserted either in a dental arch with no brackets bonded on the teeth, or where the fixed appliance archwire(s) is too narrow or flexible to support surgical hooks. Mini-implant fixation in surgical patients with compromised dentitions While most orthognathic patients begin their orthognathic treatment as teenagers with healthy teeth and periodontal tissues, there are also many patients who present with more challenging dentitions in terms of absent teeth (hypodontia or early tooth losses), periodontal deficiencies and short dental roots. The latter is a particular problem when it affects multiple incisor teeth (Figure 4). These features mean that forces from both orthodontic archwire and intermaxillary (orthodontic and surgical) traction should be minimized in order to avoid iatrogenic damage, such as the extrusion or destabilization of vulnerable teeth or an exacerbation of any periodontal loss. The use of mini-implants in these compromised dentitions greatly facilitates comprehensive orthognathic treatment, without
enhanced risks to the dentition. For example, when patients present with short or very tapered incisor roots (commonly seen in the maxillary arch in class III surgical cases), then its feasible to proceed to surgery without the need for full engagement of a rigid (e.g. 0.01960.025-inch) stainless steel archwire. This spares the application of excessive forces on these teeth, in the form of both presurgical orthodontic forces, and also surgical forces in the form of IMF and post-operative traction (Figure 4). The useofmolarintrusion tooptimize vertical control in orthognathic patients Conventional clinical management of ‘long face’ patients, who present with an excessive lower anterior face height and maxillo-mandibular planes angle, involves a maxillary impaction osteotomy movement to reduce the vertical skeletal discrepancy. Although many patients with the predominant feature of an anterior open bite can now be treated non-surgically, by the use of mini-implant molar intrusion (Cousley, 2013; Cousley, 2014), orthognathic surgery is still indicated for problems such as vertical maxillary excess and when there is a coexistent class III or substantial class II antero-posterior skeletal discrepancy. Conventional orthognathic management in these cases involves bimaxillary surgery. However,
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Figure 5 Pre-treatment photographs of an 18-year-old woman who presented with a Class III dentofacial deformity, an increased mandibular plane angle and a small AOB (a, b). Treatment commenced with an upper fixed appliance, then a TPA and palatal mini-implant traction were added (c, d). At the pre-operative stage, after 10 months of treatment, both a reverse overjet and positive overbite had been achieved (e, f). Cephalometric superimposition indicated that the maxillary molar intrusion and associated mandibular anticlockwise rotation had produced a positive overbite despite the lower incisor decompensation (g). A mandibular setback osteotomy resulted in a Class I occlusion and facial profile, with the appearance of a normal mandibular angle (h, i), despite the cephalometric superimposition showing a surgical increase in the maxillo-mandibular planes angle (j). Class I occlusal and facial profile features were achieved, plus a reduction in the lower facial vertical parameters (k, l)
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Figure 6 Pre-treatment photographs and lateral cephalogram (a–c) of a 22-year-old woman who presented with a Class
II division 2 malocclusion mandibular retrognathia, increased anterior facial height, a gummy smile and an AOB. The first premolars were absent and consequently it would be difficult to normalize the upper incisor inclinations. Furthermore, a differential maxillary impaction would have exacerbated the retroclined appearance of the maxillary incisors. Therefore, the treatment included pre-operative maxillary molar intrusion treatment. This commenced after initial alignment and levelling (d, e), and continued until the AOB was corrected while maintaining the upper incisor level (f–h). A 6 mm anterior and posterior maxillary impaction then corrected the excessive upper incisor display and lip incompetence, as seen in post-operative illustrations (i, j), without compromising the final incisor positions and inclinations (k, l)
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instead of undergoing surgery to both jaws, some of these patients may now be managed by the use of mini-implant intrusion of the maxillary molar teeth combined with a mandibular osteotomy. In effect, the molar intrusion reduces the vertical discrepancy and increases the overbite, while the mandibular procedure addresses the class II or III anteroposterior features. This new clinical approach aims to optimize the treatment outcome while minimizing surgical and recovery time, mid-facial and nasal side effects/morbidity, and both healthcare and patient costs (Figure 5). It is also possible to combine mini-implant molar intrusion with maxillary surgical impaction in order to optimize outcomes in terms of the maxillary molar and incisor vertical positions and inclination (torque), and reduce the potential nasal side-effects associated with large surgical impactions. This is particularly valuable when the maxillary incisors appear retroclined before treatment, and a differential maxillary impaction would result in the relative appearance of these incisors’ inclination becoming worse (Figure 6). This hybrid approach may also enable the orthognathic team to exceed the range of vertical molar changes which can be achieved with either (miniimplant) molar intrusion or (surgical) posterior impaction treatments alone, expanding the vertical orthognathic envelope and possibly making post-operative relapse more manageable. The purpose of this paper is to introduce this combined intrusion and impaction concept, accepting that this hybrid approach warrants further clinical and research investigation. Conclusions Orthodontic mini-implants are widely used as anchorage adjuncts during orthodontic (only) treatment, but they also provide benefits for orthognathic patients in terms of reduced risks compared to IMF screws, by facilitating ‘surgery first’ approaches, and in the management of patients with compromised dentitions and excessive vertical facial growth. In the latter context, it is now possible to manage some cases with vertical growth problems with a combination of molar intrusion and single jaw orthognathic surgery.
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Disclaimer statements Contributors Both authors have contributed to the writing (body) of the paper and in supplying suitable illustrations. Funding None. Conflicts of interest One of the authors (RC) has a commercial interest in Infinitas mini-implants, but the treatment details discussed here are generalizable to other mini-implant systems. Ethics approval None.
References Arthur G, Berardo N. A simplified technique of maxillomandibular fixation. Oral Maxillofac Surg 1989; 47: 1234. Buchter A, Wiechmann D, Gaertner C, Hendrik M, Vogeler M, Wiesmann HP, et al. Load-related bone modelling at the interface of orthodontic microimplants. Clin Oral Implant Res 2006; 17: 714–722. Coletti DP, Salama A, Caccamese JF. Application of intermaxillary fixation screws in maxillofacial trauma. J Oral Maxillofac Surg 2007; 65: 1746– 1750. Cornelius CP, Ehrenfeld M. The Use of MMF Screws: surgical technique, indications, contraindications, and common problems. Craniomaxillofac Trauma Reconstr 2010; 3: 55–80. Cousley RRJ. A stent-guided mini-implant system. J Clin Orthod 2009; 43: 403– 407. Cousley RRJ. The Orthodontic Mini-implant Clinical Handbook. London: Wiley-Blackwell. 2013. Cousley RRJ. Molar intrusion in the management of anterior openbite and ‘high angle’ Class II malocclusions. J Orthod 2014; to be published. Cousley RRJ, Parberry DJ. Surgical stents for the accurate insertion of both selftapping and self-drilling orthodontic mini-implants. J Clin Orthod 2006; 40: 412–417. Gracco A, Cirignaco A, Cozzani M, Boccaccio A, Pappalettere C, Vitale G. Numerical/experimental analysis of the stress field around miniscrews for orthodontic anchorage. Eur J Orthod 2009; 31: 12–20. Hashemi HM, Parhiz A. Complications using intermaxillary fixation screws. J Oral Maxillofac Surg 2011; 69: 1411–1414. Herna´ndez-Alfaro F, Guijarro-Martı´nez R, Molina-Coral A, Badı´a-Escriche CJ. ‘Surgery first’ in bimaxillary orthognathic surgery. Oral Maxillofac Surg 2011; 69: e201–e207. Kim JH, Mahdavie NN, Evans CA. Guidelines for ‘Surgery First’ orthodontic treatment. In Bourzgui F, (ed). Orthodontics — Basic Aspects and Clinical Considerations. Rijeka: InTech, 2012, 265-300. Nagasaka H, Sugawara J, Kawamura H, Nanda RJ. ‘Surgery first’ skeletal Class III correction using the Skeletal Anchorage System. Clin Orthod 2009; 43: 97–105. Ure DS, Oliver DR, Kim KB, Melo AC, Buschang PH. Stability changes of miniscrew implants over time. A pilot resonance frequency analysis. Angle Orthod 2011; 81: 994–1000.
Journal of Orthodontics, Vol. 41, 2014, S54–S61
Mini-implant applications in orthognathic surgical treatment Richard R. J. Cousley1 and Mark J. Turner2 1
Orthodontic Department, Peterborough and Stamford Hospitals NHS Foundation Trust, UK; 2Department of Oral and Maxillofacial Surgery, Peterborough and Stamford Hospitals NHS Foundation Trust, UK
Orthognathic surgical treatment conventionally relies on the use of full arch fixed orthodontic appliances. However, the introduction of orthodontic mini-implants has altered surgical options in terms of providing an alternative to fixation (intermaxillary fixation, IMF) screws and even to maxillary osteotomy. This paper describes the integration of mini-implants within orthognathic treatments in terms of ‘surgery first’ treatments and by introducing the concept of the conversion of bimaxillary cases into mandible-only surgery treatments. Key words: Orthodontic mini-implant, TAD, surgery first, orthognathic surgery, vertical anchorage Received 7 May 2014; accepted 25 May 2014
Introduction Given that orthodontic mini-implants were developed in the late 1990s from maxillofacial bone screw technology, it seems appropriate for them to be applied now as an adjunct to maxillofacial surgery. For example, some orthognathic surgical patients benefit from the use of mini-implants for intermaxillary fixation (IMF) and traction purposes, instead of conventional surgical hooks on orthodontic fixed appliances. This is especially the case where the treatment plan involves either the use of lingual fixed appliances or aligners (rather than labial brackets), or a ‘surgery first’ approach. Interestingly, the concept of using modified surgical screws to achieve intra-operative IMF (Arthur and Berardo, 1989) predates the introduction of mini-implants, and IMF screws are now used extensively in Oral and Maxillofacial Surgery. They offer significant advantages over traditional toothborne methods (eyelet wires and arch bars) of applying IMF, including less periodontal trauma, easier maintenance of oral hygiene, and the avoidance of tooth extrusion problems. The insertion of IMF screws is also much quicker than the application of traditional tooth borne IMF methods, does not require a healthy dentition, and is less likely to expose the operator to needle-stick type injury (caused by eyelet wire ends). A recent review of the IMF screws supplied by six manufacturers reported that they have the following typical features: titanium or stainless steel composition, 2 mm body diameter, 9–21 mm lengths and both self-tapping and self-drilling formats (Cornelius and Ehrenfeld, 2010). Address for correspondence: R. Cousley, Orthodontic Department, Peterborough City Hospital, Bretton Gate, Peterborough PE3 9GZ, UK. Email: [email protected] # 2014 British Orthodontic Society
The body and thread designs correspond to the osteosynthesis mini-screws produced by these respective surgical manufacturers. Notably, there appears to be a difference between the recommended and actual uses of these IMF screws, since the commercial literature advises against their use in paediatric cases and recommends their insertion at sites apical to the dental roots. However, clinical reports indicate that many surgeons site IMF screws interproximally (Hashemi and Parhiz, 2011), perhaps because it is clinically easier to insert them through attached mucosa rather than the mobile soft tissues at the sub-apical level. This may partly account for the reportedly high failure rate (6–25%) of IMF screws in trauma cases (Coletti et al., 2007), since the relatively large (2 mm) diameter and length of IMF screws greatly increases the risk of root contact (Figure 1a), especially in sites where interproximal access is limited, e.g. by the convergent tipping of adjacent roots. Interproximal insertion also increases the risk of root damage, irrespective of their short term (intra-operative) use (Hashemi and Parhiz, 2011). Furthermore, the high profile and bulky head size of an IMF screw means that the head projects out towards the lip and cheek, increasing patient discomfort. This also potentially destabilizes the screw if traction is required over a period of weeks or months, because an unfavourable lever effect generates excessive strain at the cortical bone rim (Buchter et al., 2006; Gracco et al., 2009). Orthodontic mini-implants overcome many of these problems, because they are available with a smaller body
DOI 10.1179/1465313314Y.0000000106
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Mini-implants in orthognathic surgery
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(a) Radiograph showing six IMF screws in a trauma case where several screws are likely to have been drilled into tooth roots (despite reasonable interproximal spaces being present) and this caused the fracture of one of the screws. The upper midline screw is also coronally inclined. (b) Photograph comparing 6 and 9 mm (body) length miniimplants, with 1.5 mm body diameters, and a 2 mm diameter IMF screw. The mini-implant head is also smaller, facilitating wire and elastic placement, and avoiding lip/cheek trauma. (c, d) Post-operative photograph and panoramic radiograph (OPG) showing that four mandibular mini-implants have been inserted or angled too coronally by an inexperienced surgeon (yet IMF was successfully applied). (e) Five analogues have been inserted into a stone model, enabling their positions to be carefully checked before fabrication of a guidance stent. (f) A 3D stent being used to guide five mini-implants insertions, where no maxillary appliance exists pre-operatively
Figure 1
diameter (e.g. 1.5 mm), designed for interproximal sites, easy to remove, entail minimal risks, and many designs have a lower head and neck profile than IMF screws (Figure 1b). The head design may even be customized specifically for ease of application of intermaxillary wire and elastic traction, and contoured for patient comfort. Mini-implants are particularly useful in trauma cases
which can be managed with a period of IMF, such as the closed reduction of mildly displaced condylar fractures where there is a tendency to develop condyle-ramus telescoping, resulting in an anterior open bite, especially in those patients with a high mandibular plane angle. Mini-implants may be inserted under local anaesthesia in anterior sites in these patients and are better tolerated
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than IMF screws (where the protrusive profile would irritate the lip). From a clinical perspective, it is important that maxillofacial surgeons understand the design and technique differences between their typical armamentarium, in terms of IMF and osteosynthesis screws (which they routinely use to stabilize fixation plates), and orthodontic mini-implants. In particular, the latter involves a selfdrilling insertion technique directly into the interproximal bone and using relatively low force/insertion torque. Deviations from the correct technique may result in positional problems (Figure 1c and d) which lead to limited primary stability and potential root damage; screw fracture; and a compromise in longer-term (secondary) stability, if mini-implants are planned to remain in situ post-operatively. This is because their primary stability in bone declines within 3 weeks, before the remodelling process then provides secondary stability (Ure et al., 2011). Furthermore, it may be helpful if a guidance stent is available for surgeons, especially where intra-oral access and/or interproximal space are limited. An ideal stent provides physical, not just visual, guidance for the screwdriver, to replicate the ideal position and three-dimensional directions of the mini-implant insertions intra-operatively,
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following a pre-surgical planning stage (Figure 1e and f) (Cousley and Parberry, 2006; Cousley, 2009). The integral use of mini-implants within orthognathic surgical treatments will be discussed here using three specific clinical scenarios: ‘Surgery First’ treatment, miniimplant fixation in surgical patients with compromised dentitions, and the use of molar intrusion to optimize vertical control in orthognathic patients. ‘Surgery First’ treatment The ‘Surgery First’ concept was introduced by Nagasaka et al. (2009) in a case report where four anterior (two maxillary and two mandibular) mini-implants were used as temporary anchorage in a class III orthognathic case where minimal pre-surgical orthodontics had been performed. This concept has been further developed for bimaxillary surgery and often relies on mini-implant usage for both intra-operative IMF and post-operative elastic traction (Herna´ndez-Alfaro et al., 2011; Kim et al., 2012). Patients with short dental roots may also benefit from this form of IMF since it minimizes the risks of root resorption and extrusion, which are associated with tooth-borne IMF and elastic traction.
Figure 2 Pre- and post-operative photographs (a, c) and a post-operative lateral cephalogram (b) of a 46-year-old man who presented with a post-traumatic Class III malocclusion and both anterior and right lateral openbites. Ten mini-implants were inserted, either parallel to the occlusal plane or apically angulated (b), and used for intraoperative IMF during a maxillary osteotomy. A Class I occlusion, with good bilateral occlusal interdigitation, was achieved without the need for orthodontics, and this was stable one year later (d)
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Pre-treatment photograph (a) and lateral cephalogram (b) of a 16-year-old girl who presented with a Class III malocclusion. Her maxillary arch alignment and arch form were sufficient to enable mandibular surgery to proceed following lower arch orthodontics (c) and the insertion of five maxillary mini-implants, as seen on postoperative radiographs (d, e). The mini-implants were also used post-operatively for elastic traction (f, g) to correct asymmetrical Class III occlusal contacts. The mini-implants were explanted and the maxillary teeth bonded 1 month after surgery (h) and all appliances debonded 6 months later, after a total of 14-month treatment (i)
Figure 3
The ‘Surgery First’ approach involves patients having their orthognathic surgery early during their combined treatment process, with only a brief or even no period of time with pre-surgical fixed appliances in situ. The feasibility of this approach depends on whether a realistic class I malocclusion can be achieved without the need for extensive pre-surgical orthodontics. Therefore, the potential immediate post-operative occlusion must be assessed using the patient’s study models to determine the suitability of individual patients for this approach. Appropriate patients typically present with either post-traumatic (Figure 2) or class III dentofacial deformities (Figure 3). In particular, there should be no occlusal interferences, caused by teeth such as palatally displaced upper lateral incisors or over-erupted canines, which would prevent a reasonable interdigitation of the immediate post-operative occlusion.
The ‘Surgery First’ approach aims to avoid the patient experiencing a worsening of their malocclusion and facial profile with pre-surgical orthodontic decompensation, and to increase treatment efficiency (by reducing the total time in fixed appliances) (Kim et al., 2012). However, it does require fixation points for IMF purposes (in lieu of surgical hooks on fixed appliances). Such fixation can be achieved with the use of orthodontic mini-implants (Cousley, 2013). In such circumstances, the patient’s pretreatment OPG should be examined for potential miniimplant insertion sites and whether root proximities would prevent placement of mini-implants at suitable points around the dental arches for stable IMF. Where the roots appear to be close or they are incompletely visualized on the panoramic radiography, then it is advisable to take supplementary intra-oral periapical radiographs or conebeam computed tomography views to provide accurate
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(a) An OPG taken following a 10 mm mandibular advancement osteotomy. The right plate fixation was unstable, resulting in vertical collapse, premature contact of the right molars and an antero-left lateral openbite. The short upper incisor lengths contra-indicated normal elastic traction so the occlusion was stabilized by new mandibular fixation, and three maxillary mini-implants coupled with an anterior box elastic (b–d)
Figure 4
information on the root proximity and morphology. These mini-implants are used for intra-operative IMF and, unlike IMF screws, they remain in place in case postoperative intermaxillary traction is required (Figure 3f and g). They may be inserted either in a dental arch with no brackets bonded on the teeth, or where the fixed appliance archwire(s) is too narrow or flexible to support surgical hooks. Mini-implant fixation in surgical patients with compromised dentitions While most orthognathic patients begin their orthognathic treatment as teenagers with healthy teeth and periodontal tissues, there are also many patients who present with more challenging dentitions in terms of absent teeth (hypodontia or early tooth losses), periodontal deficiencies and short dental roots. The latter is a particular problem when it affects multiple incisor teeth (Figure 4). These features mean that forces from both orthodontic archwire and intermaxillary (orthodontic and surgical) traction should be minimized in order to avoid iatrogenic damage, such as the extrusion or destabilization of vulnerable teeth or an exacerbation of any periodontal loss. The use of mini-implants in these compromised dentitions greatly facilitates comprehensive orthognathic treatment, without
enhanced risks to the dentition. For example, when patients present with short or very tapered incisor roots (commonly seen in the maxillary arch in class III surgical cases), then its feasible to proceed to surgery without the need for full engagement of a rigid (e.g. 0.01960.025-inch) stainless steel archwire. This spares the application of excessive forces on these teeth, in the form of both presurgical orthodontic forces, and also surgical forces in the form of IMF and post-operative traction (Figure 4). The useofmolarintrusion tooptimize vertical control in orthognathic patients Conventional clinical management of ‘long face’ patients, who present with an excessive lower anterior face height and maxillo-mandibular planes angle, involves a maxillary impaction osteotomy movement to reduce the vertical skeletal discrepancy. Although many patients with the predominant feature of an anterior open bite can now be treated non-surgically, by the use of mini-implant molar intrusion (Cousley, 2013; Cousley, 2014), orthognathic surgery is still indicated for problems such as vertical maxillary excess and when there is a coexistent class III or substantial class II antero-posterior skeletal discrepancy. Conventional orthognathic management in these cases involves bimaxillary surgery. However,
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Figure 5 Pre-treatment photographs of an 18-year-old woman who presented with a Class III dentofacial deformity, an increased mandibular plane angle and a small AOB (a, b). Treatment commenced with an upper fixed appliance, then a TPA and palatal mini-implant traction were added (c, d). At the pre-operative stage, after 10 months of treatment, both a reverse overjet and positive overbite had been achieved (e, f). Cephalometric superimposition indicated that the maxillary molar intrusion and associated mandibular anticlockwise rotation had produced a positive overbite despite the lower incisor decompensation (g). A mandibular setback osteotomy resulted in a Class I occlusion and facial profile, with the appearance of a normal mandibular angle (h, i), despite the cephalometric superimposition showing a surgical increase in the maxillo-mandibular planes angle (j). Class I occlusal and facial profile features were achieved, plus a reduction in the lower facial vertical parameters (k, l)
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Figure 6 Pre-treatment photographs and lateral cephalogram (a–c) of a 22-year-old woman who presented with a Class
II division 2 malocclusion mandibular retrognathia, increased anterior facial height, a gummy smile and an AOB. The first premolars were absent and consequently it would be difficult to normalize the upper incisor inclinations. Furthermore, a differential maxillary impaction would have exacerbated the retroclined appearance of the maxillary incisors. Therefore, the treatment included pre-operative maxillary molar intrusion treatment. This commenced after initial alignment and levelling (d, e), and continued until the AOB was corrected while maintaining the upper incisor level (f–h). A 6 mm anterior and posterior maxillary impaction then corrected the excessive upper incisor display and lip incompetence, as seen in post-operative illustrations (i, j), without compromising the final incisor positions and inclinations (k, l)
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instead of undergoing surgery to both jaws, some of these patients may now be managed by the use of mini-implant intrusion of the maxillary molar teeth combined with a mandibular osteotomy. In effect, the molar intrusion reduces the vertical discrepancy and increases the overbite, while the mandibular procedure addresses the class II or III anteroposterior features. This new clinical approach aims to optimize the treatment outcome while minimizing surgical and recovery time, mid-facial and nasal side effects/morbidity, and both healthcare and patient costs (Figure 5). It is also possible to combine mini-implant molar intrusion with maxillary surgical impaction in order to optimize outcomes in terms of the maxillary molar and incisor vertical positions and inclination (torque), and reduce the potential nasal side-effects associated with large surgical impactions. This is particularly valuable when the maxillary incisors appear retroclined before treatment, and a differential maxillary impaction would result in the relative appearance of these incisors’ inclination becoming worse (Figure 6). This hybrid approach may also enable the orthognathic team to exceed the range of vertical molar changes which can be achieved with either (miniimplant) molar intrusion or (surgical) posterior impaction treatments alone, expanding the vertical orthognathic envelope and possibly making post-operative relapse more manageable. The purpose of this paper is to introduce this combined intrusion and impaction concept, accepting that this hybrid approach warrants further clinical and research investigation. Conclusions Orthodontic mini-implants are widely used as anchorage adjuncts during orthodontic (only) treatment, but they also provide benefits for orthognathic patients in terms of reduced risks compared to IMF screws, by facilitating ‘surgery first’ approaches, and in the management of patients with compromised dentitions and excessive vertical facial growth. In the latter context, it is now possible to manage some cases with vertical growth problems with a combination of molar intrusion and single jaw orthognathic surgery.
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Disclaimer statements Contributors Both authors have contributed to the writing (body) of the paper and in supplying suitable illustrations. Funding None. Conflicts of interest One of the authors (RC) has a commercial interest in Infinitas mini-implants, but the treatment details discussed here are generalizable to other mini-implant systems. Ethics approval None.
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