Self-Ligation and the Periodontally Compromised Patient: A Different Perspective

Self-Ligation and the Periodontally Compromised Patient: A Different Perspective Dimitrios Mavreas Orthodontic therapy is not contraindicated for patients with advanced periodontal destruction, provided that factors such as inflammation, plaque, subgingival calculus, and occlusal trauma are well controlled both before and during the orthodontic treatment. The application of extremely light continuous forces might have a better effect on the cell biology of tooth movements. By minimizing necrosis, and the subsequent hyalinization and indirect resorption, it might be possible to achieve continuous progress in tooth movement, avoiding the repeated interruptions occurring when the blood vessels are occluded, and reducing the great risk for further bone loss when treatment is rendered for individuals with decreased osseous support. A new generation of low friction, passive self-ligating brackets, in combination with newer wire and coil materials and longer activation spans, seems to be capable of exerting lower force levels providing more favorable periodontal reactions in patients with previous bone loss. A patient treated following these principles and using these newer technologies is presented. (Semin Orthod 2008;14:36-45.) © 2008 Elsevier Inc. All rights reserved.

rthodontic treatment has traditionally been provided to children and adolescents with intact dentitions. For more than two decades treatment has also been increasingly sought by adults who believe that they can benefit from it. The adult population may differ from growing individuals in many respects; adults, and more particularly elderly adults, have old and failing restorations, edentulous spaces, abraded teeth, periodontal bone defects, gingival problems, and a variety of other restorative and periodontal problems that could compromise the orthodontic result.1,2 Periodontal diseases include a group of chronic inflammatory disorders encompassing destructive and nondestructive diseases of the periodontal supporting tissues of the teeth. Chronic periodontitis is a common disease and may occur in most age groups, but is most prevalent among adults and

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Private Practice, 238 Kifissias Avenue, 152 31, Chalandri, Greece. Address correspondence to Dimitrios Mavreas, 26 Varnali Street, 146 71, Kastri, Greece. E-mail: [email protected] © 2008 Elsevier Inc. All rights reserved. 1073-8746/08/1401-0$30.00/0 doi:10.1053/j.sodo.2007.12.004

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seniors worldwide. Approximately 48% of U.S. adults have chronic periodontitis, and similar or higher rates have been reported in other populations. Moderate and advanced periodontitis is more prevalent among older age groups and rates of 70% or more have been reported in certain populations. In Europe it is estimated that between 13% and 54% of 35- to 44-year-old individuals have 3.5- to 5.5-mm probing depths, although the estimates may be conservative because they were derived from poorly documented surveys.3 Pressure from the lips, cheeks, and tongue in the rest position, and the forces produced by the metabolic activity of the periodontal membrane, are the two major factors affecting the balance that dictates the position of the teeth.4 When the periodontium is intact the periodontal membrane counteracts possible soft tissue imbalances. However, when the periodontium is compromized, the teeth might be more susceptible to migration.

Orthodontic-Periodontal Considerations Periodontal disease was considered for years as a contraindication to orthodontic therapy since it was thought of as an additional factor that could

Seminars in Orthodontics, Vol 14, No 1 (March), 2008: pp 36-45

The Periodontally Compromised Patient

contribute to rapid tooth loss. It has been shown that orthodontic forces in the presence of plaque can create intraosseous defects, and that following rotation and intrusion of teeth, loss of attachment can be observed.5 The combination of orthodontic forces, inflammation, and traumatic forces can cause more rapid destruction than that produced by inflammation alone.6 It is also known that in the presence of periodontitis, traumatic forces develop that combined with inflammation can act synergistically, accelerating the development of the periodontal disease.7 Orthodontic tooth movement in adults can be slower than tooth movement in adolescents due to differences in the biomechanical properties of the adult periodontium. Reduced cellular activity in adults facilitates the formation of hyaline zones and the conversion of collagen fibers is much slower than in children and teenagers.8,9 Heavy orthodontic forces overcoming the blood pressure of the capillaries cause crushing of the periodontal ligament on the pressure side, resulting in hyalinization and slowing of the tooth movement. Gentle forces can cause light ischemia with concurrent bone resorption and formation and enhance tooth movement,10 whereas regeneration of the periodontal ligament does not occur when inflammation is present in the periodontal tissues.5 Thus, a prerequisite to orthodontic treatment is the elimination of the subgingival inflammation. Orthodontic therapy might even enhance the possibilities of saving and restoring a deteriorated dentition.10-14 The rearrangement of the dental arch may facilitate oral hygiene and positively influence the outcome of the periodontal treatment, while the observable esthetic improvement may motivate the individual even further regarding the pursuit of their oral rehabilitation. It has been shown that orthodontic repositioning of tipped molars has beneficial effects on the periodontium. Considerable and predictable morphologic alterations to the crestal bone accompany tooth uprighting, even though the connective tissue attachment level remains unchanged along the root surface.15-17 Also, the movement through intraosseous defects of teeth with reduced but healthy periodontium is possible, without further loss of attachment.18,19 A patient with advanced periodontitis usually presents with extruded teeth, labial anterior tooth

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migration, and increased interdental spaces. The prevalence of pathologic migration of anterior teeth in patients with moderate to severe periodontitis may reach 30%.20 These changes in tooth position might hinder oral hygiene and affect the result of the periodontal treatment. The success of the orthodontic treatment of these patients depends heavily on their periodontal management. Preorthodontic periodontal therapy is directed toward the etiologic factors including plaque, subgingival calculus, and occlusal trauma. Occlusal therapy is an integral part of periodontal therapy. Failure to treat occlusal trauma appropriately in patients with chronic periodontitis may result in progressive loss of bone and an adverse change in prognosis, and could result in tooth loss.21 Root planing and subgingival debridement are performed to help diminish inflammation, bleeding, and suppuration. Following a stabilization period, the patient is reevaluated and the tissue response is assessed. The periodontist determines if the patient is stable enough periodontally to proceed with orthodontic treatment. Systematic scaling and cleaning might be necessary on a 3-monthly basis,13 and occasionally even shorter recall periods could be indicated. Some areas in the mouth may require periodontal surgical treatment before the initiation of tooth movement.22

Force Type and Magnitude—Tissue Reaction The ideal orthodontic treatment requires the application of forces capable of achieving the maximum speed in tooth movement combined with the minimum damage to the root, the periodontal ligament, and the alveolar bone.23 “After more than half a century of research on orthodontic tooth movement, it is disappointing to conclude that the answer to the question of the optimal force is still far away.”24 Various models regarding the rate of tooth movement and the applied magnitude of force have been proposed by Quinn and Yoshikawa,25 and the mechanostat theory of Frost can be adopted to represent the tissue reaction to the applied stress.26,27 It has been suggested that a minute force, leading to a minute change in pressure, might be able to switch on tooth movement. The latter implies that forces of greater magni-

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tude often used in orthodontic treatment do not necessarily produce more efficient tooth movement. On the contrary, they might overload the periodontal tissues and cause negative effects that will hinder tooth movement.28 Oxygen is considered as the catalyst for the remodeling of the periodontium. If vascularity is interrupted in the periodontal space between bone and the teeth, oxygen is no longer available and cellular activity is slowed or stopped.29 Direct resorption, which is considered as the most desirable in orthodontic movements, can be perceived as a remodeling induced by underloading of the alveolar wall, and apposition as modeling induced by the load exerted by stretched fibers. Indirect resorption takes place when ischemia and hyalinization of the periodontal ligament (PDL) is generated by high stress values.27 This type of resorption is considered as traumatic and time consuming since it takes weeks for the PDL to revascularize at the cellular level.30,31 The time required for the healing of the tissues following hyalinization constitutes a long lapse in the process of treatment. The amount of tooth movement observed on rat teeth in response to intermittent force was less than that in response to continuous force.32 Horizontal tooth movement with continuous force was more effective than with interrupted continuous force on humans. Histological sections of experimental teeth showed no difference in the

amount or severity of root resorption between the two types of forces.33 It has been shown that by applying stresses of low magnitude, the lag phase in tooth movement can be eliminated and effective tooth movement can be produced.34 With conventional straight wire techniques, the magnitude of applied force is usually high. In a seminal article Koenig and Burstone showed by using a mathematical model that vertical forces that develop in the case of a 0.016⬙ stainless steel wire inserted in two slightly angulated brackets with a 7-mm interbracket distance can reach almost 500 g. When the wire is not free to slide during activation, horizontal forces develop that might reach the extreme value of 20,202 g. These large horizontal forces could subject the teeth to a “round trip” as the horizontal forces reverse themselves as the teeth assume new positions. These horizontal forces can be responsible for producing undesired rotational effects and mesiodistal contact, and by binding the crowns at their points of contact minimizing or reducing tooth movement. When the wire had the freedom to slide, the horizontal forces were of relatively low magnitude.35 Under the influence of these high forces, necrotic phenomena and tissue degeneration might occur, not only following each activation, but also within the period between activations since the magnitude of activation exceeds the capacity of the PDL to

Figure 1. Pretreatment facial photographs. (Color version of figure is available online.)

The Periodontally Compromised Patient

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Figure 2. Pretreatment intraoral photographs. (Color version of figure is available online.)

respond optimally. The ability for ideal optimal tooth movement is hindered even further when preadjusted twin brackets and wires tied either with metal or elastic ties are considered.36,37

Self-Ligation, Wire Selection, and Clinical Practice Based on these facts, it seems that extremely light continuous forces might have a better effect on the cell biology of tooth movements. By minimizing necrosis, and the subsequent hyalinization and indirect resorption, it might be possible to achieve continuous progress in tooth movement, avoiding the repeated interruptions occurring when the blood vessels are occluded, and without the great risk for further bone loss when treatment is rendered to individuals with decreased osseous support. A prerequisite in this situation is the ability to minimize and control the forces exerted during orthodontic treatment. Recently, the self-ligation concept was revived.38 A new generation of self-ligating brackets has been gaining acceptance by the orthodon-

tic community.39-41 Secure archwire engagement and thus better rotational and torque control,41 less chairside assistance and faster ligation/archwire removal,42-44 fewer appointments for treatment completion,45,46 decreased total treatment time,45,46 and most importantly dramatic decrease in friction44,47-50 are among the advantages that have been attributed to them, and in principle apply to all self-ligating brackets, although to a different degree for each design. Pseudoelastic and thermoelastic wires are generally considered to have the properties to deliver forces of low magnitude. However, their unloading forces can be as high as 879 g/mm for a 0.016⬙ ⫻ 0.022⬙ wire.51 To obtain forces lower than 100 g per tooth from austenitic superelastic nickel titanium, indicated for periodontally compromised patients, it is necessary to select wires of smaller diameters and abandon the use of rectangular wires during the alignment phase of treatment.51 Even the 100 g of force per tooth on a severely compromised periodontium can be considered as “heavy” and should be reduced. Thus, the smallest available diameter

Figure 3. Initial periapical radiographs.

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Figure 4. Bonding of the mandibular arch with a maxillary anterior bite plate present. (Color version of figure is available online.)

wires might be more appropriate in patients who have reduced bone and gingival support. Another controversial factor that might have been overlooked in clinical practice is the frequency of appliance activation. Traditionally, orthodontists follow a 4-week activation cycle corresponding to the bone resorptive portion of the human remodeling cycle that lasts about 1 month.52 Animal experiments have shown that when appliances were reactivated following total deactivation, tooth movement could be more efficient.53 Wires with extensive and constant unloading curves (eg, superelastic thermally activated wires), which under circumstances of reduced friction like those previously described, may remain active for prolonged periods of time, and could allow for less frequent activations since their total deactivation might take a longer period of time. Clinical experience has shown that activation intervals of 8 to 10 weeks might be more appropriate for enhancing tooth movement. Occasionally, especially in cases where severe crowding is present or when transverse dentoalveolar expansion is desirable, these intervals may even be prolonged further. The low friction characterizing passive selfligating brackets, the freedom of the small pseudoelastic wires to move within the brackets,

and the exertion of very light forces with minimal permanent deformation of the wire for extended periods of time all fulfill the definition of “convergent technologies,” which is the ultimate goal in what is considered as “front line” industry. These might be the proper arsenal for treating patients with a reduced but controlled and healthy periodontium. The following is a report of a patient who had severe periodontal damage and who was treated by applying the principles described in this article. When compared with patients with similarly compromised periodontal tissues treated with more conventional techniques, differences in outcomes could be detected.54 This approach to periodontally compromised patients appears to be more appropriate based on the present day understanding of force levels and tissue responses.

Case Report Diagnosis and Etiology The patient was a woman 22 years of age whose chief complaint was of severe extrusion of the maxillary incisors teeth. She had no history of any systemic disease. The patient had a history of previous orthodontic treatment at the age of 14,

Table 1. Sequence of Wire Replacement* Mandibular Arch

Time of Insertion

0.012⬙ nickel titanium 0.012⬙ nickel titanium 0.014 ⫻ 0.025⬙ nickel titanium 0.016 ⫻ 0.025⬙ nickel titanium 0.017 ⫻ 0.025⬙ TMA (purple)

Bonding day 1 month (replaced initial) 3 months 6 months 8 months

Maxillary Arch

Time of Insertion

0.012⬙ nickel titanium 0.014⬙ nickel titanium 0.014 ⫻ 0.025⬙ nickel titanium 0.016 ⫻ 0.025⬙ stainless steel

5 months (bonding) 6.5 months 8.5 months 10 months

*Treatment was completed in 12 months. TMA ⫽ titanium molybdenum alloy.

The Periodontally Compromised Patient

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arch. The mandibular molars were mesially tipped due to closing of previous extraction spaces. In addition generalized wear facets were detected and the patient was diagnosed as having a parafunctional bruxism habit.

Treatment Objectives The objectives were to provide the patient with morphological features that would eliminate trauma, allow proper cleaning of the teeth, and reestablish proper esthetics.

Treatment Progress Figure 5. Bonding of the maxillary arch at the new increased vertical dimension. (Color version of figure is available online.)

which included the extraction of the lower first premolar teeth. The initial examination (Figs 1 and 2) revealed trauma to the maxillary incisors due to the overbite and significant recession of the attached gingiva in both the maxillary and mandibular anterior segments. Periodontal probing revealed deep pockets in addition to bleeding in almost the entire arch. The pockets were deepest around the maxillary and mandibular incisors. The central incisors in both arches had excessive mobility. Radiographically, bone loss was more pronounced at the mandibular and maxillary incisor area (vertical defects at teeth numbers 11, 21, and 41) and at the maxillary molar area (Fig 3). A diagnosis of aggressive or early onset periodontitis was made. The patient had an Angle Class III molar relationship with a Class II canine relationship. The overbite was 6 mm and the overjet 5 mm and there was moderate crowding in the lower

The patient was initially fitted with a maxillary bite plate to eliminate traumatic contact between the anterior maxillary and mandibular teeth. The bite plate was used throughout the entire period that the patient was under periodontal treatment since this was considered necessary by the periodontist. After the completion of the periodontal treatment, bonding with Damon 2 (Ormco Corp., 1717 W. Collins Ave., Orange, CA 92867) self-ligating brackets was performed initially on the lower teeth with the bite plate present in the mouth to prevent the development of premature contacts with the maxillary anterior teeth while resolving the crowding in the lower arch (Fig 4). At the same time the orthodontic treatment would result in a clockwise rotation of the mandible, which would allow space for uprighting the lower molars since mandibular opening rotation occurs with the (pseudo) eruption of these teeth. The sequence in wire replacement during the entire treatment period is noted in Table 1. The upper arch was bonded 5 months into treatment when contact had been established posteriorly at the new increased vertical dimension (Fig 5). It

Figure 6. 0.016 ⫻ 0.025⬙ stainless steel wire in the maxillary and 0.017 ⫻ 0.025⬙ titanium molybdenum alloy (honeydew) wire in the mandibular arch. (Color version of figure is available online.)

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Figure 7. Postreatment facial photographs. (Color version of figure is available online.)

should be noted that the highly flexible nickel titanium wires were used for prolonged periods of time to keep stress levels on the teeth as low as possible. Even during the last part of the orthodontic treatment the working wire on the lower teeth was a low friction honeydew 0.017 ⫻ 0.025⬙ titanium molybdenum alloy (Ormco Corp.) wire

bent with a reverse curve of Spee to finally upright the lower molars and enhance the intrusion and proclination of the lower incisors. The thicker stainless steel wire used in the maxillary arch was an 0.016 ⫻ 0.025⬙ (Fig 6). The maxillary central incisors were reduced in height by 1 mm each in an attempt to improve the crown-root

Figure 8. Postreatment intraoral photographs. (Color version of figure is available online.)

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Figure 9. Postreatment periapical radiographs.

ratio. During the last 2 months of the treatment, light Class II elastics ([1/4]⬙ , 60 oz.) were used in an attempt to correct the sagittal relationship. The total treatment time was 12.5 months. Throughout the active treatment period the patient was under careful periodontal monitoring at 2-monthly intervals, and scaling and polishing was performed whenever considered necessary by the periodontist. Retention included permanent fixation of maxillary and mandibular canines and incisors as well as a maxillary occlusal splint (stabilization type) for night wearing. The purpose that the splint would serve was to reduce the adverse effects on the periodontal tissues of any nocturnal parafunctional activity such as clenching or bruxing by the patient.

Treatment Results Treatment for this patient led to improved facial and dental esthetics and the lips closed naturally (Figs 7 and 8). A Class I canine relationship was obtained with a normal overjet and overbite, although a small amount of midline deviation still existed. The amount of gingival recession of the maxillary anterior teeth was changed after orthodontic treatment. Pocket depths had decreased significantly. Periapical radiographs confirmed flattening of the interproximal bone topography. New bone was also found at the maxillary and mandibular incisors areas (Fig 9). Good root parallelism was obtained after the tooth uprighting procedures. Bone levels did not change at the alveolar bone crest. Occlusal

stresses were distributed broadly with the aid of selective reshaping at the end of orthodontic treatment, and an environment conducive to good oral hygiene was created, even in this severely periodontally compromised situation.

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31. Proffit WR, Fields HW: The biologic basis of orthodontic therapy, in Proffit WR, Fields HW (eds): Contemporary Orthodontics. St Louis, CV Mosby, 1993, pp 266-288 32. Hayashi H, Konoo T, Yamaguchi K: Intermittent 8-hour activation in orthodontic molar movement. Am J Orthod Dentofacial Orthop 125:302-309, 2004 33. Owman-Moll P, Kurol J, Lundgren D: Continuous versus interrupted continuous orthodontic force related to early tooth movement and root resorption. Angle Orthod 65:395-402, 1995 34. Iwasaki LR, Haack JE, Nickel JC: Human tooth movement in response to continuous stress of low magnitude. Am J Orthod Dentofacial Orthop 117:175-183, 2000 35. Koenig HA, Burstone CJ: Force systems from an ideal arch—large deflection considerations. Angle Orthod 59: 11-16, 1989 36. Moore MM, Harrington E, Rock WP: Factors affecting friction in the pre-adjusted appliance. Eur J Orthod 26:579-583, 2004 37. Khambay B, Millett D, McHugh S: Evaluation of methods of archwire ligation on frictional resistance. Eur J Orthod 6:327-332, 2004 38. Berger J: Self-ligation in the year 2000. J Clin Orthod 4:74-81, 2000 39. Damon DH: The rationale, evolution and clinical application of the self-ligating bracket. Clin Orthod Res 1:5261, 1998 40. Damon DH: The Damon low friction bracket: a biologically compatible straight-wire system. J Clin Orthod 32: 670-680, 1998 41. Harradine NWT: Self ligating brackets: where are we now? J Orthod 30:262-273, 2003 42. Hanson H: JCO interviews Dr. G. Herbert Hanson on the SPEED bracket. J Clin Orthod 10:183-9, 1986 43. Shivapuja PS, Berger J: A comparative study of conventional ligation and self-ligation bracket systems. Am J Orthod Dentofacial Orthop 106:472-480, 1994 44. Voudouris JC: Interactive edgewise mechanisms: form and function comparison with conventional edgewise brackets. Am J Orthod Dentofacial Orthop 111:119-140, 1997 45. Eberting JJ, Straja SR, Tuncay OC: Treatment time, outcome, and patient satisfaction comparisons of Damon and conventional brackets. Clin Orthod Res 4:228-234, 2001 46. Harradine NWT: Self-ligating brackets and treatment efficiency. Clin Orthod Res 4:220-227, 2001 47. Thorstenson BS, Kusy RP: Resistance to sliding of selfligating brackets versus conventional stainless steel twin brackets with second order angulation in the dry and wet (saliva) states. Am J Orthod Dentofacial Orthop 120:361370, 2001 48. Khambay B, Millet D, McHugh S: Evaluation of methods of archwire ligation on frictional resistance. Eur J Orthod 26:327-332, 2004 49. Cacciafesta V, Sfondrini M, Ricciardi A, et al: Evaluation of stainless steel and esthetic self-ligating brackets in various bracket-wire combinations. Am J Orthod Dentofacial Orthop 124:395-402, 2003 50. Henao SP, Kusy RP: Evaluation of the frictional resistance of conventional and self-ligating bracket designs using standardized archwires and dental typodonts. Angle Orthod 74:202-211, 2004

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51. Santoro M, Nicolay OF, Cangialosi TJ: Pseudoelasticity and thermoelasticity of nickeltitanium alloys: a clinically oriented review. Part II: deactivation forces. Am J Orthod Dentofacial Orthop 119:594-603, 2001 52. Frost HM: Some ABC’s of skeletal pathophysiology. 6. The growth/modelling/remodelling distinction. Calcif Tissue Int 49:301-302, 1991

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53. Gu G, Lemery SA, King GJ: Effect of appliance reactivation after decay of initial activation on osteoclasts. Tooth movement, and root resorption. Angle Orthod 69:515-532, 1999 54. Maeda S, Maeda Y, Ono Y, et al: Interdisciplinary treatment of a patient with severe pathologic tooth migration caused by localized aggressive periodontitis. Am J Orthod Dentofacial Orthop 127:374-384, 2005