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Ask an Expert T H I N G S Y O U W A N T T O K N O W Repositioning of the Gingival Margin by Extrusion and Intrusion In one of my recent cases, I used active intrusion of two maxillary central incisors to reposition their gingival margins in an apical direction. These teeth were then restored with porcelain laminate veneers, and the final result was esthetically improved with regard to both clinical crown lengths and labial marginal gingival levels. This case indicates to me that orthodontic treatment can contribute to results that are difficult, if not impossible, to obtain by other means of esthetic dentistry. Furthermore, a recent AJODO article1 from a team in Hong Kong demonstrated that the labial gingival margin of a maxillary canine substituting for a congenitally missing lateral incisor was moved almost 9 mm incisally by means of orthodontic extrusion. These cases imply that the potential of an orthodontist in improving gingival levels may often be overlooked by other dentists. As far as I know, most research on orthodontic intrusion and extrusion of teeth has dealt with tissue reactions other than changes of the gingival levels. What is actually the present knowledge or state-of-the-art when it comes to changes in crown lengths and repositioning of gingival levels associated with tooth movements in the vertical plane? —Arni Thordarson, Reykjavik, Iceland BJÖRN U. ZACHRISSON, OSLO, NORWAY Evaluating crown length discrepancies Ideally, maxillary central incisors are equal in length and the lateral incisors are slightly shorter. The gingival margin of the lateral incisor is located more incisally than on the central incisor. The maxillary canines are about the same length as the central incisors, and their cusp tips are located at the same level as the incisal edges of the centrals. The gingival margins of the canines are at the same height as those of the central incisors.2 If the difference in crown length and gingival contour of the maxillary incisors is substantial, the esthetic appearance can be unsatisfactory, depending on the tooth display on smiling. The discrepancy in crown length is accentuated (1) if a central incisor is abraded or fractured and allowed to erupt, (2) when maxillary canines are substituted for lateral incisors3 or (3) when lateral incisors are moved orthodontically to replace central incisors.4 If both central incisors are shorter than the lateral incisors, like in your case (Fig 1a), your treatment strategy to simultaneously intrude both central incisors to reposition their gingival margins apically (Fig 1b) and create space for porcelain laminate veneers or crowns (Fig 1c) is the optimal method. Extrusion Selective orthodontic extrusion of one, or more, teeth is easy to achieve from a biomechanical point of view. Biologically, such movements closely resemble 72 COPYRIGHT © 2002 BY QUINTESSENCE PUBLISHING CO, INC. PRINTING OF THIS DOCUMENT IS RESTRICTED TO PERSONAL USE ONLY. NO PART OF THIS ARTICLE MAY BE REPRODUCED OR TRANSMITTED IN ANY FORM WITHOUT WRITTEN PERMISSION FROM THE PUBLISHER. a c b Fig 1 Frontal view of female patient, 28 years of age, with a Class II, Division 2 malocclusion, in whom the pretreatment labial gingival levels of both maxillary central incisors were located more incisally than the gingival levels of the lateral incisors and canines (a). The clinical crowns of the central incisors were short, due to abrasive wear and supraeruption. During the orthodontic treatment, the central incisors were actively intruded to normalize the gingival levels of the six anterior teeth (b). Two porcelain laminate veneers (courtesy of Dr Sverker Toreskog, Göteborg, Sweden) were used for crown lengthening (c). (Orthodontic treatment by Dr Arni Thordarson, Reykjavik, Iceland) the natural eruptive tooth movement. The stretching of the gingival and most coronal periodontal ligament fibers leads to coronal migration of the gingiva and attachment apparatus. To allow forced eruption without supraocclusion and occlusal interferences, the crown of the tooth will need to be continuously shortened by grinding (Figs 2 and 3). Since the vertical dimension of the alveolar process and gingiva around the extruded tooth is increased, whereas the osseous and gingival structure of neighboring teeth remain unchanged, 5 a change in the contour of the hard and soft tissues surrounding the extruded tooth will be observed (Figs 2 and 3). Orthodontic extrusion of a “hopeless” tooth that needs to be extracted is thus an excellent method for improvement of the marginal bone and gingival levels associated with the surgical placement of implants. The effect of orthodontic extrusion on the periodontal tissues has been assessed in both clinical studies and animal experiments. Early studies6-9 documented that extrusion results in (1) bone apposition at the alveolar crest as well as at the apex of the relocated tooth, (2) a normal relationship with the cemento-enamel junction (CEJ), and (3) an increase of the width of the zone of attached gingiva (ie, distance from free gingival margin to mucogingival line minus sulcus depth10). These findings demonstrate that the marginal periodontium migrates with the erupting tooth and that the mucogingival junction remains stable. If a coronal displacement of the gingiva and supracrestal connective tissue is not aimed at, and crestal bone apposition is undesired, the forced eruption should be combined with fiberotomy procedures repeated at least every 2 weeks.5,11 The movement of the labial gingival margins with extrusion (3, 6, and 9 mm) of maxillary incisors was studied clinically and histologically in monkeys by Kajiyama, et al.12 Two tattoo marks were placed to indicate the vertical positions of the clinical sulcus bottom and the mucogingival junction. The results showed that the CEJ followed the extruded teeth closely, and the tattoo mark representing the sulcus bottom followed the teeth about 90%. The labial gingival margins followed the teeth about 80%, as the clinical crown length increased with about 20%. The sulcus depth was slightly reduced on the extruded teeth, which could be a temporary reaction. The distance between the two tattoo marks increased; that is, the width of the attached gingiva increased. 73 COPYRIGHT © 2002 BY QUINTESSENCE PUBLISHING CO, INC. PRINTING OF THIS DOCUMENT IS RESTRICTED TO PERSONAL USE ONLY. NO PART OF THIS ARTICLE MAY BE REPRODUCED OR TRANSMITTED IN ANY FORM WITHOUT WRITTEN PERMISSION FROM THE PUBLISHER. a c b Fig 2 Marked labial gingival recession of the maxillary right lateral and central incisors (arrows) in female patient, 55 years of age (a). The brackets on these teeth were rebonded in an apical location and the incisal edges were ground to allow forced eruption without occlusal interferences (b). After 3 months, the gingival levels were more optimal. Four porcelain laminate veneers were then made for esthetic reasons (courtesy of Dr Roy Samuelsson, Oslo, Norway). Note posttreatment symmetry of gingival levels of the six anterior maxillary teeth (c). a b d e c Fig 3 Marked labial gingival recession on maxillary right lateral incisor in female patient, 57 years of age. The exposed root is discolored because of previous endodontic treatment (arrow in a). Bracket on lateral incisor was bonded in an apical location (b). Incisal (arrow in c) and lingual equilibration (d) was made to avoid occlusal interferences during the orthodontic extrusion. After 3 months, the gingiva is repositioned incisally (c). Note amount of grinding (b and c) and that the gingiva did not completely follow the extrusion (see text for explanation), so there is more dark root exposed posttreatment (compare b and c). New, more esthetic, restorations were made on the anterior teeth (courtesy of Dr Roy Samuelsson) after the orthodontic treatment (e and f). f Similarly, Berglundh, et al11 observed in experiments with dogs that orthodontic extrusion without adjunctive fiberotomy induced coronal “growth” of the periodontium. Experimental roots were forced to extrude an average distance of 4.5 mm. The probing depths remained unchanged and the gingival margin receded only by an average of 0.5 mm. This implies that orthodontic extrusion may change the position of the gingival margin and bone crest without undue encroachment of the supracrestal attachment apparatus. The width of the zone of attached gingiva increased, confirming the observations that the marginal periodontium migrates with the erupting tooth, whereas the location of the mucogingival junction remains stable.7,13,14 74 COPYRIGHT © 2002 BY QUINTESSENCE PUBLISHING CO, INC. PRINTING OF THIS DOCUMENT IS RESTRICTED TO PERSONAL USE ONLY. NO PART OF THIS ARTICLE MAY BE REPRODUCED OR TRANSMITTED IN ANY FORM WITHOUT WRITTEN PERMISSION FROM THE PUBLISHER. a b c d e f Fig 4 Active intrusion á la Kokich2,16 with small archwire bends on either side of supraerupted maxillary right central incisor in young adult female patient (a to c). These bends produce an interrupted continuous force with rest periods between the activations. After the orthodontic intrusion of the right central incisor and its labial gingiva, a porcelain laminate veneer (courtesy of Dr Sverker Toreskog) was made to lengthen the clinical crown (d to f) and improve the esthetic result. Together, these animal studies indicated that although the labial gingiva will generally follow an orthodontically extruded tooth, it may be prudent for a clinician to predict that the amount of vertical gain in gingival level will be about 80% of the distance that a tooth is extruded (see Figs 2 and 3). There are few clinical studies in humans on orthodontic extrusion to correct gingival recessions. However, the esthetic improvement in gingival levels in Figs 2 and 3, and in the case report mentioned above,1 is remarkable and should constitute a piece of information for dentists. Intrusion Similar to the case with extrusion, metric and histologic studies have been made after experimental intrusion (1.5 to 5.5 mm) of incisors in monkeys. According to Murakami, et al,15 the gingiva moved about 60% of the distance when the teeth were intruded with a continuous force of 80 to 100 g. The clinical crown shortened and the gingival sulcus deepened because of an accumulation of gingival tissue, not due to swelling of the gingival margin or migration of the sulcus bottom beyond the CEJ. The distance between the incisor edge and the sulcus bottom was unchanged. The data were taken right after the intrusion, so future studies are needed to find out whether the accumulation of gingiva in the animals is temporary or not. Kokich, et al16 reported on five cases with either fractured or traumatically avulsed central incisors in which selective intrusion and restorative techniques were used during the finishing stages of orthodontic treatment to improve the esthetic result. An interrupted, continuous force with small archwire bends on each side of the tooth to be intruded (Figs 4a and 4b) was used for leveling of gingival margins on supraerupted teeth. The stability of tooth intrusion is most likely related to the occlusion. If occlusal contact is re-established after intrusion, the intruded tooth probably will not re-erupt.2 If, due to inadequate oral hygiene measures during the orthodontic treatment or other reasons, some increased probing pocket depth is found at the time of debonding, the 75 COPYRIGHT © 2002 BY QUINTESSENCE PUBLISHING CO, INC. PRINTING OF THIS DOCUMENT IS RESTRICTED TO PERSONAL USE ONLY. NO PART OF THIS ARTICLE MAY BE REPRODUCED OR TRANSMITTED IN ANY FORM WITHOUT WRITTEN PERMISSION FROM THE PUBLISHER. A a b c d e f Fig 5 Traumatic injury case with ankylosed maxillary right central incisor (arrow) in girl, 8 years of age (a). The case was treated by careful extraction of the ankylosed incisor and mesial movement of all teeth in the maxillary right quadrant. During treatment, the lateral incisor to replace the extracted right central incisor was intruded with interrupted continuous forces to make the gingival level more similar to that of the left central incisor (b). The canine to replace the lateral incisor was extruded (c) to move the gingival margin incisally. A local gingivectomy was needed to level the gingiva of the “new” right and the intact left central incisors (d). At a later visit, gingivectomies were also made on the right first premolar to substitute for the canine and on the left lateral incisor. A porcelain laminate veneer was made on the mesially moved lateral incisor, and the chipped left central incisor edge was restored with a composite resin “corner” (both courtesy of Dr Sverker Toreskog). The final result is an almost natural-looking dentition (e and f). incisor intrusion may be supplemented with a simple gingivectomy to correct the crown length discrepancies (Fig 5). A permanent crown length increase corresponding to close to 50% of the original probing depth can be expected when the gingivectomy is made to the bottom of the pocket in young patients.17 In other words, about half the amount of excised gingival tissue will regenerate within some months. However, the gingivectomy after the healing period must not expose the cementum of the tooth, which can lead to tooth sensitivity and an undesirable esthetic result. If inflammation occurs because of a violation of the biologic width, corrective periodontal surgery with flap procedure and ostectomy/osteoplasty is necessary to complete the repositioning of the gingival margin. The alveolar crest should generally be positioned at a distance of at least 3 mm from the future crown margin when prosthetic reconstructions are planned.18 In esthetically critical and visible areas, any occurrence of gingival recession should be observed for about 6 months before a final prosthetic restoration is inserted.18 The effect on crown lengths and gingival levels by intrusion of pathologically extruded incisors in adults with severe periodontal tissue breakdown is discussed elsewhere.19,20 Conclusion The gingiva around a tooth moves along with the tooth in whatever direction the tooth is moved orthodontically. Through slow extrusion or selective intrusion of the appropriate teeth and either reduction or restoration of the incisal edges, the gingival contours and crown lengths of incisors can be made more esthetic. Orthodontic extrusion may be a viable biologic alternative to gingival grafting in some cases of marked labial recession on incisors, particularly if they have been treated endodontically. 76 COPYRIGHT © 2002 BY QUINTESSENCE PUBLISHING CO, INC. PRINTING OF THIS DOCUMENT IS RESTRICTED TO PERSONAL USE ONLY. NO PART OF THIS ARTICLE MAY BE REPRODUCED OR TRANSMITTED IN ANY FORM WITHOUT WRITTEN PERMISSION FROM THE PUBLISHER. References 1. Chay SH, Rabie ABM. Repositioning of the gingival margin by extrusion. Am J Orthod Dentofacial Orthop 2002;122:95–102. 2. Kokich VG. Esthetics and anterior tooth position: An orthodontic perspective. Part I: Crown length. J Esthet Dent 1993;5:19–23. 3. Rosa M, Zachrisson BU. Integrating esthetic dentistry and space closure in patients with missing maxillary lateral incisors. J Clin Orthod 2001;35:221–234. 4. Zachrisson BU. Improving orthodontic results in cases with maxillary incisors missing. Am J Orthod 1978;73:274–289. 5. Kozlovsky A, Tal H, Soldinger M, Straus M. Two different techniques of forced eruption as an aid in the treatment of severely damaged teeth. J Israel Dent Assoc 1988;6:3–8. 6. Reitan K. Clinical and histologic observations on tooth movement during and after orthodontic treatment. Am J Orthod 1967;53:721–745. 7. Batenhorst KF, Bowers GM, Williams JE Jr. Tissue changes resulting from facial tipping and extrusion of incisors in monkeys. J Periodontol 1974;45:660–668. 8. Simon JHS, Lythgoe JB, Torabinejad M. Clinical and histologic evaluation of extruded endodontically treated teeth in dogs. Oral Surg 1980;50:361–371. 9. Van Venroy JR, Yukna RA. Orthodontic extrusion of single teeth affected with advanced periodontal disease. Am J Orthod 1985;87:67–74. 10. Hall WB. The current status of mucogingival problems and their therapy. J Periodont 1981;52:569–575. 11. Berglundh T, Marinello CP, Lindhe J, Thilander B, Liljenberg B. Periodontal tissue reactions to orthodontic extrusion. J Clin Periodontol 1991;18:330–336. 12. Kajiyama K, Murakami T, Yokota S. Gingival reactions after experimentally induced extrusion of the upper incisors in monkeys. Am J Orthod Dentofacial Orthop 1993;104:36–47. 13. Ainamo J, Talari A. The increase with age of the width of attached gingiva. J Periodont Res 1976;11:182–188. 14. Ainamo A. Influence of age on the location of the maxillary mucogingival junction. J Periodont Res 1978;13:189–193. 15. Murakami T, Yokota S, Takahama Y. Periodontal changes after experimentally induced intrusion of the upper incisors in Macaca fuscata monkeys. Am J Orthod Dentofacial Orthop 1989;95:115–126. 16. Kokich VG, Nappen DL, Shapiro PA. Gingival contour and clinical crown length: Their effect on the esthetic appearance of maxillary anterior teeth. Am J Orthod 1984;86:89–94. 17. Monefeldt I, Zachrisson BU. Adjustment of clinical crown height by gingivectomy following orthodontic space closure. Angle Orthod 1977;47:256–264. 18. Brägger U, Lauchenauer D, Lang NP. Surgical lengthening of the clinical crown. J Clin Periodontol 1992;19:58–63. 19. Zachrisson BU. Orthodontics and periodontics. In: Lindhe J, Karring T, Lang NP (eds). Clinical Periodontology and Implant Dentistry. Copenhagen: Munksgaard 1997;741–793. 20. Cardaropoli D, Re S, Corrente G, Abundo R. Intrusion of migrated incisors with infrabony defects in adult periodontal patients. Am J Orthod Dentofacial Orthop 2001;120:671–675. Have a question you would like to see featured in this column? Send it to: T. M. Graber, Editor-in-Chief or E-mail to: [email protected] University of Illinois at Chicago, College of Dentistry 801 South Paulina, M/C 842 Chicago, Illinois 60612, USA 77 COPYRIGHT © 2002 BY QUINTESSENCE PUBLISHING CO, INC. PRINTING OF THIS DOCUMENT IS RESTRICTED TO PERSONAL USE ONLY. NO PART OF THIS ARTICLE MAY BE REPRODUCED OR TRANSMITTED IN ANY FORM WITHOUT WRITTEN PERMISSION FROM THE PUBLISHER.