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Three-dimensional evaluation of surgically assisted implant bone-borne rapid maxillary expansion: A pilot study
CLINICIAN’S CORNER
Three-dimensional evaluation of surgically assisted implant bone-borne rapid maxillary expansion: A pilot study Eve Tausche,a Lars Hansen,b Volker Hietschold,c Manuel O. Lagravère,d and Winfried Harzere Dresden, Germany, and Edmonton, Alberta, Canada Introduction: The purpose of this study was to evaluate 3-dimensional changes in dental, alveolar, and skeletal structures caused by a bone-borne implant-supported rapid maxillary expansion device (Dresden distractor). Methods: Axial computed tomography scans of 10 patients (mean age, 25.3 years) treated with the Dresden distractor were examined. Scans were taken immediately before and 9 months after expansion. Distances in all 3 dimensions were calculated for 38 skeletal, alveolar, and dental landmarks with respect to the reference point ELSA (point equidistant to both foramina spinosa). Results: In the transverse dimension, a V-shaped opening of the suture was shown; the greatest amount of opening was anteriorly directed, with convergence of the suture opening in the posterior aspect of the palate. The expansion of the maxillary dental arch showed a V pattern similar to the opening of the suture. In the frontal view, expansion caused a wedge-shaped opening with its base at the central incisors and the estimated center of rotation next to the frontonasal suture. The alveolar processes tipped buccally (9.9° to 13.3°) as did the molars (2.5° to 3.5°) and the premolars (3.0° to 3.9°). Less tipping of teeth compared with skeletal tipping (about 6° to 9° less) is related to the torque effect of the fixed appliance. Conclusions: The Dresden distractor is a minimally invasive bone-borne expansion appliance that protects teeth by inducing more skeletal than dental changes. This might be a precondition for stable postsurgical occlusion. (Am J Orthod Dentofacial Orthop 2007;131:00)
R
apid maxillary expansion (RME) has become a useful treatment method for severe maxillary transverse deficiencies and posterior crossbites1,2 since its introduction by Angell in 1860.3 In some cases, improvement of nasal obstruction was reported.4,5 RME exerts high forces, up to 227 or 450 N,6-8 that can easily split the midpalatal suture in young patients.2,9 Separation becomes difficult after the midpalatal suture interlocks in late adolescence and even more difficult after fusion in adults because synchondrosis does not occur. RME should be surgically assisted in girls 2 years earlier than in boys.10 There is controversy about the age limit for conservative RME.2,11-13 In spite of the surgical intervention, all severe side effects incurred by transmitting exa
Prof. Dr. Med., Department of Orthodontics, Technical University, Dresden, Germany. b Prof. Med. Dent., Department of Orthodontics, Technical University, Dresden, Germany. c Prof. Med. Dent., Department of Orthodontics, Technical University, Dresden, Germany. d Dr. Rer. Nat., Department of Radiology, Technical University, Dresden, Germany. e MS, Department of Dentistry, University of Alberta, Edmonton, Alberta, Canada. Supported by ITI Foundation, Basel (Switzerland). Reprint requests to: Winfried Harzer, Technical University Carl Gustav Carus, Department of Orthodontics, Fetscherstrasse 74, 01307 Dresden, Germany; e-mail, [email protected]. Submitted, February 2006; revised and accepted, July 2006. 0889-5406/$32.00 Copyright © 2007 by the American Association of Orthodontists. doi:10.1016/j.ajodo.2006.07.021
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pansion forces via the teeth cannot be avoided.14,15 These side effects include loss of pulp vitality, extrusion, root resorption, bony dehiscence, and buccal tipping of the anchor teeth.6,9,10 An alternative to this method is fixing the RME appliance directly to the bone. Historically, ankylosed teeth16 and aluminium oxide implants17 were used as abutments for sutural expansion in animals. In man, osteosynthesis plates made it possible to transfer expansion forces directly to the bone.18-21 A disadvantage to this procedure is the need of a more invasive operation, with a higher risk of infection20 and speech problems because of the appliance’s effect of limiting tongue movement. Our purpose in this study was to execute a 3-dimensional analysis of the movement of teeth, alveolar processes, and skeletal structures caused by a bone-borne RME device, the Dresden distractor (DD). SUBJECTS AND METHODS
The sample consisted of 6 women and 4 men, 18 to 26 years old (mean age, 25.3 years), undergoing RME with the DD. All adults requiring surgically assisted RME from May 2004 to November 2005 were recruited. All patients consented to the treatment procedure. There were no dropouts or appliance failures. In 1 subject, surgical assistance was necessary twice because no opening of the suture after the first operation was recorded. No negative side effects, eg, infections or significant pain, were recorded. Initial diagnostic findings in all patients showed severe
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Fig 3. Intraoral aspect of DD. Fig 1. DD directly fixed to bone with implant (left) and bone screw (right).
Fig 4. Transpalatal arch fixed to implant. Fig 2. Segmented crossed archwires and coil spring for space opening.
maxillary transverse deficiencies combined with Class II or Class III malocclusion or open bite, which made the second orthognathic surgical intervention necessary. Expansion was surgically assisted by using the method of Glassman et al.10 The DD required minimally invasive procedures and was placed during the osteotomy. It was designed to be fixed to the hard palate with an implant on 1 side and a self-tapping bone screw on the other22,23 (Fig 1). To control and improve the symmetric and parallel expansion in the anterior segments of the maxilla, anterior guidance for separating the maxillary halves was provided by crossed, segmented archwires and a tension coil spring for space opening in the incisor region like a tripod (Fig 2). After expansion, the DD was left in place for 3 to 6 months for retention. (Fig 3). Then the implant was used for further anchorage while the transpalatal arch was fixed to the implant (Fig 4). Simultaneous to expansion, orthodontic alignment was performed. The expansion screw was activated 4 times a day (twice in the morning, twice in the evening) for 8 days (± 2) with 29 quarter turns (24 to 36) of 0.25 mm each, causing an average screw expansion of 7.25 mm. Immediately after expansion, the teeth were aligned with a straight wire appliance with an .018-in slot. The diastema was closed by tight ligatures only, without active tension. When taking the second computed tomography (CT) scan, a .016 to .022-in steel wire was placed in the .018-in slot.
Axial spiral CT scans parallel to the occlusal plane were taken before surgically assisted RME and 9 months (± 4) after placement of the appliance, ie, before othognathic surgery. CT reconstruction was carried out in 0.5- to 0.8-mm slices. A specialized radiologist evaluated the CT scans twice with 14 days between the evaluations. By using the program e-film, version 1.5.3 (Aycan, Wuerzburg, Germany), 5 reference points (Fig 5) at the cranial base (right and left auditory external meatus, right and left foramina spinosa, and foramen magnum) and 42 points on teeth, alveolar processes, and skeletal structures were defined.24,25 Using the reference points above allowed verification of treatment changes because, at the age 5 years, this area of the cranial base was reported to have achieved 85% of its total size.26,27 The following points were measured. Dental points (Fig 6): uI, interincisal coronal width (right and left): landmark on mesial surfaces of both maxillary central incisors; uC, upper canine (right and left): point on the middle of the buccal surface of the maxillary canines, corresponding to the bracket slot (this coronal landmark was safer and easier to identify than the cusp tip in axial slices); uB, upper first bicuspid (right and left): point on the middle of the buccal surface of the maxillary first premolars corresponding to the bracket slot; uM, upper first molar (right and left): point on the middle of the buccal surface of the maxillary first molars corresponding to the bracket slot; uIa, interincisal apex width (right and left): point in apices of both maxillary central incisors; uCa, upper canine apex (right and left): point in
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Fig 5. Reference points.
Fig 6. Dental points.
apices of both maxillary canines; uBa, upper first bicuspid buccal apex (right and left): point in apices of both maxillary buccal premolars; uMa, upper first molar buccal apex (right and left), point in apices of both maxillary buccal molars. Dentoalveolar points (Fig 7): ep, endoprämolare (right and left): medial point on inner surface of alveolar ridge corresponding to first maxillary premolar; EP, ectoprämolare (right and left): medial point on outer surface of alveolar ridge corresponding to first maxillary premolar; em, endomolare (right and left): medial point on inner surface of alveolar ridge corresponding to first maxillary molar; EM, ectomolare (right and left): medial point on outer surface of alveolar ridge corresponding to first maxillary molar; epa, endoprämolare apical (right and left): point on inner surface of alveolar ridge corresponding to apex of first premolar; Epa, ectoprämolare apical (right and left): point on outer surface of alveolar ridge corresponding to apex of first premolar; ema, endomolare apical (right and left): point on inner surface of alveolar ridge corresponding to apex of first molar; Ema, ectomolare apical (right and left): point on outer surface of alveolar ridge corresponding to apex of first molar. Skeletal points (Figs 7 and 8): O, low border of orbit (right and left): point
on the lowest part of the lower orbit border; P, piriform (right and left): outermost point on the nasal wall; ANS, anterior nasal spine: anterior nasal spine located above Point A; PNS, posterior nasal spine; Z, zygomaxillare (right and left): lowest point on suture between zygomatic and maxillary bones; A, Point A: Subspinale, the most dorsally located point on the contour of the maxilla; B, Point B: Supramental, the most dorsally located point on the contour of the mandible (symphysis). The reference point ELSA24 (X = 0, Y = 0, Z = 0) at the center of the line connecting the geometric centers of each foramen spinosum was identified (Fig 5). ELSA was chosen because the foramina spinosa were small circles when viewed axially and easy to locate by using the condyle and the glenoid fossa as guides.25 Then, a reference plane (XY horizontal plane) was created by using both the auditory external meatus and ELSA. A second plane (YZ vertical plane) was located perpendicularly to the XY horizontal plane passing through the medial edge of the foramen magnum. By default, the third plane was located perpendicular to the other 2. Coordinates in all other points were obtained with respect to the reference ELSA. The systematic error for point location (SD, 0.627 to 0.806 mm) was
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Fig 9. CT fusion of RME with DD: yellow, pre-expansion; grey, postexpansion.
Fig 7. Dentoalveolar and skeletal points.
Fig 10. Minor dental tipping by RME with DD.
Fig 8. Skeletal points.
checked by taking 3 preoperative and postoperative measurements of 5 randomly selected patients. The time between each measurement session was 14 days. RESULTS
The amount of screw expansion (7.25 mm = 100%) was successfully transmitted 93% to the premolars (6.72 mm [SD, 2.58]) and 89% to the molars (6.44 mm [SD, 1.92]) (Table I).
Fig 11. Tipping of teeth effected by tooth-borne RME.
The transverse increase of the alveolar crest was between 7.15 (SD, 2.3) and 7.18 mm (SD, 1.88) in the molar region, and 7.27 (SD, 2.75) and 7.76 mm (SD, 3.18) in the premolar region. Screw expansion was transmitted 99% in the molar region and 100% respectively 107% in the premolar region (Table I). In the transverse
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Table I. Transverse
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expansion between teeth and alveolar crests and skeletal structures (mm)
Teeth Maxillary central incisors (diastema) Maxillary canines Maxillary first premolars Maxillary first molars Apices of maxillary central incisors Apices of maxillary canines Buccal apices of first premolars Mesiobuccal apices of maxillary first molars Alveolar crest Ectoprämolare Endoprämolare Ectomolare Endomolare Skeletal structures Lower margins of orbitae Piriform Anterior nasal spine Posterior nasal spine Zygomaxillare Point A Point B
Transverse expansion (range)
SD
Significance
Percentage of transmitted expansion of screw (7.25 mm = 100%)
4.57 (2.44–6.7) 5.59 (2.84–8.34) 6.72 (4.14–9.3) 6.44 (4.52–8.36) 3.25 (0.36–6.14) 5.72 (2.33–9.11) 5.79 (3.14–8.44) 6.53 (4.46–8.6)
2.13 2.75 2.58 1.92 2.89 3.39 2.65 2.07
* * * * * * * *
63% 77% 93% 89% 45% 79% 79% 90%
7.27 (4.52–10.02) 7.76 (4.58–10.94) 7.15 (4.85–9.45) 7.18 (5.3–9.06)
2.75 3.18 2.3 1.88
* * * *
100% 107% 99% 99%
0.012 (0.002–0.022) 1.59 (1.01–2.17) 3.91 (1.42–6.4) 1.42 (–0.61–3.45) 0.11 (0.01–0.21) 4.18 (1.15–7.21) –0.17 (–0.37–0.03)
0.01 0.58 2.49 2.03 0.1 3.03 0.2
*
54%
*
58%
*(P <.05).
Table II. Buccal tipping of teeth and alveolar crest (°) Tipping at measuring point, lateral
Tipping at measuring point, medial
Average tipping
Significance
Teeth Maxillary first premolar, right Maxillary first premolar, left Maxillary first molar, right Maxillary first molar, left
3 3.9 3.5 2.5
* * * *
Alveolar crest Premolar region, right Premolar region, left Molar region, right Molar region, left
Ectoprämolare 11.1 Ectoprämolare 10.8 Ectomolare 10.6 Ectomolare 11.8
Endoprämolare 13.3 Endoprämolare 9.9 Endomolare 11.8 Endomolare 10.2
12.2
*
10.4
*
11.2
*
11
*
*(P <.05).
dimension, a V-shaped opening of the suture and the dentition was shown, with the greatest amount of opening anteriorly directed. Expansion caused tipping of teeth (2.5° to 3.9°) and alveolar processes (10.4° to 12.2°) (Table II). Skeletal structures underwent the following changes. Piriform and the lower margins of the orbitae did not change
significantly. The anterior nasal spine showed a significant transverse increase of 3.91 mm (SD, 2.49 mm). However, there was no significant transverse increase in the posterior nasal spine. Changes at the zygomaxillare point were also insignificant. The transverse relation increased significantly at Point A by 4.18 mm (SD, 3.03 mm), whereas Point B underwent no signifi-
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Table III. Tipping of teeth (°) compared with previous studies of surgically assisted RME Distraction modus (DD) Byloff and Mossaz37 Chung and Goldman43 Northway and Meade44
Mossaz et al38
Maxillary first premolar, right
3
—
6.48
5
—
Maxillary first premolar, left
3.9
—
6.48
5
—
Maxillary first molar, right
3.5
9.63
7.04
3 (lingual)
5–20
Maxillary first molar, left
2.5
9.63
7.04
3 (lingual)
5–20
cant changes in the transverse dimension. In the frontal view, expansion caused a pyramidal opening with its base at the central incisors and the estimated center of rotation next to the frontonasal suture. DISCUSSION
ELSA was used as a reference point because the foramina spinosa’s location has a low identification error in both the vertical and horizontal planes,28 and also the foramina spinosa are stable structures because growth is completed in that area at a young age.26,27 This reference point is suitable because of its distance to the expansion area and its fixed position in the basal region of the skull. Changes can be measured at the other measuring points in all 3 dimensions with respect to ELSA. The amount of dental tipping was less in comparison with studies using traditional tooth-borne RME (Table III), although it is obvious that there are great differences between surgical and nonsurgical assisted RME independent of tooth-borne or bone-borne procedure.29 The interdental cleft opening of 4.57 mm confirms a successful expansion and is comparable with other studies.10,11 The opening of the midpalatal suture with the DD is V-shaped in the frontal and horizontal planes. The V opens cranially and anteriorly in the frontal and horizontal plane. These findings agree with previous studies on tooth-borne expansion.9,30-33 Despite surgical assistance, the maxilla continued to be fixed in the pterygoid process area because a down fracture was not carried out, opposite to complete LeFort I osteotomies.34-36 Average increases in the transverse dimension at the alveolar bone were 7.52 mm in the premolar region and 7.17 mm in the molar region. These are greater skeletal increases than were found in other studies with tooth-borne expanders.37,38 The reason for this could be the direct transmission of force to the palatal bone compared with the shock-absorber effect of the periodontal ligament in patients with tooth-borne expansion. The opening movement consisted of a translation and a rotation component, as described by Braun et al.39 The esti-
mated center of rotation is located in the rear midpalatal suture at the height of the third molars and in the area of the frontonasal suture.39 Teeth showed a corresponding V-shaped opening movement with dorsal convergence corresponding to the skeletal findings. Width decreased from 6.72 mm in the first premolar region to 6.44 mm in the area of first molars. The degree of expansion agrees with that noted in previous investigations.11,37,38,40 Nevertheless, some findings contradict those with tooth-borne expansion. Previous studies used tooth-borne appliances with a typical inverted V-expansion of the dental arch for skeletal movement. By using traditional tooth-borne expansion appliances, the posterior dentition undergoes the greatest expansion with a gradually lessening effect toward the anterior dental arch. Whereas the midpalatal suture responds with greater expansion at the anterior palate, the dental expansion’s inverted V pattern correlates to a progressive anteroposterior increase in skeletal resistance.41 Patients treated with the DD had similar V-shaped dental arches and alveolar processes that showed the protective manner in which this method treats the teeth, because its effect is more skeletal than that of a tooth-borne expander. There was 0.8 mm more expansion in the premolar region and 0.73 mm more in the molar region as measured at the alveolar bone than at the teeth (Fig 9). Screw expansion was transmitted to the alveolar bone at a higher rate in comparison with transmission to teeth. These findings can be explained by the direct force application to the bone and the bracket torque effect. The points where forces are transferred by the implantsupported screw to the maxilla are at the top of the palatal bone and thus closer to the center of resistance than with a tooth-borne appliance. It was reported that tooth-borne expansion is less efficient in the skeletal region.37,38,42 Skeletal amount of overall expansion is 15% to 84% in the molar region in patients with surgically assisted, dental fixed expansion.42 A V-shape converging cranially was found in the frontal plane. Width increased on average 4.18 mm at A-point
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and 3.91 mm at anterior nasal spine. The center of rotation corresponded to previous findings near the frontonasal suture.39 The rotation component became visible by buccal tipping of the alveolar crests 11.2° on average. Comparing the smaller buccal tipping of 2.54° tp 3.98° of the maxillary crowns with these findings, the greater skeletal effect becomes obvious, and consequently, the dental protection. When comparing with studies of surgically assisted tooth-borne appliances, the DD showed less dental tipping (Table III) (Figs 10 and 11).37,38,43,44 With conventional tooth-borne Hyrax appliances, regarding expansion force transmission via the teeth, tipping is always greater or at least equal to alveolar ridge tipping. With the DD, the degree of skeletal tipping is greater than the degree of dental tipping caused by the forces transferred directly to the bone. In addition to expansion, orthodontic tooth movements are possible (Fig 3). Torque can raise the teeth and prevent hanging palatal cusps responsible for unwanted occlusal contacts, relapse, and bite opening. Thus, the DD can be used with only a little transverse overcorrection of 0.5 to 1.5 mm.6 A postretention phase relapse was not observed because of the further use of the palatal implant for fixation of the transpalatal bar (Fig 4). Contrary to the DD appliance, overcorrection for the tooth-borne expansion method is recommended until the maxillary palatal cusps are in contact with the mandibular buccal cusps to balance the relapse.45 Chung and Goldman43 even recommended overcorrection in surgically assisted cases. No significant transversal changes in the low orbit borders were found due to their position above the osteotomy line. The increase in width between both piriforms on the outermost nasal rim was also insignificant. Nevertheless, Sandikcioglu and Hazar46 found a significant expansion of 2.1 mm at that landmark.46 An explanation for this is that their patients did not undergo surgical assistance. The same factor applies to the zygomaxillare, because that point was above the line of osteotomy in our patients. No surgery was done in their reference group. The maxilla stayed connected to the facial structures. In our patients, the maxilllary lateral walls were separated, avoiding transmission of forces. Overall, on one hand, our results with a small sample size and no control group must be confirmed with further studies, but, on the other hand, the advantages of CT analysis relative to standard posteroanterior cephalometric analysis for determining craniofacial changes associated with RME and superimpositions give this pilot study high validity. The use of CT allows measurements with lower projection, magnification, and distortion errors. Because this analysis uses internal landmarks and reference planes, measurement errors related to patient positioning in cephalometric analyses were avoided.
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A further advantage of CT-generated imaging is the availability of nontraditional landmarks. In posteroanterior cephalograms, a landmark, chosen based on what can be reproducibly identified, might not be the best representation of the structure of interest. A landmark selected from CT can allow a more valid representation of the structure of interest than posteroanterior cephalometric landmarks. CONCLUSIONS
1. RME with the DD showed V-shaped opening of the suture, dental arch, and alveolar processes with the greatest amount of opening anteriorly directed, converging in the posterior aspect of the palate. 2. In the frontal view, expansion caused a wedge-shaped opening with its base at the central incisors and the estimated center of rotation next to the frontonasal suture. 3. Direct force application to the bone and the torque effect of rectangular archwires resulted in good skeletal effectiveness combined with protection of the teeth. Thus, the teeth tipped 6° to 9° less than the alveolar processes. Root resorption, bony dehiscence, and buccal tipping of teeth were prevented. The DD is also suitable for patients with reduced periodontics, missing teeth, or edentulous maxillae. 4. After removal of the DD, the implant can be used for anchorage to support a transpalatal arch. REFERENCES 1. Derichsweiler H. Gaumennahterweiterung. München: Hanser; 1956. 2. Timms DJ. A study of basal movement with rapid maxillary expansion. Am J Orthod 1980;77:500-7. 3. Angell E. Treatment of irregularities of the permanent teeth or adult teeth. Dent Cosmos 1860;1:540-4. 4. Kunkel M, Ekert O, Wagner W. Veränderungen des nasalen Atemwegs durch transversale Distraktion des Oberkiefers. Mund Kiefer Gesichtschir 1999;3:12-6. 5. Wried S, Kunkel M, Zentner A, Wahlmann UW. Surgically assisted rapid palatal expansion. An acoustic rhinometric, morphometric and sonographic investigation. J Orofac Orthop 2001;62:107-15. 6. Kraut RA. Surgically assisted rapid maxillary expansion by opening the midpalatal suture. J Oral Maxillofac Surg 1984;42:651-5. 7. Isaacson RJ, Wood JL, Ingram AH. Forces produced by rapid maxillary expansion. I and II. Angle Orthod 1964;34:256-70. 8. Isaacson RJ, Zimring JF. Forces produced during rapid maxillary expansion. Angle Orthod 1965;35:178-86. 9. Haas AJ. The treatment of maxillary deficiency by opening the midpalatal suture. Angle Orthod 1965;3:201-17. 10. Glassman AS, Nahigian SJ, Medway JM, Aronowitz HI. Conservative surgical orthodontic adult rapid palatal expansion: sixteen cases. Am J Orthod 1984;86:207-13. 11. Neubert J, Somsiri S, Howaldt HP, Bitter K. Die operative Gaumennahterweiterung durch eine modifizierte Le Fort I osteotomie. DZZ Mund Kiefer Gesichtschir 1989;13:57-64.
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12. Handelman CS. Nonsurgical rapid maxillary alveolar expansion in adults: a clinical evaluation. Angle Orthod 1997;67:291-308. 13. Handelman CS, Wang L, BeGole E, Haas AJ. Nonsurgical rapid maxillary expansion in adults: report on 47 cases using the Haas expander. Angle Orthod 2000;70:129-44. 14. Bertele G, Mercanti M, Stella F. Structural dentofacial variations in maxilla expansion. Minerva Stomatol 1999;48:101-13. 15. Feller KU, Herzmann K, Schimming R, Eckelt U. Gaumennahtsprengung nach glassmann. Mund Kiefer Gesichtschir 1998;2:26-9. 16. Guyman GW, Kokich VG, Oswald RJ. Ankylosed teeth as abutments for palatal expansion in the rhesus monkey. Am J Orthod 1980;77:486-99. 17. Turley PK, Shapiro PA, Moffett BC. The loading of bioglasscoated aluminium oxide implants to produce sutural expansion of the maxillary complex in the pigtail monkey (Macaca nemestrina). Arch Oral Biol 1980;25:459-64. 18. Gerlach KL, Zahl C. Transversal palatal expansion using a palatal distractor. J Orofac Orthop 2003;64:443-9. 19. Mommaerts MY. Transpalatal distraction as a method of maxillary expansion. Br J Oral Maxillofac Surg 1999;37:268-72. 20. Klier B, Zenk W, Langbein U. Stellt die GNE mittels Palatinaldistraktor eine Alternative zur chirurgisch unterstützten Erweiterung mit einer Hyraxapparatur dar? Kieferorthop 2005;19:9-16. 21. Zahl C, Gerlach KL. Palatal distractor. An innovative approach for palatal expansion. Mund Kiefer Gesichtschir 2002;6:446-9. 22. Harzer W, Schneider M, Gedrange T, Tausche E. Direct bone placement of the hyrax fixation screw for surgically assisted rapid palatal expansion (SARPE). J Oral Maxillofac Surg 2006;64:1313-7. 23. Harzer W, Schneider M, Gedrange T. Rapid maxillary expansion with palatal anchorage of the hyrax expansion screw—pilot study with case presentation. J Orofac Orthop 2004;65:419-24. 24. Lagravère MO, Major PW. Proposed reference point for 3dimensional cephalometric analysis with cone-beam computerized tomography. Am J Orthod Dentofacial Orthop 2005;128:657-60. 25. Lagravère MO, Hansen L, Harzer W, Major PW. Plane orientation for standardization in 3-dimensional cephalometric analysis with computerized tomography imaging. Am J Orthod Dentofacial Orthop 2006;129:601-4. 26. Waitzman AA, PosnickJC, Armstrong DC, Pron GE. Craniofacial measurements based on computed tomography: part II. Normal values and growth trends. Cleft Palate Craniofac J 1992;29:118-28. 27. Friede H. Normal development and growth of human neurocranium and cranial base. Scand J Plast Reconstr Surg 1981;15:163-9. 28. Williamson PC, Major PW, Nebbe B, Glover KE. Landmark identification error in submentovertex cephalometrics. A computerized method determining the condylar long axis. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 1998;86:360-9.
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29. Lagravère MO, Major P, Flores-Mir C. Dental and skeletal changes following surgically assisted rapid maxillary expansion. Int J Oral Maxillofac Surg 2006;35:481-7. 30. Haas AJ. Palatal expansion: just the beginning of dentofacial orthopedics. Am J Orthod 1970;57:219-55. 31. Haas AJ. Long-term post-treatment evaluation of rapid palatal expansion. Angle Orthod 1980;50:189-217. 32. Ekström C, Henrikson C, Jensen R. Mineralization in the midpalatal suture after orthodontic expansion. Am J Orthod 1977;71:449-55. 33. Wertz RA. Skeletal and dental changes accompanying rapid midpalatal suture opening. Am J Orthod 1970;58:41-66. 34. Haas AJ. Rapid expansion of the maxillary dental arch and nasal cavity by opening the midpalatal suture. Angle Orthod 1961;31:73-90. 35. Bell RA. A review of maxillary expansion in relation to rate of expansion and patient’s age. Am J Orthod 1982;81:32-7. 36. Reed N, Ghosh J, Nanda RS. Comparison of treatment outcomes with banded and bonded RPE appliances. Am J Orthod Dentofacial Orthop 1999;116:31-40. 37. Byloff FK, Mossaz CF. Skeletal and dental changes following surgically assisted rapid palatal expansion. Eur J Orthod 2004;26:403-9. 38. Mossaz CF, Byloff FK, Richter M. Unilateral and bilateral corticotomies for correction of maxillary transverse discrepancies. Eur J Orthod 1992;14:110-6. 39. Braun S, Bottrel A, Lee KG, Lunazzi JJ, Legan H. The biomechanics of rapid maxillary sutural expansion. Am J Orthod Dentofacial Orthop 2000;118:257-61. 40. Cross DL, McDonald JP. Effect of rapid maxillary expansion on skeletal, dental and nasal structures: a postero-anterior cephalometric study. Eur J Orthod 2000;22:519-28. 41. Davidovitch M, Efstathiou S, Sarne O, Vardimon AD. Skeletal and dental response to rapid maxillary expansion with 2- versus 4-band appliances. Am J Orthod Dentofacial Orthop 2005;127:483-92. 42. Kuo PC, Will LA. Surgical-orthodontic treatment of maxillary construction. State of the art. Oral and Maxillofac Surg Clin of North Am. 1990;2:751-9. 43. Chung CH, Goldman A. Dental tipping immediately after surgically assisted RPE. Eur J Orthod 2003;25:353-8. 44. Northway WM, Meade JB Jr. Surgically assisted rapid maxillary expansion: a comparison of technique, response and stability. Angle Orthod 1997;67:309-20. 45. Krebs A. Midpalatal expansion studies by the implant method over a seven-year period. Rep Congr Eur Orthod Soc 1964;40:131-42. 46. Sandikcioglu M, Hazar S. Skeletal and dental changes after maxillary expansion in the mixed dentition. Am J Orthod Dentofacial Orthop 1997;111:321-7.
Three-dimensional evaluation of surgically assisted implant bone-borne rapid maxillary expansion: A pilot study Eve Tausche,a Lars Hansen,b Volker Hietschold,c Manuel O. Lagravère,d and Winfried Harzere Dresden, Germany, and Edmonton, Alberta, Canada Introduction: The purpose of this study was to evaluate 3-dimensional changes in dental, alveolar, and skeletal structures caused by a bone-borne implant-supported rapid maxillary expansion device (Dresden distractor). Methods: Axial computed tomography scans of 10 patients (mean age, 25.3 years) treated with the Dresden distractor were examined. Scans were taken immediately before and 9 months after expansion. Distances in all 3 dimensions were calculated for 38 skeletal, alveolar, and dental landmarks with respect to the reference point ELSA (point equidistant to both foramina spinosa). Results: In the transverse dimension, a V-shaped opening of the suture was shown; the greatest amount of opening was anteriorly directed, with convergence of the suture opening in the posterior aspect of the palate. The expansion of the maxillary dental arch showed a V pattern similar to the opening of the suture. In the frontal view, expansion caused a wedge-shaped opening with its base at the central incisors and the estimated center of rotation next to the frontonasal suture. The alveolar processes tipped buccally (9.9° to 13.3°) as did the molars (2.5° to 3.5°) and the premolars (3.0° to 3.9°). Less tipping of teeth compared with skeletal tipping (about 6° to 9° less) is related to the torque effect of the fixed appliance. Conclusions: The Dresden distractor is a minimally invasive bone-borne expansion appliance that protects teeth by inducing more skeletal than dental changes. This might be a precondition for stable postsurgical occlusion. (Am J Orthod Dentofacial Orthop 2007;131:00)
R
apid maxillary expansion (RME) has become a useful treatment method for severe maxillary transverse deficiencies and posterior crossbites1,2 since its introduction by Angell in 1860.3 In some cases, improvement of nasal obstruction was reported.4,5 RME exerts high forces, up to 227 or 450 N,6-8 that can easily split the midpalatal suture in young patients.2,9 Separation becomes difficult after the midpalatal suture interlocks in late adolescence and even more difficult after fusion in adults because synchondrosis does not occur. RME should be surgically assisted in girls 2 years earlier than in boys.10 There is controversy about the age limit for conservative RME.2,11-13 In spite of the surgical intervention, all severe side effects incurred by transmitting exa
Prof. Dr. Med., Department of Orthodontics, Technical University, Dresden, Germany. b Prof. Med. Dent., Department of Orthodontics, Technical University, Dresden, Germany. c Prof. Med. Dent., Department of Orthodontics, Technical University, Dresden, Germany. d Dr. Rer. Nat., Department of Radiology, Technical University, Dresden, Germany. e MS, Department of Dentistry, University of Alberta, Edmonton, Alberta, Canada. Supported by ITI Foundation, Basel (Switzerland). Reprint requests to: Winfried Harzer, Technical University Carl Gustav Carus, Department of Orthodontics, Fetscherstrasse 74, 01307 Dresden, Germany; e-mail, [email protected]. Submitted, February 2006; revised and accepted, July 2006. 0889-5406/$32.00 Copyright © 2007 by the American Association of Orthodontists. doi:10.1016/j.ajodo.2006.07.021
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pansion forces via the teeth cannot be avoided.14,15 These side effects include loss of pulp vitality, extrusion, root resorption, bony dehiscence, and buccal tipping of the anchor teeth.6,9,10 An alternative to this method is fixing the RME appliance directly to the bone. Historically, ankylosed teeth16 and aluminium oxide implants17 were used as abutments for sutural expansion in animals. In man, osteosynthesis plates made it possible to transfer expansion forces directly to the bone.18-21 A disadvantage to this procedure is the need of a more invasive operation, with a higher risk of infection20 and speech problems because of the appliance’s effect of limiting tongue movement. Our purpose in this study was to execute a 3-dimensional analysis of the movement of teeth, alveolar processes, and skeletal structures caused by a bone-borne RME device, the Dresden distractor (DD). SUBJECTS AND METHODS
The sample consisted of 6 women and 4 men, 18 to 26 years old (mean age, 25.3 years), undergoing RME with the DD. All adults requiring surgically assisted RME from May 2004 to November 2005 were recruited. All patients consented to the treatment procedure. There were no dropouts or appliance failures. In 1 subject, surgical assistance was necessary twice because no opening of the suture after the first operation was recorded. No negative side effects, eg, infections or significant pain, were recorded. Initial diagnostic findings in all patients showed severe
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Fig 3. Intraoral aspect of DD. Fig 1. DD directly fixed to bone with implant (left) and bone screw (right).
Fig 4. Transpalatal arch fixed to implant. Fig 2. Segmented crossed archwires and coil spring for space opening.
maxillary transverse deficiencies combined with Class II or Class III malocclusion or open bite, which made the second orthognathic surgical intervention necessary. Expansion was surgically assisted by using the method of Glassman et al.10 The DD required minimally invasive procedures and was placed during the osteotomy. It was designed to be fixed to the hard palate with an implant on 1 side and a self-tapping bone screw on the other22,23 (Fig 1). To control and improve the symmetric and parallel expansion in the anterior segments of the maxilla, anterior guidance for separating the maxillary halves was provided by crossed, segmented archwires and a tension coil spring for space opening in the incisor region like a tripod (Fig 2). After expansion, the DD was left in place for 3 to 6 months for retention. (Fig 3). Then the implant was used for further anchorage while the transpalatal arch was fixed to the implant (Fig 4). Simultaneous to expansion, orthodontic alignment was performed. The expansion screw was activated 4 times a day (twice in the morning, twice in the evening) for 8 days (± 2) with 29 quarter turns (24 to 36) of 0.25 mm each, causing an average screw expansion of 7.25 mm. Immediately after expansion, the teeth were aligned with a straight wire appliance with an .018-in slot. The diastema was closed by tight ligatures only, without active tension. When taking the second computed tomography (CT) scan, a .016 to .022-in steel wire was placed in the .018-in slot.
Axial spiral CT scans parallel to the occlusal plane were taken before surgically assisted RME and 9 months (± 4) after placement of the appliance, ie, before othognathic surgery. CT reconstruction was carried out in 0.5- to 0.8-mm slices. A specialized radiologist evaluated the CT scans twice with 14 days between the evaluations. By using the program e-film, version 1.5.3 (Aycan, Wuerzburg, Germany), 5 reference points (Fig 5) at the cranial base (right and left auditory external meatus, right and left foramina spinosa, and foramen magnum) and 42 points on teeth, alveolar processes, and skeletal structures were defined.24,25 Using the reference points above allowed verification of treatment changes because, at the age 5 years, this area of the cranial base was reported to have achieved 85% of its total size.26,27 The following points were measured. Dental points (Fig 6): uI, interincisal coronal width (right and left): landmark on mesial surfaces of both maxillary central incisors; uC, upper canine (right and left): point on the middle of the buccal surface of the maxillary canines, corresponding to the bracket slot (this coronal landmark was safer and easier to identify than the cusp tip in axial slices); uB, upper first bicuspid (right and left): point on the middle of the buccal surface of the maxillary first premolars corresponding to the bracket slot; uM, upper first molar (right and left): point on the middle of the buccal surface of the maxillary first molars corresponding to the bracket slot; uIa, interincisal apex width (right and left): point in apices of both maxillary central incisors; uCa, upper canine apex (right and left): point in
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Fig 5. Reference points.
Fig 6. Dental points.
apices of both maxillary canines; uBa, upper first bicuspid buccal apex (right and left): point in apices of both maxillary buccal premolars; uMa, upper first molar buccal apex (right and left), point in apices of both maxillary buccal molars. Dentoalveolar points (Fig 7): ep, endoprämolare (right and left): medial point on inner surface of alveolar ridge corresponding to first maxillary premolar; EP, ectoprämolare (right and left): medial point on outer surface of alveolar ridge corresponding to first maxillary premolar; em, endomolare (right and left): medial point on inner surface of alveolar ridge corresponding to first maxillary molar; EM, ectomolare (right and left): medial point on outer surface of alveolar ridge corresponding to first maxillary molar; epa, endoprämolare apical (right and left): point on inner surface of alveolar ridge corresponding to apex of first premolar; Epa, ectoprämolare apical (right and left): point on outer surface of alveolar ridge corresponding to apex of first premolar; ema, endomolare apical (right and left): point on inner surface of alveolar ridge corresponding to apex of first molar; Ema, ectomolare apical (right and left): point on outer surface of alveolar ridge corresponding to apex of first molar. Skeletal points (Figs 7 and 8): O, low border of orbit (right and left): point
on the lowest part of the lower orbit border; P, piriform (right and left): outermost point on the nasal wall; ANS, anterior nasal spine: anterior nasal spine located above Point A; PNS, posterior nasal spine; Z, zygomaxillare (right and left): lowest point on suture between zygomatic and maxillary bones; A, Point A: Subspinale, the most dorsally located point on the contour of the maxilla; B, Point B: Supramental, the most dorsally located point on the contour of the mandible (symphysis). The reference point ELSA24 (X = 0, Y = 0, Z = 0) at the center of the line connecting the geometric centers of each foramen spinosum was identified (Fig 5). ELSA was chosen because the foramina spinosa were small circles when viewed axially and easy to locate by using the condyle and the glenoid fossa as guides.25 Then, a reference plane (XY horizontal plane) was created by using both the auditory external meatus and ELSA. A second plane (YZ vertical plane) was located perpendicularly to the XY horizontal plane passing through the medial edge of the foramen magnum. By default, the third plane was located perpendicular to the other 2. Coordinates in all other points were obtained with respect to the reference ELSA. The systematic error for point location (SD, 0.627 to 0.806 mm) was
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Fig 9. CT fusion of RME with DD: yellow, pre-expansion; grey, postexpansion.
Fig 7. Dentoalveolar and skeletal points.
Fig 10. Minor dental tipping by RME with DD.
Fig 8. Skeletal points.
checked by taking 3 preoperative and postoperative measurements of 5 randomly selected patients. The time between each measurement session was 14 days. RESULTS
The amount of screw expansion (7.25 mm = 100%) was successfully transmitted 93% to the premolars (6.72 mm [SD, 2.58]) and 89% to the molars (6.44 mm [SD, 1.92]) (Table I).
Fig 11. Tipping of teeth effected by tooth-borne RME.
The transverse increase of the alveolar crest was between 7.15 (SD, 2.3) and 7.18 mm (SD, 1.88) in the molar region, and 7.27 (SD, 2.75) and 7.76 mm (SD, 3.18) in the premolar region. Screw expansion was transmitted 99% in the molar region and 100% respectively 107% in the premolar region (Table I). In the transverse
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Table I. Transverse
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expansion between teeth and alveolar crests and skeletal structures (mm)
Teeth Maxillary central incisors (diastema) Maxillary canines Maxillary first premolars Maxillary first molars Apices of maxillary central incisors Apices of maxillary canines Buccal apices of first premolars Mesiobuccal apices of maxillary first molars Alveolar crest Ectoprämolare Endoprämolare Ectomolare Endomolare Skeletal structures Lower margins of orbitae Piriform Anterior nasal spine Posterior nasal spine Zygomaxillare Point A Point B
Transverse expansion (range)
SD
Significance
Percentage of transmitted expansion of screw (7.25 mm = 100%)
4.57 (2.44–6.7) 5.59 (2.84–8.34) 6.72 (4.14–9.3) 6.44 (4.52–8.36) 3.25 (0.36–6.14) 5.72 (2.33–9.11) 5.79 (3.14–8.44) 6.53 (4.46–8.6)
2.13 2.75 2.58 1.92 2.89 3.39 2.65 2.07
* * * * * * * *
63% 77% 93% 89% 45% 79% 79% 90%
7.27 (4.52–10.02) 7.76 (4.58–10.94) 7.15 (4.85–9.45) 7.18 (5.3–9.06)
2.75 3.18 2.3 1.88
* * * *
100% 107% 99% 99%
0.012 (0.002–0.022) 1.59 (1.01–2.17) 3.91 (1.42–6.4) 1.42 (–0.61–3.45) 0.11 (0.01–0.21) 4.18 (1.15–7.21) –0.17 (–0.37–0.03)
0.01 0.58 2.49 2.03 0.1 3.03 0.2
*
54%
*
58%
*(P <.05).
Table II. Buccal tipping of teeth and alveolar crest (°) Tipping at measuring point, lateral
Tipping at measuring point, medial
Average tipping
Significance
Teeth Maxillary first premolar, right Maxillary first premolar, left Maxillary first molar, right Maxillary first molar, left
3 3.9 3.5 2.5
* * * *
Alveolar crest Premolar region, right Premolar region, left Molar region, right Molar region, left
Ectoprämolare 11.1 Ectoprämolare 10.8 Ectomolare 10.6 Ectomolare 11.8
Endoprämolare 13.3 Endoprämolare 9.9 Endomolare 11.8 Endomolare 10.2
12.2
*
10.4
*
11.2
*
11
*
*(P <.05).
dimension, a V-shaped opening of the suture and the dentition was shown, with the greatest amount of opening anteriorly directed. Expansion caused tipping of teeth (2.5° to 3.9°) and alveolar processes (10.4° to 12.2°) (Table II). Skeletal structures underwent the following changes. Piriform and the lower margins of the orbitae did not change
significantly. The anterior nasal spine showed a significant transverse increase of 3.91 mm (SD, 2.49 mm). However, there was no significant transverse increase in the posterior nasal spine. Changes at the zygomaxillare point were also insignificant. The transverse relation increased significantly at Point A by 4.18 mm (SD, 3.03 mm), whereas Point B underwent no signifi-
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Table III. Tipping of teeth (°) compared with previous studies of surgically assisted RME Distraction modus (DD) Byloff and Mossaz37 Chung and Goldman43 Northway and Meade44
Mossaz et al38
Maxillary first premolar, right
3
—
6.48
5
—
Maxillary first premolar, left
3.9
—
6.48
5
—
Maxillary first molar, right
3.5
9.63
7.04
3 (lingual)
5–20
Maxillary first molar, left
2.5
9.63
7.04
3 (lingual)
5–20
cant changes in the transverse dimension. In the frontal view, expansion caused a pyramidal opening with its base at the central incisors and the estimated center of rotation next to the frontonasal suture. DISCUSSION
ELSA was used as a reference point because the foramina spinosa’s location has a low identification error in both the vertical and horizontal planes,28 and also the foramina spinosa are stable structures because growth is completed in that area at a young age.26,27 This reference point is suitable because of its distance to the expansion area and its fixed position in the basal region of the skull. Changes can be measured at the other measuring points in all 3 dimensions with respect to ELSA. The amount of dental tipping was less in comparison with studies using traditional tooth-borne RME (Table III), although it is obvious that there are great differences between surgical and nonsurgical assisted RME independent of tooth-borne or bone-borne procedure.29 The interdental cleft opening of 4.57 mm confirms a successful expansion and is comparable with other studies.10,11 The opening of the midpalatal suture with the DD is V-shaped in the frontal and horizontal planes. The V opens cranially and anteriorly in the frontal and horizontal plane. These findings agree with previous studies on tooth-borne expansion.9,30-33 Despite surgical assistance, the maxilla continued to be fixed in the pterygoid process area because a down fracture was not carried out, opposite to complete LeFort I osteotomies.34-36 Average increases in the transverse dimension at the alveolar bone were 7.52 mm in the premolar region and 7.17 mm in the molar region. These are greater skeletal increases than were found in other studies with tooth-borne expanders.37,38 The reason for this could be the direct transmission of force to the palatal bone compared with the shock-absorber effect of the periodontal ligament in patients with tooth-borne expansion. The opening movement consisted of a translation and a rotation component, as described by Braun et al.39 The esti-
mated center of rotation is located in the rear midpalatal suture at the height of the third molars and in the area of the frontonasal suture.39 Teeth showed a corresponding V-shaped opening movement with dorsal convergence corresponding to the skeletal findings. Width decreased from 6.72 mm in the first premolar region to 6.44 mm in the area of first molars. The degree of expansion agrees with that noted in previous investigations.11,37,38,40 Nevertheless, some findings contradict those with tooth-borne expansion. Previous studies used tooth-borne appliances with a typical inverted V-expansion of the dental arch for skeletal movement. By using traditional tooth-borne expansion appliances, the posterior dentition undergoes the greatest expansion with a gradually lessening effect toward the anterior dental arch. Whereas the midpalatal suture responds with greater expansion at the anterior palate, the dental expansion’s inverted V pattern correlates to a progressive anteroposterior increase in skeletal resistance.41 Patients treated with the DD had similar V-shaped dental arches and alveolar processes that showed the protective manner in which this method treats the teeth, because its effect is more skeletal than that of a tooth-borne expander. There was 0.8 mm more expansion in the premolar region and 0.73 mm more in the molar region as measured at the alveolar bone than at the teeth (Fig 9). Screw expansion was transmitted to the alveolar bone at a higher rate in comparison with transmission to teeth. These findings can be explained by the direct force application to the bone and the bracket torque effect. The points where forces are transferred by the implantsupported screw to the maxilla are at the top of the palatal bone and thus closer to the center of resistance than with a tooth-borne appliance. It was reported that tooth-borne expansion is less efficient in the skeletal region.37,38,42 Skeletal amount of overall expansion is 15% to 84% in the molar region in patients with surgically assisted, dental fixed expansion.42 A V-shape converging cranially was found in the frontal plane. Width increased on average 4.18 mm at A-point
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and 3.91 mm at anterior nasal spine. The center of rotation corresponded to previous findings near the frontonasal suture.39 The rotation component became visible by buccal tipping of the alveolar crests 11.2° on average. Comparing the smaller buccal tipping of 2.54° tp 3.98° of the maxillary crowns with these findings, the greater skeletal effect becomes obvious, and consequently, the dental protection. When comparing with studies of surgically assisted tooth-borne appliances, the DD showed less dental tipping (Table III) (Figs 10 and 11).37,38,43,44 With conventional tooth-borne Hyrax appliances, regarding expansion force transmission via the teeth, tipping is always greater or at least equal to alveolar ridge tipping. With the DD, the degree of skeletal tipping is greater than the degree of dental tipping caused by the forces transferred directly to the bone. In addition to expansion, orthodontic tooth movements are possible (Fig 3). Torque can raise the teeth and prevent hanging palatal cusps responsible for unwanted occlusal contacts, relapse, and bite opening. Thus, the DD can be used with only a little transverse overcorrection of 0.5 to 1.5 mm.6 A postretention phase relapse was not observed because of the further use of the palatal implant for fixation of the transpalatal bar (Fig 4). Contrary to the DD appliance, overcorrection for the tooth-borne expansion method is recommended until the maxillary palatal cusps are in contact with the mandibular buccal cusps to balance the relapse.45 Chung and Goldman43 even recommended overcorrection in surgically assisted cases. No significant transversal changes in the low orbit borders were found due to their position above the osteotomy line. The increase in width between both piriforms on the outermost nasal rim was also insignificant. Nevertheless, Sandikcioglu and Hazar46 found a significant expansion of 2.1 mm at that landmark.46 An explanation for this is that their patients did not undergo surgical assistance. The same factor applies to the zygomaxillare, because that point was above the line of osteotomy in our patients. No surgery was done in their reference group. The maxilla stayed connected to the facial structures. In our patients, the maxilllary lateral walls were separated, avoiding transmission of forces. Overall, on one hand, our results with a small sample size and no control group must be confirmed with further studies, but, on the other hand, the advantages of CT analysis relative to standard posteroanterior cephalometric analysis for determining craniofacial changes associated with RME and superimpositions give this pilot study high validity. The use of CT allows measurements with lower projection, magnification, and distortion errors. Because this analysis uses internal landmarks and reference planes, measurement errors related to patient positioning in cephalometric analyses were avoided.
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A further advantage of CT-generated imaging is the availability of nontraditional landmarks. In posteroanterior cephalograms, a landmark, chosen based on what can be reproducibly identified, might not be the best representation of the structure of interest. A landmark selected from CT can allow a more valid representation of the structure of interest than posteroanterior cephalometric landmarks. CONCLUSIONS
1. RME with the DD showed V-shaped opening of the suture, dental arch, and alveolar processes with the greatest amount of opening anteriorly directed, converging in the posterior aspect of the palate. 2. In the frontal view, expansion caused a wedge-shaped opening with its base at the central incisors and the estimated center of rotation next to the frontonasal suture. 3. Direct force application to the bone and the torque effect of rectangular archwires resulted in good skeletal effectiveness combined with protection of the teeth. Thus, the teeth tipped 6° to 9° less than the alveolar processes. Root resorption, bony dehiscence, and buccal tipping of teeth were prevented. The DD is also suitable for patients with reduced periodontics, missing teeth, or edentulous maxillae. 4. After removal of the DD, the implant can be used for anchorage to support a transpalatal arch. REFERENCES 1. Derichsweiler H. Gaumennahterweiterung. München: Hanser; 1956. 2. Timms DJ. A study of basal movement with rapid maxillary expansion. Am J Orthod 1980;77:500-7. 3. Angell E. Treatment of irregularities of the permanent teeth or adult teeth. Dent Cosmos 1860;1:540-4. 4. Kunkel M, Ekert O, Wagner W. Veränderungen des nasalen Atemwegs durch transversale Distraktion des Oberkiefers. Mund Kiefer Gesichtschir 1999;3:12-6. 5. Wried S, Kunkel M, Zentner A, Wahlmann UW. Surgically assisted rapid palatal expansion. An acoustic rhinometric, morphometric and sonographic investigation. J Orofac Orthop 2001;62:107-15. 6. Kraut RA. Surgically assisted rapid maxillary expansion by opening the midpalatal suture. J Oral Maxillofac Surg 1984;42:651-5. 7. Isaacson RJ, Wood JL, Ingram AH. Forces produced by rapid maxillary expansion. I and II. Angle Orthod 1964;34:256-70. 8. Isaacson RJ, Zimring JF. Forces produced during rapid maxillary expansion. Angle Orthod 1965;35:178-86. 9. Haas AJ. The treatment of maxillary deficiency by opening the midpalatal suture. Angle Orthod 1965;3:201-17. 10. Glassman AS, Nahigian SJ, Medway JM, Aronowitz HI. Conservative surgical orthodontic adult rapid palatal expansion: sixteen cases. Am J Orthod 1984;86:207-13. 11. Neubert J, Somsiri S, Howaldt HP, Bitter K. Die operative Gaumennahterweiterung durch eine modifizierte Le Fort I osteotomie. DZZ Mund Kiefer Gesichtschir 1989;13:57-64.
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12. Handelman CS. Nonsurgical rapid maxillary alveolar expansion in adults: a clinical evaluation. Angle Orthod 1997;67:291-308. 13. Handelman CS, Wang L, BeGole E, Haas AJ. Nonsurgical rapid maxillary expansion in adults: report on 47 cases using the Haas expander. Angle Orthod 2000;70:129-44. 14. Bertele G, Mercanti M, Stella F. Structural dentofacial variations in maxilla expansion. Minerva Stomatol 1999;48:101-13. 15. Feller KU, Herzmann K, Schimming R, Eckelt U. Gaumennahtsprengung nach glassmann. Mund Kiefer Gesichtschir 1998;2:26-9. 16. Guyman GW, Kokich VG, Oswald RJ. Ankylosed teeth as abutments for palatal expansion in the rhesus monkey. Am J Orthod 1980;77:486-99. 17. Turley PK, Shapiro PA, Moffett BC. The loading of bioglasscoated aluminium oxide implants to produce sutural expansion of the maxillary complex in the pigtail monkey (Macaca nemestrina). Arch Oral Biol 1980;25:459-64. 18. Gerlach KL, Zahl C. Transversal palatal expansion using a palatal distractor. J Orofac Orthop 2003;64:443-9. 19. Mommaerts MY. Transpalatal distraction as a method of maxillary expansion. Br J Oral Maxillofac Surg 1999;37:268-72. 20. Klier B, Zenk W, Langbein U. Stellt die GNE mittels Palatinaldistraktor eine Alternative zur chirurgisch unterstützten Erweiterung mit einer Hyraxapparatur dar? Kieferorthop 2005;19:9-16. 21. Zahl C, Gerlach KL. Palatal distractor. An innovative approach for palatal expansion. Mund Kiefer Gesichtschir 2002;6:446-9. 22. Harzer W, Schneider M, Gedrange T, Tausche E. Direct bone placement of the hyrax fixation screw for surgically assisted rapid palatal expansion (SARPE). J Oral Maxillofac Surg 2006;64:1313-7. 23. Harzer W, Schneider M, Gedrange T. Rapid maxillary expansion with palatal anchorage of the hyrax expansion screw—pilot study with case presentation. J Orofac Orthop 2004;65:419-24. 24. Lagravère MO, Major PW. Proposed reference point for 3dimensional cephalometric analysis with cone-beam computerized tomography. Am J Orthod Dentofacial Orthop 2005;128:657-60. 25. Lagravère MO, Hansen L, Harzer W, Major PW. Plane orientation for standardization in 3-dimensional cephalometric analysis with computerized tomography imaging. Am J Orthod Dentofacial Orthop 2006;129:601-4. 26. Waitzman AA, PosnickJC, Armstrong DC, Pron GE. Craniofacial measurements based on computed tomography: part II. Normal values and growth trends. Cleft Palate Craniofac J 1992;29:118-28. 27. Friede H. Normal development and growth of human neurocranium and cranial base. Scand J Plast Reconstr Surg 1981;15:163-9. 28. Williamson PC, Major PW, Nebbe B, Glover KE. Landmark identification error in submentovertex cephalometrics. A computerized method determining the condylar long axis. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 1998;86:360-9.
Tausche et al
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29. Lagravère MO, Major P, Flores-Mir C. Dental and skeletal changes following surgically assisted rapid maxillary expansion. Int J Oral Maxillofac Surg 2006;35:481-7. 30. Haas AJ. Palatal expansion: just the beginning of dentofacial orthopedics. Am J Orthod 1970;57:219-55. 31. Haas AJ. Long-term post-treatment evaluation of rapid palatal expansion. Angle Orthod 1980;50:189-217. 32. Ekström C, Henrikson C, Jensen R. Mineralization in the midpalatal suture after orthodontic expansion. Am J Orthod 1977;71:449-55. 33. Wertz RA. Skeletal and dental changes accompanying rapid midpalatal suture opening. Am J Orthod 1970;58:41-66. 34. Haas AJ. Rapid expansion of the maxillary dental arch and nasal cavity by opening the midpalatal suture. Angle Orthod 1961;31:73-90. 35. Bell RA. A review of maxillary expansion in relation to rate of expansion and patient’s age. Am J Orthod 1982;81:32-7. 36. Reed N, Ghosh J, Nanda RS. Comparison of treatment outcomes with banded and bonded RPE appliances. Am J Orthod Dentofacial Orthop 1999;116:31-40. 37. Byloff FK, Mossaz CF. Skeletal and dental changes following surgically assisted rapid palatal expansion. Eur J Orthod 2004;26:403-9. 38. Mossaz CF, Byloff FK, Richter M. Unilateral and bilateral corticotomies for correction of maxillary transverse discrepancies. Eur J Orthod 1992;14:110-6. 39. Braun S, Bottrel A, Lee KG, Lunazzi JJ, Legan H. The biomechanics of rapid maxillary sutural expansion. Am J Orthod Dentofacial Orthop 2000;118:257-61. 40. Cross DL, McDonald JP. Effect of rapid maxillary expansion on skeletal, dental and nasal structures: a postero-anterior cephalometric study. Eur J Orthod 2000;22:519-28. 41. Davidovitch M, Efstathiou S, Sarne O, Vardimon AD. Skeletal and dental response to rapid maxillary expansion with 2- versus 4-band appliances. Am J Orthod Dentofacial Orthop 2005;127:483-92. 42. Kuo PC, Will LA. Surgical-orthodontic treatment of maxillary construction. State of the art. Oral and Maxillofac Surg Clin of North Am. 1990;2:751-9. 43. Chung CH, Goldman A. Dental tipping immediately after surgically assisted RPE. Eur J Orthod 2003;25:353-8. 44. Northway WM, Meade JB Jr. Surgically assisted rapid maxillary expansion: a comparison of technique, response and stability. Angle Orthod 1997;67:309-20. 45. Krebs A. Midpalatal expansion studies by the implant method over a seven-year period. Rep Congr Eur Orthod Soc 1964;40:131-42. 46. Sandikcioglu M, Hazar S. Skeletal and dental changes after maxillary expansion in the mixed dentition. Am J Orthod Dentofacial Orthop 1997;111:321-7.