Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
10.5005/jp-journals-10021-1200 RESEARCH ARTICLE Revathi Peddu et al Mechanical Reaction of Facial Skeleton to Rapid Palatal Expansion Devices using Laser Holography: An in vitro Study 1 Revathi Peddu, 2Uma Maheswari, 3Kalyani Sreedhar Mallavarapu 4 Shyam Kumar Bandaru, 5Sai Prakash Adusumilli, 6SRK Reddy ABSTRACT Introduction: Rapid palatal expansion of the midpalatal suture is an effective method for the correction of transverse malocclusions. This study was conducted to compare the reaction of circum-maxillary sutures and center of resistance of molar to the Hyrax appliance with different degrees of activations and the Spring jet appliance using laser holography on a freshly macerated skull. Materials and methods: A freshly macerated skull with well-aligned teeth and intact dental arches was used as the experimental model. The Hyrax appliance and Spring jet appliances were fabricated and analyzed qualitatively and quantitatively by using double exposure hologram. Hyrax was activated two ¼ turns, four ¼ turns and eight ¼ turns. The Spring jet is activated and double exposure hologram was recorded. Results: Results were obtained qualitatively by observing the fringes, and quantitatively by counting the number of fringes. The Spring jet showed fringes only in the first molar area, whereas the Hyrax showed fringes along the circum-maxillary sutures and the first molar area; and the number of fringes increased with the number of turns. Conclusion: Hyrax appliance activation produced mechanical reactions on the teeth, alveolar bone, maxilla and the circum-maxillary bones and sutures. The displacement and fringes increased progressively with two, four and eight turns activation of hyrax. The pattern of the fringes was more circular around the nasomaxillary complex and zygomaticomaxillary sutures, suggesting rotational displacement of the maxilla. The number and pattern of fringes produced by the Spring jet appliances suggest that it produces only dentoalveolar changes and minimal orthopedic affects. Keywords: Rapid palatal expansion, Hyrax appliance, Spring jet appliance, Laser holography. How to cite this article: Peddu R, Maheswari U, Mallavarapu KS, Bandaru SK, Adusumilli SP, Reddy SRK. Mechanical Reaction of Facial Skeleton to Rapid Palatal Expansion Devices using Laser Holography: An in vitro Study. J Indian Orthod Soc 2013;47(4):426-432. INTRODUCTION Rapid palatal expansion of the midpalatal suture is an important part of the clinician’s armamentarium in the correction of malocclusions. Rapid maxillary expansion by opening of the midpalatal suture is extremely advantageous in the treatment of: 1. Both surgical and nonsurgical Class III cases especially the nonsurgical ones. 2. Cases of real and relative maxillary deficiency. 3. Cases of inadequate nasal capacity exhibiting chronic nasal respiratory problems. 4. The mature cleft palate patient. 1,2,4-6 Professor, 3Senior Lecturer Department of Orthodontics, Meenakshi Ammal Dental College Chennai, Tamil Nadu, India 2 1,3-6 Department of Orthodontics, Sibar Institute of Dental Sciences Guntur, Andhra Pradesh, India Corresponding Author: Revathi Peddu, Professor, Department of Orthodontics, Sibar Institute of Dental Sciences, Guntur, Andhra Pradesh India, Phone: 09848885654, e-mail: [email protected] Received on: 29/4/13 Accepted after Revision: 25/6/13 426 5. Selected arch length problems to avoid the profile disturbances so frequently associated with removal of teeth (Andrew).1 It has been reported that the transverse forces applied by the Hyrax appliance is of sufficient magnitude to overcome the bioelastic strength of the sutural elements to bring about the orthopedic separation of the maxillary segment. Newer appliances like the Spring jet introduced by Aldocarano2 which incorporates the NiTi open coil spring in a telescopic device has been shown to produce rapid maxillary expansion. The mechanical reactions of hard bony and dental tissues are a very important aspect in the overall dynamics of orthodontic appliance activity. An acquaintance with these processes allows the orthodontist to influence the structures of the maxillary complex remote from the dentoalveolar region. The amount of rapid maxillary separation was displayed nearly three-quarters of a century ago3 by invasive procedures like reflecting a flap of palatal mucosa put forward by Federspiel4 while Price5 employed simple probing between the separated palatal process. Isaascon6,7 measured the forces using deformation gauge on a metal piece of the expander. The mechanical reactions to the rapid maxillary expansion has been analyzed by various methods like Teleradiographic head JIOS Mechanical Reaction of Facial Skeleton to Rapid Palatal Expansion Devices using Laser Holography: An in vitro Study Films (Krebs,8,9 Hershey10), occlusal radiographs by Wertz.11 Experimental animals studies were done by West (1964),12 Starnbach, Bayne, Cleall Subtelny (1966)13 and Gardner and Kronman (1971).14 Laser holography has been shown to be a valuable method in which the initial microstresses (or) fringe patterns resulting from various applied forces to the human skull can be seen and recorded. Holography is a technique of recording three-dimensional images of objects. This method has become vital in measurement techniques where influence of very small deformation of objects under study becomes significant. Leith and Upatniks applied laser to holography in 1960 and found series of application in dentistry such as study of elastic deformations of soldered gold joints,15 qualitative studies of various dental structures, measurement of elastic deformation of prosthodontic appliance,11 determination of centers of rotation of teeth. Hence, this study sought to compare the reaction of frontonasal, nasomaxillary, intermaxillary, zygomaticomaxillary, zygomaticotemporal sutures and center of resistance of molar to the Hyrax appliance with different degrees of activations and the recently introduced Spring jet appliance using laser holography on a freshly macerated skull. Fig. 1: Freshly macerated skull AIMS AND OBJECTIVES 1. To study the mechanical reactions of frontonasal, internasal, nasomaxillary, intermaxillary, zygomaticomaxillary, zygomaticotemporal sutures and an area corresponding to the center of resistance of the first molar using Hyrax appliance with the different degrees of activations (two ¼ turns, four ¼ turns, eight ¼ turns). 2. To study the mechanical forces produced on the sutures with the Spring jet appliance. 3. To compare the mechanical forces between the Hyrax appliance and Spring jet appliance. Fig. 2: Skull coated with magnesium oxide MATERIALS AND METHODS Preparation of Experimental Models A freshly macerated skull (without mandible) with well-aligned teeth and intact dental arches (Fig. 1) obtained from Government Medical College, Chennai, was used as the experimental model. The skull was stored in Ringer’s lactate solution to minimize the changes. The skull was coated with magnesium oxide (Fig. 2) just prior to recording of the hologram. Preformed bands were adapted on the first premolar and molars of the maxillary dentition of the skull, impressions swere made using alginate impression material and the bands were then transferred. Stone cast were poured with the bands in place. Hyrax appliance was adapted (11 mm expansion) and soldered to the bands, and the appliance was fabricated (Fig. 3). Spring jet appliance was fabricated in the other model (Fig. 4). Fig. 3: Hyrax placed on the model The hyrax appliance consists of a midpalatal jackscrew (11 mm Dentarum) assembly which as four rigid 0.060 inch stainless steel shafts radiating outward from the screw. Each shaft was adapted to the premolar and molar bands to which they were soldered. The Journal of Indian Orthodontic Society, October-December 2013;47(4):426-432 427 Revathi Peddu et al Spring Jet (American Orthodontics) Fig. 4: Spring jet appliance placed on the model It consisted of a director unit which was formed into a ‘U’ shape keeping the legs parallel to each other at 5 mm distance. They were cut to proper length and the ends were smoothened. The second direction unit was formed as a mirror image of the former one. The two units slide into one another and were checked for friction free movement. The second unit is then cut to size and the units were again rechecked. Double ‘U’ was positioned on the working model and the anteriorposterior tube positions were noted relative to the first molars and fixed in place. The connecting framework 0.645 mm was formed on each side and they were soldered, cleaned and polished. According to force deflection chart (Chart 1), two 7 mm springs segments were assembled on double ‘U’ sections with locks. The expansions screws and the frameworks were placed close to the roof of the palate, without impinging on the palatal soft tissue. Activation of the Spring jet: The activation lock was released using Allen key (Fig. 7). The appliance was thus activated and double exposure hologram was recorded. Stabilization of The Experimental Model (Fig. 8) Fig. 5: Two one-fourth turns activation of hyrax–frontal and lateral view The skull with the fabricated screw set up was then fastened to a heavy metal framework. The metal frame consists of two vertical bars attached to the base. Vertical bars were used to fix the skull in the occipital region with the help of the screws. Iron struts were welded to the base so as to hold the skull rigidly to prevent any minor movements during the experiment. The skull was fixed such that the occlusal plane was kept parallel to the base of the support. Holographic Setup (Figs 9 and 10) The holographic unit consisted of a source of He-Ne laser with wavelength of 0.6238 microns, beam splitter, mirrors, beam expanders, object photographic plate and plate holder. The skull was used as the object. RESULTS Fig. 6: Four one-fourth turns activation of hyrax–frontal and lateral view Activation of the Appliance Hyrax: This appliance was activated two ¼ turns (Fig. 5) by using the key provided. Then the double exposure hologram was recorded. Similar procedures was repeated for four ¼ turns (Fig. 6) and eight ¼ turns. 428 These holographic plates were developed and the images were recorded with a camera in two-dimensional photographs. The holograms were interpreted from the photographs by following method put forward by Ryszard J Pryputriewicz (1969). A grid of three horizontal and three vertical lines which represent the projections of the planes in which the deformations and displacement of the sutures were measured, were drawn on the photographs of the interferograms (Fig. 11). The fringes Chart 1: Force-deflection chart from the Spring jet appliance 400 gm Spring 0.018 × 0.055 Compression (mm) 1 Maximum force 39 Minimum force 30 2 112 90 3 185 155 4 260 232 5 327 300 6 404 377 7 473 442 JIOS Mechanical Reaction of Facial Skeleton to Rapid Palatal Expansion Devices using Laser Holography: An in vitro Study Fig. 10: Recording of hologram Fig. 7: Activation of Spring jet appliance–frontal and lateral view Fig. 11: Interpretation of results Fig. 8: Stabilization of the skull Interpretation of Results Holographic interpretation can be done in two ways: 1. Qualitative analysis: By direct observation of the fringes (Graphs 1 and 2). 2. Quantitative analysis: By making measurements either by directly counting the number of fringes (or) fringe spacing on the hologram (or) by making measurements on photographs (Graphs 3 and 4). The sutures were represented by the following grids: Nasomaxillary suture Zygomaticomaxillary Fig. 9: Experimental apparatus–holographic unit were counted for each suture on the x and y axis. The x-axis lines were represented as a b c c1 and y-axis as ABC Al on the lateral view and d e f and D E F on the frontal view respectively. Nasomaxillary suture, zygomaticomaxillary, zygomaticotemporal and center of resistance of molar were evaluated in the lateral view and frontonasal, intermaxillary, zygomaticomaxillary sutures were evaluated in the frontal view. Zygomaticotemporal Center of resistance of molar Frontonasal Intermaxillary aA Right/Left bBcDcF aC c1 A1 dE fE The displacements were calculated from the number of fringes using the following formula: n d = ——— 2 The Journal of Indian Orthodontic Society, October-December 2013;47(4):426-432 429 Revathi Peddu et al where, d = displacement in nm n = no. of fringes 632.8 × 109 nm = He—Ne laser wavelength = ——————— 2 Analysis of the interferograms showed that transverse maxillary expansion by the Hyrax appliance induced initial mechanical reactions not only of the alveolar bone and teeth but also of the entire maxilla, all the circum-maxillary sutures and the surrounding bones. These changes were evident even when the Hyrax was activated initially by two turns. The direction of interference fringes on the bony surface was also identical for all loading degrees; whereas their number increase corresponded to the increased amount of widening. This indicates that the mechanical reactions in these experiments were qualitatively, the same at the lowest as well as at the highest loading degree. Quantitatively the number of fringes increased with two, four, eight ¼ turns. There was minimal fringe pattern with two ¼ turns activation of Hyrax with the same number of fringes in the frontonasal, intermaxillary, zygomaticomaxillary, zygomaticotemporal and center of resistance of molar. Similar trend could be observed at the four-turn activation. As the activation force was increased to eight turns, the number of fringes increased significantly at all sutures, and the fringes were seen in a more circular direction around the nasomaxillary complex and zygomaticomaxillary suture (Tables 1 and 2). Interpretation of the fringe pattern of the Spring jet appliance indicated moderate changes at the intermaxillary suture comparable to four ¼ turns activation of Hyrax. There was very minimal change at the other frontonasal, zygomaticomaxillary, zygomaticotemporal sutures, and the most of the fringes were concentrated around the center of resistance of the molars (see Tables 1 and 2). DISCUSSION To understand the actual function of an orthodontic appliance the modern orthodontist must continually expand his knowledge of orthodontic forces induced at the point of contact of the appliance with soft and hard orofacial tissues, the distribution of these forces and their transformation while passing through the tissue, the biologic and mechanical tissue reactions to the applied forces. One of the foremost proponents of the concepts of rapid palatal expansion is the Graph 1: Holographic interpretation of firnge numbers frontal view Graph 2: Holographic interpretation of fringe numbers lateral view Graph 3: Holographic interpretaion of lateral view—amount of displacement in nm Graph 4: Holographic interpretation of lateral—amount of displacement in nm 430 JIOS Mechanical Reaction of Facial Skeleton to Rapid Palatal Expansion Devices using Laser Holography: An in vitro Study Table 1: Holographic interpretation of frontal view—fringe numbers Hyrax Frontonasal suture Number of fringes Intermaxillary Zygomaticomaxillary suture suture 2 4 8 Spring jet 1 2 6 0 1 2 4 3 Right Left 1 2 7 1 1 2 7 1 Table 2: Holographic interpretation of frontal view—amount of displacement (in nm) Hyrax 2 4 8 Spring jet Frontonasal suture (nm) 000316.4 000632.8 0001898.4 0 Intermaxillary suture (nm) 000316.4 000632.8 0001265.6 000949.2 Zygomaticomaxillary suture Right Left 000316.4 000632.8 0002214.8 000632.8 000320.2 000598.4 0002208.2 000636.6 Haas Appliance in 1961, and since then rapid palatal expansion has been the mainstay in management of skeletal transverse discrepancies. In this study, holographic interferometry was applied to evaluate the skeletal displacements of sutures with two different expansion appliances. Andrej Zentner et al (1996),16 derived a method that combined the advantage of classical optical interferometry and those of holography and allows the measurement of displacement of relatively large surface at the level of light wavelength. In several earlier investigation, researchers have proved the practicability, validity, and advantages of holographic interferometry,17 when applied in orthodontic research. Skeletal displacement was evaluated in the present work using a zero-order fringe interpretation technique. It was chosen because it has several important advantages including precision, the ability to discriminate between various types of displacement, simplicity of the optical set-up and convenience of using photographs for evaluation. Holographic study was performed on a freshly macerated skull as the modulus of elasticity of bone is several orders of magnitude higher than that of the remaining connective tissues,18 and skeletal reaction therefore probably represents the major component of the displacement in vivo.19 The use of a macerated skull in the present study seemed justified as an approximation of the situation in vivo. Furthermore, a macerated skull is to be used because a wet specimen would require substantially longer exposure times during holographic procedures and could change in shape through evaporation.20 The use of a single skull served the purpose of the present study, i.e. to compare the effects of Spring jet and Hyrax expansion appliances applied in different degrees of activation under otherwise identical experimental conditions. The use of several skulls was rejected in order to avoid the additional variable caused by individual skull, holography which might obscure subtle qualitative and quantitative differences in displacement. Furthermore, a single skull was used due to the difficulty of obtaining a freshly macerated young skull with full complement of teeth and the cost of holographic plates. Satisfactory precision accuracy and reproducibility of the experimental arrangement employed in the present investigation were confirmed in the precursor trials. The results of the present investigations showed that the transverse orthopedic expansion produced mechanical reactions on the teeth and the entire maxilla, all the circummaxillary sutures and the surrounding bones. The activation of the Hyrax: Two ¼ turns produced minimal displacement (000316.4 nm) at the frontonasal, intermaxillary, zygomaticomaxillary and zygomaticotemporal sutures, while moderate displacement was noted at the center of resistance of molar (000949.2). There was a progressive increase with four ¼ turns at the sutures, and center of resistance of the molar. With an activation of eight ¼ turns, the fringe effect was maximum at the sutures and the center of resistance of first molar (0002214.8) (0003480.4). In most rapid palatal expansion appliances according to Hass ¼ revolution of the screw equals 0.2 mm of lateral displacement. Thus two ¼ turns produces 0.4 mm and four ½ turns produces 0.8 mm, eight ¼ turns produces–1.6 mm. Hass also reported the forces produced by this appliances as ranging from 3 to 10 pounds. 21 The displacement in the holographic study is recorded in nanometers. Hence, it cannot be quantitatively compared to the forces produced clinically. Increase in the fringes associated with increase in the appliance activations coincides with study by Dubravko Pavlin and Dalibor Vukicevic (1984).22 This suggested that increase in arch width with every screw activation occurs partially because of the deformation within the alveolar bone and partially because of the changed position of the maxilla in relation to the skull bones. The qualitative holographic interpretation demonstrated convergence of the fringes at discrete areas approximating the frontonasal suture. The fringe pattern on the zygoma was oblique in direction indicating the displacement of the bone by rotation and lateral bending. The fringes were clearly visible on the surrounding maxillary bones, which indicated that the expansion forces were transmitted to these bones. Similar results were obtained by Stanley Braun, Alexandre Bottrel (Sept 2000).23 Lee et al (1997)24 who studied the holographic interpretation with protraction and rapid palatal expansion found similar results. The Spring jet, introduced by Aldocarano (1999)2 is a relatively new appliance incorporating a NiTi open coil spring which produces 473 gm of force on activation. The present study included the Spring jet appliance to study its effect and compare the reactions with that of Hyrax. The results indicate that the Spring jet appliance produces changes mainly at the intermaxillary and the center of resistance of molar. Thus, it can be inferred that changes are mainly concentrated on the dentoalveolar region only. When comparing the number of fringes produced with the activation of Spring jet appliance in the intermaxillary area, a total number of three fringes were recorded. This could be compared with the Hyrax activation of four turns, where the number of fringes was only two. While The Journal of Indian Orthodontic Society, October-December 2013;47(4):426-432 431 Revathi Peddu et al no fringes were noted in the sutures remote from the dentoalveolar region viz–zygomaticotemporal, zygomaticomaxillary and frontonasal with this Spring jet appliance. Thus, it can be inferred that the mechanical reaction of the Spring jet were more in the intermaxillary area and an area close to the center of resistance of the first molar. The mechanical reaction of Spring jet on the sutures cannot be compared due to lack of the studies on the appliance. Clinically; thus it can be concluded on the basis of these findings that the remodeling with in the maxillary sutures are responsible for the jaw expansion and downward and forward movement of the maxilla associated with the rapid palatal expansion. Results of the Spring jet appliance suggest that it produced mostly dentoalveolar and very minimal orthopedic changes. This holographic study was made on a dry human skull and could not be directly correlated with the biomechanical reactions of the live structures due to the change of mechanical properties of bone on loss of humidity and soft tissues. The decreased humidity causes the gradual increase in friction and decreases displacement progressively.25 Nevertheless, the knowledge of the mechanical reaction allows orthodontist for a better understanding about the final therapeutic effects of appliance and the correct application of orthopedic appliance on sutures and bones of craniofacial system. CONCLUSION The results were interpreted using zero order fringe interpretation technique, on the photographs, on selected vertical and horizontal planes. The results can be concluded as follows: 1. Activation of Hyrax appliance produced mechanical reactions on the teeth, alveolar bone, maxilla and the circum-maxillary bones and sutures. 2. As the displacement increased, the number of fringes increased progressively with two, four and eight turn activation of Hyrax. 3. The pattern of the fringes was more circular around the nasomaxillary complex and zygomaticomaxillary sutures suggesting rotational displacement of the maxilla. 4. The number and pattern of fringes produced by the Spring jet appliances suggest that it produces only dentoalveolar changes and minimal orthopedic effects. Thus, increase in dental arch width with Hyrax appliance can be attributed deformation of alveolar process, lateral dental tipping and rotational movement of maxilla within the sutures. Hence, the Hyrax appliance is indicated in cases requiring maximum orthopedic changes and Spring jet can be advocated in dentoalveolar transverse discrepancies. REFERENCES 1. Haas AJ. Palatal expansion: just the beginning of dentofacial orthopedics. Am J Orthod 1970;57:219-255. 2. Carano A. The Spring jet for slow palatal expansion. J Clin Orthod 1999;33(9):527-531. 432 3. Timms DJ. A study of basal movement with rapid maxillary expansion. Am J Orthod 1980;77:500-507. 4. Federspiel MN. Discussion on paper by Dewey M: development of the maxillae with reference to opening the median suture. Items of Interest 1913;35:271-282. 5. Price WA. Some contributions to dental and medical science. Dent Summary 1914;34:253-290. 6. Isaacson RJ, Wood JL, Ingram AH. Forces produced by rapid maxillary expansion part-I design of the force measuring system. Angle Orthod 1964;34:256-260. 7. Isaacson RJ, Ingram AH. Forces produced by rapid maxillary part-II forces presented during treatment. Angle Orthod 1964;3:261-269. 8. Krebs A. Expansion of the mid-palatal suture studied by means of metallic implants. Trans Eur Orthod Society 1959;17:491-501. 9. Krebs A. Midpalatal suture expansion studies by the implant method over a seven-year period. Rep Congr Eur Orthod Soc 1964;40:131-142. 10. Hersley HG, Stewant BL, Warren DW. Changes in nasal airway resistance associated with rapid maxillary expansion. Am J Orthod 1976;69:274-284. 11. Wertz RA. Changes in nasal airflow incident to rapid maxillary expansion. Angle Orthod 1968;38:1-9. 12. West IM. Histologic study of sutural tissue changes accompanying palatal splitting in the monkey. Master’s Thesis University of Illinois; 1964. 13. Starbanch H, Bayne D, Cleall J, Subtelty JD. Facioskeletal and dental changes resulting from rapid maxillary expansion. Angle Orthod 1966;36:152-164. 14. Gardner GE, Kronman JH. Cranioskeletal displacements caused by rapid palatal expansion in the rhesus monkey. Am J Orthod 1971;59:146-155. 15. Wictorin L, Bjelkhagen H, Abrumson N. Holographic investigation of the elastic deformation of defective gold joints. Acta Odontol Scand 1972;30:659-670. 16. Zentner A, Sergl HG, Filippidis G. A holographic study of variations in bone deformations resulting from different headgear forces in a macerated human skull. Angle Orthod 1996;6:463-472. 17. Pryputniewicz RJ, Bowley WW. Techniques of holographic displacement measurement: an experimental comparison. Appl Opt 1978;17:1748-1756. 18. Yamada H, Evens FG. Strength of biological materials. Baltimore: Williams & Wilkins; 1970. 19. Kragt G, Ten Bosch JJ, Borsboom PC. Measurement of bone displacement in a macerated human skull induced by orthodontic forces a holographic study. J Biomech 1979;12(12):905-910. 20. Fuchs P, Schott D. Holografische inferometry zur darstellung von verformungendesmenschlichen gesichtsschadels. Schweiz Monstsschur Zohnmed 1973;83:1468-1482. 21. Ladner PT, Muhl ZF. Changes concurrent with orthodontic treatment with maxillary expansion is a primary goal. Am J Orthod Dentofacial Orthop 1995;108:184-193. 22. Pavlin D, Vukicevic D. Mechanical reactions of facial skeleton to maxillary expansion determined by laser holography. Am J Orthod 1984 Jun;85:498-507. 23. Braun S, Bottrel JA, Lee KG, Lunazzi JJ, Legan HL. The biomechanics of rapid maxillary sutural expansion. Am J Orthod 2000;118:257-261. 24. Lee KG, Ryu YK, Park YC, Rudolph DJ. A study of holographic interferometry on the initial reaction of maxillofacial complex during protraction. Am J Orthod 1997;111:623-632. 25. Vest CM.- Holographic interferometry. New York: Wiley; 1979. 465 p.