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
A COMPARISON OF UPPER INCISOR TORQUE BETWEEN TWO METHODS OF EXTRACTION SPACE CLOSURE Kyle Jamison, D.M.D. A Thesis Presented to the Graduate Faculty of Saint Louis University in Partial Fulfillment of the Requirements for the Degree of Master of Science in Dentistry 2014 COMMITTEE IN CHARGE OF CANDIDACY: Associate Clinical Professor Donald R. Oliver, Chairperson and Advisor Professor Eustaquio A. Araujo Associate Professor Ki Beom Kim i DEDICATION To my wife, Dayna, whose love and support through the years has made everything possible. To my parents, Brad and Shaunna, who have always believed in me and have supported me in every endeavor I have pursued. To my children, Kylie, Tre, and Kellen, whose unconditional love has given me more joy than I could have ever imagined. ii ACKNOLWLEDGEMENTS Thank you to Dr. Oliver for his mentorship and for his attention to detail throughout this process. Without his guidance this would not have been possible. Thank you to Drs. Araujo and Kim for serving on my committee and helping me to organize my study. Thank you to Dr. Behrents for helping me with random questions about cephalometrics along the way, and helping to find my sample. iii TABLE OF CONTENTS List of Tables. . . . . . . . . . . . . . . . . . . . . vi List of Figures. . . . . . . . . . . . . . . . . . . . .vii CHAPTER 1: INTRODUCTION Description of the problem. . . . . . . . . . . . . .1 CHAPTER 2: REVIEW OF THE LITERATURE Introduction and History. . . . . . . . . . . . . . 3 Defining Torque. . . . . . . . . . . . . . . . . . .5 Torque, Occlusion and Arch-Length. . . . . . . . . . 6 Measuring Torque. . . . . . . . . . . . . . . . . . .9 Sources of Torque Variation and Expression. . . . .11 Torsional Play. . . . . . . . . . . . . . . . 12 Manufacturing Processes. . . . . . . . . . . .14 Torque and Bracket Systems. . . . . . . . . . . . . 14 Comparing Bracket Systems. . . . . . . . . . . 16 Self-Ligating Brackets and Torque. . . . . . . 17 Archwire Properties and Torque. . . . . . . . . . . 19 Effects of Loops. . . . . . . . . . . . . . . .20 Summary and Purpose. . . . . . . . . . . . . . . . .21 Literature Cited. . . . . . . . . . . . . . . . . . 24 CHAPTER 3: JOURNAL ARTICLE Abstract. . . . . . . . . . . . . . . . . . . . . . 27 Introduction. . . . . . . . . . . . . . . . . . . . 29 Materials and Methods. . . . . . . . . . . . . . . .32 Method. . . . . . . . . . . . . . . . . . . . .32 Standard Edgwise Sample. . . . . . . . . . . . 35 Retranol® Sample. . . . . . . . . . . . . . . .36 Error of the Method. . . . . . . . . . . . . . 37 Reliability. . . . . . . . . . . . . . . . . . 37 Results. . . . . . . . . . . . . . . . . . . . . . .38 Sample Demographics. . . . . . . . . . . . . . 38 Age and Treatment Duration. . . . . . . . 38 ANB and SN-GoGn. . . . . . . . . . . . . . . . 39 Upper Incisor. . . . . . . . . . . . . . . . . 40 Lower Incisor. . . . . . . . . . . . . . . . . 42 Upper Molar. . . . . . . . . . . . . . . . . . 43 Lower Molar. . . . . . . . . . . . . . . . . . 45 E Plane. . . . . . . . . . . . . . . . . . . . 46 Discussion. . . . . . . . . . . . . . . . . . . . . 46 Sample Demographics. . . . . . . . . . . . . . 46 Age. . . . . . . . . . . . . . . . . . . .47 iv Growth. . . . . . . . . . . . . . . . . . . . .47 Upper Incisor. . . . . . . . . . . . . . . . . 48 Comparison to Previous Studies. . . . . . . . .48 Standard Edgewise Studies. . . . . . . . .48 Reverse-Curve NiTi. . . . . . . . . . . . 49 Conclusions. . . . . . . . . . . . . . . . . . . . .50 Literature Cited. . . . . . . . . . . . . . . . . . 51 Appendix. . . . . . . . . . . . . . . . . . . . . . . . .54 Vita Auctoris. . . . . . . . . . . . . . . . . . . . . . 57 v LIST OF TABLES Table 2.1: Theoretical and measured torque loss with different bracket-wire combinations. . . . . 13 Table 2.2: Torque values for three bracket prescriptions. . . . . . . . . . . . . . . . . . . . . . . .16 Table 3.1: Summary of ages and treatment time for standard edgewise and Retranol® groups. . . . . . . . 39 Table 3.2: Summary of ANB and SN-GoGn for both standard edgewise and Retranol® groups. . . . . . . . 39 Table 3.3: A summary of the upper incisor (U1) changes for standard edgewise and Retranol® groups. . . .41 Table 3.4: A summary of the lower incisor changes with standard edgewise and Retranol® groups. . . .43 Table 3.5: Summary of upper molar (U6) changes with standard edgewise and Retranol® groups. . . .44 Table 3.6: Summary of lower molar (L6) changes with standard edgewise and Retranol® groups. . . .45 Table 3.7: Summary of upper and lower lips to E-Plane in both standard edgewise and Retranol groups. .45 Table 3.8: Comparison of upper incisor inclinations from previous extraction studies. . . . . . . . . 49 Table A.1: Landmarks and Definitions. . . . . . . . . . 54 Table A.2: Measurement Abbreviation Key. . . . . . . . .55 vi LIST OF FIGURES Figure 2.1: Improperly inclined anterior crowns result in all upper contacts being mesial, leading to improper occlusion. . . . . . . . . . . . . .7 Figure 2.2: Improper anterior torque may lead to incorrect assumption of a Bolton discrepancy. . . . . .8 Figure 3.1: X-Y coordinate grid system constructed from SN-7 degrees and SN-7 degrees perpendicular.33 Figure 3.2: Angular Measurements. . . . . . . . . . . . 34 Figure 3.3: Vertical and Horizontal measurements. . . . 35 Figure 3.4: Upper incisor (U1) and upper molar (U6) changes in the standard edgewise and Retranol® group. . . . . . . . . . . . . . . . . . . .41 vii CHAPTER 1: INTRODUCTION Description of the Problem In orthodontics, having proper buccolingual inclination, or torque, of the anterior teeth is critical for successful treatment. Not only is torque important for esthetic reasons, but it also has space and occlusal considerations as well. In extraction cases, torque control is of vital importance because this treatment often involves large retractions of the anterior teeth that often results in lingual tipping of the upper incisors. The orthodontist should have a thorough understanding of how their appliances and mechanics affect the final upper incisor torque following anterior tooth retraction. There have been numerous studies comparing the changes in upper incisor inclination after various different treatments. However, no study has compared upper incisor inclinations in four bicuspid extraction cases comparing patients treated using a standard edgewise (zero tip, zero torque) appliance with rectangular stainless steel archwires and closing loops, and patients treated with a Roth appliance and a Retranol® (a preformed, accentuated curve “work-hardened” nickel titanium) archwire and elastomeric chain with sliding mechanics. The prime 1 motivation of this study is to evaluate differences in upper incisor inclinations before and after orthodontic treatment, following the above described methods of space closure. This study will also evaluate other dental and soft tissue changes that occurred as a result of treatment, specifically, measurements will be made on the upper and lower incisors (horizontal and vertical), the upper and lower molars (horizontal and vertical), and the position of the lips (in relation to E-plane). 2 CHAPTER 2: REVIEW OF THE LITERATURE Introduction and History The inclination of the upper incisors (sometimes called torque) is important to the esthetics of a smile and as such has been recognized for decades if not centuries. As part of orthodontic biomechanics, orthodontists have concerned themselves with achieving the best upper incisor inclination for their patients. In the late 1800s and early 1900s various appliances were developed to affect torque. Examples include the E-arch, the pin and tube, and the ribbon arch. These early appliances were either too difficult to use, or had relatively poor ability to control root position. Introduced in 1928, Angle’s edgewise appliance using gold and gold-platinum alloys ultimately became the basis of most modern systems. After much experimentation, Angle settled on a .022 X .028 inch bracket slot, with a .022 X .028 inch precious metal wire. This appliance was found to be more user friendly and allowed for excellent control of crown and root position in all three planes of space.1 Eventually steel archwires replaced the gold wires used in Angle’s edgewise appliance. Because steel archwires are considerably more stiff than gold, a 3 reduction of the bracket slot size to .018 inches was possible while still maintaining similar forces and torque control to the original .022 inch appliance when using a full size steel archwire. However, the use of undersized wires in an edgewise appliance is a good way to reduce the frictional component when sliding teeth along an archwire (Proffit suggests at least .002 inches of clearance to minimize friction1). Therefore, the original .022 inch slot would have an advantage over the .018 inch slot when closing spaces, but would be at a disadvantage with torque control because the springiness and range of action are so limited in full size steel wires that effective torque is nearly impossible.1 To overcome the torque issues associated with using the .022 bracket slot, orthodontists employ torqueing auxiliaries, undersized steel wires with exaggerated inclinations, and rectangular NiTi and betaTitanium (TMA) wires.1 Over the years, Angle’s original appliance has gone through many changes, but the basic idea of a rectangular wire in a rectangular slot has remained. One major change came in 1970 when Andrews introduced the Straight-Wire Appliance to orthodontics.2 He developed the appliance in order to minimize the amount of arch-wire bends needed to 4 finish an orthodontic case. Among his improvements was the addition of “torque” in the bracket, which was inclined for each individual tooth type.2 This was the beginning of the so-called “prescription appliance”. Today, most orthodontists use some variation of a prescription appliance, however, there are many who continue to utilize a standard edgewise appliance with zero tip and zero torque incorporated into the brackets. Defining Torque Rauch defined torque as “the force that enables the orthodontist to control the axial inclinations of teeth and to place them in the harmonizing positions that are so desirable for a nicely finished result.”3 Torque can either be passive, which puts no action or force on the tooth when engaged in the appliance, or, active, which has a definite action or force on the tooth crown.3 Rauch further defines torque on the basis of action upon the crown of the tooth. Thus, buccal or labial torque, tend to tip the crown of the tooth buccally or labially, and the roots of the tooth lingually. Lingual crown torque moves the crown of the tooth lingually, and the roots of the tooth buccally.3 5 Torque, Occlusion and Arch-length In 1972, Andrews developed his “six keys to normal occlusion.”4 His third key deals with Crown Inclination (labiolingual or buccolingual inclination) or torque.4 In his paper Andrews describes the importance of proper anterior crown inclination (torque) because it not only affects the overbite, but the posterior occlusion as well. In speaking of the anterior crown inclination, he explains that “when too straight-up and –down they lose their functional harmony and overeruption results…the upper posterior crowns are forward of their normal position when the upper anterior crowns are insufficiently inclined.”4 (See Fig. 2.1) In other words, if the upper incisors are inadequately torqued, complete Class II correction may be difficult or impossible to achieve unless tooth structure is removed in the lower arch. 6 Fig.2.1. A, Improperly inclined anterior crowns result in all upper contacts being mesial, leading to improper occlusion. B, Demonstration on an overlay that when the anterior crowns are properly inclined the contact points move distally, allowing for normal occlusion. (Adapted from Andrews, 19724.) He further illustrates that improper anterior torque may often lead to the incorrect assumption of a tooth-size discrepancy if the posterior teeth are in correct occlusion and there are remaining spaces between the anterior and posterior occlusion as shown in Figure 2.2.4 7 Fig. 2.2. Improper anterior torque may lead to incorrect assumption of a Bolton discrepancy if there is no remaining overjet and there are spaces between the anterior and posterior occlusion. (Adapted from O’Higgins, 19996). While Andrews described this problem of insufficient anterior tooth inclination, several researchers have attempted to quantify the loss of arch length that results from improper incisor angulation.5,6 Most recently, O’Higgins and colleagues designed a study to investigate Andrew’s hypothesis that there are space implications with improper crown torque of the incisors. Using acrylic and natural teeth on typodonts, the investigators measured arch-length changes as the inclinations of the incisors were changed. For natural teeth, they found on average 8 that a 5 degree increase in inclination of the upper incisors resulted in a 1mm increase in arch length.6 Thus, in orthodontic cases which require Class II correction, and especially in extraction cases, maintenance and control of upper incisor torque is of vital importance for complete Class II correction. Measuring Torque Clinically, torque refers to the buccopalatal crown/root inclination of a tooth.7 Typically the buccopalatal inclination or torque of the upper incisors is measured cephalometrically by tracing the long axis of the upper central incisor and extending the line until it intersects with a stable reference line, such as the S-N line or palatal plane. In the Steiner cephalometric analysis, the upper incisor inclination is measured by the angle of intersection with the Nasion-A point line, with a calculated norm value of 22 degrees. There have been several studies that have used U1-NA to compare Steiner’s analysis to specific populations8,9. Perhaps the most commonly used measure of upper incisor inclination in the literature is U1-SN. U1-SN is the angle of intersection between a line extending from through the long axis upper incisor to the Sella-Nasion 9 line. The University of Michigan performed a growth study with 47 males and 36 females where they took lateral cephalograms every year from the ages of 6 to 16. The results of this study were published in An Atlas of Craniofacial Growth10. The researchers found that from the ages of 8-years-old to 16-years-old, U1-SN stays relatively stable, ranging from 102.6 to 105.6 in both male and female populations10. Several researchers have used U1-SN to measure upper incisor inclinations before and after treatment.11,12,13,14 In Luppanapornlarp and Johnston’s sample of 30 Caucasian patients treated with four bicuspid extractions, the average U1-SN angle was 104.3 degrees before treatment, and 99.7 degrees after standard edgewise orthodontic treatment.11 Demir and colleagues studied the effects of upper premolar extraction only on the dentofacial structures in Class II div. 1 patients treated with an edgewise appliance and headgear. The initial pre-treatment mean U1-SN value was 103.7 degrees, which decreased to 97.7 degrees post-treatment, a difference of -6.0 degrees.12 Bishara and colleagues also studied the effects of extractions in Class II div. 1 patients compared to patients treated without extractions. 10 There was a -9.8 degree change in U1-SN in the extraction patients and a -3.2 degree change in U1-SN in the non-extraction group, a significant difference14. Işiksal and colleagues compared smile esthetics among extraction and non-extraction patients treated with an edgewise appliance, and an untreated control group. In this study, the final U1-SN in the non-extraction and control groups was 104.7 +/- 6.12, and 103.3 +/- 4.8 degrees respectively, while the extraction group U1-SN was 100.2 +/-5.3 degrees, a significant difference.13 Pandis et al. compared changes in U1-SN in extraction and non-extraction orthodontic cases using a .022 inch Roth prescription. In this study, the extraction spaces were closed using a 0.019 X 0.025 inch NiTi wire with reverse curve of Spee and elastomeric chain (similar to the method of closure in the current study). They found that the mean changes for U1-SN were not significant between extraction and non-extraction groups.15 Sources of Torque Variation and Expression While orthodontists have long understood the importance of anterior torque control, the maintenance and expression of torque has remained a difficult challenge. The difficulty with torque control arises from several 11 different sources, including material properties, manufacturing processes, and clinical procedures.16 Torsional Play Perhaps one of the most important variations in torque expression is the interaction of the archwire and bracket slot (along with the initial position of the tooth). In a typical orthodontic sequence, the orthodontist gradually progresses from light round wires, to heavy rectangular wires. It is by engaging the edges of the rectangular wires with the edges of the bracket slot that torque can be maintained or expressed. However, in most clinical situations, the orthodontist almost never completely fills the bracket slot because of the patient discomfort associated with larger archwires and the difficultly of wire insertion into the slot.16 When the slot remains incompletely filled by the archwire, a portion of the torque built into the slot remains unexpressed, which gives rise to slot-wire “play” or third order clearance.16 Sebanc et al. describe the torsional play as “the amount of rotation that the wire initially, in the passive state, must be twisted to engage the bracket and generate biomechanical torque.”17 Meling and colleagues further describe the concept of “effective torque,” which “will 12 equal bracket torque plus incorporated wire torque minus torsional play.”18 Several investigators have calculated and measured the amount of archwire-slot play that exists between different archwire-slot combinations (See Table 1). The data from Table 1 show the difference between the theoretical (calculated or nominal) torque loss and the actual (measured) torque loss. Table 2.1 shows that almost 100% of the built-in torque can be lost if a low-torque prescription is used.16 For example, if a Roth appliance, which uses 12 degrees of torque on the upper central incisor, is used with a .019 X .025 inch rectangular archwire in a .022 inch slot, there may be up to 14.5 degrees of archwire-slot play (in each direction), which is 2.5 degrees greater than the built-in bracket torque. Table 2.1. Theoretical and measured torque loss with different bracket-wire combinations. (Table adapted from Gioka et al.)16 Wire crosssection (in) 0.016 X 0.022 Slot Size (in) 0.018 Torque loss (degrees) theoretical* 9.5 Torque loss (degrees) measured 14.1 0.017 X 0.025 0.018 6.0 6.2 0.018 X 0.025 0.022 15.2 20.1 0.019 X 0.025 0.022 10.5 14.5 *Theoretical values derived from trigonometric estimation of slot-wire play. 13 Manufacturing Processes Play between the archwire and bracket slot is not the only source of variation to affect clinical torque expression, but the manufacturing process of brackets and wires itself can produce inaccuracies and errors that may lead to discrepancies between estimated (nominal) and measured (actual) torque.16 The process of bracket slot manufacturing introduces grooves, metal particles, and striations that may prevent complete archwire seating within the bracket slot.16 Any manufacturing process produces minor variations in slot size and torque consistency. Gioka and Eliades report that the reported torque values can differ from the actual torque values by as much as 5% to 10%.16 In addition, bracket manufacturers often slightly increase the size of the bracket slot and decrease the wire size to prevent the possibility of the wire not fitting within the bracket slot. Companies will often also round or bevel the edges of the archwire to allow easier archwire insertion.16 Torque and Bracket Systems Various bracket prescriptions have been developed with a wide range of values for the upper incisor torque (Table 2.2). The original edgewise appliance, which is still in 14 wide use today, uses zero degrees of torque for all brackets. The Andrews appliance, developed in the 1970s, had brackets for extraction and non-extraction cases, which were then subdivided into different bracket sets based on the amount of crowding in the lower arch.19 To reduce the need for a large inventory of brackets, Roth developed a set of brackets that would be applicable to most orthodontic cases. Among Roth’s changes to the Andrews appliance, he increased both tip and torque on brackets in the anterior region.19 McLaughlin, Bennett and Trevisi (MBT) then introduced their own prescription to the orthodontic market. One alteration in the MBT prescription was an increase in palatal root torque in the upper anterior teeth. It was their observation that there was a loss of torque in other appliances in the upper anterior region, especially during overjet reduction or space closure.19,20 15 Table 2.2. Torque values for three bracket prescriptions (degrees). (Adapted from Thickett et al.)19 Upper Lower MBT 17 10 -7 -7 -7 -14 -14 Roth 12 8 -2 -7 -7 -14 -14 Andrews 7 3 -7 -7 -7 -9 -9 TEETH 1 2 3 4 5 6 7 Andrews -1 -1 -11 -17 -22 -30 -33 Roth -1 -1 -11 -17 -22 -30 -30 MBT -6 -6 -6 -12 -17 -20 -10 Comparing Bracket Systems Many researchers have performed studies to determine the effects of different bracket systems on the upper incisor torque. Moesi and colleagues found that nine experienced orthodontists could not subjectively distinguish between orthodontic cases treated with either a Roth or MBT prescription.20 In another study, Ugur et al. compared upper incisor inclinations in non-extraction orthodontic cases treated with either a standard edgewise appliance or a Roth prescription. They found that there was no significant variation between mean upper incisor torque values comparing standard edgewise and Roth treatment groups with non-extraction treatment.21 16 Self-Ligating Brackets and Torque The advent of self-ligating bracket systems has spurred researchers to investigate claims of improved torque expression because of more consistent wire engagement due to the absence of elastic modules that degrade over time.15 Conversely, there is also the argument that torque control is perhaps more difficult with selfligating brackets (in particular, passive self-ligating brackets) because of the absence of elastic modules or steel ligation that help to seat the archwire in the base of the slot22. brackets. There are two basic types of self-ligating Passive self-ligating brackets have a clip, that when closed, does not actively seat the archwire in the bracket slot. Active self-ligating brackets have a clip that exerts a force on the labial surface of the archwire to seat it in the base of the slot. Pandis and colleagues15 performed a randomized clinical trial to assess the efficiency of self-ligating and conventional brackets in torque control in extraction and non-extraction cases. The authors found no difference in upper incisor inclinations (U1-SN) between the two bracket systems. It was their conclusion that the efficiency of self-ligating brackets in delivering torque to the upper 17 incisors is equal to the performance of the conventionally ligated brackets in extraction and non-extraction cases.15 It has been proposed that because the active clip on an active self-ligating bracket invades the bracket slot, it might place an effective torqueing force at a smaller “slop” angle than a passive bracket22. Badawi and associates23 tested this theory and compared torque expression between active and passive self-ligating brackets with .019 X .025 inch stainless steel archwires in an .022 inch bracket slot. They found that there was a significant difference in the engagement angle between the two bracket types. On average, torque started to be expressed at 7.5 degrees of torsion for active selfligating brackets, and at 15 degrees of torsion for passive self-ligating brackets23. The author’s conclusion is that active self-ligating brackets are more effective in torque expression than passive self-ligating brackets.23 Sifakakis and colleagues compared maxillary incisor torqueing moments with reverse-curve NiTi archwires using conventional and self-ligating brackets.24 The conventional brackets in their study had the lowest torqueing values (10.8 N/mm), while the self-ligating brackets had torqueing values between 16.5-16.9 N/mm.24 18 This finding suggests that self-ligating brackets may be more efficient than conventionally ligated brackets at delivering torque to upper incisors when reverse-curve NiTi wires are used during leveling. Archwire Properties and Torque Torque expression is also greatly influenced by the properties of the archwire used in the appliance. In orthodontics, archwires of different dimensions and composition are used based on the preference of the orthodontist and the needs of the case. The most common materials used for archwires are nickel-titanium (NiTi), stainless steel, and beta-titanium (TMA). Archambault and colleagues compared the torque expression between stainless steel, TMA, and nickeltitanium wires in self-ligating brackets.25 They found that for low twist angles (<12 degrees) the differences in torque expression between wires were not statistically significant. This is because at 12 degrees of wire torsion, the wire was near the end of the torque play region and at the beginning of the partially engaged region. When the wire was twisted over 24 degrees, stainless steel wires showed 1.5 to 2 times the torque expression of TMA and 2.5 to 3 times that of NiTi.25 19 Meling and colleagues examined different stainless steels wires tested in torsion.18 The authors were working under the assumption that the ideal torqueing moment for a single tooth is 1500 g/mm, or 15 N/mm, and that 20 N/mm is the upper limit and 5 N/mm is the lower limit. They also measured the amount of torsional play in the wire-bracket combinations and found that with an .018 inch bracket slot and a 0.016 X 0.022 inch wire, there was a mean torsional play of 18.5 degrees, with a range of 16.6 degrees to 20.4 degrees. They found that the amount of twist necessary to achieve a 20 N/mm moment ranged from 24.6 degrees to 29.2 degrees.18 They attribute this variation to the wide range in torsional play, and as a result, makes the precise delivery of torsional moments difficult achieve using stainless steel wires.18 Effects of Loops A common method for space closure in orthodontic extraction cases is with the use of closing loops. After initial leveling, aligning, and canine retraction, closing loops are typically bent into a 0.019 X 0.025 inch stainless steel archwire in the standard edgewise appliance. One advantage of the closing loops is that the anterior teeth can be retracted without the need for the 20 teeth to slide along the archwire (sliding mechanics). Odegaard and colleagues describe that a negative side effect of the closing loop is that the application of force creates a tipping moment to the anterior segment; therefore it is necessary to apply torque to the anterior segment of wire to negate the tipping action.26 In addition, because loops increase the length of the archwire between brackets, there is a loss of torsional stiffness to the anterior segment while retraction is taking place.26 Summary and Purpose From the above review of the literature, the importance of upper incisor torque control, for reasons of arch-length preservation and occlusal stability has been presented. Furthermore, the sources of torque variation and the effect that closing loops have on the torsional stiffness of archwires has been shown. With these factors in mind, is there any advantage to extraction space closure using Retranol® (a preformed, accentuated curve “workhardened” nickel-titanium) wires and elastomeric chain over closing loops on .019 X .025 inch stainless steel archwires? The rationale for using preformed, accentuated curve NiTi wires for space closure is several-fold. 21 First, NiTi wires have increased springback over stainless steel. Higher springback is beneficial to delivery of torque because it enables larger activations with resultant increased working times.18 Thus, a greater degree of torque can be pre-activated into the wire and remain active over a longer period of time. Second, a pre-formed reverse curve NiTi wire is a continuous archwire, and therefore does not have the same torsional issues that arise with wires that have closing loops. A third benefit is the constant bite- opening effect the pre-formed NiTi wires afford. While anterior teeth are moved posteriorly into an extraction space, there is a tendency for extrusion. The accentuated curve of the pre-formed NiTi wire provides a constant counteraction to this extrusion, as well as from the extrusive force on the anterior teeth from Class II elastics. Fourth, reverse curve NiTi wires have been shown to produce torqueing values between 16.5-16.9 N/mm when used with active self-ligating brackets.24 This is within the accepted range of 5-20 N/mm, and near the ideal of 15 N/mm for torqueing an upper central incisor.18 Pandis and colleagues used a similar method of space closure to compare extraction and non-extraction groups using a Roth prescription. The results of the study were 22 unique among studies of this type because the final U1-SN was similar between extraction and non-extraction groups.15 Did the use of pre-angulated brackets using a Roth prescription make the difference in this study, or was it the use of the pre-formed NiTi archwires during space closure? There have been comparisons between standard edgewise and pre-torqued brackets in relation to upper incisor angulation in which the differences were not significant.21 But, the comparison of upper incisor angulation has yet to be made comparing standard edgewise to pre-angulated brackets in four bicuspid extraction cases using the above described two methods of space closure. 23 Literature Cited 1. Proffit WR, Fields Jr HW, Sarver DM. Contemporary orthodontics: Elsevier Health Sciences; 2006. 2. Andrews LF. The straight-wire appliance, origin, controversy, commentary. J Clinic Orthod. 1976;10:99114. 3. Rauch ED. Torque and its application to orthodontics. Am J Orthod. 1959;45:817-30. 4. Andrews LF. The six keys to normal occlusion. Am J Orthod. 1972;62:296-309. 5. Hussels W, Nanda RS. Effect of maxillary incisor angulation and inclination on arch length. Am J Orthod Dentofacial Orthop. 1987;91:233-9. 6. O'Higgins EA, Kirschen RH, Lee RT. The influence of maxillary incisor inclination on arch length. Br J Orthod. 1999;26:97-102. 7. Archambault A, Lacoursiere R, Badawi H, Major PW, Carey J, Flores-Mir C. Torque expression in stainless steel orthodontic brackets. A systematic review. Angle Orthod. 2010;80:201-10. 8. Atit M, Deshmukh S, Rahalkar J, Subramanian V, Naik C, Darda M. Mean values of Steiner, Tweed, Ricketts and McNamara analysis in Maratha ethnic population: A cephalometric study. APOS Trends in Orthod. 2013;3:137. 9. Garcia CJ. Cephalometric evaluation of Mexican Americans using the Downs and Steiner analyses. Am J Orthod. 1975;68:67-74. 10. Riolo ML, Moyers RE, McNamara JA, Hunter WS. An atlas of craniofacial growth: cephalometric standards from the University School Growth Study, the University of Michigan: Center for Human Growth and Development, University of Michigan; 1974. 11. Luppanapornlarp S, Johnston Jr LE. The effects of premolar-extraction: a long-term comparison of outcomes in "clear-cut" extraction and nonextraction Class II patients. Angle Orthod. 1993;63:257-72. 24 12. Demir A, Uysal T, Sari Z, Basciftci FA. Effects of camouflage treatment on dentofacial structures in Class II division 1 mandibular retrognathic patients. Eur J Orthod. 2005;27:524-31. 13. Işiksal E, Hazar S, Akyalçin S. Smile esthetics: Perception and comparison of treated and untreated smiles. Am J Orthod Dentofacial Orthop. 2006;129:8-16. 14. Bishara SE, Cummins DM, Zaher AR. Treatment and posttreatment changes in patients with Class II, Division 1 malocclusion after extraction and nonextraction treatment. Am J Orthod Dentofacial Orthop. 1997;111:18-27. 15. Pandis N, Strigou S, Eliades T. Maxillary incisor torque with conventional and self-ligating brackets: A prospective clinical trial. Orthod and Craniofacial Research. 2006;9:193-8. 16. Gioka C, Eliades T. Materials-induced variation in the torque expression of preadjusted appliances. Am J Orthod Dentofacial Orthop. 2004;125:323-8. 17. Sebanc J, Brantley WA, Pincsak JJ, Conover JP. Variability of effective root torque as a function of edge bevel on orthodontic arch wires. Am J Orthod. 1984;86:43-51. 18. Meling TR, Odegaard J, Meling EO. On mechanical properties of square and rectangular stainless steel wires tested in torsion. Am J Orthod Dentofacial Orthop. 1997;111:310-20. 19. Thickett E, Taylor NG, Hodge T. Choosing a pre-adjusted orthodontic appliance prescription for anterior teeth. J Orthod. 2007;34:95-100. 20. Moesi B, bracket outcome Orthod. Dyer F, Benson PE. Roth versus MBT: Does prescription have an effect on the subjective of pre-adjusted edgewise treatment? Eur J 2013;35:236-43. 21. Ugur T, Yukay F. Normal faciolingual inclinations of tooth crowns compared with treatment groups of standard and pretorqued brackets. Am J Orthod Dentofacial Orthop. 1997;112:50-7. 25 22. Graber LW, Vanarsdall Jr RL, Vig KW. Orthodontics: current principles and techniques: Elsevier Health Sciences; 2011. 23. Badawi HM, Toogood RW, Carey JP, Heo G, Major PW. Torque expression of self-ligating brackets. Am J Orthod Dentofacial Orthop. 2008;133:721-8. 24. Sifakakis I, Pandis N, Makou M, Eliades T, Bourauel C. A comparative assessment of the forces and moments generated at the maxillary incisors between conventional and self-ligating brackets using a reverse curve of Spee NiTi archwire. Aus Orthod J. 2010;26:127-33. 25. Archambault A, Major TW, Carey JP, Heo G, Badawi H, Major PW. A comparison of torque expression between stainless steel, titanium molybdenum alloy, and copper nickel titanium wires in metallic self-ligating brackets. Angle Orthod. 2010;80:884-9. 26. Odegaard J, Meling T, Meling E. The effects of loops on the torsional stiffnesses of rectangular wires: an in vitro study. Am J Orthod Dentofacial Orthop. 1996;109:496-505. 26 CHAPTER 3: JOURNAL ARTICLE Abstract Purpose: The purpose of this study is to determine if there is a significant difference in upper incisor inclination (torque) in four bicuspid extraction cases between two different methods of space closure. Materials and Methods: Two samples of 30 adolescent, Caucasian, Class II div. 1 patients treated with four bicuspid extractions were obtained from two separate private orthodontic practices. The first group was treated using the Tweed-Merrifield approach using a standard edgewise (zero-tip, zero-torque) appliance with rectangular stainless steel archwires with closing loops for space closure. The second group used a pre-angulated, self-ligation, Roth prescription appliance with Retranol® (“work-hardened” reverse-curve NiTi) archwires and sliding mechanics. Pre-treatment and post- treatment cephalograms were used to measure four angular and 12 linear measurements. Independent T-tests were performed to analyze the differences between the groups before and after treatment. Results: There was a statistically significant difference between the final upper incisor inclination (U1-SN), and final lower incisor inclination (IMPA) between the groups. 27 There were no other significant differences between the groups as measured in the upper and lower molars, the vertical and horizontal position of the upper and lower incisors and the upper and lower lips in relation to the E-plane. Conclusions: The Retranol® group had significantly higher upper incisor inclination at the end of treatment. Lower incisor inclination (IMPA) was also significantly higher in the Retranol® group. There were no other significant differences in the measured variables between the groups. 28 Introduction Having the correct buccolingual inclination of the upper incisors is important for correct occlusal relationships, anterior guidance, and proper esthetics in orthodontic treatment.1 Insufficient upper incisor torque affects the arch-length and may inhibit complete Class II correction.2 Studies have shown that for every 5 degrees of change in anterior inclination, about 1mm of arch length is gained.3,4,5 When premolars are extracted, the anterior teeth often require large increments of retraction that can cause lingual tipping of the upper incisors (torque-loss). Many studies have shown that there is often a significant loss of anterior torque in premolar extraction cases with traditional edgewise mechanics.6,7,8,9 One study compared an extraction group with space closure on a reverse-curve NiTi wire using a Roth prescription to a non-extraction group. They found the mean changes for U1-SN was not significant between the groups.10 Torque expression is generally achieved by increasing archwire dimensions, until the edges of a rectangular wire engage the edges of the bracket slot. However, the dimensions of the final wire almost never completely fill 29 the bracket slot, and a certain amount of “play” or “slop” exists, which leaves a certain amount of torque unexpressed.11 The amount of archwire-bracket-slot “play” has been theoretically and experimentally calculated,11 and there often exists a considerable discrepancy between the two values.12 The variation between theoretical and experimentally calculated torque values can be attributed to several factors including, variations in archwire13,14,15 and bracket12 slot dimensions, archwire beveling, bracket deformation16, tooth position, and bracket placement errors.17 There have been numerous advancements in bracket torque prescriptions to counteract torque loss2,18,19. Many researchers have compared different bracket systems with respect to upper incisor inclination19,20. Ugur and colleagues compared upper incisor inclinations in nonextraction patients treated with a standard edgewise appliance and a Roth prescription appliance, and they found no difference between the groups20. Researchers have also examined the effects of selfligating brackets on upper incisor torque control.10,21,22,23 Badawi et al. compared torqueing moments with active and passive self-ligating brackets. 30 They found a significant difference between the engagement angle between the groups (7.5 degrees for active, 15 degrees for passive).22 Sifakakis et al. compared torqueing moments using reversecurve NiTi wires with conventional and self-ligating brackets. They found that torqueing moments were higher with the self-ligating brackets.23 Many researchers have compared different types of archwires tested in torsion.24, 25 Meling and colleagues found that precise torque delivery with stainless steel wire is difficult due to torsional play and the narrow working range of twist to achieve the ideal torqueing moment.24 Closing loops are commonly used in orthodontics to close extraction spaces because teeth can be retracted without friction. Odegaard and colleagues have described that when activated, closing loops create a lingual tipping moment on the anterior teeth, and therefore it is necessary to apply torque to the anterior segment.26 Closing loops have also been shown to decrease the torsional stiffness of the wire and therefore also decreases the torsional moment delivered to the upper incisors.26 Several researchers have utilized and proposed using pre-torqued or reverse-curve NiTi wires for torqueing or 31 space closure applications.10,27,23 Sifakakis describes that reverse-curve NiTi wires deliver an intrusive force to the anterior teeth, as well as a labio-palatal torqueing moment.23 Pandis et al. used reverse curve of Spee NiTi wires during space closure in four bicuspid extraction cases.10 Materials and Methods Method Pre-treatment and post-treatment cephalograms from two different samples were hand-traced. Two reference planes were constructed on each cephalogram similar to the method used previously by Lemery28. The reference planes served as an X-Y coordinate grid and were used to make the linear measurements (with exception of the upper and lower lips to E-plane). A horizontal line was made at the Sella-Nasion line minus 7 degrees (SN-7) through Sella. A vertical line was constructed perpendicular to the SN-7 line, also through Sella (Fig. 3.1). Four angular (ANB, U1-SN, IMPA, and SN-GoGn)(Fig. 3.2) and twelve linear (U1 vertical, U1 horizontal, L1 vertical, L1 horizontal, U6 vertical, U6 horizontal, L6 vertical, L6 horizontal, E-plane to upper lip, E-plane to lower lip, Menton vertical, Menton horizontal)(Fig. 3.3) measurements were made on both the 32 pre-treatment and post-treatment cephalograms and all data were entered into an Excel spreadsheet for data analysis and manipulation. Fig 3.1. X-Y coordinate grid system constructed from SN-7 degrees and SN-7 degrees perpendicular. 33 Fig. 3.2. Angular measurements: ANB, U1-SN, IMPA, SN-GoGn. 34 Fig. 3.3. Vertical and horizontal (AP) measurements. Standard Edgewise Sample A sample of 30 Caucasian, previously treated Class II div. 1 patients was obtained from a single private practice orthodontist who practices using the Tweed-Merrifield approach. All patients were treated with a standard edgewise appliance (zero tip, zero torque), and had four bicuspids extracted before treatment. As part of their orthodontic treatment, all patients had extraction space closure with rectangular stainless steel wires and closing loops. Headgear and Class II elastics were used to treat 35 this group of patients at the discretion of the orthodontist. Of the 30 patients that met the inclusion criteria, 25 were female, and 5 were male. Each patient required a pre-treatment and post-treatment cephalogram of good quality, with the teeth in occlusion and the lips relaxed. Retranol® Sample A sample of 30 Caucasian, previously treated Class II div. 1 patients was obtained from a single private practice orthodontist. All patients were treated with a Roth straight-wire appliance, and had four bicuspids extracted before orthodontic treatment. Extraction space closure was done using .019 X .025 inch Retranol® wires with elastomeric chain (sliding mechanics), after retraction of the cuspids. Headgear, temporary anchorage mini-screws, and Class II elastics were used as needed at the discretion of the orthodontist. A sample of 25 female and 5 male patients was chosen from the patients that met the inclusion criteria in order to closely match the patient profile of the standard edgewise group. Each patient required a pre-treatment and post-treatment cephalogram of good quality with the teeth in occlusion and the lips relaxed. 36 Error of the Method The Retranol samples radiographs were calibrated using Dolphin Imaging and printed to actual life size. A correction for magnification of -12.9% was applied to the standard edgewise group to account for the magnification in the sample. This value was calculated using a calibrated bar in the radiographs. This amount of correction for magnification is similar to that applied in the Michigan Growth Study29. Reliability Cronbach’s alpha was used to determine consistency of the measurements. Reliability is considered to be “adequate” when intra-class correlations re greater than or equal to 0.80. Ten percent of both samples (3 patients from each group) were randomly selected and re-measured to test for intra-examiner reliability. The actual results of the Cronbach’s alpha were well above 0.90 for all variables measured. This showed that the measured and repeated measurements were at an acceptable level of reliability for accuracy of measurements. 37 Results All data were imputed in SPSS and independent t-tests were used to analyze the linear and angular measures for both pre-treatment and post-treatment results for both groups, with a significance level of p ≤ 0.05. When considering the vertical and horizontal changes of the incisors and molars that occurred during the treatment, one must account for growth of the maxilla and mandible during this period. Attempts were made to match the samples by age, gender distribution, and treatment time to minimize any differences that may occur due to growth. Sample Demographics Age and Treatment Duration The starting and final ages for both groups is summarized in table 3.1. There were no significant differences in either start or final ages between groups. There was a significant difference in average treatment time between the groups (p=0.002). However, treatment duration is a complex issue and the efficiency of the two treatments was not a primary focus of this study. The age and treatment duration for the two groups is summarized in Table 3.1. 38 Table 3.1. Summary of ages and treatment time for standard edgewise and Retranol® groups. Age or Treatment time Start Age Standard Edgewise Mean ± SD 12.8 ± 1.5 Retranol® Mean ± SD t Sig. (2tailed) 13.2 ± 1.2 -1.036 .305 Final Age 15.2 ± 1.6 15.3 ± 1.2 -2.50 .803 2.2 ± 0.2 3.17 .002* Treatment 2.5 ± 0.5 Duration *denotes p≤0.05 ANB and SN-GoGn The start and final ANB and SN-GoGn were similar for both groups. There were no significant differences between the groups. See table 3.2 for a summary of ANB and SN-GoGn changes. Table 3.2 Summary of ANB and SN-GoGn for both standard edgewise and Retranol® groups. Measurement ANB Start ANB Final SN-GoGn Start SN-GoGn Final Standard edgewise Mean ± SD 4.6 ± 1.9 2.2 ± 1.7 30.9 ± 4.8 Retranol® Mean ± SD t Sig. (twotailed) 4.2 ± 1.7 2.4 ± 1.5 32.3 ± 5.2 1.024 -.422 -1.045 .301 .674 .301 31.5 ± 5.7 32.3 ± 6.6 -.514 .609 39 Upper Incisor The standard edgewise group had a starting U1-SN of 106.1 ± 6.0 degrees. The Retranol® group had a starting U1-SN of 103.4 ± 7.2 degrees. The average starting difference of U1-SN between the groups was 2.7 degrees. However, this difference was not significant (p=.125). The standard edgewise group had a final U1-SN of 101.9 ± 6.9 degrees (see Fig. 3.2). This represented a difference of -4.2 degrees from the start U1-SN value. The Retranol group had a final U1-SN of 106.1 ± 6.1 degrees. This represented a difference of +2.7 degrees from the start value. The difference between the groups was statistically significant (p=.015). The start and final vertical and horizontal position of the upper incisors was not significant between the groups. A summary of the upper incisor changes can be found in table 3.3. 40 Fig. 3.4. Upper incisor (U1) and upper molar (U6) changes in the standard edgewise group (Black line) and the Retranol® group (Gray line). Solid lines: pre-treatment. Dotted lines: post-treatment. Figure is not to scale. Table 3.3. A summary of the upper incisor (U1) changes for standard edgewise and Retranol® groups. Measurement U1-SN Start U1-SN Final Standard Edgewise Mean ± SD 106.1 ± 6.0 101.9 ± 6.9 65.1 ± 4.2 U1 Vertical Start U1 Vertical 67.3 ± 4.1 Final U1 67.6 ± 5.8 Horizontal Start U1 64.4 ± 5.6 Horizontal Final *denotes p≤.05 Retranol® Mean ± SD t Sig. (2tailed) 103.4 ± 7.2 106.1 ± 6.1 65.2 ± 3.7 1.556 .125 -2.495 .015* -.082 .935 66.8 ± 3.9 .459 .648 65.5 ± 6.0 1.433 .157 63.6 ± 6.1 .528 .599 41 Lower Incisor The starting IMPA difference between the groups was not significant (p=.594). The final IMPA in the standard edgewise group was 90.5 ± 5.8 degrees, a difference of -3.1 degrees. The final IMPA in the Retranol® group was 95.9 ± 6.5 degrees, a difference of +1.3 degrees. The difference in final IMPA was significant between the groups (p<.001). A summary comparing the treatment effects of the lower incisor can be found in Table 3.4. The start and final position vertical and horizontal position of the lower incisors was not significant (Table 3.4). 42 Table 3.4. A summary of the lower incisor changes with standard edgewise and Retranol® groups. Measurement Standard Edgewise Mean ± SD 93.6 ± 6.0 Retranol® Mean ± SD t Sig. (2tailed) 94.6 ± 7.2 -.535 .594 ± 5.8 95.9 ± 6.5 -3.370 <.001* ± 4.4 62.7 ± 3.5 -1.530 .131 ± 3.8 65.6 ± 3.8 -.271 .788 ± 5.5 61.3 ± 5.5 .495 .622 ± 5.8 60.5 ± 5.9 .802 .426 IMPA Start (degrees) IMPA Final 90.5 (degrees) L1 Vertical 61.2 Start (mm) L1 Vertical 65.3 Final (mm) L1 62.0 Horizontal Start (mm) L1 61.7 Horizontal Final (mm) *denotes p<.05 Upper Molar Vertical and horizontal starting position and changes to the upper molar (U6) in both the standard edgewise and Retranol® groups were similar and there were no significant differences between groups. A summary of the U6 changes can be seen in Table 3.5. 43 Table 3.5. Summary of upper molar (U6) changes with standard edgewise and Retranol® groups. Measurement U6 Vertical Start U6 Vertical Final U6 Horizontal Start U6 Horizontal Final Standard Edgewise Mean ± SD 55.1 ± 3.4 Retranol® Mean ± SD t Sig. (2tailed) 56.2 ± 2.8 -1.405 .165 58.1 ± 3.4 59.4 ± 3.1 -1.528 .132 29.6 ± 4.4 29.3 ± 4.3 .230 .819 32.5 ± 4.8 33.4 ± 5.3 -.650 .518 Lower Molar Vertical and horizontal starting position and changes to the lower molar (L6) in both the standard edgewise and Retranol® groups were similar and there were no significant differences between groups. A summary of the L6 changes can be seen in Table 3.6. 44 Table 3.6: Summary of lower molar (L6) changes with standard edgewise and Retranol® groups. Measurement L6 Vertical Start L6 Vertical Final L6 Horizontal Start L6 Horizontal Final Standard Edgewise Mean ± SD 60.7 ± 3.6 Retranol® Mean ± SD t Sig. (2tailed) 61.0 ± 3.0 -.297 .767 64.2 ± 3.9 64.6 ± 3.2 -.430 .669 29.0 ± 4.7 28.0 ± 4.6 .803 .425 33.4 ± 5.2 33.8 ± 5.4 -.319 .751 E Plane There were no significant differences between the groups with the upper and lower lip to E plane before or after treatment. Table 3.7 provides a summary of the upper and lower changes during treatment. Table 3.7. Summary of upper and lower lips to E-Plane in both standard edgewise and Retranol groups. Measurement L Lip/E Plane Start L Lip/E Plane Final U Lip/E Plane Start U Lip/E Plane Final Standard Edgewise Mean ± SD -1.0 ± 2.8 Retranol Mean ± SD t Sig. (2tailed) -1.7 ± 2.6 1.018 .313 -4.0 ± 2.4 -4.5 ± 2.4 .933 .355 -2.1 ± 3.2 -3.2 ± 1.6 1.682 .098 -5.9 ± 2.7 -6.0 ± 2.1 .026 .979 45 Discussion The purpose of this study was to determine if there was a significant difference in the final upper incisor angulation between cases treated with a standard edgewise appliance with closing loops on rectangular stainless steel wires, and a Roth prescription appliance with space closure using Retranol® (“work-hardened” preformed, reverse-curve NiTi) archwires and sliding mechanics. In addition to upper incisor angulation (U1-SN), three other angular and 12 linear measurements were made on the upper and lower incisors, upper and lower molars, Menton, and the upper and lower lips to E-plane. Sample Demographics Attempts were made to match the samples closely in regard to age, treatment time, and gender composition. The goal, in this regard, was to minimize any differences in growth that occurred during the treatment period. In other words, if growth is similar between the groups, then any changes seen in pre-and –post treatment cephalograms due to growth, will cancel out. 46 Age There was a 0.4 years difference in starting age between the groups (standard edgewise = 12.8 +/- 1.5 years, Retranol® = 13.2 +/- 1.2 years). was not significant. This difference, however, A difference of several months would unlikely produce any significant differences in size between the groups at the start of treatment, and indeed, did not. The average age of the two groups at the end of treatment was virtually the same, with a difference of only 0.1 years (standard edgewise = 15.2 +/- 1.6 years, Retranol® = 15.3 +/- 1.6 years). The length of treatment difference was significant between the groups (p=0.002), however, the purpose of this study was not to determine efficiency of the space closure or total time in treatment. Treatment duration is a complex topic and involves treatment mechanics along with practice management decisions, and therefore, it is not appropriate to determine that one method of space closure is more efficient than another based on this methodology. Growth Both groups had similar overall size, and showed similar growth during the treatment period. The ANB angle was similar in both groups before and after treatment. 47 Similar initial size and growth was seen in both vertical and horizontal directions as measured at Menton, indicating that mandibular growth was similar in both groups. Upper Incisor There was a significant difference between the final upper incisor inclination (U1-SN) between the groups (p=.015). The starting position of the upper incisors in the standard edgewise group, on average, were more protrusive than in the Retranol® group (about 2.1 mm more anterior, and 2.7 degrees greater U1-SN). However, these starting differences were not statistically significant. After final treatment, the standard edgewise group lost -4.2 degrees of torque and the Retranol® group gained +2.7 degrees. Comparison to previous studies Standard Edgewise Studies There have been many previous studies that have shown a similar loss of upper incisor torque in extraction cases when treated with a standard edgewise appliance.6,7,8,9 Luppanapornlarp and colleagues,6 saw a torque loss of -4.6 degrees in their sample of standard edgewise patients treated with four bicuspid extractions. 48 Demir et al. also saw a significant torque loss in their study using standard edgewise appliances (-6.0 degrees)7. Bishara and colleagues9 saw a loss of -9.8 degrees in U1-SN after extractions. Table 3.8. Comparison of upper incisor inclinations from previous extraction studies. Study Treatment type Luppanpornlarp6 et al., 1993 Demir7 et al., 2005 Jamison et al., 2014 Jamison et al., 2014 Standard edgewise Standard edgewise Standard edgewise Roth appliance with Retranol® U1-SN start (degrees) 104.3 U1-SN Final (degrees) 99.7 U1-SN Change (degrees) -4.6 103.7 97.7 -6.0 106.1 101.9 -4.2 103.4 106.1 +2.7 Reverse-curve NiTi The method of space closure in the Retranol® group was similar in method to that used in a study by Pandis and colleagues.10 They compared upper incisor inclination in extraction and non-extraction groups, and used .019 X .025 inch reverse-curve NiTi wires with elastomeric chain in a Roth prescription. This study was the only one found in which there was not a significant difference in U1-SN in an extraction case.10 Sifakakis et al.23 found that torqueing moments with active self-ligating brackets and reverse49 curve NiTi wires were between 16.5-16.9 N/mm. This value is within the agreed range (5-20 N/mm) necessary for torqueing a maxillary central incisor. While the exact torqueing moment of the Retranol® wire is unknown, it is reasonable to assume that based on previous studies, it would generate a torqueing moment within the biologic range listed in the literature. Conclusions 1. The Retranol® group showed significantly more upper incisor inclination than the standard edgewise group at the end of treatment. 2. Lower incisor inclination (IMPA) was also significantly higher at the end of treatment in the Retranol® group. 3. No other dental or soft tissue variables were significantly different between the groups. 50 Literature Cited 1. Rauch ED. Torque and its application to orthodontics. Am J Orthod. 1959;45:817-30. 2. Andrews LF. The six keys to normal occlusion. Am J Orthod. 1972;62:296-309. 3. Hussels W, Nanda RS. Effect of maxillary incisor angulation and inclination on arch length. Am J Orthod Dentofacial Orthop. 1987;91:233-9. 4. O'Higgins EA, Kirschen RH, Lee RT. The influence of maxillary incisor inclination on arch length. Br J Orthod. 1999;26:97-102. 5. Archambault A, Lacoursiere R, Badawi H, Major PW, Carey J, Flores-Mir C. Torque expression in stainless steel orthodontic brackets. A systematic review. Angle Orthod. 2010;80:201-10. 6. Luppanapornlarp S, Johnston Jr LE. The effects of premolar-extraction: a long-term comparison of outcomes in "clear-cut" extraction and nonextraction Class II patients. Angle Orthod. 1993;63:257-72. 7. Demir A, Uysal T, Sari Z, Basciftci FA. Effects of camouflage treatment on dentofacial structures in Class II division 1 mandibular retrognathic patients. Eur J Orthod. 2005;27:524-31. 8. Işiksal E, Hazar S, Akyalçin S. Smile esthetics: Perception and comparison of treated and untreated smiles. Am J Orthod Dentofacial Orthop. 2006;129:8-16. 9. Bishara SE, Cummins DM, Zaher AR. Treatment and posttreatment changes in patients with Class II, Division 1 malocclusion after extraction and nonextraction treatment. Am J Orthod Dentofacial Orthop. 1997;111:18-27. 10. Pandis N, Strigou S, Eliades T. Maxillary incisor torque with conventional and self-ligating brackets: A prospective clinical trial. Orthod and Craniofacial Research. 2006;9:193-8. 51 11. Gioka C, Eliades T. Materials-induced variation in the torque expression of preadjusted appliances. Am J Orthod Dentofacial Orthop. 2004;125:323-8. 12. Sebanc J, Brantley WA, Pincsak JJ, Conover JP. Variability of effective root torque as a function of edge bevel on orthodontic arch wires. Am J Orthod. 1984;86:43-51. 13. Ødegaard J, Meling E, Meling T. An evaluation of the torsional moments developed in orthodontic applications. An in vitro study. Am J Orthod Dentofacial Orthop. 1994;105:392-400. 14. Meling TR, Ødegaard J. On the variability of crosssectional dimensions and torsional properties of rectangular nickel-titanium arch wires. Am J Orthod Dentofacial Orthop. 1998;113:546-57. 15. Siatkowski RE. Loss of anterior torque control due to variations in bracket slot and archwire dimensions. J Clinic Orthod. 1999;33:508. 16. Flores DA, Choi LK, Caruso JM, Tomlinson JL, Scott GE, Jeiroudi MT. Deformation of metal brackets: a comparative study. Angle Orthod. 1994;64:283-90. 17. Balut N, Klapper L, Sandrik J, Bowman D. Variations in bracket placement in the preadjusted orthodontic appliance. Am J Orthod Dentofacial Orthop. 1992;102:62-7. 18. Thickett E, Taylor NG, Hodge T. Choosing a pre-adjusted orthodontic appliance prescription for anterior teeth. J Orthod. 2007;34:95-100. 19. Moesi B, bracket outcome Orthod. Dyer F, Benson PE. Roth versus MBT: Does prescription have an effect on the subjective of pre-adjusted edgewise treatment? Eur J 2013;35:236-43. 20. Ugur T, Yukay F. Normal faciolingual inclinations of tooth crowns compared with treatment groups of standard and pretorqued brackets. Am journal Orthod Dentofacial Orthop. 1997;112:50-7. 52 21. Graber LW, Vanarsdall Jr RL, Vig KW. Orthodontics: current principles and techniques: Elsevier Health Sciences; 2011. 22. Badawi HM, Toogood RW, Carey JP, Heo G, Major PW. Torque expression of self-ligating brackets. Am J Orthod Dentofacial Orthop. 2008;133:721-8. 23. Sifakakis I, Pandis N, Makou M, Eliades T, Bourauel C. A comparative assessment of the forces and moments generated at the maxillary incisors between conventional and self-ligating brackets using a reverse curve of Spee NiTi archwire. Aus Orthod J. 2010;26:127-33. 24. Meling TR, Odegaard J, Meling EO. On mechanical properties of square and rectangular stainless steel wires tested in torsion. Am J Orthod Dentofacial Orthop. 1997;111:310-20. 25. Archambault A, Major TW, Carey JP, Heo G, Badawi H, Major PW. A comparison of torque expression between stainless steel, titanium molybdenum alloy, and copper nickel titanium wires in metallic self-ligating brackets. Angle Orthod. 2010;80:884-9. 26. Odegaard J, Meling T, Meling E. The effects of loops on the torsional stiffnesses of rectangular wires: an in vitro study. Am J Orthod Dentofacial Orthop. 1996;109:496-505. 27. Mittal N, Xia Z, Chen J, Stewart KT, Liu SS. Threedimensional quantification of pretorqued nickeltitanium wires in edgewise and prescription brackets. Angle Orthod. 2013;83:484-90. 28. Lemery S. A longitudinal cephalometric study of the soft tissue profile of male and female Class I and Class II subjects. Master's Thesis. St. Louis: St. Louis University. 2006. 29. Riolo ML, Moyers RE, McNamara JA, Hunter WS. An atlas of craniofacial growth: cephalometric standards from the University School Growth Study, the University of Michigan: Center for Human Growth and Development, University of Michigan; 1974. 53 APPENDIX Materials and Methods Details Table A.1. Landmarks and Definitions Abbreviation Landmark A Subspinale Definition The deepest midline point of the curve of the maxilla between the anterior nasal spine and prosthion. The most posterior point in the midline of the symphyseal of the mandible in the concavity between infradentale and pogonion. A line connecting the soft tissue pogonion to the tip of the nose. The most anterior and inferior midline point on the external contour of the symphysis of the mandible. The incisal tip of the lower central incisor. B Supramentale E-Plane E-Plane Gn Gnathion L1 Lower Incisor L Lip Lower Lip L6 Lower Molar Me Menton N Nasion Point at the junction of the nasal bone and frontal bone. U1 Upper Incisor The incisal tip of the upper central incisor. U Lip Upper Lip The most anterior point on the curvature of the upper lip. The most anterior point on the curvature of the lower lip. The posterior contact (height of contour) of the mandibular first molar. The most inferior point on the symphyseal outline. 54 Table A.1. Landmarks and Definitions (continued). Abbreviation Landmark Upper Molar U6 S Sella Definition The posterior contact (height of contour) of the maxillary first molar. The center of the pituitary fossa of the sphenoid bone. Determined by inspection. Table A.2. Measurement Abbreviation Key Abbreviation ANB Measurement Angle formed by connecting A point, Nasion, and B point. The angle formed by the intersection of the long axis of the upper central incisor and the SN line. The angle formed by a line extending from the long axis of the lower central incisor intersecting the mandibular plane. The angle formed by the Sella-Nasion line intersecting with a line formed by the mandibular plane. The vertical distance from the SN-7 line to the upper central incisor tip measured perpendicularly. The horizontal distance from a line perpendicular to SN-7 (through Sella) to the upper central incisor tip. The vertical distance from the SN-7 line to the lower central incisor tip measured perpendicularly. U1-SN IMPA SN-GoGn U1-Vert (mm) U1-Horizontal (AP) (mm) L1-Vert (mm) 55 Table A.2. Measurement Abbreviation Key (continued) Abbreviation Measurement L1-Horizontal (AP) (mm) The horizontal distance from a line perpendicular to SN-7 (through Sella) to the lower central incisor tip. The vertical distance from the SN-7 line to the upper first molar at the height of contour on the distal surface measured perpendicularly. The horizontal distance from a line perpendicular to SN-7 (through Sella) to the upper first molar at the height of contour on the distal surface. The vertical distance from the SN-7 line to the lower first molar at the height of contour on the distal surface measured perpendicularly. The horizontal distance from a line perpendicular to SN-7 (through Sella) to the lower first molar at the height of contour on the distal surface. Distance in mm of the lower lip to the E-plane. U6-Vert (mm) U6-Horizontal (AP) L6-Vert L6-Horizontal (AP) Lower Lip/E-Plane Upper Lip/E-Plane Distance in mm of the upper lip to the E-plane. Menton Vert The horizontal distance from a line perpendicular to SN-7 (through Sella) to Menton. The vertical distance from the SN-7 line to Menton measured perpendicularly. Menton Horizontal (AP) 56 VITA AUCTORIS Kyle Jamison was born July 14, 1981 in West Covina, California to Brad and Shaunna Jamison. From the age of 5 years old, he was raised in Folsom, California along with his five brothers. After graduating from Folsom High School, he served a two-year LDS mission in Madagascar where he learned to speak French and Malagasy. After his mission he earned a degree in biology from California State University Sacramento, where he graduated Summa Cum Laude. He continued his education at the University Of Nevada Las Vegas School Of Dental Medicine, where he earned multiple academics honors including graduating Summa Cum Laude, and being inducted into the Omicron Kappa Upsilon honor society. He was then accepted into the orthodontic program at Saint Louis University where he will graduate in December 2014. He plans to move back to California and open his own orthodontic practice. Kyle married his wife Dayna in 2003 in California. They have 3 wonderful children, Kylie, Tre, and Kellen. 57