CURRICULUM VITAE Kyle Higginbottom

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1 CURRICULUM VITAE Kyle Higginbottom I. Education Baltimore College of Dental Surgery, Dental School, University of Maryland Orthodontic Residency Baltimore, MD Anticipated June 2014 Orthodontics Certificate; M.S in Biomedical Science Baltimore College of Dental Surgery, Dental School, University of Maryland Baltimore, MD Doctor of Dental Surgery, Magna Cum Laude, May 2011 Washington College Chestertown, MD Major: Biology Bachelor of Science, Magna Cum Laude, May 2007 Chesapeake College Wye Mills, MD College courses were taken during high school II. Professional Experience Orthodontic Externship Dr. Tarun Saini, Saini Orthodontics Over the period of 3 weeks, Dr. Tarun Saini and Dr. Raj Saini will be reviewing various types of cases and appliances. Attention will also be focused on treatment planning cases with Cone Beam Computed Tomography scans. August 2010 Orthodontic Clerkship Dr. Frederick Preis, University of Maryland Dental School This program provides participation in didactic seminars, clinical patient treatment, postgraduate rotation, and research. In addition, students are exposed to the biomechanics of tooth movement, laboratory procedures including appliance construction and organizational dentistry. Students participate in diagnosis and treatment planning via case presentations. August 2010 May 2011 Orthodontic Study Group Dr. Tarun Saini, Saini Orthodontics This group allows a few dental students to receive additional exposure to the specialty of orthodontics. Topics such as treatment planning orthodontic cases, CBCT and how to read the scan, Dolphin software, as well as several journal articles have all been covered. March 2009 Present

2 Pediatric Dentistry Clerkship University of Maryland Dental School This course allows selected Year III students to pursue further studies in pediatric dentistry specially designed to meet their needs and interests. Students devote a portion of their clinic time to this specialized program; the remaining clinic time is spent in the comprehensive treatment of patients in the regular program. The course includes clinical activities in the undergraduate and postgraduate clinics and didactic seminars. Enrichment activities include humanities seminars, public health experiences, and career planning. July 2009 June 2010 Orthodontic Interest Group University of Maryland Dental School Membership includes participation in lunchtime lectures in topics of interest in orthodontics. I am currently the organizer of this group Orthodontic Practice Assistant/Sterilization technician Dr. Mark Higginbottom, Higginbottom Orthodontics Sterilization technician, developed radiographs, and assisted with lab work III. Research and Teaching Experience Lecture Ortho-Perio Seminar series University of Maryland Dental School Presented on the topic of TADs October 2012 Lecture Ortho-Pedo Seminar series University of Maryland Dental School Presented on the topic of CL III Treatment June 2012 Orthodontic Course University of Maryland Dental School Lectured on Diagnosis and Treatment planning to 3rd year Dental students present Growth and Development Course University of Maryland Dental School Lectured on Growth and Development to 2nd year Dental students, UMB 2012-present Teaching Assistant in Orthodontics Lab University of Maryland Dental School Reviewed Clinical and Laboratory procedures with 2nd year Dental students present

3 Student Researcher/ Researcher s Assistant Dr. Gary Hack University of Maryland Dental School We were investigating if there was a correlation between schizophrenia and dental anomalies IV. Professional Activities American Student Dental Association Member Maryland Student Dental Association Member 2007-present Academy of General Dentistry Member Hispanic Dental Association Member American Association of Orthodontics Member 2011-present V. Service Activities and Committee Assignments Class of 2011 Community Service Chair Hispanic Dental Association Treasurer Committee on Dental Recruitment and Admissions Baltimore College of Dental Surgery, Dental School, University of Maryland This committee gives dental students the opportunity to be involved in the application process. August Class of 2011 Community Service Committee Baltimore College of Dental Surgery, Dental School, University of Maryland This committee helps to organize and participate in community service events throughout the year Over 80 hours of community service include HDA Helping Haiti Smile Fundraiser University of Maryland Dental School January 2010

4 Dentistry Today University of Maryland Dental School June 2009, June 2010 Oral Hygiene Visits Phelps Luck Elementary School Columbia, MD (Coordinator) May 2009, May 2010 Wolfe Street Academy Baltimore, MD April 2009 Ronald McDonald House Baltimore, MD June 2009, April 2010 Oral Cancer Walk Baltimore, MD April 2009, April 2010 BCDS Iron Chef Fundraiser for Quest for Care University of Maryland Dental School March 2009 Habitat for Humanity Baltimore, MD May 2009 Angel Tree Project University of Maryland Dental School (Coordinator) To provide Christmas/other religious holiday gifts to the less fortunate students at Phelps Luck Elementary School Columbia, MD December 2008, December 2009, December 2010 Phelps Luck after school program Columbia, MD Voter Registration University of Maryland Dental School October 2008 HUM Lunch University of Maryland Dental School We served lunch to members of the HUM program February 2011 VI. Honors Dean s Award for Outstanding Community Service Baltimore College of Dental Surgery, Dental School, University of Maryland Awarded to those students who perform an average of 25 hours of community services per semester starting in the Spring semester of

5 Gorgas Odontological Honorary Society Baltimore College of Dental Surgery, Dental School, University of Maryland To be eligible for membership, a student must rank in the top one-third of the class, must have achieved and maintained a minimum grade point average of 3.00 in all combined courses, and must not have repeated for scholastic reasons any subject. Speakers prominent in the dental and medical fields are invited to address members at monthly meetings Gamma Pi Delta Prosthodontic Honor Society Baltimore College of Dental Surgery, Dental School, University of Maryland An honorary student dental organization with scholarship and interest in the field of prosthetic dentistry as a basis for admission. The objective of the organization is the advancement of prosthetic dentistry through lectures, table clinics, and other academic activities that stimulate the creative interest of students and the profession in general , President The Department of Biology Professional Award Washington College Awarded to the graduation biology major who has demonstrated academic excellence, is pursuing a professional degree, and has a strong potential for success in a professional field. May 2007 Beta Beta Beta Biological National Honor Society Washington College VII. Licensure and Testing NERB Certificate May 2011 Invisalign Certification 2011-present

6 ABSTRACT Title of Thesis: The Effect of Annealing on the Elastic Modulus of Orthodontic Wires Kyle Higginbottom, D.D.S, Master of Science, 2014 Thesis Directed By: Robert Williams, D.M.D., M.A. Clinical Associate Professor Department of Orthodontics, University of Maryland, Baltimore Introduction: Nickel Titanium orthodontic wires are currently used in orthodontic treatment due to their heat activated properties and their delivery of constant force. The objective of this study was to determine the effect of annealing on the elastic modulus of Nickel Titanium, Stainless Steel and Beta-titanium (TMA) wires. Different points along the wire were tested in order to determine how far from the annealed ends the elastic modulus of the wires was affected. Methods: Eighty (80) orthodontic wires consisting of 4 equal groups (SS/TMA/Classic Nitinol /Super Elastic Nitinol ) were used as the specimens for this study. All wires were measured and marked at 5mm measurements, and cut into 33.00mm sections. The wires were heated with a butane torch until the first 13.00mm of the wires were red hot. Load deflection tests using an Instron universal testing machine were run at 5mm distances from the end of the wire that had been annealed. The change in elastic modulus was then determined. Results: There was a significant difference (F = , p = ) in the change in elastic modulus for the four distances. There was also a significant difference (F = , p = ) in the

7 change in elastic modulus for the four wire types. There was a significant interaction (F = , p = 0.005) between wire type and distance, however this interaction negated the differences between the wires. Conclusion: 1) There are significant differences in the changes in elastic modulus between the areas of the wires within the annealed section and those areas 5mm and 10mm away from the annealed section. The change in elastic modulus within the annealed section was significantly greater at 8 mm than it was at 13mm, and this was significantly greater than 18mm and 23mm (5mm and 10mm beyond the annealed section). However, there was no statistical difference in the change in elastic modulus between 5mm and 10mm away from the annealed section (18mm and 23mm respectively). 2) Regardless of the wire type, no clinically important effects were seen 5mm and 10mm beyond the annealed portion.

8 The Effect of Annealing on the Elastic Modulus of Orthodontic Wires by Kyle Higginbottom Thesis submitted to the Faculty of the Graduate School of the University of Maryland, Baltimore in partial fulfillment of the requirements for the degree of Master of Science 2014

9 TABLE OF CONTENTS INTRODUCTION... 1 LITERATURE REVIEW...3 Stainless Steel (SS) Wires...4 Nickel Titanium (NiTi) Wires...6 Beta Titanium (TMA) Wires...7 PURPOSE OF THIS STUDY...9 HYPOTHESES...10 Null Hypotheses...10 Research Hypotheses...10 MATERIAL AND METHODS...11 Procedures...11 Statistical analysis...14 RESULTS...15 DISCUSSION...21 Hypothesis versus Results - Distances...21 Hypothesis versus Results - Wire Types...22 Clinical Implications...24 Research Limitations...25 Future Research...26 CONCLUSIONS...27 REFERENCES...28 i

10 List of Tables Table 1 Initial Elastic Modulus in Different Wire Types (GPa)...15 Table 2 Annealed Elastic Modulus in Different Wire Types (GPa)...16 Table 3 Two way ANOVA comparing the Elastic Modulus Differences for Distance/Wire Type/and Their Interaction...17 Table 4 Change in Elastic Modulus between Different Wire Types at Different Distances...19 ii

11 List of Figures Figure 1 Bracket Engagement Force of Orthodontic Wires (Source: Unitek Corp.)...3 Figure 2 Working Force of Orthodontic Wires (Provided by Unitek)...4 Figure 3 Example of Archwire with Un/Annealed sides...12 Figure 4 Instron Machine used to test each wire with a 3 point bending method...12 Figure 5 Graph Displaying the Slope of the Curve in the Elastic Portion...14 Figure 6 Initial Elastic Modulus in Different Wire Types...15 Figure 7 Annealed Elastic Modulus in Different Wire Types...16 Figure 8 Change in Elastic Modulus in different Wire Types...17 Figure 9 Change in Elastic Modulus at different distances (mm)...18 Figure 10 Interaction of the Change in Elastic Modulus between distance and wire type...19 Figure 10a Concentrated view of the interaction of the change in Elastic Modulus between Distance and Wire Type Beyond the Annealed End (18mm and 23mm)...20 iii

12 Introduction The technology involved in producing orthodontic archwires has progressed significantly since the time they were first utilized. In orthodontics, characteristics of the wires are extremely important to the success of the treatment, and wires with the correct properties should be chosen during the different stages of treatment. In the initial stages of tooth alignment, a very light wire with a low modulus of elasticity, high springback, and low constant delivery of force should be used. The modulus of elasticity is the tendency for an object to be deformed elastically when a force there is a force applied. It can also be defined as the slope of the object s stress strain curve in the elastic deformation region (Askeland 2006). During various stages of treatment, it is important for the wire to be cinched behind the most posterior tooth to prevent the anterior teeth from flaring or allowing the wire to slip through the most posterior attachment due to deflection of the archwire during function, which can be accomplished by annealing the wires. The process of annealing occurs in stages and uses heat to make a material more workable. Heat is used to increase the rate of diffusion and provides the energy needed to break bonds. The first stage of this process, recovery, results in softening of the metal through removal of dislocations along with internal stresses. The second stage, recrystallization, occurs as new strain free grains grow to replace the grains that have been deformed by the internal stresses. Grain growth, the third stage, occurs as the microstructure begins to become more coarse, making it so the metal loses a substantial amount of its original strength (Verhoeven, 1975). In extraction cases, it is also necessary to use a wire that is rigid enough when bodily moving the teeth through the extraction spaces and to prevent tipping. The wire should also have a low coefficient of friction to allow for minimal 1

13 resistance when moving the teeth during this phase of treatment. It is also important to have the correct dimension rectangular wire in place, to maintain proper torque while anterior teeth are being retracted. During the finishing stages of treatment, it is important for the wire to be formable and accept bends in order to achieve the most esthetic and functional result. 2

14 Literature Review Throughout the past century, there have been numerous developments and advancements in the field of orthodontics. One of the most significant is the development of different orthodontic archwires. An ideal orthodontic wire should provide light continuous force in order to reduce patient discomfort, root resorption, and hyalinization of the periodontal ligament. Some of the other properties to consider when selecting orthodontic wires include esthetics, friction, formability, weldability, resilience and springback. Figures 1 & 2 display the engagement force and working forces of different wire types. Nitinol wires at the lower end of the force spectrum deliver lighter forces and are active over a longer period of time. Stainless Steel wires at the higher end of the spectrum deliver a higher force. TMA is located between these two types of wires and is a good compromise between the two wires. Figure 1 Bracket Engagement Force of Orthodontic Wires (Source: Unitek Corp.) 3

15 Figure 2 Working Force of Orthodontic Wires (Provided by Unitek) Stainless Steel (SS) Wires Stainless steel orthodontic wires were first produced in the 1940 s and are the most common type of wire used today. There have been numerous modifications to the composition of stainless steel alloys over the years. In the 1940 s, austenitic stainless steel began to displace gold as the primary alloy for wires in orthodontics. By the 1950 s, type 300 series stainless steel alloys were used for most orthodontic materials. These alloys derive most of their strength from cold-working and carbon interstitial hardening. Cold-working is a process that uses dislocation movements and dislocation generation 4

16 within the crystal structure of the material through plastic deformation to strengthen a metal. Normally a composition of 17-25% chromium and 8-25% nickel is used in order to achieve the most effective properties. In order for the alloy to become stainless, at least 10-13% must be chromium. This allows a coherent oxide layer to form on the surface, making it passive (Flinn 1986). When at least 8% of nickel is present in the alloy, the single phase structure of austenite is stabilized, and the overall corrosion resistance is enhanced (Budinski 1996). The carbon content is purposely kept below 0.20% in order to reduce the formation of chromium carbides that can ultimately foster the corrosion of austenitic steels (Harvey 1982). The modulus of elasticity for stainless steel wires range from 23,000,000 to 29,000,000 p.s.i. ( GPa GPa)(Goldberg 1977). This high modulus of elasticity necessitates that a smaller diameter wire be used for aligning the teeth when lower forces are indicated. This smaller diameter may result in unwanted tooth movement due to a poorer bracket to wire fit. Along with the high modulus of elasticity, stainless steel wires have a high yield strength. Yield strength is an indication of a maximum amount of stress that can be developed within a material without causing plastic deformation. As a result of this higher modulus of elasticity, higher forces are produced that are dissipated over a shorter period of time when compared to beta-titanium or Nitinol wires. Stainless steel wires can be joined by either welding or soldering, but precautions need to be taken so as to not overheat the wire and compromise the properties. Stainless steel wires are good for closing extraction spaces when using sliding mechanics due to low friction produced at the bracket/wire interface. 5

17 Nickel Titanium (NiTi) Wires In the late 1960s, the Navy was studying new alloys exhibiting shape memory. One of these was named Nitinol because of its composition and where it was developed (Nickel Titanium Naval Ordnance Laboratory). This group of wires displays properties that had never been seen before in the orthodontic field. Shape memory allows the wires to return to a previously manufactured shape when heated through its transitional temperature range, and this is one of the most impressive properties in this type of wire. The change from the distorted to original form is paralleled by a change from the martensitic to austenitic phase (Andreasen 1978). In the martensitic phase, the grain structure is bodycentered or cubic-centered, and in the austenitic phase, the grain structure is face-centered or hexagonal close packed (Tonner, 1994). The martensitic phase represents the more flexible material, while the austenitic phase represents the stiffer material. It was through the efforts of Dr. George Andreasen and Unitek in the 70s, that the first nickel titanium alloy was marketed to orthodontists as Nitinol. This was a martensitic stabilized alloy composed of 52% nickel, 45% titanium, and 3% chromium. This combination of metals allowed for good springback, flexibility and a low modulus of elasticity (4,800,000 p.s.i.) (33.10 GPa), which make large elastic deflections possible (Andreasen 1978). Nitinol has greater springback and a larger recoverable energy when it is activated to the same amount of bending and torqueing when compared to stainless steel or beta-titanium wires (Drake 1982). This increased energy and a more constant delivery of forces when compared with stainless steel wires allows for fewer wire changes. Solid state solution hardening and cold working are the basic strengthening mechanisms used for this alloy. Due to Nitinol s elastic properties, it has limited formability, and springback properties 6

18 are decreased after bending (Lopez 1979). There are two other Nitinol -type alloys in addition to the martensitic stabilized alloy that undergo some form of Shape Memory Effects (SME) and are superelastic (Kusy 1991). These are known as austenitic active alloy and a martensitic active alloy. It wasn t until the late 1980s that these new NiTi wires with active austenitic grain structure appeared. In recent years, there has been development of heat activated NiTi wire that becomes dead soft when it is chilled below 20 C and achieves optimum activation at 37 C (or other specified temperatures). This wire has the lowest recovery forces of the NiTi wires, which makes it more desirable for tooth movement and easier bracket engagement. There has also been development of a Super Elastic NiTi wire, which is more flexible compared to the Classic Nitinol due to the phase transformations that take place as the wire is working. This type of wire transitions from austenitic to martensitic as the wire is deflected and then wants to return to the original austenitic phase as it is placed in the oral cavity. This wire has low recovery forces for gentle movement and has full shape recovery with less distortion, making it extremely elastic for easy placement and gentle recovery. Beta Titanium (TMA) Wires Beta-titanium, also known as Titanium Molybdenum Alloy (TMA), was introduced to the orthodontic profession in the early 1980s. It has a combination of properties somewhere between NiTi and SS with its high springback and formability and low stiffness. TMA has a modulus of elasticity of approximately 9,400,000 p.s.i. (64.81 GPa), which is about twice that of Nitinol and less than half that of stainless steel. Beta-titanium wire can be deflected almost twice as much as stainless steel without permanent deformation and it 7

19 delivers about half the force of comparable stainless steel wires. The formability of TMA is similar to that of stainless steel (Goldberg 1979). Beta-titanium can be welded and has corrosion resistance that is comparable to stainless steel (Goldberg 1982). TMA has a higher amount of friction at the bracket-wire interface, so it isn t as efficient as stainless steel when closing extraction spaces (Garner 1986). However, it is good for auxiliary springs and for finishing wires, especially rectangular wires utilized in the late stages of edgewise treatment. 8

20 Purpose of This Study The purpose of this study was to: 1) Determine the effects of annealing on the elastic modulus of Nitinol (Classic and Super Elastic), Stainless Steel, and Beta-titanium (TMA) wires. 2) Determine how far from the annealed ends the elastic modulus of the wires is affected. 9

21 Hypotheses H 0 : There is no difference in the change of the modulus of elasticity at 8mm, 13mm, 18mm, and 23mm away from the annealed end of a wire. H 0 : There is no difference in the change of the modulus of elasticity irrespective of the type of wire used (Classic Nitinol /Super-elastic Nitinol /SS/TMA). H 0 : There is no significant interaction between the distance from the annealed end and the type of wire in regard to the change in the modulus of elasticity. Research Hypothesis: H 1 : The change in modulus of elasticity will be greater closer to the annealed end vs. further away from the annealed end. H 1 : There is a difference in the change of the modulus of elasticity depending on what wire is used. H 1 : There is a significant interaction between the distance from the annealed end and the type of wire in regards to the change in the modulus of elasticity. 10

22 Material And Methods Procedures The total sample (N=80) was divided into 4 groups (Classic Nitinol /Super-elastic Nitinol /SS/TMA), with each group having both annealed and unannealed samples. One end of each arch wire was used for an annealed sample and one end for an unannealed sample (See Figure 3). All of the arch wires were provided by Unitek and were.016x.022 inch in dimension. Prior to any testing, distances of 3.00/8.00/13.00/18.00/23.00mm were measured from the end of the wire using a Carrera Precision Digital caliper and marked using a fine tipped Sharpie marker. These marks indicated the beginning of the annealed section (3mm), the middle of the annealed section (8mm), the end of the annealed section (13mm), 5mm past the annealed section (18mm), and 10mm past the annealed section (23mm). Load deflection tests were performed at all of these distances (8.00/13.00/18.00/23.00mm) using an Instron machine (Figure 4). The load deflection test was a 3 point action at these different distances along the wires. Measurements were made only during loading and not during unloading of the specimen. The first 13mm of the end of the wires was the annealed section of the wires. 11

23 Figure 3 Example of Archwire with Un/Annealed sides Figure 4 Instron Machine used to test each wire with a 3 point bending method. The data was plotted using a program called TestWorks4. The motor of the Instron machine was calibrated prior to starting each of the eight measurements for all 80 samples. Before testing, each wire was sectioned to a total length of 33mm to prevent the wire from touching anything except the 3 points being tested. This allowed the archwire to be split into annealed and unannealed sections. For each sample, the wire was placed 12

24 exactly in the middle (front-to-back and side-to-side) of the test block and the crosshead was loaded to 0.1N so that it was just touching the wire. All wires were deflected to 2.5mm with a crosshead speed of.5mm/min +/ mm/mm. For the annealed wire samples, a butane torch was used to anneal the end of the wire for a total distance of 13mm. To keep the temperature of the heat source consistent, the wires were held at a distance of 22mm from the end of the torch, while annealing. This distance was measured every time at each end of the wire prior to annealing to make sure that all parts of the wire were 22mm from the end of the torch. After each test was performed, the elastic modulus was calculated. Two points along the graph in the elastic portion were identified to indicate the slope of the curve. These points were used in order for the program to calculate the modulus of elasticity. Using this data, all unannealed values were subtracted from annealed values to determine the change in the modulus of elasticity. 13

25 Figure 5 Graph Displaying the Slope of the Curve in the Elastic Portion Statistical analysis A two-way analysis of variance (ANOVA) was used to determine if there were significant differences in the elastic modulus of the four wire types (Classic Nitinol /Super-elastic Nitinol /SS/TMA) and the four distances (8/13/18/23mm). A Tukey s honestly significant difference (HSD) test was utilized to evaluate any differences in the levels within each independent variable. Finally, a test was completed to examine the interaction between distance and wire types. All statistical analyses were performed using the SPSS Base 20.0 statistical package (SPSS, Inc Chicago, IL). A p value of 0.05 was considered significant. 14

26 Results Stainless Steel had the highest initial elastic modulus, which was followed by TMA and Classic Nitinol, and finally Super Elastic Nitinol had the lowest initial elastic modulus (See Table 1/Figure 6). This ordering of wires was the same for the annealed elastic modulus (See Table 2/Figure 7). Table 1 - Initial Elastic Modulus in Different Wire Types (GPa) Mean SD SE SS TMA Classic

27 Table 2 - Annealed Elastic Modulus in Different Wire Types (GPa) Mean SE SS TMA Classic SD There was a significant difference (F = , p = ) in the change in elastic modulus (EM annealed EM unannealed) between the four wire types (See Table 3/Figure 8). For Super Elastic Nitinol, the change in EM was / This was a significantly greater change than for all other wire types. For Stainless Steel, the change in EM was / This mean change was significantly greater than for TMA and Classic Nitinol. There was no significant difference between the change in EM for TMA (8.03 +/- 9.68) and Classic Nitinol (7.93 +/ ). 16

28 Table 3 - Two way ANOVA comparing the Elastic Modulus Differences for Distance/Wire Type/and Their Interaction Variable Mean SD F p Wire Type SE a* SS b TMA 8.03 c 9.68 CLASSIC 7.93 c Distance a* b c (-)0.11 c 2.27 Distance x Wire Type * - Means with different letters are significantly different There was a significant difference (F = , p = ) in the change in elastic modulus (EM annealed EM unannealed) between the four distances (See Table 17

29 3/Figure 9). In the middle of the annealed section (8mm), the change in EM was / This was a significantly greater increase in elastic modulus than for all other distances. At the end of the annealed section (13mm), the change in EM was / This mean change was significantly greater than for 5mm and 10mm past the annealed section (18mm and 23mm). There was no significant difference for the change in EM between 18mm (0.88 +/- 2.49) and 23mm ( /- 2.27). There was a significant interaction (F = , p = 0.005) between the wire types and distance, however this interaction negated the differences between the wires since the changes didn t occur at all distances. The mean change in elastic modulus of the four wires was different at 8mm and 13mm (within the annealed section), but this is clinically irrelevant since this is a non-working portion of the wire. Figure 10 shows the entire 18

30 interaction between the wire types and distance. Figure 10a shows the interaction that takes place between 18mm and 23mm. There is an interaction between the change in the modulus of elasticity for SS and TMA at those distances. At 18mm, SS had the greatest change in elastic modulus (1.84 +/- 3.58) and TMA had the smallest change ( /- 2.62), whereas at 23mm, SS had the smallest change in elastic modulus ( /- 3.20) and TMA had the greatest change (0.50 +/- 2.21) (See Table 4). Table 4 - Change in Elastic Modulus between Different Wire Types at Different Distances 8mm SD 13mm SD 18mm SD 23mm SD SS TMA CLASSIC SE

31 20

32 Discussion This study utilized a total of 80 samples, 20 samples in each of the four wire groups. For each wire, measurements were taken within the annealed section (8mm and 13mm), and 5mm and 10mm past the annealed section (18mm and 23mm). Although there was no power analysis performed, the observed power (post hoc) was 100% for all three analyses (Distance/Wire Type/Interaction), so that N was sufficient for this study. The Partial Eta Square for distance was.84, for wire type it was.36, and for interaction it was.37. Partial Eta Square is a post hoc measure of effect size. The effect size for distance (.84) was considerably larger than for wire type (.36) and their interaction (.37). Therefore, one can be more confident in the results for distance than the other two. This may be due to the effects of the significant interaction on the wire types. Hypothesis versus Results Distances Although the interaction theoretically negated both significant main effects (wire type and distance), the actual interaction shown in Figure 10 and 10a shows no clinically important interaction for distance. Therefore, the significant differences found for distance are valid. In general, as the distance from the annealed end increased, the change in elastic modulus decreased. The change in elastic modulus was greater at the distances of 8mm and 13mm and decreased at the other two distances, 18mm and 23mm. Specifically, the change in elastic modulus was significantly greater at 8mm than it was at 13mm, and the change in elastic modulus was significantly greater at 13mm than it was at either 18mm or 23mm. These results confirm the first research hypothesis of this study that the change in modulus of elasticity was greater closer to the annealed end vs. further from the annealed end. There was a large difference in the change in elastic modulus 21

33 between 8mm and 13mm (28.61 and respectively, see Table 4). This is the part of the wire that is within the annealed portion and would not to be a working part of the wire since it is beyond the most posterior attachment. There was a minimal difference in the change in elastic modulus between 18mm and 23mm (1.84 and -1.32, see Table 4). A negative change in elastic modulus indicates that the elastic modulus got smaller after the annealing process. However, due to the magnitude, this difference (at 18mm and 23mm), is not a clinically important change in the elastic modulus. It should be noted that 18mm and 23mm are 5 mm and 10 mm away from the annealed portion of the wire. This suggests that the change in elastic modulus will have a minimal effect beyond the annealed section in the working part of the wire. However, these effects would have to be replicated for this result to be confirmed. Hypothesis versus Results Wire Type The results of the interaction between the distance and wire type, shown in Figure 10/10a, negate the significant differences in the wire types displayed in Figure 9. The main effect results for wire type show that TMA and Classic Nitinol had the least amount of change in elastic modulus, followed by Stainless Steel, and finally the most change occurred with Super Elastic Nitinol. However, as mentioned previously, these results were negated because there was a significant interaction in the change of elastic modulus between the wire types tested in this study. These results confirmed the third research hypothesis that there was a significant interaction between the distance from the annealed end and the type of wire in regards to the change in modulus of elasticity (see Figure 10). However, the true interaction only took place between 18mm and 23mm, which is 5mm to 10mm away from the annealed section (see Figure 10a) in the working part of the wire. 22

34 Stainless Steel, Classic Nitinol and Super Elastic Nitinol behaved as expected. Their change in elastic modulus decreased as the distance from the annealed section increased (from 18mm to 23mm). Stainless Steel behaved the same at these distances as the other two wires but the drop in the change in elastic modulus was much greater (from 1.84 to ). The change in elastic modulus increased for TMA as the distance from the annealed section increased (from 18mm to 23mm), but it was not clinically important (see Table 4 and Figure 10a). The clinician should not be concerned about any of the wire types tested in this study when working 5mm past the annealed section due to the relatively minimal change in elastic modulus at this distance. 23

35 Clinical Implications Even though there was a change in the modulus of elasticity 5mm and 10mm away from the annealed portion, it was determined that there would not be any clinically important effects since the change was minimal compared to the original elastic modulus. 24

36 Research Limitations The amount of time that the wire was exposed to the flame could have been better monitored. A stopwatch might have been used to monitor the amount of time that the wire was exposed to the flame. A device might also have been fabricated to allow the flame to travel along the distance of the annealed section at a constant rate. The temperature of the flame wasn t monitored, which could also have led to inconsistent results. A thermometer might have been used to measure the part of the flame that the wire passed through in order to insure a constant temperature. Even though the distance was kept the same by the stop (see Methods & Materials) from the wire to the flame there still may have been some slight variation in the temperature of the flame. If inconsistent temperatures were found, a thermometer would need to continually monitor temperature while annealing the wires. 25

37 Future Research One potential area of future research would be to investigate different wire types other than those included in this study. In addition, measurements at 3mm intervals could be used instead of 5mm to increase accuracy. 26

38 Conclusion This study was designed to determine the effect of annealing on the changes in elastic modulus of various wires. Based on the results of this study we can conclude the following: 1. There are significant differences in the change in elastic modulus between the areas of the wires within the annealed section and those areas 5mm and 10mm away from the annealed section. The change in elastic modulus within the annealed section was significantly greater at 8 mm than it was at 13mm, and this was significantly greater than 18mm and 23mm (5mm and 10mm beyond the annealed section). However, there was no statistical difference in the change in elastic modulus between 5mm and 10mm away from the annealed section (18mm and 23mm respectively). 2. Regardless of the wire type, no clinically important effects were seen 5mm and 10mm beyond the annealed portion. 27

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40 Proffit, W. R. Biomechanics and mechanics. In: Contemporary Orthodontics. 3rd ed. St Louis, Mo: CV Mosby; 2000: