![679VOLUME XLVIII NUMBER 11
Dr. Bowman is a Contributing Editor of the Journal of Clinical
Orthodontics; an Adjunct Associate Professor, St. Louis University,
St. Louis; a straight-wire instructor, University of Michigan, Ann
Arbor, MI; an Assistant Clinical Professor, Case Western Reserve
University, Cleveland; a Visiting Clinical Lecturer, Seton Hill
University, Greensburg, PA; and in the private practice of orthodon-
tics at 1314 W. Milham Ave., Portage, MI 49024; e-mail: drjwyred@
aol.com.
In addition to producing biological effects,
vibration may also work on a biomechanical level
to accentuate orthodontic tooth movement. Braun
and colleagues credited the dynamic environment
of the oral cavity (“vibrational” perturbations) as
the primary influence in moderating the rate of
tooth movement with fixed appliances.15 Research-
ers at the University of Missouri-Kansas City
found that the most important factor was the am-
plitude of archwire vibrations.16 Other authors have
refuted the simplistic claims that “reducing [elas-
tic] friction” by the mere choice of appliance can
shorten treatment time. It is actually the inelastic
friction (or “notching”) that must be overcome
with perturbations, and all brackets are subject to
that property—we are not just sliding pearls along
a string.17-19 Consequently, it appears that vibration
could affect the rate of orthodontic tooth move-
ment in two ways: reducing the “lag” phase by
stimulating changes in the periodontal apparatus,
or inducing mechanical perturbations within the
appliance interface.
Materials and Methods
This retrospective evaluation of the effects
of vibration on the time required for mandibular
leveling and alignment included 117 consecu-
tively treated Class II nonextraction patients (47
male, 70 female) who underwent maxillary molar
distalization and concurrent mandibular leveling
and alignment (Table 1). Thirty patients were
enrolled in the AcceleDent vibration (AD) group
(mean age = 13.1 years) and 37 in the study con-
trol (SC) group (mean age = 12.8 years). The
pre-AD (PAD) control group comprised 50 Class
II patients (mean age = 14.3 years) who were
treated prior to the initiation of a separate pro-
spective examination of the effects of vibration
on molar distalization, whose results will be pub-
lished later.
Each patient presented with a half-to-full-
step Class II molar relationship and mild-to-mod-
erate crowding. The nonextraction treatment in-
volved a miniscrew-supported Horseshoe Jet**
maxillary molar distalizer20 and a preadjusted
.022" Butterfly System***21 mandibular appliance
(Figs. 2-4). Upon completion of molar distaliza-
tion, the Horseshoe Jet was “locked” to serve as
**AOA Orthodontic Appliances, Sturtevant, WI; www.aoalab.
com.
***Trademark of American Orthodontics, Sheboygan, WI; www.
americanortho.com.
Fig. 1 A. AcceleDent* activator and charging port (images used by permission of OrthoAccel Technolo-
gies). B. AcceleDent device in use.
A B](https://image.slidesharecdn.com/theeffectofvibrationontherateoflevelingandalignment-150405164536-conversion-gate01/85/The-effect-of-vibration-on-the-rate-of-leveling-and-alignment-2-320.jpg)
The effect of vibration on the rate of leveling and alignment
- 1. 678 JCO/NOVEMBER 2014© 2014 JCO, Inc. S. JAY BOWMAN, DMD, MSD The Effect of Vibration on the Rate of Leveling and Alignment Kurz received a patent for a vibrating headgear/ mouthpiece device.5 In 1986, investigators at the Children’s Clinical Hospital No. 2 of Kiev con- cluded that vibration at 50Hz for 60-360 seconds every two or three days reduced the time needed to move a tooth by a factor of 1.5-2 times.6 Al- though academic interest in the orthodontic effects of vibration waned until the beginning of the 21st century, it persisted in orthopedic medicine. Beginning in 2003, animal studies demon- strated an increased sutural response7,8 and more rapid tooth movement after vibratory stimula- tion.9,10 One investigation did find an inhibition of translational tooth movement in rats during a brief two-week experimental period,11 but another re- ported a 40% increase in the rate of tooth move- ment in mice after light daily vibration over four weeks.12 Since vibration stimulates inflammation, these animal models suggested the potential to alter the periodontal apparatus or create osteo- genic effects13 through genetic expression, cyto- kine activity, cellular changes,14 or recruitment, thereby enhancing tooth movement. Numerous concepts have been developed with the aim of increasing the speed of orthodontic tooth movement and potentially reducing overall treatment time. Unfortunately, most have failed to generate the supporting data needed to gain wide acceptance.1,2 Even if treatment time were not a significant issue for many patients and practitio- ners,3 the prospect of improving the effectiveness of biomechanics through enhanced tooth move- ment would be a worthy goal that warrants further clinical investigation. The purpose of this study was to evaluate the effects of vibration with AcceleDent* (Fig. 1) on the speed of orthodontic leveling and alignment. Biological and Mechanical Effects of Vibration As early as 1979, Shapiro and colleagues reported the use of pulsating force-induced piezo- electricity to stimulate tooth movement.4 In 1982, TABLE 1 DEMOGRAPHICS AcceleDent (AD) Study Control (SC) Pre-AD Control (PAD) p N 30 37 50 Male 13 (43.3%) 12 (32.4%) 22 (44.0%) 0.5092* Female 17 (56.7%) 25 (67.6%) 28 (56.0%) Mean age 13.1 ± 1.3 years 12.8 ± 1.0 years 14.3 ± 4.2 years 0.0579** *Chi-square testing. **Analysis of variance. In pairwise comparisons using t-tests with Bonferroni correction, only SC vs. PAD (p = .0159) was statistically significant. *Registered trademark of OrthoAccel Technologies, Bellaire, TX; www.acceledent.com. ©2014 JCO, Inc. May not be distributed without permission. www.jco-online.com
- 2. 679VOLUME XLVIII NUMBER 11 Dr. Bowman is a Contributing Editor of the Journal of Clinical Orthodontics; an Adjunct Associate Professor, St. Louis University, St. Louis; a straight-wire instructor, University of Michigan, Ann Arbor, MI; an Assistant Clinical Professor, Case Western Reserve University, Cleveland; a Visiting Clinical Lecturer, Seton Hill University, Greensburg, PA; and in the private practice of orthodon- tics at 1314 W. Milham Ave., Portage, MI 49024; e-mail: drjwyred@ aol.com. In addition to producing biological effects, vibration may also work on a biomechanical level to accentuate orthodontic tooth movement. Braun and colleagues credited the dynamic environment of the oral cavity (“vibrational” perturbations) as the primary influence in moderating the rate of tooth movement with fixed appliances.15 Research- ers at the University of Missouri-Kansas City found that the most important factor was the am- plitude of archwire vibrations.16 Other authors have refuted the simplistic claims that “reducing [elas- tic] friction” by the mere choice of appliance can shorten treatment time. It is actually the inelastic friction (or “notching”) that must be overcome with perturbations, and all brackets are subject to that property—we are not just sliding pearls along a string.17-19 Consequently, it appears that vibration could affect the rate of orthodontic tooth move- ment in two ways: reducing the “lag” phase by stimulating changes in the periodontal apparatus, or inducing mechanical perturbations within the appliance interface. Materials and Methods This retrospective evaluation of the effects of vibration on the time required for mandibular leveling and alignment included 117 consecu- tively treated Class II nonextraction patients (47 male, 70 female) who underwent maxillary molar distalization and concurrent mandibular leveling and alignment (Table 1). Thirty patients were enrolled in the AcceleDent vibration (AD) group (mean age = 13.1 years) and 37 in the study con- trol (SC) group (mean age = 12.8 years). The pre-AD (PAD) control group comprised 50 Class II patients (mean age = 14.3 years) who were treated prior to the initiation of a separate pro- spective examination of the effects of vibration on molar distalization, whose results will be pub- lished later. Each patient presented with a half-to-full- step Class II molar relationship and mild-to-mod- erate crowding. The nonextraction treatment in- volved a miniscrew-supported Horseshoe Jet** maxillary molar distalizer20 and a preadjusted .022" Butterfly System***21 mandibular appliance (Figs. 2-4). Upon completion of molar distaliza- tion, the Horseshoe Jet was “locked” to serve as **AOA Orthodontic Appliances, Sturtevant, WI; www.aoalab. com. ***Trademark of American Orthodontics, Sheboygan, WI; www. americanortho.com. Fig. 1 A. AcceleDent* activator and charging port (images used by permission of OrthoAccel Technolo- gies). B. AcceleDent device in use. A B
- 3. 680 JCO/NOVEMBER 2014 The Effect of Vibration on the Rate of Leveling and Alignment indirect miniscrew anchorage for subsequent re- traction of the remaining maxillary teeth, and up- per brackets were bonded for the finishing stage. The PAD patients had been previously treat- ed with orthodontic adjustments at five-to-seven- week intervals. The AD and SC subjects were instructed to return every four weeks as part of a different prospective investigation of molar distal- Fig. 2 A. 14-year-old female Class II patient before treatment. B. After placement of Horseshoe Jet** max- illary molar distalizer and preadjusted Butterfly System*** mandibular brackets with initial .016" nickel tita- nium archwire. Patient was scheduled for appointments every four weeks and instructed to use Accele- Dent vibration unit for 20 minutes per day (continued on next page). A B B
- 4. 681VOLUME XLVIII NUMBER 11 Bowman Leveling was defined as the sufficient resolu- tion of vertical dental discrepancies to allow com- plete seating of a rectangular archwire with a min- imum dimension of .019" × .025" stainless steel into the bracket slots (Figs. 2D, 3C, 4C). Although most subjects achieved this degree of leveling with a three-wire sequence, some also received an in- terim .017" × .025" stainless steel or .019" × .025" nickel titanium archwire before the larger stainless steel working wire was placed. Some patients were excluded from the study because their archwire sequences were interrupted by earlier bonding of second-molar brackets prior to insertion of the .019" × .025" stainless steel wires. This reduced the sample size for completion of leveling from 117 to 93 subjects. The time points and subjective goals selected for analysis did not guarantee that all rotations were absolutely resolved, nor that every curve of ization. Otherwise, all patients experienced the same sequence of treatment mechanics. Each patient in the AD sample received an AcceleDent vibrational unit with directions to use the device 20 minutes per day during the entire course of orthodontic treatment. The AcceleDent activator supplies mild vibration (30Hz, .25N) to the teeth as the patient lightly bites down on a mouthpiece to hold the device in place.22 For purposes of this study, alignment was defined as the sufficient resolution of dental ir- regularities to permit complete seating of a rect- angular archwire with a minimum dimension of .017" × .025" stainless steel or superelastic alloy (but smaller than .019" × .025" stainless steel) into .022" × .028" brackets (Fig. 2C). Every patient began treatment with an .016" nickel titanium arch- wire, usually followed by .017" × .025" nickel titanium. Fig. 2 (cont.) C. Mandibular .019" × .025" nickel titanium archwire inserted after 95 days of treatment, marking end of alignment phase. D. Mandibular .019" × .025" stainless steel archwire inserted after six months of treatment, marking completion of leveling. E. Maxillary brackets bonded and second molars banded after seven months of treatment (continued on next page). C D E
- 5. 682 JCO/NOVEMBER 2014 The Effect of Vibration on the Rate of Leveling and Alignment Spee was completely leveled, when the working archwire was placed. Since the clinical decisions were all made by the same orthodontist and all patients were selected for the same type of treat- ment mechanics, it seems reasonable to make com- parisons among these three groups. Statistical analysis was conducted using SAS version 9.2.† The significance of differences in age was tested by analysis of variance, while gender differences were evaluated with chi-square testing. For the primary outcomes, two-sided t-tests were used to compare the three groups, using a two- tailed significance level of .05. Results Although the PAD group was older on aver- age than the other two samples, no statistically significant differences in age were found (Table 1). Likewise, there were no significant differences among the three groups in terms of gender. The average time period needed to attain alignment of the mandibular dentition (Table 2) was shorter in the AD group (93 days) than in either the SC group (120 days) or the PAD control group (131 days). The .017" × .025" archwire was Fig. 2 (cont.) F. Treatment completed in 20 months. †SAS Institute, Cary, NC; www.sas.com. F
- 6. 683VOLUME XLVIII NUMBER 11 Bowman than other sequences tested.24 In contrast, both Ong and colleagues25 and Jian and colleagues26 found no significant differences in alignment ef- ficiency among three typical archwire sequences. In the Ong study, the time needed to reach an .016" × .022" stainless steel working archwire with an .018" appliance was 4.0-4.4 months using a three- wire sequence: .014" nickel titanium or copper nickel titanium followed by .017" × .017", .016" × .022", or .014" × .025" heat-activated superelastic wires.25 These authors attributed the faster leveling and alignment in comparison to the Mandall study23 to the replacement of archwires “as soon as complete engagement was possible”, also noting “decreased ‘play’ in an .018" slot appliance”. Interestingly enough, neither group found any dif- ference in alignment efficiency between conven- tional nickel titanium and superelastic heat- activated wires. In the present study, a three-to-four-wire se- quence (similar to that of the Mandall23 and Flores- Mir24 investigations) was used to reach a rectan- gular stainless steel working wire in the mandibular arch. This required an average of five months with vibration (AD) or seven months without vibration (PAD). The difference between our results and those of Ong and colleagues25 may simply confirm their supposition that the difference in tolerance placed in the AD patients about 27 days earlier (29% faster) on average than in the SC patients and 38 days earlier (40% faster) than in the PAD sub- jects. It is important to note that these differences, while clinically relevant, were not statistically significant. The average time needed to achieve leveling (Table 2) in the AD group was 160 days—48 days less than in the SC patients (30% faster) and 55 days less than in the PAD patients (35% faster). In other words, leveling took a little more than five months with vibration, compared to seven months without vibration. These differences were both clinically and statistically significant. Discussion Alignment and Leveling in the Mandibular Arch Mandall and colleagues reported that the mean time required to reach a mandibular .019" × .025" working archwire with an .022" appliance was 6.8-9.3 months, depending on which of three archwire sequences was chosen.23 Flores-Mir agreed that an archwire sequence of .016" nickel titanium, .018" × .025" nickel titanium, and .019" × .025" stainless steel was slightly more efficient TABLE 2 TIME REQUIRED FOR ALIGNMENT AND LEVELING AcceleDent (AD) Study Control (SC) Pre-AD Control (PAD) p* Alignment 0.0988 N 30 37 50 Mean 93.0 ± 50.3 days 119.9 ± 75.8 days 130.5 ± 85.8 days Median 81.5 days 100.0 days 115.0 days Range 37-228 days 49-346 days 22-385 days Leveling 0.0265** N 25 29 39 Mean 160.0 ± 65.7 days 208.3 ± 77.0 days 215.3 ± 93.8 days Median 141.0 days 186.0 days 200.0 days Range 56-344 days 116-393 days 83-419 days *Analysis of variance. **In pairwise comparisons using t-tests with Bonferroni correction, AD vs. SC (p = .0486) and AD vs. PAD (p = .0224) were statistically significant.
- 7. 684 JCO/NOVEMBER 2014 The Effect of Vibration on the Rate of Leveling and Alignment Fig. 3 A. 13-year-old female Class II patient before treatment. B. After insertion of maxillary Horseshoe Jet, bonding of mandibular Butterfly System brackets, and delivery of AcceleDent. C. After 55 days of alignment and 83 days of leveling. D. Maxillary brackets bonded and right canine exposed with diode laser after nine months of treatment (continued on next page). A C D B
- 8. 685VOLUME XLVIII NUMBER 11 Bowman PAD) in either leveling or alignment, even though the SC patients were seen at more regimented four- week intervals compared to the five-to-seven-week appointment windows for PAD subjects. This find- ing lends additional support to the validity of the three-way comparative analysis. Effects of Vibration on the Rate of Tooth Movement In a preliminary clinical trial of an Accele- Dent prototype with 14 patients, Kau and col- leagues noted 2.1mm of tooth movement per month in the mandibular arch (twice the normally reported rate) and 3mm per month in the maxillary arch.22 In a more comprehensive randomized con- trolled trial of AcceleDent, Pavlin reported 2.71mm per month of initial maxillary dental alignment in 23 premolar-extraction patients—a 51% reduction in treatment time compared to the control group, with no adverse findings such as root resorption or pain.28 The differences in align- ment speed may be attributed to the typically fast- er tooth movement in the maxillary arch; in addi- between .022" and .018" slots was responsible for the difference in the rate of alignment—espe- cially since succeeding wires were inserted as soon as possible in both studies. Because this was a retrospective investiga- tion, we did not consider collecting progress re- cords at time points representing the completion of leveling and alignment. Therefore, an objective comparative analysis such as the Peer Assessment Rating, Irregularity Index, or ABO score could not be used. On the other hand, the retrospective design prevented the introduction of a Hawthorne Effect (“preferential” alteration of archwire se- quences or appointment intervals among the three samples) or a susceptibility bias that might have affected the results27; in fact, the subjects were already enrolled in a separate prospective trial. Furthermore, the study design precluded any de- tection or exclusion biases, since all patients pre- sented with similar malocclusions, were treated similarly, and were not selected out of a group of finished cases. No statistically significant difference was found between the two control groups (SC and Fig. 3 (cont.) E. Treatment completed in 20 months. E
- 9. 686 JCO/NOVEMBER 2014 The Effect of Vibration on the Rate of Leveling and Alignment Fig. 4 A. 12-year-old female Class II patient before treatment. B. After insertion of maxillary Horseshoe Jet, bonding of mandibular Butterfly System brackets, and delivery of AcceleDent. C. After 37 days of alignment and 95 days of leveling. D. Maxillary brackets bonded after 14 months of treatment (continued on next page). A C D B
- 10. 687VOLUME XLVIII NUMBER 11 Bowman no statistical significance in the rate of alignment with vibration compared to control samples. Nev- ertheless, we did find a significant increase in the speed of leveling, which could not have been ac- complished without the cumulative reduction in alignment time resulting from the application of vibration. Conclusion In the present study, the amount of time re- quired to achieve both dental alignment and level- ing in Class II nonextraction treatment was re- duced by using an AcceleDent device to apply vibration. Overall, we found a clinically beneficial and statistically significant 30% increase in the rate of tooth movement during orthodontic leveling of the mandibular dentition. Future research on the effects of vibration should focus on other aspects of orthodontic treatment, different biomechanics, pain reduction, gene expression, and tissue re- sponses, along with testing of alternative force levels, frequencies, and durations of vibration. tion, the extraction spaces likely facilitated more rapid resolution of irregularities, compared to the speed of mandibular alignment without extractions noted in the present study. In contrast, Miles and colleagues found no significant difference in the initial dental align- ment of 66 consecutively treated orthodontic pa- tients, appointed every five weeks over a 2.5-month period, when half the patients were given a vibrat- ing device (111Hz, .06N) to use for 20 minutes per day.29 As the investigators acknowledged, however, they used consecutive patients rather than a more homogeneous sample, and the vibrational forces were applied at a higher frequency and lower force level than in comparable studies. Moreover, data collection was invariably discontinued after 10 weeks of alignment with only an .014" thermal nickel titanium archwire in an .018" appliance, while data for the present study continued to be collected until leveling was completed. It has yet to be determined exactly how the force, frequency, and duration of vibration contribute to the rate of tooth movement. Like Miles and colleagues,29 our study found Fig. 4 (cont.) E. Treatment completed in 20 months. E
- 11. 688 JCO/NOVEMBER 2014 The Effect of Vibration on the Rate of Leveling and Alignment ACKNOWLEDGMENTS: The author would like to thank Sheri Smith, President, Courante Oncology Clinical Research Services, Excelsior, MN, for her statistical analysis and OrthoAccel Tech nologies for their assistance with the AcceleDent units. REFERENCES 1. McNamara, J.A. Jr.; Hatch, N.; and Kapila, S.D.: Effective and Efficient Orthodontic Tooth Movement, Craniofacial Growth Series, vol. 48, Department of Orthodontics and Pediatric Dentistry, School of Dentistry and Center for Human Growth and Development, University of Michigan, Ann Arbor, 2011. 2. Liou, E.: Accelerated orthodontic tooth movement, in Evidence-Based Clinical Orthodontics, ed. P.G. Miles, D.J. Rinchuse, and D.J. Rinchuse, Quintessence Publishing, Chicago, 2012, pp. 179-199. 3. Uribe, F.; Padala, S.; Allareddy, V.; and Nanda, R.: Patients’, parents’, and orthodontists’ perceptions of the need for and costs of additional procedures to reduce treatment time, Am. J. Orthod. 145(4 suppl):S65-73, 2014. 4. Shapiro, E.; Roeber, F.W.; and Klempner, L.S.: Orthodontic movement using pulsating force-induced piezoelectricity, Am. J. Orthod. 76:59-66, 1979. 5. Kurz, C.H.: Vibrational orthodontic appliance, U.S. Patent No. 4348178, Sept. 7, 1982. 6. Krishtab, S.I.; Doroshenko, S.I.; and Liutik, G.I.: Use of vibra- tory action on the teeth to accelerate orthodontic treatment, Stomatologiia (Mosk.) 65:61-63, 1986. 7. Kopher, R.A. and Mao, J.J.: Suture growth modulated by the oscillatory component of micromechanical strain, J. Bone Miner. Res. 18:521-528, 2003. 8. Peptan, A.L.; Lopez, A.; Kopher, R.A.; and Mao, J.J.: Re sponses of intramembranous bone and sutures upon in vivo cyclic tensile and compressive loading, Bone 42:432-438, 2008. 9. Darendeliler, M.A.; Zea, A.; Shen, G.; and Zoellner, H.: Effects of pulsed electromagnetic field vibration on tooth movement induced by magnetic and mechanical forces: A pre- liminary study, Austral. Dent. J. 52:282-287, 2007. 10. Nishimura, M.; Chiba, M.; Ohashi, T.; Sato, M.; Shimizu, Y.; Igarashi, K.; and Mitani, H.: Periodontal tissue activation by vibration: Intermittent stimulation by resonance vibration ac- celerates experimental tooth movement in rats, Am. J. Orthod. 133:572-583, 2008. 11. Kalajzic, Z.; Peluso, E.B.; Utreja, A.; Dyment, N.; Nihara, J.; Xu, M.; Chen, J.; Uribe, F.; and Wadhwa, S.: Effect of cyclical forces on the periodontal ligament and alveolar bone remodel- ing during orthodontic tooth movement, Angle Orthod. 84:297-303, 2014. 12. Liu, D.: Acceleration of orthodontic tooth movement by me- chanical vibration, AADR General Session, Washington, DC, March 2010. 13. Alikhani, M.; Khoo, E.; Alyami, B.; Raptis, M.; Salgueiro, M.; Oliveira, S.M.; Boskey, A.; and Teixeria, C.C.: Osteogenic effect of high-frequency acceleration on alveolar bone, J. Dent. Res. 91:413-419, 2012. 14. Liu, D.: Histomorphometric study of orthodontic tooth move- ment under mechanical vibration, AADR General Session, San Diego, March 2011. 15. Braun, S.; Bluestein, M.; Moore, B.K.; and Benson, G.: Friction in perspective, Am. J. Orthod. 115:619-627, 1999. 16. Olson, J.E.; Liu, Y.; Nickel, J.C.; Walker, M.P.; and Iwasaki, L.R.: Archwire vibration and stick-slip behavior at the bracket- archwire interface, Am. J. Orthod. 142:314-322, 2012. 17. Pandis, N.; Polychronopoulou, A.; and Eliades, T.: Active or passive self-ligating brackets? A randomized controlled trial of comparative efficiency in resolving maxillary anterior crowding in adolescents, Am. J. Orthod. 137:12.e1-6, 2010. 18. Fleming, P.S. and Johal, A.: Self-ligating brackets in orthodon- tics: A systematic review, Angle Orthod. 80:575-584, 2010. 19. Songra, G.; Clover, M.; Atack, N.E.; Ewings, P.; Sherrif, M.; Sandy, J.R.; and Ireland, A.J.: Comparative assessment of alignment efficiency and space closure of active and passive self-ligating vs conventional appliances in adolescents: A single-center randomized controlled trial, Am. J. Orthod. 145:569-578, 2014. 20. Bowman, S.J.: Class II combination therapy: Molar distaliza- tion and fixed functionals, in Current Therapy in Orthodontics, ed. R. Nanda and S. Kapila, Mosby Elsevier, St. Louis, 2009, pp. 115-136. 21. Bowman, S.J. and Carano, A.: Butterfly bracket system, J. Clin. Orthod. 38:274-287, 2004. 22. Kau, C.H.; Nguyen, J.T.; and English, J.D.: The clinical evalu- ation of a novel cyclical force generating device in orthodon- tics, Orthod. Practice 1:43-44, 2010. 23. Mandall, N.A.; Lowe, C.; Worthington, H.; Sandler, J.; Derwent, S.; Abdi-Oskouei, M.; and Ward, S.: Which ortho- dontic archwire sequence? A randomized clinical trial, Eur. J. Orthod. 28:561-566, 2006. 24. Flores-Mir, C.: Attaining a working archwire—which se- quence? Evid. Based Dent. 8:48, 2007. 25. Ong, E.; Ho, C.; and Miles, P.: Alignment efficiency and dis- comfort of three orthodontic archwire sequences: A random- ized clinical trial, J. Orthod. 38:32-39, 2001. 26. Jian, F.; Lai, W.; Furness, S.; McIntyre, G.T.; Millett, D.T.; Hickman, J.; and Wang, J.: Initial arch wires for tooth align- ment during orthodontic treatment with fixed appliances, Cochran Database Syst. Rev. 4:CD007859, 2013. 27. Johnston, L.E. Jr.: Moving forward by looking back: “Retrospective” clinical studies, J. Orthod. 29:221-226, 2002. 28. Pavlin, D.: Modulation of tooth movement by vibratory forces, 41st Annual Moyers Symposium, University of Michigan, Ann Arbor, March 9, 2014. 29. Miles, P.; Smith, H.; Weyant, R.; and Rinchuse, D.J.: The ef- fects of a vibrational appliance on tooth movement and patient discomfort: A prospective randomized clinical trial, Austral. Orthod. J. 28:213-218, 2012.