Retention and stability with light forces in orthodontics

Retention and stability with light forces in orthodontics By Dr Derek Mahoney Many clinicians misquote the research from Seattle, Washington to make it appear that non-extraction, expansion style cases have greater relapse potential than extraction cases. For more than forty years, research in the Department of Orthodontics at the University of Washington (Seattle WA) has focused on a growing collection of more than 800 sets of patient records to assess stability and relapse of orthodontic treatment. All the patients included in this sample had concluded treatment a decade or more before the last set of data. Evaluation of treated premolar extraction patients, treated lower incisor extraction patients, treated non-extraction cases with generalized spacing, and patients treated with arch enlargement strategies, together with untreated norms showed similar physiological changes i.e. there is no more lower incisor stability in the extraction cases versus those patients that were treated with arch enlargement.(1) What general dentists must understand is that if patients want perfectly straight teeth for life they must be prepared to have fixed retainers for life. This comment has been backed up by numerous reports in the scientific literature, but the question I pose is should we offer our patients wider smiles, fuller lip profiles, and permanent retention versus premolar extractions and permanent retention? There is no doubt relapse is expected unless permanent retention is used. With the Damon philosophy, (which is more than just an expensive bracket), we expect less relapse because the teeth are moved within bone and not through bone. By using a low friction and LOW FORCE system (not more than 25gm/cm2) we allow bone to develop around the roots permitting better, but not perfect stability. This is supported by the CT scans taken at the end of treatment. Readers would be advised to look at the article by Dr. Damon in the latest Clinical Impressions magazine.(2) In this article Damon shows a patient that would normally be a four bicuspid extraction case which he has treated non-extraction. This case illustrates that with the Damon system: 1.Clinicians can gain significant transverse arch width without rapid palatal expansion. 2.Gains in posterior arch width result primarily from bodily movement. 3.Bone displays remodeling. 4.The Damon approach in this case appears to be very stable after 5 years of no posterior retention. Some of Damon’s cases now have nine year records after treatment and again show stability of posterior arch adaptation (as opposed to arch expansion). It must also be noted that the Damon philosophy suggests an archform that is not over-expansive in the cuspid area and allows more expansion in the bicuspid and molar area, where we know that we get more stability.(3) Dr. Damon suggests permanent retention, which Dwight does even more so in bilateral crossbite and anterior openbite cases where nobody seems to have the correct answers regarding retention. The suggestion that Damon type expansion is biologically sound and stable has not been scientifically validated, but I feel that it is biologically sound as it has been validated by the numerous CT scans which show bony apposition post treatment. No other technique has yet shown this, but it is correct in saying that the results are not yet published, but only shown in the different lectures of Dr. Damon. It will probably take another five years before we get a clinical randomized trial. Clinicians employing the Begg technique state that light forces are not new, but what is new is the concept of keeping the forces below 25gm per square cm, not overpowering the lip and cheek musculature, thus avoiding excessive tipping of the teeth. The teeth are then placed in a neutral corridor in balance with the facial musculature. Here are some more scientific facts….. 1.The range of variation of the maxillary width within primitive societies is low while in industrialized societies it is high. This shows that it is not controlled by the genes. 2.Careful study of the literature discloses a rather astonishing fact; even the critics have found that about half the expansion is usually permanent, and where relapse did take place, it was usually in the alveolus and not in the vault. Labret (4) found the widening here “maintained in all instances”; a view that was supported in the same year by the implant studies of Skieller (7) and later by Mayoral & Aristeguinta (5). John Mew (6) using a special semi-rapid rate of expansion at 1mm per week found that there was no relapse two and a half years out of retention. “The net expansion had been 3.5 mm and this had subsequently not relapsed”, but Dr. Mew was also training the patients to keep their mouths closed. This may be a major factor because patients with open mouth postures are known to have narrower maxillae. We know that clinical effectiveness is usually measured in cost, time, ease, etc and that the simpler methods are often found to provide the most “effective” if not the best results. From a paymaster’s point of view it is hard to justify any method that is less effective and as you know the final assessment of orthodontic effectiveness is usually made at the end of treatment regardless of subsequent changes. Obviously this acts as a real deterrent to the development of improved techniques which may take longer and require greater skills. Unfortunately, it is not easy for us to demonstrate the advantage of more complex methods if they are dependent on high levels of co-operation or require special clinical skills. This is especially true for Head Gear, Functional Appliances and long-term retention where co-operation may be in doubt and clinical skills vary widely. One method might have greater potential (be more “efficacious”) but is only “effective” with some clinicians and some patients. Never-the-less it may be possible to compare “efficaciousness” by selecting the “best results” achieved by a number of different techniques. Under these circumstances the numbers of patients in each group becomes less important as it can reasonably be assumed that the cases selected, represent the “best results” of the technique in question. In addition any selection is of more or less equal consequence and therefore relatively random. Comparing the “best results” may be the only method of testing “efficaciousness” when assessing the potential of techniques that require high clinical skills and patient co-operation. My Damon treatment outcomes are certainly amongst the best results when compared to previous expansion techniques. In the last few decades there has been a number of long term studies to evaluate the effect of different treatment modalities. The main topics of discussion have been related to the timing of treatment i.e. early or late and also the treatment options i.e. extraction or non-extraction, orthopaedic treatment with headgear or functional appliance therapy.(8-14) If one closely analyzes these studies you will find a very few of the methodologies presented are sound. Most of the studies dealing with extraction versus non extraction treatment options compared short and long term treatment outcomes without looking at the similarity of both groups at the commencement of treatment.(15-16) To have a scientifically correct comparison, the end of treatment outcomes should be compared only in those patients who are similar and thus equally susceptible to both treatment modalities. In the study by Pacquette and co workers, boarderline cases were compared for extraction and non extraction.(17) By boarderline they meant that the case only exhibited 4 – 5mm of crowding and thus could be treated either with or without extractions. When the cases were evaluated, on average 14.5 years after orthodontic treatment, the results showed that the upper incisors, as well as the upper and lower lips, were 2 mm more retruded in the extraction cases compared with the non-extraction cases. Any clinicians would consider this 2 mm insignificant and of no consequence, however, according to constructive profile studies a change of a few millimeters in one feature is enough to alter the appeal of the rest of the face.(18) In a similar study, Bowman and Johnston found that extraction patients demonstrated 1.8 mm less lip protrusion than non-extraction patients. So to summarize I wish to state that the case I demonstrated in my article showed considerable expansion, but was treated with the principles of Damon and thus the end of treatment CT scans showed more bone around the teeth at the end of orthodontic treatment than before. Although I do not have many Damon cases five years post retention I currently have, in my two practices, over 700 case records of patients who were treated as second opinions against four bicuspid extractions. I have successfully treated these 700 individuals without removing premolar teeth and we now have 10 years post treatment records with perfect stability. This is due not only to the fixed retention employed, but also due to the fact that the majority of these 700 patients were treated during their pubertal growth phase. I welcome any clinician to assess these long term records which I will eventually hope to publish in an attempt to change people’s perception of the need for premolar extractions versus arch development as part of the an orthodontic treatment plan. In this way people may realize that achieving beautiful facial profiles and wide smiles, via arch development, is certainly not a mystery. References 1. Little, RM Stability and relapse of mandibular anterior alignment...University of Washington studies, Semin Orthod 1999; 5:191-204. 2. Damon D, Clinical Impressions, Volume 15, No. 1 2006, page 16 & 17. 3. BeGolle EA, Fox DL, Sadowski C. AJODO 1998 Mar;113(3):307-315. 4. Labret, L.M.L. “Expansion with Labiolingual and Removable Appliances”.Am. J. Orthod. 1964 (50). 786-787. 5. Mayoral, P. & Aristeguinta, R. “What Happens with palatal Dysjunction”. J. Clin. Orth. 12. 561-565. 1978. 6. Mew, JRC “Relapse Following Maxillary Expansion: A Study of 25 Consecutive Cases” American Journal of Orthodontics. 83: 56-61 1983. 7. Skieller, V. “Expansion of the midpalatal suture by removable plates analysed by the implant method” Transactions of Eur. Orthod. Soc. P.p. 143-158. 1964. 8. Baumrind S. Korn EL: Patterns of change in mandibular and facial shape associated with the use of forces to retract the maxilla. Am J Orthod. 80:31-47, 1981 9. Johnston LE: A comparative analysis of Class II treatments, in Vig PS, Ribbens KA, eds: Science and Clinical Judgement in Orthodontics. Monograph No. 19, Craniofacial Growth Series. Ann Arbor, Center for Human Growth Development, University of Michigan Press, 1986, pp 103-148 10. Tulloch JF, Phillips C, Koch G, Proffit WR: The effect of early intervention on skeletal pattern in Class II malocclusion: a randomized clinical trial. Am J Orthod Dentofacial Orthop 111:391-400, 1997 11. Keeling SD, Wheeler TT, King GJ, et al: Anteroposterior skeletal and dental changes after early Class II treatment with bionators and headgear. Am J Orthod Dentofacial Orthop 113:40-50, 1998 12. Ghafari J, Shofer FS, Hunt-Jacobsson U, et al: Headgear versus functional regulator in the early treatment of Class II, Division 1 malocclusion: a randomized clnical study. Am J Orthod Dentofacial Orthop 113:51-61, 1998 13. Tulloch CFC, Phillips C, Proffit WR: Benefit of early Class II treatment: progress report of a two-phase randomized clinical trial. Am J. Orthod Dentofacial Orthop 113:62-72, 1998 14. Boley JC, Pontier JP, Smith S, Fullbright M: Facial changes in extraction and nonextraction patients. Angle Orthod 68:539-546, 1998 15. Zierhut EC, Joondeph DR, Artun J, Little RM: Long-term profile changes associated with successfully treated extraction and nonextraction Class II Division 1 malocclusions. Angle Orthod 70:208-219, 2000 16. Luppanapornlarp S, Johnston LE: The effects of premolar extraction: a long term comparison of outcomes in a “clear-cut” extraction and non-extraction Class II patients. Angle Orthod 63:257-272, 1993 17. Paquette DE, Beattie JR, Johnston LE: A long term comparison of non-extraction and premolar extraction edge-wise therapy “borderline” Class II patients. Am J Orthod Dentofacial Orthop 102:1-14, 1992 18. Romani KL, Agahi F, Nanda R, Zernik JH: Evaluation of horizontal and vertical differences in facial profiles by orthodontists and lay people. Angle Orthod 63:175-182, 1993 19. Bowman SJ, Johnston LE Jr: The esthetic impact of extraction and nonextraction treatments on Caucasian patients. Angle Orthod 70:3-10, 2000 20. Johnston LE Jr: Functional appliances: a mortgage on mandibular position. Aust Orthod J 14:154-157, 1996