Orthodontics on Trial
Mark Lowey MSc FDS BDS MOrth DOrth LDS RCS (Eng.) MNTF
Orthodontics on Trial. A Cautionary Tale. Part I
Orthodontic treatment and acceptance of orthodontics as a form of treatment by the population at large has been steadily increasing over the last forty years. This increase in demand brings with it additional challenges. General Dental practitioners have a limited time during undergraduate training to appreciate many of the concepts involved in clinical orthodontics yet at the same time they are often called upon to act as an arbiter on behalf of the patient. Increasingly Generalists also offer orthodontic treatment as part of the overall treatment for a patient. They may also be asked about different types of appliances, differing treatment plans between Orthodontists, extraction versus non extraction, retention and “relapse”. Many of the questions parents or patients may have can fall well outside of the scope of general dentistry.
The following discusses some of the scientific evidence in relationship to Orthodontics in an attempt to fill in some of these gaps and describes in detail a very modern problem related to a specific case.
“Stability and relapse”
The first dental myth which requires some detailed discussion is the term “stability”. It is a cosy concept that teeth should remain “stable” throughout life. Unfortunately this is not true for around 66.6% of the population It is therefore normal for teeth to move throughout life for most of the population regardless of whether they have had treatment or not. The amount and direction of movement is wholly unpredictable. Little has dedicated a considerable part of his clinical life to exploring this issue. [1-36] Lower incisor crowding appears to occur regardless of the following:-
- The Orthodontist.
- The appliances used, fixed or removable.
- The duration of treatment.
- The type of wires used.
- Whether premolar extractions have been undertaken or not.
- Whether wisdom teeth are present or not.
He has found that patients with more severe index scores before treatment tended to be less stable after treatment but individual variation was considerable and minimizing treatment change was no guarantee of post treatment stability. Even teeth which are perfectly aligned naturally as a teenager without the assistance of Orthodontic treatment are liable to move later in life and the percentage of the population affected appears to be the about the same.
As in most medical research whether the clinical attribute measured is anything from birth risk to life expectancy predicting percentages for any given population can be undertaken fairly well. However the difficulty lies in making a prediction for one particular individual. Then reliability vanishes. The same is also the case for movement of teeth regardless of treatment. The same is also the case when considering the risks of retaining unerupted third molars versus removing them. If the risk of an event happening to an individual is 1:1,000,000 it matters little to the individual concerned if they are the 1. For that individual the risk has been 100%.
Little has presented cases which have had all 8 premolar teeth removed as part of an Orthodontic treatment which still demonstrate late lower incisor crowding. He has presented cases with congenitally missing third molars which still demonstrate late lower incisor crowding.
Obviously there is a percentage of the population who are fortunate and whose teeth move little throughout life. This concept is not appreciated widely enough in the general population even when patients are told of its scientific validity. While it is generally understood that the process of ageing will produce change such as greying hair, wrinkling of skin and deterioration in eyesight. The fact that the same process occurs with teeth seems illogical. For patients and some clinicians to accept that teeth move throughout life for the majority of the population is counterintuitive. While a patient given spectacles at age 15 would not expect them to last a life time the same is not true of a patient given a course of Orthodontic treatment.
The clinical argument about what produces a stabile result at the end of Orthodontic treatment has been debated endlessly since the introduction of Orthodontics as a form dental of treatment. Violently expressed opposing opinions and beliefs by Orthodontists claiming that one form of treatment is better than another or more importantly one form of treatment has been undertaken poorly compared to another have been recorded since the very onset of Orthodontic treatment as an entity:-
- If only teeth had been taken out.
- If only different teeth had been taken out
- If only teeth had not been taken out
- If only the third molars hadn’t come into the mouth
- If only head gear had been used
- If only a functional had been used
- If only fixed appliance x had been used and not appliance y
- If only I had done it instead of orthodontist y.
- If only the appliances had been kept on longer
- If only the appliances had not been on so long
- If only the retainers had been kept on longer
- If only the patient hadn’t grown so much and in that direction
- If only the patient had grown more and in that direction
- If only the teeth had been placed on a specific Cephalometric line
These statements can and have been used to promote certain forms of treatment and retrospectively criticise previous courses of treatment. The field is therefore open for a variety of opinions all equally invalid and unpredictable. This lack of scientific certainty and the existence of firmly held opposing opinions by different clinical experts can be exploited by an aggressive legal system geared more to recovering funds on a no win no fee basis than exploring the whys and wherefores of Orthodontic opinion and research.
In reality the cases which appear to remain “stable” more than others according to Little are
- Those with a missing or single extracted lower incisor 
- Those with mild generalised spacing [4,5,7,11,12]
Equally important is the direct corollary of this that the term “relapse” should be either discontinued or used with extreme caution. Teeth do not “relapse” to a set position because for the majority no such set position exists. Change is normal and predictions of certainty regarding position or stability of teeth unattainable goals for the majority of patients, whether they have had treatment or not.
The concept of “crowding” and premolar extractions to “relieve crowding” needs to be examined bearing in mind not only Little’s findings but others. The choice appears to be that premolar extractions generally will cause the incisors to retrocline while keeping premolars tends to procline incisors. Both treatment routes can lead to good aesthetic results or poor aesthetic results often dependent on growth. Growth in itself is also an additional wholly unpredictable factor which also needs to be taken into consideration during planning.( Fig 1)
In growing Class II patients upper premolar extractions tend to result in retroclined upper incisors which can increase with age. This may require surgery to correct later as damage can occur to the lower incisors in some cases. (Fig2) The aesthetics of retroclined incisors is generally considered to be poor. Maintaining upper premolars in growing Cl III cases tend to procline upper incisors which can increase with increased mandibular growth. ( Fig 3) Extraction of upper premolars tends to allow retroclination of upper incisors in growing Cl III patients. This is often undertaken because of “crowded” upper canines. This can result in significant reverse Overjets which may later require surgery to correct. (Fig 4)
Another widely held false belief is that premolar extractions will always allow third molars to erupt[20,22].
The argument about extractions has been unresolved for more than 100 years. Indeed Edward Hartley Angle opened the first Orthodontic congress in 1901 and in discussing extractions described the extraction of teeth as:-
“Pernicious rarely wise and alas far too often resorted to by those who should resort to less harmful, far wiser, and more effectual and scientific plans of treatment”.
Melsen and other authors reported the following:-
” Interestingly, a considerable variety of opinion concerning what constitutes “good orthodontics” has characterized our profession since its beginnings. No consensus exists today and some opinions even appear to be mutually exclusive. This disparate value system revolves around perceptions of quality and usefulness of procedures from the clinician’s perspective. Disagreements are the rule rather than the exception.”
In their sample of Extraction therapy patients with Class II/2 malocclusion Stellzig et al. found that “The results derived from Cephalometric analysis demonstrated that profile flattening was also observed in untreated Class II/2 cases during the growth period.” “extraction groups revealed a significantly marked recession of the upper lip after premolar extraction. In contrast only slight increased flattening after second molar extraction was observed compared with the untreated patients of the control group.”
Moffit  reported that “ From our point of view, the claim that premolar extraction facilitates third molar eruption should be seen in an extremely critical light”
Attempts have been made to identify what makes a case stable or not but unfortunately to date this particular holy grail has eluded the Orthodontic community.
The Class II division 2 malocclusion is a clinical entity, which presents considerable difficulty in the provision of a stable result . Selwyn Barnet felt that the success of treatment lies in correction of the transverse, anterior-posterior and vertical discrepancies. (Fig 5)
Houston and Tulley, thought that stability depended on the importance of correcting the inter-incisal angle and edge centroid relationship was paramount. In order to achieve this Houston stated that it is essential to reduce the inter-incisal angle towards 125 degrees, bringing the lower incisor tip anterior to the upper incisor centroid.
This was also considered evident from the results of an earlier study of 60 treated patients by Mills  who concluded that stability was dependent on satisfactory reduction of the inter-incisal angle and the overbite. Despite this fact he also presented an example in 1981 from this sample where during treatment the lower incisors had been proclined beyond the A Pog line and then had continued to procline beyond the A Pog line after debanding and retention.
Ethnic variation affects these attempts at defining predictors. Lara Carrillo found that the interincisal angle of the 240 male and female Mexican subjects sampled for their assessment of Normative data found the interincisal angle to be 130.5 + 7 degrees. They explored how their result varied when compared with other investigators results in differing ethnic groups. They also found that there was significant sexual dimorphism especially in linear measurements.
Once again the attempts to try and identify Normative data for different ethnic groups, which could then be used as targets for treatment goals, which could then in return deliver stable treatment results remains illusive.
Headgear has been used by many to reduce the need for premolar extractions. (Fig 6) A cautionary note is required here as most dentists are unaware of the risks associated with head gear. In 1988 in the UK a patient lost her sight following a suspected trivial injury which introduced oral bacteria into her eye from a facebow.
A 12 year old girl presented the morning after an insubstantial injury to the left eye. Antibiotics were given ½ hourly, penicillin,methicillin,gentamycin and intravenously i.v penicillin,genntamycin, metronidazole.
The first operation was undertaken that same day included A-biotics were administration directly into the eye.
The next day during the second operation sic. “the cornea was found to be even more necrotic with extensive infiltrate loosening the sutures.” the authors then reported that “By the fourth day the patient was taken back to theatre and the left eye removed” Three weeks later she developed sympathetic endopthalmitis. “the longterm prognosis for her right eye is uncertain”
This chilling report and the associated research is worthy of mention to all clinicians and patients still using head gear. In 1982 an American Association of Orthodontics survey reported that from 4,798 replies 216 injuries were identified. Of these 133 were Intraoral, 31 to the face, 41 to the eyes. There were 5 cases of blindness.
Commendable changes in facebow design have been made but have not been universally accepted. Risks still remain and all patients using head gear should be advised of them. Russell H.A. Samuells and Malcolm L. Jones  reported that in the 23 European countries they examined 17 cases of substantiated blindness were reported. Headgear detachment in their unit took place in 25-40% of cases at night.
They concluded that sic. “It is a sensitive matter, not well reported and difficult to survey” and that regardless of prompt and prolonged treatment loss of vision can occur.
In general practice Dentists are unaware of some of the risks of the use of head gear which also include Nickel allergy, Alopecia and dermatitis. Compliance is also mixed and head gear itself can result in over retroclined upper incisors. While clinicians often claim the use of head gear is reducing large numbers are still sold. Orthocare a UK supplier reported that between Apr 08-09 they sold 1902 Head gears obviously as a retailer they are unaware if patients are advised or not of the attendant risks.
The A Pog line.
Various Cephalometric landmarks analysis and lines have been used historically to assist in the justification of extraction versus non extraction therapy. The most commonly used line for this purpose being the A Pog line. Placing or moving the incisor teeth on or away from this particular line has also been inaccurately claimed as a measure of “stability”.
Houston WJ, Edler R. examined Long-term stability of the lower labial segment relative to the A-Pog line. Cephalometric records of 47 cases treated with the Begg technique were examined with a view to assessing both the effects of treatment and long-term change. The cases were treated by a single operator (Dr H. Brouwer) whose long-term records were taken on average over 10 years out of retention. Special reference was made of the use of A-Pog line as a guide to lower incisor stability. They found that “There was marked individual variation in both response to treatment and long-term change” and that “the A-Pog line was not found to be a reliable guide to lower incisor stability. In 62 per cent of the cases examined, the lower incisors tended to return towards their original positions after retention, whilst in the remaining cases the changes were extremely variable.”
Looi LK, Mills JR.  Contrasted different forms of treatment on facial profile. They compared retrospectively the effect on the soft tissues of two contrasting forms of treatment for Class II, Division 1 malocclusion. The first group of 30 persons exhibited uncrowded dentitions and were treated without extractions by means of the Andresen activator. No other appliance was used. The second group was also composed of 30 persons. These subjects were treated with the Begg appliance in its classical form. All of the Begg subjects showed varying amounts of crowding and were treated by extraction of four first premolars. It was believed that the Andresen appliance would maintain the incisors in the most labial position possible, while the Begg group with premolar extractions would involve the maximum lingual incisal movement. These groups were compared with a third group of 22 untreated persons who also exhibited Class II, Division 1 malocclusions.
In both the treated groups they found that the overjets were successfully reduced by retraction of the upper incisors; in the Begg group only, retraction of lower incisors was also performed. The upper incisors were retracted substantially more in the Begg group than in the Andresen group, but there was only a slight difference within the two groups in the final position of the upper lip relative to a vertical reference line through Sella. There was also a slight difference in the lengths of upper and lower lips within the two treated groups. The lower lip followed the lower incisors more closely in the Begg group. They concluded however that there “was a wide variation in individual response in all three groups”.
Sims AP, Springate SD. retrospectively compared Cephalometric measurements in order to assess the stability of the lower labial segment between treatment groups using the Andresen appliance and non extraction and first premolar extractions and the Begg appliances in Class II div 1 cases. Using four angular and two linear measurements, the lower labial segment was found to procline during Andresen therapy (1-2 degrees, 1-2 mm), and on withdrawal of the appliance it retroclined by about one-half of the in-treatment proclination (0.4-0.8 degrees, 0.1-0.5 mm). During extraction Begg mechanics, the lower incisors were found to retrocline (1.3-1.5 degrees, 0.4-0.9 mm), and they continued to retrocline following removal of the appliance (0.2-3.0 degrees, 0.8-1.1 mm). In general, the variables used to measure lower incisor position demonstrated only very small changes, and were near method error. They discussed reliability of these changes and considered that the axial inclination of the lower incisor in relation to the mandibular plane is the most consistent and therefore still the most useful clinical measurement of lower incisor change available from Cephalometric radiographs. It should be noted that they concluded that this was a useful measurement of change and not stability. The difficulties in assessing both repeatable Landmark identification in the incisor region and measurement error should also not be underestimated .[51-56]
This is of particular interest when considering bimaxillary proclination cases. In such cases the classic landmarks of A, B and Pog can often bear little relationship to the position of the teeth. Variation is the rule amongst different racial groups and there is also considerable sexual dimorphism. The dogma of treating one particular individual or group of individuals to one particular set of Cephalometric “norms” should be avoided.
The Eights debate
It may or may not be true that in any one given individual extraction of third molars may reduce lower incisor crowding. However this is of little help when applied to a population. The NICE guidelines have unfortunately not helped in this regard. The criticism concerning removal of symptomless third molars levelled at Oral surgeons appears to be the implication that the motivation for removal of symptomless third molars is purely for financial gain rather than clinical need. The wholesale application across the NHS of the NICE guidelines with respect to third molar removal has lead to some interesting problems. Indeed it would appear that the NICE guidelines have simply delayed the inevitable. In addition the routine taking of panoramic radiographs to identify potential or actual problems is discouraged. Unfortunately this can also lead to under or missed diagnosis.
A longer term perspective could and should have been taken. It would have been feasible and preferable to monitor the non extraction approach of third molars to assess and identify actually how many developed cysts, ameloblastomas, etc. The current generation who some would say have been denied extractions are the same generation who are expected to live longer develop more diabetes heart disease and the attendant complications of such illnesses. Any clinician who has been called to extract an infected third molar on a sick elderly patient who is on anticoagulants first concern is that removal of the tooth could threaten the patient’s life.
Extraction of third molars before root formation is complete versus later extraction is and has always been a hotly debated topic. Evidence suggests also that as each decade passes third molar extraction becomes technically more difficult and the complications more difficult to manage. The White paper on Third molar data draws specific conclusions from each clinical aspect in relation to third molar removal supported by the available evidence and is an excellent resource which encompasses most of the clinical debate.
A genuine appraisal of the benefits of early extraction are that the risks of later pathology are reduced. Apparently symptomless third molars once removed and examined for pathology can also reveal underlying disease. Mesgarzadeh AH, et al  examined one hundred eighty-five impacted third molars from 170 patients . Two pathologists found that 53% of the specimens had developed pathology 38% Dent. Cysts 5.8% Ameloblastoma 4% Actinomyces. The incidence of pathology was higher in the age group of 20-30 years, in men compared to women and in the mandible compared to the maxilla. Three Pathologists looked for Pathologic change in soft tissues associated with radiographically 'normal' third molar impactions. Glosser JW, Campbell JH.  A diagnosis of dentigerous cyst was made in 31 cases; 22 of 60 mandibular specimens (37%) and nine of 36 maxillary specimens (25%) were affected. No disease other than dentigerous cyst was seen. They concluded that the incidence of dentigerous cyst associated with impacted third molar teeth is higher than reported in radiographic studies alone.
Zhang LL, et al. in an attempt to identify prevelance retrospectively analysed cases treated in British Columbia between 1998 and 2007 they confirmed that over that nine year period 2082 of the 2029 cases examined had histolgically confirmed Dentigerous cysts.
Sham et al found 5 Ameloblastomas in their sample examined between 1996 and 2006.
Tawfik MA, Zyada MM  examined Odontogenic tumors in Dakahlia, Egypt the analysis of 82 cases found that (96.3%) were benign and (3.7%) were malignant. Ameloblastoma (41.5%) was the most frequent type, followed by keratocystic odontogenic tumor (19.5%), odontoma (13.4%), and odontogenic myxoma (8.5%). The mean age of the patients was 29.57 years, with a wide range (4-80 years) and demonstrated Geographic variation. They reported that of all swellings in the mouth 9% are Odontogenic tumours, 1% Ameloblastomas, 80% appear in the mandible .
M. Chatterjee, K. Balaram, P Mc Dermott  reported how a Metastatic breast Carcinoma presented as a Dentigerous cyst on OPG associated with an unerupted third molar and altered sensation in the right lower lip.
The debate about removal or retention of third molars is comprehensively covered from both sides of the fence by Rafetto and Hill in Removal of asymptomatic third molars: a supporting view.and Removal of asymptomatic third molars: an opposing view. Respectively.[62,63]
The Sevens debate
Extraction of second molars is a rare occurrence in most practices. While extraction of first molars is generally accepted as a rational treatment in the UK for cases in which damaged or hyperplastic first molars. It is not universally accepted  for example in Norway despite the fact that there is a greater prevalence of hyperplastic first molars in Scandinavia.
In contrast extraction of second molar teeth is generally viewed with disdain at least and on occasion with horror. The most comprehensive review of cases treated with removal of 7’s was undertaken by Orton Gibbs et al 
The effect of extraction of permanent second molars on the dentofacial complex of patients treated with the Tip-Edge appliance was examined by Greatex et al.,  Ruiken HM et al., reported that “Extraction of second molars as an orthodontic measure is a simple procedure which can lead to good clinical results” Waters and Harris  undertook a Cephalometric comparison of maxillary second molar extraction and non extraction treatments in patients with Cl II malocclusions. They found “ more anterior crowding in non extraction group” and that the “extraction group finished treatment 7 months earlier than average” concluding that “In properly selected Class II malocclusions second molar extraction is a viable alternative treatment choice.”
Broadbent J  went further “Second molar extraction technique has revolutionised orthodontic treatment. “ He reported that “the extraction of second molars have predictable good results in a high percentage of cases” but warned that “Diagnosis and case selection is paramount!” The orthodontist must diagnose and determine if and when second molar replacement would be in each individual patient’s best interest with respect to best possible facial aesthetics, functional occlusion and health of the jaw joints. “ After extraction of maxillary second molars. The results showed that generally the eruption of third molars was accelerated. Most maxillary third molars will successfully erupt into an acceptable position by the late teens” Battagel and Ryan ( compared spontaneous lower arch changes with and without second molar extractions “In the extraction sample buccal segment retraction was associated with increases in all lower arch dimensions and a reduction of crowding .”
A Richardson ME Richardson [75,76] concluded that “Ninety-nine percent of the third molars upright mesiodistally and that 96% of the lower third molars erupted in good or acceptable positions”
The effect of extraction of four second permanent molar on the incisor overbite was also examined Richardson ME Richardson A [75,76] and they reported an “increase in overbite was greater in subjects whose overbite was already reduced.” This particularly benefits High MM angle patients.
So while not a widespread form of treatment it remains useful. (Fig 7). The necessity to upright later third molars is a relatively rare occurrence and easy to undertake [70,77].
The inevitable conclusion from Little’s research is that all patients must be warned that at the end of Orthodontic treatment or even if their teeth are naturally aligned as teenagers that with time the risks of this changing is 66.6%. They should also be advised that this may or may not be associated with later eruption of their third molars and may be unrelated to the fact that they have had either teeth removed or retained as part of their orthodontic treatment. It also means that all patients must be advised that life long retention is required if their occlusion is to be retained. Further that this movement is unpredictable for any one given individual and for any one tooth of that individual. This leads on to the next clinical problem of how should teeth be retained.
The advantage of removable retainers are that they are not in the mouth 24 hours per day which reduces the long term problems associated with plaque accumulation and possible periodontal disease. The disadvantages are patient compliance and loss of appliances. Occlusal coverage appliances often known as “blow down” retainers often wear on the occlusal surface and so can require replacement more often than non occlusal coverage appliances such as Hawley appliances.
Fixed retainers vary but have the disadvantage that they are in the mouth 24 hours per day and tend to accumulate plaque and calculus with time which can lead to periodontal problems. They can break some times without the patient’s knowledge and then teeth can move requiring a further course of fixed appliance therapy to correct. (Fig 8) Fixed retainers can also allow teeth to rotate or move en bloc.
There is a common misconception that because fixed retainers are simply that “fixed”, then they require no maintenance and will last a lifetime without problems.
Littles work also means that if fixed retainers were placed in 100% of patients 34.4% of the time this would be unnecessary.
The difficulty being identifying which 34.4% of patients do not require retention. In this respect it is worthwhile considered the remark attributed to Hawley that he would gladly give 50% of his fees for treatment to anyone who would be willing to take over his cases once the appliances were removed.
One commercially available solution which tries to address the periodontal issues is the Linglock appliance. It is a flossabale fixed retainer. (Fig 9)The disadvantages of this retainer are the technical ones of placement and that they can also become detached.
This perplexing state of affairs has resulted in various forms retention regimes. Some clinicians will used fixed appliances on 100% of their patients. Some will use removable retainers for various time periods and durations. The scientific evidence is that fixed and removable retention regimes are no better or worse than each other. Some clinicians use fixed retainers for a while and then remove them and place removable retainers. Some use fixed and removable retainers. Some use “active “ removable retainers. Unfortunately all methods come up against the same problems that Little’s research has revealed and of course the issues of compliance. How Kau probably summarised it best in the title of his paper “Orthodontic retention regimes: will we ever have the answer?” he concluded that there is insufficient research data on which to base our clinical practice on retention at present. There is an urgent need for high quality randomised controlled trials in this crucial area of orthodontic practice.
While this has depressing connotations for Orthodontists and patients alike it should be remembered that without treatment tooth movement also occurs. Leaving aside function in general people appreciate the aesthetic value of aligned teeth and do not appreciate it’s deterioration. If clinicians were able to provide a “magic pillow” which if used every night prevented wrinkles and grey hair the demand would be great. Lifelong nocturnal retainers can prevent tooth alignment deterioration.
Type of fixed appliance used.
Various commercial claims are made for and have always been made for one particular fixed appliance system over another. Once again the field is open to a variety of opinions all equally invalid and lacking in predictability. Following a patient examination Orton remarked the following to the author:
“Isn’t it strange how the teeth don’t seem to remember which brackets were used ?”
The patient had been treated with an appliance he did not like and their teeth had moved after treatment.
At that time the debate was whether the “new” Straight wire system was “better and produced more stable results” than either the Standard Edgewise system or Begg fixed appliances system. His comment could have been applied with equal validity to which Orthodontist had placed the brackets to whether teeth had either been removed or not or to which Cephalometric landmarks or measurements had been used in planning.
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