THE EDITOR'S CORNER
The Problem in Orthodontics
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The Problem in Orthodontics
There are few circumstances more frustrating in anyorthodontic practice than the all-too-common situation inwhich a patient whose case was finished successfully afew months earlier shows up one day, and some hard-wonaspect of the correction has relapsed. The lower anteriorsmay have become crowded, a previously closed open bitemay have reopened, or perhaps a stubborn upper midlinediastema that was completely resolved at the end of treatmentmay have reappeared, seemingly overnight. Thepatient or parents invariably hold the doctor to blame.
Relapse haunts us all. Dr. Albin Oppenheim, one ofthe great figures of the early days of orthodontics, wasquoted as saying, "Retention is one of the most difficultproblems in orthodontia; in fact, it is The Problem." Idon't know of a single practicing orthodontist who woulddisagree with him. The subject has been approached froma variety of perspectives, which Joondeph has succinctlydescribed as the four orthodontic schools of thought.The Occlusion School sees the final occlusion as the mostpotent factor in determining long-term stability. NormanKingsley was the strongest proponent of this philosophy,which held sway in the early part of the 20th century. Tothe Apical Base School, as expounded by Axel Lundstromand his disciples around 1925, maintenance of the intercanineand intermolar widths at pretreatment dimensionsis of paramount importance. The Mandibular IncisorSchool, whose most famous advocate was Charles Tweed,holds that positioning the lower incisors "upright overbasal bone" is the single most important factor. The MusculatureSchool considers proper function and musclebalance to be the ultimate determinants.
Like most physiologic phenomena, however, orthodonticstability is multifactorial. The degree of influenceof each factor championed by the different schools ofthought varies from patient to patient, and even from onetime to another within an individual case. Oppenheim'smessage remains as pertinent today as it was in theRoaring Twenties--retention is The Problem inorthodontics.
The question is actually a simple one: Howdo we keep the teeth where we put them duringtreatment? Perhaps the soundest advice I'veheard came from the chair of the orthodontic programin which I trained, Dr. Daniel Subtelny ofthe Eastman Dental Center in Rochester, NewYork. Typical of his brand of folk wisdom, Dr.Subtelny used to admonish me and my classmates,"Let the punishment fit the crime." Inother words, build a mechanism into the retainerto treat the original features of the malocclusion.Since each case is unique, each retainer isunique. This has been termed the DifferentialRetention Principle.
For example, in a Class II case, the lowerincisors should be permanently retained if theyhave been moved forward more than 2mm duringtreatment. To prevent or control skeletal relapse,night-time wear of a Kloehn-type headgear orfunctional appliance is indicated. For a severeinitial Class II problem or a young patient withconsiderable active growth remaining, it is assumedthat an anteroposterior relapse tendencyexists, and that a 1-2mm change in sagittal relationshipsshould be addressed in retention withongoing Class II elastics and overcorrection. In aClass III case, it is recognized that skeletal relapseresults from continuing growth of themandible and thus will be difficult to control. Althoughrestraining forces applied to the mandible,such as chin cups, have never been proveneffective in any evidence-based investigation,they remain at the top of our list of non-surgicaloptions for moderate-to-severe cases. In a mildClass III patient, a functional appliance or positioneris generally able to maintain the occlusalrelationships during post-treatment growth.
Vertical problems can be addressed underthe same philosophy. In a deep-bite case, aremovable maxillary retainer with a built-in biteplate can prevent post-treatment closure. Likewise,a high-angle anterior open bite can best beretained by building posterior bite blocks into aremovable maxillary retainer and applying ahigh-pull headgear at night to control molareruption.
An unscientific review of my own practiceindicates that for me, at least, lower incisorcrowding is the most common reason for patientsto seek care for orthodontic relapse. A number ofauthors have suggested explanations for this vexingphenomenon over the years. To summarizethe various theories about the etiology of lowerincisor crowding relapse: Late mandibulargrowth results in a forward or downward rotationof the mandible, which carries the incisors intothe lip and its underlying musculature. This producesa force acting to tip the incisors distally,which ultimately results in incisor crowding. Theimplied corollary to the hypothesis is that lowerincisor positions should be maintained until therate of mandibular growth declines to adult levels.
As with so many other problems in orthodontics,patient cooperation becomes a limitingfactor. Fortunately, we have a relatively simpleand inexpensive solution in the fixed lowerretainer. Most of the customization needed to satisfyDr. Subtelny's "let the punishment fit thecrime" dictum can be built into the acrylic of anupper wraparound Hawley-type appliance, whilethe fixed lower lingual retainer can be worn withoutloss or failure until well into the adult years.
The overwhelming popularity of the fixedlower retainer is emphasized by the number ofmodifications that appear in print every year.Banded 6-6 or 3-3 designs, bonded 3-3s, wroughtwires, braided wires, semicircular wires, monofilaments,and pliable fibers have all been tried.Each of these concepts has its pluses and minuses,its supporters and its critics. In this issue, wepresent four new variations on the theme, each ofwhich holds promise as a valuable addition to thearmamentarium of a busy practice. Still, despitethe plethora of new ideas for addressing relapsethat keep springing up, I suspect that The Problemwill be with us for years to come.