Class II

Our second topic: why are there so many ways to correct “Overbites”

Class II malocclusions or overjets (commonly, but incorrectly, called “overbites”) are one of the most common problems in orthodontics. Despite the customary Angle Class II classification, patients who exhibit excessive overjets are not a homogeneous group. The following all can produce excessive overjets.

Ø Protrusive maxilla
Ø Deficient (retrognathic) mandible
Ø Good posterior occlusion (Class I) with flared upper incisors
Ø Good posterior occlusion (Class I) with lingually verted lower anteriors
Ø Good skeletal alignment but the maxillary dentition is mesial to the mandibular dentition
Ø And of course a combination of 2 or more of the above problems

In addition to these sagittal problems, the vertical facial pattern influences the degree of overjet and the ease of correction. Further complicating the correction is the amount of growth the patient has left, as all class II problems are much harder to deal with when the patients are skeletally mature.

Understanding that Class II’s encompass a variety of problems makes it easier to see why there are a variety of ways to correct these problems. And, going with the theme of our newsletters, different orthodontists have different “philosophies” on how to achieve this correction.

As every orthodontist will tell you: most class II malocclusions are caused in large part by a deficient mandible. So why has so much traditional orthodontic treatment been aimed at retracting the maxilla and maxillary teeth with the use of headgears, molar distilizing appliances, upper premolar extractions and elastic band wear? The simple answer is: “its hard to grow mandibles” (some would even say it is impossible to “grow” mandibles!) Unfortunately computers don’t know this, and many patients are “promised” great facial improvements with the newest patient education software; and orthodontic companies and labs have an incentive to sell these innovative appliances. The fact that a promoter can show you anecdotally a patient who seems to have had a great response to a “mandible grower appliance” is no guarantee that this can be done on a regular basis.

Over the years various appliances such as the removable functionals e.g., Bionators, Activators, Frankels, Twin Blocks, Monoblocks, and the fixed “functional” appliances e.g., Herbst, MARA, Forsus, have been tried with the aim of stimulating mandibular growth over and above what would normally occur. As they have been “introduced” they were met with a great deal of enthusiasm followed unfortunately, a few years later, by disillusionment and a jump to the next silver bullet. Nonetheless many orthodontists (and general dentists) believe very strongly in this type of treatment. Why is that? Well often they do seem to work! Overjets do correct, but the big question is: do they “grow” mandibles and if they don’t are they worth the effort?
Being human we often see what we want to see. If we put in an appliance promoted to “grow” a small lower jaw and 6 months later the overjet is corrected, the logical assumption is that the appliance did what we wanted it to do! The facts however are that growing mandibles is one aspect of orthodontic treatment that has been well studied. The scientific consensus is that there is no or minimal long-term increase in mandibular growth over what would have been expected from normal growth. The overjet correction was really obtained in the same fashion as traditional orthodontic treatment: incremental improvements of the maxilla, mandible, and both dentoalveolar arches. Of course there are cases where one can show very significant improvements in mandibular position with the use of these appliances, but these cases are unusual and unpredictable, and probably would have occurred with more traditional treatment. Nevertheless we do use these appliances; sometimes because they require less patient cooperation (the fixed versions), and sometimes because the patient is so obviously mandibular deficient that we hope that we may get lucky and get a great response.

So what are some of the more predictable treatment options for “overjets”?

Ø In growing individuals headgears still work well to slow the maxilla’s normal forward growth and let the mandible catch up. Sometimes this is a good option while waiting for tooth eruption and fixed appliance therapy and a great option if the maxilla is protrusive. Of course getting sufficient wear is a major problem.
Ø For patients with mild to moderate class II’s, elastic bands work well but they have the “side effect” of pulling the lower dentition forward off the bone support. There is an esthetic and stability limit to how protrusive the lower anteriors can be. And, with the natural mesial movement of the teeth in the arches over time, excessively protrusive anteriors can become unacceptable 10, 20 and 30 years later. For patients with crowding, the excessive lower protrusion can be overcome with lower extractions. Although much easier than headgears, elastic cooperation can be a problem with certain patients.
Ø Upper first premolar extractions can be used; especially with severe Class II’s with good lower arches in nongrowing patients. Care must be used not to overly retract the incisors relative to the facial profile. A major advantage is the ability to avoid patient cooperation problems and negative forward movement of the lower arch. Contrary to some “experts” no negative TMJ problems are associated with this treatment.
Ø Noncooperative molar distilizing appliances e.g., Pendulum, Wilson. Reciprocal mesial movement of the anterior teeth however usually limits the effectiveness of these appliances. Although promoted as not needing patient cooperation, Class II elastics are often required to back up these appliances.
Ø Often the best treatment is a camouflaged, compensated dentition with the upper anteriors slightly lingual and the mandibular anteriors slightly flared.
Ø For some severe problems ideal overjet cannot be obtained without using techniques that the patient rejects (surgery, extractions, braces, etc.) For these patients a Hollywood Smile (straight teeth but an uncorrected “bite”) can be offered
Ø Notwithstanding the Align Technologies computer animation showing overjet correction, it is extremely difficult to correct significant Class II malalignment with Invisalign.
Ø Perhaps one of the most exciting new advances in orthodontics may be the use of implants or temporary anchorage devices (TAD’s) that provide anchorage without the negative reciprocal mesial movements.

Bottom Line: how do we treat these patients? We weigh all the factors including the severity of the problem, likely patient cooperation, predictability of correction, facial esthetics (and on and on ….). In the end there are many ways of achieving a good correction and it is our job to come up with the best way for each individual patient. Not only should different techniques be used for the different types of Class II’s but, since there are positive and negative effects for each technique, different approaches are possible for the same problem.
To say that upper premolars should never be removed or that headgears are no longer needed is to take valuable tools out of the orthodontist’s armamentarium. And when the only alternative for full correction is full braces and a surgical procedure what’s wrong with giving a patient (after going over all of the alternatives) straight teeth and less than “ideal” bite? Sure there are negatives to various approaches but sometimes the alternatives are no better or even worse. It is the orthodontist’s responsibility to evaluate the pros and cons of the various techniques and, in consultation with the patient, parents and dentist come up with the best option for each patient... and this is what we try to do!