Xbow System Lectures
The Four Tool Boxes for Class II Treatment
Informed consent is the legal responsibility of the orthodontist to explain the pros and cons of all possible treatment options, and to help the patient and their family determine which option is best for them.
One type of Class II bite problem is when there is a horizontal gap between the upper and lower front teeth, also known as excess overjet. 53% of the population has a Class II bite with an overjet greater than 3mm. 15% of the population has a moderate to severe Class II bite problem with 5mm or more of overjet.
The cause of excess overjet is usually a small or receding lower jaw and chin, but there can also be a protrusion of the upper front teeth.
The Four Tool Boxes Analogy
In Dr. Higgins’ office there are four different options for the treatment of a Class II bite problem.
- The Surgery Tool Box
Braces to straighten the teeth and place the front teeth and lips in an ideal position, followed by surgery to lengthen the lower jaw, is often the best option to correct the bite and balance the appearance of the nose, lips, and chin.
- The Traditional Treatment Tool Box
Braces and the extraction of two upper teeth are used to retract or “pull back” the upper front teeth to correct the bite and camouflage the small or receding lower jaw and chin. We call this Class II compensation. This is a good choice if the upper front teeth are crowded or protruding. The down side of this treatment is it can result in loss of upper lip fullness.
- The Crossbow Tool Box
The Crossbow Class II Corrector shares the correction between the upper and lower teeth. It moves upper teeth back and lower teeth forward. This minimizes the retraction of the upper front teeth and upper lip. This is another type of Class II compensation. It is meant to be used in a growing patient, and works best if the patient is in their growth spurt. The down side is that it still moves the upper lip back, just not as much as traditional extraction treatment. It also moves the lower lip forward, which can be a plus or a minus. Even if surgery is the best option, most patients still choose the Crossbow Tool Box, to avoid surgery and extractions. Sometimes the Crossbow is not a good option, especially if the patient is finished growing, or if the lower front teeth are crowded or protruded, or if the lower lip is protruded.
- The Class II Elastic Tool Box
Braces or Aligners combined with Class II elastics is probably the most common treatment in use today. It is popular because it is the least expensive. It requires the least effort by the orthodontist, but the most effort by the patient. Simply put, if the patient does not wear the elastics, they end up with straight teeth but with a remaining bite problem, or excess overjet. If the patient wears the elastics well, the result may be similar to the Crossbow, with two exceptions. One, Class II elastics have a tendency to pull the upper front teeth down, making a gummy smile worse. Two, when used with aligners Class II elastics may push the lower front teeth out of the bone, exposing the roots. The other problem with aligners is they require much more patient cooperation than braces, and there are many tooth movements that aligners don’t do well or not at all. This is why the best orthodontists that use aligners use them in conjunction with braces. Braces are still used to do the “heavy lifting”.The general rule is it is best to choose a treatment plan that decreases elastic wear and patient cooperation because poor cooperation can increase the length of treatment. Long treatment time increases the risk of root resorption (root shortening) and decalcification (white spot lesions or cavities).Dr. Higgins has developed systems that decrease the time in braces to 12 to 18 months, even for extraction treatment. This includes indirect (precision) bonding of brackets (braces). He also uses a low force technique with a smaller bracket slot and smaller wires compared to the majority of orthodontists. This is more comfortable for the patients and may result in less root resorption.The Crossbow appliance is part of Dr. Higgins’ “foundation building” philosophy of treatment. It is based on the principle of waiting until all teeth have erupted, including second molars, before placing full braces. “Building the foundation” includes establishing a normal upper jaw width with an expander (RME), correcting a Class II bite with a Crossbow appliance, and opening space for upper canine teeth with partial braces (RME X 6).Dr. Higgins is a clinical assistant professor at the University of British Columbia. More information can be found on the Crossbow website at www.crossboworthodontic.com.
- Treat the biggest problem first.
- Sequence treatment based on the eruption.
- Begin with primary maxillary expansion if there is a posterior crossbite or if the maxillary lateral incisors are impacted. These teeth erupt at 8 to 9 years old on average.
- Time first phase treatment when the first bicuspids are erupting at 10 to 12 years old to make room for the erupting maxillary canines at 11 to 12 years. This will reduce the incidence of impacted maxillary canines.
- Don't place full edgewise appliances until the second molars have erupted or you will prolong your second phase treatment and increase decalcification and root resorption.
- Save cooperation with Class II elastics in deep overbite cases until you are in full-size stainless steel arch wires and the overjet is reduced enough to place a bite turbo.
- Try to postpone IPR (interproximal reduction) of the incisors until all spaces are closed, the buccal occlusion is Class I, and the overbite and overjet are corrected. The goal is to create long, flat interproximal contacts without black triangles keeping in mind not to create a tooth mass discrepancy. This is impossible to do with early IPR.
- Always go back to the foundation base during treatment to make sure the patient can breathe through the nose, keep the tongue on the anterior palate, swallow without a tongue thrust, and keep the lips together at rest, if possible.
- Initial, posterior Crossbite, & Anterior Crowding
4 Years After Maxillary Expansion
Initial, posterior crossbite and anterior crowding