Next in this mini-series I would like to discuss the “orthopedic” aspect of orthodontics, which entails growth modification. There are three dimensions that we will discuss: the transverse dimension of growth; this is the “width” dimension or x-axis when looking at your face straight-on. Next will discuss the vertical dimension of growth, or y-axis. Lastly, we will address the anteroposterior dimension; this is the growth direction from looking from a profile stance or the z-axis when looking straight on. This imbalanced relationship is commonly known as a skeletal malocclusion.
In terms of facial skeletal growth, the transverse “width” dimension of growth completes earliest in life, years before one’s adolescent growth spurt. Commonly, many children with deficiency in this aspect have what is called a posterior crossbite. A crossbite is when the lower jaw is wider than the upper jaw because there is an inadequate amount of transverse growth in the maxilla (upper jaw) relative to the mandible (lower jaw). Those who have had cleft lip/palate surgical repair early in life also may present with a skeletal growth inadequacy due to the scar tissue impeding on growth thereafter. The scar tissue will affect the other two dimensions of growth, as well, but to keep this section simple we will only discuss the transverse. Conversely, the lower jaw may be overdeveloped which causes both an anterior and posterior crossbite; often times this is genetically driven. You may recall learning in European history about the Hapsburg family – that this royal family was known by their prognathic chin! This relationship we will discuss again later.
Rapid palatal expansion (RPE) is the primary intervention to address a posterior crossbite. This is done ideally in the early adolescent years before a child’s growth spurt, and can be done in kids as young as four if indicated. Surprisingly the younger kids will often tolerate the treatment better than the ten year olds! RPE treatment opens the palatal suture, which is partially fused in children. This suture stitches the (initially two) segments of the maxillary bone into one. New bone deposits as the expander incrementally pulls the maxillary bone segments wider apart. Once the posterior crossbite is resolved, your orthodontist will terminate active expansion of the RPE and allow for a stabilization period of approximately six months. Adults can also gain benefits from palatal expansion; however, the suture is fused in adulthood so the movement has to be done much slower. Surgically-assisted RPE (aka a SARPE procedure) is an option, as well. Although it works great for adults, it is not the best-tolerated procedure, as it is a surgery after all. Orthodontic archwires may also achieve transverse expansion; however, the movement is mostly dental and not skeletal/bony movement.
Next, we will discuss growth in the vertical dimension. Particularly, I would like to mention a facial characteristic coined Adenoid Faces or “Long Face Syndrome”. This feature correlates with sleep disordered breathing in children, which is a topic I’ve mentioned in other blogs and I care about fundamentally. Sleep disordered breathing is more common than one may think, occurring at a rate of 1-4% of children. Most likely that number is higher in reality. Any amount of snoring in a child is NOT normal! It is important to make sure that children are getting adequate oxygen intake during sleep, because it will affect skeletal growth and overall health.
Long face syndrome is associated with a vertical lower facial growth pattern, as a compensatory mechanism of a blocked airway. These children will often be mouth breathers with an underdeveloped and high-vaulted maxilla. This vertical growth pattern rotates the lower jaw backwards, and the chin may look receded as a consequence. The lips may not be able to touch together without straining the muscles as a result of the vertical growth pattern, which is called lip incompetence. In addition, you may notice a “gummy smile” aka gums above the teeth showing because of the excessive vertical development. A clinical term for this feature is vertical maxillary excess. These patients may tilt their head forward when relaxed, this is an additional compensatory mechanism to help open the airway. Sometimes they may develop a tongue thrust habit and open-bite, which often goes hand-in-hand with mouth-breathing. You may notice bags under the eyes, which is called subocular venous pooling. This results from poor oxygenation, and these kids may looked tired (because they are tired!).
Did you know that sleep-disordered breathing may be associated with bed-wetting, ADHD diagnoses, poor academic performance and childhood obesity?! It’s important to address! RPE treatment helps develop the maxilla and convert mouth breathers to nasal breathers. This change alone with normalize growth patterns in a significant way. Tooth positioners help guide adult teeth to their proper position without crowding, as well. Some children may need tonsils and adenoid tissues removed, if enlarged and causing upper airway blockage. It is important to consult with an ENT or pediatric sleep physician to manage comprehensively.
The last dimension of growth that we will discuss is the A-P dimension, which corresponds with dental and skeletal malocclusions. This is the facial dimension that most people are familiar with when understanding orthodontic problems. There are three categories: Class I, II, and III. Class I occlusion is the ideal interlocking of the jaws and upper and lower molars; in the simplest terms the lower molar is approximately a half-tooth’s width more anterior to the upper molar. Meanwhile, a class II relationship occurs when someone has either an overdeveloped upper jaw and/or underdeveloped lower jaw. This often presents as a retrusive lower jaw and what we call a convex facial profile. Conversely, a class III relationship is the direct opposite: an underdeveloped maxilla and/or overdeveloped mandible (remember the Hapsburg family image?!). Here, the lower jaw protrudes and one has what we call a concave facial profile.
Interestingly, the body’s spinal posture will compensate for skeletal malocclusions, as a compensation for the airway! This truly shows the interconnectedness of our bodies. In class II, the spine postures forward to compensate a recessive mandible and in class III the spine rotates backwards.
Orthodontic early intervention with A-P skeletal discrepancies is a debated practice. In terms of a class II malocclusion, I recommend intervening early primarily for psychosocial reasons or if the child is very physically active. The upper front teeth, if protruding as in most class II relationships, are at a higher risk of trauma. If a child does not feel confident because of their “buck teeth”, then I also recommend intervening. Some of these children have habits such as a lip trap of thumb-sucking, and I also recommend intervening if the malocclusion is in part due to a habit. This will enable more ideal growth patterns. I will be discussing habits in the next post, don’t worry. Headgears have been used historically to orthopedically restrain maxillary growth in the A-P dimension. However, as someone who is passionate about maximizing skeletal growth potential for the sake of maintaining airway patency, I won’t endorse headgear treatment. Functional appliances to treat class II malocclusion have also been employed, but have become less popular. Generally speaking, many orthodontists will wait until the patient is in their growth spurt years to treat a class II malocclusion.
Meanwhile, more orthodontists will intervene for those who present with early signs of a class III malocclusion. This is different from the pseudo-class III I mentioned in the last post. Considerations for early intervention of a class III malocclusion comprise aiming to avoid surgical correction during a comprehensive orthodontic treatment phase and similarly for psychosocial reasons. A facemask, also known as a reverse pull headgear, is the most common therapy. Another device called a chin-cup is similar. Facemask treatment is usually done in conjunction with RPE treatment. The aim is to orthopedically protract (advance) the upper jaw, as well as widen via RPE. Loosening the palatal suture has been shown to improve results of this therapy. In some cases, class I growth patterns continue once an ideal jaw relationship is established. This is not always the case unfortunately, since class III malocclusions often are genetically driven.
Now that we’ve discussed developmental dental and skeletal reasons for interceptive orthodontics, we will next discuss habits and preventative measures to conclude this series! Stay tuned :-)