Kirt Simmons
Kirt Simmons, Assistant Professor and Orthodontic Director: "Dental and craniofacial concerns associated with Noonan Syndrome
Kirt Simmons has trained in orthodontics and craniofacial anomalies. He also has a PhD in pharmacology.
Although everyone appreciates how much a baby grows, they probably don't think about how much the face and teeth must develop; a baby's brain is 80% of it's adult size, but the face still has a lot of growing to do.
The most common craniofacial anomalies are disorders involving clefting, where the face does not completely form.
Dental tissues can be affected by many of the same things that cause problems with stature, so quite often statural problems will also have problems associated with the craniofacial region. Both soft tissues (e.g. gums, tongue, and lips) and hard tissues (bones and teeth) can be affected, and teeth can show a retardation in growth, reduction in size and quantity, or a combination. For example, in kids who are purely growth hormone deficient there can be some definite effects on dentition, such as:
The jaws can also be affected, with growth and development being delayed, a small top jaw, and an even smaller bottom jaw.
Noonan Syndrome was initially classified under a lot of different conditions, for whilst Turner's Syndrome has a fairly simple test, but NS does not. In Turner's Syndrome an early eruption of the permanent teeth is common; they may also have smaller teeth with short roots and a simpler shape than average.
NS is probably under-diagnosed, as only 'obvious' individuals may be identified; we don't really know much about the mild forms as it hasn't really been studied well, and there is a lot of misdiagnosis.
Individuals with NS tend to show classic facies, but with a wide variability in appearance. One common feature affecting the mouth is a high arched palate, although as far as we know there are no particular implications from this.
Another classic condition of the mouth associated with NS are 'bulges' in the palate; these are soft tissue bulges, and are essentially the same in Turner's Syndrome. We are not talking about bony bumps in the middle of the palate here (which are a variant of normal), but soft bulges at the sides of the palate. If an individual has a normal height palate but has bulges at the sides that impinge, this can make the palate look high-arched. We are not sure of the causes of these bulges, but they are probably related to the causes of other soft tissue differences.
It is also possible to get some degree of clefting of the palate in NS, the most minor form of which is a bifid uvula. A submucous cleft may look normal, but underneath the soft tissue the bone is further forward than normal, which many make it difficult to fully close off the mouth from the nose. In an open cleft a gap in the roof of the mouth is visible.
If an individual has a submucous cleft, a tonsillectomy may result in speech problems, so this should be ruled out before surgery.
One report described a three-generation family with NS, and all affected individuals had anomalies of the lateral incisors (top front side teeth); some were missing, some had extras, and in others they were malpositioned or malformed. When the lateral incisors are missing, the incisors may spread apart into the gap, and canines may come further forward than they should, so it may not be immediately obvious that there are teeth missing.
If there really is a problem with the lateral incisors, several different things can be done, such as just removing the teeth and letting the canines substitute, or putting in bridges, retainers or implants.
Facies in NS tend to include a wide mouth, more prominent upper lip, less prominent upper jaw, small lower jaw and narrower upper and lower jaws, giving an impression of a narrow, triangular face. By looking at the skull and taking standardised x-rays it is possible to plot growth, and from this it appears that 'classic facies' tend to be reduced with age. The difference between someone with NS and someone without therefore tends to minimise as they get older, so essentially they come into the 'within normal' limits.
Class 2 malocclusion is a situation where the bottom jaw is small relative to the top jaw or the bottom teeth are back from the upper teeth leading to an overbite and a 'convex' profile.
A lot of individuals can benefit from braces.
An increase in lower face height has also been noted in NS, and a number of papers mention cherubism (giant cell lesions of the jaws). This gives the face a round podgy appearance as the lesions fill out the jaws. Generally this is a self-resolving condition as it tends to disappear with age, and so normally requires no treatment.
Neurofibromatosis is more serious as the neurofibromas don't resolve and can be more difficult to deal with. It is therefore necessary to differentiate between cherubism and NF, and this can be done quite simply by biopsy.
Other conditions in NS that have a relevance to dentistry include bleeding disorders, congenital heart disease, and delayed puberty.
In some individuals blood clotting tests may give normal results, but they may still have problems with surgery. At least one paper describes an individual with NS who had serious problems following jaw surgery, and who nearly didn't recover due to serious bleeding, so if tooth extractions, gum or oral surgery are required, it would definitely be necessary to rule this out.
With cardiac problems there is a risk of bacteria from the mouth getting into the blood during invasive procedures and causing bacterial heart infection. This is a serious condition and so prophylactic antibiotics should be given.
When a diagnosis of NS is made, even if the child is very young it is advisable for them to see a children's specialist and probably an orthodontist to get standardised x-rays just to see how the individual is going to grow. This is like going to a paediatrician and monitoring height and weight: much more useful information can be gained from keeping records than from just a one-off measurement.
Dental radiography cannot however be done on a 2 year-old, although it is recommended that it's done by around 5 years of age. It is advisable to try to find someone with craniofacial, cleft-lip or palate problems, although this can be difficult.
Delayed puberty is an issue as it may end up delaying orthodontic treatment.
Growth hormone therapy definitely has effects on the teeth and jaws. But the exact effects are not known even in Turner's Syndrome where GH therapy has been used a lot more often than in NS as there have been very few patients studied. It was advised that children see an orthodontist to get some records made before going on GH, and hopefully in the future we will be able to look back at these to give us some idea as to what to expect.
In GH deficiency the effects have been documented, but there is concern that if individuals get too much GH (as in gigantism) there can be tremendous effects on the face. The bottom jaw seems to be more sensitive than the top jaw due to differences in how they grow, and there are concerns that a large bottom jaw may result.
There have been reports of patients with NS having smaller teeth and a spaced dentition, but Kirt Simmons said he hadn't seen this and in fact actually tended to see the opposite: crowding and a narrow top jaw. But how much is due to NS, hypotonia etc, is difficult to tell - unfortunately we just don't know what the underlying problem is.
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