Skeletal Class III dentofacial deformity, commonly referred to as underbite, is fairly common in Singapore. Those seeking treatment are usually teenagers or young adults, and are still dependent on their parents for consent as well as finances. While some parents are supportive, others are dead set against the idea of surgery. Those who are against surgery may look for less invasive alternatives to mask the underbite. Such masking can be done by camouflage orthodontics or in some cases, veneers and crowns. Such compromised treatment is not ideal and may lead to other problems.
How do veneers and crowns correct underbite?
Most underbite patients are concern about the reverse overjet i.e. that the lower incisors are in front of the upper incisors, leaving a gap in between. The open bite is often masked by a habitual contraction of the lip muscles to close the gap. This often becomes so much a part of the patient that relaxing the lips when awake takes conscious effort. The upper jaw being less developed also lack support for the upper lip, resulting in a collapsed lip. The front teeth are not contacting and hence pose a functional problem in that the incisors cannot be used to cut food. One of the common complaints among underbite patients is that when they eat a burger, they cannot bite off the patty with the bun.
What are veneers?
So, treatment is often sought to correct both the functional as well as aesthetic deficits. Surgery is the ideal treatment as it can correct the jaw relation to its proper position. Veneers and crowns, on the other hand, seek to mask the effect by changing the size and shape of the upper front teeth so that they are able to occlude against corresponding lower front teeth. Veneers, also known as laminates, are porcelain shells that are bonded onto the front surfaces of the upper incisors and canines. They are often used in cosmetic dentistry to give that “Hollywood smile”. By making them extra thick, the front teeth can be built up to the point where they can contact the lower teeth. Such veneered teeth may look like teeth from the front view, but when viewed from the back, there are thick platforms for the lower teeth to bite on. For the minor underbite, they may be sufficient to cover the gap caused by the underbite and also to achieve contact with the lower teeth.
What are crowns?
Crowns are porcelain jackets that are fitted over the teeth. To fit a porcelain crown, the tooth must be substantially shaved down. Teeth that are rotated may require a crown instead of veneer to create the extension outward to achieve contact with the opposing teeth. Compared with veneers, whereby only a layer of enamel is removed from the facial surface of the teeth, crowns requires removal of all enamel and a bit of dentine from all surfaces of the tooth. It is a far more invasive procedure but is sometimes needed to achieve the masking of the underbite.
What's the problem with such camouflage treatment?
- eccentric loading
the biting force exerted on the veneered teeth does not pass through the natural axis of the tooth. The lower incisors biting on the veneers that are extending out from the upper incisors may cause the unintended movement of the teeth
- Tooth decay
Bonding agents that “glue” that veneers onto the teeth surfaces may leak after some years resulting in gaps between the laminates and the teeth. These gaps traps plaque which may then lead to dental decay as laminated teeth have less enamel for protection against caries.
- Tooth sensitivity
Once gaps appear under the laminates, the exposed surfaces of the teeth where enamel has been reduced will feel sensitive
- Gum inflammation
With plaque accumulation under the veneers, gingivitis develops. This gives rise to swollen and bleeding gums, which if left untreated may lead to loosening of the teeth.
- Porcelain cracks
The ceramics used in dental restorations need to be supported by tooth structure. Excessive extension of the porcelain laminates beyond the tooth predisposes them to cracks due to a lack of support.
Regardless of the downside of using veneers to camouflage an underbite, some patients, especially the younger ones who are not mentally ready for surgery or whose parents are not prepared to consent to surgery, may opt for it as a temporary measure. As a temporary solution, any reduction of modification of the teeth for the veneers must be done minimally or avoided completely. Close monitoring is needed for such laminates so that problems can be detected early and complications such as tooth decay and gum disease can be prevented or treated early. Patients opting for such compromised treatment should also be aware that replacement of the veneers may be needed periodically.
Converting to orthognathic surgery
When the patient is ready for jaw surgery, these veneers must be removed and the teeth restored to their original position for proper planning. In some cases, a period of presurgical orthodontics is needed while in others, surgery can be done first to reposition the jaws into an ideal position with post-surgical orthodontics moving the teeth into proper occlusion.
Management is more complicated and time consuming for such cases due to the masking effect of the veneers. If maintenance had not been meticulously carried out, some teeth may be compromised and may need to be extracted or may require additional procedures such as root canal treatment. If significant reduction of enamel had been done for the camouflage veneers, removal will lead to sensitivity and a permanent laminate will be needed to protect the exposed dentine. Such laminated teeth will also compromise the orthodontic treatment as the brackets do not bond as well to porcelain laminates as they do to enamel.
Ideally, jaw surgery for underbite is the proper treatment to go for. If surgery is not possible due to age or other social reasons and is to be deferred for later, it is better to leave the deformity untreated than to camouflage it with veneers as it will make future surgery a lot of difficult.