EXPANSION FOR CROSS-BITES

Posterior crossbites where the top back teeth bite inside the lower teeth are relatively common affecting up to ~16% of children with their baby or milk teeth. Crossbites seldom self-correct and so some form of expansion of the top jaw is usually required. We have various options ranging from partial braces with elastics to plates and fixed expanders but what is the most effective way to correct a crossbite?

For a single tooth crossbite your #orthodontist may elect to use buttons and elastics but for multiple teeth they are more likely to choose a removable plate or a fixed #expander such as a quad-helix appliance or a rapid-maxillary expander (RME), also known as a rapid-palatal expander (RPE). Plates can be successful but rely on compliance from the patient with ~20-30% not cooperating - which makes the orthodontists job a bit harder :-/ . Research has demonstrated that the fixed type of expanders (quad-helix, RME/RPE) remove this compliance issue as they are cemented in place and so tend to be more successful and offer slightly more expansion (~1mm).

A posterior #crossbite (circled in green on the right) can result in a slide of the lower jaw to one side on closing creating a bite asymmetry and midline discrepancy (purple lines). Expansion to correct the bite interference can correct some asymmetries (as in this example) while others will have a persistent asymmetry that may require future treatment. Treatment of asymmetries will be the topic of a future Blog. Expansion can also be used to create space as covered in a previous Blog. So if you have a posterior crossbite, visit your orthodontist for them to assess the most appropriate appliance that best suits your needs.

Dr Peter Miles is the orthodontist at Newwave Orthodontics in Caloundra, Australia and teaches orthodontics part-time at the University of Queensland. He is a visiting lecturer at Seton Hill University in the USA as well as lectures internationally. Peter is one of the editors and authors of the orthodontic textbook, 'Evidence-Based Clinical Orthodontics'.

MYOFUNCTIONAL APPLIANCES - WHAT'S THE EVIDENCE?

Myofunctional therapy is treatment aimed at changing muscle (Myo = muscle) function and possibly influencing jaw growth and the position of the teeth. Myofunctional appliances have been around in various forms for many years. These can include lip shields and screens, eruption guidance appliances and the T4K™.  Although claims are made that they alter muscle function resulting in improved facial growth, better alignment, and more stable results, what evidence is there to support these claims?

There are a number of studies examining the clinical effects of the eruption guidance appliance and the T4K™ and they provide clinical evidence as to the compliance and effect of these appliances.1-5 These appliances are available in a small range of sizes where one is selected to suit an individual rather than being custom made from an impression/scan. Possibly due to this generic fit, one study found 31% of patients did not wear the appliance.1 A randomised trial of the T4K™ vs. a custom made Activator appliance found the Activator caused less discomfort than the T4K™ and was more acceptable.6 All five studies showed that treatment at age 5-9 was quite long (13-36 months) and protrusion of the top teeth was reduced by only a small amount (1.5-2.5mm).1-5 A study of the T4K™ appliance showed it had no growth effect.3 Another study on the eruption guidance appliance followed patients over time and found the small 2mm improvement in crowding relapsed to the initial state which shows it is not stable.4 A 2mm improvement in bite depth was also unstable and relapsed leaving only 0.5mm of change.

A 2mm change is considered a minor improvement and could be treated once all adult teeth have erupted (~age 12-13) in one phase of treatment. This results in a reduced overall treatment time as well as potentially less cost than doing two or more phases of treatment. Clinical trials in the both the USA and the United Kingdom where patients were randomly assigned to early or late treatment have shown that when patients were treated early for much more severe protrusions (7mm rather than 2mm) they could be treated equally as well by delaying treatment until all the baby teeth had been lost.7,8 The result of treating later (~ age 12-13 years of age) was a shorter overall treatment and less cost. However a case can be made for early treatment to reduce protrusive teeth when the appearance or function is concerning the patient or for a small reduction in the risk of trauma to the front teeth (see my previous post on trauma).

So if you are unsure about whether early treatment is required for your child, consult your orthodontist. Some problems such as crossbites and impacted teeth can be detected and treated more effectively if found early. Your orthodontist is an expert in growth and development and can best determine if early treatment or simply monitoring your child is indicated to achieve the most efficient and cost-effective treatment at the most appropriate time.

References:
1. Keski-Nisula. American Journal of Orthodontics & Dentofacial Orthopedics 2008;133:254-60
2. Methenitou. Journal of Pedodontics 1990;14:219-30
3. Usumez. Angle Orthodontist 2004;74:605-60
4. Janson. American Journal of Orthodontics & Dentofacial Orthopedics 2007;131:717-28
5. Myrland et al. European Journal of Orthodontics 2015;37:128-134
6. Idris. European Journal of Paediatric Dentistry 2012;13:219-24
7. Tulloch. American Journal of Orthodontics & Dentofacial Orthopedics 2004;125:657-67
8. O’Brien. American Journal of Orthodontics & Dentofacial Orthopedics 2009;135:573-9

Dr Peter Miles is the orthodontist at Newwave Orthodontics in Caloundra, Australia and teaches orthodontics part-time at the University of Queensland and is a visiting lecturer at Seton Hill University in the USA. Peter is one of the editors and authors of the orthodontic textbook, 'Evidence-Based Clinical Orthodontics'. Importantly, he has no financial interest in any products discussed in these Blogs.

QUICK OR FAST BRACES - DO THEY EXIST?

Claims of faster treatment are easy to make and we would all like this but is it realistic? In the 1960's and 70's Begg braces/brackets were very popular and were thought to provide faster treatment as they allowed very rapid tipping and alignment. However this was at the price of less control over the root position which took more time to recover later and so they are seldom used nowadays. Other bracket designs that allow tipping have been shown to actually be slower than conventional brackets when closing extraction spaces.

More recently self-ligating brackets such as the Damon bracket, Smart-Clip, In-Ovation, Quick and more were introduced with claims of faster treatment. This was marketed well and became quite popular but with little evidence to support the claims. Dr Miles conducted the first prospective clinical trial and found there was actually no difference during initial alignment which was later confirmed by other researchers. The most recent evidence suggests that despite the claims of faster treatment, the self-ligating brackets may actually be slower than conventional #braces by about 2 months! Braces claiming to be fast are use brackets and wires just like conventional systems and so would not be expected to be any quicker. They claim lower friction but this allows the greater tipping and lack of control seen in earlier systems that proved to be slower. Let's look at an analogy - when you build a house the frame goes up quickly but then seems to slow when the smaller jobs are taking place such as the painting, tiling, etc. - but you don't want to move into your new home without this done do you? The same with braces - the initial alignment of teeth can be quite rapid but these are the simple tipping movements and the roots have not been moved into their correct and more stable positions. Your bite may need correction with elastics or other techniques and this is also a slower movement. These are the ‘detailing’ stages of #orthodontics and are slower and less obvious but very important for the most aesthetic and stable result possible.

The skill of the practitioner in placing the brackets as accurately as possible and using the correct wires, mechanics and appointment intervals affect your treatment duration. However treatment time is also affected by patient cooperation (e.g. are you wearing your elastics as directed?) and biological variation – everyone is different and their teeth move at different rates and respond in varying amounts. The same wire and adjustments will have differing responses in different people and your orthodontist will adjust your treatment based upon what they observe. Even extremely precise methods of bracket positioning using computer-aided design and manufacture, or robotic wire-bending are prone to the same problems of variation in response. Orthodontists are aiming for the best outcome possible for you and this variation is why your #orthodontist cannot give precise times to the eternal question; "When am I getting my braces off?".

Dr Peter Miles is the orthodontist at Newwave Orthodontics in Caloundra, Australia and teaches orthodontics part-time at the University of Queensland and is a visiting lecturer at Seton Hill University in the USA. Peter is one of the editors and authors of the orthodontic textbook, 'Evidence-Based Clinical Orthodontics'. Importantly, he has no financial interest in any products mentioned in these Blogs.

WHAT TO DO ABOUT THUMB SUCKING AND TONGUE THRUST?

Open bites or front teeth not overlapping can be caused by habits with fingers, lips or the tongue placed between the teeth but how should we treat them? Habits can often be corrected early with minimal intervention. We prefer to see the habit reducing as the adult incisors erupt, about age 6, but even those at ages 9-10 stopping the habit results in improvement of the #openbite. Many children stop themselves by age 6 as they interact with their peers and decide it is not as socially acceptable.

Those that persist beyond age 6 we suggest initially trying reminder and reward strategies as in this case on the right. Remind the child in a non-threatening manner and set a goal e.g. praise them when they have refrained and perhaps have a small reward if they have stopped for a week (to involve the child in treatment). Reminders can be physical such as a sock, mitten or hand puppet at night. An elastic elbow support over the elbow to make it harder to bend the elbow to suck the thumb could be considered. Thumb ‘paints’ work for some but others will simply suck it off. If these attempts do not work, then a more intrusive reminder such as a thumb crib/habit appliance can be fixed in place by an orthodontist. Some persist due to emotional issues and the habit is a comforting device so when the child is upset, they are more likely to suck and it is more difficult to correct as the underlying cause is still present. Scolding them will simply make this worse.

A long held concept is that a tongue thrust swallow is the cause of open bites but it is actually an adaptation to an open bite (to swallow you need a seal at the front and so the tongue is placed between the teeth). We swallow about 600-1000 times per day for 1 second each (~10-17 minutes per day) which is not enough time to cause the open bite, it takes hours to move teeth not minutes. However, ‘habits’ such as thumb sucking or forward resting posture of the tongue between the teeth can be of sufficient duration to cause an open bite. Some may need help with exercises to retrain the tongue to position itself correctly and a Speech Pathologist can help with this. If these strategies are not working, then consult your orthodontist to consider placing a thumb or tongue crib as a final resort.

DOES EARLY TREATMENT OF PROTRUSIVE TEETH PREVENT TRAUMA?

 

Protrusive or bucked top teeth are at a higher risk of trauma but how much is this risk and should you seek early #orthodontic treatment to reduce the risk? Kids run around and can't be protected from all harm so it is no surprise that some trauma will occur. A recent systematic review, one of the highest levels of scientific evidence, found that the risk of trauma in children having orthodontic treatment at the ages of 9 - 10 was 19.8% while those receiving later treatment in adolescence (say ~13) it was 29.2% so there is a 9.4% additional risk of trauma if delaying treatment.

This sounds ominous to some but most are not at additional risk. The studies this review were based upon also concluded that early treatment led to more overall time and cost than later treatment. Some would therefore choose to delay treatment but some of the more active/sporty patients or those not willing to bear the risk will seek early treatment. However what type of trauma are we talking about? This is discussed in the textbook I helped edit and author titled, Evidence-Based Clinical Orthodontics.

One of the clinical trials included in the review quantified the types of trauma seen in those receiving early or late treatment and they found that 80% of the trauma was in the enamel only (small chips as pictured) while 19% were more involved and into dentine while only 1% had reached the nerve. If we then consider major trauma to be only the dentine and nerve involvements (or any knocked out) this is only ~20% of all the additional trauma. This then gives 20% of 9.4% (or 0.2 x 9.4%) which is only a 1.9% higher risk of a major trauma if delaying treatment until the age of ~13 rather than treating at age 9-10. This then allows you to make a more informed choice about the risk of trauma if choosing to delay treatment of protrusive upper teeth until all the adult teeth have erupted.

Dr Peter Miles is the orthodontist at Newwave Orthodontics in Caloundra, Australia and teaches orthodontics part-time at the University of Queensland and is a visiting lecturer at Seton Hill University in the USA.

CAN EXPANSION PREVENT EXTRACTIONS?

 

Expansion is a strategy that can be used to create space but how much can we expand and how much space do we obtain? When undergoing #orthodontic treatment, most patients and orthodontists would prefer to avoid #extractions. In most cases (~80%) extractions are avoided but some cases it is indicated to reduce crowding, to help improve the bite, reduce the risk of relapse, or to reduce the risk of the gums receding. Rapid palatal expanders are a common appliance used to correct crossbites (top teeth biting inside the lowers) and this correction tends to be very stable. Expansion also creates space but not as much as you may think.

When assessing the amount of arch perimeter or space gained (to reduce crowding) with #expansion it was found that only about 1mm of space is created for every 3mm of expansion of the back molar teeth. Research into expansion beyond correcting crossbites shows that although quite large expansion can be achieved, it invariably relapses back to within 2-3mm of the original dimensions. We therefore can only gain ~3mm of stable expansion which only creates about 1mm of space for reducing crowding - not much really! Fortunately this is not the only strategy orthodontists have for creating space as I discuss in the textbook, Evidence-Based Clinical Orthodontics. We can treat more moderate crowding (5-6mm) by involving other techniques such as incisor proclination (up to ~2mm is stable and this creates ~2mm of space), interproximal reduction/thinning can be used if prudent and E-space maintenance (a future Blog) can contribute ~3-4mm of additional room.

SHOULD YOU REMOVE YOUR WISDOM TEETH TO PREVENT CROWDING?

As adolescents get older their teeth can move in their late teens, about the same time as their #wisdom-teeth erupt - but is that the cause of any movement or just poor timing? Researchers have examined whether wisdom teeth can cause crowding and the following statements can be made:

There is no difference in incisor #crowding between people who have third molars impacted, erupted normally, congenitally absent or extracted early (Ades et al, American Journal of Orthodontics 1990).

Direct measurement of the pressure before and after third molar extraction reveals no forward pressure from impacted third molars (Southard et al, American Journal of Orthodontics 1991).

Removal of third molars resulted in only 1.1mm difference so extraction to reduce or prevent late incisor crowding is not justified (Harradine et al, British Journal of Orthodontics 1998).

So there is minimal reason (1mm) to believe that extraction of third molars will alleviate or prevent crowding of incisors. So what are the causes of the crowding? The picture is not yet clear enough to say for sure, but the jaw narrows throughout adult life. This may be due to late jaw growth and ageing changes in the gums which compress the teeth.

Unfortunately, a retainer is the only way to reliably prevent incisor crowding and #orthodontic tooth movement the only way to treat it.


Dr Peter Miles is the orthodontist at Newwave Orthodontics in Caloundra, Australia and teaches orthodontics part-time at the University of Queensland and is a visiting lecturer at Seton Hill University in the USA.