What is a Twin Block Appliance?

A twin block appliance is a type of orthodontic treatment used to correct jaw position and posture, while optimising bone growth. The appliance consists of two removable acrylic plates that clip onto the upper and lower teeth. Although twin block appliances can be removed, they should be worn for 24 hours a day for the best results. The upper plate usually includes an expansion screw, which can be adjusted at home on a regular basis.

How Do Twin Block Orthodontics Work?

The upper plate hugs the palate and usually hooks over the molars or premolars using small metal clasps or wire clips. In some cases, the upper plate includes a built-in expansion screw. Turning this screw regularly with a small key slowly widens the upper jaw in cases where the arch is too narrow. It works by applying constant outward pressure on the jaw bone, widening the arch and the median palatine suture.

The lower plate hooks over the premolars or first permanent molars. Small wire clips sit near the lower front teeth (incisors and canines). The blocks attached to both the upper and lower plates are slightly misaligned, which is necessary for the appliance to fulfil its purpose.

When the mouth is closed, the interlocking acrylic blocks meet and slide against each other at an angle. This sliding action forces the lower jaw to shift forward, rather than resting in a backward posture. Holding the lower jaw forward day and night encourages the jaw’s natural biting force to stimulate bone growth and correct malocclusions. 

Benefits of Orthodontic Twin Bock Appliances

A caveat worth knowing before diving into the benefits of twin block appliances is that their success depends heavily on patient cooperation. Because they are removable, some patients may not see the same results if they don’t consistently wear both the upper and lower plates. Failing to wear the appliances as instructed can limit many of these benefits.

Twin block appliances also tend to be more effective when growth potential is still present and the median palatine suture hasn’t fused. This is usually during adolescence, when the bones are still flexible and less fixed. That said, it’s still possible to see results in adults, which we explore in more detail further down the article.

Reach out to our team at Fox Orthodontics if you are unsure whether the treatment is right for you. 

Specific Dental Problems a Twin Block Plate Treats

The primary dental concern a twin block treatment aims to correct is Class II malocclusion. This refers to severe overbites that can sometimes require orthodontic surgery later in life if left untreated.

Specific cases of malocclusions:

• Excessive Overjet: Commonly known as “buck teeth,” where the upper front teeth stick out significantly past the lower front teeth
• Deep Overbite: A vertical misalignment where the upper front teeth excessively overlap the lower front teeth when biting down
• Mandibular Retrognathism: A structural or skeletal imbalance where the lower jaw (mandible) is too short or positioned too far back.
• Narrow Upper Arch and Crossbites: Many twin block designs incorporate an expansion screw to widen a narrow upper palate, fixing crossbites where upper teeth bite inside the lower teeth
• Posterior Dental Openings/Eruption Control: Twin blocks alter the vertical bite dimension, unlocking the back teeth to let molars erupt properly into a stable, aligned bite. 

Benefits by Age Groups

Timing is an important factor to consider with twin block orthodontic treatments, as they work by guiding jaw growth rather than moving teeth. Here’s how their effectiveness and benefits break down by age:

Early childhood (before 8 years)
Twin block treatment is generally not recommended. Permanent teeth are required for the appliance to anchor, and at this age they often haven’t erupted. Growth spurts also are yet to start, so orthodontists usually wait until closer to the appropriate developmental window.

Pre-adolescence (roughly 8 to 10 years)
Some orthodontists will start early treatment if there’s a significant skeletal issue. However, pre-adolescence is still considered earlier than the typical sweet spot. Cooperation can also be harder to secure at this age, and since the primary pubertal growth hasn’t begun, jaw-repositioning effects are limited.

Peak adolescent growth spurt (roughly 10 to 14 years, varies by sex)
This is generally the ideal window, and where twin blocks are most effective. Girls tend to hit their growth spurt earlier (around 10 to 12) than boys (around 12 to 14). During this period:

• The mandible and median palatine suture are most responsive to forward-guided growth and expansion
• Skeletal correction (not just dental correction) is achievable
• Results tend to be more stable long-term because actual bone growth was influenced, not just tooth position

Late adolescence (mid-to-late teens)
Still workable, but growth potential begins to taper off at this stage. Benefits shift more toward dental/dento-alveolar changes (moving teeth and the surrounding bone) rather than true skeletal jaw growth. Improvement is still possible, but tends to be less dramatic on the skeletal side.

Adulthood (post-growth, generally 18+)
Twin blocks lose most of their core benefit here since there’s no significant jaw growth to guide. Skeletal Class II issues in adults are typically addressed instead with camouflage orthodontics (moving teeth to compensate) or orthognathic (jaw) surgery combined with braces. They can still help some cases, but it’s best to speak to an orthodontist before making the decision. 

The key takeaway here is the value of early intervention. The benefits of a twin block treatment rely heavily on the bone growth stage of adolescence, as it harnesses natural growth rather than simply moving teeth or aiding alignment. Booking a consultation with our team at Fox Orthodontics will allow us to pinpoint what stage of bone development you’re at, as this can vary across patients. We can then help determine if a twin block treatment is right for you.

What to Expect: Twin Black Braces Treatment

All orthodontic treatments come with a certain set of expectations, whether you’re looking at twin blocks or standard braces. For a twin block treatment, orthodontists start by taking impressions, photos, and x-rays of the teeth to custom-make the appliance based on how much movement is required.

Upon receiving the upper and lower plates, there is an initial adjustment period. This is usually the most challenging stage of treatment as it can feel strange having a foreign object constantly in the mouth. Patients can expect:

• Excess saliva for the first few days
• Speech changes like a lisp or slight difficulty with certain sounds (typically improves within days to a couple weeks) 
• Discomfort, soreness or pain, especially in the jaw muscles and joints, since the appliance is actively repositioning the bite (usually fades after 5 days)
• Difficulty eating initially (soft foods are recommended at first, as eating with it in can feel awkward)
• Some gagging or bulkiness sensation, particularly at the back of the mouth

Generally, the initial adjustment phase only lasts 1 to 2 weeks. 

Daily wear routine

Twin blocks should be worn 24/7 to optimise results, however a slight drop off to 20 hours a day will still be effective. The plates should only be removed for eating and cleaning. This part of the treatment depends entirely on patient compliance, as inconsistent wear significantly slows or limits results.

Follow-up visits

Patients should expect check-ups roughly every 4 to 8 weeks. An orthodontist will:

• Monitor bite changes and jaw position
• Adjust or add acrylic to the blocks as the bite shifts
• Check for appliance fit as teeth move and jaws grow
• Sometimes activate the appliance further to advance the jaw position more

Timeline

Active twin block treatment typically lasts 9 to 12 months, though this can vary based on the severity of the case and how consistently it’s worn. However, it is important to note that twin block treatment is often used as the initial phase of a larger treatment plan. It’s very common to follow up with fixed braces for another 12 to 24 months. This will fine-tune the tooth alignment once the skeletal correction has been achieved.

Retention

After twin block treatment, a retainer (sometimes a modified twin block or a different type) can be used to hold the new bite position while the second phase of treatment is planned. If a patient isn’t receiving further treatment, this retainer simply allows growth to continue without changing the new alignment.

Looking After Your Twin Block Appliance

Looking after a twin block appliance is relatively straightforward and doesn’t require much effort. As a removable device, it’s one of the easier orthodontic treatments to keep clean.

Cleaning & Maintenance

Patients should rinse the device with lukewarm water every time they remove it. The blocks can be cleaned daily using a soft brush, and they can also be soaked a couple of times a week in a denture or retainer cleaner. Avoid using hot water or harsh chemicals on the appliance, and check it regularly for any damage. A damaged appliance may compromise the effectiveness of treatment.

Eating & Speaking

Eating and speaking are the two hardest adjustments to make when starting treatment with a twin block appliance. However, this adjustment is temporary and will usually return to normal after a few weeks of wear.

For eating, under your orthodontist’s guidance, you may be able to remove the device during meals. If wearing the twin block appliance while eating, avoid sticky, extremely hot, or hard foods that are likely to get trapped in or damage the device. Cleaning it after every meal is also a very effective way of maintaining its integrity.

Speaking can change when first wearing the twin block appliance. Patients may notice their words slurring or a lisp starting to develop. This is temporary and will return to normal once the tongue becomes familiar with the device’s presence in the mouth. However, speaking regularly, especially loudly and repeating challenging words, will help.  

Alternatives to Twin Block Appliance: A Quick Comparison 

How Fox Orthodontics Can Help

For over 40 years, our family-run practice has been treating dental concerns in Sydney. We are a team of specialist orthodontists who tailor our services and recommendations depending on our patients’ dental concerns and personal preferences. Our approach is patient-centred, providing tailored and individualised treatment to every concern brought to our practice.

We also understand that orthodontic treatment can be costly, which can deter some people from getting the care they deserve. For that reason, Fox Orthodontics offers flexible, interest-free payment plans that can be tailored to suit our patients’ budgets.

Book a consultation with us to begin your journey towards a healthier, happier mouth