Dentist’s guide: Using clear aligners to improve crown or bridge restorations

Dentist’s guide: Using clear aligners to improve crown or bridge restorations image

A clear aligner treatment can help to simplify a crown or bridge restoration, and contribute to achieving a better overall outcome.  

Crown and bridge restorations can be complex. Dentists must carefully examine the remaining tooth structure, potentially cut away a considerable amount of tooth material, and get the reshaping and preparation process exactly right to ensure the best treatment outcome. 

However, Dr Lawrence Neville, principal dentist and owner of Spa Dental in Sydney, says that using clear aligner treatments to straighten or reposition teeth prior to a crown and bridge restoration can make the job significantly easier. 

“If the patient’s teeth are crossed or rotated, you’ll probably need to cut away the tooth quite a lot as part of the preparation for a crown or bridge restoration,” he explains. “The problem with that is that the more material you cut away from the tooth, the less surface area you have for bonding. The chance of killing the tooth or damaging nerves may also increase when you’re cutting away a significant portion.”

Dr Neville says clear aligners help to solve this problem. “We basically want to put the teeth into the right position first with clear aligners. If we straighten the teeth, it means we can be a lot more minimal with how much tooth we need to cut away. That will also mean that we won’t have to use a bulky ceramic, and we’ll get a much nicer overall result.” 

The same concept applies for veneers, and Dr Neville says clear aligner treatments are generally safe for a wide range of patients.

“Good general oral and gum health is typically an advantage, but there’s no real age limit for clear aligners. It can be an effective treatment for patients from 19 to 99. In fact, we have many clear aligner patients in their 60s, 70s and even 80s.”

Clear aligner treatment also tends not to affect normal crown and bridge restoration processes and protocols. It’s simply about creating conditions that may simplify the restoration preparation that’s required. 

Here, we set out a straight-forward five-step workflow for managing a combined clear aligner and crown or bridge restoration…

1. Identify the right treatment option

To begin, it’s important to determine whether a dental crown or bridge restoration is the best treatment option for the patient. This will require a thorough examination of the remaining tooth structure. There should be at least 1-2mm of tooth remaining above the gum line. Also, if any cracking continues under the gum line, then a patient may not be a suitable candidate for a crown or bridge restoration.

In those cases, a dental implant may be a more effective treatment option. Avant makes dental implant treatments much easier with our 3D-printed surgical guides that lock into place like a splint. A metal sleeve is then used to stop the drill at the exact bone depth required. 

Dr Neville also points out that crown or bridge restorations may also not be the best treatment option for purely cosmetic cases. He says considering a clear aligner treatment first, then reassessing the patient for a possible veneer treatment could be a better choice. 

“We find that a lot of people come and see us and say they really want crowns or veneers because their teeth are not straight or in the right position,” he says. “But, depending on the patient’s situation, crowns or veneers are not necessarily the best treatment option.”

Instead, Dr Neville says he may suggest a clear aligner treatment and teeth whitening first, then ask the patient to reassess their cosmetic goals. 

“Once we straighten the teeth with clear aligners and do a whitening treatment, sometimes patients will be satisfied and not want to go ahead with further cosmetic work,” he explains. “Otherwise, we might be able to achieve their goals with veneers rather than a crown or bridge treatment.”  

Whether you choose to go ahead with a crown or bridge restoration, veneers or a clear aligner treatment, it’s important to first identify and address any causative factors or underlying issues. For example, if cracks are present in the patients teeth or their cosmetic issues are caused by grinding, then bruxism might be at play.

In that case, a bruxism occlusal splint may be required to protect restorative or cosmetic work. Today, more advanced manufacturing techniques and more sophisticated materials have replaced hard acrylic materials that were prone to warping during the curing process. 

Thermoplastics, for example, are often used to give dental splints greater flexibility to drastically improve patient comfort.  

2. Plan the clear aligner treatment 

Whether you’re using a clear aligner treatment to adjust teeth position before a crown or bridge restoration or veneer treatment, or have simply recommended an initial clear aligner treatment as the first port of call – the clear aligner planning process remains fundamentally the same.

For example, Avant’s Refine Aligner solution is making clear aligner treatment easier – and more accessible – than ever. As part of the treatment planning process, we can help you decide when each movement occurs, including expansion, rotations, intrusion, extrusion, mesialisation and digitalisation. And we can plan the amount of interproximal reduction needed for improved teeth movement.

All we need is a standard intraoral scan (or a physical impression), clinical photos, lateral ceph/OPG radiographs, and a cone beam for root movement analysis if needed.

Patients will of course be interested in the clear aligner treatment timeline. While minor clear aligner treatments can be completed in four to eight weeks, Dr Neville explains that the patient’s particular bone structure and gum health will influence the tooth movement rate. 

He also warns to resist speeding up treatment timelines under pressure from patients as faster than necessary clear aligner treatments can increase the chance of the patient experiencing post-orthodontic relapse

3. Start the clear aligner treatment

Once the scan or impression, photos, lateral ceph/OPG radiographs, and cone beam (if required) are supplied, Avant reviews the case and provides a PDF treatment plan and a video showing the movement of the treatment for your review and approval.

Some dentists choose to use the video to illustrate the stages of the aligner treatment to the patient. This can be helpful to set patient expectations, and ensure they have a clear vision for the movement goal of each stage in the treatment. Providing this overall vision of the treatment to the patient can also help to improve patient compliance and ensure they understand the importance of consistent use of the Refine Aligner trays throughout all stages of the treatment.  

Once the clear aligner treatment plan is approved, Avant custom fabricates Refiner Aligner trays from medical grade TGA-approved materials and completes a quality control check. 

We then deliver the patient kit to your practice. This includes an aligner case, removal key, chewies and up to the first six trays. Dr Neville suggests asking the patient to come in to check that the first tray is an accurate fit, and to discuss any comfort concerns the patient may have.

If there is any issue with fit – or any other questions or concerns from the patient – Avant provides immediate phone or instant messaging access to the same lab technicians making your patients’ aligners. 

Dr Neville also suggests calling the patient back in for regular assessments throughout clear aligner treatment. Ensuring that each stage is progressing as planned is important for achieving the best possible final outcome. 

4. Continue with the crown or bridge restoration

With the clear aligner treatment complete and the teeth now in the correct position, it’s time to proceed with the crown or bridge restoration. Dr Neville says all the usual crown and bridge procedures and protocols apply from this point. 

However, it’s worth noting that material choice can be a game changer for crown and bridge restorations. Dr Neville has been using dental zirconia in his practice for around eight years, and chooses zirconia for its superior strength and low-wear properties.  

Avant offers Aidite’s 3D Pro Zir as a zirconia option for crown and bridge restorations. It uses a gradient layering manufacturing process for chip-proof construction to achieve a new level in bio compatibility with strength at the incisal layer very similar to the strength of natural enamel — without the excessive abrasiveness of older products.

That essentially means that 3D Pro Zir wears at a similar rate as natural enamel while protecting adjacent dentition from abrasion. It is also suitable for hand polishing and chair-side grinding. 

Dr Neville also explains that zirconia restorations typically require a specific tooth preparation technique. That includes a minimum of 0.6 – 0.8mm space for wall thickness, or 1.0mm to 1.5mm wall thickness space. You also need to identify a clearly visible and continuous circumferential chamfer, with reduction at least 0.5mm-0.7mm at the gingival margin.

It’s also recommended to set an approximately 8° angle for the horizontal and vertical preparation of the tooth, with a chamfer style margin. Incisal edges need to be rounded, and the preparation should not have any undercuts or a gutter preparation.

5. Prevent post-orthodontic relapse

With the crown and bridge restoration complete, attention now turns to preventing post-orthodontic relapse. While all patients can experience tooth movement following a restoration, Dr Neville says the extent and degree of the initial straightening tends to impact the likelihood of post-orthodontic relapse. 

“For example, if you moved a tooth from a 90-degree angle all the way around to zero, that tooth has more chance of relapsing than a tooth that may have only required a 20-degree adjustment,” he explains. 

Fixed wire retainers, or the consistent use of removable retainers, are critical for preventing post-orthodontic relapse. Dr Neville typically recommends fixed wire retainers to patients who are unwilling or unable to commit to the proper use of removable retainers. Poor oral hygiene can be a signal that the patient may struggle to commit to removable retainers, or patients who are apprehensive about removable retainers during your initial discussion may also be good candidates for fixed or lingual wire retainers. 

It can also be helpful to explain to patients that fixed wire retainers tend to attract more plaque, whereas removable retainers are made from thin plastic or polyurethane material that can be easily removed from the mouth for cleaning. This is perhaps the most important benefit of removable retainers, and can help to secure a stronger patient commitment.

Dr Neville recommends calling the patient back in for six-monthly appointments to check for any tooth movement. This also gives the patient an opportunity to raise any comfort issues or any other challenges they’re facing that could be affecting their consistent use of the retainers. Patients with fixed wire retainers may also require plaque removal. 

Avant makes post-orthodontic retainers very straight forward. On request, we can store the patient’s case file and can immediately manufacture replacement retainers with no need to resupply scans or impressions.  

The final word

Clear aligners can be an effective pre-restoration treatment option to straighten or reposition teeth to help reduce or simplify the crown or bridge preparation requirements. In doing so, clear aligner treatment can contribute to stronger bonding, reduce the risk of tooth death or nerve damage, and achieve a better aesthetic result with the use of a less bulky ceramic.

The key consideration is proper clear aligner treatment planning with clear tooth movement goals assigned to each stage. For our Refine Aligner treatments, Avant provides a PDF treatment plan and a video showing the movement of the treatment for the dentist’s review and approval.

Once the clear aligner treatment has been successfully completed, normal crown or bridge restoration protocols typically apply. Material choice is also critical at this point. Dental zirconia tends to offer superior strength, low-wear properties and a potentially better aesthetic outcome. 

From there, some thought should be given to preventing post-orthodontic relapse. Whether you recommend a fixed wire retainer or a removable plastic retainer will depend on the patient’s commitment level and personal preference. 

Regular six-monthly follow-up is also recommended to check for the early signs of post-orthodontic relapse, and to maintain the patient’s general oral health.

 

Want to find out more about partnering with Avant for clear aligner treatments and crown or bridge restorations? Please email contact@avantdental.com.au or phone 1800 287 336.

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