Paediatric Zirconia Crowns – What you should know as a general dentist or oral health therapist/hygienist
Before you scroll past thinking ‘I’m not even planning to do any paediatric zirconia crowns’, this is not a How To blog! With the growing popularity of paediatric zirconia crowns as an aesthetic option, it is inevitable that patients or parents may inquire about them. Additionally, you might encounter these crowns during routine care, including managing complications. This blog highlights practical tips for general practitioners based on our experience and insights from Dr. LaRee Johnson's recent seminar on zirconia crowns and the upcoming NuSmile BioFlx Crowns (not available in Aus yet). We have compiled a bunch of tips from this seminar, and from our day to day practice on the Sunshine Coast, focusing on helpful tips for the general practitioner.
These are becoming ever increasingly popular with around 1/3 of parents requesting them for their children. Medico-legally it is essential to ensure that parents are informed about this option.. Sadly we do see parents in our clinic that are really frustrated that they were not given the option of a white crown.
Some Zirconia crowns we did on a 4 year old - 3 years later
Some Zirconia crowns we did on a 4 year old - 3 years later
What are paediatric zirconia crowns and when are they indicated?
Zirconia paediatric crowns offer patients an alternative to stainless steel when full coverage is indicated for primary teeth. If you do not offer zirconia in your practice, and your patient is after a more aesthetic option, then referral may be indicated. In our discussions with parents, pros and cons are discussed
Zirconia is more aesthetic than SSC, but is about $150 - 200 more expensive per tooth, due to the higher product cost and technique sensitive procedure. In a child who needs multiple crowns, this cost difference can be significant.
If a child needs quite a number of crowns, commonly parents may opt for zirconia crown on the D’s and stainless steel crowns on the E’s. This balances aesthetics, cost and ease of placement.
Zirconia on D’s and SSC on E’s
Zirconia takes longer to place than SSC, and requires more tooth reduction, because they are a rigid crown and fit must be passive. Compare this to SSC which requires minimal tooth preparation due to the snap fit nature. Or no prep at all for a hall crown. You can place them under local anaesthetic, however if you have to do a lot of them, you should consider some more firepower such as a general anaesthetic as multiple longer visits can fatigue / break children.
Zirconia Crowns on D’s and SSC on E’s - a much more aesthetic option
For early childhood caries and trauma to deciduous anterior teeth, Zirconia crowns have become more popular than Strip Crowns. Strip crowns have moderately high failure and repair rates. Zirconia, if placed well, will not fracture and aesthetically look FAR superior.
Anterior Zirconia crowns
Because zirconia is only held in by the cement, they are at more risk of debond. However, because the tooth is already prepared, it is usually a simple task to recement one in the chair. (see notes more on this later). Compare this to a Strip crown which requires more compliance to repair chairside, or SSC which we pretty much never see ‘fall out’ due to its snap fit.
Whilst rare, nickel allergy presents in 0.1-0.2% of the population – this would be a contraindication for SSC, and may mean zirconia is the best option for these children.
In children with heavy bruxism, they can perforate SSC and so zirconia may be a better option for them.
What can go wrong, and how do we manage complications?
As mentioned above, occasionally, a Zn crown can debond due to cement failure. It is possible a patient may present to you with a Zn crown in their hand that has fallen out, whether it was placed by you, or someone else. Ideally, the size would be observed (either from the etching on the palatal surface of the crown itself, or from notes reviewed/obtained), and a brand new crown taken from the box to recement. This means the fitting surface is brand new and ready to cement. Lightly wipe or pumice the tooth and dry as best you can, fill the crown with cement (RMGIC such as Rely-X or Fuji Plus for posteriors, a more viscous one for anteriors such as Fuji II LC) and push on and hold with good pressure as your assistant spot cures from all surfaces. Then clean cement from the margins and complete full cure. If the crown moves after spot curing, then the bonding of the crown may be compromised and ideally, a fresh one would be obtained and try again.
If your clinic does not have zirconia crowns on hand, then it would be reasonable to use the original and recement in the same way. You can use a ceramic primer to ‘prep’ the surface. Then warn the parents that if it debonds again, it would be best to see the original clinic for provision of a new one (since there would be contamination of the fitting surface of the original)
Zirconia can fracture, and whilst it is very rare (we have had 3 in our clinic out of more than 1000 crowns), children with parafunctional habits can end up damaging their crowns. If it is chipping just within the zirconia, then possibly smoothing rough edges and monitoring is all that is required. If most of the crown is sound, but some has sheared off exposing tooth underneath, then a composite repair can be attempted (as per usual CR procedure), but warn the patient if it fails again, then removing and replacing may be indicated.
If you need to remove a Zirconia crown, you can get a pair of forceps, place on the crown and lightly squeeze. This will usually split the crown and it can then be peeled/flicked off in pieces. Using a high speed drill to remove a crown is hard going!
Previously, it had been thought that zirconia opposing a SSC was not a good situation due to the different wear factors. However, with the increasing evolution of the gloss finishes, we are now told this is totally fine to do, so long as the gloss finish is not removed (ie DO NOT adjust the occlusion of a zirconia crown). For example, you may see a patient who has previously had Zn placed, and they now need a hall crown on the opposing tooth – this is fine, just warn them that the SSC may leave metal markings on the zirconia. Not to worry, this can be polished off with prophy paste.
Excess cement. Despite best efforts during placement, on occasion, excessive marginal cement may be detected on follow up radiographs, or by patient complaints of gingival discomfort after the procedure. Where possible, this can removed with use of floss, hand scalers, probe or U/S. Use of a little topical LA on the gingiva may help make it a little more comfortable.
Do you need to do a pulpotomy to place a Zirconia Crown?
No! When zirconia crowns were first launched many practitioners opted for ‘elective pulpotomies’ due to the increased reduction. As time and evidence has progressed, we know that the same criteria for pulpotomies and SSC apply to Zirconia crowns. That is, if the decay is at the pulp - do a pulpotomy. If there is a clear band of dentine you do not need to do one
In saying that, on occasion, particularly for lower D’s you do get very close to the pulp. So, we do find on rare occasions - maybe around 1/30 that you need to do a pulpotomy as we got a bit close to the pulp to fit the crown. But it is the exception and not the rule.
What is BioFlx and what do I need to know?
NuSmile BioFlx crowns offer a flexible, tooth-colored option with reduced tooth preparation compared to zirconia. However, they may not achieve the same level of aesthetics and are prone to wear and staining. These crowns are better suited for operators transitioning from SSCs but may not replace zirconia as the superior aesthetic choice.
To be honest I do not see a great place for these. They are easier to place than zirconia crowns, but they don’t look awesome and still require some prep. Once you get comfortable with zirconia it only takes and extra few minutes to place them
Summary
Zirconia crowns are becoming an increasing restorative option for paediatric dentistry. They look a hell of a lot better, but do have some limitations in set-up costs and prep time etc. If you want further information about them you can find them at https://tp-dc.com.au/ and training videos at https://www.nusmile.com/nusmile-webinars
We hope this has helped
Tim and Erica