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Curing Sick White Fillings!

11/11/2012

 

Curing Sick White Fillings!

These days more and more people are demanding tooth coloured fillings, either for cosmetic reasons or because they are concerned about the ingredients used in dental amalgam. There are a number of ways we can provide these. In selected cases we may use crowns, veneers or porcelain inlays but the most common way of producing a tooth coloured filling is with composite resin.

How do we use it? Should it be layered and if so in how many increments? Should we use a bulk-fill technique? A flowable? A sandwich technique? What type of composite? Microfil, nanofil, hybrid? And then what method of bonding? 4th generation or 7th perhaps?

All these questions are beyond the scope of this article. Composite is not ‘white amalgam’. It is technique-sensitive; its reliable use requires practice and experience. Everything from cavity preparation to the type of matrix used is different and all these things require expert tuition. Any practitioners using composite should make sure their knowledge stays up to date.

OK. We’ve placed a posterior composite filling. It looks good. There’s just a couple of problems; the patient returns a week later saying the tooth hurts or 6 months later with severe staining at the edges.

Whatever kind of composite we use; whatever our technique one thing is common to all of these materials. They must be properly cured. This is a step many practitioners spend too little time on but the extra seconds spent ensuring the material is properly hardened can save hours of re-treatment and patient angst later!

The dental industry is partly to blame for the neglect in realising the importance of curing. Remarkably, dental manufacturers (unlike many dentists, apparently) believe they are in business to make a profit and sometimes are guilty in their promotions of telling the truth but not the whole truth. We’ve all seen the sort of advert I’m alluding to here: ‘Our new Whizzo Universal Composite can be cured in 6-foot layers in under 2 seconds!’ Well maybe it can but you’d need access to the latest Death Laser from your favourite sci-fi channel to achieve this!

The hard fact is that there are Laws of Physics. From them come unfortunate rules about the transmission of light. Light decreases in an inverse-square proportion from the centre of the source. That means the light produced at the edge of the lens of your curing lamp is only a fraction of the intensity of light in the middle. Penetration is also important. Read the small print on the composite use leaflet. It’ll recommend light of a certain intensity to penetrate the full thickness of the suggested maximum depth of increment. Can your curing lamp provide this? Have you checked it recently? Old curing lamps become more and more inefficient.

I’m an old-fashioned sort of chap. Running an amalgam-free practice I’ve been using composite routinely for anterior and posterior fillings since 1994. Since then materials have changed but the laws of physics haven’t! I’ve tried fast cure, ramp cure, PAC lamps and others and have had success with all but only by providing adequate curing times.

What are the consequences of incomplete curing? Well, the most serious is the dreaded ‘soggy bottom’ where the basal layer of composite remains in a plastic state. This is guaranteed failure; pain almost certainly, collapse of the filling quite often and a massively-increased risk of secondary caries. Not a practice-builder! The other most common effect of incomplete curing displays as stained margins or even delamination of the edge of the filling. Remember, your patient wanted this restoration to look aesthetic! How are you going to explain this? Blame the material? Modern composites are incredibly fine materials created from years of on-going research by teams of PhDs! If you really don’t trust the material how are you going to explain to the patient why you used it in the first place? What are you going to do about it?

Prevention is better than cure and many problems with the cure of composite can be easily prevented:

  • Read the information sheet that comes with the composite. Make sure you understand the precise requirements
  • Check the output of your curing lamp. Make sure it’s up to the job
  • Never cure more than the recommended depth of increment. In many composites this is 2 mm.
  • Cure each increment for the recommended time. Darker composites usually need more time so where 20secs may be adequate for a 2mm increment of B1, B4 is likely to need 40secs
  • Move the curing light around the filling ensuring every part of the edge is cured for the recommended time
  • If possible use 2 curing lamps. Dentist or therapist holds one, dental nurse the other
  • Keep the tooth cool during curing. After the first 10secs (when the surface is cured) rinse the tooth with the triple syringe and continue doing this. Curing lamps generate a lot of heat. If you don’t believe this put the lamp against the skin of your wrist, turn it on and see how long you can stand it. (Don’t try this at home!) Fried nerves don’t improve the prospect of a comfortable result!

Why is my practice amalgam-free? It isn’t because of any health concerns, it’s because modern materials, used properly, have important advantages. Amalgam can expand during setting causing external and internal cracks, it doesn’t adhere to teeth so to keep it there we have to dig a bigger hole. As well as this it is frankly less than pretty and this is of importance to modern consumers.

Composite addresses these problems. Modern research has shown that properly used it is as reliable and long-lasting as other filling materials. It’s disadvantages  include it being technique-sensitive and time-consuming. Yes, it is time-consuming. You can probably place up to 4 amalgams in the time it takes to properly place 1 composite but this should be reflected in your fee.

If you do decide composite is the material of choice, learn to use it properly. There are many postgraduate courses available.

Modern techniques make the use of composite quicker, not quick! Come to terms that it is going to take longer to use and don’t skimp on time; particularly the time spent on curing!

 

Philip Lewis has a general dental practice in Freshwater, Isle of Wight

He can be contacted at: Philip-Lewis@btconnect.com

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