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This is the last in our series of blogs on Composite filling material. It may be a good time to re-read the first two issues.
In this blog we will look at the disadvantages of composite filling material.
Here we go:
1) Shrinkage, sensitivity, and recurrent decay
Composite filling material in its natural state is pliable and soft. This is an important characteristic of the material as we need to place and condense it into the cavity preparation after the decay is removed.
Once the soft composite is densely packed, we shine an ultraviolet (UV) light onto it which causes it to harden. This hardening of the filling material is called ‘curing.’
With the older generation of composites, the curing process caused some undesirable effects to occur with the composite filling material. It caused ‘shrinkage’ to occur. Shrinkage is the pulling away of the filling material from the walls of the cavity preparation…It is important to note that we need the filling material to be tightly packed against the walls of the cavity preparation. Shrinkage causes gaps or openings to occur between the interface of the filling material and the tooth structure. These gaps result in what’s known as micro leakage. We discussed micro leakage in a previous blog, “Microleakage – What is it?” posted on April 8th, 2013.
Gaps between the filling material and tooth structure can result in plaque, food particles and saliva leaching into the tooth. This can cause re-decay to occur in addition to the likelihood of developing tooth sensitivity i.e. to cold and sweets…so gaps are unacceptable in dentistry at the tooth-filling interface…there must be a tight seal.
As mentioned previously, composite shrinkage and the accompanying re-decay and sensitivity, were more of a problem with the older generation of composites than the ones of today.
To get technical, the newer materials are made up of Silorane resin as compared to the older Methyl Methlymethacrylates.
2) Composite material is not as durable as amalgam
It may not be able to handle the pressure of biting and chewing as well as silver fillings, especially if it’s a large filling. However, even large fillings made up of amalgam are not as strong as natural tooth structure. This is why we suggest crowns (caps) for teeth with large restorations.
Because a large white filling may not be able to withstand too much stress, it may be prone to chipping or fracturing. As mentioned in the previous blog, this can be repaired quite readily.
3) Placing a white filling is very technique-sensitive
There must be a dry field in order to have the material adhere and remain in the cavity preparation. If moisture such as saliva or blood is present, then the filling will not likely stay in the tooth.
This is why we use suction and cotton rolls in a patient’s mouth…to maintain a dry field.
Moisture control is also an issue with silver fillings but not to the same extent as with white fillings.
4) Placing a white filling is more time consuming than placing an amalgam
With a white filling, there are several steps that need to be taken to ensure success…this in addition to maintaining a dry field (#3 above). This may be difficult at times, especially with an anxious patient who can’t sit in the dental chair for extended periods of time. And as well, difficult for those who can’t keep their mouths open for too long. Proper scheduling of appointments is key!
5) Some insurance companies don’t cover white fillings on back (molar) teeth
The most likely reason is that the insurance company doesn’t feel that a back tooth needs to have a white filling and be esthetically pleasing. They look at it more as an issue of function, not esthetics. Insurance companies will usually cover for white fillings on the front (anterior) and side (premolar) teeth. White fillings are more costly than silver fillings.
6) The shade of a white filling may darken over time
Chances of this are increased if one is a coffee, tea or wine drinker. The best strategy is to keep the white fillings as clean as possible…one may also benefit from drinking a beverage through a straw to avoid contact with the filling material.
In any case if a white filling does discolour over time, it can easily be replaced.
7) White fillings tend to wear more readily than silver fillings
…especially when they are large fillings as compared to smaller ones…White fillings tend to hold up better if they are small as opposed to large.
These are the main disadvantages of white filling material.
I hope you enjoyed this mini-series on composite filling material and I have been able to answer some questions that you may have had.
Keep well and all the best!
Dr. Robert Axelrad, Brampton’s Gentle Dentist