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Material Choices in Dentistry
Chapters in this Section:
Chapter V.1 – Anesthesia and Isolation
Chapter V.2 – Fillings – back teeth – Silver Amalgam
Chapter V.3 – Fillings – front teeth – Composite Resin
Chapter V.4 – Fillings – the Rise of Adhesive Dentistry
Chapter V.5 – Gold Fillings and Inlays
Chapter V.6 – Gold Onlays and Crowns
Chapter V.7 – Porcelain Onlays and Crowns
Chapter V.8 – Gold versus Porcelain versus Both
Chapter V.9 – Buildups
Chapter V.10 – Root Canals
Chapter V.11 – Extractions
Chapter V.12 – Periodontal Therapies
Chapter V.13 – Tooth Replacement
Chapter V.14 – Implants
Chapter V.15 – The Collapsed Bite and Full Mouth Rehabilitation
Chapter V.16 – Full Dentures
Chapter V.17 – Orthodontics
Chapter V.18 – Cosmetic Dentistry
Chapter V.19 – Dentistry for Kids
Introduction to this Section
We are by now pretty well informed about all the things that can go wrong with the mouth – including, teeth, gums, joints, bone, lips, tongue, etc. Now, what are we going to do about fixing these things?
Most of this Section will concentrate on the teeth themselves. The range of options for restoring a tooth is so large that many factors need to be considered. The next ten chapters will answer questions about single tooth restorations. Then individual chapters will deal with treatments for gum disease, missing teeth, grinding, joint pain, crooked teeth, facial abnormalities of esthetic concern, and general dentistry for kids.
After studying Section V you should be very well informed about dentistry as an art and as a science. You should know as much in some areas as a student just getting out of dental school. The way dentistry SHOULD be done, however, and the way it IS done are often two different things. Part VII will address the realities of dentistry in a competitive marketplace. Be sure to read this final section before heading out to get some work done!
The Materials Choice in Restorative Dentistry
The basis of all restorative dentistry is the choice of materials that we can use to repair the teeth. It is important enough that an overview in this introduction to the Restoration Section is appropriate.
Over the last 50 years the technology of dental materials has taken a huge step forward – or many steps. In the 50’s we learned to make artificial tooth crowns that combined metal and porcelain. In the 60’s we learned to use plastic resins in restoring teeth that were compatible with tooth characteristics. In the 80’s we learned to adhesively BOND (glue) various materials to tooth structure, including resins, porcelain, gold and even amalgam. We also learned to cut artificial crowns to fit prepared teeth on a milling machine, much like in a metal-shop.
So, with all this innovation, how do we decide what is the best for the patient? GOOD QUESTION! Have all of these innovations been made to benefit the patient, the dentist, the manufacturer, or some combination? When we have a choice between two or three approaches for restoring a tooth, what criteria are used to pick the best, and is it the same for every patient?
To begin to get a feeling about some of the materials choices – we can check out the Pros and Cons of each – starting from the oldest materials.
An amalgam, is by definition, a compounding of something with mercury, the liquid metal used in thermometers before the digital age. Many metals amalgamate with mercury – but for dentistry we use a powder formed mostly from silver, tin and copper. The mixing process creates a solid mass where the mercury is bound very tightly into the solid, and this solid material has been used for over 100 years to restore teeth.
Fears of mercury toxicity have circulated widely when people became more aware of the POTENTIAL health effects of mercury in amalgam. While medical treatments decades ago sometimes involved DRINKING large amounts of liquid mercury METAL, when mercury is in its ORGANIC form it enters the body FAR more easily – for example when obtained from eating fish. The pictures of W. Eugene Smith in Minamata, Japan in the 60s demonstrated the birth defects which follow ingestion of huge amounts of organo-mercury from fish.
There is now a Minamata Accord, which proposes to phase out the use of dental amalgam over some period of time. Of course, the replacement of this material by something “better” is crucial, and proving to be a significant challenge. Even “similar” is a challenge!
The largest and most complete study of potential toxicity of DENTAL amalgam on humans showed no significant concern in a typical American population. And the American Dental Association does not recommend discouraging restoration of patients with amalgam. In fact, telling a patient that the amalgam is bad for them and replacement is in their best interest is considered malpractice. Given that the well done amalgam restoration will last the rest of their life, and the resin alternative must be replaced every 5-7 years, a significant case can be made for the amalgam being the healthier material to use!
There are, however, many who would tell you about the dangers of amalgam, and the benefits of its removal – just do your homework! Amalgam is considered the restorative material with the longest lifetime in the mouth – sixty years would not be surprising. This approaches a lifetime restoration even in view of today’s increasing longevity. When well placed and polished, amalgam has a silver, metallic appearance – otherwise , if let rough, it tarnishes like silver. But a CAN look nice, although not natural, but decorative. It is inexpensive, forgiving, and most dentists can do it reasonably well.
For a simple filling what are the materials choices?
The choices are Dental silver amalgam, composite resin, porcelain and gold. Amalgam must be placed directly into the tooth, once the decay has been removed and the remaining tooth structure is shaped appropriately. Composite resin can be placed directly, or made in a lab to fit a plaster model of the prepared tooth, and then cemented in. Porcelain must be made in the lab or on a computer-driven milling machine, and then cemented. Gold is generally made in the lab as an inlay, but certain kinds of gold can be put into the tooth directly. My mother still had several of these that were done during World War II when she died in 2016.
What if the tooth is mostly missing?
If the tooth is mostly missing, either due to decay removal or breakage or both, then the choice of materials is somewhat different – often amalgam can be used to rebuild large sections of a tooth, but the most common option is to make a crown – either from metal, porcelain or a combination of both. The choices here are made on the basis of cost, longevity and appearance.
For crowns – indirectly made and cemented – just as we saw for the direct restorations, there are Pros and Cons to each type of material that we might choose. In any particular case we may have a legitimate choice of two or three methods, but sometimes the difficulty of the case, or financial abilities of the patient, may severely limit our choices.
There will be more to say about the various options later – but for now – consider that with gold crowns it is possible in many instances to do them so they cannot be seen, preserving the esthetics, and they do not break, last far longer than ceramic crowns, and are very kind to the opposing teeth (they don’t grind them away, as does porcelain). Porcelain and other ceramics, whether used with a metal substructure or as the ceramic by itself, are used when restoring surfaces of teeth which are highly visible. Their main disadvantage is that they wear away the opposing teeth.
The science of Dental Materials is more complex than we will cover thoroughly, but the nature of the materials and pros and cons of each when used to restore part or all of a tooth, or to replace teeth, is something we should know something about.
While this section is just an introduction to the subject, more will be said specifically about WHAT and WHO determines the materials and methods that are used to restore your teeth in subsequent sections.