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Mathematics Provides Better Attachment For Dental Crowns
Dental treatment involving crown replacements costs the Swedish tax
payers hundreds of millions SEK each year. Researchers at Chalmers
University of Technology are developing a new method for determining
exactly how to optimally prepare a tooth to place a crown on it. The
method is expected to result in significantly cheaper and faster
treatment, and improved quality and reliability of the crown
Each year, dentists put hundreds of thousands of new dental crowns into
the mouths of Swedish patients. They firstly have to grind the teeth to
which the crowns are to be attached. This is a procedure that is still
much of an art and depends completely on the individual dentist's skill.
But dentists will soon benefit from a computer program being produced
by a group of researchers at Chalmers, at the initiative of the company
Nobel Biocare. The researchers are now planning to run clinical tests.
"With current software, you can measure the damaged tooth's dimensions
by laser scanning," explains Chalmers researcher Evan Shellshear. "The
software then computes the optimal shape of the ground tooth, and the
output is a 3-D visualisation of it. You also get a 3-D animation
showing precise suggestions for manoeuvring the cutting tool in order to
achieve the final tooth shape safely."
The software is based on advanced mathematical models and on
state-of-the-art visualisation technology. The researchers have based
their computations on roughly a dozen international guidelines for how
teeth should be shaped before being fitted with dental crowns.
The guidelines cover things like the ratios between the height and width
of the tooth, and how thick a layer needs to be ground down in order to
leave enough space for the crown. The researchers have converted every
guideline into an equation, dividing each tooth into tens of thousands
of sections. From that, the software performs an optimisation, leaving
the patient with as much of the healthy tooth as possible.
"Most dentists are very skilful, but no human being can achieve this
sort of optimisation as efficiently as a computer program," says the
Chalmers researcher and dentist Matts Andersson. "If the tooth does not
have a good fit with the crown, bacteria can accumulate in the gaps,
resulting in caries and loosening of the teeth. A bad fit can also lead
to problems with the jaw joint or that the dental crown simply falls
The researchers' new method should therefore reduce the risk of patients
suffering such problems. It would also shorten the time needed for
treatment, and save large amounts of money.
"I estimate that the treatment sessions would be 10% shorter," says
Matts Andersson. "That would result in savings of SEK 176 million per
year. But the biggest benefit would probably be an improvement in
quality, increasing the life of the dental crowns and reducing the
number of remakes."
The Chalmers researchers have also produced 3-D software that dental
students can use for learning how to grind teeth. Currently, students
have no access to simulation programs with defined objectives. In the
new software, the objective is the optimum tooth shape, and those
undergoing training will know how close to the objective their effort