Anthony Doesburg: Computer-aided dentistry cuts the stress level

Technology is coming to the aid of people for whom a visit to the dentist is a barely endurable ordeal.

Computer-aided design and manufacturing (CAD/CAM) systems mean some procedures that used to require a couple of sessions in the dentist's chair can now be done in one.

And microprocessor-controlled sedation is allowing dentists to keep victims - er, patients - happy but awake during the whole horrible business.

Graham Shaw is an Auckland dentist who is using both types of equipment and he sings the praises of high-tech dentistry, particularly for people who are short of time. If you're short of money, though, you might think twice - a crown at his Herne Bay clinic will cost you $1450.

But chances are a demonstration of the CAD/CAM system and description of the pleasures of sedation - recreational use of the drugs used isn't unheard of - would persuade you the premium was worth it compared to the $1000 another dentist might charge.

The system's biggest selling point is that a crown - effectively replacing about half the visible part of the tooth - can be fitted in one go. That's because it is made on the spot, rather than by a technician in a distant lab.

Most people in need of a crown make an initial visit to their dentist, during which the cracked or decayed part of the troublesome tooth is ground away and measurements taken for the replacement material.

A temporary cap is then cemented in place until a second visit a couple of weeks later when the permanent crown is fitted.

Shaw, though, can do the whole job in a single hour-and-a-half sitting.

"It was a massive learning curve," says Shaw, who watched the technology go through several generations before taking the plunge.

And a big investment. A top-of-the-line Cerec CAD/CAM system of the type he has, from German company Sirona, leaves little change out of $200,000.

It has two components: a PC-based acquisition unit for taking a photograph of the tooth being restored and designing a suitable crown; and a milling unit that follows the instructions of the CAD file to transform a block of porcelain into a perfectly fitting tooth replacement.

After some final polishing the crown is cemented in place, and can be expected to last 20 or more years.

Designing a crown on the acquisition unit, a modified PC running Microsoft Windows, takes Shaw about 10 minutes. Rather than putting the patient through the unpleasant process of biting into putty-like material to take a tooth impression, a scan of the antagonist tooth - the one that opposes the tooth being restored - determines where the crown's peaks and valleys need to go.

This is overlaid on one of several available templates of teeth of different shapes and sizes, and the design tweaked to ensure crown strength and snugness of fit with surrounding teeth. Then, just like hitting "print" to output a document, the file is sent to the milling machine.

Within another 10 minutes, a pair of water-cooled high-speed diamond burrs have faithfully formed the crown.

At Shaw's clinic, a controlled injection of the sedative Propofol can keep the patient blissfully unaware of all the manufacturing activity. The drug is administered at a rate determined by the patient's body mass index, and a brain activity monitor tells Shaw whether it is having the desired effect.

If that sounds like your ideal of the dental experience, relatively few practices offer it. Graham Head, Cerec specialist at Sirona New Zealand, says there are just under 100 CAD/CAM systems in use here by about 160 dentists.

"The trouble with the medical and the dental market is that ... when they are looking at the integrity of a product to go into somebody's mouth and be there for the rest of their lives, they tend to be conservative, rather than jumping into something."

Conservative's not the word David Crum, executive director of the New Zealand Dental Association, would use. He thinks the 10 per cent or so of New Zealand dentists using CAD/CAM probably matches the proportion of the population prepared to pay the premium for that treatment.

"The most significant reason why it doesn't have a larger uptake is the cost of the system ... and that's a cost that flows through to your patients."

One factor that is changing is that, 20 years after the technology was commercialised, new dentists are finally being exposed to it. Dusan Kuzmanovic, a senior lecturer at the University of Otago Dental School, says use of CAD/CAM systems is becoming a standard part of dentistry training.

Cross your fingers that it's coming to a dentist near you.

Anthony Doesburg is an Auckland technology journalist.