Three-Body Wear of Enamel Against Full Crown Ceramics

The new machine creates the same clinically-relevant wear patterns that model abrasion and attrition wear on each specimen with triple the capacity of their original model.

The test frame, which uses smaller solenoids than their four-station model, is capable of loading up to 100N. It is shown here with 20mm flexural spans. Fixtures for compression and shear loading have also been developed. Each specimen is immersed in an individual chamber with circulating heated water.

The control system features a GUI developed by IOTech that allows independent control of the load level, frequency and cycle limit of each chamber.

Proto-tech’s new system is priced at under $40,000.

The LED Curebox is a novel way to prepare flexural bars of  light-cured composite. Glass tubing with a square inside dimension of 2 x 2mm is loaded with composite and placed inside the chamber of the LED Curebox. Pressing the “start” button activates the arrays of bright blue LEDs that line the chamber, quickly and completely curing the composite. The time-consuming and imprecise chore of curing the bar with multiple exposures from a hand-held light curing gun can be eliminated with this handy new tool, made even better with the new intensity meter.

The LCD display reads the value of the intensity, up to 200 mW/cm2, without adding to the $995 price of the unit, available from Proto-tech. Complete with a built-in timer, intensity control, and power supply. Find out more by visiting http://www.oralwear.com.

For example, here is a Dental Materials Fact Sheet developed by the State of California to inform patients.

http://www.dbc.ca.gov/formspubs/pub_dmfs2004.pdf.

This is the safety brochure developed by the ADA

http://www.ada.org/prof/resources/topics/materials/dental_fillings_facts_full.pdf

Here is the FAQ developed by the FDA about materials safety.

http://www.fda.gov/cdrh/consumer/amalgams.html

This is an FAQ about Dental Materials Research at NIST.

http://www.nist.gov/public_affairs/factsheet/100396.htm

The historic canals with hand-operated locks

I just returned from installing three instruments at the Dental School at the University of Birmingham in the UK. That was a great trip. My clients, Will and Owen, were very welcoming and great to work with. They showed me some authentic sights of this historic city. I’ve been really fortunate in my career to have visited many interesting cities around the world and met alot of great people. Sadly I hardly ever get to bring my wife and daughter along.  The days are usually full and they would be on their own.  But I look forward to returning to Birmingham again someday. They have some great plans for their new instruments. It was a thrill to be bringing equipment to the city that was basically the birthplace of the Industrial Revolution in the late 1700s, mostly through family-owned small businesses, alot like Proto-tech itself!

But besides the pit-crew work, I spent many hours making and breaking different kinds of composite specimens. Jack hired another tech, a woman named Jane with a chemistry degree, to also run experiments. She was the first in a long line of techs, students, professors and visiting scholars that I had the pleasure of working with. Eventually we had characterized the water uptake,  fracture toughness (four ways) with fractography, the degree of conversion, UV resistance, and a few other properties. Having fulfilled the Specific Aims, Jack was planning on getting into wear research and developing a new wear machine rather than reproducing anything that was currently in use. ( They might have been commercially available, but just barely.)

So I started building different motorized machines along the lines of some vague criteria, i.e. a pin on plate applying around 100N with a third body slurry.  It required a complex motion because it needed to generate both abrasion and attrition in each wear pattern. This was the prevailing description of composite wear at the time, as clinical studies talked about OCA (occlusion contact area) wear being attrition and CFA (contact free area) wear being abrasion. The first model had three chambers and used ball bearings and springs to generate the force. There was a wide variety of results as we tried different geometries. This phase actually continued for many months.

Those days I would ride the bus from my home in Milwaukie. My mother was a widow and had a nice house and we got along fine. The bus riding was a good opportunity read, often reprints, and to meet single young ladies. I had a hot car too, and would meet up with my buddy to have a beer and play pool on Sunday nights (why Sunday? can’t remember). I took a couple of weeks and visited friends in Alaska, and went to the Dominican Republic with a volunteer group. It was a pretty carefree lifestyle for me, but it didn’t last long.

Determining the presence of this naughty phase required an SEM with x-ray spectrometers, and

An ARL Mocroprobe

this beast resided in a dark corner of the lab, one of the first built by ARL, a long defunct company, flanked by a hodgepodge of archaic computers and photographic equipment. I considered it a vote of confidence that Jerry trained me in how to fire up and take basic SEMs with his personal contraption. However I was glad when Jack secured a recent JEOL SEM with lots of automated features. It did not however have the X-ray capability so the old beast remained in the basement and the new scope was installed in a spare room on another floor.

Another early project was determining the water uptake and elution from composite, a rather fundamental property that had not at that point been systematically evaluated. The labwork was simple enough, cure a soak a bunch of pellets of composite, weigh them, let them dry, weigh again, compute differences. But as was often the case, one answer led to two questions, and we had to try baking the composite to drive out more water, then soaking them in ethanol and so on. I found that making up subsequent studies was a fun kind of goose chase, and that editing manuscripts required a certain diplomacy (yay, my first co-author credit).