|The microscribe. © Tim Fedak.
The Creation of a Micro-Scribe for the Preparation of Small, Delicate Fossil Material
This note details some modifications that can be made to a sonic scaler commonly found in any dental hygienist office to create a very precise air scribe tool for fossil preparation.
The idea of using ultrasonic energy for removing residue from objects is not a new one. Although there has been some literature which does discuss the use of an ultrasonic bath to prepare fossil material (Pojeta and Balanc 1989), the use of the ultrasonic scaler has apparently received no attention.
There are several different styles and models of sonic scalers used by professional dental hygienists. This paper and the experience of the author is limited to the Star Dental (manufacturer) Titan® SW model sonic scaler. Please note that the modifications discussed here may or may not be transferable to other makes and models.
The Titan® SW sonic scaler is an air powered tool used in the dental profession to remove hard calculus deposits and stains from above and below the gum line (Star Dental 1999). Compressed air (at 40 psi) enters the base of the scaler where it generates a high frequency vibration (6400 cycles/sec) before traveling back out the base of the scaler. The ultrasonic vibration travels through the scaler handle to the working end of the tool, powering curved tips designed to fit under the patients gum line. A water tube, also traveling from the base of the handle through the scaler to the curved tips, provides a water rinse to remove debris from the cleaned teeth. Both the air and water flow are controlled by a round metal foot pedal, connected to the scaler and the air/water sources by rubber tubing.
Modifications for the paleo lab
The sonic scaler allows a dental hygienist to remove the buildup of hard deposits without harming the patients teeth or causing discomfort. Obviously there are different tool requirements in the dentists chair compared to the paleo lab, and there are several important modifications which need to be made.
Perhaps the first and most obvious problem is the water rinse used in the dental office to clear the gum line of loosened debris. Most mechanical preparation of fossil material does not permit the soaking of the fossil and/or matrix and luckily the water source is not essential to the scaler’s performance. The water rinse is optional and is easily eliminated by simply not connecting the water hook-ups on the base of the scaler.
Our next concern involves the curved tips provided by the manufacturer. Several designs of metal tips provide different access in and around the tooth surface. The tips are easily changed, simply screwing into the scaler body and tightened by hand.
The force the curved tips experience in the dental office is minimal under the careful touch of a good dental hygienist. When we bring the Scaler into the prep lab, the manufacturer’s tips perform small scale disruption of the rock matrix, but the tips are quickly worn down and rapidly decrease in effectiveness. The manufacturers tips are not designed for the hardness of sedimentary rock commonly found in a fossil preparation lab.
|The microscribe. © Tim Fedak.
The use of carbide tungsten steel rod for fossil preparation is common (May et al. 1995, Amaral 1995) and this material can also be effectively adapted for the sonic scaler. A long lasting and very sharply pointed tip can be made by replacing the manufacturers (screw in) tips with a M3 x 0.5 (see Notes) metric machine screw which has been drilled with a 1/16" drill and fitted with a 5/32" carbide rod. The carbide rod is held in the drilled hole of the machine screw with standard 5-minute epoxy placed down the complete depth of the hole and with a small surplus at the top of the hole (see figure).
Attachment of the sharpened carbide tip allows the scaler to be applied to rock matrix with very good results. It is important to keep the tip sharp to ensure that the vibration force is focussed on the smallest area possible.
The sonic scaler differs from a typical air scribe in several ways. An important difference in the two tools is that unlike most air scribes, the excess air does not leave the scaler where the tool is contacting the matrix surface, but rather exits at the base of the tool. By attaching a short, 80cm long section of surgical tubing to the air exit port, the exit air can be used to blow debris away from the working area. This debris blower can provide immediate visibility of the bone material as it is exposed or the air can be moved away to prevent loose bone fragments from being blown away. This hose also prevents the exit air from being blown into the preparator’s face, so it is recommended a hose be attached even if the exit air is not wanted for clearing the working area of debris.
There are several styles of foot pedal used in the dental industry but not all seem equally relevant to the paleo lab. Beyond overall quality the differences in various foot pedal designs have to do with the types of hook-ups available (air or air and water lines), and the types of switches incorporated in the pedal (variable or a simple on/off switch). For the application of the scaler in the prep lab a simple foot pedal which has only air in and out ports and no water feed ports is acceptable.
Having a foot pedal with water feed ports is not a problem as long as the ports are not hooked up; but ordering a pedal with this option may prove more expensive. Also, a pedal with a variable switch is preferred, allowing for fine control of the air flow and thus the tools operating strength.
Preparators in most labs will be concerned with the vibration coming from the tools they use and the possible development of carpal-tunnel syndrome. A foam tube encasing the scaler and positioned to accommodate the users grip may help to reduce the vibrations transmitted to the operators hand.
Implications for fossil preparation
The 6400 cycle/sec. vibration frequency provides very strong yet localized disruption of rock matrix upon contact with the sharpened carbide tip. The sonic scaler has been used to perform mechanical preparation in a similar manner as the Chicago Pneumatic air scribes but on a much smaller scale and with a greater precision and control. The amount of material able to be removed in any amount of time is much smaller than the typical air scribe, so this tool has a specific and perhaps narrow “use niche” in the paleo lab.
The retrofitted scaler seems to work well as a final approach tool, or for extremely small and fragile material. Very fragile fossil bone material as small as .5 cm long and .15 cm wide has been comfortably prepared with this method. The variable strength of the tool (controlled by the foot pedal) allows an increased approachability to small, delicate fossil material, which is encased in a hard matrix, otherwise difficult to prepare by hand.
|Using the microscribe. © Tim Fedak.
M3 x 0.5 is a metric measurement for machine screws; the width of the screw is 3 mm and the distance between each thread is 0.5 mm.
Thanks to Ken Adams, Ian Morrison, Marilyn Fox, and Maxine Westhead for their encouragement. Also, thanks to the Nova Scotia Museum Palaeontology Research Grant, 1999, for providing funds for the preparation of the problematic fossil material which required the development of this tool.
- Amaral, W. 1995. Microscopic preparation. Pp. 129-140 in P. Leiggi and P. May (eds.), Vertebrate Paleontological Techniques, Volume 1. Cambridge University Press.
- May, P., P. Reser, and P. Leiggi. 1995. Macrovertebrate preparation. Pp. 113-129 in P. Leiggi and P. May (eds.), Vertebrate Paleontological Techniques, Volume 1. Cambridge University Press.
- Pojeta, J., and M. Balanc. 1989. Uses of ultrasonic cleaners in paleontological laboratories. Pp. 213-217 in R. Feldmann, R. Chapman, and J. Hannibal (eds.), Paleotechniques. The Paleontological Society Special Publication No. 4, Department of Geological Sciences, The University of Tennessee, Knoxville.
- Star Dental, Titan SW Sonic Scaler promotional material. Star Dental, 1816 Colonial Village Lane, Lancaster, PA 17601-5864. Phone (800/275/3320). Web (www.dentalez.com).