Processing Stabilised Mammoth Molars

Stabilised mammoth molar is used for knife scales, gun grips, inlay work, components for musical instruments, jewellery and restoration work. It is valued for its appearance: the worn surface of a mammoth tooth shows a distinctive banded, mosaic-like pattern formed by the contrasting dental tissues within the tooth.

It is also one of the more difficult materials an artisan will put through a workshop, and for a reason worth understanding before any tool touches it. A mammoth molar is not a uniform substance. It is an assembly of three dental tissues of markedly different hardness, and almost every difficulty encountered when drilling, grinding or finishing it follows from that single fact.

This guide explains the structure, what stabilisation does and does not achieve, and how to approach drilling, shaping and dust control. It covers general principles and the reasoning behind them. It is not a complete workshop manual, and the right method for any particular piece depends on its condition, its dimensions, the quality of its stabilisation and the equipment in front of you.

A note on scope before going further: this guide concerns stabilised mammoth molar, not mammoth ivory. The two materials behave differently under tools, and advice for one should not be applied to the other. Mammoth ivory is treated separately in "Cutting Mammoth Ivory".

Understanding the Structure

A proboscidean molar is built on a different plan from most mammalian teeth, and the difference is the reason it machines the way it does.

The tooth is composed of transverse plates, also called lamellae. In each plate, a core of dentine is enfolded within a layer of enamel. These individual plates are then bound to one another by cementum, forming the complete tooth. A third molar of Mammuthus primigenius typically comprises somewhere in the region of twenty to twenty-eight such plates.

This matters because it is not the arrangement found in a human tooth, where enamel caps the crown and cementum covers the root. In a mammoth molar the cementum genuinely is the material binding the structure together, filling the spaces between the lamellae. Anyone reasoning from general dental anatomy will misjudge how the material is put together, and consequently how it will behave.

The three tissues differ substantially in hardness, and this is the governing fact for everything that follows. Enamel is the most highly mineralised of the dental tissues; dentine is considerably less so. Published figures for modern dental tissue put enamel at roughly 96% mineral by weight against approximately 70% for dentine, and measurements on human teeth illustrate the scale of the resulting difference: one study recorded a Vickers microhardness of about 275 HV for enamel against about 66 HV for dentine, a difference of roughly fourfold.

Those are figures for modern human teeth. They should not be read as measurements of fossil mammoth tissue, whose composition fossilisation can alter; they are given to indicate the order of the difference. Work on mammoth molars themselves confirms the same ordering independently. Experimentally derived wear rates for Mammuthus dental tissues place enamel as the most wear-resistant of the three, with secondary dentine and coronal cementum the least.

A cutting edge crossing a mammoth molar therefore passes repeatedly between a very hard material and a much softer one, at every plate boundary. That alternation is the source of nearly every practical difficulty: drills wander, abrasives cut unevenly, and chipping tends to occur where the tissues meet or where the material is locally weakened.

It also explains why mammoth ivory is more straightforward to work. Tusk ivory is predominantly dentine, with a cementum layer on the outside and no enamel at all. It is comparatively homogeneous; a molar is not.

Why Stabilisation Matters, and What It Cannot Do

After tens of thousands of years in permafrost, fossil molar is frequently porous and friable, particularly where the dentine and cementum have deteriorated. In that condition the material is poorly suited to machining: it can crumble under a cutting edge rather than cut cleanly.

Stabilisation addresses this by impregnating the material with a liquid resin, drawn into the pore structure under vacuum, pressure or a combination of the two, and then cured. The resin fills voids and bonds friable areas, substantially improving cohesion and workability.

What stabilisation cannot do is make the material uniform. It does not remove the hardness contrast between enamel, dentine and cementum, because that contrast is structural rather than a consequence of deterioration. It does not close pre-existing fractures that run through the piece, and it does not eliminate the risk of chipping. A well-stabilised molar is markedly easier to work than an untreated one, and it still requires careful machining.

The quality of the treatment also varies. Resin that has not penetrated fully leaves soft zones beneath a sound-looking surface, which will be discovered at the worst possible moment — usually under a drill. This is the practical reason for sourcing material that has been professionally stabilised rather than attempting to work raw fossil molar or material of unknown treatment.

Drilling

Because the enamel is so highly mineralised, drilling a mammoth molar places greater demands on tooling than drilling ivory does, and tool wear is correspondingly faster. Sharp, suitable tooling matters more here than with most materials, and a bit that has begun to dull will tend to burnish and generate heat rather than cut.

Two problems recur. The first is wander: as the bit crosses from softer dentine or cementum into hard enamel, it may deflect sideways rather than continue straight. The second is breakout, where the bit emerges through the far face and lifts material away around the exit.

Several principles reduce both.

Carbide tooling is generally the sensible choice, given the abrasiveness of the enamel. A relatively high rotational speed with light, steady feed pressure tends to give better results than slow drilling with heavy pressure, because it reduces the tendency of the bit to grab as it crosses a tissue boundary. The limit on this is heat. Excessive heat can damage the resin or affect the integrity of the stabilised material, and cured resins differ in how they behave at elevated temperature depending on their chemistry. Short passes, clearing the swarf, and letting the piece cool are more productive than pushing a hole through in one go. Follow the tool manufacturer's guidance on speeds for the bit you are using.

The workpiece must be held securely. A piece that shifts as the bit crosses into enamel is far more likely to crack.

Breakout is best addressed by supporting the material where the bit will exit. In our own workshop practice, we reinforce the back face of thinner pieces — as a working rule, those under about 10 millimetres — with a backing plate, typically a G10 spacer bonded with cyanoacrylate adhesive. Both surfaces must be clean, flat and true before bonding, or the backing will not do its job. The spacer can usually be left in place and incorporated into the finished piece. This is a threshold we have found reliable for our own material rather than a universal rule; the actual risk depends on hole diameter, proximity to an edge, the internal structure at that point and how well the piece is supported.

For thicker pieces, drilling from both faces to meet near the centre avoids an exit face altogether. Mark and align the hole axis carefully on both sides before starting, since poor alignment produces a stepped or doglegged passage that is worse than a clean breakout would have been.

Grinding, Shaping and Surface Repairs

A belt grinder or belt sander with a rigid platen behind the abrasive gives the most controlled result. The rigid backing is what prevents the belt from conforming to the surface and producing a wavy profile across the alternating hard and soft bands — the same hardness contrast that causes trouble when drilling will, on a slack belt, grind the softer cementum and dentine away faster than the enamel.

For rough removal of material, coarse abrasives in the region of 40 grit are appropriate. Grit numbers here follow the common coated-abrasive grading used on belts; grading systems differ, so compare by the actual particle size where it matters. As the piece approaches its final shape, moving to finer grades — 60, 80 and upward — reduces the risk of tearing material out at a plate boundary. The finer the grain, the gentler the action at those junctions. These are shaping grits, not a finishing schedule; bringing a piece to a polished surface requires a progression of considerably finer abrasives afterwards, selected for the finish you want.

Heat is the main hazard during shaping, for the same reason as in drilling. Excessive heat can damage the cured resin and the fossil material alike. Light, controlled passes, keeping the piece moving rather than dwelling in one spot, and inspecting a worn belt are the practical controls. A worn abrasive cuts inefficiently and generates more heat for the same material removal, which makes belt condition a safety matter as well as a quality one.

Surface defects need judgement rather than a reflex. Distinguish first between a genuine void or fracture and the natural structure of the tooth. The lines and boundaries between enamel, dentine and cementum are what give mammoth molar its character, and filling them would both be unnecessary and spoil the appearance. A true crack or cavity is a different matter and can often be filled with a compatible adhesive — cyanoacrylate is commonly used — applied sparingly and levelled flush once cured. Test on an inconspicuous area first: adhesives can differ in gloss and colour from the surrounding material once polished, and excess is difficult to remove cleanly.

A defect that moves, that runs deep through the piece, or that reappears after filling is a structural matter and not a finishing one. Adding more adhesive will not resolve it, and the piece may not be suitable for the intended use.

Dust Safety

Drilling, grinding and sanding stabilised mammoth molar can generate fine airborne dust from both the fossil material and the cured resin. Avoid inhaling this dust. Check the relevant safety information for any resin, adhesive or other product used during processing, since their compositions differ.

Control it at the source first. Established occupational hygiene practice places engineering controls above personal protective equipment: extraction at the tool, adequate ventilation, and work practices that generate less dust in the first place. Where your equipment and the process allow it, working wet is highly effective at suppressing airborne dust, subject to the usual electrical precautions and the suitability of the machine.

Respiratory protection is an additional measure, not a substitute for the above. Use a properly selected and correctly fitted particulate respirator appropriate to the exposure and to the requirements that apply where you work — in Europe, filtering facepieces are classified under EN 149 as FFP1 to FFP3; in the United States, NIOSH classifications such as N95 and P100 apply. A respirator only performs as rated if it fits and is worn correctly, and facial hair at the seal will defeat it.

Wear eye protection. Fine particles thrown from a belt are a genuine hazard.

Clean up without putting the dust back into the air. Do not dry sweep and do not use compressed air to blow surfaces down. Vacuum extraction with a suitable filter, or damp wiping, keeps settled dust settled.

A Note on What This Guide Is

The scientific discussion above draws on published research into mammoth molars and dental tissues, and the sources are listed below. The workshop recommendations — the drilling approach, the 10 millimetre backing threshold, the grit progression — reflect our own experience with our own material over many years. They are starting points that have served us and our customers well, not laws of nature. An experienced artisan with different equipment may reasonably arrive at a different method, and the piece in front of you always has the final say.

If you have any further questions or require further explanations, please email us: info@arcticantiques.com

Bibliography:

Ferretti, M. P. (2003). "Structure and evolution of mammoth molar enamel". Acta Palaeontologica Polonica, 48(3): 383–396. On the lamellar construction of the proboscidean molar: dentine enfolded within enamel to form each plate, with the plates adhered to one another by cementum.

Lister, A.; Bahn, P. (2007). Mammoths: Giants of the Ice Age. Revised edition. University of California Press. On the number of molar plates in Mammuthus primigenius, cited for that figure by Ferretti (2003).

Chun, K. J.; Choi, H. H.; Lee, J. Y. (2014). "Comparison of mechanical property and role between enamel and dentin in the human teeth". Journal of Dental Biomechanics, 5: 1758736014520809. DOI: 10.1177/1758736014520809. Vickers microhardness of human dental hard tissues: enamel approximately 274.8 HV, dentine approximately 65.6 HV. These are measurements of modern human teeth, not of fossil mammoth material.

Nanci, A. Ten Cate's Oral Histology: Development, Structure, and Function. Elsevier. On the mineral content of modern dental tissue — enamel approximately 96% by weight, dentine approximately 70% — and on the distinct roles of enamel, dentine and cementum. A reference for general dental anatomy and composition, not for measurements of fossil material.

Grejtak, T.; Hunt, T. C.; Whalen, N. S.; Hendricks, S. K.; Babuska, T. F.; Craig, R. L.; Varma, S.; Jia, X.; Norell, M. A.; Pathak, S.; Vermaak, N.; Druckenmiller, P. S.; Erickson, G. M.; Krick, B. A. "Paleotribological models using preserved fossil tissue properties reveal functional significance of Eurasian mammoth dental evolution". Acta Biomaterialia, 218: 182–190. Experimentally derived wear rates for fossil and extant proboscidean dental tissues, and on coronal cementum infilling the inter-lamellar spaces of the molar.

Locke, M. (2008). "Structure of ivory". Journal of Morphology, 269(4): 423–450. On the structure of tusk dentine, relevant here to the contrast between mammoth ivory and mammoth molar.

Espinoza, E. O.; Mann, M.-J. (1991). Identification Guide for Ivory and Ivory Substitutes. World Wildlife Fund and The Conservation Foundation; subsequently published by the CITES Secretariat. On the dental tissues of proboscidean material.

Canadian Conservation Institute. Care of Ivory, Bone, Horn and Antler, CCI Notes 6/1. On the porosity and physical vulnerability of ivory and osseous material generally. Cited for the characteristics of the material, not for resin stabilisation or machining method.

Health and Safety Executive (United Kingdom). Control of Substances Hazardous to Health (COSHH) guidance, on the hierarchy of control and the principle that engineering controls precede personal protective equipment, and guidance on local exhaust ventilation: hse.gov.uk/coshh

European Standard EN 149, Respiratory protective devices — Filtering half masks to protect against particles, defining the FFP1, FFP2 and FFP3 classifications.

National Institute for Occupational Safety and Health (NIOSH), 42 CFR Part 84, defining the N-, R- and P-series particulate respirator classifications including N95 and P100; and NIOSH guidance on facial hair interfering with the seal of a tight-fitting respirator.