The basis for cementum aging is the cyclic nature of cementum growth, which results in an annular pattern of “rings” in the tooth like that formed in the wood of trees. A darkly staining ring, or “annulus,” is formed during winter. Abundant, lightly staining cementum is formed during the growth seasons of spring and summer. The underlying physiologic/metabolic mechanisms for cyclic cementum growth are not known. Very darkly staining rings are formed in southern regions of North America, but it is generally true that most mammals in these regions have less distinct annuli than their counterparts in more northern regions. Incidentally, human teeth have similar annuli but the deposition pattern is irregular compared to that of most wild mammals. (Matson’s has no expertise in the aging of human teeth.)
Tooth section of a 4 year old black bear killed in spring season
Matson’s uses a standardized cementum aging model for each species. The original models are expanded on a continuing basis, with additional experience.
All cementum aging done at Matson’s is by certified agers. Gary Matson is qualified to age all species.
Cementum age analysis training is ongoing at our lab. Technicians are certified when results compare with Gary’s with a precision of 85-95%, a level that varies with population and species. After a technician is certified to age a given population of a species, Gary checks 10% of each sample aged by that technician, for quality control, before the age report is sent.
Standardized Tooth Type
Matson’s cementum age analyses are not only species-specific, but also are based on a standardized tooth type. Mixing of different tooth types in a sample to be aged can cause error not only because of differences in age at eruption but also because of anatomical differences in the cementum patterns of different tooth types.
Standardized Tooth Types
Most Artiodactyla (cloven-hoofed mammals): Primary incisor (I1)
Most carnivores: Lower canine
Bears: Upper premolar one (UPM1)
Martens and fishers: Lower premolar four (LPM4)
Mountain lion: Upper premolar two (UPM2)
Standardized Type for Aging Live Mammals
Artiodactyla: Lower canine
Most carnivores: PM1 (upper or lower)
Mountain lion: UPM2
Lynx and bobcat: Lateral incisor (there is no PM2)
Matson’s is unable to process archeological and anthropological specimens. Typically, analysis is sought for specimens obtained from archeological digs to determine mammal age and season of kill.
The decalcification in our tooth processing protocol dissolves the mineral of the tooth, leaving behind the collagenous ground substance. The decalcified tooth section is composed almost entirely of this collagen, which contains the annular structures that are counted to determine age.
In most specimens that have been in the soil for long periods, the collagen has been replaced by minerals. After decalcification, there is no intact collagen and no annular structure. Techniques that don’t involve decalcification are more suitable for archeological materials.
Remarkable exceptions are specimens that have been preserved frozen in arctic regions.