TECHNICAL NOTE Vicki L. Wedel, 1 Ph.D. Determination of Season at Death Using Dental Cementum Increment Analysis*  ABSTRACT: Dental cementum anchors teeth into their sockets via the periodontal ligament. In mammals, dental cementum is laid down in alter- nating opaque and translucent bands representing winter (dormant) and summer (growth) seasons. Each pair of bands represents 1 year of life. Esti- mates of age at death based on counting pairs of bands are highly accurate. If the timing of the transition between winter and summer bands could be identified in humans, dental cementum increment analysis could be used to specify the season at death. This pilot project attempts to determine when these transitions occur and thus provide forensic anthropologists with a technique that would refine our estimates of postmortem interval. Extracted teeth were obtained from a local oral surgeon, embedded, sectioned, ground, polished, and examined under transmitted polarized light. The outermost increment was identified and measured along with other randomly chosen like bands. A transition from translucent to opaque bands was observed in teeth extracted in early October, while teeth extracted in early April exhibited nascent translucent bands. Further, significant correlations were observed between band thickness and number of days into either season, suggesting that band width increases as either season progresses. In this blind study, extracted teeth were effectively sorted into the spring ⁄ summer or fall ⁄ winter season 99% of the time. KEYWORDS: forensic science, forensic anthropology, season at death, dental cementum, postmortem interval Forensic anthropologists are often called upon to estimate time since death in decomposing and skeletonized human remains. Esti- mates are based on the overall condition of the remains, the pres- ence of insect activity, and the decomposition microenvironment. Postmortem interval (PMI) estimates are usually expressed as broad ranges of months or years, especially when forensic anthropologists are not present at the time of recovery. Dental cementum increment analysis has the potential to help forensic anthropologists be much more specific in PMI determinations. Dental cementum anchors teeth via the periodontal ligament to the alveolar bone. In cementum formation, hypermineralized layers of extracellular matrix alternate with less mineralized layers, creat- ing alternating dark and light bands, analogous to tree rings. Cementum is first laid down immediately before the tooth erupts and additional layers are added throughout life. The main compo- nents of cementum layers are collagen bundles that become miner- alized by hydroxyapatite crystals. Research with comparative samples of known-age and known date-of-death individuals has demonstrated a consistent relationship between annual seasons and the formation of distinct increment types (1,2). The winter or arrested cementum increment appears under polarized light as an opaque band, while the summer or growth increment appears as a translucent band (Fig. 1). Together these bands represent 1 year of an individual’s life, pro- viding an annual record of that person’s life history. The total num- ber of pairs of opaque and translucent increments provides a means of determining the individual’s age at death within two and one half year ranges of error (1). To derive age at death, the number of pairs of bands is added to the age at which the tooth is known to erupt. In addition, cementum increments of increased thickness have been correlated with stressful events including pregnancy (3). Dirks et al. (3), for example, correlated increased increment thick- ness with menarche and first postweaning dry and rainy seasons in Ethiopian yellow baboons. Zooarchaeologists have long used dental cementum increment analysis to estimate season at death in mammals (4,5), yet no pub- lished studies have tested this method in humans. The current study builds on Wedel and Peabody (6) and Wedel and Bowman (7) and examines one full calendar year’s worth of samples in an attempt to identify the timing of increment formation in humans, and thus provide a method by which season at death could be determined in forensic cases. Materials and Methods Extracted teeth were obtained from patients of a local oral surgeon. Extraction was conducted for a variety of reasons ranging from orthodontics, periodontal disease, fitting for dentures, etc. Because the teeth were obtained from one dental office only, the donations came in sporadically at times, with only one donation for the month of December, 2004, and no donations for the month of January while the office was closed (Fig. 2). The cooperating oral surgeon was at his busiest in the months of October, March, and April. From each individual, the dental office staff acquired informed consent according to procedures approved by the University of Cali- fornia Santa Cruz Human Subjects Committee. Staff members recorded the individual’s date of birth and the date of the extrac- tion, which is used here as a proxy for date of death. Recent stud- ies involving human teeth (1,8–10) have indicated that no statistical difference exists in cementum accumulation of different teeth within a single individual. For this reason no specific tooth was required. The study sample was comprised of all tooth types, including incisors, canines, premolars, and molars. 1 University of California, Merced, School of Social Sciences, Humanities, and Arts, Merced, CA 95343. *Presented at the 57th Annual Meeting of the American Academy of Forensic Sciences in Seattle, WA, February 20–25, 2006.  This project was funded by a 2005 Forensic Sciences Foundation Acorn Grant. Received 28 Oct. 2006; and in revised form 11 April 2007; accepted 21 April 2007; published 21 Dec. 2007. J Forensic Sci, November 2007, Vol. 52, No. 6 doi: 10.1111/j.1556-4029.2007.00546.x Available online at: www.blackwell-synergy.com 1334 Ó 2007 American Academy of Forensic Sciences