When fire consumes a home, a vehicle, or an aircraft, one of the most pressing questions facing investigators is whether the victims can be identified at all. Extreme heat shreds DNA into fragments too small to analyze, and forensic teams often have only charred remains to work with. Teeth have long been considered the last bastion of genetic information in burned bodies, thanks to their dense mineralized armor. But a new study from researchers at China People’s Police University and BGI Forensic, published in the International Journal of Legal Medicine, provides the most detailed picture yet of exactly when that bastion falls — and the answer turns out to depend more on how long a tooth bakes than on how hot the oven gets.
The research team, led by Zirui Lu, Changle Li, Jinghui Yang, Xiaotong Wang, Jing Jin, and Fei Huang, systematically exposed dental samples to temperatures ranging from 200 to 500 degrees Celsius for periods of 10 and 20 minutes, then attempted to recover three different classes of genetic markers. Short tandem repeats, or STRs, are the workhorses of forensic identification, generating the familiar DNA profiles used in criminal databases. Single nucleotide polymorphisms, or SNPs, offer an alternative that can succeed even when DNA is badly fragmented because the target regions are shorter. Mitochondrial DNA, or mtDNA, exists in hundreds to thousands of copies per cell and has traditionally been the fallback for degraded samples. By tracking all three simultaneously, the researchers could construct a thermal survival hierarchy that had never been quantified this precisely.
The results reveal a startling sensitivity to time. At 200 degrees Celsius, extending the heating duration from 10 to 20 minutes caused STR detection to plummet from 97.09 percent to 81.39 percent, SNP detection to drop from 99.53 percent to 91.08 percent, and mtDNA sequencing coverage to collapse from an almost perfect 99.96 percent to a dismal 27.26 percent. In other words, simply doubling the exposure time — even at a temperature well below that of a typical house fire — was enough to wipe out nearly three-quarters of the recoverable mitochondrial genome. Within the 200 to 220 degree Celsius range, the duration of exposure exerted a stronger effect on DNA integrity than the temperature itself, a finding that challenges the intuition that heat intensity should be the dominant variable.
The critical cliff edge came at 250 degrees Celsius. After just 10 minutes at that temperature, no genetic markers of any type could be recovered from the dental pulp. By contrast, at 220 degrees Celsius for 10 minutes, nuclear DNA retained full detectability at 100 percent and mtDNA coverage still reached 76.48 percent. Prolonging the treatment to 20 minutes at 220 degrees drove STR detection down to 66.99 percent, SNP detection to 99.3 percent, and mtDNA coverage to 28.84 percent. For fire investigators, this defines a practical threshold: teeth that have been heated beyond roughly 250 degrees for any meaningful duration are unlikely to yield a conventional DNA profile, and sampling strategies must be planned accordingly.
Perhaps the most counterintuitive finding concerns mitochondrial DNA. Forensic practice has long treated mtDNA as the most durable target, relying on its enormous copy number to survive conditions that destroy nuclear DNA. This study demonstrates the opposite under thermal stress: mtDNA is actually more heat-vulnerable than nuclear DNA. The authors attribute this to three structural weaknesses. Unlike nuclear DNA, which is wrapped around histone proteins that shield it from damage, mtDNA lacks histone protection entirely. Its genome is also rich in adenine and thymine, the two nucleotides joined by only two hydrogen bonds rather than three, making those regions easier to denature. Finally, heat disrupts the circular conformation of the mitochondrial genome, breaking the closed loop that normally protects it from exonuclease attack. The high copy number, it turns out, simply cannot compensate for these structural drawbacks.
The study also compared the protective value of the tooth’s internal environment against its exterior. Bloodstains deposited on tooth surfaces — representing the kind of trace evidence that might cling to recovered remains — proved far less thermally tolerant than the pulp sealed inside. After 20 minutes at 200 degrees Celsius, STR and SNP detection rates in the surface bloodstains fell to 72.58 percent and 88.38 percent respectively, and mitochondrial DNA became completely undetectable. At 220 degrees for 10 minutes, the bloodstains still yielded an STR detection rate of 97.5 percent and full SNP detection at 100 percent, but mtDNA coverage dropped to a mere 16.9 percent. After 20 minutes at that same temperature, every marker type was unrecoverable. The mineralized shell of the tooth, in short, shields the pulp far more effectively than any surface stain can protect itself, reinforcing the long-standing recommendation that dental pulp should be the sampling site of choice.
Technically, the team employed two complementary genotyping strategies: capillary electrophoresis of STR markers, the gold-standard method used in forensic laboratories worldwide, and massively parallel sequencing, or MPS, which reads millions of DNA fragments simultaneously and can target short SNP amplicons suitable for degraded samples. They calculated marker detection rates across the temperature and time matrix and quantified mtDNA sequencing coverage to assess how much of the mitochondrial genome remained readable. The short-fragment MPS-SNP approach proved the most resilient across the thermal gradient, and the authors recommend it as the preferred strategy for severely degraded specimens where conventional STR profiling would fail.
The implications reach back to some of the most challenging identification efforts in modern history. DNA profiling of burned and fragmented remains has been central to victim identification after the World Trade Center attacks, the Bali and Jakarta bombings, and countless aviation disasters. Each of these efforts confronted the same fundamental problem: knowing which tissue to sample and which genetic technology to deploy when heat has already done its damage. By establishing precise temperature-time thresholds and a clear stability hierarchy — SNP greater than STR greater than mtDNA — the new study gives forensic laboratories a decision framework grounded in controlled experimental data rather than anecdotal experience. Exposure duration, the authors argue, should be treated as a formal parameter when assessing specimen quality, alongside the gross thermal appearance of the tooth itself.
The research was approved by the Scientific Research Ethics Committee of the Forensic Appraisal Center of the Ministry of Public Security and was funded through several Chinese national and institutional programs, including the National Key Research and Development Program of China. Its practical guidance is straightforward: prioritize dental pulp for DNA sampling from fire-exposed dental specimens, factor in the likely duration of heating when evaluating what remains recoverable, and turn to short-fragment MPS-SNP genotyping when degradation is severe. As wildfires intensify and urban fires remain a persistent threat worldwide, the humble tooth — and the delicate balance of time and temperature written into its DNA — may determine whether families ever receive answers about their lost loved ones.
Subject of Research: Forensic DNA recovery of STR, SNP, and mitochondrial DNA from teeth after thermal exposure
Article Title: Comparative study of STR, SNP, and mtDNA recovery in teeth after thermal exposure
Article References: Lu, Z., Li, C., Yang, J., Wang, X., Jin, J., & Huang, F. (2026). Comparative study of STR, SNP, and mtDNA recovery in teeth after thermal exposure. International Journal of Legal Medicine. https://doi.org/10.1007/s00414-026-04005-7
Image Credits: AI Generated
DOI: 10.1007/s00414-026-04005-7
Keywords: forensic science, DNA profiling, teeth, thermal degradation, STR, SNP, mitochondrial DNA, dental pulp, massively parallel sequencing, fire victims, DNA identification, International Journal of Legal Medicine
Cite Scienmag News
APA
MLA
Chicago
Ophelia Keating. (September 12, 2026). Teeth Under Fire: Time, Not Just Temperature, Decides DNA Survival. Scienmag. https://scienmag.com/teeth-under-fire-time-not-just-temperature-decides-dna-survival/
Ophelia Keating. “Teeth Under Fire: Time, Not Just Temperature, Decides DNA Survival.” Scienmag, 12 September 2026, https://scienmag.com/teeth-under-fire-time-not-just-temperature-decides-dna-survival/. Accessed 12 September 2026.
Ophelia Keating. “Teeth Under Fire: Time, Not Just Temperature, Decides DNA Survival.” Scienmag. September 12, 2026. https://scienmag.com/teeth-under-fire-time-not-just-temperature-decides-dna-survival/
Copy citation
Download RIS
Tags: dental pulpDNA identificationDNA profilingeffectiveness of dental DNA recovery after fire exposurefire victimsforensic challenges in massforensic DNA analysis in burned remainsforensic identification techniques for charred remainsforensic scienceimpact of fire on STR and SNP markersimpact of heat duration on DNA preservation in teethinfluence of temperature and time on DNA fragment integrityInternational Journal of Legal Medicinelimits of DNA analysis in burned bodiesmassively parallel sequencingmitochondrial DNArecent advancements in fire victim identificationresilience of dental tissue to extreme heatrole of teeth as DNA reservoirs in forensic investigationsSNPSTRteeththermal degradationthermal degradation of genetic markers in forensic science
