The microbiology of dentin invasion

The National Institute of Dental and Craniofacial Research awarded The Children's Hospital Corporation, doing business as Boston Children's Hospital, $539,217 on September 3, 2026, under the Oral Diseases and Disorders Research program (CFDA 93.121) to investigate the microbiology of dentin invasion in dental caries.

The project addresses how cariogenic microbes invade dentin—the tooth structure beneath enamel—and reach the pulp, causing toothaches, periapical inflammation, abscess, and systemic infection. The research characterizes the spatial distribution and identity of bacterial and fungal species that colonize dentin tubules, determines their capacity to invade and traverse the tubular network, and identifies mechanisms that distinguish dentin caries from surface biofilm pathogenesis. Recent technical innovations in histologic approaches have revealed that dentin caries exhibits dissolution from within tubules and a unique microbial spatial biology in which individual tubules harbor either fungi or bacteria predominantly, unlike surface biofilms where mixed consortia occur.

Work is performed at Boston Children's Hospital in Boston, Massachusetts, with a period of performance from September 3, 2026, through September 2, 2027. The assistance type is a Project Grant, consistent with the National Institute of Dental and Craniofacial Research's mission to advance fundamental knowledge about dental, oral, and craniofacial health and translate findings into prevention and treatment strategies.

Abstract

Dental caries is the most common chronic disease of childhood. Severe forms are common, can cause pain and serious systemic infections, and are costly to treat. Caries begins by undermining the outer tooth enamel which eventually fractures, creating a visible cavitation that eventually reaches the underlying dentin. The serious consequences of caries: toothaches, periapical inflammation and abscess, as well as facial infection from tissue invasion, all result from microbial access through the dentin tubules to the pulp, the living core of the tooth. Despite its critical role in pathogenesis, the mechanism of microbial invasion of dentin is largely unstudied, and methods to overcome the challenges of studying this hard tissue are underdeveloped. Once microbes destroy the enamel and reach the dentin, preliminary studies suggest that the biology changes. Dentin, unlike enamel, has a much higher protein content, lower mineral content, and is structured around a network of microchannels that communicate directly with the pulp. These channels provide a fast-track conduit for microbial invasion that is very different from the enamel with its solid crystal structure overlaid with a well- studied surface biofilm. Recent technical innovations by this team of investigators in adapting histologic approaches have provided new insights. Based on these recent studies, dentin caries appears to be driven by dissolution of tooth structure from within the tubules and exhibits a unique microbial spatial biology within tubules that is unlike that found in surface biofilms. Both fungi and bacteria-filled tubules are common, but unlike surface biofilms, single tubules primarily harbor either fungi or bacteria, but not both. To better understand dentin caries, we need to first spatially identify the species or consortia of species that are involved, and then determine their ability to invade tubules, and their ability to advance the lesion front by destruction of dentin. Aim 1 will comprehensively determine species-level bacterial and fungal microbial profiles in carious dentin as a function of depth within a carious lesion using DNA sequencing of serial sections of carious human teeth. Aim 2 will characterize the high-resolution spatial biology of these bacteria and fungi within dentinal tubules in human teeth and then test their invasive potential in an in vitro dentin model system. Aim 3 will identify the species or consortia of species responsible for demineralization and collagen degradation in tubule invasion, elucidating mechanisms of microbial penetration, demineralization, and collagen degradation using clinical samples and in vitro model systems that mimic the dentin environment. These aims address a significant and critical stage of caries , microbes invading through dentin towards the pulp. They will identify the microbes responsible for invasion, demineralization, collagen degradation and they will begin to elucidate the mechanistic basis of critical microbe-microbe interactions. IT is a conceptually innovative new direction in caries research, targeting an understudied, and key pathogenic process, and could lead to improved preventive and therapeutic strategies for a significant public health problem.