Excess albumin in enamel is a characteristic of the prevalent developmental dental defect known as chalky teeth or molar hypomineralization (MH). This study uses proteomic analyses of pig teeth to discern between developmental origin and post-eruptive contamination and to assess the similarity to hypomineralized human enamel. Here, the objective is to address the urgent need for an animal model to uncover the etiology of MH and to improve treatment. Porcine enamel is chalky and soft at eruption; yet, it hardens quickly to form a hard surface and then resembles human teeth with demarcated enamel opacities. Proteomic analyses of enamel from erupted teeth, serum, and saliva from pigs aged 4 (n = 3) and 8 weeks (n = 2) and human (n = 4) molars with demarcated enamel opacities show alpha-fetoprotein (AFP). AFP expression is limited to pre- and perinatal development and its presence in enamel indicates pre- or perinatal inclusion. In contrast, albumin is expressed after birth, indicating postnatal inclusion into enamel. Peptides were extracted from enamel and analyzed by nano-liquid chromatography-tandem mass spectrometry (nanoLC-MS/MS) after tryptic digestion. The mean total protein number was 337 in the enamel of all teeth with 13 different unique tryptic peptides of porcine AFP in all enamel samples but none in saliva samples. Similarities in the composition, micro-hardness, and microstructure underscore the usefulness of the porcine model to uncover the MH etiology, cellular mechanisms of albumin inclusion, and treatment for demarcated opacities.

Background: Silver diamine fluoride (SDF) is a dental biomaterial with cariostatic properties that are thought to be owing to, in part, to its antimicrobial activity. This study examines the mechanisms by which SDF may impact the oral microbiota. Methods: This case-control study uses samples from carious lesions of primary teeth with or without SDF treatment; the authors used microbial viability testing and next-generation sequencing to compare untreated or SDF-treated carious surface biofilm and subsurface carious dentin. Results: Viability testing of surface biofilm from carious lesions with or without SDF treatment visualized by confocal laser scanning microscopy revealed no change in microbial viability several weeks after SDF treatment. Microbial community composition of carious surface biofilm before and after SDF treatment was determined using 16S rRNA gene sequencing. Comparison of the microbiota by permutational multivariate analysis of variance revealed no significant difference between the carious surface biofilm before and after SDF treatment. To examine for changes in subsurface bacteria in the setting of SDF treatment, excavated subsurface carious dentin from untreated or SDF-treated carious lesions were profiled using 16S rRNA gene sequencing and compared with permutational multivariate analysis of variance, which revealed a significant difference between SDF-treated and untreated lesions (P =.006). The mean abundance of 15 species was significantly different between no SDF and SDF-treated subsurface carious dentin samples on the basis of negative binomial regression analysis. Conclusions: Although SDF does not significantly alter the carious surface biofilm microbial community composition, it promotes a shift in community membership deeper within dentin tubules, representing a previously unrecognized mechanism of action for SDF in caries arrest.

In this work, we exploit recent advances in metagenomic assembly and bacteriophage identification to describe the phage content of saliva from 5 mother-baby pairs sampled twice 7 - 11 months apart during the first year of the babies’ lives. We identify 25 phage genomes that are comprised of one to 71 contigs, with 16 having a single contig. At the detectable level, phage were sparsely distributed with the most common one being present in 4 of the 20 samples, derived from two mothers and one baby. However, if they were present in the early time point sample from an individual, they were also present in the later sample from the same person more frequently than expected by chance. The nucleotide diversity (π) in phage from the same sample or the same person was much lower than between different individuals, indicating dominance of one strain in each person. This was different from bacterial genomes, which had higher diversity indicating the presence of multiple strains within an individual. We identify likely bacterial hosts for 16 of the 25 phage, including an apparent inovirus that is capable of integrating in the dif site of Haemophilus species. It appears that phage in the oral cavity are sparsely distributed, but can be maintained for months once acquired.