Acquired pellicle on restorative material surfaces : a proteomics and microbiomics study

Abstract

The acquired pellicle serves as an interface between dental surfaces and the oral environment, playing a critical role in mediating early oral bacterial colonization. The development of dental biomaterials that modify the pellicle composition, and thereby help to shape the bacterial colonization, relies on a comprehensive appreciation of pellicle composition on dental materials. This study investigated and compared the protein composition of the acquired pellicle and the bacterial composition of the subsequent early dental plaque on various restorative materials using a proteomics and microbiomics approach.

Firstly, 2-h acquired pellicle formed in situ on smooth (average roughness < 0.2 μm) bovine teeth, resin composite (RC), glass ionomer cement (GIC), or casein phosphopeptide-amorphous calcium phosphate-modified GIC (CPP-ACP GIC, 3% w/w) were investigated. Specimens were mounted in custom-made appliance, then worn by ten healthy volunteers (mean age 26 ± 2 years). Individual level protein identification resulted in a total of 1,444 (487-1,086/person), 1,454 (645-1,051/person), 1,731 (454-1,475/person), or 1,597 (423-1,261/person) pellicle proteins detectable on bovine tooth, RC, GIC, or CPP-ACP GIC, respectively. Two hundred and sixty-five “core pellicle proteins” were identified, independent of substrate or the participant involved. Additionally, 1,072 (304-793/person) proteins were identifiable in the whole saliva, with 217 “core salivary proteins” detected. Among these proteins, 130 were present in both saliva and pellicle samples of all subjects. Quantitative proteomic analysis demonstrated prominent inter-individual variation in pellicle protein profile. Differential expression analysis revealed that only a few proteins exhibit different abundance among pellicle samples. When compared to the saliva, an overall similar distribution pattern was observed among pellicle formed on different materials regarding proteins showing both increased and decreased abundance. Seventy-five proteins displayed an increased abundance, while 17 proteins exhibited decreased abundance on all substrates (p < 0.05). Some of the increased proteins were identified as being related to “calcium-dependent protein binding” or “cell-cell adhesion mediator activity” by Gene Ontology enrichment analysis.

Meanwhile, the early dental plaque on different restorative material surfaces was investigated by placing the same batch of specimens (bovine tooth, RC, GIC, CPP-ACP GIC) in the oral cavity of the same participants for 12 hours. The colonized bacteria were evaluated using q-PCR and 16S rRNA gene sequencing. The in situ bacterial colonization, in terms of both total bacterial biomass and bacterial community composition, was similar among the restorative materials tested. The microbiota of early plaque comprised similar “core microbiota”, which were dominated by Streptococcus, Haemophilus, Neisseria, Gemella, and Prevotella, regardless of the type of underlying surface. Beta-diversity analyses revealed that most differences in the microbiota profile among samples were attributed to inter-individual variation, rather than the different materials. The microbial community composition of 12-hour in situ plaque appeared different from that of whole saliva.

The current work demonstrated similar protein composition of the 2-h in situ pellicle, as well as similar bacterial composition of the 12-h in situ plaque, on the tested smooth restorative material and tooth surfaces. The present findings may contribute to a better understanding of the process of protein adsorption and bacterial colonization on dental material surfaces.