A Co-Association of Streptococcus mutans and Veillonella parvula/dispar in Root Caries Patients and In Vitro Biofilms.

Root caries in geriatric patients is a growing problem as more people are maintaining their natural teeth into advanced age. We determined the levels of various bacterial species previously implicated in root caries disease or health using quantitative real-time PCR in a pilot study of 7 patients with 1 to 4 root caries lesions per person. Levels of 12 different species on diseased roots compared to healthy (contralateral control) roots were measured. Four species were found at significantly higher levels on diseased roots (Streptococcus mutans, Veillonella parvula/dispar, Actinomyces naeslundii/viscosus, and Capnocytophaga granulosa) compared across all plaque samples. The level of colonization by these species varied dramatically (up to 1,000-fold) between patients, indicating different patients have different bacteria contributing to root caries disease. Neither of the two species previously reported to correlate with healthy roots (C. granulosa and Delftia acidovorans) showed statistically significant protective roles in our population, although D. acidovorans showed a trend toward higher levels on healthy teeth (P = 0.08). There was a significant positive correlation between higher levels of S. mutans and V. parvula/dispar on the same diseased teeth. In vitro mixed biofilm studies demonstrated that co-culturing S. mutans and V. parvula leads to a 50 to 150% increase in sucrose-dependent biofilm mass compared to S. mutans alone, depending on the growth conditions, while V. parvula alone did not form in vitro biofilms. The presence of V. parvula also decreased the acidification of S. mutans biofilms when grown in artificial saliva and enhanced the health of mixed biofilms.

Multicellular bacteria deploy the type VI secretion system to preemptively strike neighboring cells.

The Type VI Secretion System (T6SS) functions in bacteria as a contractile nanomachine that punctures and delivers lethal effectors to a target cell. Virtually nothing is known about the lifestyle or physiology that dictates when bacteria normally produce their T6SS, which prevents a clear understanding of how bacteria benefit from its action in their natural habitat. Proteus mirabilis undergoes a characteristic developmental process to coordinate a multicellular swarming behavior and will discriminate itself from another Proteus isolate during swarming, resulting in a visible boundary termed a Dienes line. Using transposon mutagenesis, we discovered that this recognition phenomenon requires the lethal action of the T6SS. All mutants identified in the genetic screen had insertions within a single 33.5-kb region that encodes a T6SS and cognate Hcp-VrgG-linked effectors. The identified T6SS and primary effector operons were characterized by killing assays, by construction of additional mutants, by complementation, and by examining the activity of the type VI secretion system in real-time using live-cell microscopy on opposing swarms. We show that lethal T6SS-dependent activity occurs when a dominant strain infiltrates deeply beyond the boundary of the two swarms. Using this multicellular model, we found that social recognition in bacteria, underlying killing, and immunity to killing all require cell-cell contact, can be assigned to specific genes, and are dependent on the T6SS. The ability to survive a lethal T6SS attack equates to "recognition". In contrast to the current model of T6SS being an offensive or defensive weapon our findings support a preemptive mechanism by which an entire population indiscriminately uses the T6SS for contact-dependent delivery of effectors during its cooperative mode of growth.

Supernumerary tooth autotransplantation to replace missing maxillary central incisor using three-dimensional replica: A 6-year follow-up.

INTRODUCTION: Tooth autotransplantation is a viable surgical treatment option for patients with missing permanent teeth. Premolars are generally used for autotransplantation but often require extensive modifications. This case report evaluates the use of supernumerary tooth as an alternative option for premolar autotransplantation. This report shows successful supernumerary tooth autotransplantation with 6-year follow-up. METHODS: A 13-year-old male with non-contributory medical history was referred for a missing maxillary left central incisor (#9) and presence of a supernumerary tooth. The clinical and radiographic examination revealed presence of supernumerary tooth with similar dimensions to a central incisor. The treatment plan included autotransplantation of the supernumerary tooth to replace the missing central incisor (short-term) and future implant replacement of the autotransplanted tooth when jaw growth ceases (long-term). The patient and parents consented to treatment. A 3-D tooth replica was constructed based on CBCT analyses. Site #9 was prepared using split ridge technique to create a socket to house the 3-D replica. Upon achieving proper socket form, the supernumerary tooth was extracted and autotransplanted in the prepared socket. The supernumerary tooth was splinted, and the bite opened posteriorly using composite to eliminate any occlusal interferences. RESULTS: The patient was followed up clinically and radiographically. The autotransplanted supernumerary tooth integrated well within the newly created socket and remained functional at the 6-year follow-up. CONCLUSIONS: The current case presents successful management of supernumerary tooth autotransplantation with 6-year follow-up. The results show stable periodontium with satisfactory functional and aesthetic results.