There is both conflicting and promising evidence that administration of “good” bacteria, or probiotics, prevents biofilm-related infections. Despite data showing that probiotics contribute to maintaining a healthy gut, a review by Claudia Vuotto and colleagues from the IRCCS Fondazione Santa Lucia, Rome, Italy, suggests that the effects of probiotics on other conditions in which bacteria grow as aggregates in biofilms are unclear. Several lactic-acid producing bacteria benefit the host by reducing the growth of toxic bacteria and stimulating an immune response. However, for the treatment of biofilm-associated oral diseases, genitourinary and wound infections, the effects are highly dependent on the biofilm's composition and the probiotic strain that is used. Further studies are required to identify the most effective strains to eradicate such biofilms and tackle one of the most urgent challenges in anti-bacterial drug development.
Sucrose sugar and xylitol sweetener both activate genes involved in tooth decay in a bacterium commonly found in the human mouth. Eva-Maria Decker and her colleagues at the University of Tübingen, Germany, cultured Streptococcus mutans in a glucose-rich broth and in the same broth containing sucrose or xylitol. The bacteria formed complex communities called biofilms under all three conditions. The presence of sucrose increased the bacteria’s metabolic activity throughout the various biofilm layers. Despite previous claims that xylitol helps prevent cavities, the natural sweetener did not affect bacterial viability. Both sucrose- and xylitol-supplemented media led to increased expression of several genes involved in biofilm formation. The study, one of only a few concerning the effects of xylitol on S. mutans biofilms, calls into question the effectiveness of xylitol in preventing tooth decay.
Maps of chromosomal modifications could help scientists to better understand the timing and organization of tooth development. Chromosomal DNA is arranged around proteins called histones, which can be chemically modified at different sites. These modifications can boost or suppress gene activity, and researchers led by Xue-Dong Zhou of Sichuan University set out to examine their involvement in tooth formation. They examined two different histone modifications, one activating and one suppressing, at five different time-points in pulp and enamel development. They found that many sites in the young tooth exhibit both modifications, a state believed to prime cells to respond rapidly to developmental signals. Indeed, immature cells showed gene-activating modifications while more developed enamel and pulp cells tended to show inhibitory modifications. Closer examination of these patterns could lead to a more detailed timeline of tooth development.
Understanding of the pathogenesis of oral cancer could be enhanced by an animal stem cell model created by scientists in Taiwan. Oral squamous cell carcinoma (OSCC) accounts for 90% of oral malignancies worldwide. Tobacco chewing has led to high rates of OSCC in males in Central and Eastern Asia, in particular. Although the behaviour of cancer stem cells is known to be crucial in the early stages of the disease, little is understood about OSCC stem cell mechanisms. Now, Yuk-Kwan Chen and colleagues at Kaohsiung Medical University have developed the first viable model for OSCC stem cell study, successfully culturing and extracting cancer stem cells from rabbit OSCC. These cells possess useful traits for further study including self-renewal and the ability to initiate tumor growth.
Decreased immune response and colonization by certain bacteria may increase risk of bisphosphonate-related osteonecrosis of the jaw (BRONJ). Deepak Saxena of the New York University College of Dentistry, USA, and colleagues have shown that cancer patients who have been treated with bisphosphonates to reduce bone loss can, paradoxically, experience localized bone loss from the jaw. In a study of 30 oral surgery patients, Saxena and colleagues used a genetic approach to identify oral bacteria in BRONJ lesions and compared the immune responses of BRONJ patients and controls. BRONJ patients showed decreased immune response and more frequent colonization by opportunistic pathogens such as Parvimonas, Fusobacterium, Eubacterium besides, Streptococcus onto the BP-bound bone contributing to jaw necrosis. Some unnamed or uncultured bacteria were only found in BRONJ and bisphosphonate-treated patients. This study of the relationship between microbial colonization and immune response provides insights into the disease process in BRONJ.
Root canal surgeries performed with a new kind of material could successfully entrap problematic bacteria and prevent tooth abscesses. A team led by Kee-Yeon Kum from the Seoul National University School of Dentistry, South Korea, prepared roots from 60 extracted human premolar teeth. They exposed half of the teeth to Enterococcus faecalis, a bacterium commonly found in infections in root-canal treated teeth, the remaining teeth acting as controls. The roots were then filled with either a phosphate-buffered saline (PBS) solution or OrthoMTA, a newly developed type of mineral trioxide aggregate (MTA) cement composed mainly of tricalcium silicate. After incubation periods ranging from one to 16 weeks, the researchers examined the teeth using scanning electron microscopy. They found that OrthoMTA-filled roots had higher rates of mineralization and could seal or ‘entomb’ the bacteria dentinal tubules.
A plant-derived compound with therapeutic potential may inhibit pain signals through its effects on specific nerve cell proteins. Scientists have recently begun exploring the anti-cancer, anti-inflammatory and neurological effects of chlorogenic acid (CGA), a molecule produced by bamboo and other plants. Jie-Fei Shen and colleagues at Sichuan University in China examined the effects of CGA on two ‘potassium-gated voltage channel’ (KV) proteins, which participate in nerve cell signaling. The researchers examined cells from the rat trigeminal ganglion, a nervous system structure that detects and responds to pain. CGA increased the activity of both KV proteins, and Shen and colleagues predict that the resulting response would gradually dampen trigeminal pain signaling. These findings could assist the development of drugs that block the severe discomfort associated with inflammatory and neuropathic pain.
Non-veneered zirconia crowns respond well to clinical polishing leaving a smooth finish to help combat decay, research from Germany states. Zirconia (zirconium oxide) is a high-strength material commonly used for all-ceramic tooth restoration. Zirconia crowns are often veneered with dental porcelain but the veneer is prone to chipping, particularly during the clinical polishing and grinding carried out after dental restoration procedures. The resulting rough surfaces can wear down opposing teeth and attract plaque. Rim Hmaidouch and co-workers at the Johann Wolfgang Goethe University in Frankfurt tested the effect of polishing and grinding on zirconia crowns with and without veneers, aiming to find the best quality finish. They found that, after grinding and polishing procedures, glazed zirconia with no porcelain veneer had fewer defects and less surface roughness than veneered zirconia.
We report a 59-year-old patient with malignant acanthosis nigricans associated with metastasis of endometrial carcinoma. The patient presented papillomatosis lesions that appeared to be benign on multiple skins of body folds, particularly on lips. The lesions in lips and axilla had histological characteristic appearances of acanthosis nigricans, while the masses in abdomen and pelvis were metastasis endometrial adenocarcinoma. The article highlights the importance of biopsy and histopathological diagnosis in presumed benign lesions and the role of doctors in screening for body internal tumors.
Mineral trioxide aggregate (MTA) is considered at the present time as the gold standard for root-end filling in endodontic surgery. However, this biocompatible material presents several drawbacks such as a long setting time and handling difficulties. The aim of this article is to present a new commercialized calcium silicate-based material named Biodentine with physical improved properties compared to MTA in a clinical application. Two endodontic microsurgeries were performed by using specific armamentarium (microsurgical instrumentation, ultrasonic tips) under high-power magnification with an operatory microscope. Biodentine was used as a root-end filling in order to seal the root canal system. The two cases were considered completely healed at 1 year and were followed for one more year. The 2-year follow-up consolidated the previous observation with absence of clinical symptoms and radiographic evidence of regeneration of the periapical tissues.