The diverse immune responses provided by T cells in the lining of the oral cavity have been reviewed by US and Chinese researchers. The oral-pharyngeal cavity is the gateway to the gastrointestinal (GI) and respiratory tracts, and is exposed to microbes, food particles and other substances. The oral mucosal layers contain many different types of T cells that protect against infection but detailed knowledge of their function is limited. WanJun Chen, Qian-Ming Chen and co-workers at the National Institutes of Health in Maryland, and Sichuan University in Chengdu, base their review on the more established knowledge of the GI mucosal system. They find that the oral cavity lining has many similar functions to the lining of the GI but produces some unique signalling proteins. The authors highlight the need for more research into this important immune barrier.

A protein involved in tooth mineralization, although found in the nucleus, does not seem to play a role there during tooth formation. Dentin matrix protein 1 (DMP1) is present both in the nucleus and in the cytoplasm of odontoblasts, cells that form part of the dental pulp. To examine DMP1's role during embryonic tooth development, a team led by Jian-Quan Feng of the Texas A&M University Baylor College of Dentistry, USA, bred transgenic mice that only express DMP in the nucleus. These mice displayed dental defects and delayed tooth eruption similar to the defects seen in mouse strains with no functional versions of DMP1 in the nucleus or the cytoplasm. A human patient with a DMP1 gene mutation that causes only nuclear protein localization also exhibited tooth abnormalities consistent with rickets.

Bone-forming cells drastically alter their gene expression patterns in response to the hormone estrogen, according to researchers in China. A team led by Hui-Qiang Sun from Shandong University used microarray analyses to identify all the genes in a mouse bone-forming cell line (MC3T3-E1), where expression increased or decreased following treatment with a form of estrogen known as 17-β estradiol. Approximately 5 400 genes showed changed expression patterns. The researchers classified these genes into more than 1 500 different functional groups involved in approximately 50 different molecular pathways. In general, genes associated with cell proliferation and differentiation were switched on by estrogen, whereas genes involved in programmed cell death and bone resorption were switched off by the hormone treatment. The findings could guide therapies that aim to promote bone regeneration.

A strategy for suppressing enzymes involved in inflammation could improve patient response to endodontic repair of damaged pulp tissue, report dental researchers in Korea. Direct pulp capping can preserve the health of an infected tooth, although tissue inflammation can undermine the efficacy of this intervention. Proteins known as matrix metalloproteinases (MMPs) contribute to inflammation in numerous different cell types including dental pulp. Sun-Young Kim and colleagues at Kyung Hee University identified a molecule that may limit MMPs’ effects. They found that all-trans retinoic acid (ATRA), a derivative of vitamin A, can reduce production of MMP-2 at non-toxic doses in cultured human dental pulp cells. Although ATRA did not inhibit production of MMP-9, another enzyme involved in pulp cell inflammation, follow-up experiments using inflamed as well as healthy pulp cells should help clarify ATRA’s anti-inflammatory effects.

Stem cells injected into damaged salivary glands help promote tissue healing, according to a study in rats. A team led by Nicole Rotter from the Ulm University Medical Center, Germany, surgically injured submandibular salivary glands in rats. The researchers then injected mesenchymal stem cells (MSCs) derived from a rat bone marrow cell line into the tail veins. They observed a migration of the stem cells into both healthy and damaged salivary glands. Rotter and her colleagues also injected the MSCs directly into the rats' salivary glands, where the stem cells recruited immune cells, including leukocytes and macrophages, to the site of injury. MSC therapy thus promotes beneficial immune responses and could help people overcome the dry mouth side effects that result from salivary gland damage associated with radiation administered for head and neck cancer.

A screening tool that uses multispectral light can help clinicians and dentists discriminate between oral cancer and other mouth diseases. The Identafi device uses three different types of light to diagnose abnormalities in the oral mucosa. Standard examinations of mouth lesions can be made with white light; violet light reveals tissue fluorescence and amber-green light can then reveal differences in blood supply between healthy and diseased tissues. Diana Messadi and her colleagues at the University of California, Los Angeles, School of Dentistry, USA, tested the device in 21 people with various oral lesions. The researchers also took tissue biopsies and measured levels of CD34, a marker for endothelial cells. They showed the reflectance of green-amber light correlated with the degree of cellular abnormality. This pilot study supports the use of Identafi for detecting cancerous and precancerous oral lesions.

Plant-derived compounds called proanthocyanidins can protect tooth dentin from breakdown by enzymes. A team led by Ji-Hua Chen from the Fourth Military Medical University in Xi'an, China, treated human third molars with a grape-seed extract rich in proanthocyanidins, a naturally occurring plant compound. The researchers exposed slabs of dentin from these teeth to enzymes that break down collagen, an important structural protein in dentin. Collagen breakdown is one of the main reasons for the deterioration of resin-dentin bonds over time. They found that dentin specimens treated with proanthocyanidin exhibited lower levels of collagen breakdown and maintained higher bond strengths than non-treated control samples. The proanthocyanidin treatment also inhibited the dental tissue from producing gelatinases, enzymes that further break down collagen. This type of treatment could help strengthen the bonding of dentin for clinical applications.

Examining the angulation of molars could inform orthodontists about the best way to treat malocclusions, according to a large Chinese study. Malocclusion, or misalignment of teeth, has often been classified based on the position of incisors but molars are arguably more important for maintaining strong tooth anchorage. Tian-Min Xu at Peking University in Beijing and co-workers examined medical records and X-rays from 1, 403 malocclusion patients to extract data on molar angles. The data showed that the upper first molar tended to angle towards the back of the mouth in adolescents but angled forwards in adults. The team also found significant relationships between molar angulation and the relative positions of the maxilla and mandible. This unprecedented dataset should help dental practitioners to understand the long-term effects of orthodontic appliances on tooth anchorage and alignment.

The fibrous epulis, a common tumor-like lesion of the gingiva, appears in the interdental papilla as a result of local irritation. Lesions are asymptomatic and have a variable growth rate. A 75-year-old woman was referred for the evaluation of a large painless gingival mass. It had started 10 years back and has been increasing in size the last year. No bone involvement was noted. The tumor was totally removed by excision with surgical scalpel under local anesthesia without teeth extraction. The microscopic findings were suggestive of a fibrous epulis. Differential diagnosis, clinical considerations and factors to prevent recurrence are discussed.

Spindle cell lipoma (SCL) is a benign lipomatous neoplasm typically located in the posterior neck and back of older males. It presents as a well-circumscribed mass in the buccal mucosa, tongue, floor of the mouth or hard palate. There are only two case reports of SCL in the gingiva and alveolar ridge. Here, we report a case of SCL in the mandibular mucogingival junction of a 68-year-old male. Clinical, histopathological and immunohistochemical findings are presented. Although oral SCL is rare, it should be considered in the differential diagnosis of spindle cell neoplasms occurring in the oral cavity.