The use of stem cells to accelerate bone regeneration has been monitored in real time in rats using three-dimensional imaging. The work was carried out by Khalid Al-Hezaimi and colleagues at King Saud University, Saudi Arabia, in collaboration with No-Hee Park of the University of California. Mesenchymal stem cells were harvested from rat hind leg bones. The researchers then drilled holes in rat skulls and filled them with stem cells covered with collagen membrane with and without tricalcium phosphate granules, or collagen membrane alone. Micro-computed tomography revealed that differentiation of stem cells into mature bone cells took approximately 2 weeks. Bone regeneration over a 10-week period was significantly faster with the stem cell treatments. Adding tricalcium phosphate weakened the regenerated bone, despite previous work suggesting it might promote bone cell formation

A hormone secreted by bone-forming cells may play a critical role in the bone disorders in kidney disease. In their review Quan Yan, from the West China Hospital of Stomatology in Chengdu, and colleagues noted that levels of fibroblast growth factor 23 (FGF-23) increase with a decline in kidney function. Elevated levels have been linked to end-stage renal disease, cardiovascular disease and death. The mechanisms underlying this association with poor outcomes could be explained by the hormone’s ability to increase inflammation. FGF-23 is also thought to play a critical role in mineral ion disorders and bone metabolism in these patients. The authors suggest studying whether deactivating FGF-23 in kidney disease would halt bone damage without having other adverse effects on the body.

Collagen gel containing basic fibroblast growth factor could assist the regeneration of submandibular glands after damage during surgery. The slow healing of these large salivary glands, which lie beneath the floor of the mouth, causes difficulties with speaking, swallowing and digestion, and an increased susceptibility to oral infection. These problems can significantly impair a patient's quality of life. Fumitaka Kobayashi at Tokyo Dental College and co-workers explored the healing potential of basic fibroblast growth factor in collagen gel using rats that had been wounded to model surgical damage. They also monitored the proliferation and development of the specific types of cell involved in repairing the wounded tissue. Treating the wounds using collagen containing growth factor accelerated and improved healing to a greater extent than using collagen gel alone.

Overgrown molars in some prairie voles could help explain the development of continuously growing teeth in rodents, say US researchers. All rodents have incisors that grow continuously throughout their lives but voles also possess continuously growing molars. Andrew Jheon at the University of California, San Francisco, and co-workers noticed that three animals in their vole colony showed unusually large molar protuberances and that these characteristics were passed on to their offspring. In some cases, the extra-large molars became infected or even broke through into the brain. The incisors of the affected voles appeared to be normal, leading the researchers to suggest that there are important genetic regulatory differences between incisors and molars. Specifically, the unrestricted molar growth may be caused by mis-regulation of a unique group of molar dental stem cells.

Diseases of the mouth lining, or oral mucosa, occur with a loss of nerve endings crucial for sensing touch, research from Germany suggests. The perception of touch in the oral mucosa involves Merkel cells, which join to Aβ-nerve fibres to send impulses to the central nervous system. Yüksel Korkmaz and co-workers at the University of Cologne examined the distribution of Merkel cells and Aβ fibres in healthy tissues and in tissues with the diseases lichen planus and hyperkeratosis. They found that the diseased tissues contained far fewer Aβ-nerve endings, and these were rarely joined to Merkel cells, implying that both diseases impair the sense of touch in the mouth. Based on their findings, the researchers suggest that a healthy mucosa is essential before applying dental prostheses. This will facilitate a harmonic occlusion and protect the oral mucosa against harmful unphysiological occlusal forces, which may occur after impaired sensation in the mouth.

A combination of vitamin D₃ and the hormone calcitonin may restore normal growth of the lower jaw bone in young patients with diabetes. Diabetes impairs the growth of bones, including those of the head and face, potentially causing dental problems in young patients. Vitamin D₃, which is produced by human skin exposed to sunlight, is known to improve survival of cells that build new bone; calcitonin is known to decrease the activity of cells that resorb bone. Mona Abbassy at King Abdulaziz University in Jeddah, Saudi Arabia, hypothesized that combining the two treatments could have synergistic effects and studied the effects in young rats, using molars as indicators of bone growth. Intermittent injections of vitamin D₃ and calcitonin restored normal bone growth, and show promise for treatment of young patients with diabetes.

The combined use of antibacterial toothpaste and mouthwash containing essential oils affects bacterial growth on retainers. Following orthodontic treatment, fixed retainers are often used to prevent teeth moving back to pre-treatment positions. However, bacteria causing oral disease tend to accumulate along the retention wires. A team from the Netherlands led by Yijin Ren at the University Medical Center Groningen has examined the effect of various oral health-care regimens on bacterial growth on retention wires. Although the use of antibacterial toothpaste alone decreased the viability of bacteria on the wires, a greater effect was observed when a mouthwash was subsequently used. Using both products minimized the growth of certain pathogenic bacteria, suggesting that the toothpaste makes small changes to the surfaces of the bacterial cells, facilitating their removal by the oils in the mouthwash.

The antibacterial activity of dental composites with ammonium polymer additives depends on the polymers' chain length. Dental composites formed from calcium phosphate in its nanoparticulate form are used as a remineralization agent for tooth lesions and to prevent tooth decay. To further prevent decay, which occurs following bacterial biofilm formation, antibacterial agents can be added to the composites. Hockin HK Xu, University of Maryland, USA, Yu-Xing Bai at Capital Medical University in Beijing, and colleagues synthesized quaternary ammonium methacrylates with chain lengths varying from 3 to 18 carbons, and assessed their anti-biofilm activity in calcium phosphate composites. The antibacterial efficacy increased with chain length until a maximum was reached at 16, the efficacy decreasing thereafter. The maximum efficacy resulted in a 10-fold reduction in biofilm metabolic activity and acid production, without any detrimental mechanical effects.

A therapeutic technique based on electromagnetic pulses may provide relief from pain caused by grinding teeth during sleep. Sleep bruxism is a condition in which sufferers grind their teeth continuously at night, causing significant discomfort and jaw pain. In a pilot study, Jing-Lu Zhang at Nanjing Medical University, China, and co-workers investigated the effects of a non-invasive technique called repetitive transcranial magnetic stimulation (rTMS) on sleep bruxism in 12 patients. The team used electromagnetic coils to send 20 min of targeted magnetic pulses to the primary motor cortex of each patient every day for 5 days. The patients rated their levels of pain before, during and after rTMS treatment, and reported a significant drop in soreness levels. Further trials will verify if rTMS therapy is beneficial for those suffering from sleep bruxism.