Dental Tribune Asia Pacific Edition No.7+8, 2017

04 WORLD NEWS Dental Tribune Asia Paciﬁ c Edition | 7+8/2017 Researchers identify DNA sections responsible for periodontitis By DTI BERLIN, Germany: An international network of researchers led by sci- entists at the Charité—Universi- tätsmedizin Berlin in Germany has identiﬁ ed variations of certain DNA sequences that are clearly as- sociated with an increased risk of developing different forms of per- iodontal disease. For at least two gene regions, the study team found a highly signiﬁ cant association with the disease. In a genome-wide association study, the group, led by Prof. Arne Schäfer from the Charité Institute for Dental and Craniofacial Scien- ces, investigated the relationship between sequence differences in genetic information and the inci- dence of the disease in several thousand patients with aggressive and chronic periodontitis. The re- sults were compared with healthy individuals. “This type of study is very sys- tematic in nature. It aims to iden- tify the genes that have an effect on a person’s risk of developing a speciﬁ c disease,” Schäfer ex- plained. Millions of DNA sequence variants, distributed throughout the genome and describing most of a person’s genetic information, were examined in various patient groups. “DNA sequence variations can have an effect on a person’s risk of developing a particular dis- ease. By comparing frequencies of variants in patients and healthy controls, it is possible to ﬁ nd which areas of a chromosome are associated with the disease,” he added. The scientists found two gene regions that appeared to be associ- ated with an increased risk of de- veloping different forms of perio- dontitis. One of the two regions is responsible for the synthesis of al- pha-defensins (antimicrobial pep- tides), which are produced by spe- cialised immune cells. These im- mune cells, neutrophils, are part of the body’s immune response and are involved in the identiﬁ ca- tion and destruction of microor- ganisms. The second gene region inhibits the activation of these immune cells. “Our results show that the dif- ferent forms of gum disease share a common genetic origin,” said Schäfer. He emphasised: “This means that there are groups of pa- tients who are susceptible to de- veloping gum disease, but whose susceptibility is independent of other risk factors, such as smok- ing, oral hygiene or aging.” Worldwide, the prevalence of severe periodontal disease is es- timated to be about 11 per cent. The disease is considered com- plex because individual suscepti- bility is determined by the inter- action between the oral microbi- ome and the immune system, smoking and diet, as well as by metabolic disorders such as dia- betes mellitus. The response of the body to these factors is largely inﬂ uenced by the individual’s ge- netic make-up. The study, titled “A ge- nome-wide association study identiﬁ es nucleotide variants at SIGLEC5 and DEFA1A3 as risk loci for periodontitis”, was published in the July issue of the Human Molecular Genetics jour- nal. © Plan-B/Shutterstock.co m Less is more: Study looks into the traits of a “perfect” smile By DTI MINNEAPOLIS, USA: Lopsided, big, toothy, shy—smiles are described in many different ways. However, according to research from the University of Minnesota, how peo- ple perceive the facial expression in social interaction and non-ver- bal communication can differ sig- niﬁ cantly. In the study, the researchers asked 802 study participants to rate 27 computer-animated smiles on their perceived effectiveness (very bad to very good), genuine- ness (fake vs. genuine), pleasant- ness (creepy to pleasant) and emo- tion expressed (anger, contempt, disgust, fear, happiness, sadness or surprise). The animated expres- sion was altered by variations in the mouth angle, the extent of the smile, the degree to which teeth were shown and how symmetri- cally the smile developed. The ﬁ ndings suggest that for a winning smile—one that is per- ceived as effective, genuine and pleasant—less is more. In the study, smiles with a medium angle tended to be more favorably judged, while wide open-mouth smiles were often interpreted as a sign of fear or contempt. In fact, Asking participants to rate computer-animated smiles, researchers at the University of Minnesota investigated the traits that can distinguish a likeable grin from a grimace. the two lowest-rated smiles were both very toothy. Although research has sug- gested that facial symmetry is often perceived as being more beautiful than asymmetry, slightly crooked smiles were rated higher in the current study. According to the researchers, this result is con- sistent with principles of smile de- sign, in which dynamic symmetry, that is being very similar but not identical, allows for a more vital, dynamic, unique and natural smile compared with static symmetry. The study’s results could have broad applications in a variety of areas, such as facial reanimation surgery and rehabilitation in in- dividuals who have suffered from trauma, cerebrovascular accidents, neurological conditions, cancers or infections that have robbed them of the ability to express emotions through facial movement. The psychological and social consequences of facial impairment can be extensive. Research has shown that individuals with par- tial facial paralysis are often misin- terpreted, have trouble communi- cating, and often report symptoms such as anxiety and depression. The study, titled “Dynamic properties of successful smiles,” was published on 28 June in the PLOS ONE journal.

Dental Tribune Asia Pacific Edition No.7+8, 2017

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