Decayed-tooth
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  Decayed-tooth infected from mother and others !!   Report 1.                        On 1974,  W.H.O researched hiltribe-peoples living in Karakoram Mountains about the actual-situation of 108 people.   As a result, they research-team proved that the number of people having a decayed-tooth is very few.  The rate of experienced people with a decayed-tooth in Japan was 94.3% in the population.  But, Hiltribe-peoples living in Karakoram Mountains, its rate was 23.1% in all.  And, The research team investigated about the number of a decayed-tooth and an experienced decayed-tooth in the past.    Its average number was 7 teeth.   But, Hiltribe-peoples living in Karakoram Mountains, its average number was 0.5 teeth only !    Surprisingly, there was not a dentist in its village.   Moreover, they have not a habit to brush a tooth. 
  Report 2.                      One man living in Yokohama, Japan. He aparently has not experienced a decayed-tooth since he was born.   Usually, he brushes his tooth after a breakfast once a day. Its time is 19 seconds only. too short-time !!    He don't brush his tooth after dinner and before going to bed.    The research-team examined his teeth about "Streptococcus-mutans".then, Streptococcus-mutans was not detected in his mouth.     As a result of research,  the number of people who has not experienced a decayed-tooth in the past; is 3% in all.     Dental plaque                                         Dental-Plaque is constituted with water<80%> and organic-compound<20%>.    Its organic-compound is constituted with bacteria and its metabolic-substances.    Calcified-tartar pasted up to a tooth is called "Calculus".  More than 100,000,000,000-bacteria contains in a dental-plaque 1g.  
   
                                              Streptococcus-salivarius     Streptococcus-mitis              Streptococcus-sanguinis       Streptococcus-mitior               Streptococcus-mutans           Porphyromonas-gingivalis         Bacterionema-matruchotii          Propionbacterium-acnes                                             These bacteria is not exist in a mouth after just birth।    Apparently,.....A decayed-tooth is a kind of an infectious-disease.     Most people infects mouth-bacteria from mother, father and others until become 3 years old.    The case infected from mother's saliva through a feeding-milk bottle is the most plenty of case.    With using a spoon after holding a food in mother's mouth, bacteria infects into a baby's mouth !    The period from 1year7months to 2year7months is most highly contagious.    If a baby don't be infect bacteria, it is hardly possible to become a decayed-tooth from that time.   Because good-bacteria increases on teeth.    And, they makes an Oral-Biofilm around each tooth.     In Japan, Dentists recommends not to use a milk-bottle for a baby.