STATISTICAL RESEARCH ON THE DENTAL HYGIENE OF PREMATURE INFANTS

Part 1: On the Decay of the Deciduous Teethand the Body Weight

Abstract

When medical examination of small infants and premature infants in Tokyo City were made, clinical tests on teeth were also made at the same time. When premature infants, that is, infants whose number of months within the womb was less than nine and a half months, and the weight of the body at the time of birth less than 2500 grams, were picked out from the results obtained on the above mentioned occasion, it was found that there were the following number of premature infants, and number of teeth.
Male infants 162 Number of teeth 2056
Female infants 209 Number of teeth 2664
Total number of infants 371 Total number of teeth 4720
Precise study was conducted on these infants.
For male and female infants below 2 years of age, an inspection was held every two months, infants two years of age, every six months, infants above three years of age, once every year.
The infants weighing between 2301 and 2500 grams at birth were put into “heavy (A) class” and infants weighing 2300 grams or less put into the “ light (B) class ”.
Next, the def condition, that is, the percentage of decayed experienced infants, the average number of decayed teeth per person and percentage of decayed experienced teeth were obtained.
The results were compared with those reported by MISU (1960) concerning the def condition of ordinary infants. Furthermore, the present body weight was divided into three groups, namely, “ heavy ”, “medium ”, and “ light ”, in accordance with the limit of M±1/2σ given by the body growth value reported by FUNAKAWA (1961).
After that, the relation between the def condition and growth type of those belonging to the groups of “ A to A ”, “ B to A ”, “ A to B ”, and “B to B” were studied.
When the def condition was observed according to the age and type of teeth, the following results were obtained.
1. As for the def for ordinary infants compared with the infants according to the weight of the body the time of birth, the premature infants show a higher of decay than the ordinary infants. As for the “ A ” group and the “ B ” group of the premature infants, both exhibit rather similar tendency.
2. As for the def condition according to the type of growth, under two years of age, all show similar values. However, for infants two years of age or above, “A to B” groups show the highest rate followed by “B to B” groups. The “A to A” and “B to A” groups show rather similar tendency. This is shown in the case of average number of decayed teeth per person and percentage of decayed experienced teeth.
3. As for the def condition according to the types of teeth, the deciduous upper central incisor and upper lateral incisor teeth show a high rate in the order of “A to B”, “B to B”, “A to A”, “B to A” groups. As for the deciduous canine teeth, a similar tendency could be observed for all groups, up to the age of three years. As for the 1st and 2nd deciduous molar teeth, both the upper and lower teeth show decay earlier for the “A to B”, and “B to B” groups than for any other groups. This tendency grows with the increase in age.
4. From the above mentioned facts, the writer firmly believes that for the dental measures concerning the premature infants, special attention should be placed on the infants which show a retarded growth rather than the actual body weight at the time of birth.
Especially for a two years old infant, care should be exerted towards the upper deciduous central, and uppers deciduous lateral incisor teeth, For a three year old infant, special attention should be placed on the 1st and 2nd deciduous molar teeth.