Effect of Some Environmental Factors on Sequence of Permanent Tooth Eruption

Although the chronology of tooth eruption is often dealt with in dental literature, there are inadequate data available on the sequence of eruption. Statements are restricted mostly to the sequence of the mean eruption ages of the different teeth, without taking into consideration the individual values scattered around the mean. In this way the impression is created that the eruption sequence of the teeth follows a definitive and regular pattern. The fact that this impression is wrong was pointed out by Livy ' as early as 1885. In a survey of permanent tooth eruption of some 4,000 children at Bolton, England, he published a comparison of the eruption sequences of the upper and lower mates of all tooth units on an individual basis. An inadequate attempt was made nearly 40 years later, as has been reported by Unglaube,2 to demonstrate variations of the eruption sequence, since combined data of males and females and apparently of upper and lower tooth mates were analyzed. Generally, however, no attention has been paid to the vari-ability of tooth eruption sequence. Hellman3 has written of his belief that mean erup-tion ages are a reliable criterion in judging tooth eruption sequence. According to his report, differences of the eruption sequence, as stated in reliance on mean eruption ages, are characteristic of different types of orthodontic anomalies. Adler and G6deny4 have reported a simple and efficient method permitting a study of tooth eruption sequence on an individual basis by relying upon one single clinical survey. * By this method, sequence of eruption was studied in the permanent dentition (1) between upper and lower mates, (2) between selected teeth of the upper jaw, (3) between selected teeth of the lower jaw, and (4) between selected tooth entities from the upper and other ones from the lower jaw.5 Differences in the eruption sequence have been shown between males and females.6 In contrast to the variability of the eruption sequence of the permanent teeth, the regularity of sequence has been demonstrated in the deciduous dentition.7 This method was used somewhat earlier than by us, in a pilot study that has been reported by Ephland.8 Tooth eruption sequence has been studied recently-using other methods-by Lo