Triangular teeth

About a decade ago, I lived in Manila, Philippines for a while. I met a couple of US college students who were working with street children in Manila. Anyone who thinks poverty in the US is just the worst needs to look outside this country to see how much worse it can get. (https://en.wikipedia.org/wiki/Street_children_in_the_Philippines) The street children in Manila beg and sell flowers in the street, weaving around traffic and breathing in exhaust. It is common for them to inhale dangerous chemicals like glue. They have awful tooth decay because carbonated beverages are cheaper than milk, so they drink a lot of cola and other soda pop; on numerous occasions I saw young Filipino children with mouths full of triangular teeth from tooth decay.

Primary teeth are more susceptible to tooth decay from soda pop than are "adult" teeth:

Comparison of the microhardness of primary and permanent teeth after immersion in two types of carbonated beverages.
OBJECTIVES:
The consumption of carbonated beverages is one of the etiological factors that cause dental erosion. The purpose of this research was to compare changes in the microhardness of permanent and primary teeth after immersion in two types of carbonated beverages.MATERIALS AND METHODS:
This investigation was done on 30 healthy permanent molars and 30 healthy primary canines. Each group of primary and permanent teeth was subdivided into three groups of 10 teeth. The teeth was immersed in 40 ml of each of the three beverages for 5 min. One subgroup was immersed in water (as a control). The next was immersed in Lemon Delster and the last subgroup was immersed in Coca-Cola. The microhardness of enamel was measured using the Vickers method before and after immersion. Finally, the data was analyzed by paired t-test, one-way analysis of variance, and t-test.RESULTS:
Microhardness reduction in the primary teeth was significant in both the Lemon Delster and Coca-Cola groups (P < 0.05). This reduction was also statistically significant in the permanent teeth (P < 0.05). A comparison of the enamel changes in the primary teeth with permanent teeth after immersion in both beverages showed a greater microhardness reduction in the primary teeth in both the experimental groups.CONCLUSIONS:
Coca-Cola and Lemon Delster caused a significant reduction of microhardness in tooth enamel. This reduction was greater in primary teeth than in permanent teeth, and was also greater after immersion in Coca-Cola than after immersion in Lemon Delster.

https://www.ncbi.nlm.nih.gov/pubmed/27583223