Cannot confirm the above, but there are plenty of examples where cavities rates went DOWN when fluoridation ended, for example:
Caries frequency before and after discontinuation of water fluoridation in Kuopio, Finland
In spite of discontinued water fluoridation, no indication of an increasing trend of caries could be found in Kuopio. The mean numbers of fluoride varnish and sealant applications decreased sharply in both towns between 1992 and 1995. In spite of that caries declined.
Patterns of dental caries following the cessation of water fluoridation” [Canada]
The prevalence of caries (assessed in 5,927 children, grades 2, 3, 8, 9) decreased over time in the fluoridation-ended community while remaining unchanged in the fluoridated community.
Caries prevalence after cessation of water fluoridation La Salud, Cuba
In the past, caries has usually increased after cessation of water fluoridation. More recently an opposite trend could be observed: following the cessation of drinking water fluoridation, in contrast to an expected rise in caries prevalence, DMFT and DMFS values remained at a low level for 6-9-year-olds and to decrease for 10/11-year-olds. In the 12/13-year-olds, there was a significant decrease.
Decline of caries prevalence after the cessation of water fluoridation in the former East Germany
In contrast to the anticipated increase in dental caries following the cessation of water fluoridation in the cities Chemnitz and Plauen, a significant fall in caries prevalence was observed. This corresponded to the national caries decline and appears to be a new population-wide phenomenon. There is still no explanation for the pattern.
…dental caries in 12-year-old children residing in cities with and without fluoridated water supply… [São Paulo, Brazil]
There was no statistically significant difference between DMFT in municipalities of the same size, regardless of the presence or absence of fluoride in the water supply… Prevalence of caries in the region was ‘high’, with a DMFT of 4.82, thus failing to reach the goals set for the year 2000.
The fluoride content of drinking water and caries experience in 15-19 year old school children in Iba-dan, Nigeria
955 students aged 15-19 years randomly selected from eleven secondary schools in Ibadan metropolis were examined for dental caries. The fluoride level of the different water sources was between 0.02 and 0.03 ppm. [only] Forty-four (4.6%) of the children had dental caries. In conclusion, both the fluoride level and caries prevalence were low.
Prevalence and severity of dental caries in adolescents… [Mexico]
In an analysis of caries severity (DMFT > or = 4), both adolescents with very mild/mild and moder-ate/severe dental fluorosis have higher caries severity. Fluoride exposure (measured through fluorosis presence) does not appear to be reducing the caries prevalence (DMFT > 0) or caries severity (DMFT > or = 4) in these high-altitude communities.
[The effects of a break in water fluoridation [11 months] on the development of dental caries and fluorosis” Durham, North Carolina
It was concluded that while the break had little effect on caries, dental fluorosis is sensitive to even small changes in fluoride exposure from drinking water, and this sensitivity is greater at 1 to 3 years of age than at 4 or 5 years.