What really determines whether fluoride is safe, is the amount that is swallowed,” says Amid I. Ismail, BDS, MPH, MBA, DrPH, and Dean, Temple University, School of Dentistry in Dear Doctor Magazine. (1)
Dr. Ismail says, “Fluoride occurs naturally in soil, fresh and seawater varying dramatically in levels from as low as 0.01 to 8ppm or more....In actuality the “optimal” (most desirable or satisfactory) level is virtually impossible to calculate because of variations in fluoride levels in all sorts of foods and beverages. 
'For example, people living in temperate climates drink less than those in tropical climates. However, it cannot even be assumed that because a person lives in a community with non-fluoridated water, they are receiving low levels of fluoride. Fluoride ingestion can also result from drinking substantial amounts of soft drinks or juices. Most bottled waters contain less than 0.3 ppm; however, some contain close to or more than 1 ppm.”
"Breast milk and cow's milk are very low in fluoride,” says Ismail. Manufacturers voluntarily lowered fluoride levels in infant formula. But when concentrated infant formula is mixed with fluoridated water, infant formula fluoride levels are higher, says Dr. Ismail. Federal agencies, health departments and organized dentistry advise using non-fluoridated water to make infant formula to avoid damaging babies' teeth.
“Also, soy-based formulas are consistently higher in fluoride content than milk-based products. Other foods that have high fluoride content are teas, dry infant cereals and processed chicken, fish and seafood products,” says Ismail.

“It should also be emphasized that “topical” fluorides such as toothpaste can also have a systemic effect if inadvertently swallowed by young children,” cautions Dr. Ismail. Fluoride also gets absorbed into the bloodstream even when not swallowed.

"Tooth mottling should be monitored in communities to assess fluoride intake and recommendations made accordingly,” writes Ismail. 

However, few communities follow Dr. Ismail's advice and fluoridate the water without considering residents’ total fluoride intake from other sources. In fact, a Connersville, Indiana, study indicated children already ingested too much fluoride; but dentists lobbied successfully for fluoridation anyway. To our knowledge, no dental fluorosis studies have ever been published on this population.

Dr. Ismail questions whether mild fluorosis is acceptable any more with esthetics becoming more important in this day and age. He says, “decisions concerning this tradeoff could warrant reconsideration. Fluorosis varies in appearance from small white striations to stained pitting and severe brown mottling of enamel,” he writes.

“The main documented risk factors for fluorosis (in no particular order) are fluoride in water, infant formula reconstituted with fluoridated water, supplements and dentifrices,” he writes.

Dr. Ismail reports that “Commissioned by the EPA, a 2006 National Research Council (NRC) study has sparked the latest controversy. In addition to unsightly enamel fluorosis at 4 ppm and above, it claims: a possible increased risk of bone fracture in certain conditions; skeletal fluorosis; and potential to cause bone cancer...”

“Fluoride is incorporated into bone...after a point though it can make bone more brittle and at higher levels can cause “skeletal” fluorosis, which has a greater potential for painful joints and even fractures,” reports Ismail.

“The over use of fluoride during the first six to eight years of life represents the important period of tooth development when enamel fluorosis can occur. It is critical for parents to monitor fluoride sources to reduce the occurrence of white spots from fluorosis,” he writes.

The Centers for Disease Control reports that 60% of adolescents now suffer with dental fluorosis – 3% of it is moderate or severe. At the same time tooth decay rates are increasing in toddlers and untreated tooth decay has become epidemic.

In Kentucky, despite a 1977 fluoridation state-wide mandate, preschoolers cavity rates went from 28% in 1987 to 47% in 2001, according to the July/August 2003 journal, Pediatric Dentistry,

According to an 11/27/2011 news article, “In recent years, Northern Kentucky health officials have encountered more children with cavities in a state known for some of the worst teeth in the nation. Kentucky has the second highest rate of toothlessness in the U.S. The national average is 20.5 percent, while 38 percent of Kentuckians have lost their teeth.”(2) 
The article quotes Linda Poynter, the Northern Kentucky Health Department's oral health program manager. "I've seen too many 5-year-olds with rampant decay who are going to have a body full of abscesses, if (their dental problems) aren't taken care of," Poynter said.
The article continues, “In recent years, pupils in the Northern Kentucky schools that the local health department visits are experiencing more tooth decay. The percentage of students with tooth decay was 45 percent in 2009. That rose to 47 percent in 2010, and so far this school year, 49 percent of the children screened have tooth decay.”

It’s not just Kentucky, tooth decay went up after fluoridation began in San Antonio, Texas, also.

Last week, KENS 5 – TV reported “After 9 years and $3 million of adding fluoride, research shows tooth decay hasn’t dropped among the poorest of Bexar County’s children. It has only increased—up 13% in 2010, the latest date that data was available.
One out of two children in the Head Start program who were checked for cavities had some decay last year.”

Actually tooth decay crises are occurring in all fluoridated cities, states and countries. 

Fluoride Supplements Just as Useless

Dr. Ismail reported "There is weak and inconsistent evidence that the use of fluoride supplements prevents dental caries [cavities] in primary teeth," according to a systematic review of fluoride supplement research published in the November 2008 Journal of the American Dental Association. Dr. Ismail is also an organizer of the American Dental Association Clinical Recommendation Panels on Fluoride Supplement.

“This review confirmed that, in non-fluoridated communities, the use of fluoride supplements during the first 6 years of life is associated with a significant increase in the risk of developing dental fluorosis, write researchers Ismail&Bandekar and first published in Community Dentistry and Oral Epidemiology, February 1999 and to the ADA's website July 2007 but then taken down.

The FDA never safety tested nor approved fluoride supplements for use in children or adults.(4)

1) Dear Doctor Magazine, “Fluoride&Fluoridation in Dentistry”

2) “N.Ky. kids' teeth at risk,” NKY.com
“Added to our drinking water: A chemical 'more toxic than lead'? “ by Joe Conger