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Paul Melters’ response to Johnny Johnson’s 2nd reply
concerning the 5 studies listed by
Louise Mantella in Comment 47741 - Ken Perrott blog.
December 9, 2013

COMMENT 48528  Paul Melters  December 10, 2013 at 10:12 am

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In COMMENT 47956, Johnny Johnson wrote:

JOHNSON: “Dr. Jayanth Kumar, a member of the 2006 NRC Panel which reviewed the U.S. EPA’ MCL for natural fluoride levels in drinking water, ‘Fluoride in Drinking Water: A Scientific Review of EPA’s Standards”, and an internationally renowned dental & fluoride researcher...”

PM Response: I am very familiar with the 2006 NRC report, and also with Kumar’s work.
Please note that Hardy Limeback - also a member of the NRC panel and equally distinguished “internationally renowned dental & fluoride researcher” -  does not agree with Kumar on this matter at all. You know this already from your communication with Limeback on various blogs.

Now, to your points:

JOHNSON/KUMAR: "Kumar....wrote the following when I asked him about the statements that were being made from the referenced studies conducted in Mexico: 

“The NRC report reviewed most of the cited studies in the email and found several limitations."

PM Response: You must be referring to some other email and not the post by Mantella? The NRC (2006) could not have possibly reviewed the two Mexican studies cited by Mantella, as they were published in 2007 and 2008. So obviously - this is nonsense? What email are you referring to?

JOHNSON/KUMAR:  “These studies didn’t take into account other factors when assessing the relationship between dental fluorosis and caries. In addition, these studies are based on small number of children drawn from areas where the fluoride content is much higher than that compared to the US.

PM Response: Again - what studies are you referring to?

JOHNSON/KUMAR: “Furthermore, the analysis is either conducted at the population level or child level but not at the tooth level. To address these deficiencies, we analyzed a national survey data that included a large number of children (n=16,873) with known fluoride history. We derived population estimates (weighted) at the child level and tooth level using methods appropriate for complex survey data. We confirmed the findings using multivariate methods.”

PM Response: I will gladly discuss Kumar and his own paper at some other time on this website, as there are many questionable “data manipulations” observable. For now, we’ll stick to his criticisms of the “Mexican papers”.

JOHNSON/KUMAR:  “I am citing the paper by Pontigo-Loyola AP et al., (J Public Health Dent 67(1):8-13, 2007) to illustrate why the findings from these types of studies are not applicable to the population exposed to fluoridation in the US. This was a study of children living at high altitude (>6,560 ft) exposed to fluoride in drinking water that exceeded 1.38 mg/L (most children) in Hidalgo state, one of the many states included in the nationwide fluoridated domestic salt program.

PM Response:

Re: water -  the fluoride in water was 1.38 ppm in San Marcos [128 children (8.3%)/first 6 years of
life] and 1.42 ppm in Tula Centra [821 children (53.4%)/first 6 years of life)]. Those concentrations are only slightly higher than the upper limit of F- in US waters deemed “optimal” at the time
(1.2 ppm).

Re: Salt Fluoridation - at the time this study took place (1999), the 12 year-old children here were already 4 years old when the salt fluoridation program was implemented. The 15-year-olds were 7 years old. The salt program plays no real role here.

Re: Altitude - this is only of concern when considering WHAT is causing the DF. It is well established that at higher altitudes much lesser amounts of F are able to produce dental fluorosis of all grades.

JOHNSON/KUMAR: “The authors point out that “in general, a high prevalence of fluorosis was observed in all three communities (>80 percent), with almost a third of the overall study population having moderate to severe fluorosis”. If the population has this high level of moderate to severe fluorosis and every child was exposed to fluoride, it becomes difficult to assess the relationship between fluorosis and caries.”

PM Response: Just an attempt at diverting from the real issue. Most of the observed fluorosis was mild/very mild (52.1%) and it was also in THIS grade of dental fluorosis that an increase in caries severity was found.

Pontigo-Loyola: “When we compared high-severity caries group (DMFT ≥ 4 as cutoff point), we observed higher caries severity in children with fluorosis (9.6 percent in very mild/mild, and 10.6 percent in moderate/severe) than children without fluorosis (7.8 percent).”


“...prevalence of DMFT ≥4 in fluorosis-free children was 13.5, while 15.5 and 17.1 was observed in children with very mild/mild and moderate/severe fluorosis."

re: the following statement -  “If the population has this high level of moderate to severe fluorosis and every child was exposed to fluoride, it becomes difficult to assess the relationship between fluorosis and caries.” - what exactly does that mean?  When isn’t a child exposed to fluoride? And why would it be difficult? Perhaps Kumar is referring to the fact that many “experts” think they see caries when it is actually fluorosis and vice versa? I look forward to this explanation!

JOHNSON/KUMAR: “Also, it is difficult to ascertain if the “Filled” component of DMFT is the result of caries or to improve esthetics.”

PM Response: Another diversion tactic. Even without the “filled” component, there is clear evidence of increase in caries AND caries severity. As the authors state - “In the distribution of components of the caries index, 72.2 percent of the index was ascribable to the “decayed” component.” (See Table 2 in Pontigo 2007.)

JOHNSON/KUMAR: With respect to SES and caries relationship, the authors reported that - “we observed the opposite trend: the better the socioeconomic position, the higher the prevalence of caries”. The authors state that they found factors such as age, gender, dental visit, SES and locale had an effect on DMFT in the bivariate analysis. If this is the case, then one has to control for these factors in a multivariate analysis if one wants to examine the association between fluorosis and caries. In summary, the population is not comparable to the US, ascertainment of the filling component is not clear, the analytical method lacks sophistication, and therefore the interpretation is questionable.”

PM Response: In summary, you have not provided ANY real reason why interpretation is questionable. As the findings are comparable with many other studies on the subject - including several, more recent ones from Mexico (Azpeita-Valadez et al, 2008; Garcia-Perez et al, 2013; Molina-Frechero et al, 2012) -  it is the study by Kumar and Iida which is most suspect. The various shortcomings in the Kumar/Iida paper will be addressed in a separate post on this website (fluoridedentalexperts.com).

JOHNSON: “This is why I stated what I did in my earlier post that reviews of literature, by expert groups like the NRC Panel, are so very important in determining the scientific value and contribution that any published literature will make to the body of evidence on a topic.”

PM Response:  Several points.

1) Once again - the 2006 NRC has very little to do with studies published AFTER its publication 2006. I am sure you understand that now, right? 3 of the 5 studies listed by Mantella were published AFTER the NRC report.

2) It would be great if one could have this much confidence in an “expert group”. However, the 2006 NRC Report was far from perfect and has many flaws. Regardless of this - you’ve been abusing this 2006 NRC report on countless occasions, bending the information contained in it to fit whatever your agenda was at the time.

May I remind you of the ridiculous - and entirely false - statement:

JOHNSON: “The NRC Panel concluded that under 4ppm, NO ADVERSE HEALTH EFFECTS OCCUR” (Emphasis Johnson)

You once again failed to provide ONE study as requested:

Please provide ONE study capable of demonstrating this “effective and safe” effect of CWF that has accounted for established confounding factors such as race, gender, age, total intake, tooth eruption, brushing and other oral hygiene factors, SES.



Paul Melters

Azpeitia-Valadez Mde L, Rodríguez-Frausto M, Sánchez-Hernández MA. Prevalence of dental fluorosis in children between 6 to 15 years old. Rev Med Inst Mex Seguro Soc 46(1):67-72 (2008)

Garcia-Perrez A, Irigoyen-Camacho ME, Borges-Yanez A. Fluorosis and Dental Caries in Mexican Schoolchildren Residing in Areas with Different Water Fluoride Concentrations and Receiving Fluoridated Salt. Caries Res 47(4):299-308 (2013)

Molina-Frechero N, Pierdant-Rodríguez AI, Oropeza-Oropeza A, Bologna-Molina R. Fluorosis and dental caries: an assessment of risk factors in Mexican children. Rev Invest Clin. 2012 64(1):67-73 (2012)