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HomeMy WebLinkAboutEloise Kailin MAY 8 2015 August 25,ao4,lettefrom Hardy Umeback DDS,PhD, to the Israeli Minister of Health, YaelGermum CITY OF FOR F ANGELES Dear Minister German: |have been following the debate on fluoridation in Israel for some time. � |served IS years on the US National Academies of Sciences Subcommittee on Fluoride in Drinking Water. ' � � The NAS is sometimes referred to as the'Supreme Court of Science',an organization that sets up unbiased(or balanced)committees to review scientific issues of concern to Americans.The committee on which I served examined the health effects of fluoride in drinking water. our report, published March 22, 2006'canbefoundon|inuathtt2://www.?ap`e,uy/c.a1a|og.Ph,P7recon1_�=l15?l� Our committee was funded by the US cpA—wr were charged NOT to examine the benefits of fluoridation but we certainly reviewed all relevant literature on the toxicity of fluoride,including those at low levels of intake,including the toxic side effects offluoridation. The EPA has still not made a ruling on the maximum contaminant level goal(MCLG)for fluoride, while the Department ofHuman Health Services, being concerned about the dental f|uomd,that fluoridation is causing,has lowered its recommendation for levels of fluoride in drinking water to 0.7 mg/L (ppm).The American Dental Association and the Center for Disease Control in the U5 both agreed that fluoridated tap water should not be used to make up infant formula,since that increases the risk of dental fluorosis.To me,dental fluorosis is a biomarker for fluoride poisoning,not just of developing teeth but of all mineralizing tissues. Health Canada,taking the recommendation of only profluoriclation experts, continues to recommend fluoridation(now at u lowered level of 0.7 ppm)despite mounting evidence that the optimum therapeutic level of fluoride in drinking water,if there is even any benefit at all,is at 0.35 ppm or less. I have personally conducted years of funded research at the University of Toronto on the topic of fluorosis (fluoride poisoning)and bone effects of fluoride intake. A bone study,for which we received national funding,comparing hipbones of people who live in Toronto(fluoridated since 1963)to the bones of people from Montreal(Montreal has never been fluoridated),suggested disturbing negative changes in the bone quality ofTorontonians.This is not something that was supposed tn happen. Fluoridation was only supposed to affect teeth. Since we studied a cross section of the population as they were selected for hip replacement,we were unable to examine only those people who were exposed to fluoridation for a lifetime. If we had been able to do this,we would have seen a much greater negative effect of fluoride since fluoride accumulates with age(our study confirmed thot). The NAS committee examined the literature on the effects of fluoride on bone up until 2006.Since that time there have been more studies to confirm the link between fluoridation and bone changes,as well as a link to bone cancer.Our Toronto vs Montreal study was not included in the 2006 review by the U5 National Academies of Sciences because it only just got published in2O1O. 1 am also the co-author of studies that show that too much fluoride accumulation in the dentin of teeth (the tissue that supports enamel)causes its properties to change as well. I suspect that a lifetime of fluoride accumulation on teeth causes them to be more brittle and fracture more easily.This effect of fluoridation has never been examined. As a practicing dentist,I have been diagnosing and treating patients with dental fluorosis for over 30 years. My research on dental fluorosis(confirmed by the studies reported in the 2006 NRC report as well as the York review)show fluoridation significantly increases the numbers of patients seeking expensive cosmetic repairs. No one in public health has ever accounted for the added costs of treating dental fluorosis when considering the cost-benefit ratio of fluoridation. Our 2006 NRC(NAS)report also concluded that there is a likelihood that fluoride can promote bone cancer.On page 336 it is stated Fluoride appears to have the potential to initiate or promote cancers, particularly of the bone, but the evidence to date is tentative and mixed(Tables 10-4 and 10-5).This alone should force the EPA to set a fluoride maximum contaminant level goal for fluoride in drinking water at ZERO(as it did for arsenic).The EPA has not yet made a decision as to fluoride's carcinogenicity. In addition we now know that fluoride is neurotoxic and that children with noticeable fluorosis have lowered IQs. I have looked at this from all angles and I have to conclude that fluoridated cities would save money on fluoridation costs, parents would save on costly dental bills treating dental fluorosis,dental decay rates would remain unchanged or even continue to decline(as has been demonstrated in many modern fluoridation cessation studies)and the health of city residents would improve when industrial waste products are no longer added/to the drinking water(I find it absurd that the fluoride used to fluoridate drinking water is derived from industrial waste without purification,increasing carcinogenic heavy metal levels,such as arsenic and radionuclides, in the drinking water). In my opinion,purposely adding carcinogens to the drinking water at levels that are known to increase cancer rates(e.g.arsenic at parts per billion), in my opinion,is against all concepts of'do no harm'. Lawsuits have now been launched to hold those responsible for this practice accountable. Several Canadian cities have decided it is not worth continuing the practice of fluoridation.These can be viewed at COF-COF.ca.The number of communities that are no longer fluoridating their drinking water has reduced the total percentage of Canadians on artificially fluoridated water down from 2/3 to about 1/3. There is no doubt in my mind that fluoridation has next to no benefit in terms of reduced dental decay.The modern literature is clear on that. Fluoridation cessation studies fail to show an increase in dental decay. In fact,caries rates continue to drop.The York review, held up as the best evidence for'safe and effective'for fluoridation is flawed because a) it could not find a single randomized,double blinded clinical trial, b) none of the clinical trials adjusted for confounding factors known to affect dental decay such as vitamin D levels,daily sugar intake,sweeteners,fissure sealants etc..c)lumping modern studies with very old studies when decay rates were a lot higher resulted in an over-estimate of the benefit. In the 1950's,when fluoridation started to catch on, it was claimed that there was as much as a 40% benefit. Despite the evidence being very weak,fluoridation might have been worthwhile,especially since fluoridated toothpastes were not introduced until the late 1960's.After the introduction of fluoridated toothpaste,the benefit of fluoridation declined. Now,if there is any benefit at all,one could expect perhaps a 5-10%benefit in children. If half the children are already cavity free and the average decay rates are only two cavities per child it means cities have to fluoridate for 20 years in order to save one decayed surface for every fifth child. More recent studies conducted in Australia show that a lifetime of fluoridation MIGHT save about one tooth from decay from childhood to middle age.Clearly,that is NOT a policy that demonstrates fiscal responsibility and cities that do not do due diligence in terms of cost- benefit analysis are wasting tax payers money and may actually be putting their councillors in a position of liability.The claim that for every$1 spent on fluoridation saves$38 was never accurate and is currently exceedingly misleading. It simply is a lie. No government agency anywhere in the world is properly monitoring the accumulation of fluoride in people consuming fluoridated water.You cannot medicate people without knowing whether they are overdosing on the medication and whether there are any long-term negative health effects. Fluoride added to drinking water has NOT been shown to be safe and effective. In fact,as more and more peer-reviewed studies on fluoride toxicity appear in the literature, it has become clear to me that the pendulum is certainly shifting to'not safe,and no longer effective'. I would be more than happy to provide you and all the Israeli experts in the CC list a full list of peer- reviewed studies on which I have based my expert opinion expressed in this email. You have made the right decision NOT to fluoridate in Israel. Congratulations. Sincerely, Dr.Hardy Limeback BSc, PhD, DDS Professor Emeritus and Former Head of Preventive Dentistry, Faculty of Dentistry, University of Toronto I 214 Guest editorial Water fluoridation intervention:dentistry's crown jewel or dark hour 214 Fluoride 40(4)214-221 Osmunson October-December 2007 Editor's Note: The ten figures in the following guest editorial are available in full color on the Fluoride website: www.fluorideresearch.org. WATER FLUORIDATION INTERVENTION: DENTISTRY'S CROWN JEWEL OR DARK HOUR? SUMMARY: When applied to the community at large, water fluoridation does not show effectiveness. Dental fluorosis is both a health risk and a health care cost for initial treatment with restorations and replacement of restorations. Caries in pits and fissures of teeth can be especially problematic for diagnosis in fluoridated teeth,and delay in recognition of such decay can result in greater tooth loss and larger restorations. The possibility that fluoride exposure may increase the risk of tooth fracture must also be considered. From a dental standpoint,any need for fluoridation intervention is open to serious question. Keywords: Dental fluorosis; Fluoridation; Fluoride dental "bomb"; Tooth cusp fracture; Tooth veneers. Although the practice of water fluoridation is recognized as controversial,' both its proponents and opponents generally agree on two fundamental aspects: (1) reduction in tooth decay is the potential benefit from ingesting fluoride, and (2) dental fluorosis is caused by fluoride exposure during early years of life. Dental benefits not evident: "Evidence for whether an intervention works when applied in the community at large is referred to as its effectiveness. . . . Effectiveness studies more accurately reflect results that may be expected from the implementation of interventions."2 The implementation of fluoridation began over 60 years ago, and today proponents continue to claim fluoridation provides a 20-40% reduction in dental decay.3 If their claim is correct, then substantial evidence for such effectiveness should be evident in the community at large. As seen in their plots of dental caries rates for 12-year-old children collected by the World Health Organization for the years 1965-2000 and reported by Neurath4 and by Cheng,5 little difference in rates of tooth decay is found with or without fluoridation or fluoridated salt intervention in developed countries. Comparing the decay rate of any single developed country over time reveals a decrease in dental decay, regardless of fluoridation. Certainly the "halo" or `ubiquitous effect" theory, which suggests the anti-caries benefit of fluoridated water extends beyond the individual public fluoridated water user through shipping of processed foods and beverages and mixed water use froth school; home, or work have a significant impact on individuals within a community or perhaps neighboring communities, but would have negligible-worldwide effect. Arranging the 50 USA states based on the percentage of their whole population fluoridated and the confounding factor of`socioeconomic status (Figure 1),x',7>K one finds that about 82% of the wealthy and 55% of the poor are reporting very good to excellent teeth regardless of fluoridation. Thus, evidence for effectiveness of fluoridation is clearly lacking from this LS national comparison. In 1996, 46% of public water users in Washington State were fluoridated and a plot of percent fluoridation versus dental decay rates of third-grade children in the 215 Guest editorial Water fluoridation intervention:dentistry's crown jewel or dark hour 215 Fluoride 40(4)214-221 Osmunson October-December 2007 39 counties indicates no evidence of reduction of dental decay with increased fluoridation (Figure 2).9 Nevertheless, Washington State dental health officials disregarded such evidence and continued aggressively and successfully to promote fluoridation. The percentage of 100.0 the whole population of i fifty USA 80.0 States and the District of 60 0 - Columbia on p0 AA. fluoridated Alyff Y RA water and the 40.0 percentage in each state of high and low 20.0 i income I reporting very good/excellent 0.0 teeth 1 4 7 101316 19 22 25 28 3134 37 40 43 46 49 Fifty USA States and the District of Columbia ranked in order of the percentage of their whole population on fluoridated water % high income reporting very good/excellent teeth low income reporting very good/excellent teeth __T % receiving fluoridated water Figure 1. Fifty USA States and the District of Columbia ranked in order of the percentage of their whole population on fluoridated water and the percentage in each state of high and low income reporting very good/excellent teeth. To arrive at the percentage of whole population fluoridated, the USGS percent of those served by public water was multiplied by the percent on fluoridated public water. Washington State currently has 59% of the population on public water systems receiving fluoridated water. By contrast, neighboring Oregon has only 19%.7 Confounding factors of higher socioeconomics, 10 greater access to dental care are in Washington State's favor, yet Oregon with only a third as much fluoridation appears to generally have similar or better oral health overall.1 1-13 A comparison of Kaiser Health Maintenance Organization (IlMO) patients in NW Oregon and SW Washington State reveals mixed results: higher dental costs in some community water fluoridated areas (CWF) and in some non-fluoridated (NF) areas. The authors state, "Clark County, the most reliably fluoridated locale, often had the highest costs overall, the highest number and cost of restorative procedures, and the highest number of S/PRR {sealants and preventive resin restorations)."14 And NF Portland metro, with the largest number of subjects, showed lower dental expenses. If all subjects in the study had been fluoridated, the 216 Guest editorial Water fluoridation intervention:dentistry's crown jewel or dark hour 216 Fluoride 40(4)214-221 Osmunson October-December 2007 data indicates Kaiser IIM.O would have experienced a true increase in net dental expenses of about 4%. Disregarding evidence of the whole, the c011ciusion cheriAl picks evidence, "SLIargesting that CWF may in fact have been cost saving at the dine the study was carried out" with savings in dental treatments of perhaps $0.67 per person year (0.3"/0).t`t Costs for fluoridation equipment installation and maintenance, dental (not covered by Kaiser) and medical damage, and bottled water for infants and non-consenting adults were not considered. The percentage of 100 thirty-nine Washington State counties plotted in 90 order of the percentage of 80 residents receiving fluoridated public water and 3rd grade 70 students evaluated for treated and % 60 untreated decayed or filled tooth surfaces 50 40 30 20 10 5 9 13 17 21 25 29 33 37 Thirty-nine Washington State counties plotted in order of the percentage of residents receiving fluoridated public water % caries prevalence in 3rd graders linear caries prevalence in 3rd graders % receiving fluoridated water Figure 2. Thirty-nine Washington State counties plotted in order of the percentage of residents receiving fluoridated public water and 3rd grade students evaluated for treated and untreated decayed or filled tooth surfaces. Recently, Pizzo has concluded, "several studies conducted in fluoridated and non-fluoridated communities suggested that this method of delivering fluoride may be unnecessary for caries prevention."i 5 Likewise, a careful review of data by 217 Guest editorial Water fluoridation intervention:dentistry's crown jewel or dark hour 217 Fluoride 40(4)214-221 Osmunson October-December 2007 Komarek found no convincing evidence for a beneficial effect of fluoride intake to deter caries development.16 Dental fluorosis: According to the American Dental Association, "The only known risk associated with the use of fluoride is mild enamel (dental) fluorosis which is a cosmetic effect with no known health consequences."3 Proof that dental fluorosis indeed has a health consequence is the dental treatment provided to correct dental fluorosis. Cosmetic dentistry has risk of tooth loss, root canals, increased periodontal disease, complications of occlusion, and could certainly offset any theoretical cost savings from fluoridation. (Figures 3 and 4). l'M '^5 � Photograph Dr Tony Soileau � a , � Y Figure 3. Teeth with dental -` fluorosis. A . Photograph Dr Tony Soileau Figure 4. Restored teeth. The disagreeable cosmetic appearance can sometimes be reduced with bleaching, but the effect is only temporary, and occasionally bleaching can make the appearance worse. Lower cost composite resin materials can provide a temporary cosmetic improvement, and recalcification of the hypocalcified dental fluorosis enamel is being tried. Damage should NOT be measured by the amount of treatment provided but rather by the amount of damage experienced. When true costs for tooth pathology are considered, both treated and non-treated decay are generally combined (decayed, missing, filled). True costs for dental fluorosis should also include t damage to teeth both treated and untreated. Cosmetic damage is indeed real damage to the teeth. i 218 Guest editorial Water fluoridation intervention:dentistry's crown jewel or dark hour 218 Fluoride 40(4)214-221 Osmunson October-December 2007 "Fluoride bomb": Proponents of fluoridation allege ingested fluoride reduces dental decay on the smooth surfaces of the teeth, but they concede there appears to be little benefit to the pits and fissures of the teeth. Clinically, detecting decay in the pits and fissures of the teeth can be difficult (Figure 5) until the enamel breaks away or the tooth turns gray. Clinicians sometimes refer to a severely decayed tooth as "bombed out." Photograph Dr Ray Voller r� Figure 5. Decay in the grooves. TZti � F. �i A fluoridated "bombed out" tooth clinically can have unique characteristics of good smooth surface enamel yet have extensive dentin decay in the pits and fissures. In contrast, the non-fluoridated bombed out tooth may chip next to the pits and fissures before as much dentin damage occurs and provide earlier detection of the decay by patient or clinician, explaining in part the lack of effectiveness with fluoridation. Cautious removal of the dark groove reveals a deep "bomb" of decay (Figure 6). Photographs Dr Ray Voller i��g,1 t��girs Figure 6. Access for decay. ; b \ m,a l As the soft rotten dentin is removed, the clinician's concern rises as this "tiny dark spot" often belies significant hidden dentin damage and may require extensive restoration or treatment with a crown and/or root canal (Figures 7 and 8). Thus the potential benefit of fluoridation on the smooth surface enamel may have complicated or delayed the diagnosis of dentin decay in the pits and fissures. Early reports suggesting fluoridation reduces tooth decay could have been flawed in part by the difficulty in diagnosing pit and fissure decay. 219 Guest editorial Water fluoridation intervention:dentistry's crown jewel or dark hour 219 Fluoride 40(4)214-221 Osmunson October-December 2007 Incomplete and complete tooth fi°acture: After dental decay and periodontal disease, fractured teeth are the third most common cause of tooth loss,17 but to date no identifiable cause has been found for 30 to 50% of fractured teeth.18 In a survey of North Carolina dentists, 5% of all non-hygiene visits to their practices were complete cusp fractures.19 When the costs for treatment of complete dental fractures, which often include crowns, endodontics, extractions, bridges, and implants, and the treatment for prevention of incomplete tooth fractures, is added to the costs for retreatments, the true lifetime cost for fractured teeth could represent the single greatest dental expense for adults (Figures 9 and 10). Photograph Dr Ray Voller -- Figure 7. Most decay removed. ..3 r a / S AkrU 3 rJ.k1 Photograph Dr Ray Voller yo Y Figure 8. Restorations placed � � 4 > VAR i � a x anb. *r. , Figures 9 and 10 represent a classic case of complete cusp fracture. Preventive treatment was declined and complete cusp fracture a year later was not a surprise. In view of a reported correlation between dental fluorosis and the frequency of bone fractures in adults and children,20 consideration of a possible relationship between fluoridation and tooth fracture is prudent. Fluoride alters the chemical composition and the physical and mechanical characteristics of teeth. Evaluating dentin with ultrasound, Vieira concluded that dentin fluoride is an indicator of dentin structural properties.21 Ultrasound is an assessment tool for determining bone and tooth fragility and consequence of fracture. In the dental literature, cusp fracture rates of 2.0%, 4.4%, and 7% per year have been reported for posterior teeth. In the Netherlands, not fluoridated for about 35 years, a recent study found 2.0% per year (20.5 per 1,000 person-years) posterior 220 Guest editorial Water fluoridation intervention:dentistry's crown jewel or dark hour 220 Fluoride 40(4)214-221 Osmunson October-December 2007 cusp fracture rate.22 A preliminary report of complete cusp fractures in non- fluoridated Portland, Oregon (19% CWF state wide) found a posterior cusp fracture rate of 4.4%.23 A third study in highly fluoridated North Carolina (85% CWF state wide) found a 7% posterior cusp fracture rate. `4 Photograph Dr Ray Voller SO z t Figure 9.Fractured mesial lingual cusp. JR b Photograph Dr Ray Voller , Figure 10. Loose fractured cusp f x removed. n ash wl Although the North Carolina and Netherlands studies should not be directly compared, they merit comparative examination. The North Carolina study was a relatively closed private paid HMO panel, while the Netherlands's nationally funded dental payment is similar but more inclusive. It is possible that the fluoridated North Carolina subjects with more tooth fractures had larger dental restorations, lower socioeconomics, poorer diet and hygiene. However, larger restorations in fluoridated North Carolina would not support the effectiveness of fluoridation. Obviously, further studies are needed to clarify what effect fluoride might have on the incidence and etiology of decay and fractured teeth. In conclusion, after decades of public health intervention with water fluoridation, the lack of evidence showing community effectiveness for reducing dental caries, along with the known and reasonably suspected fluoride damage to teeth, is reason enough to reconsider fluoridation. The lack of lower dental. costs in fluoridated areas could be explained, in part, by such difficulties as diagnosing the `fluoride bomb", increased tooth fractures, dental fluorosis repairs, or simply attributing a decline in tooth decay to fluoride rather than the effects of socioeconomics. For these as well as other reasons, support for fluoridation has 221 Guest editorial Water fluoridation intervention:dentistry's crown jewel or dark hour 221 Fluoride 40(4)214-221 Osmunson October-December 2007 waned, and today many prolessional dental organizations no longer recommend the ingestion of fluoride supplements.25 Bill Osmunson, DDS, MPH Aesthetic Dentistry of Bellevue and Lake Oswego bill @smilesofbellevue.com Bellevue, WA 98004 REFERENCES 1 Spittle B. Fluoridation promotion by scientists in 2006: an example of "tardive photopsia." Fluoride 2006;39(3):157-62. 2 McDonagh MS, Whiting PF, Wilson PM, Sutton AJ, Chestnutt I, Cooper J, et al. Systematic review of water fluoridation. BMJ 2000;321:855-9. Full report available from: http://www.york.ac.uk/inst/crd/ fluorid.htm.Analysis and comment available from: http://www.fluoridealert.org/york.htm. 3 Ada.org [homepage on the Internet]. Chicago: American Dental Association; c1995-2007 [cited 2007 Dec 1]. Available from: http://www.ada.org/prof/resources/positions/statements/ fluoride community_effective.asp 4 Neurath C. Tooth decay trends for 12 year olds in nonfluoridated and fluoridated countries Fluoride. 2005;38(4):324-5. 5 Cheng KK,Chalmers I,Sheldon TA.Adding fluoride to water supplies. BMJ 2007 Oct 6;335(7622):699- 702. 6 US Department of Health and Human Services, Administration of Maternal and Child Health Bureau, National Survey of Children's Health. 2003 [2005; cited 2007 Nov 25] Available from: http:// mchb.hrsa.gov/oralhealth/portrait/l cct.htm 7 US Centers for Disease Control and Prevention,Oral Health Resources,Water Fluoridation Fact Sheet [Cited 2006, page temporarily removed 20071, Available from: http://www.cdc.gov/OralHealth/ facts heets/ind ex.htm#4 and then Fluoridation Statistics 2002. 8 United States Department of Interior, US Geological Survey, Estimated Use of Water in the United States in 2000 [cited 20071. Available from: http://pubs.usgs.gov/circ/2004/circl268/htdoes/ table05.html 9 Leroux BG, Maynard RJ, Domoto P, Zhu C, Milgrom P. The estimation of caries prevalence in small areas. J Dent Res 1996 Dec;75(12):1947-56. 10 US Census Bureau, State & County Quick Facts [last revised 2007 Aug; cited Nov 2007 Nov 25] Available from: http://quickfacts.census.gov/qfd/states/41000.html 11 Oregon Department of Human Services Center for Health Statistics—Adult Survey, Behavioral Risk Factor Surveillance System, (BRFSS) [2002; cited 2007 Nov 25]. Available from: http:// www.dhs.state.or.us/dhs/ph/chs/brfs/02/orahea/dentvisi.shtml http://apps.nccd.cdc.gov/brfss/ display.asp?state=WA&cat=OH&yr=2004&gkey=6610&grp=0&SUBMIT4=Go Sample size OR 3509 and WA 12,926 2004 data. 12 Washington State Department of Health, Smile Survey 2005 Report [2006 Mar; cited 2007 Nov 25]. Available from: http://www.doh.wa.gov/cfh/Oral Health/Documents/Smi[eSurvey2005FulI Report.pdf 13 Oregon Department of Human Services, An Oral Health Data Report, [2004 Ju; Cited 2007 Nov 251. Available from: http://www.oregon.gov/DHS/ph/oralhealth/docs/ databook.pdf#search='Oregon%20Decay%20experience 14 Maupome G, Gullion C, Peters D, Little S. A comparison of dental treatment utilization and costs by HMO members living in fluoridated and nonfluoridated areas.J Public Health Dent 2007;67(4):224-33. Abstract in this issue of Fluoride, p. 255. 15 Pizzo G, Piscopo MR, Pizzo I, Giuliana, G. Community water fluoridation and caries prevention: a critical review. Clin Oral Invest 2007 Sep;1 1(3):189-93. Epub 2007 Feb 27. 16 Komarek A, Lesaffre E, Harkanen T, Declerck D, Virtanen J. A Bayesian analysis of multivariate doubly-interval-censored dental data. Biostatistics 2005;6(1):145-55. 17 Geurtsen W,Schwarze T,G0nay H. Diagnosis,therapy,and prevention of the cracked tooth syndrome. Quintessence Int 2003 Jun;34(6):409-17. 18 Patel DK, Burke FJ. Fractures of posterior teeth: a review and analysis of associated factors, Prim Dent Care 1995 Mar;2(1):6-10. 19 Bader JD, Shugars DA, Roberson TM. Using crowns to prevent tooth fracture. Community Dent Oral Epidemiol 1996;24:47-51. 20 Alarcon-Herrera MT, Martin-Dominguez IR, Trejo-Vazquez R, Rodriguez-Dozal S. Well water fluoride, dental fluorosis, and bone fractures in the Guadiana Valley of Mexico. Fluoride 2001;34(2):139-49. 21 Vieira AP, Hancock R, Dumitriu M, Limeback H, Grynpas MD. Fluoride's effect on human dentin ultrasound velocity(elastic modulus)and tubule size. Eur J Oral Sci 2006 Feb;114(1):83-8. 22 Fermis WMM, Kuijs RH, Kreulen CM, Roeters FJM,Creugers NHJ, Burgersdijk RCW.A survey of cusp fractures in population of general dental practices. Int J Prosth 2002;15(6):559-63. 23 Bader JD, Martin JA, Shugars DA. Incidence rates for complete cusp fracture. Community Dent Oral Epidemiol 2001 Oct;29(5):346-53. 24 Bader JD, Shugars DA, Martin JA. Risk indicators for posterior tooth fracture. J Am Dent Assoc 2004 June;135:883-92. 25 Zimmer S, Jahn KR, Barthel CR. Recommendations for the use of fluoride in caries prevention. Oral Health Prev Dent 2003;1(1):45-51. _ j Copyright©2007 International Society for Fluoride Research. www.fluorideresearch.org www.fluorideresearch.com www.fluorideresearch.net Editorial Office:727 Brighton Road, Ocean View, Dunedin 9035, New Zealand.