20 Oral Pathology Furthermore, fluoride appears to have the potential to initiate or promote cancers, particularly of the bone, but the evidence to date is tentative and mixed. Biologically, the link between fluorides in tap water and bone cancer in childhood period is highly plausible.6 Approximately 99 percent of ingested fluoride is deposited in the skeleton with about 50 percent of the daily ingested fluoride being deposited directly into bone.23 Fluoride is also confirmed as a mitogen agent in humans that increases the proliferation of osteoblasts.24, 25 Its uptake in bone increases during periods of rapid skeletal growth23, therefore, the effect of fluoride to cause bone cancer would be strongest during periods of rapid growth particularly in males.6 Furthermore, several studies have demonstrated fluoride to be genotoxic to mammalian cells that it induces DNA breaks and chromosomal aberration in bone -forming cells where osteosarcoma arises.26, 27, 28 There are conflicting data regarding the association between fluoride concentration in drinking water and the incidence of osteosarcoma in man and animals. Several studies showed positive relationship between fluoride in drinking water and osteosarcoma.6,7,29,30,31 In contrast, other studies found no association.32, 33, 34, 35, 36, 37 The result of this study demonstrated the fluoride concentration in drinking water in both communities (Libya and Egypt). In the north-western region of Libya, tap water samples were selected from different parts of the north-western costal region. The fluoride level in this region ranged between 0.49-3.9 ppm with a mean of 1.38 ppm, while in Egypt where the Nile River is the main source of drinking water, the fluoride level ranged between 0.41-0.42 ppm with a mean of 0.41.5 ppm. The clinic-pathological data of this study showed that among the Libyan cases there were 20 cases of osteosarcoma occurred between 10-44 years of age with a mean age of 22 years. The incidence of this tumour under the age of 30 years was 85% and just 15% above 30 years of age. The peak incidence (50%) of all cases of osteoDental News, Volume XXII, Number III, 2015
sarcoma occurred between 10-19 years. Moreover. It is noted that females were most frequently affected than males in fluoridated community which accounts for about 65% of cases and of ratio of approximately 2:1 females to males. This result is consistent with the finding of (Ayala38, who stated that osteosarcoma was more common in females than males. This slight predominance could be attributed to the dimorphic sexual pattern of post-pubertal bone growth due to earlier adolescence growth spurt in girls. The results of Egyptian cases where the fluoride in drinking water is at low concentration (0.410.42 ppm), all 20 cases of osteosarcoma occurred between ages 11-59 years with a mean age of 30 years. The incidence of osteosarcoma in this non-fluoridated community was 65% under 30 years of age and 40% under 20 years of age. It is noted in this study in non-fluoridated community that the males were more frequently affected than females which accounts for about 65%. Of osteosarcoma cases with a ratio of approximately 2:1 males to females In general, this study revealed a significance difference in the pattern of age and sex distribution of osteosarcoma in fluoridated community compared to non-fluoridated community. This difference could be attributed to the effect of fluoride on osteoblastic activity which is sensitive to fluoride. These results are in accordance with the findings of National Toxicology Program (NTP 2005), animal study which found equivocal evidence for correlation between fluoride in tap water and osteosarcoma for males but not for females29 and from two ecological studies that found an association for males but not for females less than twenty years of age.6, 7, 30, 31 Bassin’s study measured the risk of osteosacoma before age 20 years based on exposures to fluoride in drinking water during each year of age in childhood. The methodology employed is rigorous and fluoride levels in tap water for each study participant were confirmed for each year of exposure during childhood. The analysis shows significantly elevated risks of bone cancer