Thursday, August 13, 2015

Cellphone use may be harmful for people with dental braces

A new peer-reviewed study found that cell phone use significantly increased nickel concentration in the saliva of 50 adult patients who wore dental braces (i.e., fixed orthodontic appliances) as compared to when they did not use their cell phones for a week. Moreover, patients who spoke more on their cell phone had a greater increase in salivary nickel concentration. 

The “adverse effect of radiation on the release of nickel was more prominent in women” because they spoke more on their cell phones. The females averaged 53 minutes during the week they used their cell phones whereas the males averaged 23 minutes.

Nickel is a known toxic and carcinogenic metal. It is also a common cause of metal-induced contact allergic dermatitis. Nickel-containing alloys are often used in orthodontics for metallic brackets, arch wires, and bands.

Previous research either found no increase in salivary nickel concentration after a fixed orthodontic appliance was inserted or a significant increase that tapered off within three weeks after insertion.  The patients in the current study had orthodontic appliances for 2-4 months before they participated to control for this potential confounding effect of time.

The Federal Communications Commission (FCC) requires all cell phone models be tested for their Specific Absorption Rate (SAR), a measure of the maximum amount of microwave radiation absorbed by the head and the body. SAR is measured in a laboratory using an artificial model of a large adult male with different fluids to simulate human tissue. The SAR testing procedure, adopted in 1996, was criticized by the Government Accountability Office in 2012 because it does not simulate today’s typical user or the way cell phones are typically used. The artificial head does not contain any metal (e.g., dental fillings, dental braces, metallic earrings or eyeglass frames) which could increase the radiation absorption beyond that measured in the laboratory. The artificial body test makes the unrealistic assumption that  consumers will carry their cell phones in manufacturer-approved holders that keeps the phones a minimum distance away from their bodies. 

Today many children are cell phone users.  The young child’s brain absorbs twice the radiation as the adult’s brain. The SAR testing procedure does not take this into account.  

Although the current study was conducted on young adults who had fixed orthodontic appliances, the results should have relevance for children who are more likely to be fitted for dental braces than adults.

The paper did not describe the specific types of fixed orthodontic appliances the patients had.

The abstract for the study and excerpts from the paper appear below.


Saghiri MA, Orangi J, Asatourian A, Mehriar P, Sheibani N. Effect of mobile phone use on metal ion release from fixed orthodontic appliances. Am J Orthod Dentofacial Orthop. 2015 Jun;147(6):719-24. doi: 10.1016/j.ajodo.2015.01.023.


INTRODUCTION:  The aim of this study was to evaluate the effect of exposure to radiofrequency electromagnetic fields emitted by mobile phones on the level of nickel in saliva.

METHODS:  Fifty healthy patients with fixed orthodontic appliances were asked not to use their cell phones for a week, and their saliva samples were taken at the end of the week (control group). The patients recorded their time of mobile phone usage during the next week and returned for a second saliva collection (experimental group). Samples at both times were taken between 8:00 and 10:00 pm, and the nickel levels were measured. Two-tailed paired-samples t test, linear regression, independent t test, and 1-way analysis of variance were used for data analysis.

RESULTS:  The 2-tailed paired-samples t test showed significant differences between the levels of nickel in the control and experimental groups (t [49] = 9.967; P <0.001). The linear regression test showed a significant relationship between mobile phone usage time and the nickel release (F [1, 48] = 60.263; P <0.001; R(2) = 0.577).

CONCLUSIONS:  Mobile phone usage has a time-dependent influence on the concentration of nickel in the saliva of patients with orthodontic appliances.


•  Radiofrequencies from mobile phones and nickel concentrations in saliva were examined.
•  Mobile phone radiation is positively correlated with nickel concentration in saliva.
•  Nickel concentrations in saliva were different in men and women.


An integral part of modern telecommunication is the mobile phone, which may have negative effects on different organs and cells. These negative impacts culminate from radiofrequency electromagnetic radiation (RFER) emitted from mobile phones. From 1990 to 2011, worldwide mobile phone subscriptions grew from 12.4 million to over 5.6 billion, and the global pandemic usage of mobile phones was about 70% as of 2011.  Insufficient understanding of the potential adverse health effects of mobile phones have raised concerns among health care professionals.

According to the proximity of mobile phones to the oral cavity during the conversation period and the metallic orthodontic appliances in the mouth, there might be a serious risk in exposure of these appliances to the mobile phone radiation. Archwires, headgear, bands, and brackets used in orthodontics mainly consist of nickel. The harmful effects of nickel have been systematically investigated at the levels of the cells, tissues, organs, and organisms.  According to the International Agency for Research on Cancer, nickel compounds are classified as carcinogenic to humans, but it is still unclear which forms of nickel pose the greatest risk. Nickel complexes in the form of arsenides and sulphides are carcinogenic, allergenic, and mutating substances even at nontoxic concentrations. Nickel might induce DNA alterations mainly through basic damage and DNA-strand scission in G12 cultured cells. Empirically, a biologic limit of 30 μg per gram has been proposed for nickel in the urine of workers exposed to soluble nickel compounds at the end of their shifts.

Nickel is a common metal that can cause allergic contact dermatitis more than all other metals. Previous studies have indicated that approximately 10% of the population is sensitive to nickel, and this sensitivity is more commonly seen in female patients.

The anatomic location of the parotid gland (at the anterior border of the external ear and between the mandibular ramus and the sternocleidomastoid muscle, 4- to 10-mm deep under the skin surface) makes it a conceivable candidate to be influenced by exposure to RFER on the side of the head where the mobile phone is held. Some researchers, in both human and animal studies, have confirmed that mobile phones cause significant increases in salivary oxidative stress, salivary flow, total proteins, and albumin, whereas amylase activity was decreased. In a nationwide case-control study, Sadetzki et al examined the correlation between parotid gland tumors and mobile phone usage and indicated a positive dose-dependent response trend. Thus, the RFER emitted from mobile phones may influence the amount of nickel released from the fixed orthodontic appliances.

… the aim of this study was to test the hypothesis that exposure to RFER emitted by mobile phones can affect the level of nickel in saliva. In addition, the effect of different times of exposure to the RFER was evaluated on the concentration of nickel in saliva.

Fifty healthy patients (25 men, 25 women; average age, 25.2 years; range, 23-26 years) who had fixed orthodontic appliances were selected for the study. Candidates needed placement of full orthodontic appliances for at least 2 months and no more than 4 months to satisfy the inclusion criterion.

During the regular checkups, the patients were asked not to use their cell phones for 1 week, and saliva samples were taken from them at the end of the week (this was considered the control group). For the next visit, a chronometer was given to the patients to calculate how many minutes they used their cell phone during the second week of the experiment. At the end of the second week, saliva samples were again collected, and the sexes, ages, and cell phone usage times were also recorded; this was considered the experimental group. The saliva samples were sent to the laboratory for further analysis.

The main outcome of the study was a significantly higher concentration of nickel ions in patients' saliva after using their mobile phones compared with the control group. The mobile phones used in this study had emissions of radiation in the normal range of 800 to 2200 MHz, as mentioned above.

The concentrations of salivary calcium, magnesium, and phosphate were lower in the mobile user group.  Our results showed that the concentrations of nickel ions after using a cell phone for 1 week were significantly higher than the concentrations in the control group. This might be attributed to the greater flow rate and the lower concentration of the components in saliva, which in turn result in more nickel released from fixed orthodontic appliances into the saliva.

The linear regression test showed a positive significant increase in nickel concentration with mobile phone usage time. In other words, the longer the exposure to the RFEF emitted by a mobile phone, the greater the concentration of nickel in saliva.

According to results of our study, mobile phone radiation might cause DNA damage indirectly by influencing the release of nickel from fixed orthodontic appliances. Thus, the necessity of studying the effects of this radiation on metal ions released from fixed orthodontic appliances in adjacent tissues seems to be undeniable.

According to the outcomes of this study, it can be concluded that mobile phone radiation, regardless of the type of phone, can influence the concentration of nickel in saliva in a time-dependent manner. In addition, this adverse effect of radiation on the release of nickel was more prominent in women because of longer usage times. Future large-scale studies, which should include more parameters such as the effects on the parotid glands or the saliva flow rate, are needed.