Management and Disposal of Mercury and Amalgam in the Dental Clinics of South India: A Cross-Sectional Study.

CONTEXT: Dental offices are known to be one of the largest users of inorganic mercury in the preparation of amalgam-a restorative material which, if not handled and disposed through scientific methods, can pose grave threats to the biosphere. AIMS: The objective of this study was to assess and record the mercury management and disposal strategies of dental practitioners belonging to the two South Indian states, Kerala and Tamil Nadu. SUBJECTS AND METHODS: A questionnaire regarding the usage and disposal of a filling material containing mercury (amalgam) was designed and distributed online. The 150 dental practitioners partaking in this study responded anonymously.
RESULTS: The results were statistically analyzed using chi-square test and the P value was evaluated. The usage of amalgam was correlated with the age of the practitioner and the nature of practice and it was found to be statistically significant. The number of fillings was correlated with the years of practice and locality of the clinic, which were found to be statistically significant.
CONCLUSIONS: This study showed that mercury was widely preferred and utilized even today as a restorative material by dentists and dental specialists, despite the availability of other alternative strategies. Only a minor section of practitioners were found to be aware of the global changes in the guidelines pertaining to the handling and disposal of amalgam. We feel that Safe Mercury Amalgam Removal Technique, amalgam safety rules, and amalgam-free practice should be a part of the academic curriculum and continuing dental education.

INTRODUCTION

Dental amalgam, a combination of silver alloy powder mixed with mercury, is one of the most preferred restorative materials among dentists because of its various advantages over other restorative materials. Amalgam has been used in dentistry for several decades owing to its low cost, durability, bacteriostatic effect, and strength. As a result, dental clinics are a major channel that serves as an outlet for mercury into the environment. The aim of this study was to assess and record the mercury management and disposal strategies of dental practitioners.

SUBJECTS AND METHODS

Institutional ethical committee clearance was obtained prior to the start of the study. This study was conducted among the general dentists and dental specialists practicing in South Indian states. An anonymous questionnaire regarding the usage and disposal of a filling material containing mercury (amalgam) was designed using Google Forms and circulated online by random sampling method in WhatsApp groups consisting of around 750 practitioners based out of Tamil Nadu and Kerala, India, out of which 150 responded to the survey within the stipulated deadline date. In the circulated questionnaire, participating practitioners who did not use silver amalgam consequently did not record their responses to the questions pertaining to amalgam usage whereas general questions pertaining to mercury safety were answered by all the participants.

RESULTS

The responses thus received were compiled and tabulated in Microsoft Excel followed by statistical analysis using the SPSS software (version 11.5, IBM Corporation, Armonk, New York, USA). The data were subjected to chi-square test and the P value was evaluated to study the significance.

Of all the respondents, there were 13.33% practitioners belonging to the age group of younger than 25 years, 40% of practitioners belonging to the age group 26–35 years, 29.33% in the age group 36–45 years, and 17.33% older than of 45 years. The male to female ratio of the respondents was found to be 1.27 with 56% male and 44% females.

Of the participants of the survey, 50% were general practitioners whereas 42% were specialized in various branches of dentistry and 8% were endodontists—specialized in filling and conserving the decayed teeth.

When the total number of years in active dental practice was evaluated, 42.67% had less than 5 years of practice, 14.00% had 5–10 years of practice, and 22.67% had 11–20 years of practice whereas 20.67% had more than 20 years of clinical experience.

As far as the locality of the clinic of the respondents is concerned, rural practice accounted only for 9.33% of the participants, semi-urban practitioners were 46.67%, and urban practitioners making up 44% of the total practitioners.

Dental amalgam was used in their clinic by 57.33% of the partaking practitioners, and 42.67% of dentists refrained from dental amalgam in their practice.

Further, the usage of amalgam was correlated with age, sex, nature of practice, and experience of the practitioner and also with the locality of clinic. When amalgam usage was compared with age, the P value was 0.008 and hence was deemed significant. When amalgam usage was compared with the nature of the practice, the P value was 0.003, which is highly significant. With the other parameters tested, it was found to be not significant as in Table 1.

Table 1

Comparison of the age, sex, nature of practice, years of practice, and locality of clinic with use of dental amalgam in clinic

		Use dental amalgam in clinic				Total	Chi-square test	P
		No		Yes
		N	%	N	%
Age in years	Up to 25	6	30	14	70	20	11.70	0.008*
	26–35	25	42	35	58	60
	36–45	27	61	17	39	44
	Above 45	6	23	20	77	26
Sex	Male	34	40	50	60	84	0.37	0.541
	Female	30	45	36	55	66
Nature of practitioner	General practitioner	24	32	51	68	75	11.66	0.003*
	Specialist	37	59	26	41	63
	Endodontist	3	25	9	75	12
Years of practice	Less than 5	24	38	40	63	64	5.34	0.149
	5–10	12	57	9	43	21
	11–20	18	53	16	47	34
	More than 20	10	32	21	68	31
Locality of clinic	Rural	4	29	10	71	14	1.68	0.432
	Semi-urban	29	41	41	59	70
	Urban	31	47	35	53	66
Total		64	43	86	57	150

*Significant at 5 %

When the number of amalgam fillings performed per day by the dental practitioners was correlated with age, sex, nature of practice, and experience of the practitioner and also with the locality of clinic, it was observed that the experience of the practitioner on correlation generated a P value of 0.013, hence holding significance. With the other parameters mentioned earlier, it was found to be not significant as in Table 2.

Table 2

Comparison of the age, sex, nature of practice, years of practice, and locality of clinic with number of dental amalgam fillings performed per day in clinic

		Number of dental amalgam fillings approximately performed in a day						Total	Chi-square test	P
		Less than 5		5–10		11–20
		N	%	N	%	N	%
Age in years	Up to 25	11	79	2	14	1	7	14	1.93	0.926
	26–35	25	71	5	14	5	14	35
	36–45	14	82	2	12	1	6	17
	Above 45	16	80	3	15	1	5	20
Sex	Male	40	80	5	10	5	10	50	1.57	0.457
	Female	26	72	7	19	3	8	36
Nature of practitioner	General practitioner	35	69	11	22	5	10	51	7.55	0.109
	Specialist	22	85	1	4	3	12	26
	Endodontist	9	100					9
Years of practice	Less than 5	31	78	6	15	3	8	40	16.21	0.013*
	5–10	5	56			4	44	9
	11–20	13	81	3	19			16
	More than 20	17	81	3	14	1	5	21
Locality of clinic	Rural	9	90	1	10			10	12.79	0.012*
	Semi-urban	26	63	11	27	4	10	41
	Urban	31	89			4	11	35
Total		66	77	12	14	8	9	86

*Significant at 5%

DISCUSSION

Despite the unparalleled strength and durability offered by dental amalgam over any other restorative material, health hazards posed by mercury present in amalgam to both the dental practitioner and mainly the patient, as well as the environmental threat arising from the unscientific methods of disposal of extracted amalgam-containing tooth and other residue from the packaging of mercury, heavily outweigh the advantages it offers.

From the data compiled in our study, it can be surmised that 40% of the dental practitioners who participated in the survey were between the ages 26 and 35 years, which may be attributed to the fact that newer generation is technologically inclined. A lion’s share of the responses was received from dentists in urban and semi-urban regions (90.67%). In stark contrast, only 9.33% were from the rural practitioners, which may be attributed to the fact that rural population lack technological awareness or have difficulty in accessing the Internet.

Of the practitioners giving the survey, 32% were of the opinion that amalgam poses no significant short-term or long-term health hazards to both the practitioner and the patient whereas another 27.33% were unsure about its safety or the lack thereof. This explains why dental amalgam is strongly preferred as a restorative material in South India by the dental practitioners. On the other side of the spectrum, 40.67% of the responses were that dental amalgam is unsafe for both patient and dentists, indicating that this can trigger a considerable number of mercury-free clinics in the region.

In a study conducted[1] in Saudi Arabia in 1996, it was found that though 75% of the dentists were aware of the existing controversy surrounding amalgam safety, 85% believed in its safety. Another study in Nigeria (Udoye and Aguwa[2]) reported that a greater number of specialists than general dentists (74.5%) affirmed that dental amalgam is safe, whereas more general dentists (14.9%) than specialists (4.3%) reported dental amalgam to be hazardous. Dental practitioners of our area had better awareness of amalgam compared to these studies.

Some of the possible reasons for 57.33% of the dental practitioners utilizing dental amalgam in their practice over other restorative materials might be the exceptional strength and durability it offers and also the fact that from an economic point of view, it is cheaper and affordable to a larger section of the society.

Our study revealed that of those who utilized amalgam, 27.33% used it in its powder and liquid form which involves the mixing of silver alloy powder and liquid mercury using mortar and pestle and squeezing them using thick cloth, which arguably is the most unsafe method of handling mercury because it can result in the expulsion of mercury droplets in the indoor environment—in turn leading to inhalation by the practitioner and patients. Of those who utilized amalgam, 14% resorted to the capsule method, which is the safest method wherein silver powder and mercury are forced together in a capsule by provision of a vibration. The remnants from this method can be recycled. Of the dental practitioners, 16% used both these forms of dental amalgam in their practice.

It can be surmised from the responses that 44% of the dental practitioners performed less than 5 dental amalgam fillings per day, 8% reported performing 5–10 fillings, and 5.33% performed 11–20 fillings per day. Findings from a similar study performed in Nigeria[3] reported that the majority of the practitioners (77.8%) reported to be performing less than 5 fillings per day whereas a study[4] at Pune, India, reported that 43% of dentists performed less than 5 dental amalgam fillings per day.

It is observed from this study that 19.33% of the total practitioners disposed amalgam remnants along with other routine wastes, 22% stored it in tight containers whereas only 16% disposed it separately. Studies conducted in Bangkok[5] and in Palestine[6] align with our findings, i.e., a major chunk of practitioners do not separate the wastes, resulting in it ending up as a part of regular refuse. It was reported in a study in the Indian capital city of New Delhi that dentists at a teaching hospital were not aware of biomedical waste management and needed training.[7] It was also reported that New Delhi releases approximately 51 kg of mercury as a result of improper disposal of amalgam annually, which is unregulated and reckless. Contrastingly, a particular study on similar lines in a dental school in Turkey[8] reported that in majority of the practices, waste collection protocols were being adhered to. The stark contrast here could be due to the fact that the study in Turkey was conducted in a dental school where exposure and awareness regarding current protocols are greater when compared to many of the other studies that were conducted among a population of practicing dentists.

In the case of extracted teeth containing dental amalgam fillings, 30.67% of dental practitioners disposed them along with routine wastes without any segregation, 12.67% kept them in closed containers while only 14% disposed of it separately. The fact that a large portion of the practitioners do not opt for waste segregation and scientific methods of mercury disposal highlights that they do not view it as a major hazard to health and environment. Only 16% of the practitioners reported the separate disposal of dental amalgam despite the presence of third party agencies in these states who segregate and dispose of these clinical wastes in a scientific manner.[9]

In our study, among the participating dental practitioners, 47% had heard of dental amalgam recycling whereas only 28% reported to being aware of the Safe Mercury Amalgam Removal Technique (SMART).

The SMART[10] as recommended by International Academy of Oral Medicine and Toxicology broadly involves reducing the risk of mercury exposure faced by the practitioner and patient by means of installing an amalgam separator to collect mercury amalgam waste; installation of an adequate filtration system such as a high-volume air filtration system in the clinic premises in order to remove the mercury vapor generated in the restorative procedure; provision of a suitable adsorbent such as charcoal slurry or chlorella to the patient to rinse and swallow; and making use of proper protective equipment for both the practitioner and patient such as face shields and hair/head coverings, non-latex nitrile gloves, a full-body, impermeable barrier and dental dams and saliva ejector to shield the patient from exposure and ingestion. In addition, it is also recommended that in case of removal of fillings, the dental amalgam should be sectioned and removed as chunks of largest possible size using a small-diameter carbide drill. The need for adhering to these standards is further emphasized in the dosimetry study,[11] which reported that dental practitioners were found to have on an average, urinary mercury levels that were four times that of normal. Consequently, dental practitioners were at an increased risk of suffering from kidney disorders.

The dental practitioners as well as their support staff should be made aware of the scientific guidelines of storing mercury and the mopping of mercury spills. Usage of fine mesh to trap amalgam waste as endorsed by ISO 14011 Environmental Audit Procedures is also effective in reducing the exposure. If the waste water emanating from the clinics contain a mercury concentration higher than 2000 ppm, treatment to reduce the mercury concentration is required before it is released into the general sewers. In addition, as recommended in the Food and Drug Administration guidelines, dental amalgam fillings should be used only in patients older than 6 years.[12] Our study indicates that 45% of the practitioners who gave the survey reported that they faced patient enquiry on the safety of dental amalgam fillings. The fact that a majority of the practitioners are either unsure about dental amalgam safety or feel that it poses no hazards increases the need for an increased awareness to be created among practitioners and in turn in patients.

CONCLUSION

This study proves that silver alloy (mercury) dental amalgam is widely preferred as a restorative material by general practitioners as well as specialists despite the advent of hazard-free alternatives whereas a considerable chunk of practitioners who participated in the survey were of the opinion that dental amalgam was safe or were inconclusive of its safety. The matter at hand is further exacerbated by the unscientific disposal strategies followed by a considerable number of the practitioners, which can result in a wide spectrum of issues ranging from vapor ingestion to water table infiltration. Thus, it is imperative that the existing practitioners need to be made aware of the global changes in the guidelines pertaining to the handling and disposal of amalgam while the inclusion of SMART techniques, dental amalgam safety protocols, and the benefits of mercury-free practices should be made a part of the existing academic curriculum. Every individual has equal responsibility in saving and protecting the environment for the future generations.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.