Crown LA, May JA. Zinc toxicity: denture adhesives, bone marrow failure and polyneuropathy. Tenn Med. 2012; 105:39-42
Barton AL, Fisher RA, Smith GD. Zinc poisoning from excessive denture fixative use masquerading as myelopolyneuropathy and hypocupraemia. Ann Clin Biochem. 2011; 48:383-385 https://doi.org/10.1258/acb.2011.010282
A 52-year-old male attended a dental hospital following a referral from a royal infirmary regarding hyperzincaemia (zinc toxicity) and hypocupraemia (low copper levels). The patient had been using an excessive amount of over-the-counter zinc oxide temporary dental material for the previous 18 months owing to a phobia of dentists and misconception about amalgam fillings as caries. This resulted in acquired peripheral neuropathy, muscle weakness and the inability to walk without wheelchair aid. We present the reasons clear warnings should be in place and education is required for the general public when self-prescribing with ‘at-home’ dental kits.
CPD/Clinical Relevance: It is important to break down patient barriers to accessing dental care.
Article
We present an unusual case of a 52-year-old male who was admitted to the care of a haematology team at a royal infirmary suffering from hyperzincaemia (zinc toxicity), hypocupraemia (copper deficiency), neutropenia and anaemia with reticulocytopenia of unknown origin.
He presented with an 18-month history of the following symptoms: increasing peripheral neuropathy; bilateral wrist and foot drop; worsening hearing, which required a hearing aid; and reduced mobility, which required a wheelchair. The patient reported good health prior to the start of the symptoms.
During a 10-week inpatient stay, treatments for reversal of the hyperzincaemia and hypocupraemia were given, and a cause for both was identified. The medical team discovered he had applied an excessive amount of over-the-counter temporary dental filling, covering his entire dentition. He had used approximately four packets per week for the previous 18 months. He had mistakenly confused dark amalgam restorations for dental caries, believing he had extensive cavities.
Medical treatment included zinc chelation therapy with sodium calcium edetate and intravenous copper infusions for several weeks, as advised from a national poisons expert and clinicians at TOXBASE1 who were consulted because of the rarity of the case.
Owing to excessive use of temporary dental cement, a specialist referral to a dental hospital was made. The patient complained of no pain from his oral cavity. He had not attended a general dental practitioner in 30 years because of dental phobia, and admitted his use of excessive temporary dental cement was due to his misconception of caries.
Social and medical history
He smoked 15 cigarettes per day, was of no fixed abode and took the following medications prescribed by his medical teams: sodium calcium edetate, thiamine, high-protein milk, copper citrate, sodium docusate and pregabalin.
Intra-oral examination
All buccal, lingual and palatal embrasure spaces were covered in a copious amount of temporary zinc oxide dental cement (Figure 1). The temporary dental cement also covered most of the gingival tissues and occlusal surfaces of his posterior teeth and a full assessment of hard and soft tissues, including periodontal probing, was not possible.
Figure 1. (a–c) At presentation, the patient's teeth and gingival tissues were covered with temporary zinc oxide dental cement.
Special investigations
No teeth were tender to percussion. Initial OPG examination was not diagnostically acceptable because the radiopaque temporary zinc oxide dental cement obscured bone levels and prevented full assessment of teeth (Figure 2). The OPG was repeated at a review appointment following acclimatization and gross supragingival scaling, which revealed many teeth to be of hopeless prognosis (Figure 3).
Figure 2. The radiopaque temporary zinc oxide dental cement obscured bone levels in the OPG taken at presentation and prevented a full assessment.Figure 3. The OPG taken following gross supragingival scaling.
Treatment
It was explained to the patient that he should immediately cease the excessive use of temporary dental cement because it would be detrimental to his health if continued. Stabilization of oral healthcare by managing periodontal and dental disease was completed as appropriate, including extractions of teeth deemed to have hopeless prognosis.
Discussion
The COVID-19 pandemic saw national closures of general dental practices and emergency dental services resulting in delays to accessing dental care,2 especially for new patients. Fallow times and increased waiting lists created additional barriers to patients' ability to access dental treatment. During this time, there was an increase in self-prescribing, such as paracetamol, and even in one author's experience, an attempted self-extraction with dental forceps purchased on the internet.
The wide availability of ‘DIY dental kits’, such as temporary dental cements and filling materials, allowed patients to provide their own ‘at-home’ dentistry. Several temporary dental cements and filling kits containing zinc oxide are available on the market. The authors of this case report identified several retailers in the UK selling temporary dental cement/filling kits in large national and international chemists and online.
Many of the package instructions fail to highlight the maximum recommended usage times and dangers of overuse. The authors of this case report suggest companies should consider the addition of warning labels to outer packaging and instruction leaflets to highlight the dangers of excessive use of zinc-containing products to the general public.
A literature search revealed several cases reports of zinc toxicity from excessive use of denture fixatives containing zinc oxide,3,4,5,6,7,8,9 but none from temporary dental filling kits containing zinc oxide. The market leaders for denture fixatives are Fixodent (P&G, Cincinnati, OH, USA) and Poligrip (GSK, Brentford, UK).10 Fixodent contains several warnings regarding maximum doses to prevent hyperzincaemia and Poligrip is zinc free.
A 3-month haematological review of the patient in Februrary 2022 showed resolution of his deranged full blood count, zinc and copper levels, but no change in his progressive peripheral neuropathy neurological difficulties (motor weakness), which remained profound. A further review was planned after 6 months for a reassessment of his blood tests. Neurology and physiotherapy referrals were also made.
This case highlights the importance of patient education about the use of temporary dental filling kits for ‘at-home dentistry’ and the dangers of self-prescribing.
