A 46-year-old male presented complaining about the discoloration of his teeth. Brown stains had been present earlier in life, in his primary dentition, and in the dentitions of other relatives and several residents of his town. Apart from joint stiffness and back pain, possibly due to his heavy work duties as a manual worker in a paint factory, he had no other serious medical problems. The patient was on no medication and could not recall any tetracycline use by his mother while pregnant, nor by himself up to the age of 8 years. He smoked a packet of 20 cigarettes per day and drank 3 glasses of wine per day.
Extra-oral examination revealed nothing of note.
Oral examination showed all his teeth to be of normal size and shape with minimal tooth surface loss, but with a brown discoloration and also pits and grooves in the enamel (Figure 1). This discoloration was in his anterior maxillary teeth, and lighter in his mandibular teeth, where there were white or yellow or slight brown enamel zones. Despite poor oral hygiene, most of his teeth were caries free.
Figure 1. Teeth discoloration.
Q1. Which is the probable cause of his teeth discoloration?
Amelogenesis imperfecta;
Habits;
Alkaptonuria;
Fluorosis;
Tetracycline staining.
Q1. The answer to which is the probable cause of his teeth discoloration?
Amelogenesis imperfecta is a rare inherited condition which affects the enamel matrix formation and mineralization. This condition results in discoloured (brown or white), pitted or grooved deciduous and permanent teeth. This patient's teeth showed some characteristics of amelogenesis imperfecta, such as pits and grooves and a white and brown zone of discoloration, but had attrition.
Habits, such as excessive smoking, drinking of wine, tea or coffee and chronic mouthwash use (especially chlorhexidine) can cause a brown tooth discoloration by absorption of stains into tooth surface deposits, such as plaque or acquired pellicle. Chromogenic bacteria can cause a black/brown stain in the cervical part of the teeth in some children with good oral hygiene and low caries; this is termed ‘black stain’. The workplace of our patient is rich in extrinsic metals and could contribute, together with his smoking and drinking habits, to his tooth discoloration. However, this is not the main cause, as brown stains had also been seen in his primary dentition and in the dentitions of other relatives and several residents of his town.
Alkaptonuria is a disease characterized by the incomplete metabolism of tyrosine and phenylalanine, promoting the formation of homogentisic acid (HGA) which causes the urine to turn black on air exposure and the skin to darken and the permanent teeth to appear brown. Accumulation of the HGA in the joints also causes disease. Our patient has some, but not all, the characteristics of this disease, such as the brown colour of his teeth, joint problems (pain, stiffness) and a positive family history. However, other important findings, such as the unchanged colour of his urine, the lack of pigmented sclerae and the increased tooth discoloration among other residents in his own town, makes this diagnosis most unlikely.
Fluorosis is a developmental disturbance of dental enamel caused by fluoride overexposure during the first 8 years of life. It is characterized by white striations in the enamel (mild form) to a deep permanent diffuse brown discoloration (severe form). Our patient appears to have all the clinical characteristics of fluorosis. This is in agreement with the fact that he has lived all his life in a town where the natural fluoride concentration in the drinking water exceeds 3.8 mg/L.
The fluoride excess interacts with the mineralized tissues, such as teeth or bones, increasing their resistance to demineralization. Fluoride is found in drinking water, foods and drinks, and toothpastes and mouthwashes. Fluorosis occurs when the patient consumes water with a fluoride concentration of >2 mg/L or takes excess fluoride tablets (>2 tablets/day) for many months, or overuses toothpastes or mouthwashes (>5 times/day) for years.
Tetracycline staining is a typical adverse effect when this broad spectrum antimicrobial has been given to women during the second or third trimesters of pregnancy, or to breast-feeding mothers or to children up to 8 years of age. This stain consists of discrete yellow to grey or brown lines in both dentitions which are directly correlated to the stage of tooth development at the time of tetracycline exposure. The tetracycline binds to calcium ions forming a stable complex of tetracycline calcium orthophosphate. Permanent teeth tend to show a more diffuse and darker discoloration due to oxidation than do affected primary teeth.
