He was the full-term product of a normal pregnancy, and has had a normal postnatal course with no hospitalizations. He drinks tap water supplied by your city. He eats a balanced diet including daily fruits, vegetables, and meat and without abnormal eating patterns. He does not take any supplements except a multivitamin. He is growing well and has a normal physical examination, only notable for black staining on the teeth.
The most likely cause of this is:
A. Tetracycline use during his gestation
B. Iron staining
C. Excessive fluoride
E. Inadequate teeth brushing
The correct answer is B.
Staining of the teeth can be intrinsic or extrinsic. Examples of intrinsic include hereditary conditions (of enamel formation or systemic illnesses or metabolic diseases) or tetracycline use during pregnancy or while the teeth are forming. Extrinsic causes include iron supplements, poor oral hygiene leading to caries (usually white stains early on and brown stains later), or abnormal food habits. This figure shows a case of black extrinsic staining, which is the result of vitamins containing iron.
Minocycline can also cause staining of the teeth post eruption. It would be difficult to develop fluorosis from municipal water without also having a habit of eating toothpaste or taking fluoride supplements. One third of the US population does not have access to fluoridated public water. (Page 1361, Section 20: Disorders of the Oral Cavity, Chapter 378: Oral Pathology)
Question & Explanation and Photo: Cabana MD. Rudolph’s Pediatrics, 22e, Self-Assessment and Board Review; 2014.