Pediatric Dentistry · patient case question
Which sequence correctly ranks the MOST commonly congenitally missing permanent teeth?
Patient case: Eight-year-old with an unerupted central incisor
Patient: Male, 8 years old, accompanied by his mother
Chief complaint: Mother: “His front tooth still hasn't come in and the other one came in a year ago.”
History: Healthy. No trauma history. No medications.
Findings: Mixed dentition. Tooth #9 is erupted; #8 is unerupted with adequate space. A periapical of the anterior maxilla is of poor quality, but an inverted conical tooth is visible in the midline above the incisor roots. A triangular radiopacity appears in the corner of the film.
Show answer and explanation
Correct answer: C. Third molars > mandibular second premolars > maxillary lateral incisors
- A. Third molars, not lateral incisors, head the list.
- B. This is the commonly-chosen distractor. It ranks maxillary lateral incisors above mandibular second premolars, whereas the mandibular second premolar is the more frequently absent of the two.
- C. CORRECT. Third molars are by a wide margin the most commonly absent teeth, affecting roughly 20 to 25 percent of people. Excluding third molars, the ranking is mandibular SECOND PREMOLARS first, then MAXILLARY LATERAL INCISORS, then maxillary second premolars. The pattern makes developmental sense: the last tooth to form in each morphologic class is the most vulnerable to agenesis.
- D. This inverts the order and places lateral incisors ahead of third molars, which is not supported by prevalence data.
Note: Clinically: a missing lateral incisor should prompt you to look for an impacted or ectopic canine, since the lateral's root normally guides canine eruption.
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