Pediatric Dentistry · patient case with 3 questions
Premature loss of primary molars in the mixed dentition
Patient: Female, 6 years old
Chief Complaint: Referred after two primary molars were extracted because of gross caries.
Background: Tooth T (the mandibular right second primary molar) and tooth L (the mandibular left first primary molar) have both been lost prematurely.
Current Findings: The permanent mandibular first molars have not yet erupted. The permanent lateral incisors are unerupted. No crowding is evident in the anterior segment. She is otherwise healthy.
Question 1
Which appliance is indicated for the space left by tooth L, and how is it classified?
Show answer and explanation
Correct answer: C. A band and loop — fixed and unilateral
- A. The band and loop is cemented in place, not removable. Removable maintainers depend on patient compliance and are used in different circumstances.
- B. The lower lingual holding arch is bilateral and requires the permanent incisors to have erupted; it is used for BILATERAL mandibular space maintenance.
- C. CORRECT. The band and loop is a FIXED, UNILATERAL, non-functional space maintainer. It is banded to the tooth distal to the space with a wire loop contacting the tooth mesial to it, holding the mesiodistal dimension open. It is the standard choice after loss of a single primary molar.
- D. The Nance holding arch is a bilateral MAXILLARY appliance with an acrylic button resting on the anterior palate. This patient's loss is mandibular.
Question 2
Which appliance is indicated for the space left by tooth T?
Show answer and explanation
Correct answer: C. A distal shoe
- A. The Nance holding arch is maxillary and bilateral, and it also depends on erupted permanent molars for anchorage.
- B. Doing nothing allows the permanent first molar to erupt mesially, shortening arch length and causing impaction of the second premolar.
- C. CORRECT. Tooth T is the SECOND primary molar, and the permanent first molar has not yet erupted. Nothing distal remains to band, and the erupting first molar will drift mesially into the space unless it is guided. The distal shoe carries an intra-alveolar extension into the tissue that contacts the mesial surface of the unerupted permanent first molar and directs its eruption. It is fixed and unilateral.
- D. A band and loop requires an abutment DISTAL to the space. With the second primary molar gone and the first permanent molar unerupted, there is no such abutment.
Note: The distal shoe demands a healthy periodontium and is contraindicated where infection risk is high — the intra-alveolar blade sits in the tissue. It is replaced with a band and loop once the permanent first molar erupts.
Question 3
At what point is a space maintainer no longer required?
Show answer and explanation
Correct answer: B. Once the permanent lateral incisor and the permanent first molar have erupted
- A. Waiting for the permanent canine is far too late — the canine erupts around age 11 to 12, well after space loss would have occurred.
- B. The general rule taught for this decision is that no space maintainer is needed once the permanent LATERAL INCISOR and the permanent FIRST MOLAR have erupted. Their eruption marks the point at which arch dimension has been established and the incisor liability period has passed, so the risk of significant space loss from a lost primary tooth drops sharply.
- C. Waiting for full exfoliation of the primary dentition removes the very reason for the appliance long after it mattered.
- D. Chronological age is a poor guide; dental development varies widely between children of the same age.