A young patient in the mixed dentition

Correct answer: C. Her dental age is ahead of her chronological age

• A. Early eruption within a year of the norm is a normal variation, not pathology. Markedly premature eruption would prompt a look at endocrine causes such as hyperthyroidism or precocious puberty.
• B. Delayed dental age would mean teeth erupting later than expected, which is the reverse of what is described.
• C. Correct. Mandibular permanent central incisors normally erupt at 6 to 7 years. Eruption at 5 means dental development has run ahead of chronological age, which is a normal variation. Dental age is judged from calcification stages and eruption sequence and is a more reliable developmental index than eruption timing alone.
• D. If the two matched, eruption would occur at the expected 6 to 7 years.

Correct answer: A. 0.50 mg

• A. Correct. Under the ADA and AAPD schedule, where water fluoride is below 0.3 ppm, children aged 3 to 6 receive 0.50 mg of fluoride ion daily. Supplements are prescribed only after the fluoride content of all water sources the child drinks has been established.
• B. 1.0 mg is the dose for children aged 6 to 16 years where water fluoride is below 0.3 ppm.
• C. 0.25 mg is the dose for children aged 6 months to 3 years in a deficient water supply.
• D. A supplement is indicated where water fluoride is inadequate and the child is at caries risk. Prescribing without checking all water sources risks fluorosis.

Correct answer: B. Around 3 years

• A. First permanent molars begin calcifying at birth, which is why they record perinatal disturbances.
• B. Correct. Permanent second molars begin calcifying at roughly 2.5 to 3 years, crown completion follows at 7 to 8 years, and eruption occurs at 11 to 13. Knowing initiation timings matters when interpreting enamel defects, because the insult can be dated to the period of crown formation.
• C. By 8 years the crown of the second molar is already complete or nearly so.
• D. By 12 years the second molar is erupting, well past the start of calcification.

Note: The recall author was uncertain between 3 and 8 years. Three years is correct for the start of calcification; 8 is approximately when the crown is complete.

Correct answer: B. Less than 2 mm

• A. At 3 mm closure is doubtful; the threshold is 2 mm, and this patient's 3 mm gap sits on the wrong side of it.
• B. Correct. A diastema under 2 mm in the mixed dentition usually closes on its own as the permanent laterals and canines erupt and push the centrals together, the so-called ugly duckling stage resolving. Beyond 2 mm spontaneous closure becomes progressively less likely and orthodontic or frenal assessment is warranted.
• C. Larger than 2 mm predicts poorer spontaneous closure, not better.
• D. Above 4 mm spontaneous closure is unlikely and intervention should be planned, after ruling out a mesiodens or a thick fibrous frenum with a notched interdental crest.

Correct answer: B. Odontoclasts

• A. Fibroblasts produce and remodel the collagen of the periodontal ligament and gingival connective tissue.
• B. Correct. Odontoclasts are multinucleated cells of the monocyte-macrophage line, functionally and morphologically like osteoclasts but acting on dental hard tissue. They resorb dentin and cementum through a ruffled border, creating Howship's lacunae in the root surface.
• C. Cementoblasts deposit cementum; they build rather than resorb.
• D. Osteoblasts form bone. Osteoclasts resorb the bone overlying an erupting tooth, which is a separate process from root resorption.

Note: The eruption pathway is cleared by osteoclasts resorbing overlying bone, while the primary root is resorbed by odontoclasts. Both are needed, and which one is being asked about depends on the tissue.

Correct answer: A. Odontoclasts derived from the inflamed pulp

• A. Correct. Internal resorption begins within the canal. Chronic pulpal inflammation, usually following trauma or deep caries, recruits monocyte-derived odontoclasts to the canal wall, which resorb dentin outward. The classic sign is a smooth, symmetrical, ballooned widening of the canal that moves with the tooth on a shifted radiograph, unlike an external lesion.
• B. The resorbing cell is the same odontoclast whatever surface it attacks; the distinction that matters is whether it approaches from the pulp or from the periodontium.
• C. Cells from the periodontal ligament produce external resorption, which attacks from outside the root inward.
• D. Ameloblasts form enamel and are lost once the crown is complete.

Correct answer: A. Dens invaginatus

• A. Correct. Dens invaginatus, also called dens in dente, arises from infolding of the enamel organ before mineralisation. Maxillary lateral incisors are by far the most commonly affected. The invagination gives caries direct access to the pulp, so a tooth can become necrotic while looking clinically intact, which is why prophylactic sealing is advised.
• B. Concrescence is union of two teeth by cementum alone after their roots have formed.
• C. Taurodontism is an elongated pulp chamber with apically displaced furcation, giving the bull-like shape, and involves multirooted teeth.
• D. Dens evaginatus is an outward projection, a tubercle on the occlusal surface of premolars or the cingulum of anteriors, that wears or fractures and exposes a pulp horn.

Correct answer: B. Minimal sedation, or anxiolysis

• A. Deep sedation means the patient is not easily roused and may need airway support.
• B. Correct. Minimal sedation is a drug-induced state in which the patient responds normally to verbal command. Cognition and coordination may be impaired but ventilation and cardiovascular function are unaffected. Nitrous oxide at these concentrations reliably produces this level, which is why it is the most widely used sedative in paediatric dentistry.
• C. Moderate sedation, previously called conscious sedation, means purposeful response to repeated or painful stimulation with a maintained airway.
• D. A pharmacological agent has been administered and is producing an anxiolytic effect, so this is sedation, just at its lightest level.

Correct answer: A. Immature teeth with open apices have a better chance of pulpal survival and are monitored before intervening

• A. Correct. An open apex with a wide blood supply gives far better revascularisation potential than a mature tooth with a constricted foramen. Current trauma guidance is to monitor with regular clinical and radiographic review and to intervene only when definite signs of necrosis appear, so that root development can continue.
• B. Post-traumatic discolouration may be transient, reflecting pulpal haemorrhage and haemoglobin breakdown, and can regress over weeks. Necrosis is diagnosed on the accumulation of signs, not on colour alone.
• C. The reverse is true. Immature teeth are more likely to survive and to revascularise.
• D. Sensibility testing is unreliable for weeks to months after trauma because of transient neural disruption, and a false negative in that window is common.