American Board of Orthodontics Written Examination: Selective Preparation Guide Study Guide

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In a loaded animal model, deleting osteocyte RANKL decreases compression-side osteoclast numbers and tooth displacement despite comparable appliance force. Interpret the paired findings as evidence that osteocyte signaling contributes to resorption that permits displacement.

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Both SNA and SNB change unexpectedly after an automated retracing. Inspect the shared cranial landmarks and reference line before interpreting the paired change as coordinated movement of both jaws.

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An experimental intervention reduces osteoclast numbers and tooth displacement but does not measure bone formation. Attribute the direct evidence to impaired resorption; do not claim increased osteoblast activity without a formation-specific measurement.

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A child has clavicular abnormalities, delayed permanent-tooth eruption, and a heterozygous RUNX2 variant predicted to reduce functional protein. Explain the combined phenotype through inadequate developmental transcription-factor dosage.

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A formulation containing epinephrine lasts longer than an otherwise comparable formulation. Separate the two mechanisms: sodium-channel inhibition accounts for anesthesia, while reduced local vascular uptake helps prolong its action.

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A heterozygous parent with cleidocranial dysplasia has two children who did not inherit the familial variant. The probability that a third child inherits it remains one-half; the preceding outcomes do not make transmission overdue.

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A patient with retained primary teeth and multiple unerupted permanent teeth can bring the shoulders unusually close together. Integrate the dental findings with possible clavicular hypoplasia and investigate a syndromic developmental explanation rather than treating each tooth independently.

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A child has disproportionate short limbs and an established achondroplasia diagnosis. When comparing molecular explanations, select excessive FGFR3 activity affecting cartilage-based growth rather than reduced RUNX2 dosage or deficient RANKL-mediated osteoclast differentiation in alveolar bone.

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Several posterior teeth remain infraoccluded without a visible obstruction, and teeth distal to the first affected tooth share the failure. Consider primary failure of eruption before applying traction. Contrast this pattern with a single obstructed tooth or a tooth already fused to bone.

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Variant-receptor cells respond weakly to ligand but strongly to a reagent that directly activates adenylyl cyclase. Conclude that cAMP generation remains possible and investigate receptor expression or coupling rather than declaring the entire downstream pathway nonfunctional.

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An infant has an intact lip but an opening in the palate. Explain that palatal development can be disrupted without a visible lip cleft, and arrange assessment around the child's specific feeding and later speech needs.

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An orthodontic patient reports persistent dry mouth and dry eyes and develops new cervical lesions despite previously stable oral health. Consider salivary dysfunction in the risk assessment and coordinate medical evaluation while strengthening individualized oral prevention.

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After using a conventional detachable low-speed handpiece, the team must clean and heat sterilize it before another patient, even if a barrier covered its exterior. For a cordless device independent of air and waterlines, verify FDA clearance and implement its validated reprocessing instructions rather than assuming that exterior disinfection is sufficient.

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A new patient reports no known infectious conditions. Before a procedure with anticipated splashing, use exposure-appropriate protective equipment and hand hygiene rather than reducing precautions on the basis of the patient's reassuring history alone that day.

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An impacted tooth's relationship to adjacent roots remains uncertain after examination and appropriate two-dimensional imaging. If resolving that relationship will change the surgical or orthodontic plan, consider a limited-region CBCT selected for the diagnostic question.

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A justified scan is needed only to assess one impacted maxillary canine and nearby roots. Select coverage that includes the relevant anatomy while excluding unnecessary craniofacial regions, provided the chosen field can answer the clinical question.

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An adolescent reports an occasional click but has no pain, locking, or difficulty opening and eating. Document the finding, explain its usual significance, and advise reassessment if symptoms or functional limitations subsequently develop during follow-up.

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A patient develops painful chewing and intermittent inability to open fully. Assess the history, range of movement, and muscle and joint findings before attributing the problem to a recent appliance adjustment or selecting a corrective procedure.

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A patient describes aching with chewing, and palpation over a masticatory muscle reproduces the familiar ache. Opening remains unrestricted and there is no locking. Document the muscular findings rather than diagnosing a joint disorder solely because an incidental click is also audible.

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In a retention trial, a computer generates the treatment sequence, and an independent coordinating center releases each assignment only after eligibility and enrollment are confirmed. Clinicians therefore cannot use the next assignment to direct patients with greater initial crowding toward a preferred retainer. Assess sequence generation and concealment separately, then examine follow-up completeness and consistent outcome measurement.

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Two otherwise comparable local anesthetic formulations differ by the presence of epinephrine. Explain a longer local effect through slower vascular absorption, while recognizing that the anesthetic molecule itself remains responsible for inhibiting nerve conduction locally.

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New lesions occur in 12 of 120 intervention patients and 24 of 120 comparison patients. Risks are 0.10 and 0.20, so the intervention-to-comparison risk ratio is 0.50 over the study's stated follow-up period.

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An adverse outcome occurs in 8% of one group and 20% of another. Subtracting intervention risk from comparison risk gives a 12-percentage-point absolute reduction, which can be communicated alongside the relative comparison to patients.

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A reference standard identifies 50 affected patients, and a screening test detects 45. Sensitivity is 45 divided by 50, or 90%. The five missed affected patients belong in the denominator as false negatives for this calculation.

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Among 80 people without the target condition, a test classifies 72 as negative and eight as positive. Specificity is 72 divided by 80, or 90%; the eight false positives reduce specificity in this sample.

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An adult collapses in the clinic, remains unresponsive, and makes occasional gasps. No definite pulse is felt within 10 seconds. Activate the emergency response, begin CPR, and have another team member bring the AED promptly.

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A treatment-effect estimate has a wide confidence interval spanning both little benefit and substantial benefit. Recognize imprecision and discuss the range of compatible effects rather than reporting only the favorable point estimate to the patient.

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A patient develops early noncavitated white lesions near brackets. Strengthen plaque and dietary control and select appropriate topical fluoride measures to support remineralization, while monitoring whether the lesions remain active or progress during subsequent orthodontic visits.

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A patient signs an extraction consent form but says they do not understand the alternatives. Pause the decision, explain the options in understandable terms, invite questions, and document the resulting discussion before proceeding with treatment.

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A primary molar becomes increasingly lower than neighboring teeth over serial growth visits. Consider ankylosis-related failure to accompany dentoalveolar development and evaluate the successor and local space effects before choosing observation or intervention for that child.

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A patient has interdental attachment loss at two nonadjacent teeth, with findings consistent with periodontal destruction and no alternative local explanation. Recognize the case criterion, then characterize extent, severity, complexity, and progression risk through a full assessment.

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A patient has widespread bleeding around brackets but no qualifying attachment loss. Identify gingival inflammation and improve plaque control, while avoiding a periodontitis label based solely on bleeding and continuing appropriate periodontal assessment over subsequent visits.

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A patient brushes twice daily but sips sweetened drinks repeatedly and has dry mouth. Address exposure frequency and salivary risk alongside plaque control and fluoride, because brushing frequency alone does not capture the mineral balance around brackets.

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A 1.5 N force has a line of action 8 mm perpendicular to a tooth's reference point. Its moment magnitude is 12 N·mm; specify the rotational direction from the geometry before combining it with other moments.

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A force produces an 18 N·mm clockwise moment and an applied couple contributes 12 N·mm counterclockwise. With clockwise positive, the net is 6 N·mm clockwise; assess resultant force separately before predicting the complete movement tendency.

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Two parallel forces of 2 N act in opposite directions with 5 mm separation. Their net force is zero and their couple moment is 10 N·mm, with direction determined by the arrangement of the force pair.

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An ideal cantilever delivers 0.8 N at a selected activation. Doubling its free length while keeping material, cross-section, and activation unchanged predicts 0.1 N, provided elastic behavior and the same end-loading conditions remain valid throughout.

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Two ideal wire segments have equal length and cross-section but different elastic moduli. Under equivalent boundary conditions, the higher-modulus segment is stiffer; if dimensions also differ, compare the complete structural stiffness rather than modulus alone.

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A rectangular wire is rotated so its greater cross-sectional dimension resists the planned bending direction. With material and length unchanged, expect increased bending stiffness because more material lies farther from the relevant neutral axis in that orientation.

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Two wires deflect similarly under an initial load, but one retains a bend after unloading while the other returns close to its starting form. The second demonstrates greater recovery under that particular activation and test condition.

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A laboratory graph shows a broad, relatively flat unloading segment after substantial wire activation. Relate that segment to limited force variation during decreasing deflection, while checking whether the clinical activation falls within the tested plateau range.

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A tracing records SNA of 83 degrees and SNB of 77 degrees. Calculate ANB as 6 degrees, then examine the broader skeletal, dental, and facial findings before assigning the meaning of that sagittal relationship clinically.

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Serial images appear to show a changed jaw relationship, but the later image has obvious asymmetry from head rotation. Review positioning and tracing quality before claiming treatment-induced change, and obtain additional imaging only when clinically justified.

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An automated report shows an unexpected sagittal discrepancy, and point A appears placed on an overlapping contour. Correct the landmark using its anatomical definition, recalculate dependent measurements, and reassess the diagnosis before changing the treatment plan.

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A lower incisor moves forward on a cranial-base superimposition while the mandible also advances. Compare a mandibular regional registration on the internal symphyseal cortex and inferior alveolar canal before assigning the entire displacement to incisor movement within the jaw.

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In an illustrative comparison, an upper molar appears 3 mm farther inferiorly on a cranial-base superimposition but only 1 mm farther inferiorly after appropriate maxillary regional registration. The regional finding supports 1 mm of eruption relative to the maxilla; the overall change also reflects maxillary displacement and possibly rotation. Establish vertical registration from the relevant skeletal contours before attributing the entire apparent descent to dental eruption.

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Both arches are aligned, but planned anterior contacts remain incompatible with the measured tooth-width relationship. Recheck the defined width sums and consider a relative tooth-size discrepancy before adding further arch space or changing incisor position alone.

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A defined arch segment has 69 mm of available perimeter and requires 74 mm for the included teeth. Available minus required space is minus 5 mm, indicating a 5 mm deficiency within that measured segment.

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Two patients each have 6 mm of crowding, but one has protrusive incisors and the other has retrusive incisors with a flat profile. Compare their full objectives before assuming that an identical extraction pattern serves both patients.

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A child's mandibular midline is centered before tooth contact but shifts laterally into a unilateral posterior crossbite on closure. Document the shift and assess the transverse relationships rather than interpreting the habitual bite as a purely fixed asymmetry.

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Comparable serial images show continuing apical shortening during active incisor movement. Reassess the force system and remaining objectives, discuss the finding with the patient, and consider interrupting active loading rather than automatically continuing the same mechanics.

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A patient reports stable alignment, but examination reveals one detached segment of a bonded retainer and localized plaque accumulation. Address the appliance defect and hygiene needs rather than waiting for visible displacement to confirm loss of retention.

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A maxillary molar has a 0.8 mm central-groove alignment discrepancy. A mandibular molar has aligned buccal cusps but a 0.8 mm lingual-cusp offset. Score one alignment point for the maxillary molar; the mandibular lingual-cusp offset is not the alignment reference.

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An adult has attractive alignment goals but qualifying attachment loss and widespread bleeding. Establish the periodontal diagnosis and address inflammatory disease with the periodontal team before proceeding with the original movement plan unchanged.

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A single tooth has a localized attachment defect and findings suggesting pulpal disease, while nonadjacent teeth lack qualifying loss. Investigate the endodontic explanation and coordinate tooth-specific management rather than assigning generalized periodontitis from that defect.

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A patient requires anterior retraction while preserving molar position. Compare direct miniscrew loading with tooth-borne reinforcement by asking which structures receive the reciprocal reaction and whether the selected arrangement matches the intended anchorage objective during space closure.

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Two adolescents have the same cervical maturation stage but different recent height-growth patterns. Avoid assigning identical remaining mandibular growth to both; integrate the serial observations and broader developmental evidence when discussing timing and expected treatment effects.

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When explaining the development of standardized outcome assessment, connect the 1994 investigation to subsequent field testing and the 1999 use of model/radiographic grading. For example, two examiners assessing the same marginal-ridge discrepancy can apply a shared measurement criterion and compare their judgments. Defined criteria make disagreement easier to identify and address, supporting reproducibility without making assessment infallible.

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New chalky lesions appear around brackets in a patient who frequently drinks sweetened beverages. Review plaque control, exposure frequency, saliva, and fluoride, then reassess lesion activity rather than assuming debonding alone will resolve the risk environment.

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A child with cleft involvement needs orthodontic space management while the team is planning additional surgery and restorative care. Agree on the next shared objective and timing before moving teeth into positions that could conflict with later procedures.