BCO cheat sheet

Problem list hierarchy: prioritize by (1) airway/function, (2) skeletal discrepancy severity, (3) dental compensation, (4) esthetics; treatment objectives are written per problem, not per appliance.

Cephalometric norms are population means with SD ~2-3°; a value within 1 SD of the matched ethnic/sex norm is generally not a treatment target by itself.

Model analysis: arch length discrepancy = arch perimeter minus sum of mesiodistal widths; crowding <4 mm per arch is usually resolvable by distalization, 4-8 mm often needs extraction or interproximal reduction, >8 mm usually needs extraction.

Class II division 1 vs division 2 differ by incisor inclination, not molar relation; division 2 shows retroclined central incisors with often deep overbite and increased interincisal angle.

Facial profile assessment: E-line (nose tip to soft-tissue pogonion); lower lip 2 mm behind and upper lip 4 mm behind the E-line are common adult Caucasian references.

Impacted canine localization requires both parallax (two periapical views) and CBCT when resorption of adjacent roots is suspected; panoramic alone misrepresents buccolingual position.

Growth status: cervical vertebral maturation stages CS3-CS4 bracket the pubertal growth spurt; hand-wrist and midpalatal suture staging add corroboration.

Informed consent for orthodontics must document root resorption, decalcification, gingival recession, relapse, and the option of no treatment.

Cranial vault grows predominantly by intramembranous apposition at sutures; growth ceases earliest (neural growth completed ~7 years).

Mandible grows by endochondral replacement at the condylar cartilage plus surface apposition/resorption; the condyle is a growth site, not the primary growth center.

Cephalocaudal gradient: the head doubles in size by ~6 months and reaches ~90% of adult size by 6 years; facial growth continues into the late teens.

Maxillary growth displacement is downward and forward with apposition at the posterior and inferior surfaces (tuberosity, alveolar process, palate).

Dental age indicators: Nolla stages, Demirjian stages, and the cervical vertebral method; dental age diverges from chronologic age by up to 2 years normally.

Functional matrix theory: soft tissue volume and function (nasal cavity, tongue, muscles) drive skeletal adaptation; airway obstruction can alter mandibular posture and growth direction.

Class III growth is often characterized by maxillary deficiency rather than true mandibular excess; distinguish by SNA, SNB, and effective maxillary/mandibular length.

Timing rule: orthopedic maxillary protraction is most efficient before ~10-12 years, while mandibular advancement by functional appliance works best at the pubertal spurt.

Optimal continuous force range: ~50-100 g for intrusion, ~100-200 g for extrusion, ~150-250 g for translation of posterior teeth; PDL pressure ~20-26 g/cm² is the capillary pressure threshold.

Center of resistance of a single-rooted tooth lies ~1/3 of root length apical to the alveolar crest; of a multirooted posterior tooth, near the furcation.

Moment-to-force ratio determines movement type: pure translation needs M/F equal to the distance from bracket to center of resistance; lower M/F gives uncontrolled tipping, higher gives controlled tipping/root movement.

Biological phases of tooth movement: initial rapid displacement (seconds-minutes), hyalinization/lag phase (days-weeks), then linear acceleration with undermining resorption.

Light continuous force produces frontal resorption and direct bone formation; heavy force causes PDL ischemia, hyalinization, and undermining resorption with a longer lag.

Anchorage classification: maximum, moderate, and minimum; reciprocal tooth movement occurs when forces are balanced, and anchorage loss is proportional to the reactive force applied.

Friction in sliding mechanics depends on ligation force, surface roughness, and saliva; self-ligating brackets do not eliminate friction, only reduce it at low angulation.

Root resorption risk increases with heavy force, long duration, intrusion, and premolar extraction; severe resorption (>4 mm) warrants force reduction and radiographic monitoring.

Bracket prescription (e.g., MBT, Roth) encodes tip, torque, and in-out values; slot size 0.022 in accommodates 0.019 x 0.025 in wire for sliding, while 0.018 in slot uses 0.017 x 0.025 in.

Archwire sequence: 0.014 NiTi → 0.016 NiTi → 0.016 x 0.022 NiTi → 0.019 x 0.025 stainless steel; NiTi for alignment, stainless for sliding and space closure.

Rapid maxillary expansion: ~0.5-1 mm/day of activation, ~5-7 mm total, with split at the midpalatal suture; age under ~15 years improves skeletal response.

Clear aligner staging: attachments and interproximal reduction are required for rotations >20° and for bodily movement; aligner force delivery is weakest for extrusion and torque.

Temporary anchorage devices: 1.2-2.0 mm diameter, placed in attached gingiva, minimum 4-6 mm of bone; loading can be immediate but torque should be avoided.

Extraction decision: premolar extraction is indicated when crowding exceeds arch perimeter by >6-8 mm, or when incisor protrusion requires retraction beyond 2-3 mm.

Debonding protocol: remove brackets, polish adhesive, take final records, and deliver retainers within days; enamel damage risk is reduced by using a debonding plier at the bracket base.

Emergency management: wire irritation is managed by wax and clipping; avulsed tooth should be replanted within 60 minutes in saline or milk and splinted for 2 weeks.

Le Fort I advancement of 5-10 mm is common for maxillary hypoplasia; larger movements require bone grafting and carry relapse risk from soft tissue tension.

Bilateral sagittal split osteotomy (BSSO) is the workhorse for mandibular advancement/retrusion; relapse is greater for large advancements (>10 mm) and for condylar resorption cases.

Surgical sequencing: single-jaw vs bimaxillary; bimaxillary surgery allows differential impaction/advancement and improves airway and esthetics simultaneously.

Virtual surgical planning (VSP) with CBCT and splints improves accuracy; planned movements should be checked against soft tissue prediction (2:1 to 3:1 ratio for chin advancement).

Orthodontic preparation before surgery includes leveling, decompensation of incisors, and coordination of arches; surgery is timed when growth is complete (CVM stage 5 or hand-wrist maturity).

Skeletal anchorage options: mini-implants, palatal implants, zygomatic anchorage, and miniplates; each provides absolute anchorage for en masse retraction or intrusion.

Post-surgical relapse: 1-2 mm in the first year is common; rigid internal fixation and occlusal splints reduce relapse, and retention with elastics is often continued for months.

Airway assessment: bimaxillary advancement increases posterior airway space; mandibular setback can narrow the airway and should be evaluated in patients with sleep apnea.

Cleft lip with or without palate occurs in ~1 in 700 births; isolated cleft palate ~1 in 2000; multifactorial inheritance with recurrence risk ~4% for one affected child.

Timeline: lip repair at 3-6 months (rule of 10s: 10 weeks, 10 lb, 10 g/dL hemoglobin), palate repair at 9-18 months to preserve speech development.

Presurgical infant orthopedics (nasoalveolar molding) approximates alveolar segments and reshapes the nasal cartilage before lip repair.

Alveolar bone grafting is typically performed at 6-9 years, before eruption of the permanent canine, when the canine root is 1/2 to 2/3 formed.

Cleft palate repair techniques: Furlow double-opposing Z-plasty lengthens the palate; von Langenbeck and Bardach push-back procedures close the defect.

Velopharyngeal insufficiency is assessed by nasoendoscopy and videofluoroscopy; management includes speech therapy, pharyngeal flap, or sphincter pharyngoplasty.

Syndromic associations: Pierre Robin sequence (micrognathia, glossoptosis, airway obstruction), Treacher Collins (mandibulofacial dysostosis), Apert/Crouzon (craniosynostosis).

Cleft patients require long-term multidisciplinary care: orthodontics, speech therapy, audiology, and psychosocial support through adolescence.

TMD classification (DC/TMD): myalgia, arthralgia, disc displacement with/without reduction, degenerative joint disease, and subluxation.

Disc displacement with reduction: reciprocal click, reduces on opening; with reduction, the click occurs at a reproducible interincisal distance and the patient can open fully.

Disc displacement without reduction: limited opening (<40 mm), deviation to the affected side, and no click; MRI is the reference standard for disc position.

First-line TMD management is conservative: patient education, soft diet, NSAIDs, muscle relaxants, occlusal splint, and physical therapy; irreversible occlusal adjustment is not first-line.

Occlusal splints: stabilization splints reduce parafunction and load; they do not permanently alter occlusion and should be adjusted for even contacts.

Red flags for orofacial pain: unilateral persistent pain, paresthesia, trismus, weight loss, and unexplained swelling warrant imaging and referral to rule out malignancy or infection.

Bruxism is managed with behavioral therapy, botulinum toxin in selected cases, and splint therapy; it is not cured by occlusal adjustment.

TMJ imaging: panoramic for screening, CBCT for bony changes, MRI for disc and soft tissue; arthrocentesis is used for closed lock and inflammatory joint disease.

Relapse causes: periodontal fiber recoil, gingival fiber memory, occlusal forces, growth, and failure to address the original etiology (e.g., tongue thrust).

Lower incisor irregularity recurs in most patients; a bonded lingual retainer from canine to canine is the most reliable long-term retention for the lower arch.

Retention protocols: fixed lingual retainers plus removable vacuum-formed retainers; full-time wear for 6-12 months, then night-time wear indefinitely in many cases.

Intercanine width increases achieved during treatment tend to relapse; arch form should be maintained within the original envelope to reduce instability.

Growth after treatment causes relapse in growing patients; retention should continue until growth is complete, and growth prediction should be discussed at consent.

Impacted or transposed teeth and severe rotations have higher relapse risk; supracrestal fiberotomy can reduce rotational relapse.

Retainer maintenance: fixed retainers require periodic checks for debonding and calculus; vacuum-formed retainers need replacement every 1-2 years.

Stability evidence: long-term studies show mandibular incisor alignment deteriorates over 10+ years regardless of retainer type, so lifelong retention is often recommended.

Informed consent requires disclosure of diagnosis, treatment options including no treatment, material risks, and the opportunity for questions; documentation should be signed and dated.

Minors: consent from a parent or legal guardian; assent from the child when developmentally appropriate, and confidentiality boundaries explained.

Record keeping: retain orthodontic records (models, radiographs, photos, notes) per jurisdiction, commonly 7-10 years after the last visit or until age of majority plus the retention period.

Advertising and social media: patient images require written HIPAA-compliant authorization; before/after photos must not be misleading and cannot guarantee outcomes.

Conflicts of interest: disclose financial relationships with appliance manufacturers and any referral incentives; fee splitting without disclosure is unethical.

Scope of practice: orthodontists should not delegate diagnosis or treatment planning to auxiliaries; expanded-duty assistants may perform only delegated reversible procedures.

Practice metrics: production vs collection ratio, case acceptance rate, and overhead percentage are standard management indicators; overhead typically runs 60-70% of collections.

Termination of care: provide written notice, offer records transfer, and ensure continuity; abandonment without notice is an ethical and legal violation.

Evidence hierarchy: systematic reviews/meta-analyses > randomized controlled trials > cohort > case-control > case series > expert opinion.

PICO framework: Population, Intervention, Comparison, Outcome; a well-formed question is the first step of evidence-based practice.

Randomization reduces selection bias; allocation concealment and blinding reduce performance and detection bias; intention-to-treat analysis preserves randomization benefits.

Effect size: mean difference for continuous outcomes, risk ratio or odds ratio for binary outcomes; confidence intervals indicate precision and statistical significance.

Statistical vs clinical significance: a p-value <0.05 does not imply a clinically meaningful effect; minimal clinically important difference should be defined a priori.

Systematic review quality is assessed with AMSTAR or GRADE; risk of bias in RCTs is assessed with the Cochrane RoB tool.

Publication bias is detected with funnel plots and Egger's test; small positive studies are more likely to be published.

Critical appraisal of orthodontic literature: check sample size calculation, blinding, dropouts, and whether the outcome measure (e.g., PAR index) is validated.