Cheat Sheet - Level III Formative (Unit A II-IV + Unit B)

Purpose

Concise, table-first answers to the Level III formative objectives: Unit A Parts II–IV (biologic response, mechanical principles, anchorage & the edgewise appliance) and all of Unit B (space management, crossbites, vertical problems/habits, adjunctive adult orthodontics). Content is organized by topic, not by objective — each block ends with an italic Covers … tag mapping it back to the objective numbers in Level III Unit A Learning Objectives and Level III Unit B learning Objectives. Unit A Part I (diagnosis) is intentionally excluded; see Cheat Sheet - Space Analysis for space-analysis mechanics.

Objectives	Section
A-II.1–3	Biologic Response to Orthodontic Force
A-III.1–4	Removable Appliances & Active Hawley Design
A-III.5–7	Biomechanics: Force, Moment & Wire Properties
A-IV.1–6	Anchorage & the Contemporary Edgewise (Straightwire) Appliance
B-1.1–7, B-2.1–6	Space Management, Maintenance & Regaining
B-3.1–11	Crossbites in Children
B-4.1–5	Vertical Problems & Habits
B-5.1–11	Adjunctive Orthodontics in Adults

Biologic Response to Orthodontic Force

Pressure-Tension Theory: The Cascade (Light Sustained Force)

The PDL is a fluid-filled shock absorber — the first event with any force is always alveolar bone bending; the biologic cascade only starts once fluid is squeezed out and cells feel pressure. Sustained light force has two effects: mechanical distortion of PDL cells (releasing cell contents) and altered blood flow (↓ on pressure side, ↑ on tension side → O₂/CO₂ change → chemical messengers). Signals are chemical, not electrical.

Time	Event (light force, ~ optimal)
<1 sec	Bone bends; tooth moves relative to facial skeleton, not yet within PDL
1–2 sec	PDL fluid expressed; tooth displaces within its socket → pressure + tension sides
3–5 sec	Vessels partially compressed (pressure side) / dilated (tension side); cells distorted
~1 min	Blood flow altered; prostaglandins + cytokines released (Khouw India-ink studies visualised the vascular change)
~4 hrs	↑ cyclic AMP (Davidovitch) — cell differentiation begins
~2 days	Osteoclasts/osteoblasts remodel socket → tooth movement by frontal resorption

Proffit’s light-force timeline: blood-flow change in seconds, prostaglandins/cytokines in minutes, cAMP at ~4 h, frontal-resorption movement at ~2 days.

Covers A-II.1

Light vs Heavy Force: Frontal vs Undermining Resorption

flowchart TD
    F[Sustained force on tooth] --> B[Bone bending, PDL fluid expressed]
    B --> L["LIGHT force: vessels partially compressed"]
    B --> H["HEAVY force: vessels 100% occluded (3–5 sec)"]
    L --> L1[PDL cells survive → local differentiation]
    L1 --> L2["Frontal resorption — lamina dura resorbed from PDL side, movement at ~2 days, smooth & continuous"]
    H --> H1["Sterile necrosis = hyalinization (no cartilage, no bacteria)"]
    H1 --> H2["Cells must come from marrow / adjacent PDL; osteoclasts attack lamina dura from underside (3–5 days)"]
    H2 --> H3["Undermining resorption — lamina dura removed in 7–14 days → sudden jump, then delay repeats"]

• ==Hyalinization = sterile necrosis== of avascular PDL (looks like hyaline cartilage histologically; it is not).
• Small necrotic zone → cells from adjacent PDL; large zone → bone marrow via undermining resorption (Howship’s lacunae on the underside of the lamina dura).
• Light force moves teeth more early in treatment than heavy force — delay, jump, delay is inefficient and destructive.
• Clinical sign of excessive force: a very loose tooth (lamina dura loss).

Heavy-force sequence: vessel occlusion in 3–5 s → sterile necrosis (hyalinization) → movement delayed to 7–14 days via undermining resorption.

Undermining resorption histology — Howship’s lacunae on the underside of the lamina dura, osteoclasts attacking from the marrow side of a hyalinized zone.

Force duration rules

• Light continuous force = ideal. Heavy continuous = destructive (repeated undermining resorption, no repair window). Heavy interrupted (decays to zero) = acceptable but inefficient/painful.
• Reactivate no sooner than every 3 weeks (4–6 typical): 7–14 days movement + ~2 weeks repair.
• Removable-appliance wear threshold: 4–8 hrs/day — below it, nothing moves.

Covers A-II.1

Optimal Force by Movement Type

One optimal PDL pressure; force varies with the PDL area loaded.

Movement	Optimal force	Why
Intrusion	~10 g	Pressure concentrated at apex only (highest pressure per gram)
Tipping	~50 g	Half the PDL loaded, greatest at apex + crest
Rotation / Extrusion	~50 g	Irregular roots mean these always tip too
Torque (root movement)	~75 g	Loading intermediate between tipping and bodily
Bodily (translation)	~100 g	Entire PDL side loaded evenly (lowest pressure per gram)

Covers A-II.1, A-II.3

Biologic Electricity: Piezoelectric / Bioelectric Theory

• Piezoelectricity: force distorts a crystalline lattice (bone mineral + collagen) → electron shift → brief current; force release → equal reverse current. Rapid decay; rhythmic pulses with chewing/walking.
• Role: maintains calcification and remodelling of loaded bone — including alveolar bone. Loss of rhythmic loading explains post-extraction ridge resorption and astronaut bone loss.
• Piezoelectricity is NOT the signal for orthodontic tooth movement — 1960s pulsed-force experiments failed; the pressure-tension (chemical) theory stands. Electrical fields can alter membrane potentials/cell entry, but this remains experimental.

Piezoelectric effect — deforming the crystalline structure produces a brief current that decays and reverses on release: maintains alveolar bone, does not move teeth.

Exam one-liner

Bioelectric signals = bone maintenance and turnover; chemical pressure-tension signals = orthodontic tooth movement. Classic MCQ distractor.

Covers A-II.2

Force Levels and Anchorage (Differential Force)

Anchorage = resistance to unwanted tooth movement — everything that opposes movement. The anchorage value of a tooth ≈ its root (PDL) surface area: multirooted molars > premolars > incisors.

• Light force preserves anchorage; heavy force burns it: light force reaches optimal pressure in the small-PDL movement unit while the large-PDL anchor unit stays below threshold. Heavy force pushes the movement unit onto the flat plateau of the pressure–response curve (hyalinized, stalled) while the anchor teeth now feel enough pressure to move.
• Example (premolar extraction): anchor unit = 5+6+7, movement unit = canine → canine moves, molars stay. Uncontrolled heavy force can drag molars mesially — and retracting a molar is ~10x harder than moving a premolar.

Relative anchorage values — the larger a tooth’s root (PDL) surface area, the greater its resistance to unwanted movement.

Anchorage type	Principle
Simple	Unequal units linked — tooth with smaller PDL area moves more
Reciprocal	Equal PDL areas → equal and opposite movement
Reinforced	Add teeth (e.g., second molar) to enlarge the anchor unit
Stationary	Anchor unit resists by bodily movement while movement unit tips (force through centre of resistance)

Covers A-II.3

Sources: 03 - Biologic Response to Orthodontic Force, L2 3A unit review_slides, Level III Orthodontics LOs

Removable Appliances & Active Hawley Design

Anchorage Principles in Appliance Design

Anchorage = resistance to the reaction force. Every appliance needs a movement unit and an anchor unit; design minimises the reaction reaching the anchor by:

• Light force — enough to move the target tooth but below the PDL threshold of the anchor unit (light force preserves anchorage; heavy force burns it and can hyalinize the target’s PDL, stalling the tooth you want to move while the anchor drifts).
• Enlarge the anchor unit’s PDL area — aim for anchor : movement PDL ratio ≥ 2:1 (4:1 with sliding mechanics); anything less approaches reciprocal anchorage (equal-value teeth connected → equal, opposite movement).
• Reinforcement — add more teeth, cross-arch elastics, extraoral force (headgear → cranial vault), or skeletal anchorage (TADs).
• Stationary anchorage — pit bodily movement of the anchor against tipping of the movement unit (force routed nearer the centre of resistance), roughly halving the reaction felt.
• In a removable plate specifically: anchorage = all clasped teeth plus palatal coverage (acrylic against the vault + mucosa massively enlarges the “anchor surface”). Forces that overwhelm this don’t move anchor teeth — they displace the appliance.

Retracting a molar that has drifted mesially is ~10× harder than moving a premolar — losing anchorage (e.g. Class I slipping to Class II molar) is far costlier than preserving it.

Covers A-III.1

Types of Removable Appliances

Appliance	Mechanism	Indications	Limitations
Functional / orthopaedic (activator, Twin Block — lower ramp + upper expansion screw; Frankel — shields hold lips/cheeks off dentition; bionator; fixed Herbst/MARA)	Construction bite posturing the mandible — for Class II, condyles brought down + forward out of the fossa → guides jaw growth, not teeth	Growing Class II child with mandibular deficiency (Class III use = mandible rotated down-back, only viable in short-face children)	Effects taper — final mandibular size ends close to untreated; compliance-dependent
Crozat	All-precious-metal (gold) framework; gold fingersprings + molar clasps engaging MB/DB undercuts; transverse connectors for lateral expansion	Slow expansion / mild tipping	Tipping only; slower than steel-spring equivalents
Hawley-type active plate	Acrylic baseplate + clasps + finger springs (light, continuous, large range) or jackscrew (¼ turn = 0.25 mm; heavy, rapidly decaying force)	Tipping over a few mm — e.g. anterior crossbite of an incisor; slow arch expansion (split/Schwarz plate)	Single-point contact → tipping only; screw force is unphysiologic for individual teeth
Clear aligners	Series of vacuum-formed trays, each ≤ 0.5 mm movement/step; bonded attachments improve grip	Adults/older adolescents; mild crowding via interproximal reduction; near-invisible	Growth can’t be modelled; rotation & extrusion need attachments (tipping/intrusion don’t); poor for extraction cases

Functional appliance effects (know all three): ① accelerated mandibular growth that later tapers; ② headgear effect — soft-tissue reaction restrains forward maxillary growth; ③ Class II elastics effect — upper incisors tip back, lowers forward. Clasps and labial bow on a functional are stabilising only — keep the bow off the incisors (lingual tipping wastes the overjet reduction growth would provide).

Covers A-III.2

Twin Block — lower ramp postures the mandible forward; upper expansion screw.

Active Hawley: Component-by-Component Design

flowchart TD
    H[Active Hawley plate] --> A["ACTIVE<br/>Finger spring (SS, helix)<br/>or jackscrew<br/>light continuous force → tipping"]
    H --> R["RETENTIVE<br/>Adams clasps (6s), ball/C-clasps,<br/>labial bow on incisors"]
    H --> C["CONNECTOR<br/>Rigid acrylic baseplate —<br/>embeds springs, carries clasps"]
    H --> N["ANCHORAGE / REACTIVE<br/>All clasped teeth<br/>+ palatal acrylic coverage"]
    A -- reaction force --> N
    R -- "must out-resist spring's reaction<br/>or plate unseats" --> A

Component	Recommendation
(a) Active	Finger spring (double helix, guarded under acrylic or free) — stainless steel (NiTi cannot be bent); activated down to the cervical of the tooth; reactivate ~every 2 weeks. Jackscrew for block/arch movement only (heavy, decaying force, patient-activated). Labial bow can be activated (springs closed) to retrocline flared incisors.
(b) Retention	Adams clasp on the 6s — still the most effective clasp holding a plate against working springs; tighten by bending gingivally where the wire exits the acrylic, or arrowheads inward. Ball/C-clasps on premolars; labial (Hawley) bow engages canines/incisors anteriorly. Retention must exceed the springs’ displacing reaction or the plate lifts in function.
(c) Connector	Acrylic baseplate — must stay rigid; embeds the springs/screw, unites all units, contributes retention by close palatal fit.
(d) Reactive / anchorage	Every clasped tooth not being moved + palatal coverage. This is why a plate can only tip 1–2 teeth at a time — the anchor pool must dwarf the movement unit.

Anything beyond tipping (bodily movement, torque, rotation) needs two-point contact → a fixed attachment. A removable spring touches the crown at one point, so removables essentially only tip teeth.

Covers A-III.3, A-III.1

Active plate with finger springs correcting an anterior crossbite — the classic active-Hawley indication.

Wire Selection for Active Hawley Components

Memorise this table (stainless steel, mm):

Component	Wire size
Labial bow (lab bow)	0.7–0.8 mm
Adams clasp — molars	0.7 mm
Adams clasp — premolars	0.6 mm
Finger spring — guarded (under acrylic)	0.6 mm
Finger spring — unguarded	0.7 mm
Ball clasp	0.7 mm
C-clasp	0.7 mm

Logic of selection:

• Active elements are thinner (0.6–0.7) → more resilient → a lighter, more constant force over the deactivation range. Retentive elements are thicker (0.7–0.8) → stiff, so they resist displacement without deforming.
• Rule: pick the smallest wire whose strength survives activation + occlusal load (a spring that permanently deforms is useless), then regain springiness/range by lengthening the beam — a helix/loop, not a thinner wire. (Doubling diameter: strength ×8, stiffness ×16, range ×½; doubling length: springiness ×8, range ×4.)
• A guarded spring can be 0.6 mm because the acrylic guard protects it from distortion; unguarded needs 0.7 mm for inherent strength.

The helix trick: bending a helix into a finger spring lengthens the wire — more springiness and range with little strength cost.

Proffit's general window for removable-appliance steel is 22–30 mil (≈0.55–0.75 mm) — the clinic values above sit inside it. Superelastic NiTi has essentially zero formability, so all clasps and springs are bent from stainless steel.

Covers A-III.4, A-III.3

Sources: L2 3A unit review_slides, 04 - Mechanical Principles in Controlling Orthodontic Force, 14 10 Contemporary Orthodontic Appliances

Biomechanics: Force, Moment & Wire Properties

Core Definitions

Term	Definition
Force (F)	A load applied to the tooth (gm clinically; N in research; 1 N ≈ 100 gm). Applied at the crown/bracket — never at the centre of resistance
Moment (M)	Tendency to rotate = force × perpendicular distance to centre of resistance (gm·mm). A vector: magnitude + direction
Couple	Two equal, opposite, non-colinear parallel forces → a pure moment (Mc): rotation with no displacement
Fulcrum	The pivot point the tooth actually turns about during movement (= the centre of rotation)
Centre of resistance (CRes)	Theoretical balance point ≈ middle of the bone-encased root (Burstone: ~2/3 from apex; just above furcation for molars). Force through it → pure bodily movement — but it lies under bone, so a bracket can never sit there
Centre of rotation (CRot)	The actual point of rotation for a given force system; its position shifts with the Mc/MF ratio (coincides with CRes for a single force; moves to infinity for translation)
Anchorage	Resistance to unwanted (reaction) tooth movement — every action force has an equal and opposite reaction on the anchor unit

A couple — two equal, opposite forces — creates a pure moment: rotation about the centre of resistance with no displacement.

Covers A-III.5

Why a Single Force Tips the Tooth

• The bracket sits ~15 mm from CRes on a maxillary incisor, so the force line never passes through CRes → an unavoidable moment of the force: MF = F × d.
• Example: 100 gm at bracket → ==MF = 100 × 15 = 1500 gm·mm== → crown displaces, tooth rotates about CRes (uncontrolled tipping): crown one way, apex the other; PDL crushed at the apex on one side and alveolar crest on the other.
• To stop the tipping, add a couple (Mc) in the opposite direction. A rectangular wire twisted in a rectangular slot (or bracket torque) supplies it via two-point contact — which is why anything beyond tipping needs a fixed appliance (a finger spring = one-point contact = tipping only).
• Bracket-corner forces are large but harmless: 1500 gm·mm across a 4 mm bracket (2 mm moment arm) = 375 gm per corner — the PDL feels only the net force once Mc cancels MF.

Single force (Mc/MF = 0): the tooth tips about its centre of resistance — crown and apex move in opposite directions.

Covers A-III.5, A-III.7

Tooth Movement = Mc/MF Ratio

The type of tooth movement is defined by the ratio of the couple’s moment to the force’s moment:

Mc/MF	Movement	Centre of rotation
0 (no couple)	Uncontrolled tipping	At CRes (crown and apex move opposite ways)
>0 but <1	Controlled tipping	Displaced apically, away from CRes
=== 1	Bodily movement (translation)	Infinitely far away==
>1	Torque / root movement (apex moves more than crown)	Displaced beyond the crown

flowchart LR
    A["Mc/MF = 0<br>Uncontrolled tipping<br>(rotates about CRes)"] --> B["0 < Mc/MF < 1<br>Controlled tipping<br>(CRot shifts apically)"]
    B --> C["Mc/MF = 1<br>Bodily movement<br>(CRot at infinity)"]
    C --> D["Mc/MF > 1<br>Root torque<br>(apex moves more than crown)"]

Mc/MF = 1: the couple’s moment cancels the force’s moment — the tooth translates bodily, centre of rotation at infinity.

Bodily movement worked example

100 gm force, 15 mm to CRes → need Mc = 1500 gm·mm equal and opposite so Mc cancels MF → tooth translates; PDL loaded evenly (compression one side, tension the other).

Covers A-III.5, A-III.7

Wire Size, Length & the Force Delivered

Three properties read off the force/deflection curve — stiffness = slope (springiness = 1/stiffness), strength = load at yield, range = deflection to permanent deformation; Strength = Stiffness × Range. For a cantilever beam (finger spring):

Change	Strength	Stiffness/springiness	Range
Double diameter	×8 (∝ d³)	×16 stiffer (∝ d⁴)	×½ (∝ 1/d)
Double length	×½ (∝ 1/L)	×8 springier (∝ L³)	×4 (∝ L²)

• Supported beams (archwire segment between brackets) show the same laws but are stronger and stiffer with less range than a cantilever; rigid attachment at both ends ≈ 2× stronger, 4× stiffer than one free to slide.
• Round vs rectangular: rectangular wires (16×22, 19×25, 21×25 mil) engage the slot and control torque/rotation; round wire cannot control rotation.
• Length is cheap, diameter is expensive: lengthening gains far more springiness and range than it costs in strength — hence the helix in a finger spring and loops in an archwire.

Choosing wires

Active elements: springy + long range for light continuous force → small cross-section, added length (loops/helix), or superelastic NiTi (flat unloading plateau ≈ constant ~50 gm for alignment). Stabilising/anchor wires: large stiff rectangular steel — high stiffness means minimal deflection, so anchor teeth barely feel activation. Material strength sets the minimum usable wire size; steel’s strength lets it be smaller than gold or titanium.

Covers A-III.6

Tipping vs Bodily Movement — Summary

	Tipping	Bodily movement
Force system	Single force (one-point contact)	Force + couple, Mc/MF = 1 (two-point contact)
Appliance	Removable (finger spring) suffices	Fixed appliance essentially required
PDL loading	Concentrated: apex + alveolar crest	Even over root surface
Optimal force	~35–60 gm	~70–120 gm (needs more force, hence larger Mc)

Two finger springs can theoretically form a couple, but a 50 gm net force would need ~200 gm and ~150 gm opposing activations — enough to unseat the plate. Practical bottom line: removable appliances tip; fixed appliances do everything else.

Covers A-III.7

Sources: 04 - Mechanical Principles in Controlling Orthodontic Force, L2 3A unit review_slides, 13 9 Mechanical Principles in Orthodontic Force Control

Anchorage & the Contemporary Edgewise (Straightwire) Appliance

Single Force vs Two-Force System (Mc/MF Ratio)

A single force at the bracket never passes through the centre of resistance → uncontrolled tipping about CRes; adding a couple (two-force system) walks the movement along the Mc/MF ladder: 0 tipping → <1 controlled tipping → 1 translation → >1 root torque — the full table and diagram are in § Biomechanics above. Two extra facts for this objective set:

• The couple only cancels the moment — the PDL still feels just the net force (e.g. bodily movement of a maxillary incisor: 100 gm force + 1500 gm·mm opposing couple).
• One-point contact (removable finger spring) → tipping only; two-point contact (rectangular wire in a bracket slot) is mandatory for bodily movement/torque — and the tiny moment arm inside a slot means the bracket-corner forces of the couple are very large.

Covers A-IV.1–A-IV.2

Reduced Bone Support (Perio-Compromised Tooth)

flowchart LR
    A[Alveolar bone loss] --> B[CR shifts apically<br>~2/3 of remaining root from apex]
    B --> C[Longer moment arm<br>bracket → CR]
    C --> D[Same force ⇒<br>LARGER tipping moment MF]
    A --> E[Smaller PDL area]
    E --> F[Optimal pressure reached<br>with less force]
    D & F --> G[Use LOWER force +<br>HIGHER Mc to keep Mc/MF at 1]

• Reduce the force (reduced PDL area hits optimal pressure sooner) and increase the counterbalancing couple — MF rises with the longer arm, so Mc must rise with it for bodily movement (effectively a higher M/F ratio at the bracket).
• Bone loss lowers the anchorage value of affected teeth — posterior perio bone loss is a classic indication for skeletal (TAD/mini-plate) anchorage when maximum retraction is needed.
• Heavy force on a reduced periodontium burns anchorage even faster; force on inflamed tissue accelerates crestal bone loss.

Warning

Old extraction sites (narrowed, shortened ridge) require cortical bone remodelling — very slow, heavy strain on anchor teeth; in adults it is often poor judgement to attempt closure.

Covers A-IV.3

Anchorage: Types & Control

==Anchorage = resistance to unwanted tooth movement; anchorage value tracks PDL (root) surface area — molar > canine > incisor; double-rooted teeth resist more. Differential movement needs the anchor unit’s PDL pressure well below the movement tooth’s (aim ≥ 3:1 pressure ratio==) on the steep leg of the force–response curve.

Type	Mechanism	Example
Simple	Two connected units; each moves per its relative anchorage value	Power chain premolar→molar: premolar moves more
Reciprocal	Equal anchorage values pitted against each other → equal, opposite movement	Closing a midline diastema
Reinforced	Add more PDL area to anchor unit (same arch, opposite arch, or TADs)	Adding 2nd molar; inter-arch elastics
Stationary	Anchor unit restricted to bodily movement while movement unit tips (bodily loads 2× the PDL area of tipping)	Incisors tip back vs molars held bodily — retracts ~2×
Cortical	Cortical bone remodels slowly — usually opposes movement rather than helping	Old extraction site
Skeletal (TADs)	Bone screws / mini-plates: no PDL → perfect anchorage (as is an ankylosed tooth or implant)	Zygomatic mini-plates for max retraction, posterior intrusion, whole-arch distalisation (min age ~11)

• Light forces preserve anchorage control; heavy force “burns” anchorage — extra force barely speeds the movement tooth but drags the anchor teeth up the response curve (and heavy force can hyalinise the PDL, stalling movement).

Burning anchorage: extra force barely speeds the movement tooth but drags the anchor teeth up the pressure–response curve.

• Headgear is a poor anchorage reinforcer: force too heavy, wear too interrupted.
• Sliding mechanics add ~100 gm resistance-to-sliding on top of ~250 gm/side, straining anchorage → two-stage closure (canine first) or closing loops (no sliding).

Intrusion needs a one-couple (determinate) system, ~10 gm/tooth (20 gm for two incisors). Continuous archwires are net extrusive; two-couple systems are indeterminate and unpredictable.

Covers A-IV.1–A-IV.3

Straightwire Adaptations: The Three Orders of Bends

Angle’s 1925 edgewise used identical brackets on every tooth, so all three orders were hand-bent into every archwire. The contemporary (straightwire) appliance builds the compensation into the bracket so a flat wire sits passively — the built-in tip and torque values are the appliance prescription.

Order	Plane / compensates for	Old edgewise bend	Straightwire adaptation
First (in-out)	Faciolingual — labial surface thickness varies tooth to tooth	In-out bends (lateral insets, canine/molar offsets)	Variable bracket base thickness / tube position
Second (angulation/tip)	Mesiodistal root angulation	Angulation (“artistic”) bends	Bracket/slot angled to the long axis (built-in tip)
Third (torque)	Faciolingual root inclination — needs rectangular wire	Twist (torsion) placed along the rectangular wire	Torque cut into the slot/bracket base inclination

First-order (in-out) compensation built into the bracket: variable base thickness replaces the insets/offsets once bent into every archwire.

• Prescriptions differ: upper central torque — Andrews 7°, Roth 12°, MBT 17°; upper canine tip — Andrews 11°, Roth 13°, MBT 8°. Torque varies most between systems.
• Undersized rectangular wire ⇒ slot play ⇒ far less torque expressed than the prescription implies.
• A group-average prescription positions only the average tooth: finishing/detailing bends are still needed — reduced, not eliminated.

Built-in torque mostly prevents well-positioned teeth from moving (e.g. keeping incisor inclination during mechanics) rather than actively torquing roots.

Covers A-IV.4–A-IV.6

Sources: 05 - Orthodontic Anchorage and Controlled Tooth Movement, L2 3A unit review_slides, Level III Orthodontics LOs, 14 10 Contemporary Orthodontic Appliances

Space Management, Maintenance & Regaining (B-1, B-2)

Diagnostic Workup Before Any Space Decision

• Records: trimmed study casts/digital models (all 4 incisors + both 6s erupted), Boley gauge/dividers to 0.1 mm, radiographs (OPG) confirming all successors present + staging root development, facial profile analysis (lip posture, competence, incisor position, skeletal relationship) — synthesised on the UNC form (Sections 1–6 = numbers, 7–10 = interpretation; curve of Spee is NOT on the form).
• Lecturer’s 5 key questions: When was the tooth lost? How much space lost (>3 mm?)? Dental age / time to eruption (6-month rule)? Agenesis (maintain for prosthesis vs close)? Facial form — lip competence/fullness?
• Crowding grades: 0–2 mm mild, 2–4 mm moderate, >4 mm severe (refer), >10 mm very severe.
• Etiology of loss matters: loss from caries/trauma with adequate space = maintenance problem; loss caused by crowding (e.g. ==early unilateral loss of a lower primary canine = erupting lateral resorbed it → significant crowding + midline shift==; manage with contralateral extraction + lower lingual arch ± 2×4) = space-deficiency symptom a maintainer can’t fix; absent successor = decide whether to hold space at all (prosthesis vs closure vs drift).

Covers B-2.1, B-2.3

The Phenomenon of Space Loss

• Space loss starts almost immediately after primary molar loss and is well established by 3 months — adjacent teeth mesially drift and distally tip (tipping + mesiolingual rotation, not bodily movement). If lost >3 months ago → assume loss has occurred → regain, don’t just maintain.
• Superimposed physiological changes: early mesial shift (6s erupt, close primate spaces); late mesial shift at 11–12 y (primary E exfoliation → 6s consume leeway space). Ages 6–18: mandibular arch loses ~4 mm circumference, ~1 mm length; maxilla gains only ~1 mm.
• Clue on exam: skeletal Class I child with Class II molars = maxillary space loss; Class III molars = mandibular space loss.

Classic localized space loss: the first permanent molar drifted mesially and rotated after premature loss of the second primary molar.

Covers B-2.4

Maintain vs Regain — Decision Tree

graph TD
    A[Premature loss of primary molar] --> B{Successor present<br/>and normal?}
    B -- No --> C[Long-term plan: hold space for<br/>prosthesis vs orthodontic closure vs drift]
    B -- Yes --> D{Space analysis:<br/>space adequate?}
    D -- "No: crowding >4 mm" --> E[Refer — comprehensive tx<br/>8-10 mm: consider serial extraction]
    D -- "Mild generalized <4 mm" --> F[Space management:<br/>lingual arch before E exfoliation<br/>to hold leeway space]
    D -- "Yes, localized" --> G{Lost >3 months ago /<br/>space already lost?}
    G -- "Yes, loss <=3 mm" --> H[Regain space, then<br/>ALWAYS place maintainer]
    G -- "Yes, loss >3 mm" --> E
    G -- No --> I{Successor erupts<br/>within 6 months?<br/>root 1/2-2/3+ formed}
    I -- Yes --> J[Observe only]
    I -- No --> K[Space maintainer<br/>choose by teeth lost + eruption status]

• Maintain if successor >6 months from eruption; observe if <6 months (root >1/2–2/3 formed). Dental age (eruption at 2/3–3/4 root formation; ~1 month per 1 mm of overlying bone) beats chronological age.
• Leeway space: 0.9 mm/quadrant maxilla, 1.8 mm/quadrant mandible (~3–4 mm/lower arch) — space management (passive lingual arch before Es exfoliate ± disking) handles generalized crowding <4 mm. Trade-off: blocking the late mesial shift may forfeit Class I molars → may need maxillary molar distalization (headgear/pendulum).
• Relevancy: these same factors (amount + location of discrepancy, timing, successor status, compliance, arch) select the rung on the whole ladder — observe → maintain → regain → manage leeway → serial extraction → comprehensive/refer.

Proffit’s own decision flowchart for space maintenance after loss of a single primary molar — cross-check against the tree above.

Covers B-2.5, B-2.6, B-1.1, B-1.5

Space Maintainers (with Construction)

Appliance	Design / construction	Indications	Contraindications / limits
Band & loop (crown & loop variant)	36-mil wire loop soldered to molar band; contoured to abutment, within 1.5 mm of ridge, must not restrict primary canine; optional occlusal rest	Single primary 1st molar loss (primary/mixed dentition); bilateral B&L if both Ds lost before incisors erupt	Holds one tooth’s space only; not load-bearing; passive — cannot regain; band adaptation on Ds difficult; ~18-month survival (cement failure)
Lower lingual arch (LLA)	36-mil wire, adjustment loops mesial to 6s, rests on incisor cingula 1–1.5 mm off tissue, keyhole step-back so premolars erupt; ideal arch form	Multiple posterior losses with 6s + permanent incisors erupted; space management (leeway); midline-shift cases	Contraindicated before permanent lower incisors erupt (they erupt lingually — arch impedes them); 25–30% failure
Nance arch	Lingual arch + acrylic palatal button (no incisor contact); bands on 6s	Maxillary multiple posterior losses, 6s erupted	Button hygiene/tissue irritation; deep bite makes a maxillary incisor-contacting arch fail — use Nance/TPA instead
Transpalatal arch (TPA)	Palatal wire 6-to-6	Maxillary maintenance; sole maintainer only if one side of arch intact	Not adequate alone after bilateral loss
Distal shoe	36-mil loop + intra-alveolar blade on band; blade set from radiograph ~1 mm below mesial marginal ridge of unerupted 6	Loss of primary E before 6 erupts (but prefer pulpectomy — intact E is the better maintainer)	Avoid in SBE-risk/immunocompromised patients; can fail (molar drifts under blade → remove, regain later)
Removable acrylic partial denture	Adams clasps, acrylic into extraction sites ± pontics	Multiple losses per segment (spans too long for B&L, incisors unerupted so no LLA); anterior esthetics	Compliance-dependent; poor retention on primary teeth (no height of contour) — fixed generally beats removable in children

Anterior space maintenance is generally unnecessary — arch circumference is not lost after primary incisor loss. All maintainers need 3–6-monthly recall and avoidance of hard/sticky/chewy foods — never "insert and forget".

Band & loop — the workhorse fixed maintainer for single primary first molar loss.

Distal shoe — subgingival blade guides eruption of the unerupted 6 after loss of the primary E.

Covers B-1.1, B-1.3, B-1.4

Space Regaining (limit: ≤3 mm, localized only)

Appliance	Amount / mechanism	Anchorage & notes
Removable plate + helical fingerspring (URA)	Up to 3 mm over 3–4 months; distal tipping + spontaneous de-rotation of one molar	Adams clasps; 28-mil spring activated ~2 mm/month → 1 mm movement; full-time wear; best in maxilla
URA + expansion screw	Tipping; activate slowly: 1/4 turn 2–3×/week or appliance stops seating	Clasp retention is limiting — dislodging forces cap the force applied
Fixed coil spring on segmental wire / band-loop-with-coils	Bodily movement possible	Needs anchorage reinforcement (modified Nance)
Active lingual arch	Bilateral mandibular: tips molars distally + proclines incisors (loops opened)	Heavy round steel — tiny activations only, by dentist out of mouth; molar-band anchorage
Lip bumper	~3 mm; lip force → distal molar tipping; tongue proclines incisors indirectly	Mandible; compliance if removable; poor maintainer — swap to lingual arch after
Asymmetric cervical-pull headgear	Unilateral maxillary distalization + uprighting (longer outer bow on affected side)	Extraoral anchorage; compliance-dependent
Pendulum (lecturer)	Distalizes both upper molars; springs into molar tubes, acrylic Nance-like button	Compliance-free headgear alternative

• Maxilla is easier (palatal anchorage + extraoral force option); mandibular removables fail (irritation, breakage, retention) → prefer active LLA/lip bumper (bilateral) or fixed (unilateral).
• Band & loop and distal shoe are passive — they can NEVER regain space; LLA and TPA can be activated to do both.

Lip bumper — lip force distalizes the lower molars while unopposed tongue pressure proclines the incisors.

Regaining must ALWAYS be followed by a space maintainer or the space is rapidly lost again. If loss >3 mm, bilateral/generalized, or a second phase is coming anyway — accept and treat comprehensively later.

Covers B-1.2, B-1.3, B-1.4, B-1.5

Midline Diastema & Spacing — Causes

Cause	Key features / action
”Ugly duckling” stage (physiologic)	Unerupted canines press lateral roots mesially, crowns distally; diastema prevalence falls ~25% (early mixed) → ~7% (12–17 y). Wait — closes as canines erupt. Don’t tip lateral roots into canine crowns (root resorption — aligner-era warning)
Supernumerary (mesiodens) / intrabony lesion	Diastema >2 mm is unlikely to self-close — investigate (OPG, occlusal, small-FOV CBCT)
Missing permanent laterals	Centrals drift distally into the space
Digit-sucking habit	Spaced + proclined uppers; stop habit first, then retract (Hawley bow, ~2 mm/month)
Prominent labial frenum	Blamed more than proven — close space first; frenectomy only if retention fails
Normal primary spacing	Primate + interdental spacing is the norm; crowded (or perfectly tight) primary incisors predict permanent crowding

Never loop an unsupported elastic around the centrals — it slips apically and can extract both teeth. ≤2 mm diastemas can be tipped closed with a removable + fingersprings; >2 mm needs bodily movement + retention.

Covers B-1.6

Spacing ↔ Protrusion

• Potential crowding expresses itself two ways: actual crowding (teeth upright over basal bone, rotated/tipped) or protrusion (teeth align at the lips’ expense). Final incisor position = tongue–lip equilibrium.
• Protrusive lips, lip incompetence >4 mm, or proclined incisors (>~22° over norm) mean the patient is “crowded” even with aligned teeth — the space analysis then OVERESTIMATES available space; retract the flaring and the true deficiency appears. These patients usually need premolar extractions.
• Expansion to relieve crowding must not create protrusion, strip alveolar bone/attachment, or exceed soft-tissue tolerance. Crowding + protrusion together = anterior displacement limit already reached.

Lip incompetence and mentalis strain from protrusive incisors — protrusion signals “crowding” even when the arches look aligned.

Covers B-1.7, B-2.1

Alternative Space Analyses (brief — see Cheat Sheet - Space Analysis)

• All methods = space available (4 arch segments, mesial 6 to mesial 6) − space required (measured incisors + estimated 3-4-5s). They differ only in the estimate: radiographic measurement (periapicals + magnification correction), Moyers proportionality tables, Hixon–Oldfather/Staley-Kerber (radiograph + correlation, mandible only), Tanaka–Johnston (UNC form): ½ (sum of 4 lower incisors) + 10.5 mm (lower quadrant) / + 11.0 mm (upper quadrant) — lower incisors predict both arches. Tables derive from northern-European children — caution in other populations. Leeway contribution ≈ 3 mm (lecturer).

Covers B-2.2

The regaining sequence: drift → active regaining → space reopened → fixed maintainer.

Sources: 01 - Space Management in Preadolescent Children, L2 3b review_slides, Level III Orthodontics LOs, 04 - Space Analysis and Its Interpretation, 15 11 Moderate Nonskeletal Problems in Preadolescent Children, Cheat Sheet - Space Analysis

Crossbites in Children (B-3)

Anterior Crossbite: Skeletal vs Dental vs Functional (Pseudo Class III)

	Skeletal	Dental	Functional shift (pseudo Class III)
Findings	Multiple incisors in crossbite; incompatible arch forms; Class III profile in CR and MI; mandible cannot be retruded	1–2 teeth in crossbite; jaws normally related; teeth displaced relative to their basal bone	Manipulable to edge-to-edge incisors with Class I molars in CR; shifts forward into MI → crossbite + Class III molars + “prognathic” profile
Etiology	Class III: maxillary deficiency (retruded/vertically deficient maxilla) or mandibular excess; combinations	Crowding deflecting eruption path (permanent incisor buds develop palatal to primary incisors), retained primaries, supernumeraries, Class II div 2 retroclined uppers	Dental crossbite creating an occlusal interference → anterior CR–MI slide (still a dental crossbite, not jaw distortion)
Treatment	Refer early: reverse-pull headgear (max deficiency, early mixed), chin cup (mand excess — poor long-term success, patient outgrows it), Class III elastics to miniplates (from ~age 11); often surgery later	Simple tipping appliances once space confirmed (removable spring plate or 2×4)	Treat ASAP — correcting the dental crossbite eliminates the shift and the apparent skeletal discrepancy

flowchart TD
    A[Anterior crossbite in MI] --> B{Check occlusion in CR:<br/>shift present?}
    B -->|Edge-to-edge in CR,<br/>Class I molars| C[Pseudo Class III<br/>dental + functional shift]
    B -->|No shift, mandible<br/>cannot retrude| D{How many teeth?}
    D -->|1-2 teeth| E[Dental crossbite]
    D -->|Multiple incisors,<br/>Class III profile| F[Skeletal Class III]
    C --> G[Space analysis then tip incisors:<br/>removable spring plate or 2x4]
    E --> G
    F --> H[Refer: protraction headgear /<br/>chin cup / miniplate elastics / surgery]

Covers B-3.1–B-3.3

Etiologic & Treatment Factors + Rationale for Correction

• Space: ==most common cause of nonskeletal anterior crossbite = lack of space== — a 7 mm incisor cannot enter a 3 mm space. Do a space analysis first. Gain space by proclining incisors, extracting adjacent primary teeth (bilaterally, may allow self-correction if caught pre-eruption), or disking primaries.
• Tooth orientation/position: deflected eruption path → tipping suffices; bodily movement or rotation needs fixed appliances (a rotated central may require primary canine extraction for space).
• Intermaxillary relationship: always assess in CR — exclude underlying Class III; anterior + posterior crossbite together = highly suggestive of skeletal Class III.
• Eruption timing: correction rarely indicated in primary dentition; intervene in early mixed dentition before compensations develop.
• Rationale (all four): eliminate CR–MI functional interferences; restore interincisal contact (prevent abnormal incisal wear, restricted excursions); prevent perio damage to labially driven lower incisors (loss of attached gingiva, recession); allow correction of localized space loss.

Covers B-3.4–B-3.5

Anterior Crossbite Treatment — Timing & Appliance Design

Appliance	Design	Key numbers
Removable acrylic plate	Adams clasps on 6s, 20 mil SS finger spring, labial bow canine-to-canine; no expansion screw; bite plane usually unneeded in young children	Worn 24 h/day; activate 1.5–2 mm/month → ~1 mm movement/month
Fixed 2×4	Bonds on 4 incisors + bands on 2 molars; controls tip, torque, bodily movement; no compliance issue	Preferred when rotation/bodily movement needed
Lingual arch + whip/finger springs	Cemented; tipping only	Simple fabrication
Retention	Passive removable/Hawley ~2 months post-correction	Continue until positive overbite established — overbite is the natural retainer

Fixed 2×4 (bands on the 6s, brackets on the four incisors) correcting an anterior crossbite with control in all three planes.

Add resin to lingual incisor surfaces so the finger spring doesn't slide incisally; good clasp retention counters the spring's dislodging force.

Covers B-3.6

Posterior Crossbite: Facial Form & Etiology

• Facial form matters because expansion opens the bite: any transverse force on posterior teeth has a vertical vector — extrudes molars and tips lingual cusps down. Helpful in short face/shallow MP angle; harmful in long face/steep MP angle → use bonded expander with bite blocks; complex transverse–vertical cases → surgery.
• Etiology: narrow maxilla (most common), wide mandible, lingually tipped upper posteriors with normal maxilla, prolonged digit sucking (buccinator tone constricts arch; classic triad: overjet ↑ + open bite + posterior crossbite), AP Class III discrepancy with normal-width jaws (lower arch sits relatively wider).
• Model clues: V-shaped vs U-shaped arch mismatch = skeletal; buccally-tipped upper molars compensating a narrow maxilla = skeletal; lingually-tipped molars on normal base = dental.

Skeletal posterior crossbite: the maxilla itself is narrow, posterior teeth often tipped buccally in compensation — contrast with a dental crossbite from lingually tipped molars on a normal base.

Covers B-3.7–B-3.8

The Three Posterior-Crossbite Presentations

Presentation	Midline behaviour	Occlusal findings	Treatment
Bilateral maxillary constriction (severe, no shift)	Midlines coincident CR = MI	Bilateral crossbite in both CR and MI	Bilateral expansion (may defer to early permanent dentition)
Bilateral constriction + mandibular shift (most common)	Lower midline deviates toward crossbite side in MI; coincident in CR	Edge-to-edge in CR → lateral shift into “unilateral” crossbite in MI	Treat as soon as discovered — bilateral expansion; equilibrate primary canines if isolated interference
True unilateral constriction	No shift; midline deviation same in CR and MI	Unilateral crossbite in both CR and MI; asymmetric maxillary arch	Asymmetric expansion (unequal-arm W-arch/quad helix, cross-elastics) — refer

flowchart TD
    A[Apparent unilateral posterior<br/>crossbite in MI] --> B{Guide mandible to CR:<br/>midline shift on closure?}
    B -->|Yes - midline deviates to<br/>crossbite side in MI| C[Bilateral constriction +<br/>functional shift]
    B -->|No shift| D{Maxillary arch symmetric?}
    D -->|Yes| E[True bilateral constriction]
    D -->|No| F[True unilateral crossbite<br/>intra-arch or jaw asymmetry]
    C --> G[Bilateral expansion NOW:<br/>W-arch / quad helix]
    E --> G
    F --> H[Refer - asymmetric expansion]

Covers B-3.9

Rationale, Timing & Appliances for Posterior Crossbite

• Rationale: untreated shift → undesirable soft-tissue growth modification, dental compensation, abnormal wear of primary/permanent teeth, reduced maxillary arch space. Shift-driven crossbites: treat as soon as discovered, even primary dentition if cooperative (but delay if permanent 6s erupt within 6 months — include them).

Age / suture	Appliance	Force & rate	Protocol
Preadolescent 8–11 yr (suture open — before mid-palatal interdigitation, which begins ~12 yr)	Quad helix / W-arch (preferred)	36 mil SS on banded 6s, 1 mm off tissue; 2–4 lb → ~2 mm/month	Pre-activate 3–4 mm (≈½ molar width); 2–3 mo active + 3 mo passive retention; quad helix = springier + thumb-habit reminder
Adolescent (interdigitated suture)	RPE (banded/bonded jackscrew)	0.5–1.0 mm/day; cumulative 10–20 lb; ≥10 mm in 2–3 wk	Midline diastema opens then self-closes; slow expansion 0.25 mm every other day; both end ~50% skeletal / 50% dental; 3–4 mo retention
Young child (<8)	W-arch/quad helix only — RPE contraindicated (midface/nasal distortion)	Moderate forces open the patent suture	—
Adult (fused suture)	Surgically assisted expansion	—	—
Compliance-limited	Removable split plate (slow: 0.25 mm/wk activations)	Weak — forces unseat plate	Less effective than fixed

Cemented quad helix (pre-activated ~3–4 mm, 2–4 lb, ~2 mm expansion/month) — the preferred expander while the midpalatal suture is open.

Covers B-3.10–B-3.11

Sources: 02 - Crossbites and Vertical Problems in Children, L2 3b review_slides

Vertical Problems & Habits (B-4)

Definition, Classification & Aetiology

• Vertical problem = discrepancy of overbite/face height: dental (teeth displaced on their base — impeded incisor eruption, over-erupted lower incisors or posteriors; often easy to fix) vs skeletal (jaw proportions/rotation at fault; difficult, may need surgery).
• Aetiologies: prolonged digit sucking (labially tipped upper incisors, lingually tipped lowers, impeded incisor eruption + posterior over-eruption, narrowed maxilla → overjet ↑, open bite, posterior crossbite), inherited growth pattern, altered resting soft-tissue/respiratory posture. Effect depends on duration (>4–6 h/day) more than intensity.
• Tongue thrust is an adaptation to an open bite, not its cause — myofunctional therapy is not effective.

Covers B-4.1

Epidemiology

• Tongue-thrust swallow ~10× more prevalent than anterior open bite at every age >6 — a weak aetiologic agent; sucking habits likewise commoner than open bite (most children stay under the duration threshold; most stop before school age).
• Open bite more prevalent in people of African descent; deep bite more prevalent in those of European descent (inherited skeletal proportion). Severe adolescent open bite almost always has a skeletal component and worsens through the pubertal spurt.

Covers B-4.2

Deep Bite vs Open Bite

	Skeletal deep bite (short face)	Skeletal open bite (long face)	Dental deep bite	Dental open bite
Skeletal pattern	Low MP angle, long ramus (↑ posterior FH), ↓ lower AFH, Class II div 2, everted prominent lips, ↓ posterior eruption	Steep MP angle, ↑ anterior / ↓ posterior FH, normal upper face, over-erupted posteriors, posterior maxilla tipped down	Normal vertical proportions; Class II with excess overjet	Good facial proportions
Growth direction	Mandible rotates up-and-forward (anterior rotation)	Mandible rotates down-and-back; excess vertical maxillary growth	—	—
Aetiology	Inherited pattern	Inherited pattern ± mouth breathing/posture	Lower incisors free to over-erupt to palatal mucosa → deep curve of Spee	Thumb habit (mixed dentition)
Treatment + timing	Deep-bite functional appliance preferred over cervical headgear — blocks eruption of upper posteriors + both incisor segments, lets lower posteriors erupt (levels Spee, ↑ face height); reasonably effective; treat during growth (mixed dentition if impinging overbite damages tissue)	High-pull headgear to molars (12 oz/side, 14 h/day) → to maxillary splint → functional appliance with posterior bite blocks → combination; ==even the combination barely alters the long-face pattern — severe cases = orthognathic surgery; must span all of active growth	Relative intrusion in a growing adolescent: hold incisors, let posteriors erupt with vertical growth	Stop the habit before permanent incisors erupt → spontaneous closure==

Growth physiology: posterior eruption sets mandibular position — 1 mm of posterior elongation opens the bite ~2 mm anteriorly; restricting posterior eruption lets the mandible rotate up-and-forward. Duration of light resting pressures (5–10 g for hours) shapes the dentition, not heavy intermittent forces.

Covers B-4.3–B-4.4

Habit Management & Treatment Timing

• Escalating sequence (child must want to stop; never punitive): finger bandage reminder → reward therapy → elbow bandage → cemented lingual arch with 0.038” soldered anterior crib (reminder + interferes with thumb position; habit open bite can close in ~6 months if vertical growth remains).
• High-pull headgear can be added to control posterior eruption/vertical dimension while the tongue/habit is controlled.
• Bite-block appliances close open bites mainly by incisor eruption, not mandibular rotation; retention must run until vertical growth ends (late teens). Combined AP + vertical problems → refer.

Before/after a cemented anterior crib: stopping the thumb habit allows spontaneous closure of a dental anterior open bite.

Covers B-4.5

Sources: 02 - Crossbites and Vertical Problems in Children, L2 3b review_slides

Adjunctive Orthodontics in Adults (B-5)

Indications & Diagnostic Set-Ups

• Adjunctive treatment = tooth movement to facilitate disease control and restoration, not to idealise occlusion; partial fixed appliance, completed in ≤6 months (longer → team ortho/perio/restorative care). Sequence: control pathology → orthodontics → definitive perio/restorative work.
• Anterior repositioning indications — maxilla: redistribute a central diastema/spacing around small laterals before build-ups or veneers (crowning a diastema alone = “world’s largest central incisors”); mandible: crowding blocking restoration, irritating tissue, or hindering perio control. Extracting one lower incisor deepens the bite and reduces lip support (subtly ages the patient) — lower incisor alignment is the most difficult adjunctive procedure.
• Diagnostic set-up (cut/reposition/wax teeth on duplicate casts, or digital): tests space feasibility, anchorage, root positions and interferences before any stripping or extraction; the restorative dentist specifies final space distribution. Records: periapicals + articulator-mounted casts more often than in children; ceph usually unnecessary in non-growers.

Covers B-5.1–B-5.2

Periodontal Implications

• Active disease controlled first (bleeding on probing = best indicator); perio recall every 2–3 months during treatment.
• Half the bone lost → half the force (PDL volume halved; same force = double the PDL pressure): bodily premolar movement drops from 100 g to 50 g, and the centre of resistance moves apically (10 → 15 mm) so a relatively larger couple (750 g·mm vs 1000 g·mm system) is needed for root control.
• Uprighting eliminates the plaque-harbouring mesial pseudopocket and redirects occlusal load axially; crown-height reduction improves crown–root ratio. Avoid intrusion in adjunctive care (root resorption, loss of control) — reduce crown height of elongated teeth instead.

Uprighting a mesially tipped molar shallows the mesial pseudopocket and redirects occlusal load along the long axis.

Covers B-5.4

Appliances by Clinical Problem

Problem	Active unit	Reactive (anchor) unit	Mechanics & timing	Side effects	Retention
Molar uprighting	Tipped 2nd molar (band or bonded tube; 2 tubes handy)	Canine + both premolars, + bonded canine-to-canine lingual arch in mandible only (irritates tongue in maxilla); brackets placed in a straight line so a passive wire doesn’t spend anchorage	Extract 3rd molar first if tipping distally. 1) Flexible NiTi wire (mild tip) or auxiliary uprighting spring (severe tip; ~40 g); 2) compressed coil on rigid sliding wire (≥0.002” clearance: .018–.020 in .022 slot, loose ties) to consolidate space; T-loop (17×25 SS) for mesial root movement if 8 retained. ~4 months	Uprighting extrudes the molar — reduce occlusal surface progressively; cross-elastics (~100 g) fix a coexisting crossbite but extrude both teeth	Wire in attachments (weeks) or bonded intracoronal wire (longer); ==bridge/implant = the permanent retainer — place ASAP==
Extrusion of fractured tooth (forced eruption)	Fractured tooth (bonded button, rebonded higher as it moves)	Adjacent teeth on rigid segment (preferred) or opposing arch via vertical elastic (less constant force)	50–100 g light force, ~1 mm/week; distance = defect to surface + 1 mm margin + 2 mm gingival attachment (e.g. 5 mm for a fracture 2 mm subcrestal); see every 1–2 wk to reduce occlusion and control inflammation	Excess force → tissue damage, ankylosis; bone + gingiva follow the tooth → gingivoplasty usually needed (still less than crown lengthening)	Hold ≥4 wk (3–6 wk stabilisation) — bond the now-passive spring as the retainer — until stretched fibres reorganise
Diastema closure / incisor alignment	Incisors to be repositioned	Posterior segment (bond back to 2nd premolars/molars)	Segmented elastomeric chain (continuous chain = too much force) to close; compressed coils on light SS wire to open lateral spaces; build-ups immediately at debond; 5–6 months. Aligners: ≤0.5 mm/stage, 2 wk each — fine for mild crowding, poor for space closure	Midline tissue bunching → possible frenotomy; incisor retraction reduces lip support	Closed diastema always tends to reopen (circumferential gingival fibres) — flexible bonded lingual wire indefinitely, not a rigid bar; suckdown retainer placed at debond if restorations delayed

T-loop segment activated in the molar tube — the couple tips the crown distally to upright a mesially tipped second molar.

Forced eruption of a fractured tooth: loop spring to a bonded occlusal button, ~100 g light extrusive force, ~1 mm/week.

Covers B-5.3, B-5.5–B-5.8, B-5.11

Tolerance & Treatment Time

• Removable appliances fail adults: no couple → no root/rotation control, interrupted force, speech/comfort problems (aligners share the mechanical limits without bonded attachments, but are better tolerated than acrylic plates). Niche: multiple missing teeth with long unsupported wire spans.
• First 2 weeks are the worst — warn, don’t just reassure; supply wax + ibuprofen. Adults get sorer teeth and more ulcers than children, dislike palate coverage, prefer bonded retainers.
• Expected times: adjunctive ≤6 months (uprighting ~4 mo; incisor repositioning 5–6 mo; extrusion 5 wk–3 mo); aligner cases overrun on compliance (16 aligners: theoretical 32 wk → ~1 yr). Adult treatment is more predictable than children’s — no growth or cooperation variables.

Covers B-5.9–B-5.10

Retention Summary

Plan retention before debond — repositioned adult teeth drift immediately. Uprighted molar → bonded wire until bridge/implant (permanent retainer). Extruded tooth → passive bonded spring ≥4 wk. Diastema → flexible bonded wire indefinitely. Lower incisors → clip-on wire-acrylic retainer nightly indefinitely (holds alignment and controls overbite; upper suckdown can then be discarded after a few months). Severely rotated teeth → fiberotomy before appliance removal.

The two fixed-retainer options after uprighting: wire held in the appliance attachments (short-term) vs bonded intracoronal wire (preferred until the bridge/implant becomes the permanent retainer).

Covers B-5.11

Sources: 03 - Concepts of Adjunctive Orthodontic Treatment, 04 - Adjunctive Orthodontic Treatment Procedures, L2 3b review_slides