Board Review

Rene S. Johe, DMD

UMDNJ-NJDS

Drift of Teeth

• Mesial and occlusal

• Throughout life

• Slows down in adults

• With missing teeth posterior segments tip mesially or supererupt, necessitating molar/premolar uprighting

Eruption

• Permanent incisors erupt lingually compared to their primary counterpart

• Permanent canines usually erupt buccally compared to their primary counterpart

Malocclusions

• Know Class I, II, and III malocclusion concepts

• Class I malocclusion has a well related skeleton, rotated and/or crowded teeth

• Class II relationship– Mandibular canines DISTAL to

maxillary canines

Growth concepts

• Sites of Growth– Maxillary tuberosity– Mandibular lingual tuberosity (Ramus)– Alveolar growth

• Growth and Deposition / Resorption– V principle– Remodeling / Relocation

Class III cases

• Anterior crossbites– Correct as soon as possible

• Skeletal problem

• Late growth

• Maxillary crowding probable

• May be associated with a shift (pseudo-class III occlusion)

Cephalometric Radiographs

• Landmarks– Sella, Pogonion, Menton, Orbitale, A

point, B point, etc

• ANB values– >5 degrees – Skeletal Class II– <0 degrees – Skeletal Class III

• Value Norms– SNA – 82 deg– SNB – 80 deg

Moyers / Space Analysis

• Moyers Analysis measures LOWER INCISORS and predicts CANINES and PREMOLARS

• Bolton Analysis evaluates a tooth size discrepancy– Ratio LESS than normal - relative

maxillary excess– Ratio MORE than normal - relative

mandibular excess

Molar Uprighting

• Typically due to missing teeth (premolars)

• Involves fixed appliances

• Problems encountered– Periodontal defects– Occlusion (open bite problems)– Long treatment time

Class II types

• Class II div I– Normal growth tendency– Maxillary incisors proclined, large

overjet

• Class II div II– Horizontal growth tendency– Maxillary central incisors retroclined,

maxillary laterals proclined– Deep bite

Supernumerary teeth

• Vast majority in the maxilla (90%)

• Most common is mesiodens, then paramolars

• Others include– Maxillary lateral incisors– Maxillary premolars– Mandibular premolars

• Feature of Cleidocranial Dysplasia

Oligodontia

• Also called (partial) anodontia, hypodontia

• Most common missing teeth are– Third molars– Maxillary lateral incisors tied with– Mandibular 2nd premolars

• Feature of Ectodermal Dysplasia

Tooth Movement

• PDL– Elastic, reactive tissue

• Biologic Electric theory• Pressure Tension theory

• Movement– High Force

• Blood vessels occluded (Hyalinized), Undermining Resorption

– Low Force • Blood Vessels not occluded, Frontal Resorption

– Ideal force depends on root area, type of movement, and other factors

Orthodontic forces

• Ideal forces are light– Different forces are ideal for different

teeth, depending on root surface area– The bone will remodel with ideal light

forces

• Strong forces– Produces undermining resorption– Produces hyalinized connective tissue

Properties of Wires

• Stainless steel– High stiffness, high load/deflection

curve

• Nickel titanium– Low stiffness, low load/deflection ratio– Exhibits hysteresis

• Deactivation force less than activation force

– Martensite (pseudoelastic) vs Austenite

Space Maintainers

• Fixed– Band and Loop– Distal Shoe– Lingual Arch– Nance Appliance / TPA appliance

• Removable (some space regaining)– Lip Bumper– Headgear

Lower Incisor crowding

• Normal in females age 7-11– Incisor liabilty

• Occurs due to mesial drift of teeth and late mandibular growth

• NOT related to 3rd molar eruption

Primate spaces

• Location– Mesial to maxillary canines, distal to

mandibular canines– Used up by erupting incisors

Leeway space

Terminal Plane Relationships in Primary

Dentition

Etiology of Malocclusion

• Genetics– Less than 50% cause

• Epigenic (Epigenetic)– Habits– Early primary tooth loss

• Distal eruption of lateral incisor causing loss of primary canine

• Loss of primary second molar causing mesial drift of permanent 1st molar

– Trauma

Appositional bone growth vs Interstitial bone growth

• Interstitial– Occurs at sutures

• two-sided periostial membrane

• Usually requires cartilage

• Appositional– Enlarges the existing portions of bones

• Does not require cartilage

• Requires periosteum and endosteum

Endochondral vs Intramembranous ossification

• Cranial Base– Endochondral, some genetic control at

synchondroses

• All other facial bones including Maxilla and Mandible– Intramembranous, little or no genetic

control

Steiner Values

• SNA– 82 degrees

• < = retrognathic, > = prognathic

• SNB– 80 degrees

• < = retrognathic, > = prognathic

• ANB– 2 degrees

• < rel max retrognathia or mand prognathia• < rel mand retrognathia or max prognathia

Overbite vs Overjet

• Overbite– Can be Deep or Negative (Openbite)– Changes with craniofacial growth– Mandibular incisors touch palate –

Impinging overbite

• Overjet– Can be due to

• Incisor proclination or retroclination• Skeletal discepancy• Negative overjet = crossbite

Chronological vs Dental Age

• Can vary by a significant amount• It is possible for:

– A 9 year old to have a full complement of permanent teeth

– A 14 year old to have 12 primary teeth remaining

• Different races display different dental ages at set chronological ages.

Fixed vs Removable Appliances

• Removable Appliances– head gear– lip bumper– face mask– Schwartz

• Fixed Appliances– Standard Edgewise– Straight Wire– Hyrax, Haas expanders– Crozat appliance

Hawley Retainer

• Most commonly utilized retainer• Advantages

– Anterior tooth control– Allows some settling of occlusion– Easy to adjust

• Disadvantages– Canine control– Occlusal interferences– Extraction treatment relapse concerns with

clasps

Dental Spacing

• Can be normal– Mixed dentition in maxillary arch

• Can be due to– Small teeth (tooth size discrepancy)– Frenum– Habits (tongue thrust, thumb sucking)

Causes of Open Bites

• Skeletal– Vertical growth can be due to

genetics, mouth breathing

• Habits– Tongue thrust– Thumb sucking

Serial Extraction

A planned sequence of tooth removal that can reduce crowding and irregularity during the transition from the primary to the permanent dentition.

Used in severe crowding cases where transverse expansion in the mixed dentition will likely be unsuccessful.

Indications for Serial Extraction

• 1) No skeletal problem exists

• 2) Large space discrepancy

• 3) Normal overbite

Impactions

• Most common – Maxillary canines– Mandibular third molars

• Less common– Incisors– Mandibular canines– Premolars

• Usually require exposure• Tooth may become ankylosed

Headgear Types + Effects

Cervical and High Pull Headgear

Straight Pull is a combination of both

Fixed appliances

• Brackets are bonded to the teeth.

• Archwires are wires that connect all the teeth in one arch.

• Ties (metal or rubber) hold the archwires into the brackets.

Alignment and leveling

• Goals

– Bring teeth into alignment

– Correct vertical discrepancies

– Derotate teeth where necessary

– Establish a more ideal arch shape

Correction of molar relationship and space closure

• Goals– Correction to Class I molar

relationship if 4 bicuspids were extracted or non-extraction treatment

– Correction to Class I canine relationship

– Close (extraction) spaces if present– Correct overjet relationship

Finishing

• Goals

– Parallel tooth roots

– Align tooth marginal ridges

– Idealize occlusion

– Idealize esthetics and function

– Utilize elastics as necessary

Types of tooth Movements

• Intrusion

• Extrusion

• Tip

• Rotation

• Torque

Removable Appliances

• Clasps– Adams, C clasps, Ball clasps– Labial bow– Springs (finger, mattress, etc)– Screws (expansion, mini)

Posterior Crossbites

• Skeletal– Narrow maxilla– Molars not tipped palatally

• Dental– Normal maxillary base– Molars tipped palatally– Associated with habits / soft tissue

Retention

• Growth throughout life

• Reactive and passive, not active

• Transseptal and Supracrestal fibers

• Intercanine width

• Overcorrection

• Relapse is not predictable

• Third molars do not cause incisor crowding

Soft tissue Appearance of Skeletal Problems

• Class III– Scleral Display– Lack of Zygoma– Midface deficiency– Vertical Growth

• Class II– Small mandible (90%)– Horizontal Growth

Transseptal and supracrestal Fibers

• Attached to cementum

• Elastic fibers

• Are difficult to remodel

• Increase risk of relapse

• Necessitates either:– Overcorrection– Fiberotomy

Speech Effects

• Several malocclusion characteristics can have speech effects. Their etiology can be different. The most common are:– Open bites– Spacing– Incisor irregularity

Iatrogenic Orthodontic Problems

• All orthodontics is intrusive and can therefore have iatrogenic side effects such as:– Irritation– Pain– Plaque problems– Allergic reactions

Elastics

• Utilized to:– Correct molar/canine relationship– Intercuspate occlusion– Different types for different

malocclusions• Class I• Class II• Class III