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104 Cards in this Set
- Front
- Back
PDL and 2 other major components
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0.5mm in width around tooth
Cellular elements - Undifferentiated mesenchymal cells. Fibroblasts & Osteoblasts. Vasculature & neural elements Tissue fluids |
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Response to normal function
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Tooth contact lasts for less than 1 second
- Fibers and tissue fluids in PDL help dissipate the forces and transfer to bone which bends - Upon opening, distance between mandibular molars decreases 2-3mm |
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Response to heavy function
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<1s - Fluid incompressible and bone bends
1-2s - PDL fluid express and tooth moves in PDL space 3-5s - Fluid squeezed out, tissue compressed, and immediate pain if pressure is heavy |
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Bioelectric theory
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- Relates tooth movement to bone metabolism controlled by the electric signals that are produced when alveolar bone flexes and bends
- Piezoelectricity in which deformation of crystal structure produces a flow of electric current as electrons are displaced from one part of crystal lattice to another. Dissapates, and equivalent but opposite signal when released. |
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Pressure tension theory
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Cellular changes produced by chemical messengers
- Pressure within PDL is increased or reduced which changes diameter of blood vessels in ligament space - Blood flow on both pressure and tension side decreases but more on pressure side. - If too much pressure is applied. Area of PDL lose their cells and undergo hyalinization. |
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Two types of bone resorption
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Frontal resorption - Occurs in portion of bone immediately adjacent to area of PDL under pressure. From light ortho forces
Undermining resporption - Hyalinization. Occurs around and behind portion of alveolar bone that lies directly adjacent to area of hyalinized zone of PDL. From heavy forces. |
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Periods of tooth movement
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Frontal resorption is found in secondary period after hyalinized tissue has disappeared.
- For any bone remodeling to occur, minimum of 6hrs/day force must be applied. |
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Bone deposition
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Incipient cell proliferation occurs 30-40hrs after application of orthodontic forces
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Intermediate plexus
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At the junction of principle fibers in the center of ligament is network of fibers running in all directions called intermediate plexus
- Rearrangement of principle fibers to adjust to tooth movement |
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Magnitude of force
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Common range is 50-400gms of force
Light is below 50-75gm Heavy is 150gm of above |
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Tipping axes
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Biological axis - Amt of force delivered to tooth and area of PDL over which its distributed
Pivitol(Mechanical) axis - When single force is applied against crown of toot and it rotates around center of resistance. Halfway down root. |
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Tipping
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Simplest orthodontic movement
- Produced when a single force is applied against crown |
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Torque
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Tipping of apex
- Initial region is near middle of root - Crown movement only is crown torque, and root movement only is root torque. - To achieve pure root torque, arch wire must be cinched |
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Translation/Bodily movement
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Two forces applied simultaneously to a crown so total PDL area is loaded uniformly
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Intrusion
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Force concentrated over small area at apex
- Lightly controlled force |
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Extrusion
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Ideally produces no areas of compression and only tension
- Can devitalize a tooth of excessive |
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Types of forces & examples
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Continuous force- Keeps constant magnitude for duration of application without change in delivery system. NiTi coil spring.
Interrupted force - Dissipating forces. Magnitude decreases over short period of time after initial application. Power chain Intermittent force - Removable appliance in which force is only applied when appliance is worn. Headgear Functional force - Provided by muscle activity during normal oral function. Activator appliance. Rarely used as tooth moving force |
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Drug effects on Orthodontic force
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Increase - Vit D and prostaglandin
Inhibit - Bisphosphonates, NSAIDS, Corticosteroids, doxycyclin inhibits osteoclast recruitment, anti-arrhythmics, anti-malarials, anti-convulsants |
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Anchorage
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Resistance to unwanted tooth movement
- Other teeth - Palate - Extraoral force - Implants in bone |
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Reciprocal tooth movement
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- Forces applied to teeth and arch segments are equal . Requires same total PDL area over which tooth force is distributed
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Reinforced anchorage
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When one segment or tooth is required to move a greater distance than another
- Add additional teeth to anchor unit - Extraoral force - Transpalatal/Translingual unit |
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Absolute anchorage
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Implants either dental or orthodontic
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Stationary anchorage
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Pitting bodily movement of one group of teeth against the tipping on another
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Cortical anchorage
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When roots of teeth move out of medullary bone and into cortical bone which is resistant to remodeling and resorption.
- may cause root resorption |
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Root resorption
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Microresorption - Can occur during ortho treatment. Transitory and confied to cementum. Replaced by secondary cementum.
Progressive Resorption - May occur during ortho. Permanent loss of tooth structure leading to shortening from apex. Idiopathic resorption - Not associated with ortho and occurs in all individuals to some extent. Usually microresorption |
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Factors leading to increased chance for root resorption
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Most are microresorption and will be repaired by cementum
Increased risk: - Prolonged tipping - Continuous bodily movement, or bodily movement of 4mm or greater - Intrusion - Blunted or pipette shaped roots |
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Crestal bone loss
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When resorption on inner walls of socket is not accompanied by appositional response on outer surfaces and crestal bone is lost.
- Most often associated with excessive tipping |
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Pulpal death
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Very rare occurance and usually occurs with poorly controlled orthodontic force or extrusion
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Effects of orthodontic force on maxilla and midface
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Maxilla sutures - Zygoma, pterygoid plates, frontonasal area, palate
- Requires heavy intermittent forces for 12-14hrs/day - most effective at night since GH is mostly released during evening |
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Effects of orthodontic force on mandible
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Not as easily accomplished as maxilla
- Extraoral force aimed at condyle only loads a small portion of condyle - Most common is chin cup to cause functional ankylosis |
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Functional appliances
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- Originally used to treat class 2 division 1 where primary deformity is in mandible
External (Primary)- Primary motivating influences developed by appliance. Objective is to take advantage of natural forces and transmit them to selected area. Internal(Secondary) - Reactions of tissues to primary forces. |
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Clark Twin block appliance
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Modern double plate with guide planes at 70 degrees with lower plane mesial to upper
- Corrects Class 2 malocclusions |
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Serial extraction
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Planned extractions to reduce crowding and irregularity during transition from primary to permanent. Teeth erupt through keratinized tissue.
- Not a substitute for mechanotherapy - Makes future treatment period shorter and less complicated. |
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Sequence alert
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If permanent tooth erupts on one side but other does not within 6 months. Take radiograph to evaluate cause
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Extraction and eruption
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If less than 1/2 root development, will delay eruption due to formation of scar tissue and can cause impaction.
If more than 1/2 root development, extraction can accelerate eruption |
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Ideal criteria for serial extractions
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Skeletal and molar class 1
- True hereditary tooth size jaw size discrepancy. - Large arch perimeter deficiency greater or equal to 10mm - Normal OJ and OB |
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Signs of developing tooth arch discrepancy
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- Anterior crowding
- Impacted permanent lower incisors - Abnormal resorption and premature exfoliation of primary cuspids. - Midline deviation - Gingival recession and alveolar destruction usually on labial surface of mand central |
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Goal of serial extraction and classic sequence
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To encourage emergence of first premolar ahead of cuspid so premolar can be extracted early to allow space for cuspid to erupt in more favorable position
- Primary lower incisor if necessary - Primary canines to allow alignment of incisors - Primary first molars when underlying premolar has 1/2-2/3 of root formed - Permanent first premolars before eruption of permanent canines - Mandible usually requires enucleation to surgically remove premolar |
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Sequelae of serial extraction
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Incisors drift lingually
Permanent canines erupt distally into extraction space Posterior teeth drift mesially Some spacing may still remain and need fixed ortho treatment |
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Why avoid enucleation
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Premolar eruption brings alveolar bone with it
Early enucleation can leave bone defect that may persist |
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Serial extractions Miscellaneous
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Can be performed in one arch only
Class II pts can be treated with serial extraction, but may worsen class 2. Avoid serial extraction in skeletal class 2. |
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Crossbite correction
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Posterior crossbites and mild anterior crossbites should be corrected in first stage while severe anterior crossbite is not corrected til second stage.
- During expansion, some extrusion may occur, or mandible will rotate down and back. Advantageous in deep bite and mild class 3 but problem in long faced patient. |
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Expansion
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Rapid - Activation for 2-3wk and retention for 3-4 months. 0.5mm per day
Slow - Activation for 2.5 months and retention for 2 months. 1mm/wk - Overcorrect by 25% to compensate for relapse |
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Facebow/Heavy labial archwire
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Innerbow of facebow is heavy labial arch and used to expand upper molars.
- Almost always needed in pts with Class 2 |
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Transpalatal arch
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For tooth movement, it needs some springiness
- More flexible, the better for tooth movement but less it adds to anchorage stability. - Quad helix design is high flexible and excellent when anchorage is of no concern |
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Cross elastics
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From lingual of upper molars to buccal of lower molars
- Stong extrusive component - In adolescents, can be used for short period because extrusion is compensated by vertical growth of ramus. - In adults, use with great caution or may accentuate downward and backward rotation of mandible. |
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Method of attachment for impacted teeth
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Least desirable - Wire ligature around tooth.
Best - Bond an attachment such as a button or hook on crown and tie a gold chain to it |
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Mechanical approach to align unerupted teeth
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- Open space
- Heavy archwire - Apply traction no later than 2-3wks post surgery - Niti overlaying heavy archwire |
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Ankylosis
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Will cause displacement of anchor teeth
Can be freed by slight luxation. Critical to apply ortho force immediately after luxation to prevent re-ankylosis |
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Impacted lower second molars
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When mesial ridge unlocked, tooth often erupts naturally
- May use separator or brass wire For severe cases, surgically expose buccal surface of crown and bond attachment so spring can be used to tip it distally and bring it into arch |
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Diastema closure
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Often complicated by insertion of labial frenum into a notch in alveolar bone
- Fibrous tissue should be removed after space closure to prevent scar tissue interruption - Don't excise frenum itself, but simple incision is used to access interdental area and frenum sutured at higher level. |
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Leveling by extrusion (Relative intrusion)
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Can use exaggerated curve of spee in maxilla and reverse curve of spee in mandible
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Leveling by Intrusion
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Light continuous force directed toward apex. 2 ways
Bypass arches - Best for patients in mixed or early permanent with some growth left. Use light wires Begg technique: Anchor bend mesial to 1st molars bypassing premolars Rickett's utility arch: Step down bend between first molar and lateral Segmented archwires for leveling - Recommended for max control over anterior and posterior segments. |
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Weakness of Intrusion leveling
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- Only 1st molar is available as posterior anchorage, and extrusion can occur
- Intrusive force against incisors is applied anterior to center of resistance and tipping forward can occur |
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2 Strategies to prevent forward movement of incisors during intrusion
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1) Space closing force created by tying depressing arch back against posterior segments. Produces strain on posterior segments.
2) Vary point of force application against incisor segment. Put force through crest of anterior segment between mesial or distal to laterals |
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Problem of molar extrusion
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- Reaction to intrusion of incisors is extrusion and distal tipping of posterior segments
- 4 times as much incisor intrusion as molar extrusion in nongrowing adults - Utility arch can be used for more favorable intrusion to extrusion ratio |
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Inherited malocclusion
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1) Disproportion between size of teeth and jaws
2) Disproportion between size of upper and lower jaws - Genetics play a greater role particularly with Class III malocclusion and long face |
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Disturbaces in embryo development
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20% of pregnancies are terminated due to lethal embryo defects
Fewer than 1% of children needing ortho had a embryological disturbance |
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Acromegaly
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Caused by excessive secretion of GH from anterior pituitary
- Class III Malocclusion - Condylar catilage proliferates |
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Hemimandibular hypertrophy
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Unknown cause of unilateral excessive mandibular growth
- 15-20yr females are most common group |
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Achondroplasia
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-Short limbs
-Cranial base does not lengthen normally due to deficiency at synchondroses -Maxilla not translated forward normally. Thus midface deficiency |
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Cleidocranial Dysostosis
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Autosomal dominant
- Short stature with 5ft avg height - Defective clavicles causing hypermobility of shoulders - Fontanels remain open for life with prominent frontal, parietal and occipital bones. Globular/square shaped skull - Normal mental development Oral - Underdeveloped maxilla with prolonged retention of primary teeth. - Supernumerary teeth with Cyst formation and dilacerated roots can occur |
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Down's chromosomal abnormality
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90% Non-disjunction during meiosis
5% Translocation during meiosis 2-3% Mosaicism. Non disjunction during mitosis |
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Down's oral manifestations
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Underdeveloped maxilla with narrow high arched palate.
- Often missing teeth with conical shaped incisors, premolars, and molars 60% Class III, 70% Posterior crossbite, 15% anterior open bite Less caries due to delayed eruption |
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Ectodermal dysplasia
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1) Anhidrotic ectodermal dysplasia - More common. Mostly sex linked, but females are affected too. Hypodontia, Hypotrichosis, Hypohidrosis
2) Hidrotic ectodermal dysplasia - Normal sweat and sebaceous glands with normal teeth. Dystrophy of finger and toe nails. Hyperkeratosis of palms and soles. |
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Incontientia Pigmenti
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Dominant sex linked and all involves females b/c lethal in males
- Honeycombed vesicles early in infancy on extremedies. Fades after two but residual pigments remain. 35-40% of time CNS can be involved causing retardation and convulsions. - Oral: Teeth only. Missing or malformed |
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Pierre Robin syndrome
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Micrognathias
Cleft palate Glossoptosis - No evidence of genetics - Possible arrested mand development of mechanical pressure of chin against chest |
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Craniofacial Dysostosis
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aka Crouzon's syndrome
- Autosomal dominant or sporadic - Coronal, saggital and lambdoidal suture are prematurely closed - Hypoplastic maxilla with crowding, due to underdevelopment. Cross bites, missing and unerupted teeth. |
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Mandibulofacial dysostosis
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Aka treacher collins' syndrome
- Autosomal dominant - Underdeveloped maxilla and mandible - Cleft palate or narrow high arched arched palate |
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Apert syndrome
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Distortions of head and face with webbing of hands and feet
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Tooth size analysis
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Appx 5% of population have a degree of disproportion in tooth size discrepancy.
- Most common being max laterals |
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Space closure with primary dentition
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Mand 2nd primary molar spaces highest closure
Then Max 2nd primary molars Then Max and Mand 1st primary molars State of eruption and occlusion of 1st permanent molars influences potential for space loss following early extraction of primary molar |
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Space closure timing
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Immediate space maintenance is required due to space closure usually during 1st 6months following extraction
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Incisors space maintainer indications
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Baume type II
Early loss at age 4 or less Loss of more than one incisor |
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Primary canine maintenance indications
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Maxillary cuspid loss is infrequent
Mandibular cuspid loss can be due to caries, trauma, or frequently due to eruption of mand laterals. Indication of serious space deficiency. Lower lingual holding arch with spurs contacting distal of laterals - Best placed during final stages of lateral incisor eruption or after full eruption |
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Unilateral First primary molars space maintenance
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Space maintenance is not indicated if lost in full primary dentition
- Band and loop off 2nd primary molar - Stainless steel bridge of serious carious involvement - Unilateral appliances are disadvantageous b/c primary cuspid exfoliates prior to eruption of first bicuspid. |
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Bilateral First primary molar space maintenance
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During primary dentition and eruption of 1st permanent molars
- Fixed bilateral not indicated due to interference with permanent incisor eruption. - Use removable acrylic space maintainer - After eruption of 1st permanent molars - Not indicated if in stable permanent molar occlusion or eminent emergence of 1st bicuspid. - Use LLHA or Nance in max if indicated |
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Second primary molar space maintenance
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In primary dentition - Removable acrylic space maintainer only to prevent supraeruption of opposing tooth
- NO evidence supports moving of tooth in basal bone so no Distal shoe used here - As erupting 1st permanent erupts use removable appliance - After eruption of 1st permanent molars use LLHA |
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General guidelines for space maintainers
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- When in doubt, place space maintainer
- Use fixed maintainer when possible. - Use bilateral maintainer whenever possible |
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Unfavorable sequelae associated with space maintainers
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Decalcified areas may develop beneath bands luted with Zinc phosphate cement
- Select tight band, and topica flouride Soft tissue lesions beneath acrylic saddle or from sharp ends of wires. May interfere with eruption of permanent teeth or cause malocclusion if active |
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Indications and contraindications for space regaining
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Indications:
- No major occlusal disharmonies - Space loss is no greater than 3mm per quadrant in max and 2mm per quadrant in mand and due to mesial tipping of crown Contraind: - Due to size discrepancy rather than space loss - More space loss than allowed |
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Split-Block Hawley type appliance
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Effectively distalize maxillary or mandibular first permanent molars
- Esp useful for unilateral movement - 2 to 3mm distalization in 4-8wks - Forces may cause labial movement of anterior teeth |
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Lip bumper
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Used to bilaterally distalize mandibular first permanent molars
- Fit appx 3mm anterior to mandibular incisors - 1-2mm distalization with continued use for 6-12 months |
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Brass ligature wire
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Used to treatment ectopic eruption that has not caused premature exfoliation of primary teeth
- loop between 1st permanent and second primary - Tightened to regain space |
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Extraoral space regaining appliances
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Headgear used to tip or distalize maxillary first permanent molars
Elastic material exert force on labial arch wire fitted on 1st permanent molars Anchorage from occipital or cervical area. High pull headgear, cervical pull, straight pull 1-3mm distalization with 6-12 months of therapy |
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Skeletal vs Dental
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Full cusp bilateral posterior crossbite is likely to have skeletal component
Unilateral posterior crossbite due to maxillary or mandibular skeletal asymmetry Posterior crossbite much more likely due to displacement of maxillary teeth than mandibular |
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Anterior cross bite
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If crossbite is discovered before permanent tooth completes eruption, adjacent primary can be extracted to prevent midline shift
- In young child, best method is to tip maxillary and mandibular teeth out of crossbite is removable appliance with fingerspring for maxillary facial movement or active labial bow for lingual mand movement |
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Correction of dental posterior crossbites
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Heavy Labial bow
Transpalatal arch Cross elastics |
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Skeletal posterior crossbites
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Often appears to be unilateral problem but is in fact the result of a mild bilateral constriction of the upper arch that creates a shift of mandible to one side for closure
One of the few conditions where treatment is indicated in primary dentition |
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Maxillary unilateral crossbite
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Treat with W-arch or quad with different arm lengths
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Simultaneous expansion of anterior and posterior teeth
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Divide baseplate in 3 rather than 2
- Y plate |
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Bionator
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Lingual flanges stimuate forward posturing of mandible
- Shelves or blocks between teeth provide vertical control |
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Twin-block appliance
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Individual max and mandibular plates with ramps that guide the mandible forward when patient closes down
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Herbst appliance
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Only fixed functional appliance to move mandible forward
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Frankel appliance
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Only tissue-borne functional appliance
- Lingual pad dictates mandibular position |
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Fitting bands
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Upper molar band - should be placed with finger pressure on mesial and distal. Then at MB and DL corners with band pusher. Final seating with bite stick on DL
Lower molar band - Fingers at proximan, then heavy biting forces on buccal only Premolar bands - Maxillary alternate pressure on buccal and lingual while mand designed for heavy forces on buccal only |
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Retension philosophies
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Occlusion school
Apical base school - Intercanine and intermolar widths Mandibular incisor school Musculature school |
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Three major reasons for retention
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Gingival and PD tissues are affected and require time to reorganize
Teeth may be in an inherently unstable position Changes produced by growth may alter treatment |
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Principles of retension
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Full time retention for first 3-4 months
- Teeth should be free to flex to promote reorganization of PDL - Due to slow response of gingival fibers, retention should be continued for atleast 12 months |
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Maturity of dental pattern
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Female skeletal and dental pattern matures by 13th yr while males mature somewhat after 15th year
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Overcorrection and rotation
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Little evidence exists to indicate that overrotation is successful in preventing return to former position
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Cases requiring permanent or semi-permanent retention
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- Expansion cases esp in mandible
- Cases with considerable generalized spacing - Severe rotations or labio-lingual malpositions - Diastema |
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Relapse tendancy in Class 2
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Continue headgear to upper molars at night with retainer to hold teeth in alignment
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Retention after Class 3
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Mild class 3, functional appliance or positioner may be enough to maintain occlusal relationship
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