Second Semester Flashcards
How does late mandibular growth contribute to incisor irregularity?
No primary cause (multifactorial and multiple theories)
1) It is NOT true that the erupting third molars push against mandibular teeth causing crowding
2) Mesial movement of posterior teeth possibly due to physiologic drift, occlusal forces, muscle function and/or eruption patterns
3) Lingual movement of anterior teeth possibly due to differential jaw growth. Forces from maxillary arch and labial soft tissues cause uprighting of mandibular incisors. Forces incisors to occupy a smaller arch perimeter
4) changes in facial muscles/soft tissues
What is expected to happen with arch form as an individual ages?
1) Decrease in maxillary and mandibular inter-canine width
2) increase in incisor irregularity/crowding
3) Males tend to show a greater changes than females. Decrease in both arch depth and inter-molar width
4) A tapered arch-form becomes more tapered with time
5) Ovoid or square arch-forms become more squared with time
6) Mandibular archform becomes more rounded with age (shorter/broader)
Define tooth eruption.
Movement of tooth in alveolar bone until the CEJ meets the crestal alveolar bone height
Define alveolar drift
The dragging of the alveolar bone that occurs when tooth movement occurs
Define active stabilization
Equilibrium between the muscles, occlusion, and PDL
In regards to tooth movement, the pressure side of the PDL allows for bone ___ and the tension side of the PDL allows for bone ___
Resorption (osteoclastic activity)
Deposition (osteoblastic activity)
According to the Vastardis (2000) article, which are the most common missing teeth? (In order, with percentages)
1) Third molars (20%)
2) Second premolars (3.4%)
3) Lateral incisors (2.2%)
What is the most effective timing for growth modification based on the Ressinger article?
During evening hours - night (starting at 8pm, peaking at 10pm, then ending around 6am)
What factors are used in treatment planning for replacement or retention of deciduous teeth?
1) condition of crown, root, and periodontium
2) pt’s age
3) amount of crowding present
4) vertical position relative to occlusion
5) AP skeletal and dental relationships
6) pt’s preferences
In comparison to permanent premolars, retained deciduous molars are [wider/narrower] mesio-distally, [shorter/taller] occlusal-gingivally, the roots are more [divergent/convergent], and are [less/more] likely to ankylose than permanent teeth.
Wider
Shorter
Divergent
More
What is primary failure of eruption (PFE)?
PFE is when non-ankylosed teeth fail to erupt due to malfunction of the eruption mechanism. Resorption of overlaying tissue will occur, but no tooth movement will occur.
Usually occurs unilaterally in posterior teeth and will affect all the teeth posterior to it, potentially leading to posterior open bite.
What are some possible causes of PFE?
Genetics (familial connection)
Idiopathic
Failure of eruption, could actually be due to a mechanical influence (not PFE), so it is important to properly diagnose the cause of failure of eruption.
List four methods to estimate growth from the Jacobsen article.
1) Regression
2) Theoretical
3) Time series
4) Experimental
List limitations/errors of traditional superimposition per Jacobsen article
1) Head positioning errors
2) Errors in identifying landmarks on ceph
According to the Bork 1969 article, forward rotation of the mandible is commonly found in ___ and ___ patients
Brachycephalic (and deep bite)
Mesocephalic
According to the Buschang 2017 article, what is the most accurate assessment of skeletal maturity and why?
Hand-wrist radiograph (typically left hand) is more accurate than evaluating the cervical vertebrae because there are 11 indices which are more accurate and more clearly defined than cervical stages.
Where did Ricketts (1972) collect patient data from. What is a potential downfall of this source to extrapolate predictive measurements?
Used data from his own practice which could cause bias, not representing the full population
List some dolichocephalic characteristics
Long narrow face Protrusive/prominent nose Deep set eyes “Hooked” turned down nose Retruded chin Class 2 tendency Long tapered archforms Steep MPA
What are two features in black patients that commonly cause class 3 skeletal presentation?
1) Bimaxillary protrusion
2) wide mandibular ramus
Of the two ethnic group studied in Nojima et al 2001, which group had larger inter-canine and inter-molar widths and increased arch depth?
Caucasians (more than Japanese)
Who is the father of genetics according to the Carlson 2015 article?
August Wiseman
What are prominent nasomaxillary features for a class 2 div 1 individual?
deep-set eyes
Prominent cheekbones
Bending nose as compensation
25% more nose growth than maxilla growth
Nasomaxillary complex is more forward and longer vertically
How does the width of the ramus factor into a class 2 div 1 individual?
Narrow ramus = mandibular retrusion
What is a contributing factor resulting in backward (clockwise) rotation of the mandible?
Facial and alveolar vertical growth is greater than vertical growth of the condyles
List differences between class 2 div 1 and class 2 div 2 presentations
Class 2 div 1: lip incompetence, lower lip caught under maxillary incisors, increased LAFH, proclined U/L incisors, increased OJ
Class 2 div 2: deep bite, low MPA, proclined U2s and retroclined U1s, short LAFH, decreased OJ, gummy smile
How does lip pressure affect the development of class 2 div 2 incisors?
Upper incisors erupt further than normal resulting in increased pressure of the lower lip against the incisal portion of the teeth which tips the U1s back. Then, when the laterals erupt they must procline to fit into a reduced arch perimeter.
As overbite increases, functional overjet [increases/decreases]
Decreases
What is the incidence for unilateral crossbite? What percentage is thought to be due to a functional shift?
5.9-9.4%
67-79%
In an individual with unilateral posterior crossbite, do you expect the bite force to vary from the crossbite side to the crossbite side? Why?
There has not been shown to be a difference in bite force varying from side-to-side. However, patients with unilateral crossbite demonstrate less bite force than patients without crossbite.
Describe the anticipated condylar positions (both crossbite and non-crossbite sides for an individual with unilateral crossbite.
The condylar position in the non-crossbite side is positioned down and out whereas the condyle is not positioned down and out on the crossbite side. The asymmetric positioning of the condyles can lead to asymmetric growth of the condyles
The joint is abnormal on the non-crossbite side because its rotating along the other condyle.
Describe how Harvold studied airway in primates.
The nasal passages of primates were plugged and a wedge was used to influence the placement of the tongue. After a certain duration, the plugs and wedge were removed to observe if the growth pattern and breathing pattern of the primates was altered.
What did Harvold find in his airway study in primates?
1) primates with plugged noses developed adenoid faces
2) Wedge was shown to not interfere with occlusion, yet down and back rotation of the mandible occurred accompanied with anterior open bite, steep MPA, and long faces
3) Nasal airway obstruction did not change mandibular shape or growth direction
4) Authors thought that mandibular positioning is more important than nasal airway in determining facial development but when plugs removed, most of the problems did NOT resolve and the chimpanzees adapted
summarize Linder-Aronson contribution to airway
1) Children with nasopharyngeal obstruction with enlarged adenoids have reduced nasal airflow and larger LAFH. Not able to conclude if dolichocephalic and airway cause one or the other.
2) Tested the hypothesis that the establishment of nasal respiration in children with severe nasopharyngeal obstruction can be eliminated as a factor in determining mandibular growth direction.
3) Study design: 81 children had adenoidectomies. 60 were eligible. 48 went from mouth to nose breathing. Followed 38 (10 dropped out).
From the Zara’s (1997) article, what are the predictors of reduced nasal volume in 7-12 year old children?
BMI
Passive smoking
Identify the list of characteristics for a patient that presents with adenoid facies.
Mouth breathing Increased LAFH Class 2 dental Lip incompetency Posterior crossbite Short upper lip Open bit tendency Narrow alar base
List methods of measuring nasal obstruction
CT MRI Cephalometrics Rhinometry (to measure pressure differences in airways) Fibro-optic endoscope (to look directly at the tissues) Plethymography Nasal peak flow assessment Acoustic reflection
What is the etiology of obstructive sleep apnea (OSA)?
1) An obstruction of the airway that occurs while sleeping that interferes with the patients sleep.
2) OSA is due to increased collapsibility of the upper airway (influenced by impaired neuromuscular tone)
3) Respiratory effort is increased in a constricted airway. Increase in serum CO2 and decrease serum O2 occurs.
4) Increased work for breathing causes a cortical arousal which increases sympathetic activity leading to increased HR and BP and a tendency for cardiac arrhythmia
5) Multifactorial: craniofacial structures, neuromuscular tone, hormonal fluctuation, obesity, rostral fluid shifts, genetic predisposition
OSA can only be definitively diagnosed by…
A physician/ENT (a sleep study is usually conducted)
In the article by Badell, what happened to the maxillary molars with headgear treatment and after headgear discontinued?
Maxillary molar was found to move distally 2.3mm and intrude 0.1mm with 10.6 degrees of tip when it had the HG treatment occurring
After HG was discontinued, it returned to its original position. Uprighted and downward and forward growth of 3mm
What did Kim et al (2001) show for the use of cervical pull headgear in regards to rotation of the mandible?
This study did not support the clinical dogma that cervical pull head gear causes opening rotation of the mandible by extrusion of the maxillary first molar. Also there was no change in mandibular growth and the mandibular rotation was similar in both groups
Does cervical pull headgear affect the morphology and posture of the cervical vertebrae?
Measurements of cervical posture showed no significant changes and therefore there was no change in cervical vertebrae posture due to the wear of cervical headgear.
What are criteria for predicting successful use of a functional appliance in class 2 malocclusions?
1) Well aligned arches
2) class 1 - mild class 2 skeletal pattern
3) Forward posturing of the mandible will improve/maintain soft tissue profile
4) Active growth
5) compliance
6) overjet < 7mm
7) Pt does not have overly proclined lower incisors
8) No open-bite tendency
What did the Turley article show for early treatment with reverse pull facemask?
Early treatment with reverse pull facemask results in better outcomes, but successful treatment is still possible in older patients
1) youngest group (4-7) showed significantly greater increases in SNA than older group (10-14)
2) average maxillary advancement = 3.3mm (2/21 = 5-8mm)(5/21 increased SNA by 4-5 degrees)
3) mandibular clockwise rotations accounted for 25% of the correction
What are possible predictors of long-term failure in reverse pull facemask?
1) Increased mandibular length
2) Decreased posterior vertical facial height
3) increased OB
4) no different in saddle angle
5) Acute cranial base angle between middle and posterior cranial fossa
6) more forward position of mandible relative to cranial base
7) increased gonial angle
According to Carter 1998, what are some changes you see in adults as they age?
1) Decrease in arch width, length, and perimeter
2) Decrease in inter-canine width (1-1.5mm)
3) Increase in lower incisor crowding (1.5-2mm) (although 3% of males and 7% of females showed reduction in crowding)
4) OB, OJ, and COS were stable
According to Henrikson (2001), as adults age there is a [increase/decrease] in inter-canine width in both maxilla and mandible (~__mm). [increase/decrease in incisor irregularity].
Decrease (0.7mm)
Increase
According to Bondevik (1998) [males/females] showed greatest changes in occlusion between ages 23 and 34.
Males
According to Henrikson (2001) from ages 13-31, males [increase/decrease] in intermolar width, and [increase/decrease] in arch depth
Increase
Decrease
According to Henrikson (2001), from ages 13-31 there is greater change in arch form noted in [males/females].
Males (little change in females)
According to Henrikson (2001), tapered arch forms become ____ with age, but normal/square archforms become ___ with age
More tapered
More squared
True or false… there are a lot of changes that occur in OB, OJ, and CoS with age.
False, these are all stable
What happens to the dentition with aging from 26 to mid-40s?
1) Changes are small over this time period (<0.55mm) (Bondevik 1998)
2) Lots of variation between individuals
3) Males show more change than females
4) Resolution of spacing in mandible (increased crowding)
5) OB and OJ remain stable
6) Arch forms become shorter and broader/more square
7) Mandibular collapse over time, decrease in inter-canine width
As the jaws grow, teeth erupt into the space to balance the position of jaw change. If the teeth are unable to compensate sufficiently, ___ occurs.
Malocclusion
Once in the oral cavity, teeth don’t possess their own motive mechanism, but instead move by a process of ___
Alveolar drift
After a tooth emerges into the mouth, further eruption depends on ____, including but perhaps not limited to formation, cross-linkage, and maturational shortening of ___
Metabolic events within the PDL
Collagen fibers
True or false.. the PDL undergoes its own remodeling (just as bone does to provide movement) and requires considerable and on-going relinkage of connecting fibers
True
The middle layer of the PDL called the ___ acts as ____. It consists of linkage fibrils that provide connection for inner and outer layers. The double-sided histogenic membrane functions to convert ___ to __ by the suspension of each tooth
Intermediate plexus
An adjustment area
Pressure to tension
A proposed source of the propulsive mechanical force that brings about eruption, drift, and other tooth movements is provided by ___ on the resorptive sides of the sockets.
Actively contractile fibroblasts (myofibroblasts)
What are the two basic functional reasons for tooth drift?
Maintain tooth contact by closing any space resultant in dental arch growth and to keep it closed with interproximal wear
True or false.. tooth drift only occurs in a mesial direction
False.. it takes place in all three dimensions. The PDL allows drift vertically, horizontally, and transversely
What is the piezo-electric effect on bone?
1) It is a bioelectric stimulus that is caused by bone flexure
2) It serves as a first messenger (but not the only messenger) to osteoblasts/clastic of PDL leading to changing of bone
3) The bone will remodel until biomechanical and bioelectric equilibrium is attained and the signals turn off
4) If a bend in bone occurs, resorption occurs on convex side, deposition occurs on concave side.
What is active stabilization?
An equilibrium between masticatory forces (muscles and occlusion) and the PDL exists. The ability of the PDL to generate a force, and thereby contribute to the set of forces that determine the equilibrium, is active stabilization.
What does active stabilization imply?
Active stabilization implies a threshold for orthodontic force, since forces below the stabilization level would be expected to be ineffective. The threshold, then, would vary depending on the extent to which existin soft tissue pressures were already being resisted by the stabilization mechanism
When does the PDL act like a membrane and when does it act like a ligament?
Membrane - During growth and development, and establishment of occlusion
Ligament - active stabilization
The PDL is considered a double-sided ___ membrane, converting ___ on teeth into ___ on bone by suspension of each tooth.
Histogenic
Pressure
Tension
The PDL provides a biological system for eruption, enabling each individual tooth to acquire a functional occlusal position, provides for the growth and remodeling maintenance of alveolar bone, provides a ___ and ___ supply as well as ___ that are needed for development and provides the vertical and horizontal drifting of teeth and accompanying remodeling alveolar bone
Vascular
Nerve
Undifferentiated cells
The middle layer of the PDL is called the ___ and consists of ___ which provide connections between the innermost and outermost ___ layers.
Intermediate plexus
Slender pre-collagenous linkage fibrils
Dense coarse fibrous
___ of the PDL allows for remodeling and movements of the teeth
Continuous re-linking
The side of the PDL attached to the alveolar bone and cementum is made of ____ fibers
Coarse collagenous
True or false… all three layers of the PDL remodel and grow from one location to the next as the tooth drifts
True
Fibers buried in newly formed bone continue to reform fibers that become the coarse attachemnet by bundling of fibers. Thus the PDL stays the same from one location to another
The tension side of the membrane is ___ and causes fibers to connect to bone and tooth. Fibers buried in new bone and ___ continue to reform fibers that become the ___ by ___
Osteoblastic
Linkage fibrils
Coarse attachment by bundling of fibers
The pressure side of the PDL causes a sheet of ___ on the alveolar bone wall. ___ occurs, ___ is laid down, and ___ grow into the space. Thus a strong connection is maintained betwen bone and tooth. This produces the PDL under ___ on the resorptive side and myofibril contraction causing tooth movement.
Osteoclastic
Resorption of bone
Ground substance
Fibers
Tension
What is the difference between tooth changes with growth and tooth changes with movement?
Tooth changes with natural growth occur as part of the inherent growth pattern (dental compensation, tooth drift, alveolar drift, etc.)
Ortho tooth movement overrides that inherent system and modifies it. Tension on one side, resorption on the other (doesn’t occur in natural tooth movement)
When there is a discrepancy in jaw growth, the teeth try to compensate, but if its too great, you get ___
Malocclusion
As the jaws grow, teeth erupt and drift into the space to even out the jaw changes. Molar eruption is influenced more by ___ while incisor eruption is influenced more by ___
Jaw rotation
Vertical dimensions
In a class 3 malocclusion caused by maxillary deficiency and/or mandibular prognathism, the maxillary teeth are guided in a ___ direction as they try to catch up with the lower jaw resulting in ___. Meanwhile the lower incisors try not to escape the upper arch leading to ___ lower incisors.
Forward
Proclination of the upper incisors
Upright/retroclined
What is the evidence supported in Southard’s article about mesial force created by third molars?
There was no increase in mesial pressure from unerupted thirds leading to lower incisor crowding. Thirds do not cause mandibular anterior crowding. Removal of thirds for exclusive purpose of relieving interdental pressure thereby preventing crowding is unwarranted.
Study design: extracted a third molar on one side but not the other. Found there was no difference between the two sides.
Is there a genetic component to missing teeth?
Yes, but there are many factors, not just a single gene. 60 syndromes are associated with agenesis. There are also isolated forms that could be X-linked, recessive, dominant, etc.
Vastardis (2000) identified a specific gene On chromosome ___ called _____, that with a ___ mutation led to agenesis of all the families studied with missing teeth.
4p
MSX1
Point
True or false… absence of teeth affects alveolar drift
True
Describe Butler’s theory of tooth agenesis
3 morphological fields (incisors, canine, premolars and molars)
1 key tooth presumed to be most stable and the flanking teeth are less stable
Describe Svinhufvud’s theory of tooth agenesis
Tooth agenesis occurs in areas of embryonic fusion (max lateral at nasal and lateral maxillary, 2nd premolar at end of deciduous dentition, mandibular lateral incisor at fusion of mandibular process)
Describe Kjaer’s theory of tooth agenesis
Agenesis occurs where innervation occurs last in area
What are the two mechanisms required for tooth eruption?
1) resorption of alveolar bone above the tooth
2) active eruption mechanism that moves the tooth to its final position in the mouth
___ hormone appears to be an important factor in tooth eruption .
Growth hormone. (eruption coincides with hormone release)
GH deficiency results in delayed eruption. GH affects insulin-like growth factors (affecting velocity of eruption). GH can affect odontogenic is, osteogenesis, and bone remodeling
____ is the only developmental process whereby a semi-hard tissue, the tooth, must escape its shell, the alveolar bone which it is encased.
Tooth eruption
The ____ is essential for eruption. It is a loose connective tissue sac which surrounds each tooth. Influx of ____ into it are needed to resorb alveolar bone to form a pathway for eruption. If you remove it, the tooth does not erupt, whereas if you insert an inert object into it, it will erupt.
Dental follicle
Mononuclear cells (which are osteoclast precursors)
In tooth eruption, ___ is a glycoprotein that is degraded at the onset of eruption. ____ and ____ recruits mononuclear cells to the area. The ___ gene is needed for differentiation of mononucleocytes into osteoclasts, which is needed for the eruption of teeth. ____ is also required for eruption, causing mononuclear cells to come together and to start osteoclastic activity and bone resorption essential for eruption.
DF96
MCP-1
EGF
C-fos gene
CSF-1
If a tooth is mechanically blocked, do the roots still form? What does this indicate?
Yes, but you will see dilacerations. this indicates that something went wrong during tooth development
What are the major take-home messages from all of Wise’s articles about tooth eruption?
1) There are a lot of factors involved in tooth eruption
2) It is not a single process, but is biochemically and genetically complex involving multiple pathways
3) resorption is critical for eruption
4) If there is a major interruption in the process, there is a lack of eruption of teeth
According to Biederman, deciduous teeth are ___x more likely to ankylose than permanent teeth
10
True or false.. according to a study at the University of Iowa, Mandibular deciduous molars have better survival rates than maxillary deciduous molars
False. Maxillary deciduous molars had better survival status
Because deciduous molars have divergent roots and thin enamel, it is difficult to reduce the crown size. Therefore, you need to finish in a ___ relationship
End-to-end L6 (canine should still be class 1)
According to a study at the University of Iowa, there is a ___% chance that a primary molar would last a long time if healthy and well-maintained
80-90%
Alternative treatment: prosthesis, implants. But it is still not as good as original teeth in maintaining alveolar bone height
PFE is due to a malfunction in which process?
Eruption mechanism (could be resultant from many variables). Unsure of the exact eruption mechanism that is altered, but it is believed to be an abnormality in the PDL.
Note that mechanical obstruction can cause failure of eruption but it is not considered PFE!
Why do primary teeth rarely have eruption problems?
Primary teeth are never enveloped in bone like permanent teeth
What are the causes of the active eruption mechanism?
Hydrostatic pressure in PDL due to vascular pressure
Forces from active metabolism in PDL
Cross-linking of collagen
True of false… PFE is typically bilateral in apperance
False, it is typically unilateral
Proffit states that familial PFE is caused by a loss of function in the ___ gene
PTH1R
What often happens when you apply orthodontic force on teeth affected by PFE?
They will ankylose after 1-2mm of movement
May create intrusion of adjacent teeth
What is a common mechanical obstruction that can lead to failure of eruption? What is the treatment?
Ankylosed deciduous teeth
Remove the obstruction and observe for eruption. If the permanent tooth does not erupt, then there likely is a defective eruptive mechanism and the tooth will probably ankylose.
If a tooth erupts but not fully into occlusion, what could be causing the problem?
Lip/tongue interference
What are 4 ways to treat PFE?
1) Extract with orthodontic space closure or prosthesis
2) Small segment osteotomies to surgically position teeth without disturbing PDL (alveolar osteotoomy) (bone grafting often necessary) (orthodontic force is contraindicated because it will ankylose the teeth)
3) Leave the tooth in place and make overdenture or prosthetic replacement
4) Coronal build-up
What is the defect in cleidocranial dysostosis affecting tooth eruption?
Underlying biochemical abnormality unknown but defect is seen in the removal of bone. The mechanical obstruction from abnormal resorption of overlying bone is the problem, not the eruptive mechanism. When overlying tissues are removed, the teeth can be moved orthodontically and treated normally
What are the clinical dental features of cleidocranial dysostosis and how do you treat it?
Absence/reduction of clavicles
Alterations in skull proportions
Multiple supernumerary teeth
Failure of most permanent teeth to emerge from alveolus
Treatment is to remove overlying tissue/bone and orthodontically move teeth into arch.
True or false… PFE usually affects one tooth at a time whereas mechanical failure of eruption affects multiple teeth
False… PFE usually affects more than one tooth and mechanical failure of eruption usually affects one tooth
Define eruption
Crypt to occlusion; the devleopmental process responsible for moving a tooth from its crypt position through the alveolar process into the oral cavity to its final position of occlusion with its antagonist
Define emergence
Popping through gingiva; describes the moment of apperance of any part of the cusp or crown through the gingiva; synonymous with moment of eruption
Define impacted teeth
Those teeth that are prevented from erupting by some physical barrier in their path
Define primary retention
Used to describe the cessation of eruption of a normally placed and developed tooth germ before emergence, for which no physical barrier can be identified
Define pseudoanodontia
Descriptive term that indicates clinical but not radiographic absences of teeth that should normally be present in the oral cavity for the patients dental and chronological age
Define embedded teeth
Teeth with no obvious physical obstruction in their path; they remain unerupted usually because a lack of eruptive force
Describe submerged teeth
Refer to a clinical condition whereby, after eruption, teeth become ankylosed and lose their ability to maintain the continuous eruptive potential as the jaws grow; such teeth then seem to lose contact with their antagonists and might eventually be more or less reincluded in the oral tissues
Define paradoxical eruption
Used to represent abnormal patterns of eruption and can encompass many of the above conditions
chornologic delayed tooth eruption occurs if the expected tooth eruption time is greater than __ standard deviations form the mean
Two
When the root is ___ to ___ developed you should see the crown emerge
2/3 to 3/4
Contralateral teeth should erupt within __ months of the contralateral tooth
6
According to the Bjork study, what are 4 characteristics of a favorably growing mandible?
1) acute gonial angle
2) wide symphysis
3) anteriorly inclined condylar head
4) low MPA
According to the Bjork study, what are 6 characteristics of an unfavorably growing mandible?
1) high MPA
2) obtuse gonial angle
3) antegonial notching
4) narrow ramus
5) tear-drop shaped symphysis
6) vertically or posteriorly inclined condylar head
What are the 4 less readily identified landmarks on a ceph?
Portion
Condylion
Orbitale
Nasion
(Gives doubt to Frankfort Horizontal)
What are the four most reliably identifiable points on a ceph?
1) gnathion
2) nasion
3) sella
4) articulare
How does dolphin predict growth?
Adds small mm measurements (AKA average growth increments of the population) to what already exists
Good in the short term but not long term - present growth is not a good indicator of future growth
What is the principle of Rickett’s arcial growth of the mandible?
1) the mandible grows in a pattern of a logarithmic spiral
- This spiral (AKA growth spiral) is seen frequently in nature. The angle between the tangent and the radius vector is the same for all points of the spiral
2) growth occurs by superior-anterior apposition at the ramus on a curve or arc through Xi point (center of ramus) from Dc (a middle point on the condylar neck) to the Pm (suprpagonion)
3) The radius of the circle is determined by the distance from mental protuberance to point Eva (oblique ridge on medial of ramus)
How did Ricketts predict growth using the logarithmic spiral?
1) developed an arc from Dc to Xi to Pm
2) Identified radius by measuring distance form mental protuberance to point Eva
3) Growth would continue along this arc at 2.5mm per year
The occlusal plane holds a strong tendency to pass through __ point
Xi
When Xi is connected to Pm (superpogonion) it defines the __ of the mandible
Corpus axis
Describe Rickett’s study evaluating arcial growth of the mandible
1) Used 40 patients from his office with no orthodontic treatment and made a bunch of measurements on the cephs.
2) developed an arch from Dc to Xi to Pm
3) compared time points of age 8 to 13 and superimposed cephs on Xi point and corpus axis
4) results showed that the mandible bent by 1/2 degree each year. Findings suggested that the true arc of growth of the mandible is somewhere between the Xi point and the anterior border of the ramus (R1) and between the condylar and coronoid processes
5) Rickett’s also used mandibles from cadavers and compared them to his patients
- However, he cherry picked his cases to prove a point so it is heavily biased
Why is the lower border of the mandible an inaccurate location to use to predict growth?
The lower border of mandible is resorptive
True or false.. the mandible grows in a linear fashion
False. It seems to grow along a curve
True or false.. the lower border of developing third molar germ appears to be a stable point until roots begin to form
True
What is a type 1 forward rotation of the mandible?
rotation about the condyle. Pushes the mandible up
What is a type 2 mandibular forward rotation?
Rotation about the incisal edges. Posterior mandible rotates away from the maxilla
Increases posterior facial height and increases vertical length of ramus/condyle. But, because of resorption at the gonial angle the height in this region may not actually increase significantly
Occurs from bending of cranial base from lowering of mid-cranial base resulting in lowering of condylar fossae
Eruption of molars keeps pace with the rotation (occlusal plane goes posterior down)
Wha is a type 3 mandibular forward rotation?
Rotation occurs about the premolars.
Results in deep bites and chin prominence
Underdeveloped LAFH when posterior face height increases
Influences inclination of incisors and results in crowding in incisors
True or false… backward rotation of the mandible does not occur as frequently as forward rotation
True
What is a type 1 backward rotation of the mandible?
Rotation about the TMJ
Occurs from opening the bite in orthodontic treatment
Increases LAFH
May result in open bite
What is a type 2 backward rotation of the mandible?
Rotation about the distal molars
Mandible rotates posteriorly
Backward (posterior) growth of condyles
Increases LAFH
open bite tendency
According to Bjork, a vertical grower will show a [more/less] curvy mandibular canal than the contour of the mandible and angle of the jaw (antegonial notch)
More
According to Bjork, an open bite tendency has a [decrease/increase] of the interincisal angle
Increase
According to Bjork, with a vertical growth tendency, the bicuspid angle becomes [more/less] pronounced, whereas in a brachyfacial case would be more ___
More
Upright
What were the 7 structural areas Bjork looked at to predict growth?
1) Inclination of condylar head (backwards = vertical)
2) curvature of mandibular canal (curvy = vertical
3) Shape of lower border of mandible (antegonial notch = vertical)
4) inclination of symphysis (forward = vertical)
5) interincisal angle (more acute= vertical)
6) interpremolar angle (more acute = vertical)
7) LAFH (increase = vertical)
An extreme forward rotation of the mandible will result in ___ whereas an extreme backward rotation of the mandible will result in ___. How do you treat these?
Deep bite - use bite plane to allow tooth eruption, delay extraction or dont extract
Open bite - delay treatment and extraction until after pubertal growth
According to Skieller (1984) retroclined mandibular symphysis is indicative of ___ growers whereas proclination of the symphysis is indicative of ___
Forward
Backward rotation
however, this information is inadequate to permit clinically useful prediction to be made relative to magnitude or direction of future mandibular growth
What differences exist between black and white patients relative to arch size, form, and type of malocclusion?
Blacks typically have larger teeth, arch widths, and arch lengths than whites
Archforms are more square than the ovoid archform of whites
Blacks has wider intercanine width than whites
Blacks have less incisor crowding compared to whites and Hispanics
Blacks have can more bulbous foreheads and flatter/wider noses
Mandibular ramus is broad in blacks
Blacks are the most common race with bimaxillary protrusion
In blacks, the mandibular ramus is typically ___ than in whites
Broader
Asians and southern/Eastern Europeans have a predominantly ___ headform. They have a wider, nasal bridge, and flatter shorter nose. Shorter midface and forehead is more upright and mandible is more prominent. Asians have fewer class ___ tendencies
Brachyfacial
2
Blacks tend to have what kind of headform?
Elongated dolicocephalic (more anteriorly inclined open middle cranial fossa
In blacks, they have a [long/short] horizontal mandibular corpus relative to maxilla. The forehead is more ___ (not as protrusive as Caucasian).
Long
Upright and bulbous
True or false… bimaxillary protrusion allows the clinician a greater range of dental compensation in treatment of anterior crossbite.
True
How does the black class 3 presentation differ from Asian or Caucasian?
The basicranium does not usually have a posterosuperior alignment of the middle cranial fossa (upper jaw is further forward)
Broad mandibular ramus and bimaxillary protrusion often most common cause of class 3
__ and __ is the most common cause of class 3 in blacks. What are common treatments?
Broad mandibular ramus - surgery for narrowing of ramus
Bimaxillary protrusion - ext U5s L4s
Arch size is __% larger in blacks due to greater arch __ and ___
19%
Width and depth
True or false… black arch forms can be expanded a couple mm outside the Caucasian arch form, especially in the premolar/molar region
True
True or false… arch dimensions are larger in males than females
True
____ are not genetically influenced whereas ___ are genetically influenced
Tooth positions
Arch dimensions
According to Buschang 2003, approximately __% of the population has little or no crowding and ___% have severe crowding
50%
17%
According to Buschang 2003, men are [more/less] crowded than women. Poor people are [more/less] crowded than wealthy. Older adults are [more/less] crowded than than young adults. List most crowded race to least crowded.
More
More
More
Mexican Americans, whites, blacks
In what things do hereditary influences play a stronger role?
Tooth crown size Hypodontia Supernumerary teeth Abnormal tooth shape Ectopic maxillary canines Submerged primary molars Skeletal headform
Dento-alveolar region has a stronger environmental influence than hereditary
True or false.. the greater the genetic component to a malocclusion the worse the prognosis for a successful outcome by means of orthodontic intervention
True
Define epigenomics
Intrinsic and extrinsic environmental factors regulating gene expression
What are some treatment differences between dolicho and brachy patients?
Brachy: try not to extract because it is more difficult to move teeth; it will deepen bite and decrease an already short LAFH. Good to use CPHG, bite turbos, and class 2 elastics. Don’t overexpand because it will give you a flat smile arc.
Dolicho: extract more often. Important to control the vertical. Expansion is usually necessary to allow for better OB. Good to use expanders, anterior elastics, HPHG, intrusion
What is the common Caucasian profile?
Very mild retrognathic profile due to compensatory factors
Chin is ~5mm behind line
What are some characteristics in individuals with a prominent nasomaxillary complex?
Deep set eyes Prominent cheekbones Bend in nose as compensation Class 1 malocclusion (jaws are back from where cranium is) 25% more nose growth than maxilla growth
How does the maxilla compensate for a backward rotation of the mandible?
Grows downwards
Where are the two points of rotation of the mandible? Describe them
Condyle (displacement rotation, compensates for vertical size of midface and alignment of middle cranial fossa)
Gonial angle (remodeling rotation, also important to accommodate displacement rotation)
If the maxilla and mandible are rotated up, the occlusal plane is tipped up and may result in a class __ pattern. Some patients may compensate by…
2
Growing more mandible (Increase in gonial angle or increase in corpus length)
If the maxilla and mandible are rotated downward, the occlusal plane is tipped down and it may result in a class __ pattern. An increase of the gonial angle may be contributing to this. This pattern is often indicates surgery
3
If the nasomaxillary complex is too long, it can cause ___ placement of the mandible resulting in a ___ pattern.
Down and back
Class 2
(Forward alignment of middle cranial fossa does the same thing)
If the nasomaxillary complex is too short it may have a mandibular ___ effect because it rotates in a __ direction giving it a ___ pattern
Protrusive
Upward and forward
Class 3
Closed basicranial angle can also do the same thing
Dentally, class 2 div 1 malocclusion have excessive ___, normal ___, ___ lower incisors, and ___ positioned U6s
OJ
Upper incisors
Proclined
Mesially
True or false… because growth and alveolar drift occur together you can get poor growth but still end up class 1 dental due to compensations. Likewise you could have good growth but end up class 2 dental
True
In class 2 div 1 presentation, the symphysis looks like a ___, approaching the upper anterior teeth
Tear drop
Growth compensations are morphological adjustments during facial development to maintain a state of functional and structural equilibrium. What are some frequently encountered compensations?
compensations in the ramus of the mandible Palatal rotations Anterior crowding Gonial angle remodeling Occlusal plane rotations
What are the areas of compensation during growth of the mandible?
Rotation Gonial angle Curve of spee Incisor compensation Mandible: increased ramus width and corpus length
What are two ways to represent the occlusal plane?
Traditional = draw a line along contact points of all teeth to the midpoint of overlap of upper and lower incisors
Functional occlusal plane = run a line from posterior most molar contact point straight to the anterior most premolar contact point (incisors not considered)
The curve of spee is a developmental adjustment to compensate for ____
Anterior open bite
What is the difference between cross sectional and longitudinal studies?
Cross sectional - rely on snapshots of the average state of growth of a sample population at a given point in time
Longitudinal - follow the growth curve of individual subjects over time giving a much more accurate picture of how people grow
Angle considered the ___ as the most stable tooth relative to the cranium. Rothstein disagreed though and that thought the position is variable. You cannot use dental terminology to define skeletal discrepancies
U6
Why does the mandible rotate forward with age?
Differential jaw growth in the vertical dimension
True or false… class 2 molar commonly spontaneously corrects itself with differential jaw growth. about ___% of class 2 malocclusion will self correct with differential jaw growth
False
5%
What happens to the mandibular plane over time?
It flattens, but less improvement is seen with steep planes
all groups show mandibular forward rotation with age
According to the study done by You (2001), while maxillary and mandibular dentition both moved forward on basal bone, the mandibular dentition moved [further, not as far] forward as the basal bone did
Not as far
Therefore, the mandibular dentition moves backwards relative to pogonion, therefore uprighting the incisors (contributing to crowding?)
True or false… in the study done by You 2001, there was no significant difference found in growth of normal individuals and class 2 individuals
True
This explains why class 2 is not necessarily self-correcting
Class 2 treatment requires breaking up the occlusion (unlocking interdigitation) and holding the ___
Maxillary molar (changing the growth of the maxilla down only instead of down and forward)
____ refers to the tendency for the mandible to grow at a different rate and longer duration than the maxilla use to the cephalo-caudal gradient of growth. This growth can be taken advantage of by the clinician to overcome a poor dentoalveolar relationship caused by an initially poor skeletal relationship
Differential jaw growth
Late mandibular differential growth can also result in dental compensatory changes in the maxillary such as ____. The late mandibular growth against the stationary maxilla also may contribute to ___
Proclination of upper incisors
Late incisor crowding
What is the foot in shoe theory coined by McNamara?
The idea was that if you did expansion of the maxillary arch, the lower arch will grow to match the larger “shoe” to correct the class 2 malocclusion.
This has been proven to be NOT true. RPE does NOT result in spontaneous correction of class 2
What can you do to treat a class 2 malocclusion if the problem is due to maxillary excess?
Headgear to redirect growth of maxilla downward while restraining the horizontal component of growth. Use high-pull for high angle cases and cervical pull for low angle cases.
In a non-growing patient with severe maxillary excess, can do a lefort with autorotation with an advancement genioplasty
What can you do to treat a class 2 situation if it was due to a deficient mandible?
Functional appliance to move mandible forward and achieve a headgear effect holding the maxilla back. In the long term though, the early treatment gains will be overcome by the normal growth pattern reassertion itself. Most changes are dentoalveolar
In non-growing patients, mandibular advancement surgery
In class 2 div 2, the U1s are over-erupted, and there is a __ correlation between lip line and incisal pressure. Meanwhile there is a ___ correlation between lip line and cervical pressure. Why is this significant?
Positive
Negative
Pressure is greatest at the incisal edge than cervical (causes the teeth to upright)
Which, class 2 div 1 or class 2 div 2 have a higher lip line?
Class 2 div 2
Why do the upper laterals stick out of the arch in a class 2 div 2 scenario?
The laterals stick out because they are erupting in an arch of smaller arch length. Actually, the laterals are in more appropriate arch form than the centrals
Describe the differences in growth between high and low angle patients according to the studies by Chung and Wong.
High angle:
- lower incisor increases in protrusion/proclination
- Straigtening of profile (not as much as low angle)
- Differential jaw growth (not as much as low angle)
Low angle:
- Upright Lower incisors
- More vertical ramus growth
- more flattening of gonial angle
Describe the study conducted by Chung and Wong that described differences in growth change between high and low angle patients. What did they find?
Divided a sample of untreated class 2 patients into 3 groups based on MPA (low, average, high) longitudinal 9-18.
1) SNA and SNB increased in all groups
2) ANB decreased in all groups
3) Skeletal convexity decreased in all groups (low angle more-so)
4) mandibular body length increased in all groups
5) MPA decreased in all groups (not as much in high angle group)
6) No significant differences in palatal plane (highly variable)
7) LAFH increased in all groups
8) posterior face height increased in all groups (low angle more-so)
9) Ramus height increased in all groups (low angle more-so)
10) anterior cranial base height increased in all groups
11) posterior cranial base height increased in all groups (less in high angle)
12) Y axis increased ~2degrees in all groups (boys more than girls)
13) lower incisors retruded/retroclined in low angle, protruded/proclined in high angle
14) linear measurement increases larger in males than females
Do class 2 malocclusions correct with growth?
Most likely not.
Although there is differential jaw growth, teeth stay “locked” in their malocclusion so the mandibular dentition does not move as far forward as the basal bone
Class 2 treatment requires breaking up the occlusion and holding the maxillary molar
If you disrupt the occlusion, about 5-10% will self correct and ~50% get 2mm correction.
A study by Liu 2001 examined the molar rotation and lingual cusp relation in class 2 scenario. by looking at the palatal cusp occlusion with the lower molar, you can determine the severity of the case. Describe the study’s findings.
1/4 step class 2 buccal had lingual class 1 1/2 step class 2 buccal, 55% had lingual class 1 Full step class 2 buccal, 83% had 1/2 step class 2 lingual Only 17% were full step class 2 on lingual cusp
** derotating the U6s can help with class correction
Derotating U6s can not only help with class correction but it can also allow up to ___mm space gain
3
What are the typical presentations of class 2 div 1 and class 2 div 2?
Class 2 div 1: lip incompetence, or lip position can be mentalis strain and lower lip caught under maxillary incisor
Class 2 div 2: deep bite, Lowe MPA, short facial height, proclined laterals
How are class 2 div 2 malocclusions typically treated?
Disrupt entire occlusion
First Intrude and procline upper incisors (will make smile less gummy), then bond lowers
Treat non-ext (ext will collapse and deepen the bite)
Banding 2nd molars is recomended with functional appliances
class 2 elastics (easier in children)
May need surgical treatment plan
There is a relatively low incidence of class 2 div 2 cases. About __% in Caucasian, ___% in blacks.
- 7%
1. 6%
Explain the concept and the evidence of the mandible being trapped distally in class 2 div 2 malocclusion cases.
Class 2 div 2 pts have deep bites. The theory was that the mandible can’t continue to grow because its trapped by the deep bite thus displacing the condyle distally. Demisch et al showed that even if you procline the upper incisors (eliminating deep bite trap) the mandible doesn’t move forward. So the idea that the mandible gets trapped is NOT true.
What are the clinical implications of treating class 2 div 2 cases in adults?
Difficult to treat due to musculature, black triangles, no growth potential
Surgery (BSSO with genioplasty) - but it doesn’t work well because tissue tends to stay forward/chin projection (no good surgical solution)
Align teeth and do alveolar advancement of the mandible
What is the incidence of unilateral crossbites?
5.9-9.4%
Of present unilateral crossbites, what percentage are functional crossbites?
67-79%
Functional crossbites usually have [asymmetric/symmetric] mandibles but are positioned [asymetrically/symmetrically]
Symmetric
Asymmetrically
Skeletal unilateral crossbites are characterized by ___ mandible
Asymmetric
True or false… as suggested in the literature, functional crossbites may lead to morphological changes and produce skeletal crossbite
True
In the case of a functional unilateral crossbite, asymmetry is seen in the position of the condyle in the fossa. Describe this asymmetry
Crossbite side: condyle is more superior and posterior in fossa
Non-crossbite side: condyle is positioned down and out
A study by Pinto (2001) aimed to evaluate the morphological asymmetry of children with functional crossbites before and after orthodontic treatment. What did the study find?
Pretreatment:
- noncrossbite side larger than crossbite side (~1.6mm)
- Ramus length longer on functional shift side
- mandible position asymmetric to cranial reference
- Larger joint spaces for the non-crossbite side than crossbite side
Posttreatment:
- asymmetry not present in morphological, positional, or joint spaces
With a unilateral crossbite, a mandibular shift results in an AP shift on the ___ side
Non-crossbite
True or false… the results of the Pinto (2001) study suggest that the functional shift can cause skeletal asymmetry. If so, where do the changes occur?
True
Most changes occur in the anterior ramus of the non-crossbite side
True or false… the Pinto (2001) study suggests that treatment reduces or eliminates both postural and skeletal asymmetries that would be caused by a unilateral crossbite with functional shift
True
True or false.. patients with an abnormal functional pattern often continue the abnormal chewing pattern even after correction
True. Because of the neuromusculature
Long-term functional shift can result in a ___
Cant
Why do adults with a unilateral crossbite not necessarily have a functional shift?
Musculoskeletal adaptation
What can cause unilateral crossbites?
Habit (environmental/etiological, thumbsucking)
Constricted maxilla
Unfavorable growth does not necessarily go away if treated early on (bad growers continue bad growth)
Sometimes if you treat too early, the patient can relapse
In a functional unilateral posterior crossbite, is increased joint space found on the non-crossbite side or crossbite side?
Non-crossbite side
Compensatory growth with ___ can eliminate positional and skeletal asymmetries due to functional posterior crossbite noted before treatment.
Early expansion therapy
Why is it better to treat kids early who have a unilateral posterior functional crossbite?
If treatment is delayed they will get musculoskeletal adaptation and asymmetric cell proliferation in the condyle leading to mandibular skeletal asymmetry and abnormal chewing cycle.
How do you evaluate if there is a functional shift?
If midlines are on in CR, then functional shift
If midlines are off in CR, then growing asymmetrically
Crossbite patients have [more/less] movement of jaw in chewing than non-crossbite control, but in a [similar/different] pattern.
More
Similar
do patients with crossbite tend to struggle more to chew on the crossbite or non-crossbite side?
Crossbite side
Is the chewing cycle duration longer or shorter for crossbite patients pre-treatment? What happens after treatment?
Longer pre-treatment
After treatment, cycle duration is reduced and no longer significantly different from control. However the chewing pattern remains different than controls, although slightly more similar.
If the functional shift due to posterior crossbite is treated, the ___ and ___ return to normal, but the ___ does not. Therefore, ___ may be a problem.
Morphology of mandible and disc
Neuromuscular pattern
Retention
According to Kiliaridis (2000), in patients with unilateral posterior functional crossbite, the masseter was [thicker/thinner] on the crossbite side than the non-crossbite side.
Thinner
Maximum bite force is [greater/less] in crossbite patients than in non-crossbite patients. How does the maximum bite force differ from side to side in a pt in crossbite?
Less
Does not differ between sides
True or false… although improved, pts who have been successfully treated for posterior crossbite still have less biting force than controls
True
Discuss why treatment of crossbite in children is advantageous compared to waiting to adulthood.
Kids should be treated early so growth can re-compensate and allow for normal morphology to return. This can help avoid untoward effects like TMD, asymmetry, and CR-CO shifts.
How should you treat unilateral posterior crossbites in adults?
Consider leaving crossbite as is. Expansion would require SARPE or asymmetric mechanics.
Functional shifts are not typically seen in adults because they had musculoskeletal adaptation and have grown into asymmetry.
What is the theory of how mouth breathing can affect growth?
Mouth breathing can cause abnormal dentofacial growth by the following: Head tilts up Mandible rotates down and back Incisors retrocline Tapered archform Posterior crossbite
How might kids outgrow mouthbreathing?
Lymphatic tissue of the adenoids and pharyngeal tonsils decreases in relative size beginning around age 9
In the Linder-Aronson on adenoidectomies, children with adenoid hyperplasia tend to have ____ faces, ___ tongue placement, ___ mandibles, and more ___. After the adenoidectomies, the patients tended towards ___
Long and narrow
Lower
Steeper
Open bites
Normal
Describe adenoid facies characteristics. What is the cause
Long face syndrome Adenoidal enlargement Open mouth posture Small nostrils Short upper lip Maxillary vertical excess with gummy smile Narrow V-shaped arches Anterior open bite Posterior crossbites Lower positioning of tongue
Caused by adenoidal enlargement causing upper airway constriction
Conclusion to be drawn from many of the airways studies is the changed facial morphology and mandibular growth directions resulted only when…
The mandible was held in a chronically lowered position
The Linder Aronson (1986) study found that after adenoidectomies [girls/boys] had more horizontal growth than controls. However, a similar change could not be proved for the [girls/boys]
Girls
Boys
Linder-Aronson found that lymphoid tissue on the posterior nasopharyngeal wall is thickest at ___ years of age and subsequently decreases until age ___. There is a slight increase at age __, then continues to decrease.
5
10
10-11
What is the prevalence of children snoring?
At least 4.3%
How may mouth breathing lead to posterior crossbite?
Mouth breathing may lead to a change in the balance between tongue and cheek pressures. Tongue pressure reduced buccally so the cheek pressure will cause the posterior teeth to be moved lingually
What is the theory of how nasal obstruction can lead to incisor crowding?
Nasal obstruction causes patients to be a mouth breather, causing down and back rotation of mandible
Less tongue pressure and increased lip pressure causes the incisors to retrude/retrocline leading to incisor crowding
Some chronic mouth breathers unconsciously maintain a __ head position. Patients with head position like this are also associated with ___. Hellsing thought that this head position caused increased ___ which initiates malocclusion
Extended or upwardly rotated.
increased LAFH and steep inclination of MP
Lip pressure
True or false… many studies document a clear relationship between airway obstruction and dentofacial development, whereas some fail to demonstrate any relationships.
True.
A current concept for the etiology of malocclusion is that the development of malocclusion can be seen as a disruption in __ mechanisms during growth, which adapts the ____ to variations in the Sagittal, vertical, or transverse jaw relationships. So changes in the morphological pattern for mouth breathers doesn’t result in the same effect for all patients because of the efficiency of this ____ mechanism.
Compensatory
Dental alveolar arches
Dentoalveolar compensatory
What are the most important factors in determining the morphological outcome regarding mouth breathers?
Mandibular, tongue, and head posture in response to nasal obstruction
What is SNORT?
Simultaneous Nasal Oral Respiratory Technique = evaluates Nasal resistance, cross-sectional area, peak nasal airflow rate, and oral and nasal percentage air intake
True or false… SNORT is better than other measuring techniques (rhinometry, acoustic reflection, ceph analysis) because….
True
It provides more accurate and reliable information and is less cumbersome
What are the findings of the Linder Erickson Woodside study? What problems are associated with that study relative to airway?
After adenoidectomy, 80% of children who were mouth breathers became nasal breathers
Found that nasal breathing changed growth to more horizontal pattern in girls
Problems: biased because the study only selected patients who converted from mouth to nasal breathers to study their growth pattern. Didn’t have any data on mandibular growth direction before the surgery. Used a unstable landmark to measure mandibular growth (gnathion)
What happens to airway resistance from 7-18 years of age?
Overall airway resistance DECREASES with age.
However, at puberty, the adenoids/tonsils enlarge for a brief period of time which increases airway resistance. Then the lymphatic tissue continues to decrease in size.
Not that the airway can change from day to day
True or false… newborns are obligatory mouth breathers
False. They are obligatory nasal breathers
What are common causes of nasal obstruction?
Inflammation of nasal mucosa due to allergies, infection, etc.
Allergic rhinitis (can result in nasal/sinus polyps)
Nasopharyngeal adenoid hyperplasia
Nasal septal deviation
What is the conclusion you can draw about the relationship between mode of breathing and malocclusion?
Can’t make conclusion. Little evidence that mouth breathing causes a change in dentofacial morphology or that if a patient converted from mouth to nasal breather that there is any change in morphology.
Cannot advise removal of adenoids for orthodontic purposes
RPE does increase nasal width and volume, and increases nasal airflow, but doesn’t necessarily mean it will help with changing from mouth to nasal breathing
Most evidence for mouth breathing and growth is too variable, inconsistent, and weak to warrant a cause and effect relationship
Ballared and Gwynne-Evans reported that ___ was not necessarily associated with mouth-breathing
Lip incompetence
Reduction of nasal component of respiration is not a “disease” but it is an…
Arbitrary point on a continuum of 100% nasal breathing to zero
Sensitivity and specificity of diagnostic tests for impaired nasal breathing are [good/poor] indicators of nasal resistance, peak flow rate, and percentage of nasal air flow. Why?
Poor. They are inconsistent
How should you construct cervical pull head gear?
Long outberbow 15-20 degree bent upward
400-600g of force
Rest comfortably between lips when activated
Outerbow should be just clear of facial tissues
1cm of expansion posteriorly
Cervical neck strap
Due to differential jaw growth, there is a [decreasing/increasing] prominence of the chin with growth relative to the forehead. Males show a [greater/lesser] increase than females. The maxilla becomes relatively [more/less] protrusive with growth
Increasing
Greater
Less
The nose grows downward and forward more than other parts of the facial profile. It grows at about __mm every year at a steady rate.
1.33mm
What are the post-treatment changes expected after discontinuation of HG
Normal downward and forward growth of maxilla
Maxillary molar recovered to original position (uprighted and downward and forward growth of 3mm)
Changes in anterior face height, mandibualr lenght, point B and pogionon all reflect tremendous amount of post treatment growth
The study by Kim 2001 did not support the clinical dogma that cervical pull headgear…
Causes opening rotation of the mandible by extrusion of the maxillary first molar
What were the conclusions of the Kirjavaienen 2000 article about cervical pull headgear?
CPHG alone can be used to correct Class 2 div 1 malocclusion WITHOUT extruding the maxillary molars
for correction, it was crucial to expand the inner bow and to ensure no other appliance was in place that would bind the teeth together
There was little to no change in the inclination of incisors (suggesting all skeletal change)
Cervical pull head gear(or any HG) works by allowing differential jaw growth. Growth of the mandible occurs while holding the upper dentoalveolus. There is [an increase/ no increase] in MPA seen with cervical pull headgear.
No increase. However, normal decrease in MPA is not seen in treatment
A study by Melsen 2003 evaluated the intramaxillary molar movement after 8 months of CPHG. The study found that there was no difference in molar extrusion with change in ____. There was however, more tipping with the bow bent ___ and more bodily molar change when the bow was bent ___. Growth returned to normal after discontinuation of HG.
Arm position
Down
Up
A pend-x appliance is a tooth borne appliance that will require __ movement of ___ to achieve ___ and __ movement of the molars. In contrast, premolars and incisors drift ___ with HG treatment.
Mesial movement of premolars
Distal and palatal
Distally
Describe the treatment effects and effects of growth using class 2 elastics
Disrupts occlusion and allows for differential jaw growth. Changes occlusal plane angle (rotated in clockwise direction), reclines lower incisors, retroclines upper incisors, extrudes molars, mesializes mandibular dentition. Encourages upward and forward drift of mandibular alveolus.
Describe the treatment effects using a distal jet.
Disrupts occlusion and allows for differential jaw growth. Holds the upper molar relative to forward maxillary alveolar drift (relative distalization) tips U6s back. Anterior anchorage loss and flaring of U incisors with no TADs
Describe the treatment effects of the pendulum appliance
Disrupts occlusion and allows for differential jaw growth. Holds the upper molar relative to forward maxillary alveolar drift and tips back U6s. U6s also rotate distal palatally, mesial buccally. Anterior anchorage loss with premolars drifting mesially and flaring of U incisors with no TADs.
Describe the treatment effects of the bionator
Disrupts occlusion and allows for differential jaw growth. Holds U6s. Encourages lower dentoalveolus upward and forward movement. Rotates mandible down and back
What happens if you use a functional appliance with a patient with a flat articular eminence?
When lower jaw is postured forward you get posterior contact and it wont work.
Do cervical headgears affect the vertical component?
According to Kim 2001, the U6 extruded 1mm (not significant) compared to control. The MPA increased 0.25 degrees immediately after treatment while the control decreased in MPA . Kloen’s article also showed that there’s was no change in the vertical as long as you had a long outer bow angled upward to minimize molar tip.
How many hours per day is required for HG and for how many months?
12-14 hrs per day
For at least 12 months
What are the growth effects with long term good headgear wear?
Skeletal: change maxillary growth direction to downward instead of downward and forward. (Restrains forward growth). Increases differential jaw growth by disrupting occlusion
Dentoalveolar: holds the U6s to allow lower dentoalveolus to grow upward and forward
HG is a temporary intervention, but doesn’t actually change a patients growth: mainly disrupts the occlusion to help correct class 2
What are the criteria for successful use of functional appliances?
Well aligned upper and lower arches
Class 1 to mild class 2 skeletal pattern
Forward posture of the mandible by the patient will give satisfactory soft tissue profile
A person who is undergoing active growth
The greater the ___ the less the chance of success of functional appliances. Less than ___mm has a 98% success rate. Whereas __mm show less success at 55%
Overjet
7mm
7-11mm
With normal growth, the SNB generally increases __-__ degrees
2-3
Is increased or decreased overbite better for successful functional appliance therapy?
Increased overbite
True or false… most data shows that both HG and Herbst produce equally attractive profile in class 2 div 1 cases
True
How do functional appliances work?
1) Utilizes differential jaw growth
2) stops forward eruption
3) encourages forward and vertical mandibular molar alveolar development
4) little net increase in mandibular growth (maybe 1mm of condylar growth)
5) Early increase in mandibular growth does not increase long-term potential for mandibular growth
6) primary effects are dentoalveolar
In effect, the functional appliances takes out a ___ on the mandibular position that is amortized by the subsequent growth of the condyle
Mortgage
True or false… the dentoalveolar effects of functional appliances on lower incisors is greater in adolescents than adults
False. It is greater in adults than adolescents
Regarding facial change in class 2 div 1 with mandibular deficiency, using functional appliances, what is the facial and skeletal change? What is immediate change and long term change?
- Profiles improve over time due to differential jaw growth (immediate and after treatment)
- The reason for immediate profile improvement with functional appliances is that the mandible is being postured forward by the appliance
The Turley 2002 study treated patients with expansion and facemask at different ages. The ___ group showed statistically greater increases in SNA than the ___ group
Younger
Older
The Turley 2002 showed the average maxillary advancement with reverse pull headgear to be ___mm. Though 6/12 patients showed 5-8mm. 5/21 patients showed SNA changes of 4-5 degrees. Mandibular clockwise rotation accounted for __% of the total correction.
3.3mm
25%
There is a wide range of recommendations for optimal timing for facemask therapy. Studies show that you can still get significant treatment differences in older children (up to age ___), but greater skeletal response occurs in younger children.
12
What do studies show regarding stability of facemask therapy?
Little is known of stability
Ultimately, facemask therapy does not normalize growth and after treatment, class 3 patients will continue to grow class 3, so you need to over-correct to compensate
True or false.. expansion significantly aids in class 3 correction
False
When should you do phase 2 orthodontics in class 3 patients?
Postpone as long as possible. Especially in males
___ is the main cause of post-tx class 3 relapse
Late mandibular growth
Reverse pull facemask works by stimulating ___ and __ growth of the maxilla. It will also rotate the maxilla ___ up and ___ down. It will extrude ___ teeth causing ___ and ___ rotation of the mandible increasing ___ and ___. It may cause __ of the upper incisors due to mesial dental movement.
Forward and downward
Anterior up and posterior down
Maxillary posterior
Down and back
LAFH and MPA
Proclination
the downward and backward rotation of the mandible as a consequence of maxilla movement in reverse-pull facemask therapy is a major factor in establishing ___
Anterior overjet
The average duration of treatment of reverse pull facemask was ___ in nonexpansion groups. So expansion with facemask will result in ___
Longer
Shorter treatment duration
Facemask therapy is most effective in children less than ___ years old.
10
In addition to shorter treatment duration, expansion during reverse pull headgear can…
Result in less proclination of maxillary incisors (more skeletal than dental effects)
If a patient exhibits a significant increase in ___ during facemask treatment, chances for long-term stability may be reduced
LAFH
True or false..the Frankel appliances is not as effective in treating class as reverse pull facemask
True
According to Baccetti, what are the indicators of failure for reverse pull facemask therapy?
Acute cranial base angle between middle and posterior cranial fossae. (Acute angle would project the mandible forward)
Increased mandibular length and ramus height
According to Ghiz, what are the indicators of failure for reverse pull facemask therapy?
More forward position of the mandible relative to cranial base
Longer mandible
Shorter ramus
Increased gonial angle
According to Wells, Sarver, and Proffit 2006, what are the indicators of failure of reverse pull facemask therapy?
Decreased posterior vertical facial height
Increased mandibular length
OB
No differences in saddle angle (N-S-Ar)
