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
