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Notes from Proffit 2019
All the information was highlighted and written in a simple way
to read and memorised, Please open the book for the graphs and
tables in addition to the clinical pictures.
Dr.Yousef Nasrawi
2021-2022
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, Dr.Yousef Nasrawi
1
Malocclusion and Dentofacial Deformity in
Contemporary Society The development of
Orthodontics
- Norman Kingsley’s was the first to use extra oral force to correct protruding
teeth, in addition to treatment of cleft lip and palate.
- Angle’s postulate was that the upper first molars were the key to occlusion and
that the upper and lower molars should be related so that the mesiobuccal cusp
of the upper molar occludes in the buccal groove of the lower molar.
- Angle then described three classes of malocclusion, based on the occlusal
relationships of the first molars, in addition to the forth class (Normal occlusion):
• Class I: Normal relationship of the molars, but line of occlusion incorrect because of malposed
teeth, rotations, or other causes
• Class II: Lower molar distally positioned relative to upper molar, line of occlusion not specified
• Class III: Lower molar mesially positioned relative to upper molar, line of occlusion not specified.
- Line of occlusion in the upper arch (related to angle): smooth (catenary) curve
passing through the central fossa of each upper molar and across the cingulum
of the upper canine and incisor teeth.
- Line of occlusion in the lower arch (related to angle): same line runs along the
buccal cusps and incisal edges of the lower teeth.
- Tweed and Begg reinforced the idea for extraction which will:
1) Enhance the facial esthetics.
2) Achieve better stability of the occlusal relationships.
- Cephalometric radiography came to widespread use after world war II
- The soft tissue paradigm states that both the orthodontic and orthographic
treatment are determined by soft tissue of the face not by teeth or bones.
(Go back to table 1.1, page 4)
- What difference does the soft tissue paradigm make in planning treatment? There
are several major effects:
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, Dr.Yousef Nasrawi
1) Soft tissue adaptations and relationships, the proportion of the soft tissue
integument of the face & relationship of the dentition to the lips and face are the
major determinant of facial appearance.
2) Functional occlusion, it is important to arrange the occlusion to minimize the
chance of injury to the soft tissue (ex: soft tissue around TMJ).
3) Solving the patient problems.
-The National Health and Nutrition Estimates Survey III (NHANES III): have evaluated
the characteristics of malocclusion which include :
1) Irregularity Index.
2) Prevalence & Midline diastema > 2mm.
3) Prevalence of posterior Crossbite.
4) Overjet & Overbite
- Incisor irregularity usually is expressed as the irregularity index: the total of the
millimeter distances from the contact point on each incisor tooth to the contact
point that it should touch. (With the most percentage for Mexican-American)
- A space between adjacent teeth is called a diastema. A maxillary midline
diastema is relatively common, Spontaneous correction of a childhood diastema
is most likely when its width is less than 2 mm.
- From age 8 -10, over half of US children have well aligned incisors
- The percentage with excellent alignment decreases in the age 12 to 17 years,
which remain stable relatively in the upper arch, but worsens in the lower arch for
adults.
- 34% of adults have well aligned lower incisors.
- 15% of adolescents and adults have severely or extremely irregular incisors.
- 26% of children have a midline diastema > 2mm space
- 6% of adults have a noticeable diastema, blacks are 2X to have a midline
diastema.
- Overjet of 5mm or more suggest class II malocclusion, occurs in 23% of children,
15% in youths and 13% of adults. (Only 1/3 have ideal AP incisor relationship)
- Severe deep bite is 2X prevalent in whites, which is more prevalent than open
bite.
- Open bite more than 2mm is 5X more prevalent in blacks than in whites.
- 30% have normal occlusion
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, Dr.Yousef Nasrawi
- 50% - 55% Class I malocclusion. (60% in Bristol Notes)
- 15% Class II malocclusion.(More prevalent in whites of European decent)
- 1% Class III malocclusion. (More prevalent in Asian decent) (More in Hispanic
than whites to blacks)
- Modern human have quite underdeveloped jaws. (DECREASE in size of teeth,
size of jaw, and number of teeth)
- Class III was found more in South Pacific Islanders.
- Buccal Crossbite was found more in Australian Aborigine.
- Corruccini, reported a higher prevalence of crowding, posterior crossbite, and
buccal segment discrepancy in urbanized youths compared with rural Punjabi
youths of northern India.
- Who needs treatment?
1) Social discrimination because of facial appearance.( Major reason people seek
orthodontic treatment is to minimize psychosocial problems related to their
dental and facial appearance.These problems are not “just cosmetic.” They can
have a major effect on the quality of life.)
2) Problems with oral function including difficulties in jaw movement (TMD).
(Tongue and lips position related to the teeth do NOT effect the swallowing and
speech) , (Cross bite and relation with TMJ may have a positive correlation in
coefficients of 0.3-0.4)
3) Greater susceptibility to trauma, periodontal disease or tooth decay.
- Tongue & lip posture adapt to the position of the teeth so that swallowing rarely
is affected.
- 1 among 3 children with untreated Class II malocclusion will experience trauma to
the upper incisors , results only minor chip in the enamel, so it is not a strong
argument for early treatment of all class II problems.
- With previous trauma and age younger than 9 years, the risk of additional trauma
is 8.4X higher than children with no trauma.
- OJ > 9mm increased the trauma to upper incisors by 45%
- Malocclusion has little if any impact on diseases of the teeth or supporting
structures.
- An individual’s willingness and motivation determine oral hygiene much more
than how well the teeth are aligned.
- Family income, is a major determine of how many children receive treatment.
- Occlusal trauma, once thought to be important in the development of periodontal
disease, now is recognized to be a secondary, not a primary, etiologic factor.
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- Long-term studies have shown no indication that orthodontic treatment
increased the chance of later periodontal problems.
- Both psychosocial and functional handicaps can produce significant need for
orthodontic treatment. The evidence is less clear that orthodontic treatment
reduces the development of later dental disease.
- There now are two major methods for scoring the severity of malocclusion: the
peer assessment rating (PAR) system, developed in the United Kingdom, and the
American Board of Orthodontics (ABO) discrepancy index, developed in the
United States. (Both Score system consider just the dentition, not the skeletal or
facial characteristic).
- PAR scores are calculated from measurements of maxillary and mandibular
anterior alignment (crowding and spacing), buccal segment occlusion
(anteroposterior, transverse, and vertical), overjet or reverse overjet, overbite, and
midline discrepancies, with use of a weighting scale for each characteristic.
- ABO index scores are calculated similarly, with the difference primarily that it
adds three cephalometric measurements. (ANB angle, IMPA, and SN-GoGn
angle)
- The Index of Treatment Need (IOTN), developed by Brook and Shaw in the
United Kingdom, was designed to evaluate need for treatment. It places patients
in five grades from “no need for treatment” to “treatment required” that correlate
reasonably well with clinician’s judgments of need for treatment.
- IOTN, assessed both DENTAL (derived from occlusion + alignment) & ESTHETIC
components (derived from comparison of 10 photos for dental appearance)
(Open IOTN in Page 13)
- Dentists usually judge that only about 1/3 of their patients have normal
occlusion, and they suggest treatment for about 55%. (Children in IOTN grade 3
and some of grade 2 in the group who would benefit from orthodontics).
- Nearly 5% of the lowest income group and 10% to 15% of intermediate income
groups reported some orthodontic treatment. This reflects the importance given
to orthodontic treatment.
- In the 1980s, a “baby bust” period, the increasing number of adult patients was
the major source of the overall increase in orthodontics.
- In the 1990s, a “baby boom” period, the number of adult patients increased a
little but most of the growth involved treatment of children, so the adult
percentage declined
- 27% of all orthodontic treatment were adults according to American Association
of orthodontists in 2014.
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2
Concepts of Growth and Development
- In general term for the growth, it means ( increasing in size or number) and for
term development always refer to increase in complexity.
- In fetal life at about 3rd month of intrauterine development, the head takes up
almost 50% of the Total body LENGTH, at this stage, cranium represent more
than half the total head.
- In contrast to the head, (Limbs are still rudimentary and the trunk is
underdeveloped).
- By the time of birth, the trunk and limbs have grown faster than head and face, so
the percentage for the head decreased to 30%, then it will decreased more in
adult to reach 12% (1/8)
- At birth, Legs represents about 1/3 of the total body length, whereas in the adult
they represent about 1/2.
- More growth of the lower limbs than the upper limbs during the postnatal life.
- The axis of increased growth extending from the head towards the feet called
“CEPHALOCAUDAL GRADIENT OF GROWTH”.
- Relative decrease in the head size after birth shows that, MUSCULAR and
SKELETAL elements grows faster than brain and central nervous system.
- The gradient of growth also found in the face, in mandible which being farther
away from the brain, tends to grow MORE and LATER than the maxilla, which is
closer to the cranium.
- Scammon’s curves for growth of the four major tissue systems of the body
(Lymphoid, Neural, General, Genital).
- Growth of the NEURAL tissues is nearly complete by 6 or 7 years of age.
- GENERAL body tissues, including muscle, bone, and viscera, show an S-shaped
curve, with a definite slowing of the rate of growth during childhood and an
acceleration at puberty.
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