Growth Rotations
www.indiandentalacademy.com
1
INDIAN DENTAL ACADEMY Leader in continuing dental education www.indiandentalacademy.com
www.indiandentalacademy.com
2
“An intensive study of the growth of the human head will inevitably lead to the realization that it involves the most complicated anatomical complex in all creation. The interrelationships are infinite and the causes and effects of these relationships are almost imponderable. The more our knowledge increases the more our ignorance www.indiandentalacademy.com 3 unfolds.
Introduction Terminologies Concepts of Mandibular Rotations Concepts of Maxillary Rotations Tooth eruption and facial development Prediction of growth rotations Clinical implications of Rotations Conclusion
www.indiandentalacademy.com
4
Introduction  First publication on the growth of the face-18th century.  Hunter suggested that mandible lengthens due to resorption of the anterior surface of ramus and deposition posteriorly. www.indiandentalacademy.com
5
Introduction
Growth was studied www.indiandentalacademy.com using stains and inserting metal wires 6
Introduction Cephalometrics introduced in 1930s.
Originally used to reveal the anatomy of head.
Since longitudinal study is possible it was used to test various concepts concerning the mechanisms of postnatal enlargement of head. www.indiandentalacademy.com
7
Introduction  Measurements and tracings showed little changes in the facial form.  The development in the form of the face was considered static.
www.indiandentalacademy.com
8
 With the use of metallic implants as markers it was seen that mandibular corpus rotates during growth but the shape is kept stable by surface remodeling.
www.indiandentalacademy.com
9
www.indiandentalacademy.com
10
Introduction Lande in 1952 observed that the lower border becomes less steeply inclined with growth. The phrase ‘growth rotation’ was introduced by Bjork in 1955. Metallic implants were precise markers from which sites and amount of growth and resorption could be found. Superimposing two consecutive tracings showed that the older mandible had rotated. www.indiandentalacademy.com
11
Types of rotation Forward rotation (Bjork)/ Counterclockwise (Schudy)
Backward rotation (Bjork) / Clockwise (Schudy) www.indiandentalacademy.com
12
Posterior growth is greater than the anterior growth www.indiandentalacademy.com
13
Anterior growth is greater than posterior growth. www.indiandentalacademy.com
14
Terminologies.  1965-Schudy introduced clockwise and counterclockwise rotation.  1969-Bjork discussed different directions of rotation of the mandibular implant line and the relation of these to mandibular form.
www.indiandentalacademy.com
15
1970-Odegard described rotation as the change in the orientation that can occur between implant line and lower border of the mandible. 1977-Lavergne and Gasson described the terms Positional and Morphogenetic rotations. 1983-Bjork and Skieller gave the termsTotal rotation. Matrix rotation. Intramatrix rotation. www.indiandentalacademy.com
16
1985-Dibbets introduced the term Counterbalancing rotation. 1988-Solow,Houston True rotation. Apparent rotation. Angular remodeling of the lower border. Proffit- used the terms Internal rotation. Total rotation . www.indiandentalacademy.com
External rotation.
17
www.indiandentalacademy.com
18
Core
www.indiandentalacademy.com
19
www.indiandentalacademy.com
20
Total / True / Internal  Is the rotation of the mandibular corpus and is measured as a change in inclination of the implant line, in the mandibular corpus relative to the anterior cranial base.
www.indiandentalacademy.com
21
When implant line rotates forward relative to the S-N , total rotation is designated negative. Converging S-N lines-forward rotation.
www.indiandentalacademy.com
22
www.indiandentalacademy.com
23
MATRIX / APPARENT /TOTAL Rotation of the soft tissue matrix of the mandible relative to the anterior cranial base. Soft tissue matrix is defined by a tangential mandibular line . www.indiandentalacademy.com
24
Negative when mandibular line rotates forward relative to S-N line. ‘Pendulum movement’. Centre of rotation at the condyle.
www.indiandentalacademy.com
25
www.indiandentalacademy.com
26
Intramatrix / Angular remodeling of lower border / External rotation-
Defined by the change in inclination of the implant line relative to the tangential mandibular line.
www.indiandentalacademy.com
27
www.indiandentalacademy.com
28
Rotation of the corpus inside the soft tissue matrix.
Forward rotation of the corpus relative to the tangential line is negative. Centre of rotation some where in the corpus. Dependent on the rotation of maxilla and occlusion of teeth. www.indiandentalacademy.com
29
----
+
+ + + ++
www.indiandentalacademy.com
30
+ ---
+ + + ++
-
www.indiandentalacademy.com
31
According to Bjork and Skieller
The mandible “wiggles” within the matrix
This wiggling is associated with the corpus but is caused by the growing condyle.
Rotation results from or compensates for, a genetically determined program.
www.indiandentalacademy.com
32
ANGULAR REMODELING OF LOWER BORDER Rotation should be used to describe the angular movement of one rigid body relative to another. Single body changes in form-surface accretion and removal- Angular changes Makes a terminological distinction between-the measure of the amount of remodeling that occurs at the mandibular border and the rotational process that causes it. www.indiandentalacademy.com
33
BJORK
SOLOW,HOUSTON
PROFFIT
Rotation of the mandibular core relative to cranial base.
Total Rotation
True Rotation
Internal Rotation
Rotation of mandibular plane relative to cranial base.
Matrix Rotation
Apparent Rotation
Total Rotation
Rotation of mandibular plane relative to core of the mandible.
Intramatrix Rotation
Angular External Remodeling of Rotation lower border
www.indiandentalacademy.com
34
TOTAL ROTATION = MATRIX ROTATION + INTRAMATRIX ROTATION
www.indiandentalacademy.com
35
Direction of total rotation more forward than the matrix rotation pronounced remodeling takes place at the lower border of the mandible. Forward intramatrix rotation lifts up the anterior part of the corpus from the soft tissue matrix-APPOSITION. Posterior part pressed down into the matrix-RESORPTION. www.indiandentalacademy.com
36
 The center of rotation for total rotation depends on the other 2 centers.  The vertical facial development is strongly related to the rotation of both the jaws.  Average individual-rotation 4-adult life Total rotation: -15.4o Matrix
: -4.1o (27%)
Intramatrix : -11.3o (73%) www.indiandentalacademy.com
37
 Total Rotation- Matrix Rotation =Intramatrix Rotation
 Expression of remodeling at the lower border. www.indiandentalacademy.com
38
Positional and Morphogenetic Rotation.  Introduced by Lavergne and Gasson.
Positional Rotation Describes the position of mandible within the head.
www.indiandentalacademy.com
39
Morphogenetic Rotation Concerns the shape of the mandible. Superimposition done on line through condylion and pogonion. The angle formed between the 2 implant linesdegree of morphogenetic rotation. Similar to Bjork’s intramatrix but not identical. www.indiandentalacademy.com
40
 Bjork considered key factor of intramatrix to be found in a rotation of mandibular corpus inside the matrix.  Lavergne and Gasson – consider the forward and backward growth of the ramus the main mechanism for shortening and elongating the effective length. www.indiandentalacademy.com
41
 Sagittal discrepancies-minimized by opening and closing the mandible.
www.indiandentalacademy.com
42
“It is a compensating mechanism which is capable of enlarging or reducing mandibular length as measured along the condylion-pogonion diagonal”
www.indiandentalacademy.com
43
www.indiandentalacademy.com
44
The Third Option-Dibbets The first option-Bjork and Skieller’s Intramatrix rotation-rotation of the mandibular core relative to the lower border is the result of genetically determined condylar growth. The second option-Hunterian concept or the Morphogenetic rotation . www.indiandentalacademy.com
45
Bjork’s Approach •SUPERIMPOSITION SUGGESTS A ROTATION.
www.indiandentalacademy.com
46
Superimposed on the implants Change in the inclination of the implant line relative to the mandibular plane. www.indiandentalacademy.com 47
This suggests1.when the mandibles are superimposed on the their contours they are identical in shape and size. 2.The condyle grows on a circular arc (c-c’) with radius from the chin to condyle. This concludes1.The external configuration need not change. 2.Any depositional-resorptive activity maintains the original contours. www.indiandentalacademy.com
48
The painting may be rotated within the frame but the external outline, configuration and dimensionality, of the frame is not lost. www.indiandentalacademy.com
49
‘Every deflection of condylar growth direction creates the possibility of compensatory remodeling mostly of the lower border resulting in intramatrix rotation’.
Actual effect of growth of the condylar cartilage is neutralized to a given extent.
www.indiandentalacademy.com
50
 The second option-The Hunterian concept or principle of Morphogenetic rotation. Superimposition based on traditional Hunterian conception of Posterior ramal deposition and Anterior ramal resorption. Enlarging and reducing the mandibular length measured along the Co-Pog line. www.indiandentalacademy.com
51
 The third option-Based on 2 divergent patterns of mandibular growth. 1.Intramatrix rotation with absence of enlargement. 2.Linear condylar growth-evidencing mandibular enlargement. Suggested mechanism -
COUNTERBALANCING ROTATION www.indiandentalacademy.com
52
COUNTERBALANCING ROTATION“It pertains to the circular condylar growth, accompanied by selective co-ordinated remodeling , which does not contribute to the incremental growth of the mandible�. 1.The actual path of the condyle relative to fixed and stable points inside the mandible is accompanied by selective remodeling-neutralizes growth. 2.Resuts in selective enlargement of the mandible, apart and distinct from mechanisms that have been described in literature. www.indiandentalacademy.com
53
Counterbalancing Proportion
It is the quotient between mandibular and condylar incremental growth and is expressed as a percentage. Condylar growth and mandibular growth are weighted in relation to one another. The proportion gives a percentage of condylar relocation that has contributed to actual mandibular enlargement. www.indiandentalacademy.com
54
 Mandibular growth= Pg-Ar1-PgAr2
 Condylar growth=distance from Ar1 to Ar2. Counterbalancing proportion= Growth from Ar-Pg x 100% Condylar incremental growth www.indiandentalacademy.com
55
According to the concept of congruous mandibular growth the proportion should be 100%. But study done by Dibbets shows that it ranges from 50% to 90%. This percentage strongly correlates type of malocclusion. Class III-85% Class I -76% Class II-59% www.indiandentalacademy.com
56
Concepts of Mandibular rotations
What causes mandibular rotation ?
www.indiandentalacademy.com
57
Enlow’s concept.  The ramus has a sequence of remodeling changes to provide for 4 basic functions. 1. Elongation of the corpus. 2. Accommodates for horizontal growth of middle cranial fossa and pharynx. 3. Accommodates for vertical growth of nasomaxillary complex. 4. To position the mandibular corpus in proper position to maxillary corpus. www.indiandentalacademy.com
58
The ramus provides intrinsic capacity for adaptation . If its adequate then class I occlusion results.
MANDIBULAR ROTATIONS
Displacement
Remodeling www.indiandentalacademy.com
59
Displacement  Changes in the junctional contact with the cranial floor and maxilla.  Cranial base angleOpen-downward and backward rotation of mandible. Closed-forward rotation.
www.indiandentalacademy.com
60
www.indiandentalacademy.com
61
Closed angle
www.indiandentalacademy.com
Open angle
62
Short nasomaxillary complex-forward rotations
www.indiandentalacademy.com
63
Long nasomaxillary complex – backwad rotations
www.indiandentalacademy.com
64
Remodeling
www.indiandentalacademy.com
65
 Mandible has to remodel to1.Produce a more upright ramus. 2.To accommodate for displacement rotations.
www.indiandentalacademy.com
66
 Opening and closing of the gonial angle compensates for extreme forward or backward rotation.
www.indiandentalacademy.com
67
Ramal remodeling Ramus moves posteriorly-increasing the length of the corpus. Grows horizontally to match the growth of the pharyngeal space. Ceases when growth stops www.indiandentalacademy.com
68
 2nd type of remodeling.  Makes ramus more upright but does not increase the horizontal dimension.
www.indiandentalacademy.com
69
Schudy’s concept Variation in the growth at the condyles and the molar area is responsible for the rotation of the corpus of the mandible. Clockwise rotation-More posterior vertical growth than condylar growth. Counterclockwise-More condylar growth than the combined vertical growth. www.indiandentalacademy.com
70
www.indiandentalacademy.com
71
Vertical ‘elements’ of growth Growth at the condyles = I- AP growth of nasion. II- Vertical growth of corpus of maxilla. III-Vertical growth of maxillary alveolar process. IV-Vertical growth of mandibular alveolar process. www.indiandentalacademy.com
72
Posterior growth analysis  Ratio between the vertical and horizontal growth.  A=I+II+III+IV
www.indiandentalacademy.com
73
Bjork’s concept Implant studies show-growth of the mandible occurs essentially at the condyles. The anterior aspect of the chin-stable. Lower border of the mandibleAt the symphysis-apposition. At the angle -resorption. The appositional and resorptive areas may change-determining the type of growth. www.indiandentalacademy.com
74
The growth of the condyle occurs in a upward and forward curving manner. The center of rotation may be located-posteriorly or anteriorly or somewhere in between. The center may not always lie at the TMJ.
www.indiandentalacademy.com
75
www.indiandentalacademy.com
76
FORWARD ROTATION THREE TYPES: TYPE I -center at the TMJ.
-underdeveloped anterior face height. -deep bite. Cause: occlusalwww.indiandentalacademy.com imbalance or powerful musculature.
77
www.indiandentalacademy.com
78
ď ś Type II -center at the incisal edges of the lower teeth. - marked increase in posterior face height and normal anterior face height.
Increase in posterior face height
Lowering of the middle cranial fossa.
Increased height of ramus
www.indiandentalacademy.com
79
Increase in ramus height maybe due to vertical growth of the condyle. But this vertical lowering manifestes as forward rotation –muscular and ligamentous attachments. Eruption of the molars keep pace with the www.indiandentalacademy.com rotation.
80
www.indiandentalacademy.com
81
ď śType III -center of rotation is at the premolars. -deep bite occurs. cause: Anomalous occlusion-large overjets. www.indiandentalacademy.com
82
www.indiandentalacademy.com
83
The inclination of teeth influenced by jaw rotations. Path of eruption of teeth-mesial. Crowding occurs in the anterior segment‘PACKING’
www.indiandentalacademy.com
84
BACKWARD ROTATION  TWO TYPES: ď ś Type I -center at the TMJ. -underdevelopment of the posterior face height occurs-open bite. causes: 1.middle cranial fossa is raised. 2.orthodontic bite raising appliance. www.indiandentalacademy.com 3.oxycephaly.
85
www.indiandentalacademy.com
86
ď śTYPE II -center at distal most occluding molars. Cause: sagittal (backward ) growth of the condyle. -The mandible is carried forward but due to muscle and ligaments attachments its rotated backwards.
www.indiandentalacademy.com
87
- the eruption of lower molars was hindered-the rotation not due to overeruption.
-seen in condylar hypoplasia.
www.indiandentalacademy.com
88
www.indiandentalacademy.com
89
www.indiandentalacademy.com
90
Thank you www.indiandentalacademy.com Leader in continuing dental education
www.indiandentalacademy.com
91