2. RAMUS
The significance of the ramus of the mandible is
mostly that it provides an attachment base for
masticatory muscles.
Key role of ramus in placing the corpus and dental
arch into ever-changing fit with growing maxilla and
face limitless structural variation
special developmental significance of the ramus is a
highlight of craniofacial growth.
s not the bony ramus itself that does the job, but
rather its osteogenic, chondrogenic, and fibrogenic
connective tissues
3. Every area and surface throughout the entire
mandible participates directly in its remodeling
process.
The mandibular remodeling description one of the
most important structural parts, the ramus. It is
important because
(1) it positions the lower arch in occlusion with the
upper
(2) it is continuously adaptive to the multitude of
changing craniofacial conditions.
4. The principal vectors of mandibular "growth" are
posterior and superior.
The ramus is thereby remodeled in a generally
posterosuperior manner while the mandible as a
whole becomes displaced anteriorly and inferiorly.
This allows posterior lengthening of the corpus and
dental arch.
5. Summary diagram of the growth of the mandible.
Growth directions involving periosteal resorption are
indicated by arrows pointing into the bone surface,
and growth directions involving periosteal deposition
are represented by arrows pointing out of the bone
surface.
6.
7. The posterior development of the mandibular bony
arch simultaneously proceeds into the region that
was previously occupied by the ramus. This requires
a remodeling conversion from what used to be
ramus into what then becomes mandibular corpus.
That is,.the whole ramus becomes relocated
posteriorly by resorptive and depository remodeling,
and the former anterior part of the ramus is
structurally altered into an addition to the corpus,
which thereby becomes lengthened by this
remodeling process. The remodeling movement of
the ramus in a backward direction.
8. LINGUAL TUBEROSITY
This is an important structure because it is the direct
anatomic equivalent of the maxillary tuberosity
9. .the lingual tuberosity a major site of growth for the
mandible.
.also the effective boundary between the two basic
parts of the mandible: the ramus and the corpus.
The lingual tuberosity grows posteriorly by deposits
on its posteriorfacing surface,
the lingual tuberosity protrudes noticeably in a
lingual (medial) direction, and that it lies well toward
the midline from the ramus.
The prominence of the tuberosity is augmented by
the presence of a large resorptive field just below it
called lingual fossa.
10. The combination of
periosteal resorption in
the fossa and deposition
on the medial-facing
surface of the tuberosity
itself greatly accentuates
the contours of both
regions
11. The tuberosity remodels (relocates) in an almost
directly posterior direction, with only a relatively slight
lateral shift.
12. The posterior growth of the tuberosity is
accomplished by continued new deposits of bone on
its posterior-facing exposure. As this takes place,
that part of the ramus just behind the tuberosity
remodels medially
13. THE RAMUS-TO-CORPUS REMODELLING
CONVERSION
the whole ramus is also becoming relocated in a
posterior direction at the same time.
arch length has been increased and the corpus has
been lengthened by
(1) deposits on the posterior surface of the lingual
tuberosity and the contiguous lingual side of the ramus
and
(2) a resultant lingual shift of the anterior part of the
ramus to become added to the corpus.
14. relocation continues from the
tiny mandible of the fetus to
the attainment of full adult
mandibular size.
posterior ramus movement
implies a straight line
backward growth process in a
two dimensional plane, as
represented by a and b in
Figure 4-5.
picture of ramus growth
shows, simply, resorption on
the anterior edge and
deposition on the posterior
edge.
15. In d, the growth direction thus follows the x arrows,
rather than the straightline axis shown by the y
arrows.
16. Do YOU THINK THE
Remodeling activity does occur
only on the anterior and
posterior margins of the
ramus?????????
17. The coronoid process
has a propeller-like twist,
so that its lingual side
faces three general
directions all at once:
posteriorly, superiorly, and
medially.
When bone is added onto
the lingual side of the
coronoid process, its
growth proceeds
superiorly part of the
ramus thereby becomes
increased in vertical
dimension(4-6)
18. coronoid process lengthens vertically, even though
additions are made on the medial (lingual) surfaces
same deposits of bone on the lingual side also bring
about a posterior direction of growth movement
These same deposits of bone on the lingual side
also function to carry the base of the coronoid
process and the anterior part of the ramus in a
medial direction in order to add this part to the
lengthening corpus, which lies well medial to the
coronoid process.
19. in 1 is relocated and
its former location
becomes remodeled
into the posterior part
of the corpus in 2.
20. the buccal side of the coronoid process has a
resorptive type of periosteal surface.
The superior part of the ramus, including the whole
area just below the mandibular (sigmoid) notch and
the superior (not lateral or medial) portion of the
condylar neck, grows superiorly by deposition on the
lingual side and resorption from the buccal side.
21. The lower part of the
ramus below the
coronoid process also
has a twisted contour.
Its buccal side faces
posteriorly toward the
direction of backward
growth and thus, has a
depository type of
surface (Fig. 4-8).
The opposite lingual
side, facing away from
the direction of growth,
is resorptive.
22. also resorptive field on the
ventral edge of the ramus,
as illustrated by Figure 4-
15.
23. A single field of surface resorption is present on the
inferior edge of the mandible at the ramus-corpus
junction. This forms the antegonial notch by remodeling
from the ramus just behind it as the ramus relocates
posteriorly (Fig. 4-9).
24. The condyle generally has an obliquely upward and
backward growth direction.
Ramus development often involves a remodeling rotation
of the whole ramus, and a resorptive field then occurs on
the posterior margin below the condyle, as illustrated by
Figures 4-13 and J.... 4-15.
25. mandibular foramen likewise relocates backward
and upward by deposition on the anterior and
resorption from the posterior part of its rim.
26. The Mandibular Condyle
it is a major site of growth, having considerable
clinical significance.
An endochondral growth mechanism is required for
this part of the mandible because the condyle grows
in a direction toward its articulation into the face of
direct pressure.
27. Endochondral growth occurs only at the articular
contact part of the condyle, because thIS IS where
pressure exists at levels that would be beyond the
tolerance of the bone's vascular soft tissue
membrane.
28. As seen in Figure 4-10B, the endochondral bone tissue
(b) formed in association with the condylar cartilage (a )
is laid down only in the medullary portion of the condyle.
The enclosing bony cortices (c) are produced. by
periosteal-endosteal osteogenic activity.
29. The condylar question
What happen for mandibular function if it was
totally lacking condyles exist in nature?
normal anatomic position; the bony arch is properly
placed for occlusion, and the mandible functions
(albeit with distress) in masticatory movements even
though it lacks an articulation.
30. It is believed that increased amounts of pressure on
the cartilage serve to inhibit the rate of cell division
and proliferation. Decreased amounts of pressure
appear to stimulate and accelerate growth.
Presumably, forces applied to the mandible in such a
way that they increase the level of pressure on the
condyle would result in a shorter mandible if this
were done during the period of active condylar
growth. Similarly, a release of some of the
compressive force acting on the condylar cartilage
would produce a larger mandible if done during the
active growth period.
