Cranial base angle in relation to malocclusion. for orthodontics

1. CRANIAL BASE ANGLE IN
RELATION TO MALOCCLUSION
Dr Muhammad Nawaz
Orthodontics department SPH/BMC Quetta.
Email.
Muhammadnawaz_panezai@yahoo.com

2. CONTENTS
• ANATOMY OF CRANIAL BASE.
• THE FUNCTION CRANIAL BASE
• GROWTH OF CRANIAL BASE .
• SYNCHONDROSES.
• SPHENO-OCCIPITAL SYNCHONDROSIS
• CRANIAL BASE ANGLE
• INCREASE IN CRANIAL BASE LENGTH
• DECREASE IN CRANIAL BASE LENGTH
• HEADFORM AND MALOCCLUSION TENDENCIES
• REFERENCE OF CRANIAL BASE ANGLE
• SUMMARY

3. Anatomy of cranial base
Figure 7.7a
Hypophyseal fossa
of sella turcica
Middle cranial
fossa
Temporal bone
(petrous part)
Posterior
cranial fossa
Parietal bone
Occipital bone
Foramen magnum
(a) Superior view of the skull, calvaria removed
Frontal bone
Olfactory foramina
Optic canal
Foramen rotundum
Foramen ovale
Foramen spinosum
Jugular foramen
Hypoglossal canal
Foramen lacerum
Internal acoustic
meatus
Cribriform plateEthmoid
bone Crista galli
Sphenoid
Anterior cranial fossa
Lesser wing
Greater wing
View

4. CRANIAL FOSSA

5. THE FUNCTION CRANIAL BASE
(i) Lodges all the lobes of cerebrum;
(ii) Bears the weight of the rapidly expanding brain;
(iii) Provides a passage way for all the cranial nerves
exiting and blood vessels entering the brain;
(iv) Provides a thrust(template) for the anterior
growth of the facial skeleton.
(vault, common function is the protection of brain.)

6. GROWTH OF CRANIAL BASE
1.Cranial base(basicranium) or floor is formed by
endochondral ossification.
2. In the prenatal life, cranial base is a large
irregular piece of cartilage. it is divided into
anterior, middle and posterior cranial fossae by
bony elevations.

7. CRANIAL BASE GROWTH MAY BE
ATTRIBUTED
following causes, namely:
(i) Displacement of bone due to expanding
lobes of brain and growth at synchondroses;
(ii) Secondary fill-in ossification
of the sutures (playing a minor role);
(iii) Cortical remodeling.

10. • synchondroses are concentrated at the
midline axis. only ANTEROPOSTERIOR growth
in the midline of cranial base is contributed by
synchondrosis.
• The LATERAL EXPANSION is mostly due to the
expansion of lobes of the brain.

11. • Summarizing the growth of cranial base, increase in
size of the cranial base is due to primary displacement
of bones due to growth of functional matrix, i.e. lobes
of brain and linear displacement caused by growth at
synchondroses mainly sphenoccipital.
• Arterial cranial base growth complete 6 years.(bishara
49page)
• The cartilage modeling is particularly true of the
midline structures. As one moves laterally, growth at
sutures and surface remodeling become more
important.(profit)

12. SYNCHONDROSES
• a cartilaginous joint(hyaline cartilage) is termed a
synchondrosis.
• An example of a synchondrosis joint is the first
sternocostal joint (where the first rib meets the
sternum)
• Cranial base
(midline) etc

13. SYNCHONDROSES
• Cranial base(midline)
1.fronto-ethmoidal
synchondrosis
2. spheno-frontal
synchondrosis
3.spheno-ethmoidal
synchondrosis.(3-5yrs)
4.intersphenoid
synchondrosis
(birth fused)
5. spheno-occipital
synchondrosis(12-15yr)
(principle growth
cartilage of basicranium)

14. SYNCHONDROSES
• Middle part cranial base
• Growth centre
• Bipolar growth cartilage
• Face maker of cranial base

15. SPHENO-OCCIPITAL SYNCHONDROSIS

16. SPHENO-OCCIPITAL SYNCHONDROSIS
1.Major contribution in post natal growth
2.Fused at (girls 12-13yrs)
(boys 14-15yrs)
(12-15yrs)
3.Ossified at 20yrs
4. Pressure adapted growth mechanism

17. SPHENO-OCCIPITAL SYNCHONDROSIS
• The spheno-occipital
synchondrosis is anterior
to the temporomandibular
joints but posterior to
the anterior cranial fossa
and therefore its growth is
significant clinically as it
influences the overall
facial skeletal pattern

18. (i) Low cranial base angle associated with Class III skeletal pattern. View (ii)
Large cranial base angle associated with a Class II skeletal pattern.

19. • In the same way, the overall shape of the
cranial base affects the jaw relationship, with
a smaller cranial base angle tending to cause a
Class III skeletal pattern, and a larger cranial
base angle being more likely to be associated
with a Class II skeletal pattern .

20. CRANIAL BASE ANGLE
1.Anterior cranial
base(S-N)
2.Posterior cranial
base(S-Ba)
(S-Ar)
3. N-S-Ba
4. N-S-Ar

21. CRANIAL BASE ANGLE
• The anterior cranial base relates to the
position of the maxilla,
• where as the posterior cranial base relates to
the positions of the glenoid fossa and the
mandible
• A small cranial-base angle (NSBa) and a short
cranial-base length (S-N) are major
morphologic features of skeletal Class III
patients.

22. CRANIAL BASE ANGLE
• Clinical Norm:
• 129° +/- 4° acc. to the Zurich-Analysis
• 130° +/- 6° acc. to the University of Ulm,
Hasund and Schmuth

23. CRANIAL BASE ANGLE
• Age 4years 20 years
• male 132.2° +/- 5.9° 129.4° +/- 5.4°
• female 132.9° +/- 4.9° 131.7° +/- 4.2°

24. INCREASE IN CRANIAL BASE LENGTH
• The influence of cranial base length on the
relationship between the maxilla and mandible. With
an increase in cranial base length, there is a tendency
towards a skeletal II pattern

25. DECREASE IN CRANIAL BASE LENGTH
• The influence of cranial base angle on the skeletal
relationship. With an increase in cranial base angle, there is a
tendency towards a skeletal II pattern. When the angle
reduces, the skeletal pattern is likely to tend towards a Class
III relationship.

26. REFERENCE OF CRANIAL BASE ANGLE
• most studies show that individuals with larger
cranial base angles and/or larger anterior and
posterior cranial base lengths tend to be
retrognathic (i.e., Class II),
• whereas those with the smaller lengths and
angles tend to be prognathic (i.e., Class III).
(Graber 5ed page 240)

27. REFERENCE OF CRANIAL BASE ANGLE
• Class II: Maxillary Prognathism.This relationship may be because the
maxilla itself is forward or may result from a
long anterior cranial base. Also, the crania
l base angle may be flat, creating a
downward and forward position
of the nasomaxillary complex.
This in turn may rotate the mandible
down and back
(Proportional Facial Analysis
Graber 5ed page 430)

28. REFERENCE OF CRANIAL BASE ANGLE
• High Angle (Hyperdivergent).large cranial base angle (which is
responsible for a downward
and forward position of the
nasomaxillary complex),
and a downward and
backward position of the
mandible.
(Proportional Facial
Analysis
Graber 5ed page 434)

29. REFERENCE OF CRANIAL BASE ANGLE
• Low Angle (Hypodivergent) A small cranial base angle is
responsible for an upward and backward position of the
nasomaxillary complex and an upward and forward position
of the mandible(Proportional Facial Analysis Graber 5ed page
435)

30. HEADFORM AND MALOCCLUSION
TENDENCIES
• DOLICHOCEPHALIC headform, the brain is
horizontally long and relatively narrow
• basicranium that is somewhat more flat
• whole nasomaxillary complex is placed in a
more protrusive position relative to the
mandible because of the forward basicranial
rotation.

31. DOLICHOCEPHALIC headform

32. DOLICHOCEPHALIC headform
• The two-way forward placement of the maxilla and backward
placement of the mandibular corpus results in a tendency
toward mandibular retrusion, and the placement of the
molars results in a Class II position
• The resultant profile is
retrognathic .open
cranial base angle

33. DOLICHOCEPHALIC

34. BRACHYCEPHALIC headform
• BRACHYCEPHALIC headform have a rounder,
wider brain. The facial result is a more
posterior placement of the maxilla.
• horizontal length of the nasomaxillary
complex is also relatively short.
• brachycephalized basicranium is wider but less
elongate in the anteroposterior dimension,
the middle and anterior cranial fossae.

35. brachycephalic
• The composite result is a relative retrusion of the
nasomaxillary complex and a more forward relat ive
placement of the entire mandible. This causes a greater
tendency toward a prognathic profile and a Class III molar
relationship.

36. brachycephalic

37. How does a face undergo intrinsic
compensations
• In the situation, the mandible was placed in a retrusive (retrognathic)
position owning to its downward and backward rotation resulting from the
more open type of cranial base flexure (and/or a vertically long
nasomaxillary complex).
• The mandibular ramus,
however, can compensate
by an increase in its
horizontal dimension

38. GROWTH PATTERN OF
CLASS II MALOCCLUSIONS
• Enlow et al (1971) and Enlow and McNamara (1973)
stated that the cranial floor is the foundation on which
the human face develops and demonstrated that the
dimensions of the middle cranial fossa considerably
influences the relationship between the nasomaxillary
complex and the mandible.
• According to them A more open cranial base flexure
during growth often occur in dolichocephalic faces, in
which the midface is positioned more anteriorly, the
mandible is rotated downward and backward often
resulting in class II malocclusion

39. GROWTH PATTERN OF
CLASS II MALOCCLUSIONS
• Andreson and Popovich (1989) have also
noted that in class II children, the jaws,
especially the mandible, had a more posterior
position under the cranium, and there was a
more open flexure of the cranial base and
shorter lower cranial height.

40. GROWTH PATTERN OF
CLASS III MALOCCLUSIONS
• Stapf (1948) subdivided class III deformities into typical
type (exhibiting mandibular overgrowth) and atypical
type (exhibiting a diminutive maxilla).
• Ellis and McNamara (1984) stated
1. retrusive maxilla with prognathic mandible most
common skeletal relationship accounting for 30 % of all
class III cases.
2. Maxillary retrusion with normal mandibular
prominence was found in 19.5 % of the individuals .
3. normal maxilla with mandibular protrusion was
found in 19.1 percent of the individuals.

41. Reference of Cranial base angle

42. Reference of Cranial base angle

43. Reference of Cranial base angle
Increased length in the anterior cranial base
contributes to midface protrusion, whereas
increased obtusity of the cranial base angle or
lengthening of the posterior cranial base will
tend to position the temporomandibular
articulation more retrusively;

44. Reference of Cranial base angle
• Mandibular Prognathism.-Patients with
mandibular prognathism show a Class III
maxillo-mandibular relationship, an excessive
cranial base-mandible dimension both
horizontally and vertically, and may show a
diminished cranial base angle.

45. Reference of Cranial base angle
• true mandibular prognathism, is brought
about by either a large mandible or an acute
cranial base angle with an anterior positioning
of the glenoid fossa with protrusion of the
mandible beyond a normal maxillary arch.

46. Reference of Cranial base angle
• Increase(obtuse) cranial base angle -
mandibular retrognathia
• Decrease(acute) cranial base angle - forwards
position of mand
• longer cranial base -prognathic max
(Hopkins et al., 1968)

47. Cranial-base morphology in adults
with skeletal Class III malocclusion
• Cranial-base morphology in adults with a skeletal
Class III malocclusion is different from that in a
skeletal Class I malocclusion. Smaller cranial-base
angles (NSBa and SeSBa), steeper posterior
cranial bases (FH-SBa), more inferiorly positioned
sphenoidale(Se), and more anteriorly positioned
basion(Ba) are major characteristics of skeletal
Class III malocclusions. These characteristics play
important roles in the establishment of a skeletal
Class III malocclusion. (Am J Orthod Dentofacial
Orthop 2014;146:82-91)

48. Anterior cranial-base time-related
changes: A systematic review
• CONCLUSIONS
1. A consistent agreement was identified that the anterior cranial base
as a whole is not a stable structure.Different areas of this structure
complete growth at different stages of life.
2. The cribriform plate was found to be the first structure in the
anterior cranial base to complete growth (by age 4), followed by the
presphenoid region(by age7),making them the best cranial-base
superimposition areas.
3. Sella turcica remodels and moves backward and downward during
growth. Bone apposition in the frontal region and the increase in the
size of the frontal sinus (both affecting nasion) contribute to the
increase in the length of the anterior cranial base (delineated by the
sella-nasion distance) until adulthood.
(Am J Orthod Dentofacial Orthop 2014;146:21-32)

49. summary
• Cranial base Angle .
1.increase(obtuse) class II
2. decrease(acute) class III
• Length
1. anterial cranial base increase class II
2. posterial cranial base increase
1. angle increase = class II
2. angle decrease = class III

50. • Thank you