brief notes about alveolar bone related to periodontics

1. Alveolar bone
By,
M.J.Renganath
M.D.S 1st year
Department of Periodontics

2. CONTENTS
 Introduction
 Development and Anatomy
 Histologic features
 Radiographic features
 Pathologies involving loss of Alveolar bone
 Alveolar bone & implants
 Repair and regeneration
 Conclusion
 References

3. Introduction
 The term periodontium describes tissues which:
1. Anchor the teeth to the bones of the jaws
2. Provide interdental linkage of the teeth within the dental arch
3. Facilitate epithelial lining of the oral cavity in the region of the erupted tooth.
 The developmental, biological and functional unit of periodontium:
1. Gingiva
2. Root cementum
3. Periodontal ligament
4. Alveolar bone proper

4. Alveolar bone
 Alveolar bone is defined as the parts of maxilla and mandible that form
and support the socket of teeth.
CLINICAL PERIODONTOLOGY AND IMPLANT DENTISTRY- Jan Lindhe pg:34
 Together with the root cementum and periodontal ligament, the alveolar
bone constitutes the attachment apparatus of the teeth.
 Forms when tooth erupts to provide osseous attachment to the forming
PDL, disappears gradually after tooth is lost.
 Develops and undergo remodeling with tooth formation, hence tooth-
dependent bony structures.
 Size, shape, location and function of teeth determine their morphology.

5. Alveolar bone

6. Development
 Formed during fetal growth by intramembranous ossification and consists of
a calcified matrix with osteocytes enclosed within spaces called lacunae.
 During embryogenesis, the skeleton forms by either a direct or indirect
ossification process.
 In the case of the mandible and the maxilla, mesenchymal progenitor cells
condensate and undergo direct differentiation into osteoblasts, a process
known as intramembranous osteogenesis.
 Alveolar bone lost as a result of an injury, disease, or trauma undergoes a
repair process that is essentially a combination of endochondral and
intramembranous complementary osteogenic processes (Rabie et al., 1996;
Virolainen et al., 1995).
 A similar process occurs in most of the bone-related implant site
development techniques, where osteoconduction, osteoinduction, and
osteogenesis are exploited.

7. Anatomy
 Alveolar process consists of:
1. External plate of cortical bone
2. Inner socket wall- Alveolar bone proper
3. Cancellous trabeculae- Supporting alveolar bone

8. Alveolar process

9. Cortical bone and cancellous bone

10. Trabeculae
 2 main types
Type1:
 The interdental and interradicular trabeculae are regular & horizontal in a
ladder like arrangement.
 This type is seen most often in mandible.
Type 2:
 Shows irregularly arranged, numerous, delicate interdental and
interradicular trabeculae.
 This type is more common in maxilla.

11. Trabecular pattern of alveolar bone

12. Haversian system
 Consists of the haversian canal and the Volkmann’s canal.
 Haversian canal located in the center of the osteon.
 Volkmann’s canal are the connecting vessels which connect the Haversian
canal.
 They provides nutrition to the bone.

13. Haversian canal

14. Histologic features
 Three types of cells are distinguished:
1. Osteoblasts
2. Osteocytes
3. Osteoclasts
Osteoblasts:
 Produce the organic matrix of bone are differentiated from pluripotent
follicle cells.
 Comprise a mixed population of preodontoblasts with large nuclei and
fibroblast like cells with small nuclei

15. Osteocytes:
 Arise from odontoblasts which becomes entrapped into bone.
 Located in bony lacunae and are connected by long cell projections.
 Immature osteocytes are smaller than osteoblasts, but have a similar
structure.
 Mature osteocytes have a reduced set of organelles.
Osteoclasts:
 Large, multinucleated giant cells, located on the surface pits of the
bone(Howship’s lacunae).
 Arise by fusion of hematopoietic, mononuclear precursors of bone marrow.
 Resorption of bone is facilitated by acidic phosphatases and other
hydrolytic enzymes.

16. Osteoblasts and osteoclasts
 The combined process of bone formation and resorption by simultaneous
activity of osteoblasts and osteoclasts is called as coupling.

17. Formation of osteoclasts

18. Resorption activity

19. Intercellular matrix
 Bone consists of 2/3rd inorganic matter and 1/3rd organic matrix.
Inorganic matter:
 Calcium
 Phosphate
 Hydroxyl
 Carbonate
 Citrate
 Trace amounts of sodium, magnesium and fluorine.

20. Organic matrix:
 Type 1 collagen- 90%
 Noncollagenous proteins such as :
• Osteocalcin
• Osteonectin
• Bone morphogenetic protein
• Phosphoproteins
• proteoglycans

21. Bone morphogenic protein
 These are well studied group of growth factors belongs to the transforming
growth factor(TGF-β) subfamily, involved in the process of bone healing.
 BMP induces the formation of both bone and cartilage by stimulating the
cellular events of mesenchymal progenitor cells.
 However, only a subset of BMPs, most notably BMP 2,4,6,7,9 has
osteoinductive activity.

22. Guided bone regeneration
 Guided Bone Regeneration (GBR) was originally developed by Hurley et al.
in 1959 and Boyne in 1964.
 Barrier membranes are used, which are bio-inert materials that serve to
protect the blood clot and prevent soft tissue cells (epithelium and
connective tissue) from migrating into the bone defect, allowing
osteogenic cells to be established.
 Barrier membranes could be either resorbable or non resorbable.
 Osteoblasts derived from the periosteum and bone are selectively induced
on the osseous defect area, facilitating new bone formation.

23.  GBR using a barrier membrane has become widely used for bone
regeneration of osseous dehiscences and fenestrations and for localized
ridge augmentation and immediate implant placement.
 GBR in implant therapy is especially useful for fixture placement with dehis-
cence defects or fenestration defects.
 In alveolar ridges with marked facial/buc- cal depressions or in knife-edge
alveolar crests, the position and direction of fix- ture placement is restricted.
 Improvement of alveolar ridge morphology becomes possible, however,
with GBR.

24. Radiographic features
 The interdental bone normally is outlined by a thin, radiopaque line
adjacent to the periodontal ligament (PDL) and at the alveolar crest,
referred to as the lamina dura.
 Because the lamina dura represents the cortical bone lining the tooth
socket, the shape and position of the root and changes in the angulation
of the x-ray beam produce considerable variations in its appearance.

25. Radiographic features
Lamina dura

26. conditions involving loss of Alveolar
bone
 The various causes of alveolar bone loss are:
I. Extension of gingival inflammation
II. Trauma from occlusion
III. Systemic factors
IV. Orthodontic treatment
V. Periodontitis
VI. Periodontal abscess
VII. Food impaction
VIII. Overhanging restoration
IX. Adjacent tooth extraction
X. Ill-fitting prosthesis

27. Extension of gingival inflammation
 Most common cause of bone loss in periodontal disease is extension of
inflammation from marginal gingiva into supporting periodontal tissues.
 Inflammatory invasion of bone surface and intial bone loss that follows mark
the transition from gingivitis to periodontitis.
 the transition from gingivitis to periodontitis is associated with changes in
compostion of bacterial plaque.
 In advanced stages number of motile organisms and spirochetes increases.

28. Mechanism of bone destruction
 Factors involved are bacterial and host mediated
 Bacterial plaque induces bone progenitor cells into osteoclasts
 In aggressive periodontitis, bacterial micro colonies have been found
between collagen fibers and over the bone surface, suggesting a direct
effect.
 Host factors released by inflammatory cells are capable of inducing bone
resorption.
 These include host produce prostaglandins, IL-1a IL- β and TNF-a.

29. Pathways of inflammation

30.  Extends along the collagen fiber bundles and follows the course of blood
vessels through loosely arranged tissues around them into the alveolar bone
 Interproximally, inflammation spreads to the loose connective tissue around
the blood vessel channels that perforate the crest of the interdental
septum at the center of the crest, towards the side of the crest or at the
angle of the septum.
 Also, inflammation may enter the bone through more than one channel.
 Spread of inflammation from gingiva directly to PDL is less frequent.

31.  Facially and lingually, inflammation from the gingiva spreads along the
outer periosteal surface of the bone and penetrates into the marrow
spaces through vessel channels in the outer cortex.
 It courses from gingiva to the bone, inflammation destroys the gingival and
transeptal fibers, reducing them to disorganized granular fragments
interspersed among the inflammatory cells and edema.

32. Trauma from occlusion
 Trauma from occlusion can produce bone destruction either in the absence or
presence of inflammation.
 These changes are reversible in that they can be repaired if the offending
forces are removed.
 However, persistent trauma from occlusion results in funnel shaped widening of
the crestal portion of the periodontal ligament, with resorption of the adjacent
bone.
 These changes, cause the bony crest to have an angular shape.
 It represent adaptation of the periodontal tissues aimed at cushioning
increased occlusal forces, but the modified bone shape may weaken tooth
support and cause tooth mobility.
 When combined with inflammation, trauma from occlusion aggravates the
bone destruction caused by the inflammation and causes bizarre bone
patterns.

33. Trauma from occlusion
Occlusal force beyond physiological limits
Increased compression& tension of PDL
Increased osteoclasis
Necrosis of PDL and bone
Resorption of bone and tooth structure

34. Trauma from occlusion

35. Systemic factors
 In recent years, interest has increased in the possible relationship between
periodontal bone loss and osteoporosis.
 Osteoporosis is a physiologic condition of post menopausal women
resulting in loss of bone mineral content and structural bone changes.
 Periodontal bone loss may also occur in generalized skeletal disturbances
by mechanism that may be totally unrelated to usual periodontal
problems.

36. Systemic factors
Diabetes mellitus:
 A majority of well controlled studies show a higher prevalence and severity
of periodontal disease in diabetic patients than in nondiabetic patients
with similar local factors.
 Findings include a greater loss of attachment, increased bleeding on
probing, and increased tooth mobility.
 As with other systemic conditions, diabetes does not cause gingivitis or
periodontitis, but evidence indicates, it alters the response of periodontal
tissues to local factors, hastening bone loss & delays post surgical healing.
 Alteration in collagen metabolism plays a significant role.

37.  Hyperparathyroidism also known as osteitis fibrosa cystica or Von
Recklinghausen’s bone disease, exhibits loss of lamina dura and giant cell
tumors in the jaws.
 Loss of lamina dura may also occur in Paget’s disease, fibrous dysplasia
and osteomalacia.
 Reports have suggested that 25-50% of patients with hyperparathyroidism
have oral changes that includes malocclusion and tooth mobility.
 Radiographic evidence of alveolar osteoporosis with closely meshed
trabeculae, widening of PDL space, absence of lamina dura.

38. Orthodontic treatment
 Bone resorption occurs when there is increased orthodontic forces beyond
the physiological limits.
 Rapid orthodontic movement leads to the insufficient Lag phase period
that tends to resorb the alveolar bone to which the force is directed.
 It is more common in adult patients undergoing orthodontic treatment.
 Whereas in other side, the single angular defect od interdental craters
could be eliminated by the orthodontic movement of the involved teeth.

39.  Orthodontic relapse, apical root resorption, and crestal
alveolar bone levels-Wendy Sharpe et al
 American Journal of Orthodontics and Dentofacial Orthopedics;Volume 91, Issue 3,
Pages 252–258, March 1987
 This investigation examined the relationship of postorthodontic treatment relapse to crestal
alveolar bone support and root resorption.
 The subjects in the relapse group had undergone longer periods of treatment and
exhibited significantly greater crestal alveolar bone level distances, indicating greater loss
of bone support than that observed in the non-relapse group.
 The distances that teeth were translated seemed to affect the extent crestal bone loss
with smaller amounts of tooth translation seemingly more prone to demonstrate tissue loss.

40. Various Bone destructive patterns in
periodontal disease:
 Horizontal bone loss
 Vertical/Angular defects
 Osseous craters
 Bulbous bone contours
 Reversed architecture
 Ledges
 Furcation involvement

41. Horizontal bone loss
 When the bone loss occurs on a plane that is parallel to a line drawn from
the CEJ of a tooth to that of an adjacent tooth, it is called horizontal bone
loss.
 It is one of the common pattern of bone loss in periodontal disease.
 Significant feature of aggressive periodontitis.
 The bone margin remains roughly perpendicular to the tooth surface.

42. Horizontal bone loss

43. Localized Aggressive Periodontitis
 Localized Aggressive Periodontitis Localized aggressive (formerly “localized
juvenile”) periodontitis is characterized by the following:
1. 1. Initially, bone loss in the maxillary and mandibular incisor and/or first
molar areas, usually bilaterally, resulting in vertical, arc like destructive
patterns.
2. 2. As the disease progresses, loss of alveolar bone may become
generalized but remains less pronounced in the premolar areas.

44. Localized Aggressive Periodontitis

45. Vertical bone loss
 Vertical or angular defects occur in an oblique direction, leaving a
hollowed-out trough in the bone alongside the root.
 The base of the defect is located apical to the surrounding bone.
 Resorptive bone patterns may take a vertical or funnel form, resulting in
formation of infrabony defects.
 Vertical bone loss usually consists of one or many infrabony pockets,
because the base of the pocket is usually located apical to the crest of the
surrounding bone.
 Angular defects are classified on the basis of the number of osseous walls

46. Vertical bone loss

47. Bone wall defects
Classified by Goldman and Cohen(1958)
 One walled osseous defects where only one wall is present.
 The one wall vertical defect is called as hemiseptum.
 Two walled osseous defects where two walls are present.
 Three walled osseous defects where three walls are present.
 Interproximal vertical defects can often be detected radiographically,
whereas radicular surface vertical defects are not readily visible.

48. Bone wall defects

49. Interdental osseous craters
 Interdental osseous craters are concavities in the crest of the alveolar septa
centered under the contact point of adjacent teeth.
 As cancellous bone is more vascular and less dense than cortical bone it is
likely that, the central cancellous part of a broad alveolar septum will
resorb more rapidly than the lateral parts made up of cortical bone forming
interdental crater.
 Following are the reasons for the high frequency of interdental craters:
a) The interdental area collects plaque and is difficult to clean.
b) The normal flat or even concave faciolingual shape of the interdental septum in
lower molars may favor crater formation.
c) Vascular patterns from the gingiva to the center of the crest may provide a
pathway for inflammation.

50. Interdental osseous craters

51. Bony exostosis
 Bulbous bone contours are bony enlargements caused by exostoses,
adaptation to function, or buttressing bone formation which are found
frequently in the maxilla than in the mandible.
 Exostosis is a localized harmless idiopathic thickening of bony tissue, whose
cause is unknown.
 Depending on their location in the jaws, they are identified as torus
mandibularis (lingual mandibular plate) or torus palatinus (hard palate).
 A peculiar condition consisting of bone exostosis has been reported to
occur in some patients after undergoing either a skin graft vestibuloplasty
or an autogenous free gingival graft.
 A definitive female sex predilection is characteristic of this condition, which
usually presents in the canine- premolar area of the mandible or maxilla.

52. Bony exostosis

53. Reversed architecture & Ledges
 Reversed architecture forms when the interdental septum resorbs more
rapidly than radicular bone.
 Ledges are plateau-like bone margins caused by resorption of thickened
bony plates.
 Furcation involvement refers to the invasion of the bifurcation and
trifurcation of multirooted teeth by periodontal disease.

54. Reversed architecture
Ledges

55. Furcation involvement

56. Fenestration and dehiscence
 Fenestrations are the isolated areas in which root is denuded of bone and
marginal bone is intact.
 Dehiscences are the denuded areas that extend through the marginal bone.
 Dehiscence and fenestration are both associated with extreme buccal or
lingual version of teeth.
 It occurs in 20% of all teeth. The defects are very important clinically because
where they occur the root is covered only by the periosteum and overlying
gingiva.

57. Fenestration and dehiscence

58. Periodontal abscess
 Periodontal abscesses are classified according to location as follows:
1. Abscess in the supporting periodontal tissues along the lateral aspect of
the root.
2. Abscess in the soft tissue wall of a deep periodontal pocket.
 The former is related to bone resorption around the tooth due to its
progression in size.

59. Periodontal abscess

60. Food impaction
 Interdental bone defects often occur where proximal contact is abnormal
or absent.
 Pressure and irritation from food impaction contribute to the inverted bone
architecture.
 In some cases, the poor proximal relationship may result from a shift in tooth
position because of extensive bone destruction preceding food impaction.
 In such patients, food impaction is a complicating factor rather than the
cause of the bone defect

61. Food impaction

62. Overhanging restoration
 Overhanging restoration either in exaggerated crown margins or in class 2
restorations leads to angular bone loss.
 It is most common in class 2 amalgam restorations with overhanging
margins.
 Bone loss occurs due to impingement of the gingiva, followed by the
inflammatory process that leads to bone loss.

63. Over hanging restoration

64. Adjacent tooth extraction
 Normally, tooth extracted adjacent to a tooth will show significant bone
loss in the extraction site.
 In case of extraction of a periodontally weakened tooth, adjacent tooth
will tend to show severe bone loss of interdental septa.
 More common in delayed extraction of impacted 3rd molar.
 Adjacent tooth tends to tilt towards the extracted site.

65. Extracted adjacent tooth

66. Ill-fitting prosthesis
 Being one of the major factors for periodontal tissue destruction.
 Most common in removable partial denture users.
 Improper seating and design of the prosthesis could irritate the gingiva that
leads to the sequence of periodontal tissues inflammation.
 Long term prosthesis users without periodic evaluation are attributed to this
consequence.

67. pic

68. Alveolar bone in implants
 Osseointegration is basically a union between bone and the implant
surface.
 It is not an absolute phenomenon and can be measured as the proportion
of the total implant surface that is in contact with bone.
 Greater levels of bone contact occur in cortical bone than in cancellous
bone, where marrow spaces are often adjacent to the implant surface.
 Therefore, bone with well-formed cortices and dense trabeculation offer
the greatest potential for high degrees of bone to implant contact.
 The degree of bone contact may increase with time.

69. Repair and regeneration
 Remodelling is the major pathway of bony changes in shape, resistance to
force, repair of wounds.
 The bone resorption with bone formation constitutes the remodelling
throughout the life.
 Bone remodelling involves osteoblasts and osteoclasts which form and
resorb the mineralized connective tissue of the bone.
 Regulation of bone remodelling involves harmones and local factors acting
in an autocrine and the paracrine manner.
 Bone contains 99% of body`s calcium ions, Hence the major source for
calcium release when the calcium blood level decreases, which is
monitored by parathyroid gland.

70. Bone resorption
Decrease in blood calcium
Mediated by receptors on chief cells of parathyroid gland
Release parathyroid hormone(PTH)
Osteoblast stimulation to release il1and il6
Monocytes in bone area
Multinucleated osteoclasts
Resorbs bone

71. Remodelling
 Alveolar bone is least stable of the periodontal tissues because of the
constant state of flux
 Internal remodelling takes place by means of resorption and formation
regulated by local and systemic factors
 Local factors include functional requirements on the tooth and age related
changes in the bone cells
 Systemic factors are hormonal (PTH), calcitonin, vitamin D3
 Remodelling affects its height contour and density and is manifestated in
the following:
1. Adjacent to PDL.
2. In relation to periosteum of facial and lingual plates.
3. Along endosteal surface of marrow spaces.

72. Conclusion
 Alveolar bone is of utmost important for the healthy periodontium.
 Thorough knowledge about pathologies involving alveolar bone enhances
basic methods in treating them.
 Eliminating the bone loss is still being a challenge in treating periodontitis.
 A better understanding of cell and molecular biology of developing and
regenerating alveolar bone offers appropriate idea in treating it for
regeneration.

73. References
 Carranza’s clinical periodontology- 11th edition
 Periodontology The essentials- H.P.MUELLER
 Clinical periodontology and implant dentistry- Jan Lindhe(5th edition)
 Chambers TJ: The cellular basis of bone resorption, Clin Orthop, p283, sep
1980.
 Elliot JR, Bowers GM: Alveolar dehiscence and fenestration, periodontics
1:245, 1963
 Goodson JM et al: the relationship between attachment level loss and
alveolar bone loss, J Clin periodontal 11:348, 1984.