Dentistry periodontics histology

1. Alveolar boneAlveolar bone
• The alveolar process is defined as the parts of the maxilla and the
mandible that form and support the
sockets of the teeth.
• The alveolar process develops in conjunction with the
development and eruption of the teeth.
• The alveolar process consists of bone which is formed both by
cells from the dental follicle (alveolar bone proper) and cells which
are independent of tooth development.
• Together with the root cementum and the periodontal membrane,
the alveolar bone constitutes the attachment apparatus of the
teeth, the main function of which is to distribute and resorb forces
generated by, for example, mastication and other tooth contacts.

2. • the bone which covers the root surfaces is considerably thicker at
the palatal than at the buccal aspect of the jaw. The walls of the
sockets are lined by cortical bone and
the area between the sockets and between the compact
jaw bone walls is occupied by cancellous bone. The
cancellous bone occupies most of the interdental
septa but only a relatively small portion of the buccal
and palatal bone plates. The cancellous bone contains
bone trabeculae, the architecture and size of which are
partly genetically determined and partly the result of
the forces to which the teeth are exposed during function.
• The bone plate is thick at the palatal aspect and on the buccal
aspect of the molars but thin in the buccal anterior region.
• The bone lining the wall of the sockets (alveolar bone proper) is
often continuous with the compact or cortical bone at the lingual
and buccal
• In the incisor and premolar regions, the bone plate at the buccal
aspects of the teeth is considerably thinner than at the lingual
aspect. In the molar region, the bone is thicker at the buccal than
at the lingual surfaces.

3. At the buccal aspect of the jaws, the bone
coverage is sometimes missing at the coronal portion
of the roots, forming a so-called dehiscence (D). If
some bone is present in the most coronal portion of
such an area the defect is called a fenestration (F).

4. Note, for instance, how the presence of the oblique line (linea obliqua)
results in a shelf-like bone process (arrows) at the buccal aspect
of the second and third molars.

5. • Fig. 1-76 shows a section through the periodontal
ligament (PL), tooth (T), and the alveolar bone (AB).
The blood vessels in the periodontal ligament and the
alveolar bone appear black because the blood system
was perfused with ink. The compact bone (alveolar
bone proper) which lines the tooth socket, and in a
radiograph (Fig. 1-57) appears as “lamina dura” (LD),
is perforated by numerous Volkmann’s canals
(arrows)
through which blood vessels, lymphatics, and nerve
fi bers pass from the alveolar bone (AB) to the peri
odontal ligament (PL). This layer of bone into which
the principal fi bers are inserted (Sharpey’s fi bers) is
sometimes called “bundle bone”. From a functional
and structural point of view, this “bundle bone” has
many features in common with the cementum layer
on the root surfaces.
1-76

6. • The bone tissue can be divided into two
compartments: mineralized bone (MB) and bone
marrow (BM). The mineralized bone is made up
of lamellae – lamellar bone– while the bone
marrow contains adipocytes (ad),vascular
structures (v), and undifferentiated mesenchymal
cells
• The mineralized, lamellar bone includes
two types of bone tissue: the bone of the alveolar
process (AB) and the alveolar bone proper (ABP),
which covers the alveolus.

7. • The alveolar bone proper (ABP), on the
other hand, together with the
periodontal ligament (PDL) and the
cementum (C),is responsible for the
attachment between the tooth
and the skeleton.
• AB and ABP may, as a result of altered
functional demands, undergo adaptive
changes

8. • The blood vessel is surrounded by concentric, mineralized
lamellae to form the osteon. The space between the different
osteons is filled with so-called interstitial lamellae. The osteons in
the lamellar bone are not only structural units but also metabolic
units. Thus, the nutrition of the bone is secured by the blood
vessels in the Haversian canals and connecting vessels in the
Volkmann canals.

9. • The alveolar bone proper (ABP)
includes circumferential lamellae and
contains Sharpey’s fibers which
extend into the periodontal ligament.
Three active osteons (brown) with a blood vessel
(red) in the Haversian canal (HC). Interstitial lamella
(green) is located between the osteons (O) and
represents an old and partly remodelled osteon.
The alveolar bone proper (ABP) is presented by the
dark lines into which the Sharpey’s fi bers (SF) insert.

10. Fig. 1-82 illustrates an area of the alveolar bone in
which bone formation occurs. The osteoblasts
(arrows), the bone-forming cells, are producing bone
matrix (osteoid) consisting of collagen fi bers, glyco
proteins, and proteoglycans. The bone matrix or the
osteoid undergoes mineralization by the deposition
of minerals such as calcium and phosphate, which
are subsequently transformed into hydroxyapatite.

11. Fig. 1-83 The drawing illustrates how osteocytes,
present in the mineralized bone, communicate with
osteoblasts on the bone surface through canaliculi.

12. • The resulting canalicular–lacunar
system is essential for cell
metabolism by allowing diffusion of
nutrients and waste products
The surface between the osteocytes
with their cytoplasmic processes on the
one side, and the mineralized matrix on
the other, is very large. It has been
calculated that the interface between
cells and matrix in a cube of bone, 10 ×
10 × 10 cm, amounts to approximately
250 m2.
This enormous surface of exchange
serves as a regulator

14. • The resorption of bone is always associated with
osteoclasts (Ocl) These cells are giant cells specialized
in the breakdown of mineralized matrix (bone, dentin,
cementum) and are probably developed from blood
monocytes. The resorption occurs by the release of acid
substances (lactic acid, etc.) which form an
acidic environment in which the mineral salts of the
bone tissue become dissolved. Remaining organic
substances are eliminated by enzymes and osteoclastic
phagocytosis. Actively resorbing osteoclasts adhere
to the bone surface and produce lacunar pits called
Howship’s lacunae (dotted line). They are mobile and
capable of migrating over the bone surface. The
photomicrograph demonstrates osteoclastic activity at
the surface of alveolar bone (AB).
active remodeling contains bone multicellular unit (BMU)

15. Collagen fibers of the periodontal ligament (PL) insert in the
mineralized bone which lines the wall of the tooth socket. This
bone, called alveolar bone proper or bundle bone (BB), has a high
turnover rate.
the portions of the collagen fibers which are inserted inside the
bundle bone are called Sharpey’s fibers (SF). These fibers are
mineralized at their periphery, but often have a non-mineralized
central core.
The collagen fiber bundles inserting in the bundle bone
generally have a larger diameter and are less numerous than the
corresponding fiber bundles in the cementum on the opposite side
of the periodontal ligament.
Individual bundles of fibers can be followed all the way from the
alveolar bone to the cementum. However, despite being in the
same bundle of fibers, the collagen adjacent to the bone is
always less mature than that adjacent to the cementum.
The collagen on the tooth side has a low turnover rate. Thus,
while the collagen adjacent to the bone is renewed relatively
rapidly, the collagen adjacent to the root surface is renewed slowly
or not at all.
Note the occurrence of osteoblasts (OB) and osteocytes (OC)

16. • Both the cortical and cancellous
alveolar bone are constantly
undergoing remodeling
• Trabicular bone =cancellous=spongy