The document discusses bone density and its importance in implant dentistry. It describes four classifications of bone density (D1-D4) based on macroscopic characteristics, with D1 being the densest. The anterior mandible typically has the densest D1/D2 bone, while the posterior maxilla has the least dense D4 bone. Determining bone density accurately using CT scans is important for developing an appropriate treatment plan and ensuring implant success long-term by avoiding pathological overload conditions.

2. Presenter Name:
Dr.Riad Mahmud
Resident of
Prosthodontics,
BSMMU
Date:15: 11: 2016

3. The external and internal architecture of bone controls virtually every
facet of the practice of implant dentistry.
The density of available bone in an edentulous site is a determining
factor in
 Treatment planning,
 Implant design,
 Surgical approach,
 Healing time, and
 Initial progressive bone loading during prosthetic
reconstruction..

4. The quality of bone is often dependent upon the arch position.
The most dense bone is usually observed in
 the anterior mandible, followed by
 the anterior maxilla
 posterior mandible, and the least dense bone is typically
found in
 the posterior maxilla.

5. Following a standard surgical and prosthetic protocol, Adell et al.
reported
 an approximately 10% greater success rate in the anterior mandible
as compared with the anterior maxilla.
Schnitman et al. also noted lower success rates
 in the posterior mandible as compared with the anterior mandible
when the same protocol was followed.
The highest clinical failure rates have been reported
 in the posterior maxilla, where the force magnitude is greater and the
bone density is poorer.

6. Bone is an organ that is able to change in relation to a number of
factors,
 hormones,
 vitamins, and
 mechanical influences.
Biomechanical parameters
 duration of edentulous state.

7. Bone metabolic hormones: PTH,
Vitamin D,
Calcitonin
Growth hormones:
Somatotropin, IGF-I, IGF-II
Sex steroids:
testosterone,
estrogen

8. FACTORS: PEAK LOAD IN MICROSTRAIN
Mechanical†
Disuse atrophy <200
Bone maintenance 200 to 2500
Physiologic hypertrophy 2500 to 4000
Pathologic overload >4000
*me = percent deformation μ10–4. †

9. Frost proposed a model of four histologic patterns for compact bone as
it relates to mechanical adaptation to strain.
 The pathologic overload zone,
 Mild overload zone,
 Adapted window, and
 Acute disuse window
Density of alveolar bone evolves as a result of mechanical deformation
from microstrain. (The greater the magnitude of stress applied to the
bone, the greater the strain observed in the bone)

10. Four zones for bone related to mechanical adaption to strain before spontaneous
fracture. The acute disuse window is the lowest microstrain amount.
The adapted window is an ideal physiologic loading zone.
The mild overload zone causes microfracture and triggers an increase in bone
remodeling, which produces more woven bone.
The pathologic overload zone causes increase in fatigue fractures, remodeling, and
bone resorption.

11. Four zones for bone related to mechanical adaption to strain
before spontaneous fracture.
 Lowest microstrain amount.
 Ideal physiologic loading zone.
 Causes microfracture and triggers an increase in bone
remodeling, which produces more woven bone.
 Causes increase in fatigue fractures, remodeling, and bone
resorption.

13. The trabecular bone in a dentate mandible is more coarse.
The mandible a independent structure, is a force-absorbing element.

14. Biomechanical functions
 An independent structure,
 A
 When teeth are present,
 Outer cortical bone is denser and thicker and
 Trabecular bone is more coarse and dense.

15. The trabecular bone of each jaw has structural variations.
The trabecular bone is most dense next to the teeth, where it forms the
cribriform plate. Between the teeth, the bone is usually most dense
near the crest and least dense at the apex.

16. Biomechanical functions
(Any strain to the maxilla is transferred by the zygomatic arch and palate away
from the brain and orbit ).
 Has a thin cortical plate and fine trabecular bone supporting the
teeth.
 most dense around the teeth (cribriform plate) and
 more dense around the teeth at the crest, compared with the
regions around the apices

17. The dentate maxilla has a finer trabecular pattern compared with the
mandible. The maxilla is a force distribution unit and is designed to
protect the orbit and brain.

18. Linkow, in 1970, classified bone density into three categories:
 This ideal bone type consists of evenly spaced trabeculae with
small cancellated spaces.
 The bone has slightly larger cancellated spaces with less
uniformity of the osseous pattern.
 Large marrow-filled spaces exist between bone trabeculae.

19. Class III bone results in a loose-fitting implant
Class II bone was satisfactory for implants
Class I bone was the most ideal foundation for implant
prostheses.

20. In 1985, Lekholm and Zarb listed Four bone qualities for the anterior
region of the jaws.
is composed of homogenous compact bone.
has a thick layer of cortical bone surrounding dense
trabecular bone.
has a thin layer of cortical bone surrounding dense
trabecular bone of favorable strength.
has a thin layer of cortical bone surrounding a core of low-
density trabecular bone.

21. In 1988, Misch proposed four bone density groups
 Independent of the regions of the jaws.
 Based on macroscopic cortical and trabecular bone characteristics.

22. BONE DENSITY DESCRIPTION TACTILE ANALOG TYPICAL
ANATOMICAL
LOCATION
D1 Dense cortical Oak or maple wood Anterior mandible.
D2 Posterior mandible White pine or spruce
wood
Anterior mandible
Posterior mandible
Anterior maxilla
D3
Porous cortical
(thin)and fine
trabecular
Balsa wood Anterior maxilla
Posterior maxilla
Posterior mandible
D4
Fine trabecular Styrofoam Posteriormaxilla.

23. BONE ANTERIOR
MAXILLA
POSTERIOR
MAXILL
ANTERIOR
MANDIBLE
POSTERIOR
MANDIBLE
D1 0 0 6 3
D2 25 10 66 50
D3 65 50 25 46
D4 10 40 3 1

25. The four macroscopic bone qualities are, from left to right,
D1, D2, D3, and D4.

26. The four macroscopic bone qualities are, from left to right,
D1, D2, D3, and D4.

27. The four macroscopic bone qualities are, from left to right,
D1, D2, D3, and D4.

28. The four macroscopic bone qualities are, from left to right,
D1, D2, D3, and D4.

29. The four macroscopic bone qualities are, from left to right,
D1, D2, D3, and D4.

30. D1 bone density has the greatest amount of bone-implant contact.
Because stress equals force divided by area, the increase in the area of
contact results in a decreased amount of stress.

31. A cross section of a D2 mandible in the region of the mental foramen. A
thick cortical plate exists on the crest and a coarse trabecular bone
pattern exists within.

32. A posterior maxilla demonstrating D3 bone with a thin
porous cortical plate on the crest with fine trabecular bone
underneath.

33. In a D4 posterior maxilla, the posterior crestal region has little to no
cortical bone on the crest and is composed primarily of fine
trabecular bone.

34. A, In a finite element analysis study of D1 and D2 bone with a Division
A, B, or C bone volume predicted no implant failure.
B, In a finite element analysis study of D3 bone of one third the
strength, no failure was predicted in Division A bone.
C, In a finite element analysis study, D4 bone was inadequate in strength
for implant success, even in Division A bone volume.

35. Division A,
D1/D2 100% Density
Ultimate compression strength: 22.5 Mpa
No failure predicted

36. Division B,
D3 50% Density
Ultimate compression strength: 7.5 MPa
No failure predicted

37. Division C,
D4 25% Density
Ultimate compression strength 3.5 MPa
Failure predicted

38. A range of bone loss has been observed in implants with similar load
conditions.
The magnitude of a prosthetic load may remain similar and give one of
the following three different clinical situations at the bone-implant
interface, based on bone density:
(1) Physiologic bone loads in the adapted window zone and no marginal
bone loss,
(2) Mild overload to pathologic overload bone loads and crestal bone loss,
or
(3) Generalized pathologic overload and implant failure.
Therefore, to obtain a similar clinical result in each implant prosthesis, the
variables in each patient must be either eliminated or accounted for in the
treatment plan.

39. Periapical or panoramic radiographs are not very beneficial to
determine bone density.
Bone density may be more precisely determined by
Tomographic radiographs.
Especially computerized tomogram.
CT produces axial images of the patient’s anatomy,
perpendicular to the long axis of the body.
Each CT axial image has 260,000 pixels, and each pixel has a CT
number (Hounsfield unit) related to the density of the tissues
within the pixel.
In general, the higher the CT number, the denser the tissue.

40. Modern CT scanners can resolve objects less than 0.5 mm apart.
Software is available to electronically position the implant on
the CT scan and evaluate to Hounsfield numbers in contact with
the implant.
The Misch bone density classification may be evaluated on the
CT images by correlating Hounsfield units ranges.
The very soft bone observed after some immaterialized bone
grafts may be 50 to 200 units.

41. D1: >1250 Hounsfield units
D2: 850 to 1250 Hounsfield units
D3: 350 to 850 Hounsfield units
D4: 150 to 350 Hounsfield units
D5: <150 Hounsfield units
.

42. The patient is first examined,
Most common radiographic evaluation
A panoramic radiograph.
The initial treatment plan is presented to the patient
using the anatomical location as an index of the
bone density:
Anterior mandible and single tooth replacement is D2,
Anterior maxilla and posterior mandible is D3, and
Posterior maxilla is D4.

43. Bone density/Treatment plan
Stress = Force/Area
Decreased Bone density = Increase Implant area by -
Implant number
Implant width
Implant length
Implant design
Implant surface condition

44.  Scientific rationale of strength,
 Modulus of elasticity,
 Bone-implant contact percent, and
 Stress transfer difference related to bone density has to
be addressed.

45. The bone density by location method is the first way the dentist can
estimate the bone density in the implant sites to develop an initial
treatment plan.
Therefore the initial treatment plan before computed tomographic (CT)
radiographic scans or surgery suggests
o The anterior maxilla is treated as D3 bone,
o The posterior maxilla as D4 bone,
o The anterior mandible as D2 bone, and
o The posterior mandible as D3 bone.
A more accurate determination of bone density is made with
computerized tomograms before surgery or tactilely during implant
surgery.

46.  The bone-loading process from occlusal forces becomes a
critical factor in long-term implant survival.
 The bone density under load is directly related to the bone
strength and is therefore a critical parameter for long-term
survival.

47. Must remain within the physiologic to mild overload zone;
otherwise, Pathologic overload With
 Associated bone loss and
 Micro fracture, and
 Implant mobility may occur.

48.  Atraumatic bone preparation,
 Close approximation of living bone to the biocompatible
implant surface, and
 Absence of movement at the interface during healing.