Residual Ridge Resorption-Prosthodontics

1. RESIDUAl RIDGE
RESORPTION
Reg. no.-1551of2012-13
Dept. of Prosthodontics and Crown $ Bridges
North Bengal Dental College & Hospital

2. CONTENTS
•Introduction.
•Basic concept of bone.
•Mechanism of bone resorption
•Pathology of RRR
•Pathophysiology of RRR
•Pathogenesis of RRR
•Changes in maxilla and mandible
•Epidemiology of RRR

3. •Etiology of RRR
•Calcium homeostasis and RRR
•Osteoporosis and RRR
•Management of RRR
•Summary
•Conclusion
•References

4. INTRODUCTION
Residual ridge is a term used to
describe the shape of the clinical
alveolar ridge after healing of bone
and soft tissues after tooth extractions.
It consists of the denture-bearing
mucosa, submucosa and periosteum,
and the underlying residual alveolar
bone.

5. •After tooth extraction, a cascade of
inflammatory reactions is immediately activated,
and the extraction socket is temporarily closed by
the blood clot.
•Epithelial tissue begins its proliferation and
migration within the first week and the disrupted
tissue integrity is quickly restored.
•The most striking feature of the extraction
wound healing is that even after the healing of
wounds, the residual alveolar ridge bone
undergoes a life-long catabolic remodeling.

6. •The size of the residual ridge is reduced most
rapidly in the first 6 months, but the bone
resorption activity continues throughout life at
a slower rate, resulting in removal of a large
amount of jaw structure.
•This unique phenomeneon has been described
as RESIDUAL RIDGE RESORPTION (RRR).
•The rate of RRR is different among persons
and even at different sites in the same person.

7. The mechanical aspect of bone remodeling is
usually associated with Wolff’s law of bone
transformation (1892) which states that “Every
Change In The Form And Function Of Bone , Or
Of Their Function Alone,is Followed By Certain
Definite Changes In Their Internal Architecture,
And Equally Definite Alteration In Their External
Conformation, In Accordance With Mathematical
Laws.”, which simply means that bone remodels in
response to the forces applied. However, the mere
reference to ‘Wolff’s law’ in relation to bone
resorption is an inadequate explanation of this
complex physiologic process.

8. Consequences of RRR
•Apparent loss of sulcus width and depth.
•Displacement of the muscle attachment closer to
the crest of the residual ridge.
•Loss of vertical dimension of occlusion.
•Reduction of lower face height.
•An anterior rotation of the mandible.
•Increase in relative prognathia.

9. •Changes in inter-alveolar ridge relationship.
•Morphological changes such as sharp, spiny,
uneven residual ridges.
•Resorption of the mandibular canal wall and
exposure of the mandibular nerve.
•Location of the mental foramina close to the top
of the mandibular residual ridge.
This provides serious problems to the clinician
on how to provide adequate support, stability and
retention of the denture.

10. Basic concept of bone:
A basic concept of bone structure and its
functional elements must be clear before
bone resorption can be understood. The
structural elements of bone are:
a)Osteocytes found in bone lacunae.
b)The intercellular substance or bone matrix
consisting of fibrils and calcified cementing
substance.
c) Osteoblasts.
d)Osteoclasts

11. (a) OSTEOCYTES:
These are small, flattened and rounded cells
embedded in the bone lacunae.
They are the main cells, of the developed bone
and are derived from the matured osteoblasts.
Function:
• Help to maintain bone as a living tissue
because of their metabolic activity.
• Play an important role in maintaining the
exchange of calcium between bone and extra
cellular fluid.
(B) CALCIFIED CEMENTING SUBSTANCE:
Consists of mainly polymerized glycoproteins
and mineral salts namely CaCo3 and
phosphate which are bound to these protein
substances.

12. (C) OSTEOBLASTS:
Concerned with bone formation and are situated on
the outer surface of bone in a continuous layer.
Functions:
• Responsible for synthesis of bone matrix.
• Role in calcification.
(D) OSTEOCLASTS:
They are the giant multinucleated cells found in the
lacunae of bone matrix.
Functions:
• Responsible for bone resorption during bone
remodeling. Bone resorption always requires the
simultaneous elimination of organic and inorganic
components of the intercellular substance.

13. MECHANISM OF BONE
RESORPTION
•The organic components of the intercellular
substance are removed by proteolytic action of
the osteoclasts.
•Then, the Ca salts (inorganic) are dissolved
by a chelating action of the osteoclasts.
•As resorption takes place, the osteocytes
released may revert to osteoblasts or become
osteoclasts, depending on the physiologic and
pathologic demands.
Histologically, bone apposition and
resorption take place in close approximation,
making possible the bone balance of shape and
size.

14. PATHOLOGY OF RRR
GROSS PATHOLOGY:
The basic structural change in RRR is a
reduction in the size of the bony ridge under the
mucoperiosteum. It is primarily a localized loss of
bone structure. In some situations, this loss of bone
may leave the overlying mucoperiosteum
excessive and redundant. In order to provide a
simplified method for categorizing the most
common residual ridge configurations, a system of
six orders of RR form has been described.

15. Order 1 - Pre extraction
Order 2 - Post extraction
Order 3 - High, well-
rounded
Order 4 - Knife edge
Order 5 - Low, well-
rounded
Order 6 - Depressed

16. I II III IV V VI

17. •It is clear that RRR does not stop with the
residual ridge , but may well go below where
the apices of the teeth were, sometimes
leaving only a thin cortical plate on the
inferior border of the mandible or virtually no
maxillary alveolar process on the upper jaw.
•Sometimes a knife edge ridge maybe masked
by a redundant or inflamed soft tissue, which
can be detected by palpation or by Lateral
cephalometric radiographs.

18. •It is a normal function of bone to undergo
constant remodeling throughout life through
the process of bone resorption and bone
formation.
•Growth : ↑ Bone formation.
•Osteoporosis/localized periodontal disease: ↑
Bone resorption.
PATHOPHYSIOLOGY OF RRR

19. RRR is a localized pathologic loss of bone that is
not built back by simply removing the causative
factors.
Yet, the physiologic process of internal bone
remodeling goes on even in the presence of this
pathologic external osteoclastic activity that is
responsible for the loss of so much of bone
substance.
•It has been shown that remodeling takes place in
3 dimensions such that certain portions of bone
become narrower to the extent that all existing
cortical bone in that area is removed by external
osteoclastic activity and is replaced by a new
cortical layer that is formed by simultaneous
endosteal bone formation.

20. •Even if a great deal of RR is removed in total,
there is often a cortical layer of bone over the crest
of the ridge. This means that new bone has been
laid down inside the RR in advance of the external
osteoclastic removal of bone.
•The mechanism of the reduction of the mandibular
residual ridge actually represents a modified version
of the Enlow’s “V” principle, showing external
resorption accompanied by endosteal deposition.

22. Based on the clinical fact that :
•RRR is not inevitable
• Its rate varies
• The rate of resorption is greater that the rate of
formation in some patients ,
….RRR should be considered a pathologic
process.

23. Order I: pre-extraction: The tooth is in its socket
with thin labial and lingual cortical plates merged with
the lamina dura.
Order II: postextraction: The healing period includes
clot formation and organisation, filling of the socket
with the trabecular bone and epithelisation over the
socket site. The edges of the residual ridge are still
sharp.
Order III: High , well rounded residual ridge: The
cortical plates are rounded off by external osteoclastic
resorption, narrowing of the crest of the ridge begins
and remodelling of the internal trabecular structure
takes place.
PATHOGENESIS OF RRR

24. Order IV: Knife edge RR : Sharp narrowing of the
labio-lingual diameter of the crest of the ridge with
a compensatory internal remodelling leading to a
sharp crest of the ridge.
Order V: Low well rounded RR : Progressive labio
lingual narrowing of knife edge ridge leads to a
widely rounded and lower residual ridge.
Order VI: Depressed RR: Eventually further
progression of the resorption leads to a flat,
depressed ridge.

25. I II III IV V VI

27. •RRR is chronic, progressive, irreversible
and cumulative. Usually, RRR proceeds
slowly over a long period of time flowing
from one stage imperceptibly to the next.
•Autonomous regrowth has not been
reported. Annual increaments of bone loss
have a cumulative effect leaving less and
less residual ridge.

28. •Maxillary teeth are generally directed
downward and outward, so bone reduction
generally is upward and inward.
•Since the outer cortical plate is thinner than the
inner cortical plate, resorption from the outer
cortex tends to be greater and more rapid.
•As the maxilla becomes smaller in all
dimensions, the denture bearing area (basal seat)
decreases.
CHANGES IN MAXILLA AND
MANDIBLE

29. •The bone of the maxillae resorbs primarily
from the occlusal surface and from the buccal
and labial surfaces.
•Thus the maxillary residual ridge looses
height and maxillary arch becomes narrower
from side to side and shorter
anteroposteriorly.

31. •The anterior Mandibular teeth generally incline
upward and forward to the occlusal plane,
whereas the posterior teeth are either vertical or
incline slightly lingually.
•The mandibular ridge resorbs primarily from the
occlusal surface.
•Because the mandible is wider at its inferior
border than at the residual alveolar ridge in the
posterior part of the mouth, resorption, in effect,
moves the left and right ridges progressively
farther apart.

33. •The mandibular arch appears to become wider,
while the maxillary arch becomes narrower.
•Thus, RRR is centripetal in maxilla and
centrifugal in mandible.
•The cross section shrinkage in the molar region,
is downward and outward. In the anterior region it
is first downward and backward ,and then moves
forward.
•The surface of the arches maybe resorbed out of
parallelism which can result in diminished
stability of dentures.
•Severe ridge resorption can also result in
increased inter arch space.

35. EPIDEMIOLOGY OF RRR:
•To date, it would appear that RRR is world-
wide, occurs in males and females, young and
old, sickness and in health, with and without
dentures and is unrelated to the primary reason
for the extraction of the teeth (Caries /
periodontal disease).
•Rate of RRR is variable
-between persons.
-within the same person at diff. times.
-within the same person at diff. sites.

36. It is postulated that RRR is a
multifactorial, biomechanical disease
that results from a combination of:
• Anatomic
• Metabolic
• Functional
• Prosthetic factors
ETIOLOGY OF RRR

37. ANATOMIC FACTORS
It is postulated that RRR varies with the quantity and
quality of the bone of the residual ridges:
RRR α anatomic factors
1. The amount of bone:
• It is not a good prognostic factor for the rate of RRR,
because it has been seen that some large ridges resorb
rapidly and some knife edge ridges may remain with
little changes for long periods of time.
•Although the broad ridge may have a greater
potential for bone loss, the rate of vertical bone loss
may actually be slower than that of a small ridge
because there is more bone to be resorbed per unit of
time and because the rate of resorption also depends
on the density of bone.

38. 2. Quality of bone:
On theoretic grounds, the denser the
bone, the slower the rate of resorption because
there is more bone to be resorbed per unit of
time.
METABOLIC FACTORS
Generally, body metabolism is the net sum of all
the building up (anabolism) and the tearing
down (catabolism) going on it the body.
RRR α bone resorption factors
bone formation factors

39. In equilibrium the two antagonistic actions
(of osteoblasts and osteoclasts) are in balance. In
growth, although resorption is constantly taking
place in the remodeling of bones as they grow,
increased osteoblastic activity more than makes up
for the bone destruction.
Whereas in osteoporosis, osteoblasts are
hypoactive, and, in the resorption related to
hyperparathyroidism, increased osteoblastic
activity is unable to keep up with the increased
osteoclastic activity. The normal equilibrium may
be upset and pathologic bone loss may occur if
either bone resorption is increased or bone
formation is decreased, or if both occur.

40. Since bone metabolism is dependent on
cell metabolism, anything that influences cell
metabolism of osteoblasts and osteoclasts is
important.
The thyroid hormone affects the rate of
metabolism of cells in general and hence the
activity of both, the osteoblasts and osteoclasts.
Parathyroid hormone influences the
excretion of phosphorous in the kidney and also
directly influences osteoclasts.

41. •The degree of absorption of Ca, P and proteins
determines the amount of building blocks
available for the growth and maintenance of bone.
•Vit C aids in bone matrix formation.
•Vit D acts through its influence on the rate of
absorption of calcium in the intestines and on the
citric acid content of bone.
•Various members of Vit B complex are necessary
for bone cell metabolism.

42. According to Reifenstein, in the young
person, there is a relative predominance of
anabolic hormones (estrogen and testosterone)
over the anti anabolic hormones( cortisone and
hydrocortisone) resulting in continued growth
of skeleton.
He further states that, as people get
older, the anabolic hormones are so reduced
that the antianabolic hormones are in relative
excess with the result that bone resorption may
take place faster than bone formation and that
bone mass may be reduced.

43. FUNCTIONAL FACTORS
Forces within the physiological limits
are beneficial in their massaging effect. On the
other hand, increased or sustained pressure
produces bone resorption.
Bone that is used as by regular physical
activity will tend to strengthen within certain
limits , while bone that is in disuse will tend to
atrophy.

44. DISUSE ATROPHY
•It is directly proportional to the extent of
disuse.
•It does not result from the direct loss of non
functional bone, but the lack of replacement of
bone not needed for function.
•After the loss of natural teeth, bone cannot be
stimulated by a denture base as the teeth did
internally. The lack of internal stimuli
contributes to the disuse atrophy.

45. •The amount and frequency of stress and its
distribution and duration are important factors.
•The reaction of bone to pressure can cause both
apposition and resorption
•Whenever pressure interferes with the blood or
nerve supply of the bone, resorption occurs.
•The interference maybe due to pressure directly
from the bone or inflammatory in origin.

46. PROSTHETIC FACTORS
 Excessive stress resulting from artificial
environment:
• Human tissues have not evolved in nature to
accept ranges of artificial things and the
denture acts as an artificial entity.
 Abuse of tissues from lack of rest:
• Abused tissues are always manifested with a
slung, glistering surface. Bone is moldable. It
can tolerate masticatory forces within the
limits of physiologic tolerance but exceeding
that it causes damaging forces which will
result in resorption of the alveolar bone and
alteration in tissue form .

47.  Long continued use of ill fitting dentures:
• In ill fitting dentures, there is an improper
relation of the denture base to the supporting
tissue. Ill fitting dentures may be due to :
• Long use
• Loss of bone
• Incorrect occlusion
• Incorrect jaw relation

48.  Under extended dentures:
• Lead to less retentive dentures and
increase load per unit area. Common
sites are:
• Lingual flange
• Buccal shelf area
• Retromylohyoid area
• Retromolar pad

49.  Faulty improper procedures employing
compression forces:
• Before impression procedures, care has to be
taken on selection of trays. If the tray selected is
too large, it will distort the tissues around the
borders of the impression, away from the
tissues. If it is too small, the border tissues will
collapse inward onto the residual ridge. This
will reduce the support of the lips by the denture
flange.
• The use of minimal and selective pressure
impression techniques should be implicated in
order to avoid distortion of the mucosa and
ridge area which may be under considerable
pressure otherwise.

50.  Error in relating maxilla to the cranial
landmarks (orientation relation):
The plane of the maxilla should be oriented to
the facial reference line (Camper’s plane or ala
tragus line). If not, may cause instability of denture
leading to resorption.
 Lack of freeway space due to increased vertical
dimension of occlusion:
Freeway space is present in the teeth in the
physiologic rest position. It is normally 2-8mm but
in complete dentures it is around 2mm. At times,
due to lack of freeway space the bone resorbs
because of increased vertical height in an attempt to
create the space.

51.  Incorrect Centric relation record:
If the Centric relation is not recorded
properly, the mandibular teeth will not occlude
properly with those on the maxillary arch. This
proper occlusion is essential to the health of bony
support. Otherwise, during eccentric movement, it
causes pressure on bone due to failure of denture
stability. Hence resorption of base occurs.

52. Faults in selection and placement of posterior
teeth:
The selection of proper tooth size is based on :
•Capacity of ridges to receive and resist the
forces of mastication.
•Space available for the teeth.
•When the ridge is weak, resorbed and
covered by only lining mucosa, then the
use of the posterior teeth should be smaller.
This will limit the occlusal surface, which
in turn will minimize the forces directed to
such a ridge.

53.  If occlusal corrections are not done:
• These errors which may be caused due to
processing techniques if not corrected causes
premature contacts resulting in increased stress.
• Selective grinding should be done to minimize
lateral stress and resulting tissue trauma.
 Overclosure:
• The loss of proper vertical dimension after the
insertion of complete dentures results in the
triggering of a cyclic series of events detrimental to
the health of the residual alveolar ridge.
• Overclosure causes the mandible to be moved or
rotated in an upward and forward direction causing
occlusal disharmony and excessive trauma to
anterior region .

54. Bone resorption and Ca homeostasis:
The only sources of Ca for the body are
•Diet
•Bone reservoir.
Ca homeostasis is maintained by controlling
Ca obtained from these 2 sources. This can occur by
altering internal absorption mechanisms (income) or
tubular reabsorption (recycling) or by liberation of Ca
from the skeleton via resorption (savings).
There is a reciprocal relationship between Ca
concentration and bone resorption to maintain Ca
homeostasis. As the level of serum calcium develops,
resorption is stimulated and factors that would inhibit
resorption are depressed.

55. Skeletal depletion of calcium occurs as a
result of stimulation of parathyroid gland and the
alveolar bone is the first to be affected. This is due to
the function of parathyroid hormone in maintaining
the blood calcium level by mobilizing it from bones
by osteoclastic activity.
Simultaneously , there is an increased renal
excretion of phosphate, which disturbs the blood
calcium:phosphorous ratio by raising the blood
calcium level. This results in mobilization of
phosphates from bones by osteoclastic activity.
•Under these conditions , alveolar bone becomes
susceptible to diseases like osteoporosis.

56. OSTEOPOROSIS AND RRR
Osteoporosis is characterized by low bone
mass and micro architectural deterioration of the
bone, which leads to increased bone fragility and
risk of fracture. It has two forms.
The more prevalent Type I (post menopausal)
affects women for a decade or so after menopause.
The Type II ( senile or idiopathic) attacks males and
females at any age for no obvious reason.
RRR may be a manifestation of Type I osteoporosis
.
•Both cortical and trabecular bone are affected.

57. TREATMENT FOR OSTEOPOROSIS
•Estrogen replacement therapy
•Ca supplement
•Good nutrition and regular exercise
•New drugs for systemic osteoporosis are
under evaluation, including
biophosphonates to inhibit osteoclasts
and injections and calcitonin to reduce
resorption.
Detection of bone loss i.e. radiographs
•Digital subtraction radiography
•Dual energy x-ray absorptiometry

58. Methods of evaluation of bone loss in RRR
• Radiographs:
- Cephalometrics
- Panoramic
• Tetracycline labeling
• Mercury porosimetry
• Anatomic studies
• Remount jig procedure

59. Radiograph showing gross
resorption of residual ridges

60. Radiograph showing Atwood’s
six orders of residual ridge resorption

61. Systemic evaluation
Diet
Tissue treatment therapy
Pre prosthetic surgery
Prosthetic management:
-Impression techniques.
-Denture base selection.
-Teeth selection and arrangement.
-Implant supported prosthesis.
MANAGEMENT OF RRR

62. 1. Systemic evaluation
•Any systemic condition that can contribute to
the degeneration of the bone condition should be
corrected and stabilized, for e.g.: osteoporosis,
hyperparathyroidism, diabetes mellitus.
•Any dental treatment should follow only after
the condition is under control and the patient is
fit for treatment.
•In cases where limited help can be given, the
patient should be counseled about its effect on
dental health.

63. 2. Diet
•Patients with bone disease need a diet high in
proteins, vitamins and mineral content.
•Should reduce or stop intake of refined
carbohydrates, white flour, and white sugar.
•In all dietary prescriptions , the consistency of
food prescribed must take into account the
patients ability to masticate.
Tissue Treatment Therapy.
•Soft conditioning materials can be used to
rejuvenate the tissue-bearing area.
•Hypertrophied tissues, previously treated by
surgery, can be reconditioned by using this
material.

64. Pre-prosthetic surgery
It aims at providing a good healthy surface for
the insertion of the dentures.
It includes all the surgical procedures by virtue
of which an ideal smooth, healthy U shaped ridge
, without any unfavourable undercuts or bony
growths and with sufficient vestibular depth is
achieved.
It includes the following surgical procedures:
•Ridge correction.
•Ridge extension/vestibuloplasty.
•Ridge augmentation
•Surgical correction of maxillomandibular
relation.

65. Ridge Corrective surgery
Soft tissue deformities
•Labial frenectomy.
•Lingual frenectomy.
•High buccal frenal attachments.
•Hyperplasia of soft tissues.
Bony deformities
•Sharp irregular ridge.
•Alveoloplasty.
•Alveolectomy.
•Excision of tori and genial tubercles.

67. Ridge extension surgery/vestibuloplasty:
•Labial.
•Lingual.
•High mental foramen.
•Zygomaticoplasty.
•Tuberoplasty.

69. Labial vestibuloplasty using
modified labial incision

70. Labial vestibuloplasty
using ridge incision

72. Ridge augmentation
It is aimed at :
•Increase in the ridge height and width
providing a large denture bearing area ,
•Protection of neuro vascular bundles
•Restoration of proper maxillomandibular arch
relationship.
Ridge augmentation has been tried with:
•Bone transplants
•Autogenous and homogenous cartilage
•Hydroxylapatite
•Acrylic implants.

73. PROSTHETIC MANAGEMENT.
1). Impression technique
In patients with severely resorbed ridges, lack
of ideal amount of supporting structures decreases
support and the encroachment of the surrounding
mobile tissues onto the denture border reduces both
stability and retention. Thus the main aim of the
impression procedure is to gain maximum area of
coverage. For e.g., in mandibular ridge, obtaining a
fairly long retromylohyoid flange helps to achieve a
better border seal and retention.
Selection of proper trays and the correct
impression procedure is very essential for an
accurate impression.

74. Selective pressure
technique
This technique is most widely advocated to
manage RRR.
It makes it possible to confine the forces acting on
the denture to the stress bearing areas .
This helps in better withstanding the mechanical
forces induced by denture wearing.

75. • Winkler describes a technique which uses tissue
conditioners. An over extended primary
impression of alginate is made.
• Occlusal wax rims are constructed and the borders
are adjusted so that the lingual flange and
sublingual crescent area are in harmony with the
resting and acting phases of the floor of the mouth
by an open and closed – mouth technique.

76. 3 applications of conditioning material are
used – each application approximately 3-10
minutes. The third and final wash is made with a
light bodied material. This technique results in the
impression that has tissue placing effect with
relatively thick, buccal, lingual and sublingual
crescent area borders.
Miller used mouth-temperature waxes
instead of tissue conditioners.

77. Mucodynamic technique
It is intended to integrate the changes in the
shape of the vestibules when functional movements
are made. A highly viscous thermoplastic reversible
impression material is placed in the custom tray,
then carefully adapted to the residual ridge and held
with light and uniform pressure while the
functional movements are made. As soon as the
entire surface is smooth and the buccal and lingual
borders are molded to the outer circumference
without any folds, the impression is complete.

78. 2. Selection of denture base
For degenerative ridge patients there are three types
of denture bases:
•Methyl methacrylate resin denture bases
•Cast metal bases
•Processed resilient , lined denture bases

79. Methyl methacrylate resin denture bases
•These are the standard bases normally used.
•These bases are quickly and easily processed.
•Dimensionally stable.
•But in a short time the base appears to soften and
change color, and is not strong.

80. Cast metal bases
Main advantage is the great accuracy of
fit to the tissues by surface tension, than acrylic
denture bases.
They maybe of gold, chromium cobalt or
aluminium.

81. Processed resilient , lined denture bases
Its greatest advantage is its cushioning effect on
the mucosa and its ability to distort and spring
back.
Indications:
•Patients with severely undercut ridges, but for
whom surgery is contraindicated.
•Patients with parafunctional mandibular
movement habits.
•Patients with flat ridge and delicate tissues.

83. Limitations
They can be used only under a hard-
processed acrylic resin base, and the lining
works best when there is a 2 mm thickness.
Deterioration of the liner in some
mouths.
In spite of this , it can be held up well in
dentures by proper cleansing and brushing
with soft tooth brush.

84. Teeth selection and arrangement
Teeth can be selected acc. to their form and
size:
•Anatomic or cuspal teeth
•Semi anatomic teeth
•Non anatomic or zero degree teeth.
The following requirements have to be
met during teeth arrangement:
•Stability of occlusion in centric relation.
•Balanced occlusion for eccentric contacts.
•Unlocking of the cusps mesio distally to
accommodate the settling of denture bases.

85.  Control of horizontal force by buccolingual cusp
height reduction acc. to residual ridge shape and
inter arch space.
 Functional balance by favorable tooth to ridge
crest position.
 Cutting and shearing efficiency.
 Anterior clearance of teeth during mastication.
 Minimal occlusal stop areas for reduced pressure
during function.
 Teeth should be placed in neutral zone to create
co ordination between the primary and secondary
masticatory organs.

86. Relative to each other, the maxillary and
mandibular residual ridges are known to be in a
favorable position for normal arrangement of
posterior teeth if the connecting line between the
midridge line of the max. and mand. residual
ridges are at an angle of more than 80 degrees.
An angle less than 80 degrees necessitates a
cross bite or reverse occlusion arrangement of
posterior teeth.
A prognathic mandible necessitates the
arrangement of anterior teeth in a reverse
occlusion.

88. •Non anatomic teeth have known to cause
fewer denture sore spots and lesser ridge
resorption
•Semi anatomic reverse curve posterior teeth
favor the lower ridge
•Anatomic posterior teeth cause more denture
soreness and ridge resorption
•Few studies state that anatomic posterior
occlusion favors lower dentures and non
anatomic posterior teeth favor upper denture.

89. Implant Supported Prosthesis
The various problems associated with RRR
and stability of removable soft tissue borne
dentures have aroused interest in dental
implantology to provide stable mechanical support
to the dental prosthesis.
This is because of the following advantages
offered by implant supported prosthesis:
•Overall volume of bone is maintained.
•Efficiency to take up stress and strain.
•There is 20 fold decrease in the loss of structure
with implants when compared with resorption that
occurs with removable prosthesis.
•Preventive implant is given following extraction
to retard ridge resorption.

90. •Maintenance of alveolar bone.
•Maintenance of occlusal vertical dimension.
•Height of alveolar bone is found to be
maintained as long as the implant remains
•healthy.
•Improved psychological health.
•Regained proprioception.
•Increased stability, retention and phonetics.
•Maintenance of structure and function of
muscles of mastication and facial expression.
•Immune to caries.
•Increased trabeculation and density of bone.

91. PROSTHODONTIC
CLASSIFICATION OF IMPLANTS
FP-1 : Fixed prosthesis replacing only crown.
FP-2 : Fixed prosthesis replacing crown and
portion of root.
FP-3 : Fixed prosthesis replacing missing
crowns and portion of the edentulous site.
RP-4 : Removable prosthesis : overdenture
supported by implants.
RP-5 : Removable prosthesis : overdenture
supported by both soft tissue and implant.

92. The success of implant supported
prosthesis, however, depends on the technical
knowledge and mastery of the implantologist,
and is directly related to the selection of
patient and implant, surgical technique,
follow up procedures and patient
acceptability.

93. Residual ridge resorption is a chronic,
progressive, irreversible, and disabling disease , of
multifactorial origin.
Much is known about its pathology and
pathophysiology, but a lot remains to know about its
pathogenesis, epidemiology and etiology.
RRR requires a multiple approach for diagnosis
and treatment planning.
The cause must be detected, by the aid of a physician,
and then eliminated or stabilized before dentures are
constructed. Construction of a stable functioning
denture and a regular follow up treatment can help in
the restoration of function, and thus, the restoration of
the physical and mental vitality of the patient.
SUMMARY

94. The preservation of supporting tissues is a sacred
trust that cannot be ignored.
•The application of the basic concepts and the
advances made in the basic sciences will help to
keep this trust in the hands of the dental
profession.
As prosthodontists, we need to perform the most
meticulous and intelligent prosthodontic care of
the patient within our capabilities.
…and then , it would not seem a nebulous hope
that some day there will be control over residual
ridge resorption.
CONCLUSION

95. References
•Winkler S : Essentials of complete denture
prosthodontics. 2nd edition,2000.
•Boucher CO : Prosthodontic treatment for
edentulous patients. 12th edition,2004.
•Misch CE : Contemporary implant dentistry.
2nd edition,1999.
•www.google.com
•www.wikipedia.com