3. The most common residual ridge configurations, a system of six
orders of residual ridge form has been described3 (Fig. 3-2):
Order I, pre-extraction;
Order II, post-extraction;
Order III, high, well-rounded;
Order IV, knife edge;
Order V, low,well-rounded;
Order VI, depressed.
4. Lateral cephalometric radiographs provide the most accurate method for
determining the amount of residual ridge and the rate of RRR over a period of
time (Fig. 3-5).
5. The panoramic radiographic technique described by Wical and Swoope is a
simple, useful method for arriving at a gross estimate of the amount of RRR to
date in a given patient (Fig. 3-7).
6. Microscopic pathology
Microscopic studies have revealed evidence of
osteoclastic activity on external surface of the crest of
residual ridge. The scalloped margins of Howship's
lacunae contain visible osteoclasts .
Frequently, the scalloped external surface seems
inactive, without visible bone resorbing cells and is
covered by non osteogenic periosteum. Microscopic
studies of mucoperiosteum has shown varying degree of
keratinization , acanthosis, edema and varying degree of
inflammatory cells such as lymphocytes and plasma
cells (Figure 4).
7. PATHOGENESIS
RRR is chronic, progressive, cumulative and irreversible.
The annual increments of bone loss have a cumulative effect leaving
less and less residual ridge.
Both cancellous and trabecular bone resorbed no matter how well
they are calcilfied . RRR can go below mucobuccal fold, the muscle
attachments, the genial tubercles, the mylohyoid ridge, and the level
of periapical bone
8. Etiology
It is entirely possible that RRR is a multifactorial
disease and that the rate of RRR depends not on one
single factor but on the concurrence of two or more
factors, which may be called cofactors.
Factors could be divided into four categories:
anatomic, metabolic, functional, and prosthetic
9. Anatomic factors
It includes size and shape of the ridge, type of bone, type
of mucoperiosteum, bone quality and form before
extraction.
It is postulated that RRR varies with the quantity and
quality of the bone of the residual ridges:
RRR directly proportional anatomic factors
10. 1)RRR varies with quality and quantity of the bone of residual
ridge. If there is more bone there will be more resorption.
2)To evaluate the present status of the residual ridge to
determine what has gone before. If a ridge has existed as
high and well-rounded for several years it will continue to do like
so.
3) Large well rounded ridges and broad palates seem to be
favourable anatomic factors.
4) Another anatomic factor is density.
11. metabolic factors
They include such things as age, sex, hormonal
imbalance, osteoporosis.
In older individuals bone resorption is more as compared
to bone formation.
The ridge atrophy would be in harmony with the potential
senile atrophy of old age
12. Certain local bone resorbing factors are also important. They include:
a) Endotoxins – from dental plaque ( plaque can occur in edentulous
mouth, in patients who do not clean their dentures.
b) Osteoclast activating factor.
c)Prostaglandin.
d) Human gingival bone resorption stimulating factor
e) Heparin – cofactor in bone resorption secreted by the mast cells
f) Others include trauma under ill-fitting denture,
g) Systemic factors – include circulating oestrogen, thyroxine, growth
hormone, androgens, calcium, phosphorus, vitamin D, proteins and
fluorides .
13. Mechanical force
Force is an cofactor in RRR that can be expressed as RRR force.
If considering force not only the amount of force but also the
frequency of force, the duration of force, the area over which the
force is distributed, the damping effect of the underlying tissue.
14. The amount of force applied to the bone may be affected
inversely by the damping effect or the energy absorption.
The damping effect may take place in mucoperiosteum and
since mucoperiosteum varies in its viscoelastic properties
patient from patient and from maxilla to mandible, its energy
absorption qualities may also influence the rate of RRR
15. Prosthetic factors
These factors include
a) Broad area coverage – to reduce force per unit area
b) Decreased number of dental units
c) Decreased buccolingual width of the teeth
d) Improved tooth form –to decrease the amount of force
required to penetrate bolus of food
16. e) Avoidance of inclined planes
f) Centralization of occlusal contacts –to increase
stability
g) Provision of adequate tongue room for proper
speech
h) Adequate interocclusal distance
17. treatment
RRR is complex multifactorial process so ideally we treat this by
preventing it.1) Improving patients denture foundation and ridge relation:
a) Non-Surgical methods –
a) rest for supporting tissue by using soft liner or by massaging
b) Correction of VD and occlusion
c) Jaw exercises
18. d) Surgical methods – performing various preprosthetic surgeries
such as removal of any bony prominences, removing
unfavourable frenum attachments or epulisfissuratum or
papillomatosis and any pressure on mental foramen. Apart from
this localised or generalised hyperplastic replacement of resorbed
ridges can also be done
19. 2) Enlargement of denture bearing areas through ridge
augmentation and vestibuloplasty can also be done.
3) Root tooth analogues can also be placed by means of
osseointegrated implants – after dental extractions, the
residual alveolar bone undergoes a period of accelerated
resorption, followed by bone loss. The use of implant
supported fixed prosthesis can be treatment of choice to
prevent residual ridge resorption
