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Rationale of Dental Implant

The increased need and use of implant-related treatment results from the combined effect of a number of factors. These are covered in the following subsections:

Aging Population
Aging population is an important factor to be considered in implant dentistry. Life expectancy has increased significantly past the age of retirement. Social pleasures continue throughout advanced life. In the past, geriatric dentistry meant inexpensive treatment emphasizing nonsurgical approaches. Today the full scope of dental services for elderly patients is increasing in importance to both the public and profession because of the increasing age of our society. Treatment alternatives including methods to obtain a fixed prosthesis with implant support are thus becoming popular.

Anatomic Consequences of Edentulism

Anatomic consequences could be due to bony structures or soft tissue.

a) Consequences on the bony structures
Basal bone forms the dental skeletal structure. Wolff’s law states that the bone remodels in relationship to the forces applied. With a change in the function of the bone everytime, a definite change occurs in the internal architecture and external configuration. When a tooth is lost, the lack of stimulation to the residual bone causes a decrease in trabeculae and bone density in the area, with loss in the external width,then height, and then of the bone volume. This issue, of utmost importance, has been ignored in the past by traditional dentistry. The patient is often not educated about the anatomic changes and the potential consequences of continued bone loss. The bone loss often accelerates on wearing a poorly fitting soft tissue-borne prosthesis. The continued atrophy of the posterior mandible eventually causes prominent mylohyoid and internal oblique ridges covered by thin, movable, unattached mucosa, prominent superior genial tubercles with the resulting elevation of prosthesis with contraction of mylohyoid and buccinator muscles serving as a posterior support. In a partially edentulous patient wearing a removable soft tissue-borne prosthesis, the natural abutment teeth, on which direct and indirect retainers are designed, are submitted to additional lateral forces. In addition, these teeth being often compromised by deficient periodontal support, many partial dentures are designed to minimize the forces applied to them. The result is an increase in mobility of the removable prosthesis and greater soft tissue support. These conditions protect the remaining teeth, but accelerate the bone loss in the edentulous regions. Thus implants have come out as an answer to these problems.

b) Soft tissue Consequences

As bone looses width, height, volume, the attached gingiva gradually decreases and is prone to abrasions caused by the overlying prosthesis. In addition high muscle attachments and hypermobile tissue often complicates the situation. The tongue of the patient with edentulous ridges often enlarges to accommodate the increase in space formerly occupied by the teeth. As a result the stability of removable prosthesis is jeopardised or further decreases.

Decreased Performance of The Removable Prosthesis

Removable soft tissue-borne partial dentures have one of the lowest patient acceptance rates in dentistry. Those patients wearing the partial dentures often exhibit greater mobility of the abutment teeth, greater plaque retention, increased bleeding upon probing, more incidence of caries, and accelerated bone loss in the edentulous regions. Therefore alternative therapies that improve oral conditions and maintain bone are often warranted.

Psychological Aspects of Tooth Loss

The psychological effects of total edentulism are complex and varied, and range from very minimal to a state of neuroticism. Although complete dentures are able to satisfy the esthetic needs of many patients, there are those who feel that their social life is significantly affected because of the inconsistent denture fit, embarrassing circumstances, and need for continued application of denture adhesive.In contrast, 80 per cent of the patients treated with implant supported prosthesis judged an overall improvement in their psychological health and perceived implant supported prosthesis as an integral part of their body.

Preservation of Tooth Structure
Fixed partial dentures have been considered the standard of treatment prior to advent of implant therapy. However, to obtain optimal esthetic results with the fixed partial dentures, a significant reduction in the amount of tooth structure is necessary occasionally predisposing to endodontic, periodontal interventions and structural sequelae. Single tooth implant survival has been demonstrated to be the most predictable method of tooth replacement. There have been no reports of loss of adjacent teeth when single tooth implant restorations have been undertaken, this is vastly different to when treatment is rendered with a FPD which may require the span to be extended further, additional endodontic and periodontal treatment thus further compromising the long term stability of the prosthesis.

Provision of Additional Tooth Support
Transitioning a patient from a complete denture to an implant supported fixed prosthesis have resulted in a dramatic improvement in the masticatory performance.Complete denture patients are not able to exert equivalent forces due to the limitation of discomfort in the soft tissues arising as a result of increased pressure on denture bearing areas. The patient with an implant supported fixed prosthesis can exert much more force than with a complete denture. The improved stability and retention of implant supported prosthesis is a vast improvement on soft tissue supported dentures.

 
Retrievability
Implant restorations can be screw retained, cement retained or a combination of two. Thus one additional advantage of implant supported restorations is retrievability.Retrievability is advantageous for reservicing, replacement or salvaging of the restoration.Thus the use of dental implants to provide support for prosthesis offers a multitude of advantages which can be enlisted as follows:

a) Maintenance of bone

b) Maintenance of occlusal vertical dimension

c) Tooth positioned for esthetics.( preserves facial looks and restores a natural smile)

d) Proper occlusion

e) Improved psychological health

f) Increased stability and retention

g) Improved phonetics

h) Reduced removable prosthesis size(eliminates palate and full extension flanges)

i) Improved success rate of prosthesis

j) Increased survival time of restoration

k) Maintenance of muscles of mastication and facial expression.

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