INTRODUCTION
The goal of modern dentistry is to restore the patient to normal contour, function, comfort, esthetics, speech, and health, regardless of the atrophy, disease or injury of stomatognathic system. Teeth are integral part of the stomatognathic system. The primary function of teeth is to prepare food for swallowing as well as to initiate and facilitate digestion. Teeth are also necessary for the articulation of speech and proper looks.
Normal versus abnormal anatomy from tooth generates a compromised repaired structure both in function and form. A balance of force provides an anatomically steady-state when teeth are present. With loss of even one tooth element, however steady-state is broken and a variety of progressive changes takes place. Loss of tooth/teeth results in loss of structural balance, inefficient oral function and poor esthetics. Besides caries, periodontal disease and positional changes of remaining natural teeth, the edentulous state may lead to a feeling of inconvenience and sometimes severe handi-capness. Hence, replacement of the lost tooth/teeth is essential to maintain the occlusal function and optimum oral health apart from its masticatory and esthetic needs. Also the feeling of inconvenience and handicapness can be avoided by replacement of teeth. Several methods are being used for replacement of missing tooth/teeth with natural or synthetic substitutes since centuries.
Conventional rehabilitation methods include tissue supported, tooth supported or dual supported removable dentures. Acrylic removable partial dentures are very common, as they are very 3economical. But removable partial dentures have certain drawbacks such as reduced masticatory efficiency and discomfort due to soft tissue support, difficulty in speech due to prosthesis size (palate and flanges), inconvenience and lack of confidence in patients due to less retentive prosthesis. The patients wearing partial dentures often exhibit greater mobility of abutment teeth, plaque retention, increased bleeding on probing, more incidences of caries and accelerated bone loss in the edentulous regions.
Another modality of restoration of missing teeth is fixed partial denture, which takes the support of adjacent teeth. Fixed partial dentures provide better masticatory efficiency, comfort and added confidence to patients. But, it needs the preparation of the adjacent healthy teeth. Further caries, sensitivity and periodontal disease of the abutments are seen in fixed partial denture patients in the long-term.
The latest modality of treatment of partial and completely edentulous patients is dental implants (Figs 1.1 and 1.2).
Dental implants are made of biocompatible materials and they are surgically inserted into the jawbone primarily as a prosthodontic foundation. The endosteal dental implants or root form implants are commonly used. Endosteal dental implants are similar to the natural tooth root and restoration of missing teeth does not need adjacent tooth support primarily. Also, implant stimulates the supporting bone and maintains its dimensions similar to that of healthy roots. Implant supported prosthesis does not require soft tissue support and improves oral comfort. Thus, implant supported prosthesis offers several advantages over the removable and fixed partial dentures.
HISTORY
‘The first sub-periosteal implant was originally developed and placed in the United States by Gershokoff and Goldberg in 1949. Later on thousands of such implants have been placed. But, the advent of two-stage endosseous root form implants has 5affected those sub-periosteal cases that have more than 10 mm of residual vertical bone available in the symphyseal area of the mandible. Also the transmandibular implant may be an option for cases with less than 7 mm of the vertical symphyseal bone.
The endosseous implants may be root forms or blade forms. The root form implants are most often used for the restoration of partially or completely edentulous arches.
The ancient Chineese 4000 years ago, Egyptians 2000 years ago and Incas 1500 years ago knew to use the root form implants. The most recent history was in 1809, Maggiolo introduced the usage of gold in the shape of the tooth root. In 1887, Harris reported the usage of porcelain and in early 1900s. Lambotte fabricated implants of many materials and identified corrosion of these metals in the body tissues. In 1909, Greenfield gave latticed cage design, made of iridioplatinum. In 1938, Strock introduced surgical cobalt chromium molybdenum alloy for implantation. He designed a two-stage screw implant in 1946 that was implanted without a permucosal post. The first submerged implant placed by Strock was functioning even 50 years later.
The implant interface was described then as “ankylosis”, which may be equated to the clinical term “rigid fixation”.
In 1948, Formiggini, developed the first successful metal spiral screw implant and is regarded as the “Father of Modern Endosseous Implantology”.
In 1960, titanium blade implant was introduced by Linkow. In 1987, Weiss stated the development of a functionally oriented, peri-implant connective 6tissue that dampen or absorb the forces of mastication, “the fibro-osseous integration”. An initial clinical report gives the restoration of a maxillary lateral incisor with blade type implants in a case of narrow ridge of l.2 mm width, with a clinical success of 12 years. Some examples of the blade forms are Biolox (fabricated from aluminum oxide) and Osteoplate-2000, Oraltronics.
The term “osseointegration” was first defined by Branemark. He did extensive experimental studies on the microscopic circulation of bone marrow healing which greatly influenced the implant concepts. One of the best known implant system used worldwide is the Branemark system. In 1965; ‘Branemark implants’ were placed in patients for the first time. They were of screw-type implants made of pure titanium, without any special surface modification. Unlike his predecessors, Branemark studied every aspect of implant design, including biological, mechanical, physiogical and functional phenomena relative to the success of the endosteal implant.
The intramobile cylinder (IMZ) has been used clinically since 1974, which has an elastic compensating component inserted between the implant and the prosthetic superstructure.
The elastic intramobile element acts as a periodontal ligament of a natural tooth providing shock absorption and also a force distribution. The IMZ system is made available with surface coatings (such as titanium plasma spray and apatite coating). In the same year (1974), the Tubingen implant was developed by Prof Schulte. The Frialit-Tubingen 7immediate implant is the first root-shaped implant system adapted to the socket, made of bio-ceramic with regularly spaced lacunae. The Frialit-2 implant system introduced later (1992) is a root analog stepped design in the form of stepped cylinders and stepped screws. The ITI Bonefit implant system was developed by the “International Team for Implanto-logy’ (ITI) and consists of three different basic types: hollow cylinder, hollow screw and solid screw, may be a single-stage or a two-stage system. The two stage system is placed transgingivally in contrast to other systems. In 1977, the Straumann Co. in collaboration with Dr Phillipe Ledermann, developed the TPS (Titanium Plasma Sprayed) screw type implant similar to the single stage ITI screw implant. This implant was mainly designed to use in the edentulous mandible. The Ha-Ti (Hand-Titanium) implant system clinically used since 1985 is a conical, step-screw, pure titanium implant with self tapping threads.
For centuries, people have attempted to replace missing teeth using implantation.
In this way there are over 100 different dental implant systems commercially available world wide for the restoration of partially or completely edentulous arches. ‘To a beginner, restoration using the dental implants has become difficult as one has to choose the right implant system. Also it is important to know that the Council on Dental Materials, Instruments and Equipment (CDMIE) which is an arm of American Dental Association (ADA) has established an “acceptance program” to set standards for implant quality control.8
SCOPE OF IMPLANT TREATMENT
Over the last decade, reconstruction with implants has changed considerably. Implants are basically used in prosthetic rehabilitation in edentulous, partially edentulous, and single tooth cases. Its applications in new areas such as maxillofacial prosthodontics, the anchoring of hearing aids and in orthodontic therapy are also considered nowadays. If the potential benefits of such uses are to be maximized, then it is essential that implant treatment be selected on logical basis and placed within the context of the full range of treatment modalities available in restorative dentistry. Today's implants practitioner considers a broad and complex set of interwoven factors before formulating an implant-treatment plan. The entire scope of treatment has progressed originally from the tooth replacement to surgically oriented implant reconstruction and more restorative approach for rehabilitation of stomatognathic system.
SUMMARY
The use of endosteal implants for dental rehabilitation of patients represents one of the most technologically advanced forms of dentistry available today. Endosteal implants are effective and appropriate for replacing single teeth, as well as for rehabilitating edentulous arches. Basic advantage of implants is to preserve the alveolar bone similar to the healthy tooth. Dental implants can stabilize maxillofacial prosthesis. With the help of all health care professionals involved in the care of these patients will increase success rates.