Dental Implants are classified according to:
1. Implant Design
2. Implant Properties
3. Implant attachment mechanism

Types of Implants According to Design

1. Endosteal Implant is a device that is placed into the alveolar and/or basal bone of maxilla or mandible and transects only one cortical plate.

Shapes
a. cylindrical cones
b. thin plates

Example of Endosteal Implant
a. Blade Implant was developed independently in 1976 by 2 groups led by Linkow and Roberts. it is consists of thin plates embeded into bone. It is used for narrow spaces such as posterior edentulous areas.
b. Ramus Frame Implant is a horse shoe shaped stainless steel device inserted into the mandible from one retromolar pad to the other, passing through the anterior symphysis area.
c. Root Form Implants was designed to mimic shape of tooth root for directional load distribution and for proper positioning in the bone. It has the most documented success level of the endosteal implants.

2. Subperiosteal Implant employs an implant substructure and superstructure. It was first developed by Dahl on 1940 and refined by Berman in 1951. The custom cast frame is placed directly beneath the periosteum overlying the bony cortex. It can be used to restore partially dentate or completely edentuluos jaws. It is used when there is inadequate bone for endosseous implants.

3. Transosteal Implants combine the subperiosteal and endosteal components. It penetrates both cortical plates and passes through the full thickness of the alveolar bone. Mandibular Staple Implant was developed by Small in 1968 and modified by Bosker in 1982 with transmandibular implants (TMI) made of gold alloy.

4. Epithelial Implant is inserted into the oral mucosa. It is associated with a very simple surgical technique. It requires the mucosa be used as attachment site for the metal inserts.

Implant Properties

Implant biomaterial can be classified according to their composition and their physical, mechanical, chemical and biological properties. Ranked comparisons of properties , elastic moduli, tensile strength and ductility are oftenly included in the Classification.

Attachment Mechanisms

Classification of Implants According to the Nature of Attachment Mechanisms

1. Periodontal Fibers is the most ideal form of attachment but there is no known implant material or system at present that can stimulate the groth of these fibers.
2. Osseointegration is the direct contact between bone and the surface of implant. It is the direct adaptation of bone to implants without any other intermediate interstitial tissue.
It can also be achieved through the use of bioactive materials that simulate the formation of bone along the surface of the implant. Second mechanism of osseointegration involved de novo bone formation wherein a mineralized interfacial matrix is deposited along the implant surface.

Reference

Anusavice K: Phillips’s Science of Dental Materials, Saunders, Elsevier Science, 2003