Modern Dental Implantology: Classification of Implants

Ⅰ Classification of Implants

Based on the method of implantation, implants can be classified into endosteal implants, subperiosteal implants, and transmandibular implants. The corresponding implants are referred to as endosteal implants, subperiosteal implants, and transmandibular implants, respectively. Additionally, based on their function, implants can be categorized into dental implants, orthodontic anchorage implants, and craniofacial implants.

Ⅱ Endosteal Implants

Endosteal implants (endosseous implants) can be divided into root form implants, blade form implants, and mini implants.

Ⅲ Root Form Implants

One of the characteristics of modern implant technology is that the shape of the implant resembles the natural tooth root. This type of implant is known as a root form implant and is a type of endosteal implant. Currently, root form implants are made from pure titanium or titanium alloy, with surfaces either mechanically polished or roughened to achieve excellent osseointegration, ensuring long-term stability within the jawbone.

When describing implant shapes, unless otherwise specified, "implant" generally refers to root form implants. The basic shapes of root form implants include screw root form implants, cylinder root form implants, and combination root form implants.

Combination root form implants have features of both screw and cylinder implants, such as step-screw implants and step-cylinder implants. The threads of screw implants are often designed in various shapes, including V-shaped, square, and rectangular. Implants can be solid or hollow, with hollow implants being rarely used due to their tendency to break. The surgical methods for placing root form implants include submerged and non-submerged techniques.

The placement methods for implants are divided into screw-in (like screw implants), press-fit (like cylinder implants and step-cylinder implants), and press-in/screw-in (like step-screw implants). Some screw implants also have self-tapping capabilities.

Root form implants are suitable for various types of tooth loss and all implant restoration methods, such as single crowns, splinted crowns, bridges, and fixed, removable, and overdenture prostheses.

The minimum required bone volume is a vertical height greater than 8mm and a mesiodistal and buccolingual width greater than 6.3mm. When bone volume is insufficient, bone grafting or guided bone regeneration techniques can be used to increase bone volume.

From a functional perspective, many products have emerged with functional implant names, such as esthetic implants, immediate implants, and immediate loading implants.

Ⅳ Blade Form Implants

Blade form implants have various shapes resembling blades. They are mainly used when the buccolingual width of the available bone is insufficient and cannot be augmented.

Blade form implants include preformed and custom-cast versions, both of which can be trimmed and shaped during surgery. Due to their weak necks, which are prone to fracture and can damage osseointegration, they are now rarely used.

Ⅴ Mini Implants

Mini implants are small-diameter, self-tapping implants with a narrow neck, such as Crete Mince and MDI (mini dental implants). They are implanted between natural teeth, between implants, or between natural teeth and implants. They are primarily used to increase the retention of fixed bridges and provide long-term support for the superstructure of implant bridges. They can also be used for temporary support of transitional dentures in fixed implant restorations.

Ⅵ Subperiosteal Implants

Subperiosteal implants are placed between the periosteum and the bone surface and are used in cases of severe jawbone atrophy where endosteal implants cannot be utilized. Subperiosteal implants are mainly used to support fixed or overdenture implant restorations for partial and complete dentures.

The manufacturing process of subperiosteal implants is extremely complex (requiring design and casting on an impression or using CAD-CAM technology), and the surgical exposure range is large, making them rarely used clinically.

Ⅶ Transmandibular Implants

Transmandibular implants are used in cases of severe mandibular atrophy to support overdentures. These implants consist of a horizontal retention plate fixed below the lower border of the mandible, retention screws, a threaded column passing through the mandible, and an abutment. A submental incision is required, and the mandible must have a certain thickness: a vertical height greater than 6mm and a buccolingual thickness greater than 5mm.

Ⅷ Orthodontic Anchorage Implants

Orthodontic anchorage implants include both endosteal and subperiosteal types, and they are used for orthodontic anchorage purposes.

Ⅸ Craniofacial Implants

Craniofacial implants are used to support and retain maxillofacial prostheses, such as ear, eye, and nose prosthetics, as well as dental prostheses.