Up until recently, the only treatment options for tooth loss were bridges and dentures. Today, dental implants are also offered as replacement for missing teeth.
Dental implants are substitute tooth roots. Their purpose is to give a base for a patient’s permanent or substitute teeth. The implants are created to parallel a patient’s natural teeth structure.
The implant industry, or treatments to change lost or missing teeth under surgery, is expanding in the United States. The number of implants performed by dentists in 2006 exceeded 5 million, with a failure rate of 2 to 4 percent. By 2018, the dental implant and prosthetic market in the United States is predicted to reach $6.4 billion. The orthopedics market is predicted to reach $46 billion.
Over 40,000 arthroplasties in the hip and knee need revision every year. With a market this strong, it is essential to find methods to make implants stable. Implant stability is based on the principal concept of osseointegration, a structural and functional link between living bone and the exterior of an artificial implant. Osseointegration happens when dental implants placed in jawbones are effective. The metal section of the implant is placed into the jawbone and the bone fastens onto the implant. It extends around the implant and reinforces it.
Osseointegration can be referred to as bone connection. Introduced by Gottlieb Leventhal in 1951 and later coined by Per-Ingvar Branemark in 1983, osseointegration occurs without the exchange of any soft tissue. There are many factors that determine whether an implant will osseointegrate, including drilling techniques, implant macrogeometry—the surface texture of the implant frame—implant nanometer and micrometer scale and quality of host bone.
Osseointegration can be split into two scopes: primary stability and secondary stability. Primary stability is the initial interlocking between implant and osseous tissue, or tissue that creates the section of the bone organs that make up the skeletal system. This is measured through insertion torque, which represents the defiance of bone during implant placement. In order for an implant to osseointegrate, it must have adequate primary stability. The torque at which an implant is placed into bone is the way of measuring primary stability and is usually around 30 Newtons.
Osseointegration is also dependent on secondary stability, which is the growth of bone through the healing chambers of an implant. Implants are made of titanium, as it is the best metal alloy for osseointegration and is made up of threads or healing chambers.
Each of these healing chambers is meant to allow for bone to grow through it so that the bone can be anchored around the implant and hold it in place.Secondary stability is measured through bone implant contact and bone area fraction occupancy. An implant from an animal will be placed in a system and left for a certain number of weeks to allow for healing. On further analysis, it appears that there is usually a dip in stability between the beginning and end period of healing.
This is due to the transition between primary and secondary stability. As the bone that was already in this area undergoes necrosis—an abnormal collapse of cells—and the new bone begins to grow, there is a dip in stability.
Osseodensification provides a new method of drilling for implants that takes advantage of the drilling site. Currently, almost all drilling techniques are done in subtractive drilling. This means that bone spicules, a label used to describe a symptom connected to an eye disease, that are present in the osteotomy site would be removed during instrumentation, or the use of tools when treating a patient.
However, this new method would densify the bone. It is as if someone were drilling into drywall. When drilling into drywall, plaster falls out of the drilling site. However, with this new drilling technique, it will get densified around the site where there was a surgical operation to shorten or expand the bone. This creates a ring around the hole.
This is important because it allows for the greater production of bone chips, which are nucleating bone surfaces. These bone chips will be present in the healing chambers and allow for more bone growth in the healing chambers, which will lead to better secondary stability and thus osseointegration.
This technique is especially useful for individuals with osteoporosis, a widespread disease that weakens bones. There is greater osteoclast activity in the teeth as compared to in the body, which can lead to a lower bone density.
In places with low bone density, it is difficult to place implants, and thus this method will prove very helpful. It is also useful for patients with inadequate alveolar ridges, the hard ridges in the mouth behind the roots of the teeth.
The bone in the mandible, the lower jaw of a vertebrate animal, is not enough for the placement of an implant. This drilling technique allows bone to be densified so there is more bone to provide stability.
This method is being tested with different drilling speeds as it has been discovered that faster drilling speeds lead to better osseointegration. Different factors are also being tested, such as putting the implants through acid etching, the cutting of a hard surface by a destructive chemical, to increase surface tension and placing the implant with a certain diameter in relation to the osteotomy site.