dentistry Dentistry, also known as dental medicine and oral medicine, is the branch of medicine focused on the teeth, gums, and mouth. It consists of the study, diagnosis, prevention, management, and treatment of diseases, disorders, and conditions o ...

, platform switching is a method used to preserve

alveolar bone The alveolar process () or alveolar bone is the thickened ridge of bone that contains the tooth sockets on the jaw bones (in humans, the maxilla and the mandible). The structures are covered by gums as part of the oral cavity. The synonymous ter ...

levels around

dental implant A dental implant (also known as an endosseous implant or fixture) is a prosthesis that interfaces with the bone of the jaw or skull to support a dental prosthesis such as a crown, bridge, denture, or facial prosthesis or to act as an orthodonti ...

s. The concept refers to placing screwed or friction fit restorative abutments of narrower diameter on implants of wider diameter, rather than placing abutments of similar diameters, referred to as ''platform matching''. Discovered by accident in the late 1980s, the benefits of platform switching have become the focus of implant-related research with increasing frequency. Numerous peer-reviewed articles and recent systematic reviews have revealed that platform switching can be considered a means of preventing initial peri-implant bone loss.

Concept

After being placed in a surgical procedure, dental implants undergo

osseointegration Osseointegration (from Latin ''osseus'' " bony" and ''integrare'' "to make whole") is the direct structural and functional connection between living bone and the surface of a load-bearing artificial implant ("load-bearing" as defined by Albrekt ...

, during which time the surrounding bone grows into intimate contact with the surface of the implants and the implants become fused to the bone. When this process has been deemed to have occurred to a sufficient extent, the implants are fitted with restorative abutments in order to allow dental restorations (e.g.

crown A crown is a traditional form of head adornment, or hat, worn by monarchs as a symbol of their power and dignity. A crown is often, by extension, a symbol of the monarch's government or items endorsed by it. The word itself is used, partic ...

denture Dentures (also known as false teeth) are prosthetic devices constructed to replace missing teeth, and are supported by the surrounding soft and hard tissues of the oral cavity. Conventional dentures are removable (removable partial denture or ...

s, etc.) to be cemented on, screwed down or otherwise attached. Historically, the

diameter In geometry, a diameter of a circle is any straight line segment that passes through the center of the circle and whose endpoints lie on the circle. It can also be defined as the longest chord of the circle. Both definitions are also valid for ...

of the abutment matched the diameter of the implant platform; for example, a 4.8 mm-wide abutment was placed on a 4.8 mm-wide implant—this can be termed ''platform-matching''.Canullo L, et al. Platform switching and marginal bone-level alterations: The results of a randomized-controlled trial, ''Clin Oral Implants Res'' 2010;21:115-121. When ''platform switching'', a narrower abutment diameter for a given implant platform diameter is used; for example, a 4.8 mm-wide implant may be restored with a 3.8 mm-wide or 4.2 mm-wide abutment.

History

The introduction of wide-diameter dental implants in the late 1980s created a situation in which mismatched standard-diameter abutments were used simply because of the lack of commercial availability of components to match the wide-diameter implants.

Serendipitously Serendipity is an unplanned fortunate discovery. Serendipity is a common occurrence throughout the history of product invention and scientific discovery. Etymology The first noted use of "serendipity" was by Horace Walpole on 28 January 1754. I ...

, it was found that these implants exhibited less-than-expected initial crestal bone loss—the effect of bone modeling at the crest of the alveolar bone into which dental implants are placed—during healing. Several early clinical reports demonstrated enhanced soft (

gingiva The gums or gingiva (plural: ''gingivae'') consist of the mucosal tissue that lies over the mandible and maxilla inside the mouth. Gum health and disease can have an effect on general health. Structure The gums are part of the soft tissue lini ...

) and hard (

bone A bone is a Stiffness, rigid Organ (biology), organ that constitutes part of the skeleton in most vertebrate animals. Bones protect the various other organs of the body, produce red blood cell, red and white blood cells, store minerals, provid ...

) tissue responses to these platform switched implants, leading many implant companies to incorporate platform switching into their implant systems even for narrower-body implants.Lazzara RJ, et al. Platform switching: A new concept in implant dentistry for controlling postoperative crestal bone levels. ''Int J Perio Rest Dent'' 2006;26:9-17

Rationale

It has been observed that some degree of bone resorption occurs at the crest of bone following implant placement. Through extensive investigation, it has been discovered that the extent of bone resorption is related to both the texture of the surfaces of the implant and abutment at and the morphology of the implant-abutment junction (IAJ). A number of investigators have zeroed in on the proposed inflammatory

cell Cell most often refers to: * Cell (biology), the functional basic unit of life Cell may also refer to: Locations * Monastic cell, a small room, hut, or cave in which a religious recluse lives, alternatively the small precursor of a monastery w ...

infiltrate that forms a zone around the IAJ. Although not yet fully understood, the current theory of the benefit of platform switching is related to the physical repositioning of the IAJ away from the outer edge of the implant and the surrounding bone, thereby containing the inflammatory infiltrate within the width of the platform switch. In line with the supposed mechanism of action, it is not merely the introduction of a platform switch, but the ''magnitude'' of the implant-abutment diameter mismatch, that makes a difference. Difference in bone levels became

statistically significant In statistical hypothesis testing, a result has statistical significance when it is very unlikely to have occurred given the null hypothesis (simply by chance alone). More precisely, a study's defined significance level, denoted by \alpha, is the p ...

when the implant-abutment diameter mismatch was greater than 0.8 mm, providing a 0.4 mm circumferential width of platform switch when the center of the abutment is aligned with and fixed to the center of the implant.

Proposed benefits

Biologic width

Very much like teeth, implants exposed to the oral cavity exhibit what is known as a minimum

biologic width Crown lengthening is a surgical procedure performed by a dentist, or more frequently a specialist periodontist. There are a number of reasons for considering crown lengthening in a treatment plan. Commonly, the procedure is used to expose a greate ...

. Biologic width is the minimum thickness of soft tissue that envelops the

that surrounds teeth and into which endosseous dental implants are placed, and has classically been described as having a

mean There are several kinds of mean in mathematics, especially in statistics. Each mean serves to summarize a given group of data, often to better understand the overall value (magnitude and sign) of a given data set. For a data set, the ''arithme ...

of 2.04 mm: 0.97 mm of

epithelium Epithelium or epithelial tissue is one of the four basic types of animal tissue, along with connective tissue, muscle tissue and nervous tissue. It is a thin, continuous, protective layer of compactly packed cells with a little intercellul ...

and 1.07 mm of underlying soft

connective tissue Connective tissue is one of the four primary types of animal tissue, along with epithelial tissue, muscle tissue, and nervous tissue. It develops from the mesenchyme derived from the mesoderm the middle embryonic germ layer. Connective tiss ...

. Around implants, biologic width formation has classically led to about 1.5 - 2 mm of bone loss in the vertical dimension at the coronal aspect of the implants because the abutment that attaches to the implant was often removed many times to allow for impression taking, abutment changing and other related clinical functions. As such, the epithelial and connective tissue protection for the bone was unable to reliably form on the continuously disrupted abutment attachment surface and in reaction to this, bone loss occurred on the implant in order to provide the dimension necessary for the epithelium and soft connective tissue attachment to the implant fixture itself—this defined early implant placement and was often colloquially referred to as "bone loss to the first thread." This vertical loss of bone (''X'' in the diagram at right) diminishes the bone-to-implant contact, contributing to a potential decrease in long-term biomechanical stability and has been well researched.Tarnow DP, et al. The effect of inter-implant distance on the height of the inter-implant bone crest. ''J Perio'' 2000;71:546-549.

Horizontal component of biologic width

Recently, the lateral extent of this vertical bone loss around implants has been investigated—in other words, the thickness of bone loss that exists as a halo around the implant at its most coronal aspect—and has been termed the ''horizontal component of the biologic width'' (''Y'' in the diagram at right), and research reveals that it is approximately 1.4 mm.

Horizontal component affecting crestal bone loss between adjacent implants

Because of this established mean horizontal dimension of the immediate crestal bone loss around dental implants, an issue arises when implants are placed into adjacent sites in the mouth. If the implants are placed too closely together, the overlap of the horizontal components of each implant's biologic width serves to increase the effective vertical crestal bone loss between the implants. This was first reported by

Dennis Tarnow Dennis Perry Tarnow (b. May 28) is an American dentist specializing in dental implant research. He is director of implant dentistry at Columbia University College of Dental Medicine and a speaker on the subject of implant dentistry.interproximal papilla between implants.Rodríguez-Ciurana X, et al. The effect of interimplant distance on the height of the interimplant bone crest when using platform-switched implants. ''Int J Perio Rest Dent'' 2009;29:141–151. By platform switching, implants can be placed closer to teeth and to each other while maintaining more crestal bone.

Horizontal component affecting buccal plate in narrow alveolar crests

Another clinical example in which the horizontal extent of crestal bone loss due to biologic width formation can negatively affect the peri-implant bony architecture is a situation in which the buccal plate of the alveolar process is very thin and lies wholly or substantially within the halo of the horizontal component of the biologic width. If an implant is placed within 1.5 mm of the

facial A facial is a family of skin care treatments for the face, including steam, exfoliation (physical and chemical), extraction, creams, lotions, facial masks, peels, and massage. They are normally performed in beauty salons, but are also a com ...

aspect of the buccal plate, it will be obliterated for a vertical distance of approximately 1.5-2 mm by the formation of the biologic width on the body of the implant fixture, which can lead to complications related to esthetics and long-term maintenance.

Platform switching and the vertical component of biologic width

Because the abutment is narrower in diameter than the implant fixture, a certain amount of the implant platform is exposed when an implant is platform switched, and this exposed area of the platform can allow for the tissues of the biologic width --

junctional epithelium The junctional epithelium (JE) is that epithelium which lies at, and in health also defines, the base of the gingival sulcus. The probing depth of the gingival sulcus is measured by a calibrated periodontal probe. In a healthy-case scenario, the pr ...

and soft connective tissue—to begin forming here, requiring less bone to be resorbed to make room for attachment on the lateral surface of the implant fixture. Platform switching has been shown to have the potential to reduce the vertical bone resorption by as much as 70%.Vela-Nebot X, et al. Benefits of an implant platform modification technique to reduce crestal bone resorption. ''Implant Dent'' 2006;15:313–320.

Platform switching and the horizontal component of biologic width

Furthermore, by platform switching implants that are 3 mm apart or less or within 1.5 mm of the facial aspect of a thin buccal plate, the implant-abutment junction (IAJ) is shifted onto the implant platform away from the peri-implant bone, mitigating the deleterious impact of the inflammatory zone at the microgap of the implant-abutment junction on the bone, allowing for a reduction in the horizontal extent of bone loss.

References

{{DEFAULTSORT:Platform Switching Prosthodontology