Platform switching

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This dental radiograph displays two identical 5.0 mm diameter Biomet 3i tapered dental implants placed into the lower right mandible. The healing abutment on the more posterior implant [left] is platform matched (it shares the same 5.0 mm diameter as the implant platform), while the healing abutment on the more anterior implant [right] is platform switched (it possesses a 4.1 mm diameter). Platform switch.jpg
This dental radiograph displays two identical 5.0 mm diameter Biomet 3i tapered dental implants placed into the lower right mandible. The healing abutment on the more posterior implant [left] is platform matched (it shares the same 5.0 mm diameter as the implant platform), while the healing abutment on the more anterior implant [right] is platform switched (it possesses a 4.1 mm diameter).

In dentistry, platform switching is a method used to preserve alveolar bone levels around dental implants. 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.

Dentistry branch of medicine

Dentistry, also known as Dental and Oral Medicine, is a branch of medicine that consists of the study, diagnosis, prevention, and treatment of diseases, disorders, and conditions of the oral cavity, commonly in the dentition but also the oral mucosa, and of adjacent and related structures and tissues, particularly in the maxillofacial area. Although primarily associated with teeth among the general public, the field of dentistry or dental medicine is not limited to teeth but includes other aspects of the craniofacial complex including the temporomandibular joint and other supporting, muscular, lymphatic, nervous, vascular, and anatomical structures.

Dental implant surgical component that interfaces with the bone of the jaw or skull to support a dental prosthesis.

A dental implant is a surgical component that interfaces with the bone of the jaw or skull to support a dental prosthesis such as a crown, bridge, denture, facial prosthesis or to act as an orthodontic anchor. The basis for modern dental implants is a biologic process called osseointegration, in which materials such as titanium form an intimate bond to bone. The implant fixture is first placed so that it is likely to osseointegrate, then a dental prosthetic is added. A variable amount of healing time is required for osseointegration before either the dental prosthetic is attached to the implant or an abutment is placed which will hold a dental prosthetic.

Contents

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, 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. crowns, dentures, etc.) to be cemented on, screwed down or otherwise attached.

Osseointegration is the direct structural and functional connection between living bone and the surface of a load-bearing artificial implant. A more recent definition defines osseointegration as "functional ankylosis ", where new bone is laid down directly on the implant surface and the implant exhibits mechanical stability. Osseointegration has enhanced the science of medical bone and joint replacement techniques as well as dental implants and improving prosthetics for amputees.

Crown (dentistry)

A crown, sometimes known as dental cap, is a type of dental restoration which completely caps or encircles a tooth or dental implant. Crowns are often needed when a large cavity threatens the ongoing health of a tooth. They are typically bonded to the tooth using a dental cement. Crowns can be made from many materials, which are usually fabricated using indirect methods. Crowns are often used to improve the strength or appearance of teeth. While inarguably beneficial to dental health, the procedure and materials can be relatively expensive.

Historically, the diameter 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. [1]

Diameter straight line segment that passes through the center of a circle

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 the diameter of a sphere.

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. [1]

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, 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) and hard (bone) tissue responses to these platform switched implants, leading many implant companies to incorporate platform switching into their implant systems even for narrower-body implants. [2] [3]

Serendipity means an unplanned, fortunate discovery. Serendipity is a common occurrence throughout the history of product invention and scientific discovery. In recent years, the phenomenon has become a potential design principle in online activity for preventing filter bubbles and echo chambers.

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 infiltrate that forms a zone around the IAJ. [4] 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. [3]

Implant-abutment junction

In implant dentistry, the implant-abutment junction (IAJ) refers to the location of intimate contact between a dental implant and its restorative abutment.

Inflammation signs of activation of the immune system

Inflammation is part of the complex biological response of body tissues to harmful stimuli, such as pathogens, damaged cells, or irritants, and is a protective response involving immune cells, blood vessels, and molecular mediators. The function of inflammation is to eliminate the initial cause of cell injury, clear out necrotic cells and tissues damaged from the original insult and the inflammatory process, and initiate tissue repair.

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 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. [5]

Proposed benefits

X indicates the vertical dimension known as biologic width, while Y indicates the horizontal component of the biologic width. (Legend: Bone is purple, implant is gray) Horizontalcomponentof biologic width.jpg
X indicates the vertical dimension known as biologic width, while Y indicates the horizontal component of the biologic width. (Legend: Bone is purple, implant is gray)

Biologic width

Very much like teeth, implants exposed to the oral cavity exhibit what is known as a minimum biologic width. [6] Biologic width is the minimum thickness of soft tissue that envelops the alveolar bone that surrounds teeth and into which endosseous dental implants are placed, and has classically been described as having a mean of 2.04 mm: 0.97 mm of epithelium and 1.07 mm of underlying soft connective tissue. [7]

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 [8] 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 [9] and has been well researched. [10]

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. [10]

Horizontal component affecting crestal bone loss between adjacent implants

Crestal bone height as a function of distance between implants. [10]
Distance between implantsBone loss
≤3 mm apart (n=25)1.04 mm
>3 mm apart (n=11)0.45 mm

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. [10] This was first reported by Dennis Tarnow et al. in 2000 in a study that demonstrated that the distance between the most coronal aspect of the inter-implant bone and an imaginary line drawn between the implant platforms was greater when adjacent implants were placed ≤3 mm apart.

Increased loss of inter-implant bone in the vertical dimension due to this overlap of horizontal components of the adjacent implants' biologic width can have ramifications in the anterior esthetic zone because it decreases bony support for the interproximal papilla between implants. [9] 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 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, [9] 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 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. [11] Platform switching has been shown to have the potential to reduce the vertical bone resorption by as much as 70%. [12]

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. [3]

Related Research Articles

Periodontal fiber group of specialized connective tissue fibers that essentially attach a tooth to the alveolar bone within which it sits

The periodontal ligament, commonly abbreviated as the PDL, is a group of specialized connective tissue fibers that essentially attach a tooth to the alveolar bone within which it sits. It inserts into root cementum one side and onto alveolar bone on the other.

Periodontology or periodontics is the specialty of dentistry that studies supporting structures of teeth, as well as diseases and conditions that affect them. The supporting tissues are known as the periodontium, which includes the gingiva (gums), alveolar bone, cementum, and the periodontal ligament. A person who practices this specialty is known as a periodontist.

Alveolar process thickened ridge of bone that contains the tooth sockets (dental alveoli) on bones that hold teeth

The alveolar process is the thickened ridge of bone that contains the tooth sockets on the jaw bones that hold teeth. In humans, the tooth-bearing bones are the maxilla and the mandible. The curved part of each alveolar process on the jaw is called the alveolar arch.

Edentulism

Edentulism or toothlessness is the condition of being toothless to at least some degree; in organisms that naturally have teeth (dentition), it is the result of tooth loss. Loss of some teeth is called partial edentulism, whereas loss of all teeth is called complete edentulism. Persons who have lost teeth are edentulous (edentate), whereas those who have not lost teeth can be called dentate by comparison. For example, a scientific study may include a partially edentulous group and a healthy dentate control group.

Sinus lift

Maxillary sinus floor augmentation is a surgical procedure which aims to increase the amount of bone in the posterior maxilla, in the area of the premolar and molar teeth, by lifting the lower Schneiderian membrane and placing a bone graft.

Gingival graft

A gingival graft, also called gum graft or periodontal plastic surgery, is a generic name for any of a number of periodontal surgical procedures in which the gum tissue is grafted. The aim may be to cover exposed root surfaces or merely to augment the band of keratinized tissue.

Crown lengthening

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 greater amount of tooth structure for the purpose of subsequently restoring the tooth prosthetically. However, other indications include accessing subgingival caries, accessing perforations and to treat aesthetic disproportions such as a gummy smile. There are a number of procedures used to achieve an increase in crown length.

In dentistry, enamel matrix derivative (EMD) is an extract of porcine fetal tooth material used to biomimetically stimulate the soft and hard tissues surrounding teeth to regrow following tissue destruction.

Furcation defect

In dentistry, a furcation defect is bone loss, usually a result of periodontal disease, affecting the base of the root trunk of a tooth where two or more roots meet. The extent and configuration of the defect are factors in both diagnosis and treatment planning.

Socket preservation or alveolar ridge preservation (ARP) is a procedure to reduce bone loss after tooth extraction to preserve the dental alveolus in the alveolar bone. A platelet rich fibrin (PRF) membrane containing bone growth enhancing elements is placed in the wound or a bone grafting material or scaffold is placed in the socket of an extracted tooth at the time of extraction. The socket is then directly closed with stitches or covered with a non-resorbable or resorbable membrane and sutured. After extraction, jaw bone has to be preserved to keep the socket in its original shape. Without socket preservation, the bone quickly resorbs resulting in 30–60% loss in bone volume in the six months after dental extraction. The jaw bone will never revert to its original shape once bone is lost and tissue contour has changed.

Peri-implantitis

Peri-implantitis is a destructive inflammatory process affecting the soft and hard tissues surrounding dental implants. The soft tissues become inflamed whereas the alveolar bone, which surrounds the implant for the purposes of retention, is lost overtime. The bone loss involved in peri-implantitis differentiates this condition from peri-mucositis, a reversible inflammatory reaction involving only the soft tissues around the implant.

In dentistry, numerous types of classification schemes have been developed to describe the teeth and gum tissue in a way that categorizes various defects. All of these classification schemes combine to provide the periodontal diagnosis of the aforementioned tissues in their various states of health and disease.

Running room

In implant dentistry, running room refers to the apico-coronal distance between the platform of a dental implant and the gingival margin. It is a critical factor in restorative implant dentistry because it is effectively the "vertical distance [available subgingivaly] to make a transition from the smaller diameter prosthetic platform of an implant to the larger cross-sectional cervical shape of the tooth being restored." The term was coined by Jonathan Zamzok, a Manhattan prosthodontist, in the late 1990s.

Peri-implant mucositis is defined as an inflammatory lesion of the peri-implant mucosa in the absence of continuing marginal bone loss.

Clinical attachment loss (CAL) is the predominant clinical manifestation and determinant of periodontal disease.

Bicon Dental Implants

Bicon Dental Implants is a privately owned company located in Boston, MA. The company specializes in short dental implants that use a locking taper or cold welding connection to secure the abutment to the implant. Bicon is notable and worthy of mention for the following three reasons: First, Bicon implants are extremely short in length. The size of Bicon implants allow them to be placed in regions that are crowded with natural teeth and/or implants, or in regions that would otherwise require bone grafting. Second, the implants do not have the screw-form design typical of other available implants. Third, the abutments are connected to the implant via a locking taper. This is notable from both a medical and engineering standpoint as no other implant company offers an implant with a biological seal at the implant/abutment interface; almost all other implants possess an internal screw to connect their abutments.

A complete denture is a removable appliance used when all teeth within a jaw have been lost and need to be prosthetically replaced. In contrast to a partial denture, a complete denture is constructed when there are no more teeth left in an arch, hence it is an exclusively tissue-supported prosthesis. A complete denture can be opposed by natural dentition, a partial or complete denture, fixed appliances or, sometimes, soft tissues.

Overdenture

Overdenture is any removable dental prosthesis that covers and rests on one or more remaining natural teeth, the roots of natural teeth, and/or dental implants. It is one of the most practical measures used in preventive dentistry. Overdentures can be either tooth supported or implant supported. It is found to help in the preservation of alveolar bone and delay the process of complete edentulism.

References

  1. 1 2 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.
  2. ↑ Baumgarten H, et al. A new implant design for crestal bone preservation: Initial observations and case report. Pract Proceed Aesthet Dent 2005;17:735-740.
  3. 1 2 3 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
  4. ↑ Ericsson I, et al. Different types of inflammatory reactions in peri-implant soft tissues. J Clin Perio 1995;22:255-261.
  5. ↑ Atieh MA, et al. Platform switching for marginal bone preservation around dental implants: A systematic review and meta-analysis. J Perio 2010;81:1350-1366.
  6. ↑ Cochran DL, et al. Biologic width around titanium implants: a histometric analysis of the implanto-gingival junction around unloaded and loaded non-submerged implants in the canine mandible. J Perio 1997;68:186-198.
  7. ↑ Gargiulo AW, et al. Dimensions and relations of the dentogingival junction in humans. J Perio 1961;32:261-267.
  8. ↑ Hermann JS, et al. Crestal bone changes around titanium implants: a radiographic evaluation of unloaded non-submerged and submerged implants in the canine mandible. J Perio 1997;68:1117-1130.
  9. 1 2 3 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.
  10. 1 2 3 4 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.
  11. ↑ Greenstein G, et al. Treatment planning implant dentistry with a 2 mm twist drill. Compendium 2010;31(2):2-10
  12. ↑ Vela-Nebot X, et al. Benefits of an implant platform modification technique to reduce crestal bone resorption. Implant Dent 2006;15:313–320.

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