Implantology

Dental implantology is a set of surgical techniques aiming at the functional rehabilitation of a patient affected by total or partial edentulism, by using dental implants, i.e. metal elements surgically inserted in the mandibular or maxillary bone, or above them but under the gum. These elements are fitted with connectors to fasten them to fixed or removable prostheses, to enable chewing functionality. Such implants can have different shapes, they can be inserted in different positions, with different techniques, then connected to prostheses at different times.

Implants

Currently, implants are almost all made of titanium. The most commonly used are of the endosteal types; in most cases they are left submerged under the gum for a time period depending on their position. Dental implantology is subdivided in endosteal and justaosteal. This latter one utilizes only grid-shaped implants with an exposed fixed head. Depending on how they are loaded, they may be made of chrome-cobalt-molybdenum if they are not destined for osteointegration, or they may be made of titanium and inserted with appropriate surgical techniques to favor the formation of bone above their structure.

Endosteal implantology is much more widespread, uses cylinder or cone-shaped implants, more or less threaded on the outside and with variously shaped internal connections to support emerging abutments. Less frequently, implants are cylinders or cones without external threads, but with similar internal connections to support abutments, or screws with emerging heads machined as single pieces, therefore without any connections, or blades, or needles. Based on surgical protocol, we may have submerged or transmucosal implantology. Based on the time of use we may have immediate, early or deferred load.

Endosteal implantology is basically subdivided into two important schools: the Italian school and the Swedish school. Italian school implantology historically preceded the Swedish school, is less widespread, but conceptually just as important as the Swedish one.

The Italian school introduced the first implant specifically designed for immediate load, titanium for implant fabrication (Stefano M. Tramonte), the concept of biological space around implant bodies, and the intraoral welder (PL. Mondani).

The Swedish school introduced the osteointegration method, first developed by Invar Branemark, based on deferred load and aiming at making the implantological surgery more predictable. It utilizes endosteal, screw shaped implants with prosthetic connection, deferred load, which imposes a waiting time of 3 to 4 months in the mandible and 5 to 6 months in the maxilla. The original Branemark protocol and the implants utilized have been modified in various ways to shorten implant waiting times, and, in general, treatment times. The Swedish school has introduced very important innovations in production and surgical techniques: surface treatments for implant surfaces, tissue regeneration techniques for bone and mucosa, vertical and horizontal augmentation techniques. In general, the Swedish school has introduced surgical techniques aimed at making implant sites more adequate for the placement of their implants, because, by their very nature, they are less adaptable to anatomical conditions than the Italian school implants.

The material most frequently used for implant production is titanium, in commercially pure form or in its dental alloys. This is a biocompatible material that does not elicit any reaction from patient’s tissues (commonly known as rejection). Implants, positioned in the patient’s bone, are strongly incorporated in it by physiological bone regeneration actions, bringing to osteointegration, both in the case of deferred load (Swedish school) and in the case of immediate load (Italian school).

History

The history of the beginning of implantology is lost far back in time, and we do not know exactly when the idea of inserting an artificial tooth in a socket first started. We only know for sure that it was done. We have very interesting ancient archaeological findings displaying insertions of pieces of carved shells, minerals or bones. In more recent times, in the 19th century, the attempts to realize implantological surgeries multiplied, but were inevitably stifled by inadequate materials, primitive surgical techniques and anesthetics, the absence of antibiotics, and the total ignorance of occlusal principles.

In the first half of the 20th century we witness a great variety of attempts that are definitely more concrete, and the registration of numerous patents. We should remember the patent by Adams in 1938 regarding the first submerged implant, very similar to the subsequent one by Branemark, and the experiments by Formiggini, considered as the father of modern implantology (1947).

In 1961 the first implant specifically designed for immediate load was produced (Tramonte), presenting a biological space, and 1964saw the introduction of titanium in implantology (Tramonte). In the 1960s and 70s important histological studies were made by Pasqualini. In 1972 Garbaccio formulated the theory of bicorticalism and designed the related implant. In 1975 Mondani designed the intraoral welder (syncrystallizer), and at the end of the 70s the Branemark submerged implant became more frequently used, solving some of the prosthetic issues presented by immediate load implants. From then on, submerged implantology became widespread, thanks to its ease of use by inexperienced implantologists. Submerged implants multiplied, and were modified at a very rapid pace, in an attempt to correct the few chronic shortcomings affecting them, in spite of their great success.

As one of the first Klaus F. Müller described 1978 in his manual in German language all materials and methods used in the world of implant dentistry at this time. ^[1]

The x-ray controlling from 1976/77 shows an subperiosteal implant (according Cherchéve) in the maxilla. Two implant tripods (according Pruin) in the lower canine region and two stabilized blade Implants (according Heinrich) in the molar region.

Reconstructive surgery was developed at the same time, to solve many of the bone problems greatly limiting the use of submerged implants. Modern implantology, with immediate or deferred load, is a well tested and reliable discipline, capable of solving almost all edentulism problems, both functional and aesthetic.^{[citation needed]}

Types

3 types of implants are widely used and recognized as the most effective in masticatory and aesthetic functions restoration today :

1. Root form 2-piece implants
2. Compressive implants
3. Basal implants

§ Two component root form implants are used to create single and multiple restorations with delayed loading in the upper and lower jaws in all types of bone tissue. Modifications with active thread make the transgingival fixing and immediate loading possible, A sufficient volume of bone tissue is required in terms of height and width.

§ Compressive implants are a single-component implants with a compressive thread. They are used for multiple restorations with immediate loading in the upper and lower jaws with soft and hard bone in cases of deficiency of bone tissue. Flap and transgingival fixing can be used.

§ Basal implants are used to create multiple restorations in the upper and lower jaws and for placement directly into alveolar processes. The structural characteristics allow placement in zones with severe deficit of bone tissue width and height, in the sockets of extracted teeth, and transgingivally.

Osteointegration and fibrous integration

With our current knowledge, we attribute to the word osteointegration the meaning of union between bone and implant which remains stable under load, and guarantees chewing functionality without clinical signs or symptoms. We call fibrous integration a partial failure that allows the implant suffering it to function for a few years with a progressive loss of stability and increase of related issues (pain on pressure, soft tissue inflammation, etc.)

Implants can have different shapes: cylindrical body and prosthetic connection, threaded cylinder, conical, threaded conical, single piece without prosthetic connection, blade, needle, net. These last ones are much less used because of their inherent difficulty, but they adequate to solve particularly difficult situations where bone reconstruction techniques cannot be used.

Endosteal implants using deferred load protocols are the most commonly used, the most thoroughly clinically tested and the most verified with international protocols published on the most important scientific journals. However all implants osseointegrate, provided they are made of titanium. The word “osseointegrated” referred to the surgical technique in the past, to distinguish the deferred load the protocol producing osteointegration, as opposed to immediate loading protocol producing fibrous integration, therefore implant failure, can no longer be used with this meaning. Today we know that both implant surgeries, performed according to deferred load protocol and according to immediate loading protocol, result in osteointegration, provided that titanium implants are used. Titanium produces that particular union between implant and bone defined as osteointegration.

Implantology methods

Implantology methods consist mostly of two surgical techniques:

• two stage: the first stage is “submerged,” where the implant is inserted under the mucosa, which is then sutured. Then, after 2 to 6 months, the mucosa is reopened and an abutment is screwed on the implant;

• one stage: the implant is inserted, but its head is protruding out of the mucosa. It is then left to heal (always from two to six months) by osteointegration, or it can be loaded immediately, with an appropriate temporary or permanent prosthesis, depending on the case. Of course, single piece implants are only one stage, immediate loading implants.

Professional qualifications

Normally, a dentist or a surgeon trained as a dentist is dealing with dental implants. In Italy the professional specialty of “Implantologist” does not exist. In France, for instance, there is the “University diploma of surgery and implant prosthesis” (DUCPI), so that a non-specialized dentist should not position any implants beyond the maxillary sinus. Pre-prosthetic and pre-implantar surgery, which is the preparation of the alveolar bone for dental implant and prosthesis placement, are performed by the dentist, or, in some cases, by a maxillo-facial surgeon. Since these surgeries are specialized, it is a good practice to verify that the specialist chosen to perform them is properly qualified, by checking his/her qualifications in the Italian national federation website (www.fnomceo.it), or by checking his/her curriculum studiorum on the order of physicians site of the related province.

Some European insurance companies demand proof of experience from the dentist who places implants in order to provide insurance coverage for the patient and the professional.

Surgery protocols

The “implantologist” and/or surgeon creates a site in the patient’s bone (corresponding to the new tooth to be placed or replaced), by using a set of calibrated burs, then inserts an endosteal dental implant. For the implant to osseointegrate, it is necessary to achieve a good primary stability, with no mobility or movement limited to a few micrometres (according to Brunsky et al.). The bone-implant interface is of the order of a few nanometres, otherwise the implant does not support its load and must be removed.

According to some implantologists (Linkow), fibrous integration (a body defense phenomenon that surrounds the foreign body with a fibrous capsule) may be acceptable for loading a crown. Technically the implant has failed and the surgery has not been successful, but, in some cases, implants with fibrous integration can be functional for years with full patient satisfaction. However, fibrous integration is a failure.

Currently, the most commonly used implants are the ones of the Swedish school, that can be inserted with a deferred load protocol, with surfaces treated by various technologies, to facilitate the control of all parameters and the highest degree of implant success predictability. Generally, functional load with a fixed prosthesis is applied later, after 3 to 4 months for the mandible, and after 5 to 6 months for the maxilla. In some cases, but not all, it is possible to immediately load the implants, but to be able to do it some basic criteria must be followed:

• the presence of a certain amount of bone,
• primary stability of the implants after placement,
• good gingival support,
• absence of bruxism (teeth grinding) and of serious malocclusion,
• presence of a good occlusal balance (a correct occlusal plane).

Clearly, a serious specialistic evaluation is also necessary, to examine the coexistence of all these factors, otherwise the choice should fall on a traditional technique (of a submerged or non-submerged type), using implants that require a longer, but safer waiting time before the application of a functional load.

Italian school immediately loading implants, and the related surgical techniques, give success percentages comparable to the ones obtained with deferred loading, but involve a longer learning curve and require greater experience. However, this system allows the patient to have fixed temporary teeth at the end of the implant surgery session even in cases where a deferred load would have been necessary with Swedish school implants.

Implants have an almost unlimited lifetime (the longest studies span 25 years), if daily maintenance is performed. The greatest risks for implants are:

• immediately after placement peri-implantitis can set in; this is an inflammation and infection of the structures surrounding the implant, followed by failed osteointegration;
• incorrect load of the implants, with incorrect crowns or prostheses, that can create bone resorption in time, with bone loss reaching the deepest implant threads, possibly causing implant loss. In order to avoid such implant failures, it is necessary to build good fixed or removable prostheses, with well balanced occlusion, to maintain a good daily hygiene, and undergo regular checkups.

Also, it must be pointed out that smoking and diabetes can compromise osteointegration and implant duration. Implants can replace a single tooth by placing a crown over an implant, a group of contiguous teeth (bridge on implants), a full arch, or they may be used to stabilize an upper or lower overdenture.

Implant success criteria

• Absence of persistent pain at implant site
• Absence of recurring infection
• Absence of implant mobility
• Absence of radiolucency around the implant

References

Bibliography

• Clinica Implantoprotesica di Ugo Pasqualini, Marco Pasqualini, Ariesdue, 2008,
• Insuccessi in implantologia: definizioni, cause, classificazione, terapia, aspetti medico-legali. Odontoiatria pratica, di Antonio Pierazzini, UTET, 2001.
• Il successo in implantologia, di Enrico G. Bartolucci, C. Mangano, Masson, 2004.
• Osseointegrazione clinica: i principi di Brånemark, di Gian Antonio Favero, Masson, 1994.
• Annali di Stomatologia - Su alcuni casi particolarmente interessanti di impianto endosseo con vite autofilettante - Vol XV - Aprile 1966