|Year : 2011 | Volume
| Issue : 1 | Page : 4-9
Transitional implants: An asset to implantology
Mohit G Kheur
Department of Prosthodontics, M A Rangoonwala College of Dental Sciences and Research Centre, Pune, India
|Date of Web Publication||4-Mar-2011|
Mohit G Kheur
Department of Prosthodontics, M A Rangoonwala College of Dental Sciences and Research Centre, Pune
Source of Support: None, Conflict of Interest: None
| Abstract|| |
The use of dental implants to support either fixed crowns and bridges or removable dentures has made it possible for many patients to experience an artificial dentition that is as esthetic and functional as their natural teeth were. Dental implant treatment has evolved over the years. Progress in implantology has been focused at increasing patient's comfort by reducing the treatment time and achieving esthetic and functional rehabilitation as early as possible. Although this has been achieved to a large extent by the use of immediate loading concepts, the same cannot be applied to all clinical situations. There are still many clinical situations wherein the patient would have to go through a waiting period after a surgical procedure (it could be the surgery to place a dental implant or bone grafting surgery, or even extraction of some teeth). During such a waiting period, the patient needs to function on a fixed temporary restoration till the final restoration can be placed. This has been made possible today by the advent of transitional implants which have been designed for and are placed along with the conventional implants for the replacement of the patient's missing dentition and enabling the patient to experience the benefits of implantology immediately. This paper presents an overview of transitional implants and its clinical application.
Keywords: Osseointegration, transitional implants, temporization
|How to cite this article:|
Kheur MG. Transitional implants: An asset to implantology. J Interdiscip Dentistry 2011;1:4-9
The use of dental implants to support either fixed crowns and bridges or removable dentures has made it possible for many patients to experience an artificial dentition that is as esthetic and functional as their natural teeth were. Dental implant treatment has evolved over the years. The greatest impact on implantology, which now forms its basis, is the concept of osseointegration.  Progress in all fields of dentistry, especially implantology, has been focused at increasing patient's comfort by reducing the treatment time and achieving esthetic and functional rehabilitation as early as possible. Although this has been achieved to a large extent by the use of immediate loading concepts, the same cannot be applied to all clinical situations. There are still many clinical situations wherein the patient would have to go through a waiting period after a surgical procedure (it could be the surgery to place a dental implant or bone grafting surgery, or even extraction of some teeth). During such a waiting period, the patient needs to function on a fixed temporary restoration till the final restoration can be placed. This has been made possible today by the advent of transitional implants which have been designed for and are placed along with the conventional implants for the very same purpose. 
Transitional implants are narrow diameter implants that were developed to support provisional fixed restorations during the phase of osseointegration of the definitive implants and are usually placed simultaneously with definitive implants. 
They are placed in a non submerged fashion in a single stage surgical procedure and are designed to be immediately loaded.
Typically they are placed between the definitive implants, following a set of guidelines, as discussed subsequently, and allow for their load free osseointegration. The patient can function normally and at the same time have good esthetics and phonetics with the help of good provisional/temporary restorations fixed to such transitional implants.
They are removed with manual tools at the end of the provisional phase. The definitive implants are then restored according to the main treatment plan.
| Evolution of Transitional Implants|| |
The concept of osseointegration, i.e. direct anchorage of pure/alloyed titanium in the jaw bone, was a great breakthrough in oral rehabilitation.  Experimental and clinical evidence led to the establishment of clinical guidelines for achieving predictable osseointegration with titanium implants.
For a long time, submerging of the implant by means of a two-stage procedure was thought to be a prerequisite. This is the classical Branemark protocol and involves placing of the implant in the bone and covering it with a muco-periosteal flap.  The implant is uncovered after a submerged healing period. However, various studies beginning with those carried out on the ITI system of implants demonstrated good results with a non submerged/ single stage procedure, i.e. a procedure wherein the implant was placed in the bone with the healing abutment attached to it at the same stage and mucosa sutured circumferentially around it. 
Such single stage procedures are gaining in popularity but can be utilized only when the suitably long (more than 10 mm) implants are inserted with a high 'primary stability' (high insertion torque), in patient's native bone and in a mouth free of periodontal disease. In the past, implants were placed in regions of adequate bone, albeit with little/no regard to rules of prosthodontics. Today's implantology is more 'prosthetically driven'.
Over the last two decades, the ability to accurately assess bone quality and quantity has greatly simplified the treatment planning process. CT scanning, use of three-dimensional reformatted imagery and related software, e.g. Simplant (Columbia Scientific Inc, Columbia) has added to our ever increasing diagnostic armamentarium. Advances in techniques and materials have facilitated rebuilding ridge height and volume, preventing some of the surgical and prosthetic problems that used to be encountered. Today's reality is that a sound foundation can be prepared for future health, function and esthetics using modern implantology.
Yet, in the world of implantology of today, two major difficulties remain:
- Maintenance of soft tissue and stabilization of the rebuilt ridges continues to be a problematic area.
- Stable stress-free restorations have not been provided for patients to wear during the lengthy healing period required for osseointegration.
The problems posed by these difficulties have ultimately resulted in poor esthetic outcomes, and fixture instability, subsequent micro-motion and ultimate failure.
From a patient's view point also, there is a lot of objection to functioning without a temporary restoration for a few days (immediately after surgery) and then to wear a soft lined removable prosthesis till the completion of the definitive restoration. As a result, many patients are unwilling to pursue recommended implant treatment.
Two of the popular methods followed to avoid giving the patient a temporary removable prosthesis are using serial extractions with implants placed in stages and immediate loading of implants.  Both these techniques have their drawbacks and limited applications.
These concerns have led to the development of transitional implants which permit uninterrupted healing of the surgical site - either following implant placement or if the area has been built up with augmentation materials and use of barrier membranes.
To address these needs, Dr. Jack Wimmer of Park Dental (Park Dental Studies, New York) introduced temporary or provisional implants in the form of the Lew Screw in the 1970s. Dr. Victor Sendax later developed the Sendax Mini Dental Implant System (Imtec Corp, Ardmore,OK). The work of Paul Petrungaro with the Dentatus System (Dentatus AB, Hagerten, Sweden) along with that of numerous clinicians further extended this concept.
In addition to the above, transitional implants permit immediate replacement of the patient's missing dentition and enabling the patient to experience the benefits of implantology immediately. Today, for most clinical situations, completing pre-operative treatment without providing transitional implants is an incomplete treatment plan at best.
| Clinical Applications of Transitional Implants|| |
The main rationale for use of transitional implants is to provide retention, stability and support for a fixed provisional prosthesis during the time required for osseointegration of conventional implants.
The other applications documented for transitional implants are:
- To provide a fixed provisional for protecting an osseous grafted site.
- To provide a vertical stop for a fixed prosthetic reconstruction during the healing period.
- To provide stability to the surgical stent during implant placement. ,,
- To eliminate need for a temporary tissue borne restoration.
- Act as an orthodontic anchor for quick and effective movement of other teeth. ,
- Though not used for provisionalisation in these situations, transitional implants are also used to
- Stabilize existent dentures. 
- Replace congenitally missing maxillary lateral incisors.
- Repair of broken bridges.
Using transitional implants to support a temporary restoration also permits you to work through phonetic and occlusal difficulties as well as esthetics of the final restoration. In the transitional phase, while the temporary restorations are in function, the patient can experience all the benefits of the final restoration and implant therapy as a whole. Potential difficulties in speech, esthetics and mastication can be addressed before final restorations are even fabricated. Patients no longer need to confine or restrict their daily activities after implant placement for want of functioning temporary teeth.
| Clinical Procedure for Use of Transitional Implants|| |
Location of transitional implants
Transitional implants are placed after the definitive implants are in position. Generally in a fully edentulous mandible, four transitional implants are recommended for a fixed provisional restoration. However for a fully edentulous maxilla, at least five transitional implants are required for a similar result [Figure 1].
|Figure 1: Maxillary and mandibular transitional implants placed adjacent to conventional implants|
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For partially edentulous situations, two or three transitional implants are used. The number of pontics should generally be restricted to two, for posterior regions if a temporary bridge is being made. 
They should be placed at least 1.5 mm from adjacent teeth and the distance between any transitional implant and a definitive implant must be at least 1.5-2 mm. 
| Contra Indications for Transitional Implants|| |
Transitional implants are contra indicated when
- There is less than 10 mm of cortical bone available for good anchorage and initial stability.
- There is insufficient space available to place a sufficient number of implants to anchor the fixed provisional restoration. 
If the transitional implant is shortened because of lack of bone height, the bio-engineering of the case should be reviewed and consideration should be given to placing additional implants to increase the support.
| Design of Transitional Implants|| |
A few of the commercially available transitional implant systems are:
- Immediate Provisional Implant System- IPI (Nobel Biocare, Yorba Linda, CA, USA,)
- Modular Transitional Implant System - MTI (Dentatus, New York, NY, USA,)
- Mini Dental Implant System - MDI (Imtec, Ardmore, OK)
- Temporary Implant - (Bicon, Boston, MA)
TRN/TRI Implants - (Hi-Tec implants)
Transitional implants are generally made of commercially pure titanium or titanium alloy and are designed as one piece implants with crown and root components [Figure 2],[Figure 3],[Figure 4].
Although the designs differ from system to system, the basic design is of a self threading tapered screw with a diameter of 1.8-2.4 mm  and intra-bony length of 7 -14 mm. The length of these implants can be shortened by a simple disc. The head can also be bent to change its angulation up to 45 degrees to achieve parallelism between abutments. The abutment head generally has a 5 degree taper, which makes it optimal for retention of cement retained prostheses. A flat side on the abutment generally facilitates proper placement and orientation of the insertion and removal instruments, transfer copings and alignment of the laboratory analogs in the master model if needed.
A transitional implant system kit also contains all the instrumentation required for preparing the osseous receptor sites as well as inserting, removing, aligning, and paralleling of implants.
Only one drill, a 1.5 mm or 2 mm twist drill is required for placement of the implants. The kit also includes an insertion wrench, a hand wrench, a ratchet adaptor, paralleling pins, bending tool, and retrieving tool.
| Clinical Steps Involved in Planning Out a Case|| |
Developing a comprehensive treatment plan:- The importance of a written comprehensive treatment plan cannot be overemphasized. It should include all the proposed steps, including seemingly minor ones and must allow sufficient time for contingency procedures.
Treatment planning begins at the initial consultation stage when the patient completes a detailed questionnaire.
Panoramic and tomographic radiographs, if necessary, are taken. Two sets of impressions are made. A face bow transfer and bite registration is done. The casts are thus mounted on a semi-adjustable articulator.
A wax up of the case is done on one of the models. Care is taken to achieve an ideal occlusal plane and to incorporate a functionally sound occlusal scheme in the wax-up itself.
This step generally enhances not only patient-doctor communication, but it also supports communication between the surgeon, the restorative dentist and the laboratory technician. From a surgical stand point, the proper position and angulations of implants can be determined and the need for bone augmentation procedures can be realized before implant placement itself. The retention of natural teeth and their role in the treatment plan can also be evaluated.
When considering the prosthodontic aspect, the use of transitional implants is decided as well as the number of implants to be placed. The best possible angulations for implants can be decided from the stand point of the occlusion planned for the case as well the esthetic aspects. Even other procedures besides the primary implant treatment can be evaluated and planned, such as a crown lengthening on a particular tooth, an elective endodontic procedure to correct the occlusal plane, or an orthodontic procedure to bring about better alignment and occlusion of teeth before initiating treatment.
Upon completion, the wax up is duplicated and two stents are fabricated. A clear vacuum formed stent is used during surgery to determine ideal implant location, angulation and bone/soft tissue sites that require augmentation. The second stent may be made from silicone and is used to develop the provisional restoration immediately after surgery. The detail obtained from the putty stent allows the accuracy of the wax-up to be transferred to the provisional restorations for function and esthetics. Unless these procedures are done, most technicians are required to interpret and execute a prosthetic case with little/no relevant information - mostly from imagination which always leads to patient's disappointment, greater chair side time, and at times, costly remakes.
Once the diagnostic wax- up is ready, there is a joint consultation between patient, surgeon, and the restorative dentist. The laboratory technician may also be present if required. Questions about the number of implants to be placed, whether bone grafting or soft tissue augmentation would be required, the type of restoration, the duration of treatment are discussed and explained to the patient.
Following this, the implant placement surgery is executed. The conventional implants are placed in their positions as dictated by the main treatment plan. The transitional implants are then placed using guidelines as discussed previously.
| Simple Methods of Fabricating Temporary Restorations on Transitional Implants|| |
The next step is to restore the case esthetically and functionally using fixed provisional restorations. This can be carried out using one of the following methods:
- If the patient has a denture, then the denture can be adjusted by trimming the flanges and generous relieving of the tissue surface. Transfer copings are seated on the abutments in the mouth and self-cure resin or a hard soft liner is placed in the denture. The denture is seated in the mouth and the patient is asked to close in centric occlusion. Once the resin sets, the denture is removed; the excess resin is trimmed and care is taken to verify that there is no soft tissue impingement. The denture can be now be secured with temporary cement or may be used as a removable appliance.
- For partially edentulous situations, a plaster model is made by duplicating the wax up. Subsequently a clear poly-vinyl template (like the one used to make night guard or bleaching trays) is made over the duplicated model using an Omnivac machine. This is used at the time of surgery. After the final and transitional implants are in place, a temporary restorative material is placed in the template and it is seated over the transitional implants. Care is taken to make the template in such a way that it covers the wax-up portion for replacing the teeth and also a few remaining natural teeth. That way it can be held in a stable manner in the mouth when using it with restorative resin filled inside, during fabrication of the temporary prosthesis.
- A simple method to follow is to make impressions after placement of the transitional implants and have the temporary restorations made in the laboratory. These can subsequently be adjusted in the mouth and cemented using a temporary luting agent.
[Figure 5],[Figure 6],[Figure 7],[Figure 8],[Figure 9],[Figure 10].
|Figure 5: Pre treatment view - showing lower distal extension situation, supra eruption of upper posteriors and abnormal occlusal plane|
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|Figure 6: Upper and lower casts mounted on a semi-adjustable articulator, case at wax-up stage. Occlusal plane corrected by restoration of upper posteriors and denture teeth arranged on lower cast in occlusion|
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|Figure 7: Surgical template prepared after duplicating the lower cast. Red marks indicate location of conventional/final implants, blue areas indicate positions of transitional implants|
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|Figure 9: Two transitional implants in place adjacent to the conventional implants|
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|Figure 10: Fixed provisional restorations cemented on the upper teeth and lower transitional implants|
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| Removal of Transitional Implants|| |
At the second stage (uncovering of implants), the transitional implants are removed. The patient is administered a local anesthetic and the provisional restoration is removed. No incision is necessary for removal of the transitional implants. The ratchet arm and the inserting tool are used in the reverse mode and the transitional implants are backed out of position. 
| Conclusion|| |
The use of transitional implant for supporting restorations during the phase of osseointegration of the definitive implants has been shown to be appropriate, productive, and highly rewarding. The ultimate result of following such a protocol is an enhanced quality of life for the patient.
Besides promoting function, by using provisional restorations on transitional implants, dentists can assess patient's concerns and make necessary amendments to the provisional and final restorations. There is no doubt that transitional implants have become part of the standard of care of modern implantology.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7], [Figure 8], [Figure 9], [Figure 10]