Early or immediate loading of dental implants to restore the edentulous mandible

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Early or immediate loading of dental implants to restore the edentulous mandible
Jason Nijjer
Compton Implants
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In 1977, Branemark and his coworkers published the first long-term follow-up study on dental implants(1). Since that time there have been numerous advances in the materials, techniques, and usage of dental implants. There has been a continuous progression form the two-stage surgical protocol, to the single-stage, and finally to single-stage with immediate or early loading. This paper will discuss the reasoning behind each of the surgical protocols as well as some of the requirements. It will then focus on the current use of immediate or early loading to restore function of the edentulous mandible.
In the early studies on dental implants the two stage surgical protocol was used. The main reasons for using this approach were to 1) minimize the risk of infection, 2) prevent apical down growth of mucosal epithelium, and 3) minimize the risk of undue early loading during the initial healing period. The 3 to 6 month stress-free healing period was considered to be an ultimate prerequisite for this procedure. Only on completion of this healing period are the mucosa piercing abutments placed and the supraconstruction connected(2). Over the years this original Branemark protocol for implant placement proved to have a high level of predictability and success. Soon after researchers began investigating the use of a single stage surgical protocol which achieved osseointegration with the use of non-submerged implants. This protocol still included the 3 to 6 month healing period. However upon completion a second surgery is not required, the cover screw or healing abutment is removed and the definitive restoration is placed. Clinical conditions for which the single stage technique may be utilized are as follows(3): 1) good quality bone (type I or II), 2) adequate bone width and height (sufficient for placement of a 3.8 mm diameter, 12 - 16 mm long implant), 3) adequate keratinized soft tissue (at least 3mm), 4) the presence of adjacent teeth that can absorb the occlusal forces and thus protect the implant from function that could initiate movement, and 5) the ability to completely stabilize the implant at the time of placement.
The ability to achieve primary stability is considered to be one of the critical objectives in obtaining a successful outcome. However it appears that primary stability would be jeopardized with single stage implants as to some extent these implants will be directly and unpredictably loaded during function in the healing period. Despite this fact implants placed with the single stage protocol demonstrate the same success as those placed with the original two stage protocol. Consequently, the current trend is not to consider any movement detrimental to osseointegration but rather micromovements beyond a critical threshold. Researchers have found that the critical threshold, although dependent on the type of implant morphology and implant surface, seems to be between 50 and 150 ¨µm(4). From this knowledge it would be reasonable to assume that implants placed with primary stability could be put into function immediately as long as the forces are controlled and below the critical micromovement threshold. Immediate loading would offer many advantages to the patient and dentist over the two stage or single stage protocol. One of the most important advantages to the patient is they would not be required to wear a temporary prosthesis over the long treatment period. For many patients this is of great inconvenience, and is sometimes the reason for not choosing implant supported restorations. In addition the placement of a provisional at the time of implant surgery offers esthetic, psychological, and functional advantages as compared to the use of a temporary removable prosthesis. With immediate placement of a provisional restoration the length of treatment can be reduced, since both soft and hard tissues will heal concurrently. In this procedure the provisional duplicates the definitive restoration so that the soft tissue contours can match the desired outcome. If on the other hand the provisional is placed after the implant has osseointegrated an additional 3 to 6 months is required to achieve the correct tissue contours(5).
Reference:
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