From practitioner to practitioner - ZZI 02/2011

Implant repositioning osteotomy for changing the position
of osseointegrated implants

M. Suhr1, F.-A. Preusse1, C. Arndt1

The options in the treatment of fully osseointegrated implants in an incorrect or unusable position include not utilising the implant (“sleeping implant”), surgical removal of the implant and complete replanning, providing it with superstructure and accepting the situation, or performing an implant repositioning osteotomy (IRO). In the latter procedure, emphasis is placed on ensuring an adequate bone- and blood-supply and adequate fixation of the implant-bearing bony segment. This can be accomplished by wire or plate osseosynthesis, fixing abutments into a splint incorporating temporary crowns, or by bone-grafting and impaction. Adequate planning, obtaining an informed consent from the patient with presentation of all the options and frequent and repeated foto-documentation are essential components in ensuring an outcome acceptable to the patient.

Keywords: implant; repositioning osteotomy; model surgery; surgical splint; ceramic implants

Introduction

Successful primary osseointegration of dental implants and lifelong success requires an adequate bone-supply (implant surface fully covered by bone, > 2 mm buccal and lingual bone thickness, implants 12 mm or longer in length, 4 mm or greater in diameter) and a favourable crown to implant ratio (preferably 33 % : 66 %) [4]. The implants need to be axially correct and in line with the dental arch. Bone-grafting prior to implant placement is a prerequisite in cases of advanced bony atrophy, yet has certain restrictions: the maximal thickness of cortical transplants is probably around 5 mm, and of spongy bone transplants probably around 11 mm. Bone-graft success depends on the quality of recipient bone and surrounding soft-tissue. As large a bony contact surface area as possible is required in order to ensure successful ingrowth of the vessles in the Haversian canals. A single bone-graft operation may not suffice to ensure optimal placement of the implant, and serial bone-grafting is occasionally difficult to motivate patients for.

This and a multitude of other reasons account for the frequency with which implants are placed in suboptimal positions. When they have successfully osseointegrated, the question arises as to how best to provide these with an acceptable superstructure. Patients should be informed about the possibility of successfully adjusting the position and axial alignment by an implant repositioning osteotomy [1–3, 5–8]

Patient cohort and selection

We retrospectively examined eleven implants in six randomly selected patients out of our cohort of 24 treated by this method over the last five years (Tab. 1). This selection revealed a surprisingly broad range of methods of fixation used and the fact that occasionally one-piece implants (such as circonium) had to be adjusted.

 

Planning

The two principal and central concepts are wedge transposition on the one hand (changing the axial alignment) and parallel osteotomy lines [2, 7] on the other (moving the implant towards the occlusal plane). The osteotomy lines of the bone-block containing the implant must be parallel and preserve bone of about 2 mm around the implant. The further osteo-tomy is then performed parallel to the first and to the neighbouring tooth root, the third vertical well above the apex of the implant. In cases where a wedge transposition is planned, the wedge osteotomy lines are parallel to the implant and tooth root respectively (see Fig. 1). Pencil drawings on paper copies of the radiographs are helpful in planning, discussion and consent.

A model, from which a splint is constructed, showing the intended final position of each implants’ superstructure and therefore ideal implant neck position, should accompany all planning and provide an additional platform for discussion. The splint may incorporate provisional crowns which are placed on to the abutments and fixed with temporary cement or contain composite crowns and therefore serve as provisional removable prostheses where implants are osteotomised without abutments in place. When provisional crowns on implant abutments are incorporated into the splint, this must be worn without interruption for three months. Surgery may take place a few days after removal of the superstructure.

Operative procedure

Up to two implants may reasonably be operated on under local anaesthesia. More than this amount seems to be more easily treated under full anaesthesia with nasal intubation, as extensive osteotomies with an oscillating osseoscalpel and levering with the chisel are of some discomfort to the patient.

Mucoperiosteal flaps are raised buccally where imminent danger exists to surrounding structures such as tooth roots and adequate exposure is required in order to perform safe surgery (e.g. Fig. 3). Periosteal splitting is performed early in the surgery, in order to ensure tension-free wound closure.

The buccal mucoperiosteum may be left intact where sufficient room is available between the implant-bearing bone and neighbouring tooth roots and implants. This “closed” procedure may ensure a better blood-supply to the osteotomised segment [3]. The osseoscalpel (Aesculap GD305) is used to perform the osteotomy under saline cooling through the unraised mucoperiosteum, which the blade tears and stretches rather than cuts.

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