 Astra Tech
BioManagement Complex
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 Surgical techniques
A wide range of different surgical techniques are applied when placing implants under different preconditions. The summaries below show that one- and two-stage surgery, immediate placement in extraction sockets, bone augmentation and sinus lift can be successfully and predictably performed using the Astra Tech Implant System'".
 A prospective, randomized-controlled clinical trial to evaluate bone preservation using implants with different geometry placed into extraction sockets in the maxilla
Immediate placement of dental implants into extrac
Hon sockets has been demonstrated clinically and his-
tologically to be as predictable as implant placement
healed sites. The immediate placement of dental
implants in extraction sockets is associated with
residual bone defects between the walls of the extracclin Oral Impl Res t'°n socket and the neck of the implant at the time
of placement. Depending on the size of this defect,
various studies have recommended the use of regenerative materials or barrier membranes to fill or cover these gaps thus preventing epithelial or connective tissue cell ingress, favoring bone regeneration. While some studies can demonstrate that immediate placement in an extraction socket may prevent or decrease the hard tissue loss which predictably follows tooth loss, others have shown that as new bone is formed around the implant, corresponding bone loss from the buccal and lingual aspects of the ridge can be demonstrated.
Purpose: The aim of this prospective, randomized, controlled multi centre study was to determine the association between the size of the void established using two different implant configurations and the amount of buccal/palatal bone loss occurring during healing following implant installation into extraction sockets.
Material and Methods: Ninety-three patients (£18 years) requiring the extraction of a maxillary tooth in the 15 to 25 region fulfilled strict inclusion criteria for this study. Following the atraumatic extraction of the tooth using a periotome, patients were randomly allocated to group A or B. Group A utilized uniformly cylindrical implants whereas group B utilized implants which were cylindrical in the apical aspect but tapered cervically. All implants (MicroThread'" OsseoSpeed'" Astra Tech AB, Sweden) were placed with healing abutments according to the manufacturer's protocol. In order to evaluate the bone at time of placement and to describe the size of any defects between the socket walls and the implant surface, the following landmarks were defined: Implant surface (IS), Implant Rim (IR), Top of bone crest (BC), Inner border of bone crest 1 mm from BC (IBC), Outer border of bone crest 1 mm from BC (OBC) and base of the defect (DB). After placement, the following measurements were taken, by independent examiners, on the buccal and palatal aspects of each implant, to the nearest millimeter using a standard periodontal probe: IS-IBC (Horizontal defect), IS-OBC (Horizontal distance from implant to outer crest of ridge), IR-DB (Vertical Defect), IR-BC (vertical distance from implant rim to bone crest). The buccal and palatal bone wall thickness was measured with calipers. A strict postoperative regime followed, with review after 1 week. Implants were allowed to heal for 16 weeks prior to re-entry to repeat the previous measurements prior to restoration.
The results were subjected to statistical analysis at the 95% confidence interval to test the null hypothesis that the reduction in the buccal bone plate thickness is constant, irrespective of the size of the void established by using different implant geometries,
Results: The mean reductions in IS-OBC, and IR-DB were not significantly different between the two groups on either the buccal or palatal aspects. Similarly, whilst there was no difference between the groups in reduction of IR-BC, the reduction was seen to be more pronounced at the buccal aspect. The measurement IS-IBC showed a significantly greater amount of reduction in group A than in group B on both the buccal and palatal aspects, p < 0.05.
Discussion and Conclusions: This study reinforces and corroborates the findings of numerous previous studies which have demonstrated that following tooth removal, the buccolingual ridge dimension decreases and buccal vertical crest reductions are seen to occur as a result of tooth loss. This marked decrease can be seen to occur regardless of immediate implant placement, the geometry of the implant, or a flapless surgery protocol. Whilst the ridge reductions measured in this study were fairly substantial, it must be considered that additional changes may in fact occur during the later phases of remodeling. This, together with the marked decrease in the vertical crest especially on the buccal aspect, reinforces the importance of proper planning prior to implant placement and positioning, especially in the esthetic zone to ensure that ridge alterations do not compromise the esthetic outcome of the case. |
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