The Astra Tech Implant System™ has been documented when used to support a wide range of prosthetic solutions. Good clinical and mechanical results have been obtained for single tooth, fixed partial and complete prostheses as well as for removable overdentures. Please read more about it in this section.
A short-term clinical evaluation of immediately restored maxillary TiOblast single-tooth implants
Purpose: The purpose of this study was to evaluate the short-term clinical outcome of single tooth Astra Tech implants placed in the maxilla and immediately restored with cementless friction-fit temporary crowns using the Abutment ST and the ST impression coping/healing cap.
Material and Methods: Thirty-three patients consecutively treatment planned for replacement of single missing units were enrolled to the study. Patients either presented with a failing natural tooth or with an already healed extraction site. Patients were required to be systemically healthy and smokers were included.
For patients with failing teeth, these were atraumatically extracted using the periotome, and osteotomy sites were prepared per socket. The point of entry for these osteotomies was in the most palatoapical position to avoid fenestration of the delicate labial plate. For healed sites a scalloped palatocrestal incision was utilized with minimal flap reflection. Osteotomy preparation essentially followed manufacturer's recommendations, except for use of the conical drill which was either abandoned or only used against the palatal shelf of bone in larger extraction sockets. It was a requirement that implants (Astra Tech ST 4.5) achieved a primary rotational stability of 25 Ncm otherwise they were excluded from the study.
An abutment ST 0.0 mm was routinely used and the abutment screw torqued to 25 Ncm. An ST impression coping was then adjusted into a cap and used as a core for the fabrication of a chairside tem-porary crown. This was typically achieved by grind-ing a matching denture tooth down to a veneer and bonding it to the cap with autopolymerizing meth-ylmethacrylate. This technique presented the advantage that the temporary crowns could be left friction fit, without the need to initially use cement in a fresh surgical site. The crown was kept clear of centric and excursive contacts. Subsequent regular removal of the temporary crown after one month of healing allowed for direct submucosal irrigation with chlor-hexidine to maintain healthy soft tissues. All patients were followed up regularly until the time of definitive restoration placement which was typically of an all-ceramic type.
Baseline radiographs were taken using a Rinn device. Patients were reviewed at 6 months, one year and annually thereafter. The most recent radiograph was used to evaluate marginal bone changes relative to a fixed reference point on the implant at the level of the fixture/abutment junction.
Results: Eight patients were excluded due to inadequate primary rotational stability of their implants. For the remaining 25 patients, 28 implants were available for evaluation. Only one implant failed due to a perceptible mobility one month after surgery. The remaining 96.4% continued to survive under occlusal load for up to 30 months in function with a mean marginal bone loss of only 0.4 mm, with 37.5% recording no marginal bone loss at all with respect to the reference level.
Indeed a number of implants demonstrated bone above the implant/abutment junction. Loosening or failure of the temporary crowns occurred in 39% of cases necessitating their cementation or re-fabrication. It is clear that early cementation would signifi-cantly reduce this complication.
Discussion: The current study supports the use of the Astra Tech implant system for the immediate tempo-rization of implants to replace failed or missing teeth. The high survival and excellent marginal bone data would indicate that the design of this implant yields a favourable peri-implant tissue response between marginal bone and the implant/abutment junction. The mean distance between these levels was only 0.4 mm suggesting that favourable soft tissue esthetics can be achieved. The use of a friction-fit tempo-rary crown offered a simple and esthetic solution to temporisation. However the use of a small amount of temporary cement could help reduce incidence of crown loosening and/or fracture.
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