Statement of problem Various implant impression techniques, such as the splint, pick-up, and transfer techniques, have been introduced, and some techniques may be more accurate than others. Also, clinically, some factors, including the angulation or depth of implants, may affect the accuracy of the implant impressions. Purpose The purposes of this review were to: (1) investigate the accuracy of published implant impression techniques, and (2) examine the clinical factors affecting implant impression accuracy. Material and methods An electronic search was performed in June 2008 of MEDLINE, EMBASE, and Cochrane Library databases with the key words implant, implants, impression, and impressions. To be included, the study had to investigate the accuracy of implant impressions and be published in an English peer-reviewed journal. In addition, a hand search was performed to enrich the results for the time period from January 1980 to May 2008. After executing the search strategies, 41 articles were selected to be included in the review process. Results All of the selected articles were in vitro studies. Of the 17 studies that compared the accuracy between the splint and nonsplint techniques, 7 advocated the splint technique, 3 advocated the nonsplint technique, and 7 reported no difference. Fourteen studies compared the accuracy of pick-up and transfer impression techniques, and 5 showed more accurate impression with the pick-up techniques, 2 with the transfer technique, and 7 showed no difference. The number of implants affected the comparison of the pick-up and splint techniques. Eleven studies compared the accuracy of polyether and vinyl polysiloxane (VPS), and 10 of 11 reported no difference between the 2 materials. Four studies examined the effect of implant angulation on the accuracy of impressions. Two studies reported higher accuracy with straight implants, while the other 2 reported there was no angulation effect. Conclusions The review of abutment level or implant level internal connection implants indicated that more studies reported greater accuracy with the splint technique than with the nonsplint technique. For situations in which there were 3 or fewer implants, most studies showed no difference between the pick-up and transfer techniques, whereas for 4 or more implants, more studies showed higher accuracy with the pick-up technique. Polyether and VPS were the recommended materials for the implant impressions. (J Prosthet Dent 2008;100:285-291)

The accuracy of implant impressions: a systematic review.

I the 35 years since the concept of osseointegration was first applied to human patients, there have been many advances in the understanding and application of implant dentistry as a method for the replacement of missing teeth. Osseointegration as first defined by Branemark is a scientific milestone that delineates a certain sense of separation of the old from the new in implant dentistry. Osseointegration was a watershed event that has forever changed the way dentists view their options when confronted with a patient requiring tooth replacement. While dental implant therapy was an option for tooth replacement for many years prior to the publication of Branemark’s work, he gave the field a scientific basis and a sense of respectability it had lacked previously. This was particularly true in academic institutions, where dental implants were largely ignored as a viable choice for tooth replacement. Dental implants are now a major focus of didactic and clinical education in 3 dental specialties and soon will likely become mainstream in undergraduate dental school clinics. Osseointegration is the single factor that has most dramatically changed the discipline and specialty of prosthodontics since the introduction of fluoridated water. The evolution and change seen in basic science and the surgical understanding of dental implant therapy have perhaps been more far reaching than parallel advances in knowledge of the restorative aspect of dental implants. As the 20th century draws to a close, it is appropriate to review the significant advances and changes in implant prosthodontics that have occurred over the past 2 decades and, more importantly, describe future directions of investigation that are paramount to the advancement of dental implant therapy as a beneficial treatment modality.

/pdf/implant-prosthodontics-current-perspective-and-future-3ymarqhxmt.pdf

Implant prosthodontics: current perspective and future directions.

Statement of problem In the past 5 years, the use of intraoral digitizers has increased However, data are lacking on the accuracy of scanning implant restorative platforms for prosthodontics with intraoral digitizers Purpose The purpose of this clinical pilot study was to assess the applicability and accuracy of intraoral scans by using abutments designed for scanning (scan abutments) in edentulous mandibles Material and methods Twenty-five participants with complete mandibular overdentures retained by 2 implants and frameworks were included in this study Scan abutments were placed on the implants intraorally and scanned with the iTero intraoral scanner Also, scan abutments were placed on the implant analogs of the definitive casts and scanned with an extraoral laboratory scanner (Lava Scan ST scanner) Two 3-dimensional computer-aided design models of the scan abutments with predetermined center lines were subsequently imported and registered, together with each of the scanned equivalents The distance between the centers of the top of the scan abutments and the angulations between the scan abutments was assessed These values were compared with the measurements made on the 3-dimensional scans of the definitive casts, which were the participants' original definitive casts used for fabrication of soldered bars The threshold for distance error was established to be 100 μm Results Four of the 25 intraoral scans were not suitable for research because the intraoral scanner was not able to stitch the separate scans together Five of the 21 suitable scans demonstrated an interimplant distance error >100 μm Three of the 25 intraoral scans showed interimplant angulation errors >04 degrees Only 1 scan showed both an acceptable interimplant distance ( Conclusions Based on the intraoral scans obtained in this study, distance and angulation errors were too large to fabricate well-fitting frameworks on implants in edentulous mandibles The main reason for the unreliable scans seemed to be the lack of anatomic landmarks for scanning

Applicability and accuracy of an intraoral scanner for scanning multiple implants in edentulous mandibles: A pilot study

Prosthodontic focus on the restoration of osseointegrated dental implants has evolved dramatically in the last 20 years. Many of the original guiding principles for restoring implants have changed and/or disappeared altogether, and new ideas have taken their place. It is appropriate that this evolution be examined with a 2-fold focus. First, the art and science of prosthodontics as it relates to dental implants today is the result of very real and important lessons learned during the past 2 decades. Second, an appreciation of the history of implant prosthodontics as it relates to osseointegration gives insight into the future direction of research and clinical exploration aimed at continually improving the state of the art and, ultimately, the quality of care provided to patients. This article reviews what the authors consider the most important aspects of the evolution of osseointegrated implants. Pertinent literature was selected for citation, but the discussion does not represent a comprehensive review of the literature.

Twenty years of progress in implant prosthodontics

Statement of Problem. To circumvent the difficulty of achieving a passive framework fit, some authors have suggested that multiple adjacent implants be restored individually. This protocol requires that each unit be able to withstand mastication forces. Non-splinted restorations have numerous interproximal contacts that require adjustments prior to placement, with an unknown outcome relative to load transfer. Purpose. This in vitro simulation study examined the effect of splinting and interproximal contact tightness on passivity of fit and the load transfer characteristics of implant restorations. Material and Methods. A photoelastic model of a human partially edentulous left mandible with 3 screw-type implants (3.75 × 10 mm) was fabricated. For non-splinted restorations, individual crowns were fabricated on 3 custom-milled titanium abutments. After the units were cemented, 5 levels of interproximal contact tightness were evaluated: open, ideal (8 μm shim stock drags without tearing), light (ideal +10 μm), medium (ideal + 50 μm), and heavy (ideal + 90 μm). For splinted restorations, five 3-unit fixed partial dentures were fabricated, internally adjusted with silicone disclosing material, and cemented to the model. Changes in stress distribution under simulated non-loaded and loaded conditions (6.8 kg) were analyzed with a polariscope. Results. In the simulated alveolar structures, non-splinted restorations with heavier interproximal contacts were associated with increased tensile stresses between implants; occlusal loads tended to concentrate around the specific loaded implant. Splinted restorations shared the occlusal loads and distributed the stresses more evenly between the implants when force was applied. The load-sharing effect was most evident on the center implant but also was seen on the terminal abutments of the splinted restorations. Conclusion. The results of this in vitro study suggest that excessive contact tightness between individual crowns can lead to a non-passive situation. In this experiment, splinted restorations exhibited better load sharing than non-splinted restorations. (J Prosthet Dent 2002;87:528-35.)

Effect of splinting and interproximal contact tightness on load transfer by implant restorations.

Statement of problem. Passive fit of implant-supported–prosthesis frameworks has been suggested as a prerequisite for successful long-term osseointegration. However, there are no scientific guidelines as to what is passive fit and how to achieve and measure it. Purpose. The purpose of this article is to discuss passive fit and to review the various clinical methods that have been suggested for evaluating implant framework fit. Methods. The dental literature was reviewed to identify the clinical methods that have been used to evaluate implant framework fit. Conclusions. The suggested levels of passive fit are empirical. Numerous techniques have been advocated to evaluate the prosthesis-implant interface, but none individually provides objective results. It is suggested that clinicians use a combination of the available methods to minimize misfits. (J Prosthet Dent 1999;81:7-13.)

Khaled Bohsali

Papers

Clinical methods for evaluating implant framework fit