A New Technique for Retaining Double Crowns on Implants via Custom-Positioned Vertical Screws Eberhard Frisch, Dr Med Dent, MSca/Dirk Ziebolz, Priv Doz Dr Med Dent, MScb/ Petra Ratka-Krüger, Prof Dr Med Dentc/Sven Rinke, Priv Doz Dr Med Dent, MScd
This report describes the use of custom-positioned vertical screws (CVS) to attach primary telescopic crowns to implant abutments. In a private practice setting, 37 patients with 40 double crown–retained implant overdentures (IODs) with a clearance fit (Marburg double crowns) were followed. All primary crowns on the 120 implant abutments were retained using CVS. After a mean followup period of 3.55 ± 1.37 years (range: 1.5 to 6.3 years), one abutment screwloosening incident was reported (incidence: 0.08%). No loosening of any of the screw-retained primary crowns occurred. CVS may represent a viable fixation concept for IODs. Int J Prosthodont 2014;27:577–578. doi: 10.11607/ijp.3882
P
rimary telescopic crowns can be secured to implants via cementation or screw retention, but both techniques have specific limitations. Cemented restorations may lose retention; a review of implantsupported single-tooth restorations revealed a 5.5% loss of retention rate over 5 years.1 Peri-implantitis has been associated with excess residual cement,2 whereas screw-retained prostheses offer the advantage of retrievability—although screws also may loosen. The screw-loosening rates for single-tooth restorations using conventional axial screws are reported to range from 2.4% to 12.7%.3 The authors developed a method for connecting primary telescopes by creating screwaccess holes that are custom-positioned in an optimal vertical orientation parallel to the path of insertion on top of the primary crown. This design diminishes the associated risk of cement-related complications, offers retrievability of the restoration, and facilitates intraoral handling when compared to horizontal screw designs. This study describes the custom-positioned vertical screw (CVS) technique and provides clinical data from a 3-year follow-up.
aPrivate
Practice, Hofgeismar, Germany. Professor, Department of Operative Dentistry and Periodontology, University Medical Centre Leipzig, Leipzig, Germany. cHead of Periodontology, Department of Operative Dentistry and Periodontology, University of Freiburg, Freiburg, Germany. dPrivate Practice, Hanau, Germany. bAssistant
Correspondence to: Dr Eberhard Frisch, Markt 3, 34369 Hofgeismar, Germany. Fax: +49 5671 925027. Email: [email protected] ©2014 by Quintessence Publishing Co Inc.
Materials and Methods This retrospective study was performed in a private practice (Northern Hessia Implant Center, Hofgeismar, Germany). Based on the analysis of primary patient data, the study evaluated the clinical outcomes of double crown–retained implant overdentures (IODs) retained via Marburg double crowns (MDCs). The study was reviewed and authorized by the Ethics Commission of the Albert-Ludwigs-University, Freiburg, Germany (application no. 46/10-120329). The telescopic crowns were designed as MDCs with clearance fit4 and an additional retention element (TK Snap, Si-tec) on implants with a morse taper connection (Ankylos, Dentsply) and teeth. The secondary structures of all IODs were cast in one piece with no solder or welding joints. The dental laboratory technique for achieving a vertical screw axis parallel to the path of insertion is demonstrated in Figs 1 to 3. The clinical intraoral aspect of one of the patients with integrated primary crowns is shown in Fig 4.
Results Thirty-seven consecutive patients (22 women, 15 men; age: 70.58 ± 8.57 years) comprised the convenience sample. They were provided with 40 IODs supported by 120 implants and 61 teeth. The mean observational period was 3.55 ± 1.37 (range: 1.55 to 6.29) years. At the time of data acquisition, all implants and IODs were in situ and functional. Therefore, the cumulative survival rate (CSR) for the IODs retained by MDCs was 100% after 3.55 years. Screw loosening of 1 of the 120 (0.83%) taper-anchored abutments was observed but was corrected by retightening the abutment screw
Volume 27, Number 6, 2014
577
© 2014 BY QUINTESSENCE PUBLISHING CO, INC. PRINTING OF THIS DOCUMENT IS RESTRICTED TO PERSONAL USE ONLY. NO PART MAY BE REPRODUCED OR TRANSMITTED IN ANY FORM WITHOUT WRITTEN PERMISSION FROM THE PUBLISHER.
Retaining Double Crowns on Implants via Custom-Positioned Vertical Screws
Fig 1 Drilling a custompositioned thread hole strictly according to the milled telescope surface. (View of laboratory cast with artificial gingiva.)
Fig 2 Custom-positioned screw retention in the abutment. Note that the screw with the taper head is in situ. The implant axis is inclined toward the vestibule. (View of cast without artificial gingiva.)
Fig 3 Final shape of telescopic crown with custompositioned axial screw retention. (View of laboratory crown surrounded by artificial gingival tissue.)
a promising initial clinical performance with limited technical complications. Most of the maintenance interventions (61.54%) were prostheses related (0.061 T/P/Y), which is similar to reports from other clinical trials on IODs supported by telescopic crowns.5
Conclusions
Fig 4 Intraoral view of four primary telescopes with achieved axial orientation of the individually positioned retention screws.
to torque. None of the individually positioned axial screws that connected the primary telescopes to the abutments was affected by loosening, which yielded a success rate of 100%. The maintenance requirements related to implants or the implant-abutment connection or the abutment–primary telescope connection resulted in 0.008 treatments per patient per year (T/P/Y). The follow-up included an additional 12 patient visits for prosthetic maintenance. Eight of these related to dentures (0.06 T/P/Y), including 2 cases of relining, 2 denture teeth fractures, 2 veneer repairs, and 2 occlusal corrections. In four cases, recementation of the tooth-supported primary telescopes was needed (0.03 T/P/Y).
Discussion The small sample size and relatively short observational period precluded drawing significant conclusions. However, MDC-retained IODs clearly showed
578
The use of CVS to retain primary telescopic crowns on implant abutments ensures retrievability of the restoration and appears to result in low maintenance requirements. Controlled clinical trials with larger sample sizes and longer observational periods should be conducted.
Acknowledgments The authors reported no conflicts of interest related to this study.
References 1. Jung RE, Pjetursson BE, Glauser R, Zembic A, Zwahlen M, Lang NP. A systematic review of the 5-year survival and complication rates of implant-supported single crowns. Clin Oral Implants Res 2008;19:119–130. 2. Wilson TG Jr. The positive relationship between excess cement and peri-implant disease: A prospective clinical endoscopic study. J Periodontol 2009;80:1388–1392. 3. Theoharidou A, Petridis HP, Tzannas K, Garefis P. Abutment screw loosening in single-implant restorations: A systematic review. Int J Oral Maxillofac Implants 2008;23:681–690. 4. Wenz HJ, Lehmann KM. A telescopic crown concept for the restoration of the partially edentulous arch: The Marburg double crown system. Int J Prosthodont 1998;11:541–550. 5. Krennmair G, Weinländer M, Krainhöfner M, Piehslinger E. Implant-supported mandibular overdentures retained with ball or telescopic crown attachments: A 3-year prospective study. Int J Prosthodont 2006;19:164–170.
The International Journal of Prosthodontics
© 2014 BY QUINTESSENCE PUBLISHING CO, INC. PRINTING OF THIS DOCUMENT IS RESTRICTED TO PERSONAL USE ONLY. NO PART MAY BE REPRODUCED OR TRANSMITTED IN ANY FORM WITHOUT WRITTEN PERMISSION FROM THE PUBLISHER.
This report describes the use of custom-positioned vertical screws (CVS) to attach primary telescopic crowns to implant abutments. In a private practice setting, 37 patients with 40 double crown–retained implant overdentures (IODs) with a clearance fit (Marburg double crowns) were followed. All primary crowns on the 120 implant abutments were retained using CVS. After a mean followup period of 3.55 ± 1.37 years (range: 1.5 to 6.3 years), one abutment screwloosening incident was reported (incidence: 0.08%). No loosening of any of the screw-retained primary crowns occurred. CVS may represent a viable fixation concept for IODs. Int J Prosthodont 2014;27:577–578. doi: 10.11607/ijp.3882
P
rimary telescopic crowns can be secured to implants via cementation or screw retention, but both techniques have specific limitations. Cemented restorations may lose retention; a review of implantsupported single-tooth restorations revealed a 5.5% loss of retention rate over 5 years.1 Peri-implantitis has been associated with excess residual cement,2 whereas screw-retained prostheses offer the advantage of retrievability—although screws also may loosen. The screw-loosening rates for single-tooth restorations using conventional axial screws are reported to range from 2.4% to 12.7%.3 The authors developed a method for connecting primary telescopes by creating screwaccess holes that are custom-positioned in an optimal vertical orientation parallel to the path of insertion on top of the primary crown. This design diminishes the associated risk of cement-related complications, offers retrievability of the restoration, and facilitates intraoral handling when compared to horizontal screw designs. This study describes the custom-positioned vertical screw (CVS) technique and provides clinical data from a 3-year follow-up.
aPrivate
Practice, Hofgeismar, Germany. Professor, Department of Operative Dentistry and Periodontology, University Medical Centre Leipzig, Leipzig, Germany. cHead of Periodontology, Department of Operative Dentistry and Periodontology, University of Freiburg, Freiburg, Germany. dPrivate Practice, Hanau, Germany. bAssistant
Correspondence to: Dr Eberhard Frisch, Markt 3, 34369 Hofgeismar, Germany. Fax: +49 5671 925027. Email: [email protected] ©2014 by Quintessence Publishing Co Inc.
Materials and Methods This retrospective study was performed in a private practice (Northern Hessia Implant Center, Hofgeismar, Germany). Based on the analysis of primary patient data, the study evaluated the clinical outcomes of double crown–retained implant overdentures (IODs) retained via Marburg double crowns (MDCs). The study was reviewed and authorized by the Ethics Commission of the Albert-Ludwigs-University, Freiburg, Germany (application no. 46/10-120329). The telescopic crowns were designed as MDCs with clearance fit4 and an additional retention element (TK Snap, Si-tec) on implants with a morse taper connection (Ankylos, Dentsply) and teeth. The secondary structures of all IODs were cast in one piece with no solder or welding joints. The dental laboratory technique for achieving a vertical screw axis parallel to the path of insertion is demonstrated in Figs 1 to 3. The clinical intraoral aspect of one of the patients with integrated primary crowns is shown in Fig 4.
Results Thirty-seven consecutive patients (22 women, 15 men; age: 70.58 ± 8.57 years) comprised the convenience sample. They were provided with 40 IODs supported by 120 implants and 61 teeth. The mean observational period was 3.55 ± 1.37 (range: 1.55 to 6.29) years. At the time of data acquisition, all implants and IODs were in situ and functional. Therefore, the cumulative survival rate (CSR) for the IODs retained by MDCs was 100% after 3.55 years. Screw loosening of 1 of the 120 (0.83%) taper-anchored abutments was observed but was corrected by retightening the abutment screw
Volume 27, Number 6, 2014
577
© 2014 BY QUINTESSENCE PUBLISHING CO, INC. PRINTING OF THIS DOCUMENT IS RESTRICTED TO PERSONAL USE ONLY. NO PART MAY BE REPRODUCED OR TRANSMITTED IN ANY FORM WITHOUT WRITTEN PERMISSION FROM THE PUBLISHER.
Retaining Double Crowns on Implants via Custom-Positioned Vertical Screws
Fig 1 Drilling a custompositioned thread hole strictly according to the milled telescope surface. (View of laboratory cast with artificial gingiva.)
Fig 2 Custom-positioned screw retention in the abutment. Note that the screw with the taper head is in situ. The implant axis is inclined toward the vestibule. (View of cast without artificial gingiva.)
Fig 3 Final shape of telescopic crown with custompositioned axial screw retention. (View of laboratory crown surrounded by artificial gingival tissue.)
a promising initial clinical performance with limited technical complications. Most of the maintenance interventions (61.54%) were prostheses related (0.061 T/P/Y), which is similar to reports from other clinical trials on IODs supported by telescopic crowns.5
Conclusions
Fig 4 Intraoral view of four primary telescopes with achieved axial orientation of the individually positioned retention screws.
to torque. None of the individually positioned axial screws that connected the primary telescopes to the abutments was affected by loosening, which yielded a success rate of 100%. The maintenance requirements related to implants or the implant-abutment connection or the abutment–primary telescope connection resulted in 0.008 treatments per patient per year (T/P/Y). The follow-up included an additional 12 patient visits for prosthetic maintenance. Eight of these related to dentures (0.06 T/P/Y), including 2 cases of relining, 2 denture teeth fractures, 2 veneer repairs, and 2 occlusal corrections. In four cases, recementation of the tooth-supported primary telescopes was needed (0.03 T/P/Y).
Discussion The small sample size and relatively short observational period precluded drawing significant conclusions. However, MDC-retained IODs clearly showed
578
The use of CVS to retain primary telescopic crowns on implant abutments ensures retrievability of the restoration and appears to result in low maintenance requirements. Controlled clinical trials with larger sample sizes and longer observational periods should be conducted.
Acknowledgments The authors reported no conflicts of interest related to this study.
References 1. Jung RE, Pjetursson BE, Glauser R, Zembic A, Zwahlen M, Lang NP. A systematic review of the 5-year survival and complication rates of implant-supported single crowns. Clin Oral Implants Res 2008;19:119–130. 2. Wilson TG Jr. The positive relationship between excess cement and peri-implant disease: A prospective clinical endoscopic study. J Periodontol 2009;80:1388–1392. 3. Theoharidou A, Petridis HP, Tzannas K, Garefis P. Abutment screw loosening in single-implant restorations: A systematic review. Int J Oral Maxillofac Implants 2008;23:681–690. 4. Wenz HJ, Lehmann KM. A telescopic crown concept for the restoration of the partially edentulous arch: The Marburg double crown system. Int J Prosthodont 1998;11:541–550. 5. Krennmair G, Weinländer M, Krainhöfner M, Piehslinger E. Implant-supported mandibular overdentures retained with ball or telescopic crown attachments: A 3-year prospective study. Int J Prosthodont 2006;19:164–170.
The International Journal of Prosthodontics
© 2014 BY QUINTESSENCE PUBLISHING CO, INC. PRINTING OF THIS DOCUMENT IS RESTRICTED TO PERSONAL USE ONLY. NO PART MAY BE REPRODUCED OR TRANSMITTED IN ANY FORM WITHOUT WRITTEN PERMISSION FROM THE PUBLISHER.
