PubMed · 4905461
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G Paizis. [Basic principles in making and improving cast crowns].. https://pubmed.ncbi.nlm.nih.gov/4905461/
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Clinical experiences for the past 9 years have demonstrated the practicability of the O-ring coping attachment, a modification of the telescopic crown-and-sleeve coping retainers, for removable partial dentures. A circumferential groove placed in the primary coping receives an elastomeric O-ring that fits into a corresponding groove made in the internal surface of the telescopic crown. The O-ring not only provides controllable retention but also acts as a shock absorber. Long-term retention of the prostheses can be easily maintained by periodic replacements of the O-rings. Sophisticated procedures and expensive machines are not required to make the prostheses. Excellent patient acceptance and the versatility in clinical applications make this system one of the winning designs for removable partial prosthodontics.
Primary splinting of fixtures with bar attachments has proved to be clinically effective for overdentures on osseointegrated implants in the edentulous mandible. However, in vitro investigations indicate that a more favourable force transfer to the individual fixtures can be attained by secondary splinting of four implants with conical double crowns. This observation could be confirmed in the present study by measurement of implant deflection in a model of the mandible by means of interferometric optical holography. Telescope crowns with conical interface brought about functionally more even movement characteristics of the implants compared to rigid or jointed bar attachments. Moreover, the conical double crowns always ensured a stable position of the denture in contrast to jointed attachments. These results underscore the need to test conical double crowns clinically as anchors for overdentures on osseointegrated implants.
It has been shown that iatrogenic preparation damage increases caries progression and the need for restorative therapy of the adjacent tooth. The aim of this study was to quantify the damage of the adjacent tooth using three different preparation techniques: (1) diamond bur alone; (2) diamond bur combined with the EVA system and the Cavishape file; (3) diamond bur combined with an axial margin trimmer. All 136 preparations were performed by dental practitioners in their own practice. Examination of the area directly opposite to the axial box margin revealed significantly less damage (p < 0.01) using additionally the EVA system with the Cavishape file or the axial margin trimmer compared to using only diamond burs. The area opposite between the two box margins, which was in all three methods prepared only by the diamond bur, showed no significant differences between the methods under study. There were only a few teeth (overall 5%) with no damage of the adjacent surface. In order to reduce iatrogenic damage for the adjacent teeth the preparation technique has to be modified.