fa The Effects of New Design of Access Hole on Porcelain Fracture Resistance of Implant-Supported Crowns پروتزهای دندانی Prothtodontics پژوهشي Research <b> Statement of the Problem:</b> One disadvantage of cement-retained crowns is the lack of predictable irretrievability. This problem can be overcome through designing a screw access hole in the metal substructure of cement-retained restoration and using porcelain stain to define this area.<div>  <b>Purpose: </b>This study aimed to evaluate the influence of existence of screw access hole on porcelain fracture resistance of metal-ceramic implant-supported crowns. </div><div>  <b>Materials and Method</b>: Thirty six standardized metal-ceramic crowns were fabricated and divided into 3 groups (n=12) group 1 conventional cement-retained metal-ceramic crowns as control group, group 2 cement-retained MC crowns in which porcelain stain was used to define the location of screw access channel, and group 3 cement-retained metal-ceramic crowns in the metal substructure of which a hole and ledge was designed in the location of screw access channel. The specimens were cemented (TempBond, Kerr) to their dedicated abutments. A hole was made in the location of screw access channel in group 2 and 3 and filled with photo-polymerized composite resin (3M ESPE). All specimens were thermocycled and loaded in universal testing machine at crosshead speed of 2mm/min until fracture. Mean values of load at fracture were calculated in each group and compared with One-way ANOVA (α=0.05).</div><div><b> Results</b>: Mean value of the load required to fracture the restorations was 1947±487 N in group 1, 1927±539 N in group 2, and 2170±738 N in group 3. No statistically significant difference was found between the fracture resistance values of the three groups (p> 0.05) </div><div>  <b>Conclusion</b>: Presence of screw access channel in cement-retained implant restorations does not compromise fracture resistance.</div><hr><p class="MsoNormal" style="text-align: left direction: ltr unicode-bidi: embed"><b>Source: </b>Journal of Dentistry Shiraz University of Medical Sciences </p> <p class="MsoNormal" style="text-align: left direction: ltr unicode-bidi: embed"><a href="http://dentjods.sums.ac.ir/index.php/JDSUMS/article/view/913" target="_blank"><font color="#0000ff">Full Text</font></a></p> 0 0 http://idai.ir/browse.php?a_code=A-10-32-3115&slc_lang=fa&sid=1 Reza Derafshi 100319475328460014388 100319475328460014388 No Dept. of Prosthodontics, School of Dentistry, Shiraz University of Medical Sciences, Shiraz, Iran. Mitra Farzin 100319475328460014389 100319475328460014389 No Dept. of Prosthodontics, School of Dentistry, Shiraz University of Medical Sciences, Shiraz, Iran. Masoumeh Taghva 100319475328460014390 100319475328460014390 No Dept. of Prosthodontics, School of Dentistry, Shiraz University of Medical Sciences, Shiraz, Iran Hossein Heidari dr.hheidary@gmail.com 100319475328460014391 100319475328460014391 Yes Dept. of Prosthodontics, School of Dentistry, Shiraz University of Medical Sciences, Shiraz, Iran Berivan Atashkar 100319475328460014392 100319475328460014392 No Dept. of Prosthodontics, School of Dentistry, Shiraz University of Medical Sciences, Shiraz, Iran