ABSTRACT
Statement of the Problem: 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
Purpose: This study aimed to evaluate the influence of existence of screw access hole on porcelain fracture resistance of metal-ceramic implant-supported crowns
Materials and Method: Thirty six standardized metal-ceramic crowns were fabricated and divided into 3 groups [n=12]; group 1 conventional cement-retained metalceramic 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 [alpha=0.05]
Results: 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]
Conclusion: Presence of screw access channel in cement-retained implant restorations does not compromise fracture resistance
ABSTRACT
Statement of the Problem: Implant-retained overdenture can improve the stability of dentures and prevent bone loss. Overdenture-wearing patients need special hygiene care
Purpose: The aim of this study was to evaluate the effects of various denture cleansers on the retention of Dio orange O-rings
Method and Materials: In this experimental study, 40 Dio orange O-rings were divided into 4 groups [10 O-rings each] and each group was soaked for equivalent of 6 months in the following solutions: 5.25% NaOCl [1:10 dilution], Corega cleanser tabs, Professional cleanser tabs and water [as the control group]. After 6 months, O-rings were tested for 2inch/minutes of tensile force. The peak load-todislodgement was recorded. Data were imported to SPSS18 and were analyzed by One-Way ANOVA and Tukey HSD test [p
Results: Denture cleansing solutions have significant effects on the reduction of retentive value of O-rings [p
Conclusion: This in-vitro study demonstrated that the retention of O-rings was affected when soaked in cleansing solutions. NaOCl caused more reduction in retentive value compared to effervescent cleansers and would not be recommended for cleansing O-rings. These results should be interpreted clinically and the role of other factors in the retention of O-rings should be considered in order to recommend the best cleanser for O-ring overdentures