Physical properties and comparative strength of a bioactive luting cement.

UNLABELLED: New dental cement formulations require testing to determine physical and mechanical laboratory properties. OBJECTIVES: To test an experimental calcium aluminate/glass-ionomer cement, Ceramir C and B (CC and B), regarding compressive strength (CS), film thickness (FT), net setting time (ST) and Vickers hardness. An additional test to evaluate potential dimensional change/expansion properties of this cement was also conducted. METHODS AND MATERIALS: CS was measured according to a slightly modified ISO 9917:2003 for the CC and B specimens. The samples were not clamped while being exposed to relative humidity of great than 90 percent at 37 degrees C for 10 minutes before being stored in phosphate-buffered saline at 37 degrees C. For the CS, four groups were tested: Group 1-CC and B; Group 2-RelyX Luting Cement; Group 3-Fuji Plus; and Group 4-RelyX Unicem. Samples from all groups were stored for 24 hours before testing. Only CCandB was tested for ST and FT according to ISO 9917:2003. The FT was tested 2 minutes after mixing. Vickers hardness was evaluated using the CSM Microhardness Indentation Tester using zinc phosphate cement as a comparison material. Expansion testing included evaluating potential cracks in feldspathic porcelain jacket crowns (PJCs). RESULTS: The mean and standard deviation after 24 hours were expressed in MPa: Group 1 equals 160 plus or equal to 27; Group 2 equals 96 plus or equal to 10; Group 3 equals 138 plus or equal to 15; Group 4 equals 157 plus or equal to 10. A single-factor ANOVA demonstrated statistically significant differences between the groups (P less than 0.001). Pair-wise statistical comparison demonstrated a statistically significant difference between Groups 1 and 2. No statistically significant differences were found between other groups. The FT was 16.8 plus or equal to 0.9 and the ST was 4.8 plus or equal to 0.1 min. Vickers hardness for Ceramir C and B was 68.3 plus or equal to 17.2 and was statistically significantly higher (P less than 0.05) than Fleck's Zinc Phosphate cement at Vickers hardness of 51.4 plus or equal to 10. There was no evidence of cracks due to radial expansion in PJCs by the Ceramir C and B cement. CONCLUSION: All luting cements tested demonstrated compressive strengths well in excess of the ISO requirement for water-based cements of no less than 50 MPa. Ceramir C and B showed significantly higher CS than RelyX Luting Cement after 24 hours, but was not significantly higher than either Fuji Plus or RelyX Unicem. The ST and FT values of CC and B conform to and are within the boundaries of the requirements of the standard. Surface hardness was statistically higher than and comparable to zinc phosphate cement. There was no evidence of potentially clinically significant and deleterious expansion behavior by this cement. All cements tested demonstrated acceptable strength properties. Within the limits of this study, Ceramir C and B is deemed to possess physical properties suitable for a dental luting cement.

Prospective observation of a new bioactive luting cement: 2-year follow-up.

PURPOSE: A pilot study was conducted to determine the 2-year clinical performance of a new bioactive dental cement (Ceramir C&B, formerly XeraCem) for permanent cementation. MATERIALS AND METHODS: The cement used in this study is a new formulation class, a hybrid material comprising calcium aluminate and glass ionomer. Thirty-eight crowns and fixed partial denture (FPD) abutments were cemented in 17 patients. Thirty-one of the abutment teeth were vital, 7 nonvital. Six reconstructions were FPDs comprising 14 abutment teeth (12 vital/2 nonvital). A two-unit fixed splint was also included. Preparation parameters and cement characteristics (dispensing, working time, seating characteristics, ease of cement removal) were recorded. Baseline and postcementation data were recorded for marginal integrity, marginal discoloration, secondary caries, retention, and gingival inflammation. Tooth sensitivity was assessed at pre- and postcementation time points using categorical and visual analogue scale (VAS) assessment measures. RESULTS: Mixing of the cement was reported as "easy." Clinical working time for this cement was deemed acceptable. Assessment of seating characteristics indicated all restorations were seated completely after cementation. Cement removal was determined to be "easy." Fifteen of 17 subjects were available for 1-year recall examination; 13 patients were available for the 2-year recall examination. Restorations at 2-year recall examination included 17 single-unit, full-coverage crown restorations, four 3-unit FPDs comprising 8 abutments, and one 2-unit splint. No retentive failures or sensitivity were recorded at 2-year recall. Marginal integrities of all restorations/abutments at 2 years were rated in the "alpha" category. Average VAS score for tooth sensitivity decreased from 7.63 mm at baseline to 0.44 mm at 6-month recall, 0.20 mm at 1-year recall, and 0.00 mm at 2-year recall. The average gingival index score for gingival inflammation decreased from 0.56 at baseline to 0.11 at 6-month recall, then 0.16 at 1-year recall, and 0.21 at 2-year recall. CONCLUSIONS: Two-year recall data yielded no loss of retention, no secondary caries, no marginal discolorations, and no subjective sensitivity. All restorations rated "alpha" for marginal integrity at the 2-year recall. After periodic recalls up to 2 years, the new bioactive cement tested thus far has performed favorably as a luting agent for permanent cementation.

Comparison of detachment forces of two implant overdenture attachment types: effect of detachment speed.

PURPOSE: To compare detachment (retentive) force for overdenture retainers used with conventional and "mini" implant designs over a range of different detachment (separation) speeds. METHODS: Two dental implant fixtures [Sendax MDI ("mini" dental implant) and Replace Select (conventional dental implant design)] with ball attachments were mounted in brass cylinders. Corresponding attachments were processed into acrylic denture resin blocks and connected to the ball attachments on the implants. The fixture/attachment assemblies were placed in an Instron testing system under ambient room temperature and humidity conditions (approximately 72 degrees F and 35-65% relative humidity). The assemblies were separated under tensile load at 11 speeds from 10-500 mm/minute with 10 replicates at each speed. Maximum detachment (separation) force was recorded. Mean, minimum, maximum, standard deviation and range of maximum detachment (separation) force was calculated. To test the hypothesis "the Sendax MDI and the Replace Select have the same average detachment force, at a given detachment speed", one-way ANOVA was performed. To test the hypothesis that "all detachment speeds have the same average maximum detachment force", one-way ANOVA was performed. To test the hypothesis that "the distribution of maximum detachment forces is the same for all detachment speeds", non-parametric Kruskal-Wallis analysis was performed. RESULTS: For Replace Select, the mean of the maximum force varied from 6.02-3.46 N with a downward trend as detachment speed increased. For Sendax MDI, the mean of the maximum force varied from 3.43-2.86 N. One-way ANOVA and Kruskal-Wallis analyses supported rejection of the hypotheses stated above with more than 99.99% confidence. Within the limitations of this study, the retentive properties of the Sendax MDI and the Replace Select attachment properties were different. Detachment speed had an effect on separation force for the two attachments in this study. Given the range of velocities possible in masticatory function; implant overdenture attachments, optimally, should be evaluated at more than one detachment speed to evaluate clinically-relevant, strain-rate behavior.