An in vitro trial on the effect of arch form on connector size requirements in long span anterior zirconia fixed dental prostheses.

PURPOSE: To test the fracture resistance of maxillary canine to canine fixed partial denture with four missing incisors, with increasing anterior-cantilevers of the pontics and varying connector sizes. MATERIALS AND METHODS: Two 3D-printed titanium alloy (Ti6Al4V) models mimicking a maxillary canine to canine fixed partial denture (FPD) with four pontics replacing the incisors were used as master models. Zirconia FPDs were digitally designed and milled with two different connector sizes (9 and 12 mm2 ) each with three different anterior cantilevers (7, 10, and 13 mm) accounting for 6 test groups. Seven samples were milled for each group generating a total of 42 samples. The zirconia FPDs were cemented on the titanium model using resin modified glass ionomer cement and the model fixated to a variable angle vice. A sinusoidal cyclic waveform load from 50 to 280N was applied using a universal testing machine at a frequency of 30 cycles per second and a total of 5 million cycles. RESULTS: The results of Fisher's exact tests showed that the difference in the proportion of fractured versus nonfractured fixed partial dentures was not statistically significant when comparing the 9 with the 12 mm2 connector size (p = 1.00), as well as when comparing the six test groups (p = 0.2338); on the other hand, it proved to be statistically significant when comparing the 7 mm cantilever with the 10 and 13 mm cantilevers combined (p = 0.0407) indicating that a 7 mm anterior spread of the pontics showed a significantly greater proportion of fixed partial dentures that fractured. CONCLUSIONS: Fracture susceptibility was not a function of cantilever length in this testing configuration for anterior FPDs. Retainer crown thickness seems to be a more important parameter than connector size thickness. Based on the results, a smaller connector size (9 mm2 ) can be used to improve the esthetics of pontics in long span anterior FPDs.

Human Gingival Epithelial Growth In Vitro on a Polymer-Infiltrated Ceramic Network Restorative Material.

PURPOSE: To investigate the growth of primary human gingival epithelial (HGE) cells on polymer-infiltrated ceramic network (PICN) material (Vita Enamic) with different surface roughnesses. MATERIALS AND METHODS: PICN material specimens were polished with either silica carbide paper (grit-polished) or the manufacturer's polishing wheels (wheel-polished), and the surface roughness (Ra ) measured. HGE cells were seeded and grown for 1, 3, or 6 days. Growth on tissue culture plastic was used as a control. Non-linear regression analysis was used to examine the effect of surface roughness on cell growth. RESULTS: HGE cell growth on tissue culture plastic fitted an exponential growth model over the 6-day experimental period (R2 = 0.966). Through day 6, cell density on PICN decreased with increasing surface roughness, with a fit to an exponential decay model (R2 = 0.666). A threshold Ra value of 0.254 µm (95% CI 0.177-0.332) was determined as an upper limit for exponential growth. Cell growth was greatest on the group of specimens with Ra value below 0.127µm. Specimens polished by the manufacturer's method produced surface roughness of 0.118 µm and below. CONCLUSIONS: PICN material polished to a smooth surface (Ra < 0.254 µm) resulted in exponential growth of HGE cell growth compared to rough surfaces. Polishing PICN material as smooth as possible (below a Ra of 0.127 µm) was found to maximize epithelial cell growth on the PICN material surface. The manufacturer's polishing method achieved a sufficiently smooth surface. These results are contrary to previous research regarding surface roughness of transgingival implant restoration components. The study results suggest that smoother restorative material surfaces could improve peri-implant soft tissue health.

Digital capture, design, and manufacturing of an extraoral device for a clarinet player with Bell's palsy.

An extraoral device was fabricated to assist a clarinet player with Bell's palsy. The device was fabricated by using stereophotogrammetry, digital design, and additive manufacturing technologies.