Accuracy and surface roughness of Co-Cr partial denture frameworks with different digital fabrication methods.

STATEMENT OF PROBLEM: Traditional removable partial denture (RPD) manufacture is being phased out in favor of computer-aided design and computer-aided manufacturing (CAD-CAM) techniques and rapid prototyping (RP), which provide more efficient methods of producing RPD frameworks. However, studies comparing the accuracy and surface roughness of these approaches on RPD frameworks are still scarce. PURPOSE: The purpose of this in vitro study was to evaluate the accuracy and surface roughness of class I cobalt chromium (Co-Cr) removable partial denture frameworks digitally constructed using 2 different CAD-CAM technologies: direct milling (DM) and selective laser melting (SLM). MATERIAL AND METHODS: An educational maxillary stone cast was scanned to create a resin model after rest seat preparation. The resin model was scanned, and an RPD framework was digitally designed. Sixteen frameworks were constructed (n=8). Two groups were defined. In the direct milling (DM) group, the standard tessellation language (STL) file of the RPD framework was used to mill the design from a Co-Cr blank directly. In the selective laser melting (SLM) group, the STL file of the RPD framework was used to print the design from Co-Cr powder using the selective laser melting technique. Geomagic Control X software program was used to measure the accuracy of the fabricated frameworks. Surface roughness was tested using optical profilometry. An unpaired t test was used to compare the 2 groups (α=.05). RESULTS: The DM group showed significantly higher mean ±standard deviation accuracy (189 ±9 µm) (P<.001) compared with the SLM group (456 ±122 µm). Regarding the surface roughness, the DM group (0.157 ±0.001 mm) showed significantly lower surface roughness (P<.001) compared with the SLM group (0.256 ±0.001 mm). CONCLUSIONS: The direct milling fabrication technique enabled the fabrication of Co-Cr RPD frameworks with higher accuracy and less surface roughness when compared with the 3-dimensionally printed SLM technique.

Influence of titanium and titanium-zirconium alloy as implant materials on implant stability of maxillary implant retained overdenture: a randomized clinical trial.

BACKGROUND: Long-term success of implant restoration depends on many factors one of them is the sufficient implant stability which is lowered in compromised bone density sites such as the maxilla as it is categorized as type III & IV bone, so searching for a new innovation and updates in implant material and features is very mandatory. So, the aim of this study was to compare between two implant materials (roxolid and traditional titanium) on the primary and secondary stability of implant retained maxillary overdenture. METHODS: Eighteen completely edentulous patients were selected. All patients received maxillary implant-retained overdentures and lower complete dentures; patients were divided equally into two groups according to the type of implant materials. Group A received a total number of 36 implants made of roxolid material and Group B received a total number of 36 implants made of traditional titanium alloys. Implant stability was assessed using ostell device, the primary implant stability was measured at the day of implant installation however, secondary implant stability was measured after six weeks of implant placement. Paired t-test was used to compare between primary and secondary stability in the same group and an independent t-test was used to compare between the two groups with a significant level < 0.05. RESULTS: Independent t-test revealed a significant difference between the two groups with p -value = 0.0141 regarding primary stability and p-value < 0.001 regarding secondary stability, as roxolid implant group was statistically higher stability than titanium group in both. Paired t- test showed a statistically significant difference in roxolid implant group with p-value = 0.0122 however, there was non-statistically significant difference in titanium group with p-value = 0.636. Mann Whitney test showed a significant difference between the two groups regarding amount of change in stability with p value = 0.191. roxolid implant group showed a higher amount of change in stability than the titanium implant group. CONCLUSION: Within the limitation of this study, it could be concluded that: Roxolid implants showed promising results regarding primary and secondary stability compared to conventional Titanium implants and can be a better alternative in implant retained maxillary overdentures. TRIAL REGISTRATION: Retrospectively NCT06334770 at 26-3-2024.

Evaluation of the Accuracy and Adaptation of BioHPP Removable Partial Denture Frameworks Constructed by Milling vs the Pressing Technique.

PURPOSE: To evaluate the accuracy and adaptation of BioHPP removable partial denture frameworks constructed from milling vs the pressing technique. MATERIALS AND METHODS: This in vitro study was applied on an educational maxillary stone model with bilateral bounded saddles. Two different manufacturing techniques were used, and thus two groups were defined: (1) the pressed group, in which 20 BioHPP frameworks were constructed by milling a castable resin that was pressed into BioHPP using the lost wax technique; and (2) the milled group, in which 20 BioHPP frameworks were constructed directly by milling the BioHPP blanks. The accuracy of the frameworks was evaluated using Geomagic Control X software, and the gap distance was captured using a stereomicroscope. RESULTS: The milled group showed higher values of accuracy than the pressed group in the x, y, and z axes, and according to Student t test, this difference was statistically significant in the x and z axes. Regarding the adaptation of the frameworks, the milled group showed lower adaptation values than the pressed group. Student t test showed that this difference was statistically significant regarding adaptation of the major connector. However, there was no statistically significant difference concerning adaptation of the denture bases between the two groups. CONCLUSION: Within the limitations of this study, it could be concluded that: (1) the milling technique could be used to fabricate BioHPP RPD frameworks with higher accuracy than the pressing technique; and (2) the pressing technique showed less gap distance (ie, better adaptation) at the area of the major connector.