Comparing the trueness of 3D printing and conventional casting for removable partial denture metal framework fabrication in different mandibular major connectors designs: An in vitro study.

STATEMENT OF PROBLEM: To ensure long-term stability and performance, removable partial dentures (RPDs) must be fitted precisely. Although 3-dimensional (3D) printing has been widely used, studies comparing various methods of manufacturing and designs for mandibular removable partial denture (RPD) frameworks are lacking.

PURPOSE: The aim of this in vitro study was to compare the trueness of RPD metal frameworks with 2 different major connector design types (lingual bar and lingual plate) fabricated with direct and indirect metal 3D printing with those fabricated with the conventional lost wax technique.

MATERIAL AND

METHODS

A Type IV stone cast of a Kennedy classification II modification 1 partially edentulous mandibular arch was prepared as the reference cast. A total of 30 definitive casts were fabricated from the reference cast and scanned into standard tessellation language (STL) files. Ten of these casts were used to fabricate cobalt chromium (Co-Cr) frameworks with the conventional lost wax technique (CLW group), 10 were used to fabricate frameworks by printing into a castable resin pattern followed by conventional casting (RPC group), and 10 were used to print metal frameworks directly using a selective laser melting printer (DSLM group). For each fabrication method, the group was divided into 2 design types: 5 casts for lingual plate frameworks and 5 for lingual bar frameworks (n=5). All metal frameworks were scanned and superimposed with the definitive casts with the Geomagic Control X software program. Gap discrepancies were measured as mean ±standard deviation (trueness), and the data were statistically analyzed with the 2-way ANOVA test (α=.05) to determine the interaction of the fabrication methods and design types on trueness. The Tukey HSD test was used to compare mean trueness among groups (α=.05).

RESULTS

The CLW group demonstrated the highest overall gap discrepancies in the lingual plate frameworks, measuring 0.207 ±0.035 mm, whereas the DSLM group recorded the lowest value at 0.141 ±0.022 mm. No statistically significant difference was found between the DSLM and RPC groups (P>.05). The DSLM group exhibited the lowest mean gap for the lingual bar frameworks, 0.091 ±0.016 mm, with no significant difference between the RPC and CLW groups (P>.05). The 2-way ANOVA indicated that trueness was significantly affected by fabrication methods and design types. The color mapping of the lingual plate and bar in the DSLM frameworks shows minimal deviations relative to other groups.

CONCLUSIONS

The direct and indirect 3D printing of lingual plate RPD frameworks demonstrated better trueness compared with conventional casting methods. Direct 3D metal printing showed better fit and lower discrepancy for lingual bar designs. Both conventional and 3D printing methods demonstrated clinically acceptable adaptation.