By Susan Prater-Kudlats, DMD
The injection molding technique is gaining popularity for dental clinicians due to its wide array of procedural applications. This technique involves injecting a low viscosity resin composite through a transparent silicone index made from a diagnostic wax-up, aiming to replicate the mock-up.
Having the capability to quickly and predictably transfer a mock-up into a patient’s mouth using composite resin allows clinicians to offer their patients alternative treatment options. This procedure provides an effective way to restore multiple teeth in the arch as temporary, transitional and/or permanent restorations. (FIG. 1)
Before photo of a worn/broken lower dentition (#’s 21-27) before using the injection molding technique.
The first step was to design a 3D digital wax-up model of the desired outcome. Then a duplicate model was made with every other tooth eliminated from the initial design. In this case, the smile designs were outsourced to the Evident Hub, utilizing Exocad software. The two models were 3D printed on the Einstein printer by Desktop Health, using Model Z resin. One model with every tooth and one with every other tooth.
The silicone matrices were fabricated by dispensing the Affinity Crystal Clear Matrix Impression Material (Clinician’s Choice) into the Clear Impression Trays (Clinician’s Choice) and seating the material on the respective 3D printed models. (FIG. 2) Once set, the silicone matrices were removed from the clear trays.
Fabrication of the two silicone matrices.
Then the matrices were prepared by making a small opening, leading from the intaglio surface of the matrices to the outer surface. The access hole was created using a composite syringe tip to puncture the intaglio surface of the matrix and push it through to the outer surface. The location of the holes are incisal/occlusal to the teeth that are to be restored. First, the access holes for the duplicate model were prepared, leading to tooth #’s 21, 23, 25 and 27, as #’s 22, 24 and 26 were deactivated on this model. The second matrix was of the full wax-up, and vent holes were created leading to #’s 22, 24 and 26.
Minimal preparations were done on all teeth, which includes removal of decay, 2mm bevel preparations with a 7901 flame shaped bur (Brasseler) and air abrasion. PTFE tape was placed on #’s 22, 24 and 26. Etching and bonding procedures were done on #’s 21, 23, 25 and 27. The first matrix was placed and the Evanesce Flow Composite (Clinician’s Choice) was injected through the tiny access holes, followed by polymerization of the composite resin through the clear matrix. (FIG. 3)
Evanesce Flow (Clinician’s Choice) was injected through access holes into the clear matrix.
After the first set of teeth were restored, finished with Neodiamond pointed cone bur (ref #3314.10VF) and polished with ceramic polishing wheels: coarse blue (FLW14C), medium pink (FLW14M), and fine gray (FLW14F), the same procedure was done to restore #’s 22, 24 and 26. Finally, the occlusion was adjusted to achieve bilateral simultaneous equal-intensity contacts.
Highlights the restored lower dentition after using the injection molding technique.