Optimizing Adhesion for 3D Printed Materials
Procedures and strategies to improve bond strength to restorations and appliances
March 1, 2025
Volume 21
,
Issue 2
,
March 2025
Page(s): p. 8
For clinicians who use digital workflows, 3D printing offers a cost-effective way to produce in-office models, prostheses, and appliances. Digital workflows allow dentists to use intraoral scanners to capture patient data, which can then be used to plan, design, and fabricate various aspects of treatment. Working with digital files offers several advantages, including automated planning and design, the elimination of traditional wet laboratories, the ability to work remotely, improved communication with patients and colleagues, and efficient digital storage of case information.
Although digital planning provides many benefits, eventually, the design must transition into the physical realm. Traditionally, milling was the primary method used to convert digital designs into physical objects. Today, 3D printing provides a more accessible and cost-effective alternative, enabling clinicians to directly create physical objects from digital designs within their offices. When compared with milling, 3D printing is significantly less expensive, with the necessary equipment-such as the printer and curing box-typically being around 10 times more affordable than milling equipment, such as mills and furnaces.
For clinicians who are considering 3D printing, it's important to assess the specific applications and needs of the technology to ensure that it aligns with treatment goals and practice capabilities. Common uses of 3D printing in dentistry include the creation of models, temporary and permanent crowns, occlusal splints, dentures, hybrid prostheses, and surgical guides. There are no commercially available in-office ceramic printers, so the materials for current 3D printers are all resin-based. Although these materials do not have the mechanical strength of milled ceramic, their ductility can be beneficial for appliances such as splints and dentures. A recent study in our laboratory found that 3D printed resin crowns with 50% filler demonstrated a similar survival rate to lithium disilicate crowns after 2 million cycles of occlusal fatigue loading.1
In clinical settings, there may be a need to bond to the surface of 3D printed materials, particularly restorations. Because 3D printed materials are all resin-based, they should be treated like resin composites when bonding. The following sections outline procedures and strategies for bonding to these materials in various clinical situations.
Relining a 3D Printed Temporary Crown
A common method of fabricating 3D printed temporary crowns involves the creation of "shell temporaries." In this technique, the digital design of the final restoration is modified to create a hollowed-out crown with a thin exterior shell. The shell is printed and then relined in the patient's mouth after tooth preparation. Two recent studies have reported mixed results on the effectiveness of relining temporary 3D printed materials.2,3 One study found that relining with PMMA provided better bond strength than relining with composite or bisacryl, while the other study found no significant difference. Of note, one key difference between the studies was that the protocol followed in the first study did not involve sandblasting the surface before bonding. Internal testing in our laboratory has shown that sandblasting improves the bond strength to temporary crown 3D printed materials, whether using PMMA or bisacryl. In summary, shell temporaries can be effectively relined in two ways: (1) Sandblast the inner surface with alumina, apply a coat of PMMA monomer, and fill with PMMA; or (2) Sandblast the inner surface with alumina and fill with bisacryl material.
Bonding to a 3D Printed Crown
Essentially, 3D printed crowns are composed of resin and ceramic filler particles. Bonding to the ceramic particles can be achieved using a silane primer, such as those used for bonding to glass-ceramic crowns and veneers. But because 3D printed crowns also contain resin, the use of an adhesive, such as those used for bonding direct composite restorations, can further enhance adhesion. The matrix of a 3D printed crown is resin, as opposed to the glass matrix of a ceramic crown; therefore, hydrofluoric acid etching is not indicated. Instead, sandblasting with alumina is necessary to create the surface texture for bonding. Our laboratory has found that the optimal bonding procedure is to sandblast with alumina, apply a layer of adhesive, and then apply a resin cement. Applying a layer of silane before the adhesive is optional.4
Adding to a Hybrid Prosthesis
The process of bonding to a hybrid prosthesis material is similar to bonding to a crown material because they are compositionally similar. The main difference is that sandblasting the area of interest may not be feasible. Therefore, the protocol would be to optionally sandblast the area of interest, optionally apply a layer of silane, apply a layer of adhesive, cure the adhesive, and then apply a resin-based repair or characterization material.
Adding to a 3D-Printed Splint
There are situations in which it may be necessary to add material to a 3D printed splint to restore occlusal contact. Internal testing conducted in our laboratory has shown that applying an adhesive and curing it before adding flowable composite significantly improved bond strength. Notably, the bond strength to 3D printed splints was found to be significantly greater than that to a milled splint material.
About the Author
Nate Lawson, DMD, PhD
Director/Associate Professor
Division of Biomaterials
University of Alabama at Birmingham
School of Dentistry
Birmingham, Alabama
References
1. Bora PV, Lawson NC, Givan DA, et al. Enamel wear and fatigue resistance of 3D printed resin compared with lithium disilicate. J Prosthet Dent. 2024:S0022-3913(24)00717-0.
2. Palavicini J, Quin SL, Zakkour W, et al. Bond strength of reline materials to 3D-printed provisional crown resins. Polymers (Basel). 2023;15(18):3745.
3. Albahri R, Yoon HI, Lee JD, et al. Shear bond strength of provisional repair materials bonded to 3D printed resin. J Dent Sci. 2021;16(1):261-267.
4. Hammamy M, Rueda SR, Pio A, et al. Effect of air particle abrasion and primers on bond strength to 3D-printed crown materials. Materials (Basel). 2025;18(2):265.
