Mechanical and Physical Properties of Durable Prosthetic Restorations Printed Using 3D Technology in Comparison with Hybrid Ceramics and Milled Restorations—A Systematic Review

Abstract

Background/Objectives: Additive manufacturing (AM) technology has emerged as an innovative approach in dentistry. Recently, manufacturers have developed permanent resins engineered explicitly for the fabrication of definitive prostheses using AM techniques. This systematic review evaluated the mechanical and physical properties of 3D-printed permanent resins in comparison to milled resins and hybrid ceramics for the fabrication of indirect dental restorations. Methods: Three electronic databases—Scopus, Web of Science, and PubMed—were searched for English-language articles. Two independent researchers conducted study selection, data extraction, quality assessment, and the evaluation of the certainty of evidence. In vitro studies assessing the mechanical and physical properties of the permanent resins were included in this review. Results: A total of 1779 articles were identified through electronic databases. Following full-text screening and eligibility assessment, 13 studies published between 2023 and 2024 were included in this qualitative review. The investigated outcomes included physical properties (surface roughness, color changes, water sorption/solubility) and mechanical properties (flexural strength, elastic modulus, microhardness). Conclusions: Three-dimensionally printed permanent resins show promising potential for fabricating indirect dental restorations. However, the current evidence regarding their mechanical and physical properties remain limited and inconsistent, mainly due to variability in study methodologies.

1. Introduction

The digital revolution in dentistry has facilitated the widespread integration of advanced technologies, such as computer-aided design/computer-aided manufacturing (CAD/CAM), to fabricate fixed dental prostheses. CAD/CAM systems offer several advantages over conventional methods, including the elimination of the need for recording impressions, wax pattern fabrication, and casting, thereby reducing the risk of procedural errors [1,2]. CAD/CAM systems based on subtractive manufacturing are used to produce restorations with accurate dimensions. However, milling uses solid blocks that are cut into desired shapes, resulting in material wastage and additional costs for milling tools [1,2].

Lately, three-dimensional (3D) printing and additive manufacturing have gained popularity due to their ability to fabricate complex structures by layering materials. Additive manufacturing is more economical than milling, as it minimizes wastage, reduces total production costs and time, and enables the easy printing of complex structures. Two widely used 3D printing techniques in dental prostheses are digital light projection (DLP) technology, which utilizes a digital projector screen to project images of each layer across the entire platform, and stereolithography (SLA), which employs a laser to create points that form the layers [2,3,4]. Newer materials developed for the fabrication of fixed dental prostheses include milled materials such as feldspathic ceramics, zirconia, and leucite-reinforced and lithium disilicate glass ceramics, as well as printable materials like printed permanent resins [5,6].

Newer 3D-printed permanent resins typically comprise two basic components, including the matrix of resin polymer and ceramic-based filler particles. Their properties vary depending on their composition, with improvements resulting from an increase in filler content or changes in the matrix composition, particle shape, size, and the polymerization method [7,8]. A significant drawback of printable resins is their high filler content. It has been demonstrated that adding more fillers can hinder the flow of the resin during the build process, increasing the chances of air bubbles being trapped or the formation of non-homogeneous microstructure areas, thereby compromising mechanical properties. Currently available 3D-printable resins have a lower filler content (30–50 wt%). Reduced filler content directly correlates with the mechanical and physical properties of these resins [9,10].

Multiple in vitro studies have evaluated the mechanical [11,12,13,14] and physical properties [6,11,13,14,15,16,17] of various 3D-printed permanent resins, yielding varied results. Several in vitro studies have compared the mechanical and physical properties of various printed resins with those of milled and hybrid ceramics [2,18,19,20,21].

Three-dimensionally printed permanent resins are a relatively recent addition to the materials available in the market, used for the fabrication of inlays, onlays, veneers, crowns, and short-span fixed dental prostheses. However, no systematic review currently exists that compares the physical and mechanical properties of 3D-printed permanent resins with those of milled resins and hybrid ceramics. These outcomes are crucial for evidence-based material selection in clinical practice for creating definitive crowns and fixed dental prostheses. Therefore, this systematic review aims to assess and compare the physical and mechanical properties of permanent resins used in fixed prosthetic restorations, based on the 3D printing and milling procedures.

The proposed null hypothesis suggests that 3D-printed permanent resins exhibit no difference in physical and mechanical properties compared to milled resins and hybrid ceramics.

2. Materials and Methods

This systematic review was conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines [22].

2.1. Selection Criteria

The inclusion and exclusion criteria are given in

Table 1. Inclusion and exclusion criteria.

Inclusion Criteria	Exclusion Criteria
In vitro studies.	Studies in any language other than English.
Studies published in English.	Review papers, dissertations, case/technical reports, letters to editors, unpublished abstracts, and commentaries.
Studies assessing the physical properties of 3D-printed permanent resins with those of any other materials used to fabricate indirect prosthetic restorations.	Studies comparing the adaptation, marginal fit, and accuracy of 3D-printed permanent resin crowns with those of other materials, with only material properties evaluated.
Studies evaluating the mechanical properties of 3D-printed permanent resins with those of any other materials used for fabricating indirect prosthetic restorations.	Studies assessing the effects of different printing parameters on the accuracy and other properties of 3D-printed permanent resins.
Studies that compare the physical properties and mechanical or any other properties of different 3D-printed permanent resins.

.

2.2. Exposure and Outcome

The PICO question was the following: Do 3D-printed permanent resins exhibit similar mechanical and/or physical properties in comparison to milled resins and hybrid ceramic materials?’ PICO is explained in

Table 2. PICO according to focused question.

Participant	Permanent resins
Intervention	3D-printing
Comparison	Milled resin and hybrid ceramics
Outcome	Physical/mechanical properties

.

2.3. Search Strategy

Two independent reviewers (SBV and KS) systematically searched three electronic databases—Scopus, MEDLINE-PubMed, and Web of Science for articles published from 2014 to 2024. The search was conducted in December 2024 using combinations of the keywords listed in

Table 3. Search strategy used in various databases.

Database	Search Terms
PubMed	(“crowns”[MeSH Terms] OR “crowns”[All Fields] OR (“dental”[All Fields] AND “crown”[All Fields]) OR “dental crown”[All Fields] OR (“denture, partial, fixed”[MeSH Terms] OR (“denture”[All Fields] AND “partial”[All Fields] AND “fixed”[All Fields]) OR “fixed partial denture”[All Fields] OR (“fixed”[All Fields] AND “partial”[All Fields] AND “denture”[All Fields])) OR (“3D”[All Fields] AND (“printed”[All Fields] OR “printing”[MeSH Terms] OR “printing”[All Fields] OR “print”[All Fields] OR “printings”[All Fields] OR “prints”[All Fields]) AND (“permanent”[All Fields] OR “permanently”[All Fields] OR “permanents”[All Fields]) AND (“resin s”[All Fields] OR “resinous”[All Fields] OR “resins, plant”[MeSH Terms] OR (“resins”[All Fields] AND “plant”[All Fields]) OR “plant resins”[All Fields] OR “resin”[All Fields] OR “resins”[All Fields]) AND (“material”[All Fields] OR “material s”[All Fields] OR “materials”[All Fields])) OR (“3D”[All Fields] AND (“printed”[All Fields] OR “printing”[MeSH Terms] OR “printing”[All Fields] OR “print”[All Fields] OR “printings”[All Fields] OR “prints”[All Fields]) AND (“permanent”[All Fields] OR “permanently”[All Fields] OR “permanents”[All Fields]) AND (“material”[All Fields] OR “material s”[All Fields] OR “materials”[All Fields]) AND ((“mechanical”[All Fields] OR “mechanically”[All Fields] OR “mechanicals”[All Fields] OR “mechanics”[MeSH Terms] OR “mechanics”[All Fields] OR “mechanic”[All Fields]) AND (“properties”[All Fields] OR “property”[All Fields])) AND (“physical phenomena”[MeSH Terms] OR (“physical”[All Fields] AND “phenomena”[All Fields]) OR “physical phenomena”[All Fields] OR (“physical”[All Fields] AND “properties”[All Fields]) OR “physical properties”[All Fields]))) AND ((“biological products”[MeSH Terms] OR (“biological”[All Fields] AND “products”[All Fields]) OR “biological products”[All Fields] OR “biologic”[All Fields] OR “biologicals”[All Fields] OR “biological factors”[MeSH Terms] OR (“biological”[All Fields] AND “factors”[All Fields]) OR “biological factors”[All Fields] OR “biologics”[All Fields] OR “biologically”[All Fields] OR “biology”[MeSH Terms] OR “biology”[All Fields] OR “biological”[All Fields]) AND (“properties”[All Fields] OR “property”[All Fields]))) AND ((y_10[Filter]) AND (classical article[Filter] OR clinical study[Filter] OR clinical trial[Filter] OR clinical trial protocol[Filter] OR comparative study[Filter] OR randomized controlled trial[Filter]) AND (English[Filter]))
Scopus	(TITLE-ABS-KEY (dental crown) OR TITLE-ABS-KEY (fixed partial denture) OR TITLE-ABS-KEY (3D printed resin materials) AND TITLE-ABS-KEY (mechanical properties) AND TITLE-ABS-KEY (physical properties))
Web of science	ALL = (dental crown) OR ALL = (fixed partial denture) AND ALL = (3D printed permanent resin materials) AND ALL = (Physical properties) AND ALL = (mechanical properties) AND ALL = (biological properties)

. The search results were exported to EndNote X 20.4.1 (Clarivate Analytics, USA, https://endnote.com/), where duplicates were removed prior to screening. Two independent reviewers (VN and KS) utilized the Rayyan online tool to screen titles and abstracts and select appropriate studies. The full texts of the selected articles were then assessed for eligibility by two other independent reviewers (VTG and SBV). Any disagreements during the article selection were solved by a third reviewer (SB). The search strategy is explained in Figure 1.

2.4. Data Extraction Process

Two authors (SBV and VN) independently extracted data from the selected studies using a datasheet prepared using in Microsoft Excel 365 (Microsoft Corporation, Redmond, Washington, DC, USA). The collected data was categorized as studies analyzing physical properties (PPs) like surface roughness, color changes, and water solubility and studies analyzing mechanical properties (MPs) like flexural strength, microhardness, and the elastic modulus (

Table 4. Summary of the studies involved in this review.

Sl No	Author/Year	Study Type	Brand Name/Manufacturer of Materials Studied	Composition	Properties Examined	Sample Size (n)	Technique Used for Specimen Fabrication/Printing Parameters	Dimensions and Shape of Specimens
1.	Di Fiore et al., 2024 [11]	In vitro	Saremco print Crowntec (Saremco Dental AG) Varseo Smile Crown Plus (Bego GmbH)	Composite resins Resin ceramic hybrid material	MPs—flexural strength (FS), elastic modulus, microhardness PP—surface roughness	n = 40 for FS and elastic modulus (20 in each group) n = 10 for microhardness (5 in each group) n = 20 for water sorption and solubility, surface roughness	3D-printed with DLP Layer thickness—50 μm Orientation—0°	(25 × 2 × 2 mm) rectangular bars (Ø15 × 3 mm) and (Ø15 × 1 mm) circular disks
2.	Korkmaz et al., 2024 [12]	In vitro	Saremco crowntec Senertec P-Crown V2 Senertec P-Crown V3	Flowable polymer based on methacrylic acid ester Resin with ceramic fillers	MP—flexural strength	n = 60 aged and non-aged (10 in each group)	SLA Layer thickness—50 μm Orientation—90°	(25 × 2 × 2 mm) rectangular bars
3.	Krajangta et al., 2024 [17]	In vitro	Varseosmile crown plus, VS Cerasmart, CS	Resin–ceramic hybrid material Milled resin ceramic hybrid material	PPs—color and translucency changes	n = 60 (n = 15, immersed in distilled water, coffee)	3D-printed with DLP Layer thickness—50 μm Orientation—N/M Milled	(12 × 14 × 1.5) rectangular bars
4.	Nam EN et al., 2024 [13]	In vitro	Formlabs, Graphy Tera Harz permanent	Methacrylic acid ester-based 3D-printed permanent resin 3D-printed resins	MPs—flexural strength, Vickers hardness PPs—color stability, surface roughness	n = 45 (n = 5, no treatment, glazed, sand glazed)	3D-printed with DLP Layer thickness—50 μm Orientation—N/M	(10 × 18 × 4) rectangular bars (9 × 2) circular disks
5.	Çakmak G et al., 2023 [19]	In vitro	Crowntec, CT VarseoSmile Crown Plus, VS Brilliant Crios, BC Enamic, VE Mark II, VM	3D-printed composite resin 3D-printed hybrid composite resins Milled reinforced composite resin Milled polymer-infiltrated ceramic network Milled felspathic ceramic	MP—microhardness PP—surface roughness	n = (10)	3D-printed with DLP Layer thickness—50 μm Orientation—N/M Wet-sliced with precision cutter	(Ø10 × 1 mm) circular disks
6.	Karaoğlanoğlu et al., 2023 [20]	In vitro	Cerasmart 270 (GC, Zahnfabrik, Germany) Grandio Blocs (VOCO GmbH, Germany) Crowntec (Saremco Dental AG, Switzerland) Permanent Crown (Formlabs, USA)	Nanoceramic CAD/CAM block Nanohybrid CAD/ CAM block 3D-printed permanent resin Methacrylic acid ester-based printed permanent resin	MP—microhardness PPs—surface roughness, color changes	n = 96 (n = 8, immersed in tea, coffee, and distilled water)	Precision cutting machine 3D-printed with DLP 3D-printed with SLA Layer thickness—50 μm Orientation—N/M	(12 × 8 × 2) rectangular bars
7.	Vichi A et al., 2024 [15]	In vitro	Permanent Crown (Formlabs, USA)	Methacrylic acid ester-based printed permanent resin	PPs—surface roughness, color changes	n = 80 (n = 10) 8 different finishing and polishing methods Sof-Lex™ Spiral Wheels (SW), Identoflex Lucent no paste (Ln), Sof-Lex™ XT Pop-on Disc (SD), Identoflex Lucent + paste (Lp), resin nitrogen polymerized (NG), Optiglaze (OG), Opti1Step (OS), and HiLusterPLUS (HL)	3D-printed with SLA Layer thickness—50 μm Orientation—N/M	(14 × 14 × 5 mm) square shape
8.	Ezmek et al., 2023 [16]	In vitro	Permanent Crown (Formlabs, USA)	Methacrylic acid ester-based 3D-printed permanent resin	PP—color changes	n = 120 (n = 10) a. mechanical polishing; b. Optiglaze (GC Dental Products Corp, Aichi, Japan); c. Vita Akzent LC (VITA Zahnfabrik, Bad Säckingen, Germany). subgroups immersed in distilled water, coffee, tea, and red wine	3D-printed with SLA Layer thickness—50 μm Orientation—0°	(10 mm × 1.5 mm) circular disks
9.	Bozogullari et al., 2023 [6]	In vitro	Crowntec Permanent Crown Resin	3D-printed permanent resin Methacrylic acid ester-based 3D-printed permanent resin	PPs—color stability, stainability, surface roughness	N = 150 (n = 10 for material surface roughness) (n = 20 for material for color stability and stainability)	3D-printed with DLP 3D-printed with stereolithography Layer thickness—50 μm Orientation—90°	rectangular-shaped specimens (14 × 12 × 2 mm)
10.	Tasin et al., 2024 [21]	In vitro	VarseoSmile Crownplus (VSP), Permanent Crown (PC) IPS e.max CAD (LDS) Vita Enamic (PICN), Cerasmart (RNC)	3D-printed permanent resin Methacrylic acid ester-based printed permanent resin Lithium disilicate-based glass-matrix ceramic Polymer-infiltrated feldspathic ceramic Polymer-infiltrated feldspathic ceramic Composite resin material	PPs—color changes, translucency	n = 60 (n = 12 per group)	3D-printed with DLP 3D-printed with SLA Layer thickness—50 μm Orientation—0°	plate-shaped specimens (12 × 12 × 1 mm)
11.	Kang et al., 2023 [14]	In vitro	Tera Harz TC-80DP Graphy, Seoul, Korea. Permanent Crown Formlabs, Somerville, MA, USA.	UDMA resin Bis-EMA (BEMA) resin	MP—flexural strength	n = 196	3D-printed with DLP 3D-printed with SLA	bar-shaped specimens (25 mm × 2 × 2 mm)
12.	Çakmak et al., 2023 [18]	In vitro	Crowntech (CT) VarseoSmile Crownplus (VS) Cera Smart (CS)	3D-printed resin 3D-printed resin Nanoceramic resin	PP—surface roughness, color stability	n = 90 (n = 30 per group)	3D-printed with DLP Layer thickness—50 μm Orientation—0°	rectangular-shaped (14 × 12 × 1 mm)
13.	Temizci et al., 2024 [2]	In vitro	Saremco Print Crowntec [SC] Formlabs Permanent Crown Resin [FP]) Vita Mark II [VM] Cerasmart 270 [CS] Vita Enamic [VE]	Composite-based resin Composite-based resin Feldspatic glass ceramic Polymer infiltrated ceramic Hybrid nanoceramic	MPs—flexural strength, microhardness	n = 200 (n = 40 per group)	3D-printed with DLP 3D-printed with SLA Layer thickness—50 μm Orientation—90°	disk-shaped specimens (13 × 1.2 mm) for flexural strength 100 square specimens (14 × 14 × 2 mm) for VHN test

).

2.5. Quality Assessment of Selected Studies

The quality of the selected in vitro studies was assessed using the Modified CONSORT scale, described by Faggion C. for in vitro studies [23,24]. The scale consists of the following domains: 1. Abstract; 2. Introduction (2a. scientific background; 2b. objectives and null hypotheses); 3. Methodology (intervention, outcomes, sample size, randomization, blinding, and statistical method); 4. Results (outcomes and estimation); 5. Other information (funding). Fourteen items were included to assess the risk of bias in the selected studies. Each item that was met by a study was marked as “yes”, while those that did not meet the requirements were marked as “no” (

Table 5. Quality assessment of the included in vitro studies.

Item	1	2a	2b	3	4	5	6	7	8	9	10	11	12	13	14
Di Fiore A et al., 2024 [11]	Yes	Yes	Yes	Yes	Yes	Yes	No	No	No	No	Yes	Yes	No	No	Yes
Kormaz et al., 2024 [12]	Yes	Yes	Yes	Yes	Yes	Yes	No	No	No	No	Yes	Yes	No	No	Yes
Krajangta et al., 2024 [17]	No	Yes	Yes	Yes	Yes	Yes	No	No	No	No	Yes	Yes	No	Yes	Yes
Nam et al., 2024 [13]	Yes	Yes	Yes	Yes	Yes	No	No	No	No	No	Yes	Yes	No	Yes	Yes
Çakmak G et al., 2023 [19]	Yes	Yes	Yes	Yes	Yes	No	No	No	No	No	Yes	Yes	No	Yes	Yes
Karaoğlanoğlu S et al., 2023 [20]	Yes	Yes	Yes	Yes	Yes	No	No	No	No	No	Yes	Yes	No	Yes	Yes
Vichi et al., 2024 [15]	Yes	Yes	Yes	Yes	Yes	No	No	No	No	No	Yes	Yes	No	Yes	Yes
Ezmek B et al., 2023 [16]	Yes	Yes	Yes	Yes	Yes	No	No	No	No	No	Yes	Yes	No	Yes	Yes
Bozogulları HN et al. 2024 [6]	No	Yes	Yes	Yes	Yes	No	No	No	No	No	Yes	Yes	No	Yes	Yes
Tasin S et al., 2024 [21]	Yes	Yes	Yes	Yes	Yes	Yes	No	No	No	No	Yes	Yes	No	Yes	Yes
Kang, YJ et al., 2023 [14]	Yes	Yes	Yes	Yes	Yes	No	No	No	No	No	Yes	Yes	No	Yes	Yes
Çakmak G et al., 2023 [18]	Yes	Yes	Yes	Yes	Yes	No	No	No	No	No	Yes	Yes	No	Yes	Yes
Temizci T et al., 2024 [2]	Yes	Yes	Yes	Yes	Yes	Yes	No	No	No	No	Yes	Yes	No	Yes	Yes

).

2.6. Quantitative Assessment

The final values for each physical/mechanical property are presented in individual tables (

Table 6. Surface roughness results.

Sl No	Author/Year	SR Before	SR After Surface Treatment	Medium of Exposure Causing Changes in Surface Roughness	Measuring Device Used	Conclusion
1.	Di Fiore et al., 2024 [11]	Saramco—0.52 ± 0.05 μm Varseo smile—0.54 ± 0.04 μm	0.97 ± 0.06 μm 0.88 ± 0.05 μm	Toothbrushing simulated device with total of 10,000 cycles	Noncontact profilometer	The surface roughness of both 3D-printed resins was affected by brushing simulation.
2.	Nam et al., 2024[13]	Formlabs No treatment—0.47 ± 0.12 μm Glazing—0.03 ± 0.02 μm Sand glazing—0.03 ± 0.01 μm Graphy No treatment—0.47 ± 0.12 μm Glazing—0.03 ± 0.02 μm Sand glazing—0.03 ± 0.01 μm	Formlabs No treatment—0.08 ± 0.00 μm Glazing—0.02 ± 0.00 μm Sand glazing—0.02 ± 0.00 μm Graphy No treatment—0.23 ± 0.14 μm Glazing—0.05 ± 0.04 μm Sand glazing—0.07 ± 0.05 μm	Artificial toothbrushing device specimen brushed for 20,000 cycles	Stylus profilometer	Samples with sand-glazed and glazed surfaces exhibited low surface roughness.
3.	Karaoğlanoğlu et al., 2023 [20]	Grandio Blocs Baseline—0.187 ± 0.01 μm Cerasmart 270 Baseline—0.146 ± 0.01 μm Crowntec Baseline—0.187 ± 0.01 μm Permanent Crown Baseline—0.191 ± 0.01 μm	Grandio Blocs Coffee—0.196 ± 0.01 μm Tea—0.198 ± 0.01 μm Water—0.193 ± 0.01 μm Cerasmart 270 Coffee—0.154 ± 0.01 μm Tea—0.156 ± 0.02 μm Water—0.148 ± 0.01 μm Crowntec Coffee—0.195 ± 0.02 μm Tea—0.198 ± 0.02 μm Water—0.189 ± 0.01 μm Permanent Crown Coffee—0.195 ± 0.02 μm Tea—198 ± 0.01 μm Water—0.193 ± 0.01 μm	Immersion in coffee, tea, and distilled water and stored in incubator for 30 days at 37 °C	Contact Profilometer	Cerasmart 270 showed the lowest surface roughness, Grandio blocs and Crowntec showed the same values, and Permanent Crown showed more surface roughness.
4.	Vichi et al., 2024 [15]	Permanent Crown (Formlabs, USA)	NG—0.25 μm SD—0.44 μm OG—0.46 μm Lp—0.52 μm Ln—0.59 μm OS—0.73 μm SW—0.77 μm HL—0.83 μm	Finishing and polishing methods Sof-Lex™ Spiral Wheels (SW), Sof-Lex™ XT Pop-on Disc (SD), Identoflex Lucent no paste (Ln), Identoflex Lucent + paste (Lp), resin nitrogen polymerized (NG), Optiglaze (OG), Opti1Step (OS), and HiLusterPLUS (HL)	Profilometer	NG > SD = OG = Lp; Lp = Ln; Ln = OS; OS = SW; and SW = HL.
5.	Bozogullari et al., 2023 [6]	Crowntec SC 0.039 ± 0.005 μm Permanent Crown—0.044 ± 0.004 μm Cerasmart 270—0.037 ± 0.008 μm Vita Enamic—0.174 ± 0.043 μm Vitamark II—0.096 ± 0.035 C μm	Crowntec SC 0.038 ± 0.007 μm Permanent Crown 0.045 ± 0.009 μm Cerasmart 270 0.041 ± 0.008 μm Vita Enamic 0.201 ± 0.041 μm Vitamark II 0.115 ± 0.031 μm	Thermocycling, 5000 cycles	Profilometer	Ra values before thermocycling: VE > VM > PC > SC > CS. Ra values after thermocycling: VE > VM > PC > CS > SC. In general, surface roughness increased after thermocycling.
6.	Kang et al., 2023 [14]	Tera Harz TC-80DP Control—0.63 ± 0.05 μm Permanent Crown Control—0.68 ± 0.08 μm	Tera Harz TC-80DP at 0.1/0.2/0.3 MPa with 50 µm alumina 0.32 ± 0.04/0.93 ± 0.05/1.73 ± 0.16 μm Tera Harz TC-80DP at 0.1/0.2/0.3 MPa with 100 µm alumina 0.62 ± 0.45/1.62 ± 0.29/1.44 ± 0.2 μm Permanent Crown at 0.1/0.2/0.3 MPa with 50 µm alumina 0.96 ± 0.68/1.29 ± 0.09/2.34 ± 0.30 μm Permanent Crown at 0.1/0.2/0.3 MPa with 100 µm alumina 1.10 ± 0.15/2.77 ± 0.47/3.23 ± 0.74 μm	Air particle abrasion using alumina particles of 50 and 110 µm, 10,000 thermal cycles	Field emission scanning electron microscope	Both the resins presented porosity on the surface after the surface treatment with alumina particles. Deep cracks and irregular deep areas were observed in the Permanent Crown group treated with coarse particles under high pressure. Increase in surface roughness observed with sandblasting particle size and the pressure of the 3D printing resin.
7.	Çakmak et al., 2023 [18]	Cerasmart—CP/OG/VA 0.27 ± 0.09/0.23 ± 0.10/0.24 ± 0.03 μm Crown tech—CP/OG/VA 0.49 ± 0.24/0.5 ± 0.19/0.6 ± 0.28 μm VarseoSmile Crown Plus—CP/OG/VA 0.37 ± 0.06/0.29 ± 0.06/0.3 ± 0.04 μm	Cerasmart—CP/OG/VA 0.1 ± 0.01/0.14 ± 0.05/0.28 ± 0.01 μm Crown tech—CP/OG/VA 0.19 ± 0.11/0.31 ± 0.12/0.40 ± 0.17 μm VarseoSmile Crown Plus—CP/OG/VA 0.16 ± 0.11/0.21 ± 0.10/0.26 ± 0.12 μm	Conventional polishing (control-CP)/application of surface sealant (Optiglaze; GC Corp (OG)/ Vita Akzent LC; Vita Zahnfabrik (VA)) Coffee thermal cycling, 10,000 cycles	Profilometer	Before polishing: conventional polishing—CT > VA > CS OG-CT > VA > CS VA-C T > VA > CS. After Coffee thermal cycling and polishing: conventional polishing—CT > VA > CS OG-CT > VA > CS VA-C T > VA > CS. The Ra of CS was similar to or lower than the Ra of other materials, regardless of the polishing technique. CP mostly led to lower Ra values than other polishing techniques, whereas VA resulted in a high Ra regardless of the material-time.
8.	Çakmak et al., 2023 [19]	VarseoSmile Crown Plus (VS)—3.58 ± 1.01 μm Crown tech (CT)2.79 ± 1.10 μm BRILLIANT Crios (BC)—0.27 ± 0.03 μm Enamic (VE)—0.64 ± 0.32 μm Mark II (VM)—0.70 ± 0.11 μm	VarseoSmile Crown Plus (VS) After polishing/after brushing/coffee thermocycling 0.36 ± 0.12/0.85 ± 0.47/0.43 ± 0.16 μm Crown tech (CT)—0.71 ± 0.62/0.61 ± 0.14/0.40 ± 0.11 μm BRILLIANT Crios (BC)—0.15 ± 0.05/0.81 ± 0.14/0.74 ± 0.14 μm Enamic (VE)—0.25 ± 0.04/0.27 ± 0.06/0.20 ± 0.03 μm Mark II (VM)—0.17 ± 0.05/0.14 ± 0.03/0.17 ± 0.03 μm	VarseoSmile and Crown tech—conventional polishing BRILLIANT Crios and Enamic—two-step polishing kit VM: Mark II—finishing with flexible disks, polishing using diamond polishing paste 25,000 cycles of artificial brushing using automatic brushing machine 10,000 thermal cycles	Profilometer	Before polishing—VS > CT > VE > VM > BC After polishing—CT > VS > VE > VM > BC After brushing—VS > BC > CT > VE > VM After coffee thermal cycling—BC > VS > CT > VE > VM Before polishing, all materials had their highest surface roughness except BC, where roughness increased after brushing and coffee thermal cycling.

,

Table 7. Color change results.

Sl No	Author/year	Medium of Immersion/Surface Treatment	Aging/Duration of Immersion	3D-Printed Permanent Resin—Mean Color Changes	Milled Resin—Mean Color Change	Instrument Used	Conclusion
1.	Krajangta et al., 2024 [17]	Immersion in Water Coffee	30 days of immersion	Varseo smile crown plus ∆TP = −1.37 (0.17 units) immersed in water ∆TP = −0.23 (0.06) units immersed in coffee	Cerasmart ∆TP = −1.03 (0.54) units immersed in water ∆TP = −0.39(0.6) units immersed in coffee	Spectrophotometer Vita Easyshade™ Advance 4.0	The translucency of both resins reduced after immersion in water and coffee.
2.	Nam et al., 2024 [13]	Resin surface with no treatment/glazed/sand glazed Immersion in Coffee Curry Distilled water	30 days of immersion	∆E Form labs—No treatment/glazed/sand glazed Coffee—7.5 ± 3.6, 7.0 ± 1.3, 6.3 ± 1.1 units Curry—18.5 ± 14.1, 2.6 ± 1.2, 1.9 ± 0.5 units Distilled water—1.7 ± 0.3, 2.4 ± 0.7, 3.0 ± 0.3 units Graphy Coffee—2.6 ± 0.8, 3.4 ± 1.3, 3.2 ± 1.9 units Curry—18.7 ± 4.2, 6.4 ± 2.8, 5.4 ± 1.4 units Distilled water—3.8 ± 0.6, 6.4 ± 0.7, 5.6 ± 0.2 units	NA	Colorimeter	Greater color changes were observed in untreated samples than glazed and sand-glazed samples and they varied with the surface treatment.
3.	Karaoğlanoğlu et al., 2023 [20]	Immersion in tea, coffee, and distilled water; stored at 37 °C	30 days of immersion	∆E at 1 day/7 days/30 days Crowntec Coffee—0.4 ± 0.1/1.5 ± 0.2/3.2 ± 0.4 units Tea—0.9 ± 0.2/4.1 ± 0.4/6.3 ± 0.5 units Water—0.3 ± 0.1/0.4 ± 0.1/0.6 ± 0.1 units Permanent Crown Coffee—0.6 ± 0.1/1.4 ± 0.2/2.7 ± 0.2 units Tea—0.8 ± 0.2/3.9 ± 0.3/5.6 ± 0.3 units Water—0.4 ± 0.1/0.6 ± 0.1/0.7 ± 0.1 units	∆E at 1 day/7 days/30 days Grandio Blocs Coffee—0.5 ± 0.1/1.3 ± 0.2/1.8 ± 0.1 units Tea—0.9 ± 0.1/3.6 ± 0.3/4.2 ± 0.3 units Water—0.3 ± 0.1/0.5 ± 0.1/0.7 ± 0.1 units Cerasmart 270 Coffee—0.6 ± 0.1/1.2 ± 0.2/1.8 ± 0.2 units Tea—0.8 ± 0.1/3.4 ± 0.3/4.4 ± 0.3 units Water—0.4 ± 0.1/0.6 ± 0.1/0.7 ± 0.1 units	Spectrophotometer device	Color changes observed in 3D-printed resins and resin-based CAD/CAM blocks immersed in tea and coffee were similar on the first and seventh days, with greater color changes noted in the 3D-printed resins after 30 days.
4.	Ezmek et al., 2023 [16]	a. mechanical polishing. b. Optiglaze (GC Dental Products Corp, Aichi, Japan); c. Vita Akzent LC (VITA Zahnfabrik, Bad Säckingen, Germany); later immersion in distilled water, coffee, tea, and red wine	30 days of immersion	Distilled water/coffee/tea/red wine Mechanical polishing 0.77 ± 0.19/3.65 ± 0.95/3.56 ± 1.00/4.90 ± 1.48 units Optiglaze 1.05 ± 0.27/0.87 ± 0.23/0.65 ± 0.12/0.47 ± 0.21 units Vita Akzent LC 1.88 ± 0.30/2.85 ± 0.28/1.66 ± 0.55/0.92 ± 0.30 units	NA	Spectrophotometer	Mechanical polishing groups showed the highest ΔE00 values. The most significant discoloration in the mechanical polishing group was due to red wine. Optiglaze reduced the discoloration caused by all beverages in the 3D-printed resin group. Vita Akzent LC reduced discoloration caused by tea and red wine.
5.	Bozo gullari et al., 2023 [6]	Immersion in distilled water and coffee after thermocycling	7 days at 37 °C	∆E00 Crowntec SC Distilled water—before/after 2.57 ± 0.56/3.62 ± 0.48 units Coffee 2.53 ± 0.61/5.36 ± 0.58 units Permanent Crown Distilled water 0.93 ± 0.25/1.04 ± 0.51 units Coffee 0.90 ± 0.28/1.99 ± 0.26 units	Cerasmart Distilled water 1.17 ± 0.37/1.29 ± 0.43 units Coffee 1.18 ± 0.37/1.44 ± 0.33 units Vita Enamic Distilled water 1.19 ± 0.39/1.20 ± 0.44 units Coffee 1.24 ± 0.34/2.36 ± 1.53 units Vitamark II Distilled water 0.75 ± 0.07/0.76 ± 0.10 units Coffee 0.77 ± 0.04/2.18 ± 0.34 units	Spectrophotometer	The highest mean ∆E00 values were seen in the SC group (2.57_0.56), followed by those in VE (1.20_0.44), CS (1.18_0.37), FP (0.93_0.25), and VM (0.76_0.10). The highest mean DE00 values in coffee solution (5.36_0.58) and distilled water (3.62_0.48) were seen in SC group. The lowest mean DE00 values (0.77_0.04) in distilled water at T2 were seen in the VM group. The CS group also showed the lowest mean DE00 value (1.44_0.33) in coffee Crowntec and Vita Enamic showed unacceptable color changes.
6.	Tasin et al., 2024 [21]	Immersed in coffee and thermocycled for 10,000 cycles	Immersion in coffee	∆E00 VarseoSmile Crown plus (VSP) 1.38/−0.65 units Permanent Crown (PC) 1.35/−0.43 units	∆E00/∆RTA00 IPS e.max CAD (LDS) 0.48/−0.17 units Vita Enamic (PICN) 0.96/-0.24 units Cerasmart (RNC) 1.03/−0.37 units	Spectrophotometer	The highest ΔE00 values were found in VSP and PC, and the lowest ΔE00 values were found in LDS. The highest|ΔRTP00 |values were observed for VSP, and the lowest|ΔRTP00|values were found in LDS after coffee thermocycling.
7.	Çakmak et al., 2023 [18]	Immersed in coffee after polishing and thermocycled for 10,000 cycles	Immersion in coffee	∆E00 Crown Tech—Conventional polishing/optiglaze/Vita Akzent 0.89 ± 0.18/1.04 ± 0.60/1.52 ± 0.84 units VarseoSmile Crown Plus 1.98 ± 0.18/1.38 ± 0.59/1.77 ± 0.68 units	∆E00 Cerasmart—Conventional polishing/optiglaze/Vita Akzent 0.47 ± 0.34/0.99 ± 0.42/1.04 ± 0.35 units	Spectrophotometer	Polishing techniques affected the ΔE00 values of CS and VS while only CP affected the ΔE00 values among tested materials. CS OG < VA < CP VS OG < CP < VS CS-VA had moderately unacceptable color change.
8.	Çakmak et al., 2023 [19]	Polishing/brushing/coffee thermal cycling	Tooth brushing, 25000 cycles Coffee thermal cycling, 10,000 cycles	∆E00 Crown Tech After polishing/after brushing/coffee thermal cycling 1.74 ± 0.52/1.47 ± 0.46/2.44 ± 0.52units VarseoSmile Crown Plus (VS) After polishing/after brushing/coffee thermal cycling 1.19 ± 0.68/9.35 ± 0.54/9.13 ± 1.41 units	∆E00 Enamic,(VM) After polishing/after brushing/coffee thermal cycling 0.87 ± 0.40/1.25 ± 0.29/0.92 ± 0.14 units BRILLIANT Crios (BC) After polishing/after brushing/coffee thermal cycling 1.27 ± 0.55/0.47 ± 0.20/1.14 ± 0.59 units Mark II (VM) After polishing/after brushing/coffee thermal cycling 0.87 ± 0.40/1.25 ± 0.29/0.92 ± 0.14 units	Spectrophotometer	After polishing: CT > BC > VS > VM > VE. After brushing: VS > CT > VM > VE > BC. After coffee thermal cycling: VS > CT > BC > VM > VE. VS had the highest ΔE00 values.

,

Table 8. Water sorption/solubility results.

Sl No	Author/Year	Water Sorption	Solubility	Conclusion
1.	Di Fiore et al., 2024 [11]	Saramco—11.52 ± 0.6 g/mm3 Varseo smile—12.43 ± 0.4 g/mm3	1.36 ± 0.4 g/mm3 0.98 ± 0.3 g/mm3	After 21 days, both the resins showed significant difference in water sorption values.

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Table 9. Flexural strength results.

Sl No	Author and Year	Mean/Median Values of Maximum Force for 3D-Printed Resins	Mean/Median Values of Maximum Force for Milled/Hybrid Ceramics	Exposure Medium/Aging Technique	Machine Used for Testing	Conclusion
1.	Di Fiore et al., 2024 [11]	Saramco—123.4 ± 8.7 MPa (dry) 97.5 ± 15.2 MPa (30 days after storage) Varseo smile—109.9 ± 15.8 (dry) 94.2 ± 11.7 MPa (30 days after storage)	NA	Stored in distilled water for 30 days at 37 ± 1 °C.	UTM	The flexural strength of both 3D-CRs decreased due to artificial aging.
2.	Korkmaz et al., 2024 [12]	Saremco Crowntec Aged—88.04 MPa Non-aged—92.06 MPa Senertec P—Crown V2 Aged—57.03 MPa Non-aged—63.13 MPa Senertec P—Crown V3 Aged—65.88 MPa Non-aged—71.81 MPa	NA	Thermocycling, 10,000 cycles	UTM	Saremco Crowntec aged and non-aged groups > Senertek P Crown V3 > Senertek P Crown V2. Artificial aging decreased values of flexural strength in all 3D-printed resin groups.
3.	Nam et al., 2024 [13]	Formlabs No treatment—133.1 ± 16.2 MPa Glazing—146.6 ± 19.0 MPa Sand glazing—136.2 ± 13.7 MPa Graphy No treatment—130.6 ± 9.2 MPa Glazing—161.5 ± 6.1 MPa Sand glazing—158.9 ± 11.8 MPa	NA	Glazing—surfaces were coated by a resin-exclusive photocuring glazing solution (OPTIGLAZE, GC Corporation, Tokyo, Japan); Sand glazed surfaces were coated by a resin exclusive photocuring glazing solution after sandblasting with 50 μm aluminum oxide particles	UTM	The flexural strength of Formlabs samples was significantly lower regardless of surface treatment.
4.	Kang et al., 2023 [14]	Tera Harz TC-80DP Before—Control/0.1/0.2/0.3 MPa with 50 µm alumina 141.11/141.35/134.30/130.02 MPa Before—Control/0.1/0.2/0.3 MPa with 110 µm alumina 141.11/134.52/133.82/121.77 MPa After—Control/0.1/0.2/0.3 MPa with 50 µm alumina 134.57/112.15/112.77/110.22 MPa After—Control/0.1/0.2/0.3 MPa with 110 µm alumina 134.57/106.85/106.61/108.29 MPa Permanent Crown Before—Control/0.1/0.2/0.3 MPa with 50 µm alumina 125.68/111.99/112.88/112.42 MPa Before—Control/0.1/0.2/0.3 MPa with 100 µm alumina 125.68/89.330/84.455/83.786 MPa After—Control/0.1/0.2/0.3 MPa with 50 µm alumina 72.455/84.268/71.277/74.170 MPa After—Control/0.1/0.2/0.3 MPa with 100 µm alumina 72.455/71.036/78.991/70.848 MPa	N/A	Air particle abrasion using 50 and 110 µm alumina particles 10,000 thermal cycles between 5 °C and 55 °C in distilled water	UTM	The Tera Harz group exhibited higher flexural strength compared with the Permanent Crown group. Flexural strength decreased significantly after thermocycling in both groups.
5.	Temizci et al., 2024 [2]	Saremco Print Crowntec [SC] Non-aging—232.67 ± 5.94 MPa Aging—215.31 ± 6.39b MPa Formlabs Permanent Crown Resin [FP] Non-aging—234.67 ± 6.14 MPa Aging—230.23 ± 10.35 MPa	Vita Mark II [VM] Non-aging—173.49 ± 3.47 MPa Aging—153.49 ± 5.37 MPa Cerasmart 270 [CS] Non-aging—296.11 ± 11.56 MPa Aging—278.05 ± 6.11 MPa Vita Enamic [VE] Non-aging—173.99 ± 1.99 MPa Aging—173.63 ± 4.77 MPa	Thermocycling, 5000 cycles	UTM	CS > FP > SC > VE > VM after thermal cycling. Thermal cycling had an insignificant effect on flexural strength values for all tested materials.

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Table 10. Microhardness results.

Sl No	Author/Year	Mean Microhardness of 3D-Printed Resin	Mean Microhardness of Milled Resin	Surface Treatment/Exposure Medium	Machine Used for Testing	Conclusion
1.	Di Fiore et al., 2024 [11]	Saramco—33.2 ± 0.8 Hv (dry); 31.7 ± 0.9 Hv (30 days after storage) Varseo smile—31.5 ± 0.6 (dry); 29.6 ± 1.0 Hv (30 days after storage)	NA	Stored for 30 days in distilled water at 37 ± 1 °C	Microhardness tester	No significant difference between two groups.
2.	Nam et al., 2024 [13]	Formlabs No treatment—25.4 ± 3.1 Hv Glazing—26.5 ± 2.4 Hv Sand glazing—30.5 ± 3.9 Hv Graphy No treatment —9.7 ± 1.7 Hv Glazing—11.5 ± 1.2 Hv Sand glazing—11.2 ± 1.2 Hv	NA	No treatment Glazed Sand glazed	Microhardness indentation device	VHN of Formlabs-samples was higher than that of graphy samples.
3.	Karaoğlanoğlu et al., 2023 [20]	Crowntec Baseline—30.0 ± 1.3 Hv Coffee—29.9 ± 1.2 Hv Tea—29.8 ± 1.3 Hv Water—31.0 ± 1.2 Hv Permanent Crown Baseline—37.4 ± 1.3 Hv Coffee—36.6 ± 1.7 Hv Tea—35.8 ± 1.7 Hv Water—37.4 ± 1.4 Hv	Grandio Blocs Baseline 203.9 ± 3.6 Hv Coffee—192.8 ± 4.7 Hv Tea—180.8 ± 3.9 Hv Water—199.1 ± 4.5 Hv Cerasmart 270 Baseline—109.5 ± 1.9 Hv Coffee—103.8 ± 2.7 Hv Tea—98.3 ± 2.4 Hv Water—102.8 ± 3.8 Hv	Immersion in coffee tea and distilled water and stored in incubator at 37 °C for 30 days.	Vickers microhardness tester	Grandio Blocs CAD/CAM Block > Cerasmart 270 > Permanent Crown > Crowntec.
4.	Çakmak et al., 2023 [19]	Varseo Smile Crown Plus (VS) After polishing/after brushing/coffee thermal cycling 34.57 ± 1.23/33.26 ± 1.62/32.47 ± 1.78 Hv Crown Tech (CT) After polishing/after brushing/coffee thermal cycling 30.59 ± 2.95/29.74 ± 2.66/30.49 ± 3.91 Hv	BRILLIANT Crios (BC) 82.2 ± 7.08/80.26 ± 6.81/73.76 ± 4.69 Hv Enamic VE 286.3 ± 22.87/282 ± 13.14/266.47 ± 19.72 Hv Mark II (VM) 680.55 ± 37.73/679.93 ± 28.32/558.66 ± 39.82 Hv	25,000 cycles of artificial brushing using an automatic brushing machine Immersion in coffee and 10,000 thermal cycles	Vickers microhardness tester	VM > VE > BC > VS > CT. VS and CT had lowest microhardness values followed by VM, VE, and BC in decreasing order. Microhardness of VM reduced after coffee thermocycling.
5.	Temizci et al., 2024 [2]	Saremco Print Crowntec [SC] Non-aging –232.67 ± 5.94 Hv Aging—215.31 ± 6.39 Hv Formlabs Permanent Crown Resin [FP] Non-aging—234.67 ± 6.14 Hv Aging—230.23 ± 10.35 Hv	Vita Mark II [VM] Non-aging—173.49 ± 3.47 Hv Aging—153.49 ± 5.37 Hv Cerasmart 270 [CS] Non-aging—296.11 ± 11.56 Hv Aging—278.05 ± 6.11 Hv Vita Enamic [VE] Non-aging—173.99 ± 1.99 Hv Aging—173.63 ± 4.77 Hv	Thermocycling, 5000 cycles	Emcotest- Durascan G5 hardness testing device	VM > VE > CS > FP > SC. 3D-printed resin groups exhibited lowest VHN values. Effect of thermocycling significantly affected only VE and VM groups.

and

Table 11. Elastic modulus results.

Sl No	Author/Year	Mean/Median Values of Maximum Force	Exposure Medium/Aging Technique	Machine Used for Testing	Conclusion
1.	Di Fiore et al., 2024 [11]	Saramco—4.20 ± 0.3 Gpa (dry); 4.00 ± 0.2 Gpa (30 days after storage) Varseo smile—3.82 ± 0.2 Gpa (dry); 3.70 ± 0.1 Gpa (30 days after storage)	Stored in distilled water for 30 days at 37 ± 1 °C	UTM	Significant difference was found between Crowntec 3D CR, Saremco Print, and Varseo Smile Crown Plus 3D CR after immersion in water for 30 days.

). The collected data were assessed for eligibility for a meta-analysis; however, a meta-analysis could not be performed due to substantial variations among the included studies. The variations included different materials tested in various conditions. Variations were also observed in aging techniques, including thermocycling (5000 cycles and 10,000 cycles), storage in distilled water, polishing techniques, immersion in various media (coffee, tea, water, and red wine), and artificial brushing cycles (10,000 cycles and 25,000 cycles). In addition to the printing techniques (SLA, DLP) and printing orientations (0° and 90°), which further added complexity to the meta-analysis, the variations between the included studies made a quantitative meta-analysis unfeasible. As a result, a qualitative descriptive analysis was conducted.

3. Results

3.1. Findings from the Literature Search

A total of 1779 documents were found after searching all three databases (PubMed/Medline, Scopus, Web of Science). Upon review, 70 duplicate titles were identified and excluded. A total of 1683 papers were excluded after screening the title and abstract because they did not meet the selection criteria. The full-text review of the remaining 26 articles was performed, and a manual search for further studies was conducted from the reference list of these articles; however, no further critical studies were identified. Of the 26 chosen articles, 13 were excluded further because they did not meet the selection criteria. As a result, 13 articles were ultimately included in this systematic review for qualitative analysis (Figure 1). The data from the selected studies was extracted into a preformatted table, which included details like authors’ names and publication year, type of the study, properties investigated, sample size, brand name and manufacturer, material composition, specimen fabrication technology, specimen dimensions and shape, printing orientation, and layer thickness [Table 3]. The results of the quality analysis of the selected studies are presented in Table 5. Details on each property tested are presented in Table 6, Table 7, Table 8, Table 9, Table 10 and Table 11. These tables include information on the exposed agent and aging method, the machine used for testing, results for each property, and the authors’ conclusions.

3.2. Features of the Selected Studies

This review included only in vitro studies published in 2023 and 2024. Four of the included studies compared the physical properties, such as surface roughness, color changes, and water solubility/sorption, of printed resins with those of milled resins/hybrid ceramics. Three studies compared the mechanical properties, such as microhardness, flexural strength, and the modulus of elasticity, of the printed resins with those of milled resins/hybrid ceramics. One study compared the mechanical properties of various printed resins, and four studies analyzed the physical properties of various printed permanent resins. Three studies evaluated both physical and mechanical properties of various printed permanent resins.

3.3. Assessment of Quality of Selected Studies

All the thirteen studies included were in vitro studies. Of the 182 entries, 118 (64.83%) were positively reported. Each study included information on the abstract, introduction, intervention, outcomes, statistical analysis, and results (Items 2–4, 10, 11, and 14). Eleven studies featured a structured abstract, but none discussed the limitations of the trial (Item 12). Additionally, eleven studies specified details on sources of funding (Item 13). Five studies stated the method of sample size calculations (Item 5). None of the studies explained about the random allocation sequence generation (Item 6) or about allocation concealment (Item 7). No information was obtained from any of the studies about blinding of examiners or researchers who created the random allocation (Items 8 and 9) (Table 5).

3.4. Results from Studies Assessing Physical Properties

3.4.1. Surface Roughness

The surface roughness of printed resins and various materials was compared in eight studies (Table 6). Two studies assessed the difference in surface roughness of different printed permanent resins prior to and after artificial aging [11,13]. The materials tested initially demonstrated mean surface roughness values that exceeded the clinical threshold of 0.2 μm, however, brushing increased surface roughness [11]. Vichi et al. observed the impact of eight different polishing methods on the surface roughness of printed permanent resin. They found that multi-step finishing and polishing systems were more effective in achieving smoother surfaces compared to one-step and two-step systems [15]. Kang et al. studied the impact of airborne particle abrasion using different particle sizes of alumina on surface roughness. They observed an increase in surface roughness when sandblasting was performed with larger particle sizes and higher pressure, and the treated surface displayed porosity after the procedure [14]. The surface roughness of milled resin, hybrid ceramics, and printed permanent resins was examined in four studies [6,18,19,20]. After polishing, the printed permanent resins displayed surface roughness values comparable to those of resin-based CAD/CAM materials [20]. The printed permanent resins exhibited similar surface roughness values to those of CAD/CAM resins after polishing [20]. Bozogulları et al. in their study observed that one of the investigated polymer-infiltrated network ceramic materials had the highest Ra values, and the 3D-printed permanent resin had lower Ra values [6].

3.4.2. Color Changes

Color changes in 3D-printed permanent resins with different materials were evaluated in eight studies (Table 7). Two studies assessed the color changes in different printed permanent resins with various surface treatments, including no surface treatment, glazed, and sand glazed, before and after immersion in different media, such as distilled water, coffee, and curry [13,17]. The samples showed color changes, which varied with the surface treatment. The untreated samples showed greater changes compared to the glazed and sand-glazed samples. Karaoğlanoğlu et al. studied the color changes in printed permanent resins and milled resins after immersion in different media like coffee, tea, and distilled water and concluded that printed resins showed similar color changes to those of milled resins after the first and seventh days; however, more changes were observed after 30 days of immersion [20]. Two studies [6,21] analyzed color changes after immersion in distilled water and coffee and exposure to 10,000 cycles of thermocycling, finding that one of the investigated 3D-printed resins showed unacceptable color change [6].

3.4.3. Water Sorption/Solubility

Di Fiore et al. [11] examined the water sorption/solubility of two printed permanent resins, with their findings conforming to the ISO 4049:2019 standard [25], which specifies a maximum water sorption (Wsp ≤ 40 μg/mm³) and solubility (Wsl ≤ 7.5 μg/mm³). A notable difference in water sorption was seen between the two resins after 21 days, which was attributed to variations in filler content (Table 8). Specifically, a lower filler content resulted in a larger polymer matrix, leading to increased water sorption [26,27].

3.5. Results from Studies Assessing Mechanical Properties

3.5.1. Flexural Strength

Five studies evaluated the flexural strength of printed permanent resins with various materials (Table 9). Two studies assessed the flexural strength of different printed permanent resins after artificial aging and thermocycling [11,12]. Di Fiore et al. assessed the flexural strength of the printed permanent resin before and after artificial aging, observing a decrease in flexural strength in the tested materials after aging [11]. Korkmaz et al. assessed the flexural strength of printed permanent resins before and after 10,000 cycles of thermocycling, finding a reduction in flexural strength following thermocycling [12]. Two studies analyzed the flexural strength of 3D-printed resins after being subjected to various surface treatments, such as glazing/sand glazing and sand blasting with alumina particles, which also showed a reduction in flexural strength after thermocycling [13,14]. Temizci et al. investigated the effect of thermocycling on the flexural strength of printed permanent resin and hybrid ceramics [2].

3.5.2. Microhardness

Five studies evaluated the microhardness of 3D-printed permanent resins using various materials (Table 10). One study assessed the microhardness of different 3D-printed permanent resins before and after immersion in distilled water for 30 days [11]. Nam et al. investigated the effect of glazing and sand glazing on the microhardness of printed permanent resins [13]. Two studies compared the effect of thermocycling and artificial brushing on the microhardness of printed permanent resins and milled resins/hybrid ceramic materials [2,19]. One study compared the effect of immersion in coffee, tea, and distilled water on microhardness [20].

3.5.3. Elastic Modulus

Di Fiore et al. [11] examined the elastic modulus of two 3D-printed permanent resins, both in their dry state and after being immersed in water. They found a significant difference in the properties of the two resins after immersion in water for 30 days (Table 11). The lower average Young’s modulus values were linked to the structure of the inorganic fillers and their lesser content. Specifically, irregular and faceted-shaped fillers with sharp angles prevent the even distribution of mechanical stresses and have been associated with increased cracking [28,29].

4. Discussion

This systematic review analyzed the mechanical and physical properties of 3D-printed permanent resins and compared them with those of milled resins and hybrid ceramics. Nevertheless, it was noted that the existing evidence on 3D-printed permanent resins for definitive restorations is limited and lacks reliability due to considerable heterogeneity in the research methods employed. This may be because 3D-printed permanent resin materials are comparatively new, and various in vitro studies have analyzed different properties under varying conditions. The physical and mechanical properties of 3D-printed resins are critical in selecting suitable materials for the fabrication of crowns and fixed dental prosthesis, as they directly influence the clinical performance and longevity of these restorations. The flexural strength and elastic modulus of the materials can withstand occlusal forces and resist deformation or wear over time in the oral environment. Additionally, factors like water absorption and surface hardness affect the marginal integrity and overall fit of prostheses. The key findings indicate that the mechanical and physical properties of 3D-printed permanent resins were affected when exposed to artificial aging, thermocycling, polishing techniques, immersion in various media (such as water, tea, coffee, and red wine), and artificial brushing cycles. The 3D-printed permanent resins demonstrated notably different parameters when the mechanical and physical properties were tested, leading to the rejection of the tested null hypothesis.

4.1. Physical Properties

The physical properties, including surface roughness, color changes, and water sorption/solubility, of printed permanent resins were compared with those of various milled resins and hybrid ceramics. Surface roughness, which refers to the unevenness of a material’s surface, is typically measured as the roughness average (Ra). This value represents the mean of all the absolute distances of the profile within a given length [11,30]. In studies evaluating surface roughness of various printed resins, the mean Ra values were found to exceed the clinically acceptable threshold of 0.2 μm. Surface roughness was measured by the ISO 4287:2021 standard, both before and after artificial brushing [11,31]. Surface irregularities and roughness in dental restorations contribute to enhanced bacterial adhesion and plaque accumulation. Materials with roughness values higher than 0.2 μm create small pockets or retention areas that promote the accumulation of bacterial plaque, making it more difficult to maintain oral hygiene and potentially leading to oral health problems [20,32]. Different 3D-printed resins exhibited varying surface roughness values, which were influenced by factors such as the thickness of the printing layer and the material’s position on the build platform. These two variables, along with the material’s hardness, significantly contribute to determining surface roughness [33]. Generally, higher hardness is linked to lower surface roughness, as observed in the study performed by Al-Dulaijan et al. where the tested 3D-printed resin group exhibited surface roughness values in the range of 0.12 and 0.22 μm. Average hardness values ranged from 30.17 to 34.62 VHN, exhibiting an inverse relationship between hardness and surface roughness [34]. Additional factors, such as the grain size of the toothpaste, the type of toothbrush bristles, and finishing and polishing techniques, also affect surface smoothness [33,35]. Nam et al. reported that the Ra values of glazed and sand-glazed samples were lower than those of untreated samples. The untreated samples exhibited the highest Ra values, emphasizing the significance of surface glazing in reducing roughness. Polishing or glazing restoration can improve its longevity in the mouth and help reduce plaque buildup [13]. Additionally, Vichi et al. found that multi-step polishing systems were more effective at enhancing surface smoothness in 3D-printed resins than single-step or two-step systems [15]. Kang et al. found that surface roughness varied based on resin composition and surface treatments, mainly when different alumina particle sizes were used. As abrasion particle size and pressure increased, a porous surface was created, increasing surface roughness [14]. In comparison to milled resins and hybrid ceramic materials, 3D-printed resins exhibited similar Ra values after polishing, as well as after 30 days of immersion in tea, distilled water, and coffee [20]. Despite polishing, brushing, and coffee thermocycling, the surface roughness of permanent resins remained above the clinically acceptable threshold [19]. Camak et al. investigated the impact of polishing methods and coffee thermocycling on the surface roughness of printed and milled resins. Polishing techniques generally reduce surface roughness, with conventional polishing proving more effective than other techniques, including the application of surface sealant [18]. The material type and polishing technique were found to influence surface roughness over time [18].

Significant color changes were noticed in 3D-printed resin samples—untreated, glazed, and sand-glazed—after 30 days of immersion in distilled water, tea, and coffee. The most significant color changes were observed in the untreated resin samples. This could be because the glazed resin samples have layers of light-cured transparent resin coating that penetrates the surface, filling micropores and defects. This layer helps reduce porosity and microleakage, making the surface less susceptible to staining and color changes compared to untreated surfaces [13,34]. Ezmek et al. investigated the effect of three distinct polishing methods on the color stainability of resin samples that were immersed in coffee, tea, distilled water, and red wine for 30 days. Results revealed that the mechanically polished group exhibited the most significant color changes, with red wine causing the most substantial discoloration. In contrast, the glazed samples demonstrated reduced discoloration across all beverages, highlighting that glazing effectively minimizes staining and helps maintain the esthetic appearance of resin material [16]. Krajangta et al. [17] and Karaoğlanoğlu et al. [20] observed significant color changes in printed resins compared to those in milled resin/hybrid ceramics after 30 days of immersion in tea, coffee, and distilled water. Bozogullari et al. noted that one group of printed resin showed unacceptable color change compared to milled resin when subjected to coffee thermocycling [6]. Tasin et al. [21] observed that printed resins and milled resin/hybrid ceramics exhibited a yellowish, darkened, and opaque appearance after coffee thermocycling, even though the color change was within clinically acceptable thresholds. Camak et al. observed the influence of different polishing techniques and coffee thermocycling on printed resin and milled hybrid ceramics, and both materials showed acceptable color changes with any polishing method [18].

4.2. Mechanical Properties

The mechanical properties, including flexural strength and microhardness, of printed permanent resins were compared with those of various milled resins and hybrid ceramics. For printed resins to be viable for dental restorations, they must withstand the masticatory forces and thermal changes common in the oral environment, as these factors can significantly impact their properties. These properties should be tested in an environment that mimics the oral cavity. Thermocycling is an artificial aging process designed to simulate the temperature fluctuations that restorative materials undergo during intraoral use, which can impact the properties of resin materials [12,30].

Several studies [11,12,13] have demonstrated that 3D materials have average flexural strength values that exceeded the minimum 80 MPa requirement for resin materials, as specified in the ISO 4049:2019 standard [25]. The values of flexural strength may serve as an indicator of the material’s clinical performance. However, the values changed after water immersion and thermocycling, and these changes were statistically significant, as observed in studies by Di Fiore et al., Korkmaz et al., and Kang et al. [11,12,14]. The 3D-printed resins, when subjected to thermocycling, exhibited increased water sorption and solubility, which in turn decreased their flexural strength. The initial flexural strength values varied among different 3D-printed resins, which could be attributed to variations in chemical compositions, material viscosities, printing methods with varying polymerization patterns, and post-curing durations. However, the mean flexural strength of all the tested materials decreased similarly after being stored in water for 30 days or exposed to 10,000 cycles of thermocycling [11,12]. Variation in flexural strength was also observed between unglazed, glazed, and sand-glazed surfaces. The glazed samples with photocuring glazing solution and sand-glazed exhibited higher flexural strength than untreated samples. Applying a glazing solution enhanced flexural strength by bonding with the monomers on the surface of the printed permanent resin. Additionally, photopolymerization improves the strength of printed resins [13,31,32]. Kang et al. reported a difference in flexural strength among resin samples with varying compositions and surface treatments, as well as different alumina particle sizes. A significant reduction in flexural strength following the increase in pressure and particle size was observed after thermocycling [14]. In comparison to milled resins and hybrid ceramics, the 3D-printed resins exhibited similar flexural strength, and it remained unaffected after 5000 cycles of thermocycling. Nonetheless, the chemical composition directly affected the mechanical properties of the resins [2].

Various studies have evaluated the microhardness of different 3D-printed permanent resins by measuring the Vickers hardness number (VHN), as it assesses surface hardness and indicates the degree of resin transformation. One tested resin showed different hardness values owing to its distinct composition [11]. Printed resins have polymeric structures, similar to those of inorganic fillers, and their microhardness values depend on the ceramic filler content [19]. Variation in VHN was also observed between unglazed, glazed, and sand-glazed samples. The glazed samples and sand-glazed samples showed greater values than untreated surfaces [13]. In comparison to milled resins and hybrid ceramics, the 3D-printed resins exhibited lower microhardness values; however, the hardness values remained unaffected after the samples were immersed in coffee, tea, and distilled water [20]. In contrast, thermocycling affected the microhardness values [2,19]. This could be attributed to the susceptibility of the tested 3D-printed resins to surface degradation following physical and thermal stresses [19].

5. Limitations and Future Directions

Despite the valuable insights provided by the studies included in this review, several limitations should be considered.

• All the studies reviewed were in vitro studies, which may not have fully simulated the complex conditions encountered in the oral environment. In vivo studies are crucial for confirming the clinical relevance of these findings.
• It is evident that the composition significantly influences the observed properties and behavior of materials. The materials under study were commercially sourced, and their exact formulations are not publicly disclosed in detail. This necessarily limits the generalizability and reproducibility of the findings.
• The limited number of studies and their relatively short follow-up periods suggest that more long-term research is needed to gain a better understanding of the durability and performance of 3D-printed resins over time.
• Future research should focus on exploring standard surface treatments, material compositions, and printing technologies to enhance the properties of 3D-printed resins further. Additionally, studies that examine the impact of various environmental factors (e.g., exposure to saliva, temperature, and mechanical loading) on the properties of these materials will provide more comprehensive data for their clinical use.

6. Conclusions

In conclusion, while 3D-printed permanent resins show potential for use as indirect dental restorations, the current evidence on their physical and mechanical properties remains limited and inconsistent due to variations in study methods. This research suggests that 3D-printed resins tend to exhibit surface roughness, color changes, and mechanical properties that are affected by factors such as polishing, artificial aging, and exposure to various beverages. These materials generally meet the necessary standards for flexural strength and hardness, but their performance can vary depending on their composition and the specific conditions to which they are exposed. Further research on these materials is essential due to the rapid integration of 3D-printed restorations into clinical practice, driven by their efficiency, customization, and cost-effectiveness. Despite showing similar properties to milled resins and hybrid ceramics in many areas, more standardized and long-term studies are needed to fully understand the reliability and durability of 3D-printed resins as definitive materials for crowns and fixed partial dentures for clinical use.