Three-dimensional printing in contemporary fixed prosthodontics: A technique article

Effect of 3D printer, implant analog system, and implant angulation on the accuracy of analog position in implant casts

OBJECTIVES

To evaluate the accumulative effect of 3D printer, implant analog systems, and implant angulation on the accuracy of analog position in implant casts.

METHODS

A reference cast, presenting a case of a three-unit implant-supported prosthesis, was scanned with a coordinate measurement machine, producing the first reference data set (CMM, n = 1). The second reference data set (n = 10) was prepared using an intraoral scanner (IOS) (Trios4). Test quadrant casts were produced using three DLP type 3D printers, Max (MAX UV385), Pro (PRO 4K65 UV), and Nex (NextDent 5100), and three implant analog systems, El (Elos), Nt (Nt-trading), and St (Straumann) (n = 90). Stone casts were also produced via analog impressions (Stone, n = 10). After digitization, the accuracy of 3D distance, local angulation (angle between implants) and global angulation (angle between the implant center axis and an axis perpendicular to the global plane) was evaluated by comparing the reference (CMM, IOS), test (3D print), and control (Stone) groups using metrology software. Data were statistically analyzed using three-way ANOVA and Tukey`s tests (α=0.05).

RESULTS

IOS was truer in 3D implant distance and more precise in capturing local angulation than Stone (p ≤ 0.05). Other measurements were similar between both groups (p > 0.05). The amount of error introduced in the workflow by IOS and 3D printing was mostly similar (p > 0.05). 3D printed casts had similar or even higher accuracy than Stone group (p > 0.05). In most cases, higher trueness was achieved when using PRO 4K65 UV 3D printer and Elos implant analog system (p ≤ 0.05).

CONCLUSION

3D printer, implant analog system, and implant angulation have a significant effect on the accuracy of analog position in implant casts. Limited-span implant-supported cases could be reproduced digitally with similar accuracy as conventional methods.

CLINICAL SIGNIFICANCE

A fully digital workflow with a carefully selected 3D printer and implant analog system can increase the accuracy of digitally produced implant casts with comparable accuracy to conventional workflow.

Experimental study on dimensional variations of 3D printed dental models based on printing orientation

This research investigates the trueness and precision of 3D printing technology in dental applications, specifically focusing on dimensional variations observed in models printed at different angles. The methodology involved importing a dental model into slicing software, adjusting its orientation, and implementing support structures for stability. Subsequently, the model underwent 3D printing five times for each orientation using appropriate equipment and underwent post-processing steps, including cleaning, washing, and UV-light post-curing. The printed models were then scanned using a specialized desktop scanner for further analysis. Accuracy assessment was carried out using dedicated software, employing an algorithm for precise alignment by comparing the scanned files. Color deviation maps were utilized to visually represent variations, aiming to evaluate how positioning during printing influences the trueness and precision of 3D-printed dental models. Trueness and precision analyses involved the Shapiro-Wilk test for normality and a one-way ANOVA to compare means of three independent groups, with statistical analyses conducted using IBM SPSS Statistics software. The color maps derived from 3D comparisons revealed positive and negative deviations, represented by distinct colors. Comparative results indicated that models positioned at 0° exhibited the least dimensional deviation, whereas those at 90° showed the highest. Regarding precision, models printed at 0° demonstrated the highest reproducibility, while those at 15° exhibited the lowest. Based on the desired level of precision, it is recommended that printed models be produced at an inclination angle of 0°.

Influence of hydrothermal aging on the shear bond strength of 3D printed denture-base resin to different relining materials

OBJECTIVES

This study evaluated the repairability of three-dimensional printed (3DP) denture bases based on different conventional relining materials and aging.

MATERIAL AND METHODS

The groups for surface characterization (surface-roughness and contact-angle measurements) were divided based on the denture base and surface treatment. Shear bond strength test and failure-mode analysis were conducted by a combination of three variables: denture base, relining materials, and hydrothermal aging (HA). The initial characterization involved quantifying the surface roughness (n = 10) and contact angle (n = 10) of denture base specimens with and without sandblasting (SB) treatment. Four relining materials (Kooliner [K], Vertex Self-Curing [V], Tokuyama Rebase II (Normal) [T], and Ufi Gel Hard [U]) were applied to 3DP, heat-cured (HC), and self-cured (SC) denture-base resin specimens. Shear bond strength (n = 15) and failure-mode analyses (n = 15) were performed before and after HA, along with evaluations of the fractured surfaces (n = 4). Statistical analyses were performed using a two-way analysis of variance (ANOVA) for surface characterization, and a three-way ANOVA was conducted for shear bond strength.

RESULTS

The surface roughness peaked in HC groups and increased after SB. The 3DP group displayed significantly lower contact angles, which increased after treatment, similar to the surface roughness. The shear bond strength was significantly lower for 3DP and HC denture bases than for SC denture bases, and peaked for U at 10.65 ± 1.88 MPa (mean ± SD). HA decreased the shear bond strength relative to untreated samples. Furthermore, 3DP, HC, and SC mainly showed mixed or cohesive failures with V, T, and U. K, on the other hand, trended toward adhesive failures when bonded with HC and SC.

CONCLUSION

This study has validated the repairability of 3DP dentures through relining them with common materials used in clinical practice. The repairability of the 3DP denture base was on par with that of conventional materials, but it decreased after aging. Notably, U, which had a postadhesive application, proved to be the most effective material for repairing 3DP dentures.

Mechanical Properties of Additively Manufactured and Milled Interim 3-Unit Fixed Dental Prostheses

PURPOSE

To investigate the survival and mechanical properties of 3-unit interim fixed dental prostheses (FDPs) made with additive manufacturing (AM) technology compared to milled and conventional manual fabrication.

MATERIALS AND METHODS

Sixty 3-unit interim FDPs replacing the first left mandibular molar were divided in 6 groups (n = 10): manual (Man) (Protemp 4), milled (Mil) (Telio-CAD Multi), and 4 additive manufacturing (AM) groups were subdivided into 4 AM technology subgroups: direct light positioning (DLP) (Rapidshape P30 [RS]), and stereolitography (SLA) (Formlabs 2 [FL]) and the type of printed interim polymer (P Pro C&B [St] and SHERAprint-cb [Sh]) (RS-St, RS-Sh, FL-St, and FL-Sh). Survival and complications were assessed after thermomechanical aging. The surviving samples were tested for fracture resistance. Kaplan-Meier test followed by log-rank test to show differences between groups was used to calculate the survival and complication rates. For fracture strength, one-way ANOVA and Tukey-b post hoc test were used to compare groups. Descriptive statistics was used for failure modes and Pearson chi-square to compare groups (α = 0.05).

RESULTS

Survival rates among groups varied from 100% (Man, Mil and FL-Sh), 70% (FL-St), 50% (RS-Sh), and 20% (RS-Sh) (p < 0.001), respectively. Additional events were observed in 50% to 80% in FL-St, RS-St, and RS-Sh groups (p < 0.001). Man, FL-St, and RS-S showed lower mean static load resistance (p < 0.001). Fracture through the connector between tooth 35 and the pontic was the most prevalent type of failure.

CONCLUSION

The manufacturing method, type of resin, and the printing mode had a significant influence on the mechanical properties of AM interim 3-unit FDPs.

3D Printing of Dental Prostheses: Current and Emerging Applications

Revolutionary fabrication technologies such as three-dimensional (3D) printing to develop dental structures are expected to replace traditional methods due to their ability to establish constructs with the required mechanical properties and detailed structures. Three-dimensional printing, as an additive manufacturing approach, has the potential to rapidly fabricate complex dental prostheses by employing a bottom-up strategy in a layer-by-layer fashion. This new technology allows dentists to extend their degree of freedom in selecting, creating, and performing the required treatments. Three-dimensional printing has been narrowly employed in the fabrication of various kinds of prostheses and implants. There is still an on-demand production procedure that offers a reasonable method with superior efficiency to engineer multifaceted dental constructs. This review article aims to cover the most recent applications of 3D printing techniques in the manufacturing of dental prosthetics. More specifically, after describing various 3D printing techniques and their advantages/disadvantages, the applications of 3D printing in dental prostheses are elaborated in various examples in the literature. Different 3D printing techniques have the capability to use different materials, including thermoplastic polymers, ceramics, and metals with distinctive suitability for dental applications, which are discussed in this article. The relevant limitations and challenges that currently limit the efficacy of 3D printing in this field are also reviewed. This review article has employed five major scientific databases, including Google Scholar, PubMed, ScienceDirect, Web of Science, and Scopus, with appropriate keywords to find the most relevant literature in the subject of dental prostheses 3D printing.

Role of 3D Printing in Post-op Rehabilitation of Palatal Bone Loss by Mucormycosis: A Survey

BACKGROUND

Three dimensions (3D) modeling, printing, and manufacturing can help in personalized and customized surgical reconstruction of complex defects in the craniofacial region with precision by manipulating tissues based on the preoperative assessment, planning the shape of metal and alloplastic materials, and reduction in the total cost and time of the surgery.

AIM

The present survey study aimed to assess the approach of treating surgeons towards the role of 3D printing in post-op rehabilitation of palatal bone loss by mucormycosis.

METHODS

One thousand eyes nose and throat (ENT) and maxillofacial surgeons were given a pre-formed structured survey questionnaire to be filled by subjects themselves for their view on the role of 3D printing for rehabilitation and reconstruction of palatal bone loss due to mucormycosis.

RESULTS

Efficacy of 3D printing to print the pneumatic sinus design and palatal contour helping to design accurate support with a lightweight prosthesis, 67.2% (n=672) subjects whereas, exact duplication of the excised tissue, 85.4% (n=854) subjects, to detect and duplicate undercuts, 58.4% (n=584) subjects, 3D printing can be helpful as the proper extension of impression 73.2% (n=732) subjects responded positively. For reconstruction of a lost palate by prosthesis 91.2% (n=912) of study participants, in making obturators using Titanium framework and Polyetheretherketone (PEEK) was given a positive response by 82.2% (n=822) subjects, to fabricate prosthesis obturator required in palatal perforation in case of mucormycosis was given a positive response by 88.1% (n=881) subjects, the role of 3D printing to overlay zygomatic implant prosthesis was responded positively by 68.9% (n=689) study subjects.

CONCLUSION

The present survey study concludes that 3D printing is a reliable and accurate method for palatal reconstruction following bone destruction by mucormycosis as reported by the majority of ENT and maxillofacial surgeons.

Virtual Planning and Rapid 3D Prototyping Surgical Guide for Anterior Crown Lengthening Surgery: A Clinical Case Report

Progress with additive 3D printing is revolutionizing biomaterial manufacturing, including clinical dentistry and prosthodontics. Among the several 3D additive printing technologies, stereolithography is very popular as it utilizes light-activated resin for precise resolution. A simplified digital technique was used to fabricate two designs of a surgical guide for crown lengthening. Two cases are presented that utilized digital DICOM files obtained with computed tomography (CT) imaging and processed using four CAD software (Blue Sky Plan, Exocad, Meshmixer and 3D Slicer). The final models were converted to standard tesselation (STL) files and the guides were 3D printed with an additive sterelithography (SLA) printer. The first case was fabricated with a bone model from CBCT data, and the second case was generated with intraoral and wax-up scans alone. Both methods appear to be equally effective compared to using a conventional method of guide frabication. However, proximal bone reduction was a concern with both designs. Digitally fabricated 3D printed surgical guide for crown lengthening has merit and a practical design is needed for future clinical validation. This article is protected by copyright. All rights reserved.

Comparison of the Mechanical Properties of Temporary Abutments Made of Polyetheretherketone and Photopolymeric Resin

Background:

Provisional abutments are widely used in the rehabilitation of dental implants as it allows the use of a provisional crown in order to restore patient aesthetics while the final restoration is being carried out; most of the temporary abutments available on the market are made of titanium alloygrade V (type Ti-6Al-4Va) and polyetheretherketone (PEEK), a material that exhibits very low adhesion to polymethylmethacrylate (PMMA).

Objective:

This research is aimed to compare the mechanical properties of commercially available PEEK abutments and abutments made using an additive technique with photopolymeric resin.

Methods:

Eighteen commercial temporary abutments manufactured in PEEK and eighteen experimental abutments manufactured by 3D printing using photopolymeric resin were used. The two groups of abutments were subjected to compression, bending and adhesion tests using six abutments of each type by test. Statistical analysis was performed with STATA 14 software. The data were analyzed by means of the Wilcoxon Mann-Whitney test, as these were two independent samples of reduced size. Values ​​lower than (p <0.05) were considered statistically significant in all tests and rejected the null hypothesis of equality between the group medians.

Conclusion:

The results indicate that it is possible to make abutments with good mechanical properties in photopolymeric resin (CLEAR FLGP04) using additive techniques to be used as temporary abutments.

Esthetic treatment planning with digital animation of the smile dynamics: A technique to create a 4-dimensional virtual patient

A method is presented for obtaining a virtual 4-dimensional patient that replicates the intended esthetic treatment. The process involves facial and intraoral scanning to acquire records and software manipulation to enable a virtual waxing of the smile. Once the digital design is complete, patient information can be merged to generate an animated video of the projected rehabilitation, displaying movement and smile dynamics. This strategy provides a noninvasive and reliable diagnostic tool for predicting clinical outcomes.

Digital versus conventional workflow for the fabrication of physical casts for fixed prosthodontics: A systematic review of accuracy

STATEMENT OF PROBLEM

A consensus on the accuracy of additively manufactured casts in comparison with those fabricated by using conventional techniques for fixed dental prostheses is lacking.

PURPOSE

The purpose of this systematic review was to determine the accuracy of additively manufactured casts for tooth- or implant-supported fixed dental prostheses in comparison with that of gypsum casts.

MATERIAL AND METHODS

This study adhered to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines and was registered with the International Prospective Register of Systematic Reviews (PROSPERO) database (CDR42020161006). Eight databases were searched in December 2019 and updated in September 2020. Studies evaluating the dimensional accuracy of additively manufactured casts for fixed dental prostheses in comparison with that of gypsum casts were included. An adapted checklist for reporting in vitro studies (Checklist for Reporting In vitro Studies guidelines) was used to assess the risk of bias.

RESULTS

Eight studies evaluating tooth-supported fixed dental prosthesis casts and 7 studies evaluating implant-supported fixed dental prosthesis casts were eligible for this review. Gypsum casts showed greater accuracy (trueness and precision) in most studies, although additively manufactured casts also yielded highly precise data. One study was associated with a low risk of bias, 9 with a moderate risk of bias, and 5 with a high risk of bias.

CONCLUSIONS

In vitro studies showed that additively manufactured casts and gypsum casts share similar accuracy within the acceptable range for the fabrication of casts. The quality of scanned data, additive manufacture technology, printing settings, and postprocessing procedures plays an essential role in the accuracy of additively manufactured casts. Clinical studies are required to confirm these findings.

The Modern and Digital Transformation of Oral Health Care: A Mini Review

Dentistry is a part of the field of medicine which is advocated in this digital revolution. The increasing trend in dentistry digitalization has led to the advancement in computer-derived data processing and manufacturing. This progress has been exponentially supported by the Internet of medical things (IoMT), big data and analytical algorithm, internet and communication technologies (ICT) including digital social media, augmented and virtual reality (AR and VR), and artificial intelligence (AI). The interplay between these sophisticated digital aspects has dramatically changed the healthcare and biomedical sectors, especially for dentistry. This myriad of applications of technologies will not only be able to streamline oral health care, facilitate workflow, increase oral health at a fraction of the current conventional cost, relieve dentist and dental auxiliary staff from routine and laborious tasks, but also ignite participatory in personalized oral health care. This narrative article review highlights recent dentistry digitalization encompassing technological advancement, limitations, challenges, and conceptual theoretical modern approaches in oral health prevention and care, particularly in ensuring the quality, efficiency, and strategic dental care in the modern era of dentistry.

Impact of Layer Thickness and Storage Time on the Properties of 3D-Printed Dental Dies

The purpose of this study was to evaluate the effect of printing layer thickness on the repeatability and surface roughness of 3D-printed dies and detect the effect of layer thickness and storage time on the dimensional stability of 3D-printed dies. One stereolithography (STL) file of an upper molar prepared for a full ceramic crown was used to print three groups of dies: 25 µm, 50 µm, and 100 µm. Repeatability was evaluated by linear and area measurements with a digital caliper and a digital metrology microscope. Dimensional stability was analyzed at 3 weeks, 6 months, and 1 year of storage time. Surface roughness parameters were measured with a 3D confocal laser scanning microscope. Statistics were completed using one-way analysis of variance and Tukey’s post hoc tests, p < 0.05. Printing time decreased as layer thickness increased. All groups showed high repeatability and comparable surface roughness while showing differences in their linear dimensions and surface areas. At the 3 week storage interval, dimensional changes were observed in all groups. Within this experimental study’s constraints, it can be concluded that changing the 3D-printing layer thickness does not affect the repeatability or the surface roughness of the product; meanwhile, changes to the layer thickness and storage time influence the dimensional stability of 3D-printed dies.

Dental 3D-Printing: Transferring Art from the Laboratories to the Clinics

The rise of three-dimensional (3D) printing technology has changed the face of dentistry over the past decade. 3D printing is a versatile technique that allows the fabrication of fully automated, tailor-made treatment plans, thereby delivering personalized dental devices and aids to the patients. It is highly efficient, reproducible, and provides fast and accurate results in an affordable manner. With persistent efforts among dentists for refining their practice, dental clinics are now acclimatizing from conventional treatment methods to a fully digital workflow to treat their patients. Apart from its clinical success, 3D printing techniques are now employed in developing haptic simulators, precise models for dental education, including patient awareness. In this narrative review, we discuss the evolution and current trends in 3D printing applications among various areas of dentistry. We aim to focus on the process of the digital workflow used in the clinical diagnosis of different dental conditions and how they are transferred from laboratories to clinics. A brief outlook on the most recent manufacturing methods of 3D printed objects and their current and future implications are also discussed.

Accuracy evaluation of complete-arch models manufactured by three different 3D printing technologies: a three-dimensional analysis

Purpose This study aimed to evaluate the trueness and precision of complete-arch models printed with three-dimensional printers via three different printing technologies.Methods An arch-shaped master model was designed using software (RapidForm XOR2, 3D Systems Inc., USA), and the digital master model was printed 10 times with three-dimensional printers using stereolithography (SLA), direct light processing (DLP), and Polyjet technology (n = 30). The printed models were then scanned with an industrial scanner to create the respective digital models. All digital models were compared with the master model, and an evaluation of the trueness was performed by model superimposition with Geomagic Control software (3D Systems, Rock Hill, SC, USA). Precision was determined for each case by superimposing some combination of the 10 datasets in each group.Results The trueness of the printed models was 46.2 µm for the DLP printer, 51.6 µm for the SLA printer, and 58.6 µm for the Polyjet printer. The DLP models were significantly better than the Polyjet models (p = .005). However, the Polyjet models (30.4 µm) were more precise than the SLA (37.6 µm) and DLP (43.6 µm) models (p < .001, p = .016). Furthermore, the SLA (11.8 µm) was the most accurate printer in the Z-direction (p = .016, p = .002).Conclusions The 3D printing technologies showed significant differences in the precision and trueness of complete-arch measurements. Although DLP was more accurate other tested 3D printers, the accuracy of all 3D printed models was within clinical tolerance, and they were clinically acceptable and could be used for the production of fixed restorations.

Impacts of contracted endodontic cavities compared to traditional endodontic cavities in premolars

BACKGROUND

This study aims to compare the percentage of dentin removed, instrumentation efficacy, root canal filling and load at fracture between contracted endodontic cavities, and traditional endodontic cavities on root canal therapy in premolars.

METHODS

Forty extracted intact human first premolars were imaged with micro-CT and randomly assigned to the contracted endodontic cavity (CEC) or traditional endodontic cavity (TEC) groups. CEC was prepared with the aid of a 3D-printed template, canals were prepared with a 0.04 taper M-Two rotary instrument, and cavities were restored with resin. Specimens were loaded to fracture in an Instron Universal Testing Machine after a fatigue phase. The data were analyzed by the independent samples T test and Mann-Whitney U test, appropriate post hoc tests.

RESULTS

In the premolars tested in vitro, the percentage of dentin removed in the premolars with two dental roots in the CEC group (3.85% ± 0.42%) was significantly smaller (P < 0.05) than in the TEC group (4.94% ± 0.5%). The untouched canal wall (UCW) after instrumentation for TECs (16.43% ± 6.56%) was significantly lower (P < .05) than the UCW (24.42% ± 9.19%) for CECs in single-rooted premolars. No significant differences were observed in the increased canal volume and surface areas in premolars between the TEC and CEC groups (P > 0.05). CECs conserved coronal dentin in premolars with two dental roots but no impact on the instrument efficacy. There were no differences between the CEC groups and the TEC groups in the percentage of filling material and voids (P > 0.05). In addition, the mean load at failure of premolars did not significantly differ between the CEC and TEC groups and there was no significant difference in the type of fracture (P > 0.05).

CONCLUSION

The results of this study suggest that CEC could not improve the fracture resistance of the endodontically treated premolars. The instrumentation efficacy and the percentage of filling material did not significantly differ between CECs and TECs in premolars.

Creating a digital duplicate denture file using a desktop scanner and an open-source software program: A dental technique

This article describes a digital technique for obtaining a standard tessellation language (STL) file of a complete denture using a desktop scanner and an open-source software program. Accurate recording of the surface details of the denture in 3D was performed using a desktop scanner. The generated STL file from this technique represents a digital duplicate of the scanned denture. This file can be used for surgical implant placement planning, fabricating a duplicate denture, and storing the scanned denture as a digital file for future use.

Fabrication technique for a custom implant emergence profile on 3D printed casts

A procedure is described for fabricating a removable resilient soft-tissue replica that accurately replicates the contoured emergence profile of an interim implant-supported restoration on a cast fabricated by 3D printing. The technique uses digital scanning and 3D printing technologies to produce a 3D printed replica of the implant-supported interim crown, which is then used to fabricate the custom soft-tissue replica. This straightforward technique allows the accurate replication of the emergence profile without retaining the interim crown or fabricating a new one. No additional clinical appointments are needed.

A technique to record the gingival configuration of an interim implant-supported fixed partial denture

Transferring the soft tissue around an interim implant-supported fixed partial denture to the definitive cast is difficult. A technique that can accurately record the soft tissue configuration when making an impression for an implant-supported fixed partial denture is described.