Accuracy of surgical guides made from conventional and a combination of digital scanning and rapid prototyping techniques

In vitro comparison of guide planes for removable partial dentures prepared with CAD-CAM-assisted templates, guiding rod templates, and freehand

OBJECTIVES

This study aimed to evaluate the accuracy of computer-aided design and computer-aided manufacturing (CAD-CAM)-assisted templates (CCAT), guiding rod templates (GRT), and freehand (FH) preparation of guide planes.

METHODS

Forty-five identical maxillary resin casts were divided into three groups, in which the guide planes of the two abutment teeth were prepared using a CCAT (n=15), GRT (n=15), and FH (n=15). The CCAT and GRT were digitally designed on a digital cast of virtually prepared guide planes and fabricated using three-dimensional printing (3DP) technology. To assess the 3D trueness, the prepared guide planes were digitally scanned and compared to the virtually designed guide planes. The angle deviation was measured to assess the trueness of the direction of the guide plane preparation. Shapiro-Wilk and Levene's tests were used to check the normality and equivalence of the variance of the data. The data were compared by using the Kruskal‒Wallis H test (α=0.05).

RESULTS

The CCAT group exhibited significantly better 3D trueness (78.5±19.8 μm) than the GRT group (211.3±42.4 μm, p<0.05) and the FH group (198.9±44.3 μm, p<0.05). Additionally, the CCAT group (1.31±0.50°) showed significantly smaller direction trueness compared to the GRT (4.65±0.72°, p<0.05) and FH (5.64±0.70°, p<0.05) groups.

CONCLUSIONS

The novel CAD-CAM-assisted template significantly improved the quality of the guide planes compared with the GRT and FH procedures. This enhancement suggests that removable partial dentures can be predictably inserted immediately after guide plane preparation.

CLINICAL SIGNIFICANCE

CAD-CAM-assisted templates improve the quality of guide plane preparation.

Current applications of 3D printing in dental implantology: A scoping review mapping the evidence

OBJECTIVES

This scoping review aimed to identify the available evidence in the use of 3D printing technology in dental implantology. Due to the broad scope of the subject and its application in implantology, three main areas of focus were identified: (1) customized dental implants, (2) manufacturing workflow for surgical implant guides, and (3) related implant-supported prostheses factors, which include the metallic primary frameworks, secondary ceramic or polymer superstructures, and 3D implant analog models.

MATERIALS AND METHODS

Online databases (Medline, Cochrane, Embase, and CINAHL) were used to identify the studies published up to February 2023 in English. Two experienced reviewers performed independently the screening and selection among the 1737 studies identified. The articles evaluated the additive manufacturing (AM) technology, materials, printing, and post-processing parameters regarding dental implantology.

RESULTS

The 132 full-text studies that met the inclusion criteria were examined. Thirteen studies of customized dental implants, 22 studies about the workflow for surgical implant guides, and 30 studies of related implant-supported prostheses factors were included.

CONCLUSIONS

(1) The clinical evidence about AM titanium and zirconia implants is scarce. Early data on survival rates, osseointegration, and mechanical properties are being reported. (2) 3D printing is a proven manufacturing technology to produce surgical implant guides. Adherence to the manufacturer's instructions is crucial and the best accuracy was achieved using MultiJet printer. (3) The quality of 3D printed prosthetic structures and superstructures is improving remarkably, especially on metallic alloys. However, better marginal fit and mechanical properties can be achieved with milling technology for metals and ceramics.

Effect of Post-Printing Conditions on the Mechanical and Optical Properties of 3D-Printed Dental Resin

This study aimed to evaluate the flexural strength (FS), surface wear, and optical properties of 3D-printed dental resins subjected to different post-printing conditions. A total of 240 specimens (2 × 2 × 25 mm³) were 3D-printed using resin materials for permanent (VaresoSmile Crown Plus) VSC and temporary (VaresoSmile Temp) VST restorations. Specimens underwent five post-printing conditions: no post-printing cure; post-cured in a Form Cure curing unit; Visio Beta Vacuum; Ivoclar Targis; or heat-cured (150 °C) for 30 min. Each group of specimens (n = 24) was tested either directly after post-curing, after 24 h of dry storage, or following hydrothermal accelerated aging in boiling water for 16 h. The three-point bending test was used to evaluate the FS. The two-body wear test was performed on 50 disc-shaped specimens (n = 5/group). Surface gloss and translucency were measured for permanent VSC specimens (n = 5/group). SEM/EDS and statistical analyses were performed. The Form Cure device yielded the highest FS and lowest wear depth (p < 0.05). Hydrothermal aging significantly reduced FS. There were no statistical differences in FS and wear values between materials subjected to same post-printing conditions. VSC groups exhibited similar optical properties across different post-printing treatments. Post-printing treatment conditions had a significant impact on the FS and wear of the 3D-printed resin, while optical properties remained unaffected.

Immediate implant placement in the posterior mandibular region was assisted by dynamic real-time navigation: a retrospective study

BACKGROUND

Efficient utilization of residual bone volume and the prevention of inferior alveolar nerve injury are critical considerations in immediate implant placement (IIP) within the posterior mandibular region. Addressing these challenges, this study focuses on the clinical efficacy and implant accuracy of dynamic real-time navigation, an emerging technology designed to enhance precision in implantation procedures.

METHODS

This study included 84 patients with 130 implants undergoing immediate placement in the posterior mandibular region. Stratified into dynamic navigation, static guide plate, and freehand implant groups, clinical indicators, including initial stability, distance to the inferior alveolar nerve canal, depth of implant placement, and various deviations, were systematically recorded. Statistical analysis, employing 1- or 2-way ANOVA and Student's t-test, allowed for a comprehensive evaluation of the efficacy of each technique.

RESULTS

All 130 implants were successfully placed with an average torque of 22.53 ± 5.93 N.cm. In the navigation group, the distance to the inferior alveolar nerve and the depth of implant placement were significantly greater compared to the guide plate and freehand groups (P < 0.05). Implant deviation was significantly smaller in both the navigation and guide plate groups compared to the freehand group(P < 0.05). Additionally, the navigation group exhibited significantly reduced root and angle deviations compared to the guide plate group(P < 0.05), highlighting the superior precision of navigation-assisted immediate implant placement.

CONCLUSIONS

It is more advantageous to use dynamic navigation rather than a static guide plate and free-hand implant insertion for immediate posterior mandibular implant implantation.

Digital versus conventional surgical guide fabrication: A randomized crossover study on operator preference, difficulty, effectiveness, and operating time

AIM

If surgical guide fabrication is introduced in a dental education program, a digital and conventional workflow can be used. This study evaluated operator preference, perceived difficulty and effectiveness and operating time of both fabrication methods.

MATERIALS AND METHODS

Forty participants in a university setting (students, n = 20; dentists, n = 20) with varying levels of dental experience, but no experience in surgical guide fabrication, were randomly assigned to consecutively fabricate surgical guides on a standardized training model, with either the digital or conventional workflow first. The operating time was measured, and operator preference and the perception of difficulty and effectiveness were assessed with a questionnaire. T tests were used for statistical analysis (α = .05).

RESULT

Of the students, 95% preferred the digital workflow and of the dentists 70%. The perceived difficulty of the digital workflow was significantly lower than the conventional workflow in the student group. Both groups perceived the digital workflow to be more effective. The mean operating time (mm:ss) amounted 12:34 ± 2:24 (students) and 18:07 ± 6:03 (dentists) for the digital, and 22:20 ± 3:59 (students) and 20:16 ± 4:03 (dentists) for the conventional workflow.

CONCLUSION

Both students and dentists prefer the digital workflow for surgical guide fabrication. Students perceive the digital workflow as less difficult and more effective than the conventional workflow. The operating time for surgical guide fabrication is shorter with a digital workflow. This study indicates that digital fabrication techniques for surgical guides are preferred to be incorporated into the dental curriculum to teach students about treatment planning in implant dentistry.

Three-dimensional (3D) printing in dental practice: Applications, areas of interest, and level of evidence

OBJECTIVES

The aim of this review to overview three-dimensional (3D) printing technologies available for different dental disciplines, considering the applicability of such technologies and materials development.

MATERIALS AND METHODS

Source Arksey and O'Malley's five stages framework using PubMed, EMBASE, and Scopus (Elsevier) databases managed this review. Papers focusing on 3D printing in dentistry and written in English were screened. Scientific productivity by the number of publications, areas of interest, and the focus of the investigations in each dental discipline were extracted.

RESULTS

Nine hundred thirty-four studies using 3D printing in dentistry were assessed. Limited clinical trials were observed, especially in Restorative, endodontics, and pediatric dentistry. Laboratory or animal studies are not reliable for clinical success, suggesting that clinical trials are a good approach to validate the new methods' outcomes and ensure that the benefits outweigh the risk. The most common application for 3D printing technologies is to facilitate conventional dental procedures.

CONCLUSIONS

The constantly improving quality of 3D printing applications has contributed to increasing the popularity of these technologies in dentistry; however, long-term clinical studies are necessary to assist in defining standards and endorsing the safe application of 3D printing in dental practice.

CLINICAL RELEVANCE

The recent progress in 3D materials has improved dental practice capabilities over the last decade. Understanding the current status of 3D printing in dentistry is essential to facilitate translating its applications from laboratory to the clinical setting.

Accuracy of Guided Implant Surgery in the Partially Edentulous Jaw Using Digital impression versus Desktop Scanner and CBCT cast scan: Randomized Clinical Trial

AIM: The aim of the study is to compare the accuracy of surgical guided implant produced by intraoral scanner, desktop scanner, and CBCT cast scan. SUBJECTS AND METHODS: A total of 63 dental implants were placed using 14 surgical guides. A total of 15 subjects, eight males and seven females (eight bilateral cases and seven unliteral cases), with mean age of 45 years (38–55 years) were included in the study. Patients were randomly divided into three groups (n = 21 each): Group 1: Surgical guide manufactured using intraoral digital impression. Group 2: Surgical guide manufactured using model cast scanning by CBCT while Group 3: Surgical guide manufactured using model cast scanning by desktop scanner the linear and angular deviations of inserted planned implants were measured. RESULTS: In the intraoral scan group, the mean angular deviation, platform 3D deviation, apical 3D deviation, and vertical deviation were 2.5°, 0.7 mm, 1.1 mm, and 0.6 mm, respectively. While in desktop scanner group, the mean angular deviation, platform 3D deviation, apical 3D deviation, and vertical deviation were 2.6°, 0.1 mm, 1.1 mm, and 1.1 mm, respectively. In the CBCT scan group, the mean angular deviation, 3D platform deviation, 3D apical deviation, and vertical deviation were 3.5°, 1.3 mm, 1.6 mm, and 1.7 mm, respectively. There is no statistically significance difference between intraoral scanner, CBCT cast scan, and desktop scanning on implant deviation that was observed. CONCLUSION: There was no statistically significance difference between intraoral scanner, CBCT cast scan, and desktop scanning on implant deviation that was observed although IOS shows better accuracy and least mean angular deviation.

Fabrication of a CAD-CAM combination matrix for trial restorations: A dental technique

The trial restoration increases outcome predictability in restorative treatments, enhances communication among specialists and patients, and guides tooth preparations. It should reproduce the planned design precisely because many decisions will be made based on the transferred design. Traditionally, a diagnostic waxing design is transferred to the mouth with a flexible silicone matrix. However, a rigid matrix would ensure an accurate transfer of the planned design by avoiding the deformation of the silicone index. A step-by-step technique for fabricating a computer-aided design and computer-aided manufactured (CAD-CAM) rigid matrix relined with polyvinyl siloxane material to fabricate a trial restoration is presented. The technique ensures accurate detail reproduction and dimensional stability, avoiding deformation and ensuring a predictable transfer of the planned design.

Fabrication of immediately loaded implant-retained maxillary overdenture with flapless surgery using a CAD/CAM surgical guide: A technical report

This report describes a digital workflow and two-year follow-up of an immediately loaded implant-retained overdenture using flapless surgery and a computer-aided design/computer-aided manufacturing (CAD/CAM) surgical guide. A prosthetically-driven approach, utilising a three-dimensional (3D) planning software and a CAD/CAM surgical guide, was used to place four implants in the edentulous maxillary arch of a 59-year-old male patient. All four implants were inserted through the surgical guide without raising soft tissue flaps. After placement, the patient was delivered an immediately loaded maxillary overdenture. Surgical implant placement was well tolerated by the patient, who reported no discomfort. Following a four-month period, a new implant-retained maxillary overdenture reinforced by a metal framework was fabricated and delivered to the patient. There were no adverse issues noted with neither the implants nor the maxillary overdenture during the two-year follow up period. The technique using the workflow described in this report may be a predictable and affordable alternative in the restoration of edentulous arches as compared to full-arch fixed restorations.

Accuracy of additive manufacturing in stomatology

With the rapid development of the three-dimensional (3D) printing technology in recent decades, precise and personalized manufacturing has been achieved gradually, bringing benefit to biomedical application, especially stomatology clinical practice. So far, 3D printing has been widely applied to prosthodontics, orthodontics, and maxillofacial surgery procedures, realizing accurate, efficient operation processes and promising treatment outcomes. Although the printing accuracy has improved, further exploration is still needed. Herein, we summarized the various additive manufacturing techniques and their applications in dentistry while highlighting the importance of accuracy (precision and trueness).

Effect of different storage conditions on the fit of 3D-printed occlusal devices used to treat temporomandibular disorders

STATEMENT OF PROBLEM

Research-based storage guidelines for 3-dimensional (3D)-printed occlusal devices are lacking.

PURPOSE

The purpose of this in vitro study was to investigate the dimensional stability of the internal surface of 3D-printed occlusal devices under different storage conditions.

MATERIAL AND METHODS

Maxillary and mandibular dental casts were scanned and exported to a 3D printer to fabricate 30 occlusal devices. The specimens were stored under 3 different conditions (n=10): air dried and stored under natural light (group DL), stored in a dark container with water (group W), and air dried and stored in a dark container (group D). The intaglio surfaces of the occlusal devices were scanned by a laboratory scanner at 4 time points: immediately after polymerization (t₀, control), after 1 day (t₁), after 7 days (t₂), and after 27 days (t₃). The dimensional changes of the fitting surfaces between t₀ and t₁ (Δt₁), t₀ and t₂ (Δt₂), and t₀ and t₃ (Δt₃) were measured by using best fit alignment in a surface analysis software program. In addition, comparisons were made between the posterior and anterior sections. Statistical analysis was completed with Kolmogorov-Smirnov, 1-way ANOVA, Friedman, Kruskal-Wallis, Mann-Whitney, and unpaired t tests.

RESULTS

The root mean square (RMS) of group DL between Δt₁ and Δt₂ (P=.002) and between Δt₁ and Δt₃ (P=.002) showed a statistically significant difference. The RMS of group W between Δt₁ and Δt₃ (P=.008) showed a statistically significant difference. When the groups were compared with each other at the different time points, the DL group showed a statistically significant difference compared with groups W and D at Δt₁. The examination of different areas of the occlusal device (right molar, incisor, and left molar sites) indicated no statistically significant differences in RMS among all groups (P>.05).

CONCLUSIONS

The occlusal devices of group DL showed the least dimensional change of the fitting surface for Δt₁ in comparison with group W and D, while no statistically significant differences were found among the groups for Δt₂ and Δt₃. In terms of the different locations, no statistically significant differences were found among the 3 locations for any given group after 27 days.

Reducing errors in guided implant surgery to optimize treatment outcomes

Clinical considerations and treatment criteria in implant placement are constantly evolving. Prosthetically driven implant surgery has become the standard of care to improve short and long-term functional and esthetic outcomes. Therefore, implant position and angulation are planned according to the available bone, anatomical structures, and the requirements of the future prosthetic superstructure. In parallel with these developments, significant progress has been made in data imaging and different software technologies to allow the integration of data within a digital file format. Digitalization in implant surgery enables optimal planning of implant position, as well as the ability to transfer this planning to the surgical field-a process defined as "computer-supported implant planning and guided surgery." The aims of the present review are as follows: (a) to critically appraise the indications and potential "added value" of guided implant surgery, elaborating the main differences between dynamic and static guidance; and (b) to discuss the most important clinical considerations relevant for the different steps of the workflow that might influence the surgical outcome and to offer recommendations on how to avoid or reduce process errors in order to optimize treatment outcomes.

Comparing digital and traditional guides in first molar implant surgery: A randomized clinical trial

BACKGROUND:

There are few studies on the differences in clinical outcomes with implant guides made by different methods in cases with a single tooth loss and adjacent tooth support

OBJECTIVE:

To compare the use of digital and traditional implant guides in patients whose first molars are absent and who are undergoing implant restoration.

METHODS:

This study included 42 patients with first molars missing who were randomly divided into two groups: the digital group (n= 21) and the control group (n= 21). A CAD/CAM digital implant guide was used in the digital group, whereas a traditional impression was used in the control group. Then, the labor time, the intraoral fit of the implant guide, and the deviation of the screw access channel position were compared between the two groups.

RESULTS:

The impression time and implant surgery time in the digital group were less than in the traditional group. The intraoral first fit of the guide in the digital group was higher than in the control group (P< 0.05). The one-time satisfaction rate of the digital group was 100%, while five cases in the control group needed to be redone. In the digital group, there was no significant difference in the deviation of the screw access channel position between implants on the left and right sides. In the control group, the deviation of the screw access channel position on the right side was significantly lower than on the left side. Overall, the deviation of the screw access channel position was significantly lower in the digital group than in the control group.

CONCLUSIONS:

In a first molar implant, the digital implant guide can effectively reduce the clinical operative time and the screw access deviation and improve efficiency. The clinical results with the digital guide provide a basis for its use in implant therapy for single missing teeth.

Effect of Printing Layer Thickness on the Trueness and Margin Quality of 3D-Printed Interim Dental Crowns

The information in the literature on the effect of printing layer thickness on interim 3D-printed crowns is limited. In the present study, the effect of layer thickness on the trueness and margin quality of 3D-printed composite resin crowns was investigated and compared with milled crowns. The crowns were printed in 3 different layer thicknesses (20, 50, and 100 μm) by using a hybrid resin based on acrylic esters with inorganic microfillers or milled from polymethylmethacrylate (PMMA) discs and digitized with an intraoral scanner (test scans). The compare tool of the 3D analysis software was used to superimpose the test scans and the computer-aided design file by using the manual alignment tool and to virtually separate the surfaces. Deviations at different surfaces on crowns were calculated by using root mean square (RMS). Margin quality of crowns was examined under a stereomicroscope and graded. The data were evaluated with one-way ANOVA and Tukey HSD tests. The layer thickness affected the trueness and margin quality of 3D-printed interim crowns. Milled crowns had higher trueness on intaglio and intaglio occlusal surfaces than 100 μm-layer thickness crowns. Milled crowns had the highest margin quality, while 20 μm and 100 μm layer thickness printed crowns had the lowest. The quality varied depending on the location of the margin.

Comparison of implant placement accuracy in two different preoperative digital workflows: navigated vs. pilot-drill-guided surgery

Background

The aim of the study is to evaluate the accuracy of a new implant navigation system on two different digital workflows.

Methods

A total of 18 phantom jaws consisting of hard and non-warping plastic and resembling edentulous jaws were used to stimulate a clinical circumstance. A conventional pilot-drill guide was conducted by a technician, and a master model was set by using this laboratory-produced guide. After cone beam computed tomography (CBCT) and 3D scanning of the master models, two different digital workflows (marker tray in CBCT and 3D-printed tray) were performed based on the Digital Imaging Communication in Medicine files and standard tessellation language files. Eight Straumann implants (4.1 mm × 10 mm) were placed in each model, six models for each group, resulting in 144 implant placements in total. Postoperative CBCT were taken, and deviations at the entry point and apex as well as angular deviations were measured compared to the master model.

Results

The mean total deviations at the implant entry point for MTC (marker tray in CBCT), 3dPT (3d-printed tray), and PDG (pilot-drill guide) were 1.024 ± 0.446 mm, 1.027 ± 0.455 mm, and 1.009 ± 0.415 mm, respectively, and the mean total deviations at the implant apex were 1.026 ± 0.383 mm, 1.116 ± 0.530 mm, and 1.068 ± 0.384 mm. The angular deviation for the MTC group was 2.22 ± 1.54°. The 3dPT group revealed an angular deviation of 1.95 ± 1.35°, whereas the PDG group showed a mean angular deviation of 2.67 ± 1.58°. Although there were no significant differences among the three groups (P > 0.05), the navigation groups showed lesser angular deviations compared to the pilot-drill-guide (PDG) group. Implants in the 3D-printed tray navigation group showed higher deviations at both entry point and apex.

Conclusions

The accuracy of the evaluated navigation system was similar with the accuracy of a pilot-drill guide. Accuracy of both preoperative workflows (marker tray in CBCT or 3D-printed tray) was reliable for clinical use.

Influence of cleaning methods after 3D printing on two-body wear and fracture load of resin-based temporary crown and bridge material

OBJECTIVES

To investigate the impact of different cleaning methods on the fracture load and two-body wear of additively manufactured three-unit fixed dental prostheses (FDP) for long-term temporary use, compared to the respective outcomes of milled provisional PMMA FDPs.

MATERIALS AND METHODS

Shape congruent three-unit FDPs were 3D printed using three different resin-based materials [FPT, GCT, NMF] or milled [TEL] (N = 48, n = 16 per group). After printing, the FDPs were cleaned using: Isopropanol (ISO), Yellow Magic 7 (YEL), or centrifugal force (CEN). Chewing simulation was carried out with a vertical load of 50 N (480,000 × 5 °C/55 °C). Two-body wear and fracture load were measured. Data were analyzed using global univariate ANOVA with partial eta squared, Kruskal-Wallis H, Mann-Whitney U, and Spearman's rho test (p < 0.05).

RESULTS

TEL showed less wear resistance than FPT (p = 0.001) for all cleaning methods tested. Concerning vertical material loss, NMF and GCT were in the same range of value (p = 0.419-0.997), except within FDPs cleaned in ISO (p = 0.021). FPT showed no impact of cleaning method on wear resistance (p = 0.219-0.692). TEL (p < 0.001) showed the highest and FPT (p < 0.001) the lowest fracture load. Regarding the cleaning methods, specimens treated with ISO showed lower fracture load than specimens cleaned with CEN (p = 0.044) or YEL (p = 0.036).

CONCLUSIONS

The material selection and the cleaning method can have an impact on two-body wear and fracture load results.

CLINICAL RELEVANCE

Printed restorations showed superior two-body wear resistance compared to milled FDPs but lower fracture load values. Regarding cleaning methods, ISO showed a negative effect on fracture load compared to the other methods tested.

Assessing the Radiological Density and Accuracy of Mandible Polymer Anatomical Structures Manufactured Using 3D Printing Technologies

Nowadays, 3D printing technologies are among the rapidly developing technologies applied to manufacture even the most geometrically complex models, however no techniques dominate in the area of craniofacial applications. This study included 12 different anatomical structures of the mandible, which were obtained during the process of reconstructing data from the Siemens Somatom Sensation Open 40 system. The manufacturing process used for the 12 structures involved the use of 8 3D printers and 12 different polymer materials. Verification of the accuracy and radiological density was performed with the CT160Xi Benchtop tomography system. The most accurate results were obtained in the case of models manufactured using the following materials: E-Model (Standard Deviation (SD) = 0.145 mm), FullCure 830 (SD = 0.188 mm), VeroClear (SD = 0.128 mm), Digital ABS-Ivory (SD = 0.117 mm), and E-Partial (SD = 0.129 mm). In the case of radiological density, ABS-M30 was similar to spongious bone, PC-10 was similar to the liver, and Polylactic acid (PLA) and Polyethylene terephthalate (PET) were similar to the spleen. Acrylic resin materials were able to imitate the pancreas, kidney, brain, and heart. The presented results constitute valuable guidelines that may improve currently used radiological phantoms and may provide support to surgeons in the process of performing more precise treatments within the mandible area.

Computer-guided implant surgery for immediate implanting and loading: The STIL technique

A method is described for minimizing errors in positioning a surgical template during the insertion of implants immediately after extraction and the placement of interim prostheses with immediate loading. The technique, called sequential template immediate loading (STIL), uses modular templates to fix pins before extracting the teeth, thus giving a reliable position for the subsequent templates for inserting the implant and placing the interim prosthesis.

Fully Digital Workflow for Planning Static Guided Implant Surgery: A Prospective Accuracy Study

The accuracy of static guided implant surgery (sGIS) using conventional planning workflow has been extensively examined; however, more information is required to justify the application of fully digital planning protocol. The purpose of this study was to investigate the clinical accuracy of sGIS with a fully digital planning workflow. Twenty-one partially edentulous patients were enrolled in this prospective study. Cone-beam computed tomography (CBCT) and intraoral scans were taken and superimposed by matching the dental surface images directly (surface registration protocol) or by matching fiducial markers on a stereolithographic (SLA) radiographic template fabricated from the digital data of the intraoral scan (fiducial marker registration protocol). Virtual implant treatment plans were then determined, and tooth-supported SLA surgical guides were fabricated according to the plans. Twenty-six implant surgeries were performed via the surgical guide by one surgeon. Pre- and post-operative CBCT images were superimposed, and the positional and angular deviations between placed and planned implants were measured with metrology software. A total of 43 fully guided implants were placed, in which 25 implants were planned with the surface registration protocol. Implants planned based on the surface registration protocol had a larger mean angular deviation than the fiducial marker registration protocol. No significant differences were found for any deviations of the examined variables. Within the limits of this study, we concluded that the clinical accuracy of the sGIS planned with a fully digital workflow was consistent with the conventional workflow for partially edentulous patients.

Fabricating a chairside CAD-CAM radiographic and surgical guide for dental implants: A dental technique

The conventional method of diagnosing and treatment planning an implant-supported restoration involves making a diagnostic alginate impression and fabricating a radiographic and surgical guide. The procedure described uses an intraoral scanner and milling unit to fabricate a chairside computer-aided design and computer-aided manufacturing radiographic and surgical guide for use with a cone beam computed tomography system.

Guided implant surgery risks and their prevention

Ideal implant placement may reduce surgical complications, such as nerve injury and lingual cortical plate perforation, and minimize the likelihood of functional and prosthetic compromises. Guided implant surgery (GIS) has been used as the means to achieve ideal implant placement. GIS refers to the process of digital planning, custom-guide fabrication, and implant placement using the custom guide and an implant system-specific guided surgery kit. GIS includes numerous additional steps beyond the initial prosthetic diagnosis, treatment planning, and fabrication of surgical guide. Substantial errors can occur at each of these individual steps and can accumulate, significantly impacting the final accuracy of the process with potentially disastrous deviations from proper implant placement. Pertinent overall strategies to reduce or eliminate these risks can be summarized as follows: complete understanding of the possible risks is fundamental; knowledge of the systems and tools used is essential; consistent verification of both diagnostic and surgical procedures after each step is crucial; proper training and surgical experience are critical. This review article summarizes information on the accuracy and efficacy of GIS, provides insight on the potential risks and problems associated with each procedural step, and offers clinically relevant recommendations to minimize or eliminate these risks.

Endodontic re-treatment and restorative treatment of a dens invaginatus type II through new technologies

Background

The complex anatomy of dens invaginatus makes access cavity to root canal system difficult, which has an impact on the prognosis of these teeth. A novel technique, based on new technologies, is proposed to make access cavity conservative and guided with minimal dental structure lost.

Material and Methods

This case report shows the root canal retreatment and the endodontic surgery of a dens invaginatus type II in a left lateral upper incisor previously treated which was affected by a chronic apical abscess and an apical fracture. A Cone Beam Computed Tomography was performed to better diagnosis the dental anatomy. An intraoral scan was performed to get a digital 3D model. A computer-guided implant planning software was used to plan the access cavity and design the splint guided. Finally, the clinical crown was restored by a resin nanoceramic veneer made by a chairside system made up of an intraoral scanning unit and a grinding unit. Last, the authors carried through the endodontic surgery to extract the apical fractured fragment.

Results

Follow-up appointments at 6, 12 and 18 months showed a radiographic reduction of the periapical lesion and absence of clinical signs.

Conclusions

The splint guide allowed a guided and conservative access cavity to root canal system. It facilitates the root canal retreatment and improves the prognosis of the teeth with dental malformations.

Key words:CAD-CAM, Cone-Beam Computed Tomography, dens in dente, dens invaginatus, dental pulp cavity, endodontics.

Fracture load of 3D-printed fixed dental prostheses compared with milled and conventionally fabricated ones: the impact of resin material, build direction, post-curing, and artificial aging-an in vitro study

OBJECTIVE

To investigate the impact of 3D print material, build direction, post-curing, and artificial aging on fracture load of fixed dental prostheses (FDPs).

MATERIALS AND METHODS

Three-unit FDPs were 3D-printed using experimental resin (EXP), NextDent C&B (CB), Freeprint temp (FT), and 3Delta temp (DT). In the first part, the impacts of build direction and artificial aging were tested. FDPs were manufactured with their long-axis positioned either occlusal, buccal, or distal to the printer's platform. Fracture load was measured after artificial aging (H₂O: 21 days, 37 °C). In the second part, the impact of post-curing was tested. FDPs were post-cured using Labolight DUO, Otoflash G171, and LC-3DPrint Box. While the positive control group was milled from TelioCAD (TC), the negative control group was fabricated from a conventional interim material Luxatemp (LT). The measured initial fracture loads were compared with those after artificial aging. Each subgroup contained 15 specimens. Data were analyzed using Kolmogorov-Smirnov test, one-way ANOVA followed by Scheffé post hoc test, t test, Kruskal-Wallis test, and Mann-Whitney U test (p < 0.05). The univariate ANOVA with partial eta squared (η_P²) was used to analyze the impact of test parameters on fracture load.

RESULTS

Specimens manufactured with their long-axis positioned distal to the printer's platform showed higher fracture load than occlusal ones (p = 0.049). The highest values were observed for CB, followed by DT (p < 0.001). EXP showed the lowest values, followed by FT (p < 0.001). After artificial aging, a decrease of fracture load for EXP (p < 0.001) and DT (p < 0.001) was observed. The highest impact on values was exerted by interactions between 3D print material and post-curing unit (η_P² = 0.233, p < 0.001), followed by the 3D print material (η_P² = 0.219, p < 0.001) and curing device (η_P² = 0.108, p < 0.001).

CONCLUSIONS

Build direction, post-curing, artificial aging, and material have an impact on the mechanical stability of printed FDPs.

CLINICAL RELEVANCE

The correct post-curing strategy is mandatory to ensure mechanical stability of 3D-printed FDPs. Additively manufactured FDPs are more prone to artificial aging than conventionally fabricated ones.

Optimizing accuracy in computer-guided implant surgery with a superimposition-anchor microscrew system: A clinical report

The accuracy of computer-guided implant placement decreases when the remaining teeth are poorly distributed. This clinical report demonstrates a protocol for using a superimposition-anchor microscrew (SAM) system to improve the accuracy of computer-guided implant surgery in a posterior unilateral edentulous area. The SAM functioned as a fiducial marker for image superimposition and as an anchor for guide positioning. Applying the SAM system to computer-guided implant surgery enhances the accuracy of implant placement by minimizing possible errors occurring during image registration and guide positioning.

Accuracy of the match between cone beam computed tomography and model scan data in template-guided implant planning: A prospective controlled clinical study

BACKGROUND

Template-guided implant placement is a method for optimal implant positioning from a prosthetic and surgical viewpoint. The treatment planning is based on three-dimensional X-ray data and model scan data, as well as on prosthetic planning (set-up). These data are matched (superimposed) with the aid of an X-ray template or by manual matching without special referencing.

PURPOSE

The objective of this prospective controlled clinical study was to determine and compare the accuracy of the match with and without an additional X-ray template.

MATERIALS AND METHODS

The DICOM data of the cone beam computed tomography (CBCT) were converted into surface data sets and then superimposed on model scan data using three different methods (manually, based on an X-ray template, or semi-automatically with computer assistance). The mean deviations between these results of these matching methods were investigated.

RESULTS

The procedures achieved a matching accuracy of 0.2 mm on average. This corresponds to the resolution of the CBCT (0.2 voxels). Further studies are necessary to verify the procedure even for patients with few (0-4) residual teeth.

CONCLUSION

In the presence of a sufficient number of residual teeth, the manual matching of model scan data with CBCT data is sufficiently accurate for implant planning and template-guided implementation. The results of the present study suggest that X-ray templates can be dispensed with saving the patient a substantial amount of time and money.

Current and emerging applications of 3D printing in medicine

Three-dimensional (3D) printing enables the production of anatomically matched and patient-specific devices and constructs with high tunability and complexity. It also allows on-demand fabrication with high productivity in a cost-effective manner. As a result, 3D printing has become a leading manufacturing technique in healthcare and medicine for a wide range of applications including dentistry, tissue engineering and regenerative medicine, engineered tissue models, medical devices, anatomical models and drug formulation. Today, 3D printing is widely adopted by the healthcare industry and academia. It provides commercially available medical products and a platform for emerging research areas including tissue and organ printing. In this review, our goal is to discuss the current and emerging applications of 3D printing in medicine. A brief summary on additive manufacturing technologies and available printable materials is also given. The technological and regulatory barriers that are slowing down the full implementation of 3D printing in the medical field are also discussed.

Marginal and internal fit of metal copings fabricated with rapid prototyping and conventional waxing

STATEMENT OF PROBLEM

Given the limitations of conventional waxing, computer-aided design and computer-aided manufacturing (CAD-CAM) technologies have been developed as alternative methods of making patterns.

PURPOSE

The purpose of this in vitro study was to compare the marginal and internal fit of metal copings derived from wax patterns fabricated by rapid prototyping (RP) to those created by the conventional handmade technique.

MATERIAL AND METHODS

Twenty-four standardized brass dies were milled and divided into 2 groups (n=12) according to the wax pattern fabrication method. The CAD-RP group was assigned to the experimental group, and the conventional group to the control group. The cross-sectional technique was used to assess the marginal and internal discrepancies at 15 points on the master die by using a digital microscope. An independent t test was used for statistical analysis (α=.01).

RESULTS

The CAD-RP group had a total mean (±SD) for absolute marginal discrepancy of 117.1 (±11.5) μm and a mean marginal discrepancy of 89.8 (±8.3) μm. The conventional group had an absolute marginal discrepancy 88.1 (±10.7) μm and a mean marginal discrepancy of 69.5 (±15.6) μm. The overall mean (±SD) of the total internal discrepancy, separately calculated as the axial internal discrepancy and occlusal internal discrepancy, was 95.9 (±8.0) μm for the CAD-RP group and 76.9 (±10.2) μm for the conventional group. The independent t test results showed significant differences between the 2 groups. The CAD-RP group had larger discrepancies at all measured areas than the conventional group, which was statistically significant (P<.01).

CONCLUSIONS

Within the limitations of this in vitro study, the conventional method of wax pattern fabrication produced copings with better marginal and internal fit than the CAD-RP method. However, the marginal and internal fit for both groups were within clinically acceptable ranges.