A Novel Full-Digital Protocol (SCAN-PLAN-MAKE-DONE®) for the Design and Fabrication of Implant-Supported Monolithic Translucent Zirconia Crowns Cemented on Customized Hybrid Abutments: A Retrospective Clinical Study on 25 Patients

3D-printed Short-span Hybrid Composite Implant-supported Restorations Fabricated Through Tilting Stereolithography: A Retrospective Clinical Study on 85 Patients with 1 Year of Follow-up

PURPOSE

To report the clinical results obtained with fixed short-span (single crowns [SCs] and fixed partial prostheses [FPPs]) implant-supported hybrid composite restorations fabricated through tilting stereolithography (TSLA).

METHODS

This retrospective clinical study included 85 patients who had been restored with 95 fixed short-span implant-supported hybrid composite (Irix Max®, DWS Systems) restorations (70 SCs and 25 FPPs up to three units) fabricated with TSLA. The full-digital model-free workflow was based on intraoral implant scanning, computer-assisted design (CAD) and 3D printing using TSLA (Dfab®, DWS Systems). The primary outcomes were the marginal adaptation, the quality of the occlusal and interproximal contact points, and the chromatic integration of the restorations, assessed independently by two experienced operators (a prosthodontist and a periodontist). A score from 1 to 5 (with 5 as the highest value, 4 for satisfactory quality, 3 for acceptable quality, and 2 and 1 as the lowest values, expressing unsatisfactory quality) was assigned by each operator to each restoration at delivery. The secondary outcomes were the survival and success of the restorations at the 1-year follow-up. The restoration was defined as successful in the absence of any complications throughout the follow-up period. A statistical analysis was conducted.

RESULTS

For the quality of the marginal closure and occlusal and interproximal contact points, the 3D-printed hybrid composite restorations scored highly; the aesthetic integration was satisfactory. One year after placement, all restorations survived, with a low incidence (4.2% overall, 5.7% SCs) of complications (two abutment screw loosenings, two decementation of the restorations, and one upper portion of the hybrid abutment decemented from the titanium base), for a success rate of 95.8%.

CONCLUSIONS

Within the limits of this study (retrospective design, follow-up limited to 1 year from the delivery, and only cemented restorations included) fixed short-span implant-supported hybrid composite crowns and bridges fabricated through TSLA were clinically precise, presenting a low incidence of complications at 1 year.

STATEMENT OF CLINICAL RELEVANCE

The use of TSLA printing technology can open new perspectives for the treatment of small edentulous gaps with definitive implant-supported prosthetic restorations.

Analysis of implant precision in guided surgery: comparison of two methods

BACKGROUND

Implantology represents the therapy of choice for the rehabilitation of a partially or totally edentulous jaw in a healthy patient. Nowadays, it is possible to exploit of modern preoperative planning software, increasingly precise radiographic examinations (CBCT) and CAD/CAM technologies that allow designing devices directly on the computer to be sent to a milling center which produces the desired product, such as stereolithographic templates.

METHODS

The prospective clinical study in question aims to evaluate the accuracy between two different surgical guides using peek and metal guide bushings. Twenty-nine implants were placed: for the control group, 17 3i, T3 implants were used, while for the test group, 12 Xive S plus implants were used.

RESULTS

The result obtained shows that the deviations in the distribution of the control group and the test group are the same in the apical-coronal, vestibulo-palatal and mesio-distal direction. For the control group, the mean deviation was 1.394±0.644923 at the entry point of the implants and 1.85655±1.0765 at the most apical point of the implants. For the test group the mean deviation was 1.10157±0.312721 at the entry point of the implants and 1.54514±0.572100 at the most apical point of the implants.

CONCLUSIONS

The peek guide bushings have the same deviation as the metal ones. There is no difference in the method used, but precision must be sought in other elements, such as the patient's anatomy and maximum precision in the guide production phase.

Retention of hybrid-abutment-crowns with offset implant placement: influence of Crown materials and Ti-base height

BACKGROUND

The purpose of the current study was to assess the impact of three esthetic CAD/CAM material, titanium base height and their interaction on the retention strength of a hybrid-abutment-crown.

METHODS

A total of 42 hybrid-abutment crowns with identical external geometries were designed in CAD software to fit two different Ti-Base abutment heights (n = 42/abutment height): either short (S) with 4 mm (n = 21) or long (L) 7 mm (n = 21) height. Each main group was divided into 3 subgroups (n = 7), according to esthetic crown material, Zirconia (Z), Lithium disilicate (L) and Hybrid ceramic (V). A universal primer and an adhesive resin cement were used for bonding according to the manufacturer instructions. Artificial aging in form of water storage (30 days), chewing simulation (50,000-cycles, 49 N, 1.67 Hz) and thermal cyclic (5000 cycles at 5-55 °C) were applied, specimens were pulled-out under tension load in (N) using a universal testing machine. Two and one-way ANOVA and Post Hoc Tukey test were used for statistical analysis.

RESULTS

Long lithium disilicate (LL) group showed the highest retention (738.7 ± 178.5) followed by short lithium disilicate (LS) group (688.6 ± 169.9). Meanwhile, short zirconia (ZS) showed the lowest retention strength (231.1 ± 86.9).

CONCLUSION

CAD/CAM fabricated lithium disilicate hybrid-abutment-crown can be used instead of conventional crowns over implant abutment. Etchable ceramics are recommended as a material of choice for CAD/CAM fabricated hybrid-abutment-crowns instead of zirconia in terms of retention durability.

Clinical performance of single implant prostheses restored using titanium base abutments: A systematic review and meta-analysis

PURPOSE

The aim of this review was to evaluate the survival rates of restorations utilizing titanium base abutments (TBA) for restoring single-unit implant prostheses.

MATERIALS AND METHODS

This review was conducted following the preferred reporting items for systematic reviews and meta-analyses (PRISMA) guidelines. The focus question was: In patients who require the restoration of a single dental implant utilizing a titanium base abutment, what are the determining factors and outcomes relating to implant prosthesis prognosis and survival? A comprehensive search of databases (PubMed, EMBASE, and Cochrane Library) was conducted on 16 April 2023 and updated on 5 May 2023. Randomized clinical trials (RCT), retrospective studies and prospective studies, reporting on the use of TBA for single implant prostheses, were reviewed. A Cochrane collaboration risk of bias assessment analysis was performed for randomized clinical studies, and the Newcastle-Ottawa Scale tool was applied for non-randomized studies. A meta-analysis was performed on clinical trials reporting on survival rates of both TBA and other abutments. Other clinical studies, reporting on TBA only, were included for descriptive statistics.

RESULTS

The search provided 1159 titles after duplicates were removed. Six RCTs were included to perform a meta-analysis and compare the survival of the TBA to other abutments [OR 0.74; 95% CI: 0.21-2.63, heterogeneity; I2 0%; p = .99]. Twenty-three prospective and retrospective studies fulfilled the criteria and were included in the meta-analysis after 12 months of function. A total of 857 single implant-supported prostheses fabricated with a TBA were included. TBA abutments have an estimate 98.6% survival rate after 1 year in function (95% CI: 97.9%-99.4%). The mean follow-up period was 31.2 ± 16.9 months.

CONCLUSIONS

Single implant prosthesis restored with titanium base abutments showed favourable short-term survival rates.

Atraumatic intraoral scans and virtual hybrid casts for custom implant abutments and zirconia implants: Accuracy of the workflow

STATEMENT OF PROBLEM

Making impressions of 2-piece implants is typically associated with the repeated disassembly and reassembly of superstructures and related to soft-tissue trauma. Intraoral scanning of 1-piece zirconia implants is problematic because scan bodies are not readily available. Whether using virtual hybrid casts generated by merging intraoral scan data with the known surface geometry of abutments can solve these difficulties is not clear because data on accuracy of the workflow are sparse.

PURPOSE

The purpose of this in vitro study was to evaluate the accuracy of virtual hybrid casts with respect to the impact of different gingival situations. The workflow was designed to render pointless the use of impression posts and scan bodies and avoid any displacement of the gingiva.

MATERIAL AND METHODS

The mandibular right first molar in a typodont was replaced with a 2-piece titanium implant with a custom abutment and then a 1-piece zirconia implant. Three situations representing different gingival heights covering the abutments were simulated. Twelve intraoral scans were made for each situation to capture the recordable parts of the abutments, and virtual hybrid casts were constructed by superimposing and merging the intraoral scan data with the original laboratory scan data of the abutments. Hybrid casts were compared with reference data by using the root mean square error. Scan body-related and cast scan-related protocols were performed representing conventional digital workflows. Statistical analysis with the Kolmogorov-Smirnov, Kruskal-Wallis, and Mann-Whitney U tests with the Bonferroni correction was conducted with a statistical software program (α=.05).

RESULTS

Deviation was low in the hybrid casts of the custom abutment when the entire abutment was recorded (6.5 μm; IQR: 3.0 μm), when the preparation margin was disguised (7.0 μm; IQR: 1.0 μm), and when half of the abutment was covered (8.0 μm; IQR: 4.0 μm). The accuracy in the 1-piece zirconia implant was 10.0 μm (IQR: 4.0 μm) when the whole surface of the abutment was visible and 12.5 μm (IQR: 6.0 μm) when the preparation margin was covered. When only half of the abutment was captured, a larger deviation of 22.0 μm (IQR: 7.0 μm) was observed. The hybrid cast concept demonstrated superior accuracy compared with protocols using scan bodies (76.0 μm; IQR: 27.0 μm) and cast scans (23.0 μm; IQR: 15.0 μm).

CONCLUSIONS

Digital intraoral scanning and the generation of virtual hybrid casts provide high accuracy and are suitable for the fabrication of single-implant-supported restorations. The atraumatic procedure avoids tissue manipulation and reduces clinical effort.

Prosthetic complications with monolithic or micro-veneered implant-supported zirconia single-unit, multiple-unit, and complete-arch prostheses on titanium base abutments: A single center retrospective study with mean follow-up period of 72.35 months

BACKGROUND

The influence of prosthetic design on prosthetic complications when monolithic or micro-veneered zirconia prostheses are supported with titanium base (ti-base) abutments is not well-known.

PURPOSE

The purpose of this single center, retrospective study was to assess the prevalence of prosthetic complications with monolithic or micro-veneered single-unit, multi-unit, and complete-arch zirconia prostheses supported with ti-base abutments (implant level or multi-unit abutment level).

MATERIAL AND METHODS

This study retrospectively evaluated the electronic health record (EHR) of participants who received either monolithic or micro-veneered implant-supported single-unit, multi-unit, and/or complete-arch prostheses supported by ti-base or zirconia-ti-base hybrid abutments delivered between the years 2010 and 2021. Data were analyzed by using logistic regression and Exact Mantel-Haenszel chi-square test (α = 0.05) to assess the clinical performance of prostheses and complications including crown decementation, feldspathic porcelain chipping, prosthesis fracture, zirconia-ti-base hybrid abutment decementation, abutment screw loosening, screw fracture, abutment fracture, implant loss, and prosthesis remake.

RESULTS

The study included 94 participants (50 female, 44 male) with a mean age of 59.5 years (range: 24-101 years of age). The retrospective EHR evaluation yielded 82 single-unit, 51 multi-unit, and 20 complete-arch prostheses on 325 implants. Among 153 prostheses delivered, 108 were micro-veneered (47 single-unit, 41 multi-unit, and 20 complete-arch prostheses) and 45 were monolithic. The average duration was 72.35 months (6.02 years) with a follow-up period of 5-132 months. From the time of insertion to the time of EHR review, of 153 prostheses, 78.43% did not exhibit any prosthetic complication. However, 33 prostheses (21.57%) from 29 participants (30.85%) had at least one prosthetic complication. Only four patients (4.25%) experienced two or more prosthetic complications. Prosthetic design affected the probability of having a complication (p = 0.005); complete-arch prostheses had higher probability (p ≤ 0.028). Single-unit prostheses had lower probability of complication than multi-unit prostheses (p = 0.005). The most commonly observed complication was fracture of veneering material (5.88%) followed by prosthetic screw loosening (4.57%) and decementation between the zirconia and the ti-base abutment (2.61%). Micro-veneered complete-arch prostheses had higher probability of having chipping than that of not having (p < 0.001), and other micro-veneered prosthetic designs had similar probability of chipping with that of complete-arch prostheses (p ≥ 0.082). Frequency of chipping was affected by veneering (p < 0.001). Monolithic prostheses had lower probability of chipping than micro-veneered prostheses, regardless of the prosthetic design (p < 0.001).

CONCLUSIONS

The frequency of prosthetic complications varied depending on prosthetic design. Complete-arch prostheses had the highest probability of complications while the single-unit prostheses had the lowest. Micro-veneered prostheses had higher probability for chipping than monolithic prostheses. Probability of chipping was similar for micro-veneered single-unit, multi-unit, and complete-arch zirconia prostheses.

Clinical outcomes of implant-supported monolithic zirconia crowns and fixed partial dentures: A systematic review

PURPOSE

To determine the survival rates of implant-supported monolithic zirconia crowns and fixed partial dentures (FPD).

MATERIAL AND METHODS

An electronic search for articles in the English language literature published from January 1, 2001 to September 17, 2021 was performed using PubMed, Scopus, and CENTRAL search engines. After applying predetermined inclusion and exclusion criteria, the definitive list of selected articles was used for calculating the interval survival rate (ISR) and cumulative survival rate (CSR). Restoration failure in this study was defined as the fracture or compromise of any part of the ceramic restoration that required the removal or remake of the implant-supported restoration.

RESULTS

The electronic search resulted in 457 titles. The systematic application of inclusion and exclusion criteria resulted in 14 clinical studies that addressed the clinical outcomes of implant-supported monolithic zirconia crowns and fixed partial dentures. Of these, 3 were randomized controlled trials, 5 were prospective studies, and 6 were retrospective studies. Follow-up periods ranged from 1 to 5 years. Of the 644 implant-supported monolithic zirconia restorations computed in this systematic review, there was only 1 reported failure of the monolithic zirconia restorative material over a follow-up period of up to 5 years, for a cumulative survival rate of 99.84%. At the maximum follow-up interval of 5 years, the cumulative survival rate for monolithic zirconia single crowns was 100% and the cumulative survival rate for monolithic zirconia fixed partial dentures was 99.60%.

CONCLUSIONS

Implant-supported monolithic zirconia single crowns and fixed partial dentures have excellent short-term (<5 years) survival rates but the evidence for medium-term survival (>5 years) and beyond is lacking.

Reliability of automatic finish line detection for tooth preparation in dental computer-aided software

PURPOSE

This study aimed to investigate the accuracy of automatic tooth finish line registration compared to manual registration with regard to various finish line configurations and dental computer-aided design (CAD) software.

METHODS

Finish line registrations were performed on 15 digital tooth models with different finish line configurations (edge roundness radius = 0 mm, 0.2 mm, and 0.4 mm; edge angle = 30°, 60°, 90°, 120°, and 150°) using automatic and manual methods for designing virtual copings (N = 150). The discrepancies between the registered finish line extracted from the copings and the actual finish line segmented from the digitized tooth model were measured. Three-way analysis of variance (ANOVA) and post-hoc analyses with Bonferroni correction (α = 0.05) were used to analyze the results.

RESULTS

The finish line configurations, registration methods, and CAD software interacted with the accuracy of the registered finish line (p = 0.001). The automatic finish line registration method exhibited larger error values than the manual method, especially at high finish line edge roundness and obtuse edge angles for both EXOCAD and R2CAD software (p < 0.001). The difference in dental CAD software affected the registration accuracy in the automatic method (p < 0.001), but not in the manual method (p = 0.676).

CONCLUSIONS

Finish line registration errors may occur when the automatic registration method is applied to the indistinct edge of tooth preparation. The accuracy of the automatic finish line registration could differ according to the CAD software program.

A Comparative Study Between Hybrid Abutments and Standard Abutments in Implant-Supported Prosthesis: A Split-Mouth Clinical Trial

Background Implant-supported prostheses are widely used to replace extracted teeth. Therefore, studies on abutments' designs, shapes, and benefits had increased in recent years, as the design of the standard abutment still poses many problems in periodontal and cosmetic aspects. So, could the hybrid abutment solve some of these problems? Aim We aim to conduct a clinical comparison between standard and hybrid abutments in terms of the state of peri-implant gingival tissues and patients' aesthetic and functional satisfaction after the cementation of the final prostheses. Material and methods The study sample consisted of 10 patients, with 20 dental implants. Each patient received two implants as a standard abutment was placed over one implant and a hybrid abutment was placed over the other. Clinical assessment of the peri-implant gingival tissue and patients' aesthetic and functional satisfaction was performed (immediately, three months, six months, and one year) after the cementation of the final prostheses. The Mann-Whitney U test was used to detect statistically significant differences between groups. Results The percentage of the thick gingival biotype was 80%, and the percentage of the thin gingival biotype was 20% in each group during the follow-up periods. In addition, all papilla fill the whole interdental space in all samples of the two groups after six months and one year. Finally, there were no significant differences in patients' aesthetic satisfaction between groups during one year of follow-up (P = 0.631), and there were no significant differences in patients' functional satisfaction between groups during one year of follow-up (P = 0.684). Conclusion Within the limitations of the current work, there are no differences between standard and hybrid abutments in terms of affecting the peri-implant gingival tissue and patients' aesthetic and functional satisfaction.

Clinical assessment of different implant-supported esthetic crown systems fabricated with semi-digital workflow: Two-year prospective study

OBJECTIVE

To assess the clinical outcome of three esthetic implant-supported crown systems fabricated with semi-digital workflow and their influence on the clinical outcome of dental implants.

MATERIAL AND METHODS

A total of 30 participants had received dental implants restoring missing maxillary first/second premolars. After 6 weeks, customized zirconia abutments were early loaded. Two months later, the definitive crowns were fabricated using semi-digital workflow and cemented. According to the crown material, 3 groups were randomly allocated; group (Z): ultrahigh-translucent monolithic zirconia, group (C): resin-matrix ceramic and group (P): polyetherketoneketone veneered with light-cured composite resin. Clinical outcomes including the survival and success rates were evaluated at baseline, 6, 12, 18, and 24 months.

RESULTS

The survival rate for all studied groups was 100%, while their success rate was 100% for group (Z) and 90% for group (C) and group (P). Based on the functional implant prosthodontic score, a statistically significant difference was detected between group (Z) and group (P) (p < 0.001) as well as between group (C) and group (P) (p = 0.01).

CONCLUSIONS

The zirconia group had the most favorable clinical behavior, while the polyetherketoneketone had the least. All crown systems had comparable success rates with similar values of the peri-implant marginal bone loss.

CLINICAL SIGNIFICANCE

Using semi-digital workflow, ultrahigh-translucent monolithic zirconia, resin-matrix ceramic and polyetherketoneketone veneered with light-cured composite resin can be considered as favorable implant-supported crowns. The implant-supported crown system based on polyetherketoneketone veneered with light-cured composite resin is counted as a promising esthetic and restorative option.

Clinical Outcome of Fully Digital Workflow for Single-Implant-Supported Crowns: A Retrospective Clinical Study

A digital workflow by means of intraoral scanners and computer tomography has been used in dental implantology, allowing clinicians to be potentially more accurate and precise. Computer-Aided Design and Computer-Aided Manufacturing (CAD-CAM) and 3D models facilitate the process from treatment planning to the surgical procedure, up to the implant placement and final prosthesis. The aim of the present retrospective study was to evaluate a fully digital workflow for single-tooth implant rehabilitation. A total of 19 patients (22 implants) were included in the present study, with a mean follow-up time of 2 years. A fully digital workflow was performed on each patient through the planning, design and printing of a surgical guide, following a digital impression made with an intraoral scanner, computer-tomography-guided implant placement and, finally, with the delivery of a CAD-CAM crown. The two-year follow-up results were satisfactory in terms of the aesthetic yield and precision of the prosthesis. In single-implant-supported restorations, due to digital protocols and digital planning, a reduced number of clinical sessions was registered and the treatment plan results were more predictable. Future studies are needed to understand the application of fully digital protocols in cases of partially or totally edentulous patients.

In Vitro Comparison of Three Intraoral Scanners for Implant-Supported Dental Prostheses

With continuing technological developments, there have been advances in the field of fixed prosthetics, particularly in impression-taking techniques. These technological advances mean that a wide variety of diagnostic and/or rehabilitation possibilities can be explored without the need for physical models. The aim of this study was to evaluate the accuracy of three intraoral scanners used in oral implant rehabilitation using an extraoral scanner as a reference and varying the scanning area. Three models representing different clinical scenarios were scanned 15 times by each intraoral scanner and three times by the extraoral scanner. The readings were analyzed and overlaid using engineering software (Geomagic^® Control X software (Artec Europe, Luxembourg)). Statistically significant differences in accuracy were found between the three intraoral scanners, iTero^® (Align Technology Inc., San Jose, CA, USA), Medit^® (Medit^®: Seoul, Korea), and Planmeca^® (Planmeca^®: Helsinki, Finland). In all clinical scenarios, the iTero^® scanner had the best trueness (24.4 μm), followed by the Medit^® (26.4 μm) and Planmeca^® (42.1 μm). The Medit^® showed the best precision (18.00 μm) followed by the iTero^® (19.20 μm) and Planmeca^® (34.30 μm). We concluded that the iTero^® scanner had the highest reproducibility and accuracy in the clinical setting.

Revolution of Current Dental Zirconia: A Comprehensive Review

The aim of this article is to comprehensively review the revolution of dental zirconia (Zir), including its types, properties, applications, and cementation procedures. A comprehensive search of PubMed and Embase was conducted. The search was limited to manuscripts published in English. The final search was conducted in October 2021. Newly developed monolithic Zir ceramics have substantially enhanced esthetics and translucency. However, this material must be further studied in vitro and in vivo to determine its long-term ability to maintain its exceptional properties. According to the literature, monolithic translucent Zir has had promising results and a high survival rate. Thus, the utilization of this material is indicated when strength and esthetics are needed. Both the materials and methods used for cementation of monolithic Zir have significantly improved, encouraging dentists to use this material, especially when a conservative approach is required. Zir restorations showed promising outcomes, particularly for monolithic Zir crowns supported with implant and fixed dental prostheses.

A systematic review and meta-analysis evaluating the survival, the failure, and the complication rates of veneered and monolithic all-ceramic implant-supported single crowns

Objective

To assess the survival, failure, and complication rates of veneered and monolithic all‐ceramic implant‐supported single crowns (SCs).

Methods

Literature search was conducted in Medline (PubMed), Embase, and Cochrane Central Register of Controlled Trials until September 2020 for randomized, prospective, and retrospective clinical trials with follow‐up time of at least 1 year, evaluating the outcome of veneered and/or monolithic all‐ceramic SCs supported by titanium dental implants. Survival and complication rates were analyzed using robust Poisson's regression models.

Results

Forty‐nine RCTs and prospective studies reporting on 57 material cohorts were included. Meta‐analysis of the included studies indicated an estimated 3‐year survival rate of veneered‐reinforced glass‐ceramic implant‐supported SCs of 97.6% (95% CI: 87.0%–99.6%). The estimated 3‐year survival rates were 97.0% (95% CI: 94.0%–98.5%) for monolithic‐reinforced glass‐ceramic implant SCs, 96.9% (95% CI: 93.4%–98.6%) for veneered densely sintered alumina SCs, 96.3% (95% CI: 93.9%–97.7%) for veneered zirconia SCs, 96.1% (95% CI: 93.4%–97.8%) for monolithic zirconia SCs and only 36.3% (95% CI: 0.04%–87.7%) for resin‐matrix‐ceramic (RMC) SCs. With the exception of RMC SCs (p < 0.0001), the differences in survival rates between the materials did not reach statistical significance. Veneered SCs showed significantly (p = 0.017) higher annual ceramic chipping rates (1.65%) compared with monolithic SCs (0.39%). The location of the SCs, anterior vs. posterior, did not influence survival and chipping rates.

Conclusions

With the exception of RMC SCs, veneered and monolithic implant‐supported ceramic SCs showed favorable short‐term survival and complication rates. Significantly higher rates for ceramic chipping, however, were reported for veneered compared with monolithic ceramic SCs.

Production time, effectiveness and costs of additive and subtractive computer-aided manufacturing (CAM) of implant prostheses: A systematic review

OBJECTIVE

To systematically review the dental literature for clinical studies reporting on production time, effectiveness and/or costs of additive and subtractive computer-aided manufacturing (CAM) of implant prostheses.

MATERIALS AND METHODS

A systematic electronic search for clinical studies from 1990 until June 2020 was performed using the online databases Medline, Embase and Cochrane. Time required for the computer-aided design (CAD) process, the CAM process, and the delivery of the CAD-CAM prostheses were extracted. In addition, articles reporting on the effectiveness and the costs of both manufacturing technologies were included.

RESULTS

Nine clinical studies were included reporting on subtractive CAM (s-CAM; 8 studies) and additive CAM (a-CAM; 1 study). Eight studies reported on the s-CAM of prosthetic and auxiliary components for single implant crowns. One study applied a-CAM for the fabrication of an implant bar prototype. Time was provided for the CAD process of implant models (range 4.9-11.8 min), abutments (range 19.7-32.7 min) and crowns (range 11.1-37.6 min). The time for s-CAM of single implant crown components (abutment/crown) ranged between 8.2 and 25 min. Post-processing (e.g. sintering) was a time-consuming process (up to 530 min). At delivery, monolithic/veneered CAD-CAM implant crowns resulted in additional adjustments chairside (51%/93%) or labside (11%/19%).

CONCLUSIONS

No scientific evidence exists on production time, effectiveness and costs of digital workflows comparing s-CAM and a-CAM. For both technologies, post-processing may substantially contribute to the production time. Considering effectiveness, monolithic CAD-CAM implant crowns may be preferred compared to veneered CAD-CAM crowns.

Artificial Intelligence in Biomedical Applications of Zirconia

Artificial intelligence (AI) is rapidly developed based on computer technology, which can perform tasks that customarily require human intelligence by building intelligent software or machines. As a subfield of AI, machine learning (ML) can learn from the intrinsic statistical patterns and structures in data through algorithms to predict invisible data. With the increasing interest in aesthetics in dentistry, zirconia has drawn lots of attention due to its superior biocompatibility, aesthetically pleasing, high corrosion resistance, good mechanical properties, and absence of reported allergic reactions. The evolution of AI and ML led to the development of novel approaches for the biomedical applications of zirconia in dental devices. AI techniques in zirconia-related research and clinical applications have attracted much attention due to their ability to analyze data and reveal correlations between complex phenomena. The AI applications in the field of zirconia science change according to the application direction of zirconia. Therefore, in this article, we focused on AI in biomedical applications of zirconia in dental devices and AI in zirconia-related applications in dentistry.

Factors Influencing Marginal Bone Loss around Dental Implants: A Narrative Review

Implant supported dental prostheses are increasingly used in dental practice. The aim of this narrative review is to present the influence of transmucosal surface of prosthetic abutment and implant on peri-implant tissue. The article describes causes of bone loss around the dental implant. Moreover, properties of different materials are compared and discussed. The advantages, disadvantages, and biomechanical concept of different implant-abutment connections are presented. The location of connections in relation to the bone level and the influence of microgap between the abutment and implant are described. Additionally, the implant abutments for cemented and screwed prosthetic restorations are compared. The influence of implant and abutment surface at the transmucosal level on peri-implant soft tissue is discussed. Finally, the biological aspect of abutment-implant connection is analyzed.

Hybrid abutment during prosthetic planning and oral rehabilitation

BACKGROUND

The present study aims to describe through a literature review, the characteristics and properties of hybrid abutments, as well as their proper use as a new rehabilitation strategy.

METHODS

A bibliographic search was conducted in the main health databases Pubmed (www.pubmed.gov) and Google Scholar (www.scholar.google.com.br), in which studies published from 2001 to 2020 were collected. Laboratory studies, case reports, systematic and literature reviews were included. Therefore, articles that do not adress the characteristics and properties of hybrid abutments were excluded. In addition, studies that did not report the use of hybrid abutments as a new rehabilitation strategy.

RESULTS

According to the inclusion and exclusion criteria, 80 research articles were selected and 20 were excluded, while 25 in vitro, 17 in vivo and 9 in silico studies were reviewed.

CONCLUSIONS

The literature demonstrates that hybrid abutments are an excellent alternative in cases of implant-supported rehabilitation, presenting high esthetic results, associated with good soft tissue response, periimplant marginal bone stability and adequate stress distribution during the masticatory loads dissipation.

Effect of crown height on the screw joint stability of zirconia screw-retained crowns

STATEMENT OF PROBLEM

Medium- to long-term data for the performance of zirconia crowns with titanium (Ti) bases are sparse, particularly when the crown height space and occlusal loads are high.

PURPOSE

The purpose of this in vitro study was to assess the effect of the height of zirconia screw-retained implant crowns with a Ti base on the screw joint stability after cyclic loading. A secondary aim was to investigate the survival of zirconia crowns of different heights after cyclic loading.

MATERIAL AND METHODS

Twenty-one internal connection implants were secured between fiberglass-reinforced epoxy resin sleeves. Mandibular first molar monolithic zirconia crowns with 3 different heights (6 mm, 10 mm, and 14 mm) were milled and bonded to the Ti bases (n=7). The screws were tightened to 30 Ncm, and a 30-degree 120-N cyclic load was applied to the crowns at 2 Hz for 5 million cycles. After 5 million cycles, the crowns were evaluated for stability, and the same protocol was repeated for 275-N and 435-N loads for 5 million cycles each. After loading, the detorque values were recorded. Failure was characterized based on whether the crown, screw, and/or implant fracture was observed. The detorque values were analyzed by using a 1-way-ANOVA with the restricted maximum likelihood estimation. The percentage of torque loss was calculated. The LIFETEST procedure was used to analyze the survival probability of the groups (α=.05).

RESULTS

The effect of crown height on the detorque values of screws was not found to be statistically significant (P>.05). The mean detorque value for 6-mm crowns was 23.5 Ncm, 24.4 Ncm for 10-mm crowns, and 22.1 Ncm for 14-mm crowns. A significant effect of crown height was found on the survival (P=.006), and the time-to-failure survival of 14-mm crowns was significantly lower than the survival of 6 mm and 10 mm crowns (P=.020), where no failures were observed. Four 14-mm crowns failed between the 1 and 2 million cycles after the loads were increased to 435 N. The failure modes were the same for all the crowns, implants, and screws fractured.

CONCLUSIONS

When the tested internal connection implant was used, the crown height did not affect the detorque values, and 14-mm crowns performed similarly to the shorter crowns in terms of torque loss after cyclic loading. However, survival of the 14-mm crown-implant complex was lower, resulting in screw and implant fractures.

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 direct digital workflow in fixed implant prosthodontics: a narrative review

BACKGROUND

The purpose of this narrative review was to examine the applicability of IOS procedures regarding single and multiple fixed implant restorations. Clinical outcomes for monolithic zirconia and lithium disilicate restorations produced through a direct digital workflow were reported.

METHODS

A MEDLINE (Pubmed) search of the relevant English-language literature spanning from January 1st 2015 until March 31st 2020 was conducted. In vitro studies comparing digital implant impression accuracy by different IOS devices or in vitro studies examining differences in accuracy between digital and conventional impression procedures were included. Also, RCTs, clinical trials and case series on the success and/or survival of monolithic zirconia and lithium disilicate restorations on implants, manufactured completely digitally were included. In vitro and in vivo studies reporting on restorations produced through an indirect digital workflow, case reports and non-English language articles were excluded. The aim was to investigate the accuracy of IOS for single and multiple fixed implant restorations compared to the conventional impression methods and report on the variables that influence it. Finally, this study aimed to report on the survival and success of fixed implant-retained restorations fabricated using the direct digital workflow.

RESULTS

For the single and short-span implant sites, IOS accuracy was high and the deviations in the position of the virtual implant fell within the acceptable clinical limits. In the complete edentulous arch with multiple implants, no consensus regarding the superiority of the conventional, splinted, custom tray impression procedure compared to the IOS impression was identified. Moreover, complete-arch IOS impressions were more accurate than conventional, non-splinted, open or close tray impressions. Factors related to scanbody design as well as scanner generation, scanning range and interimplant distance were found to influence complete-arch scanning accuracy. Single implant-retained monolithic restorations exhibited high success and survival rates and minor complications for short to medium follow-up periods.

CONCLUSIONS

The vast majority of identified studies were in vitro and this limited their clinical significance. Nevertheless, intraoral scanning exhibited high accuracy both for single and multiple implant restorations. Available literature on single-implant monolithic restorations manufactured through a complete digital workflow shows promising results for a follow-up of 3-5 years.

Ceramic Materials and Technologies Applied to Digital Works in Implant-Supported Restorative Dentistry

Computer-aided design and manufacturing technology has been closely associated with implant-supported restoration. The digital system employed for prosthodontic restorations comprises data acquisition, processing, and manufacturing using subtractive or additive methods. As digital implantology has developed, optical scanning, computer-based digital algorithms, fabricating techniques, and numerical control skills have all rapidly improved in terms of their accuracy, which has resulted in the development of new ceramic materials with advanced esthetics and durability for clinical application. This study reviews the application of digital technology in implant-supported dental restoration and explores two globally utilized ceramic restorative materials: Yttria-stabilized tetragonal zirconia polycrystalline and lithium disilicate glass ceramics.

Artificial intelligence in fixed implant prosthodontics: a retrospective study of 106 implant-supported monolithic zirconia crowns inserted in the posterior jaws of 90 patients

Background

Artificial intelligence (AI) is a branch of computer science concerned with building smart software or machines capable of performing tasks that typically require human intelligence. We present a protocol for the use of AI to fabricate implant-supported monolithic zirconia crowns (MZCs) cemented on customized hybrid abutments.

Methods

The study protocol consisted of: (1) intraoral scan of the implant position; (2) design of the individual abutment and temporary crown using computer-aided design (CAD) software; (3) milling of the zirconia abutment and the temporary polymethyl-methacrylate (PMMA) crown, with extraoral cementation of the zirconia abutment on the relative titanium bonding base, to generate an individual hybrid abutment; (4) clinical application of the hybrid abutment and the temporary PMMA crown; (5) intraoral scan of the hybrid abutment; (6) CAD of the final crown with automated margin line design using AI; (7) milling, sintering and characterisation of the final MZC; and (8) clinical application of the MZC. The outcome variables were mathematical (quality of the fabrication of the individual zirconia abutment) and clinical, such as (1) quality of the marginal adaptation, (2) of interproximal contact points and (3) of occlusal contacts, (4) chromatic integration, (5) survival and (6) success of MZCs. A careful statistical analysis was performed.

Results

90 patients (35 males, 55 females; mean age 53.3 ± 13.7 years) restored with 106 implant-supported MZCs were included in the study. The follow-up varied from 6 months to 3 years. The quality of the fabrication of individual hybrid abutments revealed a mean deviation of 44 μm (± 6.3) between the original CAD design of the zirconia abutment, and the mesh of the zirconia abutment captured intraorally at the end of the provisionalization. At the delivery of the MZCs, the marginal adaptation, quality of interproximal and occlusal contacts, and aesthetic integration were excellent. The three-year cumulative survival and success of the MZCs were 99.0% and 91.3%, respectively.

Conclusions

AI seems to represent a reliable tool for the restoration of single implants with MZCs cemented on customised hybrid abutments via a full digital workflow. Further studies are needed to confirm these positive results.

An Experimental Strategy for Capturing the Margins of Prepared Single Teeth with an Intraoral Scanner: A Prospective Clinical Study on 30 Patients

Purpose: To present an experimental strategy for successfully capturing the margins of prepared single teeth with an intraoral scanner (IOS). Methods: The protocol was as follows: (1) an intraoral impression was captured with an IOS, without taking care of the visibility of the margins; (2) a partial analog impression was taken by means of a 3D-printed custom tray filled with polyvinylsiloxane light, after the removal of a retraction cord; (3) the hollow portion of the analog impression, with the preparation margins clearly visible, was scanned extraorally with the same IOS; (4) the scan of the analog impression was imported into computer-assisted-design (CAD) software, where its normals were inverted; (5) the scan with inverted normals was registered on the first intraoral scan, and replaced it; (6) the technician designed the final restoration, which was fabricated and delivered for application. The study outcomes were: (1) the marginal adaptation of the final crown; (2) the quality of interproximal contacts; and (3) the quality of occlusal contacts. Results: Thirty patients (18 males, 12 females; mean age 51.3 ± 11.6 years) were selected for this study. All these patients were restored with a monolithic translucent zirconia crown, fabricated following the aforementioned protocol. The clinical precision and the marginal adaptation of the crowns were optimal, interproximal contact points were perfect, and the only necessary adaptations were occlusal, with some minor precontacts that had to be polished. Conclusions: The present protocol seems to be compatible with the fabrication of clinically precise zirconia crowns. Further studies are needed to confirm these results.

Zirconia crowns cemented on titanium bars using CAD/CAM: a five-year follow-up prospective clinical study of 9 patients

BACKGROUND

The purpose of this prospective clinical study was to evaluate clinical results of the passive fit of the substructure in the Toronto bridge and the chipping or delamination of the ceramic veneering on the zirconia-support, after 5 years, in nine patients rehabilitated with zirconia crowns cemented on titanium bars using CAD/CAM technology.

METHODS

A total of nine healthy patient fully edentulous in the upper and lower jaws with non-contributory past medical anamnesis needing full fixed total prosthesis maxilla and mandible were included in this clinical study, where a total 9 mandibles and 9 jaws were treated. The inclusion criteria in order for a patient to participate in the study were: a signed consent form, fully edentulous in the upper and lower jaws, required a full fixed total prosthesis restoration. The exclusion criteria were age limitation of less than 18 years old, chemotherapy, head and neck radiation therapy, diabetes or periodontal disease, smoking and severe illness. All patients received zirconia crowns cemented on titanium bars using CAD/CAM technology. The primary outcome of this study was to examine the survival rate of the zirconia crowns cemented on titanium bars using CAD/CAM technology during the observation period. Any chipping or delamination of the zirconia crowns of the restorations was considered as failure. The secondary outcome was to evaluate the passive fit of the substructure on the implants, loose of occlusal screws, implant survival and satisfactory occlusion.

RESULTS

In 5 years of follow-up no evidence of chipping or delamination of the ceramic veneering on the zirconia crown supported were observed. Fifteen finished protesis (93.75%) showed satisfactory occlusion and only one case (6.25%) required significant occlusal adjustment. During the first year recall all bars were stable (100%) no mobility of protheses was recorded. After 5 years all bars were stable (100%) and no mobility of protheses was recorded.

CONCLUSION

The computerized workflow for the process of building bar and prosthesis ensures reproducible results and excellent adaptation and passive insertion of them, as well as conditions for avoiding mechanical complications and guarantees stability of screw-implant abutments.

Clinical behavior of second-generation zirconia monolithic posterior restorations: Two-year results of a prospective study with Ex vivo analyses including patients with clinical signs of bruxism

OBJECTIVES

This study aimed to investigate (1) clinical outcomes of second-generation zirconia restorations, including patients with bruxism clinical signs, and (2) the material wear process.

METHODS

A total of 95 posterior monolithic zirconia tooth-elements in 45 patients were evaluated, 85 on implants and 10 on natural teeth, and 20.3% of restorations being fixed partial dentures (FPDs). Occlusal contact point areas were determined and half of those areas were left unglazed and just polished. Restorations were clinically evaluated following criteria of the World Dental Federation and antagonistic teeth were examined at each evaluation time. Wear ex vivo analyses using SEM and 3D laser profilometry were performed at baseline and after 6 months, 1 year, and 2 years respectively, temporarily removing the prostheses.

RESULTS

The Kaplan-Meier survival rate of restorations was 93.3% (100% for FPDs) and the success rate was 81.8%, with 4 abutment debondings, 3 tooth-supported crown debondings (provisional cement use), 1 restoration fracture, 1 minor chipping, 1 core fracture, 1 root fracture, and 2 implant losses. 80% of catastrophic failures occurred in patients with clinical signs of bruxism (61.7% of patients). Complications were also observed on antagonistic teeth (3 catastrophic failures). Clinical evaluation of the restorations showed good results from the aesthetic, functional, and biological perspective. Zirconia wear was inferior to 15 μm, while glaze wear was observed on all occlusal contact areas after 1 year.

CONCLUSIONS

Monolithic zirconia FPDs are promising but the failure rate of single-unit restorations was not as high as expected in this sample including patients with bruxism clinical signs.

CLINICAL SIGNIFICANCE

Within study limitations, FPDs showed excellent short-term results but further research is needed for single-unit restorations considering samples, which do not exclude bruxers. The weak link is the restoration support or the antagonist tooth, one hypothesis being that zirconia stiffness and lack of resilience do not promote occlusal stress damping.

Monolithic Zirconia: An Update to Current Knowledge. Optical Properties, Wear, and Clinical Performance

The purpose of this paper was to update the knowledge concerning the wear, translucency, as well as clinical performance of monolithic zirconia ceramics, aiming at highlighting their advantages and weaknesses through data presented in recent literature. New ultra-translucent and multicolor monolithic zirconia ceramics present considerably improved aesthetics and translucency, which, according to the literature reviewed, is similar to those of the more translucent lithium disilicate ceramics. A profound advantage is their high strength at thin geometries preserving their mechanical integrity. Based on the reviewed articles, monolithic zirconia ceramics cause minimal wear of antagonists, especially if appropriately polished, although no evidence still exists regarding the ultra-translucent compositions. Concerning the survival of monolithic zirconia restorations, the present review demonstrates the findings of the existing short-term studies, which reveal promising results after evaluating their performance for up to 5 or 7 years. Although a significant increase in translucency has been achieved, new translucent monolithic zirconia ceramics have to be further evaluated both in vitro and in vivo for their long-term potential to preserve their outstanding properties. Due to limited studies evaluating the wear properties of ultra-translucent material, no sound conclusions can be made, whereas well-designed clinical studies are urgently needed to enlighten issues of prognosis and long-term survival.

Trueness and precision of 5 intraoral scanners in the impressions of single and multiple implants: a comparative in vitro study

BACKGROUND

Until now, a few studies have addressed the accuracy of intraoral scanners (IOSs) in implantology. Hence, the aim of this in vitro study was to assess the accuracy of 5 different IOSs in the impressions of single and multiple implants, and to compare them.

METHODS

Plaster models were prepared, representative of a partially edentulous maxilla (PEM) to be restored with a single crown (SC) and a partial prosthesis (PP), and a totally edentulous maxilla (TEM) to be restored with a full-arch (FA). These models were scanned with a desktop scanner, to capture reference models (RMs), and with 5 IOSs (CS 3600®, Trios3®, Omnicam®, DWIO®, Emerald®); 10 scans were taken for each model, using each IOS. All IOS datasets were loaded into a reverse-engineering software where they were superimposed on the corresponding RMs, to evaluate trueness, and superimposed on each other within groups, to determine precision. A statistical analysis was performed.

RESULTS

In the SC, CS 3600® had the best trueness (15.2 ± 0.8 μm), followed by Trios3® (22.3 ± 0.5 μm), DWIO® (27.8 ± 3.2 μm), Omnicam® (28.4 ± 4.5 μm), Emerald® (43.1 ± 11.5 μm). In the PP, CS 3600® had the best trueness (23 ± 1.1 μm), followed by Trios3® (28.5 ± 0.5 μm), Omnicam® (38.1 ± 8.8 μm), Emerald® (49.3 ± 5.5 μm), DWIO® (49.8 ± 5 μm). In the FA, CS 3600® had the best trueness (44.9 ± 8.9 μm), followed by Trios3® (46.3 ± 4.9 μm), Emerald® (66.3 ± 5.6 μm), Omnicam® (70.4 ± 11.9 μm), DWIO® (92.1 ± 24.1 μm). Significant differences were found between the IOSs; a significant difference in trueness was found between the contexts (SC vs. PP vs. FA). In the SC, CS 3600® had the best precision (11.3 ± 1.1 μm), followed by Trios3® (15.2 ± 0.8 μm), DWIO® (27.1 ± 10.7 μm), Omnicam® (30.6 ± 3.3 μm), Emerald® (32.8 ± 10.7 μm). In the PP, CS 3600® had the best precision (17 ± 2.3 μm), followed by Trios3® (21 ± 1.9 μm), Emerald® (29.9 ± 8.9 μm), DWIO® (34.8 ± 10.8 μm), Omnicam® (43.2 ± 9.4 μm). In the FA, Trios3® had the best precision (35.6 ± 3.4 μm), followed by CS 3600® (35.7 ± 4.3 μm), Emerald® (61.5 ± 18.1 μm), Omnicam® (89.3 ± 14 μm), DWIO® (111 ± 24.8 μm). Significant differences were found between the IOSs; a significant difference in precision was found between the contexts (SC vs. PP vs. FA).

CONCLUSIONS

The IOSs showed significant differences between them, both in trueness and in precision. The mathematical error increased in the transition from SC to PP up to FA, both in trueness than in precision.

Combining Intraoral and Face Scans for the Design and Fabrication of Computer-Assisted Design/Computer-Assisted Manufacturing (CAD/CAM) Polyether-Ether-Ketone (PEEK) Implant-Supported Bars for Maxillary Overdentures

PURPOSE

To present a digital method that combines intraoral and face scanning for the computer-assisted design/computer-assisted manufacturing (CAD/CAM) fabrication of implant-supported bars for maxillary overdentures.

METHODS

Over a 2-year period, all patients presenting to a private dental clinic with a removable complete denture in the maxilla, seeking rehabilitation with implants, were considered for inclusion in this study. Inclusion criteria were fully edentulous maxilla, functional problems with the preexisting denture, opposing dentition, and sufficient bone volume to insert four implants. Exclusion criteria were age < 55 years, need for bone augmentation, uncompensated diabetes mellitus, immunocompromised status, radio- and/or chemotherapy, and previous treatment with oral and/or intravenous aminobisphosphonates. All patients were rehabilitated with a maxillary overdenture supported by a CAD/CAM polyether-ether-ketone (PEEK) implant-supported bar. The outcomes of the study were the passive fit/adaptation of the bar, the 1-year implant survival, and the success rates of the implant-supported overdentures.

RESULTS

15 patients (6 males, 9 females; mean age 68.8 ± 4.7 years) received 60 implants and were rehabilitated with a maxillary overdenture supported by a PEEK bar, designed and milled from an intraoral digital impression. The intraoral scans were integrated with face scans, in order to design each bar with all available patient data (soft tissues, prosthesis, implants, and face) in the correct spatial position. When testing the 3D-printed resin bar, 12 bars out of 15 (80%) had a perfect passive adaptation and fit; in contrast, 3 out of 15 (20%) did not have a sufficient passive fit or adaptation. No implants were lost, for a 1-year survival of 100% (60/60 surviving implants). However, some complications (two fixtures with peri-implantitis in the same patient and two repaired overdentures in two different patients) occurred. This determined a 1-year success rate of 80% for the implant-supported overdenture.

CONCLUSIONS

In this study, the combination of intraoral and face scans allowed to successfully restore fully edentulous patients with maxillary overdentures supported by 4 implants and a CAD/CAM PEEK bar. Further studies are needed to confirm these outcomes.