Clinical Fitting and Adjustment Time for Implant-Supported Crowns Comparing Digital and Conventional Workflows

Comparison of accuracy in digital and conventional cross-mounting

STATEMENT OF PROBLEM

The use of digital interocclusal registration scans for virtual articulation and mounting has been studied extensively; however, the accuracy of the cross-mounting procedures in a digital workflow is not well understood.

PURPOSE

The purpose of this in vitro study was to compare the accuracy of digital and conventional cross-mounting by measuring the 3-dimensional deviation at each step of sequential cross-mounting.

MATERIAL AND METHODS

A set of reference casts and complete arch interim restorations was prepared for complete arch complete-coverage restorations, hand-articulated, and mounted in an articulator. The reference casts were then scanned with and without the interim restorations to generate 4 reference casts for cross-mounting. For the conventional group, 15 sets of the 4 casts were printed. Polyvinyl siloxane interocclusal registration records were made of the reference casts for each set, and casts were sequentially cross-mounted. For the digital workflow, 15 sets of bilateral interocclusal registration scans were made of the mounted reference casts and used to align the cast scans. Three-dimensional deviations at 2 anterior and 2 posterior points were recorded between the experimental mountings and the reference casts on each set of casts. Nonpaired t test and analysis of variance (ANOVA) were used to compare the average discrepancy between the 2 groups, and the pooled anterior versus posterior discrepancies were compared (α=.05).

RESULTS

A significant difference was found between conventional and digital cross-mounting procedures (P<.001), but no significant difference was found in either group, conventional (P=.116) or digital (P=.987), at each step of the sequential mountings. The mean ±standard deviation at the final set of related casts in the conventional workflow was 201.6 ±137.0 μm and that in the digital group was 50.3 ±47.5 μm, with a significant difference between anterior and posterior deviations in the digital group (P=.028), but not in the conventional group (P=.143). The mean ±standard deviation anterior conventional deviation was 175.6 ±119.2 μm and that in the digital group was 36.9 ±30.9 μm. The mean ±standard deviation posterior conventional deviation was 227.6 ±50.2 μm and that in the digital group was 63.7 ±57.2 μm.

CONCLUSIONS

Digital cross-mounting was more accurate than conventional cross-mounting, although increased deviation was found in the anterior region compared with the posterior region.

Comparative analyses of time efficiency and cost in fabricating fixed implant-supported prostheses in digital, hybrid, and conventional workflows: A systematic review and meta-analysis

STATEMENT OF PROBLEM

Economic considerations affect whether new technologies are adopted in dental practice. Limited evidence exists regarding the time and cost efficiency of different workflows for fabricating implant-supported restorations.

PURPOSE

The purpose of this systematic review and meta-analysis was to compare the time and cost involved in fabricating fixed implant-supported prostheses using digital, hybrid, and conventional methods throughout the entire prosthetic treatment by analyzing both clinical and laboratory steps.

MATERIAL AND METHODS

A systematic review was conducted following the Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA)-P 2015 guidelines. The methods and inclusion criteria were specified in a protocol registered with the International Prospective Register of Systematic Reviews (PROSPERO) (registration number CRD42023458734). The databases PubMed, Cochrane, and PROSPERO were searched using keywords: (Prosthodontic OR restorative dentistry OR denture) AND (CAD CAM OR Digital workflow OR Computer Dentistry OR Digital Design) AND (Economic OR cost OR Financial OR time efficiency). Two investigators selected articles independently.

RESULTS

A qualitative synthesis of 12 articles published from 2010 to 2023 showed that digital scans took less time than conventional impressions (P<.05) in 7 out of 9 articles. Additionally, 8 articles revealed significant reductions in laboratory working time with digital workflows, intermediate times with hybrid workflows, and longer times with conventional workflows (P<.001). Meta-analysis confirmed the time efficiency of digital scanning over conventional impressions (Hedges g=1.65, 95% CI [0.33, 2.98]) and a substantial reduction in laboratory time with digital workflows compared with other workflows (Hedges g=6.55, 95% CI [2.69; 10.42]). However, no significant difference was found in adjustment time between digital and other workflows (Hedges g=0.91, 95% CI [-0.72; 2.55]). Direct laboratory costs were observed to be higher in conventional workflows compared with hybrid or digital workflows, with hybrid workflows also showing elevated costs compared with digital workflows (P<.05).

CONCLUSIONS

The digital workflow demonstrates potential benefits in reducing scan time, laboratory processing time, and direct laboratory costs for implant-supported restorations in partial edentulism. Further research is needed to validate these findings, particularly for long-span implant-supported fixed partial prostheses.

Zirconia CAD-CAM Crowns Behavior after Intraoral Digital Impression in Normal versus Dysfunctional Patients: 3 Years Retrospective Study

OBJECTIVES

 The aim of this study was to evaluate the clinical performance and possible complications of single zirconia crowns fabricated using an intraoral digital computer-aided design-computer-aided manufacturing (CAD-CAM) protocol in normal and dysfunctional patients after 3 years of follow-up.

MATERIALS AND METHODS

 Seventy patients were included in this study. The teeth were prepared with a knife-edge marginal design, and temporary crowns were placed. Digital impressions were taken using optical scanning, and the frameworks were milled using the same technology. The veneering process was performed by the same dental technician. The occlusal corrections were made before cementation. The outcomes were evaluated in terms of survival, failures, and complications. The marginal adaptation of the crowns was also assessed.

RESULTS

 The digital protocol for single zirconia crowns resulted in satisfactory outcomes, with high rates of survival and minimal complications after 3 years of follow-up. The marginal adaptation of the crowns was excellent, with 93% of the restorations achieving the ideal marginal adaptation, while 7% had minor deviations. Parafunctions were found in 41.9% of the prosthetic rehabilitation, but no significant differences were observed between the normal and dysfunctional groups regarding the survival and complications of the crowns.

CONCLUSION

 The digital protocol for single zirconia crowns is a reliable and predictable treatment option, even for patients with parafunction, when proper occlusal corrections are performed before cementation. The use of intraoral digital CAD-CAM technologies with optical impressions can simplify procedures, reduce the workflow time, and minimize the variables linked to the human factor.

Accuracy of artificial intelligence-designed single-molar dental prostheses: A feasibility study

STATEMENT OF PROBLEM

Computer-aided design and computer-aided manufacturing (CAD-CAM) technology has greatly improved the efficiency of the fabrication of dental prostheses. However, the design process (CAD stage) is still time-consuming and labor intensive.

PURPOSE

The purpose of this feasibility study was to investigate the accuracy of a novel artificial intelligence (AI) system in designing biomimetic single-molar dental prostheses by comparing and matching them to the natural molar teeth.

MATERIAL AND METHODS

A total of 169 maxillary casts were obtained from healthy dentate participants. The casts were digitized, duplicated, and processed with the removal of the maxillary right first molar. A total of 159 pairs of original and processed casts were input into the Generative Adversarial Networks (GANs) for training. In validation, 10 sets of processed casts were input into the AI system, and 10 AI-designed teeth were generated through backpropagation. Individual AI-designed teeth were then superimposed onto each of the 10 original teeth, and the morphological differences in mean Hausdorff distance were measured. True reconstruction was defined as correct matching between the AI-designed and original teeth with the smallest mean Hausdorff distance. The ratio of true reconstruction was calculated as the Intersection-over-Union. The reconstruction performance of the AI system was determined by the Hausdorff distance and Intersection-over-Union.

RESULTS

Data of validation showed that the mean Hausdorff distance ranged from 0.441 to 0.752 mm and the Intersection-over-Union of the system was 0.600 (60%).

CONCLUSIONS

This study demonstrated the feasibility of AI in designing single-molar dental prostheses. With further training and optimization of algorithms, the accuracy of biomimetic AI-designed dental prostheses could be further enhanced.

Comparison of Conventional and Digital Workflows in the Fabrication of Fixed Prostheses: A Systematic Review

When considering dental restorations, the use of fixed partial dentures is one of the most widely accepted treatment options. In the past, fabrication was done using traditional techniques and the conventional workflow was by far the popular method; however, nowadays digital workflows are being used as a means to produce the prosthesis. This systematic review aims to compare the workflows by considering their respective qualities, such as precision, efficiency, cost-effectiveness, and clinical performance. A complete search has been carried out to incorporate any relevant studies published between the years 2012 and 2023 in databases such as Scopus, Web of Science, PubMed, ScienceDirect, and Cochrane Library. Two independent reviewers screened articles for inclusion and assessed the studies' methodological quality rating via the NIH Tool. A total of 22 relevant articles were reviewed after a systematic search strategy. The main outcome of the review was digital workflows were found to reduce working time, eliminate the selection of trays, minimize material consumption, and enhance patient comfort and acceptance. The studies also showed that digital workflows resulted in greater patient satisfaction and higher success rates than conventional workflows. Workflows for digital dentistry demonstrated to be better than traditional ones due to the cost-effectiveness, accuracy, and time optimization for the fabrication of fixed prostheses.

Verification of the accuracy of dynamic navigation for conventional and mouthpiece methods: in vivo study

BACKGROUND

Dynamic navigation for implant placement is becoming popular under the concept of top-down treatment. The purpose of this study is to verify the accuracy of a dynamic navigation system for implant placement.

METHODS

Implant placement was performed on 38 patients using 50 implant fixtures. Patients in group C were treated using a conventional method, in which thermoplastic clips were fixed to the teeth, and patients in group M were treated using thermoplastic clips fixed to a mouthpiece attached to the teeth. The groups were compared to verify whether an accuracy difference existed. A treatment planning support program for dental implants was used to superimpose the postoperative computed tomography data on the preoperative implant design data to measure the entry point, apex point, and angular deviation.

RESULTS

The accuracy of group C was 1.36 ± 0.51 mm for entry point, 1.30 ± 0.59 mm for apex point, and 3.20 ± 0.74° for angular deviation. The accuracy of group M was 1.06 ± 0.31 mm for the entry point, 1.02 ± 0.30 mm for the apex point, and 2.91 ± 0.97° for angular deviation. Significant differences were observed in the entry and apex points between the two groups.

CONCLUSIONS

The results indicate that group M exhibited better accuracy than group C, indicating that the stability of the thermoplastic clip is important for ensuring the accuracy of the dynamic navigation system. No previous studies have verified the accuracy of this system using the mouthpiece method, and additional data is required to confirm its accuracy for dental implant placement. The mouthpiece method improves the accuracy of implant placement and provides a safer implant treatment than the conventional method.

TRIAL REGISTRATION

University hospital Medical Information Network Clinical Trials Registry (UMIN-CTR), Registration Number: UMIN000051949, URL: https://center6.umin.ac.jp/cgi-open-bin/ctr_e/ctr_view_his.cgi on August 21, 2023.

A randomized clinical trial comparing the clinical fit and chairside adjustment time for implant-supported crowns fabricated by fully digital and partially digital techniques

STATEMENT OF PROBLEM

Implant-supported crowns made in both fully and partially digital workflows have been evaluated, but these studies have been mainly performed in vitro. Moreover, data on the comparison of clinical fitting and adjustment time for implant-supported crowns are limited.

PURPOSE

The purpose of this randomized clinical trial was to evaluate the clinical fit and adjustment time for implant-supported crowns produced by a partially and fully digital workflow in partially edentulous participants.

MATERIAL AND METHODS

Twenty-eight participants who had received 2 adjacent implants in posterior sites were enrolled, each receiving 2 custom titanium abutments and a splinted monolithic zirconia restoration. Restorations of the control group (n=14) were produced from a digital scan and a cast-free digital workflow, while the restorations of the test group (n=14) were from a conventional impression and a partially digital workflow. A blinded investigator delivered the restorations. The clinical adjustment was performed incrementally, and a digital chronometer recorded the time required for the evaluation and adjustment at each step. An independent t test, Mann-Whitney U test, and the Fisher exact test were used to evaluate the results (α=.05).

RESULTS

The total mean adjustment time in the control group (12.49 minutes) was significantly longer than that of the test group (11.27 minutes) (P<.001). For the occlusal contact points, significantly less clinical adjustment time was required with the cast-free digital workflow (5.31 minutes) than with the model-based partially digital workflow (6.06 minutes) (P=.001). On other surfaces, no significant difference was found between the 2 groups (P>.05). All crowns could be successfully delivered after 2 clinical appointments (impression and delivery). Remakes were not necessary for any restorations in the test or control group.

CONCLUSIONS

The parameters of occlusal adjustment time and total adjustment time of the fully digital workflow were significantly shorter than those of the partially digital workflow.

Accuracy of digital implant impressions obtained using intraoral scanners: a systematic review and meta-analysis of in vivo studies

PURPOSE

This systematic review aimed to investigate the accuracy of intraoral scan (IOS) impressions of implant-supported restorations in in vivo studies.

METHODS

A systematic electronic search and review of studies on the accuracy of IOS implant impressions were conducted to analyze the peer-reviewed literature published between 1989 and August 2023. The bias analysis was performed by two reviewers. Data on the study characteristics, accuracy outcomes, and related variables were extracted. A meta-analysis of randomized control trials was performed to investigate the impact of IOS on peri-implant crestal bone loss and the time involved in the impression procedure.

RESULTS

Ten in vivo studies were included in this systematic review for final analysis. Six studies investigated the trueness of IOS impressions, but did not reach the same conclusions. One study assessed the precision of IOS impressions for a single implant. Four clinical studies examined the accuracy of IOS implant impressions with a follow-up of 1-2 years. In full arches, IOS impression procedure needed significantly less time than conventional one (mean difference for procedure time was 8.59 min [6.78, 10.40 min], P < 0.001), prosthetic survival rate was 100%, and marginal bone levels of all participants could be stably maintained (mean difference in marginal bone loss at 12 months was 0.03 mm [-0.08, 0.14 mm], P = 0.55).

CONCLUSIONS

The accuracy of IOS impressions of implant-supported restorations varied greatly depending on the scanning strategy. The trueness and precision of IOS in the partial and complete arches remain unclear and require further assessment. Based on follow-up clinical studies, IOS impressions were accurate in clinical practice. However, these results should be interpreted with caution, as some evidences are obtained from the same research group.

Trueness and precision of complete arch dentate digital models produced by intraoral and desktop scanners: An ex-vivo study

OBJECTIVES

The study aimed to compare the trueness and precision of five intraoral scanners (Emerald S, iTero Element 5D, Medit i700, Primescan, and Trios 4) and two indirect digitization techniques for both teeth and soft tissues on fresh mandibular and maxillary cadaver jaws.

METHODS

The maxilla and mandible of a fully dentate cadaver were scanned by the ATOS industrial scanner to create a master model. Then, the specimens were scanned eight times by each intraoral scanner (IOS). In addition, 8 polyvinylsiloxane (PVS) impressions were made and digitized with a Medit T710 desktop scanner. Stone models were then poured and again scanned with the desktop scanner. All IOS, PVS, and stone models were compared to the master model to calculate the mean absolute surface deviation for mandibular teeth, maxillary teeth, and palate.

RESULTS

For mandibular teeth, the PVS trueness was only significantly better than the Medit i700 (p < 0.001) and Primescan (p < 0.05). In maxillary teeth, the PVS trueness was significantly better than all IOSs (p < 0.05-0.001); the stone trueness was significantly better than Emerald S (p < 0.01), Medit i700 (p < 0.001) and Primescan (p < 0.01). In the palate, PVS and stone trueness were significantly lower than the iTero Element 5D (p < 0.01) and Trios 4 (p < p < 0.01). Stone trueness was significantly lower than the Medit i700 (p < 0.05). The precision in the palate was significantly lower for PVS and stone than for Emerald S (p < 0.01, p < 0.05), iTero Element 5D (p < 0.01, p < 0.01), Primescan (p < 0.001, p < 0.001), and Trios 4 (p < 0.001, p < 0.01). Significant differences in trueness between the IOSs were observed only in the mandibular teeth. The Medit i700 performed worse than Emerald S (p < 0.01) and iTero Element 5D (p < 0.01). For mandibular teeth, the Medit i700 was significantly more precise than Primescan (p < 0.01) and the Emerald S (p < 0.05). The Trios 4 was significantly less precise than Emerald S (p < 0.05). The precision of Medit i700 was significantly worse than iTero Element 5D (p < 0.01) for maxillary teeth, as well as the Primescan (p < 0.01) and Trios 4 (p < 0.05) for the palate.

CONCLUSIONS

In general, indirectly digitized models from PVS impressions had higher trueness than IOS for maxillary teeth; precision between the two methods was similar. IOS was more accurate for palatal tissues. The differences in trueness and precision for mandibular teeth between the various techniques were negligible.

CLINICAL SIGNIFICANCE

All investigated IOSs and indirect digitization could be used for complete arch scanning in mandibular and maxillary dentate arches. However, direct optical digitization is preferable for the palate due to the low accuracy of physical impression techniques for soft tissues.

A double-blind randomized within-subject study to evaluate clinical applicability of four digital workflows for the fabrication of posterior single implant crown

OBJECTIVE

To compare efficiency and clinical efficacy of posterior single implant crowns (PSIC) fabricated using four digital workflows.

MATERIALS AND METHODS

Twenty-two patients with one missing first molar were included. Each patient received four screw-retained implant crowns fabricated through four different workflows including a fully digital workflow with immediate digital impression (Group i-IOS), a fully digital workflow with digital impression after implant osseointegration (Group d-IOS), a model-based hybrid workflow using immediate analogue impression (Group i-AI), and a model-based hybrid workflow with conventional analogue impression after implant osseointegration (Group d-AI). The crown delivery sequence was randomized and blinded. The efficiency for each workflow and clinical outcome of each crown were recorded.

RESULTS

The average clinical working time in fully digital workflows (i-IOS 46.90 min, d-IOS 45.66 min) was significantly lower than that in the hybrid workflows (i-AI 54.59 min, d-AI 55.96 min; p < .001). Significantly more laboratory time was spent in hybrid workflows (i-AI 839.60 min, d-AI 811.73 min) as compared to fully digital workflows (i-IOS 606.25 min, d-IOS 607.83 min, p < .01). No significant differences in the chairside time at delivery were found. More crowns in Group i-AI (15%) needed additional laboratory interventions than in the other groups (p = .029).

CONCLUSION

Digital impression and model-free fully digital workflow improved prosthetic efficiency in the fabrication of PSIC. With the limitation that the results were only applicable to the implant system used and the digital technologies applied, findings suggested that workflows integrating immediate impression with implant surgery procedure was clinically applicable for restoration of PSIC.

Accuracy of photogrammetric imaging versus conventional impressions for complete arch implant-supported fixed dental prostheses: A comparative clinical study

STATEMENT OF PROBLEM

Clinical studies on the accuracy of the photogrammetric imaging technique for complete arch implant-supported fixed dental prostheses are lacking.

PURPOSE

The purpose of this clinical study was to evaluate the accuracy (trueness) of photogrammetric imaging for complete arch implant-supported prostheses by comparing photogrammetric imaging with verified conventional splinted impressions.

MATERIAL AND METHODS

Completely edentulous arches with at least 4 implants were included. Both photogrammetric imaging and conventional splinted impressions were performed in each jaw. The conventional casts were verified and scanned by using a laboratory scanner as the control. The distances and angulations between different implants (interimplant distances and interimplant angulations) were measured in all photogrammetric and conventional standard tessellation language (STL) files by using a reverse-engineering software program. The distance deviations between the photogrammetric and conventional impressions of the same participant were calculated as the primary outcome, and the angular deviations were obtained as the secondary outcome with descriptive analyses. The comparison between distance deviations and the clinically acceptable level of deviations (150 μm) was conducted by using the 1-sample t test. The effect of interimplant distances, interimplant angulations, and jaw (maxilla or mandible) on deviations was analyzed by using the Spearman correlation analysis, Kruskal-Wallis test, or Student t test, depending on the type of data (α=0.05 for all tests).

RESULTS

Fourteen edentulous jaws were included. The overall distance deviation of photogrammetric imaging was 70 ±57 μm, significantly lower than the clinically acceptable level of misfit (150 μm; P<.001). The overall angular deviation was 0.432 ±0.348 degrees. The distance deviations were correlated with interimplant distances with a correlation coefficient (r) of 0.371 (P=.002). Interimplant angulation was not correlated with distance or angular deviations (P=.914, P=.914). Jaw was not correlated with distance or angular deviations either (P=.190, P=.209).

CONCLUSIONS

The accuracy (trueness) of photogrammetric imaging of complete arch implant-supported prostheses was within a clinically acceptable range of errors. Distance deviations increased with greater interimplant distances. Interimplant angulations and jaw (maxilla or mandible) had no significant effect on the accuracy of photogrammetric imaging.

CAD/CAM Abutments in the Esthetic Zone: A Systematic Review and Meta-Analysis of Soft Tissue Stability

Computer-aided design and computer-aided manufacturing customized abutments are increasingly used in everyday clinical practice. Nevertheless, solid scientific evidence is currently lacking regarding their potential advantages in terms of soft tissue stability. The main aim of this systematic review and meta-analysis was to compare the soft tissue outcomes of prefabricated versus customized (CAD/CAM) abutments. The present review was registered with PROSPERO (CRD42020161875) and the protocol was developed according to the PRISMA statement. An electronic search was performed on three databases (PubMed, Embase and Cochrane Central) up to May 2023. Data extraction was followed by qualitative and quantitative analysis of the included studies. Three randomized controlled clinical trials and three controlled clinical trials (number of patients = 230; number of dental implants = 230) with a follow-up of between 12 and 36 months were included. No significant differences were observed between prefabricated versus customized (CAD/CAM) abutments regarding midfacial mucosal recession, interproximal papillae and pink aesthetic score (PES) after 12 months. Conclusion: The potential benefits of CAD/CAM abutments on soft tissues should be better clarified in future investigations. The usage of customized CAD/CAM abutments in everyday clinical practice should be based on a careful case-by-case evaluation (CRD42020161875).

Effect of a novel interocclusal recording method on occlusal accuracy of implant-supported fixed prostheses: A randomized clinical trial

OBJECTIVES

To investigate the effect of a novel interocclusal recording method on the occlusal accuracy of implant-supported fixed prostheses for partially dentate patients with distal extension.

MATERIALS AND METHODS

Twenty patients with two or more adjacent teeth missing in the distal extension and scheduled to receive implant-supported fixed prostheses were enrolled. Two interocclusal recording methods were used: placing polyvinyl siloxane (PVS) on the interocclusal recording caps (test), and placing PVS on healing abutments (control). The intraoral occlusal contacts in maximal intercuspal position (MIP) were compared with those in the mounted casts to calculate sensitivity and positive predictive value (PPV). Then, patients were randomly allocated into two groups to determine which interocclusal record would be used. The implant prostheses' evaluations mainly included occlusal adjustment height, volume, and time, occlusal contact score based on articulating paper examination. Paired-samples t-test, Mann-Whitney U test, and least squares regression analyzed the statistic differences.

RESULTS

The test method had higher sensitivity to detect intraoral occlusal contacts than the control method (p = .002), but similar PPV (p = .10). During the prostheses' evaluations, the occlusal adjustment height in the test group was significantly lower than that in the control group [99.4 (53.2, 134.2) vs. 159.0 (82.3, 247.8) μm, p = .03], while the occlusal contact score before adjustment was higher (p = .006). The groups had similar occlusal adjustment volume and time.

CONCLUSIONS

The novel interocclusal recording method for implant-supported fixed prostheses was more accurate and could reduce the occlusal adjustment.

Patient-reported outcome measures compared to professional dental assessments of monolithic ZrO2 implant fixed dental prostheses in complete digital workflows: A double-blind crossover randomized controlled trial

PURPOSE

This double-blind randomized controlled trial analyzed patient-reported outcome measures in terms of subjective patient satisfaction compared to objective dental evaluation of prosthetic treatment with 3-unit monolithic zirconium dioxide implant fixed dental prostheses (iFDPs) in 3 digital workflows.

MATERIAL AND METHODS

Twenty patients were restored with 3 iFDPs each on Straumann TL-implants with 2 completely digital workflows using different intraoral optical scanning systems with model-free fabrication of the restoration (Trios 3/3Shape [Test-1]; Virtuo Vivo/Straumann [Test-2]), and mixed analog-digital workflow with conventional impressions and digitized gypsum casts (Impregum/3M Espe [Control]). The order of impression-taking and the prosthetic try-in were randomly allocated. Sixty iFDPs were compared for patient satisfaction and dental evaluation using ANOVA.

RESULTS

For iFDP evaluation, patients generally provided more favorable ratings than dental experts, regardless of the workflow. ANOVA revealed no significant difference for overall satisfaction when comparing Test-1, Test-2, or Control, either for patients (f-ratio: 0.13; p = 0.876) or dentist (f-ratio: 1.55: p = 0.221). Secondary, patients clearly favored the digital impression workflows over the conventional approach (f-ratio: 14.57; p < 0.001). Overall, the 3Shape workflow (Test-1) received the highest scores for all analyses.

CONCLUSIONS

The different digital workflows demonstrated minor influence on the subjective and objective evaluation of the monolithic zirconium dioxide iFDPs in nonesthetic regions; however, the dentist may significantly increase patient satisfaction by choosing intraoral scanning instead of conventional impressions. The dentist has to consider individual patients' needs to fulfill their expectations for a personalized solution.

Occlusal adjustment of 3-unit tooth-supported fixed dental prostheses fabricated with complete-digital and -analog workflows: A crossover clinical trial

AIM

This prospective crossover clinical trial aimed to compare the complete-digital and -analog workflows in terms of occlusal adjustment of 3-unit tooth-supported fixed dental prostheses, operator, and patient preferences.

MATERIALS AND METHOD

This study included twelve patients receiving fourteen 3-unit posterior FDPs. 2 FDPs were made for each restoration site: one fabricated in complete-digital workflow comprising intraoral scan with static bite registration (Trios 3) and a monolithic zirconia FDP (test); the other fabricated in complete-analog workflow comprising conventional impression/face-bow transfer and a porcelain-fused-to-metal FDP (control). The FDPs (n=28) were intraorally/provisionally fixed, and quadrant-like intraoral scans were taken for every FDP before & after their occlusal adjustments. Pre- and post-adjustment scans of each FDP were then superimposed using best-fit alignment (GOM Inspect) to measure the volumetric occlusal adjustment amount (mm³) (3Matic) (Mann Whitney U, α=0.05). The patient and operator experience for digital and analog workflows were evaluated using visual analog scales (Wilcoxon test, α=0.05).

RESULTS

Mean occlusal adjustments were 7.63 mm³ [±7.02] and 25.95 mm³ [±39.61] for test and control groups, respectively. The volumetric adjustment difference was clinically noticeable but not significant (P=0.12). The impression and digital workflow adjustment were perceived more favorably by both operator (P=0.003, P=0.046, respectively) and the patients (P=0.003, P=0.002, respectively).

CONCLUSIONS

Within the limitations of this clinical study, the complete digital workflow with digital static bite-registration provided high occlusal accuracy for short-span tooth-supported FDPs. In addition, the patient and operator preferences significantly favored the digital workflow.

CLINICAL SIGNIFICANCE

Complete-digital workflow employing intraoral scanning and model-free fabrication of monolithic-Zr short-span tooth-supported FDPs offers an effective treatment modality with sufficient occlusal accuracy. Therefore complete-digital workflow is a valid alternative for complete-analog workflow comprising conventional impression, face-bow transfer, and use of a semi-adjustable articulator.

Conventional and digital impressions for complete-arch implant-supported fixed prostheses: time, implant quantity effect and patient satisfaction

PURPOSE

To evaluate and compare the effect of impression type (conventional vs digital) and the number of implants on the time from the impressions to the generation of working casts of mandibular implant-supported fixed complete-arch frameworks, as well as on patient satisfaction.

MATERIALS AND METHODS

17 participants, 3 or 4 implants, received 2 types of digital impression methods (DI) and conventional (CI). In DI, two techniques were performed: scanning with the scan bodies (SC) and scanning with a device attached to the scan bodies (SD) (BR 10 2019 026265 6). In CI, the making of a solid index (SI) and open-tray impression (OT) were used. The outcomes were used to evaluate the time and the participant satisfaction with conventional and digital impressions. The time was evaluated through the timing of the time obtained in the workflow in the conventional and digital impression. The effect of the number of implants on time was also assessed. Satisfaction was assessed through a questionnaire based on seven. The Wilcoxon test used to identify the statistical difference between the groups in terms of time. The Mann-Whitney test was used to analyze the relationship between the time and the number of implants. Fisher's test was used to assess the patient satisfaction (P < .05).

RESULTS

The time with DI was shorter than with CI (DI, x̃=02:58; CI, x̃=31:48) (P < .0001). The arches rehabilitated with 3 implants required shorter digital impression time (3: x̃=05:36; 4: x̃=09:16) (P < .0001). Regarding satisfaction, the DI was more comfortable and pain-free than the CI (P < .005).

CONCLUSION

Digital impressions required shorter chair time and had higher patient acceptance than conventional impressions.

In vitro accuracy of digital and conventional impressions in the partially edentulous maxilla

OBJECTIVES

This in vitro study compared the dimensional accuracy of conventional impressions (CI) with that of digital impressions (DI) in a partially edentulous maxilla. DIs were made by two intraoral scanners, Omnicam (OC) and Primescan (PS).

MATERIALS AND METHODS

CI and both intraoral scanners were used to take 30 impressions of two identical reference models. CIs were poured with type 4 gypsum and the saw-cut models were digitized. The reference models simulated a maxilla with six prepared teeth that accommodated a cross-arch fixed partial denture. Center points of five precision balls and center points at the margin level of each prepared tooth were used to detect changes in dimensions and tooth axis between the reference model and the scans.

RESULTS

For DI, the largest deviations (176 µm for OC and 122 µm for PS) occurred over the cross-arch. For CI, the largest deviation (118 µm) occurred over the anterior segment. For shorter distances up to a quadrant, DI was superior to CI. For longer scan distances, DI was comparable (2 sextant and anterior segment) or inferior (cross-arch) to CI. Vertical and tooth axis deviations were significantly smaller for CI than for DI (p < 0.001).

CONCLUSIONS

The impression method affected the impression accuracy of a partially edentulous maxilla with prepared teeth. DI is recommended for scans up to a quadrant. Larger scan volumes are not yet suitable for fabricating a fixed partial denture because of the high scatter of accuracy values.

CLINICAL RELEVANCE

In contrast to conventional impressions, digital impressions lead to comparable or better results concerning scans up to a quadrant. Consequently, for larger scan volumes, several smaller scans should be performed or, if restoration-related not possible, it is recommended to take conventional impressions.

Efficiency of occlusal and interproximal adjustments in CAD-CAM manufactured single implant crowns - cast-free vs 3D printed cast-based

PURPOSE

The aim of this study was to evaluate the efficiency of occlusal and interproximal adjustments of single implant crowns (SIC), comparing a digital cast-free approach (CF) and a protocol using 3D printed casts (PC).

MATERIALS AND METHODS

A titanium implant was inserted at position of lower right first molar in a typodont. The implant position was scanned using an intraoral scanner and SICs were fabricated accordingly. Ten crowns (CF; n = 10) were subject to a digital cast-free workflow without any labside occlusal and interproximal modifications. Ten other identical crowns (PC) were adjusted to 3D printed casts before delivery. All crowns were then adapted to the testing model, simulating chair-side adjustments during clinical placement. Adjustment time, quantity of adjustments, and contact relationship were assessed. Data were analyzed using SPSS software (P < .05).

RESULTS

Median and interquartile range (IQR) of clinical adjustment time was 02:44 (IQR 00:45) minutes in group CF and 01:46 (IQR 00:21) minutes in group PC. Laboratory and clinical adjustment time in group PC was 04:25 (IQR 00:59) minutes in total. Mean and standard deviation (±SD) of root mean squared error (RMSE) of quantity of clinical adjustments was 45 ± 7 µm in group CF and 34 ± 6 µm in group PC. RMSE of total adjustments was 61 ± 11 µm in group PC. Quality of occlusal contacts was better in group CF.

CONCLUSION

Time effort for clinical adjustments was higher in the cast-free protocol, whereas quantity of modifications was lower, and the occlusal contact relationship was found more favourable.

Mechanical Performance of Chairside Ceramic CAD/CAM Restorations and Zirconia Abutments with Different Internal Implant Connections: In Vitro Study and Finite Element Analysis

(computer-aided design-computer-aided manufacturing) CAD/CAM monolithic restorations connected to zirconia abutments manufactured with a chairside workflow are becoming a more common restorative option. However, their mechanical performance is still uncertain. The aim of this study was to evaluate the mechanical behavior of a combination of a zirconia abutment and monolithic all-ceramic zirconia and lithium disilicate crown manufactured with a chairside workflow, connected to titanium implants with two types of internal connection—tube in tube connection and conical connection with platform switching. They were thermally cycled from 5 °C to 55 °C and were subjected to a static and fatigue test following ISO 14801. The fractured specimens from the fatigue test were examined by SEM (scanning electron microscopy). Simulations of the stress distribution over the different parts of the restorative complex during the mechanical tests were evaluated by means of (finite element analysis) FEA. The mechanical performance of the zirconia abutment with an internal conical connection was higher than that of the tube in tube connection. Additionally, the use of disilicate or zirconia all-ceramic chairside CAD/CAM monolithic restorations has similar results in terms of mechanical fracture and fatigue resistance. Stress distribution affects the implant/restoration complex depending on the connection design. Zirconia abutments and monolithic restorations seem to be highly reliable in terms of mechanical resistance.

Time-efficiency and cost-analysis comparing three digital workflows for treatment with monolithic zirconia implant fixed dental prostheses: A double-blinded RCT

OBJECTIVES

This double-blinded randomized controlled trial investigated economic performance indicators (EPI) in terms of time-efficiency and production costs of 3-unit monolithic zirconium-dioxide (ZrO2) implant fixed dental prostheses (iFDP) in three different workflows.

METHODS

Twenty patients with two Straumann Tissue-Level-Implants received three iFDPs; two were fabricated in proprietary complete digital workflows with intraoral optical scanning and model-free fabrication with company-related CAD/CAM lab-software while one iFDP was manufactured on digitized casts from conventional impressions. The sequence of impression-taking for the three workflows (TRIOS 3/3Shape [Test-1]; Virtuo Vivo/Dental Wings [Test-2]; Impregum/3M Espe [Control]) was randomly allocated. Sixty iFDPs bonded to ti-base abutments were analyzed. Clinical and technical worksteps for Test-1/Test-2/Control were recorded and evaluated for time-efficiency including cost-analysis (CHF=Swiss Francs) using ANOVA-Tests (significance level α=0.05).

RESULTS

Mean total work time, as the sum of clinical plus technical steps, was 97.5 min (SD ± 23.6) for Test-1, 193.1 min (SD ± 25.2) for Test-2, and 172.6 min (SD ± 27.4) for Control. Times were significantly different between Test-1/Test-2 (p < 0.00001), Test-1/Control (p < 0.00001), and Test-2/Control (p < 0.03610). Technical costs were 566 CHF (SD ± 49.3) for Test-1, 711 CHF (SD ± 78.8) for Test-2, 812 CHF (SD ± 89.6) for Control, and were also significantly different for all comparisons (p < 0.00001).

CONCLUSIONS

Test-1 demonstrated the best performance for time-efficiency, Test-2 revealed the worst result. This indicates that digital workflows are not the same and not necessarily superior to analog workflows of monolithic ZrO2 iFDPs. Complexity decreases by reducing the number of steps following complete digital workflows, resulting in lower production costs compared to the mixed analog-digital workflow with conventional impressions.

CLINICAL SIGNIFICANCE

Complete digital workflows comprising intraoral optical scanning without physical models for treatment with monolithic ZrO2 iFDPs is an efficient alternative to mixed analog-digital workflows with conventional impressions and labside digitization of dental casts.

Randomized Clinical Trial comparing clinical adjustment times of CAD/CAM screw-retained posterior crowns on ti-base abutments created with digital or conventional impressions. One-year follow-up

OBJECTIVES

The purpose of this randomized clinical trial was to compare the required time of potential clinical adjustments of posterior screw-retained monolithic zirconia implant retained crowns based on intraoral optical scanning (IOS) or conventional impressions.

MATERIALS AND METHODS

Patients with posterior tissue level implants (Straumann RN) replacing solitary teeth were recruited. Of all patients, impressions were taken with both an IOS (3M™ TDS) and a conventional (polyether) pick-up impression. Randomization was performed after impression taking and patients were to receive either a crown based on the digital or the conventional impression. The time required for adjustments at placement was recorded. Additionally, restoration survival and mechanical complications with a follow-up of one year were documented.

RESULTS

Thirty two patients with 45 implants were included: 23 restorations in the test (IOS) and 22 in the control (conventional) group. The average adjustment time was 3.35 min (SD ± 3.38, range: 0-11 min) for the digital versus 6.09 min (SD ± 4.63, range: 0-18 min) for the conventional impressions (p = .039). A proper fit (no adjustments required) was achieved 39,1% in the digital and 18,2% conventional group respectively. All 45 restorations could be placed within the two planned appointments and only two minor mechanical complications occurred during the first year of function.

CONCLUSIONS

The use of IOS resulted in shorter adjustment times at try-in than conventional impressions for solitary CAD/CAM implant restorations. Screw-retained solitary monolithic zirconia restorations on ti-base abutments show low complication- and survival rates in the short term.

Clinical Evaluation of Resin Composite CAD/CAM Restorations Placed by Undergraduate Students

To evaluate the clinical outcomes of resin composite CAD/CAM restorations in a prospective cohort study, and to assess patient and operator satisfaction after restoration placement, 59 indirect resin composite were placed by supervised undergraduate students, of which 43 restorations were followed over a mean period of 28 months (14–44 months) and evaluated using USPHS criteria. Patient and operator satisfaction levels were assessed using a visual analogue scale (VAS) after restoration placement. A total of 37 patients and 47 restorations were included for further study. Four teeth were extracted—three due to extensive drug-induced secondary caries in the same patient, and one tooth due to large periapical periodontitis after 44 months of service. The overall survival rate was 91.4%, and success rate was 87.2%. Differences between baseline and endpoint scores were significant for marginal discoloration (p < 0.05) and adaptation (p < 0.001). Color match (p < 0.05) and surface texture (p < 0.001) differed significantly, affecting all restoration types. VAS scores for patient and operator satisfaction showed a significant rank correlation (p < 0.01), and pairwise comparison showed significant differences for mean overall patient and operator VAS scores (p < 0.001). Lava Ultimate CAD/CAM may be considered a suitable material for overlays and endocrown restorations when combined with IDS, air abrasion, and MDP-containing adhesive systems. Marginal disintegration may present in inlays and onlays over time.

A Double-Blind Crossover RCT Analyzing Technical and Clinical Performance of Monolithic ZrO2 Implant Fixed Dental Prostheses (iFDP) in Three Different Digital Workflows

This double-blind randomized controlled trial with a crossover design analyzed the technical and clinical performance of three-unit monolithic ZrO₂ implant-fixed dental prostheses (iFDPs), prepared using two complete digital workflows (Test-1, Test-2) and one mixed analog–digital workflow (Control). Each of the 20 study patients received three iFDPs, resulting in 60 restorations for analysis. The quality of the restorations was assessed by analyzing laboratory cross-mounting and calculating the chairside adjustment time required during fitting. All iFDPs could be produced successfully with all three workflows. The highest cross-mounting success rate was observed for the original pairing iFDP/model of the Control group. Overall, 60% of iFDPs prepared with Test-1 workflow did not require chairside adjustment compared with 50% for Test-2 and 30% for Controls. The mean total chairside adjustment time, as the sum of interproximal, pontic, and occlusal corrections was 2.59 ± 2.51 min (Control), 2.88 ± 2.86 min (Test-1), and 3.87 ± 3.02 min (Test-2). All tested workflows were feasible for treatment with iFDPs in posterior sites on a soft tissue level type implant system. For clinical routine, it has to be considered that chairside adjustments may be necessary, at least in every second patient, independent on the workflow used.

The accuracy of single implant scans with a healing abutment-scanpeg system compared with the scans of a scanbody and conventional impressions: An in vitro study

PURPOSE

To compare the accuracy of polyvinylsiloxane (PVS) impressions and intraoral scans when a healing abutment-scanpeg system (HASP) or a conventional scanbody (CSB) was used on a single implant.

MATERIALS AND METHODS

A maxillary model with an implant (4.0 × 11 mm) (Neoss) and a CSB or an HASP (Neoss) was scanned by using a laboratory scanner (Ceramill Map 600; Amann Girrbach) (reference scans) and an intraoral scanner (Trios 3) (n = 10). PVS open-tray impressions were also made and stone casts of the model with a CSB were digitized with the laboratory scanner. Intraoral scanner and cast scans were superimposed to their reference scans. On superimposed scans, points were selected on HASP and CSB to calculate distance deviations (at points 1-4) and angular deviations (at points 5 and 6 on CSB and PVS, and 5-8 on HASP) between scans (trueness), and their variation (precision). The deviation data was analyzed with ANOVA and pairwise comparisons (trueness) with Tukey's adjustment, and F-tests (precision).

RESULTS

At point 1, PVS had lower trueness than CSB (difference in means (DIMs) = 0.184 mm, p = 0.006) and HASP (DIMs = 0.122 mm, p = 0.042). At point 3, CSB had higher trueness than HASP (DIMs = 0.134 mm, p = 0.001). Angular deviations with PVS were higher than with CSB (DIMs = 0.6°, p = 0.013) and HASP (DIMs = 0.7°, p = 0.005). CSB had higher precision than PVS (p < 0.05). HASP had higher precision than PVS for distance (Point 1)(p < 0.001) and angular deviations (p < 0.05). Deviation differences within the HASP parts were not significant.

CONCLUSION

The accuracy of intraoral scans and PVS impressions of an implant was similar.

CLINICAL RELEVANCE

The combined healing abutment-scanpeg system and the conventional scanbody can be recommended for scans of anterior single implants with the intraoral scanner used.

Clinical Evaluation of Crestal Bone Levels, Peri-Implant Indices, and Mucosal Margin Position of Immediately Impressed Posterior Dental Implants: A Cross-Sectional Study

PURPOSE

This is a cross-sectional clinical study to evaluate crestal bone levels, mucosal margin position, probing depths, bleeding on probing, and plaque and bleeding indices of implants restored with an immediate impression workflow compared to implants restored with a delayed impression workflow.

MATERIALS AND METHODS

Patients who had received a posterior single implant crown in the premolar and molar regions were identified and scheduled for a single-visit study appointment. Outcome measurements included soft tissues peri-implant indices, peri-implant mucosal margin position, and crestal bone levels. Several systemic-, local-, and prosthesis-related factors were recorded. Bitewing radiographs were used to assess crestal bone levels. Wilcoxon rank sum test was used to compare the medians of continuous measurements and Pearson chi-square test (or Fisher's exact test) was used to compare the distributions of categorical variables between the two groups.

RESULTS

Twenty eight patients were included. Crestal bone levels, peri-implant mucosal margin position and peri-implant soft tissue parameters for the immediately impressed group were not statistically different from the delayed impressed group, except for probing depth for the immediately impressed buccal site, which was less than that of the delayed group. Mesial bone level for cement-retained crowns was significantly more coronal than for screw-retained ones.

CONCLUSIONS

While an isolated statistical difference was found in probing depth, the current study suggests that there is no clinically significant difference between implants impressed with immediate and delayed implant workflows when considering crestal bone levels, peri-implant mucosal margin position, and most peri-implant indices.

Patient Satisfaction with Implant-Supported Monolithic and Partially Veneered Zirconia Restorations

The digital workflow and the application of Computer-Aided Manufacturing (CAM) to prosthodontics present the clinician with the possibility of adopting new materials that confer several advantages. Especially in the case of zirconia, these innovations have profoundly changed daily practice. This paper compares the satisfaction and perception of patients who received implant-supported single crowns (SC) and fixed partial dentures (FPD) made from zirconia, either monolithic or partially veneered, after 3 years of follow-up; the success and survival rate of these restorations were also measured. Forty patients, who had been previously treated with implant-supported SC or FPD, either monolithic or partially veneered, and submitted to a yearly maintenance program, were recalled 3 years after their treatment and requested to complete an 8-question questionnaire regarding their perceptions of the treatment. Any mechanical or biological complication that had occurred from the time of delivery was also recorded. Patients that experienced ≥1 complication were less likely to be prone to repeat the treatment. The 3-year success rate was 92.6% for monolithic restoration and 92.3% for partially veneered restoration, while the survival rate was 100% for both restorations. The 3-year follow-up found that monolithic and partially veneered zirconia restorations are both well-accepted treatment options, and patients preferred the veneered restorations (0.76, p < 0.05) from an aesthetic point of view. According to our results, monolithic and veneered zirconia restorations are both reliable treatment options and are both equally accepted by patients.

Comparison of peri-implant clinical outcomes of digitally customized and prefabricated abutments: A systematic review and meta-analysis

BACKGROUND

Digitally customized abutments are increasingly used in contemporary implant prosthodontics.

PURPOSE

This systematic review and meta-analysis aimed at comparing the peri-implant clinical outcomes of digitally customized and prefabricated abutments.

MATERIALS AND METHODS

The search strategies included electronic databases (PubMed, Embase, Scopus, and Cochrane clinical trials database) and related journals up to September, 2020. A qualitative and quantitative synthesis was performed on data extracted from the included studies.

RESULTS

Three RCTs (number of patients = 120; number of dental implants = 120) and two prospective cohort studies (number of patients = 144; number of dental implants = 144) with one to three-year follow-up periods were included. The quantitative analyses did not demonstrate a significant difference between digitally customized and prefabricated abutments for peri-implant pocket depth (P = 0.62), plaque index (P = 0.67), bleeding on probing (P = 0.43), keratinized mucosa width (P = 0.75), and pink aesthetic score (P = 0.30) at one-year follow-up visit. The qualitative analyses for marginal bone level change, calculus accumulation, implant survival rate, implant success rate, white aesthetic score, and patient-reported outcomes did not demonstrate a significant difference between two groups during 1 to 3-year follow-up visits.

CONCLUSION

The current data do not provide evidence of significant differences between two abutment fabrication methods in terms of peri-implant clinical outcomes within short-term period (CRD42020170807).

Evaluation of implant-supported connecting crowns fabricated by optical and conventional impression methods

PURPOSE

To investigate the accuracy of implant-supported connecting crowns fabricated with digital definitive casts and conventional definitive casts.

METHODS

Using a master model with two implant bodies inserted into the right mandibular molar area, 10 digital definitive casts were fabricated. Additionally,10 conventional definitive casts were fabricated. The distance and angle between the two abutments of each definitive cast were compared. To compare the amount of lift of the incisal pin, each of the 10 superstructures was fabricated via computer-aided design/computer-aided manufacturing and then returned to the master model.

RESULTS

No significant difference was observed for either the angle or the distance between the two abutments. The amount of lift of the incisal pin when the superstructure obtained via the optical method was returned to the master model was significantly larger than that when the superstructure obtained via the conventional method was returned to the definitive cast and the master model. No significant difference was observed after occlusal adjustment of the superstructures obtained using the conventional method.

CONCLUSIONS

The precision of definitive casts obtained via the optical method was virtually equal to that of definitive casts obtained via the conventional method. The accuracy of implant-supported connecting crowns fabricated using the optical method was significantly lower than that of implant-supported connecting crowns fabricated using the conventional method. This is attributed to the alignment of the maxillary and mandibular digital definitive casts.

Fatigue fracture resistance of titanium and chairside CAD-CAM zirconia implant abutments supporting zirconia crowns: An in vitro comparative and finite element analysis study

STATEMENT OF PROBLEM

Zirconia abutments with a titanium base are promising candidates to substitute for titanium abutments based on clinical studies reporting good short-term survival rates. However, information on the long-term performance of zirconia abutments supporting ceramic crowns is scarce.

PURPOSE

This in vitro comparative and finite element analysis study compared the fatigue life performance of ceramic computer-aided design and computer-aided manufacturing (CAD-CAM) monolithic restorations and zirconia abutments fabricated with a chairside workflow connected to a titanium interface versus titanium abutments.

MATERIAL AND METHODS

Twenty-two internal connection implants were divided into 2 groups, one with a zirconia abutment and monolithic ceramic zirconia crown (ZZ) and the other with a titanium abutment and zirconia crown (TiZ). They were subjected to a fatigue test to determine the fatigue limit and fatigue performance of each group as per International Organization for Standardization (ISO) 14801. Microstructural analysis of the fracture surfaces was conducted by using a scanning electron microscope (SEM). Simulations of the in vitro study were also conducted by means of finite element analysis (FEA) to assess the stress distribution over the different parts of the restoration.

RESULTS

The fatigue limit was 250 N for the TiZ group and 325 N for the ZZ group. In both groups, the screw was the part most susceptible to fatigue and was where the failure initiated. In the zirconia abutment models, the stress on the screw was reduced.

CONCLUSIONS

Chairside CAD-CAM zirconia abutments with a titanium base supporting zirconia crowns had higher fatigue fracture resistance compared with that of titanium abutments.

Fracture strength of various titanium-based, CAD-CAM and PFM implant crowns

OBJECTIVE

CAD-CAM has dramatically advanced dental restorative procedures to include implant-supported crowns. The purpose of this study was to compare the fracture resistance following mechanical loading and thermocycling of various screw-retained and cement-retained ceramic and polymethylmethacrylate material combinations using the TiBase abutment compared to PFM implant-supported crowns.

OVERVIEW

Twelve implant restorations were fabricated for each of eight groups. Three groups were screw-retained and five groups were cement-retained implant restorations. The ceramic and polymethylmethacrylate restorations were fabricated on the TiBase abutment while the PFM restorations were fabricated on an UCLA abutment. Data were analyzed with a one way Analysis of Variance and Tukey's post-hoc test to evaluate the effect of abutment and crown type on fracture load (alpha = 0.05). A significant difference was found in the maximum fracture load between groups (P < 0.001).

CONCLUSIONS

The screw-retained implant restorations demonstrated higher fracture loads than their cement-retained counterparts. The TiBase abutment compared favorably to the UCLA abutment.

CLINICAL SIGNIFICANCE

The TiBase abutment is a titanium insert which combines the esthetics of a ceramic abutment with the mechanical properties of a titanium abutment and should be considered a viable clinical alternative to the conventional implant-supported PFM crown based on theses in vitro results and in context of in vivo studies. The lithium disilicate hybrid abutment/crown implant-supported restoration utilizing the TiBase abutment may be an ideal clinical choice due to simplicity, single appointment CAD-CAM, and esthetics.

Comparison of Intraoral and Extraoral Digital Scanners: Evaluation of Surface Topography and Precision

The aim of this study was to evaluate the surface topography and the precision measurements of different intraoral and extraoral digital scanners. A reference model of a maxillary arch with four implant analogs was prepared and scanned by three intraoral and two extraoral scanners. The reference model was scanned fifteen times with each digital scanning system, investigating the surface topography and precision measurements for the same-arch and cross-arch measurements. The data was exported to 3D inspection and mesh-processing software (GOM Inspect, Braunschweig, Germany). Statistical analysis was performed using a one-way Analysis of Variance (ANOVA) with the Tukey method for pairwise comparisons. The effect of parameters on generating the surface topography was analyzed by Univariate Linear Regression Analysis. Of the scanner systems evaluated, iTero (IT) exhibited the most number of triangulation points, followed by Trios 3 Shape (TR) and Straumann Cares (SC). There were no significant differences observed in the surface topography when comparing flat and contoured surfaces, the anterior and posterior position, and interproximal areas. For the precision measurement in the same quadrant, no statistical difference was noted between intra- and extraoral scanners. However, the extraoral scanners showed substantially higher precision measurements for the cross-arch measurement. Surface topography did not correlate to precision. Rather, precision correlated with the scanning mechanism. For a quadrant scanning, both intraoral and extraoral scanners are recommended, but extraoral scanners are recommended for a full-arch scanning.

Clinical efficiency and patient preference of digital and conventional workflow for single implant crowns using immediate and regular digital impression: A meta-analysis

OBJECTIVE

To assess whether digital workflow gives better results than the conventional one in the single implant crowns, when analyzing the impression time, patient preference, time efficiency, and adjustment time.

MATERIAL AND METHODS

MEDLINE, Embase, and Cochrane were searched and supplemented via hand search up to June 19, 2019. Only clinical trials assessing conventional versus digital workflows for single implant crowns were included. Impression time was evaluated using random effects meta-analysis, while patient preference, adjustment time, and time efficiency were reported descriptively.

RESULTS

Among 1,334 publications identified, ten studies were included. The random effects models revealed statistically significant reduction in time in the digital impression group when compared to the conventional group by the mean meta-analysis (MD: 8.22 [95% CI: 5.48, 10.96]). Analysis from immediate digital impression versus conventional (MD: 3.84 [95% CI: 3.30, 4.39]) and regular digital impression versus conventional (MD:10.67 [95% CI: 5.70, 15.65]) showed statistically significant reduction in time on using the digital impression. Impression time in the digital process ranged between 6 min 39 s and 20 min, whereas for conventional, it was between 11.7 and 28.47 min. Patients showed greater preference for digital impression. Adjustment time in the digital process ranged between 1.96 and 14 min, whereas for conventional, it was between 3.02 and 12 min. Time efficiency in the digital process ranged between 36.8 and 185.4 min, whereas for conventional, it was between 55.6 and 332 min.

CONCLUSION

The digital workflow has demonstrated better clinical efficiency considering impression time, patient preference, and time efficiency. According to the adjustment time, different results were presented.

In-vitro polishing of CAD/CAM ceramic restorations: An evaluation with SEM and confocal profilometry

AIM

The objective of this In-vitro investigation was to analyze and compare the surface after polishing of 63 all-ceramic restorations fabricated out of monolithic zirconium dioxide (ZIR), lithium disilicate (LS) or feldspathic ceramic (FC) under standardized laboratory conditions with different protocols. The primary outcome was defined as the roughness (R_a/S_a) of different ceramic surfaces after distinctive polishing procedures.

MATERIAL AND METHODS

The study set-up consisted of three main groups: ZIR, LS, FC (20 crowns each), every group divided into two sub-groups (10 crowns each) depending on the polishing method. The untouched glazed surface of one crown per material served as a control. Every crown displayed a defined supra-contact at the palatal cusp which was removed with a fine grain (38-45 μm) diamond bur. Surface polishing was carried out with either a two-step system (one kit for zirconium dioxide (ZIR₂), another kit for lithium disilicate (LS₂) and feldspatic ceramic (FC₂)), or a three-step system (ZIR₃, LS₃, FC₃) under standardized conditions. Roughness parameters (R_a and S_a) were measured by means of confocal profilometry. Specimens were also visually inspected with scanning electron microscopy (SEM). Statistical analyses were performed using SPSS Statistics software.

RESULTS

Visual examination of the specimens using SEM showed several inhomogeneities on the glazed surface of the control samples, i.e. pores and particles. On every test sample, the grinding curves of the diamond bur were still recognizable. Polishing revealed similar median R_a 0.491 μm (ZIR₂) and 0.434 μm (LS₂) after two-step polishing (p = 0.754), and 0.311 μm (ZIR₃) and 0.208 μm (LS₃) after three-step polishing (p = 0.917). Surface roughness in group FC measured 0.889 μm (FC₂) after the two-step polishing process and 0.903 μm (FC₃) following three-step surface refinement. No significant difference was detectable between surface roughness of glazed controls compared to either polished surfaces with two-step or three-step treatment within one material. ZIR and LS presented significantly lower median roughness R_a after two-step and three-step procedures than test samples of FC, measured subsequent to either of the polishing methods (p = 0.016, p = 0.009).

CONCLUSION

The surface roughness of ZIR, LS and FC crowns after the use of chairside polishing kits was comparable with the roughness measured before occlusal adjustment. A two-step procedure showed as good results as a three-step process. A smoother surface was obtained for ZIR and LS compared to FC with both polishing protocols.

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.

The current clinical relevancy of intraoral scanners in implant dentistry

Optical technology has provided a paradigm shift in implant dentistry. However, there is little information about the use of optical technology in implant dentistry, since this technology is relatively new and has been evolving under the current conditions. In the present narrative literature review, the effects of intraoral scanners (IOSs) use on accuracy and the operating time, as well as safety and patient perception, in implant dentistry were evaluated from the clinical perspective. The accuracy of digital scans with IOSs was comparable to the conventional impression techniques for single or partial prostheses, and the digital scans with IOSs are time efficient when taking impressions for single- or double-abutments. However, the accuracy and time efficiency are decreased for multiple implant scans or large-area scans with IOSs use. Patient satisfaction with and preference for IOSs scans are generally superior to those with conventional impression procedures.

Accuracy of digital and conventional dental implant impressions for fixed partial dentures: A comparative clinical study

PURPOSE

The newest technologies for digital implant impression (DII) taking are developing rapidly and showing acceptable clinical results. However, scientific literature is lacking data from clinical studies about the accuracy of DII. The aim of this study was to compare digital and conventional dental implant impressions (CII) in a clinical environment.

MATERIALS AND METHODS

Twenty-four fixed zirconia restorations supported by 2 implants were fabricated using conventional open-tray impression technique with splinted transfers (CII group) and scan with Trios 3 IOS (3Shape) (DII group). After multiple verification procedures, master models were scanned using laboratory scanner D800 (3Shape). 3D models from conventional and digital workflow were imported to reverse engineering software and superimposed with high resolution 3D CAD models of scan bodies. Distance between center points, angulation, rotation, vertical shift, and surface mismatch of the scan bodies were measured and compared between conventional and digital impressions.

RESULTS

Statistically significant differences were found for: a) inter-implant distance, b) rotation, c) vertical shift, and d) surface mismatch differences, comparing DII and CII groups for mesial and dist al implant scan bodies (P≤.05).

CONCLUSION

Recorded linear differences between digital and conventional impressions were of limited clinical significance with two implant-supported restorations.

Intrasubject comparison of digital vs. conventional workflow for screw-retained single-implant crowns: Prosthodontic and patient-centered outcomes

OBJECTIVES

The aim of this intrasubject clinical study was to measure and compare prosthodontic and patient-reported outcome measures (PROMs) in the fabrication of implant-supported, all-ceramic single crowns with a full digital workflow and a conventional workflow.

MATERIALS AND METHODS

Thirty-one patients were subjected to first a digital (test group) and then a conventional impression (control group) at the same visit. From the intraoral optical scanner (IOS), a screw-retained, monolithic crown was delivered according to a complete digital workflow (no cast), whereas a veneered crown on a zirconia (Zi) frame was provided as a control treatment. Both crowns were assessed during the clinical stages of try-in. Prosthodontic outcomes (contact points, occlusion, PROMs, and esthetic results using the white esthetic score [WES]) were assessed.

RESULTS

Occlusion and interproximal contacts showed comparable results for the two workflows (p = 0.37 and p = 0.36, respectively), whereas the global WES was significantly higher (p < 0.0001) in the control group. Patient satisfaction scores, using visual analog scales (VAS), were significantly better for IOS than for conventional impressions (p = 0.0098). On the contrary, patients' perception of the esthetic outcomes showed significantly higher value (p < 0.0001) in the control group.

CONCLUSIONS

Both workflows allowed the delivery of ceramic crowns within two appointments. The clinical fit was acceptable in both groups. A better esthetic outcome, in both patients' and clinicians' opinions, was found in the control group. PROMs showed higher satisfaction with the IOS.

Immediate loading of multiple splinted implants via complete digital workflow: A pilot clinical study with 1-year follow-up

BACKGROUND

Complete digital workflow attracts more attention in implant dentistry.

OBJECTIVES

To explore the feasibility and short-term clinical results of immediate loading of multiple implants with fixed temporary bridges (2-4 teeth span) by complete digital workflow, and to evaluate the three-dimensional (3D) deviation of digital impression comparing with traditional impression method.

MATERIAL AND METHODS

A total of 31 partial edentulous patients (16 females and 15 males) were recruited in this study. Digital impressions were taken immediately after implant placement, and implant-supported splinted temporary bridges were fabricated through a full digital approach (model free) and delivered within 24 hours. Final restorations were finished 4 months after surgery via traditional impression technique. Subjects were followed 1 year after treatment. 3D impression deviations were analyzed by comparing the digital and conventional impression methods. Time costs for the full digital approach were recorded. Implant survival rate, marginal bone levels were evaluated.

RESULTS

All the recruited subjects finished this study. Seventy-four implants were surgically placed and immediately loaded with 34 temporary bridges fabricated through a full digital approach. Digital impression deviation compared with traditional impression method was 27.43 ± 13.47 μm. Time costs for chair side and laboratory were 32.55 ± 4.73 and 69.30 ± 10.87 minutes, respectively. Marginal bone alterations were -1.58 mm and -1.69 mm at the time of 4 and 12 months after surgery. The implants had a survival rate of 100% at the 1-year follow-up time.

CONCLUSIONS

Immediate loading of multiple implants in partial edentulous (2-4 teeth span) patients with full digital approach is clinically applicable. The 3D discrepancy between digital and traditional impression is within clinical acceptable range.

Conventional versus Digital Impressions for Full Arch Screw-Retained Maxillary Rehabilitations: A Randomized Clinical Trial

Background: The objective of this study was to compare conventional versus digital impressions for Full-Arch maxillary rehabilitations. Methods: Patients selected for this study were treated with full-arch screw-retained rehabilitations supported by six immediately loaded dental implants. Patients have been scheduled randomly into control (conventional impression group, CIG) and test (digital impression group, DIG) groups respectively for a fully conventional workflow and a fully digital workflow. In both groups, within 24 h, temporary prostheses were delivered. Four months after the implant positioning, the two groups dealt with the fabrication of definitive restorations: conventional pick-up was performed in the control group, and definitive digital impressions were carried out in the test group. The time involved following these two procedures was recorded. Patients underwent intraoral digital radiographs to evaluate the accuracy of the framework-implant connection, check for the presence of voids at the bar-implant connection and measure bone level. Criteria used to assess success at the prosthetic level were the occurrence of prosthetic maintenance, the absence of fractures of the acrylic resin superstructure and voids. Results: A total of 50 patients received immediately loaded prostheses supported by six implants (total 300 implants). A fixture and prosthetic survival rate of 100% was observed. All digital X-ray examinations revealed a bar-implant connection accuracy and no voids. Differences that were not statistically significant (p > 0.05) in marginal bone loss were found between control and test groups. Significantly less time was spent to perform digital impression procedure (p < 0.05). Conclusions: Clinical and radiological results of the test group advocate a satisfactory accuracy and predictability of the intraoral scanner (IOS) to be a reliable alternative in clinical practice for implant full-arch rehabilitations and suggest fabrication of definitive restorations with a successful marginal fit precision.

Is the use of digital technologies for the fabrication of implant-supported reconstructions more efficient and/or more effective than conventional techniques: A systematic review

OBJECTIVE

To identify clinical studies evaluating efficiency and/or effectiveness of digital technologies as compared to conventional manufacturing procedures for the fabrication of implant-supported reconstructions.

MATERIALS AND METHODS

A systematic search from 1990 through July 2017 was performed using the online databases Medline, Embase, and Cochrane-Central-Register-of-Controlled-Trials. Literature on efficiency and/or effectiveness during the impression session, the manufacturing process, and the delivery session were included.

RESULTS

In total, 12 clinical studies were included. No meta-analysis was performed due to a large heterogeneity of the study protocols. Nine publications reported on posterior single implant crowns (SIC) and three on full-arch reconstructions. Mean impression time with intraoral scanners ranged between 6.7 and 19.8 min, whereas the range for conventional impressions was 8.8 and 18.4 min. In a fully digital workflow (FD-WF) for posterior SIC, mean fabrication time ranged between 46.8 and 54.5 min (prefabricated abutment) and 68.0 min (customized abutment). In a hybrid workflow (H-WF) including a digitally customized abutment and a manual veneering, mean fabrication time ranged between 132.5 and 158.1 min. For a conventional porcelain-fused-to-metal-crown, a mean time of 189.8 min was reported. The mean time for the delivery of posterior SIC ranged between 7.3 and 7.4 min (FD-WF), 10.5 and 12.5 min (H-WF), and 15.3 min (conventional workflow, C-WF). The FD-WF for posterior SIC was more effective than the H-/C-WF.

CONCLUSIONS

The implementation of the studied digital technologies increased time efficiency for the laboratory fabrication of implant-supported reconstructions. For posterior SIC, the model-free fabrication, the use of prefabricated abutments, and the monolithic design was most time efficient and most effective.

Digital versus Traditional Workflow for Posterior Maxillary Rehabilitations Supported by One Straight and One Tilted Implant: A 3-Year Prospective Comparative Study

Objectives

The aim of the study was to evaluate and compare digital and traditional prosthetic workflow for posterior maxillary restorations supported by an upright and a distally tilted implant at 3-year follow-up.

Materials and Methods

Twenty-four patients were treated in the posterior maxilla with 24 immediately loaded axial and 24 distally tilted implants supporting 3-unit or 4-unit screw-retained prostheses. Three months after initial loading patients were randomly stratified into two groups: definitive traditional impressions were carried out in the control group, while digital impressions were performed in the test group. The framework-implant connection accuracy was evaluated by means intraoral digital radiographs at 3, 6, 12, and 36 months of follow-up examinations. Outcome considerations comprised implant and prosthetic survival and success rates, marginal bone level changes, and required clinical time to take impressions.

Results

A total of 24 patients received immediately loaded screw-retained prostheses supported by an upright and a distally tilted implant (total 48 implants). No implant dropouts occurred, showing an overall survival rate of 100% for both groups. None of the 24 fixed prostheses were lost during the observation period (prosthetic survival rate of 100%). No statistically significant differences in marginal bone loss were found between control and test groups. The digital impression procedure required on average less clinical time than the conventional procedure.

Conclusions

Clinical and radiologic results suggest that digital impression is a predictable procedure for posterior maxillary restorations supported by an upright and a distally tilted implant.

Digital technology in fixed implant prosthodontics

Digital protocols are increasingly influencing prosthodontic treatment concepts. Implant-supported single-unit and short-span reconstructions will benefit mostly from the present digital trends. In these protocols, monolithic implant crowns connected to prefabricated titanium abutments, which are created based on data obtained from an intraoral scan followed by virtual design and production, without the need of a physical master cast, have to be considered in lieu of conventional manufacturing techniques for posterior implant restorations. No space for storage is needed in the complete digital workflow, and if a remake is required a replica of the original reconstruction can be produced quickly and inexpensively using rapid prototyping. The technological process is split into subtractive methods, such as milling or laser ablation, and additive processing, such as three-dimensional printing and selective laser melting. The dimensions of the supra-implant soft-tissue architecture can be calculated in advance of implant placement, according to the morphologic copy, and consequently are individualized for each patient. All these technologies have to be considered before implementing new digital dental workflows in daily routine. The correct indication and application are prerequisite and crucial for the success of the overall therapy, and, finally, for a satisfied patient. This includes a teamwork approach and equally affects the clinician, the dental assistant and the technician as well. The digitization process has the potential to change the entire dental profession. The major benefits will be reduced production costs, improvement in time efficiency and fulfilment of patients' perceptions of a modernized treatment concept.

Accuracy of multi-unit implant impression: traditional techniques versus a digital procedure

OBJECTIVES

The objective of this study was to evaluate the accuracy of different impression techniques on multiple implants.

MATERIAL AND METHODS

A master cast simulating a jaw with four implants was used. Eight impression techniques were tested: open tray-polyether#1, open tray plus splint of impression copings with acrylic resin-polyether#1, closed tray-polyether#1, open tray-polyether#2, open tray-splint-polyether#2, closed tray-polyether#2, open tray-impression plaster, and digital impression (DI). Five impressions of the master cast were taken with each traditional impression (TI) technique, pouring 35 sample casts. Three different clinicians took 5 DI each (n = 15). A three-dimensional coordinate measurement machine (CMM) was used to measure implant angulation and inter-implant distances on TI casts. TI data and DI Standard Tessellation Language datasets were compared with the master cast. The best and the worst impressions made with TI and DI were selected to fabricate four milled titanium frameworks. Passive fit was evaluated through Sheffield test, screwing each framework on the master cast. Gaps between framework-implant analogs were measured through a stereomicroscope (×40 magnification).

RESULTS

Statistically significant differences in accuracy were found comparing the different impression techniques by CMM (p < 0.01). DI performed the best, while TI techniques revealed a greater variability in the results. Sheffield test revealed a mean gap of 0.022 ± 0.023 mm (the best TI), 0.063 ± 0.059 mm (the worst TI), 0.015 ± 0.011 mm (the best DI), and 0.019 ± 0.015 mm (the worst DI).

CONCLUSIONS

Within the limits of this in vitro study, the digital impression showed better accuracy compared to conventional impressioning.

CLINICAL RELEVANCE

The digital impression might offer a viable alternative to traditional impressions for fabrication of full-arch implant-supported prostheses with satisfactory passive fit.

Reconstruction of Mandible: A Fully Digital Workflow From Visualized Iliac Bone Grafting to Implant Restoration

PURPOSE

Although digital aids can help surgeons compensate for the shortcomings of traditional mandibular reconstruction techniques to perform surgery more precisely and effectively, the use of these digital techniques has often been fragmented, divided, and incomplete. This article describes the workflow of a fully digital mandibular reconstruction to explore the proper indications and discusses innovations based on the accuracy and effectiveness of digital techniques.

MATERIALS AND METHODS

A restoration-oriented mandibular reconstruction was performed by applying different digital techniques. Preoperative virtual surgery and rapid prototyping were used to aid the vascularized iliac bone graft surgery, which offered a solid basis for the ensuing treatment. Subsequently, implant rehabilitation was accomplished with the assistance of computer-assisted design and manufacture, laser treatment, and selective laser melting techniques.

RESULT

The workflow of the fully digital mandibular reconstruction successfully achieved a restoration-oriented treatment. These predictable, accurate, and effective digital techniques improved the consistency of pretreatment design and follow-up treatment. The treatment sequence achieved high predictability and reproducibility owing to the use of digital techniques.

CONCLUSION

This study shows that a digital workflow can be predictable, accurate, and effective, which suggests that it could be a valid digital protocol for developing a treatment sequence for patients with jaw defects caused by trauma, congenital anomalies, or mandibular tumor resection.

Monolithic implant-supported lithium disilicate (LS2) crowns in a complete digital workflow: A prospective clinical trial with a 2-year follow-up

BACKGROUND

The technical development of digital processing allows the production of anatomically full-contoured implant-supported restorations.

PURPOSE

The aim of this prospective clinical trial was to analyze the treatment concept of monolithic lithium disilicate (LS2) single-unit restorations in a complete digital workflow.

MATERIAL AND METHODS

Forty-four patients were restored with 50 screw-retained monolithic implant LS2 crowns bonded to pre-fabricated titanium abutments on soft tissue level implants (Institut Straumann AG, Basel, Switzerland) in premolar and molar sites. All implant restorations were digitally designed after intraoral optical scanning (IOS) and CAD/CAM-processing without physical model situations. Study participants were clinically and radiographically examined based on an annually performed follow-up. The "Functional Implant Prosthodontic Score" (FIPS) was applied for objective outcome assessment after 2 years of loading. Five variables were defined for FIPS evaluation, resulting in a maximum score of 10 per implant restoration. Descriptive statistics were calculated for mean scores standard deviations, medians, and Q₂₅ -Q₇₅ .

RESULTS

All patients could be successfully treated within two clinical appointments. No clinical modifications were necessary for the seating of the monolithic crowns, neither for interproximal nor occlusal sites. The implant LS2 restorations demonstrated survival rates of 100% without any technical or biological complications after 2 years. The mean total FIPS score was 7.7 ± 1.0, ranging from 6 to 10.

CONCLUSIONS

CAD/CAM-produced monolithic implant crowns out of LS2 in a complete digital workflow seem to be a feasible treatment concept for the rehabilitation of single-tooth gaps in posterior sites under mid-term observation.