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.


Background and rationale
The best possible dental prosthesis solutions and their continuous progress are due to the presence of prosthodontic methods.Traditionally, fixed partial denture (FPD) fabrication has remained closely associated with conventional workflows.While in the past years, new technologies have come into focus, digital technologies have become the new trend and show promise to be more smart and dynamic solutions.All clinicians need to understand this paradigm change and their comparative analysis is significant to facilitate evidence-based clinical decision-making [1][2][3][4][5].

Scope of the review
This study will focus on the systematic review inclusive of many different aspects in terms of conventional and digital workflow in the fabrication of fixed dental prostheses.With the scope spanning across a whole spectrum of aspects such as accuracy, marginal and internal fit level, efficiency, cost-effectiveness, patientreported outcome measures, and longevity, it is therefore critical to ensure these innovations are standardized, accessible, and of high quality [6][7][8].

Objective
Moreover, the main purpose of this review is to evaluate literature sources and give a clear summary that addresses the benefits and disadvantages pertaining to the traditional and digital workflows during the procedure of fabrication of FPDs.We will narrowly concentrate on the thorough scrutiny of the available evidence and provide observations that should help the clinicians to match the most suitable approach to an individual patient considering both his/her needs and clinic requirements.The PICO question was framed to identify and structure the fundamental components of systematic review: "Is a complete digital workflow with intraoral optical scanning (IOS) plus virtual design plus monolithic restoration for patients receiving prosthodontic treatments with tooth-supported or implant-supported fixed reconstructions comparable to conventional workflows with conventional impression and/or conventional casting and/or lost-wax-technique and/or framework and veneering in terms of feasibility in general or success-analysis including precision and accuracy assessment or economics or aesthetics or patient-centered factors?"A MEDLINE (PubMed), Cochrane, Scopus, Science directory, and ScienceDirect search was conducted using the following search terms which were grouped into categories: Population: adult patients who require FPD or fixed dental prosthesis, Intervention: digital workflow in fabrication of FPD, Control: conventional workflow in fabrication of FPD and Outcome: success rate, accuracy, precision, time efficiency, cost efficiency, patient satisfaction, feasibility.

Search Strategy
A systematic search was performed in the following online databases: Scopus, Web of Science, PubMed, Science Direct, and Cochrane Library.Searches were conducted from 2012 to 2023; conference proceedings and abstracts were also accessed when possible.Electronic search strategies were customized to each database.Language was restricted to English in the search strategy.The Mesh (Medical Subject Headings) terms and keywords were paired together with the use of Boolean operators "AND" and "OR" to make keywords.

Inclusion Criteria
Clinical trials and cross-sectional studies (RCT, non-RCT), studies on adult population with missing teeth and endodontically treated teeth, studies in which digital workflows were used for the fabrication of FPDs, studies in which conventional workflows were used for the fabrication of FPDs, articles with English language or other where English translation is possible, and articles from January 2012 to June 2023 were included.

Exclusion Criteria
Case reports, reviews, expert opinions, in-vitro studies, only abstracts, and studies on primary teeth/pediatric patients were excluded.

Systematic Search Strategy
Two independent reviewers (MM and SH) meticulously conducted a three-step selection process to identify relevant studies.The first stage was title scan where irrelevant studies were excluded based on a quick title review.The second stage was abstract and summary dive in which summaries and abstracts were examined to filter for studies based on the study type, digital intervention type, patient population size, and outcome variables assessed.The third stage was data extraction in which full texts of shortlisted studies were rigorously reviewed.Data relevant to study eligibility was extracted using a pre-defined form.

Data Extraction
The details of all the studies were collected as follows: year of publication, Name of the authors, study design, type of workflow or restoration, outcome assessed, and results.The data was collected by the reviewers separately and was converted in the form of a data extraction sheet, followed by compilation of the study results.

Study Risk of Bias and Quality Assessment
The quality and risk of bias of the included studies were assessed by the two independent reviewers.First, the duplicate sources were removed, and then study titles and abstracts were reviewed to ensure they are relevant.Following that, a full text review was done and the studies that fulfilled the inclusion criteria were included.Critical appraisal of randomized controlled trials (RCTs) and observational studies was done according to the NIH tool.The initial search resulted in 11790 articles.After removing irrelevant and duplicate articles, 121 full-text studies remained.These were then screened based on their titles and abstracts to assess eligibility according to the pre-defined inclusion/exclusion criteria.Ultimately, 22 articles were selected for in-depth qualitative analysis.Figure 1 describes the study selection process for this systematic review as per the PRISMA protocol [9].Among these, 12 studies were RCTs, and the other 10 were non-randomized such as prospective cohort and observational studies.

Bias Assessment Within Individual Studies
Risk of bias in the RCT was divided considering the following criteria: the overall low risk of bias of the findings if all of the criteria were met; the unclear risk of bias if some criteria were met but at least one of them was only partially met; the high risk of bias if the findings lacked the fulfillment of at least one of the criteria."High risk of bias" would imply "poor quality" and be assigned a grade."Low risk of bias" refers to the grade of "good quality" rating.Four of the included RCTs would be considered to have a low-risk bias which makes them good quality while the other eight would be found to have an unclear risk bias which denotes that they are fair quality (Tables 1, 2).The NIH tool was employed to evaluate the quality of the included studies [32].Two studies scored a low risk of bias translating to good quality and eight studies scored an unclear risk of bias translating to fair quality (Tables 1, 2).Results of individual studies are shown in Table 3.The mean operating time for the DW crowns was less than CW.The mean total adjustment times of CW was more than DW.

No. Year Author
The mean score regarding self-perception of the esthetic outcome was also more for DW.No significant differences in the FIPS and PES.However, the conventional workflow showed better values for the papillae.Vertical margin discrepancy -greater than 120 μm in crowns -CAD-CAM systems and below 100 μm -conventional technique.
Internal discrepancy was less for crowns fabricated with an analog workflow.

Discussion
The studies compared the digital workflow and conventional workflow based on different factors.

Time Efficiency
Zhang et al. [16] and Capparé et al. [18] found that complete digital workflows significantly reduced the clinical and laboratory times.The median adjustment count was also lower in the digital group.Cheng et al. [19] and Mangano et al. [11], found that the mean laboratory and clinical time was lesser for the digital workflow.Ren et al. [20] found that the mean chair-side time and laboratory time were significantly shorter in the test group (provisional + Zr crowns IOS and digital workflow) compared to the control group (provisional + Zr crowns using conventional impressions and hybrid workflow).Pan et al. [15] concluded that the digital workflow was more time-efficient compared to the conventional workflow.The operating and adjusting times were lesser for the digital workflow according to Fiore et al. [25] and Sailer et al. [12].In summary, the studies consistently showed that digital workflows were associated with improved time efficiency compared to conventional workflows, leading to shorter laboratory and clinical times among different types of dental prostheses.

Cost Efficiency
The research of Joda et al. [23] suggested that the digital workflow resulted in considerably lower production costs than the mixed and digital workflows.Additionally, a research study by Joda and Bragger [22] and Mangano et al. [11] showed that the direct treatment costs were statistically lower for the digital workflow compared to the traditional workflow.According to the study by Zhang et al. [16], the cost efficiency was evaluated using production costs, and it was revealed that costs were lower with the digital version.Nonetheless, it is necessary to take into account the fact that the exact price difference and the amount of time and expenses saved may be different when determining other workflows and materials used in other clinical settings.In order to determine whether digital workflows are more cost-efficient than traditional methods for dental restoration, further research or a specific cost analysis would be needed.

Patient Satisfaction
The study by Delize et al. [27] reported a statistically significant higher visual analog scale (VAS) satisfaction scores for IOS when compared with traditional impressions.It is clear that patients reported less taste disturbance with IOS and compared to conventional impressions.On the other hand, the patients' aesthetic outcomes in the control group that used the conventional workflow with veneered zirconia (control group) received a high value in this study.Patient satisfaction was consistent regarding the procedure duration, comfort level, anxiety level, and nausea according to Kunavisarut et al. [17], but taste irritation was significantly less in the case of IOS than conventional impressions.Similarly, in the study by De Angelis [28], patients demonstrated satisfaction results among the digital workflow that were evaluated on the convenience, anxiety, taste, nausea, pain, and breathing problems on the VAS questionnaire.Another important finding of the study is that the mean time for the digital workflow had improved significantly.The result of the study by Rattanapanich et al. [13] showed that there was no difference in the patient satisfaction regarding implant loading approach of digital workflow compared to traditional implant therapy at the one-year follow-up.According to Capparé et al. [18], patients preferred the digital workflow over the conventional workflow.

Operator Satisfaction
The assessment of operator satisfaction was performed in the study by De Angelis et al. [28] by using VAS questionnaires.The questionnaire obtained better results with the digital workflow regarding anxiety relief, convenience in the use, satisfaction with taste, discomfort caused by nausea, relief of chest pain, and difficulty breathing.The digital protocol's scores were better than those for the conventional procedure in terms of anxiety incidences, convenience, uncomfortable impression procedures, and workflow.To elaborate further, the digital method led to the reduction in the meantime and the number of visits, which stated a higher satisfaction degree among operators with the digital manner.The work carried out by Sven Mühlemann et al. [14] reported that statistical differences did not occur during the accuracy assessment for both groups while there was a trend towards a better marginal adaptation for the traditionally fabricated crowns.However, the study concluded that the overall treatment time did not bring about any constructional difference.According to Yuce et al. [26], the mean marginal and internal adaptation values of heat-pressed and CAD/CAM veneers were not statistically different.According to Seth et al. [21], both participants and students preferred the digital approach.In general, the studies concluded that user satisfaction was higher in digital than in conventional system and digital workflow correlated with shorter duration of time and higher usability for operators.Moreover, the digital approach would be proven to be more time-efficient in some cases, resulting in an operator satisfaction increase.

Accuracy and Fit of Prostheses
Clinical marginal fit: In the study of the clinical marginal fit of ZrO 2 crowns, the authors did not find a difference between the use of digital or conventional impressions (p>0.05)(Sakornwimon et al. [10]).
Research by Zhang et al. [16] didn't find any differences in marginal fit, proximal contact and crown morphology for the digital and conventional workgroups (p> 0. 5).The test group in the study by Zhang et al. [16] had less adjustment and greater accuracy than the control group.The study by Pan et al. [15] proved to be the same regarding the contact interproximally and occlusal contact for digital and conventional fabrication processes.The accuracy of digital workflows, with special emphasis on the precision of a clinical marginal fit, patient's suitability, adjustments, fabricating precision, and contact quality seems at the same level as conventional ones.The results might have the specific outcome, yet they may be different for different restoration types used.This demonstrates that the accuracy or the quality of the outcomes was similar with these two workflows.

Prosthodontic Outcomes
A study by Delize et al. [27] found comparable results for occlusion and interproximal contacts for two workflows but showed significantly higher aesthetic results and patient satisfaction scores for the conventional workflow.Edinger et al. [30] measured the pink esthetic score and functional implant prosthetic score and there were found to be no significant differences between the two workflows.A 2020 study by De Angelis et al. [28] showed that the results were assessed using VAS questionnaires for both the patients and operators.According to the results, the digital workflow was better in terms of convenience, anxiety, taste, nausea sensation, pain, breathing difficulties and duration of the procedure, all suggesting the likelihood of digital workflow being beneficial for the patients and the operator.In addition, a clinical trial was conducted in a controlled environment through randomization in 2019 by Rattanapanich et al. [13], which compared immediate loading implant treatment by the digital approach with conventional loading implant treatment.The analysis consisted of the evaluation of clinical results, radiographic bone level and patient satisfaction.The findings of the study were similar, in which there was no statistically significant difference in the implant success rate and marginal bone level, whether the digital workflow or the conventional implant treatment was used.While on the other hand, there was a significant difference between the two groups in respect of their degree of satisfaction towards implant prosthetic function in favor of the conventional group.The 2023 prospective clinical study by Sanchez-Lara et al. [31] determined marginal and internal gaps between crowns and the prepared tooth.The outcomes were that the marginal dimension discrepancies in the medial and lateral directions differed among various protocols, with the ones made with CAD-CAM technology showing a variation in the marginal discrepancy across different systems of scanning and fabrication methods.This suggests that the digital workflow has potential to take an edge on FPD achievement by way of specific fit or precision compared to traditional methods, again in relation to the specific approaches and technologies under consideration.

Success Rate and Feasibility
In the study by Joda et al. [23], it was found that laboratory cross-mounting was feasible for three reconstruction pairings, revealing a 15% vice versa transfer success rate for the digital workflow.Moreover, with the digital workflow, the average clinical adjustment time was substantially less when compared with the procedures performed using the conventional method.In a cross-over clinical trial conducted in 2022 by Hashemi et al. [29], the effectiveness of traditional impressions and digital impressions was compared with respect to various factors such as proper fit, occlusion, aesthetics, and treatment duration.Marginal boneloss was not statistically different between the two workflows according to Ferrini et al. [24].In summary, the investigations demonstrate that the application of digital workflows offers advantages relative to FPD fabrication, for instance, reduced discomfort for patients and staff and greater precision made possible ultimately not only by faster production but also potential cost cutting.

Conclusions
This collection includes studies that show a comparison between the digital and conventional workflow in dental implant and prosthodontic treatments that includes different aspects such as treatment outcomes, patient satisfaction, precision, time efficiency, and cost-effectiveness.In all these studies, the results obtained point to several key findings that are highlighted.These benefits involve considerable time and cost reduction from the digital process when compared to the conventional one.Both these methods end up with the same ratings of patient satisfaction with the final restorations.Digital workflow illustrated that the laboratory and total fabrication times got shorter and required less chairside adjustment in particular cases.Besides, the digital approach indicated a positive effect in terms of the patient-oriented factors, such as anxiety, high convenience, taste perception, nausea sensation, and pain.The study's findings, however, not only indicate advantages for dental workflows digitally but also for esthetic outcomes, particularly if an IOS is used.Nevertheless, patient satisfaction-related aspects such as implant prosthetic function and esthetics may have variable results in both digital and conventional workflows.Hence, the consequences of this research may influence the work of dentists as well as the treatment of patients by introducing some considerations regarding cost efficiency, time efficiency, patient-focused outcomes, and esthetic results.

FIGURE 1 :
FIGURE 1: PRISMA Flow Diagram for Study Selection (2020) PRISMA: Preferred Reporting Items for Systematic Review and Meta-Analysis

TABLE 2 : Quality Assessment in Non-randomized Studies (NIH)
NA: Not applicable; NR: not reported.