Trueness and fit of complete-arch implant-supported frameworks in new-generation additively and subtractively manufactured polymers: An in-vitro study.

BACKGROUND: There is limited knowledge on the fabrication trueness and fit of additively or subtractively manufactured complete-arch implant-supported frameworks in recently introduced polymers. PURPOSE: To evaluate the trueness and marginal fit of additively or subtractively manufactured polymer-based complete-arch implant-supported frameworks, comparing with those of strength gradient zirconia frameworks. MATERIALS AND METHODS: A typodont model with 4 implants (left first molar (abutment 1), left canine (abutment 2), right canine (abutment 3), and right first molar (abutment 4)) was digitized (ATOS Core 80 5MP) and an implant-supported complete-arch framework was designed. This design file was used to fabricate frameworks from 5 different materials: strength gradient zirconia (SM-ZR), high impact polymer composite (SM-CR), nanographene-reinforced PMMA (SM-GR), PMMA (SM-PM), and additively manufactured temporary resin (AM) (n = 10). These frameworks were digitized and each scan file was virtually segmented into 4 regions (abutments, occlusal, overall without occlusal, and overall). The surface deviations at these regions, and linear and interimplant distance deviations were evaluated (Geomagic Control X). Marginal gaps were evaluated according to triple-scan protocol after seating frameworks on the model with the 1-screw test. Data were statistically analyzed (α = 0.05). RESULTS: Surface deviations of all regions differed among tested materials (p ≤ 0.001). AM frameworks mostly had surface deviations that were similar to or lower than those of other materials (p ≤ 0.031), except for the occlusal surface, where it mostly had higher deviations (p ≤ 0.013). Abutment 4 of SM-CR had higher linear deviations than abutment 2 (p = 0.025), and material type did not affect the linear deviations within abutments (p ≥ 0.171). Interimplant distance deviations differed within and among materials (p ≤ 0.017), except for those between abutments 1 and 2 among materials (p = 0.387). Marginal gaps of subtractively manufactured materials differed among abutments, while those of abutments 3 and 4 differed among materials (p ≤ 0.003). AM frameworks mostly had lower marginal gaps at abutments 3 and 4 (p ≤ 0.048). CONCLUSIONS: Although there was no clear trend among tested materials for measured deviations, marginal gaps of additively manufactured resin were mostly lower than those of subtractively manufactured materials and did not differ among abutment sites. Nevertheless, the differences in measured deviations among materials were small and marginal gaps were within the previously reported acceptability thresholds.

In vitro evaluation of the impact of intraoral scanner, scanning aids, and the scanned arch on the scan accuracy of edentulous arches.

PURPOSE: To assess the accuracy of complete maxillary and mandibular edentulous arch scans obtained using two different intraoral scanners (IOSs), with and without scanning aids, and to compare these results to those obtained using conventional impression methods. MATERIALS AND METHODS: Two IOSs were used (TRIOS 4 [TRI] and Emerald S [EMR]) to scan maxillary and mandibular typodonts. The typodonts were scanned without scanning aids [TRI_WSA and EMR_WSA groups] (n = 10). The typodonts were then scanned under four scanning aid conditions (n = 10): composite markers [TRI_MRK and EMR_MRK groups], scanning spray [TRI_SPR and EMR_SPR groups], pressure indicating paste [TRI_PIP and EMR_PIP groups], and liquid-type scanning aid [TRI_LQD and EMR_LQD groups]. Conventional impressions of both arches were also made using irreversible hydrocolloids in stock trays [IHC] and using polyvinyl siloxane (PVS) impression material in custom trays (n = 10) which were digitized using a laboratory scanner. Using a metrology software program, all scans were compared to a reference scan in order to assess trueness and to each other to assess precision. Trueness and precision were expressed as the root mean square (RMS) of the absolute deviation values and the statistical analysis was modeled on a logarithmic scale using fixed-effects models to meet model assumptions (α = 0.05). RESULTS: The main effect of arch (p = 0.004), scanner (p < 0.001), scanning aid (p = 0.041), and the interaction between scanner and scanning aid (p = 0.027) had a significant effect on mean RMS values of trueness. The arch (p = 0.015) and scanner (p < 0.001) had a significant effect on the mean RMS values of precision. The maxillary arch had better accuracy compared to the mandible. The TRIOS 4 scanner had better accuracy than both the Emerald S scanner and conventional impressions. The Emerald S had better precision than conventional impressions. The scanning spray and liquid-type scanning aids produced the best trueness with the TRIOS 4 scanner, while the liquid-type scanning aid and composite markers produced the best trueness for the Emerald S scanner. CONCLUSION: The scanned arch and the type of scanner had a significant effect on the accuracy of digital scans of completely edentulous arches. The scanning aid had a significant effect on the trueness of digital scans of completely edentulous arches which varied depending on the scanner used.

Level of evidence analysis of the Saudi Dental Journal: A bibliometric analysis of publications from 2012 to 2021.

Objectives: The Level of Evidence (LOE) ranking system is used to measure the methodological quality of research. This study aimed to analyze and evaluate the trends of LOEs in articles published in the Saudi Dental Journal (SDJ) between 2012 and 2021. Methodology: The bibliometric details of all articles published from 2012 to 2021 were extracted from the SDJ website. All articles, expect editorials, were included in the analysis. The articles were divided based on LOEs, dental specialties, number of authors, and centers. The citation metrics were obtained from Google Scholar, and the statistical analysis was performed using JMP Pro 15.2.0 software. Results: Five hundred twenty-two articles were selected for analysis. They had an average of 21.19 citations per article, and a growing trend in the number of articles was observed. Authors from 40 countries contributed to the articles, with the most contributions from the Kingdom of Saudi Arabia. Most articles (n = 269; 51.53%) were LOE IV and V, while a low proportion (5.56%) were LOE I articles. Aside from miscellaneous articles, periodontics composed most of the LOE I studies, followed by endodontics, and oral and maxillofacial Surgery (OMFS). Orthodontics had the highest number of LOE II studies, pediatric dentistry had the most LOE IV, and prosthodontics had the most LOE V studies. No significant correlations were found between LOE and the number of authors or centers. However, a significant correlation was found in the distribution of LOE contributed by academic institutes. Conclusion: The study results highlight that most articles were LOE IV and V, whereas nominal LOE I articles were found. Furthermore, there is a need to encourage dental scientists to carry out high-quality evidence studies. Professional dental societies can play a pivotal role in this regard.

Polytetrafluoroethylene tape spacer for direct splinted teeth-supported provisional restoration: A dental technique.

Provisional restoration is essential for function, esthetics, occlusion, and tissue health. However, when multiple teeth are involved, making a direct splinted provisional restoration could be challenging due to the combined undercuts between the prepared teeth. This article describes a dental technique using polytetrafluoroethylene (PTFE) tape as a spacer to fabricate a splinted provisional restoration for multiple prepared teeth. The PTFE tape spacer will compensate for discrepancies in the path of insertion between prepared teeth, thus facilitating the removal of the direct splinted provisional restoration intact.

Impact of intraoral scanner, scanning strategy, and scanned arch on the scan accuracy of edentulous arches: An in vitro study.

STATEMENT OF PROBLEM: The scanning strategy used when making complete arch digital scans affects the accuracy of the scan, and the accuracy of the strategy may be influenced by the scanner used. However, these effects have not been investigated thoroughly with complete arch edentulous scanning. PURPOSE: The purpose of this in vitro study was to determine the effect of scanning strategies and the scanned arch on the accuracy of complete arch edentulous scans using 2 intraoral scanner (IOS) systems. MATERIAL AND METHODS: Two IOSs were used (TRIOS 4 and Emerald S) to scan maxillary and mandibular typodonts using 6 scanning strategies (test scans), and conventional impressions of both arches were also made. By using a metrology software program, test scans were superimposed onto a reference scan, and the root mean square (RMS) of the absolute deviation values was calculated to express trueness. The sample with the best trueness was used as reference onto which the remaining samples from the same group were superimposed, and the RMS of the absolute deviation values was calculated to express precision. Statistical modeling was applied using the fixed effects models (α=.05). RESULTS: The main effects of scanner and strategy significantly impacted the trueness RMS values (P<.001), with significant interactions between them (P=.012). The main effects of scanner, strategy, and arch significantly impacted the precision of RMS values (P=.004), (P=.033), and (P=.023). Conventional impressions and the TRIOS 4 scanner had comparable accuracy, while the Emerald S scanner was inferior to both. P-O-B had the highest overall accuracy and strategy ZZ had the worst. Better precision was found with the maxillary arch. CONCLUSIONS: The scanner type and scanning strategy significantly impacted the accuracy of the digital scans of completely edentulous arches, with a significant interaction between scanner and strategy. The arch being scanned had a significant effect on scan precision but not on scan trueness.

Complete-Arch Implant Rehabilitation with the Aid of Computer-Assisted Implant Surgery and Transitional Implants: A New Digital Approach

This case report describes a new digital workflow for computer-assisted implant surgery in an edentulous patient using transitional implants to support a fixed surgical template and interim prosthesis. The accuracy of the final implant position using the described protocol was evaluated and compared to the outcomes obtained using other types of surgical templates. This novel digital approach appears to enhance the accuracy of implant positioning for edentulous patients and seems to be comparable to a tooth-supported surgical template.

The impact of cone beam computer tomography field of view on the precision of digital intra-oral scan registration for static computer-assisted implant surgery: A CBCT analysis.

OBJECTIVES: Registration of intra-oral surface scans to cone beam computer tomography (CBCT) is critical in the digital workflow for static computer-aided implant surgery (sCAIS). This study aimed to assess the impact of CBCT field of view (FoV) on the precision of digital intra-oral scan registration. MATERIALS AND METHODS: Cone beam computer tomography data and intra-oral scans from 20 patients were included. Small FoV CBCT's were created by digitally segmenting a large FoV into three sextants. Virtual implant planning was performed. Digital intra-oral scans were repeatedly registered onto their corresponding large and small FoV CBCT datasets. The distances and angulations between the matching implant positions of each repeated registration were used to determine the precision of the registration process. Wilcoxon Signed Rank Paired Tests were used to compare the differences between large FoV and small FoV. The threshold for statistical significance was set at p = .05. RESULTS: Differences in 3D implant position based on the registration precision between small FoV and large FoV present at both the implant entry point (0.37 ± 0.25 mm vs 0.35 ± 0.23 mm, p = .482) and implant tip (0.49 ± 0.34 mm vs 0.37 ± 0.24 mm, p < .001). Differences in overall angular precision were observed between small FOV and large FoV (1.43 ± 1.36° vs 0.51 ± 0.38°, p < .001). CONCLUSION: CBCT with a small FoV is accompanied by greater precision errors in intra-oral scan registration. However, when sufficient well-distributed teeth are visible in small FoV CBCT, the precision of digital intra-oral scan registration appears to be within clinically acceptable limits for sCAIS.

A clinical study comparing digital scanning and conventional impression making for implant-supported prostheses: A crossover clinical trial.

STATEMENT OF PROBLEM: The impact of discrepancies between casts produced from digital scans and conventional impressions on the clinical performance of definitive restorations has not been fully investigated. PURPOSE: The purpose of this crossover clinical trial was to evaluate the clinical performance of single implant-supported restorations fabricated with the digital scanning technique and computer-aided design and computer-aided manufacturing (CAD-CAM) casts compared with the conventional impression technique and gypsum casts in terms of efficiency, accuracy, and participant preference. MATERIAL AND METHODS: Thirty participants underwent conventional impressions and digital scans of a single implant-supported restoration. Two crowns were fabricated for the same implant with each technique. The time taken for each procedure was recorded. After the accuracy and efficiency analysis of both crowns, the better crown was delivered. A questionnaire was used to assess participant preference and comfort with the techniques. The Wilcoxon signed-rank test was used to compare the time measurements, and multiple comparisons were performed using the Bonferroni method. The chi-square test was used to compare the implant locations of delivered crowns (α=.05). RESULTS: The total time for the conventional impression technique was 14.16 minutes, while that for the digital scanning technique was significantly less at 11.28 minutes (P<.001). Remake times were 0.56 minutes for conventional impressions and 2.27 for digital scans, also significantly different (P<.001). The adjustment time taken in delivering the crowns was 4.35 minutes for conventional impressions and 3.78 minutes for conventional impressions, which was not statistically significant (P=.940). Of the crowns chosen for delivery, 46.7% were from conventional impressions and 53.3% from digital scans. Participants preferred the digital scanning technique (89%) to the conventional impression technique (11%). CONCLUSIONS: The digital scanning technique was more efficient than the conventional impression technique for single implant-supported restorations. Digital scans and CAD-CAM implant casts had accuracy comparable with that of conventional impressions and gypsum casts. Most participants preferred digital scans to conventional impressions.

Tilted versus axial implant distribution in the posterior edentulous maxilla: A CBCT analysis.

OBJECTIVES: This study aimed to determine whether distally angulating an implant is a successful strategy to avoid the maxillary sinus and the need for bone augmentation, while increasing the anterior-posterior (A-P) implant distribution in the edentulous maxilla. MATERIALS AND METHODS: In 115 patients with edentulous maxillae, virtual implant planning was performed utilizing cone-beam computer tomographs. Axial (8 mm length) and tilted (12 mm length) dental implants with 30-degree and 45-degree angulation were virtually positioned to avoid entering the maxillary sinus, while maximizing A-P distribution. Measurements were made between the tilted and axial implants to assess the change in A-P distribution of implants at the implant and abutment levels. RESULTS: Forty-seven sites (20.4%) were not able to have either treatment modality with insufficient bone for implant placement. Axial implants were placed more distally than 45-degree and 30-degree tilted implants in 24% and 42% of sites, respectively. The average change in A-P spread measured at the implant level, for 30- and 45-degree tilted implants was -0.25 mm (95% CI -0.76, 0.26) and 1.9 mm (95% CI 1.4, 2.3), respectively. When measured from the center of each multi-unit abutment the average increase in A-P distances for tilted implants appears larger in the 30-degree and 45-degree groups by 0.97 mm and 1.74 mm, respectively compared to measurements at the implant level. CONCLUSIONS: Angulating 12 mm implants provides a limited increase in A-P distribution of implants in edentulous rehabilitation in most situations. In certain patients, the use of 8mm axial implants may provide a greater A-P spread.

Designing a complete-arch digital trial tooth arrangement for completely edentulous patients by using an open-source CAD software program: A dental technique.

A method for creating a complete-arch digital trial tooth arrangement for completely edentulous patients is described. The technique demonstrates an effective way to reproduce the dental and gingival anatomies by using a free 3D modeling software program. This cost-effective, time-saving, and versatile method allows dental professionals to digitally plan challenging treatments for completely edentulous patients. The technique can also be used to fabricate diagnostic prostheses and implant-supported interim prostheses.

Preservation of Soft Tissue Contours Using Computer-Aided Design/Computer-Assisted Manufacturing Healing Abutment with Guided Surgery in the Esthetic Area: Case Report.

This case report describes a digital workflow for a computer-aided design/computer-assisted manufacturing (CAD/CAM) healing abutment used in immediate implant placement in the esthetic zone. The design of the healing abutment was based on the existing tooth anatomy in order to provide anatomical support to the gingival tissues and to preserve the gingival contours of the natural tooth. This approach enhances the esthetic outcome of the definitive implant restoration. The surgical procedure including the guided bone regeneration is simplified, postoperative morbidity is reduced, and excessive occlusal loading during healing is limited.

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

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

A Modified Implant Surgical Guide for the Administration of Maxillary Nerve Block Anesthesia Intraorally via the Greater Palatine Foramen: Case Report.

Block anesthesia for the maxillary division (V2) of the trigeminal nerve is a suitable approach when an entire quadrant of teeth and/or associated structures are involved. The most effective approach to anesthetize the maxillary branch is intraorally via the greater palatine canal. This case report describes the use of a computer-aided design/computer-assisted manufacturing (CAD/CAM) implant surgical template designed with a guide channel to allow for the administration of maxillary nerve block through the greater palatine canal.

Impact of number of registration points on the positional accuracy of a prosthetic treatment plan incorporated into a cone beam computed tomography scan by surface scan registration: An in vitro study.

OBJECTIVES: To evaluate the accuracy of a prosthetic treatment plan incorporation into a cone beam computed tomography (CBCT) scan using point-based registration with three registration points selected and to evaluate the impact of number of registration points on prosthetic plan accuracy. MATERIAL AND METHODS: A CBCT scan of a completely dentate master model with removable teeth was exposed after removing the mandibular left first premolar, second premolar, and first molar. A digital scan of the master model with all teeth present was made by scanning a stone replica using a laboratory scanner. The digital model was registered onto the three-dimensional (3D) volume rendering of the CBCT scan using implant planning software. The point-based registration was repeated using three, four, five, six, seven, eight, nine, and 10 reference points. Metrology software was used to measure the 3D deviation of the registered models for each reference point group on standard tessellation language (STL) files obtained from the CBCT scans. An STL file of the master model with all teeth present obtained from another CBCT scan was used as reference. RESULTS: Using three registration points, the registered prosthetic plan had a mean absolute deviation of 17.63 µm from the reference. Increasing the number of registration points failed to demonstrate statistically significant effects on the deviation (p > 0.05). CONCLUSIONS: For this clinical scenario, three registration points provided adequate accuracy for prosthetic plan incorporation into CBCT scans. Increasing the number of registration points had no significant impact on the prosthetic plan accuracy in this study.

Positional accuracy of a prosthetic treatment plan incorporated into a cone beam computed tomography scan using surface scan registration.

STATEMENT OF PROBLEM: The registration of surface scans onto cone beam computed tomography (CBCT) scans has been proposed as a method of visualizing different anatomic structures and the prosthetic treatment plan simultaneously. This method also overcomes some of the problems associated with conventional radiographic templates. However, it has not been thoroughly investigated or validated for use in implant dentistry. PURPOSE: The purpose of this in vitro study was to evaluate the accuracy of a prosthetic treatment plan surface scan incorporated into a CBCT scan and to compare it to conventional radiographic templates for single tooth replacement. MATERIAL AND METHODS: Direct surface scans of a completely dentate master model with removable radiopaque teeth were made using an intraoral scanner, and indirect surface scans of a stone duplicate of the master model were made using a laboratory scanner. To simulate a clinical scenario, the mandibular left first molar was removed. A CBCT scan of the clinical scenario was made. The surface scans were registered onto the CBCT scans. Radiographic templates for the clinical scenario were fabricated, and the master model was subsequently scanned using the same CBCT scanner with each radiographic template seated. Metrology software was used to assess the accuracy of each method by measuring the 3-dimensional deviation on standard tessellation language (STL) files generated from the CBCT scans against an STL file of the completely dentate master model generated from a CBCT scan. One-way ANOVA and the Tukey HSD test were used for statistical analysis (α=.05). RESULTS: The incorporation technique had a significant effect on deviation from the master model (P=.004). The overall mean 3-dimensional deviation was 0.04 mm for direct surface scan registrations, 0.03 mm for indirect surface scan registrations, and 0.33 mm for radiographic templates. Radiographic templates were significantly less accurate compared with both surface scan registration methods (P<.001), whereas no statistically significant difference in accuracy was found between the registration of a laboratory scan and that of an intraoral scan (P=.94). CONCLUSIONS: Intraoral and laboratory surface scan registration on CBCT scans were more accurate than radiographic templates for prosthetic treatment plan incorporation. The accuracy of the registration of an intraoral scan and a laboratory scan was comparable.

Modification of clinically short Locator abutments using laser welding.

As dental implants continue to survive longer, managing and maintaining implant prostheses can be complicated by the lack of compatible parts or the discontinuation of implant systems. This report describes a laser welding procedure for the management of clinically short Locator abutments (Zest Anchors Inc) that lacked a commercially available, compatible alternative.

Effect of length and location of edentulous area on the accuracy of prosthetic treatment plan incorporation into cone-beam computed tomography scans.

BACKGROUND: Effects of length and location of the edentulous area on the accuracy of prosthetic treatment plan incorporation into cone-beam computed tomography (CBCT) scans has not been investigated. PURPOSE: To evaluate the effect of length and location of the edentulous area on the accuracy of prosthetic treatment plan incorporation into CBCT scans using different methods. MATERIAL AND METHODS: Direct digital scans of a completely dentate master model with removable radiopaque teeth were made using an intraoral scanner, and digital scans of stone duplicates of the master model were made using a laboratory scanner. Specific teeth were removed to simulate different clinical situations and their CBCT scans were made. Surface scans were registered onto the CBCT scans. Radiographic templates for each clinical situation were also fabricated and used during CBCT scans of the master models. Using metrology software, three-dimensional (3D) deviation was measured on standard tesselation language (STL) files created from the CBCT scans against an STL file of the master model created from a CBCT scan. Statistical analysis was done using the MIXED procedure in a statistical software and Tukey HSD test (α =.05). RESULTS: The interaction between location and method was significant (P = .009). Location had no significant effect on registration methods (P > .05), but on the radiographic templates (P = .011). Length of the edentulous area did not have any significant effect (P > .05). CONCLUSIONS: Accuracy of digital image registration methods was similar and higher than that of radiographic templates in all clinical situations. Tooth-bound radiographic templates were significantly more accurate than the free-end templates. The results of this study suggest using image registration instead of radiographic templates when planning dental implants, particularly in free-end situations.

A technique for the removal of a wedged implant abutment fragment or debonded titanium base.

A technique for the retrieval of wedged implant fragments is described. The technique is suitable for fractured zirconia and metal abutments and titanium bases left behind after fracture or debonding of the custom zirconia abutment from the titanium base of an implant-supported prosthesis. This straightforward, noninvasive, technique facilitates the removal of the fragments or titanium bases without risking damage to the implant, surrounding bone, or soft tissues.

A risk-based decision making tree for managing fractured abutment and prosthetic screws: A systematic review.

STATEMENT OF PROBLEM: In implant dentistry, a variety of techniques are used to manage fractured abutment and prosthetic screws. All of them pose various degrees of difficulty to both the clinician and patient and risk involving damage to the implants and prostheses. PURPOSE: The purpose of this systematic review was to classify and organize the various reported techniques for managing fractured abutment and or prosthetic screws into a risk-based, decision making tree that could be used to guide the clinician through this difficult and time-consuming clinical procedure. MATERIAL AND METHODS: A systematic search of the PubMed/MEDLINE database for articles published before June 2016 was performed by 2 independent reviewers. Studies published in English that described a clinical technique to retrieve or manage a fractured abutment or prosthetic screws were included. Techniques were classified according to risk of irreversible damage to the implant. Low-risk techniques were defined as those involving the use of basic hand instruments and instrument modification; moderate-risk techniques were defined as those involving the use of screw retrieval kits, rotary instruments, and screw modification; and high-risk techniques were defined as those involving modification of the implant. Published techniques were then organized into a decision-making tree. RESULTS: A total of 35 articles were included. The reported techniques ranged from straightforward instrumentation and instrument modification to screw or implant modifications. Seven techniques were considered low risk, 17 moderate risk, and 11 high risk. CONCLUSIONS: The proposed risk-based decision tree is a useful tool in helping clinicians choose the most appropriate strategy or sequence of strategies that offers maximum benefit to the patient while minimizing associated risks.