Use of intraoral digital scanning for a CAD/CAM-fabricated milled bar and superstructure framework for an implant-supported, removable complete dental prosthesis

Effect of different impression coping and scan body designs on the accuracy of conventional versus digital implant impressions: An in vitro study

OBJECTIVES

This in vitro study compared the accuracy of conventional versus digital impression techniques for angulated and straight implants using two different impression coping and scan body designs.

METHODS

Two implant systems were used: Straumann and Dentegris. Two implants were placed for each system, straight and angulated at 15 degrees mesiodistally. Conventional impressions were made using the splinted open-tray technique using narrow impression coping (NIC) and wide impression coping (WIC). The stone casts produced from the conventional impression were digitized with a lab scanner (3Shape D2000). Digital impressions were made using four intraoral scanners (IOS): 3Shape Trios 3, Medit i700, Cerec Omnicam, and Emerald Planmeca using short scanbodies (SSB) and long scanbodies (LSB). The scanning was repeated ten times to generate the Standard Tessellation Language (STL) files. The distance and angle deviations between impression copings and scanbodies were measured in reference to the master model.

RESULTS

The trueness and precision of SSB and WIC were significantly better than LSB and NIC (p<0.001). The range trueness of the platform deviation was better with SSB (37.1 to 51.9) than LSB (89.6 to 127.9 μm) and for WIC than NIC in conventional impressions (58.2 and 75.1 μm, respectively). The trueness of the angle deviation of digital scans with SSB (0.11 to 0.25 degrees) was significantly better than scans with LSB (0.31 to 0.57 degrees) and for WIC than NIC (0.21 and 0.52 degrees, respectively). The precision of the platform deviation of digital scans with SSB (12.4 to 34.5 μm) was higher than other scans and conventional impressions (42.9 to 71.4 μm). The precision of the angle deviation of Medit i700 and Trios 3 with SSB (0.17 and 0.20 degrees, respectively) was higher than other scans with SSB and conventional impressions (0.54 to 1.63 degrees).

CONCLUSIONS

Digital scans with SSB were more accurate than conventional splinted open-tray impressions. The type of impression coping and scanbody significantly affected the impression accuracy.

CLINICAL SIGNIFICANCE

The use of a short scanbody can increase the accuracy of digital impressions, and wide impression coping can increase the accuracy of conventional impressions, resulting in improved clinical outcomes.

Recent advances in additive manufacturing of patient-specific devices for dental and maxillofacial rehabilitation

OBJECTIVES

Customization and the production of patient-specific devices, tailoring the unique anatomy of each patient's jaw and facial structures, are the new frontiers in dentistry and maxillofacial surgery. As a technological advancement, additive manufacturing has been applied to produce customized objects based on 3D computerized models. Therefore, this paper presents advances in additive manufacturing strategies for patient-specific devices in diverse dental specialties.

METHODS

This paper overviews current 3D printing techniques to fabricate dental and maxillofacial devices. Then, the most recent literature (2018-2023) available in scientific databases reporting advances in 3D-printed patient-specific devices for dental and maxillofacial applications is critically discussed, focusing on the major outcomes, material-related details, and potential clinical advantages.

RESULTS

The recent application of 3D-printed customized devices in oral prosthodontics, implantology and maxillofacial surgery, periodontics, orthodontics, and endodontics are presented. Moreover, the potential application of 4D printing as an advanced manufacturing technology and the challenges and future perspectives for additive manufacturing in the dental and maxillofacial area are reported.

SIGNIFICANCE

Additive manufacturing techniques have been designed to benefit several areas of dentistry, and the technologies, materials, and devices continue to be optimized. Image-based and accurately printed patient-specific devices to replace, repair, and regenerate dental and maxillofacial structures hold significant potential to maximize the standard of care in dentistry.

Use of Individually Designed CAD/CAM Suprastructures for Dental Reconstruction in Patients with Cleft Lip and Palate

This patient series reports the outcomes of CAD/CAM prosthetic reconstructions in patients with cleft lip and palate (n = 9, aged 27 to 76) who have experienced significant failure with conventional restorative and fixed prosthodontic treatments. The objective of the protocol is to establish a functional and patient-friendly prosthetic structure for individuals with unilateral/bilateral cleft lip and palate (UCLP/BCLP) while minimising the requirement for specialised follow-up care in the cleft unit. The study data were obtained from a retrospective cohort at Helsinki University Hospital. Prosthetic reconstructions were performed using CAD/CAM bar structures by the Atlantis 2in1 system or Createch removable telescope structures, supported by four to eight maxillary dental implants. Out of the nine patients, seven experienced no complications. One prosthesis fracture occurred after 16 months due to a design error in the original framework, and one patient experienced failure of osseointegration in a dental fixture (specifically, one fixture out of the eight maxillary implants in this patient). In total, 56 implants were successfully placed. The maxillary dentition of elderly patients with cleft lip and palate often poses challenges due to periodontal and reconstructive issues. An implant-supported CAD/CAM bar with a removable telescope suprastructure offers an easily maintained and functional solution for dental rehabilitation.

Clinical Applications of Intraoral Scanning in Removable Prosthodontics: A Literature Review

PURPOSE

This review aimed to identify the reported intraoral scanning applications in fabricating different types of removable prostheses in the field of prosthodontics.

METHODS

A comprehensive electronic search was performed using the PubMed and MEDLINE databases. This review included in vitro studies and clinical reports published between January 2013 and March 2021. The main keywords were as follows: intraoral scanning, digital impression, computerized digital impression, removable prosthesis, chairside computer-aided design/computer-assisted manufacturing, digital complete denture, digital immediate complete denture, digital interim complete denture, digital removable partial denture, digital removable overdenture, digital obturator, digital occlusal splints, and digital maxillofacial prostheses.

RESULTS

In total, 33 papers (22 clinical reports, 8 papers focused on dental techniques, and 3 clinical studies) were included in the final analysis.

CONCLUSIONS

The efficiency of using intraoral scanning in the field of removable prosthodontics was documented. However, there is a need for more clinical studies to identify intraoral scanning-usage protocols and to yield reliable and valid data.

A digital approach to robust and esthetic implant overdenture construction

OBJECTIVE

Overdenture therapy is an important option for implant rehabilitation. However, numerous reports suggest that mechanical/technical complications and failures can limit therapeutic success. The goal of this report is to illustrate a digital approach to design and construction of a robust overdenture with high-esthetic value.

MATERIALS AND METHODS

Beginning with new denture design to establish esthetic parameters, 3D modeling of a metal framework and the denture teeth are completed in a connected manner. This enables connection of rapidly printed, prototype dentition that is attached directly to the framework without intervening wax or acrylic components. Following evaluation of the dentition and required adjustments, the final dentition is milled from resin and processed to the selective laser sintered framework.

RESULTS

The advantages of the digital workflow include the control of dimensions and strength of the framework, the esthetic relationship of the framework to the dentition and the facilitation of esthetic try-in of the dentition.

CONCLUSION

Enhancing a robust overdenture can be readily achieved using a digital workflow.

CLINICAL SIGNIFICANCE

The use of digital technology enables the clinical team to plan and produce prostheses with dimensions and contours that support long-term function and esthetics. The clinical chair time can be potentially reduced by use of digital design that facilitates try-in and reduces major errors by improved communication between the patient, dentist, and technician.

Accuracy of 3-dimensional printing of dental casts: A proposal for quality standardization

STATEMENT OF PROBLEM

A digital workflow in fixed prosthodontics may use a 3D printer to obtain a cast for porcelain application. Standards exist that define the accuracy of traditional casts, but the accuracy requirements of 3D-printed casts have not been defined.

PURPOSE

The purpose of this retrospective study was to investigate how the accuracy of 3D-printed casts affected prosthesis fit and whether they correctly reproduced interproximal contacts.

MATERIAL AND METHODS

Copings with different die spacings were used to test different 3D-printed casts of the same dental arch. The accuracy of the 3D casts was assessed by imaging and comparing the resulting standard tessellation language (STL) files with the original through a matching software program. Accuracy scores were then correlated with a score measuring how well the copings fit the casts. The first data set was obtained from a patient receiving restoration of the 4 maxillary incisors. The teeth were prepared, the dental arch was imaged intraorally, and 10 resin casts were printed with four 3D printers. Two sets of 4 zirconia test copings were prepared, and 3 clinicians assessed their fit on each cast. A further set of casts was created from a second patient requiring prosthetic restoration for 5 adjacent teeth to assess whether undersizing affected the best fit of the copings on their dies.

RESULTS

The clinical scores and accuracy scores did not correlate. The results suggested that printed dies showing a certain degree of undersizing might provide a better fit than those showing better correspondence to the actual anatomic structure. The oversized dies were the worst. Only 7 of 17 casts being assessed were deemed suitable for veneering of the copings. The undersized casts tested clinically better than casts printed by using the same printer under standard settings.

CONCLUSIONS

This retrospective study indicated that 3D-printed casts that do not allow copings to fit appropriately usually show mean excess oversizing. Axially undersizing the printed dies on casts might allow a better fit of copings to be veneered.

Accuracy of virtual interocclusal records for partially edentulous patients

STATEMENT OF PROBLEM

Intraoral scans and virtual interocclusal records (VIRs) are widely used for contemporary prosthodontic treatment of patients with partial edentulism. The accuracy of VIRs in various clinical conditions is unclear.

PURPOSE

The purpose of this in vitro study was to investigate whether the span and location of edentulous areas affect the accuracy of VIRs.

MATERIAL AND METHODS

Five sets of master stone casts were duplicated from a typodont model (Prosthetic Restoration Jaw Model; Nissin Dental) and then assigned into 5 study groups. Six pairs of interarch markers were placed on the master stone casts as reference points for measurements. The 5 study groups were group 1-Post: 1 posterior tooth missing; group 3-Post: 3 posterior teeth missing; group 6-Ant: 6 anterior teeth missing; group Bil-Post: bilateral posterior teeth missing; and group Dent: completely dentate arch. Master stone casts along with VIRs were scanned 10 times in each group by using an intraoral scanner (IOS) (Dental Wings Intraoral Scanner; Dental Wings Inc). Digital measurement of distances between the interarch markers was obtained on all digitally articulated casts and compared with the manual measurements (with electronic calipers with an accuracy of 0.02 mm). In addition, the differences (absolute values) between the digital and manual measurements were calculated at the edentulous locations for the groups 1-Post, 3-Post, 6-Ant, and Bil-Post and were compared with the corresponding interarch marker positions in the group Dent. Two-sample t tests were used for the statistical analysis (α=.05).

RESULTS

The overall differences (mean ±standard deviation) between digital and manual measurements were group 1-Post: 0.10 ±0.19 mm, group 3-Post: 0.28 ±0.63 mm; group 6-Ant: 0.19 ±0.20 mm; group Bil-Post: 0.28 ±0.25 mm; and group Dent: 0.05 ±0.18 mm. Group Dent was the only group with no significant differences between digital and manual measurements at all 6 interarch marker positions and was used as the reference to analyze the measurements in the edentulous areas. No statistical difference was found (P=.237) at the group 1-Post's edentulous area when compared with the group Dent. In the group 3-Post, the edentulous areas showed statistically significant difference when compared with those of the group Dent (P=.002 and P=.003). In the group 6-Ant, the edentulous areas showed statistical differences when compared with those of the group Dent (P=.019 and P=.008). In the group Bil-Post, only 1 side of the edentulous areas showed statistical differences when compared with group Dent (P=.006 and P=.034).

CONCLUSIONS

The span and location of edentulous areas impact the accuracy of VIRs. For a single missing posterior tooth, VIRs could achieve a high level of accuracy comparable with that of the dentate condition. Unilateral and bilateral extended edentulous spans with 3 or more missing posterior teeth and the extended edentulous span in the anterior region all affected the accuracy of VIRs.

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.

A Clinical Comparative Study of 3-Dimensional Accuracy between Digital and Conventional Implant Impression Techniques

PURPOSE

To evaluate the accuracy of a digital implant impression technique using a TRIOS 3Shape intraoral scanner (IOS) compared to conventional implant impression techniques (pick-up and transfer) in clinical situations.

MATERIALS AND METHODS

Thirty-six patients who had two implants (Implantium, internal connection) ranging in diameter between 3.8 and 4.8 mm in posterior regions participated in this study after signing a consent form. Thirty-six reference models (RM) were fabricated by attaching two impression copings intraorally, splinted with autopolymerizing acrylic resin, verified by sectioning through the middle of the index, and rejoined again with freshly mixed autopolymerizing acrylic resin pattern (Pattern Resin) with the brush bead method. After that, the splinted assemblies were attached to implant analogs (DANSE) and impressed with type III dental stone (Gypsum Microstone) in standard plastic die lock trays. Thirty-six working casts were fabricated for each conventional impression technique (i.e., pick-up and transfer). Thirty-six digital impressions were made with a TRIOS 3Shape IOS. Eight of the digitally scanned files were damaged; 28 digital scan files were retrieved to STL format. A coordinate-measuring machine (CMM) was used to record linear displacement measurements (x, y, and z-coordinates), interimplant distances, and angular displacements for the RMs and conventionally fabricated working casts. CATIA 3D evaluation software was used to assess the digital STL files for the same variables as the CMM measurements. CMM measurements made on the RMs and conventionally fabricated working casts were compared with 3D software measurements made on the digitally scanned files. Data were statistically analyzed using the generalized estimating equation (GEE) with an exchangeable correlation matrix and linear method, followed by the Bonferroni method for pairwise comparisons (α = 0.05).

RESULTS

The results showed significant differences between the pick-up and digital groups in all of the measured variables (p < 0.001). Concerning the transfer and digital groups, the results were statistically significant in angular displacement (p < 0.001), distance measurements (p = 0.01), and linear displacement (p = 0.03); however, between the pick-up and transfer groups, there was no statistical significance in all of the measured variables (interimplant distance deviation, linear displacement, and angular displacement deviations).

CONCLUSIONS

According to the results of this study, the digital implant impression technique had the least accuracy. Based on the study outcomes, distance and angulation errors associated with the intraoral digital implant impressions were too large to fabricate well-fitting restorations for partially edentulous patients. The pick-up implant impression technique was the most accurate, and the transfer technique revealed comparable accuracy to it.

Intraoral scanners in dentistry: a review of the current literature

BACKGROUND

Intraoral scanners (IOS) are devices for capturing direct optical impressions in dentistry. The purpose of this narrative review on the use of IOS was to: (1) identify the advantages/disadvantages of using optical impressions compared to conventional impressions; (2) investigate if optical impressions are as accurate as conventional impressions; (3) evaluate the differences between the IOS currently available commercially; (4) determine the current clinical applications/limitations in the use of IOS.

METHODS

Electronic database searches were performed using specific keywords and MeSH terms. The searches were confined to full-text articles written in English and published in peer-reviewed journals between January 2007 and June 2017.

RESULTS

One hundred thirty-two studies were included in the present review; among them, 20 were previous literature reviews, 78 were in vivo clinical studies (6 randomized controlled/crossover trials, 31 controlled/comparative studies; 24 cohort studies/case series; 17 case reports) and 34 were in vitro comparative studies.

CONCLUSIONS

Optical impressions reduce patient discomfort; IOS are time-efficient and simplify clinical procedures for the dentist, eliminating plaster models and allowing better communication with the dental technician and with patients; however, with IOS, it can be difficult to detect deep margin lines in prepared teeth and/or in case of bleeding, there is a learning curve, and there are purchasing and managing costs. The current IOS are sufficiently accurate for capturing impressions for fabricating a whole series of prosthetic restorations (inlays/onlays, copings and frameworks, single crowns and fixed partial dentures) on both natural teeth and implants; in addition, they can be used for smile design, and to fabricate posts and cores, removable partial prostheses and obturators. The literature to date does not support the use of IOS in long-span restorations with natural teeth or implants. Finally, IOS can be integrated in implant dentistry for guided surgery and in orthodontics for fabricating aligners and custom-made devices.

3D RECONSTRUCTION AND SLM SURVEY FOR DENTAL IMPLANTS

This research studies an integrated dental 3D reconstruction scanning method which combines impression model scanning, intraoral camera scanning and CT scanning. In the dental integrated scanning, tooth root data is acquired from CT DICOM data and 3D reconstruction is processed by Mimics®software developed from Materialise. The tooth crown and the tooth bridge 3D data are obtained by scanning the tooth impression model or scanning with an intraoral scanner. Also, it surveys that the dental prosthesis are fabricated with traditional methods and printed with Select Laser Melting (SLM) technology. In the research, it presents that SLM additive manufacturing (AM) method can fabricate customized dental prosthesis with high dimensional accuracy.

3D printing in dentistry

3D printing has been hailed as a disruptive technology which will change manufacturing. Used in aerospace, defence, art and design, 3D printing is becoming a subject of great interest in surgery. The technology has a particular resonance with dentistry, and with advances in 3D imaging and modelling technologies such as cone beam computed tomography and intraoral scanning, and with the relatively long history of the use of CAD CAM technologies in dentistry, it will become of increasing importance. Uses of 3D printing include the production of drill guides for dental implants, the production of physical models for prosthodontics, orthodontics and surgery, the manufacture of dental, craniomaxillofacial and orthopaedic implants, and the fabrication of copings and frameworks for implant and dental restorations. This paper reviews the types of 3D printing technologies available and their various applications in dentistry and in maxillofacial surgery.

Misfit evaluation of dental implant-supported metal frameworks manufactured with different techniques: Photoelastic and strain gauge measurements

This study aims to compare in-vitro the fitting accuracy of implant-supported metal frameworks used for full-arch orthodontic restoration. The hypotheses tested were as follows: (1) for a fixed implant morphology, strains developed within the framework depend on how the framework had been fabricated and (2) stresses transferred to the implant–bone interface are related to the amount of framework misfit. Metal frameworks were fabricated using four different manufacturing techniques: conventional lost-wax casting, resin cement luting, electrospark erosion, and computer-aided design/computer-aided manufacturing milling. Each framework was instrumented with three strain gauges to measure strains developed because of prosthetic misfit, while quantitative photoelastic analysis was used to assess the effect of misfit at the implant–resin interface. All the tested frameworks presented stress polarization around the fixtures. After screw tightening, significantly greater strains were observed in the lost-wax superstructure, while the lowest strains were observed in the luted framework, demonstrating consistent adaptation and passive fitting. No significant difference in stress distribution and marginal fit was found for bars fabricated by either computer-aided design/computer-aided manufacturing or spark erosion. This study suggested that, in spite of known limitations of in-vitro testing, direct luting of mesostructures and abutments should be the first clinical option for the treatment of complete edentulism, ensuring consistent passive fitting and effective cost–benefit ratio.