Comparing the accuracy of occlusal vertical dimension transfer in CAD-CAM dentures.

PURPOSE: There are different methods to transfer occlusal vertical dimension (OVD) when fabricating complete dentures, but it is not clear which method yields the most accurate transfer. This study investigated the accuracy of transferring the OVD of the maxillary/mandibular relationship when designing and fabricating digital dentures by evaluating two commonly used workflows: duplicate dentures (DDs) and occlusion rims (ORs). MATERIALS AND METHODS: Mounted edentulous casts were used to simulate a completely edentulous patient. These casts were used in two workflows: (1) DD workflow where complete dentures were fabricated and relined (n = 15), and (2) OR where final impressions and ORs were constructed (n = 15). Relined dentures and ORs with fiduciary markers were then scanned and virtually articulated, then exported as STL files. A scan of the articulated casts (simulated patients) with fiduciary markers embedded was also exported as an STL file and used as a control. STL files for each workflow were superimposed over the control and analyzed in 3D inspection software (Geomagic Control X, 3D Systems, NC) for deviations (mm) at three different locations. Average 3D deviations were compared among the groups using a two-way ANOVA (α-0.05). RESULTS: The average deviation for OR was significantly larger than DD at all locations of measurement [F = 46.00, p < 0.0001]. The majority of the measurements (98.9%) had a positive deviation value, indicating increased OVD. The overall deviation for the OR group from the control was 0.72 ± 0.13 mm versus 0.45 ± 0.23 mm for the DD group. There was no difference in deviation between the points of measurement and no interaction between the location and method [F = 0.02, p < 0.98]. CONCLUSIONS: The DD workflow exhibited less deviation in the transfer of OVD than the OR workflow. However, the deviation was small and may not be clinically significant.

Facial Contour Preservation of Anterior Immediate Single-Tooth Replacement With the Socket Shield Technique Versus Connective Tissue Graft: A Case Report.

The socket shield technique and subepithelial connective tissue graft following immediate implant placement with provisionalization had been advocated for peri-implant facial contour and gingival architecture preservation. This case report used three-dimensional volumetric analysis to longitudinally assess the peri-implant facial contour change before and after these procedures. The results demonstrated comparable and acceptable preservation of peri-implant facial contour between the two procedures after 2 years of function.

Scanning accuracy with splinted and unsplinted implant scan bodies for the edentulous arch at implant level: an in vitro study.

Accuracy of completely edentulous arch scanning with implant scan bodies has not been completely validated for intraoral scanners. For desktop laboratory scanners validations were found in the literature. The aim of this in vitro study was to compare the dimensional accuracy of scanning with splinted and unsplinted scan bodies on a completely edentulous maxillary arch with 6 implants. A maxillary edentulous master cast with 6 implants was used as control for all implant level impressions. 6 implants were digitally planned and placed at different angulation of 0, 0  17° and 30°. A contact coordinate measuring machine (CMM) was used to generate baseline linear measurements of the master cast. Four test groups included: 2 intraoral scanners Trios (3shape, Copenhagen, Denmark) and True Definition (3M ESPE, St Paul, MN), one industrial scanner Atos (Core optical 3D scanner) and one conventional impression group scanned with laboratory scanner Dental Wings 7 Series. Each scan recording was made with splinted and unsplinted scan bodies. Digital datasets of all measurements were compared with the CMM baseline values using PolyWorks® InnovMetric Software in order to assess the linear and angular deviations and determine the accuracy of complete arch digital impression. Factorial ANOVA showed significant effect with splinting, scanner type, inter-implant distance and implant angulation for linear deviations. Splinted scan bodies revealed elevated linear and angular deviation values for all scanners with significantly highest deviations for True Definition scanner. Significant correlation was found between inter-implant distance and linear deviation (r =0.45, P =<0.001) with increased linear deviations among all scanners, regardless of splinting. ( P <0.05). Significant effect on accuracy was seen for angular deviation with splinting, scanner type and implant angulation; significant difference was found between 0° and 30° implant angulation ( P =0.035) with more deviation with 30° implant angulation. The accuracy of the complete arch implant digital impression using splinted scan bodies was significantly reduced for measurements that crossed the arch midline. The digital impression technique using a broad splint design to connect scan bodies was not found to improve the scan accuracy for intraoral scanners.

Additive Manufacturing for Complete Denture Fabrication: A Narrative Review.

PURPOSE: To evaluate and compare the benefits and limitations of additive manufacturing for complete denture fabrication. METHODS: A PubMed and Google Scholar search for topics pertaining to additive manufacturing for complete dentures was performed. The resulting articles were then divided into topics to allow a narrative review. DISCUSSION: Determining how printing compares with conventional and milled dentures is critical for the widespread adoption of this fabrication technique. Physical properties, denture tooth bond strength, denture base adaptation and soft-liner bond strength are discussed to establish how printing compares. CONCLUSIONS: Printing offers many advantages over milled and conventionally processed dentures; however, many questions need to be answered by research. The advantages include reduced cost of most printers compared to milling machines, less material waste, ability to print multiple dentures simultaneously, and complex designs can be fabricated that otherwise could not be milled. Current research has shown flexural strength, fracture toughness, color stability, and denture base adaptation are reduced for printed dentures when compared with milled dentures. Print orientation has been shown to influence accuracy, strength, surface roughness and C. albicans adherence which is not seen with conventional or milled denture materials. These factors do not represent a criticism of printing but rather indicate the need for more research with this new and promising denture fabrication technique. Since printing offers numerous benefits to complete denture fabrication it is likely to have a more significant role in complete denture fabrication in years to come as knowledge increases and materials/techniques continue to advance.

What Occlusal Scheme Should Be Used with Removable Partial Dentures?

PURPOSE: Multiple clinical studies have been published comparing different philosophies of complete denture occlusion and different types of denture teeth. However, it is unclear whether comparable data are available for occlusal schemes used with removable partial dentures (RPDs). Therefore, this review investigated the dental literature related to occlusal schemes for RPDs. MATERIALS AND METHODS: A PubMed search of English language articles was performed using the term "removable partial denture, occlusion" with 765 results. When the term "occlusion in removable partial prosthodontics" was used there were 784 results. Seventy-four articles were identified using the different search term of "RPD, occlusion" while use of the term "occlusal scheme, with removable partial dentures" listed 18 publications. The term "removable partial denture, occlusion, literature reviews" produced 38 potential publications related to the topic. Using the term "removable partial denture occlusion systematic review" resulted in 2 citations. Using the term "RPD occlusion literature review" resulted in one foreign language manuscript whereas using the term "RPD occlusion systematic review" resulted in one article unrelated to dentistry. The term "clinical studies of RPD occlusion" produced 5 results with none related to the topic. There were 23 results using the term "clinical studies of removable partial denture occlusion" with one potentially related to RPD occlusal schemes. RESULTS: A review of the titles and abstracts revealed 12 articles that appeared to contain specific information about the occlusal scheme used with RPDs. Following a detailed review of those publications, only 4 contained recommendations for RPD occlusion and were included in this review. The available information regarding the recommendations for occlusal schemes in these articles was based on expert opinion. A decision was made to include a hand search of 9 textbooks containing varying amounts of information related to occlusal schemes for RPDs, but no evidence-based references related to RPD occlusal schemes were found in the textbooks. Since this entire review is based on expert opinion, no attempt was made to critique the opinions expressed by these authors but rather to present their perspectives for evaluation by readers. CONCLUSIONS: The occlusion developed with RPDs should be physiologically harmonious, allowing the supporting structures to remain in a good state of health with functional stress distributed among all the occluding teeth. Multiple authors indicate the occlusion in maximum intercuspation/centric occlusion should incorporate bilateral posterior contacts with no deflective occlusal contacts. When most occlusal contacts on natural teeth are missing, it has been proposed that extension base RPDs have their occlusal contacts developed in centric occlusion. Regarding eccentric occlusal relationships, a balanced occlusal scheme has been recommended by multiple authors with one author advocating use of a lingualized balanced. An anterior guided (canine-protected) occlusion has also been recommended when the canines are present and not periodontally compromised. When RPDs oppose a complete denture, several authors indicate a bilateral balanced occlusion should be used to help stabilize the complete denture.

Should Digital Complete Dentures Be Part of A Contemporary Prosthodontic Education?

Digital complete dentures should be incorporated into a contemporary dental school education due to factors that include the substantial increase in the number of scientific publications devoted to digital dentures, the increased number of companies producing these prostheses, and the expanded use by practitioners. These factors increased recently due to multiple advantages of digital dentures that are described. Based on positive clinical experiences with such prostheses, preclinical curriculum changes were made with examples presented of both didactic and laboratory courses that now include digital dentures. Perspectives are presented regarding online laboratory procedures where a substantial portion can be performed at home through remote instruction.

CAD/CAM Complete Denture Systems and Physical Properties: A Review of the Literature.

PURPOSE: CAD/CAM complete dentures have increased in popularity and a wide variety of systems are currently available. These prostheses present many advantages for clinicians, technicians and patients. Subtractive manufacturing is used by most of the available systems while a few manufacturers use an additive manufacturing technique. This article describes the currently available systems and materials available for the fabrication of CAD/CAM complete dentures and reviews the literature relative to their physical properties. METHODS: A comprehensive review of the literature was completed to enumerate the currently available techniques to fabricate CAD/CAM complete dentures and discuss their physical properties. A search of English language peer-reviewed literature was undertaken using MEDLINE and PubMed on research articles published between 2000 and 2019. A hand search of relevant dental journals was also completed. RESULTS: The literature indicates the physical properties of CAD/CAM milled poly(methylmethacrylate) or PMMA as it is commonly described is superior to conventionally processed PMMA for the fabrication of complete dentures. CONCLUSION: The incorporation of CAD/CAM technology into complete denture design and fabrication streamlines the clinical and laboratory processes and provides improved physical properties that enhance denture quality.

Accuracy of 3D Printed Models Created by Two Technologies of Printers with Different Designs of Model Base.

PURPOSE: To evaluate the accuracy of three-dimensional (3D) printed models manufactured using two different printer technologies with different model base designs. MATERIALS AND METHODS: A maxillary typodont was scanned using a desktop scanner to generate the Standard Tessellation Language (STL) file as a reference scan. After the scanning procedure, the STL file was exported to Model Builder™ for designing the following two types of the model bases: a solid base design and a hollow base design with a 2.0 mm thickness of the external shell. Each design was printed to produce 10 models using a Continuous Liquid Interface Production (CLIP) printer and a Digital Light Processing (DLP) printer. The following four groups were tested: CLIP with solid base (CS); CLIP with hollow base (CH); DLP with solid base (DS); and DLP with hollow base (DH). A total of 40 models were scanned using the same desktop scanner to generate the STL files for evaluation of the accuracy by evaluation of trueness and precision. All STL files were superimposed with the control STL file via surface matching software and a comparison was performed using the 3D color mapping function and a 2D comparison of 48 points selected on the tested model. The data were collected by measuring the deviation between the tested model and the reference scan. Trueness was calculated by using the comparison among four tested groups. The Kruskal-Wallis analysis was conducted to assess the overall statistical significance of differences among the tested groups (α = 0.05). For precision measurement, the evaluation was conducted using Intraclass Correlation Coefficient (ICC) value at 95% confident interval to determine the deviation within the same tested groups. RESULTS: The median values for the deviated distance of the four tested groups were 0.045 (CH), 0.035 (CS), 0.077 (DH), and 0.077 mm (DS). There were no statistically significant differences between the trueness of the two groups when using the same printers regardless of the designs of model base (p > 0.05). However, when comparing the two printers using the same model base design and the two different designs of model base, there were statistically significant differences in trueness (p < 0.05). The 3D printed models created using CLIP technology had higher trueness than the DLP technology printer. Precision of the 3D printed model was displayed in ICC value. The ICC values of four tested groups were 0.968 (CH), 0.981 (CS), 0.969 (DH), and 0.983 (DS). All tested groups were classified as exhibiting an excellent level of precision based on 95% confident interval of the ICC estimation. CONCLUSIONS: The accuracy of 3D printed models was affected by the printer technology regardless of whether the model base was solid or hollow. The CLIP technology printer produced significantly less variation from the reference model than the DLP printer. However, all of the 3D printed models were determined to exhibit a clinically acceptable level of accuracy based on the recorded dimensions being less than 100 µm different than the reference model.

Surface Roughness of Monolithic and Layered Zirconia Restorations at Different Stages of Finishing and Polishing: An In Vitro Study.

PURPOSE: To evaluate surface roughness and topography of different zirconia-based restorations at various steps of finishing and polishing. MATERIALS AND METHODS: Seventy-five zirconia discs were fabricated and divided into 3 layered and 2 monolithic groups: layered conventional (VM9; Vita), layered pressed (PM9; Vita), layered digital (TriLuxe Forte; Vita), opaque monolithic (Ceramill Zi; Amann Girrbach), and translucent monolithic (Zolid FX; Amann Girrbach). Surface roughness testing (Ra, Rz) and scanning electron microscopy were performed at the glazed, unglazed, finished, polished, super-polished, and super-polished with diamond paste steps. One-way ANOVA and Tukey tests were used for statistical analysis. RESULTS: There were significant differences in all groups among the different steps (p < 0.001, F = 77.67 for layered conventional; p < 0.001, F = 133.90 for layered pressed; p < 0.001, F = 47.94 for layered digital; p < 0.001, F = 48.05 for zirconia opaque; p < 0.001, F = 43.91 for zirconia translucent). For the layered groups, glazed stage was significantly different from all other steps (p < 0.001). For the layered conventional and digital groups, polishing using diamond paste was not significantly different from the polished and super-polished steps (p = 0.448, p = 0.153), while for the layered pressed group, polishing using diamond paste was not significantly different from the super polished step (p = 0.815). For monolithic groups, there were no significant differences between the polished and super-polished steps (p = 0.957 for zirconia opaque, p = 1.00 for zirconia translucent). Both the diamond paste and super-polished steps showed no significant differences (p = 0.620, p = 0.550) from the glazed surface in the opaque zirconia group. CONCLUSIONS: Surface roughness of monolithic and layered zirconia was improved by polishing; however, only opaque zirconia reached the level of surface roughness of the glazed stage. Type of buildup affected the surface roughness of adjusted ceramics, with monolithic zirconia showing lower surface roughness than layered zirconia. Polishing with diamond paste provided no significant improvement in the surface roughness of monolithic or layered zirconia.

Errors associated with digital preview of computer-engineered complete dentures and guidelines for reducing them: A technique article.

Patient reports, clinical studies, and systematic reviews reveal a rapid increase in interest in computer-engineered complete dentures (CECDs). The advantages of CECDs include a reduced number of visits, improved fit and retention, and electronic archiving. However, patient dissatisfaction has been reported with CECDs, which may be due to the lack of a trial placement appointment. This technique article identifies errors that occur when CECDs are previewed digitally and proposes guidelines and a checklist to reduce complications such as inadequate esthetics, poor tooth arrangement, misaligned occlusal plane, and inappropriate denture base characteristics.

Three-dimensional printing in contemporary fixed prosthodontics: A technique article.

Digital dentistry has gained in popularity among clinicians and laboratory technicians because of its versatile applications. Three-dimensional (3D) printing has been applied in many areas of dentistry as it offers efficiency, affordability, accessibility, reproducibility, speed, and accuracy. This article describes a technique where 3D printing is used to fabricate a die-trimmed cast and to replicate gingival tissue and implant analogs. The digital workflow that replaces the conventional laboratory procedure is outlined.

A 3D-printed guide for lateral approach sinus grafting: A dental technique.

Lateral approach sinus grafting has become a routine and predictable surgical method of augmenting the pneumatized sinus for implant placement. Outlining the lateral window access can be a challenging task for the clinician to envision and execute. Improper extension and access to the maxillary sinus can prevent proper placement of graft materials and lead to complications. The purpose of this report was to demonstrate a technique that will allow the precise planning of the lateral approach using radiographic information and 3-dimensional (3D) software to 3D-print a surgical guide.

Comparison of denture tooth movement between CAD-CAM and conventional fabrication techniques.

STATEMENT OF PROBLEM: Data comparing the denture tooth movement of computer-aided design and computer-aided manufacturing (CAD-CAM) and conventional denture processing techniques are lacking. PURPOSE: The purpose of this in vitro study was to compare the denture tooth movement of pack-and-press, fluid resin, injection, CAD-CAM-bonded, and CAD-CAM monolithic techniques for fabricating dentures to determine which process produces the most accurate and reproducible prosthesis. MATERIAL AND METHODS: A total of 50 dentures were evaluated, 10 for each of the 5 groups. A master denture was fabricated and milled from prepolymerized poly(methyl methacrylate). For the conventional processing techniques (pack-and-press, fluid resin, and injection) a polyvinyl siloxane putty mold of the master denture was made in which denture teeth were placed and molten wax injected. The cameo surface of each wax-festooned denture was laser scanned, resulting in a standard tessellation language (STL) format file. The CAD-CAM dentures included 2 subgroups: CAD-CAM-bonded teeth in which the denture teeth were bonded into the milled denture base and CAD-CAM monolithic teeth in which the denture teeth were milled as part of the denture base. After all specimens had been fabricated, they were hydrated for 24 hours, and the cameo surface laser scanned. The preprocessing and postprocessing scan files of each denture were superimposed using surface-matching software. Measurements were made at 64 locations, allowing evaluation of denture tooth movement in a buccal, lingual, mesial-distal, and occlusal direction. The use of median and interquartile range values was used to assess accuracy and reproducibility. Levene and Kruskal-Wallis analyses of variance were used to evaluate differences between processing techniques (α=.05). RESULTS: The CAD-CAM monolithic technique was the most accurate, followed by fluid resin, CAD-CAM-bonded, pack-and-press, and injection. CAD-CAM monolithic technique was the most reproducible, followed by pack-and-press, CAD-CAM-bonded, injection, and fluid resin. Techniques involving compression during processing showed increased positive occlusal tooth movement compared with techniques not involving compression. CONCLUSIONS: CAD-CAM monolithic dentures produced the best combination of accuracy and reproducibility of the tested techniques. The results from this study demonstrate that varying amounts of tooth movement can be expected depending on the processing technique. However, the clinical significance of these differences is unknown.

Clinical complications and quality assessments with computer-engineered complete dentures: A systematic review.

STATEMENT OF PROBLEM: Computer-engineered complete dentures (CECDs) have significant potential as shown by recent reports of outcomes and specific applications. An understanding of complications and quality assessment factors associated with CECDs from compiled data is lacking in published reports. PURPOSE: The purpose of this systematic review was to determine the clinical complications and quality assessments related to CECDs. MATERIAL AND METHODS: Electronic searches of publications in English from January 1984 to September 2016 were performed in MEDLINE and Cochrane databases, with the results enriched by manual searches and citation mining to address 2 population intervention comparison outcome (PICO) questions: what are the clinical complications associated with CECDs, and what are the quality assessments with CECDs? RESULTS: A review of 5 selected articles (limited data) on CECDs revealed patient dissatisfaction related to overall outcome (25.49%), inadequate retention (20.73%), and esthetic concerns (15.09%) as common complications. Quality assessment factors that were used to report complications were identified. CONCLUSIONS: Patient dissatisfaction, inadequate retention, and inadequate esthetics were the most common complications with CECDs. The addition of a trial placement option for CECDs could result in a better clinical outcome, reducing the incidence of other complications related to occlusal vertical dimension, centric relationship, tooth arrangement, and esthetics, improving patient satisfaction, and reducing remakes. The difficulty in reading the digital preview for an objective assessment before fabrication is a unique but not a common, complication for CECDs.

Comparison of denture base adaptation between CAD-CAM and conventional fabrication techniques.

STATEMENT OF PROBLEM: Currently no data comparing the denture base adaptation of CAD-CAM and conventional denture processing techniques have been reported. PURPOSE: The purpose of this in vitro study was to compare the denture base adaptation of pack and press, pour, injection, and CAD-CAM techniques for fabricating dentures to determine which process produces the most accurate and reproducible adaptation. MATERIAL AND METHODS: A definitive cast was duplicated to create 40 gypsum casts that were laser scanned before any fabrication procedures were initiated. A master denture was made using the CAD-CAM process and was then used to create a putty mold for the fabrication of 30 standardized wax festooned dentures, 10 for each of the conventional processing techniques (pack and press, pour, injection). Scan files from 10 casts were sent to Global Dental Science, LLC for fabrication of the CAD-CAM test specimens. After specimens for each of the 4 techniques had been fabricated, they were hydrated for 24 hours and the intaglio surface laser scanned. The scan file of each denture was superimposed on the scan file of the corresponding preprocessing cast using surface matching software. Measurements were made at 60 locations, providing evaluation of fit discrepancies at the following areas: apex of the denture border, 6 mm from the denture border, crest of the ridge, palate, and posterior palatal seal. The use of median and interquartile range was used to assess accuracy and reproducibility. The Levine and Kruskal-Wallis analysis of variance was used to evaluate differences between processing techniques at the 5 specified locations (α=.05). RESULTS: The ranking of results based on median and interquartile range determined that the accuracy and reproducibility of the CAD-CAM technique was more consistently localized around zero at 3 of the 5 locations. Therefore, the CAD-CAM technique showed the best combination of accuracy and reproducibility among the tested fabrication techniques. The pack and press technique was more accurate at 2 of the 5 locations; however, its interquartile range (reproducibility) was the greatest of the 4 tested processing techniques. The pour technique was the most reproducible at 2 of the 5 locations; however, its accuracy was the lowest of the tested techniques. CONCLUSIONS: The CAD-CAM fabrication process was the most accurate and reproducible denture fabrication technique when compared with pack and press, pour, and injection denture base processing techniques.

Current techniques in CAD/CAM denture fabrication.

Recently, the use of computer-aided design/computer-aided manufacturing (CAD/CAM) to produce complete dentures has seen exponential growth in the dental market, and the number of commercially available CAD/CAM denture systems grows every year. The purpose of this article is to describe the clinical and laboratory procedures of 5 CAD/CAM denture systems.

A comparison of gingival display with a requested smile, Duchenne smile, grimace of disgust, and funnel-shaped expression.

STATEMENT OF PROBLEM: A patient's smile may not elicit the maximum amount of maxillary gingiva. PURPOSE: The purpose of this study was to measure the amount of gingival display with 4 different facial expressions. MATERIAL AND METHODS: Video images of 91 randomly selected adults were evaluated to measure the height of gingival display at the maxillary anterior teeth and first premolars when participants were asked to give their biggest smile (requested smile), make a Duchenne smile, mimic an intense grimace of disgust (grimace), and produce a funnel-shaped expression (funnel). Measurements were compared with the Friedman Test with post hoc comparisons (α=.05 for all tests). RESULTS: The intraclass correlation coefficient was (95% CI)=0.913(0.623, 0.984). At the central and lateral incisors, the grimace and funnel expressions produced the greatest amounts of gingival display. At the canines and the first premolars, both smiles (requested and Duchenne) exhibited the largest amount of gingival display of the 4 facial expressions. CONCLUSIONS: Neither smile type revealed a significantly greater amount of gingival display above the maxillary central or lateral incisors but the grimace and funnel facial expressions did (P ≤.001). Above the maxillary canines, both smiles displayed a significantly greater amount of gingiva than did the funnel expression (P<.001), but only the Duchenne smile displayed a greater amount than did the grimace expression (P=.05). Superiorly to the maxillary first premolars, both smile types revealed significantly greater amounts of soft tissue when compared with the other 2 facial expressions (P<.001).

3D Printing of Complete Dentures: A Narrative Review.

To explore the applications of 3D printing for the fabrication of complete dentures, a literature search was conducted using PubMed to identify articles related to the topic of 3D-printed complete dentures. A search was conducted that included the following keywords: digital complete denture workflow, printed complete denture, additive manufacturing complete denture, digital complete denture, CAD/CAM complete denture. Articles published before 2016 were excluded to increase the relevancy of reporting results. Determining how 3D-printed dentures compare to conventional and milled dentures is important to better understand how they can be used clinically. Material strength, color stability, and denture base adaptation are discussed. Currently, the area of greatest innovation is with printing resins and improving physical and esthetic properties. As with every innovation, multiple generations of materials are created before the gold standard is achieved. While the ideal printed denture material does not currently exist, based on the published research, printed dentures have material strength that meets ISO standards, with denture base adaptation similar to conventionally processed dentures. Clinically, it is likely that printed dentures will have more challenges with fractures, color stability, and staining. However, printed dentures offer many benefits, and the current limitations will be addressed as new materials are developed. We are currently at the beginning of what is an exciting future for printed dentures.