Comparison of biogenerically reconstructed and waxed-up complete occlusal surfaces with respect to the original tooth morphology

Comparison of the morphological accuracy of automatic crowns designed by multiple computer-aided design software programs with different levels of dentition information acquisition

STATEMENT OF PROBLEM

Information on the morphological accuracy of crowns automatically produced by different computer-aided design (CAD) software programs for multilevel dentition defects is limited.

PURPOSE

The purpose of this in vitro study was to compare the morphological accuracy of crowns fabricated using different CAD software programs with different design theories for multilevel dentition defects.

MATERIAL AND METHODS

Four dentition defect types (the standard group, the abrasion group, the adjacent-teeth-missing group, and the antagonist-tooth-missing group, n=10) were fabricated to represent different levels of missing dentition information. Two design modes (the library mode and correlation mode) of 3 common CAD software programs (3Shape [3Shape A/S], CEREC [Dentsply Sirona], and exocad DentalCAD [exocad GmbH]) were used to design crowns automatically, and the morphologies of the generated crowns and original teeth were recorded. The root mean square (RMS) value was calculated to evaluate the morphological deviations between the autogenerated crowns and original teeth using the 3D matching system (Geomagic GmbH). As each group in this study represented 3 factors, the mean differences between the treatment combinations and the interaction effects were analyzed by performing factorial analysis of variance (α=.05).

RESULTS

The RMS values of autogenerated crowns designed using the correlation method were significantly lower than those designed using the library method of each software program in the 4 groups (P<.05). The RMS values of crowns designed by the 3Shape and CEREC software programs in library mode under conditions with dentition information loss were lower than those of crowns designed by the exocad software program (P<.05). Changes in the acquisition of dental information did not decrease the CEREC design accuracy (P>.05), while they did decrease the 3Shape and exocad design accuracy (P<.05).

CONCLUSIONS

The correlation method showed higher accuracy in rebuilding the original morphology of the teeth than the library method. Both the 3Shape and CEREC software programs showed higher accuracy than the exocad software program in library mode under conditions with dentition information loss, while CEREC showed higher stability than the 3Shape and exocad software programs.

Precise tooth design using deep learning-based templates

OBJECTIVES

In prosthodontic procedures, traditional computer-aided design (CAD) is often time-consuming and lacks accuracy in shape restoration. In this study, we combined implicit template and deep learning (DL) to construct a precise neural network for personalized tooth defect restoration.

METHODS

Ninety models of right maxillary central incisor (80 for training, 10 for validation) were collected. A DL model named ToothDIT was trained to establish an implicit template and a neural network capable of predicting unique identifications. In the validation stage, teeth in validation set were processed into corner, incisive, and medium defects. The defective teeth were inputted into ToothDIT to predict the unique identification, which actuated the deformation of the implicit template to generate the highly customized template (DIT) for the target tooth. Morphological restorations were executed with templates from template shape library (TSL), average tooth template (ATT), and DIT in Exocad (GmbH, Germany). RMSestimate, width, length, aspect ratio, incisal edge curvature, incisive end retraction, and guiding inclination were introduced to assess the restorative accuracy. Statistical analysis was conducted using two-way ANOVA and paired t-test for overall and detailed differences.

RESULTS

DIT displayed significantly smaller RMSestimate than TSL and ATT. In 2D detailed analysis, DIT exhibited significantly less deviations from the natural teeth compared to TSL and ATT.

CONCLUSION

The proposed DL model successfully reconstructed the morphology of anterior teeth with various degrees of defects and achieved satisfactory accuracy. This approach provides a more reliable reference for prostheses design, resulting in enhanced accuracy in morphological restoration.

CLINICAL SIGNIFICANCE

This DL model holds promise in assisting dentists and technicians in obtaining morphology templates that closely resemble the original shape of the defective teeth. These customized templates serve as a foundation for enhancing the efficiency and precision of digital restorative design for defective teeth.

Discrepancies in the occlusal devices designed by an experienced dental laboratory technician and by 2 artificial intelligence-based automatic programs

STATEMENT OF PROBLEM

Artificial intelligence (AI) models have been developed for different applications, including the automatic design of occlusal devices; however, the design discrepancies of an experienced dental laboratory technician and these AI automatic programs remain unknown.

PURPOSE

The purpose of this in vitro study was to compare the overall, intaglio, and occlusal surface discrepancies of the occlusal device designs completed by an experienced dental laboratory technician and two AI automatic design programs.

MATERIAL AND METHODS

Virtually articulated maxillary and mandibular diagnostic casts were obtained in a standard tessellation language (STL) file format. Three groups were created depending on the operator or program used to design the occlusal devices: an experienced dental laboratory technician (control group) and two AI programs, namely Medit Splints from Medit (Medit group) and Automate from 3Shape A/S (3Shape group) (n=10). To minimize the discrepancies in the parameter designs among the groups tested, the same printing material and design parameters were selected. In the control group, the dental laboratory technician imported the articulated scans into a dental design program (DentalCAD) and designed a maxillary occlusal device. The occlusal device designs were exported in STL format. In the Medit and 3Shape groups, the diagnostic casts were imported into the respective AI programs. The AI programs automatically designed the occlusal device without any further operator intervention. The occlusal device designs were exported in STL format. Among the 10 occlusal designs of the control group, a random design (shuffle deck of cards) was used as a reference file to calculate the overall, intaglio, and occlusal discrepancies in the specimens of the AI groups by using a program (Medit Design). The root mean square (RMS) error was calculated. Kruskal-Wallis, and post hoc Dwass-Steel-Critchlow-Fligner pairwise comparison tests were used to analyze the trueness of the data. The Levene test was used to assess the precision data (α=.05).

RESULTS

Significant overall (P<.001), intaglio (P<.001), and occlusal RMS median value (P<.001) discrepancies were found among the groups. Significant overall RMS median discrepancies were observed between the control and the Medit groups (P<.001) and the control and 3Shape groups (P<.001). Additionally, significant intaglio RMS median discrepancies were found between the control and the Medit groups (P<.001), the Medit and 3Shape groups (P<.001), and the control and 3Shape groups (P=.008). Lastly, significant occlusal RMS median discrepancies were found between the control and the 3Shape groups (P<.001) and the Medit and 3Shape groups (P<.001). The AI-based software programs tested were able to automatically design occlusal devices with less than a 100-µm trueness discrepancy compared with the dental laboratory technician. The Levene test revealed significant overall (P<.001), intaglio (P<.001), and occlusal (P<.001) precision among the groups tested.

CONCLUSIONS

The use of a dental laboratory technique influenced the overall, intaglio, and occlusal trueness of the occlusal device designs obtained. No differences were observed in the precision of occlusal device designs acquired among the groups tested.

Applications, functions, and accuracy of artificial intelligence in restorative dentistry: A literature review

OBJECTIVE

The applications of artificial intelligence (AI) are increasing in restorative dentistry; however, the AI performance is unclear for dental professionals. The purpose of this narrative review was to evaluate the applications, functions, and accuracy of AI in diverse aspects of restorative dentistry including caries detection, tooth preparation margin detection, tooth restoration design, metal structure casting, dental restoration/implant detection, removable partial denture design, and tooth shade determination.

OVERVIEW

An electronic search was performed on Medline/PubMed, Embase, Web of Science, Cochrane, Scopus, and Google Scholar databases. English-language articles, published from January 1, 2000, to March 1, 2022, relevant to the aforementioned aspects were selected using the key terms of artificial intelligence, machine learning, deep learning, artificial neural networks, convolutional neural networks, clustering, soft computing, automated planning, computational learning, computer vision, and automated reasoning as inclusion criteria. A manual search was also performed. Therefore, 157 articles were included, reviewed, and discussed.

CONCLUSIONS

Based on the current literature, the AI models have shown promising performance in the mentioned aspects when being compared with traditional approaches in terms of accuracy; however, as these models are still in development, more studies are required to validate their accuracy and apply them to routine clinical practice.

CLINICAL SIGNIFICANCE

AI with its specific functions has shown successful applications with acceptable accuracy in diverse aspects of restorative dentistry. The understanding of these functions may lead to novel applications with optimal accuracy for AI in restorative dentistry.

Artificial intelligence models for tooth-supported fixed and removable prosthodontics: A systematic review

STATEMENT OF PROBLEM

Artificial intelligence applications are increasing in prosthodontics. Still, the current development and performance of artificial intelligence in prosthodontic applications has not yet been systematically documented and analyzed.

PURPOSE

The purpose of this systematic review was to assess the performance of the artificial intelligence models in prosthodontics for tooth shade selection, automation of restoration design, mapping the tooth preparation finishing line, optimizing the manufacturing casting, predicting facial changes in patients with removable prostheses, and designing removable partial dentures.

MATERIAL AND METHODS

An electronic systematic review was performed in MEDLINE/PubMed, EMBASE, Web of Science, Cochrane, and Scopus. A manual search was also conducted. Studies with artificial intelligence models were selected based on 6 criteria: tooth shade selection, automated fabrication of dental restorations, mapping the finishing line of tooth preparations, optimizing the manufacturing casting process, predicting facial changes in patients with removable prostheses, and designing removable partial dentures. Two investigators independently evaluated the quality assessment of the studies by applying the Joanna Briggs Institute Critical Appraisal Checklist for Quasi-Experimental Studies (nonrandomized experimental studies). A third investigator was consulted to resolve lack of consensus.

RESULTS

A total of 36 articles were reviewed and classified into 6 groups based on the application of the artificial intelligence model. One article reported on the development of an artificial intelligence model for tooth shade selection, reporting better shade matching than with conventional visual selection; 14 articles reported on the feasibility of automated design of dental restorations using different artificial intelligence models; 1 artificial intelligence model was able to mark the margin line without manual interaction with an average accuracy ranging from 90.6% to 97.4%; 2 investigations developed artificial intelligence algorithms for optimizing the manufacturing casting process, reporting an improvement of the design process, minimizing the porosity on the cast metal, and reducing the overall manufacturing time; 1 study proposed an artificial intelligence model that was able to predict facial changes in patients using removable prostheses; and 17 investigations that developed clinical decision support, expert systems for designing removable partial dentures for clinicians and educational purposes, computer-aided learning with video interactive programs for student learning, and automated removable partial denture design.

CONCLUSIONS

Artificial intelligence models have shown the potential for providing a reliable diagnostic tool for tooth shade selection, automated restoration design, mapping the preparation finishing line, optimizing the manufacturing casting, predicting facial changes in patients with removable prostheses, and designing removable partial dentures, but they are still in development. Additional studies are needed to further develop and assess their clinical performance.

Facial Line Angles: A Key to Tooth-like Rehabilitation

Recently, improvement of appearance and a quest for beauty have become a primary concern for patients. It is a challenging task for a clinician to achieve esthetic integration of prosthetic pieces for anterior teeth, particularly for highly demanding patients who give attention to particular details. The challenge is harder when only one tooth has to be restored. The objective is to achieve a fully and perfectly integrated rehabilitation with natural dentition. Poorly described, facial line angles are key to the success of achieving the desired tooth shape, especially for the maxillary central incisor. They influence both the shape and color of the tooth through optical illusion. Their misplacement could certainly spoil the esthetic outcome. Thus, it is mandatory to respect and recreate them. The objective of the present study was to define and then to highlight their importance. It also aimed to give some tips on how to perfect the shape of prosthetic teeth through a clinical case of central incisor esthetic rehabilitation.

Initial biocompatibility of novel resins for 3D printed fixed dental prostheses

OBJECTIVES

Several materials for 3D printing of fixed dental prostheses (FDP) have been recently introduced. This study aims to evaluate the initial biocompatibility of novel printable resins for manufacturing temporary and permanent FDP.

METHODS

Specimens of five printable resins (VarseoSmile Crown plus, NextDent C&B MFH, VarseoSmile Temp, Temp PRINT, P Pro Crown & Bridge), two types of resins for subtractive manufacturing (Tetric CAD, Telio CAD) and two types of resins with conventional curing processes (Tetric EvoCeram, Protemp 4) were produced and finished. Post-processing was strictly performed according to the manufacturer's protocol. Biocompatibility was evaluated by eluting specimens with cell culture medium and treating human gingival fibroblast cells with the eluates. A 72-hour continuous read cell viability assay measuring the reducing potential of the cells was performed. The cellular inflammatory response in terms of IL-6 and PGE₂ levels was determined with specific ELISAs. Oxidative stress was determined by measuring oxidized glutathione concentrations after exposure to the resin eluates. A luminescence-based apoptosis assay was used to detect apoptosis.

RESULTS

Tetric CAD and Telio CAD were slightly toxic. All other resins were moderately to severely cytotoxic. VarseoSmile Crown plus and P Pro Crown & Bridge significantly enhanced PGE₂ levels. Higher concentrations of oxidized gluthatione were determined in the presence of Telio CAD, VarseoSmile Temp and P Pro Crown & Bridge. Tetric EvoCeram and Protemp 4 reduced intracellular gluthatione levels. All printable resins slightly induced apoptosis.

SIGNIFICANCE

Further post-processing steps such as additional curing and washing may improve the biocompatibility of printable materials.

Step-by-Step Esthetic Rehabilitation with Chairside System

In modern dentistry, Computer-Aided Design and Manufacturing (CAD/CAM) is a promising technology that allows fabrication of prosthetic restorations through milling procedures. Over years, with the continuous improvement of technology, direct CAD/CAM or “chairside” technology is becoming a widespread approach which offers immediate rehabilitation with long-term rates reported by several studies compared to conventional techniques. All steps are generally carried out in the dental office during the same treatment session. The present paper is about a healthy female patient with a decayed 36 tooth which was restored by ceramic onlay using Planmeca's PlanCAD system. Through the present clinical case, a detailed protocol of chairside technology would be presented from the digital impression to the milling process. It would detail impression steps. It would also highlight especially the virtual design confection of prosthetic restoration using a biogeneric model included in the software. It also illustrated tools which could be used by the dentist to perform the design. Also, some useful tips would be presented in order to perform the confection. On this subject, various studies showed the viability of such technology. To summarize, referring to previous studies, this promising technology allows especially time-saving and patient's comfort compared to the indirect one.

Design of occlusal wear facets of fixed dental prostheses driven by personalized mandibular movement

STATEMENT OF PROBLEM

Existing virtual articulators simulate mandibular movement by using various parameters and are used to design restorations. However, they are not able to reproduce actual patient movements, and the designs of occlusal wear facets by them and by personalized mandibular movement have not been compared.

PURPOSE

The purpose of this clinical study was to establish a clinical application protocol for a virtual articulator based on previous research and to evaluate the accuracy of the occlusal wear facets designed by it.

MATERIAL AND METHODS

The gypsum casts of 12 participants were scanned with a cast scanner as the original data. A single crown, 3-unit splinted crowns, a 5-unit fixed partial denture, and a fixed complete denture were virtually prepared on the digital mandibular casts by using the Geomagic Studio 2013 software program. High points were created at the wear facets, and corresponding digital wax patterns with occlusal interferences were generated. The exocad software program was used to design corresponding restorations with the copy method. Static (STA restoration) and dynamic (DYN restoration) occlusal adjustments were carried out with the built-in virtual articulator. The mandibular movements of participants were recorded by the novel virtual articulator system, and the occlusal surfaces of the digital wax patterns were adjusted (FUN restoration). The restorations adjusted with the 3 methods were compared with the original data. The mean value and root mean square (RMS) of 3D deviation and positive volumes (V+) in the occlusal direction were measured. Depending on the normality, 1-way ANOVA and the Kruskal-Wallis test were used to analyze the influence of occlusal surface design methods on the morphology of occlusal wear facets (α=.05).

RESULTS

The mean deviation of the 4 kinds of STA restorations ranged from 0.19 mm to 0.22 mm, the DYN restorations from 0.13 mm to 0.17 mm, and the FUN restorations from 0.03 mm to 0.09 mm. A significant difference was found between the STA and FUN restorations of the 3-unit splinted crowns and 5-unit fixed partial dentures (Ρ=.013, Ρ=.021). The mean values of 3D deviation and V+ decreased from the STA group to the DYN group and then to the FUN group. The RMS and V+ were statistically similar (Ρ>.05).

CONCLUSIONS

The preliminary results of the study indicate that the FUN 3-unit splinted crowns and 5-unit fixed partial dentures designed with the self-developed virtual articulator were better than the STA restorations. The FUN restorations were more coincident with the morphology of the wear facets on the original teeth.

Comparison between Occlusal Errors of Single Posterior Crowns Adjusted Using Patient Specific Motion or Conventional Methods

Recently, digital technology has been used in dentistry to enhance accuracy and to reduce operative time. Due to advances in digital technology, the integration of individual mandibular motion into the mapping of the occlusal surface is being attempted. The Patient Specific Motion (PSM) is one such method. However, it is not clear whether the occlusal design that is adjusted using PSM could clinically show reduced occlusal error compared to conventional methods based on static occlusion. In this clinical comparative study including fifteen patients with a single posterior zirconia crown treatment, the occlusal surface after a clinical adjustment was compared to no adjustment (NA; design based on static occlusion), PSM (adjusted using PSM), and adjustment using a semi-adjustable articulator (SA) for the assessment of occlusal error. The root mean square (RMS; μm), average deviation value (±AVG; μm), and proportion inside the tolerance (in Tol; %) were calculated using the entire, subdivided occlusal surface and the out of tolerance area. Using a one-way ANOVA, the RMS and +AVG from the out of tolerance area showed a statistical difference between PSM (202.3 ± 39.8 for RMS, 173.1 ± 31.3 for +AVG) and NA (257.0 ± 73.9 for RMS, 210.9 ± 48.6 for +AVG). For the entire and subdivided occlusal surfaces, there were no significant differences. In the color-coded map analysis, PSM demonstrated a reduced occlusal error compared to NA. In conclusion, adjustment occlusal design using PSM is a simple and effective method for reducing occlusal errors that are difficult to identify in a current computer-aided design (CAD) workflow with static occlusion.

Automatic Digital Design of the Occlusal Anatomy of Monolithic Zirconia Crowns Compared to Dental Technicians' Digital Waxing: A Controlled Clinical Trial

PURPOSE

Reconstructing the occlusal morphology of posterior teeth in definitive dental prosthesis can be challenging. The use of the correlation technique enables replication of the information and occlusal anatomy of interim dental prostheses to the definitive ones. The purpose of this controlled clinical trial was to compare the static and dynamic contacts (SDC) of monolithic zirconia crowns designed with correlation and library techniques.

MATERIAL AND METHODS

Twenty-four patients were included in the study for a total of 28 molars. For each abutment tooth, an interim crown was fabricated and two digital scans, with and without the interim crown in place were made. Two single crowns were designed using correlation and library techniques. Fifty-six monolithic zirconia crowns were milled. The interim and definitive crowns were evaluated intraorally for SDC by using a 24-μm-thick blue articulating foil. After removing the interim and definite crowns, extraoral photographs were taken to calculate the SDC area using software (ImageJ) and analyzed by the Kruskal-Wallis test.

RESULTS

The average and ± standard deviation (SD) of area of the occlusal marks on interim crowns was 32.27 ± 3.45 mm² . Definitive crowns designed by using the correlation technique had an area of 31.01 ± 3.73 mm² ; the area in the library technique was 36.85 ± 5.78 mm² . No statistically significant difference was found (p = 0.091) between the occlusal mark areas of the interim and definitive crowns designed by using the correlation technique. Whereas, there were significant differences between the areas of occlusal marks of the interim and definitive crowns designed by using the library technique, and between the areas of occlusal marks of definitive crowns designed by using the correlation and library techniques (p < 0.001).

CONCLUSION

The average area of the SDC of monolithic zirconia crowns designed by using the correlation technique was similar to that of interim crowns. The library technique was less effective when replicating the SDC compared to the correlation technique.

Evaluation of the measurement precision and accuracy in the dental CAD/CAM system

The purpose of this study is to investigate the precision and trueness of the occlusal contact record obtained with a dental CAD/CAM device (ARCTICA). Sandblasted spherical steel balls with diameters of 10-20 mm were measured using ARCTICA and a three-dimensional measurement device (FN503). The radius of each steel ball was calculated from the measured value and the difference between the measured and nominal values was obtained. Upper/lower dental arch casts were measured and processed for occlusal contact image creation using both devices. The graphical images of the occlusal contacts at the intercuspal position obtained from both systems and an occlusal analysis device (BE-1) were compared with the occlusal contact area. Excellent correlation was observed between the measurement results of ARCTICA and FN503 (p<0.001, R²: 0.99). The occlusal contact areas were 186.0 mm² (ARCTICA), 192.8 mm² (FN503), and 196.1 mm² (BE-1). This study showed that ARCTICA is capable of conducting highly accurate measurements and generating a graphical image of occlusal contacts with good reliability.

Comparative evaluation of the morphological accuracy of dental crowns fabricated by different technologies

STATEMENT OF PROBLEM

Information on the morphological accuracy of crowns produced by different technologies is limited.

PURPOSE

The purpose of this in vitro study was to compare the morphology and contacts of crowns fabricated with intraoral systems, extraoral systems, and conventional method.

MATERIAL AND METHODS

A typodont mandibular first molar (Nissin Dental Product) received a complete ceramic crown preparation and a reference crown. Microcomputed tomography (μCT) was used to obtain the virtual data (REF) of the reference crown. Three groups of replicated crowns were made: intraoral scanning system (TRIOS), extraoral scanning system (D700), and the conventional method (CONV) (n=8). The groups TRIOS and D700 were designed by the correlation method. All crowns were scanned with μCT to obtain 3D data. The data were superimposed on each other or the REF in an inspection software to evaluate precision and trueness. The contact penetration area of the occlusal surfaces of the crowns was calculated. An independent sample t test and 1-way ANOVA with the post hoc least significant difference (LSD) test were used to compare the data (α=.05).

RESULTS

The crowns fabricated with the extraoral scanners showed significantly lower root mean square (RMS) values for trueness (F=1456.90, df=2, P<.001) and precision (F=188.88, df=2, P<.001) than the others. The penetration contact area ratio and the differences in the CONV group were both significantly higher than those of the other groups.

CONCLUSIONS

The average discrepancies of the crown morphology fabricated from the extraoral scanning were significantly lower than those from others. The conventional method restored the occlusal contact with significantly less accuracy than the other groups.

Comparison and evaluation of the morphology of crowns generated by biogeneric design technique with CEREC chairside system

Objectives

To better guide clinicians to choose the appropriate chairside system, we compared and evaluated the morphology of crowns generated by three different biogeneric design modes (biogeneric copy (BC), biogeneric individual (BI), and biogeneric reference (BR)) of the CEREC software.

Methods

Maxillary and mandibular casts were obtained from twelve volunteers and digital impressions were acquired. All ceramic crown preparations of all right maxillary central incisors were prepared and digital impressions were taken. Then, crowns were automatically designed under BC, BI and BR modes separately and their morphologies were evaluated by six doctors. The “optimal fitting alignment” and “3D analysis” functions of the Geomagic Qualify software were carried out between original teeth and auto-generated full crowns. The auto-generated crowns were modified by a technician according to clinical criteria and the adjustment time was recorded. The discrepancies between technician modified crowns and the auto-generated full crowns were evaluated with the same functions in the Geomagic Qualify software.

Results

The subjective evaluation results of BC group were significantly better than those of BI and BR group (p < 0.05). Compared with the original teeth and modified crowns, auto-generated crowns in BC group all had the smallest differences, followed by BR and BI group (p < 0.05). BC group needed the shortest adjustment time than BI and BR group (p < 0.05).

Conclusions

Using crowns generated by BC mode is more aesthetic and suitable in clinics use than those generated by BI and BR modes and can reduce clinic adjustment time.

Assessment of CAD-CAM zirconia crowns designed with 2 different methods: A self-controlled clinical trial

STATEMENT OF PROBLEM

In computer-aided design and computer-aided manufacturing (CAD-CAM) dentistry, the correlation method is an efficient way to design complete crowns. However, the occlusal relationship and patient satisfaction with prostheses fabricated using this method remain unclear.

PURPOSE

The purpose of this clinical trial was to compare the occlusion of monolithic zirconia crowns designed using the correlation and library methods.

MATERIAL AND METHODS

Twenty-three teeth of 21 participants received 2 monolithic zirconia crowns designed by using the correlation or the library method. Defective teeth were scanned using an intraoral scanner to obtain references and working casts from before and after the preparation. Before cementation, the occlusal relationship of both crowns and patient satisfaction were evaluated, and the occlusal adjustment time was recorded.

RESULTS

The correlation method resulted in less lateral occlusal interference of the crowns than the library method (P<.01). The occlusal adjustment times of the correlation and library conditions were 455.8 ±357.1 seconds and 575.3 ±488.0 seconds, respectively (P>.05). Relative occlusal force was significantly higher in the correlation than in the library condition and was related to before preparation relative occlusal force (r=0.706, P<.01). The visual analog score before occlusal adjustment was higher in the correlation than in the library condition (P<.05). The occlusal contacts, occlusal contact distributions, and number of occlusal contacts did not differ between conditions (P>.05).

CONCLUSIONS

Better eccentric occlusion and reduced lateral occlusal interference were obtained when the correlation method was used to design crowns. The correlation method yielded higher relative occlusal force, which helped to restore the original occlusal force.

Polymer-infiltrated ceramic CAD/CAM inlays and partial coverage restorations: 3-year results of a prospective clinical study over 5 years

OBJECTIVE

The aim of this prospective clinical 5-year study was to evaluate the long-term behavior of monolithic computer-aided design and computer-aided manufacturing (CAD/CAM)-fabricated minimally invasive polymer-infiltrated ceramic network (PICN) inlays and partial coverage restorations (PCR).

MATERIAL AND METHODS

Posterior teeth of 47 patients were restored with 103 restorations (45 inlays, 58 PCRs). After defect-oriented preparations, monolithic PICN restorations of VITA Enamic were fabricated with a CAD/CAM system (inEoS blue/CEREC inLab MCXL) and adhesively bonded (Variolink II). Clinical reevaluations were so far performed at baseline and 6, 12, 24, and 36 months after insertion according to modified United States Public Health Service (USPHS) criteria. Absolute failures were demonstrated by Kaplan-Meier survival rate and relative failures by Kaplan-Meier success rate. A logistic regression model was adjusted for modified USPHS criteria to investigate time and restoration effects (p < 0.05).

RESULTS

After an observation time of 3 years, survival rates were 97.4% for inlays and 95.6% for PCRs. Three restorations had to be replaced due to clinically unacceptable fractures. Secondary caries and debonding were not observed. The 3-year Kaplan-Meier success rate was 84.8% for inlays and 82.4% for PCRs. The decrease in marginal adaption (p = 0.0005), increase in marginal discoloration (p < 0.0001), and surface roughness (p = 0.0005) over time were significant. Color match and anatomic form were excellent. No significant differences were found between both types of restorations for survival (p = 0.716) and success rate (p = 0.431).

CONCLUSIONS

Minimally invasive PICN restorations showed a favorable clinical performance over an observation period of 36 months. However, clinical long-term data have to be awaited.

CLINICAL RELEVANCE

PICN restorations are a suitable treatment option for posterior inlays and PCRs.

Computer-aided analysis of digital dental impressions obtained from intraoral and extraoral scanners

STATEMENT OF PROBLEM

The internal and marginal adaptation of a computer-aided design and computer-aided manufacturing (CAD-CAM) prosthesis relies on the quality of the 3-dimensional image. The quality of imaging systems requires evaluation.

PURPOSE

The purpose of this in vitro study was to evaluate and compare the trueness of intraoral and extraoral scanners in scanning prepared teeth.

MATERIAL AND METHODS

Ten acrylic resin teeth to be used as a reference dataset were prepared according to standard guidelines and scanned with an industrial computed tomography system. Data were acquired with 4 scanner devices (n=10): the Trios intraoral scanner (TIS), the D250 extraoral scanner (DES), the Cerec Bluecam intraoral scanner (CBIS), and the Cerec InEosX5 extraoral scanner (CIES). For intraoral scanners, each tooth was digitized individually. Extraoral scanning was obtained from dental casts of each prepared tooth. The discrepancy between each scan and its respective reference model was obtained by deviation analysis (μm) and volume/area difference (μm). Statistical analysis was performed using linear models for repeated measurement factors test and 1-way ANOVA (α=.05).

RESULTS

No significant differences in deviation values were found among scanners. For CBIS and CIES, the deviation was significantly higher (P<.05) for occlusal and cervical surfaces. With regard to volume differences, no statistically significant differences were found (TIS=340 ±230 μm; DES=380 ±360 μm; CBIS=780 ±770 μm; CIES=340 ±300 μm).

CONCLUSIONS

Intraoral and extraoral scanners showed similar trueness in scanning prepared teeth. Higher discrepancies are expected to occur in the cervical region and on the occlusal surface.

CEREC Chairside System to Register and Design the Occlusion in Restorative Dentistry: A Systematic Literature Review

OBJECTIVE

The aim of this review was to update the literature with regard to the digital methods available by CEREC Chairside system to register and design the occlusion, to report their efficacy and technical innovations in the field of Restorative Dentistry. A search strategy was performed using the key-words: "virtual articulator," or "CAD-CAM and occlusal recording," or "CAD-CAM and occlusion register," or "CAD-CAM and occlusal contacts," or "CAD-CAM and prosthesis."

MATERIAL AND METHODS

Inclusion criteria comprised studies evaluating the use of digital methods available by CEREC System for occlusal registration and design during prosthodontics treatment. PubMed and Cochrane library and reference lists were searched up to January 2016.

RESULTS

The search resulted in 280 articles after removing duplicates. Subsequently, 233 records were excluded and 49 studies were selected for reading in full. Eleven articles were considered eligible for the systematic review (4 in vitro and 7 clinical studies).

CONCLUSION

Scientific evidence suggests that digital methods were accurate to register and design the occlusion of dental prostheses. Nevertheless, further clinical studies are required to establish a conclusion with regard to its accuracy in prosthodontics treatment.

CLINICAL SIGNIFICANCE

Digital technologies allow the design of occlusal surfaces of CAD-CAM fabricated prostheses using innovative approaches. This systematic review aimed to update the literature to help dentists determine the most appropriate digital method to register and design the occlusal surface of CAD-CAM crowns. (J Esthet Restor Dent 28:208-220, 2016).

Evaluation of biogeneric design techniques with CEREC CAD/CAM system

PURPOSE

The aim of this study was to evaluate occlusal contacts generated by 3 different biogeneric design modes (individual (BI), copy (BC), reference (BR)) of CEREC software and to assess the designs subjectively.

MATERIALS AND METHODS

Ten pairs of maxillary and mandibular casts were obtained from full dentate individuals. Gypsum cast contacts were quantified with articulating paper and digital impressions were taken. Then, all ceramic crown preparation was performed on the left first molar teeth and digital impressions of prepared teeth were made. BI, BC, and BR crowns were designed. Occlusal images of designs including occlusal contacts were superimposed on the gypsum cast images and corresponding contacts were determined. Three designs were evaluated by the students.

RESULTS

The results of the study revealed that there was significant difference among the number of contacts of gypsum cast and digital models (P<.05). The comparison of the percentage of virtual contacts of three crown designs which were identical to the contacts of original gypsum cast revealed that BI and BR designs showed significantly higher percentages of identical contacts compared with BC design (P<.05). Subjective assessment revealed that students generally found BI designs and BR designs natural regarding naturalness of fissure morphology and cusp shape and cusp tip position. For general occlusal morphology, student groups generally found BI design "too strong" or "perfect", BC design "too weak", and BR design "perfect".

CONCLUSION

On a prepared tooth, three different biogeneric design modes of a CAD/CAM software reveals different crown designs regarding occlusal contacts and morphology.

Comparison of chairside and laboratory CAD/CAM to conventional produced all-ceramic crowns regarding morphology, occlusion, and aesthetics

OBJECTIVES

There are many ways to produce all-ceramic crowns. Computer-aided design and computer-aided manufacturing (CAD/CAM) procedures compete against conventional fabricated restorations. As different methods of production may produce variable results, this study aims to compare chairside and laboratory-based CAD/CAM systems to conventional crowns regarding their similarity to original tooth morphology, number of occlusal contacts, occlusal adjustment time, and subjective aesthetic perception.

MATERIAL AND METHODS

Impressions of caries-free jaws were taken, and the resulting gypsum casts were scanned with a laboratory scanner. Preparations for all-ceramic full crowns were performed on first molars, and three different restorations were made: CEREC restorations (CER), laboratory-produced CAD/CAM crowns (LABCAD), and conventional waxed-up/pressed ceramic crowns (CONV). Time for occlusal adaptation and the number of occlusal contacts were noted. Two dentists performed aesthetic gradings of restorations. Statistical analysis included one-way ANOVA with least significant difference (LSD) post hoc test, t test, and Kruskal-Wallis test.

RESULTS

Metrical deviations of the re-scanned crowns to the original, unprepared tooth surface were 220.55 ± 54.31 μm for CER, 265.94 ± 61.39 for LABCAD, and 252.44 ± 68.77 μm for CONV group. One-way ANOVA showed significant lower deviations for the CER group. LABCAD crowns showed significantly more occlusal contacts, whereas CONV crowns required the least time for occlusal adaptation and showed excellent aesthetic gradings.

CONCLUSION

All three methods had pros and cons regarding different parameters. Further improvements of CAD/CAM software shall lead to restorations comparable to conventional restorations in all aspects, especially in aesthetics.

CLINICAL RELEVANCE

All tested methods of production for all-ceramic crowns produced clinically acceptable results. Thus, in an individual case, the method chosen can be determined by the dentist's preference.