Crown Preparation Research Articles

Hall Technique for Carious Primary Molars: A Review of the Literature.

The high frequency of caries in primary teeth and its inadequate treatment are major public health problems during childhood. Nowadays, the Hall technique is one of the methods used for biological sealing in carious lesions in primary molars. Thus, the bacteria will be sealed from oral environment and the caries will be inactive. The objective of this article was to provide an updated search on the Hall technique description, indication, contraindication, advantages, concerns, success and failure, cost-effectiveness, acceptability, and preference in pediatric dentistry, and to compare the Hall technique with traditional crown preparation and conventional treatment options for carious primary molars. A discussion of the recently published articles on the Hall technique reveals that the Hall technique is considered a promising restorative option with high acceptability and longevity; with low failure rate for managing carious primary molars compared to conventional treatment modalities used in primary care settings. Furthermore, the survival rate of stainless steel crowns (SSCs) is considered high, whether provided using Hall technique or traditional preparation by a pediatric dentist. Thus, the Hall technique can be an effective addition to the clinician’s range of treatment options for carious primary molars. However, it should be chosen in restricted cases.

Laboratory Technician Assessment of the Quality of Single-Unit Crown Preparations and Impressions as Predictors of the Clinical Acceptability of Crowns as Determined by the Treating Dentist: Findings from the National Dental Practice-Based Research Network.

In-laboratory assessment by laboratory technicians may offer insight to increase clinical success of dental crowns, and research in this area is lacking. Dentists in the National Dental Practice-Based Research Network enrolled patients in a study about single-unit crowns; laboratory technicians evaluated the quality of tooth preparations and impressions. The primary outcome for each crown was clinical acceptability (CAC), as judged by the treating dentist. A secondary outcome was "Goodness of Fit (GOF)," a composite score of several aspects of clinical fit, also judged by the study dentist. A mixed-effects logistic regression was used to analyze associations between laboratory technician ratings and the CAC and GOF. Dentists (n = 205) evaluated 3731 crowns. Technicians ranked the marginal detail of impressions as good or excellent in 92% of cases; other aspects of the impression were ranked good or excellent 88% of the time. Regarding tooth preparation, about 90% of preparations were considered adequate (neither excessive nor inadequate reduction). Factors associated with higher CAC were more preparation taper, and use of optical imaging. Factors associated with better GOF were higher impression quality, greater occlusal reduction, more preparation taper, and optical imaging. Overall quality of preparations and impressions was very high, as evaluated by laboratory technicians. Several clinical parameters were associated with higher CAC and GOF. Clinicians who struggle with crown remakes might consider less conservative tooth preparation, as well as using digital impression technology.

Evaluation of the Precision of Different Intraoral Scanner-Computer Aided Design (CAD) Software Combinations in Digital Dentistry.

BackgroundThe aim of this study was to evaluate the precision of correlation between intraoral scanners and computer aided design (CAD) software programs used during scanning and designing phases of digital dentistry. In the present study, CAD software programs that accept data in Standard Tessellation Language (STL) and proprietary format have been evaluated and data loss has been examined in the scanned data.Material/MethodsA single unit crown preparation was conducted for maxillary right first molar on a fully dentulous model. The prepared tooth was scanned with a high precision industrial scanner (ATOS Core 80) and the reference digital model was obtained. The dental model was further scanned 10 times using 3 different intraoral scanners (CEREC Omnicam AC, TRIOS 3 Color Pod, and Aadva IOS 100). The data obtained from the reference scanner and intraoral scanners were transferred to different CAD programs (CEREC inLab, TRIOS Design Studio, Exocad) and digital crowns were designed for each scanned data-CAD combination. After that, the data losses that occurred between these transfers were evaluated by superimposition technique in a special software (VR Mesh v7.5) (α=0.05).ResultsAmong the all combinations of scanner and software, Omnicam AC-InLab was determined to be the most precise combination through the full digital workflow since the Omnicam AC-Exocad combination showed the highest deviations.ConclusionsWithin the limitations of this in vitro study, it was determined that the combinations of scanners and associated CAD programs yielded more accurate results, and data loss was revealed when the scanned data converted from the proprietary format to the STL format.

An Evaluation on Full Coverage Crown Preparation: An Institutional Analysis

Introduction: Undergraduate (UG) dental students are trained for fixed prosthodontics course clinically in teaching institutions during the clinical years. However, there is a lack of objective data on the quality of fixed prostheses preparations done by UG students on their patients for academic and clinical staff. Aim: To evaluate the full-coverage crown preparations performed by UG dental students in the university clinical teaching programme. Materials and Methods: This study was a clinical audit done in the Faculty of Dentistry, Universiti Sains Islam, Malaysia (USIM) from April to July 2018. The demographic and clinical data were collected from the patients’ notes and included relevant information of patients such as age, gender and others. Full-coverage crowns were analysed and crown preparation assessments were done using specific criteria and standards. The descriptive data were measured in frequency and percentage for categorical variables and mean and standard deviation for continuous data. Results: A total of 31 patients fitted with 45 units of full-coverage crowns were analysed. The mean age of patients treated by fifth year dental students was 40.5 (±14.16) years. A 51% Porcelain Fused to Metal (PFM) crown provided to the patients. On the whole, UG undergoing the dentistry programme in the institution scored the lowest (51%) on proximal reduction and the highest (97.7%) on producing smooth and continuous preparation. Conclusion: Majority of the crowns prepared by students have acceptable preparation except in proximal reduction and cervical margin preparation that can be improved upon and emphasised further during the teaching and learning sessions.

Automatic evaluation of crown preparation using image processing techniques: A substitute to faculty scoring in dental education

Background:This study presents a new and innovative experimental method, including software and its prerequisite instruments, to use image processing techniques for crown preparation analysis.Method:A platform was designed and constructed to take images from artificial teeth in different angles and directions and to process and analyze them by the proposed method to evaluate the quality and quantity of crown preparation. For each tooth, two series of images were taken from the artificial teeth before and after preparation, and image series were registered by two semi-automated and automated methods to transform them into one coordinate system. Region of interest was segmented by user interaction, and tooth region was segmented by substeps such as transformation to hue, saturation, and value color space, edge detection, morphology operations, and contour extraction. Finally, the amount and angle of crown preparation were computed and compared with standard measures to evaluate the quality of crown preparation. The proposed method was applied to a local dataset collected from Isfahan University of Medical Sciences.Results:Difference between the angle of crown preparation computed by the proposed method and that of the experts showed a mean absolute error of 7.17°. The correlation between the segmented regions by the proposed method and those of the experts was also evaluated by the Intersection over Union (IOU) criterion. The best and worst performances achieved in cases by IOU were 0.94 and 0.76, respectively. Finally, the segmentation results of the proposed method indicated an average IOU of 0.89 in all images.Conclusion:Students can use this method as an assessment tool in preclinical tooth preparation to compare their crown work with standard parameters.

Asymptomatic COVID-19 patients and possible screening before an emergency aerosol related endodontic protocols in dental clinic-A Review.

Dentistry is related to the cure of oral and dental infections, so exposure and proximity of dental practitioners to oral and nasal fluids of a patient is very obvious. Before you proceed for an aerosol-generating procedure like RCT, and crown preparations, diagnosis, and screening of COVID-19 is very important, as failure may end up infecting yourself and would become a source of infection to your patient community. Due to limitations of data, medicines, and PPE shortage all around the world, screening of asymptomatic carriers of COVID-19 is very troublesome but necessary. To avoid any silent positive patient, the possible way is to ensure mandatory testing of every patient before you treat it. As the door to door surveillance of COVID-19 patients seems near to impossible in the Pandemic era for densely populated developing countries like India. The possible screening regimes include personal surveillance and contact tracing in the very first appointments. So, on the basis of the knowledge and sources we have so far, we have tried to classify the asymptomatic patients seen in the clinics and their possible screening management there. As it is said classification of a disease, is the first step toward a deep understanding of it. After screening, suspects can be sent to more resourceful places for their managements, and incidences of community spread of the disease through dental clinics can be avoided.

Caso Clínico: Reabilitação Cerâmica Anterior com Sistema CAD/CAM

Due to the constant search for a harmonic smile, the level of demand and the expectations of patients become high, enabling the development of new materials and dental techniques that aim at more conservative procedures and more and more predictable results aesthetically. Techniques with Computer Aided Design and Computer Aided Manufacturing (CAD / CAM) have occupied a prominent place in Dentistry. This is due to the fact that computer aided design or computer aided manufacturing offers a restoration method that lowers the risk of human error and provides highly aesthetic results in a reduced clinical time, albeit at relatively high costs. The objective of the present study is to present, through a clinical case report, an aesthetic rehabilitation through the practical application of the CAD / CAM system. With the completion of the case, it was possible to observe aesthetic improvement through the preparation of the anterior ceramic crowns and improvement of the occlusal condition with the manufacture of a removable upper prosthesis, which enables greater durability of the ceramic crowns, as it better distributes the occlusal loads among the elements, avoiding excessive loads at the site of new indirect restorations. This case report was carried out in two dental sessions, achieving patient aesthetic satisfaction. It has a short-term follow-up, therefore, cases with long-term follow-up are necessary to prove the success of this technique. The high technological cost can be considered a limitation, but there is a notable advance in Dentistry to improve the quality of treatment in extremely short periods.

Comparing the accuracy of six intraoral scanners on prepared teeth and effect of scanning sequence.

PURPOSEThe aim of this study was to evaluate the accuracy of six recently introduced intraoral scanners (IOSs) for single crown preparations isolated from the complete arch, and to determine the effect of scanning sequence on accuracy.MATERIALS AND METHODSA complete arch with right and left canine preparations for single crowns was used as a study model. The reference dataset was obtained by scanning the complete arch using a highly accurate industrial scanner (ATOS Core 80, GOM GmbH). Six different IOSs (Trios, iTero, Planmeca Emerald, Cerec Omnicam, Primescan, and Virtuo Vivo) were used to scan the model ten times each. The scans performed with each IOS were divided into two groups, based on whether the scanning sequence started from the right or left quadrant (n=5). The accuracy of digital impression was evaluated using three-dimensional analyzing software (Geomagic Studio 12, 3D Systems). The Kruskal Wallis and Mann-Whitney U statistical tests for trueness analysis and the One-way ANOVA test for precision analysis were performed (α=.05).RESULTSThe trueness and precision values were the lowest with the Primescan (25 and 10 µm), followed by Trios (40.5 and 11 µm), Omnicam (41.5 µm and 18 µm), Virtuo Vivo (52 and 37 µm), iTero (70 and 12 µm) and Emerald (73.5 and 60 µm). Regarding trueness, iTero showed more deviation when scanning started from the right (P=.009).CONCLUSIONThe accuracy of digital impressions varied depending on the IOS and scanning sequence used. Primescan had the highest accuracy, while Emerald showed the most deviation in accuracy for single crown preparations.

Volumetric analyses of restorative crown preparations in simulated-premolar and -molar teeth

Crowns or abutments of fixed partial denture tooth preparations to restore natural teeth or implant-supported restorations require tooth or abutment reduction in a tapered format. Low angulations of axial wall taper to the long axis of the tooth or abutment have been shown to increase the restoration’s stability during masticatory function with large occlusal loads. The tooth preparation and luting agent stabilize the restoration during these loading cycles to prevent dislodgement. Restoration dislodgement represents a catastrophic failure of the prosthesis in function. The preparation attributes contribute to prevent displacement failure and reduce luting agent tensile and shear stresses. Low axial wall taper levels increase resistance to rotational displacement. Increasing axial wall angulations produces negative consequences including reduced rotational resistance, reduced surface area and increased volume of remaining tooth structure. These three considerations have been shown to involve three variables: preparation vertical height, horizontal base width from rotational axis and rotational axis vertical height compared to the opposing axial resisting wall. Natural tooth preparations are completed by a restorative dentist with a hand-held high-speed handpiece with cutting instruments within the oral cavity; while implant-supported custom abutments are prepared in a similar manner but machined outside the oral cavity. As a result, the machined abutment is more controlled for ideal taper in inanimate materials compared to the intraoral tooth preparation on human vital tissues. This experimental study will analyze the preparation of simulated-vital tooth premolars and molars for volume loss at ideal and non-ideal axial wall angulations with variation of vertical heights and vital pulpal tissue volumes.

In vitro evaluation of fracture resistance and cyclic fatigue resistance of computer-aided design-on and hand-layered zirconia crowns following cementation on epoxy dies.

Aim:This in vitro study was to compare the fracture resistance and cyclic fatigue resistance of hand-layered zirconia crowns and computer-aided design (CAD)-on crowns (lithium disilicate with zirconium oxide).Settings and Design:Comparative -Invitro study design.Materials and Methods:All ceramic crown preparation was done on a mandibular molar ivorine tooth, impression made, and duplicated. Twenty hand-layered zirconia crowns and twenty CAD-on crowns were fabricated using CAD/computer-aided manufacturing (CAD/CAM) technique. All crowns were cemented to their respective dies using resin cement for evaluating fracture resistance and cyclic fatigue resistance using universal testing machine.Statistical Analysis Used:Independent samples t-test, Mann–Whitney U-test, and Shapiro–Wilk test were used.Results:The mean fracture resistance of CAD-on crowns (2660.50 ± 501.303 N) was significantly more than that of hand-layered zirconia crowns (1963.60 ± 452.895 N) (independent samples t-test, P < 0.023). Cyclic fatigue resistance test results showed that the mean number of cycles before failure for hand-layered zirconia crowns was 175,297 and for CAD-on crowns was 212,097 (Mann–Whitney U-test, P < 0.012).Conclusion:CAD-on crowns were found to have significantly higher fracture resistance and cyclic fatigue resistance properties than hand-layered zirconia crowns.

Assessment of Total Occlusal Convergence for Crown Preparation: A Comparative Study

Aim: The aim of the study was to assess the total occlusal convergence guessing by sight and ruler methods and compare with the snapshots for accuracy. Materials and methods: The methods used for total occlusal convergence (TOC) preparation were assessed among students, interns, and dental specialists after die preparation and compared with the snapshots for accuracy. Results: In all, 47% of the specialist’s observation achieved the recommended TOC angle, while 29.25% was obtained by undergraduates. Conclusion: In conclusion, specialist’s observation was better in both ruler and sight guessing methods compared to dental students and interns.

Comparison of Digital and Conventional Impression Methods by Preclinical Students: Efficiency and Future Expectations.

ABSTRACTAims and Objectives:The purpose of this study is to compare digital and conventional impression methods by preclinical students in terms of time and ease and to evaluate their preferences and future expectations.Materials and Methods:Twenty volunteered, 2nd year preclinical students (11 females and 9 males) participated in this study. Students took digital and conventional impressions of the left lower first molar which was made full ceramic crown preparation and opposite full arch from a typodont model (Frasaco, Frasaco GmbH, Tettnang, Germany). They used intraoral scanner (CEREC Omnicam, Sirona Dental GmbH, Bensheim, Germany) for digital impression and also used additional type (Express XT Penta H, 3M ESPE, Seefeld, Germany) and condensation type (Zetaplus, Zhermack SpA, Badia Polesine, Italy) silicones for conventional impression. Their taking impression time was measured. Before taking impression and after taking impression, two kinds of questionnaires were conducted to students about their preference, ease of impression methods, and their future expectations. Statistical analysis was performed by IBM SPSS 23 and Excel 2010 version. Differences between conventional and digital impression in terms of time were analyzed by student’s-t paired test and effect of gender was analyzed by students’s-t independent test.Results:There were statistically significant differences between digital and conventional impression methods in terms of taking impression and total impression time (P < 0.001). But there wasn’t any statistically significant difference between two methods in terms of preparation time. About 85% of students preferred the digital impression method and also 85% of students found that the digital impression method was easy. 95% of students expected to find intraoral scanner in the clinic where working first time.Conclusions:As a result of this study, it has been seen that the students preferred the digital impression method to the conventional impression method and found that the digital impression method was easier.

Simulation training for ceramic crown preparation in the dental setting using a virtual educational system.

The aim was to evaluate the effectiveness of a pre-clinical training of ceramic crown preparation using the Virtual Educational System for Dentistry. Fifty-seven dental students were recruited to prepare a ceramic crown under the guidance of the Real-time Dental Training and Evaluation System (RDTES) in order to collect pre-learning data. They participated in the online virtual learning course independently on the Virtual Learning Network Platform (VLNP). One week later, the students were invited to complete their post-learning crown preparation with the RDTES. A questionnaire survey explored students' perceived benefits or drawbacks of the virtual educational system. Students were allocated into Group A (n=15), B (n=24) and C (n=18) based on their pre-learning performance. Differences of assessment results amongst different groups were evaluated by ANOVA and Kruskal-Wallis tests. The pre- and post-learning assessment results in all groups were compared using paired t tests or Wilcoxon signed rank tests. The error scores for four assessment items (instrument selection, preparation section, preparation reduction, preparation surface and profile) and total score of outcome assessment after the virtual learning were significantly different with those before the virtual learning (P<0.05). There were significant interactions between time and student group in the mean scores of process and outcome assessments (P<0.001), except for the assessment item "damage of adjacent teeth." The application of a Virtual Educational System for Dentistry with the VLNP and RDTES in pre-clinical operative training helps students improve their clinical skills.

3D Printed Teeth with Enamel and Dentin Layer for Educating Dental Students in Crown Preparation.

Commonly used model teeth are so far uniform in color and hardness. There is no discrimination between enamel and dentin part of a tooth. This condition makes it difficult to train a preparation technique, which is adapted to real tooth substance. The aim of this study was to design and establish a 3D printed tooth with different layers for enamel and dentin for education in crown preparation. A printable tooth with different layers for enamel and dentin was designed, and all 38 fourth-year dental students in the first clinical course in prosthodontics and 30 experienced dentists were trained during a voluntary hands-on course in 2019. Prior to the study, the students had used standard model teeth and real-teeth models in their preclinical education. They had experience in caries removal and preparation on real patients. The perceived benefits of the 3D printed tooth were evaluated by a questionnaire. All individuals in both groups completed the questionnaire, for a 100% response rate. The results showed that the printed tooth was given an overall mean grade of 2.3 (students) and 2.0 (experts) on a scale from 1=excellent to 5=poor. The difference in hardness between the dentin and enamel layer was given a mean of 2.4 (students and experts) and the difference in color a 1.7 (students) and 1.8 (experts). The tooth model with the prepared tooth illustrating an ideal preparation was graded 1.6 (students and experts). In this study, the students had the opportunity to learn a correct crown preparation on a printed tooth with different material properties for enamel and dentin. The learning effect with this tooth model was rated as good on the questionnaire by both students and expert dentists.

A Comparative Evaluation of Shear Bond Strength of Orthodontic Brackets Bonded to Porcelain Fused Metal Crowns Treated with Different Surface Conditioning Techniques―An Invitro Study

With the increase in adult orthodontic treatment comes the need to find a reliable method for bonding orthodontic brackets onto metal or ceramic crowns and fixed partial dentures. In this study, shear bond strength and surface roughness tests by scanning electron microscope study were used to examine the effect of 5 different surface conditioning methods: 37% phosphoric acid gel, 9% Hydrofluoric acid, sandblasting + 9% Hydrofluoric acid, Sandblasting + Silane, Fine diamond bur roughening + silane for bonding metal brackets to ceramic surfaces of feldspathic porcelain. A total of 60 human maxillary premolar teeth extracted for therapeutic purposes from patients seeking orthodontic treatment were collected, and 50 ceramic crowns were fabricated onto the premolar teeth following crown preparation. 10 natural teeth were used as controls, they were acid etched in conventional manner using 37% phosphoric acid. Metal brackets were bonded using a light-curing composite. The samples were stored in distilled water at physiological temperature (37oC) for 1 day, and thermocycled 500 times between 5°C and 55°C. Shear bond tests were performed with a universal testing device, and the results were statistically analysed. Ceramic surfaces conditioned with sand blasting followed by application of Silane produced maximum bond strength of 12.34 ± 0.95 MPa comparable or even better than the control group 11.03 ± 1.63 MPa followed by 9% Hydrofluoric acid 11.48 ± 0.98 MPa & Fine Diamond Bur roughening + Silane 9.28 ± 1.11 MPa. Ceramic surfaces conditioned with 37% Ortho Phosphoric acid produced least SBS of 5.51 ± 0.88 MPa and hence not suitable for bonding Orthodontic brackets in a clinical scenario. Statistical tests showed significant difference between and within the groups in shear bond strength and P value also was highly significant, i.e. ***p<0.001. The SEM photomicrographs of all the six different surface preparations revealed different surface morphologies & were corroborative of SBS values. Even though 9% Hydrofluoric acid and Fine diamond bur roughening produced clinically acceptable SBS values, because of their technique sensitivity and side effects, they have to be used with great care and caution. sand blasting followed by the application of Silane coupling agent was found to be the best porcelain surface conditioning method.

CAD-CAM assisted investment casting for preparation of dental crowns

This paper highlights detailed procedure for preparation of dental crowns (DC) by CAD-CAM assisted investment casting (IC) as a case study. Along with biocompatibility and bioactivity required for DC, it must possess good surface finish (required for aesthetic sense), acceptable dimensional accuracy (required for assembly purposes) and good surface hardness (required while chewing). In this paper efforts were made for improving surface hardness, finish, and dimensional accuracy of DC by controlling composition/proportion of Ni and Cr in IC process. Further in this case study stir casting (SC) assisted Ni and Cr based metal matrix composites (MMC) has been prepared in investment mould. The result of study reveals that different material composition influenced the microstructure and the hardness of the MMC prepared. Further with change in weight percentage of Ni and Cr, different microstructures with particle clustering was observed. The results are also supported with 3D rendered images.

Split crown technique for mass propagation of pineapple (Ananas comosus L.) var. queen

The major problem limiting large scale commercial production and/or expansion of pineapple production is the difficulty in obtaining large quantity of quality planting materials due to slow rate of multiplication by conventional methods of propagation that mostly relies on the use of suckers and slips. The study investigated the effect of the methods of crown preparation on the sucker production of pineapple var. Queen and to evaluate the horticultural qualities of suckers produced from plantlets prepared using different methods of crown preparation. Destroying the growing point without splitting reduced percentage survival of plantlets but destroying the meristem and splitting the crown into two or four sections improved survival comparable to the intact crown. Destruction of the growing point and then splitting the crown promoted emergence and increased the number of suckers relative to the intact crown which did not produce suckers after, 3 months from planting. Increasing the number of sections prepared per crown (from two to four) did not reduce the number of suckers produced per plantlet and thus increased the multiplication rate by 7 and 8 times, respectively. The method of crown preparation did not significantly influence the early growth performance (survival, height, number size of leaves) of the harvested &amp; suckers during the first 6 months potting. Among the three methods of crown after preparation, destroying the meristem and splitting into two or four produced more number of ready-to-plant Queen pineapple suckers (1-ft tall) within a period of 5 months.

Use of Digital Technology to Improve Objective and Reliable Assessment in Dental Student Simulation Laboratories.

The aim of this study was to assess inter-and intra-grader agreement with the use of digital scanning and a tooth preparation assessment software program in comparison to the current traditional visual grading method in a dental student simulation laboratory. Students' typodont teeth preparations from previous practical examinations were used (cast crown n=50; cast fixed partial denture abutments n=50). Five preclinical instructors received calibration training and evaluated each of the preparations by the traditional visual grading method using a rubric. The same preparations were assessed by the same instructors using a tooth preparation assessment software program (PrepCheck, Sirona). The results showed that intra-grader agreement was significantly higher when grades were determined by PrepCheck compared to the traditional visual grading method. The traditional method was associated with significantly greater inter-grader disagreement in comparison to grading using PrepCheck (p<0.05). When the average final grade for students' crown preparations by each grader was compared for the traditional method and PrepCheck, significant differences were found for all graders (p<0.001). In this study, the use of the PrepCheck software program greatly improved intra-and inter-grader agreement during grading in a student simulation laboratory. Digital technology may improve the objectivity and reliability of assessments by preclinical evaluators.

Clinical performance of chairside monolithic lithium disilicate glass-ceramic CAD-CAM crowns.

To evaluate the clinical performance and the effect of various patient and provider-related factors on the longevity of chairside monolithic posterior lithium disilicate glass-ceramic (LDGC) computer-aided design (CAD)-computer-aided manufacturing (CAM) crowns provided by predoctoral students. A sample of posterior LDGC CAD-CAM crowns was evaluated. Crown preparations were milled chairside using the CEREC Omnicam system and cemented with Rely-X Unicem or Calibra Universal resin cements. Clinical assessment of the crowns and supporting periodontal structures was performed using the modified California Dental Association (CDA) criteria. Intraoral photographs as well as radiographs were taken for further assessment by two evaluators. Kaplan-Meier survival analysis was performed. A total of 40 crowns were inserted in 32 patients and evaluated for 4 years. Three complications were observed (two-technical and one-biological). No chipping or fracture of crowns was observed. No significant association was found between age, sex, periodontal condition, tooth type, tooth vitality, cement type, and longevity. The 4-year cumulative survival and success rates were 95.0 and 92.3%, respectively. Chairside LDGC CAD-CAM crowns exhibited a high survival rate after 4 years in function and were shown to be a viable and reliable treatment option for posterior teeth. The high survival rate of chairside CAD-CAM crowns observed in this study suggests the likelihood of predictable performance in the predoctoral setup.

3D Printed Teeth for the Preclinical Education of Dental Students.

A need for more realistic tooth models for education has often been expressed by dental students. The aim of this study was to design and create 3D printed teeth with anatomical details for use in preclinical dental education. A tooth with realistic carious lesions and pulp cavity was designed, and this tooth was used in 2018 with 47 dental students for preclinical education in caries excavation, direct capping of the pulp, core build-up, and crown preparation. The students had the ability to identify the carious lesions by a simulated radiograph and by tactile sense of the consistency. The benefits of the 3D printed tooth were evaluated by a questionnaire. The printed tooth was evaluated by grades (1=excellent, 2=good, 3=satisfactory, 4=adequate, 5=poor). The students gave the tooth an overall mean grade of 1.9, with a grade of 2.0 for the haptic impression, 1.5 for the exercise, 1.9 for the examination, and 1.5 for high practical relevance in contrast to a standard model tooth. The new features of the printed tooth were given a mean grade of 2.0 for the radiograph, 2.3 for consistency of the caries, 2.0 for the tooth filling, and 1.7 for the pulp capping as realistic. The students had the possibility to generate a complete concept for prosthodontic tooth treatment on an artificial 3D printed tooth.