Tooth Preparation Research Articles

Influence of the Operator`s Experience, Working Time, and Working Position on the Quality of the Margin Width: In Vitro Study

Background and Objectives: Appropriate tooth preparation is mandatory to obtain a perfect marginal fit of fixed restorations. The heavy chamfer is the most commonly used finish line, especially for minimally invasive tooth preparation. The aim of the study was to compare the width of the finish line obtained during tooth preparation performed by experienced (university lecturers) and inexperienced persons (dental students) in different working times and positions. Materials and Methods: Forty left upper-second molars were prepared on the simulator by each participant, totalizing 160 prepared teeth. A new round-end tapered diamond was used to obtain the 0.5 mm width of the heavy chamfer. The prepared teeth were photographed using a Canon D5300 camera with a macro lens attached to a tripod. The measurements were made with the Image-Pro Insight software selecting the same eight reference points. From these points, perpendicular lines were drawn above the finish line to the axial walls and the distance between the chamfer's outer edge and the axial wall's inner edge was measured. GraphPad Instat and NCSS Dowson Edition software were used. The statistical significance was set at p < 0.05. The mean (M) and standard deviation (SD) were calculated. The used tests: one sample t-test, ANOVA test, and Tukey-Kramer Multiple Comparisons Test. Results: Statistically significant differences were obtained according to the experience of the participant, preparation time, patient's position, and the chamfer width on the prepared tooth different surfaces. Conclusions: Daytime or weeklong tiredness and patient position do not affect the width of the heavy chamfer prepared by experienced and inexperienced persons. The experience and the operator's working position influence the width of the prepared finish line.

Experience of the Students after Transition from Preclinical Fixed Prosthodontic Training to Clinical Phase Survey

Introduction: Accurate preclinical prosthodontics training is a part of curriculum monitored so that the preclinical students perform the operation with much attention and care enabling the educators to improve the preclinical training. The aim of the study is to assess the students’ preclinical knowledge and skills of fixed prosthodontic training after transition to clinical training. Materials and Methods: A questionnaire survey is conducted among the students involved in clinical practice of the fixed partial dentures. Results: All 100% of the students were aware of the importance of the abutment evaluation before tooth preparation. Hundred percent of the students performed radiograph evaluation of the tooth and 47% of them expressed difficulty in correlating pulp size and position of the tooth radiographically. The majority of the students (84, 84%) thought that there is much difference in the tactile sense between natural teeth and typodont teeth. Pulp health preservation is vital for all restorative procedures; hence, this response from the students should be considered more carefully. More than half of the respondents, 74 students (74%), thought that clinical variation of tooth position is a difficult challenge during the transition stage. Tooth position variations such as supra-eruption, tilting, and drifting are common in the clinical situation which cannot be simulated in the preclinical training. However, most of the students feel that it was a formidable challenge in the initial stage of clinical training. Conclusion: Preclinical training is the most challenging for the educationist. Managing the transition for students from preclinical learning to providing patient care in the clinic is an important issue for oral health-care educators

The effect of different tooth preparation finishing procedures and immediate dentin sealing on the scanning accuracy of different intraoral scanners

PurposeTo measure the effect of different tooth preparation finishing procedures (super-coarse grit, fine grit, and air-particle abrasion) and immediate dentin sealing (IDS) on the scanning accuracy of 4 intraoral scanners (IOSs). Material and methodsA tooth preparation for a full-coverage restoration was performed on an extracted mandibular molar using super-coarse diamond burs. Four groups were created depending on the tooth preparation finishing procedure: super-coarse grit (bur with a grit size of 150 µm) (SCG group), fine grit (bur with a grit size of 30 µm) (FG), air-particle abrasion with 27-µm aluminum oxide particles (APA group), and IDS (IDS group). Each group was divided into 5 subgroups according to the scanning system used to digitize the tooth preparation: laboratory scanner (control subgroup) (T710; Medit), Trios 4 (Trios subgroup), CS 3800 (CS subgroup), i700 wireless (i700 subgroup), and iTero Element 5D Plus (iTero subgroup) (n=20). For each subgroup, the control file was aligned with each experimental scan using the best-fit algorithm and an engineering program (Geomagic Control X). The discrepancy between the control and experimental files of each subgroup was computed by measuring the root mean square (RMS) error. Two-way ANOVA and Tukey tests were used to analyze the data (α=.05). ResultsTooth preparation finishing procedures (P<.001) and the IOS assessed (P<.001) were significant predictors of the trueness and precision values obtained. The highest trueness and precision values were measured in the APA group, while the IDS group had the lowest trueness and precision. Additionally, the i700 subgroup obtained the highest trueness and precision values, while the CS and Trios subgroups had the lowest trueness and precision values. ConclusionsThe different tooth preparations finishing procedures tested influenced on the scanning accuracy of the 4 IOSs considered. The air-particle abrasion procedure obtained the best accuracy values. The trueness discrepancies measured among all the subgroups was 19µm and the precision discrepancies measured among all the subgroups was 4.69 µm. Clinical SignificanceThe tooth preparation finishing procedure used can reduce the intraoral scanning accuracy of any of the intraoral scanners tested. The air-particle abrasion finishing procedure might be recommended for maximizing the scanning accuracy of the IOSs tested.

The analysis and feedback from the performance of pre-clinical operation skills tests for clerkship in School of Dentistry, National Taiwan University in 2022

Background/purposeThe simulated pre-clinical operation skill test (PCOST) is part of the objective structured clinical examination (OSCE) and designed for clinical practice using manikins, physical typodonts, and instruments in the laboratory. This study tried to evaluate the influencing factors of the PCOST results for dental students. Materials and methodsThe 32 5th-year dental students of the dental school of National Taiwan University (NTU) joined the PCOST. The contents of PCOST included two specialties: operative dentistry (OD) and prosthodontics (PS). The examination content of OD was tooth 36 mesio-occluso-distal (MOD) cavity preparation, and that of PS was crown preparation and temporary crown fabrication of tooth 11. Several factors including the gender, age, and dental student admission ways (with or without the skill tests) were evaluated. Each scoring item was calculated. The students also filled the feedback questionnaire about the examination questions and suggestions for the PCOST. ResultsFor both OD and PS, there were no significant differences in the mean PCOST scores between male and female dental students, between two groups of dental students with or without the skill tests in the admission process, and among three different age groups of dental students. According to the feedback questionnaire from the participated dental students, they were satisfied with the PCOST. ConclusionThe PCOST is a good simulated examination in clinical practice. However, we still need to collect more PCOST data and feedback to revise the guideline of the PCOST, and to promote the performance of clinical works of dental students.

Evaluation of the marginal fit of finish line designs of novel CAD/CAM restoration materials

Aim: The purpose of this study is to compare the marginal fit of crowns manufactured using different CAD/CAM materials on 2 different types of finish line design.&#x0D; Material and method: Tooth preparations were made by creating 2 different finish lines (rounded shoulder, chamfer) on an acrylic mandibular second premolar model. Impressions were taken on each preparation using polyvinylsiloxane impression material, and blocks with three different compositions including lithium disilicate (LDS), zirconia-reinforced lithium silicate (ZLS), and monolithic zirconia (MZ) (UP.CAD, Celtra Duo, and VITA YZ HT) were produced using a CAD/CAM (computer-aided-design and computer-aided-manufacturing) milling device (VHF R5) (n=10). The marginal gap values of the crown restorations were measured by the same operator using a stereomicroscope (LEICA DVM6). Histogram plots and the Kolmogorov-Smirnov test were used to test the normality of the distributions of the variables. The non-normally distributed (nonparametric) variables were compared using the Mann-Whitney U test for two groups and the Kruskal-Wallis test for more than two groups.&#x0D; Results: The marginal gap values were compared between finish line designs separately for each material. Accordingly, the marginal gap values of the rounded shoulder finish line were smaller than those of the chamfer finish line in all materials. The marginal gap values were also compared among the materials separately for each finish line type. Accordingly, the marginal gap values of the VITA YZ HT material were smaller than those of the Celtra Duo (ZLS) and UP.CAD (LDS) materials for both finish line designs. There was no significant difference between Celtra Duo and UP.CAD.&#x0D; Conclusion: The finish line design is a factor that affects marginal fit. Monolithic zirconia is more appropriate for clinical use as it shows a better marginal fit compared to LDS and ZLS.

Efficiency of HEPA-filtered extra-oral suction unit on aerosols during prosthetic dental preparation: A pilot study.

Aerosols formed during dental treatments have a huge risk for the spread of bacteria and viruses. This study is aimed at determining which part of the working area and at what size aerosol is formed and ensuring more effective use of HEPA-filtered devices. Anterior tooth preparation was performed by one dentist with one patient. Particle measurements were made using an airborne particle counter and were taken at four different locations: the chest of the patient, the chest of the dentist, the center of the room, and near the window. Three groups were determined for this study: group 1: measurement in a 24-h ventilated room (before the tooth preparation, empty room), group 2: measurement with the use of saliva ejector (SE), and group 3: measurement with the use of saliva ejector and HEPA-filtered extra-oral suction (HEOS) unit. The particles generated during tooth preparation were separated according to their sizes; the concentration in different locations of the room and the efficiency of the HEOS unit were examined. The present study showed that as the particle size increases, the rate of spread away from the dentist's working area decreases. The HEPA-filtered extra-oral suction unit is more effective on particles smaller than 0.5 microns. Therefore, infection control methods should be arranged according to these results. The effective and accurate use of HEPA-filtered devices in clinics significantly reduces the spread of bacterial and viral infections and cross-infection.

Modular Digital and 3D-Printed Dental Models with Applicability in Dental Education.

Background and Objectives: The ever more complex modern dental education requires permanent adaptation to expanding medical knowledge and new advancements in digital technologies as well as intensification of interdisciplinary collaboration. Our study presents a newly developed computerized method allowing virtual case simulation on modular digital dental models and 3D-printing of the obtained digital models; additionally, undergraduate dental students' opinion on the advanced method is investigated in this paper. Materials and Methods: Based on the digitalization of didactic dental models, the proposed method generates modular digital dental models that can be easily converted into different types of partial edentulism scenarios, thus allowing the development of a digital library. Three-dimensionally printed simulated dental models can subsequently be manufactured based on the previously obtained digital models. The opinion of a group of undergraduate dental students (n = 205) on the proposed method was assessed via a questionnaire, administered as a Google form, sent via email. Results: The modular digital models allow students to perform repeated virtual simulations of any possible partial edentulism cases, to project 3D virtual treatment plans and to observe the subtle differences between diverse teeth preparations; the resulting 3D-printed models could be used in students' practical training. The proposed method received positive feedback from the undergraduate students. Conclusions: The advanced method is adequate for dental students' training, enabling the gradual design of modular digital dental models with partial edentulism, from simple to complex cases, and the hands-on training on corresponding 3D-printed dental models.

One Year Clinical Evaluation Of Translucent Zirconia Crowns In Dental Esthetic Zone With Biologically Oriented Preparation Technique Versus Conventional Preparation (RCT)

Statement of the problem: Tooth preparation with horizontal finish line requires removal of reasonable amount of tooth structure at the cervical area which affects the remaining tooth structure at this area. Therefore, more conservative preparation design such as biologically oriented preparation technique (BOPT) might be needed to save tooth structure at the cervical area. The Purpose: To Evaluate the effect of Conventional preparation design (horizontal), and Biologically Oriented Preparation Technique (BOPT), on Marginal adaptation, fracture and gingival inflammation score of the translucent zirconia crown in dental esthetic zone. Methodology:, 44 monolithic translucent zirconia single crowns were fabricated inn dental esthetic zone . The patients were separated randomly into two groups. Group1: (horizontal preparation design) Group2: BOPT. After final cementation. The Modified United States Public Health Service (MUSPH) criteria for restoration clinical evaluations were used to assess marginal adaption. Gingival inflammation was assessed using gingival inflammation index. Evaluation of the restoration was at intervals of three, six, nine, and twelve months. Results: Comparison between two groups at different intervals regarding marginal adaptation, fracture and gingival inflammation score revealed statistically insignificant difference. Conclusions: Within limitations of the present one year follow up randomized clinical trial, the following conclusions could be drawn: 1.The conventional and BOPT preparation designs both clinically accepted to provide successful dental restoration The lower gingival inflammation score of the restored teeth with the conventional preparation design compared to that of the BOPT, may not be conclusive as regard the study time frame, indicating that increasing the follow-up period might alter the present finding. Clinical implications: Beyond of all the prosthodontic preparation techniques, knowledge of B.O.P.T. (Biological Oriented Preparation Technique) allows us to achieve predictable and consistent results in terms of periodontal health and gingiva architecture surrounding ceramic restoration. Nevertheless, long term studies are necessary to ensure the benefits of this techniques.

A novel chairside technique to assess the interocclusal clearance and abutment axial walls during tooth preparation.

The importance of a judicious and unerring abutment tooth preparation in the field of prosthodontics has always been paramount. It is not uncommon for many clinicians to face challenges during laboratory fabrication of fixed prostheses, caused due to inappropriate occlusal clearance and over axial wall taper of the abutment tooth. With evolving technologies and methods, the modus operandi for attaining such tooth preparation is varying; however, every technique has its own shortcomings. The technique mentioned in the article is cost-effective as it uses modified Heister mouth gag forceps to achieve the desired objective of evaluating the prepared abutment morphology three-dimensionally with minimum chairside time.

Biomechanical Behaviour of Abutment Teeth Prepared using the Biologically Oriented Preparation Technique: A Systematic Review

Background: The biologically oriented preparation technique (BOPT) is a protocol in which a vertical tooth preparation is done without margins, elimination of cemento-enamel junction followed by gingitage and an immediate provisional restoration with the aim of adapting the marginal periodontal tissues to a newer crown emergence profile created by the laboratory fabricated prosthesis. However, there is limited documented scientific evidence on this topic. Purpose: The purpose of this systematic review was to assess the biological and mechanical behaviour of abutment teeth prepared using the BOPT through a review of documented clinical evidence. Materials and Methods: This review followed the recommendations of the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. Using the key words, an electronic search was completed in databases such as PubMed, EBSCO, Google Scholar, Research Gate and Scopus without placing any restriction on the year of publication. Manual search was also done. The search strategy included articles published until 30 September, 2022. Two investigators independently evaluated the quality of the studies that met the inclusion criteria by applying the Joanna Briggs Institute critical appraisal checklist. The lack of consensus was resolved by a third investigator. A fourth investigator provided final data verification and technical support. Results: Eight articles that fulfilled the proposed inclusion criteria for the review were selected, which included 1 randomised control trial, 3 prospective clinical studies, 1 longitudinal study, 2 clinical reports and a case report on an extracted tooth. Population or problem, intervention, comparison, outcome format was applicable only to one randomised control trial and three prospective studies. All the studies have shown that the biomechanical behaviour of abutment teeth prepared using the BOPT technique in terms of emergence profile, gingival health, marginal stability and bleeding on probing was similar to the conventional method. However, it was observed that all the articles published had a common author. Conclusions: Although a favourable biomechanical behaviour of abutment teeth prepared using BOPT was documented, long-term follow-up studies are required before its implementation. Clinical Implications: BOPT can be considered an alternative to the conventional tooth preparation technique. However, long-term clinical research is required for further recommendation.

Comparison and evaluation of the effect of polymerization of resin-modified glass ionomer cement and dual-cure resin cement on the crystalline structure of dentin using synchrotron X-ray diffraction and its clinical correlation with postoperative sensitivity.

To compare the effect of polymerization of resin-modified glass ionomer cement and dual-cure resin cement on the crystalline structure and to correlate it clinically with postoperative sensitivity. The evaluation of crystalline strain in the dentin slabs was done using Synchrotron X-ray diffraction. The post operative sensitivity was measured clinically using Schiff's sensitivity scale. A total of 44 extracted and noncarious premolars were collected. Dentin slabs of dimensions 2 mm × 2 mm × 1.5 mm were prepared from the buccal aspect of the extracted teeth. The dentin slabs were then divided into two groups, Group A dual-cured resin cement and Group B resin-modified glass ionomer cement was applied. The dentin slabs first underwent synchrotron X-ray diffraction before and after the application of cement. Forty-two patients who were undergoing complete metal fixed prostheses on vital posterior abutments were selected. In this, 21 vital abutments were included in each group. Tooth preparation and fabrication of complete metal prostheses were done in the conventional manner and cemented using the 2 luting cements in Groups A and B, respectively. Dentinal hypersensitivity was measured using Schiff 's scale, postcementation, after 1 week and 1 month. Independent t-test was done for comparing the two cements in two cements in terms of lattice strain. Mann-Whitney U-test was done for comparing the cements with respect to dentinal hypersensitivity. Spearman's correlation coefficient was used for clinical correlation between dentinal hypersensitivity and crystalline strain. The lattice strain generated in dual cure resin cement was higher than that in resin-modified glass ionomer cement and was statistically significant. Postcementation hypersensitivity was higher in dual-cured resin than resin-modified glass ionomer cement but was not statistically significant in the follow-up visits. Spearman's correlation coefficients did not reveal any significant clinical correlation between lattice strain and dentinal hypersensitivity. Dual cure resin cements generate greater lattice strain as compared to resin modified glass ionomer cements.

4 ve 5. Sınıf Diş Hekimliği Öğrencilerinin Protetik Diş Tedavisi Klinik Stajı Deneyimlerinin Değerlendirilmesi: Kesitsel Araştırma

Objective: This study aims to evaluate the prosthodontic internship experiences of 4th and 5th grade dentistry students in terms of clinical procedures and patient-physician relationships. Material and Methods: A questionnaire consisting of a total of 26 closed and open-ended questions was created through Google Forms and shared with students' representatives of each grade. It included 5-point Likert scale to allow dentistry students to evaluate prosthodontic treatment procedures. A total of 143 dentistry students were included in the study. The data were statistically analyzed using the Pearson chi-square test and the Bonferroni-corrected Z-test. Results: Of the dentistry students, 58% were 4th graders, 42% were 5th graders, 63.6% reported to consider themselves sufficient when planning treatment, 50.4% reported to spend around 30 min-1 hour for a tooth preparation, 56.8% reported border moulding as the most challenging complete denture clinical procedure, and 77.5% reported to feel strongly responsible for patients whom they treat. In addition, there was no statistically significant difference between the students' perceptions of whether the treatment they applied was ideal according to their grades (p=0.089). Conclusion: In general, dentistry students have the most difficulty in tooth preparation among fixed prosthesis clinical procedures and in border molding among total prosthesis clinical procedures. The 5th graders were more successful than the 4th graders in some clinical procedures that required correct use of time and dexterity.

An In vitro study to evaluate the depth of reduction achieved by three different techniques for porcelain fused to metal crown preparation

Introduction: A near-ideal preparation lays the foundation and is required for adequate retention and resistance for fixed partial dentures. It is advisable to achieve a near-ideal preparation for the longevity of the prosthesis. Materials and Methods: Thirty maxillary left central incisors were mounted on the acrylic block. The samples were divided into groups with ten specimens: Group A-Free hand, Group B-Index, and Group C-Depth gauge. Group A was prepared using the freehand method, Group B was prepared using the putty index, and Group C was prepared using depth gauge bur. An index was prepared before and placed back on the tooth after preparation, and the gap was filled with low-viscosity elastomer. The thickness of the impression was measured at five different points under the microscope. The statistical analysis was done using one-way analysis of variance and Student's t-tests. Results: The preparations (dimensions) achieved by the freehand method were 2.02 mm, 1.70 mm, 1.11 mm, 0.90 mm, and 0.60 mm respectively at five predetermined points. Similarly, for putty index these were 1.76 mm, 1.21 mm, 0.95 mm, 1.32 mm, 0.71 mm respectively at five predetermined points. Likewise, with depth gauge bur it were 1.88 mm, 1.35 mm, 0.77 mm, 1.09 mm, 0.73 mm, respectively, at five predetermined points. There was a significant difference between the Groups (P < 0.001). Intergroup comparisons between Group A, Group B and Group C showed a significant difference. Group A showed near-ideal preparation in the palatal cervical region compared to Group B and Group C. Conclusion: The freehand technique was the least effective of the three techniques. The use of depth gauge bur had yielded the preparation near the ideal and should be considered during tooth preparation.

Influence of Treatment and Prevention Measures on the Dynamics of Laboratory Indicators of Periodont during the Manufacture of Non-Removable Dentures

Formulation of the problem. One of the most common complications in the process of orthopedic treatment with non-remavable dentures is the injury of the gums of the supporting teeth, which, under unfavorable conditions of the body, can lead to inflammatory changes in the periodontal of the supporting teeth. Objectives of this study was the quantitative and qualitative changes in indicators of gum liquid: its amount and the presence in it of mediators of inflammation – histamine and serotonin. Materials and methods. The study included 68 people aged 20 to 50 years with healthy periodont and generalized periodontitis volume of the initial-first degree, who first made non-removable dentures. The first group included 32 individuals without pathological changes in periodontal tissues. The second group consisted of 36 people with generalized periodontitis of initial – first degree. Results. Before orthopedic treatment, the level of gum liquid in group II was significantly higher than in the group I (0.41 ± 0,02 mm² according 1,5 ± 0,07 mm²). After tooth preparation, the number of gum liquid increased sharply in both observation groups compared to baseline. Patients in both groups using the proposed treatment-and-prophylactic regimen had a significantly lower level of gum liquid compared to subgroups, where no treatment-and-prophylactic procedures were applied. Conclusions. In all patients, who made non-removable dentures, the amount of gum fluid and histamine and serotonin content increased. The proposed therapeutic and prophylactic complex showed pronounced anti-inflammatory effect during orthopedic treatment.

Reliability of automatic finish line detection for tooth preparation in dental computer-aided software.

This study aimed to investigate the accuracy of automatic tooth finish line registration compared to manual registration with regard to various finish line configurations and dental computer-aided design (CAD) software. Finish line registrations were performed on 15 digital tooth models with different finish line configurations (edge roundness radius = 0 mm, 0.2 mm, and 0.4 mm; edge angle = 30°, 60°, 90°, 120°, and 150°) using automatic and manual methods for designing virtual copings (N = 150). The discrepancies between the registered finish line extracted from the copings and the actual finish line segmented from the digitized tooth model were measured. Three-way analysis of variance (ANOVA) and post-hoc analyses with Bonferroni correction (α = 0.05) were used to analyze the results. The finish line configurations, registration methods, and CAD software interacted with the accuracy of the registered finish line (p = 0.001). The automatic finish line registration method exhibited larger error values than the manual method, especially at high finish line edge roundness and obtuse edge angles for both EXOCAD and R2CAD software (p < 0.001). The difference in dental CAD software affected the registration accuracy in the automatic method (p < 0.001), but not in the manual method (p = 0.676). Finish line registration errors may occur when the automatic registration method is applied to the indistinct edge of tooth preparation. The accuracy of the automatic finish line registration could differ according to the CAD software program.

Accuracy of the preparation depth in mixed targeted restorative space type veneers assisted by different guides: An in vitro study.

Most veneers are mixed targeted restorative space (MTRS)-type restorations that are partially within the original tooth and require inconsistent preparation depths. This study aimed to evaluate the accuracy of the preparation depth for MTRS veneer preparation. MTRS veneer preparation models were developed using the twisted maxillary central incisor (MCI) as the original tooth and the standard MCI as the waxing. Veneer preparations were performed using freehand (MF), silicone (MS), thermoplastic (MT), 3D-printed uniform (MD), and auto-stop (MA) guides. The prepared and original MCI were scanned and superimposed using a custom-made base. The mean absolute differences (MADs) were measured to evaluate the accuracy of the preparation depth. Statistical analysis was performed using the multivariate analysis of variance (MANOVA) test (α=0.05). The accuracy of the preparation depth was 0.237±0.090, 0.191±0.099, 0.149±0.078, 0.093±0.050, and 0.059±0.040 mm in MF, MS, MT, MD, and MA, respectively. The MADs between the groups were significant (P<0.05). The accuracy of the trial restoration was 0.140±0.081 mm in the MS, and the accuracy of the guiding tube was 0.055±0.033, 0.036±0.011, and 0.033±0.010 mm in the MT, MD, and MA, respectively. In MTRS veneer preparation for MCI, tooth preparation guides improved the accuracy of the preparation depth by visualizing the TRS profile and providing clear measurement points. The accuracy of the guide is influenced by its flexibility, and the accuracy of the preparation depth is affected by the accuracy of the measurement points.

Trueness and surface characteristics of 3-dimensional printed casts made with different technologies

Statement of problemThree-dimensional (3D) printers should be capable of fabricating products with high accuracy for potential use in a wide range of dental applications. The trueness and surface characteristics of 3D-printed casts made with different technologies remain unclear. PurposeThe purpose of this in vitro study was to evaluate the trueness and surface characteristics of 4 types of dental casts printed using 6 different 3D printers. Material and methodsFour dental casts prepared for intracoronal and extracoronal restorations were printed using 6 different 3D printers—2 printers of each printing technology (FDM: Creator, Lugo; DLP: D2, ND5100; SLA: Form 2, Form 3). The printed casts were scanned to obtain standard tessellation language (STL) data sets that were superimposed onto the reference to evaluate their trueness (n=15). Trueness was measured based on overall deviations for each cast and for sectional deviations within the cavities. For qualitative evaluation, the surface characteristics of the 3D-printed casts were analyzed by using a digital camera, stereomicroscope, and scanning electron microscope. Statistical analyses were conducted using the Kruskal-Wallis test, followed by multiple Mann-Whitney U tests for pairwise comparisons among groups (α=.05). ResultsThe overall median trueness values were lowest with the Form 3 (27.9 μm), followed by the ND5100 (30.0 μm), Lugo (37.1 μm), D2 (41.4 μm), Form 2 (46.9 μm), and Creator (83.3 μm) (P<.05). Sectional deviations within the cavity were generally greater than overall deviation. Macroscopic and microscopic images showed that the reproduced casts had the smoothest surface with the SLA, followed by the DLP and FDM printers. Horizontal layers were more discernible with the FDM printer. ConclusionsThe trueness of the 3D-printed casts was influenced by the type of tooth preparation and was printer dependent. Among the tested 3D printers, the Form 3 produced the most accurate casts, while the Creator produced the least accurate casts.

Digital Interactive Design and Robot-Assisted Preparation Experiment of Tooth Veneer Preparation: An in Vitro Proof-of-Concept

In the fixed prosthesis process dental prosthesis treatment, the dentist needs to conceive the morphology of the tooth preparation and make numerous micro-adjustments by manual operation. This study aims to establish a digital design system for accurate designing of veneer preparation and study the trajectory planning of the robot-assisted preparation. According to the standard operation requirements, the projection line segmentation method based on point drawing is proposed for interactive selection to ensure the margin smoothness of the preparation area. The preparation depth is parameterized, and the foldback point correction method based on secondary segmentation is used for repairing the offset preparation area to ensure surface smoothness. The fenestration preparation model was obtained in the digital interactive design software. The model is divided into two feature areas which are interpolated by the B-spline curve and NURBS surface, respectively. The isoparametric curve method is used to plan the preparation trajectory. The experimental and theoretical values of the target feature points from the X, Y and Z coordinate directions were also calculated and analyzed. The experiment is carried out by the physical prototype of the tooth preparation robot. The maximum error of the feature points on the preparation are 0.180 mm, 0.104 mm and 0.142 mm in X, Y and Z directions, respectively. The confidence interval of the system error is stable within 0.30 mm. The error of the feature points verifies the feasibility of the digital interactive design system and the correctness of the trajectory planning of tooth veneer preparation. The system could have the potential to assist dentists in the precise design of the veneer preparation, improve the processing efficiency and ensure the effect of tooth veneer prosthesis.

An in vitro comparison of the marginal fit of provisional crowns using the virtual tooth preparation workflow against the traditional technique.

This study investigates the effectiveness of an innovative virtual tooth preparation workflow for the fabrication of dental crowns using cone-beam computed tomography (CBCT) and intraoral scanners (IOSs) with conventional workflow using extraoral/laboratory scanners. This in vitro experimental study was conducted in the laboratory of a university in Chennai, India. The dental laboratory and research facilities at the institution were utilized for the fabrication of the temporary crowns and the data acquisition process. Institutional approval was obtained from the university. It was basically a comparison between the virtual prep technique using CBCT and IOS and the conventional digital technique using extra oral scanners (EOS) for temporary crown fabrication. The sample size was estimated using an effect size of 1.5004, assuming a normal distribution, a significance level of 0.05, and a power of 0.95 in G power software. Based on this calculation, an extracted second lower molar was used to fabricate 10 samples in each group. The samples were divided into three groups: the CBCT (Group 1), the IOS (Group 2), and laboratory scanner (Group 3 as control) groups. The vertical marginal gap of all the surfaces of the crown was evaluated using a scanning electron microscope. Data were analyzed using one-way ANOVA using the SPSS software version 26.0, IBM, Armonk, NY, USA. Acceptable marginal discrepancy values were obtained in all three groups. There was no significant difference in the marginal discrepancy recorded (P = 0.113). Virtual tooth preparation using CBCT and IOSs can be used as an alternative to the conventional workflow for provisional crown and bridge fabrication.

Computer-aided design software-enabled preclinical prosthodontic training: A digital education technique.

The prosthodontics preclinical training modules involve textbook-based two-dimensional (2D) ideal images and practicing on manikin models to emulate ideal tooth preparations and teeth arrangements. Relying solely on 2D images as objectives for preclinical exercises limits the trainee's creative skills to instructions of textbooks and clinical instructions received. With advancements in digital dentistry, dental trainees should have early exposure to the three-dimensional (3D) rendering of ideal preclinical objectives. A dental education technique using computer-aided design software and smartphones is described that will allow 3D rendering of ideal prosthodontic training assignments allowing early exposure to digital dentistry for dental training students.