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Using software for assessment of restorative work on typodonts in the simulation laboratory may enhance the objective evaluation of student work. The study aimed to evaluate the inter-rater and intra-rater reliability using 3-D scans from the Planmeca Emerald™ intra-oral scanner with Romexis Compare® software for assessing preparations for preformed metal crowns (PMCs). Three operators independently recorded 3-D scans and digitally measured the features of 30 PMC preparations on typodont primary teeth (# 75). Using Romexis Compare® software, preparations were measured from mesial, distal and occlusal aspects. Measurements were repeated after 2 weeks. The intraclass correlation coefficient (ICC) was used to measure the reliability of measurements between operators and within the one operator. For measuring the extent of tooth reduction, there was excellent intra-rater reliability for each operator (ICC 0.96–0.99). The highest inter-rater reliability was for measurements of the occlusal surface (0.946 and 0.956), followed by the mesial surface (0.852 and 0.862) and then the distal surface (0.746 and 0.724). This method was useful and reliable for measuring features of PMC preparation, but with some limitations. Improving the software to provide specific assistance tools would empower greater uptake of this method as an adjunct to traditional visual grading tool in paediatric dentistry preclinical teaching.

Summary Background Orthodontic patients wearing fixed appliances are susceptible to traumatic dental injuries during contact-sport. This laboratory study investigated the protective qualities of orthodontic mouthguards using impact-testing to a typodont fitted with a fixed appliance through peak load transfer and retention of the mouthguard. Methods Seven orthodontic mouthguards [three custom-made (Medium-CM, Heavy-CM, Heavy-pro-CM); three commercially-available mouth-formed (Shock-Doctor® Ultra Braces, Opro® Ortho-Gold Braces, Opro® Ortho-Bronze Braces) and a Shock-Doctor® Instant-Fit] were fitted to a maxillary arch typodont bonded with a fixed appliance and impact-tested using 0.5 or 1 Joule (J) energy via hockey-ball, cricket-ball or steel-ball projectile. A load-cell recorded peak load transfer through mouthguard to typodont with retention scored in a binary manner dependent upon any displacement following impact. Differences across mouthguards were calculated with ANOVA or Kruskal–Wallis test for normal and non-normal data, respectively. Post hoc comparisons across mouthguards were conducted via Dunnett's test with Sidak correction. Results Only the three custom-made and Opro® Ortho-Gold Braces were not displaced by impact-testing. For these, Opro® Ortho-Gold Braces transferred the smallest load for 3/6 impact-tests, followed by Medium-CM. Heavy-pro-CM performed poorly, ranking penultimate or worst for all impact-tests. Significant differences were found between mouthguards for cricket-ball and steel-ball set-ups. The Opro® Ortho-Gold Braces performed better than the Heavy and Heavy-pro-CM for 0.5 J cricket-ball impact-test (P < 0.05), whilst Medium-CM performed better than Heavy-pro-CM. For 1 J cricket-ball, there were significant differences between Medium-CM and Heavy-pro-CM (P < 0.05). For 0.5 J steel-ball, the Medium-CM performed significantly better than both Heavy-pro-CM and Opro® Ortho-Gold Braces (P < 0.05), whilst Heavy-CM performed better than the Heavy-pro-CM (P < 0.05). For the 1 J steel-ball, Medium and Heavy-CM performed better than Opro® Ortho-Gold Braces (P < 0.05). Conclusions Opro® Ortho-Gold and Medium-CM mouthguards offer the best protection for low-impact sports, whilst Medium or Heavy-CM mouthguards are recommended for high-impact sport.

AIM The World Health Organization (WHO) periodontal probe is recommended for epidemiologic surveys and periodontal screening, but its ability to identify subgingival dental calculus (DC) relative to a #11/12 explorer is not known. This study compared in vitro the ability of the WHO probe and a #11/12 explorer to detect subgingival DC. MATERIALS AND METHODS Three typodont models with randomly distributed artificial DC on mandibular molar and premolar root surfaces were assessed with a WHO periodontal probe and a #11/12 explorer by two periodontists. The diagnostic performance of the two instruments for subgingival DC detection was compared using 2 × 2 contingency table analysis. RESULTS A #11/12 explorer provided better reproducibility, a higher level of sensitivity, higher positive predictive values, higher negative predictive values, and greater overall accuracy (diagnostic effectiveness) (76.9% vs. 68.5% for the first periodontist; 87.0% vs. 75.0% for the second periodontist) for detection of subgingival DC than the WHO probe. CONCLUSION The in vitro diagnostic performance of a #11/12 explorer was superior to the WHO periodontal probe for identification of subgingival DC. CLINICAL SIGNIFICANCE A #11/12 explorer, rather than the WHO probe, is recommended for identification of subgingival DC.

Introduction This study evaluated the success rate of and tooth substance removal required for computer-guided preparation of endodontic access cavities. Methods Thirty acrylic typodont teeth with root canals (10 each of tooth numbers 11, 14, and 17) were randomly allocated to a study or control group (15 teeth per group). In the study group, teeth were fixed in acrylic resin and subsequently digitized using a laboratory scanner. A cone-beam computed tomographic scan was then taken. Access cavity preparations were planned virtually, and a template was 3-dimensionally printed. In the control group, access cavities were prepared using the conventional access technique. Tooth substance removal was assessed by weighing teeth before and after preparation. Volume loss was analyzed statistically by use of the Wilcoxon-Mann-Whitney test at a significance level of P Results Using guided endodontics, 93.3% of root canals were located successfully compared with 100% of root canals using the conventional technique. In the control group, the mean tooth substance removal was 16.1 ± 3.7 mm³ for incisors, 44.2 ± 8.9 mm³ for premolars, and 99.3 ± 3.1 mm³ for molars. In the study group, significantly less tooth substance was removed; substance loss was 10.3 ± 1.1 mm³ for incisors, 29.3 ± 4.2 mm³ for premolars, and 51.8 ± 5.3 mm³ for molars. Conclusions The use of guided endodontics in normally calcified teeth enables the preservation of a significant amount of tooth substance. However, this advantage must be carefully balanced against a greater radiation burden and risk of perforation, higher costs, and more difficult debridement and visualization of the pulp chamber and root canals.

Background In restorative dentistry, the use of high-speed air turbine, which generates aerosols, can be associated with the transmission of airborne diseases. New laser technologies could be useful in reducing the amount of aerosols, but there is a lack of scientific research on this topic. Material and methods This is a descriptive study to analyze the amount of aerosols produced after class I cavity preparation using high-speed air turbine (group 1) and Er,Cr:YSGG laser with two different parameters (groups 2 and 3). Fluorescein dye was incorporated into the coolant reservoir in order to visualize the production of aerosols during each procedure. Tooth preparation was performed in a typodont with human lower molar tooth under rubber dam isolation. The procedure was carried out in a transparent plastic box to avoid aerosols dispersion. Sixteen grade I cellulose filter discs were distributed along the surfaces of the box. The area contaminated with aerosols in the filters was measured using ultraviolet illumination. Results In group 1, the contaminated surface area covered with fluorescein dye reached 77.3% (1349 cm2) of the total; in group 2 (laser with 80% water) we observed 7.3% (128 cm2) and in group 3 (laser with 40% water) it was 3.8% (68 cm2). The reduction in water parameter from 80% to 40% coincided with 48% reduction of the contaminated area on the filter discs. Focusing on the surfaces of the box, we noted that the mean contamination on the left side was more than on the right side in all three experimental groups. In group 1 using air turbine, we measured a mean of 102.6[±7.5 SD]cm2 on the left side, compared to 70.6[±32.3 SD]cm2 on the right side. In laser groups 2 and 3, a mean of 12.8[±14.9 SD]cm2 and 6.8 [±5.7SD]cm2, respectively, was described on the left surface versus 0 cm2 of surface contamination on the right surface. Conclusions The contaminated area during the procedure of class I cavity preparation, is reduced by 70% using Er,Cr:YSGG laser compared to high-speed turbine. A slightly higher contamination was observed between laser groups with 80% versus 40% water. The use of Er,Cr:YSGG laser in restorative dentistry can be a valid treatment alternative to reduce aerosols production compared to conventional high-speed rotary instruments. Key words:Er,Cr:YSGG laser, Aerosols, SARS-CoV-2, Rotary instruments, conservative dentistry.

Objective: Research on evaluation of crowns made by the latest contemporary dental computer-aided design/computer-aided manufacturing (CAD/CAM) systems for their marginal adaptation is scarce. The purpose of this in vitro study was to evaluate the marginal integrity of crowns fabricated by the latest Chairside Economical Restorations of Esthetic Ceramic (CEREC) system using 2 different finish line preparation designs: chamfer and shoulder. Materials and Methods: Typodont teeth were divided equally into 2 groups, A and B. The teeth were prepared for full coverage crowns with a shoulder (group A) and chamfer (group B) finish line design. An experienced prosthodontist prepared all crown preparations. Evaluation of 6 sites per sample was completed by 2 calibrated, experienced prosthodontists using the modified US Public Health Services (USPHS) criteria. The descriptive statistics and Z-test were used to evaluate the results. Results: A total of 180 teeth were included in the study (90 teeth in each group). Only 2 crowns in group A and 1 crown in group B were clinically unacceptable. There was no statistical significance (p = 0.282) between the 2 groups regarding finish line design. Conclusions: The CEREC system provides clinically acceptable crowns and can safely be utilized in dental treatment. Therefore, CAD/CAM restorations could be considered as a safe treatment modality by dental professionals.

Statement of problem Digital scans have increasingly become an alternative to conventional impressions. Although previous studies have analyzed the accuracy of the available intraoral scanners (IOSs), the effect of the light scanning conditions on the accuracy of those IOS systems remains unclear. Purpose The purpose of this in vitro study was to measure the impact of lighting conditions on the accuracy (trueness and precision) of different IOSs. Material and methods A typodont was digitized by using an extraoral scanner (L2i; Imetric) to obtain a reference standard tessellation language (STL) file. Three IOSs were evaluated—iTero Element, CEREC Omnicam, and TRIOS 3—with 4 lighting conditions—chair light 10 000 lux, room light 1003 lux, natural light 500 lux, and no light 0 lux. Ten digital scans per group were recorded. The STL file was used as a reference to measure the discrepancy between the digitized typodont and digital scans by using the MeshLab software program. The Kruskal-Wallis, 1-way ANOVA, and pairwise comparison were used to analyze the data. Results Significant differences for trueness and precision mean values were observed across different IOSs tested with the same lighting conditions and across different lighting conditions for a given IOS. In all groups, precision mean values were higher than their trueness values, indicating low relative precision. Conclusions Ambient lighting conditions influenced the accuracy (trueness and precision) of the IOSs tested. The recommended lighting conditions depend on the IOS selected. For iTero Element, chair and room light conditions resulted in better accuracy mean values. For CEREC Omnicam, zero light resulted in better accuracy, and for TRIOS 3, room light resulted in better accuracy.

Objectives The integration of computer-aided design and manufacturing technologies in diagnosis, treatment planning, and fabrication of prosthetic restoration is changing the way in which prosthodontic treatment is provided to patients. The aim of this study was to compare the accuracy of three-dimensional (3D) printed casts produced from the intraoral scanner using stereolithographic (SLA) 3D printing technique, their digital replicas, and conventional stone casts. Materials and Methods In this in vitro study, a typodont of maxillary and mandibular arches with full dentate ivory teeth was used as a reference cast. The typodont was digitized using Trios 3Shape intraoral scanner to create digital casts. The digital files were converted into 3D printed physical casts using a prototyping machine that utilizes the stereolithography printing technology and photocurable polymer as printing material. Linear measurements (mesiodistal and occlusocervical) and interarch measurements (intercanine and intermolar) were made for digital and prototyped models and were compared with the original stone casts. The reference teeth were canines, first premolars and second premolars in the maxillary and mandibular arches on the right and left sides. The measurements on printed and conventional casts were done by digital caliper while on digital casts; Geomagic Qualify software was used. Statistical Analysis One-way analysis of variance (ANOVA) was used to compare measurements among groups. Results Digital casts showed significantly higher error than the other two groups in all linear and interarch measurements. The mean errors of the digital cast in occlusocervical (OC) and mesiodistal (MD) measurements (0.016 and 0.006, respectively) were higher compared with those in the other two groups (OC, 0.004 and 0.007 and MD, 0.003 and 0.005 [p < 0.0001 and p = 0.02, respectively]). Also, digital mean error in intermolar width (IMW) and intercanine width (ICW) (0.142 and 0.113, respectively) were greater than the other two groups (IMW, 0.019 and 0.008 and ICW, 0.021 and 0.011 [p < 0.0001]). However, the errors were within the acceptable clinical range. Conclusion The 3D printed casts may be considered as a substitute for stone casts with clinically acceptable accuracy that can be used in diagnosis, treatment planning, and fabrication of prosthetic restorations.

Statement of the problem: The curiosity of many prosthodontists was attracted towards CAD/CAM technology combined with the newly specifically designed ceramic materials to achieve superb esthetic restorations for their patients. The new ceramic materials with their different mechanical properties might have an impact on their machinability particularly for producing thin esthetic restorations.Purpose: The purpose of this investigation was to evaluate the marginal quality of three different ceramic veneers: Leucite reinforced, hybrid and lithium di-silicate in terms of edge chipping and chipping factor using different machining protocols.Materials and methods: In order to achieve the purpose of this study, a maxillary central incisor of a Typodont was prepared for a feather edge veneer preparation to receive forty five ceramic veneers that were milled from three different materials using the Cerec CAD/CAM system. The three tested materials were leucite-reinforced glass ceramic (IPS Empress CAD), hybrid ceramic (Vita Enamic), and lithium di-silicate glass ceramic (IPS e.max CAD). The forty five veneers were classified into three groups according to the type of the material fifteen each, that were further divided into three subgroups of five specimens each according to the three tested machining speeds: normal, fast, and two-step. A digital camera was used for taking top images for the tested veneer margins that were imported into image analysis software to measure the peripheral veneer circumference (P). A stereomicroscope was used to measure the amount of marginal chipping of each veneer in microns (L). The chipping factor (CF) was calculated using the following equation: CF= L/P x 100, where (L) is the amount of marginal chipping and (P) is the marginal circumference of each veneer. The data of the chipping factor of each veneer margins were recorded and tabulated to be statistically analyzed in order to detect the influence of either the ceramic material or the machining protocol on the quality of the veneer margins in terms of edge chipping.Results: Effect of ceramic type regardless of machining protocol: The statistical analysis of the obtained data revealed that e.max CAD (LD) showed the statistically significant highest mean chipping factor value (7.25 ± 2.56) followed by IPS Empress CAD (LR) (4.01 ± 0.83), and the least mean value was obtained with Vita Enamic (HC) (2.83 ± 1.56). Effect of machining protocol regardless of ceramic type: there was a statistically significant difference between the three milling techniques, where fast milling showed the highest mean chipping factor value (6.30±2.97), followed by normal milling (4.89±2.22) where the least chipping factor mean value (2.90±1.60) was obtained with the two-step milling.Conclusions:The edge quality of thin ceramic CAD/CAM restorations proved to be material dependent.The machinability for producing thin CAD/CAM ceramic restorations influenced significantly their marginal quality.The prosthodontist should be aware and knowledgeable about the mechanical properties of the recent CAD/CAM ceramic materials in order to choose the optimum one with the convenient milling protocol during the treatment planning to get the best clinical performance.

Background and Objectives: One of the important steps toward achieving a successful fixed partial denture treatment is the fabrication of interim restorations with good marginal adaptation. Poor marginal adaptation of the interim restorations will allow ingress of fluids and microorganisms between the restorations and may lead to caries and pulpitis. The objective of this study was to evaluate and compare the marginal accuracy of interim restorations made from two polymethyl methacrylate (PMMA) and two bis-acryl materials. Materials and Methods: An in vitro method was used to replicate a clinical procedure in which the interim crown was made using a direct technique. A maxillary first molar typodont tooth was prepared to receive a full cast crown restoration having 1 mm chamfer and a taper of 5°, and then the prepared artificial tooth was cast into a cobalt chromium metal die. Wax patterns were prepared on the metal die using type 2 inlay wax for full metal crowns. The impression of the die along with the wax pattern was made with a putty-type polyvinyl siloxane, and this impression was used as a mold for making interim restorations. Two PMMA and two bis-acryl provisional crown materials were distributed as follows: Group A: Unifast Trad (GC Dental), Group B: DPI self-cure tooth molding material, Group C: Structur 2 QM (VOCO), and Group D: Cool Temp Natural (Coltene/Whaledent). A total of 60 interim restorations from all the four materials were fabricated (15 interim restorations from each material). The marginal discrepancy of the interim restoration was determined by measuring the space between the margin of the interim restoration and the finish line of the metal die at four vertical reference lines previously marked at the midpoint of the metal die finish line at the buccal, palatal, mesial, and distal surfaces of the die. The marginal gaps were visualized at ×45 magnification using a stereomicroscope and interpreted using ProgRes image capture software. Results: The mean marginal discrepancy calculated in PMMA materials was 269 µm for DPI and 205 µm for Unifast Trad, and the mean marginal gap for the bis-acryl material was 171 µm for Cool Temp and 140 µm for Structur 2 QM. Interpretation and Conclusion: Comparison of marginal accuracy showed that bis-acryl provisional crown material showed better marginal accuracy than PMMA provisional crown material. Among the materials tested, Structur 2 QM showed the best marginal accuracy, and the least marginal accuracy was shown by DPI.

Complete-arch digital scans are becoming popular as digital dentistry is adopted for expanded clinical situations such as complete-arch prostheses, removable prostheses, extensive implant-supported treatment, and orthodontic aligners. Whether the scan pattern technique affects the trueness and precision of complete-arch scans and whether differences in accuracy exist among different scanners remain unclear. Furthermore, each manufacturer recommends a different scan pattern, but evidence of the superiority of the manufacturer's recommended pattern is lacking.The purpose of this in vitro study was to determine whether the scan pattern affects the trueness, precision, and speed of complete-arch digital scans performed by using 4 different digital scanning systems.A custom model used as the reference standard was fabricated with teeth having the same refractive index as dentin and enamel to simulate the natural dentition. The scan of the custom typodont was obtained by using an ATOS III Triple Scan 3D optical scanner. This study evaluated the CEREC Omnicam, Planmeca Emerald, Align iTero Element, and 3Shape TRIOS 3. Experimental scans were obtained from each of the 4 different digital scanning systems by using 4 unique scan patterns by experienced clinicians. Four experimental scans were acquired from each of the scanners by using 4 distinct scan patterns for a total of 16 scans for each scanner. Scan patterns 1 to 4 were based on the operator manuals for each different scanner. The scan time was recorded for each scan. All experimental scans were converted to standard tessellation language (STL) format, and a comprehensive metrology program, Geomagic Control X, was used to compare the reference standard scan with the experimental scans.For trueness, the scanner (P.001), scan pattern (P=.001), and their interaction (P.001) were found to be significant. Overall, scan pattern 2 showed the highest average trueness and precision. Likewise, for overall scan pattern precision, the scanner, scan pattern, and their interaction were found to be significant (P.001).Scan pattern affected trueness and precision for some scanners, but not for others. Differences exist in the complete-arch scan speed, trueness, and precision of individual scanners. Scan pattern can play an important role in the success of digital scanning.

OBJECTIVE This study aimed to evaluate the influence of the presence of adjacent teeth on the accuracy of intraoral scanning (IOS) systems for class II inlay preparation. MATERIALS AND METHODS The mesio-occlusal inlay preparation was prepared in an anatomical model of the maxillary molar. The prepared tooth was secured to a typodont with the mesial adjacent tooth removed or in situ. Ten digital impressions of the inlay preparation were acquired using three IOS systems (CEREC Primescan, 3Shape TRIOS 3, and Medit i500). A laboratory scanner (3Shape E3) was used to obtain the reference scan data. The mean absolute deviation values were calculated to evaluate the accuracy of the digital models. RESULTS The group with the adjacent teeth present showed lower trueness and precision compared to that without the adjacent tooth (p

Objectives Deciding when cuspal coverage is needed for posterior teeth is considered a challenge for dentists. The aims were to assess dentists' decision making regarding the need for cuspal coverage for vital teeth (VT) and endodontically treated teeth (ETT) with varying amounts of tooth structure loss and to identify clinical situations of dissimilarity and uncertainty in decision making. Materials and Methods A random sample of 182 dentists were invited to participate in the survey. The survey included photos of 13 posterior teeth: six VT and seven ETT. The clinical situations selected were based on a hypothetical scale of typodont teeth with ascending amounts of tooth structure loss. A brief description of each situation was provided. Each dentist was asked to decide whether cuspal coverage is needed, not needed, or unsure. Descriptive analyses using SPSS were conducted. Seventy‐five percent was chosen as a cutoff point for assessing similarity in decision making. The unsure answer reflected uncertainty. Associations were assessed using chi‐square test. Results One hundred twenty dentists participated (65.9% response rate, 70 females). Median for years of experience was 3.5 (interquartile range 1.1–10.8). Analyses revealed a similarity percentage of

Statement of problem The primary manufacturing method of zirconia ceramic crowns is computer-aided design and computer-aided manufacture (CAD-CAM), but a disadvantage of this technique is material waste. Three-dimensional (3D) printing, which has been recently introduced into dentistry, has improved the processing of polymers and metals, but not yet of ceramic crowns. Purpose The purpose of this in vitro study was to evaluate the 3D trueness of zirconia crowns fabricated by 3D printing to investigate the potential application of this technology in dental ceramic restorations. Material and methods A typodont tooth was prepared for a ceramic crown, and a digital crown was designed using the CAD software. The digital crown was processed either with a 3D-printing system or with a dental milling system. The crowns were scanned using a dental laboratory scanner, and the data collected for each crown were divided into 4 parts (the external surface, intaglio surface, marginal area, and intaglio occlusal surface). Finally, the trueness of each part was determined using the 3D inspection software. The 3D trueness of the crowns fabricated by either 3D printing or milling was compared by a 1-sided test (α=.05). Results The trueness of the external surface, intaglio surface, marginal area, and intaglio occlusal surface of the 3D-printed crowns was no worse than the corresponding trueness of the CAD-CAM crowns (P Conclusions Zirconia crowns produced by 3D printing meet the trueness requirements, and 3D printing may be suitable for fabricating zirconia crowns.

PURPOSE The purpose of this study is to survey clinicians' choice of peri-implant instrument selection and the application used to probe dental implants as well as to evaluate peri-implant probing force and pressure applied as compared to that reported in current literature. MATERIALS AND METHODS 48 clinicians (16 periodontists/periodontal residents, 16 restorative dentists and 16 hygienists) participated in the study. A questionnaire to determine the frequency and method of probing dental implants was provided and subject to the Chi-square test. Each participant was given a choice of three periodontal probes (Marquis, UNC15, Plastic) to use on the typodont and probing force was recorded blindly. Probing force and pressure data were analyzed with ANOVA among subject groups as well as probe types per site; where statistical differences (p < .05) were detected, Tukey's posthoc test was applied. RESULTS The questionnaire resulted in a variety of answers although the majority demonstrated an agreement on probing implants in everyday practice. There was no significant difference among provider groups in regard to instrument selection, probing forces and pressure in both maxilla and mandible although the mean probing forces and pressures in all provider groups were higher than the suggested value reported in the literature. CONCLUSION This study indicates that there are variations among clinical provider groups with regard to peri-implant probe instrument type used and forces applied, though these are not statistically significant. Probe tip diameter should be considered to avoid BOP false positives when probing dental implants especially as the forces generally used by the clinicians may be higher than advised.

Introduction: Marginal integrity is a challenging goal revealing an accurate restoration with definite marginal adaptation thus inflammation of gingival tissues and bone destruction correlate directly with a poor marginal property of the restoration. These days improved vision is essential in dentistry upgrading exactness and flawlessness. Objectives: To assess the impact of amplification on the marginal adaptation of CAD/CAM monolithic lithium disilicate crowns. Materials and Methods: In-vitro study using 16 upper right cuspid typodont teeth; divided into two entities according to tooth preparation approach (n=8). Group I teeth preparation without magnification (control group), Group II teeth preparation utilizing the dental operating microscope (DOM) under magnification of 16x. Optical impressions were taken through scanning by Sirona inEOS X5 extra-oral scanner where full anatomical crowns were structured, processed, Sintered and glazed. CBCT was utilized to quantify the minimal gapes before and after cementation/aging. Results: Marginal gaps were significantly increased after cementation and aging in both groups yet still inside the worthy minimal gap values. Group II demonstrated recognizable less marginal gaps. Conclusions: Operating microscopy OM is a significant supplement to the armamentarium of present-day dentistry. It helps set the bar of greatness and flawlessness at the most elevated level including every dental field.

Poor marginal adaptation may give rise to a series of biological complications. Despite its importance, comparative studies on marginal adaptation of metal-ceramic fixed restorations fabricated with newer methods are limited.Therefore, it was aimed to assess the marginal accuracy of copings fabricated with subtractive and additive manners used in contemporary dentistry.For a typodont model, 60 three-unit cobalt-chrome metal copings were fabricated by selective laser sintering (SLS), hard alloy milling (HAM), and soft alloy milling (SAM) in comparison to casting (C). Marginal discrepancy assessment was performed by using replication technique. Mesiodistal and buccopalatal cross-sections of silicone replicas were investigated under a stereomicroscope at × 80 magnification. A total of 960 measurements were subsequently made by means of corresponding image-review software on captured images after calibration of the software to μm scale. Obtained data were subjected to nonparametric Kruskal Wallis and Tamhane post-hoc tests (α =0.05).Marginal adaptation of C group was significantly inferior to test groups in both canine- and premolar-teeth measurements (P0.05). Marginal fit was found to be tooth dependent (P0.001). HAM, SAM, and SLS groups exhibited analogous marginal discrepancy values on canine-tooth measurements. Differences among these groups were not statistically significant (P0.05). SAM and SLS groups demonstrated better marginal adaptation than others on premolar-tooth measurements. Also, no statistically significant difference was detected between SAM and SLS groups (P0.05).SAM group demonstrated superior marginal accuracy. All groups had clinically acceptable marginal discrepancy values (120 μm), except cast group.

El objetivo de esta investigación fue analizar los ángulos de convergencia en preparaciones dentarias para coronas realizadas en tipodontos, por estudiantes de décimo semestre de Odontología Unach. Las preparaciones dentales para coronas poseen características de retención y resistencia, principios fundamentales que ofrecen éxito y longevidad de la corona definitiva. Varios investigadores a nivel mundial han desarrollado diversos métodos para evaluar los ángulos de convergencia de las preparaciones extracoronarias; sin embargo, en nuestro medio, no existen estudios acerca de la medición de estos ángulos. Esta investigación fue de carácter experimental, transversal y observacional, se obtuvieron 32 preparaciones dentarias para coronas de recubrimiento completo, cada estudiante tuvo 60 minutos para tallar dos preparaciones dentarias en simuladores clínicos. Los tipodontos fueron escaneados y digitalizados mediante el escáner CAD-CAM Ceramill Database versión 1.0 año 2010 del Laboratorio “BrothersDent” para producir imágenes tridimensionales. El software iTero midió los ángulos vestíbulo-lingual (VL) y mesio-distal (MD) de cada preparación. Los ángulos más pequeño y más grande observados fueron 3.1° y 102.5° para molares mandibulares. El promedio del ángulo VL para dientes anteriores fue 40,38 ±4,38° en varones y 36,97 ±3,95° en mujeres y el promedio del ángulo MD fue 44,68 ±5,51° en varones y 40,08 ±3,99° en mujeres. Para dientes posteriores el promedio VL fue 27,46 ±7,82° en varones y 40,98 ±4,63° en mujeres; y el promedio del ángulo MD fue 40,73 ±5,95° en varones y 50,62 ±7,00° en mujeres. En conclusión, los ángulos de convergencia logrados por estudiantes fueron mayores que los ideales recomendados según Shillingburg.

Introduction Since the introduction of the digital dental assessment systems, there has been a shift towards this trend as it appears to provide a more accurate, reliable, time efficient, and reproducible assessment. The Planmeca Emerald scanner coupled with Romexis Compare software allows students and staff to objectively assess individual crown preparations, receive numerical values of key dimensions, and subsequently undergo comparison with ideal crown preparation dimensions. Objectives To measure the inter‐ and intra‐rater reliability using the intra‐oral scanner and Romexis Compare for prosthodontic crown preparations, and to evaluate the possible implementation of this software as a grading and self‐assessment tool in a preclinical setting. Methods The Planmeca scanner and Romexis Compare were used to compare the difference between 30 experimental preparations (n = 15 anterior teeth, n = 15 posterior teeth) with their respective unprepared typodont teeth. Three student examiners (W., K., V.) independently scanned the typodont teeth in pre‐formed standardized and non‐standardized putty jigs. Each preparation was measured from facial, lingual, incisal/occlusal, and margin surfaces. A second trial was completed after 2 weeks to assess intra‐rater reliability. The data were tabulated, graphed, and analyzed using SPSS and GraphPad Prism. Results The results of the study show greater consistencies in inter‐operator measurements for anterior teeth. Some variations, however, were found in posterior teeth measurements between the operators. The results of the intra‐rater measurements appear to be relatively consistent. Conclusion With some limitations, Romexis Compare can be used as a reliable and repeatable method for objective and consistent evaluation of student prosthodontic preparations in a preclinical setting.

Evidence for the accuracy of a recently introduced intraoral scanner is lacking.The purpose of this in vitro study was to evaluate and compare the trueness (validity) and precision (reliability) of 2 intraoral scanners by scanning a quadrant and a sextant.A maxillary typodont with plastic teeth made from a shade A3 polymethyl methacrylate was scanned (n=10) with each intraoral scanner (Planmeca Emerald and 3Shape TRIOS 3) to obtain sextant and quadrant scans. Control scans were made with an industrial optical scanner. The scans were analyzed with a 3D reverse engineering software program and an independent samples t test and general linear model 2-way analysis of variance (α=.05).The 3Shape TRIOS 3 scanner showed no significant difference between the sextant and quadrant scans in trueness (P=.118) or in precision (P.285). The Emerald scanner had statistically significant higher trueness for the sextant scan (P=.007). The 3Shape TRIOS 3 scanner had better performance in trueness and precision when compared with the Emerald scanner.The 3Shape TRIOS 3 scanner was found to be more accurate than the Emerald scanner in terms of trueness and precision, regardless of the scanning field. The Emerald scanner's trueness decreased as the scanning field increased from a sextant to a quadrant.

Objective: The objective of this in-vitro study was to evaluate the marginal and internal fit of a lithium disilicate inlays fabricated by two CAD/CAM systems (extra-oral and intra-oral scanning), and conventional heat-press technique. Materials and methods: Mandibular first molars were used for inlay restorations in a typodont model. Three groups (n=12 each) of inlays were fabricated by Computer Aided Design/ Computer Aided Manufacturing (CAD/CAM) technology using intraoral and extraoral scanning devices, and conventional heat-press method. Replica technique was used to assess the discrepancies. Internal and marginal gaps were measured at 4 points on each side with stereomicroscope at 200x magnification. One-way variance analysis test (ANOVA) and paired-samples t-test were used for analyzing the results. Results: The fit values were statistically significantly influenced by the production method in total discrepancy comparisons (p= .000). Intraoral scanner group demonstrated the lowest marginal and internal gap values whereas conventional heat-press group showed the highest results. Statistically significant differences were found for fit values with respect to the groups (p

Statement of the problem: researches studying the accuracy of the 3D printed dies were very rare.Aim: The aim of the current study was to assess the difference in accuracy and reproducibility of the three dimensionally printed dies versus the stone dies.Materials& Methods: A maxillary typodont (D13PP-TR.1; Nissan, Kyoto, Japan) model with missing upper 1st molar was prepared as master model. Two types of dies were obtained from the master model (n=6). Group 1 was the conventional stone dies using type IV stone (GC FujiRock EP; GC) while group 2 representing the 3D printed dies (Dent2 Mogassam LLC Co. Egypt, Cairo) using resin (industrial blended resin, Funtodo Co. Netherlands). All working models were scanned (Open Technologies 3D scanner, Brescia, Italy) and STL file was superimposed on the STL file of the master model with the best-fit alignment method to analyze the volumetric changes and color maps were provided using 3Shape 3D software software. The mean average distance between the master dies and the working dies in all groups was recorded. Data were fed to the computer and analyzed using IBM SPSS software package version 20.0. Quantitative data were explored for normality using Kolmogorov-Smirnov and Shapiro-Wilk tests. Results: There were no statistically significant differences in volumetric discrepancies between stone model (0.186±0.231) mm3 as a (mean±SD) and 3D printed model (0.176±0.211) mm3 as a mean±SD. Conclusion: Digital work flow can eventually replace the conventional techniques with minimal volumetric discrepancies in 3D printed dies.

Objective Clinicians have been slow to adopt digital impression technologies due possibly to perceived technique sensitivities involved in data acquisition. This research has two aims: determine whether scan pattern and sequence affects the accuracy of the three-dimensional (3D) model created from this digital impression and to compare the 5 imaging systems with regards to their scanning accuracy for sextant impressions. Materials and methods Six digital intraoral impression systems were used to scan a typodont sextant with optical properties similar to natural teeth. The impressions were taken using five different scan patterns and the resulting digital models were overlayed on a master digital model to determine the accuracy of each scanner performing each scan pattern. Furthermore, regardless of scan pattern, each digital impression system was evaluated for accuracy to the other systems in this same manner. Results No differences of significance were noted in the accuracy of 3D models created using six distinct scan patterns with one exception involving the CEREC Omnicam. Planmeca Planscan was determined to be the truest scanner while 3Shape Trios was determined to be the most precise for sextant impression making. Conclusions Scan pattern does not significantly affect the accuracy of the resulting digital model for sextant scanning. Clinical significance Companies who make digital impression systems often recommend a scan pattern specific for their system. However, every clinical scanning scenario is different and may require a different approach. Knowing how important scan pattern is with regards to accuracy would be helpful for guiding a growing number of practitioners who are utilizing this technology.

Purpose: To evaluate the influence of fabrication method and finish line design on marginal and internal fit of full-coverage interim restorations. Methods: Four typodont models of maxillary central-incisor were prepared for full-coverage restorations. Four groups were defined; knife-edge (KE), chamfer (C), rounded-shoulder (RS), rounded-shoulder with bevel (RSB). All preparations were digitally scanned. A total of 80 restorations were fabricated; 20 per group (SLA/3D-printed n = 10, milled n = 10). All restorations were positioned on the master die and scanned using micro-computed tomography. The mean gaps were measured digitally (ImageJ). The results were compared using MANOVA (α =.05). Results: Internal and marginal gaps were significantly influenced by fabrication method (P =.000) and finish-line design (P =.000). 3D-Printed restorations showed statistically significant lower mean gap compared to milled restorations at all points (P =.000). The mean internal gap for 3D-printed restorations were 66, 149, 130, 95 μm and for milled restorations were 89, 177, 185, 154 μm for KE, C, RS, RSB respectively. The mean absolute marginal discrepancy in 3D-printed restorations were (30, 41, 30, 28 μm) and in milled restorations were (56, 54, 52, 38 μm) for KE, C, RS, RSB respectively. Conclusions: The fabrication methods showed more of an influence on the fit compared to the effect of the finish-line design in both milled and printed restorations. SLA-printed interim restorations exhibit lower marginal and internal gap than milled restorations. Nonetheless, for both techniques, all values were within the reported values for CAD/CAM restorations. Significance: 3D-printing can offer an alternative fabrication method comparable to those of milled restorations.

Many clinicians use hand screwdrivers to tighten prosthetic and abutment screws. The impact of the screwdriver type, the location of the implant, and the sex of the practitioner on the generated torque is not well understood.The purpose of this in vitro study was to compare the torque generated by different hand screwdrivers when used in the anterior and posterior regions and to evaluate the correlation between the applied torque and the sex and body mass index (BMI) of the practitioner.A mandibular typodont with anterior and posterior implants was mounted in a mannequin head. Fifty clinicians (6 prosthodontists, 8 graduate prosthodontic students, and 36 dental students) used their maximum force to tighten the abutment screws in the anterior and posterior regions, using 3 different hand screwdrivers, with handles of different shapes and sizes (small, medium, and large). The torque values generated were measured using torque meters connected to the implants. The generated torque, sex, age, height, and weight were also recorded for each clinician. A generalized linear model was used to find correlations between the different factors and the generated torque (α=.05).Significant differences were observed among the applied torque values when different screwdrivers were used (P.001). Higher torque values were generated in the anterior region than in the posterior region (P.001). The interaction of the sex and BMI of the participants significantly affected the generated torque values (P=.044).The type of screwdriver and location of the implant affected the generated torque. Torque values generated by the large screwdriver were higher than those of small and medium screwdrivers. Higher torque was applied in the anterior region.

PURPOSE To compare the marginal fit of lithium disilicate (LD) crowns fabricated with digital impression and manufacturing (DD), digital impression and traditional pressed manufacturing (DP), and traditional impression and manufacturing (TP). MATERIALS AND METHODS Tooth #15 was prepared for all-ceramic crowns on an ivorine typodont. There were 45 LD crowns fabricated using three techniques: DD, DP, and TP. Microcomputed tomography (micro-CT) was used to assess the 2D and 3D marginal fit of crowns in all three groups. The 2D vertical marginal gap (MG) measurements were done at 20 systematically selected points/crown, while the 3D measurements represented the 3D volume of the gap measured circumferentially at the crown margin. Frequencies of different marginal discrepancies were also recorded, including overextension (OE), underextension (UE), and marginal chipping. Crowns with vertical MG > 120 μm at more than five points were considered unacceptable and were rejected. The results were analyzed by one-way ANOVA with Scheffe post hoc test (α = 0.05). RESULTS DD crowns demonstrated significantly smaller mean vertical MG (33.3 ± 19.99 μm) compared to DP (54.08 ± 32.34 μm) and TP (51.88 ± 35.34 μm) crowns. Similarly, MG volume was significantly lower in the DD group (3.32 ± 0.58 mm3 ) compared to TP group (4.16 ± 0.59 mm3 ). The mean MG volume for the DP group (3.55 ± 0.78 mm3 ) was not significantly different from the other groups. The occurrence of underextension error was higher in DP (6.25%) and TP (5.4%) than in DD (0.33%) group, while overextension was more frequent in DD (37.67%) than in TP (28.85%) and DP (18.75%) groups. Overall, 4 out of 45 crowns fabricated were deemed unacceptable based on the vertical MG measurements (three in TP group and one in DP group; all crowns in DD group were deemed acceptable). CONCLUSION The results suggested that digital impression and CAD/CAM technology is a suitable, better alternative to traditional impression and manufacturing.

PURPOSE This in vitro study aimed to analyze and compare the reproducibility of zirconia and lithium disilicate crowns manufactured by digital workflow. MATERIALS AND METHODS A typodont model with a prepped upper first molar was set in a phantom head, and a digital impression was obtained with a video intraoral scanner (CEREC Omnicam; Sirona GmbH), from which a single crown was designed and manufactured with CAD/CAM into a zirconia crown and lithium disilicate crown (n=12). Reproducibility of each crown was quantitatively retrieved by superimposing the digitized data of the crown in 3D inspection software, and differences were graphically mapped in color. Areas with large differences were analyzed with digital microscopy. Mean quadratic deviations (RMS) quantitatively obtained from each ceramic group were statistically analyzed with Student's t-test (α=.05). RESULTS The RMS value of lithium disilicate crown was 29.2 (4.1) µm and 17.6 (5.5) µm on the outer and inner surfaces, respectively, whereas these values were 18.6 (2.0) µm and 20.6 (5.1) µm for the zirconia crown. Reproducibility of zirconia and lithium disilicate crowns had a statistically significant difference only on the outer surface (P

Objective This study aimed to evaluate the ability of the proposed technique in producing restorations that exhibit mimesis with tooth structure and to define a restorative clinical protocol. Materials and Methods For this study a typodont was used. The right upper central incisor with Class IV lesion was restored with the layering technique (reference tooth, RT). For the left upper central incisor with Class IV lesion, six teeth were restored monochromatically (test teeth, TT), using DA3.5 (n = 3) and DA4 (n = 3) composite resins—resulting in six unsatisfactory color restorations. TT were divided into six groups depending on the color of unsatisfactory restoration and preparation depth. First, a preparation was realized on the labial surface with 0.5 mm, 0.7 mm or 1.0 mm of depth. A second preparation was then performed to reproduce the dentinal mamelons. Next, adhesive procedures were performed and the teeth restored. Opaque halo, opalescent halo and vestibular enamel were then reproduced by the addition of different composite resins. The RT and TT were photographed side by side in typodont to obtain six photographic prints. The photographs of the groups were subjected to visual evaluation by 120 volunteers via a questionnaire. Data were analyzed by the prevalence of answers, and Chi-square test was used to investigate the association between variables at .05 significance. Furthermore, ΔE of groups was evaluated in comparison RT. Results The results demonstrated that the moderate intensity restorations (DA3.5) with depths of 0.5 mm and 0.7 mm had the highest prevalence of acceptance. For severe intensity restorations (DA4), the preparation depth of 1.0 mm obtained better acceptance. Conclusions The technique was able to modify the final color of Class IV restorations, producing satisfactory color restorations. CLINICAL SIGNIFICANCE This technique can be used for color correction in cases of Class IV restorations, in situations where there is no time for immediate layered restoration, and as a restorative technique.

Purpose To evaluate the marginal gaps of CAD/CAM (CEREC 3) produced crowns made from leucite-reinforced glass-ceramic (IPS Empress CAD) blocks (LG), and lithium-disilicate (IPS e.max CAD) blocks before (LD-B), and after (LD-A) crystallization firing. Materials and Methods A human molar tooth (#19) was mounted with adjacent teeth on a typodont and prepared for a full-coverage ceramic crown. The typodont was assembled in the mannequin head to simulate clinical conditions. After tooth preparation 15 individual optical impressions were taken by the same operator using titanium dioxide powder and a CEREC 3 camera per manufacturer's instructions. One operator designed and machined the crowns in leucite-reinforced glass-ceramic blocks (n = 5) and lithium-disilicate blocks (n = 10) using the CEREC 3 system. The crowns were rigidly seated on the prepared tooth, and marginal gaps (μm) were measured with an optical microscope (500×) at 12 points, 3 on each of the M, B, D, and L surfaces of the leucite-reinforced glass-ceramic crowns and the lithium-disilicate crowns before and after crystallization firing. Results were analyzed by two-way ANOVA followed by a Tukey's post hoc multiple comparison test (α = 0.05). Results The overall mean marginal gaps (μm) for the crowns evaluated were: LG = 49.2 ± 5.5, LD-B = 42.9 ± 12.2, and LD-A = 57.2 ± 16.0. The marginal gaps for LG and LD-B were not significantly different, but both were significantly less than for LD-A. Conclusions The type of ceramic material did not affect the marginal gap of CAD/CAM crowns. The crystallization firing process required for lithium-disilicate crowns resulted in a significant increase in marginal gap size, likely due to shrinkage of the ceramic during the crystallization process. Clinical Relevance: The marginal gap of CAD/CAM-fabricated lithium disilicate crowns increases following crystallization firing. The marginal gap still remains within clinically acceptable parameters.

Background/purpose One of the major educational goals in preclinical dental education is to learn tooth preparation techniques. The purpose of this study was to evaluate the influence of different preparation designs on the development of the manual dexterity of students, in order to perform a state-of-the-art tooth preparation. Material and methods Seventy-two 1 st semester students were divided into two groups and educated in tooth preparation for a ceramic anterior single crown. One group received cylindrical burs with a rounded edge to prepare a typodont model with a shoulder finishing line, while the other group had cylindrical burs with round noses to prepare a chamfer finishing line. All preparations were digitized and evaluated using special software focusing on the parameters of preparation depth and preparation angle. In addition, violation of the adjacent teeth was estimated. Data was statistically evaluated at a level of significance of 5%. Results The preparation design used did not show a statistically significant influence on the preparation depth or on the preparation angle. A trend to a higher tooth structure removal as required was detected. Furthermore, no influence of the type of preparation design on the number of violated adjacent teeth was found. Conclusion In preclinical dental education, the type of preparation design was found to have no influence on the measured parameters representing the quality of the preparation.

PURPOSE This study compared the marginal gaps of computer-aided design/computer-aided manufacture (CAD/CAM)-fabricated all-ceramic crowns constructed from scanned impressions and models and with two different occlusal reduction designs. MATERIALS AND METHODS Two typodont mandibular first molars were prepared to receive CAD/CAM-fabricated all-ceramic crowns. Both molars were prepared to ideal crown reduction, the first with anatomical occlusal reduction (AOR) and the second with completely flat occlusal reduction (FOR). Nine polyvinyl siloxane impressions (PVS) were taken, and nine stone replicas fabricated for each preparation. All impressions and stone models were scanned using a laser scanner (Planmeca Planscan, E4D technologies), and 36 lithium disilicate (IPS e.max CAD) crowns were milled. The marginal gap was measured in four locations using a light stereomicroscope. RESULTS Crowns constructed from preparations with both occlusal reduction designs demonstrated similar marginal gaps (FOR = 97.98; AOR = 89.12; P = .739). However, all crowns constructed from scanned impressions presented significantly larger marginal gaps than the crowns fabricated from scanned models (impressions = 109.26; models = 77.84; P = .002). CONCLUSION Scanning stone models produced all-ceramic crowns with significantly smaller marginal gaps than scanning impressions, irrespective of the occlusal reduction design.

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

Background Marginal fit is critical for the success and longevity of a dental restoration. Zirconia crowns can be fabricated either chair-side, in a dental laboratory or in a milling center; each can give different marginal fits results. However, discussion of the marginal fit of zirconia crowns when different fabrication methods are compared is lacking in the literature. Purpose To compare the marginal discrepancy (MD) and absolute marginal discrepancy (AMD) of computer-aided design, and computer-aided manufacturing (CAD-CAM) used in a dental laboratory and a milling center for producing monolithic zirconia crowns. Methods The marginal fit of 30 zirconia crowns cemented to typodont teeth was evaluated by means of a sectioning technique. Fifteen crowns were fabricated with a CEREC inLAB MC X5 from IPS e.max ZirCAD blocks. Fifteen crowns were fabricated using a LAVA milling center from LAVA Plus Zirconia Blocks. The 30 crowns were sectioned with a precision saw, and MD and AMD were subsequently measured using a light microscope. Data were analyzed using the one-way ANOVA technique to investigate significant differences in the marginal fit between the two fabrication systems (α = .05). Results The AMD dimension of the CEREC inLAB system was significantly smaller (P

The aim of this study was to evaluate teeth prepared for computer-aided design/computer-aided manufacturing (CAD/CAM) restorations by senior dental students using recently developed rubrics. The rubrics used evaluation criteria based on four factors: retention or resistance form; marginal or internal adaption or manufacturing process; biology, esthetics, or durability of restorative material; and intraoral scanner impression. In academic year 2018-19, four faculty members used the rubrics to assess 111 first maxillary right premolars (tooth no. 4) prepared for lithium disilicate crowns and 223 second maxillary right premolars (tooth no. 5) and first maxillary right molars (tooth no. 3) prepared for monolithic zirconia partial fixed dental prostheses. The preparations had been performed on typodont teeth. The most common errors identified for tooth preparations were in the finish line quality (136 errors in 223 prostheses), a criterion that is crucial for quality CAD/CAM restorations. To prevent poorly fit CAD/CAM restoration preparations that result from an unacceptable finish line quality, students need to understand the rationale used to develop detailed rubrics and adhere to the defined critera.

Approaches that reproduce dental hygiene regimens under controlled conditions have applications in preclinical research. We have applied standardized, reproducible brushing regimes to typodonts coated in simulated or biological plaques to assess the effects on tooth cleaning of toothbrush/dentifrice regimens. Replicated typodonts were coated with OccludeTM or GlogermTM indicators to simulate plaque, and brushed reproducibly using a mechanical brushing simulator to compare the cleaning of occlusal surfaces before and after brushing with water or a dentifrice. An in vitro model using salivary inocula to cultivate oral biofilms on typodont surfaces was then developed to evaluate removal of disclosed plaque by new toothbrushes in comparison to toothbrushes with wear equivalent to 3 months of use. Analyses of typodonts brushed under controlled conditions significantly (p < 0.01) distinguished between brushed and unbrushed surfaces and between the use of water vs. dentifrice for the removal of simulated interproximal plaque (p < 0.05). New toothbrushes removed significantly (p < 0.05) more biological plaque from typodont surfaces than brushes that had been worn by repeated brushing. Through controlled and defined brushing of typodonts with simulated and biological plaques, the effectiveness of dental hygiene regimens was compared under reproducible conditions. Data indicate that the cleaning effectiveness of brushing was augmented by the addition of dentifrice and that new brushes were significantly more effective than brushes with substantial wear from previous use. Whilst we have focussed on the occlusal surfaces of molars and worn brushes, the method could be applied to a range of other tooth surfaces and oral hygiene regimens.

Limited evidence is available comparing the differences between pre-operative and post-operative 3D implant positions from the viewpoint of prosthetics. We aimed to investigate the differences between preplanned positions of virtual provisional restorations and their actual positions following fully guided single-implant placement. Ten maxillary typodonts with missing right central incisors were imaged using cone-beam computed tomography, and digital impressions were obtained using an intraoral scanner. These data were imported into implant-planning software, following which the provisional restorations were designed. After data superimposition, an appropriate implant position was determined, and a computer-assisted implant surgical guide was designed for each typodont. Orders generated from the implant-planning software were imported into relevant computer-aided design software to design the custom abutments. The abutments, provisional restorations, and surgical guides were fabricated, and each restoration was cemented to the corresponding abutments, generating a screw-type immediate provisional restoration. The implants were placed using the surgical guides, and the screw-type provisional restorations were engaged to the implants. The typodonts were then rescanned using the intraoral scanner. The restorations designed at the treatment planning stage were compared with those in the post-operative scan using metrology software. The angular deviation around the central axis of the implant was measured, and the differences in the crown position were converted to root mean square (RMS) values. The post-operative provisional restorations exhibited an absolute angular deviation of 6.94 &plusmn, 5.78&deg, and an RMS value of 85.8 &plusmn, 20.2 &micro, m when compared with their positions in the pre-operative stage. Within the limitations of the present in vitro study, the results highlight the potential application of customized prefabricated immediate provisional restorations after single-implant placement.

In Part I of this study, evidence was presented that visual inspection (VI) of dental student waxups exhibited low precision (ICC=0.332) and accuracy, resulting in questionable grade validity. VI inappropriately assesses morphology in part due to oversimplified grading rubrics and inappropriate application of ratio measurement to ordinal data. The aim of Part II of this study was to develop, apply, and compare with VI a digital assessment workflow and report the outcomes. After inclusion criteria were met, 67 (83%) student waxups were scanned with an intraoral scanner and analyzed using open source surface comparison software. Each was digitally compared to the homologous standard typodont tooth. Percentage contour variation within a stipulated tolerance was computed. The acceptable tolerance was derived from clinical literature reporting how contour deviations impact the biological and biomechanical stability of teeth and periodontium. Surface roughness of each waxup was also computed and compared with the reference teeth. A formula for digital assessment was developed and applied to each waxup. On average, digital grades exceeded the VI assessments, while correcting individual errors for greater accuracy and precision (ICC=0.866). Students were able to easily apply the digital workflow for visualization and accurate self-evaluation. In this study, a digital grading workflow was developed that used portable data formats and freely available open source analysis software, so the method could be introduced at any dental school where intraoral scanning is available.

BACKGROUND The Bologna reform resulted in a drastic restructuring of pre-clinical training courses at the University of Zurich. The aim of this study was to assess student pre-clinical scaling/root planning skills after just 8.5 hours of manual training. MATERIAL AND METHODS Three consecutive classes of dental students (n = 41; n = 34; n = 48) were tasked with removing lacquer concrement from the maxillary left canine on a typodont using Gracey and universal (Deppeler M23A) curettes. At baseline (prior to instruction), a timed five-minute session of scaling/root planning was undertaken. The second scaling/root planning session was held immediately following training. Eight experienced dental hygienists and eight lay people served as positive and negative controls, using the same instruments and time limit, respectively. Instrumented teeth were collected, scanned and planimetrically analysed for the percentage of tooth surface cleaned. Statistical analyses were performed to assess the dental students' improvement after the training (Wilcoxon signed-rank test) and to compare it to that of laypeople and dental hygienists (Kruskal-Wallis rank sum test followed by Conover's post hoc test). RESULTS At baseline, the dental students' mean scaling scores of the cleaned surfaces were not significantly different than those of laypeople (29.8%, 31.0%, 42% vs 27.9%). However, after 8.5 hours of manual training, the students' ability to clean the maxillary tooth improved significantly and they achieved mean removal values of 61.7%, 79.5% and 76% compared to the 67.4% (P

Monolithic zirconia crowns fabricated with computer-aided design and computer-aided manufacturing (CAD-CAM) have recently become a common practice for the restoration of posterior teeth. The marginal fit of monolithic zirconia crowns may be affected by different cement space parameters set in the CAD software. Information is scarce regarding the effect of cement space on the marginal fit of monolithic zirconia crowns fabricated with CAD-CAM technology.The purpose of this in vitro study was to evaluate the effect of cement space on the marginal fit of CAD-CAM-fabricated monolithic zirconia crowns before cementation.Fifteen right maxillary first molar typodont teeth with standardized anatomic preparations for complete-coverage ceramic crowns were scanned with a 3-dimensional laboratory scanner. Crowns were designed 3-dimensionally using software and then milled from presintered monolithic zirconia blocks in a computer numerical control dental milling machine. The cement space was set at 25 μm around the margins for all groups, and additional cement space starting 1 mm above the finish lines of the teeth was set at 30 μm for group 25-30, 40 μm for group 25-40, and 50 μm for group 25-50 in the CAD software. A total of 120 images (3 groups, 5 crowns per group, 8 sites per crown) were measured for vertical marginal discrepancy under a stereoscopic zoom microscope and the data were statistically analyzed with 1-way analysis of variance, followed by the Tukey honestly significant difference test (α=.05).The results showed that different cement space values had statistically significant effect on the mean vertical marginal discrepancy value of tested crowns (P.001). The mean marginal discrepancy was 85 μm for group 25-30, 68 μm for group 25-40, and 53 μm for group 25-50.Within the limitations of this in vitro study, it was concluded that the cement space had a significant effect on the marginal fit of CAD-CAM-fabricated monolithic zirconia crowns. The marginal fit improved as the cement space decreased.

Statement of problem Although the number of lithium disilicate crowns fabricated with computer-aided design and computer-aided manufacturing (CAD-CAM) technology has increased, the accuracy of the prostheses produced by using digital pathways remains unknown. Purpose The purpose of this in vitro study was to compare marginal and internal discrepancies of lithium disilicate crowns fabricated from digital and conventional impressions. Material and methods A typodont mandibular first molar was prepared for a lithium disilicate crown, and 20 duplicate dies were fabricated by milling poly(methyl methacrylate) resin blocks from laboratory scans. Four groups of 5 lithium disilicate crowns each were created by using a CS3500 (Carestream Dental) intraoral digital impression; Trios (3shape) intraoral digital impression; Ceramill Map400 (Amann Girrbach) extraoral digital impression; and a heat-press technique as a control group. All of the IPS e.max CAD (Ivoclar Vivadent AG) crowns were produced using a 5-axis milling engine (Ceramill Motion2). The lithium disilicate crowns were cemented with zinc phosphate cement under finger pressure. Marginal and internal discrepancies were measured using micro-computed tomography (SkyScan1172). One-way ANOVAs with the Tukey honest significant differences test were used for statistical analysis of the data (α=.05). Results The mean marginal discrepancies of CS3500 lithium disilicate crowns were 129.6 μm, 200.9 μm for Ceramill Map400, and 207.8 μm 176.1 μm for the heat-press technique; and the internal discrepancy volumes for CS3500 were 25.3 mm 3 , 40.7 mm 3 for Trios, 29.1 mm 3 for Ceramill Map400, and 29.1 and 31.4 mm 3 for the heat-press technique. The CS3500 group showed a significantly better marginal discrepancy than the other 3 groups and a smaller internal discrepancy volume than the Trios group ( P Conclusions Significant differences were found between IPS e.max CAD crowns produced using 2 intraoral digital impressions, whereas no differences were found between IPS e.max CAD crowns produced from an extraoral digital impression and IPS e.max Press crowns produced using a heat-press technique.

Objective: We evaluated the effects of tooth displacement on frictional force when conventional ligating lingual brackets (CL-LBs), CL-LBs with a narrow bracket width, and self-ligating lingual brackets (SL-LBs) were used with initial leveling and alignment wires. Methods: CL-LBs (7th Generation), CLLBs with a narrow bracket width (STb), and SL-LBs (In-Ovation L) were tested under three tooth displacement conditions: no displacement (control); a 2-mm palatal displacement (PD) of the maxillary right lateral incisor (MXLI); and a 2-mm gingival displacement (GD) of the maxillary right canine (MXC) (nine groups, n = 7 per group). A stereolithographic typodont system and artificial saliva were used. Static and kinetic frictional forces (SFF and KFF, respectively) were measured while drawing a 0.013-inch copper-nickel-titanium archwire through brackets at 0.5 mm/min for 5 minutes at 36.5 o C. Results: The In-Ovation L exhibited lower SFF under control conditions and lower KFF under all displacement conditions than the 7th Generation and STb (all p < 0.001). No significant difference in SFF existed between the In-Ovation L and STb for a 2-mm GD of the MXC and 2-mm PD of the MXLI. A 2-mm GD of the MXC produced higher SFF and KFF than a 2-mm PD of the MXLI in all brackets (all p < 0.001). Conclusions: CLLBs with narrow bracket widths exhibited higher KFF than SL-LBs under tooth displacement conditions. CL-LBs and ligation methods should be developed to produce SFF and KFF as low as those in SL-LBs during the initial and leveling stage. [Korean J Orthod 2016;46(2):87-95]

To assess the reliability of inter-radicular measurements taken using dental pantomograms (DPT), long cone periapical radiographs (LCPA) and cone bean computed tomography (CBCT).A typodont simulating a hypodontia patient undergoing fixed appliance treatment was used. LCPAs, DPT, I-CAT and Accuitomo CBCT images were taken and the distances between the edentulous spans were measured at the midpoint of the roots and the cemento-enamel junctions (CEJ) of adjacent teeth. The results of each modality were compared to each other to the actual inter-radicular space.The DPT overestimated inter-radicular widths by 2 mm or more [mean: 2.48; 95% confidence interval (CI): -1.09 to 6.05 mm]. The LCPA overestimated the inter-radicular widths by 1.5 mm with a 95% CI of -0.095 to 4.03 mm. The mean differences between gold standard (model) and Accuitomo was 0.57 mm (95% CI: -0.37 to 1.51 mm) for the root mean and 0.22 mm (95% CI: -0.52 to 0.96 mm) for the CEJ. This was similar to the differences between the model and I-CAT where the inter-radicular root mean difference was 0.38 mm (95% CI: -0.38 to 1.14 mm) and the CEJ mean difference was 0.21 mm (95% CI: -0.50 to 0.92 mm).The CBCT overestimated the root distance by 0.48 mm and the CEJ width by 0.22 mm, which is clinically irrelevant for implant placement. The DPT overestimated inter-radicular width by 2 mm and the LCPA by 1.5 mm and this difference may put roots of adjacent teeth at risk during implant placement.

To assess the accuracy of various intraoral scanners (IOSs) and to investigate the existence of mutual compatibility that affects the accuracy between IOS and 3-dimensional (3D) printing using a scan quadrant model. For clinical implication, crown preparations and cavity design according to prosthetic diagnosis and treatment considerations must be acquired by a digital scanner. The selected typodont model was scanned using a reference scanner, from which reference (Ref) standard tessellation language (STL) data were created. Data obtained by scanning the typodont model with IOSs based on three different technologies were divided into three groups (CS3600, i500, and Trios3). Scanned data from the groups were divided into sub-groups of digital light processing (DLP), fused deposition modeling (FDM), and stereolithography apparatus (SLA), based on which 3D printed models (3DP) were fabricated. The 3DP dental models were scanned to obtain a total of 90 3DP STL datasets. The best-fit algorithm of 3D analysis software was used for teeth and arch measurements, while trueness was analyzed by calculating the average deviation among measured values based on superimposition of Ref and IOS and 3DP data. The differences between Ref and IOS (Ref-IOS), Ref and 3DP (Ref-IOS/3DP), and IOS and 3DP data (IOS-3DP) were compared and analyzed, while accuracy within each of the three main groups was assessed. For statistical analysis, the Kruskal&ndash, Wallis, Mann&ndash, Whitney U, and repeated measures ANOVA test were used (p &lt, 0.05). The major finding is that the mutual relationships between IOSs and 3D printers vary depending on the combination. However, i500 intraoral scanner and DLP 3D printer was the combination that showed the best trueness value.

Statement of problem Intraoral scans and virtual interocclusal records (VIRs) are widely used for contemporary prosthodontic treatment of patients with partial edentulism. The accuracy of VIRs in various clinical conditions is unclear. Purpose The purpose of this in vitro study was to investigate whether the span and location of edentulous areas affect the accuracy of VIRs. Material and methods Five sets of master stone casts were duplicated from a typodont model (Prosthetic Restoration Jaw Model; Nissin Dental) and then assigned into 5 study groups. Six pairs of interarch markers were placed on the master stone casts as reference points for measurements. The 5 study groups were group 1-Post: 1 posterior tooth missing; group 3-Post: 3 posterior teeth missing; group 6-Ant: 6 anterior teeth missing; group Bil-Post: bilateral posterior teeth missing; and group Dent: completely dentate arch. Master stone casts along with VIRs were scanned 10 times in each group by using an intraoral scanner (IOS) (Dental Wings Intraoral Scanner; Dental Wings Inc). Digital measurement of distances between the interarch markers was obtained on all digitally articulated casts and compared with the manual measurements (with electronic calipers with an accuracy of 0.02 mm). In addition, the differences (absolute values) between the digital and manual measurements were calculated at the edentulous locations for the groups 1-Post, 3-Post, 6-Ant, and Bil-Post and were compared with the corresponding interarch marker positions in the group Dent. Two-sample t tests were used for the statistical analysis (α=.05). Results The overall differences (mean ±standard deviation) between digital and manual measurements were group 1-Post: 0.10 ±0.19 mm, group 3-Post: 0.28 ±0.63 mm; group 6-Ant: 0.19 ±0.20 mm; group Bil-Post: 0.28 ±0.25 mm; and group Dent: 0.05 ±0.18 mm. Group Dent was the only group with no significant differences between digital and manual measurements at all 6 interarch marker positions and was used as the reference to analyze the measurements in the edentulous areas. No statistical difference was found (P=.237) at the group 1-Post's edentulous area when compared with the group Dent. In the group 3-Post, the edentulous areas showed statistically significant difference when compared with those of the group Dent (P=.002 and P=.003). In the group 6-Ant, the edentulous areas showed statistical differences when compared with those of the group Dent (P=.019 and P=.008). In the group Bil-Post, only 1 side of the edentulous areas showed statistical differences when compared with group Dent (P=.006 and P=.034). Conclusions The span and location of edentulous areas impact the accuracy of VIRs. For a single missing posterior tooth, VIRs could achieve a high level of accuracy comparable with that of the dentate condition. Unilateral and bilateral extended edentulous spans with 3 or more missing posterior teeth and the extended edentulous span in the anterior region all affected the accuracy of VIRs.

Statement of problem The use of intraoral scanning (IOS) to replace conventional impressions has become popular. However, the learning time required to use these devices effectively is unknown. Purpose The purpose of this in vitro study was to investigate the learning rate, plateau, and difficulty level over repetitive IOS among prosthodontic residents. Material and methods Twenty participants with no experience of IOS were recruited. Maxillary and mandibular typodont casts were attached to a manikin head. Participants received training on the IOS device (Omnicam; Dentsply Sirona) and performed maxillary, mandibular, and buccal IOS for 9 trials. The time required for scanning (ST) and the perception of difficulty were recorded. The percentage ratio of time for each trial to the best performance was calculated. A nonlinear regression model was used to estimate the learning plateau and rate. Results The findings for maxillary, mandibular, buccal, and total IOS were as follows: ST: 106 ±40 seconds (69 ±24%), 96 ±34 seconds (68 ±22%), 74 ±31 seconds (65 ±22%), and 276 ±88 seconds (72 ±20%); learning plateau: 83.40%, 80.60%, 74.30%, and 85.10%; learning rate: 5.37, 5.01, 3.81, and 4.98. With repetition of the trials, the difficulty level decreased from 6 to 4. Conclusions The repetitive use of IOS showed a learning phase of 5 trials to achieve competence of 80% of their best performance. The scanning time and difficulty level decreased with the repetitive use of IOS.

Background and objective: An expectation of beautiful smiles at the end of orthodontic treatment is a primary concern to each patient, but is also equally concerned with appearance while undergoing treatment. The development of appliances that combine both acceptable aesthetics for the patient and adequate technical performance for the clinician is the ultimate goal. The aim of this study was to compare three different aesthetic orthodontic techniques with different biomechanics in order to quantify the efficiency of these techniques in alignment of displaced upper right central incisor and investigating the effects of these variables on alignment considering its tipping and rotation. Methods: The sample consisted of three groups with each group including 15 samples; (1) conventional buccal technique group, (2) lingual technique group and (3) Inman Aligner group, all on a typodont simulation system (dentsply). Preoperative and postoperative digital images were taken and analyzed using Autodesk AutoCAD software. Results: The conventional buccal technique gave rise to the highest mean of tooth tipping and rotation followed by the lingual technique. The Inman Aligner produced the least level of tooth tipping and rotation. Conclusion: The best method of alignment is the conventional buccal technique followed by the lingual technique. The least favourable one is the Inman Aligner.

In this study, we aimed to evaluate the influence of clinical experience and the type of tooth (incisors, canines, and premolars) on the vertical accuracy of bracket placement with the Boone gauge.For this analysis, 4 groups were defined. Group 1 was composed of undergraduate students from the dental school with no previous experience in bonding orthodontic attachments; group 2 was composed of graduate students in the dental school; group 3 consisted of orthodontists with a maximum of 5 years of clinical experience; and group 4 comprised orthodontists with more than 5 years of clinical experience. Each group included 6 participants. A typodont was simulated with a Class I crowded malocclusion that reproduced the same occlusal characteristics for all groups to be bonded. All participants were instructed to bond 0.022 × 0.028-in edgewise brackets on the labial surfaces of the maxillary and mandibular incisors, canines, and premolars at a height of 4 mm from the incisal edge or the labial cusp tip. After each bonding procedure, all teeth were photographed after being removed from the typodont and positioned in a stabilizing device adapted to a camera stand.The analyses of the variations showed that group 1 had the closest mean to 4 mm. However, this group also showed the greatest variance (0.433) (P0.001). The smallest variations were observed in group 2 (variance, 0.093), followed by group 4 (variance, 0.094). The comparison of the means obtained in the groups of teeth at 4 mm demonstrated that the incisors showed a statistically significant difference (P0.001), whereas canines (P = 0.133) and premolars (P = 0.913) did not.Operators are prone to fail in the placement of orthodontic attachments with the Boone gauge, despite their clinical experience in orthodontics. In the comparison of the groups of teeth, the incisors showed a statistically significant difference in relation to the height suggested for bracket placement with the Boone gauge.

This study compared the performance of three laser fluorescence (LF) devices (DIAGNOdent Classic, DIAGNOdent Pen and KEY3 laser) under standardized laboratory conditions for detecting subgingival deposits of calculus on root surfaces of extracted teeth in typodonts. While some studies show the efficacy of LF devices for calculus detection compared with conventional periodontal probes, little is known regarding the differential performance of different LF devices. In this laboratory study, extracted teeth were set in an anatomical configuration in stone typodont models in a phantom head and impression material used to replicate periodontal soft tissues. A total of 240 sites were assessed on three occasions using the three different LF devices and results compared to direct microscopic examination of the roots of the extracted teeth under magnification. The KEY3 showed greater accuracy (86.4 %) than the DIAGNOdent Pen (84 %) and DIAGNOdent Classic (80.2 %). The intra-examiner reproducibility was also higher for the KEY3 (mean Cohen kappa 0.74) than the DIAGNOdent Pen (0.66) and DIAGNOdent Classic (0.6). Of the three LF devices, the KEY3 has greater accuracy and reproducibility.

The use of computers to aid in instruction and help decrease the subjective component of assessment is steadily increasing. One of the potential barriers to the effective utilization of CAD/CAM technology for assessment purposes is the efficient scanning of the teeth being used for comparison. The purpose of this pilot study was to determine if the use of different typodonts, of the same make and model, has any significant effect on the percent comparison results when using E4D Compare. Tooth #30 was prepared by a faculty member to represent what dental students at Georgia Regents University are taught as the ideal preparation for a full gold crown. Ten typodonts of the same make and model were selected for comparison. Three different examples of students' preparations were scanned and compared to the ideal preparation. Each of the three student preparations was subjected to ten trials (occasions), one for each typodont, at five tolerance levels: 0.1 mm, 0.2 mm, 0.3 mm, 0.4 mm, and 0.5 mm. The intraclass correlation coefficient (ICC) was used to measure the intrarater agreement among the typodonts at the various tolerance levels. The agreement coefficients (0.971-0.984) indicated very little variability attributable to the use of a different typodont. The high agreement coefficients achieved using different typodonts of the same make and model provide evidence for the interchangeability of typodonts when assessing a student's performance in the preclinical simulation environment.

The problems associated with intra- and interexaminer reliability when assessing preclinical performance continue to hinder dental educators' ability to provide accurate and meaningful feedback to students. Many studies have been conducted to evaluate the validity of utilizing various technologies to assist educators in achieving that goal. The purpose of this study was to compare two different versions of E4D Compare software to determine if either could be expected to deliver consistent and reliable comparative results, independent of the individual utilizing the technology. Five faculty members obtained E4D digital images of students' attempts (sample model) at ideal gold crown preparations for tooth #30 performed on typodont teeth. These images were compared to an ideal (master model) preparation utilizing two versions of E4D Compare software. The percent correlations between and within these faculty members were recorded and averaged. The intraclass correlation coefficient was used to measure both inter- and intrarater agreement among the examiners. The study found that using the older version of E4D Compare did not result in acceptable intra- or interrater agreement among the examiners. However, the newer version of E4D Compare, when combined with the Nevo scanner, resulted in a remarkable degree of agreement both between and within the examiners. These results suggest that consistent and reliable results can be expected when utilizing this technology under the protocol described in this study.