Comparison of the dimensional and morphological accuracy of three-dimensional digital dental casts digitized using different methods.

The purpose of this study was to compare the accuracy of digital dental casts from plaster cast scanning (PCS), impression scanning (IPS), intraoral scanning (IOS), and cone-beam computed tomography (CBCT) scanning (CCS) methods. The maxillary and mandibular dental casts of 15 patients who needed CBCT scans for oral examination or treatment were digitized via four methods. 12 linear distance measurements of all digital dental casts were selected and acquired with software and compared to those of the reference plaster cast to evaluate the dimensional accuracy. Three-dimensional deviation analysis of the IPS, IOS and CCS groups with respect to the reference PCS group was performed to evaluate the morphological accuracy. The discrepancy in linear distances between the digital dental casts and reference plaster casts was statistically significant (p < 0.01). The dimensional accuracies of the PCS (0.06 ± 0.12 mm) and IPS (0.03 ± 0.05 mm) casts were better than those of the IOS (0.37 ± 0.30 mm) and CCS (0.54 ± 0.40 mm) casts. The one-sample t test showed that there were statistically significant differences between the discrepancies in 8 of the linear distances for the PCS group and 9 of the linear distances for the IPS group between the digital dental casts and reference plaster casts, with an ideal error of 0.00 (p < 0.05). The sequence of morphological accuracy from good to poor was maxillary and mandibular IPS, mandibular IOS; maxillary IOS; and maxillary and mandibular CCS. The accuracy of the digital dental casts from the PCS and IPS methods was greater than that of IOS and CCS methods. Although accuracy of the digital dental cast from IOS was low, it satisfied the clinical requirements for fixed restorations in small units. The accuracy of the digital dental cast from CCS was poorest and could only be used for procedures with lower accuracy requirements.

Fit accuracy in the rest region of RPDs fabricated by digital technologies and conventional lost-wax casting: a systematic review and meta-analysis.

BACKGROUND: Digital technologies have recently been introduced into the fabrication of removable partial dentures (RPDs). However, it is still unclear whether the digitally fabricated RPDs fit better than conventionally cast ones in the rest region. The aim of this study was to evaluate the fit accuracy in the rest region of RPDs fabricated by digital technologies and compare it to those made by conventional lost-wax (CLW) technique. METHODS: A comprehensive search was conducted in Cochrane Library, PubMed, EMbase, Web of Science and SpringerLink. Studies published up to August 2022 were collected. Two authors analyzed the studies independently and assessed the risk of bias on the modified methodological index for non-randomized studies (MINORS) scale. The mean values of gap distance between rests and corresponding rest seats of each study were extracted as outcome. A random-effects model at a significance level of P < 0.05 was used in the global comparison and subgroup analysis was carried out. RESULTS: Overall, 11 articles out of 1214 complied with the inclusion criteria and were selected, including 2 randomized controlled trials (RCTs), 1 non-randomized clinical trial and 8 in vitro studies. Quantitative data from Meta-analysis revealed that fit accuracy in the rest region of RPDs fabricated with CLW showed no statistically significant difference with digital techniques (SMD = 0.33, 95%CI (-0.18, 0.83), P = 0.21). Subgroup analysis revealed a significantly better fit accuracy of CLW-fabricated RPDs in the rest region than either additive manufacturing (AM) groups or indirect groups (P = 0.03, P = 0.00), in which wax or resin patterns are milled or printed before conventional casting. While milled RPDs fit significantly better than cast ones in the rest region (P = 0.00). With digital relief and heat treatment, hybrid manufactured (HM) clasps obtained better fit accuracy in the rest region (P < 0.05). In addition, finishing and polishing procedure had no significant influence in the fit accuracy in all groups (P = 0.83). CONCLUSIONS: RPDs fabricated by digital technologies exhibit comparable fit accuracy in rest region with those made by CLW. Digital technologies may be a promising alternative to CLW for the fabrication of RPDs and additional studies are recommended to provide stronger evidence. TRIAL REGISTRATION: CRD42020201313.

Analysis of microstructure and fatigue of cast versus selective laser-melted dental Co-Cr alloy.

STATEMENT OF PROBLEM: The forces exerted on teeth and prostheses during mastication are repeated and dynamic, resulting in fatigue damage to dental prostheses. Most fractures of dental restorations are fatigue failure. The 4-point bend fatigue behavior of Co-Cr-Mo-W alloys manufactured by investment casting (CAST) and selective laser melting (SLM) has received little attention. PURPOSE: The purpose of this in vitro study was to evaluate the 4-point bend fatigue property of dental Co-Cr alloys and determine the relationship between microstructure and the 4-point bend fatigue property of Co-Cr alloys created by traditional casting and SLM. These can guide the use of Co-Cr alloy in dentistry. MATERIAL AND METHODS: Co-Cr-Mo-W alloys were fabricated with a dimension of 45×2×2 mm by investment casting and SLM. The 3-point bend test measured the ultimate bend strength with 3 specimens in each group. The 4-point bend fatigue test evaluated the fatigue life under various stresses, with 6 specimens in each group. The specimens were mechanically ground, polished, and electrochemically etched. Scanning electron microscopy was used to identify the microstructures of both etched specimens and fracture surfaces. X-ray diffraction investigations were used to determine the phases. Significant differences in the bend strength were analyzed by using the independent samples t test (α=.05), and the fatigue test was analyzed with ANCOVA (α=.05). RESULTS: The mean ±standard deviation bend strength of SLM specimens was 1837 ±3 MPa, higher than the 1200 ±6 MPa for CAST specimens (P<.05). The maximum bend stress of the SLM specimens without fatigue failure was 735 MPa, which was statistically higher than the 394 MPa for CAST specimens (P<.05). The microstructure characteristics of the SLM alloy contributed to its excellent fatigue performance. In SLM alloy, the γ phase constituted the majority with some ε and Laves phases, while the cast alloy possessed higher ε and Laves phases. The grains of SLM alloy were equiaxed and fine, and the second phases were fine and dispersive. In contrast, the cast alloy possessed clear dendrites, and the second phases were sizable. CONCLUSIONS: The SLM dental Co-Cr-Mo-W alloy had statistically better 4-point bend fatigue properties than cast alloy, which was associated with an improved microstructure.

Effects of build orientation on adaptation of casting patterns for three-unit partial fixed dental prostheses fabricated by using digital light projection.

STATEMENT OF PROBLEM: The lost-wax technique is commonly used for fabricating partial fixed dental prostheses. The casting patterns can be fabricated by using vat photopolymerization (a type of additive manufacturing), but the adaptation of these casting patterns has not been elucidated. PURPOSE: The purpose of this in vitro study was to evaluate the effect of build orientation on the adaptation of casting patterns fabricated by digital light projection (DLP). MATERIAL AND METHODS: A 3-unit partial fixed dental prosthesis with mandibular left second premolar and second molar abutment teeth was scanned and virtually designed with a computer-aided design software program. The cement space was designed to be 30 µm. Specimens were fabricated with 3 build orientations: 0 degrees (with the occlusal surface parallel to the platform), 30 degrees, and 45 degrees (by rotating the file along the long axis). The casting patterns were fabricated by using DLP (Cara Print 4.0) with a photopolymerizable monomer (dima Print Cast Q). Photopolymerization, cleaning, and postpolymerization processes were performed according to the manufacturer's instructions. The adaptation of the specimens was examined by using a silicone replica method. The vertical marginal discrepancy and axial wall, occlusal, and marginal gaps were measured by using a digital measuring microscope. The effect of build orientation at each cross-sectional area was statistically analyzed by using the Kruskal-Wallis test followed by the pairwise Wilcoxon rank sum test with Bonferroni correction (α=.05). RESULTS: Excess polymerized resin was observed along the intaglio buccal wall at build orientations of 30 degrees and 45 degrees. Vertical marginal discrepancies in the buccolingual section ranged from -50 to 248 µm, while those in the mesiodistal section ranged from -25 to 182 µm. The gaps in the buccolingual section ranged from 0 to 236 µm, while those in the mesiodistal section ranged from 0 to 177 µm. According to the observation of vertical marginal discrepancies and gaps, the 30-degree specimens inclined during insertion, and the 45-degree specimens were not completely seated. However, the marginal gaps of the 0- and 30-degree specimens were within the clinically acceptable limit of 120 µm. CONCLUSIONS: The limited data indicated that the build orientation influenced the adaptation of casting patterns for 3-unit partial fixed dental prostheses fabricated by using DLP. A build orientation of 0 degrees is recommended for fabricating casting patterns for 3-unit partial fixed dental prostheses because no excess polymerization of the intaglio buccal wall was observed.

Selective laser sintering versus conventional lost-wax casting for single metal copings: A systematic review and meta-analysis.

STATEMENT OF PROBLEM: Evidence comparing the marginal and internal fit of single metal copings fabricated via selective laser sintering and conventional lost-wax casting is inadequate. PURPOSE: The purpose of this systematic review was to compare the fit of single metal copings fabricated via selective laser sintering and lost-wax casting. Moreover, the effects of different variables on fit accuracy were determined. MATERIAL AND METHODS: Google Scholar, ScienceDirect, SpringerLink, and Wiley databases were searched electronically as well as manually. The mean absolute marginal gap, marginal gap, internal gap, axial gap, and occlusal gap values of single metal copings fabricated via selective laser sintering and lost-wax casting were statistically analyzed to determine and evaluate the factors affecting the fit accuracy (α=.05). RESULTS: Single metal copings fabricated via selective laser sintering had mean absolute marginal gaps and occlusal gaps similar to those of copings fabricated via lost-wax casting, based on a subgroup meta-analysis of gaps evaluated using stereomicroscopy (P>.05). The fit of single metal copings was not affected by the type of tooth (P>.05). The conventional impression, the indirect digital scan, and the direct digital scan led to similar values of mean axial gap, internal gap, and marginal gap for the copings fabricated via lost-wax casting (P>.05). The indirect and direct digital scans led to similar values of mean axial gap, internal gap, and marginal gap for the copings fabricated via selective laser sintering (P>.05). Printed wax patterns provided significantly smaller mean axial gap values than milled plastic or milled wax patterns for the copings fabricated via lost-wax casting (P<.05). Printed, milled, and conventional wax patterns had similar mean marginal gaps and internal gaps for the copings fabricated via lost-wax casting (P>.05). For single copings fabricated via lost-wax casting, Ni-Cr and Co-Cr had similar mean internal gaps (P>.05). CONCLUSIONS: No statistically significant differences were found between single metal copings fabricated via selective laser sintering and lost-wax casting. Selective laser sintering can satisfy the clinical requirement for single metal copings.

Influence of ceramic firing on marginal gap accuracy and metal-ceramic bond strength of 3D-printed Co-Cr frameworks.

STATEMENT OF PROBLEM: The marginal gap and ceramic bond strength of metal-ceramic restorations are important for success. However, studies evaluating the marginal gap and ceramic bond strength of fixed partial dentures (FPDs) produced with 3D printing technologies such as selective laser melting (SLM) are scarce. PURPOSE: The purpose of this in vitro study was to investigate the marginal gap of cobalt-chromium (Co-Cr) alloy frameworks produced by SLM technology before and after ceramic firing. Additionally, the metal-ceramic bond strength was evaluated with the Schwickerath crack-initiation test according to the International Standards Organization (ISO) 9693-1:2012. MATERIAL AND METHODS: Conventional impressions were made, and the definitive cast of a patient requiring a 4-unit FPD was scanned. After designing the FPD, the files were sent to a service center for the fabrication of a metal master model, 80 Co-Cr frameworks, and 80 flat specimens (25×3×0.5 mm) with SLM technology. The marginal gap between frameworks and the abutment tooth of the metal master model was nondestructively measured by using an optical coordinate-measuring machine. A total of 80 sets, consisting of 1 framework and 1 flat specimen, were sent to 80 dental laboratory technicians for ceramic firing. Detailed instructions for correct manipulation of the framework and flat specimen were provided. The marginal gap was remeasured, and the 3-point bend test was used to evaluate metal-ceramic bond strength. RESULTS: Only 28 of the 80 dental technicians returned the specimens within a prespecified time and/or in adequate condition. The mean ±standard deviation marginal gap of the framework before ceramic firing was 25 ±9 µm and 34 ±12 µm after firing. The difference was statistically significant (P=.001). The mean ±standard deviation 3-point bend strength was 33 ±9 MPa. CONCLUSIONS: Ceramic firing affected the marginal gap; however, all Co-Cr frameworks had a marginal gap lower than 120 µm, which is reported to be a clinically acceptable limit. Most of the specimens (80%) had a metal-ceramic bond strength value higher than the 25-MPa ISO 9693 requirement. Five of 28 dental laboratory technicians were not able to comply with ceramic firing instructions.

Comparative Analysis of Marginal Accuracy of Complete Crowns Fabricated by Using Ringless and Metal Ring Investment Systems: An In Vitro Study.

AIM: To compare the vertical margin accuracy of lost wax castings produced by the conventional casting technique with all metal (WIRONIUM®) and PFM alloy (WIRON®99) using a metal ring and ringless system. MATERIALS AND METHODS: A brass die assembly was used to fabricate standardized wax pattern crowns. A total of 100 wax patterns were made with both ringless and metal ring investment systems. Wax patterns were readapted and refined on the master die and divided into two groups, namely, group I and group II with 50 wax patterns in each group. Group I (ringless system) and group II (metal ring system) were further divided into subgroups having a sample size of 25 in each group. Each coping was invested and cast individually. The marginal discrepancy between the metal die and the castings were measured by a stereomicroscope and AutoCAD software 2013. Measurement was made on the facial area of the metal die. RESULTS: The resultant casts obtained from different casting systems show statistically significant difference found between the marginal discrepancies using metal ring and ringless castings system, and statistically nonsignificant difference was found between the marginal discrepancies using all metal alloy (WIRONIUM®) and PFM alloy (WIRON®99) within the same group. CONCLUSION: The marginal discrepancy for castings made with ringless casting system was less when compared to metal ring casting system, and there was no difference in marginal discrepancy when compared to all metal alloy (WIRONIUM®) and PFM alloy (WIRON®99) within the same group. CLINICAL SIGNIFICANCE: Marginal fit is influenced by several factors including type of crown, tooth preparation geometry, dimensional accuracy of impression materials, factors related to dental casting, type of cement, luting pressure, duration of cementation, and use of occlusal vents or die spacers.

Marginal discrepancy of 3-unit Co-Cr metal copings fabricated with additive and subtractive manners: A comparative study.

BACKGROUND: 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. AIM: Therefore, it was aimed to assess the marginal accuracy of copings fabricated with subtractive and additive manners used in contemporary dentistry. MATERIALS AND METHODS: 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). RESULTS: Marginal adaptation of C group was significantly inferior to test groups in both canine- and premolar-teeth measurements (P < 0.05). Marginal fit was found to be tooth dependent (P < 0.001). HAM, SAM, and SLS groups exhibited analogous marginal discrepancy values on canine-tooth measurements. Differences among these groups were not statistically significant (P > 0.05). 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 (P > 0.05). CONCLUSIONS: SAM group demonstrated superior marginal accuracy. All groups had clinically acceptable marginal discrepancy values (<120 µm), except cast group.

Profound approach to check legitimacy of an old technique used to gauge palatal rugae.

AIMS: The present study aimed at assessing two fixed points of reference from where the mesial and distal point of all rugae can be measured so that the exact movement of particular rugae in any direction can be evaluated and assessing the changes in the palatal rugae after orthodontic treatment. METHODS: A longitudinal study conducted among a sample of 20 (8 male and 12 female) adult patients. Pre- and post-orthodontic treatment casts of patients were obtained from the Department of Orthodontics College of Dentistry Jazan University. Antero-posterior linear distances (Technique I) between medial and lateral points of primary, secondary and tertiary rugae were measured. Also, the transverse linear distance (Technique II) between medial and lateral points of right and left rugae were measured. Technique III involved marking two fixed points and using these two points a third point is located on the medial or lateral end of rugae of right and left side in pre and post-treatment orthodontic casts. The independent sample t-test was employed to compare gender. Difference between the pre- and post-treatment mean values were checked by the paired t-test. RESULTS: Technique III successfully showed the statistically significant difference (P ≤ 0.05, 95% CI) in the overall pre and post-treatment values on the patients' cast (N = 20) which was not observed with a technique I and technique II. CONCLUSION: The triangle created by the three reference points in the technique III was able to identify the changes in the palatine rugae more precisely than the technique I and Technique II.

Adaptation of removable partial denture frameworks fabricated by selective laser melting.

STATEMENT OF PROBLEM: Selective laser melting (SLM) is a novel 3-dimensional (3D) printing technology that can directly form the metal frameworks of removable partial dentures. The adaptation of SLM frameworks has not been thoroughly evaluated. PURPOSE: The purpose of this in vitro study was to evaluate the tissue surface adaptation of removable partial denture frameworks fabricated by an SLM technique. MATERIAL AND METHODS: Four types of maxillary partial edentulous resin models were custom made: bilateral second premolars and molars missing, bilateral premolars and first molars missing, all teeth missing except 2 canines, and 2 central incisors missing. According to these dentition-defect patterns, 4 types (I, II, III, and IV) of virtual removable partial denture frameworks were designed, and an SLM printer was used for 3D printing using cobalt-chromium (Co-Cr) alloys (repeated 3 times). As a control, refractory casts duplicated from the resin models were used to fabricate denture frameworks by the lost-wax casting technique. Average gaps and maximum gaps between frameworks and models were measured using the silicone impression material. Two-way ANOVA was used to determine the influence of production methods and design types on the gaps (α=.05). RESULTS: The 2-way ANOVA showed that average gaps were significantly influenced by the production methods and design types, as well as their interactions (P<.001). With design Types I and II, the average gaps of the SLM-printed frameworks were larger than those of the cast ones (P<.001). However, no such differences were found for design Type III, P=.325, or IV, P=.862. CONCLUSIONS: SLM-printed frameworks achieved an acceptable adaptation. However, among frameworks with a large span and relatively more retainers and clasps, the adaptation of those made by the precision casting technique was slightly better than that of those printed by the SLM technique.

Marginal fit of metal-ceramic crowns fabricated by using a casting and two selective laser melting processes before and after ceramic firing.

STATEMENT OF PROBLEM: Few studies have investigated changes in the marginal fit of metal-ceramic restorations fabricated by selective laser melting (SLM) techniques after the application of veneering ceramic. PURPOSE: The purpose of this in vitro study was to evaluate the marginal fit (silicone replica technique) and internal porosity (cross-section analysis) of cobalt-chromium (Co-Cr) alloy metal crowns prepared by using 2 SLM processes together with a casting technique before and after ceramic veneering. MATERIAL AND METHODS: Cast single Co-Cr crowns and SLM-processed crowns with large (SLML) or small (SLMS) porosity were prepared (n=20/group), and half were subjected to ceramic veneering. On a single Co-Cr master die, the marginal discrepancy (MD) and absolute marginal discrepancy (AMD) of the crowns were measured by using the silicone replica technique, in which each replica was cut into 4 sections before and after ceramic veneering (n=10 for each subgroup). After marginal fit measurements, each metal coping was cross-sectioned into 4 parts, and 5 rectangular optical microscope images were acquired on both outer corners of each quarter. The porosity was then calculated as the ratio of the black-to-white pixels on the binarized images. The data were analyzed by 2-way ANOVA and the post hoc test (Tukey or Student t test) (α=.05). RESULTS: Before ceramic veneering, the 2 SLM groups showed significantly larger MDs than the casting group (56.4 ±10.4 µm) (P<.05). A significant increase in MD after ceramic veneering was detected only in the SLML group (P<.001). The AMD values showed a similar trend with MD values. The 2 SLM groups (in particular, SLML) showed a significantly higher amount of porosity than the casting group before ceramic veneering (P<.001). Only the SLML group showed a significant decrease in the amount of porosity after ceramic veneering (P<.001). CONCLUSIONS: Within the limitations of this in vitro study, large internal porosity within the SLM-fabricated Co-Cr metal copings affected the marginal fit of the metal-ceramic crowns. However, all the MD values of the 3 groups were lower than the acceptable range even after the application of veneering ceramic.

Internal adaptation of cobalt-chromium posts fabricated by selective laser melting technology.

STATEMENT OF PROBLEM: Selective laser melting (SLM) has become popular in prosthetic dentistry. However, only limited information is available for the internal adaptation of cobalt-chromium (Co-Cr) posts fabricated by SLM. PURPOSE: The purpose of this in vitro study was to investigate the internal adaptation of Co-Cr metal posts fabricated by SLM technique. MATERIAL AND METHODS: Thirty-six Co-Cr metal posts were fabricated by conventional casting, subtractive computer-aided design and computer-aided manufacturing (CAD-CAM), and additive CAD-CAM, by making an impression from a standardized model of a tooth with a single root canal. Posts and the dies were bonded with cement. Specimens were then sectioned horizontally by using a grinding and polishing machine, and 3 different cross-sections of each post were chosen to represent the apical, middle, and coronal regions. The areas of cement were photographed by using a stereomicroscope at an original magnification of ×32 and measured using image-measuring software. From each group, 1 specimen was randomly selected and observed by using scanning electron microscopy. One-way ANOVA and Tukey honestly significant difference test were performed to identify differences among groups with regard to internal adaptation (α=.05). RESULT: The internal adaptation of the SLM group did not differ from that of the CAD-CAM milling group at 3 cross-section levels (P>.05). At the apical and coronal cross-section levels, the cement area of SLM group was smaller than that of the cast group (P<.05). However, at the middle cross-section level, the cement area of the cast group was significantly smaller than that of the SLM group (P<.05). Use of scanning electron microscopy showed both the SLM group and the CAD-CAM milling group exhibited homogeneous microstructures. However, the cast group showed a typical discontinuous dendritic solidification microstructure. CONCLUSIONS: The internal adaptation of SLM was not inferior to that of the CAD-CAM milling group or the cast group. The SLM technique seems a promising choice for fabricating dental posts.

Assessment of the trueness and tissue surface adaptation of CAD-CAM maxillary denture bases manufactured using digital light processing.

STATEMENT OF PROBLEM: Limited information is available evaluating the trueness and tissue surface adaptation of computer-aided design and computer-aided manufacturing (CAD-CAM) maxillary denture bases fabricated using digital light processing (DLP). PURPOSE: The purpose of this in vitro study was to evaluate the trueness of DLP-fabricated denture bases and to compare the tissue surface adaptation of DLP with milling (MIL) and pack and press (PAP). MATERIAL AND METHODS: The maxillary denture bases were virtually designed on the reference cast and were fabricated using DLP and MIL. Their intaglio surfaces were scanned and superimposed on the reference computer-aided design denture base to evaluate the trueness. A total of 20 denture bases (10 per technique) were also fabricated on the duplicated master casts using DLP and MIL. Ten denture bases were additionally made using PAP. The intaglio surfaces of the dentures were scanned and superimposed on the corresponding casts to compare the degree of tissue surface adaptation among the 3 techniques. The Mann-Whitney test and Kruskal-Wallis ANOVA were used for statistical analyses (α=.05). RESULTS: The trueness of the DLP denture base was significantly better than that of the MIL denture base (P<.001). Statistically significant differences were detected with respect to tissue surface adaptation of the denture base among the groups (P<.001). The DLP denture base showed the best denture base fit among the 3 techniques with a small interquartile range. CONCLUSIONS: Within the limitations of this in vitro study, the DLP maxillary denture base showed better trueness and tissue surface adaptation of ≤100 µm of the 3-dimensional surface deviation than the MIL and PAP denture bases.

Comparison of marginal fit between CAD-CAM and hot-press lithium disilicate crowns.

STATEMENT OF PROBLEM: Hot-pressing and computer-aided design and computer-aided manufacturing (CAD-CAM) are major techniques for the fabrication of lithium disilicate crowns. They exhibit different accuracies regarding marginal fit, an important factor in restoration survival. However, studies comparing the marginal fit of different fabrication methods are lacking. PURPOSE: The purpose of this in vitro study was to compare the marginal discrepancy (MD) and absolute marginal discrepancy (AMD) of lithium disilicate crowns produced by the hot-press and CAD-CAM techniques. MATERIAL AND METHODS: Thirty typodont teeth were divided into 2 groups. Fifteen teeth were scanned with the CEREC Omnicam intraoral scanner, and crowns were fabricated with the CEREC MC XL chairside CAD-CAM milling unit from IPS e.max CAD blocks. Fifteen typodont teeth were sent to a dental laboratory, and lithium disilicate crowns were fabricated from IPS e.max press ingots using the hot-press technique. The 30 crowns were cemented and then sectioned with a precision saw. The MD and AMD were measured for each crown with a light microscope. One-way ANOVA was conducted to analyze significant differences in crown marginal fit between the fabrication systems (α=.05). RESULTS: For the CAD-CAM technique, the mean values of the AMD measurements were 115 µm, and for the hot-press technique, 130 µm. The MD measurements were 87 µm for the CAD-CAM technique and 90 µm for the hot-press technique. One-way ANOVA revealed no significant differences between the fabrication methods regarding marginal fit (P>.05). CONCLUSIONS: No significant differences were found between the fabrication methods tested. Both the CAD-CAM and hot-press techniques for producing monolithic lithium disilicate crowns produced MD values of less than 120 µm, within the clinically acceptable range.

Treatment of a Class II Division 1 malocclusion with the combination of a myofunctional trainer and fixed appliances.

This case report describes the combined use of a myofunctional Trainer for Braces and fixed appliances to treat a 10-year-old girl with a Class II Division 1 malocclusion that featured severe maxillary incisor protrusion, a large overjet, and a V-shaped maxillary arch. She had a convex profile with an underdeveloped mandible. The superiority of myofunctional training in the case was to eliminate mouth breathing and lip sucking habits, train the oral musculature, stimulate mandibular growth, and make braces work more efficiently. The posttreatment facial photographs show improvement in the facial profile. Proper occlusion and facial balance were created, which were quite stable as demonstrated by the patient's 4-year follow-up records.

Transverse and torque dental changes after passive self-ligating fixed therapy: A two-year follow-up study.

INTRODUCTION: Self-ligating appliances are purposed to expand the arches, but evidence on stability of the result is lacking. We measured the width of maxillary and mandibular arches and torque changes after treatment with the use of passive self-ligating appliances and assessed stability at the 2-year follow-up. METHODS: Maxillary and mandibular 3-dimensional (3D) models from 32 subjects (mean initial age 14.9 ± 0.9 years), consecutively treated with the use of self-ligating appliances, were obtained before, immediately after, and 2 years after treatment. Dental arches were examined with the use of 3D software to evaluate differences in transverse arch dimensions and torque values. RESULTS: An incremental increase of arch widths was recorded, especially regarding maxillary and mandibular premolars. The increase in the transverse diameters was associated with a significant positive torque gain. No significant changes in arch perimeter and depth were recorded. In the retention period, slight significant changes in transverse diameters were recorded, and a transverse diameter constriction detected. Torque values remained almost unchanged in the follow-up period. CONCLUSIONS: Transverse arch dimensions, along with torque values, increased significantly after treatment with the use of a passive self-ligating appliance. In the 2 years following treatment, a tendency to transverse diameter restriction, especially for the maxillary and mandibular premolars, was observed.

Effect of Cast Modification on Denture Base Adaptation Following Maxillary Complete Denture Processing.

PURPOSE: To investigate the effect of cast modifications on denture base adaptation in coronal and sagittal projections following maxillary complete denture processing. MATERIALS AND METHODS: A total of 60 edentulous maxillary casts (n = 10) were distributed among six groups. Group 1 was the control group with no modification, groups 2 through 6 included a butterfly postdam preparation, groups 3 and 4 also included a 10-mm wide/4-mm deep box with addition of four round holes in group 4, and groups 5 and 6 also included a 20-mm wide/4-mm deep box with addition of four round holes in group 6. The boxes were prepared at the mid-heel area of the casts. Two layers of baseplate wax (1 mm each) were used to standardize denture base thickness across the groups. A standard technique was used to replicate the denture tooth set-up, and standardized processing was done for all the groups. Following deflasking, casts with the dentures were sectioned in the coronal and sagittal directions. Microscopic pictures were taken at preselected points. Data were organized in tables, and statistical analyses were performed using repeated measure ANOVA, Tukey post hoc tests, and post hoc comparison tests set at 5% level of significance. RESULTS: Maximum gaps were measured at the mid-palatal area followed by nearby areas and the areas near ridge crests in both coronal and sagittal projections. The analyses revealed significant differences between the groups in coronal projection (1/2, 3/4, 5/6) and sagittal projection (1, 2, 3/4, 5/6) without significant differences within the pairs. The groups were ranked from the highest group 1 to the lowest group 6 relative to the gap means. Post hoc comparisons showed that points 1C and 2A had the highest gap means across the study groups. CONCLUSIONS: Within the limitations of this study, it can be extrapolated that the denture base adaptation can be effectively increased with the box preparation at the mid-heel aspect of the casts. Significant reduction of gaps was seen when the box size increased from 10 to 20 mm in coronal and sagittal projections; however, the addition of four holes had no significant effect on gap size alterations.

Putty Index for Tripoding.

Precise orientation and transfer of the selected path of insertion and removal is a critical step in cast removable partial denture prosthesis design. An easy technique for registering the same is described using addition silicon putty and a used diamond disk.

CAD/CAM Constructed Poly(etheretherketone) (PEEK) Framework of Kennedy Class I Removable Partial Denture: A Clinical Report.

The prevalence of partially edentulous adults that could be treated by removable partial dentures (RPDs) is estimated to be greater than 20% in some regions of the United States. Problems related to traditional materials for RPD construction have been documented. Advances in polymer-based materials and digital fabrication strategies would allow increased biocompatibility, durability, and elasticity, as well as more esthetically pleasing and cost-effective benefits. This article reports on poly(etheretherketone) RPD framework produced by digital and milling technology.

Comparison of the Fit of Lithium Disilicate Crowns made from Conventional, Digital, or Conventional/Digital Techniques.

PURPOSE: To evaluate the fit of single crowns fabricated using conventional, digital, or cast digitization methods. MATERIALS AND METHODS: One subject with a peg-shaped maxillary lateral incisor was selected in this study. Tooth preparation for an all-ceramic crown was performed and 10 conventional poly(vinyl siloxane) impressions, and 10 digital impressions using an intraoral scanner were made. Each working cast was scanned using a laboratory scanner and an intraoral scanner. Four groups were tested Group 1: conventional impressions. Group 2: cast laboratory scans. Group 3: cast scans using intraoral scanner. Group 4: direct intraoral scans. For group 1, heat-pressed glass ceramic crowns (IPS e.max Press) were fabricated using casts produced from the conventional impressions. For groups 2-4, crowns were milled using ceramic blocks (IPS e.max CAD). Ten crowns were fabricated for each group. Marginal and internal gaps were measured using a replica technique. Replicas were sectioned mesiodistally and buccolingually and were observed under a stereomicroscope. Three measurements were selected for each cut: occlusal, axial, and marginal. Statistical analysis was performed using two-way ANOVA and Tukey HSD tests. RESULTS: For each replica, 6 measurements were made for the mesiodistal and the same for the buccolingual cuts, producing 12 measurement points per crown (4 measurements for marginal, 4 for axial, 4 for occlusal), 120 measurements for each group (40 measurements for marginal, 40 for axial, 40 for occlusal), and 480 measurements in total. Two-way ANOVA revealed location to be a significant factor (p = 0.001). No significant differences among groups (p = 0.456), and no interactions between groups and locations (p = 0.221) were found. Means for the occlusal site were significantly larger than other sites in most group combinations, while the difference between the marginal and axial sites was not significant. No significant differences among groups were found for each measurement. The marginal gaps ranged from 125.46 ± 25.39 µm for group 3 to 135.59 ± 24.07 µm for group 4. The smallest axial mean was in group 1 (98.10 ± 18.77 µm), and the largest was 127.25 ± 19.79 µm in group 4. The smallest occlusal mean was in group 2 (166.53 ± 36.51 µm), and the largest occlusal mean was in group 3 (203.32 ± 80.24 µm). CONCLUSIONS: Ceramic crowns, which were made using all-digital approach or cast digitization by a laboratory or intraoral scanner had comparable fit to those produced by conventional approach.