Publications by authors named "Seok-Hwan Cho"

28 Publications

  • Page 1 of 1

Comparison of tensile bond strength of denture reline materials on denture bases fabricated with CAD-CAM technology.

J Prosthet Dent 2021 Aug 6. Epub 2021 Aug 6.

Associate Professor, Department of Comprehensive Dentistry, Texas A&M University College of Dentistry, Dallas, Texas.

Statement Of Problem: Studies that have analyzed the bond strength of resilient denture liners to milled denture bases are sparse, and the authors are unaware of research that has investigated the tensile bond strength of denture relining materials to 3D-printed denture bases.

Purpose: The purpose of this in vitro study was to evaluate the tensile bond strength of both hard and soft denture reline materials on denture bases fabricated by 3D printing and computer-aided design and computer-aided manufacture (CAD-CAM) milling technology.

Material And Methods: Injected, milled, and printed denture base specimens were fabricated (n=30) and bonded to 5 different denture reline materials: soft chairside reline (Coe Soft and PermaSoft), hard chairside reline (Tokuyama Rebase ii and Kooliner), and hard laboratory reline (ProBase Cold). Specimens of each reline material were divided into 5 groups (n=10) and were placed in distilled water for 24 hours before tensile testing. Maximum tensile stress values before failure were recorded, and the failure mode was also determined. The type of failure was analyzed by a scanning electron microscope. Statistics were analyzed with 2-way ANOVA and multiple comparison tests (α=.05).

Results: Overall, no statistically significant difference in tensile bond strength was found in the injected, milled, and printed denture groups. However, the printed denture base group demonstrated significantly lower values of tensile bond strength (P<.05) with PermaSoft, Tokuyama Rebase ii, and ProBase Cold groups than other denture base groups (milled and injected). The milled denture bases had the highest mean value of tensile bond strength with 4 of the 5 denture relining materials tested (Coe Soft, PermaSoft, Tokuyama Rebase ii, and Kooliner). No statistically significant difference (P>.05) was found among the injected, milled, and printed denture bases when relined with Kooliner. When comparing the denture reline type, the lowest values were seen with the soft chairside relining materials, and highest values with the hard laboratory reline material. Among the modes of failure, adhesive failures were observed predominantly with the printed denture base materials relined with soft chairside relining materials, while cohesive and mixed modes of failure were found in the milled and injected denture base groups.

Conclusions: The printed denture bases had significantly lower tensile bond strength values than the injection and milled denture bases with the PermaSoft, Tokuyama Rebase ii, and ProBase Cold denture relines, while milled denture bases demonstrated the highest values of tensile bond strength for all chairside relining groups. In addition, the soft chairside relining materials showed the lowest tensile bond strength values regardless of the denture processing method with respect to the denture base type (injected, printed, and milled) compared with the hard relining materials.
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http://dx.doi.org/10.1016/j.prosdent.2021.06.047DOI Listing
August 2021

Accuracy of anterior denture tooth arrangements of CAD-CAM complete removable dental prostheses made with a tooth mold template.

J Prosthet Dent 2021 Jul 27. Epub 2021 Jul 27.

Private practice, Athens, Greece.

Statement Of Problem: Research evaluating the accuracy of anterior tooth mold templates to computer-aided design and computer-aided manufacture (CAD-CAM) fabricated complete removable dental prostheses (CRDPs) is limited.

Purpose: The purpose of this in vitro study was to investigate the accuracy of the anterior denture tooth arrangement on CAD-CAM complete removable dental prostheses made with the anterior tooth mold template.

Material And Methods: A maxillary and mandibular edentulous model was mounted on a semiadjustable articulator to simulate a patient's maxillary arch. Definitive impressions and jaw relation records were made as per the manufacturer's protocol. A maxillary and mandibular anatomic measuring device was completely seated onto the edentulous models, centered on the edentulous model midline, and horizontally positioned parallel to the mandibular ridge. A medium-size anterior tooth mold template sticker was attached on the anatomic measuring device to identify the maxillary dental midline and incisal edge position and was sent to the manufacturer as the proposed tooth arrangement reference for the definitive complete removable dental prostheses. A total of 10 milled complete removable dental prostheses were generated for 2 groups by using 2 different tooth arrangement techniques. One group (n=5) used the monobloc milling technique without bonding of denture teeth, while the other group (n=5) used the bonding system for denture teeth on the milled denture base. For comparison, a camera mounted on a tripod was used for photographic documentation. Reference markers placed on the edentulous model were used to orient and measure the difference of 4 aspects of the anterior tooth arrangement: average incisal edge position, intercanine distance, midline, and clinical crown length of the left central incisor. The difference values between the tooth mold template and definitive complete removable dental prostheses were statistically analyzed by multivariate ANOVA (α=.05) and 1-sample t tests (adjusted α=.0125).

Results: Overall, statistically significant differences were found between the tooth mold template (control) and definitive complete removable dental prostheses at all measuring aspects except for the midline of the midline of the milled arrangement technique (P<.0125). In terms of the midline value, the value of the milled group did not show a significant difference compared with tooth mold template (-0.19 mm). However, the value of the bonded group indicated a significant difference of midline (0.44 mm toward to the left of the tooth mold template midline). When the complete removable dental prosthesis milled denture tooth and complete removable dental prosthesis bonded denture tooth techniques were compared, there was no difference in the tested variables between the milled and the bonded groups (P>.0125).

Conclusions: The tooth mold template did not represent an accurate position for definitive complete removable dental prostheses for either the milled or bonded techniques. The largest differences were found at the average incisal edge of the anterior teeth and the intercanine distance for both groups. However, there was overall no clinical difference between the 2 groups (milled and bonded) of CAD-CAM complete removable dental prostheses.
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http://dx.doi.org/10.1016/j.prosdent.2021.06.039DOI Listing
July 2021

Combined bone- and mucosa-supported 3D-printed guide for sinus slot preparation and prosthetically driven zygomatic implant placement.

J Prosthet Dent 2021 Mar 29. Epub 2021 Mar 29.

Private practice, Fayetteville, Ark.

The use of zygomatic implants to rehabilitate the severely atrophic maxilla has been well documented since first being introduced by Brånemark. Placement of zygomatic implants is technically complex, with catastrophic complications and numerous prosthetic challenges resulting from imprecise placement. The purpose of this report was to demonstrate a technique that allows transfer of the preoperatively planned sinus slot position to the surgical field by using cone beam computed tomography (CBCT) and an implant planning software program to fabricate a combined bone- and mucosa-supported 3D-printed surgical guide. This facilitates optimal zygomatic implant positioning and promotes favorable biomechanics with a predictable prosthetic outcome.
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http://dx.doi.org/10.1016/j.prosdent.2021.02.024DOI Listing
March 2021

A 3D-Printed Guide to Assist in Sinus Slot Preparation for the Optimization of Zygomatic Implant Axis Trajectory.

J Prosthodont 2020 Feb 11;29(2):179-184. Epub 2020 Jan 11.

Private Practice, Fayetteville, AR.

Zygomatic implants have become a predictable treatment modality for the rehabilitation of the severely atrophic maxilla. Due to differing anatomic variations, proximity to vital anatomic structures and limited intraoperative visibility, the placement of zygomatic implants can be a difficult task; compromised implant positioning may ultimately lead to postoperative surgical and prosthetic complications. The purpose of this report is to demonstrate a technique that allows for the transfer of the sinus slot position. Ultimately, this optimizes zygomatic implant axis trajectory from preoperative prosthetic planning by using cone beam computed tomography (CBCT) and 3-dimensional (3D) planning software to fabricate a stereolithographic 3D-printed surgical guide.
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http://dx.doi.org/10.1111/jopr.13139DOI Listing
February 2020

An accessory technique for the intraoral removal of a fractured implant abutment screw.

J Prosthet Dent 2018 Dec 14;120(6):812-815. Epub 2018 Jul 14.

Associate Professor and Program Director, Graduate Prosthodontics, Department of Restorative Sciences, Texas A&M University College of Dentistry, Dallas, Texas.

As the use of dental implants becomes more prevalent, mechanical complications become more common. When an implant abutment screw fractures, it can be difficult to retrieve the retained fragment. The purpose of this article is to describe a technique to remove the abutment screw fragments without damaging the implant body or its screw threads.
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http://dx.doi.org/10.1016/j.prosdent.2018.01.026DOI Listing
December 2018

A method of locating the abutment screw access channel with cone-beam computed tomography and a 3D-printed drilling guide.

J Prosthet Dent 2018 Feb 26;119(2):210-213. Epub 2017 May 26.

Associate Professor and Director, Department of General Dental Sciences, Graduate Prosthodontics, Marquette University School of Dentistry, Milwaukee, Wis.

In managing loose abutment screws, locating precisely the position of the screw access channel is difficult. This technique describes the use of cone-beam computed tomography (CBCT) and surgical guide planning software to locate the screw access channel with the intention of retrieving a loosened cement-retained implant-supported prosthesis. The method minimizes damage to the abutment crown assembly.
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http://dx.doi.org/10.1016/j.prosdent.2017.04.001DOI Listing
February 2018

Interproximal distance analysis of stereolithographic casts made by CAD-CAM technology: An in vitro study.

J Prosthet Dent 2017 Nov 3;118(5):624-630. Epub 2017 May 3.

Professor, Department of Mathematics, Statistics, and Computer Science, Marquette University, Milwaukee, Wis.

Statement Of Problem: The accuracy of interproximal distances of the definitive casts made by computer-aided design and computer-aided manufacturing (CAD-CAM) technology is not yet known.

Purpose: The purpose of this in vitro study was to compare the interproximal distances of stereolithographic casts made by CAD-CAM technology with those of stone casts made by the conventional method.

Material And Methods: Dentoform teeth were prepared for a single ceramic crown on the maxillary left central incisor, a 3-unit fixed dental prosthesis (FDP) on the second premolar for a metal-ceramic crown, and a maxillary right first molar for a metal crown. Twenty digital intraoral impressions were made on the dentoform with an intraoral digital impression scanner. The digital impression files were used to fabricate 20 sets of stereolithographic casts, 10 definitive casts for the single ceramic crown, and 10 definitive casts for the FDP. Furthermore, 20 stone casts were made by the conventional method using polyvinyl siloxane impression material with a custom tray. Each definitive cast for stereolithographic cast and stone cast consisted of removable die-sectioned casts (DC) and nonsectioned solid casts (SC). Measurements of interproximal distance of each cast were made using CAD software to provide mean ±standard deviation (SD) values. Data were first analyzed by repeated measures analysis of variance (ANOVA), using different methods of cast fabrication (stone and stereolithography) as one within subject factor and different cast types (DC and SC) as another within subject factor. Post hoc analyses were performed to investigate the differences between stone and stereolithographic casts depending upon the results from the repeated measures ANOVA (α=.05).

Results: Analysis of interproximal distances showed the mean ±SD value of the single ceramic crown group was 31.2 ±24.5 μm for stone casts and 261.0 ±116.1 μm for stereolithographic casts, whereas the mean ±SD value for the FDP group was 46.0 ±35.0 μm for stone casts and 292.8 ±216.6 μm for stereolithographic casts. For both the single ceramic crown and the FDP groups, there were significant differences in interproximal distances between stereolithographic casts and stone casts (P<.001). In addition, the comparisons of DC with SC of stone and stereolithographic casts for the single ceramic crown and FDP groups demonstrated there was statistically significant differences among interproximal distances between DC stereolithographic casts and SC stereolithographic casts only for the FDP group (P<.001).

Conclusions: For both the single ceramic crown and the FDP groups, the stereolithographic cast group showed significantly larger interproximal distances than the stone cast group. In terms of the comparison between DC and SC, DC stereolithographic casts for the FDP group only showed significantly larger interproximal values than those of the SC stereolithographic casts for the FDP group.
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http://dx.doi.org/10.1016/j.prosdent.2017.01.027DOI Listing
November 2017

A method of facilitating the fabrication of access openings for implant-supported complete fixed dental prostheses.

J Prosthet Dent 2017 Jun 17;117(6):814-816. Epub 2017 Feb 17.

Associate Professor and Director, Department of General Dental Sciences, Graduate Prosthodontics, Marquette University School of Dentistry, Milwaukee, Wis.

This report describes a method for fabricating access openings for implant-supported complete fixed dental prostheses (ICFP) by using a dental milling machine and silicone putty matrix. The method can help clinicians achieve the accurate and precise fabrication of access openings for ICFPs without excessive grinding.
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http://dx.doi.org/10.1016/j.prosdent.2016.10.026DOI Listing
June 2017

Evaluation of die trim morphology made by CAD-CAM technology.

J Prosthet Dent 2017 Sep 17;118(3):406-412. Epub 2017 Feb 17.

Professor and Assistant Program Director, Postgraduate Program in Prosthodontics, Marquette University School of Dentistry, Milwaukee, Wis.

Statement Of Problem: The die contour can affect the emergence profile of prosthetic restorations. However, little information is available regarding the congruency between a stereolithographic (SLA) die and its corresponding natural tooth.

Purpose: The purpose of this vitro study was to evaluate the shapes of SLA die in comparison with the subgingival contour of a prepared tooth to be restored with a ceramic crown.

Material And Methods: Twenty extracted human teeth, 10 incisors, and 10 molars, were disinfected and mounted in a typodont model. The teeth were prepared for a ceramic restoration. Definitive impressions were made using an intraoral scanner from which 20 SLA casts with removable dies were fabricated. The removable dies and corresponding human teeth were digitized using a 3-dimensional desktop scanner and evaluated with computer-aided design software. The subgingival morphology with regard to angle, length, and volume at the buccolingual and mesiodistal surfaces and at zones A, B, C, and D were compared. Data were first analyzed with repeated measures analysis of variance (ANOVA), using locations (buccolingual and mesiodistal), zones (A, B, C, and D), and model type (SLA and Natural) as within-subject factors and tooth type (molar and incisor) as the between-subject factor. Post hoc analyses were performed to investigate the difference between natural teeth and corresponding SLA models, depending upon the interaction effect from the repeated measures ANOVA (α=.05).

Results: For angle analysis, the incisor group demonstrated a significant difference between the natural tooth and SLA die on the buccolingual surfaces (P<.05), whereas the molar group demonstrated a significant difference at the mesiodistal surfaces (P<.05). For the evaluation of length and volume, the incisor group showed significant differences in zone D on both the buccolingual (P<.05) and the mesiodistal (P<.05) surfaces. However, significant differences in zones C (P<.05) and D (P<.05) on the buccolingual surfaces and in all zones on the mesiodistal surfaces were observed in the molar group.

Conclusions: For the comparison of angles, SLA dies did not replicate the subgingival contour of natural teeth on the buccolingual surfaces of the incisal groups. For the comparison of length and volume, SLA dies were more concave and did not replicate the subgingival contour of natural teeth in the incisal and molar groups.
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http://dx.doi.org/10.1016/j.prosdent.2016.10.027DOI Listing
September 2017

Edge chipping resistance and flexural strength of polymer infiltrated ceramic network and resin nanoceramic restorative materials.

J Prosthet Dent 2016 Sep 5;116(3):397-403. Epub 2016 May 5.

Professor and Director, Graduate Dental Biomaterials, Department of General Dental Sciences, Marquette University School of Dentistry, Milwaukee, Wis. Electronic address:

Statement Of Problem: Two novel restorative materials, a polymer infiltrated ceramic network (PICN) and a resin nanoceramic (RNC), for computer-assisted design and computer-assisted manufacturing (CAD-CAM) applications have recently become commercially available. Little independent evidence regarding their mechanical properties exists to facilitate material selection.

Purpose: The purpose of this in vitro study was to measure the edge chipping resistance and flexural strength of the PICN and RNC materials and compare them with 2 commonly used feldspathic ceramic (FC) and leucite reinforced glass-ceramic (LRGC) CAD-CAM materials that share the same clinical indications.

Material And Methods: PICN, RNC, FC, and LRGC material specimens were obtained by sectioning commercially available CAD-CAM blocks. Edge chipping test specimens (n=20/material) were adhesively attached to a resin substrate before testing. Edge chips were produced using a 120-degree, sharp, conical diamond indenter mounted on a universal testing machine and positioned 0.1 to 0.7 mm horizontally from the specimen's edge. The chipping force was plotted against distance to the edge, and the data were fitted to linear and quadratic equations. One-way ANOVA determined intergroup differences (α=.05) in edge chipping toughness. Beam specimens (n=22/material) were tested for determining flexural strength using a 3-point bend test. Weibull statistics determined intergroup differences (α=.05). Flexural modulus and work of fracture were also calculated, and 1-way ANOVA determined intergroup differences (α=.05) RESULTS: Significant (P<.05) differences were found among the 4 CAD-CAM materials for the 4 mechanical properties. Specifically, the material rankings were edge chipping toughness: RNC>LRGC=FC>PICN; flexural strength: RNC=LRGC>PICN>FC; flexural modulus: RNCLRGC=PICN>FC.

Conclusions: The RNC material demonstrated superior performance for the mechanical properties tested compared with the other 3 materials.
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http://dx.doi.org/10.1016/j.prosdent.2016.02.014DOI Listing
September 2016

Accuracy and precision of occlusal contacts of stereolithographic casts mounted by digital interocclusal registrations.

J Prosthet Dent 2016 Aug 9;116(2):231-6. Epub 2016 Apr 9.

Professor, Department of Mathematics, Statistics, and Computer Science, Marquette University, Milwaukee, Wis.

Statement Of Problem: Little peer-reviewed information is available regarding the accuracy and precision of the occlusal contact reproduction of digitally mounted stereolithographic casts.

Purpose: The purpose of this in vitro study was to evaluate the accuracy and precision of occlusal contacts among stereolithographic casts mounted by digital occlusal registrations.

Material And Methods: Four complete anatomic dentoforms were arbitrarily mounted on a semi-adjustable articulator in maximal intercuspal position and served as the 4 different simulated patients (SP). A total of 60 digital impressions and digital interocclusal registrations were made with a digital intraoral scanner to fabricate 15 sets of mounted stereolithographic (SLA) definitive casts for each dentoform. After receiving a total of 60 SLA casts, polyvinyl siloxane (PVS) interocclusal records were made for each set. The occlusal contacts for each set of SLA casts were measured by recording the amount of light transmitted through the interocclusal records. To evaluate the accuracy between the SP and their respective SLA casts, the areas of actual contact (AC) and near contact (NC) were calculated. For precision analysis, the coefficient of variation (CoV) was used. The data was analyzed with t tests for accuracy and the McKay and Vangel test for precision (α=.05).

Results: The accuracy analysis showed a statistically significant difference between the SP and the SLA cast of each dentoform (P<.05). For the AC in all dentoforms, a significant increase was found in the areas of actual contact of SLA casts compared with the contacts present in the SP (P<.05). Conversely, for the NC in all dentoforms, a significant decrease was found in the occlusal contact areas of the SLA casts compared with the contacts in the SP (P<.05). The precision analysis demonstrated the different CoV values between AC (5.8 to 8.8%) and NC (21.4 to 44.6%) of digitally mounted SLA casts, indicating that the overall precision of the SLA cast was low.

Conclusions: For the accuracy evaluation, statistically significant differences were found between the occlusal contacts of all digitally mounted SLA casts groups, with an increase in AC values and a decrease in NC values. For the precision assessment, the CoV values of the AC and NC showed the digitally articulated cast's inability to reproduce the uniform occlusal contacts.
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http://dx.doi.org/10.1016/j.prosdent.2016.01.029DOI Listing
August 2016

Effect of toothbrushing on shade and surface roughness of extrinsically stained pressable ceramics.

J Prosthet Dent 2016 Apr 14;115(4):489-94. Epub 2015 Nov 14.

Associate Professor and Director, Department of General Dental Sciences, Graduate Dental Biomaterials, Marquette University School of Dentistry, Milwaukee, Wis.

Statement Of Problem: The effect of toothbrushing on extrinsically stained pressable ceramic materials is unknown.

Purpose: The purpose of this in vitro study was to investigate the effects of toothbrushing on the shade and surface roughness of extrinsically stained, pressable ceramics.

Material And Methods: Two materials, leucite-based (IPS Empress Esthetic [EE]; Ivoclar Vivadent AG) and lithium disilicate-based ceramic (IPS e.max Press [EP]; Ivoclar Vivadent AG), were studied. For each material, 24 disk-shaped specimens, 10 mm (diameter)×3 mm (height) were fabricated. Three different methods (n=8) of applying extrinsic stains were performed on each material: glazed only (G, control group); stained then glazed (SG); and stained and glazed together (T). The specimens were brushed with a multistation brushing machine under a load of 1.96 N at a rate of 90 strokes per minute with a soft and straight toothbrush (Oral-B #35) and a 1:1 toothpaste and distilled water slurry. Shade and roughness were measured at baseline and at 72, 144, 216, and 288 hours, which is equivalent to 3, 6, 9, and 12 years of simulated toothbrushing for 2 minutes twice a day. A repeated measures ANOVA with staining technique as a fixed factor was used to evaluate shade and roughness (α=.05).

Results: For EE groups, no significant change was found after 12 years of simulated toothbrushing regarding shade and surface roughness, irrespective of staining techniques (P>.05). However, EP groups demonstrated a significant shade change and an increase in surface roughness after 12 years of simulated toothbrushing. Shade change was found to depend on the method of applying stain. For the EP-SG technique, a significant shade change was observed only at the 9- to 12-year interval (P=.047). However, the EP-T technique demonstrated a significant difference in shade between baseline and 3 years (P=.005) and in the 6- to 9-year interval (P=.005). Surface roughness was only significantly affected at baseline and 3 years for the EP-T group (P=.005).

Conclusions: For the shade and surface roughness of the EE groups, no statistically significant difference was found after 12 years of toothbrushing, irrespective of the staining technique. The shade and surface roughness of the EP groups were significantly statistically affected by toothbrushing time; only shade changes were found to depend on technique.
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http://dx.doi.org/10.1016/j.prosdent.2015.09.013DOI Listing
April 2016

Effect of Different Thicknesses of Pressable Ceramic Veneers on Polymerization of Light-cured and Dual-cured Resin Cements.

J Contemp Dent Pract 2015 05 1;16(5):347-52. Epub 2015 May 1.

Division of Biostatistics, Medical College of Wisconsin Milwaukee, Wisconsin, USA.

Aim: This study evaluated the effects of ceramic veneer thicknesses on the polymerization of two different resin cements.

Materials And Methods: A total of 80 ceramic veneer disks were fabricated by using a pressable ceramic material (e.max Press; Ivoclar Vivadent) from a Low Translucency (LT) ingot (A1 shade). These disks were divided into light-cured (LC; NX3 Nexus LC; Kerr) and dual-cured (DC; NX3 Nexus DC; Kerr) and each group was further divided into four subgroups, based on ceramic disk thickness (0.3, 0.6, 0.9, and 1.2 mm). The values of Vickers microhardness (MH) and degree of conversion (DOC) were obtained for each specimen after a 24-hour storage period. Association between ceramic thickness, resin cement type, and light intensity readings (mW/cm(2)) with respect to microhardness and degree of conversion was statistically evaluated by using analysis of variance (ANOVA).

Results: For the DOC values, there was no significant difference observed among the LC resin cement subgroups, except in the 1.2 mm subgroup; only the DOC value (14.0 ± 7.4%) of 1.2 mm DC resin cement had significantly difference from that value (28.9 ± 7.5%) of 1.2 mm LC resin cement (p < 0.05). For the MH values between LC and DC resin cement groups, there was statistically significant difference (p < 0.05); overall, the MH values of LC resin cement groups demonstrated higher values than DC resin cement groups. On the other hands, among the DC resin cement subgroups, the MH values of 1.2 mm DC subgroup was significantly lower than the 0.3 mm and 0.6 mm subgroups (p < 0.05). However, among the LC subgroups, there was no statistically significant difference among them (p > 0.05).

Conclusion: The degree of conversion and hardness of the resin cement was unaffected with veneering thicknesses between 0.3 and 0.9 mm. However, the DC resin cement group resulted in a significantly lower DOC and MH values for the 1.2 mm subgroup.

Clinical Significance: While clinically adequate polymerization of LC resin cement can be achieved with a maximum 1.2 mm of porcelain veneer restoration, the increase of curing time or light intensity is clinically needed for DC resin cements at the thickness of more than 0.9 mm.
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http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4659509PMC
http://dx.doi.org/10.5005/jp-journals-10024-1688DOI Listing
May 2015

Color-to-grayscale conversion using a smart phone camera for value comparison.

Authors:
Seok-Hwan Cho

J Prosthet Dent 2015 Sep 2;114(3):462-3. Epub 2015 Jun 2.

Assistant Professor, Department of General Dental Sciences, Marquette University School of Dentistry, Milwaukee, Wis. Electronic address:

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http://dx.doi.org/10.1016/j.prosdent.2015.04.009DOI Listing
September 2015

Custom total occlusal convergence angle sticker fabrication.

J Prosthet Dent 2015 Sep 23;114(3):335-8. Epub 2015 May 23.

Professor and Director, Graduate Prosthodontics, Department of Restorative Sciences, Baylor College of Dentistry, Texas A&M Health Science Center, Dallas, Texas.

This article describes a method of fabricating a custom total occlusal convergence angle sticker with photo editing software and label stickers. The custom total occlusal convergence angle sticker can help clinicians achieve an accurate degree of taper during axial wall reduction of tooth preparation.
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http://dx.doi.org/10.1016/j.prosdent.2015.03.014DOI Listing
September 2015

Using a thermoplastic sheet to add palatal rugae to a complete removable dental prosthesis.

J Prosthet Dent 2015 Sep 23;114(3):464-5. Epub 2015 May 23.

Professor and Director, Graduate Prosthodontics, Department of Restorative Sciences, Baylor College of Dentistry, Texas A&M Health Science Center, Dallas, Texas.

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http://dx.doi.org/10.1016/j.prosdent.2015.03.013DOI Listing
September 2015

Customized occlusal reduction guide made from a thermoplastic sheet.

J Prosthet Dent 2015 Aug 20;114(2):307-8. Epub 2015 May 20.

Professor, Department of Restorative Sciences, Baylor College of Dentistry, Texas A&M Health Science Center, Dallas, Texas.

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http://dx.doi.org/10.1016/j.prosdent.2015.02.028DOI Listing
August 2015

Labial reduction guide for laminate veneer preparation.

J Prosthet Dent 2015 Oct 5;114(4):490-2. Epub 2015 Jun 5.

Professor, Department of Restorative Sciences, Baylor College of Dentistry, Texas A&M Health Science Center, Dallas, Texas.

This article describes a method of fabricating a labial reduction guide for laminate veneer preparations by using a digital tire tread depth gauge and orthodontic wire. The labial reduction guide can help clinicians to achieve accurate reduction of the labial surface.
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http://dx.doi.org/10.1016/j.prosdent.2015.02.019DOI Listing
October 2015

Morphologic custom shade guide fabricated with feldspathic ceramic.

J Prosthet Dent 2015 Jun 29;113(6):660-1. Epub 2015 Apr 29.

Professor, Graduate Prosthodontics, Department of Restorative Sciences, Baylor College of Dentistry, Texas A&M Health Science Center, Dallas, Texas.

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http://dx.doi.org/10.1016/j.prosdent.2015.02.014DOI Listing
June 2015

Die spacer thickness reproduction for central incisor crown fabrication with combined computer-aided design and 3D printing technology: an in vitro study.

J Prosthet Dent 2015 May 18;113(5):398-404. Epub 2015 Mar 18.

Assistant Professor, Division of Biostatistics, Medical College of Wisconsin, Milwaukee, Wis.

Statement Of Problem: The inability to control die spacer thickness has been reported. However, little information is available on the congruency between the computer-aided design parameters for die spacer thickness and the actual printout.

Purpose: The purpose of this study was to evaluate the accuracy and precision of the die spacer thickness achieved by combining computer-aided design and 3-dimensional printing technology.

Material And Methods: An ivorine maxillary central incisor was prepared for a ceramic crown. The prepared tooth was duplicated by using polyvinyl siloxane duplicating silicone, and 80 die-stone models were produced from Type IV dental stone. The dies were randomly divided into 5 groups with assigned die spacer thicknesses of 25 μm, 45 μm, 65 μm, 85 μm, and 105 μm (n=16). The printed resin copings, obtained from a printer (ProJet DP 3000; 3D Systems), were cemented onto their respective die-stone models with self-adhesive resin cement and stored at room temperature until sectioning into halves in a buccolingual direction. The internal gap was measured at 5 defined locations per side of the sectioned die. Images of the printed resin coping/die-stone model internal gap dimensions were obtained with an inverted bright field metallurgical microscope at ×100 magnification. The acquired digital image was calibrated, and measurements were made using image analysis software. Mixed models (α=.05) were used to evaluate accuracy. A false discovery rate at 5% was used to adjust for multiple testing. Coefficient of variation was used to determine the precision for each group and was evaluated statistically with the Wald test (α=.05).

Results: The accuracy, expressed in terms of the mean differences between the prescribed die spacer thickness and the measured internal gap (standard deviation), was 50 μm (11) for the 25 μm group simulated die spacer thickness, 30 μm (10) for the 45 μm group, 15 μm (14) for the 65 μm group, 3 μm (23) for the 85 μm group, and -10 μm (32) for the 105 μm group. The precision mean of the measurements, expressed as a coefficient of variation, ranged between 14% and 33% for the 5 groups.

Conclusions: For the accuracy evaluation, statistically significant differences were found for all the groups, except the group of 85 μm. For the precision assessment, the coefficient of variation was above 10% for all groups, showing the printer's inability to reproduce the uniform internal gap within the same group.
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http://dx.doi.org/10.1016/j.prosdent.2014.11.004DOI Listing
May 2015

Comparison of accuracy and reproducibility of casts made by digital and conventional methods.

J Prosthet Dent 2015 Apr 11;113(4):310-5. Epub 2015 Feb 11.

Associate Professor, Policlinic of Prosthetic Dentistry and Material Science, Jena University Hospital, Friedrich Schiller University, Jena, Germany; Adjunct Associate Professor, Department of Surgical Science, Marquette University School of Dentistry, Milwaukee, Wis.

Statement Of Problem: Little peer-reviewed information is available regarding the accuracy and reproducibility of digitally fabricated casts compared to conventional nondigital methods.

Purpose: The purpose of this in vitro study was to compare the accuracy and reproducibility of a digital impression and cast fabrication with a conventional impression and cast fabrication.

Material And Methods: Conventional impressions were made via a 1-step single viscosity technique with vinyl siloxanether material of a typodont master model, and conventional casts were cast from dental stone. Digital impressions were obtained with a digital scanner, and digital stereolithographic models were printed. The typodont and fabricated casts were digitized with a structured light scanner and saved in surface tessellation language (STL) format. All STL records were superimposed via a best-fit method. The digital impression and cast fabrication method was compared with the conventional impression and cast fabrication method for discrepancy, accuracy, and reproducibility. The Levene test was used to determine equality of variances, and a 1-way ANOVA was conducted to assess the overall statistical significance of differences among the groups (n=5, α=.05).

Results: No significant statistical difference was found between the digital cast and conventional casts in the internal area or finish line area (P>.05). In addition, there was no statistically significant difference between these 2 techniques for a fixed dental prosthesis or single crown (P>.05). However, statistically significant differences were observed for overall areas of the casts in terms of accuracy (P<.01) and reproducibility (P<.001). Digital impression and cast fabrication were less accurate and reproducible than conventional impression and cast fabrication methods.

Conclusions: No statistically significant difference was found between the digital cast and conventional cast groups in the internal and finish line areas. However, in terms of the reproducibility and accuracy of the entire cast area, the conventional cast was significantly better than the digital cast.
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http://dx.doi.org/10.1016/j.prosdent.2014.09.027DOI Listing
April 2015

Complete removable dental prosthesis with the swing lock system: a clinical report.

J Prosthet Dent 2014 Nov 30;112(5):1035-7. Epub 2014 Jul 30.

Assistant Professor and Director, Predoctoral Prosthodontics and Biomaterials, Department of General Dental Sciences, Marquette University School of Dentistry, Milwaukee, Wis. Electronic address:

This clinical report describes the fabrication of a maxillary complete removable dental prosthesis with the swing lock system. The patient presented with large undercuts on the buccal and labial areas of the edentulous maxillary arch and a history of various failed alveoloplasty procedures that had attempted to remove the exostoses preventing denture insertion. The prosthodontic planning and treatment approach are discussed.
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http://dx.doi.org/10.1016/j.prosdent.2014.05.025DOI Listing
November 2014

Preprosthetic minor tooth movement with thermoplastic appliances and interproximal stripping: a clinical report.

Authors:
Seok-Hwan Cho

J Prosthet Dent 2014 Nov 17;112(5):1017-20. Epub 2014 Jul 17.

Assistant Professor, Department of General Dental Sciences, Marquette University School of Dentistry, Milwaukee, Wis. Electronic address:

This clinical report describes preprosthodontic minor tooth movement with serial thermoplastic appliances and interproximal stripping. A patient with rotated and labially tipped anterior teeth sought care with a request for improved appearance. The prosthodontic planning and treatment approach are discussed.
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http://dx.doi.org/10.1016/j.prosdent.2014.06.009DOI Listing
November 2014

Mirror-image anterior crown fabrication with computer-aided design and rapid prototyping technology: a clinical report.

J Prosthet Dent 2013 Feb;109(2):75-8

Department of General Dental Sciences, Marquette University School of Dentistry, Milwaukee, Wis., USA.

This clinical report describes the fabrication of a maxillary central incisor single crown with rapid prototyping (RP) technology. A patient with a recently replaced metal ceramic crown had discomfort due to the nonanatomic lingual contour of the crown. With computer-aided design (CAD) software and rapid prototyping (RP) technology, the shape of the contralateral central incisor was duplicated and reproduced to make a mirror-image for a new crown. The prosthodontic planning and treatment approach are discussed.
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http://dx.doi.org/10.1016/S0022-3913(13)60018-9DOI Listing
February 2013

The effect of multiple firings on the marginal integrity of pressable ceramic single crowns.

J Prosthet Dent 2012 Jan;107(1):17-23

Department of General Dental Sciences, Marquette University School of Dentistry, Milwaukee, WI, USA.

Statement Of Problem: The marginal adaptation of metal ceramic crowns is affected by firing cycles for veneering porcelain application. The effect of multiple firings on the marginal integrity of pressable ceramic core crowns is unknown.

Purpose: The purpose of this in vitro study was to evaluate the effect of repeated firing cycles on the marginal discrepancy of veneered (layered) pressable ceramic anterior crowns with 2 different finish line configurations.

Material And Methods: Forty pressable ceramic single anterior complete crowns were fabricated from 2 systems (IPS Empress Esthetic and IPS e.max Press) with 2 finish line designs (shoulder, chamfer) on epoxy resin dies. Specimens were divided into 4 groups of 10, and measurements were made after pressing (control) and after 5 veneer firing stages: 1) wash, 2) first incisal, 3) second incisal, 4) characterization and glazing, and 5) corrective. The change in vertical marginal discrepancy was measured with a light microscope at 4 locations: facial (F), mesial (M), lingual (L), and distal (D) surfaces. One-way ANOVA (α-=.05) was used to evaluate the marginal change. A Student-Newman-Keuls test was also used for comparison among the groups.

Results: There were no significant changes in the vertical marginal integrity related to ceramic type and marginal location and their interactions. However, there was a significant marginal integrity change during the characterization and glazing firing stage. (P<.05)

Conclusions: The marginal gap increased for both systems during veneer application and decreased during the characterization and glazing firing cycle. The total marginal fit change after 5 firings was 0.33 μm for IPS e.max Press, and 0.27 μm for IPS Empress Esthetic.
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http://dx.doi.org/10.1016/S0022-3913(12)60011-0DOI Listing
January 2012

Bastadins, cyclic tetramers of brominated-tyrosine derivatives, selectively inhibit the proliferation of endothelial cells.

J Nat Med 2006 Jul 13;60(3):231-235. Epub 2006 May 13.

Graduate School of Pharmaceutical Sciences, Osaka University, 1-6 Yamada-oka, Suita, Osaka, 565-0871, Japan.

Eight bastadins, tetramers of brominated-tyrosine derivatives, were isolated from the marine sponge Ianthella basta, and their anti-proliferative activities against endothelial cells were examined. A structure-activity relationship study of these compounds revealed that a macrocyclic structure was crucial, and a bastarane-type skeleton was important for the selective activity of these bastadins against endothelial cells. A conformational analysis of the bastadins was also carried out by molecular mechanics calculation.
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http://dx.doi.org/10.1007/s11418-006-0045-3DOI Listing
July 2006

Effect of die spacer thickness on shear bond strength of porcelain laminate veneers.

J Prosthet Dent 2006 Mar;95(3):201-8

Department of Dental Biomaterials Science, College of Dentistry and Dental Research Institute, Seoul National University, Korea.

Statement Of Problem: The application of die spacer may affect the shear bond strength (SBS) of porcelain laminate veneer (PLV). However, there is no standard for the amount of die spacer necessary for the fabrication of PLV restorations.

Purpose: The purpose of this study was to evaluate the SBS differences between enamel and a feldspathic PLV as a function of die spacer thickness.

Material And Methods: Eighty rectangular (5 x 3 x 1 mm) PLV (Super Porcelain EX-3) specimens were made using stone blocks on which die spacer (Nice Fit) was applied in different thicknesses (0, 2, 4, or 6 coats) (n = 20). Before bonding, all PLV specimens were pretreated with airborne-particle abrasion (1-, 2-, 3-, or 4-bar pressure; 10 sec/10-mm distance or 5 sec/20-mm distance) and cleaned with an ultrasonic cleanser. A vertically flat surface on the labial enamel of 80 freshly extracted sound teeth was prepared with a low-speed diamond-coated saw. The PLV specimens were bonded to the etched enamel specimens using a composite resin cement (RelyX Veneer). Forty enamel-ceramic specimens (Group NTc) were maintained in deionized water at room temperature for 1 week after cementation, and the other 40 specimens (Group Tc) were subjected to thermal cycling treatment (2500 cycles, 5 degrees C to 60 degrees C, 15-second dwell time). The SBS measurement was performed with a universal testing machine. The results were compared with a 2-way analysis of variance (ANOVA), and mean values were compared with Fisher's Protected Least Significant Difference (PLSD) intervals (alpha = .05).

Results: For Group NTc specimens, the SBS values (MPa) were 8.7 +/- 2.6 (no coat), 12.6 +/- 4.8 (2 coats), 10.7 +/- 2.9 (4 coats), and 9.6 +/- 2.8 (6 coats). For Group Tc specimens, the SBS values were 4.1 +/- 2.0 (no coat), 7.1 +/- 3.4 (2 coats), 6.8 +/- 2.1 (4 coats), and 6.1 +/- 2.4 (6 coats). Two-way ANOVA showed that the SBS was influenced by the thermal cycling and the number of coats, but there was no significant interaction between the 2 variables. The Fisher's PLSD interval for the SBS for comparisons among the number of coats was 0.95. The group with 2 coats of die spacer showed higher SBS values than the group with no coat, whereas groups with more than 2 coats of die spacer resulted in similar SBS values when compared to each other. The thermal cycling treatment resulted in a significant decrease of the SBS. Group Tc showed a trend similar to Group NTc.

Conclusion: Within the limitations of this study it was found that the appropriate application of die spacer exerts a favorable influence on the SBS of composite-bonded PLV. The 2-coat application of die spacer provides suitable space to accommodate the cement thickness.
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http://dx.doi.org/10.1016/j.prosdent.2005.12.011DOI Listing
March 2006

Bastadin 6, a spongean brominated tyrosine derivative, inhibits tumor angiogenesis by inducing selective apoptosis to endothelial cells.

Anticancer Drugs 2006 Mar;17(3):269-78

Graduate School of Pharmaceutical Sciences, Osaka University, Osaka, Japan.

Bastadin 6, a macrocyclic tetramer of a brominated tyrosine derivative, was isolated from a marine sponge and its anti-angiogenic activity was evaluated. Bastadin 6 was found to inhibit vascular endothelial growth factor (VEGF)- or basic fibroblast growth factor (bFGF)-dependent proliferation (IC50=0.052 micromol/l) of human umbilical vein endothelial cells (HUVECs) 20- to 100-fold selectively in comparison with normal fibroblast (3Y1) or several tumor cells (KB3-1, K562 and Neuro2A). Bastadin 6 also inhibited VEGF- or bFGF-induced tubular formation (0.1 micromol/l, 6 h treatment) and VEGF-induced migration (1 micromol/l, 4 h treatment) of HUVECs. Moreover, bastadin 6 almost completely blocked VEGF- or bFGF-induced in vivo neovascularization in the mice corneal assay and suppressed growth of s.c. inoculated A431 solid tumor in nude mice (100 mg/kg, i.p.). Bastadin 6 induced cell death of HUVECs with an apoptotic phenotype, whereas it showed no effect on the VEGF-induced auto-phosphorylation of VEGF receptors Flt-1 and KDR/Flk-1. These results suggest that the anti-angiogenic effect of bastadin 6 is closely related to selective induction activity of apoptosis against endothelial cells.
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http://dx.doi.org/10.1097/00001813-200603000-00005DOI Listing
March 2006
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