Taxonomic discordance of immersive realities in dentistry: A systematic scoping review.: Taxonomic discordance of immersive realities

OBJECTIVES

This review aimed to map taxonomy frameworks, descriptions, and applications of immersive technologies in the dental literature.

DATA

The Preferred reporting items for systematic reviews and meta-analyses extension for scoping reviews (PRISMA-ScR) guidelines was followed, and the protocol was registered at open science framework platform (https://doi.org/10.17605/OSF.IO/H6N8M).

SOURCES

Systematic search was conducted in MEDLINE (via PubMed), Scopus, and Cochrane Library databases, and complemented by manual search.

STUDY SELECTION

A total of 84 articles were included, with 81% between 2019 and 2023. Most studies were experimental (62%), including education (25%), protocol feasibility (20%), in vitro (11%), and cadaver (6%). Other study types included clinical report/technique article (24%), clinical study (9%), technical note/tip to reader (4%), and randomized controlled trial (1%). Three-quarters of the included studies were published in oral and maxillofacial surgery (38%), dental education (26%), and implant (12%) disciplines. Methods of display included head mounted display device (HMD) (55%), see through screen (32%), 2D screen display (11%), and projector display (2%). Descriptions of immersive realities were fragmented and inconsistent with lack of clear taxonomy framework for the umbrella and the subset terms including virtual reality (VR), augmented reality (AR), mixed reality (MR), augmented virtuality (AV), extended reality, and X reality.

CONCLUSIONS

Immersive reality applications in dentistry are gaining popularity with a notable surge in the number of publications in the last 5 years. Ambiguities are apparent in the descriptions of immersive realities. A taxonomy framework based on method of display (full or partial) and reality class (VR, AR, or MR) is proposed.

CLINICAL SIGNIFICANCE

Understanding different reality classes can be perplexing due to their blurred boundaries and conceptual overlapping. Immersive technologies offer novel educational and clinical applications. This domain is fast developing. With the current fragmented and inconsistent terminologies, a comprehensive taxonomy framework is necessary.

Dental implant placement with immersive technologies: A preliminary clinical report of augmented and mixed reality applications

A preliminary clinical report of implant placements with 2 immersive reality technologies is described: augmented reality with head mounted display and mixed reality with a tablet PC. Both immersive realities are promising and could facilitate innovative dental applications. However, mixed reality requires further development for clinical optimization.

Additively manufactured CAD-CAM complete dentures with intraoral scanning and cast digitization: A controlled clinical trial

PURPOSE

To assess, clinically, patient satisfaction of additively manufactured complete dentures with intraoral scanning and hybrid cast digitization in comparison with conventional complete dentures.

MATERIALS AND METHODS

Participants who were edentulous in both arches were recruited and received three types of complete dentures (CDs): conventionally manufactured with conventional impression (CC), additively manufactured with intraoral scanning (AMI), and additively manufactured with cast digitization (AMH). Definitive impressions of the edentulous arches were made with medium viscosity polyvinyl siloxane (Hydrorise Monophase; Zhermack, Italy) for the CC group, intraoral scanning (TRIOS 4; 3Shape, Copenhagen, Denmark) for the AMI group, and laboratory scanning of the definitive casts (Ceramill Map400 AMANNGIRRBACH, Pforzheim, Deutschland) for the AMH group. The trial dentures of the CC group were scanned for occlusion registrations of the AMI and AMH groups and were used to guide the designing process (Exocad 3.0 Galway; Exocad GmbH). The AMI and AMH dentures were additively manufactured with a vat-polymerization 3D printer (Sonic XL 4K; phrozen, Taiwan). Patient satisfaction and clinical outcome were assessed with OHIP EDENT, and 14-factor criteria, respectively. Statistical analyses were performed with paired sample t-test and one-way repeated measure ANOVA for satisfaction, Wilcoxon signed rank test for clinical outcome, and Pearson's r (r) for effect size, with α = 0.05.

RESULTS

A total of 20 participants were included. Satisfaction had no statistically significant difference within or among the groups (p < 0.105). Within-group comparison between the two arches showed no statistical significance for the clinical outcome except for a significantly higher maxillary AMI score (p = 0.01, r = -0.40 with medium effect size). For among group's comparison; AMI had a significantly lower score than CC for the maxillary and mandibular arches (p = 0.01, r = -0.40, medium effect size, and p = 0.003, r = -0.47, medium effect size), and significantly lower score than the mandibular AMH (p = 0.03, r = -0.47, medium effect size), with significantly lower quality in teeth arrangement and retention domains for the AMI, and teeth arrangement for the AMH, in comparison with CC.

CONCLUSIONS

Patient satisfaction with both types of additively manufactured dentures is comparable to conventional dentures. The comparable overall clinical outcomes between hybrid and conventional dentures indicate that additive manufacturing is an acceptable clinical substitute for the conventional methods. However, additively manufactured dentures made with intraoral scanning have lower clinical quality and retention than hybrid and conventional dentures, particularly for the mandibular arch. Teeth arrangement of both additively manufactured dentures is clinically inferior to the conventional denture.

Virtual patient representation with silicone guide and a 3D scanner accessory for a user-friendly facial scanning workflow: A clinical report of smile design and ceramic veneers

Digital smile design and ceramic veneers are described with virtual patient representation. The procedure included facial scanning with a 3D scanner accessory (Structure sensor pro; Occipital Inc) mounted on a tablet computer (iPad; Apple Inc) and an innovative chairside silicone guide to replace the intraoral scan body for a straightforward and user-friendly workflow.

Evaluation of Marginal and Internal Fit of Ceramic Laminate Veneers Fabricated with Five Intraoral Scanners and Indirect Digitization

The long-term success of ceramic laminate veneers (CLVs) is influenced by the marginal and internal fit of the restorations. However, studies comparing the fit of CLVs using different intraoral scanners or the indirect digitization technique are lacking. The purpose of this study was therefore to assess the marginal and internal fit of CAD/CAM-milled CLVs using different intraoral scanners and the indirect digitalization technique. An ivorine typodont maxillary left-central incisor was prepared; the tooth and the neighboring teeth were scanned and used as a template to print ninety 3D partial models. Thereafter, ceramic laminate veneers (CLVs) (N = 90) were milled from IPS-Emax CAD blocks and divided into six equal groups (15 specimens each) according to the type of intraoral scanner (IOS), as follows: Omnicam IOS, SC3600 IOS, Trios 3 IOS, Emerald IOS, I500 IOS. Fifteen further CLVs were fabricated using the conventional indirect digitalization technique. After cementation on the resin dies and embedding in clear epoxy resin, specimens were sectioned inciso-gingivally and mesio-distally. At the incisal and cervical positions, the marginal discrepancy was measured and evaluated in addition to the internal gap at six locations using SEM (200×). Differences between gap measurements among the six groups were determined using ANOVA. Games-Howell multiple comparisons for homogenous variances and LSD multiple comparisons for non-homogenous variances were used with 95% confidence intervals. The significance level was set at 0.05. The lowest mean absolute marginal gap at the incisal margins (AMGI) was recorded for Omnicam group (203.28 ± 80.14) µm, while the highest mean absolute marginal gap at the cervical margins (AMGC) was recorded for Omnicam group (147.16 ± 59.78) µm. The mean AMGC was reported to be significantly different between the conventional technique (146.75 ± 38.43) µm and Trios 3 (91.86 ± (35.51) µm; p = 0.001) and between Emerald (112.37 ± (50.31) µm; p = 0.042) and I500 (86.95 ± (41.55) µm; p < 0.001). The mean MGI was found to be significantly different between the conventional technique (114.11 ± (43.45) µm and I500 group (186.99 ± (73.84) µm) only (p = 0.035). However, no significant differences were found in the mean MGI between all types of IOSs. The means of AMG and MG were significantly different at incisal or cervical areas between the conventional technique and IOSs and within the scanner groups (p > 0.05). Marginal gaps were higher in the incisal region compared to the cervical region with both the indirect digitization technique and the IOSs. Ceramic laminate veneers (CLVs) fabricated using IOSs produced overall internal and marginal fit adaptation results comparable to CLVs fabricated from the indirect digitalization method, and both techniques produced clinically acceptable results.

Trueness of intraoral scanning of edentulous arches: A comparative clinical study

PURPOSE

To compare the accuracy of intraoral scanning (IOS) of the edentulous arch with the hybrid protocol of cast digitization (CD), and to investigate the effect of arch type and area on trueness.

MATERIALS AND METHODS

Participants that were edentulous in both arches were recruited. Two impression protocols were used; the IOS as the test protocol with an IOS device (TRIOS 4; 3Shape, Denmark), and the CD as the control, including tracing compound (TRACING STICKS; Kemdent, UK) for border molding, polyvinyl siloxane (Hydrorise Monophase; Zhermack, Italy) for impression, and cast digitization with a laboratory scanner (ceramill® map400, AMANNGIRRBACH, Germany). Scanned files were exported to a 3D inspection software (Geomagic Control X; 3D Systems, NC) for trueness analysis. The CD file (reference file) for each participant was split into 2 areas; the dynamic area representing the mobile tissues at the peripheral border, and the static area representing the rest of the arch. Statistical analyses were performed with 1-sample t-test for the difference between CD and IOS protocols, paired sample t-test for the difference between the static and dynamic areas for each arch, and an independent sample t-test for the difference between the maxillary and mandibular arches for each area, with α = 0.05. Effect size was calculated with Cohen's d (d), with 0.2 as small, 0.5 as medium, and 0.8 as large.

RESULTS

A total of 21 participants were included. The difference between the IOS and CD protocol was significant for all subset comparisons (p < 0.001, d: 2.5-6.2, large effect size). Dynamic areas had lower trueness in comparison with static areas (p < 0.001, d = 4.57, large effect size for the maxillary arch, p < 0.001, d = 3.96, large effect size for the mandibular arch). Mandibular arch had lower trueness in comparison with the maxillary arch (p < 0.001, d = 1.45, large effect size for the static areas, p = 0.009, d = 0.85, large effect size for the dynamic areas, p < 0.001, d = 1.71, large effect size for all areas). Color difference map showed marked positive deviation in the buccal dynamic areas of both arches, and nonmatching areas with evident overstretching.

CONCLUSIONS

While the IOS of edentulous arches could be feasible for attached mucosa, providing a functional shape for the peripheral border remains a challenge, with a thinner and more outward border for the IOS in comparison with the CD protocol. The IOS of the mandibular arch is more difficult and has lower trueness in comparison with the maxillary arch.

Additive Manufacturing of Dental Ceramics: A Systematic Review and Meta-Analysis

PURPOSE

The purpose of this systematic review and meta-analysis was to evaluate the effect of using additive manufacturing (AM) for dental ceramic fabrication in comparison with subtractive manufacturing (SM), and to evaluate the effect of the type of AM technology on dental ceramic fabrication.

MATERIALS AND METHODS

A search was conducted electronically in MEDLINE (via PubMed), EBSCOhost, Scopus, and Cochran Library databases, and also by other methods (table of contents screening, backward and forward citations, and grey literature search) up to February 12, 2022, to identify records evaluating additive manufacturing of ceramics for dental purposes in comparison with subtractive manufacturing. A minimum of 2 review authors conducted tstudy selection, quality assessment, and data extraction. Quality assessment was performed with Joanna Briggs Institute tool, and the quantitative synthesis was performed with the Comprehensive Meta-Analysis program (CMA, Biostat Inc). Hedges's g for effect size was calculated, with 0.2 as small, 0.5 as medium, and 0.8 as large. Heterogeneity was assessed with I² and prediction interval (PI) statistics. Publication bias was investigated with funnel plots and grey literature search. Certainty of evidence was assessed with the Grading of Recommendations: Assessment, Development, and Evaluation (GRADE) tool.

RESULTS

A total of 28 studies were included for the qualitative and quantitative synthesis; 11 in vitro studies on accuracy, 1 in vivo study on color, and 16 in vitro studies on physical and mechanical properties. Meta-analysis showed overall higher accuracy for SM compared with AM, with medium effect size (0.679, CI: 0.173 to 1.185, p = 0.009) and also for marginal (g = 1.05, CI: 0.344 to 1.760, p = 0.004), occlusal (g = 2.24, CI: 0.718 to 3.766, p = 0.004), and total (g = 4.544, CI: -0.234 to 9.323, p = 0.062) with large effect size; whereas AM had higher accuracy than SM with small effect size for the external (g = -0.238, CI: -1.215 to 0.739), p = 0.633), and internal (g = -0.403, CI: -1.273 to 0.467, p = 0.364) surfaces. For technology, self-glazed zirconia protocol had the smallest effect size (g = -0.049, CI: -0.878 to 0.78, p = 0.907), followed by stereolithography (g = 0.305, CI: -0.289 to 0.9, p = 0.314), and digital light processing (g = 1.819, CI: 0.662 to 2.976, p = 0.002) technologies. Flexural strength was higher for ceramics made by SM in comparison to AM with large effect size (g = -2.868, CI: -4.371 to -1.365, p < 0.001). Only 1 study reported on color, favoring ceramics made through combined AM and SM.

CONCLUSIONS

Subtractive manufacturing had better overall accuracy, particularly for the marginal and occlusal areas, higher flexural strength, and more favorable hardness, fracture toughness, porosity, fatigue, and volumetric shrinkage; whereas AM had more favorable elastic modulus and wettability. Both methods had favorable biocompatibility. All studies on accuracy and mechanical properties were in vitro, with high heterogeneity and low to very low certainty of evidence. There is a lack of studies on color match and esthetics.

I See Faces! A Review on Face Perception and Attractiveness with a Prosthodontic Peek at Cognitive Psychology

A human face contains a wealth of information about an individual, with which an observer can instinctively make a judgment on the attractiveness of the face. However, despite the profuse literature on facial and smile attractiveness, their origins, determinants, and perceptions remain controversial. The axiom in face processing research is that a face is perceived as an amalgamation of its features, and is referred to as "whole" or "holistic" perception. It is pertinent to the clinician involved in the provision of esthetic restorations to understand this holistic process of face recognition and perception of smile attractiveness. This review paper addresses face recognition and perception of attractiveness by reviewing the holistic perception of faces, including the multidimensional face-space model, and also reviews the smile and facial attractiveness according to the average, multiple motive, and secondary sex characteristics theories.

Analysis of the effect magnitude of different parameters on smile attractiveness

OBJECTIVE

To evaluate the effect magnitude of different parameters on smile attractiveness.

MATERIALS AND METHODS

A reference and 13 images were produced by manipulating 13 parameters. Image rating was performed with a 4-point Likert scale from least attractive (1) to most attractive (4). Image raters included laypeople, dental students, dentists, and dental specialists. Friedman and Wilcoxon image were used for estimate of effect size. Parameters were classified into small (0.10- < 0.30), medium (0.30- < 0.5), or large (≥0.50).

RESULTS

A total of 1040 people participated with good consistency (α = 0.861), and moderate reliability (0.64-0.7). The reference image had the highest rank (laypeople:11.79, dental background: 12.55). For effect size; gingival margin level (-0.11, -0.01), teeth width proportion (-0.09, -0.10), inverted smile arch (-0.09, -0.21), commissure line cant (-0.15, -0.17) and low smile (-0.24, -0.23) had small effect size; occlusal plane cant (-0.36, -0.49), midline cant (-0.36, -0.48), and midline shift (-0.37, -0.49) had medium effect size; diastema (-0.55, -0.54) and color (-0.56, -0.56) had large effect size for the laypeople and dental groups. High smile (-0.42, -0.51), incisor edge symmetry (-0.46, -0.54) had medium effect size in laypeople group and large effect size in the dental group. Width to length tooth proportion (-0.26, -0.39) had small effect size in the laypeople group and medium effect size in the dental group.

CONCLUSIONS

Smile parameters had different effect magnitude on smile attractiveness and were classified into small, medium, or large parameters. Neither laypeople nor professionals have a collective judgment on what constitutes a beautiful smile.

CLINICAL SIGNIFICANCE

This study investigated the effect magnitudes of 13 smile parameters and presented a small, medium, and large smile parameters classification. It should provide the clinician with an insight into the expected effect each parameter has on the smile.

Effect of CAD/CAM Bur Deterioration on the Surface Roughness of Ceramic Crowns

PURPOSE

To evaluate the effect of repetitive milling on the surface roughness of ceramic crowns.

MATERIALS AND METHODS

Twenty feldspathic ceramic crowns (VITABLOCS Mark II; Vita Zahnfabrik, Bad Säckingen, Germany) milled with hard milling protocol, and 20 zirconia crowns (5Y-TZP, inCoris TZI; Dentsply Sirona, York, PA) milled with soft milling protocol, using a 5-axis milling machine (inLab MC X5; Dentsply Sirona) were investigated. Atomic force microscopy (SPM SmartSPM™-1000) was used for surface roughness measurements (Ra, RMS). Pearson correlation between bur deterioration percentage as provided by the software of the milling machine and surface roughness was performed with an (r) range between 1 and -1. Trend analysis between the 2-half and among the 4-quarter bur lifetime was performed with linear contrast analysis and partial eta squared (η) for estimate of effect size. Analysis of mean variance between the zirconia and feldspathic ceramic groups was performed with a t-test, with α = 0.05.

RESULTS

Correlation analysis showed small correlation for Ra, RMS (r = -0.02, -0.16 for the feldspathic ceramic crowns and r = 0.044, 0.034 for the zirconia crowns), and no significant differences for the 2-half and 4-quarter groups (p > 0.05) for both crown types. Estimate of effect size was rated as medium for the 2-half groups (Ra = 0.420, RMS = 0.395) and large for the 4-quarter groups (RA = 0.22, F = 1.48, RMS = 0.19, F = 1.26) for the feldspathic ceramic crowns, and small effect size for the 2-half groups (Ra = 0.18, RMS = 0.20) and the 4-quarter groups (Ra = 0.035, RMS = 0.037) for the zirconia crowns. There was no significant difference (p = 0.178, F = 0.016. p = 0.088, F = 0.002) between the feldspathic ceramic and zirconia crowns with medium and large effect size (0.45, 0.57) for RA and RMS.

CONCLUSIONS

Milling zirconia and feldspathic ceramic crowns had small correlation between bur deterioration and surface roughness when the burs were used within their recommended lifetime. However, hard milled feldspathic ceramic crowns had higher surface roughness than the soft milled zirconia crowns. Bur deterioration had a larger effect on the surface roughness of the feldspathic ceramic crowns than the zirconia crowns.

Effect of CAD-CAM tool deterioration on the trueness of ceramic restorations

STATEMENT OF PROBLEM

Tools will gradually deteriorate with repetitive milling. However, tool lifetime can vary depending on the type of milling machine, the hardness of the ceramic material, and the size of the restoration. Studies evaluating the effect of tool deterioration on the trueness of milled restorations are lacking.

PURPOSE

The purpose of this study was to evaluate the effect of tool deterioration on the trueness of milled restorations.

MATERIAL AND METHODS

A patient requiring a ceramic crown was recruited. Repetitive milling of zirconia crowns (inCoris TZI; Dentsply Sirona) with tungsten carbide rotary instruments and glass-ceramic crowns (VITABLOCS mark II; Vita Zahnfabrik) with diamond rotary instruments was performed by using a 5-axis milling machine (inLab MC X5; Dentsply Sirona) until the machine software indicated replacing the largest tool. The percentage of deterioration for the largest tool was recorded before each milling. The trueness for different crown areas was evaluated by using a 3-dimensional evaluation software (Geomagic Control X; 3D systems), and the crowns were clinically evaluated. The crowns were grouped into 4 quadrants as per the deterioration percentage. The Pearson correlation (r) between the deterioration percentage and trueness and linear contrast analysis (partial eta squared [η]) among the groups were performed.

RESULTS

Glass-ceramic crown areas had low correlation except for mesial (high, r=0.63, high, η=0.37) and distal (medium, r=0.42, high, η= 0.34) areas, whereas zirconia crowns had low correlation for inner and internal areas and medium to high correlation for mesial (r= -0.31, η=0.33), distal (r= -0.53, η=0.36), occlusal (r= -0.32, η=0.164), external (r= 0.69, η=0.52), and marginal (r= -0.44, η=0.19) areas. Zirconia crowns had excellent marginal fit and occlusal contact and light to excellent proximal contact, whereas glass-ceramic crowns had excellent marginal fit, minor to major occlusal correction, and heavy proximal contact.

CONCLUSIONS

The effect of tool deterioration on trueness depended on material type and crown area. Only proximal areas were affected in the glass-ceramic crowns, whereas external, proximal, occlusal, and marginal areas were affected in the zirconia crowns. Trueness did not necessarily reflect the clinical quality of the crown, as both crown types were clinically satisfactory. Although zirconia crowns were overmilled in comparison with the reference design and glass-ceramic crowns, they had better clinical quality.

Effect of Milling Protocols on Trueness and Precision of Ceramic Crowns

PURPOSE

To investigate the effect of different milling protocols for different ceramic materials on the trueness and precision of milled ceramic crowns.

MATERIALS AND METHODS

A definitive impression from a patient requiring a ceramic crown was used to fabricate forty glass ceramic crowns (VITABLOCS mark II, Vita Zahnfabrik) milled with wet, hard milling protocol, and 40 zirconia crowns (inCoris TZI, Dentsply, Sirona) milled with dry, soft milling protocol, using a 5-axis milling machine (inLab MC X5; Dentsply Sirona). Trueness and precision for different crown areas were evaluated with a 3D evaluation software (Geomagic Control X, 3D systems). Statistical analysis was performed between the 2 crown types with independent t-test, and analysis of variances followed by Bonferroni tests among crown areas for each crown.

RESULTS

All areas of the glass ceramic crowns had higher trueness than the zirconia crown areas (p < 0.05). Crown areas of each crown type had significantly different trueness values (p < 0.001, F = 175.17 for glass crowns, p < 0.001, F = 35.04 for zirconia crowns). Glass crowns had 3.78 µm precision, while zirconia crowns had 4.12 µm precision, with a precision difference range between the 2 types of crowns from 0.32 µm for the inner surface to 6.5 µm for the marginal surface.

CONCLUSIONS

Type of ceramic material and milling protocol affected trueness of the milled crown, with higher trueness for the hardmilled glass crowns than the soft milled zirconia crowns. Soft milled zirconia crowns were generally overmilled in comparison with the reference design and glass crowns. However, glass crowns exhibited more undermilling in thin and deep areas. The crown area affected trueness, with external areas having better trueness than internal areas. The 5-axis milling machine had high precision, which was minimally affected by the ceramic type, milling protocol, or crown area.

Learning curve of intraoral scanning by prosthodontic residents

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.

Surface Roughness of Monolithic and Layered Zirconia Restorations at Different Stages of Finishing and Polishing: An In Vitro Study

PURPOSE

To evaluate surface roughness and topography of different zirconia-based restorations at various steps of finishing and polishing.

MATERIALS AND METHODS

Seventy-five zirconia discs were fabricated and divided into 3 layered and 2 monolithic groups: layered conventional (VM9; Vita), layered pressed (PM9; Vita), layered digital (TriLuxe Forte; Vita), opaque monolithic (Ceramill Zi; Amann Girrbach), and translucent monolithic (Zolid FX; Amann Girrbach). Surface roughness testing (Ra, Rz) and scanning electron microscopy were performed at the glazed, unglazed, finished, polished, super-polished, and super-polished with diamond paste steps. One-way ANOVA and Tukey tests were used for statistical analysis.

RESULTS

There were significant differences in all groups among the different steps (p < 0.001, F = 77.67 for layered conventional; p < 0.001, F = 133.90 for layered pressed; p < 0.001, F = 47.94 for layered digital; p < 0.001, F = 48.05 for zirconia opaque; p < 0.001, F = 43.91 for zirconia translucent). For the layered groups, glazed stage was significantly different from all other steps (p < 0.001). For the layered conventional and digital groups, polishing using diamond paste was not significantly different from the polished and super-polished steps (p = 0.448, p = 0.153), while for the layered pressed group, polishing using diamond paste was not significantly different from the super polished step (p = 0.815). For monolithic groups, there were no significant differences between the polished and super-polished steps (p = 0.957 for zirconia opaque, p = 1.00 for zirconia translucent). Both the diamond paste and super-polished steps showed no significant differences (p = 0.620, p = 0.550) from the glazed surface in the opaque zirconia group.

CONCLUSIONS

Surface roughness of monolithic and layered zirconia was improved by polishing; however, only opaque zirconia reached the level of surface roughness of the glazed stage. Type of buildup affected the surface roughness of adjusted ceramics, with monolithic zirconia showing lower surface roughness than layered zirconia. Polishing with diamond paste provided no significant improvement in the surface roughness of monolithic or layered zirconia.

The Effect of Ceramic Type and Background Color on Shade Reproducibility of All-Ceramic Restorations

PURPOSE

To investigate the effects of background color on shade reproduction using CAD/CAM zirconia and lithium disilicate ceramics.

MATERIALS AND METHODS

A plastic tooth was prepared for an all-ceramic crown and scanned. Tooth-shaped light background dies were manufactured. Full-contour crowns were milled from translucent zirconia (ZT) and low translucency lithium disilicates (E [LT]). Copings from opaque zirconia (Z) and medium opacity lithium disilicate (E[MO]) ceramics were milled and layered with veneering porcelain to full contour. Metal copings were used to produce a dark background. Specimens were divided into 8 groups with 3 variables: background color, ceramic type, and translucency. Crowns were cemented using composite resin cement. Color was measured with a spectrophotometer. Color difference (∆E) was calculated using the CIEDE2000 formula between the specimens and the target shade, A1. Statistical analysis was performed using a nested design 3-way ANOVA and Tukey multiple comparisons.

RESULTS

The closest ∆E to target shade was produced by E (LT) (2.13 ± 0.19) on the dark background. This increased significantly to 2.90 ± 0.19 on the light background (p = 0.03). The e.max (MO) groups significantly increased (p = 0.001) to 4.40 ± 0.22 and 4.47 ± 0.4, (p = 1.00) for the dark and light backgrounds, respectively. ∆E for the zirconia groups were higher and ranged from 4.85 ± 0.48 to 5.60 ± 0.48 in the ZT groups (p = 0.04) and 6.5 ± 0.82 to 7.75 ± 0.53 (p = 0.001) for Z groups from dark to light backgrounds. There was an overall lack of chromaticity between the specimens and the target shade A1 CONCLUSIONS: Ceramic color was affected by ceramic type, background, and translucency. Lithium disilicate appeared to be better than zirconia in shade reproduction. Less-opaque materials matched the target shade better, while opaque materials and low translucencies were more suitable for dark backgrounds.

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.

The taper of cast post preparation measured using innovative image processing technique

BACKGROUND

No documentation in the literature about taper of cast posts. This study was conducted to measure the degree of cast posts taper, and to evaluate its suitability based on the anatomy aspects of the common candidate teeth for post reconstruction.

METHODS

Working casts for cast posts, prepared using Gates Glidden drills, were collected. Impressions of post spaces were made using polyvinyl siloxan putty/wash technique. Digital camera with a 10' high quality lens was used for capturing two digital images for each impression; one in the Facio-Lingual (FL) and the other in the Mesio-Distal (MD) directions. Automated image processing program was developed to measure the degree of canal taper. Data were analyzed using Statistical Package for Social Sciences software and One way Analysis of Variance.

RESULTS

Eighty four dies for cast posts were collected: 16 for each maxillary anterior teeth subgroup, and 18 for each maxillary and mandibular premolar subgroup. Mean of total taper for all preparations was 10.7 degree. There were no statistical differences among the total taper of all groups (P = .256) or between the MD and FL taper for each subgroup. Mean FL taper for the maxillary first premolars was lower significantly (P = .003) than the maxillary FL taper of the second premolars. FL taper was higher than the MD taper in all teeth except the maxillary first premolars.

CONCLUSIONS

Taper produced did not reflect the differences among the anatomy of teeth. While this technique deemed satisfactory in the maxillary anterior teeth, the same could not be said for the maxillary first premolars. Careful attention to the root anatomy is mandatory.

A clinical study on the effects of cordless and conventional retraction techniques on the gingival and periodontal health

AIM

To investigate the influence of two cordless techniques on the periodontium in comparison with conventional cords.

MATERIAL AND METHODS

Dental students (n=60) with healthy gingival conditions were recruited - an expanding poly vinyl siloxane material (Magic Foam Cord), a paste-like material (Expasyl), and a conventional retraction cord (Ultrapak) were applied on the buccal aspects of three premolars of each subject. Probing depth, clinical attachment level, gingival index (GI), plaque index, mobility, bleeding, and sensitivity were assessed at baseline, and at 1 and 7 days after application. Data were analysed using Kruskal-Wallis and Mann-Whittney tests (alpha=0.05).

RESULTS

The periodontal parameters were not statistically significant among the groups at all time intervals except for the GI, which was increased for all groups after 1 day. The highest was in Expasyl (p=0.011). After 7 days, the GI returned to a non-significant level compared with baseline except for Expasyl, which was still significant (p=0.044). Expasyl induced sensitivity in four subjects. Bleeding was only induced by Ultrapak in 28.3% and 26.7% during and after retraction, respectively.

CONCLUSIONS

All techniques caused a temporary gingival inflammation; the greatest was in Expasyl, which also showed slower recovery. Cordless techniques did not induce bleeding during or after retraction.

Foreign Body Ingestion and Aspiration in Dentistry: A Review of the Literature and Reports of Three Cases

This article reviews several cases of foreign body ingestion or inhalation reported in the literature. Prevention, complication and management of this event are discussed and three case reports presented. Two of the cases were bridge ingestion and one was ingestion of an orthodontic band. The three cases were managed by watchful waiting and the ingested foreign bodies came out in the stools without complications.