Contemporary Concepts of Adhesive Cementation of Glass-Fiber Posts: A Narrative Review.

(1) Background: Cementation of glass fiber posts to root canals has been associated with various failures, especially debonding. This narrative review aims to present the contemporary concepts concerning the adhesive cementation of glass fiber post and to discuss the optimal management of these factors. (2) Methods: Electronic search was performed in MEDLINE/Pub Med and Google Scholar using selected keywords examining the parameters post length, surface treatment of glass fiber posts, post space preparation and dentin pretreatment, resin cement selection, adhesive systems and hybrid layer formation, and clinical techniques. (3) Results: The search led to the selection of 44 articles. Epoxy resin-based endodontic sealers are recommended and the use of temporary cement in the root canal should be avoided. The minimum length of a glass fiber post adhesively cemented to a root canal is 5 mm. Irrigating the root canals with chlorhexidine, MTAD, or EDTA (alone or in combination with NaOCl) after post space preparation seems to enhance the bond strength. Silane application on the surface of the post seems to be beneficial. Concerning resin cements and adhesive systems, the results were rather inconclusive. Finally, resin cement should be applied inside the root canal with an elongation tip and photoactivation should be delayed. (4) Conclusions: Contemporary concepts of adhesive cementation of glass fiber posts can indeed improve the bond between glass fiber posts, resin cement, and root canal dentin, however, evidence coming from long-term randomized prospective clinical trials is needed in order to obtain safer conclusions.

Perceptibility and acceptability of lightness difference of a single maxillary central incisor.

OBJECTIVES: The aim of this study was to assess the lightness difference perceptibility and acceptability thresholds, for a single maxillary central incisor, and to investigate possible differences in these thresholds regarding the direction (+ΔL* vs. -ΔL*), the observer group (dentists vs. laypersons), and the gender and age of the observers. MATERIALS AND METHODS: A series of images with varying lightness (L*), were created by altering the right maxillary central incisor of a male Caucasian, on a frontal view full-portrait image. Digital modification of one central incisor by 1 ΔL* unit resulted in 15 different images: one control, seven with increased and seven with decreased lightness. The images were presented in random order, on a digitally calibrated monitor, to 158 observers, grouped into 79 dentists, and 79 laypersons, who were asked to evaluate every image and answer whether they perceive a difference and if yes, whether they accept this difference. A multifactorial analysis of covariance was performed to analyze the perception and acceptance of any difference in the central incisors and to estimate the thresholds. The statistical significance level was α = 0.05. RESULTS: Overall, the magnitude of ΔL*, direction of ΔL*, observer group and age were each significant (p < 0.001), as was gender (p = 0.03). The effect of the magnitude of ΔL* interacted with its direction and the observer group (p = 0.045), and the effect of age interacted with the direction of ΔL*, and the gender and the group of the observers. Estimated 50%:50% perceptibility thresholds ranged from 0.1 to 2.7, and 50%:50% acceptability thresholds ranged from 2.3 to 4.5. Overall, dentists perceived lightness differences at lower magnitudes than laypersons; difference in lightness was perceived and accepted at lower magnitudes when the tooth become lighter instead of darker; and female observers perceived and accepted lightness differences at lower magnitudes compared to males. As age increased overall, differences of lightness were perceived and accepted at higher magnitudes. CONCLUSIONS: Perceptibility and acceptability of lightness differences of a single maxillary central incisor are affected by the magnitude and the direction of lightness change, as well as the gender, the age, and the type of the observers. CLINICAL SIGNIFICANCE: Even small changes in lightness are perceivable; however, thresholds of perception and acceptance are dependent on the magnitude and the direction of change and are also dependent on the observer, with women, dentists and younger people perceiving and accepting changes at lower magnitudes of ΔL*.

The Influence of a Single Infrapositioned Anterior Ankylosed Tooth or Implant Supported Restoration In Smile Attractiveness.

OBJECTIVES: To investigate the influence of a single infrapositioned ankylosed tooth or implant supported restoration, in smile attractiveness. MATERIAL AND METHODS: A series of 48 digital modified images, simulating a varying degree of infraposition(from 0.25 to 2.0 mm, with a step of 0.25 mm), was created for each one of the maxillary anterior tooth, by altering the full-portrait image of a smiling male adult, in medium and high smile lines. For the model with the high smile line, also a series of 24 digital modified images simulating infraposition of a single anterior tooth with a restored incisal edge was created. Smile attractiveness for each one of the images was evaluated from 160 participants (80 dentists and 80 laypersons), implementing a visual analog scale. RESULTS: For the images with the high smile line, an infraposition ≥ 0.25mm in central incisor's region and ≥ 0.5mm in the region of the lateral incisor or the canine, had a negative effect on the perceived smile attractiveness both for the dentists and the laypersons. Regarding the medium smile line, an infraposition ≥ 0.5mm in central and lateral incisor's region, had a negative effect on the perceived smile attractiveness for both groups of observers. In the area of the canine, infraposition ≥ 0.5mm for the dentists and ≥ 0.75mm for the laypersons, had a negative impact on the smile attractiveness. CONCLUSIONS: Even a minor infraposition of a single maxillary anterior ankylosed tooth or implant supported restoration, can reduce the perceived attractiveness of the face. Infraposition in canine's area can be better tolerated in a medium, compared to a high smile line. In patients with a high smile line prosthetic intervention in order to restore the incisal edge of an infrapositioned tooth, without to harmonize the gingival contour, can be beneficial for the lateral incisor, ineffective for the central incisor and unfavorable for the canine.

The impact of dental midline angulation towards the facial flow curve on the esthetics of an asymmetric face: Perspective of laypeople and orthodontists.

PURPOSE: The objective of the present article was to evaluate the impact of dental midline angulation in asymmetrical faces. MATERIALS AND METHODS: A full-portrait image was used to create a set of digitally modified images with a different degree of facial asymmetry, towards the right and the left side of the face respectively. Half of the images were designed with an equivalent angulation of the dental midline in respect to the curve of the lower third of the face and half of them without. Through a web survey, 250 laypeople and 250 orthodontists were asked to assess the attractiveness of each image separately. RESULTS: As the asymmetry of the face was increased, facial attractiveness was further decreased both for laypersons and orthodontists. For each one of the modified images, when the dental midline was following the curve that was formed from the inclination of the simulated asymmetry of the face, the smile attractiveness scores were significantly higher compared to a straight dental midline. CONCLUSION: Facial asymmetries derived from the inclination of the nose, the chin and the commissural line of the lips can significantly affect the smile attractiveness. An orientation of the dental midline towards the facial asymmetry in order to follow the facial curve, can be beneficial for the smile attractiveness compared to a perpendicular to the face dental midline. During the design of a smile, clinicians have to take into consideration deviations in facial midline, in order their restorations to be in harmony with the rest of the face. CLINICAL SIGNIFICANCE: During the design of a smile, clinicians have to take into consideration deviations in the facial midline, in order their restorations to be in harmony with the rest of the face.

Surface profile characterization of prefabricated resin composite veneers following simulated abrasion. An in vitro study.

Background: The surface of resin composite veneers is susceptible to the effect of the oral environment and surface profile characterization of different veneer systems is of importance to the longevity and clinical performance of the materials. The aim of the present study was to evaluate surface profile properties, as defined by gloss and roughness parameters, of prefabricated resin composite veneers (PCV) and compare with a laboratory resin composite (LRC) system, following simulated abrasion. Material and Methods: Twenty eight composite veneers equally divided to a prefabricated composite veneer (PCV) system and a laboratory resin composite (LRC) (control group) were tested following abrasion under a toothbrush simulator. Alterations in gloss (ΔGloss) and roughness (ΔSa, ΔSz, ΔSci, ΔSdr) parameters were examined (after- before abrasion) using a glossmeter and a 3D-optical profilometer, respectively. Correlation matrices between ΔGloss and ΔRoughness parameters were sought across the two resin composite veneer groups. Results: Τhere was weak evidence that the PCV group exhibited less change in surface gloss after experimental abrasion (PCV vs LRC: mean difference ΔGloss in GU, (MD: -1.7; 95% CI: -3.3, -0.1; p=0.04). For the roughness parameters, ΔSci in nm3/nm2 (MD : 0.2; 95% CI: 0.1, 0.3; p=0.002) and ΔSdr in percentage (MD: 10.6; 95% CI: 3.7, 17.5; p=0.004), exhibited the most pronounced differences between the groups with strong evidence demonstrating greater changes for the PCV group compared to the LRC. No strong correlation pattern could be identified between changes in gloss and roughness parameters across the groups. Conclusions: After abrasion, both PCV and LCR showed an increase in surface gloss, while the PCV group demonstrated a rougher core surface profile than LRC. Key words:Prefabricated, resin composite, veneers, gloss, roughness.

A digital protocol for the management of the restorative margin and the emergence profile of vertical prepared teeth.

PURPOSE: To describe a digital workflow for the management of the emergence profile and restoration's finishing line on vertical prepared teeth, utilizing a digital data set. MATERIAL & METHODS: The scan of the prepared teeth the day of the preparation, the scan of the provisional restoration placed on the preparation after soft tissue maturation and the scan of the provisional restoration outside of the oral cavity, are combined under a common data set, that can provide all the necessary information in order to design the final restoration. RESULTS: The presented digital technique can facilitate the implementation of the vertical preparation, as the desired finish line can be defined by the clinician and be transferred predictable to the dental lab. Current approach provides also, an alternative gingival management method, taken advantage of the displacement of soft tissue in the appointment of vertical preparation. CONCLUSIONS: The positioning of the final finishing line on vertical prepared teeth, the management of the soft tissue and the fabrication of the final restoration, can be facilitated combining digital data sets, that have been obtained during a distinct phase of the treatment.

Esthetic rehabilitation through crown lengthening and laminate veneers.

AIM: To describe a digital workflow utilizing 3D printing technology to guide esthetic crown lengthening and control tooth preparation. CLINICAL CONSIDERATIONS: After the initial intraoral and face scans, an esthetic treatment plan was performed digitally based on the patient's personality and face type using artificial intelligence-based 3D smile design software. A 3D-printed tray relined with silicone over a 3D-printed model was used for the mock-up. A 3D-printed guide was implemented to assist esthetic crown lengthening by incorporating, simultaneously, information about the desired free gingival line and the alveolar bone level. Based on the initial planning, a set of reduction guides was 3D printed to check and correct the tooth preparation. Prior to the start of construction of the final monolithic restorations, their design was verified using 3D-printed prototypes. A stabilization splint was digitally designed and 3D printed to protect and maintain the final result. CONCLUSIONS: Technologic advances can improve the predictability of an interdisciplinary esthetic approach. Digital planning can be transferred to clinical reality using a digital workflow, utilizing a set of appropriate 3D-printed guides, which can help to control clinical procedures based on the initial planning. CLINICAL SIGNIFICANCE: By following the proposed step-by-step workflow, clinicians can achieve predictable results through an interdisciplinary approach, guiding both the periodontal plastic surgery and the restorative treatment after an individualized CAD/CAD procedure for 3D-printed guides.

Accuracy of Indirect Veneer Mock-Up in Comparison to Diagnostic Wax-Up.

PURPOSE: To evaluate the dimensional discrepancy between the diagnostic wax-up and the resulting mock-up. MATERIAL AND METHODS: A maxillary model with misaligned teeth was scanned, and an initial cast was 3D printed. A total of 60 identical casts were 3D printed from the initial one after scanning. Based on a digital additive veneer wax-up on the six anterior teeth, 10 more casts were 3D printed. The specimens were allocated to seven groups (n = 10) as follows-group 1: transparent silicone matrix with a flowable light-cured composite resin; group 2: same as group 1 but with the addition of a prefabricated transparent tray; group 3: silicone impression putty (65 Shore A) and light-body silicone impression material with a dual-cured bisacryl resin; group 4: same as group 3 but without the light-body silicone; group 5: silicone laboratory putty (92 Shore A) with a dual-cured bisacryl resin; group 6: silicone laboratory putty (92 Shore A) with PMMA; group 7: wax-up casts (control). Scans from the mock-ups were coregistered, segmented, and superimposed with the scans from the wax-up. The difference between the mock-up and the wax-up was quantified by morphologic operations. Results were analyzed by Kruskal-Wallis test and Dunn post hoc test (P < .05). RESULTS: All mock-ups were larger than the wax-up. Significant differences were found for every labial surface third. The incisal third was the least accurate third while the middle third the most accurate. The most accurate were groups 2 and 5, and the largest discrepancy was observed in group 6. CONCLUSIONS: The analog mock-up differs dimensionally from the wax-up, regardless of the technique/materials used.

In-Vitro Comparison of Fracture Strength of Endocrowns and Overlays in Endodontically Treated Teeth Manufactured with Monolithic Lithium Disilicate and Zirconia.

To evaluate the fracture strength and the failure mode of endodontically treated molars restored with monolithic lithium disilicate and zirconia endocrowns and overlays. A total of 48 extracted mandibular molars were endodontically treated, decoronated 2 mm above the cementoenamel junction and divided into four 12-specimen groups. Group ELD: lithium disilicate endocrowns. Group EZ: monolithic zirconia endocrowns. Group OLD: lithium disilicate overlays. Group OZ: monolithic zirconia overlays. Overlays did not extend in the pulp chamber and endocrowns extended in the pulp chamber 2 mm. After adhesive bonding of the restorations, the specimens were subjected to thermocycling (×5000 cycles) and then to fracture resistance testing at lateral static loading (1 mm/min) at a universal testing machine. The failure mode of the specimens was qualitatively evaluated. Differences in means were compared using with t-tests for independent samples or Mann-Whitney test (p < 0.05). Weibull distribution analysis was also performed. Group ELD showed significantly higher fracture strength than all other groups (p = 0.001), and the highest Weibull modulus. Conclusions: Lithium disilicate endocrowns exhibit higher fracture strength and are more reliable compared to the other types of restorations examined. Endocrowns had more catastrophic failures compared to overlays.

Is a Wiggling-Motion Modified Two-Step Impression Technique as Accurate as Conventional Techniques in Restorative Dentistry?

BACKGROUND: The purpose of this study was to evaluate dental impression accuracy of one-step and two-step techniques compared to a modified two-step technique. METHODS: Four impression techniques were compared: (1) a one-step double mix (DM) technique, (2) a cut-out (CO) technique, in which space relief was created using a blade and a laboratory bur, (3) a membrane (ME) technique, in which space relief was created by placing a PVC membrane on top of the putty material during the primary impression, and (4) a wiggling motion (WI) technique, in which PVC membrane was placed and additional wiggling movements were performed during the first 20 s when the primary impression was seated upon the master model (MM). Impressions were poured with type IV stone. Casts were scanned with a laboratory scanner and measurements were made for each cast using three-dimensional analysis software. RESULTS: All groups presented differences compared to MM group, in at least one intra-abutment distance. Groups DM and ME presented the most significant differences, in three and two distances, respectively, whereas CO and WI presented one significant different distance compared to MM. There were no differences between MM and the four techniques for inter-abutment distances. CONCLUSIONS: WI yielded similar results with CO technique. Both performed better than the other groups.

Perception of smile attractiveness among laypeople and orthodontists regarding the buccal corridor space, as it is defined by the eyes. An innovated technique.

OBJECTIVE: To investigate whether there is a relationship between the distance between the iris and pupil with the ideal size of buccal corridors. MATERIALS AND METHODS: A full-portrait image of a male Caucasian was used to create a set of 11 digitally modified images with different buccal corridor space. A web-based cross-sectional study was designed and distributed via an online survey to 200 laypeople and 200 orthodontists to assess image attractiveness, using a Visual analogue scale. For the statistical analysis, Wilcoxon signed-rank and Mann-Whitney U tests were used. The significance level was set at p < 0.05. RESULTS: The response rate for laypeople was 70% (n = 139), while the rate for orthodontists was 73% (n = 146). For the layperson group, the maximum smile attractiveness score was 10% of buccal width reduction, compared to the iris-pupillary distance, while for the orthodontists, it was 20%. The attractiveness of the smile was significantly reduced in both groups when the buccal corridor width was increased in comparison to the iris-pupillary distance. CONCLUSION: The length between the mesial part of the iris and the distal of the pupil, may constitutes a landmark for the estimation of the desired width of the buccal corridor. CLINICAL RELEVANCE: Inter iris-pupillary distance can be the starting point in the smile designing process, in order to perform a facial driven selection of buccal corridor size.

In Vitro Trueness and Precision of Intraoral Scanners in a Four-Implant Complete-Arch Model.

(1) Background: New intraoral (IOS) and laboratory scanners appear in the market and their trueness and precision have not been compared. (2) Methods: Seven IOS and two laboratory scanners were used to scan a mandibular edentulous model with four parallel internal hexagon implant analogues and PEEK scan bodies. Digital models in Standard Tessellation Language (STL) were created. The master model with the scan bodies was scanned (×10) with a computerized numerical control 3D Coordinate Measuring Machine (CMM). The short (distances of adjacent scan posts) and long distances (distances of the scan posts with non-adjacent sites in the arch) among the centroids of the four analogues were calculated using CMM special software. Trueness (comparisons with the master model) and precision (intragroup comparisons) were statistically compared with ANOVA, chi-square and Tukey tests. (3) Results: Laboratory scanners had the best trueness and precision compared to all IOSs for long distances. Only iTero (Align Technologies Inc., Milpitas, CA, USA) had comparable trueness with one laboratory scanner in short and long distances. For short distances, CS3600 (Carestream Health, Inc., Rochester, NY, USA), Omnicam, Primescan (Sirona Dental Sys-tems GmbH, Bens-heim, Germany) and TRIOS 4 (3Shape A/S, Copen-hagen, Denmark) had similar trueness to one laboratory scanner. From those, only Omnicam and Primescan had similar precision as the same laboratory scanner. Most IOSs seem to work better for smaller distances and are less precise in cross-arch distances. (4) Conclusions: The laboratory scanners showed significantly higher trueness and precision than all IOSs tested for the long-distance group; for the short distance, some IOSs were not different in trueness and precision than the laboratory scanners.

Accuracy of Direct Composite Veneers via Injectable Resin Composite and Silicone Matrices in Comparison to Diagnostic Wax-Up.

Purpose: To evaluate the discrepancy between the diagnostic wax-up and the resulting direct veneers using different matrices. Materials and method: A total of 48 identical misaligned models, 12 wax-up models and one 'every other tooth' wax-up model were 3D printed. Group 1: Transparent silicone matrices with holes for the injection of the flowable composite. Group 2: The same procedure as group 1, but the first three teeth were restored using the matrix constructed from the 'every other tooth' wax-up model. Group 3: Transparent silicone matrices cut for each tooth and preheated resin composite. Group 4: The same procedure as group 3, but the loaded matrix was placed first in the clear plastic tray, which was used for the matrix's fabrication. Group 5: Wax-up models (control group). Scans from the veneers were superimposed with the scans from the wax-up and compared using the Patient Monitoring software. Measurements were made at the incisal, middle and cervical third. Kruskal-Wallis test and Dunn post-hoc test (p < 0.05) were used to analyze the results. Results: No statistically significant differences were found between groups 1 and 2 and the control. Group 3 was different from the control in the incisal and middle third, and group 4 was different in the cervical third. Conclusions: (1) Use of one or two matrices and the injection of flowable composite were accurate techniques. (2) Use of a matrix for each tooth combined with a pre-heated composite was the most inaccurate technique, but the use of the clear tray in combination with the matrix improved the accuracy.

Digitally designed reduction guide to correct proclined anterior teeth: An aid before fabricating trial restorations.

Restoring teeth with ceramic laminate veneers is most often an additive procedure. However, when proclined anterior teeth are being treated, a misfitting silicone matrix will lead to inaccurate trial restorations, affecting evaluation of the definitive esthetic result and leading to inaccurate definitive preparations. Using the digital technology, a 3-dimensionally printed reduction guide can be used to remove the proclined areas as the first step before trial restorations. Then, the trial restorations and made and then the definitive preparations made through them.

Coverage error of three resin composite systems to vital unrestored maxillary anterior teeth.

OBJECTIVE: Define the color of anterior teeth of a selected population and correlate it (by using coverage error [CE] and the frequency of best match) with the final color of all possible enamel-dentine combinations of three different resin composite systems. MATERIALS AND METHODS: Color of 636 vital unrestored anterior teeth (central incisors, lateral incisors and canines; n = 212) and disk specimens (12 mm diameter, varying thickness) corresponding to enamel-dentin combinations of all available enamel (0.5 mm and 1.0 mm thickness) and dentin shades (3.0 mm thickness) of Essentia, Enamel Plus HRi and IPS Empress Direct composite systems was measured using a clinical dental spectrophotometer (Spectroshade Micro). CE and frequency of best match for all composite systems were calculated for the measured in-vivo teeth color space. RESULTS: Natural in-vivo teeth exhibit higher lightness when compared to enamel-dentin composite combinations, independently of the enamel thickness used. The best (lowest) CE was found for IPS Empress, while the highest values were found for Enamel Plus Hri independently of tooth type and enamel thickness (p < 0.001). The use of 0.5 mm instead of 1.0 mm enamel thickness within enamel-dentin composite combinations resulted in a lower CE for in-vivo tooth color (p < 0.001). CONCLUSIONS: The color space defined by all possible enamel-dentin combinations of the studied resin composite systems does not fully match the color range of anterior teeth. All composite systems examined lack combinations with lightness values as high as the population's. IPS Empress Direct composite system represented better the in-vivo teeth color. CLINICAL SIGNIFICANCE: The use of 0.5 mm enamel shade thickness is suggested when building layered restorations, as it provided better color coverage than using 1.0 mm thickness.

Digital selection of composite resin shade using cross polarized photography and a standardized white balance gray reference card.

PURPOSE: The aim of the present case report was to describe, through a clinical case, a step-by-step technique, for the digital selection of composite resin shades using cross polarization and white balance employing a standardized reference card. CASE DESCRIPTION: After intraoral impression, a digital diagnostic wax up was developed. A 3D printed cast was used to fabricate a lingual polyvinyl siloxane matrix. First a cross-polarized image of the contralateral central incisor was taken in RAW format, using a gray reference card. The digital image was manipulated using this card as a reference, to obtain reliable color values. The obtained color values, from the contralateral central incisor, were used in order to digitally find the closest combination of enamel and dentin shades between various composite systems. The values of a combination of shades of composite systems, was captured using cross-polarized images, with a gray reference card, after digital image manipulation of composite specimens, which have been created for this purpose. CONCLUSIONS: Digital evaluation and selection of composite resin system and shade, using a white balance reference card assisted by cross polarized photography, could help achieving more predictable outcomes using the stratification technique with composites. Key words:Restoration shade, composite color, composite resin, direct restoration, digital protocol.

Analog-digital hybrid impression technique in an elderly patient: A case report.

The hybrid impression technique consists of an initial alginate impression that provides a preoperative cast upon which a diagnostic wax-up and a silicone index are made. The wax-up is digitized; thus, the final altered digital impression is limited to absolute minimum time, effort and ensures comfort for the patient.

Color comparison of three layered resin composite systems with three shade guides.

OBJECTIVE: To investigate the color difference using both ΔE*ab and CIEDE2000 formulas of all combinations of all enamel and dentin shades of three different composite systems with three different shade guides, to compare the coverage error (CE) of the shade guides for each composite and to investigate whether coverage error is affected by enamel shade layer thickness (0.5 vs 1 mm). MATERIALS AND METHODS: Disk specimens from all enamel and dentin shades of Essentia, Enamel Plus HRi, and IPS Empress Direct composites were fabricated. Color measurements were performed for all enamel-dentin combinations and for two thicknesses per enamel shade: 0.5 and 1 mm. Color was measured for three shade guides: Vitapan Classical, 3DMaster, and Ivoclar. Minimum color difference between layered composites and shade tabs, closest shade tab match and CE of all shade guides were calculated for all composite shade combinations. RESULTS: In most cases, the closest match was a mismatch. CE of 3DMaster was significantly lower for IPS Empress Direct and Enamel Plus HRi at 0.5 mm enamel thickness. Shade guides exhibited higher lightness values compared to composites and composites lower chroma values compared to shade guides. CONCLUSIONS: Shade guides do not match well to the layered composites. 3DMaster performed better than the other two shade guides, in most cases.

Influence of lightness difference of single anterior tooth to smile attractiveness.

OBJECTIVES: To evaluate the influence of lightness difference of a single anterior maxillary tooth on difference smile attractiveness. METHODS: A frontal view full-portrait image of a smiling male Caucasian, was digitally modified altering a single tooth, creating a series of images with varying lightness (ΔL) for the maxillary central, lateral and canine. A total of 160 participants (80 dentists, 80 laypersons) were asked to fill out a Visual Analog Scale questionnaire for every image recording smile attractiveness. RESULTS: For central incisors ΔL≥1 negatively affected attractiveness. There was a higher tolerance for lightness mismatch when one lateral incisor is lighter and the same applies when the canine was darker. Difference in lightness affected smile attractiveness both for dentists and laypersons. No difference between males and females was observed for the dentists. For laypersons, females perceived smiles with lightness difference as significantly less attractive compared to males. Dentist's age did not affect smile attractiveness perception. Younger laypersons perceived darker color, as less attractive. CONCLUSIONS: Changes in lightness of a single anterior tooth significantly affected smile attractiveness in a different way for the central vs lateral vs canine. For the dentists, age and gender did not significantly affect smile perception, in contrast to laypeople. CLINICAL SIGNIFICANCE: Lightness differences of a single anterior tooth affects smile attractiveness.

Accuracy of complete-arch implant impression made with occlusal registration material.

STATEMENT OF PROBLEM: Which impression material, impression tray type, and implant impression technique combination produces the most accurate complete-arch impression is unclear. PURPOSE: The purpose of this in vitro study was to compare the implant impression accuracy of a completely edentulous arch made with addition silicone occlusal registration material and an open tray with the implant impression accuracy of other conventional impression techniques. MATERIAL AND METHODS: A master cast was fabricated from Type IV gypsum with four 3.8-mm diameter implants with internal hexagon located in the area of mandibular canines and first molars. Impressions (N=60) were made from the master cast using the 6 techniques investigated: group B-OC-N with occlusal registration impression material (B), open custom tray (OC), and nonsplinted impression pins (N); group B-OS-N with occlusal registration impression material (B), open plastic perforated stock tray (OS), and nonsplinted impression pins (N); group PE-OC-N with polyether medium-body impression material (PE), open custom tray (OC), and nonsplinted impression pins (N); group PE-OC-S with polyether medium-body impression material (PE), open custom tray (OC), and impression pins splinted (S) with autopolymerizing resin cut after 17 minutes and reconnected; group PE-CC-N with polyether medium-body impression material (PE), closed custom tray (CC), and nonsplinted impression pins (N); group PVS-CS-N with simultaneous double-mix polyvinyl siloxane impression material (PVS), closed stock perforated metal tray (CS), and nonsplinted impression pins (N). Type IV gypsum casts were fabricated 24 hours after making the impressions. A computerized numerical control 3D coordinate measuring machine was used to measure the absolute differences of the distances between the centroids of the 4 implants among the casts produced and the distances measured at the master cast. The Kruskal-Wallis test was used to determine differences among the experimental groups (α=.05). The Mann-Whitney U post hoc analysis was used for all group combinations. RESULTS: No significant differences were found between the test groups B-OC-N and PE-OC-S, which were more accurate than the other groups. Group B-OS-N resulted in the least accurate impressions of all experimental groups. Group PE-OC-S resulted in more accurate impressions than the PE-OC-N group. No statistically significant differences were found between groups PE-OC-N and PE-CC-N or between groups PVS-CS-N and PE-CC-N. CONCLUSIONS: For complete edentulism, the use of silicone occlusal registration material with an open custom tray and nonsplinted impression pins resulted in impressions as accurate as those produced with PE open custom tray with splinted impression pins. These 2 techniques resulted in more accurate impressions than the other 4 techniques studied.