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Background: The aim of this study was to evaluate the changing levels of stress among dental students during 8 months of a basic manual skills course in the preclinical year and to examine the association between stress and dental performance., Methods: A longitudinal study was conducted in the 2023 academic year in a total of 58 (male = 17 and female = 41; mean age = 26.43, range 22-33) undergraduate dental students at Tel Aviv University of dentistry during their fourth year of study. Depression Anxiety Stress Scale (DASS-21) and Dental Environment Stress (DES) questionnaires were used to assess the psychological well-being and the severity of DASS symptoms experienced by the students. The students' dental performances were assessed using two manual tests on plastic teeth. The questionnaires and the manual tests were used at three periods of time, T0, T1, and T2. Wilcoxon signed-rank tests were performed to compare the DASS scores and DES stressors of dental students between T0, T1, and T2. Kendall's nonparametric correlations were calculated to investigate the relationships of DES stressors and depression, anxiety, and stress scores with manual performance., Conclusions: The perception of high stress by dental students is due to the stressful education process of the preclinical year. There is an inverse correlation between the lower level of anxiety and the increase level of dental performance with 74% of the variance in dental performance explained by the anxiety score. Work-related stressors such as manual skills might reduce dental performance in contrast to non-work-related factors such as financial obligations, personal issues, and family factors, which might increase student dental performance., Competing Interests: The authors declare no conflicts of interest., (Copyright © 2024 Diva Lugassy et al.)

Background: The purpose of this pilot in-vitro study was to assess the effect of sterilization on the intra-implant axis, inter-implant axis, intra-implant distance and inter-implant distance of three implants in a straight line by using laboratory scanner (LBS) versus intra-oral scanner (IOS) with intra-oral scan bodies (ISB)., Methods: A printed 3D model with three internal hex analogs in the positions 15#,16#,17# was used. Zirkonzhan (ZZ) intra-oral scan body (ISB), two-piece titanium was used. The ZZ ISBs were scanned by 7 Series dental wings (LBS) and 30 times by Primescan (IOS) pre sterilization and 30 times post sterilization. For each scan (pre and post) stereolithography (STL) file was created and a comparison between all the scans pre sterilization and post sterilization were superimposed on the laboratory scan by using a 3D analyzing software. A Kolmogorov-Smirnov test performed followed by Wilcoxon Signed Ranks tests. (p < 0.05) Results: Post sterilization of the ZZ ISB, the mean errors were significantly increased for the inter-implant distances (p < 0.0005), intra-implant distances 1,2,3 (p < 0.0005), intra-implant axis 1,3 (p < 0.0005) and inter-implant axes 13,23 (p < 0.05). In contrast, the mean errors for intra-implant axis 2 (p < 0.0005) and inter-implant axis 12 (p < 0.0005) were significantly reduced., Conclusions: ZZ ISB showed changes in all four parameters after sterilization. The middle ISB had the largest changes in mean error regarding all four parameters. Sterilization process may affect the three-dimensional (3D) structure of the ZZ ISB after three cycles. There is a lack in the literature in this field and there is a need for further studies to explore the effect of sterilization (multiple cycles) on different ISBs and for creating an approved guidelines regarding the amount of sterilization for each ISB in the industry., (© 2024. The Author(s).)

Oral malodor still constitutes a major challenge worldwide. A strong effort is invested in eliminating volatile sulfur compound-producing oral bacteria through organic natural products such as essential oils. Fusobacterium nucleatum is a known volatile sulfur compound-producing bacteria that inspires oral malodor. The aim of the present study was to test the effect of lavender essential oil on the bacterium's ability to produce volatile sulfide compounds, the principal components of oral malodor. Lavender ( Lavandula angustifolia ) essential oil was extracted by hydrodistillation and analyzed using GC-MS. The minimal inhibitory concentration (MIC) of lavender essential oil on Fusobacterium nucleatum was determined in a previous trial. Fusobacterium nucleatum was incubated anaerobically in the presence of sub-MIC, MIC, and above MIC concentrations of lavender essential oil, as well as saline and chlorhexidine as negative and positive controls, respectively. Following incubation, volatile sulfur compound levels were measured using GC (Oralchroma), and bacterial cell membrane damage was studied using fluorescence microscopy. Chemical analysis of lavender essential oil yielded five main components, with camphor being the most abundant, accounting for nearly one-third of the total lavender essential oil volume. The MIC (4 µL/mL) of lavender essential oil reduced volatile sulfur compound secretion at a statistically significant level compared to the control (saline). Furthermore, the level of volatile sulfur compound production attributed to 1 MIC of lavender essential oil was in the range of the positive control chlorhexidine with no significant difference. When examining bacterial membrane damage, 2 MIC of lavender essential oil (i.e., 8 µL/mL) demonstrated the same, showing antibacterial membrane damage values comparative to chlorhexidine. Since lavender essential oil was found to be highly effective in hindering volatile sulfur compound production by Fusobacterium nucleatum through the induction of bacterial cell membrane damage, the results suggest that lavender essential oil may be a suitable alternative to conventional chemical-based anti-malodor agents.

Background : In everyday dentistry, monolithic single crowns can be cemented with self-adhesive resin cements. The aim of this in vitro study was to evaluate how the marginal adaptation of full monolithic zirconia-reinforced lithium silicate (ZLS) single crowns is influenced by three different self-adhesive resin cements. Methods : Forty-five typodont teeth fully prepared for full monolithic crowns were divided into three groups (fifteen each) for the use of three different self-adhesive resin cements. A fourth control group (Temp-bond) was created by taking five teeth from each group before cementation with self-adhesive resin cements. All forty-five abutments were scanned using a Primescan intra-oral scanner (IOS), followed by computer-aided design (CAD) and computer-aided manufacturing (CAM) of zirconia-reinforced lithium silicate (ZLS) full crowns using a four-axis machine. Initially, the crowns of the control group were fixed to the abutments using Temp-bond, and the marginal gap was evaluated using a scanning electron microscope (SEM). After removing the control group crowns from the abutments, fifteen crowns in each group were cemented using a different self-adhesive resin cement and observed under SEM for evaluation of the marginal gap. A Kolmogorov-Smirnov test was performed, indicating no normal distribution ( p < 0.05), followed by Mann-Whitney tests (α = 0.05). Results : The total mean marginal gap of the temp-bond control group was significantly lower compared to all three groups of self-adhesive resin cement ( p < 0.0005). The total mean marginal gap of the G-cem ONE group was significantly lower compared to the TheraCem group ( p < 0.026) and RelyX U200 group ( p < 0.008). The total mean marginal gap of the TheraCem group was significantly higher than the G-cem ONE group ( p < 0.026) but showed no significant difference with the RelyX U200 group ( p > 0.110). Conclusions : All four groups showed a clinically acceptable marginal gap (<120 microns). Although all three groups of self-adhesive resin cement showed a significant increase in the marginal gap compared to the temp-bond control group, they were within the limits of clinical acceptability. Regarding the marginal gap, in everyday dentistry, it is acceptable to use all three self-adhesive resin cements, although the G-cem ONE group exhibited the lowest marginal gap for ZLS single crowns.

This study aimed to compare the impact of CAD/CAM closed systems and open systems on the marginal gap of monolithic zirconia-reinforced lithium silicate (ZLS) ceramic crowns, as both systems are used in everyday dentistry, both chair-side and laboratory. For the closed system, 20 plastic teeth were scanned by a Primescan intra-oral scanner (IOS), and for the open system, the same number of plastic teeth were scanned by Trios 4 IOS. For the closed system, CEREC software was used, and for the open system, EXOCAD software was used. All 40 ZLS crowns were grinded by the same four-axis machine and cemented with Temp-bond, followed by self-adhesive resin cement. For each type of cement, an evaluation of the marginal gap was conducted by scanning electron microscopy (SEM). Before comparisons between the groups, a Kolmogorov-Smirnov test was performed on the study variables showing a normal distribution ( p > 0.05). Independent T tests (α = 0.05) and paired-sample T tests (α = 0.05) were used. The independent T test found no significant mean marginal gap differences in the zirconia-reinforced lithium silicate crowns bonded with Temp-bond and scanned by Primescan (28.09 μm ± 3.06) compared to Trios 4 (28.94 μm ± 3.30) ( p = 0.401), and there was no significant mean marginal gap differences in zirconia-reinforced lithium silicate crowns bonded with self-adhesive resin cement (Gcem ONE) and scanned by Primescan (46.70 μm ± 3.80) compared to Trios 4 (47.79 μm ± 2.59) ( p = 0.295). Paired-sample T tests showed significantly higher mean marginal gaps with Gcem ONE compared to Temp-bond for the total mean marginal gap when scanning with Primescan ( p = 0.0005) or Trios 4 ( p = 0.0005). In everyday dentistry, both closed systems (Primescan with Cerec) and open systems (Trios 4 with Exocad) can be used to achieve an acceptable (<120 µm) marginal gap for ZLS CELTRA ® DUO single crowns. There is a significant difference between cementation with Temp-bond and Gcem ONE self-adhesive resin cement ( p < 0.05).

Background : In this study, we aimed to compare the effects of conventional and digital impressions on several parameters (inter-implant distance, intra-implant distance, inter-implant axis, and intra-implant axis) of three implants in curved lines and straight lines by using a laboratory scanner (LBS) versus an intra-oral scanner (IOS). Methods : Two 3D models were fabricated using a printer, each model with three internal hex implants analogues at the positions of 15#,16#,17# (straight line) and 12#,13#,14# (curved line). Standard intra-oral scan bodies (ISBs) were used, and the two models were scanned using 7 Series dental wings (LBS, reference model), followed by ten scans with Primescan (digital method). Standard Tessellation Language (STL) files were created. Five polyether impressions were taken from each model (straight and curved), and gypsum type 4 models were poured; each model was scanned five times to create a total of 25 STL files for each group (conventional method). The comparison between all the STL files (conventional and digital) was made by superimposition of the STL files on the STL reference model laboratory file using a 3D analyzing software. A Kolmogorov-Smirnov test was performed, followed by Mann-Whitney tests and Wilcoxon signed-rank tests. ( p < 0.05). Results : For the conventional method, the mean errors were significantly higher for the curved line model (12-14) compared to the straight line model (15-17) for most parameters ( p < 0.05). For the digital method, the mean errors were significantly higher for the curved-line model (12-14) compared to the straight line model (15-17) in half of the parameters ( p < 0.05). Within the curved line model (12-14) and the straight line model (15-17), the mean errors between the conventional method and the digital method were not significant for most variables. Conclusions : The difference between curved lines and straight lines has an impact on the mean error of the conventional method. Both methods are reliable for straight and curved lines in partially dentate situations.

The configuration of implant-supported prostheses is considered to influence the magnitude of stress concentrations, affecting their survival rate. The purpose of this study is to determine, through strain gauge measurements during load application, the dispersion and magnitude of strain concentrations in different implant-supported prosthesis designs. All designs matched those commonly used in posterior partially edentulous states. Three implants were inserted into an epoxy resin model (PLM-4B Vishay Measurements Group Inc., Raleigh, NC, USA), allowing for the delivery of three- and four-unit crowns in different cemented configurations. Loads were applied at vertical and oblique directions over the cast crowns in six different configurations representing various posterior partially edentulous restorations. The readings from the strain gauges adhered to the implant necks' presented data on implant strain. Prostheses including cantilevers showed the highest strain among the three-unit prostheses within the prosthetic complex, and three single units showed the least (8133 µs vs. 201 µs, respectively). Angulated load application also had a role in amplifying the strains recorded, resulting in total strains of between 3.5 and 20 times higher than during vertical loading in all configurations. It can be concluded that the configuration of implant-fixed partial prosthesis changes the loads engaging the restoration, the implant, and, probably, the supporting bone.

Background: The purpose of this in vitro study was to compare the inter-implant distance, inter-implant axis, and intra-implant axis of three implants in a straight line by using a laboratory scanner (LBS) versus an intra-oral scanner (IOS) with two different intra-oral scan bodies (ISBs)., Methods: A 3D model was printed with internal hex implant analogs of three implants in positions 15#, 16#, and 17#. Two standard intra-oral scan bodies (ISBs) were used: MIS ISB (two-piece titanium) and Zirkonzhan ISB (two-piece titanium). Both ISBs were scanned using 7 Series dental wings (LBS) and 30 times using Primescan (IOS). For each scan, a stereolithography (STL) file was created and a comparison between all the scans was performed through superimposition of the STL files by using 3D analysis software (PolyWorks ® 2020; InnovMetric, Québec, QC, Canada). A Kolmogorov-Smirnov test was performed followed by a Mann-Whitney test ( p < 0.05)., Results: The change in inter-implant distance for the MIS ISB was significantly lower compared to the ZZ ( p < 0.05). The change in intra-implant angle was significantly lower for the ZZ ISB compared to MIS ( p < 0.05). The changes in inter-implant angle between the mesial and middle and between the middle and distal were significantly lower for MIS compared to ZZ in contrast to mesial to distal, which was significantly higher ( p < 0.05)., Conclusions: Both ISBs showed differences in all the parameters between the LBS and the IOS. The geometry of the scan abutment had an impact on the inter-implant distance as the changes in the inter-implant distance were significantly lower for the MIS ISB. The changes in the intra-implant angle were significantly lower for the ZZ ISB. There is a need for further research examining the influence of geometry, material, and scan abutment parts on the trueness.

Aim: To evaluate CAD/CAM milling vibrations related to zirconia disk design, framework, and location of digital crown nesting during zirconia soft milling., Materials and Methods: In the present in vitro study, 25 round zirconia disks of 98 mm (R group) and 15 D-shaped zirconia disks of 71 mm (D group) were placed in a 5-axis CAD/CAM milling unit. The R group had 3 crown milling sites (n = 75) and the D group had 2 crown milling sites (n = 30). In the R group, site A was located 57 mm, site B was 92 mm, and site C was 123 mm from the machine holder attachment. In the D group, site A was 57 mm and site C was 123 mm from the machine holder attachment. A vibration meter (VB-8200; Lutron) was connected to the disk holder, and data (mm/second) were collected during the milling process at the different nesting locations. One-way ANOVA with post-hoc tests and Bonferroni correction for multiple tests were used to compare the groups (α = 0.05)., Results: In the R group, site C exhibited the highest mean vibration values compared with site A (P = 0.001). The first and second cutting tools (2.5 and 1 mm) exhibited statistically significant differences between the D and R groups at milling sites A and C (P < 0.001 and P = 0.003, respectively)., Conclusions: Milling vibration increased as the distance between the machine holder arm and a digitally nested site increased. Round zirconia disks induced higher vibration values compared with D-shaped disks.

Background: The purpose of the study was to evaluate the changes of light reflection% on two materials (monolithic zirconia and lithium disilicate) after using two external staining kits following by thermocycling., Methods: Specimens were sectioned from monolithic zirconia (n = 60) and lithium disilicate ( n = 60) then divided into six groups ( n = 20). Two different types of external staining kits were used and applied to the specimens. The light reflection% was measured before staining, after staining and after thermocycling using a spectrophotometer., Results: The light reflection% of zirconia was significantly higher compared to lithium disilicate at the beginning of the study ( p = 0.005), after staining with kit 1 ( p = 0.005) and kit 2 ( p = 0.005) and after thermocycling ( p = 0.005). For both materials, the light reflection% was lower after staining with Kit 1 compared to kit 2 ( p < 0.043). After thermocycling, the light reflection% of lithium disilicate increased ( p = 0.027) and was unchanged with Zirconia ( p = 0.527)., Conclusions: There is a difference between the materials regarding light reflection% as the monolithic zirconia showed higher light reflection% comparing lithium disilicate throughout the entire experiment. For lithium disilicate, we recommend using kit 1 as we found that, after thermocycling, the light reflection% of kit 2 was increased.

Objective: This study aimed to evaluate the shear bond strength (SBS) of orthodontic brackets bonded to three-dimensionally (3D)-printed materials after various surface treatments and artificial aging compared with that bonded to computer-aided design/computer-aided manufacturing (CAD-CAM) polymethyl methacrylate (PMMA)-milled materials., Methods: Eighty cylindrical specimens were 3D printed and divided into the following four subgroups (n = 20 each) according to the surface treatment and artificial aging procedure. Group A, sandblasted with 50 μm aluminum oxide particles (SA) and aging; group B, sandblasted with 30 μm silica-coated alumina particles (CO) and aging; group C, SA without aging; and group D, CO without aging. For the control group, 20 CAD-CAM PMMA-milled cylindrical specimens were sandblasted with SA and aged. The SBS was measured using a universal testing machine (0.25 mm/min), examined at ×2.5 magnification for failure mode classification, and statistically analyzed ( p = 0.05)., Results: The retention obtained with the 3D-printed materials (groups A-D) was higher than that obtained with the PMMA-milled materials (control group). However, no significant difference was found between the study and control groups, except for group C (SA without aging), which showed significantly higher retention than the control group (PMMA-SA and thermocycling) ( p = 0.037). Study groups A-D predominantly exhibited a cohesive specimen mode, indicating specimen fracture., Conclusions: Orthodontic brackets bonded to 3D-printed materials exhibit acceptable bonding strengths. However, 3D-printed materials are prone to cohesive failure, which may result in crown fractures.

A failed implant site is prone to reduced alveolar bone volume, both horizontally and vertically. The present study assessed the outcome of using cancellous bone block allografts for ridge reconstruction following the removal of failed implants associated with severe bone loss. Individuals presenting with failed implants and massive bone loss were included. Cancellous bone block allografts were used for reconstruction of the atrophic alveolar ridge. Radiographic evaluation at 6 months postgrafting revealed favorable bone healing, allowing implant placement. Bone biopsy samples were taken during implant placement. Twenty-four blocks and 58 implants were placed in 16 patients. Over a mean follow-up time of 40 ± 15 months, the mean bone gain was 5 ± 0.5 mm horizontally and 7 ± 0.5 mm vertically. Block and implant survival rates were 96% (1 block failed) and 95% (3 implants failed), respectively. Histomorphometrically, the mean percentage of newly formed bone was 40%, with 20% residual cancellous block allograft and 40% marrow and connective tissue. Cancellous bone block allograft is a viable treatment alternative for reconstructing the alveolar ridge to achieve a successful second reimplantation, even in the presence of initial severe bone loss.

GBR (Guided Bone Regeneration) procedure is challenged by the risk of membrane exposure to the oral cavity and contamination. The barrier quality of these membranes serve as a mechanical block from bacterial penetration into the GBR site. The purpose of this in vitro study was to evaluate the antibacterial effect of three commercial non-resorbable polytetrafluoroethylene membranes. (Two d-PTFE membranes and one double layer e-PTFE +d-PTFE membrane). A validated in vitro model with two bacterial species (Streptococcus sanguinis and Fusobacterium nucleatum) was used. Eight samples from membrane each were placed in a 96-well microtiter plate. The experimental and positive control groups were exposed to a bacterial suspension which involved one bacterial species in each plate. Bacterial growth was monitored spectrophotometrically at 650 nm for 24 h in temperature controlled microplate spectrophotometer under anaerobic conditions. One- Sample Kolmogorov−Smirnov Normal test and the Kruskal−Wallis test was used for the statistical analysis. As shown by the bacterial growth curves obtained from the spectrophotometer readings, all three membranes resulted in bacterial growth. We have not found a statistical difference in F. nucleatum growth between different membrane samples and the positive control group. However, S. sanguinis growth was reduced significantly in the presence of two membranes (CYTOPLAST TXT-200 and NeoGenTM) when compared to the control (p < 0.01). The presence of Permamem® had no significant influence on S. sanguinis growth. Some types of commercial non-resorbable PTFE membranes may have an impact on the growth dynamics of specific bacterial species.

Background: Substantial effort is dedicated to finding the most favorable parameters that will ensure low aftercare demands among edentulous patients wearing mandibular implant supported overdentures (MISODs). The purpose of this retrospective cohort study was to compare prosthetic aftercare between MISOD patients with a simultaneous (group A) vs. a three-week settling in period (group B) prior to attachment incorporation., Methods: Forty-five patients enrolled in this study. Two implants per patient were placed using a two-stage implant insertion protocol. Second-stage surgery was performed after three months. All patients received ball attachments using the direct (chairside) incorporation method. Twenty-two patients received their dentures with simultaneous attachment activation and the rest-twenty-three patients-after a three-week settling in period. Patients' files were scanned for aftercare visits. Outcome parameters included sore spot relief, attachment incorporation, and denture repair. Additionally, gingival index measurements were compared. Confounding factors included age, gender, and implant dimensions., Results: The mean follow-up for the entire cohort was 84 ± 21 months, and the range 39-120 months. The mean number of visits for group A vs. B respectively: pressure sores relieve (3.63 ± 0.84 vs. 3.71 ± 0.61, p = 0.581), liner exchange due to loss of retention (2.09 ± 1.03 vs. 2.31 ± 1.04 p = 0.487), and gingival index (1.3 ± 0.3 vs. 1.03 ± 0.2, p = 0.653) exhibited no statistically significant differences between the tested groups. No statistically significant differences between the groups were also noted for the denture repair aftercare treatments ( p = 0.318) and the independent variables including age, gender, and implant length., Conclusions: Prosthetic aftercare in MISOD wearers is similar whether a simultaneous or a three-week settling in period for attachment incorporation is applied.

Impression technique is one of the factors affecting restoration fit accuracy, which is a major aspect influencing its survival. The purpose of this study is to compare, in vivo, the effect of two commonly used Vinyl Polysiloxane (VPS) impression techniques on the metal framework fitting of fixed partial dentures. Ninety-two consecutive patients, diagnosed as partially edentulous, treated by fixed partial denture restorations, participated in the study. Group 1-impressions ( n = 44) were subjected to the 1-step technique, while group 2 impressions ( n = 48) were subjected the 2-step technique. Three accuracy assessment common methods: probe, tactile sense and radiographic test, were used to validate the clinical fit of the metal framework. Misfit was defined as even one test failure. Twenty-one (22.8%) out of 92 metal frameworks exhibited metal frameworks misfit, whereas the other 71 (77.2%) were found to be accurate. Group 1 presented significantly ( p = 0.04) more metal frameworks misfit, 14/44 (31.8%) vs. 7/48 (14.6%). Restoration location (maxilla vs. mandible) had no statistically significant impact on the results ( p = 0.461). The use of the VPS putty/wash 2-step impression technique is recommended to improve the clinical fit of fixed partial denture restorations.

Statement of Problem: One of the disadvantages of a cemented implant restoration is the potential difficulty of retrieving it. The restoration may be destroyed during removal., Purpose: The purpose of this retrospective clinical study was to assess the long-term survival rates of cemented posterior metal ceramic implant-supported prostheses (ISPs) with a metal screw access hole., Material and Methods: During a 12-year period, 274 cemented ISPs with an abutment screw access hole in the metal framework were assessed and served as the study group, and 119 conventional cemented ISPs (without access hole) served as the control group. Participants were followed every 6 months in the first year and once a year subsequently. Ceramic fracture, screw loosening, and refabrication were the prosthetic outcome parameters evaluated at the recall. The Pearson Chi square and Fisher exact test were used to compare the outcome parameters between the control and study groups., Results: A total of 1005 implants and 393 ISPs were evaluated. Ceramic fracture occurred in 6.6% of the ISPs (6.2% test and 7.6% control). Screw loosening occurred in 3.28% of the test group and 3.36% of the control group. Refabrication of ISPs was done in 2.79% of all restorations, (1.45% test and 6.72% control [P=.012])., Conclusions: Within the limits of this study, preparing cemented ISPs with a screw access hole in the metal framework improves ISP survival rates over time and lowers the cost of maintenance without increasing the risk for porcelain fracture or screw loosening., (Copyright © 2016 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.)

Marginal fit is an important clinical factor that affects restoration longevity. The accuracy of three polyvinyl siloxane putty-wash impression techniques was compared by marginal fit assessment using the nondestructive method. A stainless steel master cast containing three abutments with three metal crowns matching the three preparations was used to make 45 impressions: group A = single-step technique (putty and wash impression materials used simultaneously), group B = two-step technique with a 2-mm relief (putty as a preliminary impression to create a 2-mm wash space followed by the wash stage), and group C = two-step technique with a polyethylene spacer (plastic spacer used with the putty impression followed by the wash stage). Accuracy was assessed using a toolmaker microscope to measure and compare the marginal gaps between each crown and finish line on the duplicated stone casts. Each abutment was further measured at the mesial, buccal, and distal aspects. One-way analysis of variance was used for statistical analysis. P values and Scheffe post hoc contrasts were calculated. Significance was determined at .05. One-way analysis of variance showed significant differences among the three impression techniques in all three abutments and at all three locations (P < .001). Group B yielded dies with minimal gaps compared to groups A and C. The two-step impression technique with 2-mm relief was the most accurate regarding the crucial clinical factor of marginal fit.

Objective: To evaluate the influence of different cement combinations on coronal microleakage in restored endodontically treated teeth using dye penetration., Method and Materials: Human, noncarious single-rooted extracted premolars (n = 60) were divided into four experimental groups (each n = 15). After endodontic treatment, different combinations of cements were used to lute prefabricated posts and complete crown restorations: zinc phosphate cement applied on posts and cast crowns (Z) or on zinc phosphate cement posts and resin cement applied on cast crowns (ZR); resin cement applied on posts and zinc phosphate cement applied on cast crowns (RZ); and resin cement applied on posts and cast crowns (R). After artificial aging through thermal cycling (5°C to 55°C) for 2,000 cycles at 38 seconds for each cycle and 15 seconds of dwell time, specimens were immersed for 72 hours in basic fuchsin at 37°C. A buccolingual section was made through the vertical axis of specimens. A Toolmaker's microscope (Mitutoyo) was used to measure (um) dye penetration. The Kruskal-Wallis nonparametric test was used to determine intergroup difference. A nonparametric Mann-Whitney test compared each group regarding its maximal linear penetration depths on the mesial and distal aspects of each specimen (a = 0.05)., Results: Dye staining was evident to some degree in all specimens. Among groups Z, ZR, and RZ, no significant difference was shown in dye-penetration depths (mean penetration scores 1,518 to 1,807 um). However, dyepenetration depth was significantly lower in group R compared to the other groups (mean penetration score 1,073 um) (P < .05)., Conclusions: Under study conditions, the cement combination offering the best coronal sealing was the one using only resin cement for both posts and crown restorations.

A precise impression is necessary for fabricating an accurately fitting cast restoration. For this purpose, Polyvinyl Siloxane (PVS) impression materials are extremely popular because of their combination of excellent physical properties, handling characteristics and dimensional stability. Its excellent clinical features remain unaffected if simple measures are guarded. This review presents several impression techniques using PVS and recommends the one that provides the most accurate impression, utilizing the superior qualities of the PVS. The one step impression technique where no control of wash bulk and thickness exists, is considered to be the least accurate impression method with measured discrepancies as large as 7 times the original inter preparation distance and 40 times the original cross arch dimensions. Furthermore, the direct contact between the less refined putty material and the tooth preparation, as well as the high prevalence of air bubble entrapment, seriously compromises restoration longevity. The two stage impression technique has proved to produce the most accurate and reliable impressions due to complete control of the wash bulk and thickness entailed. The ideal wash bulk thickness should range between 1 to 2.5 mm all around the abutment tooth in order to minimize distortion of its subsequent die. Using a "Putty Tray" at the first stage with a predetermined space encircling the abutments will allow the wash to flow to its ideal uniform bulk size at the second stage. A uniform bulk size will prevent differential setting contraction and uneven changes at the dimensions of the die. The easiest and most clinically applicable method to achieve the desired space around the preparations is by loading the Putty material with the temporary crowns in place, followed by their removal at the second stage and occupation of the created space by the wash. In general, less control of wash bulk will result in either insufficient or excessive wash material which will determine uneven dimensional changes in the impression. This, in turn, will produce ill fitting cast restoration.