Marginal integrity of prototype bioactive glass-doped resin composites in class II cavities.

OBJECTIVES: This in vitro study examined the marginal integrity of experimental composite materials doped with bioactive glass (BG). MATERIALS AND METHODS: Class-II MOD cavities were prepared and restored with one of the following composite materials: a commercial composite material as a reference (Filtek Supreme XTE), an experimental composite doped with BG 45S5 (C-20), and an experimental composite doped with a fluoride-containing BG (F-20). Six experimental groups (n = 8) were used, as each of the three composites was applied with (+) or without (-) a universal adhesive (Adper Scotchbond Multipurpose). All specimens were subjected to thermocycling (10,000 x, 5-55 °C) and then additionally stored in artificial saliva for eight weeks. Scanning electron micrographs of the mesial and the distal box were taken at three time points (initial, after thermocycling, and after eight weeks of storage in artificial saliva). The margins were classified as "continuous" and "non-continuous" and the percentage of continuous margins (PCM) was statistically analyzed (α = 0.05). RESULTS: In most experimental groups, thermocycling led to a significant decrease in PCM, while the additional 8-week aging had no significant effect. F-20 + performed significantly better (p = 0.005) after 8 weeks storage in artificial saliva than the reference material with adhesive, while no statistically significant differences were observed at the other two time points. C-20 + exhibited significantly better PCM than the reference material with adhesive after thermocycling (p = 0.026) and after 8 weeks (p = 0.003). CONCLUSIONS: Overall, the experimental composites with BG showed at least as good marginal adaptation as the commercial reference, with an indication of possible re-sealing of marginal gaps. CLINICAL RELEVANCE: Maintaining or improving the marginal integrity of composite restorations is important to prevent microleakage and its likely consequences such as pulp irritation and secondary caries.

Effect of cement type on vertical marginal discrepancy and residual excess cement in screwmentable and cementable implant-supported monolithic zirconia crowns.

The purpose of this study was to investigate the vertical marginal discrepancy (VMD) and residual excess cement (REC) of cementable and screwmentable monolithic zirconia crowns cemented with different types of cement. Abutments were attached to 40 implant analogues. Crowns were created using computer-aided design/computer-aided manufacturing technology from monolithic zirconia blocks, either with or without a screw access hole (SAC). Crowns created both ways were split into two groups and cemented with resin and zinc polycarboxylate cement under a 5-kg weight. VMD and REC values were evaluated using an X20 zoom stereomicroscope. Data were analysed using two-way ANOVA and the Bonferroni test. According to the two-way ANOVA results, REC measurements differed significantly in the crown design and cement groups. However, whilst VMD values were significantly different in both crown design groups, there was no significant difference in the cement groups. According to the Bonferroni test results, the highest REC (157.241 ± 44.29 µm) and VMD (68.052 ± 16.19 µm) values were found in the crowns without SAC and cemented with zinc polycarboxylate. Screwmentable crowns are more effective than cementable crowns in reducing REC and VMD. Whilst polycarboxylate cement reduces VMD in screwmentable crowns, resin cement is more suitable for cementable crowns.

Influence of build direction, post-polymerization time, and aging on the fracture resistance and marginal and internal discrepancies of three-dimensional printed provisional crowns.

To evaluate the effect of build direction, post-polymerization time, and aging on the fracture resistance, failure mode, margin quality and Marginal (MD) and Internal Discrepancies (ID), and degree of conversion of tridimensional (3D) printed provisional crowns using the liquid crystal display technique (LCD). A left mandibular first molar was prepared and scanned. After, a full crown was designed (ExoCad) and exported to the LCD-printer software. One hundred and eighty crowns were printed at two build directions (30°, 90°) and post-polymerized for different periods (15, 30, 45 min). Half of the samples were aged (ST) in distilled water (37 °C/90 days). The marginal quality of the crowns was evaluated by the Schriwer method under a stereomicroscope (40x). The replica technique was used to measure the MD and ID and measured under a stereomicroscope (10x), through 20 reference points defined in 5 regions: Occlusal (O), Cusp (CP), Axial (AX), Chamfer (CH), and Finish Line (F). After, the crowns were cemented onto the respective dies using temporary cement and submitted to compression test (ISO150, 1 mm/min, 100 kgf).The failure mode was classified by Burke's fracture mode. The degree of conversion was evaluated through Fourier Transform Infrared Spectroscopy. The data (µm) of MD and ID and fracture resistance (N) were subjected to ANOVA (3 factors) and Tukey's test (5%); Weibull analysis was also performed for fracture resistance data (N). For MD, ID and fracture resistance ANOVA revealed that all factors (P < .001) were significant. For aged groups, the crowns printed at 30° showed lower MD (Tukey). The O_90_30 min (172.13A µm) and O_90_15 min (170.20A µm) groups showed the highest ID values. Higher resistance values were observed for the 30_45 min (844.30A N), 30_30 min (835.35A N), and 90_30 min (820.62A N) groups (Tukey). In the margin analysis, 98.6% of the crowns printed at 30° showed smooth margins without defects. The most prevalent fracture mode (41.7%) was Burke type 5. The degree of conversion (DC) increased with increasing post-polymerization time and aging. Printing provisional crowns at 30° provided lower crown MD and ID, as well as higher fracture resistance. A post-polymerization time of 30 min resulted in higher crown fracture resistance, while aging reduced the resistance of the crowns.

Evaluation of surface microhardness and gingival marginal adaptation of three different bulk-fill flowable resin composites: A comparative study.

OBJECTIVES: To evaluate surface microhardness and gingival marginal adaptation of three different bulk-fill flowable resin composites (FB-RBCs) in Class V cavities with enamel or dentin margins before and after thermocycling (TMC). MATERIALS AND METHODS: Three available FB-RBCs were used; Palfique Bulk Flow (PaBF) (Tokuyama Dental), SDR Flow+ Bulk Fill Flowable (Dentsply Sirona), and I-Flow Bulk Fill (I-Dental). Thirty discs were prepared from each type of FB-RBCs. The discs were subjected to Vickers microhardness tester machine. Class V cavities were prepared on 180 molars. Gingival margins of half the specimens were prepared above CEJ and the other half below CEJ. Cavities were restored with FB-RBCs for gingival marginal adaptation test. Two-way ANOVA was used in microhardness, while three-way ANOVA was used for marginal adaptation. RESULTS: The used materials showed statistically significant differences in microhardness and marginal adaptation. CONCLUSIONS: Regarding microhardness, PaBF showed the highest value before TMC and SDR was the highest after TMC. Regarding marginal adaptation, SDR revealed the best marginal adaptation than PaBF and I-flow, either subjected to TMC or not. CLINICAL SIGNIFICANCE: The longevity of cervical restorations depend on both the location of the cavity margin and the material used. The microfractures in resin composite surface due to low surface microhardness as well as marginal gaps seen in laboratory studies could be considered as an indicative parameter for clinical problem associated with marginal differences.

Marginal adaptation of bulk-fill resin composites with different viscosities in class II restorations: a micro-CT evaluation.

BACKGROUND: The purpose of this study is to evaluate the marginal adaptation of bulk-fill resin composites with different viscosities (paste-like and flowable) in Class II restorations using micro-CT imaging. METHODS: Forty extracted human molars were used. Mesial and distal Class II box cavities (approximately 3 mm x 3 mm x 4 mm) were prepared for each tooth, with cavity floors located 1 mm below the enamel-cementum junction. Following adhesive application, teeth were restored using eight different groups: Group XB: X-tra Base Bulk-fill Flowable (VOCO), Group XF: X-tra Fill Bulk-fill (VOCO), Group FB: Filtek Bulk-fill Posterior (3 M ESPE), Group FF: Filtek Bulk-fill Flowable (3 M ESPE), Group BB: Beautifil-Bulk (SHOFU), Group BF: Beautifil-Bulk Flowable (SHOFU), and Group CO: "as a control group", Clearfil Majesty Posterior (KURARAY) and Group CF: "as a control group", Clearfil Majesty Flow + Clearfil Majesty Posterior (KURARAY). The restored teeth underwent an aging protocol involving 1000 cycles in a water bath fluctuating between 5 ± 1.0 °C and 55 ± 1.0 °C. Post-aging, teeth were immersed in 50% silver nitrate solution for 24 h and then in a film developer solution for 8 h. Microleakage analysis was performed using micro-CT, evaluated with 3D Slicer software. A two-way ANOVA was employed for statistical analysis. RESULTS: Two-way ANOVA results indicated significant effects of both viscosity (p < 0.0001) and composite type (p < 0.0001) on marginal adaptation. Viscosity analysis (comparing flowable and paste-like) revealed no significant differences in the FB-FF, XB-XF and BB-BF groups but significant differences in the and CO-CF group, with flowable type exhibiting less microleakage than paste-like type. CONCLUSIONS: The study suggests that while the viscosity of bulk-fill composites did not significantly affect marginal adaptation, the brand of bulk-fill composite did influence it.

Build angle effect on 3D-printed dental crowns marginal fit using digital light-processing and stereo-lithography technology: an in vitro study.

BACKGROUND: The effect of 3D printing technology and build angle on the marginal fit of printed crowns is unclear. The objective of this research was to use digital light processing (DLP) and stereo-lithography (SLA)-based 3D printing to construct single restorations with varied build angles and to analyze the crowns' marginal fit. METHODS: A prepared resin first molar was scanned utilizing an optical scanner. Three build orientations were used to construct the specimens: 0, 45, and 90º. DLP and SLA technology were used to produce the casting patterns. A digital microscope was used to measure the marginal gaps. The effect of build orientation was statistically analyzed by using Two-way ANOVA followed by pair-wise Tukey test. RESULTS: Two-way ANOVA revealed a significant effect of printer technology and build angle on the marginal discrepancy of 3D printed crowns (p < 0.001). One-way ANOVA revealed that SLA printers (55.6 [± 13.59]) showed significantly better mean [± SD] marginal discrepancy in µm than DLP printers (72 [± 13.67]) (p < 0.001). Regarding build angle, one-way ANOVA revealed significant differences between the different angles. Tukeys post-hoc test revealed that 0° (48.5 [± 9.04]) had the significantly smallest marginal discrepancy followed by 45° (62.5 [± 8.05]) then 90° (80.5 [± 8.99]) (p < 0.001). CONCLUSION: The build orientation affects the marginal discrepancy of single crowns manufactured utilizing DLP and SLA.

Effect of different fabrication workflows on the passive fit of screw-retained bar splinting two interforaminal implants: a parallel blinded randomised clinical trial.

BACKGROUND: To clinically compare the effect of the conventional and the digital workflows on the passive fit of a screw retained bar splinting two inter-foraminal implants. METHODS: The current study was designed to be a parallel triple blinded randomised clinical trial. Thirty six completely edentulous patients were selected and simply randomized into two groups; conventional group (CG) and digital group (DG). The participants, investigator and outcome assessor were blinded. In the group (CG), the bar was constructed following a conventional workflow in which an open top splinted impression and a lost wax casting technology were used. However, in group (DG), a digital workflow including a digital impression and a digital bar milling technology was adopted. Passive fit of each bar was then evaluated clinically by applying the screw resistance test using the "flag" technique in the passive and non passive situations. The screw resistance test parameter was also calculated. Unpaired t-test was used for intergroup comparison. P-value < 0.05 was the statistical significance level. The study protocol was reviewed by the Research Ethics Committee in the author's university (Rec IM051811). Registration of the clinical trial was made on clinical trials.gov ID NCT05770011. An informed consent was obtained from all participants. RESULTS: Non statistically significant difference was denoted between both groups in all situations. In the passive situation, the mean ± standard deviation values were 1789.8° ± 20.7 and1786.1° ± 30.7 for the groups (CG) and (DG) respectively. In the non passive situation, they were 1572.8° ± 54.2 and 1609.2° ± 96.9. Regarding the screw resistance test parameter, they were 217° ± 55.3 and 176° ± 98.8. CONCLUSION: Conventional and digital fabrication workflows had clinically comparable effect on the passive fit of screw retained bar attachments supported by two dental implants.

The effect of two preparation designs on the fracture resistance and marginal adaptation of two types of ceramic crowns using CAD/CAM technology (In vitro study).

BACKGROUND: Recently, prosthodontic approaches involve more conservative procedures that include less invasive finish line preparations that use less ceramic thickness. AIM OF THE STUDY: This in vitro study aimed to evaluate the effect of vertical preparation and modified vertical preparation designs on the marginal adaptation and fracture resistance of two types of ceramic crowns using CAD/CAM technology. MATERIALS AND METHODS: Two typodont maxillary first premolars were embedded in acrylic resin. Forty positive replicas of epoxy resin dies were used that were divided into two groups depending on the preparation design (n = 20); Group V (Vertical): dies with feather edge finish line and Group MV (Modified vertical): dies with feather edge finish line, where a reverse shoulder of 1 mm depth was placed on the buccal surface 1.5 mm from the occlusal surface. Each group was further subdivided into two subgroups according to the type of ceramic material (n = 10): Subgroup Va and subgroup MVa for lithium disilicate (e.max CAD) and subgroup Vb and subgroup MVb for zirconia (zolid ht+). Crown restorations were made with CAD-CAM technology. The marginal adaptation was assessed using a stereomicroscope both prior to cementation and after cementation and aging. Fracture resistance was tested with a universal testing machine, and the data were statistically analyzed. RESULTS: Marginal adaptation showed no significant differences between subgroups before or after cementation and aging. Three-way ANOVA indicated that preparation design (p = 0.516) and material (p = 0.269) had no significant effect, but cementation had a significant effect (p < 0.0001) on the marginal adaptation. According to two-way ANOVA test, Subgroup (MVb) showed the highest result followed by subgroup (Vb) and subgroub (MVa) and the least was subgroub (Va). Fracture modes showed no significant differences among the subgroups (p = 0.982). CONCLUSIONS: Marginal adaptation of lithium disilicate and zirconia crowns remained clinically acceptable regardless of preparation design. While the modified vertical preparation with a reverse shoulder notably enhanced the fracture resistance of both materials, with zirconia demonstrating superior fracture resistance compared to lithium disilicate with average values exceeding premolar biting force.

Impact of refrigeration of different Resin composite restorative materials on the marginal adaptation in class II restorations.

BACKGROUND: The pre-polymerization temperature of resin composite restorative materials could influence their adaptation to cavity details. As a current debate is existing about the refrigeration of resin composite restorative materials, this study was designed to assess the effect of refrigeration of 3 types of resin composite restorative materials with different matrix systems on their marginal adaptation in Class II restorations. METHODS: Forty-two sound maxillary molars, each with two separated Class II cavities, were used in this study. The teeth were assigned into 3 main groups (n = 14) according to the restorative /adhesive system used; an Ormocer-based composite (Admira Fusion/Futurabond M+, Voco GmbH, Cuxhaven, Germany), a methacrylate modified Ormocer-based (Ceram.X SphereTEC One/Prime&Bond Universal, Dentsply Sirona GmbH Konstanz, Germany), and a methacrylate-based (Tetric N-Ceram/Tetric N-Bond Universal, Ivoclar Vivadent AG, Schaan, Liechtenstein). Each group was then divided into 2 subgroups (n = 14) according to the gingival margin location; 1 mm above and 1 mm below the cemento-enamel junction (C.E.J). Each subgroup was further divided into 2 categories (n = 7) according to the storage temperature; stored at room temperature or stored in refrigerator at 4°- 5° C. Epoxy resin replicas were observed under scanning electron microscope (SEM) to examine the marginal gaps. A gab scoring system was used to assess the marginal adaptation of each restoration by giving scores on the basis of measurements of the maximum marginal gaps. The data obtained were statistically analyzed using the Chi-square test at a significance level of p < 0.05. RESULTS: None of the tested groups exhibited 100% gap-free margins irrespective of margin location or storage temperature. For both storage temperatures, no statistically significant difference was observed among all tested groups either with margins located above or below C.E.J (p > 0.05). As well, there was no statistically significant difference when comparing both marginal locations for each material (p > 0.05). Regarding the effect of storage temperature, statistically significant difference was only observed between the room-temperature stored groups with margins located above C.E.J and their corresponding groups stored in refrigerator (p < 0.05). CONCLUSION: The refrigeration of resin composite restorative materials prior to the restorative procedures revealed a deleterious effect on marginal adaptation of the restorations with margins located in enamel regardless the type of material used.

Evaluation of colour change, marginal adaptation, fracture strength, and failure type in maxillary and mandibular premolar zirconia endo-crowns.

OBJECTIVES: The objective of this in vitro study was to evaluate the effects of different preparation designs on the mean colour change (ΔE*), marginal adaptation, fracture resistance, and fracture types of maxillary and mandibular premolar endocrowns (ECs). METHODOLOGY: A total of 40 extracted maxillary and mandibular premolars were treated endodontically, and each type was subdivided according to the remaining axial height (remaining walls on all surfaces; 2-4 mm) and 2 mm inside the pulp chamber. Specimens were immersed in coffee for 14 days, ΔE* was determined, marginal adaptation was observed, fracture forces test was conducted, and the samples were examined visually at 10× magnification to evaluate failure type and identify fracture origin. The data were entered and analyzed using Statistical Package for Social Sciences, and significance between and within groups was evaluated through ANOVA. The p-value ≤ 0.05 was considered statistically significant. RESULTS: The ΔE* values of the maxillary premolar with 2 mm axial height were the highest (6.8 ± 0.89 units), whereas the lowest value was observed in the mandibular premolar with 4 mm axial height (2.9 ± 0.53 units). Significant differences (p < 0.05) in teeth and design were observed. The marginal adaptation of the mandibular premolar with 4 mm axial height was the highest (30.20 ± 1.53 µm), whereas the lowest marginal adaptation was observed in the maxillary premolar with 2 mm axial height (14.38 ± 0.99 µm), and the difference was statistically significant (p < 0.05). The maximum fracture force was observed in maxillary premolars with 2 mm axial height (2248.15 ± 134.74 N), and no statistically significant difference (p = 0.07) was observed between maxillary and mandibular premolars at 4 mm axial height. CONCLUSION: The recorded ΔE* values of the ECs were within clinically acceptable values or slightly higher, and the marginal adaption values were within acceptable and recommended clinical values in µm. EC preparation with 2 mm axial height in both arches recorded the highest fracture forces. Type III (split fracture) failure was recorded as the highest in the maxillary and mandibular premolar ECs with different axial wall heights.

Marginal adaptation of customized gutta percha cone with calcium silicate based sealer versus MTA and biodentine apical plugs in simulated immature permanent teeth (an in vitro study).

BACKGROUND: This study aimed to compare the marginal adaptation of a single customized gutta percha cone with calcium silicate-based sealer versus mineral trioxide aggregate (MTA) and Biodentine apical plugs in simulated immature permanent teeth. METHODS: Thirty-nine extracted human maxillary anterior teeth were selected, prepared to simulate immature permanent teeth with an apical diameter 1.1 mm, placed in moist foam and divided into three groups. Group 1: Obturation with a single customized gutta percha cone and calcium silicate sealer. Group 2: MTA apical plug. Group 3: Biodentine apical plug. After incubation, teeth were horizontally sectioned at 1 mm and 3 mm from the apex and marginal adaptation was evaluated using scanning electron microscope (SEM). RESULTS: Biodentine showed the least mean gap size at both 1 and 3 mm from the apex with no statistically significant differences compared to MTA (p > 0.05). The single customized cone with calcium silicate based sealer showed the greatest mean gap size at both 1 and 3 mm from the apex with a statistically significant difference compared to the other groups (p < 0.001). CONCLUSION: Biodentine and MTA apical plugs provide a significantly better marginal adaptation to the dentinal walls than a single customized gutta percha cone with calcium silicate based sealer in simulated immature permanent teeth.

Influence of polyether ether ketone coping crown on the adaptation of implant abutment.

OBJECTIVE: To evaluate the influence of polyether ether ketone coping crown on the adaptation of implant abutment. Methods: The vitro study was conducted at the department of Prosthodontics, Hainan Stomatological Hospital, China, from October 2021 to March 2022, and comprised patients undergoing implant surgery on first molar. Patients were divided into two groups, with group A patients receiving polyether ether ketone coping crowns, and group B receiving zirconia crowns. Replica technique was used to replicate the gap between the crowns and the abutments. The thickness of the silicone film was measured under the stereomicroscope, and the gap between the groups was compared. Data was analysed using SPSS 22. RESULTS: In group A, mean marginal gap was 82.43±25.00µm, and mean overall gap was 85.45±33.75µm. In group B, the corresponding values were 65.09±11.69µm and 78.04±26.67µm. There was a significant difference in the adaptation between the groups at the marginal and overall measurement points (p<0.05). Conclusion: Marginal and internal adaptations of polyether ether ketone coping crown for abutment could be considered clinically acceptable.

Vertical marginal gap and internal fit of virgilite-based lithium disilicate glass ceramic veneers with different preparation designs.

PURPOSE: To evaluate and compare internal fit and marginal adaptation of conventional lithium disilicate (LDS) glass ceramics and LDS containing virgilite computer-aided design and manufacturing (CAD-CAM) blocks before and after aging. MATERIALS AND METHODS: Seventy-two epoxy replicated dies from two prepared maxillary right central incisors acrylic typodont were divided into two groups of different preparation designs (n = 36): Group I, incisal butt-joint, and Group P, incisal overlap. Each group was further subdivided into two equal groups according to ceramic material (n = 18): Group E, IPS e.max CAD, and Group T, Tessera advanced lithium disilicate (ALD) CAD-CAM blocks. The replica technique was used to assess the internal fit using a stereomicroscope at 45× magnification. Laminate veneers were cemented to their corresponding epoxy dies, then the vertical marginal gap was evaluated before and after thermal cycling. Repeated measures analysis of variance (ANOVA) were used for marginal fit data and 2-way ANOVA for internal fit measurements (α = 0.05). RESULTS: For internal fit, there were no significant differences between tested groups. For vertical marginal gap results, two-way ANOVA showed that only aging had a significant effect on the vertical marginal gap (p < 0.001), while different CAD-CAM materials and preparation designs did not affect the vertical marginal gap. CONCLUSIONS: The vertical marginal gap and internal fits of IPS e.max CAD and CEREC Tessera CAD for both preparation designs were comparable. Aging significantly affected the vertical marginal gap of the laminate veneers of both materials and both preparation designs; however, all were within clinically acceptable ranges before and after aging.

Hot isostatic pressing as an alternative thermo-mechanical treatment for metallic full-arch implant-supported frameworks obtained by additive and subtractive manufacturing technology: Vertical and horizontal fit, screw removal torque, and stress analysis.

PURPOSE: To assess vertical and horizontal fit, screw removal torque, and stress analysis (considered biomechanical aspects) of full-arch implant frameworks manufactured in Ti-6Al-4V through milling, and additive manufacturing Direct Metal Laser Sintering (DMLS) and Electron Beam Melting (EBM), and the effect of the thermo-mechanical treatment Hot Isostatic Pressing (HIP) as a post-treatment after manufacturing. MATERIAL AND METHODS: Maxillary full-arch implant frameworks were made by milling, DMLS, and EBM. The biomechanical assessments were screw removal torque, strain-gauge analyses, and vertical and horizontal marginal fits. The vertical fit was assessed by the single-screw test and with all screws tightened. All frameworks were submitted to a standardized HIP cycle (920°C, 1000 bar pressure, 2 h), and the tests were repeated (α = 0.05). RESULTS: At the initial time, milled frameworks presented higher screw removal torque values, and DMLS and EBM frameworks presented lower levels of strain. Using the single-screw test, milled and DMLS frameworks presented higher vertical fit values, and with all screws tightened and horizontally, higher fit values were found for milled frameworks, followed by DMLS and EBM. After HIP, milling and EBM frameworks presented higher screw removal torque values; the lowest strain values were found for EBM. Using the single-screw test, milled and DMLS frameworks presented higher vertical fit values, and with all screws tightened and horizontally no differences were found. CONCLUSIONS: DMLS and EBM full-arch frameworks presented adequate values of screw removal torque, strain, and marginal fit, although the worst values of marginal fit were found for EBM frameworks. The HIP cycle enhanced the screw removal torque of milled and EBM frameworks and reduced the strain values of milled frameworks. The HIP represents a reliable post-treatment for Ti-6Al-4V dental prostheses produced by milling and EBM technologies.

A 2-Year Randomized Clinical Trial of Three Bonding Techniques in Non-Carious Cervical Lesions.

Background and objective: The aim of this randomized split-mouth study-controlled clinical trial was to compare the 2-year clinical performance of resin composite restorations placed at non-caries cervical lesions (NCCL) with one-step self-etch, total-etch, and selective enamel etch and self-etch adhesive techniques. Materials and methods: Thirty-two patients received three resin composite restorations each at NCCLs (Tetric EvoCeram/Ivoclar/Vivadent), bonded with a total-etch adhesive agent (ExciTE F/Ivoclar/Vivadent) and a self-etch (AdheSE One F/Ivoclar/Vivadent) without and with selective enamel etching. All restorations were evaluated by two examiners at baseline, 6-, 12-, 18-, and 24-months with FDI clinical criteria (post-operation regarding retention, caries occurrence, marginal adaptation, and marginal staining). A logistic regression analysis, a Cohen's kappa statistic, a multifactorial analysis, and X2 were performed with generalized estimating equations. Results: After 2 years, the retention rate was 86.8% for total etch, 92.26% for self-etch, and 93.63% for selective enamel etching and self-etch. No caries was detected on the restorations. Concerning marginal adaptation, the clinically perfect restorations were 26.9% for the total-etch technique, 16% for self-etch, and 25.9% for selective enamel etch and self-etch. The logistic regression model revealed that only time reduced the probability of perfect marginal adaptation. Conclusions: All three adhesive strategies provided restorations with no significant differences in the retention rate or marginal adaptation, whereas the total etch yielded better performance for marginal staining. All restorations were assessed as clinically acceptable after 2 years.

Preheating of dental composite resins: A scoping review.

OBJECTIVE: The aim of this scoping review was to analyze the available evidence on the preheating process and its effects on physicochemical properties of composite resins. MATERIALS AND METHODS: A systematic search was performed in August 2021 using PubMed/Medline, Embase, Scopus, and ISI Web of Science databases and gray literature without language or date restriction. Inclusion criteria were in vitro studies that assessed the physicochemical properties and marginal adaptation of preheated composite. Exclusion criteria were studies with experimental composite, literature reviews, clinical studies. Data from selected studies were qualitatively analyzed. RESULTS: In total, 104 studies were found from which 39 were included. The most used composite resin was Filtek Z350 XT (3 M/ESPE), preheated at 68°C in a Calset device (AdDent Inc., Danbury, CT, USA) for 5 or 15 min. Most studies showed decreased viscosity, increased conversion degree and microhardness of composite resins, and better marginal adaptation of direct and indirect restorations. Also, flexural strength was not affected, and data about bond strength were inconclusive due to heterogeneity among studies. CONCLUSION: The parameters used for preheating composite resins are heterogeneous. Preheating decreased viscosity, increased the conversion degree and microhardness of composite resins, and improved the marginal adaptation of direct and indirect restorations. CLINICAL SIGNIFICANCE: The analysis of evidence showed a high heterogeneity among preheating protocols. Preheating may benefit the handling and physicochemical properties of composite resins.

Effect of blood contamination on marginal adaptation of cold ceramic and MTA angelus: a scanning electron microscopic study.

BACKGROUND: This study aimed to assess the effect of blood contamination on marginal adaptation of cold ceramic (CC) and mineral trioxide aggregate (MTA) Angelus using scanning electron microscopy (SEM). METHODS: This in vitro experimental study was conducted on 24 extracted single-rooted human teeth. After cleaning and shaping, the root canals were filled with lateral compaction technique. The apical 3 mm of the roots was cut, and cavities with 3 mm depth were created at the apex. The teeth were randomly assigned to two group (n = 12) for the application of CC and MTA Angelus as retrograde filling materials. CC and MTA Angelus were prepared by mixing the powder with blood, and applied in the cavities. After 24 h, their marginal adaptation to the canal walls was assessed by SEM. Data were statistically analyzed by t-test (alpha = 0.05). RESULTS: The mean marginal gap was 8.98 µm in the CC, and 16.26 µm in the MTA Angelus group; this difference was statistically significant (P < 0.001). CONCLUSIONS: The present in vitro study revealed that following complete blood contamination of powder, CC showed significantly superior marginal adaptation than MTA Angelus as shown by SEM assessment.

Effect of coping materials zirconia or polyetheretherketone with different techniques of fabrication on vertical marginal gap and fracture resistance of posterior crowns with composite veneering.

BACKGROUND: Insufficient research has been conducted in the literature assessing the performance of zirconia and polyetheretherketone (PEEK) crowns in relation to the essential requirements of successful restorations, such as fracture resistance or margin adaptation. The purpose of this study was to evaluate the effect of the coping materials zirconia or PEEK with different fabrication techniques on the vertical marginal gap and fracture resistance of posterior crowns with composite veneering. METHODS: Ceramic copings (n = 18) restoring mandibular first molar were fabricated from zirconia (Zircon.x, Presidentdental, Germany), milled PEEK (PEEK CAD) (breCAM.BioHPP, Bredent, Germany) and pressed PEEK (PEEK Press) (BioHPP Granules, Bredent, Germany) six specimens each (n = 6). The copings were veneered with high impact polymer composite (HIPC) material (breCAM.HIPC, Bredent, Germany). The vertical marginal gap was captured under a magnification of 40X. Five equidistant marks on each surface of the die distinguished the points of measurement for a total of 20 readings per sample. The analysis was completed using an image analysis system (ImageJ 1.53t, National Institute of Health, USA). The specimens were loaded to failure at a crosshead speed of 1 mm/min and the load at failure was recorded to measure the fracture resistance. RESULTS: The marginal gap was analyzed using one-way ANOVA followed by Tukey's post hoc test. Fracture resistance was analyzed using Welch one-way ANOVA followed by the Games-Howell post hoc test. Marginal gap values showed a significant difference between the tested groups, with zirconia having significantly lower gap values (48.67 ± 11.98 µm) than both the PEEK CAD (108.00 ± 20.08 µm) and Press groups (108.00 ± 25.10 µm) (p < 0.001). However, the results of fracture resistance showed no significant difference (p = 0.06) with 1687.47 ± 253.29 N, 2156.82 ± 407.64 N, 2436.72 ± 725.93 N for zirconia, PEEK CAD, and Press, respectively. The significance level was p < 0.05. CONCLUSIONS: Zirconia framework crowns have a smaller vertical marginal gap than milled and pressed PEEK crowns. Crowns fabricated from zirconia, PEEK CAD, or PEEK Press frameworks and veneered with composite resin have comparable fracture resistance lower than the maximum biting force in the posterior region. CLINICAL RELEVANCE: Posterior crowns with zirconia frameworks are preferred over milled and pressed PEEK frameworks regarding margin adaptation, although all can safely survive the maximum occlusal forces without fracture.

Marginal adaptation, physicochemical and rheological properties of treated dentin matrix hydrogel as a novel injectable pulp capping material for dentin regeneration.

BACKGROUND: Treated dentin matrix hydrogel (TDMH) has been introduced as a novel injectable direct pulp capping material. In this regard, this study aimed to evaluate its marginal adaptation, physicochemical and rheological properties for the development of clinically feasible TDMH. METHODS: TDMH was applied to the pulp floor of prepared Class I cavities (n = 5), marginal adaptation was assessed by SEM at 1000 X magnification to detect gap between dentin and filling material. Five syringes were filled with TDMH and placed between the compression plates of a universal testing machine to evaluate injectability and gelation time was also evaluated by test vial inverting method. The microstructures of lyophilized TDMH were observed by SEM. Moreover, TDMH discs (n = 5) were prepared and the water uptake (%) was determined based on the equilibrium swelling theory state of hydrogels. Its solubility was measured after one week by the ISO standard method. Rheological behaviours of TDMH (n = 5) were analysed with a rotational rheometer by computing their complex shear modulus G* and their associated storage modulus (G') and loss modulus (G''). Statistical analysis was performed using F test (ANOVA) with repeated measures and Post Hoc Test (p = 0.05). RESULTS: TDMH presented an overall 92.20 ± 2.95% of continuous margins. It exhibited gelation during the first minute, and injectability mean was 66 ± 0.36%. TDMH showed a highly porous structure, and the pores were interconnected with an average diameter about 5.09 ± 3.17 µm. Swelling equilibrium gradually reached at 6 days up to 377%. The prepared hydrogels and maintained their shape after absorbing over three times their original weight of water. TDMH fulfilled the requirements of ISO 6876, demonstrating a weight loss of 1.98 ± 0.09% and linear viscoelastic behaviour with G` 479.2 ± 12.7 and G`` 230.8 ± 13.8. CONCLUSIONS: TDMH provided good marginal adaptation, appropriate physicochemical and viscoelastic properties support its use as a novel direct pulp capping material in future clinical applications.

Evaluation of the masking ability, marginal adaptation, and fracture resistance of screw-retained lithium disilicate implant-supported crowns cemented to titanium bases versus preparable abutments.

BACKGROUND: Straight preparable abutments and titanium bases (ti-base) can be used to support single-unit screw-retained lithium disilicate implant-supported restorations. The choice between using both abutments depends on many factors. The purpose of this in vitro study was to compare the masking ability, marginal adaptation, and fracture resistance of screw-retained lithium disilicate implant-supported crowns cemented to straight preparable abutments and ti-bases. METHODS: Twenty laboratory implant analogs (Straumann Bone Level; Straumann AG) were randomly divided into 2 groups (n = 10 each) according to the type of the abutment used. Preparable abutment group and ti-base group. Lithium disilicate crowns were used to restore the specimens. All specimens were subjected to thermocycling (from 5 to 55 °C for 2000 cycles) followed by cyclic loading (120 000 cycles). The vertical marginal gap between the abutment finish line and the most apical part of the crown was measured in (µm) by using a stereomicroscope after cementation and after thermocycling and cyclic loading. A spectrophotometer was used to evaluate the masking ability of the specimens after cementation. The load required to fracture the crowns was measured in Newtons (N) by using a universal testing machine after thermocycling and cyclic loading. The Shapiro-Wilk test of normality was used. The appropriate statistical test was used. RESULTS: Regarding the masking ability, the color difference (∆E) showed no statistically significant difference between the ti-base group (2.6 ± 0.2) and the preparable abutment group (2.6 ± 0.3) (P = .888). The average of the microgap values (µm) was greater in ti-basegroup after cementation (13.9 ± 9.2) than preparable group (7.63 ± 1.78) with no statistically significant difference between the 2 groups (P = .49). After cyclic loading and thermocycling, the average microgap values (µm) was significantly greater in the ti base group (21.3 ± 7.4) than in preparable group (13.3 ± 1.5) (P = .02). The load required to fracture the specimens was greater in the preparable group (1671.5 ± 143.8) than in the ti-base group (1550.2 ± 157.5) with no statistically significant difference between the 2 groups (P = .089). CONCLUSION: The abutments used in the present study did not compromise the masking ability of the screw-retained lithium disilicate implant supported crowns. Moreover, the crowns cemented to preparable abutments had better marginal adaptation and higher fracture resistance when compared to those cemented to ti-bases. CLINICAL IMPLICATIONS: Straight preparable abutments are considered as an alternative to the ti-bases when restoring single screw-retained lithium disilicate implant-supported crowns with comparable fracture resistance, marginal adaptation, and masking ability.