Evaluation of the Color Stability of Three Resin-Ceramic Materials Using a Spectrophotometer and a Digital Photography Software.

Background: Computer-aided design/computer-aided manufacturing (CAD/CAM) resin ceramics allow easier milling than glass ceramics but are suspected to be more stainable. Although Photoshop® is widely used for picture analysis, its potential for shade selection has not been properly assessed. Aim: Purpose primary: To evaluate the color stability of three CAD/CAM resin ceramics and Lithium Disilicate. Secondary: to compare the color evaluation between a spectrophotometer (Vita Easyshade compact) and Photoshop software. Materials and Methods: Three CAD/CAM resin ceramic materials (n = 10) and a fourth group of lithium disilicate were used. Half of each group were thermocycled (5°C and 55°C; 3000 cycles). All samples were immersed in colored beverages (coffee, tea and red wine) for 30 days. Values were obtained by spectrophotometry and photographs analyzed using Photoshop software. The parameters measured were CIEL*a*b, and the color difference (ΔE) was analyzed. A mixed model test was used to compare the results through time and materials (α = 0.05). The comparison between the spectrophotometer and Photoshop results was performed using the bivariate Pearson's correlation test. Results: Lithium disilicate glass ceramic exhibited less color change (ΔE = 14) than resin ceramics (15.7 < ΔE < 18.7). The least change was noted with GC Cerasmart (ΔE = 15.7) followed by Vita Enamic (ΔE = 17*) and Brilliant Crios (ΔE = 18.7*). Spectrophotometer and Photoshop values showed low correlations. Conclusions: Resin ceramics may suffer from color change in clinical use. Photoshop is technique sensitive; pictures are easily affected by the light conditions and camera settings.

Novel complete-arch pillar system (CAPS) to register implant position and maxillomandibular relationship in one single visit.

OBJECTIVES: This article presents a novel complete-arch pillar system (CAPS) to register implant position and maxillomandibular relationship in one single visit for implant-supported fixed complete dental prostheses (IFCDPs). MATERIAL AND METHODS: The novel system presents a 3-unit toolset comprising intraoral scan bodies (ISBs), lateral pillar attachments (LPAs) and occlusal pillar attachments (OPAs). A 2-stage single visit workflow by an intraoral scanner (Trios 5) was introduced. The first stage "Screw-Scan-Done" was used to describe complete-arch intraoral implant scanning using LPAs. The second stage "Screw-Occlude-Done" involved virtual occlusal recording using OPAs. Two patients with one single edentulous arch were selected for this study. In the first patient, 6 bone level implants (Bone Level Tapered, Straumann) were placed in the edentulous maxilla at positions 12, 14, 16, 22, 24 and 26. In the second patient, 4 bone level implants (NobelActive CC, Nobel Biocare) were placed in the edentulous mandible at positions 32, 35, 42 and 45. A CAD-CAM procedure was initiated with the acquired IOS data to fabricate an interim IFCDP at the same day. Periapical radiographs were obtained of the implant-prosthetic connection of the definitive IFCDPs to verify the passive fit. Metrology software (Geomagic Qualify, 3D Systems - Matlab, Mathworks) was used to assess the implant analogs position in the 3D-printed casts used for fabricating the definitive IFCDPs. A quantitative occlusal relationship analysis was performed with IOS. RESULTS: Radiographic examination revealed no gaps at implant-prosthetic connection of the definitive IFCDPs. The 3D-printed casts showed an overall average distance deviation within the clinically acceptable range of errors of 150 µm. Quantitative occlusal relationship analysis with IOS showed well-distributed contacts. CONCLUSION: Within the limitations of this study, the following conclusions can be drawn: (1) A 3-unit toolset with ISBs, LPAs and OPAs allows to register the implant position and maxillomandibular relationship in one single visit; (2) the 2-stage clinical workflow with the CAPS system facilitates the IOS data acquisition for fabrication of an interim IFCDP at the same day; (3) a passive fit was demonstrated for the interim and the definitive IFCDPs. CLINICAL SIGNIFICANCE: The CAPS system can help clinicians to register the implant position and the maxillomandibular relationship in one single visit for the fabrication of an IFCDP.

The Effect of Stacking on the Accuracy of 3D-Printed Full-Arch Dental Models.

The objective of this study was to assess the effect of stacking on the dimensional and full-arch accuracy of 3D-printed models, utilising a standardised assessment methodology. A previously validated methodology involving a standard tessellation language image (STL) reference model, comprising seven spheres on a horseshoe base resembling a dental arch, was used. Six 3D-designed STL models were prepared, optimised, and stacked horizontally using 3D Sprint software. The stacking file was transferred to the NextDent 5100 printer to build the physical models. To assess accuracy, a coordinate measuring machine (CMM) measured the diameter of the spheres n=210, and twenty-one vectors extended between the centres of each of the seven spheres (n = 630). When compared to the reference model, significant differences were observed for dimensional (p = 0.006) and full-arch accuracy (p = 0.006) for all stacked models. Additionally, significant differences were observed between the stacked models for the dimensional accuracy between the posterior (p = 0.015), left posterior (p = 0.005) and anteroposterior (p = 0.002). The maximum contraction was observed in the fourth stacked model, which demonstrated the highest median deviation and least precision within the full-arch (MD = 666 µm, IQR = 55 µm), left posterior (MD = 136 µm, IQR = 12 µm), posterior (MD = 177 µm, IQR = 14 µm) and anteroposterior (MD = 179 µm, IQR = 16 µm) arch segments. In general, the anterior and left posterior arch segments recorded the highest contractions with a median deviation of 34 µm and 29 µm, and precision of 32 µm and 22 µm, respectively. Statistically significant differences were observed between the stacked models in terms of dimensional accuracy that were within clinically acceptable thresholds. The greatest contraction was noted in the fourth model, displaying the least full-arch accuracy compared to the other models. Stacked, additively manufactured, full arch models are a viable alternative for diagnostic, orthodontic, and single-unit prosthodontic applications. In contrast, caution should be exercised when utilising stacked models for full arch high accuracy prosthodontic applications. Further research is needed to assess the impact of additional variables including different printers and resins.

Implant Placement Lateral to the Inferior Alveolar Nerve: Selective Indications and Treatment Outcomes-A Case Series.

Replacement of missing posterior mandibular teeth in severely atrophied jaws can be quite challenging. Various treatment options have been proposed for the rehabilitation of the deficient posterior mandible with implant-supported prostheses. Depending on the clinical situation, it may be feasible to place implants lateral to the inferior alveolar nerve, which represents a viable treatment option under the proper circumstances. This article defines the indications and limitations of this approach and presents the treatment planning and surgical management of three selected cases and their outcomes 1 to 5 years after implant loading.

Evaluation of Third Molar Impaction Distribution and Patterns in a Sample of Lebanese Population.

Background: Classifications of impaction based on panoramic radiographs such as the ones of Pell and Gregory and Winter are essential to allow a better understanding of third molar position regarding depth and bone coverage of the impacted tooth and to evaluate the difficulties of the surgical procedures. The aim of the study was to classify upper and lower third molars teeth in a sample of a Lebanese population and compare the data to results from other studies. Materials and Methods: Digital panoramic radiographs of 71 patients with a total of 181 wisdom teeth from patients that had been subjected for third molars extraction, from November 2016 to November 2018, were collected and analyzed. The mean age was 26.25 years. All third molars were categorized according to Pell and Gregory by using A, B, C scores for depth in upper and lower third molars, and angulations were classified according to Winter's classification. Nonparametric normality tests evaluating age group and gender distribution were conducted by utilizing the Chi-square test for age distribution and the binomial and Kruskal-Wallis tests for gender. Results: In the Pell and Gregory classification, the lower third molars showed type B impaction as the most frequent with 66.1% for the right side and 60.3% for the left side; the maxillary third molars both showed the type C impaction as the most frequent with 63.3% for the right side and 59.2% for the left side. According to the Winter classification, lower third molars showed mesio-angulation as the most frequent angle of impaction with 41.1% for right mandibular side and 46.5% for mandibular left side; As for the maxillary third molars, the disto-angulation was the most frequent angulation seen in both maxillary right and left side teeth 53.3% and 43.2%. Conclusions: Comparison of our results with other populations has shown similarities in certain criteria like angulation and relation to ramus, but most results varied. Thus, the current study can be taken as a baseline for further studies.

Comparison between Pre and Posttreatment Inclination of Maxillary Incisors in Adults: Association with Facial and Growth Axes.

Objective: The objective of the study is to evaluate the orthodontic treatment effect on maxillary incisors' inclination relative to facial and growth axes in adult subjects. Materials and Methods: Hundred consecutive nongrowing orthodontic patients with an average age of 26.24 ± 9.29 years were selected, and their T1 (initial) and T2 (final) lateral cephalograms were digitized. Cephalometric maxillary incisors' (I) inclination was measured to SN, PP, NA, NBa, and true horizontal (H). Facial and growth axes' inclinations were measured relative to NBa and H. Associations were tested using Chi-square tests for categorical data. Paired sample t-tests and Pearson's correlation were computed for continuous data. Results: Maxillary incisors' inclination, MP/SN, and ANB angle did not show statistically significant differences between T1 and T2, while mandibular incisors' inclination and interincisal angle increased significantly (P = 0.01 and P = 0.02, respectively). Facial and growth axes increased at T2 but changes were not statistically significant among the two groups. At T1, correlations between maxillary incisors' inclination and facial/growth axes were not statistically significant. Similarly, correlations between MP/SN and ANB angles on the one hand and facial/growth axes on the another hand were not statistically significant. At T2, I/PP correlated significantly with facial axis (FA)/NBa (r = 0.308; P = 0.002) and with FA/H (r = 0.268; P = 0.007). Similarly, I/SN and I/NBa correlated significantly with FA/NBa (r = 0.399; P < 0.0001 and r = 0.422; P < 0.0001 correspondingly) and with FA/H (r = 0.305; P = 0.002 and r = 0.325; P = 0.001 correspondingly). Statistically significant negative correlations existed between MP/SN angle and facial/growth axes at T2 (r values ranging -0.704 to -0.409 at P < 0.0001). Conclusions: While there was no correlation between I and facial/growth axes at pretreatment, significant and higher correlations existed at the end of the orthodontic treatment. This association reflects the connection between the corrected posttreatment position of maxillary incisors relative to the corresponding vertical pattern. Therefore, orthodontists should evaluate the position of the maxillary incisors to FA and may consider it in their treatment objectives.

Alveolar Ridge Preservation in the Esthetic Maxillary Zone: Tuberosity Punch Technique of Gingiva and Bone: A Pilot Study.

AIM: This paper aims to present an alveolar ridge preservation technique, using an autologous punch formed of hard and soft tissues harvested from the tuberosity area. MATERIALS AND METHODS: Ten residual sockets in the anterior maxilla were filled with a punch of hard and soft tissues harvested from the tuberosity area. Clinical and radiographical data were collected at the surgical extraction time 0 (T0) and 5 months during implant placement (T1), from clinical and radiological measurements using cone-beam computed tomography scans and periapical radiographs. Core biopsy was harvested during implant placement for histological and histomorphometrical analysis. RESULTS: Clinically, the alveolar ridge presented a mean width of 10.3 mm before extraction which decreased to 8.85 mm at T1, where the mean horizontal loss is 1.45 mm (standard deviation [SD] 1.03 mm). The initial ridge mean height was 11.25 mm and increased to 12.85 mm after 5 months, where the mean vertical gain is 1.6 mm (SD 0.65 mm). The radiological evaluation shows a reduction in the horizontal dimension with a mean of 1 mm; however, the sockets show stability in the vertical dimensions. Histology showed a new lamellar bone formation with some areas of woven bone. Histomorphometric analysis showed that the percentage of new bone formed was 42.44 ± 5.54% and 48.62 ± 8.66% of the connective tissue and 8.94 ± 5.28% of the residual autogenous bone. CONCLUSION: At T1, the extraction sockets showed significantly lower vertical and horizontal bone changes, compared to T0. The described preservation punch technique resulted in greater stability in the horizontal and vertical dimensions after 5 months. CLINICAL SIGNIFICANCE: Clinical and radiological results show that the punch of hard and soft tissue graft reduces hard and soft tissue dimensional alteration after tooth extraction. In addition, using autogenous bone showed histological new bone formation.

Investigation of the structure and compressive strength of a bioceramic root canal sealer reinforced with nanomaterials.

OBJECTIVES: A root canal sealer that can increase the resistance of endodontically treated teeth to compressive strength would be of great advantage. The purpose of this study is to use three different nanoparticles: multi-walled carbon nanotubes (MWCNTs), Titanium carbides (TC), and Boron nitrides (BN) into a bioceramic adhesive root canal sealer; BioRoot™ RCS, in an attempt to improve its structural and compressive strength properties. METHODS: Three composites of two weight fractions (1- and 2-wt.%) were produced by mixing each nanomaterial separately with a pre-weighed mass of Bioroot powder. The microstructural properties and compressive strength of the different hardened composites obtained were investigated. The composites have been characterized by X-ray Diffraction, Fourier transform infrared spectroscopy, and scanning electron microscopy. Compression testing was performed. RESULTS: The 1-wt.% composites, Bioroot/MWCNTs, and Bioroot/TC, except for the one reinforced with BN, displayed a significant improvement in the compressive strength compared to pristine BioRoot™ RCS. The 2-wt.% composites showed no significant improvement in the compressive strength. CONCLUSION: The addition of 1-wt.% MWCNTs and TC nanomaterials can be considered in the future for enhancing the microstructure and compressive strength properties of pristine BioRoot™ RCS.

Effect of material types on the fracture resistance of maxillary central incisors restored with CAD/CAM post and cores.

AIM: To evaluate the fracture resistance and failure pattern of endodontically treated teeth with post and cores made of different CAD/CAM materials in comparison with cast post and cores. MATERIALS AND METHODS: A total of 40 maxillary central incisors were divided into four groups. Post and cores were fabricated using the following materials: fiber-reinforced composite, high-density polymer, polymer-infiltrated ceramic network, and nonprecious metal alloy as a control group. Specimens were covered with lithium disilicate crowns and subjected to thermomechanical cyclic loading followed by fracture resistance testing until failure. One-way ANOVA followed by Bonferroni multiple comparison tests were used to determine significant differences between the four groups. The significance level was set at 0.05. 3D finite element analysis was then performed, and results were analyzed based on the von Mises stress distribution criteria and the maximum principal stress for the possible failure areas. RESULTS: No statistically significant differences were found in the fracture resistance between the four groups. In terms of unrestorable failures, no significant differences were found among the tested groups. CONCLUSION: The tested post and cores have comparable fracture resistance to that of metallic cast post and cores in the anterior region. CLINICAL SIGNIFICANCE: Post and cores made of CAD/CAM materials offer an acceptable alternative for the restoration of anterior teeth.

Effect of sintering temperature on the physiochemical properties, microstructure, and compressive strength of a bioceramic root canal sealer reinforced with multi-walled carbon nanotubes and titanium carbide.

AIM: Bioceramic root canal sealers like BioRoot RCS have received significant attention for use in endodontics. The addition of a nanophase material like multi-walled carbon nanotubes (MWCNTs) and titanium carbide (TC) to its matrix combined with pressureless sintering might have the potential for improved physiochemical, microstructure, and compressive strength properties. METHOD: ology: MWCNTs and TC nanomaterials were added at a percentage of 1 wt% to a definite weight of pristine BioRoot RCS. Two composites were prepared by ball milling followed by pressureless sintering in static nitrogen at temperatures 600 °C and 800 °C. The setting time, solubility, pH, compressive strength, and density were determined and compared to pristine BioRoot RCS. The microstructural properties of the composites were investigated by XRD, FTIR, Raman spectroscopy, and SEM. RESULTS: The final setting time before and after sintering at 600 °C of the composites was accelerated compared to Bioroot RCS (p = 0.016). The solubility of Bioroot/TC sintered at 600 °C was the lowest (p = 0.07) and its compressive strength was the highest among the sintered samples (p = 0.01). The incorporation of MWCNTs and TC had a significant increase in the compressive strength of Bioroot RCS (p < 0.05). CONCLUSION: The obtained results support the addition of nanomaterials to Bioroot RCS and the use of pressureless sintering.

Fracture Resistance of Three-unit Fixed Dental Prostheses Fabricated with Milled and 3D Printed Composite-based Materials.

AIM: To evaluate the fracture resistance of three-unit fixed dental prosthesis (FDP) made of composite, high-density polymers (HDP), fiber-reinforced composite (FRC), and metal-ceramic (MC) using different fabrication methods. MATERIALS AND METHODS: A typodont model was prepared to receive a three-unit FDP replacing a missing second maxillary premolar. The prepared model was digitally scanned using an intraoral scanner (Trios3, 3Shape, Denmark). In total, 60 FDPs were fabricated and divided into four groups (n = 15) according to the materials and fabrication method: the subtractive method was used for the FRC (Trilor, Bioloren, Italy) and the HDP (Ambarino, Creamed, Germany) groups; the HDP group was monolithic, whereas the FRC group was layered with a nanocomposite (G-aenial Sculpt, GC). The additive method was used for the 3D printed (3DP) nanocomposite (Irix Max, DWS, Italy) and the Cr-Co (Starbond CoS powder 30) infrastructure of the MC groups. The FDPs were adhesively seated on stereolithography (SLA) fabricated dies. All samples were subjected to thermomechanical loading and fracture testing. The data for maximum load (N) to fracture was statistically analyzed with one-way analysis of variance (ANOVA) followed by Games-Howell post hoc test (α = 0.05). RESULTS: The MC group reported the highest fracture resistance with a statistically significant difference (2390.87 ± 166.28 N) compared to other groups. No significance was noted between 3DP and HDP groups (1360.20 ± 148.15 N and 1312.27 ± 64.40 N, respectively), while the FRC group displayed the lowest value (839.07 ± 54.30 N). The higher frequency of nonrepairable failures was observed in the MC and FRC groups, while HDP and 3DP groups reported a high frequency of repairable failures. CONCLUSION: Significant differences were found in fracture resistance between the tested groups. The load-bearing capacity of the composite-based FPDs exceeded the range of maximum chewing forces. CLINICAL SIGNIFICANCE: 3D printed and milled composite-based materials might offer a suitable solution for the fabrication of FPDs.

Orthodontic Treatment Effect on Inclination of Maxillary Incisors and Growth Axes in Adult Patients with Various Mandibular Divergent Patterns.

AIM: To evaluate, in an adult population, the effect of orthodontic treatment on the inclination of maxillary incisors, facial, and growth axes in different mandibular divergence pattern. In addition, we aimed to determine if there is an association between the inclination of the maxillary incisors and facial and growth axes and if this association will change after orthodontic treatment. MATERIALS AND METHODS: Two-hundred and thirty-eight consecutive lateral cephalograms (119 at T1 and 119 at T2) of adult patients with an average age of 26.45 ± 9.11 years at T1 and 29.58 ± 9.36 at T2 were selected and digitized. Cephalometric maxillary incisors (I) inclination was measured to cranial base (SN), palatal plane (PP), nasion-A point (NA), nasion-basion (NBa), and true horizontal (H). Facial (FA) and growth (GA) axes' inclinations were measured relative to NBa and H. The sample was stratified in three subgroups based on cephalometric mandibular divergence to anterior SN (MP/SN). A-Hypodivergent = MP/SN ≤27° (n = 28); B-Normodivergent = 27 < MP/SN < 37° (n = 49); C-Hyperdivergent = MP/SN ≥37° (n = 42). Associations were tested using Chi-square tests for categorical data. Paired sample t-tests and Pearson's correlation were computed for continuous data. RESULTS: At T1, there was a tendency to have more proclined I in group A (I/SN = 105.59 ± 10.8°) and more retroclined in group C (I/SN = 99.06 ± 12.04°) with no statistical significance. However, at T2, maxillary incisors were statistically significant different between groups A and C (p = 0.002). Pre-treatment FA and GA were statistically significantly different among the three divergence groups (p <0.0001) with more increased angles in the group A (FA/Nba = 92.77 ± 5.07°) vs group C (FA/Nba = 86.28 ± 5.08°). This angle increases around 2° on average at posttreatment assessment (group A-p = 0.033; group B-p = 0.002). Correlations between I and facial/growth axes were not statistically significant at T1, whereas at T2 those correlations were higher and statistically significant between I/PP to FA/NBa (r = 0.408; p ≤0.0001). CONCLUSION: Correlations between the maxillary incisors' inclination and the facial/growth axes were not statistically significant initially whereas after orthodontic treatment, those correlations were higher and statistically significant. Differences in FA existed between pre- and postorthodontic groups in all divergence groups. CLINICAL SIGNIFICANCE: Orthodontists should assess the inclination of the maxillary incisors, not only to the maxilla and anterior SN but also to FA and take it into consideration in their treatment objectives.

Expression of Inflammatory Mediators in Periodontitis Over Established Diabetes: an Experimental Study in Rats.

BACKGROUND: Diabetes mellitus is characterized by hyperglycemia ensuing from deficiencies in insulin action, secretion, or both. Hyperglycemia has wide-ranging molecular and cellular effects, leading to oxidative stress, up-regulation of pro-inflammatory responses, and vascular changes. OBJECTIVES: The aim of this study was to evaluate the expressions of inflammatory markers involved in periodontal destructive process occurring in diabetes, periodontitis (PD), and both coexisting conditions. METHODS: A rat model was carried out using streptozotocin (STZ) to induce diabetes and Lipopolysaccharides (LPS) with teeth ligature to mimic periodontitis. The animals were distributed randomly into seven groups (n=12) and treated for 10 weeks with alternation between diabetes and PD. The relative quantification analysis of inflammatory markers expression: CRP, MMP-2-14, TIMP-2, IL-4, IFN-γ, was performed at the end of the experiments using western blot after protein isolation from periodontal tissue surrounding the ligation. RESULTS: The data showed that CRP, MMP-2, MMP-14, TIMP-2, and IFN-γ are involved in the process of periodontal inflammation associated with diabetes. A significant increase (p<0.05) in the expression of inflammatory markers was detected when PD is associated with preexisting diabetes in comparison with diabetes superimposed on preexisting PD. CONCLUSION: This study demonstrated that already established diabetes worsens periodontitis more than diabetes upcoming on existing periodontitis.

Marginal and Internal Adaptation of Lithium Disilicate Endocrowns Fabricated By Heat-Pressable and Subtractive Techniques.

PURPOSE: To evaluate and to compare the marginal and the internal fit of milled (MLE) and heat-pressed lithium disilicate endocrowns (PLE). MATERIALS AND METHODS: Thirty mandibular molars were prepared following the circumferential butt margin endocrown preparations; the cervical margin is parallel to the occlusal surface without ferrule design. A digital scan of molars was made using an intraoral digital scanner. The samples were separated into two groups (n = 15 per group); MLE: endocrowns were milled using LDS blocks and a 5-axis milling machine, PLE: endocrowns were heat-pressed using lost wax technique and LDS ingots. Marginal and internal adaptation were assessed using a replica technique and a stereomicroscope, selecting 32 measurements on each endocrown. Data were analyzed with one-way repeated measures ANOVA, two-way repeated measures ANOVA, student's t-test and paired student t-test (α = 0.05). RESULTS: Statistically significant interactions were recorded between fabrication technique and region (p < 0.05), F (1.97, 27.69) = 5.462. Group MLE displayed significantly smaller gaps than PLE in all regions (p < 0.001). The largest gap was observed at the pulpal floor in both groups. The internal gap was significantly larger than the marginal gap in MLE group (p < 0.001), while no statistically significant difference was observed in PLE group (p = 0.082). CONCLUSION: Heat-pressed and milled lithium disilicate endocrowns are clinically suitable, but the milled technique displayed a better fit than heat-pressed technique when marginal and internal adaptation were examined.

Fracture resistance, failure mode and stress concentration in a modified endocrown design.

PURPOSE: The purpose of this study was to assess fracture resistance, failure mode and stress concentration of a modified endocrown preparation design, under axial and lateral forces. MATERIALS AND METHODS: Forty lower molars were divided into two groups (n = 20) and were restored with lithium disilicate glass-ceramic endocrowns following 2 preparation designs: Conventional, with circumferential butt margin 2 mm above the cemento-enamel junction; and Modified, by adding 2 grooves on the mesial side of the vestibular dentinal wall and on the distal side of the lingual dentinal wall. After cementation and thermomechanical cycling loading, half of the samples (n = 10) from each group were loaded axially and the other half (n = 10) was loaded laterally. Fracture resistance and failure modes were observed and the finite element analysis (FEA) was used to identify the stress concentration. Two-way ANOVA and Chi-square tests (α = 0.05) were used for in vitro data analyzes. RESULTS: Fracture resistance showed a statistically significant difference between conventional and modified preparations (p < .001), and between axial and lateral loadings (p < .001). Conventional preparation recorded 2914 N under axial loading and 1516 N under lateral loading, while modified preparation recorded 3329 N under axial loading and 1871 N under lateral loading. FEA showed that retention grooves have reduced the stress concentration under both loads for the tooth and the restoration. CONCLUSION: Modified endocrown design showed higher fracture resistance than conventional endocrown. Lateral loading displayed a high percentage of severe fracture but under higher load to failure than the values reported for normal masticatory forces.

Cephalometric Evaluation of Maxillary Incisors Inclination, Facial, and Growth Axes in Different Vertical and Sagittal Patterns: An Original Study.

AIM: The aim of this study was to evaluate the inclination of the maxillary incisors (I), facial axis (FA), and growth axis (GA) in different vertical and sagittal patterns. MATERIALS AND METHODS: A total of 498 consecutive orthodontic patients, with an average age of 18.87 years (range = 5-63 years), were grouped based on their vertical and sagittal patterns. Maxillary incisors, FA, and GA axes were traced and their corresponding angles to nasion-basion and true horizontal lines were measured. The sample was divided into three groups based on the mandibular divergence (mandibular plane-MP/sella-nasion [SN]): Group 1-hypodivergent pattern (MP/SN ≤ 27; n = 30), Group 2-normodivergent pattern (27 < MP/SN <37; n = 254), and Group 3-hyperdivergent pattern (MP/SN ≥ 37; n = 214); the sample was then divided into three groups based on the sagittal pattern (ANB, angle between points A, Nasion and B): Group I-skeletal CLI (Class I) (0

Effect of material thickness on the fracture resistance and failure pattern of 3D-printed composite crowns.

AIM: To evaluate the fracture resistance and failure pattern of 3D-printed and milled composite resin crowns as a function of different material thicknesses. MATERIALS AND METHODS: Three typodont tooth models were prepared to receive a full coverage composite resin crown with different thicknesses (0.5, 1.0, and 1.5 mm). The prepared master casts were digitally scanned using an intraoral scanner, and the STL files were used to fabricate 60 nanocomposite crowns divided into two groups according to the material thickness (n = 10) and fabrication method: a 3D-printed group (3D) using an SLA printer with nanocomposite, and a milled group (M) using a milling machine and composite blocks. All crowns were adhesively seated on stereolithography (SLA)-fabricated dies. All samples were subjected to thermomechanical loading and fracture testing. The load to fracture [N] was recorded and the failure pattern evaluated. Data were statistically analyzed using a two-way ANOVA followed by a Bonferroni post hoc test. The level of significance was set at α = 0.05. RESULTS: The 3D group showed the highest values for fracture resistance compared with the milled group within the three tested thicknesses (P < 0.001). The 3D and M groups presented significantly higher load to fracture for the 1.5-mm thickness (2383.5 ± 188.58 N and 1284.7 ± 77.62 N, respectively) compared with the 1.0-mm thickness (1945.9 ± 65.32 N and 932.1 ± 41.29 N, respectively) and the 0.5-mm thickness, which showed the lowest values in both groups (1345.0 ± 101.15 N and 519.3 ± 32.96 N, respectively). A higher incidence of irreparable fractures was observed for the 1.5-mm thickness. CONCLUSION: 3D-printed composite resin crowns showed high fracture resistance at different material thicknesses and can be suggested as a viable solution in conservative dentistry.

Physiochemical properties of a bioceramic-based root canal sealer reinforced with multi-walled carbon nanotubes, titanium carbide and boron nitride biomaterials.

AIM: Bioceramic-containing root canal sealers are the most recently introduced sealers in endodontics. The present work reported experiments on a bioceramic-based root canal sealer with the objective of improving its physiochemical properties via reinforcement with each one of the three different nanomaterials: multi-walled carbon nanotubes (MWCNTS), titanium carbide (TC) or boron nitride (BN) in two weight percentages (1 wt% and 2 wt%). METHODOLOGY: Each nanomaterial was added to a definite weight of BioRoot root canal sealer (BioRoot™ RCS, Septodont, Saint-Maur-des-Fossés, France). Three composite groups of each weight percentage were prepared for evaluation: BioRoot/MWCNTS, BioRoot/TC and BioRoot/BN. The initial and final setting times, solubility, elution and pH values of the freshly-mixed and set samples were evaluated and compared to pristine BioRoot™ RCS. Setting times were evaluated using Gilmore needles. Solubility and elution were determined after immersion in water for 24 h. Scanning electron microscopy was used to examine the microstructure of the composite materials. RESULTS: The 1-wt. % composites possessed significantly shorter initial and final setting times compared with the pristine BioRoot™ RCS (p < 0.05). The 2-wt.% composites exhibited longer initial setting times but significantly shorter final setting times than BioRoot RCS (p < 0.05). Most of the composites had relatively lower solubility and elution profiles, with BioRoot/1-wt.% TC and BioRoot/1-wt.% BN being the lowest (p < 0.05). BioRoot™ RCS and all composites exhibited an alkaline pH profile over a period of 4 weeks and a significantly higher alkaline pH (p < 0.05) was recorded for BioRoot/1-wt.% and Bioroot/2-wt.% TC. CONCLUSIONS: A bioceramic-containing root canal sealer (BioRootTM RCS) with a shorter setting time, an alkaline pH profile, and a relatively lower solubility may be developed by incorporation of nanomaterials.

Adaptation of Complete Denture Base Fabricated by Conventional, Milling, and 3-D Printing Techniques: An In Vitro Study.

AIM: The aim of this study was to compare the adaptation of complete denture base (CDB) manufactured by three different techniques: conventional, milling, and three-dimensional (3-D) printing. MATERIALS AND METHODS: A master cast was duplicated to create 60 gypsum casts. Twenty casts (n = 20) were attributed to each group. In the computer-aided design and computer-aided manufacturing (CAD/CAM) groups (milling and 3-D printing), the 40 gypsum casts reserved for these two groups were scanned. An STL file was obtained and a master CDB was designed and then fabricated according to each technique. In the conventional group, a polyvinyl siloxane putty mold was obtained from the milled CDB, and this mold was used to fabricate 20 conventional denture bases by compression molding using the silicon-gypsum technique in a bronze flask. The inner surfaces of the obtained 60 CDB were scanned and superimposed over their corresponding master cast. Deviation analyses were calculated using digital subtraction technique. Five functional areas (posterior palatal seal, anterior border seal, crest of the ridge, maxillary tuberosities, and palate) were selected to evaluate the variations in CBD adaptation. RESULTS: Based on the results and color maps of all selected regions, milling technique offers the best adaptation. The crest of ridge in the conventional technique showed the least adaptation and the posterior palatal seal in the 3-D printing technique showed the best adaptation. CONCLUSION: Within the limitations of this study, the CAD/CAM fabrication techniques seem to offer better adaptation of CDB compared to the conventional fabrication technique. Milled CDBs presented the most homogeneous distribution of adaptation, yet the 3-D printing process seems a promising techniques that needs to be addressed and perfected. CLINICAL SIGNIFICANCE: The CAD/CAM technologies can help overcome many limitations related to conventional impressions and therefore should be well investigated to improve the edentulous patient's quality of life.

Evaluation Of The Effect Of Different Surface Treatments, Aging And Enzymatic Degradation On Zirconia-Resin Micro-Shear Bond Strength.

PURPOSE: The purpose of this study was to evaluate the effect of surface treatments on zirconia-resin bonding and the effect of aging on bond durability for one year. METHOD: Three hundred and twenty zirconia blocks were divided into 4 equal study groups. Group 1 (control): as-sintered, group 2: (GB): grit-blasted, group 3: (LAS): laser-etched, group 4: (SIE): selective infiltration etching. Composite cylinders were bonded to the zirconia with resin cement and ceramic primer. Aging was performed following 3 different aging protocols: thermocycling, storage in distilled water, or storage in an enzymatic esterase solution. Micro-shear bond strength test (µSBS) was recorded using a universal testing machine. µSBS values were analyzed using two-way Analysis of Variance followed by Tukey post-hoc tests. Level of significance was set at 0.05. RESULTS: GB, LAS and SIE groups showed significantly higher values when compared to control. Groups GB, LAS and SIE reported a significant decrease up to 50% in µSBS after water storage and enzymatic degradation, while control group reported a 90% decrease. Failure analysis showed mainly adhesive failure for control group, while the percentage of cohesive failure in resin cement was higher in SIE group compared to GB and LAS groups. CONCLUSION: Water aging and esterase solutions played a significant role by increasing bond degradation. A minimum of one-year water and esterase storage medium should be used to evaluate the durability of the bond between resin cement and zirconia.