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Sherine Mohamed Farag, Mona Mohamed Ghoneim, Rania Reda Afifi Conservative Dentistry Department, Faculty of Dentistry, Alexandria, University, Alexandria, EgyptCorrespondence: Sherine Mohamed FaragConservative Dentistry Department, Faculty of Dentistry, Alexandria University, 13 Champolion St, Azarita, Alexandria, EgyptTel +20 1552351433Email sherine.m.farag@gmail.comObjective: The purpose of this study was to compare the fracture resistance of ceramic veneers with digital die spacer settings at 20 μm, 40 μm, and 100 μm.Materials and Methods: Eighteen sound maxillary first premolars were divided into three groups (n=6) according to their digital die spacer settings: group A=20 μm, group B=40 μm, group C=100 μm. Each tooth was prepared to a depth of 0.5 mm to receive lithium disilicate veneers (IPS e.max CAD, Ivoclar Vivadent). All groups were thermocycled (2500 cycles at 5– 55°C) and subjected to fracture resistance test using a universal testing machine until failure. Failure modes were examined using a stereomicroscope.Results: The values (N) for group A=1181.34± 301.33, group B=1014.29± 291.12, and group C=841.89± 244.59. One-way ANOVA showed no statistical difference among the three groups (p=0.145). However, chi-square test showed that a significant difference was present in the modes of failure (p=0.009). Tukey’s post hoc test indicated that the failure modes of group A were statistically different from those of group C, showing 83.3% adhesive failure for group A compared to 0% adhesive failures in group C. A p-value of ≤ 0.05 was considered as statistically significant.Conclusion: Digital die spacer thickness did not influence the mean fracture resistance values of CAD/CAM lithium disilicate veneers. However, the way the failure occurred differed significantly at various die spacer thicknesses.Keywords: fracture resistance, die spacer, lithium disilicate CAD veneers, CAD/CAM, cement thickness, cement space

Objectives To evaluate the fracture resistance and marginal quality of maxillary molars restored using lithium disilicate glass-ceramic (LDG) occlusal veneers with two preparation designs. Methods Sixteen extracted maxillary molars were assigned to two groups (n = 8). In group 1 (G1), the teeth received a preparation for a conservative full-coverage occlusal veneer restoration with a 90° rounded shoulder margin. In group 2 (G2), the teeth underwent a 1-mm cusp reduction with a marginal chamfer. LDG restorations (IPS e.max CAD) were obtained with the Cerec 3 CAD/CAM system and luted with Variolink II cement. After thermomechanical aging (1 250 000 cycles), the specimens were loaded to fracture. A semiquantitative marginal seal evaluation was performed observing resin replicas of the specimens at the scanning electron microscope. Cement thickness was assessed at the stereomicroscope on sectioned specimens. Collected data were statistically analyzed by parametric and nonparametric tests. Results The maximum load to fracture was 2395.01 ± 150.96 N in G1 and 2408.39 ± 112.66 N in G2. Most of the observed specimens exhibited restorable fractures and continuous margins. Cement thickness was 132 ± 38 μm in G1 and 150 ± 41 μm in G2. No differences between the groups emerged. Conclusion This study demonstrated similar satisfactory performance of the two considered preparations designs for occlusal veneer with LDG. Clinical significance A new minimally invasive occlusal veneer preparation with marginal chamfer exhibited promising fracture resistance and marginal adaptation that were comparable to those of a standard conservative preparation for the restoration of molars with CAD/CAM lithium disilicate occlusal veneers.

Objectives Favourable results for collarless polished tapered stems have been reported, and cement creep due to taper slip may be a contributing factor. However, the ideal cement thickness around polished stems remains unknown. We investigated the influence of cement thickness on stem subsidence and cement creep. Methods We cemented six collarless polished tapered (CPT) stems (two stems each of small, medium and large sizes) into composite femurs that had been reamed with a large CPT rasp to achieve various thicknesses of the cement mantle. Two or three tantalum balls were implanted in the proximal cement in each femur. A cyclic loading test was then performed for each stem. The migration of the balls was measured three-dimensionally, using a micro-computed tomography (CT) scanner, before and after loading. A digital displacement gauge was positioned at the stem shoulder, and stem subsidence was measured continuously by the gauge. Final stem subsidence was measured at the balls at the end of each stem. Results A strong positive correlation was observed between mean cement thickness and stem subsidence in the CT slices on the balls. In the small stems, the balls moved downward to almost the same extent as the stem. There was a significant negative correlation between cement thickness and the horizontal:downward ratio of ball movement. Conclusion Collarless polished tapered stems with thicker cement mantles resulted in greater subsidence of both stem and cement. This suggests that excessive thickness of the cement mantle may interfere with effective radial cement creep. Cite this article: E. Takahashi, A. Kaneuji, R. Tsuda, Y. Numata, T. Ichiseki, K. Fukui, N. Kawahara. The influence of cement thickness on stem subsidence and cement creep in a collarless polished tapered stem: When are thick cement mantles detrimental? Bone Joint Res 2017;6:–357. DOI: 10.1302/2046-3758.65.BJR-2017-0028.R1.

Made available in DSpace on 2020-12-12T01:28:39Z (GMT). No. of bitstreams: 0 Previous issue date: 2020-10-01 Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Fundação de Amparo à Pesquisa do Estado do Rio Grande do Sul This study evaluated the influence of occlusal resin cement space on the fatigue performance of bonded-leucite crowns to a dentin-analogue material. Leucite anatomical crowns were adhesively cemented to dentin-like preparations having distinct occlusal cement space (50, 100 and 300 μm) (n = 18), and subjected to step-stress fatigue testing (150 N – 350 N; step-size: 25 N; 20,000 cycles/step; 20 Hz). Fatigue data (load and number of cycles for failure) were analyzed using Kaplan–Meier and Mantel–Cox (log-rank) tests (p

Background: Limited literature exists concerning the femoral cement mantle quality that can be achieved through an anterior approach in total hip arthroplasty (THA). We radiologically evaluated the quality and thickness of the femoral cement mantle in patients undergoing THA utilizing the direct anterior approach (DAA). Methods: Immediate postoperative anteroposterior and lateral radiographs of 116 consecutive patients who underwent hybrid or fully cemented THA using the DAA and cemented Quadra-C stem (Medacta, International, SA, Switzerland) were assessed by 2 arthroplasty surgeons blinded to the study. Surgical indications were hip osteoarthritis or subcapital hip fracture. The cement mantle and stem alignment were evaluated using the Barrack classification and Khalily methods, respectively. After calibration of radiographs, the thinnest part of the cement mantle per Gruen zone was recorded. Parameters were compared between obese and nonobese patients. Results: Agreement between raters was substantial for the cement quality in anteroposterior (k = 0.707, P ≤ .001) and moderate for lateral radiographs (k = 0.574, P ≤ 001). The cement mantle was graded A in 39.25%, B in 53.0%, and C in 7.75% of anteroposterior radiographs and similarly for lateral radiographs (40.1% A, 51.75% B, 9.5% C). 93% of stems had neutral alignment. The mean thinnest cement mantle (P = .237) and incidence of inadequate cement mantle ( .05) and stem alignment (P = .652) were comparable between obese and nonobese patients. Conclusions: DAA enables correct implantation and effective cementation of straight femoral stems. A high-quality cement mantle can be achieved using DAA even in obese patients.

Background and Objectives: This in vitro study seeks to evaluate and compare the marginal and internal fit of cobalt-chromium copings fabricated using the conventional and direct metal laser sintering (DMLS) techniques. Methods: A master model of a prepared molar tooth was made using cobalt-chromium alloy. Silicone impression of the master model was made and thirty standardized working models were then produced; twenty working models for conventional lost-wax technique and ten working models for DMLS technique. A total of twenty metal copings were fabricated using two different production techniques: conventional lost-wax method and DMLS; ten samples in each group. The conventional and DMLS copings were cemented to the working models using glass ionomer cement. Marginal gap of the copings were measured at predetermined four points. The die with the cemented copings are standardized-sectioned with a heavy duty lathe. Then, each sectioned samples were analyzed for the internal gap between the die and the metal coping using a metallurgical microscope. Digital photographs were taken at ×50 magnification and analyzed using measurement software. Statistical analysis was done by unpaired t-test and analysis of variance (ANOVA). Results: The results of this study reveal that no significant difference was present in the marginal gap of conventional and DMLS copings (P > 0.05) by means of ANOVA. The mean values of internal gap of DMLS copings were significantly greater than that of conventional copings (P < 0.05). Conclusions: Within the limitations of this in vitro study, it was concluded that the internal fit of conventional copings was superior to that of the DMLS copings. Marginal fit of the copings fabricated by two different techniques had no significant difference.

The objective of the present study was to evaluate the influence of resin cement thickness on the bond strength of prefabricated and customized glass fiber posts after storage in distilled water. Thirty human uniradicular roots were treated endodontically. The roots were divided into 3 groups: THIN (thin cement layer) - post space preparation with #0.5 drill and cementation of #0.5 post; THICK (thick cement layer) - post space preparation with #1 drill and cementation of #0.5 post; and CUSTOM (customized cement layer) - post space preparation with #1 drill and cementation of a customized post (#0.5 glass fiber posts customized with resin composite). All posts were luted with self-adhesive resin cement. The push-out test was carried out after storage for 24 h and 90 days in distilled water at 37 °C. The data were analyzed with three-way ANOVA and Tukey's test (a=0.05). Bond strengths were significantly higher for CUSTOM (9.37 MPa), than for THIN (7.85 MPa) and THICK (7.07 MPa), which were statistically similar. Considering the thirds, the bond strength varied in the sequence: apical (7.13 MPa) < middle (8.22 MPa) = coronal (8.94 MPa). Bond strength for 24 h storage was significantly higher (8.80 MPa) than for 90-day storage (7.40 MPa). It may be concluded that the thickness of resin cement influenced the bond strength of glass fiber posts. The customized posts presented higher bond strength. Storage in water for 90 days affected negatively the values of bond strength, especially for thick cement layers in the apical third. Resumo O objetivo deste estudo foi avaliar a influência da espessura da linha de cimento na resistência de união de pinos de fibra de vidro após armazenamento em água destilada. Trinta dentes humanos hígidos unirradiculares tiveram os canais tratados endodonticamente. As raízes foram distribuídas em três grupos: THIN (linha de cimento fina): conduto preparado com broca 0,5 e cimentação de pino 0,5; THICK (linha de cimento espessa): conduto preparado com broca 1 e cimentação de pino 0,5; e CUSTOM (linha de cimento personalizada): conduto preparado com broca 1 e cimentação de pino personalizada (pino 0,5 personalizado com resina composta). Os pinos foram cimentados com cimento auto-adesivo. Após armazenamento das raízes em água destilada a 37 °C por 24 h e 90 dias, o teste de cisalhamento por extrusão push-out foi realizado. Os resultados foram analisados estatisticamente por ANOVA a três fatores e teste de Tukey (a=0,05). A resistência de união foi significativamente maior para CUSTOM (9,37 MPa), do que para THIN (7,85 MPa) e THICK (7,07 MPa), que foram semelhantes entre si. Considerando-se os terços radiculares, a resistência de união variou na sequência: apical (7,13 MPa) < médio (8,22 MPa) = coronal (8,94 MPa). A resistência de união após 24 h de armazenamento em água foi significativamente maior (8,80 MPa) do que para 90 dias (7,40 MPa). Pode-se concluir que houve influência da espessura da linha de cimento na resistência de união de pinos de fibra de vidro, sendo que o uso de pinos personalizados apresentou maiores valores de resistência de união. O armazenamento em água por 90 dias afetou negativamente os valores de resistência de união, especialmente no terço apical, no grupo com linha de cimento mais espessa.

WOS: 000386328700006 This study evaluated the fracture resistance and marginal fit of CAD/CAM ceramic and composite inlays. Molars (N=80) were prepared to receive Mesio-occlusal-distal (MOD) inlays and randomly divided into four groups to be restored depending on the materials: (a) HLD: heat-pressed lithium disilicate ceramic (IPS e.max Press), (b) CLD: CAD/CAM-fabricated lithium disilicate ceramic (IPS e.max CAD), (c) NC: CAD/CAM nano-ceramic resin (Lava Ultimate), (d) RC: Indirect resin composite (Filtek P60). Each group was randomly divided into two subgroups regarding the resin cement: (a) High-viscosity resin cement (Syntac, Variolink II), (b) Self-adhesive low-viscosity cement (RelyX Ultimate). After marginal gap and cement thickness measurements, specimens were loaded to fracture in a Universal Testing Machine (1mm/min). Intact molars acted as the control group (n=10). Data were analyzed using one-way and two-way ANOVA, Tukey's tests (=0.05). Before cementation, CLD group showed significantly lower mean marginal gap (65 +/- 22.4m) and after cementation, cement thickness was again the lowest with CLD (82.6 +/- 24.6m) and the highest with HLD (108.4 +/- 21.3m) (p0.05).

Aim: This study aims to evaluate the effect of type of cement, and their thickness on stress distribution at dentin-cement interface of computer-aided designed glass fiber post using three-dimensional finite element analysis. Materials and Methods: Nine 3D models of endodontically treated maxillary second premolar were divided into three groups according to the adhesive cement used PermaCem (Group I), Variolink II (Group II), and ParaCore (Group III). Each group was further divided into subgroup a, b, and c on the basis of the thickness of the adhesive cement 50 μm, 200 μm, and 300 μm, respectively. All the models were simulated to be cemented with computer-aided designed glass fiber post and core followed by zirconia crown. The core was modeled with incomplete ferrule. The load of 200N at 45° at lingual and central fossa was applied. Maximum von Mises stresses distribution was calculated. Results: Maximum and minimum stresses in dentin were seen in the Ic and IIIa, respectively. Maximum and minimum stresses in cement were seen in IIIc and Ia, respectively. Conclusion: The von Mises stresses in dentin can be minimized by keeping the cement thickness minimum and selecting the cement whose modulus of elasticity is closest to that of dentin.

This study evaluated the effect of Er,Cr:YSGG laser on the root canal dentin after luting a fiber post. Twenty-four bovine teeth roots were prepared using NiTi instruments and filled with Sealer 26 and gutta-percha. Post spaces were prepared and roots were distributed according to dentin treatment (n = 8): 2.5%NaOCl (group control), Er,Cr:YSGG laser (1.5 W, 20 Hz, 20 s) (group test 1) or 2.5%NaOCl + Er,Cr:YSGG laser (group test 2). Fiber posts were luted using adhesive cement (Rely X U200, 3M) and roots were prepared to confocal laser scanning microscopy (CLSM) and scanning electron microscope (SEM). The morphology of interface, thickness of cement, and the gaps and tags were analyzed. Non-parametrical data for thickness of cement were submitted to Friedman and Kruskall–Wallis tests (α = 0.05) and parametrical data for gaps to ANOVA (α = 0.05). CLSM of the cement thickness and gaps revealed no significant difference in surface treatment (NaOCl, Er,Cr:YSGG laser and NaOCl + Er,Cr:YSGG laser) (p > .05) and canal thirds (cervical, middle, and apical) (p > 0.05). SEM showed tags and a residual layer of cement adhered to dentin, mainly in laser-irradiated specimens. The pretreatment of root canal with Er,Cr:YSGG laser previously to luting the fiber post with a self-adhesive cement did not influence the cement thickness and gaps but affected the dentin interaction.