Effect of Abutment Geometry and Luting Agents on the Vertical Marginal Discrepancy of Cast Copings on Implant Abutments: An In Vitro Study

Aim. Vertical marginal discrepancy (VMD) influences the success of implant-supported restorations. However, there is little literature that has investigated the influence of geometry and cementing agent on changes in VMD of metal copings on implant abutments. The objective was to evaluate the effect of the geometry of the abutment and cementing agents on VMD. Methods. Cast copings were cemented on implant abutments customized cylindrical (4, 5.5, and 7 mm) and on hexagonal implant abutments (4 mm) cemented or uncemented molded copings were placed (n = 4, totally 64 samples) with different luting agents. The VMD of the copings were measured in the coping-abutment interface at three reference points using a stereomicroscope. The independent Student’s t test was used for comparison between the two different abutment walls. The post hoc statistical analysis was performed by the Tukey test. Results. There was a significant VMD increase between noncemented and cemented cast copings using different luting agents. Abutment geometry and luting agents significantly influenced the VMD p ≤ 0.05 . Cylindrical abutment at 7 mm in height cemented with different luting agent tested showed significantly higher VMD values than cylindrical abutments of 4 mm p = 0.019 . Hexagonal abutments with a 4 mm height showed significantly higher VMD values than cylindrical 4 mm abutments using zinc oxide noneugenol and glass ionomer cements p = 0.032 . Conclusions. Abutment geometry and luting agents influence the VMD of cast copings cemented on implant abutment. The higher the cylindrical abutment, the greater the VMD, and hexagonal wall abutments promote greater marginal gap.

In vitro evaluation of the influence of titanium nitride coating on the retention force between components of two-part abutments

Background Two-part abutments are typically made up of a base composed of titanium and a ceramic build-up. The long-term outcomes are affected by the mechanical durability. The purpose of the present investigation was to evaluate and compare the retention force of two-part abutment systems with titanium or titanium nitride bases—as fixed with zirconia components and with various surface treatments. Methods A total of 60 two-part abutments were investigated—with a titanium base (n = 30) or titanium nitride coated bases (n = 30) and bonded with zirconia ceramic build-ups. The bonding surfaces were treated with aluminium oxide blasting, with an average particle size of 110 µm. The titanium bases were then pretreated with Alloy Primer or Clearfil Ceramic Primer. The ceramic build-ups were only treated with Clearfil Ceramic Primer. For twenty test specimens, no chemical pretreatment was performed. Test specimens were classified into six groups in accordance with the pretreatment (A–F; n = 10). A resin-based luting agent was employed to attach the two parts. Specimens were then subjected to artificial thermal aging (104 cycles with 5 °C/55 °C). The retention force between the two parts was then investigated with a pull-off test. The findings were analyzed by ANOVA statistics. Fracture patterns were examined by electron microscopy. Results In the absence of primer, titanium nitride coated bases gave significantly greater retention forces than other samples (p < 0.05). Chemical preconditioning with silane coupling agents did not effect on the retention force of coated bases. Conclusions The results of the current study suggested that modifying metal surfaces by coating the base with titanium nitride not only has esthetic and biological advantages, but also enhances the mechanical properties of the adhesive bond of two-part abutments.

UV-Mediated Photofunctionalization of Indirect Restorative Materials Enhances Bonding to a Resin-Based Luting Agent

Purpose. The potential of UV-mediated photofunctionalization to enhance the resin-based luting agent bonding performance to aged materials was investigated. Methods. Sixty samples of each material were prepared. Yttria-stabilized zirconia (YZr) and Pd-Au alloy (Pd-Au) plates were fabricated and sandblasted. Lithium disilicate glass-ceramic (LDS) was CAD-CAM prepared and ground with #800 SiC paper. Half of the specimens were immersed in machine oil for 24 h to simulate the carbon adsorption. Then, all of the specimens (noncarbon- and carbon-adsorbed) were submitted to UV-mediated photofunctionalization with a 15 W UV-LED (265 nm, 300 mA, 7692 μW/cm2) for 0 (control groups), 5, and 15 min and subjected to contact angle (Ɵ) measurement and bonded using a resin cement (Panavia™ V5, Kuraray Noritake, Japan). The tensile bond strength (TBS) test was performed after 24 h. The Ɵ (°) and TBS (MPa) data were statistically analyzed using two-way ANOVA and Bonferroni correction tests ( α = 0.05 ). Results. In the carbon-adsorbed groups, UV-mediated photofunctionalization for 5 min significantly decreased Ɵ of all materials and increased TBS of YZr, and UV for 15 min significantly increased the TBS of LDS and Pd-Au. In noncarbon-adsorbed groups, UV-photofunctionalization did not significantly change the Ɵ or TBS except YZr specimens UV-photofunctionalized for 15 min. Conclusion. UV-mediated photofunctionalization might have removed the adsorbed hydrocarbon molecules from the materials’ surfaces and enhanced bond strengths of Panavia™ V5 to YZr, LDS, and Pd-Au. Additionally, UV-mediated photofunctionalization improved the overall TBS of YZr. Further investigation on the optimum conditions of UV photofunctionalization on indirect restorative materials should be conducted.

What’s new for the clinician? - Excerpts from and summaries of recently published papers

Choosing an endodontic sealer clinical use is a decision that contributes to the long-term success of non-surgical root canal treatment. Sealers are used as a thin tacky paste which function as a lubricant and luting agent during obturation, allowing the core obturation material, such as gutta-percha points or other rigid materials, to slide in and become fixed in the canal. Sealers can fill voids, lateral canals, and accessory canals where core obturation materials cannot infiltrate. If the sealer does not perform its function, microleakage may cause root canal failure via clinically undetectable passage of bacteria, fluids, molecules or ions between the tooth and restorative material. It has been reported that extrusion of the sealer during root canal filling has cytotoxic effects on periapical tissues, causing periapical inflammation, necrosis and pain. Endodontic sealers are categorized by composition based on setting reaction and composition: zinc oxide eugenol, salicylate, fatty acid, glass ionomer, silicone, epoxy resin, tricalcium silicate, and methacrylate resin sealer systems. Aslan & Özkan (2021) reported on a trial that sought to evaluate the effect of two calcium silicate-based root canal sealers, Endoseal MTA and EndoSequence BC Sealer, on postoperative pain following single-visit root canal treatment on molar teeth compared to their epoxy/ amine resin-based counterpart AH Plus. The null hypotheses tested in this study were as follows:1. The type of sealer used would not change the incidence and the intensity of post-treatment endodontic pain2. The analgesic intake of patients following single-visit root canal treatment

Comparison of Volumetric Dimensional Changes of Calcium Aluminate, Resin Modified Glass Ionomers and Resin Luting Cements Among Different Storage Conditions

Objective: The aim was to evaluate the volumetric dimensional changes of calcium aluminate glass-ionomer luting agent to resin modified-Glass ionomer cement (RM-GIC), self-etch and conventional resin based cement (RBC) among different storage conditions. Methods: Twenty cylindrical specimens (7 mm × 2 mm) for four cements [Calcium aluminate (Ceramir-CM), RM-GIC (Fuji Plus-FP), RBC (Rely X Ultimate-RA) and RBC-self-etch (Rely X Unicem-RU)] were fabricated and polished. Five specimens from each material were randomly assigned to the four test conditions. These conditions were silicone oil at 22 °C and 37 °C and distilled water at 22 °C and 37 °C respectively. A resolution balance was used to measure the weight of each specimen at 1, 2, 3 and 4 weeks. Archimedes’ principle equations were used to measure volumetric dimensional changes. Ion release analysis for Ca+ and OH- of the storage medium solution of calcium aluminate cement was performed using atomic absorption spectroscopy and pH measurement respectively at 1, 2, 3 and 7 weeks. Data was analyzed using ANOVA and Tukey post hoc test. Results: A significant difference in volumetric changes (ρ < 0.05) was observed for different cements. Calcium aluminate (CM) showed maximum volumetric changes followed by FP. However, resin cements (RA and RU) showed significantly lower volumetric changes. Oil immersion exhibited shrinkage and water immersion showed volumetric expansion in all materials. Increase in duration of immersion, increased the dimensional changes (shrinkage or expansion) among all cement groups (ρ < 0.05). Both temperature and duration showed significant influence on Ca+ ion release. Conclusions: Calcium aluminate cement had the highest level of dimensional changes (17.28% and 20.52%) while both resin luting agents show least expansion without a significant difference between them. Ceramir luting agent expands significantly in water and continues to release Ca2+ ions with time and higher temperature. The clinical use of calcium aluminate cements based on the high dimensional changes observed in the study is debatable.

Micromorphology of the Adhesive Interface of Self-Adhesive Resin Cements to Enamel and Dentin

Interfaces between dentin, enamel and luting agents were characterized using low vacuum Scanning Electron Microscopy (SEM). After smear layer creation, one of three luting agents (RelyX Unicem 2, Clearfil SA Cement and Panavia F 2.0/ED Primer II) was applied on 60 enamel-dentin specimens and dual-cured or self-cured. Specimens were polished (Experiment 1) and subsequently demineralized and deproteinized (Experiment 2). Adhesive interfaces were analyzed (low vacuum SEM, ×3000). Presence of an interdiffusion zone, tag-like structures (dentin) and marginal gaps (enamel) were assessed. Non-parametrical tests (χ2-test, α = 0.05) were performed. The first null-hypothesis was that the adhesive interface micromorphology between enamel and dentin and self-adhesive resin cements (SARCs) is similar with conventional resin cement used with a self-etch adhesive (CRC+SE). The second null-hypothesis was that the micromorphology is not influenced by curing modes. Interdiffusion zones and tag-like structures (dentin) were observed more frequently for CRC+SE compared to SARCs. For each luting agent, there was a non-significant (p > 0.05) tendency for interdiffusion zone and tag-like structures detectable in more specimens after self-curing compared to dual-curing. Marginal gaps (enamel) were found only for SARCs. The first null-hypothesis was not rejected fully: Tag-like structures and interdiffusion zones in dentin were found for CRC+SE and SARCs. The second null-hypothesis was not rejected.