Internal Adaptation of Composite Fillings Made Using Universal Adhesives-A Micro-Computed Tomography Analysis.

This study aimed to evaluate internal tooth-filling interfaces of composite fillings made using universal adhesives using micro-computed tomography (µCT). Sixty class V cavities were randomly assigned into six groups: Peak Universal etch and rinse (PER), Peak Universal self-etch (PSE), Adhese Universal etch and rinse (AER), and Adhese Universal self-etch (ASE). Two further adhesives considered gold standards were used as control groups: OptiBond FL (OER) for the etch and rinse technique and Clearfil SE for the self-etch technique (CSE). All teeth were subjected to thermomechanical loading and four-year water storage. Next, they were analyzed using µCT to investigate the internal tooth-filling interfaces. The proportions between the gap volume (GV) at the tooth-filling interface and the volume of applied composite filling (FV), between the gap and cavity volumes (CV), and between the gap volumes at the tooth-filling interface of the external (EGV) and internal (IGV) parts were calculated. Adhese Universal achieved the significantly lowest gap-to-filling- and gap-to-cavity-volume ratios for both types of etching techniques comparing to those of the Peak Universal and control groups. Significant differences between the gaps in external and internal parts of the tooth-filling interface were only noted in the control groups. Internal gap formation and development at the tooth-filling interface depend on the material as well as the type of its application.

Optimal Plate Choice for High-Neck Mandibular Condyle Fracture: A Mechanistic Analysis of 16 Options.

(1) Background: Mandibular fractures are common, with the condylar process being a frequent site of injury, accounting for 25-45% of cases. This research aims to assess the mechanical suitability of various plates for high-neck condyle fractures. (2) Methods: Polyurethane models mimicking high-neck condyle fractures were utilized in this study. Sixteen distinct plate designs, constructed from titanium sheets, were tested. The figures underwent force assessments on a durability testing apparatus, and the relationship between used force and fracture movement was documented. (3) Results: For high-neck breaking, the two straight plates emerged as the most effective, aligning with established osteosynthesis standards. The second-best plate exhibited nearly half the strength of the gold standard. (4) Conclusions: In response to the aim of this study, considering the mechanical aspects, the double plain plate stands out as the optimal choice for osteosynthesis in cases of high-neck fractures of the mandibular condylar process. In addition, the authors propose the Mechanical Excellence Factor (MEF) as a superior metric for appraising a plate's mechanical force, surpassing the conventional Plate Design Factor (PDF).

Which of the 37 Plates Is the Most Mechanically Appropriate for a Low-Neck Fracture of the Mandibular Condyle? A Strength Testing.

(1) Background: The mandible is the most frequently injured component of the facial skeleton, with 25-45% of mandibular fractures involving the condylar process. This study aims to mechanically compare which plates are most suitable for use in low-neck fractures of the condyle. (2) Methods: Polyurethane mandibular models with simulated low-neck fractures were tested using 37 distinct plate designs. These plates were fabricated from 1 mm thick, grade 23 titanium sheets. The models were then subjected to force tests on a strength machine, and the correlation between applied force and fracture displacement was recorded. (3) Results: For low-neck fractures, XCP side-dedicated 3+5 and ACP-T plates demonstrated strength comparable to that of two straight plates, the current gold standard in osteosynthesis. (4) Conclusions: The Mechanical Excellence Factor (MEF) introduced by the authors provides a more accurate metric for theoretically predicting a plate's mechanical strength compared to the Plate Design Factor (PDF). Eight plate characteristics were utilized to calculate the MEF. Employing the MEF allows for rapid, preliminary validation before undertaking strength tests. Furthermore, the findings of this study can guide the selection of the most durable plate designs for subsequent fatigue testing.

Evaluation of Fracture Resistance of Occlusal Veneers Made of Different Types of Materials Depending on Their Thickness.

Pathological tooth wear is an escalating social problem. Occlusal veneers can be an alternative to traditional prosthetic restorations such as crowns, inlays, and onlays. BACKGROUND: The aim of this study is to assess the fracture resistance of occlusal veneers made of various materials depending on their thickness. METHODS: In total, 120 occlusal veneers were examined. The restorations were made of four ceramics: leucite LC (IPS Empress Esthetic), hybrid HC (Vita Enamic), lithium disilicate LDC (IPS e.max Press), and zirconium oxide ZOC (Ceramill Zolid HT). A total of 30 veneers were made of each material, 10 for each of the three thicknesses: 1 mm, 1.5 mm, 2 mm. The restorations were cemented on identical abutments duplicated from the developed phantom tooth 35 (KaVo) with composite cement (All Bond Universal). The samples prepared in this way were subjected to a compressive strength test in a universal testing machine. Statistical analysis of the results was performed. RESULTS: The average fracture resistance of occlusal veneers made of zirconium oxide ceramic was 1086-1640 N, of lithium disilicate ceramics 456-1044 N, of hybrid ceramics 449-576 N, and of leucite ceramics 257-499 N. CONCLUSIONS: Occlusal veneers made of ceramics, zirconium oxide and lithium disilicate, had the highest resistance to fractures. Restorations made of leucite ceramics turned out to be the least resistant to forces. The greater the thickness of the ceramic occlusal veneers, the greater their fracture resistance.

The Influence of Alumina Airborne-Particle Abrasion with Various Sizes of Alumina Particles on the Phase Transformation and Fracture Resistance of Zirconia-Based Dental Ceramics.

The surface of zirconia-based dental ceramic restorations require preparation prior to adhesive cementation. The purpose of this study was to assess the influence of airborne-particle abrasion with different sizes of alumina particles (50 µm, 110 µm, or 250 µm) on the mechanical strength of zirconia-based ceramics' frameworks and on the extent of phase transformations. A fracture resistance test was performed. The central surface of the frameworks was subjected to a load [N]. The identification and quantitative determination of the crystalline phase present in the zirconia specimens was assessed using X-ray diffraction. The Kruskal-Wallis one-way analysis of variance was used to establish significance (α = 0.05). The fracture resistance of zirconia-based frameworks significantly increases with an increase in the size of alumina particles used for air abrasion: 715.5 N for 250 µm alumina particles, 661.1 N for 110 µm, 608.7 N for 50 µm and the lowest for the untreated specimens (364.2 N). The X-ray diffraction analysis showed an increase in the monoclinic phase content after air abrasion: 50 µm alumina particles-26%, 110 µm-40%, 250 µm-56%, and no treatment-none. Air abrasion of the zirconia-based dental ceramics' surface with alumina particles increases the fracture resistance of zirconia copings and the monoclinic phase volume. This increase is strongly related to the alumina particle size.

Evaluation of the Relationship of Screw Pullout and Plate Fracutre in Fixation of Mandible Condyle Fractures: A Mechanistic Study.

BACKGROUND: The mandible is the most injured part of the facial skeleton, and 25-40% of mandibular fractures involve the condyle process. The aim of this study is to answer the question of the relationship between screw pullout and/or plate fracture during osteosynthesis. METHODS: We tested polyurethane models of mandibles whose condylar process was cut (simulating a fracture) and fused using plates and screws. RESULTS: A total of 672 plates were tested. A total of 25.6% of them were fractured during the test, with most being fractures of the base of the condyle. More screws (81.97%) are pulled out from the ramus than from the condyle-69.15%. CONCLUSIONS: The gold standard in the osteosynthesis of condylar fractures is two straight plates. Other than these, there is no one-size-fits-all plate for every type of fracture. Plates fixed with fewer screws (smaller plates used in higher-lying fractures) are more likely to result in screw pullout. On the other hand, in plates fixed with more screws, plate fracture is more common.

Which of 51 Plate Designs Can Most Stably Fixate the Fragments in a Fracture of the Mandibular Condyle Base?

In the surgical treatment of the most common fracture of the mandible, which is a fracture of the condylar base, a great choice of different plate shapes is observed. The aim of this study was to determine which shape gives the greatest fixation stiffness. To ensure homogeneity in comparison, tests were performed on polyurethane models divided at the level of the condylar base fracture and each were fixed with 51 plates. The plates were cut from a 1 mm thick grade 23 titanium sheet. The models were then loaded and the force required for 1 mm of fracture displacement was recorded. It was noted that in addition to osteosynthesis from two simple plates, there were also two dedicated single plates with similar rigidity. Among the large number of described designs of plates, there is considerable variation in terms of the stability of the fixation performed with them. The proposed Mechanical Excellence Factor allows a pre-evaluation of the expected rigidity of fixation with a given plate shape without the need for a loading experiment. The authors expect this to be helpful for surgeons in the application of relevant plates, as well for inventors of new plates for the osteosynthesis of basal fractures in mandibular condyle.

The Effect of Acrylic Surface Preparation on Bonding Denture Teeth to Cellulose Fiber-Reinforced Denture Base Acrylic.

Patients who require dental prosthetic restoration using frame dentures in the front part of the mouth very frequently report that teeth fall out of their dentures. However, the available scientific papers are insufficient to compare the various methods of improving the connection between the denture base and the artificial tooth and choosing the best solution. This paper focuses on providing all parameters, enabling the reproduction of tests, and accounting for all variables. The paper uses an original method of creating grooves, sandpaper, sandblasting, and cutting the acrylate layer with a burr in one and two directions. Developed surfaces were additionally subjected to detailed examination. This study used 180 specimens divided into three groups and subjected to various environments (dry, artificial saliva, and thermocycles). Shearing and tensile strength tests were performed. The best results were obtained with a carbide burr. The increase in connection durability was as follows in the case of the shear test: 116.47% in dry samples, 155.38% in samples soaked in artificial saliva, and 46.59% in samples after thermocycles. The increase in tensile resistance was: 198.96% in a dry environment, 88.10% before being soaked in artificial saliva, and 94.04% after thermocycles.

The Influence of Low-Molecular-Weight Monomers (TEGDMA, HDDMA, HEMA) on the Properties of Selected Matrices and Composites Based on Bis-GMA and UDMA.

Bisphenol A-glycidyl methacrylate (bis-GMA) and urethane dimethacrylate (UDMA) are usually combined with low-viscosity monomers to obtain more desirable viscosity, handling characteristics and general properties. The present study determined the flexural strength (FS), flexural modulus (FM), diametral tensile strength (DTS), and hardness (HV) of five matrices and composites based on these resins. The polymerization shrinkage stress (PSS) was also studied for the composites. The polymer matrices were formed using bis-GMA and UDMA. TEGDMA, HEMA and HDDMA acted as co-monomers. The composites had 45 wt.% of filler content. The highest FS and FM were obtained from the UDMA/bis-GMA/TEGDMA/HEMA matrix and the composite (matrix + filler). The best DTS values were obtained from the UDMA/bis-GMA/HEMA matrix and the composite. One of the lowest values of FS, FM, and DTS was obtained from the UDMA/bis-GMA/HDDMA matrix and the composite. All the composites demonstrated similar hardness values. The lowest polymerization shrinkage stress was observed for the UDMA/bis-GMA/TEGDMA/HEMA composite, and the highest PSS was observed for the UDMA/bis-GMA/TEGDMA/HDDMA composite. The addition of HEMA had a positive effect on the properties of the tested materials, which may be related to the improved mobility of the bis-GMA and UDMA monomers.

The Influence of Various Photoinitiators on the Properties of Commercial Dental Composites.

The aim of this article was to compare the biomechanical properties of commercial composites containing different photoinitiators: Filtek Ultimate (3M ESPE) containing camphorquinone (CQ); Estelite Σ Quick (Tokuyama Dental) with CQ in RAP Technology®; Tetric EvoCeram Bleach BLXL (Ivoclar Vivadent AG) with CQ and Lucirin TPO; and Tetric Evoceram Powerfill IVB (Ivoclar Vivadent AG) with CQ and Ivocerin TPO. All samples were cured with a polywave Valo Lamp (Ultradent Products Inc.) with 1450 mW/cm2. The microhardness, hardness by Vicker's method, diametral tensile strength, flexural strength and contraction stress with photoelastic analysis were tested. The highest hardness and microhardness were observed for Filtek Ultimate (93.82 ± 17.44 HV), but other composites also displayed sufficient values (from 52 ± 3.92 to 58,82 ± 7.33 HV). Filtek Ultimate not only demonstrated the highest DTS (48.03 ± 5.97 MPa) and FS (87.32 ± 19.03 MPa) but also the highest contraction stress (13.7 ± 0.4 MPa) during polymerization. The TetricEvoCeram Powerfill has optimal microhardness (54.27 ± 4.1 HV), DTS (32.5 ± 5.29 MPa) and FS (79.3 ± 14.37 MPa) and the lowest contraction stress (7.4 ± 1 MPa) during photopolymerization. To summarize, Filtek Ultimate demonstrated the highest microhardness, FS and DTS values; however, composites with additional photoinitiators such as Lucirin TPO and Ivocerin have the lowest polymerization shrinkage. These composites also have higher FS and DTS and microhardness than material containing CQ in Rap Technology.

Numerical Analysis of the Bond Strength between Two Methacrylic Polymers by Surface Modification.

The creation of acrylic dentures involves many stages. One of them is to prepare the surfaces of artificial teeth for connection with the denture plates. The teeth could be rubbed with a chemical reagent, the surface could be developed, or retention hooks could be created. Preparation of the surface is used to improve the bond between the teeth and the plate. Choosing the right combination affects the length of denture use. This work focuses on a numerical analysis of grooving. The purpose of this article is to select the shape and size of the grooves that would most affect the quality of the bond strength. Two types of grooves in different dimensional configurations were analyzed. The variables were groove depth and width, and the distance between the grooves. Finally, 24 configurations were obtained. Models were analyzed in terms of their angular position to the loading force. Finite element method (FEM) analysis was performed on the 3D geometry created, which consisted of two polymer bodies under the shear process. The smallest values of the stresses and strains were characterized by a sample with parallel grooves with the grooving dimensions width 0.20 mm, thickness 0.10 mm, and distance between the grooves 5.00 mm, placed at an angle of 90°. The best dimensions from the parallel (III) and cross (#) grooves were compared experimentally. Specimens with grooving III were not damaged in the shear test. The research shows that the shape of the groove affects the distribution of stresses and strains. Combining the selected method with an adequately selected chemical reagent can significantly increase the strength of the connection.

The Influence of Cement Layer Thickness on the Stress State of Metal Inlay Restorations-Photoelastic Analysis.

The successful restoration of teeth requires a good connection between the inlay and natural tissue. A strong bond may improve retention and reinforce tooth structure. The purpose of this study was to evaluate the influence of cement layer thickness on contraction stress generated during photopolymerization, and to determine the changes in stress state of the cement occurring during aging in water (over 84 days). Two cements were used: resin composite cement (NX3) and self-adhesive resin cement (Maxcem Elite Chroma). A cylindrical sample made of CuZn alloy was used to imitate the inlay. The stress state was measured by photoelastic analysis. The contraction stress of the inlay restoration was calculated for cement layer thicknesses of 25 µm, 100 µm, 200 µm, and 400 µm. For both tested materials, the lowest contraction stress was observed for the thinnest layer (25 µm), and this increased with thickness. Following water immersion, a significant reduction in contraction stress was observed due to hygroscopic expansion. Applying a thin layer (approximately 25 µm) of composite and self-adhesive resin cements resulted in high levels of expansion stresses (over -6 MPa) after water aging.

Open Rigid Internal Fixation of Low-Neck Condylar Fractures of the Mandible: Mechanical Comparison of 16 Plate Designs.

BACKGROUND: In the literature, no information on plates for low-neck mandibular condylar osteosynthesis can be found, despite the fact that 30 plate designs have already been published. The aim of this study was to compare any dedicated plates for possible use in low-neck condylar fracture osteosynthesis. METHODS: The force required for 1-mm displacement of the fixed fracture fragments and incidents of screw loosening were recorded on polyurethane mandibles among 16 designs of titanium plates fixed by 6-mm screws in a 2.0 system. RESULTS: Double-straight plate fixation was the mechanical gold standard (15.2 ± 3.5 N), followed by A-shape Condylar Plates (14.9 ± 2.1 N), X-shape Condylar Plates (14.2 ± 1.3 N) and Auto Repositioning Plates (11.8 ± 2.4 N). Screw loosening was uncommon, as a minimum of three screws were placed into the condylar part. Fewer screws were lost from the ramus part of the fixation if the plate was attached to the condylar part by three screws. Often, the stability of the ramus screws was lost when there were only two fixing screws in the condyle (p < 0.001). CONCLUSIONS: It is advisable to consider the mechanical advantages as one decides which plate to choose for open rigid internal fixation in low-neck condylar fractures, or to only be aware of the significant differences in mobility within the fracture line after fixation with different dedicated plates.

Mechanical Evaluation of Titanium Plates for Osteoesynthesis High Neck Condylar Fracture of Mandible.

BACKGROUND: In the literature no information about plates for the high-neck mandibular condylar osteosynthesis could be found despite that 30 plate designs have been published. The main course consider the basal condylar or diacapitular fractures. The aim of the study was to test mechanically all available designs (only 4 of 30 was proper) on polyurethane mandibles using an individually designed clamping system. METHODS: Forces required for a 1 mm displacement of fixed fracture fragments and incidents of screw loosening were recorded. RESULTS: It has occured that dedicated plates for fixation are much weaker than set of two straight plates (p<0.0001). General observation is the bigger plate and more screws, the better rigid stable osteosynthesis of mandibular condyle, however, there are limitations in plates design for high-neck fractures resulted in restricted operation field. CONCLUSION: Double straight plates occured to be the best mechanical fixation for high-neck fractures of the mandibular condyle. Maybe other existing plates could be used but only after prebending or that fracture required novel dedicated plates design.

Evaluation of gap formation at the composite resin-tooth interface after using universal adhesives: In vitro SEM study using the replica technique.

The aim of this study was to evaluate gap formation after using two universal adhesives, Peak Universal Bond (P), which contains chlorhexidine and Adhese Universal (A), which contains 10-MDP monomer, and to compare them with two gold standard adhesives. The adhesives were tested in different etching modes, etch-and-rinse (ER) or self-etch (SE), and under thermomechanical loading (TML). Two identical Class V cavities were prepared in each of 30 human third molar teeth, and resin-composite restorations were made. Before and after TML, replicas of the restorations were prepared. Gap formation and their frequency according to the modified classification of Blunck and Zaslansky and the width of the maximum marginal gap (MG) were separately evaluated in enamel and dentin. Gap frequency did not differ significantly only in the enamel before TML, despite the use of different adhesives or etching modes. At both timepoints, the highest MG values were obtained with the Peak Universal Bond self-etch (PSE) group in enamel (6.2 µm before TML, 12.2 µm after TML) and the Peak Universal Bond etch-and-rinse (PER) group in dentine (21.3 µm before TML, 35.5 µm after TML). After TML, there was a significant increase of gap frequency for Adhese universal self-etch (ASE) group and MG values for PER, PSE, ASE groups at the resin-enamel interface, and gap frequency and MG values for all groups at the resin-dentin interface. Universal adhesive with 10-MDP monomer have beneficial effect on the resin-dentin interface, while chlorhexidine may reduce the resistance of the universal adhesive system to oral cavity conditions.

Forces Causing One-Millimeter Displacement of Bone Fragments of Condylar Base Fractures of the Mandible after Fixation by All Available Plate Designs.

BACKGROUND: There has been no direct comparison of all existing plates dedicated for fracture osteosynthesis of mandibular condyle base until now. The aim of the study was to test mechanically all available designs of titanium plates on the market on polyurethane mandibles using an individually designed clamping system. METHODS: Forces required for a 1 mm displacement of fixed fracture and incidents of screw loosening were recorded. Results indicated the best mechanical plates among all existing designs available. RESULTS: It has occured that some of osseofixation plates should not be used any more, whereas some shape of the single plates are similar shape to two single plates shape are regarded as the best osseofixation method for condyle base fracture. CONCLUSION: General observation is the bigger plate and more screws, the better rigid stable osteosynthesis of mandibular condyle base. 4 plates of current designs of total 30 tested series can be recommended for open rigid internal fixation of fractures of the base of the mandibular condyle. The rest of 26 existing plates should not be used in condylar base fractures.

Contraction and Hydroscopic Expansion Stress of Dental Ion-Releasing Polymeric Materials.

Ion-releasing polymeric restorative materials seem to be promising solutions, due to their possible anticaries effect. However, acid functional groups (monomers) and glass filler increase hydrophilicity and, supposedly, water sorption. The purpose of the study was to evaluate the influence of water sorption of polymeric materials on the stress state at the restoration-tooth interface. Beautifil Bulk Fill Flow, Beautifil Flow Plus F00, Beautifil Flow F02, Dyract eXtra, Compoglass Flow, Ionosit, Glasiosite, TwinkiStar, Ionolux and Fuji II LC were used for the study. The stress state was measured using photoelastic analysis after: 0.5, 24, 72, 96, 168, 240, 336, 504, 672, 1344 and 2016 h. Moreover, water sorption, solubility and absorption dynamic were assessed. The water sorption, solubility and absorption dynamic of ion-releasing restorative materials are material dependent properties. The overall results indicated that the tested restorative materials showed significant stress decrease. The total reduction in contraction stress and water expansion stress was not observed for materials with low value of water sorption (Beautifil Bulk Fill, Dyract eXtra, Glasionosit and Twinky Star). The photoelastic method turned out to be inadequate to evaluate stress changes of resin modified glass-ionomer cement (RMGI, Fuji II LC and Ionolux).

The Influence of Water Sorption of Dental Light-Cured Composites on Shrinkage Stress.

The contraction stress generated during the photopolymerization of resin dental composites is the major disadvantage. The water sorption in the oral environment should counteract the contraction stress. The purpose was to evaluate the influence of the water sorption of composite materials on polymerization shrinkage stress generated at the restoration-tooth interface. The following materials were tested: Filtek Ultimate, Gradia Direct LoFlo, Heliomolar Flow, Tetric EvoCeram, Tetric EvoCeram Bulk Fill, Tetric EvoFlow, Tetric EvoFlow Bulk Fill, X-tra Base, Venus BulkFil, and Ceram.X One. The shrinkage stress was measured immediately after curing and after: 0.5 h, 24 h, 72 h, 96 h, 168 h, 240 h, 336 h, 504 h, 672 h, and 1344 h by means of photoelastic study. Moreover, water sorption and solubility were evaluated. Material samples were weighted on scale in time intervals to measure the water absorbency and the dynamic of this process. The tested materials during polymerization generated shrinkage stresses ranging from 6.3 MPa to 12.5 MPa. Upon water conditioning (56 days), the decrease in shrinkage strain (not less than 48%) was observed. The decrease in value stress in time is material-dependent.

Radio-opaque polyethylene for personalized craniomaxillofacial implants.

OBJECTIVE: This study aimed to present a new possibility to create radio-opaque implant material for craniomaxillofacial reconstruction. MATERIALS AND METHODS: The test disks made of the own compound of polyethylenes with addiction of 2, 4, and 6 % of weight TiO2 was investigated for cytotoxicity [each group 15 disks respectively]. Next, computed tomography of the disks was performed in environment of muscle and fat. Hardness, tensile modulus and strength, and compressive modulus and strength were tested too. RESULTS: Deterioration of mechanical properties of the composites containing titanium dioxide was observed [hardness, tensile modulus and strength, compressive modulus and strength, respectively: 56.7 ± 1.6 shore D, 354 ± 52, 22.5 ± 1.3, 21.8 ± 1.1, and 2995 ± 327 MPa as addiction of 2 % TiO2; 52.0 ± 0.9 shore D, 347 ± 66, 18.0 ± 0.7, 14.2 ± 0.9, and 1396 ± 477 MPa as 4 % TiO2; 51.3 ± 1.3 shore D, 316 ± 9, 17.4 ± 0.2, 13.6 ± 0.6, and 1100 ± 144 MPa as 6 % TiO2 added]. The test disks revealed no cytotoxicity effect on human osteoblasts. The new material presents mild radio-opacity which was enough to observe the implant in relation to fat and muscle, but with no visible effect of beam hardening. CONCLUSION: In view of the performed tests, the polyethylene enriched by titanium dioxide seems to be a proper material to consider manufacturing of craniomaxillofacial implants. CLINICAL RELEVANCE: Maxilloafacial surgery is still looking for new implantologic materials. The proposed one is a new way to manufacture an implant visible in computed tomography which does not interfere with its shape in radiological examination and makes it possible to observe the surrounding soft tissues.