Conventional Dental Impressions vs. Impressions Reinforced with Rigid Mouthguards.

The impression materials utilized today in dental medicine offer a good reproducibility and are easily accepted by patients. However, because they are polymer-based, they have issues regarding their dimensional stability. In this respect, the present work proposes a new type of dental impression, which is reinforced with rigid mouthguards. The aim of the study is to test the performances of such new impressions by comparing them to conventional ones-from this critical point of view, of the dimensional stability. Three types of polymeric materials were considered for both types of impressions: alginate, condensation silicone, and addition silicone. In order to obtain the new type of impressions, a manufacturing technique was developed, comprising the following phases: (i) conventional impressions were made; (ii) a plaster model was duplicated, and 15 rigid mouthguards were obtained; (iii) they were inserted in the impression technique, with each mouthguard positioned on the cast before the high-consistency material was inserted in the tray and the practitioner took the impression; (iv) the mouthguard remained in the tray and the low-viscosity material was inserted over the mouthguard; (v) the impression was positioned on the model, and after the material hardened, the mouthguard-reinforced impression was analyzed. In the evaluation of the dimensional stability, rigorous statistical analysis was essential to discern the performance differences between conventional and mouthguard-reinforced dental impressions. Statistical analyses employed non-parametric Mann-Whitney U tests because of the non-normal distribution of the data. They indicated a statistically significant improvement in the dimensional stability of addition silicone impressions when reinforced with mouthguards (p < 0.05), showcasing superior performance over conventional methods. Conversely, alginate and condensation silicone reinforced impressions did not exhibit the same level of stability improvement, suggesting the need for further optimization of these materials. In conclusion, from the three considered elastomers, addition silicone was found to be the prime candidate for high-precision dental impressions, with the potential to improve their quality from conventional impressions by utilizing the proposed reinforcing technique.

The Influence of Hydrofluoric Acid Temperature and Application Technique on Ceramic Surface Texture and Shear Bond Strength of an Adhesive Cement.

All-ceramic restorations are the foundation of modern esthetic dentistry. Clinical approaches for preparation, durability, aesthetics, and repair have been reformed by the idea of adhesive dentistry. The aim of the study and the objective question was to evaluate the impact of heated hydrofluoric acid pretreatment and the application technique's influence on the surface morphology and roughness of leucite-reinforced glass-ceramic materials (IPS Empress CAD, Ivoclar Vivadent), which is fundamental for understanding the adhesive cementation process. Scanning electron microscopy was used to observe the effectiveness of the two HF (Yellow Porcelain Etch, Cerkamed) application techniques and the HF's temperature impact on the surface topography of the ceramic. Based on surface conditioning methods, the adhesive cement (Panavia V5, Kuraray Noritake Dental Inc., Tokyo, Japan) was applied to the conditioned ceramic samples and light-cured. Shear bond strength values were correlated with the micro-retentive surface texture of the ceramic. With universal testing equipment at a 0.5 mm/min crosshead speed, SBS values between the resin cement and the ceramic material were assessed until failure. Analyzing the fractured surfaces of the specimens by digital microscopy, the failure modes were divided into three categories: adhesive, cohesive, and mixed failure. Analysis of variance (ANOVA) was used to statistically analyze the collected data. The results show that alternative treatment methods affected the material's surface characteristics and have an influence on the shear bond strength.

The Influence of a Novel, Crenelated Design of CAD-CAM Ceramic Veneers on the Debonding Strength.

(1) Background: Aesthetic dentistry has become one of the most dynamic fields in modern dental medicine. Ceramic veneers represent the most appropriate prosthetic restorations for smile enhancement, due to their minimal invasiveness and highly natural appearance. For long-term clinical success, accurate design of both tooth preparation and ceramic veneers is of paramount importance. The aims of this in vitro study were to assess the stress in anterior teeth restored with Computer-Aided Design (CAD) and Computer-Aided Manufacturing (CAM) ceramic veneers and compare the resistance to detachment and the fracture of ceramic veneers prepared using two different designs. (2) Methods: Sixteen lithium disilicate ceramic veneers were designed and milled using the CAD-CAM technology and divided into two groups according to the preparations (n = 8): Group 1, conventional (CO), with linear marginal contour and Group 2, crenelated (CR), the latter with our novel (patented) sinusoidal marginal design. All samples were bonded to anterior natural teeth. The mechanical resistance to detachment and fracture was investigated by applying bending forces on the incisal margin of the veneers in order to determine which type of preparation leads to better adhesion. An analytic method was employed, as well, and the results of the two approaches were compared. (3) Results: The mean values of the maximum force recorded at the veneer detachment were 78.82 ± 16.55 N for the CO group and 90.20 ± 29.81 N for the CR group. The relative increase, equal to 14.43%, demonstrated that the novel CR tooth preparation provided higher adhesive joints. In order to determine the stress distribution within the adhesive layer, a finite element analysis (FEA) was performed. The statistical t-test showed that the mean value of the maximum normal stresses is higher for the CR-type preparations. (4) Conclusions: The patented CR veneers represent a practical solution to augment the adhesion and mechanical properties of ceramic veneers. The obtained results demonstrated that CR adhesive joints triggered higher mechanical and adhesive forces, which subsequently led to a higher resistance to detachment and fracture.

Assessment of Different Techniques for Adhesive Cementation of All-Ceramic Systems.

Background and Objectives: Modern esthetic dentistry is based on all-ceramic restorations. Dentists still have reservations about using these restorations due to a lack of understanding of the cementation technique, which depends on the type of ceramic used. The aim of the study is to evaluate the approaches and practices of clinicians regarding the adhesive cementation of all-ceramic restorations. Materials and Methods: An online questionnaire regarding the use of all-ceramic restorations and their bonding methods was designed by distinguishing the cementation of oxide and silica-based ceramics. The survey included dentists practicing in Timiș County, Romania. The questionnaire and the evaluation of the answers were designed based on the techniques and evidence from the literature. Results: Considering the work experience, we obtained two groups: group 1-1 to 6 years and group 2-6 to 9+ years. The results revealed significant values when comparing the two groups in the surface protocol and decontamination (p = 0.005), type of cement used (p = 0.002), and isolation techniques (p = 0.002). Conclusions: The results show that many clinicians need additional training to improve their cementing technique and avoid the confusion caused by insufficient information about the interrelationship between the type of ceramic and the cementation procedure.

Micro-CT and Microscopy Study of Internal and Marginal Gap to Tooth Surface of Crenelated versus Conventional Dental Indirect Veneers.

Background and Objectives: Ceramic veneers represent the most appropriate treatment option for minimally invasive aesthetic rehabilitation. For long-term clinical success, the accurate marginal and internal adaptation of dental restorations are of paramount importance. The aim of this in vitro study is to assess the effect of a novel (patented) design of veneers compared to conventional ones on their marginal and internal gap to the prepared tooth surface. Materials and Methods: Twenty-four lithium disilicate ceramic veneers are obtained using Computer-Aided-Design (CAD) and then milled using Computer-Aided-Manufacturing (CAM). The samples are divided into two groups: 12 conventional (CO) veneers (i.e., with a linear marginal contour) and 12 crenelated (CR) veneers, the latter with the novel sinusoidal marginal design. All samples are bonded to frontal teeth, and the adhesive interfaces are analyzed using two methods, optical microscopy and micro-Computed Tomography (CT): the former for the accuracy of the marginal gap and the latter for the internal gap (as well as for the homogeneity of the luting cement) of ceramic veneers. Results: STATA and one-way ANOVA tests reveal significant differences between CO and CR veneers: (i) the marginal gap is smaller for CR (64 µm) than for CO veneers (236 µm); (ii) the internal adaptation is better for CR veneers: for a cement width of up to 120 µm, the covered surface for the CR group is 81.5%, while for the CO group it is 64.5%; (iii) the mean of the porosities within the cement is not significantly different (3.4·106 µm3 for CO and 3.9·106 µm3 for CR veneers), with a higher standard deviation for the CO group. Analytical modeling is achieved for internal gaps using the micro-CT results. The characteristic functions obtained allow us to compare the volume of luting cement for the two types of veneers. Conclusion: The novel veneers design produces an improvement in the marginal and internal adaptation of the restorations to the prepared tooth surface. Thus, it provides favorable premises for better clinical performances.

Influence of the Printing Angle and Load Direction on Flexure Strength in 3D Printed Materials for Provisional Dental Restorations.

The CAD/CAM techniques, especially additive manufacturing such as 3D printing, constitute an ever-growing part of obtaining different dental appliances and restorations. Of these, provisional restorations are of frequent use in daily dental practice and are the object of this study. Masticatory and parafunctional forces determine flexure on these prostheses. This study investigates the influence of the printing angle and loading direction of the applied force on the flexure strength of two commercially available printable resins-Detax Freeprint Temp and Nextdent MFH Vertex dental. Ten rectangular beam specimens printed at the angle of 0, 45 and 90 degrees were fabricated of each of these materials, with an addition of 10 at 0 degrees for the investigation of the load direction. Three-point bending tests were performed in a universal testing machine. Flexure strength, strain at break and Young's modulus were determined and a statistical analysis was performed on the obtained data. According to the statistical analysis, the flexural strength has a significance dependence with respect to degrees of orientation, for both investigated materials.

Endodontic fillings evaluated using en face OCT, microCT and SEM.

OBJECTIVES: The goal of endodontic therapy is mechanically cleaning and shaping the root canal system, the removal of organic and inorganic debris followed by sealing with permanent filling materials. MATERIALS AND METHODS: Therefore, the aim of this in vitro study was to engage three imagistic methods: (i) en face (ef) time domain (TD) optical coherence tomography (OCT), (ii) micro-computed tomography (µCT), and (iii) scanning electron microscopy (SEM), in terms of their efficiency in assessing the quality of endodontic fillings. So far, is settled that efOCT images can identify defects∕voids in several of the investigated root canal fillings and identify gaps of 50 µm. RESULTS: The results delivered by µCT technology also showed several imperfections of the endodontic filling but also at the interfaces formed by the sealer and the root canal walls. SEM investigations highlights the complex form of the interface formed the endodontic filling material and the walls of the root canal, as well as shortcomings of the materials from several samples. Gaps of 50 µm are identified with efOCT. CONCLUSIONS: The net advantage of OCT technology, in respect to the other two technologies consists in its non-invasiveness. The OCT axial resolution is also sufficient to see the material gaps. Another advantage of efOCT investigations is that they allow real-time imaging of complex arrangement at the interfaces of the filling material with dentinal root.

Morphological aspects in remineralizing potential of Silver Diamine Fluoride.

OBJECTIVES: The purpose of this study was to demonstrate the efficacy of Silver Diamine Fluoride (SDF) antibacterial solution in penetrating the demineralized areas of enamel. MATERIALS AND METHODS: It was considered a group of four extracted teeth (with no color fading, fissures, decay, or demineralization). Each tooth was sectioned in two equal parts, in mesio-distal direction, using a dental handpiece and a special rounded, flat bur. Each specimen was demineralized, for one minute, with 45% orthophosphoric acid, on occlusal and proximal zones. The specimens were then washed and dried with water-air dental syringe. All the probes were inspected with an optical microscope and enamel thickness was digitally measured. Advantage Arrest (Elevate Oral Care, USA), which contains SDF, was applied on the previous demineralized zones. The penetration of the substance was visually inspected with the optical microscope and electronically measured. RESULTS: It was observed an improvement in remineralizing the white spots on enamel surfaces, the optical microscope being able to detect both demineralization and the penetration of SDF through enamel. CONCLUSIONS: Based on our in vitro study, SDF (Advantage Arrest) was capable to induce/increase enamel remineralization, through SDF penetration.

The use of baropodometric analysis in musculoskeletal disorders of dentists working in orthostatic posture - a series of 3 cases.

INTRODUCTION: Musculoskeletal disorders (MSDs) caused by incorrect working posture among dentists is a serious issue and one that leads to decreased productivity and quality of life. AIM: The aim of this study was to evaluate the impact of MSDs caused by postural errors in dental healthcare professionals on the body's center of gravity through a new and innovative technique - baropodometry. METHODS: In this study we included 3 oral healthcare specialists with over 20 years experience of practicing in orthostatism, with confirmed work-related MSDs, and performed a baropodometric analysis on them. RESULTS: According to the analysis, all 3 test subjects had alterations of the body's center of gravity, with uneven distribution of pressures on the feet being recorded by the baropodometer. CONCLUSION: In an effort to maintain a good field of view and workplace in orthostatism, the subject is forced to adopt an non-ergonomic position that leads to uneven weight distribution, shifted center of gravity that eventually cause musculoskeletal disorders.

Dental Adhesive Interfaces Reinforced with Magnetic Nanoparticles: Evaluation and Modeling with Micro-CT versus Optical Microscopy.

Dental adhesives are used in a wide range of applications, including to place direct composite restorations in frontal or posterior teeth. One of the most frequent causes for the failure of composite resin restorations is microleakages. The first aim of this work is to introduce a new type of self-etched dental adhesive doped with magnetic nanoparticles (MPs) synthetized in the laboratory. The scope is to produce adhesives with a minimized width/thickness to decrease the risk of microleakages. The second aim is to assess the width/thickness of the adhesive layer in all the characteristic areas of the teeth using both the less precise but most common optical microscopy and the more accurate and volumetric micro-Computed Tomography (CT) investigations. Twenty extracted teeth have been divided into four groups: Group 1 includes 'blank' samples with adhesives that are not doped with MPs; Group 2 includes samples with adhesives doped with MPs; Groups 3 and 4 include samples with adhesives doped with MPs that are subjected to an active magnetic field for 5 and 10 min, respectively. Microscopy investigations followed by micro-CT and EDAX are performed on the adhesive. While a rather good agreement is obtained between the microscopy and micro-CT results, the capability of the latter to offer a full volumetric reconstruction of the layer is exploited to analyze the adhesion of the four considered dental materials. Thus, from micro-CT results the graphs of the surface areas as functions of the adhesive layer width are modeled mathematically, as well as the volume of sealants, for each of the four groups. To our knowledge, it is the first time that such a methodology is used. Characteristic parameters are extracted and the ascertainment of the optimal parameter that should be utilized for such assessments is discussed. The study demonstrates the adhesion improvement produced for Groups 3 and 4, where MPs are used. It also concludes that the magnetic field should be applied to the adhesive material for the longest possible exposure time (with a trade-off with the clinical duration of the treatment).

Micro-CT and optical microscopy imagistic investigations of root canal morphology.

Protecting the root's internal morphology is the first key toward the success of the endodontic treatment. Due to the vast diversity of endodontic space, it is difficult to visualize and to establish the shape and limits of the root canal, especially the morphology of apical area and lateral root canals. Optical microscopy is a classical imagistic investigation method, widely used along classical methods like radiographs that also offer limited information about root morphology and extension of decay. Micro-computed tomography (micro-CT), a modern imagistic investigation method can provide detailed three-dimensional reconstructions of root canal. Micro-CT is a non-invasive method that has the possibility to offer cross-sectional and axial images of the endodontic space. The success of root canal treatment is based on cleaning and shaping. Beyond these two procedures, sealing the endodontic space by respecting its limits is another prerequisite for long-term success of endodontic therapy. Micro-CT can perform three-dimensional reconstruction of the root canal, root canal filling and can provide accurate images of the endodontic space. The assessment of root morphology can be obtained through imagistic invasive optical microscopy and already mentioned non-invasive methods (micro-CT). The aim of this study is to illustrate and analyze the endodontic space, according to its diversity by using micro-CT, a non-invasive imagistic investigation method an also optical microscopy. The two techniques can also provide the extension of carries or demineralized substance on different levels of the root.

Zirconia enriched dental adhesive: a solution for OCT contrast enhancement. Demonstrative study by synchrotron radiation microtomography.

OBJECTIVE: The major aim of this study was to prove the capability of the optical coherence tomography (OCT) method in visualizing the integrity of the adhesive fillings and of the interfaces between the adhesive, tooth structures and composite resin. As zirconium dioxide was added to the composition of the adhesive layer in order to strengthen the backscattered light in the OCT investigation, for a better visualization of the interfaces, the determination of a proper zirconia concentration was another aim of our study. METHOD: Several class II cavities were prepared in human premolars and were filled with dental adhesive containing different zirconia concentrations and light-curing composite resin. Both OCT and synchrotron radiation microtomography (micro-CT) were used to analyse the morphology of the tooth-adhesive-composite interfaces and to investigate the adhesive layer. RESULTS: The pore distribution, both at the interfaces level and in the resin, and the analysis of the adhesive layer integrity were obtained. A good agreement between OCT and micro-CT analyses was observed in terms of detecting discontinuities in the adhesive layer. Furthermore, micro-CT showed that zirconia percentages in the adhesive higher than 20 vol.% lead to conglomerates formation, which can negatively influence mechanical properties. Meanwhile, OCT confirmed a factor of 3 for the contrast enhancement when 20% of zirconia was included in the adhesive composition. SIGNIFICANCE: The present study proved the capability of the OCT method in visualizing the morphology and integrity of zirconia doped tooth adhesive fillings, to be used for a further in vivo tool development.

Cervical microleakage in Class II cavities restored with the Sonicsys approx system.

OBJECTIVE: To investigate the cervical microleakage in Class II cavities restored with Sonicsys approx ceramic inserts and four resin-based materials. METHOD AND MATERIALS: Forty noncarious and crack-free mandibular third molars were used. These teeth were randomly assigned to four groups each containing 10 teeth. No control group was created. On each tooth, one mesial boxlike cavity was prepared using the active head Sonicsys approx no. 3. The cervical margin of each cavity was in enamel about 1 mm coronal to the cementoenamel junction. According to manufacturer's instructions, the prepared cavities were restored using a Sonicsys approx ceramic inserts no.3 and four resin-based materials as follows: group 1, Tetric Flow; group 2, Admira Flow; group 3, Nexus 2; group 4, X-Flow. After finishing and polishing, all specimens were stored in distilled water for 7 days at 37 degrees C, thermocycled 1,000 cycles between 5 degrees and 55 degrees C, and stored for 24 hours in basic fuchsine 2%. All specimens were then embedded in clear acrylic resin and sectioned along a mesial-distal plane through the middle of the cervical margin. The cervical areas of the resulting sections were examined using an optical microscope to assess the dye penetration. The registered scores were analyzed using Kruskal-Wallis and Mann-Whitney U tests. RESULTS: Microleakage was detected in each experimental group. Kruskal-Wallis test revealed statistically significant differences among groups (P = .009, alpha = .01). The Mann-Whitney U test showed significant differences between Admira Flow group and Tetric Flow (P = .011, alpha = .05), Nexus 2 (P = .001, alpha = .01), and X-Flow (P = .004, alpha = .01), respectively. CONCLUSION: Within the limitations of this study, the extent of microleakage in the cervical area (enamel) of Class II cavities restored with Sonicsys approx ceramic inserts depends on the material used for luting. The highest leakage occurred when Admira flow was used.

Chromatic behavior of porcelain fired on titanium.

OBJECTIVE: To investigate the chromatic changes of 3 porcelains after firing on titanium. METHOD AND MATERIALS: Thirty-six veneer crowns were obtained by firing 3 different porcelains to titanium: Ti22 (Noritake), Triceram (Esprident), and Vitatitankeramik (Vita). A single shade was used for each porcelain. Besides the titanium-porcelain specimens, 3 titanium-free controls (one for each porcelain) were obtained. A spectrophotometer was used to measure the color of porcelain facings of the veneer crowns and the porcelain controls. Once the chromatic digital values were recorded, the color differences between the titanium-porcelain samples and the corresponding porcelain controls were computed. The results were statistically analyzed. RESULTS: The least chromatic difference was observed for Ti22 porcelain, and the greatest difference for Triceram porcelain. Regarding the direction of the chromatic alteration after firing on titanium, very significant differences were found between the porcelains. CONCLUSION: Perceivable differences were found between the shade of the porcelain fired to titanium and that of the same porcelain fired alone. No significant differences were found between the 3 porcelains regarding the total chromatic modification.

The marginal fit of porcelain veneers on titanium copings: an in vitro study.

OBJECTIVES: To compare the cervical microleakage of titanium copings veneered with 3 porcelain-based materials with that of titanium copings veneered with 2 indirect polymeric materials. METHOD AND MATERIALS: Commercially pure, grade 2 titanium was veneered with 3 porcelain systems specially designed for fusing on titanium: Ti22 (Noritake), Triceram (Esprident), and Vitatitankeramik (Vita). Additionally, 2 polymeric materials were used for veneering titanium: Chromasit and Targis (Ivoclar). Four veneer crowns for each titanium-veneer combination were obtained. After storing the specimens in basic fuchsin, the microleakage between titanium and veneer in the cervical area was assessed by measuring the extent of dye penetration within the interface. ANOVA and post hoc statistics were used to analyze the data. RESULTS: Chromasit exhibited the highest mean microleakage score (3 +/- 0.816). The least mean microleakage at the interface was recorded for Ti22 porcelain (0 +/- 0.0), followed by Triceram (0.25 +/- 0.50), Vitatitankeramik (0.75 +/- 0.957), and Targis (1.5 +/- 1.732). Only the differences between each porcelain system and Chromasit were significant (P <.05). CONCLUSION: Within the limitations of this in vitro study, there was no significant microleakage between titanium copings and the porcelain veneers, regardless of the porcelain system. The microleakage between titanium and the polymeric materials depended on the veneering material. Leakage was significantly higher when Chromasit was used.

The microleakage between alloy and polymeric materials in veneer crowns.

OBJECTIVE: This study investigated the cervical microleakage between a cobalt-chromium (Co-Cr) alloy and four indirect polymeric veneering materials using different adhesive systems. METHOD AND MATERIALS: The Co-Cr-based alloy for fixed prosthesis used in this study (Biosil F, Degussa) was veneered with four different polymeric materials: Artglass, Chromasit, Solidex, and Superacryl. RESULTS: Superacryl produced the highest microleakage score (4 +/- 0.0). The least microleakage at the interface was produced by Artglass (1 +/- 0.816), followed by Chromasit (2 +/- 1.414) and Solidex (2.5 +/- 1.0). Only the differences between Artglass and Superacryl were significant. CONCLUSION: Within the limitations of this in vitro study, cervical microleakage between the coping and the veneer depended on the particular polymeric material used for veneering. Leakage was significantly lower when resin materials were used together with a chemical conditioning system (ie, Artglass/Siloc).

Investigation of microleakage at the interface between a Co-Cr based alloy and four polymeric veneering materials.

STATEMENT OF PROBLEM: . Marginal adaptation and resistance to microleakage are important factors for clinical success in fixed prosthodontics. Alloy corrosion that sometimes occurs under a veneer in the cervical area may result in cervical staining, a metallic taste, or even failure of the interface. PURPOSE: This study investigated cervical microleakage between a Co-Cr alloy and 4 indirect polymeric veneering materials used with different conditioning systems. MATERIAL AND METHODS: Sixteen metallic frameworks (copings) were obtained by fabricating 0.6-mm calibrated wax patterns on a master cast abutment. The wax patterns were provided with 0.4-mm beaded retention on the veneering surfaces and cast in a Co-Cr based alloy (Biosil F) used for fixed partial dentures. The Co-Cr copings were divided equally into 4 groups and veneered with 4 polymeric materials (Signum, Solidex, Superpont C+B, and Targis). Three chemical conditioning systems (Siloc, Targis-Link, and Silicoater MD) were used with the respective veneering system recommended by the manufacturer; Conolar opaque was used for Superpont C+B. No control group was created. After 2 weeks of storage in distilled water at 37 degrees C, 2000 cycles at 5-55 degrees C, and 24 hours of storage in 0.5% basic fuchsine, specimens were embedded in clear liquid casting resin and sectioned along a perpendicular cervical-incisal plane through the middle of the cervical collar. The surfaces of the resulting sections were examined in the cervical area with a metallurgical microscope to detect dye penetration. Leakage was quantitatively evaluated with the use of a scoring system (established by the authors) that indicated the presence/absence of dye in 3 regions of the cervical interface from the collar to the incisal margin. Scores were compared and analyzed with the use of 1-way analysis of variance followed by post-hoc Tukey's honestly significant difference test (P=.05). RESULTS: Superpont C+B was associated with the highest microleakage scores (3.75 +/- 0.5). The least microleakage at the interface was produced by Targis (1 +/- 0.816), followed by Solidex (2.5 +/- 1.0) and Signum (2.25 +/- 0.975). Only the difference between Targis and Superpont C+B was significant (P<.05). CONCLUSION: Within the limitations of this in vitro study, the extent of cervical microleakage between the coping and veneer depended on the particular polymeric material used for veneering. The extremes of the study were Targis/Targis-Link (lowest leakage scores) and Superpont C+B (highest leakage scores). Differences among the chemical retention systems tested were not significant.