Glycolic acid on push-out bond strength of fiber post and smear removal: an in vitro study.

This study aims to investigate glycolic acid (GA) as a final irrigant on push-out bond strength of fiber post and smear removal. Ninety mandibular premolars were stabilized with a silicone key and photographed, and canal cross-section was calculated by image processing software. Round canal morphology was selected. The specimens were divided into five groups (n = 18); 10%GA, 17%EDTA, NaOCl + 10%GA, NaOCl + 17%EDTA, and the control. Fifteen specimens were used for the push-out. Three specimens were evaluated using a scanning electron microscope after post space preparation. Two-way ANOVA and Chi-square were used for statistics. GA presented higher strength than EDTA (p < 0.05). The NaOCl + GA showed higher strength than the NaOCl + EDTA (p < 0.05). The highest values were observed in cervical and lowest in apical thirds (p < 0.05). The most failure type was between dentin and resin (p < 0.05). GA removed the smear in the post space including the apical third. The NaOCl + GA has superiority to NaOCl + EDTA on push-out strength. Glycolic acid improved the bond strength of fiber post when used as a final post space irrigant. The combination of NaOCl and glycolic acid did not negatively affect the bond strength and was more effective compared to the combination with EDTA. Glycolic acid improved the bond strength of fiber post when used as a final post space irrigant. The combination of NaOCl and glycolic acid did not negatively affect the bond strength and was more effective compared to the combination with EDTA.

Fracture Resistance of the Bundle Post System and Conventional Fiber Post with Different Lengths.

This study compares the fracture strength of teeth restored with conventional round fiber post (CP) and bundle post (BP) in two different lengths. A total of 48 mandibular premolars were selected. Endodontic treatment was performed, and the premolars were divided into four groups (n = 12 per group): Group C9 = 9-mm CP; Group C5 = 5-mm CP; Group B9 = 9-mm BP; Group B5 = 5-mm BP. Post spaces were prepared, and posts were disinfected with alcohol. Silane was applied, and posts were placed with self-etch dual-cure adhesive. The core structures were created using dual-cure adhesive and standardized core-matrix. Specimens were embedded in acrylic, and the periodontal ligament was simulated with polyvinyl-siloxane impression material. Thermocycling was performed, and specimens were then loaded at a 45-degree angle to the long axis. The failure mode was analyzed with ×5 magnification, and statistical analyses were performed. No statistical difference was found between post systems and post lengths (P > .05). Chi-square test revealed no statistical difference in the failure mode (P > .05). BP did not affect fracture resistance compared to CP. For the restoration of extremely irregular canals with a fiber post, BP can be used as an alternative system because it does not reduce the fracture strength. If necessary, longer posts can be used without decreasing the fracture resistance.

In vivo vs. in vitro color stability of hybrid ceramic and resin nanoceramic blocks used for endocrowns: A new method.

PURPOSE: To evaluate and compare in vitro and in vivo color parameters of hybrid ceramic, resin nanoceramic, and artificial acrylic resin teeth. METHODS: For the in vitro stages, 120 specimens (2 mm) were prepared from Vita Enamic (VE), Lava Ultimate (LU), CeraSmart (CS), and acrylic teeth (IV), and immersed in coffee, red wine, and distilled water for 24, 72, and 144 hours. For the in vivo stage, 16 individuals received a complete denture that had upper premolars made of VE, LU, CS blocks, and IV. The color was measured at 1, 3, and 6 months. Color difference (ΔE00), translucency (TP), and contrast ratio (CR) were obtained using a spectrophotometer. Shapiro Wilk, one-way ANOVA, and repeated measures ANOVA were used for statistical analysis. RESULTS: ΔE00 of VE and LU were higher than CS and IV (P< 0.05). ΔTP of VE and LU were lower than CS and IV (P< 0.05). ΔTP of CS was higher in red wine compared to coffee. ΔCR of CS and IV were increased with prolonged immersion (P< 0.001). ΔE00 and ΔCR were similarly affected in coffee and red wine. All discolorations were higher than clinical acceptability (ΔE00> 1.77). For in vivo stages, ΔE00 of VE and LU increased over time (P< 0.01). No difference was detected between in vivo and in vitro ΔE00 of CS (P> 0.05). ΔE00 of VE, LU, and IV was higher in in vitro stages. LU and VE showed lower color stability; their use in esthetic regions is questionable. The prolonged immersion increased discoloration. Coffee and red wine had a similar effect on discoloration and opalescence. Discoloration in laboratory conditions did not correspond to the clinical discoloration according to the new method presented in this study. CLINICAL SIGNIFICANCE: The use of CAD-CAM blocks for endocrowns is rising; however, Lava Ultimate and Vita Enamic showed lower color stability, thus, their use in esthetic regions is questionable. This is the first study that investigates the discoloration of CAD-CAM blocks in clinical use. Discoloration in laboratory conditions did not correspond to the clinical discoloration.

Finite element analysis of stress distribution in autotransplanted molars.

OBJECTIVE: The biomechanical response of an autotransplanted tooth and surrounding bone to occlusal loads is not well-known. The aim of the present study was to investigate the effect of root form and occlusal morphology on stress distribution in autotransplanted teeth and surrounding bone by using finite element analysis (FEA). METHODS: Seven FEA models representing different autotransplanted tooth situations were generated: (a) first molar, (b) third molar, (c) root canal-treated third molar, (d) root canal-treated, ankylosed, third molar, (e) crowned third molar, (f) crowned and root canal-treated third molar, (g) root canal-treated, ankylosed, and crowned third molar. Load (200 N) was applied on the occlusal surface, parallel to the long axis of the tooth. Maximum von Mises stress values on dentin and surrounding bone were calculated for each situation. RESULTS: Differences in stress distribution were observed among models. In ankylosed model, stress was primarily observed at the coronal region of the tooth. The stress was observed more at the coronal region of the tooth in crowned models compared with the non-crowned models. The stress distribution was homogeneous with root canal-treated and crowned autotransplanted tooth. CONCLUSIONS: The occlusal morphology and root form of the autotransplanted tooth affected the stress in surrounding bone at the transfer site and the biomechanical response of the tooth. The stress was more homogeneous in crowned tooth and primarily observed at the coronal region, which may decrease the risk for root resorption. CLINICAL SIGNIFICANCE: Root configuration, occlusal form and root canal treatment induce significant changes on the stress distribution on teeth and bone, including characteristic stress concentration and increased stress values. Clinicians can consider crowning autotransplanted teeth for improved stress distribution within the tooth structure.

Stress distribution of a novel bundle fiber post with curved roots and oval canals.

OBJECTIVE: The aim of this study was to compare the stress distribution of teeth with curved and straight roots with oval and round canals restored with the bundle and conventional post systems. MATERIAL AND METHODS: Six three-dimensional premolars were modeled with round and oval canals, and curved roots using the software. The bundle post and the round posts were modeled. All post models were placed on the canals. The models were subjected to 200 N oblique loading. The results were evaluated by von Mises stresses. RESULTS: This study demonstrated that the bundle post showed higher stress values compared to the conventional post. The stresses in the oval canal were higher than those in the round canal. The highest stress values were found in the curved roots. The stress distribution on the curved roots was observed in the middle and apical third of the canal. CONCLUSION: The bundle post presented higher stress compared to conventional posts. Besides, a more uniform stress distribution was observed in the bundle groups. CLINICAL SIGNIFICANCE: When a post was required in extremely irregular, wide canals and curved roots, the bundle post was the material of choice. Canal and root morphology influenced stress distribution.

Mechanical properties of glass-fibre-reinforced composite posts after laser irradiation with different energy densities.

The aim of the present study was to evaluate the effect of the surface treatments on flexural strengths and flexural modulus of glass-fibre-reinforced composite (GFRC) posts. Sixty-three posts were randomly divided into 9 groups (n = 7), and various surface treatments were performed. The control group was left untreated. Other groups were treated with 9% hydrofluoric acid, sandblasting with 120 µm Al2 O3 particles and Er,Cr:YSGG laser irradiation with different powers (1 W, 2 W, 3 W, 4 W, 5 W and 6 W). The samples were subjected to 3-point bending test, and data were calculated. Statistical analysis was performed. The flexural strengths of fibre posts treated with sandblasting, hydrofluoric acid, 1 W and 2 W laser were statistically similar with control group (P > 0.01). However, the flexural strength of fibre posts treated with 3 W, 4 W, 5 W and 6 W laser was statistically lower than control group (P < 0.01). High laser irradiations cause melting on the post surface and breaks in fibrils.

Effects of Occlusal Scheme on All-on-Four Abutments, Screws, and Prostheses: A Three-Dimensional Finite Element Study.

An ideal occlusal scheme plays an important role in a good prognosis of All-on-Four applications, as it does for other implant therapies, because of the potential impact of occlusal loads on implant prosthetic components. The aim of the present 3D finite element analysis (FEA) study was to investigate the stresses on abutments, screws, and prostheses that are generated by occlusal loads via different occlusal schemes in the All-on-Four concept. 3D models of the maxilla, mandible, implants, implant substructures, and prostheses were designed according to the All-on-Four concept. Forces were applied from the occlusal contact points formed in maximum intercuspation and eccentric movements in canine guidance occlusion (CGO), group function occlusion (GFO), and lingualized occlusion (LO). The von Mises stress values for abutment and screws and deformation values for prostheses were obtained, and results were evaluated comparatively. It was observed that the stresses on screws and abutments were more evenly distributed in GFO. Maximum deformation values for prosthesis were observed in the CFO model for lateral movement both in the maxilla and mandible. Within the limits of the present study, GFO may be suggested to reduce stresses on screws, abutments, and prostheses in the All-on-Four concept.

Effect of Different Surface Treatments Applied to Short Zirconia and Titanium Abutments.

PURPOSE: The aim of this study was to compare the effect of different surface treatments applied to short titanium and zirconia abutments on the bond strength of single-unit zirconia crowns. MATERIALS AND METHODS: Sixty titanium abutments were shortened to 3 mm in length, fixed to analogs, and embedded in acrylic blocks. Three-dimensional views of abutments were obtained by scanning; then, zirconia abutments and copings were produced. The samples, which included titanium (n = 60) and zirconia (n = 60) abutments, were divided into five different groups (n = 12), and surface treatments were carried out; 1.5-W and 3-W Er,Cr:YSGG laser treatment, AL2O3 sandblasting, and tribochemical silica coating were applied to the groups, and the control group had no surface treatment. Copings were cemented to the samples with self-adhesive resin cement. The samples were then subjected to the pull-out test, and the results were processed via statistical analysis. RESULTS: There was a significant difference between the titanium and zirconia groups (P < .001). The mean bond strength values of the titanium samples were higher than those of the zirconia samples. The tribochemical silica coating gave a higher bond strength than the other treatments when applied to titanium abutments. For the zirconia abutments, the 1.5-W laser treatment, 3-W laser treatment, tribochemical silica coating, and Al2O3 sandblasting groups differed significantly from the control group; however, they were not significantly different from each other. CONCLUSION: The bond strength of zirconia crowns to short titanium and zirconia abutments increases with surface treatments. Furthermore, the surface treatments were more effective in increasing the bond strength for the titanium abutments than for the zirconia abutments.

The effects of different surface treatments on the shear bond strengths of two dual-cure resin cements to CAD/CAM restorative materials.

PURPOSE: The aim of the present study was to investigate the effects of surface treatments on the bond strengths between polymer-containing restorative materials and two dual-cure resin cements. MATERIALS AND METHODS: In the present study, rectangular samples prepared from Lava Ultimate (LU) and Vita Enamic (VE) blocks were used. The specimen surfaces were treated using CoJet sandblasting, 50 µm Al2O3 sandblasting, % 9 HF (hydrofluoric) acid, ER,Cr:YSGG laser treatment, and Z-Prime. Dual-cure resin cements (TheraCem and 3M RelyX U 200) were applied on each specimen's treated surface. A micro-tensile device was used to evaluate shear bond strength. Statistical analysis was performed using the SAS 9.4v3. RESULTS: While the bond strength using TheraCem with LU or VE was not statistically significant (P=.164), the bond strength using U200 with VE was statistically significant (P=.006). In the TheraCem applied VE groups, Z-Prime and HF acid were statistically different from CoJet, Laser, and Sandblast groups. In comparison of TheraCem used LU group, there was a statistically significant difference between HF acid and other surface treatments. CONCLUSION: The bonding performance between the restorative materials and cements were material type-dependent and surface treatment had a large effect on the bond strength. Within the limitations of the study, the use of both U200 and TheraCem may be suggested if Z-prime was applied to intaglio surfaces of VE. The cementation of LU using TheraCem is suitable after HF acid conditioning of the restoration surfaces.

Evaluation of the Bond Strengths between Dental Porcelain and Cobalt-Chromium Metal Frameworks Manufactured with Different Techniques after the Thermal Aging Process.

PURPOSE: The present study is aimed at examining the bond strength of cobalt-chromium (Co-Cr) metal frameworks, prepared through different techniques, to a single type of low-temperature porcelain system after the thermal aging process. METHODS: A hundred and twenty Co-Cr alloy framework specimens were prepared using conventional casting, CAD/CAM, and two commercially different laser sintering devices, and dental porcelain was applied to the specimens. A single type of dental porcelain (Kuraray Noritake Dental Inc., Tokyo, Japan) was applied to the specimens. After the subgroups were determined, half of the specimens were subjected to a thermal aging process. Bond strength of specimens was evaluated using a 3-point bending test. The surfaces of the fractured specimens were evaluated using a stereomicroscope. The metal-porcelain bonding area of samples randomly selected from 8 groups has been examined with SEM under ×1000 magnifications. Normality distribution of obtained data was examined using by a Kolmogorov-Smirnov test. The obtained data of the present study was statistically analyzed with a statistical package program (SPSS for Windows 22.0, Chicago, IL, USA). RESULTS: There was a statistically significant difference between CAD/CAM and the other three methods, and the bonding value of the CAD/CAM group was the highest among the groups. Besides, the bond strength between dental porcelain and 4 differently produced metal frameworks was high enough to surpass the acceptable threshold (>25 MPa) according to the ISO 9693. There was no statistically significant difference between thermal aging applied and nonapplied groups. CONCLUSIONS: Based on this study, it could be shown that the metal-ceramic bond strength is dependent on the manufacturing method used, but it is independent of the thermal aging application. It was found that the bond strength values of all samples with and without thermal aging application exceeded the minimum acceptable value of 25 MPa recommended by the ISO 9693.

Effects of overdenture attachment systems with different working principles on stress transmission: A three-dimensional finite element study.

PURPOSE: The aim of the present study was to compare the stress distributions on the dental implants, abutments, and bone caused by different overdenture attachment types under functional chewing forces. MATERIALS AND METHODS: The 3D finite element models of the mandible, dental implants, attachment types, and prostheses were prepared. In accordance with a conventional dental implant supported overdenture design, the dental implants were positioned at the bone level in the canine teeth region bilaterally. A total of eight models using eight different attachment systems were used in this study. All the models were loaded to simulate chewing forces generated during the centric relationship (450 N), lateral movement (400 N), protrusive movement (400 N), and also in the presence of a food mass unilaterally (200 N). Stress outputs were obtained as the maximum principal stress and the equivalent von-Mises stress. RESULTS: In all attachment types, higher stress values were observed in the abutments, dental implants, and bone in the magnet attachments in different loading conditions. The highest stress values were observed among the magnet systems in the components of the Titanmagnetics model in all loading conditions (stresses were 15.4, 17.7, and 33.1 MPa on abutment, dental implant, and bone, respectively). The lowest stress value was observed in the models of Zest and O-Ring attachments. CONCLUSION: The results of the present study implied that attachment types permitting rotation and tolerating various angles created lower stresses on the bone, dental implants, and abutments.

Use of a new skin colour measurement method for the investigation of relationship between skin and tooth colour.

PURPOSE: There is conflicting information about the relationship between tooth color and skin color in the literature. The aim of the present study was evaluation of the correlation between L, a, b values of skin and tooth shade using a new skin color measurement method. MATERIALS AND METHODS: CIELab values of teeth were obtained through measurements from the middle third of the labial surfaces on central incisors of individuals using a clinical spectrophotometer. CIELab values of the skin were measured through facial images using a software which was manufactured for present study. A statistical analysis program (SAS 9.4) was used for the analysis of the data. Kolmogorov-Smirnow test, t-test, and multivariate regression analysis were used to evaluate the data (α=0.05). RESULTS: Correlations between variables revealed that while the lowest and statistically insignificant correlations were observed with a* values of the skin, significant correlations did not exceed moderate level (p < .05). When considering regression analysis results, b* values of the skin had a statistically significant effect in describing b* values of the tooth, while L* and a* values of the skin were observed to be insufficient in describing L* and a* values of the teeth. CONCLUSION: Results of this study suggest that different significant correlations were observed between the skin and tooth color for different L*, a*, and b parameters (p <0.05 and p <0.01). The results indicated that skin color can be used for tooth color selection in case of loss of natural teeth or when discoloration is present on existing teeth.

Retrospective evaluation of marginal bone loss around implants in a mandibular locator-retained denture using panoramic radiographic images and finite element analysis: A pilot study.

BACKGROUND: The follow-up of the peri-implant marginal bone loss is the most important criterion for the determination of implant success. PURPOSE: The purpose of this study is to measure marginal bone loss using panoramic radiographic images (PRI) of patients treated using a mandibular, two implant-supported, locator-retained denture and to evaluate the compatibility of these findings with those of the finite element analysis (FEA). MATERIALS AND METHODS: The PRI of patients who had a mandibular, two implant-supported, locator-retained denture were assessed, and the mesial and distal marginal bone loss of both right- and left-sided implants was measured. Mandibular and maxillary models, which have the features of bilateral balanced occlusion, were created. The surfaces of the generated models were converted in a computer-aided design model that could be transferred to the FEA software, and the forces were defined on contacts formed in maximum intercuspation, lateral, and protrusive movement position for bilateral balanced occlusion. RESULTS: The bone loss in the mesial and distal regions at the right- and left-sided implants was not statistically significant. Higher stresses were formed on the vestibular side under protrusive movement, on the lingual side under maximum intercuspation, on the distolingual side under left unilateral biting, and on the mesiolingual side under right unilateral biting in the FEA. CONCLUSION: According to FEA, peri-implant bone resorption may be higher in the buccal and palatal regions, implying that panoramic radiographs can be misleading in understanding the amount of peri-implant bone resorption.

Finite Element Stress Analysis of Applied Forces to Implants and Supporting Tissues Using the "All-on-Four" Concept with Different Occlusal Schemes.

PURPOSE: The aim of this study was to evaluate stress distributions on implants and alveolar bone due to occlusal load produced during chewing by prostheses prepared according to the All-on-Four concept with different occlusal schemes using a finite element analysis method. MATERIALS AND METHODS: On standard jaw models, teeth were set in accordance with the basic standards of canine-guided occlusion, group function occlusion, bilateral balanced occlusion (BBO), lingualized occlusion, and monoplane occlusion schemes. Three-dimensional (3D) images of these models were obtained using a surface scanner. Implants, superstructures, the maxilla, and mandible were modeled in the All-on-Four concept with 3D modeling software. Forces were defined on contacts formed in maximum intercuspation, lateral, and protrusive movement position for all 5 occlusion types. Stress outputs were recorded as maximum and minimum principal stresses (Pmax , Pmin ) and von Mises stress values for the implants. RESULTS: The highest Pmax value for the maxilla was observed in cortical bone in the group function occlusion during lateral movement (15.56 MPa). For the mandible, the highest Pmax value was observed on the cortical bone in maximum intercuspation of lingualized occlusion (72.75 MPa). The highest Pmin value for the maxilla was observed during the lateral movement in group function and for the mandible in BBO (-29.23 and -86.31 MPa, respectively). The lowest stress values were observed with canine-guided occlusion in all related conditions and on all structures. CONCLUSIONS: With the limitations of this simulation study, considering stresses on alveolar bone and implants in All-on-Four applications, the use of canine-guided occlusion may be suggested.

Assessing staining resistance of a CAD/CAM interpenetrating network composite material.

BACKGROUND: Color change of dental materials over time because of staining agents has important effects on the long-term prognosis of dental esthetic treatments. In the present study, staining resistance of an interpenetrating network composite material with different translucency levels (translucent and high translucent) and various surface procedures for finishing were investigated. METHODS: Same shade CAD/CAM interpenetrating network composite specimens having two different translucency levels were prepared using by a water cooling cutting saw. Specimens were grouped and different finishing procedures were performed. Then, specimens were kept in distilled water, red wine and coffee for different periods. Color was evaluated before and after exposure to staining liquids using a clinical spectrophotometer. RESULTS: In the 7 days Glaze group (ΔE00 > 2.2), color difference was only perceivable in the specimens kept in red wine. In the 28 days red wine high translucent groups, only the high translucent Clinical group showed a clinically acceptable (ΔE00 < 2.2) color change. In the translucent groups kept in red wine, only the translucent Glaze group showed a clinically perceivable color change (ΔE00 > 2.2). In the 28 day measurements, all the translucent groups showed a clinically perceivable color change (ΔE00 > 2.2). Of the translucent groups kept in coffee for 28 days, it was observed that only the translucent Clinical group demonstrated a clinically non-perceivable color change (ΔE00 < 2.2). CONCLUSIONS: All the translucent groups kept in red wine showed a clinically perceivable color change after 28 days. Only the high translucent Clinical Kit group showed a clinically acceptable color change. Among high translucent and translucent specimens kept in coffee only the translucent Clinical group showed a clinically acceptable color change after 28 days.

Assessment the Bond Strength of Ceramic Brackets to CAD/CAM Nanoceramic Composite and Interpenetrating Network Composite after Different Surface Treatments.

Adult orthodontics may confront problems related to the bonding performance of orthodontic brackets to new generation restorative materials used for crown or laminate restorations. The aim of the present study was to investigate the shear bond strength of ceramic brackets to two new generation CAD/CAM interpenetrating network composite and nanoceramic composite after different surface treatments. Er,Cr:YSGG Laser, hydrofluoric acid (9%), sandblasting (50 µm Al2O3), and silane were applied to the surfaces of 120 CAD/CAM specimens with 2 mm thickness and then ceramic brackets were bonded to the treated surfaces of the specimens. Bond strength was evaluated using the shear bond strength test. According to the results, CAD/CAM block types and surface treatment methods have significant effects on shear bond strength. The lowest bond strength values were found in the specimens treated with silane (3.35 ± 2.09 MPa) and highest values were found in the specimens treated with sandblast (8.92 ± 2.77 MPa). Sandblasting and hydrofluoric acid surface treatment led to the most durable bonds for the two types of CAD/CAM blocks in the present study. In conclusion, different surface treatments affect the shear bond strength of ceramic brackets to CAD/CAM interpenetrating network composite and nanoceramic composite. Among the evaluated treatments, sandblasting and hydrofluoric acid application resulted in sufficient bonding strength to ceramic brackets for both of the CAD/CAM materials.

Effects of different surface finishing procedures on the change in surface roughness and color of a polymer infiltrated ceramic network material.

PURPOSE: Polymer infiltrated ceramic network (PICN) materials, also called hybrid ceramics, are new materials in dental market. The manufacturer of the PICN material VITA Enamic suggests 3 different finishing procedures for this new material. In the present study, surface roughness and color differences caused from different finishing procedures of VITA Enamic were investigated. MATERIALS AND METHODS: 120 specimens were prepared in dimensions 2 × 10 × 12 mm from VITA Enamic hybrid ceramic blocks with 'high translucency' and 'translucency 2M2' shades. The specimens were divided into 8 groups. For each group, different finishing procedures suggested by the manufacturer were performed. Surface roughness values were determined by a tactile portable profilometer. Color changes were evaluated using a clinical spectrophotometer. The data were analyzed using one-way ANOVA and Tukey's post-hoc comparison. The significance level was set at α=0.05. RESULTS: The roughest surfaces were observed in Glaze Groups. Their surface roughness values were similar to that of the control group. Clinical Kit and Technical Kit groups did not show a statistically significant difference regarding surface roughness (P>.05). The largest color difference regarding ΔE00 was observed in Clinical Kit finishing groups. There were also statistically significant color changes between the groups (P<.05). However, all the groups showed clinically acceptable color change (ΔE00<2.25) except Clinical Kit Groups (ΔE00>2.25). CONCLUSION: Within the limitations of the present study, it may be suggested that finishing the VITA Enamic restorations by Technical Kit instead of Glaze and Clinical Kit gives better clinical performance in regard to surface roughness and shade matching.