Influence of toothbrushing methods on tightening torque with healing abutments of different lengths: An in vitro study.

STATEMENT OF PROBLEM: Early tightening torque at the implant-healing abutment interface is a recognized concern in implant treatment. However, little is known regarding the effects of toothbrushing methods on the interface established between the implant and healing abutments of different heights. PURPOSE: The purpose of this in vitro study was to evaluate the effect of different toothbrushing methods on tightening torque for healing abutments of different heights. MATERIAL AND METHODS: A total of 60 implants (Bilimplant; Proimtech) were embedded in epoxy resin blocks. The following 6 test groups were established: healing abutments with manual toothbrush group (Oral B Pro Expert All in one; Oral B) and 4 mm height (MTB-4, (which served as the control); 6 mm height (MTB-6, which served as the control); sonic toothbrush group (Philips Sonicare 3100 Series; Philips Oral Healthcare) and 4 mm height (S-4); 6 mm height (S-6); oscillating/rotating toothbrush group (Oral B Smart 6 6000N; Oral B) and 4 mm height (OR-4) and 6 mm height (OR-6). Each specimen was tightened to 15 Ncm and brushed. The digital torque meter (Cap Torque Tester Series TT01; Mark10) was used to calculate the reverse torque values. RESULTS: The highest torque loss value in the average torque losses in the test groups was 1.3 (OR-6); the lowest was 0.3 (S-4). While a significant difference was found between groups S-4 and S-6 (P=.018), no statistically significant difference was found among the other groups (P>.05). CONCLUSIONS: Torque loss was greater in the healing abutment with a height of 6 mm and with the oscillatory and rotational brushing method.

Comparison of different digital shade selection methodologies in terms of accuracy.

PURPOSE: This study aims to evaluate the accuracy of different shade selection techniques and determine the matching success of crown restorations fabricated using digital shade selection techniques. MATERIALS AND METHODS: Teeth numbers 11 and 21 were prepared on a typodont model. For the #11 tooth, six different crowns were fabricated with randomly selected colors and set as the target crowns. The following four test groups were established: Group C, where the visual shade selection was performed using the Vita 3D Master Shade Guide and the group served as the control; Group Ph, where the shade selection was performed under the guidance of dental photography; Group S, where the shade selection was performed by measuring the target tooth color using a spectrophotometer; and Group I, where the shade selection was performed by scanning the test specimens and target crowns using an intraoral scanner. Based on the test groups, 24 crowns were fabricated using different shade selection techniques. The ΔE values were calculated according to the CIEDE2000 (2:1:1) formula. The collected data were analyzed by means of a one-way analysis of variance. RESULTS: For the four test groups (Groups C, Ph, S, and I), the following mean ΔE values were obtained: 2.74, 3.62, 2.13, and 3.5, respectively. No significant differences were found among the test groups. CONCLUSION: Although there was no statistically significant difference among the shade selection techniques, Group S had relatively lower ΔE values. Moreover, according to the test results, the spectrophotometer shade selection technique may provide more successful clinical results.

Effectiveness of surface polishing after debonding of metal brackets from different CAD-CAM materials.

PURPOSE: The purposes of this study were to compare and evaluate the surface texture of different restorative computer-aided design and computer-aided manufacturing (CAD/CAM) materials before bonding and after debonding of metal orthodontic brackets. MATERIALS AND METHODS: A total of 60 rectangular ceramic test specimens (n = 20 in each group) were prepared using feldspathic ceramic blocks (FLD; served as control), hybrid ceramic blocks (HC), and lithium disilicate ceramic blocks (LDC). Surface roughness (Ra) analysis was conducted using a profilometer before bonding the metal brackets. After the debonding and polishing procedures, a second surface roughness analysis was conducted on each specimen. The shear bond strength (SBS) test was applied to each specimen using a universal test machine for debonding the metal brackets. The debonded specimens were examined under a stereomicroscope and scored using a 4-step adhesive remnant index (ARI). The Ra and SBS values and the ARI scores were saved, and the data were analyzed statistically at a significance level of 0.05. One specimen from each group was examined under atomic force microscopy to visualize surface roughness. Furthermore, one specimen from each group was additionally prepared for scanning electron microscopy analysis. RESULTS: Statistically significant differences in SBS measurements were observed between all three groups. The highest SBS values were obtained from the FLD group, the lowest from the LDC group. The HC group showed significantly (P = 0.001) lower Ra values than the LDC and FLD groups after debonding and polishing. No significant differences were observed in the ARI scores between the groups. CONCLUSIONS: Hybrid ceramics could be a suitable alternative for fixed restorations in adult patients receiving subsequent treatments with fixed orthodontic appliances.

Evaluation of the flexural strength of metal frameworks fabricated by sintering-based computer-aided manufacturing methods.

STATEMENT OF PROBLEM: Sintering-based computer-aided metal manufacturing strategies have been proposed as an alternative to hard metal milling. While these fabrication methods have been evaluated in terms of marginal and internal discrepancies and bond strength to porcelain, limited information on metal frameworks is available regarding their flexural yield strength. PURPOSE: The purpose of this in vitro study was to evaluate the flexural yield strength of 3-unit cobalt-chromium (Co-Cr) metal frameworks fabricated by hard metal milling (HMM), presintered soft metal milling (PSMM), and direct metal laser melting (DMLM) with 25-µm and 50-µm layer thicknesses. MATERIAL AND METHODS: Three-unit master metal die models were prepared. A total of 40 metal frameworks (n=10) were fabricated by using HMM (group HM), PSMM (group PSM), and DMLM with 25-µm (group LM25) and 50-µm layer thicknesses (group LM50). Metal frameworks were cemented to the master die and then subjected to a 3-point bend test. The flexural yield force was used to calculate the flexural yield strength. The data were statistically analyzed (α=.05). One metal framework from each group was evaluated with scanning electron microscopy for microstructural analysis. RESULTS: The group LM50 exhibited the lowest significant (P<.001) flexural yield strength values. The group HM exhibited higher flexural yield strength values than the other groups. No significant difference was found between the groups LM25 and PSM (P=.954) or between the groups PSM and HM (P=.111). CONCLUSIONS: The fabrication method significantly affected the flexural yield strength of metal frameworks. Metal frameworks fabricated by DMLM with a 50-µm layer thickness exhibited considerably lower flexural yield strength values.

Effect of layer thickness on the flexural strength of multiple-unit laser-sintered metal frameworks.

STATEMENT OF PROBLEM: Laser sintering devices have been increasingly used to fabricate the metal frameworks of metal-ceramic restorations. In the fabrication process, the sintering layer thickness is an important parameter; however, information on how it may affect the flexural strength of metal frameworks remains limited. PURPOSE: The purpose of this in vitro study was to evaluate the flexural strength of 3-unit and 4-unit cobalt-chromium (Co-Cr) metal frameworks laser sintered with 20-µm, 30-µm, and 40-µm layer thicknesses. MATERIAL AND METHODS: Three-unit and 4-unit master metal die models with premolar and molar abutments were prepared through direct metal laser sintering (DMLS). A total of 40 metal frameworks (n=10 for each metal die model) were fabricated by the lost-wax technique (group C, served as the control group) and through DMLS with 20-µm, 30-µm, and 40-µm layer thickness (experimental groups LS20, LS30, and LS40, respectively). Each metal framework was cemented to a master die with a polyvinyl siloxane impression material and then subjected to a 3-point bend test at a crosshead speed of 1 mm/min. The yield force of each metal framework was used to calculate the flexural strength. Data were statistically analyzed by using 1-way ANOVA followed by a Tukey honestly significant difference (HSD) test and an independent-samples t test (α=.05) The microstructure of the fracture surface was evaluated by scanning electron microscopy. RESULTS: Group C reported the lowest mean flexural strength (P<.05), whereas group LS20 reported the highest mean flexural strength, although no significant difference (P>.05) in flexural strength was observed among the DMLS groups. The 3-unit metal frameworks exhibited a statistically significant higher mean flexural strength than the 4-unit metal frameworks (P<.05). CONCLUSIONS: The sintering layer thickness did not significantly affect the flexural strength of the laser-sintered metal frameworks. However, the DMLS groups reported a higher mean flexural strength than the cast group.

A 3-dimensional finite element and in vitro analysis of endocrown restorations fabricated with different preparation designs and various restorative materials.

STATEMENT OF PROBLEM: The preparation design and fabrication materials directly affect the clinical success of endocrown restorations, and yet, knowledge is lacking about the biomechanical impact of specific designs or materials on endocrown restorations. PURPOSE: The purpose of this in vitro and finite element analysis study was to evaluate the biomechanical behavior of endocrown restorations. MATERIAL AND METHODS: A total of 36 freshly extracted mandibular first molars were collected. The teeth were prepared as per 2 different preparation geometries: with the buccal wall intact (Class 2) and without the buccal wall (Class 3). Teeth were restored with endocrowns made from 3 different fabricating materials, Vita Enamic, GC Cerasmart, and Lava Ultimate. To analyze the in vitro fracture strength, cemented endocrowns were loaded in a universal test machine with a 200-N oblique force until the restoration fractured. Finite element analysis was used to evaluate the stress distribution on both the dentin tissue and the restorative materials. The data were analyzed with a 2-way ANOVA test and the Tukey post hoc test (α=.05). RESULTS: No significant differences were found between the different preparation designs (Class 2 and Class 3) on fracture strength (P>.05). The highest mean ±standard deviation fracture strength values were found in the Lava Ultimate material (Class 2, 606.20 ±293; Class 3, 659.40 ±226 N) (P>.05), but the lowest fracture strength test values were obtained in the Vita Enamic material (Class 2, 439.60 ±136; Class 3, 340 ±98 N) (P>.05) for both preparation design test groups. CONCLUSIONS: A statistically significant difference was not found between the 2 tooth preparation classifications. However, significant differences were observed among the test groups in the Class 2 preparation specimens. The Class 2 preparation design exhibited a higher number of irreparable failures.

Evaluation of marginal discrepancy in metal frameworks fabricated by sintering-based computer-aided manufacturing methods.

PURPOSE: The aim of this in vitro study was to evaluate the effect of sintering procedures on marginal discrepancies of fixed partial metal frameworks fabricated using different sintering-based computer-aided design and computer/aided manufacturing (CAD/CAM) techniques. MATERIALS AND METHODS: Forty resin die models of prepared premolar and molar abutment teeth were fabricated using a three-dimensional (3D) printer and divided into four groups (n = 10) according to the fabrication method of metal frameworks used: HM (via hard milling), SM (via soft metal milling), L25 (via direct metal laser melting [DMLM] with a 25 µm layer thickness), and L50 (via direct DMLM with a 50 µm layer thickness). After the metal frameworks were fabricated and cemented, five vertical marginal discrepancy measurements were recorded in each site (i.e., buccal, facing the pontic, lingual, and facing away from the pontic) of both abutment teeth under a stereomicroscope (×40). Data were statistically analyzed at a significance level of 0.05. RESULTS: No statistically significant differences (P>.05) were found among the four axial sites of metal frameworks fabricated by sintering-based CAD/CAM techniques. The HM and L25 groups showed significantly (P<.001) lower marginal discrepancy values than the SM and L50 groups. CONCLUSION: Marginal discrepancy in the sites facing the pontic was not influenced by the type of sintering procedure. All fabrication methods exhibited clinically acceptable results in terms of marginal discrepancies.

Digital evaluation of laser scanning speed effects on the intaglio surface adaptation of laser-sintered metal frameworks.

STATEMENT OF PROBLEM: Laser sintering has several processing parameters, typically under the control of dental laboratory technicians. Laser scan speed is an important parameter, which has a significant effect on manufacturing time but may also affect the adaptation of restorations. However, limited information is available regarding its impact. PURPOSE: The purpose of this in vitro study was to evaluate the intaglio surface adaptation of laser-sintered cobalt-chromium single-crown frameworks sintered at laser scanning speeds of 1, 3, and 6 m/s. MATERIAL AND METHODS: A master bronze metal die was prepared and scanned by using a laboratory scanner to fabricate the metal frameworks for 4 groups (n=10). In group C, the frameworks were fabricated by using the lost-wax method (control). In group L1, L3, and L6, the frameworks were fabricated by using direct metal laser melting (DMLM) at laser scanning speeds of 1, 3, and 6 m/s. After fabrication, 3 scanning data sets were used to evaluate the intaglio surface adaptation: the master die, the intaglio surface of each metal framework, and each metal framework seated on the master die. The intaglio surface adaptation of the metal frameworks was evaluated by using a metrology software program. The data were statistically analyzed by using a 1-way ANOVA, the Tukey honestly significant difference test, and the Tamhane T2 test (α=.05). RESULTS: The highest mean intaglio surface discrepancy value was obtained from group L6, and this was significantly different from the other 3 groups (P<.001). No significant intaglio surface discrepancy differences were found among the other groups. CONCLUSION: The amount of intaglio surface discrepancy increased when the laser scanning speed reached 6 m/s.

Evaluation of the light transmission of chairside polymer infiltrated hybrid ceramics in different shades and thicknesses.

BACKGROUND:: This in vitro study aimed to evaluate the amount of polymerizing light passing through hybrid ceramic specimens in different shades and thicknesses. METHODS:: Rectangular-shaped feldspathic ceramic computer aided design and computer aided manufacturing (CAD-CAM) blocks and translucent and high translucent polymer infiltrated hybrid ceramic CAD-CAM blocks in four different shades (1M1, 1M2, 2M2, and 3M2) were sectioned in four different thicknesses (0.8, 1.5, 2, and 3 mm), and a total of 48 groups ( n = 10) were obtained. Feldspathic ceramic specimens served as the control group. The light transmission of each ceramic specimen was measured three times by using a light-emitting diode and a radiometer. Data were statistically analyzed by using univariate analysis of variance (ANOVA) followed by one-way ANOVA, Tukey honest significant difference, and Tamhane T2 tests (α = 0.05). RESULTS:: Translucent polymer infiltrated hybrid ceramic specimens exhibited significantly ( p < 0.001) lower light transmission values than high translucent polymer infiltrated hybrid ceramic and feldspathic ceramic specimens, whereas feldspathic ceramic specimens exhibited significantly ( p < 0.001) higher light transmission than translucent and high translucent polymer infiltrated hybrid ceramic specimens. The amount of light transmission significantly ( p < 0.05) decreased when the shade value decreased and the thickness increased. CONCLUSIONS:: Polymer infiltrated hybrid ceramic specimens showed lower light transmission values than feldspathic ceramic specimens, and the amount of light transmission was affected by the ceramic shade and thickness.

The effect of layer thickness on the porcelain bond strength of laser-sintered metal frameworks.

STATEMENT OF PROBLEM: Laser sintering has become a common manufacturing technique in the fabrication of metal-ceramic restorations. The layer thickness of the sintering process may affect the surface morphology and hence the porcelain bond strength. However, limited information is available on the effect of layer thickness on porcelain bond strength. PURPOSE: The purpose of this in vitro study was to evaluate the porcelain bond strength of direct metal laser-melted (DMLM) cobalt-chromium (Co-Cr) metal frameworks sintered with 25-µm and 50-µm layer thicknesses. MATERIAL AND METHODS: Thirty metal frameworks (n=10) were fabricated by using the lost-wax technique (group C [control]), DMLM with a 25-µm layer thickness (group L25), and DMLM with a 50-µm layer thickness (group L50) according to the International Organization for Standardization (ISO) 9693-1. The surface roughness of 1 metal specimen from each group was analyzed by atomic force microscopy. After porcelain firing, a 3-point bend test was applied to each metal-ceramic specimen as in ISO 9693-1. In addition, 1 metal framework from each group was prepared and examined by scanning electron microscopy to evaluate surface morphology. Data were analyzed statistically by using 1-way analysis of variance and the Tukey honestly significant difference tests (α=.05). RESULTS: Group C and group L25 showed significantly higher (P<.001) mean porcelain bond strength values than group L50, and no significant bond strength difference was found between groups C and L25. All groups generally exhibited an adhesive type of failure. CONCLUSIONS: The results indicate that layer thickness may affect the porcelain bond strength of DMLM metal frameworks.

Effect of layer thickness on the marginal and internal adaptation of laser-sintered metal frameworks.

STATEMENT OF PROBLEM: Laser sintering is commonly used for fabricating metal-ceramic restorations. The layer thickness of the sintering process may affect restoration adaptation. However, limited information is available regarding its impact. PURPOSE: The purpose of this in vitro study was to compare the marginal and internal adaptation of laser-sintered cobalt-chromium single crown frameworks sintered with layer thicknesses of 25 and 50 µm. MATERIAL AND METHODS: Thirty resin dies that represented prepared single molar abutment teeth were prepared by using a 3-dimensional printer and were divided into 3 groups (n=10) according to the method used for fabricating metal frameworks: group C, metal frameworks fabricated by using the lost-wax method (control); group L25, metal frameworks fabricated by using direct metal laser melting with a layer thickness of 25 µm; and group L50, metal frameworks fabricated by using direct metal laser melting with a layer thickness of 50 µm. After fabricating the metal frameworks, 15 vertical marginal discrepancy measurements were made in each axial region (mesial, distal, buccal, and lingual) using a stereomicroscope. Next, all the specimens were sectioned from the midline, and 5 internal discrepancy measurements were made in each internal region (inner marginal, axial, and occlusal). The data were analyzed statistically by using 1-way ANOVA, the Tukey honestly significant difference, and Tamhane T2 tests (α=.05). RESULTS: The highest marginal and internal discrepancy values were obtained for metal frameworks in group C, and these values were significantly different (P<.001) from those obtained for metal frameworks in the other 2 groups. No significant difference was observed in the marginal and internal discrepancy values of metal frameworks in groups L25 and L50. CONCLUSIONS: These results indicate that layer thickness does not affect the adaptation of laser-sintered metal frameworks, yet both sintering parameters yielded significantly lower mean marginal discrepancy values than the cast group.

Repair Success of Two Innovative Hybrid Materials as a Function of Different Surface Treatments.

PURPOSE: To evaluate surface treatments for chipping in order to avoid bonding problems between hybrid materials and composite resin and to determine the optimal surface treatment method during intraoral repair of restorations to achieve clinical success. MATERIALS AND METHODS: A total of 96 samples were prepared from computer-aided design/computer-assisted manufactured (CAD/CAM) blocks: 48 polymer-infiltrated ceramic (PIC) and 48 resin nano-ceramic (RNC). Prior to application of the surface treatments, the two test groups were each divided into four subgroups: control group; hydrofluoric acid group; hydrofluoric acid with silane group; and air-abraded with silica-coated aluminum oxide (Al2O3) sand with silane group. Each subgroup contained 12 samples. A shear bond strength (SBS) test was performed after artificial aging (5,000 cycles, 5°C to 55°C). RESULTS: For both types of ceramic used, all subgroups showed significantly higher SBS values than the control groups (P < .05). The highest SBS values for both types of ceramic were observed in the air-abraded with silica-coated Al2O3 particles group. CONCLUSION: Each of the surface treatment methods increased the SBS, with the most effective method being air abrasion with silica-coated Al2O3.

Color match of a feldspathic ceramic CAD-CAM material for ultrathin laminate veneers as a function of substrate shade, restoration color, and thickness.

STATEMENT OF PROBLEM: The final color of a ceramic restoration, especially an ultrathin veneer, is important, but selecting the correct shade is difficult because the substrate can affect the final color of the restoration. PURPOSE: The purpose of this in vitro study was to investigate the effect of substrate shade and thickness on the final color of ultrathin laminate veneers milled from feldspathic ceramic and to present a straightforward methodology with which a clinician can visualize the effects of substrate color, ceramic thickness, and prefabricated computer-aided design and computer-aided manufacturing (CAD-CAM) block color on the final color of the restoration. MATERIAL AND METHODS: All specimens were fabricated by slicing CAD-CAM feldspathic ceramic material with a precision cutter into 12×10-mm slices of approximately 0.35, 0.55, 0.75, and 1.55 mm in thickness with 10 different colors (0M1-1M1-1M2-2M1-2M2-2M3-3M1-3M2-3M3-4M1). As a background substrate, composite resin disks (12×10×2 mm) were fabricated with different shades (0M1 S, 1M1 S, 2M3 S, 3M2 S, 4M3 S, 5M3 S). The CIELab values of the polished surfaces of each specimen were measured on a background (white or simulated foundation) with a spectrophotometer by a single experienced operator, and color differences (ΔE) were calculated. Mean ±SD values were calculated and subjected to ANOVA with 2 variables (substrate and ceramic color) (α=.05). RESULTS: Combinations of a lighter substrate shade and a lighter value ceramic restoration and of a darker substrate shade and darker value ceramic restoration only changed the final color of the restoration minimally. CONCLUSIONS: The final color of a dental restoration is affected by the thickness of the restoration, the substrate color, and the ceramic color. Lighter and darker substrate colors show more color changes, and thin veneers cannot mask the substrate color.

Light transmittance and surface roughness of a feldspathic ceramic CAD-CAM material as a function of different surface treatments.

BACKGROUND: The aim of the present study was to determine the effect of different surface treatments on light transmission of aesthetic feldspathic ceramics used in CAD-CAM chairside restorations. METHODS: Forty eight feldspatic ceramic test specimens were prepared from prefabricated CAD-CAM blocks by using a slow speed diamond saw. Test specimens were prepared and divided into 4 groups (n = 12). In the control group, no surface treatments were applied on the feldspathic ceramic surfaces. In the hydrofluoric acid group, the bonding surfaces of feldspathic ceramics were etched with 9.5 % hydrofluoric acid. In the sandblasting group the feldspathic ceramic surfaces were air-abraded with 30-µm alumium oxide (Al2O3) particles and Er:YAG laser was used to irradiate the ceramic surfaces. The incident light power given by the LED device and the transmitted light power through each ceramic sample was registered using a digital LED radiometer device. Each polymerization light had a light guide with 8-mm-diameter tips. Light transmission of feldspathic ceramic samples was determined by placing it on the radiometer and irradiating the specimen for 10 s at the highest setting for each light polymerization. All specimens were coated with gold using a sputter coater and examined under a field emission scanning electron microscope. Surface roughness measurement each group were evaluated with 3D optical surface and tactile profilometers. RESULTS: One-way ANOVA test results revealed that both surface conditioning method significantly affect the light transmittance (F:412.437; p < 0.001) and the surface roughness values (F:16.386; p < 0.001). Al2O3 and Er-YAG laser application reduced the light transmission significantly (p < 0.05). CONCLUSIONS: The laser and Al2O3 applications reduced the light transmission of 1.5 mm thickness feldspathic ceramic material below the value of 400 mW/cm(2) which is critical limit for safe polymerization.

The effect of amine-free initiator system and the polymerization type on color stability of resin cements.

We investigated the short-term (4 weeks) color stability of light-cure and dual-cure resin cements. Sixty disk-shaped test specimens of adhesive resin cement (10 × 1 mm) were prepared. One feldspathic porcelain test specimen (12 × 14 × 0.8 mm) was prepared from a prefabricated ceramic block. The feldspathic sample was placed on the resin cement disk and all the measurements were performed without cementation. Specific color coordinate differences (ΔL, Δa, and Δb), and the total color differences (ΔE) were calculated after immersion in distilled water for different periods. Data were compared using one-way analysis of variance (ANOVA) (α = 0.05). The test results revealed that different chemical structures and curing modes affected the ΔE values (P < 0.05). The highest ΔE values were obtained for RelyX Unicem dual-cure cement (2.14 ± 0.40), and the lowest for NX3 light-cure cement (0.78 ± 0.34). Third generation adhesive resin cement free of tertiary amines and benzoyl peroxide showed relatively slight color change in both test groups (light-cure and dual-cure resin cement). (J Oral Sci 58, 157-161, 2016).

Investigation of the effect of titanium alloy surface coating with different techniques on titanium-porcelain bonding.

STATEMENT OF PROBLEM: The bond strength of dental porcelain to titanium is inadequate as a clinical alternative to conventional alloys for metal ceramic restorations. PURPOSE: The purpose of this in vitro study was to evaluate the effects of coating titanium surface with a micro-arc oxidation (MAO) technique and hydroxyapatite (HA) on the bond strength of porcelain to titanium surfaces. MATERIAL AND METHODS: One hundred twenty machined titanium specimens with a dimension of 25×3×0.5 mm were prepared from grade 5 titanium as the metal substrate. Specimens were divided into 6 groups (n=20) according to the surface treatment used: airborne-particle abraded (control), coated with MAO for 5 minutes, coated with MAO for 15 minutes, coated with MAO for 30 minutes, coated with HA, and combination of MAO and HA. Each group was further divided into 2 subgroups (n=10) according to the type of porcelain used: Noritake Ti-22 porcelain or Vita-Titankeramik porcelain. The bond strength was tested with a universal testing machine at a crosshead speed of 0.5 mm/min. Data were analyzed statistically with 2-way ANOVA and Tukey honest significant differences multiple comparison tests (α=.05). RESULTS: For both porcelain groups, the 30-minute MAO groups showed higher bond strength values than those of the control groups (P<.05). In the Vita Titankeramik porcelain subgroup, the specimens coated with HA did not show any statistical differences compared with those of the control group (P>.05). Surface roughness was affected significantly (P<.001) by the coating procedure compared to that of the the control group. CONCLUSIONS: Coating with either MAO or HA improved titanium-porcelain adhesion.

A Technique for Removing Implant-Retained Denture: Direct Relining Complication.

The aim of this case report is to present a technique for removing the denture which locked to ball-attachment because of excessive hard relining resin material flows around the ball-attachment. An alternative method was used in the present case. A cylindrical resin was removed with a diamond bur at the level of matrix and by this way the matrix was removed safely. The advantage of the presented method is that it may be extended to other clinical situations when facing a similar complication for implant supported dentures and also that the technique is simple and does not require special equipment.

Effects of Er:YAG Laser Pretreatment with Different Energy Levels on Bond Strength of Repairing Composite Materials.

OBJECTIVE: The purpose of this study was to investigate the effects of Erbium-doped: yttrium-aluminum-garnet (Er:YAG) laser pretreatment with different energy levels on the shear bond strength (SBS) of repairing composite materials. BACKGROUND DATA: After long-term usage of composite resins in the mouth, they can need some repair. Repairing composite bonding so it attaches to the old restoration is important for clinical success. METHODS: Sixty composite resin materials were used in this study. The aging procedure was performed with 6000 thermocycles in water from 5°C to 55°C. Different surface pretreatment methods [control (no surface treatment), sandblasting, laser treatment (energy level 75, 100, 200, and 300 mJ)] were employed, for a total of six groups. Composite resins of the same kind as their substrates were adhered onto the conditioned substrates. The SBS test was used to assess the durability of all groups. Scanning electron microscopy (SEM) analysis was performed on a representative specimen in each group. RESULTS: Among six surface-treated groups the lowest bond strength was observed in Group C (9.41 MPa) (p<0.001). Group S exhibited the highest bond strength among all groups and showed significant difference from all other groups (33.41 MPa) (p<0.001). In the Er:YAG test groups, bonding values showed varying results from 15.27±0.58 (Group L300) to 25.98±1.08 (Group L75) and showed significant increase when compared with control group (p<0.05). CONCLUSIONS: Altough the sandblasted group exhibited the highest test values, Er:YAG laser treatment on repair composite bonding to old composite may become an alternative to other surface treatment methods.

Effect of 1-piece post and core fabrication techniques on fracture strength.

PURPOSE: The purpose of this in vitro study was to evaluate and compare the fracture strengths of post and core systems produced with different fabrication techniques and materials. METHODS: Forty extracted human single-root premolars were used in this study. After root canal treatment, the teeth were randomly divided into 4 groups of 10 each as follows: group C: metallic 1-piece posts and cores fabricated by casting, and serving as the control; group CM: metallic posts and cores fabricated with the copy milled technique; group LS: 1-piece posts and cores fabricated with the laser sintering technique; and group ZR: 1-piece zirconia posts and cores fabricated with computer-aided design and computer-aided manufacturing (CAD-CAM). The posts and cores were cemented to the teeth with adhesive resin cement; then, the specimens were mounted to acrylic resin blocks, attached to an Instron Universal Testing Machine, and loaded with a crosshead speed of 1 mm/min, until fracture. Data were statistically analyzed using 1-way analysis of variance (ANOVA), followed by the post hoc Tukey test (α = 0.05). RESULTS: The highest fracture results were found in group ZR (315.4 ± 53.4 N), which showed significant differences from all other groups (p<0.05). The lowest test values were found in group C (230.2 ± 29.8 N). Group LS (250.9 ± 29.0 N), group CM (253.0 ± 22.4 N) and group C did not show any significant differences (p>0.05). CONCLUSIONS: Custom-made zirconia 1-piece posts and cores, fabricated using the CAD-CAM procedure, can be an alternative treatment method when compared with other techniques.

The effect of different surface treatments on cement-retained implant-supported restorations.

The purpose of this study was to evaluate the effects of the various surface treatment methods on the retention of single crowns on implant abutments. The study included 50 single crowns that were cemented with adhesive resin cement onto the ITI solid abutments. The specimens were randomly divided into 5 groups, each including 10 specimens according to the following surface treatments: group C, control, abutments remained unaltered as control; group L, etching with CO(2) laser; group SB, sandblasting with 50-µm Al(2)O(3); group MS: coating with titanium nitride (TiAlN) with a radiofrequency magnetron sputtering system; and group SP, silicoating by Silano-Pen. After the surface treatment procedures were finished, the casted crowns were cemented onto the abutments, and thermocycling was applied to simulate oral environment. The uniaxial tensile force was applied to all test crowns using a universal test machine (Instron) with a crosshead speed of 0.5 mm/min. The load required to dislodge each crown was recorded in Newton. The lowest tensile bond strength values were obtained with group MS (223.26 ± 14.30 N) and significantly differ from all other groups except group C. Group SB showed highest test results (506.02 ± 18.04 N) and differs from other groups (P < .05). The test values that were obtained in group MS-group C did not show significant differences (P > .05). Sandblasting is an effective method to increase bond strength. Also, Silano-Pen and laser application is advisable for increasing the crown retention to abutments. Titanium aluminum nitride coating with magnetron sputtering technique seems to be ineffective.