An In Vitro Study of Condylar Displacement Caused by Interocclusal Records: Influence of Recording Material, Storage Time, and Recording Technique.

PURPOSE: To evaluate the condylar displacement after mounting working casts using different interocclusal recording materials and to analyze the influence of the storage time and the recording technique on the displacement caused by the interocclusal record. MATERIALS AND METHODS: Eight interocclusal records were made in each of the following groups: G1: Aluwax (aluminum wax), G2: Beauty Pink wax (hydrocarbon wax compound), G3: Futar D Fast, G4: Futar Scan (G3, G4: vinylpolysiloxane), G5: Ramitec (polyether), G6: LuxaBite (composite resin based on bis-acryl), G7: LuxaBite corrected with Aluwax. A condylar-positioning indicator measured the condylar displacement in the three planes after storage of the records for two periods of 1 and 48 hours. Two-way ANOVA was used to determine the influences of recording materials and each of the following factors: (1) region (record and non-record side), (2) storage time, and (3) recording technique. The statistical significance level was set at p < 0.05. RESULTS: The vertical displacement caused by the interocclusal records in the record side after storage time of 1 hour ranged between 0.29 mm (Aluwax) and 0.14 mm (Futar Scan). The lateral displacement ranged between 0.13 mm (Aluwax) and 0.02 mm (Ramitec) while the anteroposterior displacement ranged between 0.15 mm (Ramitec) and 0.04 mm (Futar Scan). The corrected resin record showed generally lower displacement values than other materials tested (0.03, 0.02, and 0.07, respectively). On the non-record side, the values were lower than that on the record side. The condylar displacement increased after a storage time of 48 hours for all materials. Both factors, storage time and recording technique, had statistically significant influence on the condylar displacement. CONCLUSIONS: Based on the results, the vertical displacement of the condyle caused by the interocclusal records was higher than the lateral or the anteroposterior displacement. Elastomers caused statistically significantly less condylar displacement than waxes or uncorrected composite resin. Corrected LuxaBite records with Aluwax showed significantly less condylar displacement than all other materials.

Two-body wear of different ceramic materials opposed to zirconia ceramic.

STATEMENT OF PROBLEM: Little is known about the wear behavior of ceramics opposed to unveneered zirconia and whether wear varies according to microstructure, surface toughness, and flexural strength of the ceramics. PURPOSE: The purpose of this study was to evaluate the 2-body wear resistance of 5 ceramics opposing unveneered zirconia ceramic. MATERIAL AND METHODS: Yttrium-stabilized zirconia, lithium disilicate glass ceramic, leucite-reinforced glass ceramic, fluorapatite glass ceramic, and nanofluorapatite glass ceramic specimens (n=8) were tested against standardized zirconia balls. Wear tests were performed in a dual-axis mastication simulator. Wear resistance was calculated by measuring the vertical and volumetric substance loss using a laser scanner. Specimen surfaces were evaluated at x50 and x500 magnification using SEM. Data were statistically analyzed using 1-way ANOVA and Fisher's exact test (alpha=.05). RESULTS: Zirconia specimens demonstrated significantly lower vertical and volumetric loss than other ceramics (P<.05). The wear of fluorapatite and nanofluorapatite glass ceramics was significantly greater than that of leucite-reinforced and lithium disilicate glass ceramics (P<.05). SEM images showed no cracks or flaws in the zirconia and leucite-reinforced glass-ceramic specimens, indicating a mixture of attritional and adhesive wear. Other ceramic specimens exhibited cracks and chipped particle spaces which were consistent with fatigue wear. Zirconia demonstrated the lowest vertical and volumetric wear values. Leucite-reinforced and lithium disilicate glass ceramics demonstrated nonsignificant differences in volumetric wear, but these values were significantly lower than those observed for nanofluorapatite and fluorapatite glass ceramics (P<.05). CONCLUSIONS: Wear varied according to the structure of the ceramic tested. Wear was of the fatigue type, and was significantly lowest in the zirconia specimens tested.

Effects of endodontic post surface treatment, dentin conditioning, and artificial aging on the retention of glass fiber-reinforced composite resin posts.

STATEMENT OF PROBLEM: Several post surface treatments with or without the application of a bonding agent have been recommended to improve the bond strength of resin cements to posts. A regimen that produces the maximum bond strength of glass fiber-reinforced composite resin posts has not been verified. PURPOSE: The purpose of this study was to evaluate the influence of post surface conditioning methods and artificial aging on the retention and microleakage of adhesively luted glass fiber-reinforced composite resin posts. MATERIAL AND METHODS: Seventy-two endodontically treated single-rooted teeth were prepared for glass fiber-reinforced composite resin posts. The posts were submitted to 3 different surface treatments (n=24), including no treatment, etching with phosphoric acid, and airborne-particle abrasion. Subgroups of the posts (n=8) were then allocated for 3 different experimental conditions: no artificial aging, no bonding agent; no artificial aging, bonding agent; or artificial aging, bonding agent. The posts were luted with resin cement (Calibra). Post retention was measured in tension at a crosshead speed of 2 mm/min. The posts assigned for microleakage investigation were placed in fuchsin dye for 72 hours. The dislodged posts and the post spaces were examined microscopically to evaluate the mode of failure and explore the microleakage. Data were analyzed by 2-way ANOVA followed by Tukey HSD test (alpha=.05). RESULTS: The mean (SD) retention values for test groups ranged from 269 (63.8) to 349 (52.2) N. The retention values of the airborne-particle-abrasion group were significantly higher than those of the acidic-treatment and no-treatment groups. The application of bonding agent on the post surface produced no significant influence on retention. The mean retention values after artificial aging were significantly higher than without artificial aging. Microscopic evaluation demonstrated that the failure mode was primarily mixed. CONCLUSIONS: Treating the surface of the posts with phosphoric acid for 15 seconds before cementation produced no significant improvement in post retention. Airborne-particle abrasion of the surface of the post significantly improved post retention.

Effect of acid conditioning of root canal dentin on the retention of adhesively luted glass fiber-reinforced composite (FRC) posts.

PURPOSE: To assess the retention of glass FRC posts luted with resin cements after conditioning the canal dentin with different acidic treatments. METHODS: Post spaces were prepared in six groups of eight endodontically treated extracted teeth. Glass FRC posts were luted after etching the canal dentin with phosphoric acid and/or applying ED-Primer, Clearfil New Bond or XP Bond. The groups with their respective etching time, primer and cement combinations were as follows. ED: ED-Primer only and Panavia 21; ED15: 15 seconds phosphoric acid treatment, ED-Primer and Panavia 21; NB15: 15 seconds phosphoric acid treatment, Clearfil New Bond and Panavia 21; NB30: 30 seconds phosphoric acid treatment, Clearfil New Bond and Panavia 21; XP15: 15 seconds phosphoric acid treatment, XP Bond and Calibra; XP30: 30 seconds phosphoric acid treatment, XP Bond and Calibra. Specimens were stored in water for 30 days and subjected to simulated aging conditions. Post retention was measured in tension at a crosshead speed of 2 mm/minute. Analysis of variance and Bonferroni multiple range tests were conducted for data analysis. RESULTS: The mean (standard deviation) retention values in Newtons (N) were: ED: 180.9 (44.9); ED15: 278.3 (37.7); NB15: 283.8 (84.9); NB30: 187.7 (60.0), XP15: 216.8 (46.8), XP30: 199.6 (34.0). The retention values of ED15 and NB15 were significantly higher than those of ED and NB30 groups respectively. There were no statistically significant differences between XP Bond groups. Microscopic evaluation of post surfaces demonstrated that the debonding failure was adhesive at the cement-post and cement-dentin interfaces.

The influence of antagonistic surface roughness on the wear of human enamel and nanofilled composite resin artificial teeth.

STATEMENT OF PROBLEM: Depending on the applied finishing technique, ceramics may have different values of surface roughness; therefore, their abrasive effect on antagonists may vary. However, different materials may be affected differently by the surface roughness of ceramics. PURPOSE: The purpose of the present study was to evaluate and correlate the wear of human enamel and nanofilled composite resin teeth with the surface roughness of the antagonistic ceramic after simulated mastication. MATERIAL AND METHODS: Three groups of 8 human teeth and 3 groups of 8 nanofilled composite resin teeth were tested against 3 sets of 16 zirconia ceramic balls with different average surface roughness values. Each group was loaded for 300,000 cycles in a mastication simulator. Wear resistance was analyzed by measuring volume and vertical substance lost, determined with a laser scanner. Data were statistically analyzed using 2-way ANOVA. The Pearson correlation test was used to determine whether there was a relationship between the antagonistic surface roughness and the degree to which the materials had worn. RESULTS: An increase in the antagonistic surface roughness significantly increased the wear of composite resin and human enamel. The effect of the antagonistic surface roughness on the wear was significant (P<.001). The correlation between the volume loss and antagonistic surface roughness was significant (r=0.667, P<.001). CONCLUSIONS: Nanofilled composite resin and human enamel exhibited different amounts of wear. In general, human enamel showed less wear than nanofilled composite resin. Surface roughness of the antagonistic ceramic influenced the wear of human enamel more than it affected the wear of composite resin.

Wear of feldspathic ceramic, nano-filled composite resin and acrylic resin artificial teeth when opposed to different antagonists.

The aim of this study was to evaluate the wear of denture teeth and their antagonists produced by two-body and three-body wear tests. Three types of denture teeth, namely feldspathic ceramic (FC), nano-filled composite resin (NCR), and experimental acrylic resin teeth (AR), were tested. For each type two groups of eight upper premolars each were prepared. The first group was tested against cusps from the same material and the second group was tested against human enamel cusps. Each group was loaded with a total of 200,000 chewing cycles (two-body wear 100,000 cycles and three-body wear 100,000 cycles). Wear was analyzed by measuring the maximum depth and volume loss of the denture teeth using a laser scanner and by measuring the vertical loss of the antagonists using an optical macroscope. Statistically, there was no significant difference between the following combinations: FC-FC and NCR-NCR regarding the vertical and volume loss; and FC-enamel and NCR-enamel regarding the total vertical substance loss. The combinations AR-AR and AR-enamel showed higher wear values than the other combinations. For complete dentures, composite resin and ceramic teeth showed similar vertical and volume loss, whereas composite resin teeth seemed to be more suitable for partial dentures opposing natural teeth in terms of wear of teeth and antagonists.

Two-body wear of resin and ceramic denture teeth in comparison to human enamel.

OBJECTIVES: To evaluate the two-body wear resistance of different artificial denture teeth when opposed to steatite ceramic balls in a dual-axis chewing simulator. METHODS: Artificial denture teeth including the ceramic tooth Bonartic CT, the composite resin tooth Condyloform II NFC, the acrylic resin teeth Bonartic TCR, Orthognath, Polystar Selection, SR Orthotyp DCL, and Vitapan Cuspiform, and human maxillary premolars were tested in a chewing simulator. Wear resistance was analyzed measuring vertical substance loss and volume loss using profilometry and an optical macroscope after various chewing cycles (49N, up to 1,200,000 cycles). Data were statistically analyzed using one-way analysis of variance (ANOVA) followed by the Fisher test (LSD) at p< or =0.05. RESULTS: After 1,200,000 chewing cycles the mean vertical substance loss and volume loss for the composite resin teeth (117microm and 0.144mm3) were significantly lower than for all acrylic resin teeth (149-166microm and 0.220-0.292mm3) (p< or =0.05), but higher than for ceramic teeth (36microm and 0.029mm3) and for enamel (56microm and 0.033mm3) (p< or =0.05). No significant differences were found among the acrylic resin teeth for both parameters (p>0.05). SIGNIFICANCE: The composite resin showed improved in vitro two-body wear resistance compared to modern acrylic resin denture teeth; however, it showed less wear resistance than ceramic teeth and human enamel. Ceramic teeth should be preferred over natural teeth when occlusal stability is considered a high priority.

Wear resistance of nanofilled composite resin and feldspathic ceramic artificial teeth.

STATEMENT OF PROBLEM: The wear resistance of nanofilled composite resin and feldspathic ceramic artificial teeth may vary according to the material type and physical characteristics of the antagonist. PURPOSE: The purpose of this study was to evaluate the wear resistance of nanofilled composite resin and feldspathic ceramic artificial teeth after simulated mastication against steatite, zirconia, and alumina antagonists. MATERIAL AND METHODS: The study evaluated 6 groups of artificial teeth: 3 groups of 8 nanofilled composite resin teeth (Condyloform II NFC) and 3 groups of 8 feldspathic ceramic teeth (Bonartic CT). Three sets of 16 steatite, 16 zirconia, and 16 alumina cusp-shaped antagonist surfaces were fabricated and used to test wear resistance. Each group was loaded for 600,000 cycles. The wear resistance was analyzed by measuring vertical and volume substance lost (microm and mm(3), respectively), determined with a laser scanner. Data were statistically analyzed using 2-way ANOVA and Games-Howell test (alpha=.05). RESULTS: The influence of the materials tested and antagonists was statistically significant. The composite resin teeth showed significantly higher vertical and volume substance loss than ceramic teeth opposing steatite cusps (P<.001; P=.04, respectively), while composite resin teeth opposing alumina and zirconia cusps demonstrated less wear than ceramic teeth. However, the latter differences were not statistically significant. CONCLUSIONS: The wear behavior of nanofilled composite resin and feldspathic ceramic teeth varies according to the type of antagonistic material. However, alumina and zirconia ceramics caused less wear in antagonists than steatite ceramic.

Effect of dentin conditioning on retention of airborne-particle-abraded, adhesively luted glass fiber-reinforced resin posts.

STATEMENT OF PROBLEM: The smear layer covering root canal dentin as a result of post space preparation procedures may negatively affect the retention of adhesively cemented glass fiber-reinforced resin posts. PURPOSE: The purpose of this study was to evaluate the retention of airborne-particle-abraded glass fiber posts luted with 3 different bonding systems after conditioning the canal dentin with acidic conditioning methods. MATERIAL AND METHODS: Post spaces were prepared in 6 groups of 8 endodontically treated single-rooted teeth. Glass fiber-reinforced resin posts were airborne-particle abraded and luted after etching the canal dentin with phosphoric acid and/or applying XP Bond, Clearfil New Bond, or ED Primer. The groups with their respective etching time, primer, and cement combinations were as follows: XP15: 15 seconds of phosphoric acid treatment, XP Bond and Calibra; XP30: 30 seconds of phosphoric acid treatment, XP Bond and Calibra; NB15: 15 seconds of phosphoric acid treatment, Clearfil New Bond and Panavia 21; NB30: 30 seconds of phosphoric acid treatment, Clearfil New Bond and Panavia 21; ED: ED Primer only and Panavia 21; ED15: 15 seconds phosphoric acid treatment, ED Primer and Panavia 21. Specimens were stored in water for 30 days and subjected to simulated aging conditions. Post retention was measured in tension at a crosshead speed of 2 mm/min. Data were analyzed using Mann-Whitney and Kruskal-Wallis tests followed by post hoc comparisons using Langley method (alpha =.05). The dislodged posts and canals were examined microscopically at x8 and x20 magnification to evaluate the mode of failure. RESULTS: For each group, the mean (SD) retention in N was: XP15: 376.8 (39); XP30: 305.5 (27); NB15: 370.3 (31); NB30: 297.6 (52); ED: 301.6 (43); ED15: 373.8 (46). The retention values of ED15, NB15, and XP15 were significantly higher than those of ED, NB30, and XP30 groups, respectively. Microscopic evaluation demonstrated that the failure mode was primarily mixed. CONCLUSIONS: Luting posts with Panavia 21 or Calibra after etching the dentin with phosphoric acid for 15 seconds produced significantly higher retention values than treating dentin for 30 seconds or with ED Primer, only.

Long-term retention behaviour of resin matrix attachment systems for overdentures.

OBJECTIVES: The purpose of this laboratory study was to evaluate the long-term retention behaviour of two resin matrix attachment systems for overdentures and the influence of the implant angulation. METHODS: Sixteen titanium patrices of each attachment system were connected to their corresponding implant analogues and fixed in an auto curing resin either orthogonally (n=8) or 20° tilted (n=8). The corresponding matrices, one made from polyetherketoneketone (PEKK; CM LOC, Cendres+Métaux, Biel, Switzerland), one made from polyethylene (PE; Locator, Zest Anchors, Escondido, California, USA), were fixed in a stylised unilaterally removable dental prosthesis resulting in 4 groups with 8 specimens in each group. Overall, 30,000 joining and separating cycles of the matrix were performed in a chewing simulator. After each joining movement, the unilaterally removable dental prosthesis was loaded eccentrically with 100N at a distance of 12mm from the attachment to simulate clinical loading conditions. Retentive forces were measured during the test using force transducers. The statistical analysis was performed using Tukey-HSD. RESULTS: Both attachment systems showed a significant decrease in retention over time, which occurred earlier in the tilted groups than in the orthogonal groups. After 5000-30,000 joining and separating cycles the PE matrix attachment provided significantly lower retention than the PEKK matrix attachment system. CONCLUSION: Within the limitations of this investigation, the combination of a titanium patrix and a matrix made from polyetherketoneketone seems to be a promising material combination for long-term retention, also on tilted implants.

Influence of loading forces on the vertical accuracy of interocclusal records.

OBJECTIVE: To evaluate the influence of loading forces on the vertical discrepancies caused by interocclusal recording materials. METHOD AND MATERIALS: A custom-made apparatus was used to simulate the maxilla and mandible. Eight interocclusal records were made in each of the following groups: G1-Aluwax (aluminum wax; Aluwax), G2-Beauty Pink wax (hydrocarbon wax compound; Miltex), G3-Futar D, G4-Futar D Fast, G5-Futar Scan (polyvinyl siloxanes; Kettenbach), and G6-Ramitec (polyether; 3M ESPE). The vertical discrepancies were measured by an inductive displacement transducer connected to a carrier frequency amplifier after storage of the records for 1 hour at room temperature. Different compressive loading forces up to 1 kg were applied onto the upper part of the apparatus to evaluate the influence on the vertical discrepancies of the records. Two-way ANOVA was used for statistical analysis. RESULTS: The compressive loading force had a statistically significant influence on the vertical discrepancies (P<.01) (ie, higher forces reduced the vertical discrepancies). When a compressive force of 1 kg was applied to the upper part of the apparatus, the mean vertical discrepancies for G1 (11+/-3 microm) and G2 (12+/-3 microm) were statistically significantly higher than in groups G3 (1+/-1 microm), G4 (2+/-1 microm), G5 (0+/-1 microm), and G6 (-2+/-2 microm). CONCLUSION: A compressive force of 1 kg could be used to stabilize the cast during mounting procedures in an articulator using an interocclusal record made of polyvinyl siloxane without vertically changing the interocclusal relationships.

Wear of denture teeth and their human enamel antagonists.

OBJECTIVES: To evaluate the wear resistance of artificial denture teeth and their human enamel antagonists in a dual-axis chewing simulator. METHOD AND MATERIALS: Four artificial denture teeth--feldspathic ceramic, nanofilled composite resin, experimental acrylic resin with UDMA/PMMA, and interpenetrating polymer networks (IPN) acrylic resin teeth--were tested in this study. Human enamel cusps were used as antagonists. Wear resistance was analyzed by measuring the vertical substance loss and the volume loss of the denture teeth using a laser scanner after 300,000 chewing cycles. In addition, the vertical substance loss of the antagonists was evaluated using an optical macroscope. Data were statistically analyzed using ANOVA. For qualitative analysis of the wear areas, the teeth were sputter coated with gold and evaluated at magnifications of 503 and 1,0003 using SEM. RESULTS: The composite resin teeth exhibited wear that was significantly higher than that of feldspathic ceramic but lower than that of acrylic resin teeth (P<.05). Acrylic resin teeth caused no measurable wear on the enamel antagonists. The wear patterns of the feldspathic ceramic and composite resin teeth can be described as attritional, while a fatigue type of wear was observed in the acrylic resin teeth. CONCLUSION: The lowest total vertical substance loss was found for the combination composite resin-enamel. Based on the results of this study, composite resin teeth seem to be more suitable for dentures opposing natural teeth than ceramic or acrylic resin teeth in terms of wear resistance.

Wear resistance of artificial denture teeth.

This study aimed to evaluate the wear resistance of artificial teeth when opposed by antagonists made from the same material. The artificial teeth tested included ceramic teeth, nanofilled composite resin teeth, acrylic resin teeth, and experimental acrylic resin teeth. After 600,000 chewing cycles, the mean total vertical substance loss and mean volume loss for acrylic resin and experimental acrylic resin teeth were significantly lower than for ceramic and composite resin teeth. Composite resin teeth showed more wear than ceramic teeth, while acrylic resin teeth showed less wear than ceramic teeth. However, scanning electron microscopy and laser-scanner observations showed that acrylic resin teeth exhibited deformation at the contact surfaces.

Evaluation of vertical accuracy of interocclusal recording materials.

OBJECTIVE: To evaluate 4 interocclusal recording materials for their ability to reproduce accurately interocclusal relationships after a storage time of 1 or 48 hours. METHOD AND MATERIALS: A custom-made metal apparatus was used to simulate the maxilla and mandible. The vertical discrepancies were measured by a precision dial gauge. Eight inter-occlusal records were made in each of the following groups: (G1) Futar D (polyvinyl siloxane; Kettenbach), (G2) Ramitec (polyether; 3M ESPE), (G3) LuxaBite (composite resin based on bisacryl; DMG), (G4) Aluwax (aluminum wax; Aluwax Dental Products), (G5) LuxaBite corrected with LuxaBite, and (G6) LuxaBite corrected with Aluwax. The vertical discrepancies were measured after storage of the records for 1 and 48 hours at room temperature and repositioning of the records in the metal apparatus. Data were statistically analyzed using 1-way analysis of variance followed by the Games-Howell test (P < or = .05). RESULTS: After storage times of 1 and 48 hours, respectively, the mean vertical discrepancies (microm) for G1 (23/33) and G2 (25/30) were statistically significantly lower than for G3 (431/745) and G4 (110/151) (P < .05) but higher than for G5 (8/16) and G6 (7/17). There was no statistically significant difference between G1 and G2 or between G5 and G6 for either measurement. CONCLUSION: These vertical discrepancies increased after a storage time of 48 hours. However, correction of the LuxaBite records with LuxaBite or Aluwax showed significantly lower vertical discrepancies than all other materials. Clinically, the vertical discrepancies the corrected records caused could be insignificant.