Evaluation of Prosthetic Complications with Metal-Acrylic Resin Implant-Fixed Complete Dentures: A Medium- and Long-Term Retrospective Analysis with Up to 13 Years of Follow-up

PURPOSE: To present prosthetic complications observed in the medium and long term in patients treated with metal-acrylic resin implant-supported fixed complete dentures (MAIFCDs). MATERIALS AND METHODS: A total of 87 patients who were treated with MAIFCDs were included. Acrylic resin (denture teeth and base) fracture, screw loosening (prosthetic or abutment), screw (prosthetic or abutment), and framework fracture were analyzed for descriptive statistics. Product-limit survival estimates were used for the cumulative no-complication rate (CNCR) of prostheses. All results were assessed using α = .05. RESULTS: The average observation time was 42.9 months (range: 19 to 153). Of 597 implants, 8 mandibular (44.4%) and 10 maxillary implants (55.6%) failed. In total, 29 patients (33.3%) experienced no complications in an average of 7 years, and 58 patients (66.6%) experienced at least one complication. The average time for the first complication to occur was 23 months (range: 1 to 97 months). The average number of complications was 5.9/patient. Acrylic resin complications were the most frequent, followed by screw loosening, screw fracture, and framework fracture. Of those patients with complications, 9 (16%) had maxillary MAIFCDs with an average of 4 complications. In total, 28 patients (48%) had only mandibular MAIFCDs with an average of 5 complications, and 21 patients (36%) had both arches treated with MAIFCDs with an average of 9 complications. Mandibular MAIFCDPs in women had a higher CNCR compared to maxillary MAIFCDs of both women and men and when both arches of women were treated with MAIFCDs (P < .05). CONCLUSIONS: The CNCR of MAIFCDs differed depending on the arch treated and sex. Mandibular MAIFCDs in women had a lower complication rate than MAIFCDs in other arch-sex pairs. Acrylic resin related complications were commonly observed as well as prosthetic screw loosening.

Positional trueness of three removable die designs with different root geometries manufactured using stereolithographic 3D printing.

STATEMENT OF PROBLEM: Three-dimensional (3D) printed casts are a suitable alternative to dental stone casts. Contemporary dental design computer programs permit designing definitive casts with removable dies with different root geometries and retention mechanisms. Studies on the positional trueness of 3D-printed removable dies with different root geometries are lacking. PURPOSE: The purpose of this in vitro study was to investigate the 3D displacements of three 3D-printed removable die designs with different root geometries. MATERIAL AND METHODS: The digital file of a dental stone alveolar cast with root-form removable dies (MOD UJ IV Fixed Prosthetics; Ivoclar AG) was used as a reference to create 3 removable die and alveolar cast designs (Root Form, RF; Conical, CON; Cylindric, CYL) with different root geometries in 2 dental design computer programs (DentalCAD 3.1 Rijeka; exocad; GmbH; InLab CAD 22.0; Dentsply Sirona). 3 equidistant Ø1-mm spheres (C, Cervical; M, Middle; O, Occlusal) were designed on the buccal surface of the coronal portion of the removable die to evaluate their displacement. A total of 45 alveolar casts with 45 removable dies were fabricated using a stereolithographic 3D printer (Form 3; Formlabs); each die group consisted of 15 specimens. After fabrication and postprocessing, the specimens were scanned, and their digital files were analyzed in a metrology-grade computer program to evaluate the displacement of the removable dies with respect to the position of the die in the master reference file. Subsequently, the data were analyzed using a 3-way analysis of variance (ANOVA) followed by step-down Bonferroni-corrected pairwise comparisons (α=.05). RESULTS: Two statistically significant 2-way interactions were detected between the independent variables, die design and direction (P<.001), and location and direction (P<.001). The post hoc analysis identified significant differences between the displacement values of RF and CYL (P<.001) and RF and the CON (P<.001) designs on the Y axis. The measured displacements were statistically different between the C and O locations on the Y axis (P=.001) and the M and O locations on the Z axis (P=.006). CONCLUSIONS: The root geometry of a 3D-printed removable die and alveolar cast can affect seating, and variable degrees of tipping of the removable die can be seen. The seating and congruence of the removable die with the interocclusal space and relationships observed intraorally should be confirmed before adjusting indirect restorations.

The Physical Compatibility of Glycopyrrolate and Rocuronium.

OBJECTIVE: Scientific evidence has rarely, if at all, been reported in the literature demonstrating analytical confirmation of the physical compatibility and stability of glycopyrrolate and rocuronium combined. The purpose of this experiment was to determine if glycopyrrolate and rocuronium are physically compatible. METHODS: Glycopyrrolate and rocuronium were combined in various containers, observed over a 60-minute period, and compared against positive and negative controls. Measured metrics included color change, precipitate formation, Tyndall beam test, turbidity, and pH. Statistical analyses were used to assess significance of data trends. RESULTS: The combination of glycopyrrolate and rocuronium did not result in any color change, precipitate formation, a positive Tyndall beam test, or a significantly positive turbidity and did not result in any significant change in pH, regardless of container. CONCLUSION: Per the protocol used in this study, glycopyrrolate and rocuronium were determined to be physically compatible.

Color and translucency of enamel in vital maxillary central incisors.

STATEMENT OF PROBLEM: Limited data, especially in vivo data, exist regarding translucency parameter (TP) values for vital anterior nonrestored dentition. Additionally, published information on the CIELab values of vital enamel at a theoretical infinite thickness is lacking. Obtaining TP and CIELab values in a population that varies in terms of ethnicity, age, and sex would be useful to inform the development and placement of esthetic dental restorations that more accurately capture the complex optical qualities of enamel. PURPOSE: The purpose of this clinical study was to investigate in vivo the TP and CIELab values of vital anterior incisor enamel at a theoretical infinite thickness in a diverse pool of participants who varied in age, ethnicity, and sex. MATERIAL AND METHODS: Spectral reflectance measurements (380 to 780 nm at 2-nm intervals) of the mid-incisal region of vital, unrestored maxillary anterior teeth were made in 120 participants, equally divided into 2 sexes, 4 racial or ethnic groups, and 5 age ranges. Instruments were oriented to achieve 0-degree observation and 45-degree illumination, and spectral measurements were made with white and black silicone backgrounds. Reflectance spectra of the incisal enamel from both the black and white silicone backing were used to fit to the Kubelka-Munk (K-M) reflectance theory. The CIEDE2000 color difference formula was used to determine TP, and data were compared among participant demographics. CIELab color coordinate values for enamel at an infinite thickness were calculated by using a D65 illumination and CIE standard human (2-degree) observer. To determine value ranges and significant differences among participant groups, CIELab values were analyzed with a 4-way ANOVA, and TP values were analyzed with a generalized linear mixed model. Pairwise comparisons of interest were evaluated with Bonferroni-corrected Student t tests. RESULTS: For maxillary central incisor enamel, the average TP was 10.1 ±3.6, and the average CIELab color coordinates were L∗=73.5 ±7.6, a∗=2.2 ±1.8, b∗=11.9 ±8.4. TP values of incisal enamel significantly differed among specific age and ethnic groups, with general significant interactions of age and sex (P=.009), as well as ethnicity and age (P=.042). CIE color coordinates of enamel at an infinite thickness were found in the L∗ coordinate among different age groups with the same sex and ethnicity, specifically when comparing CIELab direction with the population characteristics of age (P=.011) and the interaction between age, sex, and ethnicity (P=.035). CONCLUSIONS: In vivo L∗ values and TP values of incisal enamel differed significantly among groups determined by ethnicity, age, and sex.

Coverage error of three resin composite systems to vital unrestored maxillary anterior teeth.

OBJECTIVE: Define the color of anterior teeth of a selected population and correlate it (by using coverage error [CE] and the frequency of best match) with the final color of all possible enamel-dentine combinations of three different resin composite systems. MATERIALS AND METHODS: Color of 636 vital unrestored anterior teeth (central incisors, lateral incisors and canines; n = 212) and disk specimens (12 mm diameter, varying thickness) corresponding to enamel-dentin combinations of all available enamel (0.5 mm and 1.0 mm thickness) and dentin shades (3.0 mm thickness) of Essentia, Enamel Plus HRi and IPS Empress Direct composite systems was measured using a clinical dental spectrophotometer (Spectroshade Micro). CE and frequency of best match for all composite systems were calculated for the measured in-vivo teeth color space. RESULTS: Natural in-vivo teeth exhibit higher lightness when compared to enamel-dentin composite combinations, independently of the enamel thickness used. The best (lowest) CE was found for IPS Empress, while the highest values were found for Enamel Plus Hri independently of tooth type and enamel thickness (p < 0.001). The use of 0.5 mm instead of 1.0 mm enamel thickness within enamel-dentin composite combinations resulted in a lower CE for in-vivo tooth color (p < 0.001). CONCLUSIONS: The color space defined by all possible enamel-dentin combinations of the studied resin composite systems does not fully match the color range of anterior teeth. All composite systems examined lack combinations with lightness values as high as the population's. IPS Empress Direct composite system represented better the in-vivo teeth color. CLINICAL SIGNIFICANCE: The use of 0.5 mm enamel shade thickness is suggested when building layered restorations, as it provided better color coverage than using 1.0 mm thickness.

Effect of three-dimensionally printed surface patterns on the peak tensile load of a plasticized acrylic-resin resilient liner.

STATEMENT OF PROBLEM: Stereolithographic (SLA) three-dimensional (3D) printing is considered a reliable manufacturing method for immediate complete dentures. However, studies on the implementation of computer-generated surface patterns to promote the union between printed denture base polymers and dental materials with different chemistries such as plasticized acrylic-resin resilient liners are lacking. PURPOSE: The purpose of this in vitro study was to assess the effect of 3D-printed surface patterns on the peak tensile load of a short-term plasticized acrylic-resin resilient liner. MATERIAL AND METHODS: A total of 30 denture base specimens (Denture Base LP; FormLabs) were fabricated with 3 adhesive surface designs by using an SLA 3D printer (Forms2; FormLabs). Twenty specimens were designed with surface patterns in the adhesive areas (grid and spheres); 10 specimens comprised each surface pattern group. The remaining specimens were roughened with 220-grit silicon carbide paper and served as a control. A commonly used short-term resilient liner (CoeSoft; GC-America) was applied to the adhesive surface of all the specimens. Subsequently, the specimens were kept in distilled water at 37 °C for 48 hours. The specimens were tested in a universal testing machine, and the resulting peak tensile load data were analyzed by using a 1-way analysis of variance (ANOVA) and a post hoc Tukey test (α=.05). RESULTS: The groups with surface patterns on the adhesive surface displayed higher peak tensile load values than the control group. The mean peak tensile load of the grid group was 6.73 ±0.43 N, and that for the spheres group was 6.58 ±0.33 N. The control group displayed the lowest mean peak tensile load (2.71 ±0.51 N). Statistically significant differences were detected between the mean peak tensile loads of the surface pattern groups and the control group (P<.001) No statistically significant difference was found between the mean peak tensile loads of the grid and spheres groups (P=.893). CONCLUSIONS: Incorporating surface patterns on the intaglio surface of denture bases made with Denture Base LP via SLA 3D printing can enhance their union to a plasticized acrylic-resin resilient liner. Surface patterns generated higher peak tensile load values than slightly roughening the surface of a 3D-printed denture with a 220-grit silicon carbide paper. No significant differences in the mean peak tensile loads were observed between the 2 types of surface patterns.

Adhesive strength of 3 long-term resilient liners to CAD-CAM denture base polymers and heat-polymerized polymethyl methacrylate with thermocycling.

STATEMENT OF PROBLEM: Computer-aided design and computer-aided manufacturing (CAD-CAM) technologies have become popular for manufacturing complete dentures. However, the adhesive strength of resilient liners to the polymers used to fabricate CAD-CAM complete dentures is unclear. PURPOSE: The purpose of this in vitro study was to determine the adhesive strength of 3 long-term resilient liners to CAD-CAM denture base polymers and heat-polymerized PMMA with thermocycling. MATERIAL AND METHODS: A total of 90 specimens were fabricated, 30 per group of denture base material (Lucitone 199, Ivo Base CAD, Denture Base LP). For each denture base polymer, 10 specimens were relined with 1 of 3 resilient liners (Permasoft, Mucopren Soft, Molloplast-B). Five specimens of each group were thermocycled, and the other 5 specimens were stored in distilled water. Subsequently, the adhesive strength of the specimens was assessed by tensile testing. The resulting data were analyzed by using a 3-way analysis of variance (ANOVA) (α=.05). RESULTS: After thermocycling, the adhesive strengths of all the resilient liners were found to be statistically different from each other for the same denture base polymer (P≤.012). Mucopren Soft displayed a high mean ±standard deviation adhesive strength to Lucitone 199 (1.78 ±0.32 MPa), followed by Molloplast-B (1.27 ±0.21 MPa) and Permasoft (0.66 ±0.06 MPa). For Ivo Base CAD, Molloplast-B exhibited a high mean ±standard deviation adhesive strength (1.70 ±0.36 MPa), followed by Mucopren Soft (1.11 ±0.16 MPa) and Permasoft (0.53 ±0.04 MPa). Molloplast-B displayed high mean ±standard deviation adhesive strength to Denture Base LP (1.37 ±0.08 MPa), followed by Mucopren Soft (0.68 ±0.20 MPa) and Permasoft (0.32 ±0.04 MPa). The adhesive strength of the majority of resilient liners not exposed to thermocycling was statistically different from each other for the same type of denture base polymer (P<.001). The only exception was the difference between the adhesive strength of Molloplast-B and Mucopren Soft to Lucitone 199 with mean ±standard deviation values of 1.42 ±0.18 and 1.66 ±0.40 MPa, respectively, (P=.067). Without thermocycling, the mean ±standard deviation adhesive strength to Lucitone 199 of Permasoft (0.57 ±0.02 MPa) was statistically different from that of Molloplast-B and Mucopren Soft (P<.001). Molloplast-B displayed a high mean ±standard deviation adhesive strength to Ivo Base CAD (1.83 ±0.25 MPa), followed by Mucopren Soft (1.26 ±0.19 MPa) and Permasoft (0.58 ±0.08 MPa). Molloplast-B displayed a high mean ±standard deviation adhesion to Denture Base LP (1.76 ±0.23 MPa), followed by Mucopren Soft (0.88 ±0.14 MPa) and Permasoft (0.25 ±0.06 MPa). Only Molloplast-B was significantly adversely affected by thermocycling (P=.009). CONCLUSIONS: Molloplast-B displayed high adhesive strength to both CAD-CAM denture base polymers regardless of the storage conditions. Mucopren Soft displayed high adhesion to Lucitone 199. Permasoft presented moderate adhesion to PMMA-based denture bases and low adhesion to DBLP. Combining Permasoft with Denture Base LP should be considered carefully and limited to short-term use. Thermocycling had a detrimental effect on the adhesive strength of Molloplast-B.

Color and translucency of milled polymethyl methacrylate crowns on non-tooth-colored interim abutments with different surface treatments.

STATEMENT OF PROBLEM: The interim rehabilitation of implants has become a necessity, particularly for those placed in the esthetic regions. However, the optical properties of computer-aided design and computer-aided manufacturing (CAD-CAM) polymethyl methacrylate (PMMA) crowns on interim abutments with different surface treatments are unclear. PURPOSE: The purpose of this in vitro study was to investigate the color and translucency of CAD-CAM PMMA crowns when different surface treatments were used on titanium interim abutments. MATERIAL AND METHODS: A maxillary dentate stone cast with a narrow-diameter implant analog at the left lateral incisor site was used. Three titanium interim abutments (blue) were divided into 3 groups according to the surface treatment they received: control (steam cleaning), opaqued (120-µm Al2O3 airborne-particle abrasion and opaque application), and airborne-particle abraded (120-µm Al2O3). Thirty PMMA crowns (A2 shade) were milled (n=10). The color coordinates of the crown-interim abutment pairs and a shade tab (A2) were measured by using a colorimeter. The color differences (ΔE00) between the crowns and the shade tab and the relative translucency parameter (RTP) values of the crowns were calculated by using the CIEDE2000 formula. One-way ANOVA was used to analyze the ΔE00 and RTP values with subsequent Tukey honestly significant difference tests (α=.05). RESULTS: The abutment surface treatment significantly affected the ΔE00 of interim crowns from the shade tab (P<.001), but no significant effect was found on RTP (P=.26). The control group had the highest ΔE00 from the shade tab (P≤.011). No significant difference (P=.14) was found between the opaqued and the ΔE00 of the airborne-particle abraded groups from the shade tab. CONCLUSIONS: The surface treatments of interim abutments affected the color of CAD-CAM PMMA crowns, which differed from that of the shade tab. The color of crowns on opaqued or airborne-particle abraded interim abutments was closer to the color of the shade tab. Abutment surface treatments did not affect the translucency of crown-interim abutment pairs.

Effect of crown height on the screw joint stability of zirconia screw-retained crowns.

STATEMENT OF PROBLEM: Medium- to long-term data for the performance of zirconia crowns with titanium (Ti) bases are sparse, particularly when the crown height space and occlusal loads are high. PURPOSE: The purpose of this in vitro study was to assess the effect of the height of zirconia screw-retained implant crowns with a Ti base on the screw joint stability after cyclic loading. A secondary aim was to investigate the survival of zirconia crowns of different heights after cyclic loading. MATERIAL AND METHODS: Twenty-one internal connection implants were secured between fiberglass-reinforced epoxy resin sleeves. Mandibular first molar monolithic zirconia crowns with 3 different heights (6 mm, 10 mm, and 14 mm) were milled and bonded to the Ti bases (n=7). The screws were tightened to 30 Ncm, and a 30-degree 120-N cyclic load was applied to the crowns at 2 Hz for 5 million cycles. After 5 million cycles, the crowns were evaluated for stability, and the same protocol was repeated for 275-N and 435-N loads for 5 million cycles each. After loading, the detorque values were recorded. Failure was characterized based on whether the crown, screw, and/or implant fracture was observed. The detorque values were analyzed by using a 1-way-ANOVA with the restricted maximum likelihood estimation. The percentage of torque loss was calculated. The LIFETEST procedure was used to analyze the survival probability of the groups (α=.05). RESULTS: The effect of crown height on the detorque values of screws was not found to be statistically significant (P>.05). The mean detorque value for 6-mm crowns was 23.5 Ncm, 24.4 Ncm for 10-mm crowns, and 22.1 Ncm for 14-mm crowns. A significant effect of crown height was found on the survival (P=.006), and the time-to-failure survival of 14-mm crowns was significantly lower than the survival of 6 mm and 10 mm crowns (P=.020), where no failures were observed. Four 14-mm crowns failed between the 1 and 2 million cycles after the loads were increased to 435 N. The failure modes were the same for all the crowns, implants, and screws fractured. CONCLUSIONS: When the tested internal connection implant was used, the crown height did not affect the detorque values, and 14-mm crowns performed similarly to the shorter crowns in terms of torque loss after cyclic loading. However, survival of the 14-mm crown-implant complex was lower, resulting in screw and implant fractures.

Displacement and performance of abutments in narrow-diameter implants with different internal connections.

STATEMENT OF PROBLEM: Displacement of abutments into conical connection implants during screw tightening may also occur during functional loading, creating unsettling forces that may cause loss of preload. A recent conical-hexagon connection with double friction fit (conical-hexagon connection) could prevent this axial displacement. PURPOSE: The purpose of this in vitro study was to measure the 3D axial displacement of abutments with a conical-hexagon connection or conical connection in narrow-diameter implants. Removal torque values (RTVs), preload efficiency, and survival after cyclic loading were also compared. MATERIAL AND METHODS: Narrow-diameter implants with a conical connection (Osseospeed EV, 3.0×13 mm-AST) and narrow-diameter implants with a conical-hexagon connection (Eztetic, 3.1×13 mm) were embedded in resin rods (G10) (n=6). Six titanium abutments per system were used, and their spatial relationship to the implant platforms after hand tightening was determined by using 3D digital image correlation. The abutments were tightened to the manufacturers' specified values, and the abutments' relative position was recorded again. The displacement of the abutment after tightening was calculated. The implants were subjected to cyclic loading (5×106 cycles at 2 Hz) under 200-N loads at a 30-degree angle. After cyclic loading, the RTVs of screws were measured and compared with those specified by the manufacturers to calculate preload efficiency. ANOVA was used to compare the differences in displacements after tightening and to compare differences in RTVs after cyclic loading across the groups (α=.05). RESULTS: The mean displacement in the U direction (X-axis) for the AST was -0.7 µm and -4.7 µm for ZIM, with no statistical difference (P=.73). The mean displacement in the V direction (Y-axis) for AST was -37.0 µm, and -150.0 µm for ZIM, with significant statistical difference (P<.001). The mean displacement in the W direction (Z-axis) for AST was -0.9 µm, and -23.0 µm for ZIM, with no statistical difference (P=.35). The survival of groups was similar (P=.058). During cyclic loading, 3 AST specimens fractured. After cyclic loading, mean RTV for AST was -8.77 Ncm, and -14.24 Ncm for ZIM, and these values were significantly different (P=.04). Preload efficiency was 28.1% for AST and 41.5% for ZIM. CONCLUSIONS: Greater abutment displacements were observed with the conical-hexagon connection, which required a higher torque, as specified by its manufacturer. The abutments displaced more in the V-axis in both implants. Only the conical connection implant (Ti Grade 4, commercially pure) had failures during cyclic loading, but the survival of the implants was similar. After cyclic loading, the abutment screws in both systems lost some of their torque value. The abutment screws of the conical-hexagon connection implant maintained preload more efficiently during cyclic loading than those of the conical connection implant.

ICP-MS measurements of elemental release from two palladium alloys into a corrosion testing medium for different solution volumes and agitation conditions.

STATEMENT OF PROBLEM: The in vivo release of Pd from palladium alloys into the oral environment and sensitivity reactions by patients has been of concern. However, little information is available about the variation in elemental release from different palladium alloys. PURPOSE: The purpose of this in vitro study was to compare the elemental release into a corrosion-testing medium from a high-palladium alloy (Freedom Plus, 78Pd-8Cu-5Ga-6In-2Au) and a Pd-Ag alloy (Super Star, 60Pd-28Ag-6In-5Sn) under different conditions. MATERIAL AND METHODS: Alloys were cast into Ø12×1-mm-thick disks, subjected to simulated porcelain-firing heat treatment, polished, and ultrasonically cleaned in ethanol. Three specimens of each alloy were immersed for 700 hours in a solution for in vitro corrosion testing (ISO Standard 10271) that was maintained at 37 °C. Two solution volumes (125 mL and 250 mL) were used, and the solutions were subjected to either no agitation or agitation. Elemental compositions of the solutions were analyzed by using inductively coupled plasma-mass spectroscopy (ICP-MS). Concentrations of released elements from each alloy for the 2 solution volumes and agitation conditions were compared by using the restricted maximum likelihood estimation method with a 4-way repeated-measures ANOVA, the Satterwhite degrees of freedom method, a lognormal response distribution, and the covariance structure of compound symmetry. RESULTS: For the 4 combinations of solution volume and agitation conditions, the mean amount of palladium released was 3 orders of magnitude less for the Pd-Ag alloy (0.009 to 0.017 µg/cm2 of alloy surface) compared with the Pd-Cu-Ga alloy (17.9 to 28.7 µg/cm2). Larger mean amounts of Sn, Ga, Ag, and In (0.29 to 0.39, 0.57 to 0.83, 0.71 to 1.08, and 0.91 to 1.25 µg/cm2, respectively) compared with Pd were released from the Pd-Ag alloy. Smaller amounts of Cu, Ga, and In (4.8 to 9.9, 5.9 to 12.8, and 4.2 to 9.5 µg/cm2, respectively) compared with Pd were released from the Pd-Cu-Ga alloy. The Ru released was much lower for the Pd-Ag alloy (0.002 µg/cm2) than the Pd-Cu-Ga alloy (0.032 to 0.053 µg/cm2). Statistically significant differences (P<.001) in elemental release were found for the factors of alloy and element and the alloy×element interaction. Significant differences were found for the solution volume (P=.022), solution volume×element interaction (P=.022), and alloy×solution volume×element interaction (P=.004). No significant effect was found for agitation condition. CONCLUSIONS: The relative amounts of released elements from each alloy were not proportional to the relative amounts in the composition. The amounts of Pd and Ga released from the Pd-Cu-Ga alloy were consistent with the breakdown of a Pd2Ga microstructural phase and perhaps some dissolution of the palladium solid solution matrix. Precipitates, rather than the palladium solid solution matrix, appeared to undergo greater dissolution in the Pd-Ag alloy. The Pd-Ag alloy should have lower risk of adverse biological reactions than the Pd-Cu-Ga alloy.

Effect of cyclic loading on reverse torque values of angled screw channel systems.

STATEMENT OF PROBLEM: The angled screw channel concept has become popular. However, research is lacking as to how reverse torque values of nonaxially tightened implant crowns compare with axially tightened cement-retained crowns restored on angle-correcting abutments when subjected to long-term cyclic loading. PURPOSE: The purpose of this in vitro study was to evaluate the ability of different 25-degree angled screw channel hexalobular systems to apply the target torque value on their screws, the effect of cyclic loading on their reverse torque values, and their survival compared with crowns cemented on conventional 0-degree screw channel abutments. MATERIAL AND METHODS: A total of 28 implants were divided into 4 groups. Twenty-one angled screw channel crowns were fabricated at a 25-degree angle correction by using angled titanium (Ti) bases by 3 manufacturers DY (Dynamic Tibase), DE (AngleBase), and ASC (Angulated Screw Channel) (n=7). The fourth group, UB (Universal Base, Control), had cement-retained crowns with 25-degree custom-milled, angled zirconia abutments that were cemented onto their respective Ti bases (n=7). All implants were embedded in epoxy resin blocks and tightened to manufacturer recommended values: 35 Ncm for ASC, UB, and DE and 25 Ncm for DY. Initial torque values (ITV1) were recorded. After 24 hours, the reverse torque values (24hr-RTV1) were recorded. A new set of screws was then used for each group, and the initial torque values (ITV2) were recorded. Specimens were loaded at 2 Hz for 5 million cycles under a 200-N load, and reverse torque values (RTV2) were recorded. ANOVA (α=.05) was used to compare differences in the means of deviation of initial torque values and means of reverse torque values followed by a Tukey-Kramer post hoc analysis (α=.05). Preload efficiency was calculated for each system (RTV2/ITV2), and a survival analysis was performed by using the Lifetest procedure. RESULTS: A significant difference in the means of deviation of initial torque values of the groups with 25-degree torque application (DY, DE, and ASC) was found when compared with UB at 0 degrees. ASC and DE had lower initial torque values than UB (P<.001 and P=.003 for ASC ITV1 and ITV2, P<.001 and P=.006 for DE ITV1 and ITV2). A significant difference was found in mean reverse torque values both for after 24 hours and after cyclic loading among all groups (P<.001). A significant difference was found between mean reverse torque values before and after cyclic loading for each group (P<.001). Preload efficiency was 43.8% for DY, 46.8% for DE, 54.2% for ASC, and 48.5% for UB. No significant difference was found in the time-to-failure survival among groups (P>.05). CONCLUSIONS: The hexalobular system of DY delivered comparable initial torque values to its target value at 25 degrees, similar to how UB (control group) delivered at 0 degrees. ASC and DE scored lower initial torque values than their target value compared with UB. The DY abutment, which had a lower manufacturer recommended torque value, had lower reverse torque values compared with those of other groups. Time-to-failure survival of all groups was similar. Fractures at the zirconia to titanium base connection were seen with ASC crowns.

Effect of thickness, cement shade, and coffee thermocycling on the optical properties of zirconia reinforced lithium silicate ceramic.

OBJECTIVE: To investigate the effect of thickness, cement shade, and coffee thermocycling (CTC) on the optical properties of zirconia reinforced lithium silicate (ZLS) paired with different shades of a resin cement. MATERIALS AND METHODS: Thirty ZLS specimens were prepared in two different thicknesses (0.8 and 1.5 mm) and three different resin cement shades (Tr, A2, and A3) were applied (n = 5). Color determinations were done before and after 5000 CTC by using a noncontact spectroradiometer. Color change due to CTC and relative translucency parameter (RTP) before and after CTC were calculated by using CIEDE2000. Data were analyzed using ANOVA and Bonferroni-corrected t-tests(α = 0.05). RESULTS: Material thickness and resin cement shade (P < 0.001) affected baseline color. Material thickness affected color difference (P = 0.025). Thickness, resin cement shade, and CTC (P ≤ 0.0001) affected RTP. The difference between the color changes of the 0.8- and 1.5-mm specimens combined with A2 shade cement after CTC was significant (P = 0.01). RTPs of all pairs decreased after CTC (P < 0.001). CONCLUSIONS: Cement shade and material thickness affected the baseline color. The thickness of ZLS affected the color change after CTC only with A2 resin cement and the color change was less when the ZLS was thicker. CTC reduced the translucency of all pairs. CLINICAL SIGNIFICANCE: Clinicians and patients should be aware of a potential color change after long-term coffee consumption when zirconia reinforced lithium silicate is used particularly for laminate veneers with A2 shade of the tested resin cement.

Screw stability of CAD-CAM titanium and zirconia abutments on different implants: An in vitro study.

BACKGROUND: Limited information is available regarding the removal torque values (RTVs) of screws of different abutment materials when used with different implants. PURPOSE: To evaluate the effect of implant type and abutment material (zirconia; Zir and titanium; Ti) on the RTVs of abutment screws after cyclic loading. MATERIALS AND METHODS: Internal conical connection implants (CC, OsseoSpeed TX) and modified internal conical connection implants (MCC, OsseoSpeed EV) (n = 10) were clamped in resin dies. Zir and Ti (N = 20) custom abutments were tightened to implants (20 Ncm for CC and 25 Ncm for MCC) as specified by their manufacturers. The abutments were cyclically loaded by using a sequentially increased loading protocol; 2-million cycles under 100 N, 3-million cycles under 200 N, and 2-million cycles under 300 N loads with 2 Hz. After 7 million cycles, RTVs (Ncm) were measured by using a torque gauge. The data were analyzed with ANOVA by using the restricted maximum likelihood estimation method. Tukey-Kramer adjustment was used for any significant interaction of implant-abutment pairs (α = 0.05). RESULTS: Two CC implants, 1 with Ti and 1 with Zir abutment, fractured during cyclic loading (under 300 N loads within the 6th and 7th million cycles) and discarded for statistical analysis. Only implant type had a significant effect on RTVs (p <0.001). Screws of Ti abutments on MCC implants had significantly higher RTVs than the screws of Ti (p = 0.003) and Zir (p = 0.005) abutments on CC implants. CONCLUSIONS: Implant type affected the RTVs, however, the RTVs were higher than the initial torque values for all groups. Screws of Ti abutments on implant, which required greater initial torque values had higher RTVs than the screws of Ti and Zir abutments on the implant that required smaller initial torque values. RTVs were similar for Zir and Ti abutment screws within each implant type.

Electrochemical impedance spectroscopy study of corrosion characteristics of palladium-silver dental alloys.

Electrochemical impedance spectroscopy (EIS) has been used to obtain insight into corrosion processes for three Pd-Ag alloys, and compare their behavior with an Au-Pd alloy. Five specimens of each alloy received clinically-appropriate simulated porcelain-firing heat treatment. EIS testing was performed at ambient temperature, using 0.09% NaCl, 0.9% NaCl and Fusayama solutions. EIS data are presented as Bode plots. At the open-circuit potential (OCP), the data fit a modified Randles equivalent electrical circuit with a constant phase element (CPE), and the charge-transfer resistance (RCT ) and the two CPE parameters (CPE-T and CPE-P) were determined. The area-normalized capacitance of the double layer (Cdl ) was also calculated. The EIS data at two relevant elevated potentials in the passive range were also found to fit well a modified Randles equivalent circuit with different values for the charge transfer resistance and CPE parameters. At the OCP no significant effect on RCT was found for the alloys and electrolytes, and both alloy and electrolyte significantly affected CPE-P. In vitro corrosion was controlled by charge transfer and charge accumulation processes, and the behavior differed at the elevated potentials compared to the OCP. Significant effects were found for alloy, electrolyte, and alloy/electrolyte interaction on Cdl at the OCP. The EIS parameters at elevated potentials indicate that the Pd-Ag alloys should have satisfactory clinical corrosion resistance. The EIS analyses yielded information about in vitro corrosion of these alloys that cannot be obtained from potentiodynamic polarization testing.

Effect of Crown Height on the Screw Stability of Titanium Screw-Retained Crowns.

PURPOSE: The aim of this in vitro study was to evaluate the effect of crown height on the screw stability of screw-retained titanium implant crowns subjected to cyclic loading conditions. MATERIALS AND METHODS: Twenty-one implants with internal hex connections were placed in epoxy resin holders. Mandibular first molar screw-retained titanium implant crowns with UCLA type, crown-abutment connections were CAD/CAM fabricated. Seven crowns of 3 different heights (6 mm, 10 mm, and 14 mm) were made. The crowns were seated onto the implants and screws were tightened to 30 Ncm. The implants were clamped into holders and stepwise cyclic loads were applied to the occlusal surface at 30-degree angles to the long axes of the crowns. The detorque values were measured after each 5 million cycles. Before increasing the applied load, the crowns were secured with new screws and tightened to 30 Ncm. Failure times, survival estimates and detorque values were then analyzed. (alpha = 0.05). RESULTS: Crown height did not significantly affect detorque values. However, five 14-mm crowns failed with varying fractures during the 475 N loading condition. Overall, a significantly lower survival for 14 mm crowns was found compared to 6 mm and 10 mm crowns (p = 0.004). CONCLUSIONS: Crown heights of one-piece screw-retained titanium implant crowns did not significantly affect detorque values. Screw fracture, however, was greater for crown height of 14 mm than those of 6 mm and 10 mm.

Rehearsal's effect on recall and comprehension of orthodontic informed consent.

INTRODUCTION: Proper informed consent allows patients to take an active role in their own treatment decisions, and enhanced compliance might improve treatment outcomes. The objective of this research was to determine if handwritten rehearsal of core and custom consent items would increase short-term recall and comprehension. METHODS: A total of 90 patient-parent pairs were randomly assigned to 2 groups. After case presentation, each subject was provided 10 minutes to read a modified informed consent document. Group A received visual printouts containing the 4 core elements (root resorption, decalcification, pain, and relapse/retention) likely to be encountered by all patients and up to 4 custom elements (eg, impacted teeth, orthognathic surgery, or other case-specific treatment issues). Subjects identified and wrote what the image depicted and how it could affect treatment. Group B viewed a slideshow presentation on all 18 consent elements arranged from general to specific. All participants were interviewed, and each provided their sociodemographic data, as well as completed literacy, health literacy, and state anxiety questionnaires. The groups were compared for recall and comprehension through an analysis of covariance. RESULTS: The rehearsal intervention significantly improved recall and comprehension of the core elements (P = 0.001). Rehearsal also improved custom recall and comprehension, but not significantly. Group B performed significantly better on treatment questions (P = 0.001). Overall, as anxiety increased, correct responses decreased. CONCLUSIONS: The rehearsal group improved recall and comprehension of the core and custom elements of informed consent and proved a more efficient method than an audiovisual presentation to provide informed consent. It also improved meeting legal obligations.

Surface roughness of high-performance polymers used for fixed implant-supported prostheses.

STATEMENT OF PROBLEM: High-performance polymers have been recommended by their manufacturers as a framework material for implant-supported fixed prostheses. However, little is known about the surface roughness of high-performance polymers in different compositions and whether they require layering with a composite resin or acrylic resin on the tissue surface. PURPOSE: The purpose of this in vitro study was to evaluate the surface roughness of different computer-aided design and computer-aided manufacture (CAD-CAM) high-performance polymers and the effect of polishing on their surface roughness. MATERIAL AND METHODS: Seventy high-performance polymer specimens (n=10) for 4 different polyetheretherketone (PEEK) brands (BRE, CP, ZZ, J), 1 polyetherketoneketone (PEKK) (PK), and 2 different fiber-reinforced composite resin (FRC) materials (T, TR) were milled from 7×8×30-mm CAD-CAM blocks. The surface roughness (Ra) of each specimen was measured on the same surfaces after milling (baseline) and after polishing by using a contact profilometer. Two-way repeated measures ANOVA (MIXED procedure) and the Bonferroni corrected t test (α=.05) were used to analyze the surface roughness data. RESULTS: No significant differences were found among high-performance polymers when the baseline surface roughness measurements of the materials were compared (P>.05). All materials (BRE, PK, CP, T, TR, ZZ), except for a PEEK material (J) (P<.05), had no significant differences in their surface roughness before and after polishing. After polishing, the surface roughness of the J PEEK material was higher than that of CP, PK, T, and ZZ (P<.05). CONCLUSIONS: The surface roughness of high-performance polymers in different compositions after milling was similar. Polishing increased the surface roughness of only one PEEK (J) material. All surface roughness values were above the clinical acceptability threshold of 0.2 µm.

Analysis of color differences in stained contemporary esthetic dental materials.

STATEMENT OF PROBLEM: Although contemporary analytical methods are available for application to data which exhibit a lack of equality of variances or a lack of normality in the error distribution, little guidance is provided for selecting the methods of data handling and analysis which best fit color difference data for stained esthetic materials. PURPOSE: The purposes of this in vitro study were to apply information criteria of analysis of variance (ANOVA) methods of differing error distributions and covariance structures when analyzing color differences to determine the degree of alienation among 3 Commission Internationale de l'Eclairage (CIE) color difference formulae to assess the linearity of relationships among these formulae and to independently assess differences among various computer-aided design and computer-aided manufacture (CAD-CAM) materials in any color change after common forms of staining over time. MATERIAL AND METHODS: Hybrid ceramic, resin nanoceramic, feldspathic-ceramic, and lithium-disilicate ceramic specimens (N=128) were subjected to staining from water, tea, coffee, and red wine over 1, 7, and 30 days, with color differences calculated from baseline. Akaike information criteria (AIC) and Bayesian information criteria (BIC) values were determined for Gaussian and lognormal error distributions at covariance structures of standard variance components and compound-symmetry. The analysis of variance used to analyze any significant effects on these color differences was the one with the lowest AIC and BIC values. Then, for each solution, day, and CIE color difference formula, any significant difference in the color differences between all pairs of materials was found by Bonferroni-corrected Student t tests. Those statistically significant pairwise comparisons where the larger of the color differences met or exceeded the acceptability threshold were labeled as statistically and visually noteworthy. RESULTS: For this color difference data set, the lognormal error distribution and the covariance structure of compound symmetry provided the best AIC and BIC. Because the interaction between material, solution, and day was statistically significant (P<.001), pairwise comparisons were made between all pairs of materials for each level of solution and day studied. Noteworthy differences were identified, where hybrid ceramic and resin nanoceramic each had color changes after staining in coffee and red wine that were greater than each of feldspathic-ceramic and lithium-disilicate ceramic. CONCLUSIONS: AIC and BIC values evaluate distinctively the Gaussian and lognormal error distributions when analyzing highly varying color differences. Although there is a high linear correlation between the 3 color difference formulae studied, each formula is unique, and each represents a different assessment of the perceived color difference. CAD-CAM materials, staining liquids, and time points affected the notable color changes.

In vitro evaluation of the accuracy and precision of intraoral and extraoral complete-arch scans.

STATEMENT OF PROBLEM: The accuracy of intraoral and extraoral scanners for different models of edentulousness is unclear. PURPOSE: The purpose of this in vitro evaluation was to determine the accuracy (trueness and precision) of complete-arch scans made by 3 intraoral and 1 extraoral scanners compared with an industrial 3D scanner. MATERIAL AND METHODS: Digital scans were made of a reference cast with 3 intraoral scanners (CEREC Omnicam; Dentsply Sirona, TRIOS 3; 3shape A/S; Carestream CS 3600; Carestream Dental) and an extraoral scanner (Deluxe scanner; Open Technologies). A dental maxilla model was used for tooth preparation for ceramic restorations with a shoulder finishing line. Maxillary right central and lateral incisors and third molar and maxillary left second premolar and first and third molar teeth were removed. One operator scanned the reference cast 10 times with each scanner. All the recorded standard tessellation language (STL) files were imported into an inspection software program and individually overlaid on the STL file for the reference model made by the 3D scanner. The measured distance between the distal point of the maxillary left second molar tooth and the mesial point of the maxillary left first premolar was defined as distance 1; distance 2 was defined as the distance between the mesial point of the maxillary second molar tooth and the distal point of the maxillary right first premolar tooth. The Levene test for homoscedasticity of variances was used to evaluate precision, and a 2-way repeated-measures ANOVA and Bonferroni-corrected Student t tests were used to evaluate trueness (α=.05). RESULTS: A statistically significant difference was found between the Carestream scanner and the other scanners when scanning both mucosa and teeth. The Carestream scanner had the lowest accuracy and highest magnitude mean deviation of all the scanners. CONCLUSIONS: Obtaining an accurate partial-arch impression is still challenging for some intraoral scanners. The Carestream scanner's trueness was outside the acceptable range. However, other scanners tested here appeared to be suitable alternatives to conventional impression techniques.