Translucency and flexural strength of translucent zirconia ceramics.

STATEMENT OF PROBLEM: Translucent zirconias have been developed with better esthetics than high-strength zirconias by reducing opacity. However, studies on their translucency and strength are sparse. PURPOSE: The purpose of this in vitro study was to compare the relationship between translucency and biaxial flexural strength of recently developed high-translucency zirconia, high-strength zirconia, and lithium disilicate ceramics. MATERIAL AND METHODS: Disks (n=12) were fabricated for 5 ceramic materials: high-strength zirconia (BruxZir 16 shaded), translucent zirconia (BruxZir Anterior shaded, Katana UTML, Katana STML), and lithium disilicate (IPS e.max, Press HT, and LT). A standard tessellation language (STL) file was designed, and the specimen milled, finished, and glazed according to manufacturer's instructions for each material. The translucency parameter was calculated against black and white backgrounds and white and stump shade with ND4 background by using a spectrophotometer. Biaxial flexural strength was calculated by using the 3-ball test. The load was applied at a crosshead speed of 0.5 mm/min with a 49-N load cell until failure occurred. Translucency parameter and biaxial flexural strength data were analyzed with 1-way analysis of variance (ANOVA). A Tukey honest significant difference multiple comparison test was used to determine significant differences (α=.05). RESULTS: The IPS e.max HT was more translucent against both backgrounds (32.85 for black/white and 15.34 for white/stump), while BruxZir 16 was the least translucent (19.78 for B/W and 8.83 for W/S). All groups tested differed in translucency (P<.001) except for BruxZir Anterior and Katana STML, which were not significantly different (P=.052). For biaxial flexural strength, BruxZir 16 had the highest strength (995.44 MPa) and e.max HT, the lowest (186.75 MPa). No significant differences were found between BruxZir anterior and Katana STML, Katana UTML and IPS e.max LT, or IPS e.max LT and IPS e.max HT (P>.05). Translucency parameter values using both backgrounds were strongly correlated (r=0.99). However, biaxial flexural strength values were inversely related to translucency parameter values when using black/white and white/stump shade but with high correlation (r=-0.777 and -0.756 respectively). CONCLUSIONS: Lithium disilicate was the most translucent and yet the weakest material, whereas high-strength zirconia was the most opaque ceramic and the strongest. Katana UTML had the highest translucency but was weakest among translucent and high-strength zirconia materials. Overall, translucency was negatively correlated with biaxial flexural strength.

Effect of surface treatment and manufacturing process on the shear bond strength of veneering composite resin to polyetherketoneketone (PEKK) and polyetheretherketone (PEEK).

STATEMENT OF PROBLEM: Polyaryletherketones (PAEKs) are high-performance polymer materials in which polyetheretherketone (PEEK) and polyetherketoneketone (PEKK) are the most used. Although mechanical and shear bonding strength tests have been performed on the 2 materials, studies on the influence of processing on bonding are scarce. PURPOSE: The purpose of this in vitro study was to determine the influence of the surface treatment and the manufacturing process on the shear bond strength of veneering composite resin to PEKK and PEEK. MATERIAL AND METHODS: Thirty pressed PEKK, 30 milled PEKK, and 30 milled PEEK specimens were distributed in 6 groups (n=13) as per the manufacturing process and treatment surface. The specimens were either treated with airborne-particle abrasion with 110-µm aluminum oxide, or no surface treatment was applied. Moreover, the PEKK specimens were grouped regarding their manufacturing process, as either milled or heat-pressed. The specimens were all bonded by using a methyl methacrylate-based adhesive (visio.link), and composite resin (Gradia Revolution 2) was bonded to the specimens. An Instron universal machine was used to calculate the shear bond strength between the PEEK or PEKK and the composite resin. Two specimens from each group had their topography modification assessed with a scanning electron microscope. Statistical analysis was performed by using a 3-way ANOVA for multiple comparisons (α=0.05) RESULTS: The groups that were surface treated with 110-µm aluminum oxide (Al2O3) before bonding showed significantly higher shear bond strength (P=.001) than the other groups. However, no statistically significant difference was observed among the groups, regardless of the manufacturing process (milled or heat-pressed) (P=.607). CONCLUSIONS: PEEK and PEKK surfaces treated with 110-µm aluminum oxide airborne-particle abrasion displayed better shear bond strength to composite resin. The manufacturing process (milled or heat-pressed) did not significantly affect the bond strength of PEKK when subjected to the same bonding process.

Influence of Screw Channel Angulation on the Fracture Resistance of Zirconia Abutments: An In Vitro Study.

PURPOSE: The aim of this study was to investigate the effect of implant screw channel angulation on the fracture resistance of zirconia abutments without artificial aging. MATERIALS AND METHODS: Ten implant replicas were embedded in a jig of autopolymerizing acrylic resin. Using a surveyor and a metallic platform, the implant replicas were mounted centrally and with an angulation of 30°. A maxillary left central incisor crown was fabricated from pattern resin and scanned. The digital design of a monolithic zirconia implant abutment-crown was completed using a 3D imaging software. For all specimens of this group (ASC25 ), the screw channel was positioned at 25° to the lingual. Following fabrication, the samples were attached onto the embedded implant replicas and manually torqued to 35 Ncm as recommended by the manufacturer. The monolithic zirconia implant abutment-crowns were mounted in a metallic platform, positioned perpendicular to the indenter, and subjected to loading until failure. Crosshead speed was set at 0.5 mm/min for the universal testing machine. Data from a similar in vitro study where straight zirconia custom abutments (ASC0 ) were subjected to static load until failure was used as a control group. An unpaired Student's t-test was used to determine if fracture resistance based on load at failure and maximum load in each group were significantly different from each other (ASC25 vs ASC0 ). Statistical significance level was inferred at p ≤ 0.05 RESULTS: Group ASC25 fractured at a mean (SD) load of 215.49 (47.10) N and a mean (SD) maximum load of 420.50 (17.18) N. Group ASC0 fractured at a mean (SD) load of 534.04 (133.77) N and a mean (SD) maximum load of 762.69 (109.59) N. The difference was statistically significant for both mean load and mean maximum load at failure (p ≤ 0.05). The survival rate of 0° zirconia abutments was significantly higher than that of 25° ASC zirconia abutments. CONCLUSIONS: Within the limitations of this in vitro study the mean fracture load was significantly higher in the group with a straight channel angulation.

Implant Angulation Effect on the Fracture Resistance of Monolithic Zirconia Custom Abutments: An In Vitro Study.

PURPOSE: To investigate the fracture resistance and performance of zirconia when employed for the fabrication of implant abutments with different angulations, simulating anterior maxillary oral rehabilitation. MATERIALS AND METHODS: Forty-five monolithic zirconia custom abutments of internal conical implant connection were CAD/CAM designed and fabricated. The specimens were divided into three groups (n = 15/group) according to implant-to-abutment angulation. The angulations used were; 0°, 15°, and 25°. The abutments were loaded until failure at 135° using the Universal Testing Machine (Instron, Canton, MA). Collected data were statistically analyzed using one-way ANOVA and post hoc Tukey test. RESULTS: Mean (±standard deviation) load at fracture of the zirconia abutments for the three groups were 962.37 ± 93.81 N (Gr15) > 718.25 ± 93.71 N (Gr25) > 534.05 ±133.77 N (Gr0). Statistically significant difference (p < 0.0001) was found between all groups; Gr0 vs. Gr15, Gr0 vs. Gr25, Gr15 vs. Gr25. CONCLUSIONS: Contrary to expectations, the non-angulated monolithic zirconia abutments presented the lowest fracture resistance values. Angulating the abutments 15 or 25 degrees, following the palatal resorption pattern of the premaxilla, significantly increased the in vitro fracture resistance.

Fabrication of a screw-retained restoration avoiding the facial access hole: a clinical report.

Dental implant restorations may be either screw-retained or cemented onto an abutment. While each method has its advantages and disadvantages, cemented restorations are commonly used in the maxillary arch, usually because of esthetic concerns. Available bone in the anterior maxilla dictates the placement of the implant, which may result in a facially positioned screw-access opening. Still, a growing volume of literature states that periimplant soft tissues respond more favorably to screw-retained crowns than cement-retained crowns. This clinical report outlines a treatment with a new method of fabricating a custom abutment-crown combination for a screw-retained restoration. The technique allows the channel for the screw to be placed at an angle other than parallel to the implant body. In this case, the practitioner may choose either a screw-retained or cement-retained implant restoration, where previously only a cemented restoration was possible.

Marginal and internal adaptation of milled cobalt-chromium copings.

STATEMENT OF PROBLEM: The application of computer-aided design and computer-aided manufacturing (CAD/CAM) systems to produce complete coverage restorations with different materials continues to increase. To date, insufficient information is available regarding the adaptation of recently introduced milled cobalt-chromium (Co-Cr) copings for metal ceramic restorations. PURPOSE: The purpose of this in vitro study was to evaluate the marginal and internal fit of milled Co-Cr copings produced by CAD/CAM with 2 different marginal preparation designs. MATERIAL AND METHODS: Four master dies were developed from 2 ivorine central incisors and 2 ivorine maxillary molars, 1 of each prepared with a 0.8-mm chamfer and a 1.2-mm rounded shoulder. These 4 groups of teeth were replicated with polyvinyl siloxane and used as templates to fabricate epoxy dies (n=10) for each of the 4 groups; a total of 40 epoxy resin dies. Cobalt-chromium copings of standard thickness (0.4 mm) were fabricated for each die with CAD/CAM technology. Next, the working dies were scanned with a 5-axis laser scanner to produce a 3-dimensional model. A thin layer of low-viscosity polyvinyl siloxane material was placed inside each coping and seated on the die until the material set. Copings were removed from the dies, leaving the polyvinyl siloxane intact, and these silicone-coated dies were scanned. The software superimposed the 2 scans, and the marginal openings and internal fit were measured at multiple locations. The marginal opening was determined at 4 locations: mid-buccal (mB), mid-lingual (mL), mid-mesial (mM), and mid-distal (mD), and the mean of these 4 measurement locations was referred to as the group variable "edge." The internal occlusal adaptation was measured at the midpoint from buccal to lingual and mesial to distal locations and referred to as mid-occlusal (mO). Means and standard deviations for edge (marginal adaptation) and mO were calculated for each of the 4 groups. A 2-sample t test was performed to detect differences among groups. A regression analysis was done to evaluate the interaction between the variables mO and edge (α=.05). RESULTS: Significantly smaller mean marginal openings (P=.017) were observed overall for the chamfer marginal design (anterior chamfer: 61 ±41 µm; posterior chamfer: 52 ±27 µm) compared with the shoulder design (anterior shoulder 103 ±49 µm, posterior shoulder 113 ±110 µm). The anterior chamfer had a statistically significant (P=.055) smaller mean marginal opening (61 ±41 µm) than the anterior shoulder (103 ±49 µm). No statistically significant differences (P=.119) were found between the posterior chamfer and posterior shoulder. The internal adaptation at the mO location was not significantly different among all 4 groups (P>.05). However, a regression analysis demonstrated a strong correlation (R=.842; P<.001) between the occlusal seat (mO) and marginal opening, with the smaller mean marginal opening of the chamfer design coinciding with the smaller occlusal seat values (61µm; mO: 182 µm) anterior chamfer; (52 µm; mO: 172 µm) posterior chamfer versus (103 µm; mO: 235 µm) anterior shoulder; (113 µm; mO: 242 µm) posterior shoulder. CONCLUSIONS: The milled Co-Cr copings produced with a CAD/CAM system in this study demonstrated clinically acceptable marginal fit in the range of 52 to 113 µm before ceramic application.

Impact of implantoplasty on strength of the implant-abutment complex.

PURPOSE: Implantoplasty, a procedure that is done to smooth contaminated implant surfaces, has been used in the treatment of peri-implantitis. It reduces the implant diameter, which might compromise the implant's strength. This in vitro study was designed to evaluate the effect of implantoplasty on implant strength. MATERIALS AND METHODS: Thirty-two tapered implants were used; half were 3.75 mm in diameter (narrow) and the other half were 4.7 mm in diameter (wide). All implants were connected to 20-degree angled abutments. The apical half of each implant was embedded in acrylic resin. Eight 3.75-mm- and eight 4.7-mm-diameter implants were randomly assigned to receive implantoplasty. The remaining implants did not receive implantoplasty (control group). Implantoplasty was performed with a series of diamond and polishing burs. The specimens were then loaded 30 degrees off-axis in a universal testing machine until fracture failure occurred. Bending and fracture strength values were recorded and analyzed statistically (α = .05). The fractured surfaces were evaluated under a scanning electron microscope. RESULTS: All narrow implants failed by fracture at the implant platform. The mean bending strength of narrow implants was statistically significantly reduced by implantoplasty (511.4 ± 55.9 N versus 613.9 ± 42.8 N). Implantoplasty did not affect the strength of wide implants; fracture failures occurred at the abutment screw. The fracture mode was ductile and the crack growth was oblique in direction, indicating complex stress distribution and concentration under loading. CONCLUSION: Within the limits of this study, implantoplasty appeared to weaken the strength of narrower implants. Therefore, this procedure should be performed with caution on narrower, freestanding implants that are subject to greater occlusal force (eg, posterior regions). Validation of these results is needed for different implant systems.

Material options for restoring intentionally misaligned implants on maxillary edentulous arch: a clinical report.

Without major bone grafting procedures, anatomic challenges may dictate less than ideal implant placement. When surgical correction is impossible, it may be possible to place implants on an angle and use angled abutments to compensate. This article presents 2 patient treatments where angled abutments were used to facilitate the fabrication of an implant-supported fixed complete-arch prosthesis. In both scenarios the supporting bars for the prostheses were milled in titanium. Soft tissue shaded ceramic was used to simulate the soft tissues for one patient and soft tissue shaded composite resin was used for the second. The prostheses were completed by cementing 12 individual crowns on each bar.

Precision of fit of titanium and cast implant frameworks using a new matching formula.

Statement of the Problem. Fit of prosthodontic frameworks is linked to the lifetime survival of dental implants and maintenance of surrounding bone. Purpose. The purpose of this study was to evaluate and compare the precision of fit of milled one-piece Titanium fixed complete denture frameworks to that of conventional cast frameworks. Material and Methods. Fifteen casts fabricated from a single edentulous CAD/CAM surgical guide were separated in two groups and resin patterns simulating the framework for a fixed complete denture developed. Five casts were sent to dental laboratories to invest, cast in a Palladium-Gold alloy and fit the framework. Ten casts had the resin pattern scanned for fabrication of milled bars in Titanium. Using measuring software, positions of implant replicas in the definitive model were recorded. The three dimensional spatial orientation of each implant replica was matched to the implant replica. Results. Results demonstrated the mean vertical gap of the Cast framework was 0.021 (+0.004) mm and 0.012 (0.002) mm determined by fixed and unfixed best-fit matching coordinate system. For Titanium frameworks they were 0.0037 (+0.0028) mm and 0.0024 (+0.0005) mm, respectively. Conclusions. Milled one-piece Titanium fixed complete denture frameworks provided a more accurate precision of fit then traditional cast frameworks.

A technique for indirect fabrication of a complete-arch, implant-supported, fixed provisional restoration from a radiographic template.

This article describes an alternative technique for the fabrication of a complete-arch, implant-supported, cement-retained, fixed provisional restoration. The definitive cast is fabricated from the surgical guide and the provisional restoration is fabricated indirectly from the radiographic guide. This technique is an easy and time-saving procedure to fabricate an interim prosthesis for immediate or delayed loading of implants.

Restoring implants in the esthetic zone after sculpting and capturing the periimplant tissues in rest position: a clinical report.

Obtaining an accurate representation of the soft tissue contours developed around an implant in the esthetic zone is crucial to the success of a restoration. The technique presented emphasizes "guiding" of the soft tissue by modifying a provisional restoration to obtain an emergence profile that appears natural and blends with the gingival contour of the adjacent teeth. The technique provides an accurate impression of the soft tissue through the intraoral use of autopolymerized acrylic resin supported by the impression coping and vinyl polylsiloxane impression material. The eventual restoration uses an esthetic zirconia custom abutment and an implant-supported single crown to fulfill the esthetic and functional expectations of the patient and the provider.

A maxillary anterior partially edentulous space restored with a one-piece zirconia implant fixed partial denture: a clinical report.

This article describes the treatment provided to a patient who presented with a partially edentulous maxillary anterior space exhibiting severe resorption of the residual ridge. Two endosseous implants were placed to retain the prosthesis, which restored the missing teeth. A 1-piece zirconia implant fixed partial denture with individual all-ceramic crowns was used to replace the missing portions of the soft and hard tissues. This clinical report details the treatment of this restorative dilemma.

Effect of varying coping thickness on early load-to-fracture strength of Procera AllCeram copings cemented with 2 resin-modified glass-ionomer cements.

OBJECTIVES: Clinical situations may dictate that Procera AllCeram copings (Nobel Biocare) be fabricated or adjusted to a 0.40-mm coping thickness rather than the standard 0.60 mm. The goal of the present study was to determine the relative strength of 0.40-mm aluminum oxide copings versus standard 0.60-mm aluminum oxide copings and ascertain the effect of luting agents on the load-to-fracture value of the copings. METHOD AND MATERIALS: Forty prefabricated grade 2 titanium dies, premilled to standardized dimensions of a mandibular molar, were scanned using Procera CAD/CAM. Twenty aluminum oxide copings were ordered in the standard 0.60 mm thickness and 20 in 0.40 mm. Two cements were selected. Ten copings of each thickness were cemented to the titanium dies with RelyX Luting (3M ESPE) and 10 of each thickness with Fuji Plus cement (GC). Immediately after cementation, copings were placed under 5-kg static load for 10 minutes and then stored for 1 week in a 100% humidity chamber. At the time of testing, the samples were inspected and placed in a jig to ensure uniform vertical force application. Samples were loaded to fracture at 0.5 mm/min using an Instron universal testing machine. Results were recorded and statistically analyzed using the unpaired Student's t > test. Significance was determined at confidence level P> = or < .05. RESULTS: Mean load-to-fracture for the copings cemented with RelyX Luting was 451 N for 0.40-mm and 884 N for 0.60-mm copings, and for the copings cemented with Fuji Plus, 808 N and 1,701 N, respectively. CONCLUSIONS: Aluminum oxide copings of 0.60 mm showed significantly greater load-to-fracture values than 0.40 mm copings, regardless of the luting agent used. Within the independent comparisons, copings cemented with Fuji Plus exhibited higher load-to-fracture values than copings cemented with RelyX Luting cement.

Resistance to dislodgement of zirconia copings cemented onto titanium abutments of different heights.

STATEMENT OF PROBLEM: For patients with limited interocclusal space, standard height implant abutments may not be usable. Shorter abutments may be desirable. PURPOSE: The purpose of this study was to determine the effect of the height of titanium abutments on the tensile strength required to dislodge zirconia copings. MATERIAL AND METHODS: Two experimental groups of abutments were prepared: (1) 4.3-mm platform width implant abutment with a 6.5-mm height (control), and (2) a 4.3-mm platform width implant abutment with a 5.5-mm height (shorter). Each abutment had 5 zirconia copings (custom designed) fabricated through a 3-dimensional computer-assisted design (3-D CAD) process by scanning an identical wax pattern. The zirconia copings were designed to have a 6-mm projection above the titanium abutment to accommodate a 2-mm hole. A wire was inserted through this hole to attach the zirconia coping to a universal testing machine. Each abutment was placed onto an implant embedded in a brass base designed to fit onto the universal testing machine. The zirconia copings were cemented onto the abutments with a provisional luting agent (Improv), and a tensile force was applied at a crosshead speed of 0.5 mm/min. The removal force was recorded for each specimen. An unpaired t test was used for the statistical analysis (alpha =.05). RESULTS: The mean force (SD) necessary to remove the zirconia copings (Newtons) from the 6.5-mm titanium abutment (198.09 (28.83)) was higher (P=.0078) than for the 5.5-mm abutment (124.89 (36.388)). CONCLUSIONS: By increasing the height of the abutment 1 mm and maintaining the diameter of the abutment, the resistance to tensile forces increased significantly between the 2 abutment dimensions evaluated.

Restoring a severely resorbed maxillary anterior partially edentulous space using a one-piece titanium implant fixed partial denture: a clinical report.

This article describes the treatment provided for a patient presenting with a severely resorbed partially edentulous maxillary anterior space and a previously placed implant. After the patient refused removal of the existing implant and additional grafting of hard and soft tissue, the nonsalvageable teeth were removed and 2 endosseous implants were placed. A 1-piece titanium implant fixed partial denture was used to restore the missing portions of the soft and hard tissues. This clinical report details the treatment of this challenging restorative dilemma.

Evaluation of the precision of fit between the Procera custom abutment and various implant systems.

PURPOSE: It has been suggested that the CAD/CAM Procera custom abutment may be universally applied with multiple implant systems. An acceptable fit between the internal hexagon of an abutment and the external hexagon of various implant systems, along with true interchangeability of the Procera abutment screw, would support this concept. This study determined the precision of fit of the CAD/CAM-produced Procera abutment onto the external hexagon and bearing surfaces of implants from 6 implant manufacturers and the interchangeability of the Procera abutment screw with these systems. MATERIALS AND METHODS: This investigation consisted of 3 parts: (1) direct measurement of the internal hexagon and bearing surface of each Procera abutment and the external hexagon and the bearing surface of 6 implants from 6 different systems, (2) radiographic examination of 30 Procera abutment-implant junctions following tightening to 32 Ncm to determine the precision of fit between the bearing surfaces and the top of the external hexagon of the implant with the superior surface of the internal hexagon of the abutment, and (3) examination of 3 abutment screws and 3 implants from the various manufacturers for interchangeability based on American National Standards. RESULTS: The mean flat-to-flat external hexagons of the implants measured between 2.67 and 2.69 mm. The Procera abutment's flat-to-flat internal hexagon measured 2.73 mm. The height of the various implant systems' external hexagon ranged from 0.69 to 0.81 mm. The height of the Procera abutment blanks was 0.90 mm. Radiographic examination demonstrated that not all of the manufacturers' screws fit appropriately within the internal screw bore of the Procera abutment. The internal bore of all implant systems studied had a metric thread designation of M2 x 0.4 - 6H. The metric thread designation of all abutment screws examined was M2 x 0.4 - 6g. The greatest variations in the dimensions of the abutment screws measured were seen in the diameter of the screw head, which ranged from 2.12 to 2.69 mm. DISCUSSION: The Procera abutment's internal hexagon fit the external hexagon of all implant systems evaluated. The Procera abutment screw fit the internal screw bore of the implant systems tested. CONCLUSION: The Procera abutment with its screw can be universally applied to the implant systems studied. This fact, plus the CAD/CAM feature of this system, would thus provide a dynamic approach to satisfying the design and spatial needs of implant placements observed clinically.

Evolution and use of aluminum oxide single-tooth implant abutments: a short review and presentation of two cases.

PURPOSE: This article reviews the development of esthetic implant abutments and illustrates the use of aluminum oxide implant abutments in two cases. MATERIALS AND METHODS: Two patients were restored with single-tooth implants for the replacement of anterior teeth. One patient received a prefabricated aluminum oxide abutment, which was customized by the dental technician. A second patient received a custom aluminum oxide abutment, which was designed and fabricated using CAD/CAM technology. Both cases were restored with all-ceramic crowns. RESULTS: Satisfactory functional and esthetic results were achieved in both cases. The CAD/CAM abutment required no further customization in the dental laboratory. CONCLUSION: The use of aluminum oxide ceramic abutments improves dental and mucogingival esthetics in single-implant restorations. The use of CAD/CAM technology simplifies the design and customization process. Clinical studies are required to confirm the long-term performance of this type of restoration.