Survival and success of veneered zirconia crowns.

AIM: The aim of the present study was to evaluate the long-term clinical survival and success rate of veneered zirconia crowns with a modified anatomical framework design after 10 years in function. MATERIALS AND METHODS: In total, 36 zirconia crowns were fabricated for 28 patients. An anatomically modified framework design was developed. Crowns were inserted between 2008 and 2009. A follow-up of 19 patients with 28 crowns was conducted in 2020 to document mechanical and biologic parameters. Additionally, a modified version of the pink esthetic score (PES) was documented. Patient satisfaction was assessed using United States Public Health Service (USPHS) criteria. The success and survival rates were calculated using the Kaplan-Meier analysis. RESULTS: After more than 10 years of clinical service, the survival rate of the zirconia crowns was 92.9%. Biologic complications occurred in 12% of the examined crowns, whereas technical complications occurred in 54%. Mostly, chippings (50%) and insufficient marginal gaps (50%) were observed. Most crowns were positively evaluated for more than one technical complication. Periodontal conditions with probing depths of up to 3 mm were comparable with measured values before crown delivery (73% to 75%). Most of the crowns had modified PES values of 10 or higher. Patient satisfaction was high. CONCLUSIONS: The modified framework design led to a high survival rate of the crowns but a relatively low success rate. High patient satisfaction and inconspicuous periodontal conditions were demonstrated. Biologic complications occurred far less frequently than technical complications.

Replica denture technique: improvements through the use of CAD/CAM technology.

The majority of complete dentures are not initially made for the rehabilitation of an edentulous jaw; in most cases, they replace an existing complete denture. Since the ability to adapt to a new complete denture decreases with age, the replica denture procedure represents a smart opportunity. The aim is to copy the clinically successful parts of the old prosthesis and to change the destroyed parts. There are many advantages of this technique, including increased patient acceptance, especially among older people who may not be able to adapt easily to a new prosthesis. The advantages of digital technology are very apparent in the creation of a replica prosthesis. Various cases are presented in the present article to illustrate the procedure and the advantages of this technique using the example of computer-aided fabrication with the Baltic Denture System.

Influence of sandblasting and bonding on the shear bond strength between differently pigmented polyetheretherketone (PEEK) and veneering composite after artificial aging.

OBJECTIVE: Achieving a strong bond between Polyetheretherketone (PEEK) and veneering composites is challenging due to PEEKs low surface energy. This study examined the effects of sandblasting and bonding on the shear bond strength (SBS) between veneering composite and pigmented PEEK, considering artificial aging. METHODS: Of three pigmented PEEK compounds (DC4420R, DC4450R, DC4470R; Evonic Operations GmbH, Marl, Germany), 40 specimens each were milled and polished up to 2500 grit. Prior to veneering, specimens were divided into 4 subgroups: Subgroup 1: Polishing; 2: Polishing + bonding; 3: Sandblasting; 4: Sandblasting + bonding. Sandblasting was performed using Al2O3. Adhesive was an agent containing MMA (Signum Universal Bond, Kulzer GmbH, Hanau, Germany). After veneering (Composite, Kulzer GmbH) the subgroups were divided into 2 subgroups. One subgroup was immersed in 37 °C warm distilled water for 24 h. The second subgroup was artificially aged by thermocycling (TCL) with 5000 cycles in distilled water (5 °C / 55 °C; 30 s). Surface roughness, water contact angles and failure modes were recorded. SBS was measured using a universal testing machine. RESULTS: Results demonstrated that the combination of sandblasting and bonding significantly improved the SBS compared to polishing alone. PEEK color did not significantly influence the SBS. Aging by TCL had a negative effect on the SBS. SIGNIFICANCE: Sandblasting and the use of an adhesive containing MMA were found to be effective in achieving satisfactory SBS between veneering composite and pigmented PEEK surfaces. These pretreatment methods demonstrate their potential for establishing durable and reliable bonding in clinical applications.

Esthetic and functional rehabilitation of a patient with a bilateral cleft of lip, alveolar process, and palate with anterior all-ceramic cantilever resin-bonded fixed dental prostheses.

OBJECTIVES: Addressing a single-tooth gap in the anterior region, resulting from aplasia or trauma, poses both esthetic and functional challenges. This case report presents the restoration of a young adult with a cleft, exhibiting anterior hypoplasia and aplasia in the canine and incisor regions, using all-ceramic cantilever resin-bonded fixed dental prostheses. METHOD AND MATERIALS: After verification of esthetic and functional considerations through a diagnostic wax-up and an intraoral mock-up, three anterior all-ceramic cantilever resin-bonded fixed dental prostheses made of veneered zirconium dioxide were planned in the region of the maxillary right lateral incisor and maxillary left canine. The impression was made with an intraoral scanner. The framework fit was evaluated. Glaze firing and full adhesive cementation under rubber dam followed. RESULTS: The final restoration met the patients' expectations and restored facial esthetics and function. CONCLUSIONS: All-ceramic cantilever resin-bonded fixed dental prostheses offer a promising minimally invasive therapeutic option for cleft patients.

Measured accuracy of intraoral scanners is highly dependent on methodical factors.

PURPOSE: The accuracy of intraoral and model scanners has been widely investigated with heterogeneous results, but the impact of the applied diversity of measurement methods on the outcomes remains unknown. This study aimed to evaluate the influence of methodological factors on the measurement result when comparing full-arch scans. METHODS: The evaluation referred to a 5M model to analyze whether accuracy measurements are affected by (1) the reference geometry, (2) mesh density of the standard tessellation language (STL) datasets, (3) operator, (4) inspection software, and (5) alignment procedure. STL datasets of full-arch reference models were measured with 29 different combinations of these factors. For each combination, 10 repeated measurements of the intermolar width were performed. Trueness was statistically analyzed with one-way ANOVA and T-tests, repeatability with Levene tests, and reproducibility with interclass correlation coefficients. RESULTS: Measurement method variations affected the intermolar width by up to 186 µm. The alignment algorithm had a significant effect on the measurement outcome (p = 0.001). Likewise, reference geometry influenced trueness and repeatability significantly (p = 0.001), whereas mesh density affected the repeatability only in some cases. The operator had no impact on the measurement result. The inspection software affected the repeatability but not the trueness. CONCLUSION: The factors reference geometry and alignment algorithm highly affected the measurement outcome, while the operator, inspection software, and mesh density showed no impact on the trueness of the outcome. Cylindrical reference geometries showed fewer differences than bar-shaped ones and best-fit alignments fewer variations than alignments based on boundary parameters.

Accuracy and its impact on fit of injection molded, milled and additively manufactured occlusal splints.

Occlusal devices to reduce symptoms of bruxism and temperomandibular disorders can nowadays be manufactured in a digital workflow but studies comparing the accuracy of those occlusal devices are still limited. Therefore, the aim of this investigation was to investigate the accuracy of injection molding compared with four computer-aided design (CAD) and computer-aided manufacturing (CAM) techniques for the manufacturing of occlusal devices. In addition, the number of contact points and retention were evaluated to assess clinical relevance. A conventional workflow consisting of alginate impression, wax-up, and injection molding (IM) and digital workflows including intraoral scanning, digital design, and subtractive manufacturing (SM) or additive manufacturing by using stereolithography (SLA), digital light processing (DLP), and material jetting (Polyjet) were investigated. Sixteen splints were fabricated with each method. The intaglio surfaces of the splints were laser scanned and superimposed with the reference data sets to analyze the surface deviations. In addition, the number of contact points after repositioning the splints on the reference model was evaluated with occlusal foil. Finally, the retention was measured in a tensile test. One-way ANOVA with post hoc Tukey tests were used for statistical analyses (α = .05). IM and SM splints demonstrated the highest manufacturing accuracy without significant differences to each other (P > .985). Additive manufactured splints revealed greater deviations with equal results for SLA and Polyjet (P > .949) and significantly higher deviations for DLP compared to all other groups (P < .002). Comparable retention force was measured for IM, SM, and SLA (P > .923), whereas Polyjet splints showed the greatest variability. IM and SM splints presented the most contact points (P = .505). Additive manufactured splints demonstrated fewer contacts without significant difference to each other (P > .116). It can be concluded, that there is no difference in manufacturing accuracy, retention, and number of contacts between IM and SM splints. AM splints demonstrated higher, however, clinically acceptable deviations.

Bond strength of conventional, subtractive, and additive manufactured denture bases to soft and hard relining materials.

OBJECTIVE: To investigate the tensile and flexural strength of poured, subtractive, and additive manufactured denture base methacrylates bonded to soft and hard relining materials after hydrothermal cycling and microwave irradiation. METHODS: This study included a conventional (CB), subtractive (SB), and additive (AB) base material as well as a soft (SCR) and hard (HCR) chairside and one hard laboratory-side (HLR) relining material. Reference bodies of the base materials and bonded specimens to the relining materials were produced with a rectangular cross-section. The specimens were either pre-treated by water storage (50 h, 37 °C), hydrothermal cycling (5000 cycles, 5 °C and 55 °C, 30 s each), or microwave irradiation (6 cycles, 640 W, 3 min, wet). A tensile and four-point bending test were performed for a total of 504 specimens. Data were analysed using multivariate analysis of variance (MANOVA) with post-hoc Tukey tests (α = 0.05). RESULTS: In comparison with the other reference groups SB showed marginally higher tensile and flexural strength (p < 0.047). Bond strength to SCR was affected neither by the base material nor by the pre-treatment (p > 0.085). HCR demonstrated twice the bond strength to AB compared with SB and CB (p ≤ 0.001). HLR showed the highest bond strength to CB (p ≤ 0.001). There was no difference between the specimens after hydrothermally cycling and microwave irradiation (p > 0.318). SIGNIFICANCE: The bond strength of hard relining materials to subtractive and additive manufactured denture bases differ compared with conventional pouring.

Do hydrothermal aging and microwave sterilization affect the trueness of milled, additive manufactured and injection molded denture bases?

Concepts for digital denture manufacturing are market-available but studies comparing the trueness of such dentures, either milled (MIL) or additive manufactured, compared to injection molded (IM) ones are still limited. Regarding the impact of artificial aging and microwave sterilization on this parameter, no data are available. Therefore, the purpose of this investigation was to assess the trueness of IM, MIL, and stereolithography (SLA) printed denture bases after manufacturing, hydrothermal cycling, and microwave sterilization. Sixteen edentulous maxillary plaster models were poured using a silicone mold and digitized by means of a desktop scanner. For group IM, 16 denture bases were injection molded using these models. For group MIL and SLA, the denture bases were virtually designed and manufactured referring to the digitized data. A total of 48 samples were scanned 1) after manufacturing, 2) after hydrothermal cycling (5-55 °C, N = 5,000), and after 3) three as well as 4) six cycles of microwave sterilization for 6 min each at 640 W. The 3D surface deviation of the total intaglio surface, the palate, the alveolar ridge, and the border seal region was evaluated on the basis of the root mean square estimation (RMSE) and positive and negative mean deviations with an inspection software. For statistical analysis, ANOVA and post hoc Tukey tests were performed (α = 0.05). MIL showed the lowest deviations of the total RMSE (P ≤ .006) compared with the scans of the plaster models. In comparison, IM showed increased, mainly positive, deviations (P = .006) at the border seal. SLA presented the highest total RMSE (P = .001) with increased negative deviations, likewise at the border seal. In contrast to SLA (P = .001), no differences between IM and MIL (P = .816) were measured after hydrothermal cycling. Following microwave sterilization, the trueness of SLA was higher compared to IM and MIL (P = .001), with no differences between MIL and IM (P = .153). Distortion of IM and MIL was measured after the 3rd cycle with no further changes observed thereafter (P ≥ .385). It can be concluded, that subtractive manufacturing of denture bases results in the highest trueness, followed by IM and SLA. In contrast to IM and SLA, hydrothermal cycling did not affect MIL. Solely SLA printed denture bases remained dimensionally stable after microwave sterilization.

Digital Impression-Taking Facilitates Prosthetic Rehabilitation of Microstomia Patients: A Case History Report.

In most cases, prosthetic rehabilitation of patients suffering from microstomia is inconvenient for the patient and challenging for both the dentist and dental technician. In such cases, conventional impression-taking requires an individualized tray design and modified impression techniques, amplifying the risk for impression and cast deformation and thereby compromising the final outcome. An intraoral scanner (IOS) might overcome these limitations due to its reduced size compared to an impression tray. In the present case history report, a microstomia patient was successfully restored with a telescopic prosthesis by digitizing both retaining teeth and the palate with an IOS.

Bacterial leakage and bending moments of screw-retained, composite-veneered PEEK implant crowns.

Due to its elastic modulus close to bone, the high-performance material PEEK (polyetheretherketone) represents an interesting material for implant-supported dental prostheses. Besides a damping effect of masticatory forces, it might have a sealing effect against bacterial leakage of the implant-abutment interface (IAI). So far, PEEK has only been used for provisional implant crowns. Therefore, the aim of the study was the evaluation of the bacterial tightness of screw-retained PEEK crowns on titanium implants with conical IAI during masticatory simulation and subsequent bending moment testing. Ten screw-retained implant crowns in the shape of an upper central incisor consisting of a PEEK crown framework veneered with composite were connected to NobelActive RP titanium implants (4.3 × 11.5 mm, Nobel Biocare AB, Göteborg, Sweden) with a tightening torque of 15 Ncm. Prior to tightening, the interior of the implant was inoculated with a bacterial suspension of Enterococcus faecium. The specimens were overmolded with indicating agar (Kanamycin-Aesculin-Azid-Agar (KAAA), Oxoid Limited, Basingstoke United Kingdom), that turns black in contact with E. faecium. The specimens were subjected to a cyclic masticatory simulation whereby a force of 50 N cm was applied at an angle of 30° to the implant axis for 1.2 million cycles. Afterwards, the specimens were subjected to a static loading test according to ISO 14801:2007 to determine the bending moment. During masticatory simulation neither a loosening of the implant screws nor any damage to the veneer or the PEEK framework occurred. Furthermore, no bacterial leakage could be observed in any of the specimens. The average maximum bending moment was measured at 352.13 ±â€¯48.96 N cm. Regarding masticatory forces, PEEK implant crowns seem to be applicable as definitive implant-supported restorations. Furthermore, the bacterial tightness of the IAI of screw-retained one-piece PEEK implant crowns is advantageous compared to superstructures of conventional materials. Further studies are necessary to substantiate the clinical significance of these findings.