Impact of the material and sintering protocol, layer thickness, and thermomechanical aging on the two-body wear and fracture load of 4Y-TZP crowns.

OBJECTIVES The aim of this study is to investigate the influence of the material and corresponding sintering protocol, layer thickness, and aging on the two-body wear (2BW) and fracture load (FL) of 4Y-TZP crowns. MATERIALS AND METHODS Multi-layer 4Y-TZP crowns in three thicknesses (0.5 mm/1.0 mm/1.5 mm) were sintered by high-speed (Zolid RS) or conventional (Zolid Gen-X) sintering. 2BW of ceramic and enamel antagonist after aging (1,200,000 mechanical-, 6000 thermal-cycles) was determined by 3D-scanning before and after aging and subsequent matching to determine volume and height loss (6 subgroups, n = 16/subgroup). FL was examined initially and after aging (12 subgroups, n = 16/subgroup). Fractographic analyses were performed using light-microscope imaging. Global univariate analysis of variance, one-way ANOVA, linear regression, Spearman's correlation, Kolgomorov-Smirnov, Mann-Whitney U, and t test were computed (alpha = 0.05). Weibull moduli were determined. Fracture types were analyzed using Ciba Geigy table. RESULTS Material/sintering protocol did not influence 2BW (crowns: p = 0.908, antagonists: p = 0.059). High-speed sintered Zolid RS presented similar (p = 0.325-0.633) or reduced (p < 0.001-0.047) FL as Zolid Gen-X. Both 4Y-TZPs showed an increased FL with an increasing thickness (0.5(797.3-1429 N) < 1.0(2087-2634 N) < 1.5(2683-3715 N)mm; p < 0.001). For most groups, aging negatively impacted FL (p < 0.001-0.002). Five 0.5 mm specimens fractured, four showed cracks during and after aging. CONCLUSIONS High-speed sintered crowns with a minimum thickness of 1.0 mm showed sufficient mechanical properties to withstand masticatory forces, even after a simulated aging period of 5 years. CLINICAL RELEVANCE Despite the manufacturer indicating a thickness of 0.5 mm to be suitable for single crowns, a minimum thickness of 1.0 mm should be used to ensure long-term satisfactory results

Group 4 ITI Consensus Report: Patient benefits following implant treatment in partially and fully edentulous patients

Objectives: The aim of Working Group 4 was to address patient benefits associated with implant dentistry. Focused questions on (a) dental patient-reported outcomes (dPROs), (b) improvement in orofacial function, and (c) preservation of orofacial tissues in partially and fully edentulous patients following provision of implant-retained/supported dental prostheses were addressed. Materials and methods: Three systematic reviews formed the basis for discussion. Participants developed statements and recommendations determined by group consensus based on the findings of the systematic reviews. These were then presented and accepted following further discussion and modifications as required by the plenary of the 7th ITI Consensus Conference, taking place in 2023 in Lisbon, Portugal. Results: Edentulous patients wearing complete dentures (CD) experience substantial improvements in overall dPROs and orofacial function following treatment with either complete implant-supported fixed dental prostheses (CIFDP) or implant overdentures (IODs). With respect to dPROs, mandibular IODs retained by two implants are superior to IODs retained by one implant. However, increasing the number of implants beyond two, does not further improve dPROs. In fully edentulous patients, rehabilitation with CIFDP or IOD is recommended to benefit the preservation of alveolar bone and masseter muscle thickness. Conclusions: Completely edentulous patients benefit substantially when at least the mandible is restored using an CIFDP or an IOD compared to CD. In fully edentulous patients, implant prostheses are the best option for tooth replacement. The availability of this treatment modality should be actively promoted in all edentulous communities, including those with limited access and means

Effect of Cleaning Protocol on Bond Strength between Resin Composite Cement and Three Different CAD/CAM Materials.

The present investigation tested the effect of the cleaning method on the tensile bond strength (TBS) between one resin composite cement (RCC) and three different computer aided design/computer aided manufacturing (CAD/CAM) materials, namely zirconia, lithium disilicate ceramic and resin composite. Ninety specimens were prepared from each CAD/CAM material (N = 270). The specimens were pre-treated respectively, divided into five subgroups and subjected to five different cleaning protocols, namely i. 37% phosphoric acid, ii. ethanol, iii. phosphoric acid + ethanol, iv. cleaning paste, v. distilled water. After cleaning, the specimens were either conditioned using a universal primer or a universal adhesive and bonded using a dual-curing RCC. After thermo-cycling (20,000x at 5 °C/55 °C), TBS and fracture patterns were evaluated. The data was analyzed using 1- and 2-way Analysis of Variance (ANOVA) with post-hoc Scheffé and partial eta-squared (ƞP²), Kruskal-Wallis, Mann-Whitney U and Chi2 tests (p < 0.05). The CAD/CAM material showed an impact on the BS while the cleaning protocol did not affect the results. Zirconia obtained the highest BS, followed by lithium-disilicate-ceramic. Resin composite resulted in the overall lowest BS. For most fracture patterns, the cohesive type occurred. All tested cleaning protocols resulted in same BS values within one CAD/CAM material indicating that the impact of the cleaning method for the restorative material seems to play a subordinate role in obtaining durable bond strength to resin composite cement. Further, it indicates that the recommended bonding protocols are well adjusted to the respective materials and might be able to compensate the impact of not accurately performed cleaning protocols

Variables Affecting the Accuracy of Static Computer-Assisted Implant Surgery: Bridging the Gap Between Clinical Success and Broad Application

ABSTRACT Over the past decade, the use of digital technology in implant treatment planning and static computer-assisted implant surgery (sCAIS) has revolutionized the planning and execution of guided implant surgeries. However, the predictability of achieving a high degree of accuracy when using a digital workflow and sCAIS has been a subject of debate. For sCAIS procedures to transition from clinical success in individual cases to a broadly applicable procedure, a better understanding and control of variables that affect their accuracy is essential. Recently, a research team in the Department of Oral Surgery and Stomatology at the University of Bern launched a series of in-vitro investigations to further analyze the impact and magnitude of potential variables involved in the digital treatment planning of sCAIS procedures that can have a significant effect on the accuracy of sCAIS. This article presents the rationale and summary of their findings

Fabrication of an implant-retained overdenture with ceramic crowns cemented on a polyetherketoneketone framework: A clinical report

This clinical report describes the treatment of a complex intraoral situation by fabricating a maxillary implant-retained overdenture with a high-performance polymer (polyetherketoneketone) framework and lithium disilicate crowns and mandibular tooth- and implant-supported ceramic restorations. No complications were noted in 2 years, and the patient was satisfied with function and esthetics

Mesiodistal measurements for dental implant planning: a prospective clinical study of linear measurements on cone-beam computed tomography images in comparison with caliper-based measurements on plaster casts

Althouh cone beam computed tomography (CBCT) is popular for dental implant planning, the horizontal mesiodistal space of the edentulous ridge is still conventionally measured with a handheld sliding caliper in the oral cavity or on a plaster cast. For clinical application in implant planning, our aim was to evaluate the accuracy of CBCT horizontal mesiodistal linear measurements in comparison with conventionally obtained direct measurements on plaster casts. Postoperative CBCT acquisitions and plaster casts of 27 patients with adjacent posterior mandibular implants were analyzed in a prospective clinical study. On CBCT images, two observers assessed the inter-implant distances on axial and sagittal views. On plaster casts, the inter-implant distances were measured with a digital caliper. CBCT measurements on axial and sagittal views were, on average, 0.2 mm larger than measurements on plaster casts. Correlation was perfect between measurements of the same inter-implant distance performed by the observers on CBCT images and on plaster casts. When compared with conventionally obtained direct measurements on plaster casts, CBCT views slightly overestimated (mean 0.2 mm) the horizontal mesiodistal measurements between two implants as reference points. CBCT imaging is sufficiently accurate to evaluate mesiodistal distances on axial and sagittal views for dental implant planning in clinical practice.</p

Mandibular two-implant overdentures with CAD-CAM milled bars with distal extensions or retentive anchors: a randomized controlled trial.

OBJECTIVE This randomized controlled trial (RCT) aimed to demonstrate the noninferiority of mandibular 2-implant overdentures (IODs) on a CAD-CAM milled bar with long distal extensions (MBDE) against IODs on retentive anchors (RA). METHODS Forty edentulous participants rehabilitated with a maxillary conventional denture and a mandibular 2-IOD participated in this trial. They were randomized into two groups [Control group (CG): RA + gold matrices; Experimental group (EG): MBDE + gold clip]. The outcomes included implant survival rate (ISR), chewing efficiency [quantitative (VoH) and subjective (SA) assessments], peri-implant marginal bone-levels (PI-MBL), maximum bite-force (MBF), and patient-reported outcomes [oral health impact profile (OHIP-EDENT) and denture satisfaction index (DSI)]. Outcomes were recorded at baseline (BL), two weeks (T0 ), 6-months (T1 ) and at 1-year (T2 ) after the intervention. Intra- and inter-group analyses were performed using regression models with ⍺=0.05. RESULTS 38 participants completed the T2 visit (CG: n=19, age=74.7±7.8y; EG: n=19, age=70.3±10.7y). At T2 , there was no implant loss in either of the groups (ISR=100%). There were no significant differences between the groups for the PI-MBL changes (p=0.754). Improvements occurred faster in the EG than in the CG, but over the observation time, there were no differences between the trial groups for VoH, MBF, OHIP-EDENT, and the DSI, except for SA being significantly better in the EG group (p=0.022). CONCLUSIONS The results of this RCT confirm that mandibular 2-IODs with a CAD-CAM milled bar with long distal extensions are not an inferior treatment to the conventional IODs on retentive anchors in the short term (1-year)

Effectiveness of Contour Augmentation with Guided Bone Regeneration: 10-Year Results.

In aesthetic sites, the integrity of the facial bone wall dimension in the anterior maxilla is jeopardized by physiologic and structural changes postextraction. An effective regenerative protocol is key to reestablish and maintain the hard and soft tissue dimensions over time. The present prospective case series study examined the effectiveness of early implant placement with simultaneous contour augmentation through guided bone regeneration with a 2-layer composite graft in postextraction single-tooth sites over an observation period of 10 y among 20 patients. The median peri-implant bone loss was 0.35 mm between the 1- and 10-y examination. A success rate of 95% was obtained, with pleasing aesthetic outcomes and a high median Pink Esthetic Score (8). Implant crowns (ICs) revealed significant median facial recession between IC and IC (0.17 mm). The facial bone wall dimensions were assessed by preoperative cone beam computed tomography and 2 subsequent scans taken at 6 and 10 y. The median facial bone wall thickness increased significantly from 0 mm at surgery to 1.67 mm at the 10-y examination. The facial vertical bone wall peak (DIC) was located at a median distance of 0.16 mm coronal to the implant shoulder. The facial vertical bone loss of DIC amounted to 0.02 mm between 6 and 10 y. Equivalence testing was performed for the null hypothesis of a difference of >0.2 mm per year between 2 respective time points, showing stable bone conditions. Modulating factors influencing the regenerative outcomes at 10 y were the preoperative proximal crest width and soft tissue thickness. In conclusion, the present study confirmed the long-term effectiveness of early implant placement with simultaneous contour augmentation through guided bone regeneration with a 2-layer composite graft in postextraction single-tooth sites offering stable bone conditions with low risks of mucosal recessions over an observation period of 10 y ( ClinicalTrials.gov NCT03252106)

Biological and technical complications in root cap-retained overdentures after 3-15 years in situ: a retrospective clinical study.

OBJECTIVES This retrospective clinical study investigates the frequency of biological and technical complications in patients rehabilitated by natural root-retained overdentures (RODs) with cast post-and-cores (root caps) wearing precision attachments and analyses factors influencing complication rates (e.g. oral hygiene routines). MATERIALS AND METHODS Patients formerly treated with RODs were invited for a cost-free clinical visit to evaluate their intraoral status. Furthermore, they were interviewed and patient records were screened for complications occurring since denture delivery. Statistical models include descriptive analyses, Fisher's exact test, odds ratios, and a multivariate regression model. RESULTS A total of 114 patients wearing 128 RODs with a total of 280 abutment teeth were evaluated (mean service time: 7.9 years). Technical complications occurred in 68.8% of the RODs, with matrix loosening being the most frequent complication (50.1%). Biological complications occurred in 53.9% of all RODs, with the presence of denture stomatitis being the most common biological complication (38.3%). The presence of denture stomatitis was significantly higher in the maxilla relative to the mandible (p = 0.0029), in subjects cleaning their dentures less than twice a day (p  40% (p < 0.001). CONCLUSIONS Root cap-retained overdentures with precision attachments are a viable treatment option in partially dentate subjects, even over long-term periods. However, high complication rates should be expected. CLINICAL RELEVANCE Establishing good oral hygiene is a decisive factor in preventing complications in RODs. Furthermore, CHX-containing products may not be recommended for routine domestic use

Influence of surgical guide support and implant site location on accuracy of static Computer-Assisted Implant Surgery.

OBJECTIVE To investigate the effect of surgical guide support and implant site location on the accuracy of static Computer-Assisted Implant Surgery (sCAIS) in partially edentulous patients. MATERIALS AND METHODS 375 replica implants were inserted in 85 study models. Surgical implant placement was done using static 3D printed surgical guides, which were designed to be supported either by all the teeth present in the model (full arch), or by 4-teeth), 3-teeth or 2-teeth. Each study model included three single-tooth gap (STG) situations; one extraction socket site and two implants placed in a distal extension situation. Preplanned and postoperative implant positions were compared using the treatment-evaluation tool in digital software. 3-dimensional and angular deviations were measured. Statistical analysis was done using ANOVA, and pairwise t tests and Bonferroni-Holm's adjustment were applied as a post hoc test. RESULTS Accuracy of surgical guides used in sCAIS was significantly affected by the number and type of teeth used for its support. Guides supported by 4 teeth were not significantly different from accuracy of full-arch-supported guides (p > .05). Guide support by posterior teeth was associated with an increased level of accuracy, when compared to anterior teeth guide support. Implants placed in extraction sockets were associated with significantly higher 3D and angular deviation values (p < .05), and surgical guides with a distal extension situation resulted in significantly higher deviation values (p < .05). CONCLUSION The number and location of teeth supporting the surgical guide can significantly influence the accuracy of sCAIS, with 4 teeth providing equal accuracy to full-arch guides in (STG) situations