Influence of Cementation Mode and Ferrule Design on the Fatigue Resistance of Monolithic Zirconia Endocrowns.

Background: Classic endocrowns made of dental ceramics are considered a promising alternative to traditional post-endodontic restorations. The use of circular ferrules in endocrowns is a topic of controversial discussion. Therefore, the present study aims to evaluate the effect of ferrule design and cementation mode on the fatigue resistance of zirconia endocrowns. Methods: Eighty human molars were divided into four groups (n = 20): NFC (no-ferrule, conventional cementation), NFA (no-ferrule, adhesive luting), FC (ferrule, conventional cementation) and FA (ferrule, adhesive luting). Both the classic and the modified endocrown preparation with a two-millimeter ferrule design were carried out. Endocrowns were fabricated from zirconia using the CEREC system. After thermocycling, specimens were loaded according to the step-stress test up to 1500 N. Results: Failure rate was low; 88.8% of total specimens passed the step-stress test. Fractures were distributed between all groups; no significant differences in fatigue resistance were detected for preparation design and cementation mode. Conclusions: Endocrowns appear to be a promising concept for endodontically treated molars. Ferrule and also cementation mode have only a minor influence on fatigue resistance of zirconia endocrowns. However, at very high forces, the marginal area of the ferrule represents a weak point.

IMPACT OF LOADING PROTOCOL OF 2-IMPLANT BAR-RETAINED MANDIBULAR OVERDENTURES ON ORAL HEALTH-RELATED QUALITY OF LIFE: A RANDOMIZED CONTROLLED TRIAL.

OBJECTIVES: Aim was to assess whether immediate loading (IL) is more effective than delayed loading (DL) for 2-implant bar-retained mandibular overdentures in terms of oral health-related quality of life (OHRQoL) improvement over a period of 24-month. METHODS: In this randomized controlled trial, 32 edentulous patients (mean age: 65.7 ± 10.6 years, 50.0% female) were included. Potential participants had to be unsatisfied with the retention of their current mandibular complete denture and demanded implant treatment for inclusion in the study. OHRQoL was assessed with the 49-item Oral Health Impact Profile (OHIP) at baseline before treatment and 1, 3, 6, 12, and 24 months after implant loading and insertion of implant-retained bars for overdenture support. A mixed-effects model with patients as random effect and an unstructured covariance matrix was developed to address repeated outcome measurement. RESULTS: Patients' OHRQoL impairment at baseline was substantial indicated by mean OHIP summary score of 45.1 points. OHIP summary scores decreased substantially from baseline to 1-month follow-up to a mean of 33.5 points (P = .020). OHRQoL further improved during study period indicated by OHIP summary score of 25.7 points at 24-month follow-up. Raw treatment effects (IL vs. DL) ranged from -1.2 OHIP points for 12-month follow-up to 5.8 OHIP points for 24-month follow-up. Assuming constant treatment and time effects, treatment effect was small and not statistically significant (-0.7 OHIP points; P= .918). CONCLUSION: A 2-implant bar-retained mandibular overdentures substantially improves OHRQoL over a period of at least 24 months. There seems to be no significant effect of implant loading protocol.

Influence of Implant Macro-Design, -Length, and -Diameter on Primary Implant Stability Depending on Different Bone Qualities Using Standard Drilling Protocols-An In Vitro Analysis.

(1) Background: Primary implant stability is vital for successful implant therapy. This study explores the influence of implant shape, length, and diameter on primary stability in different bone qualities. (2) Methods: Three implant systems (two parallel-walled and one tapered) with various lengths and diameters were inserted into polyurethane foam blocks of different densities (35, 25, 15, and 10 PCF) using standard drilling protocols. Primary stability was assessed through insertion torque (IT) and resonance frequency analysis (RFA). Optimal ranges were defined for IT (25 to 50 Ncm) and RFA (ISQ 60 to 80). A comparison of implant groups was conducted to determine adherence to the optimal ranges. (3) Results: Implant macro-design, -length, and -diameter and bone block density significantly influenced IT and RFA. Optimal IT was observed in 8/40 and 9/40 groups for the parallel-walled implants, while the tapered implant achieved optimal IT in 13/40 groups (within a 25-50 Ncm range). Implant diameter strongly impacted primary stability, with sufficient stability achieved in only one-third of cases despite the tapered implant's superiority. (4) Conclusions: The findings highlight the need to adapt the drilling protocol based on diverse bone qualities in clinical practice. Further investigations should explore the impact of these adapted protocols on implant outcomes.

Prevention of internal bacterial colonization of dental implants: A comparative longitudinal observational study.

OBJECTIVES: Previous studies have indicated a progressive internal bacterial colonization of implants and possible implications for peri-implant bone loss. The aim of this study was to evaluate a decontamination protocol, two disinfectants, and a sealant for their ability to prevent such a colonization. MATERIALS AND METHODS: Bacterial samples were harvested from the peri-implant sulcus (external) and following abutment removal from the implant cavity (internal) during routine supportive peri-implant care in 30 edentulous patients 2 years after they had obtained two implants. In a split-mouth design, implants were randomly assigned to receive either internal decontamination alone (10% H2 O2 , brush) or additional placement of either sealant (GS), disinfectant agent (CHX-varnish) or disinfectant gel (1% CHX-gel), in the internal cavity before remounting of abutment/suprastructure. Twelve months later, internal and external sampling was repeated. Total bacterial counts (TBCs) were determined using real-time PCR in a total of 240 samples (eight per patient). RESULTS: Total bacterial counts in the internal cavity significantly reduced overall treatment modalities 1 year after the treatments (4.0 [2.3-6.9]-fold reduction; p = .000). No significant differences between the four treatment types were found (p = .348). Comparison of internal and external sampling points revealed significant correlation (R2 = .366; p = .000) with systematically higher TBC counts in external samples. CONCLUSIONS: Within the limitations of the present study, it can be concluded that the use of disinfectant agents or a sealant did not show an additional benefit in the prevention of internal bacterial colonization of implants compared to a decontamination protocol alone.

Implant-Retained Prosthetic Rehabilitation of a Patient with Severe Oral Lichen Sclerosus.

Background: Lichen sclerosus is a rare condition that occurs in the genital area or on the extraoral skin but can also manifest orally (oral lichen sclerosus (OLS)). The condition is associated with atrophy, scarring, and functional limitations of the tissues. In the present case, an extremely pronounced variant is described, and the oral rehabilitation of the patient is presented. Case Report. The edentulous patient showed a progressive course with severely restricted mouth opening and persistent pain. Conventional dental treatment was therefore impossible. To address this issue, two implants were placed in each jaw at the position of the lateral incisors. After osseointegration and exposure of the implants, provisional bridges made of polymethyl-methacrylate were fitted to test the new jaw relation. After a successful provisional phase, an FDP in the sense of an extreme short dental arch (ESDA) has been inserted. Conclusion: The experimental treatment of the patient with only a total of four implants and the ESDA concept represented a satisfactory therapy for the patient. The patient regained her chewing ability, which significantly increased her oral health-related quality of life (OHRQoL). Still, it should be noted that this is a high-risk and experimental prosthetic treatment.

Effects of Different Titanium Surface Treatments on Adhesion, Proliferation and Differentiation of Bone Cells: An In Vitro Study.

The objective of this study was to evaluate the impacts of different sandblasting procedures in acid etching of Ti6Al4V surfaces on osteoblast cell behavior, regarding various physicochemical and topographical parameters. Furthermore, differences in osteoblast cell behavior between cpTi and Ti6Al4V SA surfaces were evaluated. Sandblasting and subsequent acid etching of cpTi and Ti6Al4V discs was performed with Al2O3 grains of different sizes and with varying blasting pressures. The micro- and nano-roughness of the experimental SA surfaces were analyzed via confocal, atomic force and scanning electron microscopy. Surface free energy and friction coefficients were determined. hFOB 1.19 cells were seeded to evaluate adhesion, proliferation and osteoblastic differentiation for up to 12 d via crystal violet assays, MTT assays, ALP activity assays and Alizarin Red staining assays. Differences in blasting procedures had significant impacts on surface macro- and micro-topography. The crystal violet assay revealed a significant inverse relationship between blasting grain size and hFOB cell growth after 7 days. This trend was also visible in the Alizarin Red assays staining after 12 d: there was significantly higher biomineralization visible in the group that was sandblasted with smaller grains (F180) when compared to standard-grain-size groups (F70). SA samples treated with reduced blasting pressure exhibited lower hFOB adhesion and growth capabilities at initial (2 h) and later time points for up to 7 days, when compared to the standard SA surface, even though micro-roughness and other relevant surface parameters were similar. Overall, etched-only surfaces consistently exhibited equivalent or higher adhesion, proliferation and differentiation capabilities when compared to all other sandblasted and etched surfaces. No differences were found between cpTi and Ti6Al4V SA surfaces. Subtle modifications in the blasting protocol for Ti6Al4V SA surfaces significantly affect the proliferative and differentiation behavior of human osteoblasts. Surface roughness parameters are not sufficient to predict osteoblast behavior on etched Ti6Al4V surfaces.

Soft tissue response to different abutment materials: A controlled and randomized human study using an experimental model.

OBJECTIVES: Aim of this study was to compare the soft tissue response to implant abutments made of titanium, zirconia, zirconia veneered with feldspar ceramics and PEEK by various clinical, histological, microbiological, and molecular biological markers in an experimental model. MATERIALS AND METHODS: A total of 40 experimental one-piece healing abutments of four different materials were mounted on bone level implants in 20 volunteering patients (split-mouth design). After a three-month period of open healing, clinical parameters at the abutments were assessed and adjacent mucosa was sampled for inflammatory cytokine mRNA concentrations and histological analysis by a novel method. In addition, PISF samples were obtained for the analysis of periodonto-pathogenic bacteria counts and active MMP-8 levels. Marginal bone level change was measured by intra oral radiographs. RESULTS: Abutments of the different materials did not exhibit significant differences regarding clinical parameters, pathogenic bacteria counts or pro-inflammatory cytokine concentrations. Likewise, no significant differences were detected regarding soft tissue morphology or bone level change. Compared to titanium abutments, significantly less mononuclear inflammatory cells were detected in the mucosa at abutments made of zirconia veneered with feldspar ceramics. CONCLUSIONS: All examined abutment materials exhibited a similar soft tissue response compared to titanium and histological data did not reveal early signs of elevated inflammation caused by PEEK- and feldspar-veneered zirconia abutments. Due to the short observation period and the small sample size, a final conclusion on the long-term suitability of those abutment materials cannot be drawn. However, based on the presented data, we consider further studies on that subject as appropriate.

Comparison of Digital Self-Assessment Systems and Faculty Feedback for Tooth Preparation in a Preclinical Simulation.

BACKGROUND: Regarding the new dental licensing regulations in Germany (AOZ), this study evaluated the effectiveness of two different digital tooth preparation validation systems in comparison to traditional faculty feedback. METHODS: Participants were randomly divided into groups: Faculty Feedback (FF: n = 33), PrepCheck® (PC: n = 32) and Dental Teacher™ (n = 32). Students had the task to prepare tooth 16 for a retentive full-cast crown. Preparations could be repeated as often as desired. Feedback was provided either by faculty staff or by digital validation systems only. Exams were conducted and graded by two independent and experienced examiners. A survey was performed to evaluate the assessment concepts. RESULTS: No statistical difference in examination performance between groups could be observed. Nevertheless, the survey showed participants preferred consulting the faculty staff rather than the digital validation systems. Students preferred practising with DT rather than with PC. CONCLUSIONS: Although both classical and digital methods showed comparable results regarding the preparation examination performance, direct feedback by the faculty staff is still appreciated by the students. A combination of both methods is mandatory since demonstration and advice by the teacher is needed. However, digital tooth preparation validation systems are predestined for free practice sessions, providing self-assessment.