Search

Purpose: This retrospective study investigated the survival rate of 174 clasp-retained removable partial dentures (CR-RPDs) made at the Department of Prosthodontics of the Regensburg University Medical Center over a 25-year period (1984 to 2009). Materials and Methods: The study analyzed the frequency of and time to the fracture of clasps, connectors, or denture bases; the occurrence of caries or periodontal lesions; the loss of abutment teeth; and the necessity of maintenance procedures such as relining or treatment of pressure areas. Results: The median follow-up time of 3 years was calculated using the inverse Kaplan-Meier method. The 5-year survival rate (time to renewal) of all CR-RPDs was 96.4%; the 10-year survival rate was 89.8%. Fractures most frequently occurred in clasps (n = 28, 16.1%) followed by major connectors (n = 9, 5.1%) and minor connectors (n = 6, 3.4%). The 5-year event-free rate for clasp fracture was 80.4%; the 10-year event-free rate was 76.9%. Caries lesions on abutment teeth were seen in 31.6% of patients, and 35.6% showed inflammation of the periodontal tissue surrounding the abutment teeth. The 5-year event-free rate for caries was 58.4%; the 10-year rate was 39.6%. A frequent complication was loss of abutment teeth (n = 15), but this complication was not age-dependent. After insertion of their prostheses, one-third of patients (n = 53, 30.5%) showed pressure areas of the mucosa. Significantly more (P < .001) pressure areas were caused by prostheses of the mandible (39.6%) than by those of the maxilla (12.5%). Conclusions: CR-RPDs showed a survival rate of approximately 90% after 10 years of oral service. The predominant complications during oral service were caries lesions, loss of abutment teeth, and fracture of clasps. [ABSTRACT FROM AUTHOR]

PURPOSE: The aim of this study was to investigate the survival rates and technical failures of removable prostheses (RPs) supported by telescopic double crown (TDC)-retained abutment teeth luted with zinc-phosphate or glass-ionomer cement. MATERIALS AND METHODS: Clinical records of 577 patients (288 women, 289 men) who received 577 TDC-retained RPs supported by 1,807 abutments at the Department of Prosthodontics of the University Hospital Regensburg, Regensburg, Germany, between 1984 and 2007 were analyzed. The 577 prostheses included 200 attached to telescopic crowns with friction fit (FFs), 62 to conical crowns (CCs), and 315 to parallel-sided telescopic crowns with clearance fit (CFs). Survival probabilities were evaluated for the RPs, loss of cementation of the inner copings, secondary caries, and abutment teeth that required endodontic treatment using the Kaplan-Meier method. A Cox regression analysis determined the impact of covariates such as sex, denture location (maxilla/mandible), Eichner classification, number of abutment teeth, and the type of double crown system used. RESULTS: The 10-year survival probability was 98.8% +/- 0.09% for FFs, 92.9% +/- 0.41% for CCs, and 86.6% +/- 0.05% for CFs. During the observation period, loss of cementation was frequently observed (FFs: 32%, CCs: 53.2%, CFs: 21.3%). After 15 years, more than 75% of patients had experienced at least one 'loss of cementation' event. In this respect, zinc-oxide phosphate and glass-ionomer cements did not show any significant difference. CONCLUSION: The long-term successful outcome of the RP experience was not compromised, although numerous clinical visits were required for maintenance. The predominant maintenance procedure was the need for recementation of the inner copings. [ABSTRACT FROM AUTHOR]

The aim of this review was to summarize the contemporary scientific evidence available regarding restorative dental treatment in patients with Amelogenesis imperfecta (AI). An electronic literature search was conducted using the search term "Amelogenesis imperfecta" in the PubMed/MEDLINE database as well as Google Scholar. Prospective and retrospective clinical studies that investigated the outcome of direct and/or indirect dental restorative treatment in patients with AI, that were published in English, and that had an observation time of at least 1 year were included in this review. The articles identified were screened and analyzed by two reviewers according to inclusion and exclusion criteria in three review rounds. Six prospective or retrospective clinical studies analyzing longevity and complications associated with dental restorative treatment in patients with AI met the inclusion criteria. Extracted data suggested that in patients with AI, indirect restorations feature superior predictability and longevity to direct restorations. As endodontic complications were infrequently observed and periodontal parameters regularly improved with the insertion of indirect restorations, dental treatment in patients with AI should focus on indirect restorations as soon as possible. While adhesive bonding techniques to enamel surfaces in patients with AI merely feature limited predictability and longevity and as the available data are scarce, further laboratory and clinical studies should be performed to investigate the performance of minimally invasive indirect restorations bonded to enamel in patients with AI. [ABSTRACT FROM AUTHOR]

Objectives: The aim of this project was to develop an instructional video that demonstrates a standardized clinical examination on patients with suspected temporomandibular disorders (TMD). After viewing the video, the learner should be knowledgeable about the examination steps and application of the examination techniques. Methods: The instructional video was created by two dentists who are experienced in assessing patients with suspected TMD. Additionally, both examiners were calibrated according to the Diagnostic Criteria for Temporomandibular Disorders (DC/TMD). The instructional video was divided into chapters. Various camera angles, key points, image enlargements, and replays were used to better depict essential aspects of the assessment. Background noise was reduced to a minimum. Results: The instructional video was modified and completed in two phases: the first by an experienced dentist and the second by a dentist specialized in TMD. The final video includes nine chapters and is 26.5 minutes in length (). Conclusion: Divided into chapters, this German instructional video shows an optimally timed, standardized clinical assessment of patients with suspected TMD.

Goal: The aim of this review is to summarize the in vitro and in vivo evidence on the performance of contemporary saliva substitutes in the treatment of xerostomia and hyposalivation caused by radiation therapy for head and neck malignancies.Methods: A literature search was conducted during July to September 2008 in PubMed, using the query terms "saliva substitute", "saliva substitute and xerostomia", "artificial saliva", and "artificial saliva and xerostomia"; for clinical studies, only studies in patients suffering from radiation-induced xerostomia have been included in the review.Results and Conclusion: Fifty-two studies met the inclusion criteria and were allotted either to the in vitro topics "viscosity", "lubrication", "wetting properties", "antimicrobial effects", and "enamel and dentin de- and remineralization", or to the in vivo topics "clinical acceptance" or "influence on plaque formation and oral mucosa and microflora". The findings suggest that there are significant differences in the performance of various saliva substitutes concerning the review parameters, yet indicate that further in vitro and in vivo studies on the properties of saliva substitutes are necessary. [ABSTRACT FROM AUTHOR]

Statement of problem. Plaque on dentures may foster the occurrence of denture stomatitis and periodontal diseases in gingival tissues adjacent to partial dentures. Thus, it is beneficial for dental materials to have a low susceptibility to plaque adhesion.Purpose. The purpose of this study was to evaluate the susceptibility of commonly used artificial teeth to adhesion of the oral bacterium Streptococcus mutans.Material and methods. Fifteen specimens each of 12 different artificial teeth were prepared by cutting standardized slabs from the buccal tooth surfaces. After normalizing size (round specimens, diameter of 5 mm, 2 mm thick), polishing (grinding paper, grain 1000 and 4000; universal polishing paste), and assessing surface roughness with a profilometric contact surface measurement device, specimens were incubated with Streptococcus mutans NCTC 10449 suspension for 2.5 hours at 37°C. A veneering composite resin (Sinfony) was used as a control. Adherent bacteria were quantified using a fluorometric assay (Resazurin reduction); relative fluorescence intensity correlates linearly with the number of adherent bacteria. Medians and 25%/75% percentiles were calculated, and statistical analysis was performed using the Kruskal-Wallis test and the Bonferroni-adjusted Mann-Whitney U test.Results. The highest values, indicating high adhesion of streptococci, were observed for filler-supplemented teeth with median relative fluorescence values ranging from 6356 to 18,770. Similar values were recorded for a double cross-linked resin tooth (6444). Significantly lowest values, ranging from 1173 to 3974, were found for unfilled PMMA acrylic resin teeth and acrylic resin teeth with an interpenetrating network (1436).Conclusions. Within the limitations of this study, it can be concluded that the adhesion of Streptococcus mutans to unfilled PMMA teeth and teeth with an interpenetrating network is lower than adhesion to artificial teeth supplemented with fillers or double cross-linked acrylic resin teeth. [ABSTRACT FROM AUTHOR]

Objectives: To investigate the survival rates and fracture resistance of dentures made from different teeth (milled, 3D-printed, fabricated), bases (milled, 3D-printed, pressed) and bonding combinations., Materials and Methods: Specimens (11 groups, n = 8 per group) were fabricated from combinations with a denture tooth (anterior tooth 21) and a denture base material. The groups consisted of combinations of teeth (6x), denture base materials (5x) and adhesive bonding options (4x). The teeth were printed, milled or prefabricated. The denture base was produced conventionally or was milled or 3D-printed. Two dentures were milled from one industrially produced block. The dentures were subjected to thermal and mechanical loading (TCML) and subsequent fracture test., Statistics: ANOVA, Bonferroni-test, Kaplan-Meier survival, Pearson correlation; α = 0.05., Results: Mean loading cycles varied between 221,869 (8), 367,610 (11), 513,616 (6) 875,371 (3) and 9,000,030 (4). ANOVA revealed significant (p ≤ 0.001) different surviving cycles. Log Rank test showed significantly (p < 0.001) different loading cycles. Fracture force after TCML varied between 129.8 +/- 97.1 N (3) and 780.8 +/- 62.5 N (9). ANOVA comparison revealed significant (p < 0.001) different fracture loadings between the individual systems. Correlation was found between fracture force and loading cycles (0.587, p < 0.001)., Conclusions: Different survival rates and fracture forces were found for dentures made of different teeth (milled, 3D-printed, prefabricated), bases (milled, 3D-printed, pressed) and bonding combinations. Milled, pressed and prefabricated systems provided longer survival and fracture force than the other tested systems., Clinical Relevance:  Optimal tooth-base combinations can help to produce a denture that is stable and resistant during clinical application., Competing Interests: Declarations. Ethical approval: Not Applicable. Informed consent: Not Applicable. Competing interests: The authors declare no competing interests., (© 2024. The Author(s).)

This in vitro study investigated how varying magnifications (5×, 10×, 20×, and 50×) using a confocal laser scanning microscope (CLSM) influence the measured surface roughness parameters, R a /S a and R z /S z , of various materials with two surface treatments. Cylindrical specimens (d ≈ 8 mm, h ≈ 3 mm, n = 10) from titanium, zirconia, glass-ceramic, denture base material, and composite underwent diamond treatment (80 μm; wet) and polishing (#4000; wet; Tegramin-25, Struers, G). The surface roughness parameters (R a /S a , R z /S z ) were measured with a CLSM (VK-100, Keyence, J) at 5×, 10×, 20×, and 50× magnifications. Line roughness (R a /R z ) was measured along a 1000 μm distance in three parallel lines, while area roughness (S a /S z ) was evaluated over a 2500 μm × 1900 μm area. The statistical analysis included ANOVA, the Bonferroni post hoc test, and Pearson correlation (SPSS 29, IBM, USA; α = 0.05). R a /S a and R z /S z showed significant differences ( p ≤ 0.001, ANOVA) across magnifications, with values decreasing as magnification increased, highest at 5× and lowest at 50×. Titanium, zirconia, and glass-ceramic showed significant measured roughness values from 5× to 50×. Denture base material and composite had lower measured roughness values, especially after polishing. Line and area roughness varied significantly, indicating that magnification affects measured values. Standardizing magnifications is essential to ensure comparability between studies. A 50× magnification captures more detailed profile information while masking larger defects.

3D printing as an additive manufacturing method has proven to be of great interest for the computerized production of oral splints. Various parameters must be taken into consideration when assessing the durability of oral splints in a wet environment, such as the mouth. The aim of this in vitro study was to assess the wear behavior and water sorption of two 3D-printed splint materials depending on their building orientation and post-processing parameters. The parameters considered included the type of post-polymerization and the type of cleaning utilized after printing. The average wear depth was between -421.8 μm and -667.5 μm. A significant influence of the building orientation ( p < 0.001) but not of the material ( p = 0.810), cleaning ( p = 0.933), or post-polymerization ( p = 0.237) on wear was demonstrated. The water sorption ranged between 13.8 μg/mm 3 and 30.3 μg/mm 3 , featuring a significant dependency on material and building orientation but not on cleaning ( p = 0.826) or post-polymerization ( p = 0.343). Material and fabrication methods should be carefully selected, because the type of material and building orientation affect the wear and water sorption of additively manufactured splint materials.

Objectives: This study investigated the influence of prophylactic treatments and thermocycling on the marginal and internal veneering interface (tooth-veneer) as well as on the surface texture of ceramic veneers., Materials and Methods: A total of 32 extracted human premolars were restored with veneers made of lithium disilicate (LDS) or zirconia-reinforced lithium silicate (ZLS). An artificial aging of the specimens was conducted via five cycles of both thermocycling (5/55°C) and prophylactic treatment (powder air polishing or ultrasonic scaling). Changes in the marginal interface and in the surface texture were examined using confocal laser scanning microscopy. The internal interface and the microstructure were investigated using micro X-ray computed tomography., Results: Artificial aging resulted in a deepening of the marginal interface across all groups (mean height: 4.51-15.74 μm, maximum height: 10.42-22.71 μm, cross-section: 256.68-1525.84 μm², regardless of the veneer material or prophylaxis method. No change in surface texture was observed. The internal interface exhibited defects for all groups after artificial aging. ZLS showed cracks in five out of eight veneers after exposure to ultrasonic scaling and thermocycling., Conclusion: Ceramic veneers exhibited a high resistance to prophylactic measures in terms of surface durability, but a deepening of the marginal interface should be taken into account. With regard to the formation of cracks within the material, the use of ultrasonic scaling is not recommended for ZLS veneers., Clinical Relevance: The influence of artificial aging, including prophylactic treatments, plays a critical role in assessing longevity for veneers in defect-oriented and esthetic dentistry., Competing Interests: Declarations. Ethical approval: This study was approved by the institutional Ethics Committee at the Medical Faculty of the Leipzig University (286/18-ek). Informed consent: Not Applicable. Competing interests: The authors declare no competing interests., (© 2024. The Author(s).)

This study aimed to investigate the efficiency of different cements for luting implant restorations. Standard restorations were bonded with different cements, including a zincoxide-based temporary cement (ZOE), a resin-modified glass ionomer cement (GIC) and a resin-based, eugenol-free cement (RBEFC). The restorations were stored under moist conditions and were subsequently subjected to thermal cycling and mechanical loading (TCML). Retention forces were determined with an axial tensile test and removabilty of the restorations was analyzed with a pneumatic crown remover. GIC provided significantly higher retention forces than RBEFC, which provided significantly higher values than ZOE. After storage, retention forces were significantly higher than after TCML. With regard to removability, no significant differences were identified between ZOE and RBEFC, but a significantly higher number of applications was required to remove restorations luted with RBEFC. All cements provided sufficient retention forces, yet removal of restoration might be more demanding if luted with RBEFC.

Aim: The objective of the present article is to demonstrate the digital workflow used to manufacture an adjusted oral splint in a patient case., Materials and Methods: A 25-year-old female patient presented for management of her bruxism. Therefore, an adjusted oral splint was manufactured. A computer-aided motion analysis of the patient was conducted (JMA Optic). Full-arch scans of the maxilla and mandible, a biocopy of the maxilla with a bite fork, and buccal scans of the centric jaw relation (Primescan) were performed. The jaw relation was determined beforehand by ballistic closing on a chairside-fabricated anterior jig. The digital construction of a Michigan splint took place in the dental laboratory. The design was nested and milled from a polymethyl methacrylate (PMMA)-containing blank (CLEARsplint Disc)., Results: The oral splint was inserted into the patient's mouth and checked to ensure a tension-free fit. The static and dynamic contact relationship was checked. During the follow-up visit, the patient reported an improvement in tension in the masticatory muscles., Conclusion: The described procedure allows for the manufacture of an adjusted oral splint through a purely digital workflow.

Lab-side-fabricated abutments and hybrid zirconia crowns, which are bonded to titanium bases with resin-based composites, require disinfection before insertion. This study investigated the effect of cleaning procedures (ultrasonic, autoclaving) and aging methods (24h, 90d, thermocycling) on the shear bond strength between alumina particle air-abraded titanium and zirconia (3Y-, 4Y- and 5Y-TZP) specimens luted with phosphate monomer containing adhesive systems and resin-based composite. Autoclaving significantly improved SBS (F (27,231) &#61; 17.265, p < .001) compared to no cleaning and three-stage disinfection. No differences were identified with regard to zirconia or aging methods. Bond strength initially benefits from autoclaving but continuously approaches the comparative values over longer periods.

Purpose: To investigate the aging and fracture resistance of screw-retained implant-supported single crowns (iSCs) fabricated from lithium disilicate containing virgilite (VLD)., Materials and Methods: iSCs were fabricated from VLD (CEREC Tessera, Dentsply Sirona) and lithium disilicate (control, n &#61; 8; IPS e.max CAD, Ivoclar) and bonded to a Ti-base abutment. VLD crowns were luted either with (VLDc, n &#61; 8) or without (VLDw, n &#61; 8) a coupling agent. iSCs were cleaned, sterilized, and screw-retained on implants. Fracture force was determined after thermal cycling and mechanical loading (TCML)., Results: All crowns survived TCML. No significant differences in mean fracture forces were identified between VLDc (1,583 N), VLDw (1,694 N), and control (1,797 N; P &#61; .639 ANOVA, P &#61; 1.000 Bonferroni)., Conclusions: Screw-retained iSCs fabricated from VLD provide acceptable stability, which is independent on the usage of a coupling agent for bonding to Ti-base abutments and sterilization.

Objectives: To evaluate three temporary luting cements in terms of their restoration loss rates, biological interactions, esthetic properties, and handling characteristics., Materials and Methods: 75 adults requiring fixed prosthodontics voluntarily participated in a single-blind, randomized controlled trial. After preparation, temporary restorations were luted with a randomly selected temporary luting cement (either Provicol QM Plus (PQP), Bifix Temp (BT), or Provicol QM Aesthetic (PQA)). Clinical examinations were performed one to two weeks after cementation. The following criteria were evaluated: tooth vitality, percussion, hypersensitivity, gingival bleeding, odor formation, esthetics, cement handling, removability, cleanability, and retention loss. Antagonistic teeth served as controls. Statistical analysis was performed using the paired t-test, one-way ANOVA, Pearson's chi-square and Fisher's exact test, where appropriate., Results: The overall loss rate of temporary restorations was 16.0%, showing no cement-specific differences. Postoperative hypersensitivity occurred in 8% of cases regardless of cement type. Esthetic impairment was reported by 31% of the PQP-fixed restorations, compared with 4.0% and 4.2% of the BT and PQA-bonded restorations. Cement application was reported to be easy in 100% of cases, excess removal in 88-96%, depending on the cement used., Conclusions: The choice of luting material affects the esthetic appearance of a temporary restoration and should be considered, particularly in restorations in esthetically demanding areas. No significant differences between the cements were identified regarding biocompatibility, handling, and loss rate., Clinical Relevance: Translucent cements can help to reduce color interferences, resulting in a more appealing appearance of the temporary restoration., (© 2024. The Author(s).)

Objectives: This study aims to explore and discuss recent advancements in tooth reconstruction utilizing deep learning (DL) techniques. A review on new DL methodologies in partial and full tooth reconstruction is conducted., Data/sources: PubMed, Google Scholar, and IEEE Xplore databases were searched for articles from 2003 to 2023., Study Selection: The review includes 9 articles published from 2018 to 2023. The selected articles showcase novel DL approaches for tooth reconstruction, while those concentrating solely on the application or review of DL methods are excluded. The review shows that data is acquired via intraoral scans or laboratory scans of dental plaster models. Common data representations are depth maps, point clouds, and voxelized point clouds. Reconstructions focus on single teeth, using data from adjacent teeth or the entire jaw. Some articles include antagonist teeth data and features like occlusal grooves and gap distance. Primary network architectures include Generative Adversarial Networks (GANs) and Transformers. Compared to conventional digital methods, DL-based tooth reconstruction reports error rates approximately two times lower., Conclusions: Generative DL models analyze dental datasets to reconstruct missing teeth by extracting insights into patterns and structures. Through specialized application, these models reconstruct morphologically and functionally sound dental structures, leveraging information from the existing teeth. The reported advancements facilitate the feasibility of DL-based dental crown reconstruction. Beyond GANs and Transformers with point clouds or voxels, recent studies indicate promising outcomes with diffusion-based architectures and innovative data representations like wavelets for 3D shape completion and inference problems., Clinical Significance: Generative network architectures employed in the analysis and reconstruction of dental structures demonstrate notable proficiency. The enhanced accuracy and efficiency of DL-based frameworks hold the potential to enhance clinical outcomes and increase patient satisfaction. The reduced reconstruction times and diminished requirement for manual intervention may lead to cost savings and improved accessibility of dental services., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Author(s). Published by Elsevier Ltd.. All rights reserved.)

Aims: Taste modifies eating behaviour, impacting body weight and potentially obesity development. The Obese Taste Bud (OTB) Study is a prospective cohort study launched in 2020 at the University of Leipzig Obesity Centre in cooperation with the HI-MAG Institute. OTB will test the hypothesis that taste cell homeostasis and taste perception are linked to obesity. Here, we provide the study design, data collection process and baseline characteristics., Materials and Methods: Participants presenting overweight, obesity or normal weight undergo taste and smell tests, anthropometric, and taste bud density (TBD) assessment on Day 1. Information on physical and mental health, eating behaviour, physical activity, and dental hygiene are obtained, while biomaterial (saliva, tongue swap, blood) is collected in the fasted state. Further blood samples are taken during a glucose tolerance test. A stool sample is collected at home prior to Day 2, on which a taste bud biopsy follows dental examination. A subsample undergoes functional magnetic resonance imaging while exposed to eating-related cognitive tasks. Follow-up investigations after conventional weight loss interventions and bariatric surgery will be included., Results: Initial results show that glycated haemoglobin levels and age are negatively associated with TBD, while an unfavourable metabolic profile, current dieting, and vegan diet are related to taste perception. Olfactory function negatively correlates with age and high-density lipoprotein cholesterol., Conclusion: Initial findings suggest that metabolic alterations are relevant for taste and smell function and TBD. By combining omics data from collected biomaterial with physiological, metabolic and psychological data related to taste perception and eating behaviour, the OTB study aims to strengthen our understanding of taste perception in obesity., (© 2024 The Authors. Diabetes, Obesity and Metabolism published by John Wiley & Sons Ltd.)

Objective: The influence of various aging protocols, representing and accelerating influences present in the dental context, on possible changes in the microstructure and mechanical properties of thermoplastics was investigated. In order to minimize the complexity of the systems, first pure polymers and then later the equivalent dental polymeric materials were analyzed., Materials and Methods: Pure polymers (Poly(methyl methacrylate) - PMMA, Polyoxymethylene homopolymer - POM-H, Polyether ether ketone - PEEK, Nylon 12 - PA12, Polypropylene - PP) were analyzed before as well as after applying different aging protocols relevant to the oral environment (ethanol, thermocycling, alkaline and acidic setting) by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The thermoanalytical parameters used were glass transition temperature (T g ), melting peak and crystallization peak temperature (T pm, T pc ) and decomposition behavior. In a second step selected commercially available dental products (Telio CAD - PMMA D , Zirlux Acetal - POM D , Juvora Natural Dental Disc - PEEK D ) aged by the protocol that previously showed strong effects were examined and additionally tested for changes in their Vickers and Martens hardness by Mann-Whitney-U test., Results: The combinations of pure polymers and viable aging protocols analyzed within this study were identified via TGA or DSC as PA12 & thermocycling, POM-H & denture cleanser/lactic acid/ethanol, PP & lactic acid. The dental polymeric materials PMMA D and POM D due to aging in lactic acid showed slight but significantly (p < 0.01) reduced Vickers and partly Martens hardness. PEEK showed the greatest material resistance within this study., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Objectives: To compare marginal gap width and depth with different cementation systems, excess removal, and after polishing., Method and Materials: In total, 80 composite crowns were milled, divided into ten groups, and cemented on identical artificial teeth. Eight crowns per group were fixed with (i) zinc phosphate cement (ZnOPh), (ii) glass-ionomer cement (GIC), (iii) resin-reinforced glass-ionomer cement (GIC mod), (iv) dual-curing adhesive composite (Comp dual), or (v) dual-curing self-adhesive composite (Comp SE dual). Excess removal was performed with a scaler after brief light-cure (tack-cure), final light-cure, during rubber or gel phase or by wiping with foam pellet. Curing was completed in chemical, dark cure, or light-curing modus. The specimens were polished and stored in water (37°C). The margins were digitized using a 3D laser-scanning microscope (VK-X100 series, Keyence). The width and the depth of the marginal gap were measured at 10 points between the crown margin and the preparation margin., Results: The width after excess removal varied between 65.1 ± 15.7 µm (Comp dual, wipe, with polishing) and 208.6 ± 266.7 µm (Comp SE dual, dark cure, without polishing). The depth varied between 29.8 ± 22.2 µm (Comp dual, wipe, with polishing) and 89.5 ± 45.2 µm (Comp SE dual, dark cure, without polishing). The impact on gap width and depth was detected for fixation material, excess removal, and polishing., Conclusion: The gap depth and width depend on the luting material and the mode of access removal. Polishing can improve the gap quality, especially for GIC and resin-based systems.

Objectives: The aim of the current study is to investigate the influence of mechanical stress as well as cleaning agents on the performance of various polyether ether ketone (PEEK) inserts for implant-retained overdentures (IOD)., Materials and Methods: Three different standard PEEK inserts were subjected to rapid artificial aging through storage in chemical denture cleaning agents (acetic acid, sodium hypochlorite, or sparkling denture cleaner) as well as demineralized water. The pre-aged PEEK inserts were then placed in unilateral IOD and subjected to 200,000 chewing loads (5 kg ~ 50 N), with 5000 thermal cycles (5/55°C), and 1100 removal/insertion cycles (vertical movement 2 mm)., Results: For all the PEEK inserts, the retention forces decreased significantly with an increasing number of mechanical load cycles and after exposure to all the cleaning agents. PEEK inserts aged by exposure to chemical cleaning agents showed a significantly higher decline in retention force than the inserts stored in water. Confocal laser scanning microscopy indicated that the decline in retention force might be caused by wear on the internal insert surface in contact with the patrix., Conclusions: Within the limitations of this study, it can be concluded that the application of chemical cleaning agents accelerates the decline in the retention forces of PEEK retentive inserts in IODs., (© 2023 The Authors. Clinical Oral Implants Research published by John Wiley & Sons Ltd.)

Denture prostheses are an ideal and extensive reservoir for microorganisms to attach to their surfaces. The aim of the study was to elucidate interactions between materials for the fabrication of denture bases and the attachment of microorganisms, focusing on respiratory pathogens and Candida species. Specimens (6 mm × 1 mm) with a standardized surface roughness (Sa = 0.1 µm) were prepared from heat-pressed polymethyl methacrylate (PMMA), CAD/CAM-processed PMMA, and CAD/CAM-processed polyether ether ketone (PEEK). The specimens were randomly placed in the vestibular areas of complete upper dentures in seven patients and were removed either after 24 h without any oral hygiene measures or after a period of four weeks. The microorganisms adherent to the surface of the specimens were cultivated and subsequently analyzed using mass spectrometry (MALDI-TOF). The means and standard deviations were calculated, and the data were analyzed using a two-way analysis of variance (ANOVA) and Tukey post-hoc test where appropriate (α = 0.05). There was a significant increase ( p ≤ 0.004) in the total bacterial counts (CFU/mL) between the first (24 h) and the second (four weeks) measurements. Regarding quantitative microbiological analyses, no significant differences between the various materials were identified. Respiratory microorganisms were detected in all samples at both measurement time points, with a large variance between different patients. Only after four weeks, Candida species were identified on all materials but not in all participants. Candida species and respiratory microorganisms accumulate on various denture base resins. While no significant differences were identified between the materials, there was a tendency towards a more pronounced accumulation of microorganisms on conventionally processed PMMA.

Chipping of implant-supported molar crowns (iSCs) is a frequently reported complication. This study aimed to investigate the in-vitro aging and fracture resistance of iSCs with a CAD/CAM resin composite veneer structure fabricated with the Rapid Layer Technology (RLT) approach. Eight iSCs per group were fabricated by using two different CAD/CAM resin composites (Shofu Block HC: SH; Grandio blocs: GB) for veneer structures, and zirconia (ZrO 2 ), polyetheretherketone (PEEK), and cobalt-chromium (CoCr; control) as framework materials. The surfaces to be bonded were sandblasted, cleaned in an ultrasonic bath, and a coupling agent was applied. A self-adhesive resin luting composite was used to adhesively lute the veneer structures to the frameworks. The crowns were semi-permanently cemented to the abutments. After storage in deionized water, iSCs were loaded in a chewing simulator (TCML, 10,000 thermal cycles 5 °C to 55 °C for 20 s, 1.2 million, loading force 50 N). Four ZrO 2 and one CoCr crown did not survive the TCML. The fracture force was determined after 24 h storage in deionized water and yielded values of ≥974 N. Lowest fracture forces were yielded in the PEEK-SH group in comparison to CoCr or ZrO 2 groups ( p ≤ 0.031). For identical framework materials, no significant influence of the veneering material was observed. All PEEK-GB frameworks fractured, and chipping occurred for ZrO 2 -SH and all CoCr frameworks. PEEK-SH and ZrO 2 -GB presented both chipping and framework fractures. Within the limitations of this in-vitro study, the RLT with a CAD/CAM resin composite veneer structure might be a promising approach to veneer iSCs. Yet, the choice of the CAD/CAM resin composite and of the framework material determine the fracture resistance.