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Abstract Objectives The current strategies to reconstruct lost peri‐implant tissues due to the disease have been largely unpredictable. The aim of this conceptual review is to discuss relevant biological and biomechanical challenges of applying reconstructive means to treat peri‐implantitis. Additionally, opportunities to improve treatment predictability are presented. Material and Methods A narrative review was conducted to fulfill the aim. Results The four interrelated negative conditions hampering effective reconstruction are: inferior tissue perfusion, unfavorable bone topography, ineffective surface treatment, and unstable wound. First, peri‐implant tissues resemble scars with reduced cellularity and vascularity, coupled with the absence of the periodontal ligament plexuses and the avascular implant and biomaterials, maintaining primary closure is a challenge, which is critical for regeneration. Second, defect morphology and bone topography surrounding implants determine the reconstructive potential. Unfortunately, noncontained defects are frequently encountered, with a combination of suprabony (horizontal bone loss) and infrabony (vertical usually involving circumferential bone loss) defects. Third, current attempts for implant surface decontamination are insufficient due to inaccessible macrostructure and rough surfaces in the micro‐scale. Histologic evaluation has shown bacteria aggregation and calcified deposits around implants. Lastly, wound stability is difficult to achieve due to inherent soft tissue biomechanical quality and quantity deficiencies and mobile bone particulates. Opportunities to tackle the abovementioned challenges include the use of novel imaging technologies, such as high‐frequency dental ultrasound and laser speckle imaging to evaluate tissue perfusion, soft tissue quality/quantity, and bone topography pre‐surgically. The use of the operating microscope could allow better visualization and removal of etiologic factors. Strategies to improve soft tissue quality may include preoperative control of soft tissue inflammation and the potential use of biologics. Methods such as fixation to stabilize the biomaterials could be beneficial. Conclusions A more nuanced understanding of the current challenges and opportunities can lead to more effective preoperative and postoperative care protocols, ultimately improving the success rate of reconstructive procedures.

Abstract Purpose To evaluate collagen scaffolds (CS) in terms of their in vitro resorption behavior, surface structure, swelling behavior, and mechanical properties in physiologically simulated environments, compared with porcine native connective tissue. Materials and methods Three test materials—one porcine collagen matrix (p-CM), two acellular dermal matrices (porcine = p-ADM, allogenic = a-ADM)—and porcine native connective tissue (p-CTG) as a control material were examined for resorption in four solutions using a high-precision scale. The solutions were artificial saliva (AS) and simulated body fluid (SBF), both with and without collagenase (0.5 U/ml at 37 °C). In addition, the surface structures of CS were analyzed using a scanning electron microscope (SEM) before and after exposure to AS or SBF. The swelling behavior of CS was evaluated by measuring volume change and liquid absorption capacity in phosphate-buffered saline (PBS). Finally, the mechanical properties of CS and p-CTG were investigated using cyclic compression testing in PBS. Results Solutions containing collagenase demonstrated high resorption rates with significant differences (p a-ADM > p-ADM. P-CM exhibited higher elastic properties than p-ADM, whereas a-ADM, like p-CTG, were barely compressible and lost structural integrity under increasing pressure. Conclusions and clinical implications Collagen scaffolds vary significantly in their physical properties, such as resorption and swelling behavior and elastic properties, depending on their microstructure and composition. When clinically applied, these differences should be taken into consideration to achieve the desired outcomes. Graphical Abstract

Background: The search for effective antimicrobial agents to mitigate peri-implant infections remains a crucial aspect of implant dentistry. This study aimed to evaluate and compare the antimicrobial efficacy of i-PRF, A-PRF+, and enamel matrix derivative (EMD) on decontaminated rough and smooth titanium (Ti) discs. Materials and Methods: Rough and smooth Ti discs were coated with multispecies biofilm and thoroughly debrided using a chitosan-bristled brush. Subsequently, i-PRF, A-PRF+, and EMD were applied. Untreated discs served as control. Residual adherent bacteria present on the treated Ti discs were visualized by SEM and quantified using culture technique, and colony-forming units (CFUs) were measured after 48 h and 7 days. Results: i-PRF demonstrated better antimicrobial effectiveness on both smooth and rough implant surfaces as compared to A-PRF+ and EMD (p < 0.001). In all the experimental groups, smooth Ti discs displayed a greater reduction in microbes compared to rough Ti discs when treated with the biologics. The major reduction in CFU values was determined after seven days. Conclusions: i-PRF as a regenerative material may also be suitable for decontaminating implant surfaces, which could influence tissue healing and regenerative outcomes positively.

Abstract Objectives To attain a collective expert opinion on the use of air powder waterjet technology (APWT) with erythritol and glycine powders in the prophylaxis and therapy of periodontal and peri‐implant diseases. Material and Methods In the first step, a modified one‐round online Delphi survey including 44 five‐point Likert scale questions was conducted among a group of 10 expert clinicians and researchers with thorough knowledge and experience in this topic. In the second step, the single questions and the survey results were discussed during a meeting, and consensus statements were formulated, respectively. Results An agreement was reached on most items, especially opinions supporting glycine and erythritol powders as favorable with respect to efficiency, safety, and comfort. More scientific evidence is needed to support the improvement in clinical attachment on teeth and implants, especially when APWT with erythritol is used. In addition, APWT needs more long‐term evaluation and studies in terms of microbiome/microbiological effects as well as effects on the inflammatory response on natural teeth and implants, also in light of a guided biofilm therapy concept. Conclusions In line with the expert opinions and supported by the evidence, it was concluded that the use of APWT with erythritol and glycine powders in nonsurgical periodontal and peri‐implant therapy and prophylaxis is patient compliant and efficient.

This study investigates the impact of various instrumentation techniques on material removal and surface changes in titanium (Ti)- and zirconia (Zr) implant discs. Ti- and Zr discs were subjected to standardized experiments using various instruments including airflow, ultrasound, carbide, and diamond burs. Instrumentation was performed for 60 s with continuous automatic motion. Abrasion and changes in surface roughness were assessed using profilometry, while scanning electron microscopy was used to examine morphological changes and particle size. Carbide burs predominantly caused abrasion on Ti discs, while diamond burs caused more abrasion on Zr discs. The Ti discs were more susceptible to surface changes. However, among the materials tested, machined Zr discs treated with diamond burs produced the largest particle. In certain cases, a statistical significance (p < 0.05) was observed between the groups, while in others, there was no considerable difference among the means (p > 0.05). These results highlighted the statistical significance of our findings. These results found diverse alterations in surface characteristics of Ti- and Zr discs due to different instruments, with carbide and diamond burs causing notable effects. The findings highlight the need for a careful balance between promoting healing and minimizing harm during implantoplasty.

Abstract Purpose To assess the dimensional establishment of a bony envelope after alveolar ridge preservation (ARP) with deproteinized bovine bone mineral (DBBM) in order to estimate the surgical feasibility of standard diameter implants placement without any additional augmentation methods. Methods PubMed, Embase and CENTRAL databases were searched for suitable titles and abstracts using PICO elements. Inclusion criteria were as follows: randomized controlled trials (RCTs) comprising at least ten systemically healthy patients; test groups comprised placement of (collagenated) DBBM w/o membrane and control groups of no grafting, respectively. Selected abstracts were checked regarding their suitability, followed by full-text screening and subsequent statistical data analysis. Probabilities and number needed to treat (NNT) for implant placement without any further need of bone graft were calculated. Results The initial database search identified 2583 studies. Finally, nine studies with a total of 177 implants placed after ARP with DBBM and 130 implants after SH were included for the quantitative and qualitative evaluation. A mean difference of 1.13 mm in ridge width in favour of ARP with DBBM could be calculated throughout all included studies (95% CI 0.28–1.98, t2 = 1–1063, I2 = 68.0%, p

Abstract Objectives To evaluate the relationship between gingival phenotype and tooth location based on selected index teeth (“Ramfjord”) and assess possible differences between women and men. Material and Methods Thirty‐six women and 20 men voluntarily participated in this investigation with an average age of 23 years (min: 19; max: 37). Gingival phenotypes (GP) were assessed by transparency of a periodontal probe through the buccal gingival margin. Results A comparable and similar GP on all index teeth was only found in seven out of the 56 subjects, that is, thin or thick only: Five participants (three male/two female) showed a uniform and constantly thick and two females a constantly thin GP. While the majority of molars (94.6%; p = 0.006) showed a thick GP, premolars (61.6%; p = 0.09) as well as incisors (70.5%; p = 0.046) were predominantly categorized as thin. In addition, significantly thicker GP was in general observed for maxillary teeth (p = 0.001) but without differences between genders (p = 0.722). Conclusion No constant GP can be expected within one dentition. The use of the “Ramfjord teeth” may serve as a quick overview and reliable method to screen GP distribution.

Abstract Background Pathologically elevated levels of matrix metalloproteinase-8 (MMP-8) and Lactoferrin in oral fluids have been associated with the presence of gingivitis/periodontitis. This study aimed to assess the origin of MMP-8 and Lactoferrin in periodontitis patients and to identify the degree to which conventional clinical parameters correlate with their presence. Methods A total of ten periodontitis and ten healthy patients were included in this study. Whole saliva (stimulated and unstimulated), parotid/sublingual glandular fluid and gingival crevicular fluid from pockets and sulci were tested for MMP-8 and Lactoferrin and protein concentrations were quantified using an ELISA assay. Clinical parameters were checked for potential associations with MMP-8 and Lactoferrin levels. Results Periodontal patients presented higher concentrations of MMP-8 and Lactoferrin in pockets than other sources (P = 0.03). Lactoferrin measurement was higher in the parotid compared to sublingual glandular fluid in periodontitis patients (P = 0.03). Increased probing pocket depth was positively correlated with high MMP-8 and Lactoferrin levels. Conclusions Periodontal pockets appear to be the major source of active matrix metalloproteinase and Lactoferrin, which also may also enter the oral cavity through the salivary glands. Since clinically healthy sites in periodontitis patients also had elevated biomarker levels, gingival crevicular fluid biomarker testing may be more predictive of future tissue breakdown than conventional clinical parameters.

Abstract Background Interleukin (IL)-35 is a novel anti-inflammatory cytokine that is produced by regulatory T cells. IL-35 mediates immunological functions and plays a protective role in several diseases such as asthma and rheumatoid arthritis. However, the role of IL-35 in gingivitis and periodontitis remains unclear. The aim of this study was to systematically review the literature and collecting the available evidence regarding the role of IL-35 in pathogenesis of periodontal disease. Methods A systematic search of electronic databases including MEDLINE, Google Scholar, Cochrane Library, Web of Science, and Scopus was conducted in November 2020 to identify studies addressing the Interleukin-35 pathobiology in periodontal disease. The identified studies were subjected to pre-identified inclusion criteria. The retrived papers were assessed by the authours independently and consensus was reached in cases where disagreement occurred. Articles written in languages other than English, case reports, letters to editors, conference abstracts, theses, and dissertations were excluded from the review. Results A total of 176 possibly relevant articles were identified through the search strategy. Finally, 15 papers which met the criteria of eligibility were included in this review by consensus. The included articles were classified based on their design and level of evidence.Three subclinical study, ten cross sectional investigation and two randomized clinical trials constituted the final set of studies in this review. At preclinical level, Il-35 showed inhibitory characteristics regarding alveolar bone resorption of animal periodontitis models. The results of observatory human studies confirmed the presence of high levels of IL-35 in saliva, GCF, serum, and gingival biopsies of patients suffering from inflammatory periodontal disease. Moreover, two included clinical trials showed that non-surgical periodontal therapy could downregulate IL-35 production in chronic periodontitis patients. Conclusion Interleukin-35 has an undeniable role in pathobiology of inflammatory periodontal disease. Further well-controlled studies are needed to better elucidate the functional pattern of IL-35 in pathogeneisis of gingival and periodontal disease.

Purpose: To systematically assess the current evidence regarding the adjunctive application of enamel matrix derivatives (EMDs) during alveolar ridge preservation (ARP) following tooth extraction. Methods: A comprehensive literature search was conducted in MEDLINE, Cochrane Library, PsycINFO, Web of Science, Google Scholar, and Scopus to identify relevant randomized controlled clinical trials (RCTs). The primary outcome parameters of this systematic review were histomorphometric and radiographic data; secondary outcomes were the feasibility of implant placement after ARP as well as patient-related outcomes such as postoperative discomfort. Results: The search identified 436 eligible articles published from 2011 to 2022, but only five were ultimately included for data extraction (146 patients). Given the substantial heterogeneity among the included studies, no meta-analysis could be performed. The authors’ qualitative analysis showed marginally improved outcomes regarding an increased percentage of new bone formation after tooth extraction and a reduction in postoperative discomfort. Conclusions: Given the potential value of EMDs in other fields of regenerative dentistry, more consideration should be given to EMDs as an adjunctive treatment option in ARP. However, more well-controlled randomized clinical trials are necessary to evaluate the exact potential and impacts of EMDs.

Inflammatory periodontal and peri-implant diseases follow dysbiotic shifts in a susceptible host. A well-established tool for microbial sample collection is the use of paper points. The purpose of this pilot study was to evaluate the use of interdental brushes compared to paper points. Biofilm samples were collected with paper points and later interdental brushes from ten patients. Five patients were represented with a community periodontal index of treatment needs (CPITN) of 0–2 around the teeth and an implant with PPD ≤ 5 mm and no radiological bone loss. The remaining five patients had a CPITN ≥ 3 and one implant with peri-implantitis. Microbial samples were analyzed with quantitative polymerase chain reaction (qPCR) and next-generation sequencing (NGS). The results showed higher amounts of DNA in samples taken by interdental brushes but also higher Ct values. Both methods detected Filifactor alocis, Porphyromonas gingivalis, Prevotella intermedia, Tannerella forsythia, and Treponema denticola in the majority of samples, while Aggregatibacter actinomycetemcomitans was rarely found. A microbial dysbiosis index showed comparable or higher values in sites with no periodontitis/peri-implantitis with interdental brushes. The results of this pilot study indicate that interdental brushes might be a valid technique for microbial sampling and particularly advantageous in the early detection of dysbiotic shifts around teeth and implants. Larger studies with more participants are needed to validate the proposed microbial sampling method with interdental brushes.

Abstract Objectives This narrative review is aiming on showing reasons for implant failure, removal techniques, and respective clinical considerations; further, the survival rate of implants in previous failed sites is examined. Materials and methods Questions have been formulated, answered, and discussed through a literature search including studies assessing implant failure and removal up to 2018. Results Studies describing reasons for implant failure, implant removal techniques, and the reinsertion of implants in a previous failed site (n = 12) were included. To date, peri‐implantitis is the main reason for late implant failure (81.9%). Trephine burs seem to be the best‐known method for implant removal. Nevertheless, the counter‐torque‐ratchet‐technique, because of the low invasiveness, should be the first choice for the clinician. Regarding zirconia implant removal, only scarce data are available. Implantation in previously failed sites irrespective of an early or late failure results in 71% to 100% survival over 5 years. Conclusion If removal is required, interventions should be based on considerations regarding minimally invasive access and management as well as predictable healing. (Post)Operative considerations should primarily depend on the defect type and the consecutive implantation plans.

Abstract Objectives Periodontal healing is often accompanied by side effects, which may cause an aesthetic deficit. The present investigation was focussed to compare patient's subjective perception of their posttherapy aesthetics with the objective measures of the results. Materials and methods Survey results from patients (subjective parameters) on oral status and aesthetics were compared against routine clinical parameters and corresponding survey results from treating dentists (objective parameters), both before and after periodontal treatment. Subjective outcome parameters were then suitably transformed and compared with the objective ones to investigate the agreement between patients' perception and actual outcomes. Results Objective recordings of periodontal status by the dentist and subjective awareness of the patient are quite contradictory to each other for almost all participants. Further, it was found that their aesthetics in the front were better after treatment, but dentist professionals targeted for future treatment needs. Conclusions In this study, it was found that patients improved aesthetically on the upper jaw front after the therapy, which was not shared by the dentists. This discrepancy was due to the clinicians' view on more aesthetic corrective procedures than on patients' need.

OBJECTIVES: To discuss first, the adequacy of the antibiotic prophylaxis regimen currently recommended for the prevention of infective endocarditis in periodontitis patients, and second, preventive measures to decrease the rate of bacteraemia after periodontal treatment. MATERIALS AND METHODS: A bibliographic literature search identifying clinical trials between January 1990 and January 2021, focusing on microorganisms in bacteraemia after periodontal treatment and bacteria in infective endocarditis, was performed. Two reviewers independently identified and screened the literature by systematically searching in Medline/Premedline, EMBASE and Cochrane Library. RESULTS: Two hundred and seventy articles were identified, of which twenty-three met the inclusion criteria. Bacteraemia rates after periodontal treatment ranged from 10–94% in the investigated patients. Mainly oral pathogens related to infective endocarditis, such as viridans group streptococci (up to 70%) and HACEK group pathogens (e.g., Aggregatibacter actinomycetemcomitans), were detected. But typical oral and periodontopathogenic species, such as Porphyromonas spp. (P.s gingivalis) (up to 50%), Actinomyces spp. (up to 30%) and Fusobacterium spp. (up to 30%), which do not usually cause infective endocarditis, were also found. Infective endocarditis episodes that might have been in association with a dental treatment were mainly caused by viridans group streptococci. Prophylactic measures like rinse application of chlorhexidine, povidone-iodine or essential oils, diode laser or systemic antibiotic prescription were described as decreasing the bacteraemia rate after periodontal interventions to 5–70%. CONCLUSION: The currently recommended systemic antibiotic prophylaxis with amoxicillin before periodontal treatment in high-risk cardiovascular patients still covers the most common oral bacteria causing infective endocarditis, namely viridans group streptococci, and therefore seems adequate in this context. Since bacteraemia, not infective endocarditis, is the endpoint in most studies, the causality between bacteraemia after periodontal treatments and infective endocarditis remains difficult to elucidate. Until more evidence is available regarding this, adherence to current guidelines for antibiotic prophylaxis in patients at high risk for infective endocarditis undergoing periodontal treatment remains recommended.

Abstract Objectives Retro MTA is a fast setting Calcium silicate cement used in endodontic regeneration procedures in recent years. Beta-tricalcium phosphate (β-TCP) is another common biomaterial used for bone augmentation procedures. The present pilot study was undertaken to evaluate and compare the efficacy of Retro MTA and a mixture of Retro MTA / β-TCP for periodontal tissue regeneration. Materials and methods In 4 beagle dogs, periodontal dehiscence type defects were created. In each side, one dehiscence defect was left empty as a control site and three treatment modalities were randomly applied for the others: Retro MTA covered with a collagen membrane, Retro MTA + β-TCP covered with a membrane and covering the defect with a membrane without any bone augmentation. After 8 weeks Animals were sacrificed and Histomorphometric and histologic analysis were conducted. Results Histologic analysis showed more cementum formation for both Retro MTA+ β-TCP (3.74 ± 0.34 mm) and Retro MTA group (3.24 ± 0.56 mm) compared to control group 1 (1. 15 ± 0.45 mm) and control group 2 (0.78 ± 0.65 mm). Formation of newly formed bone and cementum in the experimental groups were significantly higher as compared to the control groups (P

Peri-implantitis is a common biological complication in dentistry. The aim of the present study was to retrospectively analyze risk characteristics in a group of patients referred to a university-based consultation for peri-implantitis. In all, 190 initial cases from 2010 to 2019 were evaluated and descriptively summarized. The evaluation included various parameters such as periodontitis, smoking and oral hygiene status, implant position, type of prosthetic restoration and retention, mucosal quality, and further anamnestic and clinical findings related to the potential risk of developing peri-implantitis. Peri-implantitis was diagnosed in 83% of the cases, with peri-implant mucositis alone in 16% of cases; furthermore, 38% of the patients were diagnosed with active/instable periodontitis, while 14% had stable periodontitis. Residual cement was considered as a potential co-factor of peri-implant inflammation in 43% of cases. Suboptimal implant positioning was found in 19% of patients. Peri-implantitis or peri-implant mucositis was present in about one-third of patients in the absence of smoking and periodontitis factors. Of note, 6% showed no identifiable risk factors. Factors related to an increased risk of peri-implantitis should be taken into consideration when planning implant treatment. Adequate prosthetic implant position, restoration, and cleanability remain important for long-term success.

In this in vitro study, we compare the penetration of cells through different resorbable collagen membranes, which were collagenolytically degraded over different time periods. Three different resorbable collagen membranes were evaluated, including two non-cross-linked (NCL) membranes—namely, a porcine (NCL-P) and an equine (NCL-E) membrane—and an enzymatically cross-linked porcine (ECL-B) membrane. A special two-chamber model was fabricated, allowing for the placement of separating membranes, and a non-porous polyester membrane was used as a negative control (C), in order to verify the impermeability of the experimental chamber device. Round membrane samples with a diameter of 16 mm were fabricated. Eighteen membranes of each type were punched and placed on polyethylene nets as carriers. The membranes were then biodegraded—each on its carrier—in 12-well polystyrene plates: three samples of each membrane type were degraded for 1.5, 3, 6, or 12 h in 2 mL of a buffered collagenase solution, at 37 °C. For control purposes, three samples of each membrane type were not degraded, but only immersed in buffer solution for 1.5, 3, 6, or 12 h, at 37 °C. Another three samples of each type of membrane were degraded until complete dissolution, in order to determine the full hydroxyproline content for comparison. Liquid-preserved boar semen (containing at least 120 million sperm cells per milliliter) was used to test the cell occlusivity of the degraded membranes. At baseline and initial degradation, all tested membranes were tight, and no penetration was observed with up to 30 min of incubation time (results not shown). After 1.5 h, cells were partially capable of penetrating the NCL-E membrane only. One sample showed leakage, with a sperm volume of 1.7 million cells/mL over all samples. No penetration occurred in the test, NCL-P, and ECL-B groups. After a degradation time of 3 h, the NCL-P and ECL-B membranes remained occlusive to cells. All the membranes and measurements indicated leakage in the NCL-E group. After 6 h, four NCL-P measurements showed the first signs of cell penetration, as boar spermatozoa were detectable in the lower chamber (64 million cells/mL). The ECL-B membranes remained completely cell occlusive. After 12 h, four NCL-P measurements were cell penetration positive (14.6 million cells/mL), while the ECL-B group remained tight and showed no cell penetration. As the findings of our study are well in accordance with the results of several previous animal studies, it can be concluded that the surrogate model is capable of performing rapid and cheap screening of cell occlusivity for different collagen membranes in a very standardized manner. In particular, claims of long degradation resistance can be easily proven and compared. As the boar spermatozoa used in the present report had a size of 9 × 5 μm, smaller bacteria are probably also able to penetrate the leaking membranes; in this regard, our proposed study set-up may provide valuable information, although it must be acknowledged that sperm cells show active mobility and do not only translocate by growth.

This umbrella review was conducted to assess the existing literature and scientific evidence on air powder water jet technology (APWJT) in periodontal and peri-implantitis therapy. A systematic literature search for systematic reviews and meta-analyses of the last decade on the use of APWJT in periodontitis and implant patients was performed in the databases of MEDLINE/Ovid, Embase, Cochrane library and Scopus. An additional hand search on PubMed and Google Scholar was conducted. Ten articles that fit the inclusion criteria were selected after the full-text screening. Two systematic reviews, including one with a meta-analysis, investigated the use of APWJT in active periodontal therapy. The use of APWJT as an adjunct to conventional scaling and root planing (SRP) in active periodontal treatment showed improved results in the test group. Six articles, including two with a meta-analysis, reported on the use of APWJT as a stand-alone therapy or as an adjunct in supportive periodontal therapy. Similarly significant improved results were reported for the use of APWJT. Regarding the active treatment of peri-implant mucositis and peri-implantitis, four systematic reviews could not show an improved clinical outcome when APWJT was used as an adjunct to conventional treatment measures. Furthermore, one article investigated APWJT as a stand-alone therapy or as an adjunct in supportive peri-implant mucositis and peri-implantitis therapy. In systematic reviews that also investigated patient perception, APWJT was generally well-tolerated by the patient. Within the limitations of this umbrella review, it can be concluded that the use of APWJT with low-abrasive powders such as glycine, erythritol or trehalose as an adjunct in active periodontitis therapy shows similar clinical results compared to conventional SRP alone. In surgical peri-implantitis treatment, APWJT can be used adjunctively. It could be considered that the use of APWJT in supportive periodontal treatment results in a comparable clinical outcome and an enhanced patient perception, as well as a shorter clinical time.

Information about the potential oral health effects of vaping from electronic cigarettes (e-cigs) is still sparse and inconsistent. The purpose of this study was to compare the safety and cytotoxicity of e-cig liquid aerosols versus traditional cigarette (t-cig) smoke on human epithelial oral cells. T-cig smoke and e-cig aerosols were generated by a newly developed automated smoking instrument in order to simulate realistic user puffing behaviors. Air–liquid interface transwell cell cultures were exposed to standardized puff topography (puff duration: 2 s, puff volume: 35 mL, puff frequency: 1 puff every 60 s) of reference t-cigs or commercially available e-cigs at different air dilutions. Cell viability, morphology, and death rate were evaluated with MTT and TUNEL assays. The inflammatory cytokine gene expression of inflammatory genes was assessed by quantitative RT-PCR. E-cigs and t-cigs indicated similar adverse effects by enhancing cytotoxicity and cell death in a dose-dependent manner. E-cig aerosol and t-cig smoke treatment expressed upregulation of inflammatory cytokines up to 3.0-fold (p < 0.05). These results indicate that e-cig smoking may contribute to oral tissue–cell damage and tissue inflammation. Our approach allows the production of e-cig aerosol and t-cig smoke in order to identify harmful effects in oral tissues in vitro.

Actinomycosis is a chronic suppurative infection primarily caused by anaerobic gram-positive filamentous bacteria, primarily of the genus Actinomyces. Oral-cervicofacial actinomycosis is the localization found most often, presenting as a soft tissue swelling, an abscess, a mass lesion, or sometimes an ulcerative lesion. Periodontitis-like lesions, however, are rare findings. This report describes the case of a 41-year-old healthy female patient (nonsmoker), who was referred to the clinic with dull and throbbing pain in the second quadrant. Tooth 25 showed increased mobility and probing pocket depths up to 10 mm, with profuse bleeding upon probing. Radiographically, considerable interproximal horizontal bone loss was found, and the diagnosis of periodontitis stage 3, grade C was made. The situation was initially stabilized with adhesive splinting and local anti-infective therapy. Two weeks later, the bone defect was treated with guided tissue regeneration (GTR) using a xenogenic filler material (BioOss Collagen) and a resorbable membrane (Bio-Gide). Due to a suspicious appearance of the excised granulation tissue, the collected fragments were sent for histopathological evaluation. This evaluation revealed a chronic granulomatous inflammation with the presence of filamentous bacterial colonies, consistent with Actinomyces. The patient was successfully treated. While there are only few reports in the literature, actinomycotic lesions represent a rare but possible finding in cases with localized periodontal destruction. In conclusion, systematic biopsy of the infrabony tissue in localized periodontal lesions may help to provide a more accurate counting of Actinomyces-associated lesions, thereby improving diagnosis, therapy, and prevention.

Periodontitis and dental caries are two major bacterially induced, non-communicable diseases that cause the deterioration of oral health, with implications in patients’ general health. Early, precise diagnosis and personalized monitoring are essential for the efficient prevention and management of these diseases. Here, we present a disk-shaped microfluidic platform (OralDisk) compatible with chair-side use that enables analysis of non-invasively collected whole saliva samples and molecular-based detection of ten bacteria: seven periodontitis-associated (Aggregatibacter actinomycetemcomitans, Campylobacter rectus, Fusobacterium nucleatum, Prevotella intermedia, Porphyromonas gingivalis, Tannerella forsythia, Treponema denticola) and three caries-associated (oral Lactobacilli, Streptococcus mutans, Streptococcus sobrinus). Each OralDisk test required 400 µL of homogenized whole saliva. The automated workflow included bacterial DNA extraction, purification and hydrolysis probe real-time PCR detection of the target pathogens. All reagents were pre-stored within the disk and sample-to-answer processing took < 3 h using a compact, customized processing device. A technical feasibility study (25 OralDisks) was conducted using samples from healthy, periodontitis and caries patients. The comparison of the OralDisk with a lab-based reference method revealed a ~90% agreement amongst targets detected as positive and negative. This shows the OralDisk’s potential and suitability for inclusion in larger prospective implementation studies in dental care settings.

The aim of this case series was to present the clinical outcomes of non-contained intrabony periodontal defects (IPDs) treated by means of papillary preservation flaps in association with a slowly resorbable bovine pericardium membrane (BPM) and a low-temperature-treated bovine bone graft (BBG). Eight healthy, non-smoking patients (two males and six females, mean age 48 ± 8 years) with stage 3 periodontitis and at least one site with residual probing depth (PD) ≥ 6 mm associated with a non-contained IPD ≥ 3 mm were treated. Two weeks after surgery, no adverse events were observed, and an early wound healing score (EHS) of 8.1 ± 1.0 was recorded. After 1 year, the mean probing depth (PD) reduction and mean clinical attachment level gain (CAL-gain) accounted for 4.8 ± 0.7 and 3.5 ± 0.7 mm, respectively, whereas the mean gingival recession (REC) was of 1.2 ± 0.3 mm. Radiographic bone fill was observed in all cases. In conclusion, the treatment of non-contained IPDs with a slowly resorbable BPM and a low-temperature-treated BBG could be considered safe and may result in significant clinical improvements 1 year after surgery.

The wear-debris particles released by shearing forces during dental implant insertion may contribute to inflammatory reactions or osteolysis associated with peri-implantitis by stimulating inflammasome-activation. The study aim was to examine cytotoxic and pro-inflammatory effects of titanium (TiO2) and zirconia (ZrO2) particles in macrophages regarding their nature/particle concentration over time under sterile lipopolysaccharide (LPS) inflammation. Macrophages were exposed to TiO2 and ZrO2 particles (≤5 µm) in cell culture. Dental glass was used as inert control and LPS (1 μg/mL) was used to promote sterile inflammation. Cytotoxicity was determined using MTT assays and cytokine expression of TNF-α, IL-1β and IL-6 was evaluated by qRT-PCR. Data were analyzed using Student’s t-test and ANOVA (p ≤ 0.05). Cytotoxicity was significantly increased when exposed to higher concentrations of glass, TiO2 and ZrO2 (≥107 particles/mL) compared to controls (p ≤ 0.05). Macrophages challenged with TiO2 particles expressed up to ≈3.5-fold higher upregulation than ZrO2 from 12 to 48 h. However, when exposed to LPS, TiO2 and ZrO2 particle-induced pro-inflammatory gene expression was further enhanced (p ≤ 0.05). Our data suggest that ZrO2 particles produce less toxicity/inflammatory cytokine production than TiO2. The present study shows that the biological reactivity of TiO2 and ZrO2 depends on the type and concentration of particles in a time-dependent manner.

Abstract Background An in vitro model for peri-implantitis treatment was used to identify areas that are clinically difficult to clean by analyzing the pattern of residual stain after debridement with commonly employed instruments. Methods Original data from two previous publications, which simulated surgical (SA) and non-surgical (NSA) implant debridement on two different implant systems respectively, were reanalyzed regarding the localization pattern of residual stains after instrumentation. Two blinded examiners evaluated standardized photographs of 360 initially ink-stained dental implants, which were cleaned at variable defect angulations (30, 60, or 90°), using different instrument types (Gracey curette, ultrasonic scaler or air powder abrasive device) and treatment approaches (SA or NSA). Predefined implant surface areas were graded for residual stain using scores ranging from one (stain-covered) to six (clean). Score differences between respective implant areas were tested for significance by pairwise comparisons using Wilcoxon-rank-sum-tests with a significance level α = 5%. Results Best scores were found at the machined surface areas (SA: 5.58 ± 0.43, NSA: 4.76 ± 1.09), followed by the tips of the threads (SA: 4.29 ± 0.44, NSA: 4.43 ± 0.61), and areas between threads (SA: 3.79 ± 0.89, NSA: 2.42 ± 1.11). Apically facing threads were most difficult to clean (SA: 1.70 ± 0.92, NSA: 2.42 ± 1.11). Here, air powder abrasives provided the best results. Conclusion Machined surfaces at the implant shoulder were well accessible and showed least amounts of residual stain. Apically facing thread surfaces constituted the area with most residual stain regardless of treatment approach.

Periodontitis is a common immune-inflammatory oral disease. Early detection plays an important role in its prevention and progression. Saliva is a reliable medium that mirrors periodontal health and is easily obtainable for identifying periodontal biomarkers in point-of-care diagnostics. The aim of this study is to evaluate the effectiveness of diagnostic salivary tests to determine periodontal status. Whole saliva (stimulated/unstimulated) from twenty healthy and twenty stage III grade B generalized periodontitis patients was tested for lactoferrin, alkaline phosphatase, calcium, density, osmolarity, pH, phosphate, buffer capacity, salivary flow rate and dynamic viscosity. A semi-quantitative urinary strip test was used to evaluate markers of inflammation in saliva (erythrocytes, leukocytes, urobilinogen, nitrite, glucose, bilirubin, and ketones), clinical periodontal parameters and pathogenic bacteria. Concentrations of lactoferrin, hemoglobin, and leukocytes were found to be significantly higher in the stimulated and unstimulated saliva in periodontitis patients compared to healthy patients, whereas alkaline phosphatase levels were higher in unstimulated saliva of periodontitis patients (p < 0.05). Periodontal biomarker analysis using test strips may be considered rapid and easy tool for distinguishing between periodontitis and healthy patients. The increase in lactoferrin, hemoglobin, and leucocytes—determined by strip tests—may provide a non-invasive method of periodontal diagnosis.

Background: Oral preventive measures should be efficient, minimally invasive, and painless. Air-polishing has this potential. As the efficiency and abrasivity of powders are dependent on the amount of powder projected, a better understanding of this characteristic will help us to determine the most effective and least invasive device. Method: A new laboratory set-up was designed using light diffusion to measure powder consumption with high accuracy due to its high sampling rate, even at short time intervals (

This case report describes a rare case of a broken periodontal probe tip and its removal. A male patient presented himself in June 2019 due to a painful tooth in the upper left quadrant. The patient elected treatment in the dental school’s student course. In October 2019, in preparation for full-mouth rehabilitation, a complete diagnostic status was performed, including radiographs. In this context, a metal-dense fragment was identified in the apical region of the (missing) tooth 45. It was diagnosed as the broken tip of a periodontal probe (type AE P OWB). Since a PCP-12 probe is generally used in-house, iatrogenic damage during the initial examination or student course could be excluded a priori. The patient was not able to remember any treatment that could be associated with the instrument’s breaking. Since the probe fragment was palpable and a translocation could not be precluded, the patient agreed to its removal under local anesthesia, after a cone-beam CT. This article describes and discusses this particular case, with special emphasis on iatrogenic instrument fractures and their removal.

This review aimed to systematically compare microbial profiles of peri-implantitis to those of periodontitis and healthy implants. Therefore, an electronic search in five databases was conducted. For inclusion, studies assessing the microbiome of peri-implantitis in otherwise healthy patients were considered. Literature was assessed for consistent evidence of exclusive or predominant peri-implantitis microbiota. Of 158 potentially eligible articles, data of 64 studies on 3730 samples from peri-implant sites were included in this study. Different assessment methods were described in the studies, namely bacterial culture, PCR-based assessment, hybridization techniques, pyrosequencing, and transcriptomic analyses. After analysis of 13 selected culture-dependent studies, no microbial species were found to be specific for peri-implantitis. After assessment of 28 studies using PCR-based methods and a meta-analysis on 19 studies, a higher prevalence of Aggregatibacter actinomycetemcomitans and Prevotella intermedia (log-odds ratio 4.04 and 2.28, respectively) was detected in peri-implantitis biofilms compared with healthy implants. Actinomyces spp., Porphyromonas spp. and Rothia spp. were found in all five pyrosequencing studies in healthy-, periodontitis-, and peri-implantitis samples. In conclusion, the body of evidence does not show a consistent specific profile. Future studies should focus on the assessment of sites with different diagnosis for the same patient, and investigate the complex host-biofilm interaction.

Periodontitis, an inflammatory disease, is caused by biofilms with a mixed microbial etiology and involves the progressive destruction of the tooth-supporting tissues. A rising number of studies investigate the clinical potential of photodynamic therapy (PDT) as an adjunct during active therapy. The aim of the present review was to evaluate the available literature for the in vitro antimicrobial efficacy of photodynamic therapy focusing on the periodontopathogenic bacteria Aggregatibacter actinomycetemcomitans, Porphyromonas gingivalis and Fusobacterium nucleatum. The focused question was: “Is it possible to decrease (at least 3 log steps or 99.9%) or even eliminate bacterial growth by photodynamic therapy in vitro when compared to untreated control groups or control groups treated by placebo?” In general, PDT resulted in a substantial reduction of surviving bacteria. However, not all studies showed the desired reduction or elimination. The ranges of log10-reduction were 0.38 (58%) to a complete eradication (100%) for P. gingivalis, 0.21 (39%) to 100% for A. actinomycetemcomitans and 0.3 (50%) to 100% for F. nucleatum. In conclusion, further and particularly more comparable studies are needed to evaluate if PDT can be clinically successful as an adjuvant in periodontal therapy.

Bone substitute materials have witnessed tremendous development over the past decades and autogenous bone may still be considered the gold standard for many clinicians and clinical approaches in order to rebuild and restore bone defects. However, a plethora of novel xenogenic and synthetic bone substitute materials have been introduced in recent years in the field of bone regeneration. As the development of bone is actually a calcification process within a collagen fiber arrangement, the use of scaffolds in the formation of fibers may offer some advantages, along with additional handling characteristics. This review focuses on material characteristics and degradation behavior of electrospun biodegradable polyester scaffolds. Furthermore, we concentrated on the preclinical in vivo performance with regard to bone regeneration in preclinical studies. The major findings are as follows: Scaffold composition and architecture determine its biological behavior and degradation characteristics; The incorporation of inorganic substances and/or organic substances within composite scaffolds enhances new bone formation; L-poly(lactic acid) and poly(lactic-co-glycolic acid) composite scaffolds, especially when combined with basic substances like hydroxyapatite, tricalcium phosphate or demineralized bone powder, seem not to induce inflammatory tissue reactions in vivo.

This study screened the available evidence for the in vitro antimicrobial efficacy of propolis, a natural herbal resin bee product, against a selection of three bacterial species of relevance to oral diseases. For this purpose, papers dealing with laboratory studies assessing minimum inhibitory concentration (MIC), minimum bactericidal concentrations (MBC) or the agar diffusion method to analyze the antimicrobial properties of propolis on three oral pathogens (S. mutans, P. gingivalis, F. nucleatum) and a yeast (C. albicans) are reviewed. Overall, a positive antimicrobial effect could be shown. However, when compared to the commonly used control substances (e.g., specific antibiotics, antiseptics and antifungals), propolis appeared less effective, depending on the bacterial strain, and required higher concentrations than the control substances, in order to show a measurable effect. Nevertheless, propolis as a natural herbal resin bee product can be considered as a natural antiseptic agent within the range of other herbal products, like sanguinarine. Therefore, it may be a valuable compound of non-synthetic, natural origin for patients seeking complementary agents and alternatives for “hard” chemicals.

After tooth extraction, the alveolar bone undergoes a remodeling process, which leads to horizontal and vertical bone loss. These resorption processes complicate dental rehabilitation, particularly in connection with implants. Various methods of guided bone regeneration (GBR) have been described to retain the original dimension of the bone after extraction. Most procedures use filler materials and membranes to support the buccal plate and soft tissue, to stabilize the coagulum and to prevent epithelial ingrowth. It has also been suggested that resorption of the buccal bundle bone can be avoided by leaving a buccal root segment (socket shield technique) in place, because the biological integrity of the buccal periodontium (bundle bone) remains untouched. This method has also been described in connection with immediate implant placement. The present case report describes three consecutive cases in which a modified method was applied as part of a delayed implantation. The latter was carried out after six months, and during re-entry the new bone formation in the alveolar bone and the residual ridge was clinically evaluated as proof of principle. It was demonstrated that the bone was clinically preserved with this method. Possibilities and limitations are discussed and directions for future research are disclosed.

To assess the remineralizing potential of dentin matrix proteins and enamel matrix derivatives (DMPs and EMDs) after application on artificially induced dentin lesions, given the hypothesis that these materials increase the mineral uptake, binding, and mineralization. Forty-eight caries-free human premolars were used. Teeth were cut, polished, and embedded, leaving an open window on the root surface, of which one-third was covered with a flowable composite to preserve the healthy untreated dentin. Then, samples were demineralized in Buskes solution for 33 days. A micro-CT scan prior to treatment was performed. Next, the samples were randomly allocated into four groups: (A) An untreated negative control (CON), (B) application of porcine dentin matrix proteins (DMP), (C) treatment with enamel matrix derivatives (EMD, Emdogain, Straumann), and (D) amine fluoride application (AMF, Elmex fluid, GABA). All samples were placed in artificial saliva for 21 days. A second micro-CT scan was performed, after which the change in gray scaling within a defined region of interest (0.25 mm3) was analyzed. ANCOVA was applied to discover statistical differences between the different treatments. Both, treatment with AMF; (P = 0.011 versus CON) as well as with DMP (P = 0.043 versus CON) yielded a statistically significant difference compared to the control treatment. EMD treatment was not found to differ (P > 0.05). Mainly the top layer of the defects showed clear signs of remineralization, which was also evident in CON. This study was able to visually confirm the remineralization potential of demineralized dentin especially after DMP application, which, however, did not outperform AMF. Based on this, additional studies combining proteins and fluorides are now warranted and ongoing.

This work compared the assessment of clinically relevant parameters by two-dimensional, that is, full-mouth intraoral radiograph (I-O) and panoramic radiograph (OPT), and three-dimensional, that is, cone beam computed tomography (CBCT), imaging methods. Different radiographic images (CBCT, I-O and OPT) were available for a 53-year-old female patient with dental and periodontal problems. A total of 14 dental and periodontal parameters were assessed by two independent examiners and compared among the three radiographic imaging modalities. For 10 parameters (71%), the CBCT images were superior to both I-O and OPT images. In contrast, CBCT demonstrated an inferior performance compared to I-O and OPT in the assessment of caries and dental restorations. Compared to OPT, I-O provided more clinically relevant findings for 10 out of 14 parameters (71%). Agreement between I-O and OPT was found with respect to dehiscence, fenestration, the number of bone walls and the root canal cross-section. Differences between the radiographic images were more likely to be detected when maxillary teeth rather than mandibular teeth were assessed with regard to furcation involvement, root proximity and root fusion.

Improving soft tissue attachment to implant abutments is a crucial factor for enduring health and maintenance of soft peri-implant tissue health. In this in vitro study we aimed to compare the biocompatibility of three different abutment surfaces: titanium, zirconia and modified polyetheretherketone (PEEK). Surface topography, roughness and wettability were investigated with scanning electron microscopy, profilometer and contact angle meter, respectively. Human gingival epithelial keratinocytes were examined for viability, morphology, proliferation and migration by using tetrazolium salt colorimetric assay, scanning electron microscopy imaging, immunofluorescence bromodeoxyuridine analysis and scratch wound healing assays. Roughness measurements revealed differences between the investigated surfaces. Keratinocytes cultured on all examined surfaces indicated adhesion and attachment by means of scanning electron microscopy imaging. Cell viability assays showed no significant differences between the groups (p > 0.05). The modified PEEK surface similarly improved surface roughness in comparison to titanium and zirconia, which resulted in greater and equivalent cell proliferation and migration. The study methodology showed here may emphasize the importance of cell interactions with different abutment materials, which in part increases the changes of implant success. PEEK, titanium and zirconia surface types used in this study showed mostly similar epithelial biological responses.

ObjectiveTo investigate the microbial adherence and colonization of a polyspecies biofilm on 7 differently processed titanium surfaces.Material and MethodsSix-species biofilms were formed anaerobically on 5-mm-diameter sterilized, saliva-preconditioned titanium discs. Material surfaces used were either machined, stained, acid-etched or sandblasted/acid-etched (SLA). Samples of the latter two materials were also provided in a chemically modified form, with increased wettability characteristics. Surface roughness and contact angles of all materials were determined. The discs were then incubated anaerobically for up to 16.5 h. Initial microbial adherence was evaluated after 20 min incubation and further colonization after 2, 4, 8, and 16.5 h using non-selective and selective culture techniques. Results at different time points were compared using ANOVA and Scheffé post hoc analysis.ResultsThe mean differences in microorganisms colonizing after the first 20 min were in a very narrow range (4.5 to 4.8 log CFU). At up to 16.5 h, the modified SLA surface exhibited the highest values for colonization (6.9±0.2 log CFU, p

Objective To investigate the microbial adherence and colonization of a polyspecies biofilm on 7 differently processed titanium surfaces. Material and Methods Six-species biofilms were formed anaerobically on 5-mm-diameter sterilized, saliva-preconditioned titanium discs. Material surfaces used were either machined, stained, acid-etched or sandblasted/acid-etched (SLA). Samples of the latter two materials were also provided in a chemically modified form, with increased wettability characteristics. Surface roughness and contact angles of all materials were determined. The discs were then incubated anaerobically for up to 16.5 h. Initial microbial adherence was evaluated after 20 min incubation and further colonization after 2, 4, 8, and 16.5 h using non-selective and selective culture techniques. Results at different time points were compared using ANOVA and Scheffé post hoc analysis. Results The mean differences in microorganisms colonizing after the first 20 min were in a very narrow range (4.5 to 4.8 log CFU). At up to 16.5 h, the modified SLA surface exhibited the highest values for colonization (6.9±0.2 log CFU, p

On account of its proven clinical efficacy, the combination of systemically administered amoxicillin and metronidazole is frequently adjuncted to non-operative periodontal therapy and well documented. Potential drawbacks of this regimen, e.g., side effects and problems with the compliance, led to an ongoing search for alternatives. Azithromycin, an antibiotic extensively used in general medicine, has recently found its niche in periodontal therapy as well. This systematic review aimed to analyze the in vitro antimicrobial efficacy of amoxicillin plus metronidazole versus azithromycin. For this purpose, a systematic literature search was performed, and studies published up to 29 March 2018 referenced in Medline, Embase, Cochrane, and Biosis were independently screened by two authors. An additional hand search was performed and studies focusing on the evaluation of in vitro antimicrobial efficacy of amoxicillin + metronidazole or azithromycin on bacteria from the subgingival biofilm were included. English and German language research reports were considered. From 71 identified articles, only three articles were eligible for inclusion. These studies showed heterogeneity in terms of analytical methods and strains explored. However, all studies used multispecies biofilm models for analysis of the antimicrobial activity. Unanimously, studies reported on more pronounced antimicrobial effects when applying the combination of amoxicillin + metronidazole, compared to azithromycin. Based on the few studies available, the combination of amoxicillin + metronidazole seemed to display higher antimicrobial efficacy in vitro than azithromycin.

Tooth extraction causes vertical and horizontal alveolar bone loss and consequent remodeling. Several methods have been introduced in terms of so-called “ridge preservation” techniques, which mostly resemble guided bone regenerative (GBR) procedures using filler materials and membranes in order to stabilize the respective sites. This conceptual case report describes a novel approach using a degradable polylactic acid membrane covered with a collagen matrix, which aims to reshape the resorbed alveolar wall and thereby to stabilize the soft tissues during matrix formation and socket mineralization. Clinical re-entry, radiographic (CBCT) and histologic evaluation proved adequate for osteoneogenesis despite an unfavorable initial situation: An implant could be ideally placed, which was circumferentially covered by bone. This minimally invasive method could offer a new method to approach socket preservation without using filler materials and coverage of the socket entrance. However, more controlled research on this topic is needed.

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This study investigates the retention load (RL) between ZrO2 primary crowns and secondary polyetheretherketone (PEEK) crowns made by different fabrication methods with three different tapers. Standardized primary ZrO2 crowns were fabricated with three different tapers: 0°, 1°, and 2° (n = 10/group). Ten secondary crowns were fabricated (i) milled from breCam BioHPP blanks (PM); (ii) pressed from industrially fabricated PEEK pellets (PP) (BioHPP Pellet); or (iii) pressed from granular PEEK (PG) (BioHPP Granulat). One calibrated operator adjusted all crowns. In total, the RL of 90 secondary crowns were measured in pull-off tests at 50 mm/min, and each specimen was tested 20 times. Two- and one-way ANOVAs followed by a Scheffé’s post-hoc test were used for data analysis (p < 0.05). Within crowns with a 0° taper, the PP group showed significantly higher retention load values compared with the other groups. Among the 1° taper, the PM group presented significantly lower retention loads than the PP group. However, the pressing type had no impact on the results. Within the 2° taper, the fabrication method had no influence on the RL. Within the PM group, the 2° taper showed significantly higher retention load compared with the 1° taper. The taper with 0° was in the same range value as the 1° and 2° tapers. No impact of the taper on the retention value was observed between the PP groups. Within the PG groups, the 0° taper presented significantly lower RL than the 1° taper, whereas the 2° taper showed no differences. The fabrication method of the secondary PEEK crowns and taper angles showed no consistent effect within all tested groups.

This study investigated the colorimetric properties of different veneering materials on core materials. Standardized specimens (10 mm × 10 mm × 1.5 mm) reflecting four core (polyetheretherketone (PEEK), zirconia (ZrO2), cobalt–chromium–molybdenum alloy (CoCrMo), and titanium oxide (TiO2); thickness: 1.5 mm) and veneering materials (VITA Mark II, IPS e.max CAD, LAVA Ultimate and VITA Enamic, all in shade A3; thickness: 0.5, 1.0, 1.5 and 2 mm, respectively) were fabricated. Specimens were superimposed to assemblies, and the color was determined with a spectrophotometer (CieLab-System) or a chair-side color measurement device (VITA EasyShade), respectively. Data were analyzed using three-, two-, and one-way ANOVA, a Chi2-test, and a Wilson approach (p < 0.05). The measurements with EasyShade showed A2 for VITA Mark II, A3.5 for VITA Enamic, B2 for LAVA Ultimate, and B3 for IPS e.max CAD. LabE-values showed significant differences between the tested veneering materials (p < 0.001). CieLab-System and VITA EasyShade parameters of the different assemblies showed a significant impact of core (p < 0.001), veneering material (p < 0.001), and thickness of the veneering material (p < 0.001). PEEK as core material showed comparable outcomes as compared to ZrO2 and CoCrMo, with respect to CieLab-System parameters for each veneering material. The relative frequency of the measured VITA EasyShade parameters regarding PEEK cores also showed comparable results as compared to the gold standard CoCrMo, regardless of the veneering material used.

This study aimed to examine and compare the retention load values (RL) of different telescopic crown assemblies (Y-TZP and CoCr primary crowns with electroformed and Y-TZP secondary crowns each) with three different taper angles (0°, 1° and 2°). Thirty Y-TZP primary crowns with electroformed gold copings (Z/G group) and Y-TZP secondary crowns (Z/Z group) and 30 CoCr primary crowns with electroformed gold copings (C/G group) and Y-TZP secondary crowns (C/Z group), each with taper angles of 0°, 1° and 2°, were fabricated, respectively. With the exception of the electroformed gold copings, all specimens were Computer-Aided-Design/Computer-Aided-Manufacturing (CAD/CAM)-milled, then sintered and afterwards manually adapted. In order to stabilize the gold copings, they were fixed in a tertiary structure. The secondary crowns were constructed with a hook, which ensured self-alignment with an upper chain. Afterwards, 20 pull-off test cycles were performed in a universal testing machine under artificial saliva and after weighing the secondary crowns with a 5 kg object for 20 s. Data were analyzed by one-way and two-way Analysis of Variance (ANOVA). C/Z with 1° showed higher (p = 0.009) RL than 0° and 2° tapers. C/G at 1° also showed higher (p = 0.001) RL than at tapers of 0° and 2°. Z/G and C/G at 0° showed lower RL than Z/Z and C/Z (p < 0.001). Primary crowns had no impact on the 0° group. Z/G showed lower RL as compared to C/Z within the 1° group (p = 0.007) and Z/Z in the 2° group (p = 0.006). The primary crown material had no influence on RL. Electroformed copings showed lower RL. Further investigations for 1° as well as for the long-term performance after thermomechanical aging are necessary.

In prosthetic dentistry, double crown systems have proved their suitability as retainers for removable partial dentures. However, investigations in this context, regarding polyetheretherketone, are scarce. Therefore, the aim of this study was to test the retention force (RF) between polyetheretherketone (PEEK) primary and cobalt-chromium (CoCr), zirconia (ZrO2) and galvanic (GAL) secondary crowns with three different tapers. Primary PEEK-crowns were milled with the tapers 0°, 1°, and 2° (n = 10/taper, respectively). Afterwards, 90 secondary crowns were fabricated: (i) 30 CoCr-crowns milled from Ceramill Sintron (AmannGirrbach, Koblach, Austria) (n = 10/taper), (ii) 30 ZrO2-crowns milled from Ceramill ZI (AmannGirrbach, Koblach, Austria) (n = 10/taper), and (iii) 30 GAL-crowns made using electroforming (n = 10/taper). RF was measured in a pull-off test (20 pull-offs/specimen) and data were analyzed using 2-/1-way Analysis of Variance (ANOVA) followed by the Tukey-Honestly Significant Difference (HSD) post hoc test and linear regression analyses (p < 0.05). The measured mean RF values ranged between 9.6 and 38.2 N. With regard to the 0°, 1°, and 2° tapered crowns, no statistically significant differences between CoCr and ZrO2 were observed (p > 0.141). At 0° taper, no differences in retention forces between GAL, CrCr, and ZrO2 crowns were found (p = 0.075). However, at 1° and 2° taper, lower RF for GAL-crowns were observed (p < 0.009, p < 0.001, respectively). According to this laboratory study, PEEK might be a suitable material for primary crowns, regardless of the taper and the material of secondary crown. Long-term results, however, are still necessary.