Music Community, Improvisation, and Social Technologies in COVID-Era Música Huasteca.

This article examines two interrelated aspects of Mexican regional music response to the coronavirus crisis in the música huasteca community: the growth of interactive huapango livestreams as a preexisting but newly significant space for informal community gathering and cultural participation at the onset of the coronavirus pandemic, and the composition of original verses by son huasteco performers addressing the pandemic. Both the livestreams and the newly created coronavirus disease (COVID) verses reflect critical improvisatory approaches to the pandemic in música huasteca. The interactive livestreams signaled an ad hoc community infrastructure facilitated by social media and an emerging community space fostered by Do-It-Yourself (DIY) activists. Improvised COVID-related verses presented resonant local and regional themes as a community response to a global crisis. Digital ethnography conducted since March 2020 revealed a regional burst of musical creativity coupled with DIY intentionality, a leveling of access to virtual community spaces, and enhanced digital intimacies established across a wide cultural diaspora in Mexico and the USA. These responses were musically, poetically, and organizationally improvisational, as was the overall outpouring of the son huasteco music inspired by the coronavirus outbreak. Son huasteco is a folk music tradition from the Huasteca, a geo-cultural region spanning the intersection of six states in central Mexico. This study examines a selection of musical responses by discussing improvisational examples in both Spanish and the indigenous language Nahuatl, and in the virtual musical communities of the Huasteca migrant diaspora in digital events such as "Encuentro Virtual de Tríos Huastecos," the "Huapangos Sin Fronteras" festival and competition, and in the nightly gatherings on social media platforms developed during the pandemic to sustain the Huastecan cultural expression. These phenomena have served as vibrant points of transnational connection and identity in a time where physical gatherings were untenable.

Polymer-infiltrated ceramic CAD/CAM inlays and partial coverage restorations: 3-year results of a prospective clinical study over 5 years.

OBJECTIVE: The aim of this prospective clinical 5-year study was to evaluate the long-term behavior of monolithic computer-aided design and computer-aided manufacturing (CAD/CAM)-fabricated minimally invasive polymer-infiltrated ceramic network (PICN) inlays and partial coverage restorations (PCR). MATERIAL AND METHODS: Posterior teeth of 47 patients were restored with 103 restorations (45 inlays, 58 PCRs). After defect-oriented preparations, monolithic PICN restorations of VITA Enamic were fabricated with a CAD/CAM system (inEoS blue/CEREC inLab MCXL) and adhesively bonded (Variolink II). Clinical reevaluations were so far performed at baseline and 6, 12, 24, and 36 months after insertion according to modified United States Public Health Service (USPHS) criteria. Absolute failures were demonstrated by Kaplan-Meier survival rate and relative failures by Kaplan-Meier success rate. A logistic regression model was adjusted for modified USPHS criteria to investigate time and restoration effects (p < 0.05). RESULTS: After an observation time of 3 years, survival rates were 97.4% for inlays and 95.6% for PCRs. Three restorations had to be replaced due to clinically unacceptable fractures. Secondary caries and debonding were not observed. The 3-year Kaplan-Meier success rate was 84.8% for inlays and 82.4% for PCRs. The decrease in marginal adaption (p = 0.0005), increase in marginal discoloration (p < 0.0001), and surface roughness (p = 0.0005) over time were significant. Color match and anatomic form were excellent. No significant differences were found between both types of restorations for survival (p = 0.716) and success rate (p = 0.431). CONCLUSIONS: Minimally invasive PICN restorations showed a favorable clinical performance over an observation period of 36 months. However, clinical long-term data have to be awaited. CLINICAL RELEVANCE: PICN restorations are a suitable treatment option for posterior inlays and PCRs.

VISLISI trial, a prospective clinical study allowing identification of a new metalloprotease and putative virulence factor from Staphylococcus lugdunensis.

OBJECTIVE: Staphylococcus lugdunensis is a coagulase-negative staphylococcus that displays an unusually high virulence rate close to that of Staphylococcus aureus. It also shares phenotypic properties with S. aureus and several studies found putative virulence factors. The objective of the study was to describe the clinical manifestations of S. lugdunensis infections and investigate putative virulence factors. METHOD: We conducted a prospective study from November 2013 to March 2016 at the University Hospital of Strasbourg. Putative virulence factors were investigated by clumping factor detection, screening for proteolytic activity, and sequence analysis using tandem nano-liquid chromatography-mass spectrometry. RESULTS: In total, 347 positive samples for S. lugdunensis were collected, of which 129 (37.2%) were from confirmed cases of S. lugdunensis infection. Eighty-one of these 129 patients were included in the study. Bone and prosthetic joints (PJI) were the most frequent sites of infection (n=28; 34.6%) followed by skin and soft tissues (n=23; 28.4%). We identified and purified a novel protease secreted by 50 samples (61.7%), most frequently associated with samples from deep infections and PJI (pr 0.97 and pr 0.91, respectively). Protease peptide sequencing by nano-liquid chromatography-mass spectrometry revealed a novel protease bearing 62.42% identity with ShpI, a metalloprotease secreted by Staphylococcus hyicus. CONCLUSION: This study confirms the pathogenicity of S. lugdunensis, particularly in bone and PJI. We also identified a novel metalloprotease called lugdulysin that may contribute to virulence.

Management of shortened dental arches and periodontal health: 5-year results of a randomised trial.

In a multicentre randomised trial (German Research Association, grants DFG WA 831/2-1 to 2-6, WO 677/2-1.1 to 2-2.1.; controlled-trials.com ISRCTN97265367), patients with complete molar loss in one jaw received either a partial removable dental prosthesis (PRDP) with precision attachments or treatment according to the SDA concept aiming at pre-molar occlusion. The objective of this current analysis was to evaluate the influence of different treatments on periodontal health. Linear mixed regression models were fitted to quantify the differences between the treatment groups. The assessment at 5 years encompassed 59 patients (PRDP group) and 46 patients (SDA group). For the distal measuring sites of the posterior-most teeth of the study jaw, significant differences were found for the plaque index according to Silness and Löe, vertical clinical attachment loss (CAL-V), probing pocket depth (PPD) and bleeding on probing. These differences were small and showed a slightly more unfavourable course in the PRDP group. With CAL-V and PPD, significant differences were also found for the study jaw as a whole. For CAL-V, the estimated group differences over 5 years amounted to 0.27 mm (95% CI 0.05; 0.48; P = 0.016) for the study jaw and 0.25 mm (95% CI 0.05; 0.45; P = 0.014) for the distal sites of the posterior-most teeth. The respective values for PPD were 0.22 mm (95% CI 0.03; 0.41; P = 0.023) and 0.32 mm (95% CI 0.13; 0.5; P = 0.001). It can be concluded that even in a well-maintained.patient group statistically significant although minor detrimental effects of PRDPs on periodontal health are measurable.

Outcomes of implants placed with three different flapless surgical procedures: a systematic review.

The aim of this systematic review was to evaluate the outcomes of flapless surgery for implants placed using either free-hand or guided (with or without 3D navigation) surgical methods. Literature searches were conducted to collect information on survival rate, marginal bone loss, and complications of implants placed with such surgeries. Twenty-three clinical studies with a minimum of 1 year follow-up time were finally selected and reviewed. Free-hand flapless surgery demonstrated survival rates between 98.3% and 100% and mean marginal bone loss between 0.09 and 1.40 mm at 1-4 years after implant insertion. Flapless guided surgery without 3D navigation showed survival rates between 91% and 100% and mean marginal bone loss of 0.89 mm after an observation period of 2-10 years. The survival rates and mean marginal bone loss for implants placed with 3D guided flapless surgery were 89-100% and 0.55-2.6mm, respectively, at 1-5 years after implant insertion. In 17 studies, surgical and technical complications such as bone perforation, fracture of the surgical guide, and fracture of the provisional prosthesis were reported. However, none of the identified methods has demonstrated advantages over the others. Further studies are needed to confirm the predictability and effectiveness of 3D navigation techniques.

Five-year results of a prospective randomised controlled clinical trial of posterior computer-aided design-computer-aided manufacturing ZrSiO4 -ceramic crowns.

The aim of this prospective randomised controlled clinical trial was to evaluate the clinical outcome of shrinkage-free ZrSiO4 -ceramic full-coverage crowns on premolars and molars in comparison with conventional gold crowns over a 5-year period. Two hundred and twenty-three patients were included and randomly divided into two treatment groups. One hundred and twenty-three patients were restored with 123 ZrSiO4 -ceramic crowns, and 100 patients received 100 gold crowns, which served as the control. All crowns were conventionally cemented with glass-ionomer cement. After an observation period of 6, 12, 24, 36, 48 and 60 months, the survival probability (Kaplan-Meier) for the shrinkage-free ZrSiO4 -ceramic crowns was 98·3%, 92·0%, 84·7%, 79% and 73·2% and for the gold crowns, 99%, 97·9%, 95·7%, 94·6% and 92·3%, respectively. The difference between the test and control group was statistically significant (P = 0·0027). The gold crowns showed a better marginal integrity with less marginal discoloration than the ceramic crowns. The most common failure in the ceramic crown group was fracture of the crown. The 60-month results of this prospective randomised controlled clinical trial suggest that the use of these shrinkage-free ZrSiO4 -ceramic crowns in posterior tooth restorations cannot be recommended.

Success rates of prosthetic restorations on endodontically treated teeth; a systematic review after 6 years.

The aims of this systematic review were to investigate the success rates of prosthetic restorations on endodontically treated teeth and their manner of failure. PubMed and hand literature searches were conducted on studies published until June 2012. Only clinical studies on human subjects referring to the success rates of prosthetic restorations on endodontically treated teeth with a follow-up period of at least 6 years were reviewed. A total of four studies were identified. Meta-analysis showed the success rate to be 92% (CI 82-98%) for single crowns on endodontically treated teeth and 79% (72-86%) for fixed dental prostheses. Only one study reported on removable dental prostheses with a success rate of 66%. Single crowns on teeth restored without posts demonstrated a success rate of 94% (CI 84-99%), whereas where posts were placed, the success rate was lower (92% CI 82-98%). Single crowns over cast post-and-cores and prefabricated posts showed success rates of 93% (CI 82-99%) and 94% (CI 90-97%), respectively; both differences were not statistically significant (significance level of 5%). The most common reason for failure was post-debonding. Single crowns seem to be the best treatment modality for endodontically treated teeth. However, due to the low number of studies included and their design, the results of this systematic review should be interpreted with caution. Further clinical studies are needed to provide high-quality evidence on the topic.

Effect of veneering technique on the fracture resistance of zirconia fixed dental prostheses.

To compare the fracture resistance of zirconia 3-unit posterior fixed dental prostheses (FDPs) frameworks veneered with different veneering materials and techniques before and after artificial ageing. Forty-eight zirconia 3-unit FDPs, representing a missing first molar, were adhesively cemented on human teeth. The zirconia frameworks were randomly distributed according to the veneering materials and techniques into three groups, each containing 16 samples: group LV (layering technique/Vintage ZR), group LZ (layering technique/ZIROX) and group PP (CAD/CAM and press-over techniques/PressXZr). Half of each group was artificially aged through dynamic loading and thermocycling to simulate 5 years of clinical service. Afterwards, all specimens were tested for fracture resistance using compressive load. An analysis of variance (anova) was used to assess the effect of veneering ceramic and artificial ageing on fracture resistance (P < 0·05). Except for one minor cohesive chipping in group LV1, all specimens survived artificial ageing. The mean fracture resistance values (in Newton) of different non-aged (± s.d.)/aged (± s.d.) groups were as follows: LV0 2034 (± 401)/LV1 1625 (± 291); LZ0 2373 (± 718)/LZ1 1769 (± 136); and PP0 1959 (± 453)/PP1 1897 (± 329). Artificial ageing significantly reduced the fracture resistance in groups veneered with the layering technique (P < 0·05), whereas no significant effect was found in specimens veneered with the CAD/CAM and press-over techniques. All tested systems have the potential to withstand occlusal forces applied in the posterior region. The combination of the CAD/CAM and press-over techniques for the veneering process improved the overall stability after artificial ageing, relative to the layering technique.

Prognosis of immediately loaded implants and their restorations: a systematic literature review.

Immediate loading of oral implants has become popular because of the increasing demands of a shortened treatment time. This literature review evaluates the prognosis of immediately loaded implants and their restorations with immediate or delayed implant placement. Special attention was given to the impact of type of jaw, bone quality, implant length, time of implant placement and type of restoration. An electronic (PubMed) and a manual search in relevant journals were conducted until February 2012. Only publications in English, in peer-reviewed journals, were considered. Nine studies met the inclusion criteria: five studies dealt with fixed restorations, two studies with removable rehabilitation of edentulous jaws and two studies dealt with partially edentulous patients. Implant survival rates ranged from 95·8% to 100%, implant success rates in the treatment for the mandible from 79% to 100% and restoration survival rates for both jaws from 96·4% to 100%. Within the limits of this review, appropriate patient selection, primary implant stability, splinting of implants and the expertise of surgeons seem to be important for the prognosis of immediately loaded implants and their restorations. Good bone quality and use of long implants appear to play a role. However, careful interpretation is required because conclusions are based on articles with low level of evidence. While immediate loading of oral implants in the mandible shows encouraging and predictable results, further multicenter randomised controlled clinical trials with sufficient statistical power are needed to examine (i) the outcome of immediately loaded implants in the maxilla and (ii) the outcome of immediate loading of immediately placed implants.

Prognosis of implants and fixed restorations after lateral sinus elevation: a literature review.

Aim of this review was to investigate the prognosis of implants inserted in augmented sinuses and fixed restorations supported by these implants. Special attention was given to the impact of grafting material, time of implant placement, residual bone height and type of fixed restoration. An electronic search in PubMed, the German database medpilot and the Cochrane Library was executed followed by supplementary manual search in relevant journals. The search was limited to human studies published up to November 2010. Only publications in English and German, in peer-reviewed journals, were considered. After the initial search and application of selection criteria on titles and abstracts, a full-text analysis of 67 articles was performed, out of which six prospective and three retrospective studies were finally included in the review. The heterogeneous properties of the identified articles did not allow systematic analysis of the data. Success rates of implants were between 96·3% and 100%, survival rates were between 75% and 100%, and survival rates of single crowns, splinted crowns and fixed partial dentures ranged between 96·4% and 100% after a follow-up of 12-101 months. Within the limits of this review, the prognosis of implants and fixed restorations seemed not to be influenced by the type of restorations, graft material, residual bone height and time of implant placement. However, conclusions of this review are based on studies with low level of evidence; therefore, careful interpretation is required. Multicentre randomised controlled clinical trials with sufficient statistical power concentrating on few factors are needed to reach sound conclusions.

Prosthetic outcome of cement-retained implant-supported fixed dental restorations: a systematic review.

The aim of the article is to assess the current literature in terms of the prosthetic outcome of cement-retained implant-supported fixed restorations, as well as to determine the type of cement that can be recommended for clinical application. A review of the literature published up to May 2010 was conducted to identify clinical studies about cement-retained implant-supported fixed restorations. The search strategy applied was a combination of MeSH terms and free text words, including the following keywords: implants, implant-supported fixed dental prostheses (FDPs), bridges, implant-supported single crowns (SCs), cement-retained, cement fixation, cement, cementation, cement failure, retention, and loss of retention, technical complications, mechanical complications, prosthetic complication, retrievability and maintenance. Thirty-two studies met the inclusion criteria. The studies were divided into two categories: 15 short-term clinical studies with an observation period of less than 5 years, and 17 long-term clinical studies with an observation period of 5 years and more. The most common technical complications of cement-retained implant-supported fixed restorations were loss of retention, chipping and abutment screw loosening. The results of the current review revealed no guidelines about cement or cementation procedures. It may be stated that despite the questionable retrievability of cement-retained implant-supported fixed restorations, this treatment modality is a reliable and effective option, especially for implant-supported SCs and short-span FDPs. The literature does not provide accurate information about the clinical outcome of cement-retained implant-supported fixed restorations nor about the ideal type of cement that facilitates stability and maintains retrievability. Standardised randomised clinical trials will provide valuable information to this issue.

The dental patient on oral anticoagulant medication: a literature review.

Specific diseases and medications may considerably influence the delivery of oral care and the course of dental therapy. The purpose of this literature review is to examine the relationship between oral anticoagulant medication and dental treatment. Electronic and manual searches were conducted for clinical studies in the English literature for the years 1988-2010. The review process provided a total of 110 pertinent literature references, out of which 38 studies dealt with oral anticoagulants and dental treatment. Different treatment strategies relative to dental periprocedural anticoagulation regimens have been identified, and their accompanying thromboembolic and bleeding risks are being presented and discussed. Regarding to what extent a safe and successful dental treatment in patients on anticoagulant medication is feasible, the level of evidence is lacking. Until high-level data are provided, an individualised treatment approach after consultation with the physician of the patient is highly recommended.

A reinvestigation provides no evidence for sugar residues on structural proteins of poleroviruses and argues against a role for glycosylation of virus structural proteins in aphid transmission.

Poleroviruses are strictly transmitted by aphids. Glycosylation of Turnip yellows virus (TuYV) was previously reported and this modification was supposed to be required for aphid transmission. Using different approaches based on (i) a lectin-binding assay, (ii) use of specific complex glycan antibodies and (iii) mass spectrometry, we found no evidence that the structural proteins of TuYV and Cucurbit aphid-borne yellow virus (CABYV) carry glycan residues. Moreover, mutation of each of the four potential N-glycosylation sites of the structural protein sequences of CABYV indicated that, unless more than one site on the structural protein is glycosylated, N-glycosylation is not involved in aphid transmission. These results did not corroborate the previous hypothesis for the role of glycosylation in aphid transmission. They, however, revealed the presence of a glycosylated plant protein in purified polerovirus suspensions, whose function in aphid transmission should be further investigated.

Results of a prospective randomized controlled trial of posterior ZrSiO(4)-ceramic crowns.

The aim of this randomized controlled clinical trial was to evaluate over a 5-year period, the clinical outcome of shrinkage-free ZrSiO(4)-ceramic (KaVo Everest HPC) full coverage crowns on posterior teeth in comparison with conventional gold crowns that served as the control. This study reports results of a 5-year study protocol up to 24 months. Patients totalling 224 were randomly divided into two treatment groups. Of these, 123 patients were restored with 123 Everest HPC crowns, fabricated by the Kavo Everest computer-aided manufacturing (CAM) procedure and 101 patients received 101 gold crowns, but two were excluded from analysis. All crowns were conventionally cemented with glass-ionomer cement. After an observation period of 6, 12 and 24 months, the prospective survival rates (Kaplan-Meier) for the KaVo Everest HPC crowns were 97.9%, 95.1% and 89.8% and for the gold crowns 100%, 94.8% and 92.7%, respectively. There were no significant differences between the two groups (P = 0.2). The 1-year failure rates were 4.9% for the KaVo Everest HPC crowns and 5.2% for the gold crowns. The 1-year cumulative risks for loss of vitality, secondary caries, fractures, loss of crown and extraction of abutment of the analyzed abutments (88) were 8.9%, 0%, 0%, 1.1% and 1.1%, respectively, for the gold crowns and 2.8%, 0%, 4.7%, 0% and 0.9%, respectively, for the ceramic crowns (107 analyzed abutments). No perfect marginal fit was shown by 49.5% of the evaluated ceramic crowns and 26.1% of the gold crowns. Only 1.9% of the KaVo Everest HPC crowns had a marginal crevice. In conclusion, Everest HPC crowns with an adequate occlusal tooth reduction of >1.5 mm are suitable for posterior restorations, but the marginal fit shows a potential for improvement.

Chfr interacts and colocalizes with TCTP to the mitotic spindle.

Chfr is a checkpoint protein that plays an important function in cell cycle progression and tumor suppression, although its exact role and regulation are unclear. Previous studies have utilized overexpression of Chfr to determine the signaling pathway of this protein in vivo. In this study, we demonstrate, by using three different antibodies against Chfr, that the endogenous and highly overexpressed ectopic Chfr protein is localized and regulated differently in cells. Endogenous and lowly expressed ectopic Chfr are cytoplasmic and localize to the spindle during mitosis. Higher expression of ectopic Chfr correlates with a shift in the localization of this protein to the nucleus/PML bodies, and with a block of cell proliferation. In addition, endogenous and lowly expressed ectopic Chfr is stable throughout the cell cycle, whereas when highly expressed, ectopic Chfr is actively degraded during S-G2/M phases in an autoubiquitination and proteasome-dependent manner. A two-hybrid screen identified TCTP as a possible Chfr-interacting partner. Biochemical analysis with the endogenous proteins confirmed this interaction and identified beta-tubulin as an additional partner for Chfr, supporting the mitotic spindle localization of Chfr. The Chfr-TCTP interaction was stable throughout the cell cycle, but it could be diminished by the complete depolymerization of the microtubules, providing a possible mechanism where Chfr could be the sensor that detects microtubule disruption and then activates the prophase checkpoint.

Dental occlusion: a critical reflection on past, present and future concepts.

For nearly a century, the diversity of concepts about 'normal' and 'ideal' dental occlusal relationships has led to confusion in trying to describe the occlusion of any individual patient. In addition, a similar controversy arises when trying to formulate treatment plans for patients who need extensive dental restorations or orthodontic treatment. And finally, the application of occlusal concepts to patients with temporomandibular pain and dysfunction has created a third area of debate. Over the past few decades, however, an appreciable part of the tenacious dogmatic heritage of this topic has been challenged. As a result, the acceptance of morphological and functional variability of the stomatognathic system has gained increasing support, and this change has important consequences for modern dental practice. In this article, the past, present and future of the subject of occlusion will be considered.

ZrO2 three-unit fixed partial dentures: comparison of failure load before and after exposure to a mastication simulator.

This study evaluated the failure load of different zirconia-based all-ceramic fixed partial dentures (FPD) before and after artificial aging. Forty-eight zirconia frameworks for three-unit FPDs were fabricated using different manufacturing systems [(DCS), Procera (Nobel Biocare) and Cerec inLab (Sirona)], veneered using Vita VM9 (Vita Zahnfabrik) opaque ceramic and conventionally cemented on human teeth. The restorations were divided according to the system used for manufacturing the frameworks into three groups of 16 specimens each (DCS, Procera and Vita YZ-Cerec). Half of each group was artificially aged through dynamic loading and thermal cycling, whereas, the other half was not subjected to artificial aging. Subsequently, all specimens were loaded occlusally until fracture occurred using a universal testing machine. Pair-wise Wilcoxon rank tests were performed to test for differences in failure loads at a statistical significance level of 0.05. All specimens subjected to artificial aging survived with no failures. The median (IQR=x0.25-x0.75) failure loads (N) before and after artificial aging were, respectively, as follows: group DCS, 2131 (1948-2239) and 1797 (1590-2074); group Procera, 1684 (1615-1873) and 1394 (1275-1495); and group Vita YZ-Cerec, 1845 (1621-1923) and 1625 (1521-1747). No significant differences were found for comparisons between different groups before artificial aging. After artificial aging, group Procera showed significantly smaller values than group DCS (P=0.042). All tested restorations have the potential to withstand occlusal forces applied in the posterior region and can therefore represent interesting alternatives to replace metal-ceramic restorations. Further assessments are needed before recommending these restorations for daily practice.

Material characteristics of a novel shrinkage-free ZrSiO(4) ceramic for the fabrication of posterior crowns.

OBJECTIVE: To confirm the clinical applicability of a novel ZrSiO(4) (zircon) based shrinkage-free ceramic material, the flexural strength, fracture toughness and chemical solubility were tested. In addition, the fracture load of full crowns made from this material was tested after cyclic thermomechanical loading. METHODS: Flexural strength of 12 specimens was measured using a biaxial bending test. Fracture toughness was measured using 10 slotted box shaped specimens. The specimens were fractured using a universal testing machine; fracture loads were recorded. A chemical solubility test was performed in accordance with ISO norm 6872. Additionally, 32 ZrSiO(4) all-ceramic crowns were fabricated on extracted caries-free human molars. Sixteen Empress 2 and 16 PFM crowns served as a reference control. After artificial aging of 1.2 million cycles in the chewing simulator, the survival rate of the crowns was determined. The fracture load of all surviving specimens was obtained by loading the crowns until fracture in a universal testing machine. RESULTS: A flexural strength of 328MPa was found. The fracture toughness of the ZrSiO(4) ceramic was 5.16MPam(0.5). The chemical solubility amounted to 7.2microg/cm(2). All specimens survived the chewing simulation (survival rate: 100%); no crowns had to be re-cemented. A mean fracture strength of 1790N was found for Everest HPC for Empress 2 crowns, 1715N for Empress 2 crowns and 2416N for PFM crowns. Fracture loads of PFM crowns were significantly higher than for Empress 2 crowns (P=0.032) as well as ZrSiO(4)-crowns (P=0.007). There was no significant difference between ZrSiO(4)-crowns and Empress 2 crowns (P=0.743). SIGNIFICANCE: At the present stage, Everest HPC can be recommended for the fabrication of single crowns as an alternative to conventional PFM and other all-ceramic crowns, because its fracture strength exceeds average masticatory forces in the posterior region.

Fracture load and marginal fit of shrinkage-free ZrSiO4 all-ceramic crowns after chewing simulation.

The aim of this in vitro study was to evaluate the fracture load and marginal accuracy of crowns made from a shrinkage-free ZrSiO4 ceramic cemented with glass-ionomer or composite cement after chewing simulation. Thirty-two human mandibular molars were randomly divided into two groups. All teeth were prepared for and restored with shrinkage-free ZrSiO4 ceramic crowns (Everest HPC, KaVo). The crowns of group A (N = 16) were luted to the teeth using KetacCem and group B (N = 16) were adhesively cemented using Panavia21EX. Measurements of the marginal accuracy before and after cementation were made using replicas and an image analysis system. All specimens were exposed to 1.2 million cycles of thermo-mechanical fatigue in a chewing simulator. Surviving specimens were subsequently loaded until fracture in a static testing device. Fracture loads (N) were recorded. All specimens survived chewing simulation. The mean fracture loads (+/-s.d.) were Group A, 1622 N (+/-433); group B, 1957 N (+/-806). There was no significant difference between the two groups (P > 0.05). The marginal gap values before cementation were (mean +/- s.d.): Group A, 32.7 microm (+/-6.8); group B, 33.0 microm (+/-6.7). The mean marginal gap values after cementation were (+/-s.d.): Group A, 44.6 microm (+/-6.7); group B, 46.6 microm (+/-7.7). The marginal openings were significantly higher after cementation for both groups (P < 0.05). All test groups demonstrated fracture load and marginal accuracy values within the range of clinical acceptability.

Partial coverage restoration systems on molars--comparison of failure load after exposure to a mastication simulator.

This in vitro study evaluated the failure load of partial coverage restorations (PCR) made of various materials cemented on natural molars after exposure to the mastication simulator. Sixty-four maxillary molars were divided into four groups of 16 test specimens each. The specimens in one group remained unprepared (group NP); the teeth in the other groups were prepared equally according to standardized guidelines and restored with the following PCR: Group GO (Gold-Pontor-MPF; Metaux Precieux SA, Metalor, Neuchatel, Switzerland), group TA (Targis; Ivoclar Vivadent AG, Schaan, Liechtenstein) and group EM (IPS-Empress; Ivoclar Vivadent AG). The restorations in group GO were cemented conventionally, while those in groups TA and EM were luted adhesively. Groups NP and GO served as control groups. All test specimens were subjected to 1.2 million cycles (F = 49 N) in a mastication simulator. Subsequently, all test specimens were loaded occlusally until fracture occurred using an universal testing machine. All specimens withstood the masticating simulation. The median (IQR = x(0.25)-x(0.75)) failure loads were as follows: group NP: 1960.3(1480.5-2227.5) N, group TA: 1478.6(1293.4-1856.7) N and group EM: 1400.1(1043.1-1721.6) N. All test specimens of group GO achieved fracture strength values which exceeded a fracture load of 5500 N. The values of group GO were statistically significantly higher than those of groups NP, TA and EM (P < 0.00001). Furthermore, the results of group NP were significantly higher (P = 0.0226) than those of group EM. The results of groups NP and TA (P = 0.2022) as well as of groups TA and EM (P = 0.5340) did not differ significantly. The median values of all PCR systems obtained were within the limits of clinical acceptance. Long-term clinical investigations which take additional parameters into consideration are required before the composite-based Targis(R) (Ivoclar Vivadent AG) material can be recommended for indirect PCR.