Microstructure and mechanical, physical and structural properties of sustainable lightweight metakaolin-based geopolymer cements and mortars employing rice husk

This work focuses on an in-depth investigation of the formation of pores in the structure of lightweight geopolymer cements and mortars using rice husk as a foaming agent. The hardener used in this study was sodium waterglass. Metakaolin was replaced by 0, 10, 20, 30 and 40 % by mass of husk and the obtained powders were used to produce lightweight geopolymer cements and mortars. The formation of pores in the lightweight geopolymer cements was monitored using X-ray diffractometry and infrared spectroscopy while those in the mortars were assessed using apparent density and compressive strength measurements, mercury intrusion porosimetry and optical and scanning electron microscopy. The values for the compressive strength and apparent density were in the ranges of 28.92\u20130.75 MPa and 1.88\u20131.70 g/cm 3 , respectively. The results indicated that the values for the compressive strength and apparent density of geopolymer mortars decreased while those of the cumulative pore volume increased with increases in the metakaolin replacement level. Stereomicroscopic and scanning electron microscopic images showed the presence of rice husk and fibres of rice husk, respectively, in the networks. It was found that rice husk can be used as a foaming agent for producing sustainable lightweight geopolymer mortars

”one abutment-one time”: optimizing platform-switching concept. 3-year controlled prospective study

Background: The “platform-switching” concept showed better peri-implant crestal bone preservation in post-extraction immediately restored implants when compared to matching diameter abutment configuration. However repeated abutment dis/reconnections during restorative procedures from provisional to final crown could produce apical shifting of peri-implant tissues. Aim: Aim of this controlled prospective study was to evaluate on bone levels (MBL) the influence of restoration using immediately definitive abutments (one abutment-one time concept) versus provisional abutment later replaced by a definitive abutment. Materials and methods: 26 patients with 26 hopeless maxillary premolars received a post-extraction wide diameter implant. Immediately after insertion, 11 patients (Control Group, CG) were immediately restored using a platform-switched provisional titanium abutment. In 15 patients (Test Group, TG), definitive platform-switched titanium abutments were tightened. In both groups, provisional crowns were adapted, avoiding occlusal contacts. All implants were definitively restored after 3 months: for the final impression, in CG, traditional impression technique with coping transfer was adopted, dis/reconnecting abutments several times; in TG, metal prefabricated coping was used and final restoration was seated avoiding abutment disconnection. Digital standardized periapical radiographs using a customized film holder were recorded at baseline (T 0 = implant insertion), final restoration (T1=3 months after), 18 (T2) and 36 months (T3) follow-ups. The MBL was evaluated with a computerized measuring technique applied to radiographs. Digital subtraction radiography software was used to evaluate radiographic density of bone tissue around implants. The Student’s t-Test (confidence level: P<0.05) was selected to identify differences between test and control groups at different follow-ups concerning MBL values. Results: In the CG peri-implant bone resorption was 0.41mm (SD=0.15mm) at T1, 0.38mm (SD=0.12mm) at T2, 0.53mm (SD = 0.13mm) at T3. In the TG, on average, peri-implant bone resorption was 0.59 mm (SD=0.19mm) at T1, 0.31mm (SD=0.11mm) at T2, 0.32mm (SD = 0.16mm) at T3. Statistically significant difference between groups was only found at T3. At the same follow-up period, higher density in radiographic bone appearance around implant neck was recorded in the TG compared to CG. Conclusions and clinical implications: The implant/abutment stability following the minimally invasive prosthetic strategy adopted (“platform-switching” and “one abutment- one time”) could longitudinally produce additional hard tissue preservation compared to implants restored according to “platform-switching” only. Despite of the encouraging data reported, however, controlled clinical studies on larger patient sample and histologic investigations are required to confirm this hypothesis, analyzing biologic mechanism

New Geopolymers Based on Electric Arc Furnace Slag

Electric arc furnace slag (EAF-S), coming from a steel productive plant in Italy, has been used as new source for geopolymers synthesis. The slag has been geopolymerized alone and with different content of metakaolin (MK) with the aim to investigate if EAF-S content plays a role in geopolymerization process. Mechanical properties results and microstructure analysis highlight that the optimum weight ratios MK/EAF-S to be used as starting materials are 40/60, 30/70, 20/80. Moreover EAF-S, when used with MK, is directly involved in the formation of calcium-rich alumino-silicate gels

DENTAL IMPLANT SITES IN HEALTHY VERSUS DIABETIC SUBJECTS: A TWO-YEAR CLINICAL AND BACTERIOLOGICAL ASSESSMENT

The aim of this study was to analyze by Real-Time Polymerase Chain Reaction (PCR) possible differences in periimplant microbiota of patients without significant systemic diseases versus patients affected by non-insulin-dependent diabetes mellitus (NIDDM), both treated with dental implants with the same implant-abutment system. Patients suffering from NIDDM, and those with no history of major systemic diseases, treated with dental implants at the Prosthodontics Operative Unit of "Sapienza" University of Rome in the period February 2009 - March 2010 were considered. Clinical parameters as well as microbiological profile were evaluated for each implant site at 3, 6, 12, and 24 month follow-up. Crevicular fluid was collected for microbial sampling and analyzed by Real-Time PCR in order to identify the possible presence of Aggregatibacter actinomycetemcomitans, Porphyromonas gingivalis, Tannerella forsythia, Treponema denticola, Fusobacterium nucleatum and Prevotella intermedia. Eight patients suffering from NIDDM and 22 with no history of major systemic diseases were included in the present investigation, each having received one to three dental implants. All the implants had been loaded 3 months after surgery, and the average follow-up after implant placement was 26.37 +/- 3.86. Clinical parameters showed no noticeable difference between the two groups, except for the Implant Stability Quotient (ISQ) that showed significantly lower values in NIDDM patients. A slightly higher amount of the considered pathogenic bacteria were retrieved in samples collected from patients with NIDDM (7.38x105) in comparison with those of healthy subjects (6.78x10(5)), though the differences were below statistical significance. Within the limitations of the present study, a slight correlation was empirically detected between gene expression profiles of microbial populations and history of NIDDM, which however remained below the statistical significance. Further well-designed clinical studies may be useful to conclusively clarify the impact of subgingival microflora on the increased susceptibility of diabetic patients to periimplantitis

Dental implant sites in healthy versus diabetic subjects: A two-year clinical and bacteriological assessment

The aim of this study was to analyze by Real-Time Polymerase Chain Reaction (PCR) possible differences in periimplant microbiota of patients without significant systemic diseases versus patients affected by non-insulin-dependent diabetes mellitus (NIDDM), both treated with dental implants with the same implant-abutment system. Patients suffering from NIDDM, and those with no history of major systemic diseases, treated with dental implants at the Prosthodontics Operative Unit of "Sapienza" University of Rome in the period February 2009 - March 2010 were considered. Clinical parameters as well as microbiological profile were evaluated for each implant site at 3, 6, 12, and 24 month follow-up. Crevicular fluid was collected for microbial sampling and analyzed by Real-Time PCR in order to identify the possible presence of Aggregatibacter actinomycetemcomitans, Porphyromonas gingivalis, Tannerella forsythia, Treponema denticola, Fusobacterium nucleatum and Prevotella intermedia. Eight patients suffering from NIDDM and 22 with no history of major systemic diseases were included in the present investigation, each having received one to three dental implants. All the implants had been loaded 3 months after surgery, and the average follow-up after implant placement was 26.37±3.86. Clinical parameters showed no noticeable difference between the two groups, except for the Implant Stability Quotient (ISQ) that showed significantly lower values in NIDDM patients. A slightly higher amount of the considered pathogenic bacteria were retrieved in samples collected from patients with NIDDM (7.38x105) in comparison with those of healthy subjects (6.78x105), though the differences were below statistical significance. Within the limitations of the present study, a slight correlation was empirically detected between gene expression profiles of microbial populations and history of NIDDM, which however remained below the statistical significance. Further well-designed clinical studies may be useful to conclusively clarify the impact of subgingival microflora on the increased susceptibility of diabetic patients to periimplantitis

Dental Implant Sites in Healthy versus Diabetic Subjects: A Two-Year Clinical and Bacteriological Assessment

The aim of this study was to analyze by Real-Time Polymerase Chain Reaction (PCR) possible differences in periimplant microbiota of patients without significant systemic diseases versus patients affected by non-insulin-dependent diabetes mellitus (NIDDM), both treated with dental implants with the same implant-abutment system. Patients suffering from NIDDM, and those with no history of major systemic diseases, treated with dental implants at the Prosthodontics Operative Unit of “Sapienza” University of Rome in the period February 2009 - March 2010 were considered. Clinical parameters as well as microbiological profile were evaluated for each implant site at 3, 6,12, and 24 month follow-up. Crevicular fluid was collected for microbial sampling and analyzed by Real-Time PCR in order to identify the possible presence of Aggregatibacter actinomycetemcomitans, Porphyromonas gingivalis, Tannerella forsythia, Treponema denticola, Fusobacterium nucleatum and Prevotella intermedia . Eight patients suffering from NIDDM and 22 with no history of major systemic diseases were included in the present investigation, each having received one to three dental implants. All the implants had been loaded 3 months after surgery, and the average follow-up after implant placement was 26.37±3.86. Clinical parameters showed no noticeable difference between the two groups, except for the Implant Stability Quotient (ISQ) that showed significantly lower values in NIDDM patients. A slightly higher amount of the considered pathogenic bacteria were retrieved in samples collected from patients with NIDDM (7.38×105) in comparison with those of healthy subjects (6.78×10 5 ), though the differences were below statistical significance. Within the limitations of the present study, a slight correlation was empirically detected between gene expression profiles of microbial populations and history of NIDDM, which however remained below the statistical significance. Further well-designed clinical studies may be useful to conclusively clarify the impact of subgingival microflora on the increased susceptibility of diabetic patients to periimplantitis

The bisphosphonates-osteonecrosis of the jaws. Prevention, diagnosis, and treatment

Bisphosphonates (BPs) are an important class of drugs that are useful in the treatment of certain metabolic and oncologic diseases of the skeletal system. Their efficacy in the treatment and palliative care of patient with these diseases is indisputable, but avascular osteonecrosis of the jaws (B-ONJ) has recently been reported as an adverse effect of intravenous BP therapy and with prolonged therapy with oral BPs. MATERIALS AND METHODS. We reviewed the most recent scientific literature on B-ONJ in an attempt to characterize this adverse event from an epidemiological point of view and to elaborate guidelines for its diagnosis, prevention, and treatment. RESULTS. B-ONJ usually arises in the mandible, in most cases at the level of mylohyoid line; involvement of the upper jaw is less common. It normally occurs after a dental extraction or other types of oral surgery, but it can also develop spontaneously. In cases of the latter type, systemic risk factors (e.g., comorbidities, concomitant therapies), or local pathological/anatomical conditions of the oral cavity play an important role. For patients without identified risk factors, intravenous BP therapy is associated with an estimated incidence of B-ONJ between 0.8 and 1.15%; figures may be as high as 9.1% if these patients undergo dentoalveolar surgery. In patients treated with oral BF, the incidence rate ranges from 0.01 to 0.04% and increases to 0.09%-0.34% after extractions. None of the treatments currentIy used to treat B-ONJ are completely effective and predictable, so prevention is essential for patients receiving BPs. Oral and dental risk factors should be eliminated before BP therapy begins, and this requires close collaboration by the patient's physician and dentist. After BP therapy has been started, there are relative contraindications to dentoalveolar surgery, and only unavoidable procedures should be performed. If B-ONJ develops, the best clinical results are achieved with combined treatment that includes antibiotics, antiseptic mouthwashes, surgical removal of necrotic bone, surgical debridement, biostimulation with low-level laser therapy and ozone-therapy. CONCLUSIONS. B-ONJ is an uncommon but potentially serious complication of BP therapy. It can produce significant morbidity and severely diminish the quality of life. The prognosis appears poor even when appropriate treatment is provided. Since the first cases of B-ONJ have been reported, considerable advances have been made in our knowledge of the pathogenesis of this disease and its risk factors, diagnosis, prevention, therapy, and management of the complications