Translucency of bulk-fill composite materials: A systematic review.

OBJECTIVES: To conduct a systematic review on the translucency of bulk-fill (BF) composite materials, evaluating the factors influencing it and its clinical implications. MATERIALS AND METHODS: A systematic search was performed on four databases (Embase, Medline/PubMed, Scopus, and Web of Science) for articles published until October 2, 2023. Search terms were: "translucency," "translucency parameter," "contrast," "contrast ratio," "bulk," "bulk-fill," "bulk fill," "composite," "resin," "resin based," "resin-based," "restoration," and "dental." In vitro studies, written in English language, investigating BF resin-based composites translucency were included. The risk of bias was performed with the RoBDEMAT tool. RESULTS: Of 590 screened articles, 13 were included in this review. They investigated 11 high-viscosity BF and 5 low viscosity ones. The limited number of the identified studies and the heterogeneity of the extracted data did not allow to conduct a meta-analysis. CONCLUSIONS: BF materials exhibit variability in translucency due to variations in experimental designs and the heterogeneous composition. CLINICAL SIGNIFICANCE: BFs may behave differently in masking the substrate or in blending capacity.

Dentistry and Covid-19 pandemic: operative indications post-lockdown.

A new Coronavirus, the seventh member of the Coronaviridae family, identified as SARS-CoV-2, spread in late December 2019 in the territory of Wuhan in China. CoV-2019 can be transmitted directly from person to person by respiratory drops, direct contact and contaminated material. Furthermore, 2019-nCov penetrates cells similarly to the SARS coronavirus, i.e., through the ACE2 receptor. This may promote human-to-human transmission. Patients and dental professionals are exposed daily to pathogenic microorganisms, including viruses and bacteria, which infect the oral cavity and respiratory tract. Dental procedures carry the risk of 2019-nCoV infection due to their specificity. Direct transmission regards the distance between operator and patient, exposure to saliva, blood and other body fluids, the use of sharp instruments and "droplet-generating" rotating instruments, contact with the conjunctival mucosa, and finally the contact with droplets produced by coughing and nasal secretion of an infected individual without mask at short distance, increasing the biological risk for the operator. In light of the pandemic linked to COVID-19, although there is no clear scientific evidence in the literature, it is necessary to identify protections with regard to clothing, operating protocols, disinfection of environments and management of waiting rooms and front offices. This paper is a basis for operative indications for dentists and other health care professionals in phase 2 post lockdown for both private and public structures.

Evaluation of bradykinin, VEGF, and EGF biomarkers in gingival crevicular fluid and comparison of PhotoBioModulation with conventional techniques in periodontitis: a split-mouth randomized clinical trial.

Periodontal disease is a chronic progressive inflammatory process leading to damage of tooth-supporting tissues. This comparative study assessed the effect of PhotoBioModulation (PBM) versus conventional therapy, and investigated biomarkers involved in the healing process. The test group comprised twenty systemically-healthy non-smoking subjects with chronic periodontitis with the presence of two matched contro-lateral premolar sites (probing depth > 5 mm); twenty subjects without chronic periodontitis (CP) served as control group. Patients were treated at baseline, either with scaling and root planing (SRP group) or with a procedure entailing SRP supported by PBM (PBM group). The laser used was a diode laser operating at 645 nm wavelength, 10 J/cm2, and 0.5 W/cm2 with a 600 µm fiber optic. Crevicular fluid levels of bradykinin (BK), vascular endothelial growth factor (VEGF), and epidermal growth factor z (EGF) were determined at both sites. Crevicular fluid specimens from both groups were analyzed with the ELISA TEST. Clinical differences in analyzed outcomes were observed in favor of PBM treatment. Taking average values as 100%, the reduction in BK concentration was 47.68% with SRP and 68.43% with PBM on day 3; the VEGF concentration decreased by 35.73% with SRP and 48.59% with PBM on day 7; the EGF concentration increased by 55.58% with SRP and by 58.11% with PBM on day 21.Clinical parameters improved significantly in both groups (pooled mean values of probing depth decreased from 5.6 to 4.5 mm; gingival index from 1.92 to 1.1; and bleeding on probing from 49.67 to 23.23) but did not vary significantly between the PBM and the SRP group. The results confirmed that PBM have beneficial effects in the early phases of the healing process playing a role in modulation of BK, EGF, and VEGF in gingival crevicular fluid levels; both groups had significant clinical improvement over control but there was no significant difference between them, only a trend for PBM group. The overall results of the study suggest a potential benefit of PBM in conjunction with SRP in treating chronic periodontitis.

Clinical efficacy of Lactobacillus reuteri-containing lozenges in the supportive therapy of generalized periodontitis stage III and IV, grade C: 1-year results of a double-blind randomized placebo-controlled pilot study.

OBJECTIVE: The aim of this 12-month mono-centre double-blind randomized placebo-controlled clinical study was to evaluate the efficacy of Lactobacillus reuteri-containing lozenges during the supportive therapy of generalized periodontitis stage III and IV, grade C (GPIII-IVC) patients. MATERIAL AND METHODS: Twenty treated GPIII-IVC patients were randomly divided into 2 groups. The test group received two 3-month-long administrations of L. reuteri (2 lozenges/day after brushing) with a 3-month washout period, while the control one received a placebo. Outcome measures were tooth survival, complications and adverse events, change in probing pockets depth (PPD), change in probing attachment level (PAL), presence of bleeding on probing (BOP) and patient's evaluation of treatment. Measurements were collected at 3, 6, 9 and 12 months. RESULTS: At 1 year, no dropout, tooth loss, complications or adverse event were recorded. Mean PPD and mean PAL and percentages of sites with BOP were statistically improved (p < 0.05) compared with baseline in both groups, while more PPD reduction at all time points (p < 0.05) and more PAL gain at 6 months and more BOP reduction at 6 and 9 months were found in the probiotic group (p < 0.05). CONCLUSIONS: Within the limitation of the study, the use of L. reuteri probiotics lozenges improved some clinical outcomes in treated GPIII-IVC patients during maintenance therapy. Studies with a larger number of patients are needed to confirm these data. CLINICAL RELEVANCE: The use of L. reuteri probiotic lozenges could be considered as an adjunct in the maintenance therapy of GPIII-IVC patients.

Point-of-care testing for hepatitis C virus infection at an Italian dental clinic: portrait of the pilot study population.

The dental clinic is an appropriate place to promote the prevention of hepatitis C virus (HCV) infection and fast access for care of HCV-positive subjects with new-generation anti-HCV drugs. This study aimed to determine the socio-demographic profile of subjects screened for HCV virus in a dental clinic to acquire useful information for future campaigns of prevention. An easy, free-of-charge, screen salivary test was offered to patients referred to the dental clinic of San Raffaele Scientific Research Hospital in Milan, Italy for dental procedures. These patients were also asked to complete an anonymous questionnaire on demographics and risk behaviours. A total of 1388 of 2097 (66.19%) questionnaires were evaluable. The demographics of the population responding to this initiative was primarily Italians citizen (96.47%), homogeneous gender distribution (55.55%), age over 50 (609 subjects; 43.88%), with high-level education and stable professional positions. 905 subjects (65.20%) were never tested for HCV before. The test showed positive reactivity in 22 cases (1.05%); of these, 21 subjects were known to be HCV-positive, and the test confirmed their status. One subject was newly diagnosed as HCV-positive. The percentage of subjects who were never tested for HCV infection appears too high (905 subjects, i.e., 65.20%), especially among subjects with high level of education and professions, and among adults over 40 or young people (18-25). The easy screening test in dental clinic can help raise awareness, promote early diagnosis and prevention, and provide a fast link to care for HCV infection.

Distribution of Trabecular Bone Density in the Maxilla and Mandible.

INTRODUCTION: Implant osseointegration is strongly influenced by the bone quality at the implant insertion site. The present work aims to create distribution diagrams showing the average bone density at each position within the jaws. MATERIALS AND METHODS: Data were retrospectively collected from 4 oral surgeons who sought bone-density measurements during implant placement using a torque-measuring implant micromotor. Statistical analyses were performed to investigate whether bone density correlated with the patients' sex and age and whether the bone-density values at different positions within each arch correlated to each other. RESULTS: Records of 2408 patients and 6060 bone-density readings were retrieved, and density distribution diagrams were created. Density values showed a significant variation within subjects. Within the same jaw, density between adjacent positions showed significant differences. Density at a given position correlated significantly with that at the other positions in most cases. Bone density was significantly lower in women than in men; no significant correlation was found between bone density and the patient age. CONCLUSIONS: Bone density of patients displays significant interindividual variation, thus meaningful assessment must be conducted on a patient-by-patient basis.

Relationship Between Crestal Bone Levels and Crown-to-Implant Ratio of Ultra-Short Implants With a Microrough Surface: A Prospective Study With 48 Months of Follow-Up.

The aim of this cohort study was to investigate the relationship between crestal bone levels and crown-to-implant ratio of ultra-short implants, after functional loading. Sixty patients with single or partial edentulism and alveolar bone atrophy were enrolled and treated between December 2009 and January 2016. Without using bone-grafting procedures, patients were rehabilitated with ultra-short implants characterized by a microrough surface and a 6-mm length. Clinical and anatomical crown-to-implant (C/I) ratios and crestal bone levels (CBL) were measured after a follow-up period ranging from 12 to 72 months; all peri-implant and prosthetic parameters were recorded. The data collected were statistically analyzed ( P = .05). A total of 47 patients with 66 ultra-short implants were completely followed up according to described protocol. The mean follow-up was 48.5 ± 19.1 months. The mean anatomical C/I ratio was 2.2, while the mean clinical C/I ratio was 2.6 ± 0.6 at baseline and 2.8 ± 0.6 at the last follow-up appointment. Mean CBL as calculated at the baseline was 0.7 ± 0.5 mm, while at the last appointment it measured 1.0 ± 0.5 mm. The overall implant-based success rate was 96.9%, and the mean peri-implant bone loss (PBL) was 0.3 ± 0.3 mm. No statistically significant relationship was found between anatomical or clinical C/I ratio and PBL. Ultra-short implants appear to offer a predictable solution for implant-prosthetic rehabilitation in patients with edentulism and bone atrophy. A high percentage of implants were successful, with minimal crestal bone loss. The high C/I ratio did not appear to influence either peri-implant bone loss or prosthetic complication rates.

Immediate Postextractive Implants With and Without Bone Graft: 3-year Follow-up Results From a Multicenter Controlled Randomized Trial.

PURPOSE: To evaluate the outcome of single postextraction immediate implants placed with and without bone grafts in the esthetic maxillary premolar area for 3-year follow-up after loading. MATERIAL AND METHODS: After tooth extraction, 102 patients received 115 immediate dental implants. Patients were randomly allocated to immediate implant placement with (group A: 51) or without (group B: 51) anorganic bovine bone and resorbable collagen barrier. RESULTS: After 3 years (T36), 1 implant failed in each group. Thirty-seven patients showed inflammation and bleeding, 19 mucositis, and 2 periimplantitis. Statistical significant association was found between BOP and mucositis at T12 (P < 0.0005) and T36 (P < 0.0005). The mesial bone level was -0.61 mm in group B and -1.01 mm in group A (P < 0.001). The group B distal bone level was -0.71 mm and -1.12 mm in group A (P < 0.005). Group B's buccal mean probing was increased (+0.40 mm) than group A (+0.36 mm). Group B's palatal mean value was higher (+0.54 mm) than group A (+0.38 mm). No statistically significant differences were found between the 2 groups. However, the Pink Esthetic Score and patient satisfaction were higher in group B than A (P < 0.001). CONCLUSIONS: The use of anorganic bovine bone substitute with a resorbable collagen barrier in immediate postextractive implants seems to improve the esthetic outcomes after a 3-year follow-up.

The insertion torque-depth curve integral as a measure of implant primary stability: An in vitro study on polyurethane foam blocks.

STATEMENT OF PROBLEM: Recent research has shown that dynamic parameters correlate with insertion energy-that is, the total work needed to place an implant into its site-might convey more reliable information concerning immediate implant primary stability at insertion than the commonly used insertion torque (IT), the reverse torque (RT), or the implant stability quotient (ISQ). Yet knowledge on these dynamic parameters is still limited. PURPOSE: The purpose of this in vitro study was to evaluate whether an energy-related parameter, the torque-depth curve integral (I), could be a reliable measure of primary stability. This was done by assessing if (I) measurement was operator-independent, by investigating its correlation with other known primary stability parameters (IT, RT, or ISQ) by quantifying the (I) average error and correlating (I), IT, RT, and ISQ variations with bone density. MATERIAL AND METHODS: Five operators placed 200 implants in polyurethane foam blocks of different densities using a micromotor that calculated the (I) during implant placement. Primary implant stability was assessed by measuring the ISQ, IT, and RT. ANOVA tests were used to evaluate whether measurements were operator independent (P>.05 in all cases). A correlation analysis was performed between (I) and IT, ISQ, and RT. The (I) average error was calculated and compared with that of the other parameters by ANOVA. (I)-density, IT-density, ISQ-density, and RT-density plots were drawn, and their slopes were compared by ANCOVA. RESULTS: The (I) measurements were operator independent and correlated with IT, ISQ, and RT. The average error of these parameters was not significantly different (P>.05 in all cases). The (I)-density, IT-density, ISQ-density, and RT-density curves were linear in the 0.16 to 0.49 g/cm³ range, with the (I)-density curves having a significantly greater slope than those regarding the other parameters (P≤.001 in all cases). CONCLUSIONS: The torque-depth curve integral (I) provides a reliable assessment of primary stability and shows a greater sensitivity to density variations than other known primary stability parameters.

Point-of-care testing for hepatitis C virus infection at alternative and high-risk sites: an Italian pilot study in a dental clinic.

The Infectious Diseases Department and the Department of Dentistry of San Raffaele Scientific Institute in Milan conducted a screening and prevention program, the "EASY HCV-test Program," at a dental clinic to increase the identification of unrecognized infections. Using a cross-sectional community-based study design, hygienists in the dental clinic offered patients a hepatitis C virus (HCV) rapid salivary test (OraQuick ADVANCE® Rapid HCV Antibody Test) with pre- and post-test counseling prior to initiation of their oral hygiene routine. From April 2015 to November 2015, the EASY HCV test was offered to 2650 patients visiting the Center of Oral Health and Prevention at the Department of Dentistry at San Raffaele Hospital in Milan. Among them, 2077 eligible volunteers were tested. The test showed positive reactivity in 22 cases; of these, 21 subjects were known to suffer from HCV, and the test confirmed their status. One subject was newly diagnosed with HCV infection. The results of this study suggest EASY HCV test screening conducted in dental clinics may constitute an effective strategy for increasing HCV testing among people at risk for infection.

Histomorphometric Evaluation of Two Different Bone Substitutes in Sinus Floor Augmentation Procedures.

The aim of this study is to compare the histomorphometric data of deproteinized bovine bone (DBB) and a fully synthetic bone substitute, poly (lactic-co-glycolic) acid/hydroxyapatite (PLGA/HA) applied for sinus floor augmentation technique. Twelve maxillary atrophic ridges of 8 patients requiring major maxillary sinus floor augmentation were studied; the sites were randomly assigned to the study groups and reexamined at 6 months after grafting using cone beam computed tomography scans and biopsy samples harvested during dental implant placement. Total bone volume, residual graft material volume, and new bone volume were assessed. Measurable biopsies were available from 67% of test sites and 100% of control sites. Poly (lactic-co-glycolic) acid/hydroxyapatite grafts showed no trace of graft material, whereas DBB grafts had a mean graft area of 16.60%. Mean percent of newly formed bone tended to be greater for PLGA/HA than for DBB group. Mean total bone volume percent did not differ significantly: PLGA/HA = 44.45% (CI, 16.42-72.48), DBB = 44.11% (CI, 36.61-51.60). Deproteinized bovine bone and PLGA/HA produced similar total bone volumes. Poly (lactic-co-glycolic) acid/hydroxyapatite appeared to be completely replaced by newly formed bone, whereas DBB presented significant amounts of residual graft material. Poly (lactic-co-glycolic) acid/hydroxyapatite necessitates of more clinical trials to be considered suitable for sinus floor augmentation.

Dimensional Changes of Fresh Sockets With Reactive Soft Tissue Preservation: A Cone Beam CT Study.

PURPOSE: The aim of this study was to assess dimensional changes of the fresh sockets grafted with collagen sheets and maintenance of reactive soft tissue, using cone beam computed tomography (CBCT). MATERIALS AND METHODS: Tooth extractions were performed with maximum preservation of the alveolar housing, reactive soft tissue was left into the sockets and collagen sheets filled bone defects. Cone beam computed tomography were performed before and 3 months after extractions. RESULTS: One hundred forty-five teeth, 60 monoradiculars and 85 molars, were extracted. In total, 269 alveoli were evaluated. In Group A, not statistically significant differences were found between monoradiculars, whereas statistically significant differences (P < 0.05) were found between molars, both for mesial and distal alveoli. In Group B, not statistically significant differences were found between maxillary and mandibular bone changes values (P > 0.05) for all types of teeth. CONCLUSIONS: This study reported an atraumatic tooth extraction, reactive soft tissue left in situ, and grafted collagen sponge may be helpful to reduce fresh socket collapse after extraction procedures.

A Retrospective 2-Year Clinical Study of Immediate Prosthetic Rehabilitation of Edentulous Jaws with Four Implants and Prefabricated Bars.

PURPOSE: The purpose of this retrospective investigation was to evaluate the use of a prefabricated bar system for immediately loaded implants placed and restored according to the All-on-Four concept with up to 24-month follow-up. MATERIALS AND METHODS: A total of 51 patients (31 males and 20 females; mean age 63.4 years) presented with edentulous or partially edentulous jaws with severe atrophy of the posterior regions. All patients were treated with full-arch fixed prostheses (28 maxillary, 34 mandibular) each supported by four implants (two vertical, two distally tilted). The implants were immediately loaded with screw-retained full-arch restorations. Each prosthesis was supported by a prefabricated metal bar combined with high-density acrylic resin. Follow-up visits were scheduled at 6, 12, and 24 months after initial prosthetic loading. Intraoral radiographs were obtained immediately after surgery and at each follow-up visit by using a custom radiograph holder and parallel technique. Marginal bone levels were assessed using digital image analysis. Implant and prosthetic survival and success rates were evaluated. Patient satisfaction was further assessed using a 100-mm visual analog scale (VAS). Data were compared by means of the Mantel-Haenszel test. RESULTS: No drop-outs occurred. The overall implant survival rates were 100% and 98.38% for the vertical and tilted implants respectively. Two of the 62 definitive fixed prostheses were lost during the observation period due to implant failure. Since restoration replacement due to implant failure was not judged a prosthodontic failure according to the survival criteria provided in this study, the overall prosthetic survival rate was 100%. No statistically significant differences in marginal bone levels between vertical and tilted implants were detected at 24-month follow-up evaluation in either jaw. All participants were functionally and esthetically satisfied with their definitive restorations after 2 years functioning, as confirmed by the average VAS scores (masticatory function: 99.7; phonetic function: 99.5, esthetics: 99.2). CONCLUSIONS: The preliminary 24-month results indicate that immediate loading of vertical and tilted implants using the evaluated prefabricated bar system may be a viable solution for edentulous jaw rehabilitation; however, more long-term prospective clinical trials are needed to affirm the effectiveness of this surgical-prosthetic protocol.

Evaluation of resistance against bacterial microleakage of a new conical implant-abutment connection versus conventional connections: an in vitro study.

The aim of the present in vitro study was to evaluate bacterial microleakage from inside to outside the implant-abutment assembly in a new design of internal conical connection compared to eight different internal connections. The design of this connection should prevent or limit microbiologic leakage into the surrounding implant tissue, that could contribute to infections without bone loss (mucositis) or with bone loss (peri-implantits). In order to investigate bacterial microleakage, the inner part of each system was inoculated with an Escherichia coli suspension. Eight different groups were considered; each group was composed of 10 dental implants, for a total of 80 implants. Groups 1-7 were considered controls, while group 8 was the test connection (an internal connection characterized by a double taper principle). Results showed that in control implants (Group 1 to 7), little microleakage was observed after the first 6 hours (500 CFU/ µl) and, after 24 hours of incubation, they showed a significant bacterial contamination in all samples (>100.000 CFU/ µl). In group 8 (test connection) no contamination was found in the first 6 hours, with 7 out of 10 implants showing no contamination even after 96 hours. Statistically significant differences were found between Group 8 and the other groups (p<0.05), whereas no significant differences were found among implants of the control groups (from group 1 to 7). Within the limits of the present study, the new connection studied presented significantly less microleakage at 96 h in comparison with the other control internal connections.

Short-term clinical performance of zirconia single crowns with different framework designs: 3-year clinical trial.

PURPOSE: The present prospective clinical study evaluated the influence of coping design on the fracture resistance of CAD/CAM zirconia single crowns layered with dedicated ceramics. METHODS: 56 subjects were provided with 90 zirconia single crowns in posterior regions. Tooth preparations were standardized and the abutment teeth were randomly distributed into three groups, according to three different coping designs (flat design, FD; porcelain-fused-to-metal-like crowns, PFM; anatomically-guided, AG). The zirconia cores were produced using a CAD/CAM software and then were hand-layered with dedicated ceramics. All crowns were cemented with a self-adhesive resin luting agent and the patients were recalled for follow-up visits after 1 month, 6 months, 1, 2 and 3 years of clinical service. The function, esthetics and marginal adaptation of the restorations were evaluated. Statistical analyses were performed to evaluate survival and success of the restorations. RESULTS: Success rates of 100% were reported in Group 2 and Group 3 while the percentage was 80% in Group 1. Three chippings were noticed in Group 1 (FD) and two crowns needed to be replaced after 3 years, resulting in a survival rate of 93.3%. Group 2 and Group 3 had significantly higher 3-year success rates than Group 1 (P < 0.05). Based on the present clinical results, the following conclusions were drawn: the porcelain-fused-to-metal-like and the anatomically-guided frameworks for zirconia single crowns performed better clinically than the flat designed cores in posterior regions after 3 years; standardized tooth preparations achieved even thicknesses of the bilayered restorations; the proper support given to the veneering ceramic by the correct design of the zirconia framework could significantly reduce the risk of chipping during function.

Digital impressions for fabrication of definitive "all-on-four" restorations.

PURPOSE: The aim of this study was to assess the accuracy of digital impressions for "all-on-four" implant rehabilitation. MATERIALS AND METHODS: Patients edentulous in one or both jaws were randomly selected for this study. Complete arch immediately loaded prostheses supported by 4 implants (2 axial and 2 tilted) were placed. Five hours after implant placement, screw-retained full-arch temporary prostheses were positioned. After 4 months, a digital scan body was used to finalize definitive prosthesis. Radiographic assessments were obtained immediately after surgery and at each follow-up visit. Bone level measurements were reported at 6 and 12 months, and bone loss between upright and tilted implants was compared. RESULTS: Fourteen definitive cast metal frameworks prosthesis were delivered to the patients. No implant dropout occurred. All prosthesis were screwed onto the dental implants, and x-ray examinations revealed a bar-implant connection accuracy. The implant survival rate was 100% for all positioned implants. No statistically significant differences (P > 0.05) in crestal bone loss between tilted and upright implants were detected. CONCLUSIONS: Digital impression creates an accurate physical model significantly improving efficiencies for the dental team and streamlining the workflow.

Immediate rehabilitation of the posterior maxilla with extensive sinus pneumatization with one axial and one trans-sinus tilted implant: a 3-year clinical report and a classification.

Implant rehabilitation of the posterior maxilla can entail difficulties due to reduced bone quantity and poor bone quality, especially after long-term edentulism. In some patients, multiple surgeries are necessary, which may lead to higher patient morbidity and longer treatment times before a prosthetic rehabilitation can be achieved. This article presents an immediate fixed prosthesis in a posterior atrophic maxilla supported by 1 anterior axial implant and 1 posterior tilted fixture placed with an intrasinus insertion. Additionally, a classification scheme for immediate treatment for the posterior maxilla based on the available residual bone is provided.

Fracture Strength of Zirconia and Alumina Ceramic Crowns Supported by Implants.

Due to the brittleness and limited tensile strength of the veneering glass-ceramic materials, the methods that combine strong core material (as zirconia or alumina) are still under debate. The present study aims to evaluate the fracture strength and the mechanism of failure through fractographic analysis of single all-ceramic crowns supported by implants. Forty premolar cores were fabricated with CAD/CAM technology using alumina (n = 20) and zirconia (n = 20). The specimens were veneered with glass-ceramic, cemented on titanium abutments, and subjected to loading test until fracture. SEM fractographic analysis was also performed. The fracture load was 1165 (±509) N for alumina and 1638 (±662) N for zirconia with a statistically significant difference between the two groups (P = 0.026). Fractographic analysis of alumina-glass-ceramic crowns, showed the presence of catastrophic cracks through the entire thickness of the alumina core; for the zirconia-glass-ceramic crowns, the cracks involved mainly the thickness of the ceramic veneering layer. The sandblast procedure of the zirconia core influenced crack path deflection. Few samples (n = 3) showed limited microcracks of the zirconia core. Zirconia showed a significantly higher fracture strength value in implant-supported restorations, indicating the role played by the high resistant cores for premolar crowns.

Fracture toughness and hardness of a Y-TZP dental ceramic after mechanical surface treatments.

OBJECTIVES: The aim of the investigation was to evaluate the effects of surface mechanical treatments of all-Y-TZP restorations. In order to do that, surface roughness (Rs), fractal dimension (Df), fracture toughness (Ft), Vickers hardness (Hv), crack length (Cl), and opening (Co) were determined. MATERIALS AND METHODS: Y-TZP bar-shaped specimens (n = 30) were subdivided into three groups: as received by milling center (M), after coarse polishing (CP), and after fine polishing (FP). The specimens were examined under both confocal laser and electron scanning microscopes. One-way ANOVA and post hoc tests were used to analyze the data (α = 0.05). RESULTS: The FP group showed a significantly lesser amount of Rs (P < 0.05). The Df analysis confirmed the significantly lesser amount of surface complexity within the FP group (P < 0.05). The Hv values were not significantly different among the groups. The Ft was significantly lesser within the FP group (P < 0.05). At the same time, both Cl and Co were significantly higher within the FP group (P < 0.05). Likewise, the FP treatment showed a significant decrease in roughness and surface complexity associated to a decrease of fracture toughness with a significant microcrack increase. CONCLUSIONS: The present study suggests that the fine polishing procedure in all-YTZP restorations produces surface embrittlement. CLINICAL RELEVANCE: Because of the surface embrittlement, mechanical surface polishing of all-zirconia restorations should be avoided.

The utility of the electric mallet.

The aim of this study was to evaluate the efficiency of electrical mallet for tooth extraction evaluating the integrity of fresh sockets walls. From July 2009 to February 2012, 427 hopeless teeth were extracted in 156 patients: 96 males and 60 females, with a mean age of 53.2 ± 26.4 years. Two hundred fifty teeth were extracted from the maxilla and 177 from the mandible. Extractions were performed using an electrical mallet. It pushed blade in a longitudinal movement along central axis, moving up and down toward the periodontal ligament space in a repetitive manner, providing a driving mechanism of longitudinal movements. Intraoral digital radiographic examinations were performed before and immediately after dental extractions to evaluate the lamina dura setting. No fracture or loss of cortical bone plate was observed in fresh sockets of teeth extracted by electrical mallet. All the alveoli revealed full soft tissue secondary healing 2 weeks after complete root extraction. During the healing period, there were no signs of inflamed tissue or exposed bone in any of the cases. As reported in this clinical study, maximum preservation of the alveolar housing and related gingival structures may be achieved following assisted atraumatic tooth extraction by electrical mallet.