Do 3D-printed and milled tooth-supported complete monolithic zirconia crowns differ in accuracy and fit? A systematic review and meta-analysis of in vitro studies.

STATEMENT OF PROBLEM: Additive (3-dimensional printing) and subtractive (milling) methods are digital approaches to fabricating zirconia restorations. Comparisons of their resultant fabrication accuracy and restoration fit are lacking. PURPOSE: The purpose of this systematic review and meta-analysis was to evaluate the accuracy and fit of monolithic zirconia crowns fabricated by 3-dimensional printing and milling. MATERIAL AND METHODS: The PubMed (Medline), Scopus, Embase, Web of Science, Cochrane Library, and Google Scholar databases were searched up to August 2023. Eligible records were included, and the standardized mean difference (SMD) analyzed 4 outcomes: marginal fit, intaglio fit, trueness, and precision. Publication bias was analyzed with Trim-and-fill, the Egger regression test, and Begg funnel plot. Methodological quality was rated using the QUIN tool. RESULTS: A total of 15 publications were found eligible out of the initial 6539 records. The 3-dimensional printing group demonstrated a lower marginal fit (SMD=1.46, 95% CI=[0.67, 2.26], P<.001; I2=83%, P<.001) and trueness (SMD=0.69, 95% CI=[0.20, 1.18], P=.006; I2=88%, P<.001) and a significantly higher precision (SMD=-2.19, 95% CI=[-2.90, -1.48], P<.001; I2=56%, P=.045). The intaglio fit did not differ significantly across the study groups (SMD=0.77, 95% CI=[-0.22, 1.77], P=.127; I2=87%, P<.001). CONCLUSIONS: Given the high degree of heterogeneity, it can be cautiously concluded that while 3-dimensional printing led to greater precision, the outcomes of the 2 accuracy and adaptation parameters most crucial to the longevity of the restorations-trueness and marginal fit-showed the superiority of the milling technique.

Randomized clinical trial comparing monolithic and veneered zirconia three-unit posterior fixed partial dentures in a complete digital flow: three-year follow-up.

OBJECTIVES: To evaluate and to compare the clinical performance and survival rate of posterior monolithic and veneered zirconia fixed partial dentures (FPDs). MATERIAL AND METHODS: Sixty 3-unit posterior FPDs were included in the study. The patients were randomly distributed into two groups (n = 30 each) to receive either a monolithic (Zenostar T, Wieland Dental) or veneered zirconia (IPS e.max ZirCAD, Ivoclar Vivadent) FPD. Each patient received only 1 FPD. Tooth preparations were scanned (Trios 3, 3Shape), designed (Dental System 2016, 3 Shape), milled (Zenotec CAM 3.2, Wieland Dental), and cemented with a resin cement. Technical and biological outcomes and periodontal parameters were assessed. Data analysis was made using the Friedman and the Wilcoxon signed-rank tests with the Bonferroni correction and the Mann-Whitney U test. RESULTS: The survival rate at 3 years was 100% for veneered and 90% for monolithic zirconia restorations. Three monolithic zirconia FPDs were lost because of biologic complications. The main complication in the veneered zirconia FPDs was the fracture of the veneering ceramic in 4 of the veneered zirconia FPDs. No fracture of the frameworks was observed in any of the groups. All restorations were assessed as satisfactory after 3 years. No differences in periodontal parameters were observed between the groups. CONCLUSIONS: The results of this study suggest that monolithic zirconia and complete digital flow could be a viable alternative to veneered zirconia in the posterior regions. CLINICAL RELEVANCE: The monolithic zirconia restorations with a digital workflow can be a viable alternative in posterior fixed partial dentures, with good periodontal outcomes. CLINICAL TRIAL REGISTRATION NUMBER: ClinicalTrials.gov (Identifier NCT 04,879,498).

What is the prevalence of peri-implantitis? A systematic review and meta-analysis.

BACKGROUND: Peri-implantitis is a usual finding but estimates of its prevalence fluctuate very much. This may be due to the wide variety of disease definitions. This systematic review aims to estimate the overall prevalence of peri-implantitis and the effect of different study designs, function times and use of probing depth on prevalence rate. METHODS: Following electronic and manual searches of the literature published from January 2005 to December 2021, data were extracted from the studies fitting the study criteria. Fifty-seven articles were included in this study. RESULTS: Prevalence of peri-implantitis was 19.53% (95% CI 12.87-26.19) at the patient-level, and 12.53% (95% CI 11.67-13.39) at the implant-level and it remains highly variable even following restriction to the clinical case definition. The use of probing depth like diagnostic criteria affected the prevalence data. CONCLUSION: The results indicate that it remains essential the identification of the diagnostic markers for more accurate disease classification.

Influence of Digital Technologies and Framework Design on the Load to Fracture of Co-Cr Posterior Fixed Partial Denture Frameworks.

PURPOSE: To compare the load to fracture of cobalt-chromium (Co-Cr) 3-unit posterior fixed partial denture (FPD) frameworks manufactured by conventional and digital techniques and to evaluate the influence of the framework design on the fracture load. MATERIAL AND METHODS: Eighty 3-unit Co-Cr posterior FPD frameworks were fabricated with two designs: intermediate pontic (n = 40) and cantilever (n = 40). Each design was randomly divided into four groups (n = 10): casting, direct metal laser sintering, soft metal milling, and hard metal milling. After thermal cycling, all specimens were subjected to a 3-point bending test until fracture. Data were statistically analyzed using one-way ANOVA, Welch and Brown-Forsythe test, Ryan-Einot-Gabriel-Welsch F and Tamhane T2 post hoc test, Student's t test, and Weibull statistics (α = 0.05). RESULTS: Significant differences (p < 0.001; F = 39.59) were found among intermediate pontic frameworks (except between laser sintering and hard metal milling), and cantilevered frameworks (F = 36.75) (except between laser sintering and hard metal milling, and casting and soft metal milling). The cantilever groups showed load to fracture values significantly lower than those of the intermediate pontic (p < 0.001; F = 28.29). The Weibull statistics corroborated the results. CONCLUSIONS: Hard metal milling and laser sintered frameworks exhibited the highest load to fracture values. However, all tested frameworks demonstrated clinically acceptable load to fracture values. The framework design directly affected the fracture load, with drastically lower values in cantilevered frameworks.

Virtual chromoendoscopy with iSCAN as an alternative method to dye-spray chromoendoscopy for dysplasia detection in long-standing colonic inflammatory bowel disease: a case-control study.

OBJECTIVE: Patients with long-standing colonic inflammatory bowel disease (cIBD) are at increased risk of developing colorectal cancer (CRC). Dye-spray chromoendoscopy (DCE) with targeted biopsies is the preferred technique for surveillance of dysplasia. Virtual chromoendoscopy (VCE) are arising to improve detection rates and adherence to surveillance guidelines, although its role is not yet well defined. The purpose of this study is to assess the effectiveness of VCE with iSCAN as an alternative method for dysplasia detection in cIBD. METHODS: Retrospective case-control study with 191 patients included, 98 in the DCE (Indigo carmine) group and 93 in the VCE (iSCAN, twin-mode 1-3) group. The dysplasia detection and the exploration time were analysed. A logistic regression analysis was performed to ascertain the factors related to colonic dysplasia. RESULTS: A total of 44 dysplastic lesions were detected in 21 (11%) patients. No differences were found in the per lesion and the per patient analysis (dysplastic versus non-dysplastic). Median withdrawal time was shorter in the VCE group than in the DCE group (9 min versus 14 min; p < .001). Location of lesions in the right colon was independently associated with an increased risk for colonic dysplasia (OR = 4.04, 95%CI 1.11-14.65; p = .034) after adjusting for age at inclusion, age at diagnosis, high risk for CRC and Kudo pit pattern. CONCLUSIONS: VCE with iSCAN presents a similar diagnostic performance to conventional DCE in the detection of colonic dysplasia in patients with long-standing cIBD. Furthermore, VCE with iSCAN is a less time-consuming surveillance alternative to DCE.

Effect of cementation and aging on the marginal fit of veneered and monolithic zirconia and metal-ceramic CAD-CAM crowns.

STATEMENT OF PROBLEM: Marginal fit of zirconia restorations is an important criterion for their long-term success. However, in spite of the wide use of zirconia in dentistry, the relationship between marginal fit and low-temperature degradation from aging is unclear. PURPOSE: The purpose of this in vitro study was to compare the marginal adaptation of veneered and monolithic zirconia and metal-ceramic computer-aided design and computer-aided manufacturing (CAD-CAM) crowns before and after cementation and to evaluate the influence of artificial aging on the adaptation of zirconia crowns. MATERIAL AND METHODS: Seventy-two standardized dies were prepared to receive a posterior crown and randomly divided into 6 groups (n=12) as per the material and the presence or not of cement: metal-ceramic, veneered zirconia, and monolithic zirconia. The zirconia groups were subjected to accelerated low-temperature degradation through hydrothermal aging in an autoclave at 131 °C and 0.17 MPa for 5 and 20 hours. A scanning electron microscope with a magnification of ×1000 was used for marginal adaptation measurements, and X-ray diffraction (XRD) was used to characterize phase transformation degradation. The data were statistically analyzed using 2-way ANOVA, repeated measures ANOVA with Greenhouse-Geisser correction, and the t test (α=.05). RESULTS: No significant differences in the marginal discrepancy were recorded among the analyzed groups. The presence of cement did not influence marginal fit in any treatment group. No significant differences were observed in the marginal adaptation values before and after aging (P>.05). After 20 hours of aging, the monoclinic phase increase to 8.3% on veneered zirconia and to 3.1% on monolithic crowns. CONCLUSIONS: Monolithic and bilayer CAD-CAM zirconia crowns showed marginal gaps that were within an acceptable range of clinical discrepancy, regardless of cementation. Marginal adaptation was not influenced by aging. Low-temperature degradation did not lead to a significant transformation from the tetragonal to monoclinic phase.

Prospective Clinical Evaluation of Posterior Monolithic Zirconia Fixed Partial Dentures Using a Complete Digital Workflow: Two-Year Follow-Up.

PURPOSE: To evaluate the clinical performance and survival rate of posterior monolithic zirconia fixed partial dentures over a 2-year period. MATERIAL AND METHODS: A total of 20 patients, requiring 20 posterior fixed partial dentures were included in the study. Tooth preparations were scanned, and restorations were milled and cemented with a resin cement. The restorations were assessed for the quality of the surface and the color, anatomical form and marginal integrity. Periodontal status was assessed by determining the plaque index, gingival index, pocket depth, and margin index of the abutment teeth. Data were statistically analyzed using the Friedman and the Wilcoxon signed-rank tests with the Bonferroni correction. RESULTS: The survival rate at 2 years was 100%, and no biological or technical complications were observed. All restorations were assessed as satisfactory. The results obtained for gingival index and plaque index were better at 2 years follow-up, than at baseline. The margin index remained stable throughout the follow-up period. No differences in periodontal parameters were observed between abutment and control teeth. CONCLUSIONS: The high survival rate after 2 years suggest that monolithic zirconia may be an acceptable alternative to metal-ceramic and veneered zirconia restorations in the posterior region. Additional long-term, controlled studies are necessary to confirm the results.

Diagnosing Common Deadly Infections in the Era of COVID-19: A Case Report.

The COVID-19 pandemic has challenged clinicians to recognize COVID-19 as one of the diagnostic explanation for common presentations, including fever, cough, and shortness of breath. Latent tuberculosis is responsible for 80% of active tuberculosis cases in the United States, and presentation can vary from asymptomatic to disseminated disease. This potential diagnosis should be thoroughly investigated in foreign-born patients in US hospitals, regardless of travel history and presenting symptoms. We report a patient diagnosed with postpartum disseminated tuberculosis with hematogenous spread to the fetus.

Controlled release of dexamethasone sodium phosphate with biodegradable nanoparticles for preventing experimental corneal neovascularization.

Corneal neovascularization (CNV) leads to the loss of corneal transparency and vision impairment, and can ultimately cause blindness. Topical corticosteroids are the first line treatment for suppressing CNV, but poor ocular bioavailability and rapid clearance of eye drops makes frequent administration necessary. Patient compliance with frequent eye drop application regimens is poor. We developed biodegradable nanoparticles (NP) loaded with dexamethasone sodium phosphate (DSP) using zinc ion bridging, DSP-Zn-NP, with dense coatings of poly(ethylene glycol) (PEG). DSP-Zn-NP were safe and capable of providing sustained delivery of DSP to the front of the eye following subconjunctival (SCT) administration in rats. We reported that a single SCT administration of DSP-Zn-NP prevented suture-induced CNV in rats for two weeks. In contrast, the eyes receiving SCT administration of either saline or DSP solution developed extensive CNV in less than 1 week. SCT administration of DSP-Zn-NP could be an effective strategy in preventing and treating CNV.

The Marginal Fit of CAD/CAM Monolithic Ceramic and Metal-Ceramic Crowns.

PURPOSE: Studies on the marginal fit of monolithic restorations are limited. This study aimed to evaluate the marginal fit among monolithic zirconia, monolithic lithium disilicate, and conventional metal-ceramic crowns and to compare the buccal and lingual surfaces. MATERIALS AND METHODS: Thirty standardized stainless steel master dies were fabricated (height: 5 mm; convergence: 6°; chamfer: 1 mm). The dies were randomly divided into three groups (n = 10 each) according to the material used to construct the crowns: group 1 (LM): Lava Plus; group 2 (DM): IPS e.max CAD; and group 3 (MC): Metal-ceramic. The crowns were luted in a standard manner onto the stainless steel master dies using conventional glass ionomer cement. The vertical marginal gap of the restorations was evaluated under a scanning electron microscope (SEM) at 500x magnification. One-way ANOVA, Tukey´s HSD test, and Student's paired t test were used to assess the marginal discrepancy among the groups. The cutoff value for statistical significance was set at α = 0.05. RESULTS: Significant differences among the three groups (p = 0.0001) were recorded. DM group showed the lowest discrepancies (27.95 ± 9.37 µm). Significant differences were observed for the buccal (p = 0.007) and lingual (p = 0.0001) surfaces between the DM group and the other groups. CONCLUSIONS: The accuracy of fit achieved for the three groups was within the range of clinical acceptance. IPS e.max CAD showed the lowest discrepancies.

A Randomized Clinical Trial Comparing Zirconia and Metal-Ceramic Three-Unit Posterior Fixed Partial Dentures: A 5-Year Follow-Up.

PURPOSE: To compare the survival, success rates, and biological/technical complications of posterior metal-ceramic (MC) and zirconia fixed partial dentures (FPDs). MATERIALS AND METHODS: A total of 40 patients requiring 40 posterior FPDs were randomly assigned to receive 20 zirconia and 20 MC restorations. The restorations were examined 1 week (baseline) and 1, 3, and 5 years after the end of treatment. Technical and biological outcomes were compared. Data were statistically analyzed using the Wilcoxon signed-rank and Mann-Whitney U tests. RESULTS: The survival rates of both groups were 100%, and the success rates were 80% (zirconia) and 100% (MC). No biological complications were observed. Minor chipping was found in 20% of the zirconia restorations. No differences in periodontal parameters were observed between groups. CONCLUSIONS: Zirconia FPDs exhibited the same survival rate (100%) as MC FPDs after 5 years; however, the success rate was 80%, because an increased rate of chipping was observed in zirconia restorations.

Effect of Thermomechanical and Static Loading on the Load to Fracture of Metal-Ceramic, Monolithic, and Veneered Zirconia Posterior Fixed Partial Dentures.

PURPOSE: To evaluate the influence of static (not preloaded) and thermomechanical loading on the load to fracture of metal-ceramic, monolithic and veneered zirconia computer-aided design/computer-aided manufacturing (CAD/CAM) posterior fixed partial dentures (FPDs). MATERIALS AND METHODS: One hundred standardized specimens with 2 abutments screwed onto a platform were prepared from stainless steel to receive a posterior 3-unit FPD with an intermediate pontic. Specimens were randomly divided into 5 groups (n = 20): Metal-ceramic (control group), Lava Zirconia system, Vita In-Ceram YZ, IPS e.max ZirCAD, and Lava Plus. Half of the specimens of each group (n = 10) underwent no preloading, and the other half were subjected to thermomechanical loading in a masticatory simulator, and then all FPDs were loaded until fracture using a universal testing machine at a 1 mm/min crosshead speed. The load to fracture of the veneering ceramic and the load to fracture of framework (total fracture) were recorded for each specimen. Data were statistically analyzed using 2-way ANOVA, Tukey's HSD post-hoc test, Student's t test, and Weibull statistics, α = 0.05. RESULTS: Significant differences were recorded between the metal-ceramic and veneered zirconia groups for the veneering ceramic load (p < 0.001; f = 36.62; f = 57.76) in no preloading and thermomechanical loading subgroups, respectively, but no differences were observed between the static and thermomechanical loading conditions. No differences were observed among the veneered zirconia groups. For the total load to fracture, significant differences were observed according to the material (p < 0.001; f = 500.8), between the metal-ceramic and Lava Plus group and the other zirconia groups in no preloading subgroup, and between metal-ceramic and the other groups (p < 0.001; f = 303.33) in thermomechanical loading subgroup. For the type of preloading, significant differences were observed (p = 0.02; f = 5.24) between the Lava Plus group and the other groups. Thermomechanical loading significantly decreased the fracture load of the Lava Plus group (p = 0.005). The Weibull statistics corroborated the results. CONCLUSIONS: Monolithic zirconia restorations provided the highest load to fracture values among the zirconia groups tested; however, the results indicate that they must be used in the oral environment with caution, because their load to fracture was influenced by the aging simulation.

Subepidermal Calcified Nodules of the Eyelid Differ in Children and Adults.

PURPOSE: Subepidermal calcified nodule of the eyelid is considered as one of the types of calcinosis cutis. It generally occurs in children, and is not known to be associated with systemic disease. The authors report histopathological and clinical findings in 14 cases of subepidermal calcified nodule of the eyelid, including 3 older patients with unique microscopic features. METHODS: Clinical records and pathological materials were critically reviewed in each case, including von kossa, CD3, CD20, and CD68 stains. RESULTS: The 14 cases presented clinically as nodular eyelid lesions. All were treated with surgical excision. The authors found 2 distinct histopathological patterns which correlated with the patients' age. In young patients, the authors observed multiple, small calcified bodies within the dermis surrounded by chronic inflammation and granulomatous foreign body reaction. On the other hand, in elderly patients, lesions were characterized by a single, large, well-demarcated amorphous calcified deposit surrounded by fibrous tissue, without chronic inflammation or foreign body reaction. One of these patients, a 70-year-old man, also suffered from gout. The presence of subepidermal calcified nodule was not documented as a preoperative diagnostic possibility in any of the cases. CONCLUSIONS: Subepidermal calcified nodule of the eyelid is a rare condition, but should be considered in any patient presenting with a painless white to yellowish colored nodule of the ocular adnexa, particularly during the teenage years. Clinicians and pathologists should be aware that this entity has a distinct appearance and could be associated with systemic conditions in elderly patients.

Altered gene expression in conjunctival squamous cell carcinoma.

Conjunctival squamous cell carcinoma is a malignancy of the ocular surface. The molecular drivers responsible for the development and progression of this disease are not well understood. We therefore compared the transcriptional profiles of eight snap-frozen conjunctival squamous cell carcinomas and one in situ lesion with normal conjunctival specimens in order to identify diagnostic markers or therapeutic targets. RNA was analyzed using oligonucleotide microarrays, and a wide range of transcripts with altered expression identified, including many dysregulated in carcinomas arising at other sites. Among the upregulated genes, we observed more than 30-fold induction of the matrix metalloproteinases, MMP-9 and MMP-11, as well as a prominent increase in the mRNA level of a calcium-binding protein important for the intracellular calcium signaling, S100A2, which was induced over 20-fold in the tumor cohort. Clusterin was the most downregulated gene, with an approximately 180-fold reduction in the mRNA expression. These alterations were all confirmed by qPCR in the samples used for initial microarray analysis. In addition, immunohistochemical analysis confirmed the overexpression of MMP-11 and S100A2, as well as reductions in clusterin, in several independent in situ carcinomas of conjunctiva. These data identify a number of alterations, including upregulation of MMP-9, MMP-11, and S100A2, as well as downregulation of clusterin, associated with epithelial tumorigenesis in the ocular surface.

Favorable longterm outcomes of liver transplant recipients treated de novo with once-daily tacrolimus: Results of a single-center cohort.

The once-daily prolonged-release formulation of tacrolimus has been recently related with significant graft and patient mid-term survival advantages; however, practical information on the de novo administration after liver transplantation and longterm outcomes is currently lacking. This study is a 5-year retrospective analysis of a single-center cohort of liver transplant recipients treated de novo with once-daily tacrolimus (April 2008/August 2011). The study cohort consisted of 160 patients, including 23 with pretransplant renal dysfunction, with a median follow-up of 57.6 months (interquartile range, 46.6-69.0). Tacrolimus target trough levels were 5-10 ng/mL during the first 3 months after transplant, reducing progressively to <7 ng/mL after the first posttransplant year. Once-daily tacrolimus was withdrawn in 35 (21.8%) patients during follow-up, mostly due to renal dysfunction and/or metabolic syndrome. The biopsy-proven acute rejection rate was 12.5% with no cases of steroid-resistant rejection. The cumulative incidence of de novo diabetes, hypertension, and dyslipidemia were 16.9%, 31.2%, and 6.5%, respectively. Hepatocellular carcinoma recurrence rate was 2.8%. Renal function remained stable after the sixth month after transplant with a mean estimated glomerular filtration rate of 77.7 ± 19.6 mL/minute/1.73 m(2) at 5 years. None of our patients developed chronic kidney disease stage 4 or 5. Patient survival at 1, 3, and 5 years was 96.3%, 91.9%, and 88.3%, respectively. Overall survival of patients with Model for End-Stage Liver Disease (MELD) score > 25 points was not significantly different. In conclusion, our study suggests that immunosuppression based on de novo once-daily tacrolimus is feasible in routine clinical practice, showing favorable outcomes and outstanding longterm survival even in patients with high MELD scores. Liver Transplantation 22 1391-1400 2016 AASLD.

Digital workflow for monolithic and veneered zirconia and metal-ceramic posterior fixed partial dentures: A five-year prospective randomized clinical trial.

Purpose To evaluate and compare the survival, success rates, and biological and technical complications of three-unit posterior monolithic and veneered zirconia and metal-ceramic (MC) posterior fixed partial dentures (FPDs) fabricated using a digital workflow and computer-aided design and computer-aided manufacturing (CAD/CAM) over a 5-year follow-up.Methods Ninety patients in need of three-unit posterior FPDs were randomized to receive monolithic zirconia (MZ), veneered zirconia (VZ), and MC restorations (n = 30 each). Teeth preparations were scanned using an intraoral scanner, and restorations were milled and cemented with resin cement. Clinical performance and periodontal parameters were assessed at baseline and yearly up to 5 years after insertion. Data analysis was performed using the Kaplan-Meier method, Friedman test, and Wilcoxon signed-rank test with Bonferroni correction and Mann-Whitney U test.Results The 5-year survival rates of the MZ, VZ, and MC FPDs were 87%, 97%, and 100%, respectively (P = 0.04). Most complications were biological in nature. Only one MZ FPD fractured 58 months after placement. All the restorations were assessed as satisfactory at each recall. Differences were found in the gingival index score over time in the VZ and MC groups. The margin index remained stable throughout the follow-up period in both zirconia groups.Conclusions The results of this study suggest that using a digital workflow to fabricate posterior FPDs is an adequate treatment option and that monolithic zirconia could be a viable alternative to metal-ceramic or veneered zirconia. However, further long-term studies are necessary to provide stronger evidence in patients with bruxism.

Performance of posterior third-generation monolithic zirconia crowns in a complete digital workflow: A three-year prospective clinical study.

Background/purpose: Translucent monolithic zirconia restorations have recently introduced. The purpose of this study was to evaluate the clinical behavior and the survival rate of the posterior third-generation monolithic zirconia crowns (MZCs) during three years of clinical service. Materials and methods: Twenty-four patients who needed thirty crowns were enrolled in this study. Digital impressions were made, and the crowns were milled and cemented with a resin cement. The crowns outcomes were assessed using the California Dental Association's (CDA) criteria. Gingival index (GI), plaque index (PI), and periodontal probing depth (PPD) for MZCs and contralateral natural teeth (control) were assessed. Margin index (MI) for MZCs was also assessed. Data analysis was conducted using the Wilcoxon signed-rank and the Friedman tests. Results: The 3-year survival rate was 100%. All MZCs were rated as satisfactory throughout the follow-up period, and no biological or mechanical complications were observed. No differences were recorded when GI, PI and PPD at 3-year of follow-up were compared to baseline. No differences were recorded between crowned and control teeth. The MI remained stable throughout the study period. Conclusion: The third-generation monolithic zirconia appears to be a good treatment option for the rehabilitation of posterior single teeth.

Immediate Loading of Zygomatic Implants Using a Dual Scan Technique.

The immediate loading protocol has become increasingly popular due to the progressive growth in demand for a reduction in treatment times. The possibility of applying this protocol would depend on certain important factors. The application of the digital workflow mentioned in the protocol guarantees rapidity, precision, and esthetics. This report aims to describe a fully digital workflow using a dual scan impression technique to fabricate immediate fixed complete dentures (FCDs) for zygomatic and standard implants. A 58-year-old female patient requested treatment for her severely atrophic maxilla, and four unrehabilitated implants in the mandible. After proper diagnosis and planification, four zygomatic implants and two standard implants were placed. During the surgery, transmucosal abutments were placed on all implants. After suturing, the positions of the implants were recorded using a stereophotogrammetric technique, creating a standard tessellation (STL) file. In the lower arch, the second phase of the surgery was carried out: the transmucosal abutments were placed, and then the implant positions were recorded in the same way. The soft tissues were rescanned after suturing with an intraoral scanner (IOS), and all STL files were aligned to obtain the virtual final models. The pre-design after virtual modifications was aligned with the definitive models. The provisional prostheses were milled and placed after six hours after the surgery, and the definitive prostheses were placed six months after the surgery. The dual scan technique used obtained a precise fit for both the provisional and definitive FCDs. This technique might be an effective and reliable alternative for the fabrication of immediate and definitive screw-retained FCDs in a completely digital workflow. The time taken for scanning and fabrication was reduced, and the clinician's and patient's satisfaction were improved.

Effect of Surface Treatments with Low-Pressure Plasma on the Adhesion of Zirconia.

The purpose of this study was to investigate the effect of low-pressure plasma on the contact angle, shear bond strength (SBS), and the failure mode of zirconia ceramic. Zirconia specimens were divided into three groups according to the surface treatment methods as follows: sandblasting with aluminum oxide (ZR-C), sandblasting with aluminum oxide and oxygen plasma (ZR-CP), and argon plasma (ZR-P). The contact angle, SBS, and surface characteristics were tested after thermocycling. Data analysis was made using the Kruskal-Wallis test and one-way analysis of variance. Plasma treatment significantly reduced the contact angle (p < 0.001) with the lowest value for the Zr-P group. An increase in oxygen and a decrease in carbon was observed on the zirconia surface in both plasma groups. For the SBS, there were significant differences among the groups (p < 0.018), the Zr-CP group showing the highest bond strength. Mixed failures were the most frequent. Plasma treatment was effective in increasing the wettability, increasing the oxygen/carbon ratio without changing zirconia surface morphology. The sandblasting plus plasma with oxygen group exhibited the highest bond strength.

Influence of CAD/CAM systems and cement selection on marginal discrepancy of zirconia-based ceramic crowns.

PURPOSE: To analyze the effect of ceramic manufacturing technique and luting cement selection on the marginal adaptation of zirconium oxide-based all-ceramic crowns. METHODS: An extracted mandibular first premolar was prepared for a complete coverage restoration and subsequently duplicated 40 times in a liquid crystal polymer (LCP). All-ceramic crowns (n = 10) were fabricated on LCP models using the following systems: glass-infiltrated zirconia-toughened alumina (In-Ceram Zirconia) and yttrium cation-doped tetragonal zirconia polycrystals (In-Ceram YZ, Cercon, and Procera Zirconia). The restorations (n = 5) were cemented on their respective dies with glass-ionomer cement (Ketac Cem Aplicap) and resin cement (Panavia 21). The absolute marginal discrepancy of the crowns was measured before and after cementation by scanning electronic microscopy at 160 points along the circumferential margin. The data were analyzed using one-way ANOVA for repeated measures and for independent samples, Scheffé's multiple range post hoc test, and Student's t-test (alpha = 0.05). RESULTS: There were statistical differences in the mean marginal openings among the four all-ceramic systems before and after luting (P < 0.0001). The Procera restorations had the lowest pre- and post-cementation values (P < 0.0001). A significant increase in the marginal gap size caused by luting media occurred in all tested groups (P < 0.0001). Resin cement resulted in larger marginal discrepancies than glass-ionomer cement (P < 0.0001).