Alberto Ferreiroa

Clinical evaluation comparing the fit of all-ceramic crowns obtained from silicone and digital intraoral impressions based on wavefront sampling technology

OBJECTIVE The aim of this study was to compare the fit of ceramic crowns fabricated from conventional silicone impressions with the fit of ceramic crowns fabricated from intraoral digital impressions. METHODS Twenty-five participants with 30 posterior teeth with a prosthetic demand were selected for the study. Two crowns were made for each preparation. One crown was fabricated from an intraoral digital impression system (IDI group) and the other crown was fabricated from a conventional two-step silicone impression (CI group). To replicate the interface between the crown and the preparation, each crown was cemented on its corresponding clinical preparation with ultra-flow silicone. Each crown was embedded in acrylic resin to stabilise the registered interface and then cut in 2mm thick slices in a buco-lingual orientation. The internal gap was determined as the vertical distance from the internal surface of the crown to the prepared tooth surface at four points (marginal gap, axial gap, crest gap, and occlusal fossa gap) using stereomicroscopy with a magnification of 40×. Data was analysed by using Wilcoxon signed rank test (α=0.05). RESULTS Internal adaptation values were significantly affected by the impression technique (p=0.001). Mean marginal gap was 76.33 ± 65.32 μm for the crowns of the IDI group and 91.46 ± 72.17 μm for the CI group. CONCLUSION All-ceramic crowns fabricated from intraoral digital impressions with wavefront sampling technology demonstrated better internal fit than crowns manufactured from silicone impressions. CLINICAL SIGNIFICANCE Impressions obtained from an intraoral digital scanner based on wavefront sampling technology can be used for manufacturing ceramic crowns in the normal clinical practice with better results than conventional impressions with elastomers.

Zirconia in fixed prosthesis. A literature review

Statement of problem: Evidence is limited on the efficacy of zirconia-based fixed dental prostheses. Objective: To carry out a literature review of the behavior of zirconium oxide dental restorations. Material and Methods: This literature review searched the Pubmed, Scopus, Medline and Cochrane Library databases using key search words “zirconium oxide,” “zirconia,” “non-metal restorations,” “ceramic oxides,” “veneering ceramic,” “zirconia-based fixed dental prostheses”. Both in vivo and in vitro studies into zirconia-based prosthodontic restoration behavior were included. Results: Clinical studies have revealed a high rate of fracture for porcelain-veneered zirconia-based restorations that varies between 6% and 15% over a 3- to 5-year period, while for ceramo-metallic restorations the fracture rate ranges between 4 and 10% over ten years. These results provoke uncertainty as to the long-term prognosis for this material in the oral medium. The cause of veneering porcelain fractures is unknown but hypothetically they could be associated with bond failure between the veneer material and the zirconia sub-structure. Key words:Veneering ceramic, zirconia-based ceramic restoration, crown, zirconia, tooth-supported fixed prosthesis.

Marginal discrepancy of monolithic and veneered all-ceramic crowns on titanium and zirconia implant abutments before and after adhesive cementation: a scanning electron microscopy analysis.

PURPOSE To evaluate the marginal discrepancy of monolithic and veneered all-ceramic crown systems cemented on titanium (Ti) and zirconia implant abutments. MATERIAL AND METHODS Sixty customized implant abutments for a maxillary right central incisor were fabricated of Ti and zirconia (n = 30 of each) for an internal-connection implant system. All-ceramic crowns were fabricated using the following systems (n = 10 per group): monolithic with computer-aided design/computer-assisted manufacture (CAD/CAM) lithium disilicate (MLD), pressed lithium disilicate (PLD), or CAD yttrium-stabilized tetragonal zirconia polycrystal (Y-TZP). The frameworks of the PLD and Y-TZP systems were manually veneered with a fluorapatite-based ceramic. The crowns were cemented to their implant abutments, and the absolute marginal discrepancy of the gap was measured before and after cementation. Data were analyzed statistically. RESULTS Marginal discrepancies were significantly influenced by the crown system and by cementation, but the material did not significantly affect the results. Interaction terms were not significant. Y-TZP crowns on both Ti and zirconia abutments presented the smallest mean marginal discrepancies before (52.1 ± 17 μm and 56.2 ± 11 μm, respectively) and after cementation (98.7 ± 17 μm and 101.8 ± 16 μm, respectively). Before cementation, MLD crowns showed significantly larger mean marginal openings than PLD crowns on both Ti and zirconia abutments (75.2 ± 12 and 77.5 ± 13 μm for MLD, 52.1 ± 17 μm and 69.7 ± 8 μm for PLD, respectively). After cementation, both Ti and zirconia abutments with MLD crowns (113.5 ± 12 μm and 118.3 ± 14 μm, respectively) showed significantly larger values than with PLD crowns (98.7 ± 17 μm and 109.4 ± 9 μm, respectively). CONCLUSIONS Manually veneered Y-TZP crowns demonstrated more favorable marginal fit on both Ti and zirconia implant abutments before and after cementation compared to those of MLD and PLD.

Diagnosis and endodontic treatment of type II dens invaginatus by using cone-beam computed tomography and splint guides for cavity access: a case report.

BACKGROUND AND OVERVIEW Dens invaginatus (DI) is defined as a rare dental malformation. The inherent structural variants of this anatomic disorder make it difficult to perform conventional endodontic treatment procedures by means of a conservative access cavity. In this clinical case report, the authors describe the treatment of a type II DI by means of guided splints for cavity access. CASE DESCRIPTION This is a clinical report of a case of type II DI in a maxillary lateral incisor. The authors established the diagnosis by means of cone-beam computed tomography (CBCT). The authors manufactured 3 splint guides from a Digital Imaging and Communications in Medicine file and a stereolithography file obtained from a plaster model of the patient by using software for guided implant placement, for access opening, and for locating the root canals. CONCLUSIONS CBCT is an effective method for obtaining information about the root canal system in teeth with DI. In addition, guided implant surgery software is effective for manufacturing splint guides for endodontic treatment with conservative pulp chamber access. PRACTICAL IMPLICATIONS Information obtained from CBCT allows the clinician to fabricate splint guides for minimally invasive access opening in this type of case, thus reducing the loss of dental tissue.

Cemented and screw-retained implant-supported single-tooth restorations in the molar mandibular region: A retrospective comparison study after an observation period of 1 to 4 years.

Objectives: The aim of this study was to evaluate the survival and compare the appearance of different mechanical and biological complications, in screw-retained and cemented-retained single-tooth implant-supported restorations localized in the molar mandibular region, over a period of 1 to 4 years. Material and Methods: A retrospective study was carried out with a total of eighty implant-supported restorations, which were placed in eighty patients for prosthetic rehabilitation of a mandibular molar. Forty patients were rehabilitated with a cemented-retained restoration and the other forty with a screw-retained restoration. The presence of the following complications was recorded for both types of prostheses: Fractures of the ceramic veneering, loosening screws, mucositis and peri-implantitis. Debonding of the restoration was analyzed in the cemented-retained restoration group. The clinical survival of crowns was analyzed with a Kaplan-Meier test and the clinical complications were compared, using a Student t test and Log-rank test. Results: 27 patients registered some complication. The average rate of complications was 37,5% for cemented-retained restorations and 30% for screw-retained restorations. The complications more common in the cemented-retained restoration were the presence of mucositis (14,87%), while in the screw-retained restorations was the loosening screw (20%). Student t test and Log-Rank test found significant differences (p=0,001) between the screw loosening and presence of mucositis. Conclusions: The cemented-retained restorations seem to prevent screw loosening, but the presence of cement seem to increase the complications around the soft tissues, however in the screw-retained restorations the presence of mucositis and peri-implantitis are lower than cemented-retained restorations. The incidence of fracture of ceramic veneering was similar in both groups. Key words:Screw-retained restorations, cemented-retained restorations, screw loosening, peri-implant diseases and fracture ceramic veneering.

Implant-supported overdenture manufactured using CAD/CAM techniques to achieve horizontal path insertion between the primary and secondary structure: A clinical case report

This report describes the case of an edentulous patient with an atrophic maxilla and severe class III malocclusion. Prosthetic rehabilitation was performed using CAD/CAM techniques for manufacturing an implant-supported overdenture with horizontal insertion. A vestibulo-lingual insertion overdenture is a precision prosthesis with a fixation system affording a good fit between the primary and secondary structure. Both structures exhibit passive horizontal adjustment. This treatment option requires the same number of implants as implant-supported fixed dentures. The horizontal assembly system prevents the prosthesis from loosening or moving in response to axial and non-axial forces. The technique was used to rehabilitate a patient presenting an atrophic upper maxilla, with the insertion of 8 implants. No complications were reported at follow-up 3, 6 and 12 months after fitting of the prosthesis. This system offers solutions to the clinical and laboratory complications associated with hybrid prostheses, concealing emergence of the chimneys and improving implant-prosthesis hygiene.

In Vitro Evaluation of Three Methods for the Retrieval of Fractured Screw Fragments from Dental Implants

PURPOSE To compare the effectiveness of different methods of fractured screw fragment retrieval from dental implants, comparing a conventional method (use of an exploration probe and ultrasonic tips) with two mechanical retrieval kits. MATERIALS AND METHODS One hundred thirty-five screws in implant internal connections were fractured to test fragment retrieval comparing three methods: conventional method with the use of an explorer probe and ultrasonic tips (group CE), extraction with a mechanical kit with a guide cylinder (group MK1), and extraction with a mechanical kit without a guide cylinder (group MK2). Extraction success and retrieval times for each method, as well as success and retrieval times in relation to fracture depth-coronal, middle, or apical-were analyzed by means of chi-square, Fisher exact, Kruskal-Wallis, and Mann-Whitney tests (P < .05). The integrity of implant internal threads was also analyzed. RESULTS The extraction success rates for groups MK2, CE, and MK1 were 93.3%, 73.3%, and 20%, respectively. The mean ± SD extraction times were 2 minutes, 56 seconds ± 2 minutes, 9 seconds; 3 minutes, 15 seconds ± 1 minute, 48 seconds; and 13 minutes, 34 seconds ± 7 minutes, 25 seconds for groups MK2, CE, and MK1, respectively. Statistically significant differences were found in the number of fractured screws extracted and in the retrieval time. No significant differences were found for retrieval time or extraction success in relation to the depth of the fracture. CONCLUSION The mechanical kit without the guide cylinder achieved the best results with respect to the number of screw fragments retrieved, retrieval time, and preservation of implant internal threads.

Immediate placement of single implant simultaneously with immediate loading in a fresh socket associated to periapical infection: A clinical case report

Early restoration of the masticatory function, phonatory and aesthetics is some of the current goals of the therapy based on endosseous implants. Facing the classic protocols of implant insertion, which recommend a period of several months between extraction and implant placement, alternatives have been developed that demonstrate that immediate implant placement after tooth extraction permits adequate osseointegration, even in those cases where there is a periapical disease. The immediate restoration of implants after placement is a possibility where aesthetic requirements are high. This article presents a case with immediate implant placement and immediate loading of a first upper premolar with prior periapical pathology due to a vertical fracture. The immediate prosthetic was performed using the extracted crown, which is adapted to be attached to a titanium temporary abutment using a resin cement. After a 4 month healing period work began on the final prosthetic crown. The screw crown was made of zirconium oxide with a covering feldspathic ceramic. At the 12-month follow-up, there were no mechanical or biological complications. The patient gave high satisfaction marks for the overall treatment, giving visual analogue scale score of nine. Immediate post-extraction implants have arisen as an alternative to traditional implants on completely healed bone. Their main aim is to reduce treatment time and number of surgical procedures, along with other objectives such as reduced bone re-absorption and improved aesthetics. Key words:Post-extraction implants, immediate loading prosthetic, implant-retained prosthesis, periapical disease, vertical fracture.

Comparative in vitro study of two methods for gingival biotype assessment

Background The gingival thickness seems to have an important role in different dental treatments. There are different methods of quantifying this thickness, but it is not known which of them can be the most effective. The objective to assess the accuracy of two different methods for gingival thickness measurement: the transgingival needle probing (TGNP) and the tension-free caliper (TFC) in an in vitro model, by comparing them with direct physical measurements (reference standard). Material and Methods Gingival thickness (GT) was evaluated in 27 female pigs with four implant sites 1, 2 and 3mm from the gingival margin with three different methods: 1) transgingival needle probing 2) tension-free caliper and 3) Direct visualization after making a incision in the mucosa and measuring GT with a periodontal probe. Wilcoxon test for paired samples were used with a confident level of 95%. Results A total of 324 points were measured, 59% of the sites presented a thin biotype with DV, it was correctly assessed with the TGNP in 84% of the times and in 86% with the TFC. 41% of the sample presented thick biotype, 76% was the percentage measured with the TGNP and 0% of the sites evaluated with TFC resulted in this biotype. Conclusions Transgingival needle probing constitutes an accurate method when measuring GT at different levels. Tension free caliper is not a good tool for assessing the gingival biotype as long as it is unable to predict thick biotype. Key words:Periodontal Biotype, Gingival Thickness, Periodontal Tissue and Diagnosis.

Comparative study of all-ceramic crowns obtained from conventional and digital impressions: clinical findings

ObjectiveTo compare clinical aspects of all-ceramic crowns fabricated from conventional and digital impressions.MethodsThirty patients with 30 posterior teeth with the need of a crown restoration were selected. Zirconia-based ceramic crowns were made using an intraoral digital impression system (TRIOS®, 3shape) and two-step silicone impression technique. Two external blinded operators evaluated the all-ceramic crowns. Five selection items were assessed of which four were clinical: “marginal fit,” “occlusal contacts,” “interproximal contact points,” and “primary retention.” Then, the last selection item “final selection” was assessed when the operators considering all the variables had to select which of the digital or conventional crown had the best clinical conditions. Data was analyzed using Kappa index test and the Pearson’s chi-square test (α = 0.05).ResultsFor the items marginal fit and interproximal contact points, moderate agreement between the two operators was described and significant differences were found between the two study groups. Conversely, for the variables primary retention and occlusal contacts, the agreement between the operators was fair and no significant differences were found. For the final selection, a substantial agreement was reached between the two operators and significant differences were found between the two groups (p < 0.05).ConclusionIn most cases and in a significant way, the digital crowns had better clinical conditions according to both evaluators. The digital crowns were statistically superior for the interproximal contact points and marginal fit. For the variables occlusal contacts and primary retention, no difference between the two groups was observed.Clinical significanceDigital intraoral impressions can be used for manufacturing ceramic crowns, with the same or better clinical results as conventional impressions.