ABSTRACT
BACKGROUND: While working on CAD/CAM-customized abutments, the use of standard impression copings with a circular diameter produces inconsistency within the emergence profile. It may begin with a collapse of the supra-implant mucosa during impression taking, then lead to a computer-generated mismatch of the position and outline of the abutment shoulder, and consequently result in a compromised outcome of anticipated treatment. The aim of the study was to compare the virtual and clinical positions of the abutment shoulder in relation to the mucosal margin after the abutment delivery. METHODS: Conventional open-tray impression takings followed uncovering surgery. Master casts were scanned with a desktop scanner. Clinical examinations took place after abutment's insertion and temporization (T1) and prior to cementation of the definitive crown (T2). The distances between the abutment shoulder and marginal soft tissue were measured intraorally in four aspects and juxtaposed with those on the virtual model. RESULTS: The study evaluated 257 dental implants and CAD/CAM-customized abutments. As T1 and T2 showed, there was a positive correlation between the virtually designed abutment shoulder position and matching clinical location relative to the mucosal margin. In 42.1% of cases, the distance between the mucosal margin and the abutment shoulder did not change. It increased in 36.3% of cases while a decrease occurred in 21.6% of them. CONCLUSIONS: Computer-set position of the abutment shoulder in relation to the mucosal margin can be predictably implemented in clinical practice.
Subject(s)
Computer-Aided Design , Dental Abutments , Dental Prosthesis Design , Adult , Aged , Dental Implant-Abutment Design , Dental Implantation, Endosseous , Dental Marginal Adaptation , Dental Prosthesis Design/methods , Female , Humans , Male , Middle AgedABSTRACT
The puprose of this study was to evaluate retention force of conical double crowns in two material connections: gold casting alloy/gold casting alloy and gold casting alloy/gold electroforming alloy. 12 crown pairs of both material connections with the cone angles of 2°, 4° and 6° were made. Experiment of 10.000 in-and-out cycles was performed using a new device which allows the retentive force to be measured in continuous way without necessity of moving the samples to another device. It has been found that the higher the retentive force values, the lower the cone angle. Dispersion of the retention value was similar in both groups, but when cone angle was 2° or 4°, stability of retention force with the passage of time was higher in combinations with electroformed copings. The optimum solution was the cast alloy/cast alloy connection but only with cone angle 6°. However, retentive values seem to be too low to achieve proper retention of dentures.
Subject(s)
Crowns , Denture Retention , Materials Testing , Biomechanical Phenomena , Humans , KineticsABSTRACT
This study presents the results of a long-term clinical evaluation of conical crown-retained dentures fabricated using different technologies. Four different material connections between the outer and inner crowns were used: cast gold/cast gold, cast gold/electroforming, nonprecious alloy/electroforming, and titanium abutment/electroforming. Technical failures and retention values were assessed. The best clinical outcome was found with dentures in which both crowns were cast from gold alloy. The most frequent technical failures were observed in restorations with electroformed outer crowns. Better clinical outcomes were noted when the electroformed outer crowns were used in dentures retained by implants as compared to dentures on natural dentition.
Subject(s)
Crowns , Denture Design , Denture Retention , Denture, Overlay , Adult , Aged , Cementation/methods , Chromium Alloys/chemistry , Dental Abutments , Dental Implants , Dental Materials/chemistry , Dental Restoration Failure , Dental Veneers , Electrochemical Techniques , Female , Follow-Up Studies , Gold Alloys/chemistry , Humans , Jaw, Edentulous, Partially/classification , Jaw, Edentulous, Partially/rehabilitation , Longitudinal Studies , Male , Middle Aged , Stress, Mechanical , Surface Properties , Technology, Dental , Titanium/chemistryABSTRACT
The aim of the present study was evaluation the distribution of B- and T-cells and T-cell subsets in periodontal tissues from patients with different periodontitis forms. Periodontal tissue samples were collected from group P patients during routine surgical procedures, while from group C during tooth extraction for orthodontic or prosthetic purposes. Directly after collection, tissue samples were placed in a criostat or fixed in 10% buffered formalin for 24 h at room temperature. Following fixation the material was embedded in paraffin and subjected to routine histological techniques. Examinations of B- and T-lymphocytes populations and T-lymphocytes subsets were made with the use of immunohistochemical method. In C group single T and B lymphocytes were found in histological examination in pocket epithelium zones. In early onset periodontitis (EOP) patients in inflammatory infiltration lymphocytes T were dominating while in adult periodontitis (AP) patients dominating were B lymphocytes. Mean CD4/CD8 ratio in control group was 1.7 and in EOP and AP patients 1.1 and 2.6 respectively.
