Ceramic Fixed Partial Dentures Research Articles

Limited evidence suggests complete arch digital scans are less time efficient than conventional impression.

Source of funding This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectorsType of study/design Randomised controlled trial (RCT) with parallel design.Subjects This RCT was conducted at the Clinic of Fixed and Removable Prosthodontics and Dental Material Science, Centre of Dental Medicine, University of Zurich, Zurich, Switzerland. Ten patients, six women and four men, with a mean age of 62 years and an age range of 49-77 years, requiring posterior tooth-supported 3-unit fixed partial dentures (FPDs) were included in this RCT. The abutment teeth were six molars and six premolars in the maxilla and five molars and three premolars in the mandible. The patients fulfilled the following inclusion criteria: they all were >18 years, with a full mouth plaque score <25% and a full mouth bleeding score <25%. They all needed a posterior tooth-supported FPD, in which the third molar was not an abutment tooth. Only abutments with no extensive pretreatment were eligible. Adjacent and opposing teeth should be healthy or adequately restored.Treatment Three intraoral digital scanning systems (Lava C.O.S.; 3M [Lava], iTero; Align Technology Inc [iTero], Cerec Bluecam; Dentsply Sirona [Cerec]) and conventional light/regular body polyether impression in a stock tray were made on each of the included participants by the same clinician. The opposing arch impression was made in alginate. The sequence of the four techniques was computer generated and concealed in opaque sealed envelopes. Three calibrated experienced clinicians were involved in the treatment. They followed the published guidelines for preparing abutments that receive CAD/CAM ceramic FPDs. After interim prosthesis removal and double retraction cord application, the digital or the conventional impression procedure was started as dictated by the random sequence. Scans were done according to the manufacturer's guidelines, whereby Lava and Cerec required powdering of the teeth by titanium oxide and iTero did not.Main outcome Time needed for obtaining a scan or an impression was calculated. For digital scans it consisted of the time required for powdering, scanning and occlusal registration, while in conventional impression it started from the beginning of impression mixing till tray removal. The number of impression or scan remakes required until results fulfilling the quality criteria were obtained was also recorded. Visual analogue scale (VAS) was used to rate the perception of both, clinicians and patients for the procedures. Patients were asked to rate their comfort with the procedure, while clinicians rated both difficulty and comfort, where 0 indicated uncomfortable and simple and 100 difficult and comfortable. Subjective assessment of the time as judged by the clinicians and the patients was also reported.Main results Generally speaking, conventional impression was better than the three complete arch digital scans, regarding time required in seconds, difficulty for clinicians, comfort and time perception of both patients and clinicians. Number of remakes were highest in iTero (7), followed by Lava, conventional impression and finally Cerec (0). The time required for each technique differed significantly Polyether = 658 (95%CI 528-782) Cerec = 1776 (95%CI 804-2386) iTero = 1107 (785 - 2091). A significant difference was found neither among the three digital impressions, nor between the conventional impression and Lava (μ = 1091, 95%CI [717-1465]). The same findings were reported regarding difficulty for the clinicians. A significant difference was reported between conventional impression (μ = 15, 95%CI [7-24]) and both Cerec (μ = 67, 95%CI [58-77]) and iTero (μ = 43, 95%CI [25-62]). No significant difference was reported among the studied techniques regarding patients' comfort and time perceptions of both clinicians and patients except for a difference in the patients' time perception of Cerec and conventional impression, where P = .035. Regarding the clinicians' comfort a significant difference was only found between conventional impression (μ = 82, 95%CI [69-94]) and Cerec (μ = 32, 95%CI [18-46]).Conclusion Within the limitations of this RCT, it can be concluded that complete arch conventional impression is objectively less time consuming and subjectively preferred by both clinicians and patients when compared to digital scanning. Digital scanning techniques, requiring powdering, are more difficult for the clinicians than powderless ones and conventional impression.

Numerical simulation of the fracture process in ceramic FPD frameworks caused by oblique loading

Using a newly developed three-dimensional (3D) numerical modeling code, an analysis was performed of the fracture behavior in a three-unit ceramic-based fixed partial denture (FPD) framework subjected to oblique loading. All the materials in the study were treated heterogeneously; Weibull׳s distribution law was applied to the description of the heterogeneity. The Mohr–Coulomb failure criterion with tensile strength cut-off was utilized in judging whether the material was in an elastic or failed state. The simulated loading area was placed either on the buccal or the lingual cusp of a premolar-shaped pontic with the loading direction at 30°, 45°, 60°, 75° or 90° angles to the occlusal surface. The stress distribution, fracture initiation and propagation in the framework during the loading and fracture process were analyzed. This numerical simulation allowed the cause of the framework fracture to be identified as tensile stress failure. The decisive fracture was initiated in the gingival embrasure of the pontic, regardless of whether the buccal or lingual cusp of the pontic was loaded. The stress distribution and fracture propagation process of the framework could be followed step by step from beginning to end. The bearing capacity and the rigidity of the framework vary with the loading position and direction. The framework loaded with 90° towards the occlusal surface has the highest bearing capacity and the greatest rigidity. The framework loaded with 30° towards the occlusal surface has the least rigidity indicating that oblique loading has a major impact on the fracture of ceramic frameworks.

Comparative evaluation of stresses in tooth implant connected fixed partial denture by varying the implant design and position: A 3D finite element study

This study aims at evaluating stresses generated in a fixed tooth to implant connected fixed partial denture (FPD) by finite element method by varying implant design and position, in unilateral distal extension cases, i.e. for replacing mandibular 1 st and 2 nd molars. Four models were created, Model 1-A finite element model (FEA) model of a crestal implant-tooth connected metal ceramic FPD with pontic in 36 region. The 35 region simulated the second premolar. Model 2-A FEA model of a basal implant-tooth connected metal ceramic FPD. Model 3-A FEA model of a crestal implant in 36 region connected to tooth 35 and cantilevered posteriorly with pontic in 37 region, made of metal ceramic. Model 4-A FEA model of a basal implant in 36 region connected to tooth 35 and cantilevered posteriorly with pontic in 37 region, made of metal ceramic. A vertical force of 100N directed evenly on the nodes on the occlusal surface of each of the three crowns. The models displayed stress both numerically and by color coding. On comparing models 1 and 2, the model 1 showed comparatively more stresses in crestal bone area of the implant. On comparing models 3 and 4, model 3 showed lesser von misses stress values. In case of tooth implant connected FPDs without any cantilevers, basal implants show better stress distribution when compared to crestal implants. In case of cantilever designs, crestal implant design showed lower stress values, but the difference in stresses were less.

A 3D numerical simulation of stress distribution and fracture process in a zirconia‐based FPD framework

In this study, a numerical approach to the fracture behavior in a three-unit zirconia-based fixed partial denture (FPD) framework was made under mechanical loading using a newly developed three-dimensional (3D) numerical modeling code. All the materials studied were treated heterogeneously and Weibull distribution law was applied to describe the heterogeneity. The Mohr-Coulomb failure criterion with tensile strength cut-off was utilized to judge whether the material was in an elastic or failed state. For validation, the fracture pattern obtained from the numerical modeling was compared with a laboratory test; they largely correlated with each other. Similar fracture initiation sites were detected both in the numerical simulation and in an earlier fractographic analysis. The numerical simulation applied in this study clearly described the stress distribution and fracture process of zirconia-based FPD frameworks, information that could not be gained from the laboratory tests alone. Thus, the newly developed 3D numerical modeling code seems to be an efficient tool for prediction of the fracture process in ceramic FPD frameworks.

Numerical Modeling of the Fracture Process of a Three-Unit All-Ceramic Fixed Partial Denture

Fracture of dental all-ceramic restoration is often observed in clinic. And the fracture mechanisms and processes of three-unit all-ceramic fixed partial dentures (FPDs) are still not clear. In this paper, the fracture mechanism and process of a three unit zirconia ceramic FPDs framework under simulated mechanical loading are calculated by using a self-developed numerical modeling code, the RFPA2D code. Acoustic emission showed that the fracture mechanism was tensile failure and the crack started at the lower boundary of the framework. The result revealed that the framework fracture pattern obtained by using the numerical simulation agreed with that observed in a previous laboratory test. The fracture process could be followed both in step-by-step and step-in-step. The RFPA2D code is suitable for the use as a complement to other tests and clinical observations in studying stress distribution, fracture mechanism and fracture process in ceramic FPDs framework.

Stress analysis of effects of nonrigid connectors on fixed partial dentures with pier abutments

In some patients, the pattern of missing teeth may require the use of a fixed partial denture (FPD) with an intermediate pier abutment. Information is needed regarding the biomechanical behavior and the position of a nonrigid connector for this treatment option. The purpose of this study was to evaluate, by means of finite element method (FEM), the effects of rigid and nonrigid design types on stress distribution for 5-unit FPDs with pier abutments. A 3-dimensional cross-section FEM model (SAP 2000) simulating a 5-unit metal ceramic FPD with a pier abutment with rigid or nonrigid designs (connector location at the mesial region of the second molar, at the distal region of the second premolar, at the mesial region of the second premolar, and at the distal region of the canine) was developed. In the model, the canine, second premolar, and second molar served as abutments. A supporting periodontal ligament and alveolar bone (cortical and trabecular) were modeled. A 50-N static vertical occlusal load was applied on the cusp of each abutment to calculate the stress distributions. Three different types of load were evaluated: loading of all cusps to simulate maximum centric occlusion contacts, loading of the canine to simulate a single anterior contact, and loading of the second molar to simulate a posterior contact. The analysis of the von Mises stress values revealed that maximum stress concentrations were located at the load areas for all models. Also, for all models, the highest stress values were located at connectors and cervical regions of abutment teeth, especially at the pier abutment. The area of maximum stress concentration at the pier abutment was decreased by the use of a nonrigid connector at the distal region of the second premolar.

Fractographic analyses of zirconia-based fixed partial dentures

Objectives Advances in ceramic processing techniques enable clinicians and ceramists to fabricate all-ceramic fixed partial dentures (FPDs) for posterior regions using high-strength yttria-stabilized tetragonal zirconia polycrystals (Y-TZP). However, failures occur in ceramic FPDs due to their design. The objectives of this study were to determine the site of crack initiation and the causes of fracture in clinically failed zirconia-based ceramic FPDs. Methods Five clinically failed four-unit Y-TZP-based FPDs (Cercon ® ceramics, DeguDent GmbH, Hanau, Germany) were retrieved and analyzed. The fragments containing the fracture origins in the veneers (Cercon ® Ceram S Veneering Ceramic, DeguDent GmbH, Hanau, Germany) of two samples were missing but the rest of veneer structures were present. The other three samples had their veneers intact. Fracture surfaces were examined using fractographic techniques, utilizing both optical and scanning electron microscopes (SEM). Quantitative fractography and fracture mechanics principles were used to estimate the stresses at failure. Results Primary fractures initiated from the gingival surfaces of connectors at veneer surfaces in four out of the five samples. However, critical flaw sizes could be measured in three of the five cases since fracture origins were lost in the remaining two due to local fragmentation at the crack initiation site. Delaminations between glass veneer and zirconia core were observed in Y-TZP-based FPDs and a secondary fracture initiated from the zirconia core. Secondary fracture controlled the ultimate failure. Failure stresses of the fixed partial dentures that failed due to zirconia fracture ranged from 379 to 501 MPa. Fractures that had origins on the glass veneer surface had failure stresses between 31 and 38 MPa. Significance Primary fractures in clinically failed Y-TZP-based FPDs initiated from the veneer surfaces. Interfacial delamination in glass veneer/zirconia core bilayer dental ceramic structures controlled the secondary fracture initiation sites and failure stresses in Y-TZP-based fixed partial dentures.

Numerical modeling of the fracture process in a three-unit all-ceramic fixed partial denture

Objectives The main objectives were to examine the fracture mechanism and process of a ceramic fixed partial denture (FPD) framework under simulated mechanical loading using a recently developed numerical modeling code, the R-T 2D code, and also to evaluate the suitability of R-T 2D code as a tool for this purpose. Methods Using the recently developed R-T 2D code the fracture mechanism and process of a 3 U yttria–tetragonal zirconia polycrystal ceramic (Y–TZP) FPD framework was simulated under static loading. In addition, the fracture pattern obtained using the numerical simulation was compared with the fracture pattern obtained in a previous laboratory test. Results The result revealed that the framework fracture pattern obtained using the numerical simulation agreed with that observed in a previous laboratory test. Quasi-photoelastic stress fringe pattern and acoustic emission showed that the fracture mechanism was tensile failure and that the crack started at the lower boundary of the framework. The fracture process could be followed both in step-by-step and step-in-step. Significance Based on the findings in the current study, the R-T 2D code seems suitable for use as a complement to other tests and clinical observations in studying stress distribution, fracture mechanism and fracture processes in ceramic FPD frameworks.

An Alveolar Bone Augmentation Technique to Improve Esthetics in Anterior Ceramic FPDs: A Clinical Report

This clinical report describes guided bone augmentation for treatment of a facial maxillary alveolar bone defect to enhance the esthetic result for an all-ceramic fixed partial denture (FPD). A combination of decalcified freeze dried bone allograft and resorbable human pericardium, in conjunction with cortical channel expansion, was used for the augmentation process to eliminate a secondary surgical procedure. Post-operative examinations showed improvement in the alveolar bone contour. The regeneration of the missing osseous structure was accomplished to support the future esthetic soft tissue contours. This osseous regenerative technique significantly increased the functional and esthetic outcome of the final FPD by restoring the alveolar ridge defect to its original dimension.

Pressed ceramic in fixed partial dentures construction

Purpose This study compares the marginal accuracy of posterior metal ceramic (MC), all-ceramic IPS Empress®2 and experimental pressed ceramic (EPC-VP 1989/4) three-unit fixed partial dentures (FPD), before and after luting and after thermo-mechanical fatigue in a dual-axis chewing simulator. Materials and methods Caries-free human teeth (n=160) were used as abutments for the fabrication of eighty posterior three-unit FPD, divided into two test-groups, IPS Empress®2 and EPC, of 32 samples each and one control group of 16 samples metal ceramic FPD. All FPD were cemented with Variolink®II dual-curing resin cement. Half of the samples in each group were exposed to a dual-axis chewing simulator. Results The geometric mean marginal gap values (μm, before cementation, after cementation and after thermo-mechanical fatigue) amounted to 53, 63 and 62 for the ceramic metal FPD, 57, 71 and 68 for the Empress®2 FPD and 55, 67 and 68 for the EPC FPD. In all groups a statistically significant increase in marginal gap width was observed after cementation. The effect of functional loading in the chewing simulator on marginal gap was not significant. Marginal gap was lowest in the control group but differences with all-ceramic materials were small in all evaluation stages. Conclusion Within the limits of this investigation, it can be concluded that marginal gap values of these all-ceramic materials and conventional MC techniques are on a similar level. In particular, almost all marginal gap values observed in this study were within the limits of clinical acceptance.

The safety and efficacy of anterior ceramic fixed partial dentures: A review of the literature

As a result of the successful use of ceramic crowns and patient demands for metal-free, tooth-colored restorations, ceramic systems for anterior fixed partial dentures (FPDs) have become available. Although numerous in vitro studies have been published, clinical studies that evaluate anterior ceramic FPDs are few and limited. This article reviews data on ceramic FPDs published between 1966 and 2001 in the English language. Peer-reviewed articles were identified through a MEDLINE search and a hand search of relevant textbooks and annual publications; abstracts were not considered for inclusion. The available data suggest that more clinical studies (preferably randomized clinical trials) that assess the long-term outcome of anterior ceramic FPDs are required to determine whether they can serve as a viable replacement for a maxillary anterior missing tooth and, at the same time, provide patients with a safe and effective restoration, oral health, and social comfort. (J Prosthet Dent 2001;86:520-5.)