Query: Dental connectors in fixed prosthodontics success and failure

title: Fixed Prosthodontics Failure in Students' Patients at King Saud University
abstract: Anticipating longevity as well as causes and trends of failure of dental fixed prosthesis (FP) are frequent demand by both clinicians and patients. Understanding such complications should help dentists plan the treatment of patients with a more reliable prognosis.

title: The complete digital workflow in fixed prosthodontics: a systematic review
abstract: BackgroundThe continuous development in dental processing ensures new opportunities in the field of fixed prosthodontics in a complete virtual environment without any physical model situations. The aim was to compare fully digitalized workflows to conventional and/or mixed analog digital workflows for the treatment with tooth borne or implant supported fixed reconstructions. PICO strategy was executed using an electronic (MEDLINE, EMBASE, Google Scholar) plus manual search up to 2016 09 16 focusing on RCTs investigating complete digital workflows in fixed prosthodontics with regard to economics or esthetics or patient centered outcomes with or without follow up or survival/success rate analysis as well as complication assessment of at least 1 year under function. The search strategy was assembled from MeSH Terms and unspecific free text words: "Dental Prosthesis" [MeSH] OR "Crowns" [MeSH] OR "Dental Prosthesis, Implant Supported" [MeSH] OR (crown) OR (fixed dental prosthesis) OR (fixed reconstruction) OR (dental bridge) OR (implant crown) OR (implant prosthesis) OR (implant restoration) OR (implant reconstruction) AND "Computer Aided Design" [MeSH] OR (digital workflow) OR (digital technology) OR (computerized dentistry) OR (intraoral scan) OR (digital impression) OR (scanbody) OR (virtual design) OR (digital design) OR (cad/cam) OR (rapid prototyping) OR (monolithic) OR (full contour) AND "Dental Technology" [MeSH) OR (conventional workflow) OR (lost wax technique) OR (porcelain fused to metal) OR (PFM) OR (implant impression) OR (hand layering) OR (veneering) OR (framework) AND "Study, Feasibility" [MeSH] OR "Survival" [MeSH] OR "Success" [MeSH] OR "Economics" [MeSH] OR "Costs, Cost Analysis" [MeSH] OR "Esthetics, Dental" [MeSH] OR "Patient Satisfaction" [MeSH] OR (feasibility) OR (efficiency) OR (patient centered outcome).Assessment of risk of bias in selected studies was done at a 'trial level' including random sequence generation, allocation concealment, blinding, completeness of outcome data, selective reporting, and other bias using the Cochrane Collaboration tool. A judgment of risk of bias was assigned if one or more key domains had a high or unclear risk of bias. An official registration of the systematic review was not performed.ResultsThe systematic search identified 67 titles, 32 abstracts thereof were screened, and subsequently, three full texts included for data extraction. Analysed RCTs were heterogeneous without follow up. One study demonstrated that fully digitally produced dental crowns revealed the feasibility of the process itself; however, the marginal precision was lower for lithium disilicate (LS2) restorations (113.8 mm) compared to conventional metal ceramic (92.4 mm) and zirconium dioxide (ZrO2) crowns (68.5 mm) (p 0.05) Another study showed that leucite reinforced glass ceramic crowns were esthetically favoured by the patients (8/2 crowns) and clinicians (7/3 crowns) (p 0.05) The third study investigated implant crowns. The complete digital workflow was more than twofold faster (75.3 min) in comparison to the mixed analog digital workflow (156.6 min) (p 0.05) No RCTs could be found investigating multi unit fixed dental prostheses (FDP).ConclusionsThe number of RCTs testing complete digital workflows in fixed prosthodontics is low. Scientifically proven recommendations for clinical routine cannot be given at this time. Research with high quality trials seems to be slower than the industrial progress of available digital applications. Future research with well designed RCTs including follow up observation is compellingly necessary in the field of complete digital processing.

title: A Retrospective Study on the Success, Survival, and Incidence of Complications of Post Retained Restorations in Premolars Supporting Fixed Dental Prostheses with a Mean of 7 Years in Function.
abstract: To evaluate the survival and success rates of post and core restorations supporting fixed dental prostheses (FDPs) after a mean time in function of 7 years and to assess the incidences of biologic and technical complications.  Patients from the National Dental Center Singapore (NDCS) with endodontically treated premolars restored with post retained FDPs from 2007 to 2009 were recruited from the Endodontic Registry and evaluated by three clinicians. A total of 265 patients with 329 treated premolars were examined clinically. Digital radiographs were also obtained. Complications were classified as tooth or prosthesis related. Failure and complication rates were calculated based on person time at risk.  The mean time in function was 7.1 years. A total of 25 teeth in 23 patients were lost, resulting in a 7 year survival rate of 92.7% (95% CI: 89.5% 95.0% The corresponding success rate was 75.1% (95% CI: 70.5% 79.1% A total of 40 FDPs failed, resulting in a 7 year prosthetic survival rate of 88.6% (95% CI: 84.8% 91.5% Common complications observed were recurrent periodontal disease (3.9% periapical pathology (7.3% caries (3.9% porcelain chipping (9.9% and tooth fractures (5.0% For the incidence of tooth fracture, a risk analysis yielded significant associations with the number of occluding teeth (odds ratio: 4.2; 95% CI: 1.1, 16.7) and the number of adjacent teeth (odds ratio: 4.0, 95% CI: 1.5, 10.9) CONCLUSION Restoration of premolar teeth requiring root canal treatment with a post and core and crown is a viable treatment when premolar teeth have adjacent teeth.

title: Retrospective study on survival, success rate and complication of implant supported fixed prosthesis according to the materials in the posterior area
abstract: The purpose of this study was to retrospectively investigate the survival and success rate of implant supported fixed prosthesis according to the materials in the posterior area. Other purposes were to observe the complications and evaluate the factors affecting failure.  Patients who had been restored implant prosthesis in the posterior area by the same prosthodontist in the department of prosthodontics, dental hospital, Chonbuk National University, in the period from January 2011 to June 2018 were selected for the study. The patient's sex, age, material, location, type of prosthesis and complications were examined using medical records. The KaplanMeier method was used to analyze the survival and success rate. The Log rank test was conducted to compare the differences between the groups. Cox proportional hazards model was used to assess the association between potential risk factors and success rate.  A total of 364 implants were observed in 245 patients, with an average follow up of 17.1 months. A total of 5 implant prostheses failed and were removed, and the 3 and 5 year cumulative survival rate of all implant prostheses were 97.5 and 91.0, respectively. The 3 and 5 year cumulative success rate of all implant prostheses were 61.1% and 32.9% respectively. Material, sex, age, location and type of prosthesis did not affect success rate (P>.05) Complications occurred in the order of proximal contact loss (53 cases) retention loss (17 cases) peri implant mucositis (12 cases) infraocclusion (4 cases) and so on.  Considering a high cumulative survival rate of implant supported fixed prostheses, regardless of the materials, implant restored in posterior area can be considered as a reliable treatment to tooth replacement. However, regular inspections and, if necessary, repairs and adjustments are very important because of the frequent occurrence of complications.

title: Non rigid connectors in fixed prosthodontics: Current concepts with a case report
abstract: The occlusal forces applied to a fixed partial denture (FPD) are transmitted to the supporting structures through the pontic, connectors, and retainers. Variables that may influence the longevity of an FPD and its abutment include occlusion, span length, bone loss, and quality of periodontium. The excessive flexing of the long span FPD, which varies with the cube of the length of span, can lead to material failure of prosthesis or to an unfavorable response. Biomechanical factors such as overload, leverage, torque and flexing, induce abnormal stress concentration in an FPD. Stress concentration is found in the connectors of the prosthesis and in the cervical dentin area near the edentulous ridge. This factor plays an important role in the potential for failure in long span FPD. The conventional use of a nonrigid connector (NRC) aids in compensating for the difference in the resistance and retention form between the abutments. The design and passive fit of NRC is critical to the success of a long span FPD. This paper presents the current concepts in the design of an NRC and a case report of Pier abutment treated with FPD having Tenon Mortise Connector.

title: Standardizing failure, success, and survival decisions in clinical studies of ceramic and metal ceramic fixed dental prostheses.
abstract: The recent increase in reports from clinical studies of ceramic chipping has raised the question of which criteria should constitute success or failure of total ceramic prostheses. Terminologies such as minor chipping  partial chipping, technical complications [2,3] and biological complications have crept into the dental terminology and they have complicated our classification of success and failure of these crown and bridge restorations. Some journals have permitted the reporting of fractures as "complications" and they are not necessarily classified as failures in the study. One study has attempted to classify chipping fractures according to their severity and subsequent treatment [4] This is a promising approach to resolve the challenges to the classification of chipping fracture. The term 'chipping fracture' is more descriptive than 'chipping' since the latter term tends to imply an event of minor consequence. Two types of statistics are reported routinely in these studies, i.e. percent success, which is a measure of restorations that survive without any adverse effects, and percent survival, which is a measure of all restorations that survive even though they may have exhibited chipping fracture or they may have been repaired. Why has this scenario occurred? One possible explanation is that many of these types of fractures are very small and do not affect function or esthetics. Another reason is that corporate sponsors prefer to use the term chipping since it does not connote failure in the sense that the term fracture does. In any event, we need to be more precise in our scientific observations of fracture and classifications of the various types of fracture including details on the location of fracture and the prosthesis design configuration. Because of the lack of standardized methods for describing chipping fractures, materials scientists are unable to properly analyze the effect of material properties and design factors on the time dependent survival probability of ceramic fixed dental prostheses (FDPs) Based on the review of clinical trials and systematic reviews of these trials, the present study was designed to develop guidelines for classifying the functional performance, success, survival, and susceptibility to chipping fracture, and subsequent treatment of ceramic and metal ceramic restorations.  To develop comprehensive descriptive guidelines and a clinical reporting form to assist dental scientists in their analyses of chipping fracture behavior of metal ceramic and all ceramic prostheses with particular emphasis on veneered zirconia restorations. These guidelines are required to optimize the recording of fracture features that can be used to differentiate ceramic chipping fracture from bulk fracture and to assist dentists in identifying subsequent treatment that may minimize the need to replace affected restorations. A recording form for clinical fracture observations must be sufficiently clear and complete so that dental health professionals can translate the most relevant information in a context that allows their patients to fully understand the potential risks and benefits of treatment with ceramic restorations. It should clearly allow a clinician to determine whether or not a ceramic fracture constitutes a failure, which requires replacement of the prosthesis, or whether the fracture surface is relatively small or located in a nonfunctional area, i.e. one that is not contribute to occlusion, esthetics, proximal contacts, or food impaction. To accomplish this task, a review of the relevant publications of clinical trials was necessary to identify the variability in reporting of fracture events. The reviews were focused on clinical research studies of zirconia based FDPs and PFM FDPs, which had been monitored through recall exams for three years or more. These reports and systematic reviews of all relevant publications were published in English dental journals between 2004 and 2010.The primary focus in this review was on the susceptibility to chipping fracture or bulk fracture of veneered zirconia based fixed dental prostheses (FDPs) and metal ceramic FDPs, which are also referred to in this paper as porcelain fused to metal (PFM) FDPs.

title: Prospective Evaluation of Posterior Fixed Zirconia Dental Prostheses: 10 Year Clinical Results.
abstract: To investigate the clinical survival and success rates of conventionally luted three and four unit fixed dental prostheses (FDPs) with zirconia frameworks (Cercon Smart Ceramics, DeguDent) after a mean observation period of 119 36 months.  A total of 75 patients were treated in the Department of Prosthodontics at the University of Goettingen, Germany, and a total of 99 posterior FDPs were inserted and luted with zinc phosphate cement. Time dependent survival and success rates were calculated using Kaplan Meier curves, and their relationships with the type of veneer (ceramic) location (maxilla vs mandible) and span length (three unit vs four unit) were analyzed with a Cox regression model (P .05) RESULTS Of the 99 inserted FDPs, 24 were lost to follow up, 51 remained functional and passed the 10 year examination (overall survival rate: 75.0% 95% confidence interval [CI] 0.64, 0.85) and 13 were absolute failures caused by technical events (technical survival rate: 84% 95% CI: 0.64, 0.85) In 50 FDPs, relative failure required a clinical intervention to maintain function (overall success rate: 40% 95% CI: 0.29, 0.52) For 35 of these FDPs, the relative failure was caused by technical events (technical success rate: 61% 95% CI: 0.49, 0.73) None of the evaluated factors showed an association with overall or technical survival or success.  Zirconia based posterior FDPs produced with a first generation computer assisted manufacturing (CAM) system revealed high rates of absolute and relative failure, mainly due to technical events, after a mean observational period of 10 years. Further clinical studies with updated computer assisted design (CAD)/CAM systems are needed to determine the long term performance of zirconia based FDPs.

title: Load Bearing Capacity of Monolithic Zirconia Fixed Dental Prostheses Fabricated with Different Connector Designs and Embrasure Shaping Methods
abstract: To investigate the load bearing capacity and failure mode of monolithic zirconia fixed dental prostheses (FDPs) fabricated with different connector designs and embrasure shaping methods.  Seventy four unit zirconia FDPs (with two premolar pontics) were fabricated and divided into seven groups (n 10) according to the different connector designs gained by using different embrasure shaping methods. The groups were as follows: monolithic FDPs fabricated with sharp embrasures, monolithic FDPs fabricated with blunt embrasures, monolithic FDPs fabricated with blunt embrasures and no occlusal embrasures, two groups of monolithic FDPs fabricated with blunt embrasures and interproximal separations made with diamond discs at the soft stage and at the fully sintered stage, and monolithic FDPs fabricated with blunt embrasures and interproximal separation accentuated by localized porcelain build up. A final group was used as a control group, where fully veneered traditional zirconia FDPs were fabricated with default milling settings. The FDPs were artificially aged and loaded to fracture. Load to fracture and failure modes were analyzed by one way ANOVA, Tukey's post hoc test, and Fisher exact test (a 0.05)  The FDPs fabricated with interproximal porcelain separation showed significantly the highest load to fracture (1038 N 82) of all groups (p 0.001) with no significant difference compared to the FDPs with no occlusal embrasures (934 N 175; p 0.29) The FDPs fabricated with blunt embrasures showed significantly higher load to fracture (873 N 115) compared to the FDPs in the control group (689 N 75) and the FDPs with sharp embrasures (417 N 87; p 0.001) There were no significant differences between the FDPs with sharp embrasures (417 N 87) and the FDPs with interproximal disc separations (467 N 94; p 0.23) Failure mode of the FDPs fabricated with sharp embrasures and interproximal disc separations differed significantly compared to the FDPs in the other groups (p 0.001) CONCLUSIONS Sharp embrasures and interproximal separations made with diamond discs significantly decrease the load bearing capacity of monolithic zirconia FDPs compared to FDPs made with blunt embrasures. Blunt embrasures in combination with localized porcelain build up produce FDPs with high load bearing capacity in relation to loads that might be expected under clinical use.

title: Five year success rate of resin bonded fixed partial dentures: A systematic review
abstract: To assess and compare the 5 year success rate of resin bonded fixed partial dentures (RBFPDs) fabricated from different materials.  An electronic search on 3 databases from January 1965 to March of 2017 was done for human randomized clinical trials (RCTs) and prospective and retrospective cohort studies. The key words used in the search were: Bridge OR bridges OR fixed partial OR fixed dental AND resin bonded OR Maryland OR ceramic bonded. Quality assessment was done using the Newcastle Ottawa scale. Success was defined as the RBFPDs remaining in situ and not having experienced debonding, biological failures, or mechanical failures at the examination visit.  Meta analyses of the included studies showed an estimated 5 year success rate of 88.18% for the metal framework RBFPDs and 84.41% for the nonmetal framework RBFPDs. The estimated 5 year success rate for each nonmetal material category was 92.07% for zirconia, 94.26% for In Ceram alumina, and 84.83% for fiber reinforced composite. The failure rate was not statistically significant among the single, double, and multiple retainers RBFPDs (P .05) Technical complications were the main reason for failures.  The 5 year clinical performance of RBFPDs is similar to the performance of conventional fixed partial dentures (FPDs) and implant supported crowns.  Clinicians should consider using RBFPDs more often because their clinical performance is similar to the performance of conventional FPDs and implant supported crowns.

title: Evaluation of fixed partial dentures' complications among patients attending a dental college in Ahmedabad, Gujarat, India
abstract: Fixed partial denture (FPD) is the term used for denoting partial dentures that are cemented to the natural teeth or root, thereby furnishing and providing primary prosthetic support. Prosthetic failure in patients rehabilitated with dental treatment can affect the periodontal health of the abutment teeth.  The present study was conducted to evaluate the FPD's complications among patients attending a dental college in Ahmedabad, Gujarat, India.  The study was carried out among patients who visited the Department of Prosthodontics and Crown and Bridge, AMC Dental College and Hospital, Ahmedabad, Gujarat, India, as outpatients from March 2018 to August 2018. A total of 300 patients were randomly selected and interviewed.  Regarding the nature of problems faced with the FPD and crown wearers, 64% of them reported with looseness and repeated dislodgement, whereas 36% of them had no such complaints. The second most common problem encountered with the patients was inability to maintain proper oral hygiene. Nearly 54% of the patients found it difficult to maintain oral hygiene.  Knowledge regarding the clinical FPD complications enhances dentists' ability to complete a thorough diagnosis, develop the most appropriate treatment plan for patients, communicate realistic expectations to patients, and plan time intervals needed for posttreatment care in the dental institutions.