Clinical performance of non-precious metal double crowns with friction pins in severely reduced dentitions

Objectives Several in vitro studies have investigated the retention of double crowns with friction pins (DCP); however, clinical data on their long-term success have not been reported. We sought to evaluate the 5-year survival rate of DCPs in patients with severely reduced dentition (SRD) and not severely reduced dentition (NSRD). Materials and methods A total of 158 patients were treated with 182 dentures on 520 abutment teeth between 2006 and 2016. The SRD group included 144 dentures that had been inserted on 314 abutment teeth. We evaluated the influence of age, sex, jaw, number, tooth vitality, and abutment teeth localization (according to Steffel’s classification) on the 60-month survival rates of dentures and abutment teeth using the Kaplan-Meier estimator, logrank test, and Cox regression. Results The cumulative 60-month survival rate was 84.3% (CI 77.1–91.5%) for all dentures; however, the survival rate in the SRD group (80.3%; CI 71.5–89.1%) was significantly lower than in the NSRD group (100%; p = 0.04). Dentures classified in Steffel’s class A had the lowest survival rate (51.5%; CI 30.9–72.1%). Number, location, and vitality of the abutment teeth had a significant impact on survival rate. Conclusions DCP dentures showed comparable clinical long-term success to double crown systems that have been previously reported in the literature. The number, localization, and vitality of abutment teeth had the greatest influence on the survival rates of denture and abutment teeth. Clinical relevance DCP dentures have an acceptable 5-year survival rate. Clinical treatment planning must take into account key factors associated with the prognosis of the abutment teeth.

Retention force of overdenture retained with telescopic crowns: A comparison of polyether ether ketone and zirconia ceramic telescopic crowns

Introduction/Objective. Recently, new materials for double crowns have been introduced, such as zirconia and polyether ether ketone (PEEK). However, some characteristics of these materials, such as retentive force and duration of ?settling in phase,? have not been investigated sufficiently. During the ?settling in phase,? telescopic overdenture has not yet achieved its definitive retention force, and it can be harmful for periodontal tissue if the value is above optimal for a long period of time. The objective was to measure the in vitro overall pull-off force of telescopic crowns where primary crowns were made from zirconia ceramics and a survey of the ?settling in phase? duration. Methods. Forty zirconia primary telescopic crowns were produced on prepared canine teeth. Twenty secondary crowns were of PEEK and other 20 of zirconia with electroplated gold copings. The pull-off force measurements were conducted utilizing a dynamometer until a constant value was obtained. Results. The specimens of the PEEK group showed higher initial retentive force values. Settling in phase was finished between 800 and 900 cycles of separation for both groups. Comparing the value of the pull-off force between individual different cycles, a statistically significant reduction was recorded up to the 800th cycle, while between the 800th and the 900th cycle there was no difference. Conclusions. The settling in phase was finished between 800 and 900 cycles of separation in both groups. Final retentive force values for both tested telescopic groups were in the optimal range which is 5?9 N per one telescopic crown.

VARIETY AND PRINCIPLES OF COOPERATION OF DOUBLE CROWNS OF TELESCOPIC CONNECTIN

For today, problem of fixing of partial removable prostheticappliances, and more precisely it remains not fully decidedthe term of endurance and worn down of friction propertiesof telescopic connections. Therefore, the search for improvement of fixative properties of telescopic connection sremains actual. Material and methods: Analytical study of scientific sources on the problems of replacing defects in dentition with removable dentures with fixation on telescopic crowns. The aim of this work consists in that, to educe, to estimateand compare, on thebasis of the dynamic supervisions, scientific-medical information, views of authors on the role and definition of interaction of double crown sof telescopic connection, especially with the use of auxiliaryel ements of fixing. Appearance of double crowns with a resident interval, offered Strack and Hofmann in 1966, induced scientists to perfect and develop the new auxiliary elements of fixing for the improvement of retention properties of telescopic connections. The process of search took place and takesplace in various ways: - by the use of various materials (gold, ordinary alloys, thermosetting and thermoplastic polymers, powder-like metals and compos); - by the use of different technologies (punching, founding, milling, electrotype, spark-free treatment, 3d printing); - by development of new auxiliary elements ( retention pins, rings, plunger, crossbar, attachments, hobs, petals et al); - by the use of other physical phenomena ( diffusion, dry technicians, vacuum, magneti, rheological properties). The article also highlights the views of scientists on the negative and positive aspects of the proposed technical solutions. It is informed about the proposed radically new system of telescopic connection, which is based on the use of another physical phenomenon - the rheological property of materials. The uses of the known methods, new or improved additional structural elements are mainly based on bringing of those or other changes in the primitive construction of telescopic connection. Analysing the advanced studies of many researchers, it is possible to draw conclusion that advantages of fixing of removable prosthetic appliances by means of the telescopic systems are determined by the row of their possibilities. To basic advantages of double crowns it is possible to take a complete scope the external crown of supporting teeth with simultaneous implementation of retentive, stabilizing, directing and supporting functions, and also distribution of horizontal power components of the functional loading, and wide possibility of choice of the offered additional construction elements extends possibility to the specialists in the rational system of choice of the telescopic fixing. It would be desirable to mark that the telescopic system is theoptimal method of fixing of prosthetic appliance in comparingto another ways of fixing of partial removable prostheticappliance that is confirmed by the researches conducted inthis matter. Conclusion: Thus, it was educed on the basis of review of correspondingliterature, that the best terms for proceeding in masticatoryefficiency, function and aesthetics of the tooh-jaw system removal of deformation of occlusion surface of dentalrows and injuring bite for patients with the partial loss of teethit is succeeded to obtain at the use removable prostheticappliances with the telescopic system of fixing, especially withthe use of additional structural elements.