Jonas Adrian Helmut Vogler

Objectives: Due to extra-axial forces, post and core (PC) treatment has the worst survival probability in abutment teeth for telescopic crown-retained dentures (TCDs). The reason for this is a mismatch regarding the mechanical properties between PC material and dentin or a poor accuracy of fit of PC, resulting in tooth fracture or decementation. However, the inclusion of severely damaged endodontically treated teeth needing PC is often mandatory in order to achieve a stable situation for TCD. Thus, an advancement of PC treatment for TCD is of high clinical interest. Recently it has become possible to fabricate customized PC with favourable mechanical properties by using CAD/CAM technology. Methods: Thus, the aim of this investigation was to compare the performance of these PC types (CAD/CAM PC) to customized cast PC (CPC) and prefabricated fibre-reinforced PC (PFPC) in a TCD set-up using a chewing simulator. Results: The investigation group with CAD/CAM PC showed neither tooth fracture nor decementation, in contrast to the CPC and PFPC groups, in which both types of failure were recorded. Thus, CAD/CAM PC showed significantly better performance than CPC and PFPC. Conclusions: Within the limitations, CAD/CAM PCs are therefore recommendable for PC treatment with TCD.

Due to extra axial forces, post and core (PC) treatment shows the worst survival probability if the tooth is used as an abutment for telescopic crown retained dentures (TCD). The reason for this is a mismatch of the mechanical properties between PC material and dentin or a bad accuracy of fit of PC resulting in tooth fracture or decementation. However, the inclusion of severe damaged endodontically treated teeth needing PC is often mandatory in order to receive a statically stable situation for TCD. Thus, an advancement of PC treatment for TCD is of high clinical interest. Recently it is possible to fabricate customized PC with favourable mechanical properties by using CAD/CAM technology. Therefore, the aim of this study was to compare the performance of these PC (CAD/CAM PC) to customized cast PC (CPC) and prefabricated fibre-reinforced PC (PFPC) in a TCD set-up using a chewing simulator. The investigation group with CAD/CAM PC showed neither tooth fracture nor decementation in contrast to CPC and PFPC in which both types of failure were recorded. Thus, CAD/CAM PC showed significantly better performance than CPC and PFPC. Within the limitations of this study CAD/CAM PC are therefore recommendable for PC treatment with TCD.

The aim of this study was to investigate the feasibility of digital post scan (DPS) with three different intraoral scanners (IOS) and to evaluate the light reaching the apical part of the preparation, considering the influence of the type of tooth and adjacent teeth. 50 clinical cases treated with post and core (PC) were used for 3D printing of the dataset of DPS with a hole at the apical part of the preparation by virtual construction and nesting. The models covered the sensor of a luxmeter leaving only the hole for measuring the amount of light during DPS (lux-value) with Primescan (PRI), Trios 5 (TRI) and Medit i700 (MED). Feasibility of DPS was evaluated by the percentage of surface deviating <50µm from PRI (TRI/PRI, MED/PRI) in an analysis software. Moreover, a possible influence of the type of tooth that was treated with PC on DPS was evaluated. Statistical analysis was conducted using ANOVA with a significance level of p<0.05. Highly significant differences (p<0.001) were found for the light reaching the apical part of the preparation (lux-value) between PRI, TRI and MED (in decreasing order). Except from PRI, DPS was only feasible for TRI (100% of surface deviation <50µm) in three cases without adjacent teeth, showing highly significant differences between TRI/PRI and MED/PRI (p0.05). The amount of emitted light with PRI linked to the larger capturing window in comparison to TRI and MED might increase the feasibility of DPS with PRI. PRI can be recommended for DPS, whereas TRI and MED showed inferior results leading to unpredictable accuracy of fit of PC. The depth of focus given by the manufacturer of the IOS is not an indicator for the feasibility of DPS.

Telescopic crown-retained dentures (TCDs) are one of the most common types of prosthetic restorations for partially edentulous patients; however, post and core (PC) treatment shows the worst survival probability if the tooth is used as an abutment for the TCD. Due to extra axial forces, abutment tooth fracture is a common cause of failure for TCDs; thus, PC treatment is often needed to refit the existing telescopic crown (TC). However, there are no clinical survival data on whether the PC treatment was used to refit the TC after abutment tooth fracture (PC2) or the PC was already fitted at the time of TCD treatment (PC1). A total of 246 patients with 399 PC treatments were retrospectively evaluated for follow-ups up to 17.33 years. The files were analysed for PC1 and PC2. Furthermore, the influence of the jaw, type of tooth, luting material, PC material, bone attachment, therapist and cause of failure was recorded. For statistical analysis, Kaplan–Meier and Cox regression analyses were conducted. PC2 showed highly significant lower survival probabilities than PC1 (p < 0.001). Moreover, the bone attachment and the age of the patient at the time of fitting the PC crown had an influence on the survival (p < 0.001). Therefore, PC2 should be carefully discussed with the patient and PC1 should be favoured in endodontically treated abutment teeth for TCDs.