Clinical Longevity of Obturators in Patients with Jaw Defects: a Retrospective Cohort Study.

OBJECTIVES: The primary objective of the present retrospective clinical study was to determine the survival time of obturators while analyzing possible influencing factors. MATERIALS AND METHODS: This retrospective clinical cohort study analyzed the influence of various clinical factors on the survival probability of obturators and their follow-up outcomes using Kaplan‒Meier analysis. RESULTS: A total of 76 patients with 115 obturators were included in the study (47 men and 29 women, mean age 58.1 ± 18.1 years). The mean observation time was 3.0 ± 4.5 years (maximum 26.3 years). A total of 40.9% (47) of all obturators observed had to be replaced. The survival rate after 5 years was 79.5% for telescopic-crown-retained tooth-supported obturators, 86.9% for telescopic-crown-retained implant-supported obturators, 58.8% for removable full denture obturators, 22.1% for clasp-retained obturators and 0.0% for splints. The type of attachment, attendance at a regular follow-up and defect cause significantly influenced the survival of the obturators (p < .05). CONCLUSIONS: The findings obtained in this study support the recommendation of using implant-supported obturators. Telescopic-crown attachments, either tooth- or implant-supported, seem to be favorable in terms of survival time. Attendance at a strict follow-up program seems to have a major influence on the longevity of the obturators. CLINICAL RELEVANCE: The use of implant-supported obturators to cover permanent oral and maxillofacial defects is highly recommended. Additionally, the use of telescopic-crown attachments seems to be favorable in terms of survival time. Clasp-retained obturators and surgical splints should be used primarily for temporary restorations due to their shorter survival times.

Clinical performance of different types of dental prosthesis in patients with head and neck tumors-a retrospective cohort study.

OBJECTIVES: To investigate how different types of dental prosthesis perform in patients with head and neck tumors. MATERIALS AND METHODS: In this retrospective clinical cohort study, the impact of different patient-related factors was analyzed as influencing factors on the survival probability of dental prosthesis using Kaplan-Meier estimate. For analysis, the dental prosthesis was divided into groups: group 1 (fixed dental prosthesis), group 2 (removable dental prosthesis), group 3 (implant-supported dental prosthesis), and group 4 (prostheses anchored using wrought wire clasps and obturators). The incidental aftercare measures were also evaluated. RESULTS: Two hundred seventy-nine restorations were observed (mean observation: 2.7 ± 3.0 years, max.14.8 years) out of which 49 (17.6%) had to be replaced during the observation. After 5 years, 100% of group 1 restorations, 79.9% of group 2 restorations, 91.4% of group 3 restorations, and 30% of group 4 restorations were still functional. Four hundred eighty-eight dental implants were observed, of which 77 (15.8%) failed. CONCLUSIONS: Groups 1, 2, and 3 restorations showed good survival times after 5 years in function, whereas group 4 presented the worst survival times. Group 2 restorations showed the highest amount of necessary aftercare measures. CLINICAL RELEVANCE: The current investigation shows that groups 1, 2, and 3 restorations should be preferred in the prosthetic treatment planning of patients with head and neck tumors. A treatment with group 4 restorations should only be considered if no other prosthetic treatment is possible or as temporary treatment.

Chairside measurement of the marginal and internal fit of crowns: a new intraoral scan-based approach.

OBJECTIVES: To investigate the marginal and internal fit of crowns, a new intraoral scanner-based digital approach for chairside measurement (D-IOS) was systematically analysed and compared with the conventional silicone replica technique (CV-SR) and digital 3D analysis software (D-GOM). MATERIALS AND METHODS: Two models, representing different clinical situations, were constructed, and the first molar was prepared for a full-coverage crown. On the basis of an intraoral scan (Trios 3), copings of three different materials (non-precious alloy, zirconium dioxide, and resin composite) with two different cement spaces (80 µm, 50 µm) were manufactured. The fit of the copings was investigated by all three methods (CV-SR, D-IOS, D-GOM). Therefore, the cement space was visualized with low-viscosity silicone and digitalized with a second intraoral scan. Evaluation of fit by the D-IOS-method was measured in the intraoral scanner software, whereas for analysis by D-GOM, both intraoral scan datasets were transferred to 3D analysis software (GOM Inspect). The CV-SR-method was used as a control group. For all copings, the measurements were repeated five times. The data were analysed with ANOVA. RESULTS: No significant differences between the three evaluation methods and the coping materials were shown. However, in the occlusal area, the internal gap was significantly higher compared to the internal gap in the marginal and axial areas regardless of the cement space setting (p < .05). The target parameter of the cement spaces did not match the actual measured internal gaps. CONCLUSIONS: All three evaluation methods and coping materials can be used for the measurement of fit within different clinical situations. CLINICAL RELEVANCE: The digital chairside measurement implemented in the intraoral scanner software enables an easy, applicable evaluation of fit of crowns without additional laboratory devices or special software applications.

Undergraduate dental students' perspective on the implementation of digital dentistry in the preclinical curriculum: a questionnaire survey.

BACKGROUND: Digitalisation is an expanding field in dentistry and implementation of digital teaching methods in dental education is an essential part of modern education. Therefore, two digital training modules were implemented in the preclinical curriculum at the Justus Liebig University Giessen. The aim of this study was to assess the students' perspective on the implementation with a questionnaire survey. METHODS: Since the fall term 2017/18, students of the course of dental prosthodontics I attended the training module I, where they learned to use computer-aided learning (CAL) approaches for the digital analysis of tooth preparations. In training module II, students of the course of dental prosthodontics II learned how to manufacture a computer-aided design/computer-aided manufacturing restoration. After the completion of the training modules, all students starting with the fall term 2017/18 to the spring term 2019 were asked to fill in a questionnaire regarding the aspects of handling, didactic benefit, motivation, and overall assessment. RESULTS: Students rated the implementation of digital aspects in teaching as positive in terms of handling, didactic benefit, and motivation, but gave preference to the assessment of the tooth preparations by dental instructors. In addition, students assessed the feedback from the faculty regarding tips and tricks better than the digital feedback. More than 90% of the students indicated that they could imagine using an intraoral scanner for treatment of patients in the dental office in future. CONCLUSIONS: The results of the present study revealed a positive perspective of students on the implementation of digital dentistry in the preclinical curriculum. However, difficulties with CAL systems were reported and most students preferred evaluation of preparation by dental instructors. Thus, CAL approaches offer an additional teaching method besides the traditional teaching of manual skills.

Comparison of an indirect impression scanning system and two direct intraoral scanning systems in vivo.

OBJECTIVES: This in vivo study aimed to compare the marginal discrepancies of zirconia copings manufactured on the basis of two direct intraoral scanning systems and the indirect digitization of a conventional impression. MATERIALS AND METHODS: A total of 63 teeth in 23 patients were prepared to receive full-coverage crowns. Subsequently, these teeth were intraorally scanned using CEREC AC Omnicam and Cara TRIOS and a conventional impression was taken with the scannable PVS Flexitime Fast & Scan. The conventional impression was then extraorally digitized using a D700 laboratory scanner. The zirconia copings were manufactured on the basis of the resulting datasets. Silicone replicas of the copings were produced and sectioned for the measurement of the marginal discrepancy under a digital microscope. RESULTS: The statistical analysis showed no significant differences between the two intraoral scanners, the CEREC AC Omnicam (86.09 µm ± 61.46 µm) and the Cara TRIOS (88.95 µm ± 54.46 µm). However, the discrepancies of the zirconia copings obtained from the laboratory scans of conventional impressions (143.29 µm ± 100.71 µm) showed significant differences. Both intraoral scanners achieved a marginal discrepancy below 100 µm, whereas the laboratory scan exhibited considerably higher values. CONCLUSIONS: The intraoral scanners tested allow for the production of single-tooth-restorations with an adequate marginal fit, whereas the production of restorations on the basis of the scan of a conventional impression led to vast marginal gaps. CLINICAL RELEVANCE: The method of digitizing a conventional impression using a laboratory scanner seemed to have reached its limits in the clinical environment.

Microleakage of composite crowns luted on CAD/CAM-milled human molars: a new method for standardized in vitro tests.

OBJECTIVES: To investigate debonding of full crowns made of CAD/CAM composites, CAD/CAM technology was applied to manufacture standardized test abutments to increase the reproducibility of human teeth used in in vitro studies. MATERIALS AND METHODS: A virtual test abutment and the corresponding virtual crown were designed and two STL data sets were generated. Sixty-four human third molars and CAD/CAM blocks were milled using a CNC machine. Crowns of four different composite blocks (Lava Ultimate (LU), Brilliant Crios (BC), Cerasmart (CS), Experimental (EX)) were adhesively bonded with their corresponding luting system (LU: Scotchbond Universal/RelyX Ultimate; BC: One Coat 7 Universal/DuoCem; CS: G-PremioBond/G-Cem LinkForce; EX: Experimental-Bond/Experimental-Luting-Cement). Half of the specimens were chemical-cured (CC) and the others were light-cured (LC). Afterwards, specimens were artificially aged in a chewing simulator (WL-tec, 1 million cycles, 50-500 N, 2 Hz, 37 °C). Finally, a dye penetration test was used to detect debonding. For inspection, the specimens were sliced, and penetration depth was measured with a digital microscope. Data were analyzed with the Mann-Whitney U test. RESULTS: No cases of total debonding were observed after cyclic loading. However, the LC specimens showed a significantly lower amount of leakage than the CC ones (p < 0.05). Furthermore, the CC specimens exhibited broad scattering. Only the LC-EX blocks showed no debonding. The CC-CS blocks showed the highest leakage and scattering of all tested specimens. CONCLUSIONS: Natural human teeth can be manufactured by CAD/CAM technology in highly standardized test abutments for in vitro testing. For CAD/CAM composites, light curing should be performed. CLINICAL RELEVANCE: The success of a restoration depends on the long-term sealing ability of the luting materials, which avoids debonding along with microleakage. For CAD/CAM composites, separate light curing of the adhesive and luting composite is highly recommended.

The Relationship Between Narcissism and Personality Traits of the Five-Factor-Model in Adolescents and Young Adults.

Narcissism is seen as a multidimensional construct that consists of two manifestations: grandiose and vulnerable narcissism. In order to define these two manifestations, their relationship to personality factors has increasingly become of interest. However, so far no studies have considered the relationship between different phenotypes of narcissism and personality factors in adolescents. Method: In a cross-sectional study, we examine a group of adolescents (n = 98; average age 16.77 years; 23.5 % female) with regard to the relationship between Big Five personality factors and pathological narcissism using self-report instruments. This group is compared to a group of young adults (n = 38; average age 19.69 years; 25.6 % female). Results: Grandiose narcissism is primarily related to low Agreeableness and Extraversion, vulnerable narcissism to Neuroticism. We do not find differences between adolescents and young adults concerning the relationship between grandiose and vulnerable narcissism and personality traits. Discussion: Vulnerable and grandiose narcissism can be well differentiated in adolescents, and the pattern does not show substantial differences compared to young adults.

Do mandibular complete dentures made using a neutral zone technique improve speech?-A pilot study.

OBJECTIVE: The aim of this study was to evaluate speech sound production (SSP) in older edentulous patients provided with two different types of mandibular complete dentures (MCDs; conventional vs neutral zone). BACKGROUND: Regarding the fact that complete dentures (CDs) affect SSP, it is unknown whether the set-up of the artificial teeth resulting from the neutral zone technique leads to a negative impact on SSP. MATERIALS AND METHODS: For 21 participants, a conventional MCD and a MCD using a modified neutral zone technique (neutral zone dentures) were fabricated. The SSP was described using a phonetically balanced text, which was recorded digitally and evaluated. RESULTS: No significant difference in SSP was observed. CONCLUSION: Within the limits of this study, it can be concluded that the application of the neutral zone technique in the mandible has no considerable impact on SSP.

Tooth preparation for full-coverage restorations-a literature review.

OBJECTIVES: The objective of this review was to assess the current knowledge about tooth preparation for full-coverage restorations regarding the following aspects: biological parameters, preparation geometry, and technical conditions. METHODS: A systematic literature search was conducted using three electronic databases (MEDLINE, DIMDI, and Cochrane databases) in order to identify relevant citations; additionally, the process was augmented by a hand search. RESULTS: A number of 117 citations were relevant; 11 of these were reviews, 23 were clinical studies, 82 were in vitro investigations, and one was animal research. CONCLUSION: The basic form of a preparation has not changed substantially over the years, although new materials like all-ceramic systems have their own demands with regard to the details of the preparation's geometry. Estimating how much of the tooth structure can be removed without harming the tooth remains one of the biggest problems, if not the main difficulty, during tooth preparation. As the periodontal tissues may be affected by the restoration margin, a supragingival position of the margin should be preferred whenever possible. No finish line design has yet proven to be superior with regard to the marginal accuracy of the subsequent restoration. Instead, good detectability of the margin for the dental technician or intraoral scanning devices appears to be of primary importance in order to achieve a good fitting restoration. CLINICAL SIGNIFICANCE: A detailed look at the covered aspects regarding tooth preparations can help to improve clinical outcomes in daily practice.

Accuracy of single-tooth restorations based on intraoral digital and conventional impressions in patients.

OBJECTIVES: The purpose of this clinical study was to compare the marginal fit of dental crowns based on three different intraoral digital and one conventional impression methods. METHODS: Forty-nine teeth of altogether 24 patients were prepared to be treated with full-coverage restorations. Digital impressions were made using three intraoral scanners: Sirona CEREC AC Omnicam (OCam), Heraeus Cara TRIOS and 3M Lava True Definition (TDef). Furthermore, a gypsum model based on a conventional impression (EXA'lence, GC, Tokyo, Japan) was scanned with a standard laboratory scanner (3Shape D700). Based on the dataset obtained, four zirconia copings per tooth were produced. The marginal fit of the copings in the patient's mouth was assessed employing a replica technique. RESULTS: Overall, seven measurement copings did not fit and, therefore, could not be assessed. The marginal gap was 88 µm (68-136 µm) [median/interquartile range] for the TDef, 112 µm (94-149 µm) for the Cara TRIOS, 113 µm (81-157 µm) for the laboratory scanner and 149 µm (114-218 µm) for the OCam. There was a statistically significant difference between the OCam and the other groups (p < 0.05). CONCLUSION: Within the limitations of this study, it can be concluded that zirconia copings based on intraoral scans and a laboratory scans of a conventional model are comparable to one another with regard to their marginal fit. CLINICAL RELEVANCE: Regarding the results of this study, the digital intraoral impression can be considered as an alternative to a conventional impression with a consecutive digital workflow when the finish line is clearly visible and it is possible to keep it dry.

How long must a post be? A retrospective survival analysis on a large cohort with long follow-ups.

OBJECTIVES: Post and core (PC) is frequently used, but clinical evidence concerning how long a post must be is scarce. Recommendations in dental literature range from half of the root which should be incorporated, to post space preparations conducted as deep as possible increasing the risk for root perforation thus tooth loss. Therefore, the aim of this retrospective survival analysis is to evaluate the post length as well as the post-clinical crown ratio on a large patient cohort with long follow-ups. MATERIALS AND METHODS: Overall 1026 PC in 731 patients could be included in this study (2004-2023). The files were analysed due to the parameters post length and post-clinical crown ratio on X-Ray. Furthermore, the influence of the type of covering prosthetic restoration, location, type of tooth, luting material, PC material, bone attachment and therapist was evaluated. The statistical analysis was assessed using Kaplan-Meier (univariate influences) and Cox regression (multifactorial influences). RESULTS: Survival until extraction as well as decementation was significantly influenced by bone attachment and covering prosthetic restoration. Posts reaching the middle third of the root showed highly significant (p < 0.001) better survival probabilities than those reaching the coronal or apical third. Regarding the post-clinical crown ratio, no significant difference was found for post = crown/post > crown, whereas post

Post and Core Treatment to Refit Telescopic Crown-Retained Dentures after Abutment Tooth Fracture: An Evaluation of Therapy by Retrospective Survival Analysis.

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.

Survival of Double-Crown-Retained Implant-and-Tooth- Supported Removable Partial Dentures: A ≥ 5-Year Clinical Follow-up Study.

PURPOSE: To assess the survival of double-crown-retained implant-and-tooth-supported removable partial dentures (DCR-ITSRPDs), evaluate abutment survival, and identify first aftercare measures. MATERIALS AND METHODS: The influence of various factors on the survival of the DCR-ITSRPDs and the abutments were observed in this retrospective and clinical follow-up study using the Kaplan-Meier estimate. In addition, the first-required aftercare measure for each prosthesis was evaluated. RESULTS: In total, 47 DCR-ITSRPDs were investigated (mean observation: 4.3 ± 3.8 years; max: 14.3 years), 3 of which (6.4%) had to be replaced. The survival probability for DCR-ITSRPDs was 100% at 5 years and 75% at 10 years. A total of 297 abutments (120 natural teeth and 177 dental implants) were observed, 22 of which (7.4%; 6 teeth and 16 implants) failed. The survival probability for teeth was 90.2% at the 5- and 10-year mark; for dental implants, it was 90.4% at 5 years and 76.3% at 10 years. CONCLUSIONS: DCR-ITSRPDs are a successful and durable treatment option for patients with substantially reduced residual dentitions. Both prostheses and abutments show good survival times after 5 and 10 years in function. The patient-associated factors tested showed no influence on the survival of DCR-ITSRPDs and abutments. Peri-implant infection was the decisive factor for abutment loss; therefore, regular dental prophylaxis and examinations are of major importance.

Survival of teeth treated with post and core - A retrospective study of more than 1000 cases with observation periods up to 18 years.

OBJECTIVES: Even if survival of post and core (PC) itself was frequently investigated in recent literature, clinical data concerning the risk for extraction of teeth restored with PC is still scarce. Since most authors found the loss of retention of refitable post and cores as the most common cause of failure, it is impossible to draw a conclusion on tooth survival on the results of those studies. Therefore, the aim of the present study was to improve the clinical evidence on the survival of teeth treated with post and cores on a large number of cases over a long observation period. MATERIALS AND METHODS: 735 patients were treated with 1053 post and cores in the observation period (2004-2022) and could be included in the study. The patient files were analysed due to the parameters: Type of covering prosthetic restoration, location, type of tooth, luting material, post and core material, bone attachment and therapist. The survival probability was assessed using Kaplan-Meyer analysis. Cox regression was used to assess possible multifactorial influences. RESULTS: The overall average survival time until necessary extraction of a tooth restored with a post and core was 11.74 years. A root fracture in primary crown retained removeable partial dentures (RPDs) during the first five years was the most common reason for extraction in this study. A significant influence on the survival time of teeth restored with post and cores was found for the type of covering restoration, bone attachment, age of the patient and post and core material. CONCLUSIONS: Post and core restored teeth should be avoided as abutments for primary crown retained RPDs. CLINICAL SIGNIFICANCE: If it is inevitable to utilise post and core restored teeth for primary crown retained RPDs, post and core materials with matching mechanical properties to that of dentine should be preferred.

Which Patient-Related Factors Influence the Outcome of Telescopic-Retained Removable Implant-Supported Dental Prostheses in Edentulous Patients?

PURPOSE: To survey the clinical performance of telescopic-retained removable implant-supported dental prostheses (TR-RISDPs) in edentulous patients, as well as incidental maintenance measures and technical complications. MATERIALS AND METHODS: In this retrospective analysis, the former presence of oral cancer, prosthesis location (maxilla or mandible), and participation in a follow-up program were analyzed as possible factors with an influence on survival and maintenance treatments of the TR-RISDPs and dental implants using Kaplan-Meier estimates. RESULTS: A total of 86 TR-RISDPs (mean follow-up: 4.62 ± 3.24 years; maximum 13.8 years) and 465 implants (mean follow-up: 5.67 ± 3.59 years; maximum 16.5 years) were observed. Six (6.9%) of the TR-RISDPs had to be remade, and 11 (2.3%) implants failed. Regular attendance in the follow-up program showed significantly higher survival times and fewer maintenance treatments for the TRRISDPs (P < .05). Implants in patients with former oral cancer showed significantly lower survival times (P < .001). CONCLUSIONS: TR-RISDPs in edentulous patients show excellent clinical outcomes. Regular check-ups are decisive for success.

Survival time of post and cores: A 16 year retrospective follow-up study.

OBJECTIVES: The retrospective survival study (1995-2004) by Balkenhol et al. [1]. led to changes in the decision-making process for treatment with post and cores (special focus on the covering prosthetic restoration while deciding for treatment with post and cores, high primary friction at the try-in stage for conventional cementation, only indirect fabrication technique, no semi-precious alloy) in our clinic. The aim of this study was to examine the influence of these changes on the survival probability. MATERIALS AND METHODS: In the observation period (2004-2020) 653 patients received in total 953 post and cores. The patient files were analysed due to the parameters: Type of covering prosthetic restoration, location, type of tooth, luting material, post and core material, bone attachment, therapist and cause of failure. According to the previous study the survival probability was assessed using Kaplan-Meyer analysis. Cox regression was used to assess the risk of failure and identify possible covariates. RESULTS: The average survival time of the post and cores was 10.9 years. The cumulative failure rate was 28.2%. A significant influence on the survival time (Kaplan-Meyer analysis) could be found for the parameters: Type of covering prosthetic restoration, location, type of tooth, post and core material and bone attachment. The multifactorial survival analysis (Cox regression) showed a significant influence of the age of the patient at the time of fitting the post, the type of covering prosthetic restoration and the bone attachment. CONCLUSIONS: The changes in the decision-making process did not lead to a better survival probability. CLINICAL SIGNIFICANCE: The conclusions stated in the previous study were not strict enough. Treatments with post and cores should be critically scrutinized on the basis of covering prosthetic restoration and bone attachment. Post and cores under primary crown retained RPDs should be avoided because of the bad survival probability.

Survival time of post and cores after recementation: A 16-year retrospective study with special focus on loss of retention.

OBJECTIVES: Numerous studies investigating the survival time of post and cores have found that loss of retention is the most common cause of failure Nevertheless, investigations focusing on decementation, survival after recementation, and the influencing parameters in a large number of patients with long follow-up periods are lacking. Therefore, the aim of this short communication article is the survival analysis of post and cores after recementation and repeated loss of retention. MATERIALS AND METHODS: During the observation period (2004-2020), 653 patients received 953 post and cores. From these, 112 post and cores which suffered loss of retention were selected. The patient files were analysed for the following parameters: Type of covering prosthetic restoration, location, type of tooth, luting material, post and core material, bone attachment and therapist. The survival time until loss of retention or repeated decementations after recementation was documented. Survival probability was assessed using Kaplan-Meier and Cox regression analyses. RESULTS: The average time until decementation was 13.33 years. The cumulative decementation rate was 11.8%, while in 42.0% of the cases, post and cores showed multiple losses of retention. A significant influence (Kaplan-Meier analysis) was recorded for the type of covering prosthetic restoration, type of tooth, luting material, post and core material and bone attachment. The multifactorial survival analysis (Cox regression) showed a significant influence of patient's age and the type of covering prosthetic restoration. CONCLUSIONS: Once decementation occurs, recementation neither guarantees definitive fit nor necessarily predetermines repeated decementations. CLINICAL SIGNIFICANCE: Post and cores should be avoided under primary crown-retained removable partial dentures (RPD). If this treatment is inevitable, a continuous follow-up is necessary to check the denture for proper fit to the tissues to prevent overloading on the post and core.

Clinical Outcomes of Implant-Supported Dental Prostheses: A Retrospective Analysis Considering Patient-Related Factors.

PURPOSE: To investigate the clinical performance of implant-supported dental prostheses (ISDPs), this retrospective clinical study observed influencing factors on survival of the prostheses and necessary maintenance treatments during the observation time and complications of the dental implants. MATERIALS AND METHODS: Patients who were provided either with fixed implant-supported dental prostheses (FISDPs) or telescopic-retained removable implant-supported dental prostheses (TR-RISDPs) were included in this retrospective clinical study. Potential influencing factors on the survival probability of the prostheses were observed using Kaplan-Meier analysis: patient sex, type of prosthesis, location, dentition in opposing arch, participation in follow-up visits, and whether the patient had a previous history of oral cancer. The type and number of maintenance treatments and complications of dental implants were also analyzed. RESULTS: A collective of 473 patients who were provided with either FISDPs (n = 320) or TR-RISDPs (n = 153) and 1,499 implants were included in the study. 6.6% of the prostheses (24 FISDPs and 7 TR-RISDPs) had to be replaced, and 6.3% of the implants (n = 45) were lost. The calculated 5-year survival probabilities were 87.4% for FISDPs and 95.5% for TR-RISDPs. FISDPs in patients who also had ISDPs in the opposing arch showed the lowest survival probabilities (P < .05). TR-RISDPs in patients who regularly attended follow-up visits showed the highest survival rates (P < .05). Maintenance treatments had to be performed at an earlier stage for patients with TR-RISDPs, and especially for TR-RISDPs located in the mandible (P < .05). CONCLUSION: FISDPs and TR-RISDPs showed good survival rates in this study. However, when planning FISDPs, the dentition in the opposing arch should be considered to prevent possible failure. TR-RISDPs indicate a higher need for aftercare measures, especially in the early years of function. Regular attendance of follow-up visits is still a decisive factor for success.

Monitoring fatigue damage in different CAD/CAM materials: A new approach with optical coherence tomography.

PURPOSE: To investigate fatigue damage over time, monolithic posterior computer-aided-designed/computer-aided-manufactured (CAD/CAM) crowns were artificially aged in a mouth-motion-simulator, and damage was monitored with optical coherence tomography (OCT). METHODS: Forty-eight crowns were milled of six different CAD/CAM-materials (n=8), including 3Y-TZP (Lava Plus,'3Y'), 4Y-PSZ (Pritidentamultidisc,'4Y'), 5Y-PSZ (Prettauanterior,'5Y'), zirconia-reinforced lithium silicate (CeltraDuo,'ZLS'), hybrid ceramic (Vita Enamic,'VE'),and resin composite (BrilliantCrios,'COM'), and were adhesively luted on CAD/CAM-milled human molars. Specimens were artificially aged in a mouth-motion-simulator (50-500N, 2Hz, 37°C) for a period of 1 million cycles. Before loading and every 250,000 cycles, the specimens were investigated with spectral domain (SD)-OCT (RS-3000). The maximum vertical and horizontal damage were measured with imaging-processing-software (ImageJ). After testing, the specimens were sliced and analysed via light microscope (Zeiss) to compare the new OCT method with the established light microscope method. Data were subjected to ANCOVA and 2x4-ANOVA. RESULTS: No failure occurred during mouth-motion-simulation. However, all specimens (except for 3Y and 4Y) showed fatigue damage. There was a significant difference in the maximum damage between the CAD/CAM-materials (p<.05). ZLS exhibited the highest damage, followed by VE, COM and 5Y. While damage associated with 5Y was initially noticed after 750,000 cycles, all other materials already showed crack formation after 250,000 cycles. Furthermore, a linear increase in damage over time was noticed in all materials. Due to the shallow light penetration of OCT, damage in the outer area could only be visualized with light microscope. CONCLUSIONS: OCT is feasible for monitoring fatigue damage over time within different CAD/CAM-materials, particularly for subsurface damages.

Accuracy of four different intraoral scanners according to different preparation geometries.

PURPOSE: To evaluate the accuracy (trueness and precision) achievable with four intraoral scanners (IOSs) and different preparation geometries. MATERIALS AND METHODS: A model of a maxillary arch with different preparation geometries (onlay, inlay, veneer, full-crown) served as the reference master model (RMM). The RMM was scanned 10 times using four commonly used IOSs (Trios 2 [TR], 3Shape; Omnicam [OC], Dentsply Sirona; True-Definition [TD], 3M ESPE; and Primescan [PS], Dentsply Sirona). Scans were matched using a 3D measurement software (Inspect 2019, GOM) and a best-fit algorithm, and the accuracy (trueness and precision) of the preparation types of the scanning data was evaluated for positive and negative deviations separately. All data were subjected to univariate analysis of variance using SPSS version 24 (IBM). RESULTS: Mean (± SD) positive deviations ranged from 4.6 ± 0.7 µm (TR, veneer) to 25.9 ± 2.4µm (OC, full crown). Mean negative deviations ranged from -7.2 ± 0.6 µm (TR, veneer) to -26.4 ± 3.8 µm (OC, full crown). There were significant differences (P < .05) in terms of trueness and precision among the different IOSs and preparation geometries. CONCLUSION: The transfer accuracy of simple geometries was significantly more accurate than those of the more complex prosthetic geometries. Overall, however, the IOSs used in this study yielded results that were clinically useful for the investigated preparation types, and the mean positive and negative deviations were in clinically acceptable ranges.