Influence of Cementation Mode and Ferrule Design on the Fatigue Resistance of Monolithic Zirconia Endocrowns.

Background: Classic endocrowns made of dental ceramics are considered a promising alternative to traditional post-endodontic restorations. The use of circular ferrules in endocrowns is a topic of controversial discussion. Therefore, the present study aims to evaluate the effect of ferrule design and cementation mode on the fatigue resistance of zirconia endocrowns. Methods: Eighty human molars were divided into four groups (n = 20): NFC (no-ferrule, conventional cementation), NFA (no-ferrule, adhesive luting), FC (ferrule, conventional cementation) and FA (ferrule, adhesive luting). Both the classic and the modified endocrown preparation with a two-millimeter ferrule design were carried out. Endocrowns were fabricated from zirconia using the CEREC system. After thermocycling, specimens were loaded according to the step-stress test up to 1500 N. Results: Failure rate was low; 88.8% of total specimens passed the step-stress test. Fractures were distributed between all groups; no significant differences in fatigue resistance were detected for preparation design and cementation mode. Conclusions: Endocrowns appear to be a promising concept for endodontically treated molars. Ferrule and also cementation mode have only a minor influence on fatigue resistance of zirconia endocrowns. However, at very high forces, the marginal area of the ferrule represents a weak point.

Influence of Implant Macro-Design, -Length, and -Diameter on Primary Implant Stability Depending on Different Bone Qualities Using Standard Drilling Protocols-An In Vitro Analysis.

(1) Background: Primary implant stability is vital for successful implant therapy. This study explores the influence of implant shape, length, and diameter on primary stability in different bone qualities. (2) Methods: Three implant systems (two parallel-walled and one tapered) with various lengths and diameters were inserted into polyurethane foam blocks of different densities (35, 25, 15, and 10 PCF) using standard drilling protocols. Primary stability was assessed through insertion torque (IT) and resonance frequency analysis (RFA). Optimal ranges were defined for IT (25 to 50 Ncm) and RFA (ISQ 60 to 80). A comparison of implant groups was conducted to determine adherence to the optimal ranges. (3) Results: Implant macro-design, -length, and -diameter and bone block density significantly influenced IT and RFA. Optimal IT was observed in 8/40 and 9/40 groups for the parallel-walled implants, while the tapered implant achieved optimal IT in 13/40 groups (within a 25-50 Ncm range). Implant diameter strongly impacted primary stability, with sufficient stability achieved in only one-third of cases despite the tapered implant's superiority. (4) Conclusions: The findings highlight the need to adapt the drilling protocol based on diverse bone qualities in clinical practice. Further investigations should explore the impact of these adapted protocols on implant outcomes.

The relative area score for sublingual varices reliability measurement: a diagnostic study.

BACKGROUND: Sublingual varices (SV) and their predictive potential for other clinical parameters is a much studied topic in oral medicine. SVs have been well studied as predictive markers for many common diseases such as arterial hypertension, cardiovascular disease, smoking, type 2 diabetes mellitus and age. Despite many prevalence studies, it is still unclear how the reliability of SV inspection affects its predictive power. The aim of this study was to quantify the inspection reliability of SV. METHODS: In a diagnostic study, the clinical inspection of 78 patients by 23 clinicians was examined for the diagnosis of SV. Digital images of the underside of the tongue were taken from each patient. The physicians were then asked to rate them for the presence of sublingual varices (0/1) in an online inspection experiment. Statistical analysis for inter-item and inter-rater reliability was performed in a τ-equivalent measurement model with Cronbach's [Formula: see text] and Fleiss κ. RESULTS: The interrater reliability for sublingual varices was relatively low with κ = 0.397. The internal consistency of image findings for SV was relatively high with α≈ 0.937. This shows that although SV inspection is possible in principle, it has a low reliability R. This means that the inspection finding (0/1) of individual images often cannot be reproduced stably. Therefore, SV inspection is a difficult task of clinical investigation. The reliability R of SV inspection also limits the maximum linear correlation [Formula: see text] of SV with an arbitrary other parameter Y. The reliability of SV inspection R = 0.847 limits the maximum correlation to [Formula: see text] (SV, Y) = 0,920-a 100% correlation was a priori not achievable in our sample. To overcome the problem of low reliability in SV inspection, we propose the RA (relative area) score as a continuous classification system for SV, which normalises the area of visible sublingual veins to the square of the length of the tongue, providing a dimensionless measure of SV. CONCLUSIONS: The reliability of the SV inspection is relatively low. This limits the maximum possible correlation of SV with other (clinical) parameters. SV inspection reliability is an important indicator for the quality of SV as a predictive marker. This should be taken into account when interpreting previous studies on SV and has implications for future studies. The RA score could help to objectify the SV examination and thus increase its reliability.

Biomechanical analysis of different fixed dental restorations on short implants: a finite element study.

OBJECTIVES: Although the use of short implants is becoming more common for patients with atrophic alveolar ridges, their use is still quite limited. This is due to the lack of data of long-term survival compared to standard-length implants. The aim of this study was to determine the load in the bone and implant system with different superstructures. METHODS: Three kinds of prosthetic restorations were created on short implants based on CT-Data. Two short implants with different macro-geometries were used. The implants were inserted in idealised posterior lower mandibular segments and afterwards restored with a crown, a double splinted crown, and a bridge. RESULTS: The analysis was performed under load of 300 N either divided between a mesial and distal point or as a point load on the pontic/mesial crown. The different design of the implant systems had a noticeable influence on the stress in the cortical bone, in the implant system, and the displacement of the superstructure as well. CONCLUSIONS: Compared with implants of standard length, higher stresses were observed, which can lead early failure of the implant during the healing period or a late cervical bone resorption. Precise indications are essential for short implants to avoid the failure of short implants.

HOW TO IDENTIFY SUBGROUPS IN LONGITUDINAL CLINICAL DATA: TREATMENT RESPONSE PATTERNS IN PATIENTS WITH A SHORTENED DENTAL ARCH.

BACKGROUND: When dental patients seek care, treatments are not always successful,that is patients' oral health problems are not always eliminated or substantially reduced. Identifying these patients (treatment non-responders) is essential for clinical decision-making. Group-based trajectory modeling (GBTM) is rarely used in dentistry, but a promising statistical technique to identify non-responders in particular and clinical distinct patient groups in general in longitudinal data sets. AIM: Using group-based trajectory modeling, this study aimed to demonstrate how to identify oral health-related quality of life (OHRQoL) treatment response patterns by the example of patients with a shortened dental arch (SDA). METHODS: This paper is a secondary data analysis of a randomized controlled clinical trial. In this trial SDA patients received partial removable dental prostheses replacing missing teeth up to the first molars (N = 79) either or the dental arch ended with the second premolar that was present or replaced by a cantilever fixed dental prosthesis (N = 71). Up to ten follow-up examinations (1-2, 6, 12, 24, 36, 48, 60, 96, 120, and 180 months post-treatment) continued for 15 years. The outcome OHRQoL was assessed with the 49-item Oral Health Impact Profile (OHIP). Exploratory GBTM was performed to identify treatment response patterns. RESULTS: Two response patterns could be identified - "responders" and "non-responders." Responders' OHRQoL improved substantially and stayed primarily stable over the 15 years. Non-responders' OHRQoL did not improve considerably over time or worsened. While the SDA treatments were not related to the 2 response patterns, higher levels of functional, pain-related, psychological impairment in particular, and severely impaired OHRQoL in general predicted a non-responding OHRQoL pattern after treatment. Supplementary, a 3 pattern approach has been evaluated. CONCLUSIONS: Clustering patients according to certain longitudinal characteristics after treatment is generally important, but specifically identifying treatment in non-responders is central. With the increasing availability of OHRQoL data in clinical research and regular patient care, GBTM has become a powerful tool to investigate which dental treatment works for which patients.

Is There "A Best" Centric Relation Record? Centric Relation Records, Condyle Positions, and Their Practical Significance.

PURPOSE: To investigate if and how the positions of condyles in centric relation (CR) varied from each other using different CR records. MATERIALS AND METHODS: Condylar positions in CR were repeatedly recorded by four licensed clinicians in 81 stomatognathically healthy, fully dentate subjects with six different types of CR records. The maxillary casts were mounted in articulators after individual facebow transfer, and the mandibular casts were mounted with a central bearing point (CBP) registration on the tip of the Gothic arch. Mean values from three registrations of the centric condylar positions with each of the six methods were calculated, and comparative calculations were made. RESULTS: The median spatial distances of the condylar positions between the CBP and all other CR records was 0.73 ± 0.24 mm (0 to 3.19 mm). The median spatial values between the condylar positions of the different CR records ranged from 0.48 to 0.79 mm. Statistically, the positions of almost all types of registration were slightly different from each other. CONCLUSION: Different CR records reproduce slightly different positions of the mandible, which is especially true for CBP registration, whereas reproducibilities and SDs between registrations are similar. Unrefined wax-wafer registrations using bimanual manipulation have proven particularly successful with regard to precision and time requirements, as has CBP registration with regard to condylar position.

Evaluation of a novel 8-channel RX coil for speech production MRI at 0.55 T.

OBJECTIVE: Speech production MRI benefits from lower magnetic fields due to reduced off-resonance effects at air-tissue interfaces and from the use of dedicated receiver coils due to higher SNR and parallel imaging capability. Here we present a custom designed upper airway coil for 1H imaging at 0.55 Tesla and evaluate its performance in comparison with a vendor-provided prototype 16-channel head/neck coil. MATERIALS AND METHODS: Four adult volunteers were scanned with both custom speech and prototype head-neck coils. We evaluated SNR gains of each of the coils over eleven upper airway volumes-of-interest measured relative to the integrated body coil. We evaluated parallel imaging performance of both coils by computing g-factors for SENSE reconstruction of uniform and variable density Cartesian sampling schemes with R = 2, 3, and 4. RESULTS: The dedicated coil shows approximately 3.5-fold SNR efficiency compared to the head-neck coil. For R = 2 and 3, both uniform and variable density samplings have g-factor values below 1.1 in the upper airway region. For R = 4, g-factor values are higher for both trajectories. DISCUSSION: The dedicated coil configuration allows for a significant SNR gain over the head-neck coil in the articulators. This, along with favorable g values, makes the coil useful in speech production MRI.

Effects of Different Titanium Surface Treatments on Adhesion, Proliferation and Differentiation of Bone Cells: An In Vitro Study.

The objective of this study was to evaluate the impacts of different sandblasting procedures in acid etching of Ti6Al4V surfaces on osteoblast cell behavior, regarding various physicochemical and topographical parameters. Furthermore, differences in osteoblast cell behavior between cpTi and Ti6Al4V SA surfaces were evaluated. Sandblasting and subsequent acid etching of cpTi and Ti6Al4V discs was performed with Al2O3 grains of different sizes and with varying blasting pressures. The micro- and nano-roughness of the experimental SA surfaces were analyzed via confocal, atomic force and scanning electron microscopy. Surface free energy and friction coefficients were determined. hFOB 1.19 cells were seeded to evaluate adhesion, proliferation and osteoblastic differentiation for up to 12 d via crystal violet assays, MTT assays, ALP activity assays and Alizarin Red staining assays. Differences in blasting procedures had significant impacts on surface macro- and micro-topography. The crystal violet assay revealed a significant inverse relationship between blasting grain size and hFOB cell growth after 7 days. This trend was also visible in the Alizarin Red assays staining after 12 d: there was significantly higher biomineralization visible in the group that was sandblasted with smaller grains (F180) when compared to standard-grain-size groups (F70). SA samples treated with reduced blasting pressure exhibited lower hFOB adhesion and growth capabilities at initial (2 h) and later time points for up to 7 days, when compared to the standard SA surface, even though micro-roughness and other relevant surface parameters were similar. Overall, etched-only surfaces consistently exhibited equivalent or higher adhesion, proliferation and differentiation capabilities when compared to all other sandblasted and etched surfaces. No differences were found between cpTi and Ti6Al4V SA surfaces. Subtle modifications in the blasting protocol for Ti6Al4V SA surfaces significantly affect the proliferative and differentiation behavior of human osteoblasts. Surface roughness parameters are not sufficient to predict osteoblast behavior on etched Ti6Al4V surfaces.

Misfit of Complete Maxillary Dentures' Posterior Palatal Seal following Polymerisation with Four Different Autopolymerising Resins: An In Vitro Study.

BACKGROUND: The majority of complete dentures are still conventionally manufactured using a flask-and-pack technique. However, the polymerization process may introduce a distortion of the denture body. The aim of this study was to evaluate the three-dimensional fit of the posterior palatal seal of maxillary complete dentures with the original impression, and to give recommendations for scraping. METHODS: Four autopolymerising resins were used to manufacture 40 palatal plates each for high, medium and flat palates (total n = 120). The misfit was captured by taking a reline impression with a highly fluid silicone, the dimensions of which were measured with a flat-bed scanner. RESULTS: The shape of the palate had a significant impact (median p = 0.0435), but not the resin type (median p = 0.2575). It was largest for the flat palate and smallest for the high palate. The largest misfit was observed in the palatal midline area (flat-palate average median: 685 µm; high and medium palates: 620 µm) decreasing towards the lateral and anterior regions. CONCLUSIONS: The results suggest compensating for the palatal misfit that occurs with autopolymerising resins by scraping a postdam of an approximately 0.7 mm depth to the master cast, decreasing towards the anterior and lateral areas. In high and medium palates, the scraping could be less pronounced.

Comparison of two resilient attachment systems for implant-/mucosa-supported overdentures with a PEKK framework: a clinical pilot study.

OBJECTIVES: The aim of the study was to determine differences between Locator and CM LOC attachment systems regarding patient satisfaction and wear of the abutments and their inserts. Plaque accumulation onto the polyetherketoneketone (PEKK) framework and polymethylmethacrylate (PMMA) was investigated for the implant-supported overdentures. METHODS: Seventeen edentulous patients were randomised to receive either Locator or CM LOC system for the first year. The total number of implants was 53. After the randomisation, 25 implants received Locator system, and 28 implants received CM LOC system in the first year. After a period of 12 months, the attachment system was exchanged from either Locator to CM LOC or vice versa. Oral Health Impact Profile (OHIP-14) questionnaires were used to evaluate patient satisfaction, chewing comfort, and pressure lesions. Prosthesis hygiene on the PMMA and PEKK surfaces was evaluated by using Stark plaque index. After the exchange of the abutments, they were stored until the end of the 24 months, and the surface wear of the abutments was analysed using a scanning electron microscope. RESULTS: Three patients (10 implants) died shortly before the end of the first year. Two patients (7 implants) received only Locator system since CM LOC was not indictable for their implant system. Patient's satisfaction was increased when the attachment system was changed from Locator to CM LOC after 12 months of wearing time. Chewing ability and comfort were increased when the attachment system was changed from CM LOC to Locator after 12-month wearing time. There was no influence of the change of the attachment system on pressure lesions. The observed plaque accumulation was higher on the PMMA than on the PEKK surface. For the 8 investigated Locator abutments, the wear was within low and middle level. For the 28 investigated CM LOC abutments, the wear was within middle and high level for the terminal implants and between low and middle for the central implants (for patients who received 4 implants). CONCLUSIONS: Patient's satisfaction and wearing comfort can be improved with implant-supported overdentures with CM LOC abutments in comparison to Locator. There was no clear difference between both attachment systems concerning the chewing ability of the patients. Plaque accumulation was observed on both attachment systems in different areas. Plaque accumulation on PEKK surface was less than on PMMA surface. CLINICAL RELEVANCE: The CM LOC attachment system offers stable and comfortable wearing conditions for implant-supported overdentures. The use of PEKK as a framework material could reduce the incidence of pressure lesions.

IMPACT OF SHORTENED DENTAL ARCH ON ORAL HEALTH-RELATED QUALITY OF LIFE.

BACKGROUND: A shortened dental arch (SDA) is an established treatment concept for patients with missing molars. However, little is known regarding long-term course of oral health-related quality of life (OHRQoL) in patients with SDA and the benefits from replacement of missing molars. OBJECTIVE: Purpose of this multi-center randomized clinical trial was to assess OHRQoL over a period of 15 years in patients with molar replacement by a removable partial denture (RPD) compared to patients with a restored SDA without molar replacement. METHODS: Patients at least 35 years of age with all molars missing in 1 jaw and at least the canine and one premolar present on each side were included. Patients received either a precision attachment-retained, RPD for replacement of missing molars (n = 79), or the dental arch ended with the second premolar (SDA) that had to be present or replaced by a cantilever fixed dental prosthesis (n = 71). Follow-up examinations continued for 15 years. OHRQoL was assessed with the 49-item Oral Health Impact Profile (OHIP). OHIP summary and dimension scores were longitudinally modeled in the statistical analyses to assess course of OHRQoL over time applying an intention-to-treat approach. In addition, scores for the OHRQoL dimensions Oral Function, Orofacial Pain, Orofacial Appearance, and Psychosocial Impact were analyzed. RESULTS: After an initial improvement in OHRQoL indicated by a mean decrease of 20.0 OHIP points with an effect size of 0.61 in the entire study population, OHRQoL stayed relatively constant over the entire follow-up period. Assuming a constant time and treatment effects over the study period, OHRQoL did not differ statistically significant between the 2 treatments (0.4 OHIP points; 95%-CI: 7.1 - 6.2). OHRQoL after treatment did not change notably over 15 years and was statistically nonsignificant as well (P = .872). Similar findings were observed in all 4 OHRQoL dimensions. CONCLUSIONS: In patients, missing all molars in one jaw OHRQoL improved providing RPD or restoring SDA to a clinically relevant degree. Treatment-related improvement remained mostly stable over a period of at least 15 years. Therefore, patients can be informed that both treatment concepts are equivalent concerning long-term OHRQoL. Accordingly, patients' preferences regarding treatment options should be granted priority in treatment decision making with the SDA treatment option being the default.

Comparison of Digital Self-Assessment Systems and Faculty Feedback for Tooth Preparation in a Preclinical Simulation.

BACKGROUND: Regarding the new dental licensing regulations in Germany (AOZ), this study evaluated the effectiveness of two different digital tooth preparation validation systems in comparison to traditional faculty feedback. METHODS: Participants were randomly divided into groups: Faculty Feedback (FF: n = 33), PrepCheck® (PC: n = 32) and Dental Teacher™ (n = 32). Students had the task to prepare tooth 16 for a retentive full-cast crown. Preparations could be repeated as often as desired. Feedback was provided either by faculty staff or by digital validation systems only. Exams were conducted and graded by two independent and experienced examiners. A survey was performed to evaluate the assessment concepts. RESULTS: No statistical difference in examination performance between groups could be observed. Nevertheless, the survey showed participants preferred consulting the faculty staff rather than the digital validation systems. Students preferred practising with DT rather than with PC. CONCLUSIONS: Although both classical and digital methods showed comparable results regarding the preparation examination performance, direct feedback by the faculty staff is still appreciated by the students. A combination of both methods is mandatory since demonstration and advice by the teacher is needed. However, digital tooth preparation validation systems are predestined for free practice sessions, providing self-assessment.

Rehabilitation of shortened dental arches: A fifteen-year randomised trial.

BACKGROUND: Few long-term studies on treatments in the shortened dental arch (SDA) are available. OBJECTIVE: The objective of this trial was to analyse the long-term success of two different treatment concepts. METHODS: Patients over 35 years of age with missing molars in one jaw and at least the canine and one premolar present on both sides were eligible. In the partial removable dental prosthesis (PRDP) group (N = 81), molars and missing second premolars were replaced by a precision attachment retained prosthesis. In the SDA group (N = 71), the dental arch ended with the second premolar that had to be present or replaced by a cantilever fixed dental prosthesis. Follow-up examinations were carried out over 15 years. RESULTS: A comprehensive outcome variable comprised four failure categories for which Kaplan-Meier survival (success) analyses were conducted. Half of the patients exhibited a continuous preservation of the per protocol prosthetic status that remained totally unaffected by complications for more than 10 years. The event-free success rates for moderate or worse failure implied a loss of the per protocol prosthetic status. The respective survival rates fell below 50% at 14.2 years in the PRDP group and 14.3 years in the SDA group. In none of the analyses, a significant group difference was found. CONCLUSIONS: In patients with an SDA condition, changes in the prosthetic status have to be expected. The affected proportion increases almost linearly from shortly after treatment and comprises the majority after 15 years. The influence of the examined treatments on success appears to be low.

The all-on-4 concept in the maxilla-A biomechanical analysis involving high performance polymers.

A finite element analysis was used to determine the loading behavior of a full "All-on-4" bridge in the maxilla made from different framework materials. The model was generated based on data from an edentulous maxilla. Four implants were positioned according to the All-on-4 concept and a full arch restoration was created on top of the implants. Separate thrust dies were modeled directly above each of the units of the bridge. Forces of 500 N were applied to each thrust die separately. Simulations were repeated with the following variations and results were compared to determine the influence of each variation: point of force application (from tooth 16 to 26), framework material (high performance polymer HPP, titanium Ti, cobalt chromium CoCr), and healing state of the bone/implant interface. Depending on the point of force application, the bone below the HPP framework showed increased stresses (median: 180 MPa at 13) compared to the CoCr and Ti frameworks (110 MPa at 16) under immediate loading. After osseointegration, the framework material had no obvious influence on the stresses in the bone. In the osseointegrated state, maximum stresses are decreased by the tenfold. Stresses in the framework were clearly decreased with HPP compared to CoCr and Ti (75, 125, 115 MPa). Loading the anterior teeth induced higher stresses than loading the molar region due to torsional deformation. This effect increased with decreasing framework material stiffness. The framework stiffness had less distinct influence on the stresses in the restoration than the point of force application.

In vitro cytotoxicity of different dental resin-cements on human cell lines.

Adhesive resin-cements are increasingly used in modern dentistry. Nevertheless, released substances from resin materials have been shown to cause cellular toxic effects. Disc-shaped specimens from 12 different resin cements and one conventional zinc phosphate cement were prepared and used for direct stimulation of five different human cell lines via transwell cell culture system or in an indirect way using conditioned cell culture media. Cytotoxicity was determined using LDH and BCA assays. All tested cements led to a decrease of cell viability but to a distinct extent depending on cell type, luting material, and cytotoxicity assay. In general, cements exhibited a more pronounced cytotoxicity in direct stimulation experiments compared to stimulations using conditioned media. Interestingly, the conventional zinc phosphate cement showed the lowest impact on cell viability. On cellular level, highest cytotoxic effects were detected in osteoblastic cell lines. All resin cements reduced cell viability of human cells with significant differences depending on cell type and cement material. Especially, osteoblastic cells demonstrated a tremendous increase of cytotoxicity after cement exposure. Although the results of this in vitro study cannot be transferred directly to a clinical setting, it shows that eluted substances from resin cements may disturb osteoblastic homeostasis that in turn could lead to conditions favoring peri-implant bone destruction. Thus, the wide use of resin cements in every clinical situation should be scrutinized. A correct use with complete removal of all cement residues and a sufficient polymerization should be given the utmost attention in clinical usage.

Fatigue behaviour of dental crowns made from a novel high-performance polymer PEKK.

OBJECTIVES: The aim of this study was, firstly, to analyse the long-time fatigue behaviour of crowns constructed from a novel polyetherketoneketone (PEKK) polymer, using artificial prepared teeth. Secondly, to determine the effect of the material's stiffness that used as an artificial prepared tooth on the fatigue life of the PEKK crowns in comparison to human prepared teeth. METHODS: Veneered crowns with a PEKK framework were constructed on three different prepared teeth: artificial polymethyl methacrylate (PMMA) teeth, artificial CoCr teeth and extracted human teeth. As far as applicable, the loading protocol was based on EN ISO 14801:2007 for fatigue testing of dental implants. After initial static fracture tests on three specimens from each group, the remaining crowns were loaded with different force levels until fracture or until 2 × 106 loading cycles were reached. The number of loading cycles until failure was recorded. Wöhler curves were created to display the fatigue limits. RESULTS: Static fracture limits as well as fatigue limits differed for all three core materials. The static fracture tests resulted in fracture limits of 1200 (± 293) N for the PMMA group, 1330 (± 219) N for the CoCr group and 899 (± 96) N for the human tooth group. Fatigue limits of 770 N, 840 N and 720 N were determined for the PMMA group, CoCr group and human tooth group, respectively. CONCLUSIONS: The determined fatigue limit of above 720 N (depending on the core material) is sufficiently high and a good performance of this crown material is expected in the clinical loading life. The results showed that using artificial teeth instead of natural teeth for fatigue testing of crowns might result in an overestimation of the fatigue limits of the crown material. CLINICAL RELEVANCE: PEKK-made crowns offer a stable and priceworthy treatment for patients, in particular those that suffer from metal allergy.

Clinical investigations of the comparability of different methods used to display occlusal contact points.

AIM: The aim of the present study was to evaluate the number, strength, and position of occlusal contacts shown using an intraoral scanner (IOS) and a digital occlusal analysis system (T-Scan) compared with the current gold standard using occlusal foil (OF). MATERIALS AND METHODS: Occlusal contacts were analyzed for 70 volunteers using OF in maximum intercuspation (MI). The contact points obtained using the IOS were evaluated using a screenshot from Zirkonzahn.Modellier CAD software. Finally, the volunteers were asked to bite on the sensor sheet of the T-Scan system. For the evaluation of these data, the contact points of the OF and the IOS were graded as light, medium, and strong. Furthermore, the positions of the contact points were analyzed for the anterior region (premolars and molars). Parametric statistical tests were applied to analyze the differences among the three methods. RESULTS: The mean number of all contact points was similar: 29 ± 8 with the OF, 30 ± 12 with the IOS, and 24 ± 10 with the T-Scan. However, results were different in terms of the grading of the strength of contact points: mean number of light contacts: 8 ± 4 OF vs 17 ± 8 IOS and 17 ± 6 T-Scan; medium contacts: 12 ± 5 OF vs 8 ± 4 IOS and 5 ± 4 T-Scan; and strong contacts: 9 ± 5 OF vs 6 ± 6 IOS and 4 ± 2 T-Scan. The positions of the occlusal contact points were also different. CONCLUSION: The data sets showed that there were differences in the distribution of occlusal contact points evaluated using the OF, the IOS, and the T-Scan system. Although the number of detected occlusal contacts was similar, different occlusal contact protocols were determined by the three different methods.

Epidemiological trends, predictive factors, and projection of tooth loss in Germany 1997-2030: part II. Edentulism in seniors.

OBJECTIVE: This is the second part of a report on tooth loss in Germany 1997-2030. Here, we describe trends in the prevalence of edentulism in seniors 1997-2014, assess predictive factors for edentulism, and projected it into 2030. MATERIAL AND METHODS: We used data from three waves of the cross-sectional, multi-center, nationwide representative German Oral Health Studies. Overall, 3449 seniors (65-74 years) were included (1997: 1367; 2005: 1040; 2016: 1042). Age, sex, educational level, smoking status, and the cohort were entered into age-cohort binary-logistic regression models to assess the association of predictors with edentulism and to project edentulism in 2030 via Monte Carlo simulations. RESULTS: Between 1997 and 2014, the prevalence of edentulism decreased from 24.8 to 12.4%. With each year of age, the risk of being edentate increased (by 11%, p < 0.001); it was also significantly increased in female versus male (by 40%, p = 0.001), low versus medium and high educational level (up to 257%, p < 0.001), and in former and current smokers (up to 258%, p < 0.001). We predict the prevalence of edentulism to be reduced to 4.2% in 2030. The reduction will be higher in males, never and former smokers, and those with low socio-educational level. On an absolute level and despite a growing elderly population (aged 60-80 years), the number of edentate individuals will have decreased by 3.6 million in 2030 compared with 1997. CONCLUSIONS: Edentulism in seniors has declined equitably in Germany. The decline is expected to continue until 2030. Further efforts are needed to tackle the underlying risk factors. CLINICAL RELEVANCE: This study presents trends of edentulism in Germany for a period of three decades. It provides clinically relevant data for health care planning by 2030.

Periodontal health in shortened dental arches: A 10-year RCT.

PURPOSE: This analysis focused on periodontal health in shortened dental arches (SDAs). METHODS: In a randomized controlled clinical trial, patients with missing molars in one jaw and at least one premolar and canine on both sides were eligible for participation. In the partial removable dental prosthesis (PRDP) group (n = 79), molars were replaced with a precision attachment retained PRDP. In the SDA group (n == 71), the SDA up to the second premolars was either left as is or restored with fixed dental prostheses. Outcome variables were vertical clinical attachment loss (CAL-V), pocket probing depth (PPD), bleeding on probing (BOP) and plaque index (PLI). For CAL-V and PPD, the changes at six measuring points per tooth were analyzed. For BOP and PLI, patient related rates were calculated for each point in time. Statistical methods included linear regression analyses. RESULTS: In the intention-to-treat (ITT) analysis for CAL-V in the study jaw, the 10 year patient related mean changes were 0.66 mm in the PRDP group and -0.13 mm in the SDA group. The resulting mean patient related group difference of 0.79 mm (95% CI: 0.20 mm-1.38 mm) was significant (p = 0.01). There were no significant differences in the ITT analyses for PPD. For BOP and PLI, significant group differences with more favorable results for the SDA group were found. CONCLUSIONS: In view of lacking substantial differences for CAL-V and PPD, the overall differences were considered of minor clinical relevance. The results add confirmatory evidence to the shortened dental arch concept and its clinical viability (controlled-trials.com ISRCTN97265367).

Investigation of the retention forces of secondary telescopic crowns made from Pekkton® ivory in combination with primary crowns made from four different dental alloys: an in vitro study.

The aim of this study was to investigate the retention forces of secondary telescopic crowns made of polyetherketoneketone (PEKK) in combination with primary crowns made of four different dental alloys and to determine whether the retention forces change in the course of up to 5000 simulated wear cycles. A total of four groups of telescopic crowns were investigated: group 1: 10 primary crowns made of a gold alloy (NEOCAST®3), group 2: 10 primary crowns made of a non-precious metal alloy (Girobond NB), group 3: 10 primary crowns made of zirconium (Cercon®base) and group 4: 10 primary crowns made from PEKK (Pekkton®ivory). The corresponding secondary crowns were made from PEKK in all the four groups. Each pair was fixed axially in a wear simulator specifically designed for the study. Overall, 10,000 joining and separating cycles were performed for each group. To simulate intraoral conditions, a saliva substitute served as a lubricant. Force transducers were used to record the retention forces and after completing 10,000 cycles, the surface of each primary crown was examined using a scanning electron microscope (SEM). All groups showed an increase in the retention force for the first 2000 cycles which stayed constant for the remaining 8000 cycles. The Pekkton®ivory/Pekkton®ivory and NEOCAST®3/Pekkton®ivory combinations displayed mean retention force values of 16 N after a slight increase in the retention force. The Cercon®base/Pekkton®ivory and Girobond NB/Pekkton®ivory combinations displayed an initially high increase in the retention force and then showed a mean retention force of up to 29 N. All primary crowns displayed surface wear. Zirconium primary crowns showed the least wear compared to PEKK and the gold and non-precious metal alloys.