Abstract Objectives To evaluate the effect of different cement types on the incidence of failure and loss of retention of zirconia and metal‐ceramic single crowns (SCs) cemented on implant abutments. ...Methods We placed 567 implant‐supported SCs in 358 patients and retrospectively evaluated long‐term retention for up to 12.8 years. The frameworks were made from metal alloy ( n = 307) or zirconia ( n = 260). SCs were cemented with permanent (glass‐ionomer cement; n = 376) or semipermanent cement (zinc oxide non‐eugenol cement; n = 191) on standardized ( n = 446) or customized ( n = 121) abutments. Kaplan–Meier curves were used to calculate the incidence of decementation. Differences between survival curves were assessed with log‐rank tests. Cox‐regression analysis was performed to evaluate multiple risk factors. Results Of the 567 SCs, 22 failed because of technical complications and four because of implant loss. Loss of retention was observed in 50 SCs. Analysis revealed a 7% probability of loss of retention for zirconia and 16% for metal‐ceramic SCs after 10 years ( p = .011). After 5 years, loss of retention was higher for standardized abutments than for customized abutments ( p = .014). The probability of loss of retention was higher with semipermanent than with permanent cement ( p = .001). Cox‐regression analysis revealed semipermanent cement as the only significant risk factor for SC failure ( p = .026). Conclusions In contrast to semipermanent cement, permanent cement provides acceptable long‐term retention of cemented implant‐supported SCs. These possible positive effects of customized abutments have to be controlled with larger sample sizes.
Summary
The purpose of this study was to evaluate enamel wear caused by monolithic zirconia crowns and to compare this with enamel wear caused by contralateral natural antagonists. Twenty monolithic ...zirconia crowns were placed in 20 patients requiring full molar crowns. For measurement of wear, impressions of both jaws were made at baseline after crown cementation and at 6‐month follow‐up. Mean and maximum wear of the occlusal contact areas of the crowns, of their natural antagonists and of the two contralateral natural antagonists were measured by the use of plaster replicas and 3D laser scanning methods. Wear differences were investigated by the use of two‐sided paired Student's t‐tests and by linear regression analysis. Mean vertical loss (maximum vertical loss in parentheses) was 10 (43) μm for the zirconia crowns, 33 (112) μm for the opposing enamel, 10 (58) μm for the contralateral teeth and 10 (46) μm for the contralateral antagonists. Both mean and maximum enamel wear were significantly different between the antagonists of the zirconia crowns and the contralateral antagonists. Gender and activity of the masseter muscle at night (bruxism) were identified as possible confounders which significantly affected wear. Under clinical conditions, monolithic zirconia crowns seem to be associated with more wear of opposed enamel than are natural teeth. With regard to wear behaviour, clinical application of monolithic zirconia crowns is justifiable because the amount of antagonistic enamel wear after 6 months is comparable with, or even lower than, that caused by other ceramic materials in previous studies.
•FE analysis was performed to verify in-vitro test results.•All variables affected veneer failure or total failure of zirconia-based IRFPDs.•Use of resin abutment teeth leads to underestimation of ...fracture loads up to 57%.•Use of metal abutment teeth leads to overestimation of fracture loads up to 15%.•Zirconia-based IRFPDs should be tested on resiliently supported metal abutment teeth.
In the past, discrepancies between laboratory results and clinical behavior have been observed for all-ceramic restorations. This analysis of fracture resistance of zirconia-based inlay-retained fixed partial dentures (IRFPDs) aimed at identifying correlations between an in-vitro test setup and the clinical situation. The effects of tooth material, tooth mobility, restoration design, load direction, and different cements were taken into account.
The in-vitro test model and IRFPD were reverse engineered (Geomagic DesignX) and meshed predominantly with hexahedral elements (approx. 230,000 elements). Homogenous, linear-elastic behavior was assumed for all materials. On the basis of the calculated stresses (ANSYS 18.2) and already known strength distributions for the restorative materials fracture resistance of the complete restoration and force at initial damage (fracture within the veneer) was estimated on the basis of the principal stress hypothesis. Differences depending on the assumed clinical situation and effects of different variables on fracture resistance were evaluated.
All variables tested in the finite element analysis affected the calculated fracture resistance of the IRFPD. Use of resin teeth led to an underestimation of fracture resistance by up to −57%, whereas fracture resistance of IRFPDs on metal abutment teeth was close to the clinical reference (−6% to +15%). Good correlation between the clinical scenario and that using metal teeth could only be achieved when the natural resilience of the abutment teeth was simulated.
When testing fracture resistance of zirconia-based IRFPDs, metal abutment teeth in combination with simulated tooth resilience can reflect the clinical situation accurately.
To analyze the impact of different post printing cleaning methods on geometry, transmission, roughness parameters, and flexural strength of additively manufactured zirconia.
Disc-shaped specimens (N ...= 100) were 3D-printed from 3 mol%-yttria-stabilized zirconia (material: LithaCon 3Y 210; printer: CeraFab 7500, Lithoz) and were cleaned with five different methods (n = 20): (A) 25 s of airbrushing with the dedicated cleaning solution (LithaSol 30®, Lithoz) and 1-week storage in a drying oven (40 °C); (B) 25 s airbrushing (LithaSol 30®) without drying oven; (C) 30 s ultrasonic bath (US) filled with Lithasol30®; (D) 300 s US filled with LithaSol 30®; (E) 30 s US filled with LithaSol 30® followed by 40 s of airbrushing (LithaSol 30®). After cleaning, the samples were sintered. Geometry, transmission, roughness (Ra, Rz), characteristic strengths (σ0), and Weibull moduli (m) were analyzed. Statistical analyses were performed using Kolmogorov-Smirnov-, t-, Kruskal-Wallis-, and Mann-Whitney-U-tests (α < 0.05).
Short US (C) resulted in the thickest and widest samples. Highest transmission was found for US combined with airbrushing (E, p ≤ 0.004), followed by D and B (same range, p = 0.070). Roughness was lowest for US combined with airbrushing (E, p ≤ 0.039), followed by A and B (same range, p = 0.172). A (σ0 = 1030 MPa, m = 8.2), B (σ0 = 1165 MPa, m = 9.8), and E (σ0 = 1146 MPa, m = 8.3) were significantly stronger (p < 0.001) and substantially more reliable than C (σ0 = 480 MPa, m = 1.9) and D (σ0 = 486 MPa, m = 2.1).
For 3D-printed zirconia, cleaning strategy selection is important. Airbrushing (B) and short US combined with airbrushing (E) were most favorable regarding transmission, roughness, and strength. Ultrasonic cleaning alone was ineffective (short duration) or detrimental (long duration). Strategy E could be particularly promising for hollow or porous structures.
Summary The purpose of this prospective cohort study was to assess the performance of tooth‐supported, long‐span, zirconia fixed dental prostheses (FDPs). Thirty FDPs with span lengths from 36 to 46 ...mm (mean 40·33 mm), with 4–7 units and with connector dimensions ∼9 mm2 were inserted (19 in the posterior region, 11 including anterior teeth) using glass–ionomer cement. The performance of the FDPs was assessed (aesthetic evaluation, failures, hypersensitivity/tooth vitality, secondary caries, pocket depth, decementation, and chipping) at baseline and after 5 years. Cox regression analysis was performed to identify risk factors. There were 16 failures after 5 years. Framework fracture occurred for two FDPs, four FDPs had to be re‐cemented, one abutment tooth had to be treated endodontically, one abutment tooth fractured and cohesive failure of the veneer occurred for eight. Four FDPs had to be replaced, so survival was 82%. The aesthetics were rated as excellent by the patients at baseline and good at the 5‐year recall. Cox regression analysis showed that both length P = 0·05, exp(B) = 1·22 and location P = 0·019, exp(B) = 4·09 of the FDP were risk factors for failure. Compared with the previously published 2‐year results, the incidence of complications increased dramatically. Additionally, it was shown that long‐span FDPs in the molar region are at greater risk of failure than FDPs in the anterior region.
The incidence of metallic dental restorations and implants is increasing, and head and neck MR imaging is becoming challenging regarding artifacts. Our aim was to evaluate whether multiple-slab ...acquisition with view angle tilting gradient based on a sampling perfection with application-optimized contrasts by using different flip angle evolution (MSVAT-SPACE)-STIR and slice-encoding for metal artifact correction (SEMAC)-STIR are beneficial regarding artifact suppression compared with the SPACE-STIR and TSE-STIR in vitro and in vivo.
At 3T, 3D artifacts of 2 dental implants, supporting different single crowns, were evaluated. Image quality was evaluated quantitatively (normalized signal-to-noise ratio) and qualitatively (2 reads by 2 blinded radiologists). Feasibility was tested in vivo in 5 volunteers and 5 patients, respectively.
Maximum achievable resolution and the normalized signal-to-noise ratio of MSVAT-SPACE-STIR were higher compared with SEMAC-STIR. Performance in terms of artifact correction was dependent on the material composition. For highly paramagnetic materials, SEMAC-STIR was superior to MSVAT-SPACE-STIR (27.8% smaller artifact volume) and TSE-STIR (93.2% less slice distortion). However, MSVAT-SPACE-STIR reduced the artifact size compared with SPACE-STIR by 71.5%. For low-paramagnetic materials, MSVAT-SPACE-STIR performed as well as SEMAC-STIR. Furthermore, MSVAT-SPACE-STIR decreased artifact volume by 69.5% compared with SPACE-STIR. The image quality of all sequences did not differ systematically. In vivo results were comparable with in vitro results.
Regarding susceptibility artifacts and acquisition time, MSVAT-SPACE-STIR might be advantageous over SPACE-STIR for high-resolution and isotropic head and neck imaging. Only for materials with high-susceptibility differences to soft tissue, the use of SEMAC-STIR might be beneficial. Within limited acquisition times, SEMAC-STIR cannot exploit its full advantage over TSE-STIR regarding artifact suppression.
Summary The purpose of this prospective cohort study was to assess the performance of tooth‐supported, extended zirconia, fixed dental prostheses (FDPs). Thirty FDPs with span‐lengths between 36 and ...46 mm (mean: 40·33 mm), four to seven units and with connector dimensions of ∼9 mm2 were inserted (19 in the posterior region, 11 including anterior teeth) using glass–ionomer cement and assessed (aesthetic evaluation, failures, hypersensitivity/tooth vitality, secondary caries, pocket depth, decementation and chipping) at baseline and after 2 years. Differences between baseline and 2‐year recall were analysed using the Wilcoxon signed‐rank test for matched pairs. There were five failures. One FDP revealed a core fracture at the base of the connector, probably caused by a damage induced during fabrication. Two FDPs had to be recemented, one abutment tooth had to be treated endodontically and one cohesive failure of the veneer was observed. There were no significant changes of pocket depth and hypersensitivity between baseline and 2‐year recall. The aesthetics were rated as excellent by the patients at both baseline and recall. Two year clinical results of extended zirconia based FDPs with 9 mm2 connectors are promising.
In dentistry the restoration of decayed teeth is challenging and makes great demands on both the dentist and the materials. Hence, fiber-reinforced posts have been introduced. The effects of ...different variables on the ultimate load on teeth restored using fiber-reinforced posts is controversial, maybe because the results are mostly based on non-standardized in vitro tests and, therefore, give inhomogeneous results. This study combines the advantages of in vitro tests and finite element analysis (FEA) to clarify the effects of ferrule height, post length and cementation technique used for restoration. Sixty-four single rooted premolars were decoronated (ferrule height 1 or 2 mm), endodontically treated and restored using fiber posts (length 2 or 7 mm), composite fillings and metal crowns (resin bonded or cemented). After thermocycling and chewing simulation the samples were loaded until fracture, recording first damage events. Using UNIANOVA to analyze recorded fracture loads, ferrule height and cementation technique were found to be significant, i.e. increased ferrule height and resin bonding of the crown resulted in higher fracture loads. Post length had no significant effect. All conventionally cemented crowns with a 1-mm ferrule height failed during artificial ageing, in contrast to resin-bonded crowns (75% survival rate). FEA confirmed these results and provided information about stress and force distribution within the restoration. Based on the findings of in vitro tests and computations we concluded that crowns, especially those with a small ferrule height, should be resin bonded. Finally, centrally positioned fiber-reinforced posts did not contribute to load transfer as long as the bond between the tooth and composite core was intact.
Summary Aim of this study was to introduce a feasible and valid technique for the assessment of masticatory performance that is comparable to the standard sieving method. Twenty‐one chewing samples ...(Optosil) comminuted by healthy dentate adults were analysed with a sieving and scanning method. Scanning was performed using a conventional flatbed scanner (1200 dpi). All scanned images underwent image analysis (ImageJ), which yielded descriptive parameters such as area, best‐fitting ellipse for each particle. Of the 2D‐image, a volume was estimated for each particle, which was converted into a weight. To receive a discrete distribution of particle sizes comparable to sieving, five chewing samples were used to calculate a size‐dependent area‐volume‐conversion factor. The sieving procedure was carried out with a stack of 10 sieves, and the retained particles per sieve were weighed. The cumulated weights yielded by either method were curve‐fitted with the Rosin–Rammler distribution to determine the median particle size x50. The Rosin–Rammler distributions for sieving and scanning resemble each other. The distributions show a high correlation (0·919–1·0, n = 21, P < 0·01, Pearson’s correlation coefficient). The median particle sizes vary between 3·83 and 4·77 mm (mean: 4·31) for scanning and 3·53 and 4·55 mm (mean: 4·21) for sieving. On average, scanning overestimates the x50 values by 2·4%. A modified Bland–Altman plot reveals that 95% of the x50 values fall within 10% of the average x50. The scanning method is a valid, simple and feasible method to determine masticatory performance.
Older people with dementia are very dependent on nursing, and caregivers are frequently confronted with oral-care-resistant behaviour which may lead to shortcomings in oral health.
To compare oral ...hygiene and health status of institutionalised older people suffering, or not, from dementia.
Prospective cohort study (single-blind).
Institutionalised older population in south-west Germany.
Ninety-three, allocated to two groups: dementia (n = 57) and non-dementia (n = 36) based on a mini mental state examination.
Target variables were plaque control record (PCR), gingival bleeding index (GBI), community periodontal index of treatment needs (CPITN), and denture hygiene index (DHI). Differences between the dementia and non-dementia groups were evaluated by univariate testing of all target variables.
Univariate analysis revealed the amount of plaque in the dementia group was significantly higher than in the non-dementia group (p = 0.004). Mean CPITN of participants in the dementia group was significantly worse than those of participants in the non-dementia group (p < 0.001). All participants in the dementia group had periodontitis in at least one of the sextants, compared with 74% in the non-dementia group (p < 0.001). For DHI (p = 0.198) and GBI (p = 0.275) no differences were found between the groups.
Some aspects of oral hygiene and health seem to be worse for the institutionalised older people with dementia. Permanent specially adapted intervention for residents suffering from dementia in long-term care homes, and training for caregivers, is desirable to maintain life-long oral hygiene and health.
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