Diagnostic value of capsule-like rim enhancement on magnetic resonance imaging for distinguishing malignant from benign parotid tumours

The purpose of this study was to clarify the diagnostic value of capsule-like rim enhancement (CLRE) on magnetic resonance imaging (MRI) for distinguishing malignant from benign tumours of the parotid gland. We retrospectively evaluated contrast-enhanced T1-weighted images of 100 patients with malignant and benign parotid tumours for the presence, completeness, and irregularity of CLRE and its maximum thickness. We investigated any correlation of imaging and histopathological findings for 51 cases showing CLRE with available histology. The presence and completeness of CLRE did not differ significantly between benign and malignant tumours. Malignant tumours had more irregular CLRE than benign tumours (P < 0.05). The mean CLRE thickness was significantly greater for malignant (2.4 mm) than benign tumours (1.4 mm) (P < 0.0001). The two types of tumour were most accurately distinguished using a cut-off value of 1.5 mm thickness. Histopathology demonstrated the general correspondence of thick CLRE on MRI in malignant tumours with thick but sparse fibrous tissue and infiltration of tumour cells and lymphocytes, whereas thin CLRE in benign tumours typically represented dense fibrous tissue without infiltration of tumour cells. CLRE was more irregular and thicker in malignant tumours than in benign tumours, which may be of help in differentiating them.     

Clinical and oncological outcomes after surgical excision of parotid gland tumours in patients aged over 80 years

The objective of this study was to evaluate the surgical and long-term outcomes of a series of patients aged over 80 years, operated on for parotid neoplasms. Among 614 parotidectomies for neoplasms performed between 1998 and 2008, 34 patients (5.5%) aged over 80 years were identified retrospectively. Pathological examination showed a malignant tumour in 24 and a benign tumour in 10 cases. Overall survival (OS) and disease-free survival (DFS) were determined by Kaplan–Meier analysis. A search for parameters that could influence the postoperative complication rate and long-term outcomes was carried out by univariate analysis. There was no postoperative death. Eight patients (24%) had postoperative complications. Malignant histopathology (P = 0.05) and radical resection (P = 0.033) were found to have a significant negative impact on the postoperative course. Focusing on malignant tumours, only histopathological type (metastasis vs primary tumour) was found to have a negative impact on OS. The 2- and 5-year OS rates were 86% and 86%, respectively, for primary tumours, and 67% and 29%, respectively, for metastasis (P = 0.05). Malignant or benign histopathology had no impact on OS. Our results showed acceptable clinical and long-term oncological outcomes in very elderly patients operated on for parotid tumours, including malignant tumours.     

Warthin’s tumour in oral and maxillofacial regions: an 18-year retrospective study of 1084 cases in an eastern-Chinese population

There is little information in the English-language literature regarding Warthin’s tumour (WT) in the eastern-Chinese population. A large retrospective study (1084 primary tumours over a period of 18 years) was carried out to investigate the clinicopathological features (patients’ gender, age and tumour location) of these tumours in this population. A total of 994 (91.7%) patients were male and 90 (8.3%) were female, with a male/female ratio of 11:1. The mean age was 56.48 years (range 20–89 years), with a peak incidence in the fifth to seventh decade (82.1%). The favorite primary site of the tumour was the parotid gland (n = 1055), followed by intra-/peri-parotid lymph nodes (n = 13), upper neck (n = 10), submandibular gland (n = 4) and upper lip (n = 1). Multifocal WTs arose in 9.5% (103 patients) of cases whereas bilateral multifocal WTs were found in 0.65% (seven patients). In 24 (2.2%) patients, WT were found to coexist with other different types of neoplasm synchronously. The most common subtype of metaplasia was the squamous metaplasia (166/250, 66.4%). The usual treatment measure is (bilateral) superficial parotidectomy and the patients should be followed long term, in view of possible metachronous WT, even after prolonged time intervals.     

Effect of propionaldehyde or 2,3-butanedione additives on the mechanical properties of Bis-GMA analog-based composites

ObjectivesThe purpose of this study was to evaluate the effect of two additives, propionaldehyde/aldehyde or 2,3-butanedione/diketone, on mechanical properties of Bis-GMA-based composites containing TEGDMA, propoxylated Bis-GMA (CH₃Bis-GMA) or propoxylated fluorinated Bis-GMA (CF₃Bis-GMA).MethodsThree control composites, Bis-GMA/diluent monomer (25/75 mol%), and six test composites, Bis-GMA/diluent monomer/aldehyde or diketone (17/51/32 mol%) were prepared. All composites contained hybrid treated filler (barium aluminosilicate glass/pyrogenic silica; 60 wt%), and 0.2 wt% each of camphorquinone and N,N-dimethyl-p-toluidine. Degree of conversion (DC%), flexural strength (FS), modulus of elasticity (E), modulus of resilience (R) and diametral tensile strength (DTS) were determined. DC% (n = 3) was investigated by FT-IR. For FS and E, beam-shaped specimens (25 mm × 2 mm × 2 mm) were prepared (n = 6), stored for 7 days in 37 °C deionized water and tested on an Instron utilizing a three-point loading jig (0.5 mm/min). The R-values were obtained from the following equation: R = (FS)²/2E. For DTS, cylindrical specimens (4 mm × 8 mm) were prepared (n = 6), stored for 7 days in 37 °C deionized water and diametrically loaded on an Instron (0.5 mm/min). Data were analyzed by one-way ANOVA and Tukey's test (α = 0.05).ResultsIncorporation of additives led to an increase in DC%, FS and E for Bis-GMA/TEGDMA and Bis-GMA/CH₃Bis-GMA systems. R-values for all systems were unaffected by addition of additives. They had no significant effect on DC% or mechanical properties of Bis-GMA/CF₃Bis-GMA.SignificanceThe findings correlate with the ability of additives to improve degree of conversion of some composite systems thereby enhancing mechanical properties.     

Contributions of stress corrosion and cyclic fatigue to subcritical crack growth in a dental glass-ceramic

ObjectiveThe objective of this study was to test the following hypotheses: (1) both cyclic degradation and stress-corrosion mechanisms result in subcritical crack growth (SCG) in a fluorapatite glass-ceramic (IPS e.max ZirPress, Ivoclar-Vivadent) and (2) there is an interactive effect of stress corrosion and cyclic fatigue to accelerate subcritical crack growth.MethodsRectangular beam specimens were fabricated using the lost-wax process. Two groups of specimens (N = 30/group) with polished (15 μm) or air-abraded surface were tested under rapid monotonic loading. Additional polished specimens were subjected to cyclic loading at two frequencies, 2 Hz (N = 44) and 10 Hz (N = 36), and at various stress amplitudes. All tests were performed using a fully articulated four-point flexure fixture in deionized water at 37 °C. The SCG parameters were determined using the ratio of inert strength Weibull modulus to lifetime Weibull modulus. A general log-linear model was fit to the fatigue lifetime data including time to failure, frequency, peak stress, and the product of frequency and logarithm of stress in ALTA PRO software.ResultsSCG parameters determined were n = 21.7 and A = 4.99 × 10⁻⁵ for 2 Hz, and n = 19.1 and A = 7.39 × 10⁻⁶ for 10 Hz. After fitting the general log-linear model to cyclic fatigue data, the coefficients of the frequency term (α₁), the stress term (α₂), and the interaction term (α₃) had estimates and 95% confidence intervals of α₁ = −3.16 (−15.1, 6.30), α₂ = −21.2 (−34.9, −9.73), and α₃ = 0.820 (−1.59, 4.02). Only α₂ was significantly different from zero.Significance(1) Cyclic fatigue does not have a significant effect on SCG in the fluorapatite glass-ceramic evaluated and (2) there was no interactive effect between cyclic degradation and stress corrosion for this material.     

Optimization of calcium concentration of saliva with phosphoryl oligosaccharides of calcium (POs-Ca) for enamel remineralization in vitro

ObjectivePhosphoryl oligosaccharides of calcium (POs-Ca) are highly soluble calcium source made from potato starch. The aim of this study was to investigate the optimal concentrations of POs-Ca for the remineralization of subsurface enamel lesions in vitro.DesignDemineralized bovine enamel slabs (n = 5) were remineralized in vitro for 24 h at 37 °C with artificial saliva (AS) containing 0–0.74% POs-Ca to adjust the Ca/P ratio to 0.4–3.0, then sectioned and analysed by transversal microradiography (TMR). The data were analysed by Scheffe's post hoc test. The Ca/P ratio with most remineralization was used to investigate the effect of calcium on enamel remineralization (n = 11). The demineralized slabs were treated with AS with calcium-chloride- (CaCl₂-) or POs-Ca with an identical calcium content, and sectioned for TMR and wide-angle X-ray diffraction (WAXRD) analyses to evaluate the local changes in hydroxyapatite (HAp) crystal content. The data were analysed using the Mann–Whitney U-test.ResultsThe highest mineral recovery rate resulted from addition of POs-Ca to adjust the Ca/P to 1.67. At this ratio, the mineral recovery rate for AS containing POs-Ca (24.2 ± 7.4%) was significantly higher than that for AS containing CaCl₂ (12.5 ± 11.3%) (mean ± SD, p < 0.05). The recovery rate of HAp crystallites for AS containing POs-Ca (35.7 ± 10.9%) was also significantly higher than that for AS containing CaCl₂ (23.1 ± 13.5%) (p < 0.05). The restored crystallites were oriented in the same directions as in sound enamel.ConclusionsPOs-Ca effectively enhances enamel remineralization with ordered HAp at a Ca/P ratio of 1.67.     

Treatment outcome of the two-part semi-rigid oral appliance in obstructive sleep apnea

AimThe aim of this study was to assess the effectiveness of the two-part semi-rigid oral appliance, Silensor^® (Erkodent, Tuttlingen, Germany) which prevents the mandible from retracting during mouth opening.Materials and methodsTen patients with mild or moderate obstructive sleep apnea (2 males and 8 females; mean age = 62.5 ± 10.0 years) were recruited and lateral cephalometric radiographs were taken. The patients underwent polysomnography before and after 3 months of receiving treatment with the Silensor^®. The relationship between the improvement in the polysomnographic variables after the therapy and the cephalometric features was analyzed.ResultsA significant difference was observed in the apnea–hypopnea index after 3 months of Silensor^® therapy (1st (baseline), 17.1 ± 5.5; 2nd (therapy of Silensor^®), 11.0 ± 7.2, p = 0.011). Furthermore there was a significant positive correlation between the improvement in the degree of slow wave sleep (%) and the mandibular plane angle (R = 0.662, p = 0.037), as well as between the improvement in degree of slow wave sleep (%) and the lower face height (R = 0.845, p = 0.002). A significant negative correlation was observed between the improvement in degree of sleep efficiency (%) and the soft palate area (R = ?0.809, p = 0.005).ConclusionThese results suggested that keeping the nasopharyngeal airway space during mouth opening improves apnea–hypopnea index of some patients with mild or moderate obstructive sleep apnea and quality of sleep in obstructive sleep apnea patients with a long lower face height and a small soft palate.     

Digitization of simulated clinical dental impressions: Virtual three-dimensional analysis of exactness

ObjectivesTo compare the exactness of simulated clinical impressions and stone replicas of crown preparations, using digitization and virtual three-dimensional analysis.MethodsThree master dies (mandibular incisor, canine and molar) were prepared for full crowns, mounted in full dental arches in a plane line articulator. Eight impressions were taken using an experimental monophase vinyl polysiloxane-based material. Stone replicas were poured in type IV stone (Vel-Mix Stone; Kerr). The master dies and the stone replicas were digitized in a touch-probe scanner (Procera^® Forte; Nobel Biocare AB) and the impressions in a laser scanner (D250, 3Shape A/S), to create virtual models. The resulting point-clouds from the digitization of the master dies were used as CAD-Reference-Models (CRM). Discrepancies between the points in the pointclouds and the corresponding CRM were measured by a matching-software (CopyCAD 6.504 SP2; Delcam Plc). The distribution of the discrepancies was analyzed and depicted on color-difference maps.ResultsThe discrepancies of the digitized impressions and the stone replicas compared to the CRM were of similar size with a mean ± SD within 40 μm, with the exception of two of the digitized molar impressions. The precision of the digitized impressions and stone replicas did not differ significantly (F = 4.2; p = 0.053). However, the shape affected the digitization (F = 5.4; p = 0.013) and the interaction effect of shape and digitization source (impression or stone replica) was pronounced (F = 28; p < 0.0001). The reliability was high for both digitization methods, evaluated by repeated digitizations.SignificanceThe exactness of the digitized impressions varied with shape. Both impressions and stone replicas can be digitized repeatedly with a high reliability.     

Effect of the addition of thiourethane oligomers on the sol⿿gel composition of BisGMA/TEGDMA polymer networks

ObjectivesThiourethane oligomers have been shown to increase the fracture toughness and reduce the polymerization stress of methacrylate-based materials. However, network formation has not been elucidated in these materials yet. The aim of this study was to evaluate how the addition of a thiourethane oligomer (TU) influences the sol/gel composition and network structure of methacrylate-based materials using dynamic mechanical analysis and extraction methods.Materials and methodsBisGMA/TEGDMA at systematically varied mass ratios (20/80 to 80/20 wt%) were mixed with pre-polymerized thiourethane oligomers at 0 (control) or 20 wt%, synthesized by combining pentaerythritol tetra-3-mercaptopropionate with dicyclohexylmethane 4,4⿲-Diisocyanate, at 1:2 isocyanate:thiol. 0.1 wt% of 2,2-Dimethoxy-2-phenylacetophenone was added as the photoinitiator and 0.3 wt% of 2,6-di-tert-butyl-4-methylphenol was added as a free radical inhibitor. Disk specimens (0.8 ÿ 10 mm in diameter, n = 3) were photoactivated at 270 mW/ (320⿿500 nm) for 1 min. The degree of conversion (DC) was measured in near-IR (˿6165 cm^⿿1). Specimens were immersed in two different solvents (water for 7 days or dicholoromethane for 48 h). Water sorption (WS) and solubility (SL) were obtained according to ISO 4049. The leachates for both solutions were analyzed with ¹H-NMR (400 MHz, CDCL₃). Bar specimens (1 ÿ 3 ÿ 25 mm, photocured and then post-processed at 180 °C for 8 h to DC > 95%) were subjected to dynamic mechanical analysis (⿿30 to 230 °C) to obtain glass transition temperature (Tg), tan delta curves and crosslinking density (ν). Data was analyzed with two-way ANOVA/Tukey⿿s test (95%).ResultsIn general, the presence of TU increased the overall conversion. The WS was similar for all groups, but the SL decreased by 2-fold with the addition of the TU oligomer for all compositions, except BisGMA/TEGDMA 80/20. The BisGMA concentration of the leachates increased with increasing BisGMA in the initial mixture, and with the presence of thiourethane. This compositional drift of the gel with the presence of TU was attributed to the preferential dissolution of TEGDMA into the TU network. Tg and ν decreased with the addition of TU, as expected. The addition of TU produced more homogeneous networks, as evidenced by narrower breadth of the tan delta curve.ConclusionThe addition of TU affected the composition of the sol/gel in crosslinked networks, which were more homogeneous and presented 2-fold less potentially toxic leachates than the methacrylate controls.Clinical significanceThe addition of TU may produce less cytotoxic materials based on the increased conversion and reduced amount of unreacted extractables from its network after water storage.     

Effect of phase transition on the electrochemical behavior of ferredoxin embedded in an artificial lipid membrane film

The effect of the phase transition of a bilayer membrane on the electrochemical behavior of ferredoxin embedded in a cast film of artificial lipid, 2C₁₈N⁺Br⁻, was investigated. The redox potential of ferredoxin embedded in the lipid film showed a linear, positive shift from −510 (± 2) to −466 (± 3) mV (vs. Ag|AgCl|saturated KCl) with increasing temperature from 25 to 53 °C. The diffusion coefficient (D) and heterogeneous electron transfer rate constant (k°^′) were evaluated at various temperatures by means of analyzing cyclic voltammograms. The overall shape of the simulated voltammograms fitted well with the experimentally observed voltammograms at various potential sweep rates, when the estimated D and k°^′ values were used for the simulation. The results of the temperature dependence of the estimated D and k°^′ values indicated that D and k°^′ were enhanced near the phase transition temperature (T_c), 46 °C, of the lipid film. The D and k°^′ values at temperatures above the T_c were approximately two-orders and one-order of magnitude larger than those estimated at temperatures under the T_c, respectively. The estimated D and k°^′ values were 2.1–5.8 × 10⁻¹⁰ cm² s⁻¹ and 1.2–1.6 × 10⁻⁴ cm s⁻¹ at 25 °C, and 3.5–3.7 × 10⁻⁸ cm² s⁻¹ and 1.1–1.2 × 10⁻³ cm s⁻¹ at 50 °C, respectively. The electrochemical behavior of ferredoxin in the lipid film changed drastically near the T_c.     

Prediction of the upper airway growth in normal children

The purpose of the present study was to propose mathematical models for predicting the normal growth of the upper airway by using the lateral cephalograms. A set of two lateral cephalograms from each sample of 23 normal Japanese children at T1 (4.96 yr. ± 0.74) and T2 (9.47 yr. ± 1.33) was used for the analysis. For the measurements of the upper airway, 14 linear and 1 angular measurements were established. For the evaluation of craniofacial skeleton, 14 linear and 18 angular measurements were used according the traditional methods. The data were analyzed by multiple linear regression analysis. The results revealed 2 possible models for the upper airway growth prediction. The equation for the growth of the height from nasopharyngeal to the oropharyngeal airway space (MPW┬PNS-ANS) is YA = –22.753 + 0.207X₁ + 0.047X₂ + 0.042X₃, where YA is the annual growth change of MPW┬PNS-ANS, X₁ is the angle N-Pog to SN at T1, X₂ is the angle L1 to mandibular plane at T1, and X₃ is the angle Ramus plane to SN at T1 (R² = 0.692, P < 0.05). The equation for the growth of the height from the nasopharyngeal airway space to GoT-MLPW (MLPW┬PNS-ANS) is YB=17.025–0.075X₄–0.047X₅–0.075X₆, where YB is the annual growth change of MLPW┬PNS-ANS, X₄ is the angle NSAr at T1, X₅ is the angle ArGoMe at T1, and X₆ is the angle Nasal floor to SN at T1 (R² = 0.773, P < 0.05). The results of the present study could be used as models for predicting growth of the upper airway in the case evaluation and practice of pediatric dentistry.     

Only severe malocclusion correlates with mastication deficiency

ObjectivesThe relation between level of dentofacial deformity and extent of masticatory deficiency was studied.DesignThree groups of human young adults were formed: (i) subjects needing orthodontics plus orthognathic surgery (SevDFD, n = 18), (ii) subjects needing orthodontic treatment only (ModDFD, n = 12), and (iii) subjects needing no treatment (NoDFD, n = 12). For mastication tests, carrot boluses were collected at the deglutition time. Bolus particle size range was expressed as d50 value, which was compared with the Masticatory Normative Indicator (MNI). Index of treatment need (IOTN), global oral health assessment index (GOHAI) and chewing kinematic characteristics were also recorded. We used a general linear model univariate procedure followed by a Student-Newman-Keuls test.ResultsAll the SevDFD subjects showed impaired mastication with MNI above the normal limit (d50 mean = 7.23 mm). All the ModDFD subjects but one were below this limit (d50 mean = 2.54 mm), and so could adapt to a low level of masticatory impairment as also indicated by kinematics. IOTN indicated a treatment need for ModDFD (3.7 ± 0.5) and SevDFD (4.3 ± 0.6) groups, while GOHAI values were unsatisfactory only for SevDFD (42.6 ± 9.2 vs. 55.3 ± 1.9).ConclusionsOur findings emphasize the need for an objective evaluation of masticatory function to discern truly deficient mastication from mild impairment allowing satisfactory adaptation of the function. However, malocclusions are known to worsen with time justifying thus their corrections as early as possible.     

Pleomorphic adenoma and adenoid cystic carcinoma of salivary glands: E-cadherin immunoexpression and analysis of the CDH1 -160C/A polymorphism

ObjectiveDespite their similar cellular origin, pleomorphic adenomas (PA) and adenoid cystic carcinomas (ACC) present distinct behaviors. This study aimed to analyze the immunoexpression of E-cadherin in PA and ACC of salivary glands, and to investigate differences in its expression in relation to E-cadherin gene (CDH1) -160C/A polymorphism.DesignTwenty-four PA (15 cell-rich and 9 cell-poor tumors) and 24 ACC (10 tubular, 8 cribriform and 6 solid tumors) were selected for the analysis of pattern of distribution, and cellular localization of E-cadherin. In addition, E-cadherin expression was evaluated using the H-score scoring system. The CDH1 -160C/A polymorphism was investigated by PCR-RFLP.ResultsNo significant differences in pattern of distribution (p = 0.181) and cellular localization (p = 0.192) of E-cadherin were observed between PA and ACC. Comparison of PA and ACC cases revealed a higher median H-score in the latter (p = 0.036). Cell-rich PA presented a higher H-score than cell-poor tumors (p = 0.013), whereas no significant differences in E-cadherin expression were observed between ACC subtypes (p = 0.254). The heterozygous genotype of the CDH1 -160C/A polymorphism was detected in only one PA and one ACC. H-scores for tumors carrying the polymorphism were below the lower quartile of their respective groups.ConclusionsThe results suggest that E-cadherin expression in PA and ACC is mainly related to cellular composition (epithelial cells versus myoepithelial cells) and degree of differentiation of myoepithelial cells in these tumors. The CDH1 -160C/A polymorphism does not seem to significantly influence the expression of E-cadherin in PA and ACC of salivary glands.     

The effect of different cooling procedures on mechanical properties of denture base materials measured by instrumented indentation testing

PurposeTo evaluate the different cooling procedures on the mechanical properties of five heat-cured polymethyl methacrylate (PMMA) denture materials.Methods250 specimens were made equally from Meliodent (ME), Paladon 65 (PA), Probase Hot (PB), Stellon QC–20 (QC) and Vertex Rapid Simplified (VE) implementing five different cooling procedures (n = 10/procedure): A) removal from water bath, bench-cooling (10 min) and cooling under water (15 min), B) remain in water bath till room temperature, C) removal from water bath and cooling in water for 15 min, D) removal from water bath and bench cooling till room temperature and E) removal from water bath, bench cooling for 30 min and cooling under water for 15 min. The specimens were immersed in distilled water (15 days/37 ºC) and then subjected to Instrumented Indentation Testing for Martens Hardness (HM), indentation modulus (E_IT) and elastic index (η_ΙΤ). Results were statistically analyzed by two- and one-way Analysis of variance (ANOVA) plus Tukey post hoc tests (α = 0.05).ResultsThe highest values for HM were recorded for QC, PA, VE with B cooling procedure, PB with A and ME with E, for E_ΙΤ for QC, PB with A, for PA, VE with B and ME with E, and for η_IT for QC, PB with B, PB with E, ME with C and VE with D.ConclusionsThe cooling procedures recommended for PB resulted in the lowest mechanical properties. A and B may be considered as universal short- and long-cooling procedures respectively providing the highest mechanical properties for the materials tested.     

A multicentre retrospective clinico-histopathological review of 250 patients after parotidectomy

A clinicopathological review of parotid tumours treated surgically in two oral and maxillofacial surgery departments was conducted. The performance of fine needle aspiration cytology (FNAC) was also assessed. This retrospective study included 250 consecutive patients treated surgically for parotid gland-related tumours. Benign tumours (n = 211, 84.4%) were more prevalent than malignancies (n = 39, 15.6%). A predominance of pleomorphic adenoma (48.8%) was identified, and epithelial-myoepithelial carcinoma (3.6%) was the most common malignant tumour. Overall, the sensitivity and specificity of FNAC were 64% and 99%, respectively. Subgrouping resulted in sensitivity and specificity of 50% and 100% for clinically assisted FNAC versus, 72% and 99% for ultrasound guidance. Surgically, 31.6% underwent complete superficial parotidectomy and 28.4% underwent extracapsular dissection. Overall, facial nerve palsy was the most prevalent postoperative complication, affecting 29.2% (70/240); loss of function was transient in 21.2% (51/240) and permanent in 7.9% (19/240). Extracapsular dissection and superficial parotidectomy with facial nerve preservation were the treatments of choice when a benign tumour was suspected. Facial nerve palsy was quite frequent; treatment options however are scarce. Preoperative diagnostic workup using imaging and ultrasound-guided FNAC was essential in identifying malignancy so that surgical planning could be adapted.     

Bis-GMA co-polymerizations: Influence on conversion,flexural properties,fracture toughness and susceptibility to ethanol degradation of experimental composites

ObjectivesThe aim of this study was to evaluate the influence of monomer content on fracture toughness (K_Ic) before and after ethanol solution storage, flexural properties and degree of conversion (DC) of bisphenol A glycidyl methacrylate (Bis-GMA) co-polymers.MethodsFive formulations were tested, containing Bis-GMA (B) combined with TEGDMA (T), UDMA (U) or Bis-EMA (E), as follows (in mol%): 30B:70T; 30B:35T:35U; 30B:70U; 30B:35T:35E; 30B:70E. Bimodal filler was introduced at 80 wt%. Single-edge notched beams for fracture toughness (FT, 25 mm × 5 mm × 2.5 mm, a/w = 0.5, n = 20) and 10 mm × 2 mm × 1 mm beams for flexural strength (FS) and modulus (FM) determination (10 mm × 2 mm × 1 mm, n = 10) were built and then stored in distilled water for 24 h at 37 °C. All FS/FM beams and half of the FT specimens were immediately submitted to three-point bending test. The remaining FT specimens were stored in a 75%ethanol/25%water (v/v) solution for 3 months prior to testing. DC was determined with FT-Raman spectroscopy in fragments of both FT and FS/FM specimens at 24 h. Data were submitted to one-way ANOVA/Tukey test (α = 5%).ResultsThe 30B:70T composite presented the highest K_Ic value (in MPa m^1/2) at 24 h (1.3 ± 0.4), statistically similar to 30B:35T:35U and 30B:70U, while 30B:70E presented the lowest value (0.5 ± 0.1). After ethanol storage, reductions in K_Ic ranged from 33 to 72%. The 30B:70E material presented the lowest reduction in FT and 30B:70U, the highest. DC was similar among groups (69–73%), except for 30B:70U (52 ± 4%, p < 0.001). 30B:70U and 30B:35T:35U presented the highest FS (125 ± 21 and 122 ± 14 MPa, respectively), statistically different from 30B:70T or 30B:70E (92 ± 20 and 94 ± 16 MPa, respectively). Composites containing UDMA or Bis-EMA associated with Bis-GMA presented similar FM, statistically lower than 30B:35T:35U.SignificanceComposites formulated with Bis-GMA:TEGDMA:UDMA presented the best compromise between conversion and mechanical properties.     

Comparison of postoperative complications and facial nerve recovery rates after conventional and partial superficial parotidectomy of benign parotid tumours: a prospective study

The aim of this study was to compare postoperative complications and facial nerve (FN) recovery rates between conventional superficial parotidectomy (CSP) and partial superficial parotidectomy (PSP) as surgical treatment for benign parotid tumours. A prospective study was conducted on 55 consecutive patients who underwent either CSP (n = 35) or PSP (n = 20) for benign parotid tumours. The primary outcomes were FN injury, FN recovery rates, and Frey syndrome. Secondary outcomes were operative time, hospital stay, sialocele, haematoma, and auricular numbness. The degree of FN injury was evaluated at 1 week, 1, 3, 6, and 12 months postoperative using the House–Brackmann grading system. Frey syndrome was assessed using a subjective clinical questionnaire and objective Minor starch–iodine test. No patient in either group experienced permanent FN paralysis. There was a significantly higher incidence of temporary FN weakness in the CSP group (P = 0.007). The respective FN recovery rates at 1, 3, 6, and 12 months were 60%, 88.6%, 94.3%, and 100% in the CSP group and 90%, 95%, 100%, and 100% in the PSP group. No significant difference was observed between the groups regarding the incidence of Frey syndrome, sialocele, and haematoma. The operative time and hospital stay were both shorter in the PSP group. Although the PSP is a more conservative procedure with significantly reduced FN injury, operative time, and hospital stay compared to CSP, the CSP procedure shows a comparable FN recovery rate to the PSP.     

First bite syndrome after parotidectomy: a single-centre experience

The aim of this study was to investigate the prevalence of first bite syndrome (FBS) among post-parotidectomy patients and to analyse the risk factors for its occurrence. The study involved 111 adult patients operated for benign parotid tumours. After surgery, the participants were asked to assess the presence of food-related pain and the nature of the pain. Participants also answered questions on complications after parotidectomy. FBS was found in seven patients (6.3%). Sex (P = 0.036) and age (P = 0.002) differed significantly between patients with and without FBS. Female patients were found to be at higher risk of FBS, and the lower the patient’s age, the more likely FBS was to occur after surgery. Tumour location (P = 0.002) and the occurrence of disturbing symptoms before surgery (P = 0.009) had a statistically significant effect on the occurrence of FBS. A tendency towards significance for paresis of cranial nerve VII after surgery (P = 0.051) was found; this complication was more frequent in the FBS patients. FBS is a rare pain syndrome that can occur after parotidectomy and should be distinguished from postoperative pain. Proper diagnosis and implementation of the appropriate treatment can significantly improve patient quality of life.     

Health-related quality of life of parotid carcinoma patients—a comparative study with parotid adenoma patients and assessment of the influence of demographic,treatment, and pathological factors

The aim of this study was to compare the health-related quality of life (HRQoL) of patients treated for parotid carcinoma (PC) and parotid adenoma (PA). The impact of demographic, treatment, and pathological factors was analyzed within the PC group. The EORTC QLQ-C30 and QLQ-H&N35 questionnaires were completed by 45 PC patients and 46 PA patients. A number of HRQoL domains were significantly worse in the PC group than in the PA group: global health status, pain, insomnia, loss of appetite, mouth opening, swallowing problems, dry mouth, sticky saliva, problems with senses and speech, social eating, and cognitive functioning (P < 0.05). In the PC group, significantly worse scores were found for age >55 years, radical parotidectomy, neck dissection, radiotherapy, recurrence of the disease, pT3/T4 stage, pN+ status, and high-grade tumour (P < 0.05). Worse results were related to global health status, social contact, mouth opening, weight and appetite loss, physical, role, emotional, and social functioning, fatigue, speech problems, social eating, and financial difficulties. The study results demonstrate worse HRQoL in PC patients in comparison to PA patients. Older age, radical parotidectomy, neck dissection, radiotherapy, T3/T4 stage, pN+, high-grade tumours, and recurrence had a significant influence on HRQoL in PC patients.     

Graded structures for damage resistant and aesthetic all-ceramic restorations

ObjectivesClinical studies revealed several performance deficiencies with alumina- and zirconia-based all-ceramic restorations: fracture; poor aesthetic properties of ceramic cores (particularly zirconia cores); and difficulty in achieving a strong ceramic–resin-based cement bond. We aim to address these issues by developing a functionally graded glass/zirconia/glass (G/Z/G) structure with improved damage resistance, aesthetics, and cementation properties.MethodsUsing a glass powder composition developed in our laboratory and a commercial fine zirconia powder, we have successfully fabricated functionally graded G/Z/G structures. The microstructures of G/Z/G were examined utilizing a scanning electron microscopy (SEM). The crystalline phases present in G/Z/G were identified by X-ray diffraction (XRD). Young's modulus and hardness of G/Z/G were derived from nanoindentations. Critical loads for cementation radial fracture in G/Z/G plates (20 mm × 20 mm, 1.5 or 0.4 mm thick) bonded to polycarbonate substrates were determined by loading with a spherical indenter. Parallel studies were conducted on homogeneous yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) controls.ResultsThe G/Z/G structure consists of an outer surface aesthetic glass layer, a graded glass–Y-TZP layer, and a dense Y-TZP interior. The Young's modulus and hardness increase from surface to interior following power-law relations. For G/Z/G plates of 1.5 and 0.4 mm thick, critical loads for cementation radial fracture were 1990 ± 107 N (mean ± S.D., n = 6) and 227 ± 20 N (mean ± S.D., n = 6), respectively, which were ～30 and 50% higher than those for their monolithic Y-TZP counterparts (1388 ± 90 N for 1.5 mm and 113 ± 10 N for 0.4 mm thick; mean ± S.D., n = 6 for each thickness). A 1-sample t-test revealed significant difference (p < 0.001) in critical loads for radial fracture of G/Z/G and homogeneous Y-TZP for both specimen thicknesses.SignificanceOur results indicate that functionally graded G/Z/G structures exhibit improved damage resistance, aesthetics, and potentially cementation properties compared to homogeneous Y-TZP.