Increased risk for premolar tooth loss in shortened dental arches

ObjectivesTo assess sustainability of shortened dental arches (SDA) by determining time to ‘first restorative intervention’ of teeth and time to ‘tooth loss’ and comparing these outcomes with complete dental arches (CDA) and SDA plus removable dental prostheses (RDP).MethodsData (follow-up time ranged from 27.4 (SD 7.1) to 35.0 (SD 5.6) years; max. follow up: 45.8 years) from patient records of 59 subjects (23 SDA, 23 CDA, and 13 SDA plus RDP) participating in a prospective cohort study on shortened dental arches (SDA) were analysed. Group effects on survival were analysed using Cox regression models; where appropriate Kaplan–Meier analyses were done.ResultsCompared to SDA subjects, CDA subjects had a lower risk to receive a first restorative intervention in anterior teeth (HR = 0.377; 95% CI [0.205–0.695]) and premolars (HR = 0.470; 95% CI [0.226–0.977]). CDA subjects had a lower risk to lose premolars compared to SDA subjects (HR = 0.130; 95% CI [0.053–0.319]). Risk for ‘first restorative intervention’ and for ‘tooth loss’ did not significantly differ between SDA with and without RDP.ConclusionsSDA subjects had an increased risk to lose premolars and to receive a first time restoration in anterior teeth and premolars compared to CDA subjects. SDA subjects with RDP had no increased risk to receive a first restorative intervention or for tooth loss compared to SDA without RDP.Clinical relevanceSubjects with shortened dental arches can be discerned as enduring at-risk patients. It is therefore recommended that shortened dental arch subjects receive intensive and continuous care to prevent further tooth loss.     

Effect of chlorhexidine application on long-term shear bond strength of resin cements to dentin

PurposeThe purpose of this study was to investigate the effect of chlorhexidine [CH] on dentin bond strength of three resin cements after 1 year of water storage.MethodsA flat middle dentin surface was prepared on 120 extracted premolars. The teeth were randomly divided into 6 groups of 20 specimens each according to the resin cement used: Panavia F2.0, Variolink II, and RelyX Unicem, with or without CH application. After cementation of an indirect composite rod [Z250], one subgroup [n = 10] was tested after 24 h in water at 37 °C and the other subgroup [n = 10] was tested after 1 year storage in water plus thermocycling. A shear bond strength [SBS] test was performed. The data [in MPa] were analyzed with ANOVA and Tukey tests [P < 0.05].ResultsThree-way ANOVA [resin cement, CH and time] indicated that Variolink II had the highest strength [16.65 ± 3.60] and RelyX Unicem had the lowest strength [9.30 ± 4.07]. Chlorhexidine application increased SBS [13.31 ± 4.61] compared to samples without CH [12.16 ± 5.04] [P = 0.04]. Initial SBS [15.63 ± 4.37] was significantly higher than after 1 year of storage [9.85 ± 3.36] [P < 0.001]. Separate two-way ANOVA for 24-h and 1-year data showed that cement had a significant effect but CH and its interaction had no significant effect at 24 h, whereas at 1 year the two factors and their interaction differed significantly [P ≤ 0.001].ConclusionsChlorhexidine 2% can diminish the loss of bonding effectiveness over time associated to etch-and-rinse and self-etch cements, although it appears not have any effect on self-adhesive cement.     

Immediate bonding properties of universal adhesives to dentine

ObjectivesTo evaluate the dentine microtensile bond strength (μTBS), nanoleakage (NL), degree of conversion (DC) within the hybrid layer for etch-and-rinse and self-etch strategies of universal simplified adhesive systems.Methodsforty caries free extracted third molars were divided into 8 groups for μTBS (n = 5), according to the adhesive and etching strategy: Clearfil SE Bond [CSE] and Adper Single Bond 2 [SB], as controls; Peak Universal Adhesive System, self-etch [PkSe] and etch-and-rinse [PkEr]; Scotchbond Universal Adhesive, self-etch [ScSe] and etch-and-rinse [ScEr]; All Bond Universal, self-etch [AlSe] and etch-and-rinse [AlEr]. After restorations were constructed, specimens were stored in water (37 °C/24 h) and then resin–dentine sticks were prepared (0.8 mm²). The sticks were tested under tension at 0.5 mm/min. Some sticks from each tooth group were used for DC determination by micro-Raman spectroscopy or nanoleakage evaluation (NL). The pH for each solution was evaluated using a pH metre. Data were analyzed with one-way ANOVA and Tukey's test (α = 0.05).ResultsFor μTBS, only PkSe and PkEr were similar to the respective control groups (p > 0.05). AlSe showed the lowest μTBS mean (p < 0.05). For NL, ScEr, ScSe, AlSe, and AlEr showed the lowest NL similar to control groups (p < 0.05). For DC, only ScSe showed lower DC than the other materials (p < 0.05).ConclusionsPerformance of universal adhesives was shown to be material-dependent. The results indicate that this new category of universal adhesives used on dentine as either etch-and-rinse or self-etch strategies were inferior as regards at least one of the properties evaluated (μTBS, NL and DC) in comparison with the control adhesives (CSE for self-etch and SB for etch-and-rinse).     

Smoking among dental students at King Saud University: Consumption patterns and risk factors

ObjectiveTo assess smoking prevalence among dental students at King Saud University (KSU) and to determine possible risk factors of tobacco use.MethodsA self-addressed invitation letter was sent to all dental students (males and females) at KSU requesting participation in this study. Data on smoking habits, associated risk factors, and demographic factors, such as age, marital status, residency status, the student’s year of study, and grade point average, were collected by an electronic self-administered questionnaire sent via email. Data were analyzed using SPSS. Significant differences between different groups were assessed with a Pearson Chi-Square test at α = 0.05. Logistic regression analysis was used to calculate the odds ratio (OR) and 95% confidence interval (95% CI) and to determine the effect of different risk factors on students’ smoking habits.ResultsOf the 600 registered dental students, 400 students responded (230 males, 170 females), representing a response rate of 67%. More male than female students were current smokers (27.6% vs. 2.4%, p < 0.001). Most smokers used shisha tobacco only (N = 35, 51.5%), followed by both shisha tobacco and cigarettes (N = 17, 25%), or cigarettes only (N = 16, 23.5%). Male students were about 4 times more likely to be smokers if all or most of their friends were smokers compared to students who had some friends who smoked (OR = 3.9, 95% CI = 1.9–7.7). A high proportion of current smokers (47.8%) reported stress as the main reason for smoking. Twenty-six percent of dental students (N = 87) who are currently nonsmokers reported that they have used tobacco at some point in their lives. Over two thirds of sampled students (63%) believed that public tobacco usage is not well addressed in the current college curriculum.ConclusionApproximately one in every four male dental students at KSU is a smoker. Having friends who are smokers was the most important risk factor associated with smoking. There is a general belief among dental students that public tobacco use is not well addressed in the dental college curriculum.     

Excretion of dental resin monomers and metabolic intermediates via urine in guinea pigs

ObjectiveMonomers like BisGMA (Bisphenol-A-glycidyldimethacrylate) and comonomers like TEGDMA (triethyleneglycoldimethacrylate) are used in dental restorative materials in order to build up the three-dimensional network of filling materials. Since earlier investigations revealed uptake and subsequent metabolism of unpolymerized remainders of (co)monomers, the present experiment investigates the metabolic urine pattern of guinea pigs (n = 4) after application of TEGDMA or BisGMA (each dose = 0.02 mmol/kg body weight = 100%), respectively.MethodsFor the investigations BisGMA was pre-dissolved in DMSO and subsequently diluted with 0.9% NaCl solution (final DMSO concentration 1%) and TEGDMA was dissolved in 0.9% NaCl solution. The solutions were administered with a gastric tube into the animals. Control animals received either 0.9% NaCl or 0.9% NaCl solution with 1% DMSO solution.ResultsAfter 24 h in collected urine the following metabolites were identified. After administration of TEGDMA (mean relative concentration of administered substances) ± s.d. [%]; n = 4): unchanged TEGDMA: 12 ± 1.5%, MA: 2.4 ± 0.8%, and triethyleneglycol: 35 ± 2.2%. After administration of BisGMA (mean ± s.d. [%]; n = 4): unchanged BisGMA: 11.4 ± 2.7%, MA: 2.2 ± 0.6%, and bisphenol-A-bis(2,3-dihydroxypropyl)ether: 60.1 ± 5.2%).ConclusionNo further metabolites like the previously identified intermediate 2,3-epoxymethacrylic acid and derived reaction products were identified in the urine, indicating that these metabolites must have reacted further.     

Tooth sensitivity and efficacy of in-office bleaching in restored teeth

ObjectivesThe aim of this clinical trial was to evaluate efficacy (BE) and tooth sensitivity (TS) of in-office bleaching with a 35% hydrogen peroxide (HP) in patients with aesthetic restorations.MethodsHydrogen peroxide 35% was applied in two sessions, of three 15 min applications, in 15 patients with upper anterior sound teeth (S) and 15 with aesthetic restorations (R). The colour was recorded at baseline, one week and 6 months after treatment completion. Patients recorded TS on a 0–4 scale. The BE was evaluated by two-way ANOVA and Tukey's tests (α = 0.05). The percentage of patients with TS was evaluated by Fisher's exact test and TS intensity of treatments was compared with Mann–Whitney U-test (α = 0.05).ResultsAll participants experienced TS at least once during treatment. Higher TS intensity was observed in R (1.5 [1/1.75]) compared to S (0.5 [0/1.25]) during the bleaching (p < 0.05). S and R demonstrated similar tooth colour enhancement compared to baseline (p < 0.05) and both presented colour stability after 6 months of evaluation (p > 0.05).ConclusionsThe in-office bleaching with 35% HP was effective in patients with aesthetic restorations, however, a higher intensity of TS was observed during the bleaching protocol.Clinical relevanceIn-office dental bleaching can be performed in patients with adhesive restorations promoting satisfactory results; however, it can promote higher intensity of sensitivity compared to patients with sound teeth.     

Differences in the biomechanical behaviors of natural teeth and dental implants

ObjectiveThe lack of a PDL, which acts as an energy absorber, is a contributor to implants’ early failure; however, these discrepancies are not well understood because of limited in vivo research. This study investigated the discrepancy in biomechanical behaviors between natural teeth and dental implants by detecting micro-movements in vivo.MethodsWe designed a device that could measure precisely mechanical behaviors such as creep, stress relaxation, and hysteresis by using load–control displacement on teeth and implants. We also compared energy dissipation between natural teeth and dental implants by subtracting the area of the hysteresis loop of natural teeth from that of dental implants.ResultsBiphasic curves with an initial phase of rapid response and a subsequent phase of slow response were confirmed in creep and stress relaxation curves for the load–time relationship in natural teeth. By contrast, the behavior of creep or stress relaxation was less prominent when the dental implants were tested. We observed that the periodontal ligament under an axial intrusive load of 300 g in a loading rate 3 g/s could dissipate the energy of 7.35 ± 1.18 × 10^?2 mJ, approximately 50 times that of the dental implants (1.47 ± 1.22 × 10^?3) with statistically significant (p < 0.05).SignificanceWe confirmed natural teeth could achieve greater energy dissipation compared to dental implants, which owe to that natural teeth exhibited fluid and viscoelastic properties.     

Evaluation of the Candida albicans removal and mechanical properties of denture acrylics cleaned by a low-cost powered toothbrush

PurposeTo investigate the effects of using a low-cost powered toothbrush for cleaning on dental prostheses made of heat polymerized poly(methyl methacrylate), PMMA.MethodsHeat cured PMMA specimens beam with the dimensions of 45.0 mm × 6.5 mm × 4.5 mm were fabricated. The specimens were kept in water storage at 37 °C constant temperature for 0, 1, 7, 15, 30 and 60 days and randomly assigned for testing or control. Test specimens underwent brushing by using a powered toothbrush at an applied force of 2.00 N for 22 min with water as medium. Surface roughness measurement (R_a), flexural strength and efficacy of brushing to remove coated Candida albicans biofilm were investigated.ResultsThe results of the mean surface roughness value and the flexural strength were analysed by using two-way ANOVA and Tukey post hoc test at 5% significance level. In general, the specimens showed no significant changes in flexural strength after brushing. However, the flexural strength and the surface roughness value were significantly lower in specimens group after 7 days in water storage compared to the control. SEM micrographs of post-brushed specimens revealed satisfactory removal of C. albicans biofilm.ConclusionA low-cost powered toothbrush together with a liquid medium successfully removed C. albicans biofilm on dental acrylic PMMA-based prostheses, without compromising the mechanical properties.     

Simplified conditions for storing and cryopreservation of dental pulp stem cells

ObjectivesThis study aimed to simplify the collection, isolation and cryopreservation procedure of human dental pulp stem cells (DPSCs) to ease the establishment of dental stem cell banking.DesignExtracted third molars were collected and stored either in growth medium or in gentamicin-saline (480 μg/ml) for 6, 9 or 12 h. DPSCs were isolated and subjected to cryopreservation by a controlled-rate or rapid freezing method in 5 or 10% DMSO. Flow cytometry and growth pattern of DPSCs before and after cryopreservation were conducted.ResultsRate of contamination by which the extracted teeth were stored in control and gentamicin-saline were 9.1% (N = 33) and 2.3% (N = 43), respectively. Successful cell isolation rate of teeth preserved in gentamicin-saline at 6 h (92.9%) was comparable to those of growth media group (90.3%). At 9 and 12 h, the rates dropped significantly to 75% and 54%, respectively. Cryopreservation by controlled-rate freezing either in 5 or 10% DMSO resulted in a significantly higher percentage of viable cells than by rapid freezing. Cells conserved by controlled-rate freezing in 5% DMSO showed a pattern of growth similar to control unfrozen cells; 10% DMSO significantly deteriorated the growth pattern of the cells. After thawing, DPSCs conserved by controlled-rate freezing still expressed stemness characteristics, although hematopoietic stem cell markers were slightly increased.ConclusionGentamicin-saline was effective in preserving human teeth for DPSC isolation. Controlled-rate freezing in 5% DMSO gave the highest rate of cell viability. This study simplifies the storage conditions and proposes a simple method for cryopreservation of DPSCs.     

Fabrication and characterization of remineralizing dental composites containing calcium type pre-reacted glass-ionomer (PRG-Ca) fillers

ObjectiveTo fabricate and characterize dental composites with calcium type pre-reacted glass-ionomer (PRG-Ca) fillers.MethodsPRG-Ca fillers were prepared by the reaction of calcium fluoroaluminosilicate glass with polyacrylic acid. Seven dental composites were produced from the same organic matrix (70/30 wt% Bis-GMA/TEGDMA), with partial replacement of barium borosilicate (BaBSi) fillers (60 wt%) by PRG-Ca fillers (wt%): E0 (0) – control, E1 (10), E2 (20), E3 (30), E4 (40), E5 (50) and E6 (60). Enamel remineralization was evaluated in caries-like enamel lesions induced by S. mutans biofilm using micro-CT. The following properties were characterized: degree of conversion (DC%), roughness (Ra), Knoop hardness (KHN), flexural strength (FS), flexural modulus (FM), water sorption (W_sp), water solubility (W_sl), and translucency (TP). Data were analyzed to one-way ANOVA and Tukey’s HSD test (α = 0.05).ResultsAll composites with PRG-Ca induced enamel remineralization. E0 and E1 presented similar and highest DC% than E2 = E3 = E4 = E5 = E6. Ra and KHN were not influenced by PRG-Ca fillers (p < 0.05). The higher the content of PRG-Ca, the lower FS, FM and TP (p < 0.05). W_sp increased linearly with the content of PRG-Ca fillers (p < 0.05). E6 presented the highest W_sl (p < 0.05), while the W_sl of the other composites were not different from each other (p > 0.05).SignificanceIncorporation of 10–40 wt.% of PRG-Ca fillers endowed remineralizing potential to dental composites without jeopardizing the overall behavior of their physicochemical properties. Dental composites with PRG-Ca fillers seems to be a good alternative for reinforcing the enamel against caries development.     

Retention and stress distribution in distal extension removable partial dentures with and without implant association

PurposeThe present study aimed to evaluate the retention and stress distribution of conventional (C) RPD and compare to RPD associated to implant for support (IS) and retention (IR).MethodsFrameworks were cast from cp Ti (n = 18) and Co–Cr alloy (n = 18) by plasma and injected by vacuum–pressure. Conventional RPDs were compared to implant associated RPDs using a distal implant to support (IS) or to support and retain (IR) RPD. The specimens were subjected to insertion/removal cycles simulating 5 years of use and the retention force (N) was measured or evaluated. A mixed linear model was used to analyze the data (α = 0.05). Photoelastic models were qualitatively examined for stress when an occlusal load of 15 kgf was applied over support teeth and RPD.ResultsRetention force of IR RPDs is greater than IS and C RPDs for both cp Ti and Co–Cr alloy specimens. Retention force of cp Ti RPDs increased initially and was maintained throughout 5 years of simulation test while Co–Cr RPDs presented a decrease at the beginning of the test and had their retention force maintained throughout the test. Implant placement at residual alveolar ridge decreased stress around teeth, mainly in the first premolar. Stress concentration in the IS RPD is slightly greater than in the IR RPD.ConclusionThe results suggest that implant placement at the distal extension improves retention and stress distribution of RPDs.     

Clinical outcome of three-unit lithium-disilicate glass–ceramic fixed dental prostheses: Up to 8 years results

ObjectivesThe purpose of this prospective study was to evaluate the clinical outcome of crown-retained fixed dental prostheses (FDPs) made from a lithium-disilicate glass–ceramic (IPS e.max Press, Ivoclar-Vivadent).MethodsThirty-six three-unit FDPs were placed in 28 patients. The FDPs replaced teeth in the anterior (16%) and posterior (84%) regions. All teeth were prepared following a standardized protocol. The size of the proximal connector of the FDPs was 12 mm² (anterior) or 16 mm² (posterior). FDPs were cemented either with glass-ionomer cement (n = 19) or composite resin (n = 17). The following parameters were evaluated at baseline, 6 months after cementation and then annually (at abutment and contralateral teeth): probing pocket depth, plaque index, bleeding on probing, and tooth vitality.ResultsThree FDPs were defined as drop-out. The mean observation period of the remaining 33 FDPs was 86 months (range: 67–98 months): two FDPs in two patients had to be replaced (6%) because of fractures. The 8-year survival rate according to Kaplan–Meier was 93%. In addition, chipping of the veneering material was found in two FDPs (6%). Two abutments (3%) of two restorations had to be treated endodontically; and two FDPs (6%) lost retention and had to be recemented. These complications did not affect the function of the involved restorations clinically. There were no significant differences between the periodontal parameters of the test and control teeth.SignificanceShort-span crown-retained three-unit FDPs made from lithium-disilicate glass–ceramic can be used clinically irrespective of an adhesive or conventional cementation.     

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.     

Long-term nanomechanical properties and gelatinolytic activity of titanium tetrafluoride-treated adhesive dentin interface

ObjectiveThis study investigated the effects of dentin pretreatment with 2.5% titanium tetrafluoride (TiF₄) on nanomechanical properties, and the in situ gelatinolytic activity of the dentin–resin interface, for up to 6 months.MethodsTwenty-four human teeth were prepared by exposing occlusal flat dentin surfaces, and were randomly assigned to experimental groups, according to application or non-application of a TiF₄ pretreatment, and to the adhesive systems (Clearfil SE Bond or Scotchbond Universal). Resin composite (Filtek Supreme Ultra) was built up incrementally on the teeth in all the groups. Then, the specimens were sectioned and randomly selected for evaluation at 24 h, 3 months and 6 months of storage time. The reduced modulus of elasticity (E_r) and the nanohardness of the underlying dentin, as well as the hybrid layer and the adhesive layer were measured using a nanoindenter. Gelatinolytic activity at the dentin–resin interfaces was assessed by in situ zymography using quenched fluorescein-conjugated gelatin at 24 h and 6 months. Statistical analyses were performed with ANOVA and Tukey’s tests.ResultsThere were no differences in E_r and nanohardness values between adhesives systems and pretreatment (p = 0.1250). In situ zymography showed significantly higher gelatinolytic activity after 6 months for all the experimental groups (p = 0.0004), but no differences between the adhesive systems (p = 0.7708) and the surface pretreatment (p = 0.4877). Significance: Dentin pretreatment with 2.5% TiF₄ followed by self-etching adhesive systems did not influence nanomechanical properties or gelatinolytic activity of the adhesive–dentin interface layers, over time.     

Relationship between microtensile bond strength and nanoleakage at the composite–dentin interface

ObjectivesThis study evaluated the relationship between microtensile bond strength (μTBS) and occurrence of nanoleakage at the resin–dentin interface using the same specimens.MethodsResin–dentin-bonded micro-specimens (sticks with a size of 300 μm × 300 μm × 8 mm) were prepared using one of two material combinations (group I: Syntac classic/Tetric Ceram Cavifil: n = 57; group II: Prime & Bond NT/Spectrum TPH: n = 52). After immersion of the micro-specimens in 0.1% rhodamine-B solution for 1 h, nanoleakage was imaged nondestructively using a confocal laser scanning microscope (CLSM). Then the specimens were subjected to a μTBS test.ResultsFor the influence of nanoleakage on μTBS with the Syntac classic/Tetric Ceram Cavifil group, the nonparametric Spearman correlation was 0.033 at p = 0.805. For the Prime & Bond NT/Spectrum TPH group, the nonparametric Spearman correlation was 0.077 at p = 0.584.SignificanceThe degree of nanoleakage had no influence on microtensile bond strength for the Syntac classic/Tetric Ceram Cavifil or for the Prime & Bond NT/Spectrum TPH group.     

Fracture loads of screw-retained implant-supported zirconia prostheses after thermal and mechanical stress

PurposeThe objective of the present study was to evaluate fracture loads of screw-retained implant-supported zirconia prostheses after artificial aging.MethodsFour types of screw-retained implant-supported prostheses were fabricated (n = 11 each); porcelain-veneered zirconia prosthesis (PVZ), indirect composite-veneered zirconia prosthesis (IVZ), porcelain-fused-to-metal prosthesis (PFM), and monolithic zirconia prosthesis (ML). The specimens were subjected to 10,000 thermocycles and cyclic loading for 1.2 million cycles. Fracture loads were measured, and the data were analyzed with the Kruskal–Wallis and Steel–Dwass tests (α = 0.05).ResultsAll specimens survived the artificial aging procedures. The fracture loads for the PVZ (1.52 kN), IVZ (1.62 kN), and PFM groups (1.53 kN) did not significantly differ; however, the fracture load for the ML group (6.61 kN) was significantly higher than those for the other groups. The fracture load for the IVZ group was comparable to those for the PVZ and PFM groups.ConclusionsThe monolithic zirconia prostheses exhibited significantly higher fracture loads than the bilayered prostheses. All the investigated types of screw-retained implant-supported zirconia prostheses appear sufficient to resist posterior masticatory forces during long-term clinical use.     

Craniofacial growth changes and dental attrition in the primary dentition

Presence of pronounced incisal and occlusal wear in primary dentition is fairly common in children. Several factors are implied, however, the possible correlation of craniofacial growth to the occurrence of severe incisal tooth wear in children has not been described to date. Thus, this study was aimed to find any association between the craniofacial growth changes and the occurrence of severe incisal wear in children.Materials and methodsTwenty-seven sets of series of dental casts and corresponding lateral cephalograms are selected from the archive of Pediatric Dentistry, Department of Tokyo Medical and Dental University Hospital. Samples were divided into two groups based on the extent of incisal wear observed on the primary maxillary anterior teeth: slight attrition (N = 13) and severe attrition (n = 14) groups. Lateral cephalograms at early deciduous dentition at T1 (3.5 ± 0.6 years old) and late deciduous dentition at T2 (6.2 ± 0.6 years old) were manually traced and 17 linear and 22 angular measurements were measured with analyzing software (WinCeph ver.9). Annual growth rate for each sample was calculated to determine any significant difference between samples from two groups.ResultsSignificant horizontal growth of the mandible with both the reduction of anterior tooth height and increase of posterior tooth height were found in the severe attrition group. Reduction of upper incisor angle to FH plane and upper dental arch length were also related with the attrition of teeth.ConclusionsThe incisal tooth wear of deciduous teeth was significantly associated with the craniofacial growth changes.     

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.     

The nocturnal use of complete dentures and sleep stability in edentulous elders

ObjectiveTo evaluate the stability of sleep quality and the impact of nocturnal use of complete dentures on sleep quality in an elderly edentulous population over a one-year period.Materials and methodsWritten informed consent was obtained from 172 edentulous elders who agreed to enrol in a longitudinal cohort study. A total of 153 participants completed the follow-up after one year. Perceived quality of sleep and daytime sleepiness were measured using the Pittsburgh Sleep Quality Index (PSQI, score 0–21) and the Epworth Sleepiness Scale (ESS, score 0–24) at baseline (T₀) and at follow-up (T₁). Data on oral health related quality of life, type of mandibular dentures (conventional versus implant-retained mandibular overdenture), nocturnal wear of the dentures and socio-demographic status were obtained by means of the OHIP-20 questionnaire, a clinical examination form and a socio-demographic questionnaire.ResultsNo statistically significant differences were detected in the global PSQI mean scores and EES mean scores from baseline (PSQI 4.77 ± 3.32; EES 5.35 ± 3.72) to the follow-up assessment (PSQ1 5.04 ± 3.50; EES 5.53 ± 4.34). Edentate elders wearing prostheses at night had poorer daytime sleepiness scores than those who removed their prostheses at night (p = 0.003 unadjusted model; p = 0.058 adjusted for age, gender, type of prosthesis and the OHIP-20 total score).ConclusionResults of this study suggest that wearing complete dentures while sleeping has little effect on sleep quality or daytime sleepiness.