Journal of Dentistry - Articles in Press

Ethanol-wet bonding with hydrophobic adhesive may improve root dentine bonding performance - Accepted Manuscript

Dandan Pei, Xueqing Huang, Cui Huang, Yake Wang, Xiaobai Ouyang, Jing Zhang — 2012-02-20

Abstract: Objectives: The current study aimed to assess ethanol-wet dentine surfaces by atomic force microscopy (AFM), and to evaluate the efficacy of ethanol-wet bonding on root dentine by determining the shear bond strength (SBS) and interfacial nanoleakage expression.Methods: Flat dentine slices from human premolar roots were randomly grouped into five. All specimens were acid-etched, rinsed, and left moist. They were then treated with 100% ethanol for 0s (Control group), 20s (Group 1), 60s (Group 2), three 60s periods (Group 3), or stepwise ethanol application (Group 4). After treatment, each group was bonded either with Adper™ Scotchbond™ Multi-Purpose (Scotchbond) or experimental hydrophobic adhesive. Nano-scale adhesion forces (Fad) were probed by AFM and analysed using one-way ANOVA. The SBS results were analysed using two-way ANOVA. Tukey's test was employed for multiple comparisons.Results: Ethanol-wet protocols significantly decreased the value of Fad (p<0.001). When bonded with Scotchbond, ethanol treatment did not affect the bond strength (p>0.05), but decreased the interfacial nanoleakage. The SBS values of the groups bonded with hydrophobic adhesive varied with different ethanol-wet protocols (p<0.05). Decreased nanoleakage was manifested in all experimental groups, except Group 1. Compared with the classical water-wet bonding with Scotchbond in the control group, Group 4 bonded with hydrophobic adhesive exhibited a significantly higher bond strength (p<0.05).Conclusions: Ethanol-wet bonding using a stepwise ethanol application protocol may have potential benefits in the root dentine bonding of hydrophobic adhesive.

Adhesives for the restoration of non-carious cervical lesions: a systematic review - Accepted Manuscript

Brian Chee, Luke Rickman, Julian D. Satterthwaite — 2012-02-20

Abstract: Objectives: To establish whether simplified adhesives (self-etch) are as clinically effective as conventional adhesives (etch-and-rinse) with multiple application steps.Null hypothesis: There is no difference in the clinical effectiveness of the four different bonding strategies: Three-step etch-and-rinse Two-step etch-and-rinse Two-step self-etch One-step self-etchSources: Electronic databases were searched including: Cochrane Oral Health Group Trials Register, The Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE and EMBASE. In addition, studies were identified by handsearching of selected journals.Study selection: Randomised controlled trials (RCTs) comparing at least two adhesives in non-carious cervical lesions (NCCLs), with at least 18 months follow-up were selected. The primary outcome was retention loss, with marginal adaptation and marginal discoloration as secondary outcomes. Criteria for quality assessment included: random sequence generation; allocation concealment; blinding of outcome assessment; and information on withdrawals. Twenty six studies were identified that met the inclusion criteria. In general, studies were not of sufficient quality to fully address the objectives of this review.Conclusion: There is not enough evidence to support one adhesive or bonding strategy over another. Consequently, the null hypothesis of no difference cannot be supported or rejected with the data currently available. There is a need for better standardisation and reporting of randomised controlled trials investigating adhesive performance.Clinical significance: Studies with low overall risk of bias demonstrated good clinical performance for adhesives with all four bonding strategies. However, included studies showed wide variation between adhesives of the same category.

NUMERICAL ANALYSIS OF THE BIOMECHANICAL BEHAVIOR OF A WEAKENED ROOT AFTER ADHESIVE RECONSTRUCTION AND POST-CORE REHABILITATION - Accepted Manuscript

C.M.A. Mattos, E.B. Las Casas, I.G.R. Dutra, H.A. Sousa, S.M.G. Guerra — 2012-02-16

Abstract: Objectives: The purpose of this study was to perform a finite element analysis to determine whether adhesive reconstruction is able to restore the original biomechanical behavior of weakened roots, in terms of fracture resistance, when compared with post/crown-restored teeth with intact roots.Methods: A three-dimensional model of a maxillary central incisor was created. The model simulated an endodontically treated tooth restored with a glass-fiber post, a composite-resin core and a metal crown (Model 1). Based on Model 1, a new volume was created in the root cervical third that represented the area where the dentin structure was lost, resulting in a structurally damaged root (Model 2). A 100N load was applied to the palatal surface at 130° from the long axis of the tooth. After processing (Ansys® 10.0 - Canonsburg, PA, USA), the principal normal stress data were analyzed (S1: tensile; S3: compressive).Results: The models demonstrated a similar S1 distribution concentrated in the lingual cervical region but different S1 levels (Model 1: 28.7MPa, Model 2: 35.3MPa). The S3 distribution indicated differences in behavior between the models (Model 1: -18 to -27MPa along the buccal root surface; Model 2: -25 to -32MPa on the post buccal surface and along the buccal root wall).Conclusions: Although the stress distribution within the root walls remained below the ultimate stress limit of the root dentin, the adhesive reconstruction of the weakened roots did not recover the load resistance of structurally intact roots.Clinical Significance: The decision of when to prosthetically rehabilitate weakened roots with cervical dentin structural tissue loss is a challenge for clinicians. A ‘monoblock’ adhesive reconstruction has been proposed for root reinforcement. During treatment planning, the possibility of restoring the mechanical resistance of the root must be evaluated if successful long-term results are to be achieved.

Long-term protective effect of surface sealants against erosive wear by intrinsic and extrinsic acids - Uncorrected Proof

Florian J. Wegehaupt, Tobias T. Tauböck, Beatrice Sener, Thomas Attin — 2012-02-13

Abstract: Objective: To test sealants to prevent erosive tooth wear caused by extrinsic and intrinsic acids under long-term exposition.Methods: 144 bovine enamel samples were randomly allocated to twelve groups (1–12). Samples of groups 1, 5 and 9 remained unsealed (positive controls), 2, 6 and 10 were sealed with Silicon Seal Nano Mix and 3, 7 and 11 with Seal&Protect. Groups 4, 8 and 12 were sealed with flowable composite (negative controls).Groups 1–4 were immersed in artificial saliva, 5–8 in hydrochloric acid and groups 9–12 in citric acid for 28 days, respectively. After 1, 2, 4, 7, 11, 14, 21 and 28 days, solutions were renewed and enamel wear was quantified by assignation of 32P in the solutions.Results: In all immersion solutions, lowest mineral loss was observed for the negative controls whilst highest loss was observed for unsealed positive controls.In artificial saliva and citric acid, the loss from samples sealed with Seal&Protect was not significantly different compared with negative controls whilst loss in groups sealed with Silicon Seal Nano Mix was significantly higher.In hydrochloric acid, loss from samples sealed with Seal&Protect was not different compared with that of negative controls up to 4 days. Except day 1, the mineral loss in the Seal&Protect group was significantly lower compared with that of the Silicon Seal Nano Mix group.Conclusion: The tested resin based surface sealant is able to significantly reduce the erosive demineralisation of enamel caused by hydrochloric and citric acid even under long-term exposition.

Effects of structural orientation of enamel and dentine on light attenuation and local refractive index: An optical coherence tomography study - Uncorrected Proof

Ilnaz Hariri, Alireza Sadr, Yasushi Shimada, Junji Tagami, Yasunori Sumi — 2012-02-10

Abstract: Objectives: To investigate optical properties of human enamel and dentine in relationship to structural orientation of enamel prisms and dentinal tubules by optical coherence tomography (OCT).Methods: Discs of 300–400μm thickness including enamel with cross-cut or long-cut prisms and mid-coronal dentine with cross-cut, long-cut or oblique-cut tubules were obtained from 28 non-carious freshly extracted human third molars sectioned at different directions. Each disc was placed over a metal plate and B-scan images were obtained by a swept-source OCT at 1330nm centre wavelength (Dental SS-OCT Prototype 1, Panasonic Healthcare Co., Ltd, Japan). Refractive index (n) calculated from optical path length and real thickness, and OCT signal slope (OCTSS) in relation to structural orientation were statistically compared among groups (α=0.05). The discs were sectioned and observed under SEM to confirm prism or tubule orientations.Results: No significant differences were found in n and OCTSS among cross-cut and long-cut enamel groups (p>0.05). However, in dentine, there was a significant difference in both variables among different regions. In cross-cut tubule orientation, the average n and OCTSS values were significantly lower compared to other two groups (long-cut and oblique-cut) (p<0.05). There was a significant difference in both variables between enamel and dentine (p<0.05).Conclusions: Unlike enamel, refractive index and OCT signal patterns in dentine vary according to structural orientation, with dentine tubules playing the role. Attenuation of OCT signal intensity was small in enamel. The findings may contribute to a better understanding of the interactions of light with the dental tissue.Clinical significance: Precise records of refractive indices and OCT signal patterns may be important for clinical diagnosis of caries and measurement of structural depth for operative purposes using this technology. Effects of dentine structural orientation on refractive index and scattering pattern must be considered when observing human teeth by OCT cross-sectional imaging.”

Restorative material and other tooth-specific variables associated with the decision to repair or replace defective restorations: Findings from The Dental PBRN - Uncorrected Proof

2012-02-10

Abstract: Objectives: Using data from dentists participating in The Dental Practice-Based Research Network (DPBRN), the study had 2 main objectives: (1) to identify and quantify the types of restorative materials in the existing failed restorations; and (2) to identify and quantify the materials used to repair or replace those failed restorations.Methods: This cross-sectional study used a consecutive patient/restoration recruitment design. Practitioner-investigators recorded data on consecutive restorations in permanent teeth that needed repair or replacement. Data included the primary reason for repair or replacement, tooth surface(s) involved, restorative materials used, and patient demographics.Results: Data for 9875 restorations were collected from 7502 patients in 197 practices for which 75% of restorations were replaced and 25% repaired. Most of the restorations that were either repaired or replaced were amalgam (56%) for which most (56%) of the material used was direct tooth-coloured. The restorative material was 5 times more likely to be changed when the original restoration was amalgam (OR=5.2, p<.001). The likelihood of changing an amalgam restoration differed as a function of the tooth type (OR=3.0, p<.001), arch (OR=6.6, p<.001); and number of surfaces in the original restoration (OR=12.2, p<.001).Conclusion: The probability of changing from amalgam to another restorative material differed with several characteristics of the original restoration. The change was most likely to take place when (1) the treatment was a replacement; (2) the tooth was not a molar; (3) the tooth was in the maxillary arch; and (4) the original restoration involved a single surface.

An ex vivo culture model for orthodontically induced root resorption - Uncorrected Proof

W.N. Wan Hassan, P.A. Stephenson, R.J. Waddington, A.J. Sloan — 2012-02-10

Abstract: Objectives: Root resorption is a ubiquitous although undesirable sequela to orthodontic treatment. Current methods to investigate the pathophysiology have certain limitations. In pursuit to understand and develop treatment modalities for orthodontically induced root resorption, the ability to manipulate cells within their natural extracellular matrix in a three dimensional organotypic model is invaluable. The study aimed to develop a laboratory-based organotypic model to investigate the effect of orthodontic forces on the periodontium.Methods: Mandibular slices of male Wistar rats were maintained in Trowel-typed cultures at 37°C in 5% carbon dioxide in air for 7days with test specimens subjected to compressive forces at 50g and 100g by stainless steel springs. Tissue architecture and cell viability were maintained under culture conditions.Results: Osteoclast numbers increased significantly in both test groups whilst odontoclasts increased in the 50g group. Immunohistochemistry demonstrated increased dentine sialoprotein expression in both test groups, suggesting changes in mineralization-related activity due to mechanical strain.Conclusion: The study showed initial cellular and molecular changes of key markers that relate to root resorption in response to mechanical loading.Clinical significance: Severe root resorption may occur when forces applied are heavy or transmitted over an extended period and could lead to mobility and tooth loss. This ex vivo model can be used to investigate cellular and molecular processes during orthodontic tooth movement which may advance the clinical management of root resorption.

Effects of multiple firings on the mechanical properties and microstructure of veneering ceramics for zirconia frameworks - Corrected Proof

2012-02-06

Abstract: Objectives: The purpose of this study is to evaluate the effects of multiple firings on the mechanical properties and microstructure of veneering ceramics used with zirconia frameworks.Methods: Five different veneering ceramics for zirconia frameworks were used: Vintage ZR (ZR), Cerabien ZR (CZR), Vita VM9 (VM9), Cercon ceram KISS (KISS), IPS e.max ceram (e.max), and one veneering ceramic used for PFM frameworks: Vintage MP (MP). Twenty specimens were fabricated of each veneering ceramic. Ten specimens were fired twice and another ten specimens were fired ten times. Three-point flexural strength following the ISO 6872 and Vickers hardness were measured, and fracture toughness (KIC) was calculated. Density and porosity were determined. Specimens were characterized using X-ray diffraction (XRD) and scanning electron microscopy (SEM).Results: For all materials, density increased and porosity decreased after 10 firings. Significant differences in density and porosity were observed between 2 and 10 firings, with the exception of VM9 (P<0.05). There were no significant differences in flexural strength between 2 and 10 firings except for MP. The Vickers hardness of ZR, VM9, KISS and MP increased significantly after 10 firings (P<0.001). There were no significant differences in fracture toughness for ZR, CZR, VM9 and MP between 2 and 10 firings. However, e.max underwent a significant increase in fracture toughness (P=0.000), and there was a significant decrease in the toughness of KISS after 10 firings (P=0.007).Conclusion: Multiple firings could be effective for improving the densification and the hardness of veneering ceramics for zirconia restorations.Clinical significance: By 10 firings, the density and hardness of the veneering ceramics used with zirconia frameworks were raised, and porosity was reduced. However, no significant changes occurred in flexural strength, fracture toughness or microstructure.

Genetic variation in MMP20 contributes to higher caries experience - Uncorrected Proof

2012-02-06

Abstract: Matrix metalloproteinases play an important role during the initial process of enamel development and therefore may play a role in caries.Objectives: To evaluate the association between MMP20 and caries experience in Brazilian children.Methods: Eligible unrelated children with or without caries were evaluated using a cohort design. Demographic data and oral health habits were obtained though a questionnaire. Caries data was collected by clinical examination. Genotyping of the selected polymorphism was carried out by real-time PCR from genomic DNA. Allele and genotype frequencies were compared between groups with distinct caries experience and oral health habits.Results: Of 388 subjects, 161 were caries free children. There were no differences between caries levels and genotype distribution in the total cohort. When ethnic background was considered, differences in genotype distribution were observed in caries free children vs. children with caries in Caucasians (p=0.03). Differences could also be seen when poor oral hygiene was used to stratify the analysis (p=0.02). Regression analysis, adjusted for genotype and ethnicity, confirmed that ingestion of sweets between meals increases the risk of presenting carious lesions (p=0.00001; OR=2.33; 95%CI 1.53–3.54).Conclusion: Variation in MMP20 may be associated with caries experience mainly in Caucasian subjects with poor oral health habits.

Patients’ perspective on dental aesthetics in a South-eastern European community - Uncorrected Proof

2012-02-06

Abstract: Objectives: To assess the importance attributed to dental aesthetics by subjects from a Romanian community. In addition, the role played by dental colour, the group-distributions based on the self-evaluation of dental colour and the previous experience regarding whitening treatments are analysed.Methods: A multiple-choice questionnaire was administered to 540 patients in dental offices in Cluj-Napoca, Romania; the subjects were also asked to self-evaluate their dental shade, using a set of images as a comparison. Answers to the questionnaires were statistically analysed using Microsoft Excel and SPSS 13.00 (Pearson's chi-square test, Fisher's exact test, Kendall's tau b).Results: From the participants, 18.3% were motivated by aesthetic reasons to ask for treatment; most of the patients evaluated their smile as “acceptable” (38.51%) or “having some defects” (29.44%) and were self-included in groups of medium and dark shades (33.7% and 33.89%, respectively). Whilst 22.40% of the subjects considered the dental colour as being the most evident defect of their dentition, 39.07% indicated a self-perception of “an abnormal dental shade”. A strong correlation between darker self-assessed tooth colour-groups and the self-perception of an abnormal tooth colour was found (Chi square p≪0.001, Kendall's tau-c=0.44, with p≪0.001). Previous whitening treatments were reported by 8.88% of the subjects.Conclusions: Among patients who wanted to improve one of their oral functions, the majority requested changes in aesthetics. Dental shade is one of the aspects recognized as problematic by the participants, but nonetheless the percentage of patients who had previously benefited by whitening treatments was moderate.

Opalescence of bleached teeth - Corrected Proof

Max Schmeling, Hamilton Pires Maia, Luiz Narciso Baratieri — 2012-02-03

Abstract: Objectives: To evaluate the influence of tooth bleaching on the opalescence properties of enamel.Methods: Colour of 38 specimens was determined by colorimetric analysis before and after bleaching in the reflectance and transmittance modes. The results were described as CIELab colour coordinates. The Opalescent Parameter (OP) was calculated as the difference in yellow–blue colour coordinate (CIE Δb*) and red–green colour coordinate (CIE Δa*) between the reflected and transmitted colours.Results: Mean OP value of the specimens was 18.9 (±1.6) before bleaching and 16.1 (±1.0) after bleaching.Conclusions: Bleaching decreases the OP of the specimens (p>0.001). OP decrease was correlated with differences in b* colour coordinate in the transmittance mode.

Effect of cariogenic biofilm challenge on the surface hardness of direct restorative materials in situ - Corrected Proof

2012-02-03

Abstract: Objectives: The presence of cariogenic biofilm could result in surface degradation of composite and ionomeric restorative materials. Thus, this study evaluated in situ the alterations in the surface microhardness of these materials under biofilm accumulation and cariogenic challenge.Methods: In a split-mouth, double-blind, cross-over study, 10 volunteers wore palatal intra-oral devices containing bovine enamel slabs restored with composite resin (CR – Z250) or resin-modified glass ionomer (RMGI – Vitremer). Two phases of 14days were carried out, one for each restorative material. In one side of the device, biofilm was allowed to accumulate under a plastic mesh, whereas in the opposing side, regular brushing was carried out 3 times/day with a dentifrice containing 1100μg F/g as NaF. A 20% sucrose solution was applied extra-orally 10×/day on each restored dental slab. Knoop microhardness was used to calculate the percentage of surface hardness loss (%SHL).Results: All materials showed a decrease in surface hardness after the in situ period. The restorative materials presented the following average for %SHL: RMGI without biofilm accumulation=8.9 and with biofilm accumulation=25.6, CR without biofilm accumulation=14.7 and with biofilm accumulation=17.0.Conclusion: Biofilm accumulation and the presence of cariogenic challenge promoted faster degradation of ionomeric materials, but this was not observed for composite resin.Clinical significance: The oral environment affects the surface hardness of aesthetic restorative materials. Biofilm accumulation and cariogenic challenge promote surface degradation for ionomeric materials, but not for composite resin.

Gingival crevicular fluid levels of osteoprotegerin (OPG) in premenopausal and postmenopausal women with or without chronic periodontitis - Corrected Proof

2012-02-03

Abstract: Objectives: Systemic conditions may affect host susceptibility, disease progression and severity as well as treatment response. Previously, low oestrogen (E2) levels were associated with increased bone resorption, due to increased osteoclastogenesis and decreased osteoclast apoptosis. Osteoprotegerin (OPG) is an essential cytokine for osteoclastogenesis. The aim of this study was to evaluate gingival crevicular fluid (GCF) OPG levels in menopausal and premenopausal patients with or without periodontitis, and effects of phase I periodontal therapy on GCF OPG levels.Methods: Forty-four systemically healthy premenopausal and menopausal patients were recruited and divided into subgroups of periodontitis and control. Bone mineral density (BMD) and serum E2 levels were measured. Before and after phase I periodontal therapy clinical indices, including clinical attachment levels (CAL) were recorded, and GCF samples were collected. GCF OPG levels were detected by enzyme-linked immunosorbent assay. Repeated measurement ANOVA and Spearman correlation tests were used.Results: All clinical indices improved significantly after treatment(p<0.001), except Pre-M/C groups CAL reduction(p>0.05). Periodontitis groups’ OPG levels were lower than gingivitis groups(p>0.05). Following periodontal phase I therapy, GCF OPG levels increased markedly in all groups, however this alteration was found statistically insignificant (p>0.05).Conclusions: The current data revealed that GCF OPG levels were lower in periodontitis patients and phase I therapy resulted with increased GCF OPG levels, however those alterations were statistically insignificant. In addition, present data suggested that menopause do not seem to have a significant effect on periodontal status or response to phase I treatment, within the limits of this study.

Association between periodontitis and systemic bone mineral density in Japanese community-dwelling postmenopausal women - Corrected Proof

Osamu Takahashi, Akihiro Yoshihara, Kazutoshi Nakamura, Hideo Miyazaki — 2012-01-30

Abstract: Objective: The purpose of this cross-sectional study was to evaluate the association between loss of attachment (LA) which is clinical index of periodontitis and bone mineral density (BMD) of the lumbar vertebrae and femur measured with dual energy X-ray absorptiometry (DXA) in Japanese community-dwelling postmenopausal women.Subjects and methods: Subjects were 347 women aged 55–74. The oral cavity was divided into 6 areas according to the WHO's method for the determination of the clinical attachment level score (CALscore); the LA was measured at 6 sites using a WHO probe in 17, 16, 11, 26, 27, 37, 36, 31, 46, and 47, and the values were recorded in mm. Then, we assessed BMD of the lumbar vertebrae (L2–L4) and femur (femoral neck, proximal part) by DXA. Based on these data, analysis of covariance was used to estimate relation between periodontitis and systemic BMD status excluding effect of age. Multiple linear regression analysis was used to estimate relation between periodontitis and BMD adjusted for 17 variables.Results: Significant differences were observed in the mean value between the mean CALscore=0 and CALscore≥1 groups in the Z value in lumbar vertebrate (106.9±18.7 vs. 102.3±1.0, p<0.05, t-test). Multiple regression analysis was conducted using the mean LA as dependent variable. Lumbar vertebral BMD (regression coefficient: B=−1.039±0.379, p=0.007), femoral neck BMD (B=−1.332±0.627, p=0.034), and proximal femoral BMD (B=−1.329±0.536, p=0.014) all exhibited a significant negative correlation with the mean LA.Conclusion: A significant negative correlation was observed between periodontal disease and truncal bone BMD in this study.

In vivo monitoring of the bone healing process around different titanium alloy implant surfaces placed into fresh extraction sockets - Corrected Proof

2012-01-30

Abstract: Objectives: Increasing surface roughness and coating with tricalcium phosphate of titanium and titanium alloy implants has been proposed to provide better rates of osseointegration. However, how these changes in surface topography and chemistry influence the osseointegration process of immediate implants placed in fresh extraction sockets is unclear. This study investigated the influence of three clinically employed implant surfaces on the early bone healing events in vivo.Methods: Machined smooth implants were milled from grade 5 Ti6Al4V titanium. Surfaces were moderately roughened by grit blasting, which were then coated with tricalcium phosphate. Implants were placed into freshly extracted incisor sockets of mandibles of normal Wistar rats and left for 1, 3 and 9 weeks. Healing bone tissue around the implants was examined by histochemistry and immunocytochemistry to localise PCNA proliferative cells, and osteoblast differentiation markers osteopontin and osteocalcin. Positive synthesising cells were counted using image analysis.Results: Histology indicated no differences in the amount or pattern of bone formation within the healing tissue surrounding the different implant surfaces. Bone healing occurred predominantly on exposed bone surfaces (distance osteogenesis) and not on the implant surface (contact osteogenesis). No differences were observed in the number or timing of PCNA, osteopontin and osteocalcin positive cells within the bone healing tissue around each of the implant analysed.Conclusion: For immediately placed implants, the surface modifications investigated appeared to have little influence on the activity of bone forming cells surrounding the implant, probably due to the high level of distance osteogenesis seen within this scenario.Clinical significance: For immediate placement of implants into fresh extraction sockets, titanium implants with roughened surfaces and coating with tricalcium phosphate have negligible influence in accelerating the early bone healing events of osseointegration.

Bond strengths, degree of conversion of the cement and molecular structure of the adhesive–dentine joint in fibre post restorations - Corrected Proof

2012-01-27

Abstract: Objectives: Because fibre post restorations are influenced by multiple factors such as the types of bonding materials, the dentine region and the time under moist exposure, this study sought to determine the bond strength of endodontic restorations and its relation to the degree of conversion of the cement layer and the molecular structure of the dentine-bonded joints.Methods: The performance of 2 etch-and-rinse (All-Bond 2 and One-Step Plus) and 2 self-etch (Clearfil SE Bond and Xeno III) adhesives at post spaces regions, after 7d or 4m, was evaluated. FRC Postec Plus posts were cemented to the root canal with a dual-cure resin cement (Duo-Link). Transverse sections of the tooth were subjected to push-out testing, to degree-of-conversion measurements and to hybrid layer evaluation through μ-Raman spectroscopy.Results: Coronal bonding was higher than cervical and middle bonding. The hybrid layer was thicker for the etch-and-rinse systems, with thicknesses decreasing towards the middle region. The degree of conversion measured for the 3-step etch-and-rinse group after 4m was significantly higher than that for the self-etching groups.Conclusions: Although not totally stable at the adhesive–dentine interface, the 3-step etch-and-rinse adhesive in the coronal dentine provided the best bond strength, degree of conversion of the cement and hybrid layer thickness in post restorations, in both short- and long-term analyses.

Evaluation of self shade matching ability of dental students using visual and instrumental means - Corrected Proof

Samar AlSaleh, Manal Labban, Morouj AlHariri, Esam Tashkandi — 2012-01-27

Abstract: Objectives: The purpose of this study was to evaluate the ability of dental students to match the shade of their own teeth.Methods: Fifty female dental students in the College of Dentistry at King Saud University, who had not received any formal dental training in colour science or shade matching procedures, were screened for colour deficiencies and selected to participate in the study. Each subject and three clinicians selected independently the closest match for the subjects’ own right or left sound maxillary central incisors under controlled viewing conditions, using VITA classical shade guide (VITA Zahnfabrik GmbH, Bad Säckingen, Germany). Each examined central incisor and the 16 samples of VITA classical shade guide were measured with the VITA Easy Shade (VES) spectrophotometer to determine the CIELAB colour parameters. The colour differences (ΔE) between each examined tooth and the 16 samples of the shade guide were calculated. The minimum ΔE values were compared to ΔE values of the shade obtained by VES, subjects and clinicians.Results: The results showed a significant difference in the accuracy of shade selection between the instrumental and visual means. ΔE value of shade selected by clinicians was significantly lower than those selected by the subjects.Conclusions: It was concluded that, spectrophotometric shade analysis was more accurate compared to human shade assessment.Clinical significance: A reliable self-perception of the subjects’ own tooth colour, may aid in the shade matching procedures. It might lead to increased patients’ satisfaction at the finalization of the restorative procedures.

Post retentive ability of a new resin composite with low stress behaviour - Corrected Proof

2012-01-25

Abstract: Objectives: To assess by means of push-out test the post retentive potential of a new flowable resin composite with low polymerization stress.Methods: SureFil® SDR™ (Dentsply, S) was compared with the resin cement Calibra (Dentsply, C). S and C were used in combination with the adhesive XP Bond (Dentsply, XPB). In C group the Self-Cure Activator was mixed with XPB. The following types of fibre posts were luted into 30 extracted premolars: Radix Fiber Post (Dentsply, R), DT Light Post (RTD, LP), ER Dentin Post (Komet, ER), DT Light SL (VDW, SL), FibreKleer (Jeneric Pentron, F). Six posted roots per group were tested. Each root provided three to five 1mm-thick slices. Measured push-out strengths were differentiated by post space level and statistically analysed (p<0.05). The failure mode of each debonded specimen was assessed.Results: Cement type did not have a significant effect on post retention (p=0.54). Post type was a significant factor for push-out strength (p<0.001). LP exhibited significantly higher retentive strength than SL and F; push-out strengths of ER and R were significantly higher than those of F. Post retention was significantly influenced by post space level (p<0.001). Significantly higher push-out strengths were recorded at the coronal third than at the middle and apical levels. The post–cement interaction was significant (p=0.002). Posts luted with S most often failed at the cement–post interface.Conclusions: When the new flowable low-stress composite was used to lute fibre posts, similar retentive strengths to those of a marketed cement from the same manufacturer were achieved.Clinical significance: SureFil® SDR™, a flowable composite originally proposed for bulk filling of posterior restorations, exhibited post retentive strengths similar to those of a cement by the same manufacturer. With a relatively high filler load, yet a low curing stress, SureFil® SDR™ may be adequate for both post cementation and core build-up.

Chlorhexidine delivery system from titanium/polybenzyl acrylate coating: Evaluation of cytotoxicity and early bacterial adhesion - Corrected Proof

2012-01-25

Abstract: Objectives: The formation of biofilms on titanium dental implants is one of the main causes of failure of these devices. Streptococci are considered early colonizers that alter local environment favouring growing conditions for other colonizers. Chlorhexidine (CHX) is so far the most effective antimicrobial treatment against a wide variety of Gram-positive and Gram-negative organisms as well as fungi. This study was designed to develop a CHX delivery system appropriate for healing caps and abutments, with suitable drug release rate, effective as antimicrobial agent, and free of cytotoxic effects.Methods: Polybenzyl acrylate (PBA) coatings with and without CHX (Ti/PBA and Ti/PBA-CHX, respectively) and different drug loads (0.35, 0.70, and 1.40%, w/w) were assayed. The cytotoxic effect of CHX released from the different substrates on UMR106 cells was tested by alkaline phosphatase specific activity (ALP), and microscopic evaluation of the cells. Non-cytotoxic drug load (0.35%, w/w) was selected to evaluate the antimicrobial effectiveness of the system using a microbial consortium of Streptococcus species.Results: The kinetic profile of CHX delivered by Ti/PBA-CHX showed an initial fast release rate followed by a monotonic increase of delivered mass over 48h. The number of attached bacteria decreased in the following order: Ti>Ti/PBA>Ti/PBA-0.35.Conclusions: PBA-0.35 coating is effective to inhibit the adhesion of early colonizers on Ti without any cytotoxic effect on UMR-106 cells.

Effect of fibre post length and adhesive strategy on fracture resistance of endodontically treated teeth after fatigue loading - Corrected Proof

F. Zicari, B. Van Meerbeek, R. Scotti, I. Naert — 2012-01-19

Abstract: Objectives: To evaluate the effect of the length of fibre-posts and type of adhesive cement on the fracture resistance of endodontically treated teeth, after fatigue loading.Methods: Eighty extracted upper pre-molars were sectioned at the CEJ and endodontically treated. After 24h of water storage at 37°C, RelyX Posts (3M-ESPE) were cemented with Panavia F 2.0 (Kuraray) or RelyX Unicem (3M-ESPE). A standardized composite core was built. Specimens were divided into four groups depending on the post–core ratio: (A) 2/1 (control); (B) 3/2; (C) 1/1 (small diameter); (D) 1/1(large diameter) and submitted to 1,200,000 cycles using a chewing simulator (Willytech). Immediately afterwards, all specimens that survived fatigue loading were fractured using a universal loading device (Micro-tester, Instron). Data were analysed with ANOVA.Results: Four percent of the specimens failed during fatigue loading. The length of the post into the root affected the fracture resistance. The statistical outcome varied according to the inclusion of specimens failed during fatigue loading. However, the control group always had the lowest fracture resistance. The type of adhesive cement did not affect the fracture resistance. A prevalence of not-repairable failures was observed in specimens restored with the longest posts, whilst shorter posts led to more repairable failures.Conclusions: Shortening the post length and the ensuing preservation of more tooth structure, offer the potential for reparability through an in-built fail safe mechanism and may thus reduce the occurrence of catastrophic failures.

Bonding of low-shrinking composites in high C-factor cavities - Corrected Proof

A. Van Ende, A. Mine, J. De Munck, A. Poitevin, B. Van Meerbeek — 2012-01-18

Abstract: Objectives: Polymerization shrinkage causes stress at the tooth-restoration interface. The magnitude of the stress depends upon several factors, such as the configuration factor (C-factor) of the cavity, the polymerization–conversion rate and filling technique. The aim of this study was to investigate the effect of curing time and filling method when high C-factor cavities were filled with low-shrinking composites.Methods: Three low-shrinking (Filtek Silorane, 3M ESPE: FS; N’Durance, Septodont: N’D; Kalore, GC: Ka) and one conventional composite (Z100, 3M ESPE) were bonded into standardized occlusal Class-I cavities using either a two-step self-etch adhesive (Silorane System Adhesive, 3M ESPE: SSA) or a one-step self-etch adhesive (G-Bond, GC: GB). Five experimental groups were formed according to the employed adhesive/composite combination (SSA/FS, SSA/Z100, GB/N’D, GB/Ka, GB/Z100), and further divided into three subgroups conforming to curing time and filling technique (20s/bulk; 80s/bulk; 80s/layered). For each subgroup, non-trimmed 1mm×1mm sticks were prepared from five teeth to measure the micro-tensile bond strength (μTBS) to cavity-bottom dentine.Results: The two-step self-etch adhesive SSA generated higher bond strengths than the one-step self-etch adhesive GB, irrespective of the filling method. When GB was used, bulk filling with a low-shrinking composite revealed the highest bond strengths. For all composites, the layering method provided the highest bond strengths.Significance: The two-step self-etch adhesive Silorane System Adhesive (3M ESPE) performed better than the one-step self-etch adhesive G-Bond (GC), regardless of the composite used. When the latter all-in-one adhesive was used, effects of shrinkage stress became more apparent.

Titanium surface topography after brushing with fluoride and fluoride-free toothpaste simulating 10 years of use - Corrected Proof

2012-01-13

Abstract: Objectives: To conduct a controlled study contrasting titanium surface topography after procedures that simulated 10 years of brushing using toothpastes with or without fluoride.Methods: Commercially pure titanium (cp Ti) and Ti–6Al–4V disks (6mm Ø×4mm) were mirror-polished and treated according to 6 groups (n=6) as a function of immersion (I) or brushing (B) using deionised water (W), fluoride-free toothpaste (T) and fluoride toothpaste (FT). Surface topography was evaluated at baseline (pretreatment) and post-treatment, using atomic force microscope in order to obtain three-dimensional images and mean roughness. Specimens submitted to immersion were submerged in the vehicles without brushing. For brushed specimens, procedures were conducted using a linear brushing machine with a soft-bristled toothbrush. Immersion and brushing were performed for 244h. IFT and BFT samples were analysed under scanning electron microscope with Energy-Dispersive X-ray Spectroscopy (EDS). Pre and post-treatment values were compared using the paired Student T-test (α=.05). Intergroup comparisons were conducted using one-way ANOVA with Tukey post-test (α=.05).Results: cp Ti mean roughness (in nanometers) comparing pre and post-treatment were: IW, 2.29±0.55/2.33±0.17; IT, 2.24±0.46/2.02±0.38; IFT, 2.22±0.53/1.95±0.36; BW, 2.22±0.42/3.76±0.45; BT, 2.27±0.55/16.05±3.25; BFT, 2.27±0.51/22.39±5.07. Mean roughness (in nanometers) measured in Ti–6Al–4V disks (pre/post-treatment) were: IW, 1.79±0.25/2.01±0.25; IT, 1.61±0.13/1.74±0.19; IFT, 1.92±0.39/2.29±0.51; BW, 2.00±0.71/2.05±0.43; BT, 2.37±0.86/11.17±2.29; BFT, 1.83±0.50/15.73±1.78. No significant differences were seen after immersions (p>.05). Brushing increased the roughness of cp Ti and of Ti–6Al–4V (p<.01); cp Ti had topographic changes after BW, BT and BFT treatments whilst Ti–6Al–4V was significantly different only after BT and BTF. EDS has not detected fluoride or sodium ions on metal surfaces.Conclusions: Exposure to toothpastes (immersion) does not affect titanium per se; their use during brushing affects titanium topography and roughness. The associated effects of toothpaste abrasives and fluorides seem to increase roughness on titanium brushed surfaces.

The effect of ferrule on the fracture mode of endodontically treated canines restored with fibre posts and metal-ceramic or all-ceramic crowns - Corrected Proof

2012-01-13

Abstract: Objectives: The aim of this study was to evaluate the fracture mode of endodontically treated canines (ETC) restored with glass-fibre posts (GFP) and either metal-ceramic (MC) or all-ceramic (AC) crowns, in the presence or absence of 2mm ferrule height.Methods: Fifty recently extracted human maxillary canines were endodontically treated and randomly divided into 5 groups of 10 specimens each. Four groups (with or without ferrule) were restored with GFP, composite cores and either MC or AC crowns. The fifth group with intact ETC served as control. Teeth were loaded to fracture at a 135° angle to their long axis, at a cross-head speed 0.5mm/min. The fracture modes were divided through optical microscopy to repairable and irreparable. Statistical analysis was performed by means of the Fisher's Exact test.Results: All groups presented brittle fracture following bending deformation. Irreparable root fractures were the primary fracture mode independently of ferrule. The percentages (%) of repairable fractures were not statistically significant different amongst the MC and AC restored teeth independently of ferrule. However the 2mm ferrule was associated to a higher percentage of repairable fractures, especially in teeth restored with AC crowns.Conclusions: The percentage (%) of repairable fractures was higher in all-ceramic compared to metal-ceramic ETC and in restorations with ferrule, although the differences were not statistically significant.Clinical significance: This in vitro study supports evidence that neither the type of crown restoration nor the presence of ferrule affects statistically significantly the mode of fracture of ETC restored with GFP.

Intrinsic and extrinsic discolouration of dimethacrylate and silorane based composites - Corrected Proof

Çağatay Barutcigil, Mehmet Yıldız — 2012-01-06

Abstract: Objective: The purpose of this study was to evaluate the intrinsic and extrinsic colour change of dimethacrylate and silorane-based composites.Materials and methods: Five contemporary composites were included within the study (Filtek LS Low Shrink Posterior Restorative [SIL], Filtek SupremeXT [SPR], Filtek Z250 [Z25], Filtek P60 [P60], and Admira [ADM]). Twenty-five specimens (8-mm diameter, 1.5-mm thickness) were prepared for each composite. After baseline colour measurements were taken, specimens were immersed in 4 staining solutions (red wine, coffee, cola, and tea) or distilled water (n=5). After a 24-h and 1-month immersion, the colour values of each specimen were remeasured and the colour change values () were calculated. Statistical analyses were evaluated by one-way ANOVA and Tukey HSD test.Results: Amongst the solutions, red wine had the highest value in all the composite restoratives. After the final measurement, ADM exhibited the lowest discolouration, whereas SPR exhibited the highest colour change. Additionally, the colour change for SIL after 1 month in distilled water was higher than the clinically accepted cut-off of 3.3. This change was correlated with an increasing L value according to the multiple regression analysis.Conclusion: All of the restorative materials used in this study were susceptible to staining by commonly consumed beverages drinks, especially red wine and coffee; however, in water, only SIL became whiter with time.

Improved bonding of zirconia substructures to resin using a “glaze-on” technique - Corrected Proof

Peter Everson, Owen Addison, William M. Palin, F.J. Trevor Burke — 2011-12-23

Abstract: Objective: To investigate the influence of applying thin intermediary coatings of acid-etchable glasses on the shear bond strength between a methacrylate resin based cement and an yttria-stabilized zirconia dental ceramic substrate.Methods: The upper and lower surfaces of 110 sintered yttria-stabilised tetragonal zirconia polycrystalline disc-shaped specimens were polished using sequential grades of Silicon Carbide, then air-abraded with 25μm diameter alumina particles. Specimens were randomly allocated to 11 groups (A–K) (n=10), group A acting as control. The upper surface of Group A specimens was subjected to a tribochemical coating regime (CoJet, 3M ESPE). Five glazing ceramics were applied and fired according to the manufacturer's recommended firing regime. The glaze was etched with 10% HF acid and all specimens coated with a silane primer. Two differing storage regimes were employed (wet storage vs thermocycling). Shear bond strength testing specimens were created by cementing resin-based composite cylinders to the centre of the prepared ceramic surface using Rely-X Unicem (3M ESPE) resin based cement. Shear bond strength testing was performed and load at failure recorded.Results: A factorial analysis of variance at a 95% significance level demonstrated that all glazing techniques resulted in a significant increase in the shear bond strength compared with using the resin based cement alone (P<0.01), with the different glazing ceramics resulting in significant differences in mean shear bond strength (P=0.008). The differences were a function of the storage state (wet storage vs thermocycling (P=0.013)).Conclusion: The glazing techniques used in the current investigation resulted in a significantly enhanced shear bond stress to the resin based cement when compared with the current ‘gold standard’ – tribochemical coating.

Effects of primer containing silane and thiophosphate monomers on bonding resin to a leucite-reinforced ceramic - Corrected Proof

Yohsuke Taira, Miyuki Sakai, Takashi Sawase — 2011-12-12

Abstract: Objectives: Silane primers are commonly used for bonding between resin-based luting agents and ceramic restorations. The purpose of the present study was to evaluate the effects of nine silane primers on the bond strength of resin to a leucite-reinforced ceramic.Methods: The commercially available dental primers used were five silane primers (GC Ceramic Primer, GP; Clearfil Ceramic Primer, CP; Tokuso Ceramic Primer, TP; Porcelain Liner M, PM; and Monobond Plus, MB). Four experimental primers (MDS, MTS, MDS/MPII, and MTS/MPII) and two control primers (MMA and MMA/MPII) were also prepared. The ceramic specimen was ground with silicon carbide paper, primed, and then bonded to a resin composite disc using a dual-curing luting agent. After a 24-h immersion in water, the shear bond strengths were determined.Results: Shear bond testing revealed that the bond strength was significantly improved with the use of a MTS/MPII primer when compared to MDS, MTS, MMA, MDS/MPII and MMA/MPII. Although no significant differences were detected between GP, CP, PM, and MB, the primers CP, TP, PM, and MTS/MPII exhibited the highest bond strengths, followed by GP and MB, whilst the no-primer control resulted in the lowest values.Conclusion: The maximum bond strengths were obtained with CP, TP, PM, and MTS/MPII. It was suggested that the thiophosphate monomer accelerated the role of the silane monomer. When selecting a primer to bond ceramic restorations, clinicians should be aware that not only the silane monomer but also additional components of the primer considerably affect the bond strength.

Clinical fitting of CAD/CAM zirconia single crowns generated from digital intraoral impressions based on active wavefront sampling - Uncorrected Proof

Roberto Scotti, Paolo Cardelli, Paolo Baldissara, Carlo Monaco — 2011-10-17

Abstract: Objectives: The aim of this clinical trial was to test the accuracy of single all-ceramic zirconia crowns resulting from digital intraoral impressions with active wavefront sampling technology by measuring the marginal and internal fits of the crowns.Materials and methods: Thirty-seven teeth (24 anterior and 13 posterior) in fifteen patients were restored with single zirconia-ceramic crowns (Lava/Lava Ceram; 3M ESPE) generated from a digital intraoral scanner (Lava Chairside Oral Scanner; 3M ESPE). Before definitive insertion, silicone replicas were produced for all 37 crowns. The sample was cut in four sections; each section was evaluated in four points: marginal gap, mid-axial wall, axio-occlusal edge and centro-occlusal. A total of 592 measurements (148 for each evaluation point) was examined using stereomicroscopy with a magnification of 50×. The Mann–Whitney U test was used to evaluate whether there were differences between anterior and posterior values (alpha=0.05).Results: The mean values for each point were: 48.65μm (SD 29.45μm) for the marginal gap, 112.25μm (SD 55.54μm) at the mid-axial wall, 137.81μm (SD 71.31μm) at the axio-occlusal edge of the abutments, and 157.25μm (SD 75.51μm) at the centro-occlusal location. No statistical differences were found between the anterior and posterior group for each point (p-values: P1=0.39; P2=0.38; P3=0.07; P4=0.30).Conclusions: The marginal and internal fitting values obtained were within literature agreed as clinically acceptable for both anterior and posterior teeth.Clinical relevance: Single crown restorations obtained using digital intraoral impressions based on active wavefront sampling technology presented enough accuracy to be used as an alternative to the conventional impression techniques.