Journal of Dentistry

Editorial Board

2012-06-01

Adhesives for the restoration of non-carious cervical lesions: A systematic review

Brian Chee, Luke J. 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 for treatment of non-carious cervical lesions (NCCLs).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-etch for treatment of NCCLs.Sources: 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 18months follow-up were selected. The primary outcome was loss of retention/restoration loss, with marginal adaptation and marginal discolouration 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 for treatment of NCCLs. 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.

Metal–ceramic bond strength of Co–Cr alloy fabricated by selective laser melting

Nan Xiang, Xian-Zhen Xin, Jie Chen, Bin Wei — 2012-03-07

Abstract: Objectives: This study was to evaluated the metal–ceramic bond strength of a Co–Cr dental alloy prepared using a selective laser melting (SLM) technique.Methods: Two groups comprised of twenty Co–Cr metal bars each were prepared using either a SLM or traditional lost-wax casting method. Ten bars from each group were moulded into standard ISO 9693:1999 dimensions of 25mm×3mm×0.5mm with 1.1mm of porcelain fused onto an 8mm×3mm rectangular area in the centre of each bar. Metal–ceramic bonding was assessed using a three-point bending test. Fracture mode analysis and area fraction of adherence porcelain (AFAP) were determined by measuring Si content of specimens by SEM/EDS.Results: Student's t-test within the groups demonstrated no significant difference for the mean bond strength between the SLM and traditional cast sample groups. While SEM/EDS analysis indicated a mixed fracture mode on the debonding interface of both the SLM and the cast groups, the SLM group showed significantly more porcelain adherence than the control group (p<0.05).Conclusions: The SLM metal–ceramic system exhibited a bonding strength that exceeds the requirement of ISO 9691:1999(E) and it even showed a better behaviour in porcelain adherence test comparable to traditional cast methods.

Biomodification to dentin by a natural crosslinker improved the resin–dentin bonds

Ming Fang, Ruirui Liu, Yuhong Xiao, Fang Li, Danyang Wang, Rui Hou, Jihua Chen — 2012-02-24

Abstract: Objectives: Transient collagen cross-linking treatment by proanthocyanidins (PA), a natural crosslinker, was proved to increase the cross-linking degree and ultimate tensile strength of demineralised dentin. The present study aimed to investigate whether transient pretreatment by PA-based preconditioner can improve the resin–dentin bonds of various etch and rinse adhesives. The influence of solvent type, PA concentration and treatment duration were examined.Methods: PA-based preconditioners were prepared by adding powdered grape seed extract, rich in PA, to various solvents at different concentrations. They were used on demineralised dentin before the application of the bonding agent. Bond strength, failure modes and degree of conversion were evaluated via microtensile testing, field emission scanning electron microscopy and Fourier transform infrared spectroscopy, respectively.Results: Collagen cross-linking treatment by PA-based preconditioners presented a concentration- and time-dependent increase in dentin bond strength even in reduced, clinically applicable treatment duration. PA preconditioning improved bond strength of the tested water/ethanol-based adhesive better than the water/acetone-based system. Mixed fracture was the most prevalent failure mode happened on the top of the hybrid layer in PA-pretreated specimens, whilst at the bottom in non-treated controls. The degree of conversion was not significantly affected by PA pretreatment.Conclusions: Transient PA preconditioning improved resin–dentin bonds without compromise on the curing behaviours of the tested adhesives.

Effects of different implant–abutment connections on micromotion and stress distribution: Prediction of microgap formation

2012-02-27

Abstract: Objectives: The aim of this study was to analyse micromotion and stress distribution at the connections of implants and four types of abutments: internal hexagonal, internal octagonal, internal conical and trilobe.Methods: A three dimensional (3D) model of the left posterior mandible was reconstructed from medical datasets. Four dental implant systems were designed and analysed independently in a virtual simulation of a first molar replacement. Material properties, contact properties, physiological loading and boundary conditions were assigned to the 3D model. Statistical analysis was performed using one-way analysis of variance (ANOVA) with a 95% confidence interval and Tukey's Honestly Significant Difference (HSD) multiple comparison test.Results: The internal hexagonal and octagonal abutments produced similar patterns of micromotion and stress distribution due to their regular polygonal design. The internal conical abutment produced the highest magnitude of micromotion, whereas the trilobe connection showed the lowest magnitude of micromotion due to its polygonal profile.Conclusions: Non-cylindrical abutments provided a stable locking mechanism that reduced micromotion, and therefore reduced the occurrence of microgaps. However, stress tends to concentrate at the vertices of abutments, which could lead to microfractures and subsequent microgap formation.

Bonding effectiveness of a new ‘multi-mode’ adhesive to enamel and dentine

2012-02-29

Abstract: Objectives: Self-etch adhesives are well adopted in general practice, obviously primarily thanks to their ease of use and fast application time. Nevertheless, phosphoric acid is still often recommended to beforehand etch enamel following a so-called ‘selective’ enamel-etch technique, this in particular when most cavity margins end in enamel. The purpose of this study was to test if a new one-step adhesive can be applied in a multi-mode manner, this following different, either ‘full’ or ‘selective’, self-etch and etch-and-rinse approaches. Specific research hypotheses tested were that prior phosphoric-acid etching did not affect the bonding effectiveness of the one-step adhesive to enamel and dentine, and that the bonding effectiveness to dentine was also not affected when the adhesive was applied either following a ‘dry-bonding’ or ‘wet-bonding’ etch-and-rinse technique.Methods: The micro-tensile bond strength (μTBS) of the one-step self-etch adhesive G-Bond Plus (GC, Tokyo, Japan; 1-SEA) was measured when it was bonded to bur-cut enamel following either a ‘self-etch’ or an ‘etch-and-rinse’ adhesive protocol, and to bur-cut dentine when applied following either a ‘self-etch’, a ‘dry-bonding’ or a ‘wet-bonding’ etch-and-rinse adhesive protocol. Bond-strength testing was corroborated by ultra-structural analysis of the interfacial interaction at enamel and dentine using transmission electron microscopy (TEM).Results: Prior phosphoric-acid etching significantly increased the bonding effectiveness of the 1-SEA to enamel. A clearly enhanced micro-retentive surface was revealed by TEM. To dentine, no statistically significant difference in bonding effectiveness was recorded when the 1-SEA was either applied following a self-etch or both etch-and-rinse approaches. The ‘dry-bonding’ etch-and-rinse protocol was significantly more effective than its ‘wet-bonding’ version. TEM however revealed indications of low-quality hybridisation following both etch-and-rinse approaches, in particular in the form of a porous and poorly resin-infiltrated collagen mesh.Conclusions: While phosphoric-acid etching definitely improved bonding of the one-step self-etch adhesive to enamel, one should be more careful with additional phosphoric-acid etching of dentine. Although the bond strength was not reduced, the resultant adhesive interface appeared ultra-structurally more vulnerable to biodegradation.

Epigallocatechin-3-gallate (EGCG) enhances the therapeutic activity of a dental adhesive

Xijin Du, Xueqing Huang, Cui Huang, Yake Wang, Yufeng Zhang — 2012-03-14

Abstract: Objectives: The purpose of this study was to evaluate the antibacterial potential and physicochemical properties of a dental adhesive incorporated with epigallocatechin-3-gallate (EGCG) in different concentration over time.Methods: EGCG was incorporated at a ratio of 100, 200, and 300μg/ml into a dental adhesive. The effects of the cured adhesives on the growth of Streptococcus mutans were determined by direct contact test immediately or one month later and by scanning electron microscopy (SEM), respectively. Microtensile bond strength (μTBS) test was used to test the mechanical property of the adhesives immediately or six months later. The degree of conversion (DC) of the adhesives was evaluated by Fourier Transform Infrared Spectroscopy (FTIR).Results: Compared with negative control, the 200μg/ml and 300μg/ml EGCG-incorporated dental adhesive were found to exhibit inhibitory effect on the growth of S. mutans. The μTBS of the EGCG-incorporated dental adhesive was higher than the control. The DC of the adhesive system was not affected by the addition of EGCG.Conclusions: 200μg/ml EGCG incorporated dental adhesives could accomplish therapeutic goals that play in antimicrobial function whilst keeping the durability of resin–dentine bond.

Detection of proximal secondary caries at cervical class II-amalgam restoration margins in vitro

K.W. Neuhaus, J.A. Rodrigues, R. Seemann, A. Lussi — 2012-03-19

Abstract: Objectives: To compare the performance of LFpen (DIAGNOdent pen) with two different wedge-shaped tips to conventional bitewing radiography (BW) for detecting proximal secondary caries at the cervical margin of amalgam restorations in vitro.Methods: Seventy-five molars with class II amalgam restorations were selected. Depending on the marginal filling extension, data was subdivided into a crown group (C), when the filling ended in enamel, and into a root group (R), when the filling ended beyond the cementum-enamel junction. Bayesian analysis including calculation of the area under the receiver operating curve (AUC) was performed. Furthermore, Spearman correlations between caries and cofactors, such as presence of plaque or stain, occlusal ditching, marginal gap size, filling overhangs, and shortfalls, were calculated. Additionally, for group R the correlation coefficient between LFpen measurements and lesion depth was calculated. Histology served as gold standard.Results: In group C both at the D1 and D3 levels, LFpen with two different tips showed a better performance than bitewing radiography (AUC at D1: 0.83/0.79 (LFpen) and 0.63 (BW); at D3: 0.66/0.66 (LFpen) and 0.53 (BW)). In group R, the respective AUC values were 0.53/0.56 (LF) and 0.59 (BW). A significant medium correlation was observed for occlusal ditching and proximal caries. Stain accumulation at the restoration margins especially in combination with filling overhangs interfered with LFpen readings, resulting in false positive measurements.Conclusions: Compared to BW, LFpen enhances the detection of secondary caries lesions at the cervical margin of amalgam restorations that do not extend below the cementum-enamel junction.

Cuspal deflection and microleakage in premolar teeth restored with bulk-fill flowable resin-based composite base materials

2012-03-05

Abstract: Objectives: To assess the cuspal deflection and cervical microleakage of standardised Class II cavities incrementally filled with a dimethacrylate RBC or bulk-fill flowable RBC bases.Methods: Twenty-four sound upper premolar teeth with Class II cavities were allocated to three groups (n=8). Restoration of the teeth involved the placement of an RBC (GrandioSO) in eight oblique increments (Group A) or Groups B and C were restored to within 2mm of the palatal cusp in a single increment with bulk-fill flowable RBC bases (SDR and x-tra base) before the two occlusal cavity increments were placed with GrandioSO. Buccal and palatal cusp deflections were recorded postirradiation using a twin channel deflection measuring gauge. Following restoration, the teeth were thermocycled, immersed in 0.2% basic fuchsin dye for 24h, sectioned and examined for cervical microleakage.Results: The mean total cuspal deflection for the oblique incremental restoration technique was 11.26 (2.56)μm (Group A) and 4.63 (1.19)μm (Group B) and 4.73 (0.99)μm (Group C) for the bulk-fill flowable RBC bases. A significant increase in the mean total cuspal deflection for the incrementally filled GrandioSO compared with the SDR (P=0.007) and x-tra base (P=0.005) restored teeth was evident. No significant difference in the cervical microleakage scores was recorded between groups AC (P>0.05).Conclusions: The bulk-fill flowable RBC bases significantly reduced cuspal deflection compared with a conventional RBC restored in an oblique incremental filling technique with no associated change in cervical microleakage recorded.

Fungicidal amounts of antifungals are released from impregnated denture lining material for up to 28 days

2012-03-05

Abstract: Objectives: The aim of this study was to investigate the efficacy of a polymeric delivery system impregnated with chlorhexidine or fluconazole against Candida species.Methods: Self-cure poly-ethyl methacrylate and tetrahydro-furfuryl methacrylate (PEM/THFM) discs impregnated with pure fluconazole substance (FLUp), fluconazole powder from capsules (FLUc) or chlorhexidine powder (CHX) were incubated in water for up to 28 days at 37°C. The water was replaced at 24h and 3, 7, 14, 21, 28 days. The amount of released drugs and antifungal activity of the leachates was measured by bioassay. The minimal inhibitory concentration (MIC) of each drug for 46 Candida isolates was determined and compared to the released concentrations.Results: A total of 53.0% of CHX, 38.5% of FLUc and 13.2% of FLUp impregnated into the discs was leached during the 28-day incubation. Of the total amount leached, 71.8% of CHX, 75.1% of FLUc and 70.5% of FLUp was released during the first week of incubation. Antifungal activity was confirmed for up to 28 days.Conclusion: Both chlorhexidine and fluconazole become readily leached from PEM/THFM polymer up to four weeks and that the polymerisation of the acrylic does not affect the antimicrobial activity of the agents. Importantly, the amount of drugs released exceeded the MICs of most isolates also during the fourth week of incubation.Clinical significance: These findings indicate the feasibility of this treatment modality for oral candidal infections, especially denture stomatitis. But further in vivo work is warranted to determine its clinical relevance and applicability.

Durability of composite repair using different surface treatments

2012-03-14

Abstract: Objective: To evaluate the surface treatment and hydrophilicity of the bonding agent on the composite repair strength (RS), silver nitrate uptake (SNU), surface roughness (SR) and estimation of surface area (SA).Methods: Fifty resin blocks (Opallis, FGM) were polished and divided in 5 groups: no treatment (NT); roughening with a fine (FDB); medium (MDB); coarse-grit (CDB) and 50-μm aluminium oxide sandblasting (AO). A hydrophobic (Adhesive, Scotchbond Multi-Purpose Plus, 3M ESPE) or hydrophilic (Adper Single Bond 2, 3M ESPE) adhesive was applied, followed by composite placement (Opallis, FGM). Composite-composite bonded sticks (0.9mm2) were tested in tension (1.0mm/min) immediately [IM] or after 6 months [6M] of water storage. Two sticks from each tooth, at each time, were immersed in a 50% silver nitrate solution and evaluated by SEM. A profilometer was used to measure SR. SEM images were used to estimate the SA using the Image J software. Data were analysed by ANOVA and Tukey's tests.Results: The AO showed the highest CR strength for both adhesives, whilst the NT group showed the lowest, irrespective of the storage period. The diamond burs had intermediate performance. Silver nitrate deposits were seen after 6M for the hydrophilic adhesive. The ranking of SR values (Ra) from the lowest to the highest was: NT

Effect of low pH on surface rehardening efficacy of high concentration fluoride treatments on non-cavitated lesions

C. González-Cabezas, H. Jiang, M. Fontana, G. Eckert — 2012-03-14

Abstract: Objective: Professionally applied acidulated phosphate fluoride has been shown to reduce caries incidence. However, it has been suggested that its efficacy might be reduced in advanced non-cavitated lesions. This study aimed to compare the surface rehardening and fluoride uptake effect of 2%-NaF solutions at different pH on non-cavitated caries-like lesions with two different levels of demineralization.Methods: Human enamel specimens were demineralized to create early and advanced non-cavitated lesions. Specimens for each type of lesion were divided into 3 groups, treated for four minutes with either 2%-NaF pH 3.5, 2%-NaF at pH 7.0, or neutral deionized water, and exposed to a pH cycling remineralization/demineralization model for five days. An additional treatment was then done as described above followed by five more days of cycling (total of 2 treatments, ten-day pH cycling). Specimens were analyzed for surface microhardness change and fluoride uptake.Results: It was found that for both types of lesions, acidic pH fluoride treatment was significantly (p<0.05) more effective than neutral pH treatment in rehardening the lesion surface and promoting fluoride uptake. Furthermore, the low pH vs neutral pH difference in rehardening was significantly larger in the less demineralized lesions (p=0.0001). Water treatment resulted in no rehardening or fluoride uptake.Conclusions: Results from this study suggest that high concentration fluoride treatments at acidic pH are more effective in rehardening the surface of non-cavitated caries lesions and promoting fluoride uptake than those at neutral pH. This effect appears to be greater in less demineralized lesions when compared to more advanced ones.Clinical significance: The results of this investigation suggest that when no other attenuating circumstances are present (e.g., the possibility of damaging tooth-coloured restorations), high concentration fluoride treatments for high risk individuals might be more efficacious using products at low pH.

A 5-year retrospective study of survival of zirconia single crowns fitted in a private clinical setting

Anders Örtorp, Maria Lind Kihl, Gunnar E. Carlsson — 2012-03-01

Abstract: Objectives: The aim of this report was to evaluate the 5-year clinical performance and survival of zirconia (NobelProcera™) single crowns.Methods: All patients treated with porcelain-veneered zirconia single crowns in a private practice during the period October 2004 to November 2005 were included. The records were scrutinized for clinical data. Information was available for 162 patients and 205 crowns.Results: Most crowns (78%) were placed on premolars and molars. Out of the 143 crowns that were followed for 5 years, 126 (88%) did not have any complications. Of those with complications, the most common were: extraction of abutment tooth (7; 3%), loss of retention (15; 7%), need of endodontic treatment (9; 4%) and porcelain veneer fracture (6; 3%). No zirconia cores fractured. In total 19 restorations (9%) were recorded as failures: abutment tooth extraction (7), remake of crown due to lost retention (6), veneer fracture (4), persistent pain (1) and caries (1). The 5-year cumulative survival rate (CSR) was 88.8%.Conclusions: According to the present 5-year results zirconia crowns (NobelProcera™) are a promising prosthodontic alternative also in the premolar and molar regions. Out of the 143 crowns followed for 5 years, 126 (88%) did not have any complications. However, 9% of the restorations were judged as failures. Further studies are necessary to evaluate the long-term success.