Journal of Dentistry

Editorial Board

2012-02-01

Clinical guidelines for treating caries in adults following a minimal intervention policy—Evidence and consensus based report

2011-11-03

Abstract: Objectives: In 2002, FDI (World Dental Federation) published a policy advocating that caries be treated by minimal intervention (MI). This MI policy has been accepted worldwide and is taught in universities. But acceptance in general dental practice has been slower, especially in Japan where healthcare payment and practice favour drilling and filling. To help disseminate this MI policy into general practice, the Japanese Society of Conservative Dentistry developed an evidence-based clinical guideline for restoring carious permanent teeth in adult patients.Methods: The guideline was developed by a committee of nine university clinicians and a librarian. The committee selected the most frequent clinical questions in treating caries and used electronic databases to search and assess the best scientific evidence for each. Members then added their clinical experience and discussed to reach consensus on each question on treating caries with MI policy. Graded recommendations and guidance were made for each clinical question. The provisional guideline was strengthened after review and discussion with university researchers and general practitioners.Results: The guideline addresses the 16 most frequent clinical questions in treating adult caries, including restorative methods and how to tackle root caries. Recommendations for treatment using MI policy were developed using the best scientific evidence and consensus of experienced clinicians.Clinical significance: The guideline offers a practical expert view of treating caries with the MI policy that incorporates the best scientific evidence, the latest techniques, the most preferable materials and the general consensus of expert clinicians.

Micro-Raman spectroscopic analysis of the degree of conversion of composite resins containing different initiators cured by polywave or monowave LED units

Vesna Miletic, Ario Santini — 2011-11-07

Abstract: Objectives: To determine the degree of conversion (DC) over 48h post-curing of resin mixtures containing trimethylbenzoyl-diphenylphosphine oxide (TPO) initiator cured by a polywave or a monowave LED light-curing unit (LCU).Methods: In resin mixtures based on equal weight percent (wt%) of BisGMA and TEGDMA the following initiators were added: 0.2wt% camphorquinone (CQ)+0.8wt% ethyl-4-dimethylaminobenzoate (EDMAB) (Group 1); 1wt% TPO (Group 2) and 0.1wt% CQ+0.4wt% EDMAB+0.5wt% TPO (Group 3). Half of the samples in each group (n=5) were cured using a polywave (bluephase® G2, Ivoclar Vivadent) or a monowave LED LCU (bluephase®, Ivoclar Vivadent). The DC was measured using micro-Raman spectroscopy within 5min and then 1, 3, 6, 24 and 48h post-irradiation. The data were analysed using general linear model and two-way ANOVA for the factors ‘time’, ‘material’, ‘surface’ and ‘LCU’ at α=0.05.Results: The initial DC values obtained upon light curing remained similar over a 48h period. bluephase® G2 produced the highest DC in Group 2 followed by Group 3, and Group 1. bluephase® resulted in the highest DC in Group 1, followed by Group 2 and Group 3 (p<0.05).Conclusions: Unfilled resin materials containing both TPO– and CQ–amine initiators are effectively cured using bluephase® G2. Resin mixture with the same wt% of initiators is better cured when TPO is the only initiator, compared to CQ–amine only or combined TPO and CQ–amine system. After initial light cure, no additional conversion of uncured monomers was detected in an unfilled resin material over 48h at 37°C.

Calcium phosphate bone cement with 10wt% platelet-rich plasma in vitro and in vivo

Jian-Chih Chen, Chia-Ling Ko, Chi-Jen Shih, Yin-Chun Tien, Wen-Cheng Chen — 2011-11-11

Abstract: Objectives: The aim of this study was to evaluate the performance of a 10wt% platelet-rich plasma (PRP) additive composite with calcium phosphate cement (CPC) in vitro and in vivo.Methods: The in vitro testing of modulus, the apatite conversion rate, morphology, cell and alkaline phosphatase (ALP) activities, and in vivo testing of histological examinations between two groups of 10wt% PRP/CPC and CPC were characterised and compared.Results: Although the crystallite morphologies showed a retarded effect in the PRP/CPC group in vitro, the modulus results showed that the 10wt% PRP/CPC group had a significant reduction in strength but had no significant changes in the relative conversion ratio of the apatite phase with CPC only. The osteogenic evaluation of ALP expression was significantly increased by the PRP additives group with stem cells (D1) cultured for different periods (2–32days). Our histological examinations showed that greater remodelling and the phenomenon of isolated/detached CPC particles were significantly observed at 9weeks after implantation when the 10wt% PRP/CPC composite was used.Conclusion: The results demonstrate that CPC may be a potential candidate as a carrier with PRP additives for bone regeneration.

Vertical discrepancy and microleakage of laser-sintered and vacuum-cast implant-supported structures luted with different cement types

2011-11-16

Abstract: Objectives: This study aimed to evaluate the vertical misfit and microleakage of laser-sintered and vacuum-cast cement-retained implant-supported frameworks.Methods: Three-unit implant-fixed structures were constructed with: (1) laser-sintered Co–Cr (LS); (2) vacuum-cast Co–Cr (CC); and (3) vacuum-cast Pd–Au (CP). Every framework was luted onto 2 prefabricated abutments under constant seating pressure. Each alloy group was randomly divided into three subgroups (n=10) according to the cement used: (1) Ketac Cem Plus (KC); (2) Panavia F 2.0 (PF); and (3) RelyX Unicem 2 Automix (RXU). After 30 days of water ageing, vertical discrepancy was measured by SEM, and marginal microleakage was scored using a digital microscope. Three-way ANOVA and Student–Newman–Keuls tests were run to investigate the effect of alloy/fabrication technique, FDP retainer, and cement type on vertical misfit. Data for marginal microleakage were analysed with Kruskal–Wallis and Dunn's tests (α=0.05).Results: Vertical discrepancy was affected by alloy/manufacturing technique and cement type (p<0.001). Despite the luting agent, LS structures showed the best marginal adaptation, followed by CP, and CC. Within each alloy group, KC provided the best fit, whilst the use of PF or RXU resulted in no significant differences. Regardless of the framework alloy, KC exhibited the highest microleakage scores, whilst PF and RXU showed values that were comparable to each other.Conclusions: Laser-sintered Co–Cr structures achieved the best fit in the study. Notwithstanding the framework alloy, resin-modified glass-ionomer demonstrated better marginal fit but greater microleakage than did MDP-based and self-adhesive dual-cure resin cements. All groups were within the clinically acceptable misfit range.Clinical significance: Laser-sintered Co–Cr may be an alternative to cast base metal and noble alloys to obtain passive-fitting structures. Despite showing higher discrepancies, resin cements displayed lower microleakage than resin-modified glass-ionomer. Further research is necessary to determine whether low microleakage scores may guarantee a suitable seal that could compensate for misfit.

Influence of temporary cement contamination on the surface free energy and dentine bond strength of self-adhesive cements

2011-11-23

Abstract: Objectives: The surface free energy and dentine bond strength of self-adhesive cements were examined after the removal of temporary cements.Methods: The labial dentine surfaces of bovine mandibular incisors were wet ground with #600-grit SiC paper. Acrylic resin blocks were luted to the prepared dentine surfaces using HY Bond Temporary Cement Hard (HY), IP Temp Cement (IP), Fuji TEMP (FT) or Freegenol Temporary Cement (TC), and stored for 1 week. After removal of the temporary cements with an ultrasonic tip, the contact angle values of five specimens per test group were determined for the three test liquids, and the surface-energy parameters of the dentine surfaces were calculated. The dentine bond strengths of the self-adhesive cements were measured after removal of the temporary cements in a shear mode at a crosshead speed of 1.0mm/min. The data were subjected to one-way analysis of variance (ANOVA) followed by Tukey's HSD test.Results: For all surfaces, the value of the estimated surface tension component (dispersion) was relatively constant at 41.7–43.3mJm−2. After removal of the temporary cements, the value of the (hydrogen-bonding) component decreased, particularly with FT and TC. The dentine bond strength of the self-adhesive cements was significantly higher for those without temporary cement contamination (8.2–10.6MPa) than for those with temporary cement contamination (4.3–7.1MPa).Conclusions: The γS values decreased due to the decrease of values for the temporary cement-contaminated dentine. Contamination with temporary cements led to lower dentine bond strength.Clinical significance: The presence of temporary cement interferes with the bonding performance of self-adhesive cements to dentine. Care should be taken in the methods of removal of temporary cement when using self-adhesive cements.

Interfacial fracture toughness of different resin cements bonded to a lithium disilicate glass ceramic

2011-12-12

Abstract: Objectives: To evaluate the effect of HF acid etching and silane treatment on the interfacial fracture toughness of a self-adhesive and two conventional resin-based cements bonded to a lithium disilicate glass ceramic.Methods: Lithium disilicate glass ceramic discs were prepared with two different surface preparations consisting of gritblasted with aluminium oxide, and gritblasted and etched with hydrofluoric acid. Ceramic surfaces with a chevron shaped circular hole were treated by an optimized silane treatment followed by an unfilled resin and then three different resin cements (Variolink II, Panavia F2, and Multilink Sprint). Specimens were kept in distilled water at 37°C for 24h and then subjected to thermocycling. The interfacial fracture toughness was measured and mode of failures was also examined. Data were analysed using analysis of variance followed by T-test analysis.Results: No statistically significant difference in the mean fracture toughness values between the gritblasted and gritblasted and etched surfaces for Variolink II resin cement was found (P>0.05). For the gritblasted ceramic surfaces, no significant difference in the mean fracture toughness values between Panavia F2 and Variolink II was observed (P>0.05). For the gritblasted and etched ceramic surfaces, a significantly higher fracture toughness for Panavia F2 than the other cements was found (P<0.05).Conclusions: The interfacial fracture toughness for the lithium disilicate glass ceramic system was affected by the surface treatment and the type of luting agent. Dual-cured resin cements demonstrated a better bonding efficacy to the lithium disilicate glass ceramic compared to the self-adhesive resin cement.Clinical significance: The lithium disilicate glass ceramic surfaces should be gritblasted and etched to get the best bond when used with Panavia F2 and Multilink Sprint resin cements, whereas for the Variolink II only gritblasting is required. The best bond overall is achieved with Panavia F2.

Surface properties of titanium and zirconia dental implant materials and their effect on bacterial adhesion

Afya Sahib Diab Al-Radha, David Dymock, Charles Younes, Dominic O'Sullivan — 2011-12-12

Abstract: Objectives: Zirconia ceramic material has been widely used in implant dentistry. In this in vitro study the physiochemical properties of titanium and zirconia materials were investigated and the affinity of different bacteria to different materials was compared.Methods: Disc samples with different surface states were used: polished partially stabilized zirconia (PZ), titanium blasted with zirconia (TBZ), titanium blasted with zirconia then acid etched (TBZA), and polished titanium (PT) as a control. Surface topography was examined using scanning electron microscopy and profilometry. Contact angle, surface free energy (SFE), surface microhardness and chemical composition were determined.Disc samples were separately incubated with Streptococcus mitis and Prevotella nigrescens, either with or without pre-coating with human saliva, for 6h and the surface area covered by bacteria was calculated from fluorescence microscope images.Results: PZ and TBZ exhibited lower surface free energy and lesser surface wettability than PT. Also, PZ and TBZ surfaces showed lower percentage of bacterial adhesion compared with control PT surface.Conclusions: The zirconia material and titanium blasted with zirconia surface (TBZ surface) showed superior effect to titanium material in reducing the adhesion of the experimented bacteria especially after coating with saliva pellicle. Modifying titanium with zirconia lead to have the same surface properties of pure zirconia material in reducing bacterial adhesion.SFE appears to be the most important factors that determine initial bacterial adhesion to smooth surface.

Chipping behaviour of all-ceramic crowns with zirconia framework and CAD/CAM manufactured veneer

M. Schmitter, D. Mueller, S. Rues — 2011-12-19

Abstract: Objectives: The aim of this in vitro study was to assess the ultimate load to failure of zirconia based crowns veneered with CAD/CAM manufactured ceramic.Methods: 32 identical, anatoform zirconia (Sirona inCoris ZI, mono L F1) frameworks (thickness 0.6mm) were constructed (Sirona inLab 3.80). Afterwards, 16 crowns were completed using a CAD/CAM manufactured lithium disilicate ceramic veneer (IPS e.max CAD, Ivoclar Vivadent). The remaining 16 frames were veneered using conventional manual layering technique. For the CAD/CAM manufactured veneers, the connection between framework and veneer was accomplished via a glass fusion ceramics. Before fracture tests, half of the specimens underwent thermocycling and chewing simulation (1.2 million chewing cycles, force magnitude Fmax=108N). To further investigate the new technique, finite element computations were carried out on the basis of the original geometry.Results: Nearly all (87.5%) conventionally veneered crowns failed already during chewing simulation, whereas crowns with CAD/CAM manufactured veneers were non-sensitive to artificial ageing. Crowns veneered with lithium disilicate ceramic displayed ultimate loads to failure of about 1600N.Conclusion: The CAD/CAM production of veneers for restorations with zirconia framework is a promising way to reduce failures originating from material fatigue.

AFM study of the effects of collagenase and its inhibitors on dentine collagen fibrils

Xinyu Zheng, Jinhao Hu, Yadong Chen, Yunjie Zhu, Hui Chen — 2011-12-19

Abstract: Objective: This study evaluated the effects of exogenous collagenase and two collagenase inhibitors on the variation in microstructure of human collagen fibrils.Methods: Dentine specimens which were sectioned from 6 freshly extracted human caries-free third molars were wet polished. Each specimen was divided into 4 parts which were treated as experimental groups (group 1, group 2, group 3) and the control group, respectively. All the specimens were etched and further treated with NaClOaq. Subsequently, the topography of each specimen was observed using atomic force microscopy (AFM) in tapping mode in air. Group 1 was then treated with a solution of collagenase II. Group 2 was treated with a solution of collagenase II and chlorhexidine (saturated solution). Group 3 was treated with a solution of collagenase II and captopril (0.3%). The control group was treated with a buffer solution. After 3h and 6h of treatment, the topography of the collagen fibrils was measured with AFM in air, respectively.Results: AFM images of the dentine collagen fibrils were obtained after treatment with NaOClaq. Following further treatment with collagenase II, the topography of the collagen fibrils changed. Most reticular collagen fibrils disappeared after 6h. After treatment with collagenase II in the presence of chlorhexidine or captopril for 3h and 6h, the morphology of the collagen fibres was not changed obviously.Conclusions: Exogenous collagenase II effectively degraded human dentine collagen fibrils, and its collagenolytic activity was inhibited by the exogenous collagenase inhibitors, chlorhexidine and captopril.