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Biomedical subjects

A Kakaboura

Publications and source records attributed to A Kakaboura.

17 recordsLinked to original sources
PubMed2007

Evaluation of surface characteristics of dental composites using profilometry, scanning electron, atomic force microscopy and gloss-meter.

The aim of this in vitro investigation was to compare various roughness and topography measurement methods to characterize the surface quality in several types of resin composites. The initial surface quality of several resin composites was compared. The materials evaluated were of three categories: i) hybrid: TPH Spectrum; ii) reinforced microfill: Micronew and iii) microhybrid: Synergy Duo, Esthet-X, Point.4 and Palfique Estelite. Three Groups of identical disk-shaped specimens (10 x 1.5 mm) were prepared from each material (n = 6) and polished with Soflex discs. Macro-roughness (Ra) was measured with Group 1 by 2-D profilometry. Atomic Force Microscopy (AFM) gave 3-D images and micro-roughness (Ra) of Group 2. Surface optical gloss at 60 degrees was determined for Group 3. Specimens of each material were also studied by scanning electron microscopy. Macro-Ra values (microm) ranged from 0.30 to 0.56. Micro-Ra values ranged from 0.03 to 0.14 and they differed from macro-Ra values in ranking order. Percentage Gloss values ranged from 30.6 to 70.1%. The results revealed that micro-roughness showed a high correlation with gloss values (r = 0.93), whilst macro-roughness did not (r = 0.62). Moreover, the AFM method showed higher capability to distinguish surface roughness compared with the 2-D profilometry and to reveal more detailed definition of surface texture than the examination under SEM.

Composite Resins↗
PubMed2004

Marginal and internal adaptation of Class II ormocer and hybrid resin composite restorations before and after load cycling.

To overcome the shortcomings of the conventional composite restorative materials, ormocer materials have been introduced over the past few years. The purpose of this study was to evaluate the marginal and internal adaptation of two ormocer restorative systems (Admira, Voco and Definite, Degussa) compared to a hybrid composite one (TPH Spectrum, Dentsply/ DeTrey), before and after load cycling in Class II restorations. Standardized Class II restorations with cervical margins on enamel were divided into three groups ( n=16). Teeth of each group were filled with one of the restoratives tested and its respective bonding agent. Each group was divided into two equal subgroups. The marginal and internal adaptation of the first subgroup was evaluated after 7-day water storage at room temperature and of the second after cyclic loading in a mastication simulator (1.2x10(6) cycles, 49 N, 1.6 Hz). The occlusal and cervical marginal evaluation was conducted by videomicroscope and ranked as "excellent" and "not excellent". One thin section (150 microm), in mesial-distal direction, of each restoration, was examined under metallographic microscope to determine the quality of internal adaptation. The occlusal and cervical adaptation of both ormocer restorative systems was similar and clearly worse compared with the hybrid composite restorative one before as well as after load cycling. Concerning internal adaptation, no gap-free ormocer restorations were detected, whereas all Spectrum restorations presented perfect adaptation. The bonding agents of the ormocers formed layers with unacceptable features (pores, fractures) whereas that of the hybrid composite achieved perfect bonding layer even after loading. The rheological characteristics of the bonding agents of the ormocer restorative systems are proposed to be responsible for their inferior marginal and internal quality in Class II restorations compared with the hybrid composite one.

Ceramics↗
PubMed2004

The effect of sterilization methods on the light transmission characteristics and structure of light-curing tips.

The purpose of this study was to investigate the effect of various sterilization methods on the light transmission and the structural characteristics of two light-curing tips. Twenty tips from two light-curing devices [Elipar II (EL) and Heliolux II (HL)] were classified into four groups. The tips in groups A to C were subjected to sterilization with 0.2% sodium dichloroisacyanurate solution (Presept), 2% glutaraldehyde solution (Cidex) (2 h cycle(-1)) and water-steam autoclave (120 degrees C, 1 bar, 12 min cycle(-1)), respectively. A total of 2100 sterilization cycles was performed for all methods tested. The transmitted light intensity (TLI) was measured at specific sterilization time intervals by a curing radiometer (Model 100, Demetron). The final % TLI reduction of the sterilized tips was calculated relative to the corresponding control ones. The topography and composition of the front curing tip surfaces were determined using scanning electron microscopy combined with electron probe microanalyser. Autoclaving caused the lowest final TLI decrease (EL: 15%, HL: 19%) compared with Presept (EL: 60%, HL: 42%) and with Cidex (EL: 68%, HL: 52%). Cidex yielded higher TLI drop than Presept for both types of tips examined. Elipar tips were found to be more sensitive than Heliolux tips to both chemical sterilization techniques. Total or partial coating of the tip surfaces with insoluble salts after sterilization with Presept and Cidex was detected, mainly composed of Ca, Cl, Al, Pd and Mg traces. No changes were noted on the surfaces after autoclave. Water-steam autoclave is safer than the 0.2% sodium dicloroisocyanorate and 2% glutaraldehyde chemical sterilization agents regarding the light transmission characteristics and the structure of the light-curing tips.

Dental Disinfectants↗
PubMed2003

In vitro characterization of two laboratory-processed resin composites.

PURPOSE: To compare various characteristics of two new-generation laboratory-processed resin composites (BelleGlass HP/SDS-Kerr and Sinfony/3M-ESPE). The properties evaluated were degree of C=C conversion, microhardness, roughness, biaxial flexural strength and polymerization shrinkage-strain. MATERIALS AND METHODS: All specimens were subjected to a first and a second polymerization cycle according to the manufacturers' instructions. The degree of C=C conversion (DC) was recorded on rectangular (3 x 2 x 0.5mm(3)) specimens (n=3) by FT-IR micromultiple internal reflectance spectroscopy immediately after each of the two polymerization cycles. Twenty cylindrical specimens (10 x 2mm(2)) of each material were prepared for surface microhardness (n=10, VHN, 200 g load, 20s) and surface roughness (n=10, Ra) measurements. The biaxial flexural strength and stiffness were determined on disk-shaped (n=8, 15 x 0.7 mm(2)) specimens loaded to fracture at 1 mm/min crosshead speed. The polymerization shrinkage-strain was calculated with the bonded-disk method. All values were statistically analyzed by Student's unpaired t-test (p<0.05). RESULTS: The second polymerization cycle significantly increased the degree of C=C conversion for both materials (p<0.05). BelleGlass HP exhibited significantly higher degree of C=C conversion, surface microhardness, surface roughness, biaxial flexural strength and stiffness values compared to Sinfony (p<0.05). SIGNIFICANCE: Several differences exist between the materials although both products are recommended for the same clinical applications.

Composite Resins↗
PubMed2002

In vitro study of penetration of flowable resin composite and compomer into occlusal fissures.

UNLABELLED: The penetration of a sealant into the tooth fissures can establish longer retention time for a pit and fissure sealant restoration. AIM: This in vitro study was to evaluate the penetration ability of two low-viscosity resin materials, a composite and a compomer, applied with and without their bonding agents in comparison to an unfilled resin sealant. METHODS: Forty premolars with shallow/wide (group I) and forty with deep/narrow occlusal fissures (group II) were used. Each group was divided into five subgroups (A-E). The teeth in the subgroups were sealed as follows: A - Delton LC Clear (unfilled resin); B - Dyract flow (compomer); C - Prime&Bond NT (bonding agent) and Dyract flow; D - Tetric flow (resin composite); E - Syntac Sprint (bonding agent) and Tetric flow. Longitudinal sections were cut along the mesiodistal direction of fissures and examined under a videomicroscope. The resin penetration was rated according to the scale "low", "medium", "high", indicating penetration up to one third and two thirds of fissure depth and to the fissure bottom, respectively. RESULTS: These revealed the following: a) the penetration of all sealants was higher in shallow/wide than in deep/narrow fissures; b) the low-viscosity resin materials provided higher penetration than the unfilled resin sealant in shallow/wide fissures, whereas the unfilled resin achieved superior penetration rates in deep/narrow ones; c) the combination of a hydrophilic sealant (Dyract flow) with a hydrophilic bonding agent (Prime&Bond NT) significantly promoted the penetration depth in deep/narrow fissures. CONCLUSION: The penetration ability of all sealants was higher in shallow/wide than in narrow/deep fissures; low-viscosity resin composite and compomer provided higher penetration efficiency than the unfilled resin sealant in shallow/wide fissures, whereas the unfilled resin achieved superior penetration rate in deep/narrow ones. The combination of a hydrophilic sealant with a hydrophilic bonding agent significantly enhanced the penetration depth in deep/narrow fissures.

Journal Article↗
PubMed2001

Comparison of enamel colour changes associated with orthodontic bonding using two different adhesives.

The purpose of this study was to evaluate the enamel colour changes associated with bonding of brackets with a no-mix (one-phase) adhesive resin (Unite) and a glass-ionomer adhesive (GC Fuji Ortho). Thirty recently extracted premolars were used in the investigation. Black rectangular pieces of adhesive tape with a 3-mm diameter window were used to standardize the enamel surface intended for analysis. The teeth were divided into two groups of 15 teeth each, brackets (Starfire TMB) were bonded with the two adhesives, and the enamel surfaces were colourimetrically evaluated at three time intervals: (a) before bonding (baseline), (b) following debonding and cleaning, and (c) after artificial photo-ageing for 24 hours. The CIE colour parameters (L*, a*, b*) were recorded and averaged for each material, interval group, and the corresponding colour differences (delta E) were calculated. The results were statistically analysed using two-way ANOVA repeated measures, and Scheffé multiple range test at alpha = 0.05 level of significance. All differences noted exceeded the threshold for clinical detection (delta E = 3.7). The highest differences were recorded for the baseline-debonding interval for both adhesives used. No difference was found with respect to delta E between etching-mediated and no etching-mediated bonding implying that the debonding cleaning process involving adhesive grinding may be more invasive relative to acid etching with regard to enamel colour alterations.

Acid Etching, Dental↗
PubMed1998

Acid-base reaction and fluoride release profiles in visible light-cured polyacid-modified composite restoratives (compomers).

OBJECTIVE: The aim of the study was to evaluate the extent of the acid-base reaction and F- release in Compoglass (Vivadent) and Dyract (Dentsply/DeTrey) restoratives. METHODS: For evaluation of the extent of the acid-base reaction, two groups of three specimens (7 mm x 5 mm x 1 mm) were prepared for each material. The first group was immersed in distilled water, while the second was kept in dark and dry conditions. Micro-MIR FTIR spectroscopy was used to determine the extent of the acid-base reaction on directly irradiated material surfaces immediately after irradiation and following water storage for 30 min, 3 d, 1, 2, 4, 8 and 12 wks. The in-depth extent of the acid-base reaction of the specimens stored in water for 4 weeks was studied by sequential spectra acquisition after removal of the uppermost 20, 70, 100, 240 and 400 microns layer by controlled grinding and 1 wk re-immersion in water of the 400 microns reduced specimens. For the F- release measurements, five disk-shaped specimens (10 mm x 1.5 mm) were prepared from each material and stored in distilled water. The amount of F- released for the storage periods reported above was measured using an ionometer with an F- electrode. Statistical analysis was performed by ANOVA, Scheffé's test and regression analysis. RESULTS: Storage in water promoted the development of an acid-base reaction on directly irradiated surfaces which reached a saturation point after 4 weeks. Depth profiling of the 4 wk immersed specimens revealed high salt concentration at the uppermost 100 microns layer. Re-immersion in water for 1 week of the 400 microns reduced specimens increased the salt concentration again at the uppermost region. Statistically significant differences were found in the acid-base rates and the in-depth salt yields between the materials (p < 0.05). The fluoride release after a 1 week initial "bursting" period was stabilized below 2 mg l-1 (p > 0.05) in both products. No positive correlation was found between acid-base reaction and fluoride release. SIGNIFICANCE: The development of a carboxylate-rich surface layer on polyacid-modified composite restoratives after water storage may explain their lower wear resistance compared with resin composites. The dynamic nature of these surfaces may provide several advantages regarding their interaction potential with hard dental tissues and their anticariogenic properties, but also some disadvantages concerning the quality of the surface texture obtained.

Alkalies↗
PubMed1996

An FTIR study on the setting mechanism of resin-modified glass ionomer restoratives.

OBJECTIVES: An experimental method was used to assess the glass ionomer and resinous character in three "dual-cure" (Fuji II LC, Photac-Fil, Variglass) and a "triple-cure" (Vitremer) resin-modified glass ionomer restoratives to evaluate their acid-base and free-radical setting mechanisms. METHODS: Four groups (A-D) of three specimens (5 x 4 x 1 mm) were prepared from each material and subjected to the following treatments: A: mixing; B,C: mixing, 60 s irradiation, 20 min dark/dry storage; and D: mixing, 20 min dark/dry storage and then 60 s irradiation. Micro-multiple internal reflectance FTIR spectroscopy was used to determine: 1) the curing efficiency of the products immediately after irradiation; 2) the effect of irradiation 20 min after dark/dry storage on the curing efficiency; and 3) the extent of the acid-base reaction on irradiated and non-irradiated specimens after 20 min dark/dry storage. RESULTS: The curing efficiency immediately after irradiation was determined from the percentage of residual double bonds which ranged from 33-50% for these materials. Irradiation after 20 min dark/dry storage significantly reduced curing efficiency in all the products, except Variglass. The latter showed no acid-base reaction under the conditions of this study. Non-irradiated specimens after the dark storage period demonstrated higher carboxylate yields compared to their irradiated analogues. Non-irradiated specimens from Vitremer had the highest carboxylate yield and a curing efficiency of approximately 50% residual double bonds. SIGNIFICANCE: Photopolymerization seemed to greatly reduce the acid-base reaction during the early setting stages of resin-modified glass ionomer restoratives. The free-radical formation rates are slower than those achieved by chemically initiated polymerization, but they produce adequate conversion and high carboxylate salt yields. This study demonstrated an experimental model for identification and characterization of the acid-base reaction in water-containing resinmodified glass ionomer restoratives.

Acid-Base Equilibrium↗
PubMed1990

[Bonding of visible light cured composite resins to glass ionomer and Cermet cements].

The "sandwich" technique involves combination of composite resins to etched glassionomer cements, is used today in restorative dentistry. The purpose of this study is to evaluate the bond strength between several composite resins and glass ionomer or cerment cements. Cylindrical specimens of the cements Ketac-Silver, Ionobond and GC-Lining Ce-ment were inserted in a mold and their flat free surfaces were etched for 30". Cylindrical plastic tubes were set upon each one of these surfaces and filled with the Composite resins Durafill, Brilliant Lux, Estilux posterior, Estilux posterior CVS and Herculite XR. Half of the specimens transferred in tap water for 24 hours and the others after thermocycling in the first month, kept for 4 months. Shear bond strengths were determined in Monsanto Testing Machine and some fractured surfaces were examined under SEM. The results of this investigation indicate that this technique produces bond strengths between composite resins and glassioners and the combination type of resin and type of cement, affects the values of the strength. Glass cermeet--small particle resin provides the most effective strength and glass ionomer--microfill resins the least. Storage time and thermocycling don't significantly effect the bond strength. SEM examination showed that all fracture failures were obtained in the cement while the opposite resin surfaces were covered with particles of the cements.

Cermet Cements↗
PubMed1990

[Thermal diffusivity of dental cements].

Thermal insulative efficiency, is one of the desirable properties of the dental cements. In this study, the thermal diffusivity of three types of dental cements, were measured. Thermal diffusivity was determined by the following method. Two thermo-couples were used and connected to a chart record, the first was embedded in the cylindrical block of the cement specimen and the other in a mixing of ice and water (reference thermocouple). All them were set in a apparatus consisting of a double cooling bath. Calculation of thermal diffusivity were based on the curve provided of the record during cooling of the cement and a theoretical mathematic model. Values were ranged from 2,985 to 3,934 cm2.sec-1. ZOE cement exhibited the highest value, the glass-ionomers the lowest and the poly-carboxylates were average. The results showed that the thermal diffusivity of the cements is dependent from the type of the cement but the differences between them were not statistically significant. Additionally, the values obtained were about the same as the dentin, so the dental cements may consider as good thermal insulators.

Dental Cements↗
PubMed1990

[The glass ionomer cements as bases or linings].

The glass ionomer cements were developed in the early 1970s as filling restorative materials. Today, they have been modified for various clinical applications and the major of them is as base or lining, specially beneath composite resins. This paper is a literature review about the base/lining type of glass ionomers. The composition, the structure and the physicomechanical properties of this type are reported. Also, are presented the possibilities and results of their usage as base/lining in the restorations of amalgam and composite resins.

Dental Cavity Lining↗
PubMed1989

[Smear layer on prepared dentin].

Whenever dental tissues cut with a rotary instrument, a layer of grinding debris and organic film left of their surfaces, which is described by the term "smear layer". In this paper, we present the morphology and views for the formation of the smear layer. Additionally, we examine the influence of smear layer, on dentin permeability, infection by bacteria beneath dental restorations and on bonding capacity of adhesive dental materials. Following, detailed description of cleaning and chemical agents, used for smear layer removal from prepared dentin surfaces.

Dental Bonding↗
PubMed1989

[A comparative study of visible light units].

The purpose of this investigation was to examine the performance of 10 V.L.C. units according to the depth of cure of the composite resins by measuring the hardness difference (delta H) on the top and the bottom of cylindrical specimens 2.3 and 4 mm high. According to the results (a) there is a different performance between the units when the depth of cure exceeds the 2 mm (b) the type of composite resin (macrofille or microfille) has a significant influence of V.L.C. unit performance and (c) performance of the two types of V.L.C. units--with and without flexible photocolor--is almost the same.

Composite Resins↗
PubMedDate not supplied

Clinical evaluation of a polyacid-modified resin composite (compomer) in Class II restorations of primary teeth: a two-year follow-up study.

PURPOSE: The aim of the study was to assess the clinical performance of a compomer restorative material (Dyract, DeTrey/Dentsply) for the restoration of Class II cavities, extended into dentin in primary teeth. METHODS: The sample of the study consisted of 25 patients with 68 restored cavities. The restorations were evaluated with the modified Ryge criteria at baseline and after 6, 12 and 24 months. Examination was clinical, radiographic, and observation of cast replicas under scanning electron microscope (SEM). RESULTS: After 24 months, 100% of the restorations were retained, 3% presented bulk fractures, and 6% developed secondary caries at cervical margins. After 24 months, there was a significant reduction in marginal integrity while there was only slight change in anatomic form. Proximal contact was defective in 6% of the restorations and 8% showed marginal discoloration. SEM evaluation revealed a generalized occlusal and scattered marginal wear with no marginal gaps. CONCLUSION: The compomer presented acceptable clinical performance in Class II restorations of primary teeth after 24 months in service.

Calcium Hydroxide↗
PubMedDate not supplied

[Clinical behavior of posterior restorations with composite resins].

Recent advantages of composite resins have led to a greater use of these materials for restorations of posterior teeth. The composite resins have been used in posterior restorations over six years, so their clinical performance could be evaluate safety. The purpose of this literature review was to present all the results of clinical studies, concerning the behavior of posterior restorations with composite resins.

Bicuspid↗
PubMedDate not supplied

[A study of different polishing techniques for amalgams and glass-cermet cement by scanning electron microscope (SEM)].

Finishing and polishing an amalgam restoration, is considered as an important and necessary step of the restorative procedure. Various polishing techniques have been recommended to success a smooth amalgam surface. The aim of this study was to investigate the influence of three different polishing treatments on the marginal integrity and surface smoothness of restorations made of three commercially available amalgams and a glass-cermet cement. The materials used were the amalgams, Amalcap (Vivadent), Dispersalloy (Johnson and Johnson), Duralloy (Degussa) and the glass-cermet Katac-Silver (ESPE). The occlusal surfaces of the restorations were polished by the methods: I) round bur, No4-rubber cup-zinc oxide paste in a small brush, II) round bur No 4-bur-brown, green and super green (Shofu) polishing cups and points successively and III) amalgam polishing bur of 12-blades-smooth amalgam polishing bur. Photographs from unpolished and polished surfaces of the restorations, were taken with scanning electron microscope, to evaluate the polishing techniques. An improvement of marginal integrity and surface smoothness of all amalgam restorations was observed after the specimens had been polished with the three techniques. Method II, included Shofu polishers, proved the best results in comparison to the methods I and III. Polishing of glass-cermet cement was impossible with the examined techniques.

Cermet Cements↗