Light-polymerized Composite Resin Research Articles

A Comparative Evaluation of the Shear Bond Strength of Three Different Hybrid Tooth-Colored Restorative Materials to Dentin: An In-Vitro Study.

Silver amalgam, glass ionomer, resin-modified glass ionomer, compomers, light polymerized hybrid composite resin, and hybrid glass ionomer are among the most frequent restorative materials used as cavity-based or post-endodontics. Thus, to meet the needs of both patients and dentists, Cention N reimagines the traditional filling by integrating bulk placement, ion release, and durability into a dual-curing, aesthetically pleasing solution. Hoewver, we do not have enough information from studies comparing this hybrid restorative material's shear bond strengths to dentin to draw any firm conclusions. Cention N, zirconomer, and Vitremer are three hybrid tooth-colored restorative materials that were evaluated for their shear bond strength to dentin. This research aimed to compare and evaluate these materials. The purpose of this research was to use a universal Instron machine to measure the shear bond stress of three distinct hybrid tooth-colored restorative materials in relation to dentin.The research samples consisted of 45 extracted lower first premolars from humans.The teeth were then assigned into three groups of 15 samples each according to different color acrylic resin blocks, namely, group A (pink acrylic blocks), which had Cention in cement; group B (white acrylic blocks), which has zirconomer cement; and group C (violet acrylic blocks), which had Vitremer cement. There was no statistically significant difference between the three groups and the normal distribution, as shown by the negligible values in the tests involving the three groups. Put simply, each of the three categories exhibits data that follows a normal distribution. This allows for further data analysis to be conducted using the parametric test of significance. The shear bond strength of hybrid glass ionomer restorative materials has to be further investigated in both laboratory and living organism settings.

Color Stability of Provisional Restorative Materials - A Tabular Review

Temporary prosthodontic materials used for temporization for crown and bridges to protect the vital tooth or teeth from hypersensitivity. Most commonly used temporization materials are Polymethylmethacrylate (PMMA), Bis-acryl composite resin, Light polymerized composite resin, and CAD/CAM provisional restorative material. In this review we have made an attempt to discuss the advantages and disadvantages of temporary prosthetic materials in a tabular format.

In vitro comparative study between adhesion forces obtained on zirconia ceramic micromechanically treated with femtosecond laser (1027nm), carbon dioxide laser (10,600nm), and aluminum-oxide particles.

Conventional surface roughening treatments used for silica-based ceramics in order to improve subsequent adhesion become unreliable for zirconia ceramics. Laser conditioning can be a good alternative. The purpose of this in vitro study was to compare conventional (macro) shear bond strength (SBS) values obtained between resin composite and zirconium oxide ceramic samples grouped according to different micromechanical treatments received, and examine differences in surface roughness. One-hundred and fifty disks of sintered zirconia were randomly divided into 5 groups and roughened as follows: (1) Group NOT, no surface treatment; (2) Group APA, abraded with 50-μm aluminum-oxide (Al2O3) particles; (3) Group TBS, abraded with 30-μm aluminum-oxide particles covered with silica; (4) Group CO2, irradiated with a CO2 laser which emitted in continuous wave mode at 3 W of power; and (5) Group FEM, irradiated with a pulsed femtosecond laser, with an incident energy of 10μJ, a frequency of 1000Hz, and a fluence of 1.3kJ/cm2. All surfaces were treated with a MDP-containing adhesive/silane coupling agent mixture upon which were prepared and light polymerized composite resin cylinders. Shear bond strength was measured and samples were observed by scanning electron microscopy (SEM). Statistically significant differences (p < 0.05) were found among all groups, except between CO2 and FEM, which showed the highest adhesion values (15.12 ± 2.35MPa and 16.03 ± 2.73MPa). SEM revealed differences in surface patterns. CO2 laser irradiation can be an alternative to sandblasting, although it could also weaken the ceramic. Suitable surface patterns on zirconia ceramics can be obtained with ultrashort pulsed radiation emitted by a pulsed femtosecond laser.

Degree of conversion of light-polymerized composite resin in implant prosthesis screw access opening.

The mechanical and physical properties of implant screw access opening deteriorate if composite resin is not polymerized properly. Therefore, this study aimed to analyze the effect of using composite resin in implant access opening on the degree of conversion (DC). Two prosthetic materials (Co-Cr and zirconia), two types of composite resin (low and high viscosity), two light-cured resin depths (2 and 3mm), and two polymerization methods (max-mode 10s and mid-mode 20s: 16 and 22J/cm2 , respectively) were considered (n=192). The DC of the polymerized composite resin was measured through Fourier-transform infrared spectroscopy. The top and bottom surfaces of the polymerized composite resin body were observed through scanning electron microscopy. Multiple linear regression analysis and analysis of variance were used to identify significant differences in DC (α=0.05). The DC was lower when the low-viscosity composite resin (β=-0.431), light-polymerized resin depth of 2mm (β=-0.430), zirconia prosthesis (β=-0.191), and mid-mode polymerization method (β=-0.164) were used. The resin type, depth of resin to be light-cured, prosthesis material, and polymerization method had an effect on the DC. Low-viscosity composite resin should be polymerized at a low irradiance and long polymerization time (such that the light-cured resin depth does not exceed 2mm) to ensure proper composite resin polymerization in implant screw access opening.

Orthodontic wire loop for engaging dental floss or orthodontic elastomeric chain in the open tray implant impression technique

An accurate implant impression is essential for a successful implant restoration, with various impression techniques being suggested.1Kim J.H. Kim K.R. Kim S. Critical appraisal of implant impression accuracies: a systematic review.J Prosthet Dent. 2015; 114 (185-62)Abstract Full Text Full Text PDF Scopus (31) Google Scholar The open tray (pick-up) impression technique has been recommended over the closed tray impression technique for improved accuracy,2Izadi A. Heidari B. Roshanaei G. Allahbakhshi H. Fotovat F. Comparative study of dimensional accuracy in three dental implant impression techniques: open tray, closed tray with impression coping, and snap cap.J Contemp Dent Pract. 2018; 19: 974-981Crossref PubMed Scopus (6) Google Scholar although splinting the open tray impression copings is essential to prevent micromovement and for accurate 3D transfer of the implant locations to the definitive cast.3Branemark P.I. Zarb G.A. Albrektsson T. Tissue integrated prostheses: Osseointegration in clinical dentistry.1st ed. Quintessence Publishing Co, Chicago1985: 253Google Scholar Splinting can be achieved in various ways,3Branemark P.I. Zarb G.A. Albrektsson T. Tissue integrated prostheses: Osseointegration in clinical dentistry.1st ed. Quintessence Publishing Co, Chicago1985: 253Google Scholar,4Ivanhoe J.R. Adrian E.D. Krantz W.A. Edge M.J. An impression technique for osseointegrated implants.J Prosthet Dent. 1991; 66: 410-411Abstract Full Text PDF PubMed Scopus (38) Google Scholar including with dental floss and autopolymerizing resin or composite resin.4Ivanhoe J.R. Adrian E.D. Krantz W.A. Edge M.J. An impression technique for osseointegrated implants.J Prosthet Dent. 1991; 66: 410-411Abstract Full Text PDF PubMed Scopus (38) Google Scholar Placement of dental floss is cumbersome, and slippage may occur over the smooth surface of the impression coping.5Joshi A.A. Gaikwad A.M. Nadgere J.B. Ram S.M. Orthodontic elastomeric chain as an alternative to dental floss for splinting implant impression copings for complete-arch implant impressions.J Prosthet Dent. 2020; 123: 188-189Abstract Full Text Full Text PDF PubMed Scopus (4) Google Scholar Joshi et al5Joshi A.A. Gaikwad A.M. Nadgere J.B. Ram S.M. Orthodontic elastomeric chain as an alternative to dental floss for splinting implant impression copings for complete-arch implant impressions.J Prosthet Dent. 2020; 123: 188-189Abstract Full Text Full Text PDF PubMed Scopus (4) Google Scholar presented an alternative technique for splinting open tray impression copings by using orthodontic elastomeric chain and light-polymerizing composite resin. The purpose of the present article was to present a straightforward procedure for fabricating an orthodontic wire loop for engaging dental floss or orthodontic elastomeric chain in the implant impression. The orthodontic loops can be welded to the open tray impression copings by the dentist or added by the dental laboratory technician. 1.Remove the healing abutments (Healing abutment [AO]; Megagen) after satisfactory healing of the peri-implant soft tissue around the implants.2.Place pick-up (open tray) impression copings (Pick up coping [AO]; Megagen) with 10-Ncm torque and make a periapical radiograph to verify proper seating of the impression copings.3.Mark the future location of the orthodontic loops on the pick-up impression copings by using a permanent marker. The authors recommend placing the loops on the mesial and distal surfaces. Placement on the buccal and lingual surface may interfere with seating the tray and may cause tongue irritation. Remove the impression copings for the attachment of loops.4.Select 60-mm, 23-gauge orthodontic arch wire (S304 Stainless steel; G&H), make 8 to 10mm-diameter loops (Fig. 1A), and place them in the marked locations (Fig. 1B), with the ends of the wire extending away from each other.5.Wrap both ends of the orthodontic wire around the impression coping (Fig. 1C) and twist both ends of the wire to lock the loop in its place and cut excess (Fig. 1D).6.Place the impression copings with orthodontic wire loop (Fig. 2A) and attach orthodontic E chain or pass floss (Fig. 2B) through the loop. Stabilize the impression coping with autopolymerizing resin (Pattern resin; GC) (Fig. 2C) or bulk-fill flowable composite resin.Figure 2A, Intraoral placement of open tray impression coping with orthodontic wire loop. B, Dental floss engaged around orthodontic wire loop. C, Open tray impression copings stabilized with autopolymerizing resin.View Large Image Figure ViewerDownload Hi-res image Download (PPT)7.Inject low-viscosity impression material (Extreme Lite; Medicept) around the impression copings. Fill the stock tray with a high-viscosity impression material (Extreme putty; Medicept) and seat intraorally. The authors thank Dr Sabita M. Ram, Director Research, MGM Institute of Health Sciences, Navi Mumbai, and Dr Naisargi Shah, HOD, Department of Prosthodontic and Crown & Bridge, Terna dental college and hospital, Navi Mumbai, for the guidance and support. They also wish to convey a special thank you to Mr Satish karkhile, Lab technician, Department of Prosthodontics and Crown & Bridge, MGM Dental College and Hospital, Navi Mumbai, for all the laboratory support provided during the procedure.

Using modified polyetheretherketone (PEEK) as an alternative material for endocrown restorations: A short-term clinical report

A modified polyetheretherketone (PEEK) framework material veneered with indirect light-polymerized composite resin was used as an alternative material for the fabrication of an endocrown restoration for an extensively damaged molar. The elastic modulus of the polyetheretherketone framework (4 GPa) veneered with indirect composite resin could dampen the occlusal forces protecting tooth structures better than ceramic materials. This is important in the restoration of extensively damaged molars with weak roots. Long-term clinical evidence is required before recommending the application as a substitute material.

Compatibility between dental adhesive systems and dual-polymerizing composite resins

Statement of problemInformation is lacking about incompatibilities between certain types of adhesive systems and dual-polymerizing composite resins, and universal adhesives have yet to be tested with these resins. PurposeThe purpose of this in vitro study was to investigate the bonding outcome of dual-polymerizing foundation composite resins by using different categories of adhesive solutions and to determine whether incompatibilities were present. Material and methodsOne hundred and eighty caries-free, extracted third molar teeth were allocated to 9 groups (n=20), in which 3 different bonding agents (Single Bond Plus [SB]), Scotchbond Multi-purpose [MP], and Scotchbond Universal [SU]) were used to bond 3 different composite resins (CompCore AF [CC], Core Paste XP [CP], and Filtek Supreme Ultra [FS]). After restorations had been fabricated using an Ultradent device, the specimens were stored in water at 37°C for 24 hours. The specimens were tested under shear force at a rate of 0.5 mm/min. The data were analyzed with Kruskal-Wallis tests and post hoc pairwise comparisons (α=.05). ResultsAll 3 composite resins produced comparable shear bond strengths when used with MP (P=.076). However, when either SB or SU was used, the light-polymerized composite resin (FS) and 1 dual-polymerized foundation composite resin (CC) bonded significantly better than the other dual-polymerized foundation composite resin (CP) (P<.005). Both FS and CC performed best with SU but had acceptable results with all of the bonding agents. CP only performed acceptably with MP (P=.023) and had poor results with both other agents. ConclusionsDual-polymerizing composite resins can obtain equally good bond strengths as light-polymerizing alternatives. However, not all dual-polymerizing composite resins perform well with all bonding systems; some incompatibilities exist between different products.

An In Vitro study of Fracture Resistance of Weakened Tooth Roots Reinforced with Two Types of Adhesive Restorative Materials

Introduction: Composite resin (CR) is among the commonly used material for intraradicular reinforcement of weakened tooth roots. Purpose: This study was to compare the fracture resistance of experimentally weakened tooth roots reinforced using auto-polymerized composite resin and light-polymerized composite resin. Materials and Methods: Fifty-six extracted human maxillary incisors were divided into 2 groups (n = 28) and the root canals were over prepared to weaken it. The samples in Group Awere restored using lightcured CR Z100 and light-transmitting polymerizing post (Luminex), whereas Group B using auto-cured CR Alpha-dent. Both groups were placed with metal parapost cemented with a resin luting cement (Nexus 2). Specimens were subjected to compressive load (N) using Instron machine until fracture. Data were submitted to independent t test analysis of variance (p &lt; 0.05). Results: There was no significant difference (p = 0.233) in fracture resistance between the teeth reinforced with light-polymerizing and auto-polymerizing CR are 549.3 (± 95.44) and 490.7 (± 110.37) respectively. Conclusion: The use of less technique sensitive autopolymerizing CR give equivalent benefit effect on reinforcing weakened roots, as the more commonly lightpolymerized composite resin. DOI: http://dx.doi.org/10.3329/bjms.v12i1.13353 Bangladesh Journal of Medical Science Vol. 12 No. 01 January’13 pp.63-67

An In Vitro Evaluation of Flexural Strength of Two Provisional Restorative Materials Light Polymerised Resin And Autopolymerised Resin.

Statement of problem: Flexural strength is important in determining the strength of interim restorations and it is especially important in long span and long term interim restorations. Studies comparing the flexural strength of provisional restorative materials are limited and inconclusive. Aim: To compare the flexural strength of provisional restorative material fabricated using light polymerized composite resin, Urethane dimethacrylate (UDMA) and auto polymerized resin, Poly Methyl Methacrylate (PMMA) Materials And Methods: This study included 40 specimens. Twenty bar-shaped specimens were fabricated for each group Polymethyl Methacrylate (PMMA), and Urethane dimethacrylate (UDMA) with the use of a split machined metal mold. These specimens were stored in artificial saliva for 10 days. Flexural strength was calculated using three point bending test under universal testing machine. Data were analysed using student-ttest (α=0.05) @ 90% power. Results: The mean flexural strength of provisional restorative specimen fabricated using Poly Methyl Methacrylate (PMMA-134.1 Mpa) was significantly higher than Flexural strength of provisional restorative specimen fabricated using urethane dimethacrylate (UDMA-107.8 Mpa). Conclusion: Within the limitations of this study by analyzing the results, it was concluded that the flexural strength of polymethyl methacrylate (PMMA) is comparatively better than the flexural strength of Urethane dimethacrylate (UDMA). PMMA could be a better provisional restorative material for an extended period, when the patient exhibits parafunctional habits, or when long-span prosthesis is planned.

Influence of Dynamic Loading and Different Adhesive Systems on the Microleakage in Root Canals

The objective of this study was to evaluate the influence of dynamic loading and different adhesive systems on the microleakage in root canals. 80 human premolars were used in this study. The crowns of the teeth were sectioned at the cemento-enamel junction using a low speed diamond saw. After post space preparation, the roots were randomly assigned to 4 groups (n = 20) and restored with different adhesive systems. Group 1: Rely X ARC (RA) + Single Bond (SA), Group 2: Clearfil SA Cement (CL), Group 3: Panavia F 2.0 (PAN), Group 4: Rely X Unicem (RU). All the teeth were restored with the same type of glass fiber post and coronal cores built up with light-polymerizing hybrid composite resin. Half of the specimens of each group (n = 10) were subjected to additional dynamic loading in a universal testing machine. Apical parts of the roots were attached to computerized fluid filtration device for leakage measurement. The two-way ANOVA test was used first to detect overall significance, followed by two-sample t-test to identify which pairs of groups had significant differences. For each outcome statistical significance was set at p < 0.05. Dynamic loading significantly increased the microleakage values for Rely X ARC (p = 0.005), Clearfil SA Cement (p = 0.002) and Rely X Unicem groups (p = 0.001) but Panavia F 2.0 group was not affected by the dynamic loading (p = 0.111). One-way ANOVA test was applied to detect any significant differences in microleakage values for the adhesive systems. In the unloaded groups, there is no difference between the adhesive systems (p = 0.13). For the dynamically loaded groups, there is only significant difference between PAN and RA groups (p = 0.010). Post-hoc pairwise comparisons were done using Tukey’s multiple comparisons. Differences between Rely X ARC-Clearfil SA Cement and Rely X ARC-Panavia F 2.0 are statistically significant (p = 0.009, 0.013).

Use of transparent vinyl polysiloxane in a minimally invasive approach for creating composite resin undercuts for partial removable dental prostheses

A technique using a transparent vinyl polysiloxane material developed for use with light-polymerized composite resin and that does not require a lubricant is presented for creating composite resin undercuts for partial removable dental prosthesis clasps. With a surveyor, the undercut is waxed on the diagnostic cast according to the intended path of insertion. The transparent vinyl polysiloxane is used to fabricate a template for the undercut. The template is used intraorally to create the undercut in composite resin on the abutment tooth.

Effect of substrate shades on the color of ceramic laminate veneers

Ceramic laminate veneers are generally fabricated with varying thicknesses ranging from 0.3 to 1 mm, depending on the need to mask discolored teeth or slightly correct the contour of malpositioned teeth. Clinical color reproduction poses a challenge because of color interaction with the underlying substrate, whether tooth structure or esthetic restorative material. The purpose of this in vitro investigation was to measure the effect of color change resulting from applying 2 shades of ceramic material, translucent (T1) and opaque (O2), to 2 shades of composite resin substrate material, light (A3) and dark (C4), on the overall color of ceramic laminates. Forty disks were fabricated. Twenty disks (15 × 0.5 mm) were cut from pressed ceramic, 10 disks for each shade (translucent and opaque). Additionally, 20 disks (15 × 4.0 mm) were fabricated from light-polymerized composite resin material, 10 disks for each shade (light and dark). The ceramic disks were bonded to the composite resin disks with clear resin cement. The specimen combinations were divided into 4 groups (n=5). Color measurements were done with a colorimeter (Minolta Chroma Meter CR-200b) configured with diffuse illumination/0-degree viewing geometry. Mean CIE lightness (L*), chroma (C*(ab)), and hue angle (h(ab)) values were obtained. A 2-way analysis of variance (ANOVA) was used to compare the means and standard deviations between the different color combinations (α=.05), followed by Tukey's HSD post hoc test for significant interactions. The 2-way ANOVA showed significant differences (P<.001) in L*, C*(ab), and h(ab) for a change in the composite resin substrate, regardless of the ceramic material shade. There was significant color change from dark to light substrate (P=.044). The mean h(ab) (SD) of dark substrate/opaque veneer was 89.62 (1.5), while the mean h(ab) of light substrate/translucent veneer was 81.23 (1.7). Within the limitations of this study, the selected color of a 0.5 mm ceramic laminate veneer was significantly affected by the change in color of the supporting substrate.

Evaluation of the effect of various beverages and food material on the color stability of provisional materials - An in vitro study

Aim:This study evaluated the color stability of four provisional materials: 1) Poly-methyl methacrylates (DPI); 2) Bis-acryl composite (ProtempTM II – 3M ESPE); 3) Bis-acryl composite (Systemp® c and b – Ivoclar Vivadent) and 4) Light polymerized composite resin (Revotek LC- GC).Materials and Methods:The color and color difference of each specimen after immersion in different staining solutions i.e. 1) tea and artificial saliva, 2) coffee and artificial saliva, 3) Pepsi and artificial saliva, 4) turmeric solution and artificial saliva was measured using reflectance spectrophotometer with CIELAB system before immersion and after immersion at 2, 5 ,7 , 10 and 15 days.Results:Revotek LC- GC (light polymerized composite resin) was found to be the most color stable provisional restorative material followed by Protemp II (Bis-acryl composite), Systemp (Bis-acryl composite) and DPI (Methylmethacrylate resin). Turmeric solution had the maximum staining potential followed by coffee, tea and Pepsi.

A nine-year clinical case study of a resin-bonded fixed partial denture seated on the maxillary anterior teeth

This report describes the longevity of a resin-bonded fixed partial denture (RBFPD). This denture was seated on the maxillary anterior teeth with minimal tooth preparation. The RBFPD was cast from a silver-palladium alloy (Castwell M.C. 12), and the pontic was veneered with an indirect composite material (Estenia). The retainers were primed with a metal conditioner (V-Primer) and seated with a tri-n-butylborane initiated adhesive resin (Super-Bond C&B). After an observation period of eight years, a fracture occurred in the incisal edge of the central incisor abutment. The fractured area was restored with light-polymerizing composite resin and the anterior guidance was re-adjusted. RBFPD abutment teeth with deep vertical overlap should be carefully prepared to avoid abutment tooth fracture. The clinical performance of the RBFPD made from a silver-palladium-copper-gold alloy was sufficient when seated with tri-n-butylborane initiated adhesive resin after surface modification using vinyl-thiol primer. The use of vinyl-thiol primer and tri-n-butylborane initiated adhesive resin is a clinically reliable bonding system for seating resin-bonded fixed partial denture (RBFPD) made from a silver-palladium-copper-gold alloy. The RBFPD, based on a reliable bonding system, can clinically function for a long time, even if the vertical overlap of the abutment teeth is excessive.

The effect of water storage, elapsed time and contaminants on the bond strength and interfacial polymerization of a nanohybrid composite.

To systematically characterize the effect of time lapse, water storage, and selected contaminants on the bond strength of a nanofilled dental composite. Half-dumbbell-shaped samples were fabricated out of light-polymerizing composite resin. To function as substrates they were aged for 30 days in water. Prior to bonding, the substrates' surfaces were subjected to the following treatments: 1) Removing a 0.2- to 0.4-mm layer using a fluted carbide bur; 2) grit blasting with 50 microm alumina particles; 3) etching with phosphoric acid gel; 4) grit blasting followed by etching; 5) blasting with tribochemical particles followed by silane application; 6) sanding with 400-grit paper, air aging of the adherent half-sample before bonding; 7) surface contamination with saliva; 8) surface contamination with blood. In each group (n = 30), freshly polymerized (except in group 6) adherent half-samples were bonded to the substrate half-samples by a layer of unfilled adhesive resin. Fifteen full dumbbell-shaped specimens were subjected to tensile testing after 1 h and 15 after 7 days water storage. In a positive control group, freshly cured half-samples were bonded shortly after fabrication. The tensile strength was analyzed using Weibull statistics and presented in terms of the material's characteristic strength and shape parameter. Fractographs of the two weakest and strongest samples of each group were produced. The surfaces were searched to locate hackle, wake hackle and the origin of the fracture. Surface roughness and time lapse increased the bond strength of the repaired specimens. All groups in which surface roughness was produced before bonding increased in repair strength. Post-bonding aging improved strength. Fractographs yielded interpretable data whenever larger surfaces of single phase bonding resin were present. 1) Roughening and etching an aged composite's surface prior to applying a coat of unfilled resin and the filled material increases repair bond strength by up to 100%. 2) The repair bond strength of a roughened aged composite is 25% to 30% inferior to the tensile strength of solid specimens. 3) After 7 days' storage in water, no detrimental effect could be seen from saliva or blood contamination if the surfaces were properly rinsed.

Microleakage and fracture patterns of teeth restored with different posts under dynamic loading

Many studies concerned with the microleakage of endodontically treated teeth restored with posts and cores and subjected to loading can be found in the literature. However, no studies have investigated microleakage under dynamic loading with simultaneous dye penetration, which is more relevant to clinical situations. The purpose of this study was to compare microleakage and to classify fracture patterns of endodontically treated teeth restored with various post systems under dynamic loading. The crown portions of 40 human mandibular incisors were sectioned at the cementoenamel junction, and the teeth were endodontically treated. Teeth were divided into 4 groups (n=10): teeth restored with a cast post and core, prefabricated metal post (ParaPost), fiber-reinforced composite resin post (FRC Postec), and ceramic post (Cosmopost). After preparing the post space, each post was cemented with dual-polymerized resin cement (DuoLink). With the exception of the cast post-and-core group, the cores were formed directly using a light-polymerized composite resin (Light-Core). An intermittent load of 98 N at 1 Hz was applied for 50,000 cycles at an angle of 135 degrees to the long axis of the restored teeth, which were immersed in a 0.5% basic fuchsin solution. The ratio of the dyed surface area to the total area of the sectioned root surface was determined using an image analysis program. The data were analyzed by a 1-way ANOVA and Duncan's multiple range test (alpha =.05). The fracture patterns of the teeth were classified according to their fracture propagation lines. The cast post group showed a significantly higher level of microleakage compared to the other groups (P=.001). Regarding the failure mode, the FRC Postec and Cosmopost groups showed fracture patterns that would favor retreatment. The number of cycles of repeated loading was not significantly different among the groups (P=.161). Both FRC Postec and Cosmopost groups showed less microleakage under dynamic loading and fracture patterns favoring a retreatment of fractured specimens.

Influence of post-etching cleaning and connecting porcelain on the microtensile bond strength of composite resin to feldspathic porcelain

There are different methods to fabricate layered feldspathic porcelain restorations, including the refractory die technique and the hot-press technique. Standard adhesive protocol for such restorations requires etching and silanating the fitting surface of the porcelain. Variations in bond strength between porcelain and composite resin might result from the different fabrication methods for porcelain restorations. The purpose of this study was to determine differences in microtensile bond strength between composite resin (used as a luting agent) and feldspathic porcelain generated from the refractory die technique using 2 different connecting porcelains and the hot-press technique. The effect of post-etching cleaning was also investigated. Sixteen pairs of ceramic blocks (7 x 8 x 4 mm) were fabricated. Eight pairs were fabricated using feldspathic porcelain (D-B4) on refractory dies. For 4 pairs, the refractory dies were coated with a paste (Ducera Lay Connector Paste; group CON) as a connecting porcelain, and the other 4 pairs were coated with a clear translucent porcelain (CL-O; group CLO). Another 8 block pairs were fabricated using the hot-press technique (Authentic porcelain SL B00+; groups AUTH and AUTH-N). Surface conditioning of the ceramic blocks included airborne-particle abrasion followed by hydrofluoric acid etching (all groups), and post-etching cleaning with a brush/H3PO4 and ultrasonic bath immersion (cleaning not applied to group AUTH-N). All specimens were then silanated/heat dried, and blocks of the same porcelain were bonded to each other using an adhesive resin (Optibond FL) and a light-polymerizing composite resin (Z100). Specimens were stored in water for 24 hours. A nontrimming microtensile bond strength test was applied. Ten beams (0.9 x 0.9 x 8 mm) from each pair of blocks were selected for testing. Bond strength data (MPa) were analyzed with a Kruskal-Wallis test, and post hoc comparison was done using the Mann-Whitney U test (alpha = .05). Additional specimens (1 block per group) were also evaluated for the effect of conditioning steps and mode of fracture using optical microscopy and scanning electron microscopy (SEM) analysis. The mean microtensile bond strengths of CLO and AUTH groups were not significantly different from one another at 46.3 and 49.7 MPa, respectively. For both CON and AUTH-N groups, the mean bond strengths at 37.9 MPa and 24.1 MPa, respectively, were significantly different (P < .05) from the other 3 groups. Optical microscopy revealed a significant amount of white residue for all groups as a result of hydrofluoric etching. Cleaning with a microbrush and 37.5% phosphoric acid for 1 minute resulted in the removal of the crystalline debris. The SEM analysis of specimens cleaned by phosphoric acid brushing alone revealed microscopic deposits still contaminating the etched surface; those were efficiently removed after ultrasonic cleaning. The SEM analysis of fractured beams demonstrated a trend for more mixed-type failure in CON and AUTH-N specimens involving both the composite resin and the surface of the porcelain, whereas CLO and AUTH fractured surfaces were primarily confined to the composite resin. Increased resin bond strength to refractory-generated porcelain is obtained with CLO as the connecting porcelain compared to the CON paste. The AUTH porcelain exhibited the highest mean bond strength, but omission of post-etching cleaning resulted in the lowest bond strength.

A comparison of two solder registration materials: A three-dimensional analysis

Use of a segmental indexing/soldering approach for assembly of complete arch implant frameworks has been advocated by some clinicians to achieve a passively fitting framework. To the authors' knowledge, a mathematical assessment using a 3-dimensional (3-D) distortion analysis has not been performed comparing segmental framework assembly to reassembly of 1-piece complete arch frameworks that required sectioning, indexing, and soldering. The present study compared the use of 2 indexing materials, autopolymerizing acrylic resin and light-polymerized composite resin, for use in solder registration of complete-arch implant frameworks using 3 framework/indexing material combinations: gold/light-polymerized composite resin, silver palladium/autopolymerizing acrylic resin, and silver palladium/light-polymerized composite resin. Five frameworks for each alloy/index combination were fabricated, for a total of 15 frameworks. Each framework was fitted to 5 implant abutments. Measurements were made of the initial gold cylinder/abutment positions for each of the 5 sites for the 15 frameworks. The 3-D spatial orientation of each gold cylinder/abutment was calculated prior to the gold cylinders being incorporated into the framework casting and served as the control against which all measurements were compared. After the indexing/soldering procedures, the 3-D spatial orientations of the cylinders were measured, first as 2- and 3-unit solder assembled framework segments and, finally, for complete-arch frameworks. These measurements were recorded in micrometers for linear distortions and degrees for angular distortions using a coordinate measurement machine (CMM). These data were compared and statistically assessed using a 1-way analysis of variance (ANOVA). A Student-Newman-Keuls test was used to determine significance between cylinders within each indexing combination. A repeated-measures ANOVA and a Student-Newman-Keuls test were used to determine significance between alloy/index group and cylinders for each of the measurement variables with statistical significance at alpha=.05 for all statistical analyses. Mean differences and SDs of total linear change for all groups found dR (total linear change) to be 33.56 +/- 27.70 mum for gold/light-polymerized composite resin, 34.87 +/- 27.99 mum for silver palladium/autopolymerizing acrylic resin, and 31.56 +/- 24.37 mum for silver palladium/light-polymerized composite resin. Total angular change, dtheta(R), was calculated to be 0.47 +/- 0.13 degrees for gold/light-polymerized composite resin, 0.46 +/- 0.17 degrees for silver palladium/autopolymerizing acrylic resin, and 0.52 +/- 0.15 degrees for silver palladium/light-polymerizing composite resin. No significant differences were found between alloy/index combinations, except for the measured variable dtheta(y), angular change about the Y axis.

A comparative study to evaluate the marginal accuracy of provisional restorations fabricated by light polymerized resin and autopolymerized resin: A scanning electron microscope study

Background and Objectives: To compare the vertical marginal discrepancy of provisional restorations fabricated using light polymerized composite resin by direct technique and provisional restorations fabricated using auto polymerized resin by direct and indirect technique. Materials and Methods: A total of 45 provisional restorations were fabricated, 15- fabricated by using autopolymerized resin by direct technique on the metal dies and15- fabricated by indirect technique on stone dies. 15 - fabricated using light cured composite resin by direct technique on metal dies. Marginal discrepancies were calculated using scanning electron microscope (SEM). The restorations were then cemented using non-eugenol temporary cement and subjected to SEM analysis. Results: Vertical marginal discrepancy of the provisional restorations fabricated using light cured composite resin by direct technique was least when compared to the vertical marginal discrepancy of the provisional restorations fabricated using autopolymerized resin by direct and indirect technique. Among the restorations fabricated using autopolymerized resin, marginal discrepancy observed with the indirect technique was less compared to the marginal discrepancy observed with direct technique. Conclusion: The vertical marginal discrepancy of the provisional restorations fabricated using light cured composite resins by direct technique was least and had a better marginal fit compared to the provisional restorations fabricated using autopolymerized resin by direct and indirect technique. The light cured resin could be a better material used to fabricate provisional restoration with an improved marginal adaptation.

Caries-Preventive Effect of a One-Time Application of Composite Resin and Glass Ionomer Sealants after 5 Years

The aim of the present trial was to (1) compare the caries-preventive effect of glass ionomer sealants, placed according to the atraumatic restorative treatment (ART) procedure, with composite resin sealants over time and (2) investigate the caries-preventive effect after complete disappearance of sealant material. Forty-six boys and 57 girls, mean age 7.8 years, were randomly divided into two treatment groups in a parallel-group study design. A light-polymerized composite resin sealant material and a high-viscosity glass ionomer were each placed in 180 fully erupted first molars in their respective treatment groups. Evaluation took place annually for 5 years by calibrated examiners. After 5 years, 86% composite resin and 88% glass ionomer sealants did not survive. Three categories of re-exposure periods for caries development in pits and fissures after complete loss of sealants were distinguished: 0–1, 1–2 and 2–3 years. In the 2- to 3-year group, 13 and 3% of pits and fissures previously sealed with composite resin and glass ionomer, respectively, were diagnosed as having developed a dentine lesion. The relative risks (95% CI) of dentine lesion development in surfaces sealed with glass ionomer compared to those sealed with composite resin after 3, 4 and 5 years were 0.22 (0.06–0.82), 0.32 (0.14–0.73) and 0.28 (0.13–0.61), respectively. The relative risks of dentine lesion development in pits and fissures previously sealed with glass ionomer compared with composite resin over re-exposure periods of 1–2 and 2–3 years were 0.26 (0.14–0.48) and 0.25 (0.09–0.68), respectively. We conclude that the caries-preventive effect of high-viscosity glass ionomer sealants, placed using the ART procedure, was between 3.1 and 4.5 times higher than that of composite resin sealants after 3–5 years. Furthermore, high-viscosity (ART) glass ionomer sealants appear to have a four times higher chance of preventing caries development in re-exposed pits and fissures of occlusal surfaces in first molars than light-cured composite resin sealant material over a 1- to 3-year period. A well-designed clinical trial using different types of oral health personnel should be implemented to confirm these initial results.