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[Theoretical and clinical prerequisites for the use of fragments of molar roots as abutment for dentures].

Experimental and clinical studies confirmed the possibility of using fragments of a multi-root tooth as abutment tooth for a bridge denture. When planning orthodontic treatment, choosing the abutment teeth, designing the denture, and treating the patient the orthodontist should be able to use the information on the maximum allowable loading of the fragments of resected teeth. A positive factor in utilization of the remaining tooth fragment is the ratio of clinical crown and root length, which should be inversely proportional. The study showed that retention of the morphofunctional integrity of dentition is possible when using dentures ensuring the optimum regulation stress (no higher than physiologically tolerable) in abutment tissues. Analysis of remote clinical and X-ray data showed normalization of the periodontal function of tooth fragments after tooth-sparing operations in cases when the patients were fitted with prostheses with consideration for theoretically valid methods for estimation of reserve force.

Adolescent↗

Restoring anterior maxillary dentition using alumina- and zirconia-based CAD/CAM restorations.

Despite proven strength, durability, and improved esthetics, ceramometal restorations have not consistently enabled the most esthetic, lifelike reproduction of natural dentition. Also, inherent weaknesses in many metal-free materials have precluded their use in the high stress-bearing posterior region. Therefore, as a result of the need for esthetic and durable all-ceramic restorations, manufacturers have introduced ceramics with an increased alumina or zirconia content that are recommended for placement anywhere in the mouth for single units and as far back as the first premolar.

Aluminum Oxide↗

The effects of cavity preparation and lamination on bond strength and fracture of tooth-colored restorations in primary molars.

PURPOSE: This in vitro study compared bond strength and fracture modes of tooth-colored restorations in 2 types of cavity preparations in human primary molars. METHODS: Standardized Class II cavities (40 dovetail and 40 box-only preparations) in extracted human primary molars were restored with packable composite resin (PC), resin-modified glass ionomer cement (RMGIC), resin-modified glass ionomer/packable composite resin laminate (RMGIC/PC), or resin-modified glass ionomer/packable composite resin laminate with an experimental bonding agent, K-14 (RMGIC/K-14/PC). The ultimate load at fracture was measured on marginal ridges, and fractured surfaces were examined microscopically. RESULTS: The mean (+/-SD) ultimate load at fracture (ULF, in Newtons) of PC and RMGIC/K-14/PC in box-only preparations (400+/-98; 386+/-82) did not differ significantly from that found in dovetail preparations (377+/-80; 317+/-92), and the mean ULF of RMGIC and RMGIC/PC in box-only preparations (307+/-44; 325+/-72) did not differ significantly from that in dovetail preparations (352+/-71; 353+/-70). No interactions were seen between materials and preparations (P=.09). Fracture modes for restorations in dovetail (predominantly mixed) and box-only preparations (predominantly mixed and adhesive) differed significantly (P=.003), but not between restorative procedures (P=.052). CONCLUSIONS: Tooth-colored restorations placed in vitro in box-only preparations did not differ in fracture resistance from those placed in dovetail preparations. On fracture loading, resin-modified glass ionomer restorations placed in box-only preparations were more likely to show adhesive failure than those placed in dovetail preparations.

Analysis of Variance↗

Reducing microleakage in composite resin restorations: an in vitro study.

The purpose of this in vitro study was to evaluate the effect of a resin lining on microleakage around composite resin restorations. Standard slot cavities were prepared on the approximal surfaces of 48 extracted human molar teeth. The cavities were restored with two conventional or two condensable composite resins, placed with or without a flowable composite resin lining. The teeth were subjected to thermal stress and immersed in dye solution. Dye penetration was viewed with both a stereomicroscope and a scanning electron microscope. Flowable resin lining material under condensable composites may be beneficial in reducing microleakage around cervical margins.

Composite Resins↗

Bonding to worn or fractured incisal edges: shear bond strength of new adhesive systems.

OBJECTIVES: Resin composites can be proposed for the restoration of incisal edges. If a progressive wear or an old fracture is responsible for the loss of the incisal edge, the bonding substrate is likely to be sclerotic dentin, surrounded by enamel. The purpose of the study was to measure under laboratory conditions, the shear bond strength of three adhesive systems to the enamel and dentin exposed on the edge of incisors as a result of a long-time wear or an old fracture. METHOD AND MATERIALS: Thirty extracted human incisors were selected. The teeth had to exhibit some exposed dentin on their edges, a result of old fractures or wear. The 30 specimens were randomly divided into three groups. In each group, a different adhesive system was tested for the ability to efficiently bond a resin composite restoration to the dental substrate. A three-step system (Scotchbond Multipurpose Plus), a one-bottle adhesive (Scotchbond 1), and a self-etching adhesive (Prompt-L-Pop) were compared. The shear bond strength of the restored samples was measured under a loading machine. The pattern of failure that each sample underwent as a result of loading was assessed under a stereomicroscope. RESULTS: The highest values of bond strength were yielded by Scotchbond Multipurpose Plus (28.14 MPa), followed by Scotchbond 1 (16.15 MPa), and Prompt-L-Pop (9.26 MPa). These differences were statistically significant (P < .05). The most frequent pattern of failure was the combined adhesive-cohesive in resin fracture. CONCLUSION: Adhesive systems involving phosphoric acid etching of the substrate were more dependable than a self-etch adhesive when bonding a resin composite restoration to worn or fractured incisal edges.

Acid Etching, Dental↗

Shear bond strengths and microleakage of four types of dentin adhesive materials.

The aim of this investigation was to compare the microleakage of composite resin (Z-100) and shear bond strength to bovine dentin using different types of adhesive systems (Scotch Bond Multi-Purpose, All-Bond 2, One-Step, and Perma Quick) to compare and correlate microleakage to shear bond strength. For the microleakage aspect of the study, 20 class V were prepared (bovine incisors) with 90-degree cavosurface margins and were located at the cemento-enamel junction using a template. Each dentin bonding system was applied to five cavities following the manufacturer's instructions and restored with Z-100 composite resin. After 24 hours of storage in distilled water at 37 degrees C, the teeth were immersed in 2% basic fuchsin dye. All teeth were sectioned in a mesiodistal direction using a diamond saw, and each section was then inspected under a stereomacroscope. For the shear bond strength aspect of the study, 20 bovine incisors were centrally horizontally mounted in Teflon mold with cold cure acrylic resin. Flat labial dentin surfaces were prepared using different grit silicon carbide abrasive wheels. Five specimens were used for each of the bonding agent systems. Each specimen was bonded with restorative composite resin (Z-100) and applied to the treated dentinal surface through a split Teflon mold. All specimens were stored in distilled water at 37 degrees C for 24 hours. The bonds were stressed using shear forces at a crosshead speed of 0.5mm/min using an Instron Universal testing machine. Findings indicate none of the systems tested in this study were free from microleakage. Scotch bond multi-purpose achieved the best seal, with One-Step being second best, while All-Bond 2 and Perma Quick had the poorest seal. However, there were significant differences among the shear bond strengths of the four bonding systems tested. Scotch Bond Multi-Purpose has a higher bond strength to composite resin when compared to the other dentin adhesives. The study also concluded there is no association between microleakage and shear bond strength.

Analysis of Variance↗

Influence of new light curing units and bonding agents on the microleakage of Class V composite resin restorations.

PURPOSE: To evaluate the influence of four light curing units on the stress induced by polymerization of two dentin bonding systems and a composite resin. METHODS: Standardized kidney-shaped Class V cavities were prepared on the buccal and lingual surfaces at approximately 1 mm below the cemento-enamel junction (2 mm deep, 6-7 mm wide and 2 mm high). Two dentin bonding systems (DBS), Single Bond (SB), Optibond Solo Plus (OS+), and four light curing units (LCU): Astralis 7 (mode HIP 40 seconds), Elipar Highlight (soft start polymerization 40 seconds), GC e Light (8 mm tip) (fast cure of 12 seconds), and Optilux 501 (turbo tip) (fast cure of 10 seconds) were tested. The preparations were restored using the same microfilled composite (Filtek A110, shade A3). The teeth were thermocycled, immersed in a dye solution and sectioned. The enamel failures and the occlusal and cervical dentin microleakages were measured. RESULTS: No enamel and occlusal dentin microleakage was found. Concerning cervical dentin microleakage, with Single Bond, no significant difference was noted for all the light curing units (P< 0.05). With OptiBond Solo Plus, the filled adhesive, only two, the LCU Elipar and GC e Light, presented no statistical difference when all of the others exhibited statistical differences among themselves. The light intensity, the exposure duration, and the light source of the LCU are important parameters. When comparing the influence of the dentin adhesive, OS+ presented results significantly greater than SB, depending upon which lights were used. The Optilux 501 showed no significant difference. To act as a shock absorber, the adhesive needs to have time to compensate for the polymerization shrinkage.

Bisphenol A-Glycidyl Methacrylate↗

Linear displacement and force induced by polymerization shrinkage of resin-based restorative materials.

PURPOSE: To measure the linear displacement and force induced by polymerization shrinkage of a series of resin-based restorative materials. METHODS: The materials tested were 10 ultrafine midway-filled resin-based composites, mainly used in anterior restorations (Brilliant Dentin, Brilliant Enamel, Charisma F, Pertac II Aplitip, Prodigy, Resulcin, Sculpt-it, Synergy Duo, Tetric and Z100), 11 ultrafine compact-filled composites, suggested by the manufacturers as "amalgam substitutes" for posterior restorations (Alert, Ariston pHc, Definite, EXI-119, EXI-120, Nulite F, Prodigy Condensed, Prodigy High Viscosity, Solotaire, Surefil and Synergy Compact), and six polyacid-modified composites (Compoglass, Dyract, Dyract AP, Elan, F2000 and Hytac Aplitip), also known as compomers. Each property was measured for 180 seconds from the start of curing with the help of custom made devices in eight specimens for each material. Statistical evaluation of the data was performed with one-way ANOVA, Tukey's Studentized Range (HSD) Test (P= 0.05) and simple linear regression. RESULTS: Statistically significant differences among groups and among composites were found for both of the properties that were studied. The ultrafine compact-filled composites (amalgam substitutes) exhibited the least linear displacement, followed by the polyacid-modified composites (compomers) and the ultrafine midway-filled composites, with statistically significant differences among all groups. The groups followed the same order in the polymerization force, with only the compomer-amalgam substitute comparison not being statistically significantly different. The simple linear regression showed that the two studied properties were also highly correlated (r=0.89).

Analysis of Variance↗

Composite resin veneers: a new technique.

A new technique for the fabrication of composite resin direct veneers is presented. In this technique, a transparent acrylic resin matrix is fabricated before preparation of the facial surface of the tooth, to allow the adequate reproduction of contour, shape, and surface texture originally exhibited by the tooth. Advantages, as well as limitations, of the procedure are also presented.

Acrylic Resins↗

Effect of thermal and mechanical load cycling on microtensile bond strength of a total-etch adhesive system.

To evaluate the effect of thermal and mechanical cycles on dentin bond strength to cervical margins of Class II restorations, 80 box-type Class II cavities were prepared on the surfaces of bovine incisors. The cavities were restored with Single Bond (3M-ESPE) and Z-250 composite (3M-ESPE) according to manufacturer's instructions. The incisors were divided into four groups: G1-Control, G2- Thermal cycling (2,000 cycles, 5 degrees C-55 degrees C), G3- Mechanical cycling (100,000 cycles; 50N) and G4- Thermal and mechanical cycling (2,000 cycles 5 degrees C-55 degrees C/100,000 cycles; 50N). The restorations were sectioned perpendicular to the cervical bonded interface into 0.7 +/- 0.2 mm-thick slabs. The slabs were further trimmed at the interface to 1.4 +/- 0.2 mm with a fine diamond bur to produce a cross-sectional surface area of 1 mm2. All specimens were then subjected to microtensile bond testing. Means and standard deviations were expressed in MPa. The bond strength data were analyzed by one-way ANOVA and Fisher's PLSD test (p<0.05). Fracture mode analysis was performed using SEM. Bond strengths were significantly lower when thermal and mechanical cycling were performed [G4-2.41 (8.57)] when compared to the other groups [G1-28.15 (14.03); G2-27.60 (10.14); G3-27.59 (8.67)]. No differences were observed among Groups 1, 2 and 3. Interfacial fracture of the control (G1) and thermocycling (G2) groups mainly occurred between the deepest portion of the adhesive resin and the top layer of the demineralized dentin (Interphase). Mixed failure was predominant and increased when mechanical cycling was applied (G3 and G4).

Acid Etching, Dental↗

Volumetric polymerisation shrinkage of different dental restorative materials.

STATEMENT OF PROBLEM: Polymerisation shrinkage is a critical limitation of dental resins and may contribute to micro leakage. PURPOSE: The purpose of this study is to record and compare volumetric changes of various dental composites and compomers, exposed for 40 seconds to a commercial halogen light source. MATERIAL AND METHODS: Eleven light-polymerised composites and compomers were evaluated using a dilatometer that recorded the polymerisation shrinkage every 0.5 second. The mercury column pressure was measured electronically with a pressure-sensitive transducer, and the data recorded and stored in a computer. The computer also recorded the temperature, controlled the light-source and displayed the data in graphic format. Every material was tested ten times. The data were analysed by means of an ANOVA (P < 0.05). RESULTS: A high rate of shrinkage occurred for all materials in the first ten seconds of polymerisation. Surefil showed the lowest rate while TPH displayed the highest. Of the higher filled materials, Surefil (0.96%) showed the least shrinkage, followed by Z250 (0.99%), Dyract AP (1.18%), Herculite (1.27%), Compoglass (1.32%), Amelogen (1.34%) and TPH-Spectrum (1.6%). Overall, the flowable materials exhibited significantly more shrinkage (P < 0.05). For this group Compoglass Flow (2.3%) showed the least shrinkage followed by Filtec Flow (2.31%). Permaflo (3.6%) exhibited the most shrinkage followed by Dyract Flow (3%). CONCLUSION: Within the limitations of this study, it is concluded that significant differences exist among the polymerisation shrinkage of the most resins tested. An increase in the filler content of a material significantly lessens the polymerisation shrinkage while an increase in the monomer concentration causes significantly more polymerisation shrinkage. CLINICAL SIGNIFICANCE: The more flowable a composite material becomes, the more the restoration will shrink. Clinicians should take this into account when they decide on cavity design and materials to use.

Analysis of Variance↗

Bonding to root caries by a self-etching adhesive system containing MDPB.

PURPOSE: To evaluate the bonding of an experimental antibacterial fluoride-releasing adhesive system (ABF) to normal and carious dentin in human teeth with Class V root caries. METHODS: Mesiodistal sectioning removed the buccal enamel, superficial dentin and much of the carious dentin in 21 extracted human bicuspids with root surface caries. The surfaces of normal coronal and root dentin, and caries-affected and caries-infected dentin were ground with wet 600-grit SiC paper to create a standardized smear layer. Tooth surfaces were treated with the ABF according to manufacturer's instructions, and then covered with excess resin composite. After immersion in 37 degrees C water for 24 hours, the restored teeth were horizontally sectioned into serial slabs that were trimmed into hourglass shapes to isolate the bonded area to the test substrates, and then their bond strengths were measured by the microtensile bond test, and the interfaces examined by SEM and TEM. The bond strengths were statistically compared with ANOVA and Fisher's PLSD (P < 0.05). RESULTS: The bond strengths of ABF to caries-affected and caries-infected dentin were significantly lower than those to normal coronal and root dentin. SEM micrographs revealed that the hybrid layers in caries-affected and caries-infected dentin were more porous compared to the hybrid layer in normal coronal and root dentin. TEM micrographs showed that bacteria that had invaded the dentin were embedded in this adhesive monomer in caries-infected dentin. CLINICAL SIGNIFICANCE: Although the bond strength of ABF adhesive system to root carious dentin is lower than that of normal dentin, the antibacterial and fluoride-releasing properties of ABF may contribute to prevent caries progression and inhibit secondary caries.

Acid Etching, Dental↗

Effects of storage media on mechanical properties of adhesive systems.

PURPOSE: To evaluate the effects of water vs. oil storage on the mechanical properties of dental adhesives over 3 and 6 months. METHODS: Adhesive resin sheets were prepared by pouring either Single Bond (SB), One-Step (OS) or Clearfil Liner Bond 2V (CL) into a mold measuring 15 x 15 x 0.8 mm. After solvent evaporation, the adhesives were light-cured, removed from the mold and trimmed to either hourglass or I-beam shapes that were used to determine the true stress (TS) and modulus of elasticity (E), respectively. Control adhesive specimens were subjected to tensile testing at 0.6 mm/minute after 24 hours of immersion in distilled water. Experimental specimens were stored at 37 degrees C in either distilled water or mineral oil and tested after 3 and 6 months. The data were analyzed by two-way ANOVA and Tukey's test. RESULTS: Storage in water significantly decreased the TS and E of SB and OS specimens after 3 and 6 months (P < 0.05), but did not cause significant changes in either TS or E of CL specimens in the same periods (P > 0.05). Storage in oil significantly increased the TS of the three adhesives after 3 and 6 months (P > 0.05), and the same trend was observed for E value of CL sample (P > 0.05). CLINICAL SIGNIFICANCE: Exposure of cured adhesive systems to long-term immersion in water caused marked reduction in their mechanical properties. Reduced mechanical properties of the adhesive system may compromise resin/dentin bonds and have a clinical implication on the longevity of adhesive restorations.

Adhesiveness↗

An overview of the CEREC 3D CAD/CAM system.

Computer-aided design/computer-aided manufacture (CAD/CAM) technology has made steady inroads into the practice of dentistry. The CEREC CAD/CAM system can be used chairside to fabricate porcelain and composite inlays, onlays, and crowns and porcelain veneers. The latest incarnation of the CEREC system is the CEREC 3D, which provides a versatile, relatively simple, user-friendly method for fabricating esthetic restorations chairside without involving a dental laboratory. CEREC 3D may be the system that allows the average general dentist to provide chairside porcelain restorations during single-visit appointments, eliminating the need for an elastomeric impression or an interim restoration as well as the expense of a laboratory fee.

Ceramics↗

Aesthetic partial-coverage dental restorations.

The literature on the subject of aesthetic partial-coverage restorations, including laminate veneers, laminate veneer bridges, composite-resin and ceramic inlays and onlays, computer-designed restorations, and etched cast restorations, has continued to expand into the 1990s. Investigations regarding fit, longevity, wear, and microleakage, as well as descriptions of clinical techniques, were well documented world-wide in 1991. The purpose of this review is to discuss some of the more important papers published during the past year.

Ceramics↗