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Purpose: The present study was undertaken to determine the feasibility of using primary stability as a predictor of implant success in patients whose implants were immediately loaded. Materials and Methods: The study included 40 patients, in whom a total of 190 implants were placed, 102 in maxillary sites and 88 in mandibular sites. All were loaded within 72 hours of placement. Sixteen patients were completely edentulous in the mandible and/or the maxilla. The remaining 24, who were partially edentulous, received fixed partial dentures or single-implant restorations. All of the definitive implant restorations were screw retained. The criterion for loading was clinical judgment of primary stability, verified by a "screw test." Impressions were made after implant placement to facilitate the fabrication of a laboratory-made heat-processed provisional restoration from acrylic resin. Following a 4-month period for osseointegration and soft tissue healing, definitive fixed prostheses were fabricated. Results: There were no surgical complications. After 1 to 2 years, all 190 implants had survived and were considered 100% successful, as determined by independent testing of mobility and radiographic evidence of osseointegration. In 4 patients, fracture of the provisional restoration occurred during the healing period. Discussion: Clinical research has shown that immediate loading is a viable treatment modality. The favorable success rate reported in this study for rough-surfaced implants suggests that adherence to a protocol, an important parameter of which is primary stability above 32 Ncm, can lead to osseointegration. Conclusion: The results of this limited investigation suggest that patients who are partially or completely edentulous may be immediately restored with implants and fixed provisional restorations, provided that the dental implants are adequately stable immediately after their surgical placement. This alternative therapeutic approach did not appear to affect the up-to-2-year survival of the implants in this patient population. [ABSTRACT FROM AUTHOR]

The purpose of this study was to compare the effectiveness of three methods using calcium sulfate as a graft/barrier for the treatment of Class II mandibular furcation defects. Thirty-six defects in 17 patients were treated with a graft/barrier of pure calcium sulfate, calcium sulfate plus doxycycline, or demineralized freeze-dried bone allograft (DFDBA) in a 2:1 ratio by volume. Defects were randomly selected for treatment, and all measurement parameters were standardized to a light-cured acrylic resin stent at baseline and 6, 9, and 12 months. Linear regression, ANOVA, and chi-squared analysis revealed that all three groups showed significant bone fill (P < .05), vertical and horizontal probing depth reduction, defect volume reduction, and a gain in vertical clinical attachment. Furthermore, the addition of either doxycycline or DFDBA to calcium sulfate significantly enhanced the clinical outcome more than did the calcium sulfate alone, and the addition of DFDBA was more effective in the treatment of Class II mandibular furcation defects than doxycycline. [ABSTRACT FROM AUTHOR]

The hypothesis of the present study was that immediate loading of implant-supported restorations replacing single missing teeth could be a successful procedure. The present study compared the clinical success of immediately loaded single-tooth implants placed in fresh extraction sites to that of immediately loaded single-tooth implants placed in healed sites. From the years 1997 to 1998, 26 patients, ranging in age from 18 to 70 years, presented for the placement of 28 immediately loaded implants intended to support single-tooth ceramometal restorations. Nineteen implants were placed into fresh extraction sites, and 9 implants were placed into healed sites. Temporary prefabricated acrylic resin crowns were prepared and adjusted. At the time of traditional second-stage surgery (3 to 6 months after implantation), the implants were restored with single-tooth ceramometal prostheses. The survival rates were 82.4% and 100% for immediate and non-immediate implants, respectively. Follow-up ranged from 6 to 24 months from the day of implant placement, with a mean of 13 months for the immediate implants and 16.4 months for the non-immediate implants. Radiographic marginal bone loss after 3 to 6 months did not extend beyond the abutment-implant junction. Within the limits of the present investigation, immediate loading of single-tooth implants placed in healed sites is a possible treatment alternative. Immediate loading of single-tooth implants placed in fresh extraction sites carried a risk of failure approximating 20% in this patient population. [ABSTRACT FROM AUTHOR]

A technique tor manufacturing direct resin composite veneers is presented. Described are the advantages of using an acrylic resin matrix, made before the preparation is begun, to copy anatomic details. An additional step to mask previously prepared dark enamel with opaquers is also described. The advantages and limitations of the procedures are discussed. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of the investigation was to compare the performances of teeth restored with quartz fiber, carbon-quartz fiber, and zirconium-dioxide posts covered with all-ceramic crowns when subjected to a cyclic loading test performed in a wet environment. Materials and Methods: Forty single-rooted human lower premolars having similar dimensions were endodontically treated and mounted in acrylic resin blocks with a simulated periodontal ligament. The teeth were divided into three experimental groups and one control group. Post holes 8 mm long were prepared in the roots of the experimental groups in which quartz fiber, carbon-quartz fiber, and zirconium dioxide posts were cemented. In the control group, no posts were used. The crown buildup was made with composite resin. The teeth were covered with all-ceramic crowns and intermittently loaded at an angle of 45 degrees to the long axis of the tooth at a frequency of two loads per second. Results: Only one failure (root fracture + post fracture) was observed in each of the fiber post groups, while in the zirconium dioxide post group, six failures were observed (one crown fracture and 5 root fractures + post fractures). The Kaplan-Meier analysis of the three experimental groups showed that the survival rate of zirconium dioxide posts was significantly lower than that of both types of fiber post. All the experimental groups showed a survival rate higher than that of the control group. Conclusion: Fiber posts reduced to a minimum the risk of root fractures of teeth restored with composite cores and Empress crowns under the present experimental conditions (intermittent loading in a wet environment]. [ABSTRACT FROM AUTHOR]

Objective: This in vitro investigation aimed to determine the radiopacity of eight recently introduced "flowable" restorative resin composites and to compare their radiodensities to those of enamel, dentin, and a widely used composite marketed tor universal application in anterior and posterior teeth. Method and materials: A total of 45 composite specimens were fabricated in cylindrical molds and exposed to a curing light for 120 seconds. Two methods were used to determine radiopacity: a transmission densitometer and a computer-assisted densitometric image analysis station. Results: Of the eight flowable resin composites tested, only three exhibited a radiopacity equal to or greater than that of enamel, a widely followed guideline for clinicians' diagnostic ability. The radiopacity of the remaining five materials was not statistically significantly greater than that of dentin. Conclusion: The level of radiopacity of the tested flowable composites was variable; those with low radiodensity should be avoided in Class II restorations, where a clear determination of recurrent caries by the examining clinician could be compromised. (Quintessence Int 1999;30:179-184) [ABSTRACT FROM AUTHOR]

Achievement of an esthetic single-tooth restoration in the anterior segment is a difficult task for the restorative dentist. A case is described in which two congenitally missing maxillary lateral incisors were replaced with single-tooth implants. A new technique was used to restore the teeth provisionally with a polyethylene ribbon and resin replacement. Light-cured staining systems for acrylic resins and ceramics were employed to customize both the provisional and final restorations. [ABSTRACT FROM AUTHOR]

The primary objective of a provisional restoration is to promote gingival health before placement of the final restoration. A method for construction of a provisional fixed partial denture with improved marginal adaptation without the use of an indirect method is presented. A preformed shell of the provisional restoration must be fabricated from the diagnostic cast before any operative procedure attempted. The laboratory-made shells are relined intraorally to promote close adaptation to the finishing line of the preparation. A wash of cold-curing acrylic resin is applied to the margins while the bulk of the relining material is at the doughy stage. The technique provider superior results and reduced chairtime. [ABSTRACT FROM AUTHOR]

The article offers information about a study conducted to evaluate the effectivity of amalgam bonding technique and cavity preparation, as used in dentistry. The technique involves bonding amalgam to tooth, resulting in an adhesive strength similar to composite resins, by using a resin liner to bond the metal to tooth structure. To test the retention of the restorations, the restored teeth were mounted in individual acrylic blocks, placed in an Instron testing machine, and then were loaded with a stimulated occlusal force against the marginal ridge. It was found that the technique, using an adhesive resin liner in box form preparations, was effective in providing displacement under simulated occlusal loads.

The article offers information on an alternative technique in prosthodontics for making customized dental restorations with the new visible light cured (VLC) resin technology. Currently, Triad VLC resin is manufactured in four shades. The VLC resin restoration is adjusted over the abutment tooth preparations, while the necessary internal relief is made for restoration in centric occlusion. It is informed that the Triad VLC resin material is like light cured composite resins, but uses an organic filler. The filler consists of acrylic resin beads of varying sizes. Some of the advantages of VLC resins over other acrylic resins include, its accuracy of fit due to low polymerization shrinkage, low bacterial adherence, and nontoxicity and biocompatibility.

The article discusses three anterior dental veneering methods for dental cosmetic changes, direct resin veneers, indirect resin veneers, and indirect porcelain veneers. Dental veneers are classified into dental restorations fabricated by the dentist and those produced by a dental laboratory. The acrylic dental resins were replaced by conventional composite resins, which offered improved color stability and abrasion resistance. The indirect composite resins and porcelain veneers are stated to be best suited for cases of numerous discolored teeth. Full coverage direct veneers are suggested when teeth are stained and the patient desires minimal or no enamel removed. Indirect resin and porcelain veneers are stated to offer good esthetic potential with minimal operator placement skills.

The article presents a research which examines the acrylic immediate provisional bridge method as an alternative to the removable treatment partial (RTP), for the immediate replacement of lost anterior teeth. RTP, as reported, has several disadvantages including, the fabrication must be done in the laboratory, it is not functional, and it is subject to loss and accidents because it is removable. The acrylic method, as reported, eliminates most of the disadvantages of RTP, and is periodontally to the supporting structures of the teeth, if done with proper contours. The acrylic method, as reported, can be fabricated at chairside and represents the form of the final restoration, and its maintenance and home care procedures are the same as for the final restoration.

The article focuses on the methods and uses of temporary dental restorations. It discusses the chairside techniques which include simple and multiple temporary restorations usually made from an impression of the existing dentition such as wax and alginate before tooth preparation. When an impression doesn't work, a block of acrylic technique is used to form the restoration. Am adequately used temporary restoration serves various purposes including covering exposed tooth structure, maintaining the position of tooth abutments and preventing tooth from further breakdown. Tooth reduction is done after the temporary restoration has been fabricated to the ideal contours and occlusion. Related illustrations are also shown.

A case report of a chairside-fabricated indirect resin composite restoration is used to introduce a modification to a newly released one-appointment resin inlay-onlay technique. Fast-setting poly(vinyl siloxane) die material accommodates an articulated working cast within 10 minutes. The technique allows the economical construction of large, occlusal, load-bearing, extracoronal resin composite restorations. The guarded prognosis associated with extensive posterior resin composite restorations i acknowledged; nevertheless this technique remains a realistic option for those financially compromised patients who request tooth-colored restorations. [ABSTRACT FROM AUTHOR]

Ideal implant placement is ultimately determined by the requirements of the final restoration. For the surgeon placing implants, proper angulation, parallelism, and spacing are critical to the final restoration. The use of a stainless-steel drill guide sleeve in an acrylic resin surgical template can make it possible to achieve optimal placement. Communication between the restoring dentist, surgeon, and laboratory technician is enhanced by this system since dowel pins fit precisely into the sleeves and determine sleeve and, ultimately, implant position. This system allows the surgeon to negotiate bony irregularities and ramping defects with ease while preparing a more concentric implant site. [ABSTRACT FROM AUTHOR]

Placement of porcelain laminate veneers has become a relatively common procedure. Occasionally it is necessary to fabricate provisional restorations. For these situations, the use of self-curing acrylic resin and composite resin has been described in the literature. Extensive trimming and finishing procedures are often necessary, and because of the inherent fragility of the materials, the provisional restorations are prone to breakage. To improve the technique, visible light-curing acrylic resin can be used to fabricate direct provisional restorations. The material is available in several shades, has excellent manipulative properties, and does not necessarily require a custom matrix, offering significant advantages over a composite resin or self-curing acrylic resin. [ABSTRACT FROM AUTHOR]

The article presents excerpts from several research papers which appeared in previous issues of the journal, and it mentions articles about the adhesion of acrylic filling materials to enamel surfaces, the relationship between oral infection and mental disease, and a human mandible growth pattern.

Acrylic materials are used daily for the production of mobile dental restorations and orthodontic appliances. The presence of residual monomer, as a product of incomplete polymerisation of material, results in more porous structure of the material, which greatly reduces the mechanical and physical quality of the acrylic restorations and increases the absorption of liquids. The aim of this study was to examine the water absorption of different types of resin material. In the study it was assumed that the cold polymerized acrylates show a greater potential for absorbing fluid from the environment in relation to the hot polymerized acrylic. The study included two hot and two cold polymerized acrylates, and cold polymerized acrylate impregnated with aesthetic pearls. In order to determine the degree of water absorption, the mass of the samples was measured before and after one day, seven days and thirty days of immersion in a water bath of body temperature. The tested hot and cold polymerized acrylates after immersion in water bath showed standard values of water absorption. The degree of water absorption was not significantly influenced by the type and manner of polymerisation. Water absorption values were significantly higher after seven days and thirty days of water storage relative to the observational period of one day. [ABSTRACT FROM AUTHOR]

ABSTRACT Background: Accurate recording of implant location is required so that definitive restorations are properly supported and do not place additional stresses on the implants. Movement of impression copings inside the impression material using an open-tray or close-tray impression technique during clinical and laboratory phases may cause inaccuracy in transferring the three-dimensional spatial orientation of implants intraorally to the definitive cast. Consequently, the restoration may require corrective procedures. Aim: This in vitro study compared the accuracy of two different impression techniques with two different impression coping shapes using polyether impression material to obtain precise definitive casts. Materials and Methods: Two reference acrylic resin models (Technovits 4000, Heraeus Kulzer GmbH & Co., Wehrheim, Germany) with five internal connection implants having different shapes of impression copings (Implantium [Dentium, Seoul, South Korea] and Replace Select [Nobel Biocare AB, Göteborg, Sweden]) were fabricated. Twenty medium-consistency polyether impressions of these models were made with square and conical impression copings of each system using open-tray and close-tray techniques. Matching implant replicas were screwed into the impression copings in the impressions. Impressions were poured with type IV stone, and the positional accuracy of the implant replica heads in x-, y-, and z-axes (represented in [Δr]) and also rotational displacement (ΔΘ) were evaluated using a coordinate measuring machine (Mistral, DEA Brown&Sharpe, Grugliasco, Italy). These measurements (linear and rotational displacements) were compared with the measurements calculated on the reference resin models that served as control, and data were analyzed with a two-way analysis of variance at α = 0.05. Results: Less inaccuracy occurred in less retentive shape impression copings (Replace Select) compared with the more retentive one (Implantium) ( pr < .001 and pΘ < .001), but there was no significant difference between direct and indirect impression techniques ( pr and pΘ > .05). Conclusion: The impression coping shape had more impact on impression inaccuracy than impression technique did. Understanding of the magnitude and variability of distortion when employing certain impression-making methods and impression coping shapes helps the clinician to select a better implant component and impression technique. [ABSTRACT FROM AUTHOR]

- Background: Study was designed to evaluate shear bond strengths of different restorative techniques of uncomplicated enamel-dentin fractures in permanent incisors. Material and Methods: Forty human mandibular incisors were divided into four groups. One-third of their anatomical crowns from the incisal edges were cut off in three groups, representing an uncomplicated enamel-dentin fracture. Intact teeth in group 1 were used as control. In group 2, edge fragments were reattached by flowable composite (Filltek Flowable Supreme XT). In group 3, teeth were restored with universal resin composite (Filtek Z 250). In group 4, pre-impregnated glass fiber sheet (everStickNet) was positioned onto fractured surface, and then restorations were completed with resin composite. Three-step etch-and-rinse adhesive system (Adper Scotchbond Multi Purpose) was used in all test groups. Shear bond strengths of all samples were determined in universal testing machine, and data were analyzed with Kruskal-Wallis followed by Mann-Whitney U tests. Failure types were observed by light microscope. Results: Shear bond strength of sound teeth was significantly higher than those of restored teeth ( P < 0.05). Mean shear bond strengths of the reattached teeth were lower than the other two restoration types; however, differences were not statistically significant ( P > 0.05). Conclusions: Load-bearing capacity of restored teeth was not as high as sound teeth in the uncomplicated crown fracture. However, shear bond strength of different types of restorations seems close to each other. [ABSTRACT FROM AUTHOR]

Background: The use of all-in-one resin-based adhesives in clinical practice has continued to increase. The aim of this study was to evaluate retention and marginal staining of a HEMA-free all-in-one adhesive Go! (SDI, Australia) and Ice resin composite in non-carious cervical lesions (NCCLs). Methods: Forty-one restorations were placed in 13 patients (age range 44-72 years). Human Ethics Committee approval from the University of Melbourne and Dental Health Services Victoria was obtained. Restorations were bonded and placed according to the manufacturer's instructions. Enamel etching was performed on NCCL margins after cleaning with pumice and water. Patients were recalled at six months and one, two and three years. Restorations were evaluated for retention and marginal staining, and photographic records of restorations were obtained. Results: At three years, six patients were available for recall with 23 restoration sites reviewed. At the six-month recall, three restorations had been lost, with a further two lost at two years. At three years, an overall cumulative retention rate of 85% was calculated using survival analysis. Fifteen of the 23 restorations showed slight marginal staining. Conclusions: At three years, the overall retention rate of 85% indicates a satisfactory result for this new adhesive. Marginal staining was regarded as minimal. [ABSTRACT FROM AUTHOR]

The article discusses aesthetic and biomechanical precision in relation to complex dental restoration cases as of December 2009, including an analysis of the precision of fit, occlusal precision, and aesthetic precision in cases involving restorative dental procedures. Jaw relationship records (JRRs), acrylic resins, and definitive tooth impressions are also addressed, along with an examination of fit checking materials and processes.

In the last few years the carried out studies showed a growing interest towards improving the extisting resin materials and for developing of new polymer materials with better characteristics and performances, similar to those of the natural teeth. It is known and accepted that, by using composite resins in tooth restorations there are some deficiencies which haven't been completly eliminated. The aim of this study was to compare four aesthetic resin materials used in direct restorations: Tetric Evo Ceram (Ivoclar Vivadent), Filtek Supreme (3M ESPE), Restacril (Institute of Chemistry Cluj-Napoca) and Premise (Kerr), using the USPHS criteria for the clinical cases that were studied. The results we obtained show that the performences of composite resins are trustworthy, as long as they are properly placed into a prepared cavity, and the operator dentist/doctor knows and respects their placing techniques, their aspect and colour. [ABSTRACT FROM AUTHOR]

This study evaluated the influence of the method and period of storage on the adhesive bond strength of indirect composite resin to bovine dentin. Ninety bovine incisors were stored in three different solutions: 0.2% thymol, 10% formalin, and 0.2% sodium azide, during 3 periods of storage: 7 days, 30 days and 6 months, resulting in 9 groups (n = 10). The roots were cut off and the buccal surface was ground with #600-grit silicon carbide paper. The surface was conditioned with 37% phosphoric acid for 15 s and a composite resin restoration (TPH Spectrum) was fixed using a one-bottle adhesive system (Adper Single Bond) and a dual-cured resinous cement (Rely X ARC) under a load of 500 g for 5 minutes. The samples were serially cut perpendicular to the bonded interface to obtain slices of 1.2 mm in thickness. Each slab was trimmed with a cylindrical diamond bur resulting in an hourglass shape with a cross-sectional area of approximately 1 mm². The microtensile bond strength (μTBS) testing was performed in a testing machine (EMIC 2000 DL) at a 0.5 mm/minute crosshead-speed until failure. After fracture, the specimens were examined under SEM to analyze the mode of fracture. μTBS Means were expressed in MPa and the data were analyzed by two- way ANOVA (3X3) and the Tukey test (α = 0.05). The storage times of 7 and 30 days produced no significant difference irrespective of the solution type. The formalin and thymol solutions, however, did have a negative influence on bond strength when the teeth were stored for 6 months. [ABSTRACT FROM AUTHOR]

Owing to improvements in its mechanical properties and to the availability of shade and translucence resources, resin composite has become one of the most widely used restorative materials in present day Dentistry. The aim of this study was to assess the relation between the surface hardness of seven different commercial brands of resin composites (Charisma, Fill Magic, Master Fill, Natural Look, Opallis, Tetric Cerani, and Z250) and the different degrees of translucence (translucid, enamel and dentin). Vickers microhardness testing revealed significant differences among the groups. Z250 was the commercial brand that showed the best performance in the hardness test. When comparing the three groups assessed within the same brand, only Master Fill and Fill Magic presented statistically significant differences among all of the different translucencies. Natural Look was the only one that showed no significant difference among any of the three groups. Charisma, Opallis, Tetric Ceram and Z250 showed significant differences among some of the tested groups. Based on the results found in this study, it was not possible to establish a relation between translucence and the microhardness of the resin composites assessed. Depending on the material assessed, however, translucence variation did affect the microhardness values of the resin composites. [ABSTRACT FROM AUTHOR]

Objective. To determine the static load-bearing capacity of composite resin onlay restorations made of particulate filler composite (PFC) with two different types of fiber-reinforced composite (FRC) substructures. Material and Methods. Specimens were prepared to simulate an onlay restoration, composed of a 2 to 3 mm FRC layer as the substructure (short random and continuous bidirectional fiber orientation) and a 1 mm surface layer of PFC. Control specimens were prepared from plain PFC. The specimens were incrementally polymerized with a hand-light curing unit for 40 s and then post-cured in a light-curing oven for 15 min. The specimens were cemented on dentin substrate of extracted human molars using a standard adhesive resin cementation technique. The specimens ( n =8/group) were water stored either for 24 h at room temperature or for 4 weeks at 37°C before they were statically loaded until fracture using a universal testing machine. Failure modes were visually examined. Results. ANOVA revealed that all specimens with FRC substructures had higher values of static load-bearing capacity than those obtained with plain PFC ( p [ABSTRACT FROM AUTHOR]

The purpose of this study was to evaluate the wear resistance and clinical applicability of resin-modified glass ionomer cements as restorative or fissure-sealing materials. The in vitro wear of resin-modified glass ionomers was compared to conventional glass ionomers, a resin-based sealant, and a composite resin. A three-body wear test (enamel block - polymethylmethacrylate powder - experimental dental material) was performed by 20,000 cycles with a load of 4kgf/cm². The depth of wear of the experimental materials was measured and calculated using a computerized laser surface scanner. The glass ionomers generally showed more wear than the resin-based sealant and the composite resin, but there was no difference in wear between resin-modified and conventional glass ionomers. Type III ionomers (used for sealant) showed lower wear resistance than type II ionomers (used for restoration). [ABSTRACT FROM AUTHOR]

A new machine was developed to study the wear of dental filling materials in vitro. Four products: amalgam, Adaptic, Clearfil and acrylic resin were tested. Wear was measured quantitatively by weighing the specimen, and the wear pattern was studied qualitatively with a scanning electron microscope (SEM). A comparison was made with materials that were placed in the mouth for a prolonged period. It was found that the in vitro wear pattern was comparable to that found in vivo. [ABSTRACT FROM AUTHOR]

A method was developed for measuring the transverse strength of repaired acrylic samples at a single butt joint. The strength was determined for samples prepared from two types of heat polymerizing resins and two types of repair resins. The temperature elevation during curing of the repair resins was determined. Cross-linking of the resins was evaluated by immersion of samples in solvents. The appearance of the bead microstructure after various treatments was considered to indicate relaxation at the sample surface. Repaired samples of the heat polymerizing resin which exhibited relaxation after immersion in monomer, had a lower strength than samples prepared from the resin for which relaxation was not observed, although both resins were cross-linked to a similar extent. The application of pressure during curing increased the strength of the samples repaired with the rapid curing, cross-linked, repair resin. The strength of the samples repaired with the uncross-linked, slow curing, repair resin was affected by pressure only if the insertion of the repair resin between the sample parts was delayed after mixing. Variations in the powder to liquid ratio of the uncross-linked repair resin did not affect the sample strength. Wetting of the sample parts with monomer before repair, and variations in the curing temperature did not affect the sample strength for the investigated resin combinations. [ABSTRACT FROM AUTHOR]

Alternative resins to traditional denture base acrylic need to be assessed for both short- and long-term performance before their potential can he evaluated. Much dental materials testing is carried out on fresh material and a baseline of knowledge about the properties of aged material is incomplete. Studies have been carried out to examine the effects of thermal and environmental fluctuation on dental acrylic, with testing procedures reconsidered so as to resemble service conditions as closely as possible. Thermal cycling proved detrimental to the resin only when superimposed on intermittent partial drying out and resaturation. [ABSTRACT FROM AUTHOR]

A simple method of determining the doughing time of acrylic denture base materials is reported. It is suggested that the method described is suitable for standard specification testing. In addition, the effect of temperature on doughing time and the correlation between doughing and polymer particle size distribution has been determined. [ABSTRACT FROM AUTHOR]

The purpose of this investigation was to evaluate the influence of the distance of the needle tip from the apical foramen on the apical seal and the length control of the root filling material when thermoplasticized gutta-percha is injected using a sectional injection technique. Ninety-nine human single-rooted mandibular incisors and permanent premolars with straight canals were divided into three equal Groups A, B and C. In Group A the teeth had relatively the wider root canal, in Group C the narrowest, while in Group B root canal size was intermediate. The root canals of all teeth were prepared with a step-back technique. Roots of Group A were instrumented to a Size 70 4 mm short of the working length, while roots of Groups B and C to a Size 70 6 mm and 8 mm short of the working length, respectively. The teeth of all groups were covered with aluminium foil and embedded in acrylic blocks. After the placement of sealer (Roth 311) the root canals of all teeth were obturated with injection-molded thermoplasticized gutta-percha using a three-stage sectional technique. The roots remained in India ink for three days and then cleared by successive immersion in nitric acid, ascending grades of alcohol and finally in xylene. The linear dye penetration and the linear apical underextension of the root canal filling were measured by two independent examiners under a stereo microscope. There was no significant difference in the linear dye leakage between the groups. However, because of the zero value of linear underextention in Group A, significant difference was found between Group A vs B and A vs C, while no statistically significant difference was found between B and C groups. [ABSTRACT FROM AUTHOR]

During the polymerization of multifunctional monomers for dental restorations, typical final double-bond conversions range from 55 to 75%. The low conversion results in a large amount of extractable monomer, reduced adhesion to the filler, and the potential for increased swelling. In this work, the ability to increase the maximum conversion by optimizing the copolymer composition is explored. A series of multi-ethylene glycol dimethacrylate monomers of various lengths was used as a model system to determine how the copolymer composition affects the final conversion, the mechanical properties, and the predicted shrinkage. It was found that the ultimate conversion can be significantly increased, shrinkage decreased, and mechanical properties maintained. It was found that up to 30 wt% of poly(ethylene glycol) 600 dimethacrylate could be added to diethylene glycol dimethacrylate without reducing the strength and increasing the conversion. Results for other comonomer combinations were similar. [ABSTRACT FROM AUTHOR]

Most commercial dental composites contain liquid dimethacrylate monomers (including BIS-GMA or variations of it) and silica-containing compositions as inorganic reinforcing filler particles coated with methacrylate-functional silane coupling agents to bond the resin to the filler. They also contain initiators, accelerators, photo-initiators, photosensitizers, polymerization inhibitors, and UV absorbers. Durability is a major problem with posterior composites. The typical life-span of posterior composites is from three to 10 years, with large fillings usually fewer than five years. Polymerization shrinkage and inadequate adhesion to cavity walls are remaining problems. Some pulp irritation can occur if deep restorations are not placed over a protective film. Some have advocated the use of glass-ionomer cement as a lining under resin composite restorations in dentin. The concept of glass-ionomer cements (GICs) was introduced to the dental profession in the early 1970's. Current GICs may contain poly(acrylic acid) or a copolymer. Highermolecular- weight copolymers may also be used to improve the physical properties of some GICs. Stronger and less-brittle hybrid materials have been produced by the addition of watersoluble compatible polymers to form light-curing GIC formulations. The ion-leachable aluminosilicate glass powder, in an aqueous solution of a polymer or copolymer of acrylic acid, is attacked by the hydrated protons of the acid, causing the release of aluminum and calcium ions. Salt bridges are formed, and a gel matrix surrounds the unreacted glass particles. The matrix is adhesive to mineralized tissues. Provisions must be made for maintenance of the water balance of restorations for the first 24 hours. A varnish to seal newly-placed restorations is provided by most manufacturers. The introduction of metal powder to GICs significantly improved abrasion resistance. [ABSTRACT FROM AUTHOR]

Clinicians have many choices of provisional materials from which to choose when fabricating interim fixed restorations. While traditional materials are still in use today, temporary materials are continuously being updated and iniproved upon. In addition to the functional necessities required of the provisional material, it must also provide esthetic value for the patient. This article provides an overview of provisional materials, including newer bis-acryls that have helped eliminate some of the challenges associated with traditional acrylic materials. Composite resin preformed crowns for single- unit provisional applications are also discussed, along with CAD/CAM-fabricated materials. Regardless of the material selected, a provisional restoration must maintain and protect the underlying tooth structure from ill effects. [ABSTRACT FROM AUTHOR]

Background: There are a large number of composite resin restorative materials and acrylic resin denture base materials. Brushing procedures exposes them to wear. The objective was to evaluate the changes in surface roughness of 2 types of composite resin restorative materials and 4 acrylic resin denture base materials after simulated tooth brushing. Material and methods: Twenty specimens of composite resin materials (self-cure and light-cure) and seventy specimens of denture base materials (heat-cure, lightcure acrylates and acetal) were fabricated according to the manufacturer s instructions. The specimens were subjected to a custommade tooth brushing simulation device applying a force of 2N. Toothpaste slurry and water was used for the brushing procedures. Surface roughness before and after simulated tooth brushing was measured with a profilometer (Surtronic 25). Data were statistically analyzed using dependent t-tests. Results: All the materials showed changes in surface roughness. Light-cure composite resin showed significant changes in surface roughness, while the self-cure composite was more resistant to wear. Among the denture base materials the heat-cure acrylic resin showed the most significant changes and acetal resin base material was the most resistant. Conclusions: Surface changes of dental materials depended on their physical and chemical properties and the cleaning procedure. Within the limitation of this study the following could be concluded: self-cure composite was the most resistant to surface changes; the "medium" labeled toothbrush caused significant changes without using toothpaste on the surface of the light-cure composite and the heat-cure acrylic resin materials. Further studies are planned to evaluate other types of composite and acrylic resin materials using different types of toothpastes and brushes. [ABSTRACT FROM AUTHOR]

The article discusses the problem of cumulative damage of teeth in elderly people and the Class II composite restorations treatment for the problem. Topics discussed include use of amalgam as standard direct restorative material for the patients, introduction of Bowen resin and the acid-etch technique restoration technique for teeth restoration, and advantages and disadvantages of the standard Class II composite restoration in elderly patients.

The article presents a study which examined the use of radioactive tracers in determining the protective effects of dental cavity liners. The study used tritium in the monomer of self-curing acrylic filling materials in monkey teeth. The author considers the irritating effects of materials which penetrate through dental liners.