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PubMed2006

The effects of temperature and light intensity on the polymerization shrinkage of light-cured composite filling materials.

UNLABELLED: The aim of this study was to investigate the effect of light intensity on polymerization shrinkage of resin composites. The five materials tested were Lite-Fil (A) (LFA), Lite-Fil (P) (LFP), Z100, Palfique, (PAL) and Tetric (TRC). Two types of measurements were made to determine the effects of environmental temperature and light intensity. Results were analyzed by two-way analysis of variance (ANOVA) and Newman-Keuls procedure at (P<0.05). The changes in temperature and/or light intensity strongly affected composite shrinkage. The amount of shrinkage for LFP at 100% light intensity in room temperature (23 degrees C) was 1.26% and increased up to 2.29% at 60 degrees C. By raising the temperature to 37 degrees C and dropping the light intensity to 42% (459 mW/cm2), the amount of polymerization shrinkage was similar to that with full light intensity, and statistically there were no significant differences between 37 degrees C, 45 degrees C, and 60 degrees C. Lower temperatures and lower light intensities produce lower values of shrinkage. However, if the light intensity is below 28%, higher temperatures (60 degrees C) must be applied to obtain a comparable amount of shrinkage. CLINICAL RELEVANCE: Pre-heating composite resin materials at body temperature (37 degrees C) is likely to improve physical properties and compensate any drop of light intensity.

Analysis of Variance↗
PubMed2006

Effect of different bonding conditions on the shear bond strength of two compomers to bovine dentin.

AIM: Despite the improvements to compomer materials, the bond strength of these materials remains inferior to "composite/resin bonding" systems and limits their clinical use. The purpose of this study was to evaluate the effect of acidic conditioning with phosphoric acid and Prompt L-Pop (PLP) on the shear bond strength of two compomers Dyract AP (DAP) and Composan Glass (CG) to dentin. METHODS AND MATERIALS: Sixty extracted bovine teeth were used to test the shear bond strength of two compomers to flat dentin labial surfaces. The dentin specimens were randomly assigned to six groups of ten specimens each: Group 1: DAP and Prime & Bond NT (PBNT); Group 2: DAP/PBNT with a 15 second dentin etch prior to bonding; Group 3: DAP placed with PLP adhesive; Group 4: CG and Compobond NE (CBNE); Group 5: CG/CBNE with a 15 second dentin etch; and Group 6: CG placed with PLP adhesive. The specimens were stored at 37 masculineC with 100% humidity for 24 hours then mounted and sheared using an Instron Universal Testing Machine at a cross head speed of 0.5 mm/min. The results were recorded in Mega Pascals (MPa). The sheared specimens were examined under a light microscope, and the type of failure (adhesive, cohesive, or mixed) was recorded. RESULTS: The mean dentin shear bond strength value (MPa) for the groups was: Group 1 (11.6+/-3.9); Group 2 (13.2+/-3.3); Group 3 (12.4+/-2.0); Group 4 (13.0+/-4.3); Group 5 (19.3+/-3.7); and Group 6 (13.1+/-3.0). One way analysis of variance (ANOVA) and Tukey HSD post-hoc tests detected a significantly higher bond strength (P = 0.003) for group 5. For groups 1, 3, 4, and 6, the mode of failure was mostly adhesive. When acid etching of dentin was performed (groups 2 and 5), cohesive fracture within dentin was the predominant mode of failure. Acid etching and the use of PLP significantly reduced the number of adhesive fractures and reduced variability in the shear bond strength results. CONCLUSIONS: Acid etching significantly increased the shear bond strength of CG to dentin but did not affect DAP. The application of PLP resulted in a shear bond strength not statistically different from PBNT or CPNE. CG bond to dentin is improved with acid etching using phosphoric acid. However, PLP provided no significant improvement in the shear bond strength of DAP and CG.

Acid Etching, Dental↗
PubMed2006

A review of polymerization shrinkage stress: current techniques for posterior direct resin restorations.

In general excellent results cannot be guaranteed when using resin-based composites for posterior restorations. This is due to polymerization shrinkage which can still be regarded as the primary negative characteristic of composite resins. A review of available literature regarding the polymerization process, its flaws, and suggested strategies to avoid shrinkage stress was conducted. Several factors responsible for the polymerization process may negatively affect the integrity of the tooth-restoration complex. There is no straightforward way of handling adhesive restorative materials that can guarantee the reliability of a restoration. At present, the practitioner has to coexist with the problem of polymerization shrinkage and destructive shrinkage stress. However, evolving improvements associated with resin-based composite materials, dental adhesives, filling, and light curing techniques have improved the predictability of such restorations. This critical review paper is meant to be a useful contribution to the recognition and understanding of problems related to polymerization shrinkage and to provide clinicians with the opportunity to improve the quality of composite resin restorations.

Bicuspid↗
PubMed2006

Survival analysis of complete veneer crowns vs. multisurface restorations: a dental school patient population.

The purpose of this study was to compare the longevity of crowns versus large multisurface restorations in posterior teeth. The investigation used the treatment database at Virginia Commonwealth University School of Dentistry. The inclusion criteria for the final data set used for analysis were: only one restored tooth per patient, premolars with three or more restored surfaces, molars with four or more restored surfaces, molars and premolars restored with complete veneer metal crowns, or crowns veneered with metal and porcelain. The Kaplan-Meier approach was used to visualize the survival curves, and the Cox proportional hazards model was used for analysis of predictor variables. The investigation indicates crowns survive longer than large restorations and premolar restorations survive longer than molar restorations. The median survival for crowns exceeded 16.6 years, with the median survival of premolar restorations being 4.4 years and molar restorations 1.3 years. An interaction between age and treatment was discovered, with overall survival decreasing as patient age increases. The doctor supervising the treatment also affected survival with treatment supervised by specialists lasting longer than treatment supervised by nonspecialists.

Adult↗
PubMed2006

Conservative aesthetic enhancement of the anterior dentition using a predictable direct resin protocol.

Aesthetic enhancement of the maxillary dentition can be accomplished using a variety of direct and indirect methods. Composite resin procedures enable the clinician to follow a predictable, conservative, and reliable chairside protocol for improving patients' smiles. Combined with advances in adhesive materials themselves, these procedures can be used successfully in the daily practice of restorative aesthetic dentistry. This article will demonstrate the protocol used to enhance the appearance of a patient who presented with concern regarding short crown length.

Adult↗
PubMed2006

Bond strength and failure patterns of adhesive restorations in primary teeth aged in the oral environment.

PURPOSE: To evaluate the bond strength and micromorphology of the fracture pattern of adhesive composite restorations in primary teeth after long-term clinical function. METHODS: Subjects (8-10 years-old) with deep carious lesions in primary molars had their teeth restored with resin composite (Z250). The teeth were randomly divided into two groups, according to the adhesive system used: (1) Scotchbond Multi-Purpose (SMP); and (2) Clearfil SE Bond (CSE). After the clinical and radiographic follow-up period (15-17 months), the teeth were exfoliated and the adhesive restorations were subjected to microtensile bond test. RESULTS: Student's t-test revealed a statistical difference (P= 0.001) between the two adhesive systems tested (SMP = 16.8 +/- 2.62 MPa; CSE = 27.3 +/- 2.28 MPa). The micromorphology evaluation of the failure zone revealed a weak area in the demineralized dentin (SMP) and at the top of the hybrid layer (CSE).

Child↗
PubMed2006

Combined periodontal, orthodontic, and restorative treatment of pathologic migration of anterior teeth: a case report.

Pathologic tooth migration related to periodontal disease is a common chief complaint of periodontal patients. This paper describes the treatment of a case of severe periodontal disease and disfiguring pathologic migration of maxillary central incisors, which required a multidisciplinary approach. After conventional periodontal treatment was performed, the anterior diastema was closed using a combination of orthodontic therapy and restorative treatment. A 6-month follow-up examination of this case revealed resolution of the anterior pathologic migration, with gains in clinical attachment levels and a successful esthetic and functional final result.

Adult↗
PubMed2006

Bond strength of resin-based restorations polymerized with different light-curing sources.

PURPOSE: To evaluate the influence of different light-curing units on microtensile bond strength of resin composite restorations. MATERIALS AND METHODS: Standardized Class I preparations (6.0 x 4.5 mm, 2.5 mm deep) were made in extracted human third molars after abrading the cusps. Resin was inserted in bulk using a 3M ESPE restorative system [Adper Single Bond (DBA)/ Filtek Z250 (RC)]. Both materials were polymerized using different light-curing units: QTH at 540 mW/cm(2) (XL 3000, 3M ESPE); LED at 750 mW/cm(2) (Elipar FreeLight2, 3M ESPE); PAC at 2130 mW/cm(2) (Arc Light II, Air Techniques). Nine different light combinations were developed to polymerize both DBA and RC: QTH/QTH; QTH/LED; QTH/PAC; LED/LED; LED/QTH; LED/PAC; PAC/PAC; PAC/QTH; PAC/LED. Restored teeth were stored in distilled water for 24 h at 37 degrees C and then sectioned, yielding stick-shaped specimens with a bonded area of approximately 0.9 mm(2). Specimens were assessed in a testing machine at a crosshead speed of 1 mm/min. The results were analyzed using two-way ANOVA and Tukey's test at a pre-set alpha = 0.05. RESULTS: The combinations PAC/QTH and QTH/QTH presented the highest bond strength values, and LED/QTH the lowest (p < 0.05). Significantly lower values were observed in combinations when the LED light was used to polymerize DBA compared to QTH and PAC lights, irrespective of the light source used to polymerize RC (p < 0.05). Same light combinations presented similar bond strength values. CONCLUSIONS: Different light sources influence restoration bond strength. Bond strength is more dependent on the light source used for DBA than for curing RC.

Bisphenol A-Glycidyl Methacrylate↗
PubMed2006

Short fiber reinforced composite: the effect of fiber length and volume fraction.

AIM: The aim of this study was to determine the effect of short fiber volume fraction and fiber length on some mechanical properties of short fiber-reinforced composite (FRC). METHODS AND MATERIALS: Test specimens (2 x 2 x 25 mm3) and (9.5 x 5.5 x 3 mm3) were made from short random FRC and prepared with different fiber volumes (0%-22%) and fiber lengths (1-6 mm). Control specimens did not contain fiber reinforcement. The test specimens (n=6) were either dry stored or thermocycled in water (x10.000, 5-55 degrees C) before loading (three-point bending test) according to ISO 10477 or statically loaded with a steel ball (Ø 3.0 mm) with a speed of 1.0 mm/min until fracture. A universal testing machine was used to determine the flexural properties and the load-bearing capacity. Data were analyzed using analysis of variance (ANOVA) (p=0.05) and a linear regression model. RESULTS: The highest flexural strength and fracture load values were registered for specimens with 22 vol% of fibers (330 MPa and 2308 N) and with 5 mm fiber length (281 MPa and 2222 N) in dry conditions. Mechanical properties of all test specimens decreased after thermocycling. ANOVA analysis revealed all factors were affected significantly on the mechanical properties (p<0.001). CONCLUSIONS: By increasing the volume fraction and length of short fibers up to 5 mm, which was the optimum length, the mechanical properties of short FRC were improved.

Analysis of Variance↗
PubMed2006

Microleakage of seven adhesive systems in enamel and dentin.

AIM: The aim of this study was to evaluate the microleakage of seven adhesive systems on two substrates (enamel and dentin). METHODS AND MATERIALS: Class V cavities were performed in buccal and lingual surfaces of 56 bovine incisors. The cervical margin was located in dentin and the incisal margin in enamel. The specimens were randomly divided into seven groups (n=16), according to the adhesive system employed: Single Bond; Excite; One Step Plus; Gluma One Bond; Magic Bond; One Up Bond F; and One Coat Bond. The cavities were incrementally filled with a hybrid composite Filtek Z250 and polymerized with a XL 3000 light curing unit. After polishing, the specimens were submitted to thermal cycling followed by dye immersion. Leakage was evaluated under magnification (40X) based on a standard ranking. Data were subjected to statistical analysis (Kruskal-Wallis). RESULTS: Enamel margins exhibited lower leakage than dentin margins (p<0.01). The majority of the specimens were leakage-free and materials performed similarly. Conversely, in dentin most of the specimens exhibited the highest leakage degree and significant differences among materials (p<0.05) were found, with Excite exhibiting the lowest leakage degree. It was concluded enamel provided better sealing and the adhesive system was a significant factor only in dentin.

Adhesives↗
PubMed2006

Immediate polymerization shrinkage in light cured restorative resins.

The purpose of this study was to evaluate the immediate polymerization shrinkage of restorative resins following activation with different amounts of light energy. The composites used were: Z-100 (3M-ESPE), Z-250 (3M-ESPE), Ariston pHc (Ivoclar-Vivadent), Filtek P-60 (3M-ESPE), SureFil (Dentsply), Tetric Flow (Ivoclar-Vivadent), Silux Plus (3M-ESPE) and F-2000 (3M-ESPE). The percentage shrinkage after an 80-second activation was determined by means of a capillary mercury dilatometer The power of the light beam that reached the unpolymerized material was regulated at 350 mW/cm2 (Group I) or 275 mW/cm2 (Group II) positioning the end of the light source (XL-3000, 3M-ESPE) either in contact with or 5 mm from the dilatometer stopper. Four measurements were taken for each material and experimental condition, reading the dilatometer scale one minute after light activation. Data were recorded as percentage volumetric shrinkage as a function of the material volume calculated from the specimen mass and density. Analysis of variance and Tukey's test were used for statistical evaluation. Shrinkage was found to be significantly greater in Group I - 1.43% (0.43) - than in Group II -1.04 % (0.38). Some significant differences were found among some of the products. A reduction in polymerization shrinkage occurred concomitantly with the reduction in light activation energy and varied according to the organic content and the physical and chemical characteristics of each material.

Analysis of Variance↗
PubMedDate not supplied

The effect of a mouthrinse containing essential oils on dental restorative materials.

Mouthrinses that contain essential oils are effective for controlling plaque and periodontal disease. Recent studies have shown that such mouthrinses are effective at preventing the formation of biofilm in dental unit waterlines. However, there is no information in the literature regarding the effect of such mouthrinses on restorative materials used within the oral cavity. Specimens of three common restorative materials (a glass ionomer, a composite resin, and amalgam) were subjected to continuous exposure to Listerine and distilled water for 10 days; at that time, the strength, fluid sorption, and surface appearance of the specimens were compared. Specimens of the test materials also were placed in intraoral devices; volunteer patients wore these devices for 12 hours per day for a period of 10 days. During that time, the patients were instructed to rinse twice daily for 30 seconds with Listerine Cool Mint or a non-active mouthrinse. After 10 days, the specimens were salvaged from the devices and inspected by visible and SEM examination. This study indicates that routine use of mouthrinses containing essential oils (or even prolonged exposure to such mouthrinses) has no adverse effects on restorative materials that might be expected to react to such mixtures because of their chemical compositions. It was concluded that active mouthrinses do not appear to have any adverse effects on a variety of restorative biomaterials.

Absorption↗