Improved marginal adaptation of composite restorations by using different placement and light polymerization techniques.

PURPOSE: To verify the influence of placement and polymerization technique on the gap width between dentin and composite restoration. METHODS: Standardized cylindrical cavities (3 mm in diameter, 2 mm deep) with all margins in dentin were prepared on buccal and oral surfaces of 30 extracted human third molars. With regard to the different resin composite filling techniques used, the samples were randomly divided into three groups (n=20): bulk; incremental; pin. Each group was further subdivided into subgroups based on different light polymerization techniques): continuous (40 seconds); discontinuous (2 seconds of activation, followed by 10 seconds of dark interval, then light polymerization continued for 38 seconds). After finishing procedures, impressions were made using polyvinylsiloxane, and epoxy resin replicas were obtained and prepared for scanning electron microscopy. The percentage of the marginal gaps in relation to the whole margin was recorded and statistically analyzed (P)≤ 0.05). RESULTS: Marginal adaptation of composite restorations placed into the dentin cavities using pin and discontinuously light polymerized presented significantly better results than other two tested groups polymerized in the same manner. CLINICAL SIGNIFICANCE: The proposed modified incremental placement technique with a transparent glass pin reduces marginal leakage at the interface between composite restoration and dentin; leakage which can jeopardize the longevity of the restoration.

The micromorphological characterization of adhesive bond in dentin different locations.

The aim of this study was to analyse the interfacial micromorphology of total-etch adhesives and dentin structures different locations by using SEM. Standardized cylindrical cavities (3mm in diameter, 2mm deep) with all margins in dentin were prepared on occlusal and buccal surfaces of twenty extracted human third molars. A total-etch dentin adhesive system and a light-cure flowable composite (Filtek Ultimate Flowable, 3M ESPE, St. Paul, MN, USA) were used in this study. Micro-morphological SEM analysis of the marginal seal of the original tooth specimens was performed using high magnification of up to 1000×. In this study, we found the difference in interfacial micromorphology in dentin different locations. Also, marginal gap was found in both observed dentin area. Better understanding of complexity and three- dimensional variations of the tooth structure is important for prevention of clinical challenges such as postoperative sensitivity, marginal discoloration and secondary caries, which could be prevented by achieving of predictable and long-lasting adhesive bond.

Viscoelastic properties of uncured resin composites: Dynamic oscillatory shear test and fractional derivative model.

OBJECTIVE: In this study we analyze viscoelastic properties of three flowable (Wave, Wave MV, Wave HV) and one universal hybrid resin (Ice) composites, prior to setting. We developed a mathematical model containing fractional derivatives in order to describe their properties. METHODS: Isothermal experimental study was conducted on a rheometer with parallel plates. In dynamic oscillatory shear test, storage and loss modulus, as well as the complex viscosity where determined. We assumed four different fractional viscoelastic models, each belonging to one particular class, derivable from distributed-order fractional constitutive equation. The restrictions following from the Second law of thermodynamics are imposed on each model. The optimal parameters corresponding to each model are obtained by minimizing the error function that takes into account storage and loss modulus, thus obtaining the best fit to the experimental data. RESULTS: In the frequency range considered, we obtained that for Wave HV and Wave MV there exist a critical frequency for which loss and storage modulus curves intersect, defining a boundary between two different types of behavior: one in which storage modulus is larger than loss modulus and the other in which the situation is opposite. Loss and storage modulus curves for Ice and Wave do not show this type of behavior, having either elastic, or viscous effects dominating in entire frequency range considered. SIGNIFICANCE: The developed models may be used to predict behavior of four tested composites in different flow conditions (different deformation speed), thus helping to estimate optimal handling characteristics for specific clinical applications.

Micromorphological characterization of adhesive interface of sound dentin and total-etch and self-etch adhesives.

INTRODUCTION: The ultimate goal in restorative dentistry has always been to achieve strong and permanent bond between the dental tissues and filling materials. It is not easy to achieve this task because the bonding process is different for enamel and dentin-dentin is more humid and more organic than enamel. It is moisture and organic nature of dentin that make this hard tissue very complex to achieve adhesive bond. One of the first and most widely used tools for examining the adhesive bond between hard dental tissues and composite restorative materials is scanning electron microscopy. The aim of this study was scanning electron microscopy analyzes the interfacial micro morphology of total-etch and self-etch adhesives. MATERIAL AND METHODS: Micro morphological characteristics of interface between total-etch adhesive (Prime & Bond NT) in combination with the corresponding composite (Ceram X Mono) were compared with those of self-etching adhesive (AdheSE One) in, combination with the corresponding composite (Tetric EvoCeram). The specimens were observed under 1000 x magnification of scanning electron microscopy (JEOL, JSM-6460 Low Vacuum). Measurement of the thickness of the hybrid layer of the examined com posite systems was performed with the software of the device used (NIH Image Analyser). RESULTS: Micromorphological analysis of interface showed that the hybrid layer in sound dentin was well formed, its average thickness being 2.68 microm, with a large number of resin tags and a large amount of lateral branches for specimens with a composite system Prime & Bond NT-Ceram X Mono. However, the specimens' with composite systems Adhese One-Tetric EvoCeram did not show the presence of hybrid layer and the resin tags were poorly represented. CONCLUSION: The results of this study suggest that total-etch adhesives bond better with sound dentin than self-etch adhesive.

Clinical features and endodontic treatment of two-rooted mandibular canines: report of four cases.

INTRODUCTION: Predictable endodontic treatment depends on the dentist's knowledge about root canal morphology and its possible anatomic variations. The majority of mandibular canines have one root and root canal, but 15% may have two canals and a smaller number may have two distinct roots. The following clinical reports describe endodontic treatment of mandibular canines with two roots and two root canals. OUTLINE OF CASES Four clinical case reports are presented to exemplify anatomical variation in the human mandibular canine. Detailed analysis of the preoperative radiographs and careful examination of the pulp chamber floor detected the presence of two root canal orifices in all canines. Working length was determined with an electronic apex locator and biomechanical preparation was carried out by using engine driven BioRaCe Ni-Ti rotary instruments in a crown-down manner, followed by copious irrigation with 1% sodium hypochlorite. Definitive obturation was performed using cold lateral condensation with gutta-percha cones and Top Seal paste. The treatment outcome was evaluated using postoperative radiographs. CONCLUSION: Endodontists should be aware of anatomical variations of the treated teeth, and should never presume that canal systems are simple.

Crown reattachment with complicated chisel-type fracture using fiber-reinforced post.

INTRODUCTION: Maxillary incisors and specifically their crowns are the most common teeth involved in dental trauma because of their exposed position in the dental arch. Traumatized anterior teeth require quick functional and esthetic repair. In the case of a complex crown fracture, with the necessity of endodontic treatment, fiber-reinforced posts (FRC) were used to create a central support stump to restore the dental morphology. CASE REPORT: A 24-year-old male patient came to the dental clinic with dental injury to the maxillary left central incisor with a chisel-type fracture that extended subgingivally with a widely open pulp chamber. The patient reported a sports injury had occurred 1 day before. Provisional reposition of the crown was completed using a composite splint and after that endodontic treatment has been performed. Two days later, a fiber-reinforced composite resin post was placed into the canal and adhesive reattachment of the fragment also completed. The tooth was prepared for a composite resin veneer in the gingival third of the vestibular surface because of a visible fracture line. CONCLUSIONS: The combined use of a fiber-reinforced composite resin post and the original crown fragment is a simple and efficient procedure for the treatment of traumatized anterior teeth that appears to offer pleasing esthetic and functional results that is less invasive than conventional prosthodontic treatment.

Orthograde endodontic retreatment of teeth with individual cast posts: report of two cases.

INTRODUCTION: The failure of primary endodontic treatment is manifested by various clinical symptoms following endodontic therapy or, more frequently, by the development of chronic inflammatory process in the apex region without any subjective symptoms. In case of unfavorable outcome of the primary endodontic treatment, orthograde endodontic retreatment is the method of choice for a prolonged therapy. OUTLINE OF CASES: Two female patients, 47 and 44 years old, were presented at the Dental Clinic of Vojvodina for endodontic retreatment of teeth 22, 23 and 13, within the repeated prosthetic restoration. Intraradicular individual cast posts were removed using ultrasonic instruments. Remains of gutta-percha were removed by engine driven rotary re-treatment files, root canals were shaped and cleaned using the crown-down technique, and obturated with gutta-percha and epoxy-resin-based sealer using the lateral compaction technique. CONCLUSION: When there are metal posts or broken instruments in the root canal, the use of ultrasonic instruments is considered a safe method characterized by negligible tooth substance loss and minimal root damage causing fractures and perforations, and the entire procedure is effective and predictable. Non-surgical orthograde endodontic retreatment, when properly performed in accessible and penetrable root canals, achieves a high cure rate, good and lasting results and eliminates the need for radical procedures, such as apical surgery or tooth extraction. When nonsurgical endodontic retreatment is done, treated teeth must be restored by full coronal coverage as soon as possible, to prevent coronal leakage or fracture.

[One-year clinical evaluation of compomer restorations in cervical lesions of different aetiology].

INTRODUCTION: The aim of this one-year prospective clinical study was to evaluate the treatment results of compomer restorations (Dyract eXtral Dentsply/De Trey, Konstanz, Germany) with a single step self-etching dental adhesive (Xeno III Dentsply/De Trey, Konstanz, Germany) used for restoring class V lesions (non-carious and primary carious cervical lesions). MATERIAL AND METHODS: A total number of 62 class V restorations (n = 62) were placed by one dentist in 30 patients on incisors, canines and premolars. The fillings were placed due to different indications: non-carious cervical defects (n = 32) and primary carious lesions (n = 30). The restorations were evaluated by a single-blind design, according to the Modified United States Public Health Service system 6 and 12 months following the placement. The following were evaluated: retention, marginal integrity, marginal discoloration, wear; postoperative sensitivity and secondary caries. The statistical analysis compared the ratings of each criteria between materials using the Pearson chi-square or Fisher's exact test at a level of significance of 5% (p < 0.05). RESULTS: Two restorations of the non-carious lesion group were lost after 6 months, and after 12 months one restoration was lost in the group of primary carious lesions. There were no statistically significant differences between restorations for all evaluated criteria in both groups. CONCLUSION: The compomer restorations in combination with a single step self-etching dental adhesive showed acceptable clinical performance in Class V lesions after one year of clinical service.