Effect of compression load and temperature on thermomechanical tests for gutta-percha and Resilon®

Natural Polymer Eucommia Ulmoides Rubber: A Novel Material

As the second natural rubber resource, Eucommia ulmoides rubber (EUR) from Eucommia ulmoides Oliver is mainly composed of trans-1,4-polyisoprene, which is the isomer of natural rubber cis-1,4-polyisoprene from Hevea brasiliensis. In the past few years, the great potential application of EUR has received increasing attention, and there is a growing awareness that the natural polymer EUR could become an emerging research topic in field of the novel materials due to its unique and excellent duality of both rubber and plastic. To gain insight into its further development, in this review, the extraction, structure, physicochemical properties, and modification of EUR are discussed in detail. More emphasis on the potential applications in the fields of the environment, agriculture, engineering, and biomedical engineering is summarized. Finally, some insights into the challenges and perspectives of EUR are also suggested.

Effect of Distinctive Moisture Conditions on Push-out Bond Strength of Three Root Canal Sealers-An In-Vitro Study

Objective:

Endodontic sealer should adhere to both dentin and the core filling material but the moisture conditions of the canals affect the adhesive properties of the sealer. An ideal sealer with perfect moisture conditions will lead to greater strength of the restored tooth, which may provide greater resistance to tooth fracture and clinical longevity of an endodontically treated tooth. The aim of this study was to evaluate the effect of moisture conditions on the push-out bond strength of three root canal sealers: AH Plus^® (Dentsply-Tulsa Dental, Tulsa, OK), Epiphany (Pentron Clinical Technologies, Wallingford, CT), and GuttaFlow (Coltene/Whaledent, Altstatten, Switzerland).

Materials and Methods:

A total of 120 single-rooted, non-carious teeth were collected for the study and were stored in normal saline. The root canals were prepared using step-back technique. Teeth were divided into four groups based on type of drying procedure used and further subdivided into three subgroups based on the type of sealer used. The samples were cut horizontally to produce slices and then tested for push-out bond strength using Universal Testing Machine (Servo Series 50 kN; P S I Sales Private Limited, New Delhi, India). The specimens were examined for mode of fracture under magnification and the results were analyzed statistically.

Results:

Distinctive moisture conditions for all sealers were observed and the highest strength of AH Plus^® was evaluated under moist condition, Epiphany under dry condition, and GuttaFlow under normal condition, respectively.

Conclusion:

Distinctive moisture conditions affect the push-out bond strength of the sealers.

Accuracy of Gypsum Casts after Different Impression Techniques and Double Pouring

This study evaluated the accuracy of gypsum casts after different impression techniques and double pouring. Ten patients were selected and for each one it was obtained 5 partial putty/wash impressions with vinyl polysiloxane (VPS) material from teeth #13 to #16 with partial metal stock trays. The following techniques were performed: (1) one-step; two-step relief with: (2) PVC film; (3) slow-speed tungsten carbide bur and scalpel blade, (4) small movements of the tray and (5) without relief—negative control. The impressions were disinfected with 0.5% sodium hypochlorite for 10 minutes and stored during 110 and 230 minutes for the first and second pouring, respectively, with type IV gypsum. Three intra-oral lateral photographs of each patient were taken using a tripod and a customized radiographic positioner. The images were imported into ImageJ software and the total area of the buccal surface from teeth #13 to #16 was measured. A 4.0% coefficient of variance was criterion for using these measurements as Baseline values. The casts were photographed and analyzed using the same standardization for the clinical images. The area (mm²) obtained from the difference between the measurements of each gypsum cast and the Baseline value of the respective patient were calculated and analyzed by repeated-measures two way-ANOVA and Mauchly’s Sphericity test (α = 0.05). No significant effect was observed for Impression technique (P = 0.23), Second pouring (P = 0.99) and their interaction (P = 0.25). The impression techniques and double pouring did not influence the accuracy of the gypsum casts.

Quality of obturation achieved by a non-gutta-percha-based root filling system in single-rooted canals

INTRODUCTION

The present study examined the quality of obturation in root canals filled by an experimental non-gutta-percha-based (NGP) root filling system using warm vertical or cold lateral compaction. The quality of obturation was evaluated by comparing the volumetric percentage of gaps and voids identified from similar canals obturated with gutta-percha and an epoxy resin-based sealer using the same obturation techniques.

METHODS

Forty single-rooted premolars with oval-shaped canals were cleaned, shaped, and obturated with 1 of the 4 material/obturation technique combinations (n = 10). Filled canals were scanned with micro-computed tomographic imaging. Reconstructed images were analyzed for the volumetric percentage of gaps and voids at 3 canal levels (0-4, 4-8, and 8-12 mm from the working length). Roots were sectioned at the 4-mm, 8-mm, and 12-mm levels. Scanning electron microscopic images of negative replicas of root sections were examined to quantify the circumferential percentage of interfacial gaps and the area percentage of intracanal voids. Data were analyzed with parametric or nonparametric statistical methods.

RESULTS

A statistically significant difference was found for the volumetric percentage distribution of gaps and voids for "obturation technique" but not for "material." Significantly higher percentages of gaps and voids were identified in canals obturated with the NGP system using cold lateral compaction. Examination of negative replicas ascribed this difference to a higher area percentage of interfacial gaps rather than more intracanal voids.

CONCLUSIONS

Using warm vertical compaction, the NGP system fulfils the objective of 3-dimensional obturation of the canal space in a manner comparable with the results achieved with gutta-percha and a root canal sealer.

Effectiveness of gutta-percha and Resilon in filling lateral root canals using thermomechanical technique

OBJECTIVE: The aim of this study was to evaluate the effectiveness of gutta-percha and Resilon in filling lateral root canals in cervical, middle, and apical third using a thermomechanical technique. MATERIAL AND METHOD: Root canals of artificial teeth were prepared using a standard preparation. The lateral canals were fabricated using a 0.3-mm-diameter bur at 3 parts of each root. By using Tagger's hybrid technique with a McSpadden thermomechanical compactor, the root canal was filled using the following filling materials: Dentsply gutta-percha, Endopoint gutta-percha, and Resilon cones. The root canal fillings were evaluated using digitized radiographs and the Image Tool software. The percentage of filled area of each lateral canal was determined. The data were subjected to analysis of variance (ANOVA) and Tukey tests at a 5% significance level. RESULT: Resilon showed better effectiveness as a filling material. When the three thirds were compared, Resilon was more effective in the apical third than in the cervical third (p < 0.05). CONCLUSION: Resilon is an effective filling material for lateral root canals using a thermomechanical technique.