The investigation of composition and thermal behavior of two types of backfilling gutta-percha.

Background/purpose: In the warm gutta-percha technique, soft-type and regular-type gutta-percha are using for backfilling thermoplasticized injection system. However, there are limited reports about the properties of these backfilling gutta-percha. This study aimed to analyze and compare the composition, thermal behavior and compact force of two types of backfilling gutta-percha. Materials and methods: Soft-type and regular-type backfilling gutta-percha (B&L BioTech, Fairfax, VA, USA) were investigated. The inorganic and organic fractions of these gutta-perchas were separated by quantitative chemical analysis (n = 6). Their composition was analyzed using energy dispersive spectroscopy. Thermal behavior in response to temperature variations was analyzed using differential scanning calorimetry. Additionally, a compaction model was used to investigate the relation between compaction force and temperature (n = 10). Results: The soft-type contained more gutta-percha (3.69-5.85%), carbon ratio (38.96-48.52%) and less inorganic substance (86.51-90.45%), zinc ratio (29.36-35.67%). The composition ratio of two types gutta-percha were statistically significant different (P < 0.05). There were three phase transitions of the soft-type gutta-percha which started at 39.84 °C, 49.32 °C and 54.15 °C while the two phase transitions of the regular-type gutta-percha started at 40.48 °C and 53.45 °C. The glass transition temperature of the regular-type gutta-percha (44.24 °C) was higher than that of the soft-type gutta-percha (40.66 °C). Under various setting temperature, the higher compaction force in the regular-type gutta-percha was required (P < 0.05). Conclusion: The different components in gutta-percha contribute to its differences in thermal behavior. The soft-type had a higher proportion of gutta-percha and lower ZnO which makes the fluidity better than the regular-type.

The investigation of thermal behaviour and physical properties of several types of contemporary gutta-percha points.

AIM: To analyse the contents and thermal behaviour of several brands of contemporary gutta-percha points due to the variable nature of the components of gutta-percha, and the impact they can have on the physical properties of this unique material during canal filling. METHODOLOGY: Six brands of gutta-percha were investigated: Conform Fit TM Gutta-Percha Points for ProTaper Gold® (PTG) (Dentsply Sirona), ProTaper® Universal Gutta-Percha Points (PTU) (Dentsply Sirona), Autofit TM Feathered Tip Gutta Percha (Kerr), Mtwo® Gutta-Percha (VDW), Gutta Percha Root Canal Points (GC, GC Corporation) and Gutta-Percha Points ISO Color-Coded (ISO; Dentsply Sirona). The organic and inorganic fractions of gutta-percha points were separated by quantitative chemical analysis. Thermal conductivity was detected using a laser flash method. In addition, the thermal behaviour of gutta-percha in response to temperature variations was analysed using differential scanning calorimetry (DSC). Kruskal-Wallis and Dunn tests were applied for comparisons amongst groups for chemical compositions and temperature obtained from DSC. The associations between compositions and thermal conductivity were determined using simple linear regression. A p value <.05 was considered to be statistically significant. RESULTS: There were significant difference in the inorganic fractions of the gutta-percha points in percentage by weight amongst the groups (p < .05). PTG had the lowest thermal conductivity (0.42 W/m K). A positive correlation was observed between the percentage of inorganic fraction and thermal conductivity (r = 0.95). The initial phase changing temperature and peak temperature measured by DSC were significantly different when the ß-form transformed to α-form (p < .05), whereas no significant difference was found during the α-form to the amorphous-phase transition (p > .05). CONCLUSIONS: Chemical compositions and initial phase changing temperature by DSC varied according to the various brands of gutta-percha points. Conform Fit TM gutta-percha had the lowest percentage of inorganic fraction and thermal conductivity amongst these six brands of gutta-percha. Thermal conductivity had the strongest positive correlation with the percentage of inorganic components and zinc, whilst there was a negative correlation to the amount (ratio) of gutta-percha.

Tooth discoloration and the effects of internal bleaching on the novel endodontic filling material SavDen® MTA.

BACKGROUND/PURPOSE: Mineral trioxide aggregate (MTA) was widely used in endodontic therapy as bioceramic material. Although MTA has high biocompatibility, it may lead to tooth discoloration. The aim of this study was to investigate the discoloration of two different bioceramic materials and the effects of internal bleaching. METHODS: Thirty single-canal mandibular premolars were extracted and randomly assigned to three groups (n = 10), white ProRoot® MTA, SavDen® MTA and a control group. Endodontic access opening, cleaning and shaping were performed, then the teeth were obturated using the two bioceramic materials. Tooth color was recorded at baseline, day 1, and 1, 2, 4, 6, 8, 12, 16, and 24 weeks after treatment. At the end of 24 weeks, sodium perborate was used to perform internal bleaching. Tooth color was recorded at 1, 2, and 6 weeks subsequently. Teeth were measured using a DeguDent® spectrophotometer, and data were transformed into Commission Internationale de l'Eclairage (CIE) L∗a∗b∗ system. RESULTS: Teeth treated with white ProRoot® MTA showed significant color change and decrease in L∗ value. Internal bleaching leaded to decrease of the ΔE∗ value for all three groups and increase in the L∗ value. There was no difference in tooth discoloration between SavDen® MTA and the control group after obturation and internal bleaching. CONCLUSION: In terms of visual perception, white ProRoot® MTA tends to cause black and blue discoloration. SavDen® MTA, formulated with calcium lactate gluconate, could be used to reduce tooth discoloration in endodontic treatment.

Thermal behavior and viscoelastic properties of gutta-percha used for back-filling the root canal.

BACKGROUND/PURPOSE: In clinical operations, qualitative differences in the texture and operational feeling of the regular type and soft type back-filled gutta-percha are readily discernible. This study aimed to investigate and compare the thermal behavior and physical properties of the two gutta-percha materials. MATERIALS AND METHODS: The chemical compositions of regular and soft type Gutta-Percha Obturator® pellets were examined via energy dispersive X-ray spectroscopy. The thermal behaviors of the pellets during heating and cooling were evaluated using a differential scanning calorimeter. Finally, the viscoelastic properties of the two materials during cooling were assessed using a modular compact rheometer. RESULTS: The soft type gutta-percha contained a greater atomic percentage of zinc than the regular type material. In addition, the soft type gutta-percha exhibited exothermic peaks during cooling, whereas the regular type gutta-percha did not. The two materials exhibited different viscoelastic behaviors under cooling. In particular, the rate of change of the loss factor for the soft type gutta-percha was more than that of the regular type gutta-percha at temperature lower than 80°C. CONCLUSION: The soft type gutta-percha underwent significant crystallization during cooling, and therefore exhibited pronounced volume shrinkage. Furthermore, the soft type gutta-percha underwent a greater rate of change in viscoelasticity under cooling than the regular type gutta-percha, and exhibited poorer physical stability. Consequently, in the back-packing procedure, soft type gutta-percha must be compacted more often over time than regular type gutta-percha to ensure the same quality of root canal obturation.