ABSTRACT
Introduction: Expired gutta-percha (GP) can lose its mechanical properties. This study aimed to compare the tensile strength values between expired and nonexpired GP-cones and to assess the outcome of different heat temperatures on this strength. Materials and Methods: Two-hundred-forty ProTaper points were obtained from nonexpired and 2 years expired pack with two different subgroups (sealed or exposed to air and light). All groups were subjected to the following treatments: control, 90°C water bath and cool either at room temperature or 0°C and 70°C water bath and cool either at room temperature or at 0°C. The strength under the tensile load was calculated using the universal testing machine. Results: The collected data were evaluated by one-way analysis of variance. Tensile strength for all control groups did not show any difference. Significant increase in the tensile strength in groups heated for 1 min in a water bath at 70°C, the tensile strengths were 8.19 ± 2.72 Mpa and 5.94 ± 1.14 Mpa cooled at 25°C and 0°C, respectively, P ≤ 0.001. Two years expiration did not lower the tensile strength of the GP and exposure to air and light did not show any change. Appropriate storage of GP is a key factor to extend its lifespan. Conclusion: A clinician may consider using expired GP as long as there are no noticeable changes in their structure and properties. A simple chairside technique using hot water may be helpful in restoring the mechanical properties of expired GP.
ABSTRACT
BACKGROUND: Orthodontic treatment may result in undesirable side effects, such as root resorption and a decrease in the size of the pulp tissue which could be associated with the duration of the orthodontic treatment. Piezocision-assisted tooth movement was introduced as a minimally invasive surgical procedure to shorten orthodontic treatment time. This prospective randomized clinical trial was aimed to compare the pulp volume changes of maxillary anterior teeth after en-masse retraction with or without piezocision-assisted orthodontics. METHODS: Patients who required orthodontic treatment with bilateral maxillary first premolar extractions and en-masse retraction were recruited. Patients were randomly divided into extraction with piezocision, or only extraction, serving as controls. Pulp volume and root length changes of the maxillary six anterior teeth were measured and compared between the two groups using a 3-Dimensional analytical software. Paired and independent sample t-tests were used to compare within and between groups. Bivariate correlation was done between the mean change in pulp volume and its corresponding root length. The significance level was set at α = 0.05. RESULTS: A total of 23 patients were included, 12 in the piezocision, and 11 in the control group. At the end of the en-masse retraction phase, (mean = 122.74 ± 3.06 days) pulp volume was significantly decreased in all six anterior teeth in both groups (P < 0.01). The decrease in pulp volume was not statistically different between both groups, (P > 0.05). There was a statistically significant but moderate correlation only between the pulp volume change of the right canine and its root length, r = 0.44, P = 0.034. CONCLUSIONS: The effect of piezocision-assisted orthodontic tooth movement on the pulp volume was comparable to the conventional orthodontic treatment. The degree of change in pulp volume does not appear to be related to the amount of root resorption. Trial registration NCT03180151. Registered December 25, 2016, retrospectively registered, https://clinicaltrials.gov/ct2/show/record/NCT03180151 .
