Journal of Dental Medicine

Background and Aim: At the end of fixed orthodontic treatment, enamel damages are affected by amount of adhesive remnants. Thus, determining the factors involves in the amount of adhesive remnants e.g. the types of resins and the methods used for debonding is of necessity. The aim of this study was to evaluate the effect of the composite resin type and debonding pliers on enamel surface by a new method in measuring the adhesive remnant.

Materials and Methods: In this interventionally in-vitro study, 120 extracted human premolars were randomly divided into four groups of 30 each. The standard edgewise metal brackets were bonded on the teeth with two pastes self-cure composite "Concise" in the first and second groups, and with No-mix composite "Unite" in the third and fourth groups. the debonding was done by means of Lift off Debonding Instrument "LODI" (3M-Unitek), in first and third groups, and Bracket Removing Plier (Dentaurum), in the second and forth groups, respectively. After debonding, all teeth were evaluated with steriology software (stereolith version 1) for comparing the amount of adhesive remnants between the four groups. For data analysis, One-way ANOVA and independent t.test were used.

Results: The fourth group showed the lowest adhesive on the enamel surface and the most on the bracket surface with significant differences with other three groups (p<0.01).

Conclusion: The use of Dentaurum debonding plier with shear-peel force when used with the Unite adhesive (group 4), would decrease the adhesive remnants on the enamel surface.

Background and Aim: A key factor in restoring the endodontically treated teeth is ferrule preparation. When the ferrule is absent, occlusal loads may cause the post or root to fracture. The purpose of this in vitro study was to evaluate the effect of ferrule preparation on fatigue resistance of teeth restored with quartz-fiber posts.

Materials and Methods: Twenty single-rooted lower premolars having similar dimentions were randomly devided into two groups of 10. In control group the teeth were prepared with 3-mm of remaining coronal tooth structure and in test group teeth were prepared with 1-mm of remaining coronal tooth structure. The teeth were endodontically treated. 9-mm long Post holes were prepared, and D.T. light quartz-fiber(RTD,France) posts were cemented with Panavia F2(Kuraray,Japan).Then the core build up was done with Bisco core build up composite(Bisco,USA) and full metal crowns were cemented with Zinc phosphate(Harvard cement, Germany). All specimens were mounted in acrylic resin blocks and intermittently loaded (180 N) at an angulation of 45- degree to the long axis of the teeth at a frequency of 4 loads per second, until failure occurred.

Results: There was significant difference between the loads cycles of two groups studied. (p<0.0001).

Conclusion: The results of this study showed that an increased amount of coronal dentin significantly increases the fracture resistance of teeth restored with quartz-fiber posts.

Background and Aims: The bond strength between veneer ceramics and zirconia frameworks is the weakest component in the layered ceramics. Due to the possible effect of adding pigments to the core materials on the bond strength between core and veneer as well as the introduction of new ceramic materials in dentistry, the aim of this study was to compare the zirconia core-veneer microtensile bond strength using two ceramic veneers with or without coloring the core.
Materials and Methods: In this experimental study, 12 disc-shaped specimens were fabricated using a manually aided design- manually aided manufactured (MAD/MAM) zirconia core (Zirkonzahn). Two veneering ceramics of Ceram Kiss and Zirkonzahn ICE were also used to veneer the specimens. Half of the Zirkonzahn discs were remained white and the others were colored by shade A2.Then, the discs were cut into microbars (30 for each group) and the microtensile bond strength of the core-veneer was calculated. The specimens were assessed using scanning electron microscopy (SEM) and the data were analyzed using two-way ANOVA and Student's t-test.
Results: Significant differences with respect to veneer layer were found (P<0.001). No significant differences were seen among colored and uncolored cores (P=0.69).
Conclusion: According to the apparent effect of veneering ceramics on the core-veneer bond strength, careful selection of these agents is essential to achieve adequate bond strength between core and veneer to prevent delaminating and chipping failures of zirconia veneered restorations.

Background and Aims: Since a large marginal opening allows more plaque accumulation, gingival sulcular fluid flow and bone loss, microleakage, recurrent caries and periodontal disease, marginal fit is of great importance in fixed restorations. The aim of this study was to compare the marginal fit of zirconium-based all ceramic (Cercon) frameworks, made by two different approaches (Direct and Wax-up scanning).

Materials and Methods: An abutment analog, with 5.5 mm width and height, was selected as an experimental model. Twenty all ceramic cores were made for this model (10 specimens per each group). In the first group (Direct), experimental models were scanned directly using Computer Aided Design/Computer Aided Manufacturing (CAD/CAM). The core was then designed with the aid of a computer and machined. In the second group (Wax-up or CAM) a wax-up pattern was made on the experimental model and then scanned and milled from Cercon blocks. The marginal discrepancy of each specimen was recorded using a stereomicroscope (SZX9, Olympus, Japan) and digital camera (Mode TK, C1380E, JVC, Japan) and then measured by Adobe Photoshop CS software. The data were analyzed using T-test.

Results: Mean marginal discrepancy of Direct group (85.2±3.95 µm) was significantly less than that of Wax-up group (120.2±6.91 µm).

Conclusion: Improved marginal fit of zirconia ceramics was found with the direct model scanning compared with that of Wax-up scanning using CAD/CAM.

  Background and Aims: Postoperativee endodontic pain is an outstanding problem for dental patients. Therefore, a successful management of endodontic pain has become as one of the main dental objectives. The aim of the present study was to compare the postoperative endodontic pain in patients under general anesthesia versus local anesthesia.

  Materials and Methods: For conducting this clinical trial study, 50 patients having mandibular molars candidate for root canal therapy were selected. Twenty-five patients treated under general anesthesia because of their fear, anxiety or gag reflex. Other 25 patients treated under local anesthesia. All teeth were prepared using engine-driven rotary system in a crown-down technique and filled using lateral condensation technique. Heft- parker visual analog scale was used to measure the degree of pain at 6, 12, 24, and 48 hours after the treatment. Mann-Whitney, Chi-square, and T-tests were used to compare the intensity of postoperative pain between the groups.

  Results: The mean intensity of postoperative pain in local and general anesthesia groups at 6, 12 and 24 hours had statistically significant difference (P<0.05).

  Conclusion: Postoperative pain in patients who treated under general anesthesia was significantly less than the patients who treated under local anesthesia.