Journal of Dental School
Volume:37 Issue: 4, Autumn 2019

 Repeatability and accuracy of measurements made on cone-beam computed tomography (CBCT) images are critical in dental practice especially in implantology. The aim of this study was to investigate the reproducibility of linear measurements made on reconstructed CBCT images.

Methods:

 In this in vitro, experimental study, 5 radiopaque markers were attached to the molars (left and right side), premolars (left and right side) and midline areas of 10 human cadaver dry mandibles. The distance between the markers and the lower border of the mandible was measured by a digital caliper and considered as the gold standard. CBCT images were taken, and the distance between the markers and the lower mandibular border was measured on cross-sectional images by three maxillofacial radiologists using Romexis software. The same measurements were made 1 month later to assess the reproducibility of measurements. The intra-class correlation coefficient was calculated to assess the repeatability and agreement between the observers.

 Compared with the gold standard, the mean error percentage in linear measurements was calculated to be 3.25%. The overall reproducibility of CBCT linear measurements was 0.865. The inter-observer agreement was calculated to be 0.972.

CBCT showed acceptable accuracy, repeatability and reliability for linear measurements, and can be used as an accurate tool for this purpose.

 Development of white spot lesions (WSLs) in the course of orthodontic treatment would compromise the satisfaction of patients and clinicians. One suggested preventive strategy is to incorporate antimicrobial agents into orthodontic adhesive systems or to coat brackets with them. Several clinical and experimental studies have evaluated the effect of antimicrobial agents, but no consensus has been reached on the best preventive approach. Thus, the aim of this narrative review was to assess the clinical and experimental studies on the effect of incorporation of antimicrobial agents in orthodontic adhesives and brackets.

 PubMed (Medline), Scopus, and Google Scholar were searched for related articles published from 1990 to 2020. Both clinical and experimental studies were included in this review.

 Different antimicrobial agents can be added to adhesive systems to control the formation of WSLs, and also preserve the bond strength of adhesives. Same as adhesive systems, coating of brackets with antibacterial agents can be performed to control bacterial proliferation and demineralization of enamel.

 Antimicrobial agents incorporated in bonding systems or used for coating of brackets can confer antimicrobial properties with no significant negative effect on bonding properties. However, clinical and long-term studies are required to confirm their effectiveness and absence of side effects.

Objectives:

 Finishing and polishing systems may affect the surface properties of composite resins. In this in vitro study, we evaluated the surface roughness of two composite resins after polishing with three different polishing systems.

Methods :

Thirty-six specimens (8 mm diameter × 2 mm thickness) were fabricated from Kalore nanohybrid and Gradia Direct microhybrid composite in a Teflon mold and divided into four groups according to the polishing protocol (n=9): control group, Sof-Lex, Super Snap, and Jiffy. The mean surface roughness (Ra) values were determined using a profilometer and the surface of two samples in each group was observed under a scanning electron microscope (SEM). Data were analyzed using one-way and two-way ANOVA. The significance level was set at 5%.

Results:

 Profilometric evaluation showed that in both composite resins, the smoothest surfaces were obtained with Mylar strip; also Jiffy showed significantly higher Ra values than other polishing systems. Type of composite and polishing technique had significant effects on surface roughness (P=0.0001). SEM observations also showed that surface roughness of Jiffy was more than that of three other groups.

Conclusion:

 After the use of finishing and polishing systems, the surface roughness of Gradia was higher than Kalore in all polishing systems. Sof-Lex and Super Snap were effective on Gradia, and jiffy created the roughest surface.

Objectives:

 This study aimed to assess the antibacterial effects of xylitol and Stevia rebaudiana (S. rebaudiana) ethanolic extract on oral biofilm.

Methods :

A total of 96 acrylic discs were divided into two main groups for inoculation with Streptococcus mutans (S. mutans) and Streptococcus sobrinus (S. sobrinus). Each group consisted of 6 subgroups including a positive control subgroup and 5 subgroups of discs immersed in 1% or 3% xylitol solutions, 2 or 4 mg/mL S. rebaudiana, or a combination of 3% xylitol and 4 mg/mL S. rebaudiana. After incubation, the discs were rinsed and transferred to fluid universal medium. The solutions were cultured on specific culture media and incubated. The colony-forming units (CFUs) were counted for each disc. The structure of biofilm in each group was evaluated under a scanning electron microscope (SEM).

Results :

ANOVA revealed significant differences between the subgroups in both S. mutans and S. sobrinus groups (P=0.03 and P=0.01, respectively). In S. mutans group, the logarithmic mean of colony count in the positive control subgroup was 6.75 while this value was significantly lower in 2 mg/mL (5.81) and 4mg/mL (5.92) S. rebaudiana subgroups using the post hoc Dunnett's test (P=0.01 and P=0.04, respectively). The three other subgroups did not show significant differences. In S. sobrinus group, all five experimental subgroups demonstrated significantly lower colony count than the positive control group (P<0.05).

Objectives :

Canine teeth are supposed to have one single root canal, but they may have some anatomical variations. This study aimed to investigate the morphology of root canals of maxillary and mandibular canines regarding gender and age in an Iranian population using cone-beam computed tomography (CBCT).

Methods:

 Using CBCT images, 126 maxillary and 125 mandibular canines were evaluated. Root anatomy was assessed regarding root length, root curvature, number of roots and canals, and pattern of root canal system. The data were analyzed by the Kruskal Wallis and Mann-Whitney tests and multinomial regression model. 

Results:

 The mean root length of male patients was significantly higher than females (p=0.0001). The most frequent root curvatures were towards the distal and buccal. Mandibular teeth (p=0.020) and females (p=0.012) had higher frequency of root curvature. All maxillary canines had one root; whereas 1.6% of mandibular canines had two roots. High prevalence of two canals was reported (34.9% of maxillary and 18.4% of mandibular canines). The most prevalent canal patterns included type I (65.1%) followed by type III (34.9%) in maxillary canines and types I (81.6%), III (16.8%) and V (1.6%) in mandibular canines. Higher frequency of type III canal configuration was reported in maxillary teeth (p=0.001) and male patients (p=0.008). No significant difference was found in any parameter between different age groups (p>0.05).

Conclusion:

 A high percentage of type III canal configuration in canine teeth especially maxillary canines and male patients was reported. Mandibular teeth and females had higher frequency of root curvature.

Objectives :

The main disadvantage of composite resins is their polymerization shrinkage, which can lead to microleakage. The purpose of this in vitro study was to evaluate the microleakage of bulk fill and conventional composites and a new hybrid glass ionomer (GI) in class II restorations of primary molar teeth.

Methods :

In this in vitro study, 51 primary molar teeth were randomly divided into three groups. Standard class II cavities were then prepared. In group 1 the cavities were restored with Filtek bulk fill composite; in group 2, the cavities were incrementally filled with Z250 conventional composite and in group 3, EQUIA Forte hybrid GI resin was used to fill the cavities. The teeth were subjected to thermal and then mechanical thermocycling. Afterwards, the teeth were immersed in 1% methylene blue solution. The teeth were then mesiodistally sectioned, and microleakage was evaluated at the occlusal and gingival margins under a stereomicroscope and a scanning electron microscope (SEM). The Shapiro-Wilk and Kruskal-Wallis tests were used to statistically analyze the data.

Results:

 There was no statistically significant difference in the mean microleakage of bulk fill and conventional composites and hybrid GI in the occlusal (P=0.495) or gingival (P=0.293) margins. The gingival microleakage was significantly higher than occlusal microleakage in all three groups (P<0.05).

Conclusion:

 Based on the results of the present study, microleakage of Filtek bulk fill composite is the same as that of Z250 conventional composite and EQUIA Forte hybrid GI.

Root fracture occurs less frequently in comparison with other traumatic dental injuries, and accounts for about 0.5%-7% of all dental injuries in permanent dentition. Complications associated with root fracture include pulp necrosis, root resorption, and pulp canal obliteration. Maintaining tooth vitality is the mainstay of treatment of horizontal root fracture in permanent teeth.

Case Presentation:

 In this study, a clinical case of horizontal root fractures in the middle third of maxillary right and left central incisors (teeth #11 and #21) of an 8-year-old girl is reported. The patient was followed-up for 3 years. The treatment plan was watchful waiting and after 3 years, the vitality tests were still positive, and no pathology was detected on control radiographs.

 Careful clinical examination, accurate diagnosis, and regular radiographic follow-ups are necessary for efficient treatment and successful outcome of teeth with horizontal root fractures.