Influence of Voxel Size on CBCT Images for Dental Implants Planning

Objective  This study was developed to evaluate the influence of voxel size on bone measurements for implant planning.

Materials and Methods  The research was performed by using edentulous synthetic human mandibles with different levels of bone resorption. For each mandible, height and bone thickness were measured with a digital caliper. The PaX-i3d device was used to acquire the volumes of the five mandibles, with 50kVp, 4 mA, and a voxel size of 0.08 mm. After the acquisition, the images were reconstructed in the software CS three-dimensional Imaging, with four different sizes of voxels: 0.1, 0.2, 0.3, and 0.4 mm. All volumes were analyzed by a single evaluator who performed measurements to obtain bone height and thickness, using the reference points that were considered in obtaining the gold standard. The data were analyzed by ANOVA with a significance level of 5%.

Results  There was no significant difference in the measurements obtained with different voxel sizes, both for bone height measurements and bone thickness. There was no statistically significant difference in measurements in thickness in comparison to the gold standard.

Conclusion  When necessary, to measure height and bone thickness, it is possible to recommend voxel images of larger size (0.40 mm) without compromising the quality of the patient's clinical planning.

Influence of Low-Dose Protocols of CBCT on Dental Implant Planning

PURPOSE

To evaluate the influence of low-dose protocols, with different numbers of basis images, on the precision of linear bone measurements in CBCT images.

MATERIALS AND METHODS

Five polyurethane mandibles, with different levels of bone resorption, were used in this in vitro study. To obtain the reference standard, landmarks were made in the mandibular superior and buccal cortices, and then a digital caliper was used to measure the bone height and thickness at these regions. CBCT images were obtained with the PaX-i3D (Vatech) unit set at 50 kV, 4 mA, 0.2-mm voxel size and 50 × 50-mm field of view. Keeping these parameters fixed, each mandible was scanned twice, with different protocols: Low dose (L) had an acquisition time of 24 seconds and 720 basis images, and ultralow dose (UL) had an acquisition time of 15 seconds and 450 basis images. Then, measurements of bone height and thickness were performed on the images, using the previously determined landmarks as reference. The obtained data were submitted to statistical analysis, with a significance level of .05. Analysis of variance, Student t test, and intraclass correlation coefficient were employed.

RESULTS

Regarding bone height, there were no significant differences between the measurements obtained with the L and UL protocols (P = .8648). Additionally, the L and UL protocols did not differ in relation to the reference standard (P = .8717 and P = .9928, respectively). Likewise, there were no significant differences between the measurements obtained with the L and UL protocols (P = .7969) for bone thickness, nor between these protocols and the gold standard (P = .7455).

CONCLUSION

Considering the great demand for precise measurements in implantology, protocols of low-dose radiation can be used without compromising clinical planning.

Rare presentation of adenomatoid odontogenic tumor in a pediatric patient: a case report

The adenomatoid odontogenic tumor (AOT) is a painless benign tumor with slow growth, usually asymptomatic. It has three variants: follicular, extrafollicular, and peripheral. In the follicular type, the tumor is associated with an impacted tooth, and maxillary canines are the most frequently affected. Association with primary teeth is very rare. Treatment consists essentially in a total lesion enucleation. The objective of this paper is to present the clinical case of a 7-year-old female patient with an adenomatoid odontogenic tumor associated with the crown of the left lower deciduous canine (73), dislodging it to the mandibular base and consequently shifting and also impacting the permanent lower canine (33). The lesion was treated with careful enucleation, preserving the permanent canine, which then had its eruption path released favoring its migration to an ideal position.

The relationship between temporomandibular dysfunction and head and cervical posture

OBJECTIVE

This study aimed to evaluate the possibility of any correlation between disc displacement and parameters used for evaluation of skull positioning in relation to the cervical spine: craniocervical angle, suboccipital space between C0-C1, cervical curvature and position of the hyoid bone in individuals with and without symptoms of temporomandibular dysfunction.

MATERIAL AND METHODS

The patients were evaluated following the guidelines set forth by RDC/TMD. Evaluation was performed by magnetic resonance imaging for establishment of disc positioning in the temporomandibular joints (TMJs) of 30 volunteer patients without temporomandibular dysfunction symptoms and 30 patients with symptoms. Evaluation of skull positioning in relation to the cervical spine was performed on lateral cephalograms achieved with the individual in natural head position. Data were submitted to statistical analysis by Fisher's exact test at 5% significance level. To measure the degree of reproducibility/agreements between surveys, the kappa (K) statistics was used.

RESULTS

Significant differences were observed between C0-C1 measurement for both symptomatic (p=0.04) and asymptomatic (p=0.02). No statistical differences were observed regarding craniocervical angle, C1-C2 and hyoid bone position in relation to the TMJs with and without disc displacement. Although statistically significant difference was found in the C0-C1 space, no association between these and internal temporomandibular joint disorder can be considered.

CONCLUSIONS

Based on the results observed in this study, no direct relationship could be determined between the presence of disc displacement and the variables assessed.