Micro-computed tomography: high resolution imaging of bone and implants in three dimensions

Comparison of root resorption after bone-borne and tooth-borne rapid maxillary expansion evaluated with the use of microtomography

INTRODUCTION

Root resorption was compared between bone-borne and tooth tissue-borne rapid maxillary expansion patients with the use of microtomography.

METHODS

The study included 20 patients (ages 11-16 years) requiring fixed orthodontic treatment who underwent extraction of their first premolars after rapid maxillary expansion with the use of modified appliances. One side of the appliance covered the teeth with acrylic, while the other side was fixed to the palatal bone by means of a miniscrew. After 3 months' retention, the appliance was removed and teeth were extracted and examined with the use of microtomography.

RESULTS

When the apical, middle, and cervical thirds, as well as the buccal and lingual sides, were compared, the volume loss was significantly higher in the tooth tissue-borne group than in the bone-borne group (P <0.01). The least volume loss occurred on the cervical third lingual surface in the tooth tissue-borne group and on the middle third buccal surface in the bone-borne group. In the former group, least resorption occurred on the cervical third and highest resorption on the buccal side. In the latter group, surfaces showed no significant changes.

CONCLUSIONS

More root resorption occurred in the tooth tissue-borne group, mostly in the apical and middle thirds. The amount of resorption on the buccal surface was higher than that on the lingual surface.

Diagnostic imaging of trabecular bone microstructure for oral implants: a literature review

Several dental implant studies have reported that radiographic evaluation of bone quality can aid in reducing implant failure. Bone quality is assessed in terms of its quantity, density, trabecular characteristics and cells. Current imaging modalities vary widely in their efficiency in assessing trabecular structures, especially in a clinical setting. Most are very costly, require an extensive scanning procedure coupled with a high radiation dose and are only partially suitable for patient use. This review examines the current literature regarding diagnostic imaging assessment of trabecular microstructure prior to oral implant placement and suggests cone beam CT as a method of choice for evaluating trabecular bone microstructure.

Radiological and micro-computed tomography analysis of the bone at dental implants inserted 2, 3 and 4 mm apart in a minipig model with platform switching incorporated

BACKGROUND

The purpose of this study was to assess the effect of inter-implant distance on interproximal bone utilizing platform switching. Analysis of interproximal bone usually depends on traditional two-dimensional radiographic assessment. Although there has been increased reliability of current techniques, there has been an inability to track bone level changes over time and in three dimensions. Micro-CT has provided three-dimensional imaging that can be used in conjunction with traditional two-dimensional radiographic techniques.

METHODS

This study was performed on 24 female minipigs. Twelve animals received three implants with an inter-implant distance of 3 mm on one side of the mandible and another three implants on the contra-lateral side, where the implants were placed 2 mm apart creating a split mouth design. Twelve other animals received three implants with an inter-implant distance of 3 mm on one side of the mandible and another three implants on the contra-lateral side, where the implants were placed 4 mm apart creating a split mouth design too. The quantitative evaluation was performed comparatively on radiographs taken at t 0 (immediately after implantation) and at t 8 weeks (after termination). The samples were scanned by micro-computed tomography (μCT) to quantify the first bone to implant contact (fBIC) and bone volume/total volume (BV/TV). Mixed model regressions using the nonparametric Brunner-Langer method were used to determine the effect of inter-implant distance on the measured outcomes.

RESULTS

The change in bone level was determined using radiography and its mean was 0.05 mm for an inter-implant distance of 3 and 0.00 mm for a 2 mm distance (P = 0.7268). The mean of this outcome was 0.18 mm for the 3 mm and for 4 mm inter-implant distance (P = 0.9500). Micro-computed tomography showed that the fBIC was always located above the reference, 0.27 and 0.20 mm for the comparison of 2-3 mm (P = 0.4622) and 0.49 and 0.34 mm for the inter-implant distance of 3 and 4 mm (P = 0.1699). BV/TV inside the defined parallelepipedic masks reached 82.38% for the 2 mm inter-implant distance and 85.00% for 3 mm, P = 0.8432. For the comparison of the 3-4 mm inter-implant distance, the means were 84.69% and 84.38%, respectively, P = 0.8401. Non-inferiority tests for the smaller inter-implant distances for both comparisons showed similar differences and similar tolerance ranges.

CONCLUSION

The effect of a smaller interproximal distances between implants on bone level, fBIC and BV/TV assessed by two convergent investigation methods, radiology and μCT, was similar to that of larger distances. Implants can potentially be placed 2 mm apart instead of 3 mm and 3 mm apart instead of 4 mm when platform switching is utilized. Further research with a conventional platform is warranted.

In vitro synchrotron-based radiography of micro-gap formation at the implant-abutment interface of two-piece dental implants

Micro-gap formation at the implant-abutment interface of two-piece dental implants was investigated in vitro using high-resolution radiography in combination with hard X-ray synchrotron radiation. Images were taken with the specimen under different mechanical loads of up to 100 N. The aim of this investigation was to prove the existence of micro-gaps for implants with conical connections as well as to study the mechanical behavior of the mating zone of conical implants during loading. Synchrotron-based radiography in comparison with classical laboratory radiography yields high spatial resolution in combination with high contrast even when exploiting micro-sized features in highly attenuating objects. The first illustration of a micro-gap which was previously indistinguishable by laboratory methods underlines that the complex micro-mechanical behavior of implants requires further in vitro investigations where synchrotron-based micro-imaging is one of the prerequisites.

Synchrotron radiation-based microtomography of alveolar support tissues

OBJECTIVES

To study the alveolar support structures using synchrotron radiation (SR)-based microtomography with particular focus on the alveolar surface.

DESIGN

High-resolution microtomography of jaw segments of various species and subsequent three-dimensional (3D) reconstruction.

SETTING AND SAMPLE POPULATION

Microtomography was performed at the DORIS-ring of the synchrotron facility of HASYLAB/DESY in Hamburg, Germany. The samples consisted of human, simian and porcine jaw segments.

RESULTS

With SR being monochromatic, no beam-hardening artifacts could occur and the grey values in the scans were therefore directly related to the local tissue densities. Apart from the mineralized tissues, the beam energy was low enough to allow for the visualization of soft tissues like the fibers of the periodontal ligament (PDL) and blood vessels. 3D reconstructions of the alveolar bone showed that it can be rough and sharply edged. Furthermore, an intricate network of marrow cavities and blood vessels penetrates its surface. Differences in the local grey value distribution in the alveolar bone pointed to remodeling activity in the close vicinity of the PDL.

CONCLUSION

The assumption that the alveolar bone surface is smooth and continuous is not correct. This means that even small orthodontic loads can already give rise to high local stresses and strains in the bone and thus initiate remodeling processes.