Cone beam computed tomography and low-dose multislice computed tomography in orthodontics and dentistry

Objectives

The goal of the present work was to assess various computed tomography (CT) systems in term of image quality and organ doses, namely five cone-beam CT (CBCT) scanners operated at standard settings and three multislice CT (MSCT) scanners operated at greatly dose-reduced settings.

Materials and methods

Radiographic volume scans were taken on a complete human cadaveric head specimen and the image quality of each was rated by four experienced examiners according to specific skeletal structures and bone–soft tissue interfaces. Radiation doses were captured by a head-and-neck phantom (Rando; Alderson Research Laboratories). Standard protocols were used for the CBCT scans. For the MSCT scans, tube voltage and current were adjusted to minimize radiation without compromising image quality.

Results

Interobserver agreement was close to perfect, with iota coefficients of 0.931 (95?% CI 0.807–0.978) between groups 1 and 2 and 0.959 (95?% CI 0.869–1.000) between groups 1 and 3. Ratings of image quality in terms of skeletal-structure representation were slightly better for the CBCT than the MSCT scanners, although these differences were not statistically significant. The two groups of scanners applied considerably different organ doses: the lowest dose (0.03 mSv) was measured on the bone surface with a CBCT unit (Picasso Trio® from Vatech) and the highest dose (8.30 mSv) in the vicinity of the eye lens with another CBCT unit (3D Accuitomo 170® from J. Morita).

Conclusion

The various systems tested offer similar imaging quality but demonstrated distinct differences in organ dose levels. The decision on which approach to take is not between CBCT and MSCT but rather between specific models and parameter settings. If these are optimized, MSCT images providing useful clinical information can be obtained at much reduced levels of radiation. Depending on the model and setting used, MSCT radiation levels may even be lower than during CBCT scans.     

An in vitro comparison of subjective image quality of panoramic views acquired via 2D or 3D imaging

Objectives

The objective of this study is to compare subjective image quality and diagnostic validity of cone-beam CT (CBCT) panoramic reformatting with digital panoramic radiographs.

Materials and methods

Four dry human skulls and two formalin-fixed human heads were scanned using nine different CBCTs, one multi-slice CT (MSCT) and one standard digital panoramic device. Panoramic views were generated from CBCTs in four slice thicknesses. Seven observers scored image quality and visibility of 14 anatomical structures. Four observers repeated the observation after 4 weeks.

Results

Digital panoramic radiographs showed significantly better visualization of anatomical structures except for the condyle. Statistical analysis of image quality showed that the 3D imaging modalities (CBCTs and MSCT) were 7.3 times more likely to receive poor scores than the 2D modality. Yet, image quality from NewTom VGi® and 3D Accuitomo 170® was almost equivalent to that of digital panoramic radiographs with respective odds ratio estimates of 1.2 and 1.6 at 95% Wald confidence limits. A substantial overall agreement amongst observers was found. Intra-observer agreement was moderate to substantial.

Conclusions

While 2D-panoramic images are significantly better for subjective diagnosis, 2/3 of the 3D-reformatted panoramic images are moderate or good for diagnostic purposes.

Clinical relevance

Panoramic reformattings from particular CBCTs are comparable to digital panoramic images concerning the overall image quality and visualization of anatomical structures. This clinically implies that a 3D-derived panoramic view can be generated for diagnosis with a recommended 20-mm slice thickness, if CBCT data is a priori available for other purposes.     

Comparison of cone-beam and conventional multislice computed tomography for image-guided dental implant planning

Objectives

To compare the accuracy of cone-beam CT (CBCT) and multislice CT (MSCT) with regard to its use in image-guided dental implant surgery in a prospective model based study.

Material and methods

Ten photopolymer-acrylate mandibula models, each with four precise metal reference markers, were scanned with MSCT and CBCT. The six reference distances between the markers were measured by a three-axis milling machine first. The distances were then measured by (1) navigation with the Medtronic StealthStation® TREON? image-guided surgery system, (2) with the Medtronic planning-tool and (3) on the PC with the Mimics® software. Mean values were calculated for all three methods for CBCT and MSCT and were compared for statistical significance.

Results

Of all measurements, 83% of the arithmetic mean values were within the ±0.5 mm range (MSCT 88% and CBCT 78%) and 17% within the ±1.0 mm range (MSCT 12% and CBCT 22%). The absolute difference of the arithmetic mean values showed no statistically significant difference between MSCT and CBCT. The difference of the overall mean values to the reference was 0.43 mm for MSCT and 0.46 mm for CBCT.

Conclusions

The data of our study prove that the application of CBCT for the indicated purpose yielded good results comparable to those of MSCT. All three measuring methods were feasible and accuracy was statistically not different between the data acquired by MSCT and CBCT within the setting of this study.     

Influence of object location in cone beam computed tomography (NewTom 5G and 3D Accuitomo 170) on gray value measurements at an implant site

Objectives

The aim of this study was to determine the gray value variation at an implant site with different object location within the selected field of view (FOV) in two cone beam computed tomography (CBCT) scanners.

Methods

A 1-cm-thick section from the edentulous region of a dry human mandible was scanned by two CBCT scanners: 3D Accuitomo 170 (J. Morita, Kyoto, Japan) and NewTom 5G (QR Verona, Verona, Italy). Five FOVs were used with each CBCT scanner. Within each FOV, the specimen was located at different positions. The scans were converted to DICOM format. Data analysis was performed using 3Diagnosys (ver. 3.1, 3DIEMME, Cantu, Italy) and Geomagic software (Studio 2012, Morrisville, NC). On one of the scans, a probe designating the site for pre-operative implant placement was selected. The inserted virtual implant was transformed on the same region on each CBCT scan by a three-dimensional registration algorithm. The mean voxel gray value of the region around the probe was derived separately from all CBCT scans. The influence of object location within each FOV on variability of voxel gray values was assessed.

Results

In both CBCT systems, object location had a significant influence on gray value measurements (F _4,16 = 3.71, p = 0.0255 for Accuitomo and F _4,16 = 9.31, p = 0.0000 for NewTom).

Conclusions

Gray level values from CBCT images are influenced by object location within the FOV.     

Three-rooted premolar analyzed by high-resolution and cone beam CT

Objectives

The aim of this study was to analyze the variations in canal and root cross-sectional area in three-rooted maxillary premolars between high-resolution computed tomography (μCT) and cone beam computed tomography (CBCT).

Materials and methods

Sixteen extracted maxillary premolars with three distinct roots and fully formed apices were scanned using μCT and CBCT. Photoshop CS software was used to measure root and canal cross-sectional areas at the most cervical and the most apical points of each root third in images obtained using the two tomographic computed (CT) techniques, and at 30 root sections equidistant from both root ends using μCT images. Canal and root areas were compared between each method using the Student t test for paired samples and 95 % confidence intervals.

Results

Images using μCT were sharper than those obtained using CBCT. There were statistically significant differences in mean area measurements of roots and canals between the μCT and CBCT techniques (P?<?0.05). Root and canal areas had similar variations in cross-sectional μCT images and became proportionally smaller in a cervical to apical direction as the cementodentinal junction was approached, from where the area then increased apically.

Conclusion

Although variation was similar in the roots and canals under study, CBCT produced poorer image details than μCT.

Clinical relevance

Although CBCT is a strong diagnosis tool, it still needs improvement to provide accuracy in details of the root canal system, especially in cases with anatomical variations, such as the three-rooted maxillary premolars.     

Bone mineral density measurements performed by cone-beam computed tomography in the bisphosphonate-related osteonecrosis-affected jaw

Objectives

The aims of this study were to determine the bone mineral density (BMD) in bisphosphonate-related osteonecrosis of the jaw (BRONJ) by cone-beam computed tomography (CBCT) measurements and to correlate these measurements with the current stages recommended by the American Association of Oral and Maxillofacial Surgeons (AAOMS).

Methods

Bone mineral density measurements of various areas in 24 bisphosphonate-related osteonecrosis (BRON) jaws were evaluated by CBCT. Another 24 age- and sex-matched patients without any bone pathologies served as the control group. Data acquisition was highly standardized to ensure maximum reliability in the comparisons of BMD measurements by CBCT.

Results

Compared with the control group, the bisphosphonate patients had significantly higher (p????0.01) BMDs in the non-affected jaw areas ipsilateral and contralateral to the BRON within the maxilla and mandible. The highest BMDs within the BRON jaws were observed in the BRON-adjacent areas relative to the non-affected ipsilateral and contralateral areas. Regarding the correlation with the AAOMS stages, the BMDs of the evaluated areas of BRONJ showed no significant differences (p????0.05) between the stages.

Conclusions

Bisphosphonate-related bone pathologies can be detected by CBCT and are associated with increased BMDs, not only in clinically obvious BRONJ areas, but also in clinically unapparent areas, suggesting a subclinical general osteosclerosis of the jaw. The data transferability to other CBCT devices needs to be further elucidated and compared with multislice CT.     

The use of cone beam computed tomography to predetermine root canal lengths in molar teeth: a comparison between two-dimensional and three-dimensional measurements

Objectives

The aim of this study was to evaluate the accuracy of two-dimensional (2D) and three-dimensional (3D) root canal length measurements in molar teeth using cone beam computed tomography (CBCT).

Materials and methods

Root canal lengths of twenty molar teeth were measured with two different CBCT approaches. After adjusting the CBCT images, 2D measurements were performed within the sagittal plane between the apical foramen and the coronal reference (cusp). The 3D approach measured centrically in axial planes. A linear mixed model with random intercepts was fitted to compare differences between methods (2D and 3D). The correlation between CBCT measurements and the actual root canal length was evaluated using the Pearson correlation coefficient.

Results

Differences between 3D measurements and the actual root canal lengths were significantly smaller compared to the 2D approach (p?<?0.001). Mean differences were 0.32 and 0.58 mm, respectively. A high correlation was found between the actual root canal length and 3D measurements (Pearson correlation coefficient?=?0.97). Compared to the actual root canal length, 80 % of the 3D measurements were within the limits of ±0.5 mm.

Conclusions

3D measurements of root canals in molar teeth are more accurate than simple 2D measurements and show a high correlation to the actual lengths.

Clinical relevance

In cases where a CBCT is already available, root canal lengths in molar teeth can be accurately predetermined using a standardized 3D approach.     

The association between complete absence of post-treatment periapical lesion and quality of root canal filling

Aim

The technical quality of a root canal treatment is clinically judged by the apical extension and homogeneity of the filling material imaged by periapical radiographs (PA). The aim of this experiment was to evaluate the association between the technical quality of the root canal filling and treatment outcome.

Materials and methods

In 234 teeth (268 roots) that underwent root-canal treatment, the quality of the root canal filling as well as the outcome of the treatment were assessed with both PA and cone-beam computed tomography (CBCT) 2?years after treatment. Satisfactory root filling on PA was defined as 0–2?mm within the radiographic apex without voids; on CBCT scans, the apical end of the canal replaced the radiographic apex. The outcome predictors were analyzed using multivariate logistic regression.

Results

At recall, periapical radiolucent areas were absent in 198 (74%) roots on PA and 164 (61%) roots on CBCT scans. The presence of preoperative periapical radiolucency and the quality of root filling and coronal restoration were identified by both PA and CBCT as outcome predictors (p?<?0.01). Complete absence of post-treatment periapical radiolucency was observed in CBCT scans in 81% and 49% of satisfactory and unsatisfactory root fillings, respectively, as compared to 87% and 61% revealed by PA.

Conclusion

Satisfactory root fillings were associated with a favorable outcome, confirmed by both PA and CBCT.

Clinical relevance

The outcome of root canal treatment is improved once the filling is 0–2?mm from the apex, and no voids could be detected. Technical skills and performance of root canal filling procedures should be emphasized, and suitable methods should be developed in order to achieve more compacted filling materials without voids and at the correct length.     

Accuracy of full-arch scans using intraoral scanners

Objectives

This study aimed to evaluate the accuracy of intraoral scanners in full-arch scans.

Materials and methods

A representative model with 14 prepared abutments was digitized using an industrial scanner (reference scanner) as well as four intraoral scanners (iTero, CEREC AC Bluecam, Lava C.O.S., and Zfx IntraScan). Datasets obtained from different scans were loaded into 3D evaluation software, superimposed, and compared for accuracy. One-way analysis of variance (ANOVA) was implemented to compute differences within groups (precision) as well as comparisons with the reference scan (trueness). A level of statistical significance of p?<?0.05 was set.

Results

Mean trueness values ranged from 38 to 332.9 μm. Data analysis yielded statistically significant differences between CEREC AC Bluecam and other scanners as well as between Zfx IntraScan and Lava C.O.S. Mean precision values ranged from 37.9 to 99.1 μm. Statistically significant differences were found between CEREC AC Bluecam and Lava C.O.S., CEREC AC Bluecam and iTero, Zfx Intra Scan and Lava C.O.S., and Zfx Intra Scan and iTero (p?<?0.05).

Conclusions

Except for one intraoral scanner system, all tested systems showed a comparable level of accuracy for full-arch scans of prepared teeth. Further studies are needed to validate the accuracy of these scanners under clinical conditions.

Clinical relevance

Despite excellent accuracy in single-unit scans having been demonstrated, little is known about the accuracy of intraoral scanners in simultaneous scans of multiple abutments. Although most of the tested scanners showed comparable values, the results suggest that the inaccuracies of the obtained datasets may contribute to inaccuracies in the final restorations.     

Influence of cone-beam computed tomography milliamperage settings on image quality of the mandibular third molar region

Objective

To assess the image quality of the mandibular third molar region using different milliamperage (mA) settings of cone-beam computed tomography.

Methods

Twelve dry mandibles with impacted third molars were scanned with a Kodak 9000 unit (Kodak Dental Systems, Carestream Health, Rochester, NY, USA) using different mA settings (2, 4, 6.3, 8, 10, 12, and 15 mA). Two oral radiologists evaluated the images. They classified the tooth root, periodontal space, lamina dura, trabecular bone, mandibular canal, and overall image quality as excellent, good, poor, or inadequate for diagnosis. Statistical analyses were performed by one-way ANOVA with a post hoc Tukey test to investigate the influence of the mA settings in the image quality of the structures analyzed. The significance level was set at 5 %.

Results

The 15 and 12 mA settings provided the highest mean values for all the evaluated criteria, with significant differences from the values for the other mA settings. The 10, 8, and 6.3 mA settings showed no significant differences in relation to tooth root and periodontal space. For the other evaluated criteria, no significant differences were observed for the 10 and 8 mA settings. The 4 and 2 mA settings gave the lowest mean values.

Conclusions

The best low-dose protocol with good image quality was the 10 mA setting. Lower dose protocols with 8 and 6.3 mA settings can also be used for these purposes, but caution is necessary because of increased image noise.     

Comparative assessment of panoramic radiography and CBCT imaging for radiodiagnostics in the posterior maxilla

Objective

The purpose of this study was to assess whether and how the information obtained by means of cone beam computed tomography (CBCT) on maxillary posterior teeth differs from that obtained by panoramic radiography.

Materials and method

From 157 subjects (mean age 48 years, range 19–84 years; 89 females) referred to the oral imaging center, a pair of panoramic and CBCT images was selected for further analysis. Both imaging modalities were analyzed to determine the topographic relationship of maxillary teeth to the sinus floor. Pathologic conditions, apical periodontitis, and presence of soft tissue thickening were also examined with both techniques.

Results

CBCT showed an intimate relationship of the first and second molar with the maxillary sinus in 54 and 38 %, respectively. Thirty-nine apical periodontitis lesions causing reactive changes in the maxillary sinus were detected by CBCT, while just six of them were diagnosed with panoramic imaging. A total of 26 teeth with apical extension to the maxillary sinus were detected with CBCT, from which two could be identified with panoramic radiography.

Conclusion

This study emphasizes that anatomical and pathological involvement of the maxillary sinus in relation to posterior teeth is considerably high. It is of clinical importance that the 3D nature of CBCT imaging allowed a better assessment of the relationship between the maxillary sinus and posterior root apices compared to the low detection on panoramic radiographs.

Clinical relevance

CBCT imaging can be a valuable adjunct in radioanatomical and radiodiagnostic observations in the posterior maxilla. It may better visualize maxillary sinus involvement for posterior upper teeth than panoramic radiography.     

Subjective image quality assessment of cross sectional imaging methods for the symphyseal region of the mandible prior to dental implant placement

Objectives

A three dimensional appreciation of the form of the anterior mandible is required to place dental implants safely in the region. This study compared the subjective image quality of four available methods of cross sectional imaging of the symphyseal region, the lateral cephalometric view, cone beam computed tomography (CBCT), spiral tomography and the transymphyseal X-ray view.

Methods

An experimental water phantom was developed to reproduce human soft tissue around the mandible. Images were taken of four mandibles by the four X-ray techniques. Three different CBCT machines were included.The source of each image was disguised by displaying all images in the same format on the same computer screen. A protocol was developed to process the images for viewing whilst preserving their image quality.A panel of observers of ten dentists viewed the images and rated their image quality by recording their agreement with six statements on a five point Likert scale.

Results

The results showed a statistically significant difference in image quality between imaging methods. There were clear differences in the ratings between the three cone beam computed tomography machines. Small volume, high resolution CBCT provided images with the highest scores for subjective image quality.

Conclusions

Within the limitations of this study, significant differences in subjective image quality were found between imaging systems used for cross sectional imaging for the symphyseal region of the mandible prior to dental implant placement.     

Imaging of mandible invasion by oral squamous cell carcinoma using computed tomography,cone-beam computed tomography and bone scintigraphy with SPECT

Objectives

The objective of this paper is to evaluate the predictability of preoperative tumour bone invasion of the mandible by squamous cell carcinoma of the oral cavity using CT, cone-beam CT and bone scintigraphy with SPECT.

Material and methods

Eighty-four patients who had received CT, SPECT or cone-beam computed tomography (CBCT), as well as a further 48 patients who undergone all these investigations for preoperative evaluation of bone invasion were included in the study. A case–control analysis and the receiver operating characteristics were performed. Histological results of bone specimens served as the gold standard for assessment of bone invasion.

Results

CBCT and SPECT showed a comparable sensitivity for bone invasion (93 % [CI 0.816–0.972] and 96 % [CI 0.867–0.990], respectively) which was significantly higher than that of CT (63 % [CI 0.488–0.752]). Further, CBCT obtained higher specificity than SPECT (62 % [CI 0.478–0.743] and 48 % [CI 0.342–0.614], respectively), whereas CT showed the best specificity among the investigation methods (81 % [CI 0.677–0.896]).

Conclusions

CT scan provides by its high specificity and positive predictive value a precise imaging technique for clinical routine. However, CBCT shows a much higher sensitivity for cortical bone invasion and a better negative predictive value. With a significantly lower exposure dose it can rule out this invasion effectively and prevent overtreatment.

Clinical relevance

Considering the high-resolution images delivered by CBCT along with minimized artefacts in the mandible it provides an alternative imaging technique, which could be combined and accomplished with another soft-tissue imaging modality like MRI to obtain optimal hard and soft-tissue visualisation in patients with squamous cell carcinoma of the oral cavity.     

Influence of voxel size on the diagnostic ability of cone-beam computed tomography to evaluate simulated root perforations

Objectives

This study aimed to assess the use of different voxel sizes of a cone-beam computed tomography (CBCT) unit for detecting root perforations of different sizes and locations ex vivo and to compare the diagnostic possibilities of CBCT with those of periapical radiography (PR).

Methods

The study included 36 recently extracted intact human mandibular one-rooted teeth with developed apices. Root perforations of 0.2, 0.3, or 0.4 mm in diameter were drilled on the buccal and lingual sides at the cervical, middle, and apical thirds. A total of 216 portions were obtained. One tooth at a time was placed in a dry human mandible in an artificially created alveolus. Cross-sectional CBCT images were obtained using voxel resolutions of 0.4, 0.3, 0.25, and 0.2 mm. PRs were obtained using the paralleling technique in three directions in the horizontal plane: direct view, mesial angulation, and distal angulation with a 20° angle.

Results

There were no significant differences in sensitivity between 0.4/0.3 and 0.25/0.2-mm voxel resolutions. Significant differences were found between voxel sizes of 0.4/0.25, 0.4/0.2, 0.3/0.25, and 0.3/0.2 mm. The observers failed to diagnose any of the perforations using PR.

Conclusions

CBCT is a reliable imaging system for detecting root perforations that are not detectable with PR. A 0.2-mm voxel resolution was the best choice for diagnostic use in this study. Neither perforation location nor size influenced the diagnostic abilities of CBCT, except that it was harder to detect a root perforation in the apical part of the root.     

Effect of proximal box elevation with resin composite on marginal quality of ceramic inlays in vitro

Objectives

The objective of this study was to evaluate the marginal quality and resin–resin transition of milled CAD/CAM glass–ceramic inlays in deep proximal cavities with and without 3-mm proximal box elevation (PBE) using resin composites before and after thermomechanical loading.

Materials and methods

MOD cavities with one proximal box beneath the cementoenamel junction were prepared in 48 extracted human third molars. Proximal boxes ending in dentin were elevated for 3 mm with different resin composites (RelyX Unicem, G-Cem, and Maxcem Elite as self-adhesive resin cements and Clearfil Majesty Posterior as restorative resin composite in one or three layers bonded with AdheSE) or left untreated. IPS Empress CAD inlays were luted with Syntac and Variolink II (n?=?8). Marginal quality as well as the PBE–ceramic interface were analyzed under an SEM using epoxy resin replicas before and after thermomechanical loading (100,000?×?50 N and 2,500 thermocycles between +5°C and +55°C).

Results

Bonding glass–ceramic directly to dentin showed the highest amounts of gap-free margins in dentin (92%, p?<?0.05). Bonded resin composite applied in three layers achieved 84% gap-free margins in dentin; PBE with self-adhesive resin cements exhibited significantly more gaps in dentin (p?<?0.05).

Conclusions

With a meticulous layering technique and bonded resin composite, PBE may be an alternative to ceramic bonding to dentin. Self-adhesive resin cements seem not suitable for this indication.

Clinical relevance

For deep proximal boxes ending in dentin, a PBE may be an alternative to conventional techniques.     

Comparison of intraoral radiography and cone-beam computed tomography for the detection of horizontal root fractures: an in vitro study

Objectives

This study aimed to compare the diagnostic accuracy of two different cone-beam computed tomography (CBCT) units with several intraoral radiography techniques for detecting horizontal root fractures.

Methods

The study material comprised 82 extracted human maxillary incisors without root fractures that had not undergone any root canal treatment. Root fractures were created in the horizontal plane in 31 teeth by a mechanical force using a hammer with the tooth placed on a soft foundation as described in a previous study. The teeth were divided into two groups: a control group with no fractures and a test group with fractures. These were randomized to the empty maxillary anterior sockets of a dry human maxilla. Each tooth was imaged at various vertical angles using each of the following modalities: a 3D Accuitomo 170 CBCT, a NewTom 3G CBCT, a VistaScan PSP, a CCD sensor, and conventional film. Specificity and sensitivity for assessing horizontal root fracture by each radiographic technique were calculated. Chi-square statistics were used to evaluate differences between modalities. Kappa statistics assessed the agreement between observers. Results were considered significant at P?<?0.05.

Results

The kappa values for inter-observer agreement between observers ranged between 0.88 and 0.98 for the 3D Accuitomo 170, 0.82 and 0.91 for the NewTom 3G, and 0.61 and 0.72 for the different types of intraoral images. The diagnostic accuracy for detecting fracture lines in 3D Accuitomo 170 (0.93) was significantly higher than NewTom 3G (0.87), VistaScan (0.71), CCD (0.70), and CF (0.68).

Conclusions

3D Accuitomo 170 has the highest sensitivity and diagnostic accuracy for detecting horizontal root fracture among the 5 radiographic modalities examined. CBCT should be considered as the most reliable imaging modality of choice for the diagnosis of horizontal root fracture.

Clinical relevance

CBCT imaging offers the clear advantage over conventional imaging that traumatized teeth can be visualized in all three dimensions—especially the oro-facial dimension     

Self-etching aspects of a three-step etch-and-rinse adhesive

Purpose

The purpose of this study is to assess the marginal adaptation of cavities restored with a three-step etch-and-rinse adhesive, OptiBond FL (OFL) under different application protocols.

Materials and methods

Twenty-four class V cavities were prepared with half of the margins located in enamel and half in dentin. Cavities were restored with OFL and a microhybrid resin composite (Clearfil AP-X). Three groups (n?=?8) that differed in the etching technique were tested with thermomechanical loading, and specimens were subjected to quantitative marginal analysis before and after loading. Micromorphology of etching patters on enamel and dentin were observed with SEM. Data was evaluated with Kruskal–Wallis and Bonferroni post hoc test.

Results

Significantly lower percent CM (46.9?±?19.5) were found after loading on enamel in group 3 compared to group 1 (96.5?±?5.1) and group 2 (93.1?±?8.1). However, no significant differences (p?=?0.30) were observed on dentin margins.

Conclusions

Etching enamel with phosphoric acid but avoiding etching dentin before the application of OFL, optimal marginal adaptation could be obtained, evidencing a self-etching primer effect.

Clinical relevance

A reliable adhesive interface was attained with the application of the three-step etch-and-rinse OFL adhesive with a selective enamel etching, representing an advantage on restoring deep cavities.     

Inhibition of cell survival, viability and proliferation by dentin adhesives after direct and indirect exposure in vitro

Objectives

The influence of dentin adhesive systems (Scotchbond Multi-Purpose, XP Bond, Xeno V, Clearfil Protect Bond, AdheSE) on cell survival, viability and proliferation was characterized after direct and indirect exposure using different cell culture techniques.

Materials and methods

The primers and cured bonding parts were directly exposed to cells using cell culture inserts, and complete materials were analyzed in a dentin barrier test. Cell responses were examined in 3T3 mouse fibroblasts after 24- and 72-h exposure periods by the estimation of total cell numbers (survival), apoptosis (viability) and cell proliferation.

Results

Cell numbers were effectively reduced by the primers of AdheSE, Protect Bond, and Scotchbond Multi-Purpose as well as XP bond after direct exposure in a cell culture insert test device. Likewise, Scotchbond Multi-Purpose primer induced a rate of apoptosis (93.9%) even higher than detected with Protect Bond primer (91.6%). Cell proliferation was entirely inhibited by primers and by Xp Bond as well. The Scotchbond Multi-Purpose was most cytotoxic in a dentin barrier test device after a 24-h indirect exposure. It also increased the percentage of cells in apoptosis to 15.4% compared to untreated controls.

Conclusion

Unpolymerized primers of dentin adhesives were more cytotoxic than polymerized bonding counterparts. Moreover, total etch dentin adhesives were more cytotoxic than self-etch adhesives.

Clinical relevance

When dentin adhesives are used in deep cavities without a protective dentin barrier the leachable hydrophobic and hydrophilic component of dentin adhesive systems can penetrate to the pulp and may induce cytotoxic responses in pulp tissues.     

Effects of orthodontic treatment on human alveolar bone density distribution

Objectives

The objective of this study was to examine if non-invasive clinical cone beam computed tomography (CBCT)-based degree of bone mineralization (DBM) measurement can be used to detect the different results from orthodontic treatment between the maxilla and mandible in human patients.

Materials and methods

CBCT images were taken before and after orthodontic treatment from 43 patients (19 males and 24 females, 14.36?±?1.50 years). A histogram of computed tomography (CT) attenuation value, which is equivalent to the DBM, was obtained from the alveolar cortical (AC), trabecular (AT), and enamel (E) regions of each image. Mean, standard deviation (SD), and coefficient of variation (COV) of the CT attenuation values were computed. The regional variations and percentage (%) differences between the E and alveolar regions of the CT attenuation parameters at the maxilla and mandible were analyzed before and after orthodontic treatment.

Results

The AC had higher mean and variability (SD and COV) than the AT before and after treatment (p?<?0.001). The variability was higher in the mandibular AC than in the maxillar AC (p?<?0.01) independent of orthodontic treatment. The percentage (%) difference of variability of CT attenuation values changed for both AT and AC in the maxilla after orthodontic treatment, while that changed for only the AT (p?<?0.02), but not for AC, in the mandible (p?>?0.16).

Conclusions

The alveolar cortical region of the mandible responded differently to orthodontic treatment compared with other alveolar regions.

Clinical relevance

The CBCT-based DBM analysis can be used clinically to assess alveolar bone quality changes induced by orthodontic treatment to improve treatment planning and result evaluation.