Accuracy of alveolar bone measurements from cone beam computed tomography acquired using varying settings

Accuracy of intraoral ultrasound to evaluate alveolar bone level: an ex vivo study in human cadavers

OBJECTIVES

This study aimed to evaluate the reliability and accuracy of an intraoral ultrasound (US) device to evaluate alveolar bone by comparing it between different raters and to microCT (µCT) measurements.

METHODS

38 teeth distributed across three human cadavers were prepared by placing two notches on the facial enamel surface. The maxillary and mandibular teeth were imaged with a custom-designed intraoral 20 MHz ultrasound and µCT with 0.03 mm voxel size. µCT was considered the reference standard for this study. For each sample, the distance from the inferior border of the most apical notch to the tip of the alveolar bone crest on the facial aspect of the teeth was measured from the US and µCT images. Intraclass correlation coefficient (ICC) and standard deviation were calculated.

RESULTS

The intra-examiner and inter-examiner reliability for both the µCT and US alveolar bone measurements were found to be excellent (intra-examiner ICC was 0.998 for µCT and 0.997 for US, inter-examiner ICC was 0.996 for µCT and between 0.947 and 0.950 for US). The accuracy of the US was found to be good compared to µCT (ICC between 0.885 and 0.894).

CONCLUSION

The study demonstrated that intraoral ultrasound is highly reliable and accurate compared to the µCT reference standard for evaluating facial alveolar bone height.

Variations in the alveolar bone morphology in maxillary molar area: a retrospective CBCT study

BACKGROUND

This study quantitatively analyzed the anatomic structure of the alveolar bone in the maxillary molar region at three potential locations for Temporary Anchorage Device (TAD) placement. Additionally, the study compared the variability in this region across different age groups, sagittal skeletal patterns, vertical facial types, and sexes.

METHODS

In this retrospective cone-beam computed tomography study, the buccal alveolar bone was analyzed in the posterior molar area of 200 patients, the measurement items include buccal alveolar bone height, alveolar bone thickness, interradicular distance, and maxillary retromolar space.

RESULTS

Buccal alveolar height was greatest in the U56 region. The interradicular space was largest in the U56 region and increased from the alveolar crest to the sinus floor. Buccal alveolar bone thickness was highest in the U67 region and generally increased from the alveolar crest to the sinus floor. The maxillary retromolar space gradually increased from the alveolar crest to the root apex.

CONCLUSIONS

TADs are safest when placed in the buccal area between the maxillary second premolar and the first molar, particularly at the 9 mm plane. The U67 region is the optimal safe zone for TAD placement for maxillary dentition distalization. TADs placement in adolescents can be challenging. Maxillary third molar extraction can be considered for maxillary dentition distalization.

Alveolar morphometry in young adults with and without agenesis of the upper lateral incisor: A retrospective study

INTRODUCTION

We aimed to compare alveolar morphometry in young adults with agenesis of the upper lateral incisor versus the side without agenesis and versus matched controls.

MATERIAL AND METHODS

In this observational retrospective study, cone beam computed tomography scans were obtained of 36 upper hemiarches from young adults aged 15 to 30 years. The hemiarches were distributed into three groups: group 1: 12 upper hemiarches presenting agenesis of the upper lateral incisor; group 2: 12 upper hemiarches from the opposite side without agenesis of the upper lateral incisor (control group 1); and group 3: 12 upper hemiarches without agenesis of the upper lateral incisor matched for age and sex with respect to the affected group (control group 2). A trained and calibrated investigator performed all the alveolar measurements at two different times, including sagittal, coronal and axial slices of each hemiarch. Paired Student's t-tests, Chi-square and repeated measures ANOVA with Bonferroni correction were used, (P<0.05).

RESULTS

Apical mesial evaluation of group 1 (4.22±1.19mm) was significantly lower (P<0.001) than that of groups 2 (6.72±1.17mm) and 3 (7.58±1.67mm). Apical distal evaluation also showed differences (P<0.001) among the three groups, with the dimension being smaller in group 1 with agenesis (4.53±1.14mm), followed by group 2 without agenesis (6.23±1.55mm) and the healthy control group 3 (7.73±1.71mm).

CONCLUSIONS

Lateral incisor agenesis significantly reduces the alveolar dimensions of the affected area. In cases of unilateral agenesis, the unaffected side also shows sequelae, with decreased dimensions compared to cases without agenesis. This condition should be taken into account when making therapeutic decisions regarding rehabilitation with implants or canine replacement.

Alveolar bone morphology in patients with palatally-displaced maxillary lateral incisors before and after orthodontic treatment: A cone-beam computed tomography study

INTRODUCTION

Palatal displacement of maxillary anterior teeth is common in clinical practice. Previous studies have reported that the labial bone around palatally-displaced incisors is thinner than that around normally-placed teeth. Therefore, it is necessary to elucidate alveolar bone changes after alignment to guide orthodontic treatment. In this study, we investigated the alveolar bone changes around palatally-displaced maxillary lateral incisors before and after treatment, and the effects of extraction and age using cone-beam computed tomography.

METHODS

In this retrospective study, 55 patients with unilateral palatally-displaced maxillary lateral incisors were included. Three-dimensional alveolar bone changes were measured at three levels (25%, 50% and 75% of the root length) using cone-beam computed tomography. Group comparisons were made between displaced and control teeth, extraction and non-extraction groups, and adult and minor groups.

RESULTS

After orthodontic treatment, labiopalatal and palatal alveolar bone widths decreased at all measured levels. Labial alveolar bone width increased significantly at P25, but decreased at P75. Concavity decreased, while tooth-axis angle, tooth length, B-CEJ and P-CEJ increased. Changes in LB and LP at P75, B-CEJ and P-CEJ were statistically significant. After treatment, the tooth-axis angle on the PD side increased by 9.46°. The change in tooth-axis angle on the PD side was significantly smaller, and LB and LP decreased more at P75, in the extraction group.

CONCLUSIONS

Compared to the control teeth, alveolar bone thickness and height for the displaced teeth decreased more significantly after treatment. Tooth extraction and age also influenced alveolar bone changes.

Evaluation of maxillary arch width and palatal volume and depth in patients with maxillary impacted canine by CBCT

Introduction

Canines are the second most common tooth in terms of impaction. Impacted teeth can be associated with some different indices of dental arch and dentoalveolar structures. The aim of this study was to evaluate maxillary arch width as well as volume and depth of palate in patients with maxillary impacted canine by cone beam computed tomography (CBCT).

Methods

In this cross-sectional study, 45 CBCT images of patients with unilateral maxillary impacted canines were examined. All patients had palatally impacted canines. Three parameters of maxillary arch width, palatal volume and palatal depth were assessed using axial and sagittal incisions on the CBCT images. Then all the measurements on the impacted side were compared with the non-impacted side. Data were entered into SPSS software and paired sample t-test and Student's t-test were used to comparison. The significance level of 0.05 was considered.

Results

The maxillary arch width on the impacted side was significantly less than the normal side (P < 0.001). The mean depth of the palate was 14.86 ± 3.53 mm. There was a significant correlation between canine impaction and Palatal volume (R = 0.728 and P-value< 0.001), but no significant correlation between canine impaction and Maxillary arch width was shown (R = 0.15 and p-value = 0.326).

Conclusion

The impacted canine was significantly associated with a reduction in the width of the maxillary arch on the affected side, and it made no difference if the impacted side was left or right. Also, impacted canine teeth were significantly associated with volume reduction on the affected side.

Effect of voxel size in cone-beam computed tomography on surface area measurements of dehiscences and fenestrations in the lower anterior buccal region

Objectives

This study aims to assess whether different voxel sizes in cone-beam computed tomography (CBCT) affected surface area measurements of dehiscences and fenestrations in the mandibular anterior buccal region.

Materials and methods

Nineteen dry human mandibles were scanned with a surface scanner (SS). Wax was attached to the mandibles as a soft tissue equivalent. Three-dimensional digital models were generated with a CBCT unit, with voxel sizes of 0.200 mm (VS200), 0.400 mm (VS400), and 0.600 mm (VS600). The buccal surface areas of the six anterior teeth were measured (in mm²) to evaluate areas of dehiscences and fenestrations. Differences between the CBCT and SS measurements were determined in a linear mixed model analysis.

Results

The mean surface area per tooth was 88.3 ± 24.0 mm², with the SS, and 94.6 ± 26.5 (VS200), 95.1 ± 27.3 (VS400), and 96.0 ± 26.5 (VS600), with CBCT scans. Larger surface areas resulted in larger differences between CBCT and SS measurements (− 0.1 β, SE = 0.02, p < 0.001). Deviations from SS measurements were larger with VS600, compared to VS200 (1.3 β, SE = 0.05, P = 0.009). Fenestrations were undetectable with CBCT.

Conclusions

CBCT imaging magnified the surface area of dehiscences in the anterior buccal region of the mandible by 7 to 9%. The larger the voxel size, the larger the deviation from SS measurements. Fenestrations were not detectable with CBCT.

Clinical relevance

CBCT is an acceptable tool for measuring dehiscences but not fenestrations. However, CBCT overestimates the size of dehiscences, and the degree of overestimation depends on the actual dehiscence size and CBCT voxel size employed.

Relationship between alveolar-bone morphology at the mandibular incisors and their inclination in adults with low-angle, skeletal class III malocclusion—A retrospective CBCT study

Objective

To quantitatively study the effect of the labial inclination of the mandibular central incisors on the surrounding cortical and cancellous-bone morphology among patients with low-angle, skeletal class III malocclusion, by using cone-beam computed-tomography (CBCT) imaging.

Materials and methods

The CBCT images of 60 patients with low-angle, skeletal class III malocclusion were divided into lingual-inclination, upright, and labial-inclination groups. The height of the alveolar bone and the thickness and area of the cortical, cancellous, and total alveolar bone were measured separately on each side of the mandibular central incisors.

Results

The thickness of the labial cortical bone from 6 mm below the cementoenamel junction (CEJ) to the root apex; the thickness of the labial cancellous bone at the root apex; the total thickness of the alveolar bone at the root apex; the area of labial cortical bone; the total area of labial alveolar bone; and the height of the labial alveolar bone were highest in the labial-inclination group (all P<0.05). All these variables were positively correlated with the labial inclination of the mandibular central incisors (all P<0.05). There were no statistical differences between the groups for any of the measurements on the lingual side of the teeth (P>0.05).

Conclusion

The morphology of the alveolar bone on the labial but not the lingual side of the mandibular central incisors was statistically significantly correlated with the labial inclination of those teeth in patients with low-angle, skeletal class III malocclusion.

Thickness of the Buccal and Alveolar Bones Overlying Central Incisors: A Radiographic Iraqi Study

Background. Initial bone thickness has a substantial impact on the success of dental implant treatments. The objective of the current study was to analyze the thickness of the buccal and alveolar bone at the central incisors using CBCT in relation to gender and side to determine the anatomical features and choose the best implant treatment option for minimizing the surgical complications. Methods. One hundred CBCT images were investigated (50 females and 50 males, aged 20 to 50 years old). The buccal bone thickness and alveolar bone thickness were evaluated for right and left sides of each subject at three sites; C: crest (3 mm); M: middle (6 mm); A: apical (9 mm) from the cementoenamel junction. Results. The mean thickness of buccal bone was less than 2 mm on the incisors according to side and gender. Buccal bone thickness revealed a statistically significant difference between right and left sides at the apical point in both females and males with $p$ values of ( $p\le 0.001$ ) and (0.001), respectively. The buccal bone thickness displayed statistically significant differences between genders at all sites. The alveolar thickness demonstrated similar significant differences between genders except for the crest site. Conclusions. Iraqi participants had about 1 mm buccal bone thickness at 3 mm apical from the CEJ in right and left central incisors with a progressive rise in bone thickness to be less than 2 mm at the apex. Alveolar bone also showed the same increase in bone thickness from crest to apex. Bone thickness was greater in males than females. The present study provided valuable CBCT data on bone thickness of the esthetic maxillary region as a preoperative analysis for establishing an immediate implant treatment plan with aesthetically pleasing long-term outcomes.

Correlation of Panoramic Radiography, Cone-Beam Computed Tomography, and Three-Dimensional Printing in the Assessment of the Spatial Location of Impacted Mandibular Third Molars

The development of radiology, rapid prototyping techniques, and the increasingly common use of 3D printing in dentistry inspires the use of these techniques to improve diagnostic and therapeutic processes. This study aimed to conduct a retrospective comparative analysis of dental panoramic radiographs, cone-beam computed tomography, and 3D printing in preoperative assessment of the procedure's difficulty. Thirty clinical cases with a high degree of difficulty were selected, and based on evaluation with CBCT, a virtual 3D model of the region of surgical procedure was created, which was then printed using a 3D printer. The comparative analysis included the linear measurements performed in dental panoramic radiographs, cone-beam computed tomography, and 3D models in a preoperative assessment of the degree of retention and difficulty of impacted mandibular third molars in the mandible. Linear measurements performed on dental panoramic radiographs were significantly lower than in cone-beam computed tomography and 3D models. No statistically significant differences were obtained in linear measurements between 3D models and cone-beam computed tomography images except for the measurement of the lingual lamina thickness; however, due to the insignificant differences in measurements, with a mean of only 80 µm, the elective procedure of removal of the impacted third molar in the mandible may be safe.

Long-term changes in the anterior alveolar bone after orthodontic treatment with premolar extraction: A retrospective study

OBJECTIVES

To evaluate the morphometric changes in maxillary and mandibular anterior alveolar bone after orthodontic treatment and retention for 18-24 months by cone-beam computed tomography (CBCT).

SETTING AND SAMPLE POPULATION

Thirty-four adolescent patients (12 males and 22 females; mean age: 14.29 ± 1.24 years) diagnosed with bimaxillary dentoalveolar protrusion and with extractions of the 4 first premolars were included.

MATERIALS AND METHODS

The labial and lingual (palatal) alveolar bone thickness, height and root length of the maxillary and mandibular anterior teeth were assessed using CBCT imaging at the pre-treatment (T1), post-treatment (T2) and retention phases (T3). Voxel-based superimpositions of the T2 and T3 images were performed, and the distances of incisal and apical movement between T2 and T3 were measured to determine whether relapses occurred.

RESULTS

After orthodontic treatment, the labial and lingual (palatal) bone height decreased significantly (P < .05) and the labial thickness at the crestal (L1), midroot (L2), and apical levels (L3) had no significant change, while the lingual (palatal) bone thickness at all three levels decreased significantly (P < .05). After 18-24 months of retention, the lingual (palatal) height and the lingual (palatal) thickness at the crestal (L1) level increased significantly (P < .05). There were no obvious incisal and apical movements of the anterior teeth between T2 and T3 (P > .05), indicating that no relapses occurred.

CONCLUSIONS

Even though lingual (palatal) alveolar loss occurred due to the orthodontic treatment, the cervical alveolar bone seemed to recover over time. Therefore, appropriate camouflage treatment can be used in patients with bimaxillary dentoalveolar protrusion, and this treatment will not irreversibly deteriorate periodontal health and affect the orthodontic treatment stability.

Impact of orthognathic surgery on the prevalence of dehiscence in Class II and Class III surgical-orthodontic patients

OBJECTIVES

The objectives were to evaluate and compare the presence of bone dehiscence before and after orthognathic surgery.

MATERIALS AND METHODS

In this retrospective study, 90 cone-beam computed tomography (CBCT) scans from 45 patients were evaluated. Class II (n = 23) and Class III (n = 22) orthodontic patients who were being prepared for orthognathic surgery were measured. CBCT scans were obtained about 30 days prior to (T0) and 6 months after (T1) double jaw orthognathic surgery. The distance between the cemento-enamel junction (CEJ) and the alveolar bone crest was assessed at the buccal and lingual surfaces of all teeth, on both sides and arches, except for the second premolars and the second and third molars. A total of 1332 sites were measured for Class II (644) and Class III (688) patients. The software used was OsiriX (version 3.3 32-bit). Data were compared with Wilcoxon and McNemar tests at the 5% level.

RESULTS

Bone dehiscence before surgery was present in 26% and 15% of the Class II and III groups, respectively. The presence of dehiscence increased to 31% in the Class II and 20% in the Class III patients after surgery (P < .05).

CONCLUSIONS

The prevalence of dehiscence increased slightly in Class II and Class III surgical-orthodontic patients after orthognathic surgery. Temporary vascular supply reduction and oral hygiene difficulties may explain these results; however, more studies are needed.

Buccal alveolar bone changes following rapid maxillary expansion and fixed appliance therapy

OBJECTIVES

To assess factors that may be associated with buccal bone changes adjacent to maxillary first molars after rapid maxillary expansion (RME) and fixed appliance therapy.

MATERIALS AND METHODS

Pretreatment (T1) and posttreatment (T2) cone-beam computed tomography scans were obtained from 45 patients treated with RME and preadjusted edgewise appliances. Buccal alveolar bone thickness was measured adjacent to the mesiobuccal root of the maxillary first molar 4 mm, 6 mm, and 8 mm apical to the cementoenamel junction, and anatomic defects were recorded. Paired and unpaired t-tests were used to compare alveolar bone thickness at T1 and T2 and to determine whether teeth with posttreatment anatomic defects had thinner initial bone. Correlation analyses were used to examine relationships between buccal alveolar bone thickness changes and amount of expansion, initial bone thickness, age at T1, postexpansion retention time, and treatment time.

RESULTS

There was a statistically significant reduction in buccal alveolar bone thickness from T1 to T2. Approximately half (47.7%) of the teeth developed anatomic defects from T1 to T2. These teeth had significantly thinner buccal bone at T1. Reduction in alveolar bone thickness was correlated with only one tested variable: initial bone thickness.

CONCLUSIONS

RME and fixed-appliance therapy can be associated with significant reduction in buccal alveolar bone thickness and an increase in anatomic defects adjacent to the expander anchor teeth. Anchor teeth with greater initial buccal bone thickness have less reduction in buccal bone thickness and are less likely to develop posttreatment anatomic defects of buccal bone.

Evaluation of the distance between the root apices of the upper first molars and the hard palate in an Eastern Mediterranean population: A retrospective study

OBJECTIVE

The aims of this retrospective study were, first to evaluate the distance between the root apices of the upper first molars and the palatal plane (PP), and second to determine the validity (accuracy) of the use of cephalometric radiographs or panoramic X-rays compared to cone beam computed tomography (CBCT) in determining this distance.

MATERIAL AND METHODS

The distance was calculated from the root apices of the first molars to PP, on the cephalometric radiographs of 204 subjects and then 57 measurements were compared to those obtained on panoramic X-rays and CBCT images, in order to find a statistically significant difference according to age, sex, side, vertical and sagittal skeletal patterns, and to determine if 2D radiographs are suitable for this task.

RESULTS

The distance increased significantly in subjects after 20 years of age and in hyperdivergent patients, but was not influenced by sex, side or anteroposterior position of the mandible. No statistical significance was found between the calculated measurements on cephalometric and CBCT radiographs, but both were different from those taken on panoramic X-rays.

CONCLUSIONS

Cephalometric radiographs are reliable in the assessment of the distance between the roots of the upper molars and the PP. In hyperdivergent and adult patients, posterior teeth have enough space between their roots and the upper limit of the hard palate to undergo intrusion mechanics using miniscrews, but care must be taken while planning and managing these movements in order to minimize the unwanted side effects.

Tomographic evaluation of buccal bone in different skeletal patterns and incisors inclination

OBJECTIVE

The aim of this study was to correlate the absence of BB with skeletal patterns and incisor inclination using cone-beam computed tomography (CBCT).

METHODS

The sample comprised CBCT images of 45 patients undergoing orthodontic treatment. BB was classified in each third of the anterior teeth as critical, slender, regular, and thick. The skeletal pattern was determined by the ANB (A point, nasion, B point) angle and the incisor inclination using the 1.NA and 1.NB measurements and the interincisal angle (1:1).

RESULTS

In both analyses, the skeletal pattern of class II revealed better BB in the cervical and middle thirds than classes I and III. A higher proportion of critical BB was found in the middle thirds, and the apical third presented the best regular and thick BB conditions, mainly class I. Less BB was observed in middle and apical thirds in the upper incisors and in cervical thirds in lower incisors, mostly when they were more upright.

CONCLUSIONS

Knowledge of alveolar bone height and thickness can alter the treatment plan in orthodontics. During orthodontic treatment, more attention should be paid to the lower incisors and vertical teeth because of poor BB conditions, especially in class III skeletal patterns.

Relationship between CNR and visibility of anatomical structures of cone-beam computed tomography images under different exposure parameters

OBJECTIVES

The purpose of this study was to investigate the image quality of cone beam CT (CBCT) under different exposure parameters and the relationship between contrast-to-noise and visibility of eight anatomical structures.

METHODS

CBCT images for the evaluation of subjective image quality were acquired on an anthropopathic phantom containing a human skeleton embedded in soft tissue equivalent materials using 25 exposure protocols. Visibility of eight anatomical structures was evaluated by five independent observers. Using the SEDENTEXCT IQ Image Quality phantom, the contrast-to-noise ratio (CNR) was calculated by ImageJ software.

RESULTS

A reduction on the visibility of anatomical structures was seen under lower exposure parameters. However, for 84% of the protocols, visibility of anatomical structures remained acceptable even under some lower parameter settings. As CNR increased, the visibility of anatomical structures also increased correspondingly. A change point could be found in the CNR interval 29.42-36.51 after which the visibility of anatomical structures no longer increases with the increase of CNR.

CONCLUSIONS

Although CNR decrease under a lower exposure parameter, the image quality often remained acceptable at exposure levels below the manufacture's recommended settings. It is possible to standardize subjective image quality by physical factors. Currently, it is not possible to predetermine a change point CNR value due to different CBCT machine and variation of diagnostic tasks.

Prevalence of posterior alveolar bony dehiscence and fenestration in adults with posterior crossbite: a CBCT study

Background

Correcting posterior crossbite in adult patients using nonsurgical methods may involve buccolingual tooth movement. Knowing the extent of the pretreatment alveolar bony dehiscences and fenestrations in the posterior area will aid orthodontists in planning posterior crossbite patients accordingly to minimize posttreatment bony defects. Before the advent of cone beam computed tomography (CBCT), observing buccal and lingual bony defects was not possible unless other treatment needs allowed for an open-flap procedure. With CBCT technology, we can now detect posterior defects with some accuracy. The aim of the present study was to determine the prevalence of posterior alveolar bony dehiscence and fenestration in adults with posterior crossbite compared with noncrossbite adults.

Methods

The study group consisted of pretreatment CBCTs of 28 samples with at least one or more teeth in posterior crossbite or edgebite. The comparison group consisted of pretreatment CBCTs of 28 samples with no posterior crossbite or edgebite. All buccal and lingual sides of the upper and lower posterior segments were measured for the presence of dehiscence, fenestration, and combined total bony defects.

Results

The prevalence of total bony defects was higher in the study group (61.6%) than in the comparison group (52.1%) (p < 0.05). While there was no difference in prevalence between crossbite teeth in the study group and noncrossbite teeth in the comparison group, the noncrossbite teeth in the study group showed a higher prevalence of total bony defects, dehiscence, and fenestration than the noncrossbite teeth in the comparison group (p < 0.05). The prevalence of dehiscence was higher in the study group (41.2%) than in the comparison group (33.3%) (p < 0.05). Neither the prevalence of fenestration nor the mean bony defect size showed statistical significance between the two groups. First premolars showed a higher prevalence of dehiscence than other posterior teeth, and maxillary posterior teeth had a higher prevalence of fenestration than mandibular posterior teeth. Among the maxillary posterior teeth, second premolars had the least amount of fenestration.

Conclusions

Adult subjects with posterior crossbite had a higher prevalence of total bony defects and dehiscence, especially buccal dehiscence, in the posterior region than subjects with no posterior crossbite. This was due to the high prevalence observed in the noncrossbite teeth in posterior crossbite subjects.

Frequency of adequate mesiodistal space and faciolingual alveolar width for implant placement at anterior tooth positions

BACKGROUND

Prior studies have defined minimum mesiodistal space (MS) and faciolingual alveolar width (FAW) requirements for dental implant sites, and failure to observe these constraints may adversely impact peri-implant health and esthetics. However, to the authors' knowledge, no previous reports have established frequencies at which anterior tooth positions present favorable MS and FAW for implant accommodation.

METHODS

A single examiner analyzed 205 cone-beam computed tomographic images, recording MS and FAW available for implant placement at anterior tooth positions. The examiner compared measurements with standardized implant diameters to assess anticipated implant-to-tooth distances and peri-implant bone thicknesses.

RESULTS

In the esthetic zone, lateral incisor sites most frequently failed to present favorable MS. At maxillary lateral incisor positions, 22% (left) and 27% (right) of sites offered less than 2 millimeters between the proposed implant platform and the adjacent teeth. In mandibular incisor positions, implant-to-tooth distance was less than 2 mm at 79% through 97% of sites and less than 1.5 mm at 35% through 76% of sites. Over one-half of maxillary incisor sites and 78% through 95% of mandibular incisor sites exhibited FAW of less than 4 mm beyond implant diameter.

CONCLUSIONS

In the population evaluated, mandibular incisor positions frequently presented unfavorable MS to accommodate conventional narrow-diameter implants. In addition, considerable proportions of mandibular incisor and maxillary lateral incisor sites may be at risk of developing unfavorable peri-implant bone thickness when conventional narrow-diameter implants are used.

PRACTICAL IMPLICATIONS

Practitioners should consider small-diameter implants and nonimplant tooth replacement methods for many patients missing single mandibular incisors or maxillary lateral incisors.

Measurement of the bone height of mandibular incisors and canines on computed tomography-Limitations according to bone thickness

AIM

To verify the correlation between cone beam CT (CBCT) and spiral CT (SCT) images and direct measurement of the bone height and to verify whether bone thickness (BT) influences the accuracy of bone height measurement on CT.

SETTING AND SAMPLE

One hundred and fourteen measurements were obtained in 10 dry human mandibles.

MATERIALS AND METHODS

The alveolar bone height was measured on volumetric and linear images.

RESULTS

Negative, average and significant correlations (-0.622** to -0.489**) were verified between BT and the absolute error. When the alveolar bone thickness was at least 0.6 mm, the mean differences were 0.16 and 0.28 mm on linear images and 0.12 and 0.03 mm on volumetric images for CBCT and SCT. Additionally, these values ranged from -0.46 to 0.79 and -0.32 to 0.88 mm on linear images and from -0.64 to 0.67 and -0.57 to 0.62 mm on volumetric images for CBCT and SCT. When the alveolar bone thickness was less than 0.6 mm, the CT evaluation varied from -1.74 to 5.42 and -1.64 to 5.42 mm on linear images and from -3.70 to 4.28 mm and -3.49 to 4.25 mm on volumetric images for CBCT and SCT.

CONCLUSIONS

Spiral CT and CBCT images demonstrate significant correlation with direct measurement for the alveolar bone height. Measurement of the alveolar bone labial and lingual to the mandibular incisors and canines presented higher accuracy when its thickness was greater than 0.6 mm. When the thickness was less than 0.6 mm, bone dehiscence can be diagnosed despite bone being clinically present.

Novel low-dose protocols using cone beam computed tomography in dental medicine: a review focusing on indications, limitations, and future possibilities

OBJECTIVES

A narrative review on the potential use of low-dose protocols for cone beam computed tomography (CBCT) was conducted to identify indications and their relevance for various dental disciplines.

MATERIALS AND METHODS

Google Scholar was searched using the words "low-dose CBCT". Reviews, consensus papers, clinical studies, and experimental studies were eligible for the initial screening process, but for data extraction only original articles were selected. Similar search procedures were then performed with the additional search words "pedo," "ortho," "endo," "implant," "perio," and "oral surgery." Furthermore, references of included articles were examined to identify further relevant articles.

RESULTS

After screening, 27 publications remained for the data extraction process. Low-dose protocols have been reported for specialties such as pediatric dentistry (evaluating orofacial clefts, periapical lesions, impacted teeth, and autotransplantation), orthodontics (cephalometric analysis and interim assessment of treatment results), endodontics (detecting root fractures, resorptions and periapical bone loss), implant dentistry (planning implant insertion, evaluating peri-implant fenestration and dehiscence), periodontology (assessing periodontal structures), and oral and maxillofacial surgery (assessing mandibular third molars and TMJs). Nevertheless, most of the literature available is related to non-clinical studies. Furthermore, there is a lack of position statements or guidelines from authoritative bodies regarding the use of low-dose protocols in dental medicine.

CONCLUSIONS

Low-dose protocols for CBCT imaging seem to have potential in various disciplines in dental medicine ranging from pediatric dentistry to oral and maxillofacial surgery. Dose reduction is usually achieved by mAs reduction, use of partial rotations, reduced number of projections, and larger voxel sizes, but seldom by kV reduction.

CLINICAL RELEVANCE

Albeit low-dose protocols have potential to result in a reduction of dose exposure for 3D imaging due to dental indications, there is a need to more clearly specify indications and limitations to avoid indiscriminate use of standard and high-dose CBCT scans in the future on the lines of ALARA/ALADA principles.

Comparison of cone-beam computed tomography with bitewing radiography for detection of periodontal bone loss and assessment of effects of different voxel resolutions: an in vitro study

OBJECTIVE

The aim of the study was to compare intraoral radiographs and CBCT images for detection of horizontal periodontal bone loss, and to investigate the diagnostic effect of different voxel resolutions in CBCT imaging.

METHODS

A total of 240 sites with horizontal bone loss were measured on the buccal, lingual, mesial, and distal surfaces of 60 posterior teeth in four maxillary and six mandibular bones obtained from cadavers (dry skulls). Direct measurements on the dry skulls were accepted as the gold standard values. Measurements on CBCT images at two different voxel resolutions (0.250 and 0.160 mm³) and intraoral bitewing radiographs were compared with one another and with the gold standard values.

RESULTS

The measurements on the CBCT images at two voxel resolutions and bitewing radiographs did not differ significantly (p > 0.05) from the direct measurements on the dry skulls. No significant difference was found between the bitewing radiographs and CBCT images for measurements in the mesial and distal regions (p > 0.05). There was no significant difference between the measurements on the buccal and lingual surfaces at the two different voxel resolutions (p > 0.05).

CONCLUSIONS

CBCT scans are recommended for evaluation of buccal and lingual bone loss to avoid intraoral radiographs that exceed routine examination of interproximal alveolar bone loss. Furthermore, instead of basing the voxel size on the required CBCT scans, it is recommended to select the smallest possible field of view to reduce the dose of radiation.

Impact of voxel size and scan time on the accuracy of three-dimensional radiological imaging data from cone-beam computed tomography

PURPOSE

Three-dimensional (3D) radiological imaging plays an important role in surgical planning used in modern dentistry. The aim of this study was to optimize imaging parameters with a special focus on voxel size and scan time.

MATERIAL AND METHODS

A virtual 3D master model of a macerated human skull was generated using an industrial optical noncontact white light scanner. The skull was X-rayed with cone-beam computed tomography that was applied using different settings for voxel size and acquisition time (voxel edge length of 0.3 mm, scan times 4.8 s and 8.9 s; voxel edge length of 0.2 mm, scan times 14.7 s and 26.9 s). The scan was repeated 10 times at each setting. The CBCT scans were converted into 3D virtual models (actual value), which were superimposed with the 3D master model (reference value) to detect absolute differences.

RESULTS

The mean value of deviation increased with increasing voxel size and decreasing scan time. For a voxel edge length of 0.3 mm, the mean values of deviation were 0.33 mm and 0.22 mm with scan times of 4.8 s and 8.9 s, respectively. For a voxel edge length of 0.2 mm, the mean deviations were 0.16 mm and 0.14 mm with scan times of 14.7 s and 26.9 s, respectively.

CONCLUSIONS

When using small voxel sizes, the scan time does not have a significant impact on image accuracy and therefore the scan time can be shortened. However, for larger voxel sizes, shorter scan times can lead to increased inaccuracy.

Cone-beam computed tomography evaluation of bone plate and root length after maxillary expansion using tooth-borne and tooth-tissue-borne banded expanders

INTRODUCTION

The objective of this research was to evaluate the buccal bone plate and root length of maxillary permanent first molars using cone-beam computed tomography after maxillary expansion with different activation protocols.

METHODS

Cone-beam computed tomography images of growing patients were obtained from the orthodontic department of Pontifical Catholic University of Rio Grande do Sul in Brazil. The groups were Haas-type 2/4 turns, Haas-type 4/4 turns, hyrax-type 2/4 turns, and hyrax-type with alternate rapid maxillary expansions and constrictions (alt-RAMEC) 4/4 turns a day. Tooth length, periodontal insertion, alveolar bone thickness, and intermolar distances were evaluated. The data at the start of treatment and 6 months later were compared using generalized linear models. The intergroup differences were determined by univariate analysis of variance with the Bonferroni adjustment.

RESULTS

Tooth length was significantly shortened after expansion in all groups (-0.28 to -0.51 mm), except for the alt-RAMEC group. Bone level variables (bone level and bone level at the tooth tip) changed statistically in all groups, except for the Haas 4/4 turns group. There was significant periodontal attachment loss after rapid maxillary expansion with the hyrax/alt-RAMEC (5.09 mm). The hyrax/alt-RAMEC and hyrax groups had more dehiscences, fenestrations, and exposures of the root.

CONCLUSIONS

The consequence of rapid maxillary expansion using the hyrax was alveolar bone resorption, especially in the hyrax/alt-RAMEC group, whereas the Haas expander caused mild root resorption.

Influence on interradicular bone volume of Invisalign treatment for adult crowding with interproximal enamel reduction: a retrospective three-dimensional cone-beam computed tomography study

BACKGROUND

The aim of this study was to use three-dimensional datasets to identify associations between treatment for adult crowding, using Invisalign aligner and interproximal enamel reduction (IER), and changes in the volume of interradicular bone.

METHODS

A total of 60 cone-beam computed tomography (CBCT) scans from 30 adult patients (28 women, two men; 30 CBCTs pre-treatment, 30 post-treatment) were examined retrospectively in order to measure bone volume three-dimensionally. The patients' average age was 36.03 ± 9.7 years. The interradicular bone volume was measured with OsiriX at four levels in the anterior tooth areas of the maxilla and mandible. Differences in bone between T0 and T1 were analyzed with IBM SPSS 21.0 using the Wilcoxon test for paired samples.

RESULTS

Overall, a slight increase in the quantity of bone was found (0.12 ± 0.73 mm). There was a highly significant increase in bone in the mandible (0.40 ± 0.62 mm; P <  0.001), while in the maxilla there was a slight loss of bone, which was highly significant in the apical third (- 0.16 ± 0.77 mm; P = 0.001).

CONCLUSIONS

Overall, treatment for adult crowding using an aligner and IER appears to have a positive effect on interradicular bone volume, particularly in patients with severe grades of the condition (periodontally high-risk dentition). This effect is apparently independent of IER. This is extremely important with regard to the treatment outcome, since IER and root proximity have been matters of debate in the literature and teeth should remain firmly embedded in their alveolar sockets.

The usefulness of cone-beam computed tomography gray values for alveolar bone linear measurements

OBJECTIVES

To test a proof-of-concept that the accuracy and reliability of alveolar bone height measurements from orthodontic grade (large field-of-view [FOV], large voxel-size) cone-beam computed tomography (CBCT) images may be improved by using pixel gray values.

MATERIALS AND METHODS

Twenty fresh cadaver pig heads underwent CBCT scans (17 × 23 cm FOV, 0.4-mm voxel size). Buccal alveolar bone heights of maxillary first molars were measured using the conventional vision-based (VB) and the proposed gray value-assisted (GVA) methods. The GVA methods entailed localization of landmarks through observation of gray value pattern changes across tissue boundaries followed by mathematical calculation of distances between landmark pixels. Interrater reliability and accuracy of CBCT measurements made by all methods were statistically analyzed by comparing with physical measurements (gold standards).

RESULTS

The interrater reliability of CBCT measurements made by GVA methods was comparable to physical measurements but higher than those made by the VB method. The GVA (bend-down pattern) method yielded average measurements similar to physical measurements, while those obtained by the VB and the GVA (straight pattern) methods were significantly larger (repeated measures analysis of variance, P < .001). The GVA (bend-down pattern) method also produced significantly more measurements within one voxel size of physical measurements than did the VB and GVA (straight pattern) methods (Chi-square tests, P < .017).

CONCLUSIONS

These data confirm a concept that local gray value change patterns may be used to improve the accuracy and reliability of alveolar bone height measurement from large FOV and large voxel-size CBCT images.

Assessment of Bone Dimensions in the Anterior Maxilla: A Cone Beam Computed Tomography Study

PURPOSE

To evaluate labial and palatal bone thickness at the maxillary anterior teeth as well as distance from cemento-enamel junction (CEJ) to bone crest using cone beam computed tomography (CBCT).

MATERIALS AND METHODS

Measurements were obtained for maxillary anterior teeth of 120 subject CBCT volumes including thickness of labial and palatal plates of bone (coronal, middle, and apical thirds), and distance between CEJ and alveolar bone crest mid-labially, mesially, and distally.

RESULTS

The mean value of bone thickness at coronal, middle, and apical thirds of the labial side for central incisor roots were respectively: 0.73, 0.69, 0.60 (mm), for lateral incisors: 0.70, 0.61, 0.49 (mm), and for canines: 0.74, 0.53, 040 (mm). The thickness of palatal bone was significantly larger. The mean distance between CEJ and mid-labial bone crest for all sites was 2.16 mm.

CONCLUSION

Labial bone thickness is thin in the vast majority of maxillary anterior teeth. Use of CBCT facilitates planning for immediate implant placement and is helpful in the decision-making process when further bone augmentation is needed.

Alveolar bone morphology of maxillary central incisors near grafted alveolar clefts after orthodontic treatment

INTRODUCTION

The aim of this study was to evaluate the thickness and the height of the maxillary central incisors' alveolar bone near the grafted alveolar cleft area, after comprehensive orthodontic treatment.

METHODS

The sample comprised 30 patients with unilateral alveolar cleft with a mean age of 20.5 years (range, 17-25.8 years). High-resolution cone-beam computed tomography images of the maxilla were obtained 6 to 24 months after the comprehensive orthodontic treatment. The contralateral maxillary central incisor was used as a comparison group. Axial sections at the level of the central incisor root were used to measure the labial and lingual alveolar bone thicknesses. Cross sections were used to measure the bone crest heights using the cementoenamel junction as the reference. Paired t and Wilcoxon tests were used to compare the cleft and noncleft sides.

RESULTS

The labial and lingual bone thicknesses of the maxillary central incisors' alveolar bone were significantly thinner (0.16 and 0.39 mm, respectively), and the labial alveolar crest height distance was significantly greater on the cleft side compared with the noncleft side (-1.2 mm).

CONCLUSIONS

In patients with unilateral cleft lip and palate, the maxillary central incisors adjacent to the grafted alveolar cleft had thinner labial and lingual alveolar bones and an apically displaced labial alveolar crest level than the controls.

Accuracy of Bone Measurements in the Vicinity of Titanium Implants in CBCT Data Sets: A Comparison of Radiological and Histological Findings in Minipigs

Purpose

The aim of this animal study was the determination of accuracy of bone measurements in CBCT (cone-beam computed tomography) in close proximity to titanium implants.

Material and Methods

Titanium implants were inserted in eight Göttingen minipigs. 60 implants were evaluated histologically in ground section specimen and radiologically in CBCT in regard to thickness of the buccal bone. With random intercept models, the difference of histologic measurements and CBCT measurements of bone thickness was calculated.

Results

The mean histological thickness of the buccal bone was 5.09 mm (CI 4.11–6.08 mm). The four raters measured slightly less bone in CBCT than it was found in histology. The random effect was not significant (p value 1.000). Therefore, the Intraclass Correlation Coefficient (ICC) was 98.65% (CI 100.00–96.99%).

Conclusion

CBCT is an accurate technique to measure even thin bone structures in the vicinity of titanium implants.

Influence of Invisalign treatment with interproximal enamel reduction (IER) on bone volume for adult crowding: a retrospective three-dimensional cone beam computed tomography study

Background

The aim of this study was to use three-dimensional datasets to identify associations between treatment for adult crowding using Invisalign and interproximal enamel reduction (IER) and changes in the bone volume.

Methods

A total of 60 digital cone beam computed tomography (CBCT) scans from 30 patients (28 women, two men; 30 CBCTs pretreatment, 30 posttreatment) were examined retrospectively in order to record bone volume three-dimensionally before and after treatment. The patients’ average age was 36.03 ± 9.7 years. The data were collected and analyzed using the computer programs Mimics 15.0 and OsiriX. Differences in bone between T0 and T1 were analyzed with IBM SPSS 21.0 using the Wilcoxon test for paired samples.

Results

Analysis of the orovestibular bone volume showed highly significant changes (bone change P <0.001) only in the mandible where more expansion of the dental arch was carried out using proclination or protrusion. The bone lamella was thinner buccally and thicker lingually. In general, bone increases in the oral direction were slightly greater than bone losses in the vestibular direction. No significant changes were detected in the maxilla (bone change P = 0.13). Significant vertical bone loss in the bone height was detected in both the maxilla and the mandible. The largest bone loss was observed in the vestibular direction in the mandible, at a high level of significance (P <0.001).

Conclusions

Particularly in the mandible, therapeutic reduction of the vertical and sagittal bone volume shows that caution should be used in the treatment of tertiary crowding with proclination and expansion. The cortical walls appear to represent the limits for orthodontic tooth movement, at least in adult female patients.

Precision, reproducibility, and accuracy of bone crest level measurements of CBCT cross sections using different resolutions

OBJECTIVE

To evaluate the precision, reproducibility, and accuracy of alveolar crest level measurements on CBCT images obtained with different voxel sizes.

MATERIALS AND METHODS

CBCT exams were made of 12 dried human mandibles with voxel dimensions of 0.2, 0.3, and 0.4 mm. Bone crest level was measured directly on the mandibles with a digital caliper and on CBCT images. Images were measured twice by two examiners. Intra- and interexaminer precision and reproducibility were assessed using paired and t-tests, respectively. Accuracy was evaluated using t-tests.

RESULTS

Precision and reproducibility of bone crest level tomographic measurements was good for all voxel sizes evaluated. The images with 0.2-mm voxel size showed a decreased number of intraexaminer errors. A high accuracy for measurements of bone crest level was observed for all CBCT definitions, except for the mandibular incisors using the 0.4-mm voxel size.

CONCLUSIONS

Precision and reproducibility of alveolar bone level measurements were good for various voxel sizes. CBCT images demonstrated good accuracy for 0.2-mm and 0.3-mm voxel sizes. The mandibular incisor region needs better resolution than that provided by 0.4-mm voxel size for bone crest level measurements.

Use of micro-computed tomography for the assessment of periapical lesions in small rodents: a systematic review

This systematic review aimed to evaluate the literature on the acquisition-, reconstruction- and analysis parameters of micro-computed tomography (micro-CT) for the assessment of periapical lesions in rats and mice, and to illustrate the effect of variation in these parameters. The PubMed database was searched from 2000 to January 2015 (English-language publications) for reports on the use of micro-CT to evaluate periapical lesions in rats and mice. QUADAS criteria were used to rate the quality of the studies. To illustrate the effect of variations in acquisition-, reconstruction-, and analysis parameters on images of periapical lesions, micro-CT examination of two hemi-mandibles of mice, with periapical lesions around the first molar was undertaken. Twenty-one studies were identified, which analysed periapical lesions in rats or mice using micro-CT. According to the QUADAS, no study was classified as high-, seven were classified as moderate-, and 14 as low quality. The effect of variation in parameters was that voxel size may interfere with image sharpness, reconstruction may interfere with image sharpness and contrast, and inadequate plane orientation may alter the size of the periapical lesion. Nonpersonalized ROIs resulted in areas that were not part of the periapical lesion. Changing the limits of the threshold for bone-tissue visualization increased lesion size. There is no defined protocol for acquiring and analysing micro-CT images of periapical lesions in rats and mice. Furthermore, acquisition-, reconstruction- and analysis parameters are not adequately explained, which may compromise the scientific impact of the studies.

A six-site method for the evaluation of periodontal bone loss in cone-beam CT images

OBJECTIVES

In contrast to two-dimensional planar images, a measuring point is hardly repeatedly determined in a CBCT image when alveolar bone loss is assessed. Thus, the aim of the present study was to propose a six-site measuring method, which is closely related to anatomical structure, for the evaluation of alveolar bone loss in CBCT images.

METHODS

150 measuring points in 11 molars and 14 premolars from 6 patients (2 males and 4 females) were included. CBCT images of the teeth were acquired prior to periodontal surgery. Four observers measured the distances between cemento-enamel junctions and the apical bases of the periodontal bone defect at the mesio-buccal, mid-buccal, disto-buccal, mesio-lingual/palatal, mid-lingual/palatal and disto-lingual/palatal sites in CBCT images. Direct measurements of the six sites were correspondingly obtained in the subsequent periodontal surgeries. Differences between the distances measured in the CBCT images and during the surgery were analysed. Interobserver and intraobserver variances were tested.

RESULTS

No statistically significant difference was found between the surgical and CBCT measurements (p = 0.84). Diagnostic coincidence rates of four observers were 86.7%, 87.3%, 88.7% and 88.0%, respectively. The interobserver (p = 0.95) and intraobserver (p = 0.30) variances were not significant.

CONCLUSIONS

The six-site measuring method validated in the present study may be a useful three-dimensional measuring method for the evaluation of periodontal disease.