Angular distortion in the orthopantomogram

An effective approach to assessing inter-root distances using tooth models without repeated cone-beam computed tomography scans during orthodontic treatment

Objective

To propose the utilization of virtual tooth models (VTMs) created by combining tooth root data from cone-beam computed tomography (CBCT) and crown data gathered through intraoral scanning to assess inter-root distance and angulation during orthodontic treatment when repeated radiographic monitoring becomes necessary.

Methods

Patients with planned dental implant placement in edentulous areas during or after orthodontic treatment and who underwent intraoral and CBCT scans at the pretreatment and posttreatment stages were selected. Tooth models were fabricated by merging intraorally scanned crowns with the corresponding CBCT-scanned roots from the pretreatment. Tooth positions posttreatment was estimated by integrating models into posttreatment intraoral scans. Moreover, the actual positions were obtained from posttreatment CBCTs. Discrepancies in the estimated and actual tooth positions, including inter-radicular distances and inter-root angulations, were compared.

Results

The minimum inter-radicular distance between two adjacent teeth demonstrated no significant difference between the estimated and actual tooth positions. The difference in inter-root angulation was not statistically significant. Most inter-radicular distances measured at each landmark revealed no significant differences between the estimated and actual tooth positions, except at the buccolingual midpoint of the cemento-enamel junction, where a slight discrepancy was observed.

Conclusions

The tooth position of VTMs demonstrated clinically acceptable accuracy compared to CBCT scans. Additionally, VTMs can benefit both clinicians and patients by enabling accurate assessment of the inter-radicular space for dental implant placement without repeated CBCT scans.

Can the use of morning occlusal guides after oral sleep appliances cause root resorption similar to orthodontic jiggling?

OBJECTIVE

To evaluate root length changes associated with the use of mandibular advancement devices (MADs) to treat obstructive sleep apnea (OSA), in conjunction with morning occlusal guides.

METHODS

This was a retrospective cohort study where the sample included panoramic radiographs of 68 subjects (52.1 ± 8.4 years) who wore MADs in conjunction with morning occlusal guides, for at least 3 years. Root and crown lengths were measured to assess root to crown (R/C) ratios before the initiation of MAD use (T1), and after at least 3 years of wearing the MAD and the morning occlusal guide (T2). Mixed analysis of variance was used to compare R/C ratios at T1 and T2. To assess the change in root lengths and distribution of root resorption (RR) severity, relative root to crown ratio (rRCR) was calculated. Severe RR was assumed when there was > 20% reduction in pre-treatment length.

RESULTS

There were statistically significant differences between the R/C ratios at T1 compared to T2 for multiple teeth (p < 0.05). The greatest mean differences were found among the mandibular incisors(p ≤ 0.01). The mean rRCR for all teeth was > 90% indicating slight or no RR.

CONCLUSION

Statistically significant RR was found with the use of MADs with morning occlusal guides, albeit the amount of RR was not clinically significant.

PRACTICAL IMPLICATIONS

New consent forms should be developed to make patients aware that RR may occur during treatment with MADs in conjunction with morning occlusal guides.

Ectopic eruption of maxillary first permanent molars: Risk factors and association with alveolar and maxillary characteristics on children

Background/purpose

The etiology of the ectopic eruption (EE) of the maxillary first permanent molars (FPM) remains unclear and controversial. This study was designed to explore the dental and skeletal factors for EE of the FPM in children.

Materials and methods

Children aged 6-10 years were recruited to this study. Subjects were assigned to the ectopic eruption group (EEG) and the normal eruption group (NEG). Lateral cephalometric radiographs and panoramic radiographs were measured by angular and linear indices.

Results

The prevalence of EE of maxillary FPM was higher in males and at younger ages. Subjects with skeletal class III malocclusion were more likely to be diagnosed with EE of maxillary FPM. The SNA, ANB, FMIA, Wits, Ptm-A, ANS-PNS, overbite, and overjet were significantly different between the EEG and the NEG. The length of the posterior region of the maxillary alveolar bone, U6-OP, and eruptive angulation of the maxillary FPM were statistically different between the two groups.

Conclusion

Male sex, skeletal class III malocclusion, mesial inclination of the maxillary FPM, hypoplasia of the maxilla, and insufficient length of the posterior region of the maxillary alveolar bone were related to EE of the maxillary FPM.

Radiographic assessment of the peri-implant site

While peri-implant mucositis relies solely on clinical parameters, radiological assessment becomes indispensable for diagnosing peri-implantitis. Intraoral radiography, with its simplicity of application, low radiation exposure, and adequate representation of peri-implant structures, stands out as the standard of care for both immediate and follow-up assessments. Standardization by custom-made radiologic splints allows for excellent comparability with previous images and allows for the determination of even small changes in contour and density of the peri-implant bone. Furthermore, other radiographic modalities like panoramic radiography and cone beam computed tomography (CBCT) may provide useful features for specific patients and clinical cases while also showing innate limitations. Beyond the assessment of the marginal peri-implant bone level as the crucial parameter of clinical relevance, radiologic assessment may reveal various other findings related to the prosthetic restoration itself, the precision of its fit to the implant, and the peri-implant soft and hard tissues. Since such findings can be crucial for the assessment of peri-implant health and the implants' prognosis, a systematic diagnostic evaluation pathway for a thorough assessment is recommended to extract all relevant information from radiologic imaging. This article also provides an overview of the clinical and chronological indications for different imaging modalities in peri-implant issues.

Comparison of mesiodistal root angulation of teeth by conventional panoramic and cone beam computed tomography images - A cross-sectional study

INTRODUCTION

Accurate bracket positioning is required for proper root parallelism and for stable orthodontic treatment outcomes. This study aimed to determine the difference in mesiodistal root angulation of teeth measured on three radiographic images.

MATERIAL AND METHODS

A cross-sectional study was conducted using orthopantomogram (OPG), panoramic images of cone beam computed tomography (Pan-CBCT) and cone beam computed tomography (CBCT). An occlusal plane was constructed in OPG and Pan-CBCT for angular measurements. The axial and sagittal views were used for assessing the mesiodistal root angulation on CBCT. Mesiodistal root angulation differences among three radiographs were assessed using the Kruskal-Wallis test. Mann-Whitney U test was applied for pairwise comparison and multinomial logistic regression was used to determine the association of sexual dimorphism with the direction of root angulation.

RESULTS

On comparing the mesiodistal root angulation in degrees (DE) among all three groups, upper right (UR2) and left lateral incisors (UL2) were found to be statistically significant with P=0.033 and P=0.050 respectively. On pair-wise comparison, we found a statistically significant difference for upper right lateral incisor (UR2) between OPG and Pan-CBCT (P=0.045). Upper left lateral (UL2) (P=0.024) was significant in OPG and Pan-CBCT while upper left first molar (UL6) (P=0.043) in OPG and CBCT group. On comparing the sexual dimorphism in the direction of root angulation, females showed a greater tendency of mesial root angulation (5.62) times for upper right second premolar (UR5) as compared to males.

CONCLUSIONS

There were no significant difference in mesiodistal root angulation between panoramic CBCT and CBCT images. The angulation of the upper lateral incisors was found to be significant between OPG and panoramic CBCT images, whereas the angulation of the upper right lateral incisors and left first molars was significant between OPG and CBCT images. In terms on sexual dimorphism, females showed greater mesial angulation of teeth than males.

Digital evaluation and correlation of facial growth patterns assessed on lateral CEPH and orthopantomogram through ONECEPH mobile application

OBJECTIVES

This study aimed to investigate the correlation of gonial angle and three linear measurements on OPG and lateral cephalograms and their effects on the different facial patterns using the OneCeph android app.

METHOD

About 90 pre-treatment digital lateral cephalograms and OPGs of 90 patients were selected and divided into 3 categories, based on their growth patterns. The OPGs and lateral cephalograms were uploaded on the OneCeph android app. After calibrating using One linear measurement i.e. length of extracted premolar for OPG and ruler in radiograph for lateral cephalogram, Gonial angle (Ar- Go-Me), ANS-Me (LAFH), U1-NF, L1-MP were measured. The data were collected, tabulated, and subjected to statistical analysis using the SPSS software (version 20.0). The level of significance was kept at 5%.

RESULTS

Values for parameters were highest in the vertical growth pattern followed by average and horizontal in both cephalogram and OPG. Upon comparison of lateral cephalogram and OPG, no significant difference was observed in gonial angle and a significant difference in LAFH and L1-MP in all three growth patterns with OPG scores greater than cephalometric tracing. The interclass coefficient test indicated almost perfect agreement for the gonial angle between the two methods. A substantial agreement was seen for U1-NF on lateral cephalogram and OPG in the vertical group. Also, a fair agreement in the vertical and horizontal group was observed in Lower anterior mandibular height.

CONCLUSION

Vertical parameters such as gonial angle and maxillary anterior dental height can be accurately determined on an OPG by the OneCeph application.

Differences in third molar development and angulation in class II subdivision malocclusions

PURPOSE

To assess and compare the developmental stages and angulations of third molars between the class II and class I sides in class II subdivision malocclusions.

METHODS

This retrospective study was performed using panoramic x‑rays of 38 individuals (mean age: 15.5 years; 24 females, 14 males) with class II subdivision malocclusions, which were further divided into type 1 and 2 subgroups according to midline deviation, and a control group of 42 individuals (mean age: 17.0 years; 30 females, 12 males) with normal occlusion. Third molars were categorized using the developmental stages defined by the Demirjian method. Angles between the third molars and horizontal reference lines and also to the second molars were measured.

RESULTS

No difference was found in developmental stages or angulations between the left and right third molars in the control group. In the class II subdivision malocclusion cases, no difference in third molar developmental stages was observed, but the angle between the long axes of the mandibular third and second molars was significantly greater on the class II side. In the type 2 subgroup, developmental stage of the maxillary third molar was more advanced on the class II side. In both subgroups, the angles of the maxillary third molars' long axis to the interorbital plane differed significantly between the two sides.

CONCLUSION

Class II subdivision malocclusion may cause differences in third molar development and angulations between the two sides. Orthodontic treatment should be planned considering the third molars in this malocclusion.

Implant-to-nasal floor dimensions projected by panoramic radiographs in the maxillary incisor-canine region: implications for dental implant treatment

To make a comparison of panoramic radiography (PAN) and cone-beam computed tomography (CBCT) determinations of implant-to-nasal floor dimensions (INFD) in the anterior maxillary region, and to assist in determining in which tooth regions additional radiation exposure involved in CBCT scans is justifiable. Data related to INFD by PAN (PAN-D) at implant-to-nasal floor sites (central incisor, lateral incisor, canine) were gathered using 141 implant sites from 119 adult patients. INFD was estimated employing the CBCT technique as a reference method. PAN analysis equations were created for estimation of INFD by CBCT (CBCT-D) specific to implant sites. For assessment of the agreement between the PAN and CBCT methodologies, the Bland-Altman approach was employed. There were robust and significant odds ratios that implants in the canine region would fall into the underestimation groups of > 0 mm (4.5:1) (p = 0.003), > 0.5 mm (6.2:1) (p < 0.001), and > 1 mm (5.4:1) (p = 0.002). The root mean squared error (RMSE) and pure error (PE) were highest for the canine region (RMSE = 1.973 mm, PE = 2.20 mm). This research offers evidence of site-specific underestimations of available horizontal bone dimensions for implants when PAN is employed to assess the availability of vertical bone dimensions. The data suggest that it may be necessary to exclude canine regions when making assessment of INFD through PAN. Use of CBCT may, therefore, be recommended for all implant size and angulation estimations in this region.

Implant-to-root dimensions projected by panoramic radiographs inthe maxillary canine-premolar region: implications for dental implant treatment

BACKGOUND

This study aimed to compare panoramic radiography (PAN) and cone beam computed tomography (CBCT) determinations of implant-to-root dimensions (IRD) in anterior and posterior maxillary regions, and to help determine in which instances increased radiation exposure from CBCT scans may be justified.

METHODS

IRD measured by PAN (PAN-D) from implant-to-root sites (central incisor, lateral incisor, canine, first premolar, and second premolar) was collected from 418 implant sites in 110 adults. The CBCT technique was used as the reference method for the estimation of IRD. The PAN analysis equations were developed using stepwise multiple regression analysis and the Bland-Altman approach was applied to assess the agreement between PAN and CBCT methods.

RESULTS

The odds ratio that an implant at the canine-to-first premolar (9.7:1) (P = 0.000) or at the first premolar-to-second premolar region (4.5:1) (P = 0.000) belongs to the underestimation group was strong and highly significant. The root mean square error (RMSE) and pure error (PE) were highest for the canine-to-first premolar (RMSE = 0.886 mm, PE = 0.45 mm) and the first premolar-to-second premolar region (4.5:1) (RMSE = 0.944 mm, PE = 0.38 mm).

CONCLUSIONS

This study provides evidence of site-specific underestimations of available horizontal bone dimensions for implants when assessed by PAN. These data suggest that the canines and first and second premolars may have to be excluded when assessing root angulations via PAN.

Ectopic eruption of the first permanent molar: Predictive factors for irreversible outcome

INTRODUCTION

The present study aimed to analyze possible factors involved in irreversible (IRR) ectopic eruption (EE) of the first permanent molar and explore potential predictors for the IRR outcome.

METHODS

Children aged 4-11 years, with at least 1 EE and who took their first panoramic radiograph before the age of 8 years, were selected in this study. The subjects were assigned to the self-correcting (SC) and IRR groups. Patients' age, sex, distribution of EE, and accompanying dental anomalies were recorded. Eruptive angulation (EA) of the first permanent molar, the grade of root resorption in the second deciduous molar, the magnitude of impaction index (MOII), and horizontal distance were measured on the panoramic radiographs. Chi-square tests and independent-sample t test were used for nominal and continuous variables, respectively. The receiver operative characteristic curve was used to determine the critical value.

RESULTS

A total of 406 children with 634 first permanent molars, presenting EE, were enrolled, with 61.3% of the teeth in the SC group. Sex of children with EE and distribution of EE were not relevant to the IRR outcome. The presence of supernumerary teeth might be a protective factor for the IRR outcome. The increasing severity of root resorption in the second primary molar indicated an IRR outcome. A higher MOII and a larger EA suggested an IRR outcome with moderate-to-high quality. The horizontal distance exhibited debatable results, with a low predictive quality.

CONCLUSION

Close monitoring and early intervention would benefit children with increasing severity of distal atypical resorption in the second primary molar, higher MOII, and larger EA.

Root Dimensions in Patients with Mild Hypodontia and a Control Group

Objectives  The aim of this study was to compare root dimensions (length and mesiodistal widths) between subjects with mild hypodontia and an age- and sex-matched control group.

Materials and Methods  Root dimension measurements of all permanent teeth excluding third molars were made on standardly taken orthopantomograms of 50 individuals (25 hypodontia and 25 controls) attending the University of Sharjah Dental Hospital. The length and two mesiodistal widths were measured for each fully formed root. The length of the root was measured digitally by drawing a line from the midpoint and bisecting the mesiodistal cemento-enamel junction (CEJ) of the tooth and extended to its apex. The mesiodistal widths of each root were measured at the cervical region and at half way of and perpendicular to the length of the root.

Statistical Analysis  Two sample t -tests were used to compare root dimension measurements between the hypodontia and control groups.

Results  There were no significant differences between genders with regard to root length or widths measurements, and therefore genders were combined for further analysis. Patients with hypodontia have significantly shorter root lengths than controls for the upper central incisors, upper canines, first premolars, and lower first molars ( p < 0.05). Similarly, root width at the midpoint of the root was found to be less in hypodontia group than that in controls for the upper central incisors, lower first premolars, upper first molars, and all second premolars ( p < 0.05). Similar pattern of differences was found with regard to the root width at the cervical region ( p < 0.05).

Conclusions  Patients with hypodontia have shorter and narrower roots of the whole permanent dentition except the upper lateral incisors, lower incisors, lower canines, and all second molars when compared with controls. In effect, this may affect the orthodontic treatment planning and implant placement.

Spontaneous bone regeneration after surgical extraction of a horizontally impacted mandibular third molar: a retrospective panoramic radiograph analysis

Background

The mandibular third molar (M3) is typically the last permanent tooth to erupt because of insufficient space and thick soft tissues covering its surface. Problems such as alveolar bone loss, development of a periodontal pocket, exposure of cementum, gingival recession, and dental caries can be found in the adjacent second molars (M2) following M3 extraction. The specific aims of the study were to assess the amount and rate of bone regeneration on the distal surface of M2 and to evaluate the aspects of bone regeneration in terms of varying degree of impaction.

Methods

Four series of panoramic radiographic images were obtained from the selected cases, including images from the first visit, immediately after extraction, 6 weeks, and 6 months after extraction. ImageJ software® (NIH, USA) was used to measure linear distance from the region of interest to the distal root of the adjacent M2. Radiographic infrabony defect (RID) values were calculated from the measured radiographic bone height and cementoenamel junction with distortion compensation. Repeated measures of analysis of variance and one-way analysis of variance were conducted to analyze the statistical significant difference between RID and time, and a Spearman correlation test was conducted to assess the relationship between Pederson’s difficulty index (DI) and RID.

Results

A large RID (> 6 mm) can be reduced gradually and consistently over time. More than half of the samples recovered nearly to their normal healthy condition (RID ≤ 3 mm) by the 6-month follow-up. DI affected the first 6 weeks of post-extraction period and only showed a significant positive correlation with respect to the difference between baseline and final RID.

Conclusions

Additional treatments on M2 for a minimum of 6 months after an M3 extraction could be recommended. Although DI may affect bone regeneration during the early healing period, further study is required to elucidate any possible factors associated with the healing process. The DI does not cause any long-term adverse effects on bone regeneration after surgical extraction.

Comparison of Mesiodistal Root Angulation Measured from Conventional and CBCT Derived Panoramic Radiographs in Orthodontic Patients

INTRODUCTION

Use of cone beam computed tomography (CBCT) in orthodontics is increasing; however, some patients started treatment with conventional images. The objective of this study is to manipulate CBCT panoramic reconstruction to make it comparable to conventional panoramic image and to compare mesiodistal root angulations on both images.

MATERIALS AND METHODS

Concurrent conventional panoramics and CBCT volumes were obtained from 40 subjects. CBCT volumes were manipulated to generate pan-like images that mimic the occlusal plane angle of the corresponding panoramic, allowing comparison of mesiodistal root angulations and determination of the head-tilt required to produce the reconstruction.

RESULTS

Clinically meaningful differences (p < .05) in the mesiodistal root angulations between standard panoramics and CBCT reconstructions emerged for 13 out of 24 teeth (54%). Greatest variations were seen in the maxillary and mandibular sextants and in first molar regions. Ideal axial head-tilt for image acquisition was determined to be with Frankfort horizontal plane 3.3o nose down.

CONCLUSION

CBCT pan images must be used with caution due to variation between methods in specific areas of arches. The images can be useful for the assessment of mesiodistal root angulations if the volume is properly manipulated to create a pan-like image.

A preliminary study for determination of three-dimensional root apex position of the maxillary teeth using camera calibration technology

OBJECTIVES

To propose a novel method for determining the three-dimensional (3D) root apex position of maxillary teeth using a two-dimensional (2D) panoramic radiograph image and a 3D virtual maxillary cast model.

METHODS

The subjects were 10 adult orthodontic patients treated with non-extraction. The multiple camera matrices were used to define transformative relationships between tooth images of the 2D panoramic radiographs and the 3D virtual maxillary cast models. After construction of the root apex-specific projective (RASP) models, overdetermined equations were used to calculate the 3D root apex position with a direct linear transformation algorithm and the known 2D co-ordinates of the root apex in the panoramic radiograph. For verification of the estimated 3D root apex position, the RASP and 3D-CT models were superimposed using a best-fit method. Then, the values of estimation error (EE; mean, standard deviation, minimum error and maximum error) between the two models were calculated.

RESULTS

The intraclass correlation coefficient values exhibited good reliability for the landmark identification. The mean EE of all root apices of maxillary teeth was 1.88 mm. The EE values, in descending order, were as follows: canine, 2.30 mm; first premolar, 1.93 mm; second premolar, 1.91 mm; first molar, 1.83 mm; second molar, 1.82 mm; lateral incisor, 1.80 mm; and central incisor, 1.53 mm.

CONCLUSIONS

Camera calibration technology allows reliable determination of the 3D root apex position of maxillary teeth without the need for 3D-CT scan or tooth templates.

Study of edge detection task in dental panoramic radiographs

The purpose of this study is (1) to introduce a new approach for edge detection in orthopantograms (OPGs) and an improved automatic parameter selector for common edge detectors, (2) to present a comparison between our novel approach with common edge detectors and (3) to provide faster outputs without compromising quality. A new approach for edge detection based on statistical measures was introduced: (1) a set of N edge detection results is calculated from a given input image and a selected type of edge detector, (2) N correspondence maps are constructed from N edge detection results, (3) probabilities and average probabilities are computed, (4) an overall correspondence is evaluated for each correspondence map and (5) the correspondence map providing the best overall correspondence is taken as the result of edge detection procedure. A comparison with common edge detectors (the Roberts, Prewitt, Sobel, Laplacian of the Gaussian and Canny methods) with various parameter settings (304 combinations for each test image) was carried out. The methods were assessed objectively [edge mismatch error (EME), modified Hausdorff distance (MHD) and principal component analysis] and subjectively by experts in dentistry and based on time demands. The suitability of the new approach for edge detection in OPGs was confirmed by experts. The current conventional methods in edge detection in OPGs are inadequate (none of the tested methods reach an EME value or MHD value below 0.1). Our proposed approach for edge detection shows promising potential for its implementation in clinical dentistry. It enhances the accuracy of OPG interpretation and advances diagnosis and treatment planning.

Object position and image magnification in dental panoramic radiography: a theoretical analysis

OBJECTIVES

The purpose of our study was to investigate how image magnification and distortion in dental panoramic radiography are influenced by object size and position for a small round object such as a ball bearing used for calibration.

METHODS

Two ball bearings (2.5 mm and 6 mm in diameter) were placed at approximately the same position between the teeth of a plastic skull and radiographed 21 times. The skull was replaced each time. Their images were measured by software using edge detection and ellipse-fitting algorithms. Using a standard definition of magnification, equations were derived to enable an object's magnification to be determined from its position and vice versa knowing the diameter and machine parameters.

RESULTS

The average magnification of the 2.5 mm ball bearing was 1.292 (0.0445) horizontally and 1.257 (0.0067) vertically with a mean ratio of 1.028 (0.0322); standard deviations are in parentheses. The figures for the 6 mm ball bearing were 1.286 (0.0068), 1.255 (0.0018) and 1.025 (0.0061), respectively. Derived positions of each ball bearing from magnification were more consistent horizontally than vertically. There was less variation in either direction for the 6 mm ball bearing than the 2.5 mm one.

CONCLUSIONS

Automatic measurement of image size resulted in less variation in vertical magnification values than horizontal. There are only certain positions in the focal trough that achieve zero distortion. Object location can be determined from its diameter, measured magnification and machine parameters. The 6 mm diameter ball bearing is preferable to the 2.5 mm one for more reliable magnification measurement and position determination.

Accuracy of angular measurements and assessment of distortion in the mandibular third molar region on panoramic radiographs

OBJECTIVE

The objective of this study was to examine distortion on panoramic radiographs by assessing the accuracy of angular measurements in the mandibular third molar region on panoramic radiographs using computed tomography (CT).

METHODS

Images from patients referred to a radiology practice for low-dose CT scans of their lower third molars were used in this study. The angle between the long axes of the second and third molars was assessed on panoramic radiographs and the corresponding CT images. Apparent tilting of the tooth across the arch on the panoramic image and the bucco-lingual inclination on CT were also recorded and compared.

RESULTS

Eighty-eight patients had 163 mandibular third molars. The mean difference between the panoramic measurements and the CT measurements was -1.44 degrees, indicating that on the panoramic radiograph the third molar appeared less mesially inclined on average. This pattern was present in most cases, but in 64 cases the third molar appeared more mesially inclined on the panoramic radiograph. It was not possible to predict the direction of the discrepancy based on the radiographic findings. The discrepancy between the 2 measurements was greater if the third molar appeared tilted across the arch on the panoramic image, and tilted teeth showed a higher bucco-lingual inclination on reformatted CT images.

CONCLUSIONS

Distortions inherent in panoramic imaging because of projection geometry produce discrepancies in the angular measurements in the mandibular third molar regions on panoramic radiographs. Interpretation of third molar angulation from panoramic radiographs is often unreliable and may not accurately reflect the true orientation of the tooth. Apparent tilting of the tooth across the arch on the panoramic radiograph exacerbates the problem and appears to correlate with the bucco-lingual inclination of the third molar as visualized on reformatted CT images.

Mesiodistal root angulation of permanent teeth in children with mixed dentition and normal occlusion

OBJECTIVE

There is little information regarding the mesiodistal angulation of permanent teeth in mixed dentition. The aim of this study was to evaluate mesiodistal root angulation of permanent incisors, canines and first molars of 100 Brazilian children, using a new horizontal reference plane based on the midpoint of the intercuspation of primary canines and permanent first molars in panoramic radiographs during the mixed-dentition phase.

MATERIAL AND METHODS

Children were equally divided between the genders with a mean age of 8.9 years (SD=0.76), normal occlusion and no eruptive disturbances.

RESULTS

The angulation of the permanent maxillary first molars was close to the vertical, whereas the mandibular molars presented approximately 25 degrees of distal root angulation. The maxillary canines were the most distally angulated teeth, whereas the permanent mandibular canines were vertically positioned. The evaluation of the anterior maxillary area showed vertical position of permanent lateral, and central incisors with a slight distal angulation, whereas the permanent mandibular incisors tended to a mesial radicular convergence.

CONCLUSIONS

The proposed reference line could be useful in mixed dentition root angulation evaluation; there was a slight asymmetry in the mesiodistal angulation among homologous teeth, and also a small variation between the male and the female groups, but no difference between 8-and 10-year-old children.

Comparison of mesiodistal root angulation with posttreatment panoramic radiographs and cone-beam computed tomography

INTRODUCTION

Orthodontists assess mesiodistal root angulations before, during, and after orthodontic treatment as an aid in establishing proper root position. Panoramic imaging has been useful for this purpose and is a valuable screening tool in diagnosis and planning treatment of orthodontic patients. Cone-beam computed tomography (CBCT) for imaging of the craniofacial complex creates the opportunity to evaluate 3-dimensional images compared with traditional 2-dimensional images. The purpose of this project was to compare mesiodistal root angulations by using posttreatment panoramic radiographic images and CBCT scans.

METHODS

Mesiodistal root angulations from panoramic images and CBCT scans of 35 orthognathic surgery patients after orthodontic treatment were compared. The panoramic images were measured by using VixWin (Gendex Dental Systems, Des Plaines, Ill), and the CBCT scans by using InvivoDental 3D (version 4.1, Anatomage, San Jose, Calif). The mesiodistal root angulation of each maxillary and mandibular tooth was measured by using the occlusal plane as the reference line. With an intercept-only linear regression for correlated data (with an unstructured covariance structure), the global test of whether the mean vector of all differences for the teeth is zero was performed separately for the 2 arches.

RESULTS

The global test for both arches was statistically significant (P <0.001), indicating an overall difference in root angulation between measurements from panoramic and CBCT images. There was no discernible pattern in the average differences between panoramic and CBCT measurements.

CONCLUSIONS

The assessment of mesiodistal tooth angulation with panoramic radiography should be approached with caution and reinforced by a thorough clinical examination of the dentition.

[Measurement of mesiodistal root angulation for panoramic images and the effect of buccolingual root angulation]

Panoramic images were taken from an anatomically correct phantom with three different buccolingual angulations for each tooth (Original, 10 degrees buccal root torque, and 10 degrees lingual root torque). The true mesiodistal angulation of each tooth was determined with a three-dimensional coordinate measurement machine. Each tooth had at least one angle measurement that was statistically different from the other mesiodistal angles with different buccolingual orientations. Roots with buccal root orientations were projected more distally than they were in reality; and the roots lingually positioned were projected more mesially. The canine and premolars in both arches were most affected and the phenomenon was more pronounced in the maxilla than the mandible. Buccolingual orientation changes did not affect the root angulation expression on the incisor area.

Postorthodontic root approximation after opening space for maxillary lateral incisor implants

INTRODUCTION

Orthodontic space opening during adolescence is a common treatment for congenitally missing maxillary lateral incisors. Because of continued facial growth and compensatory tooth eruption, several years can elapse between completion of orthodontic treatment for a teenage patient and implant placement. There are reports that, after successful orthodontic opening of the implant space, the central incisor and canine roots reapproximate during retention and prevent implant placement.

METHODS

To study this phenomenon, the records of 94 patients with missing maxillary lateral incisors were collected. Periapical and panoramic radiographs were used to measure intercoronal and interradicular distances between the central incisor and the canine adjacent to the missing lateral incisor before and after orthodontic treatment and at implant placement.

RESULTS

Although root approximation between the adjacent central incisor and canine during retention did not occur consistently, 11% of the patients experienced relapse significant enough to prevent implant placement.

CONCLUSIONS

To ensure sufficient space for implant placement, we recommend at least 6.3 mm of intercoronal space and 5.7 mm of interradicular space between the adjacent central incisor and canine. A bonded wire or resin-bonded bridge will help to reduce root approximation that might occur during retention.

Mesiodistal angulations of the mandibular canines, premolars and molars with or without the presence of third molars

SUMMARY

The purpose of the present research was to compare the normal average values of mesiodistal axial angulation, with the mesiodistal axial angulation of canines, premolars and mandibular molars in individuals with and without the presence of the mandibular third molars. Panoramic radiographs of 19 male and 21 female Caucasians, with a mean age of 22.35 years, who had not undergone orthodontic treatment were studied. The subjects were divided into two groups: group I, 20 radiographs of subjects without, and group II, 20 radiographs of subjects with mandibular third molars. The mean values of the groups were compared using a Student's t-test. The results show that, in both groups, the mandibular premolars and molars had enhanced angulation in the mesial direction, when compared with a control group of 42 Caucasians ranging in age from 12 to 17 years with a 'normal' occlusion (P < 0.05), while the mesiodistal axial angulation of the mandibular canines was similar to the control group (P < 0.05). The two groups, when compared, exhibited similar angular values for the canines, premolars and mandibular molars (P < 0.05), indicating no influence of the third molars.

Panorametry: suggestion of a method for mandibular measurements on panoramic radiographs

Background

Orthopantomography (panoramic radiography) has been used for the study of measurements involving particularly the prediction of the eruption of impacted lower third molars and analyses of measurements of the ramus and head of mandible. The discrepancies involved with the projection of this radiographic image has stimulated the search for further ways to use it, particularly in orthodontic treatments and oral and maxillofacial surgeries. The author proposes a graphimetric method for the mandible, based on panoramic radiography. The results are expressed in linear and angular measurements, aiming at bilateral comparisons as well as the determination of the proportion of skeletal and dental structures, individually and among themselves as a whole. The method has been named Panorametry, and allows measurement of the mandible (Mandibular Panorametry) or the posterior mandibular teeth (Dental Panorametry). When combining mandible and maxilla, it should be referred to as Total Panorametry. It may also be used, in the future, with Cone Beam computed tomography (CT) images, and in this case it may be mentioned as CT Panorametry.

Influence of patient head positioning on measured axial tooth inclination in panoramic radiography

OBJECTIVE

Panoramic radiographs are routinely used to assess the mesiodistal axial inclination of teeth (MDAI) in orthodontic treatment. These radiographs are sensitive to minor deviations from standard head position that result in image distortions. The aim of this study is to measure and quantify the changes in MDAI on panoramic radiograph resulting from changes in patient head position.

MATERIALS AND METHODS

The testing devise was a human skull with guide wires placed on the facial surface of the teeth and alveolar process along the long axis of each tooth. Panoramic radiographs were captured digitally with the orientation of the skull in Frankfurt horizontal plane parallel to the floor and with 1 degrees , 2 degrees , 5 degrees , 7 degrees , and 10 degrees both superior and inferior rotations. The mesiodistal tooth angulations were determined using MIPAC software (DentalEye and LEAD Technologies, Inc. 2005).

RESULTS

The more distal the position of the tooth in the arch the greater the change in MDAI with a change in vertical head position. A maximum change of approximately 10 degrees was observed in MDAI of both the maxillary and mandibular molars with a corresponding superior head tilt of 10 degrees. The Mandibular anteriors displayed significant inconsistencies in MDAI with both superior and inferior head tilt. A superior head tilt produced a greater change in mesiodistal angulation than did an inferior head tilt.

CONCLUSIONS

Accurately taken panoramic radiographs can serve as a convenient tool for evaluating the MDAI before, during and after orthodontic treatment. Additional radiographs are recommended for the mandibular anteriors.

Near-end of treatment panoramic radiograph in the assessment of mesiodistal root angulation

OBJECTIVES

To test the hypothesis that there is no difference between the actual mesiodistal root angulation and the mesiodistal root angulation as measured on the panoramic radiograph.

MATERIALS AND METHODS

A typodont dentition was set up into a Class I occlusion. Wire struts were placed on the buccal surface of each tooth to represent their long axes. The dentition was fixed into a natural skull for imaging. The radiographic and true mesiodistal angulation of each tooth to a horizontal reference plane (the arch wire) was measured using a coordinate measuring machine (CMM). The mesiodistal root positions were then altered to a more mesial and then more distal position and the measurements were repeated.

RESULTS

Only 26.7% of the radiographic root angulations were within the clinically acceptable angular variation range of +/-2.5 degrees . The greatest variation in the upper arch occurred in the canine-premolar area where the roots were projected as being more divergent. The greatest variation in the lower arch occurred in the lateral incisor-canine region where these roots were projected as being more convergent. The extent of radiographic distortion is statistically greater in the lower arch than in the upper arch in the ideal (P < or = .05) and distal (P < or = .01) root positions.

CONCLUSIONS

The hypothesis is rejected. There is a clinically significant variation between the radiographic and the true root angulations recorded. Caution is advised when interpreting mesiodistal root angulation using this radiograph.

Displaced premolars in panoramic radiography: fact or fallacy?

OBJECTIVE

To test the null hypothesis that there is no difference between premolar position visualized on panoramic radiographs (PRs) and lateral headfilms (LHs).

MATERIALS AND METHODS

The prevalence of differences in the direction of crown angulation between PR and LH was assessed. Furthermore, brass wire markers with different sagittal and transverse angulations were placed in a dry skull. With the markers in place, LHs and PRs were taken.

RESULTS

A difference in the direction of crown angulation of unerupted second premolars between PR and LH occurred in 19.5% of patients. The reason for the angulation differences is a buccolingual orientation of the tooth, which appears as a mesiodistal angulation on the PR.

CONCLUSION

The null hypothesis was rejected since in one-fifth of the patients premolar projection differs between the panoramic radiograph and the lateral headfilm.

Mesiodistal Root Angulation Using Panoramic and Cone Beam CT

OBJECTIVE

To determine if the panoramic projection can accurately determine mesiodistal root angulations.

MATERIALS AND METHODS

A plaster study model of the dentition of each of five patients was prepared. A radiographic stent containing radiopaque markers was fabricated for each of the models. Panoramic and cone beam computed tomography (CBCT) scans were taken on each patient with the radiographic stent seated on the dentition. Root angulations for each of the radiographic images were measured and compared.

RESULTS

Root angulation was measured by three independent individuals and good reliability between measurements was demonstrated. Compared to plaster model measurements (the gold standard), the CBCT scan produced very accurate measurements of root angulation. Compared to CBCT images, panoramic projections did not provide reliable data on root angulation.

CONCLUSION

Panoramic images did not accurately represent the mesiodistal root angulations on clinical patients.

The accuracy of 4 panoramic units in the projection of mesiodistal tooth angulations

The purpose of this study was to compare the mesiodistal tooth angulations determined with a typodont/skull testing device with the images of mesiodistal tooth angulations from 4 contemporary panoramic units (OP 100, Cranex 3+, Orthophos, PM 2002 EC). A typodont testing device was constructed, and the true mesiodistal tooth angulations relative to an orthodontic archwire were determined with a 3-dimensional coordinate-measuring machine and custom-designed software. A human skull served as the matrix into which the typodont was fixed for imaging. The skull was repeatedly imaged and repositioned 5 times for each panoramic unit. The images were scanned and digitized with custom software to determine the image mesiodistal angulations. Results revealed that the majority of image angles from the 4 panoramic units were statistically significantly different from the true angle measurements. However, definite trends were noted among the panoramic units. For the maxillary teeth, the images projected the anterior roots more mesially and the posterior roots more distally, creating the appearance of exaggerated root divergence between the canine and the first premolar. For the mandibular teeth, the images projected almost all roots more mesially than they really were, with the canine and the first premolar the most severely affected. The largest angular difference for adjacent teeth occurred between the mandibular lateral incisor and the canine, with relative root parallelism projected as root convergence. It was concluded that the clinical assessment of mesiodistal tooth angulation with panoramic radiography should be approached with extreme caution and with an understanding of the inherent image distortions.

Bone height measurements on panoramic radiographs: the effect of shape and position of edentulous mandibles

OBJECTIVE

The aim of this study was to quantify the effect of mandibular angulation, position, and shape of an edentulous mandible on the distortion of its image in panoramic radiographs.

STUDY DESIGN

Five edentulous dry mandibles varying in size from small to wide and equipped with metal bars in and on top of the mandible were used. The mandibles were radiographed at nine different positions by tilting the mandible posteriorly around a transversal axis, using an orthopantomograph.

RESULTS

The length of the images of the bars on top of the mandible increased significantly by tilting the mandibles from +20 degrees to -20 degrees. The magnification factor of the images of the intrabony bars in the mandible was the largest at 0 degrees and decreased significantly by both decreasing or increasing the inclination. The size of the mandible was not related to the magnification factor.

CONCLUSION

For both diagnostic and evaluation purposes of the edentulous mandible, the panoramic radiograph is not a reliable radiographic technique unless meticulous precautions are taken for reproducible positioning of the patient in the apparatus.

Longitudinal radiographic assessment of dense bone islands of the jaws

OBJECTIVES

This study assessed dense bone island (DBI) inception and growth in jaws.

STUDY DESIGN

A population of 2991 patients (age range 5 to 35 years) was studied with at least two panoramic radiographs taken 1 to 10 years apart for each patient. Lesions were digitized and measured with computer measuring software. The size of the earliest DBI was compared with subsequent DBI measurements after the latter measurement was normalized with reference to the size of the nearest tooth.

RESULTS

Sixty-nine patients with DBIs were identified. A total of 3.1% of the patients with DBI were found in the 5- to 10-year age range, with the first patient in the DBI group found at 9.4 years. A significantly higher proportion (p = 0.002) of the unaffected patients (26%) was found in the same 5-to 10-year age range. The proportions of patients in the DBI and unaffected groups in older age ranges were similar. Assessment of DBI size changes showed that 43% of the 53 DBIs detected between 9.4 and 19 years enlarged (mean change, 212%), and 17% diminished (mean change, 49%). In comparison, 29.4% of 17 DBIs detected between 20 and 35 years enlarged (mean change, 153%), and 5.9% diminished (mean change, 60%).

CONCLUSION

Our results indicate that DBIs are labile lesions, develop during early adolescence, and retain a potential for enlargement, or to a lesser extent shrinkage, into adulthood.

Two-stage combined vestibuloplasty and partial mandibular ridge augmentation with hydroxyapatite

The preliminary results of a new two-stage technique for partial augmentation of the edentulous mandibular ridge with hydroxyapatite are reported. The technique, which has been applied to five patients, can be performed under local analgesia, and involves initial placement of temporary silicone spacers, together with submucous vestibuloplasty to preserve sulcus depth. The spacers are later replaced by dense particulate hydroxyapatite, and the connective tissue capsules that remain after removal of the spacers allow control of particle migration and minimize the amount of hydroxyapatite required.

Morphology of the maxillary lateral incisor in cases of unilateral impaction of the maxillary canine

Two groups of subjects who demonstrated unilateral maxillary canine impaction were examined, a Caucasian group and an Oriental group. It was found that there are significant differences between the groups for sex of patients seeking treatment, site of impaction (buccal/palatal), and arch form. The Oriental group was significantly more crowded in the canine area than the Caucasian group. In almost all cases the dimensions of the lateral incisor on the side of impaction were smaller than the non-impacted side, although five subjects from the Caucasian female sub-group did not conform to this pattern, and for the Oriental male sub-group the mesiodistal crown width was larger on the impacted side.

The criteria for lower second molar extraction

The benefits of lower second molar extraction are substantially reduced if the third molar fails to erupt into a satisfactory position. The selection criteria offered by the literature have been tested in a sample of 51 patients. Prediction is uncertain and cases should be followed until such time as a satisfactory third molar position has been achieved. Failure may be unilateral and more often on the right side. The need for follow-up treatment is subjective but may be as many as one in five patients.

Ectopic eruption of the maxillary permanent first molar: the effect of increased mesial angulation on arch length

Fifty-four cases of ectopically erupted maxillary permanent first molars were studied with a method using the measurements obtained from photographs of the study casts. The amount of relative loss of anteroposterior arch length of the right and left sides was shown to correlate with the increased mesial angulation of the maxillary permanent first molar. The bilateral ectopic group has a significantly larger mesial angulation of the permanent first molar on a maxilla with shorter anteroposterior arch length. The relative loss of arch length with ectopic eruption of the permanent first molar limits the use of unilateral appliances for treatment. The use of an appliance with bilateral arch support seems preferable.

Radiographs taken for orthodontic purposes in general practice

This paper deals with the orthodontic aspects of a wider survey undertaken to determine the use of radiographs in general dental practice in the county of Avon. During the sample week 218 patients had radiography for orthodontic purposes of whom 184 were below the age of 15 years. There were marked differences in the radiographs used by general practitioners and specialist orthodontists and the possible reasons for these differences are discussed.