Study on the necessity for cross-section imaging of the posterior mandible for treatment planning of standard cases in implant dentistry

Panoramic prediction equations to estimate implant- to-mandibular canal dimensions in the mandibular posterior region: implications for dental implant treatment

Background

To develop and cross-validate site-specific panoramic radiography (PAN) analysis prediction equations of implant-to-mandibular canal dimensions (IMCD) in mandibular regions posterior to the mental foramen, and to help determine in which instances CBCT technology will be a justified adjunct in clinical practice.

Methods

IMCD by PAN (Pan-D) from implant site-specific regions (first premolar, second premolar, first molar, and second molar sites) were collected from 40- to 70-year-old adolescents. They were randomly assigned to validation (n = 144) and cross-validation (n = 148) groups. The cone-beam computed tomography (CBCT) technique was used as the criterion method for the estimation of IMCD (CBCT-D). The PAN analysis equations were developed using stepwise multiple regression analysis and cross-validated using the Bland–Altman approach.

Results

There was a significant relationship between PAN-D and CBCT-D for both validation (R² = 57.8 %; p < .001) and cross-validation groups (R² = 52.5 %; p < .001). Root means-squared error (RMSE) and pure error (PE) were highest for the first molar (RMSE = 1.116 mm, PE = 1.01 mm) and the second molar region (RMSE = 1.162 mm, PE = 1.11 mm).

Conclusions

PAN-D has the potential to be developed as an indirect measure of IMCD. However, the findings suggest to exclude scoring of the first and second molars when assessing IMCD via PAN. Use of CBCT may be justified for all IMCD estimations in the first and second molars regions.

Trial registration

This study has been registered and approved by the Ethics Committee of the Martin-Luther University, Halle, Germany (2020-034).

Successful dental implantation: evaluating the accuracy of horizontal and vertical measurements on panoramic radiographs using dental implants as reference objects

BACKGROUND

The purpose of this study was to calculate the regional distortions in digital panoramic radiographs and to evaluate the accuracy of panoramic radiography in dental implant treatments. Also, it was aimed to determine the vertical and horizontal distortion rate of digital panoramic device by using dental implants as reference objects.

METHODS

A retrospective study was designed and implemented, based on the analysis of panoramic radiography records. Postoperative images of implant treatments which did not required bone augmentation procedures included in the study. Measurements were made on images of 554 implants placed, adjacent to at least one tooth in different regions of the jaws. The distortion rate was calculated by determining the ratio of the radiographic dimensions of the implants to the actual implant sizes.

RESULTS

The distortion rate of the digital panoramic device was determined as 1.11 vertically and 1.81 horizontally. Vertically, radiographic measurements were calculated lower than the actual implant lengths as 0.95 mm in the anterior, 0.70 mm in the premolar and 0.60 mm in the molar regions. Horizontally, radiographic measurements were calculated lower than the actual implant width as 0.50 mm in anterior and molar regions and 0.60 mm in premolar region, respectively. These differences were statistically significant (p < 0.001).

CONCLUSIONS

Considering the results of the device and regional distortion rates, it has been shown that digital panoramic radiography is an effective method to evaluate the existing bone height, especially in the posterior regions of the jaws, when a safe distance to the anatomical structures is maintained.

CT-based dentulous mandibular alveolar ridge measurements as predictors of crown-to-implant ratio for short and extra short dental implants

The purpose was to predict the crown-to-implant ratio variation in the edentulous posterior mandibles rehabilitated with short dental implants. Hence, vertical and horizontal dimensions of dentulous posterior mandibles in a sample of 18- to 25-year-olds were measured, and correlations of these dimensions with sex and site were investigated. Mandibular computed tomography scans from 100 subjects were considered. Vertical and horizontal bone and tooth measurements were taken at the sites of the second premolar (PM), and the mesial and distal roots of the first and second molars (M1m, M1d, M2m and M2d, respectively). A hypothetical crown-to-implant ratio (C/I R) was calculated assuming the insertion of short and extra short implants (5, 6 or 7 mm), at 1.5 mm from the inferior alveolar canal, maintaining the position of the existing occlusal plane. All vertical bone dimensions decreased from the PM to the M2d. Width measurements increased from the mesial (PM) to the distal sites (M1m, M1d, M2m and M2d). Males had significantly greater vertical and horizontal measurements than females at all sites. The mean C/I R was higher than 2 for all sizes of implant. The C/I R was lower for the second molar than for the second premolar, while it was similar for the first molar and the second premolar. Males had a higher C/I R than females. Computed tomography can be used to study the anatomical features of alveolar bone, and to predict some clinical aspects of prosthetic rehabilitation with implants, such as the crown-to-implant ratio in conditions of serious bone atrophy.

The reliability of surgeons to avoid traumatic insertion of dental implants into high-risk regions: a panoramic radiograph study

BACKGROUND

The posterior regions of the jaws usually represent a significant risk for implant surgery. A non-valid assessment of the available bone height may lead to either perforation of the maxillary sinus floor or encroachment of the inferior alveolar nerve and consequently to implant failure. This study aimed to evaluate the reliability of surgeon's decision in appraising the appropriate implant length, in respect to vital anatomical structures, using panoramic radiographs.

METHODS

Only implants that are inserted in relation to the maxillary sinus (MS) or the mandibular canal (MC) were enrolled (first premolars [1P], second premolars [2P], first molars [1M], and second molars [2M]). All preoperative panoramic radiographs were evaluated under standard conditions. The postoperative estimation (under/over) was determined depending on the available bone height (ABH) measured from the apical end of the implant to the floor of the MS and the roof of the MC using cone beam computed tomography (CBCT). Any complication or side effect that associated with overestimated implants insertion was recorded.

RESULTS

The study sample included 73 patients (predominantly females) who had consecutively received 148 implants, of which 68 were inserted in the posterior maxilla and 80 in the posterior mandible. Underestimation was recorded in 93.2% of the measurements. The remaining bone height after implants insertion was < 2 mm in the majority of underestimated cases (73.9%); they were significantly (P < 0.01) more than sites with remaining bone ≥ 2 mm (26.1%). In the posterior mandible, overestimation was significantly higher than posterior maxilla. Five cases with transient paresthesia were reported in the mandibular overestimated implants.

CONCLUSIONS

This study specified that surgeon's choice of implants length, based on panoramic radiographs, was reliable regarding the incapability to insert implants with further length in the majority of underestimated cases, the low percent of overestimated measurements, and the minor associated complications.

Effect of slice inclination and object position within the field of view on the measurement accuracy of potential implant sites on cone-beam computed tomography

Purpose

The purpose of this study was to evaluate the accuracy of linear measurements in the horizontal and vertical dimensions based on object position and slice inclination in cone-beam computed tomography (CBCT) images.

Materials and Methods

Ten dry sheep hemi-mandibles, each with 4 sites (incisor, canine, premolar, and molar), were evaluated when either centrally or peripherally positioned within the field of view (FOV) with the image slices subjected to either oblique or orthogonal inclinations. Four types of images were created of each region: central/cross-sectional, central/coronal, peripheral/cross-sectional, and peripheral/coronal. The horizontal and vertical dimensions were measured for each region of each image type. Direct measurements of each region were obtained using a digital caliper in both horizontal and vertical dimensions. CBCT and direct measurements were compared using the Bland-Altman plot method. P values <0.05 were considered to indicate statistical significance.

Results

The buccolingual dimension of the incisor and premolar areas and the height of the incisor, canine, and molar areas showed statistically significant differences on the peripheral/coronal images compared to the direct measurements (P<0.05). Molar area height in the central/coronal slices also differed significantly from the direct measurements (P<0.05). Cross-sectional images of either the central or peripheral position had no marked difference from the gold-standard values, indicating sufficient accuracy.

Conclusion

Peripheral object positioning within the FOV in combination with applying an orthogonal inclination to the slices resulted in significant inaccuracies in the horizontal and vertical measurements. The most undesirable effect was observed in the molar area and the vertical dimension.

Use of cone beam computed tomography in implant dentistry: current concepts, indications and limitations for clinical practice and research

Diagnostic radiology is an essential component of treatment planning in the field of implant dentistry. This narrative review will present current concepts for the use of cone beam computed tomography imaging, before and after implant placement, in daily clinical practice and research. Guidelines for the selection of three-dimensional imaging will be discussed, and limitations will be highlighted. Current concepts of radiation dose optimization, including novel imaging modalities using low-dose protocols, will be presented. For preoperative cross-sectional imaging, data are still not available which demonstrate that cone beam computed tomography results in fewer intraoperative complications such as nerve damage or bleeding incidents, or that implants inserted using preoperative cone beam computed tomography data sets for planning purposes will exhibit higher survival or success rates. The use of cone beam computed tomography following the insertion of dental implants should be restricted to specific postoperative complications, such as damage of neurovascular structures or postoperative infections in relation to the maxillary sinus. Regarding peri-implantitis, the diagnosis and severity of the disease should be evaluated primarily based on clinical parameters and on radiological findings based on periapical radiographs (two dimensional). The use of cone beam computed tomography scans in clinical research might not yield any evident beneficial effect for the patient included. As many of the cone beam computed tomography scans performed for research have no direct therapeutic consequence, dose optimization measures should be implemented by using appropriate exposure parameters and by reducing the field of view to the actual region of interest.

Submandibular fossa augmentation in implant dentistry

Background

There are two limiting factors for determining the dental implant fixture length in mandibular posterior edentulous region: Inferior dental canal and submandibular fossa.

Purpose

Submandibular fossa augmentation is a suggested way to overcome the problem of lingual undercut beneath the mylohyoid ridge in implant dentistry.

Materials and Methods

Patients with lingual posterior bony undercut that interferes with the placement of a standard implant with a length of 10 mm were enrolled in this study.

Results

This method was used for eight patients in 10 sites. Increased implant length and decreasing the chance of sublingual hematoma due to lingual cortical plate perforation are the results of this study.

Conclusions

Submandibular fossa augmentation is a new technique to improve the maneuver of oral surgeons to increase dental implant length in the presence of deep lingual bony undercut.

The magnification in the lower third and second molar region in the digital panoramic radiographs

Background:

The aim of this study was to determine the accuracy of linear measurements of the lower third and second molar crowns in the digital panoramic radiographs and to compare them with plaster models as the calibration standard.

Materials and Methods:

The digital panoramic radiographs and plaster models of the orthodontic patients were used in the study. Standardized metal calibration gauges (MCGs) were bonded to the buccal surface of the lower molars bilaterally. Measurements in the panoramic radiographs were done using Dolphin Imaging 11.8 Premium program.

Results:

Forty-one panoramic radiographs and diagnostic plaster models of the orthodontic patients (mean age 18.45 ± 2.35) were analyzed. Eighty-two lower third molars, 82 second molars, and 82 first molars were evaluated. The magnification coefficients (MCC) calculated according to the plaster models ranged from 1.07 to 1.08. The magnification coefficients calculated according to the bonded MCG were about 1.04. The differences between the teeth groups and right-left sides were not statistically significant (P > 0.05). Spearman correlation showed a positive medium correlation between the magnification using the calibration with plaster models and metal gauges (P < 0.05).

Conclusions:

The magnification in the lower first, second, and third molars regions showed almost the same values. The calculation of magnification coefficient using bonded metal calipers was more accurate than calculation according to the plaster models, but the differences were not statistically significant. The use of the plaster models for calibration of the magnification coefficient in the good-positioned lower molars' region might be used as an alternative to the bonded MCGs.

Comparison of Ozone and Photo-Biomodulation Therapies on Mental Nerve Injury in Rats

PURPOSE

This study compared photo-biomodulation (PBM) and ozone therapy (OT) for mental nerve injury by counting Schwann cells (SCs) and fasciculated nerve branches and measuring fascicular nerve areas.

MATERIALS AND METHODS

The effects of OT and PBM on mental nerve injury were evaluated. Mental nerves of 27 rats were partly sutured and allocated into 3 groups. Group 1 received no treatment, group 2 received OT, and group 3 received PBM. The number of fascicules beyond nerve branches and the number of SCs before and after nerve injury were evaluated histologically.

RESULTS

A better healing pattern was observed in the treatment groups. The number of SCs was markedly larger in the OT and PBM groups than in the control group.

CONCLUSIONS

Oral and maxillofacial surgeons should be familiar with the differential diagnosis, prevention, and management of neurosensory disturbances. This study provides insights into the management of neurosensory disturbances related to mental nerve injury using OT and PBM. This study clearly suggests that OT and PBM are promising novel methods for the treatment of mental nerve injury.

Localization of mandibular canal and assessment of the remaining alveolar bone in posterior segment of the mandible with single missing tooth using cone-beam computed tomography: a cross sectional comparative study

Objectives

Localization of the mandibular canal (MC) and measurement of the height and width of the available alveolar bone at the proposed implant site in the posterior segment of the mandible using cone-beam computed tomography (CBCT) in patients with a single missing tooth.

Materials and Methods

A cross-sectional study was performed where CBCT scans of the patients with a single missing tooth in the posterior segment of the mandible—premolar, I (1st) molar, and II (2nd) molar were used. The scans were assessed using OnDemand3D software (version 1.0; CyberMed Inc., Seoul, Korea) for localization of the MC asnd remaining alveolar bone both vertically (from the superior position of the MC to the crest of the alveolar ridge) and horizontally (buccolingual, 3 mm below the crest of the alveolar ridge). The findings were statistically analyzed using independent t-test.

Results

A total of 120 mandibular sites (40 sites for each of the three missing premolar, I molar, and II molar) from 91 CBCT scans were analyzed. The average heights (from the alveolar crest to the superior margin of the MC) at the premolar, I molar, and II molar areas were 15.19±2.12 mm, 14.53±2.34 mm, and 14.21±2.23 mm, respectively. The average widths, measured 3 mm below the crest of the alveolar ridge, at the premolar, I molar, and II molar areas were 6.22±1.96 mm, 6.51±1.75 mm, and 7.60±2.08 mm, respectively. There was no statistically significant difference between males and females regarding the vertical and horizontal measurements of the alveolar ridges.

Conclusion

In the study, the measurements were averaged separately for each of the single missing teeth (premolar, I molar, or II molar), giving more accurate information for dental implant placement.

Reliability of panoramic radiography in determination of neurosensory disturbances related to dental implant placement in posterior mandible

INTRODUCTION

During implantology procedures, one of the most serious complications is the damage of the inferior alveolar nerve, which may result in neurosensory disturbances (NSD). Panoramic radiographs have been considered for a primary evaluation to determine the bone height and implant-mandibular canal distance.

MATERIALS AND METHODS

One thousand five hundred ninety-seven panoramic radiographs of patients, who were treated with 3608 dental implants in Erciyes University, Oral and Maxillofacial Hospital between 2007 and 2012, were examined. Forty-eight implants were determined to be near the mandibular canal using a 2-dimensional software program.

RESULTS

A total of 48 implants were closer than 2 mm to the mandibular canal. A range of 0 to 1.9 mm distance was detected between the mandibular canal and these implants. Fourteen implants (29.16%) placed in a distance less than 1 mm to the mandibular canal, and 34 (70.83%) between 1 and 2 mm. One patient had NSD.

CONCLUSION

Determination of the dental implant length using panoramic radiography is a reliable technique to prevent neurosensory complications. However computed tomography or cone-beam computed tomography based planning of dental implants may be required for borderline cases.

Systematic Review and Meta-Analysis on Incidence of Altered Sensation of Mandibular Implant Surgery

Altered sensation (including paresthesia, dysesthesia and hypoesthesia) after mandibular implant surgery may indicate transient or permanent injury of the inferior alveolar nerve and the mental branch, and considerably lower patients’ satisfaction about the therapy. Previous studies have shown a great degree of variability on the incidence of altered sensation. We here reported the incidence of altered sensation after mandibular implant surgery based on a meta-analysis of 26 articles published between 1990.1.1 and 2016.1.1. Study quality and risk of bias was assessed and the studies with a lower score were excluded in the meta-analysis. Data synthesis was performed using the logistic-normal random-effect model. The meta-analyses revealed that the short-term (10 days after implant placement) and long-term (1 year after implant placement) incidence was 13% (95% CI, 6%-25%) and 3% (95% CI, 1%-7%), respectively. (2) For the patients who initially reported altered sensation, 80% (95% CI, 52%-94%) of them would return to normal sensation within 6 months after surgery, and 91% (95% CI, 78%-96%) of them would return to normal sensation one year after surgery. We concluded that dentist-patient communication about the risk of altered sensation is critical to treatment planning, since the short-term incidence of altered sensation is substantial (13%). When a patient reports altered sensation, regular assessment for 6 months would help tracing the changes of symptoms. In terms of long-term follow-up (1 year after surgery), the incidence is much lower (3%) and most patients (91%) would return to normal sensation.

Assessment of the Anterior Loop of the Mental Nerve Using Cone Beam Computerized Tomography Scan

The purpose of this study is to use cone-beam computerized tomography (CBCT) scans with oblique-transverse reconstruction modality to measure and compare the anterior loop length (AnLL) of the mental nerve between gender and age groups and to compare the difference between the right and left sides. Sixty-one female and 61 male CBCT scans were randomly selected for each age group: 21–40, 41–60, and 61–80 years. Both right- and left-side AnLLs were measured in each subject using i-CATVision software to measure AnLLs on the oblique transverse plane using multiplanar reconstruction. The anterior loop was identified in 85.2% of cases, with the mean AnLL of the 366 subjects (732 hemimandibles) being 1.46 ± 1.25 mm with no statistically significant difference between right and left sides or between different gender groups. However, the mean AnLL in the 21–40 year group (1.89 ± 1.35 mm) was larger than the AnLL in the 41–60 year group (1.35 ± 1.19 mm) and the 61–80 year group (1.13 ± 1.08 mm). In conclusion, when placing implants in close proximity to mental foramina, caution is recommended to avoid injury to the inferior alveolar nerve. No fixed distance anteriorly from the mental foramen should be considered safe. Using CBCT scans with the oblique-transverse method to accurately identify and measure the AnLL is of utmost importance in avoiding and protecting its integrity.

Impact of Digital Panoramic Radiograph Magnification on Vertical Measurement Accuracy

Objectives. The purpose of this panoramic radiography study was to assess the impact of image magnification on the accuracy of vertical measurements in the posterior mandible. Methods. Six dental implants, inserted in the posterior segments of a resin model, were used as reference objects. Two observers performed implant length measurements using a proprietary viewer with two preset image magnifications: the low (1.9 : 1) and the medium (3.4 : 1) image magnifications. They also measured the implant lengths in two Digital Imaging Communications in Medicine viewers set at low (1.9 : 1), medium (3.4 : 1), and high (10 : 1) image magnifications. Results. The error between the measured length and the real implant length was close to zero for all three viewers and image magnifications. The percentage of measurements equal to the real implant length was the highest (83.3%) for the high image magnification and below 30% for all viewers with the low image magnification. Conclusions. The high and medium image magnifications used in this study allowed accurate vertical measurements, with all three imaging programs, in the posterior segments of a mandibular model. This study suggests that a low image magnification should not be used for vertical measurements on digital panoramic radiographs when planning an implant in the posterior mandible.

Comparing Two Diagnostic Procedures in Planning Dental Implants to Support a Mandibular Free-Ending Removable Partial Denture

BACKGROUND

The use of a cone beam computed tomography (CBCT) for the preoperative implant planning is increasing. A clear guideline is needed in which cases of CBCT is essential.

PURPOSE

In this study, two imaging modalities (panoramic radiograph and CBCT) are compared in preoperative implant planning in the severely resorbed mandible and the influence on the observers assessments.

MATERIALS AND METHODS

Thirty-four consecutive patients with bilateral edentulous regions in the mandible were included. The feasibility of implant placement in the premolar and molar region was judged by three observers on basis of casts either with a panoramic radiograph or a CBCT.Cohen's kappa, sensitivity and specificity rates, odds of agreement and disagreement as well as the odds ratios (ORs, ratio between odds of agreement and disagreement) were calculated per observer and overall for all observers assuming the majorities agreement as the prevailing opinion.

RESULTS

Overall outcome for premolar region revealed true-positive and true-negative rates of 90% and 0%, respectively, with Cohen's kappa (κ) = -0.04. The ORs for the three observers varied between 2.6 and 158.8, with an overall OR = 76.For the molar region, overall true-positive and true-negative rates were 65% and 22% respectively, with Cohen's κ = 0.68, representing a reasonable amount of agreement. Sensitivity and specificity as well as the ORs for individual observers were fairly consistent with an overall OR = 43.

CONCLUSION

Implant placement in the resorbed posterior mandible can be well assessed with a cast in combination with a panoramic radiograph in the vast majority of the cases. Misclassification amounts to approximately 10% to 13%. In all cases of misclassification, a critical bone height, or an unclear course of the mandibular nerve or a knife edge ridge was present. In these cases, the use of a CBCT is justified.

Interactive 3D imaging technologies: application in advanced methods of jaw bone reconstruction using stem cells/pre-osteoblasts in oral surgery

Cone beam computed tomography has created a specific revolution in maxillofacial imaging, facilitating the transition of diagnosis from 2D to 3D, and expanded the role of imaging from diagnosis to the possibility of actual planning. There are many varieties of cone beam computed tomography-related software available, from basic DICOM viewers to very advanced planning modules, such as InVivo Anatomage, and SimPlant (Materialise Dental). Through the use of these programs scans can be processed into a three-dimensional high-quality simulation which enables planning of the overall treatment. In this article methods of visualization are demonstrated and compared, in the example of 2 cases of reconstruction of advanced jaw bone defects using tissue engineering. Advanced imaging methods allow one to plan a miniinvasive treatment, including assessment of the bone defect's shape and localization, planning a surgical approach and individual graft preparation.

Impact of cone-beam computed tomography on implant planning and on prediction of implant size

The aim was to investigate the impact of cone-beam computed tomography (CBCT) on implant planning and on prediction of final implant size. Consecutive patients referred for implant treatment were submitted to clinical examination, panoramic (PAN) radiography and a CBCT exam. Initial planning of implant length and width was assessed based on clinical and PAN exams, and final planning, on CBCT exam to complement diagnosis. The actual dimensions of the implants placed during surgery were compared with those obtained during initial and final planning, using the McNemmar test (p < 0.05). The final sample comprised 95 implants in 27 patients, distributed over the maxilla and mandible. Agreement in implant length was 50.5% between initial and final planning, and correct prediction of the actual implant length was 40.0% and 69.5%, using PAN and CBCT exams, respectively. Agreement in implant width assessment ranged from 69.5% to 73.7%. A paired comparison of the frequency of changes between initial or final planning and implant placement (McNemmar test) showed greater frequency of changes in initial planning for implant length (p < 0.001), but not for implant width (p = 0.850). The frequency of changes was not influenced by implant location at any stage of implant planning (chi-square test, p > 0.05). It was concluded that CBCT improves the ability of predicting the actual implant length and reduces inaccuracy in surgical dental implant planning.

Does cone-beam CT alter treatment plans? Comparison of preoperative implant planning using panoramic versus cone-beam CT images

PURPOSE

The present study was performed to compare the planning of implant placement based on panoramic radiography (PAN) and cone-beam computed tomography (CBCT) images, and to study the impact of the image dataset on the treatment planning.

MATERIALS AND METHODS

One hundred five partially edentulous patients (77 males, 28 females, mean age: 46 years, range: 26-67 years) seeking oral implant rehabilitation were referred for presurgical imaging. Imaging consisted of PAN and CBCT imaging. Four observers planned implant treatment based on the two-dimensional (2D) image datasets and at least one month later on the three-dimensional (3D) image dataset. Apart from presurgical diagnostic and dimensional measurement tasks, the observers needed to indicate the surgical confidence levels and assess the image quality in relation to the presurgical needs.

RESULTS

All observers confirmed that both imaging modalities (PAN and CBCT) gave similar values when planning implant diameter. Also, the results showed no differences between both imaging modalities for the length of implants with an anterior location. However, significant differences were found in the length of implants with a posterior location. For implant dimensions, longer lengths of the implants were planned with PAN, as confirmed by two observers. CBCT provided images with improved scores for subjective image quality and surgical confidence levels.

CONCLUSION

Within the limitations of this study, there was a trend toward PAN-based preoperative planning of implant placement leading towards the use of longer implants within the posterior jaw bone.

Risk assessment of inferior alveolar nerve injury for immediate implant placement in the posterior mandible: a virtual implant placement study

OBJECTIVES

To investigate the prevalence and morphological parameters of lingual concavity, and whether these factors are related to a higher risk of inferior alveolar nerve (IAN) injury when performing an immediate implant surgery in posterior mandible region.

METHODS

The CBCT images from 237 subjects (1008 teeth) were analysed the shape of the mandibles (C, P, U type), dimensional parameters of lingual concavity (angle, height, depth), and its relation to inferior alveolar canal (IAC) (A, B, C zone), RAC (distance from root apex to IAC) and probability of IAN injury. Multiple logistic regression modelling to determine the odds ratio of variables that made an important contribution to the probability of IAN injury and to adjust for confounding variables.

RESULTS

The U type ridge (46.7%) and the most concave point located at C zone (48.8%) are most prevalent in this region. The mandibular second molar presents highest risk for IAN injury than other tooth type (p<0.001), which were 3.82 times to occur IAN injury than the mandibular second premolar. The concave point located at A zone and B zone were 7.82 and 3.52 times than C zone to have IAN damage, respectively. The probability of IAN injury will reduce 26% for every 1mm increase in RAC (p<0.001).

CONCLUSIONS

The tooth type, morphological features of lingual concavities, and RAC are associated with risks of IAN injury during immediate implant placement.

CLINICAL SIGNIFICANCE

Pre-surgical mapping of the IAC and identification of its proximity relative to the lingual concavity in the posterior mandible regions may avoid unpleasant complications, specifically when performing immediate implant procedures.

Accuracy of computerized vertical measurements on digital orthopantomographs: posterior mandibular region

OBJECTIVES

Orthopantomographs are commonly used for diagnosis in clinical dentistry. Although the manufacturers claim a constant magnification effect, the reliability of measuring dimensions on the panoramic radiographs is not clear. The aim of this study was to evaluate the accuracy of measuring vertical dimensions in the posterior mandibular area on digital orthopantomographs.

MATERIALS AND METHODS

A retrospective survey of 20 orthopantomographs with unrestored implants (only with cover screw) in the mandibular posterior region (molars and premolars) was conducted. All radiographs were taken using the same machine by skilled technicians. Two examiners were asked to measure the vertical dimension of the implants seen on the radiographs viewed using two differently sized display screens. Inter-examiner and intra-examiner reliability tests were performed. Differences between the measured length and the actual length using each screen type were compared.

RESULTS

High coefficients of reliability were observed on intra- and inter-examiner correlation. The overall reliability of measuring the vertical dimensions of implants between both examiners for the large screen and the small screen were 97.4% (Cronbach's alpha 0.993) and 94.0% (Cronbach's alpha 0.984), respectively. There were no significant differences between the errors seen with either the large screen or the small screen, when each of them was compared to the original length (P = 0.146).

CONCLUSION

This study shows that vertical dimensions in the posterior mandibular region (molar and premolars) can be reliably measured on an orthopantomograph using a calibrated machine and special software.

Conventional radiography and cross-sectional imaging when planning dental implants in the anterior edentulous mandible to support an overdenture: a systematic review

The objectives for this systematic review were to determine if the pre-operative availability of cross-sectional imaging, such as cone beam CT, has a diagnostic impact, therapeutic impact or impact on patients' outcome when placing two dental implants in the anterior mandible to support an overdenture. The Cochrane Oral Health Group's Trials Register (CENTRAL), MEDLINE® and Embase were searched up to, and including, February 2013. Studies were considered eligible for inclusion if they compared the impact of conventional and cross-sectional imaging when placing dental implants in sites including the anterior mandible. An adapted quality assessment tool was used for the assessment of the risk of bias in included studies. Pooled quantitative analysis was not possible and, therefore, synthesis was qualitative. Of 2374 potentially eligible papers, 5 studies were included. Little can be determined from a synthesis of these studies because of their small number, clinical diversity and high risks of bias. Notwithstanding, it may be tentatively inferred that cross-sectional imaging has a therapeutic impact in the more challenging cases. In terms of impact, this review has found no evidence to support any specific imaging modality when planning dental implant placement in any region of the mouth. Therefore, those who argue that cross-sectional imaging should be used for the assessment of all dental implant sites are unsupported by evidence.

Clinical outcome of conservative treatment of injured inferior alveolar nerve during dental implant placement

OBJECTIVES

Infererior alveolar nerve (IAN) damage may be one of the distressing complications occurring during implant placement. Because of nature of closed injury, a large proportion is approached non-invasively. The purpose of this study was to analyze the outcomes of conservative management of the injured nerve during dental implant procedure.

MATERIALS AND METHODS

Sixty-four patients of implant related IAN injury, who were managed by medication or observation from January 1997 to March 2007 at the Department of Oral and Maxillofacial Surgery, Seoul National University Dental Hospital, were retrospectively investigated. The objective tests and subjective evaluations were performed to evaluate the degree of damage and duration of sensory disturbance recovery. Tests were performed on the day of the first visit and every two months afterward. Patient's initial symptoms, proximity of the implant to the IAN, time interval between implant surgery and the first visit to our clinic, and treatment after implant surgery were analyzed to determine whether these factors affected the final outcomes.

RESULTS

Among the 64 patients, 23 had a chief complaint of sensory disturbance and others with dysesthesia. The mean time until first visit to our hospital after the injury was 10.9 months.One year after nerve injury, the sensation was improved in 9 patients, whereas not improved in 38 patients, even 4 patients experienced deterioration. Better prognosis was observed in the group of patients with early visits and with implants placed or managed not too close to the IAN.

CONCLUSION

Nearly 70% of patients with IAN injury during implant placement showed no improvement in sensation or dysesthesia with the conservative management. Earlier decision for active treatment needs to be considered because of possibility of deterioration of symptoms and unsatisfactory recovery.

Accuracy of vertical height measurements on direct digital panoramic radiographs using posterior mandibular implants and metal balls as reference objects

OBJECTIVES

Conventional panoramic radiography, a widely used radiographic examination tool in implant treatment planning, allows evaluation of the available bone height before inserting posterior mandibular implants. Image distortion and vertical magnification due to projection geometry is well described for rotational panoramic radiographs. To assess the accuracy of vertical height measurements on direct digital panoramic radiographs, implants and metal balls positioned in the posterior mandible were used as radio-opaque reference objects. The reproducibility of the measuring method was assessed by the inter- and intraobserver agreements.

METHODS

Direct digital panoramic radiographs, performed using a Kodak 8000C (Eastman Kodak Company, Rochester, NY), of 17 partially edentulous patients (10 females, 7 males, mean age 65 years) were selected from an X-ray database gathered during routine clinical evaluation of implant sites. Proprietary software and a mouse-driven calliper were used to measure the radiological length of 25 implants and 18 metal reference balls, positioned in mandibular posterior segments. The distortion ratio (DR) was calculated by dividing the radiological implant length by the implant's real length and the radiological ball height by the ball's real height.

RESULTS

Mean vertical DR was 0.99 for implants and 0.97 for balls, and was unrelated to mandibular sites, side, age, gender or observer. Inter- and intraobserver agreements were acceptable for both reference objects.

CONCLUSIONS

Vertical measurements had acceptable accuracy and reproducibility when a software-based calibrated measurement tool was used, confirming that digital panoramic radiography can be reliably utilized to determine the pre-operative implant length in premolar and molar mandibular segments.

Pain sensation and postsurgical complications in posterior mandibular implant placement using ridge mapping, panoramic radiography, and infiltration anesthesia

Objectives. The aim of this study was to investigate intrasurgical and after surgical, pain and the incidence of after surgical alteration of sensation in the mandible and lower lip when placing implants in the posterior mandible using ridge mapping, panoramic radiography, and infiltration anesthesia. Methods. This was a longitudinal clinical study of healthy patients needing implant placement in the posterior mandible. After thorough examination and treatment plan using ridge mapping and panoramic radiography, all patients received dental implants under local infiltration anesthesia. The patients were then given a questionnaire to assess the pain during anesthesia and implant surgery. Change of sensation in the lower lip was evaluated by standard neurosensory examination tests at 7 days and 1 and 4 months. Prosthetic treatment was carried out 4 months postsurgery and the patients were followed for an average of 28.5 months afterwards. Results. A total of 103 implants were placed in 62 patients. Patients reported very minor pain during injection. No pain was reported during either implant placement or bone grafting procedures. No alteration of sensation in the mandible or lower lip was recorded postsurgery. Conclusion. In most cases, ridge mapping, panoramic radiography, and infiltration anesthesia are sufficient for posterior mandibular implant placement without pain or complications.

Position statement of the American Academy of Oral and Maxillofacial Radiology on selection criteria for the use of radiology in dental implantology with emphasis on cone beam computed tomography

A Position Paper Subcommittee of the American Academy of Oral and Maxillofacial Radiology (AAOMR) reviewed the literature since the original position statement on selection criteria for radiology in dental implantology, published in 2000. All current planar modalities, including intraoral, panoramic, and cephalometric, as well as cone beam computed tomography (CBCT) are discussed, along with radiation dosimetry and anatomy considerations. We provide research-based, consensus-derived clinical guidance for practitioners on the appropriate use of specific imaging modalities in dental implant treatment planning. Specifically, the AAOMR recommends that cross-sectional imaging be used for the assessment of all dental implant sites and that CBCT is the imaging method of choice for gaining this information. This document will be periodically revised to reflect new evidence.

Planning of dental implant size with digital panoramic radiographs, CBCT-generated panoramic images, and CBCT cross-sectional images

OBJECTIVES

To compare the implant size (width and length) planned with digital panoramic radiographs, cone beam computed tomography (CBCT)-generated panoramic views, or CBCT cross-sectional images, in four implant systems.

MATERIAL AND METHODS

Seventy-one patients with a total of 103 implant sites in the upper premolar and/or lower molar regions were examined with digital panoramic radiography (D-PAN) and (CBCT). A metal ball 5 mm in diameter was placed in the edentulous area for the D-PAN. CBCT data sets were reformatted to a 10-mm thick CBCT panoramic view (CBCT-pan) and 1-mm cross-sections (CBCT-cross). Measurements were performed in the images using dedicated software. All images were displayed on a monitor and assessed by three observers who outlined a dental implant by placing four reference points in the site of the implant-to-be. Differences in width and length of the implant-to-be from the three modalities were analyzed. The implant size selected in the CBCT-cross images was then compared to that selected in the other two modalities (D-PAN and CBCT-pan) for each of the implant systems separately.

RESULTS

The implant-to-be (average measurements among observers) was narrower when measured in CBCT-cross compared with both D-PAN and CBCT-Pan. For premolar sites, the width also differed significantly between D-PAN and CBCT-pan modalities. The implant-to-be was also significantly shorter when recorded in CBCT-cross than in D-PAN. In premolar sites, there were no significant differences in implant length among the three image modalities. It mattered very little for the change in implant step sizes whether CBCT-cross was compared to D-PAN or CBCT-pan images.

CONCLUSION

Our results show that the selected implant size differs when planned on panoramic or cross-section CBCT images. In most cases, implant size measured in cross-section images was narrower and shorter than implant size measured in a panoramic image or CBCT-based panoramic view.

Tilted implants for the restoration of posterior mandibles with horizontal atrophy: an alternative treatment

PURPOSE

Horizontal atrophy in the posterior mandible presents serious limitations on conventional implant placement. The purpose of this study was to evaluate the use of tilted implants angled in a buccolingual direction for restoring atrophic posterior mandibular sectors.

MATERIALS AND METHODS

A cohort study was performed of 25 patients who had partial prostheses supported by more than 1 implant (≥ 1 tilted and 1 axial implant) to restore molar areas in the mandible. When the bone thickness was at least 5 mm, axial implants were placed; when the alveolar ridge was narrower, the implant was placed with tilted angulation. The beds for these tilted implants were prepared using a lingual approach, tipping the implant apex toward the vestibule. Twelve months after loading, bone loss was evaluated and the success rates of the tilted and axial implants were calculated.

RESULTS

The study included 20 women and 5 men (mean age, 54.8 yr) who received 67 implants in the posterior mandibular sectors. Thirty-nine implants were placed with a buccal angulation and 28 implants were placed vertically. Mean bone losses of 0.59 ± 0.26 mm among the tilted implants and 0.48 ± 0.34 mm among the axial implants were observed 1 year after loading. The success rate of the tilted implants was 94.9%, and that of the axial implants was 100%. No significant differences in success rates or in bone loss between the tilted and axial implants were found at 12 months after loading.

CONCLUSIONS

Twelve months after loading, tilted implants provided good results for the restoration of posterior mandibles with horizontal atrophy and no significant differences in success rates or marginal bone loss between tilted and axial implants were observed.

Reliability of two different presurgical preparation methods for implant dentistry based on panoramic radiography and cone-beam computed tomography in cadavers

PURPOSE

Special care is necessary to avoid invading important anatomic structures during surgery when presurgical planning is made based on radiographs. However, none of these types of radiography represents a perfect modality. The purpose of this study was to determine the reliability of presurgical planning based on the use of two types of radiographic image (digital panoramic radiography [DPR] and cone-beam computed tomography [CBCT]) by beginner dentists to place implants, and to quantify differences in measurements between radiographic images and real specimens.

METHODS

Ten fresh cadavers without posterior teeth were used, and twelve practitioners who had no experience of implant surgery performed implant surgery after 10 hours of basic instruction using conventional surgical guide based on CBCT or DPR. Two types of measurement error were evaluated: 1) the presurgical measurement error, defined as that between the presurgical and postsurgical measurements in each modality of radiographic analysis, and 2) the measurement error between postsurgical radiography and the real specimen.

RESULTS

The mean presurgical measurement error was significantly smaller for CBCT than for DPR in the maxillary region, whereas it did not differ significantly between the two imaging modalities in the mandibular region. The mean measurement error between radiography and real specimens was significantly smaller for CBCT than for DPR in the maxillary region, but did not differ significantly in the mandibular region.

CONCLUSIONS

Presurgical planning can be performed safely using DPR in the mandible; however, presurgical planning using CBCT is recommended in the maxilla when a structure in a buccolingual location needs to be evaluated because this imaging modality supplies buccolingual information that cannot be obtained from DPR.

Immediate provisional restoration of single-piece zirconia implants: a prospective case series - results after 24 months of clinical function

OBJECTIVE

Aim of this prospective case series was to evaluate the outcome of immediately provisionalized single-piece zirconia implants.

MATERIAL AND METHODS

A total of 20 zirconia implants were inserted in single-tooth gaps in the maxilla (11) and mandible (9) of 20 patients. Implants were restored with all-ceramic CAD/CAM provisionals without occlusal contacts immediately after placement. Permanent all-ceramic restoration was performed 4 months after surgery. Plaque index (PI), bleeding on probing (BOP), Periotest(®) (PV), pink aesthetic score (PES), mean radiographic marginal bone levels (MBL), implant survival and success were evaluated up to 24 months.

RESULTS

Assessment of PI at baseline and follow-ups after 6, 12, 18 and 24 months revealed 27% (±5.3), 24% (±6), 23% (±6.1), 23% (±5.3) and 22% (±6.4), respectively. Evaluation of BOP revealed 25% (±5.6), 21% (±6), 21% (±7.2), 18% (±5.9) and 15% (±5.5), respectively. Implants presented stable at follow-ups (PV). PES improved, but not statistically significant from 8.13 (±1.5) at baseline to 10 (±2) 24 months after implantation. Measurements of MBL showed a significant bone loss of 1.01 mm within the first year after placement (P < 0.001) and 1.29 mm 24 months post-implant insertion, not reaching further statistically significant levels (P > 0.05). One implant was lost 4 months after placement, resulting in a survival and success rate of 95%.

CONCLUSION

Clinical and radiographic parameters demonstrated a 95% integration of immediately loaded zirconia single-piece implants. A long-term randomized-controlled clinical trial was initiated to confirm evidence of this protocol.

Position of the mental foramen on panoramic radiographs and its relation to the horizontal course of the mandibular canal: a computed tomographic analysis

AIM

The purposes of this study were (1) to investigate the bucco-lingual course of the mandibular canal in the bony structure and (2) to figure out the relationship between the position of mental foramen on panoramic radiographs and the horizontal course of the mandibular canal.

MATERIALS AND METHODS

A database of panoramic radiography and spiral computed tomography (CT) scans was searched and 100 subjects were selected based on the criteria. Mental foramina were classified into four groups according to its antero-posterior position. Three measurements were made on each slice of coronal CT scans at three different points: (1) apex of second premolar; (2) median point of two root apexes of first molar; and (3) median point of two root apexes of second molar. The bucco-lingual ratios were calculated to access the relative bucco-lingual position of the mandibular canal.

RESULTS

The distribution of subjects according to the type of mental foramen was: (1) type 3, 67%; (2) type 2, 26%; (3) type 4, 5%; and (4) type 1, 2%. The overall horizontal course of the mandibular canal was relatively constant from the second molar to first molar, whereas much significant directional change was found on the remaining course. Between types 2 and 3, no statistically significant differences were found at the level of the second molar and first molar (P = 0.461 and 0.965, respectively). Only below the second premolar, significant differences were found (P = 0.001).

CONCLUSIONS

Based on the findings of our computed tomographic image analysis, the position of mental foramen on panoramic radiographs was affected by its horizontal course of inferior alveolar nerve. The significant horizontal direction change of the course was found after the canal passing below the mandibular first molar regardless of the antero-posterior position of mental foramen.

Reliability and reproducibility of linear mandible measurements with the use of a cone-beam computed tomography and two object inclinations

OBJECTIVE

The aim of this study was to assess the influence of inclination of the object on the reliability and reproducibility of linear measurements of anatomic structures of the mandible on images obtained using cone-beam CT (CBCT).

METHODS

Ten linear dimensions between anatomical landmarks were measured in a dry mandible. The measurements were performed with a manual calliper three times by three observers. The mandible was scanned with Planmeca Promax 3D cone-beam CT (Planmeca Oy, Helsinki, Finland) with the base of the mandible parallel as well as tilted 45° to the horizontal plane. Computer measurements of the linear dimension were performed by three observers. The radiographic measurements were performed four times for each experimental setting. A total of 240 measurements were performed. Reproducibility was evaluated through comparison of standard deviation (SD) and estimation of intraclass correlation coefficient (ICC). The error was estimated as the absolute difference between the radiographic measurements and the mean manual calliper measurements.

RESULTS

The mean SD for the radiographic measurements was 0.36 mm for the horizontally positioned mandible and 0.48 mm for the inclined mandible. The ICC between examiners was 0.996 mm, between sessions was 0.990 mm and between CBCT measurements and calliper was 0.992 mm. The overall absolute mean measurement error was 0.40 mm (SD 0.39 mm). The percentage of errors that exceeded 1 mm was 6.7%.

CONCLUSION

The results revealed high reliability of measurements performed on CBCT images independently from object position, examiner's experience and high reproducibility in repeated measurements settings.

Magnification rate of digital panoramic radiographs and its effectiveness for pre-operative assessment of dental implants

OBJECTIVES

The purpose of this study was to determine the accuracy and effectiveness of digital panoramic radiographs for pre-operative assessment of dental implants.

METHODS

We selected 86 patients (221 implants) and calculated the length of the planned implant based on the distance between a selection of critical anatomical structures and the alveolar crest using the scaling tools provided in the digital panoramic system. We analysed the magnification rate and the difference between the actual inserted implant length and planned implant length according to the location of the implant placement and the clarity of anatomical structures seen in the panoramic radiographs.

RESULTS

There was no significant difference between the planned implant length and actual inserted implant length (P > 0.05). The magnification rate of the width and length of the inserted implants, seen in the digital panoramic radiographs, was 127.28 ± 13.47% and 128.22 ± 4.17%, respectively. The magnification rate of the implant width was largest in the mandibular anterior part and there was a significant difference in the magnification rate of the length of implants between the maxilla and the mandible (P < 0.05). When the clarity of anatomical structures seen in the panoramic radiographs is low, the magnification rate of the width of the inserted implants is significantly higher (P < 0.05), but there is no significant difference between the planned implant length and actual inserted implant length according to the clarity of anatomical structures (P < 0.05).

CONCLUSIONS

Digital panoramic radiography can be considered a simple, readily available and considerably accurate pre-operative assessment tool in the vertical dimension for dental implant therapy.

Reliability of the vertical magnification factor on panoramic radiographs: clinical implications for posterior mandibular implants

OBJECTIVES

Panoramic radiographs allow evaluation of the available bone height for implant treatment planning while imparting a low radiation dose. As panoramic radiography produces image distortion, reference objects are required to determine the exact magnification. This study aims to estimate a panoramic unit's vertical magnification factor (MF) by measuring the length of dental implants used as radiopaque reference objects on postoperative panoramic radiographs. We compared our findings to the vertical MF listed by the panoramic unit manufacturer, and studied the reproducibility and accuracy of our measuring method by analyzing the inter- and intraobserver agreements.

MATERIAL AND METHODS

Using a digital calliper, we measured the length of 32 implants on 17 postoperative panoramic radiographs taken with a Scanora unit. The implants were 10mm-long standard Straumann implants placed in the posterior segments of mandibles. The MF was calculated by dividing the implant's radiological length by the implant's real length.

RESULTS

The mean calculated vertical MF was 1.27 ± 0.01 (1.245-1.295) and was lower than the manufacturer's MF (1.3). The vertical MF was 1.28 ± 0.01 in the premolar and 1.27 ± 0.01 in the molar regions. There was an excellent intraobserver reliability (0.96 for observer 1; 0.93 for observer 2) and a good interobserver reliability (0.85 at measurement session 1; 0.8 at measurement session 2)

CONCLUSIONS

The observed reliability of the MF confirms that a panoramic radiograph can be used for preoperative implant length evaluation in the posterior mandibular segments. MF stability should be verified with other panoramic units. In clinical practice, using the implant length as a reference object on postoperative panoramic radiographs is a simple and effective evaluation method to estimate a panoramic unit's MF.

Comparison of panoramic and conventional cross-sectional tomography for preoperative selection of implant size

OBJECTIVE

To compare panoramic and conventional cross-sectional tomography for preoperative selection of implant size for three implant systems (Brånemark, Straumann(®), 3i).

MATERIAL AND METHODS

Presurgical panoramic (Pan) and cross-sectional tomograms (Tomo) of 121 implant sites in 121 patients scheduled for single-tooth implant treatment were recorded; in 70 of the Pans (Pan-B), a metal ball was placed in the edentulous area. By means of dedicated software, an implant with subjectively determined proper dimensions for the respective site was outlined by manually placing four reference points in each image by three observers. Additionally, four reference points corresponding to the margins of the metal ball were manually placed in Pan-Bs. The length and width of the implant were calculated after calibration to the reference ball (true magnification) in Pan-Bs and to a "standard" calibration method in all images (magnification factor 1.25 in Pans and 1.7 in Tomos). Based on the corrected dimensions, the nearest, smaller implant size was selected among those available in each of the three implant systems.

RESULTS

When comparing Pans with Tomos, selected implant size differed in on average 89% of the cases. The length differed in 69% and the width in 66%. Implants planned on Tomos were longer than those planned on Pans in 47% and narrower in 30% (<10% in posterior regions). The Straumann(®) system, with the smallest range of available implant sizes was significantly less affected by the radiographic method compared with the other two systems.

CONCLUSION

The selected implant size differed considerably when planned on panoramic or cross-sectional tomographs.

Immediate provisional restoration of screw-type implants in the posterior mandible: results after 5 years of clinical function

OBJECTIVE

The aim of this prospective study was to evaluate the outcome of immediately provisionally restored implants in the posterior mandible after a minimum of 60 months in function.

MATERIAL AND METHODS

Twenty-four patients were treated with 40 screw-type implants replacing mandibular molars and premolars. Implants were provisionalized immediately after placement. Radiographic coronal bone levels, implant survival and success were evaluated 12, 24, 36, 48 and 60 months after the final restoration.

RESULTS

Measurements of the mean marginal bone levels around immediately loaded implants after 12 months showed a significant bone loss (P<0.001) within the first year after the final restoration. Measurements of coronal bone levels after 24, 36, 48 and 60 months, respectively, showed no further significant increase of bone resorption. Two implants were lost within the first year after the final restoration, resulting in an overall survival rate of 95%; a total of three implants were recorded as failures (two implant losses and one excessive bone resorption above 50%), resulting in an overall success rate of 92.5 after an implant observation period of up to 8 years.

CONCLUSION

The present data revealed results comparable to conventionally loaded implants. Careful patient selection in combination with high primary stability seem to be key factors for immediately loaded implants. Larger long-term randomized clinical trials are needed to confirm the final evidence of this protocol as the standard treatment concept for the partially edentulous mandible.

Inferior alveolar canal course: a radiographic study

OBJECTIVES

To describe the morphology and course of the inferior alveolar canal (IAC) as it appears in digital panoramic radiographs.

MATERIALS AND METHODS

Three hundred and eighty-six digital rotational panoramic radiographs (OPG) were studied using the Clinview Software (6.1.3.7 version, Instrumentarium). Among the 386 radiographs, 86 radiographs with 5-mm steel balls were used to calculate the magnification.

RESULTS

The average magnification of radiographs in this study was 7.24+/-7.55%. The course of IAC as seen in the panoramic radiograph may be classified into four types: (1) linear curve, 12.75%, (2) spoon-shaped curve, 29.25%, (3) elliptic-arc curve, 48.5%, and (4) turning curve, 9.5%. On panoramic radiographs, the IAC appeared closest to the inferior border of the mandible in the region of the first molar. In relation to the teeth, on panoramic radiographs, the IAC appeared closest to the distal root tip of the third molar and furthest from the mesial root tip of the first molar.

CONCLUSION

In the OPG, there are four types of IAC: linear, spoon shape, elliptic-arc, and turning curve. The data found in the study may be useful for dental implant, mandibule surgery, and dental anesthesia. The limitations of the panoramic radiograph in depicting the true three-dimensional (3D) morphology of the IAC are recognized, computed tomography (CT) and cone beam (CB)3D imaging being more precise.

Evaluation of dimensional accuracy of panoramic cross-sectional tomography, its ability to identify the inferior alveolar canal, and its impact on estimation of appropriate implant dimensions in the mandibular posterior region

OBJECTIVES

To evaluate the dimensional accuracy of panoramic cross-sectional tomography, its impact on implant size estimation and its ability in identifying the inferior alveolar canal in the mandibular posterior region.

MATERIAL AND METHODS

Eight partially edentulous mandibles with 18 edentulous sites were obtained. Orthopantomograms and tomograms were made and the mandible's outline and the position of mandibular canals on tomograms were traced on a clear acetate paper. Horizontal and vertical magnification factors were calculated. The mandibular height, distance between mandibular canal and alveolar crest, maximum bucco-lingual width, distance between buccal cortex and mandibular canal, and cortical thickness at the inferior border of the mandible were measured. Potential implant sites were identified and implant sizes were estimated. Location and visibility of mandibular canals were also evaluated. The mandibles were sectioned at each site and all the above mentioned parameters were assessed which served as gold standard.

RESULTS

Mean horizontal and vertical magnification factors were 1.47 ± 0.048 and 1.53 ± 0.038. Total height and maximum bucco-lingual width were underestimated by 1.88% and 1.59%. Crest to canal distance, cortical thickness at the inferior border of the mandible and buccal cortex to mandibular canal were overestimated by 0.59%, 5.16%, and 3.64%. Implant sizes were estimated for 11 sites and changes were recorded at 2 sites between record 1 and record 2. However, there was no disagreement between record 2 and record 3. Of the canals, 61.11% were located lingually and the visibility of mandibular canals was poor in 44.44% of cases.

CONCLUSIONS

The tomograms were found to be accurate for the measurements in both horizontal and vertical planes and reliable for implant size estimation, taking into consideration proper magnification factors. They were also found to be useful in assessing the location of mandibular canal but were not very effective in discerning it.

Cone-beam CT for preoperative implant planning in the posterior mandible: visibility of anatomic landmarks

BACKGROUND

The technical development has given a new type of modality, cone-beam computed tomography (CBCT). This technique has a high potential to solve different diagnostic problems among which is preoperative planning for implants in the posterior mandible.

PURPOSE

The aim of this retrospective study was to evaluate the visibility of the mandibular canal and the marginal bone crest and the agreement between observers in images from one CBCT technique.

MATERIALS AND METHODS

Thirty consecutive patients were examined with 3D Accuitomo (J. Morita Mfg. Corp., Kyoto, Japan) in one side of the mandible, where the second premolar and molars were lost. The examined volume was 30 by 40 mm. Seven observers evaluated the visibility and the location of the mandibular canal and the marginal crest by visually deciding if the structures were clearly visible, probably visible, or invisible in one cross-sectional image, approximately 1 cm posterior to the mental foramen. In a later session, the observers also marked the two anatomic structures. If the decision was not "clearly visible" or if the anatomic structures were difficult to identify, the observers had to use other cross-sectional, axial, and/or sagittal images in the volume.

RESULTS

The confidence among the observers evaluating the marginal bone crest was high. Two observers never used any other images, and the rest took help in two to seven cases. When marking the mandibular canal, the observers, in general, used more images. In five cases (17%), all the observers only used the single cross-sectional image. The agreement on the position of the canal was also high.

CONCLUSION

With this CBCT modality (3D Accuitomo), the visibility of the mandibular canal and the marginal crest, as well as the observer agreement of the location of these structures, was high. Hence, the 3D Accuitomo can be recommended for implant planning in the posterior mandible.

Pre-operative radiographs for dental implants - are selection criteria being followed?

OBJECTIVES

To determine by anonymous survey whether the active membership of a particular dental society with variable training and clinical experience in dental implant insertion and restoration followed the published selection criteria for the pre-operative radiographic assessment of prospective dental implant osteotomy sites.

DESIGN

Postal survey.

SUBJECTS AND METHODS

A postal questionnaire was sent to all professionally active members of the British Society of Periodontology (n = 560) during July 2005. The mailing was repeated in September 2005.

RESULTS

Four hundred and fifty-nine questionnaires were returned a response rate of 81.5%. One hundred and seventy-nine (39%) respondents were not involved in placing or restoring dental implants and were excluded. Of the remaining 280 (61%), 15 (5%) clinicians limited themselves to placing implants, 85 (30%) limited themselves to restoring implants, while 181 (65%) both placed and restored their own implants. Two hundred and twenty-eight clinicians (80.8%) did not follow UK selection criteria for single sites; 217 clinicians (77.5%) did not follow the criteria for multiple sites. Two hundred and sixty-three clinicians (94%) did not follow USA selection criteria. There were no statistically significant differences in compliance based on clinical experience or the number of implants placed. The only statistically significant difference was as a result of training those clinicians who had attended formal training courses were more likely to comply with published selection criteria. Significant differences also existed between the groups in the specific cross-sectional imaging modalities chosen.

CONCLUSION

Over 80% of respondents are not following the UK or USA selection criteria for pre-implant imaging assessment. The results of this survey call into question the clinical relevance, usefulness, or knowledge of existing selection criteria. There is a need for new selection criteria developed by both radiologists and experienced implant clinicians.