|Year : 2020 | Volume
| Issue : 3 | Page : 229-234
Presurgical assessment of alveolar ridge dimensions before dental implant procedures by OPG&CBCT – A comparative study based on fryback & thornbury model
Purv S Patel1, Jigna S Shah2, Bhavin B Dudhia3, Purva B Butala4
1 PHD Scholar, Gujarat University; Department of Oral Medicine and Radiology, Ahmedabad Dental College & Hospital, Ahmedabad, Gujarat, India
2 Department of Oral Medicine and Radiology, Government Dental College & Hospital, Ahmedabad, Gujarat, India
3 Department of Oral Medicine and Radiology, Ahmedabad Dental College & Hospital, Ahmedabad, Gujarat, India
4 Department of Pedodontics and Preventive Dentistry, Ahmedabad Dental College & Hospital, Ahmedabad, Gujarat, India
|Date of Submission||04-May-2020|
|Date of Decision||20-Jul-2020|
|Date of Acceptance||23-Jul-2020|
|Date of Web Publication||29-Sep-2020|
Dr. Purv S Patel
201, Shubh Block, Shukan Towers, Opp. Judges Bungalows, Bodakdev, Ahmedabad – 380054, Gujarat
Source of Support: None, Conflict of Interest: None
| Abstract|| |
Background and Aims: Replacing missing teeth is one of the most common challenges faced by the dental surgeon. The invention of dental implants has brought about a great change in successfully delivering a fixed prosthesis to the patient. Precise radiographic assessment of available alveolar bone is of prime importance for dental implant placement. Panoramic radiograph provides an overview of the jaw bones and is considered adequate in the initial evaluation of the implant site; however, they do not provide the buccolingual dimension of the implant site. CBCT provides volumetric imaging with the ability to visualize the imaged region in virtually any plane. The objective of this study was to compare panoramic radiography (OPG) with cone-beam computed tomography (CBCT) for pre-surgical implant site evaluation. Materials and Methods: A total of 150 potential implant sites in 94 patients who were subjected to OPG and CBCT imaging previously were selected for the study. The height, width, and length of the available bone were measured for all the implant sites (except bone width which was measured on CBCT alone). Out of these, OPG & CBCT findings of 60 potential implant sites were evaluated by comparison with the surgical gold standard dimensions of actual dental implant placed. A comparison of all the values obtained with the two imaging modalities was done and the data was tabulated for statistical analysis. Results: The mean value of bone height using OPG and CBCT were found to be 12.15 mm and 11.99 mm, respectively. The mean value of the length of the edentulous jaw segment using OPG and CBCT was found to be 8.10 mm and 8.98 mm respectively. The mean value of the width of the crestal bone below the height of the crest using CBCT was found to be 5.46 mm. Conclusion: The overall results suggested that CBCT is better in depicting the bone height and bone width as compared to OPG; however, the length of the edentulous jaw segment is better depicted by OPG as compared to CBCT.
Keywords: Cone -beam computed tomography, dental implants, panoramic radiography
|How to cite this article:|
Patel PS, Shah JS, Dudhia BB, Butala PB. Presurgical assessment of alveolar ridge dimensions before dental implant procedures by OPG&CBCT – A comparative study based on fryback & thornbury model. J Indian Acad Oral Med Radiol 2020;32:229-34
|How to cite this URL:|
Patel PS, Shah JS, Dudhia BB, Butala PB. Presurgical assessment of alveolar ridge dimensions before dental implant procedures by OPG&CBCT – A comparative study based on fryback & thornbury model. J Indian Acad Oral Med Radiol [serial online] 2020 [cited 2020 Oct 30];32:229-34. Available from: https://www.jiaomr.in/text.asp?2020/32/3/229/296593
| Introduction|| |
Edentulism is a physical impairment with characteristics similar to a chronic disease such as diabetes: incurable, functionally/psychologically disruptive, and requiring specific management strategies to overcome or limit disruptive effects. Replacing missing teeth is one of the biggest challenges faced by the dental surgeon. The invention of dental implants has brought about a great change in delivering a successfully fixed prosthesis to the patient but entails few anatomic, physiologic, functional, and economic challenges.[2-5] Precise radiographic assessment of available alveolar bone and identification of characteristic bone morphology is of prime importance for dental implant placement.,,, The distance of anatomical structures, such as mental foramen, the floor of the nasal cavity, floor of the maxillary sinus, inferior alveolar canal, nerves, and vessels can significantly affect the morbidity of the surgical procedure and influence the outcome., A risk of nerve infiltration and maxillary sinus perforation exists originating from inappropriate pre-surgical planning due to the innate discrepancy between radiographic measurements and real dimensions., Hence, the role of the oral radiologist is very vital in giving accurate information about the quality and quantity of implant recipient sites which will help the clinician in practicing precise implant dentistry.
Cone-beam computed tomography (CBCT) has revolutionized diagnostic imaging in dentistry.,, CBCT imaging provides three-dimensional volumetric data construction of dental and associated maxillofacial structures with isotropic resolution and high dimensional accuracy.,, Unlike conventional intraoral, panoramic, and cephalometric radiographs, which provide 2-D images, CBCT provides volumetric imaging with the ability to visualize the imaged region in virtually any Plane at a relatively low radiation dose to the patient.,,,,,,,, CBCT has diverse applications in dentistry such as implant dentistry, endodontics, impacted teeth evaluation, orthodontics, orthognathic surgical treatment planning, temporomandibular joint evaluation, periodontics, fracture analysis, and intraosseous jawbone pathology imaging.,
The arrival of any new medical intervention, diagnostic or therapeutic, brings new challenges to clinicians., As described by Fryback and Thornbury, any new radiological technique should be efficacious from technical accuracy efficacy to societal efficacy. The basic premise that justifies the use of these imaging modalities is that the benefits must far outweigh the radiation associated risks., Such benefits may be in the form of increased diagnostic efficacy, enhanced treatment planning, better therapeutic outcomes as well as value for money. To address these principles, Fryback and Thornbury proposed a six-tiered hierarchical model to evaluate applications of new technologies for diagnostic imaging.,
Appaji Aet al. Kyung SH et al. Amarnath GS et al. Jasjit S et al. Leticia C et al. and Christos A et al. conducted similar studies comparing various parameters of bone related to implant planning and placement. Moreover, none have evaluated/validated CBCT imaging for implant planning based on the hierarchical model of Fryback and Thornbury. Hence, this study was undertaken to compare the accuracy of an existing two-dimensional modality such as OPG with a new three-dimensional imaging modality such as CBCT for evaluating a potential dental implant site based on the hierarchical model of Fryback and Thornbury.
| Materials and Methods|| |
The sample consisted of 94 individuals (150 potential dental implant sites) who previously underwent a preoperative radiographic evaluation for implant planning. Only those individuals having healthy teeth on both sides of the edentulous segment and not more than two missing teeth with previously advised OPG as well as CBCT for implant planning were included for the study. Digital panoramic radiographs (OPG) were obtained using the PaxI3D Smart machine (Vatech Co Ltd, Hwaseong-si, Gyeonggi-do, Korea) operating at 74 kVp/12 mA for 10 seconds. Cone-beam computed tomography (CBCT) was obtained with the same machine operating at 94kVp/8.7 mA for 18 seconds with a voxel size of 0.1 mm and a field of view of 10 x 8 cm2.
All the OPGs and CBCTs were evaluated independently by two radiologists with at least 2 years of experience in CBCT diagnosis. There was a gap of 15 days between the OPG and CBCT evaluation of any patient by a radiologist to avoid memory bias. Any disagreements amongst the radiologists were subsequently resolved after a discussion till they reached a mutually agreed conclusion. After 30 days, 50 panoramic radiographs and CBCT images were re-evaluated to analyze the intra-observer agreement.
The images were evaluated on a computer monitor (16 inches LED screen with 1920 x 1080 resolution) under dim lighting conditions with optimal brightness and contrast on a full-screen view of the edentulous site to ensure diagnostic accuracy.
On the OPG, the height and length of the bone at the edentulous span were measured. [Figure 1]. On the CBCT images, bone height and length of the edentulous span were measured along with the bone width. The bone height and width were measured from the transaxial sections, while the length of the edentulous span was measured from the axial, sagittal, coronal sections depending upon the site. [Figure 2]
|Figure 1: OPG image exemplifying the height and length measurement of bone at the edentulous site|
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|Figure 2: CBCT images exemplifying bone height & width measurement in transaxial section (left) and bone length measurement of edentulous site in sagittal section (right)|
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Out of all the edentulous sites under study, a total of 60 edentulous sites were subjected to osteotomy and dental implant placement under local anesthesia using a common implant system. The measurements of bone height (implant length), bone width (implant width), and the length of the edentulous span were recorded at the time of implant procedure to be used as a gold standard for assessing the accuracy of the measurements done based on OPG and CBCT images.
The hierarchical model of Fryback & Thornbury was thoroughly assessed and evaluated for each implant site by each of the two radiologists separately. All the parameters at each of the six levels of the model were carefully evaluated for each potential implant site on OPG and CBCT separately. When the modality under study seemed to satisfy the parameters for a particular level of the model, then it was addressed as score 1. Being a hierarchical model, when a radiographic modality failed at a particular level, score 0 was given and the next level evaluation was not performed. Hence, the minimum score possible for a modality for one particular implant site was 0 and the maximum possible score was 6. Typical measures of the levels described in the model are as mentioned below.
Data were analyzed using the SPSS software. The kappa statistic was used to calculate intra and inter observer agreement (less than or equal to 0.40 is a poor agreement; 0.40-0.59 is a moderate agreement; 0.60-0.74 is a good agreement and 0.75-1.00 is excellent agreement). A comparison between the OPG and CBCT findings were performed using the Fisher's exact test, with a significance level of P < 0.05. The evaluation of OPG against CBCT by Fryback & Thornbury model was done by one-way ANOVA test.
| Results|| |
The sample consisted of 94 individuals (150 potential dental implant sites) composed of 79 males (52.6%) and 71 females (47.4%) with age ranged between 20 and 69 years (mean age 44.5 years). Statistically significant differences were not observed for gender or age (P > 0.05). The Intra- and interobserver agreement kappa values for the panoramic radiographs were 0.94 (observer 1: first vs. second evaluation), 0.76 (observer 2: first vs. second evaluation), and 0.85 ( first evaluation: observer 1 vs. observer 2). For the CBCT images, the kappa images were 0.89 (observer 1: first vs. second evaluation), 0.96 (observer 2: first vs. second evaluation), and 0.92 ( first evaluation: observer 1 vs. observer 2). For both imaging modalities, the agreement was excellent.
[Table 1] summarizes the distribution of potential dental implant sites amongst male and female subjects. The table denotes that 24 sites were in the maxillary anterior region which was equally divided between males and females; 16 sites were in the mandibular anterior region out of which 10 & 6 belonged to males and females respectively; 30 sites were in the maxillary posterior region out of which 16 &14 belonged to males and females respectively while remaining 80 sites were in the mandibular posterior region out of which 41 &39 belonged to males and females, respectively.
|Table 1: Distribution of potential dental implant sites amongst male and female subjects|
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[Table 2] summarizes the comparison of bone height and length measurements done by OPG & CBCT. There were 24 cases of the maxillary anterior region for which mean bone height and bone length were 12.25 mm& 6.27 mm by OPG and 13.95 mm & 7.48 mm by CBCT with a P value of 0.338&<0.0001, respectively. There were 16 cases of the mandibular anterior region for which mean bone height and bone length were 13.69 mm & 5.1 mm by OPG and 15.15 mm & 5.44 mm by CBCT with P value of 0.0507& 0.4251, respectively. There were 30 cases of maxillary posterior region for which mean bone height and bone length were7.98& 7.32 mm by OPG and 7.94mm & 8.88 mm by CBCT with a P value of 0.9543&<0.0001, respectively. There were 80 cases of the mandibular posterior region for which mean bone height was 13.38 mm &9.6 mm by OPG and 12.29 mm & 10.23 mm by CBCT with a P value of < 0.0001&<0.0001, respectively.
|Table 2: Comparison of bone height and length measurements on OPG and CBCT|
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[Table 3] summarizes the comparison of bone height, length, and width measured from OPG & CBCT with the size of the dental implant placed at the site which was considered as the surgical gold standard. There were 21 cases of the maxillary anterior region for which mean bone height by OPG vs. CBCT was 11.47 mm vs. 13.55 mm while the surgical standard was 13.08 mm; mean bone length by OPG vs. CBCT were7.04 mm vs. 8.14 mm while the surgical standard was 6.74 mm. There were 10 cases of the mandibular anterior region for which mean bone height by OPG vs. CBCT was 7.95 mm vs. 8.26 mm while the surgical standard was 11.75 mm; mean bone length by OPG vs. CBCT were8.15 mm vs. 9.86 mm while the surgical standard was 7.21 mm. There were 8 cases of the maxillary posterior region for which mean bone height by OPG vs. CBCT was 7.95 mm vs. 8.26 mm while the surgical standard was 11.75 mm; mean bone length by OPG vs. CBCT were 8.15 mm vs. 9.86 mm while the surgical standard was 7.21 mm. There were 28 cases of the maxillary posterior region for which mean bone height by OPG vs. CBCT was 13.75 mm vs. 12.28 mm while the surgical standard was 12.4 mm; mean bone length by OPG vs. CBCT were10.41 mm vs. 10.96 mm while the surgical standard was 7.27 mm. Since the overall P value for both bone height was <0.0001, post hoc analysis was done to compare OPG as well as CBCT measurements with the surgical standard which were both found to be <0.0001. Since the overall P value for both bone length was <0.0001, post hoc analysis was done to compare OPG as well as CBCT measurements with the surgical standard which were both found to be <0.0001.
|Table 3: Comparison of bone height, length & width measured from OPG & CBCT with surgical standard|
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[Table 4] demonstrates the comparison of OPG versus CBCT scores based on the Fryback and Thornbury model. The total scores and mean for OPG and CBCT were evaluated. The total score and mean for OPG vs. CBCT for the 24 cases of the maxillary anterior region was 56 &2.33 vs. 143 & 5.95 with a P value of < 0.0001. The total score and mean for OPG vs. CBCT for the 16 cases of the mandibular anterior region was 46 & 2.875 vs. 94& 5.87 with a P value of < 0.0001. The total score and mean for OPG vs. CBCT for the 30 cases of the maxillary posterior region was 81& 2.7 vs. 177& 5.9 with a P value of < 0.0001. The total score and mean for OPG vs. CBCT for the 80 cases of the mandibular posterior region was 232& 2.9 vs. 421& 5.26 with a P value of < 0.0001. The variance of OPG was 0.184, while for CBCT it was 0.246. The F value was 2891.11 while the P value of one-way ANOVA was < 0.0001 at a 5% level of significance.
|Table 4: Comparison of OPG vs. CBCT scores based on frybackþbury model|
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| Discussion|| |
Accurate presurgical treatment planning is the key to successful dental implant rehabilitation.,, Past decades have shown a paradigm shift from a surgically-driven to a prosthetically-driven approach in dental implant therapy. Specific considerations for implant imaging should include clinical complexity, regional anatomic considerations, potential risk of complications, and aesthetic considerations in the location of implants. Panoramic images provide an overview of the jaws and are usually considered adequate in the initial evaluation, but do not display the buccolingual aspect of the alveolar bone. CBCT imaging is done with dental implantology for various purposes such as assessing the bone quantity and quality, relation to neighboring anatomical structures, before ridge augmentation, before sinus lifting, assessment of implant osseointegration, and in designing a surgical guidance template.,, An important contribution of CBCT is to evaluate local anatomy such as buccal and lingual undercuts that are not depicted on 2-D imaging.,, The widespread use of this technology in dental implantology prompted several different organizations to develop clinical guidelines for the assessment of potential dental implant sites. These include the American Academy of Oral Medicine & Radiology (AAOMR), European Academy of Osseointegration (EAO), International Congress of Oral Implantologists (ICOI), SEDENTEXCT, the Academy for Osseointegration (AO), and the International Team for Implantology (ITI).,,,, It is justified by evidence that CBCT information alters the implant treatment plan, including the size of the implant selected and a higher degree of prediction.,,
The majority of subjects selected for this study had edentulism in the maxillary and mandibular posterior region. [Table 1] This finding is following the previous studies.,, The measurement of bone height, as well as bone length, is always higher in value as depicted by CBCT rather than by OPG for all regions except only for the mandibular posterior region. The anatomical boundary in the form of mandibular canal is a limiting factor while determining the bone height in the mandibular posterior region, which may be a factor responsible for the fact that OPG is revealing a greater bone height when compared with CBCT [Table 2]. It has been established that panoramic views of the posterior maxilla will under estimate the amount of bone available for implant placement and, if relied on, will therefore, overestimate the number of clinical situations requiring a sinus augmentation. CBCT can overcome this problem as it provides more accurate measurements of the available bone height. When comparing the bone height measured from radiographs with the actual length of the dental implant placed at the edentulous site, CBCT is always more accurate when compared to OPG. This is following the previous studies., However, OPG is more accurate than CBCT when considering the bone length. This may be because the fact that bone length or the length of the edentulous span is better visualized in a two-dimensional view. CBCT software requires additional skill for orientation of the edentulous site in the axial, sagittal, or coronal plane to accurately visualize the edentulous span as well as adjacent teeth on a single section. Also, bone width can only be predicted by CBCT, and hence it is the only predictor of the dental implant diameter to be used [Table 3]. Bone width as depicted by CBCT is considered to be as accurate as ridge mapping done after surgical exposure or that done using a direct caliper. The additional cost of the three-dimensional radiographic examinations is justified because it allows for better predictability and may save patients additional time, surgery, and expenditure. In a paucity of research articles aimed at validating the use of CBCT for dental implant procedures; hence this study was conducted to perform such analysis. Also, this study has attempted to modify the Fryback& Thornbury model to make it more understandable for evaluating the potential dental implant site. This study concludes that the CBCT scores are consistently better than OPG scores for the entire sample under study; furthermore, the F value of CBCT is greater than that of OPG, hence proving CBCT to be a better radiographic modality than OPG for evaluating potential dental implant site [Table 4].
| Conclusion|| |
The dental implant osteotomy is one of the most sought-after procedure by every dentist in modern times as it carries a huge margin of profit with it, accompanied by this is a huge margin of error. Implant planning is the most vital determinant of the success of the implant procedure. Radiographic evaluation is an inherent part of implant planning. CBCT has proven to be an excellent guiding tool for virtual implant planning because of the various tools in the software provides a three-dimensional idea to the dental surgeon about the characteristics of the dental implant site. This detailed information is impossible by any two-dimensional imaging modality. CBCT-guided surgical stents are the future of implant dentistry; making CBCT even more crucial in the process of dental implant planning and placement.
The present retrospective study was conducted following approval of the institutional ethical committee (registration number ECR/1101/Inst/GJ/2018).
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2]
[Table 1], [Table 2], [Table 3], [Table 4]