David MacDonald


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Graduate Student Supervision

Master's Student Supervision (2010 - 2020)
The use of cone beam computed tomography for implant treatment planning at UBC (2020)

Purpose: Cone beam computed tomography (CBCT) has become the standard of care for many applications in the specialty of periodontics. CBCT is now taken for almost all implant related cases and there is also a clear shift towards higher resolution images. However, the increased radiation dosage from a higher resolution images must be accompanied by valid clinical justification. Aims: The first aim was to conduct an audit of all CBCT prescriptions at the UBC Faculty of Dentistry with a focus on implant related prescriptions. Concurrently, all implant related prescriptions were evaluated for compliance with the current guidelines. The second aim was to evaluate whether altering the mA and kVp values will result in measurement differences on CBCT images. Materials and Methods: Ethics approval was granted for the retrospective portion of this study (Certificates H18-01536 and H19-02001). All CBCT prescriptions were audited from Jan. 1, 2015 to Aug. 31, 2018. However, the prescriptions originating from the Graduate Periodontics and Prosthodontics programs were examined more thoroughly. A major finding from the audit was a shift towards higher resolution images for the small FOV. An in vitro experiment was conducted to determine whether changing the imaging parameters and scatter would affect the measured distance between two adjacent implants placed in a model. Results: Almost all the CBCT scans prescribed in the Periodontics and Prosthodontics departments were prescribed for the purposes of implant treatment planning. In Graduate Periodontics and Prosthodontics, 95% and 94% of the prescriptions, respectively, were compliant with the guidelines published by the AAOMR and the AAP. Manipulation of the imaging parameters did affect the measured distance between the two implants when specific mA and kVp values were compared. The scatter and metal artifacts from the addition of a third implant did not have any effect on the measured distance.Conclusion: CBCT was used judiciously for implant treatment planning in both the Graduate Periodontics and Prosthodontics department. Manipulation of CBCT parameters had a statistically significant effect on the measured distance between two adjacent implants but the potential scatter and metal artifacts from the addition of third implant did not.

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The effect of the mode of reconstruction of the CBCT on the orthodontic diagnosis and treatment planning of impacted teeth (2019)

Introduction: Cone-beam computed tomography (CBCT) became commercially available 20 years ago and has been applied to almost every area of dental practice. This is due to its better spatial resolution, lower radiation dose, and smaller footprint than computed tomography (CT). However, the current CBCT unit still has much higher radiation dose than the standard conventional 2D dental imaging. Since there is no known safe lower radiation dose limit, radiation must be ‘as-low-as-reasonably-achievable’ (ALARA).Aims: To profile the orthodontic patient pool since the inception of the Orthodontics Graduate Program at UBC to determine the number and the reason for whom CBCTs were prescribed. To compare the orthodontic diagnostic efficiency of two different 3D reconstruction methods of the CBCT images. Methods: Ethics was approved for a retrospective review of orthodontic cases and for review by orthodontic instructors of randomized multiplanar reformatting (MPR) and curved CBCT image sets. 15 datasets of similar appearing impacted maxillary canines were reconstructed into MPR and curved screenshots. The instructors were asked to disclose their length of orthodontic service and prior experience reviewing CBCT datasets. They were asked to review the screenshots to determine factors that could affect treatment such as the position of the impacted canine, presence of root resorption and dilacerated roots. Results: The review revealed 35 prescribed CBCTs that were mostly taken to investigate impacted teeth (29 cases). Of the 15 orthodontists, although the 6 females had on average 16 years of experience to their 9 male colleagues (on average of 26 years), this was not significant (P = 0.142). Furthermore, they all have some experience at reviewing MPR reconstructions which was almost identical for either sex, around 6 years; 2 males and 2 females had considerably more experience. All appeared more comfortable with the MPR rather than the curved reconstructions.Conclusions: The number of prescribed CBCT images is low because the program policy follows the “Image Gently” guidelines and the ALARA principles. So far, orthodontists are more comfortable with the MPR rather than the more panoramic-like curved reconstruction. This simply may reflect the fact that the former is the default reconstruction for most CBCT units.

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Prescriptive pattern and clinical decision making in complicated endodontic cases using cone-beam computed tomography (2017)

Purpose: Cone Beam Computed Tomography (CBCT) is an advanced but new imaging technique used in dentistry. Although it already has acquired a substantial literature, that literature does not include evidence-based evidence both for its indications-for-use and for its efficacy in comparison to the conventional approach to diagnosis and treatment planning. Aims: To determine the pattern of prescription of CBCT by all UBC dental programs with particular regard to the field-of-view (FOV). To determine whether the CBCT prescriptions by the Graduate Endodontics Program were compliant with the joint American-Academy-of-Oral-and-Maxillofacial-Radiology and American-Academy-of-Endodontics (AAOMR/AAE) position statement (viz guidelines). To determine by reference to the EPR whether CBCT changed the original diagnosis and/or treatment plans based on the initial clinical examination and the conventional radiographic.Methods: Ethics approval certificates H14-02191 and H15-03507 were granted for this retrospective study. All CBCT prescriptions were audited. The audit revealed that CBCT prescriptions by the Graduate Endodontics program were for a wide range of clinical reasons and worthy of further study. The pattern of prescription of CBCT was reviewed, by reference to electronic patient record (EPR), to determine whether it was compliant with the AAOMR/AAE guidelines. The statistical test, Chi-square was used. Results: All but one CBCT in the audit were for small and medium-sized FOVS. All 128 CBCT prescriptions (in 110 consecutive patients) were AAOMR/AAE-guidelines compliant. CBCT identified significantly more features than conventional radiography (p
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