Dental implant imaging : What do South African dentists and dental specialists prefer ?

The radiographic preferences were obtained from practitioners via an electronic survey that was disseminated during local dental conferences, electronic channels (e.g., email lists) of multiple dental schools and local dental scientific societies, and personal interviews. The survey consisted of multiplechoice questions which were designed to investigate the most common radiographic prescriptions during various treatment phases of implant therapy.

INTRODUCTION at various educational levels, competent knowledge of handling recent imaging modalities, and economic strains influence a clinician's radiographic prescription. 13 In South Africa (SA), CBCT was reported to become a common procedure and even a routine procedure in some practices for screening purposes. 14 This is especially true particularly with the absence of rigorous local radiographic guidelines which could inform specific criteria for the management of patients requiring implant therapy. In this article, the authors report on the radiographic prescriptions, preferences and clinical opinions of a sample of dental practitioners who perform implant therapy in various South African provinces.
An electronic questionnaire was developed and published online using Google ® Forms ® after obtaining ethical approval for degree purposes (Number: BM19/1/20, University of the Western Cape, South Africa). The survey was constructed with 17 open-ended multiple-choice questions. All the information with respect to the research and the questionnaire (information sheet) was attached to the survey. A consent form was presented at the beginning of the online survey. No names nor personal information was required and anonymity of the participants was maintained.
The questions were formulated to allow for anonymous and scenario-based investigations on the radiographic analysis executed/preferred during implant therapy in South Africa (in various phases of the treatment). The questions probed data on the most used imaging modalities, personal experiences, clinical preferences, and the possible factors that may influence radiographic prescriptions. Only two questions were allowed to record multiple selections (answers). The level of formal training received (e.g., general dentist, postgraduate student, specialist) and the province where participants practised, were captured.
The imaging modality preferences were assessed during different clinical situations, various anatomical regions, and embraced all the phases of dental implant therapy (planning, intra-operative, and follow-up phases). The anatomical regions that were assessed during the planning phase include the posterior mandible (unilateral, distal to first premolar region), anterior region of the maxilla/mandible (canine to canine region), posterior maxillary region (unilateral: distal to the first premolar), one jaw (mandible/ maxilla) or both jaws (full mouth), and the mental foramen region (uni/bilateral). The imaging modalities options were: periapical radiograph/s (PA) only, panoramic radiograph (PAN) only, PAN + PA, PA + CBCT, PAN + CBCT, CBCT only, and no radiographs. Motivating factors for the selection of radiographic examinations, such as cost, availability, radiation dose concerns, broad coverage (i.e., the extent of the anatomical area depicted in a single radiographic examination), dimensional accuracy (3D volumes), additional anatomical information (3D volumes), and special procedures (e.g., 3D volumes for guided implant surgery) were also explored. 142 dental clinicians participated in the survey (Table I) with the majority of them practising in the Western Cape province (Chart 1; this excluded 47 surveyees where their practice location was failed to be captured).
Panoramic radiograph accompanied by CBCT examination were the most selected imaging modalities (39%) during the implant planning phase (in all anatomical regions in the jaws). This was followed by CBCT as a single examination (29%), periapical radiograph (PA) with CBCT (19%), PAN + PA (8%), PAN only (2%), other (2%), and PA only (1%). Table II and Chart 3 (A-E) shows in detail the imaging modalities preferred for each questioned anatomical site. In general, "Three-dimensional modalities provide more anatomical information necessary for the success of the therapy" followed by "Better dimensional • Online channels (e.g., mailing lists) 71

RESULTS
• Academic institutions (interviews and online) 31 • Total number of participants 142 accuracy (if three-dimensional modalities, e.g., CBCT, were selected previously)", and followed by broad coverage of the anatomical region were the most chosen factors to influence the prescriptions of radiographic techniques during the implant planning phase (Table III and Chart 4).
During and directly after surgery (Table IV and Chart 5 A&B), periapical radiography (ASE) was the most selected modality (87% and 65%, respectively). During follow-up (Table V and Chart 6) of asymptomatic patients, PA (ASE) was also the most selected by 46%; Nonetheless, in the presence of postoperative complications, CBCT (ASE) was mostly preferred (32%). The CBCT was preferred the most during follow-up of symptomatic patients due to the extra information it provides regardless of any radiographic artefacts that could occur (caused by implants). Besides, the participants also claimed that broad coverage, availability and ease of access are factors that influence the imaging modality of choice during the follow-up phase (Table VI).
The majority of surveyees (56%) indicated that radiographic follow-up frequency (i.e., after the delivery of the prosthesis) was "After the first 6 months, 12 months, and then every year for a 10-year period" (Chart 7).
Comparisons between the level of formal training and the most frequently selected radiographic examination during various treatment phases, along with the motivating factors for their choice, were noted (Tables VII-IX).

DISCUSSION
It is evident from the results of this survey, that panoramic radiographs and CBCT were the most preferred combination for implant planning purposes among South African dentists. The CBCT modality was predominantly selected as a single examination or in combination with other modalities during the planning phase with an average of 91% of selections. Nevertheless, a variation of the preferred modalities depending on the anatomical region of the implant site was noted. Minor variations in the preferred radiographic examination were found between various dental speciali- Better dimensional accuracy (if three-dimensional modalities, e.g., CBCT, were selected previously) 87 Three-dimensional modalities provide more anatomical information necessary for the success of the therapy 110 Only three-dimensional modalities (e.g., CBCT), if guided implant surgery is considered 29 Other reasons 5 ties, therapy phases, and the anatomical regions of interest. CBCT (ASE) was predominantly favoured by OMFS and periodontists during implant planning in all anatomical regions investigated. On the contrary, prosthodontists and registrars predominantly preferred panoramic radiographs combined with CBCT. Both CBCT (ASE) and with combination with panoramic radiographs were selected by the majority of OMFR; while general practitioners pre-ferred CBCT either with panoramic radiographs or PA (only in one anatomic region investigated). During and immediately after the surgical phase, the majority of all participants preferred periapical radiographs (ASE).
During the follow-up of asymptomatic patients, PA only was preferred by periodontists, GP, registrars, and OMFR, while most prosthodontists and OMFS preferred PAN (ASE). However, during the follow-up of symptomatic patients, the prosthodontists, OMFS, OMFR, and registrars concurred on CBCT (ASE), while most GPs favoured a combination of PA and CBCT examinations. Moreover, PA and CBCT volumes and CBCT (ASE) were preferred by periodontists (39%, 39%, respectively) during the follow-up of symptomatic patients.
Fifty-six percent of participants indicated a followup frequency to be after 6, 12 months and annually afterwards for ten years.
Three-dimensional volumes were claimed to allow proper examination during the planning phase by providing extra anatomical details that are vital for the treatment success and, at the same time, advocating better dimensional accuracy. Moreover, broad coverage provided by a given imaging modality was a nonnegligible factor; while cost-related factors and radiation dose concerns were the least to affect their radiographic choices. On the other hand, 47% of participants advocated the useful use of CBCT regardless of any possible radiographic artefacts (e.g., beam hardening, caused by the implant body) during the assessment of symptomatic patients.   Inconsistency related to radiographical prescriptions for implant planning at the international level was mentioned 13 for being independent of social wealth and the level of "dental health".

In the light of international guidelines
The AAOMR2 advised in 2012 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". On the other hand, the E.A.O guidelines 8 published in 2012 stated that in case of the presence of adequate bone width after clinical evaluation, along with sufficient bone height and clear demarcation of the anatomical boundaries observed on conventional radiographs, then there is no need for further imaging.
Nevertheless, E.A.O mentioned the advantages of cross-sectional imaging e.g., better anatomical structure demarcation, promoting the prosthetic outcomes, assessment of bone defects, in case of bone augmentation, special techniques (e.g., zygomatic implants), and during computer-guided implantology. The ICOI 11 advised the use of CBCT must be justified on an individual basis and after a full clinical assessment. Nevertheless, "..., it is virtually impossible to predict which treatment cases would not benefit from having this additional information before obtaining it" 11 .
The findings of this investigation aimed at enriching the pool of evidence in South Africa with regards to the local imaging practices. Such type of evidence would help the decision-makers at local radiation regulatory authorities to formulate imaging guidelines that adapt/harmonize with the needs of the clinicians and the local working environment.

CONCLUSION
The majority of the surveyed south African dentists preferred the combination of panoramic radiographs and CBCT volumes for the implant planning phase, while the vast majority concur on the use of periapical radiographs (ASE) during and immediately after surgery. Periapical radiographs were also mostly chosen during the follow-up of asymptomatic patients and, by contrast, CBCT for those who appear with symptoms. The surveyed clinicians believe that CBCT provides extra anatomical information that is dimensionally more accurate.