Assessment of cone-beam CT technical image quality indicators and radiation dose for optimal STL model used in visual surgical planning.

OBJECTIVES: The aim of this study was to identify cone-beam computed tomography (CBCT) protocols that offer an optimal balance between effective dose and 3D model for orthognathic virtual surgery planning, using CT as a reference, and to assess whether such protocols can be defined based on technical image quality metrics. METHODS: Eleven CBCT (VISO G7, Planmeca Oy, Helsinki, Finland) scan protocols were selected out of 32 candidate protocols, based on effective dose and technical image quality measurements. Next, an anthropomorphic RANDO SK150 phantom was scanned using these 11 CBCT protocols and 2 CT scanners for bone quantity assessments. The resulting DICOM files were converted into STL models that were used for bone volume and area measurements in the predefined orbital region to assess the validity of each CBCT protocol for VSP. RESULTS: The highest CBCT bone volume and area of the STL models were obtained using normal dose protocol (F2) and ULD protocol (J13) which resulted in 48% and 96% of the mean STL bone volume and 48% and 95% of the bone area measured on CT scanners, respectively. CONCLUSIONS: The optimal normal dose CBCT protocol" F2" offered optimal bone area and volume balance for STL. The optimal CBCT protocol can be defined exhibited similar using CNR and MTF values that were similar with of those of the reference CT scanners'. CBCT scanner with selected protocols can offer a viable alternative to CT scanners for acquiring STL models for VSP at a lower effective dose.

Dental findings frequently overlooked in sinus computed tomography reports.

OBJECTIVES: Computed tomography (CT) and cone beam computed tomography (CBCT) represent the main imaging modalities used in rhinosinusitis patients and are also important in odontogenic sinusitis (OS) diagnostics. Reports, however, often lack information on dentition. Here, we aimed to determine how maxillary dentition is initially interpreted in rhinosinusitis patients' CT/CBCT reports and which dental findings in particular are potentially missed, thus needing more attention. STUDY DESIGN: CT/CBCT scans and radiological reports from 300 rhinosinusitis patients were analysed focusing specifically on dental findings. An experienced oral and maxillofacial radiologist re-evaluated the scans and the assessment was compared to the original reports using the McNemar test. RESULTS: From the 300 original reports, 233 (77.7%) mentioned the maxillary teeth. The most frequent statement (126/300, 42.0%) was 'no apical periodontitis'. Apical periodontitis and severe alveolar bone loss were significantly overlooked (p < 0.001). Amongst the 225 patients for whom the CT/CBCT report initially lacked information on dental pathology, 22 patients were diagnosed with apical periodontitis and 16 with severe alveolar bone loss upon re-evaluation. CONCLUSIONS: Dental pathology remains underreported in rhinosinusitis patients' CT/CBCT reports. Because these reports affect OS diagnostics, a routine and structured review of the maxillary teeth by a radiologist is necessary. Such examinations should encompass the maxillary teeth.

Dental health in patients with and without HPV-positive oropharyngeal and tongue cancer.

BACKGROUND: Human papilloma virus is associated with oral and oropharyngeal cancer. Our aim was to examine oral health in patients with oropharyngeal (OPSCC) and oral tongue cancer (OTSCC), expecting better oral health among OPSCC patients. MATERIAL AND METHODS: Fifty-five OPSCC patients with known HPV status and 59 OTSCC patients were randomly selected from a list of consecutive patients of the Helsinki University Hospital, Finland. Oral health was assessed from panoramic jaw radiographs. Total Dental Index (TDI) summarizing the dental health status was calculated and Finnish population study data were used for comparison. Descriptive statistics were used for analyses. RESULTS: Patients with HPV-positive OPSCC had higher periapical lesion index compared with HPV-negative OPSCC patients or with OTSCC patients. Residual roots were more common among OPSCC patients compared with OTSCC patients, because of their higher occurrence among HPV-negative OPSCC patients compared with OTSCC patients. Similarly, modified TDI score was significantly higher among OPSCC patients than among OTSCC patients, because of higher TDI score among HPV-negative OPSCC patients compared with OTSCC patients. OPSCC patients more often used a removable prosthesis than OTSCC patients. Dental health of the cancer patients was poorer when compared with the population data. CONCLUSIONS: Our study hypothesis was only partly confirmed. Periapical lesions were more prevalent among HPV-positive OPSCC patients, compared with the other groups. The number of residual roots was higher among HPV-negative subgroup. Thus, OPSCC patients had worse oral health parameters than OTSCC patients.

Surgical Treatment of Cherubism With the Use of ThreeDimensional Virtual Planning and CAD-CAM Resection Guides: A Case Report and Systematic Literature Review.

ABSTRACT: We report the use of a three-dimensional virtual surgical planning technique including both fusion and superimposition to obtain harmony and symmetry of the face in an 18-year-old woman suffering from cherubism. The treatment contained several threedimensional techniques that allowed precise planning and a predictable surgical outcome. The reduction plasty was successful, and the postoperative healing was uneventful. No relapse of the disease occurred after the surgical treatment and the sensation of the mentalis area recovered. The patient was satisfied with the aesthetic result and no additional surgery was needed. The surgical planning techniques described, and the CAD/CAM patient-specific resection guides seems to be safe and reliable in a one-step surgical treatment of cherubism patients after the disease has clearly ceased based on radiological findings. A systematic review of the literature on surgical correction of deformities due to cherubism was conducted. The systematic review of the existing literature was performed on the available studies from PubMed and Ovid Medline published before June 9, 2020. The search term was ''Cherubism.'' The inclusion criteria were: 1) full article published in English and 2) the patient had surgical treatment. We excluded the cases that included only minor surgery as biopsy or only treatment of unerupted teeth. The database identified 638 citations of which 50 met the eligibility criteria. The systematic review revealed no earlier use of surgical 3D planning in the treatment of cherubism.

Virtual Surgical Planning Combined With Intraoperative Navigation in Mandibular Bilateral Sagittal Split Osteotomy for Accurate Placement of Patient Specific Implants.

ABSTRACT: The aim of the study is to evaluate clinical methods to obtain a significantly improved fitting of patient specific implants (PSI) in bilateral sagittal split osteotomies and to evaluate the use of electromagnetic navigation as a potential guide for condyle positioning. A prospective study using (1) a solid bite registration index during preoperative computed tomography, (2) critical planning with regard to the condylar rotation, (3) a piezoelectric saw throughout the mandibular osteotomy, and (4) intraoperative navigation to determine the position of the PSIs and the mandibular segments intraoperatively was performed. Ten patients were treated. Five underwent bilateral sagittal split osteotomies and 5 bimaxillary osteotomy. All of the PSIs fitted precisely onto the mandible and the screws into the predrilled screw holes. The predetermined occlusion was obtained. A precise fitting of the PSIs in the lower jaw seems to be possible to achieve with above-mentioned methods. The intraoperative navigation system gives a possibility to verify the surgical outcome during surgery but is not accurate enough to be used as a virtual drill guide alone.

Odontogenic causes complicating the chronic rhinosinusitis diagnosis.

OBJECTIVES: Chronic rhinosinusitis (CRS) frequently stems from a dental origin, although odontogenic sinusitis (OS) remains underdiagnosed amongst different professionals. This study aimed to explore how often odontogenic causes are considered when diagnosing CRS. MATERIALS AND METHODS: Patient records from 374 new CRS patients treated at a tertiary-level ear, nose, and throat (ENT) clinic were selected. Entries and radiological reports were assessed exploring how often dentition was mentioned and OS was suspected, how often radiologists reported maxillary teeth, and how commonly typical OS microbial findings and unilateral symptoms occurred. RESULTS: Although 10.1% of the CRS diagnoses were connected to possible dental issues, teeth were not mentioned for 73.8% of patients. Radiological reports were available from 267 computed or cone beam computed tomographies, of which 25.1% did not mention the maxillary teeth. The reported maxillary teeth pathology was not considered in 31/64 (48.4%) cases. Unilateral symptoms associated with apical periodontitis (OR = 2.49, 95% CI 1.27-4.89, p = 0.008). Microbial samples were available from 88 patients, for whom Staphylococcus aureus was the most common finding (17% of samples). CONCLUSIONS: Odontogenic causes are often overlooked when diagnosing CRS. To provide adequate treatment, routine assessment of patient's dental history and status, careful radiograph evaluation, and utilization of microbial findings should be performed. Close cooperation with dentists is mandatory. CLINICAL RELEVANCE: Dental professionals should be aware of difficulties medical professionals encounter when diagnosing possible OS. Thus, sufficient knowledge of OS pathology is essential to both medical and dental professionals.

Did malpractice claims for failed dental implants decrease after introduction of CBCT in Finland?

OBJECTIVES: To examine the role of cone beam computed tomography (CBCT) in preventing failures in implant treatment. We hypothesize that the number of malpractice claims related to dental implant treatment would decrease after the first CBCT device came available in 2002 in Finland. MATERIAL AND METHODS: Data concerning malpractice claims related to dental implant treatment during the years 1997-2011 were collected from the Finnish Patient Insurance Centre (N = 330 subjects). We selected the cases that might have benefitted from the use of CBCT examination. These cases (n = 131) led to financial compensation due to permanent inferior alveolar nerve injury, improper implant position, or insufficient amount of bone for the implant. The annual total number of inserted dental implants, CBCT devices, and CBCT examinations in Finland were drawn from the national registers and used to estimate the impact of CBCT in preventing treatment failures. RESULTS: The most common reason for all failures (n = 268 implants) was an improper implant position (46.3%). The most common area of malpractices was upper front teeth (34%). We have noticed a fall in the rate of compensable malpractice cases concerning implant failure, simultaneously with CBCT technology emerging on the market. CONCLUSIONS: There may be an association between the increasing availability of CBCT equipment and the reducing frequency of compensable malpractice claims. CLINICAL RELEVANCE: It is possible that the use of CBCT may result in fewer compensable malpractice claims.

Activity of rheumatoid arthritis correlates with oral inflammatory burden.

To study oral health in patients with rheumatoid arthritis (RA) with emphasis on disease activity and treatment of RA. In this prospective cohort study 81 RA patients [53 early untreated RA (EURA) and 28 chronic RA (CRA) patients with inadequate response to synthetic disease modifying antirheumatic drugs (DMARDs)], underwent rheumatological [Disease Activity Score (28-joint) DAS28] and dental examinations [Total Dental Index (TDI), Decayed Missing Filled Teeth (DMFT) and Decayed Missing Filled Surfaces (DMFS)]. For controls, 43 volunteers were examined. After the examinations, EURA patients started treatment with synthetic DMARDs, oral and intra-articular glucocorticoids. CRA patients were candidates for biological DMARDs. The patients were re-examined mean 16 months later. Results were analyzed with descriptive statistics and logistic regression. TDI was higher in both RA groups at baseline compared to controls [EURA: 2 (2-3); CRA: 2 (1-3); controls 1 (1-3), p = 0.045]. DMFT [rs 0.561 (p = 0.002)] and DMFS [rs 0.581 (p = 0.001)] associated with DAS28 at baseline in CRA patients. After follow-up, DAS28 associated positively with DMFT [rs 0.384 (p = 0.016)] and DMFS [rs 0.334 (p = 0.038)] in EURA patients; as well as in CRA patients DMFT [rs 0.672 (p = 0.001)], DMFS [rs 0.650 (p = 0.001)]. RA patients already in the early phase of the disease had poorer oral health compared to controls. The caries indices associated with the activity of RA in both patient groups. Oral status may thus contribute to the development and further relate to the activity of RA.

Craniofacial and Dental Features in Six Children With Cherubism.

Cherubism is an autosomal-dominant benign bone disorder, characterized by fibro-osseous lesions in the mandible and maxilla commonly caused by mutations in the SH3-binding protein 2-gene. The purpose of the authors' study was to analyze craniofacial and dental features of children diagnosed with cherubism, describe their treatment, and assess their dental age compared with norms for Finnish children. Six children were diagnosed, followed up and treated due to dental and skeletal disorders caused by cherubsim. The patients were followed up for an average of 91.5 months with emphasis on the skeletal changes and development of dentition. The treatment consisted of minor orthodontic treatment, dental extractions, and exposures. One patient underwent cosmetic mandibular surgery. All patients had lesions in the lower jaw and 5 of 6 patients had lesions in the maxilla as well. The patients were characterized by varying swelling of the jaws, premature loss of deciduous teeth in the affected area and widely spaced, displaced, un-erupted, or absent permanent teeth. The dental age was delayed at younger age but near to normal or even a little ahead at older age. Even though cherubism affects the jaws, jaw positions, and malocclusion, no common dentofacial proportions associated with the disease could be confirmed by cephalometric analysis. The surgical interventions did not provoke adverse reactions or local growth of the lesions.

Malpractice claims related to tooth extractions.

OBJECTIVE: The aim of this study was to analyze malpractice claims related to tooth extractions in order to identify areas requiring emphasis and eventually to reduce the number of complications. MATERIAL AND METHODS: We compiled a file of all malpractice claims related to tooth extractions (EBA code) between 1997 and 2010 from the Finnish Patient Insurance Centre. We then examined the data with respect to date, tooth, surgery, injury diagnosis, and the authority's decision on the case. RESULTS: The material consisted of 852 completed patient cases. Most of the teeth were third molars (66 %), followed by first molars (8 %), and second molars (7 %). The majority of claims were related to operative extraction (71 %) followed by ordinary extraction (17 %) and apicoectomy of a single-rooted tooth (7 %) or multi-rooted tooth (2 %). The most common diagnosis was injury of the lingual or inferior alveolar nerve. According to the authority's decision, the patient received compensation more often in cases involving a third molar than other teeth (56 vs. 46 %, P < 0.05). CONCLUSION: The removal of a mandibular third molar was the basis for the majority of malpractice claims. CLINICAL RELEVANCE: To reduce the numbers of lingual and inferior alveolar nerve injuries, the removal of mandibular third molars necessitates recent and high-quality panoramic radiograph, preoperative assessment of the difficulty of removal, and consciousness of the variable anatomical course of the lingual nerve.

CT of facial fracture fixation: an experimental study of artefact reducing methods.

OBJECTIVES: This study aimed to determine the optimal post-operative CT imaging method that enables best visualization of facial bony structures in the vicinity of osteosynthesis material. METHODS: Conducted at Töölö Hospital (Helsinki, Finland), this study relied on scanning a phantom with CBCT, 64-slice CT and high-definition multislice CT with dual-energy scan (providing monochromatic images of 70-, 100-, 120- and 140-keV energy levels) and iterative reconstruction (IR) methods. Two radiologists assessed the image quality, and the assessments were analyzed. In addition, a physicist performed a semi-quantitative analysis of the metal-induced artefacts. RESULTS: The three subjects most easily assessed were the loose screw and both the bone structure and the fracture further away from the screw and the plate. Soft tissues adjacent to the screw and the plate remained more difficult for assessment. Both image interpreters agreed that the artefacts disturbed their assessments under dual energy. Metal artefacts disturbed the least under multislice CT with IR [adaptive statistical iterative reconstruction (ASiR) and VEO]. Neither interpreter found metal suppression helpful in CBCT. CONCLUSIONS: CBCT with or without a metal artefact reduction algorithm was not optimal for post-operative facial imaging compared with multislice CT with IR. Multislice CT with ASiR filtering offered good image quality performance with fast image volume reconstruction, representing the current sweet spot in post-operative maxillofacial imaging.

Rapid prototyped patient specific guiding implants in critical mandibular reconstruction.

Large tumours of the mandible need immediate reconstruction to provide continuity of the mandible, satisfactory function of the jaw, as well as an acceptable aesthetic outcome. In this prospective study we described the immediate reconstruction of the mandible using computer aided design and 15 rapid prototyped patient specific implants (PSI) in 14 patients suffering from benign or malignant tumours demanding continuity resection of the mandible. The scaffold PSI was filled with ß-tricalcium phosphate granules and autologous bone. Microvascular reconstruction was additionally needed in 12/15 cases. The clinical follow up was on average 33 months and the radiological follow up was on average 21 months. In nine cases the healing was uneventful. One patient lost the microvascular flap during the first postoperative week and one patient needed a revision due to perforation of the mucosa at the site of the PSI. Four patients had a major complication due to perforation of the mucosa leading to infection, which resulted in the total or partial removal of the PSI. The PSI seems to be a promising solution for treatment of patients demanding large reconstruction after mandible resection. The benefits are decreased rate of donor site complications and more accurate and prompt surgical procedure.

Ultrasonographic localization of the thyroid gland for its optimal shielding prior to lateral cephalometric radiography: a pilot study.

OBJECTIVES: Lateral cephalometric radiography is a common radiographic examination technique in children. The exclusion of the thyroid gland from the primary X-ray beam is important especially with children. However, patient treatment might require displaying the four most cranial cervical vertebrae (C1-C4) for the assessment of cervical vertebral maturation. Our aim was to present a safe way to display C1-C4 and exclude the thyroid gland from the X-ray beam during lateral cephalometric radiography. METHODS: The thyroid glands of 25, 7- to 12-year-old patients were localized by ultrasound examination and shielded prior to lateral cephalometric radiography. A roentgen-positive mark was taped on the patient's skin at the level of most cranial level of the thyroid gland in the midsagittal plane. After exposure, each lateral cephalometric radiograph (LCR) was analyzed for the visibility of the cervical vertebrae. The distance between the ear post and the highest edge of the thyroid shield (TS) at the lateral part of the neck was measured and compared with the distance between the centre of the radiological external auditory meatus, and a roentgen-positive mark was made on the LCR. RESULTS: 68% of the LCRs displayed C1-C4, and the rest of them displayed C1-C3. In all of the patients, the highest edge of the TS in the lateral parts of the neck was located in a higher position than the actual most cranial level of the thyroid gland. CONCLUSIONS: Despite localizing the thyroid gland prior to lateral cephalometric radiography, simultaneous visualization of C1-C4 and exclusion of the thyroid gland from the primary X-ray beam during lateral cephalometric radiography might not be completely possible in children because of the design and poor fitness of the TS.

Rapid prototyping modelling in oral and maxillofacial surgery: A two year retrospective study.

BACKGROUND: The use of rapid prototyping (RP) models in medicine to construct bony models is increasing. MATERIAL AND METHODS: The aim of the study was to evaluate retrospectively the indication for the use of RP models in oral and maxillofacial surgery at Helsinki University Central Hospital during 2009-2010. Also, the used computed tomography (CT) examination - multislice CT (MSCT) or cone beam CT (CBCT) - method was evaluated. RESULTS: In total 114 RP models were fabricated for 102 patients. The mean age of the patients at the time of the production of the model was 50.4 years. The indications for the modelling included malignant lesions (29%), secondary reconstruction (25%), prosthodontic treatment (22%), orthognathic surgery or asymmetry (13%), benign lesions (8%), and TMJ disorders (4%). MSCT examination was used in 92 and CBCT examination in 22 cases. Most of the models (75%) were conventional hard tissue models. Models with colored tumour or other structure(s) of interest were ordered in 24%. Two out of the 114 models were soft tissue models. CONCLUSIONS: The main benefit of the models was in treatment planning and in connection with the production of pre-bent plates or custom made implants. The RP models both facilitate and improve treatment planning and intraoperative efficiency. KEY WORDS: Rapid prototyping, radiology, computed tomography, cone beam computed tomography.

Dental cone beam CT: A review.

For the maxillofacial region, there are various indications that cannot be interpreted from 2D images and will benefit from multiplanar viewing. Dental cone beam CT (CBCT) utilises a cone- or pyramid-shaped X-ray beam using mostly flat-panel detectors for 3D image reconstruction with high spatial resolution. The vast increase in availability and amount of these CBCT devices offers many clinical benefits, and their ongoing development has potential to bring various new clinical applications for medical imaging. Additionally, there is also a need for high quality research and education. European guidelines promote the use of a medical physics expert for advice on radiation protection, patient dose optimisation, and equipment testing. In this review article, we perform a comparison of technical equipment based on manufacturer data, including scanner specific X-ray spectra, and describe issues concerning CBCT image reconstruction and image quality, and also address radiation dose issues, dosimetry, and optimisation. We also discuss clinical needs and what type of education users should have in order to operate CBCT systems safely. We will also take a look into the future and discuss the issues that still need to be solved.

Dentomaxillofacial imaging with panoramic views and cone beam CT.

Panoramic and intraoral radiographs are the basic imaging modalities used in dentistry. Often they are the only imaging techniques required for delineation of dental anatomy or pathology. Panoramic radiography produces a single image of the maxilla, mandible, teeth, temporomandibular joints and maxillary sinuses. During the exposure the x-ray source and detector rotate synchronously around the patient producing a curved surface tomography. It can be supplemented with intraoral radiographs. However, these techniques give only a two-dimensional view of complicated three-dimensional (3D) structures. As in the other fields of imaging also dentomaxillofacial imaging has moved towards 3D imaging. Since the late 1990s cone beam computed tomography (CBCT) devices have been designed specifically for dentomaxillofacial imaging, allowing accurate 3D imaging of hard tissues with a lower radiation dose, lower cost and easier availability for dentists when compared with multislice CT. Panoramic and intraoral radiographies are still the basic imaging methods in dentistry. CBCT should be used in more demanding cases. In this review the anatomy with the panoramic view will be presented as well as the benefits of the CBCT technique in comparison to the panoramic technique with some examples. Also the basics as well as common errors and pitfalls of these techniques will be discussed. Teaching Points • Panoramic and intraoral radiographs are the basic imaging methods in dentomaxillofacial radiology.• CBCT imaging allows accurate 3D imaging of hard tissues.• CBCT offers lower costs and a smaller size and radiation dose compared with MSCT.• The disadvantages of CBCT imaging are poor soft tissue contrast and artefacts.• The Sedentexct project has developed evidence-based guidelines on the use of CBCT in dentistry.

Rapid prototyped patient specific implants for reconstruction of orbital wall defects.

Defects of orbital walls can be reconstructed using implants. The authors report a safe and accurate method to reconstruct bone defects in the orbital area using patient specific implants. A detailed process description of computer aided design (CAD) reconstructive surgery (CRS) is introduced in this prospective study. The 3D volumetric virtual implant was design using MSCT data and PTCProEngineer™ 3D software. The intact orbital cavity of twelve patients was mirrored to the injured side. Specific ledges steered the implant into correct place. Postoperatively the position was assessed using image fusion. One implant (8%) was rejected due to chemical impurities, two (16%) had a false shape due to incorrect CAD. Data of thin bone did not transfer correctly to CAD and resulted in error. One implant (8%) was placed incorrectly. Duration of the CRS was in average 1.17 h, correspondingly 1.57 h using intraoperative bending technique. The CRS process has several critical stages, which are related to converting data and to incompatibility between software. The CRS process has several steps that need further studies. The data of thin bone may be lost and disturb an otherwise very precise technique. The risk of incorporating impurities into the implant must be carefully controlled.

Cone beam computed tomography in the assessment of alveolar bone grafting in children with unilateral cleft lip and palate.

OBJECTIVES: To quantify the treatment outcome of secondary alveolar bone grafting (SABG) in individuals with unilateral cleft lip and palate using cone beam computed tomography (CBCT) and to reveal needs for improvement in surgical technique. MATERIAL AND METHODS: CBCT images taken 6 months after SABG of 35 patients were analysed. Vertical and horizontal bone supports of the grafted bone at three levels of the roots of the adjacent teeth were classified, the height of the nasal floor was compared with the unaffected side, and the inter- and intraexaminer reproducibility of these evaluations was assessed. RESULTS: The grafted bone filled the defect in all three vertical measurement levels in 34 per cent. The labiopalatal thickness of the grafted bone was good in at least one-third of the root length in 66 per cent and fair in 34 per cent. Typically, the bone graft was deficient in the apical and palatal direction. Clear asymmetry in the nasal floor was found in 72 per cent. Kappa values indicated excellent agreement for all but one measured parameter. LIMITATIONS: This is a preliminary study involving only a limited number of study subjects. CONCLUSIONS: Our results showed mainly a good or fair treatment outcome. Deficiency of the bone graft was observed mostly in the apical and palatal areas of the defect. Asymmetry of the nasal floor was observed frequently. Careful insertion of the bone graft towards the palatal and apical direction of the cleft is recommended.

[Cone beam computed tomography and its clinical applications]. / Kartiokeilatietokonetomografia ja sen kliiniset sovellukset.

The rapid progress in imaging techniques has led to the introduction of new methods in many sections of radiology. While cone beam computed tomography is a fairly recent newcomer, it is a widely applied, precise three-dimensional method for imaging hard tissue structures especially in dental radiology. In addition to the precise imaging of hard tissue structures, its benefits include a smaller irradiation exposure than in conventional computed tomography, as well as lower price and, as a rule, smaller size of the equipment. With a different equipment design the method is also applicable to the imaging of soft tissues.

Availability of CBCT and iatrogenic alveolar nerve injuries.

OBJECTIVE: To examine whether the rapid increase in the availability of cone-beam computed tomography (CBCT) has changed the number of inferior alveolar nerve (IAN) injuries related to the removal of mandibular third molars in Finland. The hypothesis was that the number of nerve injuries should diminish due to better imaging methods. MATERIALS AND METHODS: The number of CBCT devices, the annual number of CBCT examinations and the number of permanent IAN injuries occurring between 1997 and 2007 were analyzed. The data was collected from three national registers: the Radiation and Nuclear Safety Authority, the Social Insurance Institution and the Patient Insurance Centre. A detailed analysis was made from the cases of permanent IAN injuries. RESULTS: The first CBCT device was registered in 2002 and the cumulative number of these devices in 2009 was 22. There was an increase from 555 to 3160 in the number of annual CBCT examinations during the period 2004-2009. The total number of permanent IAN injuries during the years 1997-2007 was 129 and remained stable throughout the period (regression analysis, p = 0.974, r (2) = 0.01). CONCLUSIONS: Contrary to this hypothesis, the availability of CBCT devices has had no significant influence on the number of IAN injuries related to mandibular third molar removals in Finland. More education should be given to optimize the use of CBCT to cover difficult cases that may give rise to complications.