The impact of cone beam computer tomography field of view on the precision of digital intra-oral scan registration for static computer-assisted implant surgery: A CBCT analysis.

OBJECTIVES: Registration of intra-oral surface scans to cone beam computer tomography (CBCT) is critical in the digital workflow for static computer-aided implant surgery (sCAIS). This study aimed to assess the impact of CBCT field of view (FoV) on the precision of digital intra-oral scan registration. MATERIALS AND METHODS: Cone beam computer tomography data and intra-oral scans from 20 patients were included. Small FoV CBCT's were created by digitally segmenting a large FoV into three sextants. Virtual implant planning was performed. Digital intra-oral scans were repeatedly registered onto their corresponding large and small FoV CBCT datasets. The distances and angulations between the matching implant positions of each repeated registration were used to determine the precision of the registration process. Wilcoxon Signed Rank Paired Tests were used to compare the differences between large FoV and small FoV. The threshold for statistical significance was set at p = .05. RESULTS: Differences in 3D implant position based on the registration precision between small FoV and large FoV present at both the implant entry point (0.37 ± 0.25 mm vs 0.35 ± 0.23 mm, p = .482) and implant tip (0.49 ± 0.34 mm vs 0.37 ± 0.24 mm, p < .001). Differences in overall angular precision were observed between small FOV and large FoV (1.43 ± 1.36° vs 0.51 ± 0.38°, p < .001). CONCLUSION: CBCT with a small FoV is accompanied by greater precision errors in intra-oral scan registration. However, when sufficient well-distributed teeth are visible in small FoV CBCT, the precision of digital intra-oral scan registration appears to be within clinically acceptable limits for sCAIS.

Tilted versus axial implant distribution in the posterior edentulous maxilla: A CBCT analysis.

OBJECTIVES: This study aimed to determine whether distally angulating an implant is a successful strategy to avoid the maxillary sinus and the need for bone augmentation, while increasing the anterior-posterior (A-P) implant distribution in the edentulous maxilla. MATERIALS AND METHODS: In 115 patients with edentulous maxillae, virtual implant planning was performed utilizing cone-beam computer tomographs. Axial (8 mm length) and tilted (12 mm length) dental implants with 30-degree and 45-degree angulation were virtually positioned to avoid entering the maxillary sinus, while maximizing A-P distribution. Measurements were made between the tilted and axial implants to assess the change in A-P distribution of implants at the implant and abutment levels. RESULTS: Forty-seven sites (20.4%) were not able to have either treatment modality with insufficient bone for implant placement. Axial implants were placed more distally than 45-degree and 30-degree tilted implants in 24% and 42% of sites, respectively. The average change in A-P spread measured at the implant level, for 30- and 45-degree tilted implants was -0.25 mm (95% CI -0.76, 0.26) and 1.9 mm (95% CI 1.4, 2.3), respectively. When measured from the center of each multi-unit abutment the average increase in A-P distances for tilted implants appears larger in the 30-degree and 45-degree groups by 0.97 mm and 1.74 mm, respectively compared to measurements at the implant level. CONCLUSIONS: Angulating 12 mm implants provides a limited increase in A-P distribution of implants in edentulous rehabilitation in most situations. In certain patients, the use of 8mm axial implants may provide a greater A-P spread.

Radiographic markers for merging virtual data sets.

A procedure for registering digital intraoral surface scans onto cone beam computed tomography in the presence of significant scatter artifact is described. The technique uses chairside-fabricated composite resin markers placed on well-distributed teeth to serve as common landmarks in each digital data set for accurate registration. This straightforward, noninvasive, and cost-effective technique facilitates registration without the need for a specialized armamentarium or radiographic templates.

Quantitative evaluation of maxillary alveolar cortical bone thickness and density using computed tomography imaging.

INTRODUCTION: Primary stability is essential to the success of orthodontic mini-implants (OMIs) and heavily depends on the mechanical retention between OMIs and their supporting bone. Alveolar cortical bone commonly serves as the supporting bone for OMIs during treatment. The purposes of this study were to characterize alveolar cortical bone thickness and density in the maxilla and to explore patient factors that may significantly affect these bone properties. METHODS: Sixty medical computed tomography scans of the maxilla were analyzed from a selected sample of patients seen at the Radiology Department of Boston Children's Hospital. Interradicular alveolar bone thickness and density were measured at 2, 4, 6, and 8 mm from the buccal and palatal alveolar bone crests using the Synapse 3D software (version 4.1; FUJIFILM Medical Systems USA, Stamford, Conn). Analyses were conducted with STATA /1C (version 12.0 for Windows; StataCorp, College Station, Tex) using multivariate mixed-effects regression models and paired t tests. RESULTS: Mean age and body mass index of the study sample were 17.88 years and 22.94 kg/m2, respectively. Cortical bone density and thickness significantly increased from the coronal (2 mm) to the apical (8 mm) regions of the alveolar bone (P <0.05). At 8 mm from the alveolar crest, interradicular buccal cortical bone was thickest (1 mm) and densest (1395 Hounsfield units) between the first and second molars. On the palatal side, the thickest bone (1.15 mm) was found between the canine and first premolar; it was similarly densest (1406 Hounsfield units) between the first premolar and canine, and between the first premolar and second premolar interradicular bones. On average, palatal cortical bone was thicker and denser compared with buccal; this difference was statistically significant (P <0.01) in the anterior and middle maxilla, with the anterior maxillary region showing the greatest difference. Female subjects have significantly denser bone compared with male subjects; however, sex is not significantly associated with bone thickness. Body mass index and age are positively associated with bone thickness and density. Radiologic absence of bone was more commonly seen in the anterior maxilla. CONCLUSIONS: Alveolar bone properties vary in the maxilla in patterns that could guide clinicians in selecting sites best suited for placement of OMIs.

Interstate Practice of Dental Teleradiology in the United States: The Effect of Licensing Requirements on Oral and Maxillofacial Radiologists' Practice Patterns.

BACKGROUND: In the United States, each state has independent licensing standards. Dentists wishing to practice in more than one state must apply to each individually. The goal of this study was to assess whether board-certified oral and maxillofacial radiologists interpreted images taken outside the states in which they were licensed and whether coverage provided by the malpractice insurance plans to which they subscribed affected their behavior. MATERIALS AND METHODS: An electronic survey was sent to all current members of the American Board of Oral and Maxillofacial Radiology, with a response rate of 74%. Descriptive statistics were calculated. RESULTS: The majority of respondents (54.6%) indicated they write reports for patients in states for which they do not have a dental license. An even larger majority (80.0%) do not know whether their malpractice insurance protects them in these cases. Qualitative responses indicate that there is confusion among practitioners as to what is legally permitted pertaining to teledentistry of this nature. CONCLUSIONS: Much of the work in which oral and maxillofacial radiologists engage may be considered teledentistry. In other settings, teledentistry has been proposed as a means to improve access to care for vulnerable populations, yet current licensure laws may make this more difficult to implement. Based on the results of our survey, many oral and maxillofacial radiologists in practice may be considered to be practicing without a license. Portability of diagnostic images may make it more difficult to enforce geographic practice boundaries. A national licensure system would be easier to enforce while maintaining high levels of patient safety.

Merging Mandibular Virtual Data Sets in Partially Edentulous Patients with a High-level of Scattering on Cone-beam CT Scans: A Technical Report.

Digital implant planning, utilizing the convergence of digital surface scanners, cone beam computer tomography (CBCT) scans, and advanced planning software, has transformed dental implantology. The merging of these data sets through triangulation of landmarks provides a detailed digital model of the jaws, facilitating precise implant positioning in edentulous areas. A critical step in this digital workflow is the accurate merging of DICOM files with STL/PLY/OBJ files, which underpins the design and fabrication of surgical templates for accurate implant placement. Errors in this phase can lead to implant mispositioning or damage to adjacent structures. Particularly in partial edentulism, the merging is based on the occlusal topography of the remaining teeth but scattering in the CBCT data-caused by interactions of radiation with radiodense materials-can complicate this process or even render it impossible. The manuscript presents a technique utilizing radiopaque markers to overcome scattering effects, ensuring accurate dataset superimposition in the mandible.

Maxillary sinus opacification after surgery in asymptomatic patients: Transient swelling of the sinus mucosa or graft dispersion into the maxillary sinus. A radiographic report of three cases after a follow-up period of at least 5 years.

Maxillary sinus grafting is a predictable regenerative technique to facilitate maxillary posterior implant placement when there is insufficient vertical bone height inferior to the maxillary sinuses to allow placement of implants of adequate dimensions. It enables an increase in vertical bone height, which makes implant placement easier. Maxillary sinus mucosal membrane perforation is one of the most common intraoperative complications during maxillary sinus grafting and may result in extrusion of graft material into the sinus. When this occurs, the mucociliary function of the maxillary sinus may expel the extruded graft material through its natural ostium, though graft particles may remain in the sinus or possibly occlude the natural ostium. After grafting, transient maxillary sinus mucosal oedema may occur. A postoperative CBCT scan may reveal varying degrees of sinus opacification, namely partial, subtotal or total. Although it is always possible to identify graft material, which may enter the sinus as a result of membrane perforation that might not even be visible to the implantologist during the surgical procedure, it is challenging to assess whether sinus opacification is due to mucosal thickening or mucus accumulation. The aim of the present case series was to offer a pragmatic approach to managing asymptomatic patients whose CBCT scans demonstrated partial, subtotal or total maxillary sinus opacification with bone graft particles that seemed to have been extruded into the sinus.

Risk indicators for gingival recession in the esthetic zone: A cross-sectional clinical, tomographic, and ultrasonographic study.

BACKGROUND: To evaluate the risk indicators associated with midfacial gingival recessions (GR) in the natural dentition esthetic regions. METHODS: Cone-beam computed tomography (CBCT) results of thirty-seven subjects presenting with 268 eligible teeth were included in the cross-sectional study. Clinical measurements included presence/absence of midfacial GR; the depth of the midfacial, mesial, and distal gingival recession; the recession type (RT); keratinized tissue width (KT); and attached gingiva width (AG). Questionnaires were utilized to capture patient-reported esthetics and dental hypersensitivity for each study tooth. Buccal bone dehiscence (cBBD) and buccal bone thickness (cBBT) were measured on the CBCT scans. High-frequency ultrasonography was performed to assess gingival thickness (GT) and buccal bone dehiscence (uBBD). Intraoral optical scanning was obtained to quantify the buccolingual position of each study site (3D profile analysis). Multilevel logistic regression analyses with generalized estimation equations were performed to assess the factors associated with the conditions of interest. RESULTS: The presence of midfacial GR was significantly associated with the history of periodontal treatment for pocket reduction (OR 7.99, p = 0.006), KT (OR 0.62, p < 0.001), cBBD (OR 2.30, p = 0.015), GT 1.5 mm from the gingival margin (OR 0.18, p = 0.04) and 3D profile 1 mm from the gingival margin (OR 1.04, p = 0.001). The depth of midfacial GR was significantly correlated to previous history of periodontal treatment (OR 0.96, p = 0.001), KT (OR -0.18, p < 0.001), presence of bone fenestration (OR 0.24, p = 0.044), and cBBD (OR 0.43, p < 0.001). The depth of midfacial GR was also the only factor associated with patient-reported esthetics (OR -3.38, p = 0.022), while KT (OR 0.77, p = 0.018) and AG (OR 0.82, p = 0.047) were significantly correlated with patient-reported dental hypersensitivity. CONCLUSIONS: Several risk indicators of midfacial and interproximal GR in the esthetic region were identified. The use of imaging technologies allowed for detection of parameters associated with the conditions of interest, and, therefore, their incorporation in future clinical studies is advocated. Ultrasonography could be preferred over CBCT for a noninvasive assessment of periodontal phenotype.

Should Dentists Treat Despite Medical Contraindications?

Dental treatment is contraindicated by some health conditions. As patients live longer and dentists treat more patients with underlying disease, patients often need general medical care before dental care can proceed. For US patients without access to health care and their dentists, lack of medical-dental integration can generate inequity, poor outcomes, and ethical questions. Individual dentists should advocate for patients who need general health care prior to dental care, but the professions of dentistry and medicine must also respond to macro-level health system gaps and failures.

Influence of Implant Diameter and Taper on Virtual Implant Placement in the Maxillary Central Incisor Position: A CBCT Analysis.

PURPOSE: This study aimed to assess the influence of implant diameter and taper on the proximity of virtually planned maxillary central incisor implants to the nasopalatine canal and adjacent anatomical structures. MATERIALS AND METHODS: Virtual implant planning was performed in the maxillary central incisor position. The distance between the implant and the incisive canal (IC) and the thickness of the surrounding buccal and palatal bone walls were measured. Implants were categorized as having an exposed implant surface, thin bone, or moderate/thick bone. Measurements were repeated for regular-/narrow-diameter and parallel/tapered implants. RESULTS: A total of 60 patients were included, and 240 implants (60 of each type: 3.3-bone level [BL], 3.3-bone level tapered [BLT], 4.1-BL, and 4.1-BLT) were planned. The percentages of implants with between 0 and 0.5 mm of remaining bone in the coronal aspect of the IC were 31.6% for 4.1-BL/BLT and 6.6% for 3.3-BL/BLT (P < .001). The percentage of implants with IC exposure was 13.3% for 4.1-BL/BLT and 6.6% for 3.3-BL/BLT (P < .001). The frequency of sites that required bone augmentation at the coronal facial aspect (< 1 mm) was 52.6% and 33.9% for 4.1-BL/BLT and 3.3-BL/BLT, respectively. At the apical portion, the percentages of sites requiring bone augmentation at the facial aspect were 59.9%, 49.9%, 31.6%, and 23.3% for 4.1-BL, 3.3-BL, 4.1-BLT, and 3.3-BLT, respectively (P < .001). CONCLUSION: The proximity of the nasopalatine canal is often < 0.5 mm from regular-diameter virtually planned implants at the most coronal aspect in the maxillary central incisor position. In these situations, the selection of narrowdiameter implants significantly lowers the incidence of implant exposure and the need for additional management of the nasopalatine canal and also results in greater residual buccal and lingual bone thicknesses surrounding the implant. As expected, tapered implants reduced the risk of implant exposure through the buccal cortex at the apical aspect.

Radiographic protrusion of dental implants in the maxillary sinus and nasal fossae: A multidisciplinary consensus utilising the modified Delphi method.

The aim of the present study was to generate an international and multidisciplinary consensus on the clinical management of implant protrusion into the maxillary sinuses and nasal fossae. A total of 31 experts participated, 23 of whom were experts in implantology (periodontologists, maxillofacial surgeons and implantologists), 6 were otolaryngologists and 2 were radiologists. All the participants were informed of the current scientific knowledge on the topic based on a systematic search of the literature. A list of statements was created and divided into three surveys: one for all participants, one for implant providers and radiologists and one for otolaryngologists and radiologists. A consensus was reached on 15 out of 17 statements. According to the participants, osseointegrated implants protruding radiographically into the maxillary sinus or nasal fossae require as much monitoring and maintenance as implants fully covered by bone. In the event of symptoms of sinusitis, collaboration between implant providers and otolaryngologists is required. Implant removal should be considered only after pharmacological and surgical management of sinusitis have failed.

Dental therapy in the United States: Are developments at the state level a reason for optimism or a cause for concern?

Access to dental care continues to be a challenge for millions of vulnerable Americans. In more than 50 nations worldwide, dental therapists (DTs), mid-level providers who deliver a limited scope of dental care under the supervision of a dentist, have helped increase access to needed care. Since 2003, when the Alaska Native Tribal Health System introduced DTs as part of the Federally authorized Alaska Community Health Aide Program, a total of 13 states have adopted the role. However, as of April 2020, there are fewer than 150 DTs in practice throughout the country, and educational and licensing requirements as well as scope of practice vary between each state. Such heterogeneity makes the training and recruitment of future DTs a challenge. This article summarizes the current state of the DT workforce in the United States and discusses the possible future of the profession as other states contemplate adopting the model in the face of ongoing oral health disparities.

A survey of dental therapists' practice patterns and training in Minnesota.

BACKGROUND: Expansion of the dental team may play a role in increasing access to oral health care. In 2009, Minnesota became the first state to formally license dental therapists (DTs). METHODS: The authors surveyed DTs and advanced dental therapists (ADTs) in Minnesota to gain a better understanding of those who enter the profession and their motivation for doing so, as well as to solicit their opinions on the overall structure of dental therapy education and the regulatory aspects of the profession. RESULTS: The response rate was 53.1%. DTs and ADTs were split on whether a dental hygiene degree should be required. Primary reasons for entering dental therapy included more autonomy and a larger scope of practice. Respondents expressed a desire for broadened prescribing rights. The median annual income was in the $81,000 through $90,000 bracket. CONCLUSIONS: Minnesota DTs and ADTs must practice in underserved communities. However, their ability to expand access to oral health care is affected by their licensure requirement, scope of practice, and prescription rights. PRACTICAL IMPLICATIONS: Policy makers considering dental therapy legislation must consider educational requirements and scope of practice when crafting state legislation. Broadening the scope of practice may allow for more impactful care for at-risk communities.

Conebeam computed tomography: legal considerations.

With the introduction of conebeam computed tomography (CBCT) in the early 2000s, oral and maxillofacial radiology fully entered the modern world of 3-dimensional (3D) radiographic imaging. Although conventional or medical computed tomography (CT) had been available since the 1970s, with few exceptions, it had not been widely used in dentistry. In the early days of conventional CT, the machines were limited in number, restricting their use to only the most beneficial of purposes--for example, imaging of the brain. The cost of a CT examination was also prohibitive. For these reasons, the modality in dentistry was used almost exclusively in oral and maxillofacial surgery and sparingly at that. Even as the limitations of access and cost disappeared, the cost-benefit ratio when the x-ray dose was compared in relation to the information to be gained was generally considered to be unfavorable for the use of CT scans in most dental applications.

Can modifying shielding, field of view, and exposure settings make the effective dose of a cone-beam computed tomography comparable to traditional radiographs used for orthodontic diagnosis?

OBJECTIVES: To analyze the effect of changes in exposure settings, field of view (FOV), and shielding on radiation to an adult and child phantom from cone-beam computed tomography (CBCT) imaging compared to panoramic and lateral cephalometric radiographs. MATERIALS AND METHODS: The effective dose to an adult and child anthropomorphic phantom by the CS 9300 using various scan protocols was recorded. Absorbed radiation was measured with optically stimulated luminescence dosimeters and effective dose calculated using 2007 International Commission on Radiological Protection tissue weighting factors. Scan protocols included different FOVs, voxel sizes, and standard versus low-dose protocols. Radiation shielding was used when it did not interfere with FOV. Panoramic and lateral cephalometric radiographs were taken with the Orthophos SL. RESULTS: Even with shielding, smaller FOVs, and increased voxel sizes, the effective dose of standard CBCT scans was higher than panoramic and lateral cephalometric radiographs. A shielded limited FOV standard scan combined with a lateral cephalometric radiograph resulted in a lower dose (P < .001) than a full FOV standard scan. Low-dose shielded scans resulted in significant dose reductions to the adult (P < .05) and child (P < .001) phantoms compared to the respective panoramic and lateral cephalometric radiographs combined. Image quality analysis was not possible with radiation equivalent phantoms. CONCLUSIONS: Unlike standard CBCTs, shielded low-dose CBCT protocols in the CS 9300 have lower effective doses than conventional radiographs for adult and child phantoms. If high resolution and cranial base visualization are necessary, combining a shielded LFOV standard exposure with a cephalometric radiograph is recommended.

Effect of dental restorations and prostheses on radiotherapy dose distribution: a Monte Carlo study.

Dental restorations, fixed prosthodontics, and implants affect dose distribution in head and neck radiation therapy due to the high atomic number of the materials utilized. The backscatter of electrons from metallic materials due to the impinging treatment x-ray results in localized dose enhancements. These dose enhancements cause localized mucositis in patients who have dental work, a significant clinical complication. We investigated the backscatter effect of 23 configurations of dental work using the EGS4nrc Monte Carlo (MC) simulation system. We found that all-metal fixed partial dentures caused the highest amount of dose enhancement--up to 33%--while amalgam restorations did not cause a significant amount. Restorations with a ceramic veneer caused up to 8% enhancement. Between 3 mm and 5 mm of water-equivalent material almost completely absorbed the backscatter. MC simulations provide an accurate estimate of backscatter dose, and may provide patient-specific estimates in future.

Minimally invasive alveolar ridge augmentation procedure (tunneling technique) using rhPDGF-BB in combination with three matrices: a case series.

This study investigated a minimally invasive surgical procedure for alveolar ridge augmentation that combined recombinant human platelet-derived growth factor BB (rhPDGF-BB) and three different matrices. The minimally invasive tunneling ridge augmentation procedure was applied to 12 patients randomized into three groups: rhPDGF-BB (0.3 mg/mL) was combined with freeze-dried bone allograft (FDBA; group A), anorganic bovine bone graft (ABBG; group B), or anorganic bovine bone graft/mineralized collagen bone substitute (ABBG/MCBS; group C). Computed tomography (CT) scans were obtained presurgically and prior to 14-week re-entry surgery. Clinical reentry revealed adequate bone volume to place implants in all patients in groups A and B and two of four patients in group C. Trephine core biopsies were obtained and evaluated by microCT, backscatter scanning electron microscopy (BE-SEM), and light microscopy. New bone formation was consistently observed with BE-SEM and histologic analysis for group A and B specimens. Newly formed woven and lamellar bone were in close contact with graft particles. The ABBG/MCBS specimens (group C) had more variable results, with fibrous encapsulation of graft particles and limited histologic evidence of new bone formation. Within the limits of this study, the FDBA and ABBG carriers appear to be appropriate scaffolds to deliver rhPDGF-BB for ridge augmentation via minimally invasive surgical techniques.

A Modified Implant Surgical Guide for the Administration of Maxillary Nerve Block Anesthesia Intraorally via the Greater Palatine Foramen: Case Report.

Block anesthesia for the maxillary division (V2) of the trigeminal nerve is a suitable approach when an entire quadrant of teeth and/or associated structures are involved. The most effective approach to anesthetize the maxillary branch is intraorally via the greater palatine canal. This case report describes the use of a computer-aided design/computer-assisted manufacturing (CAD/CAM) implant surgical template designed with a guide channel to allow for the administration of maxillary nerve block through the greater palatine canal.

Volumetric Analysis of Allogenic and Xenogenic Bone Substitutes Used in Maxillary Sinus Augmentations Utilizing Cone Beam CT: A Prospective Randomized Pilot Study.

PURPOSE: The purpose of this prospective randomized clinical pilot study was to compare the three-dimensional changes of grafted maxillary sinuses when deproteinized bovine bone (DBB) or cortical mineralized allogeneic bone (MAB) was used. MATERIALS AND METHODS: Seventeen patients were randomly assigned to receive either DBB or MAB for lateral-approach maxillary sinus augmentation. Cone beam computed tomography (CBCT) scans were performed preoperatively (T0), immediately after (T1), and at approximately 6 months posthoperatively (T2). Three-dimensional analysis of the radiographic volumetric changes was performed for DBB and MAB by measuring the difference in unoccupied sinus volumes at T1 and T2. RESULTS: In the DBB group, a statistically significant increase in unoccupied sinus volume was found at T2 when compared to T1 (P = .001). It represents a mean resorption rate of 23.8% ± 15.9%. Similarly in the MAB group, a statistically significant increase in unoccupied sinus volume was found at T2 when compared to T1 (P = .007). The mean resorption rate in the MAB group was 19.5% ± 10.1%. There was no statistically significant difference between the contraction of DBB (23.8%) and MAB (19.5%) (P = .52). CONCLUSION: Both DBB and MAB showed sufficient volume stability at T2 (mean 6.3 ± 1.6 months) postoperatively for 10- to 13-mm-implant placement without the need for additional grafting.

Dimensional accuracy of cone beam CT with varying angulation of the jaw to the X-ray beam.

OBJECTIVES: Cone beam CT (CBCT) machines do not always allow for patients to be scanned in the ideal position for image acquisition. This study aimed to investigate the influence of the position/angulation of the mandible relative to the X-ray beam of a CBCT machine. METHODS: Five sequential CBCT scans were captured of a human mandible at each angulation of 10°, 20°, 30°, and 40° using a coronal and sagittal positioning. Inspection software utilized a best-fit alignment to automatically calculate the three-dimensional variation at 15 standardized points of interest. RESULTS: Statistically significant differences were found between the dimensional accuracy of CBCT scans taken at 10° (26.3 µm) of coronal angulation, as well as those taken at 20° (-17.3 mm) and 30° (35.2 mm) of sagittal angulations (p < 0.001, 0.016, and <0.001, respectively). The largest deviations in accuracy included an overall maximum deviation of 490 mm. CONCLUSIONS: The position of the mandible with respect to the X-ray beam has a clinically insignificant effect on dimensional accuracy, up to the maximum angle of 40° assessed.