Cone beam computed tomography in implant dentistry: recommendations for clinical use

Two decades of research on CBCT imaging in DMFR - an appraisal of scientific evidence

OBJECTIVE

This article aims to appraise how scientific evidence related to CBCT has changed over the years, based on levels of evidence and diagnostic efficacy.

METHODS

A general search strategy was used in different databases (Pubmed, Embase, and Web of Science) to identify systematic reviews (SRs) on CBCT until November of 2020. The SRs included were divided according to different specialties of dentistry. A critical review of the articles was made, describing the level of evidence and efficacy.

RESULTS

In total, 75 articles were selected. There was an increase in the number of SRs on CBCT from 2014 onwards, as 83% of the SRs on this topic were published after 2013, and 72% between 2016 and to date. Twenty SRs (27%) performed meta-analysis. Only 28% of the SRs provided a detailed description of CBCT protocols. According to SR evidence, almost all specialties of dentistry have advanced concomitantly with the introduction of CBCT. The majority of SRs were related to clinical applications (level 2 of efficacy), followed by technical parameters (level 1 of efficacy). Only some CBCT models were mentioned in the SRs selected.

CONCLUSION

Over the course of 20 years, SRs related to CBCT applications for a broad range of dental specialties have been published, with the vast majority of studies at levels 1 and 2 of diagnostic efficacy. Not all CBCT models available on the market have been scientifically validated. At all times, one should remain cautious as such not to simply extrapolate in vitro results to the clinical setting. Also, considering the wide variety of CBCT devices and protocols, reported results should not be overstated or generalized, as outcomes often refer to specific CBCT devices and protocols.

MRI for the display of autologous onlay bone grafts during early healing-an experimental study

OBJECTIVES

Autologous bone grafts are the gold standard to augment deficient alveolar bone. Dimensional graft alterations during healing are not known as they are not accessible to radiography. Therefore, MRI was used to display autologous onlay bone grafts in vivo during early healing.

METHODS AND MATERIALS

Ten patients with alveolar bone atrophy and autologous onlay grafts were included. MRI was performed with a clinical MR system and an intraoral coil preoperatively (t0), 1 week (t1), 6 weeks (t2) and 12 weeks (t3) postoperatively, respectively. The graft volumes were assessed in MRI by manual segmentation by three examiners. Graft volumes for each time point were calculated and dimensional alteration was documented. Cortical and cancellous proportions of bone grafts were assessed. The intraobserver and interobserver variability were calculated. Statistical analysis was performed using a mixed linear regression model.

RESULTS

Autologous onlay bone grafts with cortical and cancellous properties were displayed in vivo in eight patients over 12 weeks. The fixation screws were visible as signal voids with a thin hyperintense fringe. The calculated volumes were between 0.12-0.74 cm³ (t1), 0.15-0.73 cm³ (t2), and 0.17-0.64 cm³ (t3). Median changes of bone graft volumes of -15% were observed. There was no significant difference between the examiners (p = 0.3).

CONCLUSIONS

MRI is eligible for the display and longitudinal observation of autologous onlay bone grafts. Image artifacts caused measurements deviations in some cases and minimized the precise assessment of graft volume. To the knowledge of the authors, this is the first study that used MRI for the longitudinal observation of autologous onlay bone grafts.

Feasibility of photon-counting spectral CT in dental applications-a comparative qualitative analysis

PURPOSE

The goal of this study was to demonstrate the feasibility of using photon-counting spectral CT for dental applications. This paper qualitatively analyzes the visibility of accessory canals (ACs) and metal artefacts from dental implants for cone-beam CT (CBCT), microtomography (microCT), and photon-counting spectral CT (PCSCT).

MATERIALS AND METHODS

All of the teeth in this study were extracted, and eight teeth in total were scanned on a CBCT scanner, a microCT scanner and on a PCSCT scanner. Six of the teeth that were scanned have accessory canals, one has a titanium rod attached to it, and one has a gutta-percha point inside it. Qualitative analysis was done to compare the different imaging modalities.

RESULTS

The subjective image analysis demonstrated similar performance in AC detection and visualisation for PCSCT and CBCT (p value >0.05). Both PCSCT and microCT performed similarly for metal artefact reduction, and both were superior to CBCT (p value <0.05).

CONCLUSION

Although microCT provides detailed information about small anatomical structures, it is not suitable for in vivo use. However, the PCSCT scanner was able to detect small anatomical structures in teeth comparable to CBCT, as well as being superior in reducing metal artefacts from dental implants. This study showed that PCSCT is a promising modality for future dentistry applications.

Artificial Intelligence for Fast and Accurate 3-Dimensional Tooth Segmentation on Cone-beam Computed Tomography

INTRODUCTION

Tooth segmentation on cone-beam computed tomographic (CBCT) imaging is a labor-intensive task considering the limited contrast resolution and potential disturbance by various artifacts. Fully automated tooth segmentation cannot be achieved by merely relying on CBCT intensity variations. This study aimed to develop and validate an artificial intelligence (AI)-driven tool for automated tooth segmentation on CBCT imaging.

METHODS

A total of 433 Digital Imaging and Communications in Medicine images of single- and double-rooted teeth randomly selected from 314 anonymized CBCT scans were imported and manually segmented. An AI-driven tooth segmentation algorithm based on a feature pyramid network was developed to automatically detect and segment teeth, replacing manual user contour placement. The AI-driven tool was evaluated based on volume comparison, intersection over union, the Dice score coefficient, morphologic surface deviation, and total segmentation time.

RESULTS

Overall, AI-driven and clinical reference segmentations resulted in very similar segmentation volumes. The mean intersection over union for full-tooth segmentation was 0.87 (±0.03) and 0.88 (±0.03) for semiautomated (SA) (clinical reference) versus fully automated AI-driven (F-AI) and refined AI-driven (R-AI) tooth segmentation, respectively. R-AI and F-AI segmentation showed an average median surface deviation from SA segmentation of 9.96 μm (±59.33 μm) and 7.85 μm (±69.55 μm), respectively. SA segmentations of single- and double-rooted teeth had a mean total time of 6.6 minutes (±76.15 seconds), F-AI segmentation of 0.5 minutes (±8.64 seconds, 12 times faster), and R-AI segmentation of 1.2 minutes (±33.02 seconds, 6 times faster).

CONCLUSIONS

This study showed a unique fast and accurate approach for AI-driven automated tooth segmentation on CBCT imaging. These results may open doors for AI-driven applications in surgical and treatment planning in oral health care.

Positioning errors of dental implants and their associations with adjacent structures and anatomical variations: A CBCT-based study

Purpose

The objective of the present study was to evaluate the prevalence of dental implants positioning errors and their associations with adjacent structures and anatomical variations by means of cone-beam computed tomography (CBCT).

Materials and Methods

CBCT images of 207 patients (584 dental implants) were evaluated by 2 oral radiologists. The distance between the implant and the adjacent teeth/implants was measured and classified as adequate (≥1.5 mm and ≥3 mm, respectively) or inadequate. The presence of thread exposure, cortical perforation, implant dehiscence, implant penetration into adjacent structures, and anatomical variations was also recorded. The incisor canal diameter and the depth of the concavity of the submandibular fossa were measured in order to evaluate their correlations with the frequency of implant penetration in these structures. Descriptive analyses, the Fisher exact test, and Spearman correlation analysis were performed (α=0.05).

Results

The overall prevalence of positioning errors was 82.9%. The most common error was the inadequate distance between the implant and the adjacent teeth/implants. The presence of anatomical variations did not significantly influence the overall prevalence of errors (P>0.05). There was a positive correlation between the diameter of the incisor canal and the frequency of implant penetration in this structure (r=0.232, P<0.05).

Conclusion

There was a high prevalence of dental implant positioning errors, and positioning errors were not associated with the presence of anatomical variations. Professionals should be aware of the space available for implant placement during the preoperative planning stage.

Dental implant location via surface scanner: a pilot study

Purpose

Implant location is performed after placement to verify that the safety of neighboring anatomic structure and the realizability of prosthetic plan. Routine postoperative location is based on radiological scanning and raises the concerns on radiation exposure and inconveniency in practice. In the present study a location method based on surface scanning was introduced and the accuracy of this method was assessed in vitro.

Material and methods

A total of 40 implants were placed in 10 resin mandible models. The models were scanned with intraoral scanner (IS group) and extraoral scanner (ES group). The implant position was located with fusing the images of surface scanning and cone beam computerized tomography (CBCT) after implant placement. Deviations were measured between positions located by surface scanner and postoperative CBCT with the parameters: central deviation at apex (cda), central deviation at hex (cdh), horizontal deviation at apex (hda), horizontal deviation at hex (hdh), vertical deviation at apex (vda), vertical deviation at hex (vdh) and angular deviation (ad).

Results

In IS group, the mean value of cda, cdh, hda, hdh, vda, vdh and ad was 0.27 mm, 0.23 mm, 0.12 mm, 0.10 mm, 0.21 mm, 0.19 mm and 0.72°, respectively. In ES group, the mean value of cda, cdh, hda, hdh, vda, vdh and ad was 0.28 mm, 0.25 mm 0.14 mm, 0.11 mm, 0.22 mm, 0.20 mm and 0.68°, respectively. The implant deviations in IS and ES groups were of no significant difference for any of the measurements.

Conclusions

Dental implant can be located via surface scanner with acceptable accuracy for postoperative verification. Further clinical investigation is needed to assess the feasibility of the method.

Comparative accuracy of cone-beam CT and conventional multislice computed tomography for real-time navigation in zygomatic implant surgery

BACKGROUND

Cone-beam computed tomography (CBCT) and conventional multislice CT (MSCT) are both used in zygomatic implant navigation surgery but the superiority of one technique versus the other remains unclear.

PURPOSE

This study compared the accuracy of CBCT and MSCT in zygomatic implant navigation surgery by calculating the deviations of implants.

MATERIAL AND METHODS

Patients with severely atrophic maxillae were classified into two groups according to the use of CBCT- or MSCT-guided navigation system. The entry and apical distance deviation, and the angle deviation of zygomatic implants were measured on fused operation images. A linear effect model was used for analysis, with statistical significance set at P < .05.

RESULTS

A total of 72 zygomatic implants were inserted as planned in 23 patients. The comparison of deviations in CBCT and MSCT groups showed a mean (± SD) entry deviation of 1.69 ± 0.59 mm vs 2.04 ± 0.78 mm (P = .146), apical deviation of 2 ± 0.68 mm vs 2.55 ± 0.85 (P < .001), and angle deviation of 2.32 ± 1.02° vs 3.23 ± 1.21° (P = .038).

CONCLUSION

Real-time zygomatic implant navigation surgery with CBCT may result in higher values for accuracy than MSCT.

Pain complications of oral implants: Is that an issue?

The use of oral implants as a form of replacing missing teeth in partial or total edentulous patients is considered the gold standard in oral rehabilitation. Although considered a history of success in contemporary dentistry, surgical complications may occur, as excessive bleeding, damage to the adjacent teeth and mandibular fractures. Persistent pain and abnormal somatosensory responses after the surgery ordinary healing time are also potential problems and may lead to the development of a condition named posttraumatic trigeminal neuropathic pain (PTNP). Though relatively rare, PTNP has a profound impact on patient's quality of life. Appropriated previous image techniques, effective anaesthetic procedures and caution during the surgical procedure and implant installation are recommended for the prevention of this condition. In case of the PTNP, different management modalities, including antidepressant and membrane stabilizer medications, as well as peripheral strategies, as the use of topical medication and the botulin toxin are presented and discussed.

Alveolar Bone Density and Width Affect Primary Implant Stability

Primary implant stability (PIS) depends on surgical technique, implant design, and recipient bone characteristics, among other factors. Bone density (BD) can be determined in Hounsfield units (HUs) using cone beam computerized tomography (CBCT). Reliable prediction of PIS could guide treatment decisions. We assessed whether PIS was associated with recipient bone characteristics, namely, BD and alveolar ridge width (ARW), measured preoperatively by CBCT. We studied a convenience sample of 160 implants placed in 48 patients in 2016 and 2017. All underwent CBCT with a radiologic/surgical guide yielding values for ARW and BD. PIS measures used were the implant stability quotient (ISQ) from resonance frequency analysis and insertion torque (IT). IT was most influenced by the HU value at 0.5 mm outside the implant placement area, followed by the value within this area, and ISQ by the HU value at 0.5 mm outside the placement area, followed by implant placement site and apical ARW. ISQ values were significantly related to ARW in coronal (P < .05), middle (P < .01), and apical (P < .01) thirds. ISQs were higher with larger-diameter implants (P < .01). ISQ and IT were strongly correlated (P < .001). PIS in terms of ISQ and IT is positively correlated with edentulous alveolar ridge BD measured by CBCT, implying that implant stability may be predicted preoperatively. Wide alveolar ridges favored lateral PIS but did not affect rotational PIS. The most significant predictor of lateral and rotational PIS in our patients was the HU value at 0.5 mm outside the implant placement area.

Breaking new ground in mineralized tissue: Assessing tissue quality in clinical and laboratory studies

Mineralized tissues, such as bone and teeth, have extraordinary mechanical properties of both strength and toughness. This mechanical behavior originates from deformation and fracture resistance mechanisms in their multi-scale structure. The term quality describes the matrix composition, multi-scale structure, remodeling dynamics, water content, and micro-damage accumulation in the tissue. Aging and disease result in changes in the tissue quality that may reduce strength and toughness and lead to elevated fracture risk. Therefore, the capability to measure the quality of mineralized tissues provides critical information on disease progression and mechanical integrity. Here, we provide an overview of clinical and laboratory-based techniques to assess the quality of mineralized tissues in health and disease. Current techniques used in clinical settings include radiography-based (radiographs, dual energy x-ray absorptiometry, EOS) and x-ray tomography-based methods (high resolution peripheral quantitative computed tomography, cone beam computed tomography). In the laboratory, tissue quality can be investigated in ex vivo samples with x-ray imaging (micro and nano-computed tomography, x-ray microscopy), electron microscopy (scanning/transmission electron imaging (SEM/STEM), backscattered scanning electron microscopy, Focused Ion Beam-SEM), light microscopy, spectroscopy (Raman spectroscopy and Fourier transform infrared spectroscopy) and assessment of mechanical behavior (mechanical testing, fracture mechanics and reference point indentation). It is important for clinicians and basic science researchers to be aware of the techniques available in different types of research. While x-ray imaging techniques translated to the clinic have provided exceptional advancements in patient care, the future challenge will be to incorporate high-resolution laboratory-based bone quality measurements into clinical settings to broaden the depth of information available to clinicians during diagnostics, treatment and management of mineralized tissue pathologies.

Cone Beam Computed Tomography Imaging in Dental Implants: A Primer for Clinical Radiologists

With the introduction of cone beam computed tomography (CBCT) into dentistry in the 1990s, radiologists have become more frequently involved in dental implant planning. This article describes the information that should be included in a radiology report to achieve a successful implantation. The justification to use CBCT during the preoperative planning phase is based on the need to evaluate patient-specific anatomy in detail (general condition of the jaw, bone quantity, and bone quality), the application of more advanced surgical techniques (maxillary sinus augmentation procedure, zygomatic implants), and the integrated presurgical planning and virtual patient approach. Postoperatively, CBCT is used when implant retrieval is anticipated and two-dimensional radiographs have not provided sufficient information, for evaluation of graft healing, or to assess complications, mostly related to neurovascular trauma.

Dentomaxillofacial CBCT: Clinical Challenges for Indication-oriented Imaging

This critical review discusses the clinical challenges for patient-specific and indication-oriented dentomaxillofacial cone beam computed tomography (CBCT). Large variations among units and protocols may lead to variable degrees of diagnostic and three-dimensional model accuracy, impacting both specific diagnostic tasks and treatment planning. Particular indications, whether diagnostic or therapeutic, may give rise to very specific challenges with regard to CBCT unit and parameter setup, considering the required image quality, segmentation accuracy, and artifact level. Considering that dental materials are in the field of view needed for diagnosis or treatment planning, artifact expression is a dominant factor in proper CBCT selection. The heterogeneity of dental CBCT units and performances may highly impact the scientific results. Thus research findings cannot be simply generalized as published evidence, and a demonstrated clinical applicability for a specific indication should not be simply extrapolated from one CBCT unit to another.

Assessing the frequency of deep lingual concavities in 826 posterior mandible sockets

PURPOSE

To evaluate the frequency of deep lingual concavities in the lower jaw, which can cause surgical complications while inserting dental implants.

METHODS

Cross-sections of the mandible alveolar ridge at the edentulous sockets were obtained via cone-beam computed tomography. Measurements were carried out using the freeware 'IC Measure' and based on the basic definitions of a previous study.

RESULTS

Most (767/826 = 93%) sockets had concavities of various degrees (30-90°), while 59 (7%) sockets had no concavity. However, the majority of the concavities (71%) were mild, with angles > 60°. The other 220 (26%) sockets had deeper concavities of <60°; among these, 12 (1%) had extremely deep concavities of <40°.

CONCLUSIONS

Only a few cases have deep lingual concavities that pose a high risk for lingual plate perforation during dental implantation.

Dental MRI: a road beyond CBCT

KEY POINTS

• Three-dimensional (3D) imaging coupled with computer-guided surgery planning is the core of the contemporary dental implant practice.• Magnetic resonance (MR)-based dental implant planning can achieve results comparable to those with cone beam computed tomography (CBCT)-based planning.• MR-based dental implant planning without radiation dose could be a potential alternative to CBCT-based planning.

Use of dental MRI for radiation-free guided dental implant planning: a prospective, in vivo study of accuracy and reliability

OBJECTIVES

To evaluate the accuracy and reliability of dental MRI for static guided implant surgery planning.

MATERIALS AND METHODS

In this prospective study, a 0.4-mm isotropic, artifact-suppressed, 3T MRI protocol was used for implant planning and surgical guide production in participants in need of dental implants. Two dentists decided on treatment plan. Surgical guides were placed intraorally during a subsequent reference cone beam computed tomography (CBCT) scan. Inter-rater and inter-modality agreement were assessed by Cohen's kappa. For each participant, dental MRI and CBCT datasets were co-registered to determine three-dimensional and angular deviations between planned and surgically guided implant positions.

RESULTS

Forty-five implants among 30 study participants were planned and evaluated (17 women, 13 men, mean age 56.9 ± 13.1 years). Inter-rater agreement (mean κ 0.814; range 0.704-0.927) and inter-modality agreement (mean κ 0.879; range 0.782-0.901) were both excellent for the dental MRI-based treatment plans. Mean three-dimensional deviations were 1.1 ± 0.7 (entry point) and 1.3 ± 0.7 mm (apex). Mean angular deviation was 2.4 ± 1.5°. CBCT-based adjustments of MRI plans were necessary for implant position in 29.5% and for implant axis in 6.8% of all implant sites. Changes were larger in the group with shortened dental arches compared with those for tooth gaps. Except for one implant site, all guides were suitable for clinical use.

CONCLUSION

This feasibility study indicates that dental MRI is reliable and sufficiently accurate for surgical guide production. Nevertheless, more studies are needed to increase its accuracy before it can be used for implant planning outside clinical trials.

KEY POINTS

• An excellent reliability for the dental MRI-based treatment plans as well as agreement between dental MRI-based and CBCT-based (reference standard) decisions were noted. • Ideal implant position was not reached in all cases by dental MRI plans. • For all but one implant site surgical guides derived from dental MRI were sufficiently accurate to perform implant placement (mean three-dimensional deviations were 1.1 ± 0.7 (entry point) and 1.3 ± 0.7 mm (apex); mean angular deviation was 2.4 ± 1.5°).

Anatomy of the mandibular canal and surrounding structures. Part II: Cancellous pattern of the mandible

PURPOSE

It is necessary to correlate cancellous bone patterns with cone beam computed tomography (CBCT) images, but this has not been done to date. The goal of this study was to establish how the superior wall of the mandibular canal (MC) on CBCT images correlates with the cancellous bone around the MC on gross anatomical findings.

METHODS

Twenty sides from 10 dry mandibles derived from six females and four males were used for this study. In order to observe the MC distally, the specimen was prepared by the method used in our previous study. The cancellous bone around the MC was observed and classified into three types: type I (trabecular pattern), type II (osteoporotic pattern), and type III (dense/irregular pattern). The mandibles were examined with CBCT and the superior wall of the MC on CBCT was scored as visible or non-visible. Finally, the scores (visible or non-visible) were compared to the type by gross observation.

RESULTS

For gross observation, a total of 80 areas were available for this study. The data were added to those from our previous study. As a result, 155 areas on 40 sides were analyzed. In dentulous sections, types I, II, and III were found in 55.8%, 20.9%, and 23.3%, respectively. In edentulous sections, the corresponding percentages were 25.0%, 41.1%, and 33.9%, respectively. The dentulous sections was more likely than edentulous to have a type I mandible in both sexes. More females than males had type II (osteoporotic) mandibles. When the superior wall of the MC was non-visible on CBCT, the cancellous bone was type II in 80%.

CONCLUSIONS

We believe the results can easily be applied to preoperative diagnosis with not only radiological but also anatomical evidence. This classification now necessitates clinical trials for further evidence.

Association between Age of Menopause and Thickness of Crestal Cortical Bone at Dental Implant Site: A Cross-Sectional Observational Study

Satisfactory host bone quality and quantity promote greater primary stability and better osseointegration, leading to a high success rate in the use of dental implants. However, the increase in life expectancy as a result of medical advancements has led to an aging population, suggesting that osteoporosis may become a problem in clinical dental implant surgery. Notably, relative to the general population, bone insufficiency is more common in women with post-menopausal osteoporosis. The objective of this study was to compare the thickness of the crestal cortical bone at prospective dental implant sites between menopausal and non-menopausal women. Prospective dental implant sites in the jawbone were evaluated in two groups of women: a younger group (<50 years old), with 149 sites in 48 women, and an older group (>50 years old) with 191 sites, in 37 women. The thickness of the crestal cortical bone at the dental implant site was measured based on each patient’s dental cone-beam computed tomography images. For both groups, one-way analysis of variance and Tukey’s post-test were used to assess the correlation between cortical bone thickness and the presence of implants in the four jawbone regions. Student’s t-test was further used to compare differences between the older and younger groups. From the retrospective study results, for both groups, thickness of the crestal cortical bone was the highest in the posterior mandible, followed by anterior mandible, anterior maxilla, and posterior maxilla. Compared with the younger group, the older group had a lower mean thickness of the crestal cortical bone. Among the four regions, however, only in the posterior maxilla was the crestal cortical bone significantly thinner in the older group than in the younger group.

Feasibility of Using a Prosthetic-Based Impression Template to Improve the Trueness and Precision of a Complete Arch Digital Impression on Four and Six Implants: An In Vitro Study

Background: Intraoral scanners (IOSs) in implantology represent a viable approach for single teeth or partial arches. However, when used for complete edentulous arches or long-span edentulous areas, it has been demonstrated that there is a need for improvement of IOS-related techniques. Therefore, the aim of this in vitro study was to assess the trueness and precision of a complete arch digital impression on four and six implants taken with or without a customized, prosthetic-based impression template. Materials and Methods: Two experimental models were prepared, representative of a complete edentulous mandible restored with four and six implants with built-in scan abutments. Models were scanned with (test group, TG) or without (control group, CG) the prosthetic-based impression template. Eight scans were taken for each model. The time needed to take impressions, error, trueness, and precision were evaluated. A statistical analysis was performed. Results: In the case of four implants, the time needed for the impression was 128.7 ± 55.3 s in the TG and 81.0 ± 23.5 s in the CG (p = 0.0416). With six scan abutments, the time was 197.5 ± 26.8 and 110.6 ± 25.2 s in the TG and CG, respectively (p = 0.0000). In the TG, no errors were experienced, while in the CG, 13 impressions were retaken due to incorrect stitching processes. In the four-implant impression, the mean angle deviation was 0.252 ± 0.068° (95% CI 0.021–0.115°) in the CG and 0.134 ± 0.053° (95% CI 0.016–0.090°) in the TG. The difference was statistically significant (p = 0.002). In the six-implant impression, the mean angle deviation was 0.373 ± 0.117° (95% CI 0.036–0.198°) in the CG and 0.100 ± 0.029° (95% CI 0.009–0.049°) in the TG (p = 0.000). In the TG, there were no statistically significant differences in the mean angle deviation within the group (p > 0.05), but there were in the CG. A colorimetric analysis showed higher deviations from the original model for the six-implant impression without a prosthetic template. Conclusions: Although all of the impressions exhibited deviation from the original model in the range of clinical acceptability, the prosthetic-based impression template significantly improved the trueness and precision of complete edentulous arches rehabilitated with four or six implants, making the complete arch digital impression more predictable.

Assessment of the configuration of the mandibular canal using cone beam computed tomography

BACKGROUND

During dental implants placement and bone augmentation procedures, it is important to determine the presence and location of mandibular canal anatomical variation in order to avoid injuries to inferior alveolar bundle. This study aimed to describe the prevalence and configuration of mandibular canal branching in the posterior region of the mandible using cone beam computed tomography (CBCT).

METHODS

The interpretation of the images was conducted according to the presence, classification and location of the mandibular canal. Horizontal and vertical distances from mandibular canal in the ramus region to the molar region was recorded. CBCT images of 751 patients, 486 women (64.7%) and 265 men (35.3%), with a mean age of 54.57 (±13.23; 14-93) years, were interpreted by one calibrated examiner.

RESULTS

Out of 1502 hemi-mandibles images, mandibular canal variations were observed in 130 (8.6%). Sixty-four (49.2%) mandibular canal variations were identified on the right side and 66 (50.8%) on the left side. The mean distances between superior cortical of the mandibular canal and the base of mandible, buccal cortical of mandibular canal and buccal cortical bone, and superior cortical of mandibular canal and alveolar ridge were 12.16 mm (±2.68), 4.17 mm (±1.30), and 12.97mm (±4.01), respectively. Type I mandibular canal variation was the most frequent (68; 52.2%), followed by type III (34; 26.1%).

CONCLUSIONS

Prevalence of mandibular canal variations was 8.6%, type I was the most common and its direction showed proximity with lingual surface in the second molar region.

Applying synthetic radiography to intraoral tomosynthesis: a step towards achieving 3D imaging in the dental clinic

OBJECTIVES

A practical approach to three-dimensional (3D) intraoral imaging would have many potential applications in clinical dentistry. Stationary intraoral tomosynthesis (sIOT) is an experimental 3D imaging technology that holds promise. The purpose of this study was to explore synthetic radiography as a tool to improve the clinical utility of the images generated by an sIOT scan.

METHODS

Extracted tooth specimens containing either caries adjacent to restorations (CAR) or vertical root fractures (VRF) were imaged by sIOT and standard dental radiography devices. Qualitative assessments were used to compare the conspicuity of these pathologies in the standard radiographs and in a set of multi-view synthetic radiographs generated from the information collected by sIOT.

RESULTS

The sIOT-based synthetic 2D radiographs contained less artefact than the image slices in the reconstructed 3D stack, which is the conventional approach to displaying information from a tomosynthesis scan. As a single sIOT scan can be used to generate synthetic radiographs from multiple viewing angles, the interproximal space was less likely to be obscured in the synthetic images compared to the standard radiograph. Additionally, the multi-view synthetic radiographs can potentially improve the display of CAR and VRFs as compared to a single standard radiograph.

CONCLUSIONS

This preliminary experience combining synthetic radiography and sIOT in extracted tooth models is encouraging and supports the ongoing study of this promising approach to 3D intraoral imaging with many potential applications.

Cone beam computed tomography analysis of the edentulous mandibular symphysis

Background/purpose

Overdenture with single symphyseal implant is one of the useful clinical approach for elderly edentulous patients. We aimed to evaluate edentulous patients with regards to the relationship between dimensions, bone characteristics, cancellous densities, and cortical thickness of the mandibular symphyseal region using cone beam computed tomography (CBCT).

Material and methods

We analyzed 103 CBCT from pre-implant investigations. All included patients were healthy without any disorders affecting bone metabolism. We performed 13 measurements for each patient: 9 of height, width, and thickness (mm) and 4 of density (Hounsfield Units; HU). Fisher's exact test was applied to examine the association between two categorical variables, the Pearson correlation coefficient to measure the strength of linear relationship between two quantitative variables. We used the two-sample Student's t-test to compare mean symphysis height between men and women, the paired Student's t-test to compare mean lingual and buccal cortical thickness. For all tests, the threshold of significance was fixed at 5%.

Results

Men and women significantly differed with regards to mean total symphysis height (p = 0.004) and the distribution of Cawood and Howell classifications (p = 0.033). Symphysis height was negatively correlated with mean density of cancellous bone (r = −0.453, p < 0.001). Mean lingual cortical thickness significantly differed from mean vestibular thickness (p < 0.001, paired Student's t-test).

Conclusion

Present findings supported that symphyseal measurements are parameters that reflect the symphysis bone characteristics, and can guide the choice of a suitable implant design.

Congruence between Meshes and Library Files of Implant Scanbodies: An In Vitro Study Comparing Five Intraoral Scanners

Purpose. To compare the reliability of five different intraoral scanners (IOSs) in the capture of implant scanbodies (SBs) and to verify the dimensional congruence between the meshes (MEs) of the SBs and the corresponding library file (LF). Methods. A gypsum cast of a fully edentulous maxilla with six implant analogues and SBs screwed on was scanned with five different IOSs (PRIMESCAN^®, CS 3700^®, MEDIT i-500^®, ITERO ELEMENTS 5D^®, and Emerald S^®). Ten scans were taken for each IOS. The resulting MEs were imported to reverse engineering software for 3D analysis, consisting of the superimposition of the SB LF onto each SB ME. Then, a quantitative and qualitative evaluation of the deviations between MEs and LF was performed. A careful statistical analysis was performed. Results. PRIMESCAN^® showed the highest congruence between SB MEs and LF, with the lowest mean absolute deviation (25.5 ± 5.0 μm), immediately followed by CS 3700^® (27.0 ± 4.3 μm); the difference between them was not significant (p = 0.1235). PRIMESCAN^® showed a significantly higher congruence than MEDIT i-500^® (29.8 ± 4.8 μm, p < 0.0001), ITERO ELEMENTS 5D^® (34.2 ± 9.3 μm, p < 0.0001), and Emerald S^® (38.3 ± 7.8 μm, p < 0.0001). CS 3700^® had a significantly higher congruence than MEDIT i-500^® (p = 0.0004), ITERO ELEMENTS 5D^® (p < 0.0001), and Emerald S^® (p < 0.0001). Significant differences were also found between MEDIT i-500^® and ITERO ELEMENTS 5D^® (p < 0.0001), MEDIT i-500^® and Emerald S^® (p < 0.0001), and ITERO ELEMENTS 5D^® and Emerald S^® (p < 0.0001). Significant differences were found among different SBs when scanned with the same IOS. The deviations of the IOSs showed different directions and patterns. With PRIMESCAN^®, ITERO ELEMENTS 5D^®, and Emerald S^®, the MEs were included inside the LF; with CS 3700^®, the LF was included in the MEs. MEDIT i-500^® showed interpolation between the MEs and LF, with no clear direction for the deviation. Conclusions. Statistically different levels of congruence were found between the SB MEs and the corresponding LF when using different IOSs. Significant differences were also found between different SBs when scanned with the same IOS. Finally, the qualitative evaluation revealed different directions and patterns for the five IOSs.

Perforation of the maxillary sinus floor during apical surgery of maxillary molars: A retrospective analysis using cone beam computed tomography

This retrospective analysis assessed a possible correlation of perforation of the maxillary sinus floor during apical surgery of maxillary molars and the distances from the treated apices/periapical radiolucencies to the sinus floor. The material included 168 apical surgeries of maxillary first or second molars performed from 1999 to 2016. In 22 (out of 33) perforation cases, a preoperative cone beam computed tomography (CBCT) was available. These cases were defined as the test group. From the pool of operated cases without sinus floor perforation, matching cases - that is, same treated tooth, similar age and same gender - were selected as a control group (N = 26). Mean linear distances from root apices or radiolucencies to sinus floor were significantly shorter in the test group compared to the control group. In conclusion, perforation cases were significantly closer to the sinus floor than cases without perforation.

Cone beam computed tomography in dentomaxillofacial radiology: a two-decade overview

OBJECTIVES

The aim of this study was to evaluate and summarise features of currently and formerly available cone beam CT (CBCT) devices from 1996 to 2019. Additionally, a recommendation for standardised reporting of CBCT characteristics was provided.

METHODS AND MATERIALS

Information about the features of all available CBCT devices was obtained from the manufacturers' available data. Moreover, site visits to newly developed CBCT machines' manufacturers were performed in order to obtain relevant information.

RESULTS

A total of 279 CBCT models from 47 manufacturers located in 12 countries (Brazil, China, Denmark, Finland, France, Germany, Italy, Japan, Republic of Korea, Slovakia, Thailand, and USA) could be listed. Overall, wide variations in CBCT features and technical specifications were identified.

CONCLUSIONS

CBCT in dentomaxillofacial radiology is a generic term applicable to a broad range of CBCT machines and features. Experimental outcomes and literature statements regarding radiation doses, imaging performance and diagnostic applicability of dental CBCT cannot be simply transferred from one CBCT model to another considering a wide variation in technical characteristics and clinical diagnostic performance. The information tabulated in the present study will be later provided on the International Association of DentoMaxilloFacial Radiology website (www.iadmfr.one).

A CBCT Based Three-Dimensional Assessment of Mandibular Posterior Region for Evaluating the Possibility of Bypassing the Inferior Alveolar Nerve While Placing Dental Implants

A high rate of nerve injury and related consequences are seen during implant placement in the posterior mandibular arch. An approach has been proposed to avoid nerve injury by dodging the inferior alveolar nerve (IAN) while placing an implant. A prospective study with a total of 240 CBCT (cone beam computed tomography) images of patients with three dentate statuses, namely, edentulous (group I), partially edentulous (group II) and dentate (group III) were included in the study. The nerve path tracing was done on CBCT images with On-demand 3D software. The three dimensions, i.e., the linear distance from the outer buccal cortical plate to the inferior alveolar nerve (BCPN), linear distance from the outer lingual cortical plate to the inferior alveolar nerve (LCPN) and linear distance from the midpoint of the alveolar crest to the inferior alveolar nerve (ACN) were assessed. The data were presented and analyzed between variables using one-way ANOVA and independent t-test in SPSS version 21.LCPN of the right 1st premolar region (p < 0.05) was significantly different among the groups with edentulous subjects recorded with the minimum value (6.50 ± 1.20 mm). Females were found to have significantly (p < 0.05) less available bone (6.03 ± 1.46 mm) on the right side of the mandibular jaw compared to males in edentulous group of patients. On comparing age groups for partially edentulous subjects, LCPN of the right 1st premolar region had significantly (p < 0.05) less available bone (6.03 ± 0.38 mm) in subjects with age ≥54 years. The IAN follows a lingual course in the molar region and later flips to the buccal side in the premolar region. The LCPN dimension in the 1st and 2nd premolar region was found to be more than 6 mm irrespective of age, gender and side of the jaw. Thus, it can be considered as a suitable site for placing implants while bypassing the IAN with CBCT assessment remaining as the mainstay in the pre-surgical phase.

A quantitative analysis of metal artifact reduction algorithm performance in volume correction with 3 CBCT devices

OBJECTIVE

The aim of this study was to quantitatively assess the performance of metal artifact reduction (MAR) algorithms on the volume of metal cylinders, considering the influence of materials, positions, and fields of view (FOVs), by using 3 cone beam computed tomography (CBCT) devices (NewTom VGi evo, Picasso Trio, and ProMax 3-D Max).

STUDY DESIGN

Nine phantoms containing cylinders of amalgam, copper-aluminum (CuAl) metal alloy, and titanium, combined in up to 3 positions, were scanned by using 2 different FOVs. MATLAB software was used to evaluate the differences between volumes before and after MAR application, and the possible interference of materials, positions, and FOVs. Wilcoxon's test and the Kruskal-Wallis test were used at a level of significance of 5%.

RESULTS

In general, images containing amalgam and CuAl showed a significant difference in volume before and after MAR application. However, no significant difference after MAR was observed (P > .05) relative to positions and FOVs. MAR had an impact on the cylinder volumes only in the NewTom VGi evo and ProMax 3-D Max scanners.

CONCLUSIONS

The performance of MAR algorithms in volume correction of metal objects is dependent on the materials and the CBCT unit.

Attitude in Radiographic Post-Operative Assessment of Dental Implants among Italian Dentists: A Cross-Sectional Survey

There is a lack of evidence in the attitude and prescribing practice of implantologists in dental implant post-operative assessment; therefore, the aims of this cross-sectional study were to investigate these habits and the knowledge about radiographic aspect of retrograde peri-implantitis (RPI) among Italian implantologists. A questionnaire was sent via email to dentists randomly selected from the register of implantology and oral surgery societies. It included three questions: the preferred X-ray after implant placement, the timing of post-operative assessment and the knowledge of the RPI radiographic representation. A final sample of 434 implantologists was included in the study. The majority of them (84.3%) perform a periapical X-ray as control radiograph and picked the correct radiographic representation of RPI (74.3%), without statistically significant differences (p > 0.05) for sex, age, years of working practice and number of implants placed per year. Just 47.7% of dentists perform a control radiograph at prostheses delivery, to establish a proper baseline. A statistically significant difference (p < 0.05) was detectable only for the number of implants placed per year, with dentists placing > 80 implants selecting the correct choice. To the best of authors’ knowledge, this is the first study to report data on attitude of implantologists in radiographic imaging after implant placement.

Dentistry 4.0 Concept in the Design and Manufacturing of Prosthetic Dental Restorations

The paper is a comprehensive but compact review of the literature on the state of illnesses of the human stomatognathic system, related consequences in the form of dental deficiencies, and the resulting need for prosthetic treatment. Types of prosthetic restorations, including implants, as well as new classes of implantable devices called implant-scaffolds with a porous part integrated with a solid core, as well as biological engineering materials with the use of living cells, have been characterized. A review of works on current trends in the technical development of dental prosthetics aiding, called Dentistry 4.0, analogous to the concept of the highest stage of Industry 4.0 of the industrial revolution, has been presented. Authors’ own augmented holistic model of Industry 4.0 has been developed and presented. The studies on the significance of cone-beam computed tomography (CBCT) in planning prosthetic treatment, as well as in the design and manufacture of prosthetic restorations, have been described. The presented and fully digital approach is a radical turnaround in both clinical procedures and the technologies of implant preparation using computer-aided design and manufacturing methods (CAD/CAM) and additive manufacturing (AM) technologies, including selective laser sintering (SLS). The authors’ research illustrates the practical application of the Dentistry 4.0 approach for several types of prosthetic restorations. The development process of the modern approach is being observed all over the world. The use of the principles of the augmented holistic model of Industry 4.0 in advanced dental engineering indicates a change in the traditional relationship between a dentist and a dental engineer. The overall conclusion demonstrates that it is inevitable and extremely beneficial to implement the idea of Dentistry 4.0 following the assumptions of the authors’ own, holistic Industry 4.0 model.

Cone beam computed tomography artefacts around dental implants with different materials influencing the detection of peri-implant bone defects

OBJECTIVES

To investigate the diagnostic accuracy of cone beam computed tomography (CBCT) for the diagnosis of peri-implant bone defects of titanium (Ti), zirconium dioxide (ZrO₂ ) or titanium-zirconium (Ti-Zr) alloy implants.

MATERIALS AND METHODS

Ti, Ti-Zr or ZrO₂ implants with two diameters (3.3 mm, 4.1 mm) and one length (10 mm) were inserted in the angle of the mandible of six fresh defrosted pig jaws. Out of the 12 implants inserted, 6 served in the test group with standardized buccal peri-implant bone defects, whereas 6 served as control without bone defects. CBCTs were performed with three acquisition protocols (standard, high and low dose) using two devices. Four observers analysed CBCTs as follows: (a) presence of a peri-implant defect; (b) presence of peri-implant artefacts and impact on defect diagnosis; and (c) linear measurements of buccal peri-implant defect including height and width (in mm).

RESULTS

CBCT device, CBCT settings, implant material, implant diameter and observer background did not significantly influence diagnostic accuracy. The sensitivity and specificity values were high for defect detection. ZrO₂ led to a lower than average diagnostic accuracy (0.781). The linear measurements of peri-implant defect were underestimated by <1 mm on average. The subjective impact of artefacts on defect diagnosis was significantly affected by implant material and observer background.

CONCLUSIONS

CBCT showed high diagnostic accuracy for peri-implant bone defect detection regardless of the device, imaging setting or implant material used. If CBCT is indicated to assess peri-implant bone disease, low dose protocols could be a promising imaging modality.

Comparing Accuracy of Implant Installation with a Navigation System (NS), a Laboratory Guide (LG), NS with LG, and Freehand Drilling

The aim of this study was to compare the accuracy of implant placement by using the conventional freehand method, the surgical guide alone, the dental navigation system alone, and the dental navigation system with a surgical guide. The participants were aged 20 years or older and were requiring dental implant surgery according to an assessment made by a dentist between July 2014 and December 2017. A total of 128 dental implants were inserted, 32 dental implants in each group, and participants with similar or identical age (i.e., 20–50 years or 50 years or above) and missing tooth locations were paired for comparison. Accuracy was measured by overlaying the real position in the postoperative Cone Beam Computerized Tomography (CBCT) on the virtual presurgical placement of the implant in a CBCT image. Using the dental navigation system with a surgical guide could help dentists to position implants more accurately. Total, longitudinal, and angular error deviation were significantly different (p < 0.0001). The same level of accuracy could be obtained for the different jaws and tooth positions. The one-way analysis of variance (ANOVA) showed that the total, longitudinal, and angular errors differed significantly (p < 0.0001). A comparison of the four dental implant surgical methods indicated that the combination of a dental implant navigation system and a surgical guide kit achieved the highest accuracy in terms of the different tooth positions and jaws.

Development of an evidence-based clinical imaging diagnostic guideline for implant planning: Joint recommendations of the Korean Academy of Oral and Maxillofacial Radiology and National Evidence-based Healthcare Collaborating Agency

Purpose

This study was conducted to develop an evidence-based clinical imaging diagnostic guideline for implant planning, taking into account efficacy, benefits, and risks.

Materials and Methods

The guideline development process employed the adaptation methodology used for Korean clinical imaging guidelines(K-CIG). Core databases(Ovid-Medline, Ovid-Embase, National Guideline Clearinghouse, Guideline International Network) and domestic databases (KoreaMed, KMbase, and KoMGI) were searched for guidelines. The retrieved articles were analyzed by 2 reviewers, and articles were selected using well-established inclusion criteria.

Results

The search identified 294 articles, of which 3 were selected as relevant guidelines. Based on those 3 guidelines, 3 recommendations for implant planning were derived.

Conclusion

We recommend radiography or cone-beam computed tomography (CBCT) scanning for individual patients judged to require a cross-sectional image after reading of a panoramic X-ray image and a conventional intraoral radiological image. Various steps should be taken to raise awareness of these recommendations among clinicians and the public, and K-CIG should be regularly reviewed and revised.

Evaluation of metal artefacts for two CBCT devices with a new dental arch phantom

OBJECTIVES

To create a new phantom design to evaluate the real impact of artefacts caused by titanium on bone structures in cone beam CT images considering different positions and quantity of metals in the dental arch, with and without metal artefact reduction (MAR).

METHODS

A three cylindrical polymethyl methacrylate (PMMA) plate phantom was designed containing eight perforations arranged to simulate the lower dental arch in the intermediate plate. Three titanium cylinders were positioned in different locations and quantities to test different clinical conditions and to quantify the impact of the metal artefact around five bone cylinders. Scans were carried out in seven different protocols (Control, A-F) in two cone beam CT devices (OP300 Maxio and Picasso Trio). Eight regions of interest around each cortical and trabecular bone were used to measure the grey value standard deviation corresponding the artefact expression in the Image J software. Both the artefact expression and the MAR effect were assessed using the Wilcoxon, Friedman (Dunn) and Kruskal-Wallis tests (significance level of 5%).

RESULTS

For both devices, MAR was statistically efficient only for the protocols E, and F. Protocol F (three metals on the adjacent area of the analysis region) showed higher artefact expression when compared to the others.

CONCLUSION

In conclusion, the new phantom design allowed the quantification of the metal artefact expression caused by titanium. The metal artefact expression is higher when more metal objects are positioned in the adjacent bone structures. MAR may not be effective to reduce artefact expression on the adjacencies of those objects for the devices studied.

Retrospective assessment of dental implant-related perforations of relevant anatomical structures and inadequate spacing between implants/teeth using cone-beam computed tomography

OBJECTIVES

To assess the prevalence of dental implant-related perforations of relevant anatomical structures and inadequate spacing between the implant and the adjacent tooth or implant, and their association with anatomical location, implant dimension, thread exposure, and presence of graft, using cone beam computed tomography (CBCT).

MATERIALS AND METHODS

CBCT scans of patients with implants were retrospectively assessed regarding the presence of implant-related perforation of adjacent anatomical structures, and inadequate mesial and distal spacing between the implant and the adjacent tooth/implant (i.e., < 1 mm or < 3 mm, respectively). Implants were classified according to anatomical location, dimensions, thread exposure, and the presence of graft (i.e., bone graft or bone substitutes). Prevalence of perforations and inadequate spacing was compared among the different implant classifications (Chi-squared test). Significance level was set at 5%.

RESULTS

A total of 1109 implants were assessed, out of which 369 (33.3%) presented perforation of adjacent structures. Prevalence of perforations in the maxilla (43.5%) was higher than in the mandible (11.3%). Inadequate spacing was found in 18.2% of the mesial and distal measurements, which was more prevalent in the maxilla (p < 0.001). Implants perforating adjacent structures or placed with inadequate spacing presented higher prevalence of thread exposure (p < 0.001). No significant difference was found between the presence of perforations or inadequate spacing and presence of graft (p > 0.05).

CONCLUSIONS

Implant-related perforations of relevant anatomical structures and inadequate spacing between the implant and the adjacent tooth/implant are relatively prevalent and more common in the maxilla. Both are associated with threads exposure.

CLINICAL RELEVANCE

Information on dental implant-related perforations and inadequate spacing can assist dental surgeons in pre-surgical planning.

Custom-made 3D printed subperiosteal titanium implants for the prosthetic restoration of the atrophic posterior mandible of elderly patients: a case series

Purpose

To present the application of custom-made 3D-printed subperiosteal implants for fixed prosthetic restoration of the atrophic posterior mandible of elderly patients.

Methods

Between January 2017 and June 2018, all partially edentulous patients aged over 65 years, with two or more missing teeth in the posterior atrophic mandible, and who did not want to undergo bone regenerative procedures, were included in this study. These patients were rehabilitated with custom-made subperiosteal implants, designed from cone beam computed tomography (CBCT) and fabricated in titanium by means of direct metal laser sintering (DMLS). The outcome measures were fit and stability of the implants at placement, duration of the intervention, implant survival, and early and late complications. All patients were followed for 1 year after surgery.

Results

Ten patients (four males, six females; mean age 69.6, SD ± 2.8, median 69, 95% CI 67.9–71.6) were included in the study. The fit of the implants was satisfactory, with a mean rating of 7 out of 10 (SD ± 1.6, median 7, 95% CI 6–8). Only two implants had insufficient fit, because of the presence of scattering in the CBCT; however, they were adapted to the sites during the interventions. The mean duration of the intervention was 44.3 min (SD ± 19.4, median 37, 95% CI 32.3–56.3). At the one-year follow-up, no implants were lost (survival rate 100%). One implant presented immediate postoperative complications with pain, discomfort and swelling, and two patients experienced late complications, having their provisional restorations fractured during the temporisation phase. All these complications were minor in nature, but the final complication rate amounted to 30% (three of ten patients).

Conclusions

Although this study has limits (small patient sample and short follow-up), DMLS has proven to be an effective method for fabricating accurate subperiosteal implants, with high survival rates. This may represent an alternative treatment procedure in elderly patients with a severely atrophic posterior mandible, since it allows avoidance of regenerative bone therapies. Further studies are needed to confirm these outcomes.

Full Digital Workflow for the Treatment of an Edentulous Patient with Guided Surgery, Immediate Loading and 3D-Printed Hybrid Prosthesis: The BARI Technique 2.0. A Case Report

Purpose: To describe a technique intended to transfer of the intermaxillary and occlusal relationships in a fully digital environment from a complete denture to an implant-supported 3D-printed hybrid prosthesis (an acrylic resin complete fixed dental prosthesis supported by implants). Methods: In edentulous cases, the physiological mandibular position should be determined before the immediate loading procedures. In some cases, the use of interim removable prostheses for a few weeks could be useful to test the new occlusion in centric relation and to verify the prosthetic project. When the correct intermaxillary relationships are achieved, it is difficult to transfer them from the provisional to the final prostheses, as impressions or scans of edentulous arches do not have reference points for intermaxillary records. This paper presents a complex case and the technique used to transfer information from a complete denture to an implant-supported prosthesis with a digital workflow. A prosthetic stent has been used to scan the edentulous mandibular arch and to record the intermaxillary relation. Results: The delivery of the hybrid implant-supported prostheses was carried out with no problems and minimal occlusal adjustments. The patient was extremely satisfied with the treatment and the situation remained stable at the 1-year follow up. Conclusions: The approach described in the present article predictably maintains prosthetic information and allows the delivery of a final implant-supported restoration with the same occlusal relationship as the one tested with the provisional diagnostic dentures.

The Accuracy of Digital Face Scans Obtained from 3D Scanners: An In Vitro Study

Face scanners promise wide applications in medicine and dentistry, including facial recognition, capturing facial emotions, facial cosmetic planning and surgery, and maxillofacial rehabilitation. Higher accuracy improves the quality of the data recorded from the face scanner, which ultimately, will improve the outcome. Although there are various face scanners available on the market, there is no evidence of a suitable face scanner for practical applications. The aim of this in vitro study was to analyze the face scans obtained from four scanners; EinScan Pro (EP), EinScan Pro 2X Plus (EP+) (Shining 3D Tech. Co., Ltd. Hangzhou, China), iPhone X (IPX) (Apple Store, Cupertino, CA, USA), and Planmeca ProMax 3D Mid (PM) (Planmeca USA, Inc. IL, USA), and to compare scans obtained from various scanners with the control (measured from Vernier caliper). This should help to identify the appropriate scanner for face scanning. A master face model was created and printed from polylactic acid using the resolution of 200 microns on x, y, and z axes and designed in Rhinoceros 3D modeling software (Rhino, Robert McNeel and Associates for Windows, Washington DC, USA). The face models were 3D scanned with four scanners, five times, according to the manufacturer's recommendations; EinScan Pro (Shining 3D Tech. Co., Ltd. Hangzhou, China), EinScan Pro 2X Plus (Shining 3D Tech. Co., Ltd. Hangzhou, China) using Shining Software, iPhone X (Apple Store, Cupertino, CA, USA) using Bellus3D Face Application (Bellus3D, version 1.6.2, Bellus3D, Inc. Campbell, CA, USA), and Planmeca ProMax 3D Mid (PM) (Planmeca USA, Inc. IL, USA). Scan data files were saved as stereolithography (STL) files for the measurements. From the STL files, digital face models are created in the computer using Rhinoceros 3D modeling software (Rhino, Robert McNeel and Associates for Windows, Washington DC, USA). Various measurements were measured five times from the reference points in three axes (x, y, and z) using a digital Vernier caliper (VC) (Mitutoyo 150 mm Digital Caliper, Mitutoyo Co., Kanagawa, Japan), and the mean was calculated, which was used as the control. Measurements were measured on the digital face models of EP, EP+, IPX, and PM using Rhinoceros 3D modeling software (Rhino, Robert McNeel and Associates for Windows, Washington DC, USA). The descriptive statistics were done from SPSS version 20 (IBM Company, Chicago, USA). One-way ANOVA with post hoc using Scheffe was done to analyze the differences between the control and the scans (EP, EP+, IPX, and PM). The significance level was set at p = 0.05. EP+ showed the highest accuracy. EP showed medium accuracy and some lesser accuracy (accurate until 10 mm of length), but IPX and PM showed the least accuracy. EP+ showed accuracy in measuring the 2 mm of depth (diameter 6 mm). All other scanners (EP, IPX, and PM) showed less accuracy in measuring depth. Finally, the accuracy of an optical scan is dependent on the technology used by each scanner. It is recommended to use EP+ for face scanning.

Best clinical practice guidance for prescribing dental radiographs in children and adolescents: an EAPD policy document

BACKGROUND

The European Academy of Paediatric Dentistry (EAPD) proposes this best clinical practice guidance to help practitioners decide when and how to prescribe dental radiographs in children and adolescents.

METHODS

Four expert working groups conducted each a systematic review of the literature. The main subjects were radiation protection, intraoral dental radiography (bitewing and periapical radiographs), panoramic radiography (PR) and cone-beam computed tomography (CBCT). In addition, three workshops were held during the corresponding EAPD Interim Seminar in Chania (Crete, Greece) in 2019. On the basis of the identified evidence, all invited experts presented their findings and during the workshops aspects of clinical relevance were discussed.

RESULTS

Several clinical-based recommendations and statements were agreed upon.

CONCLUSION

There is no or low-grade evidence about the efficacy of dental radiographic examinations in young populations. The given recommendations and rationales should be understood as best clinical practice guidance. It is essential to respect the radiological principles of an individualized and patient-specific justification. When a dental radiograph is required, its application needs to be optimized, aiming at limiting the patient's exposure to ionising radiation according to the ALADAIP principle (As Low As Diagnostically Achievable being Indication-oriented and Patient-specific).

A novel guided surgery system with a sleeveless open frame structure: a retrospective clinical study on 38 partially edentulous patients with 1 year of follow-up

Background

This retrospective clinical study aims to present results of experience with a novel guided surgery system with a sleeveless, open-frame structure, in which the surgical handpiece (not the drills used for preparation) is guided.

Methods

This study was based on an evaluation of the records of partially edentulous patients who had been treated with a sleeveless open-frame guided surgery system (TWIN-Guide®, 2Ingis, Brussels, Belgium), between January 2015 and December 2017. Inclusion criteria were patients with good systemic/oral health and a minimum follow-up of 1 year. Exclusion criteria were patients who had been treated without a guide, or with a guide with sleeves, patients with systemic/oral diseases and who did not have a follow-up of 1 year. The main outcomes were surgical (fit and stability of the surgical guide, duration of the intervention, implant stability, and any intra-operative or immediate post-operative complication), biologic, and prosthetic.

Results

Thirty-eight patients (24 males, 14 females; mean age 56.5 ± 14.0 years) were included in the study. These patients had been treated with 110 implants inserted by means of 40 sleeveless, open-frame guides. With regard to fit and stability, 34 guides were excellent, 4 acceptable, and 2 inadequate for use. The mean duration of the intervention was 23.7 (± 6.7) minutes. Immediately after placement, 2 fixtures were not stable and had to be removed. Two patients experienced pain/swelling after surgery. The 108 surviving implants were restored with 36 single crowns and 32 fixed partial prostheses (24 two-unit and 8 three-unit bridges); these restorations survived until the 1-year follow-up, with a low incidence of biologic and prosthetic complications.

Conclusions

Within the limits of this study, this novel guided surgery system with sleeveless, open frame–structure guides seems to be clinically reliable; further studies on a larger sample of patients are needed to confirm these outcomes.

Trueness of cone beam computed tomography versus intra-oral scanner derived three-dimensional digital models: An ex vivo study

OBJECTIVES

To compare the trueness of 3D digital models derived from CBCT and IOS and to evaluate their accuracy for implementation in oral implant rehabilitation.

MATERIALS AND METHODS

A dry human mandible with a full set of intact teeth was included in the study. The mandible was scanned using Trios IOS and four different CBCT machines with various protocols for generation of 3D digital models. A µCT was utilized to scan each tooth individually. Following registration and segmentation, the trueness evaluation of 3D digital models was carried out by part comparison analysis and color-coded mapping of the superimposed teeth surfaces.

RESULTS

The four CBCT-derived 3D digital models with different protocols had better trueness than Trios IOS. NewTom VGi evo (110 KV), ProMax 3D (90 kV), 3D Accuitomo 170 (90 kV), Green 21 (110 kV), and Green 21 (90 kV) showed significantly better trueness than IOS. However, 3D Accuitomo 170 and ProMax 3D CBCT devices with 70 kV protocol showed better trueness without any significant difference with IOS.

CONCLUSION

CBCT-derived 3D digital models showed better trueness when compared with IOS. When CBCT data are available for preoperative planning for oral implant rehabilitation, it may preclude the need for IOS for obtaining 3D study models.

Novel low-dose protocols using cone beam computed tomography in dental medicine: a review focusing on indications, limitations, and future possibilities

OBJECTIVES

A narrative review on the potential use of low-dose protocols for cone beam computed tomography (CBCT) was conducted to identify indications and their relevance for various dental disciplines.

MATERIALS AND METHODS

Google Scholar was searched using the words "low-dose CBCT". Reviews, consensus papers, clinical studies, and experimental studies were eligible for the initial screening process, but for data extraction only original articles were selected. Similar search procedures were then performed with the additional search words "pedo," "ortho," "endo," "implant," "perio," and "oral surgery." Furthermore, references of included articles were examined to identify further relevant articles.

RESULTS

After screening, 27 publications remained for the data extraction process. Low-dose protocols have been reported for specialties such as pediatric dentistry (evaluating orofacial clefts, periapical lesions, impacted teeth, and autotransplantation), orthodontics (cephalometric analysis and interim assessment of treatment results), endodontics (detecting root fractures, resorptions and periapical bone loss), implant dentistry (planning implant insertion, evaluating peri-implant fenestration and dehiscence), periodontology (assessing periodontal structures), and oral and maxillofacial surgery (assessing mandibular third molars and TMJs). Nevertheless, most of the literature available is related to non-clinical studies. Furthermore, there is a lack of position statements or guidelines from authoritative bodies regarding the use of low-dose protocols in dental medicine.

CONCLUSIONS

Low-dose protocols for CBCT imaging seem to have potential in various disciplines in dental medicine ranging from pediatric dentistry to oral and maxillofacial surgery. Dose reduction is usually achieved by mAs reduction, use of partial rotations, reduced number of projections, and larger voxel sizes, but seldom by kV reduction.

CLINICAL RELEVANCE

Albeit low-dose protocols have potential to result in a reduction of dose exposure for 3D imaging due to dental indications, there is a need to more clearly specify indications and limitations to avoid indiscriminate use of standard and high-dose CBCT scans in the future on the lines of ALARA/ALADA principles.

Comparative Study between a Novel In Vivo Method and CBCT for Assessment of Ridge Alterations after Socket Preservation-Pilot Study

The aim of this study was to compare two different methods for evaluation of alveolar bone resorption after the socket preservation procedure. In the current study, 9 patients with a total of nine teeth indicated for extraction were included. Patients received alveolar ridge preservation with allograft (BoneAlbumin™, OrthoSera Dental, Gyor, Hungary) or Platelet-Rich fibrin (PRF). CBCT (Planmeca ProMax 3D, Helsinki, Finland), was taken at 1 week and 4 months after the socket preservation procedure. A 3D scan, obtained with Trios (3Shape, Copenhagen, Denmark) of the alveolar bone of the surgical site and the adjacent teeth at the place of extraction was performed during the surgical procedure, immediately after the graft placement in the alveolar socket, and after 4 months. Virtual study models were generated using the three-dimensional file processing software "Meshlab" (ISTI-CNR Rome Italy). The changes of alveolar height and width were measured and analyzed. Results were taken from both methods. Radiographic examination revealed that the average value of horizontal resorption is 0.6⁻2.4 mm, and vertical resorption is 0.46⁻2.8 mm. On virtual models, the average value for horizontal resorption is 1.92⁻3.64 mm, the vertical resorption value is 0.95⁻2.10 mm. The Trios intraoral scan can provide non-invasive and more accurate quantitative insights into the dimensional changes in the alveolar ridge after the bone remodeling process. More research is needed for verification of these results.

Combining Intraoral and Face Scans for the Design and Fabrication of Computer-Assisted Design/Computer-Assisted Manufacturing (CAD/CAM) Polyether-Ether-Ketone (PEEK) Implant-Supported Bars for Maxillary Overdentures

PURPOSE

To present a digital method that combines intraoral and face scanning for the computer-assisted design/computer-assisted manufacturing (CAD/CAM) fabrication of implant-supported bars for maxillary overdentures.

METHODS

Over a 2-year period, all patients presenting to a private dental clinic with a removable complete denture in the maxilla, seeking rehabilitation with implants, were considered for inclusion in this study. Inclusion criteria were fully edentulous maxilla, functional problems with the preexisting denture, opposing dentition, and sufficient bone volume to insert four implants. Exclusion criteria were age < 55 years, need for bone augmentation, uncompensated diabetes mellitus, immunocompromised status, radio- and/or chemotherapy, and previous treatment with oral and/or intravenous aminobisphosphonates. All patients were rehabilitated with a maxillary overdenture supported by a CAD/CAM polyether-ether-ketone (PEEK) implant-supported bar. The outcomes of the study were the passive fit/adaptation of the bar, the 1-year implant survival, and the success rates of the implant-supported overdentures.

RESULTS

15 patients (6 males, 9 females; mean age 68.8 ± 4.7 years) received 60 implants and were rehabilitated with a maxillary overdenture supported by a PEEK bar, designed and milled from an intraoral digital impression. The intraoral scans were integrated with face scans, in order to design each bar with all available patient data (soft tissues, prosthesis, implants, and face) in the correct spatial position. When testing the 3D-printed resin bar, 12 bars out of 15 (80%) had a perfect passive adaptation and fit; in contrast, 3 out of 15 (20%) did not have a sufficient passive fit or adaptation. No implants were lost, for a 1-year survival of 100% (60/60 surviving implants). However, some complications (two fixtures with peri-implantitis in the same patient and two repaired overdentures in two different patients) occurred. This determined a 1-year success rate of 80% for the implant-supported overdenture.

CONCLUSIONS

In this study, the combination of intraoral and face scans allowed to successfully restore fully edentulous patients with maxillary overdentures supported by 4 implants and a CAD/CAM PEEK bar. Further studies are needed to confirm these outcomes.

Assessment of peri-implant defects at titanium and zirconium dioxide implants by means of periapical radiographs and cone beam computed tomography: An in-vitro examination

OBJECTIVE

To test the accuracy of measurement of interproximal peri-implant bone defects at titanium (Ti) and zirconium dioxide (ZrO₂ ) implants by digital periapical radiography (PR) and cone beam computed tomography (CBCT).

MATERIAL AND METHODS

A total of 18 models, each containing one Ti and one ZrO₂ implant, were cast in dental stone. Six models each were allocated to following defect groups: A-no peri-implant defect, B-1 mm width defect, C-1.5 mm width defect. The defect width was measured with a digital sliding caliper. Subsequently, the models were scanned by means of PR and CBCT. Three examiners assessed the defect width on PR and CBCT. Wilcoxon signed-rank test and Wilcoxon rank sum test were applied to detect differences between imaging techniques and implant types.

RESULTS

For PR, the deviation of the defect width measurement (mm) for groups A, B, and C amounted to 0.01 ± 0.03, -0.02 ± 0.06, and -0.00 ± 0.04 at Ti and 0.05 ± 0.02, 0.01 ± 0.03, and 0.09 ± 0.03 at ZrO₂ implants. The corresponding values (mm) for CBCT reached 0.10 ± 0.11, 0.26 ± 0.05, and 0.24 ± 0.08 at Ti and 1.07 ± 0.06, 0.64 ± 0.37, and 0.54 ± 0.17 at ZrO₂ implants. Except for Ti with defect A, measurements in PR were significantly more accurate in comparison to CBCT (p ≤ 0.05). Both methods generally yielded more accurate measurements for Ti than for ZrO₂ .

CONCLUSIONS

The assessment of interproximal peri-implant defect width at Ti and ZrO₂ implants was more accurate in PR in comparison to CBCT. Measurements in CBCT always led to an overestimation of the defect width, reaching clinical relevance for ZrO₂ implants.

Computer-Aided Surgical Simulation for Yaw Control of the Mandibular Condyle and Its Actual Application to Orthognathic Surgery: A One-Year Follow-Up Study

Background: Favourable occlusal interdigitation and an optimized position of the mandibular condyle after surgery are essential for obtaining favourable results. The position of the condyle is determined during the operation. However, it is difficult to maintain the condyle’s original position post-surgery despite the efforts of the surgeons. Indeed, a degree of rotation of the condyle is unavoidable, since it is difficult to verify whether the condyle is positioned correctly during surgery. Purpose: To maximize contact between the bone segments, the condyle was rotated around the vertical axis using surgical simulations. We examined changes to the condyle-fossa relationship after comparing virtual surgery to actual surgery. Methods: From 2015 to 2017, 20 patients were diagnosed with skeletal malocclusion and participated in computer-aided surgical simulation before undergoing orthognathic surgery. In the simulation, the mandibular condyles were rotated around the vertical axis, and the proximal segments were fixed to the distal segments using a customized miniplate and positioning device during actual surgery. This study investigated the relationship between the condyle and fossa using cone-beam computed tomography for several different time periods (preoperative (T0), virtual surgery (Tv), postoperative three days (T1) and one year (T2)). Results: The coronal and sagittal view exhibited significant differences in the mean values between T1and T0, Tv, and T2 for all joint spaces. As a result of the distance, the mean value of T2 in both the superior joint space (JS) and the lateral JS was significantly higher than that of Tv. In contrast, the mean value of Tv in the medial JS was significantly higher than that of T2. Moreover, the mean value of T2 on the axial plane was significantly larger than the values of Tv and T1. The mean value of T0 was also significantly larger than those of Tv and T1, and the mean value of Tv was larger than that of T1. Although the condyle was rotated, it exhibited a tendency to return to its preoperative position. There was no statistically significant difference in functional evaluation between T0 and T2. Conclusion: Our method of using yaw control for the condyle during virtual surgery and transferring this technique to the actual surgery can improve the conventional surgical technique by positioning the proximal segment in a pre-planned position, thus achieving optimal results.