Maxillary Scans Research Articles

Accuracy of full arch scans performed with nine different scanning patterns– an in vitro study

ObjectiveEvaluation of the accuracy of direct digitization of maxillary scans depending on the scanning strategy.Materials and methodsA maxillary model with a metal bar as a reference structure fixed between the second molars was digitized using the CEREC Primescan AC scanner (N = 225 scans). Nine scanning strategies were selected (n = 25 scans per strategy), differing in scan area segmentation (F = full jaw, H = half jaw, S = sextant) and scan movement pattern (L = linear, Z = zig-zag, C = combined). Trueness was assessed by evaluating linear differences in the X, Y, and Z axes and angular deviations (α axial, α coronal, α total) compared to a reference dataset. Statistical differences were analyzed using Kruskal-Wallis and Mann-Whitney U tests (p<0.017). Precision was analyzed by the standard deviation of linear and angular aberrations (ISO 5725-1) (p < 0.05).ResultsStrategy FL showed significantly higher trueness and precision than FZ for VE (p = 0.009), VE(y) (p = 0.010), αoverall (p = 0.004), and αaxial (p = 0.002). Strategy FC demonstrated significantly better trueness than FZ for VE (p = 0.007), αoverall (p = 0.010), and αcoronal (p = 0.013). For scan segmentation, FL showed better trueness for VE(y) (p = 0.001) and αaxial (p < 0.001) than HL. Strategy HL showed better trueness for VE(z) than for FL and SL (p = 0.001, p = 0.002). The scanning patterns FL, FC, and HL exhibited the best performance for trueness and precision.ConclusionsScanning motion and segmentation have a significant impact on the trueness and precision of full-arch scans.Clinical relevanceThe scanning strategy is decisive in enhancing the clinical workflow and the accuracy of full-arch scans.

Three-dimensional assessment of virtual clear aligner attachment removal: A prospective clinical study

In digital dentistry, virtual attachment removal (VAR) optimizes clear aligner therapy by enhancing efficiency for refinements and enabling prefabricated retainer production through the removal of attachments from a digital scan before the clinical removal of clear aligner attachments. This prospective clinical study aimed to evaluate the accuracy of VAR in the maxillary arch. A total of 110 teeth were analyzed from a sample of 54 maxillary scans from 25 subjects. Models with attachments were virtually debonded using Meshmixer (Autodesk, San Rafael, Calif) and superimposed over the control group in MeshLab. Vector Analysis Module (Canfield Scientific, Fairfield, NJ) was used to calculate and analyze 3-dimensional Euclidean distances on the buccal surfaces between the superimposed models. Statistical analysis was performed using SPSS (version 23.0, IBM, Armonk, NY). The Shapiro-Wilkes (α= 0.05) test determined a nonnormal distribution of results. The Kruskal-Wallis (α= 0.05) was used to determine differences between different tooth types and the number of attachments. The VAR protocol showed no statistical differences in the root mean square between different tooth segments with an overall tendency for inadequate attachment removal. No difference between the groups was found regarding the number of attachments when used as a main factor. The VAR technique is precise enough for the fabrication of retainers from printed dental models in a clinical setting and is not affected by the number of attachments on the tooth.

Influence of interdental spaces and the palate on the accuracy of maxillary scans acquired using different intraoral scanners.

To assess the influence of interdental spaces and scanning the palate on the accuracy of maxillary scans acquired using three intraoral scanners (IOSs). A virtual completely dentate maxillary cast without interdental spaces was obtained and modified to create 1, 2, and 3mm of interdental spacing between the anterior teeth. These three files (reference standard tessellation language files) were used to print three reference casts. The reference casts were scanned using three IOSs: TRIOS4, iTero Element 5D, and Aoralscan2. Three groups were created based on the interdental spaces: 0, 1, 2, and 3mm (n = 10). The groups were subdivided into two subgroups: no palate (NP subgroup) and palate (P subgroup). The reference STL files were used to measure the discrepancy with the experimental scans by calculating the root mean square (RMS) error. Three-way analysis of variance (ANOVA) and post hoc Tukey pairwise comparison tests were used to analyze trueness. The Levene test was used to analyze precision (α = 0.05). Trueness ranged from 91 to 139μm and precision ranged from 5 to 23μm among the subgroups tested. A significant correlation was found between IOS*group (p<0.001) and IOS*subgroup ( p<0.001). Tukey test showed significant trueness differences among the interdental spaces tested (p<0.001). The 1- and 2-mm groups obtained better trueness than the 0- and 3-mm groups (p<0.001). An 11μm mean trueness discrepancy was measured among the different interdental space groups tested. The P subgroups demonstrated significantly higher trueness when compared to the NP subgroups (p<0.001). The discrepancy between the maxillary scans with and without the palate was 4μm. Significant precision discrepancies were found (p = 0.008), with the iTero group showing the lowest precision. Interdental spaces and incorporation of the palate on maxillary intraoral scans influenced trueness and precision of the three IOSs tested. However, the scanning discrepancy measured may be of no clinical relevance.

Evaluation of Maxillary Transverse Arch Dimensions Following Leveling and Alignment with Different Archwire-Bracket Combinations During Fixed Appliance Treatment - A Retrospective Study

Background- Arch expansion is one of the non- extraction methods of gaining space. This study aims to assess and compare the arch expansion achieved during initial leveling and alignment with three different bracket-archwire combinations.&#x0D; Material and Methods- This was a retrospective study done in a university setup. From the available patient information archives, records of 30 subjects based on their advocated bracket system were identified and categorized into three groups. Their pre-treatment (T0) and post aligning (T2) 3D model maxillary scans were superimposed according to the reference points marked on the third palatal rugae using an OrthoAnalyzer software(3 shape version 19.0) to assess the changes in Intercanine width (ICW), Inter-premolar width (IPW) and Intermolar width (IMW) and arch length. For the recorded data, descriptive statistics, One-way ANOVA and Tukey HSD post hoc were analyzed using SPSS software. &#x0D; Results- Except for the Damon group that showed considerable increase in the intermolar and premolar dimensions, other groups had no statistically significant differences in terms of Intercanine width, Interpremolar width, and Intermolar width and Arch length.&#x0D; Conclusion- Changes in the transverse dimension were noticed among all the three groups with maximum in the Damon bracket and Damon archwire combination. Although the difference in expansion between groups showed no statistically significant difference, it was appreciated clinically in relieving dental crowding.

Intraoral Scanners for In Vivo 3D Imaging of the Gingiva and the Alveolar Process.

This study aimed to assess the reliability of two intraoral surface scanners for the representation of the alveolar process in vivo. Complete maxillary scans (CS 3600, Carestream and TRIOS 3, 3Shape) were repeatedly obtained from 13 fully dentate individuals. Scanner precision and agreement were tested using 3D surface superimpositions on the following reference areas: the buccal front teeth area, the entire dental arch, the entire alveolar process, or single teeth by applying an iterative closest point algorithm. Following each superimposition, the mean absolute distance (MAD) between predefined 3D model surfaces was calculated. Outcomes were analyzed through non-parametric statistics and the visualization of color-coded distance maps. When superimpositions were performed on the alveolar process, the median scanner precision was below 0.05 mm, with statistically significant but negligible differences between scanners. The agreement between the scanners was approximately 0.06 mm. When single-tooth superimpositions were used to assess the precision of adjacent alveolar soft-tissue surfaces, the median error was 0.028 mm, and there was higher agreement between the scanners. The in vivo reliability of the intraoral scanners in the alveolar surface area was high overall. Single-tooth superimpositions should be preferred for the optimal assessment of neighboring alveolar surface areas relative to the dentition.

Trueness and Precision of Economical Smartphone-Based Virtual Facebow Records.

To investigate the trueness and precision of virtual facebow records using a smartphone as a three-dimensional (3D) face scanner. Twenty repeated virtual facebow records were performed on two subjects using a smartphone as a 3D face scanner. For each subject, a virtual facebow was attached to his/her maxillary arch, and face scans were performed using a smartphone with a 3D scan application. The subject's maxillary arch intraoral scan was aligned to the face scan by the virtual facebow fork. This procedure was repeated 10 times for each subject. To investigate if the maxillary scan is located at the right position to the face, these virtual facebow records were superimposed to a cone-beam computed tomography (CBCT) head scan from the same subject by matching the face scan to the 3D face reconstruction from CBCT images. The location of maxillary arch in virtual facebow records was compared with its position in CBCT. The "trueness" of the proposed procedure is defined as the deviation between maxilla arch position in virtual facebow records and the CBCT images. The "precision" is defined as the deviation between each virtual facebow record. The linear deviation at left central incisor (#9), left first molar (#14), and right first molar (#3), as well as angular deviation of occlusal plane were analyzed with descriptive statistics. Differences between two objects were also explored with Mann Whitney U test. The 20 virtual facebow records using the smartphone 3D scanner deviated from the CBCT measurements (trueness) by 1.14 ± 0.40 mm at #9, 1.20 ± 0.50 mm at #14, 1.12 ± 0.51 mm at the #3, and 1.48 ± 0.56° in the occlusal plane. The VFTs deviated from each other by 1.06 ± 0.50 mm at #9, 1.09 ± 0.49 mm at #14, 1.11 ± 0.58 mm at #3, and 0.81 ± 0.58° in the occlusal plane. When all sites combined, the trueness was 1.14 ± 0.40 mm, and the precision was 1.08 ± 0.52 mm. Out of eight measurements, three measurements were significantly different between subjects. Nevertheless, the mean difference was small. Virtual facebow records made using smartphone-based face scan can capture the maxilla position with high trueness and precision. The deviation can be anticipated as around 1 mm in linear distance and 1° in angulation.

Comparison of the accuracy of intraoral scans between complete-arch scan and quadrant scan

ObjectiveTo compare the accuracy of complete-arch scans and quadrant scans obtained using a direct chairside intraoral scanner.Material and methodsIntraoral scans were obtained from 20 adults without missing teeth except for the third molar. Maxillary and mandibular complete-arch scans were carried out, and 4 quadrant scans for each arch were performed to obtain right posterior, right anterior, left anterior, and left posterior quadrant scans. Complete-arch scans and quadrant scans were compared with corresponding model scans using best-fit surface-based registration. Shell/shell deviations were computed for complete-arch scans and quadrant scans and compared between the complete-arch scans and each quadrant scans. In addition, shell/shell deviations were calculated also for each individual tooth in complete-arch scans to evaluate factors which influence the accuracy of intraoral scans.ResultsComplete-arch scans showed relatively greater errors (0.09 ~ 0.10 mm) when compared to quadrant scans (0.05 ~ 0.06 mm). The errors were greater in the maxillary scans than in the mandibular scans. The evaluation of errors for each tooth showed that the errors were greater in posterior teeth than in anterior teeth. Comparing the right and left errors, the right side posterior teeth showed a more substantial variance than the left side in the mandibular scans.ConclusionThe scanning accuracy has a difference between complete-arch scanning and quadrant scanning, particularly in the posterior teeth. Careful consideration is needed to avoid scanning inaccuracy for maxillary or mandibular complete-arch, particularly in the posterior area because a complete-arch scan might have potential error than a quadrant scan.

Nasopalatine canal and periapical radiolucency fusion following dentoalveolar trauma: A CBCT-based case-control study.

There is a lack of evidence regarding the radiological characteristics of a periapical radiolucency (PRL) fusion with the nasopalatine canal (NPC) following dentoalveolar trauma. The aim of this study was to assess the NPC enlargement resulting from fusion with a PRL and its relationship with the surrounding anatomical structures. A total of 100 patients was retrospectively recruited and divided into two groups: case group and control group. The case group consisted of 50 cone-beam computed tomography scans of the maxilla of patients (32 males, 18 females; age range: 11-83 years) with a known history of dentoalveolar trauma in the maxillary anterior region and the presence of an undiagnosed and/or asymptomatic NPC and PRL fusion. An age- and gender-matched control group of 50 patients (32 males, 18 females; age range: 11-82 years) without trauma history to the upper anterior teeth, demonstrating normal maxillary scans, was recruited. A subjective scoring criterion was established for assessing the characteristics of the fused lesion and its relationship with the buccal/palatal alveolar cortex, nasal cavity cortex, NPC cortical border, and maxillary sinus floor. The fused NPC and PRL was mainly lobular in appearance (88%) with non-corticated well-defined margins (80%). Male patients showed larger (68%) dimensions compared with female patients (32%). The NPC cortical bone was the most commonly perforated structure in relation to fusion (72%), whereas maxillary sinus cortical bone was the least effected (2%). A statistically significant difference was observed between the NPC dimensions in the control and test groups, with fused lesions having larger mesiolateral, craniocaudal, and buccopalatal dimensions (P < .001). Periapical radiolucencies should be treated as soon as possible before they fuse with NPC. In case of fusion, surgical enucleation should be considered as the treatment of choice.

The effective dose of different scanning protocols using the Sirona GALILEOS(®) comfort CBCT scanner.

To determine the effective dose and CT dose index (CTDI) for a range of imaging protocols using the Sirona GALILEOS(®) Comfort CBCT scanner (Sirona Dental Systems GmbH, Bensheim, Germany). Calibrated optically stimulated luminescence dosemeters were placed at 26 sites in the head and neck of a modified RANDO(®) phantom (The Phantom Laboratory, Greenwich, NY). Effective dose was calculated for 12 different scanning protocols. CTDI measurements were also performed to determine the dose-length product (DLP) and the ratio of effective dose to DLP for each scanning protocol. The effective dose for a full maxillomandibular scan at 42 mAs was 102 ± 1 μSv and remained unchanged with varying contrast and resolution settings. This compares with 71 μSv for a maxillary scan and 76 μSv for a mandibular scan with identical milliampere-seconds (mAs) at high contrast and resolution settings. Changes to mAs and beam collimation have a significant influence on effective dose. Effective dose and DLP vary linearly with mAs. A collimated maxillary or mandibular scan decreases effective dose by approximately 29% and 24%, respectively, as compared with a full maxillomandibular scan. Changes to contrast and resolution settings have little influence on effective dose. This study provides data for setting individualized patient exposure protocols to minimize patient dose from ionizing radiation used for diagnostic or treatment planning tasks in dentistry.

Integration of a maxillary model into facial surface stereophotogrammetry

Three-dimensional (3D) integration of a maxillary model into a facial model has only been possible by a complex procedure using face bow transfer after taking impressions of certain maxillary and facial parts. In this study, we aimed to develop a method for integrating a scanned maxillary model into a scan-realized facial model. A total of 19 patients with the medical indication for cone-beam computed tomography (CBCT) and orthodontic treatment were included in this study. Facial and maxillary scans were also taken. The construction of the integrated surface model required 10 steps. This integration procedure was evaluated by taking ten 3D dentofacial linear segment measurements in the integrated scan and the CBCT. These results were analyzed using descriptive statistics. All measurements demonstrated good intra-individual reliability. We observed almost perfect congruence between integrated scan and CBCT in vertical distances, while the sagittal measurements revealed more, yet clinically acceptable, deviations possibly caused by different error sources in either of the two methods. This new method is suitable for generating 3D integrated surface-scan models which can be used for growth and therapy control studies in orthodontics and other disciplines in the dentofacial fields. Since this method does not require ionizing radiation, it is highly recommendable as an application for children and adolescent patients.

Dosimetry of two extraoral direct digital imaging devices: NewTom cone beam CT and Orthophos Plus DS panoramic unit.

This study provides effective dose measurements for two extraoral direct digital imaging devices, the NewTom 9000 cone beam CT (CBCT) unit and the Orthophos Plus DS panoramic unit. Thermoluminescent dosemeters were placed at 20 sites throughout the layers of the head and neck of a tissue-equivalent RANDO phantom. Variations in phantom orientation and beam collimation were used to create three different CBCT examination techniques: a combined maxillary and mandibular scan (Max/Man), a maxillary scan and a mandibular scan. Ten exposures for each technique were used to ensure a reliable measure of radiation from the dosemeters. Average tissue-absorbed dose, weighted equivalent dose and effective dose were calculated for each major anatomical site. Effective doses of individual organs were summed with salivary gland exposures (E(SAL)) and without salivary gland exposures (E(ICRP60)) to calculate two measures of whole-body effective dose. The effective doses for CBCT were: Max/Man scan, E(ICRP60)=36.3 micro Sv, E(SAL)=77.9 micro Sv; maxillary scan, E(ICRP60)=19.9 micro Sv, E(SAL)=41.5 micro Sv; and mandibular scan, E(ICRP60)=34.7 micro Sv, E(SAL)=74.7 micro Sv. Effective doses for the panoramic examination were E(ICRP60)=6.2 micro Sv and E(SAL)=22.0 micro Sv. When viewed in the context of potential diagnostic yield, the E(ICRP60) of 36.3 micro Sv for the NewTom compares favourably with published effective doses for conventional CT (314 micro Sv) and film tomography (2-9 micro Sv per image). CBCT examinations resulted in doses that were 3-7 (E(ICRP60)) and 2-4 (E(SAL)) times the panoramic doses observed in this study.

Effective dose and risk assessment from computed tomography of the maxillofacial complex.

The effective dose from computed tomography of the maxillofacial complex has been estimated and used for an assessment of risk. For each scan sequence 64 TLDs were placed in 27 selected sites in the upper portion of a tissue-equivalent human phantom to record the equivalent dose in radiosensitive organs/tissues. Equivalent doses ranged from 0.11 mSv (bone marrow, maxillary scan) to 20 mSv (salivary glands, mandibular scan). By the use of a calculation that included the salivary glands as part of the remainder, two contiguous 1 cm axial slices of the maxilla were found to result in an effective dose of 0.1 mSv, and four contiguous 1 cm axial slices of the mandible in an effective dose of 0.76 mSv. Effective doses of this magnitude represent a probability of stochastic effects of the order of 8 X 10(-6) and 56 X 10(-6) respectively.

Absorbed doses from computed tomography for dental implant surgery: comparison with conventional tomography.

Tomography is often needed prior to implant surgery to evaluate jaw bone dimensions. Computed tomography (CT) is advocated as an alternative. The purpose of this study was to measure the absorbed doses to radiosensitive organ in the head and neck region when CT is used. Measurements were made with extruded LiF thermoluminescent dosemeters within and on an anthropomorphic phantom examined with a Philips Tomoscan LX CT scanner. Axial scanning was performed for the maxilla and both frontal, perpendicular to the alveolus, and axial for the mandible. The highest absorbed doses were at the skin surface, 38 mGy with maxillary scans, and from axial and frontal scans of the mandible 35 mGy and 37 Gy, respectively. The parotid dose was 31 mGy from maxillary scans and in the mandible the submandibular gland dose was 27 mGy with axial scanning and 16 mGy with frontal. The eye lens received its highest dose (5.5 mGy) from frontal scans of the mandible. Although outside the scanning plane the pituitary and the thyroid glands received comparatively high absorbed doses of 0.6-4.0 mGy. All organ doses measured were considerably higher than those reported for conventional tomography.