An integration protocol for aligning intraoral scans to facial scans using the nasal geometry reference in a fully dentate patient.

Advanced digital technologies have rapidly been integrated into prosthodontics to improve the digital workflow for prosthetic rehabilitation. The integration of 3D datasets acquired from various imaging sources such as intraoral scanners and facial optical scanners allows the creation of virtual patients to perform presurgical simulation and prosthetic rehabilitation. The presented technique introduced a straightforward protocol for aligning intraoral scans (Trios 4, 3Shape) to optical face scans (Face Hunter, Zirkonzahn) using a global best-fit algorithm of 3D evaluation software (GOM Inspect). Nasal geometry data were used as the matching reference to produce virtual dental patients. This integration protocol ensured that the intraoral scanner (Trios 4, 3Shape) was used not only to scan dental arches but also used effectively to scan the nose. These scans along with professional facial scans can be successfully aligned to produce virtual dental patients. As only a single fully dentate patient case with an alignment deviation of 243.6 µm was used, further research to evaluate the accuracy of this protocol is needed.

Evaluating the Feasibility and Accuracy of Digitizing a Maxillary Defect Model Simulating Various Trismus Conditions.

PURPOSE: To compare the feasibility and accuracy of using intraoral scanners to digitize a maxillary defect model simulating various trismus conditions. MATERIALS AND METHODS: Four intraoral scanners were used to digitize a maxillary defect model simulating four different degrees of trismus (mouth opening = 10, 20, 30, and 40 mm), and the scanned areas were compared. The scans were also superimposed on each other for precision analysis and on reference data for trueness analysis using 3D evaluation software. Two-way ANOVA was used to compare area, precision, and trueness among scanners and among conditions. RESULTS: The surface area for which 3D data were obtained by the intraoral scanners ranged from 2,672 to 6,613 mm2. Significant differences were observed between the scanners (P < .001) and between the trismus conditions (P < .001), with a smaller scanned surface area in severe trismus (10 mm). Trueness ranged from 0.033 to 0.301 mm, and precision from 0.022 to 0.397 mm. Significant differences in trueness and precision values were found among the scanners (P = .001 and P = .001, respectively), but not the trismus conditions (P = .260 and P = .075, respectively). CONCLUSION: Although trueness and precision differed between intraoral scanners, digitization of the maxillectomy model simulating various trismus conditions appears to be feasible from the perspective of accuracy with all of the scanners used. The smaller scanned surface area in the severe trismus condition was due to lack of data on the defect site in that condition.

Three-dimensional evaluation of the dental arch in cleft lip and palate after prosthetic treatment.

PURPOSE: This study aimed to evaluate the stability of the surface of the maxillary teeth and mucosa in cleft lip and palate (CLP) patients with a maxilla defect or tissue deficiency according to the duration of observation and cleft type. METHODS: Pairs of maxillary casts taken from 18 patients at different time points after prosthodontic treatment were investigated in this study. All 36 casts were scanned with an intraoral scanner, and the acquired images were saved in standard tesselation language (STL) files. The two STL files for each patient were then superimposed using three-dimensional (3D) evaluation software, with 3D deviations shown as a color map. Areas with a 3D deviation within ±0.100 mm were defined as stable. The influence of cleft type and duration of observation on the ratio of stable areas to the entire maxillary surface comprising the teeth and mucosa was investigated using multiple regression analysis. Statistical significance was set at p <0.05. RESULTS: Multiple regression analysis showed that the duration of observation was significantly associated with the stable area ratio (B = -23.463, P<.001), whereas cleft type was not (ß = 0.13, P = 0.301). CONCLUSIONS: The maxillary teeth and mucosa of CLP patients changed over time, with stable areas showing a negative correlation with the observation period. However, the stability of the dental arch was not significantly affected by the cleft type. 3D analysis of the casts of CLP patients allowed for measurements and to accurately assess relapse of the maxillary arch after prosthetic treatment.

Computerized optical scanning of ears: An in vitro evaluation with an intraoral scanner.

STATEMENT OF PROBLEM: Making conventional facial impressions can be uncomfortable for the patient and complicated for the prosthodontist. Using facial scanners to digitize faces is an alternative approach. However, the initial costs of the equipment have prevented their widespread use in dental practice, and the accuracy of ear scanning is unclear. PURPOSE: The purpose of this in vitro study was to investigate the accuracy of a widely used intraoral scanner for digitizing an ear model. MATERIAL AND METHODS: For reference, a silicone model of an ear was scanned with an industrial scanner. Then, the model was scanned 5 times with an intraoral scanner. Five conventional impressions of the model were made with a hydrocolloid impression material and poured with dental stone. The stone casts were then digitized with a desktop scanner. The data sets acquired with the 3 approaches were analyzed by using a 3-dimensional (3D) evaluation software program. Trueness and precision values were calculated for each approach. Linear mixed models with random intercepts were fitted to each sample to evaluate the effects of the impression method on mean deviations (α=.05). RESULTS: Mean ±standard deviation trueness and precision values were 0.097 ±0.012 mm and 0.033 ±0.015 mm, respectively, for the digital scan, and 0.092 ±0.022 mm and 0.081 ±0.024 mm for the conventional impression, showing a significantly lower deviation in precision for the digital approach (P<.001). CONCLUSIONS: The feasibility of digitizing an ear efficiently by using the investigated intraoral scanner was demonstrated, and similar trueness and significantly better precision values were achieved than when using conventional impressions. These promising results suggest the need for clinical investigations.

Triangular mesh reduction of digitized maxillectomy defects for prosthetic rehabilitation: A 3D deviation study.

OBJECTIVES: To evaluate the effect of triangular mesh reduction on the trueness of digitized complete-arch dentate and edentulous maxillectomy defects models. MATERIAL AND METHODS: Twenty gypsum maxillectomy defect models (dentate and edentulous group: n = 10) were digitized using the Trios 3 intraoral scanner, scanning the teeth, mucosa and maxillectomy defect. These datasets (reference, R0) were saved as standard tessellation language (STL) files, and triangular mesh reduction was performed using the Meshmixer reduction tool. Digital test-datasets with file sizes reduced by 50%(R1), 75%(R2), and 90%(R3) were generated (each: n = 20). Each test-dataset was compared to the R0 file using a 3D evaluation software (GOM Inspect), applying automated pre-alignment followed by a best-fit alignment, and root mean square (RMS) 3-dimensional (3D) deviations were calculated. Statistical analyses were performed, at a level of significance of α=0.05. RESULTS: The number of triangles, and STL file size were synchronized with each other and inversely proportional to the amount of mesh reduction. The resulting mean percentages of the STL file sizes were 50.00% for R1, 24.93% for R2, and 10.00% for R3. There were no 3D deviations at 50% triangular mesh reduction. The 3D deviations increased with the amount of mesh reduction: at 75% reduction the median deviations were lower (dentate:0.0016 mm, IQR:0.0015-0.0018; edentulous:0.0016 mm, IQR:0.0015-0.0016), than at 90% (dentate:0.004 mm, IQR:0.0038-0.0041; edentulous:0.003 mm, IQR:0.0036-0.0039). A statistically significant increase in 3D deviations was observed with higher degrees of mesh reduction (p<0.001). CONCLUSIONS: Triangular mesh reduction results in a significant increase in 3D deviations if the reduction is more than 75%. CLINICAL SIGNIFICANCE: Digital models of patients with maxillectomy defects can be saved with a mesh reduction of 50% without affecting the trueness. The use of a 50% mesh reduction decreases the required storage capacity by 50%.

Augmented Reality for Interactive Visualization of 3D Maxillofacial Prosthetic Data.

PURPOSE: To introduce an augmented reality (AR) application for students, patients, and practitioners to use to visualize a maxillectomy defect, the associated obturator prosthesis, and the eventual effects on the patient's facial appearance. MATERIALS AND METHODS: Various 3D virtual models related to maxillectomy defects and their prosthetic rehabilitations were used to illustrate the handheld AR application. The AR "scene" was created using Vuforia and Unity3D software. Within this scene, 3D virtual models were linked to the target image by detecting a symbol track marker. The final file was saved as an installable application and exported for Android smart devices. RESULTS: The target image containing the maxillectomy defect and the prosthetic rehabilitation were successfully visualized interactively in 3D mode using the handheld AR maxillofacial prosthetic application. CONCLUSION: An AR application for visualizing maxillofacial prosthetic data could interestingly be developed as a pedagogic tool to explain prosthetic treatments.

Feasibility of Intraoral Scanning for Data Acquisition of Maxillectomy Defects.

PURPOSE: To assess the feasibility of using an intraoral scanner for data acquisition of maxillectomy defects. MATERIALS AND METHODS: In 10 patients who had undergone a maxillectomy, the maxillectomy defects in dentate and edentulous maxillary arches were intraorally scanned. Intraoral photographs were also taken using a digital camera for comparison. RESULTS: Adequate scanning was achieved for the nondefect side of the maxilla and for residual teeth. In some cases, it was impossible to scan the maxillectomy defect, especially the deep sites. CONCLUSION: Improved intraoral scanning technology will increase the feasibility of its use in maxillofacial prosthetics.

Smartphone Application as a Low-Cost Alternative for Digitizing Facial Defects: Is It Accurate Enough for Clinical Application?

PURPOSE: To evaluate the accuracy of a smartphone application as a low-cost approach for digitizing a facial defect for 3D modeling. MATERIALS AND METHODS: A stone model of a facial defect was scanned using industrial computed tomography (reference scan) and was also scanned five times using a commercial laser scanner. A series of 24 sequenced digital photographs was taken five times by smartphone at two elevations. These images were uploaded and processed by a cloud-based server to create virtual 3D models. The 3D datasets were geometrically evaluated and compared to the reference data using 3D evaluation software. Mann-Whitney U test was used for statistical analysis, and the significance was set at P < .05. RESULTS: The overall mean 3D deviation ± standard deviation for the smartphone dataset was 604.9 ± 123.5 µm compared to 67.5 ± 0.49 µm for the laser scanner. There was a significant difference in the accuracy between the commercial laser scanner and the smartphone application (P = .009). CONCLUSION: The results showed that within the limits of this study and in reference to standard computed tomography imaging, data acquisition with a smartphone for 3D modeling is not as accurate as commercially available laser scanning.

Geometric Evaluation of the Effect of Prosthetic Rehabilitation on Facial Asymmetry in Mandibulectomy Patients.

PURPOSE: To geometrically evaluate facial asymmetry in patients with mandibulectomy defects with and without their mandibular prostheses in place and to compare the results to a nonpatient group. MATERIALS AND METHODS: Facial data from a convenience sample of 16 patients with mandibulectomy defects and a control group of 16 nonpatients were acquired using a noncontact 3D digitizer. Facial asymmetry was evaluated by superimposing a facial scan onto its mirror scan for each patient's 3D dataset using 3D evaluation software. RESULTS: Facial asymmetry was significantly different between mandibulectomy patients and control participants. As expected, asymmetry was significantly different in mandibulectomy patients with and without their prostheses. CONCLUSION: Wearing a mandibular prosthesis notably improved facial asymmetry.

Precision and Trueness of Computerized Optical Impressions in Maxillectomy Defects: An In Vitro 3D Comparison.

PURPOSE: To evaluate the precision and trueness of computerized optical impressions of maxillectomy defects. MATERIALS AND METHODS: Three different maxillectomy defect models based on the Aramany classification system were used. Reference digitization of the models was performed with an industrial computerized tomography scanner. Each model was scanned five times using an intraoral scanner (True Definition). With the use of 3D evaluation software, the 3D datasets were geometrically superimposed using a best-fit algorithm to evaluate precision and trueness. Statistical analysis was performed to determine differences between the scans. RESULTS: There was a statistically significant difference in both precision and trueness between Aramany classes (P < .001). CONCLUSION: Digitizing maxillectomy defect models with an intraoral scanner appears to be accurate and reliable.

Color change of airborne particle-abraded acrylic resin surfaces: A palatography method.

STATEMENT OF PROBLEM: A palatogram aids prosthodontists and speech pathologists in evaluating the precise prosthetic treatment needed and the effectiveness of such treatment to improve speech intelligibility. Powder is commonly used to visualize tongue-palate contact, where wetted areas of powder in the oral cavity reveal such contact during palatography. However, discomfort and the risk of aspiration are among the shortcomings of this method, and an improved method is needed. PURPOSE: The purpose of this in vitro study was to examine the feasibility of a new method of palatography that uses airborne-particle-abraded acrylic resin so that wet areas can be easily distinguished from dry areas. MATERIAL AND METHODS: Seventy-two specimens of heat-polymerized acrylic resin were prepared in 6 different resin colors. After the specimens had been airborne-particle abraded, CIELab color values for each specimen were measured using a colorimeter under dry and wet conditions and recorded. Color difference (ΔE) was then computed, and a paired Student t test, 1-way analysis of variance, and multiple comparison using the Tukey post hoc analysis were applied (α=.05). RESULTS: A significant color difference was found between the 2 conditions in all acrylic resin specimens examined. Mean ΔE ranged from 5.58 to 6.76. CONCLUSIONS: The results indicated that an airborne-particle-abraded acrylic resin surface can show color differences made by wetting on palatograms.

Digitized Speech Characteristics in Patients with Maxillectomy Defects.

PURPOSE: Accurate evaluation of speech characteristics through formant frequency measurement is important for proper speech rehabilitation in patients after maxillectomy. This study aimed to evaluate the utility of digital acoustic analysis and vowel pentagon space for the prediction of speech ability after maxillectomy, by comparing the acoustic characteristics of vowel articulation in three classes of maxillectomy defects. MATERIALS AND METHODS: Aramany's classifications I, II, and IV were used to group 27 male patients after maxillectomy. Digital acoustic analysis of five Japanese vowels-/a/, /e/, /i/, /o/, and /u/-was performed using a speech analysis system. First formant (F1) and second formant (F2) frequencies were calculated using an autocorrelation method. Data were plotted on an F1-F2 plane for each patient, and the F1 and F2 ranges were calculated. The vowel pentagon spaces were also determined. One-way ANOVA was applied to compare all results between the three groups. RESULTS: Class II maxillectomy patients had a significantly higher F2 range than did Class I and Class IV patients (p = 0.002). In contrast, there was no significant difference in the F1 range between the three classes. The vowel pentagon spaces were significantly larger in class II maxillectomy patients than in Class I and Class IV patients (p = 0.014). CONCLUSION: The results of this study indicate that the acoustic characteristics of maxillectomy patients are affected by the defect area. This finding may provide information for obturator design based on vowel articulation and defect class.

Application of Digital Technologies in Maxillofacial Prosthetics Literature: A 10-Year Observation of Five Selected Prosthodontics Journals.

PURPOSE: To identify trends in the application of various types of digital technologies in maxillofacial prosthetics by identifying these digital technologies and their characteristics and reviewing the prevalence of applied digital technologies and their recent trends in the maxillofacial prosthetics literature. MATERIALS AND METHODS: Five leading peer-reviewed prosthodontics journals were manually searched for maxillofacial prosthetics articles on the use of digital technologies published from January 2008 to December 2017. Descriptive statistics were used to analyze data collected on productivity, type of digital technology used, type of article, type of defect, number of authors, and geographic distribution. RESULTS: Of the 336 maxillofacial prosthetics articles screened, 87 (26%) were selected for analysis. A remarkable increase was found in article productivity in the last 5 years (63%) compared to the first 5 years (37%). There was also a notable increase over the last 10 years in all digital technologies used except for evaluation technologies, which remained almost constant. Case reports most frequently mentioned use of digitization technologies (61%), design technologies (66%), and rapid prototyping technologies (66%). Original research articles most frequently mentioned use of evaluation technologies (89%); 39% of these technologies were used for intraoral defects and 27% for extraoral defects. Most often, articles had four to five authors (54%). Most published articles were from the Asia-Pacific region (44%), followed by North America (22%) and Europe (20%). CONCLUSION: Although the application of digital technologies reported in the maxillofacial prosthetics literature has increased notably in leading prosthodontics journals over the last 10 years, total article productivity has remained relatively small.

Feasibility and Accuracy of Noncontact Three-Dimensional Digitizers for Geometric Facial Defects: An In Vitro Comparison.

PURPOSE: To evaluate the feasibility and accuracy of noncontact three-dimensional (3D) digitization systems for capturing facial defects. MATERIALS AND METHODS: A stone model of a facial defect was digitized using high-accuracy industrial computed tomography as a reference scan. The model was also scanned using four different types of noncontact 3D digitizers: a laser beam light-sectioning technology with camera system and three different stereophotogrammetry systems. All 3D images were reconstructed with corresponding software and saved as standard triangulated language (STL) files. The 3D datasets were geometrically evaluated and compared to the reference data using 3D evaluation software. Kruskal-Wallis H tests were performed to assess differences in absolute 3D deviations between scans, with statistical significance defined as P < .05. RESULTS: The four noncontact 3D digitization systems were feasible for digitizing the facial defect model, although the median 3D deviation of the four digitizers varied. There was a significant difference in accuracy among the digitizers (P < .001). CONCLUSION: Digitization of facial defect models using various noncontact 3D digitizers appears to be feasible and is most accurate with laser beam light-sectioning technology. Further investigations assessing digitization of facial defects among patients are required to clinically verify the results of this study.

Geometric Evaluation of the Effect of Prosthetic Rehabilitation on Facial Asymmetry in Patients with Unilateral Maxillectomy.

PURPOSE: This study aimed (1) to geometrically evaluate areas of facial asymmetry in patients with two different types of maxillectomy defect compared to a control group, (2) to geometrically evaluate the effect of an obturator prosthesis on facial asymmetry, and (3) to investigate the correlation between three-dimensional (3D) deviation values and number of missing teeth. MATERIALS AND METHODS: Facial data from 13 normal control participants and 26 participants with two types of maxillectomy defect (groups 1 and 2) were acquired with a noncontact 3D digitizer. Facial asymmetry was evaluated by superimposing a facial scan onto its mirror scan using 3D evaluation software. Facial scans with and without obturator prostheses were also superimposed to evaluate the obturator effect. The correlation between 3D deviation values and number of missing teeth was also evaluated. Statistical analyses were performed. RESULTS: Facial asymmetry was significantly different between the control group and each maxillectomy defect group (group 1: P < .0001 and P = .020 without and with obturator, respectively; group 2: P < .0001 for both conditions). There were no significant differences in asymmetry between groups 1 and 2 either without or with obturator (P = .457 and P = .980, respectively). There was a significant difference in the obturator effect between groups 1 and 2 (P = .038). 3D deviation values were positively correlated with number of missing teeth in group 1 (r = 0.594, P = .032), but not in group 2. CONCLUSION: A noncontact 3D digitizer and 3D deviation assessment were effective for analyzing facial data of maxillectomy patients. Obturators were effective for improving facial deformities in these patients.

The Role of Portable Documentation Format in Three-Dimensional Interactive Visualization in Maxillofacial Prosthetics.

Although digital technology has advanced the visualization of treatment planning and rehabilitation in prosthodontics, the field of maxillofacial prosthetics is in vital need of an accessible document for exchange of interactive three-dimensional (3D) model visualization without requiring installation of any additional software. This article introduces a 3D data documentation method for effective interactive digital visualization in maxillofacial prosthetics using a portable documentation format (PDF).

Preschool and School Phases of Postmaxillectomy Prosthetic Rehabilitation in a Child: A Clinical Report.

This report describes the postmaxillectomy prosthetic rehabilitation of a child with maxillary chondrosarcoma over an 8-year period. Specifically, it (1) describes the planning and rehabilitation procedures carried out during the period from before the operation to the time when the patient started elementary school and (2) reports the results of evaluations of the patient's oral and psychosocial function conducted during the school phase. The prosthetic treatment plan was separated into two phases (the preschool and school phases) and was started prior to surgery, when an immediate surgical obturator was designed by the surgeons. After the operation, it was considered important to provide the patient and her mother with training regarding how the defect should be cleaned, trismus prevention, and how the prosthesis should be fitted. In addition, esthetic improvements and the ability to speak clearly were also targeted during treatment planning. After surgery, obturators were fabricated in a conventional manner and fitted at the ages of 2, 4, 6, 8, and 10 years. The patient's oral function during the use of the obturators was evaluated objectively. Marked improvements in oral function were seen during both treatment phases. The patient's ability to perform psychosocial functions at school also improved during the use of the obturators.

Effect of Experimental Palatal Prosthesis on Voice Onset Time.

PURPOSE: Objective evaluation of a patient's speech is needed in prosthetic dentistry because the prostheses can affect the intelligibility of speech. Measurement of voice onset time is one evaluation method of consonant production used in phonetic science. The purpose of this study was to confirm the influence of a palatal prosthesis on consonant production by measuring voice onset time. MATERIALS AND METHODS: In this study, voice onset time was measured in 10 healthy women (mean age 26.5 years) under two conditions: with and without an experimental palatal prosthesis. In this study, voice onset time of /ta/ and /ka/ were used to determine the effect of wearing a palatal prosthesis; /pa/ was tested as a control, with the null hypothesis that voice onset time of /ta/ and /ka/ would not change when wearing a palatal prosthesis. RESULTS: Medial voice onset time of /pa/, /ta/, and /ka/ syllables without the palatal prosthesis was 22.5 ms, 19.5 ms, and 42.5 ms, whereas that with the palatal prosthesis was 22.5 ms, 23.5 ms, and 55.0 ms. Voice onset times for /ta/ and /ka/ were prolonged when wearing the experimental palatal prosthesis, whereas /pa/ showed no significant difference. CONCLUSION: Consonant production was affected by wearing a palatal prosthesis, and this change in sound was detected by measuring voice onset time.

Geometric Evaluation of the Effect of Prosthetic Rehabilitation on the Facial Appearance of Mandibulectomy Patients: A Preliminary Study.

PURPOSE: The purpose of this study was to geometrically evaluate the effect of prosthetic rehabilitation on the facial appearance of mandibulectomy patients. MATERIALS AND METHODS: Facial scans (with and without prostheses) were performed for 16 mandibulectomy patients using a noncontact three-dimensional (3D) digitizer, and 3D images were reconstructed with the corresponding software. The 3D datasets were geometrically evaluated and compared using 3D evaluation software. RESULTS: The mean difference in absolute 3D deviations for full face scans was 382.2 µm. CONCLUSION: This method may be useful in evaluating the effect of conventional prostheses on the facial appearance of individuals with mandibulectomy defects.

Feasibility and Accuracy of Digitizing Edentulous Maxillectomy Defects: A Comparative Study.

PURPOSE: The aim of this study was to evaluate the feasibility and accuracy of using an intraoral scanner to digitize edentulous maxillectomy defects. MATERIALS AND METHODS: A total of 20 maxillectomy models with two defect types were digitized using cone beam computed tomography. Conventional and digital impressions were made using silicone impression material and a laboratory optical scanner as well as a chairside intraoral scanner. The 3D datasets were analyzed using 3D evaluation software. RESULTS: Two-way analysis of variance revealed no interaction between defect types and impression methods, and the accuracy of the impression methods was significantly different (P = .0374). CONCLUSION: Digitizing edentulous maxillectomy defect models using a chairside intraoral scanner appears to be feasible and accurate.