Research progress on deep learning algorithms to assist 3D tooth segmentation of digital dental models / 口腔疾病防治

@#Three-dimensional tooth segmentation is the segmentation of single-tooth models from a digital dental model. It is an important foundation for diagnosis, planning, treatment and customized appliance manufacturing in digital orthodontics. With the deep integration of artificial intelligence technology and big data from stomatology, the use of deep learning algorithms to assist 3D tooth segmentation has gradually become mainstream. This review summarizes the current situation of deep learning algorithms that assist 3D tooth segmentation from the aspects of dataset establishment, algorithm architecture, algorithm performance, innovation and advantages, deficiencies of current research and prospects. The results of the literature review showed that deep learning tooth segmentation methods could obtain an accuracy of more than 95% and had good robustness. However, the segmentation of complex dental models, operation time and richness of the training database still need to be improved. Research and development of the "consumption reduction and strong core" algorithm, establishment of an authoritative data sample base with multiple centers, and expansion of data application depth and breadth will lead to further development in this field.

Evaluación del Índice de Korkhaus en adultos chilenos con oclusión normal / Evaluation of Korkhaus Index in Chilean adult individuals with normal occlusion

El examen de modelos es una de las múltiples herramientas diagnósticas que posee la ortodoncia y ortopedia dentomáxilofacial. Los valores con que se construyó su norma estadística están basados en poblaciones específicas y no reflejan las diferencias morfológicas existentes en el complejo cráneofacial entre las distintas etnias. El propósito de esta investigación fue identificar las longitudes transversales y sagitales de los maxilares de la población adulta mestiza chilena con oclusión normal y compararlas con el índice de Korkhaus basado en una población adulta caucásica alemana. Se reclutaron 20 estudiantes de pregrado de la Facultad de Odontología de la Universidad de Valparaíso con oclusión normal. Se registraron ambas arcadas dentarias con yeso y se aplicó el índice de Korkhaus: se midió la longitud interpremolar, la longitud intermolar, la longitud anterior superior y la longitud anterior inferior. La comparación entre los valores de la muestra y los valores referenciales del índice de Korkhaus fue hecha con la prueba de rangos de Wilcoxon mediante el software estadístico STATA 15.0 y se consideraron significativos valores de p<0,05. Se encontró una diferencia estadísticamente significativa en el valor de la longitud anterior superior (p-0,013); para la longitud interpremolar (p-0,9552) la longitud intermolar (p-0,8223) y la longitud anterior inferior (p-0,0452) no se hallaron diferencias. La mayor magnitud de la longitud anterior superior de la arcada dentaria respecto a la población adulta caucásica alemana se debe al rasgo de protrusión dentaria presente en la población mestiza chilena, lo cual no altera las características de una oclusión normal.

The model exam is one of many diagnostic tools in orthodontics and dentomaxillofacial orthopedics. The values on which the statistical norm were constructed, are based on specific populations and they do not reflect the morphological differences in the craniofacial complex between the different ethnic groups. The purpose of this study was to identify the transverse and sagittal maxillary and mandibular lengths of the Chilean mestizo adult population with normal occlusion, and compare them with the Korkhaus index based on a German Caucasian adult population. For this study 20 undergraduate students with normal occlusion were recruited from the Faculty of Dentistry of the University of Valparaíso. Both upper and lower dental casts were obtained from each student, and Korkhaus index was applied: the interpremolar length, intermolar length, upper anterior length and lower anterior length were measured. Comparison between the values of the sample and the reference values of the Korkhaus index was made with the Wilcoxon range test using the STATA 15.0 statistical software and significant values of p <0.05 were considered. A statistically significant difference was found in the value of the upper anterior length (p-0.013); for the interpremolar length (p-0.9552) the intermolar length (p-0.8223) and the lower anterior length (p-0.0452) no differences were found. The greater magnitude of the dental arch upper anterior length compared to the German Caucasian adult population is due to dental protrusion present in the Chilean mestizo population, which does not affect the normal occlusion characteristics.

The Extra-Oral Measuring Technique of Initial Restoring Force Produced by Orthodontic Archwire Based on Dental Model / 医用生物力学

Objective To realize the extra-oral measurement of initial recovery force produced by orthodontic wire using simulated dental model. Methods A clinical patient was selected as the study objective, and maxillary dental models, which were in accordance with the real dentition of patient, were fabricated by three-dimensional printing. An orthodontic force measuring system was constructed using Nano17 F/T mechanical sensors to measure the initial recovery forces on two maxillary central incisors, which were produced by a standard circle Ni-Ti wire with the diameter of 355.6 μm after the archwire was assembled on the dental model. Results Central incisor 21 suffered a lager initial orthodontic force compared with incisor 11, and the force systems on two incisors were both adverse to tooth ideal movement, therefore, an assistive device was necessary to improve force status of the teeth. When the orthodontic treatment plan was optimized, a satisfactory result was obtained after 18 months of treatment. Conclusions Force systems caused by orthodontic wire and exerted on the teeth could be accurately measured using the simulated dental model of patient, so as to predict the teeth moving type, and improve teeth treatment plan on this basis. The extra-oral measuring technique of orthodontic force provides an important reference for clinical orthodontic treatment, and creates a novel idea for the optimal design of orthodontic plan.

Accuracy of dental models fabricated by CAD/CAM milling method and 3D printing method

The purpose of this study was to evaluate the accuracy of a dental model fabricated using the CAD/CAM milling method and the 3D printing method. materials and method: this study was conducted in sequence of the digitization of the master model using an intraoral scanner, the manufacturing of working models (milling model, Multi-jet printing model and color-jet printing model) by using the scan data of the master model, the digitization of the working model by using a laboratory scanner, the superimposition of the digital data of the master model and working models using inspection software, and 3-dimensional analysis. ten measurements per group were done by one practitioner. one-way ANOVA and Tukey's post-hoc test were performed to compare the difference between the three groups. results: the overall difference in models caused by the manufacturing method was measured as 73.05µm±9.64µm, 84.52µm±4.78µm, and 96.05µm±5.43µm in the milling group, multi-jet printing group and color-jet printing group, respectively. the difference according to the shape of the teeth, the abutment teeth among the three parts was recorded with the lowest values as 19.18±2.08µm, 77.10±7.48µm, and 56.63±4.58µm. conclusions: dental models manufactured by the CAD/CAM milling method presented superior accuracy over the models manufactured by the 3D printing method. therefore, the use of optimized CAD software and appropriate materials is crucial for the fabrication accuracy of dental models.

Clinical application of an intraoral scanner for serial evaluation of orthodontic tooth movement: A preliminary study / 대한치과교정학회지

The aim of this study was to test the clinical application of an intraoral scanner for serial evaluation of orthodontic tooth movement. The maxillary dentitions of eight patients with fixed orthodontic appliances were scanned using an intraoral scanner at the beginning of treatment (T0), and at 1 month (T1), 2 months (T2), 3 months (T3), and 4 months (T4) after T0. The serial digital models were superimposed on the palatal surface as a reference area, and the linear and angular changes of the central incisors, canines, and first molars were evaluated. The intraclass correlation coefficient and method errors showed that this method was clinically acceptable. Various types of orthodontic tooth movements, including minute movements, could be observed every month. The intraoral scanner and digital superimposition technique enabled the serial evaluation of orthodontic tooth movement without taking serial impressions and/or acquiring radiographs.

Fabrication and accuracy research on 3D printing dental model based on cone beam computed tomography digital modeling / 华西口腔医学杂志

<p><b>OBJECTIVE</b>The aim of this study is to build a digital dental model with cone beam computed tomography (CBCT), to fabricate a virtual model via 3D printing, and to determine the accuracy of 3D printing dental model by comparing the result with a traditional dental cast.</p><p><b>METHODS</b>CBCT of orthodontic patients was obtained to build a digital dental model by using Mimics 10.01 and Geomagic studio software. The 3D virtual models were fabricated via fused deposition modeling technique (FDM). The 3D virtual models were compared with the traditional cast models by using a Vernier caliper. The measurements used for comparison included the width of each tooth, the length and width of the maxillary and mandibular arches, and the length of the posterior dental crest.</p><p><b>RESULTS</b>3D printing models had higher accuracy compared with the traditional cast models. The results of the paired t-test of all data showed that no statistically significant difference was observed between the two groups (P>0.05).</p><p><b>CONCLUSIONS</b>Dental digital models built with CBCT realize the digital storage of patients' dental condition. The virtual dental model fabricated via 3D printing avoids traditional impression and simplifies the clinical examination process. The 3D printing dental models produced via FDM show a high degree of accuracy. Thus, these models are appropriate for clinical practice.</p>

Study on the consistency of the position of the brackets on the digital occlusal model and the actual position af-ter indirect bonding / 口腔疾病防治

Objective@#To provide the experimental basis for the coherence of the indirect bond position by comparing the position of the bracket on the digital occlusal model and the position of the transfer to the initial plaster model.@*Methods@#Fifteen digitized models were selected for the brackets on the dental denture model, the brackets were transferred to the initial plaster model by indirect bond transfer trays, The line distance between each bracket position in digital dental model and initial plaster model was measured with OrthoRx software. @*Results @#The difference between the position of the orthodontic brackets and the position of the initial plaster model was less than 0.20 mm, and the difference was statistically significant (P < 0.05). @*Conclusion @#The position of the bracket on the digital occlusal model is consistent with that of the original plaster model, which provides a theoretical basis for digital indirect bonding.

Three-dimensional data fusion method for tooth crown and root based on curvature continuity algorithm / 北京大学学报(医学版)

Objective:To explore a three-dimensional (3D) data fusion and integration method of optical scanning tooth crowns and cone beam CT (CBCT) reconstructing tooth roots for their natural transition in the 3D profile.Methods: One mild dental crowding case was chosen from orthodontics clinics with full denture.The CBCT data were acquired to reconstruct the dental model with tooth roots by Mimics 17.0 medical imaging software, and the optical impression was taken to obtain the dentition mo-del with high precision physiological contour of crowns by Smart Optics dental scanner.The two models were doing 3D registration based on their common part of the crowns'' shape in Geomagic Studio 2012 reverse engineering software.The model coordinate system was established by defining the occlusal plane.crown-gingiva boundary was extracted from optical scanning model manually, then crown-root boundary was generated by offsetting and projecting crown-gingiva boundary to the root model.After trimming the crown and root models, the 3D fusion model with physiological contour crown and nature root was formed by curvature continuity filling algorithm finally.In the study, 10 patients with dentition mild crowded from the oral clinics were followed up with this method to obtain 3D crown and root fusion models, and 10 high qualification doctors were invited to do subjective evaluation of these fusion models.Results: This study based on commercial software platform, preliminarily realized the 3D data fusion and integration method of optical scanning tooth crowns and CBCT tooth roots with a curvature continuous shape transition.The 10 patients'' 3D crown and root fusion models were constructed successfully by the method, and the average score of the doctors'' subjective evaluation for these 10 models was 8.6 points (0-10 points).which meant that all the fusion models could basically meet the need of the oral clinics, and also showed the method in our study was feasible and efficient in orthodontics study and clinics.Conclusion: The method of this study for 3D crown and root data fusion could obtain an integrate tooth or dental model more close to the nature shape.CBCT model calibration may probably improve the precision of the fusion model.The adaptation of this method for severe dentition crowding and micromaxillary deformity needs further research.

Comparison of arch forms between Turkish and North American

ABSTRACT Objective: The aim of this study was to clarify the morphological differences in the mandibular arches of Turkish and North American white subjects. Methods: The sample included 132 Turkish (34 Class I, 58 Class II, and 40 Class III) and 160 North American (60 Class I, 50 Class II, and 50 Class III) subjects. The most facial portion of 13 proximal contact areas was digitized from photocopied images of patients' mandibular dental arches. Clinical bracket points were calculated for each tooth based on mandibular tooth thickness data. Four linear and two proportional measurements were taken. The subjects were grouped according to arch form types (tapered, ovoid and square) in order to have frequency distribution compared between ethnic groups in each Angle classification. Results: The Turkish group showed significantly lower molar depth and more significant molar width-depth (W/D) ratio in all three Angle classifications. On the other hand, the Turkish group also showed a significantly larger intercanine width in Class III malocclusion and intermolar width in Class II malocclusion. The most frequent arch forms seen were the ovoid arch form in the Turkish group and the tapered form in the white group. Conclusions: Our results demonstrate that when treating Turkish patients, one should expect to use preformed ovoid arch form orthodontic wires in a significant percentage of patients.

RESUMO Objetivo: o objetivo deste estudo foi avaliar as diferenças morfológicas entre as arcadas dentárias inferiores de indivíduos turcos e indivíduos norte-americanos leucodermas. Métodos: a amostra incluiu 132 indivíduos turcos (34 Classe I, 58 Classe II e 40 Classe III) e 160 norte-americanos (60 Classe I, 50 Classe II e 50 Classe III). A porção mais vestibular de 13 áreas de contato proximal foi digitalizada a partir de imagens impressas das arcadas dentárias inferiores dos pacientes. Os pontos de colagem dos braquetes foram calculados, para cada dente, com base em dados referentes à espessura dos dentes inferiores. Quatro medidas lineares e duas proporcionais foram obtidas. Os indivíduos foram classificados de acordo com o formato da arcada (triangular, oval e quadrada), permitindo que a frequência de cada formato fosse comparada entre os grupos étnicos, e dentro de cada classificação de Angle. Resultados: o grupo composto por indivíduos turcos apresentou profundidade da arcada na região dos molares significativamente menor, além de uma proporção largura/profundidade da arcada na região dos molares maior em todas as classificações de Angle. Em contrapartida, esse mesmo grupo mostrou maiores distâncias intercaninos nos pacientes Classe III e intermolares nos pacientes Classe II. A arcada oval foi a mais frequente no grupo composto por indivíduos turcos, enquanto a arcada triangular foi a mais frequente no grupo composto por indivíduos norte-americanos leucodermas. Conclusões: os resultados obtidos mostram que, ao tratar pacientes turcos, o profissional deve prever o uso de arcos ortodônticos pré-conformados ovais em um percentual significativo dos pacientes.

New prediction equations for the estimation of maxillary mandibular canine and premolar widths from mandibular incisors and mandibular first permanent molar widths: A digital model study / 대한치과교정학회지

OBJECTIVE: The primary aim of the study was to generate new prediction equations for the estimation of maxillary and mandibular canine and premolar widths based on mandibular incisors and first permanent molar widths. METHODS: A total of 2,340 calculations (768 based on the sum of mandibular incisor and first permanent molar widths, and 1,572 based on the maxillary and mandibular canine and premolar widths) were performed, and a digital stereomicroscope was used to derive the the digital models and measurements. Mesiodistal widths of maxillary and mandibular teeth were measured via scanned digital models. RESULTS: There was a strong positive correlation between the estimation of maxillary (r = 0.85994, r2 = 0.7395) and mandibular (r = 0.8708, r2 = 0.7582) canine and premolar widths. The intraclass correlation coefficients were statistically significant, and the coefficients were in the strong correlation range, with an average of 0.9. Linear regression analysis was used to establish prediction equations. Prediction equations were developed to estimate maxillary arches based on Y = 15.746 + 0.602 × sum of mandibular incisors and mandibular first permanent molar widths (sum of mandibular incisors [SMI] + molars), Y = 18.224 + 0.540 × (SMI + molars), and Y = 16.186 + 0.586 × (SMI + molars) for both genders, and to estimate mandibular arches the parameters used were Y = 16.391 + 0.564 × (SMI + molars), Y = 14.444 + 0.609 × (SMI + molars), and Y = 19.915 + 0.481 × (SMI + molars). CONCLUSIONS: These formulas will be helpful for orthodontic diagnosis and clinical treatment planning during the mixed dentition stage.

Evaluation of digital dental models obtained from dental cone-beam computed tomography scan of alginate impressions / 대한치과교정학회지

OBJECTIVE: To investigate the dimensional accuracy of digital dental models obtained from the dental cone-beam computed tomography (CBCT) scan of alginate impressions according to the time elapse when the impressions are stored under ambient conditions. METHODS: Alginate impressions were obtained from 20 adults using 3 different alginate materials, 2 traditional alginate materials (Alginoplast and Cavex Impressional) and 1 extended-pour alginate material (Cavex ColorChange). The impressions were stored under ambient conditions, and scanned by CBCT immediately after the impressions were taken, and then at 1 hour intervals for 6 hours. After reconstructing three-dimensional digital dental models, the models were measured and the data were analyzed to determine dimensional changes according to the elapsed time. The changes within the measurement error were regarded as clinically acceptable in this study. RESULTS: All measurements showed a decreasing tendency with an increase in the elapsed time after the impressions. Although the extended-pour alginate exhibited a less decreasing tendency than the other 2 materials, there were no statistically significant differences between the materials. Changes above the measurement error occurred between the time points of 3 and 4 hours after the impressions. CONCLUSIONS: The results of this study indicate that digital dental models can be obtained simply from a CBCT scan of alginate impressions without sending them to a remote laboratory. However, when the impressions are not stored under special conditions, they should be scanned immediately, or at least within 2 to 3 hours after the impressions are taken.

Investigation on dental model sanitation status in medical institutions in Changning District of Shanghai / 上海预防医学

Objective To investigate the sanitation status of dental model in medical institutions in Changning District of Shanghai, and to provide evidence for strengthening the disinfection management. Methods 40 medical institutions in Changning District of Shanghai were investigated by field sampling and detection. Results 92.5% of the investigated medical institutions disinfected dental models.In 168 dental model samples, the qualification rate of sanitary quality was 88.1%, while exceeded number of bacteria was the major reason for the unqualified.Among all dental model disinfection methods including ultraviolet irradiation, disinfectant soaking, disinfectant spraying and ozone, ultraviolet irradiation was the most widely used and disinfectant soaking was with the best effect.The storage sites of disinfected dental models including filling room, pollution area of sterilization room and other locations.Dental models stored in the filling room were with the highest qualification rate. Conclusion The current dental model sanitation status in medical institutions in Changning District of Shanghai is relatively unsatisfactory;supervision and inspection administration need to be strengthened by health and family planning administrative departments.

Three-dimensional Digital Evaluation of Dental Arches in Infants with Cleft Lip and/or Palate

The aim of this study was to measure and compare the dimensions of the dental arches on three-dimensional digital study models in children with and without cleft lip and palate before the primary surgery. The sample consisted of 223 digital models of children aged 3-9 months, divided into 5 groups: without craniofacial deformities, unilateral and bilateral incomplete cleft lip and alveolus, unilateral and bilateral complete cleft lip and alveolus, unilateral cleft lip and palate, and bilateral cleft lip and palate. Dental casts of the maxillary dental arches of the children were used. The dental casts underwent a process of scanning through 3D scanner and the measurements used for the correlation among groups were made on the scanned images. Statistical analysis was performed by t test and ANOVA followed by Tukey test. The results showed that the intercanine distance and anterior cleft width was wider in children with unilateral cleft lip and palate. The intertuberosity distances and posterior cleft width was wider in children with bilateral cleft lip and palate among the groups. Children with cleft lip and palate before the primary surgery had wider maxillary arch dimensions than the children without cleft lip and palate.

O propósito deste trabalho foi mensurar e comparar as dimensões dos arcos dentários em modelos digitais tridimensionais de crianças com ou sem fissuras de lábio e palato antes das cirurgias primárias. A amostra foi composta de 223 modelos de gesso de crianças, de 3 a 9 meses, divididas em 5 grupos: sem deformidades craniofaciais, fissura pré-forame incompleta, fissura pré-forame completa, fissura transforame unilateral e fissura transforame bilateral. Modelos de gesso dos arcos dentários superiores das crianças foram utilizados para avaliação. Os modelos passaram por um processo de digitalização, por meio de escâner 3D e as medidas utilizadas para a correlação entre os grupos foram realizadas diretamente nas imagens escaneadas. A análise estatística foi realizada por meio do teste t e ANOVA seguido pelo teste de Tukey. Os resultados mostraram que a distância intercaninos e a amplitude anterior da fissura foram maiores nas crianças com fissura transforame unilateral. A distância intertuberosidades e a amplitude posterior da fissura foi maior nas com fissura transforame bilateral entre os grupos estudados. As crianças com fissura de lábio e palato apresentam as dimensões dos arcos maxilares maiores que as crianças sem fissura labiopalatina antes das cirurgias primárias.

An Evaluation of Validity of Measurements using Digital Caliper and Three-dimensional Virtual Dental Models / 대한해부학회지

The measurement of tooth and the space analysis of dental study models are essential for precise diagnosis and treatment plan for orthodontic or prosthodontic cases. Traditionally, these have been done on study models with instruments, such as a divider or a caliper. At present, three-dimensional (3-D) virtual dental models are available for clinicians, supplemented by dedicated software for performing needed measurements on them. For example, Autoscan system for dental application(TM) (ASDA; INUS technology INC, Korea) is one of these systems using a non-contact 3- D scanner. The accuracy of this system has been tested and validated by the Korea Testing Laboratory. However, the outline of dental models is not simple and has many undercuts. Therefore, we sought to evaluate the accuracy of measuring models using digital calipers or ASDA to compare these two techniques. From each ten study models, 10 duplicated stone and 10 virtual models were generated. Virtual models were scanned from duplicated model because of revival of clinical situation. Then, central incisors, canines, first molars, arch (intercanine and intermolar) width of original model were measured by a digital caliper, and the same items of virtual models were measured by software. All measurements were performed twice by two experienced observers. Data were statistically analyzed by 2-way Analysis of Variance (2-way ANOVA, SPSS Ver. 11.5). The results from this study have demonstrated that virtual model is highly valid and reliable for measuring both tooth size and arch width. Although some values of virtual model are higher or lower than original dental model, the significance value is still higher than 0.97. A digital caliper seems to be a more precise instrument to perform a scientific work, ASDA's accuracy is clinically acceptable. Furthermore, considering its present advantages and future possible applications, the examined or equivalent 3-D virtual models may become the standard for clinical use.

Application of reverse engineering to reconstruction of dental models / 中华医学美学美容杂志

Objective To discuss the foreground of application of reverse engineering reconstruction of dental models and to establish the foundation of developing a system for complete denture CAD/CAM. Methods The models of an edentulous jaw were measured with reverse engineering, and the 3D models were reconstructed with a computer. Results 3D models of the edentulous jaw were achieved. The characteristics of these 3D images were clear and accurate. Conclusion CAD models are reconstructed with reverse engineering accurately and technical problems in 3D model of complete denture CAD/CAM are resolved.

Measurements of teeth, dental arch and base bone in Mongolia teenages / 实用口腔医学杂志

Objective: To obtain the data of dental measurements in healthy Mongolia teenages.Methods: Normal dentognathic models were obtained by cephalometric roentgenography in 56 teenages (30 boys and 26 girls) aged 10～17 years. The width of the tooth crown, the size of the dental arch and dental base bone were measured with a vernier. The measurments were statistically analysed.Results: The tooth crown in boys was wider than that in girls( P 0.05). There was no significant difference in Bolton index and Point index between boys and girls.Conclusion: The dental measurments may be refrences for dental clinic and research.

Study of lingual arch form of ClassⅠmalocclusions after extraction and nonextraction treatment / 实用口腔医学杂志

Objective: To compare and analyze the maxillary lingual arch forms of ClassⅠmalocclusions after extraction and non-extraction treatment respectively. Methods: 60(30 with extraction, 30 non-extraction)maxillary dental models of ClassⅠmalocclusions after orthodontic treatment were measured in lingual arch widths and depths. The data were analyzed by statistical methods and the charts of lingual arch forms were drawn. Results: The lingual arch widths and depths in anterior segments of the extraction group were significantly larger than those of the non-extraction group(P0.05). The lingual arch forms of the two groups were similar in anterior segments, and more different in premolar and first molar segments, but similar from the distal lingual cusp of the first molars. Conclusion: The lingual arch forms of the two groups are similar in appearances, but the anterior segments of the extraction group are deeper than that of the non-extraction group.

Measurement and analysis of dental arch on normal occlusion in Chongqing teenagers / 重庆医科大学学报

Objective: This study is conducted to establish the norms of the width and length of the dental arch on normal occlusion in Chongqing teenagers and to analyze the characteristics in arch dimensions,in order to provide the reference for diagnosis in orthodontics.Methods: 92 cases of normal occlusion dental model in Chongqing teenagers(45 boys and 47 girls) were selected.The width and length of the dental arch were measured with a vernier.The measurements were analysed with statistic methods and compared with those of different groups.Results: The width and length of the dental arch in boys were larger than those in girls.The form of dental arch of both boys and girls was oval.Conclusion: There were distinguishing characteristics in arch dimensions on normal occlusion in Chongqing teenagers.Ethnic differences should be considered in orthodontics.