Study on clinical efficacy of a 3D model based on crown-root integration in clear aligners / 口腔医学

Objective@#To evaluate the clinical effect of clear aligners in the anterior region in non-extraction cases by establishing a three-dimensional model of crown-root fusion to guide clinical application.@*Methods@#Eleven patients visiting the orthodontic department of Xuzhou Stomatological Hospital from December 2020 to December 2021 were collected, and the orthodontic plan was designed using Maestro 3D Dental Studio scheduling software to obtain the expected three-dimensional model of the patient's orthodontic treatment result. CBCT, intraoral scan, and 3D reconstruction software were used to create a postoperative model of the patient. The crown and root data were aligned in Geomagic Studio 2014, and differences in torque and axial inclination between the actual model after treatment and the predicted model of the anterior teeth before treatment were compared in 3-matic.@*Results@#The actual torque angles of the anterior teeth were all smaller than the predicted angles before treatment, with the highest realization rate of 77.55% for lateral incisors and the lowest of 60.70% for central incisors; the actual axial inclination angles of the anterior teeth were also smaller than the predicted angles before treatment, with the highest realization rate of 81.49% for central incisors and the lowest of 74.95% for cuspids. @*Conclusion@# A digital model of crown-root integration based on a combination of 3D reconstruction and intraoral scanning techniques is advantageous in assessing the efficacy of clear aligners. In non-extraction cases with clear aligner, the efficiency of movement is higher for small areas of the anterior region.

Compensation in Class III Malocclusions: Analysis of Tooth Crown Inclination on Digital Dental Casts / Compensação da Má Oclusão de Classe III: Análise da Inclinação das Coroas dos Dentes em Modelos Digitais

The objective of this study was to evaluate the tooth crown inclination in maxillary and mandibular arches in Class III malocclusion individuals, to identify the presence and magnitude of compensation. The study was conducted on 46 plaster casts of individuals with Class III malocclusion, of both genders (25 males and 21 females), with mean age 21 years and 1 month, with indication for compensatory orthodontic treatment. The dental casts models were scanned and the tooth crown inclinations were measured and compared with standard values by the independent t test. All tests considered a significance level of 5% (p<0.05). According to the results there was extensive variation in tooth inclination in Class III malocclusions. Values distribution for incisors highlighted the significant concentration of maxillary incisors in the area of positive values, compared with a very expressive concentration of mandibular incisors in the area of negative values. Compared with normal standards, in Class III malocclusions, the maxillary posterior teeth exhibited smaller palatal inclination than normal, while the mandibular incisors and second molars presented greater lingual inclination. It was concluded that the analysis of inclinations of all crowns of both dental arches in Class III malocclusions, compared with normal standards, evidenced the presence of natural compensation for maxillary posterior teeth, with reduced palatal inclination, as well as increased lingual inclination in mandibular incisors. The parameters of compensation naturally present in Class III malocclusions described, especially in lower incisors, would help clinicians when compensatory treatment is considered. (AU)

O objetivo deste estudo foi avaliar a inclinação das coroas dentárias nas arcadas superior e inferior em indivíduos com má oclusão de Classe III, para identificar a presença e a magnitude da compensação. O estudo foi realizado em 46 modelos de gesso de indivíduos com má oclusão de Classe III, de ambos os sexos (25 homens e 21 mulheres), com média de idade de 21 anos e 1 mês, com indicação de tratamento ortodôntico compensatório. Os modelos de gesso foram digitalizados e as inclinações da coroa dos dentes foram medidas e comparadas com os valores de normalidade pelo teste t independente. Todos os testes estatísticos adotaram um nível de significância de 5% (p <0,05). De acordo com os resultados, houve grande variação na inclinação dentária nas más oclusões de Classe III. A distribuição dos valores para os incisivos destacou a concentração significativa de incisivos superiores na área de valores positivos, em comparação com uma concentração muito expressiva de incisivos inferiores na área de valores negativos. Comparados aos padrões de normalidade, nas más oclusões de Classe III, os dentes posteriores superiores exibiram inclinação palatina menor que o normal, enquanto os incisivos e segundos molares inferiores apresentaram inclinação lingual maior. Concluiu-se que a análise das inclinações de todas as coroas de ambas as arcadas dentárias nas más oclusões de Classe III, comparadas aos padrões de normalidade, evidenciou a presença de compensação natural para os dentes posteriores superiores, com diminuição da inclinação palatina, bem como aumento da inclinação lingual dos incisivos inferiores. Os parâmetros de compensação naturalmente presentes nas más oclusões de Classe III descritos, especialmente nos incisivos inferiores, podem auxiliar o clínico quando o tratamento compensatório é considerado. (AU)

Avaliação da acurácia dos modelos dentários digitais obtidos para cirurgia ortognática / Assessment of the accuracy of digital dental models obtained for orthognathic surgery

O objetivo deste estudo laboratorial foi avaliar a acurácia dos modelos digitais obtidos por duas técnicas de escaneamento (escâner intraoral - Itero 5d Element® - e escâner de bancada -Straumann ®) de um modelo experimental (Nacional Ossos ®) da arcada superior confeccionada em poliuretano e do modelo de gesso obtido desta arcada. Os pontos A ­ 3mm acima do elemento 17; B ­ 3mm acima do elemento 14; C ­ 3mm acima do elemento 24; D ­ 3mm acima do elemento 27; E ­ cúspide mesiovestibular do elemento 16; F - ponto de contato mais incisal entre os elementos 11 e 21; G - Cúspide mesiovestibular do elemento 26 foram utilizados como referência para as medidas realizadas. As medidas foram realizadas em um software (Geomagic®) de simulação cirúrgica e analisadas quanto a validade e precisão das técnicas de escaneamento utilizadas em todos os grupos (1 a 5). O grupo 1 corresponde ao grupo padrão-ouro; o 2 ao grupo do escaneamento com escâner intraoral do modelo de poliuretano; o 3 ao escaneamento de bancada do modelo; o 4 ao escaneamento com escâner intraoral do modelo de gesso; e 5 ao escaneamento de bancada do modelo de gesso. Na análise da validação, todas as técnicas apresentaram-se válidas quando comparadas ao grupo controle com exceção da medida FG que apresentou diferenças estatisticamente significativas (p<0,05) entre os grupos 1 e 2. A precisão foi avaliada através do índice de correlação intraclasse (CCI) e todas as técnicas apresentaram-se altamente precisas com (CCI) próximo de 1. Desta forma, conclui-se que o escâner intraoral e o escâner de bancada utilizados neste estudo foram confiáveis quando comparados ao grupo controle e que os dois modelos de escâner utilizados se apresentaram com alta precisão (AU).

The objective of this experimental study was to evaluate the accuracy of digital models generated by two scanning techniques (intraoral scanner - Itero 5d Element® - and desktop scanner -Straumann ®) of an experimental model of the upper arch (Nacional Ossos ®) made of polyurethane and the plaster model obtained from this arch. Points A ­ 3mm above element 17; B ­ 3mm above element 14; C ­ 3mm above element 24; D ­ 3mm above element 27; E ­ mesiobuccal cusp of element 16; F - most incisal point of contact between elements 11 and 21; G - Mesiobuccal cusp of element 26 were used as a reference for the measurements performed. The measurements were performed in a surgical simulation software (Geomagic ®) and analyzed for the validity and precision of the scanning techniques used in all groups (1 to 5). Group 1 corresponds to the gold standard group; 2 to the scanning group with intraoral scanner of the polyurethane model; 3 to the desktop scan of the model; 4 to intraoral scanner scanning of the plaster model; and 5 to the desktop scan of the plaster model. In the validation analysis, all techniques showed to be valid compared to the control group, except the FG measure, which showed statistically significant differences (p<0.05) between groups 1 and 2. Precision was assessed using the intraclass correlation(ICC) index, and all techniques were highly accurate with an ICC close to 1. Thus, it is concluded that the intraoral scanner and the bench scanner used in this study were reliable compared to the control group and that the two scanner models used presented themselves with high precision (AU).

Research progress on root position measurement methods in orthodontic treatment using cone beam CT / 口腔疾病防治

@#Root position plays an important role in healthy, stable, and aesthetic orthodontic treatment. In the past, two-dimensional radiographic images were used to assess the accuracy and precision of tooth root positions. In recent years, the use of cone beam CT (CBCT) and its reconstructed images to measure the three-dimensional spatial position and angle of root position has become mainstream. The root position is mainly described by measuring the relationship between the root and adjacent structures in the buccolingual, vertical, and mesiodistal directions as well as the root angle. The thickness of the alveolar bone on the buccolingual side of the root represents the buccolingual position, the vertical height in the alveolar bone and the relationship between apex and maxillary sinus represents the vertical position, the interroot alveolar bone thickness represents the mesiodistal position of the root, and the root angle is mostly based on incisal mandibular plane angle, angulation, torque, and other angles in the traditional two-dimensional measurement. Fitting CBCT and digital model data can be used to monitor the relationship between root and alveolar bone during orthodontic treatment, but a more comprehensive, standardized three-dimensional tooth root position measurement method is required to make full use of the root data provided by CBCT to study the relative optimal position of the tooth root at different anatomical levels, which combines with computer technology to optimize the digital design of orthodontic diagnosis and treatment.

Root canal treatment of maxillary second molar with three mesial buccal root canals: a case report and literature review / 口腔疾病防治

Objective@#To explore the key points of clinical diagnosis and treatment of three mesiobuccal root canals.@*Methods@# In the procedure of endodontic therapy for the upper left second molar with pulpitis, through root canal exploration under a dental microscope and cone beam CT (CBCT)-assisted imaging examination, it was confirmed that the left upper second molar contained 3 roots and 5 root canals, among which the third root canal existed in the mesiobuccal root. Combined with perfect root canal preparation, cleaning, disinfection, filling and minimally invasive inlay repair, the clinical symptoms were eliminated. The patients were followed up and the related literatures were reviewed. @* Results @# One- and two-year follow-ups showed that the tooth had no discomfort and could be used normally. X-ray revealed that the filling was complete, and the periapical tissue was normal. The results of the literature review showed that the incidence of three mesiobuccal root canals in maxillary second molars was 0.11%-4.2%. It is difficult to find additional root canals only by X-ray imaging. Dentists should further determine the number and anatomical shape of root canals by CBCT and operating microscopy. When there are three mesiobuccal root canals in maxillary molars, dentists should avoid overpreparation. Healthy tooth tissue is the key to good prognosis. @* Conclusion@#During root canal therapy, clinicians should consider the anatomical variation of the root canal, should always be alert to the existence of an extra root canal, and should use CBCT, operating microscopy, ultrasound and various auxiliary instruments to locate and treat the variant root canal.

General anatomy and image reconstruction analysis of the proximal femoral trabecular structures / 中国修复重建外科杂志

Objective: To investigate the three-dimensional structure of proximal femoral trabeculae, analyze the formation mechanism, and explore its relationship with the occurrence and treatment of proximal femoral fractures. Methods: Six cadaver adult femur specimens were harvested and the gross specimens containing both trabecular system and cortical bone were established by hand scraping. All samples were scanned by micro-CT and the CT images were input into Mimics18.0 software to establish the digital proximal femoral model containing trabecular structure. The spatial distribution of trabecular system was observed, and the relations between trabecular bone and the proximal femur surface and related anatomical landmarks were analyzed in digital models. Results: The gross specimen and digital models of trabecular system were successfully established. The trabecular system of proximal femur could be divided into two groups: the horizontal and vertical trabecular. The horizontal trabecular arose from the base of greater trochanter, gone along the direction of femoral neck, and terminated at the center of femoral head. The vertical trabecular began from the base of lesser trochanter and femoral calcar, gone radically upward, and reached the femoral head. The average distance of the horizontal trabecular to the greater trochanter was 22.66 mm (range, 17.3-26.8 mm). In the femoral head, the horizontal trabecula and the vertical trabecula were fused into a kind of sphere, and the distances from the horizontal trabecula to the surface of the femoral head vary in different sections. The average distance of trabecular ball to the femoral head surface was 6.88 mm (range, 6.3-7.2 mm) in sagittal plane, 6.32 mm (range, 5.8-7.6 mm) in coronal plane, and 6.30 mm (range, 5.6-6.3 mm) in cross section. The vertical and horizontal trabeculae intersect obliquely, and the average angle of horizontal trabecular and vertical one was 140.67° (range, 129-150°). Conclusion: The trabecular system exhibits a unique spatial configuration, which is the main internal support of proximal femur. Restoration of the integrity of trabecular structure is the important goal of proximal femoral fractures.

Comparison of Three-Dimensional Accuracy between Digital Models Obtained from Impression Scan and Model Scan / 대한치과재료학회지

The purpose of the study is to compare and analyze the accuracy of digital images obtained from impression and stone model with model scanner and to find out clinical effectiveness. A mandibular left first molar composite resin tooth was made for abutment. Digital models were obtained with a same model scanner(Ceramill Map 400, Amann Girrbach, Austria); (1) Fabricated resin model was scanned(Group C). (2) 10 impressions were taken with putty and polyvinyl siloxane, then were scanned (Group I). (3) Type IV stone was poured in each impressions made in step(2) and 10 stone models were scanned(Group S). 3 dimensional super-impositional program (Geomagic control X, 3D Systems, USA) was used to analyze the STL files. Stone model scan(Group S) showed lower deviation than impression scan(Group I) compared to the control group(P < 0.001). Both Group I and Group S showed signs of expansion in the occlusion surface and margin surface while showing contraction in the axial surface. The deviations were smaller in order of occlusal plane, horizontal plane of margin and axial plane. Within the limited boundary of this study, the digital model obtained from stone model scan showed smaller deviation than the digital model obtained from impression scan.

Impact of mobile-bearing versus fixed-bearing platform prostheses of the knee joint on patellofemoral stress / 实用医学杂志

Objective To explore the feasibility of the reconstruction of three dimensional dynamic finite element model of the knee joint based on two-dimensional CT and MRI image data. To analyze the impact of mobile-bearing versus fixed-bearing platform prostheses of the knee joint on patellofemoral stress by the finite element method. Methods A three-dimensional digital model of the knee joint including bone,cartilage,meniscus, ligaments and tendons was reconstructed through the Mimics software. The best clinical bone cutting angle and implant placement position measurement were simulated according to the standard of total knee replacement by computers in a three-dimensionalknee model. A three-dimensional dynamic finite element model of mobile-bearing and fixed-bearing total knee arthroplasties was reconstructed finally. The data was analyzed by the SPSS 19.0 software. The test standard level α was 0.05. Results There was no significant difference in the peak value of patellofemoral stresses between fixed-bearing and mobile-bearing platform posterior cruciate-substituting prostheses at 0° ,30° ,60° ,90° ,or 120° of knee flexion(P>0.05). Conclusion There is no significant difference in the peak value of patellofemoral stresses between fixed-bearing and mobile-bearing platform prostheses.

Determination of Thermal Physical Parameters and Related Model of Water Extracts of Salvia Miltiorrhiza Radix et Rhizoma / 中国中医药信息杂志

Objective To determine the thermal conductivity under different temperatures and concentrations, and specific heat capacity under different concentrations of water extracts of Salvia Miltiorrhiza Radix et Rhizoma; To establish the mathematical model of thermal conductivity-temperature, thermal conductivity-concentration, thermal conductivity-temperature-concentration and specific heat capacity-concentration of water extracts of Salvia Miltiorrhiza Radix et Rhizoma. Methods Thermal conductivity and specific heat capacity were measured by the instantaneous double hot wire thermal conductivity meter and the electrothermal specific heat capacity meter. Excel, 1stOpt and MATLAB were used to analyze the experimental data. Results The method of using brix to facilitate and accurately characterize the concentration was established. The relationship between the thermal conductivity and the temperature and the concentration of water extracts of Salvia Miltiorrhiza Radix et Rhizoma were all linearly negative (λ=a-bT, λ=a-bC), and the influence of temperature and concentration on the thermal conductivity had a certain interaction. λ=a-bC-cT-dCT could be used as the temperature and the concentration on the thermal conductivity of the integrated role model. And the specific heat capacity of the extract was negatively correlated with the concentration (cp=a-bC). Conclusion The thermal conductivity and the specific heat capacity of the extract of water extracts of Salvia Miltiorrhiza Radix et Rhizoma are different at different temperatures and concentrations, and the model can be used to characterize the changing law of thermodynamics of the extracts. It can provide guidance significance for the thermal characteristics analysis in TCM pharmaceutical process and TCM production equipment selection and design, and production process control.

Establishment of the digital model of congenital deformed thorax and rib defect templates / 中华整形外科杂志

Objective@#To establish the three-dimensional digital model of congenital thoracic deformity and the rib defect templates.@*Methods@#22 patients(admitted from Feb 2000 to Feb 2016) with thoracic deformity all received continuous volumetric scanning of chest with 64 slice spiral CT and 3D model reconstruction was performed .The digital data were processed by the Mimics 17.0 software and the entity thoracic model could be made by 3D printers with these processed data. Digital normal thorax model was also reversed by the mirror method.@*Results@#These digital data models of 22 cases with thoracic deformity were established and entity models were gained by 3D printers. Normal ribs templates were made for 11 cases(5 Poland syndrome cases, 5 funnel chest cases and 1 rib defect case).@*Conclusions@#Digital model of thoracic deformity can be established by Mimics 17.0 software with processed CT scan data. 3D printers can be used to gain the entity models, which play the important role in designing accurate and personalized thoracic contour for plastic surgery in the future.

Construction of the 3D digital models of maxillofacial region based on CT and MRI images fusion / 口腔疾病防治

Objective @#To explore an efficient method for the establishment of three-dimensional (3-D) digital models of maxillofacial region including muscle tissue based on CT and MRI images fusion on a personal computer, integration of CT and MRI data, and provide accurate 3D model for biomechanical analysis. @*Methods @#A male volunteer was scanned on maxillofacial region by spiral CT and MRI. Two kinds of data obtained were imported into Mimics 15. In the three sections, namely the transverse, sagittal, coronal sections, two kinds of data were adjusted to the same anatomical layers. The most obvious anatomical points on each layer were selected as registration points. Then, the multi-points registration was implemented for data fusion. Then the bone and facial skin were segmented and 3D reconstructed using CT data, the main facial muscles were segmented and 3D reconstructed using MRI data. @*Results@#The 3D model including 3 pairs of masticatory muscles, 12 pairs of facial expression muscles, facial skin and jaw tissues were established. @*Conclusion @# The efficient registration and fusion of CT and MRI datas were accomplished. Moreover, this method can be used for further segmentation and reconstruction of other important structures in craniofacial area, such skin, blood vessel, fat, lymph node and the brain tissues.

The effects of modified expander in the orthodontic treatment of the cases with Angel Ⅰ malocclusion / 实用口腔医学杂志

Objective:To investigate efficacy of modified expander in the treatment of non-extraction patients with Angel Ⅰ maloccul-sion.Methods:1 4 Angel Ⅰcases aged 1 0 -1 4 years treated by non-extraction and fixed rapid expander.Jaw bones of the cases were laser scanned before(T1 )and after treatment(T2).The differences of arch width and length between T1 and T2 were analyzed.The In-dex of treatment complexity,outcome and need(ICON)was used to assess the pre-treatment and post-treatment study models.Data were statistically analysed with SPSS1 3.0 software.Results:The arch width increased significantly from T1 to T2.Good occlusal rela-tionship and soft tissue profiles were achieved in all cases.All cases were evaluated as greatly improved by ICON.Conclusion:AngelⅠ malocclusion can be treated successfully by increasing arch width with fixed rapid expander technique without tooth extraction.

Establishment of a digital model of juxtahepatic vena cava / 中华消化外科杂志

Objective To investigate the feasibility of establishing a digital model of juxtahepatic vena cava.Methods The clinical data of 120 participants (without liver diseases) who were admitted to the Cangzhou Central Hospital from January 2013 to May 2013 were collected.The results of computed tomography were analyzed.The diameters of juxtahepatic vena cava on different levels (P1 plane:inferior vena cava at the entrance to the right atrium,P2 plane:the upper margin of the roots of hepatic veins,P4 plane:lower boundary of liver,P5 plane:confluence of renal veins and inferior vena cava),and the circumference of the inferior vena cava and the lengths between these levels were recorded.A digital model of juxtahepatic vena cava was established by these data on the premise that the juxtahepatic vena cava was engorged.All data were analyzed using the analysis of variance,paired sample t test and independent samples t test,and correlation and regression were used in analysis of relations between there data.Results Data of the P1 plane and P2 plane were both missed in 3 cases,and the data of the P4 plane was missed in 8 cases.The theoretical diameter of hepatic vena cava at the P1,P2 and P4 planes were (28.1 ± 4.0) mm,(28.7 ± 3.5) mm and (23.5 ± 2.7) mm,respectively.The median diameter of hepatic vena cava at the P5 plane was 24.3 mm.The juxtahepatic vena cava was a 3 dimensional structure of cylinder with a slightly protruding middle part.There were significant differences in P1D-P2D,P2D-P4D,P1D-P4D (F =77.5,P ＜ 0.05).There were significant differences between P2D-P4D and P1D-P4D (t =14.893,11.210,P ＜ 0.05).The median length of hepatic vena cava between P1 and P2 planes was 7.5 mm.The lengths of hepatic vena cava between P1 and P4 planes,P2 and P4 planes were (85.2 ± 11.0)mm and (78.2 ±9.8)mm,respectively.The median length of hepatic vena cava between the P4 and P5 planes was 10.0 mm.P1D-P2D,P2D-P4D,P2D-P5D and P4D-P5D were positively correlated (r =0.862,0.308,0.186,0.788,P ＜ 0.05),while P1D-P4D and P2D-P5D did not correlated (r =0.180,0.118,P ＞0.05).P2D was correlated with the body weight,and P5 D was correlated with the age (r =0.200,0.130,P ＜ 0.05).The P1 D,P2D,P4D and P5 D of the inferior vena cava were (28.5 ± 3.7) mm,(29.0 ± 3.4) mm,(23.9 ± 2.8) mm and (24.3 ± 2.6) mm in males,and (27.8 ±4.2) mm,(28.5 ± 3.6) mm,(23.1 ± 2.5) mm and 24.0 mm in females.There were no significant difference in P1D,P2D,P4D and P5D between males and females (t =0.911,0.809,1.588,1.902,P ＞ 0.05).The length between P1 and P2 planes was negatively correlated with P1D and P2D (r =-0.245,-0.160,P ＜ 0.05),while the length between P4 and P5 planes was positively correlated with P1D (r =0.149,P ＜ 0.05).The length between P2 and P4 planes was positively correlated with P2D (r =0.195,P ＜ 0.05).The length between P1 and P2 planes did not correlated with the age,height and body weight (r =-0.092,-0.047,-0.033,P ＞ 0.05).The lengths between P2 and P4 planes,P1 and P4 planes were negatively correlated with the age (r =-0.343,-0.371,P ＜ 0.05),but positively correlated with the body weight (r =0.271,0.208,P ＜ 0.05).The length between P4 and P5 planes was positively correlated with the height and body weight (r =0.154,0.255,P ＜ 0.05).There were no significant difference in the lengths between P1 and P2 planes,P1 and P4 planes,P2 and P4 planes,P4 and P5 planes between males and females (t =-1.046,-1.274,-0.908,1.375,P ＞ O.05).The length between P2 and P4 planes was similar to the length of retrohepatic vena cava.The length between P2 and P4 planes(mm) =71.23-0.293 × age (years) +0.32 × body weight (kilogram).Conclusion The establishment of digital model of juxtahepatic vena cava based on the computed tomography imaging data is feasible,which provides basis for clinical investigation.

Anatomical measurements of proximal tibia of anterior and posterior cruciate ligament-retaining knee prosthesis / 中国组织工程研究

10.3969/j.issn.2095-4344.2013.26.004

Establishment and clinical application of individualized three-dimensional digital models of retroperitoneal space on medical CT films / 中华泌尿外科杂志

Objective To explore the feasibilities and clinical applications for sharing the medical resources and recycles by applying digital medicine technology and making the most of medical CT films from other hospitals.Methods Based on scanning data of medical CT films from other hospitals,which were in 85 cases of undergo retroperitoneal laparoscopic surgery,the 3D models were reconstructed in the computer,then were verified and navigated during operations.Meanwhile,coincidence rates were compaired between group A (slice thickness =5 mm) and group B (slice thickness ＞5 mm) in 53 cases whose renal pedicle blood vessels were exposed during the operations.Results All the 85 procedures were successfully completed.The 3D models,which could be observed freely,were consistent with intraoperative screenshots and participated in intraoperative guidance.Coincidence rates were 82.4％ (28/34) in group A and 52.6％(10/19) in group B (x2 =5.306,P =0.021).Conclusions Based on medical CT films of 5 mm slice thickness,the 3D models which are verified to have some accuration and fineness can be successfully reconstructed.The method not only can effectively avoid unnecessary repeated inspection,but also directly render in 3D form to participate in preoperative planning and intraoperative guidance.

Validity of palatal superimposition of 3-dimensional digital models in cases treated with rapid maxillary expansion and maxillary protraction headgear / 대한치과교정학회지

OBJECTIVE: The purpose of this study was to evaluate the validity of the 3-dimensional (3D) superimposition method of digital models in patients who received treatment with rapid maxillary expansion (RME) and maxillary protraction headgear. METHODS: The material consisted of pre- and post-treatment maxillary dental casts and lateral cephalograms of 30 patients, who underwent RME and maxillary protraction headgear treatment. Digital models were superimposed using the palate as a reference area. The movement of the maxillary central incisor and the first molar was measured on superimposed cephalograms and 3D digital models. To determine whether any difference existed between the 2 measuring techniques, intra-class correlation (ICC) and Bland-Altman plots were analyzed. RESULTS: The measurements on the 3D digital models and cephalograms showed a very high correlation in the antero-posterior direction (ICC, 0.956 for central incisor and 0.941 for first molar) and a moderate correlation in the vertical direction (ICC, 0.748 for central incisor and 0.717 for first molar). CONCLUSIONS: The 3D model superimposition method using the palate as a reference area is as clinically reliable for assessing antero-posterior tooth movement as cephalometric superimposition, even in cases treated with orthopedic appliances, such as RME and maxillary protraction headgear.

A method for mandibular dental arch superimposition using 3D cone beam CT and orthodontic 3D digital model / 대한치과교정학회지

OBJECTIVE: The purpose of this study was to develop superimposition method on the lower arch using 3-dimensional (3D) cone beam computed tomography (CBCT) images and orthodontic 3D digital modeling. METHODS: Integrated 3D CBCT images were acquired by substituting the dental portion of 3D CBCT images with precise dental images of an orthodontic 3D digital model. Images were acquired before and after treatment. For the superimposition, 2 superimposition methods were designed. Surface superimposition was based on the basal bone structure of the mandible by surface-to-surface matching (best-fit method). Plane superimposition was based on anatomical structures (mental and lingual foramen). For the evaluation, 10 landmarks including teeth and anatomic structures were assigned, and 30 times of superimpositions and measurements were performed to determine the more reproducible and reliable method. RESULTS: All landmarks demonstrated that the surface superimposition method produced relatively more consistent coordinate values. The mean distances of measured landmarks values from the means were statistically significantly lower with the surface superimpositions method. CONCLUSIONS: Between the 2 superimposition methods designed for the evaluation of 3D changes in the lower arch, surface superimposition was the simpler, more reproducible, reliable method.

Comparison of model analysis measurements among plaster model, laser scan digital model, and cone beam CT image / 대한치과교정학회지

OBJECTIVE: The purpose of this study was to evaluate the possibility of using a digital model and cone beam computed tomograph (CBCT) image for model analysis. METHODS: Model analyses of CBCT images, plaster models, and digital models of 20 orthodontic patients with a permanent dentition with no proximal metal restorations, were compared. RESULTS: The average differences of tooth size measurements were 0.01 to 0.20 mm, and the average difference of arch length discrepancy measurements were 0.41 mm in the maxilla and 0.82 mm in the mandible. The difference in Bolton discrepancy measurements was 0.17 mm for the anterior region and 0.44 mm overall but with no statistically significant difference. When comparing CBCT images with plaster models, the average differences in tooth size measurements were -0.22 to 0.01 mm, and the average differences in arch length discrepancy measurements were 0.43 mm in the maxilla and 0.32 mm in the mandible. Difference in Bolton discrepancy measurements were 0.35 mm in the anterior region and 1.25 mm overall. CBCT images showed significantly smaller overall Bolton discrepancy measurements. CONCLUSIONS: Although there were statistically significant differences in some model analysis measurements, the ranges of measurement errors of the digital model and CBCT images were clinically acceptable. Therefore, a digital model and CBCT image can be used for model analysis.

A study on the dental arch characteristics of bialveolar protrusion patients using a three-dimensional digital model / 대한치과교정학회지

Recent beauty trends have caused an increase in the number of bialveolar protrusion patients seeking treatment of lip protrusion. But studies of these patients are not common. Studies using their dental models are especially rare. Dental models have been measured manually or through a computer by digitizing two dimensional images of models. Nowadays, we are able to study dental models more easily and accurately by utilizing the three-dimensional (3-D) laser scanner in dentistry. An investigation was carried out to evaluate the characteristics of the dental arch in a bialveolar protrusion group in comparison with a normal group using 3-D digital models. The normal group was composed of 20 subjects who were selected from students of the School of Dentistry, Kyungpook National University. The bialveolar protrusion group was composed of 20 subjects who visited for treatment at the Department of Orthodontics, Kyungpook National University Hospital. Tooth size, arch width and arch length were measured digitally, and arch shape and the shape of the palate were drawn. Based on the results of this study, the differences of the arch characteristics in the bialveolar protrusion group were that the size of the teeth was larger, mandibular canine width and 1st premolar width were wider, and arch length was longer than in the normal group. And there were differences in the arch shape and the shape of palate between the bialveolar protrusion and normal groups.