Cast Models Research Articles

Repeatability study of the cast model for gait analysis

Repeatability study of the cast model for gait analysis

A preliminary study for determination of three-dimensional root apex position of the maxillary teeth using camera calibration technology.

To propose a novel method for determining the three-dimensional (3D) root apex position of maxillary teeth using a two-dimensional (2D) panoramic radiograph image and a 3D virtual maxillary cast model. The subjects were 10 adult orthodontic patients treated with non-extraction. The multiple camera matrices were used to define transformative relationships between tooth images of the 2D panoramic radiographs and the 3D virtual maxillary cast models. After construction of the root apex-specific projective (RASP) models, overdetermined equations were used to calculate the 3D root apex position with a direct linear transformation algorithm and the known 2D co-ordinates of the root apex in the panoramic radiograph. For verification of the estimated 3D root apex position, the RASP and 3D-CT models were superimposed using a best-fit method. Then, the values of estimation error (EE; mean, standard deviation, minimum error and maximum error) between the two models were calculated. The intraclass correlation coefficient values exhibited good reliability for the landmark identification. The mean EE of all root apices of maxillary teeth was 1.88 mm. The EE values, in descending order, were as follows: canine, 2.30 mm; first premolar, 1.93 mm; second premolar, 1.91 mm; first molar, 1.83 mm; second molar, 1.82 mm; lateral incisor, 1.80 mm; and central incisor, 1.53 mm. Camera calibration technology allows reliable determination of the 3D root apex position of maxillary teeth without the need for 3D-CT scan or tooth templates.

Non-uniform central airways ventilation model based on vascular segmentation

Improvements in the understanding of the physiology of the central airways require an appropriate representation of the non-uniform ventilation at its terminal branches. This paper proposes a new technique for estimating the non-uniform ventilation at the terminal branches by modelling the volume change of their distal peripheral airways, based on vascular segmentation. The vascular tree is used for sectioning the dynamic CT-based 3D volume of the lung at 11 time points over the breathing cycle of a research animal. Based on the mechanical coupling between the vascular tree and the remaining lung tissues, the volume change of each individual lung segment over the breathing cycle was used to estimate the non-uniform ventilation of its associated terminal branch. The 3D lung sectioning technique was validated on an airway cast model of the same animal pruned to represent the truncated dynamic CT based airway geometry. The results showed that the 3D lung sectioning technique was able to estimate the volume of the missing peripheral airways within a tolerance of 2%. In addition, the time-varying non-uniform ventilation distribution predicted by the proposed sectioning technique was validated against CT measurements of lobar ventilation and showed good agreement. This significant modelling advance can be used to estimate subject-specific non-uniform boundary conditions to obtain subject-specific numerical models of the central airway flow.

A different wax sculpture technique for implant-retained auricular prosthesis

Replacement of missing ears is a challenging task in which extensive array of materials and techniques have been employed. This article describes a different and simplified procedure for fabricating auricular prostheses very similar to the intact left ear of the patient. A 65-year-old male patient was referred to the Department of Prosthodontics with the loss of the right ear. In this case, the impression was made using hydrocolloid material (alginate) from the both defected and the opposite side. After hardening of the stone casts, a custom-made transparent splint plate was designed for the left auricular side. The splint was reversed and a cast model of the right auricular side was obtained as pouring the dental stone into transparent orthodontic splint. After getting the impression from cast model, conventional wax pattern and try on process was done. Finally, silicone elastomer was polymerized and the retention of the prosthesis acquired with the magnetic attachments. The technique described is economical, conventional, and time-saving. Furthermore, the prosthesis imitates the patient's intact auricular tissue.

Ridge augmentation using recombinant human fibroblast growth factor‐2 with biodegradable gelatin sponges incorporating β‐tricalcium phosphate: a preclinical study in dogs

Fibroblast growth factor-2 (FGF-2) regulates the proliferation and differentiation of osteogenic cells, resulting in the promotion of bone formation. Biodegradable gelatin sponges incorporating β-tricalcium phosphate (β-TCP) have been reported as a scaffold, which has the ability to control growth factor release, offering sufficient mechanical strength and efficient migration of mesenchymal cells. In this study, we evaluated the effects of the combined use of recombinant human FGF-2 (rhFGF-2) and gelatin/β-TCP sponge on ridge augmentation in dogs. Six male beagle dogs were used in this study. Twelve wk after tooth extraction, bilateral 10 × 5 mm (width × depth) saddle-type defects were created 3 mm apart from the mesial side of the maxillary canine. At the experimental sites, the defects were filled with gelatin/β-TCP sponge infiltrated with 0.3% rhFGF-2, whereas gelatin/β-TCP sponge infiltrated with saline was applied to the control sites. Eight wk after surgery, qualitative and quantitative analyses were performed. There were no signs of clinical inflammation at 8 wk after surgery. Histometric measurements revealed that new bone height at the experimental sites (2.98 ± 0.65 mm) was significantly greater than that at the control sites (1.56 ± 0.66 mm; p = 0.004). The total tissue height was greater at the experimental sites (6.62 ± 0.66 mm) than that at the control sites (5.95 ± 0.74 mm), although there was no statistical significant difference (p = 0.051). Cast model measurements revealed that the residual defect height at the experimental sites (2.31 ± 0.50 mm) was significantly smaller than that at the control sites (3.51 ± 0.78 mm; p = 0.012). The combined use of rhFGF-2 and gelatin/β-TCP sponge promotes ridge augmentation in canine saddle-type bone defects.

The CAST model: enhancing medical student and resident clinical performance through feedback.

The CAST model: enhancing medical student and resident clinical performance through feedback.

Digital casts in orthodontics: A comparison of 4 software systems

The introduction of digital cast models is inevitable in the otherwise digitized everyday life of orthodontics. The introduction of this new technology, however, is not straightforward, and selecting an appropriate system can be difficult. The aim of the study was to compare 4 orthodontic digital software systems regarding service, features, and usability. Information regarding service offered by the companies was obtained from questionnaires and Web sites. The features of each software system were collected by exploring the user manuals and the software programs. Replicas of pretreatment casts were sent to Cadent (OrthoCAD; Cadent, Carlstadt, NJ), OthoLab (O3DM; OrthoLab, Poznan, Poland), OrthoProof (DigiModel; OrthoProof, Nieuwegein, The Netherlands), and 3Shape (OrthoAnalyzer; 3Shape, Copenhagen, Denmark). The usability of the programs was assessed by experts in interaction design and usability using the "enhanced cognitive walkthrough" method: 4 tasks were defined and performed by a group of domain experts while they were observed by usability experts. The services provided by the companies were similar. Regarding the features, all 4 systems were able to perform basic measurements; however, not all provided the peer assessment rating index or the American Board of Orthodontics analysis, simulation of the treatment with braces, or digital articulation of the casts. All systems demonstrated weaknesses in usability. However, OrthoCAD and 03DM were considered to be easier to learn for first-time users. In general, the usability of these programs was poor and needs to be further developed. Hands-on training supervised by the program experts is recommended for beginners.

Reliability of measurements made on scanned cast models using the 3 Shape R 700 scanner.

In dentistry, the latest technological advancements have been incorporated primarily into diagnostic tools such as virtual dental models. The aim of this study was to evaluate the reliability of measurements made on digital cast models scanned in the 3 Shape R 700 scanner (3 Shape, Copenhagen, Denmark) that uses a non-destructive laser beam to reproduce model surfaces so that the plaster model is not destroyed. The sample consisted of 26 cast models, and 6 linear measurements were made on the cast models and compared with the same measurements on digital models. The measurements assessed were: (1) distance between mandibular canines; (2) distance between mandibular molars; (3) distance between canine and maxillary molar; (4) buccal-lingual diameter of maxillary central incisor; (5) distance between two points of the incisive papillae of maxillary and mandibular central incisors; and (6) distance between the buccal surface of the maxillary central incisor and the buccal surface of the mandibular antagonist (overjet). The Student's t-test or Wilcoxon test was used at 5% and the Lin's concordance test at 95% confidence interval. The overjet measurement was the only one that showed a statistically significant difference (p < 0.05). A high level of concordance was found for all measurements. The digital models obtained from the 3 Shape R 700 scanner are reliable and can be considered an alternative to cast models for performing measurements and analyses in orthodontic practice.

Quantitative Evaluation of Tissue Surface Adaption of CAD-Designed and 3D Printed Wax Pattern of Maxillary Complete Denture.

Objective. To quantitatively evaluate the tissue surface adaption of a maxillary complete denture wax pattern produced by CAD and 3DP. Methods. A standard edentulous maxilla plaster cast model was used, for which a wax pattern of complete denture was designed using CAD software developed in our previous study and printed using a 3D wax printer, while another wax pattern was manufactured by the traditional manual method. The cast model and the two wax patterns were scanned in the 3D scanner as “DataModel,” “DataWaxRP,” and “DataWaxManual.” After setting each wax pattern on the plaster cast, the whole model was scanned for registration. After registration, the deviations of tissue surface between “DataModel” and “DataWaxRP” and between “DataModel” and “DataWaxManual” were measured. The data was analyzed by paired t-test. Results. For both wax patterns produced by the CAD&RP method and the manual method, scanning data of tissue surface and cast surface showed a good fit in the majority. No statistically significant (P > 0.05) difference was observed between the CAD&RP method and the manual method. Conclusions. Wax pattern of maxillary complete denture produced by the CAD&3DP method is comparable with traditional manual method in the adaption to the edentulous cast model.

Comparison of Two Methods for Canine Retraction Depending on Direct Skeletal Anchorage System (CR-DSAS)

Introduction: Various anchorage techniques have been used for canine retraction. Traditional anchorage techniques have not always been very efficient. Recently, Temporary anchorage devices such as miniscrews are considered to be an effective source of anchorage for canine retraction. The purpose of this study was to compare between elastic chain and closed coil in retracting upper canines when using miniscrews as skeletal anchorage in class 2 division1 cases. Methods: Twenty-two patients with class 2 division 1 were treated with preadjusted appliances. Depending on miniscrews as direct skeletal anchorage, elastic chain and closed coil were used to retract upper canines after first premolar extraction. Cephalometric radiographs and cast models were been used to evaluate canine retraction. Results were analyzed by SPSS 15 using T student test. Results: Upper canines were retracted in 5-5.5 month; Canine crowns were retracted 6.97mm by elastic chain and 7.08 mm by closed coil. Canine apices were retracted 1.06mm by elastic chain and 1.43mm by closed coil. Anchorage loss with miniscrews was 0.07-0.2 mm. Conclusions: Miniscrews provide absolute skeletal anchorage, Canine movement with skeletal anchorage is faster than traditional techniques, Canines tipped distally when retracted depending on direct skeletal anchorage, and there was no statistical differences between elastic chain and closed coil in retracting canines. Received August 30, 2014; Accepted September 18, 2014 ; Published December 31, 2014

Evaluation of biogeneric design techniques with CEREC CAD/CAM system.

PURPOSEThe aim of this study was to evaluate occlusal contacts generated by 3 different biogeneric design modes (individual (BI), copy (BC), reference (BR)) of CEREC software and to assess the designs subjectively.MATERIALS AND METHODSTen pairs of maxillary and mandibular casts were obtained from full dentate individuals. Gypsum cast contacts were quantified with articulating paper and digital impressions were taken. Then, all ceramic crown preparation was performed on the left first molar teeth and digital impressions of prepared teeth were made. BI, BC, and BR crowns were designed. Occlusal images of designs including occlusal contacts were superimposed on the gypsum cast images and corresponding contacts were determined. Three designs were evaluated by the students.RESULTSThe results of the study revealed that there was significant difference among the number of contacts of gypsum cast and digital models (P<.05). The comparison of the percentage of virtual contacts of three crown designs which were identical to the contacts of original gypsum cast revealed that BI and BR designs showed significantly higher percentages of identical contacts compared with BC design (P<.05). Subjective assessment revealed that students generally found BI designs and BR designs natural regarding naturalness of fissure morphology and cusp shape and cusp tip position. For general occlusal morphology, student groups generally found BI design "too strong" or "perfect", BC design "too weak", and BR design "perfect".CONCLUSIONOn a prepared tooth, three different biogeneric design modes of a CAD/CAM software reveals different crown designs regarding occlusal contacts and morphology.

English

Functional orthopedic appliances used for Class II malocclusion treatment, usually work by guiding jaws growth and modifying dental positions. Among these dentoalveolar effects, it is the lower incisors buccal tipping, that helps to improve the overjet, but may cause gingival recessions, especially when associated with other etiological factors. The objective of this study was to evaluate the clinical crown length of the lower anterior teeth in individuals with Angle’s Class II malocclusion, after treatment with Frankel-2 function regulator appliance (RF-2). Fifty Class II-malocclusion individuals were divided into 2 groups: G1 – 14 male, and 11 female, treated with the Frankel-2 function regulator appliance for 18 months, with average pre-treatment age (T1) of 11 years (sd=7 months) and average post-treatment age (T2) of 12 years and 7 months (sd=7 months); and G2 – a control group with 25 individuals (12 male and 13 female) with average age at T1 of 10 years and 3 months (sd=11 months) and at T2 of 12 years and 1 month (sd=11 months), which was part of a normal occlusion sample. The 100 dental cast models were analyzed at T1 and T2, with a digital caliper, measuring the distance from the incisal edge to the most concave portion of the gingival margin of lower incisors and canines. Data were checked by a Student’s t-test and a paired t-test. Considering T2, the group 1 presented a significant increase in the crown length of all lower anterior teeth. On the other hand, in the group 2, this was observed only for the teeth 33, 42 and 43, suggesting that patients treated with RF-2 had more gingival recession than the control group.

Correlation between the Rotation of the First Molars and the Severity of Class II Division 1 Malocclusion.

This study aimed to evaluate the potential correlation between the severity of Class II division 1 malocclusion and the magnitude of mesiopalatal rotation of the maxillary first molars. Scanned images of 104 cast models were grouped according to the severity of Class II malocclusion as follows: Group 1, 1/4 Class II malocclusion; Group 2, 1/2 Class II malocclusion; Group 3, 3/4 Class II malocclusion; and Group 4, complete Class II malocclusion. The rotation was measured using parameters described by Henry, Friel, and Ricketts, referred to as indicators 1, 2, and 3, respectively. The correlation was evaluated using the Spearman's correlation coefficient. The rotational indicators were compared using one-way analysis of variance. For all statistical analyses used p < 0.05, a positive correlation was observed between the severity of Class II malocclusion and the mesiopalatal rotation of the maxillary first molar. This correlation was statistically significant for indicator 1 between Groups 1 and 3 and for indicator 2 between Groups 1 and 4, which include cases of extreme malocclusion. In conclusion, there is a positive correlation between the severity of Class II division 1 malocclusion and the magnitude of mesiopalatal rotation in the maxillary first molars.

English

The focus of this study was to test the fracture resistance of upper arch dental retainers, made by two different manipulation techniques of acrylic resin. 84 plates Wraparound type retainers were made by two different manipulation techniques forming two groups (n = 42): Group 1 (Addition Technique) and Group 2 (Pressing Technique). All the retainers were duly shaped in U form with the aid of standardized plaster cast models. During the confection process the standardizing of the retainers was conducted carefully regarding their thickness and dimensions with the aid of a gauge and a straight caliper. After confection they remained immersed in water for 24 hours at 37°C. Next, they were tested through mechanical compression until fracture in a universal mechanical testing machine. Data were analyzed by Student's t test. The significance level was set at 5% (α = 0.05). It was found that the average was of 79.12 N for Group 1 and of 77.07 N for Group 2 with a standard deviation of 17.30 N and 16.31, respectively, showing that there is no significant difference in resistance for the retainers when made through any of the two methods ( P =0.788). The addition and pressure techniques of acrylic resin do not influence the resistance to compression of the upper dental retainers.

Displacement-stress Distribution in a Femoral Bone by Optical Methods

Abstract The use of optical methods to study the field of displacements and state of stresses of the femoral bone involves identifying their applicability limits. The aim of this study is to apply these two methods for the analysis of the field of displacements and state of stresses of an isotropic compressed 3D model of a human femoral bone and highlighting the advantages and disadvantages of these two optical methods. It was shown that if the cast model respects only the outer geometry (isotropic model) of the femoral bone the area where the maximum stresses occurs is the diaphyseal area instead of the femoral neck area, as shown in literature.

Comparative characterization of maxillary expansion and alternate maxillary expansions and constrictions in rats.

The purpose of this study was to evaluate whether the cranial and circumaxillary sutures react differently to maxillary expansion (ME) and alternate maxillary expansions and constrictions (Alt-MEC) in a rat model. Twenty-two male Sprague-Dawley rats (6 weeks old) were used and divided into three groups. In ME group (n=9), an expander was activated for 5 days. In Alt-MEC group (9 animals), an alternate expansion and constriction protocol (5-day expansion and 5-day constriction for one cycle) was conducted for 2.5 cycles (25 days total). The control group comprised 4 animals with no appliances used, each of two sacrificed on day 5 and day 25 respectively. Midpalatal suture expansion or constriction levels were assessed qualitatively and quantitatively by bite-wing X-rays and cast models. Distances between two central incisors and two maxillary first molars were measured on cast models after each activation. Circumaxillary sutures (midpalatal, maxillopalatine, premaxillary, zygomaticotemporal and frontonasal suture) in each group were characterized histologically. Results showed that midpalatal suture was widened and restored after each expansion and constriction. At the end of activation, the widths between both central incisors and first molars in Alt-MEC group were significantly larger than those in ME group (P<0.05). Histologically, all five circumaxillary sutures studied were widened in multiple zones in Alt-MEC group. However, only midpalatal suture was expanded with cellular fibrous tissue filling in ME group. Significant osteoclast hyperplasia was observed in all circumaxillary sutures after alternate expansions and constrictions, but osteoclast count increase was only observed in midpalatal suture in ME group. These results suggested that cranial and circumaxillary sutures were actively reconstructed after Alt-MEC, while only midpalatal suture had active reaction after ME.

An integrated orthognathic surgery system for virtual planning and image-guided transfer without intermediate splint

Accurate surgical planning and transfer of the planning in orthognathic surgery are very important in achieving a successful surgical outcome with appropriate improvement. Conventionally, the paper surgery is performed based on a 2D cephalometric radiograph, and the results are expressed using cast models and an articulator. We developed an integrated orthognathic surgery system with 3D virtual planning and image-guided transfer. The maxillary surgery of orthognathic patients was planned virtually, and the planning results were transferred to the cast model by image guidance. During virtual planning, the displacement of the reference points was confirmed by the displacement from conventional paper surgery at each procedure. The results of virtual surgery were transferred to the physical cast models directly through image guidance. The root mean square (RMS) difference between virtual surgery and conventional model surgery was 0.75 ± 0.51 mm for 12 patients. The RMS difference between virtual surgery and image-guidance results was 0.78 ± 0.52 mm, which showed no significant difference from the difference of conventional model surgery. The image-guided orthognathic surgery system integrated with virtual planning will replace physical model surgical planning and enable transfer of the virtual planning directly without the need for an intermediate splint.

Dimensional changes in plaster cast models due to the position of the impression tray during setting

Introduction: The objective of this study was to assess whether the positioning of the impression tray could cause distortion to plaster casts during gypsum setting time.Materials and Methods: Fifteen pairs of master models were cast with alginate impression material and immediately filled with gypsum. Impressions were allowed to set with the tray in the noninverted position (Group A) or in the inverted position (Group B). The plaster models were digitized using a laser scanner (3Shape R-700, 3Shape A/S, Copenhagen, Denmark). Measurements of tooth size and distance were obtained using O3d software (Widialabs, Brazil) measurement tools. Data were analyzed by paired t-test and linear regression with 5% significance.Results and Conclusion: Most of the measurements from both groups were similar, except forthe lower intermolar distance. It was not possible to corroborate the presence of distortions due to the position of the impression tray during gypsum setting time.

Analysis of the linear dimensions of the high stability alginate cast models with casting delays

Introduction: Dimensional stability of alginate impression is important to obtain an accurate cast. This study was to find the linear dimensional changes of the cast made from delayed pour high stability alginate impression after 5 days. Methods: This experimental laboratory study used 20 samples, divided into 4 groups. First and third group were the generated cast produced by immediately pour into high stability and conventional alginate impressions. Second and fourth group were the generated cast produced by delayed pour into high stability and conventional alginate impression for 5 days in storage with 100% humidity. Dimensional changes were measured on the upper part of the cast from buccal-lingual and mesial-distal direction beside measuring on the outer distance between the upper cast used Mitutoyo digital caliper scaled 0.01 mm. The data were analyzed using ANOVA (α = 0.05).Results: Mesial-distal (a) diameter average of group I, II, IV were respectively 8.410 mm, 8.520 mm, and 8.620 mm, compared with III as control was 8.420 mm. Meanwhile, diameter averages of mesial-distal (b) were 8.314 mm, 8.416 mm, 8.513 mm, and 8.315 mm. The averages of distance between each teeth (c) were 13.312 mm, 13.240 mm 13.191 mm, and 13.316 mm. The diameter averages of buccal-lingual (d) were 8.411 mm, 8.530 mm, 8.608 mm and 8.410 mm. The diameter averages of buccal-lingual (e) were 8.350 mm, 8.441 mm, 8.524 mm, and 8.340 mm. ANOVA test of the results of distance measurements between teeth (c) produces a calculated F value of 147.850, higher than the F table value (3.239). There were significant diferencess dimensional changes on gypsum cast made from high stability alginate impression and then poured after 5 days. Conclusion: There were diferencess linier dimensional changes on gypsum cast made from high stability alginate impression and then poured after 5 days.

Accuracy of Digital Models Prepared by Spiral CT in Comparison to Standard Cast Models

Objectives: Spiral CT has the potential to overcome the limitations of standard transmission radiography and current CT based methods. Methods: The objective of this study was to compare the standard plaster models taken using alginate impression material with their digital counterparts prepared by scanning the patients with a spiral CT (Light speed Pro, General Electric medical CT scan machine, Wakesha, Wis). Results: On the basis of the results of the present study, the following could be detected: excellent agreement between both mod els as proved by the absence of significant difference and the significantly excellent agreement and association between the two modalities for the different measurements: mesiodistal width of the maxillary and mandibular teeth, and the different arches me asurements like: maxillary and arch perimeters; arch lengths; arch widths and the mandibular intercanine width. Conclusions: In conclusion; digital models are acceptable replacement for plaster casts for the routine measurements made in most orthodontic practices.