Envisioning Post-treatment Occlusions after Space Closure Using Temporary Skeletal Anchorage Devices.

Missing posterior teeth and posterior tooth extractions are commonly seen and needed within orthodontic practices. With the invention of temporary skeletal anchorage devices (TSADs), clinicians can now effectively close posterior tooth spaces. Various molar occlusions are discussed to help clinicians envision post-treatment occlusions after posterior teeth space closure using TSADs.

Accuracy of bracket positions with a CAD/CAM indirect bonding system in posterior teeth with different cusp heights.

INTRODUCTION: Our objective was to evaluate the effect of cusp height of posterior teeth (first premolar, second premolar, first molar) on the accuracy of the computer-aided design and computer-aided manufacturing (CAD-CAM) indirect bonding system. MATERIAL: Five kinds of maxillary arch models, without attrition, were divided into 2 groups: control group (with 0.5 mm of grinding) and experimental group (with the addition of 0.5 mm of wax to the cusp tip). Rapid prototype models were printed for both groups. Transfer jigs of the individual tooth brackets were designed using a digital model. 3-dimensional program to evaluate the differences between the intended digital bracket position and actual bracket position after indirect bonding. The differences were measured in the linear (mesiodistal, buccolingual, vertical) and angular (angulation, rotation, torque) dimensions. The Wilcoxon signed rank test was used for statistical analyses; significance was defined as P <0.05. RESULTS: Both groups had similar frequencies of errors between the intended and actual bracket positions. The frequencies of vertical errors over 0.5 mm were 3.3% and 6.7% in the control and experimental groups, respectively. The frequencies of angulation, rotation, and torque errors over 1° were 53.3%, 43.3%, and 60%, respectively, for the control group; and 60%, 60%, and 73.3%, respectively, for the experimental group. CONCLUSIONS: A difference in cusp height of maxillary posterior teeth did not produce a statistically significant difference in the linear and angular dimensions of bracket placement with the CAD/CAM indirect bonding system. However, given the tendency for a higher frequency in bracket placement errors in posterior teeth with larger cusp tips, cusp height should be considered when using a CAD/CAM indirect bonding system.

Comparison of the occlusal contact area of virtual models and actual models: a comparative in vitro study on Class I and Class II malocclusion models.

BACKGROUNDS: The occlusal registration of virtual models taken by intraoral scanners sometimes shows patterns which seem much different from the patients' occlusion. Therefore, this study aims to evaluate the accuracy of virtual occlusion by comparing virtual occlusal contact area with actual occlusal contact area using a plaster model in vitro. METHODS: Plaster dental models, 24 sets of Class I models and 20 sets of Class II models, were divided into a Molar, Premolar, and Anterior group. The occlusal contact areas calculated by the Prescale method and the virtual occlusion by scanning method were compared, and the ratio of the molar and incisor area were compared in order to find any particular tendencies. RESULTS: There was no significant difference between the Prescale results and the scanner results in both the molar and premolar groups (p = 0.083 and 0.053, respectively). On the other hand, there was a significant difference between the Prescale and the scanner results in the anterior group with the scanner results presenting overestimation of the occlusal contact points (p < 0.05). In Molars group, the regression analysis shows that the two variables express linear correlation and has a linear equation with a slope of 0.917. R2 is 0.930. Groups of Premolars and Anteriors had a week linear relationship and greater dispersion. CONCLUSIONS: Difference between the actual and virtual occlusion revealed in the anterior portion, where overestimation was observed in the virtual model obtained from the scanning method. Nevertheless, molar and premolar areas showed relatively accurate occlusal contact area in the virtual model.

A Study on Possibility of Clinical Application for Color Measurements of Shade Guides Using an Intraoral Digital Scanner.

PURPOSE: To assess if color measurement with intraoral scanner correlates with digital colorimeter and to evaluate the possibility of application of a digital scanner for shade selection. MATERIALS AND METHODS: The L*a*b* values of the five shade tabs (A1, A2, A3, A3.5, and A4) were obtained with an intraoral scanner (TRIOS Pod) and a colorimeter (ShadeEye). Both devices were calibrated according to the manufacturer's instructions before measurements. Color measurement values were compared with paired t-test, and a Pearson's correlation analysis was performed to evaluate the relationship of two methods. RESULTS: The L*a*b* values of the colorimeter were significantly different from those of the digital scanner (p < 0.001). The L* and b* values of both methods were strongly correlated with each other (both p < 0.05). The device repeatability in both methods were reported to be excellent (p < 0.05). Within the limitations of this study, color measurements with digital intraoral scanners and computer-assisted image analysis were in accordance with those of the colorimeter with respect to L* and b* values; however, all the coordinates of shade tabs were significantly different between two methods. CONCLUSIONS: The digital intraoral scanner may not be used as the primary method of color selection in clinical practices, considering significant differences in color parameters with colorimeter. The scanner's capability in shade selection should be further evaluated.

Accuracy of four different digital intraoral scanners: effects of the presence of orthodontic brackets and wire.

OBJECTIVE: The objective of this study was to compare the accuracy of four different digital intraoral scanners and the effects of buccal brackets and orthodontic wire. METHODS: For this study, three sets of models (Control model, BKT model with buccal bracket, and WBKT model with buccal bracket and orthodontic wire) were scanned using four different types of intraoral scanners: E4D dentist, iTero, Trios, and Zfx IntraScan. The mesiodistal width of the teeth, intercanine width, and intermolar width measured by four scanners were compared. Three-dimensional (3D) images of the brackets were taken using the four scanners. Data were analyzed with one-way ANOVA, independent t test, and post-hoc Tukey test at a significance level of P < 0.05. RESULTS: When comparing the 3D images with manual measurements using a traditional caliper, iTero and Trios showed the highest accuracy in horizontal measurements.iTero had the lowest values in Devmax-min of maxillary intermolar and intercanine widths (0.16 mm and 0.20 mm, respectively), whereas Trios had the lowest values in Devmax-min of mandibular intermolar and intercanine widths (0.36 mm and 0.14 mm, respectively). The horizontal variables were barely affected by the presence of buccal brackets and orthodontic wire. Comparison of 3D bracket images scanned by the four scanners showed differences in image distortion among the scanners. Bracket characteristics did not affect the 3D bracket images. CONCLUSIONS: The four intraoral scanners used in this study differed in accuracy. However, the results acquired by iTero and Trios were more reliable. Effects of buccal brackets and orthodontic wire on the 3D images taken by intraoral scanners were not clinically significant.

Changes in views on digital intraoral scanners among dental hygienists after training in digital impression taking.

BACKGROUNDS: Despite the rapid development of digital dentistry, the use of digital intraoral scanners remains limited. The aim of this study was to evaluate the changes in views on intraoral scanners among dental hygienists after training. METHODS: Thirty-four dental hygienists with >3 years of clinical experience participated and were divided into 2 groups : iTero and Trios groups. Participants of each group practiced the usage of both intraoral scanners, for total 12 times over 4 sessions, Questionnaires were given to participants at two different times; prior to and after the completion of the training sessions. The parameters of questionnaires included on difficulty of use, patient discomfort, awareness, preference, and clinical usefulness of intraoral scanners and comparison of two types of scanners. RESULTS: Upon the completion of the training, both iTero and Trios groups gave positive feedback on anticipated accuracy, efficiency, and clinical usefulness. More participants of the iTero group responded that the level of difficulty of use and patient discomfort was greater than Trios. Both groups preferred Trios for its clinical usefulness. CONCLUSIONS: The perceptions of dental hygienists on usage of intraoral scanner and digital impression improved positively with the training. The participants favored Trios over iTero in terms of difficulty of use , patient comfort, and clinical usefulness. This study showed that appropriate training could change the views on the efficiency of intraoral scanners positively among dental hygienists.

Condylar positional changes up to 12 months after bimaxillary surgery for skeletal class III malocclusions.

PURPOSE: Postsurgical changes in the condylar position are of great importance to surgical stability, especially in asymmetric double-jaw surgery. The aims of this study were to evaluate positional changes of the condyle up to 12 months after surgery in patients with Class III malocclusion and to identify the factors affecting postsurgical condylar position. MATERIALS AND METHODS: The study included 33 adult patients diagnosed with skeletal Class III malocclusion who underwent bimaxillary surgery and had full cone-beam volumetric imaging (CBVI) records up to 1 year after surgery. The CBV images were obtained before surgery and 2 weeks, 3 months (T2), 6 months (T3), and 12 months after surgery. Condyles with deviated and nondeviated sides were examined separately regardless of the degree of asymmetry. Analyses of variance and multiple regression analysis were performed to identify factors that could affect the position of the mandibular condyles. RESULTS: The condyles exhibited anterior displacement at T2, which returned to a more distal position afterward in the axial view, and an inward rotation in the coronal view up to T3. From the sagittal view, the deviated and nondeviated condylar sides rotated forward and remained stable after T2. The degree of menton deviation affected the angle of condylar rotation (horizontal angle). CONCLUSION: The results of this study suggest that condyles tend to move in a certain direction, and this can influence postsurgical relapse up to 6 months after surgery. However, they remain relatively stable afterward.

Molar uprighting by a nickel-titanium spring based on a setup model.

Molar uprighting is an important adjunctive treatment in orthodontics: repositioning the tilted molar eliminates the potentially pathologic condition and simplifies the ultimate restorative procedure. Although various methods for molar uprighting have been applied successfully, they still have some limitations and disadvantages in tooth movement. This article reports on a new clinical technique for molar uprighting with nickel-titanium springs based on a setup model. Two patients treated with this system are shown.

Effects of retraction force and anchorage reinforcement on occlusal force: a model study.

OBJECTIVES: The aim of this study was to investigate the effects of retraction force and anchorage reinforcement with orthodontic mini implants on occlusal force. MATERIALS AND METHODS: A strain gauge was attached to the palatal surface of the maxillary right first molar on an en masse retraction model. RESULTS: Occlusal forces were measured from this model, according to different retraction forces that were generated by elastic chain, under varied compressive forces (simulating masticatory forces). This retraction experiment was then performed again, after using anchorage reinforcement with an orthodontic mini implant. Occlusal force decreased as retraction force increased. The decrease showed a significant difference above 150g of retraction force (P < 0.05) and was more definite under compressive force higher than 150 N (P < 0.001). After anchorage reinforcement with the orthodontic mini implant, however, occlusal force did not significantly decrease with increasing retraction force. Significant differences in occlusal force were noted between the conditions with and without anchorage reinforcement when the applied retraction force was greater than 200g. CONCLUSION: Occlusal force tends to decrease during retraction, and this decrease can be prevented by anchorage reinforcement with orthodontic mini implants. LIMITATIONS: Further investigation on the actual masticatory process in humans is required for more clear clinical implication.

Comparison of tooth displacement between buccal mini-implants and palatal plate anchorage for molar distalization: a finite element study.

The purposes of this study were to mechanically evaluate distalization modalities through the application of skeletal anchorage using finite element analysis. Base models were constructed from commercial teeth models. A finite element model was created and three treatment modalities were modified to make 10 models. Modalities 1 and 2 placed mini-implants in the buccal side, and modality 3 placed a plate on the palatal side. Distalization with the palatal plate in modality 3 showed bodily molar movement and insignificant displacement of the incisors. Placing mini-implants on the buccal side in modalities 1 and 2 caused the first molar to be distally tipped and extruded, while the incisors were labially flared and intruded. Distalization with the palatal plate rather than mini-implants on the buccal side provided bodily molar movement without tipping or extrusion. It is recommended to use our findings as a clinical guide for the application of skeletal anchorage devices for molar distalization.

Volumetric changes in the upper airway after bimaxillary surgery for skeletal class III malocclusions: a case series study using 3-dimensional cone-beam computed tomography.

PURPOSE: Postsurgical changes of the airway have become a great point of interest and often have been reported to be a predisposing factor for obstructive sleep apnea after mandibular setback surgery. The purpose of this study was to evaluate the 3-dimensional volumetric changes in the upper airway space of patients who underwent bimaxillary surgery to correct Class III malocclusions. MATERIALS AND METHODS: This study was performed retrospectively in a group of patients who underwent bimaxillary surgery for Class III malocclusion and had full cone-beam computed tomographic (CBCT) images taken before surgery and 1 day, 3 months, and 6 months after surgery. The upper and lower parts of the airway volume and the diameters of the airway were measured from 2 different levels. Presurgical measurements and the amount of surgical correction were evaluated for their effect on airway volume. Data analyses were performed by analysis of variance and multiple stepwise regression analysis. RESULTS: The subjects included 21 patients (6 men and 15 women; mean age, 22.7 yrs). The surgeries were Le Fort I impaction (5.27 ± 2.58 mm impaction from the posterior nasal spine) and mandibular setback surgery (9.20 ± 4.60 mm set back from the pogonion). No statistically significant differences were found in the total airway volume for all time points. In contrast, the volume of the upper part showed an increase (12.35%) and the lower part showed a decrease (14.07%), with a statistically significant difference 6 months after surgery (P < .05). Predictor variables affecting the upper and lower parts of the airway volume were presurgical A point to Nasion-perpendicular (A to N-perp) and vertical surgical correction of the pogonion and the posterior nasal spine (P < .05). CONCLUSIONS: Bimaxillary surgery for the correction of Class III malocclusion affected the morphology by increasing the upper part and decreasing the lower part of the airway, but not the total volume.

Protraction of mandibular second and third molars into missing first molar spaces for a patient with an anterior open bite and anterior spacing.

In a young woman, aged 18 years 8 months, who had an anterior open bite and anterior spacing, the right and left mandibular first molar extraction spaces were closed by protraction of the second and third molars without reciprocal retraction of the incisors and the premolars. The amounts of protraction for the second molars were 12 mm on the right side and 11 mm on the left side. Two miniscrews were inserted into the mesiobuccal side of the edentulous spaces, and 2 more screws were inserted into the anterior sites after removing previous miniscrews. In addition, 4 miniscrews were inserted into the buccal and palatal sides between the first and second maxillary molars to intrude the maxillary posterior teeth, which had extruded into the missing mandibular spaces. Careful biomechanical consideration was used to prevent extrusion of the molars and worsening of the anterior open bite from protraction of the posterior teeth. Ultimately, the anterior open bite was corrected by both intrusion of the maxillary molars and extrusion of the maxillary anterior teeth. Excellent occlusion and correction of the anterior open bite were achieved without tipping, rotation of the posterior teeth, or other problems. The right mandibular third molar, which had been impacted at the beginning of treatment, erupted into the second molar space and functioned properly. At the 1-year follow-up examination, the patient had a slight anterior open bite, but closure of the first molar extraction spaces was well maintained.

Factors controlling anterior torque with C-implants depend on en-masse retraction without posterior appliances: biocreative therapy type II technique.

INTRODUCTION: Our objective was to evaluate the factors that affect effective torque control during en-masse anterior retraction by using intrusion overlay archwire and partially osseointegrated C-implants as the exclusive sources of anchorage without posterior bonded or banded attachments. METHODS: Base models were constructed from a dental study model. No brackets or bands were placed on the posterior maxillary dentition during retraction. Different heights of the anterior retraction hooks to the working segment archwire and different intrusion forces with an overlay archwire placed in the 0.8-mm diameter hole of the C-implant were applied to generate torque on the anterior segment of the teeth. The amount of tooth displacement after finite element analysis was exaggerated 70 times and compared with tooth axis graphs of the central and lateral incisors and the canine. RESULTS: The height of the anterior retraction hook and the amount of intrusion force had a combined effect on the labial crown torque applied to the incisors during en-masse retraction. The difference of anterior retraction hook length highly affected the torque control and also induced a tendency for canine extrusion. CONCLUSIONS: Three-dimensional en-masse retraction of the anterior teeth as an independent segment can be accomplished by using partially osseointegrated C-implants as the only source of anchorage, an intrusion overlay archwire, and a retraction hook (biocreative therapy type II technique).

Factors controlling anterior torque during C-implant-dependent en-masse retraction without posterior appliances.

INTRODUCTION: Our objective was to evaluate the factors that affect effective torque control during en-masse incisor and canine retraction when using partially osseointegrated C-implants (Cimplant, Seoul, Korea) as the exclusive source of anchorage without posterior bonded or banded appliances. METHODS: Base models were constructed from a dental study model. No brackets or bands were placed on the maxillary posterior dentition during retraction. The working archwire was modeled by using a 3-dimensional beam element (ANSYS beam 4, Swanson Analysis System, Canonsburg, Pa) with a cross section of 0.016 × 0.022-in stainless steel. Different heights of anterior retraction hooks and different degrees of gable bends were applied to the working utility archwire that was placed into the 0.8-mm diameter hole of the C-implant to generate anterior torque on the anterior segment of the teeth. The amount of tooth displacement after finite element analysis was exaggerated 70 times and compared with tooth-axis graphs of the central and lateral incisors and the canine. RESULTS: The height of the anterior retraction hook and the degree of the gable bend had a combined effect on the labial crown torque applied to the incisors during en-masse retraction. By using 30° gable bends and the longest hook, lingual root movement of the 6 anterior teeth occurred. By using 20° gable bends, the 6 anterior teeth showed a translation tendency during retraction. CONCLUSIONS: Three-dimensional en-masse retraction of the 6 anterior teeth can be accomplished by using partially osseointegrated C-implants as the only source of anchorage, gable bends, and a long retraction hook (biocreative therapy type I technique).

Effective en-masse retraction design with orthodontic mini-implant anchorage: a finite element analysis.

INTRODUCTION: The strategic design of an appliance for correcting a bialveolar protrusion by using orthodontic mini-implant anchorage and sliding mechanics must take into account the position and height of the mini-implant, the height of the anterior retraction hook and compensating curve, and midline vertical traction. In this study, we used finite element analysis to examine effective en-masse retraction with orthodontic mini-implant anchorage and sought to identify a better combination of the above factors. METHODS: Base models were constructed from a dental study model. Models with labially and lingually inclined incisors were also constructed. The center of resistance for the 6 anterior teeth in the base model was 9 mm superiorly and 13.5 mm posteriorly from the midpoint of the labial splinting wire. The working archwires were assumed to be 0.019 x 0.025-in or 0.016 x 0.022-in stainless steel. The amount of tooth displacement after finite element analysis was magnified 400 times and compared with central and lateral incisor and canine axis graphs. RESULTS AND CONCLUSIONS: The tooth displacement tendencies were similar in all 3 models. The height of the anterior retraction hook and the placement of the compensating curve had limited effects on the labial crown torque of the central incisors for en-masse retraction. The 0.016 x 0.022-in stainless steel archwire showed more tipping of teeth compared with the 0.019 x 0.025-in archwire. For high mini-implant traction and 8-mm anterior retraction hook condition, the retraction force vector was applied above the center of resistance for the 6 anterior teeth, but no bodily retraction of the 6 anterior teeth occurred. For high mini-implant traction, 2-mm anterior retraction hook, and 100-g midline vertical traction condition, the 6 anterior teeth were intruded and tipped slightly labially.

Palatal bone density in adult subjects: implications for mini-implant placement.

OBJECTIVES: To evaluate palatal bone density to allow for better selection of palatal implant anchorage sites. MATERIALS AND METHODS: Computed tomographic (CT) images were obtained from 15 males and 15 females (mean age, 27 years; range, 23-35 years). Bone density was measured in Hounsfield units (HU) at 80 coordinates at regular mediolateral and anteroposterior intervals along the midpalatal suture. RESULTS: Bone densities ranged from 805 to 1247 HU. A significant difference between male and female groups was noted, although no difference was found between left and right sides of individual palates. Palatal bone densities showed a tendency to decrease laterally and posteriorly. The midpalatal area within 3 mm of the midsagittal suture had the densest bone in the entire palate. CONCLUSION: Results suggest that mini-implants for orthodontic anchorage may be effectively placed in most areas with bone density equivalent to the palatal area if they are placed from 3 mm posterior to the incisive foramen and 1 to 5 mm to the paramedian side.

An investigation into structural behaviors of skulls chewing food in different occlusal relationships using FEM.

OBJECTIVES: This study aims to investigate the effect of different occlusal relationships on skull structural and mechanical behaviors through simulation of chewing food. METHODS: Finite element (FE) skull models of occlusion for Class I, end-on Class II, and full-cusp Class II were generated. End-on Class II and full-cusp Class II were chosen as mild and severe Class II occlusions, respectively. A simplified food bolus was introduced between the upper and lower dentition of the right molars. Chewing food was simulated in the skulls by moving the mandible. An experiment was conducted to measure strains at selective locations and compared them to the analytical results for validation. RESULTS: In the early stages of mandibular movement, masticatory forces predicted from the skull models without food were lower than the skull models with food but increased drastically after occluding teeth full enough. As a result, the relationship between masticatory force and mandible movement shows that there is no significant difference between the skull models with food and without food in the range of human masticatory force, approximately 250 N. In all the cases of skulls including a food bolus, stress was similarly propagated from the mandible to the maxilla and concentrated in the same regions, including the mandibular notch and alveolar bone around the lower molars. CONCLUSION: It is predicted that there is no significant difference of bite force-mandible movement relationships and stress distributions of skull and teeth, between end-on Class II and full-cusp Class II models. When simulating chewing activities on candy and carrot, it is also found that there is no difference of masticatory performance between Class II occlusions, from structural as well as mechanical perspectives.

Orthodontic treatment combined with autotransplantation after removal of ameloblastoma.

This article describes the use of indirect skeletal anchorage and autotransplantation in a patient who had an ameloblastoma removed. The mandibular left second and third molars were also extracted. Autogenous bone was grafted after surgical removal of the ameloblastoma, and the mandibular right third permanent molar was transplanted into the extraction space. Orthodontic treatment included a miniscrew to bring the transplanted tooth into good occlusion. Four years after treatment, the patient continued to show good results, with no recurrence of the ameloblastoma.