Fengshan Chen

Anchorage Effects of a Palatal Osseointegrated Implant with Different Fixation: A Finite Element Study

The purpose of this study was to compare the anchorage effect of the osseointegrated implant with different fixation types using finite element analysis. Three fixation types were investigated. fixation type 1: implant neck in the oral-palatal cortical bone and implant tip in the cancellous bone; fixation type 2: implant neck in the oral-palatal cortical bone and implant tip in the nasal-palatal cortical bone; fixation type 3: implant neck in the oral-palatal cortical bone and implant tip projecting into the nasal cavity. Three finite element models were constructed. Each consisted of two maxillary second premolars, their associated periodontal ligament (PDL), alveolar bones, palatal bone, palatal implant, and a transpalatal arch. Another model without an implant was used to compare with the previous models. The horizontal force (mesial five N, palatal one N) was loaded at the buccal bracket of each second premolar. The stress was calculated in the PDL and implant surrounding bone. The result showed that the palatal implant could significantly reduce von Mises stress (maximum von Mises stress was reduced 30%) and evenly distribute stress in the PDL. The stress magnitude and distribution in the PDL was almost the same in the three implant models. These results suggest that different implant fixation types have almost the same anchorage effects.

A New Method of Predicting Mandibular Length Increment on the Basis of Cervical Vertebrae

The purpose of this study was to establish an equation to predict incremental mandibular length on the basis of the analysis of the cervical vertebrae in a single cephalometric radiograph and to compare the predictive accuracy with other methods. Data comprised two groups of 23 Japanese girls between CVMS I and CVMS V. Group A was examined to construct the predication equation. Group B served to compare the predictive accuracy with the growth potential method and the growth percentage method. The following results were obtained: (1) an equation was determined to obtain mandibular length increments on the basis of the measurements in the third and fourth cervical vertebral bodies, and (2) the average error between the predicted increment and the actual increment was 1.5 mm for the equation method, 2.4 mm for the growth potential method, and 2.8 mm for the growth percentage method. These results suggest that with the use of cervical vertebral measurements, it may be possible to evaluate the mandibular growth potential.

A Special Method of Predicting Mandibular Growth Potential for Class III Malocclusion

The purpose of this study was to establish an equation to predict the mandible growth potential (GP) for Class III malocclusion on the basis of the analysis of the cervical vertebrae in a single cephalometric radiograph and to compare its predictive accuracy with other methods. Data comprised two groups each with 22 Japanese girls. Group A was examined to construct the prediction equation. Group B served to compare the predictive accuracy with the GP method and the method of Mito et al (MM). The following results were obtained: (1) an equation was determined to obtain mandible GP on the basis of measurements in the third and fourth cervical vertebral bodies and (2) the average errors between the predicted increment and the actual increment for each method were 1.45 mm for the equation, 2.91 mm for the GP method, and 2.48 mm for the MM. These results suggest that using cervical vertebral measurements might allow predicting the mandible GP length for Class III malocclusion.

Anchorage Effect of Various Shape Palatal Osseointegrated Implants: A Finite Element Study

The purpose of this study was to compare the anchorage effects of different palatal osseointegrated implants using a finite element analysis. Three types of cylinder implants (simple implant, step implant, screw implant) were investigated. Three finite element models were constructed. Each consisted of two maxillary second premolars, their associated periodontal ligament (PDL) and alveolar bones, palatal bone, palatal implant, and a transpalatal arch. Another model without an implant was used for comparison. The horizontal force (mesial 5N, palatal 1N) was loaded at the buccal bracket of each second premolar, and the stress in the PDL, implant, and implant surrounding bone was calculated. The results showed that the palatal implant could significantly reduce von Mises stress in the PDL (maximum von Mises stress was reduced 24.3-27.7%). The von Mises stress magnitude in the PDL was almost same in the three models with implants. The stress in the implant surrounding bone was very low. These results suggested that the implant is a useful tool for increasing anchorage. Adding a step is useful to lower the stress in the implant and surrounding bone, but adding a screw to a cylinder implant had little advantage in increasing the anchorage effect.

Dental Arch Widths and Mandibular-Maxillary Base Width in Class III Malocclusions with Low, Average and High MP-SN Angles

OBJECTIVE To analyze the development of the dental arches and skeletal mandibular-maxillary bases in untreated Class III malocclusions with low averages and high mandibular plane angles in subjects aged 10 to 14. MATERIALS AND METHODS The records of 50 untreated Japanese girls with Class III malocclusions at age 10 were selected from the files of patients pending orthodontic surgery. The patients included those with low (< or =27 degrees), average (27 degrees through 37 degrees) and high (>37 degrees) mandibular plane angles. The maxillary skeletal base width, biantegonial width, and maxillary and mandibular intermolar width were determined on posteroanterior cephalograms obtained at annual intervals when subjects were between 10 and 14 years of age. The difference between the maxillary and mandibular intermolar width was also calculated and reported. RESULTS All skeletal and dental transverse widths in the high-angle group were significantly smaller than those in the low-angle group (P < .05) from ages 10 to 14. On the other hand, the maxillary to mandibular molar difference was the same for the three groups (P > .05) at each age. The deviations in molar differences did increase from age 10 to age 14 in all three groups. CONCLUSION Mandibular plane angles might play a stronger role in the transverse skeletal growth of the maxilla and the mandible than the transverse dental growth of the maxilla and the mandible.

Anchorage effect of osseointegrated vs nonosseointegrated palatal implants.

Palatal implants can be used with a transpalatal arch (TPA) connected with the second premolar to provide anchorage. The purpose of this study was to compare the anchorage effects of an osseointegrated palatal implant (OPI) with a nonosseointegrated palatal implant (NOPI), using finite element analysis. One model, which was composed of two maxillary premolars, periodontal ligament (PDL), alveolar bone, a palatal implant, palatal bone, a bracket, band, and TPA, was created on the basis of the clinical situation. The palatal implant was treated as either NOPI or OPI. The force on the premolars was investigated under three conditions: a distomesial horizontal force, a buccolingual horizontal force, and a vertical intrusive force. The PDL stress was calculated and compared with a model without an implant. The result showed that OPI could reduce PDL stress significantly. (The average stress was reduced by 14.44% for the distomesial horizontal force, 60.28% for the buccolingual horizontal force, and 17.31% for the vertical intrusive force.) The NOPI showed almost the same anchorage effect as OPI. The stress on the NOPI surface was higher than that on the OPI surface, but the stress was not high enough to result in failure of the implant. These results suggested that waiting for osseointegration might be unnecessary for an orthodontic implant.

Longitudinal evaluation of the intermaxillary relationship in Class III malocclusions.

OBJECTIVE To analyze the sagittal, vertical, and transverse relationship of the maxilla and mandible in Japanese girls with Class III malocclusions. MATERIALS AND METHODS This longitudinal study utilized biannual posteroanterior and lateral cephalograms of 44 untreated subjects from age 8 to 14 years (Class I, 23 girls; Class III, 21 girls). Sagittal and vertical growths were analyzed on the basis of lateral cephalograms, and transverse growth was analyzed on the basis of posteroanterior cephalograms. RESULTS There was no significant difference in sagittal intermaxillary relationships in Class III malocclusion from age 8 to 14 years, whereas significant difference in vertical and transverse intermaxillary relationships appeared with ages during this period. When comparing Class III to Class I malocclusions at the same age point, there were significant differences in sagittal and transverse intermaxillary relationships, whereas significant difference in vertical intermaxillary relationship appeared after 12 years of age. CONCLUSION The results suggest that the sagittal intermaxillary relationships in Class III malocclusions were established before 8 years of age and remained through puberty and that the vertical and transverse intermaxillary relationships in Class III malocclusions changed with ages from 8 to 14 years.

Longitudinal intermaxillary relationships in class III malocclusions with low and high mandibular plane angles.

OBJECTIVE To analyze the sagittal, vertical, and transverse relationships of the maxilla and mandible in Japanese girls with Class III malocclusions with different inclination of mandibular plane. MATERIALS AND METHODS This longitudinal study utilized serial posteroanterior and lateral cephalograms of 56 untreated subjects from the age of 8 years until the age of 14 years (low mandibular plane angle group: n = 20; average mandibular plane angle group: n = 15; high mandibular plane angle group: n = 21). Sagittal and vertical growth was analyzed on the basis of lateral cephalograms, and transverse growth was analyzed on the basis of posteroanterior cephalograms. RESULTS There was no significant difference in intermaxillary sagittal relationships among the three groups from age 8 until 14. On the other hand, there were significant changes in the vertical and transverse intermaxillary relationships during this period. When comparing the three groups at the same age, there were significant differences in vertical and transverse intermaxillary relationships in some ages, whereas no significant difference was found in sagittal relationships in any ages. CONCLUSIONS The inclination of mandibular plane might play a role in anticipating changes in vertical and transverse intermaxillary relationships from 8 until 14 years of age.

Anchorage effect of palatal implants under various forces: A finite element study

Abstract The palatal implant can be used with a transpalatal arch (TPA) connected with the second premolar to provide anchorage. The purpose of this study was to analyze the anchorage effects of a palatal implant by using a finite element analysis. Four models (Model 1 with a 6-mm implant, Model 2 with a 4-mm implant, Model 3 without an implant, Model 4 without TPA or an implant) were created according to the clinical situation. Stress induced in three dimensions (mesial, transversal, and vertical) was investigated. The results showed that a 6-mm palatal implant could reduce periodontal ligament stress significantly (average stress was reduced 14.44% for the mesial force, 17.31% for the vertical force, and 60.28% for the transversal force separately). The 4-mm palatal implant showed almost the same anchorage effect as the 6-mm implant. TPA showed significant anchorage effect (average stress was reduced 8.16%) only when the second premolars were subjected to transversal force. These results suggest that the anchorage effect of palatal implants was related to the direction of the forces and that a 4-mm implant might have the same anchorage effect as a 6-mm implant.