Distal Inclination Research Articles

Correlation between Cleft Width and Adjacent Teeth Inclination in Patients with Unilateral Cleft Lip and Palate Using CBCT: A Retrospective Study.

To evaluate buccolingual and mesiodistal inclination of cleft-adjacent maxillary permanent central incisors (U1) and canines (U3) in patients with unilateral cleft lip and palate (UCLP) in the late mixed dentition and to investigate the correlation between the alveolar cleft width and cleft-adjacent teeth inclination using cone beam computed tomography (CBCT). Observational cross-sectional retrospective study. Department of Orthodontics, Hama University Dental School. 32 patients with UCLP (22 boys, 10 girls; mean age = 10.53 ± 1.51 years). Buccolingual and mesiodistal inclination of maxillary central incisors and canines were measured on both sides. Then, the cleft and non-cleft sides were compared using the Wilcoxon signed-rank test. Pearson's correlation was used to explore the association between the alveolar cleft width and cleft-adjacent U1 and U3 buccolingual and mesiodistal inclination. The cleft-adjacent central incisors were significantly inclined lingually and distally compared with their non-cleft antimeres (P = .003, P < .001, respectively). The cleft-adjacent canines were significantly inclined buccally and mesially compared with their non-cleft antimeres (P < .001, for both). A positive correlation was found between the buccolingual inclination of cleft-adjacent U1 and the alveolar cleft width (r = 0.49, P = .004). Patients with UCLP demonstrated a significant lingual and distal inclination of cleft-adjacent U1 and a significant buccal and mesial inclination of cleft-adjacent U3. The buccolingual inclination of cleft-adjacent U1 tends to increase with increasing the alveolar cleft width; however, the correlation was weak.

Ectopic Eruption of the Maxillary Permanent First Molar: A Brief Review and Clinical Case Report

The Ectopic Eruption of the Maxillary Permanent First Molar (EEMPFM) is an eruption anomaly, characterized for the maxillary permanent first molar’s impaction in the distal surface of the deciduous second molar. The etiology is related with change of the axial axis of eruption of the permanent first molar associated with missing space in the maxilla. The diagnosis is the combination of clinical and complementary examination. There are two types of Ectopic Eruption: the reversible and the irreversible. The irreversible type requires orthodontics treatment, because it causes root resorption of the deciduous second molar, causing its premature loss. For the treatment, procedures can be used with the aim of promoting distal inclination of the ectopic first molar, using separator elastics, removable or fixed appliances. The aim of this work is to report a clinical case of a patient of 9 years and 6 months old, female gender, who attended the Clinic presenting EEMPFM of the maxillary right permanent first molar. The treatment was a removable appliance composed with an acrylic base plate with clasps and a finger spring activated against a resin button bonded on the mesiobuccal cusp of the maxillary right permanent first molar. The correction of this anomaly was obtained with 35 days of treatment. Therefore, the sequence of procedures from diagnosis to the indication of an adequate treatment method is fundamental to obtain satisfactory results.

Effects of different distalization directions and methods on maxillary total distalization with clear aligners: a finite element study.

To analyze the effects of maxillary tooth distalization by clear aligner (CA) treatment with variations in the angular direction of the distalization force, presence of attachments, and force-application method used. A finite element model containing alveolar bone, dentition, and periodontal ligament was constructed. Analytical model groups were as follows: (1) distalization with buttons (without attachments), (2) buttons on canines (with attachments), (3) precision cuts on the canines (without attachments), and (4) precision cuts on the canines (with attachments). A distalization force of 1.5 N was applied to the button or precision cut at -30°, -20°, -10°, 0°, 10°, 20°, and 30° to the occlusal plane. As the direction of force approached +30°, the dentition inclined posteriorly. The posterior movement pattern was significantly influenced by the presence of an attachment and the direction of force, rather than the area where the force was applied. Distal inclination was dramatically reduced with attachments. A disengagement or deformation of the CA may reduce the distalization efficiency of the dentition or move the dentition in an inappropriate direction. Attachments for efficient distalization by the CA are necessary. The use of miniscrews in the direction of force parallel to the occlusal plane is more advantageous than the use of Class II elastics. Due to CA deformation, distalization with the button on the canines can be more effective for distal movement of the maxillary dentition.

Clinical three-dimensional anatomy of the femur considering navigation-aided surgery of total knee arthroplasty in Japanese patients

PurposeFew studies exist regarding sagittal alignment describing femur morphology in navigation-aided surgery. This study investigated the three-dimensional (3D) sagittal femoral alignment of the whole femur. MethodsSeventy-three consecutive patients (59 females, 14 males, mean age: 76.1 years), yielding 140 femurs, were included in this study. A computed-tomography-based patient-specific 3D femur model was used to define a mechanical axis-based reference plane. Proximal and distal femoral axis angles (PFA, DFA) to the reference plane were measured in 3D using custom software. PFA and DFA represent the proximal and distal inclination of the femoral anatomical axis in sagittal plane, respectively. ResultsPFA (10.6 ± 1.5°) was greater than DFA (2.6 ± 1.6°; P < 0.0001). DFA in females (2.3 ± 1.4°) was smaller than in males (3.9 ± 1.7°; P < 0.0001). ConclusionThis is the first report of measurement of femoral sagittal alignment related to both 3D anatomy and decision making of femoral flexion angle using navigation surgery for total knee arthroplasty. This report shows a robust DFA measurement that could be used as a template for femoral implants flexion angle when performing both conventional and navigated total knee arthroplasty.

Three-dimensional evaluation of maxillary tooth movement in extraction patients with three different miniscrew anchorage systems: a randomized controlled trial

ObjectiveTo compare the three-dimensional (3-D) movement of maxillary teeth in response to three common miniscrew anchorage systems in extraction patients with maxillary dentoalveolar protrusion.Materials and methodsThe study employed a randomized controlled single-blinded design with three arms. Thirty extraction patients who required maximum anchorage to retract maxillary anterior teeth were included and randomly allocated into three treatment groups: space closure with direct miniscrew anchorage and low crimpable hooks (DL group), indirect miniscrew anchorage and low crimpable hooks (IL group), and direct miniscrew anchorage and high crimpable hooks (DH group). Cone beam computed tomography (CBCT) images of all included patients were obtained immediately before (T0) and after (T1) space closure. The outcomes were 3-D positional changes of maxillary central incisor, lateral incisor, canine, second premolar, and first molar. The repeated measures analysis of variance with post hoc LSD test was used to evaluate differences among groups.ResultsA significant intrusion (− 1.34 mm; 95% CI, − 1.60 mm, 1.08 mm) and buccal (− 6.92°; 95% CI, − 8.67°, − 5.13°) and distal (4.90°; 95% CI, 3.75°, 6.04°) inclination of the maxillary first molars were observed in the DL group, compared to the other two groups. The mesial movement (− 0.40 mm; 95% CI, − 0.83 mm, − 0.03 mm) of the maxillary first molars was found in the IL group, while the DL (0.44 mm; 95% CI, 0.15 mm, 0.73 mm) and IL (0.62 mm; 95% CI, 0.28 mm, 0.96 mm) groups exhibited distal movement. In the DH group, the lingual inclination changes of maxillary central incisor (5.04°; 95% CI, 2.82°, 7.26°) were significantly lower, which is indicative of good lingual root torque control of the maxillary anterior teeth.ConclusionThree miniscrew anchorage systems produced significantly different 3-D maxillary tooth movement. The maxillary first molars were significantly buccally and distally inclined and intruded in patients using direct miniscrew anchorages with low crimpable hooks. Direct miniscrew anchorages with high crimpable hooks could help to achieve better lingual root torque control of the maxillary incisors.Trial registration The trial was registered at www.chictr.org.cn (ChiCTR1900026960). Registered 27 October 2019.

Three-dimensional finite element analysis of upper anterior teeth retraction and intrusion using clear aligners and mini-implants.

This study aimed to investigate the differences in treatment outcomes of upper anterior teeth retraction and intrusion with clear aligners and different types of elastics on mini-implants via the 3D finite element method. Cone-beam computed tomography (CBCT) was conducted to construct a 3D finite element model of maxillary bone, dentition, and clear aligners using Mimics, Geomagic, Solidworks, and Ansys. Four model groups were developed. Group 1 was the control group. Group 2 implanted a mini-implant between the upper second premolar and the upper first molar with a force of 0.98 N applied to the canine cut along the retracting direction for each side. Group 3 was based on Group 2, which implanted an additional mini-implant between the upper central incisors with a force of 0.98 N applied to the upper anterior teeth cuts. Group 4 was also based on Group 2, which implanted 2 additional mini-implants between the upper central and lateral incisors with a force of 0.56 N applied to the upper anterior teeth cuts for both sides. Anterior teeth torque changes, displacement patterns, and stress distributions were analyzed. Among all the experimental groups, the anterior teeth demonstrated intrusion and distal inclination, accompanied with varied degrees of torque loss. In Group 3, the maxillary and lateral incisors had the smallest sagittal coronal displacement. In Group 4, the intrusion values of the maxillary and lateral incisors were the largest among all the experimental groups. The maximum stress concentration in Group 2 was the most significant among all the experimental groups. Implanting the mini-implant between the central incisors for traction is conducive to torque control. By contrast, implanting the mini-implants between the central incisors and lateral incisors combined with vertical traction is conducive to simple intrusion, avoiding the "bowing effect" to a certain extent.

Finite Element Analysis of the Stresses Induced by One-Piece and Two-Piece Dental Implants Supporting All-on-4 Implant-Supported Prostheses.

To find out the difference in the stresses induced by one-piece monophasic and two-piece dental implants supporting All-on-4 implant-supported prostheses using finite element analysis. Two finite element maxillary models were designed: In the two-piece model, two-piece dental implants were used, and in the one-piece model, one-piece dental implants were used. The dental implants were placed according to the All-on-4 treatment concept. The anterior implants were axially placed; however, the posterior implants were placed with a distal inclination of 15 degrees. In each model, the prosthetic superstructure was designed to be a titanium implant prosthesis with zirconia crowns. Three loading scenarios were applied in this study. The first scenario simulated biting function with a total load of 250 N. The second scenario simulated incision function in which 90-N horizontal static load was applied to the palatal surface of central incisors. The third scenario simulated biting in the presence of a cantilever. In the three loading scenarios, the stresses were higher in the two-piece model. Higher stress values were recorded posteriorly rather than anteriorly in both models. One-piece dental implants induce lower stress values compared with two-piece dental implants when used in All-on-4 implant-supported prostheses.

Assessment of Third Molar Impaction Pattern in the Mandible and in the Maxilla

Aim: The aim of this study was to compare characteristics of erupted and impacted third molars in the mandible and themaxilla using quantitative measurements and determine any relationship between the eruption/impaction pattern ofthird molars in both jaws with available eruption space and tooth inclination.Material and Methods: Patients who visited to the Department of Oral and Maxillofacial Surgery at tertiary care instituteof India were screened for eligibility to join our study. The eruption status of the third molars in both jaws were examinedon orthopantomographs by measuring the distance from the line tangent to the highest points of occlusal cusps of thethird molar to that of the adjacent second molar. The presence of available space for the eruption was determined by theratio of the mesiodistal length of the third molar crown to the length of the alveolar arch distal to second molars.Results: There was sufficient space for the eruption of third molars in 17.6% of the cases in the mandible as opposedto 61.7% of the cases in the maxilla. In the mandible, 37.7% of third molars were in vertical position, 37.1% were inmesioangular position, and 19.9% were in distoangular position. In the maxilla, 62.5% of third molars were in verticalposition and 33.12% were in distal inclination. The presence of favorable parameters does not warrant full eruption ofthird molars in both jaws.Conclusion: Removal of impacted third molars is the most commonly employed procedure in oral surgery practice. Painand pericoronitis were the most common symptoms usually associated with level A impaction and vertical position.

Comparison between the designed and achieved mesiodistal angulation of maxillary canines and posterior teeth and influencing factors: First premolar extraction treatment with clear aligners

This study aimed to compare the designed and achieved mesiodistal angulation of maxillary canines and posterior teeth (MCPT) for first premolar extraction with clear aligner treatment and identify the main influencing factors for preventing MCPT tipping toward the extraction space. A total of 21 adults with first premolar extraction were recruited. The designed and achieved tooth movement of MCPT was measured by superimposing their respective pretreatment and posttreatment cone-beam computed tomography images and compared with the designed tooth movement in ClinCheck using the paired t test and scatter plot analysis. Influencing factors, including dental arch length change, canine distalization, and initial mesiodistal angulation, were analyzed using the linear mixed-effect model. Designed distal crown tipping (second premolar, 10.73 ± 3.22°; first molar, 9.83 ± 3.60°; second molar, 7.18 ± 2.36°) significantly increased the distal inclination of the second premolar (2.50° ± 5.15°; P＜0.001), first molar (1.07° ± 4.14°; P＜0.001), and second (0.70° ± 3.78°; P＜0.001). Furthermore, mesial tipping (8.59° ± 6.03°; P＜0.001) achieved appropriate distal crown tipping of canines (-6.43° ± 5.04°; P＜0.001). The implemented preliminary formulas showed that shortening of the dental arch length, the distance of canine distalization, and initial mesiodistal angulation were closely related to the antitipping design. Designed distal crown tipping of posterior teeth and mesial crown tipping of canines might prevent unwanted crown tipping toward the extraction space during space closure. The proposed preliminary formula could guide antitipping designs in clear aligner treatment.

Evaluation of biomechanics using different traction devices in distalization of maxillary molar with clear aligners: a finite element study

The study aimed to mechanically evaluate the tooth displacement of molar distalization by clear aligners combined with micro-implant through different traction devices using finite element analysis. A three-dimensional finite element model of complete maxillary dentition was constructed. Simultaneously move the maxillary first and second molars 0.2 mm distally at the height of 4 mm and 6 mm of micro-implant, and 150 g force was applied to button, precision cut and angelbutton respectively. Initial tooth movement in six different conditions of anterior tooth and molars was analyzed and calculated with ANSYS software. All the upper anterior tooth exhibited uncontrolled labial tipping and intrusion upon the six conditions, and the central incisor showed the largest tendency of crown labial inclination. Among the absolute values of crown-root displacement difference of the anterior tooth in sagittal direction, the angelbutton was the smallest, which means the torque control ability was superior to others. However, button played a more accurate role in the sagittal and vertical control of canine. With the increase of micro-implant height, the torque control ability of anterior tooth was decreased, but the intrusion trend increased. The controlled distal inclination with extrusion of the first molar and uncontrolled distal inclination with intrusion of the second molar were observed, and the angelbutton had more effective horizontal and vertical control on molars, which was close to bodily movement than others. As a new type of traction device, angelbutton has excellent anchorage control effect in clear aligners therapy of molar distalization, which further realizes the accurate expression of orthodontic force.

Investigation on the quality analysis of 1 312 single crown digital models.

This study aimed to investigate the quality of single crown digital models, enhance communication between clinicians and technicians, and improve the quality of restorations to further reduce remake rate. A total of 1 312 single crown digital models (180 anterior teeth, 294 premolars, and 838 molars) were randomly selected from a large commercial dental factory. The digital models were evaluated by three investigators with the same working experience with the same intraoral scanning system (CEREC). CEREC SW 4.4 was used in capturing the images of single crown preparations, and prepCheck 3.1 was used in evaluating the quality of single crown digital models. Approximately 6.55%, 0.08%, 81.17%, 19.59%, and 22.48% of 1 312 single crown digital models did not meet the standards of the undercut, surface quality, margin quality, buccal-lingual taper, and mesiodistal taper, respectively. Moreover, 23.25%, 28.51%, 28.43%, and 28.35% of the investigated single crown digital models did not meet the standards of the buccal inclination taper, lingual inclination taper, mesial inclination taper, and distal inclination taper, respectively. The quality of anterior teeth, premolars, molars at the margin quality, buccal-lingual taper, mesiodistal taper, buccal inclination taper, lingual inclination taper, mesial inclination taper, and distal inclination taper significantly varied in the evaluation results (P<0.01). In addition to the undercut and surface quality met the standard, the overall situation of the quality of the single crown digital preparation model was poor, and the quality of the preparation needs to be improved urgently.

All on four fixed prostheses versus implant overdentures for management of edentulous maxilla opposing mandibular 2- implant assisted overdentures

Purpose: This study aimed to compare two treatment modalities; All on four fixed prostheses and locator retained overdentures; to rehabilitate patients having problems associated with edentulous maxilla opposing mandibular implant assisted overdentures. Materials and methods: Ten patients complaining from looseness and instability of their maxillary dentures that oppose mandibular 2-implant-retained overdentures were randomly divided into 2 groups: Group I included 5 patients who received four implants according to the All-on- four Concept (2 parallel middle implants and 2 posterior implants with distal inclination). Implants were immediately loaded with fixed acrylic prosthesis, then after 6 months the prosthesis was replaced with fixed ceramometal restoration, Group II, included 5 patients who received four implants that were immediately loaded with Locator retained maxillary overdentures using new maxillary dentures. Clinical (plaque index (PI), gingival index (GI), probing depth (PD) and implant stability (IS)) and radiographic (marginal bone loss (MBL) outcomes were recorded at baseline (T0), 6 (T6) and 12 (T12) month after prosthesis insertion.

Effect of age-adjusted alignment goals and distal inclination angle on the fate of distal junctional kyphosis in cervical deformity surgery

Background:Age-adjusted alignment targets in the context of distal junctional kyphosis (DJK) development have yet to be investigated. Our aim was to assess age-adjusted alignment targets, reciprocal changes, and role of lowest instrumented level orientation in DJK development in cervical deformity (CD) patients.Methods:CD patients were evaluated based on lowest fused level: cervical (C7 or above), upper thoracic (UT: T1–T6), and lower thoracic (LT: T7–T12). Age-adjusted alignment targets were calculated using published formulas for sagittal vertical axis (SVA), pelvic incidence-lumbar lordosis (PI-LL), pelvic tilt (PT), T1 pelvic angle (TPA), and LL-thoracic kyphosis (TK). Outcome measures were cervical and global alignment parameters: Cervical SVA (cSVA), cervical lordosis, C2 slope, C2–T3 angle, C2–T3 SVA, TS-CL, PI-LL, PT, and SVA. Subanalysis matched baseline PI to assess age-adjusted alignment between DJK and non-DJK.Results:Seventy-six CD patients included. By 1Y, 20 patients developed DJK. Non-DJK patients had 27% cervical lowest instrumented vertebra (LIV), 68% UT, and 5% LT. DJK patients had 25% cervical, 50% UT, and 25% LT. There were no baseline or 1Y differences for PI, PI-LL, SVA, TPA, or PT for actual and age-adjusted targets. DJK patients had worse baseline cSVA and more severe 1Y cSVA, C2–T3 SVA, and C2 slope (P < 0.05). The distribution of over/under corrected patients and the offset between actual and ideal alignment for SVA, PT, TPA, PI-LL, and LL-TK were similar between DJK and non-DJK patients. DJK patients requiring reoperation had worse postoperative changes in all cervical parameters and trended toward larger offsets for global parameters.Conclusion:CD patients with severe baseline malalignment went on to develop postoperative DJK. Age-adjusted alignment targets did not capture differences in these populations, suggesting the need for cervical-specific goals.

The Effect of Maxillary Posterior Space Discrepancy on the Molars and Overbite in Class II Malocclusions with Different Vertical Patterns

The purpose of this cross-sectional study was to investigate the influence of maxillary posterior space discrepancy (MPDD) on angulation and vertical position of molars in patients with skeletal class II malocclusions, presenting long, short, and normal vertical growth patterns. In total, 120 lateral cephalograms of patients (mean age: 23 years) with skeletal class II malocclusion were evaluated. Patients were divided into six groups based on their vertical growth pattern (normal, long, and short faces) and the presence or absence of maxillary posterior discrepancy. Maxillary molars' sagittal angulation and vertical position were measured on cephalograms via Dolphin™ three-dimensional (3D) software (version 11.5). The comparison between groups with the same vertical dimension and different status of MPDD was done with independent t test. The analysis of analysis (ANOVA) was used to make pairwise comparison between all six groups. Finally, a multiple regression analysis was performed to evaluate the influence of molar position and MPDD on the anterior overbite. The results showed that the angulation of the maxillary first molar was not statistically different between groups with the same vertical dimension but varied in terms of MPDD. The maxillary second molar was more distally inclined in patients with MPDD than those without MPDD with short and normal facial types (p value = 0.016 and p value = 0.001, respectively). The second molar had significantly more distal angulation in long face patients than short and normal face participants, without considering the status of MPDD. The upper first and second molars were erupted more in patients with long than short or normal faces, without any influence of MPDD. The presence of MPDD caused more distal inclination of the maxillary second molar, in skeletal class II patients with short and normal vertical growth patterns. The status of MPDD and its effect on the maxillary second molar teeth should be considered in skeletal class II patients with short and normal vertical growth patterns.

Effects of Cantilever Length and Implant Inclination on the Stress Distribution of Mandibular Prosthetic Restorations Constructed from Monolithic Zirconia Ceramic.

This study aimed to biomechanically evaluate the effects of cantilever length and implant inclination on the stress distribution of mandibular prosthetic restorations constructed from monolithic zirconia ceramic. Mandibular full-arch prostheses supported by four implants constructed from monolithic zirconia were designed using either a 5-mm or 9-mm cantilever length and a 15-degree or 30-degree distal tilt for the posterior implants. A simulated static load of 600 N was applied from the right side at a 45-degree angle. Von Mises and principal stress values in superstructures were analyzed using the Mesh VR Studio program. When the effects of cantilever length were examined, in the models with the 15-degree implant tilt, stress values for posterior implants, porcelain, and cortical bone were lower when the cantilever length was shorter (5 mm). In the models with the 30-degree implant tilt, stress values in all implants (except for the anterior implant on the right) and in the porcelain superstructure were lower when the cantilever length was shorter; however, stress values for cortical and spongious bone were lower with the longer (9 mm) cantilever. When the effects of implant inclination were examined, in the models with a 5-mm cantilever, stress values for posterior implants and cortical bone were lower when the implant tilt was more severe (30 degrees). In the models with a 9-mm cantilever length, stress values for the right anterior implant, posterior implants, and cortical bone were lower when the implant tilt was less severe (15 degrees). Cantilever length and posterior implant inclination affected the distribution of force. Increasing the cantilever length led to a reduction in stress values in distally tilted posterior implants. Moreover, increasing the distal inclination led to a reduction in stress values in both the distally tilted posterior implants and cortical bone tissue in the model with a short cantilever. The monolithic zirconia full-arch porcelain superstructure was not affected by implant angulation, but was affected by cantilever length, with lower stress values observed with a longer cantilever.

Dental, skeletal and soft tissue effects of the Distal Jet appliance: A prospective clinical study.

ABSTRACTObjective: This study evaluated the dental, skeletal and soft tissue effects in Class II malocclusion patients treated with Distal Jet appliance, compared to an untreated control group. Methods: 44 patients with Class II malocclusion were divided into two groups: Group 1 (experimental) - 22 patients, mean age of 12.7 years, treated with the Distal Jet appliance for a mean period of 1.2 years; Group 2 (control) - 22 untreated patients, mean age of 12.2 years, followed by a mean period of 1.2 years. Lateral cephalograms were obtained before treatment (T0) and at the end of the distalization (T1).Independent t test was used to identify intergroup differences. Results: When compared to control group, the Distal Jet produced a significant increase in mandibular plane angle (0.7 ± 2.0o). The maxillary second molars presented distal inclination (6.6 ± 3.8o), distalization (1.1 ± 1.1 mm) and extrusion (1.3 ± 2.1 mm). The maxillary first molars distalized by 1.2 ± 1.4 mm. The maxillary first premolars mesialized by 3.4 ± 1.1 mm. The maxillary incisors showed slight labial tipping of 4.3 ± 4.7o and were protruded by 2.4 ± 1.7 mm. There were no significant changes in the facial profile. The overjet increased 1.5 ± 1.1 mm and overbite had no significant changes. Conclusion: The Distal Jet appliance is effective to distalize the maxillary first molars, but promotes increase in mandibular plane angle, distal inclination, extrusion and distalization of maxillary second molars, mesialization of maxillary first premolars, proclination and protrusion of maxillary incisors, and increase in overjet, when compared to a control group.

Dimensional changes in the palate associated with slow maxillary expansion for early treatment of posterior crossbite.

To compare palatal symmetry, dimensions, and molar angulations following early mixed-dentition slow maxillary expansion with parameters in normal controls. A total of 30 patients treated with a Haas-type expander for unilateral posterior crossbite with functional shift were compared with 30 controls matched for dental age, gender, and molar relationship. Records were taken before (T1) and after expansion (T2). Palatal width, surface area, volume, and molar angulations were measured on digitized models. Surface area and volume were split in half then divided into anterior, middle, and posterior segments to measure symmetry. Student's t-test was used to assess group differences. Mean intercanine width increased 4.65 mm, and intermolar width increased 4.76 mm. The treated mean surface area increased 127.05 mm2 compared with 10.35 mm2 in controls. The treated palatal volume increased 927.55 mm3 compared with 159.89 mm3 for controls. At T1, the controls showed significant differences in surface area and volume between the anterior palatal segments. At T2, this difference occurred in surface area of middle palatal segments of the treated sample. First permanent molars showed an increased buccal and distal inclination after treatment, opposite to controls. The increase in buccal inclination was greater on the crossbite side. The Haas-type expander results in similar expansion across the canines and first molars. A palate that is symmetrical before expansion may become asymmetric after expansion but only in the middle segment. Changes in individual molar angulation following palatal expansion can be measured without radiation imaging.

Continuous arch and rectangular loops for the correction of consistent and inconsistent load systems in extruded and tipped maxillary second molars

The aim of this research was to compare the load systems produced by rectangular loops and continuous arches for the correction of extruded secondmolars with a mesial inclination (inconsistent system) and a distal inclination (consistent system). The maxillary first molar of an acrylic model of a patient, with passive brackets and tubes bonded, was connected to a 3-dimensional load cell of an orthodontic force tester, and the secondmolar was replaced by its respective tube bonded to a second load cell. The second molar tube was moved 2.5mm occlusally and tipped 20° mesially and distally, creating an inconsistent force system and a consistent force system. For each situation, ten 0.017×0.025-in beta-titanium, 8×10-mm rectangular loops were compared with 10 0.014-in nickel-titanium continuous arches. The vertical forces-F(z)-and tipping moments-M(x)-were compared using 4t tests, at 5%. In the inconsistent group, the rectangular loop produced a larger M(x) in both molars: 2.11N.mm in the secondmolar compared with the -0.15N.mm of the continuous arches. On the first molar, the rectangular loops produced -5.58N.mm against -2.08N.mm produced by the continuous arches. The F(z) values produced at the secondmolar with each system were similar, whereas on the first molar they were different; the rectangular loops produced 0.41N, and continuous arches produced 0.53N. In the consistent group, the rectangular loops produced smaller M(x) values at the secondmolar (-3.06N.mm) than did the continuous arch (-4.25N.mm)(P=0.01), as well as a smaller F(z) value (-0.52 vs -0.92N, respectively). At the first molar, the rectangular loops produced smaller M(x) values (-2.32N.mm) than did the continuous arch (-4.18N.mm), as well as a smaller F(z) value (0.59 vs 1.10N). In the inconsistent group, only the rectangular loop produced a system of force that could correct the secondmolar. In the consistent system, both group mechanics produced a system of force compatible with the correction of the secondmolar, but the continuous wire produced larger moments. Both groups showed a tendency for mesial crown tipping of the first molar.

Effect of Distal Implant Inclination on Dislodging Forces of Different Locator Attachments Used for Mandibular Overdentures: An In Vitro Study.

To evaluate the effect of distal implant inclination on axial and nonaxial retentive forces of different Locator attachments used to retain mandibular overdentures. Four duplicate mandibular edentulous acrylic models received 2 implants in the canine areas with 0°, 5°, 10°, and 20° distal inclinations. Experimental overdentures were connected to the implants with Locator extra light retention (Le), Locator light retention (Ll), and Locator medium retention (Lm). For the 20° model, extended range Locator extra-light retention (Lee) and Locator medium retention (Lem) were used. Axial and nonaxial (anterior, posterior, lateral) retentive forces were measured initially and after 540 cycles of denture insertion and removal. Three-way mixed ANOVA was used to analyze axial and nonaxial retentive forces RESULTS: After wear simulation, 20° angulation showed the highest axial retention for Le and Ll while 5° showed the highest retention for Lm; 0° and 5° showed the highest anterior and posterior retention for Lm; 20° showed the highest lateral retention for Le and Ll. For all implant inclinations, Lm showed the highest axial and nonaxial retention, and Le and Lee showed the lowest retention for 10° and 20° inclined implants, respectively. Axial and nonaxial retention of Locator attachments for implant-retained overdentures are significantly affected by the degree of distal implant inclination and the type of nylon inserts. Lm is recommended to retain overdentures when implants have 5° or 10° distal inclination, and Le and Ll are recommended with 20° inclination to maintain high axial and nonaxial retention after wear.

The tooth, the whole tooth and nothing but the tooth: tooth shape and ontogenetic shift dynamics in the white shark Carcharodon carcharias.

Results from this study of the white shark Carcharodon carcharias include measurements obtained using a novel photographic method that reveal significant differences between the sexes in the relationship between tooth cuspidity and shark total length, and a novel ontogenetic change in male tooth shape. Males exhibit broader upper first teeth and increased distal inclination of upper third teeth with increasing length, while females do not present a consistent morphological change. Substantial individual variation, with implications for pace of life syndrome, was present in males and tooth polymorphism was suggested in females. Sexual differences and individual variation may play major roles in ontogenetic changes in tooth morphology in C. carcharias, with potential implications for their foraging biology. Such individual and sexual differences should be included in studies of ontogenetic shift dynamics in other species and systems.