Maxillary Occlusal Research Articles

Maintenance of Segmental Maxillary Expansion: The Use of Custom, Virtually Designed, and Manufactured Palatal Appliances Without the Use of an Occlusal Splint

Expansion of the maxilla using a segmental Le Fort I osteotomy is a routine and commonly used procedure in the treatment of dentofacial deformities. Although orthognathic surgery has seen tremendous advancement in technology, including virtual surgical planning and customized hardware, some room for advancement exists in the maintenance of surgical maxillary expansion. Traditionally, this has been accomplished with retention of a maxillary occlusal splint 4 to 8weeks postoperatively. This article introduces some novel techniques to help maintain this expansion, including the intraoperative transpalatal archwire and custom palatal strap appliance in conjunction with autogenous bone harvest and grafting in lieu of using occlusal-based splints. The aim of these techniques is to improve postoperative patient comfort and surgical outcomes and shorten postoperative orthodontic treatment time.

Traumatic intraoral herniation of the buccal pad of fat in pediatric patients: Report of two cases

Intraoral herniation of the buccal pad of fat is commonly occurring in the pediatric group of population. It frequently presents as an expanding pedunculated nontender, soft, nonpulsatile yellowish mass in the buccal mucosa at the level of the maxillary occlusal plane. The most common cause is traumatic injury. This article presents two such cases where extrusion of the pad of fat successfully managed by surgical excision.

Orthognathic surgery in “older” adults with Hemi-Mandibular Elongation: Long-term occlusion outcomes

PurposeThe purpose of this study was to describe a consecutive series of subjects with HME who underwent orthognathic correction after 26 years of age. The investigators hypothesized that for this group of HME subjects, bimaxillary orthognathic correction would result in a favorable initial and long-term occlusion. Materials and methodsA retrospective cohort study was implemented. The sample included a consecutive series of HME subjects >26 years of age undergoing bimaxillary osteotomies. The outcome variables were the achievement and maintenance of a corrected occlusion after surgery. We compared the occlusion at intervals before surgery (T1), 5 weeks postoperatively (T2), >2 years after surgery (T3). Descriptive and bivariate statistics were calculated. P < 0.05 was considered significant. Results13 subjects met inclusion criteria with a mean age of 36 years. All subjects underwent maxillary advancement. All subjects underwent mandibular surgery with 92% receiving advancement. Sixty-nine percent of subjects had a maxillary occlusal cant. In 12 of 13 subjects, a favorable occlusion was maintained long-term (T3) after surgery. ConclusionWe confirmed that bimaxillary orthognathic surgery in HME subjects >26 years of age results in a favorable initial occlusion which is maintained long-term. These findings are similar to that previously reported in HME subjects <26 years of age.

The Effect of Flat Dual-Cure Stabilizer Occlusal Splint in Pain Relief of Individuals Suffering from Migraine Headaches

Background:No study on the effect of dual-cure stabilizer splint without canine ramp in migraine patients is present.Objective:This study was conducted to determine the effects of maxillary flat dual-cure stabilizer occlusal splint on severity, frequency and episodes of headaches in individuals suffering from a migraine.Methods:In this interventional clinical trial, 30 eligible patients were divided into 2 groups (case and control); each group consisted of 8 men and 7 women. Dual-cure stabilizer splint was made for patients in the case group and they used the adjusted splint 20 hours a day for 6 weeks. The severity, frequency and episodes of migraine attacks before and after using the splint were determined. For grading pain, severity visual analogue scale was used. The data were analyzed using SPSS 20 and Kolmogorov-Smirnov test and paired t-test.Results:The severity, frequency, and episodes of migraine attacks before and after using the splint were reduced by 56%, 68%, and 72%, respectively. The reduction was statistically significant (p < 0.05).Discussion:Despite the effect of occlusal devices on the migraine disorder is controversial, the most researchers agree that using these appliances can be effective in reducing headache in migraine patients.Conclusion:Given the favorable effects of dual-cure stabilizer splint on reducing the severity, frequency and episodes of migraine headaches, the device can be used as an effective alternative therapy besides common pain-relieving methods.

Orthodontic treatment in conjunction with distraction osteogenesis and orthognathic surgery for severe facial asymmetry

Abstract The present case report describes the combination of orthodontic treatment and two-stage surgery used to treat a 16-year-old female with a severe maxillary occlusal cant and a mandibular deviation. The patient was diagnosed with right temporomandibular joint ankylosis six months after suffering a facial injury at five years of age. A unilateral condylectomy was performed 12 months later. A hybrid functional appliance was used between nine and 16 years of age to prevent deterioration of the maxillary occlusal cant. At 16 years and six months, it was determined that the patient required a combination of surgical and orthodontic treatment, the pre-surgical orthodontic phase of which was completed at 19 years. The surgery was performed in two stages, which involved a Le-Fort 1 procedure to intrude the maxilla in the left molar region and to extrude in the right molar region. Distraction osteogenesis was performed to achieve a lengthening of the right mandibular ramus. The second operation was a unilateral sagittal split ramus osteotomy to achieve a forward and upward rotation of the left hemimandible. As a result, the patient’s facial asymmetry and occlusion significantly improved. The improvements were well maintained and the patient remained stable after one year of retention.

Multidisciplinary treatment of a severe facial asymmetry

Abstract This case report presents the multidisciplinary treatment of an adult female who presented with a previously repaired right unilateral cleft lip and palate. The patient had been referred with a complaint of facial asymmetry, eating difficulties and a missing right central incisor. A clinical evaluation revealed severe facial asymmetry created by a mandibular deviation to the right side and a compensatory transverse cant of the maxillary occlusal plane. After pre-surgical orthodontic treatment, a Le Fort I osteotomy and a bilateral sagittal split osteotomy were performed. During post-surgical orthodontic treatment and, as a result of the rotational surgery, the maxillary left central incisor became the right central incisor. The left lateral incisor was subsequently moved toward the midline and reshaped with a composite buildup to serve as a new left central incisor. The combination of orthodontic, orthognathic and restorative treatment established a favourable occlusal and aesthetic result.

Management of a Dentigerous Cyst Associated with Mesiodens: A Case Report

1. Introduction Supernumerary tooth is defined as a developmental anomaly characterized by the presence of an extra tooth in addition to the normal dentition [1] . It can affect both maxilla and mandible; however, its occurrence in the mandible is rare [2] . While supernumerary tooth may be found in any region of the dental arch, the most common site is the palatal midline between the two maxillary central incisors, where it is termed as mesiodens [3] . Mesiodens is the most common type of supernumerary tooth which may appear as single, multiple, unilateral or bilateral. It accounts for 80% of all supernumerary teeth [3] .A mesiodens may erupt normally, stay impacted, appear inverted or take a horizontal position [3] .Unerupted mesiodens can be diagnosed by both clinical and radiographic evaluation, which can be done bypanoramic, maxillary occlusal and periapical radiographs are recommended [1] . Supernumerary tooth if left undiagnosed leads to many complications; most common one is dentigerous cyst and radicular resorption. Dentigerous cyst typically originates due to fluid accumulation between reduced enamel epithelium and the developing crown of the tooth, causing expansion of the tooth follicle & is typically attached to the cervical area of the tooth [4] . This case report presents a mesiodens associated with dentigerous cyst.

Comparison of maxillary first molar occlusal outlines of Neandertals from the Meuse River Basin of Belgium using elliptical Fourier analysis

Several Neandertals derive from the karstic caves of the Meuse river tributaries of Belgium, including Engis 2, Scladina 4A-4 and Spy 1. These may form a group that is distinct in maxillary first molar occlusal outlines compared to La Quina 5 from Southwest France. Alternatively, chronological differences may separate individuals given that Scladina 4A-4 from MIS 5 is older than the others from MIS 3. Neolithic samples (n = 42) from Belgium (Maurenne Caverne de la Cave, Hastière Caverne M, Hastière Trou Garçon, Sclaigneaux and Bois Madame) dated to 4.6–3.9 kyr provide a context for the Neandertals. Dental casts were prepared from dental impressions of the original maxillary molars. Crown and occlusal areas as well as mesiodistal lengths were measured by calibrated Motic 3.0 microscope cameras. Occlusal outlines of the casts were captured through photostereomicroscopy and non-landmark smooth tracing methods. Occlusal outlines were processed using elliptical Fourier analysis within SHAPE v1.3 which reduced amplitudes of the harmonics into principal components (PC) axes. The first two PC axes group the Neandertals, although Scladina 4A-4 falls nearly outside the convex hull for the Neolithic sample. Neandertals are imperfectly separated from the Neolithic sample on PC3 and PC4, and completely distinct on PC5 and PC6. Scladina 4A-4 differs from the other Neandertals on most PC axes. Chronology may best explain the separation of Scladina 4A-4 from the more recent fossils, and particularly Spy 1 and La Quina 5 which are the most similar in maxillary first molar occlusal outline shape.

The pterygomaxillary junction: An imaging study for surgical information of LeFort I osteotomy

Maxillary osteotomy is a common surgical procedure and often involves separation of the pterygomaxillary junction (PMJ), which is a “blinded” procedure with inherent risks. Knowledge of the PMJ structure is essential. It remains unclear whether patients with different facial types have different PMJ structures, or different surgical outcome. This study evaluated the computed tomographic images of 283 consecutive patients who received orthognathic surgery. Patients were classified into Angle class I, II, III and cleft lip/palate groups. The results showed that the PMJ was 5.1 ± 1.4 mm in thickness, 9.7 ± 1.7 mm in width, and 102.0 ± 4.0 degrees relative to the sagittal plane in the level of posterior nasal spine. There were no statistically significant differences in these measurements among the groups. The class III group demonstrated significantly smaller angle relative to the maxillary occlusal plane. The cleft group showed significantly longer vertical distance between the posterior nasal spine and the lower border of PMJ, shorter distance between the second molar and PMJ, and longer distance between the descending palatine artery and PMJ. With regard to postoperative outcome, the cleft group showed higher incidence of pterygoid plate fracture. The results in this study provide additional surgical anatomic information.

An in vitro evaluation of the maxillary occlusal plane orientation obtained with an electronic application: A preliminary investigation

Statement of problemIn the evaluation and fabrication of dental prostheses, maxillary occlusal plane orientation in the sagittal and coronal planes may affect functional and esthetic outcomes. The accuracy of a recently developed electronic application in transferring this orientation to a semiadjustable articulator has not been evaluated. PurposeThe purpose of this in vitro study was to evaluate the coronal and sagittal orientation of the occlusal plane on maxillary casts mounted with an electronic application facebow system onto a corresponding semiadjustable arcon articulator. Material and methodsA maxillary typodont was placed into a phantom head (control) oriented with the Frankfort horizontal plane parallel to the horizon. A digital protractor was used to measure the angle between the occlusal plane of the maxillary arch of the phantom head and the Frankfort horizontal plane along the sagittal and coronal planes. The commercial system (test group) was used to make 15 facebow records of the maxillary typodont within the phantom head. The system records were used to mount diagnostic casts of the maxillary typodont onto a semiadjustable arcon articulator. The same measurements were made on the mounted diagnostic casts and were compared with the control. Statistical differences between the occlusal plane of the control and the occlusal plane of the mounted maxillary casts were determined using the 1-sample t test (α=.05). ResultsThe coronal orientation of the occlusal plane was significantly different (P<.001) between test group and control. No significant differences (P>.05) were found in the sagittal orientation of the occlusal plane. ConclusionsWithin the limitations of this study, variations in the coronal plane orientation were observed with the system. Variations in this plane may lead to adverse evaluation and clinical outcomes.

Comparison of craniodentofacial morphology of children with and without unilateral cleft lip and palate

Background: This retrospective case-control study was done to investigate the cranio-dento-facial morphology of Turkish children with unilateral complete cleft lip and palate from Ege University and compare them with a normal group to highlight the effect of surgical correction on craniofacial development. Methods: 60 patients with unilateral complete cleft lip and palate were compared with 55 control children without cleft at mean ages of 13 and 15 years. The cleft lip was operated with modified Millard technique at 3 months, cleft palate was operated with von Langenbeck technique at 12 months. The patients were not given any orthopaedic or orthodontic treatment also. Angular and linear measurements of cranio-dento-facial complex were measured by using Dolphin Imaging 11.5 software programme, and the resulting data were evaluated statistically. Results: The children with unilateral complete cleft lip and palate had considerable morphological deviations when compared with the matched children without clefts. The most striking findings in the unilateral complete cleft lip and palate group: Maxillary and mandibular complex and nasal projections were retruded when compared with normal (P<0.001). Also, nasal airway dimensions were higher in control group (P<0.001). Soft tissue structure, especially upper lip thickness, upper and lower lip lengths were decreased (P<0.001, P<0.001, P<0.05, respectively) in cleft group. Maxillar anterior height was decreased (P<0.001). Besides, nasolabial angle and upper incisor inclination according to the maxillary occlusal plane (P<0.001) were increased while overjet (Mx1-Md1) were decreased (P<0.001). Conclusion: The surgical technique and the number of operations seem to be the most effective factors for maxillary retrusion in patients with unilateral complete cleft lip and palate.

Finite element analysis of different load mode on tooth movement for space closure in patient with bimaxillary protrusion

To investigate the stress distribution on the maxillary anterior teeth retracted with sliding mechanics and micro-implant anchorage using different retraction hook heights and positions. DICOM image data including maxilla and upper teeth were obtained with cone-beam CT. The three-dimensional finite element model was constructed using Mimics software. Brackets and archwire model were constructed using Creo software. The models were instantiated using Pro/Engineer software. Abaqus software was used to simulate the sliding mechanics by loading 2 N force on 0, 2, 4, 6, 8, 10 mm retraction hooks and three different positions, repectively. Rotation of the occlusal plane, the initial displacement and stress distribution of teeth were analyzed. Lingual rotation of maxillary central incisor(0.021°), gingival movement of the maxillary first molar(0.005 mm), and clockwise rotation of the maxillary occlusal plane(0.012°) were observed when the force application point located at the archwire level (0 mm). In contrast, 0.235° labial rotation of the maxillary central incisor, 0.015 mm occlusal movement of the maxillary first molar, and 0.075° anti-clockwise rotation of the maxillary occlusal plane were observed when the force application point located at the higher level(10 mm retraction hook). The more the force application point was located posteriorly at the archwire level, the less lingual rotation of the maxillary central incisor and the more buccal displacement of maxillary first molar was observed. Maxillary anterior tooth rotation and retraction, vertical displacement of posterior segment, and rotation of the occlusal plane could be controlled by adjusting the height and position of the retraction hook in space closure using miniscrew and sliding mechanics.

Anatomy and osteohistology of the basal hadrosaurid dinosaur Eotrachodon from the uppermost Santonian (Cretaceous) of southern Appalachia.

The cranial and postcranial anatomy of the basal hadrosaurid dinosaur Eotrachodon orientalis, from the uppermost Santonian of southern Appalachia (southeastern U.S.A.), is described in detail. This animal is the only known pre-Campanian non-lambeosaurine hadrosaurid, and the most complete hadrosauroid known from Appalachia. E. orientalis possesses a mosaic of plesiomorphic and derived characters in the context of Hadrosauroidea. Characters shared with basal hadrosauroids include a short and sloping maxillary ectopterygoid shelf, caudally prominent maxillary jugal process, one functional tooth per alveolus on the maxillary occlusal plane, a jugal rostral process with a shallow caudodorsal margin and medioventrally facing articular facet, a vertical dentary coronoid process with a poorly expanded apex, and tooth crowns with accessory ridges. Derived characters shared with other hadrosaurids include a circumnarial depression compartmented into three fossae (as in brachylophosaurins and Edmontosaurus), a thin everted premaxillary oral margin (as in Gryposaurus, Prosaurolophus, and Saurolophus), and a maxilla with a deep and rostrocaudally extensive rostrodorsal region with a steeply sloping premaxillary margin (as in Gryposaurus). Eotrachodon orientalis differs primarily from the other hadrosauroid from the Mooreville Chalk of Alabama, Lophorhothon atopus, in having a slender and crestless nasal whose caudodorsal margin is not invaded by the circumnarial depression. Hadrosaurus foulkii, the only other known hadrosaurid from Appalachia, is distinct from E. orientalis in having dentary teeth lacking accessory ridges and a dorsally curved shaft of the ischium. A histological section of the tibia of the E. orientalis holotype (MSC 7949) suggests that this individual was actively growing at the time of death and, thus, had the potential to become a larger animal later in development.

Stresses in the midpalatal suture in the maxillary protraction therapy: a 3D finite element analysis.

BackgroundThe aim of the present work was to evaluate the stress magnitudes and directions along the midpalatal suture in the maxillary protraction therapy.MethodsThe geometry of the maxilla and teeth were digitally reconstructed based on computer tomography images obtained from the skull of a girl in a mixed dentition stage with skeletal and dental class III malocclusion. An appliance commonly used for rapid palatal expansion (RPE) was also digitally modeled for anchorage of the protraction force and meshed for finite element analysis. The maxillary protraction was simulated applying 600 cN (300 cN for each side) directed 30° forward and downward to the maxillary occlusal plane.ResultsThe principal stresses, through the force application, exhibited similar distribution patterns. A higher stress area was observed in the region of the midpalatal suture located in front of the incisive canal. All the sections showed vectors of compressive nature.ConclusionsBecause of the compressive nature of the stresses distributed along the midpalatal suture in the maxillary protraction therapy simulation, which is opposite to the natural growth transversal tendency, maxillary expansion is advisable in clinical cases.

A Multicenter Study Using the SWAG Scale to Compare Secondary Alveolar Bone Graft Outcomes for Patients With Cleft Lip and Palate.

Objective To assess secondary alveolar bone graft (ABG) outcomes using the standardized way to assess grafts, or SWAG scale, for patients with cleft lip and palate (CLP). Design Retrospective cohort study. Setting Four cleft centers with different protocols. Methods One hundred sixty maxillary occlusal radiographs taken 3 to 18 months after secondary ABG for sequentially treated patients with CLP were assessed using the SWAG scale. Radiographs were scanned, standardized, blinded, and rated by six orthodontists using the SWAG scale. Randomized radiographs were rated twice, 24 hours apart, by the same raters. Main Outcomes Intrarater and interrater reliabilities were assessed. Means and SDs were calculated for ABG ratings using analysis of variance and Tukey tests (P < .05). Result The mean ABG age was 9.1 years (range = 7 to 10.1 years) and the mean follow-up age was 12.4 years (range = 8.2 to 20.4 years). Intrarater and interrater reliabilities were good (intrarater = 0.788, interrater = 0.705), and higher than published methods. Mean ABG ratings for the cleft centers were 4.53, 2.9, 3.63, and 5.0 and differed significantly. The two centers with the highest ABG ratings showed higher ratings for all thirds decreasing from apical to coronal. The two centers with lower ABG ratings showed poorer ABG ratings for all thirds, and the middle third received the highest ratings. Conclusions The SWAG scale overcomes the challenges of age and bone location. The SWAG method was validated for showing intercenter differences for overall bone fill as well as in vertical thirds. Surgical technique, timing, and expertise/volume were identified as possible factors related to outcome.

Impacted Central Incisor with Dilacerated Root-Treat with Ease.

A 12-year-old female patient reported to the Department of Orthodontics of Maulana Azad Institute of Dental Sciences, New Delhi with chief complaint of missing upper front tooth. On clinical examination it was found that maxillary left central incisor (21) was missing [Table/Fig-1]. No significant history of trauma or premature/delayed shedding of primary left central incisor was reported. Panoramic and maxillary occlusal view revealed impacted left central incisor with dilacerated root [Table/Fig-2,3]. Since the contralateral central incisor had erupted fully in the mouth and the root formation of the impacted central incisor was almost complete, it was decided to disimpact the tooth (21). Disimpaction was planned by surgical exposure followed by elastic traction with the help of removable appliance. Since the patient had well aligned upper and lower arches in good occlusion, it was decided to use a modified removable appliance for extrusion of 21. A removable appliance with modified labial bow was fabricated. Labial bow in the anterior region was fabricated with 22 gauge wire and helices were incorporated in the labial bow adjacent to left central incisor region. Retention was provided by the acrylic coverage in the palatal region and by well formed retentive clasps. Surgical exposure of left central incisor was performed by open exposure technique. A bondable button was placed onto the labial surface of exposed left central incisor crown [Table/Fig-4]. Patient was trained to use elastic in triangular fashion to engage button on 21, and two helices of the labial bow, which resulted in an extrusive force of 20 grams for disimpaction of 21[Table/Fig-5] [1]. Patient was advised to change the elastic daily and was reviewed every three weeks. At the end of six months, complete disimpaction of 21 was achieved with the tooth in its optimal alignment into the upper dental arch and in good relation with lower teeth [Table/Fig-6,7]. Post disimpaction panoramic view reveals tooth 21 in the optimal position with respect to maxillary occlusal plane [Table/Fig-8]. [Table/Fig-1]: Pretreatment intraoral maxillary occlusal photograph showing missing maxillary left central incisor. [Table/Fig-2,3]: Pretreatment panoramic and maxillary occlusal view showing vertically impacted maxillary left central Incisor with dilacerated root. [Table/Fig-4]: Intraoral frontal photograph after surgical exposure and with bonded attachment on labial surface of 21. [Table/Fig-5]: Intraoral frontal photograph showing mechanics for extrusion of 21 with elastic traction force. [Table/Fig-6,7]: Post treatment intraoral frontal and maxillary occlusal photographs showing 21 in alignment and good occlusion. [Table/Fig-8]: Post treatment panoramic view. In young patients, absence of maxillary anterior teeth has a major impact on esthetics, phonetics, mastication and psychosocial well being. Impaction of maxillary permanent central incisor due to dilaceration in the root is a rare condition which is associated with trauma to primary anterior tooth early in life leading to dilaceration of permanent succedaneous tooth [2]. Depending on the severity of dilacerations, decision is usually taken to either expose and align the maxillary central incisor or extract and replace it with prosthesis. Although prognosis of disimpaction of dilacerated central incisor is questionable but orthodontic alignment was preferred in this case due to two reasons. Following extraction of a tooth, the alveolar ridge becomes deficient both vertically and labiolingually which makes it unsuitable for prosthetic implant. Also, the region becomes unaesthetic for conventional prosthetic bridge placement. Any fixed prosthesis for replacement of missing central incisor cannot be given before 18 year of age to allow for completion of alveolar bone growth in growing children [3]. The removable appliance treatment chosen for this patient was a convenient treatment option with less chair side involvement with the patient. Moreover it reduces the overall treatment time required for fully bonded fixed appliance therapy since traction could be applied to the impacted tooth immediately after removable appliance insertion. Also, one of the major advantages of using this simple appliance is that it overcomes the detrimental effects encountered with fixed appliances such as demineralization and difficulty in maintenance of oral hygiene [4]. Orthodontic extrusion of an impacted tooth is usually carried out by a trained specialist by using fixed mechanics. A modified removable appliance with bonded attachment and elastic traction has been used to successfully disimpact and align maxillary central incisor in this case. Such an appliance can be fabricated and used by even a general practitioner with basic knowledge about optimal force delivery.

Evaluation of accuracy of transfer of the maxillary occlusal cant of two articulators using two facebow/semi-adjustable articulator systems: An in vivo study.

Aim:The aim of this study was to compare the accuracy of the angle made by Frankfort horizontal plane-occlusal plane on maxillary casts, mounted using the respective facebows on Artex Amann Girrbach and Hanau Wide-vue semi-adjustable articulators with cephalometrically derived Frankfort horizontal plane-occlusal plane angle as a control.Subjects and Methods:Maxillary casts of 30 subjects were mounted on Hanau Wide-vue and Artex Amann Girrbach semi-adjustable articulators following facebow transfer using respective facebows. The Frankfort horizontal plane-occlusal plane angles of these casts were measured using Wixey's digital angle gauge. They were also subjected to a lateral cephalogram, and the occlusal cant was measured using RadiAnt DICOM software.Statistical Analysis:Using Pearson correlation, the accuracy of the angle made by upper member of the articulator and occlusal plane of mounted maxillary casts in each of the articulator was compared to the Frankfort horizontal plane-occlusal plane angle in lateral cephalogram.Results:A mean difference of 1.9° was found between Hanau Wide-vue articulator and lateral cephalogram and a mean difference of 3.6° was found between Artex Amann Girrbach articulator and lateral cephalogram. Statistically, Pearson correlation value (r) obtained between Hanau Wide-vue and lateral cephalogram was 0.46 and between Artex Amann Girrbach and lateral cephalogram was 0.25.Conclusion:From the statistical value (r) derived, it can be inferred that the Frankfort horizontal plane-occlusal plane angle of the casts articulated on Hanau Wide-vue articulator was more accurate in comparison to that on Artex Amann Girrbach articulator.

Evaluation of radiographic techniques for localization of impacted maxillary canines

Maxillary canines are the most frequently impacted teeth after the third molars. The study was performed on 50 impacted maxillary canines. The selected patients were examined systematically and radiological examinations were carried out, which included two periapical, a cross-sectional maxillary occlusal radiograph, and a panoramic radiograph for each impacted canine. The two periapical radiographs were taken using the tube shift technique with a horizontal tube shift. Correct prediction of the labiolingual position of canine impaction is possible by using the same-side-lingual opposite-side-buccal (SLOB) technique. Therefore the results of this technique were used as gold standard in our study. Out of 50 impacted canines, 17 (34 %) were located bucally, 32 (64 %) palatally, and 1 (2 %) in the arch. In all, 40.7 % and 26.1 % of the impacted maxillary canines were located buccally in males and females, respectively. When compared with the results of the SLOB technique, intraoral periapical (IOPA) and occlusal (vertical and horizontal angulation) radiographs, IOPA radiographs and orthopantomograms (OPGs), and occlusal radiographs and OPGs showed statistically significant results. Although OPG also showed statistically significant results, it was a less reliable method. OPG used with occlusal radiographs yielded the most reliable results. Conventional radiography has remained the technique of choice for localization of impacted canines owing to its wide availability, low cost, and less radiation exposure when compared with other advanced modalities such as computed tomography and cone beam computed tomography.

Positional symmetry of porion and external auditory meatus in facial asymmetry.

BackgroundThe porion (Po) is used to construct the Frankfort horizontal (FH) plane for cephalometrics, and the external auditory meatus (EAM) is to transfer and mount the dental model with facebow. The classical assumption is that EAM represents Po by the parallel positioning. However, we are sometimes questioning about the possible positional disparity between Po and EAM, when the occlusal cant or facial midline is different from our clinical understandings. The purpose of this study was to evaluate the positional parallelism of Po and EAM in facial asymmetries, and also to investigate their relationship with the maxillary occlusal cant.MethodsThe 67 subjects were classified into three groups. Group I had normal subjects with facial symmetry (1.05 ± 0.52 mm of average chin deviation) with minimal occlusal cant (<1.5 mm). Asymmetry group II-A had no maxillary occlusal cant (average 0.60 ± 0.36), while asymmetry group II-B had occlusal cant (average 3.72 ± 1.47). The distances of bilateral Po, EAM, and mesiobuccal cusp tips of the maxillary first molars (Mx) from the horizontal orbital plane (Orb) and the coronal plane were measured on the three-dimensional computed tomographic images. Their right and left side distance discrepancies were calculated and statistically compared.ResultsEAM was located 10.3 mm below and 2.3 mm anterior to Po in group I. The vertical distances from Po to EAM of both sides were significantly different in group II-B (p = 0.001), while other groups were not. Interside discrepancy of the vertical distances from EAM to Mx in group II-B also showed the significant differences, as compared with those from Po to Mx and from Orb to Mx.ConclusionsThe subjects with facial asymmetry and prominent maxillary occlusal cant tend to have the symmetric position of Po but asymmetric EAM. Some caution or other measures will be helpful for them to be used during the clinical procedures.

A finite element analysis of the maxillary first molar PDL with maxillary protraction in a mixed dentition Class III malocclusion.

To analyze the stress distribution on the PDL of the maxillary first molar in a mixed dentition Class III malocclusion, using a Hyrax-type appliance and maxillary protraction. A Class III malocclusion in the mixed dentition was reconstructed based on CBCT images. The 3D FEM comprised the maxilla, alveolar bone, right first permanent molar teeth, and PDL and consisted of 1133497 nodes and 573726 elements. Maxillary protraction force was applied to a hook positioned close to the deciduous canines with 600g and at 15°, 30°, and 45° downward angles to the maxillary occlusal plane. Analysis was carried out from the top and buccal view of the sagittal plane. The magnitude of the stresses at 15°, 30°, and 45° of protraction angulation resulted in the highest stress magnitude being in the region between the distobuccal and palatal roots, as well as on the distal surface of the mesial root. The vector direction in this area showed traction and mesial movement. With 30° and 45° protraction angulations, the stress was located only between the distobuccal and palatal roots, and the vector direction was more extrusive at 15°. The suggested orthodontic movement is in the mesial direction with a small amount of extrusion with 15° angulation and greater extrusion with 30° and 45°.