Midline Discrepancy Research Articles

Palatal discrepancies and postdams

To investigate the variation in post-cure palatal discrepancy of dentures, 20 complete maxillary replica dentures were prepared on models with high and low palates and processed by conventional compression moulding and injection moulding. Measurements were made by travelling microscope of the sagittal midline discrepancies between palate and model on three occasions; after processing; after removal of part of the investing plaster; and after immersion in water for 1 month at 37 degrees C. The magnitudes of discrepancies were greatest distally, diminishing with distance anteriorly from the postdam. They increased with partial removal of plaster, and decreased slightly after immersion.

Deep Bite Case with Midline Discrepancy

Deep Bite Case with Midline Discrepancy

Quantification of the relative risk of multiple occlusal variables for muscle disorders of the stomatognathic system

Statement of problem There is no consensus on the association between occlusion and temporomandibular disorders (TMD). Purpose The purpose of this study was to quantify the relative risk of multiple occlusal variables for muscle disorders of the stomatognathic system. Material and methods Eight occlusal features: retruded contact position (RCP) to maximum intercuspation (MI) slide length, vertical overlap, horizontal overlap, unilateral posterior reverse articulation, anterior open occlusal relationship, incisor dental midline discrepancy, mediotrusive interferences, and laterotrusive interferences, were clinically assessed by the same trained operator. The sample consisted of 81 women with a Research Diagnostic Criteria for Temporomandibular Disorders (RDC/TMD) axis I diagnosis of muscle disorder, for example myofascial pain, with or without limited opening, and 48 healthy women (control group). A stepwise multiple logistic regression was used to identify the significant associations between occlusal features and disease. Results A slide from the retruded contact position to maximum intercuspation ≥2 mm and mediotrusive interferences were the only 2 occlusal features significantly associated with the presence of myofascial pain according to the RDC/TMD criterion symptoms. The odds ratio for myofascial pain was 2.57 for a slide from RCP to MI ≥2 mm and 2.45 for mediotrusive interferences. The percentage of the total log likelihood for myofascial pain explained by the significant occlusal factors amounted to 10.8% (Nagelkerke's R 2 = 0.108). The multifactorial model, including the 2 significant occlusal factors, showed an acuracy to predict disease of 66.7% (sensitivity 71.6%; specificity 58.3%). Conclusion Occlusal features showed a low predictive value to detect muscle disorders of the stomatognathic system. Multifactorial complex pathologies, such as TMD, should be studied using multivariate statistical analyses, as univariate models may overestimate some resulting associations.

Orthodontic findings in the deciduous and early mixed dentition--inferences for a preventive strategy.

The aim of the present epidemiologic study was to obtain representative basic data on the frequency, extent and age-dependence of malocclusions in the deciduous and early mixed dentition. The developmental tendencies of specific malocclusions were investigated from the aspect of orthodontic prevention. The collective comprised 8,864 preschool and school-aged children, of whom 1,225 were in the deciduous dentition (mean age 4.5 years) and 7,639 in the mixed dentition (mean age 8.9 years). The orthodontic data were clinically assessed as sagittal, transversal, or vertical single-arch and occlusal findings. In addition, the malocclusions were classified according to their primary symptoms. Early infantile habits, tongue dysfunctions, speech defects and incompetent lip closure were registered separately. 57% of the children were found to have malocclusions, with the frequency rising statistically significantly in dependence on age from the deciduous to the mixed dentition (p < or = 0.001). The mean extent of excessive overjet increased significantly from the deciduous to the mixed dentition. Crossbite with mandibular midline discrepancies were observed significantly more frequently in the deciduous dentition. Although the frequency of anterior open bite underwent a significant decline from the deciduous to the mixed dentition, open bite was the malocclusion most frequently associated with dysfunction in both groups. The significant increase in traumatic deep bite in the mixed dentition indicates an unfavorable developmental tendency in this anomaly until after the eruption of the permanent incisors. The need for preventive orthodontic therapy and for the intensified application of interceptive and early treatment measures is stressed in view of the high number of malalignments and malocclusions in the deciduous and mixed dentition and the tendency for some forms of malocclusion to deteriorate as the dentition develops.

Treatment of an adult patient with severely crowded bimaxillary protrusive Class II malocclusion with atypical extractions

Am J Orthod Dentofacial Orthop 2002;122:317-22

The influence of dental to facial midline discrepancies on dental attractiveness ratings.

This study investigated the perception of discrepancies between the dental and facial midlines by orthodontists and young laypeople. A smiling photograph of a young adult female was modified by moving the dental midline relative to the facial midline. Twenty orthodontists (10 males and 10 females) and 20 young adult laypeople (10 males and 10 females) scored the attractiveness of the smile on the original image and each of the modified images using a 10-point scale. The results showed that the images were scored as less attractive both by the orthodontists and laypeople as the size of the dental to facial midline discrepancy increased. The scores were unrelated to the direction of the midline discrepancy (left or right) or to the gender of the judge. Further analysis revealed that the orthodontists were more sensitive than laypeople to small discrepancies between the dental and facial midline. It was estimated that the probability of a layperson recording a less favourable attractiveness score when there was a 2-mm discrepancy between the dental and facial midlines was 56 per cent.

Dental asymmetry in temporomandibular disorders

In our previous study, it was reported that facial asymmetry due to mandibular lateral displacement (MLD) was significant in patients with temporomandibular disorders (TMD). In this study, dental asymmetry in TMD patients was investigated by means of PA cephalogram and study model. Lateral deviation of the midline of the mandibular occlusal table (PA-mid) and right-left difference of the molar relationship (Molar-Diff.) were examined, and their relationship with MLD was studied. PA-mid and Molar-Diff. were significantly correlated with MLD. In most cases, displaced side of the midline of the lower occlusal table was coincident with that of the mandibular skeletal midline. These results suggest that in TMD patients asymmetries in occlusal relationship of the midline of the mandibular teeth and molars were mainly due to a mandibular skeletal asymmetry and not merely due to a dental malposition on the alveolar basal bone. Many cases had a more distal occlusal relationship of the first molar on mandibular displaced side compared with that on the opposite side. A high incidence of Class II relationship was found (61.8% as a whole) and more remarkable on the mandibular displaced side. Midline discrepancy and right-left difference of the molar relationship seem to be important occlusal characteristics in patients with TMD.

Diagnosis and treatment planning ofpatients with asymmetries

The diagnosis, treatment planning, and design of mechanics for the asymmetric patient requires the differentiation between problems of dental and skeletal origin. Although much information can be gleaned from a cephalometric analysis, the clinical examination and study models offer important clues in establishing the diagnosis of skeletal discrepancy. Abnormal and asymmetric axial inclinations can either produce a dental asymmetry or, if compensatory in nature, may mask an underlying skeletal problem. The role of axial inclination in diagnosis is applied to the following situations: subdivision cases, unilateral crossbites, midline discrepancies, arch form deviations, and frontal cants to the occlusal plane. The management of axial inclination asymmetries depends on the treatment plan. Nonextraction patients may require maintenance of asymmetric compensatory axial inclinations. Surgical and extraction patients can be treated to a more ideal symmetry.

An american board of orthodontics case report: Treatment of a class I malocclusion with a significant transverse discrepancy and high mandibular plane angle

A case report of the orthodontic treatment of a female adolescent with a Class I malocclusion, complicated by a significant transverse discrepancy and a high mandibular plane angle, is presented. Early removal of a maxillary right first premolar contributed to a midline discrepancy. Treatment consisted of rapid palatal expansion and extraction of the maxillary left first premolar and the mandibular right and left second premolars. A very acceptable result was achieved despite a demonstrated vertical growth pattern.

Orthodontic residents' indications for use of the lateral TMJ tomogram and the posteroanterior cephalogram

The purpose of this study was to determine the selection criteria used by orthodontic residents for ordering a corrected lateral tomogram (LT) of the temporomandibular joint (TMJ) and a posteroanterior cephalogram (PAC) for the diagnosis of patients needing orthodontic care. The impact of the radiographs on their treatment plans was also assessed. We conducted a study of the 144 new patients assigned to eight orthodontic residents during a two-year period. The residents responded through questionnaires describing their rationale for ordering the radiographs. A LT was ordered for twenty-eight (19 percent) of the patients. The most common reasons cited for requesting the LTs were TMJ clicking (67 percent) and pain (33 percent). The residents also perceived a need to order the LT for medico-legal protection in 85 percent of these cases. The LT tended not to have an impact on treatment planning. A PAC was ordered thirty-eight times (26 percent). The most common reasons cited by residents for ordering a PAC included clinical findings of facial asymmetry (41 percent) and maxillary airway anatomy (24 percent). Medico-legal protection was a perceived need in only 12 percent of the cases. While the PAC had no impact on treatment planning for 56 percent of the cases, they did define the transverse problems as dental or skeletal for 38 percent of the cases. Six patient traits were statistically associated with PAC requests: difficulty chewing, abnormal TMJ, TMJ clicking, facial asymmetry. crossbite, and midline discrepancy. The teaching of appropriate selection criteria for ordering these radiographs needs to be emphasized early in a resident's training.

Treatment strategies for midline discrepancies

Midline discrepancies are among the most complex and commonly seen problems in clinical orthodontics. Skeletal, soft tissue, and dentoavleolar asymmetries may be present alone or in combination in a patient who has noncoincident midlines. Due to the multifactorial etiology of midline discrepancies, a thorough understanding of the components that may contribute to the problem is essential for a correct diagnosis. The treatment mechanics that are derived from the treatment plan must be biomechanically oriented in order to achieve the desired results without the introduction of adverse side effects. This article discusses strategies to correctly diagnose and treat patients with significant midline asymmetries.

Two phase treatment of a severe Class II, Division I malocclusion

From the Uniw;rsity of Tennessee, Department of Graduate Orthodontics. Presented at the May 1994 Meeting of the American Association of Orthodontists, Orlando, Fla. Associate Professor bOrthodontic Resident CProfessor Am J Orthod Dentofac Orthop 1996;109:461-5. Copyright © 1996 by the American Association of Orthodontists. 0889-5406/96/$5.(10 + 0 814/60634 sors were protrusive, and a deep mentolabial sulcus was apparent. Intraoral: The patient was in the late mixed dentition stage (Fig. 2). A Class II, Division 1 malocclusion was noted with 10 mm overjet and little overbite. Generalized maxillary spacing was present with a 3 mm midline diastema. A midline discrepancy was also present. The maxillary labial frenum inserted into the incisive papilla° Minor irregularity was present in the mandibular incisor segment. Functional assessment: A 2 mm centric relation/centric occlusion (CR/CO) discrepancy was present. No signs or symptoms of temporomandibular disfunction were seen, and the patient had a full range of mandibular motion. The patient demonstrated a tongue thrust swallowing pattern.

Extraction of a mandibular incisor in a Class I malocclusion

A single mandibular central incisor was removed to treat a Class I malocclusion with crowding and a midline discrepancy. This case report was submitted under category number 10 (optional) and it was believed that the results illustrated the Board objectives of (1) facial harmony, soft tissue balance, and proper proportion, (2) maximum health of the teeth, the supporting tissues and adjacent structures, (3) maximum esthetics, (4) optimal functional relationships, (5) treatment in harmony with the patient's facial growth, and (6) stability. Beginning, completion, and 2-year retention records are included. The text follows the guidelines established by the Board for content and length included in “Specific Instructions for Candidates.” [This case report was presented to the American Board of Orthodontics in partial fulfillment of the requirements for the certification process conducted by the Board.] (A M J O RTHOD D ENTOFAC O RTHOP 1995;108:533-41.)

A multiple logistic regression analysis of the risk and relative odds of temporomandibular disorders as a function of common occlusal features.

A multiple logistic regression analysis was used to compute the odds ratios for 11 common occlusal features for asymptomatic controls (n = 147) vs. five temporomandibular disorder groups: Disc Displacement with Reduction (n = 81), Disc Displacement without Reduction (n = 48), Osteoarthrosis with Disc Displacement History (n = 75), Primary Osteoarthrosis (n = 85), and Myalgia Only (n = 124). Features that did not contribute included: retruded contact position (RCP) to intercuspal position (ICP) occlusal slides < or = 2 mm, slide asymmetry, unilateral RCP contacts, deep overbite, minimal overjet, dental midline discrepancies, < or = 4 missing teeth, and maxillo-mandibular first molar relationship or cross-arch asymmetry. Groupings of a minimum of two to at most five occlusal variables contributed to the TMD patient groups. Significant increases in risk occurred selectively with anterior open bite (p < 0.01), unilateral maxillary lingual crossbite (p < 0.05 to p < 0.01), overjets > 6-7 mm (p < 0.05 to p < 0.01), > or > 5-6 missing posterior teeth (p < 0.05 to p < 0.01), and RCP-ICP slides > 2 mm (p < 0.05 to p < 0.01). While the contribution of occlusion to the disease groups was not zero, most of the variation in each disease population was not explained by occlusal parameters. Thus, occlusion cannot be considered the unique or dominant factor in defining TMD populations. Certain features such as anterior open bite in osteoarthrosis patients were considered to be a consequence of rather than etiological factors for the disorder.

The midline: Diagnosis and treatment

The importance of coordinated midlines often is unappreciated as it relates to the treatment plan for the orthodontic case. All three of the patient's midlines--facial, maxillary, and mandibular--must be considered if ideal correction is to be achieved. Proper differential diagnosis of the cause will allow the practitioner to appropriately use either inter- or intraarch mechanics for the resolution of midline discrepancies. Midline correction should be undertaken from the initiation of treatment and once all midlines are coordinated they should be maintained as a guide for any further force systems used in completing the case. Functional, dental, and iatrogenic midline discrepancies are discussed pertaining to their diagnosis and treatment.

An American Board of Orthodontics case report

A case report is presented of a Class III, right subdivision malocclusion in the permanent dentition. There were significant arch form asymmetries, crossbite, crowding, and a midline discrepancy. The case was treated to the standards of the American Board of Orthodontics. [This case was presented to the American Board of Orthodontics in partial fulfillment of the requirements for the certification process conducted by the Board.]

Mandibular condyle morphology in relation to malocclusions in children.

Recent studies show that forces applied to the mandible during treatment with functional appliances and other orthodontic therapies produce changes in the TMJ. Specific malocclusions might also apply forces that can produce changes in the morphology of the TMJ. This study examined 104 orthodontic patients (44 males and 60 females) prior to treatment. The size and location of the condyle was determined on submento-vertex and tomographic films which was related to clinical findings including age, sex, malocclusion type, facial type, TMJ symptoms, tooth eruption sequence, crossbites and midline discrepancies. The medio-lateral width of the condylar head correlated positively with the patients age (p less than 0.001) and sex (p less than 0.001). Also the antero-posterior widths of the condyle were correlated with age (p less than 0.05). The condylar size in males was found to be greater than in females. Midline discrepancy significantly altered the increase in condylar size during growth. Transversel anomalies had a markedly greater influence on condylar growth compared to other characteristics of occlusion. The major change in condylar size during growth occurred in medio-lateral dimension as compared to the antero-posterior. In addition, the medio-lateral width was affected by midline discrepancy but not the antero-posterior width.

Relationship of mandibular condylar position to dental occlusion factors in an asymptomatic population

This article investigates the influence of occlusion on condylar position as seen on TMJ tomograms in a group of 44 young adults with no histories of orthodontic or occlusal therapy and no objective signs of masticatory dysfunction; the sample was screened from a population of 253 students. Nonconcentric condylar position at ICP was a feature of Class II malocclusion with significantly more anterior positions in Class II, Division 1 than in Class I. Condylar position was unrelated to the amount of sagittal RCP-ICP slide, although most slides were <0.5 mm. The frequency of lateral slides was low, but was mildly related to bilaterally asymmetric condylar positions. Position was unrelated to the degree of overbite, which ranged from 0 to 10 mm. Bilateral condylar position asymmetry was not related to the direction of dental midline discrepancy, which ranged from 0 to 2 mm. No open bites or mandibular overjets were seen in this asymptomatic normal sample.

Comparison study between three tooth positioners

Maintenance of arch dimensions during treatment and retention is essential for the stability of orthodontic results. This study compared ten essential measurements between posttreatment models and three different tooth positioners. Two custom-made positioners and one prefabricated positioner were evaluated. The material for this study consisted of models of twelve patients who were treated orthodontically to a Class I occlusion. Three sets of models were made at the debanding appointment. One set was kept as the original control model. The other two sets were sent to two different laboratories for construction of custom-made positioners. Identical instructions were included. A fourth set of models was made from the prefinisher positioner that was selected for each patient. The original control model, the returned individualized setups, and the prefinisher models were compared. Changes in maxillary and mandibular intercanine and intermolar widths were recorded, along with arch length, molar classification, rotations, spaces, curve of Spee, overjet, overbite, midline discrepancies, and teeth positioned out of arch symmetry. This study showed that there was a significant difference in the mandibular intercanine and maxillary intermolar width between the control model and the prefinisher model. No significant difference in arch length, maxillary intercanine width, and mandibular intermolar width was found between the control model and the other three models. All studied models had a Class I molar relationship. Open contact points and a slight curve of Spee were found in a high percentage of cases. Rotations, midline discrepancies, overjet, and overbite were within normal limits. Arch symmetry was acceptable in all but one case. Positioners, although they appear in most cases to respect individual arch dimensions, should be checked carefully before delivery to the patient.

A radiographic study of craniofacial asymmetries as related to the dentition and midline discrepancies

A radiographic study of craniofacial asymmetries as related to the dentition and midline discrepancies