Maxillary Midline Research Articles

Agenesis of mandibular second premolars. Spontaneous space closure after extraction therapy: a 4-year follow-up.

The aim of this study was to investigate the space closure and occlusal changes in 11 subjects (mean age 11.8 years) with normal occlusion and agenesis of the mandibular second premolar, after extraction of the mandibular secondary primary molar and the maxillary second premolar on the side of the agenesis. The treatment started when the first premolars came into occlusion and the subjects were followed for 4 years. Dental casts were taken at the start of treatment and after 1, 2 and 4 years, and lateral cephalograms were taken at the start of treatment and after 2 and 4 years. Space closure, sagittal movements, rotational movements, and tipping of the first molars and first premolars and dental midline shift were measured on photographs of dental casts. Sagittal movement of the incisors was measured on lateral cephalograms. The results showed that most of the extraction space closed during the first year (55 per cent in the maxilla, 46 per cent in the mandible) and at the end of the follow-up period 89 per cent of the extraction space closed in the maxilla and 80 per cent in the mandible, leaving a mean residual extraction space of 0.9 and 2 mm respectively. In the maxilla, 70 per cent of the extraction space closed by mesial and rotational movements of the first molars. Maxillary premolars moved distally, rotated and tipped only during the first year of observation. In the mandible, the space closure occurred by mesial/rotational movements and tipping of first molars and distal movement and tipping of the first premolars. Unilateral extraction had no influence on the maxillary midline while it caused a statistically significant mandibular dental shift to the extraction side. Extraction therapy had no impact on the overjet, overbite or incisor inclination.

A class II, Division 1 malocclusion: A malocclusion with a significant mandibular arch length deficiency

The malocclusion had a dental asymmetry that was corrected with the extraction of the maxillary right and left premolars and the mandibular left first premolar. Treatment objectives included: alleviation of maxillary and mandibular arch length deficiencies, maintenance of the maxillary midline conincident with the facial midline, correction of the mandibular midline which was off to the right, overbite and overjet correction, and attainment of a Class I canine relationship on the right side. [This case was presented to the American Board of Orthodontics in partial fulfillment of the requirement for the certification process conducted by the Board.]

A postretention study of patients presenting with a maxillary median diastema.

The purpose of this study was to assess postretention stability of maxillary midline diastema closure, to search for predictors of relapse, and to test for associations between relapse and other postretention changes. The sample consisted of 35 patients with pretreatment diastemas ranging from 0.9 mm to 3.0 mm (mean 1.4, SD = 0.5) following eruption of the maxillary canines. Data were gathered from treatment charts, study models, periapical radiographs, and cephalograms taken pretreatment, posttreatment, and 1 to 26 years postretention (mean 11.4, SD = 6.4). Measurable diastema relapse was observed in only 12 cases. The majority of the relapse was 0.6 mm or less, and maximum relapse was 3.0 mm. Abnormal frenums and/or intermaxillary osseous clefts did not appear to be risk factors for relapse, and no pretreatment predictors of relapse could be established. The only posttreatment change associated with diastema relapse was proclination of the maxillary incisors (p < 0.01).

SOFT-TISSUE SURGERY TO ALLEVIATE ORTHODONTIC RELAPSE

This article has presented three soft-tissue surgical techniques that have been shown to alleviate the relapse of orthodontically treated teeth in three specific situations: (1) rotations (and possibly also labiolingual irregularities), (2) extraction site closures, and (3) maxillary midline diastemas. The anatomy and histophysiology of the periodontium have been discussed briefly as they pertain to the rationale for these surgical procedures. None of the techniques discussed, if performed as indicated, will be detrimental to the supporting periodontal tissues and all can easily become a routine part of the clinician's standard retention therapy.

Functional and morphological-occlusal aspects in children treated for unilateral posterior cross-bite.

Morphological and functional aspects were investigated in children with unilateral posterior cross-bite (UPXB) before and after treatment. Sixty-five patients with Class I malocclusion with UPXB in the mixed dentition stage (mean age 8.8 +/- 1.6 years) served as the experimental group and 10 children of comparable age, with normocclusion or very mild Class I malocclusion (without UPXB) served as controls. The morphological aspects were examined on a longitudinal basis while the functional recordings, by means of a sirognathograph, were performed in a cross-sectional fashion. Complete elimination of cross-bite was maintained in 61 per cent and was accompanied by a dramatic reduction in the prevalence of functional mandibular displacement. However, the prevalence of mandibular midline deviation related to the maxillary midline as recorded in the intercuspal position was not affected. In addition, the high prevalence of Class II subdivision relationships which accompanied the UPXB in the intercuspal position was resolved in 50 per cent of the cases only. The sirognathographic recordings of the masticatory pattern showed a very high prevalence of a 'reverse sequencing' type pattern before treatment which was significantly lower following the elimination of UPXB, but still notably higher when compared with the controls. Reasons for these results are suggested and possible inter-relationships between the morphological and functional aspects are discussed.

Correction of Mandibular Asymmetry with the Ligated Anterior Repositioning Splint

Mandibular asymmetry may be the result of unequal ramus height, unequal corpus length, or a combination of both problems. The diagnosis of asymmetry is essential in treatment planning, since a number of therapeutic options must be considered in the treatment to a seated condylar position in the glenoid fossa. When asymmetry exists, it may be necessary to: accept finished treatment with the mandibular midline to the right or left of the maxillary midline, finish the molars and canines in an end-to-end relationship on the short side, treat with asymmetric extractions, intervene surgically, or use functional appliances to enhance greater growth or remodeling of the mandible on the short side. The purpose of this study was to assess the effect of the ligated anterior repositioning splint, or LARS, in the correction of mandibular asymmetry in Class II patients.

Incidence and etiology of midline diastema in a population in south India (Madras).

In a cross-sectional study of midline diastemas in a South Indian (Madras) population, 9,774 patients aged 13-35 years were screened. True midline diastema was defined as one without periodontal/periapical involvement and with the presence of all anterior teeth in the arch. Sample purification resulted in a research sample of 166 patients with true midline diastemas. The incidence of true maxillary midline diastema (160/9774-1.6%) was greater than that of true mandibular midline diastemas (31/9774-0.3%). No direct etiologic factor for the midline diastemas was noted. Spacing in the anterior region was the most significant factor associated with the midline diastema.

Hydroxylapatite as a bone graft substitute in orthognathic surgery: histologic and histometric findings.

The use of porous hydroxylapatite (HA) as a substitute for bone in grafting associated with orthognathic surgical procedures was studied histologically and histometrically. The surgical procedures included maxillary downgrafting, advancement, setback, superior repositioning with expansion, and mandibular advancement and chin augmentation. Seventeen biopsies were obtained from nine patients after successful healing from 4.7 to 16.4 months postoperatively. Anatomic sites of the biopsies included maxillary wall, interdental region, palatal midline, chin, and mandible. In addition, nine implants representing six planned and three unplanned exposures were retrieved from nine patients. One biopsy from a successful implant was decalcified and thin-sectioned to provide better cell detail of the antral lining of the implant. The remaining biopsies were sectioned undecalcified to permit backscattered electron imaging with a scanning electron microscope. Each of the 17 biopsy specimens contained bone ingrowth. The decalcified specimen showed an intact submucosa with loss of the mucosal epithelium due to prolonged acid exposure. The biopsies were composed of 48.5% HA matrix, 18.0% bone ingrowth, and 33.5% soft tissue or vascular space. The HA matrix surface area averaged 9.4 mm2/mm3 with 62.1% of the surface covered by appositional bone ingrowth. The nine exposed implants contained connective tissue ingrowth only at their margins, with little or no bone being present. This graft-like biologic response to a porous HA matrix confirmed its ability to serve as a bone graft substitute in clinical applications. The absence of any decrease over time confirmed the relative permanence of the HA matrix. The lack of inflammatory cells in the biopsies, along with the formation of a connective tissue protective barrier in the exposed specimens, suggests that host responses to contamination were not impaired by the porous HA matrix.

The transmitted interproximal force in the anterior dental arch

The purpose of this study is to measure transmitted interproximal forces and to evaluate the contact relationships. Firstly, the development of a new measuring evice for forces between interproximal surfaces of teeth was aimed. Secondly, transmitted interproximal forces at the midline of maxilla were measured, employing the measuring device, when experimental separations were applied to interproximal areas between the central and the lateral incisor, between the lateral incisor and the cuspid, and between the cuspid and the bicuspid, respectively.The following results were obtained:1) The force transducer which was made by using piezo plastic film was very thin, and its thickness was 60 μm.2) When the experimental separations were applied, the magnitude of transmitted interproximal forces increased. As the amount of separations increased, the magnitude of transmitted interproximal forces more increased.3) Splinting a few teeth in the anterior segment increased the magnitude of the transmitted interproximal forces when the same amount of separations was applied.From this study, it is suggested that the entire arch, consisting of all the teeth, may move in such a way that all teeth perform as a unit in a functioning whole.

Incidence of the maxillary midline diastema in adults

5. Helkimo, M., Ingervall, B., and Carlsson, G. E.: Variation of retruded and muscular position of the mandible under different recording conditions. Acta Odontol Scand 29:423, 1971. 6. Strohaver, R. A.: A comparison of articulator mountings made with centric relation and myocentric position records. J PROSTHET DENT 28:379, 1972. 7. Remien, J. C., and Ash, M. M.: Myo-monitor centric: An evaluation. J PROSTHET DENT 31:137, 1974. 8. Lauritzen, A. G., and Wolford, L. W.: Occlusal relationships: The split cast method for articulating techniques. J PROSTHET DENT 14:256, 1964. 9. McCollum, B. B.: Function factors that make the mouth and teeth a vital organ. J Am Dent Assoc 14:1261, 1927. 10. Myo-monitor Instruction Manual: Recording the maxillomandibular registration. Seattle, Wash., 1977, Myo-tronics Research. 11. Hart, T. O., Malone, W. F., Sandrick, J., Bowman, D., and 12.

Management of a Maxillary Central Incisor Impacted by a Supernumerary Tooth

Supernumerary teeth in the maxillary midline are common and can present both esthetic and pathologic problems that can be extremely difficult to solve. Early detection of the mesiodens is most important if such complications are to be avoided. This case required both surgical and orthodontic treatment to bring an unerupted, impacted maxillary central incisor into position. Using a combination of conservative surgical treatment and careful orthodontic management, the tooth was brought into good position in the dental arch and injury to root structure and surrounding oral tissues was avoided.

The Rationale for Various Modes of Retention

In addition to the specific aspects of retention mentioned previously, other factors may promote postorthodontic relapse. The seasoned clinician must therefore be aware of any and all variables that may potentially affect the stability of the treatment result. For example, identification and elimination of the etiology of the malformation will enhance the potential for stable treatment. If an anterior open bite deformity is caused by thumb sucking, stability of the corrected open bite can usually be achieved if the child can eliminate the habit. If the habit is not controlled, there is little likelihood that the open bite correction can be maintained. Similarly, successful long-term closure of a maxillary midline diastema will depend primarily on identification and elimination of its etiology. Other factors that may influence posttreatment stability should be considered in the original treatment plan. For example, severe mandibular incisor irregularity may necessitate the extraction of an incisor tooth to avoid potentially unstable expansion of the anterior area of the dental arch. Adherence to accepted principles of good orthodontic therapy are also of importance for posttreatment stability. Proper axial inclination of anterior teeth may assist in preventing recurrence of deep overbite, and proper axial inclination of teeth adjacent to extraction sites may help prevent the reopening of these spaces. Maximum interdigitation of posterior teeth may not insure against the relapse of a class II malocclusion, but failure to achieve good interdigitation will certainly leave the dentition more susceptible to relapse. In 1907, Angle wrote: “After malposed teeth have been moved into the desired position, they must be mechanically supported until all of the tissues involved in their support and maintenance in their new positions shall have become thoroughly modified, both in structure and function to meet the new requirements.” 1 While it is clear that normal function and long-term retention will not necessarily prevent relapse of some aspects of a particular malocclusion, proper retentive procedures will enhance the stability of the corrected malocclusion if supported by good treatment planning and active therapy.

A study of the relationship of the dental midline to the facial median line

This report presents the results of an original investigation designed to determine (1) the prevalence in the natural dentition of a maxillary midline located in the exact middle of the mouth using the philtrum as the most reliable guide and (2) the percentage of people in whom the maxillary and mandibular midlines precisely coincide with each other. Results indicate that the midline is situated in the exact middle of the mouth in approximately 70% of people and that the maxillary and mandibular midlines fail to coincide in almost three fourths of the population.

The maxillary midline diastema: Causes and treatment considerations

The maxillary midline diastema: Causes and treatment considerations

The diastema, the frenum, the frenectomy: A clinical study

1. The pretreatment relationship between a clinically "abnormal"-appearing maxillary midline frenum and a midline diastema showed a strong, but not absolute, correlation. A certain percentage of patients demonstrated (1) a diastema but not an "abnormal" frenum or (2) no diastema but an "abnormal" frenum. 2. Diastema cases in which there were "abnormal" pretreatment frenums demonstrated a decidedly stronger potential for relapse after orthodontic closure. The exceptions to the rule were explained by the clinician's inability to differentiate between "normal" and "abnormal" frenums and by the periodontium's apparent (if not consistent) ability to recognize the frenal and interdental tissues following orthodontic tooth movement. 3. A three-stage surgical procedure was shown to be very effective in alleviating the relapse phenomenon following orthodontic treatment of diastemas. The surgical procedures were successful in avoiding many of the hazards to the periodontium associated with previous techniques.

A cephalometric appraisal of changes in the maxillofacial complex resulting from palatal suture expansion utilizing fixed appliance therapy

This retrospective study evaluated the nasolabial changes in patients who underwent surgically assisted rapid maxillary expansion (SARME) using two different approaches. Nineteen patients were included in the study, divided into two groups according to the kind of surgical approach performed: group 1 (n = 9), SARME performed through the standard Le Fort I circumvestibular approach followed by the alar base cinch, and group 2 (n = 10), SARME performed through a subtotal vestibular approach associated to a V-shaped incision at the maxillary midline in the labial frenulum region, without alar base cinch. Measurements of width, length, and nasal projection as well as upper lip length were taken from cone beam tomographic images obtained before surgery (T1) and 6 months postoperatively (T2). Both groups presented an increase in the alar base width postoperatively (P < 0.05). The approach used in group 2 resulted in smaller changes in the alar base width as measured at the superior alar curvature (P < 0.05). Nasal length and projection and upper lip length were not altered by SARME. The type of surgical approach influenced nasolabial changes, but did not eliminate increase in width of the alar base.

A procedure for midline correction

D uring orthodontic treatment, teeth are repositioned according to the dictates of both skeletal and dental harmony. The dental component indicates that the final arrangement of the teeth should conform to a Class I dental pattern with perfect alignment, proximal contact, proper axial inclination, and maximum intercuspation. These occlusal relationships will exist only under certain conditions which coordinate the dentition and the dental arches. For example, the sizes of the maxillary and mandibular teeth must be a perfect match for each other. Similarly, the maxillary and mandibular midlines must be coincident. In this instance there will be equal amounts of tooth substance on either side of the midline. Accordingly, cusp position should be suitable for maximum interdigitation. If the midlines are not coincident, maximum intercuspation is improbable because the cusp position on the side of the midline “shift” will be more posterior to its “normal” location ; on the side away from the shift, the cusps will be situated somewhat anterior to the proper position. Midline coincidence, therefore, is an essential factor in dental harmony. For this reason, the position of the midlines receives a considerable degree of attention during therapy. With this in mind, the following report will describe a procedure which may be useful to correct a midline imbalance which may be present in the final stages of treatment after alignment, space closure, etc. AS an example, let us assume that the maxillary midline is “correctly” situated and the mandibular midline is deviated to the right. As indicated, the right mandibular segment is posterior to its “correct” position and the left buccal segment is anterior. Therefore, a force system capable of applying a mesially directed component of force on the right side and a distally directed force on the left should aid in midline correction. If these movements are coordinated in a continuous arch, the incisors should move to the left, correcting the midline problem. One such system is illustrated in Fig. 1. A round wire was inserted in the mandibular arch with the following configuration: A second-order bend was formed and inserted into the right canine bracket to drive the crown of the

Perception of midline diastema in dental- and nondental-oriented individuals

Background: The perception of maxillary midline diastema differs in different individuals and continent. Culture and other factors are believed to influence the perception of maxillary midline diastema. The aim is to determine the influence of dental knowledge on the perception of maxillary midline diastema. Materials and Methods: Study was done in Nigeria, which consists of diverse ethnic and social African groups. A two-stage sampling method was done to select participants between the ages 20 and 49 years. Participants were randomly selected from the University of Lagos and Teaching Hospital, Lagos, Nigeria. A structured questionnaire including a set of color smile photographs with varying sizes of maxillary midline diastema (narrowest = 2 mm; widest = 6 mm) was administered, and grading of attractiveness of smile was done. This information was evaluated using a Likert scale. Results: Study participants were 89 and age range was between 20 and 49 years with the mean age being 27.9 ± 7.9 years. Female participants were 49.4%, while male was 50.6%. The proportion of those who were medically inclined was 47.2% and those that were nonmedically inclined were 52.8%. Prevalence of midline diastema was 16.9%. About 52% of the medically inclined and 48.9% of nonmedically inclined participants rated maxillary midline diastema of 4 mm as acceptable (P = 0.02). At 6 mm width, there was a general rating of unattractiveness with 83.3% medically inclined and 66% nonmedically inclined participants rating it unattractive (P = 0.03). A higher percent (73.8%) of the medically inclined participants did not like midline diastema (P = 0.00). Conclusion: This study was able to demonstrate the perception of maxillary midline diastema in dental and nondental professionals.

The multidisciplinary management of median diastema

Maxillary midline diastemas are a common esthetic problem that dentists must treat. Many innovative therapies have been used, varying from restorative procedures to surgery (frenectomies) and orthodontics. The importance of the presence of a maxillary midline diastema resides in its position and the concern it causes to patients. This specific diastema has been attributed to genetic and environmental factors, even though it is often a normal feature of growth, especially in primary and mixed dentition. The need for treatment is mainly attributed to esthetic and psychological reasons, rather than functional ones. Although it is often the case, treatment plans should not be selected empirically but rather should be based on adequate scientific documentation. This paper reviews different treatment techniques to manage the situation and presents three cases to illustrate a range of restorative, prosthetic and orthodontic options. Keywords: Midline diastema; dental spacing; etiology; treatment; relapse. DOI: 10.3329/bjms.v9i4.6691Bangladesh Journal of Medical Science Vol.09 No.4 July 2010 pp.234-237

Supernumerary Teeth

Supernumerary teeth may develop in any dental area but are most commonly found in the upper incisor region; an extra tooth developing in the midline is designated a “mesiodens.” All supernumerary teeth with the possible exception of some supplemental primary teeth should be extracted early because they usually produce malocclusion or dental pathosis or both. Supernumerary teeth can cause malocclusion whether they erupt or are unerupted. They account for the production of diastemata (especially at the maxillary midline), the axial malrelationship or rotation of adjoining teeth, their displacement mesiodistally or labiolingually and their impaction. When unerupted, supernumerary teeth may produce root resorption and pulpal damage of the contiguous teeth; they may undergo cystic degeneration. Because supernumerary teeth may cause these undesirable conditions, their early detection and prompt extraction is necessary in the practice of preventive dentistry and interceptive orthodontics.