Ravindra Nanda

The Use of Skeletal Anchorage in Open Bite Treatment: A Cephalometric Evaluation

The aims of the present study were to assess the effectiveness of skeletal anchorage for intrusion of maxillary posterior teeth, to correct open bite malocclusion, and to evaluate the usage of titanium miniplates for orthodontic anchorage. Anterior open bite is one of the most difficult malocclusions to treat orthodontically. Currently, surgical impaction of the maxillary posterior segment is considered to be the most effective treatment option in adult patients. Various studies have reported the use of implants as anchorage units at different sites of midfacial bones for orthodontic tooth movement. The zygomatic buttress area could be a valuable anchorage site to achieve intrusion of maxillary posterior teeth. Ten patients, 17 to 23 years old and characterized with an anterior open bite and excessive maxillary posterior growth, were included in this preliminary study. Titanium miniplates were fixed bilaterally to the zygomatic buttress area, and a force was applied bilaterally with nine mm Ni-Ti coil springs between the vertical extension of the miniplate and the first molar buccal tube. The results showed that, with the help of skeletal anchorage, maxillary posterior teeth were intruded effectively. As compared with an osteotomy, this minimally invasive surgical procedure eased treatment and reduced treatment time and did not require headgear wear or anterior box elastics for anterior open bite correction. In conclusion, the zygomatic area was found to be a useful anchorage site for intrusion of the molars in a short period of time.

Protraction of maxilla in rhesus monkeys by controlled extraoral forces

0 rthodontic treatment not only involves establishment of physiologically and anatomically functional occlusion but also envisages correction of the relationship of the maxilla and mandible to each other and to the rest of the craniofacial complex. To achieve a harmonious dentofacial relationship as a result of orthodontic treatment, extraoral devices using the neck or cranium as anchorage have been employed since the turn of the century. These extraoral appliances have been used to influence the maxillary and mandibular growth patterns by inhibiting and/or redirecting their normal growth potentials in children before and during maximal pubertal growth. Several clinical studies have shown that posteriorly directed extraoral forces applied to the maxillary first molars can inhibit or redirect the growth of the maxilla.22, 23 In retrospect, the use of extraoral forces in orthodontics was based on the premise that they inhibit the normal growth of the maxilla or mandible. Later it was noted that “heavy” extraoral forces, such as cervical or occipital headgear, will also move molars distally.2 However, as a result of clinical findings that extraoral forces “probably” remodel the midfacial bones and condyle, several animal studies have been performed to study the bony changes at the histologic level. Sproule2’ studied the effects of continuous extraoral cervical traction on the dentofacial complex of Mucaca mulutta monkeys. He reported that in the experimental group the maxilla rotated in a clockwise fashion as a result of its growth in a downward and backward direction as compared to downward and forward growth in control animals. Similar results have been reported by other investigators”, 24, 2g using the same or different species of monkeys. A histologic examination of experimental animals in these investigations revealed that the maxillofacial sutures respond significantly to extraoral forces as seen by resorption and appositional changes at these sites. The changes in the spatial

Biomechanical and clinical considerations of a modified protraction headgear

The choice of treatment of children with developing skeletal Class III malocclusions has always posed a dilemma. Chin cups and various types of reverse headgears with elastics have been used in the past to minimize the growth and development discrepancy of the midface and the mandibular bones. In the present article, a critique of commonly used protraction devices is presented. A modified protraction headgear design and the biomechanical considerations of its clinical use are presented in this study. The clinical results show that a modified protraction headgear with a chin cup helps in the correction of moderately severe Class III malocclusions by the anterior displacement of the maxilla and maxillary dentition, and possibly restricting or changing the direction of the growth of the mandible. This headgear can also be used to correct axial inclinations and/or mesial displacement of posterior teeth.

An evaluation of root resorption incident to orthodontic intrusion

A new radiographic method was developed for measuring changes in root length. With this technique, orthodontic intrusion was investigated as a potential cause of apical root resorption of maxillary incisors. The experimental group consisted of 17 patients with excessive overbite who were treated with a Burstone-type intrusion arch, which delivered a low level of force (about 15 gm per tooth). A control group was made up of 17 patients in full-arch fixed appliances who were randomly selected. After a period of approximately 4 months, the intrusion group had only slightly more root resorption than the controls, 0.6 mm versus 0.2 mm (statistically significant difference). Intrusion measured at the center of resistance of the central incisor averaged 1.9 mm. The amount of resorption was not correlated with the amount of intrusion. A weak correlation, r = 0.45, was found between resorption and movement of the apex (i.e., in addition to intrusion, there was often palatal root movement). Results of this study seem to indicate that intrusion with low forces can be effective in reducing overbite while causing only a negligible amount of apical root resorption.

Soft-tissue changes associated with maxillary incisor retraction

The nature of incisor retraction and lip adaptation is still controversial. The present study was undertaken to determine the response of upper and lower lips to maxillary and mandibular incisor movement. Cephalometric head films of thirty late-adolescent and early-adult female patients were analyzed for changes in the integumental profile with treatment. Sample selection was intended to reduce variables caused by growth and sex differences. A stepwise multiple regression analysis (forward) revealed a complex interaction between dentition, bony structures, and soft tissues of the perioral area. The lower lip was more variable than the upper lip to differences in the upper incisor movement. The upperlip at labrale superius was found to be more variable with increased retraction of the upper incisors. In the prediction equation, change of sulcus superius had a more direct relationship with retraction of labrale superius and labrale inferius than with dental movement. Pogonion and/or menton entered at statistically significant levels into four (LS, LI, SI, Stm I) of the six prediction equations, indicating that mandibular position is of paramount importance in the prediction of vertical and/or horizontal changes in the upper and lower lips. The upper lip response was related to both upper and lower incisor movement, mandibular rotation, and the lower lip. Upper incisor point position related a moderately high correlation for the prediction equation for change in labrale superius. Lower incisor movement did not correlate with change of either the upper or lower lip. The equations derived were an improvement over previous prediction methods.

Dental and orthopedic effects of high-pull headgear in treatment of Class II, Division 1 malocclusion

In the present study a prospective cephalometric investigation was undertaken to examine the skeletal and dental effects of the high-pull extraoral appliance, when the resultant force was directed through the level of trifurcation of the maxillary molars. Twelve adolescent patients with Class II, Division 1 malocclusions were selected for the study. Each patient wore the headgear for a 6-month period, an average of 12 hours a day. A group of untreated adolescent patients with Class II, Division 1 malocclusions who were in a similar age range, as well as skeletal and dental characteristics were chosen as controls. Lateral cephalometric films were taken before and after the 6-month treatment period, and before and after the observation period in the control group of patients. Our data indicate that by directing the force of the headgear approximately through the center of resistance of the maxillary molars, it is possible to accomplish simultaneously a substantial distal movement of the molars (2.6 +/- 0.6 mm), as well as significant intrusion (0.54 +/- 0.54 mm). In addition, our results demonstrate that the applied force of 500 gm was sufficient to initiate maxillary orthopedic changes in the treated patients. These changes include relative restriction of horizontal and vertical maxillary growth, as well as distal movement (mean: 0.8 mm) of the maxillary anterior border in the treatment group relative to an untreated control group. Such orthopedic changes have been previously described only in association with much higher force levels.

Effects of a fixed magnetic appliance on the dentofacial complex

The purpose of the study was to design and evaluate the effects of a fixed magnetic appliance that hinged the mandible open and exerted an intrusive force on the teeth. Ten patients between the ages of 8 years and 10 years 6 months, with Class II, Division 1 malocclusion associated with mandibular retrusion and increased lower facial height, were treated with this appliance. The length of treatment was 4 months, after which the appliance was removed and the patients were followed up for 4 months. Ten children with similar age, sex, and dentofacial characteristics acted as controls and did not receive any appliance therapy. Changes in morphology of the dentofacial complex were evaluated by use of lateral cephalograms and study models. In addition temporomandibular joint and muscle functions were assessed. During treatment mandibular length increased 3.2 mm, angle of facial convexity decreased 2.8 degrees, the upper and lower teeth intruded an average of 1.5 mm each, and the mandibular plane angle decreased 1.3 degrees. In the follow-up period, some rebound eruption was noted; however, all other changes were stable.

Effect of metabolic alteration of periodontal fibers on orthodontic tooth movement: An experimental study☆

In the present study orthodontic force was applied to the molars of rats treated with the lathyrogen beta-aminopropionitrile (BAPN). New bone formation was measured at two alveolar locations after 9 days of force application. Observation resulted in the following conclusions: 1. New alveolar bone formation in response to orthodontic force in BAPN-treated rats statistically exceeded corresponding bone formation in control animals when measured at two tension sites in the periodontal ligament. 2. BAPN administration produced disorganization of the collagenous fibers of the periodontium of experimental animals. Multiple eosinophilic cell-free areas were found distributed throughout the radicular portions of affected periodontal ligaments. Normal ligament function architecture was disrupted in treated animals. The areas of periodontium surrounding orthodontically treated teeth exhibited relatively normal organization under these conditions, while the periodontium of adjacent nonorthodontically treated teeth was markedly disorganized. Orthodontic stimulation of the periodontium of BAPN-treated rats may have disrupted the formation of eosinophilic cell-free areas characteristically seen in the periodontium of the experimental group. 3. The present results suggest that the typical histologic response to orthodontic force application can occur in the presence of a chemically and physically altered periodontium. The quantitative data collected infer that fiber tension on the alveolus may not be absolutely necessary to stimulate bone formation. Distortion of the alveolus related to force application may be a more important factor initiating bone response. However, the fibers of the periodontium may play a passive role in transferring orthodontic force to the alveolus.

Cephalometric Study of the Dentofacial Complex of North Indians

Abstract No Abstract Available. * From a thesis in partial fulfillment of the requirements for the degree of Master of Dental Surgery, Lucknow University, Lucknow. The research was supported by a grant received from the Indian Council of Medical Research, New Delhi.

Evaluation of horizontal and vertical differences in facial profiles by orthodontists and lay people.

A novel video image processing technique was used to evaluate changes in the facial profile mimicking the effects of various orthognathic surgical techniques. Incremental changes were introduced in male and female images simulating the effects of mandibular advancement or set-back, maxillary advancement or set-back, and maxillary impaction. Twenty-two clinicians and 22 lay people completed questionnaires evaluating their level of sensitivity to changes in the facial profiles and their preferences regarding alternative profiles. The results indicate that in judging realistic color video images, both orthodontists and lay people are sensitive to relatively small horizontal changes in the facial profile. In contrast, orthodontists are less sensitive to relatively large vertical changes but more sensitive to horizontal mandibular changes.