Soft to hard tissue movement ratios: orthognathic surgery in a Hispanic population.

Prediction of the movement ratio of soft to hard tissues is an important part of an orthodontic and orthognathic treatment plan. Previous studies have shown that various ethnic populations have significantly different average cephalometric measurements when compared to European-American norms. Therefore, a difference may exist in soft to hard tissue movement ratios in different ethnic populations. This study was undertaken to create norms for soft to hard tissue movement ratios for orthognathic surgery in a Hispanic population. These results were compared to previously published data on European-American populations. Presurgical and postsurgical cephalographs were traced and analyzed. The data were divided into 3 groups based on the surgical procedure performed: maxillary surgery alone, mandibular surgery alone, and treatment with a combination of maxillary and mandibular surgery. The results indicate that differences exist in soft to hard tissue ratios between the European-American and Hispanic populations. It is important to incorporate ratios for patients of Hispanic descent into a treatment planning protocol so that these patients are treated appropriately.

Prediction accuracy of soft tissue profile in orthognathic surgery.

The purpose of this study was to compare soft tissue prediction accuracy of model surgery combined with computer software prediction with that of computer software prediction alone and to assess surgical accuracy by comparing the immediate postsurgical cephalogram with the planned movement of skeletal hard tissue. The predicted and actual soft tissue changes and the corresponding skeletal changes of 16 patients were compared using the Quick Ceph Image cephalometric treatment simulation software. A custom analysis was created to measure the hard tissue and soft tissue changes that occurred as a result of the surgical procedure. On average, the predictions were not significantly different from the actual postsurgical profile changes. Surgical changes of hard tissues from presurgery to postsurgery were accurate as planned except for the position of N-ANS. All lower soft tissue points moved significantly during treatment. Quick Ceph Image offers a rapid and reliable method of profile prediction that does not require artistic skill. If predictions are interpreted with caution and transferred accurately to the model surgery, they can provide an excellent visual aid during presurgical treatment planning and patient presentation.

Antibacterial properties of current orthodontic band cements.

PURPOSE: Manufacturers commonly provide information on the physical properties of dental materials, but information on their antibacterial properties is often missing. This study determined the antibacterial properties of four currently used orthodontic band cements against three different strains of Streptococcus mutans. METHODS: The cements utilized were Durelon, Ketac, Mizzy Zinc Phosphate, and Band-Lok, a recently introduced, resin-based, dual-cure glass ionomer cement. Disk diffusion assay methodology was used to test for zones of bacterial inhibition around cement samples. Zones of inhibition were measured in millimeters using an electronic caliper. In addition to cured cement plugs and freshly mixed cement samples, a new variation, in the form of a cement plug surrounding a stainless-steel band, was tested. Twelve combinations resulted from the four cement types and three forms. RESULTS: Of the variables studied, the mix forms of Durelon, Ketac, and Mizzy Zinc Phosphate cement showed the greatest bacterial inhibition (Kruskal-Wallis, P < 0.05). Among the cements tested, Mizzy Zinc Phosphate showed the largest zones of inhibition, with Durelon and Ketac having comparable zones of inhibition (Kruskal-Wallis, P < 0.05). Band-Lok did not exhibit an inhibitory effect against any of the three strains of S. mutans tested. CONCLUSION: A "containment effect" of no bacterial inhibition was observed in the cement samples surrounded by the stainless-steel band material.

A cephalometric comparative study of the soft tissue airway dimensions in persons with hyperdivergent and normodivergent facial patterns.

PURPOSE: This study was performed to compare the dimensions of the nasopharynx, oropharnynx, and hypopharynx of persons with hyperdivergent and normodivergent facial types, and to determine whether any variations exist. PATIENTS AND METHODS: Lateral cephalometric records of a population with a normodivergent facial pattern (n = 23) and a group with a hyperdivergent facial pattern (n = 27) as evidenced by increased mandibular plane angle were used to compare the soft tissue airway dimensions. Statistical analysis consisted of Student's t-tests, Wilcoxon rank sums, and chi2. Statistical significance was set .05. RESULTS: Overall the hyperdivergent group had a narrower anteroposterior pharyngeal dimension than the normodivergent control group. This narrowing was specifically noted in the nasopharynx at the level of the hard palate and in the oropharynx at the level of the tip of the soft palate and the mandible. In addition, the posterior pharyngeal wall had a thinning at the level of the inferior border of the third cervical vertebrae, and there was a more obtuse palatal angle. The tongue was also positioned more inferiorly and posteriorly in the hyperdivergent group, as evidenced by the increased distance between the hyoid bone and the mandibular plane and the increased distance between the soft palate tip and the epiglottis. The hyperdivergent group had more retruded maxillary and mandibular apical bases and a higher Class II skeletal discrepancy. CONCLUSIONS: The narrower anteroposterior dimension of the airway in hyperdivergent patients may be attributable to skeletal features common to such patients, that is, retrusion of the maxilla and the mandible and vertical maxillary excess. Other features, such as an obtuse soft palate and low-set hyoid, also may be contributory factors. The relatively thin posterior pharyngeal wall observed in hyperdivergent patients might be a compensatory mechanism.

The effects of ion implantation on rate of tooth movement: an in vitro model.

Recently, the ion-implantation process has been applied to orthodontic wires. By altering the surface composition of a wire, the ion-implantation process supposedly decreases the frictional forces produced during tooth movement. The purpose of this study was to compare the amount of tooth movement produced by different orthodontic wire compositions, under identical conditions, by using an in vitro model. The wires tested were stainless steel, nickel-titanium (control and ion implanted), and beta-titanium (control and ion implanted). The amount of tooth movement was measured and compared. Results demonstrate that, stainless steel produced the least frictional force during in vitro tooth movement, followed by ion-implanted nickel-titanium, ion-implanted beta-titanium, untreated nickel-titanium, and finally, untreated beta-titanium. A Wilcoxon rank sum test showed statistically significant differences in the amount of movement seen with the ion-implanted wires when compared with their untreated counterparts.

Changes in the dentition secondary to palatal crib therapy in digit-suckers: a preliminary study.

This study investigated the effect of the palatal crib appliance used in the correction of open bite malocclusions secondary to fingersucking. Twelve experimental and 12 control subjects were studied for an average of 3.9 months. The sample consisted of patients who were both growing and not growing. Study models taken before and after the study period were analyzed for changes in the following dimensions: overbite, overjet, arch perimeter, arch length, and incisor angulation. Data were analyzed with student t-tests to determine statistical significance. Partial or complete closure of the open bite was achieved averaging 3.7 mm +/- 1.9 mm during the observation period in the experimental group treated with palatal crib therapy. In contrast, the control group displayed a mean bite opening of 0.4 mm +/- 0.8. These values were statistically significant at the P < 0.001 level. Open bite decreased as incisor angulation (P < 0.02), arch length (P < 0.05), and arch perimeter (P < 0.01) decreased. Overjet changes were minimal and statistically insignificant.

The effect of acetaminophen on tooth movement in rabbits.

Orthodontic patients have reported the use of analgesics during therapy. However, common anti-inflammatory analgesics, such as aspirin and ibuprofen, have been shown to slow the rate of tooth movement. Acetaminophen, another common analgesic, does not possess anti-inflammatory properties. The effect of acetaminophen on tooth movement was studied using New Zealand white rabbits. Experimental animals were matched to a control animal of the same sex and weight. Under anesthesia, springs were ligated between the lower first molar and incisor, resulting in approximation of these teeth. Under blinded conditions, seven of the rabbits received 1000 mgs of acetaminophen daily. Seven control animals received water. The animals were sacrificed after 21 days. The movement of incisors and molars was measured. Results showed considerable movement within both the experimental and control groups, but no significant difference in tooth movement between them. Acetaminophen has no effect on the rate of tooth movement in rabbits undergoing orthodontic treatment.

Comparison of Hyrax and bonded expansion appliances.

The majority of rapid maxillary expansion studies have reported the use of appliances with metal bands attached to the posterior teeth. Tooth extrusion, dental tipping, and an increase in the vertical dimension are often encountered, which may not coincide with treatment objectives. Bonded appliances using interocclusal acrylic may control the vertical dimension and expand the maxillary halves in a more bodily and symmetrical fashion. The purpose of this clinical trial was to determine, by radiographic analysis, the differences between a conventional banded expander (Hyrax) and a bonded acrylic expander. Fourteen patients who exhibited a need for expansion were enrolled in the study. The results suggest that the increase in the vertical dimension often seen with the more conventional Hyrax appliance may be minimized or negated with the bonded appliance. However, there appeared to be no significant difference between the amount of dental tipping or symmetrical expansion between the two appliances, as previously theorized.

Mesh diagram analysis: developing a norm for African Americans.

The mesh analysis is a proportionate cephalometric analysis that enables a patient to serve as his or her own control to create a template from which to assess skeletal, dental, and craniofacial disharmonies. The norms for this analysis were originally created from a white, European American sample. The purposes of this study were: (1) to create a normal mesh diagram from a black, African American population; (2) to compare mesh diagrams from black and white Americans; and (3) to evaluate the usefulness of a panel of diverse members in selecting subjects. All subjects were black Americans of African descent, had no prior orthodontic treatment, and had Class I dental occlusion with minimal crowding (4 mm or less). The panel selected as esthetically pleasing 18 males and 25 females from a group of 77 patients meeting the study criteria. Male and female normal mesh diagrams were created from the cephalographs and compared with Caucasian normal diagrams developed by Moorrees in 1976. Linear and angular components of the hard and soft tissues were compared. Comparisons were also made with previously published normal values. Differences between the African American and Caucasian samples were more notable close to the dentoalveolar complex. Similarities were limited to the soft tissue of the upper face, the cranial base, and the midface. Analysis of the panel selection results did not suggest any trends between or within race, sex, or occupation of the panel members. However, agreement between the races was good.

Mesh diagram analysis: developing a norm for Puerto Rican Americans.

Cephalometric radiography is an important diagnostic aid in orthodontics. Mesh analysis is a proportionate cephalometric method of graphically assessing disharmonies of the craniofacial complex. Original norms for this analysis were created from a white, European American sample. Norms for black Americans of African descent were developed in another study. The purposes of this investigation were: (1) to develop a standard mesh diagram from a Puerto Rican American population; (2) to compare the diagram with previously established data from the white sample; (3) to develop linear and angular means for the Legan, Burstone, Ricketts, DiPaolo, and Steiner analyses for a Puerto Rican American population; and (4) to assess the use of a panel for selecting esthetically pleasing faces. The subjects in the study had no previous orthodontic treatment, had Class I occlusion with 6 mm or less of crowding per dental arch, and had two parents and two sets of grandparents who were were born in Puerto Rico. Sixty-nine patients met the study criteria, and 50 of those patients (20 males and 30 females) were selected as having esthetically pleasing faces by the panel. Male and female norm diagrams were created and these were compared with those developed previously. Linear and angular measurements were also compared. Significant differences between the ethnic groups were found in the dentoalveolar region. Similarities were noticed in the upper face height and anterior cranial base length. The panel selection results showed no agreement within the sexes, occupations, or ethnic groups.

Surgical prediction reliability: a comparison of two computer software systems.

The purpose of this study was to test and compare the accuracy and reliability of soft tissue profile predictions generated from two computer software programs. The presurgical and postsurgical cephalometric radiographs of 28 patients were digitized onto each computer program. A customized analysis was created to determine the amount of surgical movement, as well as to compare the actual postsurgical soft tissue profile with the computer-generated prediction. The results demonstrated that, on the average, the predictions were not significantly different from the actual postsurgical profile changes. While each program generated statistically similar prediction results, marked variability was noted. There was no significant difference found in the prediction errors between patients who had one-jaw surgery and those who had two-jaw surgery. This study found that a linear relationship existed between the surgical movement and the prediction error. In general, the greater the magnitude of the surgical movement, the larger the prediction error.

Canine retraction: a comparison of two preadjusted bracket systems.

Before the 1970s, Begg and Edgewise appliances were the most commonly used appliances in orthodontics. With the introduction of preadjusted appliances, many have made claims of superiority. These claims are often unsubstantiated, as few, if any, have ever been tested in a controlled, prospective in vivo study. The purpose of this study was to compare the time required to retract canine teeth by using two different preadjusted bracket systems (Tip-Edge, TP Orthodontics, LaPorte, Ind., versus A-Company straight wire, Johnson and Johnson, San Diego, Calif.) in a human sample. Anchorage loss as a result of this movement was also evaluated. A sample of 12 patients was randomly selected from the new patient pool at the postgraduate orthodontic clinic of Montefiore Medical Center. All patients required the removal of first premolars in one or both arches as a part of their orthodontic treatment. The rate of retraction and anchorage loss were evaluated. Paired t tests were performed separately for the rates of retraction and anchorage loss. The mean rates of retraction were 1.88 mm per 3-week period and 1.63 mm per 3-week period for the Tip-Edge and A-Company brackets, respectively. There was no statistically significant difference in the rates (p > 0.05). The mean anchorage loss was 1.71 mm for the Tip-Edge bracket, and 2.33 mm for the straight wire bracket. The difference in the amount of anchorage loss was inconclusive as the sample size was too small (power was 10%).

The accuracy of measurements of three-dimensional computed tomography reconstructions.

PURPOSE: The purpose of this study was to evaluate the accuracy and reproducibility of linear measurements obtained from three-dimensional reconstructions of computed tomography (CT) scans. MATERIALS AND METHODS: Ten rectangular acrylic blocks were prepared with titanium molybdenum alloy (TMA) markers spaced from 1 to 10 mm, respectively. A plastic sphere was prepared with 10 sets of TMA markers spaced at variable intervals of 1 to 10 mm. Each object was scanned three times at 3-mm slice thicknesses and 1.5 mm with 0.5 mm overlap slice thicknesses, as well as positioned in the CT scanner in two different directions (perpendicular and parallel) to the scanning beam. Intermarker distances of the reconstructed objects were then measured using the measurement tool of the MediCAD software and compared with measurements taken by hand with a vernier caliper. RESULTS: Using the 3-mm cut protocol, the data indicated that inconsistency exists between intermarker distance in the scans when the rectangular objects were scanned parallel to the scanning beam. This finding was not seen using the 1.5-mm with 0.5-mm overlap slice thickness protocol. The intermarker distances for objects scanned perpendicular to the scanning beam were consistent but subject to demagnification in the range of 17% to 20% for both scanning protocols. CONCLUSION: The orientation of the object to the scanning beam and slice thickness protocol appear to have an impact on the accuracy and variability of linear measurements taken in the x, y, z axes.

A comparison between radiographic and sonically produced cephalometric values.

Cephalometric radiography has become a standard and invaluable means of obtaining diagnostic information for the management of malocclusion and skeletal disharmony. However, concerns over radiographic exposure, particularly in growing individuals, may limit its use, especially in longitudinal analyses. Less invasive means of obtaining vital information would be desirable. A recently introduced system (Digigraph, Dolphin Imaging Systems; Valencia, Calif) provides sonically produced representations of cranial landmarks and has been introduced by its manufacturer as an alternative to standard cephalometric radiography. The purpose of the study was to compare the validity and reproducibility of cephalometric values generated sonically on a digital image analyzer (Digigraph) with those obtained from standard cephalometric radiographs for 43 different measurements. Although 58.1% of the sonically produced measurements showed significant correlation with radiographically produced measurements, there were no trends observed for correlation, either in dental or skeletal structure classifications. Additionally, this study found the data generated from the digital image analyzer to be markedly variable, while the radiographically obtained data were reproducible.

Decreased treatment time due to changes in technique and practice philosophy.

A study was conducted to evaluate the impact of practice modifications on treatment time for patients in a private orthodontic office. Two patient groups were studied, consisting of Class I nonextraction, adult dentitions treated by one of the authors. One group (28 cases) was treated with the standard Begg technique and conventional motivation, hygiene, and finishing practices. The other (25 cases) was treated with the Tip-Edge appliance along with specific modifications to motivation, hygiene and finishing techniques. The average treatment time for the Tip-Edge group was 12.80 months versus 20.89 months for the Begg group. The use of motivational techniques and a specific mission and philosophy within a private orthodontic practice can help reduce total treatment time. The Tip-Edge appliance may reduce treatment time in Class I nonextraction therapy.

Nickel hypersensitivity in the orthodontic patient.

Nickel is one of the most common causes of allergic contact dermatitis and produces more allergic reactions than all other metals combined. Currently, several brands of orthodontic wires are made of nickel titanium alloy and potentially have a high enough nickel content to provoke manifestations of allergic reactions in the oral cavity. The objectives of this study were (1) to determine if standard orthodontic therapy can sensitize patients to nickel, and (2) to assess gingival response to nickel-containing orthodontic appliances in patients who are nickel sensitive before treatment. Nickel sensitivity patch tests were conducted to confirm hypersensitivity to nickel. Twenty-nine patients from the Division of Orthodontics, Albert Einstein/Montefiore Medical Center were tested, ranging in age from 12 to 48 years. Of the 29 patients, there were 18 female and 11 males. Five of the patients had a positive nickel patch test, a rate of 18.5%. The five patients that tested positive were all female, meaning that the overall rate for females was 27.7% (5:18). The five female patients sensitive to nickel were followed monthly by intraoral photos and gingival and plaque index scores. The remaining patients began routine orthodontic therapy and were retested 3 months into treatment to see whether sensitization occurred. Two patients converted from an initial negative patch test to a positive test. There may be a risk of sensitizing patients to nickel with long-term exposure to nickel-containing appliances as occurs in routine orthodontic therapy.

Effect of nursing caries on body weight in a pediatric population.

A review of anesthesia and sedation records of children with nursing caries was undertaken. The weights of these 115 children with otherwise noncontributory medical histories were compared to subjects matched for age, gender, race, and socioeconomic status. Nursing caries children were treated using either sedation or general anesthesia and received treatment for at least one pulpally involved tooth. Comparison subjects had no gross carious lesions. The average age for both the comparison and test groups was 3.2 years (SD = 1.01 and 0.98, respectively). While comparison patients weighed 16.2 +/- 3.08 kg, patients with nursing caries weighed only 15.2 +/- 2.66 kg. This difference was statistically significant (P < 0.005). Of the nursing caries patients, 8.7% weighed less than 80% of their ideal weight, compared with only 1.7% of the comparison patients (P < 0.02). Of nursing caries children, 19.1% were in the 10th percentile or less for weight, compared with only 7.0% of comparison subjects (P < 0.01). The mean age of "low weight" patients with nursing caries was significantly greater than for patients at or above their ideal weights, indicating that progression of nursing caries may affect growth adversely.

Comparison of the craniofacial characteristics of two syndromes associated with the Pierre Robin sequence.

The craniofacial characteristics of two syndromes commonly associated with Robin sequence were compared for 49 subjects. Lateral cephalograms were analyzed for four groupings: Group I--Stickler syndrome with versus without Robin, Group II--velocardiofacial (VCF) syndrome with versus without Robin, Group III--Stickler without Robin compared to VCF without Robin, and Group IV--Stickler with Robin compared to VCF with Robin. Thirty-two skeletal and 18 soft tissue measurements were compared. In Group I, three skeletal measurements were significantly different (SNA, SNB, and SNPg). In Group II, no significant difference was found for any of the 50 measurements. In Group III, a significant difference was demonstrated for seven parameters (one skeletal, six pharyngeal and airway). In Group IV, two skeletal and eight airway measures were significantly different. The findings indicate that the relative maxillary and mandibular retrognathia observed in Stickler/Robin patients may predispose them to the Robin sequence and vice versa; the Robin features in VCF may be caused by hypotonia rather than any craniofacial or physical obstruction of the airway; Stickler and VCF are similar in craniofacial morphology but show marked differences in pharyngeal and airway morphology; and cephalometrics should not be the sole prognosticator of the Robin sequence and its association with Stickler and VCF.

Diagnosis and treatment planning in orthodontics.

Orthodontic diagnosis and treatment planning topics have become predictable in that reports seem to be reactive to societal dilemmas rather than addressing fundamental questions of our science. Issues and reports abound on temporomandibular disorders and their relationship to orthodontics. Investigations of airway function and other topics have tended to compound misunderstandings rather than eliminate them. Furthermore, new technologies heralded as having great promise may eventually fall to the side as mere gimmickry. Well-controlled prospective studies are needed to address many fundamental issues underlying orthodontic treatment. The progress and results from these works will take time to bear fruit.