Steven J. Lindauer

Prevalence of white spot lesions during orthodontic treatment with fixed appliances

OBJECTIVE To determine the prevalence of white spot lesions (WSLs) in orthodontic patients at 6 and 12 months into treatment using the visual examination method. MATERIALS AND METHODS Patients 6 and 12 months into treatment were examined for the presence of WSLs. The control group consisted of patients who were examined for WSLs immediately after bonding. Upon clinical evaluation, teeth were given a visual score based on the extent of demineralization. RESULTS The percentages of individuals having at least one WSL were 38%, 46%, and 11% for the 6-month, 12-month, and control groups, respectively. The 6-month (P  =  .021) and 12-month groups (P  =  .005) were significantly different from the control group but were not significantly different from each other (P  =  .50). Of subjects in the study who had at least one visible WSL, 76% were males and 24% were females (P  =  .009). CONCLUSIONS This clinical study showed a sharp increase in the number of WSLs during the first 6 months of treatment that continued to rise at a slower rate to 12 months. Clinicians should evaluate the oral hygiene status of patients during the initial months of treatment and, if necessary, should implement extra measures to prevent demineralization.

Evaluation of Dental Midline Position

Maxillary midline position relative to the facial midline is stressed as an important diagnostic feature in orthodontic treatment planning. Depending on the patient, however, movement of the dental midline to be coincident with the facial midline may be difficult to achieve. In addition, evaluation of dental midline position may be complicated if other midline facial structures are not well aligned. The two objectives of the current study were to determine how far the maxillary dental midline could deviate from the facial midline and still be considered aesthetically acceptable, and to determine how the position of various midline facial landmarks affect overall facial aesthetics. One hundred twenty individuals, including orthodontists, general dentists, orthodontic patients, and parents of patients, evaluated digitally altered images of two patient-subjects to rate the acceptability of dental midline deviations and to prioritize the importance of location of various midline facial structures. The mean threshold for acceptable dental midline deviation was 2.2 +/- 1.5 mm. There was a significant difference in deviation thresholds between the two patient-subjects (P < .05). Orthodontists and dentists were significantly less tolerant of midline deviations than were patients (P < .001), with the tolerance of parents in between. When deviations of various midline facial structures were evaluated, photographs with maxillary midline and/or nose deviations were considered less aesthetic (P < .001). There were no apparent differences noted among orthodontists, dentists, patients, and parents in this part of the study.

The effects of lip bumper therapy in the mixed dentition

A prospective clinical trial was undertaken to study the effects of 6 months of continuous lip bumper therapy on patients in the mixed dentition with mild-to-moderate mandibular arch perimeter deficiency. Thirty-four patients, ages 7.9 to 13.1 years (mean = 10.2), seeking treatment in the postgraduate orthodontic clinic of the Medical College of Virginia, presented possessing 3 to 8 mm of mandibular crowding, with both mandibular primary second molars, were randomly placed in either the treatment or nontreatment group. Treated subjects underwent continuous lip bumper therapy, whereas the control subjects were monitored without undergoing any active treatment, each for 6 months. Arch dimension changes were assessed with study models. Alterations of mandibular incisor position were measured from lateral cephalometric radiographs. Mandibular left permanent first molar position changes were determined from both lateral cephalometric and tomographic radiographs, with the resolution of each imaging technique in measuring molar tooth movement also compared. It was found that significant differences in mandibular incisor inclination, molar position, arch length, and arch perimeter existed between treated and untreated subjects. In addition, multiple observer analysis showed that cephalometric examination lacks sensitivity when used to measure molar movement.

Increase in arch perimeter due to orthodontic expansion

A mathematical model was developed to compare quantitatively the effects of various types of orthodontic expansion on mandibular arch perimeter. Mandibular arch form was modeled with spline interpolation to fit a smooth curve between assigned molar, canine, and incisor positions. Starting with average arch dimensions, intermolar width, intercanine width, and midline arch length were increased individually and in combination in millimeter increments up to 5 mm, and the consequent changes in arch perimeter were measured. Increasing midline arch length by incisor advancement was nearly four times as effective in increasing arch perimeter as was molar expansion; canine expansion had an intermediate effect. Arch perimeter increments increased slightly with successive amounts of expansion for the molar, canine, and incisor. Combinations of molar-canine and canine-incisor expansion yielded results comparable to the total effects achieved by expansion of those teeth individually. Combined molar-canine expansion created increases in arch perimeter that were only slightly less than those generated by incisor advancement alone.

Moving an Ankylosed Central Incisor Using Orthodontics, Surgery and Distraction Osteogenesis

When a dentist replants an avulsed tooth, the repair process sometimes results in the cementum of the root and the alveolar bone fusing together, with the replanted tooth becoming ankylosed. When this occurs, the usual process of tooth movement with bone deposition and bone resorption at the periodontium cannot function. If dental ankylosis occurs in the maxillary incisor of a growing child, the ankylosed tooth also cannot move vertically with the subsequent vertical growth of the alveolar process. This results in the ankylosed tooth leaving the plane of occlusion and often becoming esthetically objectionable. This report describes a 12-year-old female with a central incisor that was replanted 5 years earlier, became ankylosed, and left the occlusal plane following subsequent normal vertical growth of the alveolar process. When growth was judged near completion, the tooth was moved back to the occlusal plane using a combination of orthodontics, surgical block osteotomy, and distraction osteogenesis to reposition the tooth at the proper vertical position in the arch. This approach had the advantage of bringing both the incisal edge and the gingival margin of the clinical crown to the proper height in the arch relative to their antimeres. Previous treatment procedures for ankylosed teeth have often involved the extraction of the affected tooth. When this is done, a vertical defect in the alveolar process results that often requires additional bone surgery to reconstruct the vertical height of the alveolar process. If the tooth is then replaced, the replacement tooth must reach from the final occlusal plane to the deficient ridge. This results in an excessively long clinical crown with a gingival height that does not match the adjacent teeth.

Effectiveness of an essential oil mouthrinse in improving oral health in orthodontic patients.

OBJECTIVE To test the null hypothesis that adding Listerine mouthrinse to the standard oral hygiene regimen has no added benefit for orthodontic patients in maintaining proper oral health. MATERIALS AND METHODS Patients within their first 6 months of orthodontic treatment were assigned either to the brushing + flossing (N = 25) or brushing + flossing + Listerine (N = 25) group. Initially, all of the participants received a prophylaxis and instructions on how to brush and floss. Measurements were recorded for the bleeding, gingival, and plaque indices (BI, MGI, and PI, respectively) that provided baseline values (T1). Subsequent measurements were taken at 3 months (T2) and 6 months (T3). Mean BI, MGI, and PI at T1, T2, and T3 were compared statistically between the groups using repeated measures analysis of variance. The significance level was set at P < or = .05. RESULTS The response profiles for the BI, MGI, and PI over time were significantly different between the two groups. Patients who had Listerine in their daily oral hygiene regimen exhibited significantly lower scores for all three indices at T2 and T3 than the patients who only brushed and flossed. CONCLUSIONS The hypothesis is rejected. This study shows that use of Listerine mouthrinse can reduce the amount of plaque and gingivitis in patients undergoing orthodontic treatment. Adding Listerine to the standard oral hygiene regimen may be beneficial for orthodontic patients in maintaining proper oral health, thus reducing the likelihood that white spot lesions and gingivitis will develop.

Lower arch perimeter preservation using the lingual arch

The purpose of this investigation was to determine whether the placement of a mandibular lingual arch maintained arch perimeter in the transition from the mixed to the permanent dentition, and if so, whether it was effective at preventing mesial migration of first permanent molars, or whether this migration still occurred en masse, by increased lower incisor proclination. Thirty patients were randomly assigned to either a treatment group (N = 14, mean age = 11.5 years) or a control group (N = 16, mean age = 11.3 years). Study models, cephalograms, and tomograms of the patients, taken at the beginning and at the end of the study period, were examined. Statistically significant differences between groups were found for positional changes of mandibular first molars and incisors, and changes in arch dimensions. The results indicate that the lingual arch can help reduce arch perimeter loss, but at the expense of slight mandibular incisor proclination.

Condylar movement and mandibular rotation during jaw opening.

Inaccurate description of mandibular rotation can have profound effects on orthognathic surgical treatment planning and surgical outcome, as well as affect the precision of appliances fabricated on articulators. Disagreement exists concerning movements of the condyle during jaw opening. Although mandibular function is often described as rotation around an instantaneous center located outside of the condyle, many believe that jaw opening occurs around an axis of rotation that remains fixed at the center of the condylar head. In this study, condylar movements and centers of mandibular rotation during jaw opening were examined in normal subjects with the Dolphin Sonic Digitizing System. All of the subjects demonstrated both translation and rotation of the condyle during initiation of jaw opening, and none had a center of mandibular rotation located at the condylar head. The findings support the theory of a constantly moving, instantaneous center of jaw rotation during opening that is different in every person. There were also differences in movement within the subjects between experimental trials. The uncertainty of predicting mandibular rotation for a given patient should be considered when planning surgical treatment and fabricating orthodontic appliances.

Segmented approach to simultaneous intrusion and space closure: Biomechanics of the three-piece base arch appliance

Deep overbite correction and space closure in patients with flared incisors are mechanically difficult to achieve with conventional orthodontic treatment. The purpose of this article is to present an appliance design that allows simultaneous intrusion and retraction of anterior teeth as well as correction of their axial inclinations. A three-piece base arch was used to achieve simultaneous intrusion and space closure. Various clinical situations are discussed and analyzed from a biomechanical standpoint. Sequences of treatment, appliance design, and management of side effects are described in detail. The segmented approach to simultaneous intrusion and space closure is useful for achieving precise control of tooth movements in the anteroposterior and vertical dimensions.

Chin, nose, and lips. Normal ratios, in young men and women

Existing soft tissue analyses reference profile characteristics to lines determined by surface landmarks. This study uses surface landmarks only to define an area, and soft tissue profiles are analyzed in terms of the surface area of each component part present within this area. The profiles of 66 young adults were measured, and the mean total profile area and all of the component parts except the nose were statistically larger in the men than in the women. The mean female nose was larger, but this difference was not significant. On the basis of percentage contributions, the mean female nose contributed significantly more to the total mean, female profile than the mean male nose did to the mean male total profile. The contribution of the mean male chin to the total mean male soft tissue profile was significantly larger than the contribution of the mean female chin to the total mean female profile. When compared by percent contributions, both the upper and lower lips of the men and women contributed nearly equally to their respective profiles. The overall result was that the mean female profile was more convex and the mean male profile was relatively straighter. Clinical implications of these differences are discussed.Existing soft tissue analyses reference profile characteristics to lines determined by surface landmarks. This study uses surface landmarks only to define an area, and soft tissue profiles are analyzed in terms of the surface area of each component part present within this area. The profiles of 66 young adults were measured, and the mean total profile area and all of the component parts except the nose were statistically larger in the men than in the women. The mean female nose was larger, but this difference was not significant. On the basis of percentage contributions, the mean female nose contributed significantly more to the total mean female profile than the mean male nose did to the mean male total profile. The contribution of the mean male chin to the total mean male soft tissue profile was significantly larger than the contribution of the mean female chin to the total mean female profile. When compared by percent contributions, both the upper and lower lips of the men and women contributed nearly equally to their respective profiles. The overall result was that the mean female profile was more convex and the mean male profile was relatively straighter.