Donald R. Oliver

Class II non-extraction patients treated with the Forsus Fatigue Resistant Device versus intermaxillary elastics.

OBJECTIVE To evaluate the Forsus Fatigue Resistant Device (FRD) as a compliance-free alternative to Class II elastics. MATERIALS AND METHODS A sample of 34 (14 female, 20 male) consecutively treated nonextraction FRD patients (12.6 years of age) were matched with a sample of 34 (14 female, 20 male) consecutively treated nonextraction Class II elastics patients (12.2 years of age) based on four pretreatment variables (ANB, L1-GoMe, SN-GoMe, and treatment duration). Pretreatment and posttreatment cephalometric radiographs were traced and analyzed using the pitchfork analysis and a vertical cephalometric analysis. t-Tests were used to evaluate group differences. Group differences were evaluated using t-tests. RESULTS No statistically significant differences were found in the treatment changes between the groups. There was a general trend for mesial movement of the maxilla, mandible, and dentition during treatment for both groups. The mandibular skeletal advancement and dental movements were greater than those in the maxilla, which accounted for the Class II correction. Lower incisor proclination was evident in both groups. Vertically, the maxillary and mandibular molars erupted during treatment in both groups, while lower incisors proclined. With the exception of lower molar mesial movements and total molar correction, which were significantly (P < .05) greater in the Forsus group, there were no statistically significant group differences in the treatment changes. CONCLUSIONS The Forsus FRD is an acceptable substitute for Class II elastics for noncompliant patients.

Cone Beam Computed Tomography 3D Reconstruction of the Mandibular Condyle

OBJECTIVE To determine the ideal window level and width needed for cone beam computed three-dimensional (3D) reconstruction of the condyle. MATERIALS AND METHODS Linear dimensions were measured with a digital caliper to assess the anatomic truth for 50 dry human mandibular condyles. Condyles were scanned with the i-CAT cone beam computed tomography (CBCT) and 3D-models were reconstructed. Three linear three-dimensional measurements were made on each of the 50 condyles at 8 different Hounsfield unit (HU) windows. These measurements were compared with the anatomic truth. Volumetric measurements were also completed on all 50 condyles, at 23 different window levels, to define the volumetric distribution of bone mineral density (BMD) within the condyle. RESULTS Significant differences were found in two of the three linear measurement groups at and below the recommended viewing window for osseous structures. The most accurate measurements were made within the soft tissue range for HU window levels. Volumetric distribution measurements revealed that the condyles were mostly comprised of low-density bone, and that condyles exhibiting significant changes in linear measurements were shown to have higher percentages of low-density bone than those condyles with little change from the anatomic truth. CONCLUSIONS CBCT assessment of the mandibular condyle, using the 3D reconstruction, is most accurate when accomplished at density levels below that recommended for osseous examination. However, utilizing lower window levels which extend into the soft tissue range, may compromise ones capacity to view the bony topography.

Stability of immediately loaded 3- and 6-mm miniscrew implants in beagle dogs―a pilot study

INTRODUCTION We compared the stability of 3- and 6-mm long miniscrew implants (MSIs) loaded with orthopedic force levels. METHODS Using a split-mouth experimental design, we placed MSIs into the jaws of 5 mature beagle dogs and immediately loaded them for 6 weeks. Continuous forces were applied by reciprocally loading pairs of MSIs with nickel-titanium coil springs. The mandibles had the 3-mm MSIs randomly loaded with forces of 600 or 900 g. In the maxilla, the 3- and 6-mm MSIs were randomly assigned and loaded with 600 g of force. An unloaded, control MSI was placed in each quadrant. Overall success was defined as MSIs that remained intact; net success rates excluded MSIs that had sheared off and all implants placed in a dog that frequently chewed his run bars and food bowl. RESULTS The overall success rates of the loaded and the control 6-mm MSIs were 100%. Overall and net success rates for the 3-mm experimental MSIs were 66.7% and 95.2%, respectively. Similarly, the overall and net success rates of the 3-mm control MSIs were 66.7% and 81.8%, respectively. The overall success rates of the 3-mm mandibular MSIs loaded with 900 and 600 g of force were both 60%; their net success rates were 100% with 900 g and 85.7% with 600 g. Overall success rates of the 3-mm experimental MSIs in the maxilla and the mandible were 80% and 60%, repectively. The net success rates were 100% (maxilla) and 85.7% (mandible). There were no significant (P > 0.05) differences in stability associated with force or location. The loaded 3- and 6-mm MSI pairs demonstrated significant decreases in interimplant distance, averaging 2.2 and 1.8 mm, respectively; the 3-mm MSIs loaded with 900 g showed significantly more displacement than those loaded with 600 g. CONCLUSIONS Success rates of immediately loaded 3-mm MSIs were significantly lower than those of immediately loaded 6-mm MSIs. Neither force nor location explained differences in the success rates. The linear displacements of the MSIs were associated with load amount rather than implant length.

Effects of Pilot Hole Size and Bone Density on Miniscrew Implants' Stability

PROBLEM How does pilot hole size and bone density affect the primary stability of miniscrew implants (MSIs)? METHODS Using 120 MSIs divided equally into six groups, this 2 × 3 factorial design evaluated the effects of synthetic bone density (0.64 g/cc vs 0.8 g/cc cortices) and pilot hole size (no pilot hole, 1.0 mm pilot hole, and 1.4 mm pilot hole) on maximum insertion torque and pullout strength. The maximum placement torque was measured as the last thread of the MSIs was inserted. The pullout strength test applied a vertical force at 10 mm/min until failure. RESULTS The insertion torque and pullout strength values were significantly (p ≤ .05) greater for the MSIs placed in high-density than in low-density cortical bone. The insertion torque and pullout strength decreased as pilot hole size increased, with significant (p ≤ .05) differences between all three subgroups. Insertion torque and pullout strength were significantly intercorrelated for all subgroupings, with stronger correlations in denser bone having smaller or no pilot holes. CONCLUSION Depending on bone density, pilot holes of limited size can be used to optimize primary stability by decreasing insertion torque while maintaining the pullout strength of bone.

Stability changes of miniscrew implants over time

PURPOSE To quantify in vivo changes in miniscrew implant (MSI) stability over time using resonance frequency analysis, and to determine if pilot holes and placement sites affect changes in MSI stability. MATERIALS AND METHODS Twenty-two self-tapping MSIs (1.6 mm wide and 9 mm long) were placed in the maxillae of 2 adult beagle dogs (20 months old). The Osstell Mentor was used to measure the implant stability quotient (ISQ) weekly for 8 weeks. A split-mouth design was used to evaluate the effects of 1.1-mm wide, 3-mm deep pilot holes. RESULTS The MSIs that failed showed significantly (P < .05) greater decreases in ISQ values during the first 3 weeks than the MSIs that remained stable. All of the MSIs that failed (41%) had been placed in nonkeratinized tissue. MSIs that remained stable throughout the study also showed significant decreases in ISQ values during the first 3 weeks, followed by increases during the fourth and fifth weeks. Changes in ISQ values of MSIs inserted into bone with and without pilot holes were comparable (P > .05). CONCLUSION Stability of unloaded MSIs decreased during the first 3 weeks and increased thereafter. Although the effects of pilot holes on stability could not be confirmed, placement of MSIs into nonkeratinized tissue negatively affected their stability and increased the likelihood of failures.

Facial divergence and mandibular crowding in treated subjects.

OBJECTIVE To understand the relationships between facial divergence, vertical growth, and postretention mandibular crowding. MATERIALS AND METHODS Seventy-five white extraction patients were evaluated immediately posttreatment (15.4 years) and again 16.6 years later. Hyperdivergent subjects, subjects with open bite or severe deep bites were not evaluated. Changes in incisor irregularity and tooth-size arch-length discrepancies (TSALD) were evaluated and correlated with measures of divergence and skeletal growth. RESULTS Incisor irregularity increased 0.9 mm and TSALD increased 0.7 mm after treatment; 68% of the subjects had less than 3.5 mm incisor irregularity at postretention. Male patients showed significantly more growth than female patients did. Female patients, who were significantly more hyperdivergent than male patients, showed weak to moderately weak associations between posttreatment facial divergence and crowding. Female posttreatment changes in anterior face height, lower incisor eruption, and changes in arch depth were also related to crowding; male patients showed moderate relationships between posttreatment changes in arch width and crowding. CONCLUSIONS Greater vertical growth, incisor eruption, and especially facial divergence are related to greater posttreatment mandibular crowding.

Comparison of the effects of Hawley and perfector/spring aligner retainers on postorthodontic occlusion.

INTRODUCTION The purpose of this study was to evaluate the short-term changes in posterior occlusion produced by perfector/spring aligner and Hawley retainers. METHODS In this prospective clinical study, we randomly assigned 50 patients who had completed full orthodontic treatment to a Hawley retainer group or a perfector/spring aligner retainer group. Objective and subjective measures were collected when the retainers were delivered (T1) and approximately 2 months later (T2). Blu Mousse (Parkell Bio-Materials, Farmingdale, NY) was used to quantify posterior areas of contact (<50 microm) and near contact (50-350 microm). The patients perception of occlusion was assessed by using a 7-item questionnaire. RESULTS Areas of contact and near contact (ACNC) in the Hawley group increased significantly (P <0.05) from 6.71 mm(2) at T1 to 10.97 mm(2) at T2; ACNC in the perfector/spring aligner group increased from 8.44 mm(2) at T1 to 12.95 mm(2) at T2. There were no significant (P <0.05) differences in the increases of ACNC between the Hawley group (4.50 mm(2)) and the perfector/spring aligner group (3.26 mm(2)). Spearman correlations showed that ACNC at T1 were positively related with ACNC at T2 and negatively related with T2 to T1 ACNC changes. In comparison with the Hawley group, the patients wearing perfector/spring aligner retainers reported significantly greater improvements in how well their back teeth fit together, how well they could chew tough meats, and how much pain they felt when they bit down. CONCLUSIONS ACNC increased substantially and similarly in patients wearing Hawley and perfector/spring aligner retainers. Changes over time were perceived to a greater extent by patients wearing perfector/spring aligner retainers.

Extraction vs no treatment: Long-term facial profile changes.

INTRODUCTION Long-term soft tissue response to extraction orthodontic treatment has been a subject of interest for years. The purposes of this study were to investigate long-term soft tissue profile changes in an extraction sample and to compare them with profile changes in an untreated sample. METHODS A premolar extraction-treated sample (n = 47) and an untreated control sample (n = 57) were studied. Descriptive statistics were collected, and individual t tests were used for comparison and contrast of the treated and untreated samples. RESULTS We found that the untreated soft tissue profile changed in the downward and forward direction. The treated soft tissue profile change was similar, but with more of a forward component than in the untreated sample. Most noteworthy was the finding that the soft tissue profiles of both the untreated and the treated samples were similar at the end point. CONCLUSIONS The following conclusions were derived from the study. (1) There was no substantive difference in the soft tissue profiles of the samples, but there were some differences in the directional changes between them. (2) The changes for the untreated sample were the greatest for the lips and the chin, with the change occurring in the downward and forward direction. (3) The soft tissue profiles of the extraction sample also had the greatest measurable changes in the lips and the chin, but the changes had more of a forward component than they did in the untreated sample. (4) Extraction treatment does not adversely impact soft tissue profile changes over time.

Posterior occlusion changes with a Hawley vs Perfector and Hawley retainer. A follow-up study.

OBJECTIVE To characterize postorthodontic settling of the posterior occlusion of patients wearing Hawley retainers vs patients who initially wore Perfector retainers and then switched to Hawley retainers. MATERIALS AND METHODS This follow-up study was based on 40 patients (25 Perfector and 15 Hawley), who were part of a larger sample of 50 patients randomly assigned to wear either Hawley or Perfector retainers. The Perfector patients were given Hawley retainers 2 months after retainer delivery. Occlusal bite registrations were scanned and traced to quantify posterior areas of contact and near contact (ACNC). A seven-item questionnaire was used to assess the patients perception of occlusion. Measurements were obtained at the on the day of retainer delivery, 2 months post delivery, 6 months post delivery, and 8 months post delivery. RESULTS ACNC increased significantly (P < .05) during the first 6 months of retainer wear. The ACNC of the Hawley and Perfector/Hawley groups increased by 129% and 105%, respectively, over 8 months of retention. The greatest increases in ACNC occurred during the first 2 months. The ACNC further increased between 2 and 6 months in both groups. The Perfector/Hawley group also showed slight increases in ACNC between 6 and 8 months. Overall group differences were not statistically significant. The Perfector/Hawley group perceived greater improvements in occlusion than the Hawley group, but group differences after 8 months were small. CONCLUSIONS Substantial amounts of settling occurred at decelerating rates during the first 6 months after retainer delivery. No significant differences in ACNC were found between the Hawley and Perfector/Hawley groups after 8 months of retainer wear.

Third-Order Torque and Self-Ligating Orthodontic Bracket–Type Effects on Sliding Friction

OBJECTIVE To examine the influence of third-order torque on kinetic friction in sliding mechanics involving active and passive self-ligating brackets. MATERIALS AND METHODS Wire-slot frictional forces were quantified and compared across five sets of brackets and tubes within a simulated posterior dental segment with -15 degrees , -10 degrees , -5 degrees , 0 degrees , +5 degrees , +10 degrees , and +15 degrees of torque placed in the second-premolar bracket; a working archwire was pulled through the slots. RESULTS Increasing the torque from 0 degrees to +/-15 degrees produced significant increases in frictional resistance with all five sets of brackets and tubes. At 0 degrees and +/-5 degrees of torque, generally less friction was created within the passive than within the active self-ligating bracket sets, and the conventional bracket sets with elastomeric ligation generated the most friction. At +/-10 degrees of torque, apparently with wire-slot clearance eliminated, all bracket-and-tube sets displayed similar resistances, with one exception at +10 degrees . At +/-15 degrees of torque, one passive set and one active set produced significantly larger frictional resistances than the other three sets. CONCLUSIONS Third-order torque in posterior dental segments can generate frictional resistance during anterior retraction with the archwire sliding through self-ligating bracket slots. With small torque angles, friction is less with passive than with active self-ligating brackets, but bracket design is a factor. Frictional forces are substantial, regardless of ligation if the wire-slot torque exceeds the third-order clearance.