Coordinating bracket torque and incisor inclination : Part 3: Validity of bracket torque values in achieving norm inclinations.

PURPOSE: To analyze common values of bracket torque (Andrews, Roth, MBT, Ricketts) for their validity in achieving incisor inclinations that are considered normal by different cephalometric standards. METHODS: Using the equations developed in part 1 (eU1(BOP) = 90° - BT(U1) - TCA(U1) + α1 - α2 and eL1(BOP) = 90° - BT(L1) - TCA(L1) + ß1 - ß2) (abbreviations see part 1) and the mean values (± SD) obtained as statistical measures in parts 1 and 2 of the study (α1 and ß1 [1.7° ± 0.7°], α2 [3.6° ± 0.3°], ß2 [3.2° ± 0.4°], TCA(U1) [24.6° ± 3.6°] and TCA(L1) [22.9° ± 4.3°]) expected (= theoretically anticipated) values were calculated for upper and lower incisors (U1 and L1) and compared to targeted (= cephalometric norm) values. RESULTS: For U1, there was no overlapping between the ranges of expected and targeted values, as the lowest targeted value of (58.3°; Ricketts) was higher than the highest expected value (56.5°; Andrews) relative to the bisected occlusal plane (BOP). Thus all of these torque systems will aim for flatter inclinations than prescribed by any of the norm values. Depending on target values, the various bracket systems fell short by 1.8-5.5° (Andrews), 6.8-10.5° (Roth), 11.8-15.5° (MBT), or 16.8-20.5° (Ricketts). For L1, there was good agreement of the MBT system with the Ricketts and Björk target values (Δ0.1° and Δ-0.8°, respectively), and both the Roth and Ricketts systems came close to the Bergen target value (both Δ2.3°). Depending on target values, the ranges of deviation for L1 were 6.3-13.2° for Andrews (Class II prescription), 2.3°-9.2° for Roth, -3.7 to -3.2° for MBT, and 2.3-9.2° for Ricketts. CONCLUSIONS: Common values of upper incisor bracket torque do not have acceptable validity in achieving normal incisor inclinations. A careful selection of lower bracket torque may provide satisfactory matching with some of the targeted norm values.

Coordinating bracket torque and incisor inclination : Part 1: The development of widely applicable equations.

PURPOSE: The objective of this investigation was to develop equations to describe the geometric relations among "targeted incisor inclinations" (tU1, tL1) accommodating different cephalometric norms (Ricketts, Bergen, etc.) with the "expected inclinations" (eU1, eL1), as they can be generated by bracket torque values according to Andrews, Roth, Ricketts, and MBT. METHODS: In its key parts, the present study is a theoretical work in which structural relationships are described using standard mathematical and geometric methodologies. RESULTS: The "targeted norm-inclinations" (tU1, tL1) were calculated relative to a single reference plane (BOP according to Downs), thus, allowing for a direct comparison of different cephalometric values. Referring to the "expected inclinations" (eU1, eL1), it was found that in addition to bracket torque (BT) morphological and structural parameters also have to be taken into account. These are the "torque coordination angle" (TCA) representing the variation in dental morphology and, the correction angles between BOP and the upper (uOP) (α1) or the lower (lOP) occlusal plane (ß1). Moreover, the angles α2 between an upper (uBPP) and ß2 between a lower bracket positioning plane (lBPP) and the occlusal planes (uOP, lOP) have to be considered. As a consequence, suitable equations were developed (eU1(BOP) = 90°â€¯- BT(U1) - TCA(U1) + α1 - α2, and eL1(BOP) = 90°â€¯- BT(L1) - TCA(L1) + ß1 - ß2), allowing the calculation of expected torque-dependent inclinations (eU1, eL1) and representing the prerequisite for a comparison with the cephalometric targeted values (tU1, tL1). CONCLUSIONS: By developing suitable equations, it became possible to name and quantify those parameters that are responsible for incisor inclinations and enable a comparison with targeted cephalometric values.

Compensation of skeletal Class III malocclusion by isolated extraction of mandibular teeth: Part 2: Skeletal, dentoalveolar and soft tissue parameters in comparison with nonextraction Class III therapies.

OBJECTIVES: To retrospectively compare two compensatory approaches taken in skeletal Class III patients during the main treatment stage, including a study group of multiband treatment plus isolated extraction of mandibular teeth and a control group of multiband treatment without extraction of teeth. PATIENTS AND METHODS: The extraction group included 22 (12 female, 10 male) patients receiving compensatory multiband treatment for a mean of 3.47 ± 1.14 years and 16.22 ± 1.92 years old at debonding. The nonextraction group included 24 (14 female, 10 male) patients undergoing multiband treatment for 2.76 ± 1.28 years and 15.38 ± 1.46 years old at debonding. Lateral cephalograms obtained at baseline and upon completion of active treatment were traced for skeletal, dentoalveolar, and soft tissue parameters. Welch and Wilcoxon tests were used to analyze intergroup differences (initial values, final values, initial-to-final changes) and within-group differences (p < 0.05). RESULTS: Upon completion of active treatment, the only significant intergroup differences were noted for U1NA and L1ML. Significant within-group changes over the courses of treatment were seen for SNB, MLNL, U1NA, U1NL, L1NB, L1ML, H-angle, ULipEL, and LLipEL (extraction group) or for SNB, ANB, individual ANB, Wits appraisal, U1NA, U1NL, H-angle, Naslab-a, ULipEL, and LLipEL (nonextraction group). Parameters that changed by significantly different amounts in both groups included Wits appraisal, L1NB, L1ML, and LLipEL. CONCLUSION: The added value of isolated extraction therapy basically lies in increasing the potential for retruding the lower incisor inclinations, so that compensatory treatment becomes an option even in selected patients presenting with adverse occlusal situations that would otherwise require orthognathic surgery. Given the successful outcomes in both groups, which had been established by Peer Assessment Rating (PAR) scores, it was possible to define the skeletal, dentoalveolar, and soft tissue characteristics of successful treatment more precisely than before.

Dental compensation for skeletal Class III malocclusion by isolated extraction of mandibular teeth. Part 1: Occlusal situation 12 years after completion of active treatment.

OBJECTIVES: The purpose of this work was to statistically evaluate the outcomes achieved by isolated extraction of mandibular teeth (second premolars or first molars) for Class III compensation. MATERIALS AND METHODS: Part A of the study dealt with the quality of outcomes at the end of active treatment, using weighted Peer Assessment Rating (PAR) scores determined on the basis of casts for 25 (14 female and 11 male) consecutive patients aged 16 ± 1.7 years at the time of debonding. These results were compared to the scores in a randomly selected control group of 25 (14 female and 11 male) patients who were 14.7 ± 1.9 years old at debonding. Part B evaluated the long-term stability of the outcomes based on 12 (all of them female) patients available for examination after a mean of 11.8 years. The mean weighted PAR scores obtained in both study parts were analyzed for statistical differences using a two-tailed paired Student's t-test at a significance level of p ≤ 0.05. RESULTS: Mean weighted PAR scores of 4.76 ± 3.94 and 3.92 ± 3.44 were obtained in the Class III extraction group and the control group, respectively, at the end of active treatment. This difference was not significant (p = 0.49). Among the 12 longitudinal patients, the mean score increased from 4 ± 3.46 at debonding to 6.25 ± 3.67 by the end of the 11.8-year follow-up period. This difference was significant (p = 0.0008). CONCLUSION: Treatment of Class III anomalies by isolated extraction of lower premolars or molars can yield PAR scores similar to those achieved by standard therapies. These scores, while increasing significantly, remained at a clinically acceptable level over 11.8 years. Hence this treatment modality--intended for cases that border on requiring orthognathic surgery--may also be recommended from a long-term point of view.

Therapeutic changes in the occlusal plane inclination using intermaxillary elastics.

AIM: The goal of the study was the evaluation of opposing intermaxillary elastics concerning potential change in the occlusal plane inclination relative to relevant vertical structures. PATIENTS AND METHODS: Thirty-two late adolescent, skeletally homogeneous patients (basal-sagittal relationship: neutral; basal-vertical: neutral; no transverse discrepancies) were treated either with Class II (group A; n=16) or Class III elastics (group B; n=16) for unimaxillary space closure. Mean wearing times were 26 (A) and 24 months (B). Cephalograms at the start and end of treatment were analyzed. Changes in the inclination of the occlusal plane (BOP according to Downs) relative to three reference planes (NL, ML, NSL), as well as changes in the reference planes toward each other underwent statistical testing with a two-tailed Student t-test. RESULTS: The occlusal plane shift differed significantly when opposing elastics were applied (p<0.001). The induced shift with Class II elastics (A) was clockwise, while Class III elastics were counterclockwise (A: NL-BOP: +0.9°, ML-BOP: -2.1°; B: NL-BOP: -3.1°, ML-BOP: +3°). Reference planes NL and ML underwent insignificant change towards one another (A: -1.2°; B: -0.1°). The maxillo-mandibular complex itself rotated counterclockwise toward the anterior cranial base (NSL) (A: NL-NSL: -0.8°, ML-NSL: -2°; B: NL-NSL: -0.6°, ML-NSL: -0.7°). Thus, almost no change in BOP (+0.1°, n.s.) relative to NSL was detected when Class II elastics were applied, whereas the use of Class III elastics led to a significant counterclockwise rotation (-3.7°, p<0.001) CONCLUSION: Class III elastics enhance the physiologic inclination of the maxillo-mandibular complex at the level of the occlusal plane, whereas Class II elastics oppose or even eliminate the process.

Noise exposure during ambulance flights and repatriation operations.

OBJECTIVES: Although ambulance flights are routine work and thousands of employees work in repatriation organizations, there is no data on noise exposure which may be used for preventive advice. We investigated the noise exposure of crews working in ambulance flight organizations for international patient repatriation to get the data for specific guidelines concerning noise protection. MATERIAL AND METHODS: Noise levels inside Learjet 35A, the aircraft type which is most often used for repatriation operations, were collected from locations where flight crews typically spend their time. A sound level meter class 1 meeting the DIN IEC 651 requirements was used for noise measurements, but several factors during the real flight situations caused a measurement error of ~3%. Therefore, the results fulfill the specifications for class 2. The data was collected during several real repatriation operations and was combined with the flight data (hours per day) regarding the personnel to evaluate the occupationally encountered equivalent noise level according to DIN 45645-2. RESULTS AND CONCLUSIONS: The measured noise levels were safely just below the 85 dB(A) threshold and should not induce permanent threshold shifts, provided that additional high noise exposure by non-occupational or private activities was avoided. As the levels of the noise produced by the engines outside the cabin are significantly above the 85 dB(A) threshold, the doors of the aircraft must be kept closed while the engines are running, and any activity performed outside the aircraft - or with the doors opened while the engines are running - must be done with adequate noise protection. The new EU noise directive (2003/10/EG) states that protective equipment must be made available to the aircrew to protect their hearing, though its use is not mandatory.

Routine treatment of bilateral aplasia of upper lateral incisors by orthodontic space closure without mandibular extractions.

This study aimed to gather statistically validated information on the changes in orthodontic variables in patients with bilateral upper lateral incisor aplasia treated with isolated orthodontic space closure. Data were collected from 25 (15 females, 10 males) consecutively treated, unselected adolescents [mean age at the end of treatment 16.4 years, standard deviation (SD) 1.3] after orthodontic space closure using push-and-pull mechanics (PPM). The changes in the relevant parameters were determined by comparing baseline and final lateral headfilms and casts. Following verification of normal distribution by means of a Kolmogorov-Smirnov test, a two-tailed t-test for related data was performed. SNA, ANB, OcP-NL, OcP-ML, upper space balance, overbite, overjet, bilateral molar relationship, and L1-NB changed significantly (P < or = 0.05) during treatment. The changes in overbite, overjet, spatial conditions, and molar relationship were in line with the targeted treatment objectives and within the normal range. Although the change in L1-NB was probably due to treatment, it was not clinically relevant given that the mean final values were close to normal at 22.8 degrees (SD 5.8 degrees ) for L1-NB and 95 degrees (SD 8 degrees ) for L1-ML. Isolated orthodontic space closure for bilateral upper lateral incisor aplasia using PPM can be regarded as a valid alternative to prosthetic solutions. Long-term use of Class III elastics does not lead to significant changes in relevant orthodontic parameters.

Changes in gingival recession related to orthodontic treatment of traumatic deep bites in adults.

INTRODUCTION: It was the aim of this investigation to establish whether orthodontic treatment of traumatic deep bites can restore trauma-related gingival recessions in adults. SUBJECTS AND METHODS: Forty-one incisor sites with trauma-related recession (group Tr) and 54 trauma-free sites (group NonTr) were diagnosed in the upper palatal or lower buccal regions in twelve adult patients (mean age 38.3 +/- 8.1 years). The 48 antagonistic sites on the buccal aspects of the upper incisors (Ubuc) and 47 sites on the lingual aspects of the lower incisors (L-ling) were also evaluated. Changes in clinical crown lengths achieved during treatment were measured on dental casts, and length changes in recessions were measured on screen projections of magnified intraoral photographs. RESULTS: The clinical crown lengths (mean: -1.13 +/- 0.97 mm) and recession depths (mean: -2.05 +/- 0.93 mm) decreased significantly (p < 0.001) in the trauma group (Tr). We also observed significant shortening (p < 0.05) of clinical crown lengths in the buccal sites of upper incisors (U-buc) (mean: -0.16 +/- 0.46 mm). All other changes were insignificant. CONCLUSIONS: Orthodontic treatment of traumatic deep bites involving removal of gingival trauma and intrusion of incisor teeth shows great potential in reducing the length of clinical crowns and depth of gingival recessions. In trauma-free buccal sites of upper incisors, intrusion therapy may also improve the gingival marginal contour.

Localized orthodontic space closure for unilateral aplasia of lower second premolars.

The present study aimed to determine whether routine orthodontic space closure can be successfully achieved in patients with unilateral aplasia of the lower second premolars without extracting contralateral or opposing teeth. The dental records and lateral cephalograms of 17 consecutively treated subjects (11 females, 6 males) aged between 14.8 and 19.3 years at the end of active treatment (mean 16.1 years) were analysed. The spaces were closed by 'push-and-pull' mechanics (PPM). Pre- and post-treatment data were compared using a Student's t-test. At the end of active treatment, all parameters (ANB, SNA, SNB, ML/NL, U1-NA, L1-NB, overbite and overjet, upper and lower midline, upper and lower space balance) presented mean values close to accepted norms with satisfactory standard deviations (SDs). Five indicators of success changed significantly: (1) Space closure in the aplastic region was achieved. (2) On the aplastic side, a mean mesial molar relationship of 1.12 (SD 0.18) cusp width (cw) was achieved. The mean alteration from pre- to post-treatment was 1.53 cw (SD 0.29, P

Wisdom tooth eruption secondary to localized lower molar mesialization in patients with aplastic lower second premolars.

OBJECTIVE: After localized space closure in the mandible it is desirable to preserve lower wisdom teeth as natural replacements for missing second premolars and as antagonists for upper second molars. The aim of this study was to determine whether this treatment method can obviate the need for prosthodontic restorations, implants, and third molar osteotomy. Furthermore the time point of possible third molar eruption was to be determined and whether further orthodontic interventions were required to achieve their alignment. PATIENTS AND METHODS: The test group comprised 34 patients who exhibited agenesis of one or both lower second premolars (n = 45) in conjunction with a corresponding number of third molar tooth germs. Follow-up examinations were performed 2 to 8 years after conclusion of orthodontic treatment involving push-and-pull mechanics (PPM) without extraction of any contralateral teeth. The results of the clinical retrospective follow-up examination at consecutive post-treatment endpoints were compared with two orthodontic control groups (A: 4-premolar extraction group, B: non-extraction group). RESULTS: After an average of 4 years and 2 months, the percentage of fully-erupted third molars in the agenesis group with localized space closure was 82%, compared to 29% and 28%, respectively, in the controls. These differences were statistically significant (p < or = 0.01). The success rate in the agenesis group reached 94% when the 4- to 8-year results were considered in isolation. Compared with the contralateral (non-aplastic) side, teeth on the aplastic side erupted prematurely. In 9% of the cases, minor orthodontic interventions were required to exactly position the third molars. CONCLUSION: There is high probability that mandibular third molars can be preserved after localized space closure, obviating the need for prosthodontic restorations, dental implants, and third molar osteotomies.

Assessing patient-specific decalcification risk in fixed orthodontic treatment and its impact on prophylactic procedures.

This longitudinal and prospective clinical study determined the decalcification rate during multibracket treatment (mean duration, 22 months) in 80 randomized, selected adolescents divided into 4 groups of 20 patients each. The study had 2 objectives. The first was to establish whether patient selection based on predefined caries risk indicators, ie, plaque index, approximal plaque index, D(3-4)MFT/d(3-4)mft index, initial lesions, and gingiva index, carried out before the start of treatment allows for valid predictions of the decalcification risk associated with multibracket treatment. The second objective was to determine whether an extended prophylaxis regimen, including regular mechanical tooth cleaning by a hygienist, scaling, and chlorhexidine treatment, as an adjunct to an initial prophylaxis introductory program consisting of patient motivation, oral hygiene checkups, and fluoridation, reduces or prevents decalcification more effectively than initial prophylaxis alone. The results showed that patient selection based on caries risk factors provides a simple and effective method for predicting the decalcification risk in multibracket treatment (P

Orthodontic space closure without counterbalancing extractions in patients with bilateral aplasia of the lower second premolars.

BACKGROUND: Orthodontic space closure in situations with bilateral aplastic lower second premolars without maxillary extractions is a rarely practiced treatment method. Due to the high risk of severe side effects, preference is currently given to the maintenance of deciduous second molars and subsequent prosthodontic solutions. As a combination of Class I push and Class II pull mechanics seemed likely to reduce secondary effects by transferring the anchorage site from the reactive lower anterior teeth to the more resistant upper arch, a clinical study was carried out in order to investigate effects and secondary effects of the mechanics. PATIENTS AND METHOD: Casts, panoramic radiographs and lateral headfilms of 13 consecutively treated, non-selected adolescents (seven boys, six girls, mean age at start of treatment 13 years 4 months) were evaluated. In six patients a Jasper Jumper trade mark was inserted in addition for a mean period of 6 months. RESULTS: The treatment outcome after a mean period of 3 years and 1 month showed in almost all cases the desired Class III molar occlusion of one cusp width (+/- 1/4 cw) with overbite and overjet within the normal range. Analyses of static and dynamic occlusion revealed anterior/canine protected articulation and a satisfactory number of centric contact points. A significant space gain (p