Heinrich Wehrbein

Mandibular incisors, alveolar bone, and symphysis afterorthodontic treatment. A retrospective study

The mandible of a deceased 19-year-old young woman who had been treated with an edgewise appliance was removed during autopsy. The overall tooth movements during the 19 months of treatment were reconstructed (treatment documents) and compared with the macroscopic, radiologic, and micromorphologic findings of the incisor/alveolar bone/symphysis complex of the dry mandible. The initial lateral cephalogram revealed an extremely narrow and high symphysis, with an incisor position straight above the thin bone. During treatment, the incisors had been moved to lingual (lingual root torque) and derotated. Morphologic evaluation of the dry mandible revealed lingual (oral) aspects of the roots reaching some millimeters out of the lingual alveolar bone and largely without cortical plate covering. Lateral dental contact radiographs of any bone/incisor segment showed the sagittal alveolar bone width to be smaller than the labiolingual (orobuccal) diameter of the incisor roots. A comparison of the approximate pretherapeutic alveolar bone height, which was assessed by measuring the distance from the cementoenamel junction to the most coronal margin of any root resorption in scanning electron microscopy, with that of the specimen showed a calculated bone loss on the lingual aspect extending from 2.3 to 6.9 mm. On the labial (buccal) aspect, bone loss was far less pronounced. These results suggest that in the case of a narrow and high symphysis, pronounced sagittal incisor movements and derotation during routine orthodontic treatment with a fixed appliance may be critical and lead to progressive bone loss of lingual and labial cortical plates.

Human histologic tissue response after long-term orthodontic tooth movement

UNLABELLED The maxilla of a deceased 19-year-old young woman who had been treated with an edgewise appliance was removed during autopsy. The specimen was prepared histologically in the horizontal plane. The type of tooth movement was reconstructed by comparing the treatment documents at outset (photograph of dental cast, radiograph) with the photograph and radiographs of the specimen. This permitted the histological findings to be correlated to the type of tooth movement. RESULTS the localization and extent of tissue changes at the roots depend on the type of tooth movement and the structure of the bone. In case of an atrophied alveolar bone in front of the tooth movement direction, a partial increase of osseous tissue may be induced by bone apposition in the subperiosteal layer. After tooth movement in the maxillary sinus region, however, bone resorption was found in the subperiosteal layer in front of the roots. The histologic findings are more pronounced than the radiographs would suggest. Histologically verified bony dehiscences or fenestrations in the facial or oral cortical plate could not be diagnosed by macroscopic inspection of the specimen.

Periodontal conditions after facial root tipping and palatal root torque of incisors

UNLABELLED The maxilla of a deceased 19-year-old young woman who had been treated with a fixed appliance was removed during autopsy. The sagittal movements of the incisors could be reconstructed by using the treatment records, which were also at our disposal. The anterior segment of the specimen was prepared histologically in the sagittal plane and stained with toluidine blue. RESULTS The tooth movements were executed in two phases: an uncontrolled tipping (root movement to vestibular) was followed by palatinal root torque. The histologic changes, induced by the palatinal root torque were (1) root resorption with apical slope from facioapical to orocoronal, and (2) pronounced subperiosteal bone apposition (palatinal) with partial protrusion of the cortical plate thinning toward coronal. No osseous perforations occurred. The extent and the localization of root resorptions were not verified in the orthoradial x-ray film of the specimen.

Biodegradable implants for orthodontic anchorage. A preliminary biomechanical study

The use of endosseous implants as temporary orthodontic anchoring elements has good results in many clinical applications. The development of a new orthodontic implant anchorage system comprising an implant produced of biodegradable polylactide with a metal superstructure is described. The presented bioresorbable implant anchor for orthodontics system (BIOS) implant is designed to provide orthodontic anchoring functions in adolescents and adult patients, and to then be resorbed without a foreign body reaction or signs of clinical inflammation. Shear strength and maximum vertical strength have been measured in biomechanical in vitro tests. BIOS fixtures can be loaded with horizontal shearing forces of 50 N with a mean deflection of 0.26 +/- 0.13 mm and mean vertical removal forces of 155 +/- 80 N. Clinical studies are currently being undertaken to evaluate clinical practicability and biocompatibility of the BIOS implants.

Success rate of second-generation palatal implants.

OBJECTIVE To analyze the clinical outcome of a prospective two-center study of second-generation palatal implants 6 months after functional loading. MATERIAL AND METHODS From 2005 to 2006, 30 patients aged 12 to 41 years were included in the study. In all patients, orthodontic treatment required stationary anchorage. The palatal implants (Straumann, Basel, Switzerland) were placed in the median region of the anterior palate. RESULTS All implants were initially stable at the time of placement. However, two (6.7%) were lost during the unloaded healing period. The remaining 28 (93.3%) were subjected to functional loading after a mean healing period of 12 weeks. Typical signs of slight superficial inflammation were observed in the peri-implant mucosa (n = 28). During the orthodontic loading phase, the implants were equipped with either a modified pendulum appliance for distalization or a transpalatal arch for stationary anchorage to the posterior teeth. No implant loosening or loss was registered during the active treatment period. CONCLUSIONS The failure rate of palatal implants of the second generation was low (6.7%). Slight inflammatory reactions of peri-implant tissue caused neither implant loss nor pain.

Innovative Anchorage Alternatives for Molar Distalization—an Overview*

The conventional anchorage design of an appliance for non-compliance molar distalization anchored exclusively intraorally combines an acrylic pad or button placed on the palatal mucosa with involvment of the anchoring-teeth’s periodontium. Disadvantages of this anchorage design include the difficulties it causes for proper oral hygiene, reactive forces and moments exerted on the anterior dentition, and relative contraindications based on certain dentition stages and local conditions.In this article we describe alternative anchorage designs, concentrating on types of anchorage that are applied with orthodontic anchoring implants of reduced diameter and length. Such implants offer several key advantages be yond that of facilitating proper hygiene, namely that they cause fewer or no side-effects in the anterior maxillary dentition area, and that a wider range of indications apply to children, adolescents and adults.ZusammenfassungDer konventionelle Verankerungsaufbau rein intraoral verankerter Apparaturen zur kooperationsunabhängigen Molarendistalisation im Oberkiefer erfolgt kombiniert in Form einer der palatinalen Schleimhaut anliegenden Kunststoffpelotte sowie über die Parodontien von Ankerzähnen. Nachteile dieser Verankerungsform sind eine eingeschränkte Hygienefähigkeit, reaktiv auf die anteriore Dentition wirkende Kräfte und Momente sowie relative, auf bestimmten Dentitionsstadien und Lokalbefunde beruhende Kontraindikationen.Der vorliegende Artikel beschreibt Verankerungsalternativen. Dabei stehen Verankerungsformen mit durchmesser- und längenreduzierten orthodontischen Verankerungsimplantaten im Vordergrund. Vorteilhaft zu werten sind neben einer besseren Hygienefähigkeit insbesondere geringere oder fehlende Nebenwirkungen auf die Oberkieferdentition im anterioren Bereich sowie ein erweiterter Indikationsbereich bei Kindern, Jugendlichen und Erwachsenen.

Vertical palatal bone dimensions on lateral cephalometry and cone-beam computed tomography: implications for palatal implant placement.

OBJECTIVES To evaluate the necessity of three-dimensional imaging (computed tomography [CT]/cone-beam computed tomography [CBCT]) for paramedian insertion of palatal implants. MATERIAL AND METHODS Lateral radiographs and CBCT scans were performed from 18 human skulls. For lateral cephalometry, the nasal floor (right/left) and the oral hard palate of all skulls were lined with a tin foil for contrast enhancement. The quantity of vertical bone as measured on lateral radiographs was compared with CBCT measurements obtained in median and parasagittal planes and at minimum bone height. Spearmans rank correlation coefficients were determined for bivariate correlation analysis. RESULTS The median palatal bone height on CBCT (mean 8.98 mm; standard deviation [SD] 3.4) was markedly higher than the vertical height seen on lateral radiographs (mean 6.6 mm; SD 3.2). Comparing lateral cephalometry with CBCT, the strongest association was observed at the minimum palatal bone height (r=0.926; P<0.001; Spearmans rank correlation coefficient). CONCLUSIONS Lateral radiographs allow accurate and adequate assessment of vertical bone before paramedian insertion of palatal implants. The vertical bone dimension as displayed on lateral cephalometry reflects the minimum bone height rather than maximum bone in the median plane. Therefore, a preoperative CT or CBCT is only indicated when the lateral cephalometry reveals a marginal quantity of bone.

Gingival invagination area after space closure: A histologic study

The aim of this study was to show the micromorphologic findings (epithelium, connective tissue, bone) in a region of pronounced gingival invagination after space closure by analyzing a maxilla taken in autopsy from a 19-year-old woman who was orthodontically treated. The dental records were also at our disposal. The second left premolar was congenitally absent. This area displayed before therapeutic horizontal bone atrophy. For space closure, the first upper left molar was moved mesially with a fixed appliance. After space closure, pronounced gingival invagination was diagnosed. The lateral segments of the specimen were prepared histologically in the horizontal plane. The microscopic observations revealed deep epithelial proliferation, hyperkeratinization, and one isolated keratin pearl in the connective tissue. Irrespective of location, the broad connective tissue layer showed disparate characteristics. Cell-rich, loose connective tissue with low fiber density were dominant in the subepithelial layer. The epiperiosteal layer displayed multiple tough fibers, some running parallel, some with reticular meshing, permeated with many blood vessels. Very few inflammatory cells were detected in the soft tissue. The bone had been resorbed in the mesiopalatal area of the molar (tooth movement direction) apart from one small isolated bony islet. These observations suggest that inflammatory influences were unlikely for marginal bone loss mesiopalatal to the tooth.

Distal movement of premolars to provide posterior abutments for missing molars

In 24 patients with missing molar teeth in the upper and/or in the lower jaw, 32 premolars were distalized. The mean orthodontic distalizing distance was 9.4 mm (SD 2.6). After distalization all these teeth served as posterior abutments for fixed restorations. The investigation period ranged between 2.5 to 14.1 years, average 9.6 years (SD 3.2). The clinical examination criteria were sensitivity, mobility, probing depth, sulcus bleeding index; the radiologic criteria were root resorption (lateral and apical) marginal bone level and axial position. None of the 32 premolar abutments were lost during investigation period. All the teeth maintained their vitality. The measured probing depths and sulcus bleeding indices were low. Of the teeth tested 40.6% revealed localized lateral root resorption on the pressure side; the average postorthodontic depth of root resorption was 0.7 mm (SD 0.3), and the length 2.3 mm (SD 0.6). The follow-up examination revealed a partial repair of the lateral root lesions. The extent of apical root resorption amounted to 0.9 mm (SD 1.1). The marginal bone level showed a bone loss of 0.5 mm mesially and 0.2 mm distally. The findings confirm that the distalized premolar functioning as a posterior bridge abutment represents a prognostically favorable alternative to an implant.

Apical root resorption during orthodontic treatment with aligners? A retrospective radiometric study

IntroductionObjective of this study was to investigate the incidence and severity of apical root resorptions (ARR) during orthodontic treatment with aligners.Materials and methodsThe sample comprised 100 patients (17–75 years of age) with a class I occlusion and anterior crowding before treatment, treated exclusively with aligners (Invisalign®, Align Technologies, Santa Clara, CA, USA). The following teeth were assessed: upper and lower anterior teeth and first molars. Root and crown lengths of a total of 1600 teeth were measured twice in pre- and post-treatment panoramic radiographs. Afterwards, relative changes of the root length during treatment were calculated by a root-crown-ratio taking pre- and post-treatment root and crown lengths into consideration. A reduction of this ratio was considered as a shortening of the initial root length. Additionally, tooth movements of the front teeth were assessed by lateral cephalograms and the 3-dimensonal set up of each patient.ResultsAll patients had a reduction of the pre-treatment root length with a minimum of two teeth. On average 7.36 teeth per patient were affected. 54% of 1600 measured teeth showed no measurable root reduction. A reduction of >0%-10% of the pre-treatment root length was found in 27.75%, a distinct reduction of >10%-20% in 11.94%. 6.31% of all teeth were affected with a considerable reduction of >20%. We found no statistically significant correlation between relative root length changes and the individual tooth, gender, age or sagittal and vertical orthodontic tooth movement; except for extrusion of upper front teeth, which was considered as not clinical relevant due to the small amount of mean 4% ARR.ConclusionsThe present study is the first analyzing ARR in patients with a fully implemented orthodontic treatment with aligners (i.e. resolving anterior crowding). The variety was high and no clinical relevant influence factor could be detected. A minimum of two teeth with a root length reduction was found in every patient. On average, 7.36 teeth per patient were affected.