Orthodontic load on short maxillary implants with reduced sink depth: an experimental study.

OBJECTIVE: The aim of this study was to investigate experimentally the positional stability and histomorphometric findings of length-reduced temporary anchorage devices (Orthosystem, length: 4 mm) with reduced sink depth. MATERIAL AND METHODS: For this purpose, four maxillary pre-molars ((2)P(2), (3)P(3)) were extracted from each of four foxhounds. After a 16-week alveolar healing period, 16 implants (four per dog) were inserted into the edentulous areas. Four implants (one per dog) were placed simultaneously in the mid-palatal area. The implants were intentionally submerged to about three-quarters of their length. After a 10-week unloaded implant healing period, the implants in the P3 areas and the palate were loaded (test implants) by means of transpalatal bars fixed on the implants in the P3 areas and Sentalloy traction springs ( approximately 2 N continuous force) inserted mid-sagittally between palatal implants and bars (force application period: 24 weeks). The implants in the P2 areas served as controls. RESULTS: Clinical measurements and histological evaluation revealed positional stability of the loaded fixtures. Alveolar control implants (ACI) were inserted to a mean depth of 3.2 mm, alveolar test implants (ATI) to 3.3 mm and palatal test implants (PTI) to 2.6 mm. The mean direct bone contact percentage values were 71.3% (ACI), 79.6% (ATI) and 72.2% (PTI). CONCLUSION: These results suggest that, probably due to the relatively high percentage of bone contact with implant surface, only 3 mm of intrabony implant length is sufficient to retain positional stability during long-term orthodontic loading.

Effects of orthodontic treatment with fixed functional orthopaedic appliances on the condyle-fossa relationship in the temporomandibular joint: a magnetic resonance imaging study (Part I).

OBJECTIVES: This study aimed to verify the effects that corrective treatment for skeletal Class II malocclusions with fixed functional orthopaedic appliances has on the positions of the condyle within the glenoid fossa. METHODS: Orthodontic treatment progress was monitored in 20 patients by magnetic resonance imaging (MRI) at four defined points in time. Metric analysis of the temporomandibular joints was performed on the central slices of the images obtained in the closed-mouth position. To assess the positional relationship between condyle and fossa, the width of the joint spaces was measured. To compensate for individual variation of the condyle sizes, the Joint Space Index was calculated. The displacement of the condyle from the fossa was measured in the ventral and in the caudal dimension and the effective condyle reposition was computed. RESULTS: Upon adoption of the therapeutic position, the condyles were displaced from the centric position within the fossa toward caudal and ventral. At the end of treatment, they returned to their original position. No significant differences compared with initial findings were found in the width of the anterior or posterior joint spaces. CONCLUSION: For patients who received functional orthopaedic treatment for skeletal Class II correction with a fixed functional appliance, reduction to a physiological condyle-fossa relationship occurred bilaterally in the region of the joints. Our study suggests that the improved dental occlusion was not achieved at the price of a change to an unphysiological position in the temporomandibular joints.

Effects of orthodontic treatment with fixed functional orthopaedic appliances on the disc-condyle relationship in the temporomandibular joint: a magnetic resonance imaging study (Part II).

OBJECTIVES: This study aimed to verify the effects that corrective treatment for skeletal Class II malocclusions with fixed functional orthopaedic appliances has on the relative positions of the articular disc and the mandibular condyle. METHODS: Orthodontic treatment progress was monitored in 20 patients by magnetic resonance imaging (MRI) at four defined points in time. Visual inspection of the temporomandibular joints (TMJs) was performed on three slices each (lateral, central, medial) of closed-mouth and maximum-open parasagittal MRI. Metric analysis was performed on the central slices of the images obtained in the closed-mouth position. To assess the positional relationship in the sagittal dimension between the articular disc and the mandibular condyle, both methods were used. RESULTS: The comparison of pre-treatment and post-treatment findings revealed in none of the joints that the disc-condyle relationship had been adversely affected as a consequence of the treatment. Rather, the outcome was an improved relationship in a total of eight joints. After groups of joints had been defined by disc position, metric analysis revealed a significantly improved positional relationship in those joints in which an anterior disc displacement had been found initially. CONCLUSION: Orthodontic treatment with a rigid, fixed functional appliance to correct skeletal distoclusion results in the following side effects on the disc-condyle relationship in the TMJ: the treatment does not have adverse effects on initially physiological disc-condyle relationships; in TMJs with initial partial or total anterior disc displacement, improved disc position can be achieved.

Conditioning of enamel with Nd:YAG and CO2 dental laser systems and with phosphoric acid. An in-vitro comparison of the tensile bond strength and the morphology of the enamel surface.

UNLABELLED: MATERIAL AND METHOD 1: The first stage of a three-stage in-vitro investigation used 146 maxillary incisors to identify optimum setting parameters for two CO2 and Nd:YAG standard laser systems applied in enamel conditioning for bracket bonding. RESULTS: 31 of the 75 parameter combinations investigated for the Nd:YAG laser and nine of the 71 investigated for the CO2 laser proved appropriate for further investigation of tensile strength. MATERIAL AND METHOD 2: In a second stage, tensile bond strength for the selected laser settings was determined in comparison to the conventional acid-etch technique for a further 210 teeth as the control group. RESULTS: The highest average tensile strength for the Nd:YAG laser was 4.1 MPa, with comparable values of 3.3 MPa for the CO2 Laser and 4.9 MPa for the acid-etch technique. MATERIAL AND METHOD 3: The third stage of the investigation involved comparative scanning electron microscopy of enamel surface morphology following laser application and acid-etching. RESULTS: The CO2 laser was found to produce craters of various dimensions, while the Nd:YAG laser produced honeycomb structures regionally similar to enamel samples from the acid-etch technique. CONCLUSION: The CO2 and Nd:YAG dental lasers tested produce enamel conditioning and tensile bond strength sufficient to meet the requirements of bracket bonding.

Orthodontic tooth movement in the mixed dentition. Histological study of a human specimen.

MATERIAL AND METHOD: We present a retrospective analysis of periodontal tissue reactions and clinically relevant phases of permanent tooth eruption and deciduous tooth resorption after half a year of orthodontic tooth movement in the upper and lower jaw of a deceased male (age 9 years 3 months). Specimens of the horizontal plane (lower jaw) and sagittal plane (upper jaw) were prepared by the ground microsection technique without prior decalcification. RESULTS: Histologically, reactions in the periodontal ligament presented as characteristic appositional/resorptive metaplastic processes in the areas of tension and pressure, with side effects such as root resorption and periodontal necrosis being only minor. In the upper jaw, an erupting permanent canine was closely associated with the tooth germ of the first premolar. Resorptive follicle activity had resulted in extensive erosion of the interradicular bone and root resorption in the area of the first premolars. CONCLUSION: These findings suggest that it might prove useful to take critical topographic findings as parameters for differential therapeutic decisions. Follicle-driven deciduous tooth resorption presenting partly as resorption lacunae and partly with linear characteristics was accompanied by resorptive/appositional remodeling of the alveolar socket as well as regressive changes in the supracrestal fibers of the marginal gingiva.

Self-etching primers--an alternative to the conventional acid etch technique?

MATERIAL AND METHODS: The aim of the present in vitro study was to evaluate the bonding capacity of three self-etching primers (Clearfil SE Bond [SE], Clearfil Liner Bond 2V [CLB], Novabond [NOVA]) to enamel. Two adhesive systems with a separate phosphoric acid etching procedure (Gluma Comfort Bond [GLU], Kurasper F [KU]) served as controls. 60 human incisors were used to evaluate shear bond strengths of composite cylinders to enamel. RESULTS: Significant differences were found between the groups (p < 0.001). The mean value for groups GLU, KU, CLB and SE was 24 MPa. The shear bond strength recorded for the Novabond system was significantly lower (17 MPa). CONCLUSION: The results of the present investigation indicate that enamel bonding especially with the self-etching primers CLB and SE is as effective as conventional phosphoric acid etching.

Effects of orthodontic bands on marginal periodontal tissues. A histologic study on two human specimens.

Eight banded teeth on two human specimens (9 years, male; 19 years, female) were analyzed regarding the fit of the orthodontic bands and periodontal reactions. Five teeth (three molars, two premolars) were evaluated histologically in the horizontal plane and three (one molar, two premolars) in the sagittal plane using the micro-section method according to Donath. The fit of the bands varied in occluso-apical direction. The mean of marginal gaps was x = 0.23 mm in the occlusal, x = 0.03 mm in the equatorial, and x = 0.28 mm in the cervical area. In the equatorial area the thin cement layer was largely homogeneous, whereas porosities and microfissures were found predominantly in thicker cement layers. 85% of the occlusal and cervical band margins revealed cement defects and/or erosions which were colonized by felted, partially densely compacted microbial plaque. With regard to the periodontal effects, the signs of inflammation in the buccolingual gingival areas were markedly less severe due to the supramarginal position of the band margins. The interdental gingiva of all teeth presented the histological pattern of an established gingival lesion. Leukocyte infiltration and inflammatory exudation in the area of the transseptal fibers were exceptionally pronounced in one lower molar (band exposure time: 6 months). At this site the connective tissue attachment close to the cementoenamel junction was severely damaged on the mesial surface and the pocket epithelium proliferated towards the apex, meaning progression from established gingivitis to an initial periodontal lesion. The histologic findings on these human periodontal tissues confirm that the application and hygiene control of orthodontic bands have to be performed with great care to avoid permanent periodontal destruction.

Preparation of autogenous bone grafts in two different bone mills.

The purpose of this study was to evaluate the performance of two bone mills (R Quetin Bone Mill and Micro Knochenmühle, Aesculap) for the grinding of autogenous bone (intraoral, cortical) according to the following criteria: (1) loss of bone during the grinding process, (2) particle size of the chips, (3) variability in chip size, (4) technical handling, and (5) cost-benefit ratio. The amount of material loss was determined by harvesting 30 bone cores from the mandibular symphysis of a pig. Each specimen was weighed before and after the grinding procedure on scales with an accuracy of 0.1 mg. The size and variability of the bone particles were determined histomorphometrically. Twenty-seven bone specimens from different patients were analyzed. Eight were ground with the Aesculap and 12 with the Quetin mill. Seven specimens harvested with a Brånemark implant bur served as controls. A histologic section was prepared from each specimen, and 10 bone particles per section were subjected to histomorphometric analysis. The Quetin mill was superior in all points to the Aesculap mill for the requirements of a periodontal practice.

Mesio-marginal findings at tilted molars. A histological-histomorphometric study.

The aim of this study was to investigate the mesio-marginal findings at tilted molars (TM) by means of histological-histomorphometric evaluation. Eight lateral tooth bone segments with TM (six mandibular, two maxillary) from males aged 20-32 years were compared with those of eight samples with non-tilted molars (NTM) in males aged 18-35 years. In comparison with the NTM samples, the TM revealed a higher amount of supra- and subgingival plaque, a significantly higher total number of inflammatory cells (P < 0.05) and blood vessels (P < 0.05) in the connective tissue adjacent to the junctional epithelium, and a lower density and corono-apical width of gingival fibres. No significant differences (P > 0.05) were found between the mesio-marginal bone level of the TM (mean: 978 microns) and that of the NTM (mean: 1222 microns). In contrast, indications were found that TM may affect the disto-marginal bone level of the mesial tooth.

Perioperative progress check of interdental forces following extraction of the third molars. A prospective long-term study.

With the aim of checking the progress of mesially directed forces in a complete dental arch, we measured the interdental frictional forces in a population of 44 patients with erupting maxillary and mandibular third molars. The measurements were taken preoperatively and postoperatively 1, 2, 3, 7, and 12 weeks and also 1 year after extraction or surgical removal of the third molars in all 4 quadrants. In addition, the interdental frictional forces of a total of 40 test persons in 3 control groups were similarly measured in a state of inertia, after a period of 1 hour spent in supine position, and after a 5-minute period of chewing activity. Over the first 4 to 12 weeks the interdental forces showed a significant postoperative average decrease of 16.1% in the maxilla and 18.0% in the mandible. After 1 year the average reduction in the level of interdental forces in the patient population was 10.3% in the maxilla and 10.9% in the mandible. A significant postoperative reduction in force of 40.7% was registered for third molars with a mesial angle of 66 degrees to 90 degrees to the tooth axis of the second molar in the mandible. Following a 1-year control period, the level of interdental force in the patient population was found to be on average 27.4% below the preoperative baseline value. In control group I, the margin of fluctuation of interdental forces in a state of inertia was +/- 3.5% over a 3-month period. In control group II, a significant average decrease in interdental forces was measured in the maxilla (15.1%) and mandible (13.2%) following a 1-hour period in supine position. In control group III, a non-significant average reduction in interdental forces was established in the maxilla (7.8%) and mandible (8.6%) following a 5-minute period of chewing activity.

Modified pendulum appliance including distal screw and uprighting activation for non-compliance therapy of Class-II malocclusion in children and adolescents.

In present-day orthodontics there is an increasing call for therapeutic procedures and appliances allowing those delivering the treatment maximum independence from patient cooperation. This requires both the development of new therapeutic appliances and the optimization of existing ones (via modification). The present study aims to analyze the therapeutic outcomes obtained by using a pendulum appliance (distal screw and integrated molar uprighting activation), modified and independent of patient cooperation. The dentoalveolar and skeletal outcomes and secondary outcomes were observed in 50 children and adolescents. The dentoalveolar outcomes were as follows: 72.5% of the clinically visible increase in space were gained by distal molar movement and 27.5% by mesialization of the anterior segment. The molars showed slight distal tipping and extrusion, while the incisors showed slight labial tipping. In terms of time, the molars were moved distally by an average of 0.67 mm per month. Skeletal changes taking place during treatment using the pendulum appliance are negligible. Further advantages of the pendulum appliance are independence from patient cooperation and good acceptance by patients.

Periodontal relevance of anterior crowding.

The periodontal relevance of anterior and posterior crowding concerns 3 main aspects: 1. oral hygiene/plaque retention, 2. altered topography of gingiva, septum and orofacial alveolar bone and 3. periodontal therapy (scaling, root planing, regenerative approaches). These aspects are discussed with regard to the literature and to the author's own clinical and histological findings. Present-day knowledge suggests that the following positive periodontal effects can be expected from correction of orthodontic crowding: better access for oral hygiene, improved morphology of soft and hard periodontal tissues; future research has to substantiate the value of this benefit, simplified mechanical and surgical therapy (scaling, root planing, curettage), more favorable conditions for periodontal regeneration.

Fixed lingual arch appliance for compliance-free unilateral molar distalization in the mandible. Three case studies.

An asymmetrically activated lingual arch appliance enables rapid, unilateral molar distalization in the mandible without active patient compliance. Using the segmented arch technique, the biomechanics involve only the tooth moved, in accordance with the 2-tooth concept, with a large, multi-rooted tooth segment acting as an anchoring unit. The anchorage system requires no maxillary involvement.

Osteodynamics around orthodontically loaded short maxillary implants. An experimental pilot study.

The aim of this study was to investigate experimentally the effect of long-term orthodontic loading on the activity and location of osteodynamic changes around short titanium screw implants. For this purpose 6 maxillary premolars (1P1, 2P2, 3P3) were extracted from each of 2 foxhounds. After a 16-week healing period, 8 implants (4 per dog) were inserted in the edentulous areas. Simultaneously 2 implants (1 per dog) were positioned in the palatal suture. After an 8-week implant healing period the fixtures in the P1/P2 areas (n = 4) and the palate (n = 2) were loaded (test implants) by means of Sentalloy traction springs (approximately 2 N continuous force). The fixtures in the P2/P3 areas served as controls (n = 4). The osteodynamic changes during the force application period (26 weeks) were recorded with bone labeling fluorochromes. Histological evaluation revealed a tendency towards higher remodeling activity within the peri-implant bone (up to 500 microns from the implant surface) of the loaded compared with the unloaded sample. This higher activity was found on both sides facing the loading direction as well as on the opposite sides. Furthermore, within the bone adjacent to the marginal halves of the implants on the loading direction sides, this higher remodeling activity extended more than 1000 microns from the respective implant surfaces. The results suggest that long-term orthodontic loading of short maxillary implants may increase the remodeling activity within the peri-implant bone.

Palatal implant anchorage reinforcement of posterior teeth: A prospective study.

A new orthodontic implant anchor system (Orthosystem) has been developed. This 1-piece device made from titanium consists of a screw-type endosseous section (lengths of 4 and 6 mm), a cylindrical transmucosal neck, and an abutment. Clamp caps with slots provide for attachment of square orthodontic wires (transpalatal bars) to the implant. The aim of the present prospective study was to evaluate the anchorage capacity of palatally inserted Orthosystem implants for anchorage reinforcement of posterior teeth. The sample consisted of 9 dental Class II patients (age 15 to 35 years) whose treatment plan included extraction of the maxillary first premolars. Each of the patients received 1 implant inserted into the center of the anterior palate. After a mean unloaded implant healing period of 3 months, transpalatal bars were inserted to connect the posterior teeth to the implant. Retraction of the canines and incisors was accomplished without the use of compliance-dependent headgear or Class II elastics. The degree of anchorage loss as well as the amount of canine and incisor retraction were evaluated by measurements of the casts and lateral cephalograms. The mean anchorage loss was 0.7 mm on the right side and 1.1 mm on the left (P <.05). The right and left canines were retracted 6.6 and 6.4 mm, respectively, and the mean overjet reduction was 6.2 mm. Because clinical assessment and postremoval histologic assessment both revealed stability of the short implant, the small anchorage loss was most likely from the deformation of the transpalatal bars by the orthodontic forces. Nevertheless, the treatment goal was achieved in all patients without the use of compliance-dependent auxiliaries. The clinical experience during and after implant insertion, active orthodontic treatment, retrieval of the implant, and subsequent wound healing are described.

Palatal bone support for orthodontic implant anchorage--a clinical and radiological study.

When maximal anchorage is required during orthodontic treatment, additional aids are often needed to support the anchoring teeth. While intra-oral aids may be limited in their anchorage potential, extra-oral anchoring aids are often rejected by the patients. Endosseous implants may therefore be a valuable alternative for stable intra-oral anchorage. However, the possibility of using conventional implants is insufficient, e.g. for treating purely orthodontic patients with full dentition or where extraction sites are to be closed. Therefore, the mid-sagittal area of the palate is an alternative insertion site for the placement of implants for orthodontic anchorage. The limited bone height in this area inspired this comparison between bone thickness in the implantation site as verified by probing during the implantation of Straumann Ortho-system implants, and thickness as measured on the lateral cephalogram. The results suggest that vertical bone support is at least 2 mm higher than apparent on the cephalogram. In none of 12 patients was a perforation to the nasal cavity found. However, in five subjects the implant projected into the nasal cavity on the post-operative cephalogram. These results were supported by the study of the projections of palate and wires in wire-marked skulls where the wires were placed bilaterally on the nasal floor and on the nasal crest. It is therefore concluded that the mid-sagittal area of the palate lends sufficient bony support for the implantation of small implants (4-6 mm endosseous length, diameter 3.3 mm).

Measuring system for in vivo recording of force systems in orthodontic treatment-concept and analysis of accuracy.

The aim of our developments is three-dimensional in vivo recording of those orthodontic force systems inducing tooth movements during treatment with fixed appliances. The concept presented here is the first to permit the forces and torques of these statically multiply undetermined systems to be recorded in vivo. For this purpose the force systems transmitted to the teeth from the archwire are isolated from the respective tooth by means of divisible special-design brackets and introduced into a 3D force torque sensor via a gripping appliance. The sensor is fixed with a purpose-developed device relative to the patient's dental arch. The patient's head is positioned relative to the system by means of a bite fork as well as a forehead and chin support. Electrical measurement of the mechanical quantities is carried out by a six-axis force torque sensor with semiconductor strain gauge elements, an electronical evaluator and a mobile measuring computer (PC). Extensive calibration of the sensor system has shown that the measuring uncertainty of the electrical measuring is less than 2%. Precise spatial fixing of bracket slot and archwire in the therapeutic position is crucial to the measuring accuracy of the system, as even minimum displacements affect the force system to be measured. Movements of the measuring system up to 0.04 mm result from a therapeutic force of 1.5 N. The results of extensive in vitro studies have already demonstrated that the system developed by us is suitable for the specified in vivo measuring function.

The eleventh hour or where are our orthodontic limits? Case report.

It is illustrated in a patient with periodontal attachment loss up to the apical root third that a combined periodontal/orthodontic approach may be beneficial even in seemingly hopeless cases. The problems of orthodontic limits and the positive effects of guided tissue regeneration are discussed.