Satellite cell capacity for functional adaptation of masseter muscle in Class II and Class III patients after orthognathic surgery-a pilot study

AIM

The aim of the prospective pilot study was to analyze the biomarkers CD34, Pax7, Myf5, and MyoD for stimulation of satellite cells (SCs), which are responsible for functional adaptation.

SUBJECTS AND METHODS

Forty-five Caucasian patients were consecutively recruited from the Maxillo-Facial-Surgery at TU Dresden. Eleven orthognathic Class III patients, 24 Class II patients, and 10 controls with Class I were involved in the study. Tissue samples from masseter muscle were taken from the patients pre-surgically (T1) and 7 months later (T2). Samples from controls were taken during the extraction of third molars in the mandible. Polymerase chain reaction (PCR) for relative quantification of gene expression was calculated with the delta delta cycle threshold (ΔΔCT) method.

RESULTS

The results show significant differences for the marker of SC stimulation between the controls, the patient groups, males, and females. The gene expression of CD34 was post-surgically upregulated for Class III (0.35-0.77, standard deviation [SD] = 0.39, P < 0.05) in comparison with controls. For Pax7, there was a significant difference shown between the retrognathic and the prognathic group because of downregulation in Class II patients (1.64-0.76, SD = 0.55, P < 0.05). In Class III patients, there was a significant upregulation for Myf5 (0.56-1.05, SD = 0.52, P < 0.05) after surgery too.

CONCLUSIONS

The significant decline of Pax7 in Class II patients indicates a deficiency of stimulated SC post-surgically. The expression of CD34 and Myf5 in Class II stayed unchanged. In contrast, there was an upregulation for all Class III patients, mainly in females, shown post-surgically. This may be one reason for weak functional adaptation and relapse in Class II patients.

Notch expression profile and satellite cell stimulation in masseter muscle before and after orthognathic surgery

The aim of this prospective study was to compare the expression of the Notch receptor family with the biomarker for stimulation of satellite cells (SC), which are responsible for functional adaptation. Tissue samples from the masseter muscle were taken presurgically and 7 months later. Samples from controls came from the extraction of third molars. The expression of Notch 1 to 4 and the satellite cell markers CD34, Pax7, and MyoD1 were investigated. PCR was used for relative quantification of gene expression, which was calculated with the ΔΔC_T method. The study involved 38 white patients - 10 prognathic, 18 retrognathic, and 10 orthognathic controls. The median value for Notch 1 was significantly reduced presurgically for prognathic (0.46, SD 0.45) and retrognathic (0.57, SD 0.35) patients compared with the controls. Postsurgically, Notch 2 was significantly upregulated in the prognathic group (0.55, SD 0.28/1.37, SD 0.85). Similarly, there was upregulation of Notch 3 in the prognathic group (0.33, SD 0.42/0.59, SD 1.37) and downregulation in retrognathic patients (0.59, SD 0.79/0.52, SD 0.97). Upregulations for the satellite cell markers CD34 and Pax7 were also found in prognathic patients. The significant upregulation of Notch 1-3 and CD34 in prognathics, but unchanged MyoD expression, signals high stimulation for SC and maintenance of the regeneration cell pool. A lower expression of Notch and SC in retrognathic patients could be responsible for weak functional adaptation.

Long term skeletal and dental changes between tooth-anchored versus Dresden bone-anchored rapid maxillary expansion using CBCT images in adolescents: Randomized clinical trial

OBJECTIVE

The aim of this study was to determine long-term skeletal and dental changes in tooth-anchored versus Dresden bone-anchored rapid maxillary expansion using CBCT images in adolescents.

MATERIALS AND METHODS

In all, 29 adolescent patients (11-17 years of age) needing skeletal expansion were randomly allocated to two different groups treated by either a Dresden bone-anchored expander or a conventional hyrax expander. Patients included did not have previous orthodontic treatment, were non-syndromic and had all teeth present in mouth. CBCT images were taken before expansion and two or more years after expansion. An independent T-test was used to determine the statistical significance between treatment groups and paired T-test was used to compare the results before and after expansion in each group.

RESULTS

Neither treatment group showed overall long-term different skeletal and dental changes in the transverse, anterior-posterior and vertical planes (P<0.05). Both treatment groups showed mild asymmetric skeletal expansion, but these were clinically insignificant.

CONCLUSIONS

Both expanders had similar skeletal and dental results. The greatest changes were in the transverse plane. Changes in vertical and anterior-posterior were negligible.

Predictive values of resonance frequency analysis as a diagnostic tool in palatal implant loss

OBJECTIVES

To determine the diagnostic value of resonance frequency analysis (RFA) in predicting palatal implant (PI) loss.

MATERIALS AND METHODS

RFA values of 32 patients (study center at Mainz and Dresden) were evaluated in a prospective randomized controlled trial addressing clinical performance of two loading concepts on PI (Orthosystem, Straumann, Basel, Switzerland). Group 1: conventional loading after a 12-week healing period vs group 2: immediate loading within one week after insertion. Stability was assessed by RFA after surgical insertion (T1), one week (T2), and 12 weeks (T3) later.

RESULTS

All 32 PI were clinically stable after surgical insertion; 14 PI were loaded conventionally and 18 immediately. One implant in group 1 was lost 6 weeks after insertion. One drop-out was registered in group 2. One false positive and three false negative implant stability quotients (ISQ) were observed. ISQ values of clinically stable PI in group 1 were 67.2 (SD ± 9.5) at T1, 62.3 (SD ± 11.7) at T2, and 68.2 (SD ± 5.5) at T3. Group 2 showed 67.1 (SD ± 11.7) at T1, 65.4 (SD ± 10.4) at T2, and 72.3 (SD ± 5.6) at T3. Differences between groups were not statistically significant for starting time (P = .88) and change from T1 to T2: 0.08 but were significant from T1 to T3: P = .04; (regression analysis).

CONCLUSIONS

RFA had no sensitivity for prediction of stability. General decrease after primary stability and increase with secondary stability gives support for specificity. Within the limits of the study, only the diagnostic value of RFA identifying stable palatal implants could be confirmed.

Genetic response in masseter muscle after orthognathic surgery in comparison with healthy controls - A Microarray study

One third of adult patients with orthognathic surgery of a prognathic or retrognathic mandible show relapse. The sagittal split osteotomy of the mandible leads to a displacement of both parts up to 10 mm without any changes of muscle attachment. Changed mandible length needs adaptation of muscle capacity because of changed force to moment ratio. The aim of this Microarray study was to analyze the general genetic response of masseter muscle in patients with retrognathism or prognathism of the mandible six months after surgery in comparison with healthy untreated controls. We found in tissue samples from masseter muscle a reduction of different entities between patients and controls but less in retrognathic than in prognathic patients (274/429). The different entities to controls in prognathia were reduced from 1862 to 1749 but increased in retrognathia from 1070 to 1563. We have to consider that the total amount of different entities to the controls is higher in patients with prognathic mandible (7364) because of their strong genetic controlled development compared with that in patients with retrognathic mandible (4126), which is more environmentally influenced. It can be concluded that function follows form after surgical change with high inheritance. In retrognathic patients the adaptation could be delayed or the capacity of regeneration potential is not sufficient.

Harmonisation of Dental Education in Europe - a survey about 15 years after visitation of dental schools participating in the DentEd project

INTRODUCTION

The DentEd Thematic Networks (TNP) were funded from the EU to converge and harmonise the dental curricula. Forty-four dental schools participated in this visitation process between 1998 and 2002. The aim of the survey was to evaluate the implementation of the Dented outcomes in the curricula and if the concept of core competences are integrated in the curriculum.

MATERIAL AND METHOD

In October 2012, questionnaires were sent out to all dental schools participated in the visitation process of Dented and Dented evolves. The main question blocs were as follows: structure of the curriculum and facilities, education of students, content and quality of education, assessment, research, European involvement and value of visit for the school.

RESULTS

Twenty-five dental schools (57%) answered to the questionnaire. The responder represented 20 European countries of 22, whose schools were involved (91%). The self-assessment report was stimulating the continuation of curriculum improvement. Most of them acknowledge that major competences are essential outcome for the graduated dentist. Twelve schools (58%) rated the value of the DentEd visit with strong positive influence.

DISCUSSION

The visits showed strengths, weaknesses and threats. Three-quarter of all schools implemented the European Credit Transfer System (ECTS). But most of them did not realize the unit of ECTS with modules among the Bologna process.

CONCLUSION

The self-assessment report was a core issue for the continuation of curriculum improvement. The challenge for the ongoing curriculum improvement is the implementation of the module system among the Bologna recommendations.

X-ray Microanalysis of Elements in the Masticatory Muscle after Paresis of the Right Masseter

Muscle activity and function appear to be related to ionic concentrations in the muscle. We investigated whether muscle paresis induced by injection of Botulinum toxin A (Botox) in 16-week-old pigs over a 56-day period is associated with ionic changes in the affected muscles. Tissue samples were taken from the masseter, temporalis, medial pterygoid, and geniohyoid muscles by a standardized method and used for energy-dispersive x-ray microanalysis in an environmental scanning electron microscope. The largest increase in Na+ was measured in the right and left sides of the masseter muscle in treated animals. Additionally, a significant elevation of Na+ was measured in the anterior part of the temporalis muscle and in the pterygoid muscle (P < 0.05). In temporalis and pterygoid muscles, an increase in sulfur in both sides of treated pigs’ heads was observed. Botox® has an indirect impact on ion concentrations, resulting in changes in muscle functional capacity and adaptive compensation of paretic muscle function by other muscles.

Extractions as a form of interception in the developing dentition: a randomized controlled trial

OBJECTIVE

To determine if the extractions of lower primary canines are an effective procedure to relieve crowding of the labial segment.

STUDY DESIGN

randomized controlled trial. Subject sample: 83 cases were collected in clinics in Italy, Germany and Wales. The groups were followed over a 2-year period.

METHODS

Subjects were randomly allocated to a primary canine non-extraction or extraction group. Dental casts of the patients were collected at the start and at the recall period of the trial. The outcome measures recorded were lower incisor crowding, arch length, intermolar width, overbite, overjet, lower clinical crown heights and lower incisor inclinations.

STATISTICS

The Mann-Whitney test was used to compare the differences between the extraction and non-extraction groups.

RESULTS

In both groups, crowding reduced 1.27 mm in the non-extraction group and 6.03 mm in the extraction group. The difference between the 2 groups was 4.76 mm (P<0.05). The arch perimeter decreased more in the extraction group by 2.73 mm (P<0.05). As the incisor inclination stayed essentially the same, the loss in arch length was attributed to the molars moving forward. The net gain from extracting deciduous canines was 2.03 mm.

CONCLUSIONS

There was a reduction in lower incisor crowding as a result of lower primary canine extraction. However, arch perimeter decreased more in the extraction group leaving less space for the eruption of the lower secondary canines.

A ³¹P-magnet resonance spectroscopy study on the metabolism of human masseter in individuals with different vertical facial pattern

OBJECTIVE

The objective of this study was to investigate differences in masseter metabolism by (31)P-Chemical Shift Imaging (CSI) in adult individuals with different vertical facial patterns. The clinical study should be supported by functional findings at the mRNA level after orthognathic surgery.

STUDY DESIGN

Twenty-two male volunteers (mean age 24.6) were divided into a deep-bite (NL/ML 11.8 ± 2.3°) and open-bite group (NL/ML 34.1 ± 2.6°). Vertical jaw relationship, gonial angle, and masseter volume were defined and compared with the phosphate values obtained from the (31)P spectra. Student t test and regression analysis were used.

RESULTS

Phosphocreatine related strongly to muscle volume (P < .001), gonial angle (P < .001), and ML/NL angle (P < .01). Pi was found to be related to gonial angle (P < .05). Muscle volume was found to be inversely related to ML/NL (P < .01) and to the gonial angle (P < .01).

CONCLUSIONS

A difference in masseter muscle metabolism between long- and short-faced subjects was confirmed at rest position.

[German dental and postgraduate education in the European context]

The dental curriculum in Germany is still based on a concept from 1955 with some revisions in certain aspects. All groups involved are interested in a new and more current version. In doing this, the compatibility with European concepts should be a main goal. The Association for Dental Education in Europe (ADEE), to which about 160 of the 200 European dental education associations are members, is in charge of coordinating projects to create a network of European universities, which intends to harmonize higher education in Europe and to create a core curriculum for the dentistry program. Based on a visitation and evaluation program at more than 50 oral and maxillofacial surgery centers, a paper for the profiles and competencies for future European dentists was formulated for the creation of a modular curriculum, for the integration of the ECT (European Credit Transfer) system, and for quality assurance of the dentistry curriculum. Especially for the situation in Germany, consequences must be drawn for further dentistry and postgraduate educational concepts, which are not completely identical with the ADEE concepts, but which can use elements of the basic Bologna concepts.

Profile and competences for the graduating European dentist - update 2009

This paper presents the profile and competences for the European Dentist as approved by the General Assembly of the Association for Dental Education in Europe at its annual meeting held in Helsinki in August 2009. A new taskforce was convened to update the previous document published in 2005. The updated document was then sent to all European Dental Schools, ministries of health, national dental associations and dental specialty associations or societies in Europe. The feedback received was used to improve the document. European dental schools are expected to adhere to the profile and the 17 major competences but the supporting competences may vary in detail between schools. The document will be reviewed once again in 5 years time. Feedback to the newly published document is welcomed and all dental educators are encouraged to draw upon the content of the paper to assist them in harmonising the curriculum throughout Europe with the aim of improving the quality of the dental curriculum.

Changes in nasal volume after surgically assisted bone-borne rapid maxillary expansion

INTRODUCTION

The purposes of this study were to detect, locate, and examine the changes in transverse nasal width, area, and volume from bone-borne, surgically assisted rapid maxillary expansion (SARME) with the Dresden distractor by using computer tomography (CT).

METHODS

Sixteen patients (average age, 28.7 years) underwent axial CT scanning before and 6 months after SARME. They also underwent CT fusion on specific bony structures. The nasal bone width was examined in the coronal plane. The cross-sectional images of the nasal cavity were taken of the area surrounding the apertura piriformis, the choanae, and in between. We calculated cross-sectional areas and nasal volume according to these data.

RESULTS

All but 2 patients had an increase in nasal volume of at least 5.1% (SD, 4.6%). The largest value of 35.3% (SD, 45.8%) was measured anteriorly on the nasal floor, decreasing cranially and posteriorly. This correlated with the V-shaped opening of the sutura palatina. There was no significant correlation between increase in nasal volume and transversal expansion.

CONCLUSIONS

Because most of the air we breathe passes over the lower nasal floor, SARME is likely to improve nasal breathing.

Minimally invasive rapid palatal expansion with an implant-supported hyrax screw

Rapid palatal expansion is indicated in the orthopedic treatment of transverse maxillary deficiency for correction of severe crossbite. The fixation of the appliance at the tooth crowns leads to more tipping connected with resorptions at the buccal cortical bone, fenestrations and gingival retraction. The aim of the present study was focused on the improvement of bodily movement and optimization of the surgical osteotomy (Glassman's technique) in adult patients with application of the Dresden Distractor (DD). In 18 patients, the new method with a special mechanism of adaptation involving minimized surgical intervention and direct fixation of the hyrax screw by one implant and one bone screw was tested. The implants were loaded directly by activation of the hyrax screw two times per day. CT scans were taken before and 6 months after insertion of the DD. In the horizontal and vertical planes there was a V-shaped opening of the suture in anterior and cranial direction, corroborating previous studies. Dental arch also showed this V-shape, indicating tooth protection. DD is a suitable minimally invasive tooth-independent bone-borne expansion method, protecting teeth and causing skeletal as well as dental effect with tipping reduced by 10 degrees.

CT analysis of nasal volume changes after surgically-assisted rapid maxillary expansion

OBJECTIVE

Aim of this study was to detect the changes in nasal volume due to bone-borne, surgically-assisted rapid palatal expansion (RPE) with the Dresden Distractor using computed tomography (CT).

MATERIALS AND METHODS

17 patients (mean age 28.8) underwent axial CT scanning before and 6 months after RPE. The nasal bone width was examined in the coronal plane. Cross-sectional images of the nasal cavity were taken of the area surrounding the piriform aperture, choanae and in between. Bony nasal volume was computed by connecting the three cross-sectional areas.

RESULTS

All but two patients showed a 4.8% increase in nasal volume (SD 4.6%). The highest value, 33.3% (SD 45.1%), was measured anteriorly at the level of the nasal floor. This correlated with the midpalatal suture's V-shaped opening. There was no significant correlation between an increase in nasal volume and transverse dental arch expansion.

CONCLUSION

As most of the air we breathe passes the lower nasal floor, an improvement in nasal breathing is likely.

MGF- and myostatin-mRNA regulation in masseter muscle after orthognathic surgery

Patients with prognathism and retrognathism show extensive morphologic changes after orthognathic surgery. The inability of muscles to adapt adequately might be one reason for observed relapses. The aim of this prospective study was to analyze the regulation of functional genes after surgery and changes in myosin heavy chain (MyHC) isoform expression, a potential molecular marker profile for inadequate muscle adaptation. 29 adult patients with prognathic and retrognathic mandibles were involved. A total of 232 muscle biopsies were taken from both masseter muscles presurgically and 6 months later. The mRNA expression of "mechano growth factor" (MGF), myostatin, and 3 MyHC isoforms were quantified by real-time polymerase chain reaction. The MGF mRNA was significantly up-regulated (P < .005), whereas myostatin mRNA showed no significant regulation. There was a shift in MyHC isoform expression. The MyHC-I mRNA was decreased (P < .005), whereas MyHC-IIa mRNA was increased (P < .005). The coherence of increased MGF expression and MyHC isoform shift 6 months after orthognatic surgery indicates an adequate muscle adaptation and higher mastication activity.

[Bone-supported rapid maxillary expansion with an implant-borne Hyrax screw: the Dresden Distractor]

Rapid palatal expansion is indicated in the orthopedic treatment of transverse maxillary deficiency for correction of severe crossbite. The fixation of the appliance at the teeth crowns leads to more tipping at the two halves of the maxilla than bodily transverse movement. Additional resorptions at the buccal cortical bone with fenestrations and gingival retraction were observed. The aim of the present study was focused on the improvement of bodily movement and optimization of the surgical osteotomy (Glassman's technique) in adult patients with application of the Dresden Distractor (DD). In 15 patients, the new method involving minimized surgical intervention and direct fixation of the hyrax screw by one implant and one bone screw was tested. The implants were loaded directly by activation of the screw two times per day. CT scans were taken before and six month after insertion of the DD. In the horizontal and the vertical planes there was a V-shaped opening of the suture in anterior, respective cranial direction, corroborating previous studies. Dental arch showed this V-shape as well, indicating tooth protection. If forces are transferred via teeth the progressive increase of skeletal resistance in anterior to posterior direction lead to dental tipping. DD is a suitable minimal invasive tooth-independent bone-borne expansion method, protecting teeth and causing skeletal as well as dental effect with 10 degree less tipping and as a precondition for stable post surgical occlusion.

Quality assurance, benchmarking, assessment and mutual international recognition of qualifications

The aim of this report is to provide guidance to assist in the international convergence of quality assurance, benchmarking and assessment systems to improve dental education. Proposals are developed for mutual recognition of qualifications, to aid international movement and exchange of staff and students including and supporting developing countries. Quality assurance is the responsibility of all staff involved in dental education and involves three levels: internal, institutional and external. Benchmarking information provides a subject framework. Benchmarks are useful for a variety of purposes including design and validation of programmes, examination and review; they can also strengthen the accreditation process undertaken by professional and statutory bodies. Benchmark information can be used by institutions as part of their programme approval process, to set degree standards. The standards should be developed by the dental academic community through formal groups of experts. Assessment outcomes of student learning are a measure of the quality of the learning programme. The goal of an effective assessment strategy should be that it provides the starting point for students to adopt a positive approach to effective and competent practice, reflective and lifelong learning. All assessment methods should be evidence based or based upon research. Mutual recognition of professional qualifications means that qualifications gained in one country (the home country) are recognized in another country (the host country). It empowers movement of skilled workers, which can help resolve skills shortages within participating countries. These proposals are not intended to be either exhaustive or prescriptive; they are purely for guidance and derived from the identification of what is perceived to be 'best practice'.

Early loading of plalatal implants (ortho-type II) a prospective multicenter randomized controlled clinical trial

BACKGROUND

In orthodontic treatment, anchorage control is a fundamental aspect. Usually conventional mechanism for orthodontic anchorage control can be either extraoral or intraoral that is headgear or intermaxillary elastics. Their use are combined with various side effects such as tipping of occlusal plane or undesirable movements of teeth. Especially in cases, where key-teeth are missing, conventional anchorage defined as tooth-borne anchorage will meet limitations. Therefore, the use of endosseous implants for anchorage purposes are increasingly used to achieve positional stability and maximum anchorage.

METHODS/DESIGN

The intended study is designed as a prospective, multicenter randomized controlled trial (RCT), comparing and contrasting the effect of early loading of palatal implant therapy versus implant loading after 12 weeks post implantation using the new ortho-implant type II anchor system device (Orthosystem Straumann, Basel, Switzerland). 124 participants, mainly adult males or females, whose diagnoses require temporary stationary implant-based anchorage treatment will be randomized 1:1 to one of two treatment groups: group 1 will receive a loading of implant standard therapy after a healing period of 12 week (gold standard), whereas group 2 will receive an early loading of orthodontic implants within 1 week after implant insertion. Participants will be at least followed for 12 months after implant placement. The primary endpoint is to investigate the behavior of early loaded palatal implants in order to find out if shorter healing periods might be justified to accelerate active orthodontic treatment. Secondary outcomes will focus e.g. on achievement of orthodontic treatment goals and quantity of direct implant-bone interface of removed bone specimens. As tertiary objective, a histologic and microtomography evaluation of all retrieved implants will be performed to obtain data on the performance of the SLA surface in human bone evaluation of all retrieved implants. Additionally, resonance frequency analysis (RFA, Osstell mentor) will be used at different times for clinically monitoring the implant stability and for histological comparison in order to measure the reliability of the resonance frequency measuring device.

TRIAL REGISTRATION

Current Controlled Trials ISRCTN97142521.

Myosin heavy chain mRNA isoforms in masseter muscle before and after orthognathic surgery

OBJECTIVES

Orthognathic surgery leads to changed jaw position and force vector of mastication to which the muscles must adapt. The aim of the present study was to determine the relative expression of myosin heavy chain (MyHC) messenger RNA (mRNA) isoforms in different types of human masseter muscle fiber under consideration of change in the number of occlusal contacts before and 6 months after surgery.

STUDY DESIGN

Muscle biopsies were taken from the anterior and posterior parts of both sides in 30 patients with prognathic and retrognathic mandibles. Specific mRNA MyHC analysis was made by real-time polymerase chain reaction to quantify the isoforms I, IIa, and IId/x.

RESULTS

There was a shift in the relative content from type I (46% before, 37% after) to type IIa (29% before, 42% after). This shift correlates with number of teeth in occlusion.

CONCLUSIONS

Correlation between isoform shift and number of teeth in occlusion indicates higher mastication force which stabilizes the treatment result.

Orthodontic Space Opening in Patients with Congenitally Missing Lateral Incisors

OBJECTIVE

To determine the best time to begin orthodontic treatment for patients scheduled for implants to replace congenitally missing upper lateral incisors. The aim of timing is to maximize the amount of bone available for implant insertion and to improve incisors inclination.

MATERIALS AND METHODS

Seventy-three plaster casts of 14 patients with 26 missing lateral incisors were cross sectioned in the center of the planned insertion of the implant, and the implant profile was projected into the area at three different times: T1--beginning of orthodontic treatment, T2-- end of orthodontic treatment, and T3--implant insertion. Deficiency of alveolar ridge volume needed for implantation was determined by Leica Quin analySIS software.

RESULTS

An increase of ridge-volume deficiency from 0.26 mm(2) at T1 to 3.77 mm(2) at T3 was found. During orthodontic treatment the incisors protruded about 9.4 degrees (differing from the O1-NA standard of 7.5 degrees ). To ensure optimal esthetic and functional implantation results, time management concerning orthodontic treatment has to be done carefully.

CONCLUSIONS

To avoid a high degree of alveolar bone atrophy and the risk of relapse and retreatment, orthodontic treatment involving tooth movement should not be initiated before the age of 13 years. Furthermore, it is important to maintain anchorage of the upper incisors because high incisor proclination causes extra-axial stress on the implant. An interdisciplinary approach is essential to provide the best treatment outcome.

Histological and histomorphometric investigation of the condylar cartilage of juvenile pigs after anterior mandibular displacement

The condylar cartilage of the mandible is considered a secondary growth center and represents a joint cartilage different from other cartilage structures regarding its histological structure, its histochemical and immunohistochemical properties and its growth pattern. This study aimed to histologically and histomorphometrically investigate the condylar cartilage after anterior mandibular displacement similar to functional orthopedic treatment. A total of 12 pigs (sus scrofa domesticus) aged 10 weeks were divided into an experimental group and a control group comprising 6 animals each. The experimental animals were provided bilaterally with synthetic occlusal build-ups in the posterior area which induced anterior displacement of the mandible in terminal occlusion. After 4 weeks, the temporomandibular structures were removed en bloc and the condylar cartilage was analyzed histologically and histomorphometrically. As a result, the experimental animals displayed a significantly increased total cartilage thickness of the posterocranial mandibular condyle which was primarily caused by an increase in thickness of the hypertrophic and chondogenic layers. Similarly, the proliferative layer showed a significant increase, whereas significant differences in thickness were absent in the articular layer. Increased cell proliferation was not observed in the experimental animals as compared to the controls. The changes found in the condylar cartilage area suggest that the zonal structure of the condylar cartilage may be modified by an altered spatial relationship between the mandibular condyle and the glenoid fossa.

Effects of unilateral molar distalization with a modified pendulum appliance

INTRODUCTION

The purpose of this study was to evaluate skeletal and dentoalveolar changes due to unilateral distalization and to determine side effects.

METHODS

Cephalograms and dental casts before and after distal movement of the maxillary molars with pendulum appliances in 15 consecutively treated patients (5 girls and 10 boys, 12.06 +/- 1.32 years), were included in this study. The duration of distalization was 8.46 +/- 2.23 months.

RESULTS

Cephalometric analysis showed no remarkable growth between the 2 measurement times. The mean value for distalization of the first molars was 3.83 +/- 1.09 mm, with distal tipping of 6.45 degrees . The maxillary second molars were also moved distally 2.83 +/- 1.32 mm and tipped distally 14.7 degrees . No significant changes in the position of the third molars were measured. The mean reciprocal mesial movement of the premolars was 1.18 +/- 1.31 mm, with distal tipping of 1.94 degrees . The incisors moved 0.84 +/- 0.79 mm mesially, with mesial tipping of 0.02 degrees and extrusion of 1.21 mm. There was also a significant influence on the contralateral anchorage unit. However, unilateral distalization reduced incisor proclination and induced moderate distal movement of the contralateral anchorage unit based on rotation around a virtual axis perpendicular to the Nance button.

CONCLUSIONS

Effective distal molar movement and less anchorage loss at the front teeth are advantages of unilateral distalization.

Change of mRNA amount of myosin heavy chain in masseter muscle after orthognathic surgery of patients with malocclusion

INTRODUCTION

Surgical correction of malocclusion changes the force to moment ratio of masticatory muscles inserting at the mandible caused by shortening, lengthening and rotation of the bone following osteotomy. During muscle adaptation the expression of mRNA for the myosin heavy chain (MyHC) of type I and type II fibres may be changed.

MATERIAL AND METHODS

The adaptation of the masseter muscle was investigated at the mRNA level in 10 patients 6 months after orthognathic surgery in the mandible. The competitive polymerase chain reaction (cPCR) is a suitable method for quantification of MyHC mRNA. For application of this minimal invasive method an amount of 35 mg muscle tissue was sufficient.

RESULTS

6 month postoperatively there was a deficiency of about 87% of MyHC mRNA for fibre type I and II in both groups of patients. The deficiency in patients with mesial position of the mandible was higher but not significant different to patients with distal malocclusion.

CONCLUSION

Patients should use the postoperative interval for training their masticatory muscles. This improves the stability of treatment result and prevents relapse.

Three-dimensional evaluation of surgically assisted implant bone-borne rapid maxillary expansion: A pilot study

INTRODUCTION

The purpose of this study was to evaluate 3-dimensional changes in dental, alveolar, and skeletal structures caused by a bone-borne implant-supported rapid maxillary expansion device (Dresden distractor).

METHODS

Axial computed tomography scans of 10 patients (mean age, 25.3 years) treated with the Dresden distractor were examined. Scans were taken immediately before and 9 months after expansion. Distances in all 3 dimensions were calculated for 38 skeletal, alveolar, and dental landmarks with respect to the reference point ELSA (point equidistant to both foramina spinosa).

RESULTS

In the transverse dimension, a V-shaped opening of the suture was shown; the greatest amount of opening was anteriorly directed, with convergence of the suture opening in the posterior aspect of the palate. The expansion of the maxillary dental arch showed a V pattern similar to the opening of the suture. In the frontal view, expansion caused a wedge-shaped opening with its base at the central incisors and the estimated center of rotation next to the frontonasal suture. The alveolar processes tipped buccally (9.9 degrees to 13.3 degrees) as did the molars (2.5 degrees to 3.5 degrees) and the premolars (3.0 degrees to 3.9 degrees). Less tipping of teeth compared with skeletal tipping (about 6 degrees to 9 degrees less) is related to the torque effect of the fixed appliance.

CONCLUSIONS

The Dresden distractor is a minimally invasive bone-borne expansion appliance that protects teeth by inducing more skeletal than dental changes. This might be a precondition for stable postsurgical occlusion.

Skeletally-anchored Rapid Maxillary Expansion using the Dresden Distractor

INTRODUCTION

It was the aim of this study to carry out a 3-D analysis of the teeth, alveolar and skeletal structures during bone-borne, surgically-assisted rapid maxillary expansion (RME) with the Dresden Distractor (DD). We aimed to determine whether a translatory and skeletal movement of the segments would be possible while reducing the dento-alveolar side effects associated with tooth-borne RME.

MATERIALS AND METHODS

Standardized axial computed tomography (CT) was performed on twelve patients averaging 25.3 years of age prior to and after RME with the DD. Reference planes and the triple-0-ELSA were defined bilaterally referring to the following anatomic points: the foramina spinosa, external auditory meati and the anterior margin of the foramen magnum. We measured the amount of movement that occurred before and after RME with the DD against ELSA.

RESULTS

A screw activation of 6.0 mm led to a transverse expansion of 5.55 mm in the alveolar process in the premolar region, and of 4.87 mm in the molar region, with 8 degrees to 9.8 degrees of buccal tipping and an increase in width of 6.07 mm and 5.71 mm, respectively, occurred in conjunction with only slight buccal tipping of the premolars (3.1 degrees -4.6 degrees ) and molars (1,1 degrees -2.6 degrees ). These data signify, beyond the considerable skeletal efficacy, an uprighting of the teeth due to the multibracket appliance's torque effect, and a direct transfer of the expansion forces onto the bone. Autorotation of the mandible in forward and upward directions was possible due to the considerably less dental tipping resulting from RME with the DD in comparison to tooth-borne RME. This fact demonstrated that the DD is also well-suited for patients with vertical growth pattern.

CONCLUSION

The bone-borne DD is an effective therapeutic method that spares the patient the negative side effects associated with tooth-borne RME such as root resorption, bone dehiscence, bite opening and excessive buccal tipping of the teeth. The prerequisites for stable occlusion are brought about by the fact that the expansion is skeletal in nature, with minimal dental tipping.

Orthodontic implants as anchorage appliances for unilateral mesialization: a case report

Space closure from distal to mesial is one of the most difficult orthodontic tasks. Toothborne anchorage limits the scale of tooth movement. Extraoral or intraoral appliances are used especially for unilateral space closure. As an alternative to conventional mesialization appliances, osseointegrated implants may be used for maximum anchorage in orthodontic treatment. Temporary implants inserted in the palatal suture are most common in maxillary treatment. In the case presented, temporary implants were placed in the palatal bone of a 17-year-old male patient with hypodontia of the mandibular central incisors and second premolars and the maxillary left second premolar for mesialization of the molars. Slight irritations of the tongue were registered in the first 2 weeks of use of the palatal implant. There were no other effects during treatment.

Plane orientation for standardization in 3-dimensional cephalometric analysis with computerized tomography imaging

INTRODUCTION

The purpose of this study was to propose certain landmarks and planes to standardize 3-dimensional image orientation.

METHODS

Cone-beam computerized tomographic images were obtained from 10 adolescent patients and analyzed with AMIRA software (AMIRA, Mercury Computer Systems, Berlin, Germany).

RESULTS

Four points (ELSA, right superior external auditory meatus, left superior external auditory meatus, and mid-dorsum foramen magnum) were located on each image. The axial-horizontal plane (x-y plane) was then determined by using both superior external auditory meatus and ELSA; the sagittal-vertical plane (z-y plane) was formed by ELSA and mid-dorsum foramen magnum perpendicular to the x-y plane.

CONCLUSIONS

All points had high intrareliability and were adequate for standardizing the orientation of 3-dimensional images.

An evaluation of resonance frequency analysis for the determination of the primary stability of orthodontic palatal implants. A study in human cadavers

BACKGROUND

The primary stability of short orthodontic implants is important for anchorage.

METHODS

For this study 14 cadaveric human heads were used. The stability of orthodontic implants (Straumann) with lengths of 4 and 6 mm and different localization (palatal suture or paramedially) were evaluated. The implants with length of 6 mm were only placed in the suture and primary stability was non-invasively determined with the resonance frequency (Osstell). The invasive method for the analysis of the morphometric parameters of the implant/bone contact was carried out by means of histological and radiological examinations.

RESULTS

The 6 mm implants have significant better primary stability in the palatal suture as 4 mm implants paramedially (P<0.05). No differences were found between 6 and 4 mm implants in the palatal suture and between 4 mm implants in palatal suture to paramedially. The histological and radiological results demonstrate the ability to measure the implant stability by investigation of the bone offer and density around the implant. Bone structure, especially the pore size in the trabecular bone and the precision of placement may influence the stability.

CONCLUSION

This study shows that the short implant gives sufficient bone fixation, independently of placement. The quality of implantation and bone structure are more important than the length of the orthodontic implant.

Stress, burnout and health in the clinical period of dental education

The study examined the extent of stress, burnout and health problems experienced by fourth and fifth year dental students from the three universities of Dresden, Freiburg and Bern. The objectives of the study were to: (i) identify frequent sources of stress and to report the prevalence rates of burnout and health problems in dental students, (ii) determine the rate of students suffering from severe burnout symptoms and (iii) identify stress factors related to the burnout symptoms of emotional exhaustion and depersonalization. A total of 161 dental students from Dresden, Freiburg and Bern participated in the study. They completed the Psychosocial Stress Inventory, the Maslach Burnout Inventory and the Health Survey Questionnaire. Frequent sources of stress were limitation of leisure time, examination anxiety and the transition stress that was related to the adaptation to the demands of the clinical phase of dental education. Few differences existed between the students of the fourth and the fifth study year. Study-related stress was lowest in Bern and considerably higher in Dresden. Differences of mean levels of burnout symptoms were found only for the burnout dimension of emotional exhaustion. Students from Dresden and Freiburg were more emotionally exhausted than students from Bern, students from Dresden also reported more health problems than students from Bern or Freiburg. Ten per cent of the dental students suffered from severe emotional exhaustion, 17% complained about a severe lack of accomplishment and 28% reported severe depersonalization symptoms. Forty-four per cent of the variance of emotional exhaustion was explained by study-related factors such as lack of leisure time, examination anxiety and transition stress. The only predictor of depersonalization was a lack of social integration, accounting for 3% of the variance. A lack of social integration may be an indicator of low social competence which may cause difficulties in dealing with patients adequately and therefore result in depersonalization. The results indicate a need to identify the group of students who may have insufficient social skills for dealing adequately with the patients, and to train them accordingly.

Computertomographische Untersuchung von Muskelvolumen, -querschnitt und -dichte bei Dysgnathiepatienten

PURPOSE

The individual jaw position is determined by the masticatory muscle among other factors. Before surgical treatment of malocclusions, thorough evaluation of the muscles is required to estimate the relapse risk.

MATERIALS AND METHODS

By means of computer tomography, lateral radiographs of the skull and denture models, the relationships between morphological parameters of the masticatory muscles and the jaw bone were analyzed. Furthermore, possible causes for the extent of the malocclusion are described.

RESULTS

A patient group with deep overbite was found to have significantly higher muscle densities (measured in Hounsfield units [HU]) in the medial pterygoideus muscle (59.89 +/- 3.91 HU to 48.94 +/- 4.14 HU, p < 0.01), masseter muscle, and genioglossus muscle (p < 0.05) in comparison to open bite patients. Significant differences of the muscle cross-section were measured in the masseter muscle between patients with retroclined maxillary incisors and with an open bite (5.4 +/- 0.7 cm (2) to 3.8 +/- 0.4 cm (2), p < 0.05).

CONCLUSION

The results show a correlation between different jaw positions and masticatory muscles. They also suggest that the function of each muscle may be different. Additional examinations of the muscle structures are required for verification of the influence of the masticatory muscles on facial morphology.

Myosin heavy chain protein and gene expression in the masseter muscle of adult patients with distal or mesial malocclusion

The aim of this study was to determine the amount of myosin heavy chain (MyHC) proteins and MyHC mRNA in muscles of patients with different positions of the mandible. Ten adult patients for orthognathic surgery were divided into two groups: distal and mesial malocclusion. The mRNA expression of two MyHC isoforms of the anterior and posterior part of the right and left side of the human masseter muscle was analysed with a competitive RT-PCR assay. An exogenous template that includes oligonucleotide sequences specific for sarcomeric MyHC isoforms (1 and 2x) was constructed and utilized as competitor. Different isoforms of the MyHC protein were identified by Western blot analysis. In the total mRNA pool of the masseter muscle, the MyHC 1 mRNA level was 25.5 +/- 7.6% and the MyHC 2x mRNA was 2.5 +/- 1.2%. The anterior part of the masseter muscle from patients with distal occlusion contained more type 1 and 2x MyHC mRNA, as compared to patients with mesial occlusion (P < 0.05). No difference in the protein distribution was observed. The differences in mRNA expression may be caused by the enforced stress of the masticatory muscle in distal occlusion because of the disadvantageous pivot.

Muscle Influence on Postnatal Craniofacial Development and Diagnostics

The postnatal craniofacial development is determined by exogenous and endogenous factors that may result in morphological and functional muscle changes and influence the dentoskeletal region in terms of a physiologic or dysgnathic development. Using functional appliances, efforts are made to treat skeletal malocclusions through targeted exercise and to prevent an undesirable development of the dentition and the craniofacial structures. However, the success of the treatment and the stability of the outcome are not always adequate. To illustrate the treatment processes, clinically relevant measures for diagnosing muscle function and morphology have been developed in recent years. Electromyographic investigations and bite-force measurements show an excessively high variability and the histologic examinations applied to date are restricted in their suitability for analysis of the human masticatory muscles. Animal experimental studies have meanwhile succeeded in simulating functional jaw orthopedics and in demonstrating muscle remodeling processes at the genetic level. Despite some invasiveness, the time and the small quantity of muscle tissue involved permit molecular biological measuring in the orofacial system.

Rapid Maxillary Expansion with Palatal Anchorage of the Hyrax Expansion Screw?Pilot Study with Case Presentation

BACKGROUND

Rapid maxillary expansion (RME) with the appliance fixed at the crowns of the first premolars and molars leads not only to transversal expansion but also to tipping of the anchorage teeth and a risk of increased tooth mobility as well as of root and bone resorptions. These disadvantages were to be avoided by fixing the transversal screw directly to the hard palate.

MATERIAL AND METHOD

Following preliminary experimental work to determine the extent to which the hard palate could be loaded with orthodontic implants, two female patients were treated for extreme transverse maxillary deficiency using a Hyrax expansion screw fixed on one side with an implant with the following dimensions: length 4.0 mm, diameter 3.5 mm, abutment diameter 5.00 mm (EO implant, Straumann, Freiburg i. Br., Germany), and on the other side with a bone screw between the roots of the second premolars and the first molars. Presurgical osteotomy according to Glassmann was followed immediately by loading, i. e. by expansion through activation of the screw several times per day. Additional anterior guidance of the right and left maxilla was provided by crossed segmented archwires and a tension coil spring for space opening in the incisor region. After adequate expansion by 8.0 mm and correction of the position of the buccal teeth, the Hyrax expansion screw and the osteosynthesis screw were removed. The implant served as orthodontic anchorage for a molar-to-molar transpalatal bar aimed at preventing relapse.

RESULTS AND CONCLUSIONS

The tooth axis inclination measured on cut sections of the plaster casts made at the beginning and end of treatment was largely without transversal discrepancies. Direct fixing of the transversal screw in the palatal arch prevents buccal tipping of the posterior teeth, especially in patients with a small apical base. Compared with other direct procedures involving osteosynthesis plates, this technique offers adequate guiding stability and is minimally invasive.

Torque capacity of metal and polycarbonate brackets with and without a metal slot

The aim of the present study was to investigate slot deformation and the equivalent torque capacity of polycarbonate brackets with and without a metal slot in comparison with those of a metal bracket. For this purpose, the expansion characteristics and, in a further investigation, the labial crown torque of an upper central incisor, were measured in a simulated intra-oral clinical situation, using the orthodontic measuring and simulation system (OMSS). Three types of bracket with a 0.018 inch slot were tested: polycarbonate Brillant without a metal slot, Elegance with a metal slot and the metal bracket, Mini-Mono. For testing purposes the brackets were torqued with 0.016 x 0.022 inch (0.41 x 0.56 mm) and 0.018 x 0.022 inch (0.46 x 0.56 mm) ideal stainless steel archwires. In the activating experiments, significantly higher torque losses and lower torquing moments were registered with both rectangular archwires with the polycarbonate brackets than with the metal bracket. In the simulation tests, significantly higher torquing moments were registered with the metal bracket than with the polycarbonate brackets. The values for the Elegance bracket were between those of the Mini-Mono and Brillant brackets. The OMSS model approximates the clinical situation, with the torque loss being notably higher than in the in vitro activating experiments. This is due to the adjacent teeth giving the archwire additional play. In addition, the torquing process may twist the archwire, resulting in subsidiary forces. On the basis of the present results, all three brackets can be recommended for torquing. However, in view of the high torque losses, the torques programmed in the straightwire technique must be seen as questionable. Data should be provided by the manufacturer on the bending to be expected in polycarbonate brackets, which has to be offset by additional torque, or the bracket torque should be omitted from the technical specifications.

Prevalence of malocclusions in the early mixed dentition and orthodontic treatment need

Early interceptive treatment for the elimination of factors inhibiting dental arch development and mandibular and maxillary growth is applied varyingly by orthodontists, possibly because there is little scientific evidence that such interventions are of actual benefit. The aim of this study was to determine specific factors for treatment need in the early mixed dentition period in order to obtain basic data to support early intervention. The study was part of a larger survey of 8768 children aged between 6 and 17 years. From this sample, 1975 children aged between 6 and 8 years were used to estimate the prevalence of malocclusions using the Index of Orthodontic Treatment Need (IOTN) during the early mixed dentition period. The results showed that deep overbite and overjet, both more than 3.5 mm, were the most frequent discrepancies, affecting 46.2 and 37.5 per cent of patients, respectively. An anterior open bite was registered in 17.7 per cent, crossbite in 8.2 per cent, and a reverse overjet in 3.2 per cent. A tooth width to arch length discrepancy was recorded in 12 per cent of teeth in the upper arch and in 14.3 per cent in the lower arch. The proportion of children estimated using the Dental Health Component of the IOTN to have a great or very great treatment need (grades 4 and 5) was 26.2 per cent. The higher values of treatment need during the mixed dentition period may account for temporary changes in the dentition and for the discrepancy in overjet and overbite. These discrepancies will be compensated in part during mandibular growth and development of the dental arch. Nevertheless, the findings indicate the early development of progressive malocclusion symptoms which are evidenced in the IOTN and concur with the acronym 'MOCDO' hierarchy (missing, overjet, crossbite, displacement, overbite). This early formation of progressive symptoms inhibiting or disturbing mandibular or maxillary growth or the development of the normal dental arch, i.e. crossbite, reverse overjet and increased overjet with myofunctional disorders, should be treated at an early stage.

Regional alterations in fiber type distribution, capillary density, and blood flow after lower jaw sagittal advancement in pig masticatory muscles

Muscular remodeling is known to be a prerequisite for permanent correction of mandibular-maxillary malocclusion. The objective of this study was to clarify if an increase in type I fiber number is accompanied by an increased capillary density and improved muscular blood flow. Juvenile pigs received build-ups on the molars, which induced a protrusion of 7.6 + 1.5 mm. After 4 weeks of treatment, chronic lower jaw protrusion induced a marked muscle blood flow increase in the anterior and medial regions of the superficial part of the masseter and in the medial pterygoid muscle (P < 0.05). Furthermore, an increase in capillary density and in the amount of type I fibers was found in all regions of masticatory muscles with an increased muscle blood flow (P < 0.05). Finally, the capillary-to-fiber ratio increased (P < 0.05). Muscle blood flow and capillary density showed a strong linear correlation (r = 0.89, P < 0.01). These changes suggest a complex muscle adaptation for long-term, fatigue-resistant activity during the early corrective period of mandibular-maxillary malocclusion treatment.

Three-dimensional analysis of endosseous palatal implants and bones after vertical, horizontal, and diagonal force application

The effects of bite and orthodontic forces exerted on endosseous palatal implants are not completely understood. This applies especially to the biomechanical properties inherent in the different implant geometries and resulting bone remodelling reactions on the one hand, and to the influence on the direction and magnitude of the applied forces on the other. The results of this study should help in the selection of implants for clinical use. Three types of endosseous implants (all 9 mm in length and 3.3 mm in diameter, made of titanium) were used for this investigation. Type 1 was a simple, cylinder-shaped implant; type 2 a cylinder-shaped implant with a superperiosteal step; and type 3 a cylinder-shaped implant, subperiosteally threaded, with a superperiosteal step. The load on the implant was investigated under three conditions of bite and orthodontic forces from 0.01 to 100 N (vertically, horizontally, and diagonally). The study results were calculated by means of a finite element (FE) method. Vertical loading caused bone deformation of more than 600 microeps at the simple implant. The largest deformations at this load were found in the trabecular bone with all three implant geometries. However, trabecular bone deformation was reduced by a superperiosteal step. Horizontal loading of the implants shifted the deformation from the trabecular to the cortical bone. Furthermore, a large deformation was measured at the transition from cortical to trabecular bone. The smallest deformations (less than 300 microeps) were found for implants with a superperiosteal step and diagonal loading (type 2). The use of threads provided no improvement in loading capacity. All implant types investigated showed good biomechanical properties. However, endosseous implants with a superperiosteal step had the best biomechanical properties under low loads. Thus, the trend should be to optimize the design of implants by producing small implants with additional anchorage on the bone surface.