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.

Immediate versus conventional loading of palatal implants in humans: a first report of a multicenter RCT.

This study aims to analyze the clinical performance of two loading concepts on second-generation palatal implants (Orthosystem, Straumann, Basel, Switzerland) in a prospective multicenter randomized controlled clinical trial. At the time of this interim analysis, 41 patients have been randomized on a 1:1 basis to one of two treatment groups. Group 1 underwent conventional loading of palatal implants after a healing period of 12 weeks (gold standard) while group 2 underwent immediate implant loading within 1 week after implant insertion. We report initial results at 6 months after functional loading. The primary outcome parameter was implant success (no implant mobility, no implant loss). The implants in both groups were initially stable at the time of insertion, and all were eligible for randomization. Twenty-two patients (group 1) were subjected to conventional implant loading after 12 weeks while 19 patients (group 2) received immediate functional loading within the first week after insertion. Direct (e.g. distal jet appliances) as well as indirect forms of anchorage (conventional or modified transpalatal arch) were used. The magnitude of orthodontic forces ranged between 1 and 4 N for the immediate loading group and between 1 and 5 N for the conventional loading group. One implant in group 1 was lost during the healing phase. One dropout was registered in group 2. Thirty-nine implants were functionally loaded for over 6 months now. These preliminary data provide first evidence of the fact that immediate loading of palatal implants yields equivalent success rates as conventional loading to 4 N after 6 months.

Bone density of the midpalatal suture 7 months after surgically assisted rapid palatal expansion in adults.

INTRODUCTION: The aims of this study were to analyze changes in bone density of the midpalatal suture after surgically assisted rapid palatal expansion (SARPE) with the bone-borne Dresden Distractor (DD; ITU, Dresden, Germany) via computed tomography (CT) and to compare of preoperative surgical findings with a control group. METHODS: Sixteen adult patients (mean age 24.5 years) underwent axial CT scans before and 7 months after SARPE. CT image fusion was performed for the midpalatal suture bone. Sixty-six controls (mean age 25.7 years) served for comparing age-related bone density. Bone structure and density were assessed in the coronal plane at the anterior, median, and posterior levels. RESULTS: Highest density was found in the posterior part (1046 Hounsfield units [HU]) before expansion. Seven months after SARPE, bone density was 48% (anterior), 53% (median), and 75% (posterior) compared with preoperative values. The control group showed fairly equal Hounsfield units (889 HU to 900 HU) in all parts. CONCLUSIONS: Seven months after SARPE, the midpalatal suture's density achieves just one half to three quarters of the pretreatment values. To maintain the resistance against forces from the unsplit posterior part, the retention time should be lengthened.

Shear bond strength after multiple bracket bonding with or without repeated etching.

The purpose of the study was to measure the in vitro shear bond strength (SBS) of metal brackets after multiple bonding and debonding with and without repeated etching. One hundred and twenty extracted premolars were divided into three equal groups. In group 1, the brackets were bonded and debonded three times with repeated enamel etching and in groups 2 and 3 without repeated etching. In group 2, all composite remnants were removed before bonding, while in group 3, the remnants were levelled. Analysis of variance was used to determine significant differences in SBS with Bonferroni adjustment for the multiple testing procedures. The results showed that in group 1, the mean SBS was 11.69 MPa (SD 2.65) at the first, 14.30 MPa (SD 2.69) at the second, and 12.19 MPa (SD 2.26) at the third debonding. In group 2, SBS decreased from 12.57 MPa (SD 2.54) to below 8.0 MPa. In group 3, SBS remained constant from the first (11.93 MPa; SD 2.14) to the second (12.06 MPa; SD 1.65) debonding and only decreased significantly to 9.74 MPa (SD 1.80) at the third debonding. Less composite remained on the teeth after each debonding sequence. This was characterized by a shift from adhesive remnant index (ARI) scores 2 and 3 after the first debonding to ARI scores 1 and 2 after the second debonding to predominantly scores 0 and 1 after the third debonding. After bracket loss and levelling of composite remnants, the SBS is sufficient for application of orthodontic forces. Repeated etching may involve a higher risk of enamel tear-outs during debonding.

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 ΔΔCT 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.

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.

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.

Transverse, vertical, and anterior-posterior changes between tooth-anchored versus Dresden bone-anchored rapid maxillary expansion 6 months post-expansion: A CBCT randomized controlled clinical trial.

OBJECTIVE: The main aim of this randomized clinical trial was to determine 3 dimensional skeletal and dental changes six months after the use of bone-anchored versus tooth-anchored rapid maxillary expanders in adolescents. The secondary aim was to determine the symmetrical or asymmetrical expansion pattern between both appliances. MATERIALS AND METHODS: Fifty adolescents with skeletally constricted maxilla (mean age 13-14 years) were randomly assigned into: Dresden B-RME, Hyrax T-RME, or untreated control groups. CBCT scans were taken at initial and expander removal (6 months). Three-dimensional references and treatment landmarks were identified. Orthogonal distances were calculated from those landmarks. The main outcome was to compare skeletal and dental changes in each group and the secondary outcome was to verify if these changes were symmetric or not. Data was analysed using descriptive statistics and repeated measure MANCOVA and MANOVA. RESULTS: Both treatment groups showed significant skeletal and dental expansion compared to controls. T-RME group had greater mean inter-molar crown expansion (5.66mm) than the B-RME group (4.17mm). Both T-RME and B-RME groups showed significant skeletal maxillary expansion compared to controls (mean 1.27mm and 1.31mm respectively, both p<0.01), although no significant difference was found between both appliances. B-RME group showed a lower ratio of dental to skeletal expansion than T-RME group. T-RME showed a symmetrical expansion pattern, whereas the B-RME showed an asymmetrical pattern relative to mid-sagittal plane. The extent of molar crown expansion was 1.84mm greater on the TAD-side compared to the Implant-side. T-RME group showed significant anterior movement of the maxillary first premolar and molar (1.5mm, p<0.05), and vertical dental extrusion (1.8mm). No significant dental vertical or anterior-posterior changes were noted in the B-RME group. CONCLUSIONS: T-RME and B-RME produced similar amounts of skeletal expansion. B-RME group produced a lower component of dental expansion. Due to the Dresden B-RME configuration, asymmetrical expansion was noted.

Autotransplantation of first premolar to replace a maxillary incisor - 3D-volume tomography for evaluation of the periodontal space.

UNLABELLED: The anterior maxilla is the most traumatized region during childhood and tooth loss is frequently involved. Space closure with implants is contraindicated in growing patients and maintenance of space is necessary over a long period. Transplantation of premolars from the mandible with two-third to three-quarter root formation wide open foramen provides the best prognosis for permanent survival. CASE REPORT: This report describes the management of a 10 year old girl with autotransplantation to replace an upper incisor by a lower premolar under consideration of special care for the periodontal ligament during surgical procedure. A 3-D imaging with digital volume tomography (DVT) was used 20 months after transplantation to evaluate the periodontal morphology. DISCUSSION: Autotransplantation of premolars with incomplete root formation to replace maxillary incisor is a treatment alternative after traumatic loss of teeth. There were no signs of pathosis like resorption or ankylosis and a normal periodontal space demonstrated with DVT. There is no need for endodontic treatment before transplantation. In this case of autotransplantation of a premolar, the DVT after 20 months gives evidence of a successful regeneration of the periodontal ligament.

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.

Treatment of a patient with Class II malocclusion, impacted maxillary canine with a dilacerated root, and peg-shaped lateral incisors.

The maxillary canines are important teeth in terms of esthetics and function. This case report describes the orthodontic treatment of a 12-year-old girl whose Class II malocclusion was complicated by an impacted maxillary canine and peg-shaped lateral incisors. Despite dilaceration of the root, the impacted canine was brought into alignment. The peg-shaped lateral incisors were extracted, and the spaces were closed, resulting in favorable esthetics and good occlusion in the long term.

Incisor inclination--risk factor for palatally-impacted canines.

OBJECTIVE: The purpose of this study was to evaluate the torque of upper incisors and the maxillary size in sagittal direction in patients with impacted canines. MATERIAL AND METHODS: Panoramic radiographs, cephalograms and pretreatment study models were evaluated in 199 patients (12.7 +/- 3.6 years) with impacted canines. The prevalence of malocclusions, inclination of the canine to the occlusal plane, incisors' inclination and maxillary size were determined. RESULTS: 45% of the patients showed symptoms of Class II, Division 2 malocclusion: at 18.5 degrees, the inclination of upper incisors (angle U1/NA) was lower and at 81.3 degrees the SNA angle higher than in patients with neutral conditions. CONCLUSIONS: There is no guidance for the erupting canine through the labial root torque of the upper incisors like in patients with missing lateral incisors. Patients with symptoms of Class II, Division 2 malocclusion should be regarded as a risk group for canine impaction.

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.

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.

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.

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.

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.

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.