Indian Hedgehog: A Mechanotransduction Mediator in Condylar Cartilage

Indian hedgehog (Ihh) is a critical mediator transducing mechanical signals to stimulate chondrocyte proliferation. To clarify the cellular signal transduction pathway that senses and converts mechanical signals into tissue growth in mandibular condyle, we evaluated Ihh expression and its relation to the kinetics of replicating mesenchymal cells in condylar cartilage during natural growth and mandibular advancement. Thirty-five-day-old Sprague-Dawley rats were fitted with functional appliances. Experimental animals with matched controls were doubly labeled with iododeoxyuridine and bromodeoxyuridine so that we could evaluate the cycles of the proliferative mesenchymal cells. Mandibular advancement triggered Ihh expression in condylar cartilage. A higher level of Ihh expression coincided with the increase of the replicating mesenchymal cells’ population and the shortening of the turnover time. These findings suggested that Ihh acts as a mediator of mechanotransduction that converts mechanical signals resulting from anterior mandibular displacement to stimulate cellular proliferation in condylar cartilage.

3D CBCT McNamara's cephalometric analysis in an adult southern Chinese population

Preliminary results were determined for a database on 3-dimensional (3D) cephalometrics using McNamara's analysis in an adult southern Chinese population based on cone-beam computerized tomography (CBCT). 3D dentoskeletal morphology was assessed from CBCTs from 80 (39 males; 41 females; 21-30 years) consecutive adult southern Chinese without gross craniofacial deformity or asymmetry, adopting 16 variables from McNamara's cephalometric method. For variables in relation to maxilla to cranial base, mandible to cranial base and dentition, there were no significant differences between males and females. For variables in relation to mandible to maxilla, 8 of 11 showed significant differences between males and females: Cd(L)-Gn (♂: 127.65 mm; ♀: 119.56 mm, P<0.01), Cd(R)-Gn (♂: 127.85 mm; ♀: 119.94 mm, P<0.01), Cd(L)-A (♂: 99.38 mm; ♀: 94.18 mm, P<0.01), Cd(R)-A (♂: 93.93 mm; ♀: 94.99 mm, P<0.01), MxMD-DF(L) (♂: 28.26 mm; ♀: 25.40 mm, P<0.05), MxMD-DF(R) (♂: 27.74 mm; ♀: 24.02 mm, P<0.05), ANS-Me (♂: 71.09 mm; ♀: 65.84 mm, P<0.01), and MD-P(L) (♂: 22.85°; ♀: 25.25°, P<0.05). The method errors did not exceed 0.5 mm for any variables. A preliminary CBCT cephalometric database of the population was created. The significant sexual differences in the 3D McNamara's analysis indicate that gender specific data should be made available. The sample size should be increased to create a more representative database.

The effects of Rhodiola rosea extract on 5-HT level, cell proliferation and quantity of neurons at cerebral hippocampus of depressive rats

The purpose of this study was to investigate the effects of Rhodiola rosea extract and depression on the serotonin (5-HT) level, cell proliferation and quantity of neurons at cerebral hippocampus of depressive rats induced by Chronic Mild Stress (CMS). Seventy male Sprague-Dawley rats were divided into seven groups (10 per group): normal control group, untreated depressive rat model group, negative control group, positive control group, low dosage Rhodiola rosea extract (1.5g/kg) group, medium dosage Rhodiola rosea extract (3g/kg) group and high dosage Rhodiola rosea extract (6g/kg) group. After the depressive rats induced by CMS had received Rhodiola rosea extract for 3 weeks, the 5-HT levels at cerebral hippocampus were detected by high performance liquid chromatography. Bromodeoxyuridine (BrdU) was injected in vivo to label the proliferating cells at hippocampus, and morphometry was used to count the hippocampal neurons. The results showed that the 5-HT level of the three experimental groups had recovered to normal status. The immunohistochemistry of hippocampus BrdU positive cells had returned to the normal level in the group of depressive rats with low dosage Rhodiola rosea extract. In conclusion the results demonstrated that Rhodiola rosea extract could improve 5-HT level in hippocampus in depressive rats, and low dosage Rhodiola rosea could induce neural stem cell proliferation at hippocampus to return to normal level, repairing the injured neurons at hippocampus.

Orthodontic treatment need and oral health-related quality among children

OBJECTIVES

To determine the association between the impact of oral health on quality of life (OHQoL) among children and their need for orthodontic treatment.

METHODS

Children (217) were screened for orthodontic treatment need using a number of professionally derived indices: Index of Orthodontic Treatment Need (IOTN)--Aesthetic Component (AC) and Dental Health Component (DHC); Index of Complexity, Outcome and Need (ICON) and the Dental Aesthetic Index (DAI). In addition, all children self-completed the 37-item Child Perception Questionnaire (CPQ), a measure of OHQoL, to assess Oral Symptoms (OS) experienced, Functional Limitation (FL), Emotional Well Being (EWB) and Social Well Being (SWB).

RESULTS

Different prevalence of orthodontic treatment need was observed depending on occlusal indices used (ranged from 31.6% to 85.9%). However, there were significant correlations between the different occlusal indices (p < 0.01). Significant differences in overall CPQ scores existed between those with and without an orthodontic treatment need irrespective of occlusal indices used to categorize treatment need (p < 0.05); Effect sizes ranged from 0.24 to 0.51. However no single index's categorization of treatment need could identify variations in all of CPQ domain scores (OS, FL, EWB and SWB).

CONCLUSION

Different occlusal indices (AC, DHC, ICON and DAI) prescribe a different prevalence of orthodontic treatment need. Those categorized as having an orthodontic treatment need by AC, DHC, ICON and DAI criteria had poorer overall OHQoL compared to those ascribed as not having a treatment need. None of the occlusal indices could comprehensively differentiate poorer OHQoL across all its domains.

The impact of malocclusion and its treatment on quality of life: a literature review

AIM

The aim of this paper is to review the literature relating to the impact of malocclusion, and the treatment of malocclusion, on physical, social and psychological health (i.e. quality of life, QoL).

DESIGN

English-language papers, including cross-sectional studies, retrospective and prospective longitudinal studies, randomized controlled trials, and reviews and meta-analyses were reviewed to determine the impact of malocclusion and its treatment on QoL.

RESULTS

Malocclusion and its treatment can affect physical health in terms of pain (e.g. temporomandibular disorders, and dental and gingival trauma), speech and mastication. In terms of psychological health, malocclusion and its treatment is reported to affect self-concept. Socially, malocclusion and its treatment can affect perceived attractiveness by others, social acceptance and perceived intelligence. However, the evidence is conflicting owing to differences in study designs, population's studied and methods of assessment of psychical, social and psychological health.

CONCLUSION

Much controversy exists about the impact of malocclusion and its treatment on QoL. There is a need for a more comprehensive and rigorous assessment of the impact of malocclusion and its treatment on QoL, employing standardized, valid and reliable data collection instruments.

A survey on the preference for continuing professional dental education amongst general dental practitioners who attended the 26th Asia Pacific Dental Congress

AIMS

To identify the subjects of interest and to examine the modes as well as means of study for continuing professional dental education amongst general dental practitioners who attended the 26th Asia Pacific Dental Congress, 28 May-1 June 2004, Hong Kong.

METHODS

A total of 381 general dental practitioners as the registered conference delegates from Hong Kong, Mainland China and other Asia-Pacific regions were randomly selected for the present survey. The survey was conducted through face-to-face interviews by a group of practising dentists in Hong Kong.

RESULTS

Overall, orthodontics and prosthodontics were the most popular subjects for clinical degree programmes, whilst oral implantology and cosmetic dentistry were the highly preferred subjects for continuing education courses. Concerning the preferred mode of study for degree programmes, the part-time study mode was chosen by 68.3% of the participating dentists. A didactic teaching approach was preferred by most of the participants (81.7%) for postgraduate study. The majority of the interviewees (76.5%) were interested in a proposed clinical degree programme to be offered jointly by The University of Hong Kong and a leading university in the Mainland. Overall, there was no marked difference in the preference for continuing dental education amongst the respondents from Hong Kong, Mainland China and other Asia-Pacific regions.

CONCLUSIONS

The present survey shows the currently preferred specialty areas and subjects for continuing professional dental education amongst the general dental practitioners who attended the 26th Asia Pacific Dental Congress, with didactic teaching as the most preferred mode of study on a part-time basis.

The Gold Medal of the Conjoint M. Orth. Examination of the Royal College of Surgeons of Edinburgh and the College of Dental Surgeons of Hong Kong, surgical orthodontic cases

The Conjoint Gold Medal was awarded to the candidate who scored the highest overall mark in Part II of the Membership of Orthodontics examination held by the Royal college of Surgeons of Edinburgh and the College of Dental Surgeons of Hong Kong. It is the intermediate examination for the orthodontic specialty training pathway in Hong Kong. Part of this examination involved the presentation of a fully documented fixed appliance case and a multidisciplinary case, and three other cases with condensed case histories. This article described two surgical orthodontic cases presented during the 1999 and 2002 examinations by the award winners.

Long-term dentofacial changes in Chinese obstructive sleep apnea patients after treatment with a mandibular advancement device

The objective of this study was to evaluate long-term dentofacial changes in Chinese obstructive sleep apnea (OSA) patients treated with a mandibular advancement device (MAD). Lateral cephalograms in natural head posture were obtained from 67 consecutive OSA patients (mean age = 46.9 +/- 8.9 years) treated with an MAD. The cephalograms were obtained at start of treatment (T0), after 1 year (T1), 2 years (T2), and 3 years (T3) of treatment. The lateral cephalograms were digitized twice, and the average of two readings was used for statistical analyses. Small, but statistically significant changes occurred in some dentofacial variables. The lower anterior facial height steadily increased during the observation period, and this increase was significant for the T0-T1 and T1-T2 periods and marginally significant for the T2-T3 period. A significant increase in the mandibular plane angle was observed during the T0-T1 and T2-T3 periods only. Significant reductions in the overjet and overbite were observed for the T0-T1 period but not thereafter. Statistically significant dentofacial changes were observed in this study, but they were of small magnitude. The overjet and overbite changes observed mainly occurred at the initial stage of treatment.

Repeated mechanical loading enhances the expression of Indian hedgehog in condylar cartilage

Indian hedgehog (Ihh) acts as a mechanotransduction mediator that converts mechanical strain into cellular proliferation and cartilage formation in mandibular condylar cartilage. The aim of this study was to examine the effect of repeated mechanical strain on the level of expression of Ihh and type II collagen mRNA in condylar growth. Two hundred and eighty 35 days old Sprague-Dawley rats were divided into 10 experimental and 10 control groups. Repeated mechanical loading was applied by advancing the mandible in a stepwise manner by fitting a stepwise bite jumping appliance. Animals were sacrificed together with their matched controls on 10 different time points. Total RNA was extracted from condylar cartilage immediately after dissection. Ihh and type II collagen mRNA was quantified using real-time PCR. In the experimental group, Ihh mRNA increased significantly on experimental day 7. Upon the second advancement, another peak was elicited 7 days later. Type II collagen showed a significant increase on days 21 and 44 of advancement. This indicated that mechanical loading in a repeated manner, triggers the expression of Ihh which in turn increases the number of replicating mesenchymal cells as well as the amount of the cartilage formed. Taken together these events increase condylar growth.

Identification of temporal pattern of mandibular condylar growth: a molecular and biochemical experiment

OBJECTIVES

Based on the phenomenon that expression of type X collagen and capillary endothelium correlates with endochondral ossification, the prime aim of this study was to establish the temporal pattern of condylar growth in Sprague-Dawley rats by biochemically identifying the expression of these two factors.

DESIGN

Sprague-Dawley rats were divided into five groups representing five different stages during somatic pubertal growth. In situ hybridization and immunoperoxidase were performed to examine expression of type X collagen in hypertrophic zone and capillary endothelium in erosive zone of condylar cartilage. Computer-assisted imaging analyses were conducted to allow for a quantitative assessment of the expression of these two factors, from which the temporal pattern of condylar growth was inferred.

RESULTS

(1) Synthesis of type X collagen and emergence of capillary endothelium were critical factors during the transition of condylar cartilage from chondrogenesis into osteogenesis, a biological pathway that leads to endochondral bone formation, the mode through which the condyle grows. (2) Quantitative analyses revealed the temporal pattern of the expression of these two factors, indicating that the thrust of natural growth of the condyle in the rats occurred in concomitance with somatic pubertal growth, featured by an acceleration starting from day 38, a maximum growth rate on day 56, followed by a decrease afterwards.

CONCLUSION

It is suggested that the biochemical examination of growth markers, such as type X collagen, might be a new approach to accurately depict temporal pattern of condylar growth which is too delicate to be reflected by gross measurement not only in Sprague-Dawley rats but potentially also in other species.

Skeletal effects of bite jumping therapy on the mandible - removable vs. fixed functional appliances

AUTHORS: Shen G, Hagg U, Darendeliler MA.

OBJECTIVE

Based on an extensive review of the literature, the aim of this study was to explore the mainstream consensus on the controversial topic of whether the bite jumping treatment could enhance mandibular growth.

DESIGN

The data for removable and fixed functional appliances were respectively comprehended and analyzed with regard to their attributes in mandibular growth modification. Furthermore, numerous reported findings were assessed by relating them to some important factors influencing the effects of bite jumping, such as treatment timing, treatment duration and post-treatment follow-up, to allow for a more objective and accurate evaluation.

RESULTS

The key differences between removable and fixed appliances are working hours (intermittent vs. continuous), length of treatment time (long vs. short), optimal treatment timing (before puberty growth vs. at or after puberty spurt), and mode of bite-jumping (considerable vertical opening vs. limited vertical opening). These different features lead to different treatment effects on mandibular and TMJ growth, such as the intensity of possibly increased growth (clinically less significant vs. significant), the direction of enhanced growth (vertical vs. horizontal), and the stability of treatment changes (unstable vs. stable). The short-term or long-term post-treatment relapse mainly relates to the rebound of dental position.

CONCLUSION

The immediate effects of bite jumping functional appliances on the mandibular growth enhancement are convincing during actual treatment. This extra gain of growth might be sustainable during the short-term and long-term post-treatment period.

The effect of fixed orthodontic appliances on the oral carriage of Candida species and Enterobacteriaceae

The aim of this investigation was to evaluate the prevalence of Candida and Enterobacteriaceae in a group of adolescents during fixed orthodontic appliance (FOA) therapy. The experimental group was recruited from a larger sample of orthodontic patients who were clinically examined once to obtain baseline data before active treatment. The group comprised 27 subjects; 13 males, 14 females (mean age 15.5 +/- 2.3 years). Thereafter, the experimental group was examined three times during a 3 month follow-up period after insertion of the FOA. The whole mouth plaque score was obtained, and the oral cavity was then sampled for Candida species and Enterobacteriaceae using three different microbiological culture techniques, namely the oral rinse, pooled plaque and the imprint culture.A significant increase in candidal numbers was observed after FOA insertion when the imprint technique was used (P < 0.001), although the overall candidal prevalence rates obtained using the oral rinse and pooled plaque techniques did not demonstrate such a change. The predominant Candida species isolated was C. albicans and the number of coliform carriers significantly increased after the insertion of a FOA, as detected by the oral rinse (P < 0.05) and the pooled plaque (P < 0.05) techniques. In total, eight coliform species were isolated following FOA therapy compared with the three species isolated before insertion of the appliance. The results also revealed a significant increase in plaque index due to the introduction of a FOA. Taken together, these data imply that insertion of a FOA is likely to promote oral carriage of Candida and coliform species. Furthermore, it appears that routine oral hygiene instruction and information on appliance hygiene given to these patients may not necessarily reduce plaque accumulation and possible attendant effects. Further work with a larger cohort is required to confirm these findings.

Forward mandibular positioning enhances condylar adaptation in adult rats

The aim of this investigation was to assess quantitatively the adaptive changes in the condyles of adult rats to forward mandibular positioning. The level of types II and X collagen expressed in the condyles of adult rats was compared with that formed in response to forward mandibular positioning and the levels of expression were correlated to the amount of bone formed in response to mandibular advancement. Seventy-eight 120-day-old female Sprague-Dawley rats were included in this study. The rats were randomly allocated to six groups. Each group consisted of nine rats with bite-jumping devices and four untreated controls. The animals in each group were sacrificed on days 3, 7, 14, 21, 30, and 60. Immunostaining was used for the detection of types II and X collagen, while Alcian blue-PAS was used to observe the extracellular matrix and new bone formation. The results showed that new cartilage was formed in the posterior condyle. The highest level of expression of types II and X collagen were present on day 21, the amount of increase was 247.99 and 540.08 per cent, respectively. The highest level of new bone formation was measured at day 30 of advancement when the amount of increase in new bone formation was 318.91 per cent. These findings indicate that forward mandibular positioning causes changes in the biophysical environment of the temporomandibular joint (TMJ) of adult rats that leads to condylar adaptation.

Neovascularization and bone formation in the condyle during stepwise mandibular advancement

The aims of this investigation were to identify the temporal expression of vascular endothelial growth factor (VEGF) in the mandibular condyle and to correlate it with the pattern of new bone formation during stepwise mandibular advancement. Two hundred and fifty female, 35-day-old Sprague-Dawley rats were randomly divided into 10 groups, with 10 rats allocated to the single-step bite-jumping subgroup, 10 rats to the stepwise advancement subgroup and five rats to the control subgroup. In the experimental groups, the mandibles were kept in a continuous forward position. The initial stepwise advancement commenced on day 35, whereas the second advancement started on day 65. The rats were sacrificed on experimental days 3, 7, 14, 21, 30, 33, 37, 44, 51 and 60. Sections (7 microm) were cut through the condyle in the parasagittal plane and stained with anti-VEGF antibody. Each section was counter-stained with haematoxylin for observation of the cellular response. The sections were digitized and quantitatively analysed with a computer-assisted image analysing system. The results showed that the initial advancement in the stepwise group led to significantly less expression of VEGF when compared with single advancement. However, the second advancement on day 30 resulted in a significant increase in VEGF expression when compared with the one-step group and the natural growth control group. Thus, it was concluded that changes in the amplitude of mechanical loading, produced by stepwise advancement, have a significant effect on the production of VEGF by the chondrocytes. During the later stages of advancement, more VEGF and more condylar bone was produced.

PTHrP regulates chondrocyte maturation in condylar cartilage

PTHrP is a key factor regulating the pace of endochondral ossification during skeletal development. Mandibular advancement solicits a cascade of molecular responses in condylar cartilage. However, the pace of cellular maturation and its effects on condylar growth are still unknown. The purpose of this study was to evaluate the pattern of expression of PTHrP and correlate it to cellular dynamics of chondrocytes in condylar cartilage during natural growth and mandibular advancement. We fitted 35-day-old Sprague-Dawley rats with functional appliances. Experimental animals with matched controls were labeled with bromodeoxyuridine 3 days before their death, so that mesenchymal cell differentiation could be traced. Mandibular advancement increased the number of differentiated chondroblasts and subsequently increased the cartilage volume. Higher levels of PTHrP expression in experimental animals coincided with the slowing of chondrocyte hypertrophy. Thus, mandibular advancement promoted mesenchymal cell differentiation and triggered PTHrP expression, which retarded their further maturation to allow for more growth.

[An immunohistochemical study on neovascularization in TMJ during mandibular advancement]

OBJECTIVE

Neovascularization is proved to be closely correlated with ossification. This study was designed to determine the biochemical path through which the new bone formation is enhanced in TMJ during mandibular protrusion.

METHODS

SD Rats were fitted with bite-jumping appliances to allow for an adequate advancement of the mandible. The animals were sacrificed 3, 7, 14, 21 and 30 days, respectively, after placement of the appliances. Slides with TMJ tissue were prepared for biochemical procedure. Immunohistochemical approaches were adopted to examine neovascularization in TMJ by immuno-localizing the newly formed endothelial cells. Computer-assisted image analysis system was applied to quantify the positive immunoreaction.

RESULTS

Neovascularization in connective tissue close to the condyle was 200% higher in the experimental groups than that in the control, and, within the bony tissue of the condyle, neovascularization in experimental animals was found to be 103% higher than that of the control.

CONCLUSION

Increased neovascularization triggered by mandibular protrusion might intensify new bone formation in condyle and glenoid fossa and finally lead to a growth adaptation of TMJ to bite-jumping therapy.

Factors regulating mandibular condylar growth

Factors regulating condylar growth have not been identified before. This study was designed to identify a series of these factors, such as Sox 9 transcription factor and vascular endothelial growth factor (VEGF), and also to correlate the amount of type X collagen expressed during natural growth to the amount of bone newly formed. We used 115 Sprague-Dawley rats, 35 days old, in this study. The expression of these factors was identified on protein level by using immunostaining. Type X collagen was identified on mRNA and protein levels. Sox 9 was expressed by cells in the proliferative layer and by chondrocytes. Type X was expressed only by hypertrophic chondrocytes, and its expression precedes the onset of endochondral ossification. VEGF is expressed by hypertrophic chondrocytes, and its maximum level of expression precedes the maximum level of bone formation. Condylar growth involves a sequence of transitory stages uniquely defined by molecules that are intrinsically synthesized by cells in the condyles.

The correlation between neovascularization and bone formation in the condyle during forward mandibular positioning

The aim of the present study was to investigate the temporal pattern of expression of VEGF (Vascular Endothelial Growth Factor) and new bone formation in the condyle during forward mandibular positioning. The importance of vascularization during endochondral ossification was investigated during natural growth of the condyle and compared to that after forward mandibular positioning. The goal was to further our understanding of the cellular responses during functional appliance therapy with a view to extending the experiment into maturity. One hundred and fifty 35 days old Sprague-Dawley rats, 100 fitted with a bite-jumping appliance and 50 untreated, were divided into 10 groups. One group was sacrificed on each of experimental days 3, 7, 14, 21, 30, 33, 37, 44, 51 and 60 respectively. Sagittal sections were cut and stained with VEGF antibodies and Periodic acid and Schiff's reagent (PAS). Each section was quantitatively analyzed with a computer assisted analyzing program and the temporal sequence of expression of VEGF and new bone formation during natural growth and after mandibular forward positioning was compared. There was significant increase in both vascularization and mandibular bone growth upon forward mandibular positioning and the highest amount of both were expressed in the posterior region of the condyle. The highest acceleration of vascularization preceded that of new bone formation. Thus, forward mandibular positioning was found to solicit a sequence of cellular events leading to increased vascularization and subsequently new bone formation resulting in enhanced condylar growth.

Tooth-size discrepancies among different occlusion groups of southern Chinese children

The purpose of this study was to compare Bolton anterior and overall ratios among different occlusion groups of southern Chinese children. Fifty plaster casts with Class I occlusion, 30 with Class II occlusion, and 30 with Class III occlusion were selected from a random sample of 1247 12-year-old southern Chinese children in early permanent dentition in Hong Kong. For the anterior ratio, a statistically significant difference was found between the Bolton standard and the Class III occlusion group. For the overall ratio, statistically significant differences were found between the Bolton standard and the Class II occlusion group, and between the Class II and the Class III occlusion groups. Thus specific standards are required for Class II and Class III cases from the southern Chinese population.

Concerns and motivations of skeletal Class III patients receiving orthodontic-surgical correction

The objective of this research was to study the impact of skeletal Class III malocclusion on patients' emotional status, as well as patients' motivations for seeking surgical correction of Class III malocclusion. The sample comprised 140 consecutive Chinese patients with skeletal Class III malocclusion who had been treated with a combined orthodontic-surgical approach. A retrospective analysis was performed, based on questionnaires with answers ranked on a numeric scale (O = not at all; 1 = a little; 2 = moderately; 3 = quite a bit; 4 = extremely). Sixty-seven percent of subjects (40 males and 54 females) returned completed questionnaires. Fifty-four percent had bimaxillary deformities, 32% had mandibular hyperplasia, and 14% had maxillary hypoplasia. Seventy-seven percent received bimaxillary surgery, 15% received maxillary advancement, and 8% received mandibular setback. The results showed that nearly half of the patients had a nickname related to their dentofacial problems, and 8 of 10 of these felt embarrassed or angry about their nickname. Ninety-three percent sought improvement of their facial appearance, 85% wanted an improvement in their dental appearance, and 73% desired an improvement in chewing ability. Seventy-six percent were concerned about surgical risks and 63% about possible pain. The vast majority of Class III patients undergoing orthognathic surgery suffered psychologic and functional problems related to their appearance prior to treatment. Esthetic improvement was the driving force behind seeking treatment.

Occurrence of neurotrophin receptors and transmitters in the developing Xenopus gut

The ontogeny of gut innervation in the anuran amphibian Xenopus laevis was studied using immunohistochemistry on sections of whole larvae from NF stages 38-52. Immunoreactivity to acetylated tubulin confirmed the presence of nerve fibres as early as stages 38-39. Actin immunoreactivity was found at stage 41, indicating the presence of smooth muscle cells. Trk-like neurotrophin receptors were occasionally found in nerve fibres as soon as stages 38-39. Vasoactive intestinal polypeptide (VIP) and pituitary adenylate cyclase-activating peptide (PACAP) immunoreactivities coexisted in nerves innervating the gut wall from stages 40-41, and nitric oxide synthase (NOS) from stage 42. Substance P/neurokinin A (SP/NKA) occurred at stage 42. In all these cases, the first fibres were observed in the oesophagus. Calcitonin gene-related peptide (CGRP) was first observed in nerves at stage 48. In general, VIP/PACAP and NOS innervation was denser than the tachykinin innervation. In conclusion, the development of nerve fibres in the Xenopus gut is probably dependent on neurotrophins that may act via Trk-like receptors and occur before the gut wall is fully organised morphologically. Feeding in Xenopus larvae starts at NF stage 45. The study demonstrates that several of the transmitters investigated are expressed in the gut innervation (and in endocrine cells) prior to this stage.

Patient satisfaction following orthognathic surgical correction of skeletal Class III malocclusion

The objectives of this study were to evaluate the relationship between preoperative psychologic status and attitude and postsurgical adjustment and experience of the surgical treatment. Questionnaires were sent to 140 consecutive Chinese patients with skeletal Class III malocclusion who had been treated with a combined orthodontic-surgical approach. The results showed the following: (1) immediately after the surgery 44% of patients had more pain, 57% had more numbness, and 73% had more swelling than expected; (2) most patients underwent noted marked changes in facial appearance (96%) and dental appearance (91%); (3) chewing ability improved in 71% of patients; (4) half of those with temporomandibular joint problems preoperatively experienced improvement; (5) personality and lifestyle were affected positively in about 50% of patients; (6) satisfaction with the treatment increased with time: 87% at 6 months and 92% at 24 months; and (7) a few patients (8%) regretted having undergone surgery, mainly because facial changes were not apparent. The vast majority of the present Chinese skeletal Class III patients were satisfied with the overall outcome of the continued orthodontic-surgical treatment.

An electromyographic investigation of the first six months of progressive mandibular advancement of the Herbst appliance in adolescents

The effects of the progressive activation of the Herbst appliance on the activity of the masseter and temporalis elevator muscles of the mandible were monitored in a group of 14 consecutively treated 10-15-year-old subjects with an Angle Class II, division I malocclusion. A cast silver splint Herbst appliance was activated in multiple stages at a rate of 2 mm/2 mo. The functionality of the superficial masseter and anterior portion of the temporalis muscles was monitored at maximum bite force using surface electromyography (EMG). The EMG recordings were taken at an incisal edge-to-edge position and a retruded mandibular position, both at a vertical interincisal separation of 3 mm using an acrylic bite plate. Measurements of maximum voluntary isometric clenches were taken during adaptive functional changes at pretreatment (baseline) and during the first 6 months of Herbst appliance therapy. Results showed great individual and inter- and intrasessional differences in electromyographic activity of the muscles before and during treatment. At the retruded position, the masseteric activity increased by the sixth month while temporalis activity remained at the same level. Following treatment, the masseteric imbalance was reduced, but the temporalis imbalance was unchanged. At the edge-to-edge position, masseteric activity increased by the sixth month, while temporalis activity remained unchanged. The masseteric imbalance was reduced by the sixth month, while the temporalis imbalance was reduced from the fourth month into treatment. The results imply a favorable muscular response to a progressive regime of Herbst appliance activation.

A maxillary protracting bow appliance for Class III treatment in the primary dentition

The design of a simple facial mask type appliance for the treatment of Class III with anterior crossbite in the primary dentition, is described. Its clinical effect is illustrated in two cases. The appliance is easy to make, cheap, well tolerated and efficient.

Composite autogenous bone and demineralized bone matrices used to repair defects in the parietal bone of rabbits

We compared the amount of new bone produced by endochondral and intramembranous autogenous bone grafts in the presence of demineralized bone matrices (DBMs) prepared from intramembranous bone (DBM(IM)) or endochondral bone (DBM(EC)). Thirty-five bone defects were created in the parietal bone of 20 New Zealand White rabbits. In the experimental groups, 5 defects were grafted with endochondral bone, 5 with endochondral bone mixed with DBM(IM)) (EC-DBM(IM)), 5 with intramembranous bone mixed with DBM(IM)(IM-DBM(IM)) and 6 with endochondral bone mixed with DBM(EC)(EC-DBM(EC)). In the control groups, 10 defects were left alone (passive control) and 4 were grafted with rabbit skin collagen (active control). They were all killed on day 14 and the defects were prepared for histological study. Serial sections were cut across the whole defect. Quantitative analyses were made on 202 sections of the experimental groups by image analysis. A total of 414%, 708%, and 85% more new bone was formed in defects grafted with composite EC-DBM(IM), IM-DBM(IM)and EC-DBM(EC), respectively, than those grafted with endochondral bone alone (P<0.001). No bone was formed in either passive or active controls. In conclusion, demineralized bone matrices, particularly those derived from intramembranous bone, have extremely high osteoinductive properties and greatly improve the integration of autogenous bone grafts in the skull.

Class II correction in patients treated with class II elastics and with fixed functional appliances: a comparative study

The aim of the present study was to evaluate quantitatively the skeletal and dental changes contributing to Class II corrections in subjects treated with Class II elastics (Begg technique) compared with subjects treated with fixed functional appliances (Herbst appliance). Thirty-six male patients with Class II, Division 1 malocclusions whose treatment had not included extraction were investigated. Eighteen were treated with the Begg technique, and eighteen were treated with Herbst appliance for an average period of 1.3 and 0.5 years, respectively. Lateral radiographs in habitual occlusion were taken at the start of treatment and 12 months afterwards. In the Begg group, the maxilla moved forward 1 mm more than in the Herbst group, and the mandible moved 1 mm more in the Herbst group than in the Begg group. The skeletal improvement in the Herbst group exceeded the changes in the Begg group by, on average, 2.0 mm (P <.01). The overjet reduction in the Begg group was larger (2.1 mm; P <.01) than in the Herbst group, mostly because of dental movements. The skeletal part of the overjet reduction was 4% in the Begg group compared with 51% in the Herbst group. The molar correction was similar in both groups, but in the Begg group, the skeletal improvement was 10%, compared with 66% in the Herbst group. The overbite correction and the increase in the anterior lower facial height and in the NSL/ML angle were larger in the Begg group (P <.05). The conclusions of this study were that the changes contributing to the Class II corrections in Begg and Herbst therapy were skeletal and dental. The skeletal changes were, however, larger in the Herbst-treated group. On the other hand, favorable and unfavorable vertical changes were more pronounced in the group treated with Class II elastics.

Differential immediate-early gene responses to shear stress and intraluminal pressure in intact human conduit vessels

We have previously shown distinct effects of shear stress and pressure on transcription of several potent vascular mediators. In the present study, we tested the hypothesis that c-jun and c-fos are regulated differentially by shear and pressure. Intact human umbilical veins were perfused with various combinations of shear and pressure during 1.5, 3 and 6 h. Protein and gene expressions were assessed by immunofluorescence and real-time reverse transcription PCR, respectively. Shear stress and pressure exert differential temporal effects on c-jun and c-fos gene and protein expression, and these immediate-early gene responses appear to be cell-type specific for endothelial and smooth muscle cells.

Treatment effects of simple fixed appliance and reverse headgear in correction of anterior crossbites

The aim of this study was to compare the skeletal and dental changes contributing to the correction of Class III malocclusion using a 2 x 4 appliance and reverse headgear in the mixed dentition. Seventeen consecutive patients (mean age, 9.7 years) with pseudo-Class III malocclusions and an anterior functional shift and straight or concave facial profile were treated with a simple fixed appliance. Another 20 consecutive patients (mean age, 8.5 years) with Class III incisor relationship and straight or concave facial profiles, were treated with reverse headgear. Lateral cephalometric films taken at the beginning of treatment, the end of the treatment, and 1 year after the active treatment, were analyzed with the modified Pancherz analysis. After active treatment, the overjet correction, 5.2 mm and 6.5 mm on average, respectively, were achieved using the 2 x 4 and reverse headgear. The overjet correction by the 2 x 4 appliance was due to dental changes only. In the reverse headgear group, 60% of the overjet correction was due to dental changes and 40% due to skeletal changes. During the 12 months follow-up period, the overjet was unchanged in the 2 x 4 group (1.6 mm) and decreased in the reverse headgear group, the difference being statistically significant (P <.05). The change of jaw relationship was similar between the 2 x 4 and reverse headgear groups. During the follow-up period, a decrease in overjet in the reverse headgear group was mainly due to forward growth of the mandible and proclination of lower incisors. The overjet in the 2 x 4 group was unchanged due to dental compensation (1.6 mm). To conclude there was a similar amount of overjet correction in the 2 x 4 and reverse headgear groups. Overjet correction by the simple fixed appliance was produced by dental changes whereas in the reverse headgear group, it was produced by both dental and skeletal changes.

[Expression of type X collagen in condylar cartilage during mandibular protrusion]

OBJECTIVE

This study was designed to detect type X collagen expression, at both gene and protein levels, in condylar cartilage during mandibular protrusion triggered by functional appliance.

METHODS

One hundred SD rats with age of 5 weeks were selected and divided into 5 experimental groups (n = 5) and 5 control groups (n = 5). Animals in experimental groups were imposed with bite-jumping appliances which caused identical magnitude of mandibular protrusion. The animals of experimental groups, together with their matched controls, were sacrificed 3, 7, 14, 21 and 30 days after the appliance insertion. 6 microns sections were cut from TMJ through the sagittal plane. In situ hybridization and immunohistochemical analysis were performed to detect the expression of type X collegen mRNA transcription and its protein synthesis.

RESULTS

1. Intensive staining of type X collegen mRNA was found to distribute within the whole area of hypertrophic zone, a sharp contrast to the control groups which showed very little or no staining. 2. Type X collegen protein synthesis, which was highlighted by immunofluoscent staining, was found to spread over the whole hypertrophic zone, compared to the controls that demonstrated a very little staining.

CONCLUSION

Expression of type X collagen in condylar cartilage indicates the onset of endochondral ossification in condyle in response to mandibular protrusion provoked by functional appliances.

A comparison of three superimposition methods

The purpose of this investigation was to compare the reliability of three superimposition methods: Björk's structural, Ricketts' four-position, and Pancherz's method. The material consisted of 14 pairs of cephalograms obtained before and after Herbst treatment. Each pair of cephalograms were traced and superimposed by means of the three different methods three times each. A reference grid was used to quantitatively evaluate the sagittal dental and skeletal changes. The results revealed that: (1) there was no statistically significant difference between the repeated measurements in the three methods, i.e. all three methods were reliable. (2) There was no significant difference among the three superimposition methods to evaluate the sagittal skeletal and dental changes. (3) Comparing the coefficient of reliability, none of the three methods was suitable for individual assessment, and Pancherz's method only was acceptable for assessment of patients in groups.

Bone induction using autogenous bone mixed with demineralised bone matrices

The aim of the present study was to examine the healing of endochondral (EC) autogenous bone grafts in the presence of demineralised bone matrix prepared from intramembranous bone (DBMIM), or prepared from endochondral bone (DBMEC) using quantitative analysis. Thirty bone defects were created on the parietal bone of fifteen New Zealand White rabbits. In the experimental groups, five defects were grafted with EC bone, five defects were grafted with EC bone mixed with DBMIM (EC-DBMIM) and six defects were grafted with EC bone mixed with DBMEC (EC-DBMEC). In the control groups, ten defects were left empty (passive control) and four defects were grafted with rabbit skin collagen (positive control). They were all sacrificed at day fourteen post grafting, and the defects were prepared for histological analysis. Serial sections were cut across the whole defect. Quantitative analysis was performed on 152 sections of the experimental groups by image analysis. Four hundred and fourteen per cent more new bone was formed in defects grafted with composite EC-DBMIM than those grafted with EC bone alone (p < 0.001). Eighty-five per cent more new bone was formed in defects grafted with composite EC-DBMEC than those grafted with EC bone alone (p < 0.001). No bone was formed in either passive or positive controls. In conclusion, DBM, especially DBMIM, have extremely high osteoinductive properties and greatly enhance the integration of EC bone grafts with defects created in IM bone.

The use of pendulum appliance in the treatment of Class II malocclusion

A case of correction of molar Class II using the pendulum appliance is described. Upper first molars were distalized into Class I, crowding was eliminated in the upper arch and space was provided to attain Class I relationship. Treatment lasted for 18 months. A two year follow up shows stability of the occlusion.

Cephalometric morphology of Chinese with Class II division 1 malocclusion

AIM

To investigate the craniofacial pattern of southern Chinese children with Class II Division 1 malocclusion and to compare with Chinese population norms and Caucasians with Class II Division 1 malocclusions.

MATERIALS

Lateral cephalograms obtained from 105 Chinese subjects with Class II Division 1 malocclusion.

RESULTS

There were no significant sex differences and subsequently the data were pooled. Except for the maxillary plane angle and the angle of the lower incisor relative to the mandibular plane, all of the selected dental-skeletal angular measurements showed significant differences between Chinese with Class II Division 1 malocclusion and Chinese norms.

CONCLUSION

Compared with Caucasians, Chinese with Class II Division 1 malocclusion have more prognathic maxillas, less retrusive mandibles, flatter chins, steeper mandibular plane angles and more proclined maxillary incisors.

Overjet reduction and molar correction in fixed appliance treatment of class II, division 1, malocclusions: sagittal and vertical components

The purpose of this study was to quantitatively evaluate skeletal and dental changes contributing to Class II correction in patients treated with the Begg technique. The sample consisted of 18 male subjects with Class II, division 1, malocclusions treated with fixed appliances (Begg technique, nonextraction) for an average period of 1.3 years (standard deviation, 0.24 years). Lateral radiographs in habitual occlusion taken at 6 months before the start of treatment, at the start of treatment, and 6, 12, and 18 months after the start of treatment were analyzed. During the control period, normal sagittal and vertical growth changes occurred. In the initial treatment period (0 to 6 months), the overjet reduction (6.6 mm; P <. 001) and the molar correction (2.2 mm; P <.001) were obtained mainly by dental movements. The overbite was reduced by 4.1 mm (P <.001). The NSL/ML and NL/ML angles increased by 1.5 degrees (P <.05) and 1. 4 degrees (P <.01), respectively, and the anterior lower facial height increased by 3.1 mm (P <.001). During the second period of treatment (6 to 12 months), the molar correction continued to improve, and the anterior lower facial height continued to increase. During the third period (12 to 18 months), a small relapse in overjet and overbite was noted, but the anterior lower facial height continued to increase. During the total treatment period (0 to 18 months), the overjet reduction and molar correction were 5.8 mm (P <. 001) and 3.0 mm (P <.001), respectively. Mandibular growth exceeded maxillary growth by 1.1 mm (P <.01). The overbite correction and the increase in anterior lower facial height were 3.0 mm (P <.001) and 5. 0 mm (P <.001), respectively. The NSL/ML angle increased 1.0 degrees (P <.05). The conclusions were that the changes contributing to the Class II correction were mostly dental. Vertically, the net effects of treatment were an increase in the mandibular plane angle and in lower anterior facial height.

The reproducibility of cephalometric landmarks: an experimental study on skulls

Few previous cephalometric studies have used dry skulls in order to eliminate the effects of the facial soft tissues. The aim of this study were to quantify the intra-examiner reproducibility of the commonly used cephalometric landmarks, angles and distances, using dry skulls and to compare these errors with previous error data obtained from normal cephalograms of living patients. Thirty skulls were mounted in a purpose-designed holder and repeat cephalograms of each skull were recorded and digitised. All measurements were made relative to an X-Y coordinate reference grid. Scattergrams were produced to show the characteristic distribution of the intra-examiner reproducibility errors for the landmarks, and the reproducibility of the angles and distances were tabulated. This data was compared with a related study that included the soft tissue profile. The standard deviations of the skeletal and dental angles and distances were greater in the presence of the soft tissues. These differences were up to four times larger for measurements including the location of Nasion (e.g. SNA, SNB and SNPg), which was the landmark location most affected by the presence of soft tissues, and for the distance: Incisal tip of Lower Incisor to Pogonion. Anterior Nasal Spine, in the horizontal plane, was also greatly affected by the presence of the soft tissues. By using dry skulls, the errors observed in this study may serve as standards for the rational interpretation of clinical cephalometric values.

Cephalometric and occlusal changes following maxillary expansion and protraction

A prospective clinical trial was conducted to determine the cephalometric and occlusal changes following maxillary expansion and protraction. Twenty Southern Chinese patients (eight males and 12 females with a mean age of 8.4 +/- 1.8 years) with skeletal Class III malocclusions were treated consecutively with maxillary expansion and a protraction facemask. Growth adaptation of these patients was followed for 2 years after removal of the appliances and compared with a control group of subjects with no treatment. Lateral cephalometric radiographs were used to quantify the skeletal and dental changes before treatment (T1), immediately after treatment (T2) and 2 years after removal of appliances (T3). With 8 months of treatment (T2-T1), overjet was overcorrected from a -2.0 to 3.5 mm. The maxilla moved forwards by an average of 2.1 mm and the molar relationship was improved to a Class I dental arch relationship. The palatal and occlusal planes were tilted upward 1.0 and 2.0 degrees, respectively. Two years following removal of the appliances (T3-T2), a positive overjet was maintained in 18 out of 20 patients. The maxilla continued to move forwards in the treated subjects similar to the controls. The mandible outgrew the maxilia. In most instances, dental compensation with proclination of the maxillary incisors was observed. The palatal plane returned to pre-treatment value. The occlusal plane continued to tilt upward due to eruption of the molars and proclination of the incisors. Analysis of dental casts showed a significant increase in maxillary intercanine (2.2 mm) and intermolar widths (2.3 mm) with 7 days of rapid palatal expansion followed by maxillary protraction. The percentage relapse in maxillary intermolar widths was 30-45 per cent after 1 year, in most cases with minimal retention. In the mandibular arch, the concurrent increase in intermolar width (2.3 mm) was primarily due to buccal uprighting of the posterior molars when the maxilla was protracted into a Class I skeletal relationship and was stable after 1 year. The results of this study indicate stability of orthopaedic treatment of Class III malocclusions directed at the maxilla. Despite some relapse, a net improvement in maxillomandibular relationship and a positive overjet was maintained in 18 out of 20 patients at the end of the follow-up period.

Effect of training and experience on cephalometric measurement errors on surgical patients

The aim of this study was to quantify and compare the cephalometric measurement errors (interexaminer errors) between two orthodontic residents and two oral and maxillofacial surgical residents with differing years of experience. It was hypothesized that the measurement errors would differ between observers with different training backgrounds and experience and that this would lead to significant disagreements in the cephalometric assessment of patients to receive combined orthodontic and orthognathic surgical treatment. Thirty cephalograms were used in the evaluation. Each examiner independently digitized all cephalograms twice. Common cephalometric skeletal and dental variables, 18 angular and 9 linear, were measured. Interexaminer errors were calculated using two-sample t tests for every pair of examiners. The interexaminer error was large in both landmark identification and in angular and linear measurements. The amount of error did not depend on training or experience but probably on individual conception of landmark definition and perception of landmark location. Methods to limit interexaminer measurement errors are described.

Cephalometric comparisons of Chinese and Caucasian surgical Class III patients

Pretreatment cephalometric radiographs of 30 Chinese and 30 Caucasian surgical Class III patients were studied to determine if there were skeletal and soft tissue morphology differences between the groups. Nineteen hard tissue and 13 soft tissue measurements were traced and digitized. A two-sample t test was used to analyze sex and ethnic differences between groups. A significant difference between sexes was found in the linear skeletal measurements but not in the angular measurements for both ethnic groups. Ethnic differences were found in the anterior cranial base measurement, which was significantly shorter in the Chinese sample. In addition, a larger posterior cranial base, a smaller gonial angle, and an increase in mandibular length contributed to the increase in mandibular prognathism found in the Chinese sample. Few differences between sexes were found in the soft tissue measurements. However, ethnic differences were found in maxillary and mandibular soft tissue prognathism, upper and lower lip protrusion, and nasolabial angle, which reflected the more severe underlying skeletal disharmony in the Chinese sample. When the surgical samples were compared to a reference population, an increase in skeletal measurements was found with the Chinese sample in maxillary and mandibular prognathism and dentoalveolar protrusion. Soft tissue maxillary prognathism and upper lip protrusion were found to be smaller than the reference population in the Caucasian sample but greater in the Chinese sample.

Long-term effects of Class II correction in Herbst and Bass therapy

This study compared the initial and long-term skeletal and dental effects of Herbst and Bass appliance therapy for correction of Class II malocclusion. The sample comprised 18 pairs of boys matched for growth period at the time of therapy, with similar pre-treatment sagittal and vertical jaw base relationships. One boy in each pair was treated with the Herbst and the other with the Bass appliance. At follow-up, 15 boys of the Herbst group and 17 of the Bass group were available. Lateral cephalograms in centric occlusion taken before treatment, after 6 months of treatment and at the end of growth were analysed. After 6 months of treatment the Bass appliance seemed to have a greater effect on mandibular jaw base position. The correction of overjet and sagittal molar relationship was more complete in the Herbst patients due to dental changes. At follow-up varying effects both between and within pairs were observed. Overall, the skeletal and dental changes from start of treatment to end of growth were of the same magnitude. A restraining effect on the position of the maxilla was observed in both groups, somewhat more pronounced in the Bass sample. Both treatment methods are most useful in correction of severe Class II malocclusions. It was, however, difficult to find possible differences in treatment effects between the two methods due to great individual variations of growth.

A comparative study of sagittal correction with the Herbst appliance in two different ethnic groups

The dentofacial morphology of Chinese is different from Caucasians. The purpose of this investigation was to assess the skeletal and dental changes contributing to the sagittal correction in group of consecutive Chinese children who were treated with the Herbst appliance. A comparison was made between 14 Chinese and 14 Swedish subjects who all had Herbst appliance treatment. All subjects were corrected from the Class II division 1 malocclusion to an overcorrected Class I or Class III dental relationship within a 6-8 month period. Lateral cephalograms taken before and immediately after the Herbst treatment were analysed. In general, the skeletal and dental changes during treatment were comparable between both ethnic groups. However, individual variations within the two groups were wide. It can be concluded that the Herbst appliance was equally successful in Southern Chinese children and similar treatment changes as those achieved in Swedish children could be found.

Mandibular growth during initial treatment with the Bass orthopaedic appliance in relation to age and growth periods

The aim of this study was to relate the initial orthopaedic effects of a Bass activator to age and growth periods at the time of therapy. The sample consisted of 54 boys with a severe Class II, division 1 malocclusion. The mean age at start of treatment was 11.4 years. Longitudinal records of standing height were used to assess the growth period during treatment. Three periods were established: pre-peak, peak and post-peak. The treatment period of each subject was assigned to one of these periods. Lateral cephalograms were available 6 months before treatment in 22 of the boys, and at the start of treatment and after 6 months in the whole sample. No significant growth changes were observed 6 months before treatment. During the initial 6 months of treatment a small restraining effect on the maxilla and a forward growth of the mandible was observed. A significant correlation between age and forward growth of the mandible during treatment was found in the pre-peak and peak groups. This indicates a great initial orthopaedic treatment effect in young boys in the pre-peak period and in boys with an early peak. In boys 10 years of age or older not having reached the peak period of growth, the treatment response was less pronounced.

Agenesis of mandibular second premolars. Spontaneous space closure after extraction therapy: a 4-year follow-up

The aim of this study was to investigate the space closure and occlusal changes in 11 subjects (mean age 11.8 years) with normal occlusion and agenesis of the mandibular second premolar, after extraction of the mandibular secondary primary molar and the maxillary second premolar on the side of the agenesis. The treatment started when the first premolars came into occlusion and the subjects were followed for 4 years. Dental casts were taken at the start of treatment and after 1, 2 and 4 years, and lateral cephalograms were taken at the start of treatment and after 2 and 4 years. Space closure, sagittal movements, rotational movements, and tipping of the first molars and first premolars and dental midline shift were measured on photographs of dental casts. Sagittal movement of the incisors was measured on lateral cephalograms. The results showed that most of the extraction space closed during the first year (55 per cent in the maxilla, 46 per cent in the mandible) and at the end of the follow-up period 89 per cent of the extraction space closed in the maxilla and 80 per cent in the mandible, leaving a mean residual extraction space of 0.9 and 2 mm respectively. In the maxilla, 70 per cent of the extraction space closed by mesial and rotational movements of the first molars. Maxillary premolars moved distally, rotated and tipped only during the first year of observation. In the mandible, the space closure occurred by mesial/rotational movements and tipping of first molars and distal movement and tipping of the first premolars. Unilateral extraction had no influence on the maxillary midline while it caused a statistically significant mandibular dental shift to the extraction side. Extraction therapy had no impact on the overjet, overbite or incisor inclination.

Cephalometric A point changes during and after maxillary protraction and expansion

The purpose of this study was to analyze the treatment and posttreatment maxillary changes achieved with maxillary protraction therapy. The cephalometric records of 25 consecutively treated Chinese children with Class III malocclusions (mean age 8.4 years) were analyzed for cephalometric A point changes, which were then compared with an untreated, age and sex matched Class III control sample. A cephalometric maxillary superimposition technique was used to differentiate between the skeletal and the local contributions to the total A point change. Results showed that 6 months of maxillary protraction therapy produced a mean A point advancement of 2.4 mm compared with 0.2 mm in the control group. Of this advancement, 75% was found to be due to skeletal maxillary advancement and 25% was attributed to local remodeling. Significantly less downward movement of A point was found with treatment compared with the controls, which could be related to the direction of force application. No significant differences were found in the horizontal and the vertical movements of A point between the treatment and the control groups during the 12-month posttreatment period, indicating stability of early maxillary protraction in patients with Class III malocclusions.

The effect of demineralized bone matrix on the healing of intramembranous bone grafts in rabbit skull defects

A clinical dilemma exists regarding the type of bone that should be used to replace diseased or traumatized osseous tissue. Oral, plastic, and orthopedic surgeons normally implant viable mineralized endochondral (EC) autografts or demineralized EC allografts. A few clinicians have recognized the disadvantages of using EC bone in craniofacial surgery and advocated the replacement of intramembranous (IM) bone with healthy IM bone. However, controversy and uncertainty surround our understanding of these matrices to induce bone formation. Recent studies have advocated the use of other materials with osteoinductive properties, such as demineralized bone matrix (DBM). The proposed delivery system used in this study included IM bone grafts, DBM, and fixation of the IM bone graft. The purpose of this work was to gain further insights into the mechanism of healing of IM bone, in both the presence and the absence of DBM, and to compare the healing of IM bone grafts with that of DBM alone. Critical-sized (10 x 5 mm), full-thickness bony defects in rabbit parietal bone, devoid of periosteum, were filled with IM bone graft (mandible) alone, demineralized cortical bone matrix (DBM) alone, or combined DBM-IM bone graft, or were left unfilled. Histologic changes were examined 14 days later. The IM bone graft healed through IM ossification with no intermediate cartilage stage. DBM and composite DBM-IM healed through an EC ossification with an intermediate cartilage stage. It is hypothesized that the role of the IM graft is to induce neovascularization into the defect site, and that the undifferentiated mesenchymal cells in the perivascular region of the new blood vessels are induced by the bone morphogenetic protein(s) in the DBM into bone-forming cells.