Virtual model analysis as an alternative approach to plaster model analysis: reliability and validity.

The objective of this study was to assess the feasibility of virtual models as an alternative to orthodontic plaster models. Virtual dental models (obtained from OrthoCAD) and corresponding plaster models of 80 patients in the permanent dentition were randomly selected from patients seeking orthodontic care. Inter-examiner error was assessed by measuring tooth width, overjet, overbite, intermolar width, intercanine width, and midline discrepancy. Criterion validity of virtual model analysis was determined by the agreement between the measurements from virtual and plaster models. Test-retest reliability was determined by remeasuring 10 virtual models 1 week later. Comparison analysis was assessed by calculating the mean directional differences and standardized directional differences. Correlation analysis was determined by calculating the intraclass correlation coefficients (ICCs). Both intra- and inter-examiner reliability and test-retest reliability of virtual model analysis were acceptable in measuring intercanine, intermolar, overjet, overbite, midline discrepancy, space analysis, and tooth width (ICC > 0.7). Good criterion validity was indicated by agreement between the results from the plaster and virtual models (ICC > 0.8). There were substantial agreements for canine and molar relationship classifications (κ > 0.70). The results suggest that analysis performed on virtual models is as valid as traditional plaster models for intra- and inter-arch relationship.

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.

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.

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.

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.

Alternative gene therapy strategies for the repair of craniofacial bone defects.

Craniofacial anomalies, bone defects and cartilage lesions pose a difficult and challenging problem for both the doctor and for patients and their families. Conventional therapies focus on orthopaedic surgery, grafting with autogenous bone, allogenic bone grafts, or distraction osteogenesis. However, the efficacy of these techniques is limited by high cost, donor morbidity, scarcity of tissue resources, and alterations in volume [Marx & Morales, 1988]. On the basis of recent insights into the development, growth, and adaptation of bone, together with the significant advances in recombinant DNA technology, gene therapy is increasingly becoming recognised as an alternative technique for augmenting and promoting bone regeneration in vivo. It can be applied in craniofacial skeletal tissues by transferring genes encoding for specific growth factors such as BMPs in osteoblasts, chondrocytes or progenitor cells for the purpose of enhancing protein production [Scaduto & Lieberman, 1999]. It can be performed by either direct administration of gene delivery vectors, or by transplantation of genetically modified cells. This review will focus on recent advances in molecular mechanisms of bone formation, and development in various viral and non-viral vectors for direct in vivo therapeutic gene transfer and genetically engineered cells ex vivo therapy.

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.

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.

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.

An update on the aetiology of orofacial clefts.

OBJECTIVE: To review recent data on the aetiology of cleft lip and palate. DATA SOURCES: MEDLINE literature search (1986-2003). STUDY SELECTION: Literature and data on aetiology of cleft lip and palate using the following key words: 'cleft lip', 'cleft palate', 'aetiology', and 'genetics'. DATA EXTRACTION: Relevant information and data were reviewed by the authors. DATA SYNTHESIS: Cleft lip and palate is one of the most common types of congenital malformation. The aetiology seems complex, but genetics plays a major role. Recently several genes causing syndromic cleft lip and palate have been discovered. Three of them--namely T-box transcription factor-22 (TBX22), poliovirus receptor like-1 (PVRL1), and interferon regulatory factor-6 (IRF6)--are responsible for causing X-linked cleft palate, cleft lip/palate-ectodermal dysplasia syndrome, and Van der Woude's and popliteal pterygium syndromes, respectively; they are also implied in non-syndromic cleft lip and palate. The nature and function of these genes vary widely, illustrating high vulnerability within the craniofacial developmental pathways. The aetiological complexity of non-syndromic cleft lip and palate is also exemplified by the large number of candidate genes and loci. CONCLUSIONS: The aetiology of non-syndromic cleft lip and palate is still largely unknown, but mutations in candidate genes have already been identified in a small proportion of cases of non-syndromic cleft lip and palate. Determining the relative risk of cleft lip and palate, on the basis of genetic background and environmental influence, including smoking, alcohol use, and dietary factors, will aid in genetic counselling and the development of future preventive measures.

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.

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.

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.

Early child health in Lahore, Pakistan: XIII. Primary teeth emergence.

The aim of this study was to investigate the number of emerged primary teeth at various ages from 6 to 24 months in 1347 longitudinally followed Pakistan infants sampled from four socio-economically different areas in Lahore, Pakistan; from a very poor periurban slum to a privileged upper middle class group. The emergence of the primary teeth was found to be little, or not all related to sex or to the area of living. However, in comparison with studies conducted in other continents, the Indo-Pak subcontinent population lags behind in primary teeth emergence, especially in early life. This genetic difference makes it necessary to create specific standards of primary teeth emergence for this population.

Effect of protraction headgear on Class III malocclusion.

Ten patients with skeletal Class III malocclusion in the early mixed dentition who were treated with maxillary expansion appliance and protraction headgear were compared with reasonably matched controls. Significant orthopedic effects were found after as little as 6 months of treatment. Cephalometric analysis revealed that the correction of Class III malocclusion was primarily a result of forward and downward movement of the maxilla and backward rotation of the mandible. The clinical result of one patient treated with this appliance is used to demonstrate the importance of force magnitudes and directions, as well as the design of the appliance, to the success of the treatment.

Dental development, dental age and tooth counts.

Emergence data on the 20 deciduous teeth and the first 29 permanent teeth were collected from 212 randomly selected urban Swedish children who were followed from birth to 18 years of age. The sex difference in the emergence of the deciduous teeth is less than one month, which is not statistically significant. Boys are consistently ahead of girls until the 17th deciduous tooth. From the 17th deciduous tooth on through most of the permanent dentition, girls are consistently ahead of boys. In the permanent dentition the sex difference ranges from 3 MO to 11 MO; these differences are statistically significant except for the 29th tooth. Reference data on dental age based on counts of 1-19 deciduous and 1-27 permanent teeth are tabulated and tooth emergence curves constructed. The tooth emergence curves can be used to express individual dental development in terms of standard deviation scores. Validity of dental age assessed by counts of permanent teeth is evaluated by a cross-sectional comparison with another sample of Swedish boys and girls. The mean difference between estimated age and chronological age is about one month in either sex. Precision of an individual estimate of dental development in terms of 95% confidence level (approximately equal to +/- 2 S.D.) varies from about +/- 4 months in the deciduous dentition to +/- 3 years in the permanent dentition. Assessment of dental development and dental age by means of tooth counts is a convenient and simple method, although it can only be applied at ages when emergence can be expected. It is especially useful in cross-sectional evaluations, as no serial data are required. In populations with a low incidence of caries the impact of such disturbing factors on emergence is correspondingly low, further increasing the validity of assessments of dental development based on tooth emergence.

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.

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.

Masticatory muscle pain before, during, and after treatment with orthopedic protraction headgear: a pilot study.

Protraction headgear has been used in conjunction with a palatal expansion appliance to correct Class III malocclusion with maxillary deficiency and/or mandibular prognathism. In general, 800 gm of orthopedic force is used to protract the maxilla, and 75% of this force is transmitted to the temporomandibular joint (TMJ) area via the mandible. The effect of this heavy intermittent force on the TMJ has not been reported in the literature. The objectives of this study were to determine the level of masticatory muscle pain and EMG activity in patients treated with maxillary protraction headgear. Ten patients with skeletal Class III malocclusion whose treatment plan called for maxillary protraction headgear treatment participated in this study. Nocturnal masticatory muscle activity was determined using a portable electromyographic (EMG) recording device. Subjects wore the EMG device 14 nights before treatment, 14 nights during treatment, and 14 nights 1 month after active treatment. Masticatory muscle pain level was determined by muscle palpation, scored on a scale of 0 to 3 each period, according to the method of Gross and Gale. The examiner followed a sequence outlined by Burch to examine the masticatory muscles. Results showed no significant differences for masticatory muscle activities before, during, and after treatment. Only a few patients experienced level 1 masticatory pain during treatment. None of the patients experienced masticatory muscle pain 1 month after treatment. These results demonstrate no significant increase in masticatory muscle activity or muscle pain associated with orthopedic treatment using maxillary protraction headgear.

Timing of tooth emergence. A prospective longitudinal study of Swedish urban children from birth to 18 years.

Longitudinal data on tooth emergence were collected from birth to 18 years from 212 randomly selected Swedish urban children. At 18 years, 76 per cent (160/212) of the original subjects were examined. All deciduous teeth except the mandibular second molar emerged earlier in boys than in girls, but the sex difference was only statistically significant (p less than 0.05) for the maxillary laterals and mandibular canines. All permanent teeth emerged significantly earlier in girls than in boys, the sex difference being 2.5 to 14 months.