Summary There are several reports suggesting that forward head posture is associated with temporomandibular disorders and restraint of mandibular growth, possibly due to mandibular displacement ...posteriorly. However, there have been few reports in which the condylar position was examined in forward head posture. The purpose of this study was to test the hypothesis that the condyle moves posteriorly in the forward head posture. The condylar position and electromyography from the masseter, temporal and digastric muscles were recorded on 15 healthy male adults at mandibular rest position in the natural head posture and deliberate forward head posture. The condylar position in the deliberate forward head posture was significantly more posterior than that in the natural head posture. The activity of the masseter and digastric muscles in the deliberate forward head posture was slightly increased. These results suggest that the condyle moves posteriorly in subjects with forward head posture.
Aim: A mandible bone‐borne Herbst appliance (MBBHA) would avoid the proclination of the lower incisors that occurs with any teeth‐borne functional appliance. But mapping of the bone characteristics ...at potential fixation areas around the mental foramen has not been carried out so far. The aim of this computer tomographic (CT) study was to evaluate bone thickness at specific positions around the mental foramen.
Material and methods: CT scans of 60 randomly chosen adult Hong Kong Chinese subjects (mean age 28±6.3 years) were used to measure the bi‐cortical bone thickness in the mandible in the mental foramen area. The thickness of buccal and lingual cortical and cancellous bone was assessed at the following locations: 10 mm (A10 mm) and 5 mm (A5 mm) anterior, 10 mm (P10 mm) and 5 mm (P5 mm) posterior, and 5 mm (Inf5 mm) below the mental foramen.
Results: The amount of buccal cortical bone thickness ranged between 1.89 mm, 10 mm anterior of the mental foramen, and 2.16 mm, 10 mm posterior to its location. At the A10 mm level, cortical thickness showed a marginal statistically significant difference between A5 and A10 mm. The total amount of bone thickness ranged from 10.19 to 12.06 mm.
Conclusion: At the locations studied around the mental foramen, a mean bicortical bone thickness of 10–12 mm was measured. No large variation in the thickness was found between bicortical bone thicknesses in the measured locations around the mental foramen. Thorough evaluation on a case‐by‐case basis is advisable.
To cite this article:
Al‐Kalaly AA, Wong RWK, Cheung LK, Purkayastha SK, Schätzle M, Rabie ABM. Evaluation of bone thickness around the mental foramen for potential fixation of a bone‐borne functional appliance: a computer tomography scan study. Clin. Oral Impl. Res. 21, 2010; 1288–1293. doi: 10.1111/j.1600‐0501.2010.01947.x
The aim of this study was to assess the effect of varied degrees of mandibular advancement on condylar growth. Three hundred and thirty five 35-day-old female Sprague–Dawley rats were randomly ...divided into 10 experimental groups (n = 10) and five control groups (n = 5) for analysis of new bone formation and 10 experimental groups (n = 14) and five control groups (n = 14) for molecular analysis. The experimental animals were fitted with bite-jumping appliance to advance the mandible 2 and 4 mm. The rats were sacrificed on days 3, 7, 14, 21, and 30. A computer-assisted image analysing system was used to assess the quantity of new condylar bone formation. Molecular analysis utilizing real-time reverse transcription–polymerase chain reaction was used to assess the different levels of mRNA expression of different growth markers in the condyle. One-way analysis of variance (ANOVA), with a Bonferroni multiple comparison test, showed significantly more newly formed bone in the 4 mm group compared with the 2 mm and control groups on days 21 and 30 (P < 0.05). Most of the examined growth markers demonstrated a significant increase during the 4 mm advancement (P < 0.05). Indian hedgehog (Ihh) mRNA showed a 7- and 5-fold change, parathyroid hormone-related peptide (PTHrP) a 5.2- and 3-fold change and type II collagen a 9.6- and 3.7-fold change in the 4 and 2 mm advancement groups, respectively. Varied degrees of mandibular advancement result in different quantities of new bone formation and levels of expression of growth members: Ihh, PTHrP, and type II collagen.
The purpose of the present study was to determine whether a force of 20 cN can be biologically active for tooth movement and to examine the pain intensity during the application of light (20 cN) or ...heavy (200 cN) continuous forces for 7 days.
In the first experiment, a force of 20 cN was applied to eight canines in five volunteers. The mean tooth movement during 10 weeks was 2.4 mm. In the second experiment, two forces of 20 or 200 cN were applied to maxillary premolars in 12 male subjects (aged 24-31 years) to measure pain intensity for 7 days. Spontaneous and biting pain were recorded every 2-4 hours on a 100 mm visual analogue scale (VAS). Wilcoxon signed-rank test was used for statistical analysis.
Comparing the VAS score at force initiation with the other time points, there was no significant difference in spontaneous pain for either group, or in biting pain for the light-force group. However, biting pain in the heavy-force group during the time period from 6 to 156 hours was significantly (P < 0.05) greater than that at force initiation. Comparing the VAS scores between the light- and heavy-force group, VAS scores for biting pain in the heavy-force group during the time period from 8 to 100 hours was significantly (P < 0.05) greater than that in the light-force group.
A force of 20 cN can move teeth, but pain intensity while biting may be greater approximately 8 hours to 5 days following the application of heavy continuous force compared with light force.
The outpour of new research has led to the identification of several factors that play an important role in condylar growth. The objectives of this review are to present the molecular markers that ...regulate the growth of different cells in the mandibular condyle and their impact on clinical use of functional appliance. The proliferative layer in the mandibular condyle houses a great number of undifferentiated mesenchymal cells that provide the pool of chondrogenic cells. Therefore, it is important to understand the factors that regulate the cell cycle of these replicating mesenchymal cells as well as the factors that control their differentiation to chondroblasts. These chondroblasts in turn are engaged in cartilage matrix synthesis. Therefore, it is critical to present the factors that regulate matrix formation.
The process of maturation of chondrocytes into hypertrophic chondrocytes directly impacts the number of cell replication cycles and indirectly affects growth. Therefore, it is of great importance to review the factors that regulate chondrocytes maturation. Hypertrophic chondrocytes secrete hypertrophic matrix with its type X collagen that marks the onset of endochondral ossification.
Angiogenesis is regulated by vascular endothelial growth factor (VEGF), and the new blood vessels are rich depository of mesenchymal cells. Factors that regulate the differentiation of these cells into osteogenic cells are critical to growth of the condyle.
Understanding of these markers and their levels of expression provides the basis for application of different treatment modalities in the area of growth modification. Furthermore, the identification of factors critical to condylar growth provides us with candidate genes for future gene therapy.
Introduction: An externally applied force to the cranial vault has been reported to affect the growth of the facial skeleton. However, the effect on the mandible is unclear. The purpose of this study ...was to investigate the relationship between anteroposterior cranial vault deformation and mandibular morphology.
Methods: The study sample included 44 women’s crania with intact faces and bases that were excavated from archaeological sites in the Azapa Valley in northern Chile. The crania were divided into anteroposterior deformation (AP) and undeformed (U) groups according to frontal, parietal, and occipital curvatures. The sizes of the cranial vault, middle face, and mandible were measured with calipers. Lateral cephalograms were taken and analyzed according to a conventional method.
Results: Cranial base angle, bizygomatic breadth and upper facial height, bicondylar breadth, anterior breadth, and mandibular body length were significantly larger, and the mandibular angle was significantly smaller, in the AP group than in the U group.
Conclusions: The anteroposteriorly shorter and wider cranial deformation caused by externally applied forces in infancy might affect the bone-remodeling process of the mandibular angle, leading to a smaller mandibular angle in adulthood.
Abstract Objectives We aimed to investigate the expression profile of cell cycle genes in the mandibular condyle on mechanical strain and natural growth, and quantify their expression intensity. ...Methods Three hundred and fifty 35 days old Sprague–Dawley rats were randomly divided into experimental groups fitted with bite-jumping appliances and control groups. Groups were sacrificed at days 1, 3, 7, 9, 14, 30, and 33. Then, condyles were dissected and total RNA was extracted for microarray analysis. Results Thirty-nine known cell cycle genes were present in the condyle, where Cyclin D1, PCNA, and Wnt5a were differentially expressed. Reverse transcriptase-PCR confirmed that Wnt5a showed a 2-fold increase on experimental day 1, Cyclin D1 showed a 2-fold increase on experimental day 1 and a 3-fold increase on experimental day 14, while PCNA shows 2.2-fold increase both on experimental days 9 and 30. PCNA, Cyclin D1, and Wnt5a were all expressed by cells in both the proliferative layer and erosive zone. Conclusion Mandibular advancement leads to the expression of Cyclin D1 that accelerates entry to the S phase. The increased level of PCNA indicates increased DNA replication of MSC. Then, elevated level of Wnt5a indicates the commitment of MSC to the chondrogenic lineage.
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