Condylar Growth Research Articles

Novel roles of tendon in the postnatal growth and expansion of TMJ condyle

The Temporomandibular joint (TMJ) is one of the most complex joints in the human body. TMJ is composed of the temporal bone, a disc and a movable mandibular condyle with abundant tendon attachments. Tendon has been thought to play the sole function of transmitting muscle forces to stabilize joints, yet it is largely unclear why tendon undergoes ectopic ossification in trauma or diseases, and whether it has any direct contribution to skeletal formation. This study aimed to investigate the full biological significance of tendon in TMJ growth. We first discovered that the TMJ condyle is composed of a well‐established cartilage head and an overlooked “bony head” that grows after birth and continuously expands throughout the lifespan with little signs of remodeling. Mouse X‐ray images (Fig.1a) showed little change in the cartilage head’s volume but a continuous expansion in the bony head’s mass with a low mineral content from 1 to 5 months (Fig.1b). Toluidine blue staining showed TMJ condyle had a large area of tendon attachment extending down to ramus (Fig.1c, white dotted line in lower magnification), defined by regions of tendon, interface, and TFB (Fig.1c1). The TFB morphology was distinct from endosteum‐formed bone (EFB, Fig.1c1), cartilage‐formed bone (CFB, Fig.1c2, rich in cartilage residual), or periosteum‐formed bone (PFB, Fig.1c3) in cell shape and distribution, and ECM. TEM images further revealed that the osteocytes in the TFB were large in size, irregular in shape, had small nuclei but numerous ERs and Golgi complexes, and were embedded in ECM rich in fibropositors. In contrast, the osteocytes in EFB, CFB or PFB were spindle‐shaped with larger nuclei but fewer ERs and Golgi complexes (Fig.1d). To reveal the cell source of the bony head, cell lineage tracing were used. Tracing data showed that most CFB cells originate from Col10a1+ hypertrophic chondrocytes, whereas the interface and TFB were derived from Scx+ cells (Fig.1e). RNAscope displayed high levels of Thbs4 (Thrombospondin‐4, a tendon marker) and SOST (a potent inhibitor of Wnt signaling secreted by osteocytes) mRNA in TFB at bony head (Fig.1f). The Scx‐CreERT2 tracing combined with IHC staining showed TFB maintained a mixed ECM of bone (Col1), cartilage (Aggrecan) and tendon (Periostin, Fig.1g). To further determine the role of tendon lineage in condyle expansion, we generated Scx‐CreERT2; R26RDTA (carrying a loxP‐flanked stop cassette associated with an attenuated diphtheria toxin fragment A, DTA, for the ablation of cells when Cre is active). Deletion of Scx+ cells greatly reduced the size of bony head (Fig.1h) and the thickness of interface with few Scx+/Col1+ bone cells in P28 DTA mice (Fig.1i); In conclusion, our study tendon cells, beyond their conventional role in joint movement, are key players for the postnatal growth and expansion of TMJ condyle (Fig.1j).

Inhibiting Hh Signaling in Gli1+ Osteogenic Progenitors Alleviates TMJOA

The increased prevalence of temporomandibular joint osteoarthritis (TMJOA) in children and adolescents has drawn considerable attention as it may interfere with mandibular condyle growth, resulting in dento-maxillofacial deformities. However, treatments for osteoarthritis have been ineffective at restoring the damaged bone and cartilage structures due to poor understanding of the underlying degenerative mechanism. In this study, we demonstrate that Gli1+ cells residing in the subchondral bone contribute to bone formation and homeostasis in the mandibular condyle, identifying them as osteogenic progenitors in vivo. Furthermore, we show that, in a TMJOA mouse model, derivatives of Gli1+ cells undergo excessive expansion along with increased but uneven distribution of osteogenic differentiation in the subchondral bone, which leads to abnormal subchondral bone remodeling via Hedgehog (Hh) signaling activation and to the development of TMJOA. The selective pharmacological inhibition and specific genetic inhibition of Hh signaling in Gli1+ osteogenic progenitors result in improved subchondral bone microstructure, attenuated local immune inflammatory response in the subchondral bone, and reduced degeneration of the articular cartilage, providing in vivo functional evidence that targeting Hh signaling in Gli1+ osteogenic progenitors can modulate bone homeostasis in osteoarthritis and provide a potential approach for treating TMJOA.

Efficacy of Arthroscopic Discopexy on Condylar Growth in Temporomandibular Joint Anterior Disc Displacement: A Randomized Clinical Trial

Efficacy of Arthroscopic Discopexy on Condylar Growth in Temporomandibular Joint Anterior Disc Displacement: A Randomized Clinical Trial

Reference values of mandibular condylar growth activity: a study of SUVmax with quantitative bone SPECT/CT.

To assess the condylar growth activity (CGA) with quantitative bone single photon emission computed tomography/computed tomography (SPECT/CT) to establish reference values of maximum standardized uptake value (SUVmax) and cutoff values for identifying active unilateral condylar hyperplasia (UCH) in different ages. We analyzed the CGA of 58 UCH patients and that of 125 volunteers as a control group by SUVmax of quantitative bone SPECT/CT imaging. The SUVmax and the uptake difference between bilateral condyles among different age groups were analyzed. SUVmax cutoff values for detecting active condyle were calculated by receiver operating characteristic curve analysis. The condylar SUVmax in 10-19, 20-29, 30-39, 40-49 and 50-59 years old groups of volunteers were 6.24 ± 1.39, 4.76 ± 0.98, 3.23 ± 0.64, 3.00 ± 0.61 and 2.90 ± 0.53, respectively. The uptake difference between bilateral condyles in the control group was 3.84% ± 1.71%. The affected condylar SUVmax was significantly higher than that of the contralateral condyle in active UCH patients (6.03 ± 2.85 vs. 3.96 ± 1.07; Z = -5.264; P = 0.000). SUVmax of the affected condyles in active UCH patients was not statistically higher than condylar SUVmax in the corresponding age group (6.03 ± 2.85 vs. 5.50 ± 1.41; Z = -0.173; P = 0.863). SUVmax of the unaffected condyles was significantly lower than condylar SUVmax in the corresponding age group (3.96 ± 1.07 vs. 5.50 ± 1.41; Z = -5.833; P = 0.000). SUVmax cutoff values for identifying active condyle were 6.26 and 4.53 in patients of 13-19 and 20-29 years old, respectively. The condylar SUVmax varied with age. Different cutoff values of condylar SUVmax should be employed for diagnosing active UCH for patients in different ages.

Análise microscópica na articulação temporomandibular a partir da mudança de direção do vetor de força da mandíbula em relação à base do crânio : estudo experimental em coelhos (Oryctolagus cuniculus l.)

The correlation between TMJ's growing, structure and function is consensual in the specialized literature. Until the moment, the little knowledge about post-birth changes are studied by observation of condylar growth and disc reestructuration. In an experimental model in rabbits (Oryctolagus cuniculus 1.), it was observed tecidual alterations of the TMJ's components — mandibular condyle, articular disc and temporal bone, face to a direction change of mandibular power axis, which has the incidence upon these structures. Twentyfour rabbit were divided in four groups. Two of each group formed a control group. Four experimental periods were established 15, 30, 60 and 90 days. The animals from the experimental group were submitted to surgical procedure involving the mandible right side, changing the direction of mandibular power axis, which has incidence in the TMJ. Histological observations of TMJ in the control group, at different times, the growth and development of this structure were showed, compatible to the normality. At experimental group, the change of mandibular power axis caused alteration of the mandibular condyle and the discal structure. Significative responses at temporal bone were observed too, as a process of osseous modelation, suggestive of growth of this cranial structure.

Changes of the condylar cartilage and subchondral bone in the temporomandibular joints of rats under unilateral mastication and expression of Insulin-like Growth Factor-1

This study aimed to define changes in the rat condylar cartilage and subchondral bone using the unilateral mastication model. In this study, forty 4-week-old Wistar rats were randomly divided into experimental (n=20) and control group (n=20). In the experimental group, unilateral dental splints were placed on the occlusal surface of left maxillary molars. The rats were sacrificed at 1, 2, 3, and 4 weeks after placement of the splint. Micro-CT scanning and histological staining were performed to observe the changes in the mandibular condylar cartilage and subchondral bone. Levels of insulin-like growth factor-1 (IGF-1) were determined via immunohistochemistry to analyse the occurrence of osteogenic changes. Micro-CT scanning findings demonstrated the occurrence of asymmetric growth of condyle in the experimental group. The condylar cartilage and subchondral bone exhibited degradation on the chewing side of the experimental group and showed decreased bone mineral density, thinner cartilage thickness, and increased degree of degeneration and osteoclast activity. Compared with the control group, the expression of IGF-1 was remarkably higher on the non-chewing side. Long-term unilateral mastication can lead to the occurrence of degenerative changes in the condylar cartilage and subchondral bone during growth and development. IGF-1 may play a role in promoting the process of osteogenesis.

Using 3D Medical Modeling to Evaluate the Accuracy of Single-Photon Emission Computed Tomography (SPECT) Bone Scintigraphy in Diagnosing Condylar Hyperplasia

To evaluate the accuracy of single-photon emission computed tomography (SPECT) in diagnosing unilateral condylar hyperplasia (UCH) and to describe the condylar growth of patients with UCH. Using a retrospective study design, patients with UCH who had undergone SPECT and cone-beam computed tomography (CBCT) examinations at the same time were included in the study. We used 3D medical models based on CBCT data as the gold standard. The SPECT results were compared with the model data, and the sensitivity and specificity were calculated. To further describe the condylar growth activity, statistical analysis was performed, and the P value was set at 0.05. The sample was composed of 75 patients. The sensitivity of SPECT was 55.3%, the specificity was 48.6%, and the area under the receiver operating characteristic curve was 0.53. There was no significant difference in sex between patients with and without active growth. The sensitivity and specificity of SPECT are poor, and SPECT alone is not suitable for evaluating the active stage of condylar growth. 3D medical modeling has good prospects for application in the diagnosis of condylar hyperplasia.

The effect of low intensity pulsed ultrasound on mandibular condylar growth in young adult rats

There is a need for more effective methods to enhance mandibular growth in young adults with mandibular deficiency. Previous studies suggest that low intensity pulsed ultrasound (LIPUS) can enhance mandibular growth in growing individuals. This study aimed to evaluate the potential growth changes of the mandible following 4-week LIPUS application in young adult rats. Nineteen ≈120-day-old female rats were allocated to experimental (n = 10) and control (n = 9) groups. The animals in the experimental group were treated with LIPUS to their temporomandibular joints (TMJs) bilaterally, 20 min each day for 28 consecutive days. Animals were then euthanized; gross morphological evaluation was performed on 2D photographs and 3D virtual models of hemi-mandibles, and microstructural assessment was done for the mandibular condyle (MC). Evaluation of mineralization and microarchitecture properties of subchondral cancellous bone was performed by micro-computed tomography (μCT) scanning. Qualitative and histomorphometric analysis was done on condylar cartilage and subchondral bone following Alcian Blue/PAS and Goldner's Trichrome staining. Vital flourochrome (calcein green) labeling was also utilized to determine the amount of endochondral bone growth. Gross morphological evaluations showed a slight statistically non-significant increase especially in the main condylar growth direction in the LIPUS group. Moreover, 3D evaluation depicted an enhanced periosteal bone apposition at the site of LIPUS application. Microstructural analysis revealed that LIPUS stimulates both chondrogenesis and osteogenesis and enhances endochondral bone formation in young adult rat MC. Furthermore, the effect of LIPUS on osteogenic cells of subchondral cancellous bone was notable. To conclude, LIPUS can enhance young adult rats' MC residual growth potential.

Structural changes in the trabecular bone of the mandibular condyle of growing patients with sagittal jaw discrepancy treated with the twin-block appliance.

The objective of this study was to evaluate the structural changes in the trabecular bone of the mandibular condyles in patients treated with the Twin-block functional orthopaedic appliance that act by promoting condylar growth and to compare the fractal dimension (FD) of condylar trabecular bone structure prior to treatment (T0) and after orthopaedic functional treatment (T1). This retrospective study included panoramic images of 112 individuals with a mean age of 11.04±1.30years in the study group (32 girls and 24 boys) and 11.6±.80years in the control group (29 girls and 27 boys). The standardized region of interest was selected as the right and left condylar areas close to the articulation surfaces from the twin-block (TB) group, which included patients who completed functional orthopaedic treatment and the control group, which included untreated individuals. FD values in the condylar region were analysed from the panoramic radiographs of both groups using a box-counting method with ImageJ software (version 1.52a, US National Institutes of Health). There was a significant decrease in the FD values of the right (-.038) and left (-.022) condylar region at T0 and T1 in the TB group. Between-group FD comparisons demonstrated that the TB group showed changes in the condylar region (right, P=.004; left, P=.022) compared to the control group. Functional orthopaedic forces caused a decrease in the trabecular structure of the condylar area examined.

EFFECTS OF LOW-LEVEL LASER IRRADIATION ON THE GROWTH OF THE RAT MANDIBULAR CONDYLE IN ORGAN CULTURE

<h3>Objective</h3> The present study was carried out to histologically, immunohistochemically, and histometrically investigate the effect of low-level laser irradiation by a diode laser on the growth of the rat mandibular condyle in organ culture. <h3>Methods</h3> The mandibular condyles were removed from rats' embryos on the 21st day and then cultured for 8 days. The 20 cultured condyles were divided into 4 groups: F−L− group (serumless BGJb); F+L− group (serumless BGJb with bFGF 100 ng/mL); F−L+ group (serumless BGJb and laser irradiation); and F+L+ group (serumless BGJb with bFGF 100 ng/mL and laser irradiation). The laser irradiation (output 1.3 W/cm² and wavelength 633 nm) was performed on the cultured condyle for 30 seconds every 24 hours for 5 days. Immunohistochemically, PCNA was used to analyze cell proliferation. <h3>Results</h3> The mesenchymal cells in the layer of differentiation and hypertrophy in the F+L+ group showed a marked increase in cell number and the size of the condyle. The positive cell number of PCNA in F+L− and F+L+ group was significantly higher compared with the control group. <h3>Conclusions</h3> Our data showed that low-level laser irradiation promotes cell proliferation in the cultured condyle same as in bFGF addition. It is suggested that low-level laser irradiation by a diode laser (wavelength 633 nm) stimulated the proliferation of mesenchymal cells, which resulted in an increase in the number of chondrocytes in the layers of differentiation and hypertrophy by leading to the enlargement of the condylar size.

Effects of estrogen deficiency during puberty on maxillary and mandibular growth and associated gene expression \u2013 an \u03bcCT study on rats

BackgroundEstrogen is a well-known and important hormone involved in skeletal homeostasis, which regulates genes involved in bone biology. Some studies support that estrogen is important for craniofacial growth and development. Therefore this in vivo animal study aimed to investigate, whether and in which way low estrogen levels in the prepubertal period affect craniofacial development in the postpubertal stage and to quantify the gene expression of RANK, RANKL and OPG in cranial growth sites in ovariectomized estrogen-deficient rats during puberty.MethodsControl (sham-operated, n = 18) and ovariectomy (OVX, n = 18) surgeries were performed on 21-days-old female Wistar rats. Animals euthanized at an age of 45 days (pubertal stage) were used for gene expression analyses (n = 6 per group) and immunohistochemistry of RANK, RANKL and OPG. Animals euthanized at 63 days of age (post-pubertal stage) were used for craniofacial two-dimensional and three-dimensional craniofacial measurements using μCT imaging (n = 12 per group).ResultsIn the μCT analysis of the mandible and maxilla many statistically significant differences between sham-operated and OVX groups were observed, such as increased maxillary and mandibular bone length in OVX animals (p < 0.05). Condylar volume was also significantly different between groups (p < 0.05). The sham-operated group showed a higher level of RANK expression in the midpalatal suture (p = 0.036) and the RANKL:OPG ratio levels were higher in the OVX group (p = 0.015).ConclusionsOur results suggest that estrogen deficiency during the prepubertal period is associated with alterations in the maxillary and mandibular bone length and condylar growth.

Treatment effects of functional appliances in children with Class II malocclusion with and without morphologic deviations in the upper spine

This research aimed to compare treatment effects of functional appliances between children with and without morphologic deviations in the upper spine and analyze associations between Atlas dimensions and the short- and long-term treatment effects. Sixty-eight prepubertal or pubertal children (35 boys and 33 girls; mean age, 11.47±1.39years) treated with Class II functional appliances were included. Lateral cephalograms were taken at pretreatment (T1), postfunctional appliance treatment (T2), and after retention at postpuberty (T3). Upper spine morphology and Atlas dimensions were evaluated at T1. T1-T2 and T1-T3 lateral cephalograms were superimposed using a structural method. Changes in the jaws were compared with multiple linear regression analysis between children with and without deviations in the upper spine. Associations between the changes and Atlas dimensions were analyzed by partial correlation. Children with morphologic deviations in the upper spine showed significantly more backward rotation of the mandible (P<0.01) and increased inclination of the jaws (P<0.05, P<0.01) from T1-T2 and significantly smaller condylar growth (P<0.01) from T1-T3 compared with children without the deviations. Atlas height was significantly associated with vertical and rotational changes in the mandible (P<0.01) from T1-T2 and condylar growth (P<0.05) from T1-T2 and T1-T3. Morphologic deviations in the upper spine and low Atlas height were significantly associated with smaller condylar growth induced by functional appliances in the long term. Upper spine morphology and the Atlas dimension may be valuable in phenotypic differentiation in children with Class II malocclusion for optimal treatment outcome.

Posterior Mandibular Displacement-A Systematic Review Based on Animal Studies.

Simple SummaryExtreme growth of the lower jaw is an essential determinant of facial appearance and treatment is challenging. The mandibular joint is important for mandibular growth and backward traction may be applied to address its protrusion. Nevertheless, the conclusions following animal experiments have been contradictory; additionally, joint disorders could arise because of abnormal, traumatic pressure. Our aim was to review the impact on the condyle and the jaw of their distal displacement as found in published research involving rats and rabbits, up to October 2020. In those animals, the mandibular/condylar retraction led to occlusal improvement, but some relapse might be anticipated. The mandibular condyle remained more posteriorly, restriction of further growth was observed, the posterior surface became more flattened, but it became thicker in its neck. The dimensional alterations persisted for the entire period of study and the mandible resumed its inherited growth pattern after the discontinuation of the orthopedic force. Posterior mandibular displacement may be anticipated to produce clinically significant restriction in condylar growth, mainly attributed to remodeling. The properties of the applied force may affect the timing of mandibular formation or just prove traumatic. Outcome stability is a matter of concern and more studies are required to resolve the issue.Treating extreme mandibular growth is challenging. The mandible is pushed backwards to address itsprotrusion. Nevertheless, conclusions after such displacement in animals have been contradictory. The aim of the present review is to present measurable alterations of the mandible and the condyle following retractionin healthy rats or rabbits. PubMed, Scopus and Web of Science were accessed for relevant studies up to October 2020. Eligibility was determined by the PICOS process, while the risk of bias was estimated with SYRCLE’s risk of bias tool. Retraction resulted in a more distal molar occlusion and the condyle rested more posteriorly. Mandibular anteroposterior bilateral growth restriction was achieved, the condylar process measured smaller and its angulation increased. The condylar neck thickened, its posterior surface flattened, the coronoid process was measured longer, and enlarged retromolar density was registered. Differences in the ramus height and the intercondylar distance were insignificant. Changes persisted for the period of study and subsequently the mandible resumed its inherited growth pattern. The timing of mandibular shaping and TMJ outcomes might depend on the properties of the applied force. Stability is of concern and well-structured, long-term studies are expected to resolve the issue and further clarify the results of posterior mandibular displacement.

Association between degenerative temporomandibular joint disorders, vertical facial growth, and airway dimension

BackgroundThe goal of this study was to determine whether preexisting degenerative temporomandibular joint (TMJ) disorders are associated with hyperdivergent facial phenotype and decreased airway dimensions. MethodsCone-beam computed tomography scans of adult female and male individuals, 16 years of age and older, distributed in a case group defined as those with degenerative temporomandibular joint disorder (dTMJD; n = 31) or controls with normal TMJ findings (n = 242) were included. Odds ratios were calculated based on facial type and gender. Analysis of variance was used to compare the airway volume and cross section and mandibular measurements between the groups. ResultsCondylar, ramus, and mandibular heights were significantly smaller in the case group compared with the control group. The odds of having a long face subject was significantly higher (P < 0.00001) in the dTMJD group than in the control group with 81% of the dTMJD subjects versus 11% of the control group having long vertical facial dimensions. The smallest cross-sectional area of the airway of the dTMJD group was significantly narrower (P < 0.0361) compared with the controls. Within the control group, ramus height and mandibular alveolar housing for central incisors were significantly smaller (P < 0.0001; P < 0.007) in the long face subjects. ConclusionsThe study shows that a long facial type is associated with findings of degenerative TMJ disorders and related condylar growth disturbances. These degenerative and growth changes may contribute to specific skeletal and dentofacial adaptations resulting in smaller condylar process, mandibular ramus, and body height; thinner alveolar housing at the lower incisor region; and smaller cross-sectional area of the airway.

Effect of Strontium Ranelate on Condylar Growth during Mandibular Advancement in Rats.

Strontium ranelate (SR), unlike other anti-osteoporotic agents, might not only prevent bone resorption but also might induce bone formation. The aim of this experimental study was to evaluate the effects of systemic SR on condylar growth during mandibular advancement (MA) in growing rats. Fifty-six, 8-week-old Wistar male rats weighting 160-190 g were randomly divided into four groups; one control (n=14) and three experimental (n=14). Group 1: Control group, Group 2: SR (900mg/kg daily dose), Group 3: MA, Group 4: SR +MA. The amount and direction of mandibular growth were assessed by linear measurements on the computed tomography (CT) images taken on days 1, 15, and 30. For immunohistochemical evaluation, half of the subjects in the groups were sacrificed on the 15th day (early phase) and the rest of them on the 30th day (late phase). New cartilage and bone formation areas on the condyle were analyzed by using Sox9 and Osteopontin antibodies. Early and late CT images measurements showed no significant difference between the groups (p<0.05). However, there were significant differences between the control and experimental groups in the immunohistochemical assessment. Severe immunolocalization of SOX9 and Osteopontin was observed in Group 4, while the immunolocalization scores were moderate in Group 2 and Group 3. In addition, early histological findings were similar to late results in all groups. In mandibular advancement therapy, Strontium ranelate could be therapeutically effective in avoiding relapse and reducing the duration of retention.

Impact of temporomandibular joint arthroscopic discopexy on condylar growth in adolescents: a retrospective cohort study

Objective: To compare changes of condylar height, disc length and displaced distance in adolescent temporomandibular joint (TMJ) disc displacement with or without arthroscopic discopexy. Methods: From September 2015 to November 2018, adolescents with magnetic resonance image (MRI) comfirmed disc displacement without reduction (DDwoR) were recruited in operation group (OG) and control group (CG) and were classified into five subgroups according to age (11-14 years, 15-16 years, 17-18 years, 19-20 years and 21-24 years). Changes of condylar height, disc length and displaced distance were measured before and after follow-up MRI. Student's t-test, Welch's t-test, Mann-Whitney U test, Wilcoxon signed-rank test, One-way ANOVA and Kruskal-Wallis test were used; P-value less than 0.05 was considered statistically significant. Results: One hundred and seventy two patients were recruited in the present study. One hundred and twenty six cases patients (183 joints, 17 males, 109 females, mean age 17.4±3.0 years) were in OG and 119 patients (175 joints, 20 male, 99 females, mean age 17.1±3.1) in CG. The mean follow-up time were 8.4 (2.7-22.0) and 9.5 (3.0-22.1) months respectively. Average condylar height changes of OG were significantly greater than CG (1.3±1.8 mm vs -0.6±1.5 mm, P<0.001) and differences were also seen in each age group (P<0.001). In terms of age variations, average increase of condylar height in OG were (2.4±2.2) mm, (1.3±1.7) mm, (1.6±1.7) mm, (0.8±1.9) mm, (0.4±1.1) mm respectively (P<0.001), differences were observed between 11-14 years vs 19-20 years (P<0.05), 11-14 years vs 21-24 years (P<0.01) and 17-18 years vs 21-24 years (P<0.01) subgroups; and average changes in CG were (-0.7±1.6) mm, (-0.4±1.6) mm, (-0.8±1.5) mm, (-0.3±1.4) mm and (-0.9±1.5) mm respectively (P>0.05). After follow-up in CG, further displaced disc was observed (P<0.05) while disc length remained unchanged (P>0.05). Conclusions: DDwoR in adolescents resulted in decreased TMJ condylar height while arthroscopic discopexy restored growth potential and promoted condylar new bone formation which was most prominent during growth period.

Evaluation of skeletal changes in mandibular ramus height, corpus length, and mandibular angle changes following twin block appliance therapy using cone-beam computed tomography: A clinical prospective study

Aim and Objectives: This study aims to evaluate the skeletal changes in mandibular ramus height, corpus length, and mandibular angles changes following twin block (TB) functional appliance therapy using cone-beam computed tomography (CBCT).Methodology: Fifteen patients with skeletal Class II, growing of 9–14 years of age with mandibular retrognathism, were treated with TB functional appliance treatment. Pretreatment CBCT and posttreatment CBCT were taken (T0) before treatment and (T1) at the end of the 12 months following TB therapy. The data obtained are analyzed and compared for the skeletal changes in ramus height, corpus length, and mandibular angle changes following therapy. Student's paired t-test was used compare the pre- and post-treatment periods.Results: The test results demonstrate that the Ramus height (mm) in posttreatment period was significantly increased as compared to pretreatment period. The mean increase of 1.23 mm in the ramus height between pre- and post-treatment period was statistically significant at P < 0.001, and that the corpus length (mm) in posttreatment period was significantly increased as compared to pretreatment period. The mean increase of 3.35 mm in the corpus length between pre- and post-treatment period was statistically significant at P < 0.001, and demonstrate that the mean gonial angle (degrees) in posttreatment period was significantly increased as compared to pretreatment period. This mean increase of 3.18° in the gonial angle between pre- and post-treatment period was statistically significant at P < 0.001.Conclusion: TB appliance therapy increases the ramus height, and corpus length stimulating the growth of condyle in backward and upward direction and increases the gonial angle by backward rotation of mandible.

Evaluation of the trabecular structure of the mandibular condyles by fractal analysis in patients with different dentofacial skeletal patterns

Abstract Objective: An orthodontic malocclusion may affect the temporomandibular joint structures in susceptible individuals. This study aims to investigate the bone density of the mandibular condyles in patients presenting with different dentofacial skeletal patterns. Methods: Panoramic radiographs of 200 randomly selected patients with a skeletal and dental Class I, Class II division 1, Class II division 2 and Class III malocclusion were evaluated. Bone density of the right and left mandibular condyles was measured using fractal analysis. Results: No significant difference was detected between the right and left condyles in the various malocclusion groups. However, post-hoc tests showed that Class I patients had significantly higher FD values than Class III and Class II division 1 patients in both right and left condyles following intergroup comparisons. The only significant difference between the genders was detected in the left condyle of Class II division 1 patients, as male patients were found to have significantly higher FD values than females. Conclusions: The results of the present study showed that Class II division 1 and Class III patients displayed significantly lower fractal dimension (FD) values in their mandibular condyles when compared to Class I patients. This might be associated with the possible presence of a temporomandibular disorder in Class II division I patients which resulted in changes to condylar structure, and with less bone complexity in the temporomandibular joint of older Class III patients likely due to continued condylar growth.

Biochemical regulation of condylar growth and remodelling – An overview

Condylar cartilage has been classified as an articular cartilage. It has been further categorized as a secondary cartilage. This characterization is based upon its delayed development, unique histological features and adaptive capability to external stimuli. This adaptive and remodelling capacity of condylar cartilage to forward positioning of mandible forms basis of orthodontic functional treatment. Molecular and genetic control of epiphyseal cartilage has been well documented. However condylar cartilage has received attention only in last few decades. Condylar cartilage growth has partial genetic and strong epigenetic control. Epigenetic control includes systemic factors and local factors, such as growth factors and mechanical stimuli. Various growth factors and transduction mediators bring about natural development and adaptive remodelling of condylar cartilage. Growth factors are large group of polypeptide molecule which exerts its effect by paracrine or endocrine mechanism. Growth factors can exert various effects depending on the type of receptor it interacts. Depending upon the receptor it can bring about mitotic, hypertrophic or anti proliferative effect. These molecular controls play important role in growth and homeostasis. This article is an attempt to assimilate available knowledge and current concept regarding molecular and genetic control of condylar growth. Keywords: Condylar growth, Remodelling, Growth factor.

The effect of TMJ disk repositioning by suturing through open incision on adolescent mandibular asymmetry with and without a functional orthodontic appliance

The objective of this study was to evaluate the effect of combined temporomandibular joint (TMJ) disk repositioning by suturing through open incision and orthodontic functional appliance (OFA) treatment for adolescents with mandibular asymmetry. Adolescent patients (12-20 years old) with mandibular asymmetry combined with unilateral TMJ disk displacement without reduction were treated with disk repositioning by suturing through open incision with and without postoperative OFA. Magnetic resonance imaging and posteroanterior cephalometric radiographs (PA) were used to measure and compare the changes in condylar height, joint space, and menton deviation pre- and postoperatively. Twenty-six patients were included in the study. Joint space was significantly increased postoperatively and new bone mostly formed at the superior or posterior superior part of the condyle after 6 to 18 months in all surgically treated joints. Fourteen patients with OFA had a significant increase in condylar height and menton deviation compared to 12 patients without OFA (2.29 ± 0.91 mm vs 1.22 ± 0.69 mm, P=.003; 4.56 ± 1.48 mm vs 2.01 ± 0.74 mm, P=.000). Combined treatment with TMJ disk repositioning by suturing through open incision and OFA can promote condylar growth and correct mandibular deviation in adolescent patients. Postoperative OFA can maintain the increased joint space created by disk repositioning and promote new bone formation at the superior and posterior parts of the condyle.