Effects of Improper Mechanical Force on the Production of Sonic Hedgehog, RANKL, and IL-6 in Human Periodontal Ligament Cells In Vitro.

Improper mechanical stress may induce side effects during orthodontic treatment. If the roots and alveolar bones are extensively resorbed following excess mechanical stress, unplanned tooth mobility and inflammation can occur. Although multiple factors are believed to contribute to the development of side effects, the cause is still unknown. Sonic hedgehog (Shh), one of the hedgehog signals significantly associated with cell growth and cancer development, promotes osteoclast formation in the jawbone. Shh may be associated with root and bone resorptions during orthodontic treatment. In this study, we investigated the relationships between Shh, RANKL, and IL-6 in human periodontal ligament (hPDL) cells exposed to improper mechanical force. Weights were placed on hPDL cells and human gingival fibroblasts (HGFs) for an optimal orthodontic force group (1.0 g/cm2) and a heavy orthodontic force group (4.0 g/cm2). A group with no orthodontic force was used as a control group. Real-time PCR, SDS-PAGE, and Western blotting were performed to examine the effects of orthodontic forces on the expression of Shh, RANKL, and IL-6 at 2, 4, 6, 8, 12, and 24 h after the addition of pressure. The protein expression of Shh was not clearly induced by orthodontic forces of 1.0 and 4.0 g/cm2 compared with the control in HGFs and hPDL cells. In contrast, RANKL and IL-6 gene and protein expression was significantly induced by 1.0 and 4.0 g/cm2 in hPDL cells for forces lasting 6~24 h. However, neither protein was expressed in HGFs. RANKL and IL-6 expressions in response to orthodontic forces and in the control were clearly inhibited by Shh inhibitor RU-SKI 43. Shh did not directly link to RANKL and IL-6 for root and bone resorptions by orthodontic force but was associated with cell activities to be finally guided by the production of cytokines in hPDL cells.

Micro-Osteoperforations Accelerate Tooth Movement without Exacerbating the Progression of Root Resorption in Rats.

A recent study reported that micro-osteoperforations (MOPs) accelerated tooth movement by activating alveolar bone remodeling. However, very little is known about the relationship between MOPs and external apical root resorption during orthodontic treatment. In this study, in order to investigate the mechanism through which MOPs accelerate tooth movement without exacerbating the progression of root resorption, we measured the volume of the resorbed root, and performed the terminal deoxynucleotidyl transferase (TdT)-mediated dUTP-biotin nick-end labeling (TUNEL) method on exposed MOPs during experimental tooth movements in rats. Male Wistar rats (11 weeks old) were divided into three groups: 10 g orthodontic force (optimal force) applied to the maxillary first molar (optimal force: OF group), 50 g orthodontic force application (heavy force: HF group), and 10 g force application plus three small perforations of the cortical plate (OF + MOPs group). On days 1, 4, 7, 10, and 14 after force application, the tooth movement and root volume were investigated by micro-computed tomography. Furthermore, the number of apoptotic cells in the pressured sides of the periodontal ligament (PDL) and surrounding hard tissues were determined by TUNEL staining. The OF + MOPs group exhibited a 1.8-fold increase in tooth movement on days 7, 10, and 14 compared with the OF group. On days 14, the HF group had a higher volume of root loss than the OF and OF + MOPs groups. On the same day, the number of TUNEL-positive cells in the HF group increased at the root (cementum) site whereas that in the OF group increased at the alveolar bone site. Furthermore, the number of TUNEL-positive cells in the OF + MOPs group increased at the alveolar bone site compared with the OF group. These results suggest that MOPs accelerate orthodontic tooth movement without exacerbating the progression of root resorption.

Morphological differences between the first and second maxillary premolar crowns: A three-dimensional surface homologous modeling analysis.

OBJECTIVES: The current study used a three-dimensional (3D) surface homologous modeling to analyze the structure of maxillary first premolar (P1) and second premolar (P2) crowns, to identify any morphological differences between them, particularly in their cuspal structures. METHODS: The study sample comprised 27 male elementary and junior high school students from Chiba Prefecture, Japan. Plaster casts were collected and the 3D coordinates were used to measure the crown structures. Thereafter, principal component (PC) analysis was carried out using the 3D coordinates of the homologous models, containing 4498 anatomical data points, including 9 landmarks. RESULTS: The findings indicated that P1 was significantly larger than P2, despite both teeth exhibiting similar intercuspal distances. The homologous model analysis revealed that 61.5 % of the total variance could be explained up to the fourth PC. Overall size and shape in the mesiodistal and buccolingual directions were estimated using PC1 and PC2, respectively. Both components highlighted a shape factor, indicating that the buccal cusp was more well-developed than the lingual cusp in P1 compared to P2. CONCLUSIONS: The variations in the size of the mesial and distal premolar teeth and the relationships between the cusps in the completed tooth crowns can be explained using molecular biology developmental models.

Sexual dimorphism in the three-dimensional detailed crown structure of maxillary first premolars.

OBJECTIVES: Maxillary first premolars have a unique shape because of their curvature features, positional relationship of the cusps, and most prominent points, making them different from other teeth. This study aimed to quantitatively analyze the detailed three-dimensional morphometric structure of maxillary first premolars and sexual dimorphism. METHODS: The study participants were 60 elementary and junior high school students (30 boys and 30 girls) in Japan. The distance between landmarks was measured using the three-dimensional coordinates of plaster casts, and the data collected was statistically analyzed. RESULTS: Sexual dimorphism was greater in the lingual cusp, showing greater variation in size than the buccal cusp. Boys exhibited significantly larger relative distances in the mesiodistal and buccolingual directions than girls; particularly, regarding mesiodistal diameter of the central groove, mesial slope of the buccal cusp, and distal slope of the lingual cusp. These results may be due to a slight difference in the timing of secondary enamel knots between boys and girls during the developmental stage, which was reflected in the sexual dimorphism of the completed teeth. Curvature features, cusp positions, and most prominent points were considered individual traits because they were not interrelated. CONCLUSIONS: Subtle differences during the developmental stage may lead to sexual dimorphism of the completed crown. Furthermore, the morphological characteristics of the maxillary first premolars may be related to their location in the dental arch.

Risk assessment of external apical root resorption associated with orthodontic treatment using computed tomography texture analysis.

OBJECTIVES: This study aimed to quantitatively assess maxillary central incisor roots using pre-orthodontics computed tomography (CT) texture analysis as part of a radiomics quantitative analysis. METHODS: This retrospective case-control study included 16 patients with external apical root resorption (EARR) and 16 age- and sex-matched patients without EARR, after orthodontic treatment who underwent pre-orthodontics CT for jaw deformities. All patients were treated with a fixed orthodontic appliance before and after surgical orthodontic treatment. EARR was defined as root resorption ≥ 2 mm of the left and right maxillary central incisors on CT images more than 2 years after the start of orthodontic treatment. Texture features of the maxillary central incisor with and without EARR after orthodontic treatment were analyzed using the open-access software, MaZda Ver. 3.3. Ten texture features were selected using the Fisher method in MaZda from 279 original parameters, which were calculated for each of the maxillary central incisors with and without EARR. The results were tested using the Student's t test, Welch's t test, or Mann-Whitney U test. RESULTS: Four gray-level run length matrix features and six gray-level co-occurrence matrix features displayed significant differences between both the groups (p < 0.01). CONCLUSIONS: CT texture analysis was able to quantitatively assess maxillary central incisor roots and distinguish between maxillary central incisor roots with and without EARR. CT texture analysis may be a useful method for predicting EARR after orthodontic treatment.

Genetic contribution to palatal morphology variation using three-dimensional analysis in Australian twins.

OBJECTIVE: This study aimed to provide insight into the relative contributions of genetic and environmental factors to palatal morphology variation in a cohort of Australian twins. METHODS: Healthy Australian twins, aged 12-15 years (45 monozygotic, 46 same sex dizygotic, and 32 opposite-sex dizygotic) were included in the study groups. A scanner was used to obtain three-dimensional data of the maxillary arch. Palatal depth was defined by a line to the deepest point measured from the reference plane at the mid-point of the inter-pre-molar or inter-molar line. This line was then divided into 10 equal sections in order to created 10 different depths for each palatal width. Each palatal width was divided into anterior and posterior areas. Univariate genetic analysis, using the OpenMx structural equation modelling package in R, was carried out on the quantitative data using the normal assumptions of a twin model. RESULTS: Heritability estimates for anterior palatal width ranged from 0.75 to 0.80, and from 0.78 to 0.86 for posterior palatal width. Estimates for anterior and posterior palatal depth were 0.72 and 0.86, respectively. CONCLUSIONS: Palatal morphology tends to have a moderate to relatively high genetic contribution overall. Palate height has a higher genetic contribution posteriorly than anteriorly. The width of the deep palate is under marginally less stringent genetic regulation than the width of the shallow palate.

Relation of dietary preference to masticatory movement and masticatory exercises in Japanese children.

OBJECTIVE: Modern Japanese children have decreased masticatory function, which can be explained by the dietary change to soft foods. In earlier studies involving children with mixed dentition, masticatory exercises were shown to improve masticatory function and modify dental arch growth. Grinding type of mastication with a wide path reportedly increases lateral growth of the dental arch. This study aimed to assess the relationship between masticatory movements and dietary preference, and how masticatory exercises affected masticatory movement during Hellman's dental stages IIA to IIC (period of first molar eruption). DESIGN: In 64 Japanese pre-school children, we measured masticatory movements with foods of five different levels of hardness and investigated the dietary preference for hard foods through a questionnaire. Participants were also required to perform masticatory exercises. Masticatory movements and dietary preference for hard foods were assessed at the start (T1), conclusion (T2), and after six months of exercises (T3). Participants were allocated to Wide and Narrow groups at T1 based on their masticatory path width. RESULTS: Baguettes and bananas resulted in the widest and narrowest masticatory paths, respectively, at T1. Results of questionnaire indicated that those eating hard foods had a broad grinding type of masticatory path. Masticatory exercises significantly widened the masticatory path in the Narrow group demonstrating that masticatory exercises help children learn to chew with grinding strokes. Moreover, the masticatory path remained stable on assessment at T3 (six-month follow-up). CONCLUSIONS: Masticatory exercises are effective in children who are unable to grind hard foods, affecting their dietary preferences.

Relationship between molar occlusion and masticatory movement in lateral deviation of the mandible.

INTRODUCTION: The relationship between molar occlusion and chewing patterns was examined in subjects with laterally deviated mandibles. METHODS: Twenty-three patients with mandibular deviation from the midline (4 mm or more) and skeletal Class I (0° ≤ANB ≤4°) were divided into 2 groups: normal bite and crossbite. The chewing pattern was classified as normal, reversed, or crossover. RESULTS: The normal bite group had a normal chewing pattern on the affected side 100% of the time and a reversed chewing pattern on the affected and unaffected sides 0% and 7.2% of the time, respectively. Additionally, the normal bite group showed no evidence of a crossover chewing pattern and also had significantly less axial inclination of the mandibular teeth on the affected side compared with the crossbite group; lingual inclination was also evident. The crossbite group had a normal chewing pattern on the affected and unaffected sides 0% and 55.6% of the time, respectively, and reversed and crossover chewing patterns on the affected side 55.6% and 44.4% of the time, respectively. CONCLUSIONS: A normal chewing pattern tends to result in lingual axial inclination of the mandibular molars on the affected side, as well as a more consistent chewing pattern.

Intensity of physiotherapy after anterior cruciate ligament reconstruction: a comparison of two rehabilitation regimen.

BACKGROUND: Rehabilitation is one of the most critical points after anterior cruciate ligament (ACL) reconstruction. However, the recent trend of low-cost, short-term hospitalization makes sufficient rehabilitation after ACL reconstruction difficult. LEVEL OF EVIDENCE III: 34 patients who underwent non-anatomical single bundle ACL reconstruction using a hamstring auto graft were evaluated. Twenty patients (12 males and 8 females) were transferred to a special rehabilitation hospital (RH hospital group) after operation and concentrated rehabilitation was performed up to 4 h per day. Fourteen (9 males and 5 females) patients performed clinic-based rehabilitation at a university hospital three times per week (clinic group). Strength of quadriceps and knee flexion muscles was assessed at 60 degrees /s using a Cybex II dynamometer (Lumex, Ronkonkoma, NY, USA) at 3, 6 and 9 months after ACL reconstruction. Anterior tibial translation (ATT) and pivot shift test were also evaluated. RESULTS: No significant difference in muscle recovery in the lower extremity was observed at any time point after ACL reconstruction between the clinic group and the RH hospital group. However, 3 months after operation, the average muscle strength of the RH hospital group tended to be higher than that of the clinic group. There was no significant difference in ATT or pivot shift (each group included 4 positive pivot shift subjects) in the patients who were tested between the clinic group and the RH hospital group. CONCLUSION: Concentrated rehabilitation at a rehabilitation hospital after ACL reconstruction has the potential to improve muscle strength in the lower extremities more dramatically in the early stages of post operation. However, the initial benefits of intensive physiotherapy disappear after 6 months.

The effect of relaxin treatment on skeletal muscle injuries.

BACKGROUND: Injured skeletal muscle can repair itself via spontaneous regeneration; however, the overproduction of extracellular matrix and excessive collagen deposition lead to fibrosis. Neutralization of the effect of transforming growth factor-beta 1, a key fibrotic cytokine, on myogenic cell differentiation after muscle injury can prevent fibrosis, enhance muscle regeneration, and thereby improve the functional recovery of injured muscle. HYPOTHESIS: The hormone relaxin, a member of the family of insulin-like growth factors, can act as an antifibrosis agent and improve the healing of injured muscle. STUDY DESIGN: Controlled laboratory study. METHODS: In vitro: Myoblasts (C2C12 cells) and myofibroblasts (transforming growth factor-beta 1-transfected myoblasts) were incubated with relaxin, and cell growth and differentiation were examined. Myogenic and fibrotic protein expression was determined by Western blot analysis. In vivo: Relaxin was injected intramuscularly at different time points after laceration injury. Skeletal muscle healing was evaluated via histologic, immunohistochemical, and physiologic tests. RESULTS: Relaxin treatment resulted in a dose-dependent decrease in myofibroblast proliferation, down-regulated expression of the fibrotic protein alpha-smooth muscle actin, and promoted the proliferation and differentiation of myoblasts in vitro. Relaxin therapy enhanced muscle regeneration, reduced fibrosis, and improved injured muscle strength in vivo. CONCLUSION: Administration of relaxin can significantly improve skeletal muscle healing. CLINICAL RELEVANCE: These findings may facilitate the development of techniques to eliminate fibrosis, enhance muscle regeneration, and improve functional recovery after muscle injuries.

New meniscus repair by an all-inside knot suture technique.

The indications for the all-inside knot suture technique include tears in the red-red zone or red-white zone in the meniscus, and a horizontal tear, a vertical tear, and a peripheral tear. First, find an appropriate place for a suture insertion site with a Kateran needle or a spinal needle. Make sure it exits beyond the tear in the meniscus. Once the insertion site is chosen, a suture is passed into and through the joint. The suture is slowly pulled back. You should be able to feel the tip of the suture come out of the joint capsule. If you want to make a vertical suture to suture the tear, move the suture vertically apex. Then insert the suture back into the joint through the capsule. Make sure the suture stays inside the joint. Find and grab the suture with a punch inserted from the clear cannula. Pull the suture out of the joint through the clear cannula with the punch. Tighten the knot with a knot pusher. Then confirm the stability of the sutured site with the probe. Our all-inside knot suture technique can be performed arthroscopically, allowing reliable repair of the torn meniscus.