Altered neural activation pattern during teeth clenching in temporomandibular disorders.

OBJECTIVE: The aim was to explore the neural activations during teeth clenching in TMDs patients pre- and post-treatment. SUBJECTS AND METHODS: Thirty TMDs patients and 20 controls underwent clinical evaluations and functional magnetic resonance imaging with a teeth clenching task. Eleven patients received repeat evaluation and imaging after wearing a stabilization splint for 3 months. RESULTS: During teeth clench, the TMDs patients showed decreased positive activity in the left precentral gyrus, right and left inferior temporal gyrus, and left cerebellum and increased negative activations in the right medial prefrontal cortex (P < 0.05 after AlphaSim correction). The 11 TMDs patients after treatment showed a return to normal neural activity in these areas. No brain areas in TMDs patients showed differences in activation after treatment compared with the controls, except for an increase in activation in the right cerebellum in the 11 TMDs patients (P < 0.05 after AlphaSim correction). CONCLUSION: Decreased activations in cerebral areas associated with motor and cognitive functions in TMDs patients during teeth clenching were observed. Normalized activations of these areas happened in patients after routine treatment. These findings may facilitate the understanding of TMDs pathogenesis and the therapeutic mechanisms of the stabilization splint.

Efficacy of adjunctive laser in non-surgical periodontal treatment: a systematic review and meta-analysis.

To evaluate the efficacy of the adjunctive laser therapy in conventional non-surgical treatment of chronic periodontitis, an electronic search was performed through the Cochrane Central Register of Controlled Trials (CENTRAL), PubMed, MEDLINE, EMBASE, Scopus, Web of Science, China National Knowledge Infrastructure (CNKI), and China Biology Medicine (CBM) Disc, for relevant randomized controlled trials (RCTs) or quasi-RCTs. All the 12 included studies (11 RCTs and 1 quasi-RCT) were qualified for descriptive and quantitative analysis. Outcomes were divided into two groups according to the length of follow-ups (long term and short term). Subgroup analyses were performed based on the mode of laser (inside and outside mode). Among all included researches, reduction in probing depth (PD) and gain in clinical attachment level (CAL) were presented with the mean value and 95 % confidence interval, while bleeding on probing (BOP) was assessed descriptively. Meta-analysis suggested that adjunctive laser therapy reduced PD at 3 months [mean difference (MD) = -0.26, 95 % confidence interval (CI) range = -0.43 to -0.09, p = 0.003] but did not demonstrate significant effect on the CAL at either 3 months (MD = -0.03, 95 % CI range = -0.25 to 0.19, p = 0.79) or 6 months (MD = -0.11, 95 % CI range = -0.38 to 0.16, p = 0.43). Subgroup analyses indicated that laser therapy would be more effective when the probes were set up outside the periodontal pockets.

Efficacy of low-level laser therapy for accelerating tooth movement during orthodontic treatment: a systematic review and meta-analysis.

This review aimed to evaluate the efficacy of low-level laser therapy (LLLT) for accelerating tooth movement during orthodontic treatment. An extensive electronic search was conducted by two reviewers. Randomized controlled trials (RCTs) and quasi-RCTs concerning the efficacy of LLLT for accelerating tooth movement during orthodontic treatment were searched in CENTRAL, Medline, PubMed, Embase, China Biology Medicine Disc (CBM), China National Knowledge Infrastructure (CNKI), and Google Scholar. Six RCTs and three quasi-RCTs, involving 211 patients from six countries, were selected from 173 relevant studies. All nine articles were feasible for the systematic review and meta-analysis, five of which were assessed as moderate risk of bias, while the rest were assessed as high risk of bias. The mean difference and the 95 % confidence interval (95 % CI) of accumulative moved distance of teeth were observed among all the researches. The results showed that the LLLT could accelerate orthodontic tooth movement (OTM) in 7 days (mean difference 0.19, 95 % CI [0.02, 0.37], p = 0.03) and 2 months (mean difference 1.08, 95 % CI [0.16, 2.01], p = 0.02). Moreover, a relatively lower energy density (5 and 8 J/cm(2)) was seemingly more effective than 20 and 25 J/cm(2) and even higher ones.

Efficacy of low-level laser therapy in the management of orthodontic pain: a systematic review and meta-analysis.

This review aimed to identify the efficacy of low-level laser therapy (LLLT) in the management of orthodontic pain. This systematic review and meta-analysis was carried out in accordance with Cochrane Handbook and the PRISMA statement. An extensive literature search for RCTs, quasi-RCTs, and CCTs was performed through CENTRAL, PubMed, Embase, Medline, CNKI, and CBM up to October 2011. Risk of bias assessment was performed via referring to the Cochrane tool for risk of bias assessment. Meta-analysis was implemented using Review Manager 5.1. As a result, four RCTs, two quasi-RCTs, and two CCTs were selected from 152 relevant studies, including 641 patients from six countries. The meta-analysis demonstrated that 24% risk of incidence of pain was reduced by LLLT (RR = 0.76, 95% CI range 0.63-0.92, P = 0.006). In addition, compared to the control group, LLLT brought forward "the most painful day" (MD = -0.42, 95% CI range -0.74- -0.10, P = 0.009). Furthermore, the LLLT group also implied a trend of earlier end of pain compared with the control group (MD = -1.37, 95% CI range -3.37-0.64, P = 0.18) and the pseudo-laser group (MD = -1.04, 95% CI range -4.22-2.15, P = 0.52). However, because of the methodological shortcomings and risk of bias of included trials, LLLT was proved with limited evidence in delaying pain onset and reducing pain intensity. In the future, larger and better-designed RCTs will be required to provide clearer recommendations.

Mechanical strain induces osteogenic differentiation: Cbfa1 and Ets-1 expression in stretched rat mesenchymal stem cells.

Distraction osteogenesis is an active process of bone regeneration under controlled mechanical stimulation. Osteogenic differentiation of mesenchymal stem cells (MSCs) is essential for bone formation during this process. Cbfa1 and Ets-1 (core binding factor alpha 1 and v-ets erythroblastosis virus E26 oncogene homolog 1) are transcription factors that play important roles in the differentiation of MSCs to osteoblasts. In order to mimic a single activation of a clinical distraction device, a short period of cyclic mechanical strain (40 min and 2,000 microstrains) was applied to rat MSCs. Cellular proliferation and alkaline phosphatase (ALP) activity were examined. The mRNA expression of Cbfa1 and Ets-1, as well as ALP, a specific osteoblast marker, was detected using real-time quantitative reverse transcription polymerase chain reaction. The results showed that mechanical strain can promote MSC proliferation, increase ALP activity and up-regulate the expression of Cbfa1 and Ets-1. A significant increase in Ets-1 expression was detected immediately after mechanical stimulation, but Cbfa1 expression was elevated later. The temporal expression pattern of ALP coincided perfectly with that of Cbfa1. Mechanical strain may act as a stimulator to induce differentiation of mesenchymal stem cells into osteoblasts, which is vital for bone formation in distraction osteogenesis.

Efficient azobenzene co-sensitizer for wide spectral absorption of dye-sensitized solar cells.

Two azobenzene dyes, [Cu(azobenzene-4,4'-dicarboxylate) diethylenediamine] n (ADD), [Cd(4,4'-diazenediyldibenzoato)(H2O)] n (DDB), have been designed, synthesized, and characterized as efficient co-sensitizers for dye-sensitized solar cells (DSSC). The optical, charge-transfer, electrochemical and photovoltaic properties of ADD and DDB are investigated by UV-visible spectroscopy, transient surface photovoltage measurement, cyclic voltammetry, and photocurrent-photovoltage measurement. The combination of ADD and DDB in DSSC leads to a wide spectral absorption over the whole visible range (350-700 nm). DSSC with ADD and DDB exhibits a short-circuit photocurrent density as high as 16.96 mA cm-2, open-circuit photovoltage of 0.73 V, a fill factor of 0.57, and overall light conversion efficiency of 7.1% under standard global AM1.5 solar irradiation conditions.

Callus formation enhanced by BMP-7 ex vivo gene therapy during distraction osteogenesis in rats.

This study was designed to observe the effects of bone morphogenetic protein-7 (BMP-7) ex vivo gene therapy on callus formation during rat mandibular distraction osteogenesis (DO). Fifty-four Sprague-Dawley rats underwent osteodistraction of the right mandible and were then randomly divided into three groups. Immediately after distraction, autologous bone marrow mesenchymal stem cells (MSCs) transfected with BMP-7, MSCs untransfected with BMP-7, and physiological saline were injected into the distraction gaps of the mandibles in groups A, B, and C, respectively. Nine animals from each group were euthanized at 2 and 6 weeks after completion of distraction. The distracted mandibles were removed and processed for radiographic, histological, immunohistochemical, and scanning electron microscopic examinations as well as Ca/P ratio analysis. Group A animals showed greater bone formation and earlier mineralization in the distracted callus when compared with group B. Similarly increased callus formation was found in group B than group C. Positive immunostaining of BMP-7 was observed in the distracted callus in all groups. However, BMP-7 expression was much stronger in group A compared with groups B and C. The results of this study suggest that BMP-7-mediated ex vivo gene transfer based on MSCs may accelerate callus formation in distraction osteogenesis and facilitate consolidation. Local gene therapy may ultimately be an alternative or supplemental approach to DO enhancement, especially for patients whose osteogenic potentials are compromised by diseases such as osteoporosis, severe trauma, and postoncologic irradiation.

Tooth eruption and cementum formation in the Runx2/Cbfa1 heterozygous mouse.

Cleidocranial dysplasia (CCD) is an autosomal dominant human disorder that affects development of bones and teeth. The dental disorders in CCD patients include formation of supernumerary teeth, delayed tooth eruption, and lack of formation of cellular cementum in permanent teeth. This disorder involves a mutation in the osteoblast-specific transcription factor Runx2/Cbfa1, leading to haploinsufficiency of the Runx2/Cbfa1 protein. Here, we examined if Runx2/Cbfa1 heterozygous mice (with one functional allele for Runx2/Cbfa1) exhibit similar changes in tooth eruption, and dental cementum formation as in CCD patients. Heads of Runx2/Cbfa1 heterogeneous and wildtype mice aged days 16-35 postnatally were serially sectioned and stained with hematoxylin-eosin or for tartrate resistant acid phosphatase (TRAP) to identify osteoclasts. The results showed that the eruption pattern of the first and second molars in maxilla and mandible in Runx2/Cbfa1 +/- mice was the same as in wildtype animals. No clear difference in distribution or in the (estimated) number of osteoclasts was found. Cellular cement at the apical portions of the molar roots was present in both groups. The data suggests that in the mouse one allele for Runx2/Cbfa1 is sufficient for an undisturbed tooth eruption and an apparently normal formation of the periodontium.

Spontaneous neural activity alterations in temporomandibular disorders: a cross-sectional and longitudinal resting-state functional magnetic resonance imaging study.

The involvement of the central nervous system in the pathophysiology of temporomandibular disorders (TMD) has been noticed. TMD patients have been shown dysfunction of motor performance and reduced cognitive ability in neuropsychological tests. The aim of this study is to explore the spontaneous neural activity in TMD patients with centric relation (CR)-maximum intercuspation (MI) discrepancy before and after stabilization splint treatment. Twenty-three patients and twenty controls underwent clinical evaluations, including CR-MI discrepancy, Helkimo indices and chronic pain, and resting state functional magnetic resonance imaging scans at baseline. Eleven patients repeated the evaluations and scanning after the initial wearing (T1) and 3months of wearing (T2) of the stabilization splint. The fractional amplitude of low-frequency fluctuation (fALFF) was calculated to compare the neural functions. At baseline, the patients showed decreased fALFF in the left precentral gyrus, supplementary motor area, middle frontal gyrus and right orbitofrontal cortex compared with the controls (P<0.05, AlphaSim corrected). Negative correlations were found between the fALFF in the left precentral gyrus and vertical CR-MI discrepancy of bilateral temporomandibular joints of patients (P<0.05, two-tailed). At T2, the symptoms and signs of the patients were improved, and a stable condylar position on the CR was recovered, with increased fALFF in the left precentral gyrus and left posterior insula compared with pretreatment. The fALFF decrease in the patients before treatment was no longer evident at T2 compared with the controls. The results suggested that TMD patients with CR-MI discrepancy showed significantly decreased brain activity in their frontal cortexes. The stabilization splint elicited functional recovery in these cortical areas. These findings provided insight into the cortical neuroplastic processes underlying TMD with CR-MI discrepancy and the therapeutic mechanisms of stabilization splint.

Efficacy of short-term chincup therapy for mandibular growth retardation in Class III malocclusion.

OBJECTIVE: To assess the efficacy of chincup therapy for mandibular growth retardation in early orthopedic treatment of Class III malocclusion. MATERIALS AND METHODS: An electronic search for articles reporting randomized clinical trials, controlled clinical trials, and cohort studies testing the efficacy of chincup appliance for Class III malocclusion published up to the present was done through four databases: Cochrane Central Register of Controlled Trials (CENTRAL; to March 2010), MEDLINE (1950-March 2010), EMBASE (1980-March 2010), and CBM (1978-March 2010). Study quality assessment and data extraction were done by two reviewers independently. Meta-analysis was done with the assistance of Revman 5.01. RESULTS: The search resulted in 50 articles. After selection following the established criteria, four cohort studies qualified for the final review analysis. The results showed that chincup therapy decreased SNB angle and increased ANB angle; the total pooled weighted mean difference values (95% confidence interval) were −1.18 (−1.69, −0.67; P < .00001) and 1.90 (0.60, 3.21; P = .004), respectively. Two studies showed a increase in Gonial angle (P < .05) but no significant change in the mandibular length (Cd-Gn; P = .059 and .39, respectively). One study indicated that chincup therapy exerted no effect on mandibular growth retardation, and mandibular growth continued after the treatment in a downward direction. CONCLUSION: There are insufficient data in these studies to make clear recommendations regarding the efficacy of chincup therapy in the retardation of mandibular growth.

Comparison of anchorage capacity between implant and headgear during anterior segment retraction.

OBJECTIVE: To compare the anchorage effects of the implants and the headgear for patients with anterior teeth retraction in terms of incisor retraction, anchorage loss, inclination of maxillary incisors, positional change of maxillary basal bone, and treatment duration. MATERIALS AND METHODS: An electronic search for relative randomized controlled trials (RCTs) prospective and retrospective controlled trials was done through the Cochrane Central Register of Controlled Trials (CENTRAL), PubMed, Embase, Medline, and CNKI, regardless of language of study. Study selection, methodological quality assessment, and data extraction were performed by two reviewers independently. Meta-analysis was performed when possible; otherwise descriptive assessment was done. RESULTS: The search yielded 35 articles, of which eight met the inclusion criteria and were categorized into five groups according to types of intervention. For the midpalatal implant, the anchorage loss was much less than for the headgear group, with insignificant differences in terms of anterior teeth retraction, maxillary incisor inclination, positional change of basal bone, and treatment duration. For the mini-implant, greater anterior teeth retraction and less anchorage loss were demonstrated, with inconsistent results for the other measures. For the onplant, less anchorage loss was noted, with insignificant differences for the other measures. CONCLUSIONS: The skeletal anchorage of the midpalatal implant, mini-implant, and onplant offer better alternatives to headgear, with less anchorage loss and more anterior teeth retraction. There were inconsistent results from the included studies in terms of maxillary incisor inclination, positional change of maxillary basal bone, and treatment duration. More qualified RCTs are required to provide clear recommendations.

Assessment of dental maturity of western Chinese children using Demirjian's method.

Age estimation plays an important role in forensic medicine and orthodontics. Dental maturity, expressed as dental age, is one of the common indices for age estimation. Demirjian's method, first described in 1973 and based on a large number of French-Canadian samples, is one of the most widely used methods for dental age assessment. The aim of this study is to evaluate the applicability of Demirjian's method for dental age estimation in western Chinese children. Digital panoramic radiographs of 445 children of western Chinese origin, ranging from 8 to 16 years old, were assessed in Demirjian's method. The dental maturity scores (DMSs) and dental ages of all the subjects were calculated by a single observer. The dental ages were compared to the chronological ages with a paired t-test. The general trend in this research showed that the western Chinese children demonstrated a more advanced dental age compared to French-Canadian children as previously presented by Demirjian. The mean difference in each age group between the dental age and chronological age ranged from 0.0071 to 1.2500 years in girls and from -1.0000 to 1.3000 years in boys. The standards of dental age assessment provided by Demirjian for French-Canadian children may be not suitable for western Chinese children. As a result, specific standards of dental age assessment should be established for this population.