Abutment rotational displacement of external hexagon implant system under lateral cyclic loading

Purpose This in vitro study investigated the effect of lateral cyclic loading with different load positions and periods on abutment rotational displacement (RD) of external hexagon implant system. Materials and Methods Four groups of five implant assemblies each were used. Each assembly consisted of Brånemark System® Mk IV implant (Nobel Biocare AB, Göteborg, Sweden), CeraOne® abutment (Nobel Biocare AB), and a cement‐retained casting. A cyclic load of 50 N was applied centrally and perpendicular to the long axis of the implant for groups A and B for 0.25 and 0.50 × 10⁶ cycles, respectively, while for groups C and D, the same load was applied at 4‐mm distance eccentrically for 0.25 and 0.50 × 10⁶ cycles, respectively. The displacement was evaluated by hand drawing a longitudinal line across the implant‐abutment interface. Before and after loading, the lateral distance between two reference points on the abutment and implant was measured under high resolution (×200) and the difference formed the RD value. The data were analyzed with one‐way analysis of variance and compared with Tukey test (α=0.05). Results Group D had the highest mean of RD value (55.00 ± 1.871 μm), while group A had the lowest (2.800 ± 0.837 μm). Groups A and B had a high statistically significant difference in RD values, as compared to groups C or D (p < .001). Moreover, group C had statistically significant difference from group D (p=.011). Conversely, no statistical significance was obtained when group A was compared with group B. Conclusion Within the limits of this in vitro study, the RD of the external hexagon joint components occurred significantly under eccentric lateral loading when compared to centric loading. The displacement increased significantly with longer period of eccentric lateral loading.     

正常人开闭口位颞颌关节盘磁共振影像测量分析

目的:探讨正常人颞颌关节开、闭口位关节盘的形态变化特点及意义。方法:对9名健康男性大学生(21~23 岁),用超导磁共振仪,小视野线圈,分别采用左右侧卧位,拍摄双侧TMJ矫正矢状位质子加权开口位和闭口位不同层面的MRI影像,层厚3 mm,选取其中能清楚反映关节盘形态的166张图像用电子测量尺测量其关节盘的断面面积和周长。结果:正常人颞颌关节盘闭口位影像呈窄长形,开口位影像呈哑铃形;开口位影像断面面积明显大于闭口位面积(P<0101),断面周长二者间无明显差别(P>0105)。结论:正常人开口状态下颞颌关节盘形态较闭口时明显变粗,可能是该两种状态下关节内压变化的反映。     

Relationship between functional disc position and mandibular displacement in adolescent females: posteroanterior cephalograms and magnetic resonance imaging retrospective study

The purpose of this study was to investigate the relationship between the disc positions of temporomandibular joints (TMJ), the vertical and lateral mandibular displacement (VMD and LMD, respectively) and age in female adolescents with signs and symptoms of the temporomandibular disorders (TMD). The VMD and LMD were assessed, using posteroanterior (PA) cephalograms. The disc positions were assessed by magnetic resonance imaging (MRI) and categorized as follows: normal disc position, functional disc displacement and functional disc dislocation. Excluding patients with osteoarthritis, the total number of subjects was 54 female adolescents who were grouped into three: the bilateral normal disc position group, the unilateral or bilateral functional disc displacement group, and the unilateral or bilateral functional disc dislocation group. We compared the extent of VMD and LMD between the three groups, and investigated their correlation with age. Results indicate that functional disc displacement and dislocation are related to mandibular displacement, and VMD did not correlate with age but LMD did correlate with age. This study suggests that the onset of disc displacement is related to the mandibular displacement and disturbs normal growth of the mandible three-dimensionally.     

Temporomandibular joint adaptations following two-phase therapy: an MRI study

Authors – Wadhawan N, Kumar S, Kharbanda OP, Duggal R, Sharma R Aim – To document the alterations within the condyle‐glenoid fossa (C‐GF) complex and the positional changes of the glenoid fossa in the cranium after removable functional appliance therapy and after the completion of fixed appliance therapy. Setting and Sample – The Department of Orthodontics, Centre for Dental Education and Research, All India Institute of Medical Sciences, New Delhi, India. The study sample consisted of 12 growing children (eight girls and four boys) between 10 and 14 years of age with skeletal Class II division 1 malocclusion selected on well defined criteria. Materials and Methods – All patients were treated with either the Twin Block or the Bionator appliance followed by fixed appliances. Mean total treatment duration was 28 months. The changes in and around the C‐GF complex were evaluated using MRI at pre‐treatment stage, after functional appliance therapy and at the completion of fixed mechanotherapy. Results – Forward condylar position within the glenoid fossa and articular disc retrusion with respect to the condylar head were statistically significant after functional appliance therapy. However, the condyles had a relatively concentric position within the glenoid fossa, while the articular disc resumed its pre‐treatment position at the end of the treatment. Linear measurements from the centre of the external auditory meatus to the post‐glenoid spine revealed a 1.3‐mm forward relocation of the post‐glenoid spine along the Frankfurt Horizontal plane. Conclusions – Forward relocation of the C‐GF complex seems to be one of the mechanisms of action of functional appliances, while the internal anatomic arrangement within the temporomandibular joint (TMJ) complex normalizes to its pre‐treatment position.     

人体颞下颌关节盘拉伸力学特性研究

通过对４具新鲜尸体的５个颞颌关节盘共８０个试件进行不同应变水平下的应力松弛试验和等应变速度下的拉伸破坏试验，测定了关节盘的横向拉伸力学性质，用拟线性粘弹性理论和二相理论对实验结果进行分析并建立了组织的本构方程。结果表明：关节盘的生理二相区在５％应变内；盘前带的横向拉伸强度、拉伸模量和破坏能量大于中间带和后带，中、后带差异不大；盘的应力松弛程度较低，初始应力松弛率在８％～１５％左右。同时证明，在较低应变下可以用获取的本构方程模拟关节盘的流变学特性     

Modified condylotomy versus conventional conservative treatment in painful reciprocal clicking—a preliminary prospective study in eight patients

Modified condylotomy may be relevant in severe painful reciprocal clicking of the temporomandibular joint (TMJ) where conservative treatment is insufficient. The effect of the modified condylotomy was analyzed and compared with conventional nonsurgical treatment in a randomized pilot study of eight patients, 19–44 years of age, with severe painful reciprocal clicking. Before and after treatment, assessments were performed by subjective reports, clinical recordings, and blinded evaluations of radiography and magnetic resonance imaging (MRI). Based on the clinical evaluations before treatment, all conditions were disc displacements with reduction and arthralgia (Research diagnostic criteria for temporomandibular disorders), but based on MRI, one patient had disc displacement without reduction and another had normal disc position. The treatment effect was significantly better and the disorders were significantly more reduced with condylotomy than with conventional nonsurgical treatment (P < 0.05, Mann–Whitney U test). In the surgical group, the clicking and locking had disappeared, the pain during function was significantly reduced (P < 0.05, Friedman ANOVA), and in two patients the disc position was normalized. The clicking still persisted in the nonsurgical patients and the disc position was unchanged. Our conclusion is that modified condylotomy is a promising option to reduce symptoms and signs in severe painful reciprocal clicking.     

山羊颞下颌关节盘细胞透射电镜观察

目的 用透射电镜的方法对两只1月龄健康山羊四只颞下颌关节盘的细胞及胶原结构进行了观察.方法 切取山羊双侧颞下颌关节盘,经组织学处理后行透射电镜观察细胞和胶原超微结构特征.结果 颞下颌关节盘由不均分布的细胞和胶原纤维组成,细胞有成纤维细胞样细胞和软骨细胞样细胞两种,其中成纤维细胞样细胞较软骨细胞样细胞占优势.成纤维细胞样细胞表现有细长的突起,核大,梭形或不规则形,细胞器较少.软骨细胞样细胞胞核呈圆形或椭圆形,周围少有电子透射区,细胞膜不明显,胞突少见.胶原纤维由平行排列的有周期性横纹特征的胶原原纤维组成.结论 颞下颌关节盘细胞有成纤维细胞样和软骨细胞样细胞两种,前者占优势,胶原原纤维表现有周期性横纹特征.这为颞下颌关节盘组织工程研究中细胞来源及表型分析奠定了一定基础.     

颞下颌关节盘前移位后关节组织中S-100的表达

目的：探讨颞下颌关节盘前移位后关节组织中S-100表达的变化及其意义。方法：26只日本大耳白兔，在建立颞下颌关节盘前移位动物模型后，分别于术后1周、2周、4周、6周、8周、10周和12周处死，用免疫组织化学方法检测关节组织内S-100的分布。结果：正常时S-100的表达主要位于关节盘前带和后带的软骨细胞中，双板区内无软骨细胞亦无S-100的表达。1周时下板内有少量成纤维细胞和纤维软骨细胞弱表达S-100，2周时出现少量弱表达S-100的游离软骨细胞。以后软骨细胞数目逐渐增多、S-100表达逐渐增强。10周时，可见多数强表达S-100的软骨细胞，12周时，滑膜层亦可见软骨细胞的出现及S-100的表达。结论：关节盘前移位后双板区出现软骨细胞及S-100的表达，S-100的表达可能与双板区组织的适应性改建有关。     

Anterior disk displacement of the temporomandibular joint

Summary In order to examine the diagnostic significance of typical clinical symptoms in temporomandibular joint (TMJ) disorders for diagnosis of anterior disk displacement, clinical findings were compared with the degree of disk displacement in 84 TMJs of 59 patients with TMJ disorders, who were examined clinically and by means of magnetic resonance imaging (MRI). The control group consisted of 31 subjects with no TMJ symptoms. No significant correlation between the degree of anterior disk displacement and palpation pain of the masticatory muscles or clicking/crepitus of the TMJ could be found. Joint clicking was observed in 65% of patients with TMJ symptoms in normal disk position (NDP). The percentage of joint clicking was almost the same in patients with anterior disk displacement with reposition (ADWR) (68%). There were significant correlations between active mouth opening and disk position as well as between a history of pain and disk position. Patients with NDP and ADWR had almost identical mouth opening values: 48 (±5) mm and 46 (±5) mm respectively. In contrast to these groups the mean values decreased significantly to 42 (±6) mm in patients with anterior disk displacement without reposition (ADWOR). There were no significant correlations between occlusal findings (centric relation and habitual relation, early occlusal contacts, abrasion facets) and disk position when viewed either collectively or individually.

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Anteriore Verlagerung des Discus articularis des Kiefergelenkes

Zusammenfassung Zur Überprüfung der Wertigkeit typisch klinischer Symptome für Funktionsstörungen zur Diagnose von Diskusverlagerungen wurden 84 Kiefergelenke von 59 Patienten mit Funktionsstörungen und 31 Kiefergelenke von klinisch asymptomatischen Probanden mittels Magnetresonanztomographie (MRT) untersucht und die einzelnen klinischen Befunde der Art der Diskusvergerung gegenübergestellt. Zwischen dem Grad der anterioren Diskusverlagerung und einem positiven Palpationsbefund der Kaumuskulatur, einem Palpationsschmerz der Kiefergelenke und dem Auftreten von Gelenkgeräuschen ergaben sich keine signifikanten Beziehungen. Bei funktionsgestörten Patienten zeigte sich mit 65% bei normaler Diskusposition (NDP) fast ebenso oft ein Gelenkknacken wie bei Patienten mit anteriorer Diskusverlagerung mit Reposition (VMR, 68%). Signifikante Beziehungen bestanden zwischen aktiver Mundöffnung und Diskusposition sowie anamnestisch angegebenen Schmerzen und Diskusposition. Während bei NDP- und VMR-Patienten mit 48 (±5) mm und 46 (±5) mm ähnlich hohe Mundöffnungswerte vorlagen, nahmen diese bei Patienten mit anteriorer Diskusverlagerung ohne Reposition (VOR) auf 42 (±6) mm signifikant ab. Okklusale Befunde (Differenz zwischen zentrischer und habitueller Okklusion >2 mm, vorzeitige okklusale Kontakte, Auftreten von Schliffacetten) zeigten in ihrer Gesamtheit wie auch in der Einzelbetrachtung keine signifikanten Beziehungen zur Diskusposition. Die Ergebnisse zeigen, daß für die Diagnostik von Funktionsstörungen allgemein als bedeutend anerkannte klinische Symptome in bezug auf die Art und das Vorliegen einer anterioren Diskusverlagerung allein keine sichere Aussage zulassen. Dies betrifft besonders die anteriore Diskusverlagerung ohne Reposition. Gleichzeitig wird die Zuverlässigkeit der MRT für die klinisch oft schwierige Diagnostik der Bestimmung der Diskusverlagerung bei Patienten mit Funktionsstörungen des Kausystems bestätigt.

     

The dynamic range of TMJ sounds

It is of clinical interest to record the amplitudes of temporomandibular joint (TMJ) sounds. The aim was to test the hypothesis that sealing the meatus, when placing a microphone in the ear canal affects such recording by increasing the sound pressure level (SPL). Bilateral recordings of 249 TMJ clickings were made from three subjects, using sampling rates of 48 or 96 kHz and 24 bits A/D conversion, with and without the ear canals sealed by Silicone putty. The peak-to-peak equivalent sound pressure level (peSPL) was higher (P < 0.001) when the ear canal was sealed (range of mean differences was 8.3-24.9 dB peSPL). This means that the signal to noise ratio can be improved by sealing the meatus because the electronic noise level is not increased. Most important is that the dynamic range of the clicking sounds was 62 dB that is larger than the effective dynamic range of a 16 bits sound card. Future studies are needed to establish normative peSPL values. However, cards with at least 24 bits A/D conversion will be required, especially in patients with suspected disc displacement with reduction, where the difference in loudness between opening and closing clicking often is large.