Maximum forces applied to the orbital floor after fractures

ABSTRACT: The objective of this study was to measure the force on and displacement of completely detached intraorbital tissue from thebony orbit, as a worst-case scenario after orbital trauma, to preserve the maximum load and predict the necessary strength of reconstruction materials. Six fresh-frozen human heads were used, and orbital floor defects in the right and left orbits were created by the direct impact of 3.0 J onto the globe and infraorbital rim. The orbital floor defect sizes and displacements were evaluated after performing a Le Fort I osteotomy. In addition, after the repositioning of the completely detached intraorbital tissue, the forces and displacements were measured. The mean orbital floor defect sizes were 208.3 (SD, 33.4) mm for globe impacts and 221.8 (SD, 53.1) mm for infraorbital impacts. The mean intraorbital tissue displacement after the impact and before repositioning was 5.6 (SD, 1.0) mm for globe impacts and 2.8 (SD, 0.7) mm for infraorbital impacts. After repositioning, the displacements were 0.8 (SD, 0.5) mm and 1.1 (SD, 0.7) mm, respectively. The measured forces were 0.10519 (SD, 0.00958) N without the incorporation and approximately 0.11128 (SD, 0.003599) N with the incorporation of reconstruction materials. The maximum forces on the completely detached orbital tissue were minimal (～0.11 N) and suggest the use of collagen membranes as reconstruction materials for orbital floor defects, at least in medium-sized fractures.     

A polysomnographic study on masticatory and tongue muscle activity during obstructive and central sleep apnea

Masticatory and tongue muscle activity was examined polysomnographically in 14 patients with sleep apnea syndrome and six snorers. The all‐night polysomnographic recordings included electromyograms (EMG) of the genioglossal, the masseter and the inferior head of the lateral pterygoid muscles, nasal airflow and thoracoabdominal respiratory effort. The apneas were defined and classified into three types (obstructive, central and mixed). EMG amplitudes of each muscle were measured before, during and after the obstructive and central apneas. In the apnea patients the three muscles showed significantly lower EMG amplitudes during the obstructive apnea than before the apnea, and then significantly higher amplitudes after the apnea. These findings indicate that the hypotonia of the muscles during sleep can result in obstructive apnea. There was no significant difference in the pattern of muscle activity during obstructive apnea between the apnea patients and the snorers. On the other hand, a decrease in the mean EMG amplitude during the central apnea was not observed. It is suggested that central apnea occurs independently of masticatory and tongue muscle activity.     

Iliac crest flap for mandibular reconstruction after advanced stage mandibular ameloblastoma resection

ABSTRACT: Ablative surgeries for neoplastic processes of the oral cavity, traumas, infections/inflammations, osteoradionecrosis, and congenital deformities are the most common causes of large mandibular defects. Ameloblastoma is a locally aggressive tumor that, if not treated, can gain an enormous size and cause severe facial disfigurement and functional impairment. Although the smaller lesions of ameloblastoma in the mandible are treated by conservative approaches such as marsupialization, enucleation, and curettage combined with liquid nitrogen spray cryosurgery, larger lesions require radical surgical ablation procedures resulting in large tissue defects. A large mandibular defect has deleterious effects on a person's life, with a significant loss in the quality of life unless it is reconstructed successfully. The aim of present case series report is to show the results of the multidisciplinary treatment of patients with advanced stage ameloblastoma, including tumor resection, simultaneous reconstruction with iliac crest flap, followed by placement of endosseous dental implants, and finally the prosthodontic rehabilitation.     

上颌全口义齿下骨组织吸收的有限元分析

采用有限元法模拟上颌全口义齿下的骨吸收情况，观察义齿在某一负荷条件下，其下骨组织的吸收发展过程，并通过改变负荷的位置，大小，方向及方式，对骨组织吸收的影响进行比较分析。结果表明骨吸收部位和程度与义齿咬合面的负荷位置关系密切，负荷位置不同，吸收发生部位，发展过程及吸收多少均不相同，其中负荷均匀作用于咬合面吸收程度最小，吸收程度还与负荷斩和方向等有关，侧向力作用下骨吸收严重。     

Single Nucleotide Polymorphisms in HIF-1α Gene and Residual Ridge Resorption (RRR) of Mandible in Korean Population

Tooth extraction is a routine surgical procedure in dental treatment. As a wound healing process after tooth extraction, a saddle-shaped residual ridge forms due to bone formation in the extraction socket and localized bone resorption on the external surface of the jawbone. The residual ridge is subjected to continuous bone resorption with substantial differences among individuals. In some cases, it results in excessive bone atrophy, which complicates dental restorative treatment. This unique oral wound healing process may be influenced by factors that are specific to oral tissue. HIF expression is different in oral wound healing compared to that of skin wounds. The objective of this study was to examine a genetic association between SNP of the HIF-1α gene, which is known to have high genetic diversity, and the residual ridge resorption (RRR). Two hundred and two Korean subjects (70.80 ± 9.40 years) with partially or completely edentulous mandible were recruited, and edentulous mandibular bone height was measured following the protocol of the American College of Prosthodontists. The HIF-1α allele was directly sequenced in 24 subjects resulting in the variants over 5% frequency in 95% likelihood, whereas tag-SNPs were selected to perform analysis for the remaining population. Student’s t-test and ANOVA were used for statistical analysis to examine the association between the SNPs and the RRR. Four novel variants were discovered, and a minor allele of rs11549467 was associated with the RRR of the subjects (p = 0.028). rs11549467 increases HIF-1α transactivity, enhancing angiogenesis and increasing new vessel formation. Thus, rs11549467 may play an important role in the disturbed bone remodeling balance resulting in RRR. Results of this study may be useful in developing novel genetic diagnostic tests and identifying Koreans susceptible to developing excessive jawbone atrophy after dental extraction. Most importantly, early screening using genetic information will rescue susceptible patients from the vulnerable situation of excessive jawbone atrophy where no effective prosthetic treatment is available.Key words: Single nucleotide polymorphism (SNP), HIF-1α, Residual ridge resorption (RRR), Edentulous mandible, Atrophy     

力丧失影响大鼠牙周组织前列腺素E_2表达变化的研究

为检测在牙合力正常及丧失状态下 ,大鼠牙周细胞中前列腺素 E2 (PGE2 )的动态表达 ,探讨 PGE2 在牙周组织改建过程中的分子机理。采用 HE染色和免疫组化的方法 ,观察牙周形态变化以及牙周组织中 PGE2 蛋白表达变化。结果显示 :牙合力丧失引起牙周膜结构紊乱、牙槽骨吸收 ,同时牙周细胞中 PGE2 表达较正常牙合力者明显增强。以上提示牙周组织结构与功能在改建中的一致性。     

烤瓷冠桥修复体边缘对牙龈健康的影响

目的　探讨烤瓷冠边缘的处理对牙龈健康的影响。方法　收集已做过烤瓷冠桥修复的患者 1 2 9例 ,观察分析修复体边缘的密合性、伸展度及光洁度对被修复牙牙龈健康 （牙龈出血指数 ）的影响。结果　①修复体边缘超过龈下 1mm（Ⅰ3组 ）对牙龈健康的影响最大 ,而其他各组相对较轻。②修复体边缘密合性对牙龈健康状况的影响为 :A组优于B组 ,B组优于C组和D组。结论　冠桥修复体的边缘与牙周健康密切相关 ,烤瓷冠桥修复体的边缘应尽可能光洁、密合、无悬突 ,伸展度以不超过龈缘下 1mm为宜。     

Evaluation of chewing activity in the elderly person

In the present study, we examined the chewing performance of 70 elderly persons. Self‐assessment of chewing problems and clinical classification using the modified Eichner index showed little correlation (Kappa value = 0.28; 95% confidence interval (CI) = 0.05–0.51). The sensitivity and specificity were 0.52 and 0.76, respectively. On the other hand, the mastication score determined by evaluation of a questionnaire on food intake and classification using the modified Eichner index showed high agreement (Kappa value = 0.73; 95% CI = 0.50–0.96). The sensitivity and specificity were 0.76 and 0.95, respectively. The mastication score showed significant correlation with other masticatory functions such as maximum biting force, occlusal contact area and the number of missing teeth ( P < 0.01). These results suggest that the use of a questionnaire on food intake would be informative for epidemiological surveys of chewing activity in the elderly.     

A method for quantifying positional change of the condyle on lateral tomograms by means of digital subtraction

A method is described for quantifying the positional change of the condyle on lateral tomograms of the temporomandibular joint (TMJ) by use of digital subtraction. This method permits rotational and translational changes of condylar reference points for easy measurement. Accuracy was evaluated in vitro using both TMJs of two dry human skulls and in vivo with seven volunteers. The average absolute error of the angle of rotation in vitro was 0·67°. For the anterior–posterior element of translation the average absolute error was 0·07 mm, and for the superior–inferior element of translation it was 0·06 mm. From these results, we could conclude that the method provides clinically acceptable measurement accuracy. To verify the usefulness of the method, a clinical application is presented.     

深冷处理技术对口腔中熔铸造合金耐磨性的影响

目的　以SDA-Ⅱ型中熔合金为对象 ,研究深冷处理技术对口腔中熔铸造合金耐磨性的影响 ,从而为深冷处理技术引入口腔修复领域进行初步的探索。方法　 1 5个试件分为 3组 ,分别为对照组、深冷处理组以及深冷处理加保温处理组 ,利用喷磨法和失重法测量喷磨前后试件的失重量 ,以此来代表其耐磨性 ,比较 3组的不同。结果　 3组材料喷磨后的重量损失有显著性差异 (P <0 0 5 ) ,深冷处理可以有效提高SDA-Ⅱ型中熔合金的耐磨性能 ;从耐磨性的角度而言 ,深冷处理后的保温处理对于SDA-Ⅱ型中熔合金是不必要的。结论　深冷处理技术是改善SDA-Ⅱ型中熔合金耐磨性的有效手段 ,其有可能成为改善口腔修复材料综合性能的一条简便、快捷、经济而有效的新途径.