Microleakage Evaluation in Amalgam Restorations Used with Bases

Marginal leakage in amalgam restorations often precedes the development of secondary caries. One potential way to improve the marginal seal of such restorations, and thus minimize the risk of carles development, is to apply a glassionomer base prior to amalgam placement.
This study compared microleakage resistance among amalgam restorations placed with and without light-cured glass-ionomer base materials. Preparations were made in extracted human molar teeth. Four groups were studied, including copal varnish, which was used as a control. All specimens were restored with amalgam. Results indicated significantly greater leakage at the cavity wall/base interface for restorations with a copal varnish cavity liner than for those with a glass-ionomer base. Leakage differences among bases were also found at the amalgam/base interface. Best results were obtained with a dual-cure resin-based system. These samples showed minimal leakage at both the cavity wall/base and the base/amalgam interfaces. These findings suggest that light-cured glass-ionomer bases can be effective in the prevention of microleakage in amalgam restorations.     

牙源性角化囊肿上皮细胞增殖动力学初步研究

目的探讨角化囊肿上皮细胞增殖特性,进一步了解角化囊肿的生物学行为,为临床治疗和预防复发提供一定的依据。方法采用增殖细胞核抗原（ｐｒｏｌｉｆｅｒａｔｉｎｇｃｅｌｎｕｃｌｅａｒａｎｔｉｇｅｎ,ＰＣＮＡ）免疫组化法和细胞核ＤＮＡ含量分析,对牙源性角化囊肿、根尖囊肿、含牙囊肿和造釉细胞瘤上皮细胞进行对比研究。结果角化囊肿上皮细胞增殖活跃,与造釉细胞瘤相似。提示角化囊肿生物学特性为上皮细胞主动生长,而非被动性膨胀生长。结论角化囊肿可视为具有侵袭性生长的良性肿瘤,提出命名为“牙源性角化囊性瘤”更能反应其生物学特性     

Inhibitory effects on jaw muscle activity of innocuous and noxious stimulation of facial and intraoral sites in man

Controlled mechanical stimulation of the upper lip in seven subjects resulted in a period of complete or partial inhibition of the electromyographic activity of the masseter muscle. When a painful stimulus was delivered to the lip, a later inhibitory period with a more variable duration was produced. Innocuous stimulation at various intraoral sites led to an early inhibitory period with characteristics similar to those of inhibition produced by innocuous lip stimulation. An increase in stimulus intensity to a noxious level resulted in a second period of inhibition comparable to that produced by noxious lip stimuli. The intensity of the stimulus and the level of muscle activity maintained by the subject were found to influence the incidence and duration of the inhibitory periods. Thus, innocuous and noxious stimulation, whether applied intraorally or extraorally, may result in two distinct periods of inhibition in the jaw-closing muscles. The role in orofacial function of the first inhibitory period has yet to be demonstrated, but the second period is probably involved as a protective reflex.     

Evaluation of X-Ray Projection Angulation for Successful Radix Entomolaris Diagnosis in Mandibular First Molars In Vitro

Introduction

The aim of this study was to evaluate the radiographic features of permanent three-rooted mandibular first molars with radix entomolaris (RE), investigate the correlation between anatomical classification and radiographic type of RE, and to determine the most effective horizontal beam angulation for the diagnosis of RE.

Methods

Twenty-five extracted mandibular first permanent molars with RE were selected for taking radiographs in 7 horizontal angulations. By using set criteria, 3 evaluators assessed morphologic and radiographic features of the RE and optimum beam angulation for RE diagnosis. Intraexaminer variability was analyzed with Cohen kappa test.

Results

Three types of curvature of RE presented with 3 distinct types of typical radiographic appearance on orthoradial radiographs. We classified the radiographic features of RE into 3 types, as follows: type i, type ii, and type iii. Seven teeth showed type i radiographic features. Zero-degree, 5-degree, 15-degree, and 25-degree radiographs were significantly better than the mesially angulated -15-degree and -25-degree images for detecting the type i RE images (P < .05). Fifteen-degree, 25-degree, and -25-degree horizontal beam angulations showed significantly more accurate diagnoses of RE in 8 type ii images (P < .05). Only 25-degree-angled radiographs were found to have a high diagnostic yield of type iii RE images (P < .05). A significant correlation was found between morphologic and radiographic types of RE (P < .05, contingency coefficient = 0.473). Intraexaminer variability was low, with kappa = 0.68 (P < .05).

Conclusions

RE presents 3 types of typical radiographic features on orthoradial radiographs. Additional 25-degree mesial horizontal-angled radiographs are essential for preoperative identification and evaluation of RE, especially types ii and iii.     

变形链球菌母子传播与其对牙面初始粘附关系的研究

目的:探索变形链球菌母子传播与其对牙面初始粘附能力的关系。方法:首先以AP-PCR检测Mutans streptococci(MS)在20对3~4岁儿童和母亲之间的传播,并从母亲口腔中筛选出传播株和非传播株;再采用同位素标记法,检测传播株和非传播株对SHA的粘附差异,同时对其表面蛋白粘附功能区spap-a和spap-pv分别用限制性内切酶haeⅢ和AluⅠ进行RFLP分析。结果:传播株较非传播株具有较弱的粘附力(P<0.01),spap-a和spap-pv经酶切后分别呈现的3种和2种基因型在传播和非传播人群的MS中分布不同(P<0.01)。结论:初始粘附能力弱的菌株被传播的可能性较大,不同MS株传播能力的差异可能与其表面蛋白A区,PV区的基因多态性有关。     

Reconstruction of a cranial bone defect with hydroxyapatite and free flap transfer.

The authors report a successful reconstruction of an extensive frontotemporal bone defect after craniotomy, which was complicated with infection and necessitated removal of frontal and temporal bones. The large frontotemporal bone defect was reconstructed using prefabricated hydroxyapatite blocks in combination with the free vastus lateralis muscle flap. The patient's functional and cosmetic restoration has been maintained for 10 months' follow-up.     

Physostigmine-induced salivary secretion in the rat

The purpose of this study was to see if physostigmine, a reversible cholinesterase inhibitor, affects the secretion and composition of saliva of the major salivary glands of the rat. Low doses of physostigmine did not elicit secretion. At higher doses there was significant flow from the parotid and submandibular glands within 5 min; however, no sublingual secretion was observed. The submandibular flow rate was highest for the first 5 min, then declined rapidly. The parotid flow rate initially was one-fifth of the maximum submandibular rate and then gradually decreased. The concentrations of Ca, Na and K of physostigmine-induced parotid saliva, and the Na of submandibular saliva, were similar to those with carbachol stimulation. The Ca and K concentrations of submandibular saliva were significantly higher than with carbachol or parasympathetic stimulation, and resembled those of alpha-adrenergic stimulation. The protein concentrations of physostigmine-evoked saliva from both glands were similar. The amylase activity of physostigmine-evoked parotid saliva was much higher than that of carbachol or parasympathetic stimulation. Physostigmine-evoked secretion was completely blocked by atropine, a cholinergic antagonist, and by reserpine, partially blocked by phentolamine, an alpha-adrenergic antagonist and not affected by surgical sympathectomy. Morphologically, physostigmine resulted in a moderate decrease in the number of acinar, but not ductal, secretory granules of both the parotid and submandibular glands, while the sublingual gland was unaffected. Numerous patches of parotid acini also developed vacuoles or vesicles. These results suggest that physostigmine-induced salivary secretion is mediated primarily by direct effects on cholinergic and alpha-adrenergic receptors.     

Microbial complexes in supragingival plaque

Background/aims:  To examine microbial communities in supragingival biofilm samples.
Methods:  Supragingival plaque samples were taken from 187 subjects at baseline ( n  = 4745). Fifty-five subjects provided supragingival plaque samples at 1–7 days after professional tooth cleaning ( n  = 1456); 93 subjects provided 8044 samples between 3 and 24 months post-therapy. All samples were individually analyzed for their content of 40 bacterial species using checkerboard DNA–DNA hybridization. Microbial associations among species were sought using cluster analysis and community ordination techniques for the three groups separately.
Results:  Six complexes were formed for the baseline samples. Similar complexes were formed for the samples taken 3–24 months post-therapy. However, distinct changes were observed in microbial communities in samples taken during the 7 days of plaque redevelopment. The complexes related to clinical parameters of periodontal disease.
Conclusion:  There were specific microbial complexes in supragingival plaque that were similar to those found in subgingival plaque samples with a few minor differences. The relation of previously unclustered taxa to the complexes was also described.