Talon cusp in Malaysia

Five hundred and thirty-six patients were examined for the presence of talon cusps. The anomaly was observed in 28 patients (5.2 per cent). There was no sex predilection in the occurrence. Only two patients had a bilateral occurrence, with the maxillary lateral incisors being the most commonly affected. Radiographic evidence of pulpal extension into the cusp was observed in five patients. Many of the affected teeth presented with deep developmental grooves some of which were carious and/or occlusal interference leading to malocclusion.     

牙尖斜度对上颌全口义齿基托应力分布的影响

目的:探讨后牙牙尖斜度对上颌全口义齿基托应力分布状况的影响。方法:建立0°、20°、30°三种牙尖斜度的上颌全口义齿及其支持组织的三维有限元模型,分别在全牙列、前牙列、双侧及单侧后牙列加载下,分析基托内切牙乳突区、唇系带切迹区、后牙区的综合应力值大小。结果:全牙列加载下,基托内各区基本呈现较广泛的高应力值分布,且随牙尖斜度增加而加大。前牙加载下,牙尖斜度变化对基托内应力值影响较小。双侧或单侧后牙加载下,随牙尖斜度增加,后牙区应力值呈显著增大,对切迹区应力值亦有一定影响。结论:随牙尖斜度增加,基托各区内应力值均发生变化,且变化幅度与加载方式有关。     

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目的探求适合青少年前磨牙畸形中央尖的治疗方法。方法选择2007年6月至2009年6月来济宁口腔医院儿童牙科就诊的前磨牙畸形中央尖患儿30例(54颗患牙),按就诊顺序随机分为两组:一次磨除法组(15例,29颗患牙)采用一次磨除后盖髓充填法,多次磨除法组(15例,25颗患牙)采用多次少量磨除法,随诊观察1年。结果治疗1年后复查,一次磨除法组治疗成功率为93.1%,多次磨除法组成功率为72.0%,二者差异有统计学意义(P<0.05)。结论早期在局麻下对前磨牙畸形中央尖进行磨除并盖髓充填的治疗方法有着积极的临床意义。     

全口义齿牙尖斜度与咀嚼效能和稳定性的研究

目的研究全口义齿人工牙的牙尖斜度与义齿咀嚼效能及义齿稳定性的关系,为义齿设计提供依据.方法首先采用解析几何的方法对全口义齿人工牙的牙尖斜度与咀嚼效能及稳定性之间的关系进行分析;然后选用同一品牌、同一规格3种牙尖斜度(0°、12°、33°)的人工牙后牙,用蘸印泥压印法统计各类人工牙的(牙合)面接触面积,并通过数学方法分析人工牙的(牙合)面接触面积与义齿咀嚼效能间的关系.结果牙尖斜度大者,咬切食物的分力大,但义齿受到的侧向分力也大;(牙合)面接触面积的大小顺序为33°牙＜12°牙＜0°牙,义齿行使功能时,人工牙的压强大小与(牙合)面接触面积成反比.结论使用牙尖斜度大的人工牙咀嚼效能高,但不利于义齿的稳定;牙尖斜度小的人工牙咀嚼效能低,但有利于义齿的稳定.     

Patterns of indirect fracture in intact and restored human premolar teeth

Abstract Fracture patterns of contralateral pairs of intact and restored premolar teeth were determined after dynamic loads of equal energy were applied to the medial aspects of the buccal cusps. The predominant fracture path for intact teeth ran obliquely from the occlusal fissure to the buccal cervical region, followed by fractures from the point of impact. Most teeth restored with MOD amalgams fractured from the base of the cavity, whereas those with amalgam overlays suffered less severe fractures, sited higher in the cusps. When teeth restored with MOD gold overlays and full gold crowns fractured, the site was frequently in the root. The value of cuspal protection by means of overlay techniques was confirmed by this study.     

不同牙尖斜度对下颌全口义齿软衬后稳定性影响的研究

目的：比较下颌全口义齿软衬后不同牙尖斜度条件下义齿基托组织面位移情况,分析牙尖斜度对软衬后义齿稳定性的影响.方法：采用三维有限元方法,选择标准无牙下颌牙槽嵴模型为实验对象,建立无牙下颌和软衬全口义齿有限元模型,采用双侧后牙垂直加载,牙尖斜度选取0°、10°、15°、20°、25°、30°,对义齿基托组织面位移结果进行分析.结果：（1）0°-30°不同牙尖斜度各组间垂直向位移差异无显著性;（2）不同牙尖斜度水平向位移各组间具有显著性差异（P＜0.01）,以0°与10°最小;（3）加载后不同牙尖斜度软衬模型义齿软衬层组织面与黏膜表面始终贴合.结论：全口义齿牙尖斜度在0°-30°之间时,软衬材料可以较好的适应不同牙尖斜度,水平向动度以0°与10°最小.     

Clinical problems associated with unusual cases of talon cusp

CASE REPORT: Talon cusp is an uncommon dental anomaly manifested as an accessory cusp-like structure on the crown of anterior teeth. This report describes two unusual cases of talon cusp. Case 1 showed bilateral anomalous cusps on the palatal aspects of maxillary supernumerary teeth, causing premature contact and tooth impaction. In case 2, a double-fused talon cusp was projected from the palatal surface of a large geminated central incisor. A talon cusp is not an innocuous defect, as it may provide a substantial diagnostic, treatment planning and procedural challenge. Early diagnosis and management are important to avoid complications.     

Enamel microstructure and microstrain in the fracture of human and pig molar cusps

The role of microstructure in enamel strain and breakage was investigated in human molar cusps and those of the pig, Sus scrofa. Rosette strain gauges were affixed to cusp surfaces (buccal human M3, n=15, and lingual pig M1, n=13), and a compressive load was applied to individual cusps using an MTS materials testing machine. Load and strain data were recorded simultaneously until cusp fracture, and these data were used to estimate enamel stresses, principal strains, and stiffness. Fractured and polished enamel fragments were examined in multiple planes using scanning electron microscopy (SEM). Human cusp enamel showed greater stiffness than pig enamel (P=0.02), and tensile stress at yield was higher (17.9 N/mm2 in humans versus 8.9 N/mm2 in pigs, P=0.06). SEM revealed enamel rod decussation in both human and pig enamel; however, only pig enamel showed a decussation plane between rod and inter-rod crystallites. Human inter-rod enamel was densely packed between rods, whereas in pig enamel, inter-rod enamel formed partitions between rows of enamel rods. Overall, human enamel structure enabled molar cusps to withstand horizontal tensile stress during both elastic and plastic phases of compressive loading. In contrast, pig cusp enamel was less resistant to horizontal tensile stresses, but appeared to fortify the enamel against crack propagation in multiple directions. These structural and biomechanical differences in cusp enamel are likely to reflect species-level differences in occlusal function.     

Intentional partial pulpotomy to talon cusp for tooth crown morphology correction in orthodontic treatment

This report describes a case of talon cusp treated by an intentional partial pulpotomy, which made it possible to recontour the tooth crown into the desired shape. The patient was an 11-year-old boy with a large talon cusp on the lingual surface of the right maxillary lateral incisor. He was referred to our clinic for treatment of abnormality cusp because it was expected to impede orthodontic treatment. The talon cusp was amputated using an intentional partial pulpotomy. The procedure resulted in successful recontouring of the tooth crown into the desired morphology and the dental pulp exhibited a vital reaction at three years after the operation.     

左下第二前磨牙畸形中央尖引起牙根替代性吸收、牙折和皮瘘1例报告

畸形中央尖多见于下颌前磨牙,尤以第二前磨牙最常见,偶见于上颌前磨牙,常为对称性发生：有些畸形中央尖无任何临床症状,有些会引起牙髓炎、根尖周炎等,甚至形成皮瘘,影响牙根正常发育。中国医科大学口腔医学院牙体牙髓科发现左下第二前磨牙畸形中央尖影响牙根发育,引起牙根替代性吸收及牙折和皮瘘l例一现报告如下。     

Incidence rates for oral leukoplakia and lichen planus in a Japanese population

BACKGROUND: Data on the incidence rates of potentially malignant diseases of the oral cavity in different populations is meagre. This is the first study to report on the age-specific incidence of oral leukoplakia and oral lichen planus from an industrialized country. METHODS: Annual screening for oral cancer and pre-cancer was undertaken in Municipal Health Centres in Tokoname city, Japan from 1995 to 1998. A total of 9536 volunteers aged 40-95 years participated in this programme. A cohort of 6340 (67%) subjects attended annual mouth examinations following a negative screen result at entry, allowing 13 072 person-years of observations. Some associated risk factors (tobacco and alcohol misuse) and health-related variables were also evaluated. RESULTS: Over a 4-year follow-up period, 18 new oral leukoplakias (all homogenous; 11 idiopathic and seven tobacco-associated) and 24 oral lichen planus (22 reticular, one erythematous and one ulcerative) were detected at screening and confirmed by re-examination at specialist units. The age-adjusted incidence rate for leukoplakia was 409.2 (95% CI: 90.6-727.9) in male and 70.0 (95% CI: 17.9-121.8) in female per 100,000 person-years observations. For lichen planus, the corresponding rates were 59.7 (95% CI: 7.4-112.1) and 188.0 (95% CI: 96.0-280.1). The age-adjusted incidence rate for tobacco-associated leukoplakia in males was almost 12 times compared with female (560.3 vs. 45.2 per 100,000). Age-specific incidence rates for oral leukoplakia varied by age groups. New oral leukoplakias were more prevalent on gingival/alveolar ridge (33.3%) than in other oral sites, and lichen planus at buccal site (33.3%). Prevalence of smoking habits among those positive for leukoplakia (38.9%) was higher compared with the screen-negatives (26.4%) but these differences did not reach statistical significance (P = 0.232). Regular drinking was not related to occurrence of either oral leukoplakia or oral lichen planus. In cases with diabetes mellitus, relative risk for oral lichen planus adjusted by logistic regression was 6.4 (95% CI: 2.4-17.6), suggesting an association. CONCLUSIONS: The reported incidence rates for oral leukoplakia in this Japanese population are somewhat higher to those reported from India, the risk habits of the two groups being markedly different. The reported rates for oral leukoplakia and lichen planus allow estimation of service needs in specialist oral medicine clinics and for the training of primary care dentists. A high incidence of idiopathic leukoplakia found in this study raises challenges to the strategy of screening high-risk populations aimed at conserving resources.     

上颌全口义齿基托多因素三维有限元分析

目的：研究不同腭穹隆形状时,人工牙排列位置、牙尖斜度对上颌全口义齿基托应力分布状况的影响,为上颌全口义齿修复的优化设计提供理论依据。方法：应用三维有限元应力分析法,研究在不同腭穹隆形状时,人工牙排列位置、牙尖斜度对上颌全口义齿基托应力分布状况的影响。结果：各种载荷条件(三种腭穹隆形状、五种人工牙排列位置)下,随着牙尖斜度的增加,基托的应力增大。后牙颊向偏离牙槽嵴顶,前牙唇向偏离牙槽嵴时,基托应力集中区的强度均发生变化。三种腭穹隆形状时,基托应力集中强度依次为：腭穹隆低平、腭穹隆适中、高腭穹隆。结论：牙尖斜度、腭穹隆形状和人工牙的排列位置对上颌全口义齿基托的应力集中状况有明显的影响作用。提示临床行全口义齿修复时,应考虑患者腭穹隆形状,选择适当牙尖斜度的人工牙,特别是腭穹隆低平患者。     

载荷下腭穹隆形态、牙尖斜度对上颌全口义齿基托应力分布的影响

目的:研究载荷下腭穹隆形态及牙尖斜度对上颌全口义齿基托应力分布的影响.方法:模拟5种咬合状态,对涉及牙尖斜度的尖、平、凹3种腭穹隆形态上颌全口义齿的三维有限元模型进行加载.结果:在不同载荷条件下,3种腭穹隆形态上颌全口义齿基托的切牙乳突区、后牙列区及唇系带切迹区部分或全部为应力集中区,且当牙尖斜度为2°时,中线区应力峰值较小,当牙尖斜度为0°或3°时,中线应力峰值明显增大,在所有载荷条件下,不同腭穹隆形态基托的切牙乳突区及后牙列区应力值大小为:尖型＞平型＞凹型.结论:腭穹隆形态及牙尖斜度对上颌全口义齿基托应力分布状况无明显影响,对各应力区应力值大小有影响,上颌全口义齿基托应力的分布及大小与加载方式有关.     

氢氧化钙充填根管诱导根尖形成的临床观察

对４５例４８颗儿童期有症状畸形中央尖双尖牙行氢氧化钙根和充填根尖诱导形成术。经１至４年观察，牙根尖完全发育成形有７９．２％，根尖部分发育形成有１６．６％，失败有４．２％。认为临床上有效抗感染，恰当的根管预备和根管充填的条件下，氢氧化钙能有效的诱导有症状畸形中央尖牙根尖发育形成。     

多发多病程前磨牙畸形中央尖1例

该文报道1例因畸形中央尖折断导致严重根尖周感染的患者,其双侧上颌第二前磨牙、下颌前磨牙共6颗牙均患畸形中央尖,而且患牙处于不同病变发展阶段,经对症处理,治疗效果良好。结合该罕见病例并回顾相关文献,总结畸形中央尖患牙的临床表现、分类和相应的治疗措施,为畸形中央尖患牙的早期诊疗和其继发病变的预防提供切实可行的方案。     

根尖诱导成形术治疗感染型畸形中央尖的临床观察

目的：研究感染型畸形中央尖患牙根尖诱导后的临床疗效,并观察不同根尖孔形状对牙根闭合的影响。方法：选择59个己发生牙髓感染的畸形中央尖患牙,采取根尖诱导促进牙根发育、根尖闭合。结果：经2年追踪观察,术后患牙100％临床症状消失,93．22％完成根尖封闭。14个根尖内聚型患牙术后根尖发育完成,平均闭合时间6．64个月;19个根尖平行型,8个根尖发育完成,另11个根管腔无缩窄,但根尖达到闭合,平均闭合时间10．58个月：26个根尖喇叭口型3个根尖闭合,19个在根尖孔处形成钙化桥,4个形成根管内不规则钙化桥,平均闭合时间16．91个月。随着治疗进展,患牙根尖孔直径逐步缩窄,术前根尖孔直径平均1．99mm,术后平均0．88mm,但仍高于健康对照牙（p：0．03,〈0．05）。结论：感染型畸形中央尖经根尖诱导治疗可获得良好预后。不同根尖孔形态的畸形中央尖其临床疗效无明显差别。术前根尖内聚型或平行型患牙,术后根尖发育接近生理性闭合状态,术前根尖孔呈喇叭口型者可影响牙根发育成正常根尖形态。