DEPTH OF CURE AND COMPRESSIVE STRENGTH OF DENTAL COMPOSITES CURED WITH BLUE LIGHT EMITTING DIODES (LEDs)

Objective: The primary purpose of this study was to test the hypothesis that depth of cure and compressive strength of resin composites cured using either an LED curing light or a QTH curing light would not be significantly different. The second objective was to characterize and compare the irradiance and emitted light spectra for the LED and QTH light curing units.     

INFLUENCE OF LIGHT ENERGY DENSITY ON HEAT GENERATION DURING PHOTOACTIVATION OF DENTAL COMPOSITES WITH DIFFERENT DENTIN AND COMPOSITE THICKNESS

Objective:

The aim of this study was to determine the influence of different energy densities on the heat generated during photoactivation of Filtek Z250 (3M/ESPE) and Z100 (3M/ESPE) composite resins with different dentin and composite thickness.

Material and Methods:

The temperature increase was registered with a type-K thermocouple connected to a digital thermometer (Iopetherm 46). A chemically polymerized acrylic resin base was prepared to serve as a guide for the thermocouple and as a support for 0.5-, 1.0-, and 1.5-mm-thick bovine dentin discs. Circular elastomer molds (1.0 mm-height x 3.0-mm diameter or 2.0-mm height x 3.0-mm diameter) were adapted on the acrylic resin base to standardize the composite resin thickness. A conventional halogen light-curing unit (XL 2500, 3M/ESPE) was used with light intensity of 700 mW/cm². Energy density was calculated by the light intensity applied during a certain time with values of 28 J/cm² for Z100 and 14 J/cm² for Filtek Z250. The temperature change data were subjected to three-way ANOVA and Tukey''s test at 5% level.

Results:

The higher energy density (Z100) promoted greater temperature increase (p<0.05) than the lower energy density (Filtek Z250). For both composites and all composite thicknesses, the lowest dentin thickness (0.5 mm) yielded significantly higher (p<0.05) temperature increase than the other two dentin thicknesses. The 1-mm-thick composite resin layer yielded significantly higher (p<0.05) temperature changes for both composites and all dentin thicknesses.

Conclusions:

Temperature increase was influenced by higher energy density and dentin/composite thickness.     

INFLUENCE OF THE DISTANCE OF THE CURING LIGHT SOURCE AND COMPOSITE SHADE ON HARDNESS OF TWO COMPOSITES

This study evaluated the influence of curing tip distance, shade and filler particle size on Vickers microhardness (VHN) of composite resins. Two composites were tested: Filtek Z250 microhybrid (3M ESPE; shades A1 and A3.5) and Filtek Supreme nanofilled (3M ESPE; shades A1B and A3.5B). For each resin, 42 specimens (5 mm in diameter and 2 mm height) were prepared being 21 for each shade. The specimens were exposed using a 20-second exposure to a quartz-tungsten-halogen light source with an irradiance of approximately 560 mW/cm², at the following distances: 0 mm (surface contact), 6 mm and 12 mm from composite surface. Effectiveness of cure of different resins, shades and curing distances was determined by measuring the top and bottom hardness (VHN) of specimens using a digital microhardness tester (load: 50 g; dwell time: 45 seconds) 24 hours following curing. The hardness ratio was calculated by dividing VHN of the bottom surface by VHN of top surface. Three-way ANOVA and Tukey''s post-hoc test (p<0.05) revealed statistically significant differences for all analyzed factors. As for top hardness, as microhardness ratio (bottom/top), the factors shade, distance and composite filler particle size exerted influence on resin curing. Lighter shade composites (A1 and A1B) showed higher hardness values. At 6 and 12 mm curing tip distances, hardness was lower when compared to 0 mm. The microhybrid composite resin presented higheer hardness, being its microhardness ratio satisfactory only at 0 mm for both shades and at 6 mm for the lighter shade. The nanofilled composite resin did not present satisfactory microhardness at the bottom while the microhybrid composite resin had higher hardness than the nanofilled. Composite''s curing tip distance and shade can influence hardness.     

REDUCED LIGHT ENERGY DENSITY DECREASES POST-GEL CONTRACTON WHILE MAINTAINING DEGREE OF CONVERSION IN COMPOSITES

Objective : The purpose of this study was to evaluate the effects of curing‐light energy density on degree of conversion and polymerization contraction stress of a hybrid composite resin. Materials and Methods : Specimens of Bisfil P (Bisco, Inc., Schaumburg, Illinois) were fabricated. The specimens were 5.4 mm in diameter by 1.7 mm in thickness. Five groups of six specimens were cured using different light‐intensity protocols. The control group had the highest light intensity, at 337 mW/cm². Three groups were light‐cured with modified light intensities, which were 71%, 49%, and 34% of the control intensity. In these four groups, the composite was light‐cured for 40 seconds, with only the intensity of the light varying. In the fifth group, specimens were irradiated for 20 seconds with a reduced intensity (241 mW/cm²), followed by 20 seconds at high intensity (337 mW/cm²). A light guide was positioned at 7 mm from the top surface of each specimen during the polymerization. Linear polymerization contraction was measured using electrical strain gauges positioned at the bottom of the specimens. One day after curing, specimens were polished to 600‐grit, and chips were removed with a scalpel from the top and the bottom surfaces of each of the samples to evaluate the degree of conversion using Fourier transform infrared spectroscopy. Results : The control group (337 mWlcm²) had the highest degree of conversion at top and bottom surfaces. The degree of conversion of the specimens cured with the two‐step method was not significantly different from the values of those cured at either higher or lower intensity for 40 seconds. The linear contraction strain for the specimens cured with the two‐step method was not significantly different from that of the sample cured at the lower intensity for 40 seconds. Also, the post‐gel contraction strain increased linearly as the intensity of the light increased. Conclusions : The degree of conversion was more sensitive to changes in light intensity at the bottom of the composite than at the top. Also, strain was linearly related to light intensity (i.e., greater intensity = more strain). Finally, the specimens cured with the two‐step method showed a 21.8% reduction from the contraction strain predicted from a light energy density calculation.     

颊粘膜肌瓣单独或联合颊脂垫修复舌腭缺损

应用颊粘膜瓣单独或联合颊脂垫修复舌腭缺损是一种简单而有效的手术方法。笔者自１９３９年至１９９６年，应用该方法修复舌癌切除后≤１／２舌缺损１０例，修复软腭缺损２例。瓣全部成活，吞咽、语言功能恢复快，外形满意。术后几天开口约１．５ＣＭ～２．０ｃｍ，２周后张口逐渐恢复正常。本技术为舌半侧以内缺损和软腭缺损的修复提供了可靠实用的新方法。     

COMPARISON OF RADIOGRAPHIC MEASUREMENTS OBTAINED WITH CONVENTIONAL AND INDIRECT DIGITAL IMAGING DURING ENDODONTIC TREATMENT

The aims of this study were to evaluate the quality of indirect digitized radiographic images taken during endodontic procedures and to compare the measurements recorded with this technique to those obtained from conventional radiographs. Two-hundred conventional periapical radiographs taken at the undergraduate Endodontics Clinic of the Dental School of Bauru were digitized. The conventional and indirect digitized images were compared by three examiners as to the quality and accuracy of the measurements recorded during endodontic treatment, in canal length determination, gutta-percha adaptation, lateral condensation and final obturation. The conventional radiographs were observed on a film viewer, surrounded by a dark card, and measured with magnifying glass and a millimeter ruler; the indirect digitized images were evaluated on the Digora^® for Windows software, with free utilization of the bright/contrast tool. Unlike the conventional radiographic images, all indirect digitized images were considered as having a high quality. The distance between the filling material and the root apex was 0.117 mm larger, on average, for the Digora^® system (p<0.01). The measurements achieved by the investigated radiographic methods were clinically similar and they are thus equivalent. Changes in brightness and contrast of the images using Digora^® software improved the diagnosis.     

EFFECT OF CYCLIC LOADING ON FRACTURE STRENGTH OF ENDODONTICALLY TREATED TEETH RESTORED WITH CONVENTIONAL AND ESTHETIC POSTS

Introduction:

Esthetic post and core systems were recently introduced. There are few reports regarding their behavior under cyclic loading.

Objectives:

This study compared the effect of cyclic loading on survival rate, residual strength and mode of fracture of endodontically treated teeth restored with esthetic and direct metallic post systems subjected to mechanical cyclic loading.

Materials and Methods:

Thirty canines were endodontically treated, decoronated and prepared for metal free ceramic crowns, leaving 1.5 mm of dentin for ferrule effect. They were distributed in 3 groups and restored as follows: group 1 with zirconia posts (Cosmopost) and glass-ceramic cores (IPS Empress Cosmopost); group 2 with fiber reinforced composite posts (FibreKor) and group 3 with titanium posts (AZthec Anchor). Direct resin composite (Build It FR Resin Composite) was used as core in groups 2 and 3. All specimens were restored with all ceramic crowns (IPS Empress 2). A resin cement/adhesive system (Cement It/Bond It Primer A+B) was used to lute the posts to root canals and metal free porcelain crowns to the teeth preparation. Specimens were subjected to mechanical load of 250 N for 500,000x at a frequency of 1.7 Hz and then to static load until failure in a universal testing machine. Data were analyzed using One-way ANOVA and Fischer Exact tests α=0.05.

Results:

All groups had 100% survival rate after cyclic loading; fracture strength values (SD) in N were: group 1 = 886.5(170.6), group 2 = 762.2(113.6) and group 3 = 768.9(72.9); there was no difference among groups (p=0.08); the percentage of mode of favorable fracture found was: group 1 = 60%, group 2 = 90% and group 3 = 50%; there was no correlation between the mode of failure and post and core system used (P=0.142).

Conclusions:

Esthetic post and core systems showed statistically equivalent fracture strength values, mode of failure and survival rate compared to conventional direct metallic post and resin composite core system after cyclic loading.     

光镜及电镜下观察人胚涎腺肌上皮细胞

目的：在光镜及电镜下观察人胚涎腺肌上皮细胞的形态及组织结构。方法：选择１０例７至８月流产胎儿颌下腺,９例标本用石蜡包埋,ＨＥ及台兰染色光镜下观察。２例标本经环氧树脂包埋,在电镜下观察。结果：光镜下寺染色切片,在腺泡及闰管表面可清楚地看到扁平的肌上皮细胞。电镜观察,间以粒相连拉,胞浆内含有肌微丝,细胞吕不发达。结论：肌上皮细胞在胚胎期就已形成。ＨＥ染色,该细胞难以辨认,而用台盼兰染色观察该细胞简便易     

THE ELECTROCHEMICAL PROPERTIES OF FOUR DENTAL CASTING SUPRASTRUCTURE ALLOYS COUPLED WITH TITANIUM IMPLANTS

Objectives:

As the choice of suprastructure alloy to be combined with titanium for the oral cavity is still a much debated issue, the aim of this study was to investigate the electrochemical interaction of the suprastructure/implant couples under the determined experiment conditions.

Material and Methods:

The potentiodynamic polarization curves and open-circuit potentials (OCP) of four UCLA type suprastructures coupled with straight Swiss Plus implant fixtures were taken in Afnor type artificial saliva solution at 37°C. The concentration of ions leached into artificial saliva solutions was estimated with ICP-MS. SEM images of the margins of suprastructure/implant couples were obtained before and after the electrochemical tests.

Results:

The OCP value of titanium became passive at the most negative potential. The lowest difference between the initial and constant OCP value was exhibited by the Au based suprastructure. Suprastructures made greater contributions to the potentiodynamic polarization curves of the implant/suprastructure couples. According to the ICP-MS results, Pd based and Au based couples dissolved less than Co-Ni based and Co-Cr based couples.

Conclusions:

Within the conditions this study, it may be concluded that the titanium implant forms a stable passive oxide layer in artificial saliva exposed to open air and does not affect the corrosion properties of the suprastructures. Pd based and Au based couples have been found to be more corrosion-resistant than base alloy couples.     

1988～1992年中国非综合征性唇腭裂发生率的动态变化

目的　了解我国 1988～ 1992年非综合征性唇腭裂发生率的动态变化趋势及流行病学特征。方法　采用以医院为单位的整群抽样方法 ,对 1988～ 1992年期间我国 5 0 0多所医院孕 2 8周至产后 7天的 3 2 46 40 8例围产儿 ,4349例非综合征性唇腭裂病例进行回顾性分析。结果　我国 5年非综合征性唇腭裂发生率无显著性差异 ,城乡发生率也无显著性差异。男性发生率为 14.9/万 ,女性发生率为 11.7/万 ,差异有显著性 ,非综合征性唇腭裂的性别比为 1.3∶ 1。三类非综合征性唇腭裂各自的发生率为 :CL± P:7.8/万 ,CL:3.8/万 ,CP:1.8/万。结论　我国非综合征性唇腭裂发生率无变化趋势 ,城乡无差异。男性高于女性 ,唇裂合并腭裂为最常见类型。     

唇腭裂患儿父母心理健康状况对照研究

目的　了解唇腭裂患儿父母的心理健康状况 ,为对其进行心理支持和治疗提供依据。方法　采用SCL - 90症状自评量表对唇腭裂患儿的 6 0名父母及正常儿童的 6 0名父母进行心理调查。结果　患儿组父母SCL- 90总分、阳性项目数、抑郁、焦虑和恐怖明显高于对照组 (P <0 .0 5 )。患儿组母亲在躯体化、强迫、人际关系、抑郁、焦虑、偏执、精神病性诸因子分和阳性项目数上明显高于父亲 (P <0 .0 5 )。结论　唇腭裂患儿的父母心理健康状况较差 ,尤以患儿母亲较为突出     

rhBMP-2、胶原和珊瑚复合人工骨在不同种类动物体内异位诱导新骨形成的实验研究

:目的:研究rhBAAP2,胶原,珊瑚复合骨在于同种属动物体内诱导异位成骨的活性。材料与方法:本研究采用肌袋异位成骨的动物模型,通过大体、组织学观察、组织测量等手段,研究珊瑚、型胶原、rhBMP2复合骨在大鼠、兔、狗体内异位诱导新骨形成的特点,珊瑚降解的过程。结果:rhBMP2、珊瑚和胶原复合骨在大鼠、兔、狗体内均可异位诱导骨组织形成,在大鼠体内诱导成骨量大,骨组织成熟程度高,在兔、狗体内成骨量小,成熟程度低。结论:说明rhBMP2、胶原、珊瑚复合骨在不同种属动物体内都具有异位诱导骨组织形成的活性。     

THE MANAGEMENT OF DROOLING IN CHILDREN AND PATIENTS WITH MENTAL AND PHYSICAL DISABILITIES: A LITERATURE REVIEW

Amongst the duties of the paediatric dentist is the provision of oral care to patients with the problem of drooling. Many, but certainly not all, of these patients have physical and/or learning disabilities. Various methods have been advocated for the management of drooling in the paediatric patient and older patients with disabilities, including behavioural programmes, biofeedback techniques, physiotherapy, biofunctional oral appliances, medication and surgery. It is of paramount importance that the patients and/or carers understand the advantages and disadvantages of any treatment method being considered. The paediatric dentist has an important role to play in explaining the different options to the patients and carers, and in implementing some treatment modalities, particularly non-surgical approaches. Referral to surgical specialists should be seen as 'a last resort' and suggested only if other treatment methods have been exhausted. If pharmacological or surgical treatment is carried out, careful monitoring for the development of dental caries and other problems is essential. The aim of this paper is to provide the paediatric dentist with concise overall knowledge of the causes of drooling and treatment options available.     

ADHESIVES WITH DIFFERENT PHS: EFFECT ON THE MTBS OF CHEMICALLY ACTIVATED AND LIGHT-ACTIVATED COMPOSITES TO HUMAN DENTIN

Purpose:

To evaluate the bond strength between human dentin and composites, using two light-activated single-bottle total-etch adhesive systems with different pHs combined with chemically activated and light-activated-composites. The tested hypothesis was that the dentin bond strength is not influenced by an adhesive system of low pH, combined with chemically activated or light-activated composites.

Material and Method:

Flat dentin surfaces of twenty-eight human third molars were allocated in 4 groups (n=7), depending on the adhesive system: (One Step Plus-OS and Prime & Bond NT-PB) and composite (light-activated Filtek Z-100 [Z100] and chemically activated Bisfil 2B [B2B]). Each adhesive system was applied on acid-etched dentin and then one of the composites was added to form a 5 mm-high resin block. The specimens were stored in tap water (37°C/24 h) and sectioned into two axes, x and y. This was done with a diamond disk under coolant irrigation to obtain beams with a cross-section area of approximately 0.8 mm². Each specimen was then attached to a custom-made device and submitted to the microtensile test (1 mm.min⁻¹). Data were analyzed using two-way ANOVA and Tukey’s tests (p<0.05).

Results:

The anticipated hypothesis was not confirmed (p<0.0001). The bond strengths (MPa) were not statistically different between the two adhesive systems when light-activated composite was used (OS+Z100 = 24.7±7.1ª; PB+Z100 = 23.8±5.7ª). However, with use of the chemically activated composite (B2B), PB (7.8±3.6^b MPa) showed significantly lower dentin bond strengths than OS (32.2±7.6ª).

Conclusion:

The low pH of the adhesive system can affect the bond of chemically activated composite to dentin. On the other hand, under the present conditions, the low pH did not seem to affect the bond of light-activated composites to dentin significantly.     

EFFECTIVENESS OF NaOCl ALONE OR IN COMBINATION WITH EDTA ON THE DIFFUSION OF HYDROXYL IONS RELEASED BY CALCIUM HYDROXIDE PASTE

Aim:

To evaluate the effect of different irrigant solutions employed during removal and replacement of calcium hydroxide paste on the diffusion of hydroxyl ions through root canal dentine in vitro.

Methodology:

Thirty-five maxillary and mandibular human canines with straight and fully developed roots were used. After mechanical preparation up to 1mm short of tooth length, 30 canals were filled with calcium hydroxide paste and 5 canals were left empty; all teeth had their coronal accesses properly sealed. Teeth were placed in plastic containers with distilled water, and pH was read after 30 days when the paste from 20 teeth was renewed. After removal of the paste by endodontic instrumentation and irrigation with distilled water, canals were replenished with newly mixed paste in Group 1 and 2. In these groups, final irrigation was conducted with 5 mL of EDTA followed by 5 mL of NaOCl in specimens in Group 1, and 5 mL of NaOCl only in specimens in Group 2. In 10 teeth the paste was not replenished at 30 days (Group 3). All specimens were returned to the containers with fresh distilled water, and the pH was recorded after another 30 days. The differences between the first (30d) and second (60d) pH readings were calculated and submitted to analysis of variance and individual comparisons using the Scheffeé''s test.

Results:

Results of mean analysis on differences of pH readings showed that greater diffusion had occurred on specimens in Group 3. Individual comparisons using Scheffeé''s test showed statistical significance between Groups 2 and 3, and equivalence between all other groups.

Conclusion:

It was concluded that the use of EDTA did not enhance diffusion of hydroxyl ions through root canal dentine.     

低出生体重儿、早产儿龋齿、釉质发育缺陷发病率及与釉质硬度关系的研究

目的:研究低出生体重儿、早产儿乳牙龋齿、釉质发育缺陷的发病率并探讨其与釉质硬度的关系.方法:选取低出生体重儿、早产儿及正常出生体重儿各200例进行乳牙龋齿、釉质发育缺陷统计调查.同时收集口腔科门诊治疗中的上述两类儿童的自然脱落的釉质发育正常的乳前牙各10颗做显微硬度测试,并与正常出生体重儿乳牙进行比较研究.结果:低出生体重儿、早产儿乳牙龋齿、釉质发育缺陷的发病率明显高于正常出生体重儿,但发育正常的乳牙釉质硬度与正常出生体重儿无显著差异.结论:低出生体重儿、早产儿乳牙龋齿发病率高与其釉质发育缺陷发病率高显著相关,而且仅与釉质发育缺陷的乳牙有关,与釉质发育正常的乳牙无关.     

广东籍未手术唇、腭裂患者颌面发育特点的初步研究

本文采用X线头影测量法对54例未手术广东籍唇、腭裂者的颅面骨賂间关系和颌面形态结构深度与高度进行了测量分析。结果发现未手术唇、腭裂者之颌面发育有别于正常人,主要表现在上颌位置后缩、上颌长度短、面下部高大、面下部高占全面高的比例增大。因此,临床治疗唇、腭裂时应采取综合措施。     

膜结合骨形成蛋白和单独用膜引导种植体周围骨组织再生的比较研究

为研究单纯用膜及膜结合ＢＭＰ修复与种植体有关的骨缺损的愈合速度及界面情况，应用ＨＡ喷涂钛种植体植入伴有裂状缺损的拔牙窝内。实验分两组进行，一组用聚四氟己烯膜（ＰＥＴＥ膜）结合ＢＭＰ，另一组单纯用聚四氟己烯膜。术后２、４、８、１２周分别行大体，Ｘ线，光镜观察。结果发现：单纯用膜能促进种植体周围新骨生成，而膜结合ＢＭＰ处理的种植体骨修复启动早，骨界面愈合速度较单纯用膜可提前约４～６周。两种方法为扩大种植体的适应证范围，解决植床质和量问题提供了可能     

CHANGES IN PARENTAL SATISFACTION AND ORAL HEALTH-RELATED QUALITY OF LIFE OF PRESCHOOL CHILDREN AFTER RECEIVING ATRAUMATIC RESTORATIVE TREATMENT WITH OR WITHOUT PRIOR SILVER DIAMINE FLUORIDE APPLICATION

ObjectiveTo investigate the short-term and long-term changes in parental satisfaction and oral health-related quality of life (OHRQoL) of preschool children after receiving atraumatic restorative treatment (ART) with or without prior silver diamine fluoride (SDF) application.MethodsIn a randomized controlled trial, preschool children with cavitated dentine caries lesions in their primary teeth were randomly assigned into two groups to receive either application of SDF solution or placebo (tonic water) on the caries lesions 10 weeks before receiving ART restorations. The information on parental satisfaction and OHRQoL of the children were collected through self-completed questionnaires at baseline, the 6-month and the 24-month follow-up. A five-point scale, from 1 (very dissatisfied) to 5 (very satisfied), was used by parents to indicate their satisfaction with their child's dental conditions. A higher parental satisfaction score indicates that parents were more satisfied with their child's dental condition. In addition, the Chinese version of Early Childhood Oral Health Impact Scale (ECOHIS) was adopted to assess the children's OHRQoL, and a higher ECOHIS score indicates greater negative impacts of oral health on the child's OHRQoL.ResultsA total of 194 children participated in this study, with 101 and 93 children receiving SDF and placebo application before ART restorations, respectively. After placement of ART restorations, at 6-month and 24-month follow-up, parental satisfaction scores with their child's dental health status were significantly higher compared with those at baseline (P <.001) indicating the parents were more satisfied at follow-ups. Regarding OHRQoL, no statistically significant changes were found in the child impact section (CIS), family impact section (FIS) and total ECOHIS scores in both study groups at the 6-month follow-up. In contrast, at the 24-month follow-up, the CIS (P = .025) and total ECOHIS scores (P = .015) of the children in the control group were significantly higher than those at baseline (greater negative impacts), but not the FIS score.ConclusionIn this study, after one-off placement of ART restorations irrespective of prior SDF application, short-term and long-term parental satisfaction with their child's dental health status was improved, but not the children's OHRQoL.