Biofilm composition and composite degradation during intra-oral wear

Objectives

The oral environment limits the longevity of composite-restorations due to degradation caused by chewing, salivary and biofilm-produced enzymes and acids. This study investigates degradation of two resin-composites in relation with biofilm composition in vitro and in vivo.

The effects of artificial saliva and topical fluoride treatments on the degradation of the elastic properties of orthodontic chains.

The effect of artificial saliva and topical fluoride treatments on the force relaxation and change in force delivery by three brands of elastomeric chains over a 4 week period was studied. The effect of storage in air and in the different test media on the distraction to achieve forces of 150g and 300g was determined for the chains. The effect of the test media on load relaxation of the chains was also examined. Elastomeric chains exhibit good elastic behavior when distracted to an initial force of less than 300g. When forces exceeded 300g, permanent deformation occurred and the force delivery was less predictable. Exposure to artificial saliva and topical fluoride affected the elastic properties of the elastomeric chains and increased the distraction required to deliver both the 150g and 300g force. The increase in distraction for a force of 150g, however, was relatively small and probably insignificant in the clinical setting. The distraction required to produce 300g was significantly larger and appeared to be clinically significant. Pre-stretching the elastomeric chains by 100% of their initial length was not found to be advantageous in terms of the load relaxation behavior. There was less load relaxation found in chains that were immersed in distilled water and Acidulated Phosphate Fluoride than in chains exposed only to air.     

Newly designed phantom for visual detection tests of intra-oral x-ray imaging systems

A new phantom set, which consists of ten acrylic plate phantoms with several kinds of holes, was designed for visual detection tests of intra-oral x-ray imagin systems. Detection tests of two kinds of dental x-ray films were performed using three kinds of phantoms, an aluminum test object, Burger's phantom and the new phantom set. Detection-ability curves generated against optical density were compared. Moreover, correlation between the SNR (signal-to-noise ratio) factor and detection ability was analyzed. False positive rates were also compared. To reduce the number of phantom plate that had to be tested in the new phantom set, the number of detected signals for each phantom plate was cumulatively added and statistically compared to the total number of detected signals. The signals produced with the aluminum test object were too large. The detection ability with Burger's phantom was affected by psychological effect. The detection ability with the new phantom set was most closely correlated to the SNR. False positive rates could be compared with the new phantom set but not with the aluminum test object. The new phantom with holoes smaller than 0.6mm in diameter did not figure into the results. In conclusion, the newly designed phantom set is useful for visual detection tests of intra-oral x-ray imaging systems.     

The use of gamma irradiation for the sterilization of enamel for intra-oral cariogenicity tests

The dose of gamma irradiation sufficient to sterilize enamel samples to be used for intra-oral cariogenicity tests (ICT) without alteration to the structure or solubility of the enamel was determined. Each bovine incisor used was cut vertically into eight portions and each portion assigned to one of eight groups. Group 1 was used as control while other groups were subjected to respective doses of gamma irradiation from a cobalt-60 source. Following sterilization, both control and experimental groups were incubated in nutrient broth for 7 days at 37 degrees C under aerobic and anaerobic conditions. Caries-like lesions were subsequently produced in each specimen using acidic buffer solution, and mineral loss quantified using transverse microradiography. Data were analysed statistically. There was no significant difference in mineral loss between the control and experimental groups, but the numerical value of mineral loss was lower in groups irradiated with> 4080 Gy, in addition to full sterilization and enamel discoloration to cream colour observed in these groups. Microbial growth was observed in the control group and in groups irradiated with <4080 Gy but no discoloration. With 4080 Gy full sterilization without discoloration was observed. It was concluded that 4080 Gy of gamma irradiation is optimal for sterilization of enamel samples for use in ICT.     

Effect of sterilisation methods on the structural integrity of artificial enamel caries for intra-oral cariogenicity tests

Enamel blocks bearing artificial caries are used in intra-oral appliances for cariogenicity tests. These blocks are often sterilised to prevent the possibility of cross-infection via this route. This study therefore aimed to determine the effect of sterilisation methods on the structural integrity of artificial enamel caries used for intra-oral cariogenicity tests. Four experimental groups were devised. Ten bovine incisors were used in each group. Artificial caries was produced in each tooth which was subsequently cut into two halves. One half of each tooth was reserved as control while the other was sterilised. The four groups were subjected to respective sterilisation methods: gamma irradiation (approximately equal to 25 KGy), steam autoclaving (121 degrees C for 15 min), sodium hypochlorite (12% w/v for 24 h) and povidone-iodine (7.5% w/v for 24 h). The control and sterilised specimens in each group were examined for microbial growth after incubation in nutrient broth for up to 7 days at 37 degrees C under aerobic and anaerobic conditions. Mineral loss and lesion depth were quantified from microradiographs of sections from control and sterilised specimens using transverse microradiography. Data were analysed statistically by paired Student's t-test. Microbial growth was observed only in control specimens. Gamma irradiation and NaOCL caused cream discolouration and bleaching of the enamel surface, respectively. Autoclaving, sodium hypochlorite and povidone-iodine resulted in further demineralisation of the lesions. The four sterilisation methods were all effective sterilants for artificial caries. However, gamma irradiation appears the most acceptable method considering the more adverse effects of the other methods with regards to cariogenicity tests.     

乙醇对弹力链力值衰减影响的研究

目的通过体外实验研究乙醇是否加快弹力链的力值衰减。方法将5组3个圈短距型弹力链拉伸2.45 N力值,置于37℃人工唾液环境,每日以26.9%乙醇、14%乙醇、含乙醇漱口水、无乙醇漱口水以及人工唾液处理2次,每次60 s;利用电子推拉力仪,测量弹力链在加力24 h、7 d、14 d、21 d、28 d的剩余力值大小以及各测量时间点的力值衰减百分比。结果所有时间点所测结果中,实验组剩余力值均较对照组小。另外,不同浓度乙醇组间各个时间点的剩余力值,差异无显著性;含乙醇漱口水组各时间点的剩余力值与26.9%乙醇组相当,差异无显著性;无乙醇漱口水组各时间点的剩余力值与人工唾液组相当,差异无显著性。实验组在各个测量时间点的衰减率虽有所不同,但差异无显著性。对照组在各个测量时间点的衰减率基本相似。各组的力值衰减主要发生在第1天,随后进入一个相对平缓的阶段,实验组力值衰减整体高于对照组。结论乙醇可加快弹力链力值衰减速度,在14.0%~26.9%范围内不受其浓度的影响;含乙醇漱口水中,乙醇是主要影响弹力链力值衰减的因素。     

人工唾液环境下弹力链力值衰减的相关因素分析

目的:了解连接体类型、圈数、初始力对弹力链力值衰减的影响.方法:在37℃人工唾液中保持各连接体类型、圈数组合的弹力链不同初始力时的拉伸长度,4周内在不同时间点测量各弹力链的剩余力,采用SPSS11.5软件包计算剩余力百分比并进行方差分析.结果:不同组合的弹力链力值在4h时剩余力降至初始力的60%～90%,24h时降至50%～80%,24h后的各时间点间力值相对稳定,4周时剩余力降至40%～70%.连接体类型对力值衰减影响的差异有统计学意义(P<0.01).中距型、短距型、紧密型及长距型剩余力百分比依次增大;圈数对力值衰减影响的差异有统计学意义(P<0.01),2、3、4、5个罔数剩余力百分比依次增大;初始力对力值衰减影响的差异无统计学意义(P>0.05).结论:弹力链力值在4h内衰减最快,24h后衰减趋于稳定;连接体越短,力值衰减越慢;圈数越多,力值衰减越慢;初始力对力值衰减速度无明显影响.     

Laboratory tests for assessing adaptability and stickiness of dental composites

Objective

Handling (stickiness, adaptability) of a dental composite does strongly influence quality and success of a dental restoration. The purpose was to develop an in vitro test, which allows for evaluating adaptability and stickiness.

Methods

15 dentists were asked for providing individual assessment (school scores 1–6) of five dental composites addressing adaptability and stickiness. Composites were applied with a dental plugger (d = 1.8 mm) in a class I cavity (human tooth 17). The tooth was fixed on a force gauge for simultaneous determination of application forces with varying storage (6/25 °C) and application temperatures (6/25 °C). On basis of these data tensile tests were performed with a dental plugger (application force 1 N/2 N; v = 35 mm/min) on PMMA- or human tooth plates. Composite was dosed onto the tip of the plugger and applied. Application and unplugging was performed once and unplugging forces (UF) and length of the adhesive flags (LAF) were determined at different storage (6/25 °C) and application temperatures (25/37 °C). Unplugging work (UW) was calculated from area of UF and LAF data.

Results

The individual assessment revealed significantly different temperature-dependent application forces between 0.58 N and 2.23 N. Adaptability was assessed between 2.1 and 2.8 school scores. Stickiness varied significantly between the materials (scores: 2–3.2). UW differed significantly between the materials with values between 3.20 N mm and 37.83 N mm. Between PMMA substrate or tooth slides and between 1 N or 2 N application force only small UW differences were found.

Significance

The presented in vitro unplugging work allows for an in vitro estimation of the handling parameters adaptability and stickiness.     

Effects of prestretching on force degradation of synthetic elastomeric chains.

INTRODUCTION: The purpose of this study was to evaluate the effects of prestretching on time-dependant force decay of synthetic elastomeric chains. METHODS: Five-unit (12.5 mm) and 6-unit (15.5 mm) modules (Generation II, Ormco, Glendora, Calif) were prestretched 100% for 1 hour (n = 12), 24 hours (n = 12), 2 weeks (n = 12), and 4 weeks (n = 12) in 37 degrees C distilled water. The prestretched and unprestretched (control) modules were then stretched to 30 mm in 37 degrees C water, and their forces were measured at 0 hour, 1 hour, 24 hours, and weekly for 4 weeks with a digital force gauge. RESULTS: The prestretched 5- and 6-unit modules yielded significantly lower initial force than the controls. All 5- and 6-unit prestretched and control groups showed substantial force decay during the first hour. However, at 1 hour, similar remaining forces were found in the 5-unit prestretched and control groups (P > .05), and small differences were seen in the 6-unit groups. The rates and patterns of force decay from 1 hour to 4 weeks were quite similar between the control and the prestretched modules of both the 5- and 6-unit groups. CONCLUSIONS: The effects of prestretching on force decay of elastomeric chains were noted mainly in the first hour. Thus, the clinical value of prestretching a synthetic elastomeric chain is questionable.     

Gimlet implant system and intra-oral welding

An experienced implantologist introduces a new, flexible, and versatile endosteal implant system. Requiring only a single bur, the implant may be used immediately or permitted to osteointegrate. Since intra-oral welding techniques may be used, parallelism of implants is not a requisite for the successful completion of mesiostructure double-railed bars. A variety of prosthetic techniques may be incorporated into the Gimlet system, and the implants themselves can be used in a number of locations and employed for multiple purposes.     

Oral and dental complications of intra-oral piercing

Abstract –  The present study assessed the prevalence of oral piercing among young adults and revealed the types and rate of complications following oral piecing, as well as the awareness of the complications. The study included 400 consecutive patients, who randomly arrived at a military dental office. Before dental examination, patients were requested to fill out a questionnaire regarding oral piercing, their awareness of its complications, and the occurrence of complications related to piercing. Intra-oral examination included special attention to piercing-related complications, such as tooth fractures, gingivitis, bleeding, infections, gingival recessions, etc. A total of 389 patients, 210 (54%) males and 179 (46%) females agreed to participate (97.3% response rate), with an average age of 20.08 ± 1.1 years. Of the participants, 79 (20.3%) reported having at least one type of oral piercing; lingual piercing was the most common. Swelling and bleeding after piercing were reported by 41 (51.9%) and 36 (45.7%) participants, respectively. Among the participants, 225 (57.8%) were unaware of the dangers of intra-oral piercing. Clinical examination revealed 15 fractured teeth in 11 (13.9%) participants with piercing. Gingival recessions were observed in 21 (26.6%), mostly in the mandibular incisor area. Dentists should be aware of the increasing number of patients with pierced intra- and peri-oral sites and to provide appropriate guidance to patients who contemplate body piercing involving oral sites.     

Quality control of intra-oral radiographs

This paper deals with the different stages in the process of making intra-oral radiographs and the factors which influence their quality: the X-ray equipment, operator technique, and processing and film variables. Common errors at each stage are discussed and suggestions for quality assurance measures are given.