Pulpal response to topical application of citric acid to root dentin

Abstract The purpose of the present study was to investigate the pulpal reactions to citric acid (pH 1.0) applied for 3 min to exposed root dentin. We used 48 roots of 24 maxillary and mandibular third and fourth permanent premolars from dogs divided equally into experimental (citric acid) and control (saline) roots. Following surgical exposure of the buccal root surface and the removal of the cementum with a Gracey curette, citric acid or saline was applied on the exposed dentin. The pulpal reactions were histologically evaluated 1, 7 and 15 days postoperatively using hematoxylineosin stained sections. Results obtained from 43 specimens showed no difference in the pulpal response at any of the observation intervals between citric acid and saline-treated teeth.     

Tooth surface loss and exposure to organic and inorganic acid fumes in workplace air

The effect of inorganic and organic acid fumes on teeth was explored in a cross-sectional study using blind dental examinations. A sample of 180 workers from two factories was randomly drawn. Among the 169 workers who participated in the survey, 88 were exposed to acid fumes and 81 were controls. The percentage of inorganic acid workers with tooth surface loss was 63.2%, while that for the controls was 37.7% (P less than 0.005). The corresponding figures in the organic acid company were 50.0% and 14.3% (P less than 0.02). In both companies the acid workers had significantly more often teeth with surface loss in the maxilla than their controls (P less than 0.02). Both anteriors and posteriors were affected. On the basis of the findings. it can be concluded that acid fumes at work are strongly associated with tooth surface loss.     

HF酸蚀对氧化锆陶瓷与树脂短期粘接性能的影响

目的评价常温下使用HF对Y-TZP陶瓷进行蚀刻提高其与树脂短期粘接强度的效果。方法制作Y-TZP瓷片48枚,分别进行氧化铝喷砂、室温下以40%HF酸蚀90 min和室温下以40%HF酸在超声环境下振荡15 min的方式进行表面粗化,随后在处理表面分别使用2种通用型粘接剂,制作树脂粘接试件,测试24 h水储后的剪切粘接强度。原子力显微镜测试3种粗化方式获得的表面粗糙度,并以扫描电镜观察表明微观形态。结果 2种酸蚀方法获得的表面粗糙度和粘接强度较喷砂处理显著提高。结论室温下以40%HF酸蚀可以取代氧化铝喷砂作为粗化Y-TZP陶瓷的方法。     

Adaptation by Streptococcus mutans to acid tolerance

Our previous continuous culture studies with strains of Streptococcus mutans have indicated that the organism has the capacity of adapt to growth in acidic environments. This study was undertaken to examine this question in more detail. S. mutans Ingbritt and the phosphotransferase system (PTS)-defective mutant, S. mutans DR0001/6, were grown in continuous culture at pH 7.5 and 5.5 or 5.1, and the pH optimum for glucose uptake and glycolysis and the capacity of the cells to generate pH gradients were determined over the pH range 4.5 to 8.0 with steady state, washed cells. In addition, the proton permeability of the cells was measured over the pH range by an acid pulse technique. The results indicate that the pH optimum for glucose uptake by S. mutans Ingbritt grown at pH 7.5 was 7.5 and this optimum shifted to 7.0 and 6.0 for cells grown at pH 5.5 and 5.1, whereas with the S. mutans DR0001/6, the optimum shifted from 7.5 to 7.0 for the pH 5.5 cells. A similar shift in the pH optimum for glycolysis was observed for the 2 strains, and this was particularly pronounced for cells incubated with glucose in the presence of gramicidin to dissipate proton gradients. The capacity of the cells to generate pH gradients was related to their metabolic activity, and although larger gradients were not formed by the pH 5.5 cells, these cells were nevertheless capable of maintaining gradients at a lower pH; S. mutans DR0001/6 generated 2-fold larger pH gradients at pH 5.5 than S. mutans Ingbritt.(ABSTRACT TRUNCATED AT 250 WORDS)     

Susceptibility of selected tooth-coloured dental materials to damage by common erosive acids

BACKGROUND: Erosive substances such as gastric acids, lemon juice and even the less erosive cola drinks have been extensively investigated for their destructive effects on enamel. However, their effects on the tooth-coloured restoratives has not been widely analysed. The objective of this study was to assess their effects on the more commonly used glass containing restorative materials in vitro. MATERIALS AND METHODS: Sixty-eight anterior and 24 molar tooth crowns had restorations placed of Fuji IX, Ketac Fil(+), Fuji II LC or Z100, and were painted with nail varnish to leave a 2 mm border around the restorations. Six ceramic crown surfaces were also included. The anterior crowns and porcelain samples were exposed to 0.113% HCl, 5.0% citric acid, 0.02% orthophosphoric acid or DDW for 2, 4, 8 or 16 hours at 37 degrees C. The molar restorations were exposed only for 16 hours. The surfaces of the anterior teeth were then examined by SEM to assess progressive stages of surface erosive etching. Depths of bulk loss of vulnerable restorative materials were measured in the remaining 24 molar teeth, and compared with depths of adjacent enamel loss, particularly at the margins, using Leika Microscope images of sections through these restorations. RESULTS: The traditional glass ionomer cements (GICs) were severely eroded by the HCl and citric acid solutions even following two hours of exposure, with only minor damage from phosphoric acid at the concentration tested. These materials experienced considerable bulk loss by 16 hours, comparable to or greater than that in adjacent enamel. The margins of the GIC restorations experienced greater dissolution than the body of the restorations, particularly in citric acid. Z100 Resin Composite and porcelain restorations showed no effects at all, and Fuji II LC only minor damage. CONCLUSIONS: The results demonstrate the effectiveness of porcelain and resin containing materials in providing protection of enamel in advanced cases of erosion. The traditional GIC materials are vulnerable to severe damage in patients experiencing strong citric acid or gastric acid induced erosion. However, there is evidence that protective benefits are still present and these materials should be used but only in closed sandwich restorations in such cases.     

Periodontal health and oral mucosal lesions as related to occupational exposure to acid mists

OBJECTIVES: The association between exposure to acid mists and periodontal changes and oral mucosal lesions was measured using data from an Oral Health Promotion Program in a large metal plant. The role of sociodemographic factors, lifestyle, and oral health behavior in relation to these outcomes was also examined. METHODS: This is a cross-sectional study of 665 active male workers who volunteered to participate in the oral health program. A job exposure matrix was constructed with industrial hygienist scores and job titles to estimate years of exposure to acid mists. Oral health outcomes were identified during standardized dental examinations. Unconditional logistic regression models were utilized in the analysis. RESULTS: Duration of exposure to acid mists exposure was positively associated with oral mucosal lesions among workers without lip sealing. Only age, low salaries and oral hygiene-related variables were associated with periodontal changes, and estimates varied according to lip sealing. CONCLUSIONS: Results suggest that long-term occupational exposure to acid mists is associated with oral mucosal lesions, and that absence of lip sealing may increase the intensity of exposure.     

The pulpal response to citric acid in cats

Abstract Citric acid conditioning of dentine has been proposed as an efficacious treatment for promoting re-attachment after periodontal surgery. This study investigated the pulpal reactions to periodontal surgery combined with citric acid (pH 1) demineralization of exposed dentine for 3 min. 9 cats were used as the experimental animals, with each cat providing 1 negative and 1 positive control and 2 experimental canine teeth. Evaluation was over 3 observation periods, with 3 cats in each period being sacrificed at 4, 21 and 83 days. Positive control teeth, which underwent periodontal surgery combining the removal of approximately 3 mm² of labial bone and vigorous root planning of the exposed root surfaces, displayed mild to moderate pulpal reactions during the short- and intermediate-term periods and only mild to no reactions in the long-term period. The addition of citric acid demineralization, however, resulted in 5 experimental teeth (28%) becoming abscessed or totally necrotic in the intermediate- and long-term periods. At 21 days, the frequency of adverse pulpal responses to surgery and citric acid conditioning was significantly (p<0.05) greater than to surgery alone. Although 4 experimental teeth were relatively uninflamed at the long-term period of observation, all showed irritational dentine formation. Penetration of exposed dentinal tubules by plaque bacteria was observed only in the citric acid treated teeth.     

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透明质（hyaluronic acid，HA）是一种酸性多糖，广泛分布于人体各部位，具有抗炎、抗感染、抗水肿、促进组织重建和创伤愈合的作用。本文主要对HA的生理功能及其在口腔医学领域中的应用做一综述。     

Surface characteristics of dentin experimentally exposed to hydrofluoric acid

The purpose of this study was to test the effect of hydrofluoric acid (HF) on the surface characteristics of dentin in vitro. Dentin was exposed in 50 human molars and divided into five groups according to different etching schedules: (i) no etching, (ii) 15 s HF, (iii) 15 s H3PO4, (iv) 15 s HF and 15 s H3PO4, (v) 15 s H3PO4 and 15 s HF. Teeth were examined under a scanning electron microscope equipped with energy-dispersive X-ray (EDX) or two layers of fluorescence-labeled primer followed by the composite were applied, and the teeth were sectioned and examined using confocal laser scanning microscopy (CLSM). With scanning electron microscopy, no openings of dentinal tubules were found in groups (i), (ii), and (iv). In group (v) only a few tubules were opened and in group (iii) the smear layer was completely removed and tubules appeared open. The EDX analysis revealed that fluoride was incorporated into the dentin surface when HF was used. With CLSM, distinct hybrid layers could be detected only in group (iii). In group (v) the hybrid layer appeared less established compared with group (iii). No dentin hybridization was found in groups (i), (ii), and (iv). It is concluded that HF has the ability to close the openings of dentin tubules which were opened due to etching by phosphoric acid and cannot dissolve the smear layer.     

Relationship of ascorbic acid levels of blood and gingival tissue with response to periodontal therapy

The effect of ascorbic acid megadoses on gingival clinical parameters and vitamin content of blood and gingival tissue was studied. 10 nondeficient individuals, carefully matched according to age, periodontal status, and oral hygiene level, were divided into 2 groups: one received 250 mg q.i.d. of ascorbic acid and the other a placebo. After 1 week on the tablet all patients were scaled and root planed and received oral hygiene instructions. Blood samples and clinical parameters were obtained at baseline and 2, 6, and 7 weeks after. A gingival biopsy was taken at week 6. Correlations between the clinical parameters and the ascorbic acid levels at the different time periods revealed no significant differences between the vitamin and the placebo groups, therefore suggesting that the use of megadoses of vitamin C in normal human subjects does not have a predictable or strong effect on the gingival response to initial therapy.     

Shear bond strength of a resin composite to enamel etched with maleic or phosphoric acid

The purpose of this study was to evaluate the effect of 10 per cent maleic and 37 per cent phosphoric acid on the shear bond strength of Z100 composite resin with Scotchbond Multi-Purpose adhesive to primary and permanent tooth enamel. Four groups of 20 teeth each were established: 1, permanent teeth, 10 percent maleic acid etched for 15 seconds; 2, permanent teeth, 10 per cent maleic acid etched for 30 seconds; 3, permanent teeth, 37 per cent phosphoric acid etched for 15 seconds; 4, primary teeth, 10 per cent maleic acid etched for 15 seconds. Five teeth from each group were randomly assigned for SEM examination of the etched enamel surface. Scotchbond Multi-Purpose primer and adhesive were applied to the etched enamel surface of the remaining 15 teeth and cured following the manufacturer's instructions. Z100 composite resin was placed in a nylon cylinder and cured for two 40 second intervals. Following thermocycling, the specimens were sheared on an universal testing machine and debonded areas were examined visually with a stereo microscope and with SEM. The mean shear bond strengths in MPa were: 1,17.00; 2, 14.58; 3, 14.66; 4, 11.18. ANOVA and Student-Newman-Keuls analyses revealed no statistically significant difference among the groups. SEM examination showed the majority of specimens fractured at the adhesive-resin interface.     

A case report of patient practising yoga leading to dental erosion

The article presents the case of a patient who was practising Yoga (Kunjal kriya) which led to dental erosion. Dental erosion can be due to extrinsic or intrinsic causes. The intrinsic causes include vomiting due to anorexia nervosa, regurgitation due to abnormality in gastro-intestinal tract or rumination. A 38-year-old male patient presented with a rare aetiology of dental erosion. He had practiced kunjal kriya one of the yogic exercises described in ancient India. In kunjal kriya the patient vomits on an empty stomach in order to clean his or her gastro-intestinal tract. The patient had practiced this form of exercise for over 12 years which had led to severe dental erosion. A proper case history should be evaluated for every patient so that they can be counselled for any factors that could be detrimental to dental health. Early diagnosis is paramount in recognising the aetiology of dental erosion so that detrimental effects on the dentition can be prevented.     

Human pulpal response to composite resin restorations

Abstract Composite resin restorations were placed in experimentally prepared cavities in human teeth. Various antibacterial regimens were used and the pulpal responses were studied and correlated with presence of bacteria on the cavity walls. Presence of bacteria seemed to be an important, but not the only reason for harmful pulpal responses. Good pulp protection was obtained by using a calcium hydroxide-containing base material after acid etching of cavities was carried out. The present results were compared with those from an identical study in monkeys, and good correlation was found.     

Electrochemical properties of a tetrabromo-p-benzoquinone modified carbon paste electrode. Application to the simultaneous determination of ascorbic acid,dopamine and uric acid

The electrochemical study of a tetrabromo-p-benzoquinone modified carbon paste electrode (TBQ-MCPE), as well as its efficiency for electrocatalytic oxidation of ascorbic acid, dopamine and uric acid, is described. Cyclic voltammetry was used to investigate the redox properties of this modified electrode at various solution pH values and at various scan rates. Three linear segments were found with slope values of ?58.4 mV/pH, ?28.1 mV/pH and 0.0 mV/pH in the pH range 2.0–7.1, pH 7.1–9.0 and pH 9.0–11.0, respectively. The apparent charge transfer rate constant, k_s, and transfer coefficient, α, for electron transfer between TBQ and CPE were calculated as 3.79 ± 0.10 s^?1 and 0.55, respectively. The electrode was also employed to study the electrocatalytic oxidation of AA, using cyclic voltammetry, chronoamperometry and differential pulse voltammetry as diagnostic techniques. It has been found that the oxidation of AA at the surface of TBQ-MCPE occurs at a potential of about 430 mV less positive than that of an unmodified CPE. The diffusion coefficient of AA was also estimated using chronoamperometry. The kinetic parameters such as the electron transfer coefficient, α, and heterogeneous rate constant, $k_{\mathrm{h}}^{\prime }$, for oxidation of AA at the TBQ-MCPE surface was determined using cyclic voltammetry. Differential pulse voltammetry (DPV) exhibits two linear dynamic ranges and a detection limit of 0.62 μM for AA. In DPV, the TBQ-MCPE could separate the oxidation peak potentials of AA, DA and UA present in the same solution, though at the unmodified CPE the peak potentials were indistinguishable. This modified electrode was quite effective not only to detect AA, DA and UA, but also in simultaneous determination of each component concentration in the mixture.     

Resistance to fracture of restored endodontically treated premolars

Abstract Endodontically treated premolars were restored using 5 different methods. Copper rings were filled with commercial hard-setting cement and the teeth were placed into the cement up to the level of the cemento-enamel junction. The teeth were grouped according to restorative method, mounted in an Instron TT machine and the buccal walls subjected to a slowly increasing compressive force until fracture occurred. The force of fracture of the walls of each tooth was recorded and the results in the various groups compared. All teeth fractured in a similar manner irrespective of the restorative method used. The resistance to fracture of the teeth increased significantly when MOD cavities in the teeth were acid etched prior to the restoration with a composite resin. The use of a bonding agent after acid etching did not further increase the resistance to fracture of the premolars restored with a resin. The acid etch composite resin technique was as effective in preventing fractures of the teeth when 2 mm of the resin was removed and replaced with an amalgam as when the entire cavities were filled with the resin material.     

Effect of different chelating agents on the shear bond strength of calcium silicate-based cements to coronal dentin

We evaluated the shear bond strength (SBS) of mineral trioxide aggregate (MTA) and Biodentine (BD) to coronal dentin after treatment with ethylenediaminetetraacetic acid (EDTA), phytic acid (IP6), or etidronic acid (HEDP). Sodium hypochlorite-treated dentin surfaces were randomly divided into four groups according to conditioning protocol namely, 17% EDTA, 2.5% IP6, 9% HEDP, or distilled water (DS). Specimens were further divided according to the type of cement placed on conditioned dentin and SBS was tested. The results showed that DS/MTA and IP6/MTA groups had the highest values, and there was no significant difference between these two groups. IP6/BD group showed a lower SBS value compared to IP6/MTA; however, this did not reach the level of significance. The BS to dentin was influenced by the type of calcium silicate material and chelating agent. IP6 either improved or maintained the bonding while EDTA and HEDP showed a negative or no influence effect.     

Effect of mineral supplements to citric acid on enamel erosion

The aim of this study was to evaluate the effect of mineral supplements to citric acid (1%; pH 2.21) on enamel erosion under controlled conditions in an artificial mouth. From each of 156 bovine incisors one polished enamel sample was prepared. The samples were divided among 13 experimental groups (n=12). In group 1 citric acid only was used (control). In groups 2-10 either calcium, phosphate or fluoride in various low concentrations was admixed to the citric acid. In groups 11-13 the citric acid was supplemented with a mixture of calcium, phosphate and fluoride. For demineralisation the specimens were rinsed with the respective solution for 1 min, immediately followed by a remineralisation period with artificial saliva (1 min). The specimens were cycled through this alternating procedure five times followed by rinsing for 8 h with artificial saliva. The de- and remineralisation cycle was repeated three times for each specimen interrupted by the 8 h-remineralisation periods. Before and after the experiments, the specimens were examined using microhardness testing (Knoop hardness) and laser profilometry. Hardness loss and enamel dissolution was significantly higher for the controls as compared to the remaining groups. Significantly lowest hardness loss for all groups was recorded for group 12 with admixture of calcium, phosphate and fluoride to citric acid. The significantly highest enamel loss was recorded for the controls compared to all other samples. Groups 3 and 4 revealed significantly lower and higher tissue loss compared to the remaining groups (2-13), respectively. The other groups did not differ significantly from each other. Modification of citric acid with calcium, phosphate and fluoride exerts a significant protective potential with respect to dental erosion. However, with the low concentrations applied enamel dissolution could not be completely prevented.     

Effects of additional and extended acid etching on bonding to caries-affected dentine

This study evaluated the effects of additional and extended acid etching on microtensile bond strength ( micro TBS) of two adhesive systems to sound (SD) and caries-affected dentine (CAD). Flat surfaces of CAD surrounded by SD of 36 extracted carious third molars were assigned to four treatments (i): self-etching adhesive system (Clearfil SE Bond) applied to dentine surfaces following manufacturer's instructions (MI); (ii) after additional etching for 15 s (35% phosphoric acid, PA); (iii) total-etch one-bottle adhesive (Single Bond) applied to dentine surfaces following MI; or (iv), after etching for 45 s with PA. Composite 'blocks' were built on bonded surfaces and restored teeth were vertically sectioned to obtain bonded slices of 0.7 mm thick. Slices were trimmed to create hourglass-shaped specimens (cross-sectional area of 1 mm(2)), which were tested under tension in a universal testing machine. Additional CAD and SD samples were prepared for scanning electron microscopy observations. Additional and extended etching significantly increased micro TBS to CAD; however, micro TBS of both adhesives to CAD were significantly lower than to SD. Additional and extended etching can improve bonding to CAD; however, adhesives applied on SD showed the best results for bonding.