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PubMed1981

Enamel fluoride uptake from orthodontic cements and its effect on demineralization.

This study was undertaken to determine the in vitro enamel fluoride uptake and distribution from fluoride-containing orthodontic cements after 21 days' exposure and the effect on acid demineralization. Three successive acid-etch biopsy specimens were taken from tne facial middle third of thirty maxillary central incisors. Orthodontic bands were cemented to these teeth, ten each with (A) zinc phosphate, (B) zinc phosphate containing 5 percent SnF2, and (C) silicophosphate cement, respectively. The teeth were suspended individually in synthetic saliva at 37 degrees C. in a shaking incubator for 21 days. The bands were removed, the cement was cleaned off, and three successive biopsies were carried out electrometrically and for calcium by atomic absorption spectroscopy. Fluoride concentrations were adjusted to depths of 10.0, 20.0, and 30.0 micron for the three biopsies, respectively. The acquired fluoride was calculated and the data were analyzed statistically. In addition, six teeth each with bands cemented with cements A, B, and C, respectively, were incubated in synthetic saliva for 21 days, after which the bands were loosened and the teeth were suspended for a further 3 months in a caries-producing medium. After careful cleaning, the enamel surfaces were examined by microradiography and scanning electron microscopy for demineralization. Results showed that acquired fluoride at the first depth was highest with cement C, followed by cement B, with cement A producing a net loss of fluoride. Further, the greater the fluoride uptake, the more resistant the enamel was to demineralization.

Dental Caries↗

PubMed2001

Relationships between medication intake, complaints of dry mouth, salivary flow rate and composition, and the rate of tooth demineralization in situ.

The aim of this study was to describe the relationships between the rate of tooth demineralisation and medication intake, subjective feeling of dry mouth, saliva flow, saliva composition and the salivary level of lactobacilli. The study group consisted of 28 subjects that were divided into three groups according to their unstimulated whole saliva flow rate. Group 1 had an unstimulated saliva low rate < or =0.16 ml/min (n=10), group 2 had one from 0.17--0.30 ml/min (n=9), and group 3 had one >0.30 ml/min (n=9). The rate of tooth demineralization was determined as mineral loss assessed by quantitative microradiography of human root surfaces, exposed to the oral environment for 62 days in situ. The unstimulated and stimulated saliva flow rates, pH, bicarbonate, calcium, phosphate, and protein concentrations, as well as the degree of saturation of saliva with hydroxyapatite and the saliva buffer capacity were determined. The results showed that almost all subjects developed demineralization, albeit at highly varying rates. Eighty-five percent of the subjects in group 1, 33% of the subjects in group 2, and 0% of the subjects in group 3 developed mineral loss above the mean mineral loss for all the root surfaces in this experiment. Futhermore, group 1 differed significantly from groups 2 and 3 in having a higher medication intake, a more pronounced feeling of dry mouth, lower stimulated saliva flow rate, lower stimulated bicarbonate concentration, lower unstimulated and stimulated compositional outputs (bicarbonate, calcium, phosphate, and protein), and a higher Lactobacillus level. The best explanatory variable for high mineral loss in this study was a low unstimulated saliva flow rate. In conclusion, our results suggest that an unstimulated salivary flow rate < or =0.16 ml/min as described by Navazesh et al. (1992), is a better indicator of increased caries risk due to impaired salivation, than the currently accepted definition of hyposalivation (unstimulated saliva flow rate < or =0.10 ml/min), which relates to the function of the salivary glands (Sreebny, 1992).

Adult↗

PubMed2000

Development of multi-species consortia biofilms of oral bacteria as an enamel and root caries model system.

The aim was to establish defined-species consortium plaque biofilms to investigate enamel and root caries in an artificial mouth. Strains of the putative enamel and root caries pathogens, Streptococcus mutans, Strep. sobrinus, Actinomyces naeslundii and Lactobacillus rhamnosus, were screened in batch culture for potential cariogenic properties: a low terminal pH, ability to aggregate, and catabolic diversity. The strains selected were grown as monoculture biofilms and as consortium plaque biofilms in a multiplaque artificial mouth. The biofilms were supplied with a constant flow of a simulated oral fluid and were given periodic sucrose (and in some instances glucose) to simulate meals. All the bacteria except L. rhamnosus formed large, monospecies biofilms with resting pH in the range 5.3-5.8. The consortia biofilms were larger and had a resting pH of 4.9-5.3. The consortia biofilms supplied with 8-hourly carbohydrate comprised mainly 'mutans' streptococci (58, SD 5.5%) and L. rhamnosus (42, SD 5.7%). A. naeslundii characteristically was absent or present in a low percentage (up to 4% colony-forming units). All biofilms demineralized polished bovine enamel and dentine blocks, as assessed by microradiography and enamel-surface microhardness measurement. The consortia also demineralized intact enamel and tooth roots; they were more cariogenic to enamel than any of the monoculture biofilms, as measured by enamel-surface softening, but variation in lesion depth was proportional to biofilm wet weight irrespective of acidogen composition (r = 0.93, p < 0.05). Enamel lesions had a well-mineralized intact surface and a zone of subsurface demineralization, typical of early natural lesions. Dentine and root lesions showed extensive demineralization but lacked a pronounced surface mineralized zone. Substitution of glucose for sucrose had no effect on the cariogenicity of the consortium to bovine enamel or human roots and had no major effect on the plaque composition. Continuously supplied fluoride (19 parts/10(6)) resulted in a substantially reduced enamel surface softening and subsurface demineralization of intact roots. It was concluded that consortia biofilms of selected caries pathogens generate realistic caries lesions in all tooth hard tissues under controlled growth conditions in the artificial mouth. This in vitro caries experimental model may prove useful for the study of interrelations between the plaque biofilm, tooth tissues and the oral environment, and for the development of procedures to modify the course of caries development.

Actinomyces↗

PubMed1995

Microbial induction of dentinal caries in human teeth in vitro.

The ability of Lactobacillus casei, Streptococcus sobrinus, Actinomyces viscosus, and Streptococcus salivarius to induce dental caries was determined in vitro. A class I cavity (depth: 2mm) was prepared in extracted human caries-free premolars to make dentin blocks. The blocks were inoculated with these four bacterial strains in a monoinfective fashion and were incubated under anaerobic conditions. In addition to the monoinfection groups, mixed-infection groups of L. Casei with S. sobrinus or A. viscosus were also prepared. Half of the culture medium was renewed every 3 days, and the pH of the medium was measured. After 4 or 12 wk, these dentin blocks were prepared by Brown-Brenn staining and by contact microradiography for light microscopic observation and for immunohistochemical staining. The final pH of the S. salivarius group was the highest among the experimental groups, at approximately 5.1; that of the others was approximately 4.3. Bacterial invasion into the dentinal tubules was observed in all but the S. salivarius group. Among the monoinfection groups, the S. sobrinus group showed the highest invasion rate, followed by the A. Viscosus group and the L. casei group. The invasion rate was also high in the mixed-infection groups. Immunohistochemical staining revealed invasion only by L. casei, and not by S. sobrinus and A. viscosus. The invasion rate by L. casei was higher in the mixed-infection group with either S. sobrinus or A. viscosus than in the monoinfection groups. These findings suggest that lactobacillus might play an important role in the initiation and progress of dentinal caries, and that this bacterial species might exhibit a cooperative cariogenicity when it coexists with other bacterial species that surpasses its individual cariogenicity.

Actinomyces viscosus↗

PubMed1996

A new ultrasonic canal preparation system with electronic monitoring of file tip position.

A new ultrasonic root canal preparation system has been developed that electronically monitors the location of the file tip during all instrumentation procedures. The Root ZX has been adapted for this purpose, and its filter circuit effectively cuts out the large spike noise of the ultrasonic unit. During enlargement of the canal, the ultrasonic vibration of the file can be stopped at any desired position on the meter. Extracted human tooth models with electronically measurable canals were used to test the device. Pre- and postoperative shapes of the root canals were evaluated using contact microradiography. The autostop mechanism worked correctly. Using a weak power and fine files, straightening, ledge formation, and file breakage were minimal. It seems that this system minimized the danger of overinstrumentation and could be safely applied in clinical practice.

Dental Instruments↗

PubMed2003

Detection of in vitro demineralization adjacent to restorations using quantitative light induced fluorescence (QLF).

AIM: Quantitative light-induced fluorescence (QLF) is a technique for the detection, quantification, and longitudinal monitoring of early carious lesions. The technique is non-destructive and can be used in vivo. Using the natural fluorescence of teeth, and the loss of such fluorescence in demineralized enamel, QLF is a repeatable and valid optical caries monitor. Previously used in smooth and occlusal surfaces, the purpose of this pilot study was to determine if QLF could detect, and longitudinally monitor, demineralization adjacent to a range of restorative materials. METHODS: Fifteen previously extracted lower third molars were selected based upon the lack of any visible demineralization. A single burr hole was placed on the buccal surface and the cavity restored with amalgam, composite, compomer, glass ionomer or a temporary filling material. The buccal surface was then coated in an acid resistant nail varnish leaving an exposed area around the restoration and also a similar sized control region. The teeth had QLF images taken at baseline and were then subjected to a demineralizing buffer, further QLF images were subsequently taken at 72 and 144 h. Transverse microradiography was used to confirm the presence of early, subsurface lesions at the completion of the cycle (144 h). QLF images were analyzed by a single blinded examiner and values for change in radiance fluorescence were computed. These values were recorded as loss of radiance fluorescence loss integrated over area of lesion and expressed as DeltaQ. RESULTS: The appearance of each material under QLF and the change in fluorescence is described. Amalgam, glass ionomer and the temporary material all exhibited reduced fluorescence, while composite and compomer showed increased fluorescence, when compared with surrounding enamel. There was no change in fluorescence of the materials when subjected to experimental demineralizing conditions. Readings at 72 and 144 h demonstrated demineralization adjacent to the restorations and at the exposed control. Significant differences were detected between baseline, 72 and 144 h using ANOVA on all restorations with the exception of compomer where significance was noted between baseline and 144 h, p>0.05. CONCLUSIONS: This pilot study has demonstrated the ability for QLF to detect and monitor secondary caries. Analysis techniques should be based upon the subtraction of baseline DeltaQ scores from subsequent images. Further research is required to assess the ability of QLF to detect secondary lesions in vivo.

Analysis of Variance↗

PubMed2003

Mechanical properties and biochemical activity of remineralizing resin-based Ca-PO4 cements.

OBJECTIVE: This study examined strength and bioactive (remineralizing) properties of a powder/liquid formulation (Cement I) and a more practical two-paste formulation (Cement II) of a fluoride-releasing resin-based Ca-PO(4) cement. METHODS: For the remineralization potential, the dissolution of calcium, total ionic phosphate and fluoride from set cement specimens were determined in buffered saline and saliva-like solution (SLS). Artificial caries lesions were produced on coronal dentin of extracted human molars. On each tooth, two defined areas were coated, one with a composite resin (calcium-free control), the other with either Cement I or II. After incubation in SLS, the mineral loss under the cement was analyzed by digitized microradiography and compared to that under the control. RESULTS: The diametral tensile strength of Cement II of approximately 30 MPa after 24 h and 23 MPa after 4 weeks was 2 to 3 times higher than that of Cement I (ANOVA, t-test, p<0.05). Calculations of the ion-activity products and Gibb's free energy from solution ion concentrations indicated a significant potential for the formation of fluor- and/or hydroxyapatite. Concurrently, both cements caused increases of 47% (Cement I) and 38% (Cement II) in the lesion mineral content over that underneath the corresponding controls. SIGNIFICANCE: These in vitro results suggest that the stronger Cement II could serve as a restoration-supporting lining material and could remineralize dentin in areas where complete removal of carious tissue is contra-indicated.

Apatites↗

PubMed2004

Ability of restorative and fluoride releasing materials to prevent marginal dentine demineralization.

The study aimed to define the in vitro secondary caries inhibiting potential of restorative materials currently used in dental practice. Class V restorations were prepared in extracted human third molars and immersed in a demineralizing solution (lactic acid, pH 4.5) at 37 degrees C for 2 days to simulate secondary caries formation. The bonding and the restorative systems tested in the study were: Scotchbond 1+Z 250 (Group A), Scotchbond 1+F 2000 (Group B), ABF+APX (Group C), ABF+F2000 (Group D). Perimarginal dentine, immediately close to the margin of the restoration, and exposed dentine, at approximately 0.5 mm from the margins of the restoration, after exposure to the acid solution, were investigated; protected dentine, at approximately 4 mm from the margin in a varnish-covered area, was analysed as control. Polarized light microscopy and contact transverse microradiography (TMR) were employed. The output parameters were lesion shape and size (depth in microm) of the exposed dentine, dentine mineral volume%, and integrated mineral loss (Delta Z, in %volmicrom) of the lesions. Compomers (Groups B and D) showed a thinner demineralization of the outer lesions, a less demineralization along the perimarginal dentine (inner lesion) and more caries inhibition zones or CIZs (Delta Z positive values) compared to composites (Groups A and C). In conclusion, Groups B and D materials seemed to partially counteract the marginal demineralization induced by an acid solution and favourably influence the formation of CIZs along the restorations. On the contrary, composites did not show a protective effect, probably due to an insufficient marginal seal and the lack of fluoride release.

Absorptiometry, Photon↗

PubMed1997

In vivo study of calcium phosphate cements: implantation of an alpha-tricalcium phosphate/dicalcium phosphate dibasic/tetracalcium phosphate monoxide cement paste.

alpha-Tricalcium phosphate (alpha-TCP)/dicalcium phosphate dibasic (DCPD)/tetracalcium phosphate monoxide (TeCP) cement was implanted in paste form into soft tissue (rate subcutaneous sockets) and bone tissue (defects in rabbit mandibles) to evaluate the setting behaviour of the cement and tissue responses to the cement. A histological study of the soft tissue implants revealed thin fibrous capsule formation, the appearance of multinucleated giant cells on and close to the cement surface, and small clusters of the cement near the main part of the set cement which were formed by the migration of the paste while setting. X-ray diffraction (XRD) analysis of the implanted cement showed peaks for hydroxyapatite (HA) which increased as the implant period increased. Histology and microradiography of the bone tissue implants showed well-set cement without migration, active bone formation around the cement and direct bone union to it. However, the cement disappeared from the implant site in 4 of 16 specimens where intense bleeding seemed to wash away the implants while setting. From the results of the present study, we concluded that the cement is well tolerated, especially by bone tissue. This may be related to the fact that the cement sets producing HA. The cement is a promising material as a bone substitute; however, there is a problem of migration while setting in soft tissue and of exclusion from the bone defects by intense bleeding.

Animals↗

PubMed1997

In vivo study of a calcium phosphate cement consisting of alpha-tricalcium phosphate/dicalcium phosphate dibasic/tetracalcium phosphate monoxide.

Prehardened calcium phosphate cement consisting of alpha-tricalcium phosphate (alpha-TCP), dicalcium phosphate dibasic (DCPD) and tetracalcium phosphate monoxide (TeCP) was implanted in rabbit mandibles and back muscles, and studied histologically and microradiographically. In the mandibles, new bone formation occurred around the implants and increased in quantity the longer the implant period lasted. Histology, microradiography and scanning electron microscopy (SEM) demonstrated direct contact of bone and cement. Bone response to this cement was essentially the same as to hydroxyapatite (HA) ceramics, known as a biocompatible bone substitute. Material resorption was recognized, which increased with the implant period and was greater in the surface bound by soft tissue than the surface bound by bone tissue. In the back muscles, however, no calcified tissue formation occurred. Resorption proved to be faster than in the case of the mandible implants. It was concluded that the cement, in prehardened form, has good biocompatibility and is a promising material as a bone substitute.

Animals↗

PubMedDate not supplied

Experimental cranioplasty and skeletal augmentation using an alpha-tricalcium phosphate/dicalcium phosphate dibasic/tetracalcium phosphate monoxide cement: a preliminary short-term experiment in rabbits.

Calcium phosphate cement consisting of alpha-tricalcium phosphate (alpha-TCP), dicalcium phosphate dibasic (DCPD) and tetracalcium phosphate monoxide (TeCP) was implanted into surgically created full-thickness defects in the cranial bone (bone defect experiment) and directly onto the cranial bone under the periosteum (augmentation experiment). Three months after the implantation, the implants were retrieved with the surrounding tissues and studied histologically and micrographically to evaluate if the cement can be used as a cranioplasty and skeletal augmentation material. In the bone defect experiment, successful reconstruction of the defect was seen in 8 out of 12 specimens. Four specimens, where bleeding control was difficult at the time of implantation, showed partial loss of the cement. Histological and microradiographic studies of the successfully implanted cement revealed that new bone surrounded the implant nearly completely and united directly with the cement surface. In the augmentation experiment, the augmented area maintained the hemispherical shape and was connected tightly with the host bone. Histology and microradiography demonstrated that new bone formation was seen in the gap between the cement and the host bone, and on the outer surface (periosteum side) of the cement at the edge of the implant. From this preliminary short-term study, it could be concluded that the cement is a promising material for cranioplasty and skeletal augmentation with indications that it has good osteoconductivity.

Animals↗

PubMed1996

Histopathology of Kienböck's disease. Correlation with magnetic resonance and other imaging techniques.

Histopathological studies of extracted whole lunate bones obtained from 10 patients with Stage 3 Kienböck's disease at surgery for tendon-ball replacement were correlated with magnetic resonance imaging (MRI), computed tomography (CT) and tomography images made prior to surgery. A reforming zone, or a reactive interface between the reactive new bone and granulation tissue formation, and new vascularization were observed surrounding the bone necrosis area showing empty lacunae, fatty necrosis, and disappearance of osteoid. Findings of CT, tomography and microradiography of slices of extracted lunate bone confirmed that fractures of the articular cartilage and the subchondral bone occurred secondarily by overloading, and showed the extent of the collapsed area of the lunate. MRI showed complete loss of signal intensity in T1 images of the lesion of the lunate in advanced Stage 3 Kienböck's disease. MRI is at present unable to distinguish bone necrosis, the histological reactive interface or surrounding hyperaemia in detail. However, the low-intensity arc, or the reactive interface present on MRI in early Stage 3, sometimes correlates with the histological findings of osteoid and granulation zones.

Adult↗

PubMed1996

Histologic and microradiologic comparison of block and particulate cancellous bone and marrow grafts in reconstructed mandibles being considered for dental implant placement.

PURPOSE: Patterns of healing were investigated in mandibles reconstructed with three different techniques to assess their readiness for implant placement. PATIENTS AND METHODS: The subjects were 10 patients who had undergone mandibular reconstruction with either nonvascularized iliac block bone grafts (group 1; 3 patients), particulate cancellous bone and marrow (PCBM) grafts (group 2; 3 patients) for mandibular discontinuity, or PCBM grafts for mandibular marginal defects (group 3; 4 patients). Six (groups 2 and 3) or 12 months (group 1) after mandibular reconstruction, bone biopsy specimens were obtained for histologic examination with a trephine bur. As controls, bone specimens were obtained from ungrafted mandibles of patients undergoing dental implant placement. Undecalcified specimens were embedded in polyester resin and examined by routine light microscopy and microradiography. RESULTS: The morphology of the specimens from group 1 was similar to that of group 2, but not to that of the control subjects. However, the morphology of specimens from group 3 was generally similar to that of control subjects. CONCLUSION: These results suggest that mandibular reconstruction with PCBM grafts allows the placement of dental implants sooner than reconstruction with block bone grafts.

Adult↗

PubMed1998

A comparative study of osseointegration of titanium implants in autogenous and freeze-dried bone grafts.

PURPOSE: This study was undertaken to compare the rate and degree of osseointegration of dental implants when placed into either autogenous corticocancellous chip or freeze-dried corticocancellous chip bone grafts. MATERIALS AND METHODS: The canine ilium was used as the model site. Thirty experimental and 15 control implants were placed in 15 dogs: autogenous versus freeze-dried corticocancellous chip bone grafts around the exposed implant surfaces. In addition to the placement of control implants, the apical portion of the grafted implants acted as their own control. The implants were harvested at 1, 2, and 3 months. The evaluation of the integration process was performed by means of light microscopy, microradiography, and histomorphometry. RESULTS: Using this model, the results indicate that at 1 month there was no statistical difference in the degree of osseointegration in the two bone grafts. At 2 months, there was a statistically greater degree of osseointegration noted in the autogenous corticocancellous chip sites than in the freeze-dried bone grafts. At 3 months, the degree of osseointegration in the two groups was 70% and 33%, respectively. At 3 months, there was virtually 100% integration with trabecular bone at the control implant sites. CONCLUSION: The results indicate that at 2 months postoperatively implants placed in an autogenous bone chip graft osseointegrate to a significantly greater degree than implants placed in a freeze-dried bone chip graft, and this difference remains at 3 months.

Animals↗

PubMed2001

The effect of fluoridated and non-fluoridated rewetting agents on in vitro recurrent caries.

OBJECTIVE: This study examined the in vitro caries inhibiting potential of fluoridated and non-fluoridated rewetting agents that are applied to acid-etched enamel and dentine before the use of a water-free, dentine adhesive. MATERIALS AND METHODS: Twelve caries-free premolars were divided into three groups of four teeth each. 2 x 3 x 1.5 mm cavities were prepared on the mesial and distal surfaces of each tooth, with half of the cavosurface margin in enamel and half in root dentine. In Group I (control), One-Step (Bisco, Schaumburg, USA) was applied without etching or rewetting agents. In Group II, cavities were acid-etched, rinsed, dried, and rewetted with Aqua-Prep (Bisco), a non-fluoridated rewetting agent, and then bonded with One-Step. Treatment for Group III was similar to Group II, except that Aqua-Prep F (Bisco), a fluoridated rewetting agent was used. Bonded cavities were restored with a non-fluoride-containing flowable composite (AEliteFlo, Bisco). Artificial carious lesions were induced in these specimens, from which multiple 100+/-20 microm thick longitudinal sections were prepared, yielding 16 specimens per group for evaluation with polarised light microscopy (PLM) and microradiography (MRG). Representative sections were processed for transmission electron microscopy (TEM) examination and scanning transmission electron microscopy/energy dispersive X-ray (STEM/EDX) analyses. RESULTS: The differences in demineralisation of dentine among the groups were not statistically significant for 'relative' lesion depth (p > 0.05, ANOVA, Student-Neuman-Keuls test), but highly significant for 'relative' lesion area (p < 0.001). Wall lesions were consistently present in Group I, while inhibition zones were invariably observed in Group III. 87.5% of Group II specimens exhibited neither wall lesion nor inhibition zone. TEM showed that remnant dentine apatite crystallites within the inhibition zones in Group III were larger and denser than those present within the corresponding wall lesions. STEM/EDX analyses confirmed the presence of calcium, phosphorus and fluorine in these plate-like crystallites. CONCLUSION: When used with a water-free, single-bottle dentine adhesive, a non-fluoridated rewetting agent is able to reduce, but cannot completely prevent recurrent caries. The use of a fluoridated rewetting agent is useful under the situation when microleakage occurs, by providing the additional benefit of fluoride-induced demineralisation inhibition.

Analysis of Variance↗

PubMed2001

Acid resistance of human enamel in vitro after bicarbonate application during remineralization.

OBJECTIVES: The aim of this study was to investigate the acid resistance of subsurface enamel lesions remineralized with bicarbonate solutions during remineralization. METHODS: Two experiments were carried out. In experiment 1, mineral uptake and acid resistance of remineralized enamel lesions were analyzed quantitatively by microradiography for mineral changes. Bicarbonate solutions of 0.5, 5.0 and 50.0 mM were used. In experiment 2, to clarify acid resistance mechanisms, the pH changes in demineralizing solutions on the remineralized enamel surfaces were measured continuously. Only a bicarbonate solution of 5.0 mM was used. RESULTS: In experiment 1, the bicarbonate-treated groups were more acid resistant than the non-treated groups (p<0.05). However, no statistically significant difference was observed among the different concentrations of bicarbonate. In experiment 2, the pH rise of the bicarbonate group was greater than the other groups. CONCLUSION: It was found that bicarbonate-treated enamel lesions were resistant to acid. It would suggest that bicarbonate ions applied during remineralization may have penetrated into the subsurface lesions. These ions may have worked as buffer agents against the acid challenge and inhibited the decrease in pH.

Acids↗

PubMed1999

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.

Animals↗

PubMed1999

The effect of saliva on enamel and dentine erosion.

The present study aims to assess the ability of saliva, both in vitro and in situ, to prevent surface mineral loss from enamel and dentine when exposed to an erosive challenge. Fifteen groups of four varnished thin tooth sections were stored in saliva collected from individuals taking part in the in situ study and a further eight groups, each containing four sections, were stored in deionised water. In vitro, sections were stored in saliva or water for 14 days. In addition, fifteen subjects each wore an appliance with four varnished sections. Appliances with sections were worn for 14 days. All sections were exposed to 25 ml of erosion solution for 5 min twice daily. Microradiography and image analysis of the recovered sections demonstrated significant protection of surface mineral loss from enamel and dentine by saliva in vitro and in situ compared with deionised water (p < 0.05). Significantly less mineral loss (p < 0.05) was observed for enamel and dentine stored in situ compared with storage in saliva in vitro. Generalised linear modelling demonstrated both the subject and protocol had significant effect on mineral loss. A weak positive correlation (r = 0.64) was noted when in situ and in vitro mineral loss from enamel were compared, demonstrating greater reactivity of the in vitro enamel specimens to the erosion challenge. The dentine data did not show any linear correlation. Saliva protected against mineral loss by erosion and, for enamel, in vitro results demonstrated a weak positive correlation with in situ results.

Dental Enamel↗