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PubMed2005

Effect of bonding amalgam on the reinforcement of teeth.

STATEMENT OF PROBLEM: Extensively weakened maxillary premolars may be more prone to fracture due to their small size. The weakening may be due to excessive demineralization of supporting tooth structure caused by dental caries or nonconservative or traumatic tooth preparation. PURPOSE: The purpose of this study was to determine the effect of a bonded amalgam restoration on reinforcement of weakened tooth structure. MATERIAL AND METHODS: Forty extracted noncarious maxillary premolars were collected. The teeth were prepared individually with mesio-occluso-distal (MOD) cavities with specific dimensions (cavity width buccolingually, 1.8 to 2.1 mm; palatal cusp width, 1.7 to 2.2 mm; cusp height, 4.7 to 5.0 mm) and divided into 4 groups (n=10). The first group was prepared and not restored (control). The other 3 groups were restored with amalgam (Megalloy), bonding agent (Syntac) with amalgam, and amalgam with an adhesive resin luting agent (Resinomer), respectively. Fracture load (in kg) for specimens in all groups was determined by applying a vertical splitting load through a specially shaped steel rod at a crosshead speed of 1 mm/min. The data were analyzed by 1-way analysis of variance and least significant difference statistical tests (alpha=.01). RESULTS: The mean force and standard deviation values required to fracture the cusp of the control and amalgam groups were 25.2+/-3.27 kg and 26.1+/-3.07 kg , respectively, with no significant difference between the 2 groups (P>.01). Significant differences were found between control and Syntac groups (29.8+/-2.80 kg), as well as between control and Resinomer groups (37.9+/-3.55 kg). Significant difference was also noted between Syntac and Resinomer groups (P>.01) CONCLUSION: It was concluded that the use of resin cement increased the fracture resistance of the tooth with an MOD amalgam restoration.

Analysis of Variance↗
PubMed2000

Effects of an anticariogenic casein phosphopeptide on calcium diffusion in streptococcal model dental plaques.

Casein phosphopeptides (CPP) stabilize amorphous calcium phosphate (ACP) and may be used to localize ACP in dental plaque, maintaining a state of supersaturation with respect to tooth enamel, reducing demineralization and enhancing remineralization. The aim here was to investigate these effects by measuring the effect of CPP-ACP on calcium diffusion in plaque. Using Dibdin's effusion system, calcium diffusion was measured in streptococcal model plaques. This demonstrated that by providing a large number of possible binding sites for calcium, 0.1% CPP-ACP reduces the calcium diffusion coefficient by about 65% at pH 7 and 35% at pH 5. Hence, CPP-ACP binds well to plaque, providing a large calcium reservoir within the plaque and slowing diffusion of free calcium. This is likely to restrict mineral loss during a cariogenic episode and provide a potential source of calcium for subsequent remineralization. Overall, once in place, CPP-ACP will restrict the caries process.

Analysis of Variance↗
PubMed1973

Coagulation of blood plasma of guinea pig by the bone matrix.

Optimal amounts of demineralized bone matrix possess the ability to coagulate platelet-free heparinized, citrated, and oxalated blood plasmas of guinea pigs. Clotting constituents become denatured in contact with the insoluble coagulant proteins. Quantities in excess of optimal modify plasma so that it does not gel when thrombin is added. The newly described coagulant effects are not restricted to the bone matrix, but are present also in the demineralized matrices of tooth and ivory, and in denatured tendon as well. They are regulated properties that were not demonstrated in mineralized bone or native tendon. The coagulant attributes of bone matrix are consistent with those of electropositive polymers of a specific sort.

Amines↗
PubMed2003

The current status of laser applications in dentistry.

A range of lasers is now available for use in dentistry. This paper summarizes key current and emerging applications for lasers in clinical practice. A major diagnostic application of low power lasers is the detection of caries, using fluorescence elicited from hydroxyapatite or from bacterial by-products. Laser fluorescence is an effective method for detecting and quantifying incipient occlusal and cervical carious lesions, and with further refinement could be used in the same manner for proximal lesions. Photoactivated dye techniques have been developed which use low power lasers to elicit a photochemical reaction. Photoactivated dye techniques can be used to disinfect root canals, periodontal pockets, cavity preparations and sites of peri-implantitis. Using similar principles, more powerful lasers can be used for photodynamic therapy in the treatment of malignancies of the oral mucosa. Laser-driven photochemical reactions can also be used for tooth whitening. In combination with fluoride, laser irradiation can improve the resistance of tooth structure to demineralization, and this application is of particular benefit for susceptible sites in high caries risk patients. Laser technology for caries removal, cavity preparation and soft tissue surgery is at a high state of refinement, having had several decades of development up to the present time. Used in conjunction with or as a replacement for traditional methods, it is expected that specific laser technologies will become an essential component of contemporary dental practice over the next decade.

Dental Care↗
PubMed2002

Analysis of Streptococcus mutans proteins modulated by culture under acidic conditions.

Streptococcus mutans, a major etiological agent of dental caries, causes demineralization of the tooth tissue due to the formation of acids from dietary carbohydrates. Dominant among the virulence determinants of this organism are aciduricity and acidogenicity, the abilities to grow at low pH and to produce acid, respectively. The mechanisms underlying the ability of S. mutans to survive and proliferate at low pH are currently under investigation. In this study we cultured S. mutans at pH 5.2 or 7.0 and extracted soluble cellular proteins. These were analyzed using high-resolution two-dimensional gel electrophoresis, and replicate maps of proteins expressed under each of the two conditions were generated. Proteins with modulated expression at low pH, as judged by a change in the relative integrated optical density, were excised and digested with trypsin by using an in-gel protocol. Tryptic digests were analyzed using matrix-assisted laser desorption ionization mass spectrometry to generate peptide mass fingerprints, and these were used to assign putative functions according to their homology with the translated sequences in the S. mutans genomic database. Thirty individual proteins exhibited altered expression as a result of culture of S. mutans at low pH. Up-regulated proteins (n = 18) included neutral endopeptidase, phosphoglucomutase, 60-kDa chaperonin, cell division proteins, enolase, lactate dehydrogenase, fructose bisphosphate aldolase, acetoin reductase, superoxide dismutase, and lactoylglutathione lyase. Proteins down-regulated at pH 5.2 (n = 12) included protein translation elongation factors G, Tu, and Ts, DnaK, small-subunit ribosomal protein S1P, large-subunit ribosomal protein L12P, and components of both phosphoenolpyruvate:protein phosphotransferase and multiple sugar binding transport systems. The identification of proteins differentially expressed following growth at low pH provides new information regarding the mechanisms of survival and has identified new target genes for mutagenesis studies to further assess their physiological significance.

Bacterial Proteins↗
PubMed2000

Characterization of recombinant, ureolytic Streptococcus mutans demonstrates an inverse relationship between dental plaque ureolytic capacity and cariogenicity.

Dental caries results from prolonged plaque acidification that leads to the establishment of a cariogenic microflora and demineralization of the tooth. Urease enzymes of oral bacteria hydrolyze urea to ammonia, which can neutralize plaque acids. To begin to examine the relationship between plaque ureolytic activity and the incidence of dental caries, recombinant, ureolytic strains of Streptococcus mutans were constructed. Specifically, the ureABCEFGD operon from Streptococcus salivarius 57.I was integrated into the S. mutans chromosome in such a way that the operon was transcribed from a weak, cognate promoter in S. mutans ACUS4 or a stronger promoter in S. mutans ACUS6. Both strains expressed NiCl(2)-dependent urease activity, but the maximal urease levels in ACUS6 were threefold higher than those in ACUS4. In vitro pH drop experiments demonstrated that the ability of the recombinant S. mutans strains to moderate a decrease in pH during the simultaneous metabolism of glucose and urea increased proportionately with the level of urease activity expressed. Specific-pathogen-free rats that were infected with ACUS6 and fed a cariogenic diet with drinking water containing 25 mM urea and 50 microM NiCl(2) had relatively high levels of oral urease activity, as well as dramatic decreases in the prevalence of smooth-surface caries and the severity of sulcal caries, relative to controls. Urease activity appears to influence plaque biochemistry and metabolism in a manner that reduces cariogenicity, suggesting that recombinant, ureolytic bacteria may be useful to promote dental health.

Animals↗
PubMed2004

Inhibitory effect of water-soluble chitosan on growth of Streptococcus mutans.

The present study was undertaken to evaluate the effects of pH and the degree of polymerization of chitosan on the inhibition of growth of Streptococcus mutans. Three types of chitosan, polymer, oligomer and monomer, were used at 4% (W/V) and three different levels of pH: 6.0, 6.5 and 7.4. Bactericidal activity was calculated by the growth ratio. Chitosan oligomer significantly inhibited bacterial growth at a pH value of 6.5. All three types of chitosan strongly inhibited bacterial growth at pH 6.0. Furthermore, nearly complete inhibition was obtained with 2%(W/V) chitosan solution at constant pH 6.5. This study is the first to report that water-soluble chitosan directly suppresses the growth of the typical cariogenic bacterium S. mutans even at pH 6.5, without causing demineralization of the tooth surface.

Adjuvants, Pharmaceutic↗
PubMed1991

Background factors of enamel focal demineralization in groups of Finnish and Russian children.

The aim of this study was to analyze the occurrence of EFD lesions in relation to some background factors in Finnish and Soviet children. Children aged 7, 9 and 12 years (n = 1187) were examined clinically in Helsinki, Kuopio (Finland), Moscow and Leningrad (USSR). A questionnaire sent to the parents was used to collect data on toothbrushing frequency, use of sweets, cakes, soft drinks, sugar-sweetened tea/coffee and mother's education. In addition to bivariate analysis, log-linear regression models were used for comparing the simultaneous association in two ethnic groups. In general, the Finnish children had more EFD lesions than the Soviet children did. Among the Finns no consistent associations were found between the number of EFD lesions and the use of different sugar products or differences in toothbrushing habits. The number of EFD lesions decreased consistently according to mother's education with the Finnish children, but not with the Soviet children. The final multivariate model for Finnish children included age, toothbrushing frequency, place of residence (Kuopio) and use of soft drinks. The respective model for the Soviet children included age and place of residence (Leningrad). Evidently, the demineralization process or tooth resistance differs in these two ethnic groups.

Carbonated Beverages↗
PubMed1997

Remineralization of root surfaces demineralized in solutions of differing fluoride levels.

The beneficial effects of fluoride on enamel have been well documented. However, limited data are available concerning the amount of fluoride required for beneficial effects on tooth root. Although studies have shown that fluoride inhibits root demineralization, the aim of this study was to investigate the location, extent and amount of remineralization on root dentin substrates after demineralization has occurred. The root surfaces of extracted human teeth were demineralized in a pure chemical buffer containing varying concentrations of sodium fluoride. After this lesion initiation, the same root sections were then placed into a remineralizing solution. The root sections were characterized after demineralization, and again after remineralization, by polarized light microscopy (PLM) and microradiography (MRG). Lesion depths after the demineralization phase were found to be inversely proportional to the fluoride concentration. When fluoride was present, bands or lines within the body of the lesion were observed with PLM and MRG. Using quantitative MRG, variations in mineral content and distribution were recorded. Examination of the root sections after the remineralization phase showed remineralization to have occurred on the remaining mineral and not on organic matrix devoid of mineral. The amount and location of mineral deposition may be of great significance in the arrestment and treatment of in vivo root surface caries.

Buffers↗
PubMedDate not supplied

In vitro acid resistance of CO2 and Nd-YAG laser-treated human tooth enamel.

The purposes of this study were to test the effectiveness of laser treatment (pulsed CO(2) and pulsed Nd-YAG) on in vitro acid resistance of human enamel. Thirty enamel surfaces were prepared from 10 extracted permanent premolars (3 surfaces per tooth). Two experimental surfaces on each tooth were irradiated with either CO(2) or Nd-YAG lasers. All specimens were demineralized in 10 ml lactate buffer for 24 or 72 h after laser treatment. After 24-hour acid treatment the mean concentration of calcium that dissolved into the lactate buffer in the CO(2) laser group was significantly less than in the control group, while the dissolved calcium concentration in the Nd-YAG laser group did not differ from the control group (p > 0.05). The erosion depth in the CO(2) laser group was significantly shallower than in the Nd-YAG laser group (p < 0.001). After 72-hour acid treatment, the acid resistances of neither group of laser-treated surfaces differed significantly from the controls. By scanning electron microscopy, the acid-eroded laser-treated enamel surfaces had type I and type II etching patterns, fissures, and disordered rough surfaces compared to control enamel, with a regular type II etching pattern. CO(2) laser-treated tooth enamel was more resistant to acid challenge than was Nd-YAG laser-treated enamel, given the same fluence, but neither type of laser increased acid resistance of subsurface enamel.

Acids↗
PubMed2000

A comparative profilometric in vitro study of the susceptibility of polished and natural human enamel and dentine surfaces to erosive demineralization.

This study sought to compare the depths of erosive lesions in samples from different tooth sides as well as from enamel, dentine and root surfaces, and to examine the effect of preparation and polishing of specimens on erosive demineralization. From 30 impacted human third molars, two enamel samples from the mesial, distal, buccal and oral aspects, and similar samples from the radicular dentine, were prepared. One of each pair of samples was polished whereas the other was left untreated. Four samples were also prepared from the coronal dentine. For erosive demineralization, all samples were immersed in 0.05 M citric acid for 3 h and the erosion depth was calculated profilometrically. In general, natural surfaces showed significantly smaller erosion depths than polished surfaces (p< or =0.001) and enamel samples showed greater depths than coronal dentine (not significant) and root dentine (p< or =0.001). The erosion depths of the four tooth sides correlated significantly for polished enamel and coronal dentine samples but not for natural enamel specimens. There was no correlation between erosion depths for enamel and coronal dentine, and only a weak correlation between enamel and root dentine.

Citric Acid↗
PubMed1999

Current concepts on the theories of the mechanism of action of fluoride.

The caries-preventive effect of fluoride is mainly attributed to the effects on demineralization/remineralization at the tooth oral fluids interface. Sub ppm levels of fluoride in saliva are effective in shifting the balance from demineralization, leading to caries, to remineralization. This is attributed to the fluoride-enhanced precipitation of calcium phosphates, and the formation of fluorhydroxyapatite in the dental tissues. Low fluoride levels are found in saliva after toothbrushing with fluoride containing dentifrices. Similar concentrations are ineffective in interfering with processes of growth and metabolism of bacteria, and also do not result in a significantly reduced dissolution of tooth mineral as a result of (firmly bound) fluoride incorporation. Comparative studies of fluoride efficacy have shown that higher concentrations in solution are needed in pH-cycling studies of dentine than in enamel to maintain the mineral balance or to induce remineralization. This is attributed to the greater solubility of the dentine and the smaller size of the dentine crystallites compared to enamel. Fluoride slow-release devices, in the form of fluoride-releasing restorative materials, may serve to increase the fluoride levels in saliva and plaque to levels at which caries can be prevented, also in high-risk patients. Research questions for the next millennium and future perspectives for fluoride applications should be found in the retention and slow release of fluoride after various combinations of fluoride treatment, the combination of fluoride and anti-microbial treatment, the individualization of caries prevention, and the combination of preventive schemes with new developments in caries diagnosis.

Cariostatic Agents↗
PubMed1998

Measurement of enamel remineralization using microradiography and confocal microscopy. A correlational study.

Tooth minerals are lost and regained constantly in a normal, human oral environment. Different methods have been developed to measure this gain and loss in enamel minerals; however, these methods deal with different problems, such as being time consuming or involving the use of X-rays. The aim of this study was to determine if remineralization measured in a thin enamel section (TS) by transversal microradiography (MR) can be reliably monitored by measuring lesion parameters (area, total and average dye fluorescence) on the same TS or on half a tooth (HT) with confocal laser scanning microscopy (CLSM). Thirty-six human enamel specimens were demineralized for 96h, and then half of each specimen was covered with an acid-resistant nail varnish. Specimens were divided into three groups (12/group) and subjected for 20 days to a cyclic remineralization regimen with consisted daily of a 4-hour acid challenge, four 1-min treatment periods with 0, 250 or 1,100 ppm F dentifrice slurries (1:2; dentifrice:water) and 20 h in pooled, human saliva, at room temperature. Specimens were cut and analyzed by MR, then stained with a fluorescent dye (0.1mM rhodamine B) for 1 h and analyzed using CLSM. Both MR and CLSM detected significantly greater remineralization (p<0.05) in the specimens treated with the fluoride-containing dentifrices than in the specimens treated with 0 ppm F. Significant differences were detected between specimens treated witht the fluoride-containing dentifrices by MR and CLSM (HT area and total fluorescence). Statistically significant (p<0.05) Pearson correlation coefficients were calculated between the MR and CLSM data: difference in MR mineral content (DeltaM) versus HT lesion area = 0.71; DeltaM versus HT total fluorescence = 0.70; DeltaM versus HT average fluorescence = 0.61; DeltaM versus TS lesion area = 0.88; DeltaM versus TS total fluorescence = 0.63, and DeltaM versus TS average fluorescence = 0.40. It is concluded that confocal microscopy in either TS or HT may provide valid surrogates (area and total fluorescence) for MR measurements in enamel remineralization studies.

Analysis of Variance↗
PubMed1996

Pathogenesis and modifying factors of dental erosion.

Dental erosion is caused by acidic solutions which come into contact with the teeth. Because the critical pH of dental enamel is approximately 5.5, any solution with a lower pH value may cause erosion, particularly if the attack is of long duration, and repeated over time. Saliva and salivary pellicle counteract the acid attacks but if the challenge is severe, a total destruction of tooth tissue follows. Ultrastructural studies have shown that erosive lesions are seen in prismatic enamel as characteristic demineralization patterns where either the prism cores or interprismatic areas dissolve, leading to a honeycomb structure. In aprismatic enamel the pattern of dissolution is more irregular and areas with various degrees of mineral loss are seen side by side. In dentin the first area to be affected is the peritubular dentin. With progressing lesions, the dentinal tubules become enlarged but finally disruption is seen also in the intertubular areas. If the erosion process is rapid, increased sensitivity of the teeth is the presenting symptom. However, in cases with slower progression, the patient may remain without symptoms even though the whole dentition may become severely damaged. Regarding the role of causative agents, present data does not allow the ranking of different acids with regard to their potential of causing erosion. Neither is there consensus as to how effective fluorides are in preventing the progression of erosive lesions, or how the chemical and structural factors of tooth tissue in general might modify this pathological process.

Acids↗
PubMed2001

Dental enamel formation and its impact on clinical dentistry.

The nature of tooth enamel is of inherent interest to dental professionals. The current-day clinical practice of dentistry involves the prevention of enamel demineralization, the promotion of enamel remineralization, the restoration of cavitated enamel where demineralization has become irreversible, the vital bleaching of dental enamel that has become discolored, and the diagnosis and treatment of developmental enamel malformations, which can be caused by environmental or genetic factors. On a daily basis, dental health providers make diagnostic and treatment decisions that are influenced by their understanding of tooth formation. A systemic condition during tooth development, such as high fever, can produce a pattern of enamel defects in the dentition. Knowing the timing of tooth development permits estimates about the timing of the disturbance. The process of enamel maturation continues following tooth eruption, so that erupted teeth can become less susceptible to decay over time. Mutations in the genes encoding enamel proteins lead to amelogenesis imperfecta, a collection of inherited diseases having enamel malformations as the predominant phenotype. Defects in the amelogenin gene cause X-linked amelogenesis imperfecta, and genes encoding other enamel proteins are candidates for autosomal forms. Here we review our current understanding of dental enamel formation, and relate this information to clinical circumstances where this understanding may be particularly relevant.

Amelogenesis↗
PubMed2003

Biological factors in dental caries: role of saliva and dental plaque in the dynamic process of demineralization and remineralization (part 1).

Dental caries is a complex disease process that afflicts a large proportion of the world's population, regardless of gender, age and ethnicity, although it does tend to affect more indivduals with a low socioeconomic status to a greater extent. The process of dental caries is dependent upon biological factors that are present within the saliva and dental plaque. There are many different agents within saliva and plaque that serve to protect the tooth surface against caries development. Salivary flow rate, buffering capacity, antimicrobial activity, microorganism aggregation and clearance from the oral cavity, immune surveillance, and calcium phosphate binding proteins all interact to inhibit or reverse demineralization of exposed tooth surfaces. Cariogenic bacteria levels within the saliva and plaque determine whether caries will occur or not, and the concentration in saliva and plaque are intimately related to the type of carbohydrate ingestion and the frequency of ingestion, as well as the oral hygiene practiced by the individual.

Dental Caries↗
PubMed1983

Attachment, growth and synthesis by human gingival fibroblasts on demineralized or fibronectin-treated normal and diseased tooth roots.

Regeneration of a fibrous attachment to tooth roots previously exposed to periodontal pockets requires interaction between the root surface and fibroblasts. Experiments were designed to assess whether or not fibroblasts will attach, grow and synthesize normally on tooth roots and determine the efficacy of various treatments of diseased root surfaces on these activities. Extracted teeth were collected, washed and stored frozen until used. The roots were sectioned and the surface area determined. All roots were thoroughly planed to remove most of the cementum and some were then treated with fibronectin or citric acid. Each root was placed in a Linbro well and a suspension of fibroblasts in Dulbecco Vogt medium with 10% fetal calf serum added. After cell attachment, each root was transferred to a fresh well and incubated. Some roots were examined by scanning electron microscopy. Attachment and growth were assessed by harvesting and counting cells after various incubation times. The pattern of protein synthesis was determined by preparing fluorographs from cultures pulse labeled with radioactive S35-methionine. Cells attach and grow on planed root surfaces. The number that attach to normal and diseased roots is greatly enhanced by pretreatment with fibronectin or citric acid. By day three, the cells become confluent at approximately 20,000/cm2. The pattern of proteins produced is comparable to that seen in cultures maintained in petri dishes. After root planing, cells attach, grow and synthesize equally well on diseased and normal roots.

Cell Adhesion↗