The benefit of culture-independent methods to detect bacteria and fungi in re-infected root filled teeth: a pilot study.

AIM: To identify dominant microorganisms in root filled teeth with apical periodontitis by Pan-PCRs in comparison with a culture-dependent approach, focusing on fungal species profiling. METHODOLOGY: The root filling material (gutta-percha) removed from 42 teeth with periapical radiolucencies undergoing root canal retreatments was analysed by molecular genetics techniques. Real-Time Pan-PCRs were conducted for the diagnosis of predominant bacteria (targeting 16S rDNA) and fungi (targeting ITS1-2 region). Identification of microorganisms was performed by Sanger sequencing of the PCR products and BLAST analysis. Additionally, subgingival plaque samples were collected and cultured to review the composition of the microbial flora. The McNemar test and the repeated measures anova were used for statistical analyses (significance level was set at P < 0.05). RESULTS: Overall, 42/42 plaque samples had bacterial growth, whereas 32/42 gutta-percha samples had bacterial growth with a dominance of Streptococcus spp. (12/42) and Enterococcus faecalis (9/42). The mean number of bacterial taxa per gutta-percha sample was 1.6 cultivatable taxa, significantly lower than in the plaque sample that had six taxa/sample (P < 0.001). Fungus-specific cultures were negative for gutta-percha samples, and only one plaque sample had growth of a fungus. In total, 36/42 plaque samples were positive in bacterial Pan-PCRs. In bacterial Pan-PCRs of 31/42 gutta-percha samples, dominant microorganisms were identified including Streptococcus spp. (5/42) and E. faecalis (4/42). Moreover, in 7/42 gutta-percha samples, DNA of bacteria which are difficult-to-cultivate in microbiology routine culture (Acinetobacter,Pyramidobacter,Bacteroidetes,Synergistes,Atopobium and Pseudoramibacter) was found. DNA of Candida spp. was detected in 5/42 root canals by fungal Pan-PCR (1/5) and genus-specific Candida-PCR (5/5). CONCLUSIONS: Pan-PCR assays remain appropriate as a broad-range approach for the detection of a dominant pathogen in gutta-percha samples which have less diverse microbial composition. The molecular genetic Pan-PCR approach has the advantage of detecting microorganisms that are as-yet-uncultivable or difficult-to-cultivate and should be therefore complement conventional microbiological diagnostics.

Representative survey on the reprocessing of endodontic instruments in Germany.

Aim The aim of the study was to review the implementation of hygiene guidelines for the reprocessing of endodontic files in a representative survey and to determine the time needed for the procedure.Methods A questionnaire with nine items was sent to 4,000 German dentists. In addition to obtaining personal information, it asked for the total time required for the reprocessing of instruments and contained specific questions about the cleaning procedure in order to assess whether the requirements of the German Federal Ministry of Health, as defined by the Robert Koch Institute, were complied with. Approval by the Ethics Committee was obtained. The data were analysed statistically using the Chi-square test and Cramer's V as a measurement of effect size.Results The response rate was 29.4% (n = 1,177/4,000). On 59 questionnaires, answers to several questions were missing; 1,118 questionnaires (28.0%) could be included in the evaluation. With effect sizes between 0.12 and 0.21, the survey could be classified as statistically representative of German dentists in terms of age and gender. The guidelines were adhered to by 31.7% (n = 354/1118) of respondents, while 68.3% (n = 764/1118) adhered to them either not fully, or not at all (P < 0.001). There were no significant differences in adherence to guidelines between younger (up to 44 years) and older (45 years and above) dentists (P = 0.31) or between women and men (P = 0.194). The reported time for cleaning a patient-related instrument set was more than nine minutes for 68.1% of respondents, not including the time needed for sterilisation; 5% of respondents treated files as single-use instruments.Conclusions The guidelines of the German Federal Ministry of Health for cleaning, disinfecting and sterilising endodontic files are widely disregarded in Germany. The designation and use of endodontic files as single-use instruments should be considered.

Irreversible inflammation is associated with decreased levels of the alpha1-, beta1-, and alpha2-subunits of sGC in human odontoblasts.

The nitric oxide (NO) receptor enzyme soluble guanylate cyclase (sGC) contains one prosthetic heme group as an αß heterodimer, and two heterodimer isoforms (α(1)ß(1), α(2)ß(1)) were characterized to have enzyme activity. To test the irreversible inflammation-dependent regulation of sGC in odontoblasts, we incubated decalcified frozen sections of healthy and inflamed human third molars with antibodies against ß-actin, nitrotyrosine, inducible nitric oxide synthase (iNOS), α(1)-, ß(1)-, and α(2)-subunits of sGC and analyzed them at protein levels by quantitative immunohistochemistry. The irreversible inflammation induced an increase in the signal intensities for nitrotyrosine and iNOS and a decrease for the α(1)-, ß(1)-, and α(2)-subunits of sGC in odontoblasts. Inflammatory mediators, reactive oxygen, and nitrogen species may impair the expression of the α(1)-, ß(1)-, and α(2)-subunits in odontoblasts. The decrease of sGC at the protein level in inflamed odontoblasts is compatible with a critical role for sGC to mediate biological effects of NO in health.

[Caries risk assessment - are saliva tests as well as microbiological and clinical test procedures worthwhile?]. / Kariesrisikoerkennung - Helfen Speicheltests, mikrobiologische und klinische Testverfahren weiter?

The recent representative survey has proven once more that people in Germany are affected by caries to a very different extent. Since caries can be prevented by risk-adjusted preventive programs, it would be helpful to have a possibility to determine the individual caries risk before cavities occur. Determination of a relative risk, risk screening and risk diagnosis are different levels of caries risk assessment. The present article provides information about which caries risk assessment options are available for different populations. A relative risk can be determined by the detection of Mutants Streptococci in caries-free 2-5-year-old children. With Dentoprog, a valid instrument for caries risk screening is available for 6-12-year-old school children. With respect to all other patients, a quantitative risk diagnosis can be roughly performed using the Cariogram which is based on the assessment of multiple risk parameters. The conclusion is that several options for caries risk assessment for different age groups are available. Nevertheless, there is no solution to how often a patient should appear for prevention in a dental office nor which preventive measures have to be taken to keep him/her healthy. Therefore it seems reasonable to roughly determine the recall frequency on the basis of the respective risk assessment and to adjust this frequency over time after the evaluation of disease progression.

Time-dependent activation of ERK1/2 in nerve terminals of the dentin-pulp complex following bradykinin treatment.

The extracellular signal-regulated kinases 1 and 2 (ERK1/2) have been implicated in the inflammation-dependent sensitization of nociceptors, and the inflammatory mediator bradykinin (BK) led to a reduced threshold in the nociceptor terminals, activating intracellular signaling by phosphorylating receptors and ion channels. The effects of BK on the non-transcriptional modulation of the ERK1/2 in the peripheral nociceptor terminals, including in nerve endings of the dentin-pulp complex, are unknown. The time-dependent effects of BK (10(-7) M) on the ERK1/2 phosphorylation in nerve terminals of the dentin-pulp complex were investigated by quantitative and double immunolabeling with organ bath experiments. In nerve terminals, total and p-ERK1/2 were detected. In comparison with the controls, the numbers of p-ERK1/2-positive nerve endings increased after 1 and 3 min and decreased after 10 min of BK treatment. Analysis of the data indicates that BK induces phosphorylation-mediated local activation of ERK1/2 in nerve terminals modulating nociception in the dentin-pulp complex.

Novel nano-particles as fillers for an experimental resin-based restorative material.

The purpose of this study is to compare the properties of two experimental materials, nano-material (Nano) and Microhybrid, and two trade products, Clearfil AP-X and Filtek Supreme XT. The flexural strength and modulus after 24h water storage and 5000 thermocycles, water sorption, solubility and X-ray opacity were determined according to ISO 4049. The volumetric behavior (DeltaV) after curing and after water storage was investigated with the Archimedes principle. ANOVA was calculated with p<0.05. Clearfil AP-X showed the highest flexural strength (154+/-14 MPa) and flexural modulus (11,600+/-550 MPa) prior to and after thermocycling (117+/-14 MPa and 13,000+/-300 MPa). The flexural strength of all materials decreased after thermocycling, but the flexural modulus decreased only for Filtek Supreme XT. After thermocycling, there were no significant differences in flexural strength and modulus between Filtek Supreme XT, Microhybrid and Nano. Clearfil AP-X had the lowest water sorption (22+/-1.1 microg mm(-3)) and Nano had the highest water sorption (82+/-2.6 microg mm(-3)) and solubility (27+/-2.9 microg mm(-3)) of all the materials. No significant differences occurred between the solubility of Clearfil AP-X, Filtek Supreme XT and Microhybrid. Microhybrid and Nano provided the highest X-ray opacity. Owing to the lower filler content, Nano showed higher shrinkage than the commercial materials. Nano had the highest expansion after water storage. After thermocycling, Nano performed as well as Filtek Supreme XT for flexural strength, even better for X-ray opacity but significantly worse for flexural modulus, water sorption and solubility. The performances of microhybrids were superior to those of the nano-materials.

[The early history of transmissible spongiform encephalopathies exemplified by scrapie]. / Die frühe Geschichte der transmissiblen spongiformen Enzephalopathien am Beispiel der Traberkrankheit (Scrapie).

Transmissible spongiform encephalopathies (TSE) are unique diseases in that they are sporadic, hereditary, and infectious. The transmissible pathogen--the prion--stands out from all other pathogens in being devoid of nucleic acids. Instead its most important and possibly only constituent is a host-encoded protein, the prion protein (PrP), in an alternative conformation induced by post-translational modifications. Thus TSEs belong to and are so far the only transmissible member of the continuously growing group of disorders collectively referred to as protein conformational disorders. During elucidation of these disorders, many different--and contradictory--theories have been put forward. Early researchers, mostly driven by the economic effect of these diseases upon sheep farming, engaged in heavy disputes concerning the heredity vs infectivity of scrapie. After the experimental demonstration of scrapie's infectivity during the twentieth century, research focused on elucidating the nature of the transmissible agent. The current work comprehensively summarizes the early literature available on TSE research.

Laser-induced fluorescence to discriminate between a dental composite resin and tooth.

PURPOSE: Investigation of laser-induced fluorescence of an experimental pigment (Flu) to discriminate between a filling and the tooth and its influence on the material properties of experimental dental composites. MATERIALS AND METHODS: Three experimental composites (EC) were manufactured. The standard contained no Flu, Flu-0.5 contained 0.5%, Flu-1.0 contained 1%. To judge the extent of fluorescence, specimens and fillings placed in natural teeth were irradiated with an infrared laser (980 nm, 120 mW). Flexural strength, modulus of elasticity, depth of cure, water sorption, solubility, and color (CIE-L(*)a(*)b(*)-values) were measured to investigate the influence of Flu on EC. ANOVA was calculated and the statistical significance was p < 0.05. RESULTS: Strong laser-induced green fluorescence was observed so that fillings and tooth structures were clearly discriminated. No influence of Flu on flexural strength and modulus of elasticity occurred. Water sorption and solubility were far below the limits of EN ISO 4049. Increasing Flu concentrations revealed minor but significant reduction of depth of cure, shifts to more white and red and less yellow. SIGNIFICANCE: Flu provides laser-induced fluorescence allowing an easy discrimination between fillings and teeth. Flu did not severely influence the material properties.

Bradykinin mediates phosphorylation of eNOS in odontoblasts.

While the activation of eNOS by Akt/PKB-dependent phosphorylation, leading to NO release, and the inhibition of enzyme activity by bradykinin (BK)-mediated phosphorylation of eNOS in endothelial cells are established, the phosphorylation of eNOS in odontoblasts is unknown. To clarify the regulation of eNOS in odontoblasts by BK, we examined the phosphorylation of eNOS, Akt/PKB, and ERK1/2 in odontoblasts of rat molars. BK (10(-7) M) transiently induced the phosphorylation of eNOS at Ser1177, Akt/PKB in odontoblasts, while it induced the phosphorylation of eNOS at Thr495 throughout the entire period of BK treatment. BK receptor 2 antagonist HOE 140 (10(-6) M) significantly reduced signal intensities of phosphorylated-eNOS at Ser1177, Thr495, and phosphorylated-Akt/PKB. These results suggest that BK has dual effects on the activation of eNOS in odontoblasts, the Akt/PKB-dependent up-regulation of eNOS by the transient phosphorylation at Ser1177, and the ERK1/2-independent down-regulation of eNOS by the phosphorylation at Thr495.

Impact of endodontic treatments on the rigidity of the root.

The destabilizing effect of endodontic treatment upon teeth is still controversial. The purpose of this study was to investigate the effects of different steps of endodontic treatments upon the rigidity of teeth. Extracted untreated central maxillary anterior teeth were loaded (3.75 N), and deformations of the root were assessed by Speckle pattern interferometry. The following treatments (with subsequent determination of deformability) were conducted sequentially: access preparation, manual instrumentation (Kerr files ISO-40, ISO-60, ISO-80, ISO-110), and tapered and parallel-sided post preparation. It was found that the teeth were increasingly destabilized by any treatment. While the increased deformability was not significant with the manual enlargement (p > 0.05), we found a significant destabilization after access preparation and post preparation (p < 0.05). A corresponding difference was found after conversion of the post preparation from tapered to parallel-sided (p < 0.05). Both substance loss and modifications of the natural root canal geometry play an important role in tooth rigidity.

Evaluation of dentin abrasion during professional tooth cleaning in an in vitro model.

OBJECTIVES: Professional tooth cleaning (PTC) may lead to loss of exposed dentin. The aim of the present study was to determine the absolute loss of dentin during PTC using various product combinations with an in vitro model. MATERIAL AND METHODS: Dentin specimens (72) were randomly assigned to nine groups. In four groups each, prophy brushes and prophy cups were used in combination with four different abrasives (calcium pyrophosphate, pumice, Hawe cleanic, Nupro coarse). In the ninth group, a rubber cup with embedded fluoride and abrasives was used (pasteless prophy cup). The treatment time was 37 s. Surface loss was determined by profilometry. RESULTS: The surface loss in the nine groups was as following: (1) brush/calcium pyrophosphate: 6.18 microm (a); (2) brush/pumice: 5.51 microm; (3) brush/Nupro coarse: 10.10 microm (b); (4) brush/Hawe cleanic: 1.88 (a, b); (5) prophy cup/calcium pyrophosphate 2.07 (c); (6) prophy cup/pumice: 6.07 microm; (7) prophy cup/Nupro coarse: 5.93 microm (c); (8) prophy cup/Hawe cleanic: 4.93 microm (c); (9) pasteless prophy cup: 11.86 microm (c). Groups with the same letter in parentheses are statistically significant different at p<0.05. In a pooled analysis, no statistically significant difference between brushes and prophy cups was found. CONCLUSION: In the present study, the surface loss of about eight PTC procedures was simulated. Hence, the dentin loss ranged between 0.24 and 1.48 microm per PTC. Therefore, PTC does not seem to be a main factor in dentin loss.

Microhardness changes in dentine after neonatal capsaicin application.

AIM: To determine if desensitization of the nociceptive innervation in the dental pulp has an effect on odontoblast function in the rat. METHODOLOGY: Neonatal systemic application of capsaicin was used to selectively eliminate nociceptive innervation. 12 capsaicin-treated rats were intravitally perfused at 150 days of life with 4% formaldehyde and jaws were prepared for Vicker's microhardness (VMH) measurement. As a control, 12 rats were injected with vehicle on the 3rd day of life and intravital perfusion was carried out exactly as those used for the experimental group. Immunohistological labeling of CGRP was carried out in both groups to assure the efficiency of desensitization in the experimental group. The VMH was measured in the incisors of each animal for a quantitative analysis of dentine quality. RESULTS: Vicker's microhardness was significantly higher in the control rats compared with the capsaicin-treated rats (P < 0.001). CONCLUSIONS: Neonatal systemic application of capsaicin produces changes in the quality of dentine in the rat over time and therefore it is suggestive that selective elimination of the nociceptive innervation in pulpal tissue may effect odontoblast function.

NO-cGMP signaling molecules in cells of the rat molar dentin-pulp complex.

By the formation of cyclic guanosine 3',5'-monophosphate (cGMP), nitric oxide (NO)-sensitive enzyme-soluble guanylate cyclase (sGC) plays a receptor role for NO within the NO-cGMP signaling cascade, which is involved in vasodilatation and neurotransmission. The hypothesis that NO-cGMP signaling molecules modulate cells of the dentin-pulp complex was investigated in rat molars by histochemical, immunohistochemical, immuno-ultrastructural, and organ bath techniques. NO synthase (NOS) I-III, the sGC alpha(2)-subunit/beta(1)-subunit, and cGMP were detected in odontoblasts and blood vessels. NOS I, sGC alpha(2), and cGMP were identified in nerve fibers. Treatment of rat molars with the NO donor NONOate (10(-5) M) increased cGMP staining intensities in blood vessels and odontoblasts, while NO synthase inhibitor L-NAME (10(-4) M) attenuated intensity of the reaction products for cGMP, suggesting an effect of endogenous NO on sGC. These correlations of patterns and alterations of cGMP staining intensities after treatment with the NO donor or NO inhibitor might represent an NO-sGC-cGMP signaling-dependent modulation of odontoblasts, blood vessels, and nerve fibers in the dentin-pulp complex.

Efficacy of the Cybersonic in comparison with the Braun 3D Excel and a manual toothbrush.

OBJECTIVES: To evaluate the efficacy of two power toothbrushes (Cybersonic and Braun 3D Excel) and one manual brush (Elmex super 29). MATERIAL AND METHODS: After professional toothcleaning 120 subjects were randomly assigned to three groups. Four weeks later, at baseline, the Quigley-Hein plaque index (QHI), the modified approximal plaque index (API), and the papillary bleeding index (PBI) were recorded. Thereafter the subjects used the assigned toothbrushes for 8 weeks. Improvements of the indices after 4 and 8 weeks were calculated as medians. Kruskal-Wallis- and Mann-Whitney U-test served for statistical analysis. RESULTS: All indices showed statistically significant reductions for both power toothbrushes which were superior to the manual brush (4 weeks: Cybersonic: API, 0.21; PBI, 0.25; QHI, 0.23; Braun: API, 0.20; PBI, 0.39; QHI, 0.22; Elmex: API, 0.04; PBI, 0.02; QHI, 0.07; 8 weeks: Cybersonic: API, 0.28; PBI, 0.36; QHI, 0.41; Braun: API, 0.36; PBI, 0.61; QHI, 0.35; Elmex: API, 0.03; PBI, 0.10; QHI, 0.08; p<0.001). The Braun was superior to the Cybersonic with respect to API after 8 weeks (p<0.05) and PBI after 4 and 8 weeks (p<0.01). CONCLUSION: Cybersonic and Braun 3D Excel may be more efficacious than a manual toothbrush in removing plaque and reducing gingivitis.

Immunohistochemical evidence for proteolipid protein and nestin expression in the late bell stage of developing rodent teeth.

In this study, the expression of proteolipid protein (PLP) and nestin is studied in the late bell stage of developing rodent teeth in neonatal rats. By using immunohistochemistry, it was shown that odontoblasts, ameloblasts and the stratum intermedium are positive for PLP in regions of active matrix deposition. Reactivity for nestin could be detected in the odontoblasts, stratum intermedium and in some of the apical processes of the ameloblasts. The fact that mutations in the PLP gene can cause disturbances in tooth form, number and eruption taken together with the presence of PLP reactivity in odontoblasts and ameloblasts of healthy animals, suggests a crucial role for PLP in developing teeth because of its structural supportive characteristics. These results also imply the possible use of PLP antibody as a new marker for, respectively, dentin and enamel-secreting odontoblasts and ameloblasts. PLP and nestin expression could point to a possible similarity in function between the oligodendrocyte and the odontoblast, both derived from the neural crest. To compare with the situation in human tissue, PLP and nestin expression were preliminarily tested on human dental pulp. The odontoblasts were positive for both PLP and nestin.

Determination of the dynamics of restored teeth by 3D electronic speckle pattern interferometry.

BACKGROUND AND OBJECTIVES: The difficulties typically encountered in studying the effects of restorations on tooth reinforcement are often due to the 3-dimensional (3D) nature of deformation. Therefore, electronic 3D-Speckle-Interferometry (3D-ESPI) was used to assess the impact of different restorative materials on the deformation of teeth. STUDY DESIGN/MATERIALS AND METHODS: Small and large MOD-preparations in extracted premolars were restored with gold inlays, ceramic inlays, composite resin inlays, amalgam, or composite resin. The restorations and cusps were loaded (90 N) and the deformation was assessed by 3D-ESPI. RESULTS: Teeth with small restorations were deformed only slightly and the differences between the materials were minimal (P>0.05). In contrast, teeth with large restorations displayed material-specific deformation patterns: (a) all materials led to decreased deformation as compared with unfilled teeth, (b) elastic materials caused only local deformation, (c) non-adhesive materials resulted in translation of the restoration and marginal discrepancies, (d) adhesive inlays brought about increased deformation of the luting resin composite, (e) loading of the cusps caused higher deformation than loading of the restorations, and (f) bonded restorations stabilized the cusps. CONCLUSIONS: The results show that the deformation pattern of restored teeth is material-specific but the extent of deformation is primarily limited by the remaining tooth substance.

[Dental group prophylaxis - for children only?]. / Zahnmedizinische Gruppenprophylaxe - nur für Kinder?

In Germany, caries in 12-year olds have declined by 70 % in the last decade. This was the result of a variety of preventive measures such as salt fluoridation, group related prevention in schools and kindergartens, and individualized preventive measures offered in dental offices. On a national scale, salt fluoridation seems to be the measure with the highest efficacy and efficiency. Firstly, it has the potential to reach the entire population, and secondly it is highly cost-effective. The cost-benefit ratio for salt fluoridation ranges from 25 to 80, e. g. for one Euro spent on prevention, 25 to 80 Euro can be saved in therapy. However, salt fluoridation alone cannot stop caries, and it is not at all effective in preventing gingivitis and periodontitis. Therefore, additional measures have to be taken. The cost-benefit ratio for group-related prevention ranges from 2.4 to 19.5 and for individualized prevention from 0.7 to 2.1. Besides the better cost-effectiveness, group-related prevention has the advantage of advanced target group attainment. For example, it is easy to reach children in schools whereas it is difficult to review them in a dental office. Therefore, group related-prevention should have priority. This should not be restricted to children and adolescents, seniors can also be attended in groups. In Germany, about 950,000 people live in old people's homes, and additionally about 570,000 people in nursing homes. This population often suffers from severe oral health problems such as caries, periodontitis, and diseases involving the mucosa. Taking into account that the number of elderly institutionalized people is increasing in Germany, the establishment of group-related prevention for this part of the population seems to be an important goal in health policy.

Increment technique for extended Class V restorations: an experimental study.

The application and polymerization of composite or polyacid-modified resin composites in thin layers (increment technique) for filling cavities might partially compensate for the stress associated with polymerization shrinkage. In this study, the effect of this technique on the marginal integrity of Class V polyacid-modified composite restorations was investigated. In 30 extracted premolars, extended Class V cavities were prepared with the apical margin in root dentin and the coronal margin in enamel. They were then subjected to different treatments (10 teeth in each case): a) placement and polymerization of a thin resin composite layer (Dyract-Dyract PSA) in the coronal part of the cavity (plus one increment for the residual part) (Group 1), b) a thin layer at the apical part of the cavity (plus one increment for the residual part) (Group 2) and c) restoration of the entire cavity with one increment (bulk technique) (Group 3). Following three days' storage in water, the teeth were subjected to cyclic thermal loading (4 degrees C <-> 55 degrees C, 2,000 cycles). The percentages of defective bonding detected along the total length of the restoration margin were assessed before and after thermocycling by scanning electron microscopy. Following loading and thermocycling, no significant differences were found at the restoration-enamel interface. Fewer gaps were found at the restoration-dentin interface in Group 1 (18.7 +/- 25.7%) and Group 2 (20.5 +/- 22.8%) compared to the reference Group 3 (42.2 +/- 30.6%) (Mann-Whitney U test: p<0.05). Moreover, there were no significant differences between the two increment groups (1 and 2). In a significantly larger number of cases, a completely intact dentin restoration margin was detected when a coronal increment (Group 1) (44.4%) was used instead of the bulk technique (Group 3) (13.6%) (Chi square test: p<0.05). These results indicate that gap formation can be significantly minimized by using an increment technique to restore extended Class V cavities with polyacid-modified composite materials.

An in vitro comparison of metal and transparent matrices used for bonded class II resin composite restorations.

This study compared excess formation of direct bonded Class II restorations using different matrix systems-metal or transparent. Sixty freshly extracted, non-carious, posterior human teeth were used. In all of the teeth, standardized MOD-cavities were prepared with the gingivoproximal margins located 1.0-1.5 mm cervical to the cemento-enamel junction. The prepared teeth were randomly assigned to six groups. Half were restored using metal matrices and wooden wedges; the other half were restored using transparent matrices and reflective wedges. Three different material systems were used to fill the cavities: 1) a hybrid composite (Tetric) plus an adhesive bonding agent (Syntac Classic), 2) a flowable composite (Tetric Flow) plus Syntac Classic and 3) a compomer (Dyract AP) together with an adhesive bonding agent designed for compomers (Prime & Bond NT). After the specimens were preserved in saline solution, scanning electron microscopy (SEM) assessed the amount of overhang formation at the restoration margins. The data collected indicated the use of transparent matrices resulted in significantly higher amounts of excess material at the restoration margins compared with metal matrices. Moreover, there was no significant difference between the materials when the same matrix was used. All of the dental restorations examined displayed material overhang. Based on these findings, the authors concluded that the type of matrix exerts a major impact on overhang formation, with metal matrices resulting in significantly less excess material buildup.

Cavity preparation using a superpulsed 9.6-microm CO2 laser--a histological investigation.

BACKGROUND AND OBJECTIVES: The superpulsed 9.6-microm CO(2) laser is an effective laser for ablating dental tissues and decay. This histological study compares laser class V preparations with conventional treatment to evaluate the resulting formation at the cavity walls. STUDY DESIGN/MATERIALS AND METHODS: Four class V preparations (one made with a diamond drill and three with the CO(2) laser (9.6 microm, 60 microseconds pulse width, 40 mJ pulse energy, 100 Hz, integrated scanner system, water cooling) were performed on ten extracted teeth. The cavities were filled with a composite resin partly including enamel and dentine conditioning. RESULTS: After laser preparation, no cracks or signs of carbonisation were detected. The results were comparable to those attained with conventional treatment. Following cavity filling without prior conditioning, gaps were noted at the cavosurface indicating a lack of adhesion. Dentinal bonding decreased gap formation significantly. CONCLUSION: The 9.6-microm CO(2) laser is an effective tool for cavity preparation.