Caries occurrence in a fluoridated and a nonfluoridated town in Finland: a retrospective study using longitudinal data from public dental records

The tap water of Kuopio, Finland, was fluoridated from 1959 to 1992. In the first decade of fluoridation, children in Kuopio had lower DMF values than children in Jyv?skyl?, a nearby low-fluoride town, but later differences between the towns have been small and inconsistent. The present study aimed to gain further insight into caries occurrence in Kuopio and Jyv?skyl? using longitudinal tooth-specific data from public health records on cohorts born in 1970/71 and 1980/81 (total n = 1,503). Survival analyses were used to summarize the tooth-specific times elapsed between eruption and the first filling (used as a proxy for dental caries). Generally, the first filling was placed sooner after eruption in the 1970/71 cohort than in the 1980/81 cohort. The curves for the two towns were virtually identical except for the first molars of the 1970/71 cohort, for which the percentage of filled first molars was consistently lower in Jyv?skyl? than in Kuopio. This study indicates that, among children and adolescents whose permanent teeth erupted in the mid-1970s or thereafter, even a longitudinal approach did not reveal a lower caries occurrence in the fluoridated than in the low-fluoride reference community. The main reason for the modest effect of water fluoridation in Finnish circumstances is probably the widespread use of other measures for caries prevention. The children have been exposed to such intense efforts to increase tooth resistance that the effect of water fluoridation does not show up any more. The results must not be extrapolated to countries with less intensive preventive dental care.     

Cytotoxicity of a dentine bonding agent on four different cell-lines.

The aim of this study was to compare the cytotoxicity of a recently available dentine bonding agent on four different cell-lines (three human dental pulp fibroblast cell-lines and one mouse 3T3 fibroblast cell-line). METHODOLOGY: Three human dental pulp cell-lines from 3 different donors and one established 3T3 mouse cell-line were grown and sub-cultured. Cell viability following exposure to Scothbond was then compared to a similar number of controls using the MTT assay. RESULTS: Scotchbond 1 was cytotoxic to all four cell-lines. 3T3 cells showed a survival rate of about 60% as compared to two of the human dental pulp cells which showed a significantly lower survival rate (p<0.05, Kruskal-Wallis Multiple-Comparison Test). CONCLUSION: These findings indicated that is cytotoxic to both human pulp and 3T3 cell-lines. In general, the human pulp cell-lines showed higher sensitivity than the 3T3 cell-lines. CLINICAL SIGNIFICANCE: Scotchbond 1 cannot be recommended for direct pulp capping techniques and care should be taken when using this dentine bonding agent in cavities where the remaining dentine layer is minimal.     

Effectiveness of composite cure associated with different light-curing regimes

This study investigated the use of various light-curing regimens with standardized light energy density on the effectiveness of cure of a visible light activated resin composite (Z100, 3M-ESPE). A light-cure unit (Variable Intensity Polymerizer (VIP), BISCO Inc) which permitted individual control over time and intensity, was used. The five light-curing modes investigated include Pulse Delay (PD), Pulse Cure (PC), Soft-start (SS), Turbo (T) and Control (C). Effectiveness of cure was established by measuring the top and bottom Knoop hardness of 2-mm thick composite specimens using a digital microhardness tester (n=5, load=500g; dwell time=15 seconds) immediately and at one-day post-polymerization. Data obtained was analyzed using one-way ANOVA/Scheffe's post hoc test and Independent Samples t-tests (p<0.05). Top KHN observed immediately after polymerization with C was significantly lower than PD. At one day post-polymerization, the top KHN obtained with C was significantly lower than PD, SS and T. No significant difference in bottom KHN was observed among the different curing modes immediately after curing. At one day post-polymerization, the bottom KHN obtained with C was significantly lower than SS and T. Regardless of curing regimens, top and bottom values at one day were significantly higher than those observed immediately after light polymerization. No significant difference in mean hardness ratio was observed among the different curing regimens immediately and one day later. Effectiveness of the cure at the bottom surfaces of composites may be increased by soft-start and turbo polymerization regimens.     

Volumetric polymerization shrinkage of resin composites under simulated intraoral temperature and humidity conditions

This study measured the volumetric shrinkage of resin composites polymerized under temperature and humidity conditions simulating the oral cavity and compared them to those occurring under ambient room conditions. Small, semispherical specimens of a microhybrid (Z100), microfill (Filtek A110) and flowable microhybrid (4 Seasons Flow) resin composite were manually formed and light activated for 40 seconds using a halogen light-curing unit (Spectrum Curing Light). The volumetric polymerization shrinkage of 10 specimens of each brand of resin composite was measured using a drop shape analysis unit (Drop Shape Analysis System, model DSA10 Mk2) under each of two temperature/relative humidity conditions: room conditions (22 +/- 2 degrees C and 60 +/- 5%) and those simulating intraoral conditions (35 degrees C and 92 +/- 5%). Mean volumetric shrinkage values were calculated for each resin composite and the data were analyzed using two-way analysis of variance and t-test (a=0.05) to determine if significant differences existed between the amount of volumetric polymerization shrinkage that occurred under ambient room conditions and that which occurred under simulated intraoral conditions. Mean volumetric shrinkage values measured for the resin composites were: 2.26 +/- 0.04% (ambient) and 2.61 +/- 0.04% (intraoral) for Z100; 1.96 +/- 0.04% (ambient) and 2.28 +/- 0.04% (intraoral) for Filtek A110 and 4.53 +/- 0.06% (ambient) and 5.34 +/- 0.05% (intraoral) for 4 Seasons Flow. For each resin composite, statistical analysis indicated that the amount of volumetric shrinkage measured under simulated intraoral conditions was significantly greater than what was measured under ambient room conditions (p<0.0001).     

Biofilm growth of Lactobacillus species is promoted by Actinomyces species and Streptococcus mutans

The ability of oral bacteria to integrate within a biofilm is pivotal to their survival. A dependence on the amount of biofilm growth by noncoaggregating Lactobacillus rhamnosus and Lactobacillus plantarum on coculture with Actinomyces naeslundii, Actinomyces gerencseriae, Streptococcus mutans and Veillonella parvula was investigated using an artificial-mouth culture system. Biofilm formation by the lactobacilli in mono-culture was poor. In coculture with Actinomyces species the amount of L. rhamnosus increased 7-20 times and L. plantarum 4-7 times compared to its mono-culture biofilm. S. mutans also promoted substantial biofilm growth of lactobacilli but V. parvula had no effect. We conclude that these Actinomyces species promoted growth of key Lactobacillus species in a biofilm, as did S. mutans to a smaller extent, and that the ability of individual bacteria to form mono-culture biofilms is not necessarily an indicator of their survival and pathogenic potential in a complex multispecies biofilm community.     

Polymerization shrinkage-strain kinetics of temporary crown and bridge materials.

OBJECTIVE: The purpose of this study was to measure the polymerization shrinkage kinetics of four commercially available polymer-based temporary crown and bridge materials, including the effect of ambient temperature. METHODS: Three dimethacrylate-based materials and one monomethacrylate-based material were investigated. The polymerization shrinkage-strains were measured by using the Bonded-disk method with initial specimen temperature at both 23 and 37 degrees C, with values particularly noted at 5, 10, and 120 min after mixing. Five recordings were taken for each material. The progress of the setting reaction and its temperature-dependence were evaluated by the kinetic curves, and net shrinkage and total shrinkage (inclusive of expansion magnitude) of each material were compared by independent sample t-test and one-way ANOVA. RESULTS: Most shrinkage occurred in the first 10 min after mixing although there was an early expansion especially with the monomethacylate in the first 5 min. At 120 min, the net shrinkage-strain at 23 and 37 degrees C of the materials used in this test ranged from 3.54 to 4.13%. The fastest setting dimethacrylate-based material and the monomethacrylate-based material showed higher shrinkage-strain than other materials. No significant differences of net shrinkage-strain were found between 23 and 37 degrees C, but higher shrinkage rates were measured at 37 degrees C than at 23 degrees C. SIGNIFICANCE: The Bonded-disk method is a suitable method for measuring temperature-dependence of shrinkage-strain of polymer-based temporary materials. The dimethacrylate-based materials are preferable to monomethacrylates for temporary restoration as judged by the magnitude of polymerization shrinkage-strain, the majority of which is apparent within 10 min from the start of mixing and may affect the clinical outcome.     

Children's coping with pain during dental care

OBJECTIVES: The purpose of this study was (i) to assess the coping strategies of 11-year-old children when dealing with pain at the dentist, (ii) to determine the extent to which the level of the children's dental fear and their experience with pain at the dentist are related to their ability to cope and their choice of strategies, and (iii) to analyse the possible differences between subsamples concerning dental caries. METHODS: The coping strategies were investigated using the Dental Cope Questionnaire (n = 597); the level of dental fear was assessed using the Children's Fear Survey Schedule (CFSS-DS); a question is asked whether a child had experienced pain at the dentist in the past and dental caries was assessed using the DMFS index. RESULTS: The results show that 11-year olds use a variety of coping strategies. Internal strategies are used most frequently, external coping strategies are used less frequently, and destructive strategies are hardly used. The subjects rate internal and external strategies as effective. Children with pain experience and fearful children use more coping strategies, with fearful children using more internal strategies. Reported pain and anxiety were related to the dental status. CONCLUSIONS: The use and choice of coping strategies seems to be at least partly determined by the level of dental fear and the child's experience with pain.     

The effect of German chamomile (Marticaria recutita L.) extract and tea tree (Melaleuca alternifolia L.) oil used as irrigants on removal of smear layer: a scanning electron microscopy study

AIM: To compare the cleaning effectiveness of chamomile hydroalcoholic extract and tea tree oil to 2.5% sodium hypochlorite (NaOCl) solution as an intracanal irrigant for the removal of the smear layer. METHODOLOGY: Forty extracted, single-rooted, mature, permanent, human teeth were allocated at random into one of three experimental groups of ten teeth and two control groups of five teeth. For each tooth, the pulp chamber was accessed and the canal prepared using K-type files and Gates-Glidden burs, using a step-back technique; the apical stop was prepared to a size 30. Each canal was subsequently irrigated with one of the following solutions: distilled water (as a negative control), 2.5% NaOCl + 17% ethylenediamine tetraacetic acid (EDTA) (as a positive control), chamomile or tea tree oil or 2.5% NaOCl. Each tooth was split longitudinally and prepared for examination by scanning electron microscopy (SEM). The quantity of smear layer remaining on the three levels of each canal (coronal, middle and apical) was examined using magnifications of 2000 and 5000x. The data were analysed using nonparametric Kruskal-Wallis and Mann-Whitney U-tests. RESULTS: The most effective removal of smear layer occurred with the use of NaOCl with a final rinse of 17% EDTA (negative control) followed by the use of a chamomile extract. Chamomile extract was found to be significantly more effective than distilled water and tea tree oil (P < 0.008).The use of a 2.5% NaOCl solution alone, without EDTA and that of tea tree oil, was found to have only minor effects. There was no statistical difference between distilled water, 2.5% NaOCl and tea tree oil. CONCLUSIONS: The efficacy of chamomile to remove smear layer was superior to NaOCl alone but less than NaOCl combined with EDTA.     

Gesichtsschädelaugmentationen mit porösen Polyethylenimplantaten (Medpor®)

Subject

Porous polyethylene (Medpor^®) is an alloplastic material commonly used in craniofacial reconstruction. We report about our first clinical experiences with Medpor for facial augmentation procedures.

Patients and methods

We treated 27 patients between 2001 and 2005 (11 female, 16 male) with 48 Medpor^®-implants. The indications for application of porous polyethylene implants in our clinic were congenital malformations (15), post-traumatic defects (10), and reconstructions after tumor resection (2). The implants were used for nasal/paranasal augmentations (16), for zygomatico-orbital augmentations (18), and for augmentations of the chin and malar region (11). The procedures were performed in a standardized manner. We used prefabricated, self-contoured implants and fixed them subperiosteally with titanium osteosynthesis screws. All operations were performed under general anesthesia. We evaluated the aesthetic results and the ingrowth behavior clinically and histologically.

Results

We achieved good aesthetic results and the patients showed no signs of discomfort or rejection. Four patients required a second intervention. These revision surgeries included two cases of local infections and two for aesthetic contouring. The necessary reduction of the implants allowed the harvesting of tissue and implant samples for microscopy.

Conclusion

Porous polyethylene implants showed a good fibrovascular integration without encapsulation under the light microscope. Giant cells were detected on the surface of the implants. Besides this there was evidence for resorption of the implant material. Fixation with titanium screws is very effective. No implant dislocation or implant fracture occurred. The implants showed high volume stability and were easily handled and contoured. It is not possible to visualize Medpor implants with current imaging techniques, because polyethylene shows no contrast.