Intra-oral adhesive systems for ceramic repairs: a comparison

The aim of this investigation was to compare the bond strength of restorative composite resin to dental ceramic conditioned with primers and adhesives of various commercial repair kits. Three intra-oral ceramic repair systems--Silistor (Heraeus Kulzer), Cimara (Voco), Ceramic Repair (Vivadent)--were used on all-ceramic (IPS Empress 2, Ivoclar-Vivadent) substrate. Shear bond strength of restorative composite resin to substrate was tested after thermocycling and without thermocycling (n = 10). Substrate surfaces of the specimen after loading were examined microscopically (SEM). The highest bond strengths in both water-stored (7.0 +/- 5.7 MPa) and thermocycled conditions (2.5 +/- 1.8 MPa) were obtained with the Vivadent repair system, while the lowest values were observed with the Cimara system (0.6 +/- 1.4 MPa and 0.0 +/- 0.0 MPa, respectively). Shear bond strengths appeared to be significantly affected by thermocycling (ANOVA, P < 0.05). It is concluded that there are significant differences in the bond strengths of resin composites and ceramic substrate. The roughened surface does not necessarily provide a better bond strength; the bond strength of composite decreases with storage in water and after thermocycling. Bond strength values were generally low for all of the tested materials.     

Effect of ENU (ethylnitrosourea) mutagenesis in cleft lip and/or palate pathogenesis in mice

Cleft lip and/or palate (CL/P) are caused by many factors. The aim of this study was to investigate the effects of genetic point mutations in CL/P pathogenesis. ICR and AJ strain mice were used. Ethylnitrosourea (ENU) was injected into 10-week-old male mice (G0) intraperitoneally at a dose of 250 mg/kg. The males were bred with two untreated virgin females of the same strain on day 100 after injection. The uterine contents (G1) of one female were examined on day 18.5 of pregnancy. From the other female, the offspring were delivered naturally, and F3 mice (G3) were also examined in the same way. In ICR strain mice, cleft palate only (CPO) was increased in both the G1 and G3. The frequency was significantly higher in the G3 than the G1 generation. Cleft lip was not observed. In AJ strain mice, CL/P increased in both the G1 and G3. In the G3, the frequency of CPO was increased significantly. Genes related to CPO may be recessive in phenotype. CPO and cleft lip differ from a genetic viewpoint. Point mutations play a significant role in cleft lip and palate.     

The role of dentist, practice and patient factors in the provision of dental services

OBJECTIVES: Service provision varies by dentist, practice and patient factors. However, limited subsets of these potential influences on service rates have been explored. More comprehensive models could improve our understanding of the factors influencing the pattern of care delivered. The aim of this study was to examine variation in dental services by dentist (treatment choice, practice beliefs, preferences for patients, demographics), practice (type, location, size and volume of practice) and patient (visit, demographic, oral health and socio-economic) characteristics. METHODS: A random sample of Australian dentists was surveyed in 1997-98 (response rate=60.3%). Private general practitioners (n=345) provided dentist and practice data, and service provision and patient variables were collected from a log of a typical clinical day (n=4,115 patients). Multivariate negative binomial regression models were fitted for diagnostic, preventive, restorative, extraction and prosthodontic services. RESULTS: Significant dentist factors included (P<0.05; RR=rate ratio): lower diagnostic rates (RR=0.78) for dentists with stronger practice beliefs for giving information about cost and treatment options; preventive rates were lower (RR=0.74) for male dentists and higher (RR=1.48) for younger dentists aged 20-29 years; restorative rates were higher (RR=1.27) for dentists that rated patient preferences more highly in treatment choice and in the dentist age group 30-39 years (RR=1.25); extraction rates were lower (RR=0.61) for dentists with stronger preferences for patients that would adhere with treatment but higher (RR=1.57) for dentists with stronger preferences for sociable patients; and prosthodontic rates were lower (RR=0.38) for dentists with stronger preferences for adaptable patients who were willing to cooperate when expected to do so. Practice factors included: higher preventive (RR=1.28) and prosthodontic rates (RR=2.07) in solo practice; higher preventive (RR=1.34) but lower prosthodontic rates (RR=0.42) in capital cities; lower diagnostic (RR=0.82) and extraction rates (RR=0.55) in practices with fewer other dentists; higher diagnostic (RR=1.33) and extraction (RR=1.62) rates but lower restorative rates (RR=0.84) in practices with lower patient visits per year. Patient factors included: lower preventive (RR=0.76) but higher extraction rates (RR=1.45) for emergency visits; lower extraction rates (RR=0.60) for the insured; higher diagnostic rates (RR=1.17) for new patients; higher restorative (RR=1.31) but lower prosthodontic rates (RR=0.46) for patients with decayed teeth; higher prosthodontic rates (RR=2.14) for those with dentures; and lower preventive (RR=0.66), but higher extraction (RR=2.22) and prosthodontic rates (RR=1.82) for patients from lower socio-economic status areas. CONCLUSIONS: Dental service rates were influenced by large number of small effects from a wide range of dentist, practice and patient factors. Socio-economic and geographic barriers may need broad policy innovations to be addressed, but factors such as insurance and visit type have the potential to be altered to achieve better service outcomes and there is scope for research into clinical outcomes to improve the knowledge upon which treatment decisions are based.     

Non-viral-mediated gene therapy approaches for bone repair

OBJECTIVES: Bone repair strategies continue to be developed for alternatives to autografting, allogeneic implants of banked bone, and other bone substitutes. Efforts have included the delivery of potent growth and/or differentiation factors and the use of gene therapy. For bone regeneration, gene therapy is the delivery, uptake and expression of DNA that has been localized to a wound bed. The objective of the current study is to investigate methods to enhance non-viral-mediated means of gene uptake and expression for use in bone regeneration. METHODS: Several types of DNA-polymer complexes, either applied directly to baby hamster kidney (BHK) cells, or released from a porous, resorbable gene-activated matrix (GAM), were evaluated in vitro for their ability to transfect cells with a circular plasmid DNA construct expressing green fluorescent protein. Complexes included conjugates containing a lipophilic reagent, liposomes, poly-ethyl-oxazoline, and poly-ethyleneimine (PEI). Data were subjected to analysis of variance and Fisher's protected least significant difference for multiple comparisons with significance established at p < 0.05. RESULTS: Transfection efficiencies of the liposome and PEI complexes improved in vitro when released from resorbable GAMs. The lipophilic reagent FuGene 6 demonstrated abundant uptake and expression in the initial 1- and 2-day evaluation periods. In contrast, the DNA-liposome and PEI GAM complexes demonstrated a sustained release, uptake and expression by the BHK cells at the 2-, 4-, and 7-day, and 4- and 7-day evaluation intervals, respectively. CONCLUSION: GAM technology appears to improve the functional stability and release duration of incorporated DNA-polymer complexes in the present in vitro studies. The ongoing objective of our research is to develop a localized treatment to improve the uptake and expression of plasmid DNA by non-viral-mediated gene therapy.     

An electromyographic study of masseter and anterior temporalis muscles in extra-articular myogenous TMJ pain patients compared to an asymptomatic and normal population

The purpose of this study was to evaluate the effectiveness of the therapy with a centric relation stabilization appliance (CRSA) in patients with temporomandibular disorders of myogenous origin by electromyography and compare the results with two asymptomatic control groups. Three groups of 20 patients each were selected for the study. Electromyography (EMG) of masseter and anterior temporalis muscles was performed during mandibular rest position. In the treated group, the occlusal appliance reduced the electrical activity of the analyzed muscles at right and left sides (p<0.0001), and equilibrated muscular activity between right and left sides (p<0.0001), reaching values close to the control groups. Although there was not a statistically significant difference, the normal control group presented lower EMG values than control group II and presented the lowest asymmetry index of all subjects. More than 85% of all subjects, including the controls, demonstrated a statistically significant temporal anterior activity prevalence (p<0.0001). Treatment with the CRSA reduced the activity index, although the prevalence of the temporal muscle over the masseter was maintained. The significant laterodeviating (torque) effect found in the temporomandibular disorder patients was reduced after treatment. No side prevalence was found in the control groups.     

Development of methods to enhance extrinsic tooth discoloration for comparison of toothpastes. 2. Two-product clinical study

BACKGROUND: Extrinsic staining of teeth is considered to be unsightly and a number of 'whitening' toothpastes have been formulated to inhibit or remove such tooth discoloration. The aim of this study was to compare the stain prevention of two toothpastes. METHOD: The study was a single-blind, randomised, placebo-controlled, crossover design, balanced for residual effects involving 24 healthy dentate volunteers. The treatments were as follows: (1) a whitening toothpaste product, (2) an experimental toothpaste formulation and (3) water. For each 4-day rinse period, subjects were rendered stain free on the teeth and tongue. Approximately on the hour from 09:00 to 16:00 hours, subjects rinsed with chlorhexidine mouth rinse for 1 min followed by warm black tea for 1 min. The treatment interventions were at 09:00 and 16:00 hours and before the chlorhexidine rinse. The toothpastes were rinsed as 3 g/10 ml water slurries and water as a 10 ml rinse each for 2 min. On day 5, subjects were scored for tooth and tongue stain intensity and area, and the product of these was calculated. The washout period was at least 9 days. RESULTS: Treatment differences for the teeth were highly significant but not for the tongue. Paired contrasts for tooth stain intensity, area and product were mostly all significantly in favour of reduced staining by the experimental formulation compared with water and the whitening product. There were no significant differences between water and the whitening product. CONCLUSIONS: Using a forced dietary staining method, the data support a tooth stain-inhibitory/-removal action for the experimental formulation, but not the whitening product.     

Prevalence of early childhood caries among First Nations children, District of Manitoulin, Ontario

Background. Epidemiological studies of Aboriginal communities in Canada and Native American populations in the United States have reported that early childhood caries (ECC) is highly prevalent. The purpose of this study was to determine the prevalence of ECC and dental caries in the First Nations population of 3‐ and 5‐year‐old children in the District of Manitoulin, Ontario to assist in developing effective dental health promotion strategies. Methods. All 3‐ and 5‐year‐old children in elementary schools and day‐care centres in seven First Nation communities were eligible for the survey examination. Three‐year‐old children at home and 5‐year‐old children attending school off‐reserve in six of the communities were also eligible for epidemiological survey examination of oral health status including caries, gingival and soft tissue conditions. Cases of ECC were defined as children with caries or restorations on two or more primary maxillary incisors or canines or those having a total decayed, missing, filled primary teeth (dmft) score of 4 or greater. Results. A total of 87 children (59% 5 years old, 54% females) were examined. Seventy‐four per cent of children had one or more carious lesions. Forty‐five cases of ECC were found, a prevalence of 52%. The mean dmft score for cases was 7·5 (95% CI 6·5–8·4) and 0·8 (95% CI 0·5–1·1) for non‐cases (P < 0·001). Boys in both age groups were more likely to be affected by ECC than girls. Conclusion. Our results indicate that dental caries and ECC are highly prevalent in this population, with ECC cases having 6.7 more dmft than non‐cases.     

Effect of magnification on locating the MB2 canal in maxillary molars

The purpose of this study was to determine if the surgical operating microscope and/or dental loupes could enhance the practitioner's ability to locate the second mesiobuccal canal (MB2) canal of maxillary molars in an in vivo, clinical setting. The participating endodontists documented 312 cases of root canal therapy on maxillary first and second molars. Participants that used the microscope or dental loupes located the MB2 canal with a frequency of 57.4% and 55.3%, respectively. Those using no magnification located the MB2 canal with a frequency of 18.2%. When no magnification was used, significantly fewer MB2 canals were located based by Chi-square analysis at p < 0.01. There was no significant difference between the use of the microscope and dental loupes in the frequency of locating the MB2 canal. When the maxillary first molars were considered separately, the frequency of MB2 canal detection for the microscope, dental loupes, and no magnification groups was 71.1%, 62.5%, and 17.2%, respectively. The results of this study show that the use of magnification in combined groups leads to a MB2 detection rate approximately three times that of the nonmagnification group and that the use of no magnification results in the location of significantly fewer MB2 canals. Based on these results, more emphasis should be placed on the importance of using magnification for locating the MB2 canal.