The effect of dentine location and tubule orientation on the bond strengths between resin and dentine

This study determined the influence of dentine structure on the micro-tensile bond strengths between resin and dentine of two different dentine adhesive systems (Single Bond, 3M Dental Products, St Paul, MN; MF-102 (experimental self-etching primer), GC Corporation, Tokyo, Japan). The study was separated into two main parts: bond strength measurement and investigation of the bonding interface. Twenty-two human premolars were used for the bond strength measurement. Each tooth was cut vertically, separating the tooth into mesio-distal halves. One half of the tooth was used to bond to a surface perpendicular to the dentinal tubules and other half to bond to a surface parallel to the tubules. For each half, six locations of dentine were bonded. Each material was used in accordance to the manufacturer's directions. Cylindrical hourglass-shaped specimens of 1.2 mm diameter at the bonded interface were manufactured. The bonds were stressed in tension at a crosshead speed of 1 mm/min. Mean bond strengths were compared using LSD, one-way ANOVA, and Student's t-test. The fractured surfaces were examined under a scanning electron microscope, and the frequency of fracture modes was compared using the Kruskal-Wallis and Mann-Whitney U tests. For the investigation of the bonded interface, four teeth were prepared by the same procedure used for the bond test specimens. The bonded interfaces were observed after an acid-base treatment or fracturing across the bonded interface, prior to investigation with a field-emission scanning electron microscope. For Single Bond, the bond strengths for mid-root dentine were significantly lower than for other locations (p < 0.05). For MF-102, there was no significant difference for all locations (p > 0.05). MF-102 bonded well to all locations of dentine while Single Bond showed a porous zone at the base of the hybrid layer. The bonds were not influenced by tubule orientation. The results indicate that the bond for Single Bond may be affected by its ability to penetrate demineralised dentine in different locations of a tooth. The self-etching primer of MF-102 produces a good bond and is independent of the position on the tooth.     

Dental expenditures and source of payment by race/ethnicity and other sociodemographic characteristics

OBJECTIVE: This study presents race/ethnic-specific distributions of dental expenditures and their sources of payment by socioeconomic characteristics among US working-age adults. METHODS: Data for persons aged 19-64 years from the 1987 National Medical Expenditure Survey (NMES) (n = 18,696) were used to calculate mean dental expenditures and their 95 percent confidence intervals. RESULTS: Dental expenditures were reported by 44.5 percent of participants. Non-Hispanic whites and persons with higher income were more likely to report dental expenditures than their counterparts. Among persons reporting expenditures, those with lower income had lower expenditures than higher-income persons. No differences in the amount of expenditures by race/ethnicity, sex, or employment status were observed. In all race/ethnic groups almost half the expenditures were paid out-of-pocket and one-third by dental insurance. CONCLUSION: While sociodemographic characteristics determined who had dental expenditures, they did not determine the amount or source of those expenditures.     

Microbial factors and gingival crevicular fluid aspartate aminotransferase levels

Abstract. The aim of this cross-sectional study was to investigate the clinical application of chairside tests for gingival crevicular fluid (GCF) aspartale amino-transferase (AST) levels and plaque BANA hydrolysis activity with the presence of the periodontal pathogens Porphyromonas gingivalis and Actinohacillus action-mycetemcomitans. The study comprised 100 periodontitis sites (pocket depths≥4 mm. GI = 3) from 10 patients with chronic adult periodontitis and 100 control sites (pocket depths <4 mm. GI<3) from 10 periodontally healthy patients comprising 55 healthy sites (pocket depths <4 mm. GI=0) and 45 gingivitis sites (pocket depths <4 mm, GI=1 or 2). The values for both BANA hydrolysis and AST levels were significantly higher in samples from periodontitis compared with gingivitis and healthy sites (p<0.001), A. actinomycetemcomitans was identified in 45% and P. gingivalis in 17% of periodontitis sites but neither pathogen was recovered from control sites and there was no significant correlation with (he clinical parameters measured. There was no significant relationship between the presence of P. gingivalis and/or A. actinmycetemcomitans with BANA hydrolysis or AST levels. A significant correlation (p=0.0017) was observed between BANA hydrolysis and pocket depth and between AST hydrolysis and the GI (p=0.01). This study failed to demonstrate a positive association between chairside analysis of GCF metabolites for AST levels and/or BANA hydrolysis with P. gingivalis and A. actinomycetemcomitans. However, the GCF metabolites had a significant correlation with periodontally diseased sites in patients with chronic adult periodontitis and may help confirm clinical observations.     

Comparison of clinical outcomes using a nickel titanium rotary or stainless steel hand file instrumentation technique

The purpose of this study was to evaluate the concept that novice clinicians could perform clinical endodontics better and more efficiently if the stainless steel hand file technique is replaced with a nickel titanium rotary file technique. In phase 1 of the study, every endodontic case performed by 2 groups was evaluated for total treatment time. In phase 2, the mesial roots of mandibular molars were evaluated for radiographic quality of completed obturation. The authors found that when the rotary file technique was substituted for the hand file technique, appointment time for case completion was significantly decreased (P<.001) and overall radiographic quality of mandibular molar mesial root obturation was significantly increased (P=.0009). These results support the hypothesis that novice clinicians can perform endodontic therapy more efficiently when using a nickel titanium rotary file technique. In addition, no differences were noted in the incidence of file fracture when using rotary instruments.     

Extended bleaching of tetracycline-stained teeth: a 5-year study

Bleaching tetracycline-stained teeth is the most challenging form of tooth lightening. This article reports on 44 subjects who bleached their tetracycline-stained teeth for 6 months using trays with reservoirs overnight in a half-mouth designed study and 2 of 3 different concentrations of carbamide peroxide (10%, 15% or 20%). The subjects were followed for 5 years. The area evaluated was the middle third of the teeth. More than 55% of tooth lightening occurred within 1 month; after 5 years, more than 65% of the maximum tooth whitening remained for all 3 gel concentrations. Tooth whitening can be accomplished with any of the 3 concentrations used.     

Outcome of direct restorations placed within the general dental services in England and Wales (Part 1): variation by type of restoration and re-intervention

AIM: It is the aim of this paper to consider the dental factors associated with the need for re-intervention on a restoration, such as the tooth position, size of cavity, and restoration material. METHODS: Patients whose data were included in this study were those whose birthdays were included within a set of randomly selected dates, one of which was chosen in each possible year of birth. The restoration records consisted of all those records containing directly placed restorations which related to courses of treatment of patients 18 years or older with last date on the claim form after 31st December 1990, and with date of acceptance after September 1990 and before January 2002. For each tooth treated with a direct restoration the subsequent history of intervention on that tooth was consulted, and the next date of intervention, if any could be found in the extended data set, was obtained. Thus a data set was created of direct restorations with their dates of placement and their dates, if any, of re-intervention. RESULTS: Data for over 80,000 different adult patients were analyzed, of whom 46% were male and 54% female. A total of 503,965 tooth restoration occasions were obtained from the data over a period of eleven years. Single surface amalgam restorations were found to have the longest survival --58% at 10 years, and glass ionomer the shortest 38% at 10 years. Factors which were found to reduce restoration outcome included involvement of the incisal angle in composite restorations--this resulted in a reduction in median survival of around two years--and the placement of pins in a restoration. The presence of a root filling was also found to reduce the survival of restorations in the crown of the root filled tooth. CONCLUSIONS: Small amalgam restorations have longer survival times before re-intervention than large amalgam restorations such as MOD. Composite and glass ionomer restorations perform less well than amalgam restorations. Pin placement and root filling reduce the survival time of restorations.     

New treatment protocols for avulsed teeth

Traumatized teeth present a clinical challenge with regard to their diagnosis, treatment plan and prognosis. The injuries to the permanent dentition include crown and root fractures, subluxations, luxations and tooth avulsion. Common complications are pulp necrosis, periapical pathosis and root resorption. This article will describe new clinical modalities for the treatment of avulsed teeth and discuss the rational for their use.     

Effect of four different opalescence tooth-whitening products on enamel microhardness

OBJECTIVES: The purpose was to evaluate the effect of various Opalescence tooth-whitening products on enamel. METHODS AND MATERIALS: Enamel blocks were exposed to Opalescence PF 10% Carbamide Peroxide (n = 10), Opalescence PF 20% Carbamide Peroxide (n = 10), Opalescence Trèswhite Supreme 10% Hydrogen Peroxide (n = 10) and Opalescence Quick PF 45% Carbamide Peroxide (n = 10) according to the manufacturer's instructions. The control group was enamel blocks (n = 10) kept in artificial saliva. The values were obtained before exposure and after the 14-days treatment period. Enamel blocks were kept in saliva between treatments. Indent marks on enamel blocks were examined using the scanning electron microscope for treatment effects. RESULTS: All four different Opalescence products damaged enamel. The most damage was done when treated for a long period (112 hours). SEM images also showed damage to enamel by all 4 products. Opalescence with 10% and with 20% Carbamide Peroxide showed the highest damage, which also differed significantly (p < 0.05) from the saliva control group (p < 0.05; Tukey-Kramer Multiple comparison test). CONCLUSION: All 4 Opalescence products damaged enamel. Higher damage was done by the 10% carbamide peroxide and 20% carbamide peroxide products because of the much longer exposure period (112 hours in comparison to 7 hours).     

Contraction stress related to degree of conversion and reaction kinetics

Polymerization shrinkage of composites bonded to cavity preparations generates stress on the tooth/restoration interface. The purpose of this study was to verify the influence of degree of conversion and speed of polymerization reaction on contraction stress. We prepared experimental composites with different curing rates by varying the concentration of inhibitor (butylated hydroxytoluene). We verified the effect of degree of conversion by submitting one of the composites to different photo-activation times. Contraction stress was monitored for 10 minutes in a tensilometer. Fourier-transformed infrared spectrometry was used for assessment of the degree of conversion. Volumetric shrinkage was determined by means of a mercury dilatometer. Degree of conversion and volumetric shrinkage showed a non-linear relationship with energy density. Degree of conversion showed a pronounced influence on stress. Increased inhibitor concentration reduced curing rate and contraction stress in composites, without compromising the final degree of conversion.