Biomedical subjects

J E Moorhead

Publications and source records attributed to J E Moorhead.

14 recordsLinked to original sources

PubMed2001

Middle ear prosthesis displacement in high-strength magnetic fields.

HYPOTHESIS: Middle ear prostheses made from nonmagnetic, magnetic resonance (MR)-compatible metals reportedly displace ex vivo in the presence of high magnetic fields used in MR imaging (MRI). The authors postulate that the prosthesis displacement seen with "nonmagnetic" MR-compatible prostheses ex vivo may not be clinically significant in vivo. METHODS: Middle ear prostheses made from ferromagnetic (420F stainless steel) and nonmagnetic MR-compatible metals (316L stainless steel and platinum) were examined for magnetic field interactions at 4.7 Tesla (T). Ex vivo testing consisted of measurements of the translational and rotational motion of the prosthesis induced by the static magnetic field. In vivo testing was assessed by implanting prostheses in cadaveric temporal bones and performing clinical MRI sequences. Prosthesis displacement was measured semiquantitatively. RESULTS: Angular deflection was observed in all samples made from nonmagnetic stainless steel. The negative control (platinum) demonstrated no deflection, and the positive controls (ferromagnetic stainless steel) deflected >90 degrees. Torque analysis showed movement in five of five nonmagnetic stainless steel prostheses. Prostheses made from nonmagnetic stainless steel remained in place without appreciable loosening in vivo after MRI. Prostheses made with known ferromagnetic properties were displaced at 4.7 T but not at 1.5 T. CONCLUSION: Middle ear prostheses made from low-magnetic stainless steel do move in the presence of high magnetic fields ex vivo; however, this does not appear to be clinically or statistically significant in vivo at 4.7 T. Magnetic resonance imaging should be undertaken with caution in individuals with prostheses made from stainless steel with strong ferromagnetic properties.

Electromagnetic Fields↗

PubMed2000

Age of restorations at replacement in permanent teeth in general dental practice.

The ages of 6,761 restorations replaced in permanent teeth, 6,088 in adults > or =19 years of age and 673 in adolescents < or =18 years, were available for analyses. The results showed that the median age of amalgam restorations in adults was 11 years and that of resin-based composite restorations 8 years. This difference in longevity was significant (P = 0.000 l). The median age of failed conventional glass ionomer restorations in adults was 4 years and for resin-modified glass ionomer 2 years. In adolescents, the median longevity of failed amalgam restorations was 5 years and that of composite restorations 3 years, while both types of glass ionomers had a median longevity of 2 years. The data were subdivided based on clinician gender and practice setting. The results showed that the median age of amalgam and composite restorations replaced Its male clinicians was higher than that for female clinicians irrespective of clinical setting. The median age of amalgam and composite restorations replaced by salaried dentists was significantly lower than that by private practitioners. Minor differences were noted in longevity of restorations between male and female patients. The age of replaced restorations was shortest for the group of clinicians with the least clinical experience and highest for those that graduated > or = 30 years ago.

Adolescent↗

PubMed2000

Reasons for replacement of restorations in permanent teeth in general dental practice.

OBJECTIVE: The analysis of reasons for the replacement of 9,805 amalgam, composite, glass ionomer, resin modified glass ionomer and 'other' restorations in permanent teeth in general dental practice. DESIGN: The data were subdivided on the bases of age and gender of the patients, the types of restorations and the clinicians' gender, experience and practice setting. RESULTS: The clinical diagnosis of secondary caries was the main reason for replacement of all types of restorations studied, followed by fracture of restorations, especially bulk fracture, irrespective of patient's age. Bulk discoloration was the third most common reason for replacement of resin based materials in adults, but it rarely occurred in adolescents 18 years and younger. The reasons for replacement of restorations were not associated with the gender of the patients. Subgroupings based on the clinicians' gender showed that female clinicians diagnosed secondary caries more often than male clinicians. Otherwise, the reasons for replacements were similar for both genders of clinicians. Subdivision of restorations based on the years since graduation of the clinicians resulted in small groups. The youngest group of clinicians diagnosed relatively more secondary caries both for amalgam and composite restorations than the most experienced group. CONCLUSION: The clinical diagnosis secondary caries was the main reason for replacement of all types of restorations studied.

Adolescent↗

PubMed1999

An algometer for intraoral pain tolerance measurements.

An algometer was developed to provide a variable probing force (0-200 g force) which could be used intraorally. This algometer consisted of an autoclavable probe handpiece attached to an optical encoder, which recorded probing force to a computer when a button was pressed. The probe handpiece included a 0.40 mm diameter hemispherical tip which was placed in contact with the experimental site. The probe tip was pressed against the tissue with increasing force until the subject pressed the button, at which point the pain tolerance (PT) value was recorded by the computer. Intraoral soft tissue, PT values were obtained from nine healthy adult subjects during 6 weekly visits to determine the reproducibility of PT measurements. Five gingival sulcus sites and three gingival surface sites, all adjacent to the maxillary premolars constituted the experimental area. The reproducibility of PT values using the force stimulus from the algometer was evaluated using interclass correlation coefficients (R) for each of the eight sites. Visits 1 and 2 were training and calibration visits. Visits 3 through 6 were experimental visits. The R values ranged from 0.40 to 0.79 when data from all six visits were included. R values for Visits 3 through 6 were 0.63-0.97 indicating good to excellent correlation after subjects became familiar with the procedure. A complete repeated measures analysis of variance (ANOVA) showed no significant interaction between site and visit. Duncan's multiple range test was used to compare sensitivity across the eight sites. The results indicated that the three most anterior sites were significantly (P < 0.05) more sensitive than four of the posterior sites. When the sites were grouped into: (1) gingival surface sites; (2) mid-facial sulcus sites; and (3) interproximal sulcus sites, no significant differences were found in their PT values. The algometer is well suited for intraoral investigations because of its precision, computerized data entry and easily positioned, autoclavable handpiece. This new algometer may be useful for sensory and pain studies for other parts of the body.

Adult↗

PubMed1999

Selection of restorative materials in permanent teeth in general dental practice.

In this study, we recorded the type of restoration and the materials used in 24,429 restorations in permanent teeth by 243 Norwegian clinicians in general practice. Demographic information included patient's gender and age, and clinician's gender, years since graduation, and practice setting (private or salaried). The overall recorded use of restorative materials in permanent teeth shows that 32% are amalgams, just over 40% composites, and about 25% glass ionomer type materials. Three percent are "other" materials. A marked shift away from amalgam restorations is noted both in the clinician's estimated use during the last 2 decades and by comparing the present use of materials with that in failed restorations. Tooth-colored materials are more commonly used in adolescents, especially glass ionomer materials, and in female patients. In patients < or = 18 years, amalgam is used in 25% of all restorations. The use of amalgam is similar in private practice and in public health service practice, but private practitioners use more composites and salaried dentists more glass ionomers. The clinician's gender does not have any effect on the selection of restorative materials. The change from amalgam to tooth-colored material is particularly noticeable for Class I and Class V restorations. Amalgam is the predominant material in 2- and 3-surface Class II restorations.

Adolescent↗

PubMed1998

Pain threshold values during periodontal probing: assessment of maxillary incisor and molar sites.

Probing pain threshold (PPT) assessments were conducted in the facial and oral sulci of maxillary central incisors and first molars of 10 periodontally healthy adults. All subjects were systemically healthy, free of pain, and reported no current medication usage. A computer-linked electronic probe, modified to deliver steadily increasing forces up to 200 grams, was used to collect the data. The system contained a subject operated "off-switch" which, upon activation, signaled the computer to record the subject's PPT. Assessments of each subject's PPTs were conducted on 3 separate occasions at 7-day intervals. Results indicated that the facial sulci of the incisors were the most pain sensitive. They displayed a mean PPT of 50.9 +/- 26.6 grams. The oral sulci of the incisors exhibited a mean PPT of 76.5 +/- 45.2 grams. Facial and oral sulci of the molars evidenced mean PPT values of 102.6 +/- 52.1 grams and 113.5 +/- 51.3 grams, respectively. These data suggest that sulci associated with incisor teeth are nearly twice as pain sensitive as sulci associated with molar teeth. In addition, facial sulci are significantly more pain sensitive than oral sulci. Data did not indicate a visit effect nor a side-of-mouth effect on PPT values.

Adult↗

PubMed1998

Selection of restorative materials, reasons for replacement, and longevity of restorations in Florida.

The purpose of the present study was to obtain information relating to the types of restorative materials used, the main reason for replacement of restorations, and the age of failed restorations. Dentists in general dental practice in Florida were invited to record details from their own work pertaining to restorations. The diagnostic criteria were described and coded. The clinicians were not calibrated in the use of the criteria but they could call in for further explanation if needed. The 27 clinicians involved placed 2,035 restorations of which 53% were replacements of failed restorations. The increased use of resin based restorative material was clearly evident including posterior composites. The clinical diagnosis secondary caries was the most common reason for replacement of amalgam (56%) and composite (59%) restorations. Only discoloration showed a statistically significant difference in the reason for replacement of the two types of materials. The median age of the replaced amalgam restoration was 15 years and that of composite restoration was 8 years.

Adolescent↗

PubMed1994

Guidelines for experimental studies.

OBJECTIVES: The purpose of this document is to present guidelines for the training of researchers and for the planning of experiments that ensure optimum interaction and communication among the investigators and statisticians of the research team. METHODS: The protocol described in this document is designed to systematically guide a researcher through a sequence of planning steps and checkpoints to ensure proper experimental design, data management, statistical analyses, and interpretation. RESULTS: The investigator and the statistician, as a collaborative team, will be able to determine the most effective and appropriate procedures and tools necessary for the successful completion of a research project. SIGNIFICANCE: Planning an experimental study necessitates much thought. Lack of essential communication with a statistician in the initial stages of the experimental design can doom the experiment to failure. Flawed research studies may be associated with one or more of the following: failure of the established testable hypothesis, uncontrolled biases, insufficient sample size, lack of appropriate controls, variability in specimen preparation, improper calibration of instruments or standardization of measurements, incorrect data entries, inappropriate statistical analyses, errors in interpretation of statistical analyses, and erroneously drawn conclusions. Standard guidelines will eliminate many of these potential problems.

Data Collection↗

PubMed1994

Influence of colorants on crystallization and mechanical properties of lithia-based glass-ceramics.

OBJECTIVES: The objective of the present study was to test the hypothesis that colorants such as AgNO3 and FeCl3 act as conucleating agents with P2O5 in the Li2O-Al2O3-CaO-SiO2 system and that the addition of either colorant and P2O5 produces a greater effect on crystallization and selected mechanical properties than the use of P2O5 alone. METHODS: Microstructural effects were observed by SEM and optical microscopy. Mechanical properties were determined to monitor the effects of structural changes after crystallization. These include controlled-flaw flexure strength, fracture toughness (KIC), and Vickers hardness (VHN). RESULTS: Based on a glass composition of 27.84 mol% Li2O, 2.45 mol% Al2O3, 5.88 mol% CaO, and 63.84 mol% SiO2 (LACS), the mechanical properties of LACS glass-ceramics were influenced by P2O5, the colorant type, and the colorant concentration. The mean strength of the glass-ceramic disks without P2O5 increased with AgNO3 concentration to a peak value of 188 MPa at a concentration of 0.78 mmol%. The maximum value of controlled-flaw flexure strength increased from 120 MPa for one of the FeCl3 groups to 188 MPa for one of the AgNO3 groups. The maximum fracture toughness of glass-ceramic disks without P2O5 (2.45 MPa.m1/2) was associated with a AgNO3 concentration of 0.58 mmol%. This value was significantly greater (p < 0.05) than that of the corresponding group (1.90 MPa.m1/2) which also contained P2O5. There was no significant change in KIC of glass-ceramic specimens containing P2O5 as the AgNO3 concentration increased. The increase in controlled-flaw flexure strength and fracture toughness of specimen groups containing 0.58 to 0.78 mmol% AgNO3 support its use as a colorant and as a nucleating agent in LACS glass-ceramics. SIGNIFICANCE: The development of tougher, higher strength glass-ceramics can be controlled by the use of colorants that are also effective as nucleating agents. Although certain colorants are believed to act synergistically when used in combination with known nucleating agents to enhance the fracture toughness of glass-ceramics, this effect was not observed in this study for the combined use of AgNO3 and the classical nucleating agent, P2O5. In fact, the colorant used in this study (AgNO3) was more effective than P2O5 as a nucleating agent for lithia-based glass-ceramics.

Ceramics↗

PubMed1994

Influence of P205, AgNO3, and FeCl3 on color and translucency of lithia-based glass-ceramics.

OBJECTIVES: The objective of this study was to characterize the influence of various metals, metal compounds, and P2O5 as a nucleating agent on the color and translucency of a Li2O-Al2O3-CaO-SiO2 glass-ceramic. METHODS: Glass frits of Li2O-Al2O3-CaO-SiO2 (LACS), LACS with 1 mol% P2O5 (LACSP), and/or LACS with one of 16 colorants were melted, poured into a cylindrical graphite mold, cut into disks, annealed, nucleated, crystallized, and annealed again. Ten translucency measurements of each of five disks were made using a tristimulus colorimeter and a D65 standard CIE illuminant. The color of each disk was analyzed using the CIE L*a*b* color space system (1976) as a function of colorant, colorant concentration, and P2O5. RESULTS: Mean L* values of glass-ceramic disks ranged from 63.5 for LACS containing 6.2 mmol% FeCl3 (LACSP-6.2Fe) to 84.1 for LACS. No significant difference (p > 0.05) was found between the mean L* values for LACS, LACSP, and LACS with 0.19 mmol% AgNO3 (LACS-0.19Ag). The mean contrast ratio of glass-ceramic specimens ranged from 0.42 (LACS and LACS-1.0Fe) to 0.98 (LACS-0.78Ag). Mean color difference values varied from 5.8 (LACSP-1.0Fe vs. LACS) to 36.3 (LACSP-0.78Ag vs. LACSP). SIGNIFICANCE: The results of this study indicate that, because certain colorants in glass-ceramics affect opacity as well as hue and chroma, the development of glass-ceramics should be simplified by: 1) employing a nucleating agent that does not affect hue or chroma significantly, 2) controlling fixed levels of translucency consistent with mechanical and physical property requirements, and 3) varying the hue and chroma by means of colorants that do not affect the crystallization process. This implies that the volume fraction and mean size of crystals must be controlled, since the translucency or opacity of glass-ceramics is associated with scattering of light at the interfaces between adjacent crystals, and between crystals and the glass phase because of differences in refractive indices (McMillan, 1979a).

Analysis of Variance↗

PubMed1994

Results from a three-year caries clinical trial comparing NaF and SMFP fluoride formulations.

A three-year, double blind, randomised clinical trial was conducted in Polk County, Florida from 1983-1987. The objective was to compare the effect of four dose levels of sodium monofluorophosphate (SMFP) and a single dose level of sodium fluoride (NaF) on DMFS, DMFT, and DFS Interproximal indices. A total of 8,027 children were examined clinically and radiographically at baseline, and 5,474 children completed the three-year study, which included daily supervised brushing at school. No differences existed at baseline between the five study cells on age or gender distribution, or on any of the dental indices. Results indicated that the 2000 ppm F NaF group had significantly smaller DMFS increment than the 2000 ppm F SMFP group p < 0.005. The 2000 ppm F NaF group demonstrated an 18 per cent (26 per cent for children > 10 years at baseline) reduction in DMFS over the 1500 ppm F SMFP group, the 2500 ppm F group a 15 per cent (19 per cent) reduction, and the 2000 ppm F SMFP a 5 per cent (9 per cent) reduction. Results are strongest in children at greatest risk--older children with previous caries. This study concludes that the anticaries efficacy of SMFP dentifrices rises with increasing fluoride, and that the anticaries efficacy of a 2000 ppm NaF dentifrice is superior to that of a 2000 ppm F SMFP dentifrice, p < 0.005).

Adolescent↗

PubMed1992

A fluoride dose-response evaluation in an anticaries clinical trial.

This study evaluated the dose-response relationship between four increasing levels of fluoride from 1000 to 2500 ppm F as sodium monofluorophosphate (MFP) and three-year dental caries increments, as measured by DMFS, DMFT, and DFS-A on 4424 schoolchildren. The results indicated consistent linear decreases in all three dental indices as the dose level increased to 2500 ppm F MFP, with slopes (average reductions) of 0.32 in DMFS for an increase of 1000 ppm F, 0.13 in DMFT, and 0.17 in DFS-A when all children were evaluated, p less than 0.03 for each index. For children 11 years and older at baseline, the slopes quadrupled, p less than 0.01 for each index. Age and baseline DMFS were shown to be the most important covariates to control for in the statistical models. No differences in adverse reactions, or other safety problems, were observed at the different dose levels.

Acidulated Phosphate Fluoride↗

PubMed1991

The effect of supervised brushing on caries inhibition in school age children.

A supervised brushing program was incorporated into a three-year caries clinical trial whose primary objective was to compare the efficacy between two fluoride levels of a dentifrice (1,000 and 1,500 ppm F MFP). For each of the 2,415 children completing the three-year study, the total number of supervised brushing sessions completed was available. Results indicated that children who complied well with the supervised brushing program by participating in at least 70% of the sessions had a significantly lower caries increment in both fluoride levels (p less than .001) than children who did not comply as well. After adjusting for age, sex, and baseline DMFS of the children, as well as the fluoride level received, a multiple regression model showed that supervised brushing further reduced the three year caries increment (p less than .04). The more frequent use of the higher fluoride dentifrice affords the greatest prevention of decay. The conclusion from this study is that compliance with the supervised brushing program resulted in a reduced caries increment regardless of the level of fluoride in the dentifrice.

Adolescent↗

PubMedDate not supplied

Amalgam restorations: postoperative sensitivity as a function of liner treatment and cavity depth.

The purpose of this clinical study was to assess the sensitivity reported by patients following the insertion of class 1 or class 2 amalgam restorations in the treatment of primary carious lesions of different depths. Ninety subjects with previously untreated teeth requiring restorations due to caries lesions were selected: 32 teeth had lesions that were clinically and radiographically judged to be located in the outer one-third of dentin, 30 were located in the middle one-third of dentin, and 28 were located in the inner one-third of dentin. Four different lining regimens were employed: Group 1--no linear; Group 2--two coats of Copalite liner; Group 3--a dentin adhesive resin liner (Scotchbond Multi-Purpose); Group 4--a resin-modified glass ionomer (Fuji Bond LC). Patients were contacted on days 2 and 7 postoperatively and questioned regarding the presence or absence of sensitivity, the stimuli that created the sensitivity, if any, the duration of any sensitivity, and the intensity of any sensitivity using a rating from None to Severe. If sensitivity was experienced on day 7, patients were also contacted on days 14, 30, and 90 to assess the sensitivity at those intervals. The chi-square test of independence showed no significance at the 0.05 level between the different dentin treatments and cavity depths. By day 2, 19% of lesions located in the outer one-third, 27% of lesions located in the middle one-third, and 29% of lesions located in the inner one-third of dentin were sensitive. On day 30, four teeth were still sensitive, two located in the middle one-third and two located in the outer one-third of dentin. On day 90 all teeth were without sensitivity.

Adolescent↗