Clinical decision making on extensive molar restorations.

SUMMARY Extensive loss of posterior tooth substance, which traditionally was restored with amalgam or indirect restorations, is more commonly being restored with resin-based composite restorations. Using a questionnaire, we aimed to survey dentists' clinical decision making when restoring extensive defects in posterior molar teeth. The questionnaire, which included questions on background information from the dentists, clinical cases with treatment options, and general questions about restoring extensive posterior defects, was sent to 476 dentists. The response rate was 59%. Multiple logistic regressions were used to investigate the different associations. Most of the respondents preferred a direct composite restoration when one cusp was missing, while indirect restorations were most preferred when replacing three or four cusps. Younger dentists and dentists working in the private sector had a greater tendency to choose an indirect technique compared with older colleagues. Generally, the most important influencing factor in clinical decision making was the amount of remaining tooth substance. Factors that appeared to be less important were dental advertisements, use of fluoride, and dietary habits. Female dentists perceived factors such as oral hygiene, patient requests, and economy to be more important than did their male colleagues.

Development of a femoral stem providing strong anchorage and facilitated removal. An experimental study in goats.

OBJECTIVE: Prosthetic elements must be securely anchored to bone. Should revision surgery be necessary, preservation of bone stock is crucial. The goal of this study was to develop and assess a femoral stem combining secure anchorage and facilitated removal in a goat model. METHODS: The development of the uncemented femoral stem was part of an innovation process to fulfill the combined requirements. The stem was designed with two longitudinal semicircular grooves to accommodate a drill bit to unanchor the stem. These grooves were interconnected by canals, each 1 mm in diameter. The surface was partly coated with hydroxyapatite (HA). The stems were inserted in the left hip of 35 goats. Perioperatively, the grooves were filled with autologous bone grafts, and standard cemented canine acetabular component and head were used. The pull-out force was measured six months postoperatively. Following randomization, 11 animals had the grooves of the stem drilled to remove anchoring tissue. Twelve animals were left undrilled (controls). RESULTS: There was a significant difference in mean pull-out force between the group that had been drilled (1526 N) compared with the controls (2033 N, p = 0.028). Most of the HA had been resorbed. CLINICAL SIGNIFICANCE: The stems had a high retention force. The procedure for un-anchoring by drilling significantly reduced the pull-out force.

Mapping of titanium particles in peri-implant oral mucosa by laser ablation inductively coupled plasma mass spectrometry and high-resolution optical darkfield microscopy.

The present study examines the quantity, size, element signatures and distribution of titanium particles in normal oral mucosal tissue and in oral mucosa exposed to a titanium implant. Tissue samples from six healthy patients were obtained by a full thickness biopsy taken from the edge of the oral mucosa when inserting a titanium dental implant. At the abutment insertion 6 months later, a punch test biopsy of oral mucosa was taken over the implant site. Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS) is a sensitive and specific multi-element microanalytical technique that demonstrated the presence of Ti particles in the tissue adjacent to implant cover-screws. The epithelial part of the control samples revealed more particles than the corresponding area of the test samples, consisting partly of newly formed scar tissue. High-Resolution Optical Darkfield Microscope (HR-ODM) confirmed the presence of particles in both the control and the test samples. The combination of LA-ICP-MS and HR-ODM appears to be a powerful combination for detection of particles in oral tissues; optical microscopy provides an overview with histological references, whereas LA-ICP-MS identifies the chemical composition.

Hip fracture implants increase serum metal levels.

OBJECTIVE: Hip fractures are disabling accidents in the elderly. The purpose of this prospective study was to investigate systemic exposure to metals from hip implants used for fracture fixation. MATERIAL AND METHODS: Serum levels of Cr, Ni and Mo in patients with compression hip screws (n = 22) or cervical fracture screws (n = 23) were measured by inductively coupled plasma mass spectrometry. Blood samples were collected before surgery and at 3 and 12 months postoperatively. RESULTS: At 3 months, patients with compression hip screws showed higher concentrations of Cr and Ni than did those with cervical screws. Both types of screws led to a 2-fold increase in serum Mo, which was not expected for the freestanding cervical screws. After 12 months, the levels had decreased, but the compression hip screw was still associated with higher values for Cr and Mo. CONCLUSIONS: The difference between the screws is most likely due to the potential for fretting and crevice corrosion between components in the compression hip screws. The apparent short-term systemic elevation of stainless steel elements in patients with hip screws does not support routine removal of asymptomatic hip fracture implants.

Nickel contamination from an intravenous catheter used for infusion.

At the outset of a clinical research project involving metal analyses on patients receiving metal devices in conjunction with hip fractures, unexpected high concentrations of nickel were discovered in serum samples taken before surgery. The median nickel concentration in 30 patients was 4.6 microg/l (highest 19.5 microg/l), while reference values in non-exposed persons are reported to be 0.05-1.2 microg/l. The sampling and analyzing procedures were scrutinized without positive identification of the source of contamination. A review of all relevant procedures was then undertaken. It was identified that the nickel contamination originated from the intravenous catheter which was always put in place immediately after the patient's admission to the hospital, and thus before the blood sampling. Close inspection of the intravenous catheter revealed that it contained a nickel-plated brass funnel inside the hub of the device which released nickel into the Ringer-acetate passing through the catheter. The present catheter has been the standard device used at Haukeland University Hospital for the past 6 years. Patients have consequently been exposed to small amounts of nickel. The clinical relevance of the exposure cannot be determined. For the patients included in the research project, a metal-free alternative was used. These findings show that the quality and properties of everyday medical devices should be scrutinized, at least before being used for special purposes.

Metal fragment in the temporomandibular joint: a case report.

A 56-year-old woman was referred for severe pain and restricted jaw movements with a duration of more than 10 years. In the early 1990s a discectomy on the left side had been performed where the disc was extirpated and replaced with a polymeric implant. Due to infection and pain the implant was removed about 2 months later. In the 10-year period thereafter she suffered pain from the joint, pain from the left ear, tinnitus and restricted mouth opening.A computer tomography scan revealed a foreign body, approximately 4mm in size, situated in the medial part of the glenoid fossa. The metallic foreign body was surgically removed. The pain from her left temporomandibular joint decreased and the mouth opening capacity increased. Patch-testing showed that the patient had a potential for contact allergy to nickel, chromium and cobalt. The foreign body was most probably a fractured tip of a surgical awl. Energy dispersive X-ray analysis revealed that the fragment consisted of iron and chromium. The instrument fragment could have caused the symptoms either by an allergic reaction or a direct mechanical effect.

Memory functions in persons with dental amalgam.

Memory and psychophysiological variables in persons with self-reported reactions to dental amalgam (amalgam patients: N=26) and in persons without such symptoms (controls: N=21) were compared. The groups were matched regarding age, education, and amount of amalgam. Wechsler Memory Scale-Revised was obtained for all subjects and compared to amalgam points in a dose-response design. The results demonstrated that amalgam patients function on the same level as the controls regarding memory variables, attention, concentration, and delayed recall. Psychophysiological measures of skin conductance as correlates of attention and basal memory functions, were compared in the two groups. No differences between the two groups were observed and no correlation between memory variables and exposure to amalgam could be detected.

Dental amalgam and selenium in blood.

It has been suggested that selenium (Se) exhibits protective effects against mercury (Hg) toxicity in humans due to formation of a Hg-Se complex bound to selenoprotein P in blood. The aim of the present study was to investigate Se concentrations in persons who had been examined with respect to general health problems associated with dental amalgam fillings. The Se concentrations were determined in whole-blood samples of 80 individuals by hydride generation atomic absorption spectrometry. The subjects comprised two main groups: 21 healthy controls with amalgam fillings and 20 patients who claimed symptoms from existing amalgam fillings. The median concentration of Se in blood (119.2 microg/L) was statistically significantly lower in subjects who claimed symptoms of mercury amalgam illness than in healthy subjects with amalgam (130.3 microg/L). The difference was more evident in individuals with more than 35 amalgam surfaces (P=0.003). Additional control groups without amalgam fillings comprised 19 healthy controls without amalgam experience and 20 subjects who have had amalgam fillings removed due to suspected symptoms associated with amalgam. The Se concentrations in these groups were not different from those with amalgam. It is indicated that persons with ill health self-related to dental amalgam might have a Se metabolism different from that of healthy people.

Intramedullary nailing in humeral shaft fractures. Mechanical behavior in vitro after osteosynthesis with three different intramedullary nails.

The aim of this in vitro study was to compare the mechanical behavior of fixation by the Russell-Taylor nail with the more recent Polarus nail. Fixation with an experimental nail made from polyacetal polymer was also included in the study. Thirty humeri were fractured and randomized to receive one of the three nail types. A four-point nondestructive bending test was performed, as well as torsional testing to failure. The torsional test was designed to record the amount of 'play' (uncontrolled rotation) in the bone/implant construct. The Polarus nail gave higher rigidity of the nail/bone construct than the two other types. The Russell-Taylor nailing exhibited a high degree of 'play' (uncontrolled rotation). The polyacetal nails allowed a large elastic deformation before failure.

Diagnostic value of a chelating agent in patients with symptoms allegedly caused by amalgam fillings.

The chelating agent 2,3 dimercaptopropane-1-sulfonate (DMPS) has been used in a mercury mobilization test for diagnoses in illnesses allegedly associated with the presence of amalgam restorations. DMPS is an accepted antidote to heavy metal poisoning. The aim of the present study was to evaluate the diagnostic value of DMPS in patients with symptoms self-related to their amalgam fillings. The subjects consisted of four groups: 19 healthy controls without amalgam experience; 21 healthy controls with amalgam fillings; 20 patients who claimed symptoms of "mercury poisoning" from dental amalgam; and 20 patients who had amalgam fillings removed because of such symptoms. DMPS (2 mg/kg body weight) was injected intravenously, and urine was collected prior to the injection, 30 and 120 min after the injection, and throughout the next 22 hrs. The samples were analyzed for total mercury by cold vapor atomic absorption spectrophotometry. The total median amounts of mercury excreted over 24 hrs for those with complaints allegedly associated with amalgam and for the healthy controls with amalgam fillings were similar. Persons with amalgam fillings excreted about three times more mercury than those without. The controls, who had never had amalgam fillings, and the subjects who had had their fillings removed excreted median amounts of 8.5 microg and 7.2 microg mercury, respectively. The present DMPS challenge test did not differentiate between patients with or those without complaints self-related to their amalgam fillings but did confirm the higher mercury values in patients with dental amalgam.

Dental gold alloys and contact hypersensitivity.

A total of 172 patients referred to the Norwegian National Adverse Reaction Group were patch-tested with a dental series. Of these, 25% showed a positive reaction to gold sodium thiosulfate or potassium dicyanoaurate. There was a statistically significant correlation (p=0.0019) between the presence of dental gold and a positive patch test to gold. There was a statistically significant correlation between ear piercing and a positive patch test to gold (p=0.04). In most cases, we did not find clinical correlates to positive patch tests to gold. 2 patients with objective and subjective oral/perioral and general symptoms are described as case reports. Their symptoms disappeared when gold restorations were removed. We conclude that there is an overrepresentation of gold allergies among those with dental restorations containing gold.

In vitro lymphocyte reactivity to gold compounds in the diagnosis of contact hypersensitivity.

The use of the lymphocyte transformation test (LTT) in the diagnosis of contact hypersensitivity to gold was studied in 8 patients who had positive patch tests to gold salts, and in 8 control subjects who were negative to such patch tests. Gold sodium thiosulfate and gold chloride were added to cultures of lymphocytes, which were labeled by 3H-thymidine after 96 h. The lymphocyte stimulation index was calculated as the beta-counts in stimulated cultures divided by those in control cultures. The index was statistically significantly higher for the patient group (p=0.005-0.04) than for the control group. Levels of interferon-gamma (IFN-gamma) were determined for the supernatants of the lymphocyte cultures. An index IFN-gamma, which is defined as the level of IFN-gamma in stimulated cultures divided by that in control cultures, was statistically significantly higher for the patient group (p=0.01-0.006). The LTT stimulation index showed specificity and sensitivity between 67 and 80%, the respective values for Index IFN-gamma being between 73 and 100% when the patch test was used as a reference method. Evaluation of lymphocyte reactivity might be of future interest in the diagnosis of allergic reactions to gold if the sensitivity and specificity can be improved.

Mercury and silver in saliva from subjects with symptoms self-related to amalgam fillings.

The amount of mercury released into saliva from dental amalgam fillings is currently being debated. Mercury enters saliva as vapor, ions and particles of amalgam. The aim of the present study was to determine mercury and silver concentrations in saliva of persons with amalgam fillings. Moreover, it was the aim to investigate whether amalgam particles were present in samples of stimulated saliva in control subjects. In that case, we also wanted to determine the influence of these particles on the mercury concentrations found. Fifty-three patients with a wide range of complaints self-related to their amalgam fillings were examined by the Dental Biomaterials Adverse Reaction Unit of Norway. Among other tests, stimulated saliva was collected from each patient and analyzed for mercury and silver. Mercury and silver correlated with the amount of amalgam present. There was a strong correlation between mercury and silver concentrations. Amalgam particles were found by energy dispersive X-ray analysis. It appears that a considerable part of the mercury and silver were present as amalgam particles. The present study shows that amalgam particles in saliva have to be controlled for when analyzing mercury in saliva from subjects with amalgam fillings.

Vascular and structural changes in rat femora following nailing and intramedullary occlusion.

The purpose of this study was to evaluate biomechanical, structural, and blood flow changes of the femoral canal in rats 12 weeks after intramedullary reaming, nailing, or occlusion. In one group, reaming alone was performed. In a second group, reaming was followed by use of a tight-fit steel nail. In a third group, reaming was followed by use of inert silicone that totally plugged the medullary cavity. A fourth group served as the control. The acute mechanical and vascular effects caused by reaming and nailing were determined in a separate group. Reaming and nail insertion reduced blood flow in femoral bone to about one-third. Reaming reduced bending moment by approximately 40%, whereas bending rigidity was unchanged. After 12 weeks, the cortical bone blood flow was significantly increased in both the nailed and the silicone-plugged bones compared with the reamed and control groups. The bending moment and energy absorption in the silicone group were inferior to those of the other groups. There were no differences in either the external or internal diameter or the medullary and net bone areas. In the silicone group, both the number and the area of large pores (larger than 10 microm) significantly increased in comparison with the other groups; hence, bone porosity was increased. This increment was confined to large pores. It is concluded that medullary occlusion contributes to structural and blood flow changes in bone.

[Mercury and dental amalgam fillings]. / Kvikksølv og amalgamfyllinger.

During 1993-95 a total of 169 patients (112 women, 57 men) with a wide range of complaints associated with earlier or present amalgam fillings were seen by the "Dental Biomaterials Adverse Reaction Unit" in Norway. Most patients had amalgam fillings; 19 had removed all amalgam, and 14 were in the process of replacing the amalgam fillings with other materials. Predominant symptoms were of a subjective and general nature (96% of the patients). Muscle and joint pain, headache, dizziness and feeling exhausted comprised the most common symptoms. Intra-oral pathology was observed in 48%. There was a correlation between the amount of amalgam ("amalgam score") and urinary mercury. Those without amalgam fillings and significantly lower values (median = 1.6 micrograms mercury/g creatinine) than those with amalgam fillings (medians: with amalgam = 3.5 micrograms/g; with partial removal of amalgam = 2.7 micrograms/g). Overall, in the present group of patients, no statistically significant correlation seemed to exist between the type and number of subjective symptoms or objective findings and the urinary mercury. This would indicate therefore that there is no straightforward association between urinary mercury and symptoms in the present group of patients.

Mechanical effects of different localization of the point of entry in femoral nailing.

Twenty pairs of human femora were reamed alternatively on the right or left side, with the opposite side serving as the unreamed control. The fossa piriformis (group I) or tip of the greater trochanter (group II) were chosen for introduction of the intramedullary reamer (Howmedica type). The femora were tested in vertical compression in a MTS mechanical testing machine until failure. In group I, all femora fractured through the entry portal. This happened in only 3 out of 10 in group II, where 7 fractured through the medial part of the femoral neck remote from the portal. The difference is statistically significant. Reduction in strength between the unreamed control side and the reamed femur was median 1486 (23%) in group I and 506 N (11%) in group II. Reduction in energy absorption between the control side and reamed side was median 9786 Nm (44.5%) in group I and 1142 Nm (10.5%) in group II. The difference in energy absorption reduction between groups I and II was statistically significant (P = 0.04). We conclude that reaming through an entry point (portal) in the piriformis fossa weakens the femoral neck and creates a localizing point for fracture.

Assessment of uncertainty in mechanical testing of dental materials.

A generally valid and commonly accepted model for assessing the reliability of measurements in the field of medical and dental materials is hard to establish. The results obtained in different laboratories sometimes are difficult to compare. We therefore discuss different assessors of the quality of measurements from both conceptual and operational perspectives. Especially addressed are the customary terms accuracy, error and uncertainty, these terms that often are mixed rather confusingly in expressing the quality of experiments. The aim of this work is to present the advantages of choosing uncertainty rather than error as the appropriate assessor of the reliability of measurements. The transverse deflection testing of four denture-base acrylic resins served as an experimental basis for the analysis.

Hardness, strength, and ductility of prefabricated titanium rods used in the manufacture of spark erosion crowns.

Depending on the size of the prepared tooth spark eroded and milled, Procera crowns (Nobelpharma AB, Göteborg, Sweden) are manufactured from one of five diameters of pure titanium rods. In this study microindentation hardness tests were performed on the outer 400 microns and center of 10 samples for each type of rod. Five tensile samples were also machined for each of the diameters and tested in tension in a universal testing machine. Cast titanium samples were similarly prepared and tested. Some significant differences in hardness and considerable differences in strength and ductility were identified between the prefabricated rods. In comparison, cast titanium was significantly harder and stronger but less ductile.

Biologic testing of leachable aromatic compounds from denture base materials.

The aromatic compounds phenyl benzoate (PB), phenyl salicylate (PS), and biphenyl (BP), which have previously been found to leach from poly(methyl methacrylate) denture base materials, were tested for cytotoxicity and biologic effects by L929 cells in culture. The octanol-water partition coefficient (log P(ow), a descriptor for the lipophilicity, was determined for the compounds. Cytotoxicity was evaluated by total cell growth and the plating efficiency test, and biologic effects by the total fatty acid composition of L929 cells. The commonly used tests, total cell growth and plating efficiency, did not show any significant changes of the cells due to the compounds. On the other hand, BP and PS, in particular, induced changes in the total fatty acid composition of L929 cells. The problem of bioavailability of aromatic compounds in cell culture assays and the relation to lipophilicity was addressed.

Fatty acid composition of palatal tissue from denture stomatitis patients.

Palatal biopsy specimens were obtained from patients with denture stomatitis. The fatty acids were extracted from the tissue, then separated, identified, and quantified by a gas-chromatographic technique. The sensitivity of this method enabled analyses of specimens with a wet weight of less than 1 mg. The concentration of the fatty acids C16:1 (n-7) and C24:1 (n-9) differed significantly between samples from hyperplastic and clinically healthy tissue in the denture stomatitis patients. By comparing specimens from denture stomatitis patients and non-denture subjects, the concentration of seven fatty acids, two saturated and five unsaturated, was found to be significantly different. A multivariate data-analytical method distinguished between the fatty acid composition in specimens from denture stomatitis patients and from non-denture subjects.