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PubMed1999

Subsidized dental care associated with lower mutans streptococci count in male industrial workers.

Salivary mutans streptococci count, dental status, and related factors were studied in male industrial workers (age 38-65 years) with or without access to subsidized dental care. Altogether 315 subsidized workers and 168 controls without subsidy were compared. A prior questionnaire survey had shown that the two study groups were similar in age, oral self-care habits, and socio-environmental factors. In the present study, the mean number of carious teeth was significantly lower in the subsidized group (0.4, SD 1.2) than in the control group (1.7, SD 3.2) (P< 0.001). Otherwise the study groups had similar dental status. A total of 92% subsidized employees had visited a dentist within the past 2 years, while 82% in the control group had done so (P< 0.01). According to the trend test, men in the subsidized group tended to have a lower mutans streptococci count than the control employees (P< 0.01). The logistic regression showed that the probability of having one or more carious tooth was significantly negatively associated with subsidized care and positively associated with high mutans streptococci count. It is concluded that subsidized dental care leading to a smaller number of untreated carious teeth might result in decreased levels of mutans streptococci.

Adult↗

PubMedDate not supplied

Subsidence of an uncemented canine femoral stem.

Factors contributing to subsidence were analyzed by radiographic evaluation and mechanical testing of 36 canine cadaver femora during and after insertion of an uncemented porous-coated femoral stem and by radiographic evaluation of 35 canine total hip arthroplasties. Mean percentage of canal fill in immediate postoperative radiographs, and percentage of canal fill at midimplant and distal implant locations, were accurate predictors of subsidence. Force required to implant the femoral stem was strongly correlated with force required for implant subsidence. Femoral morphology and percentage of canal fill at the middle and distal sites were accurate predictors of subsidence. Implants in femora with a stovepipe morphology (canal flare index less than or equal to 1.8) were six times more likely to subside than implants in femora that had a normal appearance (canal flare index 1.8 to 2.5), and 72 times more likely to subside than implants in champagne-fluted femora (canal flare index greater than or equal to 2.5). Femora with more than 85% mean, middle, or distal canal fill were less likely to subside.

Animals↗

PubMed2001

Effects of neck movements on stability and subsidence in cervical interbody fusion: an in vitro study.

OBJECT: The aim of this in vitro study was to determine the influence of simulated postoperative neck movements on the stabilizing effect and subsidence of four different anterior cervical interbody fusion devices. Emphasis was placed on the relation between subsidence and spinal stability. METHODS: The flexibility of 24 human cervical spine specimens was tested before and directly after being stabilized with a WING, BAK/C, AcroMed I/F cage, or with bone cement in standard flexibility tests under 50 N axial preload. Thereafter, 700 pure moment loading cycles (+/- 2 Nm) were applied in randomized directions to simulate physiological neck movements. Additional flexibility tests in combination with measurements of the subsidence depth were conducted after 50, 100, 200, 300, 500, and 700 loading cycles. In all four groups, simulated postoperative neck movements caused an increase of the range of motion (ROM) ranging from 0.4 to 3.1 degrees and of the neutral zone from 0.1 to 4.2 degrees. This increase in flexibility was most distinct in extension followed by flexion, lateral bending, and axial rotation. After cyclic loading, ROM tended to be lower in the group fitted with AcroMed cages (3.3 degrees in right lateral bending, 3.5 degrees in left axial rotation, 7.8 degrees in flexion, 8.3 degrees in extension) and in the group in which bone cement was applied (5.4 degrees, 2.5 degrees, 7.4 degrees, and 8.8 degrees, respectively) than in those fixed with the WING (6.3 degrees, 5.4 degrees, 9.7 degrees, and 6.9 degrees, respectively) and BAK cages (6.2 degrees, 4.5 degrees, 10.2 degrees, and 11.6 degrees, respectively). CONCLUSIONS: Simulated repeated neck movements not only caused an increase of the flexibility but also subsidence of the implants into the adjacent vertebrae. The relation between flexibility increase and subsidence seemed to depend on the implant design: subsiding BAK/C cages partially supported stability whereas subsiding WING cages and AcroMed cages did not.

Biomechanical Phenomena↗

PubMed2002

Graft subsidence after instrument-assisted anterior cervical fusion.

OBJECT: Bone grafts used in anterior cervical fusion (ACF) may subside postoperatively. The authors reviewed a recent series in which instrument-assisted ACF was performed to determine the degree of subsidence with respect to fusion length, use of segmental screws, and patient smoking status, age, and sex. METHODS: Charts and implant records were reviewed for all 70 patients who underwent instrument-assisted ACF during a 2-year period. The procedures, grafting materials, plate types/lengths, and patient smoking status were recorded. The immediate postoperative and follow-up lateral radiographs were analyzed. The plate lengths and lengths of the fused segments were measured in a standardized fashion. The mean intraoperative and follow-up fusion segment lengths were 54.3 and 51.9 mm, respectively. Greater subsidence occurred in multilevel fusions than in single-level fusions. There were noticeable changes in the position of plates or screws on 14 of 70 follow-up x-ray films. No new neurological deficits related to graft subsidence occurred, and the reoperation rate was 3%. There was no statistical relation between subsidence and the following variables: segmental fixation, smoking status, sex, age, or dowel size when corrected for length of the plate. Hardware migration correlated significantly with plate length in cases of two- and three-level fusions. CONCLUSIONS: The length of a fusion segment decreases in the immediate weeks following instrument-assisted ACF. Construct length is the most important determinant of subsidence. When designing multilevel cervical constructs, consideration of the effects of graft subsidence may help to avoid hardware-related complications.

Adult↗

PubMed2001

Comparison of allergic contact dermatitis cases in the private and subsidized clinics in the National Skin Centre, Singapore.

INTRODUCTION: This is an epidemiologic study to compare allergic contact dermatitis patients in the private and subsidized clinics. PATIENTS AND METHODS: All patients diagnosed to have allergic contact dermatitis in the National Skin Centre from January 1999 to June 1999 were studied retrospectively. RESULTS: More private patients were evaluated for allergic contact dermatitis than subsidized patients in the study period (138 vs. 99). The female-to-male ratio in the paying clinics was greater than in the subsidized clinics (3:1 vs. 1:1). The mean age was the same for both groups i.e., 40 years. There was a greater proportion of unskilled workers attending the subsidized clinic (24.2% vs. 5.4%). The mean duration of rash before evaluation was longer for paying patients than for subsidized patients (31 vs. 22 months), but this was not statistically significant. A significant proportion of the patients had a history of atopic disease and endogenous dermatitis. The most frequent sites for allergic contact dermatitis were the face, hands and the exposed areas of the limbs. The most common allergens were nickel, cobalt and fragrance in the paying patients; and nickel, chromate and fragrance in the subsidized patients. CONCLUSION: More female patients with allergic contact dermatitis and more atopic patients were seen in the private clinics. The forearms, fingers, feet and ears were more commonly affected in the subsidized patients.

Adolescent↗

PubMed2005

Subsidence of titanium straight stems in combination with highly viscous bone cement.

Varying results and a high rate of subsidence have been reported for the straight femoral stem (M.E. Muller) made of titanium alloy. We examined subsidence in 135 titanium-alloy straight stems implanted with high viscosity cement after 68.8+/-11.5 months using a digital high-precision method (EBRA-FCA). One revised implant showed a subsidence of 14.6 mm and another 2.5 mm over 5 years. A third implant without migration was found to be loose. The 122 implants without loosening showed a mean subsidence of 0.1+/-0.1 mm, and focal osteolysis was seen in two. Altogether, we found subsidence of the titanium stems very small. The small subsidence may be related to the use of high viscosity bone cement.

Aged↗

PubMed2001

Stem surface roughness alters creep induced subsidence and 'taper-lock' in a cemented femoral hip prosthesis.

The clinical success of polished tapered stems has been widely reported in numerous long term studies. The mechanical environment that exists for polished tapered stems, however, is not fully understood. In this investigation, a collarless, tapered femoral total hip stem with an unsupported distal tip was evaluated using a 'physiological' three-dimensional (3D) finite element analysis. It was hypothesized that stem-cement interface friction, which alters the magnitude and orientation of the cement mantle stress, would subsequently influence stem 'taper-lock' and viscoelastic relaxation of bone cement stresses. The hypothesis that creep-induced subsidence would result in increases to stem-cement normal (radial) interface stresses was also examined. Utilizing a viscoelastic material model for the bone cement in the analysis, three different stem-cement interface conditions were considered: debonded stem with zero friction coefficient (mu=0) (frictionless), debonded stem with stem-cement interface friction (mu=0.22) ('smooth' or polished) and a completely bonded stem ('rough'). Stem roughness had a profound influence on cement mantle stress, stem subsidence and cement mantle stress relaxation over the 24-h test period. The frictionless and smooth tapered stems generated compressive normal stress at the stem-cement interface creating a mechanical environment indicative of 'taper-lock'. The normal stress increased with decreasing stem-cement interface friction but decreased proximally with time and stem subsidence. Stem subsidence also increased with decreasing stem-cement interface friction. We conclude that polished stems have a greater potential to develop 'taper-lock' fixation than do rough stems. However, subsidence is not an important determinant of the maintenance of 'taper-lock'. Rather subsidence is a function of stem-cement interface friction and bone cement creep.

Aged↗

PubMed1996

Periodontal status among male industrial workers in southern Finland with or without access to subsidized dental care.

The association between subsidized dental care and periodontal status was studied in male industrial workers in southern Finland in 1994. Clinical examinations and a multiple-choice questionnaire were completed for 325 workers (age, 38-65 years) with access to subsidized dental care and 174 controls without access. The CPITN scores based on full-mouth recordings were analyzed, using both the individual and sextant as units of analysis. Overall, 6% of the subsidized group and 2% of the control group had no periodontal treatment need (p < 0.05). Deep pockets > or = 6 mm were found in 5% of the subsidized workers and 11% of the controls (p < 0.05). In the logistic regression analyses the probability of calculus was negatively associated with access to subsidized dental care. Smoking was the strongest independent factor affecting periodontal status. Our findings show a positive relationship between access to subsidized dental care and periodontal status.

Adult↗

PubMed1997

Effects of cement creep on stem subsidence and stresses in the cement mantle of a total hip replacement.

In cemented total hip prostheses, the role of creep of the acrylic cement (polymethyl methacrylate, [PMMA]) in increasing or decreasing the chance of failure of the cement mantle is a subject of ongoing controversy. In the present study we used a three-dimensional finite-element model of a cemented stem to assess the influence of cement creep on subsidence of the stem, and on the stress and strain in the cement under cyclic load, both in the short and long term. The cement layer was assigned the shear and bulk creep moduli of Zimmer regular PMMA cement, which were obtained experimentally. The stem-cement interface was modeled either as (1) completely bonded, (2) completely debonded with friction, or (3) completely debonded and frictionless. Under the cyclic load some cement creep occurred with all three bonding conditions, allowing additional subsidence of the stem and a decrease in the stress components within the cement. During the unloaded period the full recovery of the preload conditions could be reached with the completely bonded and with the frictionless interfaces. With the frictional interface there was residual cement creep, residual stresses within the cement, and residual subsidence of the stem during the unloaded period; however, the reduction of the stress was at most 13% and the subsidence was about 0.46 mm. The much larger subsidence of debonded stems that is often observed clinically might be attributed to the factors which were not included in the present model, such as circumferential bone remodeling.

Biocompatible Materials↗

PubMed2006

The relationship between stem subsidence and improvement in the radiolucency in polished tapered stems.

We studied the relationship between stem subsidence and improvement in the initial radiolucency at the bone-cement interface in polished- and rough-surface stems. Stem subsidence was seen in 34 of 42 hips (81.0%), and improvement in the initial radiolucency was seen in 15 hips (35.7%) in collarless polished tapered stems at 1 year after operation. In polished stems, stem subsidence in cases with improvement in the initial radiolucency was significantly greater than in those with no change (average 1.12 mm and 0.48 mm, P<0.005). In rough-surface stems partially coated with polymethylmethacrylate (VerSys Cemented Plus), no stem subsidence and no improvement in the initial radiolucency was seen. In polished stems, stem subsidence leads to cement creep and compressive force on the bone-cement interface and can improve the initial radiolucency.

Aged↗

PubMed1995

Subsidence of tibial components in knee arthroplasty. A comparison between conventional radiography and roentgen stereophotogrammetry.

RATIONALE AND OBJECTIVES: To assess the ability of conventional radiography to identify subsidence of tibial components. METHODS: Forty-three cases of knee arthroplasty were followed for 4 years using roentgen stereophotogrammetric analysis as the gold standard. RESULTS: Roentgen stereophotogrammetric analysis showed subsidence in all uncemented prostheses, whereas two thirds of the cemented prostheses subsided. Medially, the sensitivity of conventional radiography was low, 25%, whereas the specificity was 83%. For the other regions, the sensitivity was almost 100%, although the specificity was as low as 66% frontally and dorsally. CONCLUSIONS: Medially, where most prostheses were inserted with a slight overhang, conventional radiography identified subsidence correctly. Laterally, frontally, and dorsally, however, conventional radiography overestimated the subsidence by a factor of 2 to 3. This error was caused by bony protrusions arising in the cranial direction from the uncovered bone surfaces, thus changing the points of reference. This problem arose more commonly in uncemented cases, whereas cement seemed to seal the bone.

Biomechanical Phenomena↗

PubMed1979

Acid mine drainage and subsidence: effects of increased coal utilization.

The increases above 1975 levels for acid mine drainage and subsidence for the years 1985 and 2000 based on projections of current mining trends and the National Energy Plan are presented. No increases are projected for acid mine drainage from surface mines or waste since enforcement under present laws should control this problem. The increase in acid mine drainage from underground mines is projected to be 16 percent by 1985 and 10 percent by 2000. The smaller increase in 2000 over 1985 reflects the impact of the PL 95-87 abandoned mine program. Mine subsidence is projected to increase by 34 and 115 percent respectively for 1985 and 2000. This estimate assumes that subsidence will parallel the rate of underground coal production and that no new subsidence control measures are adopted to mitigate subsidence occurrence.

Acids↗

PubMed1989

Subsidence of the femoral component related to long-term outcome of hip replacement.

We compared the clinical outcome with femoral subsidence and radiographic changes in 102 patients at 9 to 13 years after low friction arthroplasty. In 92 cases with a satisfactory outcome there was an average of 2.3 radiological signs and mean subsidence of less than 5 mm. An unsatisfactory outcome was associated with 3.4 signs per film and with subsidence of more than 5 mm. The radiological signs we describe are often the hallmark of successful load transmission, but if they increase with time or are associated with subsidence of over 5 mm, then clinical failure is likely. Fracture of the cement tip is associated with increased subsidence and adversely affects the long-term clinical outcome.

Femur↗

PubMed1987

Femoral component loosening in hip arthroplasty. Cadaver study of subsidence and hoop strain.

To aid in understanding loosening following cemented total hip arthroplasty, we conducted a cadaver study of the proximal femur with implanted cobalt-chromium and titanium femoral components of recent design, loaded through the head of the prosthesis. Stem subsidence and strain in the proximal femur were measured. After proximal support of the implant collar was removed, we found that cobalt-chromium implants had a greater tendency to subside than titanium implants. Subsidence of a femoral component within the cement mantle caused an increase in tensile hoop strain measured in the proximal cortex. When implants were loaded until failure of the cortex, a direct relationship between increase in subsidence and increase in cortical hoop strain was demonstrated. Our data show that implants that resist subsidence into the cement mantle tend to decrease hoop strains in the proximal femoral cortex.

Bone Cements↗

PubMed1986

Femoral prosthetic subsidence after low-friction arthroplasty.

A quantitative method has been used to measure femoral prosthetic subsidence after insertion. Increased amounts of subsidence are associated with the development of radiologic signs by one year after surgery. The most marked effect occurs with fractures of the cement tip. Follow-up examination up to five years shows that the rate of subsidence usually stabilizes, or stops at about 5 mm. Less commonly, subsidence is progressive, averaging up to 2 cm at five years. Demonstrable subsidence is also associated with prostheses that subsequently go on to break. The implications are that the nonflanged femoral prostheses are end bearing, with eccentric loading of the distal cement column, which leads to radiologic signs around the cement tip, demarcation, and, eventually, fracture of the cement tip. There may also be resorptive changes in the proximal femur, characteristically demonstrated in the medial femoral neck. It is suggested that the recent improvements in cement technique and the addition of the prosthetic dorsal flange may increase the success of low-friction arthroplasty.

Bone Cements↗

PubMed1992

Subsidence of porous coated noncemented femoral components in total hip arthroplasty. A roentgen stereophotogrammetric analysis.

Roentgen stereophotogrammetric analysis was used in the evaluation of subsidence in nine noncemented femoral components of the Biomet Taperloc prosthesis. After 2 years three components had subsided 0.7-0.9 mm. No distinct symptoms related to the micromotion appeared. The subsidence in this investigation was smaller than the reported subsidence of other noncemented prostheses.

Adult↗

PubMed1998

First metacarpal subsidence during pinch after ligament reconstruction and tendon interposition basal joint arthroplasty of the thumb.

Trapeziectomy, ligament reconstruction and tendon interposition arthroplasty is one of the most commonly performed procedures to address pain and instability due to osteoarthritis at the basal joint of the thumb. To determine the effect of stress on first metacarpal subsidence, 15 ligament reconstruction and tendon interposition basal joint arthroplasties were evaluated after a mean follow-up of 32 months. Radiographs were obtained of the arthroplasty at rest and then with maximal effort key pinch stress, which is known to subject the first carpometacarpal joint to considerable axial compression stress. Compared with the preoperative x-rays, the first metacarpal had subsided 21% of the arthroplasty space at rest. Under stress, the first metacarpal was found to subside another 10.5% in height. No subluxation of the metacarpal base could be detected. Key pinch strength improved 17% from the preoperative strength. Tip-to-tip pinch strength improved 17% from the preoperative measurement. Grip strength improved 17% from the preoperative measurement. Grip strength was 9% greater than the preoperative grip strength. There was no statistical association between the amount of first metacarpal subsidence and follow-up key pinch, tip pinch, or grip strength. With axial compressive loading of the arthroplasty, such as in lateral pinch, there is some further proximal migration of the first metacarpal, but this is minimal and does not correlate with functional outcome.

Adult↗

PubMed1997

Massive early subsidence following femoral impaction grafting.

The incidence of massive early subsidence (subsidence greater than 10 mm) following impaction grafting of the femur in revision surgery is reported. The first 79 consecutive revision total hip arthroplasties using morselized allograft, polymethyl methacrylate cement, and a double-tapered, polished, collarless stem were reviewed. Nine (11%) of the 79 revision femoral prostheses showed massive subsidence, with another nine hips subsiding to a lesser degree. Further elucidation of the critical factors contributing to the initial stability of the biologic composite is required.

Adult↗