Marked and rapid change of bone shape in acutely ACL injured knees - an exploratory analysis of the Kanon trial.

BACKGROUND: To investigate changes in knee 3D bone shape over the first 5 years after acute anterior cruciate ligament (ACL) injury in participants of the randomized controlled KANON-trial. METHODS: Serial MR images over 5 years from 121 young (32 women, mean age 26.1 years) adults with an acute ACL tear in a previously un-injured knee were analyzed using statistical shape models for bone. A matched reference cohort of 176 individuals was selected from the Osteoarthritis Initiative (OAI). Primary endpoint was change in bone area of the medial femoral condyle; exploratory analyses compared results by treatment and examined other knee regions. Comparisons were made using repeated measures mixed model ANOVA with adjustment for age, sex and body mass index (BMI). RESULTS: Mean medial femur bone area increased 3.2% (78.0 [95% CI 70.2 to 86.4] mm2) over 5 years after ACL injury and most prominently in knees treated with ACL reconstruction (ACLR). A higher rate of increase occurred over the first 2 years compared to the latter 3-years (66.2 [59.3 to 73.2] vs 17.6 [12.2 to 23.0] mm2) and was 6.7 times faster than in the reference cohort. The pattern and location of shape change in the extrapolated KANON data was very similar to that observed in another knee-osteoarthritis cohort. CONCLUSION: 3D shape modelling after acute ACL injury revealed rapid bone shape changes, already evident at 3 months. The bone-change pattern after ACL injury demonstrated flattening and bone growth on the outer margins of the condyles similar to that reported in established knee osteoarthritis.

The microscopic appearance and effect of toothbrushing on extrinsically stained metal-ceramic restorations.

To clarify the nature and longevity of the extrinsic stain layer of metal-ceramic restorations, a series of experiments were undertaken. It was found, with microscopic examination, that there is little or no diffusion of the stain into the underlying porcelain and that at a thickness of 22 microns the extrinsic stain layer is grossly evident to an observer. Using a fluoride dentifrice caused no significant loss of either stain or surface integrity with 120,000 brush strokes (equivalent to 8.5 years). At 160,000 strokes (equivalent to 11.4 years) there was evidence of loss of surface integrity.

A study of interocclusal record materials.

An investigation of casts assembled by the use of seven interocclusal record materials and manipulated by three operators disclosed that: 1. Aluwax was the most variable and least reliable of all materials. 2. Superbite consistently resulted in open cast relationships. 3. The five elastomers consistently resulted in the least amount of errors. 4. The two different thicknesses of elastomeric records resulted in statistically significant different mounting discrepancies. 5. On an average, an inexperienced student performed as well as the two experienced dentists.