Experimentelle Untersuchungen über die zeitlichen Veränderungen kieferorthopädischer Kräfte

Ohne ZusammenfassungMit 12 AbbildungenNach einem Vortrag, gehalten auf der Wissenschaftlichen Jahrestagung der Deutschen Gesellschaft für Kieferorthopädie in Stuttgart vom 9. bis 13. 6. 1965.     

No alteration in bone mineral density in patients with periodontitis

Alveolar bone destruction can be magnified in the presence of generalized skeletal disorders. We questioned whether severe generalized periodontitis patients display signs of bone metabolism disturbances. Our objective was to assess skeletal bone mineral density (BMD) and biochemical bone parameters in premenopausal women with periodontitis. Forty-five patients and 40 control individuals were included in the study. We measured BMD by dual-energy x-ray absorptiometry. The results showed no difference in BMD values between the periodontitis and control groups (p > 0.05). A positive relationship between the clinical attachment level and Body Mass Index (BMI) scores was observed (p = 0.03). Increased serum creatinine levels were noted in the periodontitis group (p = 0.04). Analysis of the data suggests that there is no evidence for an association between skeletal BMD and severe periodontitis in premenopausal women. There may be a link between elevated creatinine levels and periodontitis. The persons with high BMI scores seemed to be at risk for periodontitis.     

Nanomechanical and chemical characterization of incipient in vitro carious lesions in human dental enamel

OBJECTIVE: The research was designed to examine the growth of in vitro carious lesions in dental enamel using nanoindentation and time-of-flight secondary ion mass spectroscopy (TOF-SIMS). This was intended to give maps of mechanical properties and chemistry over the cross-section of the lesions. METHODS: Incipient carious lesions were grown on the buccal faces of 20 human premolars by exposure to acid for 3, 5, 7 or 14 days. The lesions were then cut in cross-section normal to the exposed surface. The lesions' cross-sections were then examined using nanoindentation and TOF-SIMS. RESULTS: The earliest lesions (3 days of acid exposure) showed little evidence of lesion growth, but the 5, 7 and 14 days of exposure all gave lesions with a weak, demineralized interior, but a stronger, less demineralized surface zone. The thickness of the surface zone was found to diminish with the length of exposure to acid, but it was still present even after 14 days of exposure. CONCLUSION: The results indicate that carious lesions develop subsurface and that the surface zone forms by a coupled diffusion process. Mechanically the lesion has a strong surface layer, but a very weak interior which makes the lesion vulnerable to mechanical loading. However, the presence of a surface zone that retains a high mineral content and is mechanically strong suggests that lesion development can be arrested and possibly reversed even when the lesions are relatively mature.     

A removal torque and histomorphometric study of commercially pure niobium and titanium implants in rabbit bone

Screw-shaped commercially pure (c.p.) niobium and c.p. titanium implants were inserted in rabbit bone. After a healing period of 3 months, a significantly higher removal torque was demonstrated to unscrew the niobium implants (average 32.9 Ncm) compared to the c.p. titanium implants (average 25.3 Ncm). In the histomorphometric part of the study, there were no significant differences in bone-to-metal contact between the 2 implant materials. An average of 41.1% bony contact was demonstrated for the niobium screws compared to an average of 37.2% for the c.p. titanium ones. Our removal torque findings could be related to the differences that we observed between the 2 implant surfaces as indicated by SEM. Since niobium implants showed a more irregular surface topography and niobium is a softer metal than c.p. titanium, this seems the most probable reason for the differences observed in removal torque between the 2 metals. Hypothetically, a more "positive biocompatibility" of the c.p. niobium in comparison to the c.p. titanium remains as another possible reason for the observed differences. However, against such a difference in biocompatibility between c.p. niobium and c.p. titanium, there is the very similar amount of bony contact registered in the histomorphometric analysis.     

Intracranial volume in children with craniosynostosis

The intracranial volume of 104 children with craniosynostosis was measured. Premature fusion of skull sutures is thought to deny the growing brain room to expand, but contrary to traditional teaching the intracranial volume of such children is often within normal limits.     

Delayed dental development in children with isolated cleft lip and palate

Although most cases of cleft lip and palate are free of other developmental defects, children with isolated cleft lip/palate are at enhanced risk of delayed growth and reduced final size. Three variables were assessed in the permanent dentition away from the cleft site: congenital absence by tooth type (which ranged from 0 to 7%) asymmetry in developmental staging (3 times more common in cleft lip/palate than in controls), and dental age (with a mean delay of 0.9 yr in cleft lip/palate relative to controls). The pervasive nature of these measures of reduced growth potential and developmental control, which were greatest in teeth forming during infancy, suggests that the cause of the compromised growth is the adverse early postnatal environment rather than conditions intrinsic to the individual.     

An evaluation of the surface characteristics of a facial prosthetic elastomer. Part II: The surface texture

Silicone elastomers do not have an inherent surface texture but take on the surface texture of the surface against which they are processed. This study compares the surface texture of Cosmesil material, a purpose-designed facial prosthetic elastomer, and Molloplast-B material, which is a well-established material for use in the clinic. We used a profilometer to determine the roughness average, maximum roughness, and waviness of the dies, control, gypsum, and silicone test surfaces. Statistical analyses of results involved multivariate analyses of variance and Tukey's procedures to compare roughness average, maximum roughness, and waviness (in all cases p less than 0.05). The results showed that the silicone elastomers, Cosmesil and Molloplast-B, have similar surface characteristics. The only statistically significant difference was in waviness (Molloplast-B, means = 10.82 microns; Cosmesil, means = 12.82 microns). The gypsum surface yielding the most satisfactory result was the surface that had been treated with silicone paste separator. On the basis of surface characteristics, Cosmesil material is likely to cause no more surface trauma of the tissue against which it is placed than the use of Molloplast-B material.     

Surgery of the parotid region: a new approach

Many disorders of the parotid gland require treatment by subtotal or total parotidectomy. In such situations functional and esthetic complications may arise due to the location of the incisions or from permanent or temporary injuries to the facial nerve. This report describes a modified revision that gives good esthetic and functional results. A review of a similar series of cases treated surgically by the same surgeons using Yoel and Bilesio's technique showed no differences in morbility associated with parotidectomy performed using the proposed incision.     

The edentulous mandible opposing maxillary natural teeth. Treatment considerations

Treatment of a patient who requires a mandibular complete prosthesis opposing a natural maxillary dentition presents a unique set of problems for the clinician. Proper prosthodontic care can not only result in a functional and comfortable prosthesis, but may reduce the rate of resorption of the remaining mandibular ridge.