Intraindividual comparative animal study of alpha- and beta-tricalcium phosphate degradation in conjunction with simultaneous insertion of dental implants

An intraindividual comparative study of proximal tibial marrow defects in nine adult Goettinger miniature pigs (GMPs) was undertaken. The left side of the defect was filled with granular beta-tricalcium phosphate (TCP) ceramic ad modum Cerasorb, and the right side was filled with granular alpha-TCP ceramic ad modum Biobase alpha pore. Simultaneously, dental screw implants were inserted in each ceramic and fixed within the orthotopically replanted corticalis lids. Control defects were made in two other animals. The survival period ranged from 4 to 86 weeks (control study, 16 and 20 weeks). The reorganization and degree of bone regeneration, dynamics of ceramic degradation, and remodeling characteristics of the bone regenerate referring to osseo-integration of the dental implants were examined histomorphologically in nondecalcified specimens. The results reveal that both ceramic types were osteoconductive exclusively. Centripetally oriented angiogene bone regeneration occurred at the margins of the circular defects. Ceramic degradation was performed hydrolytically and within cells. Furthermore, it was demonstrated that decomposition of the intratrabecularly integrated ceramic residues underlies a dynamic process of degradation. Within 86 weeks, nearly 80% to 90% of the larger alpha-TCP granules, and nearly 90% to 95% of the beta-TCP granules were degraded. At this time, especially for the alpha-TCP modification, ceramic microparticles were found in the marrow, either unbound or within polynuclear macrophages. The predictable degradation of both ceramic types provides an early functional adaptation of bone regenerates and facilitates a biofunctional, anisotropic orientation of the neotrabeculae without delay. It is concluded that because of the initially pronounced accumulation of macrophages, dental implants should not be inserted simultaneously with ceramic, but after further progress of ceramic degradation (5 to 6 months after TCP implantation).     

Sterilization of elastic ligatures for intraoperative mandibulomaxillary immobilization

Sterilization can influence the mechanical properties of elastic ligatures used for mandibulomaxillary immobilization. The aim of this study was to compare different sterilization protocols (ethylene oxide, autoclave, irradiation, plasma sterilization, povidone-iodine for 24 hours and 70% isopropyl alcohol for 24 hours) of three elastomers (natural rubber, silicone rubber, and polyurethane). Three mechanical variables were assessed in a testing machine: breaking strength, tensile strength and tensile strength after a 24-hour load (material fatigue). Natural rubber was most susceptible to mechanical alteration by sterilization and lost 46% of its breaking strength and 43% of its tensile strength after autoclaving. Polyurethane was more resistant (multiple comparison, Tukey-Kramer), but polyurethane ligatures stuck together after autoclaving. The protocols for low-temperature sterilization, ethylene oxide, irradiation, and plasma were superior to autoclaving and the disinfecting solutions. These data suggest that polyurethane sterilized with ethylene oxide is the material of choice.     

Congenital infiltrating lipomatosis of the face

Congenital infiltrating lipomatosis of the face is a rare clinical entity. Since it was first described by Slavin and colleagues in 1989, only a few cases have been reported in the literature. A 6-year-old girl with congenital infiltrating lipomatosis of the right side of the face is presented, and treatment modalities are discussed.     

Physical examination of caffeine's effects on the enamel surface of first molar in new-born rats.

Samples of the first molars of offspring whose dams were fed a diet supplemented with caffeine were examined by scanning electron microscopy, X-ray diffractometry and electron microprobe analysis. Scanning microscopy of the enamel surface of the caffeine group revealed a consistently rougher surface than in the non-caffeine controls, both before and after acid exposure. X-ray diffraction analysis of the pulverized whole tooth in the caffeine group showed broader diffraction peaks for the lattice plane reflections (202) and (300), indicating smaller crystallites. Pure enamel samples of the caffeine group examined with a Gandolfi X-ray camera also revealed more diffuse diffraction lines than in the non-caffeine controls, further indicating smaller crystallites in the enamel. The calcium and phosphorus contents of the acid-exposed samples in both control and caffeine groups were lower than the non-acid exposed control and caffeine groups by electron microprobe analysis. After exposure to acid, the calcium and phosphorus contents of the outer surface of the enamel in the caffeine group were greatly reduced as compared to that of the non-caffeine controls. Thus various methods consistently indicate that caffeine ingestion during early growth affects the enamel surface of the first molars, resulting in impaired mineralization. Caffeine intake may therefore have a negative effect on amelogenesis and possibly increases susceptibility to dental caries.     

Diagnosis of alveolar bone changes with digital subtraction images and conventional radiographs. An in vitro study

The purpose of the present study was to compare the diagnostic properties of radiographs obtained with Ultra-Speed and Ektaspeed films when analyzed conventionally radiographs and after conversion in digital subtraction images. Artificial lesions, measuring 0.5, 0.7, 0.9, and 1.1 mm in diameter, were drilled in a dry skull with slow-speed burs. Standardized radiographs were obtained by means of acrylic bite blocks and a modification of the Rinn system. The results of this study demonstrated that sensitivity in the detection of the lesions was doubled after digitizing and displaying subtraction images compared with the conventional radiographic interpretation, independent of the use of Ektaspeed or Ultra-Speed films for the original radiographs. The diagnostic information seemed to be equal in radiographs obtained from Ultra-Speed and Ektaspeed films after digitization and image processing procedures.     

Bone regeneration adjacent to titanium dental implants using guided tissue regeneration: a report of two cases

The biologic principle of guided tissue regeneration was applied to regenerate alveolar bone in conjunction with the placement of titanium dental implants. In one case, complete osseointegration of an implant was achieved by the placement of a Teflon membrane over an implant that had been inserted into an alveolus immediately following tooth extraction. In a second case, the same biologic principle was used to increase the volume (height and width) of a resorbed, edentulous alveolar ridge to provide adequate bone dimensions for implant installation. In both cases, the membranes appear to have prevented the repopulation of the wound area by cells other than those derived from surrounding bone tissue. These two different applications of the principle of guided tissue regeneration open new avenues for reconstructive osseous surgery.     

Effect of splinting on the mechanical and histological properties of the healing periodontal ligament in the vervet monkey (Cercopithecus aethiops)

Healing of the periodontal ligament (PDL) after extrusive luxation of two upper central incisors was evaluated when one tooth was splinted and the other left untreated. One millimetre thick, transverse sections of tooth, PDL and alveolar bone were examined in a materials testing machine. Load deformation curves were recorded and a number of mechanical properties were assessed. To eliminate the influence of differences in sizes and fibre arrangements, load values were reduced by the area and deformation values by the width of the PDL, and comparisons between splinted and non-splinted teeth were made at identical root levels 2 weeks after injury. Healing was also evaluated histologically at 1, 2, 3, 4 and 8 weeks after injury. There were no significant differences in mechanical and histological properties between splinted and non-splinted teeth, which suggests that splinting is of doubtful value in treatment of extrusive luxated teeth. The values for the mechanical properties of injured PDL had returned to 50-60% of those of uninjured PDL by 2 weeks after injury, indicating a rapid healing rate.     

Dental development, dental age and tooth counts

Emergence data on the 20 deciduous teeth and the first 29 permanent teeth were collected from 212 randomly selected urban Swedish children who were followed from birth to 18 years of age. The sex difference in the emergence of the deciduous teeth is less than one month, which is not statistically significant. Boys are consistently ahead of girls until the 17th deciduous tooth. From the 17th deciduous tooth on through most of the permanent dentition, girls are consistently ahead of boys. In the permanent dentition the sex difference ranges from 3 MO to 11 MO; these differences are statistically significant except for the 29th tooth. Reference data on dental age based on counts of 1-19 deciduous and 1-27 permanent teeth are tabulated and tooth emergence curves constructed. The tooth emergence curves can be used to express individual dental development in terms of standard deviation scores. Validity of dental age assessed by counts of permanent teeth is evaluated by a cross-sectional comparison with another sample of Swedish boys and girls. The mean difference between estimated age and chronological age is about one month in either sex. Precision of an individual estimate of dental development in terms of 95% confidence level (approximately equal to +/- 2 S.D.) varies from about +/- 4 months in the deciduous dentition to +/- 3 years in the permanent dentition. Assessment of dental development and dental age by means of tooth counts is a convenient and simple method, although it can only be applied at ages when emergence can be expected. It is especially useful in cross-sectional evaluations, as no serial data are required. In populations with a low incidence of caries the impact of such disturbing factors on emergence is correspondingly low, further increasing the validity of assessments of dental development based on tooth emergence.