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PubMed1979

A scanning electron microscopic and microradiographic study of pits in fluorosed human enamel.

The aim of the present study has been to correlate the surface appearance of pitted, fluorosed enamel in the scanning electron microscope (SEM) with the microradiographic features of the underlying tissue. Intact enamel surfaces of severely fluorosed teeth appeared similar to that of normal enamel. In the unabraded surfaces discrete pits were sharply demarcated from the surrounding intact enamel surface leaving steep walls of parallel running rods. The microradiographic appearance of sections made through pits indicated that focal loss of surface enamel occurred corresponding to the inner highly hypomineralized part of the fluorotic subsurface lesion. The abrupt wall formation and the finding that the striae of Retzius never changed direction along the margins of the lesions indicated that pits in fluorosed enamel may be secondarily produced defects rather than true hypoplasias. Further evidence of the posteruptive origin of the defects was derived from the observation that enamel lamellae occasionally formed part of the lateral border. The relatively higher degree of radiopacity observed in the tissue surrounding the pit indicates a posteruptively acquired deposition of minerals in the exposed porous enamel.

Dental Enamel↗
PubMed1978

[Superficial and marginal behavior of composite filling materials in class III and II cavities as compared with conventional filling materials (author's transl)].

The superficial and marginal behavior of composite filling materials is better than that of conventional types of front tooth filling cements as regards plaque retention, danger of marginal caries, and microleakage with potential damage to the pulp caused by bacterial toxins.--According to the results obtained in vitro, Evicrol is a positive alternative to Frontasil and Achatit-biochromatic. Plastic foils are not suitable as matrices, whereas aluminum matrices have been found to meet the requirements of surface smoothness and anatomical adaptability in cavity classes III, IV, and V. Celluloid matrices show inadequate adaptational properties, although they offer smoothest surfaces. The marginal behavior of Evicrol in class II cavities in molars is virtually the same in the case of both conventional retentive preparation and modified preparation of initial occlusal-approximal defects by the enamel etching technique. Discontinuous microretentive securing of matrix tags in the enamel etch pattern corresponds neither occlusally nor approximally to the physical definition of adhesion in different areas of the enamel. Clinical comparison in a 12-month study with the results obtained in vitro restricts safe indication to classes III and V, it being necessary to give careful consideration to the directions for use.--Long-term clinical longitudinal studies are required to determine permanent successes of treatment and possible extensions of the range of indications.

Composite Resins↗
PubMed1976

Origin, diagnosis, and treatment of the dental manifestations of vitamin D-resistant rickets: review of the literature and report of case.

Previous discussions center on early diagnosis, initial treatment, and follow-up therapy for the patient with vitamin D-resistant rickets. Both the medical and dental aspects of treatment for these patients has a long-range effect on the normal developmental patterns. Although treatment is begun at an early age, some rachitic skeletal effects such as minor bowing of the legs and bossing of the skull will invariably be noticed. In patients with controlled rickets the alveolar processes undergo normal development, with apparent normal dental eruption. The poor development and calcification of the alveolus seen in the untreated patient leads to loss of the lamina dura and periodontal ligament of the teeth. Patients with resistant rickets possess a functional dentition, although not without inherent defects. Various degrees of fracture and attrition of enamel can be seen, and hypoplasia of dentin is nearly a universal result. Defects extending to the dentinoenamel junction have been shown in repeated cases. Cementum, because of its close relationship with dentin calcification, also appears abnormal. Pulp tissue may undergo abberations of physiology in resistant rickets, although further work in this respect is needed. With respect to the possible dental pathoses seen in this disease, the dental history of the patient with resistant rickets discussed in this report showed that several of the deciduous teeth, possibly the mandibular left second premolar and right first molar, and definitely the maxillary right second premolar and canine and the mandibular left canine had all undergone pulpal degeneration of apparently unknown causation. In the maxillary right second premolar and the mandibular left canine, enamel fractures were clinically and radiographically apparent. However, the maxillary right canine originally had an acute abscess with no defects other than normal, minimal wear facets. No causative factor for its necrosis could be found. Overt enamel fractures in the maxillary right second premolar and the mandibular left canine may have led to microexposures of the pulp with subsequent bacterial pulpal contamination. Suppuration present in several of the pulps when first entered during endodontic treatment, as well as chronic fistulas in several areas, support the conclusion that contamination by some means does indeed occur.

Abscess↗
PubMed1976

Intraoral cancellous bone autografts in the treatment of infrabony pockets.

One hundred infrabony pockets with one- and two-wall bony defects were treated for reattachment. Mucoperiosteal flaps were raised, the tooth surfaces were scaled and planed, and the defects curetted. Flaps were sutured tightly and the sites protected with a surgical dressing. Antibiotic coverage was used in each case. Pre- and postoperative measurements were taken by the same clinician from the cemento-enamel junction to the base of the pocket. In 56 defects cancellous bone from the same patient was placed in the defect, and in 44 defects the treatment consisted only of open curettage without bone grafts. The results showed a trend towards more favourable clinical results using bone grafts; especially in the two-wall bony defects.

Adult↗
PubMed1977

Ultrastructural study of amelogenesis imperfecta.

An ultrastructural study of teeth with amelogenesis imperfecta revealed various aspects of microcavities in the enamel surface, which ranged from isolated imprints of ameloblasts corresponding to the mildest lesions at the end of amelogenesis, to pits caused by the death of 20 to 30 ameloblasts at the beginning of amelogenesis. Abnormalities in the shape of the prisms can be observed. Further, crystals are distributed randomly within a prism or at the junction of 2 contiguous prisms while intercrystalline spaces are widened, indicating in various places the lack of a preferred orientation of the crystals. In amelogenesis imperfecta, two different crystalline periods are found: 1 of about 250 A, the other of about 500 A and over. The fact that amorphous areas are found among the crystals of enamel may be related to different stages of crystallization. However, it was not possible to find any lattice defect.

Ameloblasts↗
PubMed1979

In vivo neutron activation analysis for bone calcium (INVAA) in malignant hyperthermia susceptible patients.

Some non-rigid Malignant Hyperthermia Susceptible (MHS) patients have a greater than normal incidence of fractures. Radiologically their long bones are slightly thinner than normal. Excessive numbers of caries because of thin dental enamel may also be present. The Malignant Hyperthermic (MH) defects thus appears to involve cells of bone appendages as well as of muscle. We have measured the concentration of calcium in bone by neutron activation analysis and have found it to be reduced in both non-rigid and rigid malignant hyperthermia susceptible patients. The reductions were particularly marked for the non-rigid patients. Bone calcium concentrations were lower in males than in females and in those under 16 and over 60 years of age. This is additional evidence is favour of the hypothesis that malignant hyperthermia is a widespread defect affecting tissues and organs throughout the body.

Adult↗
PubMedDate not supplied

Formation of Ca HPO4-2H2O from enamel mineral and its relationship to caries mechanism.

Tooth enamel, when treated with dilute H3P94 solutions, dissolved incongruently with formation of large CaHPO4-2HO2O crystals. Equilibrated solutions were saturated with respect to Ca5(PO4)3OH, probably an impure, defective apatite. The CaHPO4-2H2O crystals formed at considerably higher pH values than expected becuase of enhanced solubility of the apatitic phase in enamel. Pyolysis of carious enamel revealed the presence of acidic calcium phosphate presumed to be CaHPO4-2H2O.

Calcium↗
PubMed1978

Surface characteristics of resin-coated composite restorations.

Twenty-four maxillary anterior composite restorations from a clinical study of resin coating were examined at the time of baseline evaluation and at 23 months; electroplated positive replicas, impression negative replicas, and SEMs were used for evaluation. Coated restorations had smooth surfaces after 23 months, in comparison with rough surfaces of uncoated restorations. Defects in some of the resin coatings were found at the time of baseline evaluation; these included isolated areas of the composite or etched enamel that were not covered by the resin. Later examinations showed cracking of part of the edges of resin coating, development of bare areas, thinning of the coating edges, or generalized loss of the protective coating. The defects seen immediately after placement of the coatings were probably caused by errors in technique that include: application of the resin in a layer that was too thin; surface contaminants in the area of application; moisture on the surface of the composite or enamel; and areas of inadequate enamel etching were adjacent to the cavosurface margin of the composite. The appearance of bare spots or total loss or thinning of the resin coating edges during the later examinations is caused by wearing or abrading of the resin coatings from natural or mechanical causes. This seems to be a function of the initial coating thickness and its location on the tooth.

Acid Etching, Dental↗
PubMed1979

Oculodentodigital dysplasia. Four new reports and a literature review.

Four new patients with oculodentodigital dysplasia (ODD) have been examined. The salient and fairly constant features of ODD appear to be (1) unique facial appearance, (2) microcornea with other inconstant ocular findings, (3) syndactyly of the hands with additional characteristic phalangeal aberrations, (4) diffuse skeletal dysplasia, (5) enamel dysplasia, and (6) trichosis. Echographic studies indicate that ODD globes have microcornea with otherwise normal dimensions. An increased number of vessels crossing the optic discs was observed in three patients from one family. The distance between the inner canthi and the medial orbital walls in three patients we studied suggests that previous reports of hypertelorism may have been illusions resulting from microcornea, small palpebral fissures, and variably present epicanthus.

Adolescent↗
PubMed1977

Mechanism of enamel dissolution and its prevention.

In this paper the mechanism of dental enamel dissolution is discussed. Special attention is given to the anisotropic solubility behaviour (hollow tube formation) of demineralized enamel crystallites. The combined evidence strongly indicates that this peculiar dissolution behaviour is caused by dislocations. The dislocations--linear lattice defects--are present in the crystallite center and are the cause of two active dissolution sites in each crystallite. Initial as well as later stages in the caries process are discussed. Experimental evidence is presented which indicates that the active sites can be inactivated by agents like EHDP and MFP. After inactivation, acid penetration is either prevented or strongly retarded.

Apatites↗
PubMed1977

Histologic and microradiographic observations on teeth during calcium deprivation in rats.

Adult female rats were subjected to severe calcium deprivation by feeding them a calcium-deficient diet containing oxalate (Group a). Furthermore, pregnant and lactating animals were subjected to the same diet (Group b). The mandibular teeth were examined by histologic, microradiographic and fluorescence microscopic techniques. The incisor enamel was found to be nearly unaffected by the experimental regimen; the dentin formed and mineralized during the experimental period was abnormal only in Group b. Characteristic features were reduced thickness, increased width of predentin and numerous globular defects. Both ameloblasts and odontoblasts were seemingly normal. No obvious differences could be observed between the molars from the controls and the test groups (a,b). "Cementolysis" seemed to be present to the same extent in all groups. In some of the animals of Group b some carious or erosional defects were observed in the molars. These may at least partially account for a small reduction in molar ash content observed in this group.

Animals↗
PubMed1975

Oral findings in the Morquio syndrome (mucopolysaccharidosis IV).

The Morquio syndrome is characterized by a specific pattern of platyspondylia, corneal opacities, keratosulfate excretion in the urine, and dental abnormalities. Oral examinations were performed on twelve patients with the condition. The maxillary anterior teeth were widely spaced and flared. The posterior teeth were tapered and had pointed cusp tips. The enamel was of normal hardness, and in some patients the surface was pitted. In roentgenograms, the enamel was less than one fourth its normal thickness but was of normal radiodensity. The prevalence of caries may have been reduced. The hard palates were broad and flat. The dental abnormalities in the Morquio syndrome are of a type that is unique among the group of genetic mucopolysaccharidoses. Our findings therefore support the conjecture that the biochemical defect in this condition is different from that which occurs in the other mucopolysaccharidoses.

Adolescent↗