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This study was designed to investigate by SEM the ultrastructure of the dentinal bridge formed upon pulp capping and its attachment to the contiguous dentinal walls. The pulps of 20 sound premolars and third molars were deliberately exposed and capped with a calcium hydroxide paste, Pulpdent. After 4 to 15 weeks the teeth were extracted. SEM observations suggested complete bridging, increasing in thickness after succeeding postoperative periods. Cross-sections of the specimens older than 6 weeks showed the presence of three different layers within the bridges: the superior amorphous layer was composed of tissue debris and Ca(OH)2, in the medial portion a coarse meshwork of fibers was identified as fibrodentine and the pulpal aspects exhibited tubularlike orthodentinal structures. The bridge attachment was secured by bundles of fibres linking the intertubular dentine of the pulpal walls with the dentine of the neodentinal bridge.

50 microradiographs taken in a standardized manner of midsagittal ground sections of teeth of individuals aged 18 to 56 years were densitometrically evaluated along a track passing through enamel, dentine and an aluminium stepwedge. Semi-quantitative analysis of mineral density uniformly showed an irregular platform representing circumpulpal dentine and a peripheral down slope in the region of the amelodentinal junction, representing mantle dentine. The width of this less mineralized peripheral zone measured on densitometric recordings averaged 150 microns (+/- 50). Quantitative analysis of the two dentinal regions permitted the calculation of the mineral content in terms of volume percentage using both a graphic method and an electronic computer method. The sections were also examined by polarized light microscopy which clearly visualized the presence of peripheral mantle dentine. The mean mineral density of circumpulpal dentine was 46% according to both the graphic and the computer methods; mantle dentine yielded means close to 42% according by both methods. The 4% difference in density between circumpulpal dentine and mantle dentine proved to be statistically significant; there was no significant difference between the means obtained graphically and those obtained electronically. The need for further investigation of this region of the amelodentinal junction was stressed.

In collaboration with the Research Department on vitamins and nutrition of Hoffmann-Laroche Laboratories, an experiment has been conducted, in strictly controlled dietary conditions, to study the effects of a maternal deficiency in vitamin A on the cranio-dental development of rat fetuses and of young weanling rats. A minimal dose of 6 international units per day for 100 g of body weight was required by the mothers for the gestation evolution and a natural birth. Hypovitaminosis A induced, in the fetuses, after 21 intrauterine days, a generalized delay in growth and development proportional to the deficiency severity. In the cranial base and the toothgerms, the delay reached over two fetal days. No teratogenic action was noted. The troubles observed in 21 day old fetuses seemed to disappear in young rats, 21 days after natural parturition. This compensation seemed to be related to a prolonged gestation, proportional to the vitamin deficiency and equal to the growth delay observed at the 21 fetal day. Only modifications in the molars, consisting in coronal dimension and enamel mineral density changes were still observed.

Attempts of introducing uniform techniques for the collection of statistical data on the prevalence of periodontal diseases have been made by FDI and WHO in order to arrive at valid, reproducible, and internationally comparable results. The WHO Manual of the International Classification of Diseases. Application to Dentistry offers a five digit classification of all oral diseases for statistical purposes. In contrast to morbidity statistics, epidemiological surveys must be based on adequate samples, representative for the entire population or distinct strata thereof. FDI is actually preparing guidelines for the conduct of clinical trials in periodontal diseases, comparable to those on caries incidence, indicating the proper use of indices. For the epidemiological assessment of periodontal diseases, the WHO Basic Methods (1962, 1971) have recommended the use of simple ratios of persons affected with signs of the disease. Data collected in four extensive dental surveys in Polynesian and Melanesian populations in the South Pacific served as an example to show the variety of valid information provided by these basic methods. The main results showed an early appearance of pocket formation at ages 10 to 14, preceded in a statistically significant way by calculus formation and gingivitis. A constant pattern in the sequence of attack of the various teeth by pocket formation was shown to be specific for these island populations; males were consistently more affected than females. The character of periodontal diseases prevalent among Polynesians and Melanesians was recognized to be a "dirt pyorrhea" accompanied by progressive subgingival calculus deposition and destructive periodontitis.

Of 123 teeth treated by direct pulp capping 110 could be rechecked clinically and radiographically after periods of 1 1/2 to 7 years, 4 on the average. In 25 cases a change in endodontic treatment has been recorded on the files: In 18 cases biopulpectomy was performed for symptomatic (pain) reasons considered as failure of the capping treatment; in 5 cases biopulpectomy was indicated for periodontal and prosthetic reasons (not considered as failure); in 5 cases of the 110 rechecked necrosis and periapical involvement was diagnosed. The rate of failure thus was 22 cases or 17%. This relatively high ratio of unfavorable results (Tab. VII) is in part due to lack of operative skill of the students while progressing tooth morbidity statistically established in the Genevan population also was taken into account. Advancing tooth ages according to graph figure 6 in accordance with other recent surveys were found to constitute no impediment for direct pulp capping. The success of this endodontic treatment is best ascertained by observing a strict selection of the case and the observance of an exacting operative procedure, namely: - Only accidentally exposed pulps without symptoms of previous spontaneous pain (Category I) are liable to successful conservation by direct pulp capping using calcium hydroxide. Previously painful pulps (Category II) according to Table VIII are either indirectly capped using corticosteroids particularly in young teeth or after exposure subject to coronal or radicular pulpotomy (Category III). Rigorous aseptical procedure and lasting hermetical sealing of the calcium hydroxide pulp dressing are additional prerequisites for success.

Clinical trials constitute epidemiologic experiments, in comparable groups of human populations designed to assess the preventive of curative effects of agents or measures. International organizations (FDI, WHO, CIOMS, ISO) have been instrumental in creating uniform methods, so that the findings from different sources can be validly compared. The need for a standardization of clinical trials in dentistry is particularly felt: - by the dental profession in order to make the choice of materials with the best clinically proven qualities - by the manufacturers in order to develop materials of improved clinical quality - by the public health administrators (or social security agencies), in order to either evaluate the benefit of instituted preventive and curative measure or to ascertain the best possible services A centennial history of efforts is shown to have resulted today in a broad international understanding (Table III). 1. The first chapter of this paper presents a review of the principal requirements for controlled clinical trails [8] such as officially adopted by FDI (Table V). 2. The second chapter offers a first-hand apercu of impending recommendations proposed by COMIET in two protocols [11] for the uniform conduct and evaluation of clinical trials of restorative techniques and materials. 2.1 Three standardized forms (A, B: Table IX, and C) serve to uniformly record data of the operative procedures. 2.2 The proposed standardized criteria (Tables X, XI) for the clinical appraisal of distinct materials give the advantage of having been tested already very extensively. 3. A critical review of the proposed protocols [11] reveals the necessity of: 3.1 referring to and coordinating with the already adopted principal requirements for controlled clinical trials. 3.2 generally adopting the excellent guidelines for the conduct of the study and the evaluation of observations (Tables X, XI) 3.3 taking advantage of the possibilities for reducing the recommended sample of 100 paired restorations (200 cavities)--difficult to implement in many countries--by certain measure such as preliminary in-vitro experiments, consideration of results already reported in the literature and a more systematic use of a standardized photographic serial documentation, a topic which will be the object of an ensuing paper.