Prevalence and distribution of bone defects in moderate and advanced adult periodontitis.

The purpose of the present investigation was to evaluate the prevalence and distribution of different forms of bone defects using direct observation during periodontal surgery. 286 patients with moderate or advanced adult periodontitis diagnosed during clinical and radiographic examination provided a sample of 5476 teeth. After full thickness mucoperiosteal flaps were raised, osseous defects were explored and classified according to their morphology as interdental craters, hemisepta and infrabony defects with 1, 2, 3 or 4 osseous walls. 981 defects were detected; 533 were in the maxilla and 448 in the mandible (15.4% and 22.4%, respectively, of the teeth examined). The posterior mandibular segment had the highest % of teeth with defects (33.8%) followed by the posterior maxillary segment (19.9%). The proportions of teeth with defects in the anterior segments of both arches were similar. The comparison between maxilla and mandible showed a highly significant difference for the posterior segments (p= 0.00001) but no difference for the anterior segments (p=0.88). The distribution of defects differed between the maxilla and the mandible, both for the posterior and anterior segments. Craters accounted for almost half the defects, being more prevalent in posterior segments, while hemisepta formed the lowest proportion. Anatomical variations in shape and the original morphology of the alveolar bone between the maxilla and the mandible and the anterior and posterior regions might have been the reason for the differences observed.

Clinical study of location and reproducibility of three mandibular positions in relation to body posture and muscle function.

Clinical studies have confirmed the adequate reproducibility of both centric occlusion and centric relation when used as reference positions during treatment; however, the reproducibility of the neuromuscular position has been found inadequate. This study evaluated the location and reproducibility of these three mandibular positions in relation to body posture, sitting and supine, and bilateral muscle activity before and after the insertion of a flat mandibular positioning device equilibrated to balance the muscle functions, as shown by two electromyography biofeedback instruments. Intraoral recordings were made in 11 young subjects with complete natural dentition. Acrylic resin clutches that supported a screw point in the maxillary arch and painted glass in the mandibular arch were used and positioned not to interfere with the occlusion. The distances of the screw scratch from two of the edges of the painted glass were used to measure the anteroposterior and mediolateral locations with a micrometer. The reproducibility was evaluated by measuring the scratch surface by measuring the weight of the print cutouts made from photographs of the scratches taken with a stereoscope. The location and reproducibility of centric occlusion and centric relation were not affected by body posture. A more precise posterior neuromuscular position was obtained in the supine position. The insertion of a mandibular positioning device did not affect centric occlusion but gave a more precise centric relation. Neuromuscular position became as precise as centric occlusion and was located anteroposteriorly between centric occlusion and centric relation.

Pocket formation 3 years after comprehensive periodontal therapy. A retrospective study.

The records of 50 adult patients were studied to determine the incidence of pocket formation 3 years following periodontal therapy. These patients were treated at the Post-graduate Periodontal Clinic of Tufts University School of Dental Medicine and were subsequently placed on a 3-month maintenance schedule. A total of 1080 teeth with probing depths of 3 mm or less at the end of active therapy were examined. Before treatment 305 teeth (28.2%) had probing depths of 1 to 3 mm, 480 (44.4%) had depths of 4 to 5 mm and 295 (27.4%) had depths of 6 mm or more. Three years after active treatment 944 teeth (87.4%) had probing depths of 1 to 3 mm, 110 (10.2%) had 4 to 5 mm depths and 26 (2.4%) had depths of 6 mm or more. Pockets developed more frequently in maxillary than mandibular teeth, in molars more than in any other tooth type and in those teeth which before treatment had pockets of 6 mm or more. Pockets were less likely to develop in patients with good plaque control and in patients below the age of 40.

The effect of supragingival plaque removal on anaerobic bacteria deep periodontal pockets.

A study was made to determine if the numbers of subgingival anaerobes in deep periodontal pockets can be controlled by removal of only supragingival plaque. The study was based on the premises that the subgingival flora is dependent on the supragingival plaque for its source of organisms as well as for its perpetuation. Daily professional removal of only supragingival plaque produced a statistically significant reduction per sample in subgingival facultative and obligatory anaerobes.

Age-dependent odontogenic lesions in rats after a single i.p. injection of N-nitroso-N-methylurea.

The development of a variety of odontogenic lesions was elicited by a single i.p. injection of N-nitroso-N-methylurea (NMU) at a dose of 150 mg/kg body weight. A total of 190 male Wistar/Furth rats were used in this study. The odontogenic lesions appeared macroscopically, mainly as supernumerary lower incisors, 88 +/- 3.48 (SE) days after administration of the carcinogen. Tumors were classified as compound and complex odontomas, odontoameloblastomas and ameloblastomas. 72% of rats (31 out of 43) 6 weeks old at the time of inoculation developed microscopic alterations in the odontogenic organs of the incisors; only 4% (2 of 49) of rats injected at 8 weeks of age developed similar alterations. These findings suggest the presence of an ontogenic mechanism susceptible to damage by chemical carcinogens.

Tumorigenesis at a predetermined oral site after one intraperitoneal injection of N-nitroso-N-methylurea.

Tumors in the soft tissues of the oral cavity of rats developed at predetermined sites as a result of a combination of an intraperitoneal injection of a direct-acting carcinogen. N-nitro-N-methylurea, and a continuous irritation of the buccal mucosa by a stainless steel wire. The incidence of histologically malignant tumors was significantly higher in the irritated area than in any other area of the body. These results constitute evidence for a carcinogenic mechanism whereby the cells that develop into tumors may require the promotional effect of a nonspecific, nonmutagenic stimulus.