Tooth wear and compensatory modification of the anterior dentoalveolar complex in humans.

In populations living in environments where teeth wear severely, some compensatory modification of the dentoalveolar complex is thought to occur during life whereby functional occlusion is maintained as tooth substance is lost by wear. This study investigates one aspect of this modification process: Changes in the anterior dentoalveolar complex that are accompanied with wear were examined in a series of Japanese skeletal samples. In the prehistoric Japanese hunter-gatherer population heavy wear occurs over the entire dentition. The following changes were demonstrated to have occurred in the anterior segment of the dentition accompanied by wear on the anterior teeth: The anterior teeth tip lingually with wear up to a nearly upright position to fill in interproximal spaces that would have been generated by wear, and to maintain contact relations between adjacent teeth. At the same time, the anterior surface of the maxillary alveolar process also inclines lingually to a certain extent. The amount of lingual tipping is greater in the maxillary anterior teeth than in their mandibular antagonists. It is because of this discrepancy that, with age, the horizontal component of the overlap between maxillary and mandibular anterior teeth decreases, and their bite form changes from scissor bite to edge-to-edge bite. Lesser degrees of lingual tipping of the anterior teeth were also detected in the prehistoric agriculturists and historic Japanese populations. The variation in the degree of lingual tipping observed among the samples is explained by inter-population variation in severity and pattern of tooth wear. This and other evidence suggests that mechanisms that compensate for wear in the anterior dentition may be characteristic of all living human populations, independently of the degree of wear severity endured in their environments.

Changes in the pattern of tooth wear from prehistoric to recent periods in Japan.

Although a number of studies have been performed on interpopulational variation of tooth wear patterns in recent humans, the major interest in the study of tooth wear so far has been in reconstructing the subsistence and behavior of prehistoric populations, and hence research on wear pattern changes in historic times has been superficial. The present study investigated temporal change in the pattern of wear on the permanent dentition of the Japanese through comparison of the following five groups: prehistoric hunter-gatherers, prehistoric agriculturists, medieval, premodern, and recent populations. The pattern of reduction of occlusal wear severity across these chronological groups was not similar between the anterior and posterior portions of the dentition. Occlusal wear on the anterior teeth was noticeably lighter in the prehistoric agriculturists and later populations than in the prehistoric hunter-gatherers, while clear reduction of occlusal wear on the posterior teeth occurred after medieval times. The temporal variations in the degree of mesiodistal crown diameter loss due to wear and its anterior-posterior gradient within the dentition are generally consistent with those observed in the occlusal wear pattern. Possible causative factors of these temporal changes in the wear pattern are discussed.

Changes in mandibular morphology from the Jomon to modern periods in eastern Japan.

Metric characteristics of the mandibles of modern and various historical populations from the Kanto region (east-central Japan) were compared with those of their possible ancestral populations, i.e., the Jomon population from Kanto and the Yayoi population from northern Kyushu and Yamaguchi (western Japan). The Jomon people were aboriginal Holocene inhabitants of Japan, while the Yoyoi skeletal series are considered to largely represent immigrants from the Asian continent. Compared to the presumed ancestral morphology, the mandibles of the modern and pre-modern peoples of Kanto showed a marked narrowing, as well as reduction in the regions of major masticatory muscle attachments. The main cause of this underdevelopment is likely to be a diminished chewing stress, resulting in insufficient stimulation for proper growth of the jaw bone. In contrast, symphyseal height increased compared to the earlier Kanto populations. This may be a reflection of the existence of significant Yayoi genetic contribution in the formation of the modern and pre-modern Kanto populations. On the other hand, the mandibles of the protohistoric to medieval populations of the Kanto region are morphologically closer to Jomon. Therefore, they seem to have been genealogically continuous from the native Jomon people with some degree of gene flow stemming from the immigrants.

[Study of recombinant human erythropoietin treatment on the anemia of predialysis patients].

We conducted a multiple-center joint study on the effects of recombinant human erythropoietin (rEPO) for predialysis patients. rEPO was intravenously administered to 42 predialysis patients (13 males and 29 females) with hematocrit (Ht) levels of less than 30%. The subjects were divided into group A (28 cases) in which rEPO was administered twice a week, and group B (14 cases) with rEPO administration once a week. The initial administration dosage was 6000IU/week. The Ht levels were 22.6 +/- 3.3% for group A and 23.2 +/- 2.7% for group B before the administration of rEPO, and increased to 31.0 +/- 4.0% and 27.7 +/- 3.7% respectively twelve weeks after initiating administration. The levels of effective improvement on anemia included 'markedly effective' in 17 cases (80.9%) and 'effective' in 2 cases (9.5%) in group A, and 'markedly effective' in 5 cases (41.7%) and 'effective' in 3 cases (25.0%) in group B. No significant change was seen in serum creatinine (Cr) levels during the study period. In the evaluation of renal function by reciprocal serum creatinine (1/Cr), a consistent tendency was not recognized; thus, suggesting that the rEPO administration had no effect on the renal function. No variation of blood pressure was seen. As far as side effects were concerned, headache and heavy headedness were recognized in four cases. There were, however, no cases in which the severity of the side effects dictated the discontinuation of the rEPO administration. In conclusion, rEPO was judged to be a safe and effective treatment for the anemia of predialysis patients.

Pharmacokinetics and efficacy of carvedilol in hypertensive patients with chronic renal failure and hemodialysis patients.

The efficacy, safety, and pharmacokinetics of carvedilol were investigated in an open trial performed on 13 hypertensive patients with chronic renal failure and six additional patients requiring hemodialysis. In hypertensive renal failure patients, treatment with carvedilol (5 mg/day) for 1 week produced a significant decrease in blood pressure (from 172/101 to 146/84 mm Hg) but did not change the heart rate. The pharmacokinetics of carvedilol did not change with repeated administration, and there was no accumulation of this drug. In hemodialysis patients with hypertension, the pharmacokinetics of carvedilol after a single dose of 10 mg did not vary between dialysis and nondialysis days, and blood pressure decreased significantly on both days. In addition, there was no accumulation of carvedilol during a 4-week trial of therapy, and blood pressure was decreased significantly from 170/93 to 145/83 mm Hg. There were no side effects and no abnormal laboratory findings noted during the trial. These results indicate that carvedilol is an effective and safe agent for hypertensive patients with chronic renal failure and for hemodialysis patients with hypertension and that dosage adjustments are probably not required in these clinical situations.

Pharmacokinetics and efficacy of carvedilol in chronic hemodialysis patients with hypertension.

The efficacy, safety, and pharmacokinetics of carvedilol were investigated in an open trial performed on six patients with hypertension and chronic renal failure requiring hemodialysis. The plasma level of unchanged carvedilol after a single dose of 10 mg reached a peak 1-5 h after administration both on days with and without hemodialysis. The drug was gradually metabolized thereafter and had almost disappeared from the plasma after 24 h. Blood pressure was lowered by carvedilol both on days with and without hemodialysis. No carvedilol passed through the dialysis membrane. During the 4-week administration period of carvedilol at 10 mg/day, assessment of plasma samples taken just prior to early morning administration demonstrated no drug accumulation. Blood pressure was well controlled during the administration period. Tolerance to the antihypertensive effect was not observed. Heart rate was not significantly changed at any time. There were no side effects in any of the patients during the trial, and laboratory parameters remained unchanged. These results indicate that carvedilol is a safe and effective antihypertensive agent for use in patients on chronic hemodialysis.