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A reduction in masticatory stress has been an important factor in the evolution of the human skull. Similarly, the recent increase in the occlusal variation has been related to a change in masticatory activity. The present study investigates short-term variation in craniofacial dimensions by examining cephalometrically two Finnish samples, one exposed to a hard and the other to a soft diet. The samples comprised 32 skulls, derived from the 16th and 17th centuries, and 50 living individuals. Out of 18 dimensions measured, 12 showed only non-significant differences between the samples. In the present-day sample, the cranial length and the anterior cranial base were significantly longer, and the upper incisors segment significantly higher. In the skull sample, the posterior facial height, the height of the mandibular ramus, and the antero-posterior width of the pharynx were significantly larger. The results suggest that hard diet, which requires more chewing force and time, promotes vertical growth of the ramus and anterior translocation of the maxilla. The greater posterior face height and greater height of ramus are in accordance with the earlier finding that the mandible shows more anterior growth rotation in an attritive environment. These findings support the hypothesis that the growth of the craniofacial skeleton is regulated by masticatory stress. It is suggested that both the dimensional changes and the lack of dental attrition may have contributed to the higher occlusal variation of modern individuals.

The occlusal traits of Class II occlusion in the deciduous dentition include distal terminal plane of the second deciduous molars, distal canine relation, large overjet, and large overbite. Other findings are narrow upper dental arch and maxillary base and poor anterior spacing. Skeletally, Class II children differ less from normal children. The cranial base, including the base flexure, and the maxilla are normal. The mandibular corpus and lower facial height are short, the gonial angle is large, and the dentoalveolar position of the mandible is retruded. The height of the ramus is normal, as is the skeletal position of the mandible, with the exception of the chin, which becomes slightly retruded after 5 years of age. As most skeletal traits of Class II occlusion develop later than the occlusal characteristics, it is suggested that no evidence can be found for a skeletal Class II growth pattern in the deciduous dentition. The deficient transversal growth of the maxilla and the sagittal growth of the mandible seem to cause the typical Class II occlusion. Further skeletal changes are likely to develop as secondary adaptations.

Objective: To evaluate skeletal and dentoalveolar changes induced by the eruption guidance appliance in the early mixed dentition. Materials and Methods: Pre-and posttreatment cephalometric radiographs of 115 consecutively treated children, 62 boys and 53 girls, were compared with those obtained from a control group of 104 children, 52 boys and 52 girls. Pretreatment radiographs were taken at the deciduousmixed dentition interphase (T1) and after full eruption of all permanent incisors and first molars (T2). The mean age of the children in both groups was 5.1 years at T1 and 8.4 years at T2. Results: A significant difference between the groups at T2 was found in the mandibular length, midfacial length, and maxillomandibular differential. The increase in mandibular length was 11.1 mm in the treatment group and 7.2 mm in the control group. No differences were found in measurements of maxillary position or size. There was a significant shift toward a Class I relationship in the treatment group. Labial tipping and linear protrusion of the mandibular incisors was evident in the treatment group at T2. There was no effect on the inclination or position of the maxillary incisors. Conclusions: Occlusal correction was achieved mainly through changes in the dentoalveolar region of the mandible. In addition, the appliance enhanced condylar growth resulting in a clinically significant increase in mandibular length. No effect was observed on maxillary position, maxillary size, inclination or protrusion of the maxillary incisors, or facial height.

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The chief aim of this study was to evaluate the influence of three different types of pretreatment solutions (phosphoric acid, self-etching primers, and polyacrylic acid) on enamel surfaced when used in association with one of the five orthodontic adhesive systems. In the same vein, the shear bond strength of orthodontic metal brackets was also measured to evaluate the influence of bonding procedure. After the enamel surfaces of extracted human maxillary incisors were pretreated with the five adhesive systems, scanning electron microscopy (SEM) was used to observe the effects of pretreatment on enamel. Additionally, the shear bond strength of metal brackets bonded with the five adhesives was measured (n＝6). SEM observation revealed different etching patterns on the enamel surface after pretreatment. As for shear bond strength, no statistically significant differences were observed among the five different adhesives (p>0.05). It was found that self-etching primers and polyacrylic acid produced a less aggressive etching pattern than phosphoric acid. Nonetheless, all the five adhesive systems provided acceptable bond strength and attachment of orthodontic brackets.

The purpose of the present study was to analyse cephalometrically the effects of a high-attrition environment on craniofacial morphology. The material consisted of lateral cephalograms of 32 Finnish crania and of a control sample of 50 present-day Finns. The skull sample represented Finns who had lived in the city of Turku during the 15th and 16th centuries. Marked dental attrition was seen in the skulls; the dentition of the control individuals was virtually unworn. The gonial angle, and the angle between the mandibular base and nasal floor were significantly smaller in the skull sample than in the present-day sample. In addition, the upper incisors were more palatally inclined, and the angle between the axes of the upper and lower incisors was significantly larger in the skull sample. The configuration of the cranial base, and the relationship of the clivus to the nasal floor and ramus were similar in both samples. The results indicate that intensive mastication affects mandibular growth by advancing its anterior rotation. The large interincisal angle was caused, almost equally, by the lingual tipping of the upper incisors and the anterior rotation of the mandible. It is suggested that anterior rotation is the natural growth direction of the mandible. However, several functional disturbances, including reduced masticatory stimulation due to modern diet, may promote more posteriorly directed growth.