Growth and Development

Growth refers to changes in magnitude and size. This is why economists refer to growth of economy when they mean expansion of economy in amount and magnitude. Growth is divided into pre and postnatal growth; the prenatal growth starts from the second semester until birth while the postnatal one starts from birth until death. On the other hand, development accounts for how growth happens and the term development is used almost always refer to an increase in complexity (Sadler, 2011, Sperber et al., 2001).

Proffit identified 3 possibilities for growth:

  • Increase in size of individual cells (hypertrophy)
  • Increase in number of cells (hyperplasia)
  • Cells to secrete extracellular material contributing to an increase in size independent of the number or the size of the cells themselves.

An implant study at the age of puberty
A. Bjork and  Skieller, D.D.S.
Copenhagen, Denmark

Purpose: To analyze the eruption paths of the teeth in relation to facial development and growth of the jaws. In this article emphasis is placed on the association of tooth eruption with the vertical development of the face with the aid of the implant technique.

Introduction:

During the growth and development of the face, compensatory change in the path of eruption of the teeth occur which tend to even out positional changes between the jaws. If such compensation is insufficient or does not occur at all, defective occlusion and space anomalies will result. Demonstrating the compensatory mechanisms by means of conventional longitudinal  radiographic methods is more difficult with respect to the vertical than to the sagittal development of the face thus the use of metallic implants as a reference point is a valuable technique.

Materials and Methods:

  • Twenty-one subjects were chosen nine girls and twelve boys
  • The metallic implants were inserted in both jaws, except two cases, where they were inserted only in the mandible.
  • Profile radiographs were selected that related to three stages: film B, recorded at the annual observation the puberal maximum; film A, taken 3 years previously; and film C, 3 years later. In four girls observation A was one year shorter, and in one of the boys observation C was one year shorter.

Findings and Discussion:

  • Rotation of the face
  • It is evident that the facial development is characterized by a rotation involving both jaws.
  • Two cases showed a backward rotation (positive). While for the other nineteen subjects the rotation of the mandible was forward in direction (negative)
  • A forward rotation thus seemed to be a general feature of the facial development
  • The rotations were thus more than twice as great for the mandible as for the maxilla and the range more than 3 times.
  • In forward rotation there is a marked apposition below the symphysis and the anterior part of the lower mandibular border, leading to an increase in convexity in this area, while resorption below the angle of the mandible leads to flattening
  • With a backward rotation of the mandible, there is a remodeling in the opposite direction, characterized by only slight apposition below the symphysis and the anterior part of the lower border of the mandible.
  • The compensatory remodeling at the posterior border of the ramus was dependent on the condylar growth angle
  • The development in length of the lower dental arch was more dependent on its growth in height against the sloping ramal border. (associated with the condylar growth direction)
  • The remodeling at the nasal floor varied according to the direction and magnitude of the rotation of the maxilla.

Condylar growth

  • The intensity of the condylar growth was strongly correlated with the rotation of the mandible and also significantly, but less strongly, with the rotation of the maxilla.
  • The correlations between the curvature and the rotation of both jaws were significant.
  • The intensity of the condylar growth was strongly correlated with the direction of condylar growth but not with the curving.

 Tooth eruption and growth of the face

  • The rotation of the jaws during growth exerts an influence on the path of eruption of the teeth and hence on the occlusion and tooth spacing.
  • It is clinically significant that a differentiation between the rotation of the maxilla and the amount of tooth eruption cannot be made on the basis of conventional radiographs

Summary:

A general feature of the facial development was a more or less marked forward rotation of the face, including the two jaws, but greater for the mandible. There was a strong association between the facial rotation and the condylar growth. At the lower border of the mandible about one half of the rotation was masked by a compensatory remodeling in this area. At the posterior border of the ramus about four fifths of the mandibular rotation was masked by compensatory remodeling. The rotation of the maxilla was likewise masked by remodeling of the nasal floor, which remained almost unchanged in inclination.

*The rotation of the face necessitates compensatory adaptation of the paths of eruption of the teeth. When there is full compensatory occlusal development, the lower incisors retain their inclination in the face practically undisturbed, irrespective of the rotation of the jaw, because of a forward tipping on the jaw base. The posterior teeth in the lower jaw, too, are involved in this compensatory occlusal development and are likewise tipped forward. The lower dental arch then shifts forward on the jaw base without undergoing any appreciable change in shape. The intermolar inclination remains comparatively constant as the lateral teeth in both jaws follow the rotation of the face. What clinically has been regarded, as an eruption of the upper molars appeared to be a combination of active eruption of the teeth in the jawbone and bodily rotation of the maxilla. This is a new aspect of occlusal development, which may have clinical implications.

A general conclusion that may be drawn from the results is that malocclusions are to a greater extent due to incomplete compensatory guidance of eruption than to dysplastic deformation of the dental arches. Prophylactic and interceptive measures should therefore be focused on the factors potentially responsible for impairing the compensatory mechanism. In the planning of orthodontic treatment the therapy should be designed to take into account the action of such forces on the development of the occlusion.

Conclusion

Advances in biomedical sciences and bioengineering have allowed for a revision of the functional matrix hypothesis.  It is concluded that genomic and epigenetic factors are both necessary but neither are sufficient alone for the control and regulation of morphogenesis.

Facial development and tooth eruption
An implant study at the age of puberty
A. Bjiirk, Odont. Dr., and V. Skieller, D.D.S.
Copmhngen, Denmark

Purpose: To analyze the eruption paths of the teeth in relation to facial development and growth of the jaws. In this article emphasis is placed on the association of tooth eruption with the vertical development of the face with the aid of the implant technique.

Introduction:

During the growth and development of the face, compensatory change in the path of eruption of the teeth occur which tend to even out positional changes between the jaws. If such compensation is insufficient or does not occur at all, defective occlusion and space anomalies will result. Demonstrating the compensatory mechanisms by means of conventional longitudinal  radiographic methods is more difficult with respect to the vertical than to the sagittal development of the face thus the use of metallic implants as a reference point is a valuable technique.

Materials and Methods:

  • Twenty-one subjects were chosen nine girls and twelve boys
  • The metallic implants were inserted in both jaws, except two cases, where they were inserted only in the mandible.
  • Profile radiographs were selected that related to three stages: film B, recorded at the annual observation the puberal maximum; film A, taken 3 years previously; and film C, 3 years later. In four girls observation A was one year shorter, and in one of the boys observation C was one year shorter.

Findings and Discussion:

  • Rotation of the face
  • It is evident that the facial development is characterized by a rotation involving both jaws.
  • Two cases showed a backward rotation (positive). While for the other nineteen subjects the rotation of the mandible was forward in direction (negative)
  • A forward rotation thus seemed to be a general feature of the facial development
  • The rotations were thus more than twice as great for the mandible as for the maxilla and the range more than 3 times.
  • In forward rotation there is a marked apposition below the symphysis and the anterior part of the lower mandibular border, leading to an increase in convexity in this area, while resorption below the angle of the mandible leads to flattening
  • With a backward rotation of the mandible, there is a remodeling in the opposite direction, characterized by only slight apposition below the symphysis and the anterior part of the lower border of the mandible.
  • The compensatory remodeling at the posterior border of the ramus was dependent on the condylar growth angle
  • The development in length of the lower dental arch was more dependent on its growth in height against the sloping ramal border. (associated with the condylar growth direction)
  • The remodeling at the nasal floor varied according to the direction and magnitude of the rotation of the maxilla.
  • Condylar growth
  • The intensity of the condylar growth was strongly correlated with the rotation of the mandible and also significantly, but less strongly, with the rotation of the maxilla.
  • The correlations between the curvature and the rotation of both jaws were significant.
  • The intensity of the condylar growth was strongly correlated with the direction of condylar growth but not with the curving.
  • Tooth eruption and growth of the face
  • The rotation of the jaws during growth exerts an influence on the path of eruption of the teeth and hence on the occlusion and tooth spacing.

It is clinically significant that a differentiation between the rotation of the maxilla and the amount of tooth eruption cannot be made on the basis of conventional radiographs

Summary:

  • A general feature of the facial development was a more or less marked forward rotation of the face, including the two jaws, but greater for the mandible. There was a strong association between the facial rotation and the condylar growth. At the lower border of the mandible about one half of the rotation was masked by a compensatory remodeling in this area. At the posterior border of the ramus about four fifths of the mandibular rotation was masked by compensatory remodeling. The rotation of the maxilla was likewise masked by remodeling of the nasal floor, which remained almost unchanged in inclination.
  • *The rotation of the face necessitates compensatory adaptation of the paths of eruption of the teeth. When there is full compensatory occlusal development, the lower incisors retain their inclination in the face practically undisturbed, irrespective of the rotation of the jaw, because of a forward tipping on the jaw base. The posterior teeth in the lower jaw, too, are involved in this compensatory occlusal development and are likewise tipped forward. The lower dental arch then shifts forward on the jaw base without undergoing any appreciable change in shape. The intermolar inclination remains comparatively constant as the lateral teeth in both jaws follow the rotation of the face. What clinically has been regarded, as an eruption of the upper molars appeared to be a combination of active eruption of the teeth in the jawbone and bodily rotation of the maxilla. This is a new aspect of occlusal development, which may have clinical implications.
  • A general conclusion that may be drawn from the results is that malocclusions are to a greater extent due to incomplete compensatory guidance of eruption than to dysplastic deformation of the dental arches. Prophylactic and interceptive measures should therefore be focused on the factors potentially responsible for impairing the compensatory mechanism. In the planning of orthodontic treatment the therapy should be designed to take into account the action of such forces on the development of the occlusion.

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