Long-term Effects of Orthodontic Forces on the Morphology of the Rat-incisor Socket and its Location in the Mandible

Abstract

The effect of orthodontic force application on the rat-incisor socket and mandible was studied on roentgenograms. A mean linguo-intrusive force of 19 + 0.6 g was applied continuously to the shortened left lower incisor for a period of two (group A) and four weeks (group B). A third group of rats, subjected to shortening of the left mandibular incisor only, served as a hypofunctional control (group C). A fourth group of normal rats constituted the intact control (group D). After a recovery period of three months, the animals were killed, and standardized roentgenograms of the cleaned mandibles were taken. Socket and mandibular dimensions were measured on magnified tracings of the roentgenograms. Comparison of groups A and B with the control groups, on the one hand, and of group C with group D, on the other, facilitated isolation of the hypofunctional factor. In groups A and B, the orthodontic forces caused changes in the parameters affected (i.e., socket area, alveolar bone thickness, mandibular dimensions) and not affected by hypofunction (i.e., socket angulation and location, anterior-socket length). The former finding implies modification of the adaptive capability of dental structures to functional demands. It is concluded that mechanical loading of the incisor for two to four weeks causes long-lasting changes in the socket and its surrounding bone.

Avaliação da suplementação com caseína sobre o periodonto e osso mandibular de ratos alimentados com dieta padrão e dieta de cafeteria

“…As medidas somatométricas foram analisadas por meio do programa ImageJ (Wayne Rasband do Research Services Branch, Bethesda, Estados Unidos), sendo elas: altura anterior (traçado 1), altura posterior (traçado 2), comprimento anterior (traçado 3), comprimento posterior (traçado 4) ângulo gonial (de 5-7/ plano mandibular) e área líquida (área da mandíbula menos a região de sulco). A análise dos valores de pixels, referente à escala de cinza, foi avaliada em 10 pontos distribuídos, nomeados de P1 a P10, em duas regiões da hemimandíbula (Dalmolin et al, 2018;Brin, Michaeli & Steigman, 1990). Tanto as medidas somatométricas quanto os pontos de análise de pixels estão ilustrados na Figura 1.…”

Mineral Contents and Somatometric Parameters in the Hemimandible, Tibia and Incisor of Rats Submitted to a Hypothalamic Obesity Condition

“…Density was calculated from the formula d = m/v where m = mass (g) and v = volume (cm 3 ), obtained from the Archimedes method and by the bone tomographic images taken using the GE equipment (with eight channels) at the São Camilo Hospital (Ponta Grossa city) and expressed in Hounsfield Units -(HU). Hemimandible and tibia morphology were evaluated by radiographical analysis using a Sirona CSU imaging system (80kV, 11mA, Siemens, Germany) and a Kodak Lanex 20X25 frame (USA) and radiographic film (Kodak, Brazil).The morphometry was obtained using a calibrated ruler to take measurements of the previously defined axis ( Figure 1) [31]. For the incisor, the measurements were made in three crosssections (2 mm) per animal, obtained using a diamond cutting disc (7" diameter) and a precision cutting machine (Isomet 1000) [32].…”

“…(A) Shows the tibia and the axes determined and measured: the point 1 to 1', corresponding to the length; 2-2' and 3-3', corresponding to the thickness of the epiphysis and diaphysis, respectively. (B) Shows the points measured in the hemimandible adapted from Brin et al[31]. (C) Shows the measurements taken for the incisor, according to Steigman et al[32].…”