Some studies reported that PTHrp and PTH 1-34 share a common receptor: type 1 PTH/PTHrp receptor (PTHR1),30 and 31 which is also expressed in odontoblasts.13 Calvi et al.12 showed that, in the tooth development, odontoblastic expression of the activated PTHR1 resulted in decreased dentine in the molar crowns, whereas the incisors had large amounts of dentine. These data therefore, suggest that in odontoblasts, activation of the PTHR1 triggers responses similar to those in osteoblasts, with expansion of the odontoblastic pool and changes in odontoblastic maturation and function. It is important to know how the tooth quality, which relates to the ability of the tooth to fulfil its functions,

is affected by PTH intermittent administration. find more Tooth quality can be analyzed by measuring tooth material and mechanical properties.32 Material properties are those properties specific (intrinsic) to a material, whereas mechanical properties are those properties that reveal the reaction, either elastic or plastic, of a material to an applied stress.32 In this study, material properties were analyzed by measuring elemental contents in the at.% of peritubular and intertubular dentine, calculating the Ca/P ratio, whereas mechanical property was analyzed using the degree of mineralization of dentine. EDX microanalysis, used for measuring the element PD-1 phosphorylation content

in at.% of calcium (Ca), phosphorus (P), and the Ca/P ratio in the peritubular and intertubular dentine in this study, indicated important changes in the composition of apatite from dentine following PTH treatment (Table

2). For the peritubular dentine, the P (23%) and Ca (53%) at.% content was increased in T10 animals when compared to C10 animals. In addition, the Ca/P ratio in the peritubular dentine of T10 animals was higher than C10 animals (24%), which not was observed in the intertubular dentine. The peritubular and intertubular dentine have different mechanical properties that reveal the distinct ultrastructural and biochemical composition, such as the mineralization mechanism.33 and 34 While the intertubular dentine has a collagen fibril-based matrix, the peritubular dentine is a specialized non-collagenous matrix that is rich in phosphoproteins Adenosine and Gla-proteins secreted by the odontoblasts. Both phosphoproteins and Gla-proteins have a high affinity for calcium ions and can induce apatite nucleation, suggesting an inductive role in mineralization of the tubule wall to a higher degree than the intertubular dentine.33 and 34 Different methods have been used to evaluate the degree of dentine mineralization. Microhardness testing is the method of choice for detecting changes in the consistency of the surface, as mineral lost or gain.35 and 36 The results obtained from the knoop microhardness testing, revealed that the animals of the T10 group presented a greater microhardness than did the control animals (C10) (11%), as shown in Fig. 3.