El objetivo del estudio fue evaluar los factores etiológicos asociados con la hipomineralización incisivo molar en escolares de un centro educativo estatal, Chiclayo, 2023. El estudio fue observacional, transversal y de nivel explicativo, la población de estudio fue de 313 niños de 7 a 9 años de edad y sus madres. Se incluyeron niños matriculados el 2023, de ambos sexos, con presencia de al menos una primera molar permanente, se excluyeron niños cuyas madres no aceptaron participar en el estudio mediante firma del consentimiento informado. Se realizó un examen clínico a los niños utilizando la codificación para HIM, así mismo, se aplicó un cuestionario presencial a las madres que cuenta con la validez y confiabilidad adecuados. Se obtuvo una prevalencia de HIM de 7.7%, predominando las opacidades blancas/cremas (código 2) con 37.5%, seguido de las opacidades amarillo/ marrón con un 16.7% y caries atípica con un 12.5%. Se concluyó, respecto a factores etiológicos de HIM, que obtuvieron significancia estadística, en prenatales el peso del niño al nacer, en posntnatales la ocurrencia de fiebre alta en el niño desde el nacimiento hasta los 4 años. / The aim of the study was to evaluate the etiological factors associated with molar incisor hypomineralization in school children in a state school, Chiclayo, 2023. The study was observational, cross-sectional and of explanatory level, the study population was 313 children from 7 to 9 years of age and their mothers. Children enrolled in 2023, of both sexes, with the presence of at least one permanent first molar were included; children whose mothers did not agree to participate in the study by signing the informed consent form were excluded. A clinic al examination of the children was performed using the coding for HIM, and a face-to-face questionnaire was applied to the mothers with adequate validity and reliability. A prevalence of HIM of 7.7% was obtained, predominantly white/cream opacities (code 2) with 37.5%, followed by yellow/brown opacities with 16.7% and atypical caries with 12.5%. It was concluded, with respect to etiological factors of HIM, that they obtained statistical significa nce, in prenatal the weight of the child at birth, in postnatal the occurrence of high fever in the child from birth to 4 years of age.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / A projeção de incisivos e expansão dos arcos dentários são uma alternativa valiosa à extração dentária, especialmente quando se considera a estética facial em pacientes adultos. O efeito da projeção ortodôntica dos incisivos inferiores sobre o periodonto é controverso devido às avaliações em exames bidimensionais e os aspectos multi-fatoriais que envolvem as recessões gengivais. O objetivo deste estudo foi comparar as modificações na altura da borda alveolar dos dentes ântero-inferiores de pacientes, que foram submetidos à projeção ortodôntica, com pacientes tratados sem projeção; e correlacionar estas modificações com o grau de inclinação dentária, com as alterações da distância bicanina e com o biotipo gengival. Pacientes adultos com mais de 3 mm de falta de espaço no arco inferior e curva de Spee moderada ou acentuada compuseram o grupo experimental (n=15). O grupo controle (n=7) consistiu de pacientes com bons arcos inferiores, que não necessitavam de grandes movimentos dentários. Estes pacientes foram submetidos a alinhamento e nivelamento dentário até o fio de aço .020". Tomografias computadorizadas de feixe cônico (TCFC) foram obtidas antes do tratamento e ao final da fase de alinhamento e nivelamento. As alturas das bordas alveolares (BA) de incisivos e caninos inferiores foram medidas nas TCFC em reconstruções 3D e comparadas entre os grupos e entre os tempos pelos testes-t de Student não pareado e pareado, respectivamente. As BA foram correlacionadas com o grau de inclinação dentária (IMPA), com a distância intercaninos (DIC) e com o biotipo gengival (BG) pelo teste de correlação de Pearson. Os resultados demonstraram que os caninos inferiores do grupo experimental apresentaram perda óssea significativa (p<0,005), quando comparados com o grupo controle, em média 2,5 mm. As BA dos dentes 43, 33 e 32 ao final do alinhamento e nivelamento eram significativamente maiores do que ao início do tratamento no grupo experimental (p<0,001). Não foram encontradas diferenças significativas entre as medidas iniciais e finais das BA de todos os dentes do grupo controle. Apesar destes resultados, não foram encontradas correlações entre a remodelação da BA e o IMPA, a DIC e o BG. Pode-se concluir que o aumento no comprimento do arco inferior com arcos ortodônticos contínuos aumenta a inclinação dos incisivos inferiores e a DIC. O aumento da DIC parece exercer maior efeito sobre a BA dos caninos inferiores do que a inclinação de incisivos sobre a BA dos incisivos inferiores. No entanto, as modificações da BA não estão associadas ao grau de inclinação dos incisivos, a quantidade de expansão do arco inferior e ao biotipo gengival. / Incisor proclination and dental arch expansion are a valuable choice of treatment instead of extraction, especially when considering facial aesthetics in adult patients. The effect of orthodontic projection of the lower incisors on the periodontium is controversial because of evaluation in two-dimensional exams and the multi factorial aspects of gingival recessions. The aim of this study was to compare alveolar height modifications in the lower arch of patients that were treated with orthodontic proclination, with patients treated without proclination, and correlate these modifications with the degree of dental projection, with the changes in the lower intercanine width and with gingival biotype. Adult patients with lower arch discrepancy of more than 3 mm and moderate or pronounced curve of Spee composed the experimental group (n=15). The control group (n=7) consisted of patients with good lower arches, that did not need large dental movements. These patients had their dental arches aligned and leveled up to a .020 wire. Cone beam computed tomography (CBCT) was taken before treatment and after leveling and alignment. The height of the alveolar border (AB) of the lower incisors and canines were measured on CBCT with 3D reconstruction, and compared between groups, and between times, by paired and independent Students t-test, respectively. The AB were correlated with the degree of dental inclination (IMPA), intercanine width (ICW) and gingival biotype (GB) by the Pearson correlation test. Results showed that the lower canines of the experimental group presented significant bone loss (p<0,005) when compared with the control group, with a mean of 2.5 mm. The AB of teeth 43, 33 and 32 at the end of alignment were significantly greater than at beginning of treatment for the experimental group (p<0,001). No significant differences were found between initial and final AB measurements for all control group teeth. Despite these results, no correlation was found between remodeling of AB and IMPA, ICW and GB. It can be concluded that the increase of lower arch length with continuous orthodontic archwires increases lower incisor inclination and ICW. The increase of the ICW seems to exert more effect over the AB of lower canines, than the incisor inclination over the AB of the incisors. However, AB modifications are not associated with the degree of incisors inclination, neither the amount of lower arch expansion, nor to the gingival biotype.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / A projeção de incisivos e expansão dos arcos dentários são uma alternativa valiosa à extração dentária, especialmente quando se considera a estética facial em pacientes adultos. O efeito da projeção ortodôntica dos incisivos inferiores sobre o periodonto é controverso devido às avaliações em exames bidimensionais e os aspectos multi-fatoriais que envolvem as recessões gengivais. O objetivo deste estudo foi comparar as modificações na altura da borda alveolar dos dentes ântero-inferiores de pacientes, que foram submetidos à projeção ortodôntica, com pacientes tratados sem projeção; e correlacionar estas modificações com o grau de inclinação dentária, com as alterações da distância bicanina e com o biotipo gengival. Pacientes adultos com mais de 3 mm de falta de espaço no arco inferior e curva de Spee moderada ou acentuada compuseram o grupo experimental (n=15). O grupo controle (n=7) consistiu de pacientes com bons arcos inferiores, que não necessitavam de grandes movimentos dentários. Estes pacientes foram submetidos a alinhamento e nivelamento dentário até o fio de aço .020". Tomografias computadorizadas de feixe cônico (TCFC) foram obtidas antes do tratamento e ao final da fase de alinhamento e nivelamento. As alturas das bordas alveolares (BA) de incisivos e caninos inferiores foram medidas nas TCFC em reconstruções 3D e comparadas entre os grupos e entre os tempos pelos testes-t de Student não pareado e pareado, respectivamente. As BA foram correlacionadas com o grau de inclinação dentária (IMPA), com a distância intercaninos (DIC) e com o biotipo gengival (BG) pelo teste de correlação de Pearson. Os resultados demonstraram que os caninos inferiores do grupo experimental apresentaram perda óssea significativa (p<0,005), quando comparados com o grupo controle, em média 2,5 mm. As BA dos dentes 43, 33 e 32 ao final do alinhamento e nivelamento eram significativamente maiores do que ao início do tratamento no grupo experimental (p<0,001). Não foram encontradas diferenças significativas entre as medidas iniciais e finais das BA de todos os dentes do grupo controle. Apesar destes resultados, não foram encontradas correlações entre a remodelação da BA e o IMPA, a DIC e o BG. Pode-se concluir que o aumento no comprimento do arco inferior com arcos ortodônticos contínuos aumenta a inclinação dos incisivos inferiores e a DIC. O aumento da DIC parece exercer maior efeito sobre a BA dos caninos inferiores do que a inclinação de incisivos sobre a BA dos incisivos inferiores. No entanto, as modificações da BA não estão associadas ao grau de inclinação dos incisivos, a quantidade de expansão do arco inferior e ao biotipo gengival. / Incisor proclination and dental arch expansion are a valuable choice of treatment instead of extraction, especially when considering facial aesthetics in adult patients. The effect of orthodontic projection of the lower incisors on the periodontium is controversial because of evaluation in two-dimensional exams and the multi factorial aspects of gingival recessions. The aim of this study was to compare alveolar height modifications in the lower arch of patients that were treated with orthodontic proclination, with patients treated without proclination, and correlate these modifications with the degree of dental projection, with the changes in the lower intercanine width and with gingival biotype. Adult patients with lower arch discrepancy of more than 3 mm and moderate or pronounced curve of Spee composed the experimental group (n=15). The control group (n=7) consisted of patients with good lower arches, that did not need large dental movements. These patients had their dental arches aligned and leveled up to a .020 wire. Cone beam computed tomography (CBCT) was taken before treatment and after leveling and alignment. The height of the alveolar border (AB) of the lower incisors and canines were measured on CBCT with 3D reconstruction, and compared between groups, and between times, by paired and independent Students t-test, respectively. The AB were correlated with the degree of dental inclination (IMPA), intercanine width (ICW) and gingival biotype (GB) by the Pearson correlation test. Results showed that the lower canines of the experimental group presented significant bone loss (p<0,005) when compared with the control group, with a mean of 2.5 mm. The AB of teeth 43, 33 and 32 at the end of alignment were significantly greater than at beginning of treatment for the experimental group (p<0,001). No significant differences were found between initial and final AB measurements for all control group teeth. Despite these results, no correlation was found between remodeling of AB and IMPA, ICW and GB. It can be concluded that the increase of lower arch length with continuous orthodontic archwires increases lower incisor inclination and ICW. The increase of the ICW seems to exert more effect over the AB of lower canines, than the incisor inclination over the AB of the incisors. However, AB modifications are not associated with the degree of incisors inclination, neither the amount of lower arch expansion, nor to the gingival biotype.

L’évolution de la denture des vertébrés est un sujet majeur et des plus intéressants en biologie développementale évolutive (évo-dévo). Dans ce domaine, la souris Mus musculus est traditionnellement l’animal modèle utilisé. La denture de la souris inclus quatre incisives à croissance continue et douze molaires présentant une organisation caractéristique de leurs cuspides. Le réseau moléculaire régulant le développement de ces deux types de dents est très spécifique.La cascade ERK-MAPK est impliquée lors de différentes étapes du développement dentaire. Une étude comparée du phénotype des molaires de souris mutantes pour des gènes activés à différents points de la cascade a démontré l’existence d’un phénotype caractéristique, à savoir la présence d’une dent surnuméraire en position mésiale des rangées de molaires, ainsi que la présence d’anomalie dans le nombre et la forme de certaines cuspides. Parmi ces caractères présents chez les mutants, certains rappellent des caractères ancestraux présents uniquement chez des rongeurs fossiles. Ceci appuie le rôle que la cascade ERK-MAPK a pu jouer au cours de l’évolution de la denture chez les rongeurs. En travaillant sur une lignée transgénique sur-exprimant un inhibiteur de cette cascade, j’ai pu perfectionner notre connaissance du rôle des gènes de la famille Fgf dans les processus de mise en place des centres de signalisation dentaire et de minéralisation de l’émail.Si l’on considère les incisives à croissance continue, la denture de la souris est dynamique à l’échelle de la vie d’un individu. Réalisant un suivi des incisives supérieures d’une cohorte de souris au cours de leur vieillissement, j’ai pu préciser la chronologie d’apparition de défauts liés au vieillissement. Ces défauts apparaissent sur les incisives à partir de six mois, et le plus fréquent est le développement d’un sillon visible sur l’émail de l’incisive. J’ai enfin utilisé des techniques de séquençage de nouvelle génération (NGS) pour comprendre les bases moléculaires du vieillissement des niches de cellules souches des incisives. Ce faisant, j’ai détecté des changements dans les profils d’expression de gènes régulant le maintien des cellules souches, la prolifération cellulaire et le métabolisme. La présence d’un sillon apparaît corrélée à une forte réponse immunitaire détectée dans les tissus dentaires, ce qui constitue une perspective d’étude majeure dans le but d’achever la caractérisation du vieillissement des cellules souches dentaires. / The evolution of the vertebrate dentition is among the most exciting topics in the evo-devo field, with particular attention being drawn to the mouse model. The mouse dentition includes four ever-growing incisors and twelve molars with a specific cusp pattern. Incisors and molars develop according to a tightly regulated molecular network.The ERK-MAPK cascade is involved at various stages of tooth development. Molar tooth phenotype comparisons in mutant mice for genes acting at various levels of the cascade highlighted a dental phenotype signature, which consists in the presence of a supernumerary tooth and shared cusp pattern defects. Some of these recall characters present in fossil rodents, supporting the ERK-MAPK as a good candidate to explain some evolutionary trends of the rodent dentition. By working on a mouse line over-expressing one of this pathway inhibitor in the oral epithelium, I perfect our understanding of Fgf gene role in specifying signaling center formation at the right stage, and in achieving correct mineralization.When considering evergrowing incisors, mouse dentition is also dynamic at the lifetime scale. I monitored the ageing process of the mouse upper incisors, and provided a chronology of occurrence of the variety of age-related defects display. These defects are set up from the six months on, the most frequent abnormality being the presence of an enamel groove along the surface of the incisor. Using Next Generation Sequencing technologies, I detected transcriptomic changes in the stem cell niches affecting cell proliferation and metabolism, as well as the stem cell niche functioning. The correlation found between the groove occurrence and a large immune response in dental tissues expands our concern for dental stem cell ageing.

Fixed retainer after orthodontic treatment is an increasing retention appliance. For the mandibular incisors there are two different fixed retainers that are commonly used, either a canine-to-canine retainer bonded only to the canines or a twistflex retainer bonded to each of the mandibular incisors and canines. Increased mandibular incisor irregularity seems to be a continuous process throughout life even in untreated patients. The natural physiological changes during aging causes changes like those that occur after orthodontic treatment and the removal of retainers. There are few long-term studies that have compared patients who have had a mandibular fixed retainer with patients without retention appliance after treatment, and then compared the treated patients with untreated subjects.The overall aim of this thesis was to compare and evaluate two different mandibular fixed retainers and also to compare orthodontically treated cases with untreated long-term. This thesis is based on two studies and a PAR Index evaluation was presented in the frame story:Paper I is a retrospective longitudinal study done on dental casts and lateral head radiographs from patients who had received either a canine-to-canine retainer or a twistflex retainer after treatment. Different variables were measured, were Little’s Irregularity Index was the main outcome measure. The measurements were done at four different occasions, were the last registration was 12 years after treatment, i.e. 9 years after removal of retainer. Paper II is also a retrospective longitudinal study with three different groups, one group received a fixed mandibular retainer, one group did not receive any retention appliance after treatment and the third group was untreated subjects. Measurements were done on dental casts and lateral head radiographs at four different occasions to analyze dental and skeletal changes 12 years after treatment. Also here Little’s Irregularity Index was the main outcome measure. PAR Index evaluation is done to evaluate the stability of orthodontic treatment outcome after treatment and long-term for two different retainer groups and one non-retention group. The following conclusions were drawn: Paper I•Both the canine-to-canine retainer and the twistflex retainer can be recommended since both are equally effective during retention period.•None of the retention types prevent long-term changes of mandibular incisor irregularity or available space for the mandibular incisors after removal of the retainers.•No differences in bonding failures between the two retainers were found. Paper II•There were no differences found 12 years after treatment in Little’s Irregularity Index for the mandibular incisors between the group that had a retainer and the group that had no retainer after treatment•In the untreated group, Little’s Irregularity Index was increased over time but not to the same extent as in the treated groups. •The crowding before treatment did not explain the crowding at the last registration.•The use of mandibular retainers for two to three years does not appear to prevent long-term relapse. •If the patient wants to constrain the changes that come with natural development, then lifelong retention is needed.•The overjet and overbite were stable long-term.PAR Index evaluation•Twelve years after treatment the mean reduction in PAR score was over 70 per cent only for the groups who had a mandibular retainer after treatment. However, the non-retention group had a PAR score of 66 per cent.•There were more cases in the retention groups that were ”greatly improved and/or improved” 12 years after treatment compared to the non-retention group. After treatment between 16 and 23.3 per cent of all the cases were ”worse or not improved”. Twelve years after treatment between 36 and 43.6 per cent of the total cases were ”worse or not improved”.