Changes in lower dental arch dimensions and tooth alignment in young adults without orthodontic treatment.

OBJECTIVE: The aim of this longitudinal study, comprising young adults without orthodontic treatment, was to assess spontaneous changes in lower dental arch alignment and dimensions. METHODS: Twenty pairs of dental casts of the lower arch, obtained at different time intervals, were compared. Dental casts obtained at T1 (mean age = 20.25) and T2 (mean age = 31.2) were compared by means of paired t-test (p < 0.05). RESULTS: There was significant reduction in arch dimensions: 0.43 mm for intercanine (p = 0.0089) and intermolar (p = 0.022) widths, and 1.28 mm for diagonal arch length (p < 0.001). There was a mild increase of approximately 1 mm in the irregularity index used to assess anterior alignment (p < 0.001). However, regression analysis showed that changes in the irregularity index revealed no statistically significant association with changes in the dental arch dimensions (p > 0.05). Furthermore, incisors irregularity at T2 could not be predicted due to the severity of this variable at T1 (p = 0.5051). CONCLUSION: Findings suggest that post-growth maturation of the lower dental arch leads to a reduction of dental arch dimensions as well as to a mild, yet significant, increase in dental crowding, even in individuals without orthodontic treatment. Furthermore, dental alignment in the third decade of life cannot be predicted based on the severity of dental crowding at the end of the second decade of life.

Changes in lower dental arch dimensions and tooth alignment in young adults without orthodontic treatment

OBJECTIVE: The aim of this longitudinal study, comprising young adults without orthodontic treatment, was to assess spontaneous changes in lower dental arch alignment and dimensions. METHODS: Twenty pairs of dental casts of the lower arch, obtained at different time intervals, were compared. Dental casts obtained at T1 (mean age = 20.25) and T2 (mean age = 31.2) were compared by means of paired t-test (p < 0.05). RESULTS: There was significant reduction in arch dimensions: 0.43 mm for intercanine (p = 0.0089) and intermolar (p = 0.022) widths, and 1.28 mm for diagonal arch length (p < 0.001). There was a mild increase of approximately 1 mm in the irregularity index used to assess anterior alignment (p < 0.001). However, regression analysis showed that changes in the irregularity index revealed no statistically significant association with changes in the dental arch dimensions (p > 0.05). Furthermore, incisors irregularity at T2 could not be predicted due to the severity of this variable at T1 (p = 0.5051). CONCLUSION: Findings suggest that post-growth maturation of the lower dental arch leads to a reduction of dental arch dimensions as well as to a mild, yet significant, increase in dental crowding, even in individuals without orthodontic treatment. Furthermore, dental alignment in the third decade of life cannot be predicted based on the severity of dental crowding at the end of the second decade of life. .

OBJETIVO: o objetivo deste trabalho foi avaliar, por meio de um estudo longitudinal em adultos jovens, sem tratamento ortodôntico, as alterações espontâneas do alinhamento da arcada dentária inferior e de suas dimensões. MÉTODOS: vinte pares de modelos de gesso da arcada inferior foram obtidos em dois tempos. No primeiro exame (T1), os indivíduos tinham, em média, 20,25 anos; enquanto no segundo exame (T2) a média de idade foi de 31,2 anos. Comparações entre os tempos T1 e T2 foram realizadas usando o teste t pareado (p < 0,05). RESULTADOS: houve uma redução significativa nas dimensões da arcada - de 0,43mm nas larguras intercaninos (p = 0,0089) e intermolares (p = 0,022) e de 1,28mm para o comprimento diagonal da arcada (p < 0,001). Foi observado um aumento suave, de aproximadamente 1mm, no índice de irregularidade anterior (p < 0,001). Entretanto, a análise de regressão mostrou que as mudanças no índice de irregularidade não revelaram uma associação estatisticamente significativa com as mudanças na arcada dentária (p > 0,05). Além disso, o índice de irregularidade dos incisivos em T2 não pode ser estimado, devido à severidade dessa variável em T1 (p = 0,5051). CONCLUSÃO: esses achados sugerem que a maturação da arcada dentária inferior, pós-crescimento, leva a uma redução das dimensões da arcada e um aumento suave, porém significativo, do apinhamento dentário, mesmo em indivíduos sem tratamento ortodôntico. Assim, o alinhamento dentário na terceira década de vida não pode ser previsto tendo como base a severidade do apinhamento dentário ao final da segunda década de vida. .

Evaluation of metallic brackets adhesion after the use of bleaching gels with and without amorphous calcium phosphate (ACP): in vitro study.

OBJECTIVE: To evaluate in vitro the effects of tooth whitening using gel with Amorphous Calcium Phosphate (ACP) on the bond strength of metal brackets. METHODS: Thirty-six bovine incisors were sectioned at the crown-root interface, and the crowns were then placed in PVC cylinders. The specimens were divided into 3 groups (n = 12) according to whitening treatment and type of gel used, as follows: G1 (control) - no whitening; G2 - whitening with gel not containing ACP (Whiteness Perfect - FGM), G3 - whitening with gel containing ACP (Nite White ACP - Discus Dental). Groups G2 and G3 were subjected to 14 cycles of whitening followed by an interval of 15 days before the bonding of metal brackets. Shear bond strength testing was performed on a Kratos universal test machine at a speed of 0.5 mm/min. After the mechanical test, the specimens were assessed to determine the adhesive remnant index (ARI). The results were subjected to ANOVA, Tukey's test and Kruskal-Wallis test (5%). RESULTS: Significant differences were noted between the groups. Control group (G1 - 11.10 MPa) showed a statistically higher shear bond strength than the groups that underwent whitening (G2 - 5.40 Mpa, G3 - 3.73 MPa), which did not differ from each other. There were no significant differences between the groups in terms of ARI. CONCLUSIONS: Tooth whitening reduces the bond strength of metal brackets, whereas the presence of ACP in the whitening gel has no bearing on the results.

Evaluation of metallic brackets adhesion after the use of bleaching gels with and without amorphous calcium phosphate (ACP): in vitro study

OBJECTIVE: To evaluate in vitro the effects of tooth whitening using gel with Amorphous Calcium Phosphate (ACP) on the bond strength of metal brackets. METHODS: Thirty-six bovine incisors were sectioned at the crown-root interface, and the crowns were then placed in PVC cylinders. The specimens were divided into 3 groups (n = 12) according to whitening treatment and type of gel used, as follows: G1 (control) = no whitening; G2 = whitening with gel not containing ACP (Whiteness Perfect - FGM), G3 = whitening with gel containing ACP (Nite White ACP - Discus Dental). Groups G2 and G3 were subjected to 14 cycles of whitening followed by an interval of 15 days before the bonding of metal brackets. Shear bond strength testing was performed on a Kratos universal test machine at a speed of 0.5 mm/min. After the mechanical test, the specimens were assessed to determine the adhesive remnant index (ARI). The results were subjected to ANOVA, Tukey's test and Kruskal-Wallis test (5%). RESULTS: Significant differences were noted between the groups. Control group (G1 = 11.10 MPa) showed a statistically higher shear bond strength than the groups that underwent whitening (G2 = 5.40 Mpa, G3 = 3.73 MPa), which did not differ from each other. There were no significant differences between the groups in terms of ARI. CONCLUSION: Tooth whitening reduces the bond strength of metal brackets, whereas the presence of ACP in the whitening gel has no bearing on the results.

OBJETIVO: avaliar, in vitro, a influência do clareamento dentário com gel contendo fosfato de cálcio amorfo (ACP) na resistência da união adesiva de braquetes metálicos. MÉTODOS: trinta e seis dentes incisivos bovinos foram seccionados no limite coronorradicular e tiveram suas coroas incluídas em cilindros de PVC. Os corpos de prova foram divididos em três grupos (n = 12), de acordo com a realização do tratamento clareador e tipo de gel utilizado, sendo: G1 (controle) - sem clareamento; G2 - clareamento com gel sem ACP (Whiteness Perfect, FGM); G3 - clareamento com gel contendo ACP (Nite White ACP, Discus Dental). Os grupos G2 e G3 foram submetidos a 14 ciclos de clareamento, seguidos de intervalo de espera de 15 dias para a fixação adesiva dos braquetes metálicos. O ensaio mecânico de cisalhamento foi realizado em máquina universal Kratos, com velocidade de 0,5mm/min. Após o teste mecânico, os corpos de prova foram avaliados quanto ao índice de remanescente adesivo (ARI). Os resultados foram submetidos à ANOVA, ao teste de Tukey e ao de Kruskall-Wallis (α = 5%). RESULTADOS: diferenças significativas foram observadas entre os grupos testados. O grupo controle G1 (11,1MPa) mostrou uma resistência ao cisalhamento estatisticamente superior aos grupos submetidos ao clareamento (G2 = 5,40MPa; G3 = 3,73MPa), os quais não diferiram entre si. Não se observou diferença significativa para o ARI entre os grupos estudados. CONCLUSÃO: o clareamento dentário reduz a resistência da união adesiva de braquetes metálicos, enquanto a presença de ACP no gel clareador não influencia os resultados encontrados.