Stability of first and second premolars extraction space closure.

INTRODUCTION: Premolars are the teeth most often extracted to provide space to correct crowding, excessive dental and/or labial protrusion, and to compensate for the sagittal discrepancy. After treatment, the extraction spaces have to remain closed. Nevertheless, several studies have shown a tendency for some relapse even in patients finished with an adequate occlusion. Thus, the objective of this study was to compare the stability of extraction space closure of the first and second premolars. METHODS: Dental casts of 72 patients were digitized using a 3-dimensional scanner (R700; 3Shape, Copenhagen, Denmark) and divided into 2 groups. Group 1 (29 patients; mean age, 13.79 years; 4.57 years after treatment; 116 extraction spaces) was treated with first premolar extractions, and group 2 (43 patients; mean age, 15.20 years; 3.97 years after treatment; 100 extraction spaces) was treated with second premolar extractions. Chi-square tests were used to compare the numbers of open and closed extraction spaces after treatment and at the long-term posttreatment stage. t Tests were used to compare the number of spaces posttreatment and at the long-term posttreatment stages. These tests were also performed in subgroups with completely closed extraction sites posttreatment. RESULTS: The groups showed similar numbers of extraction sites reopening. The first and second premolar extraction space closure presents a similar tendency for reopening. Considering only the patients that showed completely closed extraction spaces in the final dental models, maxillary extraction space reopening was larger in the first premolar extraction group. CONCLUSIONS: First and second premolar extraction space closure present similar stability.

Stability of first and second premolars extraction space closure / Estabilidade do fechamento dos espaços de extrações dos primeiros e segundos pré-molares

Premolars are the most commonly extracted teeth to provide space to correct crowding and excessive labial protrusion. After treatment, the extraction spaces have to remain closed. Nevertheless, several studies have shown that there is a tendency for some relapse even in patients finished with an adequate occlusion. The objective of this study was to compare the stability of extraction space closure of the first and second premolars. A sample 72 patients´ dental casts were divided into two groups. Group 1, comprised 29 patients (116 extraction spaces) were treated with first premolar extractions at a mean initial age of 13.78 years and group 2, comprised 43 patients (100 extraction spaces) were treated with second premolar extractions at a mean initial age of 15.20 years. The dental casts obtained at pretrement, posttreament and a between 3 to 4 years postretention were digitized using a 3- dimensional scanner (R700; 3Shape,Copenhagen, Denmark). Chi-Square tests were used to compare the numbers of open and closed extraction spaces after treatment and at long-term posttreatment. T tests were used to compare the amount of spaces at posttreatment and at the long-term posttreatment stages. These tests were also performed in subgroups with completely closed extraction sites at posttreatment. The groups showed similar numbers of extraction sites reopening. First and second premolar extraction space closure present a similar tendency for reopening. Considering only the cases that showed completely closed extraction spaces in the final dental models, extraction space reopening was larger in the first premolar extraction group in the maxillary arch.(AU)

Os pré-molares são os dentes mais comumente extraídos para corrigir o apinhamento dentário e à protrusão labial excessiva. Após o tratamento, os espaços das extrações deveriam permanecer fechados. Contudo, muitos estudos demostraram que existe uma tendência à reabertura dos espaços de extrações em pacientes finalizados com uma oclusão adequada. O objetivo deste estudo foi comparar a estabilidade dos espaços de extrações de primeiro e segundo prémolares. A Amostra deste estudo foi composta por 72 modelos dentários dividido em dois grupos. O Grupo 1 composto por 29 pacientes (116 espaços de extração) foram tratados com extrações dos primeiros pré-molares com idade media inicial de 13,78 anos e o grupo 2 composto por 43 pacientes (100 espaços de extração) foram tratados com extrações dos segundos pré-molares com idade media inicial de 15.20 anos. Os modelos dentários obtidos no pré-tratamento, pós-tratamento e 3 a 4 anos de controle e foram digitalizados mediante um scanner 3Shape R700 3D (3Shape A/S, Copenhagen, Dinamarca). Os testes t e do Qui-Quadrado, foram utilizados para comparar o número de espaços de extração abertos e fechados após o tratamento e pós-tratamento em longo prazo. Os resultados demostraram números similares de reabertura do espaço de extração entre os grupos. Concluiu-se que considerando apenas os casos que mostraram espaços de extração completamente fechados no final do tratamento, a quantidade de reabertura dos espaços de extrações dos primeiros pré-molares ocorre mais frequentemente que dos segundos pré-molares no arco superior.(AU)

Prevalence of extraction space reopening in different orthodontic treatment protocols.

INTRODUCTION: In this study, we aimed to compare the amount and frequency of extraction space reopening after 2- and 4-premolar extraction treatments in Class II and 4-premolar extractions in Class I malocclusion patients. METHODS: The sample comprised 105 subjects with full-cusp Class II and Class I malocclusions, divided into 3 groups. Group 1 consisted of 33 full-cusp Class II malocclusion patients treated with a 2-premolar extraction protocol. Group 2 had 34 full-cusp Class II malocclusion patients treated with 4-premolar extractions, and group 3 included 38 Class I malocclusion patients treated with 4-premolar extractions. The Peer Assessment Rating index was used to assess initial malocclusion severity and quality of the occlusal outcome, measured on dental casts. The amounts of extraction spaces were measured with a digital caliper on the final and long-term posttreatment dental casts, after an average of 9.79 years posttreatment. Intergroup comparisons were performed by analysis of variance, followed by Tukey tests and chi-square tests. RESULTS: There were no significant differences regarding the amount and frequency of extraction space reopening among the groups. CONCLUSIONS: Two- and 4-premolar extractions in Class II and 4-premolar extraction treatment in Class I malocclusion patients show similar reopening of extraction spaces in the long term.

Posterior teeth angulation in non-extraction and extraction treatment of anterior open-bite patients.

BACKGOUND: This study cephalometrically evaluated the posterior teeth angulation changes of anterior open-bite non-extraction and extraction treatment in the permanent dentition, with anterior vertical elastics. METHODS: The sample consisted of initial and final lateral headfilms of 60 patients divided into 2 groups: Group 1 consisted of 30 patients treated with non-extraction with an initial mean age of 15.26 years and treated with fixed appliances for a mean period of 2.46 years. Group 2 consisted of 30 patients treated with extractions, with an initial mean age of 14.03 years, and treated with fixed appliances for a mean period of 2.49 years. Within-group treatment changes were evaluated with paired t tests. Results were considered statistically significant at P < 0.05. RESULTS: The mandibular posterior teeth were significantly uprighted in both groups with both treatment protocols. CONCLUSIONS: Correction of anterior open bite with either non-extraction or extractions with continuous archwires and vertical anterior elastics uprights the mandibular posterior teeth.

Posterior tooth angulations in patients with anterior open bite and normal occlusion.

INTRODUCTION: The aim of this study was to compare the posterior tooth angulations in patients with open-bite malocclusion and normal occlusion. METHODS: Lateral cephalometric headfilms of 45 untreated open-bite subjects were compared with the lateral headfilms of 45 subjects with normal occlusion in the permanent dentition. The groups were matched for age and sex distribution and compared with t tests. RESULTS: The maxillary and mandibular premolars were more mesially angulated in relation to the bisected occlusal plane, and the first and second molars were significantly more distally angulated in the open-bite group in relation to the palatal and mandibular planes. CONCLUSIONS: The maxillary and mandibular premolars were more mesially angulated in relation to the bisected occlusal plane and therefore do not compensate for the divergence of the palatal and mandibular planes as the molars do.