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Summary Objective To systematically evaluate all the evidence assessing variations in the depth of the curve of Spee (COS) according to the presence/absence of different dentoskeletal characteristics. Search methods and eligibility criteria The eligibility criteria were outlined following the PECO framework, as follows: studies evaluating individuals with complete permanent dentition including second molars (P), which compared a group with a certain dentoskeletal variation (E) versus another group without the variation (C), regarding the depth of the COS (O). MEDLINE (via PubMed), Scopus, Web of Science, The Cochrane Library, LILACS and BBO (via Virtual Health Library), OpenGrey, and Google Scholar were searched up to September 2021 to identify eligible reports. Data collection and analysis Duplicates were removed from all the records retrieved. The selection process and data collection were performed independently by two review members. The risk of bias was also assessed independently and in duplicate, using the guideline described by Fowkes and Fulton. Several meta-analyses (α = 0.05) were conducted to estimate the mean differences (MD) or standardized mean differences (SMD) in the depth of COS between individuals presenting or not certain dentoskeletal characteristics. The certainty of evidence was assessed using the GRADE tool. Results Thirty-five studies were selected for qualitative synthesis, and 29 of them for quantitative synthesis. All studies had methodological limitations that affected the risk of bias and increased the likelihood that results were due to chance. Syntheses showed that Class II malocclusion (SMD = 0.87; 95% CI: 0.61, 1.13; P < 0.00001; six datasets including 260 subjects analysed), Class II division 1 (SMD = 1.09; 95% CI: 0.62, 1.56; P < 0.00001; 14 datasets including 823 subjects analysed) and Class II division 2 (SMD = 2.65; 95% CI: 1.51, 3.79; P < 0.00001; eight datasets including 476 subjects analysed) had deeper COS than Class I malocclusion. The skeletal Class II also presented higher COS values than skeletal Class I (SMD = 0.57; 95% CI: 0.02, 1.12; P = 0.04; four datasets including 299 subjects analysed). Individuals with Class III malocclusion had flatter COS than the subjects having Class I malocclusion (SMD = −0.57; 95% CI: −1.07, −0.08; P = 0.02; nine datasets including 505 individuals analysed). No difference was shown in the COS depth between skeletal Class III and Class I (P > 0.05). Deep bite individuals had higher COS depth than those with normal overbite (MD = 0.61; 95% CI: 0.41, 0.82; P < 0.00001; two datasets including 250 subjects analysed). In addition, hypodivergent individuals presented deeper COS than normodivergents (SMD = 0.62; 95% CI: 0.37, 0.86; P < 0.00001; six datasets including 305 subjects analysed), and there was no significant difference in the COS depth between hyperdivergent and normodivergent individuals (P = 0.66). The certainty of evidence was rated as very low for all the syntheses. Limitations All the quantitative syntheses included results from studies with methodological flaws. Therefore, they are potentially biased. Moreover, the evidence was also mainly affected in terms of the inconsistency of the results and the imprecision of the estimates. Conclusions Although an apparent influence of dentoskeletal Class II, Class III malocclusion, deep bite, and the hypodivergent skeletal pattern on the depth of the COS is suggested, it is not possible to make definitive conclusions on the matter due to the very low certainty of the evidence. Further high-quality research is necessary.
Summary Objective To systematically evaluate all the evidence assessing variations in the depth of the curve of Spee (COS) according to the presence/absence of different dentoskeletal characteristics. Search methods and eligibility criteria The eligibility criteria were outlined following the PECO framework, as follows: studies evaluating individuals with complete permanent dentition including second molars (P), which compared a group with a certain dentoskeletal variation (E) versus another group without the variation (C), regarding the depth of the COS (O). MEDLINE (via PubMed), Scopus, Web of Science, The Cochrane Library, LILACS and BBO (via Virtual Health Library), OpenGrey, and Google Scholar were searched up to September 2021 to identify eligible reports. Data collection and analysis Duplicates were removed from all the records retrieved. The selection process and data collection were performed independently by two review members. The risk of bias was also assessed independently and in duplicate, using the guideline described by Fowkes and Fulton. Several meta-analyses (α = 0.05) were conducted to estimate the mean differences (MD) or standardized mean differences (SMD) in the depth of COS between individuals presenting or not certain dentoskeletal characteristics. The certainty of evidence was assessed using the GRADE tool. Results Thirty-five studies were selected for qualitative synthesis, and 29 of them for quantitative synthesis. All studies had methodological limitations that affected the risk of bias and increased the likelihood that results were due to chance. Syntheses showed that Class II malocclusion (SMD = 0.87; 95% CI: 0.61, 1.13; P < 0.00001; six datasets including 260 subjects analysed), Class II division 1 (SMD = 1.09; 95% CI: 0.62, 1.56; P < 0.00001; 14 datasets including 823 subjects analysed) and Class II division 2 (SMD = 2.65; 95% CI: 1.51, 3.79; P < 0.00001; eight datasets including 476 subjects analysed) had deeper COS than Class I malocclusion. The skeletal Class II also presented higher COS values than skeletal Class I (SMD = 0.57; 95% CI: 0.02, 1.12; P = 0.04; four datasets including 299 subjects analysed). Individuals with Class III malocclusion had flatter COS than the subjects having Class I malocclusion (SMD = −0.57; 95% CI: −1.07, −0.08; P = 0.02; nine datasets including 505 individuals analysed). No difference was shown in the COS depth between skeletal Class III and Class I (P > 0.05). Deep bite individuals had higher COS depth than those with normal overbite (MD = 0.61; 95% CI: 0.41, 0.82; P < 0.00001; two datasets including 250 subjects analysed). In addition, hypodivergent individuals presented deeper COS than normodivergents (SMD = 0.62; 95% CI: 0.37, 0.86; P < 0.00001; six datasets including 305 subjects analysed), and there was no significant difference in the COS depth between hyperdivergent and normodivergent individuals (P = 0.66). The certainty of evidence was rated as very low for all the syntheses. Limitations All the quantitative syntheses included results from studies with methodological flaws. Therefore, they are potentially biased. Moreover, the evidence was also mainly affected in terms of the inconsistency of the results and the imprecision of the estimates. Conclusions Although an apparent influence of dentoskeletal Class II, Class III malocclusion, deep bite, and the hypodivergent skeletal pattern on the depth of the COS is suggested, it is not possible to make definitive conclusions on the matter due to the very low certainty of the evidence. Further high-quality research is necessary.
Background The fundamental part of every successful orthodontic treatment is the detailed treatment planning including a precise determination of the virtual treatment objective (VTO) while considering the biological and anatomical limits. The aim of this study is to investigate and to compare the feasibility of the established reference values before and after orthodontic treatment and to determine the usefulness of this parameters as guidance for the sagittal anterior, sagittal posterior and transverse biological boundaries. Materials and methods Thirty-two patients aged 9 to 18 years (12 male and 20 female) with all permanent teeth present were randomly selected for orthodontic treatment with fixed multibracket appliance regardless of the potential malocclusion. The parameters 6-PTV, 1-NB [mm] and the WALA ridge were set for the identification of the transverse, sagittal anterior and sagittal posterior tooth position. The measurements were carried out at the beginning (T0) and at the end (T1) of the orthodontic treatment. They were set in relation with their individual threshold values (G). After the results of the measurements were conducted using the software OnyxCeph3TM (version 3.2.185 (505), Image Instruments GmbH, Chemnitz, DE), they were statistically calculated in the software RStudio (2022.12.0 Build 353 © 2009–2022 Posit Software PBC). Results Among the 32 patients, the mean pre- and post-treatment changes measured through the three parameters in relation to the individual reference values were statistically significant (p < 0.01). The mean values for 6-PTV, 1-NB and the WALA ridge amounted 15.37 mm, 2.56 mm and 4.23 mm at the beginning of the treatment, while after the treatment the measured values amounted 20.31 mm, 2.4 mm and 5.55 mm. These measurements combined with the statistical analysis of the changes of WALA ridge (T0, T1) confirmed that the teeth have been successfully uprighted and aligned. Furthermore, the maxillary first molars have been moved slightly mesially, as proven by the changes in 6-PTV, without certainty as to whether bodily movement or mesial tipping took place. Additionally, the lower incisors have been protruded, slightly exceeding the individual threshold values. Conclusion The parameters investigated provide a suitable assessment tool for recording the limits of the sagittal posterior, the sagittal anterior and the transverse dimension.
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