Proposed parameters of optimal central incisor positioning in orthodontic treatment planning: A systematic review

Novel Parameter in Pre-Surgical Orthodontic Preparation: A Retrospective Study on the Role of the Upper Incisor Position and a Morphological Evaluation of the Anterior Nasal Spine

The position and inclination of the incisors play a crucial role in achieving optimal outcomes in orthodontic and orthognathic surgical treatment, given their impact on facial aesthetics. Background/objectives: Due to numerous distorting factors that affect the reliability of the ANB angle, the aim of the present work is to evaluate a more constant parameter over time, the anterior nasal spine (ANS), and explore whether aligning the incisal margin of the upper incisors with the anterior nasal spine could be a reliable indicator for achieving appropriate labial support in pre-surgical orthodontic preparation. Methods: From a pool of 500 cone beam computed tomography (CBCT) scans, 50 CBCT examinations displaying a Class 1 skeletal pattern (ANB = 2° ± 2°) with an intermediate (3.2-4 mm) or mixed (4-6 mm) sagittal maxillary position (MX), as determined by the 3D multiplanar total face approach (TFA), were selected and compared with CBCT examinations randomly chosen from the initial pool. Moreover, 12 landmarks were identified, and measurements were automatically obtained, using software, and recorded. Mean and standard deviation values were calculated for each sample. A comparison was made between the two samples, aligning the results with the morphological analysis of the anterior nasal spine and the sagittal position of the upper maxilla. Results: In Class 1 subjects, the distance between the incisal margin and the plane passed in relation to the anterior nasal spine should range between -1 mm and 1 mm, aligned with or slightly ahead of the anterior nasal spine or slightly ahead of this limit. Conclusions: The anterior nasal spine can serve as a reliable reference point for planning the position of the upper incisors, with excessive proclination or retroclination from this reference point deemed unacceptable.

Occlusal characteristics in modern humans with tooth agenesis

Non-syndromic permanent tooth agenesis affects a significant proportion of the population, especially if third molars are considered. Although tooth agenesis has been linked to a smaller craniofacial size, reduced facial convexity and a shorter skeletal face, the occlusal characteristics of individuals with tooth agenesis remain largely unexplored. Therefore, this study investigated potential associations between tooth agenesis and metric occlusal traits in 806 individuals (491 with 4.1 missing teeth per subject, including third molars, and 315 without any tooth agenesis). Dentoskeletal morphology was defined through anatomical landmarks on pre-treatment cephalometric radiographs. Multivariate regression models, adjusted for sex and age, showed that tooth agenesis was significantly associated with a reduced overjet, an increased interincisal angle, and shorter upper and lower dental arch lengths, but not with overbite. Moreover, apart from reduced tooth length and dentoalveolar effects, as the number of missing teeth increased the upper front teeth were progressively retruded according to the craniofacial complex and to the face. Thus, tooth agenesis has a substantial influence on dental and occlusal characteristics, as well as on the sagittal position and inclination of anterior teeth. These findings emphasize the necessity for personalized, multidisciplinary approaches in individuals with multiple agenesis to successfully meet treatment goals.

Treatment change comparisons between skeletal Class I and II white adolescents with 3 different vertical divergencies-Part 2: Holdaway difference

INTRODUCTION

The Holdaway difference represents the relationship of the NB line to the mandibular incisor (NB-L1) and the bony pogonion (NB-Pog). This study aimed to evaluate treatment changes of NB-L1, NB-Pog, and the Holdaway difference in patients with skeletal Class I and II relationships with 3 different skeletal divergencies.

METHODS

This retrospective study was the second part of treatment outcome assessments of 135 white adolescent patients (females, n = 69; males, n = 66; mean age, 12.8 ± 1.4 years pretreatment and 15.0 ± 1.4 years posttreatment). The NB-L1, NB-Pog, and Holdaway differences (NB-L1 - NB-Pog) were measured. The mixed-model analysis of variance was used to assess within- and between-subject effects responding to horizontal and vertical skeletal discrepancies.

RESULTS

For the group with favorable profile changes, the means of the Holdaway difference were maintained in the hypodivergent and normodivergent subgroups and reduced in the hyperdivergent subgroups for patients with skeletal Class I and II relationships. The means of NB-L1 and Holdaway difference were significantly larger in the skeletal Class II group and became greater as skeletal vertical divergencies increased. The NB-Pog means were significantly different only between the hypodivergent and hyperdivergent subgroups.

CONCLUSIONS

Based on the findings of this study, the Holdaway difference should be adjusted to individualize the incisor positions, considering not only the anteroposterior but also the vertical skeletal relationships of the patients.

Lower Incisor-Pg: A New Cephalometric Parameter to Evaluate the Anterior Limit of Dentition

Background: This present retrospective study aimed to introduce Lower Incisor-Pg and to assess how this new parameter varies with the skeletal sagittal and vertical relationships. Methods: A total of 1256 cephalometric analyses were performed using lateral cephalometric radiographs of a sample of subjects divided according to SN^Go-Gn, ANPg^, and IMPA measurements. The differences in Lower Incisor-Pg between the groups were assessed through ANOVA tests and posthoc analyses, while Pearson's correlation analysis was used to assess the correlations between the measurements. Results: The mesofacial growth pattern (61.0%) was more common than dolichofacial (30.0%) and brachyfacial (8.6%) ones in the sampled population. Regarding skeletal sagittal relationships, Class I was more frequent (70.9%) than Class II (19.3%) and Class III (9.8%). The mean value of the Lower Incisor-Pg was 3.2 ± 4.0 mm. Linear regression showed that the β coefficient was 0.45 and 0.36 for ANPg^ and SnGoGn^, respectively. Conclusions: Lower Incisor-Pg is a linear cephalometric measurement to evaluate the lower incisor sagittal position. For each degree of increase in ANPg^ and SNGoGn^, the Lower Incisor-Pg increased 0.45 mm and 0.36 mm, respectively.

Sagittal Position of the Upper Incisor in Relation to the Forehead in Peruvian Individuals with Different Skeletal Relationships

AIM

The aim of this study was to determine the sagittal position of the upper incisor considering Andrews' analysis based on the position of the forehead in Peruvian individuals with different skeletal relationships.

MATERIALS AND METHODS

This retrospective, cross-sectional study included 212 lateral head radiographs of Peruvian individuals (males: 85, mean age 21.38 ± 6.88, and females: 127, mean age 21.18 ± 6.95), with different skeletal relationships (Class I group = 96, Class II group = 57, Class III group = 59). The values of the ANB, SNA, SNB angles as well as the forehead anterior limit line (FALL) and goal anterior limit line (GALL) points were identified in the radiographs, and then a vertical line was drawn in each point to determine if the upper incisor was positioned forward (protruded), backward (retruded) or within (adequate) these lines. Two trained and calibrated investigators performed all the measurements. The Chi-square test was used to evaluate associations. A p-value < 0.05 was considered statistically significant.

RESULTS

Overall, the sagittal position of the upper incisor showed a significant association with the sagittal skeletal relationship (p = 0.001). The upper incisors showed an adequate position (41.7%), protruded position (56.10%), and retruded position (42.40%), for Class I, II, and III skeletal relationships, respectively, as highest percentages in each Class. Statistical significance was found for females only (p = 0.005).

CONCLUSION

Skeletal Class I mainly showed an adequate position of the upper central incisor, whereas for Class II a protruded position was most frequently found, and Class III presented a retruded position.

CLINICAL SIGNIFICANCE

Andrews' analysis based on the position of the forehead in Peruvian individuals is a valuable tool for orthodontic diagnosis. How to cite this article: Bazán-Mendoza JR, Arias-Modesto PB, Ruíz-Mora GA, et al. Sagittal Position of the Upper Incisor in Relation to the Forehead in Peruvian Individuals with Different Skeletal Relationships. J Contemp Dent Pract 2023;24(11):821-825.

A novel pictorial smile chart: Reliability and validity

INTRODUCTION

Smile analysis provides data on the positive and negative elements of a patient's smile. We aimed to develop a simple pictorial chart to record relevant parameters of the smile analysis in a single diagram and to investigate the reliability and validity of this chart.

METHODS

A panel of 5 orthodontists developed a graphical chart, which was reviewed by 12 orthodontists and 10 orthodontic residents. The chart comprises facial, perioral, and dentogingival zones analyzing 8 continuous and 4 discrete variables. The chart was tested on frontal smiling photographs of 40 young (aged 15-18 years) and 40 old (aged 50-55 years) patients. All measurements were performed twice with an interval of 2 weeks by 2 observers.

RESULTS

Pearson's correlation coefficients for observers and age groups varied from 0.860 to 1.000 and between observers from 0.753 to 0.999. Minor significant mean differences were found between the first and second observations, which were not clinically relevant. The kappa scores for the dichotomous variables were in perfect agreement. To test the sensitivity of the smile chart, differences between the two age groups were assessed as differences because aging is expected. In the older age group, philtrum height and visibility of mandibular incisors were significantly larger, whereas the upper lip fullness and buccal corridor visibility were significantly lesser (P <0.001).

CONCLUSIONS

The newly developed smile chart can record essential smile parameters to aid diagnosis, treatment planning, and research. The chart is simple and easy to use, has face and content validity and good reliability.

Minimally important differences in oral health-related quality of life after fixed orthodontic treatment: a prospective cohort study

Background

The minimally important difference (MID, the smallest difference that patients perceive as beneficial) has been proposed to assess whether study results are clinically meaningful, reducing the shortcoming of P-values-based approaches in the assessment of clinical outcomes. The post-treatment changes and the MID in Oral Health-Related Quality of Life (OHRQoL) among adults undergoing fixed orthodontic treatment were investigated.

Methods

Ninety-two patients (29.1 ± 6.3 years old, 18 males and 74 females) were prospectively included. Oral Health Impact Profile (OHIP-14) and United Kingdom Oral Health-related Quality of Life (OHQoL-UK) were used to assess OHRQoL at baseline and post-treatment (50.8 ± 15.7 months). Global Transition Rating (GTR) was used to assess oral health/well-being, Peer Assessment Review (PAR), and Index of Complexity, Outcome and Need (ICON) were used to assess occlusion. Wilcoxon signed-rank test was used to assess changes in OHRQoL and occlusion, Kruskal–Wallis one-way ANOVA and Mann–Whitney U-test were used to assess associations between OHRQoL and oral health/well-being or occlusion. MID for OHIP-14 and OHQoL-UK was estimated via anchor-based (PAR, ICON, GTR) and distribution-based approach (effect size, standardized response mean, standard error of measurement).

Results

The median OHIP-14 and OHQoL-UK post-treatment scores were significantly changed, indicating improved OHRQoL. Based on the agreement between different methods, the MID of OHIP-14 and OHQoL-UK were at least 15 and 6 scale points, corresponding to a large effect size (1.5–1.7).

Conclusions

Orthodontic treatment had a positive long-term impact on OHRQoL. MID for the OHIP-14 and OHQoL-UK provide guidance to interpreting the impact of orthodontic treatment on the OHRQoL of patients.