Component analysis of Class II, Division 1 discloses limitations for transfer to Class I phenotype

Variation of chin morphology and mandibular incisor length in different facial divergence patterns: New insights from CBCT records

AIM

Evaluate constitutional differences in chin morphology and volume, and mandibular tooth size, between different facial divergence patterns.

MATERIALS AND METHODS

The sample consisted of 284 pretreatment cone beam computed tomography (CBCT) images of growing and non-growing patients who were stratified into 4 groups based on mandibular plane inclination to cranial base (SN) angle. Linear and angular measurements were made on the lateral CBCT images: mandibular lateral incisor crown (I-C) total (I-A) lengths, the distances between point D (centre of symphysis) and both incisor apex (D-A) and menton (D-Me) and between cemento-enamel junction and menton (CEJ-Me); chin width at the level of the central incisor apex (CWA) and point D (CWD); and the angles of the anterior and posterior symphyseal slopes. The volume of the symphysis was measured using a specialized 3D imaging software. Group differences and associations between parameters were gauged through the three-way ANOVA analysis.

RESULTS

I-C, I-A, D-A, D-Me and CEJ-Me were greater in the hyperdivergent group (p < .001). CWA and CWD were wider in the hypodivergent group (p = .003). Volume of the chin and inter-slope angles were similar in all groups (p > .05). The anterior slope angle decreased with hyperdivegence (p < .005) in opposite pattern to the posterior slope angle (p < .005).

CONCLUSIONS

Shape differences in mandibular symphysis were observed between opposite divergence patterns. Mandibular incisors were longer with hyperdivergence and shorter with hypodivergence. However, chin volumes were similar across divergence groups. These findings underline the role of genetic and environmental factors that impact facial growth.

Novel genes linked to Class II Division 1 malocclusion with mandibular micrognathism

INTRODUCTION

Mandibular micrognathism (MM) is an underdeveloped mandible resulting from complex interactions between genetic and environmental factors. Prior research focused mainly on the genetic determinants of mandibular retrognathism, not necessarily reflecting micrognathism, thus supporting the need to study MM. This study aimed to explore the inheritance pattern and identify the candidate genes involved in the development and familial transmission of MM.

METHODS

Diagnosing probands with MM was based on clinical and lateral cephalometric data. The pedigrees were drawn for 11 identified families, 5 of whom accepted to undergo detailed data and biospecimen collection. These families included 15 MM and 13 non-MM subjects over 2-3 generations. The procedure involved the withdrawal of 5 mL of blood. Genomic DNA was isolated from blood cells to investigate protein-coding regions via whole exome sequencing. Standardized filtering steps were employed, and candidate genes were identified.

RESULTS

Most of the pedigrees suggested a Mendelian inheritance pattern and segregated in an autosomal-dominant manner. One of the families, which also underwent biospecimen, displayed an X-linked inheritance pattern of the trait. Genetic screening disclosed 8 potentially novel genes (GLUD2, ADGRG4, ARSH, TGIF1, FGFR3, ZNF181, INTS7, and WNT6). None of the recognized exonic regions were previously reported.

CONCLUSIONS

Eight novel genes were identified in association with MM in the largest number of families reported to date. The genes were X-linked in 1 family, a finding previously not observed in mandibular genetics.

Centennial inventory: the changing face of orthodontics

The American Journal of Orthodontics and Dentofacial Orthopedics celebrates its centennial, safeguarded by the nearly 115-year-old American Association of Orthodontists. This journey witnessed the rise and demise of various developments, concepts, and procedures, while basic knowledge is still needed. Various periods can be defined in the past century, but the goals remain to obtain more accurate diagnosis through precise anatomic imaging, more controlled and faster tooth movement, more discreet appliances, and the balance of esthetics, function, and stability. The most recent technologic advances have buttressed these goals. Cone-beam computed tomography has brought 3-dimensional assessment to daily usage, albeit the original enthusiasm is tempered by the risk of additional radiation. Temporary anchorage devices or miniscrews have revolutionized orthodontic practice and loom as a solid cornerstone of orthodontic science. Decortication and microperforation promise to speed up tooth displacement by stimulating vascularization. The concept of the regional acceleratory phenomenon has touched upon even the timing of orthognathic surgery. The burden of esthetic appliances remains, with the demand for "cosmetic" appliances and clear aligners. Have these developments changed the face of orthodontics? Have we engaged in another turn wherein certain treatment modalities may fade, while others join mainstream applications? These questions are addressed in this essay on the challenges, promises, and limitations of current orthodontic technology, enhancement of biologic response, and personalized treatment approaches.