Introduction

Orthodontic care primarily focuses on dental esthetics and masticatory function, but its impact on sound production is often overlooked. Sound production involves a dynamic interaction with the oral cavity, requiring orthodontists to recognize how dental anomalies and treatments influence speech. Enhanced patient care can be achieved through better treatment planning and referrals to speech pathologists for patients whose malocclusions affect speech production. This is particularly relevant for adults requiring proper speech for professional purposes.

Definition of Sound and Speech Mechanism

Sound is mechanical vibration energy requiring the coordination of neural, muscular, mechanical, aerodynamic, acoustic, and visual elements. Speech production involves four processes:

1. Language processing in the brain.
2. Motor command generation to vocal organs.
3. Articulatory movements of the oral cavity.
4. Air emission from the lungs.

Speech sounds are classified into:

• Vowels: Produced without obstruction to airflow.
• Consonants: Produced with varying obstructions in oral or nasal cavities.

Classification

• Ingram’s Classification:
  1. Dysphonia: Disorders of vocalization.
  2. Dysrhythmia: Respiratory coordination issues.
  3. Dysarthria:
     • Due to neurological abnormalities (e.g., motor neuron lesions).
     • Due to local abnormalities (e.g., jaws, teeth, palate).
  4. Non-Structural Disorders: Mental, hearing, or environmental factors.
  5. Developmental Disorders: Abnormal or delayed speech development.
  6. Mixed Disorders: Combination of the above.
• Types of Consonants:
  • Bilabial consonants: “b”, “p”, “m”
  • Labiodental consonants: “f ”, “v”
  • Dental consonants: “d”, “t”, “n”, “s”, “z”
  • Dentoalveolar consonants: “c”, “c”, “j”, “ş”
  • Frontopalatal consonants: “g”, “k”, “l”, “r”, “y” 
  • Backpalatal consonants: “g”, “ğ”
  • Pharyngeal consonant: “h”
  • Nasal consonants: “m”, “n”

Orthodontic Implications

• Malocclusion and Speech:
  • Class II Malocclusion:
    • Difficulty with bilabial sounds (“p,” “b,” “m”).
    • Compensatory mechanisms involve lower lip contacting maxillary incisors.
  • Class III Malocclusion:
    • Difficulty with labiodental sounds (“f,” “v”).
    • Common errors include bilabial production or reversed labiodental posture.
    • Dentalization leads to lisping for sounds like “t,” “d,” “s,” and “z.”
  • Open Bite:
    • Anterior lisping and distortion of anterior sounds.
    • Severe cases show more misarticulations when combined with other anomalies.
  • Diastema:
    • Impacts sounds like “l,” “n,” and “d.”
• Velopharyngeal Dysfunction: Associated with cleft palate, causing hypernasal resonance and airflow issues.
• Adaptation Mechanisms: Tongue and lips often adapt to dental irregularities, masking speech defects.

Studies

• Fymbo’s Study:
  • Analyzed 410 students, noting a higher incidence of speech difficulties in those with malocclusion.
  • Severity of speech defects correlated with the severity of dental anomalies.
• Laine et al.:
  • Narrower palates linked to sibilant speech disorders.
  • Increased open bite and overjet have greater impacts than spacing.
• Dalston and Vig:
  • Minimal long-term speech changes post-orthognathic surgery.
• Garber et al.:
  • Temporary speech errors observed post-surgery resolved within 1-3 months.

Shortcomings

• Limited Longitudinal Data: Lack of extended studies tracking speech changes post-treatment.
• Standardization Issues: No universal methods to measure malocclusion-related speech defects.
• Complex Etiology:
  • Speech defects often result from multiple factors, not just malocclusion.
  • Adaptation varies based on intelligence, emotional state, and muscle control.

Types of Anchorage Based on Maximum Anchorage Demand

Anchorage is classified into three types based on the maximum anchorage required:

Type A: Maximum Anchorage

• Definition: Anchorage demand is very high.
• Space Utilization: Not more than 1/4th of the extraction space should be closed by forward movement of anchor teeth.
• Mechanism: The extraction space is primarily closed by maximum incisor retraction.

Type B: Moderate Anchorage

• Definition: Anchorage demand is moderate.
• Space Utilization: Anchor teeth are allowed to move forward by up to half the extraction space.
• Mechanism: The extraction space is closed by a combination of incisor retraction and posterior tooth protraction.

Type C: Minimum Anchorage

• Definition: Anchorage demand is very low.
• Space Utilization: More than half of the extraction space is closed by mesial movement of the anchor teeth.
• Mechanism: The extraction space is primarily closed by protraction of posterior teeth with minimal incisor retraction.

Group B Anchorage: Biomechanics of Space Closure

Key Features

• Archwire: A working archwire with a minimal curve of Spee (e.g., 0.019 × 0.025-inch SS wire) is engaged into the bracket slots and molar tubes.
• Couples and Forces:
  • The wire generates a couple at the level of the bracket/molar tube at both ends, leading to the generation of a moment of couple (M_c).
  • Tiebacks create a force for space closure (F), generating a moment of force (M_F).
• Force and Moment Interaction:
  • At either end of the system, the moments of couple and force are created in opposite directions, canceling each other.
  • This leaves only the translatory force (F) to exist, enabling space closure.

Translational Movement

• When moments are balanced correctly:
• No vertical component of force is produced.
• No rotational tendency occurs in the system.
• Occlusal plane and overbite remain unchanged.

• Diagram: Depicts the working archwire (faded blue line) and the resulting forces and moments.
• Outcome: Translation of anterior and posterior segments without altering the occlusal plane or overbite.

Planned Imbalance of Moments

• In some scenarios, moments are deliberately imbalanced to achieve specific vertical movements:
• Posterior Teeth: Extrusion (yellow arrows).
• Anterior Teeth: Intrusion (yellow arrows).
• Effect: Opens the deep overbite by modifying the vertical dimension.

• Diagram: Illustrates the planned imbalance (thick red curved arrow) leading to controlled vertical movements.
• Outcome: Deep overbite correction through extrusion of posterior teeth and intrusion of anterior teeth.

Summary

Group B anchorage allows for controlled space closure through balanced forces and moments. By adjusting the moments, orthodontists can achieve either translational movement or vertical adjustments, making it a versatile approach in clinical orthodontics.

Bimaxillary protrusion is a condition characterized by protrusive and proclined upper and lower incisors with increased lip procumbency. It is commonly seen in African-American and Asian populations but can occur across all ethnic groups. Due to the negative perception of protrusive dentition and lips in many cultures, patients with bimaxillary protrusion often seek orthodontic treatment to improve their facial profiles. This guide summarizes key aspects of bimaxillary protrusion, including its etiology, pretreatment characteristics, treatment goals, and outcomes.

Etiology of Bimaxillary Protrusion

The etiology of bimaxillary protrusion is multifactorial, including:

• Genetic Factors: Hereditary traits influencing facial and dental structures.
• Environmental Factors:
  • Mouth breathing.
  • Tongue and lip habits.
  • Increased tongue volume.

Morphological Features

Keating’s study on Caucasian patients identified the following cephalometric traits:

Pretreatment Characteristics

Cephalometric Traits

Patients with bimaxillary protrusion exhibit the following pretreatment characteristics:

Soft Tissue Features

• Lip Position:
  • Upper and lower lips are ahead of the E-plane.
  • Lower lip: 6.0 mm ahead (Keating’s Caucasian sample).
  • Upper lip: 1.0 mm ahead (less than Keating’s 3.4 mm).
• Nasolabial Angle:
  • Found to be 94° (1 SD more acute than mixed racial norms).
  • Tan’s study on Chinese patients reported an even more acute angle (86.6°).
• Lip Thickness:
  • Increased, likely due to a higher proportion of African-American patients in the study.

Alveolar Morphology

• Alveolar Width: Reduced compared to Handelman’s norms.
• Alveolar Height: Increased, consistent with vertical facial growth patterns.
• Thin and elongated alveolus may limit retraction mechanics and necessitate surgical osteotomies in severe cases.

Orthodontic Treatment Goals

The primary objectives of treating bimaxillary protrusion include:

• Dental Goals:
  • Retraction and retroclination of maxillary and mandibular incisors.
  • Reduction in incisor proclination and protrusion.
• Soft Tissue Goals:
  • Decrease in lip procumbency and convexity.
  • Improvement in the nasolabial angle.
• Mechanics Used:
  • Extraction of four first premolars.
  • Retraction using maximum anchorage mechanics.

Flowchart: Treatment Goals and Process

1. Initial Diagnosis → 2. Extraction of Four Premolars → 3. Retraction of Incisors → 4. Profile Improvement

Treatment Outcomes

Dental and Skeletal Changes

Soft Tissue Changes

• Upper Lip Retraction:
  • Ratio of upper incisor retraction to upper lip retraction: 2.2:1 (similar to Chiasson and Hershey).
  • Nasolabial angle: Increased significantly (P < .02).
• Variability:
  • Lip response depends on factors like interlabial gap, lip redundancy, and musculature quality.

Vertical Dimension

• No significant changes in lower anterior face height or mandibular plane angle, indicating that treatment mechanics do not affect the vertical dimension.

In the world of orthodontics, Class II intermaxillary elastics have stood the test of time as a cornerstone of clinical treatment. Since their introduction by Maynard in 1843 and subsequent refinement by Henry A. Baker in the late 19th century, these small but mighty elastics have been indispensable in managing malocclusions. For orthodontic students, understanding their effects, particularly on the functional occlusal plane (FOP), is essential for mastering treatment planning and clinical decision-making.

Why Does the Functional Occlusal Plane Matter?

The occlusal plane is more than a line connecting occlusal surfaces; it’s a fundamental aspect of facial esthetics, function, and skeletal harmony. Its orientation relative to cranial and mandibular planes influences:

• Maxillary and mandibular skeletal relationships
• Facial forms and esthetics
• Occlusal function

Alterations in the occlusal plane, whether due to growth or treatment, can significantly affect treatment outcomes and post-treatment stability. As orthodontic practitioners, it’s crucial to strike a balance between functional correction and maintaining or improving esthetic harmony.

The Role of Class II Elastics

Class II elastics have long been used to address sagittal and vertical discrepancies, including the correction of Class II malocclusions and open bites. While effective, their reciprocal forces can induce both desirable and adverse effects. Reports have suggested that Class II elastics might steepen the occlusal plane, potentially leading to instability or relapse post-treatment. However, these findings were often based on small sample sizes or non-growing patients, leaving gaps in our understanding of their effects during growth phases.

What Did This Study Investigate?

To address these gaps, a recent study analyzed the effects of Class II elastics on FOP in growing patients aged 11 to 16 years. Here’s what the researchers aimed to find out:

1. Does the use of Class II elastics steepen the FOP?
2. Are these changes more pronounced in extraction cases or patients with high-angle skeletal patterns?
3. Do these changes persist or relapse after treatment?

Key Findings to Remember

1. Angular Changes in the FOP

• FOP-SN and FOP-FH: Decreased significantly from pretreatment (T0) to post-treatment (T1) and continued to decrease 1 year post-treatment (T2).
• FOP-MP: Increased from T0 to T1, likely as a reciprocal effect of FOP-SN/FH changes.

2. Influence of Skeletal Patterns

• Hyperdivergent patients showed the largest FOP angles across all time points, while hypodivergent patients had the smallest.
• Despite these differences, changes in FOP were consistent across skeletal types, indicating that Class II elastics affect all growth patterns similarly.

3. Treatment Modalities: Extraction vs. Non-Extraction

• Patients undergoing extraction treatment exhibited steeper initial FOP-MP angles, reflecting a preference to extract in such cases.
• No significant differences were observed in FOP changes between extraction and non-extraction groups during or after treatment.

Clinical Implications for Students

1. Normal Growth vs. Treatment Effects: The study suggests that changes in FOP may largely reflect normal growth patterns rather than direct effects of Class II elastics. This aligns with findings from Creekmore, Schudy, and Harris, emphasizing the importance of accounting for growth dynamics.
2. Individualized Treatment Planning: While Class II elastics are versatile, their effects on the FOP and associated structures vary based on skeletal patterns and growth trends. Orthodontic treatment must be tailored to each patient’s unique craniofacial morphology.
3. Extraction Considerations: Although extraction cases may present steeper occlusal planes initially, the use of Class II elastics does not appear to exacerbate this steepness.

Takeaways for Orthodontic Students

• Class II elastics remain a reliable tool for addressing Class II malocclusions, but understanding their nuanced effects on the FOP is key to optimizing outcomes.
• Growth patterns play a pivotal role in how the FOP evolves during treatment. Observing these changes in clinical practice can enhance your ability to predict and manage treatment outcomes.
• Finally, always consider the interplay between function, esthetics, and stability when planning orthodontic interventions.

Class II elastics may be small, but their impact on treatment is anything but. With careful planning and an understanding of growth influences, you can wield this classic tool to achieve remarkable results in your future practice.