Aetiology

Question 1

• Class II/1 Definition BSI 1983 ?

Answer 1

• Lower incisor edge occludes POSTERIOR to the cingulum plateau of the upper incisors with and INCREASED OJ. Upper incisors are EITHER PROCLINED or of AVERAGE INCLINATION.
  
  • BSI 1983

Question 2

• According to Williams and Stepens 1992 what is a Class II Intermediate occlusion ?

Answer 2

• Lower incisor edge occludes posterior to the cingulum plateau of the upper incisors. The OJ is increased anD the upper incisors are either UPRIGHT or PROCLINED.

Question 3

• Incidence of Class II/1 ?
  
  • Todd & Dodd CDH survey 1988

Answer 3

• 20% - TODD & DODD 1988 CDH SURVEY

Question 4

• Incidence of Class II Intermediate ?

Answer 4

• 10%-Williams and Stephens 1992.

Question 5

• Aetiology of Class II/1 ?
  
  • SKELETAL

Answer 5

• SKELETAL (Predominately):

​AP

• ​75% cases are assocaited with SK2- With variable degrees of MANDIBULAR RETROGNATHISM.
• Occasionally 25% assocaite with Max Prognathism.
• Increased CBA ( MD Retrognathic).
• Increased CBL-Prognathic Maxila
• Can occur with SK1- If so CLII/1 Highly likely due to HABIT.

VERTICAL:

• Varies- Usually AVERAGE or REDUCED, BUT can be increased.

​TRANSVERSE:

• Can have SMALL MANDIBLE or LARGE MX or BOTH.

FUTURE GROWTH:

• Favourable growth of FORWARD GROWTH (Anticlockwise) of the Mandible.
• Unfavourable growth is Backward growth roatation ( clockwise).

Question 6

• Aetiology of Class ii/1 ?
  
  • Soft Tissue

Answer 6

SOFT TISSUE:

SFT Tiss pattern is a REFLECTION of the UNDERLYING SKELETAL PATTERN.

• Incompetent lips- Pt attempts to achieve ant oral seal by..​​

1. Circumoral muscular activity} ^{<em>CAMOFLG SK PATRN.</em>}
2. Posturing of mandible} ^{<em>CAMOFLG SK PATRN</em>.}
3. Lip to palate} ^{Both (3 &4) cause PROCLINTN UPP INC & RETROCLINATN LINC.}
4. Tongue to lip}
5. ​Short upper lip: ^{Reduced stability of OJ reduction @ end of RX}
   
   1. Ideally @ end of RX Lower lip should contact Incisal 1/3rd of Upper Incisors
6. Strap like Lower lip: ^{<span>Reroclined Lower Inc and thefr Inc OJ.</span>}

Question 7

• Aetiology of Class II/1 ?
  
  • Habits

Answer 7

• Thimb Sucking….
  
  • Proclined Upper Inc
  • Retroclined Lower Inc
  • Red OB/AOB
  • Unilateral XBITE

Question 8

• Aetiology of CLass II/1 ?
  
  • Dental

Answer 8

• Increased OJ
• OB INCREASED ususallly INCOMPLETE. BUT if Lower COS is INCREASED or MMPA is REDUCED= COMPLETE OB.
• Class II Buccal segments
• XBITE- NOT ALWAYS
  
  • Buccal= Because of DISPLACEMNT from habit
  • Lingual= Transverse Discrepancy

Question 9

• BOS DUMMY & DIGIT SUCKING - ADVICE SHEET

Answer 9

Based on current evidence available, whichis predominantely onservational, there are no controlled clinical trials at present ?

INCIDENCE:

• 1/8 childrn in western world have sucking habit.

GENDER:

• Equivalent for males and females UNTIL the age of 1 yr, afterwhich MORE common in females.

Socioeconimic factors:

• Dummy-More common in lower socioeconomic gps.
• Digit -More common in higher socioeconomic gps.

AGE:

• Most begin 3 months. Dummy habit almost non existent after 6 yrs. Digit sucking declines at a much slower rate and is more likely to persist into permanent dentiton.

FREQUENCY OF HABIT:

• Significant effects only likely if habit exceeds 6 hrs/day.

TYPES OF FEEDING (Breast/ bottle):

• Has no effect on prevalence or type of habit.

AETIOLOGY: Two theories- Current opinion favours 2nd;​

1. Habit provides comfort and security to the child.
2. Habit is learned behaviour. Infacnts have natural sucking urge. Sometimes the urge persists after feeding. This surplus urge is satisfied with habit.​​

DENTAL EFFECT OF DUMMY:

• Primarily on decids teeth as habit usually stops before perm dentition erupts.
• Reduced OB, Producing AOB- Usually asymmetric.
• Reduction in Max Arch width, which may cause posterior xbite.
• LTM effects - usually negligible as perm dention not affected.

DENTAL EFFECTS OF DIGIT SUCKING:

• Determined by nature and intensity of habit.
• Reduced OB or AOB - often asymmetrical.
• Upper incisors are PROCLINED and LINC maybe Retroclined.
• Max arch maybe NARROWED, Producing XBIT and DISPLCMT.
• Effects often seen in permanent dentiton due to the continuation of the habit.

POSSIBLE RX APPROACHES:

• Offer advice to parents and child about habit such as;
• Encourage chid to stop. Advise on use of wallchart and daily reward.
• Advice against nagging, teasing and punishing, be positv, build up their self esteem.
• Consider use of REMINDER or physical barrier such as elastoplast, badage, cotton glove, sock, thubguard or bitter tasting paint.
• Discuss use of HABIT BREAKER- EG QHX which also corrects the narow MX.

Question 10

• WHY WORRY ABOUT INCREASED OJ WITH RE CLASS II/1 ?
• ARTUN ET AL 2005
• NGUYEN 1999 SYSTEMATIC RV

Answer 10

ARTUN ET AL 2005:

• Maxillary incisor trauma M:F= 2:1
• Risk increases 13% for every 1mm that OJ is increased.

NGUYEN 1999 SYTEMATIC REVIEW:

• OJ > 3mm 2X’S RISK of INJURY TO ANTERIOR TEETH Compared to those OJ < 3MM
• Effect of OJ less for boys then girls.

Question 11

• CHOICE OF METHOD OF RX OF CLASS II/1 DEPENDS ON ?

Answer 11

• Position of Upper incisors within face
• Position of lower incisors
• Age of pt
• Severity of OJ and likey stability of OJ reduction.
• Pt wishes
• Profile concerns

Question 12

• When considering alteing the position of the Upper incisors in a Class II/1 case which two measurements are of relevance ?

Answer 12

1. NLA
2. Zero Meridian:
   
   • TRUE Vertical from SOFT TIS NASION, PERPENDICULAR to TRUE HORIZONTAL (Frankfort plane). SOFT TISSUE POGONION SHOULD BE 0+/- 2MM to Meridian Line- AP CHIN POSITION.

LO &HUNTER 1982:

• NLA increase by 1.6⁰ for every 1MM of upper incisor retraction.

Question 13

POSITION OF LOWER INCISORS ?

Answer 13

• NORMAL INCLINATION 93 +/- 6
• PROCLINE WITH CAUTION (JUDICOUS PROCLINATION).
• MILLS:
• Lower incisors in narrow zone of stability

ACKERMAN &PROFFITT:

• Suggest limiting to 2mm/ 10 degrees of alteration.

Question 14

Methods of OJ Reduction ( Class II/1) ?

Answer 14

1. Retration of ULS
2. Protract or Procline lls
3. Maxillary Restraint
4. Facilitate Mandibular Growth
5. Orthognathic SX

Question 15

Favourable features for orthodontic RX (camoflage) in Class II/1 ?

Answer 15

Small ANB

No dental compensation ( LInc/Md and UInc/Mx)

Growing patient

Cessationof any habits

The majority of the increased OJ being due PROCLINED ULS- ie owing to a predominatly dental cause rather than an significant underlying skeletal discrepancy.

Question 16

Treatment options for CLASS 1/1 ?

Answer 16

• Functional App - Mod sk2 , Growing pt.
• URA- Retract ULS if predomonantly due to Proclined ULS
• FA +/- Anchorage reinforcement ie HG or even functional appliance prior to FA.
• Extraction Patten : U4’s (Sufficient sp near proclined ULS and to crowding to allow for relief of crowding and retraction of ULS for OJ reduciton) and L5’s ( To encourage mesial movement of L6’s to aid with correction of Class II buccal relationship).
• Orthognathic SX

Question 17

Treatment Mechanic for Class II/1 ?

Answer 17

Complete Alignment

Correct any rotations

Reduce OB- or at least get into a stiff SS aw so OB is under control

OJ reduction

Sliding VS loop mechanics ( adv and disadv)

En Masse retraction Vs Individual Tooth retraction.