• Supervisor: Prof. Maher Fouda

• Prepared by: Shafik M. Fawakherji

Lower incisors crowding in mixed dentition

Introduction

Presence of spaces between primary teeth is a feature of normal development.

Occasionally spaces develop between the deciduous incisors subsequently to their eruption.

Spacing in normal development

Failure of incisor spacing to appear before five years of age occurs in about 20 percent of cases and usually indicated crowding in permanent dentition.

It is possible to use the amount of spacing between the lower deciduous teeth as a mean of predicting the degree of crowding to be expected in their permanent successors.

The probabilities of crowding in permanent dentition according to available spaces in

lower deciduous teeth (leighton 1971)

Incisor Replacement Solutions:1. Normal spacing: developmental and primate.

2. Increase in arch width across canines.

3. Distal repositioning of mandibular canine in mandible; Incisors force mandibular canines distally into primate space.

Mandibular incisors crowding, which can be present in all classes of malocclusions, is probably the most common problem resolved by orthodontic treatment.

The space necessary for alignment can be obtained by a number of non-extraction and extraction strategies. (Gianelly 1994)

Severe anterior crowding is one of anomalies occurring in the mixed dentition, which should be referred early (i.e. at 7-9 years of age) for specialist advice. (Williams 2010)

Moorrees and Chada (1965) indicated that 1 to 2 mm of crowding is a characteristic feature in individuals who demonstrate normal alignment in the permanent dentition.

The initial incisors crowding defined as incisor liability which was quantified as approximately 1.6 mm in normal cases. (Shah 2003)

Etielogy

There is a greater correlation between dental arch size and crowding than between tooth size and crowding. Crowding may occur due to different reasons, for example; growth, decrease in dental arch length, maturation, aging of dentition, mesial drift, soft tissue pressures and tooth morphology. (Abid et al 2012)

Presence of maxillary and/or Mandibular third molars has no relation with the lower incisor crowding. (Karasawa et al 2013)

As the permanent incisor buds lie lingual as well as apical to the primary incisors, the result is a tendency of Mandibular permanent incisors to erupt lingually and slightly irregular. (Abid et al 2012)

Prevalence

The prevalence of incisor crowding was higher in the Mandibular arch than maxillary in both genders in early mix dentition and the degree of incisor crowding was significantly higher in Mandibular arch than maxillary arch. (AL-SEHAIBANY 2011)

Patients with Class II malocclusion display greater upper, lower, and overall crowding in comparison with Class I . (Groves 2010 , Rasul et al 2012)

Males possessed more Mandibular crowding and greater transverse dimensions than females. An explicit trend was observed in both arches, whereby the most crowding occurs in the lateral incisor-canine contact. (Groves 2010)

LEEWAY/ E SPACE

Leeway space is the difference between the combined mesio-distal (m-d) widths of C,D and E and the combined m-d widths of 3,4 and 5. It is about 3.4 mm in lower arch (1.7 on each side)and 1.8 mm in upper arch (0.9 on each side)

In actuality, the leeway space represents the "E" space or the difference between the m-d diameter of the second primary molar and the second premolar because the combined m-d diameter of the primary canine and first molar ( 13.64 mm) is approximately equal to the diameter (13.85 mm) of the permanent canine and first premolar; This simplifies the usual leeway space calculation.

The arch length- tooth material discrepancy is the main cause for crowding. This discrepancy can be calculated with different analysis.

The arch length could be measured on the cast using 0.010 inch soft brass wire. The wire is placed touching the mesial aspect of lower first permanent molar, then passed along the buccal cusps of premolars, incisal edges of the anteriors and finally continued the same way up to the mesial of the first molar of the contralateral side .

The brass wire should be passed along the cingulum of anterior teeth if anteriors are proclined and along the labial surface if anteriors are retroclined.

Also, a divider is useful to obtain the measurement

Previous studies found that the different types of caliper more accurate measurement than divider.

In mixed detition, different methods could be utilized to calcuate to predict the mesiodistal dimension of the unerupted cuspid and bicuspids. Fouda's method(1989) based on the use of the buccolingual width of the first permanent molar.

Upper arch: M.D dimension of 345 = (B.L dimension of 6 x2) -1

Lower arch: M.D dimension of 345 = (B.L dimension of 6 x2)

Treatment suggestions

In the early mixed dentition, one mechanism for gaining space for alignment is to preserve the leeway space with a lingual arch.

This generous space may be one reason why crowding in the mixed dentition becomes less pronounced with the development of the permanent dentition while the same crowded condition in permanent dentition may dictate extraction therapy. (Gianelly 1994)

Lingual arch is used when a primary canine is lost prematurely, disrupting the integrity of the dental arch .The opposite primary canine is then removed for purposes of symmetry and a lingual arch is inserted.

The function of the lingual arch at this stage is to prevent the lingual movement (uprighting) of the incisors with consequent loss of arch length.(Gianelly 1994)

A lingual arch is also commonly used when the lateral incisors erupt lingual to the central incisors .The function of the appliance is to prevent loss of arch length that could occur if the lateral incisors moved lingually, followed by the central incisor teeth.(Gianelly 1995, Kluemper 2000)

The incidence of lower incisor crowding is about 86% of patients in the mix dentition stage of development and in 77% of them arch length preservation by the use of lingual arch or lip bumper could provide the space for alignment.

The authors reported that best time for lip bumper utilization to distalize lower first molar 1 mm is after first premolar eruption which is a useful methods to resolve lower incisors crowding. (Gianelly 1995)

If extraction treatment is prefered, it can be delayed until the eruption of first premolars that can immediately be extracted. (Gianelly 1995,Kluemper 2000)

About 68% of patients with lower incisors crowding ,in average 5mm , were treated with passive lingual arch which took a place in early mix dentition and 87% of them had 2 mm or less crowding remaining. The increase in arch length was due to a combination of the leeway space, growth, and development. (Bernann and Gianelly 2000)

passive lower lingual arches are effective at reducing the mesial molar migration and subsequent loss of arch length occurring in the transition from the late mixed dentition to the early permanent dentition. This comes at the expense of slight mandibular incisor advancement and tipping. Rebellato et al (1997)

lingual arch is an effective appliance for maintaining space during the eruption of the permanent teeth, preserving molar anchorage, preventing arch length decrease, obtaining in some patients an arch length increase, and preventing the molars from tipping and the mandibular incisors from tipping lingually. These effects could also resolve marginal crowding by controlling space use in the mandibular arch. (Viglianisi 2010)

Crowding of lower incisors may resulted in mesial drift of lower canine in one side resulting from the lingually displaced lateral incisor.

The unfavourable sequence of eruption on the right side where the first premolar has erupted prior to the mandibular canine should be noted. Untreated, the right side will eventually mirror the left side. (Hudson 2011)

Depending on the timing of the lingual arch treatment and the extent of the crowding (4-5 mm), it may be considered prudent to extract the primary canines to allow for some self-alignment of the incisors. More severe cases of crowding should be referred for comprehensive orthodontic treatment. (Hudson 2011)

Guidelines for successful case selection and treatment with passive lower lingual arch (LLA): (Hudson 2013)

The patient should be a Class I dentally and skeletally. In Class II and III cases, the use of the LLA should form part of a comprehensive orthodontic treatment plan.

The patient’s oral hygiene should be impeccable.

Late mixed dentition treatment is appropriate.

The mandibular arch must be intact i.e no tooth loss or improperly contoured

interproximal restorations. In the case of spontaneous loss of the primary canines, the LLA should be placed within one month of the primary tooth exfoliating.

The amount of anterior crowding must be less than five mm.

Lingual Holding Arches & Guidance of Eruption (Ronald 2013)

Long-term follow-up of timed lingual holding arch placement and lower arch dimensional changes :“

1. Arch length / perimeter decreased minimally >> > reduced forward movement of molars. > reduced incisor lingual up-righting.2. Buccal arch length maintained.

3. More distal eruptive positioning of canines & premolars realized.

4. Lower incisor crowding relieved on a consistent basis at a 2 to 4 mm. level.

. A good clinical guide for timing is upon the clinical emergence of the lower canines, lower first premolars and upper first premolars.

Treatment Suggestions After lateral incisor eruption, what you see is what you get! Diagnose

and consider the following: (McDonald et al 2011)

1- DISKING OF PRIMARY CANINES 1 to 2 mm. of space per side can be achieved by disking mesiolingual

corner to provide “sluice-way” for incisor alignment. Indicated at 7 ½ to 8 ½ years of age with:

Less than 3 to 4 mm. of incisor crowding. Laterals actively erupting or aligning in arch. Intact primary canine roots (Not ectopically resorbed or normal timing of

exfoliation). Incisors lingually malpositioned. Preferred option - especially in deepbite / brachyfacial occlusion patterns.

Disking Technique:

Tapered bur ( #699 ) allows access

Must go subgingival to free contacts

Local anesthesia may be needed for subgingival slice.

Careful with laterals ( e.g. wedge )

2-EXTRACTION OF PRIMARY CANINES

Enhance symmetry, coincident midlines, incisor integrity when:

Incisor liability greater than 4 mm. Distorted incisor positioning, particularly asymmetric

eruption. Ectopic loss of primary canine unilaterally that results in

dental midline shift. Frequently Step One of serial extraction program, particularly

vertically sensitive openbite patterns.

3-“Early” Phase I arch development

Use Edgewise 2X4 to position incisors and molars toward Class I relationships with incisor integrity, midline coincidence, and normal overbite / overjet.

Discrepancies requiring arch expansion to relieve crowding and offset negative effects of space loss, ectopic loss or early canine extractions (e.g. retroclined collapsed incisors) are candidates for Phase I 2X4 treatment.

Lip bumpers possible adjunct appliance to facilitate arch development.

Remember, facial type critical factor in extraction versus non-extraction approach.;

.Brachyfacial / Deepbite >>> Prioritize arch development / expansion.

.Dolochofacial / Openbite >>> Extraction protocol much more likely.

4- ”Late” Supervision of Leeway Space

Use lower lingual arch along with selective extraction of primary molars to preserve “E-space”, control late mesial shift and lower incisor up-righting.

Timely placement of lingual arch allows distal eruptive positioning of premolars & canines (on average 1.5 mm. distal placement). Provides 2 to 4 mm. of space for relief of incisor crowding.

Initiation of Edgewise therapy to position incisors and molars toward Class I positions while controlling leeway space also applicable in timing with loss of 2nd primary molars

Tokarevich and Rublevsky(2014) reported the strategies of lower incisors crowding in mix dentition according to amount of crowding :

1. Passive space management (application of passive lingual arch) in the mixed dentition is effective in patients with the amount of mandibular incisor crowding that doesn't exceed the size of leeway space.

2. Application of active lingual arch combined with a selective interproximal reduction of deciduous canines and molars in the mixed dentition is effective in patients with the amount of mandibular incisor crowding that exceeds the size of leeway space by no more than 1 mm.

3. Application of active lingual arch combined with a selective extractions of deciduous canines and molars in the mixed dentition is effective in patients with the amount of mandibular incisor crowding that exceeds the size of leeway space by no more than 4 mm.

Case 1 (Dugoni 1998) A 8-year-old boy (early mixed dentition) in good

health. His parents’ chief concern was the crowding of his incisors ( about 4mm).

Mandibular primary first molars were extracted to allow the incisors to unravel.

A mandibular removable lingual arch was placed to hold leeway space and to align the lower incisors.

The results achieved after 18 month of treatment

ALMEIDA et al 2010) ) Case 2

An eight-year-and-two-month-old Caucasian female patient had a chief complaint of an upper inter-incisor diastema.

In the facial analysis, the patient

showed a harmonious face and a normal labial posture.

In the intraoral clinical examination, the presence of a large diastema was observed, together with several early extractions of primary teeth, with great space loss, and, consequently, a reduction of upper and lower arch length

Radiographic exam In the panoramic radiograph, presence of with

consequent lack of space due to retroclination of the permanent teeth, as was the presence of all permanent teeth, which had either erupted or were at several developmental stages, except for the third molars

:Treatment

The treatment protocol was composed of two stages: one interceptive and one comprehensive.

In the interceptive phase, a serial extraction program was performed, which aimed especially at correcting the discrepancies of the dental arch, fostering favorable conditions for a normal development of the occlusion

a) an extraoral appliance in the upper arch (cervical headgear) to obtain upper molar distalization

b) an active lip bumper, on the lower arch

c) bracket installation on the upper incisors to close the diastema, and to provide space for lateral incisor eruption.

d)Still in this stage, primary first molar extractions were indicated to accelerate eruption of first premolars, which were to be extracted sequentially to create space for the permanent canine teeth

Vyas 2013)) Case 3 An 11-year-old girl reported with chief complaint of Crowding

in lower interiors during mixed dentition.

Regarding her mandibular arch , it was revealed that the left deciduous cuspid had exfoliated, and the space between permanent lateral incisor and deciduous first molar appeared to be 25% of its original width. Mild crowding in lower interiors was also seen .

 This type of appearance can mislead many clinicians to believe that might prompt an early

 serial extraction decision involving extraction of first bicuspid

Leeway was assessed and was found to be only 1 mm less than required.

 To correct the space discrepancy Lingual arch was cement

Case 4 (Vyas 2013) A 12-year

old boy reported with complaint  of over-retained maxillary deciduous cuspid and labially erupting successors.

Perusal of his mandibular arch

 revealed 4 mm crowding in anteriors.

After another 7 months, the alignment

 further improved using lingual arch.

Donough 2014)) Case 5 A Female Patient is a typical late-mixed dentition

adolescent with lower incisors crowding .

A mandibular lingual holding arch was fabricated, and 11 months later she was ready for fixed appliances.

The ideal time to place the lower lingual holding arch is approximately 4 to 12 months prior to loss of the first mandibular primary molar.

Once the patient enters the adult dentition, the crowding has resolved.

Case 6 (Donough 2014)

A 9-year 9-month old female presented with early loss of her primary canines, and retroclined mandibular incisors (IMA = 84.4).

Her space analysis indicated that even with extraction of four premolars, there would be minimal excess space. The other concern is that with extractions, the mandibular incisors may tip further lingual, causing a deepening of the bite and flattening of her profile.

Therefore, a mandibular lingual holding arch was placed, and once the first premolars erupted, progress records were taken, and the orthodontic decided to extract the four first premolars.

When she presented 2½ years later, her crowding had been resolved, and there was no significant change in the overjet or overbite, and her mandibular incisor angulation had been maintained.

Once the upper-left canine erupted, she was ready for her fixed appliances.

Pretreatment

Post phase 1 treatment

Case 7 (Chalakkal 2016)

An 8-year-old female patient presented with a bilaterally symmetrical face with a straight pleasing profile.

On intraoral examination, all quadrants presented with primary canines and molars along with lower anterior crowding .

All permanent incisors and first molars were erupted except 16,12, and 22

The treatment objective was to selectively extract a few mandibular teeth in order to resolve lower anterior crowding; idealize the overbite; and to finish with class I molar relation with no residual spaces.

Since M5 were congenitally missing, it was not possible to perform a conventional serial extraction procedure. Therefore, instead of a C-D-4 extraction sequence, it was planned to perform a C-D-E extraction sequence.

Photos After 6 month of lower primary canines and first deciduous molar extraction

Photos at the end of lower serial extraction treatment

Case 8 (Savas et al 2016)

An 8-year-old girl presented with a complaint of a malpositioned permanent mandibular left lateral incisor.

Mandibular dental midline deviated 3 mm to the left compared to maxillary and facial midlines.

Intraoral examination showed that the crown of the permanent lateral incisor was in the place of permanent canine .

The panaromic radiograph indicated that the transposition was incomplete, with the root apices in their normal position.

CBCT results showed that the crown of permanent left mandibular lateral incisor was positioned in a permanent canine place with a 90° mesiolingual rotation. The roots remained in their natural position, and no contact between the permanent canine and lateral incisor roots was observed.

Treatment was started with the extraction of the retained primary canine.

1-week after the extraction, a removable appliance was constructed with 2 adams clasps and a modified vestibular arch on which a crimpable hook was welded. A button was attached to the lingual surface of the lateral incisor, and 1/8 inch light elastics was placed between the button and crimpable hook.

After 4 months, the lateral incisor was uprighted vertically, and it was placed in a normal position in the dental arch with minimal rotation. At this appointment, a new removable appliance including a labio-lingual spring was fabricated to correct the rotation.

At the end of 9 months of treatment and follow-up, radiographic evaluation showed that the roots of the transposed permanent mandibular lateral incisor we parallel .

There were no signs of complications associated with the tooth movement.

The uprighting and mesial movement of the permanent mandibular lateral incisor allowed the eruption of the permanent canine into the normal location, but because of the lower midline deviation and mild crowding following removable appliances, further orthodontic treatment with fixed appliances was planned .

Case 8 (Bowman 2011)

12.5-year-old male, Resolution of mandibular crowding was achieved in 11 months, without extraction or potentially unstable expansion.

Mini-screws were placed between the mandibular first and second molars at the mucogingival junction, immediately prior to the exfoliation of the mandibular second primary .

The screws provided direct anchorage for the retraction of the first premolars into the leeway space during the eruption of the second premolars

Case 9 (Bowman 2011)

A 13-year-old male with Class II, crowded late mixed dentition malocclusion featured leeway space sufficient to resolve the crowding.

Direct anchorage from mini-screws inserted between lower first and second molars was used to retract first premolars into residual “e” space as second premolars were erupting; thereby, providing space for anterior crowding.

 

Placing brackets on lower incisors should have been delayed until that space was created.

Class II relationship was corrected using prototype Jasper Jumpers, indirectly anchored by the same mini-screws to reduce adverse flaring of the lower incisors that is common with fixed functional appliances.

(Bowman 2011) Case 10 12.5-year-old female Leeway space was

effectively utilized with indirect anchorage support to lower molars from a miniscrews inserted adjacent to lower molar.

Case 11 (Bowman 2011)

Female patient age 12 and five months presented with moderate lower incisors crowding.

Sectional bayonet arms (.018” x .018”) were bonded into auxiliary tubes on mandibular first molars and bonded into the cross-slot heads of two mini-screws that were inserted between mandibular lateral incisors and canines.

The mini-screws provided indirect anchorage for retraction of first premolars into residual “e” space, followed by resolution of anterior crowding

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