A:

A:

A: One simple technique is to add together all the space needed to align the teeth at each contact – from distal of left canine to distal of right canine. In other words, estimate how much tooth enamel would need to be removed in order to provide room to align the teeth.

Let us illustrate this technique using the mandibular arch drawing shown in Figure 2.1a, which includes an unerupted mandibular right lateral incisor.

We calculated 5.7 mm of anterior crowding in this drawing. Next, repeat this technique using the arch starting with Figure 2.1h.

We calculated 6 mm of mandibular anterior crowding. Finally, repeat this technique using the arch shown starting in Figure 2.1n.

We calculate 4.6 mm of maxillary anterior crowding in Figure 2.1n. With practice, this technique is accurate and quick.

A: Mild (1–3 mm), moderate (4–8 mm), severe (≥9 mm)

A: A reliable indicator of severe developing mandibular anterior crowding is premature loss of primary canines – not lack of interdental spacing. Why? In crowded mandibular arches, the permanent lateral incisors often erupt and resorb the mesial portion of the root of deciduous canines, causing their premature loss [2].

A: Principle: for most patients, first attempt non‐extraction treatment.

• Consider monitoring (recalling) patients with crowding in the primary/early mixed dentition. This is assuming that the permanent canine and premolar roots are immature (less than ½ developed) – that is, that the canines and premolars are not close to eruption. This is also assuming that you judge the potential harm from monitoring to be minimal (e.g. the probability of root resorption from ectopically erupting teeth to be minimal).
• Consider space maintenance for patients with mild‐to‐moderate crowding in the late mixed dentition. Space maintenance (LLHA or Nance holding arch) can provide room (leeway space or “E‐space”) for permanent teeth to erupt and align in many patients without extraction of permanent teeth.
• Generally, defer extraction decisions until permanent canines and premolars erupt whenever possible (reduce unknowns before committing to irreversible treatment – including extractions). Once the permanent canines and premolars erupt, a more accurate assessment of crowding (and a clearer decision to extract) can be made.
• Generally, defer extraction decisions until anteroposterior growth is addressed (reduce unknowns before committing to irreversible treatment). Get future growth under control before extracting permanent teeth! Once you extract permanent teeth, those teeth cannot be put back even if the patient grows out of your correction.
• Exceptions to the above, when extraction of primary or permanent teeth should be considered, include cases of space regaining, ectopic eruption, incisor dehiscence, eruption into nonkeratinized gingiva, and severe crowding.
• We generally recommend serial extraction in early mixed dentition patients with severe anterior crowding and only if the patient is normal otherwise (anteroposteriorly, vertically, and transversely).

A: Options include:

• Monitoring (recall)
• Space maintenance
• Space regaining
• Eliminating tooth mass to create space by extraction of teeth or interproximal reduction (IPR) of enamel

A: Space maintenance is the prevention of arch perimeter loss (arch length loss) subsequent to primary tooth exfoliation. One important role of primary teeth is to hold space for permanent successors. When a primary tooth is lost, the adjacent erupted teeth are pulled together by transseptal fibers. They drift into the lost primary tooth space. This drifting may diminish arch perimeter, create undesirable occlusal changes, and impact erupting permanent teeth. Space maintenance seeks to prevent drifting.

A: Let us repeat the analysis we just performed:

A: We attempted non‐extraction treatment by employing space maintenance. We fabricated and cemented an LLHA. As the primary molars exfoliated, premolars replaced them, and crowding decreased (Figure 2.3a). Note the residual ~3 mm of crowding (rotated mandibular canines).

A mandibular model from another patient with mild anterior crowding is illustrated in Figure 2.3b. How would you manage this crowding? Again, employing space maintenance with an LLHA resulted in spontaneous incisor alignment (Figure 2.3c).

A: The sum of the mesiodistal widths of mandibular primary canines plus mandibular primary first molars plus mandibular primary second molars is greater than the sum of the mesiodistal widths of their permanent successors. By maintaining the distance from the permanent first molars to the incisors with an LLHA, residual space remains when the primary teeth exfoliate and their successors replace them. This is where the space comes from. This space is called leeway space.

A: Start by calculating the average mandibular leeway space per side:

• Sum of mandibular primary canine, primary first molar, and primary second molar mesiodistal widths = 5.0 mm + 7.7 mm + 9.9 mm = 22.6 mm.
• Sum of mandibular permanent canine, first premolar, and second premolar mesiodistal widths = 7.0 mm + 7.0 mm + 7.0 mm = 21.0 mm.
• Average mandibular leeway space = 22.6 mm – 21.0mm = 1.6 mm per side of arch.

Now, calculate the average maxillary leeway space per side:

• Sum of maxillary primary canine, primary first molar, and primary second molar mesiodistal widths = 7.0 mm + 7.3 mm + 8.2 mm = 22.5 mm.
• Sum of maxillary permanent canine, first premolar, and second premolar mesiodistal widths = 7.5 mm + 7.0 mm + 7.0 mm = 21.5 mm.
• Average maxillary leeway space = 22.5 mm – 21.5 mm = 1.0 mm per side of arch.

In other words, the average mandibular leeway space is 1.6 mm per side (3.2 mm for the mandibular arch), and the average maxillary leeway space is 1.0 mm per side (2 mm for the maxillary arch). This value is less than the value reported by Moyers [3, 4] (2.5 mm per side or 5 mm for the mandibular arch), but we will use our value (calculated from Wheeler’s data) because it provides a more conservative estimate of future available space. Of course, the leeway space found in any individual patient will depend upon the actual size of their primary and permanent teeth.

A: “E‐space” is the difference in mesiodistal widths between primary second molars and their permanent successors (second premolars).

A: Mandibular “E‐space” equals the difference in mesiodistal widths between mandibular primary second molars and mandibular second premolars, or: 9.9 mm – 7.0 mm = 2.9 mm per side.

A: Maxillary “E‐space” equals the difference in mesiodistal widths between maxillary primary second molars and maxillary second premolars, or: 8.2 mm – 7.0 mm = 1.2 mm per side.

A: Children will often present with erupted permanent canines and erupted first premolars but unerupted second premolars (see Figure 2.3b). In these cases, leeway space is no longer valid, but “E space” can provide an estimate of future space available (for spontaneous incisor alignment if space maintenance is employed).

A: Yes, it is smaller than “E‐space,” but for the mandible, it would equal 7.7 mm – 7.0 mm = 0.7 mm per side (the difference in mesiodistal widths between mandibular primary first molars and mandibular first premolars).

A: First, examine what happens without an LLHA (Figure 2.4a, top left and bottom left). When the mandibular primary canines and primary molars exfoliate (Figure 2.4a, top center and bottom center), leeway space is created because the sum of the primary teeth mesiodistal widths exceeds the sum of their permanent successor mesiodistal widths. Probably, as a result of transseptal fiber contraction, mandibular molars drift mesially (yellow arrows), canines and incisors drift distally (red arrows), posterior spaces close, and incisors align minimally and upright [5, 6].

This mesial molar drift can benefit an “end‐on” molar relationship, moving mandibular molars into a Class I relationship. However, mesial molar drift uses up leeway space that could be used to align crowded anterior teeth, and mandibular incisors are left crowded (Figure 2.4a, top right and bottom right).

Next, examine what happens with an LLHA. Once again, when mandibular primary canines and primary molars exfoliate (Figure 2.4b, top center and bottom center), leeway space is created. However, in this case mandibular molars attempt to drift mesially, but the molars are inhibited from doing so by the lower lingual arch pressing against the incisor lingual surfaces. Instead, transseptal fiber contraction closes the leeway space by retracting canines and retracting/aligning incisors (Figure 2.4b, top right and bottom right).

On the one hand, with an LLHA in place, an end‐on Class II molar relationship will not improve by mesial permanent molar mesial drift. Instead, the end‐on Class II relationship must be corrected by some other means (headgear, Class II functional appliance, Class II elastics, etc.). On the other hand, in patients with Class III molar relationships, an LLHA can prevent mesial molar drift and worsening of the Class III molar relationship.

One final note: mandibular first permanent molars do move slightly to the mesial with an LLHA in place. As they do this, they push the mandibular incisors slightly forward with the lingual arch bar (proclining the incisors) [5, 7]. But, the primary effect of the LLHA is spontaneous improvement of incisor alignment.

A: Our original estimate of mandibular anterior crowding for the patient in Figure 2.2 was 8.7 mm. If we assume 2.9 mm of “E‐space” per side with an LLHA (5.8 mm total), and 0.7 mm “D‐space” per side (1.4 mm total), then upon complete emergence of mandibular premolars and canines, the remaining anticipated crowding was 1.5 mm, which is close to the actual ~3 mm found.

Remember, leeway space, “E‐space”, and “D‐space” are based on average values. Every patient is different.

A: Dewey [6] and Mershon [8] first reported use of the LLHA in 1916–1917.

A: It is estimated that 76% of patients can be treated non‐extraction in the mandible with use of an LLHA [9, 10]. If 2 mm or less of crowding is permitted, this percentage increases to 84% [11]. These success percentages are the reason why we recommend first attempting non‐extraction treatment in mixed dentition patients.

A: One study reported that LLHAs are effective in reducing mandibular first permanent molar eruption by 1–2 mm over a 1–2 year period, compared with controls [11]. In growing patients, reduction of mandibular first permanent molar eruption can reduce downward and backward mandibular plane rotation, reduce LAFH, increase chin projection, and improve Class II relationships.

A: The patient is in the early mixed dentition stage of dental development with moderate mandibular incisor crowding (~6 mm anterior crowding, blocked out mandibular left lateral incisor). Placement of an LLHA before exfoliation of the primary teeth would permit some spontaneous alignment (~3.2 mm of leeway space) during the transition from mixed to permanent dentition.

A: There has been significant improvement in mandibular anterior teeth alignment.

A: Not necessarily. Consider leaving the LLHA until after placement of fixed orthodontic appliances. Why? Alignment is maintained.

We ignored this recommendation for the patient in Figures 2.5 and 2.6. Instead, we removed the LLHA, and significant crowding occurred by the time brackets were placed (Figure 2.7a).

However, following this recommendation for another patient (Figure 2.7b), you see that the LLHA was left in place until the mandibular arch was bonded with fixed appliances. At that time, the LLHA was removed (Figure 2.7c) and the permanent first molars were bonded. Anterior alignment was maintained.

A: Make an alginate impression or intraoral scan and fabricate a vacuum‐formed temporary retainer (Figure 2.9a) to hold the leeway space until you can deliver an LLHA (Figure 2.9b). Or, you can insert a segmental wire with a closed coil spring between brackets bonded on the left first premolar and left first permanent molar (Figures 2.9c and 2.9d). However, this latter approach does not prevent mesial drift of the right permanent molar when the right primary molars exfoliate.

A: In addition to maintaining arch perimeter and achieving spontaneous incisor alignment via leeway space, an LLHA can:

• Expand or constrict first molar arch width (Figure 2.10a). We wish to emphasize that this effect is bilateral. An LLHA cannot expand or constrict unilaterally (cross bite elastic wear is more suitable for unilateral arch expansion or constriction).
• Apply buccal or lingual first molar crown torque (Figure 2.10b) bilaterally, or unilaterally.
• Help eliminate an anterior tongue interposition habit (causing a dental open bite) by soldering spurs (reminders) to the anterior wire (Figure 2.10c).
• Prevent mesial molar drift in Class III patients in order to prevent worsening of the Class III relationship. If an LLHA is placed in a Class III mixed dentition patient to prevent mesial molar drift, then later the erupted premolars and anterior teeth can be retracted distally through the leeway space using TADs, J‐hook headgear, or Class III elastics as anchorage.

A: Mixed dentition space analysis (e.g. Moyers space analysis [3, 12]) evaluates the likely degree of dental crowding following permanent tooth eruption, using prediction of mesiodistal permanent premolar and canine tooth widths based on mesiodistal mandibular incisor widths.

A: Yes. First permanent molar mesial drift is minimal with an LLHA in place. As a result, second molar impaction is 10–20 times more likely (8%) in LLHA patients compared with the general population [16, 17]. Note in Figures 2.11a and 2.11b how the patient’s mandibular right second molar became impacted under the LLHA band (compared with normal eruption of the patient’s left second molar).

How would you deal with the impacted mandibular right second molar shown in Figure 2.11b? A simple solution (Figure 2.11c, left) is to remove the LLHA and bond the mandibular first molar when the remaining arch is bonded (Figure 2.11c, right). Or, the LLHA can be removed and a clear, vacuum‐formed, retainer worn by the patient until you bond the arch.

A: Lateral incisor distal drift can be prevented by soldering spurs (clasps) to the LLHA to wrap around the distal of the lateral incisors (Figure 2.12). Note that the right permanent canine is beginning to erupt and will be blocked out by the soldered spur. The left soldered spur will similarly block the left permanent canine. How would you deal with this? You can either: remove the LLHA, grind away the spurs, and re‐cement the LLHA, or, you could remake the LLHA without spurs.

A: No. If the posterior segments are symmetric, do not extract the contralateral primary canine. Instead, simply place an LLHA to prevent loss of arch perimeter. Solder a spur on the side with the lost primary canine to prevent incisor distal drift.

A: Yes. If you extract a child’s mandibular primary canines to achieve improved incisor alignment (Figure 2.13, bottom left), then you should simultaneously place an LLHA [18] (Figure 2.13, top right and bottom right) to prevent (reduce) mandibular first permanent molar mesial drift and to prevent arch perimeter loss. Once the incisors have drifted into improved alignment, consider fabricating another LLHA with spurs (clasps) distal to the lateral incisors to prevent further incisor drift.

Note: Some orthodontists would argue that the same final incisor alignment may be achieved by simply placing an LLHA, waiting for eruption of permanent teeth, and avoiding canine extractions. Be careful not to allow parents to dictate treatment.

A: Let us examine the facts first:

• Mandibular incisors are aligned.
• Mandibular left permanent canine is erupted.
• Inadequate space exists for the mandibular right permanent canine to erupt (by about 2–3 mm).
• Mandibular left first premolar is rotated and needs about 1 mm of space to be aligned properly.
• Both mandibular first premolars are partially erupted with over 2/3’s root length developed.
• “E space” of about 2.9 mm per side is present (5.8 mm total).
• “End‐on” first permanent molar occlusion.

Based upon these facts, we recommended removing the LLHA and not replacing it, since the second premolars should erupt very quickly. The permanent first molars will drift mesially – hopefully placing the patient in Class I molar occlusion. The first premolars will drift distally – providing space for mandibular left first premolar alignment and mandibular right permanent canine eruption.

A: The erupting maxillary permanent canine crowns overlap the maxillary permanent lateral incisor roots – significantly. You should address this problem now to reduce the chances of the maxillary permanent canines not erupting or resorbing the lateral incisor roots. Early treatment would include making space for the maxillary permanent canines, providing a path for their eruption, and possibly surgical exposure.

A: No matter what specific orthodontic condition you are evaluating, always step back and look for other problems the patient presents with. If you are not seeing other problems, you are not looking.

A: The Nance holding arch is the analogous space maintenance appliance for the maxillary arch. It consists of a trans‐palatal arch (TPA) soldered to maxillary first molar bands and combined with an acrylic button covering the anterior palate rugae (Figure 2.15a). A Nance holding arch can prevent mesial drift of the maxillary first molars when the maxillary primary canines or primary molars exfoliate. The average leeway space provided by an LLHA is ~1.6 mm per side, and the average leeway space provided by a Nance holding arch is ~1 mm per side.

We prefer using a Nance holding arch for maxillary space maintenance, as opposed to using a band and loop appliance attached to primary teeth. Why? Look at the radiograph in Figure 2.15b. The maxillary primary first molar will exfoliate soon. When it does, the maxillary first permanent molar will drift mesially, arch perimeter will be lost, impaction of the second premolar may occur, and the patient could swallow/aspirate the band and loop appliance. In this patient, we ordered removal of the band and loop appliance and placement of a Nance holding arch with bands cemented to the maxillary first permanent molars.

A: Space regaining is orthodontic tooth movement designed to reverse space loss resulting from tooth drift following premature primary tooth loss, tooth drift into extensive carious lesions of adjacent teeth; or ectopic tooth eruption. Techniques to regain space include the use of removable appliances, fixed appliances, or headgear.

A: The boy is in the early mixed dentition stage of dental development. His maxillary right permanent first molar is erupting ectopically (mesially) and is impacted under his maxillary right primary second molar. Arch perimeter has been lost.

A: We recommend treatment of this condition now. Potential harm includes continued arch perimeter loss as the maxillary right permanent first molar drifts mesially (resorbing the primary second molar) and impaction of the maxillary right second premolar beneath the first permanent molar.

A: Space regaining – moving the maxillary right permanent first molar distally. In doing so, arch perimeter (space) would be regained.

A: Options include:

• Insertion of an elastomeric separator between the maxillary right primary second molar and maxillary right permanent first molar to free the trapped permanent molar and push it distally. This option is not recommended here because of poor access. The mesial of the maxillary right permanent first molar is buried very apically and fitting a separator between the two teeth would be problematic. In a similar fashion, if access were available, a brass wire could be inserted around the contact and twisted to push the permanent first molar distally. Local anesthetic would most likely be required if this were attempted.
• Extraction of the maxillary right primary second molar to free the maxillary right permanent first molar and allow it to erupt. After the maxillary right permanent first molar erupts sufficiently to allow application of force, a fixed or removable appliance could be used to distalize the maxillary right permanent first molar and regain lost space. Extraction of a primary second molar may be the only choice in a case where the impacted permanent first molar is completely subgingival.
• If the maxillary right primary second molar is nonmobile, and if you have partial access to the crown of the maxillary right permanent first molar, then bond orthodontic brackets and place a segmental archwire to de‐impact and distalize the permanent first molar (Figures 2.17a and 2.17b). You may need to trap a compressed open coil spring between the permanent first molar and the primary second molar brackets to help distalize the permanent first molar. This was the option we chose.
• A Halterman appliance (Figures 2.17c–2.17e) consists of metal hooks soldered to molar bands. The hooks usually extend to the tuberosity or retromolar pad areas. A button is bonded to the tooth that needs movement. Elastomeric power chain applies tension between the hook and the button to move the tooth (see red arrows in Figure 2.17d).
• If the maxillary primary second molar has exfoliated, and if the permanent first molar has erupted and drifted mesially, then a simple removable spring appliance can be used (Figures 2.17f and 2.17g) to move the maxillary permanent molar distally and regain space. This same appliance can then be worn as a retainer. A headgear could also be used to move the maxillary molar distally – without reciprocal mesial movement of the primary teeth.

A: If you have a compliant patient, then either a removable (spring) appliance or fixed appliances may be considered. If you have a noncompliant patient, then fixed appliances should be chosen.

A: Retention options include the following:

• If the maxillary right primary second molar is nonmobile, then leave it in place as a space maintainer. The maxillary right second premolar should erupt normally.
• If the maxillary right primary second molar is mobile, then place a Nance holding arch or other retainer to maintain the regained space and prevent mesial drift of the maxillary right permanent molar.

A: A fixed appliance option (Figure 2.19a) to regain lost primary second molar space consists of banding the permanent first molar and bonding a bracket (terminal tube) to the primary first molar (or primary first molar and primary canine). A compressed open coil spring is inserted along a segmental archwire between the two teeth (leave some extra wire length at the ends but anneal and turn down the wire ends so they will not slip out of the brackets). Space is regained (Figure 2.19b) as the compressed spring pushes the permanent molar distally and the primary first molar mesially. An LLHA with soldered spur (clasp) wrapping around the primary first molar (Figure 2.19c) is then inserted to hold the regained space.

A removable option is a split plate space regaining appliance (Figure 2.20) incorporating an expansion screw. The screw is opened 0.25–0.50 mm (one–two turns) per week. Opening the screw pushes the mandibular right permanent first molar distally and the mandibular right primary first molar mesially which regains the lost space. The passive appliance can then be worn as a retainer.

A: Serial extraction is the guidance of the developing dentition by sequential extraction of primary and permanent teeth. Serial extraction is usually performed to eliminate severe crowding. The ideal serial extraction patient is in the early mixed dentition stage of development and exhibits a:

• Severe amount of anterior crowding (≥9 mm per arch). The more severe the crowding, the less residual space closure will be required after incisors are aligned.
• Normal anteroposterior relationship (Class I). If the patient presents with a Class II or Class III molar relationship, we recommend that you do not extract permanent teeth until a Class I molar relationship has been achieved – unless you are sure that future growth will maintain balance between maxillary and mandibular skeletal relationships, and that extraction of permanent teeth will help correct the Class II or Class III dental relationship.

  Some authors report successful serial extraction in Class II patients (maxillary arch treatment) and Class III patients (mandibular arch treatment) [19]. However, we recommend that it is always best to reduce unknowns before doing anything irreversible, including extracting permanent teeth. Therefore, we strongly recommend that Class II or III anteroposterior growth be addressed before serial extraction is instituted. Ideally, a Class I molar relationship should be present with minimal uncertainty regarding future jaw growth.

  

• Normal vertical relationship (minimal OB). The vertical incisor overbite will deepen (increase) following premolar extractions as incisors are retracted and uprighted. For this reason, the patient should have normal vertical skeletal relationships or have a slightly long soft tissue and skeletal LAFH, steep mandibular plane angle, and minimal OB or possibly a mild open bite but never a deep bite.
• Normal transverse relationship (well‐coordinated maxillary and mandibular arch widths without cross bites; minimal transverse compensations such as maxillary molar buccal crown torque or mandibular molar lingual crown torque). Why is this important? If the patient’s transverse relationship is normal, then you have one less problem to deal with post‐extractions.
• Normal incisor angulation or proclined incisors (protrusive lips), but not upright incisors. Why? Incisors tend to upright as they are retracted during premolar extraction space closure.

A: Let us assume a one‐to‐one correspondence between the actual size of the patient and the size of the cephalometric tracing (no magnification difference). Further, assume that her mandibular incisors are already aligned. Draw a line (dotted red line, Figure 2.21b) from the mandibular incisor apex to FH so that an angle of 68° is formed (FMIA = 68°), and measure the distance from the current mandibular incisal edge tip (along the solid red line) to its future anticipated position along the dotted red line. Here, we find that distance equals 5 mm. To retract the mandibular anterior teeth by 5 mm (Figure 2.21c, left top and left bottom) requires 5 mm of space on both the right and left sides for a total of 10 mm of space needed. This space requirement (to reduce incisor proclination) is in addition to any space needed to alleviate dental crowding.

10 mm of mandibular space is much greater than can be gained from leeway space. For this reason, a decision was made in this patient to extract her right and left mandibular first premolars (and maxillary first premolars). First premolar extractions provided 14 mm of space (two premolars × 7 mm per premolar) in each arch to retract incisors (Figure 2.21c, right top and right bottom). Following maxillary and mandibular first premolar extractions, and space closure with fixed orthodontic appliances (Figure 2.21d), her mandibular incisors uprighted to an FMIA of 69° (maxillary incisors uprighted slightly to U1to SN = 115°).

Dr. Charles Tweed provided a simple technique to calculate the space needed to upright mandibular incisors, as follows: 0.8 mm lower incisor retraction space is needed for every 1° increase in FMIA desired [20]. For our example that works out to 8 mm of retraction space needed for the patient shown in Figure 2.21a (68°– 58° = 10° × 0.8 mm/° = 8 mm). This estimate assumes minimal changes in arch form during premolar extraction space closure. When arch form changes are anticipated, a mathematical formula is available to calculate arch space used for mandibular incisor retraction [21].

Now, if a patient presents with upright incisors, then space to reduce dental crowding may be gained by proclining anterior teeth (Figure 2.21e) to a more normal incisor angulation. Incisor proclination increases arch perimeter and reduces crowding. Proclining incisors stresses the labial gingiva covering the incisor roots, and ideally the patient should have a thick labial periodontal biotype to support this movement.

A: There is no single serial extraction sequence. However, in one common sequence, the primary canines are first extracted (Figure 2.22a) when the permanent canines have attained at least one‐half of their final root length. This will create space for spontaneous alignment of permanent incisors. Permanent incisors drift distally into the extraction space, and posterior teeth may drift mesially into the extraction space. The bite may deepen as the incisors upright (Figure 2.22b).

When the first premolar roots have attained at least one‐half of their final root length, extraction of the first primary molars accelerates their eruption (Figure 2.22c). As the permanent canines erupt, extraction of permanent teeth (usually the first premolars, Figure 2.22d) facilitates canine eruption and canine distal drift (Figure 2.22e). Depending upon the magnitude of crowding, space closure will be required after the second premolars erupt (Figure 2.22f). In cases where the permanent canines erupt before the first premolars, the first premolars may be enucleated concurrently with primary first molar extractions.

A: Poor patient selection, such as performing serial extraction on marginally crowded patients. Extraction of teeth for any purpose is never taken lightly. Mild mandibular anterior crowding of 3 mm or less can usually be treated with space maintenance and preservation of leeway space. Interproximal tooth reduction (IPR) is another way to create space without tooth extractions. Extraction of permanent teeth in cases of mild anterior crowding may result in excess residual space, over‐retraction of anterior teeth during closure of these residual spaces, excessive uprighting of incisors, and bite deepening.

Figures 2.23a and 2.23b illustrate the trade‐offs between serial extraction, crowding, incisor proclination, and the need for post‐extraction orthodontic space closure. In Figure 2.23a (left), serial extraction is performed on a mandibular arch with severe initial anterior crowding and severe incisor proclination. The post‐extraction result is improved incisor inclination and the need for minimal residual space closure after eruption of permanent teeth (Figure 2.23a, right). In this case, serial extraction was an excellent choice. In Figure 2.23b (left), serial extraction is performed on a mandibular arch with minimal crowding and normal incisor inclination. The post‐extraction result is very upright incisors and large residual spaces that must be closed (Figure 2.23b, right). In this case, serial extraction was a poor choice.

Even in patients where mandibular primary canines have been prematurely lost due to excessive crowding, prediction of severe crowding is difficult before all permanent canines and premolars have erupted. So, the ultimate question is, how early should you decide to extract permanent teeth?

As a general rule, except in cases of ectopic eruption, incisor dehiscence, incisor eruption into nonkeratinized gingiva, or where you are sure the patient presents with severe crowding, it is prudent to place an LLHA until the permanent teeth have erupted to accurately assess the need for permanent teeth extractions.

A: Excluding cases of ectopic eruption, no difference in treatment outcome is found [22, 23]. Also, serial extraction might reduce active treatment time, but significant observation time precedes active treatment [23].

A: No. Incisor stability of serial extraction cases equals incisor stability of later premolar extraction cases, but mixed dentition mandibular arches (having favorable leeway space) treated with LLHAs are more stable [24, 25].

A: No. Serial extraction followed by orthodontic tooth movement does not reduce apical root resorption compared with treatment with later extractions [26].

A:

A: Premature loss of primary canines [2]. Lack of interdental spacing is not a reliable indicator of severe mandibular anterior crowding. Emma exhibits premature resorption of mandibular primary canine roots.

A: To answer this question, we will consider Emma in the light of each criterion that makes an ideal serial extraction candidate. The ideal serial extraction patient is in the early mixed dentition stage of development and exhibits a:

• Normal anteroposterior relationship (Class I). At first, you would conclude that Emma does not meet this criterion because she is Class II by 1–2 mm, bilaterally. However, you would be wrong. While it is true that Emma appears slightly Class II from the buccal (Figures 2.24j and 2.24l), in fact Emma is really Class I.

  How do we conclude this? When Emma is viewed from the lingual (Figure 2.24o and p), her permanent molars are Class I. In other words, her maxillary first permanent molars are rotated mesially (Figure 2.24m) which results in them appearing Class II when viewed from the buccal. If we simply rotate her maxillary first permanent molars around their lingual roots (rotating buccal surfaces toward the distal), then she will be Class I when viewed from both the buccal and from the lingual.

  Always check for molar rotations. Ask how the molar rotations affect your molar anteroposterior classification. Always view molars from the lingual. Emma meets the criteria of having Class I molars (although she is Class II skeletally).

• Normal vertical relationship (minimal OB). Emma presents with a long skeletal LAFH, ILG, steep MPA, and mild anterior open bite. These features are not ideal but should not preclude serial extraction since the open bite will tend to close as incisors are rotated/uprighted following premolar extractions. Emma meets this criterion.
• Normal transverse relationship (coordinated arch widths without cross bites; minimal transverse compensations). Emma has a reasonable transverse relationship and meets this criterion.
• Severe amount of anterior crowding (≥9 mm per arch). Emma meets this criterion in her mandibular arch.
• Normal incisor angulation or proclined incisors (protrusive lips), but not upright incisors. Emma meets this criterion.

In conclusion, Emma is a candidate for serial extraction. The one feature that we find disconcerting is her severely retruded mandible (skeletal Class II relationship). We would feel more comfortable with her as a serial extraction candidate if her mandible was normal.

A: No. Emma has severe mandibular anterior crowding (9 mm) coupled with severe mandibular incisor proclination. Even with space maintenance, treating her non‐extraction would increase incisor proclination and thereby worsen her open bite.

A: Emma’s parents stated that she was not growing noticeably at this time. We asked them to measure her height each month. Emma was asked to keep her tongue away from her incisors in the hope that the incisors would erupt. We decided to treat her with serial extraction. She was referred for primary canine extractions. Nine months later, Emma’s parents stated that she was growing. We asked Emma to wear a HPHG which she wore until her molars were slightly Class III. Headgear wear served us two purposes. First, moving her maxillary molars distally to slightly Class III would give us extra anchorage when we eventually began to retract her anterior teeth posteriorly. Second, restricting her maxillary growth, while permitting her mandible to continue growing forward, would improve her profile.

Her primary first molars were extracted when the roots of her first permanent premolars were ½ formed. Her permanent first premolars were extracted when they erupted. Emma was placed in fixed appliances, her arches leveled and aligned, and treatment finished. Her deband photographs are shown in Figure 2.25a–k. Note that her profile has improved, incisors have uprighted, anterior open bite has closed, lips are no longer protusive, lip competence attained, and arch alignment achieved. Serial extraction treatment for Emma was appropriate and successful.

A: Average mesiodistal widths of permanent teeth (mm) [3]:

Average mesiodistal widths of primary teeth (mm) [3]:

MAXILLARY ARCH

+5.0 mm of incisor spacing currently present, including nearly exfoliated maxillary left primary lateral incisor (Figure 2.26j).

−6.5 mm of space needed for potentially impacted maxillary right permanent lateral incisor.

−6.5 mm of space needed for potentially impacted maxillary left permanent lateral incisor.

+2 mm of anticipated leeway space (1 mm/side).

Balance = +5.0 mm − 6.5 mm −6.5 mm +2 mm = −6.0 mm.

MANDIBULAR ARCH

+3.0 mm of incisor spacing currently present (Figure 2.26k).

−5.5 mm of space needed for mandibular left permanent lateral incisor.

−5.5 mm of space needed for mandibular right permanent lateral incisor.

+3.2 mm of anticipated leeway space (1.6 mm/side).

Balance = +3.0 mm −5.5 mm −5.5 mm +3.2 mm = −4.8 mm.

That is, 6.0 mm of maxillary arch crowding and 4.8 mm of mandibular arch crowding is anticipated following eruption of all permanent teeth (if proper space maintenance is employed).

A:

A:

• The goal of early treatment is to correct developing problems – get the patient back to normal for their stage of development (including preventing complications such as resorption of adjacent tooth roots, reducing later treatment complexity, or reducing/eliminating unknowns). Correcting the ectopic eruption of her maxillary left first permanent molar, correcting her mild Class II relationship, and alleviating her anterior crowding would get her back to normal.
• Early treatment should address very specific problems with a clearly defined end point, usually within six to nine months (except for some orthopedic problems). Distal movement (de‐impacting) of her ectopically erupting maxillary left first permanent molar is a clearly defined objective which could be managed in a few months using fixed orthodontic appliances. Correcting her mild Class II relationship with orthopedics could be readily corrected with cooperation once Ameila exhibits good (statural) growth velocity. Providing room for her erupting incisors is a clearly defined solution which, with extraction of primary canines, could be managed in a short time. However, to prevent risk of arch perimeter loss, an LLHA and Nance holding arch should be placed concurrently with primary canine extractions. Finally, even with space maintenance, we estimate 6.0 mm of maxillary arch crowding and 4.8 mm of mandibular arch crowding once all permanent teeth erupt.
• Always ask: Is it necessary that I treat the patient now? What harm will come if I chose to do nothing now? It is necessary to institute early treatment now. If we do not correct her ectopically erupting maxillary left permanent first molar, then the first molar will continue to resorb the maxillary left primary second molar, erupt to the mesial, reduce arch perimeter, and impact the maxillary left second premolar.

  On the other hand, it is not necessary to deal with Amelia’s mild Class II relationship yet (her parents measure her height regularly and state that she is not growing appreciably). Nor is it necessary to address Amelia’s anterior crowding immediately (permanent canines and premolars are years from erupting). If we chose to recall in one year, then her maxillary lateral incisors will remain potentially impacted or erupt blocked out from her maxillary dental arch. Her mandibular lateral incisors will remain blocked out in a lingual position.

A: Yes and no. On the one hand, if you choose to extract her four primary canines in order to alleviate permanent incisor crowding/facilitate permanent incisor eruption, then placement of an LLHA and Nance holding arch would be prudent to prevent possible permanent first molar mesial drift and arch perimeter loss. On the other hand, if you do not extract primary canines, then space maintenance to reduce anterior crowding (via leeway space) would be unnecessary at this time since permanent canine and premolar eruption is years away.

A: Possibly. If we regain lost primary lateral incisor space now for permanent lateral incisors, then we need about 8 mm of additional anterior space in each arch (we cannot include leeway space now because primary canines and molars are still present).

8 mm of anterior space per arch could be regained via ~4 mm of central incisor proclination (i.e. ~4 mm regained on both right and left sides). 4 mm of incisor proclination seems reasonable because the labial gingival biotype of both arches is WRN (Figure 2.26h), maxillary incisors are upright (Figure 2.26e), and mandibular incisors exhibit normal angulation. However, periapical radiographs should be made of the central incisor roots to ensure a reasonable amount of root development and caution must be exercised during space regaining to ensure that bonded central incisor roots do not drive unerupted lateral incisor roots into permanent canine crowns.

A: Factors suggesting that Amelia is a candidate for serial extraction include the fact that she:

• Is in the early mixed dentition stage of development.
• Is vertically normal (OB is 20–30%).
• Exhibits a normal posterior transverse relationship.

The factor that disqualifies Amelia as an ideal candidate for serial extraction is her moderate crowding magnitude (8 mm, not severe). Further, if we include leeway space (space maintenance), only 6.0 mm of maxillary crowding and 4.8 mm of mandibular crowding is anticipated following eruption of all permanent teeth. Another factor which disqualifies her is that she is slightly Class II.

The ideal serial extraction patient is in the early mixed dentition stage of development and normal in every way, except for the presence of severe anterior crowding (≥9 mm anterior crowding in each arch). We conclude that Amelia is not an ideal candidate for serial extraction.

A: We decided to institute early treatment now. We began by bonding her maxillary left posterior teeth with fixed orthodontic appliances and trapping a compressed open coil spring between her maxillary left permanent first molar and primary second molar (Figure 2.27a). The permanent first molar was de‐impacted from under the primary second molar, thus correcting its ectopic eruption. We checked the mobility of the maxillary left primary second molar and found it to be nonmobile. We removed the fixed orthodontic appliances and retained the maxillary left primary second molar as a space maintainer (Figure 2.27b).

Later, as Amelia was beginning to enter the late mixed dentition stage of development, she was placed on a high‐pull headgear to correct her mild Class II relationship. We planned to extract Amelia’s maxillary primary canines in order to permit her maxillary permanent lateral incisors to erupt, and we planned to monitor Amelia and evaluate for mandibular space maintenance or lateral incisor space regaining. However, Amelia never followed up for treatment in spite of repeated requests to do so.

A: Space regaining. Arch perimeter (space) was lost during the molar’s ectopic eruption into the maxillary left primary second molar. This lost space was regained during correction of the ectopic eruption.

A: Changes include:

• Excess gingiva displayed in posed smile (maxillary incisors appear stepped down relative to maxillary posterior occlusal plane).
• Relatively straight profile.
• ANB angle has decreased from 4° to 2°.
• Mandibular incisors are now upright (FMIA = 74°).
• Maxillary incisors have uprighted (maxillary incisor long axis to SN line = 98°).
• Permanent dentition is now present (maxillary right primary second molar is close to exfoliation) and she is Class I at her molars.
• OB has increased to 70–80%.
• Maxillary permanent lateral incisors have erupted.
• Maxillary right permanent lateral incisor is in lingual cross bite.
• Both right permanent canines are blocked out of the arches.
• Thin labial periodontal biotype of right permanent canines and mandibular left permanent central incisor is noted (Figure 2.28g and h).
• ~6.5 mm of maxillary anterior crowding is present.
• ~5.5 mm of mandibular anterior crowding present.

A: Treatment options include:

• Recall (no treatment, monitor) – re‐evaluate in one year. We do not recommend this option. It is time to begin comprehensive fixed appliance orthodontic treatment.
• Non‐extraction treatment – leveling and aligning both arches with fixed appliances to create room for the blocked out right permanent canines. This option is appealing because Amelia’s incisors are upright, and because she has an obtuse NLA. That is, aligning her maxillary arch will procline her maxillary incisors and increase her maxillary lip support. Further, she still has maxillary right “E‐space.”

  Our concern with non‐extraction treatment is that her anterior periodontal tissues will be stressed as spaces for the right canines are opened, and areas of gingival recession could result. A periodontal consult (gingival grafting) would be recommended if this option was pursued.

• Extraction of first or second premolars – will provide space to alleviate the moderate (5.5–6.5 mm) anterior crowding without stressing periodontal tissues. However, Amelia’s incisors are already upright. Space closure following four premolar extractions would probably upright her incisors even more – potentially dishing in her profile.
• Mandibular single incisor extraction – could be a viable alternative if an anterior Bolton analysis reveals a significant mandibular anterior tooth‐size excess. If a significant (3–5 mm) mandibular anterior Bolton excess is not present, then excess anterior OJ will remain following comprehensive treatment. Maxillary periodontal tissue stress will still occur if the maxillary arch is treated non‐extraction.
• Maxillary arch alignment first – then re‐evaluation for extractions. This option offers the advantage of reducing treatment unknowns before an extraction decision is made. Using this approach, you can monitor the maxillary right permanent canine labial gingiva and observe how much anterior OJ is created following maxillary arch alignment.

A: Exhaustively consider all options (non‐extraction, extraction of anterior teeth, extraction of posterior teeth) before making your final comprehensive treatment decision.

A: A decision was made to reduce unknowns before making a non‐extraction/extraction decision. Amelia’s maxillary right primary second molar was removed, and her maxillary right second premolar erupted. Her maxillary permanent teeth (except for her maxillary right lateral incisor) were bonded with fixed orthodontic appliances, and a compressed open coil spring was trapped between her maxillary right canine and maxillary right central incisor to create room for her maxillary right lateral incisor. This was done slowly while the maxillary right canine labial gingiva was monitored.

When enough space had been created for her maxillary right lateral incisor, Amelia was placed on a posterior biteplate (orthodontic cement bonded to the occlusal surfaces of her maxillary first molars) to open her anterior bite and permit clearance for her maxillary right lateral incisor to be advanced out of cross bite. The lateral incisor was then bonded, and the cross bite was corrected.

A: As is so often the case, it was wise to reduce unknowns first (align her maxillary arch). We now recommended extraction of Amelia’s mandibular right central incisor to provide 5mm of mandibular anterior space. This extraction would be followed by placement of fixed mandibular orthodontic appliances, leveling and aligning of the mandibular arch, and shifting the mandibular right lateral incisor and right canine toward the left. Why did we choose this treatment plan?

With minimal anterior OJ (Figure 2.29a), extraction of a mandibular central incisor would:

• Provide 5 mm of space to permit aligning mandibular anterior teeth.
• Avoid stressing mandibular anterior labial periodontium which would occur with non‐extraction mandibular arch alignment.
• Avoid proclining mandibular anterior teeth into anterior cross bite which could occur with non‐extraction alignment.
• Avoid the need for maxillary anterior space creation (plus veneers to fill the spaces created), or significant mandibular interproximal enamel reduction, to create overjet with non‐extraction alignment.
• Avoid dishing in Amelia’s profile with four premolar extraction treatment.

A: You could certainly argue that extraction of the mandibular right lateral incisor would have been a better choice. Why? The crowding (blocked out mandibular right canine) was closer to the right lateral incisor than to the right central incisor. This would have made post‐extraction alignment and space closure easier. Of course, extraction of the mandibular right lateral incisor would have meant that slightly more extraction space would have been created, leading to slightly more anterior OJ at the end of treatment.

You could also argue that extracting the mandibular left central incisor would have been a better choice. Why? The labial periodontium covering the mandibular left central incisor was (and is) of a thinner biotype than the other incisors. Of course, extraction of the mandibular left central incisor would have made space closure (shifting the mandibular right central incisor and right lateral incisor to the left) more difficult.

A: She will wear Hawley retainers every night, for life. Only with lifelong retention can alignment of teeth be guaranteed. The maxillary Hawley retainer includes an anterior biteplate to disclude her posterior teeth slightly when she wears it, which should help prevent her OB from deepening. A mandibular fixed canine‐to‐canine retainer could also have been used instead of a removable mandibular retainer.

A: “Take‐home pearls” include the following:

• It was prudent to correct Amelia’s ectopically erupting maxillary left permanent first molar with early treatment. Why? If we had not moved her maxillary left permanent first molar distally, then her maxillary left second premolar could have become impacted by the ectopic mesial eruption of the permanent first molar.
• Amelia exemplifies the following principle: always ask if there are unknowns which can be eliminated before performing irreversible treatment. It was smart to level and align Amelia’s maxillary arch first with fixed orthodontic appliances (to gage resulting anterior OJ) before a decision was made regarding permanent tooth extractions. Because only minimal anterior OJ resulted after maxillary arch alignment, extraction of a mandibular incisor seemed reasonable in order to correct ~5.5 mm of mandibular anterior crowding present. If a large anterior OJ had resulted following maxillary arch alignment, then extracting a mandibular incisor would have been less desirable.
• Amelia exemplifies the following principle: exhaustively consider all non‐extraction and extraction options before making your final comprehensive treatment decision. There are always trade‐offs to consider in various extraction (or non‐extraction) options. Force yourself to consider the cost/benefit of treating the patient non‐extraction, non‐extraction with IPR, with extraction of various anterior teeth, and with extraction of various combinations of posterior teeth. Combined with the patient’s desires, consideration of all options will usually reveal the best course of treatment.
• In cases of early crowding always consider monitoring (recall only), space maintenance, space regaining, and permanent tooth extraction. All options should be considered.

A: No. You can decide to treat or recall using these records.

A:

A:

Average mesiodistal widths of permanent teeth (mm) [1]:

Average mesiodistal widths of primary teeth (mm) [1]:

MAXILLARY ARCH

+3 mm of anterior space is currently present (Figure 2.31h).

+2 mm of anticipated leeway space (1 mm/side).

Balance = +3 mm + 2 mm = +5.0 mm.

MANDIBULAR ARCH

+3 mm of anterior space present (Figure 2.31i).

−5 mm of space is needed for missing mandibular right primary canine.

+3.2 mm of anticipated leeway space (1.6 mm/side) if mandibular right primary canine was still present.

Balance = +3 mm – 5 mm + 3.2 mm = +1.2 mm.

That is, 5.0 mm of maxillary arch space and 1.2 mm of mandibular arch space is anticipated following eruption of all permanent teeth (if appropriate space maintenance is employed).

A:

• The goal of early treatment is to correct developing problems – get the patient back to normal for their stage of development (including preventing complications such as resorption of adjacent tooth roots, reducing later treatment complexity, or reducing/eliminating unknowns). Regaining lost space for her mandibular right permanent canine to erupt, shifting her mandibular midline to the left to be coincident with her maxillary midline, and reducing her deep overbite would bring Jasmine back to normal for her stage of development.
• Early treatment should address very specific problems with a clearly defined end point, usually within six to nine months (except for some orthopedic problems). We can reduce her deep bite by placing fixed orthodontic appliances (braces) and leveling her arches with increasingly larger arch wires to intrude her maxillary and mandibular incisors. Her mandibular midline can be shifted to the left (space regaining) by using the same mandibular fixed appliances and trapping an open coil spring between her mandibular right primary first molar and mandibular right permanent lateral incisor. An LLHA (with a soldered spur to prevent lateral incisor drift) can then maintain this midline correction and allow her mandibular right permanent canine to erupt. This focused early treatment could be completed in six to nine months.
• Always ask: Is it necessary that I treat the patient now? What harm will come if I choose to do nothing now? It is not necessary to treat Jasmine now. If we do not treat her early, then her mandibular right permanent canine may remain unerupted, erupt ectopically, or (if the mandibular right primary first molar exfoliates) erupt over the mandibular right first premolar (possibly impacting it). The probability of her mandibular right permanent canine causing lateral incisor root resorption is low. Finally, since her mandibular incisor palatal impingement is causing neither pain nor tissue damage, we can treat her deep bite later. We anticipate no harm by waiting.

A: Your options include the following:

• Recall (no treatment, monitor only) – re‐evaluate in six to nine months. No harm is anticipated by monitoring Jamison. Eruption of her permanent teeth should continue normally, except for her mandibular right permanent canine, which may remain unerupted, erupt over the mandibular right first premolar, or erupt ectopically.
• Space maintenance – placement of an LLHA (and possibly Nance holding arch) would gain us leeway space on her maxillary left, maxillary right, mandibular left, and “E space” plus “D space” on her mandibular right when her remaining primary teeth exfoliate. However, her permanent canine and premolar roots appear to be less than ½ developed so their eruption is not imminent.
• Space regaining – opening space for Jasmine’s mandibular right permanent canine using fixed orthodontic appliances (trapping an open coil spring between her mandibular right primary first molar and mandibular right permanent lateral incisor). Overjet may first need to be increased by placing fixed maxillary appliances, leveling her arches, and opening her bite. Later, after space is created for the mandibular right permanent canine, the space could be held using an LLHA with spurs soldered to prevent distal drifting of the permanent right lateral incisor.
• Extraction of her mandibular right primary first molar – would provide room for eruption of the mandibular right permanent canine (which is erupting ahead of her mandibular right first premolar), but could result in arch perimeter loss as the right permanent first molar drifts mesially. If an LLHA is placed at the time of primary first molar extraction, then arch perimeter loss could be prevented. Later, fixed appliances could be used to shift the mandibular midline to the left and regain space for her mandibular right first premolar. Because Jasmine’s mandibular right premolar root is <½ developed, extraction of her mandibular right primary first molar will likely delay its eruption.
• Serial extraction – is not a reasonable option. As calculated above, Jasmine could eventually have anterior spacing in both arches if space maintainers are placed. Serial extraction should be considered in cases of severe anterior crowding.
• Placement of fixed appliances (braces) to level the arches, open the deep bite, and eliminate mandibular incisor palatal impingement – would be a recommended option if her mandibular incisor palatal impingement was causing tissue damage or pain. In such a case, a quicker and less expensive solution would be to fabricate a maxillary clear retainer that covered the palate and anterior teeth only (no coverage of posterior teeth). If she wore the retainer full time, then pain and further tissue damage would be eliminated, and posterior teeth would continue to erupt – opening the anterior bite.

A: In our opinion, no. Why? Look closely at the mandibular right permanent canine in Figure 2.31d. It has erupted so far occlusally that its crown should block further distal drift of the mandibular right lateral incisor.

A: We decided to monitor and recall Jasmine in six to nine months. At that time, if her mandibular left primary canine is mobile, then we will fabricate and cement an LLHA. We anticipate no additional early treatment for Jasmine.

A: It would be reasonable to place an LLHA now. Why? If Jasmine fails to show up for her recall appointment, then we will lose arch perimeter as the premolars and permanent canines erupt and posterior teeth drift mesially (and incisors upright).

On the other hand, we do not feel that an LLHA is necessary now because the remaining permanent teeth are not ready to erupt and because we worry about band cement “washout”/enamel decalcification if we place an LLHA too early. This is an example of the options and trade‐offs you face with early crowding management.

A: In our opinion, yes. Why? The mandibular left permanent canine has erupted less than Jasmine’s right permanent canine, and the mandibular left lateral incisor is likely to continue drifting to the distal without a spur holding it.

A:

A: Following loss of her mandibular left primary lateral incisor, her mandibular permanent central incisors erupted/drifted to the left (Figure 2.33i), closing the missing primary lateral incisor space and shifting the midlines to the left. Anterior teeth drift distally, and posterior teeth drift mesially, probably as a result of transseptal fiber pull [27].

A: No additional records are needed to make this decision. However, we would recommend making a periapical radiograph (or limited field of view CT scan) of the ectopically erupting mandibular left permanent lateral incisor in order to better visualize it. This was not done.

A: We would recommend monitoring eruption of her permanent first molars.

A: Below are space estimates:

Average mesiodistal widths of permanent teeth (mm) [1]:

Average mesiodistal widths of primary teeth (mm) [1]:

MAXILLARY ARCH

+7.5 mm of anterior space is currently present (Figure 2.33h).

−8.5 mm anticipated width of left permanent central incisor required.

+6.5 mm width of right primary central incisor.

−8.5 mm width of right permanent central incisor required.

+5.1 mm width of right primary lateral incisor.

−6.5 mm width of right permanent lateral incisor required.

+5.1 mm width of left primary lateral incisor.

−6.5 mm width of left permanent lateral incisor required.

+2 mm anticipated leeway space (1 mm/side).

Balance = +7.5 mm − 8.5 mm + 6.5 mm − 8.5 mm + 5.1 mm − 6.5 mm + 5.1 mm − 6.5 mm + 2 mm

=−3.8 mm.

MANDIBULAR ARCH

−1 mm of incisor crowding is currently present, but the left primary lateral incisor is missing (Figure 2.33i).

−5.5 mm anticipated width left permanent lateral incisor.

+4.1 mm width right primary lateral incisor.

−5.5 mm anticipated width right permanent lateral incisor.

+3.2 mm of anticipated leeway space (1.6 mm/side).

Balance = −1 mm − 5.5 mm + 4.1 mm − 5.5 mm + 3.2 mm = −4.7 mm.

That is, 3.8 mm of maxillary arch crowding and 4.7 mm of mandibular arch crowding is anticipated following eruption of all permanent teeth (if proper space maintenance is employed).

A:

• The goal of early treatment is to correct developing problems – get the patient back to normal for their stage of development (including preventing complications such as resorption of adjacent tooth roots, reducing later treatment complexity, and reducing/eliminating unknowns). Ensuring that all of Bella’s permanent teeth erupt would get her back to normal for her stage of development.
• Early treatment should address very specific problems with a clearly defined end point, usually begun and ended within six to nine months (not protracted over many years, except for select orthopedic problems). Bella’s anterior crowding and ectopically erupting mandibular left permanent lateral incisor are specific problems with clearly defined end points. However, if space maintenance is employed for leeway space, then correction will take longer than nine months because permanent canines and premolars are years away from erupting.
• Always ask: Is it necessary that I treat the patient now? What harm will come if I chose to do nothing now? It is not necessary to treat Bella now, and you could choose to monitor her permanent tooth eruption. The risk of monitoring is that her mandibular left permanent lateral incisor could continue to erupt ectopically, become impacted, or possibly resorb the left central incisor root.

1. For most patients, first attempt non‐extraction treatment.
2. Generally, monitor (recall) patients with crowding in the primary/early mixed dentitions.
3. Generally, consider space maintenance for patients with mild‐to‐moderate crowding in the late mixed dentition. By employing an LLHA and taking advantage of mandibular leeway space (3.2 mm total in the arch), spontaneous crowding reduction can occur during the transition to permanent dentition.
4. Reduce unknowns. Generally, postpone extraction decisions until premolars and permanent canines erupt. Then, you can better judge their size and the magnitude of crowding.
5. Reduce unknowns. Postpone extraction decisions until anteroposterior growth is addressed/under control.
6. Consider serial extraction, or other extraction of primary and permanent teeth, in cases of:
   1. ectopic eruption
   2. incisor dehiscence
   3. eruption in nonkeratinized gingiva
   4. severe crowding (obvious extraction case)

A: All six statements are true.

A: No, we should not treat Bella with serial extraction. Let us discuss Bella in the context of each feature which would define an ideal serial extraction patient (normal in every way, except severe anterior crowding):

• Class I first molars. Bella is Class I in her primary second molars and primary canines.
• Vertically normal to slightly long soft tissue and skeletal LAFH, with minimal OB or possibly a mild open bite, but not a deep bite. Bella is normal vertically (soft tissue), but her OB is mildly deep (30%).
• Normal incisor angulation or proclined incisors, but not upright incisors. We do not have a cephalometric radiographic to accurately measure Bella’s incisor angulation. Further, only her mandibular permanent central incisors are erupted.
• Normal posterior transverse relationship (good posterior interdigitation; absence of posterior cross bites; and absence of significant transverse compensations). Bella has a normal transverse relationship.
• Severe (≥9 mm) anterior crowding – Bella does not meet this criterion. We anticipate 3.8 mm of maxillary arch crowding and 4.7 mm of mandibular arch crowding following eruption of all permanent teeth (if proper space maintenance is employed).

Based upon the above features, Bella is not an ideal candidate for serial extraction.

A: Treatment options include the following:

• Recall (monitor) – in nine to twelve months to evaluate tooth eruption. Since the mandibular left permanent lateral incisor does not appear to be causing problems (dehiscence or root resorption), monitoring Bella would seem reasonable. But if we choose this option, then we must explain the risks to her parents (mandibular left permanent lateral incisor continuing to erupt ectopically, becoming impacted, or possibly resorbing the left central incisor root). Further, we should consider additional imaging to better judge the mandibular left permanent lateral incisor situation.
• Space maintenance – placement of an LLHA and Nance holding arch as soon as the first permanent molars erupt. Because Bella’s permanent canine and premolar roots are minimally developed (their eruption is years away), and because her primary canine and primary molar roots are not resorbing (exfoliation not imminent), there is no pressing need to place space maintainers yet. Space maintainers should be placed when she approaches the late mixed dentition stage of development.

  We wish to emphasize that the 3.2 mm of anticipated mandibular leeway space could go a long way toward resolving her anterior crowding, so the importance of Bella returning for annual recall visits must be emphasized. In our clinical opinion, it is better to place space maintainers too early (and risk band cement washout) than to place them too late (and lose arch perimeter from mesial molar drift).

• Extraction of mandibular left primary canine – would aid in eruption of the mandibular left permanent lateral incisor. This is a reasonable extraction option since the mandibular left permanent lateral incisor is erupting ectopically (Figure 2.33d). Recall our guideline: early extraction of primary and permanent teeth should be considered in patients with ectopic incisor eruption, dehiscence of tissue covering incisors, incisors erupting into nonkeratinized gingiva, and severe crowding.

  If extraction of the mandibular left primary canine is the option chosen, then we would wait until both mandibular permanent first molars erupted to proceed. Why? Following extraction of the left primary canine, we would band the permanent first molars and place an LLHA with a soldered spur wrapping around the distal of the left central incisor – to prevent mesial drift of the left molars (loss of arch perimeter) and to prevent further distal drift of the mandibular left lateral incisor.

• Extraction of both right and left mandibular primary canines plus extraction of the mandibular right primary lateral incisor – would aid in eruption and alignment of mandibular permanent lateral incisors. Once again, if this were the option chosen, then we would wait until the permanent first molars erupted before proceeding. And please remember, there is a little girl attached to this option who would require bilateral mandibular anesthesia to proceed.
• Space regaining – opening space for the ectopically erupting mandibular left permanent lateral incisor is not recommended at this time. Why? Bella lacks anterior overjet. In other words, in order to create space for the mandibular left permanent lateral incisor, we will need to procline the mandibular central incisors. But, in order to procline the mandibular central incisors, we must have anterior overjet. Without overjet, you will procline/advance her mandibular incisors into cross bite.

  Space regaining may be an option once her maxillary permanent incisors erupt, but space regaining is not recommended now. Why? Because in order to create overjet, maxillary primary incisors must be proclined, and their roots will be driven reciprocally into the permanent incisor crowns.

  If space is eventually regained for the mandibular left permanent lateral incisor, then you will need to place an LLHA (with a soldered spur distal to the mandibular left central incisor) to order to maintain the opened space.

• Extraction of maxillary primary canines and remaining primary incisors – could be a viable option if the permanent incisors fail to erupt or if Bella’s maxillary permanent canine crowns begin to overlap her maxillary permanent lateral incisor roots on a panoramic image (ectopic eruption). We do not recommend this option now.
• Serial extraction – would not be appropriate for Bella. We anticipate only 3.8 mm of maxillary arch crowding and 4.7 mm of mandibular arch crowding following eruption of all her permanent teeth (if proper space maintenance is employed). Serial extraction patients should present with severe crowding (≥9 mm).

A: We recommended extraction of the mandibular left primary canine and placement of an LLHA with soldered spur wrapping around the distal of the mandibular left central incisor.

A: You can gain mandibular midline improvement if her mandibular incisors drift/shift to the right as a result of this extraction. You can lose arch perimeter if an LLHA is not placed with the extraction and if the posterior teeth drift mesially.

A: “Take‐home pearls” include:

• Additional imaging of Bella’s ectopically erupting mandibular left permanent lateral incisor may have been helpful to better visualize the situation we were initially dealing with. Practice radiation hygiene, but always request the imaging you need to properly care for your patients.
• Since all four maxillary incisors erupted normally, and since the maxillary permanent canines appear to be reasonably positioned (Figure 2.34), the decision not to extract the maxillary primary canines and remaining primary incisors appears to have been correct. It is important that Bella’s tooth eruption continues to be monitored regularly.
• The decision to monitor permanent first molar eruption was correct.
• Whenever you are concerned with arch perimeter loss in the mixed dentition following loss of primary teeth, consider including a space maintainer in your treatment plan.
• We generally do not recommend extracting primary canines in order to achieve incisor alignment or midline improvement. However, if a primary canine is extracted for those purposes, then we recommend placing an LLHA to prevent arch perimeter loss.

A: We recommended immediate placement of an LLHA and Nance holding arch (Figure 2.36). Why? Compared with Jasmine, Evan’s premolar and permanent canine root development is more advanced. In fact, Evan’s maxillary left first premolar has already erupted. By placing an LLHA and Nance holding arch now, we will utilize leeway space/“E‐space”/“D‐space” to reduce anterior crowding.

Progress photographs (Figure 2.37) show Evan after all permanent teeth have erupted (early treatment complete). Note spontaneous improvement in maxillary anterior teeth alignment and spontaneous eruption of mandibular right permanent canine.

A: Evan’s early treatment was necessary and successful.

A: Evan’s treatment underscores the importance of space maintenance. By utilizing leeway space/“E‐space”/“D‐space,” all of Evan’s permanent teeth erupted and his mandibular right canine now requires only a few millimeters of space to be aligned.

A: Because Evan’s mandibular labial periodontium has a thick biotype and his mandibular incisors are upright (Figure 2.35e, FMIA = 76°), we anticipate Evan can now undergo non‐extraction comprehensive treatment by removing the space maintainers, placing fixed orthodontic appliances, leveling his arches with wires to open his bite (which will increase his anterior overjet), and aligning his arches. His upright mandibular incisors will procline to a more normal angulation as his mandibular right canine is aligned with the arch.

A: