A: Ectopic tooth eruption occurs when a tooth does not follow its normal eruption path (Figures 3.1a and 3.1b). Adverse sequelae of ectopic tooth eruption include loss of arch perimeter, tooth impaction, and root resorption.

A:

1. The goal of early treatment is to correct developing problems – to get the patient back to normal for their stage of development, thereby reducing unknowns, later treatment complexity, and preventing complications. Correcting ectopic tooth eruption is often essential to return the patient to a normal eruption pattern, prevent arch perimeter loss, prevent impaction of adjacent teeth, and prevent root resorption.
2. Early treatment should address very specific problems with a clearly defined end point, usually within six to nine months. Ectopic tooth eruption is a perfect example of a specific problem with a treatment of short duration and a clearly defined end point.
3. Always ask: Is it necessary that I treat the patient now? What harm will come if I choose to do nothing now? Without correction, ectopic eruption can result in arch perimeter loss, tooth impaction, and root resorption.

A: Principles include:

• Create space for the ectopic tooth to erupt – clear an eruption path. This may include extracting teeth or creating space using headgear, RME, fixed orthodontic appliances, or a removable appliance.
• Space regaining to move an ectopically erupting/erupted permanent tooth back to its correct position, especially if arch perimeter has been lost. For example, if the patient in Figure 3.1a will be treated non‐extraction, then you could attempt using either fixed appliances or a removable appliance to move the maxillary right permanent first molar distally (freeing it from under the primary second molar). Or, you could extract the maxillary right primary second molar, allow the maxillary right permanent first molar to erupt into a Class II molar relationship, then move the maxillary right permanent first molar distally using fixed appliances or a removable appliance. In some cases, surgical exposure may be required to place an orthodontic bracket on an ectopically erupting tooth so that space regaining forces can be applied.
• Consider all possible anterior and posterior extraction patterns. If the patient is clearly a case that will require extraction of permanent teeth, or in instances of severe root resorption of permanent teeth, exhaustively consider all possible extraction options. For example, if the patient in Figure 3.1a is an extraction patient, then you might extract the maxillary right primary second molar (allowing the maxillary right permanent first molar to erupt into a Class II molar relationship), then extract the impacted maxillary right second premolar, or first premolar, at a later date.
  

  

As another example, in Figure 3.1b you may consider extracting the maxillary right primary canine and primary first molar to provide room to move the maxillary right permanent canine distally following its surgical exposure. Or, you could consider extracting the maxillary right lateral incisor if it is deemed hopeless to permit the maxillary right permanent canine to erupt into the lateral incisor position. Then, you could leave the permanent canine in the lateral incisor position (canine substitution case) and retain the primary canine, or you could extract the primary canine and retract the permanent canine into its correct anteroposterior position (with prosthetic replacement of the missing lateral incisor). Our point is that there are many options you should exhaustively consider, in consultation with the restorative doctor, the parent, and perhaps an endodontist.

A: After third molars, the permanent maxillary canines are the most common tooth to display ectopic eruption during development [1–3]. Palatal displacement is more common than buccal displacement by approximately threefold [3, 4].

A: Initial diagnosis of an early treatment patient may not provide a simple “yes or no” answer to the question of ectopic maxillary permanent canine eruption. Rather, diagnosis of ectopic eruption may be a developing scenario that is determined by establishing a baseline followed by careful periodic observation. This is for two reasons: (i) maxillary permanent canine development and eruption is occurring over the entire time period of the mixed dentition stage, and (ii) an ectopic path of eruption can occur at any stage during root development of the tooth [2].

A: Principles include the following:

1. Because the timing of dentition development and chronologic age vary across individuals being considered for early treatment, you must establish the stage of dentition development for your patient. This is best done by panoramic radiography. The goal here is to determine if the patient is advanced or delayed in dentition development compared to chronologic averages, allowing you to gauge the timeline of anticipated maxillary permanent canine eruption, and aiding your plan for clinical supervision.
2. Establish the spatial position of the maxillary canines relative to the permanent maxillary lateral incisors. This is determined by palpation for the developing maxillary permanent canine crowns in the buccal alveolar plate and estimating maxillary permanent canine position radiographically (using periapical radiography and Clark’s rule, or panoramic and cephalometric images, or 3‐D cephalometry) [5–7]. This allows an assessment of potential impaction or damage to adjacent teeth due to malposition of the maxillary canines and supports the decision to apply treatment early or opt for continued clinical supervision.
3. Determine if other factors may have a negative impact on continuing eruption of the maxillary permanent canines (e.g. crowding of developing permanent teeth, ectopic eruption of adjacent permanent teeth, abnormal sequence of permanent tooth development, maxillary anteroposterior or transverse deficiency, or hypodontia).

A: Using a large sample of children in the mixed dentition, and following them longitudinally, Ericson and Kurol [2, 8] observed that a palpable bulge of the buccal alveolar plate in the area apical to the primary canine and permanent lateral incisor roots was generally predictive of normal maxillary permanent canine eruption. In cases of delayed dental age, a palpable bulge was not always present, and early radiography in these cases did not always reveal abnormal position or predict ectopic eruption. However, during continued clinical supervision, if the developing canines became palpable to the buccal, they erupted without impaction. Furthermore, children who did not display palpable maxillary permanent canines after age eleven had a higher incidence of later canine impaction, prompting the recommendation for further radiographic investigation if this finding occurs during clinical supervision.

This supports our three important principles noted earlier: During early treatment diagnosis, considering the maxillary permanent canines, you must establish:

• The stage of dentition development
• The spatial position of the maxillary permanent canines
• If other factors may have a negative impact on continued eruption

A: Yes, as seen on a panoramic image, the more the maxillary permanent canine crown overlaps the lateral incisor root, the greater the chance that the canine will become palatally displaced [9]. For example, look at the panoramic image of a patient in the late mixed dentition shown in Figure 3.3. The erupting maxillary left permanent canine crown is not overlapping the left lateral incisor root, and we can predict that it will most likely erupt normally if adequate space is present. However, the maxillary right canine crown is overlapping the right lateral incisor root, so we can predict that it may become palatally displaced and impacted. The greater the overlap, the greater the likelihood of impaction.

A: The principle we should apply is to create a path for the ectopically erupting tooth to follow. One way to create a path [10, 11] is to extract the maxillary right primary canine, but the success of primary canine extraction alone has proven equivocal [12, 13]. Instead, the benefit of primary canine extraction appears to be enhanced when it is performed in conjunction with space opening procedures [12–26], including:

• Using fixed orthodontic appliances to trap a compressed open coil spring between the posterior teeth and the lateral incisor. The spring force should be kept light during space opening, and the lateral incisor bracket should be positioned to tip the lateral incisor root away from the erupting permanent canine crown (and not drive the lateral incisor root into the canine crown).

Important note: this approach will create space between the crowns of the teeth and between coronal portions of the roots but less space at the root apices where the space is needed if the canine crown is located there. For this approach to create space at the root apices, you must assure that appropriate root tip results at the root apices to diverge the roots away from the erupting tooth.

• RME (to create space both between maxillary central incisor crowns and between root apices) [27] followed by a TPA
  

  

  

• Distal movement of the posterior teeth using headgear
• Extraction of the maxillary primary first molar in addition to extraction of the primary canine
• Permanent tooth extractions

If the maxillary primary first molar is extracted in addition to the primary canine (Figures 3.4a and 3.4b), then the first premolar can erupt down and out of the way of the canine crown (assuming that the premolar root is at least at least 1/2 developed) [28]. This accelerated eruption provides space for the permanent canine and encourages its eruption. Or, if the maxillary arch can afford to be expanded (Figure 3.4c), then RME can create additional space for the maxillary permanent canine to erupt.

For the patient in Figure 3.3, we chose to extract the maxillary right primary canine and right primary first molar. The maxillary right permanent canine (and left permanent canine) then erupted uneventfully (Figure 3.4d).

A: Study results are mixed. Bonetti et al. [24] reported concomitant primary canine and first molar extractions more effective at promoting eruption of ectopically erupting permanent canines positioned palatally or centrally. Although the study found equivalent clinical success over an 18‐month postextraction observation period, the authors’ conclusions are based on significant differences in spatial positioning of maxillary permanent canines in response to simultaneous primary canine and primary first molar extractions compared to primary canine extractions alone. Hadler‐Olsen et al. [29] reported the two methods are equivalent in promoting normal eruption of palatally displaced maxillary canines, but did not see a significant improvement of maxillary canine spatial position using different measurement criteria.

In our clinical experience, concomitant primary canine and first molar extractions are more effective at promoting eruption of ectopically erupting maxillary canines when the maxillary first premolar roots are ≥1/2 developed. Why? Eruption of the first premolar is accelerated. The first premolar erupts down and away from the permanent canine crown, providing a path and additional space for the canine to erupt.

A: The further apically the vertical position of the canine cusp tip (relative to the occlusal plane) and the more horizontally tipped the canine crown, the more likely the canine will be impacted [30] (and in our clinical opinion, the more difficult it will be to erupt it orthodontically).

One study found that a vertical position <12 mm is important for spontaneous canine eruption (Figure 3.5a). An inclination of <20° (Figure 3.5b) is important for spontaneous eruption of labially displaced canines but appears to have no impact on palatally displaced canines [31]. Finally, the more mesial the permanent canine crown position relative to the incisor roots, the worse the prognosis for spontaneous eruption [11, 32].

A: Use our three principles to establish your timeline for canine eruption, the spatial position of the canine, and other factors that may impede normal eruption (e.g. crowding). If you decide treatment to improve canine eruption is warranted, you cannot guarantee spontaneous eruption of the canine. However, extraction of the primary canine in conjunction with space creation can be a reasonable early treatment.

A: The maxillary right first premolar is erupting ectopically and is blocking eruption of the maxillary right permanent canine. The maxillary left permanent canine is erupting normally.

A: Yes, we would recommend early treatment for this patient. Otherwise, the maxillary right permanent canine and first premolar could remain impacted with potential future root resorption of the maxillary right lateral incisor.

This condition is challenging. We reasoned that because of its near horizontal angulation, the maxillary right first premolar would never erupt even if we cleared a path for it. However, we decided that the least invasive early treatment would be to extract the maxillary right primary canine and both maxillary right primary molars – and recall the patient in six months (note that the premolar roots have developed to at least 1/2 of their final length). If, at the six‐month recall appointment, the position of the maxillary right first premolar and canine improved on a panoramic image, then we would continue monitoring. However, if the position of the maxillary right premolar and canine did not improve, then we would refer for surgical exposure of the maxillary right first premolar and use fixed orthodontic appliances to erupt it into the arch.

We extracted the maxillary right primary canine and both primary molars. We also placed the patient, who exhibited a Class II molar relationship, on a high‐pull headgear (preventing maxillary right first permanent molar mesial drift). We made another panoramic radiograph six months later (Figure 3.7). Remarkably, the maxillary right premolar had erupted normally along with all other permanent teeth.

How/why did this ectopic eruption pattern self‐correct? We can’t be certain, but the ectopic eruption of the maxillary right first premolar was a significant “other factor” influencing eruption of the right canine. Normalizing the ectopic eruption of the right first premolar created space for continued eruption of the right canine.

A: We would recommend early treatment for the ectopically erupting mandibular permanent canines. Otherwise, they may remain impacted and/or resorb the mandibular permanent lateral incisor roots. Treatment consisted of mandibular primary canine extractions. The mandibular permanent canines then erupted spontaneously (Figure 3.9a and b).

In addition to extraction of the mandibular primary canines, extraction of the mandibular primary first molars (Figure 3.8) may have been beneficial to encourage eruption of the mandibular first premolars and thereby make room for the mandibular permanent canines (mandibular first premolar root development was >1/2).

A: Suggestions include the following:

• Direct your surgeon to remove all bone covering the impacted canine crown in the direction you intend to move it (Figure 3.10). Why? Once the dental follicle is disrupted during surgery, there are no cells to remove bone [33]. Bone is then be removed only, and slowly, by pressure necrosis.
• Direct the surgeon to check mobility of the unerupted canine using an elevator (Figure 3.11). If the canine is non‐mobile (ankylosed), then a decision must be made either to attempt breaking the ankyloses (immediately applying an eruptive force before ankylosis recurs) or to extract the canine.
  

  

• Initially move the canine crown away from adjacent tooth roots. Do not drag the canine crown across adjacent tooth roots. Dragging the canine crown across adjacent tooth roots can result in resorption of adjacent roots [34]. Once the canine crown is clear of neighboring roots, then move it toward its future position in the arch.

Look at Figure 3.12a. Here, the elastomeric chain from the premolars is pulling the surgically exposed maxillary left canine crown across the root of the lateral incisor, possibly resorbing the lateral incisor root. To make matters worse, we bonded the left lateral incisor. Bonding the lateral incisor makes it hard for the canine to push the lateral incisor out of the way. A better approach is to first move the surgically exposed canine crown away from the incisor roots (Figure 3.12b, TPA helping to direct the elastic force) before moving the canine laterally into the arch (Figure 3.12c).

These same suggestions apply to labially impacted maxillary canines (Figure 3.13a–d) and impacted mandibular canines (Figure 3.14a–d). That is, first move the surgically exposed canine crowns away from adjacent roots before moving the canines into the arch.

• Ask your surgeon to elevate a full‐thickness mucoperiosteal palatal flap over the impacted canine crown
  

  

• Remove all palatal bone covering the canine crown to the level of the cementoenamel junction
• Place a hole in the palatal flap over the canine crown
• Suture the flap back in place [33, 35].

The canine should erupt without orthodontic force. What are your thoughts of this technique?

A: If the impacted canine is not ankylosed, then this technique should be successful in providing a path for the canine to spontaneously erupt. However, once the patient has this surgical procedure, an argument can be made for proceeding with forced (orthodontic) eruption of the exposed canine – instead of hoping for spontaneous eruption.

A: Options include:

• Monitoring (self‐correction), which is possible between 6 and 7 years of age. However, early treatment to bring the ectopically erupting permanent first molar into occlusion should begin as soon as it is realized that self‐correction will not occur [36].
  

  

• Insertion of an elastomeric separator (or twisted brass wire) between the maxillary right primary second molar and maxillary right permanent first molar to release the trapped permanent molar. In this patient, we were unable to gain access to place a separator.
• Extraction of the maxillary right primary second molar to free the maxillary right permanent first molar and allow it to erupt. We chose this option because the maxillary right primary second molar was very mobile and would exfoliate soon. After we extracted the primary second molar, the maxillary right permanent first molar erupted in a mesial position (Figure 3.16a). We next considered three options: (i) placing fixed appliances and inserting a compressed spring between the maxillary right primary first molar and permanent first molar – to move the maxillary right permanent first molar distally and regain space for the maxillary right second premolar, (ii) fabricating a removable maxillary spring appliance to move the maxillary first permanent molar distally, and (iii) banding the maxillary permanent first molars and using a headgear to move the maxillary right permanent molar distally.

We chose to band the maxillary first permanent molars (Figure 3.16b) and use a headgear to move the maxillary right permanent first molar distally. We also placed an LLHA. Once all permanent teeth had erupted, we bonded both arches with fixed orthodontic appliances, leveled and aligned the arches, and finished treatment (Figure 3.16c).

• If the maxillary right primary second molar had been nonmobile (an anchor) instead of mobile, then you could have bonded brackets and placed a segmental archwire to free the permanent first molar and move it distally (Figure 3.17). A compressed open coil spring could be trapped between the permanent first molar and the primary second molar to help push the permanent first molar distally.
  

  

  

  

• Use of a Halterman appliance which consists of a metal hook soldered to a maxillary right primary second molar band. The hook extends to the tuberosity area. A button is bonded to the maxillary right permanent first molar, and an elastomeric power chain stretched to apply tension between the hook and the button to move the permanent first molar distally. Since the maxillary right primary second molar was mobile, this approach was not employed.

A: Similar to early treatment of ectopically erupting maxillary molars, options include (Figure 3.18):

• Insertion of an elastomeric separator (or twisted brass wire) between the ectopically erupting mandibular permanent molar and primary second molar.
• Extraction of the mandibular primary second molar to free the mandibular permanent first molar and allow it to erupt. Figure 3.18a illustrates an ectopically erupting mandibular left permanent first molar. The problem is that if we extract the primary second molar and allow the permanent first molar to erupt, then the erupting molar will drift mesially and arch perimeter will be lost. To avoid this problem, place a distal shoe (Figures 3.18b and 3.18c), which allows the permanent first molar to erupt but prevents it from drifting mesially.

Once the mandibular first permanent molar erupts, you can either place an LLHA (the distal shoe will fall out when the primary first molar exfoliates) or regain space by moving the permanent first molar distally using fixed orthodontic appliances or a removable appliance. Neither was done in this patient, and the mandibular left second premolar erupted uneventfully (Figure 3.18d).

• If the mandibular primary second molar is nonmobile (useful as anchorage), and if you have access to the crown of the ectopically erupting mandibular permanent first molar Figure 3.18e, mandibular right permanent first molar), then you can bond brackets and place a segmental archwire to free the permanent first molar and move it distally (Figures 3.18f–3.18g). A compressed open‐coil spring can be trapped between the permanent first molar and the primary second molar to help move the permanent first molar distally.
• Use of a Halterman appliance (Figure 3.19, shown here erupting second molars).
• Surgical luxation, elevation, and immobilization of second molars (Figure 3.20) [37, 38].

A: In Figure 3.21a, the alveolar bone crest levels of both mandibular primary second molars are at the same level as the alveolar bone crest levels of their respective permanent first molars. This relationship is seen during normal tooth eruption (Figure 3.22a, red lines represent normal alveolar bone crest levels).

In Figure 3.22b, a large step is seen between the alveolar bone crest level of the right mandibular primary second molar and the alveolar bone crest level of the right mandibular permanent first molar. This relationship (Figure 3.22b) is indicative of primary second molar ankylosis.

A: Primary second molars often have naturally shorter clinical crowns than permanent first molars. Therefore, a patient without ankylosis could exhibit a clinical occlusal step between the shorter primary second molar crown and the taller permanent first molar crown. A clinical occlusal step is not a reliable indicator of primary tooth ankylosis.

On the other hand, a (radiographic) discrepancy in alveolar bone crest heights indicates that eruption of the normal tooth has continued while eruption of the ankylosed tooth has halted. The earlier the onset of ankylosis, the greater will be the alveolar bone crest height discrepancy.

The best way to confirm ankylosis of a tooth is to look for an alveolar bone crest height discrepancy between it and adjacent teeth. Of course, you can always check its mobility. If a primary tooth is mobile, then it is not ankylosed.

Some clinicians advocate identifying ankylosis by listening for a difference in sound between the suspect tooth and adjacent teeth when the teeth are tapped with the end of an intraoral mirror handle. We do not feel comfortable using this method. Perhaps others have better hearing than we do.

A: Transeptal fibers from the depressed, ankylosed primary second molar pull vertically on both teeth, causing them to tip [39, 40].

A: We elected to have the mandibular right primary second molar and primary first molar extracted. We also placed an LLHA. Let us explain:

If the mandibular right second premolar was in a normal position, and if the mandibular right permanent first molar was upright, then we would recommend monitoring only (recalling the patient in nine to twelve months). If this were the case, then exfoliation of the ankylosed primary second molar would be delayed by about six months, but the alveolar bone crest level at that site would eventually be normal after the second premolar erupted [41, 42].

However, the progressive infraocclusion of the mandibular right primary second molar in Figure 3.21b has resulted in severe mesial tipping of the mandibular right permanent first molar. This mesial tipping could worsen if we do nothing. Therefore, we elected to place an LLHA now. Also, we were concerned that the very low position of the mandibular right primary second molar could hinder root development of the mandibular right second premolar. Therefore, we asked a surgeon to extract the mandibular right primary second molar and right primary first molar.

A: If over a period of a year we do not see radiographic evidence of continuing primary second molar root resorption by an erupting second premolar (with > 1/2 second premolar root development), then we will extract the primary second molar.

A: Yes, it is true that early primary tooth extraction can cause delayed eruption and emergence of its successor, probably as a result of scar tissue forming a mechanical barrier [28]. As a general rule, a primary tooth should not be removed until its permanent successor has an appropriate amount of root formation – at least 1/2 of its root length.

However, in this patient (Figure 3.21b), we were concerned that if the ankylosed mandibular primary second molar remained, then the mandibular right second premolar root could not develop. Therefore, we extracted the ankylosed mandibular right primary second molar. The mandibular right primary first molar had to be extracted in order for the surgeon to gain access to the primary second molar.

A: The mandibular right second premolar is showing signs of root development and eruption away from the lower border of the mandible. We planned to remove the LLHA and upright the mandibular right permanent first molar (space regaining) using fixed orthodontic appliances or a removable appliance. We would then fabricate a new LLHA to maintain the permanent first molar in its upright position while the remaining permanent teeth erupted.

The patient did not return to our clinic for five years (Figure 3.23b). Our LLHA had been removed, but no other treatment had been performed. Note the full root development of both mandibular right premolars and significant uprighting of the mandibular right permanent first molar. Did eruptive force from the impacted mandibular right second premolar cause the permanent first molar to upright? We do not know. The patient is now in adult dentition and entering comprehensive treatment.

A: Our reasoning was as follows: if the mandibular right second premolar did not form a root and begin to erupt, then we would have extracted it and attempted to move the mandibular right permanent first molar mesially (closing the space). Because the mandibular right permanent first molar crown was already tipped forward, we would have left it tipped forward and rotated the roots forward with fixed appliances.

Therefore, we decided to leave the first permanent molar tipped forward until we could determine whether the second premolar root was developing and the tooth erupting.

A: Her maxillary right permanent first molar exhibits normal root development and has erupted to the occlusal plane. Her maxillary left permanent molar lacks root development and has failed to erupt.

A: Possible reasons include:

• Ankylosis
• Eruption blocked by the maxillary left primary second molar root
• Systemic factors found in patients with certain syndromes, such as cleidocranial dysplasia, ectodermal dysplasia, Gardner syndrome, and Apert syndrome.
• Delayed eruption
• Primary failure of eruption (PFE).

A: Yes, a simple explanation is that the maxillary left permanent first molar was extracted and that the molar we see is the maxillary permanent second molar (whose development matches that of the maxillary right permanent second molar). However, the parent stated that the maxillary left permanent first molar had never been extracted. Did the left first permanent molar never develop? We cannot be sure whether it is the first or second permanent molar.

A: Primary failure of eruption (PFE) refers to failure of a non‐ankylosed tooth to erupt due to a disturbance of the eruption mechanism [43]. A wide range of clinical variability exists, thought to be the result of variation in the timing and intensity of the dysregulation [44]. The following characteristic signs of PFE could apply to the patient in Figure 3.24 [45–48]:

• Permanent first molars are always involved and present with no apparent barrier to eruption (100% for genetically confirmed PFE).
• Posterior teeth are more frequently affected.

Other signs of PFE that do not specifically apply to the patient in Figure 3.24 include:

• If a tooth in a more anterior position is affected, then teeth more distal to that tooth are usually affected as well (i.e. when premolars are affected then molars are also likely to be affected).
• Both primary and permanent teeth can be affected.
• The condition is often bilateral (50/50 for PFE patients, versus 80/20 unilateral/bilateral for molar ankylosis).
• Teeth in both arches are often affected (91% for patients with genetically confirmed PFE).
  

  

• Affected teeth resorb the alveolar bone above the crown, may erupt into initial occlusion and then cease to erupt further, or may fail to erupt entirely.
• Affected teeth may be displaced back and forth with manual pressure (indicating that they are not initially ankylosed). However, affected teeth tend to become ankylosed as soon as orthodontic eruptive forces are applied.
• If a small area of ankylosis is broken by luxating the ankylosed tooth, it might be possible to move the tooth for a short time, but re‐ankylosis is inevitable.
• Other concurrent skeletal problems (Class III malocclusion for 63% of genetically confirmed PFE patients) and dental anomalies (tooth agenesis, microdontia of maxillary lateral incisors, anomalous root morphology) may be present.

Possible treatment options for posterior open bites resulting from PFE include:

• Restoring the involved erupted teeth with buildups or crowns after vertical growth is complete.
• Extraction of the involved teeth and replacement with bone grafts/implants.
• With first and second molar involvement, leaving the affected teeth in place and accepting a premolar occlusion.
• A segmental osteotomy or distraction osteogenesis to close the posterior open bite.
• A removable prosthetic (overlay) partial denture to provide posterior occlusion.

A: Since we were uncertain as to whether this condition resulted from PFE, ankylosis, delayed eruption of the first pemanent molar, or normal development of the second permanent molar, we decided to monitor the maxillary left permanent molar. Also, we placed an LLHA and corrected an anterior crossbite with fixed appliances (Figure 3.25).

A: The maxillary left molar was erupting. Clinically, it had pierced the gingiva. Why did this happen? We suspect that this represents normal development of the maxillary left second molar (with first molar agenesis). Or, perhaps bonding the maxillary left primary second molar freed the permanent first molar, allowing it to erupt. We decided to monitor its eruption longer. Eventually, the molar erupted (Figure 3.26b).

A: Permanent tooth eruption appears normal.

A: The maxillary second premolars are erupting symmetrically. The mandibular right second premolar has erupted. The mandibular left second premolar eruption is relatively delayed. The roots of the mandibular left primary second molar do not appear to be resorbing appreciably.

A: Possible causes include:

• Normal variation in eruption timing
• Recent ankylosis of the mandibular left primary second molar
• Mandibular left primary second molar roots failing to resorb

Treatment options include continuing to monitor eruption of the mandiblar left second premolar or extracting the mandibular left primary second molar (since root development of the mandibular left second premolar > 1/2 complete).

A: We decided to take a periapical radiographic of the mandibular left second premolar.

A: A supernumerary tooth is present, which may be blocking eruption of the mandibular left second premolar. We requested surgical extraction of the supernumerary tooth. We will continue to monitor eruption of the mandibular left second premolar.

Occasionally (Figure 3.29b), ectopically erupting premolars will resorb mainly one primary molar root, leaving the other primary root essentially intact. The primary molar will remain nonmobile. How should you proceed in a case such as this? We waited six more months, noted that the condition was unchanged, and extracted the primary second molar.

A: Second premolars [49–51].

A: Oligodontia is noted (congenitally missing more than five permanent teeth), including her missing maxillary right second premolar, mandibular right second premolar, and mandibular left second premolar. In place of the three missing second premolars are the retained primary second molars. A developing maxillary left second premolar, with minimal root development, is also present. Other permanent teeth are missing.

A: Our recommendations are as follows:

• For non‐extraction cases – if the retained primary tooth has a good crown, good root, and good bone (not ankylosed), then consider maintaining it for the long term. However, always have a contingency plan prepared in case the retained primary tooth is eventually lost. Such a contingency or “fallback” plan could include implant replacement.
  

  

• Whenever possible, avoid bonding (placing brackets on) retained primary teeth in order to reduce the risk that their roots will resorb. If you must bond (place brackets on) retained primary teeth, then try to avoid moving them.
• For non‐extraction cases – if the retained primary tooth does not have a good crown, root, or bone, then seriously consider extracting it.
• For extraction cases (e.g. cases involving severe anterior crowding) – consider extracting the retained primary tooth as one of your extraction treatment options.

A: Because all three retained primary second molars have excellent crowns, roots, and alveolar bone heights (not ankylosed), we chose to keep them. However, we informed the patient and parents that they may need to be replaced at some future date with implants.

A: You have only two choices, either you can extract the underdeveloped premolar or you can give it some time to develop. We chose to monitor it, and we gave it one year to develop. If it developed, then we would maintain space for it and allow it to erupt. If it did not develop, then we would extract it and replace it with an implant or FPD.

A: It was foolish to place fixed appliances on the retained primary second molars. If we were to retreat this treatment today, we would avoid bonding the retained primary teeth in the hope that their roots would be less likely to resorb. Also, we would avoid moving them.

A: The retained primary molars are intact. If root resorption of the primary molars has occurred, then it is not noticeable – even though they were bonded. The maxillary left second premolar developed, and erupted, beautifully.

The maxillary right second permanent molar has super‐erupted because it lacks an antagonist. If we could retreat this patient today, then we would place a right distal acrylic extension on the mandibular Hawley retainer to act as an antagonist for the maxillary right second molar (to prevent super‐eruption).

A: “Pearls” include the following:

• Retaining this patient’s primary second molars was a reasonable option because she was a non‐extraction case, and because each primary second molar had good crown, good root, and good bone.
• Whenever possible, avoid bonding and moving retained primary teeth.
• The decision to monitor the underdeveloped maxillary left second premolar was prudent. One of the hardest things for orthodontists to do is to wait and give nature time to act.
• When you leave a tooth (e.g. the maxillary right permanent second molar) unopposed, retain the patient so that the unopposed tooth does not super‐erupt. We neglected to do this here because the unopposed maxillary right second molar had not erupted at deband (Figure 3.32).

A: Options include:

• Closing the extraction space entirely (Figure 3.35).
• Not closing the extraction space or closing it partially (e.g. closing it to the size of the missing second premolar for prosthetic replacement). Following primary second molar extraction (Figure 3.36), the edentulous ridge bucco‐lingual width decreases by 25% within three years (30% within six years), while the edentulous ridge height decreases minimally by less than 2% [52].
• Restoring the extraction space using an implant when the patient reaches adulthood (Figure 3.37) or restoring with a fixed partial denture or removable partial denture.
• Autotransplantation using an extracted donor tooth from another site [53].

A: Her mandibular right second premolar is underdeveloped, erupting ectopically, and appears to be resorbing only the distal root of the mandibular right primary second molar. Her mandibular left premolar appears to be absent, but the mandibular left primary second molar appears to have a good crown, reasonable roots, and good bone level.

A decision was made to monitor eruption of the mandibular right second premolar and to maintain the retained mandibular left primary second molar. Comprehensive, non‐extraction, orthodontic treatment was begun with space being maintained for both mandibular primary second molars.

A: The mandibular right second premolar has resorbed the mandibular right primary second molar distal root and threatens to resorb the mandibular right permanent first molar mesial root. A clear step exists between both mandibular primary second molar alveolar bone crests and the alveolar bone crests of their adjacent teeth. That is, both mandibular primary second molars are ankylosed.

A: Both mandibular primary second molars were extracted. Orthodontic treatment commenced and was completed before the mandibular right second premolar had erupted. The patient was placed in retention and followed periodically.

A: The mandibular right second premolar erupted spontaneously, without surgical exposure, into a normal position with a normal alveolar crestal bone height. Extraction of the ankylosed mandibular right primary second molar followed our principle for ectopic tooth eruption treatment – create a path and space for eruption! The mandibular right permanent first molar mesial root appears to have suffered root resorption. The mandibular left edentulous area alveolar crest bone height appears to be normal.

A: Look at the magnified images of the mandibular left primary second molar area during these years (Figure 3.41). At age 12 (Figure 3.41a), the alveolar bone crest of the mandibular left primary second molar (red arrow) appears to be at approximately the same level as the alveolar bone crest of the first permanent molar (yellow arrow).

By age 13 (Figure 3.41b), a large alveolar bone crest step exists between the mandibular left primary second molar and permanent first molar. How did this happen? Eruption of the mandibular left primary second molar had halted (ankylosed), while eruption of the mandibular left permanent first molar continued. At this time, a decision was made to extract the mandibular left primary second molar.

By age 16 (Figure 3.41c), the alveolar crest step between these teeth had disappeared (note the ghost image of the mandibular left primary second molar roots). What happened? Following extraction of the mandibular left primary second molar, transeptal fibers from the mandibular left first premolar and mandibular left permanent first molar pulled vertically on the edentulous site crestal bone and elevated it [52].

A: Elevation of this crestal bone to a normal level is important for future bone grafting. In other words, grafting bone vertically can be very challenging while grafting bone bucco‐lingually can be less so. Therefore, the fact that the bone elevated spontaneously can be of significant benefit when we wish to graft for implant placement later.

A: In patients having significant anticipated future growth, it is prudent to extract ankylosed primary second molars as early as ankylosis is detected – so that normal vertical bone height of the edentulous area can be achieved.

A: If the alveolar bone crest step is small between the ankylosed tooth and adjacent permanent teeth, if the ankylosed tooth exhibits good crown and root, if minimal future growth is anticipated (minimal future eruption of normal adjacent teeth/minimal worsening of the step), and if the patient can cleanse the ankylosed tooth, then you could consider maintaining the ankylosed tooth. Note: you may wish to place an occlusal composite buildup on the ankylosed tooth to prevent the permanent first molar from tipping over it and to prevent teeth in the opposing arch from super‐erupting.

A: Yes, you can hemi‐sect ankylosed primary second molars (Figures 3.42a and 3.42b), extract the distal roots (Figures 3.42c and 3.42d), and use the mesial roots as anchors for permanent molar protraction (Figure 3.42e). Of course, only one‐half of the primary second molar space can be closed this way, and a second surgical procedure is required to remove the primary molars’ mesial roots (unless they resorb). As an alternative option, the primary second molar can be extracted and a temporary anchorage device (TAD) inserted for protraction anchorage.

A: Yes. Assuming their roots do not resorb, any ankylosed primary tooth can be used as a TAD. Your biomechanical creativity is the only limit to their usefulness.

A: The danger arises from late tooth germ development. As an example, compare the left and right mandibular second premolar regions in the eight‐year‐old shown below (Figure 3.43a). Compared to development of the mandibular left second premolar, agenesis of the mandibular right second premolar is suspected. However, it would be a mistake to extract the mandibular right primary second molar at this time (to expedite space closure). Why? Look at Figures 3.43b and 3.43c. What do you see? Crown development of the mandibular right second premolar is delayed but beginning to form. The point is this: avoid rushing to extract primary teeth lacking permanent successors. Give teeth time to develop. When in doubt, wait it out.

A: Controlled slicing (Figure 3.44) of primary second molars (lacking permanent successors) is a technique used to produce bodily mesial movement of first permanent molars [56]. We are not advocates of this treatment due to the number of operative and surgical procedures required, including surgical hemi‐section of the primary tooth.

A: Consider maintaining primary second molars in non‐extraction cases (e.g. patients with minimal anterior crowding) where the primary second molars have good crowns, good roots, and good bone.

A: Options include:

• Reducing the primary second molar mesiodistal width (~9.9 mm) to the width of a mandibular second premolar (~7 mm). This is termed “slenderizing” (Figures 3.45a–3.45c). It is done with the intent of eventually replacing the primary second molar with an implant crown the size of a second premolar. The reduced primary second molar maintains both mesiodistal space and alveolar process bone [52].

This mesiodistal width reduction also permits the mandibular permanent first molar to be moved mesially into an ideal Class I molar relationship (Figure 3.45b). However, because the primary second molar roots diverge, its roots will resorb as the permanent teeth are brought into contact with them (Figure 3.45c).

• Maintaining the primary tooth intact, and restoring it with a composite (veneer) buildup to prevent super‐eruption of opposing teeth and tipping of adjacent teeth (Figure 3.46a–c) [57].

A: The literature reveals that:

• In children followed until their mid‐ to late 20s, ~90% of retained primary second molars lacking permanent successors survive [58, 59].
• In adults followed from a mean age of 36 years to a mean age of 49 years, 86% of retained primary second molars lacking permanent successors survive. Further, we discovered that even the primary second molars that were lost survived an average of more than a decade beyond the initial examination, which approximates the lifespan of some prosthetic appliances [60, 61].
• The above findings support the recommendation that if a retained primary second molar has a good crown, root, and bone in a non‐extraction case, maintaining it intact is worthwhile (with a “fallback” plan in case it is eventually lost).

A: If the ankylosed primary second molar has good crown and root, if little or no future growth is anticipated, and if the patient can keep it clean, then consider maintaining it (Figure 3.47).

A: If you can avoid doing so, do not bond the primary tooth, do not band the primary tooth, and do not move the primary tooth (Figure 3.48). Any of these actions increases the likelihood that the primary tooth roots will resorb and your chances of maintaining it will diminish.

A: Yes. If a patient presents with any retained primary tooth lacking a permanent successor, then you should consider extracting the primary tooth if it is an extraction case and/or if the primary tooth has poor crown, poor root, or poor bone. If a patient presents with a retained primary tooth lacking a permanent successor, then you should consider maintaining the primary tooth if it is a non‐extraction case and the primary tooth has good crown, good root, and good bone. If you maintain it, always have a contingency plan in place for the patient in case the primary tooth is eventually lost.

A: Close radiographic examination of the retained mandibular left primary lateral incisor reveals a poor bone level, only one half to two thirds of its root is embedded within bone. For this reason, we recommended extracting it. Following extraction, space was created (Figure 3.49c) for a bonded FPD. Intraoral photos (Figures 3.49d and 3.49e) illustrate before and after treatment.

An argument could have been made for maintaining the mandibular left primary lateral incisor, or at least its root (decoronation), in order to maintain the alveolar process bone for as long as possible. If this were done, then the patient would need to be informed that eventual prosthetic replacement (implant, FPD) would be anticipated.

A: Start with the mandible. The retained primary second molars have good crowns, poor (resorbed) roots, and good bone levels. Although in a non‐extraction case we might argue for maintaining the mandibular primary second molars in order to maintain bone, extracting these primary teeth makes sense here in order to avoid extracting first premolars.

If we extract the mandibular primary second molars, then the patient and parent must be informed of potential root resorption during space closure. If significant root resorption occurs (as seen on a progress panoramic image made after six to nine months of space closure), then we may need to terminate space closure and treat the remaining space with prostheses.

Now consider the maxilla. Here, we have four retained primary teeth without successors. Their roots and bone levels appear poor, and their long‐term survival is questionable. So, in this extraction case we chose to keep all maxillary premolars and extract the maxillary primary teeth. We extracted maxillary primary canines, substituted maxillary first premolars as canines, and maintained the maxillary primary lateral incisors for as long as possible in order to keep bone. We planned to eventually extract the maxillary primary lateral incisors and replace them with prostheses.

Figure 3.50b is a progress radiograph following extraction of mandibular primary second molars, extraction of maxillary primary canines, fixed appliance placement, leveling and aligning of both arches, and mandibular space closure. Significant mandibular posterior tooth root resorption is noted. The patient and parents were informed of this, and a decision was made to complete treatment as soon as possible. The maxillary primary lateral incisors were very mobile and extracted at deband (Figure 3.50c). Bonded fixed partial dentures were placed to maintain space for eventual implants (Figure 3.50d), and wisdom teeth were extracted.

A: “Take home pearls” include the following:

• There are only two options for dealing with retained primary teeth lacking successors. You can either extract the retained primary teeth or you can attempt to maintain them.
• For non‐extraction cases – if the retained primary tooth has a good crown, good root, and good bone, then consider maintaining it for the long term (Figure 3.51). But, be sure to have a contingency plan prepared in case the retained primary tooth is eventually lost.
• Whenever possible, avoid bonding/banding retained primary teeth in order to reduce the risk that their roots will resorb. If you must bond/band retained primary teeth, try to avoid moving them.
• Consider extracting retained primary teeth lacking successors: (i) in extraction cases (e.g. patients with severe anterior crowding); (ii) in instances where caries, crown restoration, periodontal breakdown, or root resorption compromise the primary tooth’s longevity; and (iii) and in instances where ankylosis/infraocclusion disturb occlusal development/bone level.
• Even in non‐extraction cases – if the retained primary tooth does not have a good crown, root, or bone, seriously consider extracting it.
• If you extract a retained primary tooth lacking a successor, then treatment options for the extraction space include not closing the space at all; closing the space partially; closing the space entirely; restoring the extraction space with an implant, fixed partial denture, or removable partial denture; or autotransplanting a tooth donated from another site into the space.
• In patients having significant anticipated future growth, it is prudent to extract ankylosed primary teeth as soon as ankylosis is detected – so that normal vertical crestal bone height of the edentulous site can be achieved.
• If you decide to maintain a retained mandibular primary second molar lacking a successor, then treatment options include reducing the mesiodistal width of the primary second molar to the size of a missing mandibular second premolar (“slenderizing”) with the intent of eventually replacing the narrower primary second molar with an implant; or maintaining the primary tooth intact, and restoring it with a composite (veneer) buildup to prevent super‐eruption of opposing teeth or tipping of adjacent teeth. We recommend the latter option.
• In all orthodontic treatments, always have a “fallback plan” in case your primary plan (e.g. maintaining a primary tooth) fails.

A: Never guarantee the future eruption of any tooth. However, eruption of the boy’s maxillary second molars and mandibular right second molar is likely. The dentist and parents were informed that eruption of the mandibular left second molar would be monitored, that surgical exposure of it may be necessary, and that future comprehensive orthodontic treatment should be anticipated. The dentist first extracted the maxillary right permanent first molar (Figure 3.54) and then the remaining permanent first molars. Fortunately, all four second molars erupted (Figure 3.55).

A:

A: The answer lies in the fact that both his mandible and maxilla are retrusive. In other words, draw a line vertically down from Nasion (Figure 3.57a, green line) passing perpendicular to FH (blue line). This line is called the Nasion perpendicular line (see Appendix). An ideal maxillary anteroposterior position is one in which A‐Point lies on the Nasion perpendicular line [64, 65].

Brody’s A‐Point lies significantly behind Nasion perpendicular, indicating that his maxilla is deficient anteroposteriorly. With A‐Point being deficient, we cannot use ANB angle to judge mandibular position.

Instead, we relate his mandibular position to Nasion perpendicular, measuring the angle formed between Nasion perpendibular and the N‐B line (Figure 3.57b, red line). In Brody’s case, this angle equals 6 degrees, indicating a deficient mandible, which corroborates our clinical impression of a convex profile and retrusive chin position.

Below are space estimates:

A:

Average mesiodistal widths of permanent teeth (mm) [66]:

Average mesiodistal widths of primary teeth (mm) [66]:

Maxillary Arch

• +8.2 mm space available for maxillary right second premolar
• −7.0 mm anticipated width of maxillary right second premolar
• +6.8 mm space available for maxillary right permanent canine
• −7.5 mm anticipated width of maxillary right permanent canine
• +6.8 mm space available for maxillary left permanent central incisor
• −8.5 mm anticipated width of maxillary left central incisor
• +5.9 mm space available for maxillary left permanent canine
• −7.5 mm anticipated width of maxillary left permanent canine
• +7.3 mm width of maxillary left primary first molar
• −7.0 mm anticipated width of maxillary left first premolar
• +1.0 mm space mesial to maxillary left second premolar

  Balance = +8.2 mm –7.0 mm + 6.8 mm −7.5 mm +6.8 mm −8.5 mm +5.9mm –7.5 mm +7.3 mm −7.0 mm +1.0 mm = −2.5 mm

Mandibular Arch (since the mandibular right primary first molar is missing, we cannot use right leeway space)

• 0 mm of mandibular anterior crowding
• +20 mm arch perimeter length from mesial of right permanent first molar to mesial of right primary canine
• −7.0 mm anticipated width of mandibular right permanent canine
• −7.0 mm anticipated width of mandibular right first premolar
• −7.0 mm anticipated width of mandibular right second premolar
• +1.6 mm of anticipated left leeway space (1.6 mm/side)
• Balance = 0 mm +20 mm −7.0 mm −7.0 mm −7.0 mm +1.6 mm = +0.6 mm

That is, 2.5 mm of maxillary arch crowding and 0.6 mm of mandibular arch spacing is anticipated following eruption of all permanent teeth (if proper space maintenance is employed).

A:

A: Average ages of permanent tooth eruption (emergence through gingival tissue) are listed below [67]. At ten years and nine months of age, Brody exhibits delayed eruption of his maxillary left central incisor – by almost three years. We should be concerned that it has not erupted.

Eruption of his mandibular permanent canines appears delayed by about one year, but they will erupt soon. Eruption of all other permanent teeth appears to be on‐track.

A: Possible eruption etiologies include:

• Delayed tooth development – looking at Figure 3.56f, the root apex of the maxillary left central incisor appears to have a more open apex than the right central incisor (delayed development). Although difficult to tell from this radiographic view, if an open apex is suspected, additional periapical radiographs can confirm (or deny) the diagnosis. This was not done.
• Thick keratinized tissue blocking eruption – looking at Figures 3.56h and 3.56j, we feel that a thick band of gingival tissue is present, which could delay eruption.
• Lack of space (tooth impaction) – is probably not the cause. There appears to be a small amount of space (Figure 3.56f) between the mesial of the unerupted maxillary left central incisor crown and the root of the maxillary right central incisor. Furthermore, even though there appears to be inadequate space for the maxillary left central incisor crown to erupt aligned (Figure 3.56j), it could still erupt into a rotated position.
• Tongue interposition habit or digit‐sucking habit – are not likely causes since the maxillary right central incisor erupted normally and since the maxillary left central incisor has not even pierced the gingiva (where a habit could prevent its eruption).
• Temporary open bite occurring after normal exfoliation of the primary left central incisor – is not a likely cause since the pediatric dentist has been concerned with this problem for many months.
• Ankylosis of the maxillary left central incisor – is a possible cause. However, we could not locate previous dental radiographs, so we are unsure whether the maxillary left central incisor has ceased erupting or is simply erupting slowly.
• Premature loss of maxillary left primary central incisor – is a possible cause since scar tissue could have filled in over the permanent incisor crown following premature loss of the primary tooth. However, Brody’s mother states that the maxillary left primary central incisor was not lost early.

A: Now is the appropriate time to address Brody’s Class II problem because he is entering the late mixed dentition stage of development. There is no advantage in treating Class II relationships in the early mixed dentition except possibly a reduction in incisal trauma [68–74] (unless the patient shows good statural growth). However, if we wait until all of Brody’s permanent teeth erupt to begin Class II treatment, then we will miss useful jaw growth.

Of the three options for treating a Class II skeletal discrepancy (orthopedics, camouflage, and surgery), orthopedics is the most reasonable option at Brody’s stage of development. Class II skeletal orthopedics consists of either restricting maxillary forward growth (while permitting the mandible to continue growing forward) and/or accelerating mandibular growth. Class II orthopedic options include headgear and functional appliance treatment.

• High‐pull headgears work in growing individuals by restricting maxillary forward growth, distalizing maxillary molars, possibly reducing maxillary corpus descent and maxillary molar eruption, and allowing the mandible to continue growing forward. Cervical‐pull headgears restrict maxillary forward growth, distalize maxillary first molars, create anterior palatal plane downward rotation, and erupt maxillary first molars by less than 1 mm [75–78].
• Class II functional appliances (e.g. Herbst appliance) work in growing individuals by restricting maxillary forward growth, distalizing maxillary posterior teeth, advancing mandibular posterior teeth, accelerating condylar growth, and displacing the glenoid fossae anteriorly. Functional appliances do not enhance mandibular horizontal growth beyond that found in control subjects [79–84].

A: This is an excellent question. We investigated profile esthetic changes resulting from headgear use in growing Class II patients with protrusive, normal, and retrusive maxillae [85]. Based upon the results of our study, we concluded that in growing Class II patients, headgear treatment in conjunction with fixed orthodontic appliances is effective in improving facial profile esthetics for everyone, including Class II patients with retrusive maxillae.

A: The answer to this question is based upon the magnitude of the incisor proclination. Mandibular incisor proclination (or uprightness) depends not only upon the angulation of the incisors relative to the mandible itself (IMPA) but also upon the steepness of the mandible plane (MPA), and is reflected in the FMIA angle. An ideal FMIA is approximately 65–68°.

If a skeletal Class II adolescent presents with mild mandibular incisor proclination (e.g. FMIA = 64–60°), then we would look upon Class II functional appliance treatment more favorably than if the adolescent presents with severe incisor proclination (e.g. FMIA = 50–45°). Why? Class II functional appliance treatment will increase mandibular incisor proclination. Since Brody’s FMIA = 56°, in our clinical opinion he is borderline for Class II functional appliance treatment.

A: Principles include:

1. 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 eliminating unknowns). Correcting Brody’s unerupted maxillary left permanent central incisor, Class II relationship, and 60% OB would get Brody back on track.
2. Early treatment should address very specific problems with a clearly defined end point, usually within six to nine months. Surgical exposure and forced eruption of his maxillary left central incisor could bring it into the arch in less than nine months (assuming that it is not ankylosed). Since he has entered the late mixed dentition stage of development, and since his Class II relationship is mild (2–3 mm), correction of his Class II relationship could probably be completed in less than one year if he cooperated. OB correction could be achieved in less than nine months using fixed orthodontic appliances to level his arches.
3. Always ask: Is it necessary that I treat the patient now? What harm will come if I choose to do nothing now? There would be no harm in waiting a year to surgically expose and erupt Brody’s maxillary left central incisor, unless it is ankylosed and a vertical bony defect worsens as adjacent teeth continue to erupt. We anticipate no harm in waiting one year to address Brody’s mild Class II relationship. Finally, since no pain or tissue damage is resulting from his 60% OB, there is no need to address this problem now.

A: Unknowns include jaw growth magnitude and direction, the possibility that his maxillary left central incisor is ankylosed, an undetected CR‐CO shift, cooperation, and hygiene.

A: An LLHA is recommended in order to use the 1.6 mm left leeway space to eliminate the 1 mm anticipated crowding on the right side (+20 mm arch perimeter length from mesial of right permanent first molar to mesial of right primary canine, −7.0 mm anticipated width of mandibular right permanent canine, −7.0 mm anticipated width of mandibular right first premolar, −7.0 mm anticipated width of mandibular right second premolar = −1 mm). A Nance holding arch would be useful in the maxilla unless a headgear or Herbst appliance was employed to retract the maxillary first permanent molars distally.

A: Options include:

• Recall (no treatment, monitor only) – reevaluate in six months. This option is reasonable if Brody does not object to having a large space in his smile. If the maxillary left central incisor has not pierced the gingiva in six months, then a radiograph should be made to determine whether it is slowly erupting. If it is erupting, then a decision to continue monitoring would be reasonable. If it is not erupting, then more aggressive treatment should be considered.
• Space regaining – to open approximately 2 mm additional space for the maxillary left central incisor crown (8.5 mm total space, Figure 3.56j) using fixed orthodontic appliances. This option is reasonable while you monitor the central incisor’s eruption.
• Surgical exposure of the maxillary left central incisor’s incisal edge (gingivectomy) – is reasonable in the hope that creating a pathway through the thick gingival band will aid the central incisor’s eruption.
• Surgical exposure of maxillary left central incisor’s entire crown with apically repositioned flap followed by forced orthodontic eruption – would be a viable option once we are certain that the central incisor is not going to erupt spontaneously. If we request surgical expose of the entire crown, then we should ask the surgeon to determine (using gentle elevator luxation) whether the left central incisor is mobile or ankylosed. If it is ankylosed, then a decision must be made either to break the ankylosis and quickly erupt the tooth orthodontically, or to extract it.

Two points should be mentioned regarding apically repositioned flaps with high (very apical) tooth exposures. First, it may be impossible for the surgeon to place a very high apically repositioned flap successfully. Second, as the tooth is erupted, soft tissue will stretch – leading to potential posttreatment intrusion (relapse). In cases of high exposures, it is often best to first erupt the tooth into the arch without an apically repositioned flap and then to request a soft‐tissue grafting procedure later to provide keratinized attached gingival tissue [86, 87].

A: We banded Brody’s maxillary and mandibular first permanent molars, placed him on a high‐pull headgear which he wore at night and delivered an LLHA. Brody did not care about having the missing maxillary left central incisor space for another six months, and we decided to monitor its eruption.

If it did not erupt, then we would make a new radiograph to determine whether it was erupting slowly. At that time, we also planned to make a decision whether to expose the maxillary left central incisor incisal edge with a laser (removing the thick band of gingiva which we suspected was preventing it from erupting) or to surgically expose the entire crown, determine whether it was ankylosed, and either orthodontically erupt it or extract it.

A: Brody’s maxillary left central incisor erupted into labioversion. He is Class I, all permanent teeth are nearly erupted, and early treatment is complete. Comprehensive treatment will commence as soon as the remaining permanent teeth are fully erupted. Teeth will be banded/bonded, arches leveled and aligned, and remaining spaces closed.

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

• Brody was 10 years and 9 months old when he presented in the late mixed dentition as Class II (2‐3mm) with delayed eruption of the maxillary left permanent central incisor.
• Possible etiologies of this delayed eruption included delayed dental development, thick keratinized gingival tissue blocking/slowing eruption, lack of space (tooth impaction), tongue interposition or digit interposition habit, temporary open bite occurring after normal exfoliation of the primary left central incisor, ankylosis of the maxillary left permanent central incisor, and premature loss of the maxillary left primary central incisor. In retrospect, the etiology was probably thick gingiva covering the incisor or delayed dental development.
• If Brody’s maxillary left incisor had not erupted spontaneously, then our next step would have been to clear a path for it by performing laser gingivectomy of the thick band of gingival tissue at its incisal edge. We have witnessed instances where such a gingivectomy resulted in rapid spontaneous tooth eruption toward the occlusal plane. It gingivectomy was unsuccessful, then we would have performed a full crown surgical exposure of the incisor and attempted orthodontic eruption.

A:

A: This is a good question, and we had difficulty choosing her classification. On the one hand, her profile does curve down and back from her nose and maxillary lip (convex). On the other hand, soft‐tissue Pogonion sits slightly ahead of her zero‐meridian line (vertical line drawn down from soft tissue Nasion and perpendicular to Frankfort horizontal) indicating adequate chin projection. Considering both aspects of her profile, we chose to classify it as relatively straight, especially since her maxillary and mandibular anteroposterior skeletal positions are both normal.

A: We were forced to estimate where to place A‐Point (Figure 3.59d). Why? A‐Point is the most concave point of the anterior maxilla and should be located approximately 1–2 mm ahead of the maxillary central incisor roots (1–2 mm being the presumed thickness of the alveolar process bone over the central incisor roots). In Rebecca’s cephalometric radiograph, it was difficult to determine this location because of the unerupted central incisors.

A:

A: She exhibits both delayed and early eruption. Average ages of permanent tooth eruption (emergence through gingival tissue) are listed below [67]. At 10 years of age, Rebecca exhibits delayed eruption of her maxillary central incisors by at least two years but early eruption of her maxillary canines, maxillary second molars, mandibular second premolars, and mandibular second molars.