If the maintainance and long-term prognosis of a hypomineralized molar are questionable, its extraction can also be considered as a treatment option as ultima ratio (Fig 14-1).^1,2 However, this decision should be evaluated carefully on an interdiscipinary basis since it is always associated with extensive follow-up treatments. The orthodontist Dr. Emil Herbst already made a general comment in 1913 about extraction in orthodontics³: A decision on extraction should be considered on a case-by-case basis. Neither a general nor an uncritical application can be advocated!

Fig 14-1 Extraction within the treatment plan of the Würzburg concept (according to Bekes et al⁷; courtesy of DGKiZ). a) Low caries risk. b) High caries risk.

After extraction, usually the further treatment goal is to achieve orthodontic space closure with mesialization of the second molar.⁴ However, orthodontic cases in which the first permanent molars are extracted are generally more technically challenging than conventional premolar extraction or non-extraction treatment,⁵ as there is a large distance of orthodontically movement from distal to mesial. Therefore, early interdisciplinary collaboration between the dentist and the orthodontist is advisable in order to find the best possible treatment strategy with the shortest treatment time possible.⁶

Theoretically, a prosthetic space closure with the help of restorative or (later) implantological procedures could also be considered after the extraction. However, due to the young age of the patients, this option should rather play a minor role.²

There are many factors to be considered before extracting a 6-year molar, which are explained in detail below. These include, above all, the correct indication, the correct timing, and clarification of any necessary compensation extraction.

14.1 Indications

The extraction of MIH-affected molars is always indicated if the dentist expects an unfavorable long-term prognosis with regard to tooth maintenance and the orthodontist can also expect a successful treatment result with regard to function and esthetics, taking into account general, local, and secondary parameters (patient cooperation, preference, and socioeconomic conditions).⁷ The following dental and orthodontic indications, which will subsequently be described in more detail, can specifically be named.

14.1.1 Dental aspects

From a dental perspective, extraction of a molar affected by MIH⁷ may be considered as a therapy option in the following situations⁸:

• Severe form of hypomineralization with excessive loss of substance⁶
• Rapid progression of posteruptive enamel breakdown⁹
• Uncontrollable endodontic or periodontal problems (eg, irreversible pulpitis, apical or advanced periodontitis, high susceptability to pain)^10,11
• Strong hypersensitivity
• Severely impaired oral hygiene (eg, due to increased temperature sensitivity of the teeth)⁹
• Repeated unsuccessful (conservative-prosthetic) treatments.^10,11

14.1.2 Orthodontic aspects

From an orthodontic point of view, the following parameters are considered favorable for the extraction of a molar affected by MIH¹²:

• Extensive crowding (primary, secondary) with lack of space within the dental arches⁹ (Fig 14-2)

  

  Fig 14-2 Intraoral status, orthopantomogram, and cephalometric radiograph of a patient with a slight overbite, crowding in the mandibular anterior region, and MIH in all four 6-year molars without involvement of the incisors before the start of orthodontic treatment (source: Christian Kirschneck). a) Intraoral status: maxillary view. b) Intraoral status: mandibular view. c) Intraoral status: lateral right. d) Intraoral status: lateral left. e) Intraoral status: frontal. f) Orthopantomogram. g) Cephalometric radiograph.

• Small skeletal/apical jaw base or large tooth material
• No aplasia or previous extraction of permanent teeth (premolars)⁹
• Angle Class I with sagittal and vertical tight overbite⁸ (Fig 14-2)
• Proclined maxillary teeth or Angle Class II/1 when dental compensation is aimed for
• Extraction of (pre)molars in the opposing jaw (analogy compensatory extraction)⁸
• Vertical growth pattern with a tendency to open bite (so-called high-angle cases)1,12
• Convex facial profile with prominent lips, unobtrusive nose, and decreased nasolabial angle¹¹
• No deep recesses of the sinus maxillaris that would hinder mesialization of the second molars¹¹
• Wisdom teeth present with the possibility of placing them in the position of the mesialized second molars¹¹
• Patient age between 8 and 11.5 years.^1,13,14

From the orthodontic point of view, careful diagnostics is essential, because orthodontic space closure can have an impact on the function and esthetics of the entire stomatognathic system. In addition to the individual anamnesis, orthodontic diagnostics basically includes clinical examination, intraoral photo documentation, functional status, photo-static analysis, orthodontic model analysis and radiological imaging (orthopantomogram, cephalometric radiographs, and dental radiographs, if necessary).²

14.2 Time of extraction

If an orthodontic space closure is planned after the removal of the 6-year molars, the choice of the right time window plays an important role. The timing is generally less problematic in the maxilla than in the mandible.¹⁴ One reason for this could be the different eruption paths of the second permanent molars in the two jaws¹⁵ (Fig 14-3).

Fig 14-3 Eruption trajectories of the second and third permanent molars in the maxilla and mandible (after Stöckli et al²¹ following Schätzle et al¹) (source: Cornelia Jungwirth, Katrin Bekes).

In the maxilla, the apex of the second molar is placed more mesially in relation to the crown.¹⁵ Its crown is initially inclined distally and buccally. It normally reorients mesially as well as palatally in the process of its eruption into a more favorable position with little rotation or tipping of the clinical crown.¹

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