All About Palatal Expansion! Adult Orthodontics Considerations - Part Two
Updated: Oct 15
In Part One, we discussed several new and controversial dental devices that focus on an adults. In Part Two, we will discuss more traditional orthodontic expansion appliances and combined orthodontic and surgical procedures.
The palatal suture and the “old school” palatal expanders
Let’s take a walk through history a bit, shall we? Therapeutic transverse maxillary expansion was first written by Dr. Angell in 1860 in the Dental Cosmos journal (now known as the Journal of the American Dental Association or JADA). Here, Dr. Angell demonstrated that he was able to correct a posterior crossbite through activating a palatal expander appliance. He placed a screw that was interconnected between the maxillary premolars of a 14-year-old. When the patient returned after activating for two weeks, he observed upper arch expansion. Back then, this form of treatment was novel and highly controversial.
A century later, Dr. Haas’ research in the 1960’s solidified the efficacy of rapid maxillary expansion for clinical practice (Haas, 1961). I am fortunate to have had the opportunity to learn directly from Dr. Haas, himself, who is essentially the father of the modern palatal expander. He taught at my residency in Chicago for an impressive 57 years.
Rapid maxillary/palatal expansion (RPE) is a standard treatment for posterior crossbites. A posterior crossbite is when the maxilla (upper jaw) is narrower in width compared to the mandible (lower jaw), when looking at someone straight on. Posterior crossbites are a common finding, occurring in about ten percent of children (Thilander et al., 1984; Ciuffolo et al., 2005). While some cases might be described as dental in nature, the majority of crossbites are due to an underlying transverse maxillary skeletal deficiency (Garrett et al., 2008). Therefore, orthopedic treatment with a RPE may assist in correcting this discrepancy.
RPE offers additional clinical benefits, as well. RPE treatment may increase arch length, which helps decrease crowding or the need for dental extractions. RPE treatment assists with maxillary growth in Class III malocclusions, especially in conjunction with protraction facemask therapies.
Haas’s RPE design uses acrylic shelves, so that it is tissue-borne, and thus helped enable more skeletal expansion. However, food could get trapped under these shelves. So a more hygienic design that doesn’t rest on tissue called the Hyrax expander was also developed. These expanders have similar centers of activation with the aim of separating the midpalatal suture. Some claim that the Hyrax design has more dental tipping side effects compared to Haas’ original design; however, I’m not sure if this has been statistically measured.
A Little Review in Anatomy and Development (Just to be thorough, you can skip this part!)
The midpalatal suture runs across the midline of the hard palate in an A-P direction, dividing the maxillary bones into a left and right segment. These segments begin to fuse typically during early adolescence. In the posterior region of the hard palate, the midpalatal suture is met by the interpalatine suture, which runs perpendicularly in the transverse direction. Melson (1975) studied the suture with histological slides from 60 samples. Initially during the infantile stage, the suture is broad, then in the juvenile period it looks wavy. In adolescence there is increased interdigitation, looking more interlocked or closed. Finally, in early adulthood, intermembranous ossification and fusion occurs, beginning from the posterior towards the anterior portion of the suture. Orthopedic modification of the palate would be performed optimally before fusion.
New Expansion Protocols: What are SARPE, MARPE, MSE, DOME?
A big question asked is: can we expand adults? Traditional RPE is designed for patients whose sutures are not yet fused. There are expansion techniques that have become available for non-growing patients. We will review Surgically Assisted Rapid Palatal Expansion (SARPE), Distraction Osteogenesis Maxillary Expansion (DOME), and Miniscrew Assisted Rapid Palatal Expansion or Maxillary Skeletal Expander (MARPE/MSE), which span from most to least invasive.
As an aside, jaw surgeries that include two-piece or three-piece Le Fort 1 osteotomies will offer a purely surgical solution, without an orthopedic component (Kretschmer et al., 2010). However, this surgery is done in conjunction with pre- and/or postoperative orthodontic treatment in order to close spaces where the osteotomies were performed. In addition, a bone graft may be needed since expansion wasn’t derived orthopedically. Therefore it has been shown to be less stable (Baker et al. 1992; Chow et al., 1995).
Since there is no orthopedic component with surgery, we would observe parallel uniform transverse displacements as with an RPE (optimally). In some patients, additional jaw surgeries may be performed at the same time to correct A-P and/or vertical skeletal discrepancies. For example, in sleep apnea patients, an MMA (maxillary-mandibular advancement) surgery might be performed and surgical transverse expansion might also be considered.
SARPE is the most invasive surgical RPE option. It is a true maxillary surgery and there is notable downtime as a result. It seems to have waned in popularity because of this. SARPE was developed initially by Dr. Brown in 1938. Two of the articulating skeletal junctions of the maxilla need to be sectioned for an optimal result (the zygomaticomaxillary buttress seems to present with the most resistance to RPE, for example) (Bell and Epker, 1976; Kraut, 1984; Turvey, 1985).
Fortunately, there are now much less invasive and popularized adult expansion options that we will discuss.
Next we will review DOME (Distraction Osteogenesis Maxillary Expansion), which helps expand the nasal floor and decrease OSA symptoms, as well (Yoon et al., 2020). I liken it to a SARPE “light” procedure. One main difference between SARPE and DOME is that post-surgical expansion with a SARPE uses a tooth-borne expander, while DOME uses a bone-borne expander. Another is the level of surgical invasiveness.
According to Liu and colleagues (2017), DOME negates any need to perform pterygoid disjunction compared to a SARPE, since the DOME technique uses mini-implants. Forces are optimally placed at the height of the palatal vault and nasal floor. In these cases, per Iwasaki and colleagues’ (2020) description, a mini-implant borne expander is placed and then a surgeon performs a two-piece LeFort 1 osteotomy to wedge open the midpalatal suture. The primordial groove of the midpalatal suture is deepened using piezoelectric saw and wedge opened with straight osteotomes. A diastema is immediately seen (Liu et al., 2017). A visual opening would be observed and then the expander is turned to ensure separation until a 1-mm diastema is seen.
After waiting five days, the patient would follow typical expansion activation protocols over five weeks or so to achieve 8-10 mm expansion. I wanted to specify that this is a less invasive osteotomy than those in a SARPE or MMA jaw surgery, for example.
Typically, there is a one-week recovery period. Iwasaki and colleagues (2020) note that DOME results in expansion in an adult maxilla that is comparable to that in pediatric RPE treatment. However, Liu and colleagues (2017) recognize this is a newer procedure and that there are no long-term data in terms of skeletal and/or dental relapse.
MARPE stands for Miniscrew-Assisted Rapid Palatal Expansion, of which the MSE (Maxillary Skeletal Expander) is one popularized and highly researched design by Dr. Moon, initially developed in 2014 (Carlson et al., 2016; Suzuki et al., 2016; Brunetto et al., 2017). Usually 4-6 mini-implants are placed into the palate and sometimes piezoincision/corticotomy procedures are done in conjunction with the insertion of a custom-made maxillary expander. This procedure could take about 20-30 minutes and is performed under local anesthesia. Recovery is minimal, about 1-2 days.
The patient, as with other RPEs, will then activate the expander daily for about five weeks. Miniscrews directly apply forces to the midpalatal suture, compared to traditional expanders which use the teeth as anchors. Therefore, MARPE/MSE have shown more parallel expansion versus dental tipping in the correction of posterior crossbites, which controls bite opening and other side effects (Fuwaka et al., 2022). Yi and colleagues (2023) additionally note that it is important to evaluate midpalatal suture density an maturation via CBCT along with age as a predictor of appliance success. It is important to note that there are varying data. As I mentioned in Part One, Liu and Guilleminault (2022) did not witness opening of the palatal suture in MARPE cases in their study. I think it is highly technique sensitive, and as a newer technique, more work needs to be done to hone in on its methodology. I lastly wanted to mention that there are some special risks to note with the use of mini-screws. Although they are meant to integrate with the bone, they may rarely break, fall out or irritate the soft tissue. Traditional RPE designs can also be irritating at times, fall out, or break, as well.
When do we decide to use a traditional (non-surgical) RPE versus MARPE or DOME treatments?
In terms of orthopedic expansion, a significant challenge is that there is no clear distinction for when one is no longer a candidate for a nonsurgical RPE and when they should consider SARPE, DOME or MARPE/MSE. CBCT evaluations in adult patients are the best means to evaluate the bone quality, suture maturation, and is additionally useful in terms of treatment planning. One earlier study suggests using age (i.e. at 25 years old) as a non-surgical cutoff (Timms and Vero, 1981). Meanwhile a different study suggested a cutoff as young as 16 (Suri and Taneja, 2008).
In more recent studies (Angelieri et al., 2013; Sayar and Kilinc, 2019; Jimenez-Valdivia et al., 2019), authors observed a wider variance of suture maturation than previously thought. Traditionally, female palatal sutures begin to fuse a little earlier than males, at ages 11-13 and 14-16, respectively. That said, I’ve done nonsurgical RPE in teens older than this and have had positive outcomes. Recent CBCT studies have evaluated how much palatal fusion has occurred. Jimenez-Valdivia and colleagues (2019) found an open midpalatal suture in 70.8% of 10-15 year olds, 21.2% of 16-20 year olds, and 17% of 21-25 year olds. Therefore, there are more candidates for traditional RPE than previously considered. These findings could help a clinician select the appropriate expansion therapy options in later teens, young adults and older adult patients.
The tradeoff and distinction is whether one receives true orthopedic translational expansion versus dental tipping expansive movements. As I mentioned the suture fuses in the posterior first, which explains why there is a higher potential for dental tipping side effects in the molar regions. RPE treatment in older individuals comes with the possibility of more side effects such as pain, gingival recession, palatal mucosa ulceration/necrosis, buccal tipping of posterior teeth, reduction of buccal bone thickness, alveolar bone bending, buccal root resorption, and fenestration of the buccal cortex (Jimenez-Valdivia et al., 2019). Meanwhile, surgical expansion, as one might expect, involves possible unnecessary surgical procedures that have increased morbidity, cost, risk and recovery times. Jimenez-Valdivia and colleagues (2019) recommended RPE or MSE procedures if the suture is in the process of closing and SARPE for those whose suture is completely fused, per CBCT evaluation.
Benefits of palatal expansion
Besides correcting posterior crossbites, why do we expand?! I’ve written about RPE therapeutic outcomes in past articles such as this one. Many patients, children and adults alike, have deficient maxillas. Maxillary expansion in general is under-recognized in relationship to sleep apnea (OSA) and risk factors. I feel like the mandible size and A-P skeletal relationship are more commonly evaluated. While causes are multifactorial, I often find that small maxillas also go hand in hand with sleep disordered breathing, mouth breathing, oral habits, tongue ties and so forth. Abdelwahab and colleagues (2019) note that high arch/narrow maxilla phenotypes often present with nasal obstruction and OSA, or a high risk for developing OSA.
Furthermore, Iwasaki and colleagues (2020) saw that expansion reduced nasal airflow velocity and consequentially reduced pressure in the pharyngeal airway. This correlated with a decreased AHI and oxygen desaturation index (ODI); the airway was also less collapsible. While most OSA studies focus on the pharyngeal airway (as this directly impacts OSA), these authors observed that there is a possible influence in reducing the nasal airflow velocity to decrease the negative pressure of the pharyngeal airway, which ultimately helps reduce OSA severity. Interestingly, while the airway volume also increased, the 2-D measurements appeared similar. Yoon and colleagues (2020) similarly found that DOME treatment reduced severity of OSA, nasal obstruction and daytime sleepiness.
Stay tuned for Part Three, which will review another controversial topic: extraction versus non-extraction treatment!
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