Recent Advances in Dentistry

Orthodontic treatment without braces has been introduced more than half a century before clear aligners have been introduced in orthodontics. Clear aligners have been utilized to treat minor crowding for more than a decade. However, in the last few years, there has been increased interest and many publications came out in different prestigious peer reviewed journals about the possibility of using clear aligners to treat difficult orthodontic cases. Different companies that manufacture clear aligners for orthodontic tooth movement spent a huge time span and resources to optimize treatment results and to provide more controlled tooth movement. The research and development included, but not limited to design attachments that can provide optimum tooth control, develop new plastic material that can have shape memory in order to maximize its efficiency in tooth movement and developing protocols for different malocclusions. There is a huge global interest in using clear aligners in orthodontics, however it might take decades for traditional orthodontists to adopt clear aligners in orthodontic practice. This chapter will briefly review the available literature about the background of clear aligners and its future application in orthodontics.

This chapter will briefly discuss the science behind using clear aligners in orthodontics. Although fabricating aligners can be made by hand in the lab or using computer aided design/computer aided manufacturing system, the science behind using specific plastic material that has specific elasticity to move the teeth in the intended direction is still unclear and many manufacturers do not declare it as a major manufacturing or business secret. In a simple assumption, the clear aligner materials must be flexible enough to accommodate the existing tooth/teeth position and be stiff enough to move the teeth in the intended direction. Although seems simple, however it took major companies decades spending many millions of dollars on research and development to reach this particular balance. In the following section, a general review of what is available in the literature about clear aligners’ materials is provided.

Orthodontic treatment planning is essential before deciding what type of orthodontic treatment may be used to treat different cases. Before the development of various orthodontic appliances (standard edgewise, straight wire, self-ligating fixed bracket systems or clear aligners) one should keep in mind what are the patient’s problem list, treatment objectives and treatment planning, then based on the treatment planning, mechanics can be proposed and then one can choose or not use specific appliance based on the clinician’s level of comfort using such appliance. This chapter will briefly review the contemporary steps in diagnosis and treatment planning of orthodontic cases disregarding the type of tooth movement.

This chapter highlights the important features of clear aligners and their possible added benefit to orthodontic treatment. In particular, clear aligners disarticulate the teeth and this disarticulation makes it easy to achieve inter-arch tooth movement than with regular fixed orthodontic appliances. This chapter presents different features of clear aligners that may make tooth movement easier than fixed orthodontic appliance.

Orthodontic biomechanics is the foundation of orthodontic treatment. It is extremely important to fully understand orthodontic biomechanics before the clinician /orthodontist may utilize specific orthodontic appliance. This chapter highlights basic principles of biomechanics of tooth movement with emphasis on forces, moment, moment to force ratio and its importance in achieving different types of tooth movement. Also, this chapter provides detailed explanation of different types of tooth movement and relativity of moment to force ratio as well as center of rotation approximate location in each type of tooth movement. The application of these concepts with clear aligners is somehow different from the way fixed orthodontic appliance has been used. Explanation of these differences is presented.

Traditional approaches for treating severe crowded cases usually involve removal of some teeth with the intention to allow stable occlusion after the orthodontic treatment. However, in severe constricted cases, arch expansion could be the best approach to treat these cases without removal of permanent teeth. This chapter presents cases with severe teeth crowding and the possible treatment of these cases with clear aligners. This chapter presents moderate to severe crowding cases treated solely by clear aligners utilizing dental arch expansion. Also, this chapter presents diagnostic criteria for deciding expansion/non extraction or extraction approaches in detail.

Although it has been reported earlier in 2005 that it is difficult to achieve full correction of sagittal relationship (class II or III) either dental or skeletal using clear aligners, pioneer reports by Boyd and Dahr [1, 2] have been stimulating to the creativity of orthodontists who may modify original protocols that were provided by Boyed and Dahr. Proper designing clincheck or treatment planning in class II cases is very important utilizing the principles of both functional appliances and bioprogressive techniques. The following cases will explain how to utilize both functional appliance and bioprogressive principles using clear aligners to correct class II cases. Although, this might seem as case reports or case series, further clinical trials are required to support or otherwise provide other evidences of using clear aligners in correcting class II skeletal and dental cases.

Treatment of class III cases with clear aligners maybe a challenge. This is unlike class II where upper molars can be distalized or even do a functional appliance effect. Class III on the other hand, is different. In many growing cases, upper jaw may be required to move forward or restraining lower jaw forward growth in growing children is required. In adult patients, class III management is even more challenging. If a case presented with class III malocclusion that does not have a skeletal component, it can be manageable with clear aligners, however if there is a class III skeletal relationship, orthognathic surgery might be required. Clear aligners still may be used, however careful diagnosis and treatment planning as well as thorough communication with the patients and especially discussion of the treatment expectations is very important before, during and towards finishing of treatment.

Anterior open bite can be of dental, skeletal, functional or a combination of all three in origin. An anterior open bite is present when there is no contact between the upper and lower anterior teeth and no overbite (vertical overlap of the upper and lower incisors). The severity of open bite varies from an edge to edge relationship to a severe open bite with teeth contact only in the molar areas. Ideally, treatment of open bites should be started as early as they are diagnosed by the dentist or pediatric dentist/orthodontist. Often, early intervention can eliminate the causes of the open bite especially if they are related to a persistent habit such as thumb sucking or mouth breathing. Also, early intervention can re-direct jaw growth and establish a more favorable mandibular growth direction. This chapter will discuss treatment of open bite in non-growing patients by using clear aligner therapy and no adjunct orthognathic surgery.

There are many etiological factors that could be attributed to facial skeletal asymmetry, including but not limited to hemifacial microsomia, unilateral temporomandibular joint ankylosis especially in growing patients or hypertrophic condyle on one side due to local tumor. Functional facial asymmetry could be attributed to bilateral constricted maxilla and the patient shifts his/her mandible to one side to achieve a comfortable occlusion on one side, or it could be due to dental interference, which mainly occurs due to one tooth in cross bite, usually upper lateral incisor. In this case, treatment is recommended as soon as possible especially in growing subjects to eliminate dental interference or to expand the maxilla so that no possible remodeling can happen in both TMJ fossae and possible need for surgical intervention later in life to fix jaw asymmetry. This chapter will discuss in details careful diagnosis of a case with facial asymmetry to simplify treatment planning.

Limitations of using clear aligners include noncompliance and compromised/fair oral hygiene. Rotational tooth movement also could be a challenge. Small thin teeth are also hard to move. The following chapter will discuss these limitations and possible strategies to manage these limitations.

Surgical orthodontic treatment is usually required in cases having severe skeletal mal-relationships and malocclusion that cannot be resolved solely by orthodontic treatment. In managing surgical orthodontic cases, pre-surgical orthodontic treatment usually aims at coordinating both dental arches, eliminating dental compensation due to the skeletal mal-relationship if present and to eliminate any dental interferences once dental arches are occluding together after the skeletal malrelationship is corrected by surgical intervention. Post-surgical orthodontic treatment usually aims at finishing and detailing dental arch relationships and ensure that no interferences exist. Traditionally, pre-surgical and post-surgical orthodontic treatments are usually achieved by regular fixed orthodontic appliances and pre-surgical orthodontics usually require having the patients wearing heavy archwires in order to be used for inter-maxillary fixation after surgery. The introduction of clear aligners in surgical orthodontics was initially somehow not well-received by orthodontists and oral surgeons due to the fact that rigid archwires are needed before surgery and clear aligners may have limitations on what can be done in terms of preparing cases with skeletal mal-relationships for orthognathic surgeries. The present chapter will shed the light on surgical orthodontic cases that were treated solely by clear aligners before and after orthognathic surgeries as well as describe steps in management of such cases using clear aligners.

Future direction of clear aligners could be directed at setting up protocols that can be used in complex malocclusion cases, especially for extraction and rotation of small teeth. Materials with more stable shape memory might be introduced that are capable of producing computer animated or planned tooth movement in real situation. The implementation of CBCT in diagnosis and communication with technicians is very important. However, this would entail proper knowledge of clear aligner companies’ technician to be more aware of CBCT, limitations of tooth movement and early communication with clear aligners’ prescribers. Again, utilization of TADs together with clear aligners can provide an alternative treatment to difficult cases that are currently not considered candidates for clear aligners.