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The Dahl effect or Dahl concept is used in dentistry where a localized appliance or localized restoration is used to increase the available interocclusal space for restorations.
| | This article needs additional citations for verification .(April 2021) |
The Dahl effect or Dahl concept is used in dentistry where a localized appliance or localized restoration is used to increase the available interocclusal space for restorations.
A steep incisal guidance angle (the angle formed between the sagittal plane when the incisors are in centric occlusion and the horizontal plane) must be reduced in order to decrease excessive horizontal forces on anterior teeth, which would lead to failure. [1] The two methods used to reduce this are; to decrease the edge of the incisors and to increase the OVD (occlusal vertical dimension). The Dahl effect focuses on the latter of the two. Without increasing the OVD, needless restorative work of otherwise healthy teeth, would be required. Therefore, the Dahl concept is a more conservative technique to increase OVD.
The Dahl concept is the relative axial tooth movement that is observed when a localised appliance or localised restorations are placed in supra-occlusion and the occlusion re-establishes full arch contacts over a period of time. [2] It involves the vertical tooth movement that occurs when anterior localised appliances/restorations are placed in supra occlusion causing the posterior teeth to disclude. Rather than restoring occlusion by means of restoration, it is allowed to re-establish over time through a combination of intrusion and over-eruption. This, in turn, will increase the OVD.
The idea of creating interocclusal space was first proposed by D.J. Andersen in 1962. He introduced the concept of experimental malocclusion by inducing the over-eruption of teeth, placing restorations in the dentition in supra-occlusion. [3] Anderson carried out a study on five human adult subjects aged 19–49 years; by placing a 0.5mm metal bite-raising cap on the occlusal surface of the subjects’ lower right first permanent molars, he found that each of the subjects were able to occlude their teeth after an experimental period of 23–41 days. He observed the changes in the distances of teeth in opposing arches using reference points on the capped tooth and its opponent, where he identified the introduction of an inter-occlusal space. It was not possible, however, to determine whether the creation of this space was due to the intrusion of the teeth in contact with the bite-raising cap or the eruption of the separated teeth due to the lack of fixed reference points. [3]
In 1975, Bjørn L. Dahl from the Faculty of Dentistry of the University of Oslo became the first author through a series of papers to report the successful use of this technique for the management of the worn dentition. [4] Along with Olaf Krogstad and Kjell Karlsen, Dahl described the use of a bite-raising appliance to increase the available interocclusal space available for future restorations. [4] The removable appliance was originally cast in cobalt chromium and placed on the palatal aspects of an 18-year-old’s upper incisors which had been subject to localised attrition. Over a period of eight months, the appliance was worn 24 hours a day and over time enough space was created to allow the application of palatal gold inlays to the worn upper incisors. [2] Dahl found that it was a combination of intrusion of the anterior teeth in contact with the appliance (40%) and passive eruption of the unopposed posterior teeth (60%) that permitted the reestablishment of posterior occlusion whilst maintaining the interocclusal space. [5]
Adhesive dentistry can be used to achieve the same results today, as well as the use of provisional restorations in the treatment of anterior tooth surface loss. [6]
The Dahl concept is commonly used when an increase in the interocclusal space is required together with an increase in occlusal vertical dimension; for example when restoring a case of severe anterior tooth surface loss. Therefore, the main applications are for localised anterior wear caused by factors such as bulimia, GERD leading to severe dental erosion, resulting in insufficient interocclusal space for adequate restorations.
The apparent lack of inter-occlusal space presents a dilemma for the restorative dentist. Without the dahl concept, one main approach would be to further reduce the occlusal height of the already worn teeth. However, this would lead to a lack of axial height and thus insufficient retention and resistance for conventional extra-coronal restorations. Tooth preparation and the associated loss of coronal tissue can risk further insult to the pulp and limit the options for future restoration replacement. [2] An alternative approach is to create the necessary space by reorganising the occlusion by means of an arbitrary increase of the vertical dimension of occlusion, i.e. the use of a dahl appliance. The creation of this interocclusal space will significantly reduce the amount of tooth preparation required, especially on the already compromised palatal surfaces of the maxillary anterior teeth.
Adaptation occurs over a period of some months: compensatory eruption of the posterior teeth will occur, together with some intrusion of the anterior teeth and potential growth of the alveolar bone. This will allow the posterior occlusion to reestablish at the new increased OVD, stabilizing the increased interocclusal space.
The Dahl appliance is used to generate space between the upper and lower jaws. Traditionally this has been used in order to aid the placement of fillings on worn front teeth. Alterations to the teeth, from tooth wear or tooth loss, can lead to a decreased facial height due to physiological compensation that allows for maintenance of upper and lower teeth contact. [6] The Dahl appliance can increase the height of a patient's face and correct for this loss of facial height.
The original Dahl appliance was a removable metal bite platform made with cobalt chromium. However, today many different materials can be used.
Placing Dahl composite resin appliance on worn down front teeth can separate and stimulate eruption of the back teeth. Once the back teeth contact, restorations can be placed on the front teeth without needing to remove excessive tooth structure to accommodate the restorations.
A Dahl appliance should fulfill the following aims:
The advantages of this approach are:
The limitations of this approach are:
Planned occlusal changes can be tested using a removable appliance prior to permanent treatment. Dental composite based approaches to tooth surface loss allow for easy adjustment or removal if required. One study published in the British Dental Journal, 2011 found that patient satisfaction was high when composite restorations were used in the Dahl approach and that the median survival time was between 4.75 and 5.8 years. [11]
Bruxism is excessive teeth grinding or jaw clenching. It is an oral parafunctional activity; i.e., it is unrelated to normal function such as eating or talking. Bruxism is a common behavior; reports of prevalence range from 8% to 31% in the general population. Several symptoms are commonly associated with bruxism, including aching jaw muscles, headaches, hypersensitive teeth, tooth wear, and damage to dental restorations. Symptoms may be minimal, without patient awareness of the condition. If nothing is done, after a while many teeth start wearing down until the whole tooth is gone.
Orthodontic retainers are custom-made devices, usually made of wires or clear plastic, that hold teeth in position after surgery or any method of realigning teeth. Once a phase of orthodontic treatment has been completed to straighten teeth, there remains a lifelong risk of relapse due to a number of factors: recoil of periodontal fibres, pressure from surrounding soft tissues, the occlusion and patient’s continued growth and development. By using retainers to hold the teeth in their new position for a length of time, the surrounding periodontal fibres adapt to changes in the bone which can help minimize any changes to the final tooth position after the completion of orthodontic treatment. Retainers may also be used to treat overjets.
A mouthguard is a protective device for the mouth that covers the teeth and gums to prevent and reduce injury to the teeth, arches, lips and gums. An effective mouthguard is like a crash helmet for teeth and jaws. It also prevents the jaws coming together fully, thereby reducing the risk of jaw joint injuries and concussion. A mouthguard is most often used to prevent injury in contact sports, as a treatment for bruxism or TMD, or as part of certain dental procedures, such as tooth bleaching or sleep apnea treatment. Depending on application, it may also be called a mouth protector, mouth piece, gumshield, gumguard, nightguard, occlusal splint, bite splint, or bite plane. The dentists who specialise in sports dentistry fabricate mouthguards.
Hypodontia is defined as the developmental absence of one or more teeth excluding the third molars. It is one of the most common dental anomalies, and can have a negative impact on function, and also appearance. It rarely occurs in primary teeth and the most commonly affected are the adult second premolars and the upper lateral incisors. It usually occurs as part of a syndrome that involves other abnormalities and requires multidisciplinary treatment.
The Nociceptive trigeminal inhibition tension suppression system, is a type of occlusal splint that is claimed to prevent headache and migraine by reducing sleep bruxism. Sleep bruxism is purported to lead to a hyperactivity of the trigeminal nerve, often triggering typical migraine events. The hyperactivity of trigeminal neurons during trigemino-nociceptive stimulation is a proposed cause of migraine and is correlated with imaging of migraine sufferers. The objective of the NTI-TSS is to relax the muscles involved in clenching and bruxing, thus supposedly diminishing the chances for migraines and tension headaches to develop through the reduction in nociceptive stimulation normally caused by parafunctional activity. It is sometimes used for temporomandibular joint dysfunction (TMD).
In orthodontics, a malocclusion is a misalignment or incorrect relation between the teeth of the upper and lower dental arches when they approach each other as the jaws close. The English-language term dates from 1864; Edward Angle (1855-1930), the "father of modern orthodontics", popularised it. The word "malocclusion" derives from occlusion, and refers to the manner in which opposing teeth meet.
Dens evaginatus is a rare odontogenic developmental anomaly that is found in teeth where the outer surface appears to form an extra bump or cusp.
Dental attrition is a type of tooth wear caused by tooth-to-tooth contact, resulting in loss of tooth tissue, usually starting at the incisal or occlusal surfaces. Tooth wear is a physiological process and is commonly seen as a normal part of aging. Advanced and excessive wear and tooth surface loss can be defined as pathological in nature, requiring intervention by a dental practitioner. The pathological wear of the tooth surface can be caused by bruxism, which is clenching and grinding of the teeth. If the attrition is severe, the enamel can be completely worn away leaving underlying dentin exposed, resulting in an increased risk of dental caries and dentin hypersensitivity. It is best to identify pathological attrition at an early stage to prevent unnecessary loss of tooth structure as enamel does not regenerate.
Dental anatomy is a field of anatomy dedicated to the study of human tooth structures. The development, appearance, and classification of teeth fall within its purview. Tooth formation begins before birth, and the teeth's eventual morphology is dictated during this time. Dental anatomy is also a taxonomical science: it is concerned with the naming of teeth and the structures of which they are made, this information serving a practical purpose in dental treatment.
Occlusion, in a dental context, means simply the contact between teeth. More technically, it is the relationship between the maxillary (upper) and mandibular (lower) teeth when they approach each other, as occurs during chewing or at rest.
Crossbite is a form of malocclusion where a tooth has a more buccal or lingual position than its corresponding antagonist tooth in the upper or lower dental arch. In other words, crossbite is a lateral misalignment of the dental arches.
Serial extraction is the planned extraction of certain deciduous teeth and specific permanent teeth in an orderly sequence and predetermined pattern to guide the erupting permanent teeth into a more favorable position.
Tooth wear refers to loss of tooth substance by means other than dental caries. Tooth wear is a very common condition that occurs in approximately 97% of the population. This is a normal physiological process occurring throughout life; but with increasing lifespan of individuals and increasing retention of teeth for life, the incidence of non-carious tooth surface loss has also shown a rise. Tooth wear varies substantially between people and groups, with extreme attrition and enamel fractures common in archaeological samples, and erosion more common today.
Intrusion is a movement in the field of orthodontics where a tooth is moved partially into the bone. Intrusion is done in orthodontics to correct an anterior deep bite or in some cases intrusion of the over-erupted posterior teeth with no opposing tooth. Intrusion can be done in many ways and consists of many different types. Intrusion, in orthodontic history, was initially defined as problematic in early 1900s and was known to cause periodontal effects such as root resorption and recession. However, in mid 1950s successful intrusion with light continuous forces was demonstrated. Charles J. Burstone defined intrusion to be "the apical movement of the geometric center of the root (centroid) in respect to the occlusal plane or plane based on the long axis of tooth".
Open bite is a type of orthodontic malocclusion which has been estimated to occur in 0.6% of the people in the United States. This type of malocclusion has no vertical overlap or contact between the anterior incisors. The term "open bite" was coined by Carevelli in 1842 2 as a distinct classification of malocclusion. Different authors have described the open bite in a variety of ways. Some authors have suggested that open bite often arises when overbite is less than the usual amount. Additionally, others have contended that open bite is identified by end-on incisal relationships. Lastly, some researchers have stated that a lack of incisal contact must be present to diagnose an open bite.
A complete denture is a removable appliance used when all teeth within a jaw have been lost and need to be prosthetically replaced. In contrast to a partial denture, a complete denture is constructed when there are no more teeth left in an arch, hence it is an exclusively tissue-supported prosthesis. A complete denture can be opposed by natural dentition, a partial or complete denture, fixed appliances or, sometimes, soft tissues.
An ectopic maxillary canine is a canine which is following abnormal path of eruption in the maxilla. An impacted tooth is one which is blocked from erupting by a physical barrier in the path of eruption. Ectopic eruption may lead to impaction. Previously, it was assumed that 85% of ectopic canines are displaced palatally, however a recent study suggests the true occurrence is closer to 50%. While maxillary canines can also be displaced buccally, it is thought this arises as a result of a lack of space. Most of these cases resolve themselves with the permanent canine erupting without intervention.
Posselt's envelope of motion or Posselt's envelope of movement refers to the range of motion of the lower jaw bone, or mandible.
Orthodontic indices are one of the tools that are available for orthodontists to grade and assess malocclusion. Orthodontic indices can be useful for an epidemiologist to analyse prevalence and severity of malocclusion in any population.
Occlusion according to The Glossary of Prosthodontic Terms Ninth Edition is defined as 'the static relationship between the incising or masticating surfaces of the maxillary or mandibular teeth or tooth analogues'.
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