The association between anterior crossbite, deepbite, and temporomandibular joint morphology
Wohlberg V, Schwahn C, Gesch D, Meyer G, Kocher T, Bernhardt O. The association between anterior crossbite, deep bite and temporomandibular joint morphology validated by magnetic resonance imaging in an adult non-patient group. Ann Anat 2012;194:339-44
The morphology of the temporomandibular joint (TMJ) has been extensively studied under various occlusal conditions such as tooth loss, occlusal disharmonies, and excessive oral function or dental abrasion. However, few studies have explored the possible correlations between malocclusions and TMJ morphology. The objective of this study was to determine whether associations exist between malocclusions of the anterior teeth affecting anterior guidance and the morphologic variability of the TMJ in an adult nonpatient group. The investigators selected 148 subjects from a cross-sectional epidemiologic population-based study, based on the presence of anterior edge-to-edge bite, anterior crossbite, or deepbite without gingival contact. Magnetic resonance imaging scans were taken; eminence height, postglenoid process height, fossa depth, distance between eminence crest and the highest point of the fossa, and the eminence height/postglenoid process height ratio were used to describe TMJ morphology. The results showed that an anterior edge-to-edge bite or a crossbite is connected to reduced eminence height, and that deepbite without gingival contact is connected to an increased ratio between eminence height and postglenoid process height. In other words, the condylar path in the subjects with anterior edge-to-edge bite and crossbite can be interpreted to be reduced; in those with deepbite without gingival contact, the condylar path is steepened. Reconstructing the anterior guidance through orthodontic or prosthetic treatments must be in concordance with the TMJ morphology to allow harmonious functioning of the stomatognathic system.
Reviewed by Yang Li
Condylar remodeling accompanying splint therapy
Liu MQ, Chen HM, Yap AUJ, Fu KY. Condylar remodeling accompanying splint therapy: a cone-beam computerized tomography study of patients with temporomandibular joint disk displacement. Oral Surg Oral Med Oral Path Oral Radiol 2012;114:259-65
Temporomandibular joint (TMJ) disc displacement is the most common type of TMJ arthropathy. It can be subdivided into disc displacement with reduction and disc displacement without reduction. Patients with advanced disc displacement with reduction can experience intermittent closed-lock, restricted motion, and painful function before progression to acute disc displacement without reduction. Anterior repositioning splint therapy has been shown to be effective for the management of TMJ disc displacement with reduction. It not only allows displaced articular discs to reposition, but also leads to condylar bone remodeling that is manifested as a “double contour” on magnetic resonance imaging of the condylar heads. The aim of this study was to evaluate osseous changes accompanying anterior repositioning splint therapy in patients with TMJ disc displacement. Cone-beam computerized tomography (CBCT) data of 36 patients with intermittent or permanent closed-lock were used; 23 patients with permanent closed-lock had their displaced discs physically reduced by mandibular manipulation before anterior repositioning splint therapy. CBCT was performed before and 6 months after anterior repositioning splint therapy. The presence and location of “double contour” images suggesting condylar bone remodeling were statistically analyzed. “Double contour” images after anterior repositioning splint therapy were observed in 80% of patients, more frequently in joints with signs of displaced discs. The “double contour” appeared more often on the posterior bevel as well as the medial and middle parts of the condyles. It can be concluded that CBCT is a useful tool for monitoring osseous changes in condyles.
Reviewed by Aziz Almudhi
Condylar remodeling accompanying splint therapy
Liu MQ, Chen HM, Yap AUJ, Fu KY. Condylar remodeling accompanying splint therapy: a cone-beam computerized tomography study of patients with temporomandibular joint disk displacement. Oral Surg Oral Med Oral Path Oral Radiol 2012;114:259-65
Temporomandibular joint (TMJ) disc displacement is the most common type of TMJ arthropathy. It can be subdivided into disc displacement with reduction and disc displacement without reduction. Patients with advanced disc displacement with reduction can experience intermittent closed-lock, restricted motion, and painful function before progression to acute disc displacement without reduction. Anterior repositioning splint therapy has been shown to be effective for the management of TMJ disc displacement with reduction. It not only allows displaced articular discs to reposition, but also leads to condylar bone remodeling that is manifested as a “double contour” on magnetic resonance imaging of the condylar heads. The aim of this study was to evaluate osseous changes accompanying anterior repositioning splint therapy in patients with TMJ disc displacement. Cone-beam computerized tomography (CBCT) data of 36 patients with intermittent or permanent closed-lock were used; 23 patients with permanent closed-lock had their displaced discs physically reduced by mandibular manipulation before anterior repositioning splint therapy. CBCT was performed before and 6 months after anterior repositioning splint therapy. The presence and location of “double contour” images suggesting condylar bone remodeling were statistically analyzed. “Double contour” images after anterior repositioning splint therapy were observed in 80% of patients, more frequently in joints with signs of displaced discs. The “double contour” appeared more often on the posterior bevel as well as the medial and middle parts of the condyles. It can be concluded that CBCT is a useful tool for monitoring osseous changes in condyles.
Reviewed by Aziz Almudhi
Laser therapy in orthodontic retention and relapse
Kim SJ, Kang YG, Park JH, Kim EC, Park YG. Effects of low-intensity laser therapy on periodontal tissue remodeling during relapse and retention of orthodontically moved teeth. Lasers Med Sci 2012 Jul 20 [Epub ahead of print]
Although it is not fully understood, a primary factor in orthodontic relapse is the memory of transformed periodontal ligament (PDL) fibers. The aim of this animal study was to look at the effects of low-intensity laser therapy on PDL remodeling during orthodontic relapse and retention. The maxillary central incisors of 52 rats were divided into 5 groups: a control group, a postorthodontic relapse group with no retainers, a postorthodontic fixed retention group, a postorthodontic and low-intensity laser therapy relapse group, and a postorthodontic and low-intensity laser therapy retention group. The rats were killed on days 1, 3, and 7 after removal of the orthodontic appliances. Qualitative analysis was then done by using reverse transcriptase polymerase chain reaction for matrix metalloproteinases mRNA expression. Both the compression and the tension sides were observed for immunoreactivities of collagen and tissue inhibitor of metalloproteinase. Both the relapse and the retention groups that had low-intensity laser therapy showed significantly more expression of the 5 tested metalloproteinase mRNAs. TIMP-1 immunoreactivity was inhibited in both low-intensity laser therapy groups, whereas Col-I immunoreactivity was increased only in the low-intensity laser therapy retention group. These results suggest that low-intensity laser therapy would have differing effects on postorthodontic stability depending on retainer use. Low-intensity laser therapy combined with retainer wear might shorten the retention period by accelerating the PDL remodeling of the teeth in their new positions; however, low-intensity laser therapy used without a retainer would actually cause an increase in postorthodontic relapse. This study offers a strong foundation for future clinical studies to investigate whether low-intensity laser therapy can be used to enhance postorthodontic stability as a noninvasive biologic retainer.
Reviewed by Arash Rajaei
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