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Results for “Condylar position”

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At least 253 records · Page 14Linked to original sources

PubMed1992

The effect of maxillary first premolar extraction and incisor retraction on mandibular position: testing the central dogma of "functional orthodontics".

It has been argued by a vocal coterie of disaffected dentists that premolar extraction, incisor retraction, and "backward-pulling" mechanics conspire to "distalize" the condyles and, pari passu, to produce craniomandibular dysfunction. Given the gravity of this conjecture, it seemed appropriate to test the predictions it generates in a sample of patients of the type most often said to be at risk: 42 "edgewise" patients with Class II, Division 1 malocclusions, treated in conjunction with the extraction of two maxillary first premolars. Regional and anterior cranial-base cephalometric superimpositions were used to quantify the individual components of the molar and overjet corrections, to measure both at the chin and condyles the mandibular displacement seen during treatment, and to examine the extent to which this displacement is related to the correction of maxillary incisor protrusion. Although the present patients underwent marked upper incisor retraction (on average, about 5 mm), lip retraction was much less pronounced, and 70% of the sample showed a net forward displacement of mandibular basal bone. Significantly, changes in condylar position were not correlated with incisor retraction, as the "functional orthodontists" would have it, but rather with the changes in the buccal occlusion and the growth of the maxilla. Thus, 30% of the patients who showed evidence of distal displacement were generally nongrowing patients who underwent more than average anchorage loss in the mandible and less than average loss in the maxilla.(ABSTRACT TRUNCATED AT 250 WORDS)

Activator Appliances↗

PubMed1990

Positional changes after mandibular advancement by sagittal split osteotomies and wire osteosynthesis. Do combined orthodontics and the Dal Pont modification of the buccal osteotomy contribute to long-term stability?

Thirty-five cases of sagittal split ramus osteotomies with wire osteosynthesis as the exclusive procedure used to correct a dentoskeletal Class II deformity, were selected to form a homogeneous group for cephalometric evaluation of the short- and long-term, skeletal and dental changes. The group was statistically described as having severe micromandibulism, mild micromaxillism and mild dento-alveolar maxillary protrusion. The skeletal relapse within the first postoperative year was due to horizontal and dorsocranial rotational changes of the tooth-bearing segment. The joint-bearing segment rotated ventrocranially. As an overall result, the mandibular body was not lengthened but advanced. The relapse at the occlusal level was considerably less, partly due to the rotational component of the skeletal relapse mechanism, partly due to the compensating retroclination of the upper anterior teeth. With the condyles correctly repositioned at surgery, no relationship could be found between postoperative changes in condylar position and skeletal relapse. There was no difference in the average amount of skeletal relapse between the subgroup with the Dal Pont modification of the buccal osteotomy and the subgroup with the buccal osteotomy directed to the mandibular angle. The average skeletal relapse was greater in the combined surgical orthodontic cases, due to increased alveolar tooth mobility.

Adolescent↗

PubMed1989

The effects of temporomandibular joint internal derangement and degenerative joint disease on tomographic and arthrotomographic images.

In a blind study, 243 arthrograms were interpreted as showing normal disk position, anterior disk displacement with reduction, or anterior disk displacement without reduction. The presence or absence of a perforation of the posterior attachment or disk was recorded. Later, tomograms of the same patient were interpreted. The presence or absence of evidence of temporomandibular degenerative joint disease (TMDJD) was recorded. The condyle-to-fossa relationship was characterized as retropositioned or not retropositioned. O the 106 cases with tomographic evidence of TMDJD, 100 (94%) had arthrographic evidence of internal derangement (p less than 0.0001), whereas 47% of the cases with internal derangement (211) had evidence of TMDJD. Perforations were seen in 29 (27%) of the cases with degenerative joint disease and in none (0%) of the cases without TMDJD (p less than 0.001). In cases without TMDJD, 90% of the cases with internal derangement revealed condylar retropositioning (p less than 0.0001). With tomographic evidence of TMDJD present, the relationship between condylar position and disk position was not significant.

Arthrography↗

PubMed2002

Cranial base considerations between apnoeics and non-apnoeic snorers, and associated effects of long-term mandibular advancement on condylar and natural head position.

One hundred consecutively medically referred patients (58 apnoeic and 42 asymptomatic snorers) were reviewed cephalometrically at six-monthly intervals (6-30 months) following treatment for obstructive sleep apnoea (OSA) and/or habitual snoring by mandibular advancement. Eighty-seven males and 13 females (mean age 49 years, SD 8.5, range 33-74) were included in this study. Reference points and planes in the cranial base, nasopharynx, and mandibular condyle were digitized with a Reflex Metrograph and their means converted to linear and angular measurements. No statistically significant differences were observed between the apnoeic and non-apnoeic groups in either their skeletal or cranial base measurements. All linear cranial base dimensions were, however, reduced in the apnoeic group, with the exception of the distance (S-SE). Following mandibular advancement, statistically significant changes were observed in vertical condylar position (Cd-vert) with changes occurring at 6 (P < 0.012), 18 (P < 0.043), and 24 months (P < 0.007). No changes in horizontal condylar position (Cd-horiz) were found. Significant changes were observed in natural head position (NHP) with a reduction from an extended (NSL-vert 99.7 degrees) to a more upright NHP (NSL-vert 93.0, P < 0.001).

Adult↗

PubMed1989

[The positioner--a possibility for the fine adjustment of the occlusion objectively assessed by condylar measurements of the discrepancy between the ICP and RCP].

A group of ten adolescents was treated with fixed appliances at the Department of Stomatology and Oral and Maxillofacial Surgery, Graz. Subsequently the patients were fitted with a gnathological positioner. On the day of band removal ten sets of models were made and subsequently two, four and twelve weeks later. They were mounted on an articulator and cephalometric measurements were taken three times by each of the examiners. These records served to provide evidence of discrepancies of the condylar position between ICP and RCP in all three planes. In the second part of the examination, the patients were instructed to wear the appliance at night for another year. Casting of models, mounting in articulators and condymetric measurements were repeated as above. After wearing the positioner for three months, we observed a definite improvement of the occlusion and a wide conformity of the RCP and ICP measurements. After one year of night-time retention there was a slight increase of the mean values. In addition, we could establish statistically that condymetric model measurements are independent of the examiner and the method employed.

Adolescent↗

PubMed1998

[Results of measurement of pre- and postoperative milling models of orthodontic-surgical treatment of dysgnathia patients].

PURPOSE: Three-dimensional realisation of CT by models produced by a milling machine and stereolithography has become a useful procedure for the diagnosis of craniomaxillofacial disharmonies. We used three-dimensional milling models to verify the results of operations involving sagittal splitting of the mandible. MATERIAL AND METHODS: Fifteen models from patients with mandibular prognathism and 31 models from patients with mandibular retrognathism, made preoperatively and 6 weeks postoperatively, were examined for three-dimensional changes of the osseous anatomical structures. RESULTS: The mandibular corpus had been shifted between 1 and 3 mm forward in the group of patients with mandibular retrognathism and by the same distance backward in the first group. In the group with ventral shifting, the intercondylar distance increased by 2.9 mm, while it decreased by 1.9 mm in patients with the mandibular backshift operation. Furthermore, the distance between the muscular processes increased by 6.6 mm in the first group and decreased by 1.6 mm in the second. The Bonewill angle decreased by 1.6 degrees in patients after ventral shifting and increased by 1.7 degrees in the dorsally shifted group. Contrary changes in the left and right gonion angle were seen: if the right decreased, the left increased. The same situation was found in both groups. CONCLUSION: We noted remarkable changes in the condylar position and anatomy after sagittal splitting of the mandible.

Cephalometry↗

PubMed1989

Condylar displacement and temporomandibular joint dysfunction following bilateral sagittal split osteotomy and rigid fixation.

In this study changes in intercondylar width (ICW) and intercondylar angle (ICA) that occurred with rigid fixation after bilateral sagittal split osteotomy and mandibular advancement are documented and correlated with temporomandibular (TM) symptoms, magnitude of advancement, and mandibular shape. Even though individual changes occurred, there was no significant difference between the mean preoperative and postoperative ICA and ICW measurements. There was also no significant difference between the preoperative and postoperative incidence of TM pain or clicking. No correlation was found between the magnitude of advancement and the percent change in ICA or ICW, and the mandibular shape did not correlate to changes in ICW. This study suggests that screw osteosynthesis does not significantly change ICA or ICW. The fact that no significant increase in TM symptoms occurred indicates that the changes in condylar position that did occur were within the range of clinical adaptability of the patients.

Bone Screws↗

PubMed2005

A biomechanical evaluation of bilateral sagittal ramus osteotomy fixation techniques.

OBJECTIVES: The purpose of this investigation was to evaluate and compare the biomechanical behavior of various rigid internal fixation plates designed to aid in the condylar positioning of bilateral sagittal ramus osteotomies, to positional screws in an inverted-L pattern, and a control. MATERIALS AND METHODS: Fifty polyurethane synthetic mandible replicas (Synbone, Laudquart, Switzerland) were used in this investigation. Five controls and 5 each of 4 different fixation modalities (3 bicortical positional screws in an inverted-L pattern, monocortical 4-hole straight plates, monocortical 6-hole curved plates, and monocortical adjustable 4-hole slide plates) were subjected to vertical loading at the incisal edge and torsional loading at the molar region by an Instron 1331 (Instron, Canton, MA) servohydraulic mechanical testing unit. Mechanical deformation data within a 0 to 900 N range were recorded. Yield load, yield displacement, and stiffness were determined. Means and standard deviations were derived and compared for statistical significance using a Fisher's Protected Least Significant Differences Test with a confidence level of 95% (P < .05). Second-order polynomial best-fit curves were also created for each group to further evaluate mechanical behavior. RESULTS: For incisal edge loading, statistically significant differences were noted between the control group and all other groups for yield load and stiffness, and between the control group and straight, curved, and slide plates for yield displacement. Differences were also noted between the inverted-L and straight, strut, and slide plates for yield load; and inverted-L and straight, curved, and slide, as well as straight and slide for yield displacement. For molar loading, statistically significant differences were noted between the control group and all other groups for yield load and stiffness. Differences were noted between the slide and straight, curved, and control; as well as between the inverted-L and straight and strut plates for yield displacement. Lastly, differences were noted between the straight and curved plates, and the slide and straight, curved, and inverted-L for stiffness. CONCLUSION: In this in vitro study, differences were noted between the control and all experimental groups in their abilities to resist loads under all of the conditions tested. Differences were also noted among specific experimental groups. Yet when placed in the context of functional parameters, only the bicortical positional screws in an inverted-L pattern met the requirements for both molar loading and incisal edge loading.

Biomechanical Phenomena↗

PubMed1991

The role of muscle deconditioning for occlusal corrective procedures.

Research has indicated that the suspension mechanism of the condyle in the fossae is muscular rather than ligamentous. Therefore, in a normal condyle-disk-fossa relationship, variations in muscle tone influence condylar position and function. The proprioception of the muscles, tendons, periodontal membrane, and temporomandibular joints influence the muscle programming of centric occlusion. In many patients the usual chairside muscle deconditioning procedures are too weak and inefficient to overcome habitual closure. The role of long-term and short-term muscle deconditioning for the occlusal correction of centric relation deflective contacts has been discussed.

Centric Relation↗

PubMed1998

Changes in the dimensions of milled mandibular models after mandibular sagittal split osteotomies.

Three-dimensional models created by milling machines and stereolithography from the three-dimensional computed tomograms (CTs) have become important in the diagnosis and preoperative planning of some craniomaxillofacial irregularities. In this study three-dimensional milled models were used to verify operative results after patients had undergone bilateral sagittal split osteotomies of the mandible. Fifteen models of patients with mandibular prognathism and 31 with retrognathism were created preoperatively and 6 weeks postoperatively to examine the changes of the osseous anatomical structures in three dimensions. There was a forward shift in the mandibular corpus of between 1 and 3 mm in patients with retrognathism and a backward shift to the same extent in the group with prognathism. In the latter group the intercondylar distance increased by a mean of 2.0 (SD 1.2) mm and by 2.9 (SD 1.0) mm in patients who had had a mandibular advancement operation. Furthermore the distance between the coronoid processes increased by 6.6 (SD 1.8) mm in the retrognathic group and decreased by 1.6 (SD 1.4) mm in the prognathic group. The Bonewill angle increased by 1.7 (SD 0.4) degrees in the prognathic group and decreased by 1.6 (SD 0.3) degrees in the retrognathic group. Both increase and decrease of the homolateral gonion angle were accompanied by a contrarotary movement of the contralateral gonion angle. We conclude that remarkable changes in condylar position and anatomy take place after bilateral ramus sagittal split osteotomy.

Bone Screws↗

PubMed2000

Effects of mandibular setback on the temporomandibular joint: a comparison of oblique and sagittal split ramus osteotomy.

PURPOSE: This investigation studied the changes in temporomandibular joint function and condylar position after mandibular setback using different ramus osteotomies. PATIENTS AND METHODS: The sample consisted of 50 Chinese adults with mandibular prognathism. Twenty-eight of the patients underwent intraoral oblique ramus osteotomy (IORO), and 22 received sagittal split ramus osteotomy (SSRO) with rigid internal fixation (RIF). TMJ symptoms and radiographic findings were evaluated preoperatively and postoperatively. RESULTS: After surgery in the IORO group, the TMJ radiographs showed a significant anterior-inferior displacement of the condyle. Seventy-five percent of the preoperatively symptomatic patients reported fewer or no TMJ symptoms and no preoperatively asymptomatic patients developed new TMJ symptoms. In the SSRO group, the TMJ radiographs showed a posterior displacement of the condyle. Sixty percent of the preoperatively symptomatic patients had no improved TMJ function and 8% of asymptomatic patients developed TMJ symptoms after surgery. CONCLUSION: The results of this study show that IORO with MMF appears to be more favorable to the TMJ than the SSRO with RIF; IORO is particularly good in orthognathic surgery patients with preoperative TMJ symptoms.

Adult↗

PubMed2003

Solid-state temporomandibular joint imaging: accuracy in detecting osseous changes of degenerative joint disease and determining condylar spatial relations.

The purpose of this study was to evaluate the off-label use of an intraoral charge-coupled device (CCD) for extraoral transcranial radiography of the temporomandibular joint. Corrected linear tomograms and transcranial images made with conventional screen-film combinations and a CCD detector were compared with sectioned cadaver specimens. Radiation dosage, qualitative assessment of condylar degenerative features, and condylar position within the glenoid fossa of the 3 modalities were assessed and compared. The CCD method required special adjustments to achieve adequate quality, and it involved greater exposure than the other methods. This use of this intraoral system for extraoral imaging cannot now be recommended, but future refinements might make it more viable.

Consumer Product Safety↗

PubMed1988

Condylar displacement after oblique sliding osteotomy of the mandibular rami. A stereometric and plain radiographic study.

Condylar displacement after oblique sliding osteotomy was examined in 8 patients by X-ray stereometry and plain radiography. During the first 8 postoperative weeks the displacement was in a medial/superior/posterior direction. After removal of the intermaxillary fixation a continuous lateral translation was found together with an initial inferior and a minor anterior translation which after 6 months postoperatively changed to a posterior translation. At 12 months postoperatively a difference in findings of condylar position was found between the X-ray stereometric and plain radiographic analyses. We regard this difference as due to the sum of remodelling and method errors.

Adult↗

PubMed2005

Two- and three-dimensional orthodontic imaging using limited cone beam-computed tomography.

Considerable progress has been made in diagnostic, medical imaging devices such as computed tomography (CT). However, these devices are not used routinely in dentistry and orthodontics because of high cost, large space requirements and the high amount of radiation involved. A device using computed tomography technology has been developed for dental use called a limited cone beam dental compact-CT (3DX). The aim of this article is to demonstrate the usefulness of 3DX imaging for orthodontic diagnosis and treatment planning. We present three cases: (1) one case shows delayed eruption of the upper left second premolar, (2) the second case shows severe impaction of a maxillary second bicuspid; and (3) the third case shows temporomandibular joint disorder (TMD). In the tooth impaction cases, the CT images provided more precise information than conventional radiographic images such as improved observation of the long axis of the tooth, root condition, and overlap with bone. In the TMD case, clear and detailed temporomandibular joint images were observed and pre- and posttreatment condylar positions were easily compared. We conclude that 3DX images provide useful information for orthodontic diagnosis and treatment planning.

Adolescent↗

PubMed2003

Effect of Herbst treatment on temporomandibular joint morphology: a systematic literature review.

The purpose of this systematic review was to evaluate the effect of Herbst appliance therapy on temporomandibular joint (TMJ) morphology, with special reference to glenoid fossa remodeling, condylar remodeling, condylar position, and articular disc position. Publications of controlled trials of Herbst treatment of Class II patients using magnetic resonance imaging (MRI), computerized tomography scans, or tomography to assess TMJ morphology were identified with Medline (1966-2001), Best Evidence (1991-2001), Cochrane Database of Systematic Reviews (second quarter, 2001), and Embase (1998-2001). Case reports were excluded. Based on our search, only 5 studies met the selection criteria. All studies used internal controls with pretreatment and posttreatment imaging. Four studies used MRI, and 1 used tomograms. The 4 MRI studies used overlapping patient samples and were not considered as independent evidence. The MRI studies did not provide conclusive evidence of osseous remodeling or condyle position change. The tomography study demonstrated minor condyle position change. Methodological deficiencies prevented major conclusions regarding disc position. The reviewed studies highlight the importance of further research. Prospective controlled studies using serial MRI and tomography are required to establish the effect of Herbst treatment on TMJ morphology.

Bone Remodeling↗

PubMed2006

Early modern humans from the Pestera Muierii, Baia de Fier, Romania.

The early modern human remains from the Peştera Muierii, Romania have been directly dated to approximately 30,000 radiocarbon years before present (approximately 30 ka 14C BP) (approximately 35 ka cal BP) ("calendrical" age; based on CalPal 2005) and augment a small sample of securely dated, European, pre-28 ka 14C BP (approximately 32.5 ka cal BP) modern human remains. The Muierii fossils exhibit a suite of derived modern human features, including reduced maxillae with pronounced canine fossae, a narrow nasal aperture, small superciliary arches, an arched parietal curve, zygomatic arch above the auditory porous, laterally bulbous mastoid processes, narrow mandibular corpus, reduced anterior dentition, ventral-to-bisulcate scapular axillary border, and planoconcave tibial and fibular diaphyseal surfaces. However, these traits co-occur with contextually archaic and/or Neandertal features, including a moderately low frontal arc, a large occipital bun, a high coronoid process and asymmetrical mandibular notch, a more medial mandibular notch crest to condylar position, and a narrow scapular glenoid fossa. As with other European early modern humans, the mosaic of modern human and archaic/Neandertal features, relative to their potential Middle Paleolithic ancestral populations, indicates considerable Neandertal/modern human admixture. Moreover, the narrow scapular glenoid fossa suggests habitual movements at variance with the associated projectile technology. The reproductive and scapulohumeral functional inferences emphasize the subtle natures of behavioral contrasts between Neandertals and these early modern Europeans.

Anthropology↗

PubMed1990

Correction of mandibular asymmetry with the ligated anterior repositioning splint.

Mandibular asymmetry may be the result of unequal ramus height, unequal corpus length, or a combination of both problems. The diagnosis of asymmetry is essential in treatment planning, since a number of therapeutic options must be considered in the treatment to a seated condylar position in the glenoid fossa. When asymmetry exists, it may be necessary to: accept finished treatment with the mandibular midline to the right or left of the maxillary midline, finish the molars and canines in an end-to-end relationship on the short side, treat with asymmetric extractions, intervene surgically, or use functional appliances to enhance greater growth or remodeling of the mandible on the short side. The purpose of this study was to assess the effect of the ligated anterior repositioning splint, or LARS, in the correction of mandibular asymmetry in Class II patients.

Activator Appliances↗

PubMed2001

Dental and skeletal changes associated with long-term mandibular advancement.

STUDY OBJECTIVES: Little is known of the possible dental or skeletal side effects following the use of mandibular advancement in the treatment of obstructive sleep apnea. A study has subsequently been designed to investigate these issues. DESIGN: 100 consecutively treated medically referred patients were reviewed cephalometrically in 6-month intervals (6-30 months) following mandibular advancement therapy. SETTING: Orthodontic Private Practice. PATIENTS: 87 males, 13 females (mean age 49 years, SD 8.5, range 33-74 years). INTERVENTIONS: N/A. MEASUREMENTS AND RESULTS: Reference points and planes in the cranial base, maxilla, and mandible were digitized with a reflex metrograph and their means converted to linear and angular measurements. Significant changes following mandibular advancement were observed in lower face height, vertical condylar position, incisor angulation, overbite, and overjet. Skeletal changes were attributed to a vertical repositioning of the mandibular condyle relative to the cranial base and were present at the first review period (6 months). Dental changes occurred later with treatment with the most significant changes occurring at the final review period (30 months) which resulted in a 4.9 degrees proclination of the mandibular incisors and a reduction in overbite of 1.82mm. CONCLUSION: The data suggests that long-term use of mandibular advancement can cause dental and skeletal changes which may be progressive over time. As many consider mandibular advancement a treatment for life, it is strongly recommended that all patients be fully informed of the potential for such changes prior to treatment and undergo mandatory dental reviews with long-term mandibular advancement.

Adult↗