Temporomandibular joint disorders.

Am Fam Physician. 2007 Nov 15;76(10):1477-82

Authors: Buescher JJ

Temporomandibular joint disorders are common in adults; as many as one third of adults report having one or more symptoms, which include jaw or neck pain, headache, and clicking or grating within the joint. Most symptoms improve without treatment, but various noninvasive therapies may reduce pain for patients who have not experienced relief from self-care therapies. Physical therapy modalities (e.g., iontophoresis, phonophoresis), psychological therapies (e.g., cognitive behavior therapy), relaxation techniques, and complementary therapies (e.g., acupuncture, hypnosis) are all used for the treatment of temporomandibular joint disorders; however, no therapies have been shown to be uniformly superior for the treatment of pain or oral dysfunction. Noninvasive therapies should be attempted before pursuing invasive, permanent, or semi-permanent treatments that have the potential to cause irreparable harm. Dental occlusion therapy (e.g., oral splinting) is a common treatment for temporomandibular joint disorders, but a recent systematic review found insufficient evidence for or against its use. Some patients with intractable temporomandibular joint disorders develop chronic pain syndrome and may benefit from treatment, including antidepressants or cognitive behavior therapy.

PMID: 18052012 [PubMed - in process]

Pre-operative drilling simulation method for dental implant treatment.

Bull Tokyo Dent Coll. 2007 Feb;48(1):27-35

Authors: Arataki T, Furuya Y, Ito T, Miyashita Y, Shimamura I, Yajima Y

The position, depth and direction of implant placement are often planned based on evaluation of radiographs and study casts. Insertion planned in such a manner may not be adequate for precise and safe surgery in some cases due to inadequate working clearance in the oral cavity. In order to obtain high initial stability and ensure osseointegration at the implant-bone interface, careful and precise drilling must be performed at the implant placement site. Therefore, we propose the necessity of evaluating the operability of implant treatment-devices prior to surgery. The amount of handling space needed during implant placement surgery was determined. The results showed that for implants with a length of 7-18 mm, a vertical distance of as much as 50-60 mm was required, depending on the implant platform. These results suggest the necessity of pre-operative drilling simulation in each individual. Handling space was measured with angled heads and probes fabricated on a trial basis for pre-surgical drilling simulation in the oral cavity. We believe that these instruments may be clinically useful in estimating the amount of handling space required prior to surgery and ensuring precise implant placement. Evaluation of the intra-oral environment for handling of treatment devices should be included in the pre-surgical intra-oral evaluation of dental implant cases to avoid changes in treatment planning due to intra-oral interference during the course of surgery.

PMID: 17721064 [PubMed - indexed for MEDLINE]

[Masticatory performance in adults related to temporomandibular disorder and dental occlusion]

Pro Fono. 2007 Apr-Jun;19(2):151-8

Authors: de Felício CM, de Oliveira Melchior M, da Silva MA, dos Santos Celeghini RM

BACKGROUND: Temporomandibular disorder and mastication. AIM: To compare subjects who present temporomandibular disorders to a control group considering mastication and to analyze the related variables. METHOD: 20 subjects with temporomandibular disorder (TMD group) and 10 controls--selection based on clinical examination and anamnesis--responded to a questionnaire on the self-perception of pain severity and presence of noise in the temporomandibular joints, muscle pain, otologic symptoms, headaches, and jaw opening difficulties. The subjects were also submitted to a clinical examination regarding the number of teeth and functional occlusion--measurements of jaw opening and jaw lateral excursions, occlusal interferences, occlusal contacts of the working and non-working-side, and mastication evaluation. Mastication was evaluated in terms of time needed to eat a stuffed cookie, number of chewing strokes and type (unilateral or bilateral). The maximum force needed at first to break the cookie, verified with a TA-XT2 Texture Analyzer (Stable Micro Systems), was of 4341.8 g. The groups were compared using variance analysis and the correlations between variables were calculated using the Pearson product-moment test. RESULTS: Most of the control subjects presented bilateral pattern of mastication, whereas the TMD group tended to present the unilateral pattern. Masticatory type scores and laterality measurements were significantly higher in the control group. The TMD group presented higher means in terms of: age, time of chewing, number of chewing strokes and TMD severity. Chewing time and type were positively correlated with TMD severity and negatively correlated with number of occlusal interferences. CONCLUSION: In the TMD group, chewing differed from the normal physiological standard. The number of occlusal interferences and the severity of TMD were variables correlated to chewing.

PMID: 17710341 [PubMed - in process]

Complete denture impression techniques: evidence-based or philosophical.

Indian J Dent Res. 2007 Jul-Sep;18(3):124-7

Authors: Singla S

Code of practice is dangerous and ever-changing in today's world. Relating this to complete denture impression technique, we have been provided with a set of philosophies--"no pressure, minimal pressure, definite pressure and selective pressure". The objectives and principles of impression-making have been clearly defined. Do you think any philosophy can satisfy any operator to work on these principles and achieve these objectives? These philosophies take into consideration only the tissue part and not the complete basal seat, which comprises the periphery, the tissues and the bone structure. Under such circumstances, should we consider a code of practice dangerous or should we develop an evidence-based approach having a scientific background following certain principles, providing the flexibility to adapt to clinical procedures and to normal biological variations in patients rather than the rigidity imposed by strict laws?

PMID: 17687175 [PubMed - indexed for MEDLINE]

Importance of occlusion aspects in the completion of orthodontic treatment.

Braz Dent J. 2007;18(1):78-82

Authors: Oltramari PV, Conti AC, Navarro Rde L, Almeida MR, Almeida-Pedrin RR, Ferreira FP

The purpose of this study was to address the therapeutic goals regarding the static and functional occlusion in the completion of orthodontic treatment. For such purpose, a study population comprising 20 female treated Class II malocclusion subjects with an initial mean age of 11 years underwent a two-phase treatment (orthopedics and orthodontics). The patients were diagnosed in centric relation and were treated according to the six keys for normal occlusion and functional occlusal parameters (centric relation, vertical dimension, lateral and anterior guidances, occlusal contacts and direction of forces applied on the teeth). After removal of fixed mechanics, retainers were installed and maintained for two years. Five years after orthodontic completion, the occlusal stability of the patients was evaluated regarding molar relationship and overjet, measured in dental casts. All subjects maintained the normal molar relationship and correct overjet achieved at the end of treatment, indicating a fair level of occlusal stability. The importance of the criteria of the ideal functional occlusion to ensure a better stability after completion orthodontic treatment will be discussed in detail in this paper. In addition, some clinical situations in which localized adjustments are indicated for occlusal refinement will be described.

PMID: 17639207 [PubMed - indexed for MEDLINE]

Maximal bite force and its association with temporomandibular disorders.

Braz Dent J. 2007;18(1):65-8

Authors: Pereira-Cenci T, Pereira LJ, Cenci MS, Bonachela WC, Del Bel Cury AA

Individuals with temporomandibular disorders (TMD) are expected to have decreased maximum bite forces (MBF). This way, this study compared the MBF in subjects with TMD to a control group and also evaluated its association with age, gender, height and weight. Forty healthy adults with complete natural dentition divided into four groups according to gender and presence or absence of TMD signs/symptoms (based on the Research Diagnostic Criteria RDC) underwent a MBF test with a gnathodynamometer in molar and incisal areas. Statistical analysis was performed by ANOVA and Student-Newman-Keuls test (p=0.05), and the relationship between age, gender, weight, height and MBF was verified by Pearson's correlation test. There were no differences in MBF results between TMD and control groups (p>0.05). Female subjects exhibited lower MBF than male and MBF for the anterior area was lower than that for posterior area (p<0.05). Significant correlation was found between MBF and weight in TMD subjects (p<0.05), except for the anterior area in female subjects. There was a positive correlation between MBF and height in TMD male subjects (p<0.05). Within the limitations of this study, it is possible to conclude that bite force was not affected by TMD. Correlation between MBF and weight in TMD subjects and between MBF and height in TMD male subjects was observed.

PMID: 17639204 [PubMed - indexed for MEDLINE]

Temporomandibular disorders do not correlate with detectable alterations in body posture.

J Contemp Dent Pract. 2007;8(5):60-7

Authors: Perinetti G

AIM: This study aimed to determine if temporomandibular disorders (TMD) correlate with alterations in body posture detectable through posturography. METHODS AND MATERIALS: Thirty-five asymptomatic subjects and 35 TMD patients (34 males and 36 females; mean age, 27.7+/-8.6 years) constituted the matched control and TMD groups, respectively. Posturography was performed under four different experimental conditions: (a) eyes open with mandibular rest position (Eyes Open RP); (b) eyes open with dental occlusion (Eyes Open DO); (c) eyes closed with mandibular rest position (Eyes Closed RP); and (d) eyes closed with dental occlusion (Eyes Closed DO). The X, Y, and absolute centre of pressure displacements from the projection of a theoretical barycentre and the sway area, sway length, and sway velocity were recorded as static and dynamic posturographic parameters, respectively. RESULTS: Generally, no differences were found in any of these parameters between the groups and between the RP and DO within either Eyes Open/Closed conditions. The only differences were found under Eyes Closed as compared to Eyes Open, irrespective of the RP/DO conditions for dynamic and not for static posturographic parameters. CONCLUSION: This study failed to show detectable alterations in body posture in TMD patients.

PMID: 17618331 [PubMed - indexed for MEDLINE]

Pressure from the lips and the tongue in children with class III malocclusion.

J Zhejiang Univ Sci B. 2007 May;8(5):296-301

Authors: Ruan WH, Su JM, Ye XW

OBJECTIVE: To discuss possible relationships between class III malocclusion and perioral forces by measuring the pressure from the lips and the tongue of children with class III malocclusion. METHODS: Thirty-one children with class III malocclusion were investigated and their perioral forces were measured at rest and during swallowing under natural head position by a custom-made miniperioral force computer measuring system. RESULTS: The resting pressures exerted on the labial side and palatine side of the upper left incisor, as well as the labial side and lingual side of the lower left incisor, were 0 g/cm(2), 0 g/cm(2), 0.57 g/cm(2) and 0.23 g/cm(2), respectively. Correspondingly, the swallowing forces were 2.87 g/cm(2), 5.97 g/cm(2), 4.09 g/cm(2) and 7.89 g/cm(2), respectively. No statistical difference between muscular pressure and gender existed. During swallowing, the lingual forces were significantly higher than the labial forces (P<0.01), however, at rest there was no significantly different force between these two sides. Compared to the normal occlusion patients, children with class III malocclusion had lower perioral forces. The upper labial resting forces (P<0.01), the lower labial resting forces (P<0.05) and all the swallowing pressures from the lips and the tongue (P<0.01) showed statistical differences between the two different occlusion conditions. Meanwhile, no significant difference was found for the resting pressure from the tongue between class III malocclusion and normal occlusion. CONCLUSION: Patients with class III malocclusion have lower perioral forces and this muscle hypofunction may be secondary to the spatial relations of the jaws. The findings support the spatial matrix hypothesis.

PMID: 17542055 [PubMed - indexed for MEDLINE]

The hierarchy of stability and predictability in orthognathic surgery with rigid fixation: an update and extension.

Head Face Med. 2007;3:21

Authors: Proffit WR, Turvey TA, Phillips C

A hierarchy of stability exists among the types of surgical movements that are possible with orthognathic surgery. This report updates the hierarchy, focusing on comparison of the stability of procedures when rigid fixation is used. Two procedures not previously placed in the hierarchy now are included: correction of asymmetry is stable with rigid fixation and repositioning of the chin also is very stable. During the first post-surgical year, surgical movements in patients treated for Class II/long face problems tend to be more stable than those treated for Class III problems. Clinically relevant changes (more than 2 mm) occur in a surprisingly large percentage of orthognathic surgery patients from one to five years post-treatment, after surgical healing is complete. During the first post-surgical year, patients treated for Class II/long face problems are more stable than those treated for Class III problems; from one to five years post-treatment, some patients in both groups experience skeletal change, but the Class III patients then are more stable than the Class II/long face patients. Fewer patients exhibit long-term changes in the dental occlusion than skeletal changes, because the dentition usually adapts to the skeletal change.

PMID: 17470277 [PubMed]

A controlled clinical trial of the effects of the Twin Block and Dynamax appliances on the hard and soft tissues.

Eur J Orthod. 2007 Jun;29(3):272-82

Authors: Lee RT, Kyi CS, Mack GJ

The aim of this controlled trial was to identify and quantify skeletal, soft tissue and dental changes during treatment, and immediately post-treatment with Twin Block (TB) or Dynamax appliance using the techniques of three-dimensional (3D)optical surface laser scanning, cephalometric, and clinical measurements. Sixty-two Caucasian subjects, 36 males aged 11-14 years and 26 females aged 10-13 years were enrolled in the study. The patients were placed in two groups, matched for gender and age and subsequently allocated randomly for treatment with either a TB or Dynamax appliance. Active treatment lasted 9 months followed by 3 months' post-treatment observation. Laser scanning and clinical measurements were taken at 3-monthly intervals and final cephalometric records after 12 months. Statistical analysis was performed using Wilcoxon's matched-pairs signed-rank tests. The non-compliance rates were the same for both groups (9 per cent), but a greater incidence of breakages was found in the Dynamax group. The TB was found to produce slightly more antero-posterior skeletal change, median ANB reduction, TB=2 degrees, Dynamax 1.1 degree (P=0.006), and similar forward movements of the chin and was associated with larger increases in the vertical facial dimension, median total anterior face height increase; TB=3.2 mm, Dynamax = 2.8 mm (P=0.03). The soft tissue vertical cephalometric increases were 3.6 mm with the TB, 2.0 mm with the Dynamax (P=0.036), and with laser scanning 5.05 and 2.6 mm, respectively, a difference which is likely to be more clinically relevant. The median post-treatment changes in soft tissue pogonion were -0.65 mm in the TB and +0.22 mm in the Dynamax group. The optical surface scanning mark and measure system is a valid method for quantifying soft tissue changes.

PMID: 17456506 [PubMed - indexed for MEDLINE]

Modulation of mandibular loading and bite force in mammals during mastication.

J Exp Biol. 2007 Mar;210(Pt 6):1046-63

Authors: Ross CF, Dharia R, Herring SW, Hylander WL, Liu ZJ, Rafferty KL, Ravosa MJ, Williams SH

Modulation of force during mammalian mastication provides insight into force modulation in rhythmic, cyclic behaviors. This study uses in vivo bone strain data from the mandibular corpus to test two hypotheses regarding bite force modulation during rhythmic mastication in mammals: (1) that bite force is modulated by varying the duration of force production, or (2) that bite force is modulated by varying the rate at which force is produced. The data sample consists of rosette strain data from 40 experiments on 11 species of mammals, including six primate genera and four nonprimate species: goats, pigs, horses and alpacas. Bivariate correlation and multiple regression methods are used to assess relationships between maximum (epsilon(1)) and minimum (epsilon(2)) principal strain magnitudes and the following variables: loading time and mean loading rate from 5% of peak to peak strain, unloading time and mean unloading rate from peak to 5% of peak strain, chew cycle duration, and chew duty factor. Bivariate correlations reveal that in the majority of experiments strain magnitudes are significantly (P<0.001) correlated with strain loading and unloading rates and not with strain loading and unloading times. In those cases when strain magnitudes are also correlated with loading times, strain magnitudes are more highly correlated with loading rate than loading time. Multiple regression analyses reveal that variation in strain magnitude is best explained by variation in loading rate. Loading time and related temporal variables (such as overall chew cycle time and chew duty factor) do not explain significant amounts of additional variance. Few and only weak correlations were found between strain magnitude and chew cycle time and chew duty factor. These data suggest that bite force modulation during rhythmic mastication in mammals is mainly achieved by modulating the rate at which force is generated within a chew cycle, and less so by varying temporal parameters. Rate modulation rather than time modulation may allow rhythmic mastication to proceed at a relatively constant frequency, simplifying motor control computation.

PMID: 17337717 [PubMed - indexed for MEDLINE]

Pushing the limit: masticatory stress and adaptive plasticity in mammalian craniomandibular joints.

J Exp Biol. 2007 Feb;210(Pt 4):628-41

Authors: Ravosa MJ, Kunwar R, Stock SR, Stack MS

Excessive, repetitive and altered loading have been implicated in the initiation of a series of soft- and hard-tissue responses or ;functional adaptations' of masticatory and locomotor elements. Such adaptive plasticity in tissue types appears designed to maintain a sufficient safety factor, and thus the integrity of given element or system, for a predominant loading environment(s). Employing a mammalian species for which considerable in vivo data on masticatory behaviors are available, genetically similar domestic white rabbits were raised on diets of different mechanical properties so as to develop an experimental model of joint function in a normal range of physiological loads. These integrative experiments are used to unravel the dynamic inter-relationships among mechanical loading, tissue adaptive plasticity, norms of reaction and performance in two cranial joint systems: the mandibular symphysis and temporomandibular joint (TMJ). Here, we argue that a critical component of current and future research on adaptive plasticity in the skull, and especially cranial joints, should employ a multifaceted characterization of a functional system, one that incorporates data on myriad tissues so as to evaluate the role of altered load versus differential tissue response on the anatomical, cellular and molecular processes that contribute to the strength of such composite structures. Our study also suggests that the short-term duration of earlier analyses of cranial joint tissues may offer a limited notion of the complex process of developmental plasticity, especially as it relates to the effects of long-term variation in mechanical loads, when a joint is increasingly characterized by adaptive and degradative changes in tissue structure and composition. Indeed, it is likely that a component of the adaptive increases in rabbit TMJ and symphyseal proportions and biomineralization represent a compensatory mechanism to cartilage degradation that serves to maintain the overall functional integrity of each joint system. Therefore, while variation in cranial joint anatomy and performance among sister taxa is, in part, an epiphenomenon of interspecific differences in diet-induced masticatory stresses characterizing the individual ontogenies of the members of a species, this behavioral signal may be increasingly mitigated in over-loaded and perhaps older organisms by the interplay between adaptive and degradative tissue responses.

PMID: 17267649 [PubMed - indexed for MEDLINE]

No trade-off between biting and suction feeding performance in clariid catfishes.

J Exp Biol. 2007 Jan;210(Pt 1):27-36

Authors: Van Wassenbergh S, Herrel A, Adriaens D, Aerts P

It is generally assumed that biting performance trades off with suction performance in fish because both feeding types may place conflicting demands on the cranial musculo-skeletal system. However, the functional consequences of morphological adaptations enhancing biting on the mechanics and performance of suction feeding in fish remain obscure. In this study, suction feeding performance was compared between three clariid catfish species differing considerably in their biting capacity, by measuring the velocity of a standardized prey being sucked into the buccal cavity using high-speed cineradiography. In addition, buccal volume changes during prey capture were quantified by ellipse modelling. As all species were able to accelerate the prey to similar peak velocities, our results demonstrate the possibility for catfishes to increase bite performance considerably without compromising suction performance. The amount of buccal expansion in the ventral direction is approximately equal for all species. Consequently, the system generating expansion through ventral rotation of the lower jaw, hyoid and pectoral girdle is apparently not constrained (mechanically or architectonically) by the hypertrophy of the jaw adductors. As the effect of a reduced magnitude of lateral expansion (suspensorium abduction) on suction performance in Clariidae appears to be negligible (for example in Gymnallabes typus), these data demonstrate the dominant role of ventral expansion for producing suction in these fish.

PMID: 17170145 [PubMed - indexed for MEDLINE]

Bilateral TMJ disk displacement induces mandibular retrognathia.

J Dent Res. 2006 Dec;85(12):1118-23

Authors: Bryndahl F, Eriksson L, Legrell PE, Isberg A

Unilateral non-reducing TMJ disk displacement has been shown to retard mandibular growth on the ipsilateral side, with facial asymmetry a sequela. We hypothesized that bilateral affliction would impair mandibular growth bilaterally, generating mandibular retrognathia. Non-reducing TMJ disk displacement was surgically created in 10 growing New Zealand White rabbits. Ten additional rabbits served as a sham-operated control group. Facial growth was followed in serial cephalograms, with tantalum implants, during a period corresponding to childhood and adolescence in man. The results verified that bilateral non-reducing TMJ disk displacement retarded mandibular growth bilaterally, the extent corresponding to mandibular retrognathia in man. Maxillary growth was also retarded, but to a lesser degree. Growth impairment fluctuated over time, the most striking retardation occurring during periods of general growth acceleration. This should be taken into consideration when orthodontic treatment, aimed at stimulating mandibular growth, is initiated in adolescent individuals with non-reducing TMJ disk displacement.

PMID: 17122165 [PubMed - indexed for MEDLINE]

Influence of alveolar support on stress in periodontal structures.

J Dent Res. 2006 Dec;85(12):1087-91

Authors: Ona M, Wakabayashi N

The influence of alveolar bone support on the functional capability of a tooth remains unclear. It was hypothesized that a reduction in alveolar support causes an increase of maximum stress in the periodontal structures. Mathematical models of the maxillary incisor to simulate in vivo tooth movement were constructed with periodontium of normal or reduced bone height, and normal or widened periodontal ligament (PDL) space. Under simulated bite force, the maximum tensile stress at the lingual cervical region in the PDL increased with bone height reduction, but decreased with PDL widening. The compressive stress at the cervical region in the cortical bone was no more than 22% of the yield strength of bone, and did not increase by the height reduction with widened PDL. The result suggests that the height reduction potentially causes mechanical damage to the PDL, but, of itself, is not likely to have a negative effect on the bone.

PMID: 17122159 [PubMed - indexed for MEDLINE]

Anterior open bite treated with a palatal crib and high-pull chin cup therapy. A prospective randomized study.

Eur J Orthod. 2006 Dec;28(6):610-7

Authors: Torres F, Almeida RR, de Almeida MR, Almeida-Pedrin RR, Pedrin F, Henriques JF

The aim of this prospective randomized clinical study was to cephalometrically investigate the dentoalveolar and soft tissue changes produced by a removable appliance with a palatal crib associated with high-pull chin cup therapy in children with an Angle Class I anterior open bite (AOB) malocclusion. Thirty children (8 males and 22 females) with an initial mean age of 8.3 years and a mean AOB of 4.1 mm were treated with a removable appliance composed of a palatal crib associated with chin cup therapy for 12 months. A control group of 30 individuals (7 males and 23 females) closely matched for age, initial mean age 8.6 years, gender, and ethnicity with a mean AOB of 4.6 mm was followed without treatment. The measurements (means and standard deviations) were statistically analysed using a paired t-test. The results showed no significant differences in the level of molar eruption or in lower anterior face height, suggesting that the vertical control expected from the chin cup therapy did not occur. Dentoalveolar changes at the anterior region were evident, with statistically significant extrusion, retrusion, and lingual tipping of the maxillary and mandibular incisors (P < or = 0.05). However, these hard tissue changes did not imply soft tissue changes and the variables related to the soft profile were not statistically significantly different between the groups. The dentoalveolar changes at the anterior region of the dental arches were mainly responsible for closure of the AOB in patients treated in the mixed dentition.

PMID: 17101701 [PubMed - indexed for MEDLINE]

Autonomic cardiac modulation in obstructive sleep apnea: effect of an oral jaw-positioning appliance.

Chest. 2006 Nov;130(5):1362-8

Authors: Coruzzi P, Gualerzi M, Bernkopf E, Brambilla L, Brambilla V, Broia V, Lombardi C, Parati G

BACKGROUND: Patients with obstructive sleep apnea (OSA) are characterized by deranged cardiovascular variability, a well-established marker of cardiovascular risk. While long-term treatment with continuous positive airway pressure leads to a significant improvement of cardiovascular variability, little is known of the possibility of achieving the same results with other therapeutic approaches. The aim of our study was to investigate the responses of autonomic indexes of neural cardiac control to another type of OSA treatment based on an oral jaw-positioning appliance. METHODS: In 10 otherwise healthy subjects with OSA (OSA+) and in 10 subjects without OSA (OSA-) we measured heart rate, BP, and indices of autonomic cardiac regulation derived from time-domain and spectral analysis of R-R interval (RRI), before and after 3 months of treatment with the oral device. High-frequency (HF) power of RRI was taken as an index of parasympathetic cardiac modulation, and the ratio between low-frequency (LF) and HF RRI powers as an indirect marker of the balance between sympathetic and parasympathetic cardiac modulation. RESULTS: At baseline, in comparison with OSA- subjects, OSA+ subjects displayed a significantly lower RRI variance (p < 0.02) and reduced HF RRI powers (p < 0.001). After 3 months of treatment with the oral device, the OSA+ group showed a marked reduction in apnea-hypopnea index (p < 0.001), a lengthening in RRI and a significant increase in its variance (p < 0,02), an increased HF RRI power (from 134 +/- 26 to 502 +/- 48 ms2, p < 0.001), and a reduction in LF/HF RRI power ratio (from 3.11 +/- 0.8 to 1.5 +/- 0.5). As a result of these changes, after the 3-month treatment there were no more significant differences between the two groups in these parameters. In both OSA+ and OSA- groups, body weight, heart rate, and BP did not change over time. CONCLUSIONS: Three months of treatment with a specific oral jaw-positioning appliance improves cardiac autonomic modulation in otherwise healthy patients with OSA of mild degree.

PMID: 17099011 [PubMed - indexed for MEDLINE]

Implant therapy versus endodontic therapy.

J Am Dent Assoc. 2006 Oct;137(10):1440-3

Authors: Christensen GJ

PMID: 17012725 [PubMed - indexed for MEDLINE]

Is there an association between occlusion and periodontal destruction?: Only in limited circumstances does occlusal force contribute to periodontal disease progression.

J Am Dent Assoc. 2006 Oct;137(10):1381, 1383, 1385 passim

Authors: Deas DE, Mealey BL

PMID: 17012717 [PubMed - indexed for MEDLINE]

Is there an association between occlusion and periodontal destruction?: Yes--occlusal forces can contribute to periodontal destruction.

J Am Dent Assoc. 2006 Oct;137(10):1380, 1382, 1384 passim

Authors: Harrel SK, Nunn ME, Hallmon WW

PMID: 17012716 [PubMed - indexed for MEDLINE]

Functional adaptability of jaw-muscle spindles after bite-raising.

J Dent Res. 2006 Sep;85(9):849-53

Authors: Yabushita T, Zeredo JL, Fujita K, Toda K, Soma K

In a previous experiment, we found that masseter muscle spindles show functional plasticity after 5 to 15 days under increased occlusal vertical dimension (iOVD). In the present study, we hypothesized that spindle function would eventually recover if longer observation periods were allowed. Therefore, in this study we investigated changes in masseter muscle spindle function over periods of 1 day to 8 weeks. Masseter muscle-spindle responses to ramp-and-hold jaw stretches were recorded from the mesencephalic trigeminal nucleus in 35 barbiturate-anesthetized female Wistar rats. The rats were previously divided into Control and iOVD groups, and those in the iOVD group received a 2.0-mm composite resin build-up to the maxillary molars. In this condition, there were no statistically significant differences in masseter muscle spindle sensitivity between Control and iOVD in the six- and eight-week subgroups. Our results further indicate a high degree of adaptability in masseter muscle spindle function following changes in OVD.

PMID: 16931870 [PubMed - indexed for MEDLINE]

Toward understanding human masticatory control: serendipity and a scientific journey.

J Dent Res. 2006 Sep;85(9):801-3

Authors: Miles TS

PMID: 16931860 [PubMed - indexed for MEDLINE]

Normal torque of the buccal surface of mandibular teeth and its relationship with bracket positioning: a study in normal occlusion.

Braz Dent J. 2006;17(2):155-60

Authors: Mestriner MA, Enoki C, Mucha JN

This study evaluated the degree of buccolingual inclination of mandibular tooth crowns relative to torque. For such purpose, mandibular and maxillary stone casts from 31 Caucasian Brazilian adults with normal occlusion, pleasant facial aspect and no history of previous orthodontic treatment were examined. A custom device was developed for measuring the degree of inclination (torque) of bracket slots of orthodontic appliances relative to the occlusion plane, at three bonding height: standard (center of clinical crown), occlusal (0.5 mm occlusally from standard) and cervical (0.5 mm cervically from standard). Except for the mandibular incisors, which presented a small difference in torque from one another (lingual root torque for central incisors and buccal root torque for lateral incisors), the remaining average values are close to those found in the literature. Due to the convexity of the buccal surface, the 1-mm vertical shift of the brackets from occlusal to cervical affected the values corresponding to the normal torque, in approximately 2 degrees in central and lateral incisors, 3 degrees in canines and 8 degrees in premolars and molars.

PMID: 16924345 [PubMed - indexed for MEDLINE]

The treatment of painful temporomandibular joint clicking with oral splints: a randomized clinical trial.

J Am Dent Assoc. 2006 Aug;137(8):1108-14

Authors: Conti PC, dos Santos CN, Kogawa EM, de Castro Ferreira Conti AC, de Araujo Cdos R

BACKGROUND: The authors compared the efficacy of bilateral balanced and canine guidance (occlusal) splints in the treatment of temporomandibular joint (TMJ) pain in subjects who experienced joint clicking with a nonoccluding splint in a double-blind, controlled randomized clinical trial. METHODS: The authors randomly assigned 57 people with signs of disk displacement and TMJ pain into three groups according to the type of splint: bilateral balanced, canine guidance and nonoccluding. The authors followed the groups for six months using analysis of a visual analog scale (VAS), palpation of the TMJ and masticatory muscles, mandibular movements and joint sounds. They used repeated analysis of variance and a chi(2) test to test the hypothesis. RESULTS: The type of guidance used did not influence the pain reduction, yet both occlusal splints were superior to the nonoccluding splint, on the basis of the VAS. Despite similar outcomes in relation to opening, left lateral and protrusive movements, TMJ and muscle pain on palpation, subjects who used the occlusal splints had improved clinical outcomes. The frequency of joint noises decreased over time, with no significant differences among groups. Subjects in the groups using the occlusal splints reported more comfort. CONCLUSION: The type of lateral guidance did not influence the subjects' improvement. All of the subjects had a general improvement on the VAS, though subjects in the occlusal splint groups had better results that did subjects in the nonoccluding splint group.

PMID: 16873326 [PubMed - indexed for MEDLINE]

Occlusion.

J Am Dent Assoc. 2006 Aug;137(8):1070

Authors: Schneider R

PMID: 16873322 [PubMed - indexed for MEDLINE]

More about occlusion.

J Am Dent Assoc. 2006 Aug;137(8):1070, 1072; author reply 1072, 1074

Authors: Bryson RC

PMID: 16873321 [PubMed - indexed for MEDLINE]

Orthognathic surgery for occlusal reconstruction of old malunited jaw fracture.

Kobe J Med Sci. 2006;52(3-4):37-47

Authors: Yokoo S, Komori T, Furudoi S, Shibuya Y, Tateishi C, Hashikawa K, Tahara S, Hanagaki H

Old malunited jaw fractures of nine patients who underwent orthognathic surgery for occlusal reconstruction were clinically evaluated. Early surgery on fractures of the jaw is the optimal treatment when due attention must be paid to occlusion. Since occlusal revision surgery subsequent to inaccurate diagnosis and inappropriate surgery is certainly very difficult and often unsuccessful, surgeons need to pay special attention to this situation.

PMID: 16849871 [PubMed - indexed for MEDLINE]

Percentile curves for food acceptance response scores in assessing chewing functions in adults.

Bull Tokyo Dent Coll. 2005 Nov;46(4):123-34

Authors: Sakurai M, Tada A, Suzuki K, Yoshino K, Sugihara N, Matsukubo T

The purpose of this study was to evaluate whether percentile curves for food acceptance response scores were useful in assessing oral and occlusal conditions. We used data obtained from Chiba City Patient Surveys (males: 1,276, females: 1,381, aged 20 to 64), which were conducted in 1998 and 1999. Subjects were assigned scores of between 1 and 4 for 31 different kinds of food based on their food acceptance responses. Occlusal conditions were measured with pressure-sensitive sheets. We calculated the percentile values from 5 to 95 at intervals of five years. We divided the subjects into two groups at the twenty-fifth percentile and statistically analyzed various oral conditions in the two groups. Significant differences were found between them in the mean numbers of present, sound, and missing teeth for almost all age groups. Moreover, there were significant differences in tooth-contact area and occlusal force between the two groups. The results of multiple regression analysis revealed that the scores had a stronger correlation with occlusal conditions than number of teeth in 55-year-olds, although the effect teeth-factors had on scores was more significant in 45- to 50-year-old males. Females' scores had a stronger correlation with occlusal conditions than number of teeth in all age groups. These results indicate that the questionnaire on the acceptance of 31 different kinds of food is useful in providing a basis for oral health instruction and dental treatment aimed at improving chewing ability in adults.

PMID: 16829711 [PubMed - indexed for MEDLINE]

Primary canine and molar relationships in centric occlusion in three to six year-old Turkish children: a cross-sectional study.

J Contemp Dent Pract. 2006 Jul 1;7(3):59-66

Authors: Yilmaz Y, G&#xFC;rbüz T, Simşek S, Dalmiş A

This cross-sectional study aimed to evaluate the primary canine and the primary molar relationship in 205 (90 girls and 115 boys) three to six year-old Turkish children with the primary dentition in centric occlusion according to gender and age. In terms of the molar relationship, Class I was represented by 88.29% of all children who agreed to participate in the study, followed by Class II (7.31%), and Class III (4.4%). In terms of the canine relationship, Class I was represented by 87.8% of the sample, followed by Class II (7.8%), and Class III (4.4%). A statistically significant difference was found between age and both the canine and molar relationships (p<0.005), and a positive correlation was confirmed among them. However, the difference and correlation between the gender and the canine and molar relationships were not significant.

PMID: 16820808 [PubMed - indexed for MEDLINE]

The effect of periodontal surgery on bite force, occlusal contact area and bite pressure.

J Am Dent Assoc. 2006 Jul;137(7):978-83; quiz 1028

Authors: Alkan A, Keskiner I, Arici S, Sato S

BACKGROUND: Tooth mobility resulting from the loss of periodontal support or trauma induced by periodontal surgery may change the amount of bite force (BF) and bite pressure (BP) and number of occlusal contact areas (OCAs). The aim of the authors' study was to compare BF, BP and OCA of teeth with periodontal disease before and after periodontal surgery with similar values of healthy teeth. METHODS: The authors performed quantitative analysis of BF, BP and OCA using a pressure measurement film. Ten patients with periodontitis who needed periodontal surgery served as the test group. The authors took measurements of BF, BP, OCA and mobility (using Miller's Mobility Index) just before surgery and at one, four and 12 weeks after surgery. They also measured clinical attachment levels (CAL) before surgery and 12 weeks after surgery. Ten subjects without periodontitis served as the control group. RESULTS: Although BF and OCA increased the first week after periodontal surgery, analysis of variance (ANOVA) showed no statistically significant differences at a 95 percent confidence interval. There were statistically significant differences between first-week mobility and that at four and 12 weeks (P = .001). A factorial ANOVA showed significant interaction between BF and mobility (P < .05). CONCLUSIONS: The authors' findings suggest that changes in BF, BP and OCA were not affected by periodontal surgery. However, mean mobility values and BF are correlated. Further investigations of this measurement method involving larger study populations and a longer follow-up period are needed. CLINICAL IMPLICATIONS: It seems to be helpful to follow occlusal changes after periodontal surgery using a pressure measurement film. It also may be suggested that this measurement method could be used to evaluate the treatment prognosis.

PMID: 16803824 [PubMed - indexed for MEDLINE]

Mandibular biomechanics and development of the human chin.

J Dent Res. 2006 Jul;85(7):638-42

Authors: Ichim I, Swain M, Kieser JA

The development of the chin, a feature unique to humans, suggests a close functional linkage between jaw biomechanics and symphyseal architecture. The present study tests the hypothesis that the presence of a chin changes strain patterns in the loaded mandible. Using an anatomically correct 3-D model of a dentate mandible derived from a CT scan image, we analyzed strain patterns during incisal and molar biting. We then constructed a second mandible, without a chin, by 'defeaturing' the first model. Strain patterns of the second model were then compared and contrasted to the first. Our main finding was that chinned and non-chinned mandibles follow closely concordant patterns of strain distribution. The results suggest that the development of the human chin is unrelated to the demands placed on the mandible during function.

PMID: 16798865 [PubMed - indexed for MEDLINE]

Pharyngeal airway changes following mandibular setback surgery.

Indian J Dent Res. 2005 Oct-Dec;16(4):147-50

Authors: Ramesh BV, Vinod N, Murugesan K

Treatment of dentofacial deformities with jaw osteotomies has an effect on airway anatomy and therefore mandibular setback surgery has the potential to diminish airway size. The purpose of this study was to evaluate the effect of mandibular setback surgery on airway size. 8 consecutive patients were examined prospectively. All patients underwent mandibular setback surgery. Cephalometric analysis was performed preoperatively and 3 months post operatively with particular attention to pharyngeal airway changes. Pharyngeal airway size decreased considerably in all, patients thus predisposing to development of obstructive sleep apnea. Therefore, large anteroposterior discrepancies should be corrected by combined maxillary and mandibular osteotomies.

PMID: 16761707 [PubMed - indexed for MEDLINE]

The business of occlusion.

J Am Dent Assoc. 2006 May;137(5):666-7

Authors: Spear FM

PMID: 16739548 [PubMed - indexed for MEDLINE]

Size and orientation of masticatory muscles in patients with mandibular laterognathism.

J Dent Res. 2006 Jun;85(6):552-6

Authors: Goto TK, Nishida S, Yahagi M, Langenbach GE, Nakamura Y, Tokumori K, Sakai S, Yabuuchi H, Yoshiura K

Size measurements of jaw muscles reflect their force capabilities and correlate with facial morphology. Using MRI, we examined the size and orientation of jaw muscles in patients with mandibular laterognathism in comparison with a control group. We hypothesized that the muscles of the deviated side would be smaller than those of the non-deviated side, and that the muscles of both sides would be smaller than in controls. In patients, a comparison of deviated and non-deviated sides showed, in orientation, differences for masseter and medial pterygoid muscles, but, in size, differences only for the masseter muscle. Nevertheless, muscle sizes in patients were much smaller than in controls. Lateral displacement of the mandible can explain the orientation differences, but not the smaller muscle size, in patients. It is possible that the laterodeviation initiates an adaptive process in the entire jaw system, resulting in extensive atrophy of the jaw muscles.

PMID: 16723654 [PubMed - indexed for MEDLINE]

Effect of texture of plastic and elastic model foods on the parameters of mastication.

J Neurophysiol. 2006 Jun;95(6):3469-79

Authors: Foster KD, Woda A, Peyron MA

Mastication is continually modified throughout the chewing sequence in response to the texture of the food. The aim of this work was to compare the effects of an increase in hardness of two model food types, presenting either elastic or plastic rheological properties, on mastication. Each model food type consisted of four products of different hardness. Sensory testing experiments conducted with one group of 14 subjects showed significant perceived differences between products in terms of their increasing hardness. Fifteen other volunteers were asked to chew three replicates of each elastic and plastic product during two sessions. EMGs of masseter and temporalis muscles were recorded simultaneously with jaw movement during chewing. Numerous variables were analyzed from these masticatory recordings. Multiple linear regression analyses were used to assess the respective effects of food hardness and rheological properties on variables characterizing either the whole masticatory sequence or different stages of the sequence. Muscle activities were significantly affected by an increase in hardness regardless of the food type, whereas the shape of the cycles depended on the rheological properties. The masticatory frequency was affected by hardness at the initial stage of the sequence but overall frequency adaptation was better explained by a change in rheological behavior, with plastic products being chewed at a slower frequency. A dual hypothesis was proposed, implicating first a cortical-brain stem preprogrammed mechanism to adapt the shape of the jaw movements to the rheological properties of the food, and second, a brain stem mechanism with mainly sensory feedback from the mouth to adapt muscle force to the food hardness.

PMID: 16709719 [PubMed - indexed for MEDLINE]

The change of stress distribution on the condyle after mandibular setback surgery.

Eur J Orthod. 2006 Oct;28(5):433-9

Authors: Ueki K, Nakagawa K, Takatsuka S, Yamamoto E

The rigid-body spring model (RBSM) theory was incorporated into a model as a discrete method for analysing problems of limit, such as the stress distribution on the condyle. The purpose of this study was to evaluate the two-dimensional RBSM for determining stress on the temporomandibular joint (TMJ) in patients after orthognathic surgery. Thirty-two patients (five males and 27 females, mean age 21.4 +/- 4.9 years) with mandibular prognathism underwent bilateral sagittal split ramus osteotomy (SSRO) and setback; 48 subjects were recruited as controls. Anatomical landmarks were traced from pre- and post-operative lateral cephalograms and the information was processed using the Fortran analysis program. The force vector on the condyle, its degree, its direction, and the displacement co-ordinates (x, y) and rotation (theta) at the gonial angle were calculated. When muscular power was assumed to be 1, the post-operative degree of the force vector was higher than the pre-operative value (P < 0.05). The X co-ordinate, x, and rotation, theta, of the displacement vector in the pre-operative patients with mandibular prognathism were significantly higher than those in the control subjects (P < 0.05). There were still significant differences between the displacement values post-operatively between the patients and controls (P < 0.05). The results suggest that the degree and direction of the force vector and the resulting displacement co-ordinates can be used as parameters in a surgical model. The RBSM may also be useful in evaluating the pre- and post-operative skeletal morphology of jaw deformities.

PMID: 16679326 [PubMed - indexed for MEDLINE]

Evaluation of the centroid method of occlusion for studying mandibular and maxillary growth.

Eur J Orthod. 2006 Aug;28(4):345-51

Authors: Murata S, Nakamura S, Nagahara K

The aim of this study was to evaluate the centroid method of occlusion for studying mandibular growth and development. This novel technique comparatively expresses the direction of growth of the maxilla and mandible as a single unit. The centroid 'G' was geometrically calculated from the triangle Deltaabc, which comprised the palatal, articulare-gnathion (Ar-Gn), and A-B planes. The plane angles and positional relationship of the centroid with the upper first molar was investigated, focusing on differences between genders and malocclusions. Lateral cephalograms were obtained of 26 males and 51 females with a 'normal' Class I occlusion, 216 females with a Class III incisor relationship, and 230 females, all aged >18 years, with a Class II incisor relationship. Bolton standards and Sakamoto's data were used to determine changes in the angle of the palatal plane to the Ar-Gn plane. Non-significant levels of variation were observed in the angle of the palatal plane to the Ar-Gn plane during the developmental period from childhood to adulthood. Among Class I adult subjects, Deltaabc was similar between genders and the centroid G was located near the occlusal surface of the upper first molar. There was no difference in the area of Deltaabc between malocclusion types. The positional relationship of the centroid G with the upper first molar revealed a shift of the centroid mesially and cervically during the transition from Class III to Class I to Class II. These findings indicate that the centroid method can contribute to orthopaedic diagnosis and the planning of treatment strategies.

PMID: 16644852 [PubMed - indexed for MEDLINE]

Centric relation: A historical and contemporary orthodontic perspective.

J Am Dent Assoc. 2006 Apr;137(4):494-501

Authors: Rinchuse DJ, Kandasamy S

BACKGROUND: Centric relation (CR) has been a controversial subject in dentistry for more than a century. For at least the past four decades, issues involving CR have been of interest to orthodontists. The definition of CR has changed over the past half-century from a retruded, posterior and, for the most part, superior condyle position to an anterior-superior condyle position. TYPE OF STUDIES REVIEWED: The authors addressed the historical and contemporary orthodontic perspective of CR. The source material for this review came mainly from literature and searches the lead author accumulated over the last 30 years. As there is no evidence-based (EB) model level 3 (systemic) review on the topic of CR, the best evidence on this subject was gleaned only from a thorough examination and evaluation at EB model level 2 (experience plus best available sample studies). There was, however, enough high-quality EB model level 2 information on the topic of CR for the authors to draw conclusions on the basis of a scientific appraisal of relevant research. RESULTS: Although the reliability of CR records has been substantiated, the records' validity has little to no evidentiary support. In addition, population-based sample studies and consensus statements from national conferences support the view that the positions of the temporomandibular joint (TMJ) condyles in relation to the glenoid fossa or CR position are not diagnostic of temporomandiblar disorders. There appears to be little to no benefit of using gnathologic records and articulator-mounted dental casts to discern discrepancies in maximum intercuspation of the teeth coincident with TMJ condyles in an anterior-superior CR position in orthodontic patients. CLINICAL IMPLICATIONS: The benefit of using gnathologic CR records and articulators in orthodontics has not been substantiated by scientific evidence.

PMID: 16637479 [PubMed - indexed for MEDLINE]

Cyclical tensile force on periodontal ligament cells inhibits osteoclastogenesis through OPG induction.

J Dent Res. 2006 May;85(5):457-62

Authors: Kanzaki H, Chiba M, Sato A, Miyagawa A, Arai K, Nukatsuka S, Mitani H

The periodontal ligament (PDL) maintains homeostasis of periodontal tissue under mechanical tensile-loading caused by mastication. Occlusal load inhibits atrophic alveolar bone resorption. Previously, we discovered that continuous compressive force on PDL cells induced osteoclastogenesis-supporting activity, with up-regulation of RANKL. We hypothesized that, unlike compression, cyclical tensile force up-regulates OPG expression in PDL cells via TGF-beta up-regulation, and does not induce osteoclastogenesis-supporting activity. PDL cells were mechanically stimulated by cyclical tensile force in vitro. The conditioned media of PDL cells that had been subjected to cyclical tensile force inhibited osteoclastogenesis. Cyclical tensile force up-regulated not only RANKL mRNA expression, but also OPG mRNA expression in PDL cells. Tensile force up-regulated TGF-beta expression in PDL cells as well. Administration of neutralizing antibodies to TGF-beta inhibited OPG up-regulation under cyclical tensile-force stimulation in a dose-dependent manner. Additionally, the osteoclastogenesis-inhibitory effect of the conditioned media of PDL cells under cyclical tensile force was partially rescued by the administration of TGF-beta neutralizing antibodies. In conclusion, tensile force inhibited the osteoclastogenesis-supporting activity of PDL cells by inducing the up-regulation of OPG via TGF-beta stimulation.

PMID: 16632761 [PubMed - indexed for MEDLINE]

Model surgery technique for Le Fort I osteotomy--alteration in occlusal plane associated with upward transposition of posterior maxilla.

Bull Tokyo Dent Coll. 2005 Aug;46(3):67-78

Authors: Yosano A, Yamamoto M, Shouno T, Shiiki S, Hamase M, Kasahara K, Takaki T, Takano N, Uchiyama T, Shibahara T

It is difficult to translate analytical values into accurate model surgery by traditional methods, especially when moving the posterior maxilla. This is because cephalometric radiographic analysis generated information on movement of the posterior nasal spine (PNS) can not be recreated in model surgery. Therefore, we propose a method that accurately reflects such analysis and simulation of movement using Quick Ceph 2000 (Orthodontic Processing Corporation, USA). This will allow the enrichment of model surgery prior to actual surgery in cases where upward movement of the posterior maxilla is involved. All patients who participated in this study had skeletal mandibular prognathism characterized by a small occlusal plane angle in respect to the S-N plane. Cephalometric radiographs were taken and analyzed with the Quick Ceph 2000. Pre- and post-surgical evaluations were performed using Sassouni arc analysis and Ricketts analysis. Prior to transposition, we then prepared an anterior occlusal bite record on a model mounted on an articulator. This bite was then used as a reference when the molar parts were to be transposed upwards. The use of a occlusal bite permitted an accurate translation of the preoperative computer simulation into model surgery, thus facilitating favorable surgical results.

PMID: 16598183 [PubMed - indexed for MEDLINE]

Long term results of mandibular distraction.

J Indian Soc Pedod Prev Dent. 2006 Mar;24(1):30-9

Authors: Batra P, Ryan FS, Witherow H, Calvert ML

Mandibular distraction osteogenesis has become a popular surgical modality due to its many advantages over conventional orthognathic surgical procedures. However, in spite of the technique having been used for over 15 years, no concrete long term results are available regarding the stability of results. We discuss the various studies which have reported either in favour or against the stablility of results after distraction. We report a series of 6 cases (3 unilateral and 3 bilateral distraction) where distraction was carried out before puberty and followed them up to seven years after removal of distractors. This case series shows that results achieved by distraction osteogenesis are unstable or best unpredictable with respect to producing a permanent size increase in the mandible. The role of the distraction osteogenesis in overcoming the pterygomassetric sling is questionable. We suggest a multicenter study with adequate patient numbers treated with a similar protocol and documented after growth cessation to have meaningful conclusions on the debate of distraction osteogenesis versus orthognathic surgery.

PMID: 16582529 [PubMed - indexed for MEDLINE]

Mandibular mechanics following osteotomy and appliance placement II: Bone strain on the body and condylar neck.

J Oral Maxillofac Surg. 2006 Apr;64(4):620-7

Authors: Rafferty KL, Sun Z, Egbert MA, Baird EE, Herring SW

PURPOSE: The purpose of this investigation was to determine if the mechanical environment of the mandible is changed by osteotomy and fixation, as assessed by the measurement of bone strain on the condylar neck and mandibular corpus. MATERIALS AND METHODS: Immediately following unilateral mandibular osteotomy and distractor placement, strain gauges were attached directly to the corpus and condylar neck in a sample of domestic pigs. Bone strains were recorded during mastication and muscle stimulation. Comparisons of principal strain magnitudes and orientations were made between sides and between the osteotomy sample and a control database. RESULTS: The animals preferred to chew on the non-osteotomy side. Corpus strains were higher for osteotomy-side chewing but were comparable to the control database, regardless of chewing side. For the condyle, compared with the control database and the non-osteotomy side, the osteotomy side was underloaded in compression. Furthermore, the orientation of compressive strain was highly variable and more horizontally oriented than that of control and non-osteotomy condyles. Stimulation of the masseter and medial pterygoid loaded the mandible to normal levels. CONCLUSION: Masticatory behavior was altered, probably as a combined result of disruption of the occlusion, changes in muscle recruitment, and probable loss of sensory feedback. However, neither these changes nor damage to the muscles explain the decrease and reorientation of compressive strain on the condylar neck. Alternatively, the modified strain pattern could have arisen from positional instability of the proximal bone fragment.

PMID: 16546641 [PubMed - indexed for MEDLINE]

Mandibular mechanics after osteotomy and distraction appliance placement I: Postoperative mobility of the osteotomy site.

J Oral Maxillofac Surg. 2006 Apr;64(4):610-9

Authors: Sun Z, Rafferty KL, Egbert MA, Herring SW

PURPOSE: Fixation at the osteotomy site for mandibular distraction osteogenesis (DO) is probably not rigid, especially during mastication. Micromotion may affect the course of DO. This study aimed to measure the mobility of the fresh distractor-fixed osteotomy site in response to mastication and masticatory muscle stimulation. MATERIALS AND METHODS: Twenty-eight domestic pigs, 6 to 8 weeks old, underwent osteotomy of the right mandible and placement of a distractor appliance. Immediately after surgery, displacement at 3 different locations (superior-lateral, inferior-lateral, and inferior-medial) of the osteotomy site was assessed using ultrasound piezoelectric crystals or differential variable reluctance transducers (DVRTs). The amount of lengthening or shortening at each location was measured during mastication and muscle stimulation. Displacement was also measured for bilateral osteotomy during muscle stimulation from a subgroup of 12 pigs. RESULTS: The osteotomy site demonstrated significant mobility during power strokes of mastication with an average magnitude of 0.3 to 0.4 mm. Distinct patterns of displacement were associated with different locations, and the patterns varied between chewing sides. The most common pattern was lengthening at the superior-lateral and shortening at both inferior sites. Similar amounts of displacement were observed during the stimulation of jaw-closers (masseter and medial pterygoid), but the patterns produced by these muscles did not completely explain the masticatory pattern. Opening the osteotomy to 1.5 mm did not alter the displacements observed during muscle stimulation. Bilateral osteotomy tended to decrease displacement. CONCLUSIONS: The study demonstrates that during mastication and masticatory muscle stimulation, an acute mandibular osteotomy site is mobile despite fixation by a distractor appliance.

PMID: 16546640 [PubMed - indexed for MEDLINE]

Interdisciplinary management of anterior dental esthetics.

J Am Dent Assoc. 2006 Feb;137(2):160-9

Authors: Spear FM, Kokich VG, Mathews DP

BACKGROUND: Dental esthetics has become a popular topic among all disciplines in dentistry. When a makeover is planned for the esthetic appearance of a patient's teeth, the clinician must have a logical diagnostic approach that results in the appropriate treatment plan. With some patients, the restorative dentist cannot accomplish the correction alone but may require the assistance of other dental disciplines. APPROACH: This article describes an interdisciplinary approach to the diagnosis and management of anterior dental esthetics. The authors practice different disciplines in dentistry: restorative care, orthodontics and periodontics. However, for more than 20 years, this team has participated in an interdisciplinary dental study group that focuses on a wide variety of dental problems. One such area has been the analysis of anterior dental esthetic problems requiring interdisciplinary correction. This article will describe a unique approach to interdisciplinary dental diagnosis, beginning with esthetics but encompassing structure, function and biology to achieve an optimal result. CLINICAL IMPLICATIONS: If a clinician uses an esthetically based approach to the diagnosis of anterior dental problems, then the outcome of the esthetic treatment plan will be enhanced without sacrificing the structural, functional and biological aspects of the patient's dentition.

PMID: 16521381 [PubMed - indexed for MEDLINE]

Post-treatment development of the curve of Spee.

Eur J Orthod. 2006 Jun;28(3):262-8

Authors: Lie F, Kuitert R, Zentner A

The aim of this study was to investigate the post-treatment development of the curve of Spee (CS) and to predict its post-treatment stability on the basis of cephalometric parameters. Lateral cephalograms and study models of 135 subjects (50 males and 85 females) were taken before orthodontic treatment (T1; 12.0 +/- 1.5 years), at the end of orthodontic treatment (T2; 14.6 +/- 1.5 years), and at least 3 years out of retention (T3; 26.6 +/- 5.0 years); the curve depth (CD), location of the deepest point (LDP) of the curve, and eight cephalometric parameters were assessed. The sample was divided into a treated and an untreated lower arch group. The upper arch was treated in all patients. The sample consisted of 25 per cent Class I, 73 per cent Class II, and 2 per cent Class-III-treated malocclusions. The results showed that the post-treatment CD was frequently unstable and unexpected changes were relatively common. The LDP was displaced distally during T1-T2 and showed mesial relocation during T2-T3. Assessment of potential predictors of the post-treatment changes in CD and LDP using stepwise regression analysis showed that a deep curve at T2 was associated with a decrease of the CD during T2-T3. A combination of distal location of the LDP with proclination of the lower incisors at T2 and extraction treatment was associated with mesial relocation of the LDP during T2-T3. The results also suggest that an optimal CD of about 2.0 mm at T2 was associated with the least amount of post-treatment change.

PMID: 16495374 [PubMed - indexed for MEDLINE]

Cephalometric correction factors for bite opening--a dry skull study.

Eur J Orthod. 2006 Aug;28(4):378-82

Authors: Lam E, Quick AN, Herbison P

The lateral cephalometric radiograph supplies the clinician with valuable information regarding the facial skeletal morphology of the patient, provided that it is taken correctly. These radiographs should be taken while the patient is occluding in maximum intercuspation, failing which the exposure is often repeated, leading to an increase in patient radiation dose as well as added cost in time and materials. This study investigated the relationship between limited bite opening and selected cephalometric variables. Thirty-one dry skulls were used and five splints were constructed for each skull giving increments of bite opening from 0 to 5 mm. Six lateral radiographs per skull were taken at each increment of bite opening. The radiographs were traced and the points plotted using a reflex metrograph. A linear relationship was found between bite opening and SNB, ANB, SN-mandibular plane, and SN-Y-axis angles. Errors in digitization, superimposition, and landmark identification were determined and found to be acceptable. Regression analysis produced a highly significant (P < 0.001) gradient for each of these angular relationships, allowing a set of correction factors to be produced, which can be applied to bite openings up to 5 mm.

PMID: 16495373 [PubMed - indexed for MEDLINE]

Making fixed prostheses that are not too high.

J Am Dent Assoc. 2006 Jan;137(1):96-8

Authors: Christensen GJ

It has been observed that a high percentage of multiple crowns or FPDs arrive from laboratories too "high." This article suggests methods to create accurate alginate impressions, opposing casts and IORs. If dentists use these techniques, it is anticipated that fewer FPDs will be too high as dentists attempt to seat them in the mouth.

PMID: 16457005 [PubMed - indexed for MEDLINE]

Meta-analysis of immediate changes with rapid maxillary expansion treatment.

J Am Dent Assoc. 2006 Jan;137(1):44-53

Authors: Lagrav&#xE8;re MO, Heo G, Major PW, Flores-Mir C

BACKGROUND: The authors conducted a literature review to evaluate immediate transverse, anteroposterior, and vertical dental and skeletal changes produced by rapid maxillary expansion (RME). TYPES OF STUDIES REVIEWED: The authors reviewed clinical trials that assessed immediate dental and/or skeletal changes after RME using cephalometric analysis, model casts or both. No surgical or other simultaneous treatment was accepted during the evaluation period. RESULTS: The authors searched electronic databases and found 31 articles that met the initial inclusion criteria. The authors later rejected 12 of these articles because they did not report immediate changes, three because they lacked detailed descriptions of their results and two because of their nonconventional appliance designs. Fourteen articles satisfied th final inclusion criteria; however, they had methodological deficiencies. CLINICAL IMPLICATIONS: The greatest changes resulting from RME in the studies analyzed were dental and skeletal transverse changes. Few vertical and anteroposterior immediate changes were statistically significant, though they probably are not clinically important.

PMID: 16456998 [PubMed - indexed for MEDLINE]

A comparative study of cephalometric and arch width characteristics of Class II division 1 and division 2 malocclusions.

Eur J Orthod. 2006 Apr;28(2):179-83

Authors: Isik F, Nalbantgil D, Sayinsu K, Arun T

The aim of this compound cephalometric and arch-width study was to determine any dental and/or skeletal differences between subjects with Class II division 1 and Class II division 2 malocclusions. The dento-skeletal characteristics of Class II subjects were evaluated using lateral cephalometric radiographs and dental casts of 90 untreated patients. The sample included 46 Class II division 1 patients (19 girls and 27 boys) with a mean age of 15.27 +/- 2.48 years, and 44 Class II division 2 patients (27 girls and 17 boys) with a mean age of 15.95 +/- 3.25 years. The intermolar, interpremolar and intercanine measurements were carried out on study models. The radiographs were digitized and processed using Dolphin Imaging software. In addition to standard descriptive statistical calculations, an independent samples t-test was carried out in order to compare the two groups. The non-parametric Mann-Whitney U test was utilized for the parameters for the data which were not normally distributed. The only statistically significant difference between the groups for the study model measurements was mandibular intercanine width. The cephalometric results revealed that SNB angle was responsible for the skeletal sagittal difference between the two groups. In addition, the Class II division 1 group had higher vertical proportions and the Class II division 2 group a more concave profile with a prominent chin. The sagittal skeletal pattern of Class II division 2 subjects was found to be very similar to the Class I skeletal relationship, with no evidence of any mandibular restriction.

PMID: 16431898 [PubMed - indexed for MEDLINE]

A computerized photographic assessment of the relationship between skeletal discrepancy and mandibular outline asymmetry.

Eur J Orthod. 2006 Apr;28(2):97-102

Authors: Good S, Edler R, Wertheim D, Greenhill D

The aim of this study was to investigate the relationship between mandibular outline asymmetry and skeletal discrepancy in a sample of orthodontic patients (33 females, 33 males) aged from 8 to 19 years. Skeletal discrepancy was assessed in both the anteroposterior and vertical planes, using standard cephalometric analyses. All were photographed under standardized conditions and the photographs were then digitized for analysis using a computerized system to assess differences in four variables (area, perimeter, compactness and moment-ratio) between the right and left sides of the mandibular outline. The results showed good repeatability of the photographic, cephalometric and digitization methods. A statistically significant relationship was found between mandibular outline asymmetry and both anteroposterior and vertical skeletal discrepancy in this sample, when compared with patients with an average skeletal pattern. There appeared to be a statistically significant relationship between a reduced ANB angle (< 3 degrees) and mandibular outline asymmetry (P = 0.051), as well as between an increase in lower face height and mandibular asymmetry (P = 0.023).

PMID: 16431897 [PubMed - indexed for MEDLINE]