A preliminary anatomical study on the association of condylar and occlusal asymmetry

Comparison of self-rated pain and salivary alpha-amylase and cortisol levels during early stages of fixed orthodontic and clear aligner therapy

OBJECTIVES

To compare self-rated orthodontic pain (OP) and whole salivary alpha-amylase (αA) and cortisol levels (CL) during early stages of fixed orthodontic and clear aligner therapy (CAT).

METHODS

In groups 1 and 2, malocclusions were treated using fixed orthodontic appliances and CAT, respectively. In Group-3, individuals had normal occlusion and had never undergone orthodontic therapy. Self-rated OP was assessed using the visual-analogue-scale at baseline (T0); after 24-hours (T1) of appliance activation; and after 30 days (T2). Unstimulated whole saliva was collected and αA and CL were measured using enzyme-linked immunosorbent assay. p < .01 was considered statistically significant.

RESULTS

Twenty-four (Group-1), 24(Group-2) and 25 (Group-3) patients were included. In groups 1 and 2, participants had Class-I malocclusion with anterior-crowding in both arches. At baseline (T0) none of the participants reported pain on mastication. In groups 1 (p < .01) and 2 (p < .01), OP was higher at T1 than T2. In groups 1 and 2, αA and CL were higher at T1 (p < .01) than T0 and T2. At T1 and T2, salivary αA and CL were higher in groups 1 (p < .01) and 2 (p < .01) than Group-3. In groups 1 and 2, a significant correlation was recorded between OP and αA (p < .01) and CL (p < .01) at T1 interval.

CONCLUSION

Self-rated OP and salivary αA and CL during the early stages of fixed OT and CAT are similar. Whole salivary αA and CL and OP and are high during the first 24 hours of fixed OT and CAT activation.

[Research progress on the relationship between centric relation and orthodontic treatment]

Centric relation (CR) is one of the core research contents in orthodontics, prosthodontics, and gnathology, acting as an important physiological factor in reconstructing the occlusion and adjusting the occlusal relationship. For over a century, CR is still a controversial subject in dentistry. CR has been redefined for several times, and recently, its application has been widened in orthodontics, including orthodontic diagnosis, clinical examination and analysis, and treatment goals. The purpose of this article is to review the definition of CR, its relationship with malocclusion, and the application of this relationship in orthodontic treatment.

Tooth loss and craniofacial factors associated with changes in mandibular condylar morphology

Objective: To investigate the association between tooth loss and craniofacial factors with changes in mandibular condylar morphology. Methods: A total of 123 patients participated in this cross-sectional study. The mandibular condylar morphology was evaluated using digital panoramic radiography. The exposure variables included gender, age group, molar relationship, facial growth pattern, facial asymmetry, dental midline, posterior crossbite, presence of fixed dental prosthesis, and tooth loss. Results: Unilateral and bilateral mandibular condyle structural alterations were found in 20.3% and 28.5% of the sample, respectively. After the adjustment analysis, posterior crossbite (adjusted OR = 3.34, 95% CI = 1.23-9.06) and tooth loss (adjusted OR = 4.08, 95% CI = 1.72-9.64) were associated with the outcome. The tooth type associated with mandibular condyle structural alterations were premolars and upper molars. Conclusion: The findings suggest that posterior crossbite and tooth loss are associated with mandibular condyle structural alterations.

Effects of early unilateral mandibular first molar extraction on condylar and ramal vertical asymmetry

Objective:

The objective of the following study is to investigate the mandibular vertical asymmetry in a group of patients with early unilateral mandibular first molar extractions.

Materials and Methods:

Mandibular asymmetry index measurements (condylar, ramal and condylar-plus-ramal) were performed on the panoramic radiographs of a study group including 51 patients (mean age: 18.60 ± 1.11 years) and a control group of 51 patients (mean age: 18.53 ± 1.29 years). Group I included patients with a unilateral mandibular first molar extracted before the age of 12 years. Group II included patients with no extractions and had excellent Class I relationships, no missing teeth and slight or moderate anterior crowding. A paired t-test was used to determine possible statistically significant differences between the sides for the measurements. Student's t-test was used for the comparison of asymmetry index values between the groups and genders.

Results:

No group showed statistically significant sex-or side-specific differences for posterior vertical height measurements. Condylar asymmetry index and ramal asymmetry index measurements were not statistically different between the groups, while condylar-plus-ramal asymmetry index (CRAI) measurements were statistically different between the groups (P = 0.019).

Conclusions:

A slight difference for CRAI value was found in patients with early unilateral mandibular first molar extractions.

Establishing better biological models to understand occlusion. I: TM joint anatomic relationships

Belief in and rejection of a relationship of occlusion and temporomandibular joint (TMJ) condyle-fossa position with normal and abnormal function are still contentious issues. Clinical opinions can be strong, but support in most published data (mostly univariate) is problematic. Distribution overlap, low sensitivity and specificity are a common basis to reject any useful prediction value. Notwithstanding, a relationship of form with function is a basic tenet of biology. These are multifactor problems, but the questions mostly have not been analysed as such. This review moves the question forward by focusing on TM joint anatomic organisation as the multifactor system it is expected to be in a closed system like a synovial joint. Multifactor analysis allows the data to speak for itself and reduces bias. Classification tree analysis revealed useful prediction values and usable clinical models which are illustrated, backed up by stepwise logistic regression. Explained variance, R(2), predicting normals from pooled TMJ patients was 32·6%, sensitivity 67·9%, specificity 85·7%; 37% versus disc displacement with reduction; and 28·8% versus disc displacement without reduction. Significant osseous organisational differences between TM joints with clicking and locking suggest that this is not necessarily a single disease continuum. However, a subset of joints with clicking contained characteristics of joints with locking that might contribute to symptom progression versus resistance. Moderately strong models confirm there is a relationship between TMJ osseous organisation and function, but it should not be overstated. More than one model of normals and of TM derangement organisation is revealed. The implications to clinical decision-making are discussed.

Effects of early bilateral mandibular first molar extraction on condylar and ramal vertical asymmetry

OBJECTIVES

This study aims to investigate the mandibular vertical asymmetry in a group of adult patients who had early bilateral mandibular first molar extractions.

METHODS

Mandibular asymmetry index measurements (condylar, ramal, and condylar plus ramal) were made on the panoramic radiographs of a study group including 30 subjects (mean age, 18.22 ± 1.30 years) and a control group of 25 subjects (mean age, 18.24 ± 1.17 years). Group I comprised the control group patients with no extractions and had excellent class I relationships, no missing teeth, and slight or moderate anterior crowding. Group II included patients with a bilateral mandibular first molar teeth extracted before the age of 12 years. Student's t test was used for the comparison of asymmetry index values between the groups. A paired t test was used to determine possible statistically significant differences between the sides for condylar, ramal, and condylar plus ramal height measurements.

RESULTS

No group showed statistically significant side-specific differences for posterior vertical height measurements. Condylar asymmetry index (CAI), ramal asymmetry index, and condylar plus ramal asymmetry index measurements were not statistically different between the groups (p > 0.05).

CONCLUSIONS

CAI values were significantly high when compared with the 3 % threshold value in the both groups, but comparisons between the groups were not statistically significant.

CLINICAL RELEVANCE

This article investigates the effects of early bilateral mandibular molar teeth extraction that has never been investigated in the literature. The present study showed that the lengths of the condylar, ramal, and condylar plus ramal height were less in the study group than in a well-matched control group of without extraction.

Differential expression of IGF1, IGFR1 and IGFBP3 in mandibular condylar cartilage between male and female rats applied with malocclusion

This study was designed to investigate the expression differences of insulin-like growth factor-1 (IGF1), IGF type 1 receptor (IGFR1) and IGF-binding protein-3 (IGFBP3) in mandibular condylar cartilage between male and female rats with experimentally created malocclusion. A total of 40 male and 40 female rats were used, and malocclusion was created by moving the first molars mesially and the third molars distally in the experimental group. Animals were killed at the end of the second and fourth weeks. Haematoxylin and eosin (HE) staining was performed to monitor the changes in cartilage morphology and thickness. Immunohistochemistry and real-time PCR were used to detect the expression of IGF1, IGFR1 and IGFBP3. Osteoarthritis (OA)-like changes were observed in the experimental groups, with 2-week females showing larger OA-like regions than 2-week males (P < 0·05). Compared to their age- and sex-matched controls, both 2- and 4-week males in the experimental groups displayed increased cartilage thickness in the posterior regions (P < 0·05). Compared to their age- and sex-matched controls, the expression of IGF1 was lower in 2-week female group (P < 0·05), but higher in 4-week female, 2- and 4-week male experimental groups (P < 0.05). Similarly, the expression of IGFR1 was lower in 2-week female experimental group (P < 0.05), but higher in 2-week male experimental group (P < 0.05). The higher expression of IGFBP3 was observed in 2-week female, 2- and 4-week male experimental groups (P < 0·05). These results indicate that condylar cartilage from male and female rats respond differently to the malocclusion in early stage of OA, with more serious degeneration in females.