Smile dynamics: A comparative study of Fijians and NZ Europeans.

BACKGROUND: The Fijian 'Bula Smile' is often described as the world's friendliest; however, its description remains anecdotal. OBJECTIVE: This study aimed to describe and compare the dynamics of Fijians' smiles with those of New Zealand Europeans. METHODS: An observational study was conducted on two ethnic groups, Fijians (FJ; N = 23) and New Zealand Europeans (NZ; N = 23), age- and gender-matched. All participants were asked to watch amusing videos, and their reactions were video recorded. The videos were analysed by software to assess the frequency, duration, intensity and genuineness of smiling episodes. Based on the Facial Action Coding System, Action Unit 6 (AU6-cheek raiser), Action Unit 12 (AU12-lip corner puller) and Action Unit 25 (AU25-lips apart) were assessed. Data were analysed by generalised linear models after adjusting for personality traits. RESULTS: Fijians smiled longer than New Zealand Europeans (+19.9%; p = .027). Mean intensity of AU6 (+1.0; 95%CIs = 0.6-1.5; p < .001), AU12 (+0.5; 95%CIs = 0.1-0.9; p = .008) and AU25 (+22.3%; 95%CIs = 7.3%-37.3%; p = .005) were significantly higher in FJ group than the NZ group. CONCLUSION: Smiling features of Fijians and New Zealanders showed objective differences, the most distinctive being a higher activation of the Duchenne's marker (AU6) in the Fijian group, which is regarded as a sign of smile genuineness.

The effect of passive clear aligners on masticatory muscle activity in adults with different levels of oral parafunction.

BACKGROUND: There is limited knowledge of the possible side-effects of clear aligners on jaw function. OBJECTIVES: To determine the short-term effect of passive clear aligners (PCAs) on masticatory muscle activity (MMA), occlusal discomfort (OD) and temporomandibular disorder (TMD) symptoms in adults with different levels of self-reported oral parafunction. MATERIALS AND METHODS: Participants were screened for oral parafunctional behaviours using the oral behavioural checklist. Respondents in ≥85th and ≤15th percentiles were invited to participate and allocated to a high (HPF: N = 15) or low (lower parafunction [LPF]: N = 16) parafunction group. Participants underwent a TMD clinical examination; somatisation and somatosensory amplification were assessed by questionnaires; OD and stress were assessed by visual analogue scales. While wearing PCAs, awake-time MMA was assessed three times over 9 days using a wearable electromyography device, along with OD, stress and TMD symptoms. RESULTS: The wearing of PCAs was associated with a significant decrease in mean contraction episode amplitude in both groups (p = 0.003). OD levels increased and remained raised in all participants after insertion of the PCAs (p < 0.001), more so in the HPF group (p = 0.048). The HPF group had higher somatisation scores (p = 0.006) and reported more TMD symptoms at all time points (p ≤ 0.004). No significant changes in stress or TMD symptoms were found in either group during the study period. CONCLUSIONS: PCAs were associated with a decrease in MMA in all participants. HPF individuals had greater somatisation and reported greater discomfort when wearing PCAs than LPF individuals.

Immediate effect of clear aligners and fixed appliances on perioral soft tissues and speech.

OBJECTIVES: To compare the immediate three-dimensional (3D) perioral soft-tissue changes and impact on speech induced by clear aligners and fixed appliances. MATERIALS AND METHODS: In this repeated-measure experimental study, stereophotogrammetric 3D photographs of 40 participants were recorded before and immediately after the introduction of clear aligners and fixed appliances. The 3D surface meshes were registered to quantify changes in the direction and magnitude of nine soft tissue landmarks located on the upper and lower lips. Self-reported speech disturbance was evaluated using a questionnaire. Data were analysed using repeated-measures analysis of variance. RESULTS: In the vertical plane, the clear aligners induced inferior displacement (range 0.4-1.5 mm) for all nine landmarks (P < .01), whereas fixed appliances induced inferior displacement only of A-point (0.4 ± 0.9 mm), right crista philtri (0.5 ± 1.1 mm) and left crista philtri (0.7 ± 1.1 mm). The clear aligners induced greater vertical changes than fixed appliances for all landmarks (P < .05). In the sagittal plane, both clear aligners and fixed appliances slightly advanced all perioral landmarks, except subnasale. Fixed appliances caused greater changes than clear aligners for right cheilion (+0.8 mm), left cheilion (+0.8 mm) and labrale inferius (+0.9 mm) (P < .01). Both orthodontic appliances had a significant self-perceived effect on speech, with clear aligners affecting speech to a greater degree. CONCLUSION: Clear aligners and fixed appliances produced immediate effects on perioral soft tissues, which are most evident in the vertical plane for clear aligners, and in the sagittal plane for fixed appliances. Speech was affected by both appliances.

Three-dimensional digital assessment of typodont activations.

OBJECTIVES: Wax typodonts are widely used as pre-clinical teaching tools to test and research the complex force systems created by archwire activations, however, a limitation is the inability to quantify the resultant statically indeterminate tooth movements. The aim of this study was to develop an analogue-to-digital typodont system to quantify the effects of archwire activations on individual typodont teeth in three dimensions. METHODS: The typodont system was developed using CAD/CAM technology. Posterior expansion, squared, tapered, asymmetrical arch forms and reversed curve of Spee activations were tested with three repeats. The resulting three-dimensional movements of individual typodont teeth were assessed with six degrees of freedom (df). Cartesian coordinate systems were set for each tooth. Mesio-distal, bucco-lingual and intrusive-extrusive movements were assessed as changes in the location of the geometrically estimated centre of resistance in the x, y and z axes, respectively. Torque, tip and rotation movements were assessed as the rotations around the mesio-distal, bucco-lingual and intrusive-extrusive axes, respectively. RESULTS: Individual typodont tooth displacements from each activation could reliably be described with six df. The transversal-to-sagittal movement ratio ranged from 2:1 to 7:1, depending on the activation. Asymmetrical arch form activations caused a midline shift and affected the lateral overjet. Reversing the curve of Spee led to intrusion of incisors and second molars, extrusion of premolars and first molars and pronounced first and third order effects. CONCLUSION: The digital typodont system is a promising teaching tool. The tested activations have implications in three dimensions, which should be considered when planning tooth movements.

Retention: taking a more active role.

Retention may be particularly challenging after the correction of specific malocclusion features, such as tooth rotations, open bite and expansion, which are all inherently unstable. In this article, some indications for active retention are reviewed by highlighting a variety of clinical techniques and appliances. Active retention is discussed in relation to preservation of tooth alignment and in the three planes of space: sagittal, vertical and transverse. In some situations, an active retention regimen may be helpful to minimise or counteract relapse after orthodontic treatment and to improve patient satisfaction during the typically lengthy post-treatment period.

An in-vitro mechanical strain three-dimensional culture model: periodontal ligament cell viability, apoptosis, and endoplasmic reticulum stress response.

To develop a model to investigate a potential relationship between mechanical strain, cell responses, and endoplasmic reticulum stress in periodontal ligament (PDL) cells, primary PDL cell cultures were obtained from extracted premolars. Cells were cultured in hydrogel and subjected to 24 h of static mechanical strain, resulting in 18% dimensional substrate elongation. Cell viability, caspase-3/7 activity, and mRNA levels for 28 genes, including unfolded protein response (UPR)-related and mechanically responsive genes, serving as positive controls for stress induction, were examined. Compared with unstrained cultures, no difference in caspase activity was observed; however, viability responses differed between cell lines. Multiple UPR-related genes were differentially upregulated, with marginal statistical significance, including cAMP responsive element binding protein 3 like 3 (CREB3L3) (mean fold-regulation = 1.91), an adenosine monophosphate-dependent transcription factor with roles in UPR activation and the acute inflammatory response; and the pro-apoptotic UPR gene, endoplasmic reticulum to nucleus signaling 2 (ERN2) (mean fold-regulation = 4.01). The observed effect on cell viability following strain with no change in caspase activity suggests that reduction in viability may be mediated via caspase-3/7-independent mechanisms. Three-dimensional mechanical strain PDL cell culture models offer a method to study the role of endoplasmic reticulum stress and UPR, and provide a framework and potential UPR targets for future investigations.

Evaluation of objective and subjective treatment outcomes in orthodontic cases treated with extraction of a mandibular incisor.

OBJECTIVES: To analyze changes in occlusal characteristics following mandibular incisor extractions (MIE), to determine the usefulness of wax setups in treatment planning MIE cases and to compare the pre- and posttreatment dental attractiveness between MIE cases and nonextraction (NE) controls. MATERIALS AND METHODS: The Peer Assessment Rating (PAR) Index was used to score pre- and posttreatment dental casts of MIE cases (n = 14) and matched NE controls (n = 14). Occlusal characteristics were evaluated on diagnostic wax setups and posttreatment casts. Attractiveness of pre- and posttreatment cases judged on intraoral photographs of cases (n = 6) and controls (n = 6) were rated by 76 dental students and 10 laypeople using visual analogue scales (VAS). RESULTS: The difference in PAR score reduction (%) between the MIE and NE groups was not significant. Between the wax setup and posttreatment casts, there were moderate correlations in overjet, overbite, and right canine classification. There was no significant difference in pre- and posttreatment change in VAS scores (%) for attractiveness between the MIE (49.8 ± 4.3 [S.E.]) and control groups (40.8 ± 4.3 [S.E.]). However, there was a significant difference (P = .000) between the observer groups. CONCLUSIONS: There were no significant differences in the treatment outcomes of orthodontic cases treated with MIE or NE, indicating that MIE is a valid treatment option. A wax setup is moderately correlated with posttreatment results. Both laypeople and dental students rated posttreatment dental attractiveness higher than pretreatment in MIE and NE groups. Dental students tended to be more critical than laypeople in their ratings.

Effect of incisor retraction on facial aesthetics.

Incisor retraction may result in lip retraction, interlabial gap closure and increase of the nasolabial angle but a clear consensus on the effect of incisor retraction on facial aesthetics has not yet been achieved. Despite current evidence being weak, it seems to indicate that in a well-managed orthodontic case, with or without extractions, the soft-tissue and facial aesthetic changes are generally favourable or clinically insignificant.

Sclerostin injection enhances orthodontic tooth movement in rats.

OBJECTIVE: It was aimed to investigate the in vivo effects of local injection of sclerostin protein on orthodontic tooth movement. DESIGN: A total of 48 rats underwent orthodontic mesialization of the maxillary first molars on both sides. Local injection was given at the compression side in the alveolar bone on both maxillary sides, with sclerostin protein carried by hydrogel on one side, and the same volume of normal saline carried by hydrogel on the other side serving as the control. After two weeks, the tooth movement amount and effects on the periodontium were assessed through micro-computed tomography (µCT) analysis, tartrate-resistant acid phosphatase (TRAP) staining and immunohistochemistry (IHC) analysis. RESULTS: After two weeks of intervention, tooth movement was significantly greater in the 4 µg/kg and 20 µg/kg sclerostin injection groups, compared to the control. Analysis of the furcation area of the maxillary first molar showed that the 20 µg/kg group had significantly decreased BV/TV. At the compression side, the number of TRAP-positive osteoclasts was significantly increased in 20 µg/kg group compared to the control. The expression of RANKL was statistically higher in all the sclerostin groups, while the expression of OPG was statistically lower in the 4 µg/kg and 20 µg/kg groups, compared to the control. At the tension side, the expression of RUNX2 and COL-1 was statistically higher in the 20 µg/kg group compared to the control. CONCLUSIONS: Local injection of sclerostin protein in the alveolar bone at the compression side accelerates OTM in rats by promoting osteoclastogenesis.

Downregulation of toll-like receptor-mediated signalling pathways in oral lichen planus.

OBJECTIVE: The objective of this study was to investigate the expression of Toll-like receptors (TLR) and TLR-associated signalling pathway genes in oral lichen planus (OLP). METHODS: Initially, immunohistochemistry was used to determine TLR expression in 12 formalin-fixed archival OLP tissues with 12 non-specifically inflamed oral tissues as controls. RNA was isolated from further fresh samples of OLP and non-specifically inflamed oral tissue controls (n = 6 for both groups) and used in qRT(2)-PCR focused arrays to determine the expression of TLRs and associated signalling pathway genes. Genes with a statistical significance of ±two-fold regulation (FR) and a P-value < 0.05 were considered as significantly regulated. RESULTS: Significantly more TLR4(+) cells were present in the inflammatory infiltrate in OLP compared with the control tissues (P < 0.05). There was no statistically significant difference in the numbers of TLR2(+) and TLR8(+) cells between the groups. TLR3 was significantly downregulated in OLP (P < 0.01). TLR8 was upregulated in OLP, but the difference between the groups was not statistically significant. The TLR-mediated signalling-associated protein genes MyD88 and TIRAP were significantly downregulated (P < 0.01 and P < 0.05), as were IRAK1 (P < 0.05), MAPK8 (P < 0.01), MAP3K1 (P < 0.05), MAP4K4 (P < 0.05), REL (P < 0.01) and RELA (P < 0.01). Stress proteins HMGB1 and the heat shock protein D1 were significantly downregulated in OLP (P < 0.01). CONCLUSION: These findings suggest a downregulation of TLR-mediated signalling pathways in OLP lesions.