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.

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.

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.