Can the intra-examiner variability of Little's Irregularity Index be improved using 3D digital models of study casts?

Objectives

To compare contact point displacement measurements, used to determine the Little's Irregularity Index (LII) score on study casts and digital models of study casts by an independent examiner.

Methods

The contact point displacement measurements of the six maxillary anterior labial teeth were measured on ten study casts using digital callipers and their associated digital models using Creo Parametric software on five occasions following scanning using a LAVA Chairside Oral Scanner (LCOS) three-dimensional (3D) intra oral scanner. Means, standard deviations and coefficients of variation (CoV) were determined, data analyses (Pearson's correlation coefficients (PCCs) and Intraclass correlation coefficients (ICCs)) and statistical analyses (three and two-way analyses of variance (ANOVAs) and Independent Sample Student's t-tests) were carried out (p < 0.05).

Results

Significant positive correlations for the contact point displacement measurements were evident between all measurement time points for the study casts (r > 0.978; p < 0.0001 and ICC > 0.910; p < 0.0001) and the digital models (r > 0.963; p < 0.0001 and ICC > 0.986; p < 0.0001). The CoV results showed that the contact point displacement measurement data from the digital models was more reproducible than the study casts. Of the 50 Independent Sample Student's t-tests, 21 significant increases (p < 0.042) were reported in contact point displacement measurements <2.9 mm for the digital models compared with the study casts.

Conclusion

The use of 3D digital models can improve the reliability of LII measurements by reducing the subjectivity associated with choosing the anatomic tooth contact points and the awkwardness of measuring the contact point displacements on study casts using a cumbersome calliper technique.

Clinical significance

Intra-examiner variability in the measurement of LII is still evident with digital models suggesting that either improved software specifically aimed at the orthodontic community be identified or a new method for measuring anterior incisor crowding be sought.     

Toll‐Like Receptor 3 and 7/8 Function Is Impaired in Hepatitis C Rapid Fibrosis Progression Post‐Liver Transplantation

Recurrence of hepatitis C (HCV) postliver transplant is universal, with a subgroup developing rapid hepatic fibrosis. Toll‐like receptors (TLRs) are critical to innate antiviral responses and HCV alters TLR function to evade immune clearance. Whether TLRs play a role in rapid HCV recurrence posttransplant is unknown. We stimulated peripheral blood mononuclear cells (PBMCs) from 70 patients with HCV postliver transplant with TLR subclass‐specific ligands and measured cytokine production, TLR expression and NK cell function. Rate of fibrosis progression was calculated using posttransplant liver biopsies graded by Metavir scoring (F0–4; R = fibrosis stage/year posttransplant; rapid fibrosis defined as >0.4 units/year). Thirty of 70 (43%) patients had rapid fibrosis progression. PBMCs from HCV rapid‐fibrosers produced less IFNα with TLR7/8 stimulation (p = 0.039), less IL‐6 at baseline (p = 0.027) and with TLR3 stimulation (p = 0.008) and had lower TLR3‐mediated monocyte IL‐6 production (p = 0.028) compared with HCV slow fibrosers. TLR7/8‐mediated NKCD56 dim cell secretion of IFNγ was impaired in HCV rapid fibrosis (p = 0.006) independently of IFNα secretion and TLR7/8 expression, while cytotoxicity remained preserved. Impaired TLR3 and TLR7/8‐mediated cytokine responses may contribute to aggressive HCV recurrence postliver transplantation through impaired immune control of HCV and subsequent activation of fibrogenesis.     

Can a Specific Neck Strengthening Program Decrease Cervical Spine Injuries in a Men's Professional Rugby Union Team? A Retrospective Analysis

Cervical spine injuries in Rugby Union are a concerning issue at all levels of the game. The primary aim of this retrospective analysis conducted in a professional Rugby Union squad was to determine whether a 26-week isometric neck strengthening intervention program (13-week strengthening phase and 13-week maintenance phase) was effective in reducing the number and severity of cervical spine injuries. The secondary aim was to determine whether at week five, where the program had been the similar for all players, there was increased isometric neck strength. All 27 players who were common to both the 2007-2008 and 2008-2009 seasons were included in this analysis and data was extracted from a Sports Medicine/Sports Science database which included the squad''s injury records. Primary outcome variables included; the number of cervical spine injuries and the severity of these injuries as determined by the total number of days lost from training and competition. Secondary outcome variables included isometric neck strength in flexion, extension and left and right lateral flexion. Using non-parametric statistical methods, no significant differences were evident for the total number of cervical spine injuries (n = 8 in 2007-2008, n = 6 in 2008-2009) or time loss due to these injuries (100 days in 2007-2008, 40 days in 2008-2009). However, a significant (p = 0.03) reduction in the number of match injuries was evident from 2007-2008 (n = 11) to 2008-09 (n = 2). Non-significant increases in isometric neck strength were found in all directions examined. A significant reduction in the number of match injuries was evident in this study. However, no other significant changes to primary outcome variables were achieved. Further, no significant increases in isometric neck strength were found in this well-trained group of professional athletes.

Key Points

• While many authors have proposed that neck strengthening could be an effective strategy in preventing cervical spine injuries in Rugby Union, there is currently little information in the literature pertaining to how such a study might be conducted.
• A significant decrease in the number of injuries recorded in matches can be achieved using a specific neck strengthening program at the elite level.
• In an elite rugby union team as investigated in this study a significant increase in neck strength is difficult to achieve in a short period of time such as five weeks.

Key words: Rugby Union, cervical spine, injury, isometric, neck strength