Nonsurgical maxillary expansion: a meta-analysis
Zhou Y, Long H, Ye N, Xue J, Yang X, Liao L, et al. The effectiveness of non-surgical maxillary expansion: a meta-analysis. Eur J Orthod 2014;36:233-42
Is the decision between rapid maxillary expansion (RME) and slow maxillary expansion (SME) an important one when treatment planning for expansion? If so, which treatment modality is more effective for expansion? In this systematic review, the authors proposed to determine and compare the effectiveness of RME and SME using meta-analysis. This is the first meta-analysis to compare the 2 modalities. Fourteen studies were included in the quantitative synthesis. Four outcomes were considered (maxillary intermolar width, maxillary intercanine width, maxillary interpremolar width, and mandibular intermolar width) at 3 times (expansion, retention, and net change). The results of the meta-analysis indicate that both SME and RME are effective relative to the controls. SME is effective at expanding the maxillary arch, but its effect on mandibular intermolar width could not be determined. RME was found to be effective at expanding both the maxillary and mandibular arches. When comparing the effectiveness of the 2 expansion modalities, the authors concluded that SME is superior to RME in expanding maxillary intermolar width, whereas there was no difference between RME and SME in expansion of maxillary interpremolar and mandibular intermolar widths. However, when the results were evaluated carefully, it became apparent that this conclusion was largely based on the results of 1 heavily weighted study. Consequently, the conclusions from this meta-analysis must be viewed with caution. As the authors themselves acknowledge, reliable methods and analogous treatment protocols are necessary to strengthen their findings. In addition, evaluating effectiveness based on the amount of expansion might not be justified, since the transverse needs of each patient differ. Future investigations could consider differentiating skeletal vs dental expansion by using 3-dimensional analysis and analogous treatment protocols.
Reviewed by Blake B. Davis and Niousha Saghafi
Pulpectomy and root resorption during orthodontic tooth movement
Kaku M, Sumi H, Shikata H, Kojima S, Motokawa M, Fujita T, et al. Effects of pulpectomy on the amount of root resorption during orthodontic tooth movement. J Endod 2014;40:372-8
Research shows that root resorption (RR) is associated with macrophage colony stimulating factor and receptor activator of nuclear factor kappa-β ligand (RANKL), which lead to odontoclast differentiation. Injured pulp cells produce macrophage colony stimulating factor and RANKL in response to forces, and it is hypothesized that “stretched” and “injured” pulpal cells will ultimately lead to apical RR. Also linked with inflammatory mediator production is calcium influx via a stretch-activated channel. These authors evaluated the production of macrophage colony stimulating factor/RANKL/interleukin-1 beta/tumor necrosis factor alpha in response to tensile forces, stretch-activated channel inhibition, and differences in RR during tooth movement between pulpless and intact teeth. Pulp tissue was obtained and cultured on a membrane. The samples were subjected to forces, and experiments were performed that illustrated the effect of stretch-activated channel inhibition on mRNA expression of inflammatory factors. A split-mouth design was used in rats comparing RR between devitalized and vital molars. Experimental tensile forces led to increases in the amount of mRNA isolated with both increased duration and force levels, as well as blockage of calcium influx and reduced mRNA levels. In the rats, the control teeth showed more apical RR than did the devitalized teeth. These findings led the authors to state that light forces should be applied, and pulpal removal might be effective in patients with severe RR during tooth movement. One might argue that the experimental force application does not represent clinical forces or that the small difference in RR observed experimentally has little value considering the magnitude of RR in severe clinical cases. Although these points can have some validity, this study could provide the pilot data for subsequent studies.
Reviewed by Jantraveus Merritt and Mariana Muguerza
Pulpectomy and root resorption during orthodontic tooth movement
Kaku M, Sumi H, Shikata H, Kojima S, Motokawa M, Fujita T, et al. Effects of pulpectomy on the amount of root resorption during orthodontic tooth movement. J Endod 2014;40:372-8
Research shows that root resorption (RR) is associated with macrophage colony stimulating factor and receptor activator of nuclear factor kappa-β ligand (RANKL), which lead to odontoclast differentiation. Injured pulp cells produce macrophage colony stimulating factor and RANKL in response to forces, and it is hypothesized that “stretched” and “injured” pulpal cells will ultimately lead to apical RR. Also linked with inflammatory mediator production is calcium influx via a stretch-activated channel. These authors evaluated the production of macrophage colony stimulating factor/RANKL/interleukin-1 beta/tumor necrosis factor alpha in response to tensile forces, stretch-activated channel inhibition, and differences in RR during tooth movement between pulpless and intact teeth. Pulp tissue was obtained and cultured on a membrane. The samples were subjected to forces, and experiments were performed that illustrated the effect of stretch-activated channel inhibition on mRNA expression of inflammatory factors. A split-mouth design was used in rats comparing RR between devitalized and vital molars. Experimental tensile forces led to increases in the amount of mRNA isolated with both increased duration and force levels, as well as blockage of calcium influx and reduced mRNA levels. In the rats, the control teeth showed more apical RR than did the devitalized teeth. These findings led the authors to state that light forces should be applied, and pulpal removal might be effective in patients with severe RR during tooth movement. One might argue that the experimental force application does not represent clinical forces or that the small difference in RR observed experimentally has little value considering the magnitude of RR in severe clinical cases. Although these points can have some validity, this study could provide the pilot data for subsequent studies.
Reviewed by Jantraveus Merritt and Mariana Muguerza
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