Warin Pongsakorn, Rungsiyakull Pimduen, Rungsiyakull Chaiy, Khongkhunthian Pathawee
Center of Excellence for Dental Implantology, Faculty of Dentistry, Chiang Mai University, Chiang Mai, Thailand.
Department of Prosthodontics, Faculty of Dentistry, Chiang Mai University, Chiang Mai, Thailand.
J Prosthodont Res. 2018 Jan;62(1):35-43. doi: 10.1016/j.jpor.2017.05.002. Epub 2017 Jul 29.
To investigate the strains around mini-dental implants (MDIs) and retromolar edentulous areas when using different numbers of MDIs in order to retain mandibular overdentures.
Four different prosthetic situations were fabricated on an edentulous mandibular model including a complete denture (CD), and three overdentures, retained by four, three or two MDIs in the interforaminal region with retentive attachments. A static load of 200N was applied on the posterior teeth of the dentures under bilateral or unilateral loading conditions. The strains at the mesial and distal of the MDIs and the retromolar edentulous ridges were measured using twelve strain gauges. Comparisons of the mean microstrains among all strain gauges in all situations were analyzed.
The strain distribution determined during bilateral loading experienced a symmetrical distribution; while during unilateral loading, the recorded strains tended to change from compressive strains on the loaded side to tensile strains. Overall, the number of MDIs was found to be passively correlated to the generated compressive strain. The highest strains were recorded in the four MDIs followed by three, two MDIs retained overdenture and CD situations, respectively. The highest strain was found around the terminal MDI.
The use of a low number of MDIs tends to produce low strain values in the retromolar denture-bearing area and around the terminal MDIs during posterior loadings. However, when using a high number of MDIs, the overdenture tends to have more stability during function.
研究在使用不同数量的微型牙种植体（MDIs）以保留下颌覆盖义齿时，微型牙种植体周围以及磨牙后无牙区的应变情况。
在下颌无牙模型上制作四种不同的修复情况，包括一副全口义齿（CD），以及三副覆盖义齿，分别通过四个、三个或两个MDIs在前孔间区域并带有固位附件来固位。在双侧或单侧加载条件下，对义齿后牙施加200N的静态载荷。使用十二个应变片测量MDIs近中及远中处以及磨牙后无牙嵴处的应变。分析所有情况下所有应变片平均微应变的比较情况。
双侧加载时确定的应变分布呈对称分布；而单侧加载时，记录的应变倾向于从加载侧的压缩应变转变为拉伸应变。总体而言，发现MDIs的数量与产生的压缩应变呈负相关。最高应变分别记录在四个MDIs、三个MDIs、两个MDIs固位的覆盖义齿以及全口义齿情况下，最高应变出现在末端MDI周围。
在后牙加载过程中，使用少量MDIs往往会在磨牙后义齿承托区以及末端MDIs周围产生较低的应变值。然而，当使用大量MDIs时，覆盖义齿在功能期间往往具有更高的稳定性。
