上顎無牙嵴於印模時所受壓力之分佈及其可能影響之因子的探討

Abstract

在為全口無牙之患者做全口假牙時，必先利用印模材及印模托將無牙嵴之形態轉印出來才行。而無牙嵴是在何種型態下被轉印出，則有幾派不同的理論；不同理論的印模方式，不論是印模托之設計或是印模材之選用均不相同。但，是否這些不同之取模方式真可得到不同的印模結果，還是因著不同的印模托設計及不同印模材之使用，以致於最終竟得到殊途同歸的結果，則尚無確切的實驗可以證明！由於各學派均是以印模壓力控制的觀念來遂行其派別之理論，因此，總凡於無牙嵴之型態以及印模托之設計對印模時所生成之壓力的影響均為此研究之主要重點。 本實驗利用有系統地改變上顎無牙嵴高度，印模托之緩壓空間厚度及緩壓孔洞大小來研究探討其對於印模時所產生之壓力的影響。實驗先行製作出5種不同無牙嵴高度(由2mm至10mm，差距2mm）之單純化上顎模型。每種高度皆製作出4組不同緩壓空間厚度（由1mm至4mm，差距1mm）之相對應印模托。每組印模托再依緩壓孔洞大小分5組（由0mm至8mm，差距2mm）。每一種組合（100種組合）均以聚乙烯印模材進行5次模擬印模實驗。印模壓力變化則利用壓力感測器進行偵測，以10 Hz之頻率來作資料收集，共收集5min儲存於電腦。偵測之位置有4個，分別為無牙嵴大臼齒區(A)，門牙區(B)，小臼齒區(C)以及腭部之中心點(D)。最後將所獲得的壓力變化與6個自變項[無牙嵴高度(R)、緩壓空間(S)、緩壓孔洞(H)、無牙嵴處大臼齒區(FA)、無牙嵴處門齒區(FB)、腭部中心點(FD)]進行複迴歸多變項分析。 結果發現印模時的壓力在不同區域明顯的不同。於P值小於0.01的條件下，初期壓力與無牙嵴處門齒區(FB)與無牙嵴高度(R)有著明顯之正相關，而與緩壓空間(S)、無牙嵴處大臼齒區(FA)以及腭部中心點(FD)有著明顯之負相關，但是對於緩壓孔洞(H)則無明顯之相關性；終期壓力與無牙嵴處門齒區(FB)以及無牙嵴高度(R)有著明顯之正相關，而與緩壓空間(S)、緩壓孔洞(H)、無牙嵴處大臼齒區(FA)以及腭部中心點(FD)有著明顯之負相關！此外，印模的初期與終期壓力也分別可以不同的迴歸公式予以表現出。 由實驗可知上顎之不同區域、無牙嵴高度，印模托設計之緩壓空間厚度及緩壓孔洞大小對印模時材料所產生壓力有著顯著的影響。

Introduction: When fabricating a complete denture for an edentulous patient, impression of edentulous ridge is the key of success in initial stage. There are different concepts in which impression is taken under different conditions based on the different theories. The scholar of the different theory advocated that by altering the tray design and the selection of impression material, impressions of edentulous ridge can be taken under expected conditions to reach mucostatic, functional or selective pressure impressions; however, we need exact evidences for these clinical practice. Objectives: The purpose of this in vitro study was to evaluate the influence of ridge height and tray design on the impression pressure generated upon oral mucosa. Methods: Standardized maxillary edentulous resin models of 5 different alveolar ridge heights from 2 to 10mm with 2mm increment were made. On each model, 20 different individual resin trays were fabricated with a combination of 4 different relief space (1, 2, 3, 4mm thickness) and 5 different relief holes (0, 2, 4, 6, 8mm diameter). Polyether impressions were then performed 5 times with each individual tray on the corresponding model. The pressure change on alveolar mucosa of four regions: molar(A), incisor(B), premolar(C), and palate(D) were detected by pressure sensor and recorded with 10 Hz sampling frequency for 5 minutes. Initial and ending pressures were analyzed with multiple regression analysis. Results: The results revealed that the pressure was distinctively different at the four regions. The initial pressures were positively correlated with alveolar ridge regions B (FB) and ridge height(R), and they were negatively correlated with alveolar ridge regions D (FD), alveolar ridge regions A (FA), and relief space thickness (S) (P < 0.01). But they were rarely correlated with relief hole size (H); The ending pressures were positively correlated with alveolar ridge regions B (FB) and ridge height(R), and they were negatively correlated with alveolar ridge regions D (FD), alveolar ridge regions A (FA), relief space thickness (S), and relief hole size (H) (P < 0.01). The initial and ending pressures could be expressed by multiple regression analysis. Conclusions: The pressures during impression were obviously influenced by the alveolar ridge region, the height of alveolar ridge and tray designs including the thickness of relief space and the size of relief hole.