## 1 Introduction  
The current literature lacks substantial evidence for the effect of denture base processing techniques and posterior denture tooth forms on denture tooth shifts due to denture base resin polymerization. The aim of this study was to evaluate the combined effect of PMMA-based denture processing techniques (compression packing and injection molding) and posterior tooth forms (semi-anatomic and non-anatomic) on the linear dimensional shift of denture teeth following denture processing in both horizontal and vertical dimensions. Two different complete denture fabrication techniques were used to prepare forty ideal maxillary complete dentures using two different types of posterior tooth forms. The used fabrication techniques were conventional heat polymerized compression packing and injection molding. The posterior tooth forms used in the current study were non-anatomic tooth (0 degrees) and semi-anatomic tooth forms (approximately 20 degrees). Initial linear measurements (vertical and horizontal) were taken from pre-specified points for the central incisor and first molar. Specimens were randomly divided into four groups (\(n=10\)), and denture processing was performed using the two techniques. Final linear measurements were recorded. The linear change in dimension for all six parameters was calculated by deducting the after values from the before values. Since the discrepancies were both positive and negative in magnitude, the absolute value of the difference was taken for further analysis. This value represents the dimensional change. T-tests were used to compare the mean dimensional changes. Furthermore, the mean dimensional changes for all the six parameters were compared using a two-way analysis of variance. The alpha error was set at 5%, and a \(p\)-value of less than 0.05 was considered statistically significant. The injection molding technique showed significantly fewer tooth movements in both the vertical and horizontal measurements as compared to the conventional compression packing technique. The non-anatomic tooth showed significantly fewer changes in tooth movement as compared to semi-anatomic teeth in both the compression and injection techniques. This study can guide the selection of a proper processing technique for a particular posterior tooth form, thus minimizing occlusal discrepancies and reducing occlusal corrections during laboratory and clinical remount procedures. **Keywords: PMMA; acrylic teeth; non-anatomic teeth; semi-anatomic teeth; injection molding technique; compression molding technique; denture processing; tooth movement; denture base resin; posterior tooth form; linear dimensional change; complete denture**  
## 1 Introduction  
Complete edentulism, as defined by a loss of all permanent dentition, is a global health condition that was reported to affect a range of 7-69% of adult populations worldwide [1]. Even though implant dentistry has changed the approach of treatment planning for completely edentulous cases, conventional complete dentures remain a valid and sometimes first option, especially when implants are contraindicated in such cases. Balanced complete denture occlusion is crucial for the stability and retention of complete dentures in patients with moderate to severe alveolar ridge resorption [2]. Excessive denture tooth movements due to processing may compromise the form, esthetics and occlusion and, therefore, mean that dentures need to be remade [3]. Several factors have been reported to affect the positional stability of a denture tooth during processing. These factors include the investment method [4], investment material [5], flasking and polymerization technique [6; 7], denture base thickness [8], flask closure and cooling method [9], palatal form [10] and box preparation on the heel of the master cast [11]. In addition, [PERSON] et al. [12] studied the effect of the denture processing technique on denture tooth movement and found that CAD-CAM technology was the most accurate and reproducible in comparison to conventional packing and injection techniques.