Impact of Different Orthodontic Appliances on Mandibular Condyle, Anterior Region of Mandibular, and Maxillary Sinus Using Panoramic Radiography

Introduction

Craniofacial growth and development, as outlined by the functional matrix theory, are intricate processes in which soft tissues significantly influence the formation of hard tissues [1]. Factors such as head posture, functional anterior displacement, vertical-sagittal skeletal relationships, and surgical mandibular advancement are known to affect the maxillary sinus and mandibular condyle [2]. Consequently, many clinicians have conducted studies to explore the changes in hard and soft tissues resulting from orthodontic interventions [3].

Researchers have shown great interest in the complex interaction between the maxillary sinus and the positioning of dental roots and teeth during orthodontic treatment [4]. The dimensions of the sinus are recognized as crucial factors in the normal trajectory of craniofacial development [5].

Various removable functional dental appliances (RFAs) can be used to modify the direction and amount of growth in cases of mandibular and maxillary developmental deficiency [6]. Maxillary expansion is a dentofacial orthopedic treatment performed by separating the midpalatal suture using orthodontic appliances [7]. Monoblock and twinblock appliances are designed as a single-piece acrylic splint by combining the lower and upper bite blocks on the occlusal plane to form the monoblock appliance [8]. The twinblock appliance is introduced as a 2-part monoblock. The appliance consists of lower and upper bite blocks, which lock together at a 70° angle, with inclined planes on the front parts that position the mandible downward and forward [9]. The strong pulling forces transmitted to the maxilla via face masks help normalize the relationship with the mandibular base in a short period. Chincup treatment changes the direction of mandibular growth by rotating the chin downward and backward [10].

Similarly, orthodontic treatment affects bone density in the maxilla and mandible, particularly in specific regions such as the mandibular subregion or mandibular condyle [11,12]. According to Wolff’s law, changes in bone microstructure lead to systematic morphological alterations. Functional forces generated by orofacial muscles during rest and activity are transmitted to the bones via muscles connected to the jawbones or periodontal ligaments [13]. These effects can also influence the mandibular condyle region. The bone quality of the mandibular condyle depends on various factors, including trabecular continuity, bone geometry, micro-damages, bone tissue architecture, mineralization, and defects [14]. Bone mineral density measurements have been widely used in recent years to analyze bone structure [15]. Fractal geometric applications and fractal size measurements can be used to define the complex structure of trabecular bone [15]. Morphological changes can occur due to condyle reshaping, which accommodates developmental variations, malocclusion, trauma, and other abnormalities [12]. Since the temporomandibular joint and the bone tissues forming it are part of the craniofacial complex, orthodontists often examine these structures for diagnosis and treatment planning. Orthodontic treatments can be adjusted to prevent or address deformities that have occurred or might occur [11].

Given the significance of maxillary sinus dimensions, mandibular anterior region bone density (MABD), and mandibular condyle head bone formation (MCBF) within the craniofacial complex, orthodontists can analyze these parameters for diagnostic and treatment planning purposes. This allows for adjustments to orthodontic interventions when existing or potential anomalies are present, thereby helping to prevent complications associated with these structures. Therefore, this retrospective study of 44 patients requiring RFAs aimed to compare the use of a maxillary expansion device, twinblock/monoblock, face mask, and chincup on maxillary sinus dimensions, MABD, and MCBF using panoramic radiography.

Material and Methods

STUDY DESIGN:

In this retrospective study, pretreatment and posttreatment panoramic radiographs of individuals eligible for removable functional orthodontic treatment (Figure 1) were analyzed.

ETHICAL APPROVAL:

After all patients provided written approval, their medical and dental histories were taken. Each patient read the Helsinki Declaration before their involvement in the study. The study protocols and methodologies were approved by the IKCU Non-Pharmacological Clinical Research Ethics Committee.

PARTICIPANTS AND GROUPS:

The study included 44 patients who met specific inclusion criteria, such as the requirement for lateral cephalometric films at the start of treatment, absence of pathology in the examined region, and no congenital or acquired anomalies. To be eligible for this study, patients had to meet specific criteria. They also needed to be in good general health and have no prior history of orthodontic treatment.

The patients were divided into 4 groups based on the type of RFA used: group A: maxillary expansion appliance (11 patients); group B: twinblock/monoblock appliances (11 patients); group C: face mask appliances (11 patients); and group D: chincup appliances (11 patients).

EVALUATION OF MAXILLARY SINUS DIMENSIONS:

Maxillary sinus dimensions were assessed using panoramic radiographs taken before and after orthodontic treatment. The measurements included the maxillary sinus indentation base length (MSIL), average planar base length (MSPL), and maxillary sinus area (MSA), specifically at a height of 5 mm from the apex of the first molar. Measurements from the right and left sinuses were combined and averaged [16].

MANDIBULAR ANTERIOR REGION BONE DENSITY:

The mandibular anterior region bone density (MABD) is the bone density starting 4 mm below the line drawn from the root tips of the mandibular central teeth. Fractal analysis was used to assess trabecular bone changes and determine the fractal dimension, reflecting the complexity of repeating geometric patterns. Panoramic radiographs were converted to TIFF format, and fractal analysis was performed on these images.

MANDIBULAR CONDYLE HEAD BONE FORMATION:

The mandibular condyle head bone formation (MCBF) is the bone density measured in the mandibular condyle head region. The quality of the mandibular condyle bone was evaluated by comparing trabecular bone changes using fractal analysis. This process yielded a fractal scale value representing the complexity of recurring geometric patterns. Panoramic radiographs were converted to TIFF format for analysis [17].

RADIOGRAPHIC PROCEDURES:

Panoramic radiographs were captured using an X-ray machine (Sirona Orthophos XG ABD), with only high-quality images free from magnification issues, low contrast, and blurriness selected for analysis. Radiographs were taken with the patient in or near the natural head position. Calibration was meticulously performed using the X-ray machine’s software, to ensure a precise 1: 1 scale. Digital calibration was also conducted using the ImageJ program (Wayne Rasband, National Institutes of Health, Bethesda, MD, USA) to accurately measure maxillary sinus dimensions.

STATISTICAL ANALYSIS:

Statistical analysis was conducted using SPSS 20.0 software, with significance set at P<0.05. Sample size determination was achieved through G*Power analysis, with a significance level of 0.05 and a power of 90%, requiring a minimum of 6 patients per group. Bone density determined as a result of fractal analysis was used as the primary outcome. Primary outcome data was used to decide on the number of people in the groups using data from 3 similar articles. The normal distribution of data was assessed using the Kolmogorov-Smirnov test. Descriptive statistics are presented as mean±standard deviation. Different groups of patients were tested by using the non-parametric Mann-Whitney U test, with Bonferroni correction.

Results

MAXILLARY SINUS RESULTS:

In group A, an increase in MSIL and a decrease in MSPL and MSA were observed at the end of treatment, compared with before treatment.

In group B, an increase in MSIL, MSPL, and MSA was observed at the end of treatment, compared with before treatment.

In group C, an increase in MSIL and MSPL, with a decrease in MSA, was observed at the end of treatment, compared with before treatment.

In group D, an increase in MSIL and MSA, with a decrease in MSPL, was observed at the end of treatment, compared with before treatment.

The most significant change in MSIL was observed in group C, while the least change was in group B. For MSPL, the highest change was in group A, and the lowest was in group D. Regarding MSA, the most significant change was in group A, and the least change was in group B. The changes in MSIL, MSPL, and MSA between the groups were statistically significant (P<0.05; Table 1, Figures 2–4).

MABD RESULTS:

In groups A, B, C, and D, an increase in MABD was observed at the end of treatment, compared with before treatment. This change was greatest in group B, while the least change was in group D. The change in MABD between groups was statistically significant (P<0.05; Table 2, Figures 5, 6).

MCBF RESULTS:

In groups A, B, C, and D, an increase in average MCBF (right-left condyle average) was observed at the end of treatment, compared with before treatment. The most significant change was in group A, while the least change was in group D. The change in average MCBF between groups was statistically significant (P<0.05; Table 3, Figure 7).

Discussion

Possible changes in teeth and adjacent tissues should be carefully evaluated after orthodontic treatment, and these assessments should guide the orthodontic approach. In addition to temporomandibular disorders, changes in maxillary sinus size and mandibular anterior bone quality can be observed in individuals who have undergone orthodontic treatment. This study investigated the changes in maxillary sinus dimensions, MABD, and MCBF after orthodontic treatment with different RFAs (Figure 8).

Bone tissue is crucial to the musculoskeletal system, providing support for movement and structural functions in the human body. It consists of 2 main compartments: trabecular and cortical bone, with their proportions in total bone mass ranging from approximately 20% to 80% [18]. Despite its smaller mass, trabecular bone exhibits higher metabolic activity than does cortical bone. Various studies have shown that diseases affecting bone tissue often present earlier signs in trabecular bone [19]. With advancements in technology and the integration of computers into medical practice, early diagnosis of bone tissue diseases through trabecular bone microstructure analysis has become a prominent area of research [20].

The maxillary sinus plays a significant role in the craniofacial structure, with its dimensions influenced by various factors [21]. RFAs have also been shown to contribute to the enlargement of maxillary sinus dimensions and improvements in muscle function patterns [22]. Correcting mandibular retrusion in patients with class II malocclusion using RFAs can increase the sagittal size of the maxillary sinus [23]. However, the effects of functional appliances on the maxillary sinus airways have not been found to be significant [24]. Several lateral cephalometric studies have reported a significant increase in oropharyngeal airway dimensions in individuals with different malocclusions who undergo functional appliance treatment [25].

When reviewing studies on the potential correlation between orthodontic treatments and mandibular bone quality, some findings suggest no significant difference in mandibular bone quality between treated and untreated groups. For instance, Sadowsky and BeGole [26] compared records of patients obtained 10 years after orthodontic treatment with those of untreated patients and found no significant differences. Similarly, Sadowsky and Polson [27] concluded that fixed orthodontic treatments were not linked to changes in mandibular bone quality.

The literature suggests that orthodontic treatments may exert mechanical stress on the condyle, potentially initiating or exacerbating condylar resorption [28–31]. As a result, fractal analysis – a method for analyzing complex images by examining fundamental components – has gained traction, particularly in recent years. This method uses mathematical image analysis algorithms, and several researchers have demonstrated its utility in biological image analysis [20]. In the present study, fractal analysis was used to assess the trabecular structure of MABD and MCBF. In individuals who have undergone orthodontic treatment, the bone structure tends to exhibit a spongier nature, which may reduce the fractal dimension of trabecular bone compared with that of pretreatment. When evaluating orthodontic treatments, mandibular bone quality should be considered. The bone density in the mandibular anterior region increases in treatments involving RFAs, although this effect may be due to growth and development in patients. The anteroposterior position of the mandible can affect the genioglossus muscle and the position of the tongue root, potentially influencing maxillary sinus dimensions. The expansion of maxillary sinus dimensions when the mandible is brought forward using orthopedic devices suggests that the airway is influenced by mandibular position [32]. Additionally, it would be interesting to match the analysis of bone density with recently introduced technologies, such as smartphone applications [33] and artificial intelligence guided software [34], in order to easily consider potential modifications in craniofacial structures and obtain more reliable clinical outcomes.

This study had limitations, including a 2-dimensional imaging system being used in the measurement of sinus dimensions. If 3-dimensional imaging had been used, more detailed results could have been obtained, and sinus dimensions could have been measured with all elements in 3 dimensions. Another limitation was that a region from the maxillary region was not added to the bone density measurement in the mandibular region.

Conclusions

The effectiveness of treatment with RFAs is highly dependent on patient adherence to proper usage, making compliance with prescribed guidelines crucial for achieving optimal treatment outcomes. Notably, an increase in bone density in the mandibular and maxillary regions has been observed in patients undergoing orthodontic treatment with RFAs. This increase is likely due to the effect of these appliances on the mandibular anterior and condyle head regions, suggesting a potential connection between the use of RFAs and changes in MABD and MCBF. In this study, patients in group C displayed wider maxillary sinus dimensions, while those in groups A, B, and D exhibited narrower dimensions. However, to validate these observations, a more extensive analysis with larger patient cohorts and varied skeletal classifications is imperative. Additionally, the study uncovered significant variations in maxillary sinus dimensions among patients treated with different RFAs. Careful evaluation of potential changes in craniofacial structures is vital before proceeding with orthodontic treatments. Basing dental interventions on these assessments is key to achieving optimal results. Further clinical studies are needed to substantiate these findings and better understand the relationship between RFA use and changes in maxillary sinus dimensions.