Accuracy in Dental Implantology: The Challenge of Precision - Essay Sample

Introduction

The precision of implant placement during dental surgery has, for long, been a challenge to many dentists. Most of the time, the functional and aesthetic quality of the result depends on the specific dentist's experience. Experienced physicians produce better exactness in the mesiodistal angles compared to less experienced surgeons. In Dental implantology, accuracy can be defined as how much the dental implant post-operation position deviates from the planned location (De Santis et al., 2019). It gets measured via a CBCT (Cone Beam Computed Topography) of the patient after surgery. To minimize the chances of error posed by freehand implant placement, there exist surgical guides to help surgeons with position predictability. This review compares the positioning efficiency between freehand placement and computer surgical guided procedures.

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The Development of Dental Implant Therapy

Dental healthcare has been in constant improvement in recent decades. However, many people still lose their teeth from various circumstances. For years, the only solutions available were dentures and bridges, until dental implants were invented (Chen, Lin, and Wang, 2019). These implants are used to replace tooth roots to give a stable anchor for both fixed and removable teeth while matching the patient's natural teeth. The technique has been in use from the 1960s, when scientists like Per-Ingvar Branemark successfully inserted titanium and other metals implants into human jawbones, and attach artificial teeth to them (Vermeulen, 2017). Over time, dental implant technologies have undergone systematic evolutions.

The first type of implants is root form implants, which are mostly made of titanium and have different textures and shapes. The next class is the Zygoma implants, which can support teeth by going across the maxillary sinus while restoring the full upper composition of the patient's dental formula even after a severe tooth loss. The last class of implants is small diameter implants, which are narrow and mostly used for orthodontic anchorage (resisting tooth movement) and denture retention (Chen et al., 2018). Today, tooth-loss victims throng hospitals for dental implants, and the demand has kept rising (Vasak et al., 2011), thus the focus of the technology's efficiency at accurately replacing teeth. The search for accurate techniques motivated the invention of surgical guides.

Surgical guides help surgeons to virtually plan implants then proceed to safely, predictably, and efficiently place the implants for patients. The accuracy and enhanced speed saves the patient time and enhances their experience. Surgical guides are made by capturing impressions of the planned implant site on an intraoral scan, then generating a computer-generated three-dimensional implant planning system (Gargallo-Albiol et al., 2019). The set-up then replicates the patient's dental setting by helping the doctor to input the implant into the jaw bone with optimum accuracy, then proceeds to lead the system to position the implant on its exact planned spot using sleeves (Katsoulis & Katsoulis, 2017). There exist bone-supported, mucosal supported, and tissue-supported surgical guides depending on how they are made.

Bone-supported guides usually serve in full-arch edentulous operation cases. They obtain support from the load-carrying zones of the jaw (Moon et al., 2016). They are hard to fabricate and to perfectly place because they need a higher degree of flap reflection for access (Moon et al.). Good physician experience, accurate imaging, and proper planning can, however, help to mitigate these challenges. Mucosal-supported guides obtain them support form the soft tissues in the mouth. Their fabrication is based on available temporary prostheses. Their biggest challenges include poor retention during surgery and unstable tissue quality and thickness (Walworth, 2019). Tooth-borne guides usually easily adapt to different surgery environments. They use teeth, which are easy to reproduce, support, and retain (Misch, 2015). They mostly serve best in procedures involving fixed restorations and single implants. They are the most accurate and have shown great predictability (Seppanen, 2019).

Implant Location

The final placement of the dental implant is important because more accurate positioning enhances implant longevity (Choi et al., 2017). The typically desired implant position is the original position of the natural tooth with minimal deviation and movement as possible. The implant must be positioned correctly in the occlusocervical, faciolingual, and incisocervical angles. For a better aesthetic experience,the implant should be mesiodistally centered in the edentulous space (Figure 1) (Cullum & Deporter, 2016). This also allows the contralateral tooth to replicate morphologically accurately. This exactness will enable the teeth to smoothly grow into the desired cross-sectional geometric tooth form, from the round implant form, thus appearing normally after emergence from the tissue without being tilted on the arch (Jaju, 2015). It also enhances the form and location of soft tissue around the tooth.

Figure 1: Correct mesial placement (Cullum & Deporter, 2016).

Further, the implant must be centered in the edentulous space or slightly tilt to the side of the facial if the bone configuration allows (Figure 2) (Choi et al., 2017). Failure to observe this may make the crown to have a cervical contour or make the porcelain to overlap the soft tissue while attempting to retain the dental configuration. With overlapping porcelain, the patient will find it difficult to maintain proper oral hygiene, and it also compromises the aesthetics of the patient's dental display (Jaju, 2015). The only possible restoration is to remove the implant and place another one in the proper position.

Figure 2: Correct edentulous placement (Choi et al., 2017).

The placement of implants in the cementoenamel and apical junction allows the requisite morphological developments to occur systematically. If the implant is placed too deep, it compromises bone healing post-operation, thus may stop the soft tissue from automatically filling the spaces in the cervical embrasure. Therefore, it is recommended that space of around 2mm below the cementoenamel junction be kept (Jaju, 2015).

Figure 3: 2mm placement below the cementoenamel junction (Jaju, 2015).

The distance placed between nearby implants hinders the existence of interdental papilla. To reduce crestal bone loss in the aesthetic areas of the mouth, it is recommended that a mesiodistal distance of 3mm or more be maintained between implants (Jensen, 2011). Also, it is critical to keep a distance of 10mm anteroposterior dimension or arch curve (Jensen).

The Digital Workflow

There is no specific design to adhere to when planning a surgical guide procedure. Importantly, though, the patient must get digitized before the process. A surgeon can combine various structures to support the framework, such as bone, mucosa, teeth, and the available implant components (Figure 4) (El Askary, 2019). For completely edentulous patients, there are many guide-design options to choose from. Most physicians prefer stackable guides because they are easy to use and adaptable. For these guides, there is one foundational guide which is placed on the bones for support followed by systematic placement of all the other required guide components. For instance, the first guide is to create the necessary space for implant placement, and the second one is to guide and allow for smooth implant placement.

Another way is to use stabilization pins to move from a mucosal-borne surgical guide to a structural guide that gets anchored by mucosa and nearby bones on the jaw. Improved technology now allows one to plant and print skilled multilayered surgical guides by themselves. An example may begin with an intraoral CBCT scan done using a digital planning computer software, followed by using a 3-D printer to fabricate the final surgical guide (Figure 5). The guide made through this procedure is unique because it can line up the system, ensure correct stabilization pins placement, and remain in position until implant placement. It thus minimizes error by ensuring that there is no constant removal and reinsertion of the guide during the operation. This process enables the physician to make the final restoration shape.

Figure 4: tooth- and mucosa-based surgical guide (El Askary, 2019).

Figure 5: Intraoral scan (El Askary, 2019).

In summary, the stereolithography process begins with a CT scan using a radiographic template with a radio opaque marker. The CT scan is to preoperatively evaluate the nearby anatomical structures and bones quality and quantity. Via a rapid prototyping technique, The CT scan result then gets transmitted to a master site where the doctor can see the virtual 3-dimensional impression from all angles and customize it using computer software (Bagheri, Bell & Khan, 2012). The final approved plan is then sent to stereolithography Apparatus which scans the virtual representation, promotes further polymerization, and then finalizes the template fabrication.

Implant Placement

The most important part of this is selecting the correct size of the implant. After the 3-dimensional impression of the restoration gets approved, the headache switches to placing it in the patient's mouth. It must be done carefully to ensure the correct physiological result comes out. Transfer to the mouth is through guided surgery, as explained in the previous paragraphs. Surgical guides ease operations for doctors and patients. Other surgery techniques include freehand implant placement (which is the oldest) and computer navigated surgery' which is an upcoming trend that uses GPS technology to generate 3-dimensional maps to allow the physician to work with the best precision (Bagheri, Bell & Khan, 2012).

Accuracy of Surgical Guides

Freehand surgery has been the most common procedure of implant dentistry, and survival rates have remained higher than 90 percent. However, the process lacks the power witnessed in restorative techniques in bones of type three and four (Gultekin, Cansiz & Yalcin, 2016). Freehand surgeons usually use wax or surgical stent to enhance accuracy. Computerized Tomography (CT) scanners have helped over time to determine volume and anatomy in comparison to the expected implant size. Two-dimensional radiographs and mucoperiosteal flap raising helped in measuring tooth volume. The transfer of the planning using these two methods has not been fully precise until the intervention of computer-assisted surgery (CAS) (Mattheijer, 2019). The template generated by CAS can efficiently transfer the full CT scan information to the patient. Further, the computer-assisted design can accurately match implant design to implant site bone density before the operation so that the placement takes place with maximal bone engagement (Gultekin, Cansiz & Yalcin, 2016).

Guided surgery leads to more precise implant placement, preservation of anatomic structures, and gives a high geometrical accuracy (about 0.1mm). It also uses transparent material, which allows the doctor to see through the impression, thus enhancing efficiency. The technique is less invasive and flapless, hence results in minimal swelling and strain after the operation. It leads to shorter treatment times. Chen, Lin, and Wang (2019) conducted a study to compare the results and patient experiences after guided versus freehand implant placement during a five-year follow-up. They proved that guided techniques significantly reduce post-operative stress and marginal bone loss (Chen, et al., 2018).

Computer-guided surgery i...