**3. Immediate and delayed restoration/loading, what is the difference?**

In 1981 Albrektsson et al. suggested a protocol in which the implants are left to heal in situ for at least 3 to 4 months without loading [19]. He considered the non-loading phase a crucial period to achieve successful osseointegration and avoid fibrous tissue formation between the implant surface and the bone. On the other hand, many clinical studies proved that immediate restoration, immediate loading, or early loading are acceptable treatment modalities [20, 21]. These studies were in response to the social and psychological needs of many patients. The immediate or early treatment modalities aim to reduce the overall recovery time between the surgical intervention and the insertion of the final restoration. These approaches are known as immediate restoration protocol, immediate loading protocol, and early loading protocol.

Patients typically are uncomfortable and, in many cases, refuse to stay without their RPD for a long time, especially if it restores a lot of missing teeth or teeth in the esthetic zone. The immediate protocols can reduce the patient concerns related to the final restoration by reducing the waiting period. In some cases, a temporary restoration is immediately delivered to give the patient a hint on the form, size, and position (in some cases, the shade) of the final restoration. Moreover, the second surgical intervention can be averted through immediate protocols. To achieve a good success rate in this treatment modality, a good understanding of the topic, terminology, limitation, and biology is essential. These topics will be discussed in other chapters, but it is crucial to clarify a few terms.

The loading can be classified into four categories:


The timing of dental restoration can also be categorized to:


*Strategic Implants under Existing Partial Removable Dentures, Why, How Many, and Which… DOI: http://dx.doi.org/10.5772/intechopen.100191*

• Delayed restoration: If the dental restoration is placed intraorally after the conventional loading time, the restoration is classified as delayed restoration.

According to the previous classifications, the dentist has different types of intervention. For example, he can go for immediate restoration with conventional loading or implement early restoration with delayed loading.

In the case of the strategic implant under existing RPD, there are seven scenarios: immediate restoration with one of the four loading types, or early restoration with early, conventional, or delayed loading. The decision regarding the best approach is multifactorial: age, esthetic expectations, oral hygiene level, bone quality and quantity, and treatment expenses. According to the 2018 census supported by the International Team for Implantology (ITI), the most critical factors that may impact the loading protocol selection are patient-related factors, especially patient's general health, implant primary stability (ISQ ), bone grafting, the size and shape of the implant, and the doctor skills and experience [22]. Moreover, the ITI tried to unify the two classifications (loading and restoration timing) to make it less complicated for the clinician and easier for the researchers to perform clinical studies and compare their results. They described four protocols:


### **4. Why strategic implant?**

Improving dental treatment output by using implants to enhance the functional performance of the complete denture is a well-known approach in prosthodontics. The McGill Consensus Statement stated that the first option in treating the lower jaw edentulous patient should be two implants retained overdenture and not lower jaw conventional complete denture (CD) [23]. Overwhelming scientific evidence supports the statement [23]. The evidence emphasized the superiority of two implants retained overdenture treatment modality on the conventional CD in many aspects, such as patients' chewing efficiency, positive modification in patients' diet, patients' satisfaction with the CD stability, retention, and comfort as well as quality of life [23]. Although a lot of scientific evidence highlighted the positive impact of inserting implants under existing RPD, no similar Consensus Statement is available regarding implant-retained or implant-assisted removable partial denture [24–26].

Not all patients are suitable for implant-supported fixed dental prostheses. For example, many patients are unwilling to have an extra surgical intervention (bone grafting, sinus lifting, bone splitting, or expansion). Other patients are not suitable for such intervention because they are medically compromised or do not have adequate financial flexibility. As an alternative to inserting multiple implants, the dentist can improve the quality of the prosthodontic treatment by changing the support type of the RPD to the quadrangular-support type. The improvement can be achieved by inserting one/two standard implants or one/two/three mini-implants per quadrant to reach a symmetrical quadrangular-support type. The prostheses will be tooth implant-supported RPD instead of tooth tissue-supported RPD. This prosthodontic approach is affordable to many patients.

#### **Figure 22.**

*Upgrading the existing clasp retained lower RPD by inserting strategic mini-implants, immediate restoration with immediate loading/soft material. A- Intraoral image with lower RPD before implantation. B- Partial edentulous lower jaw before implantation. C- Tissue surface of the RPD before implantation. D- Four strategic miniimplants in the interforaminal region, tooth 32 was extracted. E- Tissue surface of the RPD after implantation, soft relining in the areas opposing the implants' head. F- Tissue surface of the RPD after 4 months, the matrix pick-up (housings). G- Intraoral image with lower RPD after the housing, clasps in esthetic zone were removed.*

*Strategic Implants under Existing Partial Removable Dentures, Why, How Many, and Which… DOI: http://dx.doi.org/10.5772/intechopen.100191*

The strategic implant is "the implant that can change the prosthetic support type to a more favorable configuration" [1]. It is a reliable way of treatment with an implant survival rate of 91.7–100% [4]. Also, it can support both the RPD and the other abutments effectively. In two clinical studies with 2 and 3 years follow-up, the survival rate of the natural teeth abutments was 100% [9, 24].

Moreover, it can improve the survival rate of the RPD. The 10-year survival rate of RPDs; clasp-retained removable partial dentures, conical crown-retained dentures, or a combination of conical crown and clasp-retained dentures is 71.3% [27]. On the other hand, clinical studies with observation periods between 1 and 12.2 years reported survival rates of 90–100% for the implant-assisted removable partial denture prostheses [7, 28–31]. This remarked difference in the survival rate plays an essential role in formulating the prosthodontic plan.

Many clinical studies have shown that implant placement in strategic locations under an existing RPD can enhance chewing efficiency, dental health-related quality of life, and patient satisfaction with speaking and eating, as well as RPD retention, stability, and support [1, 8, 32]. Above that, it gives the dentist the ability to reduce the tissue coverage and reduce the size of the RPD, which can positively impact the patient's acceptance of the RPD, especially if he suffers hyperactive gag reflex, **Figure 24**. Also, it can improve the final esthetic result by avoiding the traditional metal clasp, **Figures 19** and **22**.

Unfortunately, inserting a standard implant under the existing RPD is not always feasible. The patient may have a very narrow bone that prevents inserting a standard implant without bone grafting. A procedure that is not suitable or acceptable by some patients. In this case, mini-implants can be considered a good alternative, **Figures 22** and **25** [1, 8, 16].

## **5. Mini-implant-assisted removable partial denture**

In 1976, the U.S. Food and Drug Administration (FDA) approved the 3 mm root-form dental implant. With time, dental implants proved to be a predictable and reliable prosthodontic treatment modality with a high success rate [33–35]. After 21 years, the approval was cleared for implants less than 3 mm. The approval widens the spectrum of the patients treated with dental implants, particularly the cases with reduced bone width.

In literature, there is no standardization regarding the terminology of dental implant diameter [36]. For example, some authors considered the implants with diameters from 1.8 to 2.9 mm as small implants; others call them mini-implants [37]. Some authors defined the mini-implant as the implant with 2.2 mm [38]. Al-Johany et al. proposed a classification scheme and used four terms: Extra-narrow <3.0 mm, Narrow ≥3.0 mm to <3.75 mm, Standard 3.75 mm to <5 mm, and Wide ≥5 mm [36]. In this text, we will follow the lead of Resnik et al. and Schiegnitz et al. by considering the mini-implant as the implant with a diameter < 3.0 and the narrow-diameter implant as the implant with a diameter ≤ 3.5 [25, 37]. This implant type is mainly used in heavily atrophic jaws but with sufficient bone height. The mini-implant gives the dentist the ability to avoid bone augmentation procedure, which is considered a time and cost-consuming surgical intervention. Avoiding additional surgical procedures can reduce morbidity and possible complications such as nerve trauma, hemorrhage, postoperative pain, or infection [25]. The infection may lead to the failure of bone grafting [25]. Above that, it is less invasive than the standard implant as it requires a

smaller implant bed and no flap in a considerable number of cases [26]. Therefore, it is more appropriate for the compromised or elderly patients. Moreover, it is costeffective and affordable. On the other hand, the small diameter of the implant may create a shear load to the crestal bone. That may increase the risk of bone resorption [37, 39]. Narrow -implant has been linked to biomechanical risk factors as implant fatigue or fracture, particularly when used in the canine area where high occlusal loads are applied or in parafunctional habits patients [40].

A systematic review and meta-analysis reported that mini-implants (diameter < 3.0 mm) performed substantially worse than standard diameter implants with survival rates of 94.7 ± 5% [25]. However, narrow implants with a diameter (3–3.5 mm) have a better survival rate of 97.7 ± 2.3% [25]. Therefore, some

#### **Figure 23.**

*Narrow bone can be treated with bone grafting. Unfortunately, this is not always feasible. A- Biomechanically, the narrow implant is not always the best approach, see paragraph 5. B- Osteoplasty is used to insert a wider implant by increasing the bone width, which will impact the crown-implant ratio negatively and may place the implant near vital anatomical structure. C- One-piece mini-implant with ball attachment and preferable crown-implant ratio can be used to stabilize a complete removable denture or partial removable denture.*

## *Strategic Implants under Existing Partial Removable Dentures, Why, How Many, and Which… DOI: http://dx.doi.org/10.5772/intechopen.100191*

researchers believe the best approach for a thin bone is bone augmentation [37]. If this is not feasible, narrow implant, osteoplasty and standard implant, or one-piece miniimplant with ball attachment and removable denture can be considered, **Figure 23**.

The small diameter implant is used to replace missing individual teeth in the anterior region, lower and upper jaw [41, 42]. Mini-implant is used as an orthodontic implant or transitional or provisional implant to support interim prostheses during the healing period after extensive implantations or augmentations and bone grafting [43]. The onepiece mini-implant with ball attachment is used as assisting / anchoring element under the removable denture [1]. Strategic min-implant under existing RPD and CD proved to be a reliable and straightforward approach [1, 8, 44]. New studies reported that the one-piece mini-implant with ball attachment has a significant advantage on the final prosthodontic treatment [1, 8].

#### **Figure 24.**

*Upgrading the existing double crown retained upper RPD by inserting strategic mini-implants, immediate restoration, and delayed loading. A- Partial edentulous upper jaw before implantation. B- Tissue surface of the RPD before implantation. C- Five strategic mini-implants. D- Tissue surface of the RPD after implantation, recesses (empty notches) against the mini-implants. E- Tissue surface of the RPD after 4 months, the matrix pick-up (housings). The palate coverage was reduced. F- Intraoral image with the RPD after the housing.*

The one-piece implant mimics nature by having a solid unibody structure with no microgaps between the implant and the abutment. As a result, the possible biological complication (bone resorption) and structural flaw are reduced. Also, the flap or flapless single-stage surgery allows the dentist to implement immediate loading or immediate restoration [42]. Moreover, delayed loading is possible by preparing a recess against the mini-implant in the RPD's tissue surface. The treatment protocol can be conventional or delayed loading. However, the recess (cavity) distorts the fit of the RPD's, **Figure 24**.

On the other hand, if the mini-implants are inserted in a healthy, not compromised patent with insertion torque ≥35 Ncm, immediate loading can be considered.

#### **Figure 25.**

*Upgrading the existing double crown retained lower RPD by inserting strategic mini-implants, immediate restoration and immediate loading. A- Partial edentulous lower jaw before implantation. B- Tissue surface of the RPD before implantation. C- Two strategic mini-implants. D- Tissue surface of the RPD after implantation, the matrix pick-up (housings) inserted in the same implantation session. E- Intraoral image with the RPD in place after implantation.*

*Strategic Implants under Existing Partial Removable Dentures, Why, How Many, and Which… DOI: http://dx.doi.org/10.5772/intechopen.100191*

The immediate restoration with immediate loading can be implemented through one of two forms:


After implantation, soft relining material can restore the fit of the RPD, ease tissue pressure, and give the patient a secure feeling because the relining material encircles the implant head and minimizes RPD rocking. If all mini-implants have a high insertion torque, the patient can receive the final restoration with matrix pick-up (housings). Subsequently, no additional session for adjusting the RPD is needed. In this approach, the patient can directly feel and recognize the significant improvement in the RPD in many domains especially, retention, support stability, and chewing [1, 8].

Studies proved that inserting strategic implants under existing RPD improves patient satisfaction on short- and medium-term follow-up (3-years) [1, 43]. The improvement can be explained by the symmetrical distribution of the abutments and the increased number of the rests/abutments [1, 17]. Gorai S, et al. study reported a correlation between the rests number and denture usage [17].

## **6. Conclusion**

To sum it up, using strategic implants under existing RPD upgrade the design to more favorable support type and improve patient satisfaction with the RPD on several domains like speaking, chewing, retention, stability, and support of the RPD. This improvement could be reached earlier if the patient received immediate loading [1].

In many cases, after putting into consideration the patient's main complaint, expectation, desire, general health, intraoral/extraoral findings, evaluating the risks (do no harm) and the benefits of bone grafting and several implants, the dentist is able to provide his patient with one or few strategic standard or mini-implants that can satisfy the patients' needs *without overtreatment* "Less is more".

Strategic implants can also improve chewing ability, stabilize the occlusion, increase bite force and improve patient oral health-related quality of life. Moreover, better distribution of occlusal forces that may reduce bone resorption may be gained. Furthermore, strategic implants can improve comfort, confidence, and esthetics by reducing the RPD size and removing metal clasps from the esthetic zone.
