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During the last few decades, technology has combined well with science and innovation to bring about sweeping changes in dental treatment. People who could never afford a smile due to the sorry state of their teeth have been offered a new lease of life, courtesy of emerging technologies such as removable partial dentures (RPDs). This prosthodontics is a flexible, cost-effective, and reversible dental treatment procedure for partially edentulous patients who desire to have a new look at any stage of their lives (Sadig & Idowu 2002). Most patients are favoring this treatment method over complete dentures as it gives them a chance to retain some of their natural teeth. The prosthesis is also preferred since it gives patients the freedom to remove and reinsert their teeth without having to rely on professional assistance. Most patients seeking RPDs are often informed by their functional and aesthetic requirements, as well as the need to preserve the remaining teeth (Budtz-Jergensen, 2000). Still, some patients are only left with this alternative due to factors such as lack of teeth required to provide support for distal abutments or due to monetary constraints (Shimazaki 2004).
However, it has been found that the distal abutment tooth of Kennedys class II RPD can be potentially damaged when vertical occlusal loads are applied downwards onto the artificial free-end saddle. According to Salvador et al (2007), Kennedy class II RPDs are usually made for patients who have lost either a few or all of their natural posterior teeth on only one side of the mouth left or right in a single arch. These patients have no posterior teeth at the rear of the edentulous section, a fact that complicates the treatment procedure. Many dentists and prosthodontists offering mandibular Kennedy class II RPDs have had to contend with challenging issues of resorption of edentulous ridges and making secondary modifications on the contiguous soft tissues. These and other shortcomings facing this procedure have threatened to water down major advancements made on RPDs designs and the raw materials used to cast the partial dentures.
The major problem affecting most RPDs originates from vertical occlusal loads since the dentures may fail to lounge completely on the edentulous ridge-like would be the case with complete dentures. Rather, the RPDs derive their stability and retention from clasps of metal or plastic which are safely clipped onto the existing posterior teeth (Bowley 2002). As such, lack of or inadequate vertical support brings the problem of excessive load distribution, especially to the edentulous ridge section. Ideally, the vertical load is supposed to be distributed to the remaining posterior teeth abutments. Problems of lack of or inadequate major connector strength and inflexibility as well as disproportionate tissue coverage due to the nature of the acrylic resin material used have also been reported (Kuzmanovic, Payne, & Purton 2004). Below is an occlusal view of a mandibular RPD.
After treatment with Kennedy type II RPDs, vertical occlusal loads transmitted from several sources may eventually surpass the threshold of the physiological alignment and movement of the abutment tooth, ultimately enhancing tooth mobility (Mizuuchi et al 2002). A functional force conveyed from the new artificial teeth to the supporting abutment tooth can cause a lot of discomfort due to the disparities in the displacement of the posterior abutment tooth and the soft membranes surrounding the residue ridge. The vertical occlusal force causes some rotational movement especially when applied directly onto the distal extension denture frame, eventually occasioning harmful stress on both the supporting abutment tooth and the soft tissues surrounding the residue ridge. Various interventions have been proposed to avoid the above from happening. First, the denture design that is made for a patient must exactly fit when pulled into the base of the residue ridge (Mizuuchi et al 2002). All considerations, including the morphology of the tissues, residual ridges, and occlusal influences must be carefully analyzed before a patient is finally fitted with a Kennedy class II RPD. To avoid damaging the partial dentures, it is also imperative to perform a critical evaluation of the resorption of the underlying bone to look for weaknesses before any fitting is made. According to Shimazaki (2004), vertical occlusal loads may potentially damage the dentures due to overloading the frontal section of the edentulous maxilla.
According to Budtz-Jergensen et al (2000), damage to class II RPDs caused by excessive vertical loads can be significantly reduced by mechanically designing the dentures to achieve maximum retention through the use of two retentive clasps. The clasps should utilize diagonal retention, placing them as close to the fulcrum line as possible. To guarantee stability and strength, the posterior tooth just mesial to the partial dentures extension base should be made to serve as an abutment tooth if situations allow. Standard practice demands that the occlusal rest should also be placed mesially to minimize any risk of posterior slanting of the abutment tooth. This makes it possible for the denture to make rotations around the fulcrum line when vertical occlusal loads are applied downwards onto the artificial free-end saddle. The diagonal retentions can connect the occlusal rests on the maxillary natural teeth without exerting undue torque or pressure on the abutment tooth (Budtz-Jergensen). The whole process is made possible because the bracing arm, minor connector, and retentive clasps are all situated on the survey line. This technique has been favored by many dentists due to its ability to curtail damage of partial dentures, especially of the class II type.
To give credibility to the stated methods, Mizuuchi et al (2002) argue that both the clasp assemblies and mesial connections should be used to avoid damaging class II RPDs as they do not induce substantial pressures on the movement and stability of the abutment teeth. However, the researchers think that dentists should adapt denture bases over the commonly used residual ridges in class II RPDs to achieve better results.
With advancements in technology, mechanical interventions in prosthetic dentistry can guarantee long-term success. Many dental problems presented to dentists and prosthodontists are so severe and critical that only mechanical intervention of clasping the teeth together can guarantee success. However, in conducting a Kennedy class II RPD treatment procedure, medical specialists should always remain open to the wide range of specialist opinions available in the market today to achieve optimal results (Davenport et al 2001). Many mechanical clasps have been developed lately to assist dental patients to cope with their problems. Although its still early to judge if the available mechanical solutions accompanying Kennedy class II RPDs are successful, available data reveals that some of the clasps such as RPI clasps have been able to achieve promising results more than traditional clasps such as Akers (Shimazaki 2004). However, more research needs to be carried out to come up with ways of addressing persistent problems and shortcomings such as the issues of vertical occlusal loads, soft tissues, and ridge formations.
List of References
Bowley, J 2002. Minimal Intervention Prosthodontics: Current Knowledge and Societal Implications. Medical Principles and Practice, Volume 11, No. 1, pp. 22-31.
Budtz-Jergensen, E., Bachet, G., Grundman, M, & Borgis, S 2000. Aesthetic Considerations for the Treatment of Partially Edentulous Patients with Removable Denture. Practical Periodontics & Aesthetic Dentistry, Volume 12, No. 8, pp. 765-772. Web.
Davenport, J.C., Basker, R.M., Heath, J.R., Ralph, J.P., Glantz, P-O., & Hammond, P 2001. Prosthetics: Clasp Design. British Dental Journal, Volume 191, pp. 71-81.
Kuzmanovic, D.S., Payne, A., & Purton, D 2004. Distal Implants to Modify the Kennedy Classification of a Removable Partial Denture: A Clinical Report 1. The journal of Prosthetic Dentistry, Volume 92, No. 1, pp. 8-11.
Mizuuchi, W., Yatabe, M., Sato, M., Nishiyama, A., & Ohyama, T 2002. The Effects of Loading Locations and Direct Retainers on the Movements of the Abutment Tooth and Denture Base of Removable Partial Dentures. Journal of Medical and Dental Sciences, Volume 49, No. 1, pp. 11-18.
Sadig, W.M., Idowu, A.T 2002. Removable Partial Denture Design: A Study of a Selected Population in Saudi Arabia. The Journal of Contemporary Dental Practice, Volume 3, No. 4.
Shimazaki, M 2004. Influence of Support Ability on Abutment Tooth of Lower Distal- extension Removable Partial Denture. Ohu University Dental Journal, Volume 31, No. 2, pp. 91-101.
Salvador, M.C.G., Valle, A.L., Ribeiro, C.M., & Pareira, J.R 2007. Assessment of the Prevalence Index on Signs of Combination Syndrome in Patients Treated at Sao Paulo. Journal of Applied Oral Science, Volume 15, No. 1. Web.
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