Periodontal Considerations In RPD

Dr. Puneet Kaur Dept. of prosthodontics

ContentsIntroduction Periodontal screening

Oral hygiene Plaque and calculus scores Gingiva Periodontium Tooth mobility Radiograhic examination

Periodontal preparationInitial Phase Surgical Phase Maintanence Phase

Considerations for RPD design Conclusion References

Introduction

Generally, removable partial denture patients present a compromised situation because of loss of teeth and supporting tissues.Therefore it is of fundamental importance that, such patients be evaluated for periodontal status before commencement of any prosthetic treatment.

And, if periodontal support is compromised, therapy must be coordinated with prosthetic treatment.

Also, RPDs be designed so that they least interfere with plaque control and must not damage the oral tissues.Periodontal considerations at three levels: Periodontal screening Periodontal preparation Designing RPD

Periodontal screening in RPD patient

Aim : is to diagnose any periodontal condition that would compromise the long-term prognosis for asuccessful therapeutic outcome.

Performed using: direct vision, paplation, clinical examination, diagnostic casts and radiographs.

Includes

Oral hygiene Plaque and calculus score

GingivaPeriodontium

Tooth mobilityRadiograhic examination

Oral hygiene status

It is most important parameter of successful prosthetic treatment Disclosing solution can be used to detect debris, plaque, materia alba etc.

Also note should be made about patients oral hygiene habits. Instructions should be given for maintaining adequate oral hygiene. Reinforce instructions throughout treatment and posttreatment phase.

Plaque and calculus scores

One of many indices can be used for plaque and calculus score.

Silness and Loe 1964

Score 0 = No plaque Score 1 = A film of plaque adhering to the free gingival margin and adjacent area of the tooth. Score 2 = Moderate accumulation of soft deposits within the gingival pocket, or on the tooth and gingival margin, which can be seen with the naked eye. Score 3 = Abundance of soft matter within the gingival pocket and/or on the tooth and gingival margin.

Greene and Vermilion Calculus index:

0-No calculus present 1-Supragingival calculus covering not more than third of the exposed tooth surface. 2-Supragingival calculus covering more than one third but not more than two thirds of the exposed tooth surface or the presence of individual flecks of subgingival calculus around the cervical portion of the tooth or both. 3-Supragingival calculus covering more than two third of the exposed tooth surface or a continuos heavy band of subgingival calculus around the cervical portion of the tooth or both.

Gingiva

Colour : coral pink Contour : scalloped Consistency : firm and resilient Surface texture : stippled Position : level at which gingiva is attached to tooth surface

Periodontium

Pockets : detected with careful exploration with a periodontal probe.

Probing technique: The probe should be inserted parallel to the vertical axis of the tooth and walked circumferentially around each surface of tooth to detect areas of greatest depth.

Examined for:Presence and distribution Bleeding on probing Pocket depth Level of attachment

Type of pocket

Tooth mobility

Each tooth should be carefully evaluated for mobility.

Method: The tooth is held firmly between one metallic instrument and a finger, and an effort is made to move it in all directions.

Causes Infammation Traumatic occlusion Loss of attachment

Grades:

Normal : 0.05-0.1 mm Grade I : less than 1mm in buccolingual direction Grade II : 1-2mm mobility in buccolingual direction. Grade III : more than 2mm mobility in buccolingual direction or tooth is vertically depressible.

If etiological factors are removed, many grade I and II mobile teeth can revert back to normal and can help to retain and support RPD. Thus, mobility itself is not an indication for extraction unless the mobile tooth cannot aid in support or stability of RPD.

Radiographic examination

Full mouth dental radiographs can be used to supplement the clinical examination but should not be used as substitute for it.

A critical evaluation of following should be made: Type, location and severity of bone loss Location, severity and distribution of furcations. Periodontal ligament space alterations. Presence of calcified deposits. Location of restoration margins. Root morphology Root caries

Periodontal preparation

Periodontal therapy

The periodontal preparation of mouth usually follows any oral surgical procedures and is done simultaneously with tissue conditioning procedures. However any such preparation must be completed before restorative procedures begin.

ObjectivesRemoval and control of all etiological factors contributing to periodontal disease.Elimination of, or reduction in, pocket depth, and establishment of healthy gingival sulcus whenever possible.

Establishment of functional atraumatic occlusal relationships and tooth stability.Development of personal plaque control program and definitive maintenance schedule.

Treatment planning

Depending on the extent and severity of the periodontal changes present, a variety of therapeutic procedures, ranging from simple to relatively complex, may be indicated. Can be divided into three phases: Phase I or initial therapy

Phase II or surgical therapyPhase III or maintenance therapy

Phase I or initial therapyThe first phase is considered as disease control and its objective is to eliminate or reduce local etiological factors. The procedures preformed during this phase are: Oral hygiene instructions Scaling and root planning Elimination of local factors other then calculus Elimination of gross occlusal interferences Temporary splinting Use of nightguard

Oral hygiene instructions

The oral hygiene instructions should be carefully devised to suit needs of particular patient. For oral hygiene to be successful, patient must be convinced to follow the prescribed procedures regularly. Motivation techniques and explanation of periodontal disease are important components.

Patient should be instructed about use of disclosing solutions correct tooth brushing technique use of floss and if required use of interdental brushes or sulcular brushes.

Further treatment should be withheld till desired level of plaque control is not achieved.

Scaling and root planning

Careful scaling and root planning are fundamental in re establishment of periodontal health.

The use of ultrasonic scaler is recommended for calculus removal. This is followed by root planing using sharp periodontal curette.

Elimination of other local factors

Overhanging margins and open contacts that allow food impaction should be corrected .

Any large carious lesions where pulpal involvement is likely, must be excavated and restored.

Elimination of gross occlusal interferences

Poor occlusal contacts may act as a factor that contribute to more rapid loss of periodontal attachment. Selective grinding should be done to eliminate such contacts.

Also particular attention must be directed towards occlusal relationship of mobile teeth.An attempt is made to establish a positive planned intercuspal position that coincides with centric relation.

Guide to selective grinding

Schuyler has provided following guide to occlusal adjustments: A static coordinated occlusal contact of maximum number of teeth, in centric relation must be the first objective. If premature contact in both centric and eccentric position the cusp incline should be reduced. If premature contact is in centric only, opposing sulcus should be deepened.

Usually premature contacts in centric relation are relieved by grinding the buccal cusps of mandibular teeth and lingual cusps of maxillary teeth. In anterior teeth if premature contacts occur in both centric and eccentric relations, the incisal edges of mandibular teeth can be grinded. However, if premature contacts are in eccentric only, the lingual slopes of maxillary teeth can be corrected.

Temporary splinting

The cause of mobility in case of grade I mobile teeth must be determined and eliminated.

Such teeth then can be splinted by: Composite resin Fibre reinforced resins Cast removable splints Intracoronal attachments.

Use of night guard

The night guard may be helpful as form of temporary splint if worn at night after removal of RPD. Also it is particularly useful when one of abutment teeth has been unopposed for extended period of time, to prevent pain and sensitivity due to sudden loading of such tooth.

Phase II or surgical therapyAfter initial therapy patient is re evaluated for surgical phase. If oral hygiene is at optimal level , yet pockets are present, surgical procedures should be considered to improve periodontal health. These procedures include: Various flap surgeries Guided tissue regeneration Ressective osseous surgeries Reconstructive surgeries Treatment of furcations

Phase III or maintenance therapy

Includes:Re evaluation for presence of any local factors and Reinforcement of plaque control measures.Thorough debridement of all tooth surfaces of supragingival and subgingival plaque. The frequency of recall visits should be customized depending upon susceptibility and severity of periodontal disease.

Periodontal considerations during designing of RPDs

Effect on plaque

Several studies show an effect of RPDs on the quantity and quality of plaque.Chamrawy E.et al showed that plaque formation was enhanced on teeth in contact with RPDs and pointed out the need for proper oral hygiene. Same author in another study showed that RPDs promote the proliferation of spirilla and spirochetes at the expense of cocci and short rods, thereby altering the composition of plaque.Chamrawy E. Quantitative changes in dental plaque formation related to removable partial dentures. J Oral Rehabil 1976;3 115120. Chamrawy E. Qualitative changes in dental plaque formation relate to removable partial dentures. J Oral Rehabil 1979;6 183188.

Bissada NF et al in their study, comparing three different designs of RPD, concluded that gingival areas that are covered by parts of the RP without relief show the most adverse periodontal reactions, both clinically and histologically, whereas the uncovered areas are the least affected.

Bissada NF, Ibrahim SI, Barsoum WM. Gingival response to various types of removable partial dentures. J Periodontol 1974;45 651659.

Effects on Forces Exerted on Teeth and Tooth Mobility

It has been reported that RPD design affects the distribution of force on abutment teeth and residual alveolar ridges. Two similar photoelastic studies, compared the stresses induced on the abutment teeth by different RPD designs of direct retainers. Both studies concluded that the typical RPI retainer design (mesial rest seat and buccal I bar) produces the lowest torque on abutment teeth.

Thompson WD, Kratochvil FJ, Caputo AA. Evaluation of photoelastic stress patterns produced by various designs of bilateral distal-\extension removable partial dentures. J Prosthet Dent 1977;38: 261273. Chou T-M, Caputo AA, Moore DJ, Xiao B. Photoelastic analysis and comparison of forcetransmission characteristics of intracoronal attachments with clasp distal-extension removabl partial dentures. J Prosthet Dent 1989;62:313319.

Also, the literature suggests that clasp-retained designs produce less torque on abutment teeth than intracoronal attachment designs. Various studies concluded that there is an initial increase in tooth mobility, which comes to baseline after settling period of about 1 to 1.5 months following insertion of new RPDs.

Haralambos Petridis, Timothy J. Hempton, Periodontal Considerations in Removable Partial Denture Treatment: A Review of the LiteratureInt J Prosthodont 2001;14:164172.

Considerations for individual component of RPD

Owall et al stressed that in addition to biomechanical considerations such as stability and retention, it is of fundamental importance that RPDs be designed so that they interfere as little possible with plaque control and must not damage the oral tissues.

Such design parameters are termed as secondary prophylactic measures or hygienic principles.

The basic principle of open hygienic design is that if the base elements of the RPD do not contact either teeth or periodontium, it can not cause any injuries to these structures Also, it is emphasized to use contemporary design with reduced number of components and elimination of components whenever possible without compromising biomechanical requirementsOwell t al. RPD design and Hygienic principles. Int J of Prosthodont, 2002;15(4) 371-378

Individual component

Major connector :Should be free of movable tissues.Impingement of gingival tissue should be avoided. Relief should be provided in case of distal extensions, as they tend to rotate in function.

It should not contribute to the retention or trapping of food particles.

Margins should be located far enough from gingival margin to avoid tissue irritation. Borders of maxillary major connector should be minimum of 6mm away from gingival margin. In mandibular lingual bar major connector the superior border should be 3-4 mm away from gingival margin.

Borders should be rounded without any sharp margins. All the borders must be parallel to gingival margin . Also for stabilizing periodontally weakened teeth a manibular linguoplate major connector is recommended.

Minor connectorsMinor connectors connecting clasp assemblies to major connector must be located on proximal surfaces of abutment teeth or in the embrasure between two abutment teeth Should not be bulky to avoid any interference in function.

Minor connectors connecting rests to major connector should arise at right angles from major connector with rounded junction. Should cover as little gingiva as possible. Relief should be provided under minor connectors connecting denture base to major connector.

Also minor connector acting as approach arm for Ibar retainer, should not interfere with the contour of soft tissue around abutment.

Rests and rest seatsRests control forces acting upon remaining teeth. In distal extension situation, the occlusal rests are positioned on mesial surface rather than on distal surface of abutment tooth to distribute the occlusal forces along the long axis.

Also Kratochvil recommended that in toothborne situations, rest should extend to the center of tooth to prevent tipping action and to provide vertically directed forces to the tooth.

Rests on anterior teeth are placed as close to cervical aspect of tooth as possible to gain support advantage, to reduce torque and to establish a positive relationship between tooth and prosthesis.

To avoid unnecessary contact with marginal gingiva, the cingulum rest can be designed in a C form, with one extension to minor connector. This will reduce contact with soft tissues by half and

enhances periodontal health.

Direct retainers

Can be classified as: Intracoronal retainers

Manufactured retainers such as dolbo Custom made retainers 1. Occlusally approching 2. Gingivally approching

Extracoronal retainers

Occlusally approching clasps Approch the retentive undercut from occlusal suface. As it increases the buccolingual width of the crown, it effects the normal food flow leading to food accumulation Also as width of occlusal table is increased, greater forces are generated.

Gingivally appoching clasp

Better esthetics than occlusally approching clasp Also less tooth contact Less interference with natural tooth contours.

RPI system

Advocated by Kratochvil and KrollDesigned to accommodate functional prosthesis movement. Thus decreasing the harmful tipping or torquing forces on teeth.

Consists of

Mesioocclusal rest with minor connector placed in mesiolingual embrasure without contacting the adjacent tooth Proximal guide plate contact the guide plane on distal surface of abutment teeth I- bar retainer

There are three basic approaches to RPI system: First approach recommends that the guiding plane and proximal plate extend the entire length of proximal surface. However, because of greater contact area of guide plane more horizontal forces are directed to abutment tooth.

Second approach recommends guide plane and proximal plate to extend from marginal ridge to junction of middle and gingival third. This decrease in surface area evenly distribute functional forces between teeth and residual ridge.

Third approach recommends proximal plate that contacts only 1mm of gingival portion of guide plane

This also redistribute forces between teeth and residual ridge

Thompson WD et al in photoelastic stress pattern study, comparing nine different clasping designs concluded that: The design of a retainer with a mesial rest in conjunction with a buccal I-bar or a wrought-wire and cast lingual arm exhibited the most favourable distribution of vertically applied forces. Retainer designs with a distal rest tend to move the clinical crown distally and the root mesially at the apex, resulting in horizontal forces in the bone.Thompson WD, Kratochvil FJ, Caputo AA. Evaluation of photoelastic stress patterns produced by various designs of bilateral distal extension removable partial dentures. J Prosthet Dent 1977;38: 261273.

Placing rests of distal-extension removable partial dentures more anteriorly provides an axis of rotation that directs applied forces in a more vertical direction. The distal rest in conjunction with circumferential retainers developed greater horizontal forces within the supporting structures.

Fit of framework

Framework for RPD must be fitted to teeth and adjusted for functional movement. This will assures that the casting does not produce undue torque against abutment teeth and also controls stress transfer to the soft tissue. The physiologic adjustment of the casting can be accomplished with marking materials such disclosing wax, to show abnormal contact areas , which are then removed by grinding

Splinting the abutment teeth

Splinting the abutment teeth in RPD may minimize the hazardous effects of excessively loading the abutments. However, the preferable number of splinted teeth is debatable. Preiskel reported the need for splinting all of the anterior teeth Kratochvil et al suggested that fewer teeth need splinting.Preiskel H. Precision retainers for free end saddle prostheses. Br Den J 1969;127:462-8. Kratochvil FJ, Thompson WD, Cap&o AA. Photoelastic analysis of stress patterns on teeth and bone with attachment retainers for removable partial dentures. J Prosthet Dent 1981;46:218.

Splinting of abutments often necessitates reduction of sound tooth structure. Fixed splints also compromise periodontal health care because of the wide joints between the units of the splint Margins of fixed splints may cause gingival irritation.

Thus limiting the extent of a fixed splint may reduce such hazards.

Hussein et al in their study on effect of splinting on load distribution of extracoronal attachment with distal extension prosthesis concluded that:

Splinting the most distal abutment to the anterior tooth (twounit splint) in a distal extension extracoronal attachment RPD resulted in a significant reduction of stresses transmitted to the supporting structures.Extending the splint to include a third tooth (three unit splint) had an insignificant effect on the stresses recorded. Hence splinting can be limited to only two teeth adjacent to distal extension.

Conclusion

RPD insertion results in quantitative as well as qualitative changes in plaque accumulation. However careful examination of any existing periodontal condition and its elimination prior to prosthetic treatment can contribute to success of prosthesis. Oral hygiene instructions and periodic reinforcement is mandatory. Also, RPD must be designed according to hygienic principles and every effort should be made to reduce forces directed to supporting tissues.

References

Chamrawy E. Quantitative changes in dental plaque formation related to removable partial dentures. J Oral Rehabil 1976;3 115 120. Chamrawy E. Qualitative changes in dental plaque formation relate to removable partial dentures. J Oral Rehabil 1979;6 183188. Bissada NF, Ibrahim SI, Barsoum WM. Gingival response to various types of removable partial dentures. J Periodontol 1974;45 651659. Owell t al. RPD design and Hygienic principles. Int J of Prosthodont, 2002;15(4) 371-378 Thompson WD, Kratochvil FJ, Caputo AA. Evaluation of photoelastic stress patterns produced by various designs of bilateral distal extension removable partial dentures. J Prosthet Dent 1977;38: 261273. Preiskel H. Precision retainers for free end saddle prostheses. Br Den J 1969;127:462-8.

Kratochvil FJ, Thompson WD, Cap&o AA. Photoelastic analysis of stress patterns on teeth and bone with attachment retainers for removable partial dentures. J Prosthet Dent 1981;46:21-8. Hussein G. El Charkawi, Effect of splinting on load distribution of extracoronal attachment with distal extension prosthesis in vitroProsthet Dent 1996;76:315-20.) Newman Takei. Carranzas clinical periodontology. Tenth edition, elsevier Alan B. Carr. McCrackens removable partial prosthodontics. Eleventh edition, elsevier