DENTAL BRIDGE PROBLEMS

DENTAL BRIDGE PROBLEMS

Table of Contents

FAILURES IN FIXED PROSTHODONTICS

I have experienced patients coming and asking about the guarantee of a bridge. Neither bridges nor the teeth approximating or opposing it can carry a lifetime guarantee. Bridges do fail even when they are technically well fabricated.

The 5 Major Problems in Fixed Prosthodontics to overcome Dental Bridge Failure are during

Diagnosis and Treatment Planning

Patient Management and Mouth Hygiene

Preliminary Mouth Procedures

Tooth Preparation and Case Fabrication

Dentist – Laboratory interaction.

Diagnosis and treatment planning

Treatment expectations

Patients usually have unrealistic expectations and regard aesthetics as prime consideration. Patients should be educated about the limitations. The patient is explained about the material and its cost and shelf life. Patient should be explained about the reason for the extraction of that particular tooth or the need for recountering with a crown should be explained.

Medical and dental history

Chronic medical problem that makes the patient unable to sit in the dental chair for a sufficient length of time makes it difficult for a dentist to complete a dental procedure. Such conditions includes

Chronic osteogenic problems

Respiratory and circulatory problems

Psychologic patients can frustrate the dentist.

Chronic drug abuse patients

Chronic alcohol abuse – unreliability of the patient and physical deterioration of hard and soft tissues of the oral cavity

Pulpal involvement

Periodontal problems

Temporomandibular joint disorders

Intraoral records and radiographic examination

are taken to check for –

Adequate bone support of abutment tooth

Sufficient root length

properly shaped roots

Need of Endodontic treatment

Need of restorations

Unerupted tooth and root tips  

Mounted diagnostic casts

Occlusal interferences

Extruded and tipped abutments

Possible path of insertion problems

Intraoral examination

Mobile abutment tooth

Sensitive tooth

Oral hygiene and periodontal evaluation

Shade of the tooth

Caries

Old restorations

Oral habits

Patient management and oral hygiene

Patient should be informed about the treatment for the quoted fees

Number of appointments for respective procedure

Oral hygiene instructions cannot be neglected

Post cementation examination should be  done routinely

Radiographs should be  taken for any caries, periapical / periodontal  disease

Soft tissue response should be  checked 

Occlusion

Marginal integrity of restoration

Preliminary mouth procedures

Soft tissue treatment

Periodontal surgery if required is done prior to the start of the treatment.

Crown lengthening should  also be done if required

Edentulous ridge should be  re contoured if needed

Hard tissue treatment

Oral Prophylaxis

Occlusal equilibration (lateral interferences and prematurities)

Reshaping of tooth (incisal edges recontouring, extruded teeth reducing, reshaping proximal contacts of adjacent tooth) should be done.

Abutment tooth should be caries free.

Endodontic treatment if needed should be performed with Pins and Post and cores

Extra time and expense involved reflects in the quality and prognosis of the finished restoration.  Patient is instructed not to hurry up for the treatment course.

Miscellaneous procedures

Diagnostic wax up should be done to preview the completed case for

  •       Esthetics of the patient
  •       Functional/technical problems to the dentist
Orthodontic repositioning

Upright the abutment

Improve esthetics

Failure to use can compromise function and esthetics in many cases.

Pre-treatment occlusal splints if the vertical dimension is to be altered.

Custom incisal guide table to copy exact anterior guidance

Vertical dimension maintainer appliance/index to check occlusal reduction if there are insufficient occlusal stops to maintain occlusal dimension during tooth preparation.

 Tooth preparation and case fabrication

Retainer selection

Esthetics

strength of the tooth and retainer

Caries index

Occlusion

Pulp size

Path of insertion

Cost for the patient

Abutment preparation

Inadequate reduction – shortens the life expectancy of the restoration

Do not permit development of properly shaped cusp inclines, cusp tips and fossae.

Bulky contours – periodontal health

Inadequate facial reduction prevents shading of veneers and pontics.

Overbuilding – periodontal health

   Inadequate interproximal reduction encroaches on embrasure spaces and effects esthetics and proper cleaning.

Excessive reduction
  • Reduce retention and stability of the restoration
  • Tooth weakened and pulpal damage.

Long span bridges and pier abutment – difficulty in path of insertion

special attention to – Tipped/malaligned abutments

Preparation with grooves, boxes and pins

Precision and semi precision attachments

Preparations done on the master casts so that the results are surveyed.

Finish line should balance with- Retention and resistance form(amount of axial reduction)

Patient’s oral hygiene

Esthetics

Periodontal health

Vitality of pulp

Insufficient water and air coolant

Dull cutting instruments

Heavy pressure(excess friction and heat)

Irreversible pulpal damage.

Treatment restoration(temporary restoration)

Over extension of the margins – irritate if gingiva and soft tissue damage

Under extension – pulpal irritation from sensitivity,preparation margins get damaged.

Improper cementation – irritation to the soft tissue if excess cement is not removed.

Improper occlusion –occlusal trauma –  pulp damage

Improper proximal and occlusal contacts – teeth shift – effect fit of final restoration

Final impression procedures

  • Marginal tissues should be displaced from the prepared margin
  • Tissue retraction with mechanical or mechanochemical  methods
  • Tissue injury – hemorrhage recession periodontal pocket –affect final restoration.

Impression distortion

Removing before the final set

Expired shelf life of the material

improper mixing

Voids

Incomplete detail

Dies and working casts

Improper pouring and sectioning of the dies

Dies with voids – difficulty in making accurate wax pattern and occluding the casting

Trimmed and marked properly to avoid over/under extension of margins

Casts mounted accurately – reduce occlusal adjustments.

Final restoration

Casting accurate on cast but not on abutment

Temporary cement on abutment

Check for debris/bubbles on inside of casting

over extended margins

Excessive  proximal contacts

Dentist – laboratory interaction

Dentist needs

  • Any special instructions to be given

Laboratory needs

  • Detailed written work authorization that accurately describes the design, materials
  • Working casts properly prepared
  • Preparation properly tapered and adequately reduced

Post insertion problems

Thermal sensitivity

Results from removal of enamel and dentin which has insulating properties  and their replacement with metals which are excellent thermal conductors

Thermal diffusion through a substance is related to its thermal conductivity and its thickness.

Magnitude and duration increases if preparation is close to the pulp.

Failure to use water spray during reduction increases the potential to post insertion sensitivity.

Failure of temporary restoration to cover all prepared tooth surfaces

Loose temporary restoration that allows seepage of oral fluids over prepared surfaces

Temporary restoration that places excessive occlusal forces on the prepared tooth.

Prolonged sensitivity that does not decrease in severity with time/acute pain indicates Endodontic treatment.

Discomfort during function

Premature centric occlusal contacts/excessive contact during eccentric mandibular movements.

Occlusal adjustments usually relieves pain.

Tenderness to percussion –  heavy centric/eccentric occlusal contact.

occlusal discrepancies that are not corrected lead to Endodontic treatment.

Tooth that have been out of occlusal function for a long time initially exhibit discomfort during function when the prosthesis is placed but adjusts with time to the increased functional activity.

Gingival Inflammation

        May be caused due to the clinical procedure carried out 

  • Soft tissue removal with rotary instruments
  • Excessive tissue retraction
  • Rough/poorly fitting temporary restorations
  • Failure to completely remove remnants of impression material or temporary cement from the gingival sulcus

Inflammation decreases if patient maintains good oral hygiene 

Inflammation after cementation 

Faculty cervical contour,marginal fit,or embrasure form of the prosthesis 

Poor oral hygiene.

Retention of food

Between abutment and adjacent teeth – poor occlusal relationship or lack of adequate proximal contact.

Cusp from opposing dentition can occlude with adjacent marginal ridge such that it forces the teeth apart and wedges food interproximally.

Offending cusp should be recontoured to reduce wedging effect

Missing/poorly located proximal contact – food impaction

Properly constructed proximal contact can open up due to heavy occlusal contact causing tooth movement in response to the interferences

Lack of occlusal contact allows eruption of tooth with resulting loss of contact.

Trauma to the Cheek or Tongue

Contact with sharp/poorly polished portions of a prosthesis

Cusp to cusp or end to end occlusal relationship without normal horizontal overlap

Horizontal overlap prevents soft tissue from being caught between the occlusal surfaces.

If the occlusion is unavoidable cusps should be blunt

Sensitivity to sweets

Failure of the final prosthesis to completely cover all areas of the prepared tooth surfaces

Significant portion of the luting agent has undergone dissolution

Abutment retainer is loose – new FPD fabricated

Caries on abutment/adjacent tooth.

Tooth mobility

Poor occlusal relationship that produces heavy  centric occlusal contacts or eccentric occlusal interferences

Overloading of prosthesis causes change in periodontal ligament and supporting bone.

Occlusal adjustments should be done

Inadequate osseous support – tooth mobility in absence of excessive forces

RPD provides bilateral bracing for weakened tooth.

Neuromuscular discomfort

 Specific problem

Pain in temporomandibular joint or associated muscles is related to improper occlusion created by fixed prosthesis

Caused by premature contact.

To avoid interfering and bring other teeth into occlusion contacts muscular contraction guides the mandible to a different position.

New mandibular position can create neuromuscular pain as a result of positional changes in the ligaments and muscles associated with the temporomandibular joint.

Nonspecific complaints

Patient aware of the prosthesis being in place and feels slight discomfort.

Due to additional forces to the abutment teeth,occlusal discrepancy or presence of artificial tooth occupying a previously open area.

Complains due to –the patient does not like the prosthesis but reluctant to discuss

Financial aspects produce nonspecific complaints.

Causes of Dental Bridge Failure

Biological failures

Mechanical failures

Esthetic failures

Biological failure

Caries

Most common 

Probing of margins of the prosthesis and tooth surfaces.

Radiographs helps to detect caries interproximally

Conventional operative treatment can restore small carious lesions without the need to fabricate a new prosthesis.

Gold foil/amalgam restoration of choice for marginal caries.

Glass ionomer/composites in esthetics.

Caries in proximal surfaces require removal of the prosthesis to obtain access

Lesion is small tooth preparation can be extended to eliminate caries and a  new prosthesis is fabricates

If lesion is large an amalgam restoration is required after removal of the restoration and a new restoration fabricated

Extensive lesions – Endodontic treatment or extraction

High caries index patient – patient  should be instructed about oral hygiene, fluoride containing dentifrices, topical fluoride application

Pulp degeneration

Sensitivity that does not subside with time, intense pain, periapical abnormalities need Endodontic treatment

Access to the pulp requires preparation of a hole in prosthesis through which treatment is done.

Perforation can be restored with gold foil, amalgam or a cast metal inlay.

Casting may become loose during the access opening or porcelain may fracture-remake.

If little sound tooth structure remains after Endodontic treatment a post and core is placed and new restoration is fabricated.

Periodontal breakdown

Poor marginal adaptation

Over contouring of the axial surfaces of the retainers

Large connectors that restrict the cervical embrasure space

Large pontic

Prosthesis with rough surfaces should be recontoured/remade

Extensive bone loss – loss of abutment teeth and attached prosthesis.

Less severe breakdown is treated with surgery which lead to unacceptable relationship between the prosthesis and the soft tissue.

If abutment is lost the retainer casting can be filled with amalgam or composite and formed in the shape of pontic

Occlusal problems

Interfering centric/eccentric occlusal contacts  – tooth mobility

Detected early – occlusal adjustments – prevent permanent damage.

Long term presence of occlusal interferences can lead to severe mobility; teeth should be bilaterally braced with removable partial denture.

Interfering centric/eccentric occlusal contacts  – tooth mobility

Detected early – occlusal adjustments – prevent permanent damage.

Long term presence of occlusal interferences can lead to severe mobility; teeth should be bilaterally braced with removable partial denture.

Neuromuscular discomfort due to improper occlusion can result in prosthesis failure, as occlusal adjustments that are required to allow the mandible to be properly positioned may cause perforation of the prosthesis or make the restoration aesthetically unacceptable.

Tooth perforation

Pin/pinholes used in pin retained restorations can be improperly located and perforate the tooth laterally.

If located occlusal to the periodontal ligament  -extend the tooth preparation to cover the defect

Into the periodontal ligament – periodontal surgery and to smooth off the projecting pin .place a restoration into the perforated area

Perforations into the furcations – inaccessible for restoration – extraction

Lateral perforations can occur during Endodontic treatment / post and core preparation.

If accessible can be restored with amalgam but more often the tooth is lost. If pins perforate pulp chamber – Endodontic treatment.

Mechanical failures

Loss of retention

Patient is aware of looseness

Sensitivity to temperature or sweets

Bad taste/odour

Periodic recall include unseating existing prosthesis

Loose casting – fluids drawn under the casting, when reseated with a cervical force fluid is expressed producing bubbles as air and liquid are simultaneously displaced.

If restoration dislodged without damage and no caries – recementation of the restoration.

Recent cement failure of one abutment with no  caries – clean with hydrogen peroxide /sodium hypo chloride solution, inject cement/low viscosity composite through an access opening made in the lingual.occlusal surface.

Fill the retainer until excess appears on all the gingival margins. Allow the cement to set under biting force.

Prosthesis removal reveals lack of adequate retention by the preparation form, teeth should be modified to improve resistance and retention form, and a new prosthesis should be fabricated.

Connector failure

Can fracture under occlusal forces

Placement ,size and shape and finishing errors

Placed in contact area

Size and shape depends on length of the span, area of the arch.

Vertical dimension has more effect on strength than horizontal dimension

Short span – well shaped and less bulky   connectors.

Both cast and soldered connections fracture – internal porosity that weakened the metal.

Pontics are placed in a cantilever relationship with the retainer – excessive forces to the abutment tooth.

Difficult to detect clinically

Wedges are positioned to separate individual components to conform the correct diagnosis

Prosthesis should be removed and remade

Removable partial denture is inserted to maintain the existing space and esthetics.

Occlusal wear

Heavy chewing forces,clenching/bruxism – accelerated wear

Casting perforation develops as occlusal metal thickness is limited by tooth reduction

Detected early – gold/amalgam restoration

Occlusal surface is ceramic– wear of natural tooth, metallic restoration

Occlusal surface metal – integrity of opposing tooth is maintained.

Tooth fracture

Excessive tooth preparation( cannot resist occlusal forces)

Preparation mostly of restorative material which was not retained in sound dentin with pins.

Interfering centric/eccentric contacts

Heavy occlusal forces

Forcibly seating an improperly fitting prosthesis

Unseat a cemented bridge incorrectly.

New prosthesis that encompasses the fractured area if the fracture is coronally limited.

Fracture – pulp exposure – Endodontic treatment with post and core.

Root fractures

   Cause

  •  Trauma
  • Endodontic treatment
  • Forceful seating of a post and core
  • Seating an improperly fitting post and core.
  • Root fracture below alveolar bone crest – extraction.

Fracture ends  just below the alveolar bone – periodontal surgery, expose fracture site to be encompassed by a new prosthesis

Acrylic veneer wear

Functional loading, abrasive foods/tooth brush abrasion

Repair – autopolymerising resin  with mechanical retention (undercuts/threaded posts)

Composites – more popular.  Mechanical more resistant to wear and maintain function and appearance longer than acrylic resin.

Porcelain fracture

  1. Metal ceramic –improper design of metal frame work / problems related to occlusion
  2. All ceramic – deficiencies in tooth preparation / heavy occlusal contacts.

Laboratory related

Metal handling procedures

Improper handling of alloy during casting    – metal contamination (separation of metal and porcelain in  severe contamination)

Bubbles form at  metal-ceramic  junction – creating stress and cracks

Dentist related 

Metal ceramic Frame work design

Sharp angles/rough/irregular areas over the veneering areas – stress concentration-crack  propagation and ceramic fracture

Porcelain fracture – framework design that allows centric occlusal contact on / immediately next to metal ceramic junction

Major difference in thickness of porcelain from one area to another.

Porcelain thickness is increased on pontics, If proper tooth shaped metal framework is not developed

Internal strains develop and fractures occur under little/no load.

Preparation, impression and insertion

Thin metal casting doesn’t support porcelain – porcelain fracture.

Framework thickness of less than 0.2 mm over veneering surface – high failure rate.

Tooth preparation with slight undercut – binding of the prosthesis as it is seated – initiates crack in porcelain.

Distorted impression –  improper fit of the prostheses and crack propagation

Feather edge finish line/impression that does not record the finish line ,extension of metal beyond the finish line .Thin metal bind against the tooth  and initiate a crack  in overlying porcelain

Patient related

Occlusion

Clenching and bruxism

Night guard

Centric/eccentric occlusal interferences

Trauma/accidents/foreign objects in food.

Repair of fractured metal ceramic restorations

Best method – new prosthesis

Composites – lack of longevity.

Mechanical retention gained from undercut metal substructure.

 Color changes that makes repair obvious.

 If adequate metal thickness is available

Removal of remaining porcelain on the fractured unit to expose the underlying metal

Drilling several pinholes(4-5) into the framework to a depth of at least 2mm and making of an impression

 Creating a pin retained metal casting 0.2 – 0.3 mm thick of metal ceramic alloy to fit over the exposed framework

Fusion of porcelain  to pin retained casting

Cementation of casting

With adequate pin length – lasts longer

Recemented  –  if becomes loose

All Ceramic Crowns

Anterior – no failures

Posteriors – fractures because of occlusal load

Advanced materials – crowns on posteriors

Vertical fracture

Tapered finish line (chamfer), restoration contacts the tooth on a sloping surface, forces are produced that tend to expand the restoration and not well resisted by porcelain.

Sharp line angles/incisal edges – stress concentration.

when large portion of the proximal  preparation form is missing and not restored prior to impression, Occlusal forces when applied to the marginal ridge in which the missing tooth form is located, occlusal forces tend to rotate the restoration causing expansive forces

Rounded preparation without retention and resistance   form tends to rotate the restoration and lead to fracture of the restoration.

Lingual fracture

Semilunar lingual fracture – occlusion cervical to the cingulum of the preparation, forces to the porcelain are more shear in nature and not well resisted

Inadequate lingual tooth reduction (less than 1 mm of porcelain present)

Heavy occlusal forces.

Repairs

New restoration

Heavy occlusal forces – metal ceramic restoration

Esthetic failures

At the time of cementation – Actual failure

Color mismatch

Poor tooth contour

Poor gingival contour/colour

Poor margin placement

Poor residual pontic ridge contour

Unrealistic expectations by the patient

Delayed esthetic failure – Gingival recession

Prominent roots

Poorly fitting crowns

Excessive trauma during preparation and impression making

Subpontic tissue shrinkage

Periodontal surgery

Porosity – poorly glazed porcelain appear satisfactory at cementation but later develops black specks

Drifting of anterior teeth- loss of periodontal support

loss of posterior occlusal vertical dimension  

Loss of circumoral elasticity.

Wear – lower anteriors when opposed by porcelain.

Incorrect form /framework design that display metal

Natural teeth undergo color changes(over years)

Outline form is not contoured

Preparation of thin incisors – metallic color visible with time.

Subpontic inflammation

Pain

Swelling

Bad breath

Bad taste

Bleeding gums

Poor esthetics.

SUBPONTIC DEFECTS

Defect in subpontic area  – esthetic problems

Seibert in 1983 classified ridge defects as

Class I – facio-lingual loss of tissue with normal ridge height in an apico-coronal direction

Class II – apico-coronal loss of tissue with normal width in facio-lingual direction

Class III – combined facio-lingual and apico-coronal loss of tissue, resulting in loss of normal height and width.

Treatment

Perio surgery with grafts

Eletrosurgery

Prosthetic gingiva with removable prosthesis

Removal of a crown is done with the help of a crown removal tool or a kit.

Planned Retreatment

Retreatment should be considered because of difficulties in accurately predicting the pattern of future dental disease.

Survey contours are incorporated in the retainers of an fixed partial dentures to accommodate a future removal partial denture in the event of terminal abutment loss.

Accommodation made for future occlusal rest by increasing occlusal reduction during tooth preparation and using occlusal surfaces

Proximal boxes can be incorporated if a nonrigid rest could simplify future Retreatment.

CONCLUSION

  Treatment does not end with the fitting of restorations. Subsequent maintenance is an integral part of treatment.

 If this is not adequately prescribed, failure can occur.

Well organized & efficient post operative care is the chief mechanism for successful Fixed Prosthodontics

REFERENCES

  • Rosenstiel ,Contemporary fixed Prosthodontics,3rd edition,2001.Mosby publishers
  • Michael D Wise. Failure in Restored dentition: Management and treatment. 1996. Quintessence Jhonston’s Modern practice in fixed Prosthodontics. 4th pub.
  • Dykema. edition.1986.
  • Thayer
  • Charles J.Goodacre – clinical complications in fixed Prosthodontics, JPD 2003; 90:31-41.
  • .J.E Reuter – failures in full crown retained dental bridges.Br Dent J 1984; 157:61.
  • Greg Libby – longevity of fixed partial dentures, JPD 1997; 78:127-31.
  • Won-suck oh – effect of connector design on the fracture resistance of all ceramic fixed partial dentures, JPD 2002; 87:536-42.
  • Mirza F.D – failures in crown and bridge Prosthodontics, Journal Indian association.52; 381-383.
  • W.R.Teteruck -Failures in fixed Prosthodontics – faculty of dentistry, University of Western Ontario, division of fixed Prosthodontics, department of restorative dentistry.


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