Introduction to prognosis

Establishing the prognosis of periodontally involved tooth or teeth is indeed difficult. Various studies have found that it is very difficult to determine the exact prognosis of periodontally compromised teeth after their appropriate periodontal treatment. Hirschfeld and Wasserman (1978) 1 in a study evaluated 15,000 teeth in 600 patients at least 15 years after they were treated for advanced periodontitis. These patients were well motivated regarding professional oral health care and personal oral health care, including maintenance of oral hygiene and periodontal health. However, due to marked differences in their post-operative course, these patients lost zero to 23 teeth per patient during this period of evaluation. Similarly, in a series of studies, McGuire and Nunn (1991, 1996) 2, 3 concluded that it is difficult to predict the prognosis of teeth with an initial prognosis of less than good. In other words, it can be said that it is very difficult to establish an accurate prognosis of periodontally compromised tooth/teeth. However, with accurate analysis of the periodontal condition, occlusion, systemic factors and patient motivation a predictable prognosis can be determined most of the times. In the following sections, we shall discuss the factors which determine the prognosis of a tooth.


Prognosis is the prediction of the probable course, duration, and outcome of a disease, based on the general knowledge of the pathogenesis of the disease and the presence of risk factors for the disease 4. In dentistry prognosis of a particular tooth or teeth depends on various factors. Usually, patients commonly ask questions like, for how many years my teeth will be all right after this treatment? or what will be the life of my tooth, which is causing me trouble? All these questions are related to ………. Contents available in the book ……….. Contents available in the book …….. … Contents available in the book …….. … Contents available in the book ……..

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Types of prognosis

The prognosis can be classified in two ways. One classification of prognosis classifies it as diagnostic, therapeutic or prosthetic prognosis and the other classification classifies it as the individual and overall prognosis.

Diagnostic prognosis:

It is the prognosis of the teeth if no treatment is provided. In other words, we can say that what will be the status of the teeth under question in the future if no treatment is provided for the present periodontal condition.

Therapeutic prognosis:

It is the prognosis of the teeth after an appropriate periodontal treatment is provided. The treatment may vary from primary periodontal treatment for stopping the disease progression to regenerative procedures.

Prosthetic prognosis:

It is the prognosis of the teeth for supporting the prosthetic restoration after an appropriate periodontal treatment has been provided. It also refers to the determination of whether the prosthesis to be planned shall be therapeutic or detrimental. One should be well versed with the basic principles of fixed prosthodontics to determine prosthetic prognosis.

     While discussing the prognosis with the patient, initially, the patient should be told about the diagnostic prognosis (i.e., what will happen if no treatment is provided), then the therapeutic prognosis (i.e., status of teeth after the treatment is provided) and if indicated, the prosthetic prognosis (i.e., future prediction of prosthetic restoration of teeth after periodontal treatment).

The prognosis can also be classified as individual prognosis or overall prognosis.

Individual prognosis:

Individual tooth prognosis referrers to the prognosis of an individual tooth, based on local and prosthetic/restorative factors that have a direct effect on its prognosis. Various factors which determine individual tooth prognosis are 5,

  • Remaining bone support.
  • Probing depth.
  • Mobility.
  • Furcation involvement.
  • Crown-root ratio.
  • Tooth morphology.
  • Caries.
  • Pulpal involvement.
  • Mucogingival problems.
  • Number of remaining teeth.
  • Position and alignment of teeth.

Overall Prognosis:

It refers to the prognosis of the teeth based on the sum of various local, systemic, environmental and other factors which may affect the overall periodontal health of the teeth. Various factors which determine overall tooth prognosis are 5,

  • Age.
  • Medical status.
  • Individual tooth prognosis.
  • Complexity of prosthesis.
  • Rate of progression.
  • Host response.
  • Smoking.
  • Stress.
  • Patient cooperation.
  • Economic consideration.
  • Knowledge and ability of dentist.

Let us now discuss in detail the factors affecting the prognosis of teeth,

Factors affecting individual prognosis

Remaining bone support:

The remaining bone support is directly proportional to the prognosis of the tooth. In general, two third to one half of the investing bone is the minimal requirement for a tooth to have a favorable prognosis. However, this is a crude method for the determination of prognosis because there are various other factors such as root length, root form, root shape, single or multiple roots etc., which also have to be considered while determining the prognosis. The bone loss has to be seen in relation to root length. In teeth, with short roots, a small amount of bone loss may create a significant difference, whereas a large amount of bone loss around long roots may not result in significant loss of support. However, as bone loss exceeds ………. Contents available in the book ……….. Contents available in the book …….. … Contents available in the book …….. … Contents available in the book ……..

Probing depth:

The presence of periodontal pockets indicate active periodontal disease. In general, teeth with shallow periodontal pockets have a better prognosis than teeth with deep pockets (8 mm or more). The presence of complex pockets encompassing multiple root surfaces is a poor prognostic factor than the presence of simple pockets. However, it must be remembered that deep pockets can have a better prognosis if the bone levels are adequate and the bone defects present are amenable for regenerative therapy. Pockets present on the proximal surfaces have a better prognosis than in other areas such as furcation. Pockets present on the facial and lingual/palatal surfaces may result in loss of bony plate over the convexities of the root surface. The presence of pseudo-pockets is a good prognostic factor as these represent increase in the size of soft tissue only .


In general, increased tooth mobility is a poor prognostic factor. Firm teeth, even with advanced bone loss have a better prognosis than loose teeth. Increasing bone loss is associated with an increase in tooth mobility. When bone loss increases beyond 50%, tooth mobility increases rapidly with each millimeter of further bone loss. If the cause of tooth mobility can be eliminated (such as, trauma from occlusion) the mobility reduces and the ………. Contents available in the book ……….. Contents available in the book …….. … Contents available in the book …….. … Contents available in the book ……..

Furcation involvement:

Furcation involvement is usually seen in the first upper and lower molars 6. It is a bad prognostic factor, because furcation is difficult to access and treat. One study has demonstrated that at least one furcation of maxillary first or second molars is affected by the periodontal disease in 50% of all patients over 30 years of age 7. There are various factors associated with furcation involvement, which determines the prognosis of furcation involvement. In general, long root trunk, a wide furcation, and a crown fornix near cementum-enamel junction are poor prognostic factors for furcation involvement 8. Initial furcation involvement can be treated with non-surgical and surgical periodontal therapy and responds well to the treatment. Grade I and Grade II furcation involvement respond well to regenerative therapy. Grade III and Grade IV furcation involvements do not have a good prognosis. There are multiple factors which should be considered while establishing prognosis for the tooth with furcation involvement, these include,

  • Grade of furcation involvement.
  • Soft tissue coverage of the furcation.
  • Root trunk length.
  • Furcation size.
  • Root divergence.
  • Root separation.
  • Root concavity.
  • Crown/root ratio.
  • Grade of mobility.
  • Presence/absence of occlusal interferences.
  • Smoking and parafunctional habits.
  • Self-maintenance by the patient.

Crown-root ratio:

Teeth with short, slender and tapering roots have a poorer prognosis than teeth with long and broad roots. For example, the maxillary first premolars show increased tooth mobility because these have conical and tapered roots. Multi-rooted teeth with flared roots have a better prognosis than teeth with close together or fused roots. The broad occlusal surface is a bad prognostic factor as it may cause increased tooth mobility. A favorable crown-root ratio is considered as a good prognostic factor. Center of tooth rotation should also be considered along with crown-root ratio. More the center of rotation ………. Contents available in the book ……….. Contents available in the book …….. … Contents available in the book …….. … Contents available in the book ……..

Tooth morphology:

Tooth root morphology plays an important role in periodontal maintenance. Scaling and root planing of the root surfaces are essential for the maintenance of periodontal health. The morphological deformities of the root surface such as concavities, grooves or bizarre morphology jeopardize these procedures. The root concavities are most commonly present on the maxillary first premolar and the mesiobuccal root of the first molar. These are also seen on both the root surfaces of mandibular first molars and incisors 9.

      The presence of developmental structures such as enamel projections and developmental grooves worsen the prognosis of the involved tooth. Several studies 10-17 reported the prevalence of cervical enamel projections ranging from 8.6 % to 85 %. One study examined 5,230 extracted molars and concluded that 25.2% of mandibular molars and 15.8% of maxillary molars demonstrated the presence of cervical enamel projection 11. The presence of these projections predisposes the tooth to the formation of periodontal pocket, which many times, is difficult to treat.

Carious teeth:

In general, more the number of carious teeth, worse is the prognosis. The crown structure lost due to caries should be considered while the determination of prognosis. The grossly carious teeth should be restored to improve the overall progno-sis of teeth. Root canal treatment, post and core treatment with crown placement should be included in the treatment plan for these teeth to improve the therapeutic prognosis.

Pulpal involvement:

Any tooth, which is suspected to be endodontically involved should be thoroughly examined. Endodontic examination serves to improve treatment planning, performance, and prognosis. Long-standing endodontic involvement may result in the formation of a periapical lesion. Appropriate endodontic treatment improves the prognosis of the tooth. If the periapical lesion is large, apical surgery should be performed. More the number of endodontically involved teeth, worse is the prognosis.

Mucogingival problems:

The presence of mucogingival problems is associated with a bad prognosis. An inadequate width of attached gingiva, recession, high frenal attachment, and presence of periodontal pockets below the level of mucogingival junction are all related to poor prognosis. Appropriate surgical procedures are required to correct these problems to improve the overall prognosis of the teeth.

Number of remaining teeth:

More the number of teeth present in oral cavity better is the prognosis. This is because occlusal forces are distributed adequately among all the teeth. If few teeth are missing, the remaining teeth must bear all the masticatory and parafunctional stresses, which is a bad prognostic factor. Further, if many teeth are missing and the remaining teeth are also supporting removable or fixed prosthesis, the prognosis is even poor.

     The distribution of reaming teeth is also important. If the missing teeth are distributed in an arch in such a way that remaining teeth can withstand the occlusal forces when rehabilitated with a prosthesis, it is always a good prognostic factor. Also, the quality of remaining teeth is important. It is always better to have ………. Contents available in the book ……….. Contents available in the book …….. … Contents available in the book …….. … Contents available in the book ……..

Position and alignment of teeth:

In general, tilted, rotated or drifted teeth have a worse prognosis as compared to well-aligned teeth. This is because oral hygiene is more difficult to maintain in areas with malaligned teeth. Further, difficult to reach areas such as maxillary and mandibular posterior-most areas are more difficult to maintain as compared to the anterior areas.

Trauma from occlusion and parafunctional habits:

Abnormal occlusal forces and parafunctional habits may cause injury to the periodontal apparatus. These forces may result in mobility, wear facets, and enlargement of the periodontal ligament space. It has been demonstrated by various studies (see chapter 35), that traumatic occlusal forces combined with inflammation can cause increased bone loss and attachment loss. The correction of occlusal abnormalities should be considered as an important component of the comprehensive treatment plan. In patients with parafunctional ………. Contents available in the book ……….. Contents available in the book ……….. Contents available in the book ……….. Contents available in the book ……..

Factors affecting overall prognosis

Age of the patient:

The loss of periodontal support in relation to patient’s age is an important factor which has to be considered while determining prognosis. When comparing two patients, one 30 years old and another 65 years old having a similar periodontal bone loss, the younger patient has a poor prognosis as compared to the older patient. This is because the rate of progression of periodontal destruction is more rapid in the younger patient as compared to the older patient. It may be usually expected that the younger patient may have a greater bone reparative capacity as compared to the older patient, but a rapid bone loss in a short period of time in a younger patient does not go in favor of good bone reparative capacity.

Medical status of the patient:

The systemic condition of the patient is a very important factor in the determination of the overall prognosis. Systemic conditions, like uncontrolled diabetes mellitus, are associated with poor periodontal prognosis. Both diseases are thought to share a common pathogenesis that involves an enhanced inflamma-tory response that can be observed at the local and systemic level 18-21. A review of the literature by Kinane (1997) 22 found considerable evidence to suggest that diabetes and periodontitis have a direct relationship. Other systemic factors which affect the overall prognosis include multi-vitamin deficiency, hyperthyroidism, hyperparathyroidism, Parkinson’s disease, autism and other conditions related to mental retardation. Conditions like ………. Contents available in the book ……….. Contents available in the book ……….. Contents available in the book ……….. Contents available in the book ……..

Individual tooth prognosis:

The individual tooth prognosis should be considered while determining the overall prognosis of a patient. As already stated, the overall prognosis is the sum of multiple factors that have a direct or indirect relationship with periodontal disease progression. The individual tooth prognosis is an integral component of these factors.

Complexity of prosthesis:

The replacement of missing teeth with a prosthesis is a commonly carried out procedure. However, the complexity of the prosthesis fabricated should be considered while the determination of the prognosis. In general, the prognosis is guarded with a complex and extensively complex prosthesis as compared to the simple prosthesis or no prosthesis at all.

Rate of disease progression:

Probably, the most important factor that determines the future status of a tooth is its past periodontal status. The rate of disease progression may be rapid or slow. In patients with slow disease progression, the prognosis of teeth is always better than those with rapid disease progression. The best way to determine the rate of disease progression is careful history taking and analysis of the past dental records. The radiographic evaluation of the past and present records can be used to determine the rate of bone loss in a specified period of time.

Host response:

Inflammatory response consistent with the presence of local factors is a good prognostic factor. Patients who show a severe response to the minimal amount of plaque accumulation have a poor prognosis. Recent advances in the etiopathogenesis of periodontal diseases have provided a lot of evidence of altered immune response ………. Contents available in the book ……….. Contents available in the book ……….. Contents available in the book ……….. Contents available in the book ……..


It is a well-established fact that smoking is associated with poor prognosis in a periodontally compromised patient. The epidemiological studies have provided irrefutable evidence that smoking adversely affects the prognosis in a periodontally compromised patient and the mechanisms by which it does so 23. The periodontal disease progression associated with smoking is dose-dependent 24. It has been demonstrated that the odds ratio for the development of periodontal disease in association with smoking is 3.97 for current smokers and 1.68 for former smokers 24 and 3.25 for light smokers and 7.28 for heavy smokers 25. Various mechanisms by which smoking causes increased periodontal destruction have been discussed in the “Smoking as a risk factor for periodontal diseases”.


Stress is associated with an adverse prognosis in periodontal disease progression. The present evidence clearly suggests that emotional stress can modulate the immune system through the neural and endocrine systems in at least three different ways, including the autonomic nervous system pathway, through the release of neuropeptides and through the release of hypothalamic and pituitary hormones 26-28. The alteration in the immune response results in inadequate defense against infection, which favors periodontal disease progression. A detailed discussion of stress and periodontitis is available in “Stress as a risk factor for periodontal diseases”.

Patient cooperation and motivation:

The participation of the patient in the treatment process and the extent of compliance with recommendations and returns for maintenance visits are key factors in achieving periodontal therapeutic success 29. Various studies have demonstrated that the actual success of the treatment does not depend on the execution of the treatment but on the patient’s adherence to the oral hygiene regimen and cooperation with the dental team 30, 31. One major problem encountered by the dentists is ………. Contents available in the book ……….. Contents available in the book ……….. Contents available in the book ……….. Contents available in the book ……..

Economic considerations:

While routine periodontal therapy can be afforded by many patients, extensive periodontal surgical procedures or dental implants may raise financial concern for many patients. Keeping in mind the financial status of the patient, it is the duty of the dentist to suggest best treatment options available for that particular patient. Simple periodontal treatments can halt the progression of periodontal diseases and in a well-motivated patient, the prognosis becomes favorable.

Knowledge and ability of dentist:

The knowledge and ability of the dentist play a significant role in the overall prognosis of the patient. The initial periodontal treatment can be well executed by a general dentist, but a strict referral protocol should be employed when advanced periodontal treatment is required. Once all the treatment is completed, the general dentist can carry on with the maintenance schedule.

Categorization of prognosis

A thorough analysis of the factors discussed above guides us to determine the individual tooth and overall prognosis of a patient. It should be remembered that prognosis does not remain the same for a patient. In patients who respond well to the treatment the prognosis improves, whereas in patients where results of treatment are not as expected, the prognosis may worsen. So, it is advisable that only a provisional prognosis should be established for a patient until Phase I therapy is completed and evaluated. If the patient’s response to phase I therapy is good and there is a considerable reduction in inflammation and pocket depth the prognosis may be better than as assumed before the treatment. On the other hand, if the response to phase I therapy is not as expected, the prognosis may be worse than established before.

     One more thing to be remembered is that the prognosis changes with the disease activity. As we know that periodontal disease progresses in an episodic manner, the active period is associated with signs and symptoms of disease activity, whereas the inactive period does not demonstrate signs and symptoms of the disease.

     Hence, it is difficult to establish a prognosis for the patient. However, based on the factors discussed above, many researchers have recommended different categories of prognosis. Categories of prognosis proposed by McGuire (1991) 2 and Kwok and Caton (2007) 32 are given in the following tables. Recently, McGowan et al. (2017) 33, proposed an evidence-based periodontal prognosis model. The proposed system uses six tooth level and three patient-level factors to give each tooth a prognosis of secure, doubtful, poor or irrational to treat. The tooth level factors include ratio of bone loss: age, periodontal pocket depth, extent of furcation involvement, presence of an infrabony defect, compromising anatomical factors and the extent of tooth mobility. The patient-level factors include smoking, poorly controlled diabetes and bleeding on probing. When present, these factors downgrade the prognosis by one level as previous research has established that these factors are significantly associated with an increased risk of tooth loss.

Categories of prognosis proposed by McGuire (1991)
Very good<25% attachment loss.
Good25% attachment loss and/or class I furcation involvement.
Fair25-50% attachment loss and/or easily accessible class II furcation involvement.
Poor50-75% attachment loss and/or class II inaccessible furcation involvement, class III furcation involvement, class II mobility.
Hopeless>75% attachment loss, class III mobility.
Categories of prognosis proposed by Kwok and Caton (2007)
Favorable The periodontal status of the tooth can be stabilized with comprehensive periodontal treatment and periodontal maintenance. Future loss of the periodontal supporting tissues is unlikely.
Questionable The periodontal status of the tooth is influenced by local and/or systemic factors that may or may not be able to be controlled. The periodontium can be stabilized with comprehensive periodontal treatment and periodontal maintenance if these factors are controlled; otherwise, future periodontal breakdown may occur.
UnfavorableThe periodontal status of the tooth is influenced by local and/or systemic factors that cannot be controlled. The periodontal breakdown is likely to occur even with comprehensive periodontal treatment and maintenance.
HopelessThe tooth must be extracted.
Prognosis model proposed by McGowan et al. (2017)
Prognosis model proposed by McGowan et al. (2017)

Whether to retain or extract the involved tooth

After critically analyzing the tooth-related and patient-related factors, the decision about retaining or extracting a tooth should be made. It must be remembered that a severely involved tooth jeopardizes the adjacent teeth. Hence, retaining such a tooth is not a wise decision. Teeth should be evaluated for their periodontal status, endodontic status, periapical pathology, if present and quality and quantity of remaining tooth structure in grossly carious teeth. In teeth with furcation involvement, the grade of furcation involvement ………. Contents available in the book ……….. Contents available in the book ……….. Contents available in the book ……….. Contents available in the book ……..


Patients commonly ask about the prognosis of their dentition and it becomes the moral duty of the dentist to explain it to the best of his/her capability. Although it is very difficult to predict the exact prognosis of the tooth, but if careful examination of the dentition and patient as a whole is done, one can establish a quite accurate prognosis. In an effort to improve one’s prognostic skill, one should make a conscious effort to keep on re-evaluating the patient over a long period of time so that factors that influence the success or failure of therapy can be identified and analyzed.


References are available in the hard-copy of the website.

Periobasics: A Textbook of Periodontics and Implantology

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