Crown lengthening procedure following intentional endodontic therapy for correction of supra-erupted posterior teeth: Case series with long-term follow-up.

CONTEXT: The crown lengthening procedure (CLP) is routinely carried out to correct gingival levels and achieve esthetic contours and adequate crown lengths for restorative purposes. Though the short-term outcomes have been found to be stable, long-term results are not much reported. AIMS: To evaluate the long-term stability of the marginal bone levels, gingival levels, and the status of the teeth, which underwent endodontic therapy, followed by CLP and final restorations. SETTINGS AND
DESIGN: Institutional setting, long-term case series.
MATERIALS AND METHODS: Case records of the patients who underwent CLP and endodontic therapy for corrections of the supra-erupted teeth to regain the lost interocclusal spaces were retrieved, and the cases with complete set of the clinical and radiographs were taken. All the cases were recalled and bone levels on the radiographs, bleeding on probing, probing pocket depths, and changes in the soft tissue margins were evaluated. STATISTICAL ANALYSIS USED: Descriptive analysis.
RESULTS: A total of 25 teeth had undergone CLP and endodontic therapy and final restorations for a minimum of 24 months. The mean post-restorative duration was 50.8 ± 22.48 months (range 24-96 months). All the teeth were functional and asymptomatic with 100% survival. Interdental bone loss of 1 mm, probing pockets of 5 mm, and 1 mm buccal recession were observed in 16% of the sites. The amount of interocclusal space regained was adequate to restore the missing teeth in the opposing arch.
CONCLUSIONS: The CLP is a predictive procedure for correction of supra-erupted teeth. The survival of the teeth that underwent the procedure in the present study was 100% over 24-96 months.

INTRODUCTION

The crown lengthening procedures (CLP) are routine in the clinical practice. The exposure of tooth surface by apically displacing the gingival tissue and the bone margins facilitates placement of restorative margins on the sound tooth surface. In doing so, the procedure enables maintaining biological width of 2–3 mm that ensures health of the periodontal tissues.[123456]

Caries and fracture lines on teeth extending apical to the gingival margins, teeth with altered passive eruption, longer crown lengths to enhance esthetic outcomes and correction of supra-erupted teeth are primary reasons necessitating CLP.[7891011]

Supra-eruption of the teeth into edentulous areas is the common occurrence, which starts once the opposing tooth is lost and continues until a point of time and space that the tooth can no longer erupt. Supra-erupted teeth alter the occlusal plane as well as reduce the interocclusal space.[1112] Reclamation of the lost interocclusal space is accomplished by various methods including orthodontic intrusion of the supra-erupted teeth,[1314] re-establishing the vertical dimension of occlusion, and also by intentional endodontic therapy of the supra erupted teeth followed by a CLP and restorations.[18910]

The orthodontic intrusion of teeth is the least invasive of the approaches. The longer duration of the treatment, root resorption during the course of the treatment, and lesser degree of predictability have made orthodontic intrusion not a viable technique for the patient as well as the clinician and more so of the multi-rooted teeth.[71314]

Reclaiming the lost interocclusal space with an increase in the vertical dimension of occlusion is a preferred technique in cases requiring full mouth rehabilitation but not for localized loss of inter-occlusal spaces.

Intentional root canal therapy followed by CLP is a viable technique to correct the localized loss of interocclusal space due to supra-eruption of the opposing teeth. It has been used as a clinical practice tool in cases with time constraints with predictable short-term outcomes. However, the long-term outcomes of the procedure have not been much documented.[15161718] The aim of this long-term case series was to report on the stability of the gingival margin and marginal bone levels and the survival of teeth that had undergone intentional endodontic therapy followed by CLP and final restorations.

MATERIALS AND METHODS

After obtaining approval from the ethical committee of the institute, the study was carried out at the Departments of Conservative Dentistry and Endodontics and Department of Implantology.

Inclusion criteria

The patients meeting the inclusion criteria below were included: The teeth to have undergone endodontic treatment and CLP involving osteoectomy and not merely gingival excision in the posterior area of the jaw restored with final restorations for a minimum of 24 months. A full set of pre- and post-operative radiographs and clinical photographs to be available for evaluation. Opposing dentition to be implant-retained fixed restoration and patient willing to visit the department for a follow-up visit.

A total of 16 case records were retrieved which had undergone endodontic therapy by the same operator (SP) and CLP and implanted placement and restoration by the same operator (SK). Three cases did not have a complete set of pre- and post-operative radiographs and two of the cases did not report for follow-up were excluded. A total of 11 cases with 25 teeth fulfilling the inclusion criteria were available.

Parameters recorded

Duration since restoration, distance from the restorative margin to the gingival margin, bleeding on probing, probing pocket depths, the presence of peri-apical radiolucency, radiographic bone levels as measured from the margin of the restoration to the crest of the alveolar bone in the interdental areas and in the furcation areas of multi-rooted teeth, the presence of cervical abrasion, and fracture of restorations were recorded. The data collected are presented as a descriptive analysis.

A representative of 6 cases has been presented in Figures 1–3 (Case 1: 96 months follow-up), Figures 4–7 (Case 2: 56 months follow-up), Figure 8 (Case 3: 24 months), Figure 9 (Case 4: 92 months), Figures 10–12 (Case 5: 24 months), and Figures 13–15 (Case 6: 58 months follow-up).

Figure 1

Representative case 1: (a) Preoperative radiograph showing the supra-erupted teeth; (b) Radiograph at cementation of the final restorations; (c) Postoperative radiograph at 96 months follow-up

Figure 3

Representative case 1: (a) Final restorations with number 16, 17 at cementations; (b) Stable gingival levels at 96 months follow-up

Figure 4

Representative case 2: (a) Preoperative view showing reduced interocclusal space in number 15–17 area; (b) Number 46, 47 prepared to receive the final restorations, note the apical positioning of the gingival margin

Figure 7

Representative case 2: (a) Preoperative radiograph; (b) Radiograph at final cementation of restorations; (c) Radiograph at 56 months final restorations (note the stability of the bone levels)

Figure 8

Representative case 3: (a) Preoperative radiograph; (b) At final cementation; (c) At 24 months follow-up

Figure 9

Representative case 4: (a) Preoperative radiograph showing supra-erupted number 26; (b) At cementation of final restorations; (c) Final restorations at 96 months follow-up

Figure 10

Representative case 5: (a) Preoperative clinical view of number 23–26 showing reduced clinical crown lengths; (b) Crown lengthening procedure done; (c) Tissue levels prior to cementation of final restorations

Figure 12

Representative case 5: (a) Temporary restorations; (b) Final restorations

Figure 13

Representative case 6: (a-e) Radiographs from preoperative to follow-up

Figure 15

Representative case 6: (a) At cementation of final restorations; (b) At 58 months follow-up (note the stable gingival margins)

Representative case 1: (a) Pre-operative clinical view; (b) Teeth number 16, 17 prepared to receive the final restorations

Representative case 2: (a) Occlusal view of the number 46, 47; (b) Temporary restorations with number 46, 47

Representative case 2: (a) Final restorations with number 46, 47 at cementation; (b) Final restorations at 56 months follow-up

Representative case 5: (a) Preoperative radiograph; (b) Radiograph at cementation of final restorations; (c) Radiograph at 24 months final restorations

Representative case 6: (a) Preoperative view showing the supra erupted teeth number 24–27; (b) After crown lengthening procedure; (c and d) Temporary restoration and stable soft tissue levels

RESULTS

All 25 teeth included in the study were functional and asymptomatic, indicating 100% survival. The study results are as presented in Table 1.

Table 1

The descriptive data of the teeth that underwent CLP

The follow-up time ranged from 24 to 96 months (50.8 ± 22.42 months). All the crowns were PFM crowns with equi-gingival margins. The opposing dentition in all the cases was implanted retained crowns or bridges.

At follow-up, bleeding on probing was observed in 36% (9 of the 25) of the sites. About 16% (4 out of 25) of the sites had probable pocket depths of 5 mm, gingival recession of 1mm was observed in 8% of the sites (2 out of 25), and overgrowth of tissue in 8% of the sites (2 out of 25). Interdental bone loss of 2 mm was observed in 16% of the sites. The sites showing interdental dental bone loss were the ones with the longest duration of follow-up (56–72 months); however, bone loss in the inter-radicular areas was not observed in any of the multi-rooted teeth. One tooth (4%) had peri-apical radiolucency at recall, but was asymptomatic, but was subjected to re-treatment. The presence of the peri-apical radiolucency indicates a failed endodontic therapy in 2% of the cases (1 out of 25%), implying an overall success rate of 98%, but a survival rate of 100%. Two teeth had cervical abrasion.

DISCUSSION

This case series evaluated the long-term survival and stability of teeth that had undergone endodontic therapy and subsequently CLP and final restorations.

The survival rate of the teeth followed-up was 100%, wherein all the teeth that underwent treatment were functional and asymptomatic at follow-up. This is similar to those reported in the literature by Olsen et al.[16] and Kaldahl et al.,[17] who reported stable marginal bone levels at 5–7 years post-CLP and osteoectomy. Kaldahl et al. reported that the marginal bone levels were stable with CLP and osteoectomy as compared to gingivectomy alone.[16] The success rate of the treatments in the present study was 98% as one of the teeth had developed a peri-apical radiolucency which is classified as a failure in endodontically; however, the endodontic success rate of 98% is similar to that reported in literature,[19] who reported a 96% success in vital teeth that had undergone endodontic treatment.

The furcation area bone loss was not observed in the present study, which indicates better outcomes and predicts longer survivability of the molar teeth that have undergone CLP; however, Dibart et al.[18] reported as much as 40% of the molars that underwent CLP had furcation involvement. This was observed in sites wherein the distance from the furcation entrance to the restorative margin is <4 mm.

Buccal gingival recession observed in the study and is attributable to the related to the oral hygiene practices. This is because the teeth, which had developed gingival recession at follow-up also, had cervical abrasion indicating faulty brushing technique.

Gingival overgrowth observed in the study is observed similar to that reported by van der Velden,[20] however, there are studies reporting no over growth and stability of the soft tissue margins.[916171820212223] The gingival overgrowth is influenced by the tissue biotype, oral hygiene, achievement of steady state after a surgical injury, and response to the restorative material.

The tissue rebound after CLP is at 6–12 months postoperative is a common finding[22232425] and is attributed to the time taken for re-establishment of a new supra-alveolar soft tissue complex. In the present study over a period of 24–96 months tissue rebound was not observed, as the tissues would have settled into a steady state.

The location of restorative margin and the restorative is one more factor that influences tissue rebound. The equi-gingival restorative margins in all the cases ensured that there was no irritation to the supra-alveolar tissues from the restoration and tissues levels remained stable.[20]

Radiographs have been successfully used to identify the bone levels.[26] A fixed reference point makes it easier to identify the pre- and post-operative bone levels. Thus in the present study, the radio-opaque margin of the crowns were used as the fixed reference points. The change in the bone levels in reference to the crown margins was easily identifiable.[26] Diniz[24] et al. in a 12-month study showed that the sites treated with CLP developed a lamina dura at 3 months as observed on radiographs, and no much change in the bone levels at was observed over a 12-month period.

CONCLUSION

It can be stated that teeth that have undergone endodontic therapy followed by CLP with osseous resection and final restorations with equi-gingival margins survive for over long duration of time with stable bone and soft tissue levels. These procedures can be predictably used to correct supra-erupted teeth and gaining the necessary interoccusal space for restorative purposes resulting favorable long-term restorative outcome.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.