|Year : 2017 | Volume
| Issue : 2 | Page : 85-88
Adaptation of gingival biotype in response to prosthetic rehabilitation
Dipti S Shah, Sareen Duseja, Kalpesh Vaishnav, Rutu Paresh Shah
Department of Prosthodontics and Crown & Bridge, Karnavati School of Dentistry, Gandhinagar, Gujarat, India
|Date of Web Publication||28-Apr-2017|
Rutu Paresh Shah
236, M M Jain Society, Opp. Abu Vihar Hall, Ramnagar Sabarmati, Ahmedabad, Gujarat - 380 005
Source of Support: None, Conflict of Interest: None
Background: The gingival biotype is the width of the gingiva in the faciopalatal dimension. It is a feature of the periodontium that is susceptible to change when exposed to physical, chemical or bacterial injury or as a result of surgical or orthodontic treatment. Aim and Objective: The objective of the study undertaken was to assess the adaptation of gingival biotype following prosthetic rehabilitation. Materials and Methods: Forty individuals between 20 and 40 years with healthy periodontium and full complement of teeth with absence of clinical attachment loss or systemic disease were selected for the study. The individuals were restored with a full-coverage porcelain fused to metal with a subgingival margin on root canal-treated teeth with no gingival recession. The gingival biotype of the tooth with the restoration was evaluated in terms of thickness with the help of transparency of the probe method. Twenty individuals were selected with thick biotype and rest with thin biotype. Follow-up was done after 6 months, and the gingival biotype and gingival recession were re-evaluated. Results: It was observed that out of the twenty individuals with thick biotype, eight underwent transformation to thin biotype. Furthermore, thin gingival biotype was more prone to gingival recession as five individuals were found to have gingival recession. Conclusion: Within the limitations of the current study, it was observed that gingival biotype may undergo transformation in response to prosthetic rehabilitation from thick to a thin gingival biotype progressively over a period of time. Hence, supragingival margins should be placed wherever possible. In addition, the thin gingival biotype has a higher susceptibility towards gingival recession.
Keywords: Gingival biotype, gingival recession, prosthetic rehabilitation
|How to cite this article:|
Shah DS, Duseja S, Vaishnav K, Shah RP. Adaptation of gingival biotype in response to prosthetic rehabilitation. Adv Hum Biol 2017;7:85-8
| Introduction|| |
The biotype of the gingiva is a vital factor of concern that may alter the success of dental treatment. It may particularly affect the result of periodontal therapy along with procedures used for root coverage and also implant placement. It is important to identify the type of gingival biotype as each type of tissue biotype reacts differently to various conditions such as inflammation and restorative dental treatment. Special care must be taken while formulating a treatment plan for cases with a thin gingival biotype.
The biotype of the thin type typically consists of a fragile veil of soft tissue covering a scalloped bone which may often exhibit fenestrations or dehiscence. In such biotypes, the keratinised mucosa amount is also compromised. The thick biotype, however, envelopes a thicker plate of buccal bone.,, Hence, conversely, it can be assumed that changes in the underlying bone or exposure to gingival trauma can cause gingival biotype to undergo transformation. This may occur following violations in biological width. This may also lead to gingival recession due to crestal or cortical bone loss. The present study aims to assess whether fixed prosthetic restoration can have an irreversible change on the localised gingival biotype turning a thick fibrotic gingival biotype into a thin and more fragile one. In addition, an assessment is done herein to evaluate the role that the gingival biotype plays in the long-term outcome of a tooth restored with a full-coverage restoration.
| Materials and Methods|| |
The study was performed in accordance with ethical standards and with the approval of Ethical Committee of the institute.
Forty individuals were selected for the study: 20 with a thick gingival biotype and the other twenty with a thin gingival biotype.
The patients had to fulfil the following criteria:
- Full complement of teeth
- Presence of single porcelain fused to metal (PFM) full-coverage crown with subgingival margins
- Absence of any periodontal disease, gingival recession or mobility
- Absence of premature contacts on restored crown.
In the current study, the probe transparency (TRAN) method was used. With the help of a World Health Organization periodontal probe, the gingival biotype of the individual was assessed by gently inserting the probe into the gingival sulcus. If the outline of the probe was visible, it was categorised as a thin gingival biotype [Figure 1]. If the outline was not discernible, it was categorised as a thick gingival biotype [Figure 2]. This procedure was carried out on the natural unrestored tooth. The margin locations of the restored teeth were also noted at this stage. The participants were re-evaluated for the crown margin location and the gingival biotype after a 6-month interval.
|Figure 1: Periodontal probe outline visible through gingiva in individual with thin biotype.|
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|Figure 2: Periodontal probe not visible through gingiva in individual with thick biotype.|
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| Results|| |
Out of the twenty individuals having thick biotype, it was observed after 6-month follow-up that eight of the twenty individuals had a thin gingival biotype around the tooth with the full-coverage crown. It was also noted that, out of the twenty teeth with thin gingival biotype, five exhibited gingival recession. This was evident as the previously subgingival margins of the PFM crowns were clinically visible. [Figure 3] shows the position of gingiva with a thin gingival biotype in the mandibular right first molar restored with a PFM crown of a participant at the initial evaluation. [Figure 4] shows the position of gingiva at 6-month follow-up. It was evident that there was gingival recession as the previously placed subgingival margins are clinically visible.
|Figure 4: At 6-month follow-up showing gingival recession in thin biotype.|
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[Table 1] shows the number of individuals having thin and thin gingival biotype after 6-month interval.
[Chart 1] shows the changes in the gingival biotype and gingival recession after a 6-month interval. It should be noted that after 6 months the gingival biotype of individuals with thin biotype originally did not change but five out of them exhibited gingival recession.
Statistical analysis was performed using SPSS software version 22 (IBM Analytics, United States), and non-parametric Wilcoxon signed-rank test showed that the change in the gingival biotype of the group with originally thick gingival biotype was statistically significant (P = 0.005). The same test on the gingival recession occurring in the group with thin gingival biotype was not statistically significant. This may be attributed to the small sample size considered in the current study. However, it has a clinical value as it shows that thin gingival biotype is more prone to gingival recession.
| Discussion|| |
In 1969, Ochsenbein and Ross indicated that there were two main types of gingival anatomy – flat and highly scalloped. The authors reported that flat gingiva was associated with a square tooth form, while scalloped gingiva was associated with a tapered tooth form. The authors also proposed that the gingival contour closely mimics the contour of the underlying alveolar bone. Seibert and Lindhe used the term 'periodontal biotype' later and categorised gingiva as either thin scalloped or thick flat.
According to De Rouck et al., the thin type of gingival biotype was seen in one-third of the population they studied and was more commonly seen in women. It was observed that two-thirds of the individuals showed a thicker biotype and the individuals were predominantly males. It has been confirmed in studies that central incisors with a slender crown are less resistant to recession as opposed to more bulbous and squarish crown.
Hence, cases with a thin gingival biotype require judicious treatment planning.
Three different biotypes were proposed by Becker et al. which included a flat, scalloped and a pronounced scalloped type of gingiva. When height of bone is measured in the interproximal region to the height at direct midfacial region, the findings of the above types were flat of 2.1 mm, scalloped of 2.8 mm and pronounced scalloped of 4.1 mm. Thick biotypes show greater dimensional stability during remodelling compared to thin biotypes. It is believed that, in thicker types of biotypes, there is laminar bone present next to the outer cortical plate which gives groundwork for metabolic support. This provides stability and an enhanced prognosis. The thin biotype, the cortical plate, rapidly undergoes resorption owing to scarcity or absence of lamina bone. The gingival tissue with a thick biotype is less susceptible to recession and has greater ability to fabricate a barrier to hide the margins of restorations.
It was also found in a study conducted by Tao et al. that central incisors with thin biotypes restored with a PFM crown were more susceptible to 'aesthetic failure' due to gingival recession. The level of gingival thickness before regenerative surgery was found to be a predicting factor for further recession. It was proposed by Kois that the clinical results seen post-surgery showed a strong correlation with the form of gingiva along with that of the alveolar crest. An inferiorly located alveolar crest has greater risk of gingival recession which can lead to exposure of subgingivally placed restorative margins.,,, Patients with thick gingiva were less susceptible to gingival recession after surgical or restorative therapy.
The margins of the prosthesis should be placed in a way as to avoid the violation of biological width. The biological width is defined as the dimension of the soft tissue, which is attached to the portion of the tooth coronal to the crest of the alveolar bone. Any impingement of this distance may cause inflammation, pocket formation, gingival recession and alveolar bone loss.
For this, the rules for margin placement of a restoration according to Carranza should be followed diligently for more predictable results. The rules are as follows: if sulcus probing depth is 1.5 mm or less, place the restorative margin 0.5 mm below the gingival crest. If sulcus probes are more than 1.5 mm, place the margin half the depth of sulcus below the gingival crest. However, if a sulcus probing depth is >2 mm, especially on the facial aspect, evaluate to see whether a gingivectomy can be performed to lengthen the tooth and create a 1.5 mm sulcus, then the patient can be treated using the previous rule.
Various methods were proposed to measure gingival thickness. The thickness of gingival tissue can be assessed using the direct method, the TRAN method, by ultrasonic devices and by cone beam computed tomography scans. In the direct method or transgingival probing method, gingival thickness is judged using a periodontal probe. A thickness of >1.5 mm is categorised as thick biotype and <1.5 mm is considered as thin. This technique has intrinsic limitations, one of them being that precision of probe is nearest to 0.5 mm. Others include probe angulation and distortion of tissue while probing. Alternately, a #15 endodontic K-file with a silicone disc stop can be used instead of a periodontal probe.
The TRAN method used in the current study is the simplest technique to determine the gingival biotype, along with being least invasive. It causes minimal tissue trauma and requires no additional instruments.
Significance of the study
It is vital to study the gingival biotype before planning any prosthodontic treatment. In thin types of tissue biotypes, it is advisable to place the margins of prepared restoration supragingivally. If this is not done, in cases where a PFM restoration is given, the restoration margin may cause a greyish hue through the thin and translucent gingival tissue. This ultimately leads to aesthetically inaccurate restoration and patient dissatisfaction. Moreover, in thin tissue biotype, restorations that are contoured beyond physiologic limits will cause mucosal recession. Thicker biotypes more commonly exhibit pocket formation. However, a study with greater sample size and a longer follow-up period is a viable future research option.
Periodontal surgical techniques can significantly improve tissue quality and treatment outcome. The best method to convert a thin soft tissue into a thick biotype is by subepithelial connective tissue grafting. Other methods of soft tissue augmentation include modified roll technique and use of acellular dermal matrix.,
Providing supragingival margins in thin biotypes will not only cause minimal tissue trauma while tooth preparation but it is also easier to maintain oral hygiene. In cases where aesthetics or caries require subgingival margins, the biologic width must be maintained to prevent gingival recession.
| Conclusion|| |
The current study reflected that the gingival biotype plays an important role in the outcome of prosthetic rehabilitation. Non-judicious tooth preparation and violation of biologic width can lead to alteration in the thick gingival tissue causing it to become thinner over time. Furthermore, it was observed that thin gingival biotype was more commonly associated with gingival recession than thick biotype. Hence, supragingival margins should be preferred in such individuals. The thicker type of gingival biotype has greater resistance towards tissue recession and can better mask the margins of restorations that are placed subgingivally. Hence, by understanding the nature of tissue biotypes, it is possible to employ appropriate periodontal management while tooth preparation and gingival retraction, to minimize tissue resorption and provide more favourable results after dental treatment.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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