A systematic review on prosthodontic rehabilitation of hemimandibulectomy patients

Methodology

Screening and selection

All published case reports and case series on human subjects having hemimandibulectomy defects, fulfilling the inclusion criteria and depicting a type of prosthetic rehabilitation were considered. Only full-text articles published in the English language were included. Original research, clinical trials, laboratory studies, animal studies, editorials, questionnaire studies and reviews were excluded. Titles and abstracts were screened (HD and SK) according to the inclusion criteria, and those with unclear methodology were included in the full text assessment (Table 1).

Risk of bias assessment

Quality assessment of all the relevant studies included in the present review was performed by two reviewers (HD and BS) according to the Joanna Briggs Institute (JBI, Adelaide, Australia).4

This JBI critical appraisal tool comprises eight questions for case reports and 10 questions for case series that assess specific domains to determine the potential risk of bias and could be answered with ‘yes’, ‘no’ or ‘unclear’(Supplementary Appendix 1).

Reports scoring less than four questions out of eight as ‘yes’ (<50% JBI) in case reports and less than five answers as ‘yes’ out of 10 questions in case series were denoted as high risk of bias and were excluded. Any disagreements between reviewers were discussed and resolved by consensus.

If no consensus could be reached, a third reviewer (RJ) gave a binding verdict. The risk of bias in individual studies was determined with the following cut-offs: low risk of bias if 70% of answers scored yes, moderate risk if 50% to 69% of questions scored yes and high risk of bias if yes scores were below 50% and were excluded.

Figure 1

PRISMA flow diagram depicting the literature selection process

Study characteristics

The initial literature search from the selected databases revealed 202 records from which 19 duplicates were identified and removed. After the screening of titles and abstracts, 55 articles (58 cases) with moderate to low risk of bias were finally included after quality assessment (Figure 1).

A total of 58 individuals (28 males and 7 females) with hemimandibular defect according to the Cantor Curtis classification (class I: n= 3; class II: n= 25; class III: n= 24; class IV: n=6; class V and VI: n=0) were finally included.

Prosthetic rehabilitation

Implant-supported prosthesis (ISP) was adopted in four studies. Thirteen cases used guide flange (palatal/mandibular (MGFP)/maxillary ramp prosthesis (MRP)) for the correction of mandibular deviation, whereas twin occlusion prosthesis was delivered in 10 individuals. Interim (MGFP/MRP) followed by definitive prosthesis like cast partial denture (CPD; n=4), CPD with attachment and overlay denture was noted. In two cases, implant-supported overdenture was the treatment of choice,

Post-prosthetic Follow-Up

Post-prosthetic recall visits were reported in 28 cases with duration ranging between 48 hours to four years (n=9; < 1 month, n=27; 1 month to 1 year, n=4; >1 year). Recall visit without duration was noted in twelve cases, while follow-up was not reported among 2 cases.

Inclusion criteria

Exclusion criteria

Prosthetic alternatives according to nature and extent of the defect

Given the possibility of radiation-induced osteoradionecrosis at the bone level, prosthetic rehabilitation following resection involving radiotherapy presents placement problems for implants.

Dental implants should be placed after a year of radiation therapy as doing so correlates with a 34% higher failure rate when placed within 12 months after radiotherapy.When radiation exposure surpasses 5,000 cGy, implant failure rate rises to 33%.

A single-piece smooth surface cortically anchored implant-supported fixed partial denture put in native bone was used to successfully rehabilitate a case of class I defect demonstrating marginal mandibulectomy.15, 16, 17, 18, 19, 20

As opposed to two-piece implants, these implants are the better option in post-radiotherapy cases because they don't require active biologic osseointegration (immediate loading is possible), transmit occlusal forces at the cortical bone, lower the risk of infection, and don't have micro gap junctions, which results in the least amount of plaque accumulation that causes peri-implantitis.21

In situations where dental implants are not practical, removable CPD or CD with extracoronal semi-precision attachments is a less intrusive and more affordable treatment option.5

Due to mandibular deviation towards the resected side displaying rotation and angular course of jaw closure, a segmental mandibulectomy distal to the canine (CC class II) without hard tissue repair prevents the patient from being able to chew.

Implant supported overdenture adjunct with MRP has solved these issues and shown to be beneficial for patients who are completely edentate. This is made worse in edentate arches because unilateral occlusal forces generated during mastication cause the maxillary denture to become dislodged.

The use of monoplane teeth in conjunction with a neutrocentric concept is recommended to create a non-restrictive occlusion due to the irregular jaw connections and the angular path of closure.22

The maxillary ramp offers a wide occlusal table for comfortable mastication, stabilizes the prosthesis, and restricts mandibular deviation.

If implants are impractical, it is advised to use detachable MGFP/MRP, in which the deviation can be corrected by manipulating the mandible, and then a definitive prosthesis. 7

When mastication and aesthetics are desired but manual mandibular deviation correction is not achievable, as is typically the case after radiotherapy and scar formation, a twin occlusion—a buccal row for cheek support and a palatal row for occlusion—has shown to be helpful.4

The prognosis for treatment becomes more complicated when a class III segmental resection that extends to the midline causes increased mandibular deviation with noticeable facial disfigurement, decreased masticatory function, diminished speech, and altered occlusion with condylar rotation leading to an anterior open bite.23

Jaw exercises after resection should be started as soon as possible to enhance the maxillomandibular connection and loosen the scar contracture.

Moreover, intermaxillary fixation may reduce deviation, although it makes feeding more difficult.4

Comparing acrylic MGFP to metal guide flange, it is less expensive and has the benefit of periodic adjustment.5

The sequential adjustment process thins and weakens the acrylic flange; therefore, an inventive way to address this issue is to reinforce with wrought wire formed like a "W."24

With regard to class II problems, the twin occlusion prosthesis as described in that scenario is recommended.

In completely edentate individuals, the definitive treatment of choice is similar to class II defect.25

Because they are easy to insert and remove, flexible dentures (Valplast) are recommended in cases of restricted mouth opening and mandibular deviation.

To improve retention and attractiveness, acetal resin clasp was used in conjunction with monoplane occlusion, which reduces stress and increases stability.22

Resection of the mandible's lateral aspect is necessary for Class IV defects in order to preserve the pseudoarticulation of soft tissue and bone in the ascending ramus area.26

Due to the depressor muscle action of the normal side, it manifests as facial asymmetry, mandibular deviation, and incorrect occlusion.27

A number of therapeutic approaches, such as intermaxillary fixation, resection guidance restorations, and mandibular guiding therapy, have been suggested to lessen post-surgical mandibular deviation.28

By using an MRP in respect to the non-defect side and MGFP on the defect side to establish bilateral guidance, a comparable difficult situation with restricted interarch distance creating occlusal interference by the buccal flange of MGFP on the non-resected side has been overcome.8

This special combination of prosthesis minimizes the deviation and uses neuromuscular reprogramming activity to retrain the user to achieve appropriate occlusion.29

The authors have proposed the use of vascularized free flaps for rapid mandibular reconstruction following resection in order to improve masticatory efficiency and prevent implant placement difficulties following radiation therapy.30

For a mandible that has been rebuilt, implant prosthesis is the preferred treatment. However, the osseous graft must heal and the implants must osseointegrate over a prolonged period of time (in radiation therapy).

In the early stages of recovery, early prosthodontic intervention with MGFP and a maxillary stabilization prosthesis helps to decrease mandibular deviation, prevent maxillary teeth from being driven out of place, and improve masticatory efficiency.29

An efficient, cost-effective substitute for implants in situations where they are not practical is an interim MGFP/MRP followed by CPD.3, 22, 29

Authors have replaced the traditional complex design with a modified swing lock CPD that has the flexible arc of the acetal labial bar for improved retention and stability.5

A final prosthesis can be used after MGFP to correct mandibular deviation and anterior open bite in a difficult class IV deformity, combined with extensive neck dissection and base of the tongue.2, 4, 6

In cases where a guiding appliance is not able to adequately correct a patient's mandibular rotation, an overlay RPD can provide ideal bilateral occlusion, compensate for any residual open bite, and enhance the patient's form and function.27

The present systematic review had limitations as it was restricted only to Medline by means of PubMed and Google Scholar; so, the literature published on other databases and languages apart from English may have been omitted despite meeting all our inclusion criteria. Randomised controlled trials (RCT) were scarce in our search on the particular topic; therefore, the next level of evidence (i.e. case reports and series) was included; therefore, authors are urged to perform extensive RCTs on similar topics. Post-prosthesis observation duration was a deficit in many studies, while few reported short-term (less than one month) follow-up; therefore, future studies with long-term follow-up data are recommended for assessing the prosthesis longevity. Several data were lacking from the reviewed literature including CC classification, reconstruction type and scarring which decreases the article quality limiting us to deduce a strong correlation among the type of prosthesis to be selected for a particular situation.